TW201341598A - Silver-electroplating electrolyte and electroplating method thereof - Google Patents

Abstract

The present invention provides a silver-electroplating electrolyte and an electroplating method thereof. The silver-electroplating electrolyte contains a silver salt as the source providing silver and having a weight percentage of 3~10%; at least one or more electro-conducting salts, having a weight percentage of 1~20%; and at least one or more chelating agents, having a weight percentage of 3~20%. The silver-electroplating electrolyte according to the present invention does not require cyanide, thereby being capable of preventing environmental pollution of cyanides used in traditional silver-electroplating procedure.

Description

Silver plating electrolyte and plating method thereof

The invention relates to a silver plating electrolyte and a plating method thereof, in particular to a cyanide-free silver plating electrolyte and a plating method thereof.

Electroplating silver was first used in the electroplating jewelry process. Electroplated silver has excellent electrical conductivity and light reflectivity, and has good chemical stability to organic acids and organic bases, so it is gradually applied to the electronics industry. For example, on an LED lighting device, a surface of the LED package substrate needs to be formed with a reflective layer to reflect light. In the existing process, electroplated silver is used as a reflective layer to achieve the advantage of low cost in addition to high reflectivity. However, the use of alkaline cyanide plating solution in the production of electroplating silver, cyanide is an environmental poison, the ecological damage is quite serious, so how to avoid the use of cyanide is a necessary and urgent development trend.

In view of the above, the present invention proposes a novel cyanide-free silver plating electrolyte and a plating method thereof in response to the above-mentioned shortcomings of the prior art to meet the demand for electroplating silver process.

The main object of the present invention is to provide a silver plating electrolyte and a plating method thereof, which can avoid the poisoning of cyanide to the environment in the electroplating silver process without using cyanide.

To achieve the above object, the present invention provides a silver plating electrolyte comprising a silver salt; at least one conductive salt; and at least one chelating agent. The composition ratio of the silver plating electrolyte is 3 to 10% of the silver salt, 1 to 20% of the conductive salt, 3 to 20% of the chelating agent, and the rest is water.

The above silver salt is used as a source of silver. The above conductive salt comprises at least one of the following compounds: sodium potassium tartrate, potassium nitrate, sodium nitrate, potassium carbonate, sodium carbonate, sodium tripolyphosphate, dipotassium hydrogen phosphate, disodium hydrogen phosphate, formic acid, sodium acetate, potassium acetate, Potassium oxalate, sodium oxalate, potassium pyrophosphate, sodium pyrophosphate, potassium dihydrogen phosphate.

The above chelating agent comprises at least one of the following compounds: ammonium citrate, ammonium sulfate, ammonium nitrate, nicotinic acid, sodium thiosulfate, ammonium thiosulfate, sodium sulfite, aqueous ammonia, amber imine, imidazole.

The invention further provides a method for electroplating using the above-mentioned silver plating electrolyte, the steps of which comprise first providing a substrate to be electroplated; surface cleaning and micro-etching of the substrate; forming a thin nickel layer on the surface of the substrate; Forming a first silver layer on the surface of the nickel layer; and plating the substrate using the silver plating electrolyte of the present invention to form a second silver layer on the first silver layer.

The purpose, technical content, features and effects achieved by the present invention will be more readily understood by the detailed description of the embodiments.

The invention provides a silver plating electrolyte and a plating method thereof, which do not use cyanide, thereby avoiding environmental damage of cyanide in the conventional electroplating silver process.

The silver plating electrolyte of the present invention comprises a silver salt; at least one or more conductive salts; and at least one chelating agent. The concentration of the conductive salt used ranges from 0.01 to 100 g/l, and the concentration of the chelating agent ranges from 1 to 200 g/l. The composition ratio of the silver plating electrolyte is 3 to 10% of the silver salt, 1 to 20% of the conductive salt, 3 to 20% of the chelating agent, and the rest is water.

The above silver salt is used as a source of silver, such as silver nitrate. The above conductive salt comprises at least one of the following compounds: sodium potassium tartrate, potassium nitrate, sodium nitrate, potassium carbonate, sodium carbonate, sodium tripolyphosphate, dipotassium hydrogen phosphate, disodium hydrogen phosphate, formic acid, sodium acetate, potassium acetate, Potassium oxalate, sodium oxalate, potassium pyrophosphate, sodium pyrophosphate, potassium dihydrogen phosphate.

The above chelating agent comprises at least one of the following compounds: ammonium citrate, ammonium sulfate, ammonium nitrate, nicotinic acid, sodium thiosulfate, ammonium thiosulfate, sodium sulfite, aqueous ammonia, amber imine, imidazole.

