Reliability of CCGA and PBGA Assemblies

摘要

Area Array Packages (AAPs) with 1.27 mm pitch have been the packages of choice for commercial applications; they are now starting to be implemented for use in military and aerospace applications. Thermal cycling characteristics of plastic ball grid array (PBGA) and chip scale package (CSP) assemblies, because of their wide usage for commercial applications, have been extensively reported on in literature. Thermal cycling represents the on-off environmental condition for most electronic products and therefore is a key factor that defines reliability. However, very limited data is available for thermal cycling behavior of ceramic packages commonly used for the aerospace applications. Thermal cycles and vibration test results for ceramic ball grid array (CBGA) with 361 and 625 I/Os were reported previously by this author and the trends for cycles-to-failures for four different temperature ranges were established. This paper presents thermal cycle test results for a ceramic column grid array (CCGA) and its PBGA version, both having 560 I/Os, exposed to two different thermal cycle regimes. One of the thermal cycles was that specified by IPC 9701, i.e. -55 to 125°C; the other was in the range of-50 to 75°C representing the qualification for the specific mission. Per IPC 9701, test vehicles were built using daisy chain package and were continuously monitored. The effects of many processing 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 DOE test matrix. Optical photomicrographs were taken at various thermal cycle intervals to document damage progress and behavior. A 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 with and without corner staking are also presented.