Pad Cratering: Reliability of Assembly Level and Joint Level

摘要

The emergence of pad cratering has become an increasingly common failure mode for electronics manufacturing due to the transition to lead –free soldering. This phenomenon has become one of the first concerns between manufacturers of electronic equipment devices and other high reliability products who have focused on the failure in testing, handling or transport due to a single overload. Moreover, the number of manufacturers of servers and other electronic products report an early failure by pad cratering in thermal cycling, an occurrence practically unnoticed for SnPb soldered assemblies. There are many factors that affect pad robustness, including but not limited to design (pad size, solder mask, connecting trace, vias), stackup (resin content, glass style), resin material (filler, cure type). Preconditioning also has a significant effect on the long term reliability.The aim of the present study is to evaluate several laminate materials with respect to pad pull strength, using accepted industry testing methods. Several different design variables, such as resin filler, resin content, fiber glass reinforcement and fabrication process, were studied. Data are presented to show the effects of the above, and to highlight the long term risk associated with latent damage mechanisms.