Laser Powder Bed Fusion Additive Manufacturing of Mo and TZM Exoskeleton with Cu Infiltration for New Heat Sinks Configuration

Abstract

This study reports the fabrication and characterization of molybdenum (Mo) metal and titanium‐zirconium‐molybdenum (TZM) alloy exoskeletons with honeycomb cavity structures (HCS) that are infiltrated with oxygen‐free high conductivity (OFHC) Cu under an inert atmosphere as a potential replacement for Cu‐Mo‐Cu laminate in heat sink applications for power electronics semiconductors like GaAs. The thermal expansion behavior and the thermal loading of the starting Mo and TZM structures, and of the Cu‐infiltrated parts are evaluated. The fabricated Mo and TZM structures with density >99% and Mo‐based heat sinks with improved CTE (6.6 × 10−6 K−1) when compared to conventional Cu‐Mo‐Cu laminated heat sinks (CTE = 7.6 × 10−6 K−1). The new Mo and TZM structures promise superior performance due to their closer CTE to that of GaAs and similar semiconductors (CTE = 5.7 × 10−6 K−1). Exposure to temperatures up to 1073 K did not affect the Mo microstructure due to the inherent resistance to recrystallization, while exposure to 1373 K did reduce hardness. In contrast, TZM exoskeletons showed resistance to recrystallization even at 1373 K. The fabricated composite heat sinks showed thermal diffusivity (≈61 × 106 m2 s−1) that is within the upper limits of those reported for commercial laminated heat sinks (45 to 65 × 106 m2 s−1).