A Study On Material Balance Problem In Electrogenerated Chemical Polishing

Electrogenerated chemical polishing（EGCP）is a new ultra-precision surface processing method,and has a great potential for use in ultra-precision machining of defect-free surfaces.In EGCP] the redox mediator in the polishing solution turns into an etchant by electrochemical oxidation on an electrode surface,and the workpiece is etched by the etchant.The closer the workpiece to the electrode surface,the higher the etching rate will be,which is called “gap-sensitive etching”.The smaller machining gap will lead to the higher processing efficiency.Therefore,the gap between the electrode and the workpiece surface is usually a micro/nano gap.However,the ions is difficult to diffuse out of the processing area in the micro/nano gap.And the accumulation of these substances will have a negative impact on the entire process.Therefore,the study of this effect and proposing a solution have become a key issue in improving the effect of EGCP.During the process of EGCP,the concentration of Cu²⁺ in the processing area has a great influence on the processing efficiency.In the processing process,Cu²⁺ can not spread out of the processing area in time.Therefore,Cu²⁺ will gradually accumulate in the processing area.When the concentration of Cu²⁺ accumulated to a certain extent,it will reduce the etching efficiency.Similarly,the increase of Cu²⁺ concentration also affects the surface roughness of the copper workpiece after etching.Some measures are taken to improve the material diffusion.Lifting the electrode can improve the material diffusion efficiency,and it improves etching effect.By this way,the etching efficiency can be nearly doubled,and the surface roughness is also improved significantly.When the electrode is not lifted,the Ra of the workpiece surface after processing is 6.30 nm.By lifting the electrode,the Ra of the workpiece surface can be improved to 2.40 nm.Compared with lifting the electrode,the application of electrode with a groove can reduce the complexity of the experimental operation.And it also can effectively increase the etching efficiency.Finally,for the practical processing demands,a testing platform for EGCP is developed.The testing platform is successfully applied to the EGCP of Cu.The surface roughness Ra of the workpiece and the profile PV of the etching area are improved from 46.75 nm to 2.79 nm and from 2.13 μm to 0.90 μm respectively.