The purpose of this paper is to investigate the influence of pulse plating current density on the morphology and solderability of Pb-free Sn-Cu solder coatings prepared from alkaline stannate baths.,Sn-Cu solder coatings were produced from a plating solution containing sodium stannate, copper stannate, sodium hydroxide and sorbitol additive on copper substrates. The pulse plating experiments were conducted in galvanostatic mode. The plating current density was varied from 5 to 25 mA/cm2, and the morphology of the coatings was studied. The solderability of the coatings was assessed by spread ratio measurement after reflowing the solder coatings at 250°C.,The composition control of eutectic solders is always a challenge in plating. The findings show that Sn-Cu coatings prepared by pulse plating are composed of tetragonal s-Sn structure and Cu6Sn5 compounds irrespective of bath composition and conditions. The final coatings were very dense and smooth with nodular morphology. It was shown that a eutectic composition can be achieved if we apply a current density of ∼15-20 mA/cm2. The solderability studies suggest that solder coatings plated at and beyond 15 mA/cm2 are more suitable for solder finish applications.,The work presents key issues in pulse electroplating of Sn-Cu solder coatings from an alkaline bath. Possible strategies to control the eutectic Sn-Cu composition by plating process are recommended.

中文翻译：

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来自锡酸盐浴的脉冲镀锡铜焊料涂层

本文的目的是研究脉冲电镀电流密度对碱性锡酸盐浴制备的无铅 Sn-Cu 焊料涂层的形貌和可焊性的影响。, Sn-Cu 焊料涂层是由含有锡酸钠的电镀液制备的、铜基体上的锡酸铜、氢氧化钠和山梨糖醇添加剂。脉冲电镀实验以恒电流模式进行。电镀电流密度从 5 到 25 mA/cm2 不等，并研究了涂层的形态。镀层的可焊性是通过在 250°C 下回流焊料涂层后的铺展率测量来评估的。共晶焊料的成分控制一直是电镀中的一个挑战。结果表明，无论镀液成分和条件如何，通过脉冲电镀制备的 Sn-Cu 涂层均由四方 s-Sn 结构和 Cu6Sn5 化合物组成。最终涂层非常致密和光滑，具有结节形态。结果表明，如果我们施加约 15-20 mA/cm2 的电流密度，则可以实现共晶成分。可焊性研究表明，以 15 mA/cm2 及以上电流镀覆的焊料涂层更适合于焊接面漆应用。这项工作提出了从碱性浴中脉冲电镀 Sn-Cu 焊料涂层的关键问题。建议采用电镀工艺控制共晶 Sn-Cu 成分的可能策略。结果表明，如果我们施加约 15-20 mA/cm2 的电流密度，则可以实现共晶成分。可焊性研究表明，以 15 mA/cm2 及以上电流镀覆的焊料涂层更适合于焊接面漆应用。这项工作提出了从碱性浴中脉冲电镀 Sn-Cu 焊料涂层的关键问题。建议采用电镀工艺控制共晶 Sn-Cu 成分的可能策略。结果表明，如果我们施加约 15-20 mA/cm2 的电流密度，则可以实现共晶成分。可焊性研究表明，以 15 mA/cm2 及以上电流镀覆的焊料涂层更适合于焊接面漆应用。这项工作提出了从碱性浴中脉冲电镀 Sn-Cu 焊料涂层的关键问题。建议采用电镀工艺控制共晶 Sn-Cu 成分的可能策略。