Application of NP(EO)n with different polymerization degrees in acid bright copper plating
(Key Laboratory of Fuel Cell Technology of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China)
Abstract: To study the reason why nonylphenol ethoxylates (NP(EO)n) can be used as the brightener in acid bright copper plating and effect of NP(EO)n with different polymerization degrees on kinetic parameters of copper deposition and morphology of deposits, NP-10, NP-15, NP-20 and NP-40 were used with Cl--DPS as additives in CuSO4-H2SO4 at 50 ℃. Adsorption morphology of NP(EO)n in electric double layer on electrode and influence of NP(EO)n on electrodeposition were studied by potential scan electrochemical impedance spectroscopy, linear sweep voltammetry and chronoamperometry, respectively. The morphology and crystal orientation of deposits were characterized by scanning electron microscopy and X-ray diffractometry. The results show the adsorption layer of NP(EO)n on electrode blocks the diffusion of Cu2+, enhances the cathode polarization and refines the grain size. NP(EO)n shows different effects on electrodeposition due to the different length of hydrophilic chain. In general, the longer the length of NP(EO)n chain, the better the morphology of deposit.
Key words: nonylphenol ethoxylates; adsorption; electrolytic copper foil; nucleation; morphology