Wetting of Sn-Zn-xIn (x = 0.5, 1.0, 1.5 wt%) Alloys on Cu and Ni Substrates

Przemysław Fima,Janusz Pstruś,Anna Sypień,Tomasz Gancarz

doi:10.1007/s11665-012-0124-4

Abstract

Wetting angles of Sn-8.8Zn and Sn-8.8Zn-xIn alloys (x = 0.5, 1.0, 1.5 wt%) were studied with the sessile drop method. Wetting tests were carried out for 900 s in the presence of ORM0 flux at 493, 523, and 573 K on copper and at 523 K on nickel substrates, respectively. It was found that the addition of In to Sn-8.8Zn alloy improves its wetting on both substrates by reducing the value of apparent wetting angle. Also, with increasing temperature a decrease of wetting angle on copper is observed in the case of 0 and 1.5 wt% of In alloys. Solidified solder-substrate couples were cross-sectioned and examined with scanning electron microscopy coupled with electron dispersive X-ray analysis. Interlayers were found at the interface of solders with copper and nickel, and their compositions are close to Cu5Zn8 and Ni5Zn21 intermetallics, respectively. However, in the case of Sn-8.8Zn-1.5/Ni couple small scallops are observed instead of continuous interlayer.

Highlights

Among Pb-free alternatives to traditional solders, Sn-8.8Zn eutectic alloy has the closest melting point (m.p. $471 K) to the Sn-40Pb solder (m.p. $456 K), much lower compared to broadly used SAC solder (m.p. $490 K)
The results of wetting tests on copper and nickel substrates are shown in Fig. 1(a) and (b), respectively
Taking into account the uncertainty of wetting angle measurement (Fig. 1b), it can be assumed that the wetting angle of Sn-Zn-In alloys on Ni substrate is nearly the same

Summary

Introduction

Among Pb-free alternatives to traditional solders, Sn-8.8Zn eutectic alloy has the closest melting point (m.p. $471 K) to the Sn-40Pb solder (m.p. $456 K), much lower compared to broadly used SAC solder (m.p. $490 K). Among Pb-free alternatives to traditional solders, Sn-8.8Zn eutectic alloy has the closest melting point $456 K), much lower compared to broadly used SAC solder One important factor in favor of Sn-Zn solder is its low price per mass unit, as a result of low price of Zn. In the long term, price of zinc is roughly 10% of price of tin, which is a few orders lower than price of silver (Ref 1). As pointed out elsewhere (Ref 2, 3), the main disadvantages of Sn-Zn solder are susceptibility to oxidation and a relatively poor wettability compared to other Pb-free alternatives. Oxidation resistance, melting, mechanical properties, and microstructures of Sn-Zn

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