硫脲对聚甲基丙烯酸甲酯基材化学镀铜的影响

Effect of thiourea on electroless copper plating on polymethylmethacrylate substrate

以硫脲为添加剂、硫酸铜为主盐、次磷酸钠为还原剂，在聚甲基丙烯酸甲酯（PMMA）基材表面进行化学镀铜。研究了添加不同质量浓度（0．10、0．25、0．50、0．75和1．00mg／L）的硫脲对铜沉积速率、镀层导电性和结合力以及化学镀铜中氧化还原反应的影响，并通过扫描电镜（SEM）、能谱分析（EDS）和X射线衍射（XRD）等方法分别对镀层微观形貌、组成成分、晶体结构进行了表征。结果表明，硫脲的加入主要影响铜（111）晶面的生长，能有效提高镀层与基体之间的结合力，但对镀层成分无太大影响。随着硫脲加入量的增大，铜沉积速率和镀层导电性先减后增，而镀铜速率主要由阴极还原过程控制。适宜的硫脲添加量为0．50～0．75mg／L，此时铜沉积速率相对较低，所得镀层晶粒尺寸较小，表面电阻为40～50mΩ／cm^2，镀层结合力l～2级。

The electroless copper plating on surface of polymethylmethacrylate （PMMA） substrate was carried out with thiourea as additive, copper sulfate as main salt, and sodium hypophosphite as reductant. The influence of the thiourea added with different mass concentrations （0.10, 0.25, 0.50, 0.75, and 1.00 mg/L） on copper deposition rate, conductivity and adhesion strength of copper deposit, as well as oxidation and reduction reactions during electroless copper plating process were studied. The micro-morphology, composition, and crystal structure of the deposit were analyzed by scanning electron microscopy （SEM）, energy- dispersive spectroscopy （EDS）, and X-ray diffraction （XRD）, respectively. The results indicated that the addition of thiourea mainly affects the growth of copper（111） crystal plane, and efficiently improves the adhesion of deposit to substrate, while slightly affects the deposit composition. The deposition rate of copper and the conductivity of deposit are decreased initially and then increased with increasing the dosage of thiourea. The electroless copper plating rate is mainly controlled by cathodic reduction reaction. A suitable dosage of thiourea is 0.50-0.75 mg/L, achieving a relatively low copper deposition rate. The deposit obtained features small grain size, surface resistance of 40-50 mΩ/cm^2, and grade 1-2 adhesion strength to the substrate.