The Development Of Halogen-Free No Flow Prepreg For Rigid-Flex PCB

Rigid-flex printed circuit board(Rigid-flex PCB)refers to the PCB by using flexible copper clad laminate(CCL)and rigid CCL to interconnect in different regions.Rigid-flex PCB not only has supporting function provided by rigid CCL,but also can be bent because of flexible CCL,which can meet the requirement of three-dimensional package.Therefore it is one important way to realize miniaturization of electronic and electrical equipment.With the improvement of flexible CCL and rigid CCL performance,the rigid-flex PCB raises much higher assembling requirement to the adhesive layer material.As traditional adhesive layer material bonding sheet can't meet it,the modified semi-finished CCL,that is E-glass fiber cloth enhanced no flow prepreg with superior and cost-effective performance begins to replace it used as the adhesive material of rigid-flex PCB.In this thesis the halogen-free CCL system is studied composed of mainstream phosphorus modified epoxy resin,the composite curing system with dicyandiamide(Dicy),diaminodiphenylsulfone(DDS)and phenolicnovolac resin(PN),phosphorus flame retardant and inorganic filler.In the experiment,the effect of structural phosphorous epoxy,the curing agentproportionin the composite curing system,the type of phosphorous flame retardant and the type of inorganic filler such as silica and aluminiumhydroxide on the process and performance of prepreg are investigated.The results show that the epoxy resin has an important effect on the CCL curing performance,the best reaction ratio of curing agent to epoxy differs from the type of curing agent,the inorganic filler improves much more in CCL performance than the manufacture process,and phosphorus flame retardant should be chosen according to the component proportion of the system.The composition of halogen-free no flow prepreg can be fixed therefore.Simultaneously,the application of carboxyl-terminated butadiene-acrylonitrile rubber(CTBN),phenoxy resin and bisphenolA(BPA)in the halogen-free CCL based on epoxy resin is also studied.The influence on the production process and the improvement of properties of cured products is mainly discussed with the conclusion that the phenoxy resin and BPA can decrease the resin fluidity during curing process dramatically.Moreover,the phenoxy resin,BPA and CTBN can significantly improve the resin toughness with decreasing Tg.In conclusion,the cost-effective halogen-free no flow prepreg with high-performance has been successfully developedand passed the application verification of mass-produced rigid-flex PCB,showing that it can completely meet the requirements.