Failure analysis of plastic encapsulated circuits after autoclaving

• Comprehensive analyses are conducted to investigate the effects of moisture on plastic encapsulated microcircuits.
• The relationship between moisture and performance degradation is studied in the work.
• SAM, SEM, and EDS are utilized to indentify the failure causes.
• Oxidation and the moisture invasion induced by interface crack are ascribed to the failures.

Considering that moisture is a crucial factor affecting Plastic Encapsulate Microcircuits (PEMs), several test methods, including Temperature Humidity Bias (THB), autoclaving, and Highly Accelerated Stress Test (HAST), were proposed to assess the moisture resistance capacity of PEMs. To investigate the impact of moisture on PEMs, one certain type of Metal-Oxide -Semiconductor Field Effect Transistor (MOSFET) was selected as a representative of PEMs and underwent an autoclaving in this paper. The results demonstrate that the influences of moisture are diverse. Then a series of analyses, including electrical testing, Scanning Acoustic Microscope (SAM), bond pull testing, metallurgical microscopy, surface and cross-sectional analysis by Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS), were conducted to determine the failure cause. With the analyses, the increase of static drain-to-source on resistance is ascribed to surface oxidation. Besides, the moisture invading from the crack along the die side is deemed to contribute to the leakage current failure and the function failure. Finally, some suggestions are proposed to protect PEMs against moisture.