Conventional power electronic modules employ a direct bonded copper (DBC) substrate and multiple interface layers to dissipate heat. However, reliability issues arise due to the coefficient of thermal expansion (CTE) mismatch that exists between the metal, ceramic, and semiconductor materials in the conventional module. Significant performance enhancement can be achieved by eliminating the DBC and developing an integrated substrate/cold plate with a low CTE mismatch throughout the package. To address this need, we have demonstrated the ability to directly bond the aluminum nitride (AlN) substrate to an AlSiC heat sink through transient liquid phase bonding using a Cu–Al binary system. Fabricated samples are found to have good interfacial adhesion. The novel bond material exhibits properties analogous to AlSiC and is analyzed for thermal, mechanical, and metallographic properties. The novel structure demonstrated in this work will enable smaller, lighter, and more reliable power modules, when compared to traditional configurations.

Dispersions containing 1 mg/mL of several carbon nanomaterials were used to deposit films containing 1 to 20 layers. The electrical properties of the composite films were characterized via impedance spectroscopy along two directions: in-plane on the film topmost surface and also through the thickness. It was found that carbon black nanoparticles never achieved full in-plane interconnection while the multiwalled carbon nanotube (MWNT) and single-walled carbon nanotube were already percolated at one layer. Graphite flakes showed a complete percolation curve that allowed its resistance to change by 6-7 orders of magnitude. The differences in the microstructure, electrical response, and thermal decomposition behavior of these carbon nanomaterial-paper substrate films were explained by detailed equivalent circuit analysis of the impedance spectra. Interpretation was supplemented by scanning electron microscopy images and thermal analysis via Differential Scanning Calorimetry/Thermogravimetric Analysis (DSC/TGA). Thru-plane electrical properties were for the most part similar, although only films with short MWNT showed a clearly infiltrated network structure.

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