Interfacial fracture toughness for delamination growth prediction in a novel peripheral away package

The objective of this study is to predict interfacial delamination propagat ion that may inhibit the performance of a novel surface mountable, high inp ut/output (I/O) electronic package. Incorporation of such predictions in th e design phase of the package can lead to judicial selection of materials a nd geometric parameters such that the interfacial delamination based failur es can be avoided. This, in turn, leads to significant cost savings and sho rter time-to-market due to the shortening of the prototyping and qualificat ion testing phases. The focus of the present study is the prediction of pot ential delaminations at the encapsulant-backplate interface in a very small peripheral array (VSPA) package during manufacturing. The delamination gro wth prediction is based on the comparison of interfacial fracture parameter s obtained from the numerical simulations to appropriate critical values de termined experimentally using controlled fracture toughness tests. In this paper, the fracture toughness of the encapsulant/backplate interfac e is characterized using a fracture toughness test that requires simple tes t specimen, fixture and loading geometries, The critical interfacial fractu re toughness and the fracture mode mixity are determined using closed-form and finite element analyzes of the test specimen geometries, taking into co nsideration the effects of thermo-mechanical residual stresses resulting fr om the test specimen fabrication process. Furthermore, an experimental char acterization of the encapsulant material is also conducted in order to asse ss the effects of its time- and temperature-dependent thermomechanical resp onse on the fracture toughness of the encapsulant-backplate interface.