Microstructure evolution and thermostability of bondline based on Cu@Sn core-shell structured microparticles under high-temperature conditions. (5th October 2017)

• Record Type: Journal Article
• Authors: Hu, Tianqi; Chen, Hongtao; Li, Mingyu; Wang, Chunqing
• Is Part Of: Materials & design. Volume 131(2017)
• Page Start: 196
• Page End: 203
• Publication Date: 2017-10-05
• Subjects: Coating materials -- Intermetallics -- Liquid-solid reactions -- Microstructure -- Phase transitions; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2017.06.022
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: Cu@Sn core-shell structured particles with different coating layer thicknesses were fabricated and used as bonding materials. The microstructure evolution and thermostability of the bondline were studied under high-temperature conditions; the minimum thickness of the Sn coating layer required to consume all the inner Cu cores when forming ε-Cu3 Sn was determined; and the accompanying volume shrinkage was verified. The phase transformation pathway for particles with a thin Sn coating layer was Cu6 Sn5 → ε-Cu3 Sn → δ-Cu41 Sn11 → γ-phase → β-phase upon heating to 600 °C. Thermal instability occurs at 520 °C and 586 °C due to the formation of the Cu-rich phases. High-temperature shearing tests were conducted at 500 °C and 550 °C to verify the existence of a critical point for brittle rupture and tough rupture at approximately 520 °C. For particles with a thick Sn coating layer, the outer Sn shell completely consumes the inner Cu core when forming a ε-Cu3 Sn intermetallic phase, and no other Cu-rich phases formed when heating to 600 °C. Graphical abstract: Schematic diagrams of the microstructure evolution at 450 °C for bondlines based on Cu@Sn particles with thin and thick Sn coating layers. Highlights: Cu@Sn core-shell structured particles were fabricated and used as die attach material. Phase transformation and microstructure evolution behavior at high temperatures were studied. Thermal-mechanical instability occurs at 520 °C and vertical cracks appear after thermal shock cycling. Typical core-shell structure disappeared and volume shrinkage was verified accompanied with the phase transformation.