The Engineering Projects

Introduction to LED PCB

Hello everyone. Today is a great day that we are going to put our focus on another type of PCB. So far in the previous articles, we have looked at high speed, metalcore, high density interconnect and the ceramic types of PCBs. In this article, we are going to introduce another type of PCB that might find great use in your day-to-day interaction with the printed circuit boards. it is very important for a designer to take note of how PCBs have evolved and how they have become an important aspect in the design of successful electronic devices. It has become hardly difficult to come across any time of an electronic device that does not involve the use of printed circuit boards.

In PCB boards you come across LEDs fixed in them, and due to the evolving world of technology, things are changing so first leading to the crafting of new technologies that have led to changes in the LED areas. The LED case is an area that has involved the combination of two methods of technologies in order to come up with something else that is more efficient when it comes to solving the intended purpose. This LED PCB comes with advantages of longevity and durability.

Introduction to the LED PCBs

This is a type of PCB that is used for the purpose of lighting in the lighting appliances like modern LED bulbs. The material used in the process of making this board currently is the metal copper clad that has a very good heat-dissipating function. In general, we should note that the single layer LED PCB is made up of three layers namely the circuit layer, the ceramic layer and the insulation layer.

• The LEDs are laid directly in the circuit layer where they are mounted.
• The heat that comes out of the LED is quickly linked to the substrate layer for dissipation. This is done through the insulation layer then dissipated through the substrate layer.
• Copper, aluminum and iron are the most used thermal conductive layer material since they are readily available.
• The iron core is mostly used in motor high-end PCBs that have a lot of heat dissipation.

How to order LED PCB online?

There are numerous online PCB companies, where we can place the LED PCB order. We are going to take the example of PCBWay Fabrication House, a well renowned PCB Manufacturing House. They have an excellent support team, and it's recommended to first discuss your PCB design with the team, they will guide you at every step. So, follow these steps to place an order of LED PCB on PCBWay:

• First of all, create an account on the PCBWay official site.
• After that click on the PCBWay Calculator, which is an excellent tool to get the quote for your PCB order.

• As you can see in the above figure, I have selected Aluminium PCBs, as LED PCBs are normally aluminum PCBs to avoid heat dissipation.
• Now click on Calculate and get the quote for your order.

The LED PCB working principle

• The LED is mounted on the surface of the circuit layer and the heat that is generated when the PCB is under operation is quickly passed to the metal base layer via the insulating layer.
• This heat is then passed out by the metal base layer to achieve the purpose of heat dissipation of the device.
• See the attached diagram for a better understanding of the process;

LED PCD structure

Circuit layer

This is made up of the electrolytic copper foil and is etched to form the printed circuit board where the components are attached. When you do the comparison with the traditional boards, the LED board can carry a larger amount of current.

Insulating layer

This layer is the core technology behind this type of boards and plays greater roles in the conduction insulation and bonding of the layers.

Metal substrate layer

Here aluminum is the best choice compared to its availability and the cheap prices it offers. Stainless steel, silicon and the iron can be used if the thermal conductivity required is very high.

Types of the LED PCBs

The single layer LED PCB

This consist of the substrate layer together with a conductive layer. A solder mask together with a silkscreen offer protection functions to these layers.

• This type of the LED PCB does not have any circuit layer on the back side.
• Their structure is very thin and they are very weightless.

Double layer PCB

When you don a comparison with the single layer PCBs, you will realize that this has two copper layers which apparently makes them heavier as the number of conductive layers also increase to two.

• Double layered PCBs are durable since this type of circuit layer can withstand the high currents applied and it has the best heat dissipation mechanism.

Assembly methods of the LED PCB

There are two assembly methods that can be employed in the assembly if the LED PCBs. These methods are used to attach components on the board and we shall discuss it below;

Surface-mount assembly

This method involves mounting the electronic components directly into the board copper layer.

• the process is highly automated and offers flexible connections and offers spaces for high density connections.
• They play great roles in circuitry that require high connections and accuracy.

Through-hole assembly

This method involves the drilling of holes into the PCB boards where components are then mounted to the holes using the long leads that are then soldered and the whole filled with flux.

• The process involves a lot of inspections to make sure that the great accuracy and the effectiveness are achieved.
• This method off course provides a strong board with long durability.

Considerations while designing the LED PCBs

• Ideal board design; you must figure out which is the ideal board design that you should incorporate. In engineering everything starts with the design. It is the first step that comes in.
• Picking the proper orientation; when we talk about orientation, we are after how the flow of the circuit is achieved from one end to the other. The way in which the data and the electricity flow in the circuit is what we are referring to us the orientation.
• Component placement; in addition to the circuit and the obvious LED, there are many other components that form the printed circuit boards. these components include the resistors, the capacitors, etc. the components should be placed such that they avoid the solder side of the board were solders lie behind the through hole side of the board.
• Avoid placement of the components on the PCB outline; this will help you manage the board better and also ensure that the design is sturdy and very reliable.
• Vias should not be placed at the end of the STM Pads; vias allows the placement of circuits in tow or more layers if the PCB boards. these vias can go through the surface of the top layer through to the bottom layer. Avoid passing the via through the pads of the surface mounted devices since this will weaken the components.
• Definition of the net width design; due to consumption of different current in the circuits, the design paths will vary with the size of the tracks and this will also affect the net width of this design outcome.
• Cost optimization and the budget issues; this is how the overall budget of the designed PCB will go up to. Therefore, this must also be considered when coming up with the LED PCB.

Industrial applications of the LED PCBs

Consumer lighting

This is one of the common applications the LED PCBs where they find great use on the consumer lighting from flash lights, lamps, spotlights, lanterns to solar powered lighting applications.

Consumer electronics

LED are also becoming a common application in the electronic devices such as the computer keyboards backlights. Other devices that have employed this technology are smartphones, tablets and the televisions.

Telecommunications

Telecommunication displays and indicators use the LED PCBS because of their durability the ability to transfer heat and their longevity since telecommunication gadgets generate a lot of heat.

Transportations

LEDs have a lot of use in the traffic and the transportation industry ranging from the stop lights and the automotive themselves. In the car this PCs are found in the headlights, fog lights, brake lights, reverse lights and the indicators. Highways tunnel lighting also use this technology. The modern streetlighting system is done using the LED PCBs.

Medical

Medical lighting and the medical equipment lighting that are used for medical examination and surgery often use this type LED PCBs.

Benefits of this LED PCBs

1. Reduced consumption of power
2. More efficiency compared to the traditional boards.
3. They are smaller in size
4. This type of board is mercury free
5. It is radiofrequency free
6. It is much environment friendly
7. Cheap and this implies reduced cost.
8. It has a longer life compared to others.

How to order PCB for manufacturing from JLCPCB

JLCPCB (JiaLiChuang Co. Limited) is a worldwide PCB & PCBA Fabrication enterprise. It is a leading company in high-tech manufacturing products specializing in PCB and PCBA production. With over a decade of experience in PCB manufacturing JLCPCB has made over a million customers through online ordering by the customers of PCB manufacturing and PCBA production.

JLCPCB is a professional manufacturer of large-scale manufacturing of PCBs, well equipment, strict management, and superior quality. It deals with the production of all types of PCBs, Stencils, and SMT.

In this article, we are going to discuss widely how the company operates its ordering system of the PCBs by their customers for production through the online booking process.

JLCPCB SMT Services

Normally, SMT components are used in professional/industrial PCBs and JLCPCB offers the best SMT services. You should first check these JLCPCB SMT services to get an idea. Let me highlight its important points:

• JLCPCB offers single-sided placement on the PCB board.
• JLCPCB has an extensive Library for SMT parts and you need to select the components from there.
• JLCPCB manufacture SMT Components in-house and thus gives the best results.
• JLCPCB places automated solder paste and then performs Solder Paste Inspection(SPI).
• I have attached the SMT Assembly screenshot in the below figure:

You can check JLCPCB SMT Services from this video as well:

So, it's quite easy to order for manufacturing of Metal Core PCB on JLCPCB.

How to place an order online

Ordering of PCB at JLCPCB is not a complicated process, since the system is user-friendly to every customer. The steps below show the steps to be followed when placing an order.

STEP 1:

Register on the official site of JLCPCB, if you don’t have an account. if you already have an account just log in

STEP 2:

After login into one account. It will display a home page with a quotation calendar that will display an ordering page. On the quotation calendar, the customer would be asked to enter the size of PCB which he/she requires, quantity, layers, and thickness of their choice

STEP 3:

In this step, the customer is required to enter the PCB board details on the online calculator to get the price of the quoted items in step 2. Also, there is the minimum price which is the cheapest one for a particular PCB.

STEP 4:

Then click to “Add your Gerber file” this will upload the file. There are written guidelines on how to generate different Gerber files in the best format on the well-known circuit design program found in the company industry. A very small customer ID is always added to the PCB ordered to distinguish the PCB order from all others.

If one wants to put it in a specific location you are required to indicate the location by adding a unique text like “PBCJLPBCJL”

The system will analyze the file Gerber to confirm the dimensions and layers of the board after uploading the Gerber file.

STEP 5:

Then click the “Gerber viewer” to the design of the boards. Customers are advised to confirm the Gerber file carefully for any errors. After checking and confirming the errors and no problem is detected just click “save to cart” and continue to the next step

STEP 6:

After saving to cart then click “add new item” if you want to order multiple PCBs repeat the same steps from the beginning as you add both of them to the cart.

STEP 7:

Expand the cart and view all the details of the PCBs ordered, including the price of each one of them, its specifications, and all the number of PCBs ordered.

STEP 8:

After viewing all the details in the cart and seeing all the PCBs you wanted click the “checkout securely” button

STEP 9:

On the checkout, menu add your shipping address where are the PCBs are to be shipped. The country where the PCBs are shipped determines the rates. Also, the shipping options are found on the same page just below the address. The shipping methods available are DHL and Airmail both of them vary in their delivery time.

This is the payment method. JLCPCB offers two kinds of payment methods which include

1. Pay directly: this is the most recommended method of payment by the company. It is recommended since it ensures the high efficiency of manufacturing. If the customer file hasn’t been reviewed for production you will get a refund.
2. Review before payment: one can pay after the file has been approved. In this method, the design will not be produced until payment is made. Results of the review will be made through email. It is recommended to pay as soon as the file is approved to avoid delivery delays. When the file is not approved the order is automatically canceled.

When the order payment is made the company arranges the production where you can go through your “ACCOUNT” menu to track your order status.

Adding a new order to your existing order

Customers may sometimes feel the urge to add a new order to the existing order. This may be because may feel the items ordered are not enough or an increase in demand for the PCBs which were previously ordered

Here below we are going to go through the steps of how to add a new order to the existing order in JLCPCB.

STEP 1: log in to your account and locate the existing order.

When you log in the process will only go through if the existing order is still in the production process. If the order is finished and delivered you will not be allowed to add an order unless you make a fresh order.

STEP 2: You will open the ordering page, upload the Gerber file and add the items you want and click “combine”. Also, this will only appear if there is an extra shipping cost for the order added.

