Thermal strain analysis for flip chip packaging

摘要

To have better understanding of the effects of using different epoxies as the encapsulation and/or underfill epoxies on the fatigue life of flip chip packages, finite element analysis was conducted. The finite element analysis software, ANSYS, was used to model flip chip packages with and without underfill and encapsulation and to run thermal testing simulations. The results revealed that the package with the longest fatigue life was the one with the underfill epoxy only. Packages with both underfill and encapsulation epoxies had shorter fatigue life, while packages with the encapsulation epoxy only had the shortest fatigue life. The use of the underfill epoxy with higher Young's Modulus and lower viscosity and CTE reduces the thermal shear stress experienced by the solder joint, thus lengthening its fatigue life.