GB1317669A - Electrical resistor - Google Patents

Abstract

1317669 Glass resistor mixtures INTERNATIONAL BUSINESS MACHINES CORP 13 Dec 1971 [1 Feb 1971] 57704/71 Heading ClM [Also in Division H1] A paste for forming a resistor element comprises a powdered conductive material, e.g. a metal or metal oxide, examples of suitable metals being silver, antimony, chromium, palladium, copper and mixtures thereof, a powdered insulating material, e.g. a glass frit, dopant ions and a relatively small amount of powdered activated charcoal (wood charcoal or other) the mixture being dispersed in an inert liquid vehicle comprising a non-polar solvent combined with a resin and if desired a wetting agent. The resin is conventional and can be a natural gum, cellulosic material or synthetic resin. Suitable volatile solvents are those having a relatively low vapour pressure at room temperature and a relatively high vapour pressure at elevated temperatures, e.g. higher boiling paraffins, cycloparaffins, terpineol and mixtures thereof, or one or more of the mono and di-alky ethers of diethylene glycol or their derivatives such as diethylene glycol monobutyl ether acetate. Surfactants or dispersing agents suitable for use are, for example organic derivatives such as polyoxyethylene alcohol non-ionic surfactants, alkylaryl sulphonates, and fatty acid esters. The charcoal component of the mixture comprises preferably between 0À4% and 2.0% by weight of the total weight of the mixture and vehicle. The paste is deposited on to a substrate using conventional techniques, e.g. by being screened, dried in a furnace at a temperature in the range 100-300‹ C. and then fixed at a temperature up to about 750‹ C. In one particular mixture of the resistor paste, the powdered conductive material is lithium doped palladium oxide, the powdered insulating material is borosilicate glass and the vehicle comprises a volatile solvent and ethyl cellulose. An example of a possible conductive mixture is one in which silver, doped palladium oxide, borosilicate glass, colloidal silica and activated wood charcoal in the parts by weight 16, 21, 58, 3 and 2 respectively. A suitable vehicle for such a mixture is made from the following constituents: butyl carbatol acetate, ethylcellulose and oleyl sarcosin surfactant in the parts by weight 90, 10À0, 0À5 respectively A second possible vehicle for the above conductive mixture comprises similar constituents to the above described vehicle but replaces the butyl carbatol acetate with terpineol solvent.