阅读说明：本技术 一种无氰电镀金配方及其配置方法和电镀工艺 (Cyanide-free electrogilding formula, preparation method thereof and electrogilding process ) 是由 姚玉 于 2021-06-11 设计创作，主要内容包括：本发明一种无氰电镀金配方及其配置方法和电镀工艺,属于电镀金技术领域；所述无氰电镀金配方组成如下：HAuCl-4 0.01-0.02mol·L～(-1)、5,5-二甲基乙内酰脲0.2-0.3mol·L～(-1)、K-2CO-3 0.3-0.4mol·L～(-1)、邻菲罗啉20-40mg·L～(-1)、聚二烯丙基二甲基氯化铵5-15mg·L～(-1),氨基三亚甲基膦酸50-70g/L、有机多胺类化合物70-100g/L和聚醚类化合物0.01-0.03g/L。该配方和工艺得到的镀层质量良好,镀液具有较好的分散能力、覆盖能力、稳定性。并且镀液中不含氰化物,满足生产需求。(The invention relates to a cyanide-free electrogilding formula, a preparation method and an electroplating process thereof, belonging to the technical field of electrogilding; the cyanide-free electrogilding formula comprises the following components: HAuCl 4 0.01‑0.02mol·L ‑1 0.2-0.3 mol.L of 5, 5-dimethylhydantoin ‑1 、K 2 CO 3 0.3‑0.4mol·L ‑1 20-40 mg.L of phenanthroline ‑1 Poly-diallyl dimethyl ammonium chloride 5-15 mg.L ‑1 50-70g/L of amino trimethylene phosphonic acid, 70-100g/L of organic polyamine compound and 0.01-0.03g/L of polyether compound. The plating layer obtained by the formula and the process has good quality, and the plating solution has good dispersing capacity, covering capacity and stability.And the plating solution does not contain cyanide, thereby meeting the production requirement.)

1. The cyanide-free electrogilding formula is characterized in that electrogilding is prepared from an additive and ultrapure water, and the cyanide-free electrogilding formula comprises the following components:

HAuCl₄ 0.01-0.02mol·L^-10.2-0.3 mol.L of 5, 5-dimethylhydantoin^-1、K₂CO₃0.3-0.4mol·L^-120-40 mg.L of phenanthroline^-1Poly-diallyl dimethyl ammonium chloride 5-15 mg.L^-150-70g/L of amino trimethylene phosphonic acid, 70-100g/L of organic polyamine compound and 0.01-0.03g/L of polyether compound.

2. The cyanide-free electrogilding formulation according to claim 1, wherein the organic polyamine compound is selected from ethylenediamine or propylenediamine or a mixture of butylenediamine and ammonium citrate.

3. The cyanide-free electrogilding formulation according to claim 1, wherein the polyether compound is a propylene glycol block polyether.

4. The cyanide-free electrogilding formulation according to claim 1, wherein the electrogilding is formulated with additives and ultra pure water, the cyanide-free electrogilding formulation consisting of:

HAuCl₄ 0.015mol·L^-10.25 mol.L of 5, 5-dimethylhydantoin^-1、K₂CO₃ 0.36mol·L^-130 mg.L of phenanthroline^-110 mg.L of poly (diallyldimethylammonium chloride)^-160g/L of amino trimethylene phosphonic acid, 80g/L of organic polyamine compound and 0.02g/L of polyether compound.

5. A method for preparing a cyanide-free gold electroplating formulation according to any one of claims 1 to 4, comprising the following steps, in order:

step S1, calculating the mass of each material to be weighed according to the volume of the solution to be prepared and the process formula;

step S2, weighing the complexing agent 5, 5-dimethylhydantoin and the conductive salt K according to the calculation result₂CO₃Putting the mixture into a beaker, adding a proper amount of ultrapure water, and stirring the mixture at the temperature of 328-333K to dissolve the ultrapure water;

step S3, weighing HAuCl as main salt according to calculation result₄·4H₂Dissolving the solution in a proper amount of ultrapure water, mixing the solution obtained in the step S2 with the main salt solution, fully stirring the solution until the solution is completely colorless from yellow after constant volume is carried out, and enabling Au in the solution to be completely colorless³⁺Complete coordination with DMH.

