Study on Failure Mechanism of PCT Reliability for BT Substrate Based CSP (Chip Scale Package)

In this paper, the study on failure mechanism of moisture sensitivity reliability is reported. It focuses on the PCT conditions which are 121°C, 2atm, 100RH%, and 168 hr. The general failure mode is delamination on the interface between die attach material and die backside. Interestingly, the delamination exists as a gap of 20∼40 μm. In addition, the paper discusses the relative materials influences — for example, the moisture uptake of mold compound systems and die backside surface property effects. The degradation of the die attach material was analyzed by Dynamic Mechanic Analysis (DMA). The delamination surfaces are analyzed by Scanning Electron Microscope (SEM), and Optical Microscope (OM). Furthermore, Scanning Acoustic Tomograph (SAT) through scanning results reveals that the mold compound formula affects the amount of moisture uptake, which obviously would affect the PCT reliability.