Pressure-assisted direct bonding of copper to silicon nitride for high thermal conductivity and strong interfacial bonding strength

To achieve superior thermal and mechanical properties of copper-bonded (Cu-bonded) Si3N4 substrate, a pressure-assisted direct bonded Cu (DBC) technique was applied to bond Cu foil with Si3N4 plate. The effects of oxide layer (SiO2) thickness of Si3N4 plate on the microstructure, thermal and mechanical properties of the Si3N4-DBC samples were investigated. The successful bonding of Cu foil to Si3N4 plate was confirmed by the presence of the interfacial products of Cu2MgSiO4 and CuYO2. Additionally, it was demonstrated that a thin SiO2 layer can result in a discontinuous distribution of interfacial products while a thick one can lead to the formation of pores in SiO2 layer. Notably, the sample prepared by Si3N4 plate with 5-μm-thickness SiO2 layer and Cu foil with 5.9-μm-thickness oxide layer (Cu2O) exhibited the optimally comprehensive properties with thermal conductivity of 92 W·m−1·K−1 and shearing strength of 102 MPa, which demonstrates significant promise for application in power electronic modules.