The practical usefulness of various approaches to estimate heat spreading effects

This paper discusses the non-trivial issues associated with calculating the heat spreading from a heat source into a thermally conducting body subject to boundary conditions in steady state. It is argued that problems arise with the interpretation of heat spreading effects due to a misconception about the meaning of often-quoted flux limits and especially the physical meaning of thermal resistance. The usefulness of a number of approaches that are generally in use to analyse heat spreading effects is discussed and it is shown that the popular series resistance approach has severe limitations. A number of test cases are covered in detail and the results testify to this assertion.