Micro-nano powder surface tin plating method

Abstract

The invention belongs to the technical field of chemical tin plating, and particularly relates to a micro-nano powder surface tin plating method which comprises the following steps: pretreating powder, adding main salt, a reducing agent, a coordination agent and an antioxidant into water, and stirring until the main salt, the reducing agent, the coordination agent and the antioxidant are completely dissolved; and the pretreated powder is added into the cylinder opening liquid to be subjected to a reaction, when the surface of the solution is subjected to the reaction, the supplementing liquid is added, stirring continues to be conducted till the reaction is completed, and the micro-nano powder with the tin-plated surface is obtained. According to the method for plating tin on the surface of the micro-nano powder, tin is plated on the surface of the micro-nano split body, so that the surface energy of the material can be effectively reduced, the material can be more easily infiltrated and combined with welding flux in the welding process, the welding performance of the material is remarkably improved, and the material is high in oxidation resistance, high in conductivity, high in dispersity and high in corrosion resistance. The whole process is simple, stable and suitable for large-scale production and application.

Description

Technical Field

[0001] This invention belongs to the field of chemical tin plating technology, and particularly relates to a method for tin plating on the surface of micro-nano powders. Background Technology

[0002] In today's era of rapid technological advancement, micro- and nano-powder materials occupy a crucial position in numerous fields due to their unique physical and chemical properties. In the electronics and information industry, micro- and nano-metallic powders (such as copper and silver) possess excellent conductivity, making them key raw materials for manufacturing high-performance electronic circuits and electrode materials. In the ceramics field, non-metallic micro- and nano-powders (like alumina and titanium dioxide) are widely used in ceramic cutting tools and high-temperature coatings due to their high hardness, high-temperature resistance, and good chemical stability. In the biomedical field, certain micro- and nano-powders can be used to prepare drug carriers and biosensors; their tiny size enables precise targeted delivery and efficient detection functions.

[0003] Although metallic micro / nano powders possess inherent advantages such as excellent electrical and thermal conductivity, their reactive chemical properties make them highly susceptible to oxidation in air; for example, iron powder easily rusts. This not only alters the physicochemical properties of the powder but also affects its performance in practical applications. As for non-metallic micro / nano powders, while they exhibit high strength and high insulation, their lack of solderability and electromagnetic shielding properties compared to metals limits their direct application in fields requiring metallic characteristics. For instance, in the electronic packaging industry, non-metallic micro / nano powders alone are insufficient to achieve reliable electrical connections and signal transmission. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for tin plating on the surface of micro / nano powders. By depositing a tin plating layer on the surface of metallic or non-metallic micro / nano powders, the excellent properties of tin can be imparted to the base powder. Tin has good solderability, enabling powders that are originally difficult to solder to be used in electronic assembly processes; its relatively stable chemical properties can provide antioxidant protection for easily oxidized metal powders; simultaneously, the tin plating layer has low resistivity, which helps improve the conductivity of the powder, enhancing its electrical performance when preparing conductive composite materials or conductive pastes. In some special applications, such as the processing of metal powders in food packaging materials, the non-toxic and corrosion-resistant properties of the tin plating layer are of great significance, effectively preventing chemical reactions when metal powders come into contact with food and ensuring food safety.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for tin plating on the surface of micro / nano powders includes the following steps:

[0007] S1. Powder pretreatment: First, the powder is degreased and cleaned, and then the powder is roughened, sensitized and activated.

[0008] S2. Preparation of starter solution: Add the main salt, reducing agent, complexing agent and antioxidant to water and stir until completely dissolved;

[0009] S3. Prepare the replenishment solution: Add the main salt, reducing agent, complexing agent and antioxidant to water and stir until completely dissolved;

[0010] S3, Powder Tin Plating: Pour the starter solution from S2 into a beaker and place it in a water bath for constant temperature heating. Add the powder from S1 into the beaker. When the reaction reaches the point where there is less foam on the surface of the solution, add the replenishing solution from S3 and continue stirring until the reaction is complete. This will give you micro-nano powder with tin plating on the surface.

