Thermal Compound is a fluid substance, originally with properties akin to grease, which increases the thermal conductivity of a thermal interface by compensating for the irregular surfaces of the components.  Thermal compound is primarily used in the electronics and computer industries to assist a heatsink to dissipate heat.   (Heatsinks are used on both a CPU and GPU) Thermal Compound improves the efficiency of a heatsink by filling air gaps that occur when the irregular surface of a heat generating component (CPU or GPU) is pressed against the irregular surface of a heatsink.  Surface imperfections range in size from visible and tactile flaws such as machining marks or casting irregularities to sub-microscopic ones not visible to the naked eye.  Both the thermal conductivity and the "conformability" (i.e., the ability of the material to conform to irregular surfaces) are the important characteristics of thermal compound. At Xotic PC on most of our systems we provide two options for Thermal Compound.   Below you can read on IC Diamond 7 and Arctic Silver 5.   Both Arctic Silver 5 and IC Diamond 7 help with with the overall cooling and connection to your heatsink.   IC Diamond 7 provides the best conformability and produces the best cooling results compared to Arctic Silver 5.   Performance: With Arctic Silver 5 you can expect 3 to 12 degrees centigrade lower CPU full load core temperatures than standard thermal compounds or thermal pads when measured with a calibrated thermal diode imbedded in the CPU core.   With IC Diamond 7 you can expect 6-15 degrees centigrade lower CPU full load core temperatures than standard thermal compounds or thermal pads when measured with a calibrated thermal diode imbedded in the CPU core.   Introducing Arctic Silver 5 With its unique high-density filling of micronized silver and enhanced thermally conductive ceramic particles, Arctic Silver 5 provides a new level of performance and stability. Arctic Silver 5 is optimized for use on high-power CPUs to lower CPU operating temperatures, thus increasing overall system stability, increasing performance, and reducing fan noise. Features: Contains 99.9% pure silver: Arctic Silver 5 uses three unique shapes and sizes of pure silver particles to maximize particle-to-particle contact area and thermal transfer. High-Density: Arctic Silver 5 contains over 88% thermally Conductive filler by weight. In addition to micronized silver, Arctic Silver 5 also contains sub-micron zinc oxide, aluminum oxide and boron nitride particles. These thermally-enhanced ceramic particles improve the compound's performance and long-term stability. Controlled Triple-Phase Viscosity: Arctic Silver 5 does not contain any silicone. The suspension fluid is a proprietary mixture of advanced polysynthetic oils that work together to provide three distinctive functional phases. As it comes from the tube, Arctic Silver 5's consistency is engineered for easy application. During the CPU's initial use, the compound thins out to enhance the filling of the microscopic valleys and ensure the best physical contact between the heatsink and the CPU core. Then the compound thickens slightly over the next 50 to 200 hours of use to its final consistency designed for long-term stability. (This should not be confused with conventional phase change pads that are pre-attached to many heatsinks. Those pads melt each time they get hot then re-solidify when they cool. The viscosity changes that Arctic Silver 5 goes through are much more subtle and ultimately much more effective.) Not Electrically Conductive: Arctic Silver 5 was formulated to conduct heat, not electricity. (While much safer than electrically conductive silver and copper greases, Arctic Silver 5 should be kept away from electrical traces, pins, and leads. While it is not electrically conductive, the compound is very slightly capacitive and could potentially cause problems if it bridges two close-proximity electrical paths.) Absolute Stability: Arctic Silver 5 will not separate, run, migrate, or bleed. Compliancy: RoHS Compliant. Specifications: Thermal Conductance: >350,000W/m2 °C (0.001 inch layer) Thermal Resistance: <0.0045°C-in2/Watt (0.001 inch layer) Average Particle Size: <0.49 microns <0.000020 inch Extended Temperature Limits: Peak: –50°C to >180°C Long-Term: –50°C to 130°C