Method for electroplating palladium-nickel alloy on surfaces of copper and copper alloy parts

Abstract

A method for electroplating palladium-nickel alloy on the surfaces of copper and copper alloy parts comprises the steps that S1, the surfaces of the copper and copper alloy parts are degreased; s2, pre-corrosion is carried out; the part without oil stains on the surface is placed in a hydrochloric acid solution to be pre-corroded, and after corrosion is completed, the part is rapidly washed clean with running water; s3, emitting light; the pre-corroded part is placed in a mixed solution of chromic anhydride and sulfuric acid to be continuously shaken for bright dipping treatment; s4, scrubbing with magnesium oxide; degreasing cotton is soaked with water, then pasty magnesium oxide is dipped, the surface of the bright part is scrubbed, and the surface of the bright part is washed clean with deionized water; s5, weak corrosion; the part without water drops on the surface is placed in a hydrochloric acid solution to be continuously shaken for weak corrosion treatment; S6, copper plating is conducted; placing the part subjected to weak corrosion in a mixed solution composed of cuprous cyanide, potassium cyanide and sodium hydroxide for copper electroplating to obtain a part with a copper plating layer on the surface; s7, plating a palladium-nickel alloy; and S8, the part with the copper plating layer on the surface is placed in palladium-nickel alloy electroplating liquid to be electroplated with palladium-nickel alloy, and drying is conducted.

Description

Technical Field

[0001] This invention belongs to the technical field of palladium-nickel alloy electroplating on copper parts, and particularly relates to a method for electroplating palladium-nickel alloy on the surface of copper and copper alloy parts. Background Technology

[0002] Currently, the copper slip ring assembly inside the limited-angle motor of the ignition device experiences surface wear during rotation. To improve the wear resistance of the copper slip ring assembly, palladium is electroplated onto its surface. However, the palladium plating layer generates significant residual internal stress due to hydrogen absorption, which can easily lead to problems such as plating peeling or cracking. At the same time, the hydrogen gas generated during the palladium plating process adheres to and accumulates on the surface of the palladium layer. The intermittent retention and escape of hydrogen gas results in incomplete plating, forming pores and pits, which seriously affects the wear resistance of the plating layer and urgently needs to be solved. Summary of the Invention

[0003] This invention provides a method for electroplating palladium-nickel alloy onto the surface of copper and copper alloy parts, overcoming the shortcomings of existing technologies.

[0004] The technical solution adopted in this invention is: a method for electroplating palladium-nickel alloy onto the surface of copper and copper alloy parts, comprising the following steps: S1: Removes oil and dirt from the surface of copper and copper alloy parts; S1.1: Place the parts in gasoline or metal cleaner to remove surface oil stains until no obvious oil stains are visible. S1.2: Add a mixed solution consisting of 5-15 g / L sodium hydroxide, 20-30 g / L sodium carbonate, 30-60 g / L sodium phosphate, and 3-5 g / L sodium silicate to an ultrasonic cleaner. Then place parts that are visually free of obvious oil stains into the mixed solution and start the ultrasonic cleaner to remove oil, thereby obtaining parts with no oil stains on the surface. S2: Pre-corrosion; Place the oil-free parts in a hydrochloric acid solution with a concentration of 150-200 g / L for pre-corrosion. The pre-corrosion time is 0.5-1.5 min, and the solution temperature is 10-35℃. After corrosion, rinse the parts thoroughly with running water. S3: Brightening; The pre-etched parts are placed in a mixed solution of 90-150 g / L chromic anhydride and 20-30 g / L sulfuric acid and continuously shaken for brightening treatment. The solution temperature is 10-35℃ and the brightening time is 3-15 seconds; Remove the oxide scale and undesirable structures from the surface of the parts. S4: Magnesium oxide cleaning; Wet the degreased cotton with water and then dip it in the paste of magnesium oxide to clean the surface of the polished parts. After cleaning, rinse the parts with deionized water. Wait 30-50 seconds to observe the surface of the cleaned parts and check that there are no water droplets. S5: Weak corrosion; Place the parts with no water droplets on the surface into a hydrochloric acid solution with a concentration of 30-50 g / L and shake continuously for weak corrosion treatment. The corrosion time is 0.5-1 min. After the weak corrosion treatment is completed, rinse them with running water immediately. S6: Copper plating; The weakly etched parts are placed in a mixed solution of 25-30 g / L cuprous cyanide, 45-70 g / L potassium cyanide, and 10-20 g / L sodium hydroxide for copper plating. The copper plating current density is 0.3-2 A / dm2, the temperature is 25-40℃, and the time is 5-10 min; parts with a copper plating layer on the surface are obtained. S7: Palladium-nickel alloy plating; The parts with copper plating on the surface are placed in a palladium-nickel alloy plating solution for palladium-nickel alloy plating. The pH value of the plating solution is 7.0-7.6, the temperature is 40-50℃, the plating time is 30-35 min, the current density is 0.5-1.5 A / dm2, the deposition rate is 4-6 min / μm, and after the plating is completed, the parts are rinsed with running water to obtain a palladium-nickel alloy plating layer with a thickness of 5-8 μm. S8: Drying; After cleaning the parts with palladium-nickel alloy plating on the surface with deionized water, place them in an oven to dry and remove the stress generated in S7. The drying temperature is 40~60℃ and the drying time is 20~30min to obtain copper alloy parts or copper parts with palladium-nickel alloy plating on the surface.

