Simulation And Experiment On The Electrolytic Regeneration Of Etchant For Printed Circuit Board

Acidic cupric chloride etchant,presently widely used in processing printed circuit board,contains highly concentrated HCl and CuCl2.The printed circuit board industry generates huge amount of spent etchant every day.In order to avoid the damages to the environment and the waste of resources caused by the discharge of spent etchant,it is imperative to realize etchant regeneration and copper recovery.However,the known electrolytic regeneration and recovery methods suffer from chlorineevolution,complecated operation and control,recovered copper in powder form,etc.,thus hindering the practical application of those electrolytic methodes.In this research,two new flow schemes of electrolytic acidic cupric chloride etchant regeneration and copper recovery process were proposed,which ideally can achieve fully etchant regeneration and copper recovery.The newly proposed and previously known flow schemes were analyzed and compared through process simulations using the numerical computing environment MATLAB.The results showed that the two newly proposed flow schemes of electrolytic process have markedly lower risk of chlorine evolution and higher flexibility of operation.In order to design the pilot-scale electrolytic cell,with the aid of COMSOL Multiphysics,Navier-Stokes equations is used to simulate velocity distribution of the cathode's flow field,Navier-Stokes equations and Brinkman equations are used to simulate the velocity distribution of the anode's flow field,Laplace equation is used to simulate the current density distribution of the cell,moving boundary and the initial current distribution are used to simulate the thickness of the deposited copper vs the electrolytic time.According to the result of the simulation calculation,we have design the pilot-scale plant' s main dimensions,such as the size,the spacing,the thickness of the cathode' s and anode's,the thickness of primary flow,the number of secondary flow,the buffer's width,etc.A lab-scale electrolytic cell was first choosen to carry out etchant regeneration and copper recovery experiments,in order to test the practical operability of the proposed flow schemes.The satisfactory results encouraged us to build and experimentally operate a pilot-scale plant for etchant regeneration and copper recovery.The experimental results show that the concentrations of the cuprous and cupric ions in every stream are in agreement with those calculated.Besides,the deposited metal copper was in the form of a dense and smo oth plate.