CN101270492B - Stannum copper alloy coating, plating solution and electroplating method - Google Patents

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 oftin 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 to3ml/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

Electroplating solution and electroplating method for tin-copper alloy coating

technical field

The invention relates to the technical field of electroplating, in particular to an electroplating solution and an electroplating method for a tin-copper alloy coating. the

Background technique

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, watches, earrings, rings, necklaces and other accessories, mobile phone cases, Mobile phone accessories, etc., are not suitable for nickel plating. the

For this reason, at present, some operators use the copper-tin alloy coating as the decorative coating. The copper-tin alloy coating is usually cupronickel tin, although it does not contain nickel and will not cause skin allergies, but its 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 the _O2 in the air Or the reason for anodic oxidation in electroplating is to convert divalent tin into tetravalent tin, which leads to the accumulation of tetravalent tin, which makes the performance of the electroplating layer poor, thereby shortening the service life, and the surface brightness of the coating layer will also be poor, blackening, and fogging noodle.

Contents of the invention

The object of the present invention is to provide an electroplating solution and an electroplating method for a tin-copper alloy coating, which can make the thermal stability of the coating better, less prone to discoloration, more environmentally friendly, and avoid skin nickel allergy. the

For realizing the above object, technical solution of the present invention is:

A tin-copper alloy coating comprising at least 55-60% tin and 40-45% copper by weight. the

An electroplating solution formula for forming the tin-copper alloy coating, which includes 20-40g/l stannous chloride and 10-30g/l copper pyrophosphate as the main salt of tin and copper respectively; also includes 250- 350g/l potassium pyrophosphate as the main complexing agent, 30-40g/l alkali metal chloride salt or alkaline earth chloride salt as auxiliary complexing agent, 10-30g/l tin chloride pentahydrate as Plating solution stabilizer, the pH value is controlled at 8.0-9.0; in addition, the electroplating solution is also added with 0.5-5ml/l type I additive and 0.5-3ml/l type II additive; the type I additive contains -(CH ₂ OCH ₂ ) _n - and -(C ₆ H ₄ )-(OC ₂ H ₅ ) _n OH structure polyether compounds; and class II additives are compounds containing NH ₂ -CH ₂ -COOH, -CO-NH- structures .

The class I additive is polyethylene glycol, polyethylene glycol alkyl alcohol ether or alkylphenol polyoxyethylene ether. the

The class II additive is amino acid, gelatin or polypeptide. the

An electroplating method for forming the tin-copper alloy electroplating layer by using the above electroplating solution: first, adding the aforementioned electroplating solution of the tin-copper alloy coating in an electroplating tank; then, immersing the workpiece in the electroplating solution of the electroplating tank As the cathode, an anode is set at the same time; finally, a direct current is passed between the anode and the cathode, and the current density for forming the tin-copper alloy coating is controlled at 0.5-2ASD, and the temperature in the electroplating tank is controlled at 15-30°C. the

The anode can be activated carbon plate, stainless steel plate or DSA etc. the

The outside of the anode is covered with a PP braid. the

When potassium pyrophosphate is 250,300,350g/l in described electroplating solution, copper pyrophosphate is 17g/l, stannous chloride is 25g/l, tin chloride pentahydrate is 25g/l, and potassium chloride is 30g /l, Type I additive is 0.5ml/l, and Type II additive is 1ml/l; at this time, the temperature in the electroplating bath is 20°C; the current density is 0.8ASD. the

When potassium pyrophosphate is 250,300,350g/l in described electroplating solution, copper pyrophosphate is 17g/l, stannous chloride is 30g/l, tin chloride pentahydrate is 20g/l, and potassium chloride is 35g /l, type I additive is 1ml/l, and type II additive is 1ml/l; at this time, the temperature in the electroplating tank is 25°C; the current density is 1.2ASD. the

When potassium pyrophosphate is 250,300,350g/l in described electroplating solution, copper pyrophosphate is 17g/l, stannous chloride is 35g/l, tin chloride pentahydrate is 15g/l, and potassium chloride is 40g /l, type I additive is 1.5ml/l, and type II additive is 1.5ml/l; at this time, the temperature in the electroplating tank is 30°C; the current density is 1.6ASD. the

After adopting the above scheme, the present invention has the following advantages:

1. Since the electroplating solution of the tin-copper alloy coating of the present invention does not contain cyanide, not only the cost of sewage treatment is relatively low, but also the health of the electroplating process operators can be effectively guaranteed. Therefore, the performance of the decorative coating according to the present invention can not only meet the needs of consumers, but also does not contain any heavy metals, complies with all standards of ROHS-WEEE, and its manufacturing process conforms to environmental awareness. the

