HEDTA对甲基磺酸盐镀液中锡-银-铜三元合金共沉积的影响

Effect of HEDTA on codeposition of tin-silver-copper ternary alloy from methanesulfonate bath

以HEDTA(Nβ羟乙基乙二胺三乙酸)为主配位剂,通过极化曲线测量、电感耦合等离子体发射光谱、表面形貌分析和X射线衍射谱分析等技术研究了甲基磺酸盐镀液中HEDTA含量对Sn-Ag-Cu三元合金共沉积的影响。镀液的基础组成和工艺条件为:Sn(CH3SO3)2 0.18mol/L,Ag2O 0.006mol/L,Cu(CH3SO3)2 0.0012mol/L,硫脲0.06mol/L,烷基糖苷(APG)1g/L,pH4.0～6.0,温度25°C,电流密度7mA/cm2,时间30min。结果表明,随镀液中HEDTA含量的增加,Sn-Ag-Cu的沉积电位负移;但n(HEDTA)∶n[Sn(II)]大于2.2∶1.0时,HEDTA才可满足一定的配位要求,使沉积电位产生足够大的负移。镀液中HEDTA含量为0.6～1.2mol/L,即n(HEDTA)∶n[Sn(II)]为(3.3～6.7)∶1.0时,HEDTA的含量对镀层组成影响不大,所得Sn-Ag-Cu合金镀层结晶细致,表面平整、均匀,主要由Sn、Ag3Sn和Cu6Sn5组成。此外,随镀液中HEDTA含量的变化,镀层的结晶取向发生变化。

The effect of the content of primary complexing agent HEDTA [N-（fl-hydroxyethyl）ethylendiamine triacetic acid] on codeposition of Sn-Ag-Cu ternary alloy in methane- sulfonate bath was studied by polarization curve measurement, inductively coupled plasma emission spectroscopy, surface morphology observation, and X-ray diffraction analysis. The basic bath compositions and process parameters are as follows： Sn（CH3SO3）20.18 mol/L, Ag20 0.006 tool/L, Cu（CH3SO3）2 0.001 2 mol/L, thiourea 0.06 mol/L, alkyl glycosides （APG） 1 g/L, pH 4.0-6.0, temperature 25 ℃, current density 7 mA/cm2, and time30 min. The results show that the deposition potential shifts towards negative as the HEDTA content in bath increases. However, only when the molar ratio of HEDTA to Sn（II） is above 2.2：1.0, can HEDTA meet the complexation requirement and make the deposition potential shift towards negative enough. When the HEDTA content in bath is 0.6-1.2 tool/L, that is the molar ratio of HEDTA to Sn（II） equals to （3.3-6.7）：1.0, HEDTA content has little impact on the coating composition. The obtained Sn-Ag-Cu alloy coating is fine-grained, level, uniform, and mainly composed of Sn, Ag3Sn, and Cu6Sn5. The crystal orientation of Sn-Ag-Cu alloy coating changes as the HEDTA content in bath varies.