CN110344089B - Gold sodium sulfite plating solution and electroplating method thereof - Google Patents

Abstract

The invention discloses a gold sodium sulfite plating solution and an electroplating method thereof, relates to the field of gold plating solutions, and aims to find a gold plating solution which does not contain cyanide ions and has stable properties to replace a cyanide gold plating process, reduce the harm to the environment and operators, and simultaneously ensure that the plating solution has stable chemical and physical properties and can meet the requirements of transportation and storage. The invention provides a cyanide-free gold plating solution, wherein the gold sodium sulfite plating solution comprises gold sulfite salt, a complexing agent, a conductive agent, a current stabilizer and a buffer solution. The invention has the beneficial effects that: gold ions in the solution are more stable, and the storage time of the plating solution is longer; the brightener is added into the composition, so that the surface of the gold-plated layer is more fine and smooth, the gaps are reduced, and the surface gloss of the gold-plated layer is better; the dispersant is added into the composition, so that the plating solution has good stability and dispersibility, good uniformity, high cathode current efficiency, good welding performance of the plating layer, good corrosion resistance and good binding force.

Description

Gold sodium sulfite plating solution and electroplating method thereof

Technical Field

The invention relates to a gold sodium sulfite plating solution, relates to the field of gold plating solutions, and particularly relates to a gold sodium sulfite gold plating solution composition and a using method thereof.

Technical Field

Gold has golden yellow metal with good glossiness, low hardness, good ductility, stable chemical property, good electric conduction and heat property, thus being widely used in the fields of electric appliances, plugs, circuit board surfaces, decoration and the like. Gold is a scarce resource due to limited worldwide storage, and the excellent properties of metallic gold are usually obtained by adopting an electroplating gold process during the use process.

In the electroplating process, the basic reaction process of gold is as follows: trivalent gold obtains two electrons to be reduced into monovalent gold, and the monovalent gold obtains one electron to be reduced into simple substance gold. Under the condition that the gold ions do not exist in the presence of a complexing stabilizer, univalent gold is easy to generate disproportionation reaction and cannot stably exist in the solution; trivalent gold is relatively more stable than monovalent gold. In the solution, trivalent gold ions have higher reduction potential due to the existence of a complexing agent, and the obtained gold crystal grains of the plating layer are finer and more compact. Whereas the complex commonly used is a cyanide ion. Cyanide gold plating is a commonly used mature gold plating process, wherein cyanide ions and monovalent gold ions have very strong complexing ability and always occupy an important role in the metal plating process. The cyanide has great toxicity and can enter a human body through a digestive tract, a respiratory tract and skin, cyanide ions are separated out after the cyanide enters the human body and are combined with ferric iron of oxidative cytochrome oxidase in cell mitochondria, the reduction of the ferric iron in the oxidase is prevented, the normal respiration of cells is hindered, oxygen cannot be utilized by histiocytes, and tissues are lack of oxygen, so that the human body is trapped in an internal asphyxia state. The production process with serious personal and environmental safety hidden troubles is gradually eliminated in the processes of production, transportation, pollution discharge and the like, so that the development of cyanide-free gold plating solution is an inevitable trend in the industry, and the gold plating solution without cyanide has the greatest difficulty of stability.

At present, most of non-cyanide gold salts are trivalent gold, such as common gold trichloride, aluminum alloy acid salts and the like, except that certain operation risk exists due to gas generation in the configuration process, more reducing agents need to be added in the electroless gold plating solution to reach the reaction potential, firstly, more impurities are introduced, the difficulty in obtaining a pure gold plating layer is higher, secondly, more reducing agents are added, the disproportionation reaction is easy to occur, and the long-term storage of the plating solution is not facilitated. In other words, the key point of replacing cyanide ion gold plating solution with pollution and great harm is to find a substance capable of complexing with gold ions to replace cyanide ions, and simultaneously satisfy certain potential, conductivity and stability.

Disclosure of Invention

The cyanide gold plating process is replaced by the cyanide gold plating solution which does not contain cyanide ions and has stable properties, so that the harm to the environment and operators is reduced, and meanwhile, the chemical and physical properties of the plating solution are stable, and the requirements of transportation and storage can be met. The invention provides a cyanide-free gold plating solution, in particular to a gold sodium sulfite plating solution. The gold sodium sulfite plating solution comprises gold sulfite salt, a complexing agent, a conductive agent, a current stabilizer and a buffer solution. The gold ions in the composition exist in the form of gold sulfite salt, and are complexed with other components in the composition, the state is stable, so that the storage period of the plating solution is long, and the storage period of the stock solution without opening the cylinder is more than 12 months under the condition of normal-temperature sealing.