6. The method for preparing a formulation for cyanide-free gold electroplating according to claim 5, wherein in the steps S2 and S3, several tens of times of the required amount of the additive is weighed when the additive is weighed, a substantially saturated uniform solution is prepared according to the solubility of the additive, and the solution is converted, and then a proper amount of the solution is measured by a liquid transfer gun, added to the plating solution, and mixed uniformly to perform the electroplating experiment.

7. A method as claimed in any one of claims 1 to 4The electroplating process of cyanide-free electrogilding formula is characterized in that the current density in the electroplating process is 0.5-1.2 A.dm^-2Controlling the temperature to be 303-323K, the pH value to be 9.7 and the stirring speed to be 600-1000 rpm.

Technical Field

The invention belongs to the technical field of electrogilding, and particularly relates to a cyanide-free electrogilding formula, a preparation method thereof and an electroplating process.

Background

Gold is one of the best known noble metals, and the gold-plated layer is golden yellow, noble and elegant in appearance, good in ductility, easy to polish, good in anti-discoloration performance and capable of being processed into various shapes, so that the gold-plated layer is often used as a decorative plating layer; the gold-plated layer has stable chemical properties, basically does not react with other acids and alkalis except aqua regia, has strong corrosion resistance and good wear resistance, and is often used as a protective plating layer; the gold-plated layer has low contact resistance, good conductivity and easy welding, so the gold-plated layer is also commonly used as a functional plating layer and has wide application in the aspects of precision instruments, printed circuit boards, integrated circuits and the like.

Most of the gold electroplating adopts cyanide plating solution, but cyanide is extremely toxic, so that the development of cyanide-free gold electroplating process with performance close to that of the cyanide gold electroplating process is urgently needed. The cyanide-free gold electroplating process using 5, 5-Dimethylhydantoin (DMH) as a complexing agent has shown to have industrial applicability, but the process still has the following problems: the crystal grains of the plating layer are coarse and loose, so that the color and luster and the brightness of the plating layer are poor.

Disclosure of Invention

The invention aims to provide a cyanide-free electrogilding formula, a preparation method thereof and an electroplating process, and aims to solve the technical problem that the coating color and luster and brightness are poor due to the fact that the coating grains are large and loose in accumulation in the traditional cyanide-free electroplating process.

In order to achieve the purpose, the cyanide-free electrogilding formula, the preparation method and the specific technical scheme of the electroplating process are as follows:

the cyanide-free electrogilding formula is prepared from an additive and ultrapure water, and comprises the following components:

HAuCl₄ 0.01-0.02mol·L^-10.2-0.3 mol.L of 5, 5-Dimethylhydantoin (DMH)^-1、K₂CO₃0.3-0.4mol·L^-120-40 mg.L of Phenanthroline (PHEN)^-1Poly (diallyldimethylammonium chloride) (PDDA)5-15 mg. L^-150-70g/L of amino trimethylene phosphonic Acid (ATMP), 70-100g/L of organic polyamine compound and 0.01-0.03g/L of polyether compound.

Further, the organic polyamine compound is selected from a mixture of ethylenediamine, propylenediamine or butylenediamine and ammonium citrate.

Further, the polyether compound is propylene glycol block polyether.

Further, the electrogilding is prepared from an additive and ultrapure water, and the cyanide-free electrogilding formula comprises the following components:

HAuCl₄ 0.015mol·L^-10.25 mol.L of 5, 5-Dimethylhydantoin (DMH)^-1、K₂CO₃0.36mol·L^-130 mg.L of Phenanthroline (PHEN)^-110 mg. L of polydiallyldimethylammonium chloride (PDDA)^-160g/L of amino trimethylene phosphonic Acid (ATMP), 80g/L of organic polyamine compound and 0.02g/L of polyether compound.

