Pressure-assisted CU sintering for SiC Die-attachment application

Abstract

This dissertation investigates copper sintering as a high-temperature die-attach technology for wide bandgap (WBG) power semiconductors such as SiC and GaN. WBG devices require advanced packaging solutions to maintain performance under high power, fast switching, and elevated temperatures. The study first employs molecular dynamics simulations to elucidate sintering mechanisms, microstructure evolution, and particle size effects, showing that applied pressure promotes plastic flow, densification, and pore reduction, while substrate pinning may induce residual stresses. Next, a self-developed Cu paste was fabricated and sintered under various temperature, pressure, and time conditions. Thermal and electrical conductivity, die shear strength, and microstructural evolution were evaluated, identifying 250°C, 3 min, and 20 MPa as an optimal processing window. Mechanical characterization including indentation hardness, elastic modulus, and creep behavior demonstrates the effect of process parameters on room-temperature properties and long-term reliability. Finally, pressure-assisted Cu sintering was applied to SiC power modules and compared with Ag-sintered modules. Both static and dynamic tests, including thermal cycling and high-temperature storage, confirm that Cu-sintered modules achieve equivalent performance and reliability at lower cost. The work establishes a systematic understanding of copper sintering processes, linking simulations, materials, processing, and application, providing a robust methodology for WBG power electronics packaging.