Method for electroplating LED pin with high-gloss silver coating

Abstract

The invention relates to a method for electroplating an LED pin with a high-gloss silver coating. The method comprises the following steps: 1, adding the LED pin; 2, carrying out thermal degreasing and electric degreasing of the surface of the pin by sodium carbonate; 3, carrying out acid activation; 4, electroplating copper; 4, electroplating silver; and 6, carrying out cleaning, drying and protection treatment of the obtained coating, wherein the acid activation adopts a mixed solution containing 40-80g / L of hydrofluoric acid and 5-15g / L of sulfuric acid; the copper plating is two-step copper plating and comprises cyanide copper plating and copper sulfate plating; and the above silver plating technology is characterized in that materials used in the silver plating comprise 20-50g / L of silver nitrate, 140-200g / L of hydantoin, 30-70g / L of potash, 5-15g / L of boric acid, 120-140g / L of potassium citrate and 10-15mL of a brightener, silver plating is carried out at 20-100DEG C, the cathode current density is 0.1-2A / dm<2>, and a 99.99% pure silver plate is used as an anode. The method enables the gloss of the obtained coating to reach 1.7-1.8 in case and the extremely-thin silver coating (1mum) to be guaranteed, so demands of the subsequent welding quality and the conductive performance can be fully satisfied.

Description

technical field [0001] The invention relates to the technical field of electrodeposition, and relates to a method for electroplating high-gloss silver coatings on LED pins. Background technique [0002] As a new lighting technology, light emitting diode (Light Emitting Diode, LED) is a light emitting device that uses a semiconductor chip as a light emitting material to directly convert electrical energy into light energy. It is a cold light source with a very high photoelectric conversion rate, its energy consumption is only 1 / 8~1 / 10 of that of an incandescent lamp, and its service life can reach 100,000 hours. Since the birth of the world's first semiconductor light-emitting diode in the 1960s, with the improvement of technology and processing technology, LED has the characteristics of long life, energy saving, rich colors, safety, and environmental protection, and has been vigorously promoted by countries all over the world. Widely used in home, commercial or public place...

AI Technical Summary

Problems solved by technology

The cyanide-free bright silver plating process has been studied since the 1970s. Although some achievements have been made, the process is still not very mature. In order to obtain a bright silver coating, it is usually necessary to mechanically polish or chemically light the dark silver coating obtained by electroplating. , which not only wastes a lot of manpower and material resources, but also wastes a lot of silver in the polishing process.

There are also reports of adding a brightener to the cyanide-free silver-plating solution to directly obtain a mirror-bright silver-plated layer, but so far, bright silver-plated generally adopts organic additives (mostly containing sulfur-containing compounds that are easy to participate in the reaction) to obtain Bright silver coating, the coating obtained in this way is easy to change color, brittle and poor solderability due to sulfur content

There are also reports of adding antimony salts or selenium salts to the plating solution, but satisfactory bright coatings cannot be obtained.

[0004] However, the existing electroplating silver plating process is difficult to ensure the high gloss of the LED pins. In order to ensure the high gloss required for subsequent production, the usual method is to simply increase the thickness of the silver coating, but this will easily cause the actual coating thickness to be much larger. If the thickness is less than the target, it will easily cause waste of precious metal silver and increase the cost