Bias-Humidity Performance of Encapsulated and Unencapsulated Ti-Pd-Au Thin-Film Conductors in an Environment Contaminated with Cl2

Both encapsulated and unencapsulated Ti-Pd-Au thin-film conductors on AI2O3substrates were biased in an 85°C 80-percent RH environment contaminated with Cl2. The encapsulant was an RTV silicone rubber. During exposure to the corrosive environment, leakage currents between adjacent conductors were periodically measured and recorded. Leakage currents for the unencapsulated specimens increased with time, and many were shorted after approximately 400 h. In contrast to this behavior, there were no increases in leakage currents for the silicone rubber encapsulated conductors. At the end of the test, selected specimens were examined using a light microscope and an SEM with X-ray capability. No metal migration was observed on the encapsulated samples. The unencapsulated conductors showed dendritic growth between the electrodes; X-ray analysis showed the growths to consist of both Au and Pd. It is concluded that the RTV silicone encapsulant effectively prevents high leakage currents and subsequent metal migration on biased Ti-Pd-Au conductor specimens exposed to a moist Cl2environment. Unencapsulated samples are rapidly degraded under the same conditions with the main failure mechanism being metal migration.