Interfacial microstructure and mechanical properties of diffusion-bonded W–10Cu composite/AlN ceramic using Ni–P and Ti interlayers

Cu/AlN joints are critical for applications in electronic components and high-power electronic devices. To prevent mechanical failures at the interface of the joints resulting from mismatched thermal expansion coefficient (CTE) between Cu and AlN, the W–Cu composite with lower CTE than pure Cu can be used. The choice of interlayers for the W–Cu/AlN joint and their microstructural evolution at the interface during diffusion bonding should be evaluated. In this study, the design and characterization of Ni–P and Ti interlayers for increasing the joint quality between diffusion-bonded W–10Cu (90 wt% W and 10 wt% Cu) and AlN were developed. The effects of the Ni–P interlayer thickness (1.0 and 3.5 µm) and bonding temperature (700 and 800 °C) on the microstructure and corresponding mechanical properties of the joints were investigated. The maximum average tensile strength for the joints reached 26.76 MPa with a Ni–P interlayer thickness of 3.5 µm and bonding temperature of 800 °C. In addition, the phase distribution from the W–10Cu to AlN was determined using X-ray diffraction and electron probe X-ray microanalysis, indicating sufficient diffusion of W–Ni and Ni–Ti in the interfacial zone of the W–10Cu/Ni–P/Ti/AlN joints. Moreover, Cu atoms in W–10Cu diffused into Ni-based layers, forming a solid solution. The fracture location in the joints was influenced by the bonding temperature and thermal shock test. The tensile strength of the joints decreased 20% after thermal shock testing for 100 cycles.