Package Integrity and Reliability Effects of Mold Compound Chemistry for Power Device Application

Mold compound material plays an important role in the quality improvement and reliability performance of Power SO-8 packages. Different chemistries of epoxy-based mold compounds were successfully evaluated through material analysis, assembly performance, package delamination performance, and reliability performance. Material analysis through material characterizations, stress index calculation, and die stress simulation suggested that EMC-B has the lowest risk of package delamination and solder joint degradation due to its low stress properties. Package delamination and solder joint degradation performance proved that low stress mold compounds resulted to better mold adhesion and solder joint integrity than high stress mold compounds. EMC-B having the lowest stress induced on the die resulted to no delamination after assembly, minor delamination after thermal stress cycle and lowest solder joint degradation after thermal stress cycle. Rdson and dVsd performance after thermal stress cycle verified that solder joint degradation affects the thermal and electrical performance of the package. Overall, Power SO-8 package built using EMC-B resulted to good mold-to-die and mold-toclip adhesion, high solder joint integrity and stable thermal and electrical performance after thermal stress cycle.