电镀液添加剂成分对钯镀层的影响研究

Study on the effect of additive composition of electroplating solution on palladium coating

采用二氯四氨钯为主盐,润湿剂A、光亮剂B、稳定剂C为组合添加剂配制成电镀液,进行侯氏槽测试,电沉积获得钯镀层。通过设计正交试验对添加剂的组成及含量进行了筛选,采用扫描电子显微镜、X射线衍射表征了钯镀层的形貌和结构,考察了添加剂组分及含量对镀钯层表观形貌、微观形貌以及硬度的影响。正交试验研究结果表明:在电流密度0.85 A/dm^(2)、镀液pH 8.0,50℃施镀20 min的电镀工艺下,添加剂中稳定剂含量对于电沉积的影响较为明显,稳定剂含量大的镀层外观和硬度比较好,而光亮剂和润湿剂起辅助性作用。稳定剂与钯离子络合,阻止钯离子被还原,提高了镀液稳定性;光亮剂吸附在阴极表面,增大阴极极化值,形成活性位点,提高了晶核的生成速度,能够获得结晶细致紧密的镀层;润湿剂降低了阴极电沉积过程中产生的氢气气泡附着力,扩展了低电流区镀层,提高抗杂质干扰能力使镀层光亮平整。添加剂中各组分的协同提高了镀液整平能力及低电流密度区镀层光亮性,获得的纯钯镀层阴极电流密度范围更宽。

The plating solution was prepared by using dichlorotetrammine palladium as main salt,wetting agent A,brightener B and stabilizer C as combined additives,and Hough cell tests were conducted to obtain a palladium coating by electrodeposition.The composition and content of additives were screened through orthogonal experiments,and the morphology and structure of palladium coatings were characterized by scanning electron microscopy and X-ray diffraction.The effects of additive composition and content on the apparent morphology,micro-morphology and hardness of the palladium coating were investigated.The results of orthogonal experimental research show that under the electroplating process with a current density of 0.85 A/dm^(2),a plating solution pH value of 8.0,and a plating time of 20 minutes at 50℃,the stabilizer content in the additive has a more significant impact on electrodeposition.Coatings with high stabilizer levels have better appearance and hardness,while brighteners and wetting agents play an auxiliary role.The stabilizer is complexed with palladium ion to prevent palladium ion from being reduced and improve the stability of the bath.The brightener adsorbed on the cathode surface,increased the cathode polarization value,formed an active site,improved the formation rate of crystal nucleus,and obtained a fine and compact crystalline coating.The wetting agent reduces the adhesion of hydrogen bubbles produced during cathode electrodeposition,expands the coating in the low current region,improves the anti-impurity interference ability and makes the coating bright and smooth.Each component of the additive collaboratively improves the levelling ability of the bath and the brightness of the coating in the low current density area,and the cathodic current density range of the pure palladium coating is wider.