A thermally and electrically conductive material is provided as a mixture of a dimethylpolysiloxane, metal (or one metal coated with another metal) flakes and/or granules, a peroxide-based and/or a dimethyl hexane based catalyst, PTFE powder and a platinum based fire retardant. The thermally and electrically conductive material may be pre-formed into a film or pad and each side of the film protected with removable release layers. The thermally and electrically conductive material may alternatively be produced in a screen-printable paste. As such, a layer of the thermally and electrically conductive paste may be screen-printed on the metal surface in a complete sheet form or as a patterned film by using a stencil patterned screen mesh. Processes for manufacturing high- and low-frequency circuits that include the interface material are also provided.