Study On Plating Au-Pd-Cu Alloy In Cyanide Free Sulfite Bath

The Au-Pd-Cu alloy’s electrochemical deposition plating has excellent chemical stability, electrical conductivity, weldability and high temperature performance. It is an excellent plating for improving the surface properties of various components, so it has a wide range of applications in functional materials and decorative plating. The traditional cyanide plating bath has good dispersion capacity coverage, high current efficiency, good stability and fine crystalline coating. However, it poses a huge threat to the environment and staff due to its highly toxic. Therefore, the development of safe, environmentally friendly and non-cyanide plating solution is the new research direction of gold plating technology.In this paper, optimized the strong etching process specification of pretreatment by single factor method. Sulfite and citrate are the complexone, ammonium gold sulfite, sodium dichloro palladium and copper sulfate is the main salt, EDTA is a stabilizing agent for gold, potassium is a conductive salt, borax is a pH adjusting agentand. Researched and developed the initial processing formulation of non-cyanide sulfite for plating the alloy of Au-Pd-Cu. At the same time, the paper studyed the impact of stirring speed, temperature, pH and pulse plating process parameters (current density, duty cycle, pulse frequency) to the plating and plating bath performance. By single factor method to determine the optimum conditions:pH=9, temperature=50℃, the stirring speed=l000r/min, duty cycle=10%, frequency=900Hz, current density Ak=0.5A/dm2. The optimum formulation of the Au-Pd-Cu alloy plating determined by orthogonal test is Au(added in the form of sulfite gold sodium) lOg/L, Pd(NH3)Cl28g/L, CuSO4lg/L, Na2SO3140g/L, EDTA30g/L, Ammonium citrate80g/L, K2SO460g/L、Borax30g/L. Electroplated by the orthogonal optimal formula, the surface of plating layer is brightly golden color and uniform, plating hardness is264HvO.1, contact resistance is216mΩ, plating layer has good adhesion and corrosion resistance. The plating layer composition is Au90.4wt%Pd4.5wt%Cu5.1wt%, The plating solution current efficiency reached79%, dispersion capacity is82.17%, the coverage ability is84.52%, the stability of the bath is40days.The quality of the plating using the process specifications is good. The plating solution has a good dispersing ability, covering ability, stability and cyanide-free plating solution, the process meets the manufactural requirements.