ABSTRACT
This chapter deals with thermal spreading resistance, the heat conduction from a single heat source centered on a heat conducting substrate. Most results are quoted for a substrate or plate that has an adiabatic boundary condition at the source plane, Newtonian cooling at the opposing plane, and presumes steady-state conditions. The chapter discusses a couple of mathematically simple models that some design engineers continue to use. It looks at a heat source on semi-infinite media where the only finite geometric object is a heat source on an otherwise adiabatic plane. The chapter shows that the surface boundary condition where the Newtonian cooling is specified actually has an effect on the spreading because the boundary effect is part of the total resistance to heat flow. The greater the boundary condition resistance, the greater the conductive spreading. The heat flow lines at the left- and right-hand edges will be consistent with our choice of edge boundary conditions.
