Board-Level Drop Reliability Analysis for Fine-Pitch BGA Packages in Automotive Applications

As the demand of automotive application grown-up rapidly, electronic packages are required zero defect after manufacturing and ultra-high performance from package level to board-level reliability tests. Since automotive packages operate in dramatic temperature ranges, solder joint combination is recommended chosen high Ag lead-free solder alloy to greatly enhance the fatigue life of the board-level temperature cyclic test (TCT) performance. However, high Ag lead-free solder alloy will lower reliability of drop performance. Solder alloy selection is a key issue and trade-off for automotive application. The board-level drop reliability performance is now facing the big challenge. In this work, we would like to focus on board-level drop performance enhancement. The common package type, fine-pitch ball grid array (BGA) is widely used as automotive component. The body size of test vehicle is selected in $\mathbf{20} \times \mathbf{20}\ \mathbf{mm}^{\mathbf{2}}$ . Both experiment and numerical model were investigated to analyze board-level drop reliability of the package. The board-level drop experiment was followed JEDEC JESD22-B111A with impact profile 1500 G & 0.5 ms. A three-dimension finite element method (FEM) was used to evaluate the stress level comparison and comes out design guideline under drop test. The real-time strain response on test board between experiment and modeling are well-correlated by attaching strain gage nearby package corner. The preliminary result shows that the maximum stress and solder joint failure location are the consistent with experimental data. The influence on solder joint stress by different underfill material property, dispensing area and ball layout will be also considered into this study. Full array pattern of solder balls, high modulus underfill, and thinner package z-height can be beneficial in reducing solder joint stress.