STEP 3: when you click “combine” a new order will be added to the existing order and you can check on its progress.

 

How to track your orders

After placing your order and payment has been made successfully, you can track your order through your account on the company website. Let’s discuss the steps to track your orders.

STEP 1: Open your order history

Login to your account and account menu click order history. After clicking on order history it will direct you to a previously placed orders page where all your previous orders are listed indicating their current status

STEP 2: Check your order status

Once you open the product files column file review status will appear and also the order status in the order status column. Then click order details to learn more.

STEP 3: Track production process

When you are put I am production-ready to be processed. Click the production progress to check the process.

STEP 4: Track shipment status

Once the order has been put into production and processed shipment process takes place. Once the shipment process has started a shipment notification will be sent through your email advising you on the shipment status of your order and the shipping tracking number. One can also use the JLCPCB company website to track the parcel. While on the website click shipment tracking and all the details about your parcel and delivery time information will be displayed.

 

Instructions for ordering PCBs from JLCPCB

Some users experience confusion during the online ordering placement of the PCBs from the company. Below are instructions on some routine internal actions JLCPCB will make when they receive the order.

PCB file and Gerber file in the zip file at the same time

A Gerber file is a file containing the format of the printed circuit design which is used in the fabrication of data. So while ordering the printed circuit boards on your account if both Gerber files and PCB files are in your zip file, the system will follow the Gerber file and reject the PCB file.

Solder resistance bridges

When the person ordering the PCBs does not specify on the solder mask bridge which is importantly required, it will be ignored. When doing the solder-resistance bridge a spacing between the pins needs to be 0.254mm and special notes on doing that are required.

The English description and the attachments on the zip file

Zip file attachments such as PDF files, EXCEL, DXF files, etc are ignored and PCB will be done according to the Gerber file provided. One should ensure the correct parameters are chosen and those needed to be converted into a Gerber file when placing your order. If otherwise, zip files attachment are important should be added to the remark field.

Plated slots/edge (not longer than 6mm)

In the presence of plated slot or edge, they should not be longer than 6mm, and make a note about it when placing the order or the system will make it for you. In the case where no note is provided the company will assume it and make it in the normal process.

Software incompatible issues

Since there is the use of different software by different clients to design the printed circuit board and the software where Gerber data is processed is not the same as the software used in designing the data it sometimes causes the software incompatibility problems to appear. Due to the reason of no warning notification when transferring and importing the data into the software so it is not easily noticeable and cannot be confirmed to the customers. This makes the company responsible for some of the problems caused by software incompatibility.

Markings on base materials

There are some marking that sometimes appears on the base material. This is because of some security issues and there is a way it can be removed. There is no track on which PCB will have the mark so all the PCBs have equal chances of having the marks. One should check from their side whether it is accepted while placing the order.

Gerberview

This tab is functional for reasons of reviewing the file quickly before paying for the order. Acts as the preview button on the website. At times the website causes errors when there is something wrong to display it exactly so it is advisable before placing the order to check the file carefully when you feel there is doubt.

Design about slots/v-cut/cut out/millings

The customer should ensure the v-cut line, cut out and millings are located on the same layer with the board outline. If not on the same layer with the board line it will not appear. It is advised when one is placing the order should check carefully because when it is missed due they are not in the same layer with the board outline the company will not be responsible.

Silkscreen/text

When you want the silkscreen clear on the PCB board the width of the texts and space between letters should not be less than 0.15mm and a width of not less than 1mm. when outline is the font is made and the solid part is filled with lines the fillings then should not be less than 0.15mm. the company will not modify the silkscreen on the Gerber file but the text may be widened. If the text is not enough the company will not be responsible for any complaints made regarding unclear texts caused by nonstandard design.

Layer PCB

JLCPCB company does not make 3 layer PCBs. If one orders a 4 layer PCB with a single inner layer, the company will process it with the 4 layer process directly and confirm with the customer again. So before placing an order confirm whether there is an inner layer miss or not.

Repeat order

This is the placing of orders same just as the previous one which had been successfully processed. With these orders, the company will not make any changes to the file which was used in the production. The customer should ensure not to leave any related note for the order to be changed while placing the order since the repeated order will not be checked manually by the engineers.

Items found on the board outline

The board outline is used to show how the PCB will look like when made. So everything that needs to be included in the board should be cut out clearly on the board outline. You should avoid the least useful items to avoid confusion. When both the GKO layer and the GM1 layer are found on the Gerber file the engineers will ignore the GKO layer and make boards according to the GM1 layer. when GMI, GM2 or GM2, GM3, GM4 layers are in the Gerber file at the same time, engineers will go for the smallest number after the letter GM as the outline layer by default.

JLCPCB panel

When you place an order to JLCPCB the JLCPCB panel will panel the order by default with the v-cut. JLCPCB only panels PCBs with rectangular and circle shapes. When you penalize the boards yourself but choose “Single PCB” when ordering, the numbers of designs/boards in the Gerber file should not be greater than 5, otherwise, we may cancel this order. If “Panel by Customer” has been chosen, the designs in the panelized Gerber file should not be greater than 10.

The remark field

The remark field is used when you place your order so that you can leave a note in case of any import, but the company does not recommend the use of this option since all the orders with an English note will take a longer time to get through the audition process.

Board larger than 200mm*250mm

Large boards sometimes the company might consider them, but if the good board available can not meet the quantity like the one ordered on the website due to the high cost of production they will ship the good boards and refund the difference to you.

Thickness of board outline design

The recommended thickness design of boards outlined by the company is 0.15mm. in a case when the board is greater than 0.15mm the centerline will be followed to make the board outline

Order cancellation

Orders missing crucial information such as the board outline, solder mask layer the order will be canceled out clearly during the audit process.

Orders beyond company capabilities

Orders beyond the company and engineers’ capabilities, will be canceled directly and an email will be sent to inform you about the reason. So before placing an order kindly check your file carefully before you pay for the order to save the loss due to the cancellation.

Removal of the order number

Order removal will not affect the functions of the boards if JLCPCB puts the order number at random or miss to remove. The removal of the order number will be refunded.

Easyeda generated file

Easyeda is a free online tool that we provide to design the PCB, and you can place your order on JLCPCB easily and quickly. But if there is a manufacturer error due to the design error, we may not responsible for that.

Silkscreen and solder mask openings

When the silkscreen overlaps with the openings on the board surface, the principle of openings first will be put into consideration. we will ignore the silkscreen and make the openings on the boards only. In the case where you want to keep the silkscreen on the openings, kindly make a note in the remark column so that the company engineers and factories pay attention to it and meet the required standards.

How to order PCB boards with solder mask defined pads

solder mask clearance is larger than the copper pad it’s exposing, in most PCBs, these pads are known as Non-Solder Mask Defined pads (NSMD).

Some of the other components have another type of solder mask called Solder Mask Defined pad. Which has a clearance of solder mask that is smaller than the copper pad. One can suggest pad and solder mask clearance size in the datasheet when applying. One should ensure that at least 3 mils (0.076mm) of the mask will be printed on all sides of the copper pad. The reason is registration tolerance on the solder mask placement if the mask is smaller than the pad there are possibilities that the mask could move enough exposing bare substrate which will lead to bad results.

How to transfer SMD INFORMATION TO JLCPCB

In the ordering system, there is no given option to add details on whether the board required has an SMD pad. If CAM engineers don’t get this kind of information the solder mask clearance for SMD pads will be enlarged to its default size.

When transferring SMD information to JLCPCB the following steps are used

Write a special instruction

On your account page in the ordering system, there is a text box called “PCB Remark”

Write a special instruction informing JLCPCB that your order design has an SMD pad

Confirm production file

After writhing the special instruction on the Remark box select “yes” for the “confirm production file” option

On clicking yes, the JLCPCB engineers will come up with a production file that is required to manufacture the PCB. When the production is put into consideration a check notification will appear where you can check and confirm it before reproduction. An email will be sent to you when the file is complete and ready for production. Download the processed Gerbers, pay attention to inspect the solder mask clearance for the SMD pads

Benefits of the ordering PCBs from JLCPCB

1. Higher quality: JLCPCB has advanced its production technology by providing high precision boards suitable for industrial, military, and medical applications.
2. Low cost: the company’s mission is to efficiently increase its production of PCB board at a lower cost. JLCPCB produces the cheapest but most efficient PCBs possibly because of extremely high production efficiency, and less human resource cost.

• Fast delivery and user-friendly online ordering platform: the easy online ordering process have led the company to be a leading manufacturer of PCB with efficient and professional customer service, digital technology used in manufacturing, automatic production lines

and their able logistics partners make every step to deliver your PCBs faster.

1. Shorten turn around time: PCB prototypes can be made faster even within 24hours because of the automated equipment and the fast technology we utilize the available capacity of our factories network so that system can match your orders to one of our factories which is best suited, in the shortest turnaround time.

Conclusion

JLCPCB is a good company since it provides great customer satisfaction, as long as you consider the time differences, and try to make orders with enough time to respond during your working days, and making orders, not near the weekend, they are well worth the money saved and the simple interface.

Their chat support is fairly good, and the assembly service is also mostly good.

Introduction to Metal Core PCB

Hello everyone and welcome to this article. Previously we have been discussing different types of PCB boards and for sure we have not exhausted everything. Today we are going to focus on a very important aspect of the PCB design which is the thermal characteristics of the PCB's working environment. Up to this moment, we have interacted with boards that work best in normal working conditions. But remember there are some working conditions, that have very harsh environment such as high temperatures. Let us take for example temperature in boilers or even electric heaters. Do you think normal FR-4 boards can survive in such temperatures? Don’t you think they will melt off if exposed to high thermal radiation? Your guess is as good as mine. For us to have a solution on this matter of high thermal temperatures, there had to be introduced another type of board that could resist such an environment and gives the solution to what the designers wanted. They had to develop the metal core printed circuit boards. These types of boards are suitable in the environment where there is high heat generation and this heat needs to be dissipated away from the circuit and avoid reaching the most critical components of the same circuit which might damage them.

The rapid developments that have been achieved in the Light Emitting Diode industry more so in the area of high-power LEDs, have brought up a challenge on heat dissipation. The LEDs are always mounted on the printed circuit boards and they might end up bringing a lot of problems, especially on the heat generated from them. Without proper laid down structures to dissipate the excess heat will end up damaging the board. To solve this, designers have chosen to implement the use of metal core PCBs.

Definition of the Metal Core PCB.

• As the name indicates, the metal core printed circuit board (MCPCB) is made up of a metallic base as opposed to the traditional FR4 material.
• The metal core material is being used because it offers good heat conduction properties and hence the board will have an efficient heat dissipation mechanism.
• This heat is being dissipated as a result of heat buildup that originates from the electronics component during the operation.
• The purpose of the metal core is to ensure that it diverts the heat generated away from the crucial components of the circuit and moves it towards the less critical components such as the heat sink areas.
• This shows that this type of PCB board is significant for thermal management.
• When designing a multilayer MCPCB, the metal core layers should be spread on both sides of the board.
• Let us use an example of the 12-layer MCPCB board, the metal core will be at the bottom and the top layer and also at the center that is at the 6th layer.
• They are made up of thermal insulating layers, metal copper foil and metal plates.
• For the purpose of our article, we shall have to use MCPCB as the abbreviation of this metal core printed circuit board.

