Method for efficiently preparing micron-sized silver-plated copper powder, silver-plated copper powder and application

Abstract

The invention provides a method for efficiently preparing micron-sized silver-plated copper powder, the silver-plated copper powder and application of the silver-plated copper powder, and aims at solving the technical problems that an existing technological process is complex, a large amount of waste liquid is generated, and environmental protection is not facilitated. The preparation method comprises the following steps: directly adding the copper powder into a container filled with the solution A, ultrasonically stirring in an ultrasonic constant-temperature water bath at 30-50 DEG C, dropwise adding the solution B into the container, dropwise adding the solution C when the solution B is dropwise added to 20-30% of the rest of the solution B, continuously dropwise adding the solution B until the dropwise adding is finished, continuously stirring for at least 0.5 h after the solution C is completely dropwise added, and cooling to room temperature to obtain the copper powder. And taking out, repeatedly cleaning with deionized water and absolute ethyl alcohol for multiple times, and drying under nitrogen protection or vacuum conditions to obtain the silver-plated copper powder. The silver-plated copper powder is used for preparing a conductive adhesive, a conductive coating or a shielding film material. The preparation method is simple, no waste liquid is generated in the preparation process, the green and environment-friendly requirements are met, silver particles generated on the copper surface through replacement are more compact, and the volume resistivity is smaller.

Description

Technical Field

[0001] The invention relates to the technical field of conductive material preparation technology, and in particular to a method for efficiently preparing micron-level silver-plated copper powder, the silver-plated copper powder and applications thereof. Background Art

[0002] With the rapid development of new energy and the widespread use of smart interconnection technology, problems such as integrated circuit packaging and electromagnetic radiation pollution are becoming increasingly serious, which has brought huge challenges to the continuous iteration of electronic products. Therefore, high-performance conductive materials have become one of the important issues that electronic products urgently need to solve. Among them, metal conductive particles have become an indispensable component in the preparation of high-performance conductive materials due to their characteristics of conductivity, thermal conductivity and strong stability. Powder materials have therefore received extensive attention from scientific researchers, especially new powder materials prepared by chemical or physical methods from powders with different properties. They can make different traditional powder materials complement each other's performance, thereby producing a synergistic effect, making their comprehensive performance more suitable for different needs that cannot be met by a single powder material. Silver-plated copper powder is not only low in cost, but also has good conductivity and oxidation resistance, and is resistant to electromigration, and has a prospect for large-scale application.

[0003] The existing technical solutions for preparing silver-plated copper powder are mechanical mixing method and chemical plating method, among which chemical plating method is the most common method for preparing silver-plated copper powder by liquid phase method. According to the type of chemical reaction mechanism, it is divided into: direct replacement method and chemical reduction method. The chemical plating method mainly adds the copper powder that has been surface pretreated, cleaned and dried into a series of chemical solutions (such as hydrochloric acid, silver ammonia complex solution, activation solution and reduction solution), and reduces it in situ on the surface of the copper powder through chemical reaction to form a uniform silver coating, and finally washes the powder and vacuum dries it. Although this method produces silver-plated copper powder with relatively excellent performance, it has the following technical problems: 1. The process flow is complicated and a lot of waste liquid is generated in the process; 2. It is difficult to uniformly produce silver coating on the surface of the copper powder; 3. The experimental scheme usually contains strong acid or cyanide, which is not green and environmentally friendly; 4. The main preparation method of the silver copper powder market is chemical reduction method or electroplating process. Summary of the invention

[0004] The invention aims to provide a method for preparing micron-sized silver-plated copper powder in an efficient and green and environmentally friendly manner, which has the advantages of simple preparation process, no waste liquid generated in the preparation process, and adopts a preparation method of chemical replacement followed by chemical reduction and adds a silver complexing agent (5-5 dimethylhydantoin) into a silver plating liquid A, so that the silver particles generated by the replacement of copper are more compact, and the volume resistivity of the prepared silver-plated copper powder under the same particle size is smaller.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A method for efficiently preparing micron-level silver-plated copper powder comprises the following steps: directly adding copper powder into a container containing liquid A, ultrasonically stirring in an ultrasonic constant temperature water bath at 30-50°C, dripping liquid B into the container, and when liquid B is dripped to a residual amount of 20-30%, silver ions in liquid B replace copper atoms on the surface of copper powder, and liquid C is dripped, and liquid B is continuously dripped until the dripping is complete. Liquid C and liquid B act together to rapidly grow silver atoms on the surface of copper powder, and stirring is continued for at least 0.5h after liquid C is completely dripped, and after taking out, the mixture is repeatedly washed with deionized water and anhydrous ethanol for multiple times, and then dried under nitrogen protection or vacuum conditions to obtain silver-plated copper powder;

[0007] Among them, the main components of the A liquid include one or more of 5-5 dimethyl hydantoin, EDTA-2Na, polyethylene glycol-2000, ammonium chloride, ammonia water, butynediol and polyvinyl pyrrolidone; the main components of the B liquid include silver nitrate and ammonia water; the main components of the C liquid include a reducing agent and ammonia water, and the reducing agent is one or more of glucose, sodium hypophosphite, formaldehyde, hydrazine hydrate, sorbitol or potassium sodium tartrate.

