Abstract: A thermal shunt apparatus directs heat flux transmitted through electrical signal leads from a focal plane array (FPA) to a relatively isothermal top surface of a TE cooler. The FPA mounts with a first thermally conductive attachment to a thermal spreader plate that is highly thermally conductive. The thermal spreader plate is mounted to the top surface of the TE cooler by a second thermally conductive attachment. The combination of the relatively isothermal surfaces, the FPA thermal spreader and the TE cooler top plate, separated by the thermally conductive interface, maintains a relatively constant temperature difference between the electrical leads connected between the thermal shunt and the FPA edge. The constant temperature difference provides for constant heat flux between these points and a constant temperature gradient across the surface of the FPA.