Thermal characterization of highly conductive die attach materials

This paper deals with the development of a new test stand for determination the thermal conductivity of metals, semiconductors, highly conductive die attaches and substrates using the steady state technique. We designed the test stand and optimized it by FE simulation to have flexibility for the selection of the sample size and measurement parameters. We determine the thermal conductivity from the measured thermal resistance and the geometries of the measured samples. To measure the thermal resistance by steady state techniques one need a hot source and a heat sink. Putting the sample between these hot source and sink, so the sample will be flowed by heat and temperature gradient across the sample will be generated. The temperature gradient across the sample is measured by a thermal imaging system. The input and the output heat flow are measured by metal based heat flow sensors (HFS) which is a metal socket with integrated high precise temperature sensors. To determine the exact heat flow through the sample we analysed the heat loss by radiation and convection by a case study and calculated a correction factor for the heat flow. Different solder and die attach materials as well as metals and highly conductive substrates have been measured by the new test stand. Selected results will be presented in this paper in order to demonstrate the functionality and the accuracy of the new test stand.