巯基羧酸类有机物对无氰亚硫酸盐体系电镀金的影响

Effects of mercapto-containing carboxylic acids on gold electroplating in cyanide-free sulfite bath

通过直流电沉积、紫外-可见(UV-Vis)分光光度法、扫描电镜(SEM)、X射线衍射(XRD)等手段研究了3-巯基丙酸、巯基丁二酸、1-巯甲基环丙基乙酸和2-氨基-3-巯基丙酸4种巯基羧酸类有机物对无氰亚硫酸盐电镀金体系镀液稳定性和镀层性能的影响。结果表明:在pH 6.0~8.0范围内适量加入巯基丁二酸可以显著提高镀液的稳定性,这可能是因为巯基丁二酸与Au~+形成了稳定的配合物,镀液常温保存6个月仍清澈透明。在Au^(+)3 g/L、巯基丁二酸6.750 g/L、润湿剂3.4 mL/L、pH 6.0(柠檬酸-磷酸氢二钠缓冲体系)、温度40℃、电流密度0.5 A/dm^(2)的条件下电镀10 min,能够得到厚度为1.5~2.0μm的镀金层,其表面均匀致密,结合力、耐蚀性及可焊性良好。

The effects of 4 kinds of mercapto-containing carboxylic acids i.e.3-mercaptopropionic acid,mercaptosuccinic acid,1-(mercaptomethyl)cyclopropaneacetic acid,and 2-amino-3-mercaptopropionic acid on the stability of cyanide-free sulfite bath for gold electroplating and the properties of gold coating electrodeposited therefrom were studied by direct-current electrodeposition,ultraviolet-visible spectrophotometry(UV-Vis),scanning electron microscopy(SEM),and X-ray diffraction(XRD).The results showed that the bath stability was improved greatly by adding mercaptosuccinic acid as a complex agent,which was probably attributed to the formation of stable complexes from the reaction between mercaptosuccinic acid and Au+in the pH range from 6.0 to 8.0.The bath kept clear and transparent after be stored at room temperature for 6 months.When electroplating in a bath composed of Au^(+)3 g/L,mercaptosuccinic acid 6.750 g/L,and wetting agent 3.4 mL/L in a citric acid–sodium dihydrogen phosphate buffer at current density 0.5 A/dm^(2) and temperature 40℃for 10 min,a uniform and compact gold coating with a thickness of 1.5-2.0μm could be electrodeposited,and it also featured good adhesion,corrosion resistance,and solderability.