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Abstract

Thermal spreading (or constriction) resistance results when heat is conducted away from a finite region into a larger region (spreading resistance) or from a larger region through a smaller region (constriction resistance). Spreading or constriction resistance can be determined by solving transient or steady-state heat conduction in a solid region with appropriately applied boundary and initial conditions. When the contact areas result in imperfect contact at the microscopic level, we find an array of discrete points of contacts results. Heat transfer across the apparent contact region occurs through conduction at these discrete points of contact and across the gap if there is a gas or liquid present; otherwise, heat transfer through radiation may occur in a vacuum. In these instances, we have contact resistance. In this text, we strive to present the general theory and applications of thermal spreading and contact resistance.