Metal core PCB boards are special types of PCBs that have a metallic layer that is made up of copper or aluminum. This metallic layer is what gives it this name.

How to order Metal Core PCB?

There are many online PCB companies offering Metal Core PCB manufacturing. We are going to take the example of JLCPCB, a China-based online PCB Fabrication House. JLCPCB offers competitive rates and provides excellent results and is considered one of the best PCB manufacturers. You can place a PCB order on JLCPCB's official website.

• Open the JLCPCB official website and click on "Order Now" at the top.

• As you can see in the above figure, I have placed an order of 5 PCBs of size 100x100mm.
• At the top, I have selected Aluminium, instead of FR-4.
• It has calculated the price to $2 for 5 Pcs and you will get the delivery in 2-3 days.

Normally, SMD components are placed in Metal Core PCBs and JLCPCB offers the best SMT services. You should first check these JLCPCB SMT services to get an idea. Let me highlight its important points:

• They offer single-sided placement on the PCB board.
• JLCPCB has an extensive Library for SMT parts and you need to select the components from there.
• JLCPCB manufacture SMT Components in-house and thus gives the best results.
• JLCPCB places automated solder paste and then performs Solder Paste Inspection(SPI).
• I have attached the SMT Assembly screenshot in the below figure:

You can check JLCPCB SMT Services from this video as well:

So, it's quite easy to order for manufacturing of Metal Core PCB on JLCPCB.

Layers of metal core PCBs

When you compare the metal core PCB with other traditional standard PCBs you will realize that it has special layers. The total number of these layers on the PCB will be determined by the total number of conductive layers that you really need. They can be of single or multiple conducting layers. The layers can be categorized into three types

• Base layer
• Copper layer
• Dielectric layer.

Base Layer

• The layer is made up of metal and this is the reason the PCB has the name.
• Since it is made up of metal, the board can withstand a lot of temperature and pressure compared to the traditional FR-4 PCBs.
• The board is also very strong, lasting and durable.
• The metal core base plays the role of the heat sink where it spreads the heat away from the components a role that cannot be achieved by the use of the fans.
• This base layer can be made up of different metals although the most used types of metals are Aluminum and copper.
• Aluminum is the most preferred metal because of its cheaper prices but copper is the best when it comes to performance but is more costly.
• The thickness of this base is determined by the customer requirement or the designer specification although it is in the range of between 1 and 4 mm.

Copper layer

• It is the first layer that is present in all types of PCBs.
• It is the conduction layer that helps in the transiting of the electric signals.
• In other places, they refer to it as the circuit layer since this is where all the conductive circuits and even paths are made.
• The thickness of this layer is determined by the requirements and according to the project layers.

Dielectric layer

• This is the most important layer in the MCPCB which you will not find in the FR-4 PCB.
• We have noted that the top layer is the copper layer and the bottom layer is the metal core layer. We know that these layers are conductive and in between than they are separated by the dielectric layer which acts as the insulator for separating the two conductive layers.
• By separating the copper and the metal layer, the dielectric protects them from electric shorts.
• The main purpose of this layer is to aid in heat dissipation. It picks heat from the top copper layer, passes it through it into the metal core where it is dissipated completely.
• The size of the dielectric layer should be kept as thin as possible so that it does not have any effect on the overall thickness of the final board.

Types of metal core PCBs.

There are three major categories of the MCPCB as discussed below;

Single-sided metal core PCB

This type of metal-core PCB has the copper traces printed on one side of the board and the board comprises of the following;

• The solder mask.
• The copper circuit.
• The metal layer performs as the conductive link.
• The integrated circuit components
• The dielectric layer

The single-sided board also has a dielectric layer that is sandwiched between the copper and the metal core layer.

Double-sided metal core PCB

• This type of MCPCBs comes with a metal layer that lies between two conductive layers of the board. It also has a dielectric that is sandwiched between the copper core and the metal core.
• The metal core is usually the conductor.

Multilayer metal core PCB

It comes with over two layers hence having a structure that looks like the FR-4 type of PCB materials.

• However, this type of board is much complicated in its design.
• For this type of board to achieve maximum performance, it utilizes too many components, grounds and the signal nature.

Process for the production of the metal core PCBs.

Let us have a look at the steps that can be followed in the design of the metal core printed circuit boards as listed below;

• The first step is the creation of the design and the output. This can be done by the use of electronic design automation software such as KiCAD, Proteus, Altium, OrCAD, etc.
• Check the DFM and after checking, by using a film print the copy of the designer.
• Use the printed film to print the MCPCB and while undergoing this process, it is advised that you do it in a very clean environment to ensure that your outcome will have no errors.
• During this process, you might end up with excess copper and therefore you have to use a chemical to etch the excess copper and remove it.
• Ensure that you have punched all the alignment in a well-organized line.

After this step, you now need to confirm the digital image that you have with the original Gerber files from the designer using an inspection laser to confirm if you have done the right thing.

After the confirmation that you have done the right thing, now the design can be moved to the final process of the design. This final step involves the unpacking of the PCB layers accordingly. We are supposed to locate the drill points and this can be done by the use of the x-ray locator.

Now the board is supposed to undergo the process of plating and deposition of copper where the whole PCB is electroplated with the copper layer before the board is taken through the final process of v-scoring and profiling.

MCPCBs metal bases

The aluminum substrate

The PCBs that are made out of aluminum offer very smart heat dissipation and a good heat transfer mechanism. Aluminum PCBs are very light in weight and are used in LED lighting applications, electronic communication and audio frequency equipment. Listed below in the characteristics of the aluminum substrate;

• The thickness should be between 2 to 8 mm.
• Has a thermal conductivity that ranges between 5 to 2 watts per meter kelvin.
• The peeling strength of not less than 9lb/in
• The soldering strength; safety factor of 288 degrees centigrade for more than 180 seconds.
• Has Greater than 3000V of breakdown voltage
• 0.03 dielectric loss angle.
• Flammability of UL 94V-0.
• The size of the panel is 18” x 24”.

Copper base

PCBs made out of the copper core have better performance than those made out of aluminum. But aluminum is preferred to copper by most clients because copper is more expensive. Another disadvantage of copper core over aluminum is that copper boards are heavier and involve a tough process of machining. Copper has a higher rate of corrosion as compared to the aluminum core.

The benefits of the MCPCBs

• The metal boards can undergo etching to control the way heat that is generated by the components flows.
• These boards are very important in high vibrations systems since the components cannot fall off due to strong mounting on the metal core.
• Metals are harmless and can be recycled.
• With metal, you expect a more durable product as compared to the normal epoxy boards.
• Metals have high thermal conductivity characteristic and this means that it provides a faster means of heat transfer.

Applications of the MCPCBs

This type of board finds great use in the field of LED technology. Some of the applications are listed below;

• Light-emitting diodes both in the backlight unit and the general lighting.
• Heat sinks and heat spreaders for cooling systems.
• Power regulations and automobiles are more so in hybrid car systems.
• Used in the semiconductor thermal insulation boards. semiconductors are the top heat emitters in the PCBs and this heat requires a better method to manage it which can be offered by the MCPCBs.
• Amplifies for audio. Amplifiers can be made from the FR-4 material, but if you need quality, best performance and reliability, I would advise the use of the metal core PCBs.
• Used in the hybrid and the electric motor control system and motor drivers. These are applications that generate a lot of heat that a normal PCB cannot withstand. For this reason, MCPCBs are best suited for such applications.
• Used in the modern solar panels
• Used in the control of motion.
• Finds application in the solid-state relays.

High Density Interconnect PCB

The printed circuit board is a type of plastic where electrical and electronic components lie, laminated and fixed. In modern days, there has been increasing in the complexity of electronic components and devices and this has also led to high demand for more complex PCBs that can make this achievable. This exclusive board that has been introduced in the market includes HDI, rigid-flex, Aluminium clad, buried and blind or even a blend of all the listed types.

There is a list of so many PCB types that a designer can choose for any type of electronic project ranging from single layer PCB to other complex types like the multilayered PCBs. In general, the simplest type of PCB contains copper tracks and interconnection between the elements and components on one side of the board. These types of boards are classified as single-sided boards or one-layer side of boards. However, there are other types of boards that are complicated and will require complex methods to do their designs. These boards are probably double-layered or even multilayered.

Multilayered boards are such complex boards that will require advanced technology for their manufacturing. This is where HDI boards come into play. HDI stands for High-Density Interconnect Boards. When addressing high density interconnect boards, we are focused on higher wiring density, the smaller vias, the thinner spaces and the higher pad density that accompany this type of board. This type of board has a lot of advantages over the typical circuit boards.

Definition of HDI Boards

PCBs are made up of components that are interconnected and fixed on them. The components are connected by wiring them on the board. The wiring is in form of tracks and traces. Some boards involve small low density of wiring capacity per unit area while others involve very high density wiring capacity per unit area. HID which is an abbreviation of the high density connect boards are boards that have a high density of the wiring capacity per the unit area when you compare with the normal PCBs.

• These boards are very special as they come with finer lines, tiny vias and a high connection density of the pads than the one that is utilized in the normal boards.

• A good HDI PCB should have one or all of the following;

1. Blind and buried vias
2. Micro vias
3. Build-up lamination
4. Considerations of high signal performance.

• The HDI boards are very compact with small vias, micro-vias, spaces, pads and copper traces.

How to manufacture HDI PCB?

There are many online PCB companies that offer to manufacture High-Density PCBs. The one we highly recommend is PCBWay, china based PCB Manufacturing House. They offer the best quality product, within a specified time and have an excellent support team, ready to guide you throughout the process.

• In order to manufacture HDI PCB, log in to the PCBWay official site.
• Now click on the PCB Calculator, and at the top click on Advanced PCB, as shown in the below figure:

• In the PCB Type, select the HDI option, I have encircled it in the above figure.
• AS you can see for a single piece HDI PCB of size 100x100mm, the price is $333 and the shipping cost is $22 to USA.
• HDI PCBs are highly cost PCBs and are thus used in industrial products.

Variations in HDI PCBs.

HDI PCBs use vias and laser-drilled microvias to connect components between different multilayers. The microvias are the most preferred to offer the connections because they are much smaller and very effective when it comes to space utilization.

• We have at least five variations of the vias and microvias that can be used in the process of manufacturing the HDI PCBs.

Stacked vias

This can be either buried or blind vias which have a very important function of connecting circuits between different layers of the printed circuit board and in this case across three or more circuit layers as shown in the figure below;

Stacked microvias

They can either be blind or buried but they are conical in shape. They are vert small and they still do the function of connecting circuits between layers of the PCB as shown in the figure below.

