Cyanide-free silver plating solution, preparation method thereof and silver plating method

Abstract

The present application relates to the technical field of electroplating, in particular to a cyanide-free silver plating solution, a preparation method thereof and a silver plating method. The cyanide-free silver plating solution comprises the following components in terms of mass concentration: silver ions 10-25 g / L, potassium sulfamate 80-170 g / L, potassium pyrosulfite 30-70 g / L, imidazole propoxy condensate 0.1-1 g / L and p-anisaldehyde 0.05-0.5 g / L. The cyanide-free silver plating solution does not appear to replace the silver layer on the surface of the substrate without electricity, ensuring that the quality of the plating layer is excellent and has a high bonding force with the substrate. The cyanide-free silver plating solution has good stability and is not prone to produce precipitation during long-term use. The cyanide-free silver plating solution has a large cathode polarization effect during the electroplating process, making the silver plating layer crystallize more densely, the plating layer has high hardness, good wear resistance and low contact resistance. In addition, the cyanide-free silver plating solution does not contain cyanide, which is green, safe and environmentally friendly.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electroplating, in particular to a cyanide-free silver plating solution, a preparation method thereof and a silver plating method. BACKGROUND

[0002] The silver plating layer is widely used in the high-voltage electrical field due to its good electrical conductivity and low contact resistance. The traditional silver plating uses cyanide, which is harmful to health and the cyanide plating solution is difficult to recycle after use. Therefore, it is of great significance to develop a cyanide-free silver plating process to replace the cyanide silver plating.

[0003] In recent years, the cyanide-free silver plating process has been gradually reported. However, the existing various cyanide-free silver plating processes have the following problems: first, the silver plating layer obtained by the cyanide-free silver plating process has poor crystallinity, uneven appearance, poor adhesion and poor wear resistance, and there is a certain gap with the cyanide silver plating layer. Second, the cyanide-free silver plating solution system has complex components, the complexing agent and Ag + form unstable complex ions, and the plating solution is prone to precipitation during long-term use, and the plating solution is prone to be scrapped due to the mixing of impurity metal ions. Third, the cyanide-free silver plating process that has been actually applied has a small production scale (no more than 10,000 liters), non-standard operation and maintenance, unstable plating solution performance, unreliable silver plating quality, and is difficult to realize large-scale popularization and application. Fourth, the current silver plating process has a narrow current density range, a slow electrodeposition speed and insufficient metal luster of the plating layer.

[0004] Therefore, the present application is proposed. SUMMARY

[0005] The first object of the present application is to provide a cyanide-free silver plating solution, which does not form a replacement silver layer on the surface of the substrate without electricity, ensures excellent quality of the plating layer and high adhesion with the substrate, has good stability and is not prone to precipitation during long-term use, has a large cathode polarization effect during the electroplating process, makes the silver plating layer more dense, has high hardness, good wear resistance and low contact resistance, and does not contain cyanide, which is green, safe and environmentally friendly.

[0006] The second object of the present application is to provide a preparation method of the cyanide-free silver plating solution.

[0007] The third object of the present application is to provide a silver plating method.

[0008] In order to achieve the above objects of the present application, the following technical solutions are adopted:

[0009] The present application provides a cyanide-free silver plating solution, which comprises the following components in terms of mass concentration:

[0010] Silver ions 10-25 g / L, potassium sulfamate 80-170 g / L, potassium pyrosulfite 30-70 g / L, imidazole propoxy condensate 0.1-1 g / L and p-anisaldehyde 0.05-0.5 g / L.

[0011] Preferably, the cyanide-free silver plating solution comprises the following components in terms of mass concentration: silver ions 12-20 g / L, potassium sulfamate 100-150 g / L, potassium pyrosulfite 40-60 g / L, imidazole propoxy condensate 0.5-0.8 g / L and p-anisaldehyde 0.1-0.2 g / L.

[0012] Preferably, the silver ions are mainly provided by silver nitrate.

[0013] The application also provides a preparation method of the cyanide-free silver plating solution as described above, comprising the following steps:

[0014] After the silver source, potassium sulfamate, potassium pyrosulfite, imidazole propoxy condensate, p-anisaldehyde and solvent are uniformly mixed, the cyanide-free silver plating solution is obtained.

[0015] Preferably, the silver source comprises silver nitrate.

[0016] Preferably, the preparation method of the cyanide-free silver plating solution specifically comprises the following steps:

[0017] (a) dissolving the silver source in water to obtain a silver-containing solution; uniformly mixing the potassium sulfamate, the potassium pyrosulfite and the water to obtain a mixed solution; dissolving the imidazole propoxy condensate in the water to obtain an imidazole propoxy condensate solution; dissolving the p-anisaldehyde in ethanol to obtain a p-anisaldehyde solution;

[0018] (b) adding the silver-containing solution into the mixed solution, uniformly mixing, then sequentially adding the imidazole propoxy condensate solution and the p-anisaldehyde solution into the mixed solution, and then uniformly mixing to obtain the cyanide-free silver plating solution.