The invention also provides a preparation method of the cyanide-free electrogilding formula, which is characterized by comprising the following steps in sequence:

step S1, calculating the mass of each material to be weighed according to the volume of the solution to be prepared and the process formula;

step S2, weighing the complexing agent (DMH) and the conducting salt (K) according to the calculation result₂CO₃) Putting the mixture into a beaker, adding a proper amount of ultrapure water, and stirring the mixture at the temperature of 328-333K to dissolve the ultrapure water;

step S3, weighing the main salt (HAuCl) according to the calculation result₄·4H₂O), dissolving in a proper amount of ultrapure water, mixing the solution obtained in the step S2 with the main salt solution, fully stirring until the solution is completely colorless from yellow after constant volume is performed, and enabling Au in the solution to be completely colorless³⁺Complete coordination with DMH.

Further, in the step S2 and the step S3, since the content of the additive in the plating solution is extremely low, and some of the additives may not be accurately weighed directly by using a balance (for example, some additives are colloidal substances), the following method is adopted: weighing tens of times of the required amount, preparing a nearly saturated uniform solution (the concentration should be higher as much as possible to ensure that the influence on the total volume is small after the solution is added into the plating solution), measuring a proper amount of the solution by using a liquid transfer gun after conversion, adding the solution into the plating solution, and uniformly mixing to perform the electroplating experiment.

The invention also provides an electroplating process of the cyanide-free electrogilding formula, wherein the current density in the electroplating process is 0.5-1.2 A.dm^-2Controlling the temperature to be 303-323K, the pH value to be 9.7 and the stirring speed to be 600-1000 rpm.

The cyanide-free electrogilding formula disclosed by the invention has the following advantages: the surface of the plating layer is bright and uniform and is rose gold, the hardness of the plating layer is 264Hv0.1, the plating layer is in contact with a platinum-iridium wire to form a resistor of 216m omega, the bonding force and the corrosion resistance of the plating layer are good, the components of the plating layer are 90.4 wt% of Au, 4.5 wt% of Pd and 5.1 wt% of Cu, the current efficiency of the plating solution reaches 79%, the dispersing capacity is 82.17%, the covering capacity is 84.52%, and the stability of the plating solution is 40 days; the plating layer obtained by the formula and the process has good quality, and the plating solution has good dispersing capacity, covering capacity and stability. And the plating solution does not contain cyanide, thereby meeting the production requirement.

Drawings

FIG. 1 shows the macroscopic morphology (a) of the gold-plated layer obtained by electroplating the PDDA-containing and PHEN-containing plating solution for different time periods in this example for 3 min; (b) and 15 min.

Fig. 2 shows the macro-morphology of the gold-plated layer obtained in this example with different current densities.

FIG. 3 shows the microscopic morphology of the gold-plated layer obtained at different rotation speeds in this example (a)300rpm (b)600rpm (c)1000rpm (d)1400 rpm.

Fig. 4 shows the macroscopic features (a) (b)333K (c) (d)343K of the gold-plating layer obtained at different temperatures in this embodiment.

FIG. 5 shows the macro-morphology of the gold-plated layer (a) without additives for 3min with different additives and different plating times in this example; (b) containing main brightener for 3 min; (c) containing compound brightener for 3 min; (d) no additive, 15 min; (e) containing main brightener for 15 min; (f) contains compound brightener for 15 min.

FIG. 6 is an SEM photograph of the gold-plated layer containing different additives and different plating times in the present example (a) without additives, 3 min; (b) containing main brightener for 3 min; (c) containing compound brightener for 3 min; (d) contains compound brightener for 15 min.

Detailed Description

In order to better understand the purpose, structure and function of the present invention, a cyanide-free electrogilding formulation of the present invention will be described in detail with reference to the accompanying drawings.

