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 Pb
2
Ru
2
0
6
, 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 RuO
2
, TCR's of approximately zero were achieved. Through use of a CdO/RuO
2
functional phase in conjunction with a lead-cadmium glass system, sheet resistances ranging from about 10
\Omeg
/
Box$^b$
to 100 k
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/
Box$^b$
with controllable TCR's were obtained.