HEDP体系电镀铜层结合力的影响因素研究

Study on influencing factors on the adhesion of electroplated copper coating in HEDP system

羟基乙叉二膦酸(HEDP)镀铜是一种很有前景的无氰镀铜体系,而其中镀层结合力是保证工艺良好应用的关键之一。通过计时电位法、阴极极化曲线及划痕法等测试系统研究了HEDP/Cu^(2+)摩尔比、表面活性剂、pH值、电流密度等对镀层结合力的影响规律。结果表明,上述因素均会显著影响铜层结合力。HEDP/Cu^(2+)摩尔比小(2.0∶1)、pH值低(7~8)时,铁件表面存在明显置换铜,镀层结合力差;提高HEDP/Cu^(2+)摩尔比和镀液pH值,铜络合物更加稳定,铜置换反应得以消除;HEDP/Cu^(2+)摩尔比超过3.0∶1,pH值大于10时,镀层结合良好。表面活性剂可以增强镀液对阴极界面的润湿能力,有效改善镀层结合力,且炔醇类表面活性剂表现更佳。电流密度0.2~0.5 A/dm2时Q235钢可能处于钝态,而2.0 A/dm2时镀层出现“铜瘤”,镀层结合力均不佳。

Electroplating copper in 1-hydroxyethylidene-1,1-diphosphonic acid bath is a promising non-cyanide copper plating system,and the coating adhesion is one of the keys to ensure the good application of this process.The influence law of HEDP/Cu^(2+)molar ratio,surfactant,pH value and current density on the coating adhesion was systematically studied by chronopotentiometric,cathodic polarization curve and scratch method.The results showed that the above factors can significantly affect the adhesion of copper coating.There is obvious phenomenon of copper replacement on the surface of iron parts when the molar ratio of HEDP/Cu^(2+)is small(2.0∶1)and the pH value is low(7−8),and the coating adhesion is poor.If increasing the HEDP/Cu^(2+)molar ratio and the pH value of the bath,the complex products of copper are more stable,and the displacement reaction of copper is eliminated.The adhesion of copper coating is good when the HEDP/Cu^(2+)molar ratio exceeds 3.0∶1 and pH>10.Surfactant can enhance the wettability of the bath to the cathode interface and effectively improve the coating adhesion,and the alkynol surfactant performs better.The Q235 steel may be in a passive state under 0.2−0.5 A/dm2,and the coating will form"copper nodules"at 2.0 A/dm2,and the coating adhesion is poor.