THE EFFECT OF HUMIDITY ON AN SNO2 THICK-FILM PLANAR RESISTOR

The effect of humidity on the d.c. resistance of an SnO2:Sb:SnCl2 thick-film planar resistor on an alumina substrate is reported. The films of SnO2 are obtained using standard screen-printing technology. The thick-film paste is formulated by loading the SnO2:Sb system with varying percentages of SnCl(2)2H(2)O. An increasing percentage of SnCl2 in the SnO2:Sb system increases the sensitivity to humidity and decreases the initial resistance. A two orders of magnitude change in d.c. resistance is observed for a relative humidity change from 30 to 90%. A small hysteresis (3-10%) is observed. The response time is a few seconds (6-8), though the recovery time is slow (8-10 min).