Full Metal TIMs

ABSTRACT The high thermal conductivity of metals and alloys drives their use in thermal solutions. Metals dominate the application in heat sinks, spreaders and heat pipes because of the high conductivity as well as the ease and flexibility in fabrication. In critical heat flow situations, metals are frequently used as the thermal interface material in the thermal solution. These metal TIM materials must make intimate contact with the working surfaces to take advantage of the thermal conductivity. To achieve this bond metals are used in four different forms'solder, liquid metals, phase change metals and compressible metals. Each of these types of metal TIM achieves intimate contact with the mating surfaces with different assembly methods. The solder joint requires a reflow cycle to melt the metal well above the operating temperature to form a bond that is solid in service. The liquid metals are liquid during application and in service. Phase change metals are solid during installation and melt in service to wet the contact surfaces. Compressible metals are mechanically soft materials that can be plastically deformed in service to make intimate contact. Alloys are selected to fit the temperature, environment, and mechanical requirements of the application. We will discuss the installation and handling of the metal TIMs for reliable performance. The applications and restrictions of each type of TIM will be reviewed.