High Thermal-Conductive Packaging Composites Based on Uniform Dispersion of 2D Materials

The scaling of integrated circuits (IC) has posed significant challenges, particularly when aiming for nanometer-level scales capable of accommodating billions of transistors. To keep up with Moore's Law, IC industry has shifted towards developing three-dimensional integration (3DICs). The use of 3D packaging technology has allowed chips to incorporate numerous additional functionalities. While the calculation capability increased substantially by dielet stacking, power density per area increased as well. In this way, the design of 3DIC has intensified the research focus on thermal management. While heat dissipation is managed through metals in the TSV design of 3DIC, the additional supporting approaches of thermal dissipation capability by IC packaging remain unsolved. Conventional packaging materials have shown poor thermal conductivity, typically ranging from only 1 to 2 W/mK for decades, despite having maximum contact area with the stacked dielets. Consequently, it is crucial to develop innovative strategies to tackle these problems, potentially utilizing packaging materials with high thermal conductivity. While commercially available packaging materials like polymer and epoxy are lightweight, inexpensive, and easy to process, they suffer from low thermal conductivity properties. This is primarily because conventional techniques are unable to address the issue of percolation, where the stuffed and isolated ceramic particles blended that were used to enhance the thermal conductivity can not form the continuous phonon conductive path. In this study, we have successfully tackled this issue by dispensing 2D materials as the filler of packaging materials to develop novel composites with high thermal conductivity. The filler incorporates graphene, which exhibits excellent thermal conductivity, weaves continuous networks inside the epoxy, and forms thermal conductive network. To maintain the structural integrity and successful dispersion of the graphene, cellulose nanofibers (CNF) with 1D structures were used. The resulting graphene/CNF structures can form continuous heat dissipation network. Through the blending of the graphene/CNF filler, the thermal conductivity of the polymer, polypropylene, can be increased by 270 times, rising from 0.2 W/mK to 54 W/mK, and epoxy can be increased by 66 times, rising from 0.14 W/mK to 9.35 W/mK. While keeping the superior high thermal conductivity, our composite still maintains low leakage that shows a promising candidate for the next generation packaging materials.