CN114481107A - Gold-precipitating solution for cyanide-free chemical heavy gold precipitation and process thereof - Google Patents
Gold-precipitating solution for cyanide-free chemical heavy gold precipitation and process thereof Download PDFInfo
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- CN114481107A CN114481107A CN202210149984.4A CN202210149984A CN114481107A CN 114481107 A CN114481107 A CN 114481107A CN 202210149984 A CN202210149984 A CN 202210149984A CN 114481107 A CN114481107 A CN 114481107A
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/31—Coating with metals
- C23C18/42—Coating with noble metals
- C23C18/44—Coating with noble metals using reducing agents
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/54—Contact plating, i.e. electroless electrochemical plating
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Abstract
The invention discloses a gold-precipitating solution for cyanide-free chemical thick gold precipitation and a process thereof, wherein the gold-precipitating solution comprises the following components: cyanide-free gold salt, wherein the content of Au ions is 16-20 g/L; the complexing agent is 50-100 g/L; the buffer is 10-50 g/L; the composite reducing agent is 1-5 g/L; the surfactant is 0.5-1 g/L; the composite stabilizer is 10-20 mg/L; the corrosion inhibitor is 5-10 mg/L; the reaction accelerator is 40-80mg/L, and the silver ion is 0.5-1 mg/L; the composite reducing agent consists of sodium borohydride, glucose and hydroxylamine sulfate, and the mass concentration ratio of the sodium borohydride to the glucose to the hydroxylamine sulfate is 2:2: 1; the composite stabilizer consists of antimony potassium tartrate, hyperbranched polyurethane sulfonate and polyacrylamide according to the mass concentration ratio of 2:1: 1; the concentration ratio of the anticorrosive agent to the reaction accelerator is 1:8 when in use. The gold plating layer obtained by the invention has good adhesiveness, uniform plating layer and high deposition rate.
Description
Technical Field
The invention relates to the technical field of display panel surface treatment, in particular to a cyanide-free gold-precipitating solution for chemically precipitating thick gold and a process thereof.
Background
The gold-plating layer can meet various assembly requirements and has the performances of weldability, conductivity, high stability, oxidation resistance and the like. In China, cyanide-containing gold salt is used as a raw material in chemical gold precipitation, and because cyanide plating solution contains extremely toxic cyanide, great unsafe factors are generated in the actual production process and the treatment and disposal of related subsequent waste water and waste gas, so that the development of the cyanide gold plating solution is limited. With the increasing awareness of environmental protection, it has become a necessary trend to develop chemical gold-deposition process by exploring a suitable cyanide-free gold-deposition process to replace cyanide gold-deposition process.
In order to solve the influence caused by cyanide gold plating, the cyanide-free gold plating process is adopted more and more in the prior art along with the improvement of environmental protection consciousness of people, but the prior cyanide-free gold plating process has the following defects:
1) at present, the immersion gold with the thickness of 0.03-0.2 micron is mainly carried out by adopting a chemical immersion gold replacement mode, and the immersion gold with the thickness of more than 1 micron is mainly finished by cyanide-free reduction type gold plating; however, in the process of reducing gold plating, while the gold ions and the reducing agent are subjected to oxidation-reduction reaction, there is a displacement reaction between the matrix metal and the gold ions at the initial gold plating stage, so that the adhesion of the gold plating layer on the surface of the matrix metal is not firm enough, and the displaced matrix metal ions enter the gold plating solution to affect the normal use of the gold plating solution. Therefore, the existing replacement type gold plating is only suitable for plating thin gold, the reduction type gold plating is suitable for depositing thick gold, the thickness of the deposited gold is related to the performance of tin on the plate, the weldability of the plate can be influenced by too thick or too thin gold layer deposition, and particularly, the phenomenon that a nickel layer is excessively corroded and welding spots fall off after welding easily occurs due to too thick gold layer.
2) The reduction type gold plating solution on the market at present is extremely unstable, no suitable additive can keep the relative stability of the plating solution so far, and although the plating solution with weak reducibility can keep the stability of the plating solution and can obtain a thicker plating layer at a higher speed, the finally obtained plating layer is easy to have defects such as holes, cracks and the like, and the effect of uniform plating cannot be achieved all the time.
Disclosure of Invention
Aiming at the defects in the technology, the invention provides the gold-precipitating solution for cyanide-free chemical thick gold precipitation and the process thereof, the thick gold precipitation can be quickly and stably realized by adopting the plating solution with weak reducibility, and the obtained plating layer is uniform.
In order to achieve the aim, the invention provides a gold-precipitating solution for cyanide-free chemical thick gold precipitation, which comprises the following components in mass concentration:
the composite reducing agent consists of sodium borohydride, glucose and hydroxylamine sulfate, and the mass concentration ratio of the sodium borohydride to the glucose to the hydroxylamine sulfate is 2:2: 1;
the composite stabilizer consists of antimony potassium tartrate, hyperbranched polyurethane sulfonate and polyacrylamide according to the mass concentration ratio of 2:1: 1;
the concentration ratio of the anticorrosive agent to the reaction accelerator is 1: 8;
the components are mixed according to the proportion, the pH value is adjusted to 7-8 by sulfuric acid or potassium hydroxide, the balance is water, and the cyanide-free chemical gold precipitation solution is formed after the operation temperature is 50-70 ℃.
