无氰镀银液的浓度对成核机理、镀液和镀层性能的影响

Effect of the Concentration of Non-Cyanide Silver Plating Solution on the Electroplating Mechanism,Bath and Coating Performance

电镀过程中会因水分蒸发或母液补加使镀液浓度发生变化,因此系统研究镀液浓度变化对电镀工艺的影响具有重要的指导意义。本文采用循环伏安法(CV)和计时电流法(CA)考察了在不同浓度的无氰镀银液(含银量为7.1~19.1 g·L^(−1))下银的结晶成核机理;利用景深扩展体视显微镜和原子力显微镜(AFM)观察镀液浓度变化对镀层微观形貌的影响。镀液性能测试表明,镀液电流效率接近于100%,分散能力在80%左右,置换反应发生时间则随着浓度的降低而延长。镀层性能测试包括白度、硬度和光泽度,其中硬度随着浓度变化差别不明显,白度和光泽度随着浓度的降低总体呈下降趋势。通过对不同镀液浓度下的温度窗口和电流密度窗口的研究,确定了该工艺的理想工作范围。

During the electroplating process,the concentration of the plating solution may change due to the water evaporation or the replenishment of the mother liquor.Therefore,the study of the concentration effect on the electroplating process is of great guiding significance.In this paper,cyclic voltammetry(CV)and chronoamperometry(CA)were used to investigate the nucleation mechanism of silver deposition at different concentrations of the cyanide-free silver plating solutions(The Ag content ranges from 7.1 to 19.1 g·L^(−1)).The microstructure of the coating was characterized by a stereomicroscope with extended depth of focus and an atomic force microscope(AFM)as well.The performance test of the bath showed that the current efficiency was close to 100%,the dispersing power was about 80%,and the time of replacement reaction was prolonged with the decrease of the concentration.The comparison of the coating properties at different concentrations includes whiteness,hardness and glossiness.It showed that hardness varied little with the solution concentration,whereas whiteness and glossiness decrease with decreasing the concentration.With systematical study of the bath solution at different temperature and current density,an ideal working condition of the process was determined.