Direct Bonding of Cu to AlN Ceramic via Atmospheric Plasma Spraying

Aluminum nitride (AlN) ceramics are highly regarded for their excellent thermal and electrical properties, making them highly suitable for numerous applications in high-power electronic devices. However, directly bonding copper to AlN substrates remains a significant challenge, mainly due to the strong covalent bonds inherent in AlN, which result in poor wettability of copper on the AlN ceramic surface. To address this issue, the present study proposes a method for directly depositing a dense copper layer on AlN substrates through the atmospheric plasma spraying (APS) process, thereby obtaining a thick copper layer (~30 µm) with excellent comprehensive performance on the AlN substrates. In this study, before performing APS coating, the AlN substrates were first subjected to pre-oxidation treatment to enhance their wettability with the copper layer. Under the optimized atmospheric plasma spraying process parameters, the maximum adhesion strength of copper on the AlN substrates reached 17.56 MPa, along with a low surface resistivity of 2.66 × 10−3 Ω·mm and a relatively high room-temperature thermal conductivity of 135 W/m·K. High-resolution transmission electron microscopy (HR-TEM) was used to characterize the interface structure, and the results showed that chemical bonding was formed between the copper layer and the pre-oxidized AlN surface—this bonding effectively enhanced the interface adhesion. In addition, this paper also reports that the atmospheric plasma spraying technology can be used to precisely fabricate copper circuits directly onto AlN substrates.