Wherein the reaction accelerator is a compound of tert-butyl ester, 3-mercaptopropane sulfonic acid, 2, 6-diaminopyridine and 3-pyridine methanol, and the four compounds are as follows by mass percent: 10-20% of tert-butyl ester, 10-30% of 3-mercaptopropane sulfonic acid, 30-50% of 2, 6-diaminopyridine and 30-50% of 3-pyridinemethanol.
The preparation method of the gold precipitation solution comprises the following steps: firstly, adding cyanide-free gold salt, a complexing agent, a buffering agent and an anticorrosive agent into a stirrer for stirring, and uniformly stirring to form a mixed solution A, wherein the stirring speed is between 100 and 150 r/min; adding the composite stabilizer, the surfactant and the reaction accelerator into the mixed solution A, stirring while adding, and uniformly stirring to form a mixed solution B, wherein the stirring speed is between 150-; then, adding a composite reducing agent and silver ions into the mixed solution B, and uniformly stirring to form a mixed solution C, wherein the stirring speed is between 150 and 200 r/min; finally, adjusting the pH of the mixed solution to 7-8 by using sulfuric acid or potassium hydroxide, and forming a cyanide-free chemical gold precipitation solution after the operation temperature is 50-70 ℃.
Wherein the complexing agent is a 1, 2-ethylenediamine compound.
Wherein the cyanide-free gold salt is tetrachloro-gold acid or gold hydroxide.
Wherein the buffer is one or two of ammonium chloride and ammonium citrate; the substance containing silver ions is silver nitrate.
Wherein the surfactant is sodium methallyl sulfonate; the anticorrosive agent is sulfonated lignin.
In order to achieve the above object, the present invention further provides a gold-plating process of a cyanide-free chemical thick gold-plating solution, comprising the steps of:
step 1, performing vacuum treatment on a pretreatment solution before gold precipitation on a gold precipitation piece;
step 2, placing the treated gold immersion piece into a gold cylinder groove with the gold immersion solution of the claim, and performing a first-stage gold immersion treatment; the specific conditions of the gold precipitation treatment are as follows: the gold deposition temperature is: the gold immersion time is 5-6 minutes at 55-65 ℃, and the thickness of the obtained gold layer of the gold immersion part is 0.8-1 micron;
step 3, performing second-stage gold immersion treatment on the gold immersion part after the first-stage gold immersion treatment is completed; the immersion gold treatment comprises the following specific steps: benzotriazole is added uniformly during the gold immersion, the gold immersion temperature is 50 ℃, the gold immersion time is 3-4 minutes, and the thickness of the thick gold layer of the gold immersion part is 1.2-1.5 microns;
step 4, bombarding the surface of the heavy metal piece which is subjected to the thick gold layer treatment by adopting vacuum plasma, wherein the working medium of the vacuum plasma is nitrogen;
and 5, carrying out the next process on the metal immersion piece after the surface treatment is finished.
Wherein the volume ratio of the benzotriazole added in the step 3 to the gold precipitation solution is 80: 1; and the diameter of the benzotriazole is less than 100 nanometers.
Wherein, the high-molecular nano particles are sprayed into the gold precipitation cylinder at a high speed under the action of compressed air, and the distance between a nozzle and the liquid surface of the gold precipitation cylinder is 2-3cm during spraying; and the angle between the nozzle and the liquid horizontal plane of the gold precipitation cylinder is 30 degrees; and the jet injection flow rate was 5 ml/min.
The invention has the beneficial effects that: compared with the prior art, the gold precipitation solution for cyanide-free chemical thick gold precipitation and the process thereof have the following beneficial effects:
1) the composite reducing agent is composed of sodium borohydride, glucose and hydroxylamine sulfate, the reducing agent is compounded according to a special proportion, the stability of the gold precipitation solution cannot be influenced in the reduction process, the reaction of hydroxylamine and the glucose organic reducing agent can reduce the reaction activity of Au +, the reaction of hydroxylamine sulfate is instantly nucleated under the action of the hydroxylamine sulfate in the whole reduction process, the size of a gold core is larger, the thickness of the gold precipitation layer can be increased more quickly, and the gold precipitation rate is accelerated.
