The Effect of Test Conditions on HAST and THB Reliability Testing of Thermal Interface Material, and the Introduction of an Improved Thermal Interface Material

As the world becomes more and more dependent on electronic devices the reliability of these devices increases in importance. Reliability testing of electronic components has been reduced to a rigorous practice, and it is well defined in the literature [12-15]. Of all the materials utilized by electronic devices, Thermal Interface Materials (TIMs) are particularly important to reliability. Since the TIM enables proper thermal management of the electronic components, if the TIM fails, the entire device fails.

The testing of the individual materials utilized in a specific electronic device represents a particular challenge above and beyond that of testing the entire device, and TIMs are no exception. During the development of TIMs, the actual electronic devices are typically unavailable so the TIM designers must replicate the expected conditions of the actual electronic device (i.e. surface materials, clamping pressure, and geometry). Furthermore, in most electronic devices TIMs are utilized for multiple conditions (e.g. TIM1 for silicon / heat spreader interface, TIM2 for heat spreader / heat sink interface), therefore, unique fixtures must be employed for each condition, requiring a separate reliability test for each condition.

Most modern TIMs display adequate performance just after assembly, but after reliability testing only the truly reliable TIMs maintain their performance. Furthermore, while a TIM may show excellent reliability performance in a fixture designed to replicate one condition of the electronic device, it may show marginal to poor reliability performance when tested for another condition. This paper will discuss the importance of test conditions during the THB and HAST reliability testing of TIMs, and introduce an improved TIM that was designed based upon these findings.