Al & Cu FOIL THERMAL STRAPS (CuFS®)

(Products Discontinued)

Gold Plated Copper Foil Thermal Strap


Generally, thermal straps made with copper cables offer the best combination of durability, flexibility, thermal performance and low cost.  This is because metallic foil straps are stiff, expensive, and need to be manufactured into longer, heavier, and less efficient installation configurations with 180 degree bends or S-shapes to allow for flexibility/deflection on the lateral axis (to learn more about which strap configuration best meets your needs, visit our Thermal Straps page). However, there are instances where flexibility is not needed in all 3 axes, and tight packaging constraints (limited volume), low operating temperatures, and high thermal conductance requirements, may make an OFHC copper foil thermal strap (CuFS®) a superior alternative to cu rope or graphite straps.

Cu_Foil_Strap_2-resized-600

Though TAI offered (limited) custom CuFS® products since 2014, and our first standard line, the “F-series,” in 2016 - 2020, we have officially discontinued our metallic foil strap lines.

This decision was due to a lack of demand, as our copper and aluminum-copper hybrid straps offer exponentially greater flexibility at a lower unit cost than foil straps (while we manufacture several thousand copper cable straps annually, we never made more than a few foil straps each year), and because copper and aluminum foil straps significantly slowed down our production process with the technicians and machinists. 

As a result, if we cannot substitute a copper cable or graphite rope or sheet strap that will meet your needs, we are happy to provide you with referrals to other suppliers that still offer foil straps and manufacture the products they sell (rather than outsourcing cheap welded shunts or poor quality links from third parties). 

Pictured (Top Right): LAB GRADE Gold Plated Copper Foil Thermal Strap (November 2018). Pictured (Left): Custom, Low Profile, Foil Thermal Strap (July 2013). 

 

CuFS® Standard Product Line - DiscontinuedFlexible Thermal Links - Copper Foil Thermal Strap F5-501

TAI now offers 6 standard models, and our full line of 24 standard models (and the new CuFS™ Catalog).  TAI provides our newest copper thermal strap products in 3 fixed widths, with multiple thickness, installation configuration/design options, and with many of our popular end fitting designs. Just like our cabling/rope straps, these straps can be manufactured and shipped more quickly than custom straps (4 - 6 weeks on average).

 

 

Comparison of Thermal Conductivity

OFHC Copper Thermal Conductivity Graph

 

 Thermal Straps

Pictured (Top Left):  conductivity graph of typical cryogenic thermal strap materials. (Top Right): F5-501 CuFS® pre-conductance test and shipping (April 2018).

 

Thermal Straps__A5-501 AlTS and F5-501 CuFS

ALUMINUM FOIL THERMAL STRAPS 

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. While our CuTS® and X-Series® products are often a better substitute for an Aluminum Foil Thermal Strap (AlTS™), there are some airborne and spaceflight applications which may benefit from an AlTS™ solution (particularly those that are extremely mass sensitive, operating at 50 - 70K, and with a relatively small amount of heat to dissipate).
 
Pictured: A5-501 and F5-501 Thermal Straps being prepared for shipping (December 2018).
 

 

Limitations to Consider

While aluminum foil-based straps can be an ideal solution in certain airborne and spaceflight applications, they have largely been replaced by TAI's CuTS® and PGL™ products.  This is because our copper rope straps provide superior thermal performance and flexibility (at a lower unit cost), and our pyrolytic graphite film straps, TAI's X-Series® PGL™ (while slightly more expensive), offer superior thermal performance, at a small fraction of the mass of an equivalent aluminum link (down to operating temperatures as low as 50K).  Furthermore, TAI's PGL™ products are made using the industry's highest performing carbon material at cryogenic temperatures.
 
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, there are a number of other factors to consider including:
 
1)      Aluminum straps will occupy twice the volume of copper straps for the same thermal conductance.
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.
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