Long-Life Reliability of CSP Assemblies with and Without Underfill

ABSTRACT The test results for numerous chip scale package assembly performed under MicrotypeBGA Consortium led by the Jet Propulsion Laboratory have been published previously. The cycles-to-failure (CTF) under different thermal cycle conditions including −30 to 100°C revealed early failures of most assemblies, even a few with underfills. However, a few CSP configurations, with and without underfills, did not fail early in this temperature range. These assemblies were further thermal cycled to establish their long-life failure behavior. Thermal cycling for most test vehicles (TVs) was terminated at 3,000 cycles except for four assemblies that survived long environmental exposure. To accelerate failure even further, the underfilled assemblies were subjected to a broader temperature cycle in the range of −55 to 125°C. Additional failures were observe by 887 cycles utilizing this temperature range. Reliability test results to 3,887 combined cycles along with optical and SEM crosssectional micrographs were performed and are presented.