Abstract
The research was undertaken to establish mechanical properties of as-cast and heat-treated Sn-Zn-based alloys of binary and ternary systems as candidates for lead (Pb)-free solder materials for high-temperature applications. The heat treatment of as-cast alloys was made under different combinations of processing parameters (168 h/50 °C, 42 h/80 °C, and 24 h/110 °C). The systematic study of structure-property relationships in Sn-Zn, Sn-Zn-Ag, and Sn-Zn-Cu alloys containing the same amount of Zn (4.5, 9, 13.5 wt.%) and 1 wt.% of either Ag or Cu was conducted to identify the effects of chemical composition and heat treatment processing parameters on the alloy microstructure and mechanical behavior. Structural characterization was made using optical microscopy and scanning electron microscopy techniques coupled with EDS analysis. Mechanical properties (initial Young’s modulus E, ultimate tensile strength UTS, elastic limit R 0.05, yield point R 0.2, elongation A 5, and necking Z) were determined by means of static tensile tests. All the examined Sn-Zn-based alloys have attractive combination of mechanical characteristics, especially tensile strength, having values higher than that of common leaded solders and their substitutes of Pb-free SAC family. The results obtained demonstrate that the Sn-Zn-based alloys present competitive Pb-free solder candidates for high-temperature applications.
Highlights
In response to serious health and environmental safety problems related with the use of lead, regulatory actions have been taken in many countries to eliminate this element from solder materials for electronic devices (Ref 1)
Due to a low cost coupled with melting point close to that of conventional Sn-Pb solders, the Sn-Zn-based alloys are recognized as a possible replacement for high Pb-containing solders that are still commonly used, for high-temperature applications (Ref 1, 4-8)
More detailed structural characterization was done by means of scanning electron microscopy (SEM) using a JSM 6360LA microscope equipped with energy dispersive spectrometer (EDS) of for local chemical analysis and phase identification
Summary
In response to serious health and environmental safety problems related with the use of lead, regulatory actions have been taken in many countries to eliminate this element from solder materials for electronic devices (Ref 1). Numerous efforts has been made to develop lead (Pb)-free solders that are intended to be an alternative for the long-established family of Pb-containing solder alloys (Ref [1,2,3]). Working conditions of most electronic devices exposed to high temperature and/or thermal cycling, information on the influence of temperature on microstructure stability, and change in mechanical characteristics of bulk solder alloys is of practical importance. This research was carried out to establish mechanical properties of Sn-based alloys from the binary Sn-Zn and ternary Sn-Zn-Cu and Sn-Zn-Ag systems exposed to high temperature. The systematic studies of structure-property relationships were carried out on as-cast and heat-treated alloys containing various amounts of alloying additions to identify the effects of the alloy chemical composition and temperature exposure on microstructure variations and mechanical behavior of Sn-Zn-based alloys
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