Cracking analysis of plastic IC package in consideration of viscoelasticity

The purposes of the paper are to consider the failure phenomenon by delamin ation and crack when the encapsulant of plastic IC package under hygrotherm al loading in the IR soldering process is on viscoelastic behavior and to p resent the optimum design using fracture mechanics. The model for analysis is the plastic SOJ package with a dimpled diepad. The package model with th e perfect delamination between chip and diepad is chosen to estimate the re sistance to fracture by calculating C(t)-integrals with the change of the d esign under hygrothermal loading. The optimum design to depress the delamin ation and crack growth in the plastic IC package is presented.