Selective etching and hardness properties of quenched SAC305 solder joints

• Published in: Soldering & surface mount technology 2020-08, Vol.32 (4), p.225-233
• Main Authors: Yahaya, Muhamad Zamri, Salleh, Nor Azmira, Kheawhom, Soorathep, Illes, Balazs, Mohd Nazeri, Muhammad Firdaus, Mohamad, Ahmad Azmin
• Format: Article
• Language: English
• Subjects: Alloys; Bias; Chemical etching; Cooling; Cooling rate; Diamond pyramid hardness; Electrochemical etching; Electrodes; Electrolytes; Emission analysis; Etching; Field emission microscopy; Grain orientation; Intermetallic compounds; Investigations; Mechanical properties; Morphology; Oxidation; Phases; Photomicrographs; Quenching; Soldered joints; Solidification; Thickness; Tin base alloys; X-ray diffraction
• ISSN: 0954-0911; 1758-6836
• DOI: 10.1108/SSMT-01-2020-0001

Purpose The purpose of this paper is to investigate the morphology of intermetallic (IMC) compounds and the mechanical properties of SAC305 solder alloy under different cooling conditions. Design/methodology/approach SAC305 solder joints were prepared under different cooling conditions/rates. The performance of three different etching methods was investigated: simple chemical etching, deep etching based on the Jackson method and selective removal of β-Sn by a standard three-electrode cell method. Phase and structural analyses were conducted by X-ray diffraction (XRD). The morphology of etched solder was examined by a field emission scanning electron microscope. The hardness evaluations of the solder joints were conducted by a Vickers microhardness tester. Findings The Ag3Sn network was significantly refined by the ice-quenching process. Further, the thickness of the Cu6Sn5 layer decreased with an increase in the cooling rate. The finer Ag3Sn network and the thinner Cu6Sn5 IMC layer were the results of the reduced solidification time. The ice-quenched solder joints showed the highest hardness values because of the refinement of the Ag3Sn and Cu6Sn5 phases. Originality/value The reduction in the XRD peak intensities showed the influence of the cooling condition on the formation of the different phases. The micrographs prepared by electrochemical etching revealed better observations regarding the shape and texture of the IMC phases than those prepared by the conventional etching method. The lower grain orientation sensitivity of the electrochemical etching method (unlike chemical etching) significantly improved the micrographs and enabled accurate observation of IMC phases.