2) The stabilizer is compounded by antimony potassium tartrate, hyperbranched polyurethane sulfonate and polyacrylamide, and the hyperbranched polyurethane sulfonate is matched with the polyacrylamide, so that the problem of concentration reduction of the stabilizer in the gold precipitation process can be avoided, and the whole gold precipitation liquid can be uniformly and stably dispersed in the gold precipitation process; and the hyperbranched polyurethane sulfonate and polyacrylamide have the characteristic of high viscosity on the basis of ensuring the stability, can be adsorbed on the groove wall during chemical reaction, directly avoids continuous gold ions from being further separated out and deposited on the groove wall of the gold precipitation cylinder, has extremely strong stability, and avoids the concentration of a stabilizer from being greatly reduced in the gold precipitation process. Compared with the existing plating solution, under the same gold immersion condition, the thick gold layer obtained by the composite stabilizer has higher hardness, good binding force with a substrate and excellent corrosion resistance.
3) The invention adds the anticorrosive agent on the basis of the traditional base solution, the anticorrosive agent can be adsorbed on the metal surface, a thin protective film can be quickly formed on the surface of the thick gold layer, and the bonding force between the gold layer and the substrate is further improved.
4) The silver ion is added on the basis of the original solution, the silver ion is reduced to the gold immersion piece under the action of the reducing agent and then replaced with gold, silver is oxidized into silver ion again, the gold layer is thickened due to the circulation, the thickness of the gold layer is increased, and the gold immersion piece can further reach thick gold more quickly.
5) The invention adds the compound reducing agent, the compound stabilizing agent and the anticorrosive agent on the basis of the original components of the gold immersion solution, the reaction accelerator accelerates the activation reaction speed of the gold immersion solution, the activation time is reduced, and the anticorrosive agent quickly forms a thick gold layer protective film; particularly, specially-made components are adopted on a composite reducing agent and a composite stabilizing agent, so that gold ions with higher concentration can be rapidly and stably subjected to catalytic reduction gold deposition, and the gold deposition solution has strong stability, so that the corrosion of a nickel layer can be effectively inhibited, and a thick gold layer with the thickness of 1.2-1.5 microns can be formed under the condition that the corrosion of the nickel layer is reduced.
5) In the technology, the gold immersion is divided into two stages, because the first stage has the replacement of silver ions to form a gold layer, and the reducing agent and the stabilizing agent are both in a high-concentration state, the gold immersion of about 1 micron can be quickly realized; along with the reaction, the stability of the composite stabilizer is reduced, and in order to ensure that the whole gold immersion process is completed in a high-stability state, the polymer nano particles are added while the second gold immersion stage is carried out, and the addition of the polymer nano particles can not only ensure the high stability, but also avoid the agglomeration phenomenon on the surface of the gold layer, thereby further ensuring the uniformity of the gold layer.
6) The obtained gold deposition layer has the advantages of good adhesiveness, compact plating layer structure, uniform crystallization, stable bath solution, high impurity tolerance, high deposition rate and more environment-friendly process. Meanwhile, the cyanide-free chemical gold precipitation solution does not use potassium gold cyanide high-toxicity substances and cyanide radicals, reduces the health influence on operators and the potential safety hazard of the working environment, and also greatly reduces the burden and influence of wastewater treatment.
Detailed Description
In order to more clearly describe the present invention, the present invention is further described below.
The invention provides a gold precipitation solution for cyanide-free chemical thick gold precipitation, which comprises the following components in mass concentration:
the composite reducing agent consists of sodium borohydride, glucose and hydroxylamine sulfate, and the mass concentration ratio of the sodium borohydride to the glucose to the hydroxylamine sulfate is 2:2: 1; in order to solve the problem, the invention adopts strong reducing agent hydroxylamine sulfate and weak organic reducing agent glucose, and neutralizes by sodium borohydride, thereby ensuring that the stability of the gold-precipitating solution is not influenced by a specific proportion on the basis of ensuring the original reducibility, and the reaction of hydroxylamine and the glucose organic reducing agent can reduce the reaction activity of Au +, the instant nucleation is performed under the action of hydroxylamine sulfate in the whole reduction process, the size of a gold core is larger, further the reduction of nickel corrosion is ensured, the thickness of a gold-plating layer is increased, thereby the thickness of the gold-precipitating layer can be increased more quickly, the gold-precipitating rate is accelerated, and finally the corrosion resistance of the gold layer is remarkably improved; but also reduces nickel corrosion, improves the quality of the gold-depositing layer and is beneficial to improving the industrial production efficiency.
The composite stabilizer consists of antimony potassium tartrate, hyperbranched polyurethane sulfonate and polyacrylamide according to the mass concentration ratio of 2:1: 1; in order to obtain stable gold deposition rate, antimony potassium tartrate is generally used as a stabilizer for chemical gold plating, and as the reaction proceeds, the reducibility and stability are weakened, and gold ions are further precipitated and deposited on the wall of a gold deposition cylinder. And then in the heavy gold process of reduction, this composite stabilizer can avoid metal ion deposit when guaranteeing stable, and then makes the very stable of cohesion intensity between heavy gold layer and the base member for this heavy gold piece can not drop even under subsequent high temperature cyclic use, and then has postponed the life who plates, and this composite stabilizer is synergistic effectual moreover, does not have the heavy metal, accords with the environmental protection requirement.
