Using Thermal Interface Material: What is It and How to Use It in Aavid Genie

Thermal interface material (TIM) is a crucial part of any thermal management solution. Since it’s physically a small portion of most applications, it’s an easy component to overlook. But using thermal interface material can sometimes make or break a device and it’s associated product.

Thermal Interface Material: The Space Between…

Many engineers focus more on the heat sink design, but often forget to spend time considering how heat gets from their heat source to their heat sink. As you’re probably aware of, even the smoothest surface has some level of surface roughness. This roughness of two surfaces in contact with each other create air pockets. Since air is a good thermal insulator, this impedes heat transfer from one surface to another.

A Closer Look of the Thermal Interface between Devices and Heat Sinks

In the image below, heat coming from the black surface can only conduct through to the grey heat sink at the points highlighted in red. Orange arrows help visualize that heat is coming form the entire black surface, but is restricted through those contact points. Heat is still able to transfer through the blue air pockets, but very little compared to what conducts through those points.

Thermal Transfer Between Surfaces Illustration

 

What does Thermal Interface Material do?

This is where using thermal interface material comes in. TIM replaces most of this air with a material that is more thermally conductive. By using thermal interface material, we increase how much heat is transferred away from the heat source and into the heat sink. Since we replaced the air with a more conductive material, depicted in dark blue, and see that heat conducts across the entire surface. This improves our heat transfer away from the heat source significantly. But notice that we still have small little air pockets in little nooks and crannies, since it’t nearly impossible to remove all air in most cases.

Thermal Transfer Between Surfaces with Thermal Interface Material Illustration

Thermal interface material comes in many different types: electrically isolating or electrically conductive, silicone base or silicone free, compliant or hard, solid or liquid or both, etc. TIM selection is a very application specific decision.

Aavid Genie’s Teammate: Dr. Heat

Because of this, Aavid Genie can’t quite recommend what interface material to use yet. But we have another tool you can refer to called Dr. Heat. Dr. Heat compares different thermal interface materials against each other in your application. This tool contains a library of some of our more popular interface materials and allows you to conduct quick calculations to check if a material can meet your thermal needs.

Dr. Heat Thermal Interface Material Resistance Calculator - Boyd

Consult Dr. Heat for thermal interface material calculations.

Aavid Genie realizes this and has an interface resistance input for thermal interface materials. You’ll be able to define the TIM for each heat source. So when you have a heat source selected in the positioning diagram, you’ll see the specifications on the right update to the heat source you’ve selected.

Heat Source Positioning User Interface in Aavid Genie Screenshot

On the bottom of this card, Aavid Genie has an input to account for interface resistance from using a thermal interface material on that source. If you need help determining what TIM you need or what your interface resistance is, feel free to contact Aavid Design Engineers.

Interface Resistance Parameter Input for Heat Sources in Aavid Genie Screenshot

When using Aavid Genie, don’t forget about using thermal interface material! This small part of your thermal solution can have a big impact on your product’s performance.

What’s your favorite interface material? Email us at aavidgenie@boydcorp.com!

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