As shown in fig. 1-6, the present invention proposes to optimize the process by finding suitable additives, and researches show that when the grains are refined to the nanometer level, the coating layer presents golden brightness. In addition, because the hardness and the wear resistance of the pure gold plating layer are poor and the requirement is difficult to meet in some applications, the electroplating process of the gold alloy plating layer is developed by taking DMH as a complexing agent.

The preparation method of the electrogilding solution comprises the following steps:

the gold electroplating solution is prepared by the following method and sequence because DMH dissociates under alkaline condition and the solubility is increased:

(1) and calculating the mass of each substance to be weighed according to the volume of the solution to be prepared and the process formula.

(2) Weighing the complexing agent (DMH) and the conductive salt (K) according to the calculation result₂CO₃) Putting the mixture into a beaker, adding a proper amount of ultrapure water, and stirring the mixture at the temperature of 328-333K to dissolve the ultrapure water.

(3) Weighing the main salt (HAuCl) according to the calculation result₄·4H₂O), dissolving the solution in the step (2) in a proper amount of ultrapure water, mixing the solution in the step (2) with a main salt solution, fully stirring the solution after constant volume till the solution is changed from yellow to be completely colorless, and enabling Au in the solution to be completely colorless³⁺Complete coordination with DMH.

Because the content of the additive in the plating solution is extremely low, and part of the additive can not be accurately weighed by directly using a balance (if some additives are colloidal substances), the following method is adopted: weighing tens of times of the required amount, preparing a nearly saturated uniform solution (the concentration should be higher as much as possible to ensure that the influence on the total volume is small after the solution is added into the plating solution), measuring a proper amount of the solution by using a liquid transfer gun after conversion, adding the solution into the plating solution, and uniformly mixing to perform the electroplating experiment.

The electroplating process flow comprises the following steps:

electroplating is carried out by using the prepared solution according to the following flow: chemical degreasing of the substrate → tap water washing → activation → tap water washing → ultrapure water washing → preplating nickel → tap water washing → ultrapure water washing → electrogilding → tap water washing → ultrapure water washing → cold air or nitrogen air drying.

The chemical degreasing liquid used in the electroplating pretreatment process comprises the following components and process conditions:

NaOH 0.25mol·L^-1

Na₂CO₃ 0.5mol·L^-1

Na₃PO₄·12H₂O 0.15mol·L^-1

Na₂SiO₃·9H₂O 0.04mol·L^-1

temperature 353K

The time is 5-10 min

The activation solution used in the electroplating pretreatment process is prepared by mixing hydrochloric acid and ultrapure water according to the volume ratio of 1:1, and the activation time is 30-60 s.

The experiment used pre-nickel plated copper foil as the matrix for electrogilding. The pre-nickel plating process selects a general bright nickel plating process, takes copper foil as a cathode and a nickel plate as an anode, and carries out nickel electroplating by using a direct current stabilized voltage power supply under the conditions of water bath heating and mechanical stirring.

The process conditions of the nickel preplating are as follows:

NiSO₄·6H₂O 250～300g·L^-1

NiCl₂·6H2O 30～50g·L^-1

H₃BO₃ 35～40g·L^-1

saccharin 0.6-1.0 g.L^-1

0.3-0.5 g.L of 1, 4-butynediol^-1

Sodium dodecyl sulfate 0.05-0.15 g.L^-1

A pH of 4.0 to 6.0, a current density of 1.5 to 3.0 A.dm^-2The temperature is 313-323K.

The plating bath used in the electrogilding experiment was a small beaker of 50ml, 40ml of plating solution was used alone, the anode was a platinum sheet, the cathode was the nickel-plated copper foil described above, the power supply was a DC regulated power supply, and a constant temperature water bath was used for temperature control and mechanical agitation control. The stirring process uses a magnetic force to rotate the length to 1 cm.

