Potential Failure Mechanisms in Overlaid High Density Interconnects
R. Agarwal, M. Pecht, X. Shan, and J. Evans
Potential failure mechanisms in high density interconnects (HDI) due to mismatches in coefficients of thermal expansion and mismatches in coefficients of hygroscopic expansion are investigated. A section of an HDI package is modeled and analyzed for change in ambient relative humidity from 30% to 90% and temperature distribution during operation characterized by a junction temperature of 73ºC. The analyses reveal that the hygro-mechanical stresses are more detrimental than the thermo-mechanical tresses to the metallization/polyimide interfaces. However, in both cases, the polyimide films are under compressive stresses. These stresses can potentially lead to micro-buckling in the polyimide films and promote interfacial de-adhesion between the metallization and polyimide film due to large localized strains.
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