Patent ID: 8653842

Claim:
A thermal control unit for maintaining a set point temperature on an IC device under test (DUT) having a substrate having a die attached to an upper surface thereof, comprising: a pedestal assembly comprising a heat-conductive pedestal having a bottom end configured to contact the die of the DUT and a temperature sensor in the bottom end for monitoring the die's temperature; a temperature-control fluid circulation block having a fluid inlet and a fluid outlet configured to circulate a fluid therethrough, the block in stacked relationship along an z-axis with the heat conductive pedestal; a thermally-conductive heater between the heat-conductive pedestal and the fluid circulation block configured to provide heat to the pedestal, and further configured to transfer heat from the pedestal to the fluid circulation block; a substrate pusher configured to contact the substrate of the DUT; and a controllable force distributor configured to receive a z-axis force and controllably distribute such z-axis force between the pedestal assembly and the substrate pusher, wherein said controllable force distributor includes a force distribution block having an actuator configured to change the force transmitted to the heat conductive pedestal relative to the force transmitted to substrate pusher, wherein the actuator for changing the force transmitted to the heat conductive pedestal relative to the force transmitted to substrate pusher includes a plurality of pistons that can be actuated to exerted a z-axis force that is transmitted to the pedestal and that changes the balance of the z-axis forces transmitted to the pedestal and the substrate pusher, and wherein the plurality of pistons are adjustable and capable of providing varying levels of die force.