Development of a lead-free composite solder from Sn–Ag–Cu and Ag-coated carbon nanotubes

• Published in: Journal of materials science. Materials in electronics 2013-10, Vol.24 (10), p.3707-3715
• Main Authors: Chantaramanee, S., Wisutmethangoon, S., Sikong, L., Plookphol, T.
• Format: Article
• Language: English
• Subjects: Applied sciences; CARBON BASE MATERIALS; Characterization and Evaluation of Materials; Chemistry and Materials Science; COMPOSITES; Cross-disciplinary physics: materials science; rheology; Electrical engineering. Electrical power engineering; Electronics; Exact sciences and technology; Intermetallic compounds; Materials; Materials Science; MECHANICAL PROPERTIES; Metals. Metallurgy; MICROSTRUCTURES; Nanocomposites; Nanomaterials; Nanoscale materials and structures: fabrication and characterization; Nanostructure; Nanotubes; Optical and Electronic Materials; Physics; Production techniques; PROPERTIES; Silver; Single wall carbon nanotubes; SOLDERING ALLOYS; Solders; Surface treatment; TIN ALLOYS (50 TO 99 SN); Tin base alloys; TUBE; Wettability; WETTING
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-013-1307-y

The microelectronic applications of lead-free solders pose ever-increasing demands. We seek to improve the solder by forming composites with Ag-coated single-walled carbon nanotubes (Ag-coated SWCNTs). These were incorporated into 96.5Sn–3.0Ag–0.5Cu solder alloy with an ultrasonic mixing technique. Composite solder pastes with 0.01–0.10 wt% nanotube reinforcement were prepared. The wettability, melting temperature, microstructure and mechanical properties of the composite solders were determined, and their dependency on nanotube loading assessed. Loading with 0.01 wt% Ag-coated SWCNTs improved the composite solder’s wetting properties, and the contact angle was reduced by 45.5 %, while over loading of the coated nanotubes up to 0.10 wt% degraded the wettability. DSC results showed only slight effects on the melting behavior of the composite solders. Cross-section microstructure analysis of the spreading specimens revealed uniform distribution of the intermetallic compounds throughout the solder matrix, and EDS analysis identified the phases as β-Sn, Ag 3 Sn and Cu 6 Sn 5 . The mechanical properties of composite specimens, compared with those of unloaded 96.5Sn–3.0Ag–0.5Cu solder, had a maximal improvement in the shear strength of 11 % when the nanotube loading was 0.01 wt% of Ag-coated SWCNTs.