High Performance Metal-Based Nanocomposite Thermal Interface Materials Toward Enhanced Cooling Efficiency in Electronic Applications

The inefficient dissipation of heat is a crucial problem that limits the reliability and performance of all electronic devices. Since devices have become progressively smaller, more powerful, and more complex, they dissipate much larger amounts of heat. Currently, thermal greases, epoxy-based composites, phase change materials and solders are the most common types of thermal interface materials (TIMs) used for efficient dissipation of heat. Herein, we describe next-generation TIMs with thermal resistivity lower than existing solder TIMs and with stiffness comparable with existing epoxy-based TIMs. The approach has involved the incorporation of soft ligand functionalized boron nitride nanosheets (BNNS) in a silver metal matrix to fabricate nanocomposite TIMs. BNNS was functionalized with thiosemicarbazide (TSC) such that they have a thiol group sticking out for functionalization. Then, the TSC-BNNS was dispersed in a silver matrix using a novel electrocodeposition method where silver and TSC-BNNS are deposited on a cathode in the presence of an electric field and potential difference to form nanocomposite TIMs. The thermal conductivities were found to be 318 W.m^-1.K^-1. Later, mechanical properties of the developed TIMs investigated using nanoindentation technique showed a reduced modulus of 34.9 GPa. There was more than two-fold reduction reduced modulus of silver matrix in presence of TSC-BNNS. The hardness value corresponding to this sample was about 379 MPa, which is about 3 times lower than the measured hardness values of pure silver (950 MPa). For these materials, the total thermal resistance across interface was calculated to be 0.19-0.45 mm².K.W^-1 for a bond line thickness of 20-100 μm. Considering two extreme cases of epoxy-based and pure silver shim TIMs, our results are significant in advancing the current state of art for TIMs.