Staggered vias

When we have vias of a certain PCB layer connected without overlapping, they actually form a staggered via as shown in the figure below.

Staggered microvias

They are conical in shape but they are connected without overlapping hence forming a staggering structure as shown in the figure below;

Via in Pad

This are vias that are connected to the pad where component is lied. They are very common in HDI PCBs.

HDI structure

There are mainly two structures that aren used in the manufacturing of the HDI;

1. Buildup structure
2. Any-layer structure

Buildup structure

This is the basic structure of the high-density interconnect PCB and uses the manual mechanical drilling as well as the laser drilling.

• The first step is the lamination of the core, it is drilled by the use of the mechanical drilling, platting is done before it is finally filled.
• Microvias are added to the core, followed by the drilling, filling and the whole process is repeated.
• The N- buildup structure is made up of the formular N+C+N where N and C represents the number of the microvia in each side of the core and the core respectively.
• The figures below shows an example of the N-buildup structures using the 1-buildup and the 2-Buildup

Any layer interconnect technology

This is an advanced technology that is used in the manufacturing of the HDI PCBs. The method is highly preserved for the high-level interconnection use since we can make connection of any of the two layers of the PCB without any form of restrictions. This means that any-layer connection has a lot of flexibility when it comes to doing these connections.

• Because there is no any restriction on how the connections should be made, this leads to the saving of the board spacing to about 30%.
• However, the cost of doing this board is higher and this is due to the complexity regarding the technology involved.
• Unlike what was done in the buildup, here the micro-via is drilled first by the use of the laser drilling, followed by the repeated copper platting process, transfer and pressing of the inner image, and finally transferring of the outer layer imaging.
• The figure below is a simple demonstration of the simple any-layer manufacturing process.

• The drilling process is done by the use of the carbon dioxide laser drilling machine
• The micro-via are made by the copper filling technology which will do the coper filling by the process known as the vertical continuous platting line and the horizontal plate line.

Benefits of the HDI printed circuit boards.

This technology has found great importance in the smartphone and the tablet manufacturing. Apart from that, they have become of great use in the laptops and desktop computers. The following id the great benefits of the HDI PCBs;

1. Tighter designs; when we have a look at the high density interconnect PCB, we will realize that the board has very high intensity nature of circuit network connection. This high intensity implies that, the board takes literally less physical space. Utilization of design features such as blind and buried vias enables the designers to come up with more compact builds and this will make the HDI circuits very versatile.
2. Reliability; the connectivity that is employed in the design of the HDI boards such as the use of the blind vias and the buried vias makes them more physical reliable. This is because such types of connection are less likely to get compromised.
3. Lighter material; the material used is very light and cooler. The traditional and other PCBs use different variety of materials but the common one is the combination of copper, aluminium, fiber glass and other metals which might prove to be bulk. This is not the case with the HDI boards.
4. Sharper signals; since these types of the PCB has more compact systems, then the outcome is that the signals will have a very short distance to travel hence avoiding much disturbances that comes in with the long-distance travel. This advantage makes the signal rich their destination undisturbed hence sharper performance of the board.
5. Pocket friendly; four layers of the HDI boards are enough to perform all the functions of the standard PCB layer. The board having reduced size, it implies reduction in the coast too.
6. Low power consumption; these types of boards have high number of transistors and also signals travel a very short distance. These features play a greater role in reduced power consumption in these types of boards.

Common uses of the HDI boards.

These types of boards have found many areas of use in the modern world of technology. Let us have a look at a few areas where the high-density interconnect boards are used;

Healthcare

Due to the smaller size of the HDI boars, medical designers have found great interest in this type of board. The medicals equipment are compatible with HDI because they are very small and can fit into them for example in implants and also in the imaging equipment. The equipment play a very significant role in the treatment of the ailments and therefore smaller chips that require less intervention have to be used. Let us take an example of a heart pacemaker that is implanted in the heart to regulate the speed of the heart bit. The pacemaker should be very tiny and therefore the HDI has provided boards that can solve the size of the pacemaker issue. another good example is the colonoscopy which is passed through the colon of a human to carry out the colon examination. It is evident through research that so many people avoid the colonoscopy examination due to the painful experience but the availability of the HDI technology has drastically reduced the size of the camera and improved the visual quality of the same camera which has made the colonoscopy process less painful hence triggering the increased number of people searching for the service.

Aerospace and military.

Military use strategic equipment such as the missile and some other defense communication devices. This equipment utilizes the HDI technology in their boards since it is the only efficient available method. there have been greater changes in the aerospace technology and HDI have always provide the need solution. Communication devices such as the wireless pones and trackers are becoming very tiny in size and this is due to the involvement of too many tiny layers of the HDI boards.

Automotive industry.

The car and other automotive manufacturers are falling in love with the HDI boards simply because with this type of board you are assured of greater discoveries and innovations. This boards allows the saving of more space in the vehicle and also have an increased performance of the same vehicle. To be specific, Tesla uses the HDI technology to run the electric car system where it helps in extending the battery life of the system. Other driver assistants such as cameras, tables etc fit on the dashboard without much problems.

Digital devices.

Let us make a comparison of todays digital devices like the smartphone with what we had 10 years ago and you will make note that there is a very big improvement in size, thickness and weight. This has been made possible by the use of the HDI boards in this area. Thinner and more compatible smartwatches are also a product of the HDI boards.

Advantages of the HDI PCBs

• Compact design; the strategic use of the burred and blind microvias makes the board compact and this leads to spacing.
• High reliability; the preferred use of the stacked vias makes the board to have a super shield against the harsh environmental conditions.
• Phenomenal versatility; this board is ideal where weight, size and the performance are of great consideration.
• Cost effective; the functionality of a 6- layer standard PCB can be reduced to 4-layer HDI board without altering on its intended purpose.
• Better signal integrity; vias and pads and blind technology is what is mostly used in the HDI. It also has very short compact trucks or traces and this reduces the chance of the signals being interfered by the external forces hence achieving of very high signal integrity.

5 Common Used PCB You Should Know

The digital industry is evolving day by day. Today, computers and phones are no longer heavy. They are sleek, powerful, and very light. Actually, some smartphones are more powerful than laptops. All this is possible because of the miniaturization of the electronic gadgets' printed circuit boards (PCBs).

Printed Circuit Boards or PCBs are categorized into several types based on design specifications, manufacturing processes, and application requirements. They are used in various sectors such as automotive, medical, defense, and other areas, you can learn more information at PadPCB.

Before you select a PCB, there are several factors you need to consider. Moreover, it is essential to seek advice from professionals. Although there are several types of PCBs, the five standard PCBs are multilayer PCBs, Rigid PCBs, Flex PCBs, HDI PCBs, and Heavy Copper PCBs.

Common Types of PCBs

Let's have a look at the common types of PCBs:

1. Multilayer PCBs

One commonly used PCB is the multilayer PCB. The board has more than two copper layers and is designed in a sandwich fashion. Also, they have many double-sided conductive layers separated by several insulating material sheets.

All are laminated and bonded together through high temperatures to ensure no air gaps occur and ensure the final PCB assembly is stable.

Advantages of Multilayer PCBs

1. Compact in size – one advantage of multilayer PCBs is compressed in size. This means they can be used on numerous devices.
2. More robust – multilayer PCBs are strong and are suited for extreme environments and harsh conditions.
3. Suitable for high-speed circuits – multilayer PCBs are the best for devices that require high-speed circuits.
4. High level of design flexibility – PCBs can be used in various sectors.

What are the applications of Multilayer PCBs?

Multilayer PCBs are commonly used in laptops, computers, tablets, smartphones, medical equipment, GPS trackers, and many other complex gadgets and circuits.

2. Rigid PCBs

A Rigid Printed Circuit Board cannot be folded or twisted. The board base is made of a rigid substrate giving it strength and rigidity.

In addition, it is composed of many layers that include a copper layer, a substrate layer, a silkscreen layer, and a solder mask layer. They adhere together with heat and adhesive.

Depending on the needs, it is possible to find single-sided rigid PCBs, rigid double-sided PCBs, and rigid multilayer PCBs. Nevertheless, once a rigid PCB has been made cannot be changed or modified.

Advantages of Rigid PCBs

1. Cost-effective
2. Simplicity of diagnostics and repair
3. Solid
4. Lightweight
5. Little electronic noise
6. Capability of absorbing vibrations

What are the applications of Rigid PCBs?

Rigid PCBs are commonly used in laptops, GPS equipment, computers, mobile devices, tablets, CAT scans, X-rays, heart monitors, MRI systems, control towel instrumentation, and temperature sensors.

3. Flex PCBs

Flex PCBs or Flexible Printed Circuit Boards are designed with several printed components and circuits arranged on a flexible substrate. Flex PCBs are also known as flex circuit boards, flexible circuits, or versatile printed boards.

A flex PCB is mainly made from polyamide, transparent conductive polyester film, or polyether ether ketone.

They are made using the same elements as rigid printed boards. But with Flex circuits, the board can flex to your preferred form throughout the use. There are flex single-sided PCBs, flex double-sided PCBs, and flex multilayer PCBs.

Advantages of Flex PCBs

1. Save space due to flexibility
2. Eradicate connectors
3. Increases repeatability and reliability
4. Thermal management
5. Suitable for various applications, especially where high signal trace density is required.
6. Offer uniform electrical features for high-speed circuitry

What are the applications of Flex PCBs?

Flex PCBs are typically used in flex solar cells, LCD fabrication, cellular telephones, automotive industries, laptops, cameras, and many other devices.

4. HDI PCBs

HDI PCB or High-Density Interconnect is a PCB with several interconnections but minimal space. The components are placed nearer, and the board space is considerably reduced, but the functionality is not affected.

Advantages of HDI PCBs

1. Compact design – the combination of buried vias, blind vias, and micro vias offers the board space requirements.
2. Cost-effective – the tasks of a standard 8-layer PCB are reduced to a 6-layer HDI board without affecting the quality.
3. Phenomenal versatility – the boards (HDI PCBs) are perfect where space, weight, reliability, and performance are the primary concerns.
4. High reliability – HDI PCBs are reliable even against extreme environmental conditions.

What are the applications of HDI PCBs?

• Medical devices - are involved in HDI PCBs because they can fit in smaller gadgets such as imaging equipment and implants.
• Automotive – HDI PCBs are the most recommended to save space in automotive. This helps in providing a better driving experience.
• Smartphones and tablets – modern smartphones are HDI PCBs. These PCBs are responsible for creating smaller and thinner electronic devices.
• Military and Aerospace – HDI is integrated into most military communication gadgets such as defense systems and missiles. Moreover, HDI PCBs are suited for harsh environments and dangerous conditions.

5. Heavy Copper PCB

Heavy copper Printed Circuit Board is also known as a thick copper PCB. It features three ounces of copper. Hence, they are highly valued due to their thermal management capabilities. Due to the increased copper thickness, the board can carry more current.