[0005] The gasoline is 120#, the metal cleaning agent is water-based, and the parts are cleaned with a brush to remove surface oil stains.

[0006] The preparation method of palladium-nickel alloy electroplating solution is as follows: Add 10% deionized water to the cleaned plating tank, add nickel salt additive at a rate of 75-175 mL / L while stirring continuously, and heat the solution to 40-50℃; add conductive salt at a rate of 120-150 g / L while stirring continuously until completely dissolved; add stabilizer at a rate of 5-20 g / L while stirring continuously; add palladium chloride at a rate of 6-14 g / L while stirring continuously, and after complete dissolution, add deionized water to adjust the solution to the final volume of the plating tank, and adjust the pH value of the solution to 7.0-7.6; control and maintain the solution temperature at 40-50℃, stir and wait for 1 hour to complete the preparation.

[0007] The ultrasonic cleaner has a cleaning frequency of 40Hz, the temperature of the mixed solution is 60-80℃, and the cleaning process involves forward cleaning for 5-15 minutes, followed by reverse cleaning for 3-5 minutes.

[0008] The paste-like magnesium oxide needs to be filtered through a filter cloth to remove unreacted impurities and large particulate residues.

[0009] Compared with the prior art, the present invention has the following beneficial effects: 1. The palladium-nickel alloy coating obtained by this invention is complete and free from defects such as pores and pits. After polishing, the surface of the palladium-nickel alloy is inspected under a 5-10x microscope and there are no defects such as cracks, scratches, peeling, pits, or pitting.

[0010] 2. The palladium-nickel alloy electroplating solution used in this invention does not pollute the environment, has low cost, and the whole process is simple to operate. The electrical properties and various physical properties of the produced palladium-nickel alloy plating layer meet the technical requirements of copper slip ring components, and can completely replace palladium plating layer. Moreover, its hardness and wear resistance are superior to palladium plating layer. Detailed Implementation

[0011] The present invention will now be described in detail with reference to specific embodiments.

