Selective etching and hardness properties of quenched SAC305 solder joints

Abstract

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.

Citation

Yahaya, M.Z., Salleh, N.A., Kheawhom, S., Illes, B., Mohd Nazeri, M.F. and Mohamad, A.A. (2020), "Selective etching and hardness properties of quenched SAC305 solder joints", Soldering & Surface Mount Technology, Vol. 32 No. 4, pp. 225-233. https://doi.org/10.1108/SSMT-01-2020-0001