An electronic assembly includes a heat source having a maximum operating temperature, a heat dissipating device, a thermal interface material sandwiched between the heat source and the heat dissipating device. The thermal interface material includes a base and a plurality of first thermally conductive particles dispersed in the base. The first thermally conductive particles have a size monotonically changing from a first size less than 100 nanometers and a first melting temperature below the maximum operating temperature, to a second size larger than 100 nanometers and a second melting temperature above the maximum operating temperature when the heat source operates at a temperature above the first melting temperature and at or below the maximum operating temperature.