Chapter 3. Joint Thermal Resistance and Thermal Interface Materials Available to Purchase

Heat conduction across a joint of two solids occurs practically in every heat generated system. A significant temperature gradient occurs as heat is transferred by conduction across the joint of two solids. This is due to the thermal contact resistance generated by the surface irregularities. As shown in Figure 3.1, only a small fraction of points (less than 5%) are actually contacting each other for any two nominally flat surfaces. Therefore, additional thermal resistances, including constriction and spreading resistances are generated because of reduction of heat transfer area at the interface of two bodies. This thermal resistance of the joint is a function of the surface roughness and waviness, mechanical properties of solids, thermal properties of solids, and the contact pressure.