Cracking analysis of plastic IC package in consideration of viscoelasticity

The purpose of this paper is to consider failure phenomena by delamination and cracking when an encapsulant for plastic IC packaging under hygrothermal loading in the IR soldering process is on viscoelastic behavior and to present the optimum design using fracture mechanics. The model for analysis is the plastic SOJ (small outline J-lead) package with a dimpled diepad. A package model with perfect delamination between chip and diepad is chosen to estimate the fracture resistance by calculating C(t)-integrals with the change of the design under hygrothermal loading. The optimum design to depress delamination and crack growth in the plastic IC package is presented.