Effects Of Additives On The Microstructure And Mechanical Properties Of Electrodeposited Copper Foil And The Optimal Scheme

The electrodeposition of Cu has been a subject of recent extensive investigations because of electrodeposition copper foils have been widely used the conductors for printed circuit boards (PCBs). Additives play a major role in controlling the properties of copper foils, even small amounts of certain additives can affect the properties and aspect of the deposit.The effect of bis-(3-sulfopropyl) disulfide (SP), hydroxyethylcellulose (HEC), polyethylene glycol (PEG), gelatin and cerous sulfate on the copper electrodeposits are investigated by SEM (scanning electron microscope), microcomputer control electronic universal testing machine, high temperature drawing machine, EBSD(electron backscattered diffraction) and stress gauge. The results reveal that SP can decrease the surface roughness and improve the mechanical properties, especially for elongation at room temperature. Copper foil with maximum value comprehensive properties can be obtained with approximately 0.2 mg/L SP content. HEC can promote the growth of grain-oriented and ensure copper foil has certain roughness and improve the mechanical properties at room temperature, but reduce the tensile strength of foil at high temperature. HEC also can inhibit the pinhole, but cause copper foil warp. PEG can increase the depositon over-potential and promote the growth of grain-oriented, resulting in grain refinement and allowing the microscopic roughness of the copper foil to be lower. PEG also has the ability to inhibit the deposition of metal impurities and prevent the growth of abnormal grain. But excess PEG will reduce the tensile strength and elongation of copper foil at high temperature. The leveling and refinement effect of gelatin are well. It can improve the tensile strength and elongation of copper foil at room temperature, but reduce the tensile strength and elongation of copper foil at high temperature. And the effect of bone glue is better than collagen. RE element can obviously improve mechanical properties of the copper foil by refining and uniformly distributing grain size in the foil, where ideal grain size in the copper foil with maximum value mechanical properties can be obtained with approximately 6 mg/L RE content. The effects of different additive formula on the microstructure of bright side, mechanical properties and internal stress of electrodeposited copper foil are investigated by the orthogonal test and the best 3 additive formulas were gotten by visual diagram and data analysis. The best ratio of formula was proved by experiments:Gelatin,PEG,SP,HEC was 1.4 mg/L,1.5mg/L,0.35mg/L,0.6 mg/L, respectively. The internal stress and defects of copper foil was reduced, microstructure of bright side was:twin of 24.3%, (111) texture of 24.3% and the average grain size of 250.4nm. The grains on rough surface were distributed more uniformly and mechanical properties of copper were improved as well。The tensile strength at room temperature and high temperature were 376.5 MPa and 197.1MPa respectively, elongation at room temperature and high temperature were:5.6% and 2.8%respectively. The best formula is applyed to the pilot line, the performance of the crude foils gets better, and the quality of the products improves obviously.