Practical Aspects of Testing Methods for Thermal Interface Materials

Increasing recognition is being given to the importance of thermal interface materials as a contributor to further reduction of overall thermal resistance within semiconductor packages and electronic assemblies. This growing recognition has also drawn greater attention to the challenges of performance and reliability testing for the increasingly diverse variety of types of such materials available from many vendors. Compounding the increasing differentiation and number of types of thermal materials which must be tested is the expanding and very wide range of application requirements as new challenges arise in electronic systems design. The complicated array of thermal materials to be considered for use and changing application requirements call for better understanding of the principal differences in material characteristics by category, differences in principal testing methods and reasons such test methods exist separately, and how methods and data may be applied most appropriately. Speaking broadly, a continuing challenge is the distinction between empirical data generated in a standardized laboratory procedure, with as many variables removed as possible in order to characterize core characteristics, and the difference in results obtained in thermal performance of the same materials when applied within a set of conditions that are specific to an application. Understanding differences in principal testing procedures and how generally to interpret and make use of the data is important, especially in comparison to vendor-provided data. Manufacturers of thermal interface materials (TIMs) face different challenges in testing and selection of appropriate testing methods than do design engineers who are attempting to select a material for a given application. In addition, increasing awareness of the need to examine initial test values and potential for performance change with time and temperature are important for product reliability.