Effect of solder reflow temperature profile on plastic package delamination

Abstract

The major cause of IC package failure mechanisms such as delamination, cracking or popcorning is package saturation with moisture and subsequent exposure to high temperature during solder reflow. Different PCB reflow methods and temperature profiles are an important factor affecting this type of failure mechanism. A series of tests were carried out using three plastic packages, PBGA, TQFP and PQFP, as test vehicles in order to optimize the process conditions, material compatibility and reliability. Tests were carried out to assess the impact of different reflow methods and temperature profiles. The reflow methods tested were vapour phase reflow and convection reflow, and nine reflow temperature profiles were studied. The profile variations were ramp rate, preheat time, dwell time and peak temperature. The study also included JEDEC standard vapor phase and convection reflow temperature profiles. Package interfacial integrity was examined by SAM with C-SAM and THRU-scan/sup TM/ methods, after JEDEC moisture preconditioning, followed by delamination (popcorn) performance and compared for the influence of different reflow methods/temperature profiles. The results show that the severity of plastic package cracking and delamination can be highly dependent on solder reflow parameters. The dominant reflow factor is total heat energy applied to the package throughout the reflow time. The higher the temperature and the longer the dwell time, the more likely a package is to crack if the moisture level inside the package is nearly at, or above the critical level.