Stannum copper alloy coating, plating solution prescription and electroplating method

Abstract

The invention discloses a tin-copper alloy plating layer, a plating liquid prescription and a plating method. The plating layer calculated by weight comprises at least 55 to 60 percent of tin as well as 40 to 45 percent of copper; while the plating liquid prescription mainly includes stannous chloride of 20 to 40g / l and copper pyrophosphate of 10 to 30g / l that are respectively as the main salt of tin and copper. The prescription also includes potassium pyrophosphate of 250 to 350g / l used as a main complexing agent; potassium chloride of 30 to 40g / l used as an auxiliary complexing agent; stannic chloride pentahydrate of 10 to 30g / l to main the stability of the plating liquid; the pH value is controlled between 8.0 to 9.0; a class I additive of 0.5 to 5ml / l and a class II additive of 0.5 to 3ml / l are also added. The scheme can be adopted to lead the plating layer to have the advantages of better heat stability, hard color changing, being more environment protective and being able to avoid the skin from nickel sensitivity.

Description

technical field [0001] The invention relates to the technical field of electroplating, in particular to a tin-copper alloy coating, an electroplating solution formula and an electroplating method. Background technique [0002] Many workpieces (such as ornaments, watches or decorative accessories, mobile phones, etc.) are electroplated with a layer of decorative coating to form a bright surface, thereby playing a decorative or protective role. The early decorative coatings are usually nickel or chromium coatings, and this coating is prone to discoloration and yellowing in the aerobic ring mirror, which affects the appearance; moreover, the electroplating solution that forms the above coatings usually contains cyanide, and cyanide is poisonous. It is beneficial to the health of process workers and not conducive to environmental protection; moreover, nickel often causes skin allergies, so for products that often come into contact with human skin, such as glasses temples, watche...

AI Technical Summary

Problems solved by technology

The copper-tin alloy coating is usually cupronickel tin, although it does not contain nickel and will not cause skin allergies, but the electroplating solution also contains heavy metals such as cyanide or lead to help electroplating, which is not conducive to environmental protection

Not only that, but this kind of coating also has the following disadvantages: first, the ratio of the above-mentioned copper-tin alloy coating is that the ratio of copper is higher than that of tin, usually copper≥70%, tin≤30%, and its thermal stability is poor. It is easy to turn yellow and affect the aesthetic appearance, so it is necessary to electroplate a color coating on the copper-tin alloy coating, such as tin-cobalt coating, trivalent chromium or precious metal coating (such as palladium coating, gold coating, rhodium coating and palladium-copper alloy coating) , its role is to increase its corrosion resistance and aesthetics; secondly, the electroplating solution that forms the above-mentioned copper-tin alloy coating contains stannous pyrophosphate, which is divalent tin. During the electrolysis process, due to O in the air 2 or the reason of anodic oxidation in electroplating, which converts divalent tin into tetravalent tin, which leads to the accumulation of tetravalent tin, which makes the performance of the electroplating layer poor, which in turn shortens the service life and the surface brightness of the coating will also be poor , will turn black and produce fog