[0019] The application also provides a silver plating method using the cyanide-free silver plating solution as described above.

[0020] Preferably, the silver plating method specifically comprises the following steps:

[0021] After the cyanide-free silver plating solution is uniformly mixed with water to obtain a dilution solution, a substrate is immersed in the dilution solution for electroplating;

[0022] Preferably, the volume ratio of the cyanide-free silver plating solution to the water is 4-6:4-6.

[0023] Preferably, the pH of the dilution solution is 9-10.

[0024] Preferably, the temperature of the diluent is 30-40 DEG C during the electroplating process.

[0025] Preferably, the current density of the electroplating is 0.3-0.8 A / dm 2 .

[0026] Preferably, the substrate comprises at least one of copper and its alloys, aluminum and its alloys, and iron and its alloys.

[0027] Compared with the prior art, the present application has the following advantages:

[0028] (1) The cyanide-free silver plating solution provided by the present application does not form a replacement silver layer on the surface of the substrate without electricity, ensuring excellent plating layer quality and high adhesion to the substrate.

[0029] (2) The cyanide-free silver plating solution provided by the present application has good electrochemical stability and does not undergo electrochemical reactions, thus preventing the decline of plating solution performance due to the stability of the complexing agent and ensuring long-term stability of the cyanide-free silver plating solution.

[0030] (3) The cyanide-free silver plating solution provided by the present application has a large cathode polarization effect during the electroplating process, thus making the silver plating layer more compact, high in hardness, good in wear resistance, and low in contact resistance.

[0031] (4) The cyanide-free silver plating solution provided by the present application does not contain cyanide, which can avoid the harm of cyanide, is environmentally friendly, and reduces production costs.

[0032] (5) The silver plating method provided by the present application has the advantages of good wear resistance, high adhesion, and low contact resistance of the obtained silver plating layer, and the plating layer has good appearance quality and is basically semi-bright, with a significantly improved upper limit of current density. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed in the specific embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0034] Figure 1 The cyclic voltammogram of the complexing agent solution corresponding to Example 1 provided by the present application;

[0035] Figure 2 The cyclic voltammogram of the complexing agent solution corresponding to Comparative Example 5 provided by the present application;

[0036] Figure 3Cyclic voltammogram of the cyanide-free silver plating solution prepared for 2 years according to the present application;

[0037] Figure 4 Cyclic voltammogram of the cyanide-free silver plating solution prepared for 1 month according to the present application;

[0038] Figure 5 Cyclic voltammogram of the newly prepared cyanide-free silver plating solution according to the present application;

[0039] Figure 6 Cyclic voltammogram of the cyanide-free silver plating solution prepared for different preparation times according to the present application;

[0040] Figure 7 SEM image of the cross section of the silver plating layer and the substrate junction according to the present application;

[0041] Figure 8 Physical image of the contact operated for 0 times according to the present application;

[0042] Figure 9 Physical image of the contact operated for 200 times according to the present application;

[0043] Figure 10 Physical image of the contact operated for 500 times according to the present application;

[0044] Figure 11 Physical image of the contact operated for 1500 times according to the present application;

[0045] Figure 12 Physical image of the contact operated for 3000 times according to the present application. DETAILED DESCRIPTION

[0046] The technical solutions of the present application will be described clearly and completely in the following with reference to the drawings and specific embodiments, but those skilled in the art will understand that the following described embodiments are part of the embodiments of the present application, not all the embodiments, and are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present application. The specific conditions not mentioned in the embodiments are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments not mentioned by the manufacturer are all conventional products that can be purchased on the market.

[0047] In a first aspect, the present application provides a cyanide-free silver plating solution, comprising the following components in terms of mass concentration:

[0048] Silver ions 10-25 g / L, potassium sulfamate 80-170 g / L, potassium pyrosulfite 30-70 g / L, imidazole propoxy condensate 0.1-1 g / L and p-anisaldehyde 0.05-0.5 g / L.

[0049] The cyanide-free silver plating solution further comprises a solvent, and the solvent comprises water and / or an organic solvent. Preferably, the water comprises pure water. The organic solvent comprises ethanol. The water-soluble components in the cyanide-free silver plating solution exist in the form of ions.

[0050] That is, the cyanide-free silver plating solution comprises the following components in terms of mass concentration: silver ions 10-25 g / L, potassium sulfamate 80-170 g / L, potassium pyrosulfite 30-70 g / L, imidazole propoxy condensate 0.1-1 g / L, p-anisaldehyde 0.05-0.5 g / L and a solvent.

[0051] The mass concentration of a component refers to the mass of the component in a unit volume of the mixture.

