Passive Component Enhancements in High-Temperature Electronic Devices: A Deterioration Mechanism for Metal Electrodes in Ceramic Film Resistors

The deterioration mechanisms of chip resistors with both multilayered Au/Ni/Ag electrodes and glass-covered coatings were studied at temperatures above 250 degrees C, the possible driving temperature of future SiC high-power devices. Based on Joule heating, a heatproof temperature was set to 300 degrees C, at which the multilayered metal electrodes clearly deteriorated during the 1000 h exposure tests conducted. The main cause of deterioration was likely due to the Au-Ag interdiffusion across micropores and cracks at the Ni layer. This diffusion behavior was strongly dependent on the humidity of the atmosphere. Water molecules that adsorbed into electrode micropores and cracks were found to act as electrolytes, forming micro-Galvanic-like cells that allowed Ag to migrate from the bottom to the surface. The unignorable amount of surface-diffused Ag tended to weaken the electrical paths to the RuO2-based resistor, resulting in an increased resistance during these long-term exposure conditions over 750 h. The RuO2 layer was found to be unaffected by heat below 300-350 degrees C, where it completely covered the glass. Under an electric bias of 1.5 W, the deterioration process was found to be similar to the simple heating process. Therefore, the deterioration of the chip resistors at high temperature proceeded due to the electrochemical reactions occurring within the multilayered electrodes. This unforeseen deterioration could be suppressed by generating either a thicker Ni interlayer or utilizing a Au absorber, such as Cu, to facilitate diffusion from the top to avoid Au/Ag contact formation.