Feng Zhao

Loughborough University, Loughborough, England, United Kingdom

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Publications (3)3.47 Total impact

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    ABSTRACT: Wetting balance method is used to evaluate the effects of Ga, Al, Ag, and Ce multi-additions on the solderability of Sn–9Zn lead-free solders, results show that the optimal addition amounts of Ga, Al, Ag, and Ce is 0.2, 0.002, 0.25, and 0.15 wt% respectively. The surface property of Sn–9Zn–0.2Ga–0.002Al–0.25Ag–0.15Ce solder is studied by X-ray photoelectron spectroscopy and auger electron spectroscopy analysis; results indicate that Al aggregates on the surface as a compact aluminum oxide film which prevents the further oxidation. The aggregation of Ce on the subsurface can reduce the surface tension of solder, and improve the solderability accordingly. Meanwhile, SEM and XRD analysis indicate that Cu5Zn8 and AgZn3 intermetallic compounds form at the interface between Sn–9Zn–0.2Ga–0.002Al–0.25Ag–0.15Ce solder and Cu substrate, while AuZn3 and AuAgZn2 form at the interface between solder and Cu/Ni/Au substrate. Moreover, results also indicate that the mechanical property of soldered joints is improved duo to the dispersion strengthening effects of AgZn3 in Sn–9Zn–0.2Ga–0.002Al–0.25Ag–0.15Ce solder.
    Journal of Materials Science Materials in Electronics 01/2010; 21(2):111-119. · 1.49 Impact Factor
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    ABSTRACT: The effects of Ga–Al, Ga–Ag and Al–Ag binary additions on the wetting characteristics of Sn–9Zn–X–Y lead-free solders are studied by the wetting balance method. Experimental results show that Sn–9Zn–1.0Ga–0.3Ag, Sn–9Zn–0.005Al–0.3Ag, and Sn–9Zn–0.3Ga–0.002Al possess better wettability than the other alloys tested. The mechanism by which Ga, Al, and Ag additions improve the wettability is also proposed. It appears that dense aluminum oxide film formation and the enrichment of Ga on the surface may protect the bulk liquid solder from further oxidation. Moreover, results also indicate that, AgZn3 IMCs layer formed at the interface, which may release reaction energy during the wetting, results in improving the wettability of the solder.
    Journal of Materials Science Materials in Electronics 12/2009; 20(12):1239-1246. · 1.49 Impact Factor
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    ABSTRACT: An orthogonal method was used to evaluate the effects of Ga, Al, Ag, and Ce multi-additions on the wetting characteristics of Sn-9Zn lead-free solders by wetting balance method. The results show that the optimal loading of Ga, Al, Ag, and Ce was 0.2 wt.%, 0.002 wt.%, 0.25 wt.%, and 0.15 wt.%, respectively. Intermetallic compounds (IMCs) formed at the interface between Sn-9Zn-0.2Ga-0.002Al-0.25Ag-0.15Ce solder and Cu substrate were investigated by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) analysis. The SEM images illustrate that the IMCs can be divided into two portions from the substrate side to the solder side: a planar Cu5Zn8 layer and an additional continuous scallop-like AgZn3 layer. The EDS analysis also shows that Ga segregates in the solder abutting upon the interface. X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) of the surface components of Sn-9Zn-0.2Ga-0.002Al-0.25Ag-0.15Ce solder indicate that Al aggregates at the surface in the form of Al2O3 protective film, which prevents the further oxidation of the solder surface. On the other hand, Ce aggregates at the subsurface, which may reduce the surface tension of the solder and improve the wettability in consequence.
    Rare Metals 01/2009; 28(6):600-605. · 0.49 Impact Factor