Failure analysis of solder bumped flip chip on low-cost substrates

Failure analyses of 63wt%Sn-37wt%Pb solder bumped flip chip assemblies with underfill encapsulant are presented in this study. Emphasis is placed on solder flowed-out, nonuniform underfill and voids, and delaminations. X-ray, scanning acoustic microscope, and tomographic acoustic micro-imaging techniques are used to analyze the failure samples. Also, cross sections are examined for a better understanding of the failure mechanisms. Furthermore, nonlinear, temperature-dependent, and fracture-mechanics finite element analyses are used to determine the effects of underfill-void sizes on the flip chip solder joint reliability.