Aluminum Thermal Straps
Flexible Thermal Links
TAI no longer offers aluminum foil thermal straps, due to low customer demand and high manufacturing costs when compared with copper straps. While aluminum thermal straps/aluminum thermal links (AlTS) may be beneficial in some very limited applications, it is important to understand that AlTS are really only one type of thermal strap that should be considered for a unique combination of performance parameters. For example, AlTS can sometimes have a slight advantage over copper thermal straps (CuTS) and graphite thermal straps (GFTS) under a very narrow set of parameters that include trade offs between thermal conductance, mass, volume, and stiffness. And while aluminum thermal straps may seem ideal for a particular application, they are not able to outperform a copper or graphite thermal strap unless:
1. (In some cases) the operating temperature is between 50 K and 110 K
2. Mass is critical, and a longer S or U-shaped aluminum strap is not heavier than a shorter copper rope or carbon based strap, bridging the same gap.
3. A large enough Envelope (volume) is available to accommodate a larger thermal strap cross-section and bend geometry
Because 1100 Al has roughly one third the density of copper and half the thermal conductivity, intrinsically there is a mass benefit of up to one third less for aluminum compared to copper straps. However, even within the temperature, mass and envelope constraints referenced above, there are a number of other factors to consider including:
1) Aluminum straps will be about twice as large as copper straps for the same thermal conductance and often do not conform to a well-defined form.
2) Aluminum straps are limited to stacked-foil configurations that do not provide good flexibility on each axes. This means that curvature must be included in the thermal strap design to permit directional flexibility between the strap ends. When this is done, more mass and volume are added to the strap in order to maintain a specified thermal conductance, thereby reducing any benefit over copper braided thermal straps.
3) Aluminum readily forms an oxide that can greatly degrade thermal performance at interface locations without proper surface passivation measures.
4) Aluminum foil straps are far more expensive than TAI's CuTS™, and competing AlTS are the same price as TAI's GFTS™ products.
5) Aluminum straps have more handling and integration constraints than copper rope straps.