Effects of Ag shell morphology on sinter-bonding by thermo-compression of micron Cu@Ag/submicron Ag composite paste

Ag-coated Cu (Cu@Ag) particles with antioxidant properties and price competitiveness are considered as fillers in sinter-bonding pastes for the die attachment of wide band-gap semiconductors at low temperature such as 250 ℃. To achieve the rapid sinter-bonding of Cu@Ag particles at 250 ℃, micron Cu@Ag particles with an Ag shell composed of numerous Ag nanoplatelets (ANP) were used, and the effect of Ag shell morphology on the sinter-bondability was confirmed by comparing with conventional micron Cu@Ag particles with a smooth surface (ASS). For the high packing densities of fillers, the composite particles were prepared by mixing them with submicron Ag particles in ratios of 5:5, 6:4, and 7:3. Sinter-bonding of pastes containing the ASS/Ag or ANP/Ag composite particles with different mixing ratio (SSA55, NPA55, NPA64, and NPA73) was conducted under 10 MPa for 1–10 min with nitrogen blowing. The bondline using NPA55 exhibited a near full-density microstructure and high shear strength (25.81 MPa) when sintered for a short time of 1 min, which was a much higher value than the 14.41 MPa of SSA55. These results demonstrate that rapid sinter-bonding at 250 ℃ can be achieved using novel micron Cu@Ag particles with large surface area and high surface energy.