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High Temperature TIM for Power Modules that Eliminates Pump-out and Dry-out Failures

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Overview: Thermal interface materials (TIMs) are a necessary evil in today’s high power density inverter designs. Until now engineers have had to compromise between thermal performance, maximum operating temperature, reliability, cost, and ease of installation. We will review common failure modes associated with traditional TIM solutions and discuss new alternatives to address these concerns in current and next generation power modules.

Prashanth SubramanianMr. Prashanth Subramanian
As the manager of the New Product Development group at Graftech International, a world leader in graphite material science, Prashanth is responsible for the development and commercialization of solutions to the consumer electronics and Thermal Interface for high powered device markets. Prior to joining Graftech, Prashanth worked at SUMCO USA in the Development Engineering group providing solutions to the high-voltage device market.
Prashanth holds a degree in Electronics Engineering from Shivaji University (India) and a M.B.A. from The Ohio State University.

The following are questions presented to the speaker by the attendees during the webinar, along with answers to each.

According to yesterday’s PCM webinar, a PCM’s thermal impedance gets improved overtime while a TIM’s thermal impedance degrades. What are your thoughts?
Answer: The thermal impedance for the HT-C3200 does not change over time, in fact we have seen slight improvement for graphite based TIMs (see paper on the properties of various TIMs, the graphite tested was our Hi-Therm HT1205A, but similar performance over time can be seen for all our graphite based TIM.
Study of Thermal Interfaces Aging for Power Electronics Applications

What is thickest graphite solution available?
– The HITHERM™ range of Thermal Interface Materials are available between 127microns and 500 microns.
– The HITHERM™ HT-C3200 Thermal Interface Material is only available at a starting thickness of 200 microns, if your needs are different please feel to contact us at

Does graphite stick to the surface?
Answer: The HT-C3200 does not stick to the surface, there are no adhesives or coatings, the material is held in place when bolted down to the base plate.

How can I get a sample to evaluate?
Answer: Use this link to request samples.

What is the minimum pressure required to get a reasonable thermal resistance?
Answer: The thermal impedance decreases significantly with pressure, the improvement in performance can be felt starting around 15 psi depending on size of the part and how the force is applied, the relationship between pressure and thermal impedance can be found here.

What is a typical thermal conductivity of the material?
Answer: The in-plane (XY plane) thermal conductivity increases significantly with pressure and will be in the range of 800 W/mK at 100 psi (~700 kPa)

Can we reuse the same sheet?
Answer: The HT-C3200 retains the thickness under compression and does not have spring back, therefore we do not recommend re-using the sheets as the gap profile might have changed and the material will may not perform at its peak.

How does the cost of this compare to indium heat springs?
Answer: Please contact me at to discuss your application in more detail and estimate price for the same.

What is the through plane conductivity?
Answer: We have analyzed that the total thermal impedance has a more prominent role in the overall performance of the material in application, the total impedance to pressure information can be found here.