Abstract

Thick film resistors are widely used in consumer and industrial products such as timers, motor controls and a broad range of high performance electronic equipment. This article provides information on failures due to copper dendrite growth, silver migration, sulfur atmosphere corrosion, variation of temperature, and crack due to molding compound mechanisms. It presents case studies in which a physical analysis plan was developed and executed to investigate these sites of interest on as-manufactured and failed thick film power resistors. The analysis techniques included X-ray inspection, cross-sectioning, decapsulation, and optical and environmental scanning electron microscopy analysis. A table illustrates different failure modes and mechanisms for thick film resistors, and also potential application and manufacturing factors that cause failure mechanisms, which then describe the failure modes. The article is concluded that by preventing the failure of thick film resistors, printed circuit boards can be kept in service for their full lifetime.

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