Nonlinear analysis of plastic ball grid array solder joints

A nonlinear finite element analysis was carried out to investigate the visc oplastic deformation of solder joints in a ball grid array (BGA) package un der temperature cycling. The effects of constraint on printed circuit board (PCB) and stiffness of substrate on the deformation behavior of the solder joints were also studied. A relative damage stress was adopted to analyze the potential failure sites in the solder joints. The results indicated tha t high inelastic strain and strain energy density were developed in the joi nts close to the package center. On the other hand, high constraint and hig h relative damage stress were associated with the joint closest to the edge of the silicon chip which was regarded as the most susceptible failure sit e if cavitation instability is the dominant failure mechanism. Increasing t he external constraint on PCB causes a slight increase in stress triaxialit y (sigma (m)/sigma (eq)) and relative damage stress in the joint closest to the edge of the silicon die. The relative damage stress is not sensitive t o the Young's modulus of the substrate. (C) 2001 Kluwer Academic Publishers .