Stability of palladium oxide resistive glaze films

Abstract Process variables that affect the resistivity and TCR of the Pd-Ag glass resistor system are, for a fixed electrode system: composition, firing temperature and time, and substrate material. While the greatest changes occur via composition variations, particularly Ag and glass, substantial changes to R 8 and TCR can be made by varying the firing cycle or substrate material. For the latter, certain physical and thermal constraints may preclude a wide choice of base materials. Determining the effect of process latitude on device stability becomes the next objective. Stability of electrical parameters was determined through large-scale, long-term tests involving a matrix of 14 firing processes and 19 environmental conditions of temperature, humidity and load. Results for 3200 test hours indicated resistor drift to be within ±1 per cent under ambient humidity conditions and up to 90°C and 6 W/in 2 for most processes. Distributional drift behavior shows a progressive widening—both negative and positive—of ΔR with time. Accelerated testing done at elevated temperatures shows drift to be primarily positive, with a decreasing rate of change with time, and exhibiting three acceleration regions. Humidity tests show some moisture susceptibility when compared with lower RH controls but still of a relatively small magnitude. Various encapsulants may serve to inhibit moisture. The effects of resistor adjustment by sand abrasion and various compositions on stability were also evaluated. TCR was found to be essentially invariant under the test conditions described.