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|Evaluation of Process Indicators in High-Reliability Microelectronic Package Failure Analysis|
|Keywords: Failure Analysis, Hermetic , Process Indicator|
|Root cause investigations in High-Reliability microelectronic package assembly operations can benefit from the use of modern computational modeling to efficiently evaluate potential failure modes. This paper describes the investigation of a hermeticity failure in High-Reliability ceramic quad flat packages (CQFPs). Non-contact laser profilometry was employed to measure apparent package lid deflection following constant acceleration testing. Although the lid deflection had no direct correlation to the root cause, it provided a valuable process indicator that uncovered a non-conformance in the lid seal constant acceleration test. The computational model verified that the non-conforming test was the root-cause of the brittle failure that then led to a loss of package hermeticity. The modeling approach first utilized a static finite element (FE) approach to quantify stresses at the heel and toe of the lid seal solder fillet after various steps in the assembly and testing regiment. A metric was established that correlated those stresses to crack initiation. Then, a quasi-dynamic modeling technique was used to establish limits on the likelihood of crack propagation in the ceramic frame and failure of the seal. The modeling predictions confirmed the acceleration test and, specifically, the fixture set-up, as the root cause. Current efforts are focused on completing the experimental validation of the model prediction.|
|Jeremy Palmer, Principal Member Technical Staff
Sandia National Laboratories