[0052] That is, the cyanide-free silver plating solution comprises silver ions 10-25 g, potassium sulfamate 80-170 g, potassium pyrosulfite 30-70 g, imidazole propoxy condensate 0.1-1 g and p-anisaldehyde 0.05-0.5 g per 1 L of the cyanide-free silver plating solution, and the rest is a solvent.

[0053] The cyanide-free silver plating solution provided by the application has high wear resistance, high adhesion and low contact resistance. The cyanide-free silver plating solution not only has excellent performance and good stability, but also meets the technical requirements of high-voltage electrical products. The cyanide-free silver plating solution solves the problem that the traditional silver plating process needs to use cyanide, which does not meet the environmental protection requirements and is prone to safety accidents, and can be used for harmless electroplating processing.

[0054] Specifically, the cyanide-free silver plating solution provided by the application has a specific composition and dosage, and will not appear a replacement silver layer on the surface of the substrate without power supply, which ensures that the plating layer has excellent quality and high adhesion to the substrate.

[0055] The cyanide-free silver plating solution has good electrochemical stability and will not cause electrochemical reaction. The stability of the complexing agent will not cause the performance of the plating solution to decrease, which ensures that the cyanide-free silver plating solution remains stable for a long time and will not deteriorate.

[0056] In addition, the cyanide-free silver plating solution provided by the application has a specific composition, has a large cathode polarization effect during electroplating, and thus makes the silver plating layer more dense, has high hardness, good wear resistance and low contact resistance.

[0057] In addition, the cyanide-free silver plating solution provided by the application does not contain cyanide, which can avoid the harm of cyanide, reduce production cost, and is beneficial to the health of the operators and green and environmentally friendly.

[0058] More specifically, the potassium sulfamate in the cyanide-free silver plating solution serves as a main complexing agent to generate complex ions with silver ions, stabilizing the silver plating solution, improving cathode polarization, and making the silver plating layer fine and uniform. The potassium pyrosulfite serves as an auxiliary complexing agent to expand the range of the silver plating cathode current, reduce the brittleness of the silver plating layer, and improve the flexibility of the silver plating layer. The imidazole propoxy condensate functions as a main brightener to increase the brightness of the silver plating layer within the range of the silver plating current density. The p-anisaldehyde functions as a wetting agent to improve the brightness in the low current density area.

[0059] In some specific embodiments of the present application, the mass concentration of the silver ions includes but is not limited to any one of 12 g / L, 14 g / L, 15 g / L, 17 g / L, 19 g / L, 20 g / L, 22 g / L, 24 g / L, or a range value between any two of them; the mass concentration of the potassium sulfamate includes but is not limited to any one of 90 g / L, 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L, 150 g / L, 160 g / L, or a range value between any two of them; the mass concentration of the potassium pyrosulfite includes but is not limited to any one of 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L, 60 g / L, 65 g / L, or a range value between any two of them; the mass concentration of the imidazole propoxy condensate includes but is not limited to any one of 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, 0.6 g / L, 0.7 g / L, 0.8 g / L, 0.9 g / L, or a range value between any two of them; and the mass concentration of the p-anisaldehyde includes but is not limited to any one of 0.07 g / L, 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.45 g / L, or a range value between any two of them.

[0060] The imidazole propoxy condensate has the molecular formula C6H9ClN2O, is also known as imidazole and epichlorohydrin compound, and imidazole propoxy compound, and is a yellowish to yellow viscous liquid.

[0061] The p-anisaldehyde is also known as 4-methoxybenzaldehyde, p-methoxybenzaldehyde, and anisic aldehyde, and is a colorless to yellowish transparent liquid with a strong aniseed and hawthorn aroma.

[0062] To further comprehensively consider the wear resistance, adhesion, and contact resistance of the silver plating layer, the amounts of the components are optimized. Preferably, the cyanide-free silver plating solution includes the following components in terms of mass concentration: silver ions 12-20 g / L, potassium sulfamate 100-150 g / L, potassium pyrosulfite 40-60 g / L, imidazole propoxy condensate 0.5-0.8 g / L, and p-anisaldehyde 0.1-0.2 g / L.

[0063] Preferably, the silver ions are mainly provided by silver nitrate. Silver nitrate dissolves in the form of silver ions after mixing with solvent (water).

[0064] In a second aspect, the present application provides a preparation method of the cyanide-free silver plating solution as described above, comprising the following steps:

[0065] The silver source, potassium sulfamate, potassium pyrosulfite, imidazole propoxy condensate, p-anisaldehyde and solvent are mixed uniformly to obtain the cyanide-free silver plating solution.

[0066] The solvent comprises water and ethanol.

[0067] The preparation method has the advantages of simple operation, mild conditions, short process flow and suitability for mass production; and no cyanide is generated in the preparation process, which is green, environmentally friendly and safer.

[0068] In addition, the cyanide-free silver plating solution prepared by the preparation method has a silver plating layer with good wear resistance, high adhesion and low contact resistance.

