Development of Novel Through Mold via in Package-on-Package Using Cu-Cored Solder Ball

摘要

Recently package-on-package (PoP) and fan-out wafer level packaging (FOWLP) had emerged as the dominant packaging approach in 3D integration. The key technology of PoP is vertical interconnection using through mold via (TMV) technology. In this study, we present a novel TMV process using a Cu-cored solder ball in PoP. We used a Cu-cored solder ball and molding of epoxy molding compound without using laser drilling and Cu electroplating process. TMV filling process using Cu-cored solder ball was successfully demonstrated for FOWLP package-on-package. There were no voids and defects in the Cu-cored solder-via structure. Numerical analysis was performed to investigate the warpage and stress distribution. Numerical analysis results indicated that the Cu-cored solder-via structure can provide higher thermal-mechanical reliability compared with the conventional Cu-filled TMV. The Cu-cored solder-via structure exhibited uniform and lower stress than the conventional TMV structure. The developed FOWLP PoP successfully passed the standard reliability tests such as the moisture sensitivity test, highly accelerated stress test, thermal cycling, and unbiased highly accelerated stress test. These results indicate that the Cu-cored solder-via structure can be a promising technology for simple, high-speed, low-cost, and highly reliable fabrication of PoP.