Study on the effect of mixing proportion of micro- and nano-copper particles on sintering properties

Nano-metal sintering is a promising technology for the next generation of semiconductor packaging due to its positive effect on reliability enhancement. Compared with the silver sintering, copper-based sintering technique has more potential to be applied in die attachment field as its superiorities on lower cost, higher melting temperature without electromigration. In this study, Taguchi method is applied to study and analyze the effect of nano-/micro- particle ratio on sintering properties. Sintering temperature is also taken into account since it depends on the particle size a lot. The results show that both sintering temperature and nano-micro- ratio play significant role on influencing shear strength. The best combination is 300 nm with 1 um mixing (1:1) with over 35 MPa shear strength with 300°C sintering temperature. The fracture surface result shows that the crack propagated in the sintering body. Furthermore, the cross-section inspection reveals dense bonding and clearly sintering necking, and the porosity is lower than 12%. 227.8 W/m*K thermal conductivity and 6.0 uΩ·cm electrical resistivity are measured for the sample, which indicates the great potential for the packaging application in high power situation.