Abstract
Composite solder is a promising route to improve the properties and reliability of Sn-based lead-free solder. In this study, Cu-coated graphene nanosheets (Cu-GNSs) were synthesized using pyrolysis. Cu-GNSs reinforced Sn2.5Ag0.7Cu0.1RE composite lead-free solders were prepared via powder metallurgy. The size, distribution, and adsorption type of Cu nanoparticles on the GNSs were studied. The relation of the Cu-GNSs content and microstructure to the physical, wettability, and mechanical properties of composite solders was discussed. The results show that Cu nanoparticles (with a mean size of 13 nm) present uniform distribution and effective chemisorptions on the GNS. Microstructural evolution of composite solders is dependent on the addition of Cu-GNSs. With increasing Cu-GNSs addition, β-Sn grains become finer and the eutectic phase proportion becomes larger, while the morphology of the eutectic phase transforms from dispersion to network-type. The improvement of the tensile strength of the composite solder can be attributed to grain refinement and load transfer. While the existence of Cu-GNSs can effectively improve the wettability and slightly change the melting point, it can also lead to the decline of elongation and electrical conductivity of the composite solder.
Highlights
IntroductionSolder alloys act as the electrical and mechanical interconnection in the microelectronics package and serves an important role in the reliability and working life of electronic devices [1]
Solder alloys act as the electrical and mechanical interconnection in the microelectronics package and serves an important role in the reliability and working life of electronic devices [1].The modern design of high Input/Output density and three-dimensionality for microelectronics package technologies has inspired an urgent demand to develop novel lead-free solders of high-strength and toughness [2,3]
Cu nanoparticles on the GNSs can beinprepared by pyrolysis and of the eutectic phase can be seen in Figure 4, but no significant change fractographs is observed the7b–d)
Summary
Solder alloys act as the electrical and mechanical interconnection in the microelectronics package and serves an important role in the reliability and working life of electronic devices [1]. The modern design of high Input/Output density and three-dimensionality for microelectronics package technologies has inspired an urgent demand to develop novel lead-free solders of high-strength and toughness [2,3]. Microalloying and particle doping have been mainly utilized to improve the performance of lead-free solders. Are used as reinforcements of composite solders due to their excellent thermal, electrical, and mechanical properties [4,5]. Nai et al [6] were the first to dope CNTs into Sn-Ag-Cu-based solder and achieve an increment of wettability and microhardness. Optimization of CNTs on the Materials 2019, 12, 289; doi:10.3390/ma12020289 www.mdpi.com/journal/materials
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