2. Since the nickel release amount of the decorative coating of the present invention is less than 0.05ppm, the finished product can be used by consumers who are allergic to nickel with special constitutions, without any risk of allergies. the

3. The anti-tarnish ability of the tin-copper alloy coating of the present invention is the best, which can overcome the shortcoming that the conventional cobalt coating or nickel coating is easy to change color in oxygen, so it is not necessary to coat the tin-copper alloy coating with a layer of colored surface It can achieve the purpose of durability and no discoloration. the

4. The corrosion resistance and toughness of the tin-copper alloy coating of the present invention are higher than that of the conventional bright nickel coating, and the hardness is equivalent to that of the nickel coating, so it can replace the bright nickel coating as a decorative coating. the

Detailed ways

The coating of the present invention is a tin-copper alloy coating for forming on the surface of a workpiece, and the tin-copper alloy coating comprises at least 55-60% tin by weight, 40-45% copper, and 1% unavoidable impurities . the

The electroplating solution system that forms the aforementioned tin-copper alloy coating uses stannous chloride (20-40g/l) and copper pyrophosphate (10-30g/l) as the main salt of tin and copper respectively, and potassium pyrophosphate (250- 350g/l) as the main complexing agent, alkali metal chloride salts (such as potassium chloride, lithium chloride, sodium chloride, etc.) or alkaline earth chloride salts (such as beryllium chloride, magnesium chloride, calcium chloride, etc.) ( 30-40g/l) as an auxiliary complexing agent, tin chloride pentahydrate (10-30g/l) as a plating solution stabilizer, and the pH value is controlled at 8.0-9.0. In addition, the tin-copper alloy electroplating solution is also added with type I additives (0.5-5ml/l) and type II additives (0.5-3ml/l) to obtain a fully bright coating with good leveling properties, and its stress and coating ductility can also be controlled good. Type I additives are polyether compounds containing structures such as -(CH ₂ OCH ₂ ) _n - or -(C ₆ H ₄ )-(OC ₂ H ₅ ) _n OH (for example: polyethylene glycol, polyethylene glycol alkyl Alcohol ethers or alkylphenol polyoxyethylene ethers); and Class II additives are compounds containing NH ₂ -CH ₂ -COOH or -CO-NH- structures (for example: amino acids, gelatin, polypeptides, etc.). The biggest feature of the tin-copper alloy electroplating solution is that its electroplating efficiency is higher than many current cyanide-free tin-copper alloy electroplating solutions.

In addition, the electroplating method for forming the aforementioned tin-copper alloy coating in the present invention is as follows: first, add the aforementioned tin-copper alloy electroplating solution into an electroplating tank, the composition and concentration of the electroplating solution are shown in Tables 1 to 3 below, wherein the auxiliary complexing agent Potassium chloride is preferably used; then, the workpiece is immersed in the electroplating bath of the electroplating tank as the cathode, and the activated carbon plate is used as the anode, or a stainless steel plate or DSA (the commercial name of the Dimensonally Stable Anade oxide coating anode) can be used as the anode. Anode; Finally, direct current is passed between the anode and the cathode, and the distance between the workpiece and the anode is preferably more than 7 cm to ensure the uniformity of the coating. The power supply used is based on the surface area of the workpiece. The current density for forming the tin-copper alloy coating is controlled at 0.5-2ASD, and the temperature in the electroplating tank is controlled at 15-30°C. See Table 1 to Table 3 for details. In addition, the outside of the anode must be covered with a PP braid to prevent electrolytic roughness, etc. Defects occur. the

Table 1 Copper-tin alloy coating

Components/Operating Conditions Example 1 Example 2 Example 3 K₄P₂O₇(g/L) 250 250 250

CuP₂O₇ 3H₂O(g/L) 17 17 17 SnCl₂ 2H₂O(g/L) 25 30 35 SnCl₄·5H₂O(g/L) 25 20 15 KCl(g/L) 30 35 40 Class I additives (ml/L) 0.5 1 1.5 Type II additives (ml/L) 1 1 1.5 Temperature (°C) 20 25 30 Current Density (ASD) 0.8 1.2 1.6 anode Charcoal plate Charcoal plate Charcoal plate

