Challenges for Selecting Appropriate TIM2 Material for CPU

Priyanka Dobriyal, Sumit Soni, Chet Lee
Intel Corporation
Hillsboro, OR, USA

Ever-increasing amounts of heat in a small and very concentrated area, which can be detrimental to CPU performance. To dissipate generated heat to the external environment, a heatsink with a thermal interface material (TIM2) is mounted on the CPU. However, finding a suitable TIM2 is not simple. Some of the parameters to benchmark TIM2 include thermal conductivity, thermal interface resistance, bond line thickness, conformity and viscosity. This paper presents a case study that focuses on evaluating the thermal performance of various TIM2 materials and other critical parameters which may need further improvement from supplier's side. This paper provides a methodology for selecting and qualifying a potential TIM2 material for various applications including automotive, servers, personal computers and internet of things.

A streamlined method of TIM2 qualification aligned with product needs was documented in this paper. Materials were analyzed as-received as well as post aging. The results hence include the performance of a TIM2 material after number of years on field. Performance of TIM2 post reliability testing further provided data which extrapolates to number of years on field. Qualitative analysis by visual inspection looking for air gaps, FTIR for organic characterizations post aging vs. as-received determined changes post reliability tests. Thermal performance, chemical nature and morphologies didn't show any effect post shock and vibration. However, post baking differences were seen and documented. Thermo-mechanical studies were performed keeping CPU operating range in mind making sure that those do not affect the TIM2 performances. These results give a fairly straight forward decision making criteria for TIM2 selection.