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Clad Thermal Interface Materials

Continuing with the topic of thermal interface material options, a popular material choice is a clad metal thermal interface preform including multiple layers of various metals, or a metal preform clad with an adhesive synthetic material. For specific applications where an interface is sandwiched between two drastically different substrates, clad metal preforms are great. Using clad preforms containing multiple metals, it is possible to clad a stiff material on one side which prevents deforming and a soft, conductive material on the other.

While there are applications that these materials cater to, it is important to realize the full impact of using such a TIM material.

Bob Jarrett recently wrote a summary of the resistance impact of adding an adhesive layer to an existing metal interface material.

Bob wrote:

The adhesive on the interface will act as another interface layer, increasing the thermal resistance, additively. The typical acrylic polymer adhesive has a thermal conductivity of ~0.1 W/m-K. If this adhesive is applied as a typical ½ mil (13 μm) film, the resistance increase is:

R = x/k = (13/10000) cm / (0.1/100) W/cm-K = 0.13 cm²-°C/W.

This is added to the 0.06-0.08 cm²-°C/W for the Heat-Spring a total resistance of about 0.2 cm²-°C/W. The thin layer of adhesive more than doubles the resistance.

This posting is not meant to deter you from using cladded interface materials, just to help you realize the potential effects of using such a material. Every layer added to the interface also adds some amount of resistance.