[0008] As the preferred technical solution:

[0009] Optionally, the main components of the A solution include one or more of a 5-5 dimethylhydantoin ethanol solution with a concentration of 1~3 g / L, an EDTA-2Na aqueous solution with a concentration of 50~100 g / L, a polyethylene glycol-2000 aqueous solution with a concentration of 1~5 g / L, an ammonia chloride aqueous solution with a concentration of 50~150 ppm, an ammonia solution with a concentration of 150~300 mL / L, a butynediol aqueous solution with a concentration of 0.5~2 g / L, and a polyvinylpyrrolidone aqueous solution with a concentration of 0.5~1 g / L; the main components of the B solution include a silver nitrate aqueous solution with a concentration of 10~30 g / L and an ammonia solution with a concentration of 10~20 mL / L; the main components of the C solution include a reducing agent with a concentration of 10~30 g / L and an ammonia solution with a concentration of 10~20 mL / L.

[0010] Optionally, the mass volume ratio of the copper powder to the liquid A is (30~100) g:1 L, and the volume ratio of the added amounts of the liquid A, liquid B and liquid C is 2:2:1. More specifically, the added amount of the copper powder is 30~100 g, the added amount of the liquid A is 1 L, the added amount of the liquid B is 1 L, and the added amount of the liquid C is 0.5 L.

[0011] Optionally, the ultrasonic stirring time is 10-30 min, and the B solution and the C solution are added dropwise within 2-3 h, so as to control the concentration of chemical reagents in the reaction within a certain range to ensure sufficient and uniform reaction.

[0012] Optionally, the liquid B and the liquid C are added dropwise at a uniform rate of 5-10 mL / min, so as to control the chemical reaction to be sufficient and uniform during the reaction.

[0013] Optionally, the liquid B and the liquid C are added dropwise using a peristaltic pump.

[0014] Optionally, the following steps are included:

[0015] S1, preparation of silver plating solution

[0016] S11, prepare solution A: weigh one or more of 1-3 g of 5-5-dimethylhydantoin, 50-100 g of EDTA-2Na, 1-5 g of polyethylene glycol-2000, 50-150 mL of ammonium chloride, 150-300 mL of ammonia water, 0.5-2 g of butynediol, and 0.5-1 g of polyvinylpyrrolidone in a beaker, add to 1 L of deionized water and stir evenly;

[0017] S12, prepare solution B: dissolve 10-30 g of silver nitrate in 1 L of deionized water to prepare a silver nitrate solution, then add 10-20 mL of ammonia water dropwise and stir until the precipitate is completely dissolved to form a transparent and colorless mixed solution;

[0018] S13, preparing liquid C: dissolving 10-30 g of one or more of glucose, sodium hypophosphite, formaldehyde, hydrazine hydrate, sorbitol or potassium sodium tartrate in 1 L of deionized water, and then adding 10-20 mL / L of ammonia water dropwise and stirring;

[0019] S2, take 1L of liquid A prepared in step S11 and put it into a container, add 30-100g of copper powder therein, and stir ultrasonically in an ultrasonic constant temperature water bath at 30-50°C for 10-30min;

[0020] S3, after the end of the ultrasound, continue to drip 1L of B liquid into the container, wherein the B liquid is dripped by a peristaltic pump, the dripping rate is 5-10 mL / min, and the container is slowly stirred during the dripping process; the purpose of controlling the dripping rate to 5-10 mL / min in the present invention is that if the dripping rate is too fast, the reaction will be accelerated. When it exceeds a certain level, uniform nucleation of Ag single substance will occur to form silver particles, and coating cannot be achieved, while if the dripping rate is too slow, the reaction time will increase, resulting in energy consumption.

[0021] S4, when the amount of liquid B is 20-30% of the remaining amount, 0.5L of liquid C is added to the container, and liquid B is added continuously until the addition is complete. After liquid C is added completely, stirring is continued for at least 0.5h. Liquid C is added using a peristaltic pump at a rate of 5-10 mL / min.

