Study On Electrodeposition Technology And Properties Of Sn-Ag-Cu Alloy Coatings

With the rapid development of science and technology,people have put forward higher and higher requirements for the performance of electronic products,and the important role of electronic products or the electronic industry in the national economy has become more and more prominent.The miniaturization,complexity,lightweight,multi-function,high reliability,and long life of electronic products promote the production and development of chip electronic components（such as chip resistors,chip capacitors,chip inductors,etc.）,and promote.The fourth generation of assembly technology is the emergence of surface mount technology（SMT）.This kind of assembly technology has higher performance requirements for the solderability coating on the surface of electronic components.In the production process of chip components,electroplating is often used to obtain a coating with good performance.In the field of electronic electroplating,the traditionally used coating is Sn-Pb solderable coating,and because Pb is harmful to the human body and the environment,it is an inevitable development trend to study tin and tin-based brazing alloy coatings that can replace Sn-Pb.Among them,the Sn-Ag-Cu ternary alloy coating has the closest performance characteristics to the Sn-Pb coating,such as good solderability,good wettability,and good corrosion resistance.Excellent Sn-Ag-Cu ternary alloy.The plating layer becomes the most solderable plating layer that can replace Sn-Pb.Sn-3.0Ag-0.5Cu is the eutectic alloy in the Sn-Ag-Cu alloy,and is the most commonly used solder composition,so it is usually the target of preparation of the Sn-3.0Ag-0.5Cu coating alloy.In this paper,by studying the composition of the plating solution and adjusting the process conditions,to ensure that a good performance close to the eutectic Sn-3.0Ag-0.5Cu coating can be obtained,and on this basis,the performance of the obtained coating is evaluated.Methane-sulfonate is used as the main salt in the plating solution,and thiourea,sodium citrate,and ethylenediaminetetraacetic acid are determined as complexing agents of Sn²⁺,Ag⁺,and Cu²⁺through potentiodynamic scanning experiments,so that these three metal ions can be deposited.The potentials are close to each other to achieve the purpose of co-deposition.By analyzing the effect of different ratios of main salt and complexing agent on the appearance and micro morphology of the coating,the ratio of main salt to complexing agent is determined.Use ascorbic acid as an antioxidant to improve the stability of the plating solution.Orthogonal experiment was performed to determine the concentration of main salt,complexing agent and ascorbic acid.Adjust the process parameters such as pH,electroplating time,current density,and use the electron probe to analyze the changes in the composition of the coating,and use the field emission scanning electron microscope to observe the changes in the micro morphology of the coating to determine the appropriate process parameters.Finally,Sn-Ag-Cu alloy coatings with mass fractions of Sn,Ag,and Cu in the range of 92%-97%,2%-6%,and 0.5%-2%are obtained.The bending method and cross-cut method as well as the observation of the cross-section of the coating confirm that the bonding force between the coating and the substrate is good.The plating layer and the plating layer were welded without the use of solder,and the generation of IMC was found in the cross section of the welded joint.And use differential scanning calorimetry,Tafel curve test to determine the melting point and corrosion resistance of the coating.The plating solution and process conditions studied in this article are good.The Sn-Ag-Cu ternary alloy coating obtained from the experiment has a melting point slightly higher than that of the Sn-3.0Ag-0.5Cu solder,which is close to the eutectic composition.It has good corrosion resistance and can be used as an alternative to Sn-Pb alloy coating has good application prospects.