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 degrees C after <40 min of reflow at 250 degrees C. The die attach material was preform compressed with Cu@Sn core-shell structured microparticles. When the reflow temperature reached 232 degrees C, the outer Sn layer melted and connected the inner Cu cores. After reflow soldering at 250 degrees 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 degrees C for Cu6Sn5 and 676 degrees C for Cu3Sn). Consequently, the inner Cu cores were interconnected by the formed network-like Cu-Sn IMCs with a high remelting temperature of at least 415 degrees C. If the sample was reflowed at 250 degrees C for 40 min, the outer Cu6Sn5 layer completely transformed into Cu3Sn, and the resulting bondline could sustain a higher temperature. The shear strengths of the resulting bondlines after reflow soldering at 250 degrees C for 8 and 40 min were 29.35 and 18.78 MPa at 400 and 500 degrees C, respectively. (C) 2016 Elsevier Ltd. All rights reserved.