[0069] Preferably, the silver source comprises silver nitrate.

[0070] Preferably, the preparation method of the cyanide-free silver plating solution specifically comprises the following steps:

[0071] (a) dissolving the silver source in water to obtain a silver-containing solution; mixing the potassium sulfamate, the potassium pyrosulfite and the water uniformly to obtain a mixed solution; dissolving the imidazole propoxy condensate in the water to obtain an imidazole propoxy condensate solution; and dissolving the p-anisaldehyde in ethanol to obtain a p-anisaldehyde solution;

[0072] (b) adding the silver-containing solution into the mixed solution, uniformly mixing, then sequentially adding the imidazole propoxy condensate solution and the p-anisaldehyde solution into the mixed solution, and uniformly mixing to obtain the cyanide-free silver plating solution.

[0073] In some specific embodiments of the present application, the temperature of the mixing in step (a) and / or step (b) is 10-30°C, preferably room temperature.

[0074] In some specific embodiments of the present application, the mixing time in step (a) and / or step (b) can be any conventional time, preferably until the solution is clear.

[0075] In a third aspect, the present application provides a silver plating method using the cyanide-free silver plating solution as described above.

[0076] The silver plating layer obtained after the silver plating using the cyanide-free silver plating solution has good wear resistance, high adhesion and low contact resistance, and the cyanide-free silver plating solution can be used for a long time and is not easy to deteriorate.

[0077] In addition, the appearance quality of the silver plating layer obtained after the silver plating using the cyanide-free silver plating solution is obviously improved, the silver plating layer is basically semi-bright, and the upper limit of the current density is obviously improved.

[0078] Preferably, the silver plating method specifically comprises the following steps:

[0079] After the cyanide-free silver plating solution is uniformly mixed with water to obtain a dilute solution, the substrate is immersed in the dilute solution for electroplating.

[0080] Preferably, the volume ratio of the cyanide-free silver plating solution to the water is 4-6:4-6; including but not limited to any one of 4:6, 4.5:5.5, 5:5, 5.5:4.5, 6:4 or a range value between any two of them.

[0081] Preferably, the pH of the dilute solution is 9-10, including but not limited to any one of 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9 or a range value between any two of them.

[0082] Preferably, during the electroplating, the temperature of the dilute solution is 30-40℃; including but not limited to any one of 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, 39℃ or a range value between any two of them.

[0083] Preferably, the current density of the electroplating is 0.3-0.8A / dm 2 ; including but not limited to any one of 0.4A / dm 2 , 0.5A / dm 2 , 0.6A / dm 2 , 0.7A / dm 2 or a range value between any two of them.

[0084] The above parameters (including the dilution ratio of the cyanide-free silver plating solution and water, the pH of the dilute solution, the temperature and the current density of the electroplating) are conducive to further improving the wear resistance and adhesion of the silver plating layer and reducing the contact resistance.

[0085] Preferably, the substrate comprises at least one of copper and its alloy, aluminum and its alloy, and iron and its alloy.

[0086] The cyanide-free silver plating solution provided by the present application is suitable for plating silver on the surface of metal materials such as copper material (including metal copper or copper alloy), aluminum material (including metal aluminum or aluminum alloy, such as high-silicon aluminum alloy), iron material (including metal iron or iron alloy, such as stainless steel and ordinary carbon steel), and the like, and can obtain a plating layer with good performance, which can meet the technical requirements of high-voltage electrical products.

[0087] In some specific embodiments of the present application, the electroplating is carried out by taking the plating piece (substrate) as the cathode and a silver plate as the anode, and the area ratio of the cathode to the anode is 1:2.

[0088] The embodiments of the present application will be described in detail below with reference to examples, but those skilled in the art will understand that the following examples are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. If the specific conditions are not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the manufacturer of the reagent or instrument is not specified, it is a conventional product that can be obtained by purchase.

[0089] Example 1

[0090] The cyanide-free silver plating solution provided by the present application includes the following components in terms of mass concentration: silver ions 16 g / L, potassium sulfamate 125 g / L, potassium pyrosulfite 50 g / L, imidazole propoxy condensate 0.6 g / L, p-anisaldehyde 0.15 g / L, ethanol and water. Among them, the silver ions are provided by silver nitrate.

[0091] The preparation method of the cyanide-free silver plating solution provided by the present application includes the following steps:

[0092] (1) Dissolve silver nitrate in water at room temperature, and stir until the silver nitrate is completely dissolved to obtain a silver-containing solution.

[0093] Mix potassium sulfamate, potassium pyrosulfite and water, and stir until the mixture is clear to obtain a mixed solution.

[0094] Dissolve imidazole propoxy condensate in water, and stir until it is completely dissolved to obtain an imidazole propoxy condensate solution.

[0095] Dissolve p-anisaldehyde in ethanol, and stir until it is completely dissolved to obtain a p-anisaldehyde solution. Among them, the volume ratio of anisaldehyde to ethanol is 1:30.

