Thermal Grease X23-7921-5
Thermal grease, X-23-7921-5, is a Non-Solvent type of thermal interface material developed by Shin-Etsu Chemical Co., Ltd. (hereinafter SEC) to meet the current and future thermal management requirements of highperformance microprocessors. Its purpose is to increase heat sink effectiveness, and it is used to fill any air gap between the processor and the heat sink, because air is a thermal insulator with a thermal conductivity of only 0.027W/mK. After the processor is in the socket, the grease is applied to the raised area on top of the processor. The heat sink is then centered on the processor top, with the raised areas on the bottom of the heat sink aligned with those on the processor top. You should then gradually but firmly press the heat sink down until you can feel that the metal surface of the heat sink is in contact with the metal top of the processor. Doing so will evenly distribute the thermal grease between the two surfaces. Any excess grease can be removed by wiping with a soft cloth.
Links to Technical Data Sheets