To enables new functionality in the shortest time-to-market by stacking packages and KGD, Package-in-Package (PiP) structure has extend its application in Baseband/ASIC/Graphics processor integration, Portable electronics and power module etc. However, existed issues such as mold void due to narrow gap between packaged components will directly impact reliability of PiP products. This paper focuses on the failure analysis of a power module which was developed by PiP. The specific PiP module failed in the electrical test after MSL3 (Moisture Sensitivity Level 3) test. C-SAM and X-Ray inspection had been performed to identify defect location of the package. Destructive test was then applied for failure confirmation. Failure mechanism was setup and verified based on findings from failure analysis and mold flow simulation. Design optimization had been pursued and verified, samples built after modification all passed the MSL3 test with improved reliability performance.
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