Bond Strength Comparison of Commercial and Custom Copper Sinter Pastes Under Sinter Process Modifications

Due to the strong oxidation tendency of copper, sintering processes are preferably conducted under very low oxygen content inert or even reducing atmospheres which interferes with the advantages gained from the material property point of view that are creating a high strength monometallic joint and material cost reduction. In this paper processes are investigated and discussed to manufacture copper sinter interconnects applying nitrogen purged environments that represent a lower effort process solution. In this study, by means of a shear strength comparison, a custom-made copper sinter paste is benchmarked against a commercial product over a wide range of process variations. In addition, thermal shock tests were conducted with the commercial paste and a commercial silver paste for including ageing effect understanding. From pressurized sintered joints shear strengths up to and even higher than 70 MPa were observed, while the maximum average shear strength of joints made by pressure-less sintering only reached 22 MPa. From thermal shock ageing for up to 1000 cycles it was found that silver sinter interconnects done by pressurized sintering showed lower shear strengths then copper sinter interconnects made by pressure-less sintering yet after 330 cycles.