Observation of the solidification microstructure of Sn3.5Ag droplets prepared by CDCA technique
Observation of the solidification microstructure of Sn3.5Ag droplets prepared by CDCA technique
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DOI：
10.1007/s10854-012-0766-x
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发表时间：
2012-05
期刊：
影响因子：
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通讯作者：
Jin Zhao;Yulai Gao;Weipeng Zhang;T. Song;Q. Zhai
中科院分区：
文献类型：
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作者：
Jin Zhao;Yulai Gao;Weipeng Zhang;T. Song;Q. Zhai
采用自耗电极直流电弧技术制备了不同尺寸的Sn3.5Ag熔滴。根据牛顿冷却定律计算了液滴的冷却速率，结果表明，随着液滴尺寸从830 μm减小到43 μm，液滴的冷却速率从6.84 × 102 K/s急剧增加到2.52 × 105 K/s。冷却速度范围接近激光焊接（高达104 K/s）。结果表明，随着冷却速率的增加，β-Sn枝晶得到细化，当冷却速率为1.30 × 105 K/s时，枝晶在液滴中几乎消失，对应的尺寸尺度小于60 μm。此外，已经观察到，高冷却速率可以成功地避免片状Ag 3Sn的沉淀，并促进在实际应用中期望的纳米颗粒的形成。这些纳米颗粒均匀地分布在Sn基体中，不同液滴中纳米颗粒的平均尺寸分别为46.4 nm（380-830 μm液滴）、57.2 nm（150-250 μ m液滴）、60.6 nm（96-150 μm液滴）、63.2 nm（43-60 μm液滴）和65.3 nm（<43 μm液滴）。根据纳米颗粒的弥散强化效应，纳米颗粒的存在有利于提高Sn3.5Ag钎料合金的力学性能。
The Sn3.5Ag droplets in various sizes have been prepared by the consumable-electrode direct current arc technique. The cooling rates of the droplets have been evaluated based on Newton’s cooling law and it shows that the cooling rates of the droplets increase dramatically from 6.84 × 102to 2.52 × 105K/s as the droplet size decreases from 830 to 43 μm. The range of cooling rate is close to that of laser soldering (up to 104K/s). It has been found that the β-Sn dendrites are refined as the cooling rate increase, and when the cooling rate is 1.30 × 105K/s, which corresponding to the size scale smaller than 60 μm, the dendrites nearly disappear in the droplets. In addition, it has been observed that the high cooling rate could successfully avoid the precipitation of plate-like Ag3Sn and promote the formation of nanoparticles which are desirable in practical application. These nanoparticles uniformly distribute in the Sn matrix and the average size of nanoparticles in different droplets is 46.4 nm (in 380–830 μm droplets), 57.2 nm (in 150–250 μm droplets), 60.6 nm (in 96–150 μm droplets), 63.2 nm (in 43–60 μm droplets) and 65.3 nm (in droplets of <43 μm), respectively. According to the dispersion-strengthening effect, the existence of nanoparticles would be beneficial to improve the mechanical property of the Sn3.5Ag solder alloy.