[0012] A method for electroplating palladium-nickel alloy onto the surface of copper and copper alloy parts, comprising the following steps: S1: Removes oil and dirt from the surface of copper and copper alloy parts; S1.1: Place the parts in 120# gasoline or a metal cleaner with a volume ratio of 1% to 3% and use a brush to clean the parts to remove surface oil stains. The parts are ready when there are no obvious oil stains visible to the naked eye; wherein, the metal cleaner is water-based. S1.2: A mixed solution consisting of 5–15 g / L sodium hydroxide, 20–30 g / L sodium carbonate, 30–60 g / L sodium phosphate, and 3–5 g / L sodium silicate is added to an ultrasonic cleaner. Copper parts that are visually free of obvious oil stains are then placed in the mixed solution, and the ultrasonic cleaner is started for degreasing treatment. The ultrasonic cleaner is set at a cleaning frequency of 40 Hz, the mixed solution temperature is 60–80 °C, and the forward cleaning is performed for 5–15 minutes. Then, the reverse cleaning is performed for 3–5 minutes to obtain parts with no oil stains on the surface. S2: Pre-corrosion; Place the oil-free parts in a hydrochloric acid solution with a concentration of 150-200 g / L for pre-corrosion. The pre-corrosion time is 0.5-1.5 min, and the solution temperature is 10-35℃. After corrosion, rinse the parts thoroughly with running water. S3: Brightening; The pre-etched copper parts are placed in a mixed solution of chromic anhydride with a concentration of 90-150 g / L and sulfuric acid with a concentration of 20-30 g / L for brightening treatment by continuous shaking. The solution temperature is 10-35℃ and the brightening time is 3-15 seconds; This removes the oxide scale and undesirable structures on the surface of the parts, thereby increasing the adhesion between the coating and the substrate. S4: Magnesium oxide scrubbing; Wet degreased cotton with water and apply magnesium oxide paste to the polished surface of the parts. After scrubbing with magnesium oxide paste, rinse the copper alloy parts or copper parts with deionized water (pure water). Wait 30-50 seconds to observe if there are no water droplets on the surface of the cleaned copper alloy parts or copper parts. The magnesium oxide paste needs to be filtered through a filter cloth to remove large particles, so as to remove unreacted impurities and large particle residues and avoid scratching the surface of the parts. The filter cloth is silk cloth. S5: Weak corrosion; Place the parts with no water droplets on the surface into a 30-50 g / L hydrochloric acid solution and continuously agitate for weak corrosion treatment. The corrosion time is 0.5-1 min. After weak corrosion treatment, immediately rinse thoroughly with running water; This activates the surface of the parts and helps the copper plating adhere to the surface. S6: Copper plating; The weakly etched parts are placed in a mixed solution of 25–30 g / L cuprous cyanide, 45–70 g / L potassium cyanide, and 10–20 g / L sodium hydroxide for copper plating. The copper plating current density is 0.3–2 A / dm³. 2 The plating temperature is 25~40℃ and the plating time is 5~10min; copper alloy parts or copper parts with copper plating are obtained. The copper plating obtained by electroplating can cover the pits and other defects on the surface of the substrate material, forming a smooth and flat surface. When palladium atoms are deposited on the smooth and flat copper plating surface, they can follow the arrangement of copper atoms to carry out low-stress, highly ordered epitaxial growth, forming a dense, continuous interface with extremely low internal stress. The palladium plating is not easy to peel or fall off, which enhances the bonding force of the palladium-nickel alloy plating and obtains a palladium-nickel alloy plating of better quality.

[0013] S7: Palladium-nickel alloy plating; Parts with a copper plating layer on their surface are placed in a palladium-nickel alloy plating solution for palladium-nickel alloy plating; wherein... The electroplating solution preparation method is as follows: Add 10% deionized water to the cleaned plating tank, and add nickel salt additive (nickel sulfamate) at a rate of 75-175 mL / L while stirring continuously. Heat the solution to 45℃. Add conductive salt (ammonium sulfate or sodium sulfate) at a rate of 120-150 g / L while stirring continuously until completely dissolved. Add stabilizer (boric acid) at a rate of 5-20 g / L while stirring continuously. Add palladium chloride at a rate of 6-14 g / L while stirring continuously. After complete dissolution, add deionized water to adjust the solution to the final volume of the plating tank. Measure the pH value of the solution with a pH meter and adjust the pH value to about 7.4 with 10% (v / v) ammonia or 10% (v / v) sulfuric acid. Control and maintain the solution temperature at about 45℃, stir and wait for 1 hour to complete the electroplating solution preparation.

[0014] Electroplating time: 30–35 min; current density: 0.5–1.5 A / dm³ 2The deposition rate is 4–6 min / μm. After electroplating, the parts are rinsed with running water to obtain a palladium-nickel alloy coating with a thickness of 5–8 μm.

[0015] S8: Drying; After cleaning the parts with palladium-nickel alloy plating with deionized water (pure water), place them in an oven at a temperature of 40~60℃ for 20~30 minutes to remove stress and hydrogen embrittlement generated during the palladium-nickel alloy plating process, and obtain qualified copper alloy parts or copper parts plated with palladium-nickel alloy.

[0016] In a specific application example, the above method was used to plate a palladium-nickel alloy coating on the outer surface of a φ14+0.03 0 copper slip ring. The coating thickness was 5~8 μm. After polishing, the surface of the palladium-nickel alloy was inspected under a 5~10x microscope and found to be free of defects such as cracks, scratches, peeling, pits, and pitting, thus extending the slip ring's life. The palladium-nickel alloy coating has a semi-glossy silver-white appearance, with uniform and fine crystals. Its microhardness reaches 400mHV25, and the palladium content in the coating is 70~85%, while the nickel content is 15~30%.

[0017] The performance comparison between palladium coating and palladium-nickel alloy coating is as follows:

[0018] As can be seen from the table above, the electrical and physical properties of the palladium-nickel alloy coating produced by this invention meet the technical requirements of copper slip ring assemblies, can completely replace palladium coating, and has better hardness and wear resistance than palladium coating.