The concentration ratio of the anticorrosive agent to the reaction accelerator is 1:8 when in use; the anticorrosive agent is adsorbed on the metal surface, so that a thin protective film can be quickly formed on the surface of a thick gold layer, and the binding force between the gold layer and a substrate is further improved. And the corrosion inhibitor and the reaction accelerator form a certain proportion when in use, the reaction accelerator can accelerate the activation reaction time, the corrosion inhibitor can protect the gold layer, the excessive reaction accelerator is not beneficial to the uniform plating effect and influences the protection effect of the corrosion inhibitor, and further influences the bonding force between the gold layer and the substrate, and the proper proportion ensures that the bonding force effect between the gold layer and the substrate is better.
The components are mixed according to the proportion, the pH value is adjusted to 7-8 by sulfuric acid or potassium hydroxide, the balance is water, and the cyanide-free chemical gold precipitation solution is formed after the operation temperature is 50-70 ℃.
In this embodiment, the reaction accelerator is a compound of tert-butyl ester, 3-mercaptopropanesulfonic acid, 2, 6-diaminopyridine, and 3-pyridinomethanol, and the four are, by mass: 10-20% of tert-butyl ester, 10-30% of 3-mercaptopropane sulfonic acid, 30-50% of 2, 6-diaminopyridine and 30-50% of 3-pyridinol. 3-mercaptopropane sulfonic acid, 2, 6-diaminopyridine and 3-pyridine methanol are protected by tert-butyl ester, so that neutralization reaction of other components of the accelerator during pH value adjustment is avoided, the accuracy of the accelerator is further ensured, and the accelerator is compounded by four substances, so that the phenomenon that the operation range of a single reaction accelerator is narrow is avoided; and the setting of accurate concentration accelerates the activation reaction speed, reduces the activation time, and can quickly realize the void-free and seamless filling of the gold immersion piece during the gold immersion.
In this embodiment, the preparation method of the gold deposition solution is as follows: firstly, adding cyanide-free gold salt, a complexing agent, a buffering agent and an anticorrosive agent into a stirrer for stirring, and uniformly stirring to form a mixed solution A, wherein the stirring speed is between 100 and 150 r/min; adding the composite stabilizer, the surfactant and the reaction accelerator into the mixed solution A, stirring while adding, and uniformly stirring to form a mixed solution B, wherein the stirring speed is between 150-; then, adding a composite reducing agent and silver ions into the mixed solution B, and uniformly stirring to form a mixed solution C, wherein the stirring speed is between 150 and 200 r/min; finally, adjusting the pH of the mixed solution to 7-8 by using sulfuric acid or potassium hydroxide, and forming a cyanide-free chemical gold precipitation solution after the operation temperature is 50-70 ℃. When the solution is prepared, the cyanide-free gold salt is firstly complexed with the complexing agent, so that the gold ions of the cyanide-free gold salt can be more effectively complexed, the gold layer of the finally-deposited gold piece has better compactness, and the composite reducing agent is added at the last, so that the oxidation can be avoided, and the reducibility of the solution can be ensured. In addition, during configuration, stirring is carried out, so that all components can be matched more fully and uniformly, and finally, the gold precipitation effect of the gold precipitation liquid is better. And the reducing agent and the silver ions are added at the end so as to avoid the silver ions from being exposed in the air to cause oxidation, thereby ensuring the stability of the solution.
In this embodiment, the complexing agent is a 1, 2-ethylenediamine compound. The complexing agent of the invention adopts 1, 2-ethanediamine compound, and the plating solution contains SO4 2-、Cl-The conductive ions can provide conductive action in the replacement process due to the silver ions, so that the replacement is stably carried out. The cyanide-free gold salt is tetrachloro-gold acid or gold hydroxide. At present, gold sodium sulfite is generally adopted as cyanide-free gold salt because SO in plating solution3 2-Unstable and lead to SO by the action of oxygen in the air3 2-The concentration of the plating solution is reduced, so that the plating solution is decomposed, the physical property of the gold plating layer is unstable, and the crystallization of the plating layer is coarse, so that the effect of the gold plating layer is influenced; in order to solve the problem, the invention adopts tetrachloro-alloy acid or gold hydroxide, Au in the gold salt3+Can exist in the plating solution stably for a long time and is difficult to be changed, thereby ensuring the stability of the plating solution.
In this embodiment, the buffer is one or two of ammonium chloride and ammonium citrate. Therefore, in order to maintain the stability of the pH value of the bath solution, substances capable of stabilizing the pH value of the bath solution are required to be added into the bath solution, and ammonium chloride and ammonium citrate are used as buffering agents to maintain the stability of the pH value of the bath solution. The surfactant is sodium methallyl sulfonate, and the corrosion inhibitor is sulfonated lignin. The sulfonated lignin is a natural high molecular polymer, and can be used as an anticorrosive agent and a protective film of a gold layer, so that the surface activity is greatly enhanced.
