Die attach materials with high remelting temperatures created by bonding Cu@Sn microparticles at lower temperatures. (15th October 2016)

• Record Type: Journal Article
• Authors: Hu, Tianqi; Chen, Hongtao; Li, Mingyu
• Is Part Of: Materials & design. Volume 108(2016)
• Page Start: 383
• Page End: 390
• Publication Date: 2016-10-15
• Subjects: High-remelting-point solder -- Die attach -- Power devices -- Cu@Sn; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2016.06.099
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: 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 Cu6 Sn5 and 676 °C for Cu3 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 Cu6 Sn5 layer completely transformed into Cu3 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. Graphical abstract: Highlights: Cu cores were coated by a layer of Sn to form the Cu@Sn particles. A high re-melting temperature up to 676 °C was achieved after reflowing at 250 °C. Large shear strength can be achieved under 500 °C. Vertical cracks initiated and propagated to mitigate the stress concentration.