Advantages of Heavy Copper PCBs

1. Increased current carrying capacity, mechanical strength, and increased thermal endurance.
2. Easy incorporation with high power circuits and control circuits
3. Many copper weights on the same circuitry leads to a smaller product.
4. Heavy copper PCBs can withstand high thermal cycling.
5. Permit the use of exotic materials to their total capacity without causing a circuit failure.

What are the applications of Heavy Copper PCBs?

Some of the applications of heavy copper PCBs are overload relays, solar power converters, power converters, weapons control systems, nuclear power applications, HVAC systems, and safety and signal systems.

Summary

PCBs have modernized the electronic industry. Today, the boards are used in almost every electronic gadget you know. However, those mentioned above are the commonly used PCBs.

If you are not sure of the best PCB to consider for your applications, make sure you seek help from an expert. Moreover, it is essential to purchasing PCBs from reputed manufacturers for commercial or industrial use.

Introduction to High-Speed PCB Design

Hello everyone and welcome to this article which will be a great introduction to high-speed PCB design. For sure it is going to be a very interesting class. Let me start by posing a question; Is this something that you have ever come across in your world of PCB design? Where you spent too much time doing the schematics, selecting the right components, doing the footprint addition, generating the netlists, doing the proper layout and routing and sending the end product of your design to the manufacturer? At this level you might probably be designing standard types of PCB boards and if someone was to introduce a project that talks about signal integrity, reflections or even crosstalk, very much believe you will feel like a lost person. It might be something new to you. The reason is that such kind of task is not what you have been handling in your day-to-day design activities.

In this field of PCB design, you might not guess what your clients want in the future and sooner or later, you might be slapped with a design that involves high-speed PCB design process and at this stage be assured of finding things so hard if you have never worked with the high-speed PCB designs. Today we are going to have a look at the high-speed PCB design and this article is best suited for people who want to go beyond the horizon when it comes to printed circuit board design.

What is a high-speed PCB design?

When we introduce a high-speed PCB design, signal integrity should be the first thing that runs in your mind. When your signal integrity starts to be affected by the physical properties of your printed circuit board like the schematic, layouts etc then the design of your board is a high-speed PCB design.

Signal integrity is a set of measures that define electrical signal quality.

• When you complete the design of your PCB boards and you come across challenges such as attenuation, reflections, delays, crosstalk and so on, the feel at home and welcome to the field of high-speed PCB design.
• The amount of attention paid to these arising challenges is what makes the High-speed PCB design very unique.
• You might have been used to the design of easy boards where your focus is only on the placement of components and routing but sometimes you will come across a design that where you place your components is very important, the way you do the routing, the distance between different signals must be considered, where you place your traces and which type of components should be interconnected
• If you take all these precautions then expect a very new different type of PCB design. You will be having a whole new experience in your design work.

Having introduced what high-speed PCB design is and making note that it is all about signal integrity, now let us have a look at the signal integrity to get a proper understanding;

How to place an order for High-Speed PCB?

There are many online PCB companies, that offer High-Speed PCB designing. For this tutorial, let's take the example of PCBWay, a China-based PCB Fabrication House, that offers competitive prices for PCB designing. So, let's take a look at how to place a High-Speed PCB order on PCBWay:

• First, create a new account on the PCBWay official site.
• Click on the PCB Instant Quote tab and a PCB Calculator will open up.
• Here, click on the Advanced PCB Button at the top and you will get the calculator as shown below:

• As you can see in the above figure, I have selected High Speed in the Materials section.

PCBWay has an excellent customer support team, so if are ordering for High-Speed PCB  design, then it would be recommended to discuss your requirements with their team first.

Brief on signal and signal integrity:

When doing a PCB design of any kind, it is obvious that you will be sending some sort of signal through copper traces from the input to your desired area of interest. The signal you will be sending can either be a digital signal or an analog signal.

Digital signals

• Also referred to as the square signal and it is the output that you will always come across any digital signal that exist in this planet.
• Unlike in the analog signal which has random numbers spread all over, the digital signal has a well-organized system of outcomes represented by a high and a low point or a 1 and a 0 or even some refer to them as an off and an on.
• Let us look at the figure below which is an indication of a digital signal.

Analog signals

• This type of signals has random points of output which are made up of both negative and positive values.
• Unlike the digital signal that has on and off points, the analog signals have random results that are defined by there frequencies and the signal strength.
• The following is the output you should expect when using the analog signals.

The main issue about these signals is that they are prone to interference and this is where we bring in signal integrity because anytime a signal is affected by the environment there are some issues that arise.

Let us have a look at the following example.

Let us say you have a circuit that is transmitting signal from point 1 to point 2 in your PCB board. The point 1 can be classified as the transmitter and point 2 can be classified as the receiver. As the signal moves from point 1 to point 2, there is a likelihood that the signal is affected by different factors like;

1. Signal ringing; this occurs when there is unwanted shifting of current or voltage which will lead to the flowing of extra current in your trace hence delaying the arrival of the signal.

1. 1. Signal reflection; this is when your signal is flowing in your coper traces but the whole signal does not get to the destination since some of it is reflected back to the origin.

• Signal noise; this occurs when there is a random fluctuation of signals in your board which in turn affects the signals that are close to it. The fluctuation may end up damaging the signal data being transferred in your board.

• Signal timing; some times when you send your signal through your copper traces, they do not get to that destination in time so that it can match with the clock signals. When this happens the signal might be interpreted as a zero while in actual sence it wss one. This is called signal timing.
• Signal crosstalk; this occurs when you place two copper traces too close to each other whle the traces carry different signals. The electromagnetic radiation that canoriginate from one signal might affect the other sisgnal hence corrucpting the data flowing in it.

Remember that the listed challenges above are just some of the challenges that you might come across during the design of the PCB. Otherwise, we have so many others that we have not mentioned above and all of them just have one thing in common which is causing of disturbance to the signal you are sending from point 1 to point 2.

• Anytime the signal path is disturbed, the integrity of the data being send is corrupted and therefore, your work as a high speed PCB designer is to ensure that the integrity of the signals is protected at all cost.
• The signal should leave point 1 with a particular wave form and it should arrive at the destination which is point 2 with the same wave form and all the data intact.

How to determine if the project is high speed.

In reality, there is no a specific way to determine if the project is a high speed PCB project or not but the evaluation should be done by case to case. As we have noted in our example above, the first thing that should indicate that your project is classified as a high speed project is when you come across some signal integrity challenges in your PCB layout process.

You can identify a high speed design PCB by;

• Some specific device designs involve high speed PCB design. Some of them are designing of cell phone boards, motherboards and DSL routers are classified as high speed design projects. If you will be using specific technologies such as HDMI, SPI, UARTS, I2C and USB, just know that you will be dealing with the high speed projects.
• When the digital frequency is equal or more that the 50MHz.
• When the PCB board being designed has a very small size and the location of the components to be place creates a huge challenge to the designer.
• The main circuit is made up of so many subcircuit that are connected to each other by the use of very high speed interfaces such as the DSI and the CSI.

High speed PCB design Big Three Problems.

When working on the high speed PCB design, there are a number of issues that you will come across while trying to transmit your signal from point 1 to pint 2 and the main three challenges that you are likely to encounter are;

Integrity

Here we have to look at our signal at the destination and ask ourselves if the signal looks exactly as it should look like. If the signal does not look like it should, then it must have faced some interferences along the way which might have ruined its integrity.

Noise

The issue here is if your signal came across any form of interference during the transmission. It is obvious that PCB signals have some sought of noise in their output, but if this noise exceeds a certain limit, it might corrupt the signals being transmitted.

Timing

We are looking at how the signals are arriving at the destination. Are they arriving at the expected time with respect to other signals? Remember that all the signals in a PCB board are controlled by the clock and if the transmitted signal does not match with the clock signal then the signal is corrupted.

Correcting the Big Three Problems

The big three problem can be rectified by involving the following three solutions;

Matching

If traces have a matched length, it will ensure that the signals arrive at the same time and sync with the rates of the clock. Matching is a must thing when working with HDMI, SATA, USB, PCI Express and the DDR.

Spacing

The close you place your traces to each other, the more they are prone to noise and other forms of interferences. Therefore, it is advisable to ensure that your traces are having proper standard spacing. By placing your traces where they should be, with proper spacing reduces the amount of noise affecting your trace.

Impedance

By ensuring that you have proper impedance between your receiver and the transmitter will create a direct effect on the quality od the signal and its integrity. This will also have an impact on how your signals are exposed to the noise challenge.

Design rules and challenges for high speed design.

As it is in any engineering design work, there are rules that have to be followed when we are handling the high speed PCB design. Let us have a look at some of these challenges in depth;

Tuning of the trace length

Here if you are using the high speed interface, you have to do a signal tuning of the length of your traces in order to synchronize your signal propagation. If you miss to do the synchronization, then expect your interface to fail at very high frequencies or even not to work at all. Therefore, the tuning aspects is a very important aspect when it comes to high speed designs.

• In any high speed design, there shall be two types of interferences and that is the parallel and the serial interface.
• The parallel interface will involve the length of the trace tunning only while for the serial interface signals are united into several differential pairs.

• The tunned differential pair

• Below is the tuned length of tracks;

• Tuned parallel interfaces.

Shape of the truck

It is very rare to meet straight tracks from the source to the receiver on a PCB especially when the high speed design is involved because you have to keep bending the tracks while looking for track locations that will fine tune the trace. In real sense, tracks required smooth, rounded corners without sharp bending and you will need a lot of time to make that possible. What makes since task more time consuming is the fact that you will have to redo this so many times repeatedly until you get the optimized path.

Don’t bent tracks at 90 degrees because the width of the track changes affecting the impedance of the track. It is advised you do the bending at 45 degrees as shown in the figure below;

The impedance

Any time you are doing a PCB design, it is very important to make an observation of the single-end point ZO impedances and also as well as the differential impedances Zdiff.

Adherence to the correct impedance is one of the most important rules in the design of the PCB.

Given below are the parameters for the differential impedance calculations;

Location of the components

Component placement is one of the most important rules in process of high speed PCB design. Before you begin this process, you have to mark where you are going to place your component.

For example, you can place components according to their functions. If components do same functions or even related purpose, they should always be in the same location to each other.

Analog components should be placed in their locality, with their ground different from others to avoid the EMI.

During placement, remember that the tracks are not long and therefore you should ensure that you leave the space for tuning.

Termination

Most common type of termination is the parallel termination. This is where a resistor is placed in the track between the differential pair and as close to the receiver as possible.

The purpose of termination is for getting rid of the reflected signals in the truck and this leads to the upgrading of the data that is being transferred. When differential pairs are used, the resistor should be equal to the differential impedance or less than the differential impedance.

Grounding

In most occasion, it is very impossible to completely trace high speed interfaces in a single layer and this will require introduction of vias in order to move the traces from one layer to another.

Vias are just electroplated holes that allows you to move the tracks from one layer of the board to the other.

It is very important to ensure that you accompany the track via with a ground via. These vias are called stitching vias and they help in maintaining the use of a single reference point in the high speed PCB design.