The coating obtained by using PDDA and PHEN as compound additives has a macroscopic appearance as shown in figure 1, the brightness of the obtained coating is improved, and the color of the coating is still golden yellow without obvious change and reduction of the brightness when the coating is electroplated for a long time (15 min).

Respectively controlling the current density to 0.2A dm^-2、0.4A·dm^-2、0.6A·dm^-2、0.8A·dm^-2、1.0A·dm^-2、1.2A·dm^-2、1.4A·dm^-2And observing the macroscopic morphology of the gold-plated layer to obtain: when the current density is 0.2 A.dm^-2When the electroplating solution is used, the electroplating layer is golden yellow, but the current is small, the deposition speed is slow, the electroplating layer is thin, and part of the substrate is exposed; when the current density is gradually increased until 1.2A dm^-2The plating layer can better cover the substrate, and has golden color and good brightness; when the current density is further increased to 1.4A dm^-2The gold-plated layer begins to become dark and black, the plating layer becomes uneven, and the brightness is reduced. The current density is 0.4A dm^-2～1.2A·dm^-2The appearance of the gold-plated layer is not obviously different, the further judgment needs to be carried out from the micro-morphology, and the result is shown in figure 2, and it can be seen that when the current density is 0.4 A.dm^-2When the current density is increased to 0.6A dm, the coating has more pores^-2The number of pores was reduced but not completely eliminated, when the current density was further increased to 0.8A dm^-2、1.0A·dm^-2、1.2A·dm^-2In the case of the plating, voids are hardly observed, and the grains of the plating layer are still very fine and the deposit is very dense.

In conclusion, the current density is selected to be 0.8 A.dm-2 to 1.2 A.dm by combining macroscopic morphology and microscopic morphology^-2Is the better current density.

Stirring affects the electrodeposition process mainly by reducing concentration polarization, and because the ultimate diffusion current density is inversely proportional to the thickness of the diffusion layer, the stirring speed has a significant effect on the thickness of the diffusion layer, therefore, the stirring speed is an important parameter of the electroplating process. The stirring speed of the water bath was controlled to 0rpm (r.min)^-1)300rpm, 600rpm, 1000rpm, 1400rpm, and the macroscopic morphology of the gold-plated layer was observed to find: when the stirring is not carried out, the gold-plated layer is black, poor in brightness and easy to fall off. When the rotating speed is increased to 300rpm, the blackening of the coating is better, but obvious black can still be seen, when the rotating speed is further increased to 600rpm, the coating is golden and bright and has no obvious black, the rotating speed is further increased, and the macroscopic morphology of the coating is not changed greatly. Wherein the coating micro-morphology with a rotation speed different from 0 is shown in FIG. 3It can be seen that: when the rotating speed is only 300rpm, the surface of the plating layer is not flat, and the crystal grains are coarse; when the rotating speed is increased to 600rpm, crystal grains are obviously thinned, and the surface smoothness is improved; when the rotating speed is further increased to 1000rpm and 1400rpm, the appearance of the plating layer is not changed greatly.

In summary, when the rotation speed is greater than 600rpm, a golden and bright gold-plated layer can be obtained, and considering that when the rotation speed is too high, the plating solution may splash out, which causes unnecessary waste and increases the cost, therefore, when the stirring strength can meet the requirement of the mass transfer process, the rotation speed does not need to be increased continuously. According to the micro and macro appearance, the proper rotating speed range is selected to be 600 rpm-1000 rpm, and the rotating speed of the experiment is selected to be about 1000 rpm.