[0011] Compared with existing technologies, the production method of tin-plated copper powder of this invention has the following outstanding substantive features and significant progress:

[0012] The components in the prepared start-up and replenishment solutions complement each other. The main salt, stannous sulfate, provides a source of tin ions. The complexing agent, thiourea, forms a complexation compound with tin ions, stabilizing them and preventing hydrolysis. The antioxidant, hydroquinone, effectively prevents the oxidation of tin ions. All of these contribute to maintaining the stability of the plating solution composition, extending the service life of the plating solution, reducing the increased costs and resource waste caused by frequent plating solution replacements, ensuring the continuity and stability of the process, and facilitating large-scale production applications.

[0013] The concentrations of the main salt, stannous sulfate, and the reducing agent, sodium hypophosphite, can be adjusted within a certain range, allowing for precise control of the tin plating speed and coating thickness according to actual needs. For example, when producing powder tin-plated products of different specifications or uses, the concentrations of these two components can be flexibly adjusted to achieve a variety of coating thicknesses from thin to thick, meeting diverse market demands. This also avoids coating quality problems caused by excessively fast or slow plating speeds, such as roughness and high porosity in the coating due to excessively fast plating speeds, and low production efficiency due to excessively slow plating speeds.

[0014] Preferably, the powder degreasing and cleaning in step S1 is performed using an organic solvent, which is either acetone or ethanol. For example, the powder particles are soaked in an acetone solution, taking advantage of acetone's good solubility for oils, so that the oil stains are dissolved in the acetone. Then, through multiple rinsing, the dissolved oil stains in the acetone are removed, making the powder surface clean.

[0015] Preferably, the roughening treatment of the powder in S1 is a chemical etching method to etch the powder surface, and the etchant used in the chemical etching method is a strong acid. To increase the activity and roughness of the powder surface and improve the adhesion of the coating, the powder needs to be roughened. The hydrochloric acid used includes mixed acids such as nitric acid and sulfuric acid, which etch the powder surface, creating tiny pits and protrusions. This allows the tin layer to adhere better to these rough surfaces during tin plating, enhancing the bonding strength.

[0016] Preferably, the sensitization treatment of the powder in S1 involves immersing the powder in a sensitizing solution containing stannous chloride and hydrochloric acid. Sensitization involves adsorbing a layer of easily oxidized metal ions (such as stannous ions) onto the surface of the powder, as in this operation, by immersing the powder in a sensitizing solution containing stannous chloride and hydrochloric acid.

[0017] Preferably, the activation treatment of the powder in S1 involves replacing the stannous ions adsorbed on the surface of the sensitized powder with noble metal ions, thereby forming catalytically active noble metal particles on the powder surface. These noble metal ions include silver ions. After activation, self-catalytic active centers are provided for subsequent electroless tin plating, allowing the tin plating reaction to proceed smoothly.

[0018] Preferably, the main salt is stannous sulfate (SnSO4) with a concentration of 10-30 g / L. Stannous sulfate provides tin ions, and its concentration affects the tin plating speed and the thickness of the coating.

[0019] Preferably, the reducing agent is sodium hypophosphite (NaH2PO2) with a concentration of 15-40 g / L. Sodium hypophosphite is the driving force for the tin plating reaction. A suitable concentration can ensure the effective reduction of tin ions. Too high a concentration may lead to too fast a plating rate and poor plating quality; too low a concentration will result in too slow a plating rate.

[0020] Preferably, the ligand is thiourea (CS(NH2)2) with a concentration of 10-30 g / L. Thiourea forms a coordination compound with tin ions, stabilizing the tin ions in the plating solution and preventing them from undergoing hydrolysis or other reactions in the plating solution.

[0021] Preferably, the antioxidant is hydroquinone (C6H6O2) at a concentration of 1-5 g / L. Hydroquinone can prevent tin ions in the plating solution from being oxidized and extend the service life of the plating solution.

[0022] Preferably, the water bath heating temperature is 60-80℃. Within this temperature range, the reaction rate in the plating solution is moderate, ensuring the quality of the plating layer. If the temperature is too high, the components in the plating solution may decompose, leading to instability; if the temperature is too low, the plating speed is too slow, reducing production efficiency. The pH of both the initial plating solution and the replenishing solution is 4-6. pH affects the activity of various components in the plating solution; a suitable pH value allows the reducing agent to reach its optimal reducing capacity while ensuring that tin ions do not precipitate due to an unsuitable pH.

