Method of making a variable power resistor

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.