CN106521574B - A kind of non-cyanide plating solution for copper-plating used and preparation method thereof suitable for width pH and wide current density range - Google Patents

Abstract

The invention provides a kind of cyanide-free copper plating electroplating solution that is applicable to wide pH and wide current density range, comprises 20-90g/L aminomethylene diphosphonic acid (AMDP), 10-70g/L phytic acid (PA ) or sodium phytic acid, 0.5‑15 g/L pyrophosphate, 3‑25 g/L copper salt. The cyanide-free copper plating solution provided by the present invention has a suitable pH range of 6-13.5 and a suitable current density range of 0.2-4 ampere/square decimeter. The plating solution has a simple formula, is nontoxic, and has no cyanide pollution. , Magnesium alloy, zinc or zinc alloy substrate, and zinc-dipped aluminum are directly plated with copper to obtain excellent bonding between the copper coating and the substrate.

Description

A kind of cyanide-free copper plating electroplating solution suitable for wide pH and wide current density range and its preparation preparation method

technical field

The invention belongs to the technical field of electroplating, and in particular relates to a cyanide-free copper-plating electroplating solution, in particular to a cyanide-free copper-plating electroplating solution suitable for wide pH and wide current density ranges and a preparation method thereof.

Background technique

Acidic copper sulfate electroplating solution will undergo displacement reaction when direct copper plating on metal substrates such as iron, zinc or zinc alloy, magnesium alloy, aluminum, etc., resulting in poor bonding between the substrate and the copper coating. In order to obtain high binding force, alkaline cyanide plating solution is widely used in industry now. However, because cyanide has very high biological toxicity, it will cause major environmental and social safety hazards. The country has repeatedly issued industrial policies to eliminate cyanide-containing electroplating. Therefore, the development of cyanide-free copper plating technology is very urgent, but it is also a technical problem. The current research reports that the typical cyanide-free copper plating systems include alkaline pyrophosphate copper plating, sulfamate copper plating, citrate copper plating, organic phosphonate copper plating, organic carboxylate copper plating, etc. Chinese invention patent (patent number: 85103672) discloses a kind of alkaline cyanide-free electrolytic copper plating solution, proposes to use ethylene glycol as complexing agent. The copper plating bath with phosphorus-containing compounds in the structure as the main complexing agent is the most promising process in cyanide-free copper plating. For example, the pyrophosphate copper plating solution has been applied on some steel substrates. The copper coating obtained by the pyrophosphate system is dense, and the deposition rate is relatively high, and the copper coating can be deposited quickly in the low current density area. However, the copper plating solution with pyrophosphate as the main complexing agent has strict pH control (generally 8.13-8.19). fail. For this reason, some studies have proposed to replace the POP bond of pyrophosphate with PCP, thus developing gem-diphosphonic acid compounds composed of PCP bonds as copper complexing agents. Such compounds such as hydroxyethylidene diphosphonic acid (HEDP), amino Trimethylene phosphonic acid (ATMP), ethylenediamine tetramethylene phosphonic acid (EDTMP), aminomethylene diphosphonic acid (AMDP), etc., not only have the surface activity of pyrophosphate, but also have stronger copper than pyrophosphate The coordination ability will greatly improve the process performance of the plating solution. As early as the 1970s, the Institute of Coordination Chemistry of Nanjing University first systematically proposed the alkaline cyanide-free copper plating solution with hydroxyethylidene diphosphonic acid (HEDP) as the main complexing agent through research, and the hydroxyethylidene diphosphine The electrochemical performance of the alkaline cyanide-free copper plating solution of acid (HEDP) as the main complexing agent is also repeatedly mentioned in research papers (Fang Jingli, Ma Xinmao, Lu Weizhen. Chemical Journal of Universities, 1981, 2 (3): 285-293. Zheng Jingwu, Jiang Meiyan, Qiaoliang, et al., Study on the Effect of CO ₃ ^2- P-Hydroxyethylidene Diphosphonic Acid Copper Plating Solution, Acta Physicochemical Sinica, 2008, 24(9): 1733-1738). The Chinese invention patent (Patent No. 201010136861.4) discloses an alkaline cyanide-free copper plating solution with aminomethylene diphosphonic acid (AMDP) as the main complexing agent. Compared with the molecular structure of HEDP, the -CH3 connected to the middle carbon position is removed, and the -NH2 group is added at the same time, which makes the coordination ability with copper ions stronger. This kind of plating solution using a single organic phosphonate as a complexing agent, when the pH value is relatively high (generally pH > 9), because the sufficient ionization of -OH in the organic phosphonate can make it complex with copper ions Bit open into a stable chelate. However, in the production process, as the electroplating solution is continuously energized, the pH of the solution will be close to neutral or even acidic. At this time, the -OH in the phosphonate cannot be fully ionized, which makes the formation of copper coordination chelates unstable. Therefore, the current Cyanide-free electroplating solutions all emphasize that the pH of the solution is alkaline, and it is around 9. At the same time, it is also found that when the plating solution with a single organic phosphonate as a complexing agent encounters workpieces with complex shapes in the production process, the copper coating is often not plated or is too thin in the low current density area, so that the copper coating and the substrate bubbly. In order to improve the problem of the plating solution using a single organic phosphonate as a complexing agent, some literatures propose an electroplating solution formed by compounding multiple organic phosphonates. For example, the Chinese invention patent (patent number: 200610151222.9) discloses a method for direct cyanide-free electroplating of zinc alloy die castings. ) and ethylenediaminetetramethylenephosphonic acid (EDTMP) constitute the electroplating solution, which can directly electroplate copper on the zinc alloy die casting substrate. The three organic phosphonates mentioned in the above patents can form stable copper coordination chelates with copper ions only at high pH. Chinese invention patent (patent number CN201610065348.8) discloses a plating solution for electroplating copper on the surface of a magnesium alloy smart phone casing. The complexing agent proposed in the copper plating solution includes pyrophosphate, pyrophosphite, Hydroxyethylene diphosphonic acid and trace amounts of phytic acid, in which the content of pyrophosphate and pyrophosphite reach 240-260g/L and 55-65g/L respectively, obviously act as the main complexing agent, so it is possible When the pH value of the solution is low, some pyrophosphate radicals are easily hydrolyzed to form orthophosphate radicals, thereby rendering the copper plating solution ineffective.

