CN113355706A - Acidic copper plating solution and preparation method thereof - Google Patents

Abstract

The invention provides an acidic copper plating solution and a preparation method thereof; the acidic copper plating solution comprises an acid solution, a complexing agent, a copper salt compound and an auxiliary agent, and comprises the following components in parts by volume based on 100 parts: 5-50 parts by volume of acid solution, 10-70 parts by volume of complexing agent, 5-60 parts by volume of copper salt compound and 0.1-5 parts by volume of auxiliary agent; the acid solution comprises sulfuric acid or a mixture thereof with hydrochloric acid; the preparation method comprises dividing a rated amount of industrial pure water diluted acid solution into two parts, adding materials according to steps and mixing. The acid copper plating solution can realize cyanide-free copper plating, has strong binding force of a copper plating layer, and is suitable for the high-end process requirement of direct copper plating of steel and iron substrates, particularly direct copper plating of stainless steel.

Description

Acidic copper plating solution and preparation method thereof

Technical Field

The invention relates to the field of copper plating solution manufacturing, in particular to an acidic copper plating solution and a preparation method thereof.

Background

Copper plating is an important branch of metal surface engineering and has a wide application market. For example, steel substrates comprise stainless steel substrates, plain carbon steel substrates and cast iron substrates, and the conventional copper plating process using cyanide has good activation and complexing capabilities for plain carbon steel and cast iron substrates, but has poor effect on stainless steel; a compact passive film with firm adhesion exists on the surface of the stainless steel, and the passive film needs to be removed before copper plating, and simultaneously, the replacement reaction of copper and iron is inhibited; the traditional copper plating process uses cyanide which belongs to highly toxic substances and has serious environmental pollution, and the elimination of the cyanide is the trend of the industry; the mainstream of the current technology for replacing cyanide is to use alkaline copper plating solution.

Cyanide-free alkaline copper plating materials are shown in technical literatures, but the electroplated products generally have the industry known defects of poor coating binding force and low industrial efficiency; while the industry is dedicated to eliminating cyanide, the improvement of the process for directly plating copper on a steel substrate, particularly the direct plating copper on stainless steel, is very important.

Disclosure of Invention

The technical purpose of the invention is to provide cyanide-free acidic copper plating solution aiming at the industrial development requirement of eliminating cyanide, the acidic copper plating solution can effectively inhibit the copper-iron replacement reaction, has good activation and complexing capability on steel substrates, and can solve the industrial technical problem of stainless steel caused by a passive film.

In order to achieve the technical object, the invention provides an acidic copper plating solution, which comprises an acid solution, a complexing agent, a copper salt compound and an auxiliary agent; the acidic copper plating solution comprises the following components in parts by volume based on 100 parts: 5-50 parts by volume of acid solution, 10-70 parts by volume of complexing agent, 5-60 parts by volume of copper salt compound and 0.1-5 parts by volume of auxiliary agent; the acid solution comprises sulfuric acid or a mixture of sulfuric acid and hydrochloric acid; the complexing agent comprises one or more of EDTA, sodium hexametaphosphate, formic acid, hydrofluoric acid, thiourea, perchloric acid, cucurbituril and the like. The acid copper plating solution comprises a rated amount of industrial pure water required by preparation.

In the invention, the components of the acidic copper plating solution are characterized in that the acidic copper plating solution contains an acid solution and does not contain cyanide; the components comprise the materials and volume contents of additives; the acid solution is measured by the mass fraction of pure acid, and the water with the mass fraction of non-pure acid is taken as industrial pure water for preparing the acidic copper plating solution; the technical meaning of the complexing agent materials is not limited to the list, and the complexing agent materials also comprise ammonium bromide, methylene diphosphonic acid, ethylene diamine tetramethylene phosphoric acid, hydroxyl ethylidene diphosphonic acid, aminotrimethylene phosphoric acid, glycolic acid, stannous sulfate and the like which are commonly used in the industry.

In the components of the acidic copper plating solution, in every 100 volume parts of the mixture of sulfuric acid and hydrochloric acid, the sulfuric acid accounts for 40-99 volume parts, and the hydrochloric acid accounts for 1-40 volume parts.

