Embedded computing systems are rapidly increasing in power densities, making thermal solutions a major design concern. In most cases, designers prefer a predominantly conduction cooled approach, which provides the highest reliability. ACT’s Isothermal Card Edge, or ICE-Lok® wedgelocks, are designed to enhance card-to-chassis conduction by enhancing the heat flow through the wedgelocks by making additional contact between the card and the chassis. Learn more about ICE-Lok® and see how it is utilized to improve thermal efficiency in embedded computing systems.
For more information, read our ICE-Lok® product page.
Embedded computing systems are rapidly increasing in power densities, making thermal solutions a major design concern. In most cases, designers prefer a predominantly conduction cooled approach, which provides the highest reliability.
ACT’s Isothermal Card Edge, or ICE-Lok® wedgelocks, are designed to enhance card-to-chassis conduction by enhancing the heat flow through the wedgelocks by making additional contact between the card and the chassis. This wedgelock design offers a 30% improvement in thermal resistance compared to similar sized commercial off the shelf wedgelocks. This enables reduction of component temperatures of up to 10°C in some 100W card applications. ICE-Lok wedgelocks have been thoroughly tested for thermal and mechanical stability with repeated insertion/removal testing. They are compatible with VITA 3U, 6U and 9U cards; and the friction lock feature ensures card deformation is avoided. Let’s see how it works.
In this example, the ultimate cooling is provided by a liquid cold plate along the base of the chassis which runs fluid at 55 degrees C. The electronics board is generating 50 W concentrated near it’s center and has additional components totaling 50 W distributed across the board. To successfully reject the waste heat to the liquid cooled base, the heat must conduct from the components to the conduction card frame edge, through the mechanical retainer or wedge lock and down the card guides to the liquid base. In the baseline example, we are assuming all components are aluminum and the wedgelock is an off the shelf design.
As we analyzed the base model, you’ll notice significant temperature rise from the cold plate to the max card temperature. The total delta T is 69 C. In most cases, that delta T is not suitable for successful operation, therefore designers must find ways to reduce the thermal resistance.
The largest delta T in the system is from the centralized component to the card edge, which means the design is limited by the thermal conductivity of aluminum. By strategically embedding heat pipes, you can greatly enhance the bulk thermal conductivity of the heat spreader. The resultant embedded heat pipe card frame is known as a high thermal conductivity or HiK™ plate.
After reinserting a HiK™ frame in place of the aluminum conduction card frame the max temperature of the card drops from 124C to 96C. HiK™ plates in 6U form factors can routinely achieve thermal conductivities of 600-800 W/m-K, dependent on component placement.
The next area for thermal enhancement is at the frame to chassis interface. Off the shelf wedgelocks provide mechanical attachment, but are not efficient heat transfer devices. Due to limited surface area and poor thermal path through metal to metal interfaces, the overall delta T is pretty significant for a short conduction path. ACT’s ICE-Lok was designed to address both challenges- The design expands in all directions, contacting an additional surface on both the board frame and chassis. This provides more surface area while also bypassing metal to metal interfaces as the primary thermal path.
By changing from an off the shelf wedgelock to the thermally superior ICE-Lok, the designer continues to reduce the overall delta T of the system. The card max temperature is now 92 C, which is a total delta T of 37 C. With these two minor changes, neither of which significantly effects geometry or weight, the system operates over 30 degrees cooler than the baseline model.
The final area effecting overall delta T is the conduction through the card guide or chassis. Each sidewall must conduct heat from the card interface to the liquid cooled base. Again, the baseline is aluminum with a thermal conductivity of 167 W/m-K. To reduce this gradient, we convert the chassis to a HiK™ sidewall by embedding heat pipes.
This final change drops the overall delta T by an additional 13 C. The max card temperature is now 79 C, which is safe operating temperature for most electronics. From the baseline to the fully thermally enhanced model, the thermal savings was 45 C. This type of savings can allow for higher power densities or added margin to the system.
Thanks for joining us for this example of how ACT’s ICE-Lok wedgeloks can improve thermal performance.
For more technical information about ICE-Lok®, as well as to access an installation guide, visit our website at www.1-act.com. ICE-Lok wedgelocks are aluminum-based material available in both three-eighths and one-quarter inch cross sections with standard 3U, 6U, and 9U lengths. A variety of coatings are also available including: Clear Chem Film, Electroless Nickel, and Black Anodized. The Thermal Experts at ACT are waiting to discuss your embedded computing systems application and help you choose the right ICE-Lok wedgelocks for you.