[0023] Preferably, during the tin plating process, an appropriate stirring method, such as mechanical stirring or air stirring, is required. Stirring can ensure the uniform distribution of components in the plating solution, prevent local concentrations from being too high or too low, and also avoid the agglomeration of powder particles. For example, the mechanical stirring speed can be controlled at 100-300 r / min, which can ensure that the powder particles are uniformly dispersed in the plating solution, allowing the plating layer to be uniformly deposited on the powder surface.

[0024] Compared to existing technologies, the advantages of this invention are as follows: This invention provides a method for tin plating on the surface of micro / nano powders. By plating tin onto the surface of micro / nano components, the surface energy of the material can be effectively reduced, making it easier to wet and bond with solder during the welding process, thereby significantly improving the welding performance of the material. Furthermore, it exhibits high oxidation resistance, strong conductivity, high dispersibility, and strong corrosion resistance. The overall process is simple and stable, suitable for large-scale production applications. The concentrations of the main salt stannous sulfate and the reducing agent sodium hypophosphite can be adjusted within a certain range, allowing for precise control of the tin plating speed and coating thickness according to actual needs. The appropriate water bath reaction temperature and pH value ensure smooth tin plating and stable coating quality. Appropriate stirring ensures uniform distribution of components in the plating solution, preventing powder agglomeration. Attached Figure Description

[0025] Figure 1 This is a SEM image of the tin-plating powder of Example 1 of the present invention.

[0026] Figure 2 This is a SEM image of the tin-plating powder of Comparative Example 1 of the present invention.

[0027] Figure 3 This is a SEM image of the tin-plating powder of Comparative Example 2 of the present invention.

[0028] Figure 4 This is a SEM image of the tin-plating powder of Comparative Example 3 of the present invention.

[0029] Figure 5 This is a SEM image of the tin-plating powder of Comparative Example 4 of the present invention. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1:

[0032] In this embodiment, diamond micro powder is used as the powder, and the diamond micro powder is pretreated with the following formula:

[0033] Diamond micro powder: 30g

[0034] Degreasing agent (sodium hydroxide): 10ml (10% concentration)

[0035] Roughening (hydrochloric acid): 5ml

[0036] Sensitization (stannous chloride): 4 ml (62.5% by mass)

[0037] Activation (palladium chloride): 12 ml (0.05% by mass)

[0038] Reduced (sodium hypophosphite): 1 ml (50% by mass)

[0039] The diamond micro powder is pretreated using the following method:

[0040] 1. Add 30g of diamond powder to a 1L beaker, add 10ml of sodium hydroxide, heat in a water bath to 80 degrees Celsius, and stir for 40 minutes;

[0041] 2. Clean the diamond micro powder from the previous step until it is neutral, add 5ml of hydrochloric acid at room temperature, and stir for 60 minutes;

[0042] 3. Wash the diamond powder from the previous step until it is neutral, add 4 ml of stannous chloride, heat it in a water bath to 50 degrees Celsius, and stir for 10 minutes;

[0043] 4. Wash the diamond micro powder from the previous step until it is neutral, add 12 ml of palladium chloride, heat it in a water bath to 80 degrees Celsius, and stir for 15 minutes;

[0044] 5. Following the previous step, add 1 ml of sodium hypophosphite, heat in a water bath to 80 degrees Celsius, and continue stirring for 20 minutes;

[0045] 6. Discard the supernatant and set aside.

[0046] After completing the pretreatment of diamond micron powder, the start-up solution and replenishment solution are prepared according to the following formula, and the diamond micron powder is then tin-plated.

[0047] Starter solution:

[0048] Powder: 30g

[0049] Main salt (stannous sulfate, SnSO4): 9g

[0050] Reducing agent (sodium hypophosphite, NaH2PO2): 12g

[0051] Complexing agent (thiourea, CS(NH2)2): 9g

[0052] Antioxidant (hydroquinone, C6H6O2): 2.0g

[0053] Add water to 600ml

[0054] Water bath temperature: 65℃

[0055] pH value: 6

[0056] Replenishment fluid:

[0057] Main salt (stannous sulfate, SnSO4): 22.5g

[0058] Reducing agent (sodium hypophosphite, NaH2PO2): 30g

[0059] Complexing agent (thiourea, CS(NH2)2): 22.5g

[0060] Antioxidant (hydroquinone, C6H6O2): 3g

[0061] Add water to 1500ml

[0062] pH value: 6

[0063] Powder tin plating process:

