A copper-tin composite plating anti-nitridation process

Abstract

The invention discloses an anti-nitridation process for copper-tin composite plating, which comprises the following steps: deoiling and cleaning a workpiece, and then performing weak corrosion treatment on the workpiece with sulfuric acid; performing anodic cleaning on the workpiece, wherein the workpiece subjected to anodic cleaning needs to be taken out of the tank while electrified; performing nickel preplating: keeping the workpiece non-electrified and placing the workpiece in an electroplating solution for 2-4 minutes before nickel preplating, then preplating nickel for 1 mu m, and plating dark nickel for 1-2 mu m; performing activating treatment on the workpiece with sulfuric acid; and performing copper cyanideless electroplating, plating dark tin on the surface of the copper-electroplated layer of the workpiece, and finally performing stabilizing treatment. According to the electroplating process disclosed by the invention, the workpiece can similarly achieve the purpose of preventing nitridation, carburization and cyanogen infiltration in case of a thinner copper-plated layer, thus reducing the thickness of the copper-plated layer, reducing the copper consumption, shortening the electroplating time and improving the electroplating efficiency.

Description

technical field [0001] The invention relates to a process for preventing nitriding by copper-tin composite plating, which belongs to the technical field of metal surface treatment for preventing nitriding, carbon and cyanidation. Background technique [0002] Copper is a red ductile metal with a relative atomic mass of 63.5 and a density of 8.93g / cm3. The electrochemical equivalent Cu+ of copper is 2.372g / (A.h), and Cu2+ is 1.186g / (A.h). h), copper has poor chemical stability and is soluble in nitric acid, chromic acid and cyanide solutions. Copper is easily corroded by organic acids, and is also easily soluble in hot sulfuric acid. It reacts slowly in hydrochloric acid and dilute sulfuric acid solutions, and is not easy to react with alkali except ammonia water. Tin is a softer and more malleable metal with a relative atomic mass of 118.7 and a density of 7.3g / cm3. The electrochemical equivalent of tin Sn2+ is 2.214 / (A.h), and Sn4+ is 1.107g / (A.h). The chemical stability ...

AI Technical Summary

Problems solved by technology

In order to solve the lack of pores in the coating, the thickness of the coating is often increased. The currently used process requires the thickness of the copper coating to be greater than 50um to meet the anti-seepage requirements. However, too thick a coating leads to a long time for electroplating and copper removal (both require more than 4 hours). Consumes a lot of copper and copper removal chemicals, especially chromic anhydride (hexavalent chromium) for copper removal, which leads to increased electroplating costs, high sewage treatment costs, and potential environmental pollution