Solder Ball Reliability Assessment of Wafer Level Chip Scale Package (WLCSP) Through Power Cycling

Abstract

Failure analysis and its effects are major reliability concerns in electronic packaging. More accurate fatigue life prediction can be obtained after the consideration of all affecting loads on the electronic devices. When an electronic device is turned OFF and then turned ON multiple times, it creates a loading condition called Power Cycling. The die is the main heat source causing non-uniform temperature distribution. The solder ball reliability assessment of wafer level chip scale package (WLCSP) is done through computational methods such as Finite element analysis. WLCSPs use wafer level package technology which is an extension of the Wafer Fab process, where the final device is a die with an array pattern of the solder interconnects.

In this paper, the reliability of solder balls is determined by subjecting the board to Power Cycling and estimating the stress and failures. The mismatch in Coefficient of Thermal Expansion (CTE) between components used in WLCSP and the non-uniform temperature distribution between them, leads to the deformation of the package. Analysis is done on different thicknesses of the board to study its effect on reliability.