The technical content of realizing the performance requirements of the epoxy resin used in the thinning of CCL is relatively high. The CCL thinning technology is mainly to solve the outstanding problems of improving the rigidity of the PCB board (facilitating process operability, ensuring mechanical strength, etc.) and reducing warpage deformation. In the process of thinning CCL, in addition to the prepreg processing technology needs to be In addition to improvement and innovation, resin composition and reinforcement technology are also critical aspects. There are three main technical approaches for CCL to achieve thinning: one is to improve the hardness of glass fiber cloth, such as using S glass fiber cloth and H glass fiber cloth (JP 2001-329080), but this technical line of replacing glass fiber reinforced materials, will cause the increase of CCL manufacturing costs. The second is to add high rigidity fillers in the resin composition. However, in such a process route, the produced substrate has the problems of large wear on the drill bit, reduced hole positioning accuracy, and large hole wall roughness during drilling processing. The third is to modify the epoxy resin to improve the rigidity of the cured CCL resin composition, which is an important means to solve the low mechanical strength of thin CCL.
In the development of thin CCL, the main function of the epoxy resin used is reflected in three aspects. The first is that the modification of epoxy resin improves the rigidity of the substrate, that is, the improvement of the elastic modulus of CCL. In the second half of 2005, Matsushita Electric Co., Ltd. began to market only 40um thick non-halogenated high Tg epoxy-glass fiber cloth-based CCL (brand R-1515B). Due to the innovation of modifying the epoxy resin in the resin composition of this extremely thin CCL, the key performance item of this thin plate-the flexural modulus value is 1.3 times higher than that of the general FR-4 type CCL, especially It is 3 times higher than the general FR-4 CCL at 250°C. Due to this feature, the warpage and deformation of the substrate during the secondary high temperature reflow soldering process are significantly reduced.
Secondly, the insulation reliability of thin CCL is more important. Therefore, the epoxy resin and phenolic resin (as a curing agent) are required to have higher dielectric properties and better moisture resistance. In recent years, the invention patents of many epoxy resin manufacturers in Japan have increased in this regard. It is mainly manifested in: improving the dielectric properties and moisture resistance of epoxy resin compositions; reducing the content of inorganic chlorine and organic chlorine in epoxy resins; in order to improve the dielectric properties of epoxy resin cured products, improve the performance of phenolic resin curing agents, reduce its phenolic hydroxyl content. Another use of epoxy resin in the thinning of CCL is: the prepreg processing of thinned CCL is an important problem to be solved in the production process, and the thinned CCL resin needs to be improved in a number of properties. There are many kinds of resins that are responsible for improving different performance tasks, and need good blending and fusion. In this way, both the epoxy resin and the curing agent resin in the epoxy resin composition need to improve its compatibility and storage stability. In recent years, some epoxy resin manufacturers in Japan have published more patent results in their research here, such as Dai Nippon Ink’s paper on how to solve the problem of poor compatibility with phenolic epoxy resins, and Mitsui Chemicals’ paper on improving environmental protection. The compatibility between the oxygen resin and the phenolic resin curing agent, the problem of improving the storage stability of the resin composition, etc.
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