Mechanism On Warping And Microstructure And Mechanical Properities Of Electrolytic Copper Foils

In order to solve the warping problem of electrolytic copper foil in enterprises’production, the thesis compares production process and organizational structure ofdomestic similar copper products, selecting current density, concentration of copperion and commonly used additives as a point of entry, and discussing their influenceon copper foil organization ability. Through orthogonal test, the type and dosage ofnew additives are determined. A more ideal test and production test result have beenobtained. By improving production process, warping problem of foil is mostly solved.The thesis comprehensively analyses the origin and nature of copper stress, andinteractions between stress and texture, creatively putting forward the hypotheticgrowth process of copper grain on crystal face (model). It can better explain thegrowth phenomenon in the actual production of copper foil texture and intrinsic stress(residual stress) size.With increase in the current density, the roughness of the matte surface increasesgradually; it’s conducive to the fast growth of (111) and (220)crystal faces, but withthe further increase of the current density, the growth rate of (220) crystal plane issignificantly faster than the (111) crystal plane and the finally (220) crystal plane is indominant position; an appropriate increase of current density is conducive to theimprovement of the mechanical performance of the copper foil, but should not exceed0.7A/cm2.With the increase of the concentration of copper ion, grains on matte surfacegrow evenly gradually; roughness decreases; effect on copper foil copper foil textureis not obvious; both tensile strength and elongation increases. The ion concentrationof copper foil, also should not be too big, otherwise it’s easy to crystallization ofcopper sulfate which will block the pipeline equipment.With the increase of copper foil thickness, grains on matte surface graduallygrow up, generally between0.5-10μm.Grain shape change from the granular into hillsand becomes conical; roughness of matte surface first increases then decreases, thenincreases; texture of copper foil (111) gradually decreases, while (220) texture gradually increases; there are obvious size effect of copper foil, the tensile strengthand elongation.Additives as SP, HEC, PEG, cerium sulfate have certain grain refinementfunction, of which SP has the most rapid obvious effect. SP, HEC, and PEG areconducive to the (220) texture growth; gelatin, cerium sulfate salt to (111) texturegrowth. A certain amount of SP, gelatin, cerium sulfate salt can improve mechanicalperformance of copper foil, and cerium sulfate salt effect is the most obvious; PEGHEC, to a certain extent will reduce the copper foil mechanical performance,especially elongation.Research shows that, the copper foil warping is caused by intrinsic stress(residual stress). Compressive stress exists on shiny face and matte face, but thecompressive stress on shiny face is greater than that on matte face, so the residualstress shows toward the matte face as the compressive stress, and copper foil warpstoward the matte face. Compressive stress on shiny face mainly comes from theadditive use. Compressive stress on matte surface mainly comes from the additiveand (220) texture.HEC, PEG, SP and other additives can effectively inhibit the impurities, avoidingto produce copper foil pinhole. But excessive use of HEC, PEG, SP and otheradditives, can cause serious warping of copper foil. The texture of electrolytic copperfoil, grain size, twin boundary and interior hole and other factors may affect theintrinsic stress and warping degree of copper foil. The twin boundary and interiorhole is the main way to release stress, which can alleviate the warping degree ofcopper foil.In accordance with the dosage of SP, less than or equal to0.1mg/L, the dosage ofHEC0.3-0.5mg/L, cerium sulfate dosage0.5-1.0mg/L, we can produce theelectrolytic copper foil with12-18μm thickness meeting the requirements of standard,with improved mechanical performance, no pinhole, and no warping.Data were obtained through curve fitting, and the mathematical relation amongcurrent density, concentration of copper ion, copper foil thickness and variousadditives’ influence on the grain size, copper matte face roughness, tensile strengthand elongation can be used to guide the actual production and application. Putting forward the hypothetic grain growth process of copper foil (model) canreasonably interpret the actual situation of the intrinsic stress and texture of copperfoil. Grain surface formation must meet two necessary conditions: there must be acertain stress, and reach the size which can promote the crystal plane strain energy torelease; there must be a stable and continuous kinetic energy to provide crystalsurface atoms to transfer in space and film surface. The development direction ofcopper deposition is the formation of dense low energy structure of grain. Differentcrystal surface transformation is a kind of solid-solid phase change, along with theenergy release or absorption. Atomic density and strain energy density on differentcrystal surfaces is not the same. This research put forward the definition of crystalsurface atoms relative strain energy density. Initial growth are on crystal plane withlower atomic strain energy, when the stress reaches a certain degree, getting enoughkinetic energy, atoms on crystal face with higher strain energy density begin to grow.