光亮剂对印制电路板低温硫酸盐化学镀锡的影响

为获得结晶致密和平整的化学镀锡层,采用扫描电镜(SEM)、电化学阴极极化、X射线衍射仪(XRD)等方法研究了光亮剂PPS(丙烷磺酸吡啶嗡盐)和DEP(二乙胺基戊炔二醇)对印制电路板低温硫酸盐化学镀锡的影响。结果表明:随着光亮剂PPS和DEP添加量加大,化学镀锡速率和阴极还原电流均先增大后减小,适宜的添加浓度分别为30 mg/L和40 mg/L;化学镀液中加入PPS和DEP后,化学镀锡层表面形貌明显平整,沉积的晶粒细致;加入混合光亮剂所得锡镀层结合力良好,在Sn(101)晶面择优取向,未发现铜锡化合物,添加剂使化学镀锡产生显著的阴极极化,镀层结晶致密平整。

Effect of Brightener on Electroless Sn Plating of Printed-Circuit Board in Sulfate Bath at Low Temperature

In order to obtain dense and smooth electroless tin coating,the effects of brightener PPS (propane sulfonic pyridinium salt) and DEP (diethylamino pentyne glycol) on electroless tin plating of printed-circuit board (PCB) in sulfate bath at low temperature were studied by means of SEM,electrochemical polarization and XRD.Results showed that the rate of electroless Sn plating and cathodic reduction current increased firstly and then decreased with the increase of PPS and DEP in the bath,and the appropriate addition concentrations were 30 mg/L and 40 mg/L,respectively.After the addition of PPS and DEP in the electroless plating bath,the surface morphology of electroless tin plating layer was obviously flat and the deposited grain was fine.When the mixture additives were added in the bath,the Sn coating had good adhesion and grew preferentially in Sn (101) crystal orientation whereas the copper tin compound was not found.Finally,the cathodic polarization of the electroless tin plating was greatly enhanced with the addition of the mixed brighteners,which resulted into the formation of the compact and smooth coating.