[0064] 1. Add 9g of stannous sulfate to a 5L beaker, add 65°C pure water, and stir until completely dissolved;

[0065] 2. Add 22.5g of thiourea and 3g of hydroquinone, and stir until completely dissolved;

[0066] 3. Add sodium hypophosphite as a reducing agent and stir until completely dissolved;

[0067] 4. Use ammonia to adjust the pH to 4.5;

[0068] 5. Place the above solution in a water bath and adjust the temperature to 65 degrees Celsius;

[0069] 6. When the temperature of the solution in the beaker reaches 65 degrees Celsius, add the diamond powder;

[0070] 7. When the foam on the surface of the solution in the beaker is reduced, add the replenishing solution by using a flow pump at a speed of 50 rpm / min.

[0071] Comparative Example 1:

[0072] The rest of the contents are the same as in Example 1, except that the starter solution and top-up solution use the following formula:

[0073] Starter solution:

[0074] Powder: 30g

[0075] Main salt (stannous sulfate, SnSO4): 9g

[0076] Reducing agent (sodium hypophosphite, NaH2PO2): 12g

[0077] Complexing agent (thiourea, CS(NH2)2): 9g

[0078] Antioxidant (hydroquinone, C6H6O2): 1.2g

[0079] Add water to 600ml

[0080] Water bath temperature: 65℃

[0081] pH value: 6

[0082] Replenishment fluid:

[0083] Main salt (stannous sulfate, SnSO4): 22.5g

[0084] Reducing agent (sodium hypophosphite, NaH2PO2): 30g

[0085] Complexing agent (thiourea, CS(NH2)2): 22.5g

[0086] Antioxidant (hydroquinone, C6H6O2): 3g

[0087] Add water to 1500ml

[0088] pH value: 6

[0089] Comparative Example 2:

[0090] The rest of the contents are the same as in Example 1, except that the starter solution and top-up solution use the following formula:

[0091] Starter solution:

[0092] Powder: 30g

[0093] Main salt (stannous sulfate, SnSO4): 9g

[0094] Reducing agent (sodium hypophosphite, NaH2PO2): 12g

[0095] Complexing agent (thiourea, CS(NH2)2): 12g

[0096] Antioxidant (hydroquinone, C6H6O2): 1.2g

[0097] Add water to 600ml

[0098] Water bath temperature: 65℃

[0099] pH value: 6

[0100] Replenishment fluid:

[0101] Main salt (stannous sulfate, SnSO4): 22.5g

[0102] Reducing agent (sodium hypophosphite, NaH2PO2): 30g

[0103] Complexing agent (thiourea, CS(NH2)2): 22.5g

[0104] Antioxidant (hydroquinone, C6H6O2): 3g

[0105] Add water to 1500ml

[0106] pH value: 6

[0107] Comparative Example 3:

[0108] The rest of the contents are the same as in Example 1, except that the starter solution and top-up solution use the following formula:

[0109] Starter solution:

[0110] Powder: 30g

[0111] Main salt (stannous sulfate, SnSO4): 9g

[0112] Reducing agent (sodium hypophosphite, NaH2PO2): 12g

[0113] Complexing agent (thiourea, CS(NH2)2): 14g

[0114] Antioxidant (hydroquinone, C6H6O2): 1.2g

[0115] Add water to 600ml

[0116] Water bath temperature: 65℃

[0117] pH value: 6

[0118] Replenishment fluid:

[0119] Main salt (stannous sulfate, SnSO4): 22.5g

[0120] Reducing agent (sodium hypophosphite, NaH2PO2): 30g

[0121] Complexing agent (thiourea, CS(NH2)2): 22.5g

[0122] Antioxidant (hydroquinone, C6H6O2): 3g

[0123] Add water to 1500ml

[0124] pH value: 6

[0125] Comparative Example 4:

[0126] The rest of the contents are the same as in Example 1, except that the starter solution and top-up solution use the following formula:

[0127] Starter solution:

[0128] Powder: 30g

[0129] Main salt (stannous sulfate, SnSO4): 12g

[0130] Reducing agent (sodium hypophosphite, NaH2PO2): 12g

[0131] Complexing agent (thiourea, CS(NH2)2): 9g

[0132] Antioxidant (hydroquinone, C6H6O2): 1.2g

[0133] Add water to 600ml

[0134] Water bath temperature: 65℃

[0135] pH value: 6

[0136] Replenishment fluid:

