Modeling with structure of resins in electonic compornents

In recent years, interfacial fracture becomes one of the most important problems in the assessment of reliability of electronics packaging. Especially, underfill resin is used with solder joints in flip chip packaging for preventing the thermal fatigue fracture in solder joints. In general, the interfacial strength has been evaluated on the basis of interfacial fracture mechanics concept. However, as the size of devices decrease, it is difficult to evaluate the interfacial strength quantitatively. Most of researches in the interfacial fracture were conducted on the basis of the assumption of the perfectly bonding condition though the interface has the micro-scale structure and the bonding is often imperfect. In this study, the mechanical model of the interfacial structure of resin in electronic components was proposed. Bimaterial model with the imperfect bonding condition was examined by using a finite element analysis (FEA). Stress field in the vicinity of interface depends on the interfacial structure with the imperfect bonding. In the front of interfacial crack tip, the behavior of process zone is affected by interfacial structure. However, the instability of fracture for macroscopic crack which means the fracture toughness is governed by the stress intensity factor based on the fracture mechanics concept.