DIFFERENT THICK-FILM METHODS IN PRINTING OF ONE-ELECTRODE SEMICONDUCTOR GAS SENSORS

Different thick-film printing techniques have been used for the fabric ation of one-electrode semiconductor gas sensors in the form of thick films on insulating alumina substrate. In a typical one-electrode sens or construction, a thin platinum wire (diameter 20 mu m) spiral is emb edded inside a sintered oxide semiconductor button. The platinum wire spiral is replaced by a platinum thick-film resistor in our prototype sensor, and the oxide semiconductor is screen printed over the platinu m resistor. Both screen printing and gravure offset printing (pad prin ting) were used for the printing of platinum thick-film resistors. Tin dioxide, an n-type semiconductor, was used as the sensing (shunting) thick-film layer over the platinum resistor, and different amounts of either silver or antimony were used as additives in SnO2. H2S and CO a t different concentrations in synthetic air were used to test the resp onse properties of two different sensor types with, respectively, scre en-printed and pad-printed platinum thick-film resistors.