Thermal stress/strain analysis of ceramic quad flat pack packages and interconnections

An elastoplastic analysis of the thermal stresses and strains in a surface-mount fine-pitch assembly using a 3-D nonlinear finite-element method is presented. This fine-pitch component is the EIAJ (Electronic Industry Associates of Japan) 160-pin ceramic quad flat pack (CQFP). For comparison purposes, the EIAJ 160-pin plastic quad flat pack (PQFP) was also analyzed. Detailed stress and strain distributions and whole-field displacements of the lead frame and solder joint are provided for a better understanding of their mechanical behavior during thermal cycling. It was found that the stresses and strains in the CQFP solder joint are larger than those in the PQFP. The results presented should be useful in the design for reliability of this class of surface-mount assemblies.<>