The temperature of the plating solution affects the migration resistance and electrodeposition activity of ions in the plating solution. If the temperature is too high, the decomposition phenomenon of some components which are not stable enough can be caused, and the temperature is too high, the plating solution is evaporated too fast, so that the concentration can be changed greatly, and meanwhile, the too high temperature is not beneficial to industrial production. The temperature is respectively controlled to 303K, 313K, 323K, 333K and 343K, and the observation of the macroscopic morphology of the gold-plated layer can know that: when the temperature is gradually increased from 303K to 333K, the gold plating layer always presents a more positive golden yellow color and the brightness of the plating layer is better, but when the temperature is further increased to 343K, the color of the plating layer appears a phenomenon of slight reddening. The microtopography in which 333K and 343K are magnified by different times is shown in FIG. 4, and it can be seen that: the grain size of the crystal grains is not coarsened with the increase of the temperature, the accumulation of the crystal grains is also more compact, but when the temperature is increased to 333K, a small amount of pores appear on the surface, and when the temperature is continuously increased to 343K, the number of pores is increased. And 343K, the surface is not as flat as 333K.

In conclusion, only from the macroscopic morphology, the golden and bright plating layer can be obtained at the electroplating temperature of 303-333K, and if the requirements on the microscopic morphology are high, 303-323K can be selected as a better temperature range.

The appearances of the plating layers without and with the additives are shown in fig. 5, and considering that some practical applications also have certain requirements on the thickness of the plating layers, the gold electroplating experiments with the duration of 3min and 15min are respectively carried out, and the thicknesses of the gold plating layers of the two are respectively 0.46 μm and 2.3 μm. When the electroplating time is 3min, comparing the graphs a, b and c, the plating layer without the additive has poor uniformity, only a small part of the region presents golden yellow color, and a large part of the region presents red color, the addition of the main brightener PHEN obviously improves the color, uniformity and brightness of the plating layer, and the addition of the auxiliary brightener PDDA further ensures that the appearance of the plating layer has no obvious change. When the electroplating time is prolonged to 15min, the comparison of the graphs d, e and f shows that the plating layer without the additive is in a complete reddish brown and non-bright state, while the addition of PHEN causes the color of the plating layer to become golden yellow, but the brightness and uniformity are still poor, and the further addition of PDDA obviously improves the uniformity and brightness of the plating layer, and the color and brightness are similar to those of PHEN which acts alone for electrodeposition for 3 min. However, when PDDA alone acts, the plating layer exhibits a blackish gold color, and thus PDDA does not mainly play a role of brightening, which is to maintain the brightness and uniformity of the plating layer to some extent when the plating layer is thickened, and main brightening agent PHEN is mainly used.

The coating micro-topography was characterized using a Scanning Electron Microscope (SEM), and the additive-free and additive-containing coating micro-topography is shown in fig. 6. As is clear from FIG. 6(a), the crystal grains of the plating layer obtained from the base plating bath are coarse and loose. Loose grains will lead to red appearance of the plating layer, which is difficult to meet the requirement of decorative plating layer, and meanwhile, loose plating layer will bring poor binding force and easy impurity inclusion, when the plating layer is used as a protective plating layer, a thicker plating layer is needed to play a sufficient protection role, which leads to the increase of cost. As can be seen from fig. 6(b), the addition of PHEN makes the grains significantly refined, the packing dense, and no significant pores, so it can be concluded that refining the grains is the key to improve the performance of the plating layer. And an auxiliary brightener PDDA is further added, the grain size is similar to that of the grain size shown in the figure 6(b), but the flatness of the plating layer is obviously improved, the surface is not clustered any more, and no obvious pore exists. When the electroplating time is prolonged to 15min, as shown in fig. 6(d), the grain size of the coated grains is not obviously changed, and the flatness of the coated surface is slightly reduced, but the tendency is difficult to avoid, and the macro morphology is not influenced enough. In conclusion, the comparative analysis of the microscopic morphology shows that the main brightener plays a main role in refining crystal grains, the auxiliary brightener plays a role in leveling, and the compound additive component can make the best of the advantages and avoid the disadvantages and respectively play the advantages of the main brightener and the auxiliary brightener.

It is to be understood that the present invention has been described with reference to certain embodiments, and that various changes in the features and embodiments, or equivalent substitutions may be made therein by those skilled in the art without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.