Abstract: A heat-sink cooling apparatus and a method for attaching a heatsink to a ceramic integrated-circuit package are provided. An externally-threaded molybdenum stud is attached to and extends from a copper/tungsten slug, or attachment plate, which is brazed to the ceramic integrated-circuit package. The stud and the slug have similar thermal coefficients of expansion to reduce thermal stress at the interface therebetween. An aluminum heatsink has an internally threaded hole formed therein for receiving the externally-threaded molybdenum stud. The external threads of the harder molybdenum material engage and deform the threads formed in the aluminum heatsink to provide strong mechanical and thermal bonding between the stud and the heatsink.

Abstract: Spacers are attached to or made an integral part of the housing of a semiconductor package in order to set a desired spacing between a surface of the package housing and the heatsink. Then when the heatsink is attached to the housing, a uniform clearance is maintained between the heatsink and the surface of the housing. When such clearance is filled with an epoxy for bonding the heatsink to the housing, the bondlength of the epoxy layer will be uniform and be of the desired value.