A novel, autonomous thermal connector

A novel replacement for traditional wedgelocks used to mount PCB boards to cold plates is presented. This project began as part of a DARPA design competition to develop a field reversible thermal connector that could be repeatedly assembled and disassembled without the use of tools while providing constant thermal resistance. The team from UCLA was tasked with designing a new device to meet these constraints. The design meets the DARPA goals and significantly reduces the thermal resistance between the electrical board and the heat sink. The device consists of opposing aluminum wedges, driven by thermally actuated Nitinol springs, which slide against one another to provide the requisite locking force to hold a board in place and decrease contact resistance between the interfaces. These smart material springs push the wedges towards the outside of the device, elevating the upper surface and locking the board in place on the cold plate. The design increases the contact area between the components and decreases the thermal resistance relative to current devices. Experimental results have shown that the UCLA team has addressed the chief design problems posed by the REVCON program. Nitinol has been shown to be an effective material for use as a thermally actuated spring capable of repeatedly engaging and disengaging without the use of tools. The wedge locking force increases with rising temperature, enhancing its thermal performance. The UCLA design has been shown to out-perform similar sized current state of the art wedgelock designs in terms of thermal resistance. Reductions in thermal resistance of 30%-45% have been demonstrated and shown to be repeatable. Our prototype design increases the interfacial contact area which has a dramatic impact on performance. This means that higher power density electronics can be utilized or that more real estate will be made available on current computer boards in order to maintain current performance. Further, the use of thermally actuated leaf springs removes the need for mechanical force for installation allowing for less installation time.