Optimization of cooling time for measuring thermal properties of electronic materials using the transient plane source technique

The Hot Disk (TM) Thermal Constants Analyzer (TPS technique) belongs to the family of transient thermal analysis techniques. Direct thermal conductivity measurements can be performed in a rapid and non-intrusive manner on a wide range of materials typically with a 1 to 4 degreesC evolution of interfacial heat between the TPS sensor and sample being evaluated during a test. Prior to successive tests being conducted, this heat evolved must dissipate and the sample sensor package returned to isothermal equilibrium. The objective of this investigation was to determine the effect of varying cooling time of the TPS instrument between thermal property tests on the reproducibility and accuracy of thermal analysis data. For this investigation, a cross section of materials including silicone based electronic interface materials with various conductive fillers and selected metal alloys have been evaluated. The interface materials represent typical families of materials used in microelectronic and macroelectronic applications and the metal alloys were selected having thermal transport properties similar to where research and development is currently focused in the electronics field. Each material was tested in triplicate at each of five controlled cooling times: 30 minutes, 15 minutes, 10 minutes, 5 minutes and I minute, using optimized TPS instrument parameters unique to each specimen. In addition tests were conducted in a temperature controlled furnace at ambient temperatures of 25, 50 and 70 degreesC to investigate the effect of instrument cooling time at different temperatures. The impact of decreasing the cooling period on thermal transport property evaluations with the TPS system will be discussed.