Product Level Design Optimization for 2.5D Package Pad Cratering Reliability During Drop Impact

The conversion from using tin-lead solder joint to lead-free solder joint has raised many pad cratering failures for electronics manufacturing. This phenomenon has become more severe to the 2.5D package which has a large heatsink attached on the top. The pad cratering issue has been found during testing, handling or transport due to a single overload. The package qualification process requires that it passes the board level drop test before shipping, however, this doesn't always guarantee that the package will survive from product level drop, especially for a complicated design product. Many types of research have been conducted to improve the package's board-level pad cratering reliability, few emphases were put on the product design. The aim of the present study is to evaluate several product design parameters with respect to PCB stress, using numerical methods. Several different design variables, such as reinforcement structure, heatsink size, pad design, were studied. Data are presented to show the effects of the above factors and to highlight the main factor to cause the pad cratering failure.