Tips for high speed PCB design.

Start with a plan

This is a basic thing in PCB design and it is very important to have a plan to avoid so much errors and issues in the design process. So before doing any connections of the symbols or the net list you need a checklist at hand so that you can confirm what to do next to ensure that you have done everything accordingly. The plan will help in;

1. Organization of the system
2. The power supply
3. The signal speed
4. Sensitive signals identification.

This are not the only things that you will consider during planning but it is among the first things to do.

Every detail of your board stackup for manufacturing documentation.

After having the plan, the next thing is to ensure that your layer stackup are documented. This is where you have to contact your manufacturer in order to know which material you will use in the design and also and what type of constraints you should employ in those designs.

Expect to work with the following type of materials;

• FR-4
• Nelco
• Rogers

Floor planning

Here you have to organize your board into logical sections. Remember high speed boards are organized into many subcircuits and it is your duty as a designer to determine where each subcircuit should be placed.

This is more so for the case of the analog and digital signals which require that they placed in separate places so that they cannot interfere with each other.

Your physical floor planning should have something like what is below;

Use of power and ground plane

Now that your plan and stackup is fully laid, it is time to get into important details that you will need in order to start the design.

The size of your land patterns should be kept at minimal.

I the previous design, you might have been using very large pads maybe for easier soldering and inspection. For the high speed design, the space you leave is the key for the success and therefore pads should be 0 to 5% of the size of the components. This drop in space will always help in improving the mechanical strength of the board.

Signal routing for maximum shielding benefits

The high frequency signals will be producing a lot of electromagnetic effects as they travel from the source to the sinking region. And this might lead to two signals having an interference on each other. To avoid this, consider each of the following;

1. Minimize parallel signals
2. Ensure you maintain us much distance between your signals as possible
3. Signals between layers should be routed orthogonally.

Efficient path for current should be provided.

This will involve the use of vias so that to avoid the current path from crisscrossing each other or the ground and to make sure that the signal integrity is maintained.

Ensure that you employ the use of the 3W rules in order to minimize coupling between traces.

Use the 20H rule to ensure that the coupling is at minimal.

Introduction to Ceramic Printed Circuit Board

Hello friends and welcome to this article. Today we are going to have a look at the introduction to the ceramic printed circuit boards. we have previously introduced what a printed circuit board is and we noticed that it is a very important part that makes electronic circuits complete and well organized. Having that in mind, we had also discussed several materials that build up these PCBs and today our focus is on the ceramic types of PCBs.

Introduction to Ceramic Printed Circuit Board

• This printed circuit board is referred to as ceramic PCB because of the substrate used in the construction of this board is made up of ceramic and it finds applications in special areas.
• The process of making this board is that copper is pasted on the surface that is made up of alumina ceramic which is the substrate material at a very high amount of temperature.
• Its substrate material offers a very high value of conductivity features, very great insulation factors and provides easy soldering surfaces.
• The most preferred manufacturing process is the laser rapid metalization technique which is a very important process.
• The structure of ceramic borders is very simple when compared to other types of these boards and it offers high-level operations than what is offered by the other type of boards.
• The size of the conductive layer used in this type of board is between one micrometer and 1-millimeter thickness.

How to order Ceramic PCB

There are many online PCB companies, where we can place our PCB orders and the best of them all is JLCPCB. JLCPCB is a China-based PCB Fabrication house and offers the cheapest PCB rates. It's quite simple to place your PCB order on the JLCPCB official site. Here are the steps:

• First of all, create an account on the JLCPCB site.
• They have an online PCB calculator, where you can calculate the final price of your order by adding all your requirements.
• Next, you need to upload the Gerber file of your PCB design.
• Finally, made the payments through an online secure payment gateway, they have multiple options i.e. Visa, MasterCard, PayPal.
• That's it, once your order got ready, you will get it through DHL express delivery service.

[video width="1920" height="1080" mp4="https://www.theengineeringprojects.com/wp-content/uploads/2021/12/homeOrderVideo.mp4"][/video]

Structure of the ceramic PCB

In this discussion, we shall have a look at a single-layer ceramic PCB. It consists of; the ceramic substrate layer, the copper layer and the solder mask layer. Let us have a look at the image below which is a double-sided layer ceramic PCB constructed through the normal method of lamination.

Ceramic substrate

• Compared to the FR-4, ceramic has good thermal conductivity and thermal insulation features and there in these boards, ceramic plays two very important roles one is about thermal dissipation and the other is about providing insulation between the board’s circuit layers.
• When double or multilayer ceramic PCB is required, vias are necessary for providing connection between the layers. To achieve this, vias are drilled through the ceramic substrate by the use of laser technology.
• The drilled vias are then filled with the copper core through plating.

Copper layer

• This is in form of a thin copper foil that is bonded to the substrate by the method of magnetic sputtering.
• After bonding the copper foil on the ceramic substrate, the circuit is etched on the copper by the use of the photoresist coating of the yellow light way.

Dielectric layer

• Made up of various materials such as epoxy resins, phenolic, etc.
• It is used to bond the structures of two adjacent ceramic substrate layers.
• This substrate has poor thermal conductivity properties compared to the ceramic material hence it ends up affecting the overall thermal conductivity of this board.
• it is important to note that ceramic boards can only be used in applications that have lower heat dissipation.

Solder mask

• this has the importance of protecting the exposed copper wires from solder, metals and damages from the environmental conditions.
• The solder mask is applied on the top layer of every PCB after completion of lamination. It might be white, green, beige, red, etc in color.

Single-sided layer ceramic PCB is shown below;

We can notice that it has a copper layer, the substrate layer and the copper shield but the dielectric is missing. This is because the two ceramic layers are bonded by the PP.

Types of Ceramic PCB

Ceramic PCBs are classified according to ceramic substrate material used and also according to the manufacturing method that was used. Let us have a deeper look into these classifications below;

Classification according to the type of ceramic substrate used

Alumina PCBs

They are the most used types of ceramic PCBs and aluminum oxide is the most readily available substrate.

Aluminum nitride PCBs

They are also commonly used PCBs but they are a bit expensive when a comparison is done with the alumina PCBs.

They gave high thermal conductivity and smartly higher frequency performance again when compared to the Alumina ones.

Silicon nitride PCBs

More costly when compared with the aluminum nitride PCBs. They have higher mechanical strength and toughness hence finding greater use in the power modules such as IGBT and military modules.

Silicon carbide PCBs

This is diamond and has high thermal conductivity and electrical conductivity. They find applications in the areas of laser technology.

Boron oxide PCBs

Has dozen times boron activities than the alumina ceramics but this type of ceramic is very poisonous. They find use in high power and frequency applications

Classification according to manufacturing.

High temperature co-fired ceramic – HTCC

This is the earliest method known for PCB manufacturing. The method is suitable for high power and not for high speed or high-frequency PCB manufacturing.

Direct bonding copper method – DBC

This one requires lower temperature compared to the HTCC. They have no PTH vias and they are mainly preserved for power electronic module packaging.

Thick film ceramic PCBs

This has a requirement that the circuit line space should be at 60 micrometers. They find their use in applications that require lower power utilization.

Low temperature co-fired ceramics PCBs – LTCC

They are usually multilayer and normally three-dimensional. They are best suited for communication devices with high frequency.

Thin-film ceramic PCBs.

Has very high precision circuits but the copper layer has a limited thickness. These types of PCBs find their use in high precision devices and also in very small devices development.

Direct platting copper PCBs

They are developed from thin-film technology and can be in 3D and has very high circuit precision. They find their use in high-frequency and high-power circuits.

Characteristics of the ceramic PCBs.

Ceramic boards have very distinct characteristics that always give them an advantage over the other type of boards. below is the list of these special characteristics;

• They are excellent heat conductors.
• Offers excellent CTA component compliance.
• With ceramic PCBs expect a high level of mechanical compatibility.
• They are not easily corroded by chemicals.
• It is very simple to do a high-density outline in these types of PCB boards.

Benefits/advantages of the ceramic PCBs

The ceramic PCB boards are given high priority due to a number of material features and characteristics that they offer which proves to be beneficial in the process of PCB manufacturing. The character of heat dissipation gives this board an advantage over the traditional types of PCB boards. components of the board are placed on the boards directly without the involvement of the isolation layer and this makes the flow of heat throughout the board better compared to the other types of boards. The following are some of the benefits that make this board the most preferred;

High thermal expansion

They are the most popular in the field of electronics due to their features that are unique. One of these features is that it provides a very high thermal coefficient expansion. These boards will still offer very high thermal conductivity even when operated at high temperatures.

Adaptability

These types of boards use a metal core. The metal core is used when the board is undergoing the engineering process. The board can be changed to a rigid carrier which will offer a stiff mechanical strength. This stiffness is very crucial as it allows the board to be used in both fluids and solids.

Durability

The ceramic material offers a lasting-results to the PCBs being manufactured. The toughness of the material used in the making of the board will protect it against routine wear and tear. In addition, these boards offer high thermal resistance which will slow down the decomposition of these types of boards and therefore increase their durability.

Stability

They offer very high stability which is a result of a stable dielectric property that originates from the dielectric materials. Due to the toughness of the ceramic materials, it has a natural resistance to many chemicals.

Versatility

It has a very high melting point hence it can be used in many applications for both low and high temperatures. The best thing about these ceramic boards is that they will offer good thermal conductivity while distributing heat evenly throughout the board and different positions of the devices.

Ceramic boards disadvantage

• It is very hard to find ceramic PCB boards because they are hardly available.
• When compared to the standard boards, the ceramic boards are very expensive.
• These types of boards are highly fragile and therefore they require handling with great care.

Ceramic PCBs applications

Memory module applications

It was done in Japan when a company crested an SRAM memory module by the use of the multilayer ceramic PCB. The ceramic PCB is appreciated for both high-density PCB and low-density PCB. Another example is about the USA company that had developed the telecommunication, aerospace and missile products using this type of board.

Transmission module

This is being done by an American company that is determined is building a transmission module for radar communication using the ceramic PCB boards.

Digital PCBs

Japanese have used low-temperature PCBs in the manufacture of digital PCBs. This is used because it reduces the weight of the circuit greatly. It also reduces the volume of the circuit.

Interconnect boards;

The ceramic boards are mostly used in printed circuit boards because they support the miniaturization of the devices. It has a very high probability in the application of the boards in multilayer interconnects.

Solar panels

HTCCs and LTCCs are both applied in the process of making photovoltaic panels. In this device, we shall use multilayer ceramic PCBs to make them tough and durable.

Electrical power transmitter

There has been an increase in the use of wireless power transmission systems and this implies that most power transmission system has to use ceramic boards to achieve that ability.

Semiconductor coolers

With the introduction of very small pocket gadgets, many electronic circuits are getting miniatured. To achieve miniaturization, it starts with the use of semiconductors that have a highly reduced size. The normal boards cannot give the support needed in order to make sure that the miniaturization process is fully achieved. In order to make this possible, ceramic semiconductors have been introduced and this is accompanied by the use of ceramic PCBs.

