Improving accuracy and flexibility of ASTM D 5470 for high performance thermal interface materials

The thermal demands of current and next generation microprocessors have driven requirements for thermal interface materials (TIMs) to the point where reliable vendor data is often not available. Vendors are struggling to meet customers needs. Existing industry test standards were intended for electrical insulation materials and cannot provide accurate data for todays high performance TIMs. Manufacturers are forced to accept vendor data at risk, pay for outside testing, or bring testing in-house. This paper discusses the latter where a commercially available thermal conductivity test apparatus was brought in-house, and modifications were defined and implemented to improve its versatility and accuracy. Details of those modifications and results of validation testing are presented where accuracy is improved by an order of magnitude over the standard apparatus. The method allows for variation of contact surface type, roughness, pressure, temperature, etc.