Direct Low-temperature Sintering of Cu Nanoparticles on Laser-metallized AlN Ceramics by UV Nanosecond Laser

Aluminum nitride (AlN) ceramics are considered ideal materials for power electronics packaging substrates due to their excellent thermal conductivity and favorable thermal expansion coefficient matching with Si and GaAs. However, AlN exhibits poor wettability with metals, necessitating pre-oxidation or the introduction of solder, glass adhesives, or transition layers to establish a connection between AlN ceramics and metal conductive layers. This not only increases costs but also introduces additional thermal resistance. Laser-induced technology has emerged as an effective method for the metallization of AlN. By applying a laser to the ceramic surface, the AlN is decomposed to form a conductive aluminum layer, enabling direct connection between AlN and metals. Furthermore, the laser-based method for creating conductive circuits on ceramic substrates eliminates the need for photolithography, development, or etching processes, thereby reducing process complexity. Given the potential of laser- induced metallization, understanding the interaction between laser energy and AlN is crucial for optimizing the process. This paper investigates the effects of laser power and scanning speed on the surface morphology, chemical composition, and properties of AlN ceramics. It also prepares high-performance Cu nanoparticles, which are expected to reduce the temperature required for AlN-Cu connection from over 1000°C to 650°C, resulting in a copper film with a resistivity of 10.2 µΩ•cm (corresponding to 17.2% of the conductivity of bulk copper).