In the acidic copper plating solution, the copper salt compound comprises copper chloride, copper carbonate, copper sulfate and other salts containing copper elements.

In the acidic copper plating solution, the auxiliary agent comprises one or a mixture of more of sodium dodecyl sulfate, safranine azophenol, sodium polydithio-dipropyl sulfonate, polyethylene glycol, sodium polyethyleneimine propane sulfonate, propenyl thiourea and the like. The technical meaning of the auxiliary materials is not limited to the list, and the auxiliary materials also comprise ethylene thiourea, alkaline sophorae flavescentis, diethyl safranine azodimethylphenol, thiazolidine thioketone, fatty amine polyoxyethylene ether, thiourea, hydrolyzed protein, alkylphenol polyoxyethylene ether and the like which are commonly used in the industry.

Based on the acid copper plating solution, the invention also provides a preparation method of the acid copper plating solution, which comprises the following steps:

step 1) diluting a rated amount of industrial pure water into an acid solution, and dividing the obtained diluted acid solution into two parts by volume;

step 2) adding one part by volume of the dilute acid solution obtained in the step 1) into a container, then adding a copper salt compound, fully stirring uniformly, and obtaining a first mixed solution after dissolving and mixing;

step 3) adding the other volume part of the dilute acid solution obtained in the step 1) into another container, adding a complexing agent in a stirring state, fully stirring, adding an auxiliary agent in a stirring state, and dissolving and mixing to obtain a second mixed solution;

and 4) mixing the first mixed solution obtained in the step 2) and the second mixed solution obtained in the step 3), and fully and uniformly stirring to obtain the acidic copper plating solution.

The important difference between the acidic copper plating solution and the common copper plating solution is that the acidic copper plating solution contains an acid solution and does not contain cyanide; the existing main copper plating process for replacing cyanide adopts alkaline copper plating solution, but the cyanide-free alkaline copper plating solution has poor stability and insufficient activation capability, the copper plating process has the technical defects of small current density, low speed, heating of the copper plating solution, high energy consumption and the like, and the bonding force of a copper plating layer is poor. Therefore, the direct copper plating of steel substrates in the world developed countries still uses the traditional cyanide process as the main technical flow.

The acidic copper plating solution disclosed by the invention belongs to strong acidity, can solve the technical problem of the binding force of a stainless steel copper plating layer, and realizes cyanide-free direct copper plating on a steel matrix, including gold plating.

The method has the advantages that the provided acidic copper plating solution has good activation and complexing capabilities on the steel substrate, and the traditional technical problem caused by the passive film of stainless steel can be solved by matching with the copper plating process; the acid copper plating solution has relatively small resistance, the copper plating process can select larger current density, the copper plating layer has strong binding force, and the industrial efficiency is high.

Detailed Description

The material composition and the preparation method of the acidic copper plating solution of the present invention are further described in detail below.

The acid solution comprises sulfuric acid or a mixture of sulfuric acid and hydrochloric acid. Sulfuric acid is a conventional chemical material (formula H) well known to those skilled in the art₂SO₄) The catalyst is active binary inorganic strong acid, the mass fraction of pure concentrated sulfuric acid is 98.3 percent, and the relative density is 1.84; hydrochloric acid is commonly known as hydrochloric acid, is an aqueous solution of hydrogen chloride (HCl) gas, is colorless and transparent monobasic strong acid, has the mass fraction of about 36-38 percent and the relative density of 1.20; the general sulfuric acid and hydrochloric acid are aqueous solutions with various densities, can react with a plurality of metals, and can release a large amount of heat when mixed with water; the acid solution is measured by pure acid mass fraction, the solution with non-pure acid mass fraction is regarded as industrial pure water, for example, when the mass fraction of 1 volume part of sulfuric acid solution is 49.15%, the operation is regarded as 0.5 volume part of sulfuric acid solution, and the rest 0.5 volume part is regarded as industrial pure water; the quality grade of the acid solution has great influence on the quality of a copper-plated product, industrial pure copper plating is preferably adopted for common workpieces, and analytical pure copper plating is recommended for the surfaces of fine workpieces. The acid solution may be selected to have any relative density within the defined composition range, with a low density acid solution being advantageous for safe production operations.

