The Engineering Projects

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.

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.