CN101260551B - Cyanide-free silver electroplating method - Google Patents

Abstract

The invention relates to a cyanide-free silver electroplating method. Plating nickel on the surface of a base material, then electrically activating a nickel layer in an acid solution, and then carrying out double-pulse silver electroplating in a nicotinic acid silver electroplating system after chemical silver plating. After the treatment by the method, the surface of the base material obtains a compact silver coating with good binding force.

Description

A kind of method of cyanide-free electroplating silver

technical field

The invention relates to electroplating technology, in particular to a method for cyanide-free electroplating silver.

Background technique

Electroplating silver is widely used in electronic devices, semiconductors, instrumentation, decoration and other functional silver plating fields. At present, the electroplating silver at home and abroad is still dominated by cyanide system silver plating. Due to the serious environmental pollution caused by cyanide, with the continuous enhancement of people's awareness of environmental protection, cyanide electroplating will gradually be eliminated. Existing patent literature discloses the processing method of cyanide-free silver plating in the prior art, and relevant patent is as follows:

Patent 200510023573 relates to a cyanide-free silver plating process, which is a cyanide-free silver plating process under the action of a magnetic field and a pulse current. The method includes the following technological processes and steps: chemical degreasing of plated parts, chemical deembroidery, bright nickel plating, activation treatment, immersion silver, pulse silver plating, passivation treatment, drying, and finally obtains a finished silver plated product. The activation treatment adopts chemical methods, the complexing agent of the silver immersion solution is thiourea, and the formula of the pulse silver plating solution is: silver nitrate 50-60g/L, sodium thiosulfate 250-350g/L, potassium metabisulfite 90-110g /L, potassium sulfate 20-30g/L, boric acid 25-35g/L, brightener 5ml/L.

Patent 200710009207 relates to a cyanide-free silver plating solution, which is characterized in that the mass concentration of each component of the raw material formula of the electroplating solution is: inorganic salt or organic salt containing silver 1-200g/L, purine complexing agent 1 -800g/L, supporting electrolyte 1-200g/L, bath pH regulator 0-550g/L and electroplating additive system.

Patent 200710009208 relates to a cyanide-free electroplating solution for silver plating, which is characterized in that the mass concentration of each component of the raw material formula of the electroplating solution is: inorganic salt or organic salt containing silver 1-200g/L, pyrimidine Complexing agent 1-800g/L, supporting electrolyte 1-200g/L, bath pH regulator 0-550g/L and electroplating additive system.

Contents of the invention

The object of the present invention is to provide a method for cyanide-free electroplating silver, so as to obtain a silver plating layer with good bonding force and compactness. In order to achieve the above object, the technical solution adopted in the present invention is: a method for cyanide-free electroplating silver, comprising: nickel-plating the surface of the base material, activating the nickel-plated layer, electroplating silver on the nickel-plated layer, and activating the nickel-plated layer The nickel-plated layer is electroactivated in an acid solution, and the electro-silvering method includes electroless silver-plating on the nickel-plated layer and double-pulse electro-silvering in a nicotinic acid electroplating silver system, and is characterized in that the method of electro-activating the nickel-plated layer Yes: put the nickel-plated base material into the electroactivation tank filled with H ₂ SO ₄ solution, the H ₂ SO ₄ solution contains 80-250 ml of H ₂ SO ₄ per liter of H ₂ SO ₄ solution, H The concentration of ₂ SO ₄ is 98%, the temperature of the solution is kept at 4-8°C, the cathode current density of electroactivation is 1-2.5A/dm ² , the electroactivation time is 1-5min, and after activation, take it out and rinse it with clean water; The electroless silver plating process method is: put the base material after the activation of the nickel plating layer into the electroplating tank _containing the mixed solution of _Na2SO3 and _AgNO3 , and the content of _Na2SO3 in _each liter of the mixed solution in the electroplating tank is 100 -200g, the content of _AgNO3 is 0.8-1.5g, the solution temperature is maintained at 12-25°C, and the electroplating time is 5-60s; the process method of double-pulse electroplating silver in the niacin electroplating system is: The solution consists of niacin: 80-150g/L, AgNO ₃ : 20-55g/L, K ₂ CO ₃ : 60-100g/L, KOH: 40-65g/L, NH ₄ AC: 60-80g/L, NH ₃ ·H ₂ O: 15-40ml/L composition, the temperature of the electroplating solution is kept at 12-25°C, the forward pulse width of the double-pulse electroplating power supply is 2ms, the duty cycle is 20%, and the working time is 100ms; The width is 1ms, the duty cycle is 10%, the working time is 10ms, and the plating time is 0.5-6h.

