Graphite Sheet Embedded in an Organic Flip-Chip Package for Heat Spreading

We propose and evaluate the embedding of a graphite sheet in an organic substrate for hot-spot heat-spreading in a flip-chip semiconductor package. Graphite sheet has superior thermal characteristics, such as 1500-1700 W mK(x, y) and 5-7 W m K(z). When it is located near a heat-generating device, it is expected to spread that heat effectively. Embedding a graphite sheet in a heat-generating device may be possible, but the graphite is electrically conductive, and so must be insulated, which is challenging. We therefore propose embedding the graphite sheet in the organic substrate. In this study, the fabrication process, and the thermal, mechanical and electrical performances are evaluated. As one example of our thermal simulation results, in a two-chip-stack configuration with a 20 mm × 20 mm top chip with a heat density of 250 W cm², centered on a 0.5 mm × 0.5 mm bottom chip, our proposed structure can reduce the maximum chip temperature by 4.8° C (from 69.2° C to 64.4° C).