Study On The Processing Technique Of Epoxy Resin-Based Copper Clad Laminates For High Density Interconnection

Following the trend to further miniaturization, more functions, more intelligence of electronic and electrical equipments, High Density Interconnection (HDI) technology brings micro Via and fine lines into the manufacturing of Printed Circuits Boards (PCBs), and it will become the major technology for the future generation PCBs. HDI PCBs are usually manufactured by the method of building-up, which uses a double or four-layers key core as the base,and then builded-up conductive and insulating layer as outer layers in turn to ultimately achieve multilayer structure. Currently, FR-4 ultra-thin core of epoxy resin-based Copper Clad Laminates (CCLs) has been the main base material for HDI PCBs. The process of producing HDI PCBs is also a process for moulding boards at high temperature and pressure for many times. With increasing the build-up number, the moulding times increases, and thus the substrate of CCLs should have better heat-resistance and thermal stability.FR-4 type CCLs, which immersing the electronic grade glass fabric in the varnish of flame retardant epoxy resin, one side or both sides covered with copper foil, is one of plate material moulded by hot-press. Dicyandiamide (DICY) is usually used as the latent curing agent for epoxy resin, howevere, with the coming of the Lead-free era and widespread using of HDI technology, the heat resistance and thermal stability of the traditional DICY-Curing system can not meet the requirements for soldering of lead-free and multiple laminating. Therefore, using the phenolic novolac resin (PN) which contains more phenyl and thus higher heat resistance as the curing agent is becoming the mainstream.In this thesis, the mode of laminating cycles is used as a simulation of the process for fabricating HDI PCBs, two typical CCLs based on PN-Curing and DICY-Curing epoxy systems were prepared, respectively, and then the dependence of integrated performance (including electrical and mechanical properties, heat and moisture resistance) on the number of laminating cycles were comparatively studied. By analyzing the influence of the structure and composition of the resin system on the heat stability of cured resins, a conlusion has been drawn that the PN-Curing system consisting in fillers is the suitable system for fabricating high-grade HDI PCBs which meeting the lead-free requirements.To further understand the processing of the PN-Curing (filler) system, the curing behavior and rheological properties of PN-Curing and DICY-Curing epoxy systems were investigated comparatively, the curing kinetics were calculated, and the dynamic rheological models were achived. In addition, the influence of fillers on the rheological properties was also studied, and then the processing parameters for fabricating laminates were optimized.