Investigation on the effect of die-attaching on the mechanical properties and microstructure of nano-Cu sintered joints

Purpose This study aims to investigate the effects of die-attaching temperature, force and time on the paste overflow behavior, microstructure and shear strength of Cu-Cu sintered joints. Design/methodology/approach The dried Cu substrate was transferred to the die bonder for die-attaching operation. In the experiment, three parameters – die-attaching temperature, die-attaching force and die-attaching time – were adjusted separately. After die-attaching, the samples were sintered at 230°C and 20 MPa for 7 min. Finally, the shear strength and microstructure of the sintered joints were characterized and analyzed. Findings The experiment shows that the optimal die-attaching temperature is 70°C, a shear strength of 91.6 MPa is achieved through die-attaching at 30 kg (18.8 MPa) for 10 s, and it can reach 88.9 MPa at 10 kg (6.3 MPa) for 15 s. The die-attaching temperature effectively prevents paste overflow of post-sintering joints, an increase in die-attaching force can not only cause slight plastic deformation of Cu particles and change their initial packing state but also damage the oxide film on the surface of Cu particles, prolonging the die-attaching time enhances the effect of the die-attaching force. Originality/value The die-attaching process is a crucial link in the sintering workflow. Adjustments to its key parameters – die-attaching temperature, force and time – exert a significant impact on the performance of sintered joints. Therefore, the results of this study provide important reference value for the practical application of nano-Cu sintering technology.