[0096] (2) At room temperature, add the silver-containing solution to the mixed solution, stir until they are uniformly mixed, then sequentially add the imidazole propoxy condensate solution and the p-anisaldehyde solution, and stir again until they are uniformly mixed to obtain the cyanide-free silver plating solution.

[0097] The silver plating method provided in the embodiment comprises the following steps: mixing the cyanide-free silver plating solution prepared in the above embodiment with water to obtain a diluted solution, and then immersing a substrate into the diluted solution to perform electroplating, so as to obtain a silver plating layer. The volume ratio of the cyanide-free silver plating solution to water is 5:5. The pH of the diluted solution is 9.5. The temperature of the diluted solution during the electroplating process is 35°C. The current density of the electroplating is 0.5 A / dm 2 The substrate is a high-silicon aluminum alloy casting. The area ratio of the cathode (the high-silicon aluminum alloy casting) to the anode (a silver plate) is 1:2.

[0098] Embodiment 2

[0099] The cyanide-free silver plating solution provided in the embodiment comprises the following components in terms of mass concentration: silver ions 12 g / L, potassium sulfamate 100 g / L, potassium pyrosulfite 40 g / L, imidazole propoxy condensate 0.5 g / L, p-anisaldehyde 0.1 g / L, ethanol and water. The silver ions are provided by silver nitrate.

[0100] The preparation method of the cyanide-free silver plating solution provided in the embodiment is the same as that in Embodiment 1.

[0101] The silver plating method provided in the embodiment comprises the following steps: mixing the cyanide-free silver plating solution prepared in the above embodiment with water to obtain a diluted solution, and then immersing a substrate into the diluted solution to perform electroplating, so as to obtain a silver plating layer. The volume ratio of the cyanide-free silver plating solution to water is 4.5:5.5. The pH of the diluted solution is 9.5. The temperature of the diluted solution during the electroplating process is 30°C. The current density of the electroplating is 0.8 A / dm 2 The substrate is a high-silicon aluminum alloy casting. The area ratio of the cathode (the high-silicon aluminum alloy casting) to the anode (a silver plate) is 1:2.

[0102] Embodiment 3

[0103] The cyanide-free silver plating solution provided in the embodiment comprises the following components in terms of mass concentration: silver ions 20 g / L, potassium sulfamate 150 g / L, potassium pyrosulfite 60 g / L, imidazole propoxy condensate 0.8 g / L, p-anisaldehyde 0.2 g / L, ethanol and water. The silver ions are provided by silver nitrate.

[0104] The preparation method of the cyanide-free silver plating solution provided in the embodiment is the same as that in Embodiment 1.

[0105] The silver plating method provided in the embodiment comprises the following steps: mixing the cyanide-free silver plating solution prepared in the above embodiment with water to obtain a diluted solution, and then immersing a substrate into the diluted solution to perform electroplating, so as to obtain a silver plating layer. The volume ratio of the cyanide-free silver plating solution to water is 5.5:4.5. The pH of the diluted solution is 9.5. The temperature of the diluted solution during the electroplating process is 40°C. The current density of the electroplating is 0.3 A / dm 2The substrate is a high-silicon aluminum alloy casting. The area ratio of the cathode (high-silicon aluminum alloy casting) to the anode (silver plate) is 1:2.

[0106] Example 4

[0107] The cyanide-free silver plating solution provided in this example includes the following components in terms of mass concentration: silver ions 10 g / L, potassium sulfamate 80 g / L, potassium pyrosulfite 30 g / L, imidazole propoxy condensate 0.1 g / L, p-anisaldehyde 0.5 g / L, ethanol and water. The silver ions are provided by silver nitrate.

[0108] The preparation method of the cyanide-free silver plating solution provided in this example is the same as that in Example 1.

[0109] The silver plating method provided in this example is basically the same as that in Example 1, except that the cyanide-free silver plating solution in Example 1 is replaced by the cyanide-free silver plating solution prepared in this example 4.

[0110] Example 5

[0111] The cyanide-free silver plating solution provided in this example includes the following components in terms of mass concentration: silver ions 25 g / L, potassium sulfamate 170 g / L, potassium pyrosulfite 70 g / L, imidazole propoxy condensate 1 g / L, p-anisaldehyde 0.05 g / L, ethanol and water. The silver ions are provided by silver nitrate.

[0112] The preparation method of the cyanide-free silver plating solution provided in this example is the same as that in Example 1.

[0113] The silver plating method provided in this example is basically the same as that in Example 1, except that the cyanide-free silver plating solution in Example 1 is replaced by the cyanide-free silver plating solution prepared in this example 5.

[0114] Comparative Example 1

[0115] The composition of the cyanide-free silver plating solution provided in this comparative example and its preparation method are basically the same as those in Example 1, except that no potassium sulfamate is added in the raw material composition and preparation process.