In order to achieve the above object, the present invention further provides a gold-plating process of a cyanide-free chemical thick gold-plating solution, comprising the steps of:
step 1, performing vacuum treatment on a pretreatment solution before gold precipitation on a gold precipitation part;
step 2, placing the treated gold immersion piece into a gold cylinder groove with any one of the gold immersion solutions, and carrying out first-stage gold immersion treatment; the specific conditions of the gold precipitation treatment are as follows: the gold deposition temperature is: the gold immersion time is 5-6 minutes at 55-65 ℃, and the thickness of the obtained gold layer of the gold immersion part is 0.8-1 micron; in the first stage, silver ions and gold are subjected to displacement reaction firstly and then are reduced, and in the initial stage, the reduction effect of the composite reducing agent and the stabilization effect of the composite stabilizing agent are optimal, so that rapid gold precipitation can be realized, and the gold precipitation thickness can reach 0.8-1 micron after 5-6 minutes; in addition, under the same plating condition, the gold layer obtained by replacement and reduction is higher in hardness, better in binding force, more superior in corrosion resistance, better in high-temperature oxidation resistance and greatly improved in cost performance.
Step 3, performing second-stage gold immersion treatment on the gold immersion part after the first-stage gold immersion treatment is completed; the immersion gold treatment comprises the following specific steps: benzotriazole is added uniformly during the gold immersion, the gold immersion temperature is 50 ℃, the gold immersion time is 3-4 minutes, and the thickness of the thick gold layer of the gold immersion part is 1.2-1.5 microns; along with the prolonging of gold immersion time, the reducibility of a reducing agent and the stability of a stabilizing agent in a gold immersion solution are weakened, and the solution is easy to generate agglomeration phenomenon, particularly under the condition of higher temperature, the agglomeration causes the deposition solution to be incapable of being uniformly dispersed, and metal oxide is easier to form between a substrate and a gold layer Compactness; further improving the bonding force between the gold layer and the substrate.
Step 4, bombarding the surface of the heavy metal piece which is subjected to the thick gold layer treatment by adopting vacuum plasma, wherein the working medium of the vacuum plasma is nitrogen; the bombardment distance is controlled to be 45-50 mm; the treatment temperature is 120 ℃; the treatment time is 10-12 s; in the step, the gold immersion part is cleaned in a nitrogen bombardment mode, the cleaning degree is better than that of the existing ultrapure water cleaning effect, the close combination of the gold immersion layer and the base material is more facilitated, and the combination strength between the gold layer and the base material is further improved. The gold immersion is finished in the step, the surface of the gold immersion piece has certain brittleness along with the time, the bombardment distance is lengthened, the surface of the gold immersion piece can become compact and smooth while cleaning, and the void ratio is reduced; and the bonding degree of the coating and the base material can be further enhanced in the bombardment process.
And 5, carrying out the next process on the metal immersion piece after the surface treatment is finished.
In this embodiment, the volume ratio of benzotriazole to gold precipitation solution added in step 3 is 80: 1; and the diameter of the benzotriazole is less than 100 nanometers. Because the gold immersion solution contains the composite stabilizer, and the benzotriazole in the second gold immersion stage mainly has a stabilizing effect on the surface of a gold immersion part and a subsequent gold immersion solution, the usage amount of the benzotriazole only needs to be small to achieve the expected effect. The benzotriazole polymer nano particles are injected into a gold precipitation cylinder at a high speed under the action of compressed air, and the distance between a nozzle and the liquid surface of the gold precipitation cylinder is 2-3cm during injection; and the angle between the nozzle and the liquid level of the gold immersion cylinder is 30 degrees; and the jet injection flow rate was 5 ml/min. The closer the distance, the better the effect of spraying, adopt the mode of high-speed injection for the dispersion that polymer nano particle can be even is in heavy gold solution, and quick and original heavy gold solution fuse, and the quick dispersion accomplishes to stop the emergence of reunion phenomenon in the solution, makes the heavy gold piece that finally obtains also have good adhesion under high temperature, and heavy gold surface coating is even moreover.
The invention has the beneficial effects that: compared with the prior art, the gold precipitation solution for cyanide-free chemical precipitation of thick gold and the process thereof have the following beneficial effects:
1) the composite reducing agent is composed of sodium borohydride, glucose and hydroxylamine sulfate, the reducing agent is compounded according to a special proportion, the stability of the gold precipitation solution cannot be influenced in the reduction process, the reaction of hydroxylamine and the glucose organic reducing agent can reduce the reaction activity of Au +, the reaction of hydroxylamine sulfate is instantly nucleated under the action of the hydroxylamine sulfate in the whole reduction process, the size of a gold core is larger, the thickness of the gold precipitation layer can be increased more quickly, and the gold precipitation rate is accelerated.
