Cadmium Oxide Thick Film Resistors

Use of cadmium oxide as a nonprecious conducting material for thick film resistors was investigated. Screen printed resistors were evaluated over a firing temperature range of 630°C to 760°C. By adjusting the ratio of cadmium oxide to glass, the sheet e resistance could be varied from about 1 k\Omeg/\Box$^b$to 1 M\Omeg/\Box$^b$. The temperature coefficient of resistance (TCR) was typically -500 ppm/ °C, regardless of the amount and type of glass employed in the resistor compositions. It was shown that small amounts of RuO2 or Pb2Ru206, added separately or together, to the resistor compositions, reduced the sheet resistance several orders of magnitude and changed the TCR from a negative to positive value. Through proper adjustment of the ratio of CdO to RuO2, TCR´s of approximately zero were achieved. Through use of a CdO/RuO2functional phase in conjunction with a lead-cadmium glass system, sheet resistances ranging from about 10\Omeg/Box$^b$to 100 k\Omeg/Box$^b$with controllable TCR´s were obtained.