【作者】 项海锋； 李宁； 黎德育；

【Author】 XIANG Haifeng,LINing,LI Deyu (Department of Applied Chemistry,Harbin Institute of Technology,Harbin 150001,China)

【机构】 哈尔滨工业大学应用化学系；

【摘要】 本文采用电量法对镀层锡含量进行测定,通过研究NaH₂PO₂对镀层锡沉积量的影响,发现硫脲（TU）是锡沉积的主要推动力,而不是NaH₂PO₂。由阳极极化曲线（LSV）来考察次NaH₂PO₂的阳极氧化行为及Sn²⁺和锡金属对其的影响,研究表明Sn²⁺和锡金属对NaH₂PO₂的氧化均具有毒化作用;对镀液中NaH₂PO₂的消耗进行了滴定分析,对镀层中P含量进行了X-射线荧光光谱（XRF）、电子能谱（EDS）和等离子发射光谱（ICP-MS）分析,结果显示在误差范围内镀液中没有NaH₂PO₂的消耗,镀层中没有检测出P含量;由此认为化学镀锡中NaH₂PO₂的不具有还原剂作用。采用阴极极化曲线（LSV）研究了Sn²⁺的阴极沉积行为及NaH₂PO₂对Sn²⁺阴极沉积行为的影响,发现NaH₂PO₂对Sn²⁺的阴极沉积具有抑制作用;通过开路电位曲线（OCPT）、塔菲尔曲线（Tafel）和循环伏安曲线（CV）研究发现,NaH₂PO₂的存在会降低硫脲的对铜的络合腐蚀,从而抑制置换反应;由此认为NaH₂PO₂对锡沉积起抑制作用,防止在施镀过程出现锡泥,从而提高施镀过程镀液的稳定性。研究了NaH₂PO₂对镀液稳定的贡献,发现NaH₂PO₂可以抑制Sn²⁺被氧化成Sn⁴⁺,但会提高pH值使Sn²⁺容易水解氧化成SnO₂乳白色沉淀;少量柠檬酸可以抑制Sn²⁺的水解氧化;两者结合能够提高镀液放置过程的稳定性。更多还原

【Abstract】 In this article,the tin content of coating was measured by a kind of coulometry method,and found that thiourea was the main driving force tin deposition,rather than sodium hypophosphite by the study of the effect of sodium hypophosphite on the tin deposition.The anode oxidation behavior of the NaH₂PO₂ is investigated by Liner Sweep Voltammetry（LSV） curves,the results indicate that,SnO₂ and tin metal are the drug of The anode oxidation behavior of the NaH₂PO₂;The consumption of NaH₂PO₂ in the bath is analysed by titration,and he P content in the coating is measured by X - ray fluorescence spectrometry （XRF）,electron spectroscopy（EDS） and inductively coupled plasma- optical emission spectrometry（ICP- MS）,the results show that,there is no consumption of NaH₂PO₂ in the margin of error and no P content in the coating;Therefor,the NaH₂PO₂ doesn’t have the capability of reducer in the electoless tin plating. The cathode deposition behaviour of the Sn²⁺ and the effect of the NaH₂PO₂ on the behavior are studied by Liner Sweep Voltammetry（LSV）,found that the behavior is restrained by NaH₂PO₂.The fact that NaH₂PO₂ can reduce the offensive of thiourea on the copper to restrain the replacement reaction is found by Open Circuit Potential curve（OCPT）,Tafel Plot curve （Tafel） and the Cyclic Voltammetry curve（CV）.Thereout,the NaH₂PO₂ has the capability that can restrain the deposition of tin （Ⅱ）,can prevent the tin soil in the plating process,thereby enhancing the stability of the bath. The contribution of NaH₂PO₂ to the stability of the bath is studied and found that it can inhibit the oxidation of tin（Ⅱ） to tin（Ⅳ）,but will raise the pH value to make the tin（Ⅱ） hydrolyse and oxidate to SnO₂ which is a milky deposition;A small amount of citric acid can inhibit the hydrolysis of tin（Ⅱ）;So NaH₂PO₂ and citric acid can work together to improve the stability of the both.更多还原