For a long time, direct copper plating of steel substrates under acidic conditions has been generally considered to be infeasible, and steel substrate workpieces undergo a copper-iron displacement reaction in an acid solution according to the order of the activity of the metals "K, Na, Ca, Mg, Al, Zn, Fe, Sn, Pb, (H), Cu, Hg, Ag, Pt, Au":

Fe+CuS0₄→Cu+FeS0₄so as to generate a replacement copper layer with loose tissue and extremely poor bonding force.

The acid copper plating solution realizes direct copper plating on a steel substrate, and can be understood as follows: based on the acid-containing solution in the components, the compact passivation film layer on the surface of the steel substrate can be quickly dissolved, so that the surface is quickly activated to expose a crystal structure, and more deposition points are provided for copper ions; the coexistence effect of the complexing agents can quickly complex copper ions, and inhibit copper-iron displacement reaction by reducing the potential of the copper ions, so that the copper ions are quickly reduced to a copper coating on the surface of the steel substrate; in other words, the surface of the steel substrate does not have time to generate the conventional displacement reaction to quickly form a copper plating layer with dense crystallization and strong binding force, which is called as a new copper plating layer theoretically, so that the quick electrodeposition of copper ions on the new copper plating layer is realized.

The complexing agent is also known as chelating agent, metal sealing agent, water softener and the like in printing and dyeing industry, and is also known as complexing agent in electroplating industry. The complexing agent can be selected from a large number of complexing agents, for example, EDTA is short for ethylenediaminetetraacetic acid (called diamino ethane tetraacetate) and is a representative substance of the complexing agent, and the complexing agent has six coordination atoms and can form a stable water-soluble complex with alkali metal, rare earth element, transition metal and the like. The complexing agent can form a compound of complexing ions with metal ions, the complexing ability varies greatly at different pH values, hydrolysis and even reaction can occur when the complexing agent is improperly selected, and the complexing agent loses the complexing ability, and the combination of multiple complexing agents is recommended.

The copper salt compound is a general term of all salts with copper ions as cations, and is generally obtained by reacting copper hydroxide with corresponding acid industrially; the material displaced by the salts is commonly referred to in the electroplating industry as the main salt, of which copper salt compounds belong to one class. The chemical substance of copper salt is present on copper ions, the copper ions can generate copper through reduction reaction, the copper can generate copper ions through oxidation reaction, and the copper ions can also be obtained by dissolving or melting the copper salt in water. Because copper ions exist in alkaline solution and can generate precipitate, copper salt compounds are less used in the copper plating solution in the prior art; in the present invention, the copper ion of the copper salt compound plays an auxiliary role in rapidly forming a copper plating layer before the copper-iron substitution reaction.

The medical meaning of the auxiliary agent refers to an excipient and an additive of a medicine prescription, namely the materials except the main medicine components are generally called; it is also known in the industry as additive to add auxiliary chemicals to improve quality, yield or to impart certain application properties to the product. The choice of auxiliaries for the treatment of metal surfaces has both common properties (e.g. appearance, odor, soiling, weathering resistance, suitability for processing conditions, etc.) and industry-specific requirements, such as compatibility with the polymer, miscibility, stability and electrical properties, in particular synergistic or antagonistic effects between the auxiliaries and other materials. The relationship between the dosage of the auxiliary agent and the selection of the components is very large, improper selection causes larger dosage and poor mixing effect, and if proper selection is adopted, a plurality of auxiliary agents can mutually enhance and reduce the total dosage of the auxiliary agents.

Industrial pure water is well known to those skilled in the art, and after being pretreated by filtration, an active carbon unit, a water softener unit and the like, common raw water is continuously subjected to fine treatment and post-treatment according to process requirements, so that the content of impurities such as suspended matters, colloids, organic matters, hardness, microorganisms and the like in the water is greatly reduced; the electroplating industry sets up technical standard requirements of industrial pure water, and the selected industrial pure water needs to meet the technical standards of the electroplating industry.

