The effect of Shore hardness

The Effect of Shore Hardness on the Thermal Conductivity of Gap Pads

Gap pads are indispensable thermal interface materials (TIMs) in the electronics industry, enabling efficient heat transfer between electronic components. Choosing the right gap pad is crucial for maximizing component performance and service life. One key factor influencing the thermal behavior of gap pads is Shore hardness.

What is Shore hardness?

Shore hardness is a measure of the hardness of elastomeric materials and is specified using different scales. The Shore A scale is used for softer materials, while the Shore D scale applies to harder materials. Gap pads are available in a wide range of Shore hardness levels—typically between 20 Shore A and 80 Shore A.

How Shore hardness affects thermal conductivity

A higher Shore hardness value means the gap pad is firmer and less compressible. This can reduce effective thermal performance because the actual contact area between the gap pad and the components being cooled may decrease. Insufficient compression can lead to air pockets or gaps between the component and the gap filler, which obstruct heat transfer. For this reason, softer (lower Shore hardness) gap pads are often advantageous, as they conform better to surface irregularities and provide a larger real contact area.

Risks of Shore hardness being too low

However, a gap filler that is too soft can also have drawbacks. A very soft material may deform under pressure, resulting in insufficient mechanical stability and potentially poorer thermal performance. In addition, soft materials can lose their shape at high temperatures or over long periods of time, which can negatively affect performance.

Material formulation and fillers

The thermal conductivity of a gap pad is strongly influenced by the base material and the fillers used. Common fillers include aluminum oxide or boron nitride. As filler concentration increases, thermal conductivity and material hardness typically increase as well—while elasticity decreases. Manufacturers continuously work to find the best compromise, though these optimizations often come with higher costs.

Conclusion: Choosing the right gap pad

In summary, Shore hardness has a significant impact on the thermal performance of gap fillers. Engineers and designers should select the appropriate gap pad based on the specific requirements of the application—such as surface quality, operating conditions, and the required thermal conductivity. Carefully balancing Shore hardness with other material properties is essential to achieve optimal heat transfer and reliable long-term performance in electronic applications—while keeping cost in mind.

As you can see, the topic is somewhat complex. But fortunately, the specialists at Infratron are happy to support you in implementing the right solution for your application.