Thermal Properties and Wetting Behavior of High Temperature Zn-Al-In Solders

Abstract

Solders for ultrahigh-temperature applications were defined by Vianco as those able to sustain working conditions with temperatures as high as 573 K, with momentary temperature rise up to 623 K. Zn-Al eutectic alloy (12 at.% Al) fits such defined criteria with respect to its melting temperature. It was found that small additions of indium to Zn-Al eutectic lower its melting temperature. The aim of this work is to assess if and to what extent thermal properties and wetting behavior are affected. It was found that addition of In increases electrical resistivity and coefficient of thermal expansion value. Wetting angles on Cu and Al substrates of liquid Zn-Al eutectic-based alloys containing up to 1.5 at.% of In were studied with the sessile drop method, after wetting at 773 K in the presence of flux. A decrease of apparent wetting angle was observed with increasing concentration of In. After wetting tests solidified alloy-substrate couples were crosssectioned and examined with scanning electron microscopy coupled with electron dispersive X-ray analysis.

Effect of Cu Addition to Zn-12Al Alloy on Thermal Properties and Wettability on Cu and Al Substrates

“…With increased Cu, the electrical resistivity of the eutectic ZnAl alloy also increased. In comparison to the data on electrical resistivity for ZnAl with In, [7] the values obtained here are lower. The linear expansion of ZnAl alloys with added Cu shows the same pattern as the electrical resistivity, with increased Cu in alloys increasing the CTE.…”

“…The precipitates were analyzed and identified, using XRD, as b-CuZn, c-Cu Zn12Al1.5Cu Zn5.3Al1.57Cu 657.9 (384.9) Fig. 1-Electrical resistivity vs temperature of pure Zn, [7] eutectic ZnAl, [7] and ZnAl with Cu alloys.…”

“…Based on the alloy microstructures of the soldered joints, the addition of Cu to eutectic ZnAl causes an increase in the dissolution of Al by the liquid solder compared to ZnAl with In. [7] The compositions of Al, Cu, and Zn, as determined by EDS at the points noted in Figures 11 and 12, are shown in Table IV. Al from the substrate is present in the solder as precipitates rich in Al (point 35 in Figure 12).…”

“…In response to market demand from the aerospace, automotive, and electronics industries, solder alloys for use at temperatures up to 623 K (350°C) have been developed, on the basis of eutectic ZnAl alloys with added Ag, [6] In, [7] and Cu. [8,9] The major contribution of the Vianco team, [10] which worked on alloys in the temperature range above 573 K (300°C), is noteworthy.…”

Thermal and Microstructure Characterization of Zn-Al-Si Alloys and Chemical Reaction with Cu Substrate During Spreading

“…The presence of a higher amount of the eutectic phase is the reason of higher electrical resistivity. Gancarz et al (Ref 3,16) found that the electrical resistivity of Zn-Al-In and Zn-Al-Ag increases as temperature rises and different metal components are added: from 6.5 to 8.5 lX cm at room temperature for Zn-Al-xIn (x = 0.5-1.5 wt.%) and 6.5-7.2 lX cm for Zn-Al with addition of Ag 3.1.5 Mechanical Properties. Tensile test was used to evaluate the mechanical properties of the as-cast Zn-Al-Si alloys compared with the strength of eutectic ZnAl solder.…”