How to choose the right ceramic PCB manufacturer

When you are choosing the person or the manufacturer who can produce your board, you have to consider the manufacturer who has the superior tooling that is required to make the process successful. The manufacturer should be able to control the oxidation process so that the board can have superior thermal conductivity and higher temperature resistance.

Ensure that the manufacturer uses the automated process to do the manufacturing and this will make sure that your board is in perfect condition and of very high quality and the process will be less time-consuming.

Introduction to Surface Mount Technology

Greetings and welcome to today’s lecture. Today, we are going to focus our discussion on the Surface Mount Technology of PCB components mounting. It's our 8th tutorial in the PCB learning series and is going to be a very interesting and interactive class. In Surface-mount technology, SMT components(having small pads) are placed on the surface of the PCB board and their pads are soldered on the same side of the board.

As we discussed in our last lecture on Though-Hole Technology, there are two main methods used to mount components on PCB boards. We studied THT in the last lecture and today, we will focus on  Surface Mount Technology (SMT), we will discuss SMT classifications, types, applications, advantages and disadvantages in detail.

In the beginning, a breadboard was used to hold the components together. This had a major disadvantage because components could pull out as they remain loose in the breadboard, hence giving a hard time to designers, especially in the case of complex circuits. The engineers came out with a solution called the PCB board. Initially, Though-hole technology was used to plug components into the PCB board. Later on, with the invention of SMT components, surface-mount technology came into existence. So, let's have a look at SMT in detail:

Introduction to Surface Mount Technology

• Surface-mount technology(SMT), initially called planar mounting, is used to mount components on the surface of the PCB board.
• In Surface-mount technology, SMT components are used, which are quite small in size and have small pads, instead of leads/pins.
• In SMT, components are placed on the PCB board at their required positions and their pads are soldered with the copper markings on the board.
• Unlike THT, the component pins in SMT don't cross the PCB layer, they are soldered on the same side of the board.
• SMT is the most popular method that is being employed in today’s PCB manufacturing process because it can be purely automated hence increasing the number of boards produced and also saving on production time. With this method, the cost of the PCBs was reduced drastically, if you are doing mass production.
• As the name suggests, the components are mounted on the surface. So, there are no holes for the components mounting as in the THT method.
• Initially, the process was done manually but today it is done by the use of advanced machinery, thanks to the technological revolution.
• SMT discovery came in the 1980s when companies were struggling with the high demand for printed circuit boards. Fab houses had started shifting to mass production of the boards and therefore they had to introduce new methods of PCB assembly and mounting to speed up the process.

How to place an SMT PCB order?

There are many online PCB companies available, where we can place orders for PCB with surface mount technology. Let's take the example of JLCPCB Fabrication House, one of the leading PCB manufacturers, which offers top-quality products.

• First of all, open this JLCPCB SMT Assembly Page.
• Here you can see, it's quite easy to place the SMT order.
• First, you need to Upload the PCB Gerber Files, as shown in the below figure:

• JLCPCB has a remarkable online PCB order tracking system, which keeps you aware of the current situation of your PCB order, shown in the below figure:

• Once your SMT PCB order gets completed, you will receive it at your doorstep.

SMT Manufacturing Process

• Using the assembler, solder paste is applied on the parts where the components will be placed. The solder paste placement follows the guidelines from the design.
• Use the stencil or the solder screen to ensure that the solder has been placed in the exact required positions.
• Sometimes, stencils and assemblers might not be that accurate and it's the operator's duty to inspect the solder to ensure that it has met the required standards.
• Depending on the defect, either the assembler corrects the defect or will remove it and reapply afresh.
• The process of inspection is very important because it will determine the quality of the solder at the end of the process, hence affecting the overall functionality of the board.
  
• After inspection, the assembler will place the components accurately following the designs given by the designer. Originally, it was done manually by workers with hand tools. Today, pick-and-place machines have made work quite easy, accurate, and fast.
• After placement, the components are soldered into pads with the solder gun. Here, the board undergoes a reflow process in which it is passed through the furnace to remelt, liquefy and finally solidify the solder at component joints.
• Special devices used in the process of SMT are called Surface Mount Devices.

Types of vias

The SMT employs the use of vias in order to connect components with the PCB board. There are three types of vias that are employed throughout the process i.e.

1. Blind vias.
2. Through vias.
3. Buried vias.

Through vias

• This one connects all the layers of the PCB board by passing through all of them.
• Mostly Through vias are used for the power pins i.e. ground, Vcc etc.

Blind vias

• Blind via connects any of the external layers to neighboring two or more layers of the PCB board but won't go through all of them(as that will be Through vias).
• Blind vias are of several types as listed below:

1. Controlled depth blind via
2. Photo defined blind via
3. Laser drilled
4. Sequential laminated blind via.

Buried vias

• Buried via connects any two or more layers of the PCB board but won't touch any of the external layers.
• As the name suggests, it remains buried inside the external layers of the PCB board.
  

Machines used in SMT mounting

Here's the list of machines used in the SMT manufacturing process:

PCB Drilling Machine:

• Even though I said that the SMT components are mounted on the surfaces, so there's no drilling but remember that we discussed vias, which are required to create a connection between layers of the PCB boards.
• These vias are very tiny holes drilled into the board layers and are done by the drilling machine.

Wave Soldering Machine:

• This is used for the soldering of components on PCB pads, essential for the mass production of PCB boards.

PCB Brushing Machine:

• We have discussed the vias drilling, so after the drilling process, we have debris deposited on the PCB boards.
• This debris is removed by the PCB brushing machine.

Pick-and-Place Machine:

• Pick-and-Place Machine picks up the components, rotates them in the required direction and places them on the PCB board.
  

PCB cleaning machine:

• It does all the necessary cleaning of the board.
• It also ensures that the board is dry and free from any form of moisture.

Reflow oven:

• It contains a lot of burners and is used to smooth the soldering process.
• There are three types of Reflow ovens available:

1. Vapor Phase Oven.
2. Infrared Oven.
3. Convection Oven.

Now, let's have a look at the different types of Surface Mount Methods:

Types of Surface Mount Technology

Type I

• Only SMD components are found in this type of PCB board.

Type II

• Active surface mount devices and DIPs are located on the primary side of the PCB while the surface mount chips are on the secondary side of the board.

Type III

• In this type, you will find passive SMCs on the secondary side of the board while the primary side is made of the DIPs only.
• It contains only discrete mount components and they are all mounted on the bottom side.
• The discrete components include; transistors, resistors, capacitors etc.

Applications of the SMT components

With SMT technology, it has become possible to produce very compact and small-size boards, since machines are used to pick and place the components. Therefore, SMT technology has numerous applications in real-life fields, few are as follows:

1. Smartphone Evolution: Smartphone boards are quite small in size but complex in design because mobile phones need to be thin and light therefore, this technology has aided a lot in the evolution of the smartphone industry.
2. Computer and laptop motherboards: It has helped in the production of ultrathin laptops, tablets and computers.
3. IoT Devices: With SMT technology, IoT has moved to another level since the production of embedded boards become easy and fast.
4. Involved in the manufacturing of communication and telecommunication equipment i.e. Bluetooth, WiFi, Ethernet devices etc.
5. Medical devices in aid of health screening.
6. Finds applications in the transport area i.e. drones, space exploration equipment etc.

Advantages of the SMT components

1. They have very low RF interference because they don't have leads.
   
2. It takes lower packaging materials and this is due to the advanced manufacturing that is being involved.
3. If SMT boards are produced in panels(We will cover penalization in upcoming chapters), the process makes it easy to transport in bulk at a reduced cost.
4. The production cost has been drastically lowered compared to that of the THT product of the equivalent magnitude.
5. Component failure is very low due to the consistency of the fabrication process involved.
6. Less expensive process and very economical due to the use of more advanced technologies like PCB Panelization and pick and placing mechanism.

Disadvantages of the SMT components

1. It is not the best method to mount high-wattage components because such components dissipate a lot of heat that may end up damaging the PCB board.
2. This is made up of very tiny components and therefore if there is any damage to the circuit, it is very complex to repair/debug the board as compared to the THT components. This means time-consuming in repairing and also very expensive.
3. This type of board cannot be used in a place where rough holding is involved.
   

So, that was all for today. I hope you have enjoyed today's lecture. In the next lecture, we will have a look at the difference between these two mounting techniques i.e. THT vs SMT. Till then, take care. Have fun !!!

THT vs SMT

Hello everyone, I hope you all are doing great. Today, we are going to share the 9th chapter in the PCB learning series, where we will have a look at the difference between Through-hole and Surface-mount technology.

In our previous lectures, we studied both THT and SMT methods separately and have seen that both are used for components mounting on the PCB board. So, today, we will have a look at the difference between the two techniques. So, let's get started without wasting any time.

Through-Hole vs Surface-Mount

Let us know have a look at these differences and get to know the way forward when it comes to the process of component selection whether SMT or DIP.

Definition - THT vs SMT

• THT stands for through-hole technology.

In Through-hole technology, components are mounted by the use of holes that are systematically drilled through the layers of printed circuit boards. the components have long leads that are properly fitted in the holes and soldered.

• SMT method stands for Surface Mount Technology.

In Surface-mount technology, components are mounted on the surface of the printed circuit board. This is the most recent method employed in manufacturing of printed circuit boards.

How to Manufacture?

There are many online PCB Manufacturing companies, where you can place your SMT or THT orders. For example, let's talk about JLCPCB Fabrication House, they offer both THT and SMT fabrication. You can place your order on the official site of JLCPCB. They have an excellent support team, so while placing your order, you can discuss your design with them and they will guide you completely.

JLCPCB offers competitive prices as compared to other PCB houses and delivers quality work within the assigned time limit. They also offer seasonal discounts, so if you are a regular PCB designer, you should subscribe to JLCPCB.

Component Mounting

Through-hole Technology:

• In Through-hole Technology, DIP components are used having copper leads/wires called lead wire terminals.
• These leads are used to connect the components with copper tracks on the PCB board.
• These leads are inserted in the drilled holes on the PCB board and are soldered from the back side.
• The extra leads are then trimmed off using a cutter.
• A DIP component having two leads is shown in the below figure:
  

Surface-mount Technology;

• In Surface-mountTechnology, SMT components are used having copper flat terminals(called pads) instead of leads/wires.
• These SMT components are placed on the surface of the PCB board as mentioned in the design files and the flat terminals are soldered with the pads of the PCB board.
• An SMT component is shown in the below figure:

Manual vs Automatic Process

Through-hole Technology

• Through-hole PCB boards can be assembled both manually and automatically(with the help of machines).
• Normally manual assembling is preferred in THT boards.
  

Surface-mount Technology

• As the SMT circuits are complex in design, thus it involves the use of sophisticated systems to ensure that the process is accurate and error-prone.
• Pick-and-place machines and stencils are used in the SMT process.
• Manufacturing SMT PCB at home is too difficult so automatic processes are recommended in this case.
  

