PCB is the most important part of electronics. PCB in computers to calculators, PC board material selection should be undertaken with care and knowledge for electrical necessities of a given piece of equipment. Usually, PCB is a flat laminated composite made from non-conductive substrate materials with layers of copper circuitry buried internally or on the external surfaces.
They can be as simple as 1 or 2 layers of copper, or in high density applications they can have 50 layers or more. The flat composite surface is ideal for supporting the components that are soldered and attached to the PCB, while the copper conductors connect the components to one another electronically.
There are main different popular types of PCB material:
- Metal: Metals like copper, aluminum, and iron are generally used as the conductive layer in PCBs. Among of them, copper is the most popular. That is why most PCBs are “copper clad.” Every metal selected for use in PCBs supports the use of surface mount technology or SMT components. This is where you apply the solder mask to the metal traces and heat the board to solder the components into place. You can then do a quick quality check and test before sending the assembled PCB downstream.
- PTFE: And the second type of material used in PCB manufacturing is PTFE, also as known as Teflon. It is a pretty strong, lightweight, and flexible material. PTFE is preferred in applications with very tight tolerances because it doesn’t expand much on exposure to high temperatures. Another point in favor of this material is that it is flame resistant.
- FR-4: As the most commonly used material in PCBs, Most of us have seen the green FR-4 board to which the electrical components are mounted, though it comes in other colors. It is a glass reinforced epoxy laminate sheet. It is a composite made of woven fiberglass cloth and a flame-resistant epoxy resin binder. The epoxy used is flame retardant and water resistant. It provides good strength to weight ratios. The tensile strength offered by FR-4 is very high. FR itself stands for flame resistance. Most FR-4 boards have bromine in the epoxy laminate to help extinguish flames. One point in favor of FR-4 is that it doesn’t absorb moisture.
- Polyimide laminates: Polyimide laminates offer higher temperature performance than FR4 materials as well as a slight improvement in electrical performance properties. Polyimides materials cost more than FR4 but offer improved survivability in harsh and higher temperature environments. They also are more stable during thermal cycling, with less expansion characteristics, making them suitable for higher layer count constructions.
- Flexible laminates: Flexible laminates are thin and provide the ability to fold the electronic design, without losing electrical continuity. They do not have glass fabric for support but are built on plastic film. They are equally effective folded into a device for a one-time flex to install application, as they are in dynamic flex, where the circuits will be folded continuously for the life of the device. Flexible laminates can be made from higher temperature materials , or very low-cost materials such as polyester and PEN. Because the flexible laminates are so thin, manufacturing flexible circuits also can require a uniquely skilled workforce, specialized equipment, processing and an anticipation of lower manufacturing yields.
- Others: There are many other laminates and bonding materials on the marketplace including BT, cyanate ester, ceramics, and blended systems that combine resins to get distinct electrical and/or mechanical performance characteristics. Because the volumes are so much lower than FR4, and the manufacturing can be much more difficult, they are usually considered expensive alternatives for PCB designs.