Thermal interface assembly and method for forming a thermal interface between a microelectronic component package and heat sink

1. A thermal interface assembly for forming a thermal interface between a microelectronic component package and a heat sink such that under the application of pressure the thermal interface assembly has a total thermal resistance of no greater than about 0.03 ° C.-in 2 /W comprising, in combination, a thermal interface material consisting of a structure which is solid at room temperature and includes at least three metallic layers comprising an intermediate solid core of a high thermal conductivity metal or metal alloy which remain solid when the microelectronic component package is operational and a layer on each opposite side thereof composed of a metallic alloy having phase change properties consisting of between 10 wt %-80 wt % indium and the remainder selected from the group of metallic elements consisting of bismuth, tin, lead, cadmium, gallium, zinc, silver and combinations thereof such that at room temperature said metallic alloy layer is a solid but at a temperature corresponding to when the microelectronic component package is operational the metallic alloy layer undergoes a liquid phase change and further including a sealing member having a circular configuration in cross section spaced apart from said thermal interface material to provide an open space there-between with said sealing member being composed of a compressible material selected from the group consisting of a soft, compliant o-ring and/ or shim with said open space being of sufficient size so that said open space remains after the sealing member is compressed in response to said pressure and with the sealing member being exposed to the atmosphere for forming a seal to prevent the ingress of air from the atmosphere into said open space in contact with said thermal interface material when the microelectronic component package is operational.

2. A thermal interface assembly as defined in claim 1 wherein said material having phase change properties has a thickness of less than about 5 mils.

3. A thermal interface assembly as defined in claim 2 wherein said high thermal conductivity metal or metal alloy is selected from the transition elements of row 4 in the periodic table in addition to magnesium and aluminum from row 3 of the periodic table and alloys thereof.

4. A thermal interface assembly as defined in claim 3 wherein said material having phase change properties is a low melting metal alloy.

5. A thermal interface assembly as defined in claim 4 wherein said low melting metal alloy layer comprises in addition to indium at least between 20 wt %-50 wt % bismuth.

6. A thermal interface assembly as defined in claim 5 wherein the thickness of the low melting metal alloy layer having phase change properties is less than about 2 mils.

7. A thermal interface assembly as defined in claim 2 wherein said shim comprises a flexible shim support and a flat flexible shim section extending outwardly from the shim support for forming a platform for mounting of the O-ring.

8. A method for forming a thermal interface having a total thermal resistance of no greater than about 0.03° C.-in 2 /W between a microelectronic component package and a heat sink when held together under the application of pressure comprising the steps of interposing a thermal interface material consisting of a structure which is solid at room temperature and includes at least three metallic layers comprising an intermediate solid core of a high thermal conductivity metal or metal alloy which remain solid when the microelectronic component package is operational and a layer on each opposite side thereof composed of a metallic alloy having phase change properties consisting of between 10 wt %-80 wt % indium and the remainder selected from the group of metallic elements consisting of bismuth, tin, lead, cadmium, gallium, zinc, silver and combinations thereof such that at room temperature said metallic alloy layer is a solid but at a temperature corresponding to when the microelectronic component package is operational the metallic alloy layer undergoes a liquid phase change with the thermal interface material being disposed between said microelectronic component package and heat sink to form a thermal interface there-between and surrounding the thermal interface material with a soft compressible sealing member composed of a compressible material selected from the group consisting of a soft, compliant o-ring and/or shim having a circular configuration in cross section of sufficient dimension to form an open space there-between which remains an open space after the sealing member is compressed in response to said pressure and with the sealing member being exposed to the atmosphere for forming a seal to prevent the ingress of air from the atmosphere into said open space in contact with the thermal interface material when the microelectronic component package is operational.