2) The stabilizer is compounded by antimony potassium tartrate, hyperbranched polyurethane sulfonate and polyacrylamide, and the hyperbranched polyurethane sulfonate is matched with the polyacrylamide, so that the problem of concentration reduction of the stabilizer in the gold precipitation process can be avoided, and the whole gold precipitation liquid can be uniformly and stably dispersed in the gold precipitation process; and the hyperbranched polyurethane sulfonate and polyacrylamide have the characteristic of high viscosity on the basis of ensuring the stability, can be adsorbed on the groove wall during chemical reaction, directly avoids continuous gold ions from being further separated out and deposited on the groove wall of the gold precipitation cylinder, has extremely strong stability, and avoids the concentration of a stabilizer from being greatly reduced in the gold precipitation process. Compared with the existing plating solution, under the same gold immersion condition, the thick gold layer obtained by the composite stabilizer has higher hardness, good binding force with a substrate and excellent corrosion resistance.
3) The invention adds the anticorrosive agent on the basis of the traditional base solution, and the anticorrosive agent is prepared by mixing the components of 1:1, benzotriazole and sulfonated lignin, wherein the benzotriazole can prevent metal oxides generated by dissolution in the gold precipitation process from being formed between a matrix and a gold layer, so that the obtained gold layer is ensured to be crystallized uniformly and compact; and the anticorrosive agent can be adsorbed on the metal surface, a thin protective film can be quickly formed on the surface of the thick gold layer, and the bonding force between the gold layer and the substrate is further improved.
4) The silver ion is added on the basis of the original solution, the silver ion is reduced to the gold immersion piece under the action of the reducing agent and then replaced with gold, silver is oxidized into silver ion again, the gold layer is thickened due to the circulation, the thickness of the gold layer is increased, and the gold immersion piece can further reach thick gold more quickly.
5) The invention adds the compound reducing agent, the compound stabilizing agent and the anticorrosive agent on the basis of the original components of the gold immersion solution, the reaction accelerator accelerates the activation reaction speed of the gold immersion solution, the activation time is reduced, and the anticorrosive agent quickly forms a thick gold layer protective film; particularly, specially-made components are adopted on a composite reducing agent and a composite stabilizing agent, so that gold ions with higher concentration can be rapidly and stably subjected to catalytic reduction gold deposition, and the gold deposition solution has strong stability, so that the corrosion of a nickel layer can be effectively inhibited, and a thick gold layer with the thickness of 1.2-1.5 microns can be formed under the condition that the corrosion of the nickel layer is reduced.
6) In the technology, the gold immersion is divided into two stages, because the gold layer can be replaced by silver ions in the first stage, and the reducing agent and the stabilizing agent are both in a high-concentration state, the gold immersion of about 1.5 microns can be quickly realized; along with the reaction, the stability of the composite stabilizer is reduced, and in order to ensure that the whole gold immersion process is completed in a high-stability state, the polymer nano particles are added while the second gold immersion stage is carried out, and the addition of the polymer nano particles can not only ensure the high stability, but also avoid the agglomeration phenomenon on the surface of the gold layer, thereby further ensuring the uniformity of the gold layer.
7) The obtained gold deposition layer has the advantages of good adhesiveness, compact plating layer structure, uniform crystallization, stable bath solution, high impurity tolerance, high deposition rate and more environment-friendly process. Meanwhile, the cyanide-free chemical gold precipitation solution does not use potassium gold cyanide high-toxicity substances and cyanide radicals, reduces the health influence on operators and the potential safety hazard of the working environment, and greatly reduces the burden and influence of wastewater treatment
The following are specific examples of the present invention:
example 1
The cyanide-free chemical gold-precipitating solution comprises the following components:
the composite reducing agent consists of sodium borohydride, glucose and hydroxylamine sulfate, wherein the sodium borohydride is 0.8g/L, the glucose is 0.8g/L, and the hydroxylamine sulfate is 0.4 g/L.
The composite stabilizer consists of antimony potassium tartrate, hyperbranched polyurethane sulfonate and polyacrylamide, wherein the content of the antimony potassium tartrate is 5mg/L, the content of the hyperbranched polyurethane sulfonate is 2.5mg/L, and the content of the polyacrylamide is 2.5 mg/L.
The reaction accelerator is a compound of 10% of tert-butyl ester, 30% of 3-mercaptopropane sulfonic acid, 30% of 2, 6-diaminopyridine and 30% of 3-pyridine methanol.
After cyanide-free gold immersion is carried out on the gold immersion part by the gold immersion method, the temperature adopted in the first stage is 65 ℃ and the gold immersion time is 5 minutes, the thickness of the gold layer of the gold immersion part is 1 micron, the gold immersion temperature in the second stage is 50 ℃ and the gold immersion time is 4 minutes, and the thickness of the thick gold layer of the gold immersion part is 1.5 microns; the whole process only needs 9 minutes, and the obtained gold deposition plate layer has consistent crystal size and no cavity or crack; the microscopic observation shows that the structure of the plating layer is very compact, the crystallization of the plating layer is fine and uniform, and no crack exists; the 180-degree bending test shows that the bonding force of the plating layer is good, and no obvious crack is observed when the plating layer is amplified by 100 times.
