Warpage Studies on Large BGA Site and Corner Bridging Mitigation Method
Authors: Steven Perng, Weidong Xie, Cherif Guirguis Company: Cisco Systems, Inc. Date Published: 9/28/2014
Abstract: During the process development of large BGAs, it is observed there are corner bridging formed in some cases, where both package and fab are within spec based on Thermal Moiré technology measurement. A test vehicle is designed to study the impact of PCB features, such as VIPPO design, on soldering dynamics and subsequent defects. The results show the VIPPO and non-VIPPO mixed design tends to have more corner bridging than all dog bone or all VIPPO design. Due to the limited sample size, more study is needed to have further understanding the impact of PCB features on the rigidness of PCB material during the SMT reflow process. Before a conclusive root cause and solution is found, the Corner Standoff Block (CSB) can be used as a corner bridging mitigation tool for 1.0mm pitch BGAs.