Comparative study of PWB pad cratering subject to reflow soldering and thermal impact

Pad cratering is one of the dominant failure modes that occur in various board level reliability tests, especially under the dynamic loading. In recent years, the increasing propensity of pad cratering due to the implementation of the lead-free technology calls for the necessity of re-assessment of PWB qualification related to the pad cratering resistance. The objective of the present study is to establish a test method for evaluating the pad cratering resistance of PWB and studying the PWB degradation mechanism subject to different high temperature conditions. Three kinds of PWB with different resin systems were investigated, including one phenolic-cured system board and two dicy-cured system boards. Tg and Td of the selected PWBs were characterized using TMA and TGA. The detailed cold ball pull test procedure is presented and different pull jaws with/without standoff are evaluated in this paper. The effects of multiple reflows, thermal aging and temperature cycling on the pad cratering resistance of PWBs are discussed as well.