A card retainer mechanism is mostly the preferred tool to lock and unlock a Printed Circuit Board (PCB) into the chassis to have a conduction path as well as fasten the card simply. There is always a thermal resistance between the chassis wall and the card retainer. Depending on the design and applied torque, the thermal resistance can differ. In this study, the task of the card retainer is added to the cold plate where a high-power PCB is attached for cooling. Due to the nature of the card mechanism, there is some space and a long steel threaded screw which decreases the thermal conductivity of the overall system noticeably. Therefore, in this study, a novel precise wedge card mechanism without a moving part is included on the cold plate edges to mate both the cold plate and the chassis wall to have lower contact resistance. A high-precision milling machine is used to have a wedge on the cold plate ends and the chassis slot intersection. It is also milled with accuracy to have sufficient contact area and pressure. Mechanical tolerances are very important for both parts and a very thin thermal interface or aluminum foil can be preferred to improve the contact resistance a little more. In the end, better thermal performance is obtained with a higher contact surface without any card retainer mechanism. All studies are performed both numerically and experimentally to evaluate the novel approach. In conclusion, thermally promising results are obtained for serving in harsh environments.