Reliability Impact of Assembly Materials for Micro-BGA Components in High Reliability Applications

Electronics manufacturers of high-reliability and harsh environment equipment rely increasingly on the adoption of electronics packages from the commercial market supply chain. Chip Scale Packages (CSP) such as micro-ball grid arrays (μBGAs) provide a range of IC functions available in the format of very small size package architectures and increasingly at lower cost. To meet the stringent reliability requirements posed by such applications, stress-reducing designs, and assembly materials for μBGAs must be developed and optimised. This paper details the results from reliability tests assessing the fatigue life of μBGA solder joints for several package-board assembly configurations. Assemblies based on rigid and compliant printed circuit boards (PCBs) are discussed as well as the impact of edgebond and underfill materials on the solder joint reliability. A physics-of-failure modelling approach for assessing the reliability performance of the μBGA assemblies is developed and demonstrated. Results from the thermo-mechanical simulations were validated and the models were used to predict and explain the solder joints' physics-of-failure. The use of the modelling and experimental data for development of μBGA lifetime model is also presented and discussed.