Partial Underfill Impact Study on Solder Joint Reliability in Smartphone Application

As 5G mobile products become ubiquitous, mobile memory and storage performance must also scale to keep up with fast data download speeds. Along with mobile technology towards multifunction, design-for-reliability for mobile becomes challenging and essential. Among of reliability issues, the solder joint reliability of electronic package plays a more important role than before. This study focuses on temperature cycling (TC) solder joint reliability (SJR) performance of Universal Flash Storage (UFS) 3.1 fine pitch BGA (FBGA) package which enables faster read and write performance. Numerical studies were conducted by using the finite element analysis (FEA) technique to investigate the impact of partial underfill on SJR performance. Firstly, three patterns with no-underfill, partial underfill and full underfill are investigated in this study. Secondly, involved the thermal reliability performance of three different types of reworkable and non-reworkable underfill to compare CTE and Tg effect. This paper uncovered the reworkable underfill with high CTE may contribute negatively to thermal cycling SJR reliability. Reworkable underfill with high CTE aims to achieve excellent drop test performance with low manufacture cost. This trade-off may increase potential SJR failure risk under temperature cycling condition.