| Cyanide copper plating process has many advantages, such as good plating ability,coating crystallization meticulous, mature technology and simple process. but cyanide is deadly toxic. It is the development trend of electroplating industry in the future to invent a safety and environmental non-cyanide copper plating method to replace cyanide copper plating, HEDP copper plating process is the most likely to replace cyanide copper plating process, which were be researched for a long time and have a lot of advantages in many non-cyanide copper plating method. but it still has many aspects to improve and optimize. in this paper, we research the optimal solution composition and technological conditions of HEDP copper plating system on the basis of predecessors’ work. Using a variety of electrochemical methods and analytical techniques to research structure and properties of coating.The formula components and additives were be filtered by Hull cell test, which is fit for HEDP non-cyanide copper plating process. the influences of different component in HEDP system were investigated in this test, Then used orthogonal test to further optimize the composition of plating solution and process conditions. The system optimal bath composition and operating conditions(HEDP210g/L, Cu2(OH)2CO3:7.7g/L, K2CO3:152g/L, KOH:87g/L,pH:10.5, T04:6.0mg/L, T12:3.7mg/L,T15:0.4mg/L,50℃, Airagitation, Dk1.5~2.0A/dm2) were obtained by experiment.The plating solution has good stability and 61.6% dispersion ability; the coating grain is fine smooth, uniform, low porosity. With rotation rate 12r/min and Dk :8A/kg, The process can be used by Iron and steel parts. whether or not to join the additives, coating binding force can meet the requirements of technology application. additives will greatly improve the coating brightness, but will reduce the speed of copper plating.By cathodic polarization curves and cyclic voltammetric curves to research the electrochemical properties of plating solution. The copper layer under the optimal process was characterized by SEM, XRD and EDS. The results showed that process of cathodic reduction reaction is not reversible. concentration of copper ion, HEDP, K2CO3, additives and plating solution temperature will affect the cathodic polarization degree of plating solution. The greater the concentration of copper ion and the lower the content of HEDP & potassium carbonate, the corresponding solution of cathodic polarization degree will be decreased;Solution of the higher the temperature, molecular thermal motion more intense, ion in the solution diffusion velocity increases, the concentration polarization is reduced, cathodicpolarization gradually reduce; After mixed with appropriate amount of additives, the copper deposition potential negative shift, cathodic polarization increases, the cathodic reduction current smaller, copper ion deposition at a slower pace. from the perspective on the crystal structure,because of adding additives, coating(111) crystal plane diffraction peak intensity was improved, which have more energy to encourage the formation of crystal nucleus, more conducive to meet the requirements of the quality of plating density copper plating.Temperature of plating solution, current density, air mixing process conditions affect the coating surface microscopic morphology, the structure of the coating and the coating composition. Within the scope of the process conditions, with the increase of current density and temperature, the plating crystalline grain is greater, homogeneity is the worse and density decreased. Solution temperature of 30℃, the preferred orientation of coating is(111) crystal plane; Solution temperature of 70℃, the preferred orientation of coating is(200) crystal plane;Plating solution temperature is higher, the coating quality of copper element in percentage increased; Air mixing and adding appropriate amount of additives(T04 6.0mg/L, T12 3.7 mg/L,T15 0.4 mg/L)can get a better quality of copper plating. |
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