Table 2 Copper-tin alloy coating

Components/Operating Conditions Example 1 Example 2 Example 3 K₄P₂O₇(g/L) 300 300 300 CuP₂O₇ 3H₂O(g/L) 17 17 17 SnCl₂ 2H₂O(g/L) 25 30 35 SnCl₄·5H₂O(g/L) 25 20 15 KCl(g/L) 30 35 40 Class I additives (ml/L) 0.5 1 1.5 Type II additives (ml/L) 1 1 1.5 Temperature (°C) 20 25 30 Current Density (ASD) 0.8 1.2 1.6 anode Charcoal plate Charcoal plate Charcoal plate

Table 3 Copper-tin alloy coating

Components/Operating Conditions Example 1 Example 2 Example 3 K₄P₂O₇(g/L) 350 350 350 CuP₂O₇ 3H₂O(g/L) 17 17 17 SnCl₂ 2H₂O(g/L) 25 30 35 SnCl₄·5H₂O(g/L) 25 20 15 KCl(g/L) 30 35 40 Class I additives (ml/L) 0.5 1 1.5 Type II additives (ml/L) 1 1 1.5 Temperature (°C) 20 25 30 Current Density (ASD) 0.8 1.2 1.6 anode Charcoal plate Charcoal plate Charcoal plate

Furthermore, the product electroplated with the above-mentioned tin-copper alloy coating, in addition to the electroplating of the coating, may also include an undercoating layer between the workpiece and the aforementioned tin-copper alloy coating to increase the distance between the workpiece and the tin-copper alloy coating. Adhesion, and increase the gloss of the coating surface. And according to workpiece surface material is different, described bottom coating is also different. When the surface material of the workpiece is copper alloy, the undercoating layer includes a pre-plated copper and a copper sulfate layer; when the surface material of the workpiece is white iron or stainless steel, the undercoating layer is a pre-plated nickel layer; when the surface of the workpiece is zinc or zinc alloy, the bottom coating includes alkaline copper plating layer and pyrophosphate copper plating layer; when the workpiece is aluminum, aluminum alloy or magnesium alloy, the workpiece must be treated with zinc and chemical nickel; when the workpiece When it is β-titanium, pure titanium or titanium alloy, the bottom coating is a pre-nickel layer or pre-gold layer; when the surface material of the workpiece is non-metallic, such as ABS and other plastic materials, it is necessary to form an chemical nickel layer first. On the surface of the workpiece, then plate the aforementioned tin-copper alloy coating, and then electroplate color or paint. the

It should be noted that when the thickness of the tin-copper alloy coating of the present invention reaches more than 2 μm, although the material of the workpiece is copper-nickel or copper-iron alloy with a nickel content of 30-40% or the surface of the workpiece has an chemical nickel layer, but due to the present invention The tin-copper alloy coating has good coverage and porosity, and the nickel release measured by the EN1811-EN12412 standard can still be less than 0.05 ppm, which can meet the definition standard of nickel-free products. This kind of product can be supplied to those who are allergic to nickel. There is no risk of allergies when used by consumers. Therefore, the present invention is very suitable for protective decorative electroplating, such as glasses frames, watches, earrings, rings, necklaces and other accessories, mobile phone casings, mobile phone accessories or other products that have more contact with the face skin, so as to ensure that consumers healthy. the

According to the tin-copper alloy coating of the present invention, its thickness, hardness, nickel release, discoloration resistance, salt spray test and artificial sweat test are compared with the conventional nickel coating and copper-tin alloy coating. The results are shown in Table 4 below. the

Table 4 (The source of this table is that the workpiece substrate is copper alloy)

Plating Thickness μm Hardness HV Nickel release EN1811-EN 12412ppm Anti-tarnish ability Salt spray test ASTM B117 Artificial sweat test ISO 12870 Nickel plating ＞2 500-550 ＞＞0.05 Difference 48hr ＞24hr Cobalt coating ＞2 450-500 ＜0.05 Difference ＜16hr 16hr Copper-tin alloy coating ＞2 500-600 ＞0.05 good 48hr ＞24hr Tin-copper alloy plating ＞2 550-650 ＜0.05 good 48hr ＞24hr

It can be seen from Table 4 that the thickness of nickel coating, cobalt coating and tin-copper alloy coating can be greater than 2 μm; the hardness of nickel coating is 500-550HV, the hardness of cobalt coating is 450-500HV, and the hardness of tin-copper alloy coating is the largest, which is 550- 650HV; according to EN1811-EN12412 standards to measure the nickel release, the results show that the nickel release of the nickel coating is much greater than 0.05ppm, the nickel release of the cobalt coating and the tin-copper alloy coating is less than 0.05ppm, and the nickel release of the copper-tin alloy coating is greater than 0.05ppm; In terms of anti-tarnish ability, the nickel coating and cobalt coating are the worst, and the tin-copper alloy coating has the best anti-tarnish ability. the