Contents of the invention

The invention provides a cyanide-free copper electroplating solution suitable for wide pH and wide current density range, which solves the serious environmental pollution caused by the existing cyanide-containing plating solution, and the cyanide-free plating solution will cause the plating layer to be damaged. The substrate bonding force is not good, especially in the low current density area, there will be bubbling phenomenon in the coating, the long-term operation of the plating solution is unstable, and the pH range of the applicable solution is narrow.

The technical solution adopted by the present invention to solve technical problems is:

A cyanide-free copper plating solution suitable for wide pH and wide current density range, including 20-90g/L aminomethylene diphosphonic acid (AMDP), 10-70g/L phytic acid (PA) or inositol Sodium hexaphosphate, 0.5-15g/L pyrophosphate and 3-25g/L copper salt. The best addition amount of pyrophosphate is 0.5-15g/L. When the addition amount is lower than 0.5g/L, the coating will bubble; The binding force is poor.

Preferably, the copper salt is at least one of copper sulfate, copper chloride, basic copper carbonate and copper nitrate.

Preferably, the pyrophosphate is potassium pyrophosphate and/or sodium pyrophosphate.

The present invention simultaneously provides a kind of preparation method of the cyanide-free copper plating electroplating solution that is applicable to wide pH and wide current density range, and aminomethylene diphosphonic acid, phytic acid or sodium phytic acid, pyrophosphate water Dissolving and mixing, then adding copper salt and fully stirring and mixing, then adding sodium hydroxide or potassium hydroxide to adjust the pH of the solution to 6-13.6, stirring and dissolving to obtain the cyanide-free copper plating solution.

