Effects Of Recrystallization Annealing And Pre-stretching Deformation On Etching Properties Of 12μm Thick Rolled Copper Foil

Due to excellent electrical conductivity,thermal conductivity,flexibility,low surface roughness and alloyability,rolled copper foil is widely used in Flexible Printed Circuit（FPC）boards,intelligent equipment,aerospace,lithium-ion batteries and other fields.As an unstressed processing method,etching is a key link in the production of circuit boards.Its purpose is to remove the unprotected copper after developing to form the required circuit.With the advent of 5G communication times,various electronic components tend to be miniaturized,light weight,high speed and multi-functional,and higher requirements have been put forward on the etching performance of rolled copper foil.12μm rolled copper foil is the thinnest rolled copper foil that can be stably produced at present,which can be used to manufacture high-end FPC boards.Good etching performance of rolled copper foil is the basis for ensuring the line width and line spacing,which directly determines the performance and yield of FPC boards.This paper takes 12μm rolled copper foil as the research object,the etching process and etching mechanism was explored.Then the microstructure was regulated through the recrystallization annealing and pre-stretching deformation,and the relationship between microstructure and etching performance was systematically studied.The research results will enrich the theories on the etching of rolled copper foil,and provide the experimental data and theoretical support for the production,research and development of copper foil,and also the optimization of etching process.The main research contents and results of this paper are as follows:（1）The microscopic morphology and roughness of etched copper foil were characterized in order to research the etching process of copper foil.The etching products was analyzed,combined with electrochemical tests of copper foil,the etching mechanism of copper foil was clarfied.The research results show that the etching rate of different areas of copper foil are not the same during the etching process.And some areas exhibit higher etching rate,which will be preferentially etched into small particles.The etching of copper foil in acidic Cu Cl₂ solution is the process of continuously forming and dissolving of Cu Cl passivation film,and finally the copper foil is completely etched.The formation of passivation film is related to the concentration of Cl^-in the etching solution.（2）The etching rate and microstructure variation of copper foil were characterized in order to research the effect of recrystallization annealing on the etching performance.Based on this,the relationship between microstructure and etching rate was explored.The results show that the etching rate of copper foil is mainly influenced by the grain boundary characteristics,grain size and grain orientation.Low Angle Grain Boundaries（LAGBs）are the main factor affecting the etching rate of copper foil due to the lower energy,and the etching rate decreases with the deceasing of its proportion.Higher Random High Angle Grain Boundary Connectivity（RHGBN）,smaller grain size and lower{001}grain proportion also make the copper foil easier to etch and increase the etching rate.The microstructure variation of the only copper foil sample after etching for different times was investigated in order to further study the influence of microstructure on the etching behaviour of copper foil.The research results show that the grain boundaries play the major role in etching rate during the initial stage of etching,and the High Angle Grain Boundaries（HAGBs）are preferentially etched.With the increasing of etching time,the crystal orientation gradually becomes the main factor affecting the etching rate.And the{001}crystal plane of copper foil has the lower etching rate in the acid etching solution.（3）The etching rate,residual stress and dislocation density variation of copper foil were characterized in order to research the effect of pre-stretching deformation on the etching performance.Based on this,the relationship between residual stress,dislocation density and etching rate was explored.The research results show that the etching rate of copper foil increases and then decreases with the increasing of pre-stretching deformation.For the dislocation,the rolled copper foil has higher dislocation density,and the dislocation density gradually increases with the increasing of pre-stretching deformation.For the residual stress,the rolled copper foil has higher residual compressive stress.The residual compressive stress decreases and then turns into residual tensile stress with the increasing of pre-stretching deformation.The residual compressive stress and dislocations reduce the etching rate of the copper foil,and the residual tensile stress increases the etching rate of copper foil within a certain range.Based on the above research,the four stages of etching rate variation of copper foil during pre-stretching deformation were clarified,and the model for calculating the etching rate was constructed when the dislocation density or residual stress acts as a single factor or dual factors.