The main component of the acidic copper plating solution is industrial pure water, and the rated amount of industrial pure water is selected based on the actual application of process matching requirements, wherein the process matching requirements comprise the current density of an electroplating process and the temperature of a preparation environment; the acidic copper plating solution has poor dispersion effect by mixing with industrial pure water by a one-pot method, and is easy to cause poor quality of copper plated products and high defective rate; the preparation method of the acid copper plating solution comprises the following steps:

step 1) diluting a rated amount of industrial pure water into an acid solution, and dividing the obtained diluted acid solution into two parts by volume;

step 2) adding one part by volume of the dilute acid solution obtained in the step 1) into a container, then adding a copper salt compound, fully stirring uniformly, and obtaining a first mixed solution after dissolving and mixing;

step 3) adding the other volume part of the dilute acid solution obtained in the step 1) into another container, adding a complexing agent in a stirring state, fully stirring, adding an auxiliary agent in a stirring state, and dissolving and mixing to obtain a second mixed solution;

and 4) mixing the first mixed solution obtained in the step 2) and the second mixed solution obtained in the step 3), and fully and uniformly stirring to obtain the acidic copper plating solution.

The method comprises the steps of 1) firstly diluting a rated amount of industrial pure water into an acid solution, and technically causes that a plurality of additives including a copper salt compound, a complexing agent and an auxiliary agent have a good dispersion effect in the dilute acid solution environment; various implementation variants are possible, for example, dilute acid solutions with a density meeting the technical requirements are directly substituted for the acid solution and a nominal amount of industrial pure water; for another example, a rated amount of industrial pure water is divided into two parts by volume, one part by volume is used for the operation of step 1), and the rest is added in a state of stirring in which the first mixed solution and the second mixed solution are mixed in step 4). The industrial pure water can be added in any volume portion as long as the industrial pure water meets the dispersion requirement of additives in the storage and transportation period.

The detailed description is continued with reference to examples, which are merely recommended.

Example 1

Preparing an acidic copper plating solution, wherein the acidic copper plating solution comprises the following components in parts by volume based on 100 parts by volume:

the preparation method selects 1000 parts by volume of industrial pure water, and comprises the following steps:

1) adding 28 parts by volume of sulfuric acid into 1000 parts by volume of industrial pure water to obtain 1028 parts by volume of dilute sulfuric acid solution, and dividing the dilute sulfuric acid solution into 528 parts by volume and 500 parts by volume; during the dilution process, the sulfuric acid with the nominal density of 1.84 is slowly added into the industrial pure water, and the stirring is continuously carried out in the process;

2) adding 528 volume parts of dilute sulfuric acid solution obtained in the step 1) into a container, adding 25.5 volume parts of copper salt compound (copper sulfate), fully stirring, and carrying out dissolving and mixing to obtain a first mixed solution;

3) adding 500 parts by volume of dilute sulfuric acid solution into another container, adding 45 parts by volume of complexing agent (15 parts by volume of sodium hexametaphosphate, 20 parts by volume of EDTA and 10 parts by volume of hydrofluoric acid) in a stirring state, wherein the adding sequence is not limited, adding 1.5 parts by volume of auxiliary agent (1.4 parts by volume of sodium dodecyl sulfate and 0.1 part by volume of safranine azophenol) in a stirring state after fully stirring, and obtaining a second mixed solution after dissolving and mixing;

4) and uniformly mixing the first mixed solution and the second mixed solution to obtain 1100 parts by volume of the acidic copper plating solution.

The prepared acidic copper plating solution is used for plating copper on a steel matrix, such as plating copper on a stainless steel sheet, the stainless steel sheet is placed in an electroplating bath after being subjected to oil removal, acid cleaning and activation treatment according to the conventional procedures, the prepared acidic copper plating solution is placed in the electroplating bath and is adjusted to the concentration matched with the process, and auxiliary materials are added; the acid copper plating solution has a low resistance, allowing for the use of relatively large current densities. The copper plating layer of the stainless steel sheet after surface treatment is fine and bright, and has no bubbling, peeling and falling through a bending test and a grid drawing test, and the binding force of the copper plating layer can reach the national technical standard GB 5270-2005.

