Printed circuit boards make it possible to create modern gadgets such as Blu-Ray players, cellphones and computers. Before the PCB was invented in the 1950s, electronic devices were hand wired. Hand wiring can only go so far, and cannot handle larger and more complex devices. With the advent of PCBs, electronic devices advanced by leaps and bounds.
PCB assembly started with the use of Masonite and other related products. Today, assembly uses Teflon, woven glass polyester and fiberglass and fiberglass variants. A lot of research has been done to discover what other materials can be effectively used for manufacturing PCB. The materials used or the assembly of PCB are very important because it determines how much power and work will the PCB be able to carry out. It can actually make or break the PCB function. For example, fiberglass materials are better equipped with a rapid electronic traffic without breaking down. Also, fiberglass is able to withstand the high temperatures and pressures.
Typically, assembly uses temperatures of 170˚C and higher. The material used should be able to handle that level of heat. Materials should also be CAF-resistant. CAF means Conductive Anodic Filaments, which can compromise the electronic components and circuitry of the PCB. CAF often forms on the internal layers of the PCB. Also, materials should also have a good FR level- that is, Fire Retardant characteristic. Not only should the circuit board be able to withstand heat during PCB assembly process, it should also be able to resist fires during the actual use of the PCB in the various machines and devices it will be placed into.
The most common PCB material used is glass fiber epoxy laminate or the FR4. The standard 1.60 mm FR4 has 8 layers of glass fiber materials (7628). This material is designed for the manufacture of multi-layered high-density printed circuit boards. This is best for surface mount multi-layers, direct chip attach, wireless and automotive communications, and MCM-Ls.
Another material used is the CEM-3. It is very similar to FR4. Unlike the woven glass fabric of FR4, flies type of glass fabric is used. This material is milky white and very smooth.
Two circuit boards are recently gaining popularity – the Flex and the Rigid-flex circuit boards. These newer circuit board materials have very unique properties. They can be twisted, folded and wrapped around small or tight packaging areas. Majority of Flex materials in PCB assembly use Kapton as raw material. This is a film based on polyamide developed by DuPont Corporation. Kapton is heat resistant, constantly uses low electricity (3.6), and has good dimensional stability.
Where the PCB is used for determines the material to be used for the board. If PCBs are used for devices that utilize fast circuit speeds, such as those in wireless communications, high frequency circuit boards are needed. Materials used for PCB assembly are carefully chosen according to the purpose for which the end product is to be used. Materials need to be able to support the high demand.
Some circuit boards use reinforcement in order to improve their function, stability and durability. Reinforcements include Teflon (PTFE), quartz and Kevlar. All these aim to ensure that the PCB will be able to withstand high frequency and heat generated by the device it operates.
Other PCB assembly materials include laminate (cores) materials that are fully cured. Both sides of the board are already coated with copper. Pre-peg materials, called B-Stage, are basically glass fabrics that have been pre-impregnated with resin, but no yet fully cured. Then pre-peg materials are the ones often inserted between stacks of cores. The pre-peg melts during the lamination process, which then acts as bonds between the layers.
The invention of the printed circuit boards was a big leap for the electronics and technology industries as it allowed electronic devices to be reduced to a more comfortable and practical size.