proper and effective thermal management and heat dissipation for electronic devices from computers to led lighting to solar panels are critical for its performance and reliability.  thermal conductivity of a thermal interface adhesive or compound is commonly used as a “gauge” of how good it may be in helping to dissipate heat from a device. this should not be the only measure for the potential effectiveness as a thermal interface for different application conditions and requirements.  this article discusses the various aspects of thermal interface materials and their use.

various applications and requirements need to include at least the following:

1. whether the interface must also serve as a mechanical fastener (i.e. adhesive).  if yes:
   1. how large is the bonding area? bonding areas larger than a square centimeter will require a more flexible adhesive.
   2. are the coefficients of thermal expansion (cte) on the device and the heat-sink different? this is true with the cte of silicon (3ppm/°c) and aluminum (23 ppm/°c) or copper (18ppm/°c). using these materials the adhesive should be more flexible to absorb different shear stress and interfacial peel.
   3. is the expected operational temperature higher than a commercial specification of 85°c or above the military scale of 150°c?
   4. is the expected operational temperature expected to be lower than usual, - 20°c or -55°c? again, lower temperature will induce proportionally higher internal and interfacial stresses that are best accommodated with more flexible thermally conductive adhesive.
2. whether the interface must also serve as mechanical fastener (i.e. adhesive). if no:
   1. while thermal grease is typically the easiest to apply and get the best performance, is thermal grease acceptable for the expected life of the device without the traditional worry of “thermal cycling pumped out” or “dry out” over higher temperature operations? typically the issue of higher swings of operational temperature from ambient becomes more of a concern. the larger physical gap of the interface of more than 75 microns will reduce capillary forces and thus be more susceptible to the lower energy surface greases (e.g. silicone based) to be pumped out over long-term.
   2. how large is the bonding area? larger bonding areas than a square centimeter will require more compliant flexible adhesive.
   3. are the coefficients of thermal expansion (cte) on the device and the heat-sink very different? typically, this is true with the cte of silicon (3ppm/°c) and aluminum (23 ppm/°c) or copper (18ppm/°c). again, using these materials the adhesive should be more flexible to absorb different shear stress and interfacial peel.

to see the rest of this free article on ai technologies web site, please click here:  effective thermal management with different thermal interface materials for different applications

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