Corrosion of thin film aluminum metallization: conformal coating materials

The authors report their results on the THB performance of triple-track-tester (TTT) devices coated with room temperature vulcanized silicon rubber (RTV), silicon resin, silicon polyimide, or silicon gel. Devices with each of these conformal coating materials were aged at 85 C/85% relative humidity (RH)/A, where 40→400 V, for times up to 14000 h. It is found that the median time-to-fail is exponentially related to the applied voltage. The median life at 300 V is in excess of 30000 h for the silicon-gel-coated samples. 10000 h for the RTV-coated samples, 3000 h for the silicon-resin-coated samples, and 2000 h for the polyimide-coated samples. The difference in the median life times is due to differences in the interface bond strength between the polymer coat and the device surface