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CN-121992463-A - Cyanide-free lead-free white copper tin electroplating process

CN121992463ACN 121992463 ACN121992463 ACN 121992463ACN-121992463-A

Abstract

The application belongs to the technical field of surface treatment, and in particular relates to a cyanide-free and lead-free white copper tin electroplating process, which comprises the steps of adding copper methionine, sodium stannate, potassium hydroxide, zinc oxide, potassium carbonate, conductive salt, brightening agent, sodium phosphite, 3-ethyl aminobenzoate methylsulfonate and wetting agent to form plating solution; and starting mechanical stirring and heating to a required temperature, placing the workpiece into a plating solution, electroplating, and controlling the current density, the metal ion concentration and the temperature of the plating solution within a preset range. Copper methionine serving as a copper source is coordinated and combined with amino and carboxyl groups of methionine to form stable inner complex salt, and the copper methionine has remarkable hydrolysis resistance advantage. The polydentate group of methionine anion chelates with Cu 2+ to stabilize free Cu 2+ and also assist in refining the coating crystallization. Sodium phosphite is combined with stannate ions, so that the reduction potential of tin is reduced, and 3-aminobenzoic acid ethyl ester methylsulfonate is chelated with Cu 2+ preferentially, so that the reduction potential of copper is improved, and the problem of large difference of copper and tin potentials is solved.

Inventors

  • QIU YONGHUA

Assignees

  • 深圳市新富华表面技术有限公司

Dates

Publication Date
20260508
Application Date
20260127

Claims (10)

  1. 1. The cyanide-free and lead-free white copper tin electroplating process is characterized by comprising the following steps of: opening a cylinder, namely adding copper methionine, sodium stannate, potassium hydroxide, zinc oxide, potassium carbonate, conductive salt, brightening agent, complexing agent and wetting agent to form plating solution; Electroplating, namely starting mechanical stirring and heating to a required temperature, putting a workpiece into a plating solution, electroplating, and controlling the current density, the metal ion concentration and the temperature of the plating solution within a preset range; The complexing agent comprises sodium phosphite and ethyl 3-aminobenzoate methylsulfonate.
  2. 2. The process for the cyanide-free and lead-free copper-tin white electroplating of claim 1, wherein the plating solution comprises 90-120g/L of a conductive salt, 10-18g/L of potassium hydroxide, 20-35g/L of copper methionine, 30-35g/L of sodium stannate, 2g/L of zinc oxide, 10g/L of potassium carbonate, 0.3-1ml/L of a brightening agent, 10-30ml/L of a complexing agent, and 1-2ml/L of a wetting agent.
  3. 3. The cyanide-free lead-free white copper tin electroplating process of claim 2, wherein the conductive salt comprises, by mass, 65% -67% of sodium carbonate, 28% -30% of sodium thiocyanate and 3% -5% of sodium hydroxide; The brightening agent comprises, by mass, 1% -3% of sodium polydithio-dipropyl sulfonate, 0.5% -1.5% of polyethylene glycol, 0.5% -1.5% of 2-propyne-1-sodium sulfonate and the balance deionized water; The wetting agent comprises, by mass, 0.1% -0.3% of octyl phenol polyoxyethylene ether, 0.3% -0.7% of potassium perfluorobutyl sulfonate and the balance deionized water.
  4. 4. The cyanide-free and lead-free copper-tin white electroplating process according to claim 1 or 2, wherein the cylinder opening step further comprises adding a cylinder opening agent, and the plating solution further comprises 5-10ml/L of the cylinder opening agent; The cylinder opening agent comprises 14-16% of copper methionine, 4-6% of potassium molybdate, 3-5% of sodium methylsulfonate and the balance of deionized water according to mass ratio.
  5. 5. The cyanide-free and lead-free cupronickel tin electroplating process according to claim 1, wherein the complexing agent comprises 1.2-1.6% of sodium phosphite, 1.8-2.2% of 3-ethyl aminobenzoate methylsulfonate and the balance of deionized water.
  6. 6. The cyanide-free and lead-free white copper tin electroplating process according to claim 1, wherein in the electroplating step, the current density is 1-3A/dm2, and the plating solution is filtered 2-3 times per hour by using a filter having a filter element of 10 μm or less.
  7. 7. The cyanide-free and lead-free white copper tin electroplating process according to claim 1, wherein in the electroplating step, electroplating is performed in a hanging plating mode, wherein the copper ion content is controlled to be 8-20g/L, the tin ion content is controlled to be 10-20g/L, the zinc ion content is controlled to be 0.5-1.5g/L, the potassium hydroxide is controlled to be 10-20g/L, and the plating solution temperature is controlled to be 35-45 ℃.
  8. 8. The cyanide-free and lead-free white copper tin electroplating process according to claim 1, wherein in the electroplating step, electroplating is performed by adopting a barrel plating mode, wherein the copper ion content is controlled to be 6-10g/L, the tin ion content is controlled to be 8-12g/L, the zinc ion content is controlled to be 0.5-2g/L, the potassium hydroxide is controlled to be 10-20g/L, and the plating solution temperature is controlled to be 30-35 ℃.
  9. 9. The cyanide-free and lead-free white copper tin electroplating process according to claim 1, wherein 150g of conductive salt, 200g of potassium hydroxide, 60g of copper methionine, 100g of sodium stannate, 3g of zinc oxide, 100-300ml of brightening agent, 200-400ml of complexing agent, 100-300ml of wetting agent and 3-5ml of auxiliary agent are added to each liter of plating solution every 6000 ampere minutes.
  10. 10. The cyanide-free and lead-free white copper tin electroplating process according to claim 9, wherein the auxiliary agent comprises 38-42% of tripotassium citrate, 3-5% of sodium gluconate, 1-3% of potassium sodium tartrate and the balance of deionized water according to mass ratio.

