硫酸盐电镀锡添加剂的探讨

Exploration of Additives for Tin Electroplating in Sulfate Bath

目前,硫酸盐镀锡使用的添加剂易使镀液不稳定、变质、多泡,为此,从镀液变黄和变浊时间以及pH值等方面,筛选合适的稳定剂和不同光亮剂组合,研究其对镀液性能的影响。用电化学工作站测试钒酸盐含量对镀锡溶液开路电位以及苄叉丙酮和复合添加剂含量对镀液阴极极化曲线的影响。通过划痕试验、弯曲试验、热震试验和盐雾试验检测了添加剂对镀液和镀层性能的影响。结果表明:当钒酸盐含量为0.05 g/L时,镀锡溶液开路电位明显提高,添加1次能维持镀液70 d不变黄,90 d不浑浊;当苄叉丙酮含量为0.10 g/L,复合添加剂含量为2.3g/L时,吸附电位范围在-0.78～-0.53 V,阴极极化度提高,获得镜面光亮锡镀层的电流密度范围为0.5～5.0A/dm2;优化添加剂后阴极电流效率为93%,沉积速度为92μm/h,镀层孔隙率为0.063个/cm2,24 h中性盐雾试验为10级,结合力合格;该镀锡添加剂能还原镀液中的溶解氧和Sn4+,有效抑制Sn2+的氧化,细化镀层结晶。

In view of the instability,deterioration and foaming of tin electroplating bath induced by additives,proper stabilizers and combination of different brighteners were screened in relation to pH value as well as time for the plating bath to turn yellow and feculent.The effects of stabilizers and brighteners on the performance of the plating bath were investigated.An electro-chemical workstation was performed to investigate the effect of vanadate concentration on the open circuit potential and the effects of concentrations of benzalacetone and compound additive on the cathodic polarization curves of the plating solution.The effects of various additives on the performance of the plating bath and Sn coating were examined based on scratch test,bending test,thermal shock test and salt spray test.It was found that the open circuit potential of the plating solution rose significantly when the content of vanadate was 0.05 g/L,and relevant plating bath coud be maintained for 70 d without turning yellow and for 90 d without feculence.When the content of benzalacetone was 0.10 g/L and that of compound additive was 2.3 g/L,the extent of cathodic polarization was increased,with an adsorption poten-tial of-0.78～-0.53 V and a current density range for obtai-ning mirror-bright tin coating of 0.5～5.0 A/dm2.When the ad-ditives were optimized,a cathodic current efficiency of 93% and a deposition rate of 92 μm/h were reached,and resultant Sn coating had a porosity of 630 pores per square meter,grade of 10 for 24 h of neutral salt spray test and qualified adhesion.In one word,the additive for tin electroplating was able to reduce dis-solved oxygen and Sn4+ in the plating solution,retard the oxida-tion of Sn2+ and refine the grains of Sn coating.