Aluminum nitride ceramics have excellent electrical and thermal properties and are considered to be the most promising high thermal conductivity ceramic substrate materials. In order to seal the package structure, mount components, and connect input and output terminals, the surface and interior of the aluminum nitride ceramic substrate need to be metalized.
The reliability and performance of ceramic surface metallization have an important impact on the application of ceramic substrates, and firm bonding strength and excellent air tightness are the most basic requirements. Considering the heat dissipation of the substrate, it is also required to have a high thermal conductivity at the interface between the metal and the ceramic. The metallization methods on the surface of aluminum nitride ceramics include the thin film method, the thick film method, the high melting point metallization method, an electroless plating method, direct copper cladding method (DBC), etc.
Let me introduce the most common method – Direct copper cladding (DBC)
Direct copper cladding is a metallization method for bonding copper foil on the surface of AlN ceramics. It is a new process developed with the rise of chip-on-board packaging technology. The basic principle is to introduce oxygen element between Cu and ceramics and then form Cu/O eutectic liquid phase at 1065~1083°C, and then react with the ceramic matrix and copper foil to form Cu(AlO2)2, and in the intermediate phase, The bonding between the copper foil and the substrate is realized under the action of the Because AlN belongs to non-oxide ceramics, the key to the copper coating on its surface is to form an Al2O3 transition layer on its surface and to achieve effective bonding between the copper foil and base ceramic under the action of the transition layer.
The direct copper cladding method has good thermal conductivity, high adhesion strength, good mechanical properties, and is easy to mass-produce, but the oxidation process conditions are not easy to control.