The printed circuit board is an important component of electrical or electronic materials made of copper-clad Laminate (CCL). People of circuit board industry must know about the substrate: such as the variety of substrates, and their respective advantages and disadvantages when using, so that we’ll choose suitable substrates.
The substrate is composite material that is composed of dielectric layer (resin Resin, glass fiber Glass fiber) and high purity conductor (copper foil foil foil). The following is for the two main components to do some discussion.
There are many types of resins currently used in circuit boards such as Phenolic, Epoxy, Polytetrafluorethylene are all thermosetting resin (Thermosetted Plastic Resin).
The Phenolic Resin is polymer that the earliest R&D successfully and commercial, which is composed of liquid phenol (phenol) and liquid formaldehyde (Formaldehyde, commonly known as Formalin), solid synthetic materials are hardened and thus formed because of the continuous reaction of Cross Linkage on condition of the acid or alkaline catalytic. The important characteristic of Phenolic Resin is temperature-resistance, so the PCB is made of Phenolic Resin has advantages of temperature-resistance, even if work so high temperature environmental it still maintain the integrity of its structure and dimensional stability.
Epoxy resin is referring to molecule contains two or more than two epoxide group of organic compounds. In addition, their relative molecular quality is not high. The molecular structure of the epoxy resin based on molecular chain containing lively epoxy groups for its characteristics, epoxy groups can be placed at the end of the chain and in the middle, or forming cyclic structure. Because it contains active epoxy group in the molecular structure, so that they react with the curing agent to form an insoluble polymer with a three-dimensional network structure. The PCB made by Epoxy resin has advantages of impact resistance, temperature-resistance, more stable than others.
As Polytetrafluorethylene,which known as “non-stick coating” or “easy to clean the material. This material has advantages of acid and alkali resistance, anti-organic solvent, almost insoluble in all solvents. As we all know the PCB can’t touch water, the PCB of Polytetrafluorethylene is also water-resistance. In addition, it has the advantages of high temperature-resistance,anti-corrosion as well, so it’s widely used in PCB industry.
Glass fiber cloth
Epoxy glass fiber cloth usually make epoxy or modified epoxy resin as a binder, and fiberglass cloth as a reinforcing material, the PCB made this material is the largest production, and the most widely used around the world. There are four models: include G10(non-flame retardant), FR-4(flame retardant), G11(non-flame retardant), FR-5(flame retardant). As a matter of fact, the non-flame retardant products have decreased year by year, while more and more circuit boards have adopted FR-4 as PCB substrates.
Composite base-type copperplate
The composite base-type copperplate mainly refers to a copperplate that the insulating substrate of surface layer and core layer is composed of two kinds of reinforced materials. CEM-1 and CEM-3 are the most common among the composite base-type copperplates. Also it can be punched, but also suitable for mechanical drilling. Some CEM in size accuracy and stability has been better than the general FR-4 products, now many countries often replace FR-4 substrate with CEM-1,CEM-3 to manufacture double-sided PCB, such as Japan, Europe and the United States and other countries.
In recent years, according to PCB expert that generally adopts glass fiber cloth as PCB substrate on multi-layer manufacturing, especially FR4-type substrate material. However, due to the reduce the cost and pursuit the development of manufacturing technology, the number of adopting composite substrate materials as multi-layer PCB material will be increased in the future.