Example 2

Based on example 1, the acid solution in the acidic copper plating solution was replaced with a mixture of sulfuric acid and hydrochloric acid, wherein the sulfuric acid having a nominal relative density of 1.84 was 20 parts by volume and the hydrochloric acid having a relative density of 1.18 was 8 parts by volume, for a total of 28 parts by volume; the other components of the acidic copper plating solution are unchanged and become another component with other acidic copper plating solution. The preparation method of the acid copper plating solution of the present example was similar to that of example 1 by mixing 100 parts by volume of the acid copper plating solution with 1000 parts by volume of industrial pure water, and the industrial effect of the obtained acid copper plating solution was similar.

Example 3

Preparing another acidic copper plating solution, wherein the acidic copper plating solution comprises the following components in parts by volume based on 100 parts by volume:

300 parts by volume of industrial pure water is selected during preparation, and another acidic copper plating solution can be obtained after mixing, wherein the preparation method steps are similar to those in the example 1; the obtained acidic copper plating solution is a concentrated solution, is favorable for commodity circulation, and reduces the storage and transportation cost; when the copper plating agent is used by a specific user, a proper amount of industrial pure water and auxiliary materials are added according to specific process requirements, and the copper plating effect on the steel matrix is similar to that of the embodiment 1.

Example 4

Based on example 3, industrial pure water was changed to 3000 parts by volume by dividing 3000 parts by volume of industrial pure water into 1200 parts by volume and 1800 parts by volume first, and then:

1) adding 30 parts by volume of sulfuric acid with the mass density of 1.80 into 1200 parts by volume of industrial pure water to obtain 1230 parts by volume of dilute sulfuric acid solution, and then dividing the 1230 parts by volume of dilute sulfuric acid solution into two parts, namely 600 parts by volume and 630 parts by volume;

2) adding 600 parts by volume of the dilute sulfuric acid solution obtained in the step 1) into a container, then adding 35 parts by volume of a copper salt compound (copper sulfate), fully stirring, and obtaining a first mixed solution after mixing;

3) adding 630 parts by volume of the dilute sulfuric acid solution obtained in the step 1) into another container, adding 31 parts by volume of complexing agents (20 parts by volume of formic acid, 3 parts by volume of thiourea and 8 parts by volume of perchloric acid) in total while stirring, wherein the adding sequence is not limited, continuously adding 4 parts by volume of additives (3 parts by volume of polyethylene glycol and 1 part by volume of stannous sulfate) in total while stirring uniformly, and obtaining a second mixed solution after dissolving and mixing;

4) mixing the first mixed solution and the second mixed solution, adding 730 volume parts of dilute sulfuric acid solution obtained in the step 1) in the mixing and stirring process, and uniformly stirring to obtain 1300 volume parts of acidic copper plating solution.

This example is an implementation variation of the manufacturing method compared to example 3, in which the industrial pure water is changed from 300 parts by volume to 3000 parts by volume, wherein 1200 parts by volume of industrial pure water is used in the steps 1) to 4) to prepare the acidic copper plating solution, and the remaining 1800 parts by volume of industrial pure water is used to adjust the content density of the additive in the stage of the acidic copper plating solution entering the electric aqueduct. The copper plating effect of this example is similar to that of example 1, and for example, when a steel pipe having a diameter of 5mm is continuously plated with copper, a copper plating effect of generally 5 to 10 minutes can be obtained by rack plating for about 1 minute, the copper plating layer is fine and bright, and the copper plating layer is free from bubbling, peeling and falling in bending, lattice test and the like which are conventionally performed, and has a satisfactory adhesion force. Because the copper plating can be realized for a short time, the synchronous winding after the copper plating is favorably realized, and the industrial efficiency is improved.

Example 5

Preparing still another acidic copper plating solution comprising, based on 100 parts by volume of the components: :

the copper salt compound in this embodiment is copper chloride; the preparation method of the acid copper plating solution comprises 2000 volume parts of industrial pure water, the preparation method is similar to the example 4, the 2000 volume parts of industrial pure water are firstly divided into 1500 volume parts and 500 volume parts before the operation of the step 1), wherein 1500 volume parts of industrial pure water are used for preparing the acid copper plating solution, and the rest 500 volume parts of industrial pure water are used for adjusting the content density of the additive in the stage of feeding the acid copper plating solution into the aqueduct. The procedure for the preparation is the same as in the above example.