Preferably, the copper salt is at least one of copper sulfate, copper chloride, basic copper carbonate and copper nitrate.

Preferably, the pyrophosphate is potassium pyrophosphate and/or sodium pyrophosphate.

Preferably, the concentration of aminomethylene diphosphonic acid is 20-90g/L, the concentration of phytic acid or sodium phytate is 10-70g/L, the concentration of pyrophosphate is 0.5-15g/L, and the concentration of copper salt The concentration is 3-25g/L.

The beneficial effects of the present invention are:

1. The applicable pH range of the cyanide-free copper plating solution provided by the present invention is 6-13.5, and the applicable current density range is 0.2-4 ampere/square decimeter.

2. Aminomethylene diphosphonic acid (AMDP) and phytic acid (PA) are used as copper complex complexing agents, and pyrophosphate is used as auxiliary additives, which give full play to their respective advantages and form a complementarity. Aminomethylene diphosphonic acid (AMDP) is used as one of the main complexing agents, in the strong alkaline pH range (pH=9~13.5), compared with the traditional HEDP complexing agent system and the existing plating solution system , not only can form a more stable coordination compound with copper, but also the deep plating ability is increased by 34% compared with the cyanide copper plating system.

3. In the acidic range, phytic acid can form stable coordination compounds with many metal ions, and is now commonly used as a cleaning agent for metal pipes or a descaling agent for water quality. Therefore, phytic acid (PA) is used as one of the main complexing agents, in the pH range of weakly alkaline, neutral or even weakly acidic (pH=6-9), and the traditional HEDP complexing agent system and the existing Compared with the plating solution system, it can form a more stable coordination compound with copper. This not only means that a wide pH range can be used when preparing the solution, but also can avoid the problem of constant adjustment or even scrapping of the solution due to the fluctuation of the pH value during the use of the solution, improve the tolerance of the solution operation, and facilitate production and operation.

4. The copper coating obtained by the pyrophosphate system is dense, and the deposition rate is relatively high, and the copper coating can be deposited quickly in the low current density area. Therefore, using pyrophosphate as an auxiliary additive, compared with the traditional HEDP complexing agent system and the existing plating solution system, not only solves: when complex-shaped workpieces are electroplated, due to uneven current density distribution, plating in small current density areas No copper plating layer or too thin, so that the copper plating layer and the substrate are foamed; and it can also avoid the problem that part of the pyrophosphate is hydrolyzed when the pH value of the solution is low, which makes the copper plating solution invalid.

5. The formula of the plating solution is simple, non-toxic, and free from cyanide pollution. Direct copper plating on iron substrates, magnesium alloys, zinc or zinc alloy substrates, and galvanized aluminum can obtain excellent bonding between the copper coating and the substrate.

Description of drawings

Figure 1 shows the effect of the amount of potassium pyrophosphate added on the bonding force of the coating in the Hall cell cathode test piece.

Detailed ways

The present invention is further described below in conjunction with specific embodiment, but protection scope of the present invention is not limited thereto:

Example 1

Example 1:

A cyanide-free copper plating solution with wide pH and wide current density applicable range is prepared according to the following ratio.

Dissolve and mix the weighed methylene diphosphonic acid and copper sulfate pentahydrate with deionized water respectively, add potassium hydroxide solution while stirring and stir thoroughly, if the pH is too high due to the addition of potassium hydroxide, it can be adjusted to specified pH.

In the obtained solution, adjust the temperature of the solution to 30°C, and plate a copper coating of about 5 microns on the steel wire substrate with a diameter of Φ2 mm at a cathode current density of 1A/dm2. ^The electroplating time is 15 minutes, and the winding method is tested according to ASTM B452-2002. Bonding is intact.

Example 2:

A cyanide-free copper plating solution with wide pH and wide current density applicable range is prepared according to the following ratio.

Dissolve and mix the weighed methylene diphosphonic acid and copper chloride dihydrate with deionized water respectively, add sodium hydroxide solution during stirring and stir thoroughly, if the pH is too high due to the addition of potassium hydroxide, it can be adjusted with sulfuric acid to the specified pH.

