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Thermal straps and thermal busses rely on high conductivity materials to transport thermal energy away from heat sources to a safer region, even in the most challenging environments. Thermal busses offer conduction cooling in a rigid, high strength configuration whereas thermal straps enable consistent thermal performance in a flexible format. These conduction-based thermal management systems do not rely on any moving components and exhibit long and reliable lifetimes, even in microgravity conditions.
Aluminum and copper are widely used materials for thermal straps and thermal busses, but Eaton’s material expertise enable us to utilize other film materials such as graphite to enhance the performance of thermal straps and busses.
Eaton leverages its manufacturing expertise to combine graphite into assemblies to create passive, lightweight, reliable and highly thermally conductive solutions called k-Core®. Our proprietary process enables us to hermetically seal annealed pyrolytic graphite into an encapsulating metal, protecting the brittle graphite, but reducing the weight of the parent metal.
Thermal busses integrated with k-Core® combine the lightweight benefits of graphite with the strength of copper or aluminum and offer increased thermal conductivity compared to the enveloping material.
By utilizing flexible materials like copper foil, aluminum foil or polyimide film to contain and support graphite sheets, thermal straps with k-Core® offer both performance and physical flexibility in your thermal management solution.
Thermal straps, also called thermal links, provide a flexible, lightweight conduction path for moving heat to a cooling solution. This advanced solid conduction solution consists of highly conductive, flexible materials connected to headers to mount on separate surfaces which enable point-to-point heat transfer. Thermal straps are a completely passive solution, eliminating maintenance costs in a lightweight solution for semi-dynamic, weight sensitive applications. Eaton customizes thermal straps to meet conductance, stiffness or flexibility and mass requirements.
Custom metal foil thermal strap assemblies are fabricated from a variety of metals including aluminum and copper. With special consolidation methods, Eaton can fabricate thermal straps with metal foils as thin as 0.0005 to 0.0100 inches to ensure high conductance and high flexibility.
Eaton’s k-Core® (encapsulated graphite) thermal straps are highly conductive and formable for semi-dynamic heat transfer components. Encapsulated graphite thermal straps are fabricated with annealed pyrolytic graphite (APG) sheets, a highly thermally conductive material, contained in a stronger yet flexible film material, like polyimide, copper or aluminum foil designs. k-Core® thermal straps perform effectively with aluminum encapsulant thicknesses of as little as 0.002 inches. Encapsulated graphite thermal straps offer a solution that bends with the strength of the external material with a higher effective thermal conductivity and less weight than a completely metal construction.
Encapsulated graphite thermal straps are lighter in weight, smaller in size and offer better conduction than traditional thermal solutions. Eaton’s thermal straps increase design flexibility while maintaining performance. APG straps can achieve a thermal conductivity up to 1200 W/mK. Typically, encapsulated graphite thermal straps are 3 to 5 times more conductive per unit mass than aluminum foil designs and 9 to 15 times per unit mass of copper. k-Core® thermal straps also show increased conductivity at cryogenic temperatures and are proven effective in dissipating heat from high-powered electronic components without maintenance.
A thermal bus is a conductive, rigid component that serves as a pathway for passive heat transfer. Thermal busses are an ideal solution where active systems like air cooling or liquid cooling are not viable options. Without any moving components like fans or pumps, thermal busses transport heat reliably for extended lifetimes ensuring consistent thermal management for your application.
By encapsulating lightweight, but highly thermally conductive annealed pyrolytic graphite, Eaton’s k-Core® thermal busses can act as a drop-in replacement for solid metal solutions. Thermal busses leveraging APG cores help significantly reduce semiconductor temperatures with less weight, which is critical in demanding space, defense and transportation applications.
Encapsulated graphite thermal busses can reach in-plane conductivities up to 1700 W/mK at isotropic room temperatures. The thermal coefficient of thermal expansion (CTE) of thermal busses can also be tailored to match semiconductor devices for reliable direct mounting.
Performance comparison |
Aluminum |
k-Core® (Encapsulated graphite) |
| Foils | 137, each 0.004” thick | 10, each 0.014” thick |
| Strap thickness | 0.55" | 0.14" |
| Conductance | 0.65 W/K | 0.82 W/K |
| Weight | 0.85 lbs | 0.17 lbs |
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