CEM-3：Characteristics and Use
CEM-3 is a composite copper-clad laminate, which is improved from FR-4. The fabric and core of the substrate used in the composite substrate printed board are composed of different reinforcing materials. The mechanical properties and manufacturing cost of composite copper-clad laminate are between those of
paper-based copper-clad laminate and epoxy glass fiber cloth copper-clad laminate. The copper-clad laminate substrate used for a composite matrix is mainly CEM (Composite Epoxy Material) series, among which CEM-1 and CEM-3 are the most representative. In structure, CEM-3 is made of glass felt (also known as non-woven fabric) impregnated with epoxy resin, then bonded with glass fiber cloth on both sides, then compounded with copper foil, and hot-pressed. The difference between FR-4 and FR-4 is that most glass fiber cloth is replaced by glass felt, which increases the degree of “shearing” in terms of mechanical properties. Generally, CEM-3 is directly made into the double-sided copper-clad plate. During drilling, the processing convenience of the CEM-3 plate is higher than that of FR-4. The reason is that the glass felt is looser in structure than glass fiber, and it is also superior to FR-4 in punching processing.
- The production process of CEM-3
CEM-3 is a new type of printed circuit board material based on FR-4. In recent years, Japan has used CEM-3 extensively to replace FR-4, even exceeding the amount of FR-4. CEM-3 is used in about 55% of double panels. The CEM-3 process is similar to that of FR-4. The glass felt can be glued either vertically or horizontally, using the same epoxy resin system as FR-4. The glass transition temperature, immersion resistance, stripping strength, water absorption, electrical breakdown, insulation resistance, and UL index of CEM-3 can meet the FR-4 standard, but the difference is that the bending strength of CEM-3 is low. CEM-3 metalized hole processing is not a problem, the drilling bit wear rate is low, it is easy to punch and stamp forming, and thickness size accuracy is high, but the metalized appearance of the punch is slightly poor.
- The characteristics of CEM-3
(1) Cost is lower than FR-4;
(2) CEM-3 is thinner and less accurate than FR4;
(3) After PCB welding, the degree of distortion is also higher than that of FR-4.
(4) CEM-3 has the same performance and working conditions as FR-4, but it has good machinability.
(5) The bending strength of CEM-3 is lower than that of FR-4, and the thermal expansion is greater than
that of FR-4;
(6) It is also better than some FR-4 products in terms of anti-leakage mark (CTI), size accuracy and
size stability of plates.
- The use of CEM-3
Shenzhen Pacific Insulation Material Co.is the first one to develop, research and produce the CEM-3 in China, Ltd. The CEM-3 produced by the company is usually 10-15% cheaper than FR-4, and the product quality meets international NEMA and IPC standards. There is a view that CEM-3 and FR-4 can be interchanged, so the double panel with FR-4 can generally be used as the replacement object. Since CEM-3 and FR-4 have similar performance, it is possible to substitute them on multilayered boards. Due to the fierce price competition of printed circuit boards, the four-layer board market has also begun to consider the choice of CEM-3. However, for sheets (<0.8mm), there is no price advantage. At present, the printed circuit board made of CEM-3 is now used in faxes, copiers, instruments, telephones, automotive electronics, home appliances, and other products. To better adapt to the development of the market, CEM-3 is likely to move towards lighter, thinner, more functional, and Technological Development in the future. The future application prospects of CEM-3 are bright. CEM-3 material and CEM-3 base-plate.