Dual function circuit board, a resistor element therefor, and a circuit embodying the element

A dual function circuit board substrate has a layer or sheet of ultrathin metal of relatively high electrical resistivity having a selected sheet resistivity characteristic bonded to a thin layer or sheet of metal of relatively high electrical conductivity. The layer of high electrical resistivity material is adhered to one side of a layer of organic electrically insulating material, and a heat-sink metal layer is adhered to an opposite side of the organic insulating layer to withdraw heat from the layer of high electrical resistivity material. The thin layers of high electrical resisivity and conductivity materials are selectively etched from the organic layer material to form a select circuit, and the layer of high electrical conductivity material is selectively etched from portions of the circuit to form one or more resistor elements having selected electrical resistances in the circuit. A multiplicity of particles of material of relatively higher thermal conductivity than the organic material is dispersed in the organic material to enhance heat withdrawal from the circuit, particularly at the locations of the resistor element, to permit the resistor elements to be compactly proportioned to provide said electrical resistance while maintaining operating temperature of the resistance elements in the circuit within a selected temperature range.