Reliable copper-silicon nitride composites as circuit carriers for power electronics
Structured metal-ceramic substrates are an important component for power electronic assemblies as circuit carriers. Existing solutions, such as direct bonded copper-aluminum oxide (DBC) or active metal brazing (AMB), no longer meet the requirements of electromobility and the potential of new silicon carbide (SiC)-based semiconductor components. SiC increases the demands on the substrates for mounting the semiconductors and cooling the circuits. Composites with silicon nitride ceramics (Si3N4) with their outstanding mechanical properties promise a solution. This makes metal-ceramic substrates possible that exhibit significantly improved stability against active and passive thermal cycles in power electronic assemblies.
In the CuSiN joint project, Fraunhofer IKTS and its partners developed reliable and high-performance copper-silicon nitride composites (Cu-Si3N4) using active brazing. Ceramic Si3N4 substrates with thicknesses < 320 μm, produced by multiwire sawing of sintered Si3N4 blocks, already exhibit thermal conductivities > 90-100 W m-1K-1 and strengths > 700 MPa. The basis for this is formed by particularly low-oxygen Si3N4 powders in combination with aluminum-free additives. Another new feature is the possibility of sintering compact Si3N4 compacts with dimensions of up to 5.5 x 7.5 inches to form homogeneous and high-quality structures.