Novel Ag salt paste for large area Cu-Cu bonding in low temperature low pressure and air condition

In this study, a novel Ag salt paste (Ag β-ketocarboxylate (C 5 O 3 H 7 Ag)) was proposed to achieve robustly and large-area (35 × 35 mm ² ) bare Cu to Cu bonding in a low temperature low pressure in air conditions. The thermal behaviors and microstructure evolution of the Ag salt paste was investigated to investigate the decomposition of Ag salt paste and interface bonding mechanism. The large-area bonded plate exhibit low porosity about 10% and low percentage of voids, which result in ultra-high bonding strength over 54 MPa. In addition, the solvents and formic acid (CH 2 O 2 ) in Ag salt paste successfully prevent the occurrence of oxidation of Cu substrate during sintering process in air condition. The large area Cu-Cu joint structure was also implemented into a high temperature ageing process at the 250°C for 500 h. The shear strength did almost not any decrease during the ageing, still larger than 50 MPa, and the interface of Cu-Ag still robust bonding without any Cu oxide after ageing for 500 h.