A Study On The Position Effects And The Formability For Micro-Pneumatic Bulge Of Electroformed Copper Foil

The demand for micro-parts is increasing with the transformation of manufacturing to miniaturization.Because of the excellent forming performance of copper foil,people can obtain the complex and small parts through the micro pneumatic bulge,especially the MEMS system components.Electroforming is a common copper foil preparation methods.As one of the micro forming techniques,micro pneumatic bulge becomes more and more popular for its high forming precision with few spring-back and the performance of forming complex parts at one time.The improvement of the billet thickness uniformity and the performance homogeneity helps to improve the quality of micro pneumatic bulge parts.Therefore,carrying out the research thickness uniformity and the performance homogeneity of copper electroforming,especially furthering the study on micro pneumatic bulge have great theoretical and practical value for the development of micro forming technology.This thesis studied the influence of duty cycle current density,power source property and electroforming time on the uniformity of electroformed copper foil,using the orthogonal experiment method to optimize the process and determine the process of preparing copper foil with good uniformity.The copper foil prepared by this process is used as micro pneumatic bulge raw material to study the internal stress and microstructure and tensile properties of the electroformed copper foil.The orthogonal test method is implemented to study the bulging temperature,pressure and heat treatment process on the ultimate bulging height to obtain optimal parameters.The main conclusions of this thesis are presented as follows.A kind of copper foil with the better uniformity than the others in the previous literatures was prepared.The optimal technical process adopts pulse reverse current power.30%of the positive duty cycle,10%of the negative duty cycle.2A/dm2 of current density.and 92 minutes of electroforming time.The minimun coefficient of variation reached 1.54%.The thickness of electroformed copper foil shows certain rules in various directions(the position 5>1>2>3>4 of rules).In this thesis,the internal stresses of the copper foil prepared by the pulse reverse current are significantly difference while the microstructure is basically the same.Electroformed copper foil has high purity.high strength,but poor plasticity.In the case of the same thickness.the tensile strength is higher than that reported in the literature.The tensile strength has a positional effect,which is closely related to the preferred orientation of grains in different positions.(111)and(200)texture can enhance the tensile strength of copper foil,whereas(220)texture reduces the tensile strength of copper foil.The heat treatment process has the greatest influence on the ultimate bulging height,and the original microstructure without heat treatment is fine and the bulging height is the highest.The optimal technical process adopts raw materials without heat treatment,bulging temperature 450?,pressure 2.4MPa.