亚硫酸钠-柠檬酸钾体系络合剂对镀金层性能的影响

Effect of Sodium Sulfite Potassium Citrate Complexing Agent on Properties of Gold Plating Layer

目的 研究亚硫酸钠-柠檬酸钾体系络合剂对可伐基板镀金层共晶焊接性能的影响机理,从而优化络合剂含量工艺范围,提升镀金层金锗共晶可焊性。方法 采用扫描电子显微镜及能谱仪(SEM-EDS)、X射线衍射仪(XRD)、极化曲线等分析方法,结合镀金层孔隙、金锗共晶焊接润湿性和剪切强度测试,研究了亚硫酸钠-柠檬酸钾体系络合剂,对镀金层表面金锗焊料润湿性,金锗共晶层结合力、表面和截面形貌、结晶状态、孔隙,以及金锗共晶焊接界面微观形貌等的影响。结果 亚硫酸钠和柠檬酸钾均能起到络合剂作用,当络合剂亚硫酸钠质量浓度为120~160 g/L和柠檬酸钾质量浓度为40~60 g/L时,络合剂含量的增加可使镀金液阴极过电位明显增大,从而使所制备的镀金层结晶更加致密。当络合剂亚硫酸钠质量浓度为160~200 g/L、柠檬酸钾质量浓度为60~100g/L时,电沉积的镀金层表面明显平整,截面形貌致密,孔隙少,且以(311)晶面择优生长,晶粒尺寸为43.7nm,晶面间距为0.123nm,金锗焊料润湿良好,金锗共晶层结合力较大,剪切强度可达3 MPa以上,可满足金锗共晶焊接使用要求。结论 亚硫酸钠-柠檬酸钾体系络合剂含量对镀金层的结晶状态和致密性影响明显,镀金层结晶状态和致密性与其表面金锗共晶可焊性有直接关系,镀金层越结晶致密越有利于其表面共晶焊接质量,通过控制亚硫酸钠-柠檬酸钾络合剂含量可有效提高镀金层表面金锗共晶焊接质量。

In order to study the influence mechanism of the complexing agent in the cyanide-free sodium nitrite-potassium citrate gold plating solution on the eutectic welding performance of Kovar substrate electrodeposited gold plating layer,so as to optimize the process range of the complexant content,improve the eutectic solderability of the gold plating layer,and expand the application of the sulfite-free gold plating process in the field of high-precision electronic equipment manufacturing,the effects of complexing agent in sodium nitrite-potassium citrate gold plating solution on the wettability of Au-Ge solder on the surface of gold plating layer,the adhesion of Au-Ge eutectic layer,surface and cross-sectional morphology,crystalline state,pores and micro morphology of Au-Ge eutectic welding interface were studied,by the methods of Scanning Electron Microscope and Energy dispersive spectrometer(SEM-EDS),X-ray diffraction(XRD),and polarization curve,and the test of the porosity,wettability and shear strength of the gold-plated layer.The results show that the sodium sulfite and potassium citrate in gold plating solution can act as complexing agent.When the content of sodium sulfite and potassium citrate in the range of 120-160 g/L and 40-60 g/L,the surface of electrodeposited gold plating layer is weld abnormally and the micromorphology of electrodeposited gold plating layer surface and section presents cotton shape,loose,many pores,and the electrodeposited gold plating layer presents relatively large crystal size,and grows preferentially on(111)and(200)crystal face,and the electrodeposited gold plating layer cystal sizes are 95.5 nm and 66.4 nm respectively,and the interplanar spacing is 0.234 nm and 0.204 nm respectively.The content of complexing agent in gold plating solution has an obvious influence on the crystallization state and compactness of electrodeposited gold plating layer.The increase of complexing agent content can increase the cathodic overpotential of cyanide free gold plating solution,so as to make the prepared gold plating crystal more compact.The crystallization state and compactness of the electrodeposited gold plating layer is directly related to its gold germanium eutectic weldability.When the crystal size and crystal spacing of electrodeposited gold plating layer are smaller,and the compactness of electrodeposited gold plating layer is better,the surface eutectic welding quality of electrodeposited gold plating layer is better.When the content of sodium sulfite is 160-200 g/L and the content of potassium citrate is 60-100 g/L,the gold plating layer micromorphology of surface and section is obviously flat,dense,few pores and the gold plating layer presents relatively small grains,and grows preferentially on(311)crystal face,and the gold plating layer grain size is 43.7 nm,and the interplanar spacing is 0.123 nm,and the gold germanium solder on the surface of the gold plating layer is well wetted,the bonding force of the gold germanium eutectic layer is large,can reach more than 3 MPa,which meets the requirements of gold germanium eutectic welding.By reasonably controlling the content of sodium sulfite and potassium citrate in gold plating solution within a reasonable range,the crystallization state and compactness of electrodeposited gold plating layer can effectively controlled and the quality of eutectic welding on the surface of electrodeposited gold plating layer can be effectively improved.