Elimination Of Thermal Face Warpage Of Soldered Fin-in-groove Heat Sinks
Original Publication Date: 2003-May-19
Included in the Prior Art Database: 2003-May-19
Large copper heat sinks for cooling electronics hardware, such as the multi-chip module (MCM), are a challenge to manufacture. The dense fin geometry allows few, cost effective, manufacturing options but to solder the copper fins into grooves cut in a copper heat sink base. The problem with the soldered fin-in-groove design is that it is not possible to maintain a flat thermal face required for good thermal interface between the heat-sink base and the MCM cover. This invention overcomes the heat-sink thermal face warpage problem by using a solder that has a thermal coefficient of expansion (TCE) that is slightly lower than the TCE of copper (=17 ppm per degree C). A simple change of the solder material from the usual Pb-Sn solder (TCE = 25 ppm per degree C) to one with a TCE of 12-15 ppm per degree C changes the thermal face from a thermally undesirable concave shape to a much more desirable convex shape.