Investigation of microstructure and wetting behavior of Sn–3.0Ag–0.5Cu (SAC305) lead-free solder with additions of 1.0 wt % SiC on copper substrate

• Published in: Intermetallics Vol. 128; p. 106991
• Main Authors: Pal, Manoj Kumar, Gergely, Gréta, Koncz-Horváth, Dániel, Gácsi, Zoltán
• Format: Journal Article
• Language: English
• Published: Barking Elsevier Ltd 01-01-2021; Elsevier BV
• Subjects: Contact angle; Copper; Cracks; Ductile-brittle transition; Free energy; Lead free; Lead–free solder; Metallurgical analysis; Microcracks; Microstructure; Nucleation; Powder metallurgy; RA (Rosin activated) flux; Silicon carbide; Solders; Spread factor; Spread ratio; Substrates; Thickness; Tin; Tin base alloys; Wetting; RA (Rosin activated) flux; Lead–free solder; Silicon carbide; Contact angle; Spread ratio; Spread factor
• ISSN: 0966-9795; 1879-0216
• DOI: 10.1016/j.intermet.2020.106991

The current investigation was conducted to understand the effect of 1wt. % silicon carbide (SiC) in the Sn–3.5Ag–0.5Cu (SAC305) lead-free solder alloy which was produced by the powder metallurgy method. A systematic investigation of the microstructure of the solidified composite solder along with its wetting behavior was carried out at different reflow temperatures (230°C–290°C). From microstructure investigation, it was clear that SiC ceramic particles influence the development of IMCs at the Cu–Sn interface and refine microstructure in the bulk solder region. Micro-cracks were detected at Cu/SAC interface and also in the Cu6Sn5 layer. This is due to the development of extremely (brittle) intermetallic layer and ductile nature of Sn–3.0Ag–0.5Cu solder. The intermetallic layer thickness increased substantially with the increase of reflow temperatures (230°C–290°C). A uniform distribution of SiC, Ag3Sn, and Cu6Sn5 IMCs were found in the bulk b-Sn matrix. The result shows that the SiC particles promote the extra nucleation sites for the development of b-Sn phase and IMCs in the solidified structure. In addition to this, SiC particles, b-Sn dendrites and IMCs can prevent dislocation slippage which helps in attaining a strong solder joint due to strong strengthening effect. The results showed that the spread ratio, spread factor, and the relative spread area (RSA) increased while the equilibrium contact angle decreased with an increase in reflow temperature. This can be attributed to the strong adsorption effect and high surface free energy of the SiC particles.
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•SAC305- 1%SiC composite solder is prepared by the powder metallurgy method.•Pores and cracks are detected in the Cu6Sn5 IMC.•Spreading area (RSA), spreading ratio, and spread factor is analyzed corresponding to the reflow temperatures.•Contact angles are measured by direct and indirect methods.