Study On Electrochemical Mechanical Polishing Process Of Pure Copper

Large-diameter-thickness pure copper planar members used in precision physics experiments have the characteristics of poor rigidity,sensitivity to force and thermal load,strong plasticity,and poor machinability;these characteristics lead to the processing of pure copper using common mechanical methods.Defects such as workpiece deformation,residual stress,and surface damage occur during the assembly.Electrochemical mechanical polishing(ECMP)mainly uses electrochemical corrosion to remove materials,which is not limited by the mechanical properties and mechanical properties of the materials,and there is no processing stress.However,the current research on ECMP of pure copper materials is limited to pure copper for integrated circuits or pure copper workpieces with small aspect ratio.The research content is mostly surface roughness or material removal rate.The existing ECMP process is used to process large-diameter-thickness ratio pure copper planar members,which may cause problems such as deterioration of workpiece flatness caused by uneven material removal in the sheet,and cannot meet the requirements of precision physical experiments for high surface precision of workpieces.Therefore,the ECMP process of pure copper planar members with ?100 mm×3 mm is studied to verify the feasibility of processing large diameter-thickness ratio pure copper planar members.The main research contents of this paper are as follows:Screen the ECMP polishing solution formulation.By consulting the literature,five kinds of acidic polishing liquids and five kinds of alkaline polishing liquids were selected,and a polishing liquid which generates a barrier film potential interval width was selected by polarization curve,and the formulation was blocked by an energy spectrometer(EDS).The elemental composition of the membrane.The formulation of the polishing solution is: 0.5 mol/L glycine + 0.1 mol/L thiosalicylic acid(TSA)+1 wt.% polyethylene glycol + 0.4 mol/L KOH.The formulation is electrochemically reacted with copper by a TSA at a high potential to form a barrier film on the surface of the workpiece,so that there is a long potential interval for generating a barrier film.After determining the formulation of the polishing solution,the effect of ECMP material removal non-uniformity on flatness was investigated.The ECMP material removal non-uniformity model was derived based on Faraday's law and polishing trajectory equation,and its accuracy was verified experimentally.The results show that the polishing pad with the hole pattern of the leaf order can be used to remove the material evenly when the polishing pad and the workpiece rotation speed ratio are between 40/45 and 40/50 and the eccentricity is between 50 and 60 mm.High-profile precision pure copper planar member.After the material was removed uniformly,the effect of ECMP anode potential on material removal rate and surface roughness was investigated.The effect of anode potential on material removal rate and surface roughness was obtained by single factor experiment under selected polishing pad,speed ratio and eccentricity.Finally,the surface integrity of the workpiece after ECMP is studied.The residual stress,microhardness and subsurface damage layer of the workpiece after grinding and ECMP were measured by laser speckle small hole method,Vickers microhardness tester and scanning electron microscope.The results show that the ECMP process can remove the residual stress and subsurface damage layer generated by the grinding process,reduce the microhardness of the surface of the workpiece,and obtain a pure copper planar member with high surface integrity.The above research results show that ECMP is an effective process for processing large diameter and thickness ratio pure copper planar members.