The present invention has the following advantages:

1. The binding force is guaranteed through electrochemical activation, so that cyanide-free silver plating can be applied, thereby reducing the pollution to the environment to the greatest extent.

2. The use of double-pulse electroplating power supply can effectively reduce the thickness of the coating and save costs while improving the corrosion resistance.

Detailed ways

Example 1

Silver plated over stainless steel. The stainless steel model is 316L. Remove the oxide film on the surface, immerse in 100ml/L hydrochloric acid (d=1.19) for 30min to activate the surface, the temperature of the acid solution is 12°C. Nickel electroplating is carried out in the plating solution of NiSO ₄ 7H ₂ O: 270g/L, NiCl ₂ 7H ₂ O: 50g/L, H ₃ BO ₃ : 35g/L. The electroplating process is: electroplating temperature: 20°C, Electroplating time: 3min, cathode current: 2.0A/dm ² . The electrochemically activated nickel plating _layer is carried out in an electroactivation bath, and the nickel-plated material is placed in an electroactivation _bath filled with _H2SO4 solution, and the _H2SO4 solution contains 100 per liter of _H2SO4 solution _. Milliliters of H ₂ SO ₄ , the concentration of H ₂ SO ₄ is 98%, the temperature of the solution is kept at 8°C, the cathode current density of electroactivation is 1.5A/dm ² , and the electroactivation time is 5min. After activation, take it out and rinse it with clean water. Carry out electroless silver plating again, put the material after nickel plating layer activation into the plating tank that is equipped with Na ₂ SO ₃ and AgNO ₃ mixed solution, the content of Na ₂ SO ₃ in every liter of mixed solution in the plating tank is 150g, AgNO ₃ The content is 0.8g, the solution temperature is kept at 25°C, and the silver plating time is 5s. Finally, double-pulse silver plating in the niacin electroplating silver system, the niacin electroplating silver solution consists of niacin: 100g/L, AgNO ₃ : 35g/L, K ₂ CO ₃ : 80g/L, KOH: 55g/L, NH ₄ AC: 70g/L, NH ₃ ·H ₂ O: 30ml/L, the temperature of the electroplating solution is kept at 25°C, the electroplating time is 3h, the forward pulse width of the double-pulse electroplating power supply is 2ms, and the duty cycle is 20%. The time is 100ms; the reverse pulse width is 1ms, the duty cycle is 10%, and the working time is 10ms.

Example 2

Plating silver on copper. First, a layer of nickel is electroplated on copper by common methods, and then the nickel plating layer is activated electrochemically. The electrochemical activation of the nickel plating layer is carried out in an electroactivation tank, and the nickel-plated copper is placed in _{a H2SO4} solution. In the electro-activation tank, the H ₂ SO ₄ solution contains 250 ml of H ₂ SO ₄ per liter of H ₂ SO ₄ solution, the concentration of H ₂ SO ₄ is 98%, the temperature of the solution is kept at 4°C, and the cathode current density of electro-activation is 1.0A/dm ² , the electrical activation time is 1min, after activation, take it out and rinse it with clean water. Carry out electroless silver plating again, put the copper after nickel plating layer activation into the plating tank that is equipped with Na ₂ SO ₃ and AgNO ₃ mixed solution, in the plating tank, Na ₂ SO ₃ content is 100g in every liter of mixed solution, AgNO ₃ The content is 1g, the solution temperature is kept at 20°C, and the silver plating time is 30s. Finally, double-pulse silver electroplating in the nicotinic acid electroplating silver system, the nicotinic acid electroplating silver solution consists of nicotinic acid: 150g/L, AgNO ₃ : 55g/L, K ₂ CO ₃ : 100g/L, KOH: 65g/L, NH ₄ AC: 80g/L, NH ₃ ·H ₂ O: 40ml/L, the temperature of the electroplating solution is kept at 20°C, the electroplating time is 0.5h, the forward pulse width of the double-pulse electroplating power supply is 2ms, and the duty cycle is 20%. The working time is 100ms; the reverse pulse width is 1ms, the duty cycle is 10%, and the working time is 10ms.

