Controlling the Amount of Copper Formate Shells Surrounding Cu Flakes via Wet Method and Thermo-Compression Sinter Bonding between Cu Finishes in Air Using Flakes

To bond a semiconductor power chip on substrate using the formation of bondlines exhibiting long-term mechanical durability at high temperatures such as 300 °C, compression-assisted sinter bonding between Cu finishes was carried out 300–350 °C in air. flakes approximately 7 µm were used main filler material; their surfaces modified by pretreatment formic acid solution, and existing oxide layers transformed into copper formate shells. increase amount shells, shell transformation reaction controlled deliberate addition 30 nm Cu2O particles sustained for 50 min. The shells formed decomposed peak temperature 250 forming pure Cu, which rapidly induced sintering Cu-finish–flake interfaces. Therefore, paste containing showed sufficient shear strength 26.3 MPa even air after only 3 min under 5 350 °C. Although bimodal-type presented near-full-density bondline structures within adding particles, strengths with respect to time trends values less than MPa, owing excessive oxidation Cu.