나노 솔더링 기술에 의한 Ag계 복합 잉크의 고속 소결

To develop a fast formation method of conductive films by liquid phase sintering using a normal reflow process, a composite ink was fabricated by mixing a commercial ink containing Ag particles of 60 nm size and Sn-58Bi nanoparticles of 40 nm average size. In addition, the composite ink was spin-coated and reflow soldered at the nanoscale, that is finally transformed into a conductive film. Although the sheet resistance in a film made of pure Ag nanoparticles was as high as 1.24 Ω/□ under the temperature profile with a peak temperature of 174°, the sheet resistance values after the addition of 0.003 g flux and Sn-58Bi nanoparticles became considerably low. In special, the sheet resistance decreased to the minimum values of 0.18 Ω/□ when the added amount of Sn-58Bi was 12 wt.%. Ag particles in a microstructure in the composite films grew into outstandingly big grains through agglomeration among the Ag particles by melting and wetting of Sn-58Bi and connectivity between the grains was also considerably enhanced. Meanwhile, the amount of unreacted Sn- 58Bi nanoparticles between the agglomerated grains increase and contact property between the agglomerated grains decrease when the added amount exceeded 12 wt.%, which gradually increasing the resistance. Excessive flux addition of 0.006 g increased the sheet resistance.