It’s best to start this discussion with a more scientific definition. CTE mismatch is a phenomenon that occurs when two materials with different coefficients of thermal expansion (CTEs) are joined together. When the temperature of the joint changes, the two materials will expand or contract at different rates, which can cause stress and eventually lead to failure.
The CTE is a measure of how much a material expands or contracts in response to a change in temperature. For example, steel has a CTE of about 12 × 10^-6 per degree Celsius, which means that for every 1 degree Celsius increase in temperature, steel will expand by 0.0012%.
When two materials with different CTEs are joined together, the material with the higher CTE will expand more than the material with the lower CTE. This can cause stress in the joint, as the two materials try to pull apart. If the stress is too great, it can cause the joint to fail.
If you’ve gotten this far, you probably already understand why this is a concern when designing electronics. CTE mismatch can lead to component failure, and that’s why its such a concern with thermal interface materials.
This is what gave rise to the softer and softer thermal pads, also known as Gap Pads in this industry. The technology has grown quite significantly over the years. Many suppliers offer pads that are thick, soft and tacky, so that they are able to absorb the expansion and contraction of different materials in an electronic assembly, while maintaining the interface and keeping the heat flowing the in the direction you want.
As always, if you want to take this a step further and find the TIM that is right for you, reach out and we’ll get you on your way.
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