Interfacial strength and microstructure of AlN/Cu joints produced by a novel brazing method facilitated by porous-copper layer and Ag foil

Abstract The reliability of wide-bandgap (WBG) semiconductors used as power electronics is closely related to the high thermal conductivity of AlN-metalized substrates. Thus, the bonding of AlN ceramics with metals is a key issue for the production of reliable AlN-metalized substrates. This paper reports on a new method for producing AlN/Cu joints by employing a novel film-metallization production process, which involves a porous network of Cu layer and Ag foil. The microstructure and the phases formed at the interface of the AlN/Cu joints produced at various brazing temperatures and times, were analyzed by scanning electron microscopy and X-ray diffraction analysis. Strong joints with shear strength of 48.5 MPa were produced after brazing at 850 °C for 10 min. The typical microstructure at the interfacial reaction zone was Cu / Ag(s) + Cu(s) / CuAlO2 + Al2O3 + Cu(s) / AlN. The experimental results manifest the crucial role of the Ag-Cu eutectic liquid phase, formed by the reaction between the Cu layer and the Ag foil, and of the porous network of the Cu layer deposited on the surface of the AlN ceramic substrate, since both of them effectively favor the reduction of the residual thermal stresses in the joint and result in strong ceramic/metal joins.