Study On Formula And Technology Of Plating Au-Cu Alloy In Sulfite Plating Solution

Pure gold coating has good electrical conductivity,thermal conductivity,ductility,heat-resistant and corrosion resistance.However,other elements are often added to the coating in order to improve the performance due to its low hardness and poor wear resistance.Adding copper in gold coating can not only maintain the original performance,but also improve the hardness and wear resistance of the coating.Thus,Au-Cu alloy coating has been widely applied to the field of gold electroplating.At present,cyanide is widely used to gold plating.Its coating has better quality.However,cyanide is deadly toxic which does great harm to human body and the environment.Therefore,the development of cyanide free gold plating solution with good performance is the main research direction for electroplating workers.In this thesis,organic polyphosphoric acid is chosen as the auxiliary complexing agent of sulfite gold plating.The polarization phenomenon of adding ATMP plating solution is analyzed by electrochemical workstation.The results show that ATMP can aggravate the cathodic electrochemical polarization phenomenon such that the quality of the coating is improved.Then,the electroplating system of sodium sulfite-HEDP-ATMP is determined.In this study,with the orthogonal experiment,by evaluating the appearance,hardness and contact resistance of the coating,the optimal solution formula is obtained as follows: gold 10g/L,copper sulfate 1.5g/L,sodium sulfite 160g/L,potassium sulfate 80g/L,HEDP 80g/L,and ATMP 60 g / L.The sequence of the single factor experimental parameters is designed based on polarization analysis.Meanwhile,the impact of different plating process parameters on the coating surface quality and plating solution deposition rate is also studied.The optimal process parameters are as follows: 0.35A/dm2 current density,9 pH value,65℃ plating temperature and 900r/min stirring speed.In this thesis,the Au-Cu alloy coating has uniform brightness surface,good adhesion,good corrosion resistance;the micro hardness of the coating is 175.48Hv;the gold element mass fraction of the coating is 95.39% shown by the electronic probe test results and the copper element mass fraction is 4.61%.The current efficiency of plating solution is 91.67%,the covering power is 85.42%,the dispersion capacity is 81.17%,and the stability is good,the solution can be stored for more than 5 months.This technology is applied to the processing of the conductive rod.The problem of micro groove bottom burning is solved by improving the process parameters.Thus,the conductive rod can be produced with good conductivity and corrosion resistance.