Migration of Silver from Silver-Loaded Polyimide Adhesive Chip Bonds at High Temperatures

A degradation mechanism found at high temperatures in a commercial silver-loaded polyimide chip adhesive is discussed. The adhesive was used to attach semiconductor diodes to headers for potential use in the geothermal well probe program. Aging the mounted devices at 300°C for 1100 h resulted in a bias dependent migration of the silver out of the adhesive. This effect was accompanied by an increased series resistance and weakened bond strength.