Description

Cyanide-free lead-free white copper tin electroplating process Technical Field The application belongs to the technical field of surface treatment, and particularly relates to a cyanide-free and lead-free white copper tin electroplating process. Background The white copper tin plating layer has silvery white decorative appearance and excellent corrosion resistance and wear resistance, is a core plating layer system with both functionality and decoration in the electroplating industry, and is widely applied to the fields of hardware, electronics, automobiles and the like. However, the traditional white copper tin electroplating process long-term depends on cyanide as a complexing agent, although stable copper tin codeposition can be realized, and the cyanide is extremely toxic due to the fact that the cyanide is used as the complexing agent, and not only is serious threat to the health of operators, but also a large amount of high-toxicity wastewater is generated in the production process, so that the wastewater is extremely difficult to treat, and if the wastewater is improperly discharged, irreversible pollution is caused to ecological environments such as soil, water and the like. In addition, part of the traditional white copper tin electroplating process contains lead, and lead is used as a heavy metal pollutant, is easy to enrich in organisms, does not meet the requirements of modern environmental protection and health, and is difficult to meet the strict standards of the international market on the heavy metal content of the product. In recent years, the developed cyanide-free cupronickel tin electroplating process (main stream cyanide-free system such as pyrophosphate and citrate system) has obvious limitation, and the cyanide-free cupronickel tin plating solution has complex components and high concentration (such as the concentration of pyrophosphate is often 150-200 g/L), so that the total dissolved solids of the wastewater exceeds the standard, and the wastewater is still difficult to reach the standard for discharge after treatment. Meanwhile, the performance of the cyanide-free white copper tin plating layer is either insufficient in hardness or too brittle. In a pyrophosphate system, the difference of complexing stability of pyrophosphate, copper ions and tin ions is large, copper ions are reduced and deposited preferentially, copper and tin in a coating are uneven in proportion, crystal particles are coarse and are loosely arranged, so that the hardness of the coating is generally only 300-400HV, the wear-resistant scene requirement can not be met, the complexing capacity of a citrate system is weak, the stability of a plating solution is poor, the reduction potential difference of copper and tin ions is obviously increased, ion adsorption is uneven easily in the deposition process, stress concentration is formed in the coating, and brittleness is obviously increased. Disclosure of Invention The embodiment of the application aims to provide a cyanide-free lead-free white copper tin electroplating process, which aims to solve the technical problem that the environmental compliance of plating solution and the mechanical property of a plating layer are difficult to be considered by a main flow cyanide-free system in the prior art. The technical scheme adopted by the application is that the cyanide-free lead-free white copper tin electroplating process comprises the following steps of: opening a cylinder, namely adding copper methionine, sodium stannate, potassium hydroxide, zinc oxide, potassium carbonate, conductive salt, brightening agent, complexing agent and wetting agent to form plating solution; Electroplating, namely starting mechanical stirring and heating to a required temperature, putting a workpiece into a plating solution, electroplating, and controlling the current density, the metal ion concentration and the temperature of the plating solution within a preset range; The complexing agent comprises sodium phosphite and ethyl 3-aminobenzoate methylsulfonate. Optionally, the plating solution comprises 90-120g/L of conductive salt, 10-18g/L of potassium hydroxide, 20-35g/L of copper methionine, 30-35g/L of sodium stannate, 2g/L of zinc oxide, 10g/L of potassium carbonate, 0.3-1ml/L of brightening agent, 10-30ml/L of complexing agent and 1-2ml/L of wetting agent. Optionally, the conductive salt comprises 65-67% of sodium carbonate, 28-30% of sodium thiocyanate and 3-5% of sodium hydroxide in mass ratio; The brightening agent comprises, by mass, 1% -3% of sodium polydithio-dipropyl sulfonate, 0.5% -1.5% of polyethylene glycol, 0.5% -1.5% of 2-propyne-1-sodium sulfonate and the balance deionized water; The wetting agent comprises, by mass, 0.1% -0.3% of octyl phenol polyoxyethylene ether, 0.3% -0.7% of potassium perfluorobutyl sulfonate and the balance deionized water. Optionally, the cylinder opening step further comprises adding a cylinder opening agent, and the plating solution further