Abstract
Sn-0.7Cu-0.075Al solder alloy adding with Ce and La had been successfully prepared by applying ball-milling and vacuum arc remelting. The influence of Ce and La on microstructure and corrosion behavior of Sn-0.7Cu-0.075Al solder alloy was investigated. The results showed that Ce (La)-containing solders had refined grains and obvious directional tendency due to the dispersive refiner (CeO2 and La2O3). Electrochemical potentiodynamic curves revealed three different stages of the reaction, including anodic and cathodic processes, prepassivation section, and stable passivation stages. The self-corrosion potential (Ecorr) of alloys with Ce and La addition were a little bit more negative, hardly making a difference on corrosion occurrence. However, the corrosion current density (Icorr) and passivation current density (Ip) decreased by two-thirds and one-half respectively, which indicated a better corrosion resistant after adding rare earths. The recorded micrographs of corroded surface at different polarized points witnessed the formation of corrosion product film both on prepassivation and passivation stage. Moreover, the cross section of corrosion product film showed the coarse, loose film in Sn-0.7Cu-0.075Al solder and adherent, compact film in Ce (La)-containing solders, which further indicated an excellent anti-corrosion property.
Highlights
Toxic Pb in Sn-Pb solder swarmed into the waste streams of electronic industries in the past years, and restrictive regulations have been worked to make wide usage of a variety of lead-free solders possible [1,2]
This result matched those with the previous literature that researched on Sn-0.7Cu alloy [32,33,34]
As for Sn-0.7Cu alloy adding Al, the existence of Al depends on its content: the Al-Cu binary compound is formed preferentially according to thermodynamics; very little Al atom solid solutes in Sn matrix could be possible based on the Al-Sn phase diagram; another situation could be Al particles exist in Sn matrix as the reference [35]
Summary
Toxic Pb in Sn-Pb solder swarmed into the waste streams of electronic industries in the past years, and restrictive regulations have been worked to make wide usage of a variety of lead-free solders possible [1,2]. The near eutectic Sn-Cu alloy system is a suitable alternative due to its low cost and good mechanical properties [3,4]. Since lower brazing temperature is not necessary for wave soldering, Sn-Cu solders have widely come into commercial use in that area [5,6]. Microelectronic equipment meets the requirements against corrosive media, as a result, protecting ecosystems and human health from dissolved heavy metal content should be put on the agenda [7,8]. The study of corrosion behavior of Sn-Cu alloys is imperative.
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