Wetting of Al pads by Sn–8.8Zn and Sn–8.7Zn–1.5(Ag, In) alloys

Abstract

Wetting of Al (99 %) pads by Sn-8.8Zn, Sn-8.7Zn-1.5In, and Sn-8.7Zn-1.5Ag (wt%) alloys was studied by means of the sessile drop method. The tests were carried out at 250°C, using Amasan ALU33Ò flux, for up to 60 min. We used a setup that allows fast transfer of a sample to and from the hot zone of the furnace. Solidified alloy-substrate couples were cross sectioned and examined by scanning electron microscopy and energy dispersive X-ray analysis. The studied alloys wet Al pads as the wetting angles, determined after cleaning the flux residue from solidified alloy-substrate couples, are lower than 35 degrees. Wetting angles of Sn-8.7Zn-1.5Ag (wt%) alloy are higher and wetting areas are smaller than those of the remaining alloys, possibly due to a small gap between the melting and test temperatures. There is no clear dependence of the wetting angle and spreading area on time.Microstructures of cross-sectioned samples indicate that alloys dissolve the substrate and penetrate along grain boundaries. Since there is no significant difference between the same solder/Al interfaces at different wetting times, it is assumed that the microstructure evolves in \5 min.

Wetting of Sn-Zn-Ga and Sn-Zn-Na Alloys on Al and Ni Substrate

“…At 503 K (230°C), the spreading area on Al reduced with time, which could be correlated with undissolved IMC precipitates and Na movement to the surface area being blocked. Similar results were obtained for the spreading area for eutectic Sn-Zn on Al substrate, 8,30 compared with Sn-Zn alloy with Ga and Na additions. Furthermore, with increased temperature [from 523 K to 773 K (250°C to 500°C, respectively) 8 ] and time (from 5 min to 60 min 30 ), the spreading area reduced.…”

“…Similar results were obtained for the spreading area for eutectic Sn-Zn on Al substrate, 8,30 compared with Sn-Zn alloy with Ga and Na additions. Furthermore, with increased temperature [from 523 K to 773 K (250°C to 500°C, respectively) 8 ] and time (from 5 min to 60 min 30 ), the spreading area reduced. The same behavior was observed for SnZn with Ag and In alloys.…”

“…The same behavior was observed for SnZn with Ag and In alloys. 30 During the soldering process on Al substrate, the microstructure of a cross section at time and temperature dependency (Figs. 2 and 3) was observed.…”

“…[25][26][27][28][29] The formation of aluminum dendrites is based on the dissolution of aluminum grains, which are dissolved from their centers by the surrounding Sn solder. 24 On the other hand, the addition of Ag 23,30 and In 30,31 to SnZn alloys improves mechanical and wetting properties. The results in Ref.…”

Preface to the HTC 2012 special issue

“…The first covers the topic of wetting of ceramics by silicon alloys [1], the second discusses our current understanding of dissolutive wetting [2], and the third explores wetting and joining of high temperature materials based on diborides [3]. The section containing full manuscripts opens with a paper describing a new software tool for simulating interface morphology [4], followed by a series of papers on interface thermodynamics [5][6][7][8][9][10][11][12], and non-reactive and reactive wetting systems [13][14][15][16][17][18][19][20][21][22][23][24][25][26]. This is followed by a series of papers exploring the use of sessile drop experiments, reactive wetting, and applied joining and processing.…”