Die attach materials with high remelting temperatures created by bonding Cu@Sn microparticles at lower temperatures

This paper presents a novel die attach material that withstands high working temperatures of up to 676   °C after <   40   min of reflow at 250   °C. The die attach material was preform compressed with Cu@Sn core-shell structured microparticles . When the reflow temperature reached 232   °C, the outer Sn layer melted and connected the inner Cu cores. After reflow soldering at 250   °C for 8   min, the outer Sn completely transformed into network-like Cu-Sn intermetallic compounds (IMCs), which have a higher remelting temperature than Sn (415   °C for Cu 6 Sn 5 and 676   °C for Cu 3 Sn). Consequently, the inner Cu cores were interconnected by the formed network-like Cu-Sn IMCs with a high remelting temperature of at least 415   °C. If the sample was reflowed at 250   °C for 40   min, the outer Cu 6 Sn 5 layer completely transformed into Cu 3 Sn, and the resulting bondline could sustain a higher temperature. The shear strengths of the resulting bondlines after reflow soldering at 250   °C for 8 and 40   min were 29.35 and 18.78   MPa at 400 and 500   °C, respectively.