Reliability and new failure modes of encapsulated flip chip on board under thermal shock testing

Abstract

The thermomechanical reliability of flip chip on board (FCOB) assembly under thermal shock test is addressed in this paper by investigation of different material/process combinations (underfill, flux, reflow atmospheres). It is verified that solder fatigue is the dominate failure mechanism and delamination has obvious adverse effect on the solder joint lifetime. Periodic solder joint crack is first reported in this study and is determined to be related to glass fiber distribution in the PCB.