Thermo-mechanical deformation of underfilled flip-chip packaging

Abstract

An experimental technique of in-situ moire interferometry has been applied to investigate the thermo-mechanical deformations induced by to thermal loading in an underfilled flip-chip-on-board packaging. Thermo-mechanical deformations and shear strains generated from CTE mismatch are determined experimentally as a function of thermal loading. Semi-quantitative agreement is established between measured and FEA-simulated deformations. The results show that moire interferometry with in-situ thermal loading capabilities is effective for experimental studies of electronic packaging. Through this study, the role of underfill in reducing shear strains over solder bumps and thus in improving solder shear fatigue reliability is clarified. A methodology is demonstrated to differentiate effects of underfill properties on packaging thermo-mechanical performance.