Printed circuit boards are now a common part of our daily routine. We are using PC Board Fabrication in almost every electronic device we are using for our work and entertainment purposes. Whether it is a mobile phone, or a screen, or a remote for television, every device consists of a printed circuit board. That’s the reason understanding its working is kind of crucial these days.
When we discuss printed circuit boards, we need to understand their layers. PCBs have various layers, and these layers are concerned with their working. These layers will vary according to their working. For example, most multilayer PCBs are used when the device is complex, and we need multiple functionalities. Now let us understand how we do lamination in printed circuit boards and how it is related to layers of PCBs.
As we have discussed before, there are many types of printed circuit boards. They are both single-layer and multiple layers depending upon the functionality of the device. So, for multiple layers of printed circuit boards, lamination is required.
We can say that lamination is a process in which successive layers of materials are built and then binding those layers to strengthen those layers to protect different substances.
One of the important steps in building a printed circuit board is lamination. Circuit board manufacturers do the lamination process to make sure that copper is not conducting a current or signal inadvertently. There is a substrate in the printed circuit board that plays the role of canvas on which all the components of printed circuit board assembly are attached. Copper is laminated to that substrate. Lamination is an integral part of printed circuit board manufacturing. The lamination process will vary according to the requirement of the circuit board. The type of lamination you choose for your circuit board will decide its reliability and performance for the particular device.
Now we have understood what lamination is. Let’s understand the role of fabrication and then we will see how both these terms are related and how the lamination process takes place.
Different layers of the circuit board are placed together on a particular surface pattern to be used in printed circuit board manufacturing. Fabrication is the method of assembly for circuit boards that are used in different electronic devices such as computers and phones. fabricated PCBs are used for customer special products. Sometimes the manufacturers fabricate the circuit board in the house or sometimes they hire a third party to do so.
It is being said that fabrication is the skeleton of any circuit board. Why is that? Fabrication is the process in which we give or transform the sketch of the circuit board into a structural existence. The specifications are provided for the circuit board and fabrication is a way to transform the sketch into the physical design. There are few techniques that are used for this purpose. We will explain those techniques later.
Lamination is the backbone of circuit board fabrication. For better understanding, let’s discuss the types of laminations.
If you are not aware of the types of printed circuit boards then you are more likely to face difficulties in designing the circuit board. Types of laminations in circuit boards will help you analyze the designing and the development stages your circuit will go through. Hence the type of lamination will decide the overall reliability, stability, and performance of the printed circuit board. There are four layers of a simple printed circuit board that are compulsory for basic performance. These layers are:
• Solder mask
And then comes the lamination which is used to hold these layers together. The lamination is done under pressure and temperature. Thermoset resins are used in this process to create a uniform thickness that is required for the process. Typical numbers and letters are used to show the type of lamination which basically shows the characteristics of the product used in lamination. These characteristics are dielectric constant, the tensile strength of the product, shear strength of the material, loss factor, glass transition temperature, fire retardant, and the rate of change of thickness with temperature. For example, if you see FR-4 then it is sure that FR-4 is the most used product in the lamination process. There are different types of lamination that are done in printed circuit boards. The explanation is given below:
1. High TG epoxy:
High TG epoxy is used for multilayer printed circuit boards, and it is most suitable for them. as we already know that multilayer PCBs are used in complex devices from which we need higher functionality. For better epoxy rate in those PCBs, high TG epoxy lamination is used. There are certain characteristics of high TG epoxy. Such as high chemical resistance and increasing heat. TG epoxy is used when we are concerned with tolerating high heat. The temperature in this lamination is similar to the melting point. These characteristics will increase the rigidity of the circuit board and the performance. This Tg is best for ROHS PCB assembly.
You have probably heard FR-4 in the world of lamination before because it is the most widely and commonly used material for lamination. The reason for its popularity is its characteristics of a good trench to weight ratio. This material is flame-resistant which makes it more reliable. The mechanical, electrical, and physical properties of the material stay maintained when there is an increase in temperature because of flame-resistant properties.
3. High-performance FR-4:
As clear from the name, high-performance FR-4 is used when we are supposed to make a multilayer and multiform complexed purpose printed circuit board. TG is the temperature variation that is higher in high-performance FR-4. This increase results in high stability and maintainability. Also increase in TG performs better in high-frequency circuits because of low dielectric powers.
Polyimides are also used in multilayered printed circuit boards. Polyimides are used in lamination where we need extreme environmental stability. Rigid, flexible, and high-density circuit boards require polyimides in the lamination process. Mechanical, thermal, and chemical properties of the material can be increased by using polyimides. Due to these properties, polyimides are highly recommended for heavy applications such as military, aerospace, consumer electronics, and automotive.
5. BT Epoxy:
If you need high standard thermal, electrical, and mechanical properties in printed circuit boards then BT Epoxy is the best available choice among all. This laminate is designed to use in multilayer PCBs, and it helps in bond strength at high temperatures. BT epoxy is recommended and suitable for lead-free printed circuit boards.
There are particular issues with using Teflon in a printed circuit board that results in conventional board shops. But despite this fact, Teflon is highly recommended and suitable for high-frequency applications. Teflon is available in many different types. The most used type is woven Teflon with glass. This material is very flexible and makes SMT assembly a little more difficult.
7. Copper Clad:
Glass fiber and wood pulp paper are used in copper-clad laminators as a reinforcing material. High voltage circuits require copper-clad laminates. These circuits are mostly based on some kind of specific size, appearance, specification, chemical, environmental and physical performance.
We have understood the types of lamination. As we know that fabrication is done by the process of lamination. To better understand the process of lamination, we need to understand the techniques. There are certain techniques to perform lamination for fabrication in printed circuits boards. There is a stage in fabrication in which inner layers and foil are heated and pressed into the circuit board. Lamination is required for this stage. Different methods and materials will be used in circuit board fabrication depending on the requirement of the printed circuit board.
Teflon microwaves laminates are used in circuit boards where high-speed signal flow is required such as RF., they are ideal PCBAs for radio frequency applications because of their high properties of minimal electric loss, reliable dielectric constant, and tight depth tolerance.
In this method of lamination, multilayer PCBA is fabricated in several layers. Thin etched boards and trace layers are used in this lamination that is then bonded. Internal layers are placed under high temperature and pressure and are heated intensely. The Circuit board is then laminated with dry photosensitive resistance as the printed board cools down slowly and pressure also releases gradually.
The most modern technique for PCB fabrication is sequential lamination. This technique is widely used for PCBs having two subsets. An insulating material is placed between the layers of PCB in order to create a subset of PCB. Then the standard lamination process of circuit boards is implemented. This method requires more time and cost for the process. But this is the fundamental technology that is being used for the fabrication process in multilayer PCBs.
High density interconnects (HDI) printed circuit boards are not possible to develop without sequential lamination. HDI is now the most advanced place for electronics so sequentially implementing lamination can ensure the benefit of manufacturers.
PNCONLINE is the market leader as a circuit board manufacturer and will assist in the overall assembling process.
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