Thermal Interface Material

A thermal interface material (TIM) fills the gaps between mating components to reduce resistance to heat conduction. TIMs are most often used between the heat-generating component and the metal housing or other heat dissipating surface of a device.

TIMs come in various forms including gels, greases and pastes as well as pads. The choice of which type to use is based on the specific application and performance requirements of the project. Choosing the right TIM for your application requires evaluating both inherent thermal conductivity and wet out. Inherent thermal conductivity, measured in Watts per meter-Kelvin (W/mK) is a measure of how much heat the material can transfer over time and wet out is how easily the material spreads to fill gaps, replacing air, which has poor thermal conductivity.

Gels and greases offer excellent thermal conductivity with a low viscosity making them easy to apply to small areas where space is limited. They are also good for gap-filling applications where a thicker layer of material is needed. However, they can be more difficult to handle for one-off applications and are prone to pump out when exposed to vibration or thermal cycling.

Pads, on the other hand, are a solid form of TIM and offer high thermal conductivity with low wet out characteristics. They are easy to apply and give consistent results across multiple boards. They are also available in a variety of shapes to accommodate different gap sizes. Some are shaped to match the footprint of the heat sink while others are designed for varying tolerance stack-ups.

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