An Innovative Rework Solution To Assembled IC Components
Authors: Mary Liu, Ph.D., and Wusheng Yin, Ph.D. and Mark J. Walz Company: YINCAE Advanced Materials, LLC and Training & Tooling Associates Date Published: 10/16/2011
Abstract: Reworking advanced IC components such as BGA, CSP, POP and small flip chip, is an extremely difficult and expensive process; but it is also a cost-saving process. Traditionally, capillary underfill has been used to enhance mechanical reliability of advanced IC components such as BGA, CSP, POP and WL-CSP. Although manufacturers claim these underfills are reworkable, large underfilled parts are still damaged due to the difficulty of the rework process. There remains a trade-off between reliability enhancement and reworkability caused by underfilling. YINCAE has developed a solder joint encapsulant, which not only enhances solder joint strength at least five times, but also retains excellent solder joint integrity. The implementation of SMT256 can improve the process yield, eliminating voids and cracks in solder joint, eliminating head-in-pillow issues for large components during the lead free reflow process. The results from thermal cycling tests indicated that the first failure cycles using SMT256 is as high as 6000 cycles, at least 4000 – 5000 cycles higher than other process. The most important innovation is that the reworkability of solder joint encapsulant is the same as for the solder. All details will be reviewed in our full paper.