Example 6

On the basis of the acidic copper plating solution of example 5, the acid solution technology is changed into 1520 parts by volume of dilute acid solution, and the dilute acid solution contains 20 parts by volume of pure sulfuric acid; changing copper chloride to 25 parts by volume of copper carbonate; the components of the complexing agent and the auxiliary agent are the same as those in example 5.

In this example, 1520 parts by volume of dilute sulfuric acid solution was mixed with 25 parts by volume of copper carbonate, complexing agent and auxiliary agent, and the mixing process of the preparation method was similar to the above example, and a similar acidic copper plating solution was obtained.

Example 7

Preparing still another acidic copper plating solution, which comprises the following components based on 100 parts by volume:

the preparation method of the acid copper plating solution comprises 600 parts by volume of industrial pure water and comprises the following steps: firstly, diluting 30 parts by volume of acid solution (diluted mixed solution of sulfuric acid and hydrochloric acid) by using industrial pure water, dividing 630 parts by volume of mixed diluted acid solution into two parts by volume of 315 parts by volume, respectively mixing the two parts with the copper salt compound, the complexing agent and the auxiliary agent in the embodiment, and obtaining a concentrated acidic copper plating solution by the same mixing preparation process in steps as the embodiment 1, which is favorable for commodity circulation, can effectively reduce storage and transportation cost and brings flexibility of specific application for users.

Example 8

Based on the acidic additive in example 7, the sodium lauryl sulfate as the auxiliary in example 7 was replaced with a fatty amine polyoxyethylene ether in an amount of 0.5 parts by volume, and the acid solution, the copper salt compound and the complexing agent in the acidic additive were the same as in example 7.

Claims (5)

1. An acidic copper plating solution is characterized by comprising an acid solution, a complexing agent, a copper salt compound and an auxiliary agent; the acidic copper plating solution comprises the following components in parts by volume based on 100 parts: 5-50 parts by volume of acid solution, 10-70 parts by volume of complexing agent, 5-60 parts by volume of copper salt compound and 0.1-5 parts by volume of auxiliary agent; the acid solution comprises sulfuric acid or a mixture of sulfuric acid and hydrochloric acid; the complexing agent comprises one or more of EDTA, sodium hexametaphosphate, formic acid, hydrofluoric acid, thiourea, perchloric acid, cucurbituril and the like.

2. The acidic copper plating solution according to claim 1, wherein the sulfuric acid is present in an amount of 40 to 99 parts by volume and the hydrochloric acid is present in an amount of 1 to 40 parts by volume per 100 parts by volume of the mixture of sulfuric acid and hydrochloric acid.

3. The acidic copper plating solution of claim 1 wherein the copper salt compound comprises copper chloride, copper carbonate, copper sulfate and other salts containing copper elements.

4. The acidic copper plating solution according to claim 1, wherein the material of the assistant comprises one or more of sodium dodecyl sulfate, safranine azophenol, sodium polydithio-dipropyl sulfonate, polyethylene glycol, sodium polyethyleneimine propane sulfonate, and propenyl thiourea.

5. A method for producing an acidic copper plating solution according to any of claims 1 to 4, comprising the steps of:

step 1) diluting a rated amount of industrial pure water into an acid solution, and dividing the obtained diluted acid solution into two parts by volume;

step 2) adding one part by volume of the dilute acid solution obtained in the step 1) into a container, then adding a copper salt compound, fully stirring uniformly, and obtaining a first mixed solution after dissolving and mixing;

step 3) adding the other volume part of the dilute acid solution obtained in the step 1) into another container, adding a complexing agent in a stirring state, fully stirring, adding an auxiliary agent in a stirring state, and dissolving and mixing to obtain a second mixed solution;

and 4) mixing the first mixed solution obtained in the step 2) and the second mixed solution obtained in the step 3), and fully and uniformly stirring to obtain the acidic copper plating solution.