[0137] Main salt (stannous sulfate, SnSO4): 22.5g

[0138] Reducing agent (sodium hypophosphite, NaH2PO2): 30g

[0139] Complexing agent (thiourea, CS(NH2)2): 22.5g

[0140] Antioxidant (hydroquinone, C6H6O2): 3g

[0141] Add water to 1500ml

[0142] pH value: 6

[0143] like Figure 1-5As shown, scanning electron microscopy (SEM) tests were performed on the above embodiments and comparative examples, and their SEM images and corresponding analyses are as follows:

[0144] Figure 1 The image shown is an SEM image of Example 1. The results show that the coating quality of the diamond micropowder surface is normal, with no partial uncoated areas, and the dispersion of the powder particles is normal.

[0145] Figure 2 The image shown is a SEM image of Comparative Example 1. The results show that the coating on the surface of the diamond micropowder is rough and there are instances of incomplete coating and cracking.

[0146] Figure 3 The image shown is a SEM image of Comparative Example 2. The results show that the coating quality on the surface of the diamond micropowder is normal, but some areas have incomplete coating.

[0147] Figure 4 The SEM image for Comparative Example 3 shows that the coating quality on the surface of the diamond micropowder is normal, with no partial missed coating, but agglomeration of powder particles is observed.

[0148] Figure 5 The SEM image for Comparative Example 4 shows that the coating quality of the diamond micropowder surface is rough, with serious incomplete coating, and the dispersion between powder particles is normal.

[0149] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A method for tin plating on the surface of micro / nano powders, characterized in that, Includes the following steps: S1. Powder pretreatment: First, the powder is degreased and cleaned, and then the powder is roughened, sensitized and activated. S2. Preparation of starter solution: Add the main salt, reducing agent, complexing agent and antioxidant to water and stir until completely dissolved; S3. Prepare the replenishment solution: Add the main salt, reducing agent, complexing agent and antioxidant to water and stir until completely dissolved; S3, Powder Tin Plating: Pour the starter solution from S2 into a beaker and place it in a water bath for constant temperature heating. Add the powder from S1 into the beaker. When the reaction reaches the point where there is less foam on the surface of the solution, add the replenishing solution from S3 and continue stirring until the reaction is complete. This will give you micro-nano powder with tin plating on the surface.

2. The method for tin plating on the surface of micro / nano powders according to claim 1, characterized in that: In step S1, the powder is cleaned by using an organic solvent, which is either acetone or ethanol.

3. The method for tin plating on the surface of micro / nano powders according to claim 1, characterized in that: The roughening treatment of the powder in S1 is to use chemical etching to etch the powder surface, and the etchant used in the chemical etching method is a strong acid.

4. The method for tin plating on the surface of micro / nano powders according to claim 1, characterized in that: The sensitization treatment of the powder in S1 involves immersing the powder in a sensitizing solution containing stannous chloride and hydrochloric acid.

5. The method for tin plating on the surface of micro / nano powders according to claim 1, characterized in that: The activation treatment of the powder in S1 involves replacing the stannous ions adsorbed on the surface of the sensitized powder with noble metal ions, thereby forming catalytically active noble metal particles on the powder surface. The noble metal ions include silver ions.

6. The method for tin plating on the surface of micro / nano powders according to claim 1, characterized in that: The main salt is stannous sulfate (SnSO4) with a concentration of 10-30 g / L.

7. The method for tin plating on the surface of micro / nano powders according to claim 1, characterized in that: The reducing agent is sodium hypophosphite (NaH2PO2) with a concentration of 15-40 g / L.

8. The method for tin plating on the surface of micro / nano powders according to claim 1, characterized in that: The ligand is thiourea (CS(NH2)2) with a concentration of 10-30 g / L.

9. The method for tin plating on the surface of micro / nano powders according to claim 1, characterized in that: The antioxidant is hydroquinone (C6H6O2) with a concentration of 1-5 g / L.

10. The method for tin plating on the surface of micro / nano powders according to claim 1, characterized in that: The water bath is heated to 60-80℃, and the pH of both the start-up solution and the replenishment solution is 4-6.

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