A thermally conductive wedgelock having improved thermal conductivity is used to secure a circuit card assembly in a card guide slot formed in a housing of an electronics package. The circuit card assembly has a thermal mounting plate that is used to secure the assembly in the slot. The thermally conductive wedgelock secures the circuit card assembly in the housing and conductively couples heat from the circuit card assembly to the housing by way of the card guide slot. The wedgelock provides a secondary heat path to the card guide slot to housing in addition to the primary heat path through the thermal mounting plate. Apparatus is provide for expanding the wedgelock in the card guide slot to secure the circuit card assembly therein. The thermally conductive wedgelock may be made of copper or other metal having high thermal conductivity. The wedgelock preferably comprises two tapered wedges, and has a guide that prevents rotation between the adjacent wedges.