TABLE OF CONTENTS Tim Williams
It is in the nature of electronic components to dissipate power while they are operating. Any flow of current through a nonideal component will develop some power within that component, which in turn causes a rise in temperature. The rise may be no more than a small fraction of a degree Celsius when less than a milliwatt is dissipated, extending to several tens or even hundreds of degrees when the dissipation is measured in watts. Since excess temperature kills components, some way must be found to maintain the component operating temperature at a reasonable level. This is known as thermal management.
Heat transfer through the thermal interface is accomplished by one or more of three mechanisms: conduction, convection and radiation. The attractiveness of thermal analysis to electronics designers is that it can easily be understood by means of an electrical analog. Visualize the flow of heat as emanating from the component which is dissipating power, passing through some form of thermal interface and out to the environment, which is assumed to have a constant ambient temperature TA and infinite ability to sink heat. Then the heat source can be represented electrically as a current source; the thermal impedances as resistances; the temperature at any given point is the voltage with respect to 0V; and thermal inertia can be represented by capacitance with respect to 0V. The 0V reference itself doesn't have an exact thermal analog, but it is convenient to represent it as 0 C,...