The above-mentioned tin-copper alloy coating can overcome the shortcoming that the aforementioned cobalt coating or nickel coating is easy to change color in oxygen, so the tin-copper alloy coating does not need to be plated with a layer of colored surface coating to achieve the purpose of durability and no discoloration. However, if it is used as a surface layer and maintains a silvery white luster without oxidation and discoloration under oxygen, it needs to be coated with an organic film (Varnish). In addition, the corrosion resistance and toughness of the tin-copper alloy coating are higher than that of the conventional bright nickel coating, and the hardness is equivalent to that of the nickel coating, so it can replace the bright nickel coating as a decorative coating. the

Although the present invention is disclosed with the aforementioned preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection should be defined by the claims. the

Claims (9)

1. the electroplate liquid of a stannum copper alloy coating, described stannum copper alloy coating comprises the tin of 55-60% and the copper of 40-45% by weight; It is characterized in that: the cupric pyrophosphate that this electroplate liquid comprises the tin protochloride of 20-40g/l and 10-30g/l is respectively as the main salt of tin and copper; The potassium pyrophosphate that also comprises 250-350g/l is as main complexing agent, and the basic metal family villaumite of 30-40g/l or alkaline earths villaumite are as auxiliary complex-former, and the five hydration tin chlorides of 10-30g/l are as the bath stability agent, and the pH value is controlled at 8.0～9.0; In addition, this electroplate liquid also adds the I class additive of 0.5～5ml/l and the II class additive of 0.5～3ml/l; This I class additive is for containing-(CH ₂OCH ₂) _n-or-(C ₆H ₄)-(OC ₂H ₅) _nThe polyether compound of OH structure; And II class additive is for containing NH ₂-CH ₂-COOH or-compound of CO-NH-structure.

2. the electroplate liquid of stannum copper alloy coating as claimed in claim 1, it is characterized in that: described I class additive is polyoxyethylene glycol, polyalkylene glycol alkyl alcohol ether or alkylphenol polyoxyethylene.

3. the electroplate liquid of stannum copper alloy coating as claimed in claim 1, it is characterized in that: described II class additive is amino acid, gelatin or polypeptide.

4. adopt the described electroplate liquid of claim 1 to form the electro-plating method of gun-metal electrolytic coating, it is characterized in that this method is: at first, in a plating tank, add the electroplate liquid of the described stannum copper alloy coating of claim 1; Then, with workpiece soak place this plating tank electroplate liquid as negative electrode, anode is set simultaneously; At last, leading to direct current between anode and the negative electrode, and the current density of formation stannum copper alloy coating is controlled at 0.5-2ASD, and temperature is controlled at 15-30 ℃ in the plating tank.

5. as the electro-plating method of gun-metal electrolytic coating as described in the claim 4, it is characterized in that: described anode is active carbon slab, stainless steel plate or DSA.

6. as the electro-plating method of gun-metal electrolytic coating as described in the claim 4, it is characterized in that: described anode external is entangled with the PP braid.

7. as the electro-plating method of gun-metal electrolytic coating as described in the claim 4, it is characterized in that: described electroplate liquid when potassium pyrophosphate is 250,300, during 350g/l, cupric pyrophosphate is 17g/l, tin protochloride is 25g/l, five hydration tin chlorides are 25g/l, Repone K is 30g/l, and I class additive is 0.5ml/l, and II class additive is 1ml/l; At this moment, temperature is 20 ℃ in the described plating tank; Current density is 0.8ASD.

8. as the electro-plating method of gun-metal electrolytic coating as described in the claim 4, it is characterized in that: described electroplate liquid when potassium pyrophosphate is 250,300, during 350g/l, cupric pyrophosphate is 17g/l, tin protochloride is 30g/l, five hydration tin chlorides are 20g/l, Repone K is 35g/l, and I class additive is 1ml/l, and II class additive is 1ml/l; At this moment, temperature is 25 ℃ in the described plating tank; Current density is 1.2ASD.

9. as the electro-plating method of gun-metal electrolytic coating as described in the claim 4, it is characterized in that: described electroplate liquid when potassium pyrophosphate is 250,300, during 350g/l, cupric pyrophosphate is 17g/l, tin protochloride is 35g/l, five hydration tin chlorides are 15g/l, Repone K is 40g/l, and I class additive is 1.5ml/l, and II class additive is 1.5ml/l; At this moment, temperature is 30 ℃ in the described plating tank; Current density is 1.6ASD.