Microstructural evolution of 96.5Sn–3Ag–0.5Cu lead free solder reinforced with nickel-coated graphene reinforcements under large temperature gradient
journal contributionposted on 01.02.2018, 11:18 by Guang Chen, Li Liu, Vadim Silberschmidt, Changqing Liu, Fengshun Wu, Y.C. Chan
In this study, 96.5Sn–3Ag–0.5Cu (SAC305) lead-free composite solder containing graphene nanosheets (GNS) decorated with Ni nanoparticles (Ni-GNS) was prepared using a powder metallurgy method. A lab-made set-up and a corresponding Cu/solder/Cu sample design for assessing thermo-migration (TM) was established. The feasibility of this setup for TM stressing using an infrared thermal imaging method was verified; a temperature gradient in a solder joint was observed at 1240 K/cm. Microstructural evolution and diffusion of Cu in both plain and composite solder joints were then studied under TM stressing conditions. Compared to unreinforced SAC305 solder, the process of diffusion of Cu atoms in the composite solder joint was significantly reduced. The interfacial intermetallic compounds (IMCs) present in the composite solder joint also provide a more stable morphology after the TM test for 600 h. Furthermore, during the TM test, the Ni-GNS reinforcement affects the formation, migration and distribution of Ni–Cu–Sn and Cu–Sn IMCs by influencing the dissolution rate of Cu atoms.
This work was supported by the National Nature Science Foundation of China (Grant No. 61574068), the Fundamental Research Funds for the Central Universities (No. 2016JCTD112) and the Marie Curie International Research Staff Exchange Scheme Project within the 7th European Community Framework Programme (Grant No. PIRSES-GA-2010-269113).
- Mechanical, Electrical and Manufacturing Engineering