How to Estimate Heat Spreading Effects in Practice

Abstract

The nontrivial issues associated with calculating the steady state heat spreading effects generated by a heat source on top of a multilayer assembly such as a printed circuit board are discussed. 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 analyze 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.