In the obtained solution, adjust the temperature of the solution to 50°C, and plate a copper coating of about 5 microns on the steel wire substrate with a diameter of Φ2 mm at a cathode current density of 0.5 A/dm2. ^The electroplating time is 30 minutes, and the winding method is used according to ASTM B452-2002. The test binding is intact.

Example 3:

Prepare a cyanide-free copper plating electroplating solution with a wide pH range according to the following ratio

Dissolve and mix the weighed methylene diphosphonic acid and copper chloride dihydrate with deionized water respectively, add sodium hydroxide solution during stirring and stir thoroughly, if the pH is too high due to the addition of potassium hydroxide, it can be adjusted with sulfuric acid to the specified pH.

In the obtained solution, adjust the temperature of the solution to 55°C, and plate a copper coating of about 5 microns on the steel wire substrate with a diameter of Φ2 mm at a cathode current density of ² A/dm2. The electroplating time is 7 minutes, and the winding method is tested according to ASTM B452-2002. Bonding is intact.

Comparative example 1

Adopt the same formula as Example 1, the difference is that the addition of potassium pyrophosphate is 0.4g/L.

Comparative example 2

Adopt the same formula as Example 1, the difference is that the addition of potassium pyrophosphate is 16g/L.

Using the Hall cell as an experiment, the plating solutions of Examples 1-3 and Comparative Example I-2 are directly plated copper on the steel substrate, and then the coating is thickened by acidic copper plating and nickel plating, and heated in a 300°C oven After 30 minutes, quickly take it out and quench it in water, and observe the bubbling phenomenon of the coating in different current density areas. It is found that the addition of pyrophosphate is within the 0.5-15g/L proposed by the present invention, and the coating does not have bubbling, but beyond the range proposed by the present invention, the coating has bubbling or even peeling, especially in the low current density area, combined with The phenomenon of poor strength is more obvious. In the Hall cell cathode test piece, the effect diagram of the addition of potassium pyrophosphate on the bonding force of the coating is shown in Figure 1.

The above only lists preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereto. Any changes made by those skilled in the art within the scope of the claims of the present invention all fall within the protection scope of the present invention.

Claims (7)

1. a kind of non-cyanide plating solution for copper-plating used suitable for width pH and wide current density range, which is characterized in that the electroplate liquid packet Include 20-90g/L amino methane di 2 ethylhexyl phosphonic acids, 10-70g/L phytic acids or sodium phytate, 0.5-15g/L pyrophosphates and 3-25g/L mantoquitas.

2. electroplate liquid as described in claim 1, which is characterized in that the mantoquita be copper sulphate, copper chloride, basic copper carbonate and At least one of copper nitrate.

3. electroplate liquid as described in claim 1, which is characterized in that the pyrophosphate is potassium pyrophosphate and/or sodium pyrophosphate.

4. the preparation method suitable for width pH and the non-cyanide plating solution for copper-plating used of wide current density range, which is characterized in that by amino Methene di 2 ethylhexyl phosphonic acid, phytic acid or sodium phytate, pyrophosphate are mixed with water dissolution, and mantoquita is then added and is sufficiently stirred Mixing, adds sodium hydroxide or potassium hydroxide adjusts pH value of solution to 6-13.5, and stirring and dissolving is molten up to the cyanide-free copper electroplating Liquid.

5. preparation method as claimed in claim 4, which is characterized in that the mantoquita is copper sulphate, copper chloride, basic copper carbonate At least one of with copper nitrate.

6. preparation method as claimed in claim 4, which is characterized in that the pyrophosphate is potassium pyrophosphate and/or pyrophosphoric acid Sodium.

7. preparation method as claimed in claim 4, which is characterized in that a concentration of 20-90g/L of amino methane di 2 ethylhexyl phosphonic acid, Phytic acid or a concentration of 10-70g/L of sodium phytate, a concentration of 0.5-15g/L of pyrophosphate, a concentration of 3- of mantoquita 25g/L。