FR-4 is made by laminating copper foil and glass fiber cloth impregnated with flame-retardant epoxy resin, while CEM-3 is different from FR-4 in that it uses a composite substrate of glass cloth and glass felt, also called composite substrate, instead of pure glass cloth.
The production process of CEM-3 is similar to that of FR-4. Glass felt can be glued vertically or horizontally, and the epoxy resin system used is the same as FR-4. In order to improve the performance, it can be modified, and usually a certain amount of filler needs to be added. The pressing pressure is generally half lower than that of FR-4. In order to meet different thickness requirements, glass mats with different standard weights can be used, such as 50g, 75g, 105g.
Second, the performance of CEM-3
In order to replace FR-4, CEM-3 must meet all kinds of performance of FR-4. At present, CEM-3 has overcome the defects of poor metallization quality, warpage and poor dimensional stability of early CEM-3 products by improving resin system, glass felt and lamination manufacturing process. The glass transition temperature, immersion welding resistance, peeling strength, water absorption, electrical breakdown, insulation resistance and UL index of CEM-3 all meet the FR-4 standard, but the difference is that the bending strength of CEM-3 is low.
In FR-4, the thermal expansion is greater than FR-4.
CEM-3 has no problem in machining metallized holes, with low bit wear rate, easy punching and high accuracy in thickness and size, but the metallized appearance of punched holes is slightly worse. Third, the market application of CEM-3
UL thinks that CEM-3 and FR-4 can be interchanged, so the double panel using FR-4 can generally be used as the replacement object. Because the performance of CEM-3 is similar to that of FR-4, it is possible to replace it on the multilayer board.
Due to the fierce price competition of printed circuit boards, CEM-3 is also considered in the four-layer board market. But for thin plates (
The printed circuit board made of CEM-3 has been used in fax machines, copiers, instruments, telephones, automotive electronics, household appliances and other products.
The earliest manufacturer in China to develop and produce CEM-3 is Shenzhen Pacific Thermal Insulation Material Co., Ltd. The CEM-3 produced by this company is usually cheaper than FR-4 10~ 15%, and the product quality meets the international NEMA and IPC standards.
In recent years, other domestic copper clad laminate factories have also begun to develop or mass-produce this new composite substrate.
Fourthly, further improvement and development of CEM-3 substrate.
In order to further adapt to the SMT assembly of electronic products and develop in the direction of light weight, thinness, miniaturization and multifunction, CEM-3-based materials need to be further improved and perfected in the future, mainly from the following four aspects:
Optimization of 1. filler. The crystal form, viscosity, amount and dosage of crystal water of filler will affect the immersion welding resistance, dimensional stability, reliability and transparency of hole metallization of molded substrate.
2. Improvement of resin system. The adoption of novolak resin can improve the high frequency characteristics, machinability and reliability of hole metallization of the substrate.
3. The improvement of non-woven glass felt and the surface treatment of glass fiber are beneficial to improve the insulation resistance under wet conditions.
4. The ratio of glass fiber length can improve the dimensional stability.
With the continuous improvement of the performance of CEM-3 substrate, its application in the world is becoming more and more popular. In recent years, in addition to Japan, the production and application of CEM-3 have also developed rapidly in South Korea and Taiwan Province Province of China, with the growth rate much higher than that of FR-4. It is believed that this new composite substrate will achieve greater development in the next century.
Domestic electronic product designers are not familiar with CEM-3 products, mainly because there are few manufacturers and insufficient publicity, so electronic products using CEM-3 printed circuit boards are not common. With Japanese, Korean, Hongkong and Taiwan Province investing in Chinese mainland, it is believed that the production and application of CEM-3 in China will be promoted in the next few years.