Microstructure evolution and thermostability of bondline based on Cu@Sn core-shell structured microparticles under high-temperature conditions

Publication date: 5 October 2017
Source:Materials & Design, Volume 131
Author(s): Tianqi Hu, Hongtao Chen, Mingyu Li, Chunqing Wang
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-Cu3Sn was determined; and the accompanying volume shrinkage was verified. The phase transformation pathway for particles with a thin Sn coating layer was Cu6Sn5→ε-Cu3Sn→δ-Cu41Sn11→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-Cu3Sn intermetallic phase, and no other Cu-rich phases formed when heating to 600°C.

Graphical abstract

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