EFFECTS OF Zn CONCENTRATION ON WETTABILITY OF Sn-Zn ALLOY ON Cu AND ON THE INTERFACIAL MICROSTRUCTURE BETWEEN Sn-Zn ALLOY AND Cu
来源期刊：Acta Metallurgica Sinica2006年第4期
论文作者：L. Zhou X.Q. Wei H.Z. Huang G.L. Guo X.D. Liu
Key words：lead-free solder; Sn-Zn alloy; wettability; interface; intermetallic compound;
Abstract: The potential of using a hypoeutectic, instead of eutectic, Sn-Zn alloy as a lead-free solder has been discussed. The nonequilibrium melting behaviors of a series of Sn-Zn alloys were examined by differential thermal analysis. It was found that at a heating rate of 5℃/min, Sn-6.5Zn exhibited no melting range. Dipping and spreading tests were carried out to characterize the wettability of Sn-Zn alloys on Cu. Both tests exhibited that Sn-6.5Zn has significantly better wettability on Cu than Sn-9Zn. The reaction layers formed during the spreading tests were examined. When the Zn concentration fell between 2.5wt%-9wt%, two reaction layers were formed at the interface, a thick and flat Cu5Zn8 adjacent to Cu and a thin and irregular Cu-Zn-Sn layer adjacent to the allay. Only a Cu6Sn5 layer was formed when the Zn concentration decreased to 0.5wt%. The total thickness of the reaction layer(s) between the alloy and Cu was found to increase linearly with the Zn concentration.
L. Zhou1，X.Q. Wei1，H.Z. Huang1，G.L. Guo2，X.D. Liu2
(1.School of Materials Science and Engineering, Nanchang University, Nanchang 330047, China;
2.East China Institute of Technology, Fuzhou 344000, China)
Abstract:The potential of using a hypoeutectic, instead of eutectic, Sn-Zn alloy as a lead-free solder has been discussed. The nonequilibrium melting behaviors of a series of Sn-Zn alloys were examined by differential thermal analysis. It was found that at a heating rate of 5℃/min, Sn-6.5Zn exhibited no melting range. Dipping and spreading tests were carried out to characterize the wettability of Sn-Zn alloys on Cu. Both tests exhibited that Sn-6.5Zn has significantly better wettability on Cu than Sn-9Zn. The reaction layers formed during the spreading tests were examined. When the Zn concentration fell between 2.5wt%-9wt%, two reaction layers were formed at the interface, a thick and flat Cu5Zn8 adjacent to Cu and a thin and irregular Cu-Zn-Sn layer adjacent to the allay. Only a Cu6Sn5 layer was formed when the Zn concentration decreased to 0.5wt%. The total thickness of the reaction layer(s) between the alloy and Cu was found to increase linearly with the Zn concentration.
Key words:lead-free solder; Sn-Zn alloy; wettability; interface; intermetallic compound;
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