Electro-thermo-mechanical design and electromigration analysis for Package-On-Package (POP)

A comprehensive integrated electro-thermo coupling model is developed to investigate the electro-thermo-mechanical effects and electromigration analysis on Package-on-Package (POP) in this paper. POP packaging involves in ultra thin gold wire (φ=1mil) on wirebonding and Sn4.0Ag0.6Cu (SAC405) solder ball on package. The current density arising in the aluminum pad (wirebonding) and in the Copper trace above SAC405 solder ball imply the hot spot where results in an electromigration along the current direction. Finite element predictions reveal the maximum electro-thermo-mechanical effective stress is located at the regions where electromigration potentially occurred. Reliability on electro-thermo-mechanical for wirebonding and SAC405 solder ball is evaluated. Current crowding, temperature distribution and electro-thermo induced effective stress distribution are predicted. A series of comprehensive parametric studies were conducted in this research.