For TIM materials what is the difference between Thermal Conductivity and Thermal Impedance?

TIM or Thermal Interface Materials have a high thermal conductivity to enable heat to pass from the hot component to a heat sink or the heat conductive chassis of the product.

One important aspect when selecting a TIM for your application is knowing the material’s ability to transfer heat, which is often given by way of thermal conductivity. All TIM materials have different thermal conductivity performance which is measured as Watts / meter-Kelvin (W/mk). An example would be our T-P-9 series Void Filler which has a Thermal Conductivity Value of 5 W/mk. With any TIM the higher the value the better, however, when choosing a material, it would also be useful to understand the Thermal Impedance of the material.

Thermal Conductivity is a material property, it is not dependent on the shape/size/thickness of the finished product. Thermal Impedance is a useful measurement to understand when looking at thermal efficiency as this takes into account the thickness of the material. In short, Thermal Impedance is a measure of how fast heat will flow through a particular piece of TIM. When selecting a material, it is therefore important to consider both the Thermal Conductivity and thickness required as this will in turn determine the overall thermal performance of the system.