[0116] The silver plating method provided in this comparative example is basically the same as that in Example 1, except that the cyanide-free silver plating solution in Example 1 is replaced by the cyanide-free silver plating solution prepared in this comparative example 1.

[0117] Comparative Example 2

[0118] The composition of the cyanide-free silver plating solution provided in this comparative example and its preparation method are basically the same as those in Example 1, except that no potassium pyrosulfite is added in the raw material composition and preparation process.

[0119] The silver plating method provided by the present comparative example is basically the same as that of Example 1, except that the cyanide-free silver plating solution in Example 1 is replaced by the cyanide-free silver plating solution prepared in Comparative Example 2.

[0120] Comparative Example 3

[0121] The composition of the cyanide-free silver plating solution provided by the present comparative example and the method for preparing the same are basically the same as those of Example 1, except that the imidazole propoxy condensate is not added in the raw material composition and the preparation process.

[0122] The silver plating method provided by the present comparative example is basically the same as that of Example 1, except that the cyanide-free silver plating solution in Example 1 is replaced by the cyanide-free silver plating solution prepared in Comparative Example 3.

[0123] Comparative Example 4

[0124] The composition of the cyanide-free silver plating solution provided by the present comparative example and the method for preparing the same are basically the same as those of Example 1, except that the p-anisaldehyde is not added in the raw material composition and the preparation process.

[0125] The silver plating method provided by the present comparative example is basically the same as that of Example 1, except that the cyanide-free silver plating solution in Example 1 is replaced by the cyanide-free silver plating solution prepared in Comparative Example 4.

[0126] Comparative Example 5

[0127] The commercially available cyanide-free silver plating solution is Ag50, produced by Electrochem, USA.

[0128] Comparative Example 6

[0129] The commercially available cyanide-containing silver plating solution is produced by Anmet.

[0130] Experimental Example 1

[0131] The stability of the silver plating solutions prepared in each of the above examples and comparative examples is detected by copper coupon replacement test method, and the results are shown in Table 1.

[0132] The method for detecting the stability of each group of silver plating solutions by copper coupon replacement test includes: placing copper coupons into each group of prepared silver plating solutions, observing and recording the surface changes of each group of copper coupons under the condition of sufficient stirring. When white deposits appear on the surface of the copper coupons, it is proved that the plating solution cannot withstand the copper replacement test, and the replacement time is recorded.

[0133] Table 1 Stability results of silver plating solutions prepared in each group

[0134] Group Tolerable replacement time (min) Whether the copper test piece changes Example 1 20 No change Example 2 20 No change Example 3 20 No change Example 4 18 White attachments appear Example 5 15 White attachments appear Comparative Example 1 3 White attachments appear Comparative Example 2 2 White attachments appear Comparative Example 3 12 White attachments appear Comparative Example 4 10 White attachments appear Comparative Example 5 4 Silver is replaced Comparative Example 6 Instantaneous Silver is replaced

[0135] As can be seen from Table 1, the silver plating solution prepared by each embodiment of the present application has better stability, and the silver plating solution can resist copper displacement reaction for a longer time. This shows that the complex formed by the complexing agent provided by the present application has better binding strength with the silver ions. In this way, it can be ensured that there is greater cathode polarization in the electroplating process, and the displacement silver layer will not appear on the surface of the substrate without electricity, thereby ensuring that the plating layer has excellent quality and has higher binding force with the substrate. +

[0136] Further, the complexing agent forms a complex with the Ag + ions, and the complexing agent needs to undergo a large range of potential changes in the electroplating process. The complexing agent needs to maintain its electrochemical stability in a large potential range, i.e., it is necessary to ensure that the complexing agent will not undergo redox reaction in the working potential range, so as to ensure the stability of the plating solution. In order to explore the electrochemical window of the complexing agent and check whether the complexing agent will undergo electrochemical reaction in the electroplating process, the electrochemical window of the complexing agent solution of Example 1 without silver ions (i.e., the components of Example 1 without adding silver ions) and the complexing agent solution of Comparative Example 5 without silver ions (i.e., the components of Comparative Example 5 without adding silver ions) were tested by cyclic voltammetry (the pH values of the complexing agent solutions of Example 1 and Comparative Example 5 are the same), and the results are shown in Figure 1 and Figure 2

[0137] The test conditions of the cyclic voltammetry are as follows: a 3mm glassy carbon electrode (GCE) is used as a working electrode, a mercury oxide electrode (Hg / HgO) is used as a reference electrode, a platinum plate (Pt) is used as a counter electrode, the scanning speed is 10mV / s, and the test temperature is 40℃.

