Thick film resistive heater compositions comprising Ag and RuO
View Patent ↗Thick film resistor paste compositions, and methods for making the thick film compositions are disclosed. The compositions include a resistor composition dispersed in an organic vehicle. The resistor composition has 3 to 60% by weight RuO 2 conductive material, 5 to 75% by weight Ag conductive material, 15 to 60% by weight glass frit and optionally up to 10% by weight copper oxide or precursor thereof, and up to 20% by weight bismuth oxide or precursor thereof. Optionally the glass is (by weight) 25-45% SiO 2 , 2-15% Al 2 O 3 , 0-3% ZrO 2 , 0-8% B 2 O 3 , 5-15% CuO, 0-8% BaO, 0-3% P 2 O 5 , and 20-50% Bi 2 O 3 . The resistor composition when printed to a dry thickness and fired at a temperature between 750° C. and 950° C. achieves a sheet resistivity between 10 and 10,000 milliohms/square and a hot temperature coefficient of resistivity of 1000 ppm/C or higher. The fired resistor composition may achieve a resistance thickness ratio (R tr ) value between 0.75 and 1.50.
1. A thick film resistor paste composition comprising a resistor composition dispersed in an organic vehicle, said resistor composition comprising:
(a) 3 to 60% by weight RuO 2 conductive material,
(b) 5 to 75% by weight Ag conductive material,
(c) 15 to 60% by weight glass, wherein the glass comprises by weight 25-45 wt % SiO 2 , 5-15 wt % CuO and 20-50 wt % Bi 2 O 3 ,
(d) 0 to 10% by weight copper oxide or precursor thereof, and
(e) 0 to 20% by weight bismuth oxide or precursor thereof
wherein said resistor composition when printed to a dry thickness of 25.4 microns using a mesh of 200 to 350 and fired at a temperature between 750° C. and 950° C. achieves a sheet resistivity between 10 and 10,000 milliohms/square, a hot temperature coefficient of resistivity of 1000 ppm/C or higher and a resistance thickness ratio (R tr ) value between 0.75 and 1.50.
2. A fired resistor composition wherein the resistor composition is that of claim 1 .