The technical scheme provided by the invention is as follows:

the gold sodium sulfite plating solution comprises

Gold salt, 8-15g/L of sulfite gold salt;

primary complexing agent, preferably anhydrous sodium sulfite (chemically pure): ammonium sulfite with the mass ratio of 5:1, 70-100 g/L; a second complexing agent, preferably dipotassium hydrogen phosphate (chemically pure): the mass ratio of potassium citrate (chemical purity) is 2.0-2.5:1, 10-30 g/L;

current stabilizer, organic aldehydes: the mass ratio of the alcohol ethers is 1:1, 1-5 g/L;

a pH buffering agent, preferably boric acid-borax buffer solution, with the mass ratio of 6.5-7.2:1, 0.2M borate, 30-50 g/L;

an antioxidant, preferably triammonium citrate, 0.06-0.1 g/L;

a dispersion refiner, preferably polyoxyethylene fatty alcohol ether 1-3 g/L;

masking agents, preferably EDTA-2 Na: triethanolamine (chemically pure), with the mass ratio of 3:1, 20-30 g/L;

brightener, preferably beta-naphthol ethoxylate, 0.5-1.5 g/L.

The second purpose of the invention is to provide an electroplating method of the gold sodium sulfite plating solution, wherein the engineering operation process parameters are as follows:

the temperature is 50-60 DEG C

The pH value is 7.8-8.5

The deposition rate is 80-150 mg/A.min

The ratio of the number (area) of the anode and the cathode is more than or equal to 1:1

The plating solution is filtered and stirred for 4 to 6 times per hour, and the filtering aperture is less than or equal to 1.5 mu m by using a filter element.

The invention has the beneficial effects that:

the gold sodium sulfite plating solution forms stable complex ion clusters through the comprehensive action among gold sulfite salt, a stabilizer and other combined components, so that gold ions in the solution are more stable, the storage time of the plating solution is longer, and the stock solution without opening the cylinder can be stored for more than 12 months under the normal-temperature sealing condition; the brightener is added into the composition, so that the surface of the gold-plated layer is more fine and smooth, the gaps are reduced, and the surface gloss of the gold-plated layer is better; the dispersant is added into the composition, so that the plating solution has good stability and dispersibility, good uniformity, high cathode current efficiency, good welding performance of the plating layer, good corrosion resistance and good binding force.

The gold plating solution can replace an ideal substitute for cyanide gold plating, meet the requirement of environment-friendly electroplating, widely meet the requirement of electronic communication industry on gold plating of components, and be applied to gold plating of the surfaces of copper, nickel and silver substrates, gold plating of ceramic ornaments and spectacle frame materials, and gold plating by using sulfite, wherein the plating layer is bright and delicate and is firmly combined.

Drawings

FIG. 1 is an atomic force microscope image of a gold coating obtained from a composition of the present invention;

FIG. 2 is a scan of a control workpiece.

Detailed Description

A sulfite gold plating composition comprising:

gold salt sulfite 10 g/L;

main complexing agent anhydrous sodium sulfite (chemical pure): ammonium sulfite with the mass ratio of 5:1 and 80 g/L;

dipotassium hydrogen phosphate (chemically pure) as a second complexing agent: potassium citrate (chemical purity), the mass ratio is 2.4:1, 15 g/L; current stabilizer organic aldehydes: alcohol ethers, selected from furfural: cyclohexanediol monomethyl ether in a mass ratio of 1:1, 2 g/L;

pH buffer boric acid-borax buffer solution with the mass ratio of 6.6:1, 0.2M borate, 40 g/L;

0.06-0.1g/L of antioxidant triammonium citrate;

1-3g/L of dispersion refiner polyoxyethylene fatty alcohol ether;

masking agent EDTA-2 Na: triethanolamine (chemically pure), with the mass ratio of 3:1, 20-30 g/L;

brightener beta-naphthol ethoxylate, 0.5-1.5 g/L.

Electroplating with the electroplating solution, wherein the engineering operation process parameters

The temperature is 55 ℃;

the pH value is 8.0;

the deposition rate is 120 mg/A.min;

the anode-cathode ratio is 2: 1;

the plating solution is filtered and stirred for 5 times per hour, and the filter element has a filter pore diameter of 1 mu m.

