An electronic assembly having a microelectronic die, a heat spreader and a heat sink. A first thermal interface material is disposed between the microelectronic die and the heat spreader. A second thermal interface material is disposed between the heat spreader and a heat sink. The first and second interface materials each comprising a phase change polymer, a solderable material and a plurality of thermally conductive non-fusible particles. The solderable material interconnecting the non-fusible particles to form a plurality of columnar structures within the phase change polymer.