Further, the silver plating electrolyte of the present invention may be added with a pH adjusting agent such as potassium hydroxide (KOH), ammonia water, nitric acid or phosphoric acid. The pH adjuster accounts for 1 to 5% by weight of the total silver plating electrolyte.

Continuing, as shown in FIG. 1 , which is a method for electroplating using the silver-plated electrolyte of the present invention, the steps comprising: providing a substrate to be electroplated as described in step S1; as described in step S2 The so-called substrate surface cleaning and micro-etching step; further, as described in step S3, first plating a thin nickel layer on the surface of the substrate; as described in step S4, the substrate is subjected to a pre-dip silver process to form a surface of the nickel layer. a first silver layer; and finally, as described in step S5, the substrate is electroplated using the silver plating electrolyte of the present invention to form a second silver layer on the first silver layer.

The step of cleaning and micro-etching the substrate surface in step S2 comprises first performing electrolytic degreasing on the substrate to remove grease or dirt on the surface of the substrate, and then micro-etching the substrate to remove oxides on the surface of the substrate. The surface of the substrate is slightly roughened, and then the substrate is pickled to remove oxides on the surface of the substrate and to maintain the cleanliness of the surface of the substrate.

In step S5, the substrate is electroplated using the silver-plated electrolyte of the present invention to have a current density of 0.05 to 5 ASD, a temperature of 20 to 40 ° C, and a pH of 7 to 11.

The above is only the preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Therefore, any changes or modifications of the features and spirits of the present invention should be included in the scope of the present invention.

Figure 1 is a flow chart showing the steps of electroplating using the silver-plated electrolyte of the present invention.

Claims (14)

A silver plating electrolyte comprising: a silver salt in a weight percentage of 3 to 10%, the silver salt as a silver source; at least one conductive salt in a weight percentage of 1 to 20%; at least one or more The chelating agent is from 3 to 20% by weight; and the balance is water. The silver plating electrolyte according to claim 1, wherein the concentration of the conductive salt ranges from 0.01 to 100 g/l. The silver plating electrolyte according to claim 1, wherein the concentration of the chelating agent ranges from 1 to 200 g/l. The silver plating electrolyte according to claim 1, which further comprises a pH adjusting agent. The silver plating electrolyte according to claim 4, wherein the pH adjuster is selected from the group consisting of potassium hydroxide (KOH), ammonia water, nitric acid or phosphoric acid. The silver plating electrolyte according to claim 4, wherein the pH adjuster accounts for 1 to 5% by weight of the silver plating electrolyte. The silver plating electrolyte of claim 1, wherein the silver salt is silver nitrate. The silver plating electrolyte according to claim 1, wherein the conductive salt comprises at least one of the following compounds: sodium potassium tartrate, potassium nitrate, sodium nitrate, potassium carbonate, sodium carbonate, sodium tripolyphosphate, dipotassium hydrogen phosphate, phosphoric acid. Disodium hydrogen, formic acid, sodium acetate, potassium acetate, potassium oxalate, sodium oxalate, potassium pyrophosphate, sodium pyrophosphate, potassium dihydrogen phosphate. The silver plating electrolyte according to claim 1, wherein the chelating agent comprises at least one of the following compounds: ammonium citrate, ammonium sulfate, ammonium nitrate, nicotinic acid, sodium thiosulfate, ammonium thiosulfate, sodium sulfite, aqueous ammonia. , amber imine, imidazole. A method for electroplating using the silver plating electrolyte according to claim 1 or 4, the method comprising: providing a substrate to be electroplated; performing surface cleaning and micro-etching on the substrate; forming a surface on the surface of the substrate a thin nickel layer; forming a first silver layer on the surface of the nickel layer; and plating the substrate with the low cyanide silver plating electrolyte to form a second silver layer on the first silver layer. The method according to claim 10, wherein the substrate is plated with a silver plating electrolyte for a current density of 0.5 to 100 ASD, a temperature of 10 to 60 ° C, and a pH of 7 to 12. The method of claim 10, wherein the step of surface cleaning and micro-etching the substrate comprises: electrolytically degreasing the substrate to remove grease or dirt on the surface of the substrate; Etching to remove oxides on the surface of the substrate and to slightly roughen the surface of the substrate; and pickling the substrate to remove oxides on the surface of the substrate and maintain the cleanliness of the surface of the substrate. The method of claim 10, wherein the step of forming the first silver layer on the surface of the nickel layer is to form the first silver layer by a pre-dip silver process. The method of claim 10, wherein the nickel layer is formed on the surface of the substrate by electroplating.