焦磷酸盐溶液体系电镀白铜锡工艺

Process of white copper-tin alloy electroplating with pyrophosphate bath

研究了溶液组成、pH、温度、阴极电流密度、施镀时间等对白铜锡合金镀层外观、厚度及成分的影响。较优的镀液组成及工艺条件为:Cu2P2O7·3H2O30g/L,Sn2P2O74g/L,K4P2O7·3H2O200～250g/L,K2HPO480g/L,pH8.8,温度28～30°C,阴极电流密度0.6～1.0A/dm2,时间20min。在该工艺条件下,所得白铜锡合金镀层表面均匀、白亮,锡含量为40%～50%(质量分数),抗变色能力强,与铜基体结合力好,可替代镍镀层。

The effects of bath composition, pH, temperature, cathodic current density and plating time on the appearance, thickness and composition of white Cu-Sn alloy deposit were studied. The optimal bath formulation and operation conditions are as follows： Cu2P2O7·3H2O 30 g/L, Sn2P2O7 4 g/L, K4P2O7·3H2O 200-250 g/L, K2HPO4 80 g/L, temperature 28-30 ℃, pH 8.8, cathodic current density 0.6-1.0 A/dm2 and time 20 min. Under the given process conditions, the Cu-Sn alloy deposit is uniform and bright and contains tin 40%-50% （mass fraction）. The Cu-Sn alloy deposit has the advantages of high discoloration resistance and good adhesion to copper substrate. It can be used for substituting nickel coating.