[0138] As can be seen from Figure 1 and Figure 2 , the electrochemical window of the complexing system of Comparative Example 5 is-1.25V-0.9V, the electrochemical window of the complexing system of Example 1 is-1.3V-1.0V, the oxygen evolution potential of the complexing agent solution of Example 1 is higher than that of the complexing agent solution of Comparative Example 5, and the hydrogen evolution potential of the complexing agent solution of Example 1 is lower than that of the complexing agent of Comparative Example 5. It can be seen that the electrochemical stability of the complexing agent solution of Example 1 is better than that of the complexing agent of Comparative Example 5. In the electroplating process, the complexing agent of Example 1 can better ensure its electrochemical stability, and will not undergo electrochemical reaction, so as to prevent the performance of the plating solution from being reduced due to the stability problem of the complexing agent.

[0139] ​​Further, the stability of the cyanide-free silver plating solution prepared at different preparation times was investigated. In addition to the replacement time, the change of the plating solution after being placed or used for a period of time was also observed to evaluate the stability of the cyanide-free silver plating solution. The CV curves (cyclic voltammograms) of the cyanide-free silver plating solutions prepared at different preparation times (2 years, 1 month and newly prepared, respectively) were tested to determine the stability of the cyanide-free silver plating solution. The chemical compositions of the cyanide-free silver plating solutions prepared at different preparation times in each group were the same as those in Example 1.

[0140] The cyclic voltammogram of the cyanide-free silver plating solution prepared for 2 years is shown in FIG. 4. Figure 3 The cyclic voltammogram of the cyanide-free silver plating solution prepared for 1 month is shown in FIG. 5. Figure 4 The cyclic voltammogram of the newly prepared cyanide-free silver plating solution is shown in FIG. 6. Figure 5 The comparative graph of the cyclic voltammograms of the cyanide-free silver plating solutions prepared at different preparation times is shown in FIG. 7. Figure 6

[0141] As can be seen from FIG. 4, the electrochemical window of the cyanide-free silver plating solution prepared for 2 years is -0.75 V to 0.9 V. Figures 3 to 5 As can be seen from FIG. 5, the electrochemical window of the cyanide-free silver plating solution prepared for 1 month is -0.85 V to 1.0 V. Figure 6 As can be seen from FIG. 6, the electrochemical window of the newly prepared cyanide-free silver plating solution is -0.75 V to 1.0 V.

[0142] Experimental Example 2

[0143] The hardness (Vickers hardness HV0.1 of the cross section of the silver plating layer) of the silver plating layer obtained in each of the above examples and comparative examples was detected by a micro Vickers hardness tester, and the results are shown in Table 2 below.

[0144] Table 2: Hardness results of the silver plating layer of each group

[0145] Group Vickers hardness (HV) High-voltage electrical technology requirements (≥ 120 HV) Example 1 122 Compliant Example 2 121 Compliant Example 3 121 Compliant Example 4 120 Compliant Example 5 121 Compliant Comparative Example 1 93 Not compliant Comparative Example 2 97 Not compliant Comparative Example 3 93 Not compliant Comparative Example 4 90 Not compliant Comparative Example 5 96 Not compliant Comparative Example 6 98 Not compliant

[0146] As can be seen from Table 2, the silver plating layer obtained by the present application has higher hardness.

[0147] Meanwhile, the microscopic morphology of the cross section of the silver plating layer and the substrate at the bonding site was observed by a scanning electron microscope (SEM), and the results are shown in FIG. 8. Figure 7

[0148] Experimental Example 3

[0149] ​​The wear resistance and circuit resistance of the silver plating layer obtained in Example 1 were detected, and the wear degree of the silver plating layer was observed by 3000 times of opening and closing operation of the moving and static contacts (the silver plating layer has a thickness of 30-40 μm) of the product circuit breaker arc-extinguishing chamber; and the contact resistance of the corresponding part was measured every certain number of operations to detect whether the circuit resistance value meets the technical requirements.

[0150] The test procedure was as follows: ① the moving and static contacts of the two-phase circuit breaker arc-extinguishing chamber were replaced; ② the resistance of the corresponding part was detected before the test; ③ the opening and closing time and speed were adjusted according to the technical requirements, and the chamber was vacuumized and then filled with air to 0.6 MPa; ④ the resistance of the corresponding part was measured every certain number of operations, and the wear of the silver plating part was observed.

[0151] The actual photographs of the contacts after 0 times, 200 times, 500 times, 1500 times and 3000 times of opening and closing operation are shown in Figure 8 , Figure 9 , Figure 10 , Figure 11 and Figure 12 , respectively. Figure 8 It can be seen that the contacts are in the non-worn state, and from Figures 9 to 12 it can be seen that the wear is uniform and the surface morphology is good.

[0152] Meanwhile, the detection results of the circuit resistance value are shown in Table 3.

[0153] Table 3 Detection results of the circuit resistance value (unit: μΩ)

[0154] Operation times 0 times 200 times 500 times 1500 times 3000 times Moving contact A - moving contact B 6 7 10 28 6 Moving contact A - pressure cylinder 1 4 1 9 4 Moving contact B - pressure cylinder 3 3 2 16 4 Whether qualified Qualified Qualified Qualified Qualified Qualified

[0155] From the above experimental results, it can be seen that the silver plating layer prepared from the cyanide-free silver plating solution has good wear resistance and low contact resistance.

