Thermal cycle reliability and failure mechanisms of CCGA and PBGA assemblies with and without corner staking

Abstract

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. For high reliability applications, numerous area array packages are available with the same design pattern both in ceramic and plastic packages. This paper compares assembly reliability of ceramic and plastic package with the same I/O and pattern. The ceramic package was in the form of CCGA with 560 I/Os peripheral array with the same pad design as its plastic counterpart. The effects of the following key parameters on reliability of both CCGA and PBGA assemblies were investigated. Thermal cycle ranges, -50/75/spl deg/C, -55/100/spl deg/C, and -55/125/spl deg/C; corner staking on failure mechanisms for two thermal cycle profiles, -55/125/spl deg/C and -50/75/spl deg/C; and package interchangeability, i.e. using PBGA package on CGA pad design with a larger pad; heat sink attachment on the top of package. Packages were assembled on polyimide board and their daisy chains were continuously monitored. Optical photomicrographs were taken at various thermal cycle intervals to document damage progress and behavior. Representative samples along with their cross-sectional photomicrographs at higher magnification, taken by scanning electron microscopy (SEM), are also presented. These were used to determine crack propagation and failure analyses for packages with and without corner staking.