Firstly, the method comprises the following steps: the above process is adopted for electroplating to obtain an experimental group workpiece as an experimental group, in addition, the same electroplating is carried out by adopting the same method by adopting a commercial cyanide-free gold plating solution (gold trichloride), except that the plating solutions are different, other parameters are the same, a control group workpiece is obtained, and the following experimental verification is carried out on the two workpieces:

(1) the surface topography of the electroplated control group workpiece and the electroplated experimental group workpiece are respectively observed, and the naked eyes can see that compared with the control group workpiece, the surface of the gold layer of the experimental group workpiece is more detailed, smoother and more uniform, and the gold plating layer on the surface of the control group workpiece is rougher.

(2) And then, carrying out microscopic morphology observation on the surfaces of the control group workpiece and the experimental workpiece, wherein the equipment comprises the following steps: brook AFM test, scan range: 50um, scanning frequency: 0.8HZ pixel: 256 × 256, fig. 1 is a scan of the experimental group of workpieces, and fig. 2 is a scan of the control group of workpieces.

As can be seen from FIG. 1, the gold plating layer obtained by the composition of the present invention has a granular shape under an atomic force microscope, uniform grain size distribution, good crystalline state, flat grain, planar whole surface and layered gold layer.

As can be seen from FIG. 2, the gold plating layer obtained by using the commercial cyanide-free gold plating solution (gold trichloride) does not form obvious small round crystal grain particles on the surface of the gold plating layer under an atomic force microscope, the whole gold crystal grains are adhered and covered on the bottom plate, the height difference is generated, and the gold is columnar crystal and has obvious difference with an adverse gold surface.

Secondly, the method comprises the following steps: the liquid medicine is verified by storage test

The gold plating solution in the embodiment is placed in a beaker, the preservative film covers impurities such as dust and the like, but the impurities do not isolate air and are not completely sealed, a stirrer is placed for stirring, the gold plating solution is placed in a room temperature environment, direct strong light is avoided, and the change condition of the gold plating solution is observed every day. The appearance color of the gold plating solution changes after standing for 20 days, and the gold plating solution has no obvious color change after standing for 20 days, is transparent and colorless, has no precipitate or solid suspended matter in the solution, and is clear.

After a commercially available gold plating solution (gold trichloride) is left standing for 20 days, the solution turns yellow, and a brownish yellow precipitate is generated in the solution. Because the oxidation resistance of the commercial gold plating solution (gold trichloride) is low, the initial sodium sulfite concentration is high (about 120g/L), the sodium sulfite is oxidized by air into sodium sulfate after being placed for a period of time, the complexing ability is lost, and the gold in the solution is separated out.

Compared with the prior art, the gold plating solution and the workpiece provided by the invention have the advantages that the performance and the effect are compared, the gold plating solution has better stability, can be stored for a longer time, and the bonding force test of the plating layer of the workpiece is better than that of the plating layer of the workpiece sold on the market.

The combined comparison of the two is shown in the following table:

Claims (3)

1. the gold sodium sulfite plating solution is characterized by comprising

8-15g/L of gold sulfite;

80-130g/L of complexing agent;

1-5g/L of current stabilizer;

pH buffer 30-50 g/L;

0.06-0.1g/L of antioxidant;

1-3g/L of dispersion refiner;

20-30g/L of masking agent;

the complexing agent comprises 70-100g/L of main complexing agent and 10-30g/L of second complexing agent;

the main complexing agent comprises anhydrous sodium sulfite and ammonium sulfite with the mass ratio of 5: 1;

the second complexing agent comprises dipotassium hydrogen phosphate and potassium citrate with the mass ratio of (2.0-2.5) to 1;

the current stabilizer comprises an organic aldehyde substance and alcohol ether with the mass ratio of 1: 1;

the antioxidant is triammonium citrate;

the masking agent is EDTA-2Na and triethanolamine in a mass ratio of 3: 1;

the dispersion refiner is polyoxyethylene fatty alcohol ether.

2. The gold sodium sulfite bath of claim 1 further comprising 0.5 to 1.5g/L of a brightener.

3. The electroplating method of the gold sodium sulfite solution as recited in any one of claims 1 to 2, wherein the electroplating is carried out by using the following technical parameters:

the temperature is 50-60 ℃;

the pH value is 7.8-8.5;

the deposition rate is 80-150 mg/A.min;

the quantity ratio of the anode to the cathode is more than or equal to 1: 1;

the plating solution is filtered and stirred for 4 to 6 times per hour, and the filtering aperture is less than or equal to 1.5 mu m by using a filter element.

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