Example 3

Electroplated silver on pure titanium. Electroplate a layer of nickel on pure titanium by the usual method, and then electrochemically activate the nickel plating layer. The electrochemical activation of the nickel plating layer is carried out in an electroactivation tank. Put the nickel-plated titanium into the _electrolytic tank containing _H2SO4 solution In the activation tank, the H ₂ SO ₄ solution contains 80 milliliters of H ₂ SO ₄ per liter of H ₂ SO ₄ solution, the concentration of H ₂ SO ₄ is 98%, the temperature of the solution is kept at 6°C, and the cathode current density for electroactivation is 2.5A/dm ² , the electrical activation time is 3min, after activation, take it out and rinse it with clean water. Carry out electroless silver plating again, put the titanium after the nickel plating layer activation into the plating tank that is equipped with Na ₂ SO ₃ and AgNO ₃ mixed solution, the Na ₂ SO ₃ content in the mixed solution per liter in the plating tank is 200g, AgNO ₃ The content is 1.5g, the solution temperature is maintained at 12°C, and the silver plating time is 60s. Finally, double-pulse silver plating in the nicotinic acid silver plating system, the nicotinic acid silver plating solution consists of nicotinic acid: 80g/L, AgNO ₃ : 20g/L, K ₂ CO ₃ : 60g/L, KOH: 40g/L, NH ₄ AC: 60g/L, NH ₃ ·H ₂ O: 15ml/L, the temperature of the electroplating solution is kept at 12°C, the electroplating time is 6h, the forward pulse width of the double-pulse electroplating power supply is 2ms, and the duty cycle is 20%. The time is 100ms; the reverse pulse width is 1ms, the duty cycle is 10%, and the working time is 10ms.

The coating of above-mentioned embodiment all passes through following test:

1) Appearance

The appearance of the coating is uniform and compact, bright, without defects such as peeling, bubbling, and spots. The 200x 3D image obtained by the ultra-deep surface morphology microscope shows that the coating is microscopically wavy, without pores, and the flatness of the entire silver coating is 4 μm.

2) binding force

Use a scratch needle to draw several scratches deep to the substrate on the coating. These scratches are parallel and staggered to each other. The distance between the scratches is not greater than 2mm. No phenomenon such as peeling off of the coating is observed.

Claims (1)

1. A method for cyanide-free electroplating silver, comprising: base material surface nickel-plated, nickel-plated layer activation treatment, electroplating silver on the nickel-plated layer, nickel-plated layer activation treatment is that the nickel-plated layer is electrically activated in acid solution Treatment, the silver electroplating method comprises chemical silver plating on the nickel plating layer and double pulse electroplating silver in the nicotinic acid electroplating silver system, it is characterized in that the method for electroactivating the nickel plating layer is: put the base material of nickel plating on the surface into In the electroactivation cell filled with H ₂ SO ₄ solution, the H ₂ SO ₄ solution contains 80-250 ml of H 2 SO ₄ per liter of H ₂ SO ₄ solution, the concentration of _{H 2 SO 4} is 98%, and the solution temperature is kept At 4-8°C, the cathode current density of electroactivation is 1-2.5A/dm ² , and the electroactivation time is 1-5min. After activation, take it out and rinse it with clean water; the electroless silver plating process method is: The matrix material after layer activation is put into an electroplating tank containing a mixed solution of Na ₂ SO ₃ and AgNO ₃ , the content of Na ₂ SO ₃ in each liter of mixed solution in the electroplating tank is 100-200g, and the content of AgNO ₃ is 0.8-1.5g , the solution temperature is maintained at 12-25°C, and the electroplating time is 5-60s; the process method of double-pulse electroplating silver in the nicotinic acid electroplating silver system is: the nicotinic acid electroplating silver solution is composed of nicotinic acid: 80-150g/L, AgNO ₃ : 20-55g/L, K ₂ CO ₃ : 60-100g/L, KOH: 40-65g/L, NH ₄ AC: 60-80g/L, NH ₃ ·H ₂ O: 15-40ml/L Composition, the temperature of the electroplating solution is kept at 12-25°C, the forward pulse width of the double-pulse electroplating power supply is 2ms, the duty cycle is 20%, and the working time is 100ms; the reverse pulse width is 1ms, and the duty cycle is 10%. The working time is 10ms, and the plating time is 0.5-6h.