Ferroalloys

Silicon Chromium

An unusual low-temperature failure mode was uncovered during reliability testing of 2 kω/sq. SiCr resistors. Resistor arrays were fabricated by integrated circuit production methods. Life-tests were performed at 125°, 25° and −25°C at current densities up to 106 A/cm2. Passivated and unpassivated arrays were assembled in glass-sealed ceramic packages. Typical mean drift at the above temperatures of passivated resistors in hermetic or non-hermetic packages (>10−6 std cm3/s) after 1000 h operation (20 V, 2 × 105 A/cm2) was < 0.6%. Unpassivated resistors had similar stability when operated at 125°C, but had mean times to failure of ∼ 30,000 h when operated at −25°C in hermetic packages and ∼ 350 h in non-hermetic packages. Failures also occurred in air-sealed TO-5 cans, heated at 495°C for 15 mins, and then operated at −25°C. Failures involved anodic resistor corrosion, and in non-hermetic packages, anodic or cathodic aluminum corrosion.

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