[0019] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Therefore, all equivalent variations made to the content described in the claims of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method for electroplating palladium-nickel alloy onto the surface of copper and copper alloy parts, characterized in that... The steps are as follows: S1: Removes oil and dirt from the surface of copper and copper alloy parts; S1.1: Place the parts in gasoline or metal cleaner to remove surface oil stains until no obvious oil stains are visible. S1.2: Add a mixed solution consisting of 5-15 g / L sodium hydroxide, 20-30 g / L sodium carbonate, 30-60 g / L sodium phosphate, and 3-5 g / L sodium silicate to an ultrasonic cleaner. Then place parts that are visually free of obvious oil stains into the mixed solution and start the ultrasonic cleaner to remove oil, thereby obtaining parts with no oil stains on the surface. S2: Pre-corrosion; Place the oil-free parts in a hydrochloric acid solution with a concentration of 150-200 g / L for pre-corrosion. The pre-corrosion time is 0.5-1.5 min, and the solution temperature is 10-35℃. After corrosion, rinse the parts thoroughly with running water. S3: Brightening; The pre-etched parts are placed in a mixed solution of 90-150 g / L chromic anhydride and 20-30 g / L sulfuric acid and continuously shaken for brightening treatment. The solution temperature is 10-35℃ and the brightening time is 3-15 seconds; Remove the oxide scale and undesirable structures from the surface of the parts. S4: Magnesium oxide cleaning; Wet the degreased cotton with water and then dip it in the paste of magnesium oxide to clean the surface of the polished parts. After cleaning, rinse the parts with deionized water. Wait 30-50 seconds to observe the surface of the cleaned parts and check that there are no water droplets. S5: Weak corrosion; Place the parts with no water droplets on the surface into a hydrochloric acid solution with a concentration of 30-50 g / L and shake continuously for weak corrosion treatment. The corrosion time is 0.5-1 min. After the weak corrosion treatment is completed, rinse them with running water immediately. S6: Copper plating; The weakly etched parts are placed in a mixed solution of 25–30 g / L cuprous cyanide, 45–70 g / L potassium cyanide, and 10–20 g / L sodium hydroxide for copper plating. The plating current density is 0.3–2 A / dm³. 2 The temperature is 25~40℃ and the time is 5~10min; a part with a copper plating layer on the surface is obtained. S7: Palladium-nickel alloy plating; Plating parts with a copper plating layer on their surface into a palladium-nickel alloy plating solution for palladium-nickel alloy plating. The solution pH is 7.0–7.6, the temperature is 40–50℃, the plating time is 30–35 min, and the current density is 0.5–1.5 A / dm³. 2 The deposition rate is 4-6 min / μm. After electroplating, the parts are rinsed with running water to obtain a palladium-nickel alloy coating with a thickness of 5-8 μm. S8: Drying; After cleaning the parts with palladium-nickel alloy plating on the surface with deionized water, place them in an oven to dry and remove the stress generated in S7. The drying temperature is 40~60℃ and the drying time is 20~30min to obtain copper alloy parts or copper parts with palladium-nickel alloy plating on the surface.

2. The method for electroplating palladium-nickel alloy onto the surface of copper and copper alloy parts according to claim 1, characterized in that: In step S1.1, the gasoline is 120#, the metal cleaning agent is water-based, and a brush is used to scrub the parts to remove surface oil stains.

3. The method for electroplating palladium-nickel alloy onto the surface of copper and copper alloy parts according to claim 1, characterized in that, In step S7, the preparation method of the palladium-nickel alloy electroplating solution is as follows: Add 10% deionized water to the cleaned plating tank, add nickel salt additive at a rate of 75-175 mL / L while stirring continuously, and heat the solution to 40-50℃; add conductive salt at a rate of 120-150 g / L while stirring continuously until completely dissolved; add stabilizer at a rate of 5-20 g / L while stirring continuously; add palladium chloride at a rate of 6-14 g / L while stirring continuously, and after complete dissolution, add deionized water to adjust the solution to the final volume of the plating tank, and adjust the pH value of the solution to 7.0-7.6; control and maintain the solution temperature at 40-50℃, stir and wait for 1 hour to complete the preparation.

4. The method for electroplating palladium-nickel alloy onto the surface of copper and copper alloy parts according to claim 1, characterized in that: In step S1.2, the ultrasonic cleaner has a cleaning frequency of 40Hz, the temperature of the mixed solution is 60-80℃, and the cleaning process involves forward cleaning for 5-15 minutes followed by reverse cleaning for 3-5 minutes.

5. The method for electroplating palladium-nickel alloy onto the surface of copper and copper alloy parts according to claim 1, characterized in that: In step S4, the paste-like magnesium oxide needs to be filtered through a filter cloth to remove unreacted impurities and large particulate residues.

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