Research On Environmentally Friendly Electroless Plating Technology For Copper-plated Silver On Plastic Substrates

At present, an increasing number of study on metallization of material surface was reported and metallization methods were also abundant, such as vapor deposition, ion sputtering, metal powder spraying, arc spraying, electroplating and electroless plating, etc. In this paper, metallization research of material was discussed by using the method of electroless deposition. Plastic (PVC) and metal copper were respectively chosen as the research objects for chemical silver plating, electroless copper plating and immersion silver. Meanwhile, the successful plating conditions were discussed comprehensively and systematically. The main contents of this paper were mainly divided into the following three parts:1. The technology research of electroless silver plating on plastic (PVC)The plastic (PVC) was chosen as the research object of electroless silver plating. By exploring the coarsening and sensitization conditions in the process of pretreatment, the plastic substrate with uniformly rough surface was obtained and it met the experimental requirement. The stable plating solution consisted of silver nitrate as the silver source, glucose as the reducing agent and sodium thiosulfate as the stabilizer. With the surface resistance as judgment standard, the silver nitrate concentration of 2.08 g/L, the sodium hydroxide concentration of 0.24 g/L, the glucose concentration of 7.27 g/L, the ammonia content of 0.53%, the sodium thiosulfate concentration of 0.024 g/L and the temperature of 20? were determined to be the best bath formula through the orthogonal test. Finally, shiny silver layer with good conductive capacity, high bonding strength and fine oxidation resistance was successfully prepared.2. The technology research of electroless copper plating environmentally on plastic (PVC)The PVC plastic was chosen as the research substrate of electroless copper plating, and the surface of the substrate was modified by using a method of mechanical roughening combined with ferric hydroxide colloid attachment instead of traditional chemical roughening. By comparing the attaching situation of the colloid in the different conditions, the optimum soaking condition was determined. The plating bath with good effect was prepared by using glyoxylic acid in place of formaldehyde and adding EDTA·2Na and potassium sodium tartrate as composite complexing agent. Meanwhile, ?, ?-dipyridyl was added to adjust the quality of the coating. The copper sulfate concentration of 12 g/L, the disodium ethylenediamine tetraacetate concentration of 18 g/L, the potassium sodium tartrate concentration of 12 g/L, the ?, a-dipyridine concentration of 2 mg/L, the glyoxylic acid concentration of 10 g/L, the pH value of 2 and the temperature of 60? were determined to be the suitable plating solution formula through the orthogonal experiment that took the deposition rate as well as the appearance as the comprehensive evaluation standard. Under this condition, the surfactant PEG6000 was added in the bath to improve the quality of coating and the copper coating with good conductive effect and nice appearance was prepared finally.3. The technology research of immersion silver on the copper matrixLight bulbs with copper silk were chosen as matrix materials to prepare silver layer. With the discussion of pretreatment conditions, such as oil removal, rust removal and micro-etching, the substrates that accorded with the requirement of plating conditions were obtained. They were plated in the tap water solution with the method of cyanide-free silver plating. The stable plating solution was prepared by adding potassium bromide, ethylenediamine and a, a-dipyridine as compound complexing agent and using boric acid, ammonia and nitric acid to adjust pH value. In the bath, phenol was also added as antioxidant. The silver nitrate concentration of 1.25 g/L, the ethylenediamine concentration of 7.08 g/L, the potassium bromide concentration of 304 g/L, the a, a-dipyridine concentration of 14.3 mg/L, the boric acid concentration of 0.71 g/L, the phenol content of 0.36%, the pH value of 2 and the temperature of 50? were regarded as the optimum condition of immersion Ag through orthogonal test with weight gain rate as judg standard. Finally, the surfactant PEG6000/PVP was added to adjust the quality of coating, and bright silver coating could be got with high adhesion strength, good weldability, fine electric conductivity and nice oxidation resistance.