A metal encased multilayer stack of graphite sheets used as a passive thermal conductor. In the stack, each sheet has a plane high thermal conductivity along a first axis and a plane of lower thermal conductivity along a second axis. The stack is created to have a three-dimensional shape including a length and a width, and the first axis is aligned parallel to said length, the multilayer stack having a height less than the width. A first metal structure surrounds the multilayer stack of graphite sheets, with the metal structure encasing the multilayer stack along the length, width and height of the multilayer stack.