Investigation on thermal cycling life prediction of PBGA microprocessor components with wavy patterned interface layer

Abstract

In modern electronic packaging industries, plastic ball grid array (PBGA) has been widely used as the microprocessor components. Upon thermal cycling due to the generation of thermal stresses, the PBGA package may undergo fatigue failure in the solder balls and thus it became a matter of interest for researchers to model the PBGA package to calculate its thermal cycling life. This study aims in 3D finite element modeling of the slice model of a PBGA package to calculate the accumulated plastic dissipation energy per cycle in the solder joint, which is often considered as an indication of damage accumulation in the solder joint of the PBGA package. The thermal cycling simulation is performed between-40 to 125 o C and the associated life to failure is predicted using obtained finite element results and life prediction theory. As researchers have already showed, the failure of the solder joint usually starts at the corner of the solder-copper interface layer and then it propagates along the interface or through the body of the solder depending on the mechanical properties and shape of the solder ball. Traditionally, a flat interface layer is always maintained in the manufacturing of the PBGA packages. For the first time, this research focuses on the effects of the interface geometry on the damage accumulation in the critical solder joint hence the life for crack initiation as well as crack propagation of the package. Instead of a flat circular solder-copper interface layer, a wavy patterned interface layer is considered in the simulation. Finite element analysis results show that thermal life and crack propagation in the solder ball greatly depends on the geometry of the solder joints. The volume averaged plastic energy dissipation accumulated per cycle is reduced when a wavy patterned interface layer is considered which may be due to the fact that more surfaces come in contact with each other reducing stress and therefore the no. of cycles before failure increased in case of wavy patterned interface layer.