Numerical stress analysis of resin cracking in LSI plastic packages under temperature cyclic loading

Numerical stress analysis of resin cracking occurring in plastic packages during temperature cyclic loading was carried out using a thermoelastic finite-element method (FEM) for the nonlinear contact problem. Through the use of the linear fracture mechanics approach to the bimaterial problem, the analysis provides a fracture parameter and indicates the direction in which resin cracking occurs. Temperature cycling tests using actual plastic packages were also performed to verify the validity of the analysis results experimentally. It was found that the test results agreed well with the analytical results. It was also clear that the delamination occurring between dissimilar materials determines the degree to which resin cracking occurs quantitatively and the most harmful delamination occurs in the die bonding layer. The resin cracking mechanism was studied and a countermeasure against it was proposed.