Claims
- 1. A method of making a variable power resistor, comprising:
- (a) plasma spraying an electrically insulating, thermally conductive ceramic coating on a front face of a heat sink;
- (b) screen printing a plurality of discrete thick film conductive circuit pads onto the electrically insulating, thermally conductive ceramic coating, wherein the conductive circuit pads comprise about 10 wt. % to about 70 wt. % of a lead borosilicate glass matrix, about 15 wt. % to about 20 wt. % zirconium spinel reinforcing particles, and up to about 90 wt. % coprecipitated palladium and silver conductive particles in an amount effective to provide a resistance of up to about 0.5 ohms/square;
- (c) screen printing a thick film resistive layer over portions of the conductive circuit pads such that the circuit pads are electrically connected in series through the thick film resistive layer, wherein the resistive layer comprises about 5 wt. % to about 70 wt. % of a lead borosilicate glass matrix, about 15 wt. % to about 20 wt. % zirconium spinel reinforcing particles, and more than about 5 wt. % coprecipitated palladium and silver conductive particles in an amount effective to provide a resistance of greater than 0.5 ohms/square; and
- (d) installing a moveable contactor capable of contacting the circuit pads in order to vary the resistance of the resistor.
- 2. The method of claim 1 wherein the heat sink comprises a material selected from the group consisting of aluminum, copper, and zinc.
- 3. The method of claim 1 wherein the electrically insulating, thermally conductive ceramic coating comprises alumina.
- 4. The method of claim 1 wherein the electrically insulating, thermally conductive ceramic coating is about 0.002 in to about 0.010 in thick.
- 5. The method of claim 1 wherein the conductive circuit pads are about 10 microns to about 40 microns thick.
- 6. The method of claim 1 wherein the resistive layer is about 10 microns to about 40 microns thick.
Parent Case Info
This is a division of copending application Ser. No. 07/629,885 filed on Dec. 19, 1990 now U.S. Pat. No. 5,119,063.
US Referenced Citations (4)
Divisions (1)
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Number |
Date |
Country |
Parent |
629885 |
Dec 1990 |
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