Effect of Area Array Package Types on Assembly Reliability And Comments on IPC-9701A

Status of thermal cycle test results for a nonfunctional daisy-chained peripheral ceramic column grid array (CCGA) and its plastic ball grid array (PBGA) version, both having 560 I/Os, were presented in the last year conference. Test results included environmental data for three different thermal cycle regimes (-55/125°C, -55/100°C, and -50/75°C). The updated findings for these test vehicles with two different package types will be presented. In a recent reliability investigation a fully populated CCGA with 717 I/Os was also considered for assembly reliability evaluation. The functional package is a field programmable gate array that has much higher processing power than its previous version. This new package is smaller in dimension, has no interposer, and has a thinner column wrapped with copper for reliability improvement. This paper will also present thermal cycle test results for this package assembly and its plastic version with 728 I/Os, which were exposed to two different cycle regimes. The cycle profiles were those specified by IPC-9701A for tin-lead, i.e. -55 to 100°C and -55 to 125°C. Per IPC-9701A, test vehicles were built using daisy chain package and were continuously monitored. The effects of many process and assembly variables including corner staking, commonly used for improving resistance to mechanical loading such as drop and vibration loads, were also considered as part of the test matrix. Optical photomicrographs were taken at various thermal cycle intervals to document damage progress and behavior. Representative samples of these along with cross-sectional photomicrographs at higher magnification taken by scanning electron microscopy (SEM) to determine crack propagation and failure analyses for packages are also presented. Appendix A was added to provide back-up information for IPC-9701A and discuss the effects of key thermal cycle parameters and projection for lead-free versus lead-based solder joints.