Un "Lok"-ing the Thermal Bottle Neck in Military Chassis

It is well known that the largest thermal gradient in military chassis is located between the card and the frame.  For reference, in the typical military chassis, seen below, there are 3 primary thermal resistances:

  1. Heat Spreading from source components to the card edge
  2. Conducting heat through a mechanical retainer clamp (wedgelock)
  3. Rejecting heat from the chassis

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The major thermal bottleneck is position #2, where the card is connected to the chassis frame.  The currently accepted solution is to use wedgelocks, available from a variety commercial suppliers.  Sure, these wedgelocks also provide some thermal relief, but have never been optimized for this purpose.  Their main benefit is to provide mechanical stability of the cards within the frame.  However, in some critical military applications, lowering the operating temperature of the electronic components, even a few degrees, can be the difference between success and catastrophe.

After hearing customers experience pain caused by the wedgelock thermal bottleneck, ACT took action! Through concept brainstorming, internal research and development and a funded SBIR project, ACT developed the Isothermal Card Edge retainer clamp: ICE-Lok™.

The value of this innovation is its simplicity- when analyzing the thermal challenge, it was quickly realized that the driving force of the poor heat transfer was (1) limited contact area and (2) metal to metal interfaces. The ICE-Lok™ was designed to expand in both directions creating additional surface area for heat transfer. The added benefit is the heat naturally passes from board to chassis or board-ICE-Lok™-chassis without the need to for sequential heat transfer through metal interfaces within the clamp. Altogether, the ICE-Lok™ has demonstrated over 30% thermal improvement over traditional COTS wedgelocks. See the Figure below for heat path of ICE-Lok™ compared to traditional wedgelock.

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And all this is achieved without compromising mechanical integrity.

ACT has a pending patent for this design and is currently working with customers to further optimize the design!

 For more information visit our ICE-Lok page