Example 2
The cyanide-free chemical gold precipitation solution comprises the following components:
the composite reducing agent is composed of sodium borohydride, glucose and hydroxylamine sulfate, wherein the sodium borohydride is 2g/L, the glucose is 2g/L, and the hydroxylamine sulfate is 1 g/L.
The composite stabilizer consists of 7.5mg/L of antimony potassium tartrate, 3.75mg/L of hyperbranched polyurethane sulfonate and 3.75mg/L of polyacrylamide.
The reaction accelerator is a compound of 15% of tert-butyl ester, 25% of 3-mercaptopropane sulfonic acid, 30% of 2, 6-diaminopyridine and 30% of 3-pyridine methanol.
After cyanide-free gold immersion is carried out on the gold immersion part by the gold immersion method, the gold immersion temperature adopted in the first stage is 55 ℃, the gold immersion time is 5 minutes, the thickness of the gold layer of the gold immersion part is 0.8 micrometer, the gold immersion temperature in the second stage is 50 ℃, the gold immersion time is 3 minutes, and the thickness of the thick gold layer of the gold immersion part is 1.2 micrometers; the whole process only needs 8 minutes, and the obtained gold immersion plate layer has consistent crystallization size and no cavity or crack; the microscopic observation shows that the structure of the plating layer is very compact, the crystallization of the plating layer is fine and uniform, and no crack exists; the 180-degree bending test shows that the bonding force of the plating layer is good, and no obvious crack is observed when the plating layer is amplified by 100 times.
Example 3
The cyanide-free chemical gold-precipitating solution comprises the following components:
the composite reducing agent consists of sodium borohydride, glucose and hydroxylamine sulfate, wherein the sodium borohydride is 0.4g/L, the glucose is 0.4g/L, and the hydroxylamine sulfate is 0.2 g/L.
The composite stabilizer consists of 10mg/L of antimony potassium tartrate, 5mg/L of hyperbranched polyurethane sulfonate and 5mg/L of polyacrylamide.
The reaction accelerator is a compound of 10% of tert-butyl ester, 10% of 3-mercaptopropane sulfonic acid, 30% of 2, 6-diaminopyridine and 50% of 3-pyridine methanol.
After cyanide-free gold immersion is carried out on the gold immersion part by the gold immersion method, the gold immersion temperature adopted in the first stage is 55 ℃, the gold immersion time is 5 minutes, the thickness of the gold layer of the gold immersion part is 0.9 micrometer, the gold immersion temperature in the second stage is 50 ℃, the gold immersion time is 4 minutes, and the thickness of the thick gold layer of the gold immersion part is 1.3 micrometers; the whole process only needs 9 minutes, and the obtained gold deposition plate layer has consistent crystal size and no cavity or crack; the microscopic observation shows that the structure of the plating layer is very compact, the crystallization of the plating layer is fine and uniform, and no crack exists; the 180-degree bending test shows that the bonding force of the plating layer is good, and no obvious crack is observed when the plating layer is amplified by 100 times.
Comparative example 1
Adjusting the pH to 8 with sulfuric acid or potassium hydroxide;
the balance being water.
Operating temperature: at 60 ℃.
When the component is used for gold immersion by a traditional gold immersion method, the thickness of the gold immersion can reach 0.6 micron, little gold ions exist in the gold immersion on the wall of the gold immersion part after the gold immersion, the surface lattices of the gold immersion part are different in size, and obvious cracks are observed by amplifying 100 times, which indicates that a boundary layer exists between the gold layer and the nickel layer to cause the cracks.
The metal immersion parts obtained in the three specific examples and the comparative example 1 were subjected to a friction polishing test, and the specific operation method was: placing the metal sinking piece in a vibration polishing machine, and performing a friction polishing test by using a soap water solution as a lubricant; the metal immersion parts obtained in the specific examples 1-3 have uniform surface coating and flat appearance, and no bubbling phenomenon occurs; however, in comparative example 1, the surface had a remarkable foaming phenomenon.
Through the three specific examples of the invention and the comparative example 1, compared with the example 1, because the compound stabilizer, the accelerated reactant, the anticorrosive agent, the silver ions and the compound reducing agent are not adopted, the conventional gold deposition method is adopted, the gold deposition thickness is small, the expected requirements cannot be met, and the product percent of pass is not high; the binding force between the plating layer and the base material is not high; the gold layer of the gold immersion part obtained by the invention has smooth appearance and uniform plating layer crystal lattice size; the microscopic observation shows that the structure of the plating layer is very compact, the crystallization of the plating layer is fine and uniform, and no crack exists; through 180-degree bending test, the bonding force of the plating layer is good, and no obvious crack is observed when the plating layer is amplified by 100 times; by using a friction polishing experiment method, the surface of the plated part obtained by the invention is firm and uniform, and the phenomenon of foaming is completely avoided, which shows that the bonding force between the gold immersion layer obtained by the invention and the base material is very good, thereby perfectly ensuring the compactness of the gold layer structure.