Stencils

Stencil is a modern technique to place solder paste on a bare circuit board. This paste forms the deposits on the board that is used to hold the components in place.

Through-hole Technology:

• The through-hole technology does not involve the use of stencils since the components are mounted in holes and are soldered on the other side.

Surface-mount Technology

• The surface mount technology uses stencils for the process to be smooth.
• Solder paste is poured through a stencil on the PCB board and then SMT components are placed on it.
  

Vias

Vias are small drilled holes between the PCB layers to electrically join traces of the circuitry.

[TEPImg11]

Through-hole Technology

• For the through-hole technology, vias are not that necessary since the components are connected through the holes to the other layers of the boards.

Surface-mount Technology

• The surface-mount devices employ the use of the vias to connect between layers of the board. Since components are mounted on the same layer, it is very necessary to employ the vias to interconnect between the layers of the PCB board.

Debugging

• Through-hole technology mounting components and boards are quite easy to debug/repair, that's why, THT is used when a prototype or testing is required.
• Surface-mount technology components are quite difficult to debug/repair because they are very small in size.

Soldering

Through-hole Technology

• Wave Soldering is used in THT boards.
• It's an in-line soldering process that treats the solder with flux.
• The solder is melted after getting heated and then immersed on the PCB board.
  

[TEPImg12]

Surface-mount Technology

• Reflow soldering is used in SMT boards.
• In reflow soldering, a solder paste is used to mount components temporarily on the board by the use of the pads after which the entire design is preheated.

[TEPImg13]

Component Types

• Through-hole technology uses lead capacitors and resistors, DIP and GPA components.

• The surface mount technology uses LCCCP, SPOIC, QFP, BGA, SOT, LCC, chip resistors/capacitors etc.

Assembly Density

• Through-hole technology is used when a low density of components is required.
• Surface mount technology is used where a high density of components is required.

Solder Joint

Through-hole Technology

• For the through-hole technology, the solder joint connects the component lead to the board through a hole drilled on it.
• The solder is applied on the lower side of the board and the upper side is filled with the flux.

Surface-mount Technology

• For the surface mount devices, the board is first spread with the solder paste, after that components with pads are placed accordingly on the soldered points and then the solder is melted to fix the components on the board.

Cost of Production

The cost of production for the two methods varies, normally determined by the type of manufacturing process and the components used.

Through-hole Technology

• Through-hole technology proves to be the most expensive. when it comes to initial production because it involves drilling holes to mount the components.
• But when it comes to routine maintenance of the THT boards, the cost is relatively low since it is very easy to replace any component on the boards. THT is easily repairable.

Surface-mount Technology

• Surface-mount devices are cheaper when it comes to initial manufacturing.
• The process is purely automated hence saving oh human labor costs.
• Also, the process does not involve the use of holes in the mounting of the components hence reducing costs.
• The boards are produced in bulk through the process of PCB panelization, this also lowers the cost of production of the boards.
• Now, there is one challenge with this type of board, the maintenance cost is too demanding. You will need a lot of expertise to change any faulty component. Some of them cannot be changed since they are so tiny. Therefore, in most cases, if the board has a problem, you might end up buying a new one hence it is very expensive when it comes to maintenance and repair.

Applications

Through-hole Technology

• Through-hole technology is preferred in hobbyists and academic projects, because of simple circuits to design.
• THT Boards are also used in areas where strong mechanical strength is required such as in military equipment and equipment with high vibrations. This is because their soldered joints are mechanically strong.

Surface-mount Technology

• Surface-mount devices are preferred in the industry sector where commercial products are designed because SMT is cheap, lightweight and small in size.
• The manufacturing time of SMT boards is quite low, especially in mass production, because its manufacturing process is purely automated.

So, that was all for today. I hope you have enjoyed today's lecture, let me know if you need any help with it. Thanks for reading.

Introduction to Through Hole Technology(THT)

Greetings and welcome to today’s lecture. It's our 7th tutorial in the PCB learning series. In our previous lectures, we have studied the two main types of PCB i.e. Single-sided and Double-sided PCB. Today is going to be a very interesting and interactive class about Through Hole Technology(THT), which is applied in the process of designing printed circuit boards.

A PCB board has a properly designed circuit on it and it's composed of connecting traces/paths and various electronic components. The electronic components are mounted on the board in two different ways i.e. Through-hole and Surface-mount. We will cover Surface-mount in our next lecture and today, we will discuss how to mount components on PCB boards using though-hole technology.

So, let's get started with Through-hole technology:

Introduction to Through-Hole Technology of PCB Design

• In Through-Hole Technology(THT), small holes are drilled in the PCB board to mount the components.
• The normal-sized components(unlike SMD components) have long copper leads/pins and are plugged into these drilled PCB holes and soldered from the other side. The extra leads are trimmed off.
• In through-hole technology, components are placed on one side of the board and soldered on the other side, where the copper foil is present.
• Through-hole technology is normally used in single-sided boards.
  

History of Through-hole Technology

• THT is the oldest among these PCB components' attachment methods.
• For quite a long time, it remained the standard method to use in the PCB assembly process.
• In the 1980s, when the surface mount technology process was introduced in the field of PCB assembly, designers thought that the THT method will become extinct but that is still not the case.

Why do we still need THT?

• The surface mount technology, being advanced had many advantages over the old Through-hole technology but because of low cost, THT is still operating.
• Some high-power components that required strong connections could not be fitted by the surface mount process, THT is the only option that could be used in such a process.
• For example, the connection of the terminal blocks, power jacks and other power connectors can not be done by any other method apart from the THT.
• Also, equipment working in places with high temperatures and vibrations can only have boards that are connected through the through-hole technology.
• Therefore, while others thought that, the entry of the surface mount devices was the end of the through-hole technology, their thought was disapproved over time, as of today, through-hole technology remains one of the important mounting processes in the manufacturing of the PCB.

How to place THT PCB Order?

There are many online PCB Fabrication Houses, that provide Through Hole PCB board services. One of them is JLCPCB Manufacturing House, which offers this facility of mounting Through Hole components as well as SMT components, a sister company of EasyEDA. JLCPCB is a top-notch PCB Fabrication House, provides low rates for PCB orders.

JLCPCB has an excellent support team, so you should discuss your PCB order with them first. They will completely guide you and will give you the final price and time to complete it. JLCPCB provides a perfect product as per your requirements, a personal experience.

THT Process

• Drill holes on the PCB following the clients’ design.
• Holes have several specifications from location to diameter sizes.
• In the design folder submitted by the designer, there is a very specific file named drill file. This is the file that will give the location and sizes of the holes to be drilled on the boards accordingly.
• Select the components, that must have long leads and every component has its own specification. Components are mentioned in the BOM files, schematics and the GERBER files. If you go through the files, you will get the components to be used in the design, whether, THT or SMD components. THT components will be selected in this case.
• The next phase is to place the components on the board and ensure that their leads are on the holes as defined in the design. This process can be done manually by human hands or can be done by pick-and-place machines that have been designed specifically for this purpose.
• Ensuring that the components are in the positions described in the design to avoid any errors.
  
• Solder the terminals on the board accordingly. Soldering is one of the most important processes in THT PCB design.

• Soldering is done by use of the soldering gun which is of different varieties as shown below:

Initially, this process was done manually and was time-consuming, but today, due to AI technology, it has become quite simple and automated to design through-hole technology. An automated insertion machine helps in inserting the electrical elements into the drilled holes of the PCB before the soldering process starts.

Classifications of Through Hole Components

We have talked about the electrical components being placed on the PCB boards through the hole.s These components can be classified into two main types:

1. Radial-leads components.
2. Axial-leads components.

Radial-leads Components

• In Radial-leads components, all the leads originate from one side of the component.
• The components can be mounted either vertically or horizontally.
• Radial-lead components include capacitors, op-amp, power regulators(LM317, LM7805) etc.

Vertical mounting of Radial THT components

• In this case, the component is placed perpendicular to the board while the base is placed parallel to the board. Soldering is done on one side of the terminal and the other side is filled with flax.

Horizontal mounting of Radial THT components

• The component body is fixed horizontally as you can see in the image above.
• The leads exhibit a very nice bend and spacing. This allows the proper filling of the solder on the component hence forming the strongest bond.
• The component is free from vibration effects as it is well-fixed on the board.

The Axial leads Components.

• In axial-leads components, the leads appear from opposite sides of the component package.
• Axial components are placed horizontally over the PCB board and are strongly attached to the sheet.
• Common examples are diodes, resistors etc.

Vertical axial mounting method.

• One side of the mounting lead is long and allows room for its bending to achieve horizontal fixing.
• It has a strong mechanical joint as it can allow soldering on both sides of the board.

THT Components types

Single-ended

This is mostly used in integrated circuit embedded systems. Those ICs that have terminals on one single side are said to be single-ended THT components. See the attached figure below.

Double ended

Again, it is applied in ICs systems. Some IC for example the 8051 AT89C51 have pins that are arranged in two files each from its side of the length as shown below. The type of THT that will be used to fix them in the PCB is called double-ended THT mounting.

Pin grid arrays THTs

In this type of THT, the components have so many pins that are arranged throughout the component in a grid manner. See the example of such components below.

Applications of THT

• High voltage areas eg in the medical equipment. When high voltages are involved, there is a possibility of shorts and overheating of the components. Since this type of component mounting provides a strong joint, thus THT comes in handy.
  
• High mechanical stress devices eg military equipment. High stress, requires strong joints to avoid breakages. This can only be offered via the THT type of mounting.
• High power areas eg in the steam boilers. High power is accompanied by vibrations and magnetic forces. This type of mounting is good for such devices.
• High temperatures operating devices eg in the nuclear plants. High temperature means the possibility of high reliability. Hence, we can use THT as it can be easy to replace components in case of problems.
• Prototyping and testing of components since it is the most flexible method offering easy ways for replacement of components during the process.

Advantages of THT

1. The use of the THT method will ensure that you have a very strong mechanical bond between your components and PCB board.
2. THT-bound components have high resistance to wear and tear and this is made possible by the use of the large soldering deposits at the terminals.
3. The THT components are very easy to swap/repair, thus, best for prototyping works.
4. It is best suited for places where strong mechanical applications are needed such as aerospace and military equipment.

Disadvantages of the THT method of PCB components Mounting.

1. Due to the drilling of the required holes, the production machines have to be very accurate.
   
2. Drilling of the holes requires some additional time, hence THT method takes a longer time compared to other methods.
3. This method limits the available routing paths for the multilayer PCBs because the drilled holes have to go through the given layers.
4. The technology being used in the industrial mass production of THT is less reliable compared to other methods.

The through-hole technology PCB mounting is the best method to be used when manufacturing large PCB boards. It is best for mechanically strong component mounting and also the cheapest when it comes to doing testing and prototypes. It can't be extinct and it will never.

So, that was all for today. In the next lecture, we will discuss the second method of mounting components on PCB boards named Surface-mount technology. Till then, take care!!!