[0156] Experimental Example 4

[0157] The bonding strength of the silver plating layer obtained in each of the above examples and each of the comparative examples was detected by thermal shock test and grinding test. Specifically, the cyanide-free silver plating solution, the preparation method and the silver plating method provided in each of the examples and each of the comparative examples were used to prepare 100 finger seats (each group has 100 finger seats) containing silver plating layers on high-silicon aluminum alloy castings-finger seats, and then the thermal shock test and the grinding test were performed on the finger seats containing silver plating layers in each group. The results are shown in Table 4.

[0158] In the thermal shock test, the test conditions were as follows: after being kept at 120℃ for 60 minutes, the finger seats were taken out and naturally cooled at room temperature, and the bubbling was observed.

[0159] The probe finger seat passed the thermal shock experiment is continuously used for grinding experiment, the edge of the steel wire wheel is used for grinding the silver plating layer, namely the position of the silver plating surface and the non-silver plating surface, the grinding direction is from the base metal to the cover layer, and whether the plating layer is peeled from the base body is observed.

[0160] Table 4: Thermal shock experiment results and grinding experiment results of silver plating layers of each group

[0161]

[0162]

[0163] It can be seen from Table 4 that the silver plating layer prepared by the method has better bonding strength.

[0164] Although the present application has been illustrated and described with reference to specific embodiments, it is realized that the above examples are merely used to illustrate the technical solutions of the present application, and are not intended to limit the present application; it should be understood by those skilled in the art that the technical solutions recorded in the above examples can be modified, or some or all of the technical features can be replaced equivalently without departing from the spirit and scope of the present application; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application; therefore, this means that all these replacements and modifications within the scope of the present application are included in the appended claims.

Claims

1. A cyanide-free silver plating solution, characterized in that, Including the following components as measured by mass concentration: Silver ions 10~25g / L, potassium aminosulfonate 80~170g / L, potassium metabisulfite 30~70g / L, imidazole propoxy condensate 0.1~1g / L and p-anisaldehyde 0.05~0.5g / L.

2. The cyanide-free silver plating solution according to claim 1, characterized in that, The cyanide-free silver plating solution comprises the following components by mass concentration: 12-20 g / L silver ions, 100-150 g / L potassium aminosulfonate, 40-60 g / L potassium metabisulfite, 0.5-0.8 g / L imidazole propoxy condensate, and 0.1-0.2 g / L p-anisaldehyde.

3. The cyanide-free silver plating solution according to claim 1, characterized in that, The silver ions are provided by silver nitrate.

4. The method for preparing the cyanide-free silver plating solution according to any one of claims 1 to 3, characterized in that, Includes the following steps: The silver source, potassium aminosulfonate, potassium metabisulfite, imidazole propoxy condensate, p-anisaldehyde and solvent are mixed evenly to obtain the cyanide-free silver plating solution.

5. The method for preparing the cyanide-free silver plating solution according to claim 4, characterized in that, The silver source includes silver nitrate.

6. The method for preparing the cyanide-free silver plating solution according to claim 4, characterized in that, The preparation method of the cyanide-free silver plating solution specifically includes the following steps: (a) The silver source is dissolved in water to obtain a silver-containing solution; the potassium aminosulfonate, the potassium metabisulfite, and water are mixed evenly to obtain a mixed solution; the imidazole propoxy condensate is dissolved in water to obtain an imidazole propoxy condensate solution; the p-anisaldehyde is dissolved in ethanol to obtain a p-anisaldehyde solution. (b) Add the silver-containing solution to the mixed solution, mix well, then add the imidazole propoxy condensate solution and the p-anisaldehyde solution in sequence, and mix well to obtain the cyanide-free silver plating solution.

7. A silver plating method, characterized in that, The cyanide-free silver plating solution described in any one of claims 1 to 3 is used.

8. The silver plating method according to claim 7, characterized in that, The silver plating method specifically includes the following steps: After the cyanide-free silver plating solution is mixed evenly with water to obtain a diluted solution, the substrate is immersed in the diluted solution for electroplating.

9. The silver plating method according to claim 8, characterized in that, The volume ratio of the cyanide-free silver plating solution to the water is 4~6:4~6.

10. The silver plating method according to claim 8, characterized in that, The pH of the diluent is 9-10.

11. The silver plating method according to claim 8, characterized in that, During the electroplating process, the temperature of the diluent is 30~40℃.

12. The silver plating method according to claim 11, characterized in that, The electroplating current density is 0.3~0.8 A / dm². 2 .

13. The silver plating method according to claim 8, characterized in that, The substrate includes at least one of copper and its alloys, aluminum and its alloys, and iron and its alloys.

Images