Effects of gelatin, thiourea, and chloride ions on the nanostructure of copper film prepared by electrodeposition

The type and amount of additives in the electrolyte have a great impact on the grain size and surface morphology copper coating obtained by electrodeposition. In this paper, the effects of gelatin, thiourea, and chloride ions under various concentrations on the grain size and surface morphology of the nano-copper layers prepared by pulse electrodeposition were studied in detail. Then, the influence of the change of additive content on the electrolyte was investigated according to the polarization curve. Results show that adding a small amount of gelatin or thiourea to the electrolyte reduced the grain size of the coating with its surface morphology changed from the original dendritic clusters to spherical clusters as well. The addition of chlorine ions can reduce the inhomogeneity of the coating surface due to the edge effect during the electrodeposition process. Applied as a nanocrystalline substrate, a layer of nanocrystalline Cu coating with a thickness of about 20um was deposited on the surface of the polycrystalline copper by the above-mentioned process. Finally, using SAC305 as the solder, single-crystal copper, nanocrystalline copper， and polycrystalline copper as the substrate respectively, the effect of the grain size of the substrate on the soldering process, interface products, and morphology were investigated.