The above disclosure is only an example of the present invention, but the present invention is not limited thereto, and any variations that can be made by those skilled in the art should fall within the scope of the present invention.
Claims (10)
1. The gold precipitation solution for cyanide-free chemical thick gold precipitation is characterized by comprising the following components in mass concentration:
the composite reducing agent consists of sodium borohydride, glucose and hydroxylamine sulfate, and the mass concentration ratio of the sodium borohydride to the glucose to the hydroxylamine sulfate is 2:2: 1;
the composite stabilizer consists of antimony potassium tartrate, hyperbranched polyurethane sulfonate and polyacrylamide according to the mass concentration ratio of 2:1: 1;
the concentration ratio of the anticorrosive agent to the reaction accelerator is 1:8 when in use;
the components are mixed according to the proportion, the pH value is adjusted to 7-8 by sulfuric acid or potassium hydroxide, the balance is water, and the cyanide-free chemical gold precipitation solution is formed after the operation temperature is 50-70 ℃.
2. The gold deposition solution for cyanide-free electroless thick gold deposition according to claim 1, wherein the reaction accelerator is a complex of tert-butyl ester, 3-mercaptopropanesulfonic acid, 2, 6-diaminopyridine and 3-pyridinemethanol, and the four are, in mass percent: 10-20% of tert-butyl ester, 10-30% of 3-mercaptopropane sulfonic acid, 30-50% of 2, 6-diaminopyridine and 30-50% of 3-pyridinol.
3. The gold-precipitating solution for cyanide-free chemical deposition of thick gold according to claim 1, wherein the gold-precipitating solution is prepared by the following steps: firstly, adding cyanide-free gold salt, a complexing agent, a buffering agent and an anticorrosive agent into a stirrer for stirring, and uniformly stirring to form a mixed solution A, wherein the stirring speed is between 100 and 150 r/min; adding the composite stabilizer, the surfactant and the reaction accelerator into the mixed solution A, stirring while adding, and uniformly stirring to form a mixed solution B, wherein the stirring speed is between 150-; then, adding a composite reducing agent and silver ions into the mixed solution B, and uniformly stirring to form a mixed solution C, wherein the stirring speed is between 150 and 200 r/min; finally, adjusting the pH of the mixed solution to 7-8 by using sulfuric acid or potassium hydroxide, and forming a cyanide-free chemical gold precipitation solution after the operation temperature is 50-70 ℃.
4. The gold-precipitating solution for cyanide-free chemical precipitation of thick gold according to claim 1, wherein the complexing agent is a 1, 2-ethanediamine compound.
5. The gold plating solution for cyanide-free electroless thick gold plating according to claim 1, wherein the cyanide-free gold salt is tetrachloro-alloying acid or gold hydroxide.
6. The gold-precipitating solution for cyanide-free chemical precipitation of thick gold according to claim 1, wherein the buffer is one or both of ammonium chloride and ammonium citrate; the substance containing silver ions is silver nitrate.
7. The gold-precipitating solution for cyanide-free chemical precipitation of thick gold according to claim 1, wherein the surfactant is sodium methallylsulfonate; the anticorrosive agent is sulfonated lignin.
8. A gold immersion process of a cyanide-free chemical thick gold immersion solution is characterized by comprising the following steps:
step 1, performing vacuum treatment on a pretreatment solution before gold precipitation on a gold precipitation piece;
step 2, placing the treated gold precipitation piece into a gold cylinder groove with the gold precipitation solution according to any one of claims 1 to 7, and performing a first-stage gold precipitation treatment; the specific conditions of the gold precipitation treatment are as follows: the gold deposition temperature is: the gold immersion time is 5-6 minutes at 55-65 ℃, and the thickness of the obtained gold layer of the gold immersion part is 0.8-1 micron;
step 3, performing second-stage gold immersion treatment on the gold immersion part after the first-stage gold immersion treatment is completed; the immersion gold treatment comprises the following specific steps: benzotriazole is added uniformly during the gold immersion, the gold immersion temperature is 50 ℃, the gold immersion time is 3-4 minutes, and the thickness of the thick gold layer of the gold immersion part is 1.2-1.5 microns;
step 4, bombarding the surface of the heavy metal part subjected to the thick gold layer treatment by adopting vacuum plasma, wherein the working medium of the vacuum plasma is nitrogen;
and 5, carrying out the next process on the metal immersion piece after the surface treatment is finished.
9. The gold immersion process of the gold immersion solution for cyanide-free chemical immersion of thick gold according to claim 8, wherein the volume ratio of benzotriazole added in the step 3 to the gold immersion solution is 80: 1; and the diameter of the benzotriazole is less than 100 nanometers.
10. The process of claim 9, wherein the polymeric nanoparticles are ejected into the gold immersion cylinder at a high speed by compressed air, and the distance from the nozzle to the surface of the gold immersion cylinder is 2-3 cm; and the angle between the nozzle and the liquid horizontal plane of the gold precipitation cylinder is 30 degrees; and the jet injection flow rate was 5 ml/min.
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