[0022] S5, after taking out the obtained mixture from the container, repeatedly washing it with deionized water and anhydrous ethanol for multiple times, and drying it under nitrogen protection or vacuum conditions to obtain silver-plated copper powder, wherein the drying temperature is 40-100° C. and the drying time is 30-120 min.

[0023] The present invention also provides a silver-plated copper powder, which is prepared by the method as described above, has an average particle size D50 of 5 to 10 μm, and a volume resistivity of 1.55 to 8 mΩ·mm.

[0024] The present invention also provides an application of the silver-plated copper powder as described above, wherein the silver-plated copper powder is used to prepare conductive adhesive, conductive coating or shielding film material.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The method for preparing micron-level silver-plated copper powder omits the pretreatment process of the copper powder, making the whole process simpler. The silver-plated copper powder can be prepared by putting the copper powder into liquid A and adding liquid B and liquid C drop by drop, thereby avoiding the generation of more waste liquid in the process. The silver-plating liquid used does not use strong acid or cyanide, which meets the requirements of green environmental protection. In addition, by adding a silver complexing agent (5-5 dimethylhydantoin) into the silver-plating liquid, and then performing chemical replacement and chemical reduction, the silver particles generated by copper surface replacement are more compact, and the volume resistivity of the prepared silver-plated copper powder with the same particle size is smaller. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 The SEM images of the silver-plated copper powder prepared in Example 1, Example 7 and Example 8;

[0029] Wherein (a) corresponds to Example 1, (b) corresponds to Example 7, and (c) corresponds to Example 8;

[0030] Figure 2 Schematic diagram of the reaction mechanism of the present invention;

[0031] Figure 3 This is a photo of a shielding film material prepared from the silver-plated copper powder obtained in Example 1, with a thickness of 0.2 mm;

[0032] Figure 4It is a comparison curve of electromagnetic shielding effectiveness of the present invention, commercial product 1 and commercial product 2;

[0033] Figure 5 This is a photo of the powder;

[0034] Wherein (a) is a photo of the silver-plated copper powder of Example 3, and (b) is a photo of the silver-plated copper powder of a competitor;

[0035] Figure 6 This is a powder EDS scan photo;

[0036] Among them, (a) is the EDS scanning photo of the silver-plated copper powder of Example 3, and (b) is the EDS scanning photo of the silver-plated copper powder of the competitor. DETAILED DESCRIPTION

[0037] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0038] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0039] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0040] The embodiment of the present invention provides a method for efficiently preparing micron-level silver-plated copper powder, wherein the copper powder is directly added into a container containing liquid A, ultrasonically stirred in an ultrasonic constant temperature water bath at 30-50° C. for 10-30 minutes, and then liquid B is uniformly added to the container, and when liquid B is added to 20-30% of the remaining amount, liquid C is continuously added at a uniform speed, and stirring is continued for 0.5-1 hour after liquid C is completely added, and after being taken out, the powder is repeatedly washed with deionized water and anhydrous ethanol for multiple times, and then dried under nitrogen protection or vacuum conditions, so as to obtain the silver-plated copper powder;

[0041] Among them, the main components of liquid A include one or more of 5-5 dimethylhydantoin, EDTA-2Na, polyethylene glycol-2000, ammonium chloride, ammonia water, butynediol and polyvinyl pyrrolidone; the main components of liquid B include silver nitrate and ammonia water; the main components of liquid C include reducing agent and ammonia water, and the reducing agent is one or more of glucose, sodium hypophosphite, formaldehyde, hydrazine hydrate, sorbitol or potassium sodium tartrate.

[0042] Among them, the main components of liquid A include one or more of 5-5-dimethylhydantoin 1~3g / L, EDTA-2Na 50~100 g / L, polyethylene glycol-2000 1~5g / L, ammonium chloride 50~150ppm, ammonia water 150~300 mL / L, butynediol 0.5~2 g / L and polyvinylpyrrolidone 0.5~1g / L; the main components of liquid B include silver nitrate 10~30g / L and ammonia water 10~20 mL / L; the main components of liquid C include reducing agent 10~30g / L and ammonia water 10~20 mL / L.

[0043] The mass volume ratio of copper powder to liquid A is (30~100) g:1L, and the volume ratio of liquid A, liquid B and liquid C added is 2:2:1.

[0044] Add liquid B and liquid C within 2 to 3 hours.

[0045] The drop rate of solution B and solution C is 5~10 mL / min.

[0046] A peristaltic pump was used to add liquid B and liquid C.

[0047] The silver-plated copper powder D50 prepared by the above method has an average particle size of 5-10 μm, a spheroidization rate of 90-95%, and a volume resistivity of 1.55-8 mΩ·mm.

[0048] The silver-plated copper powder prepared above is used to prepare conductive glue or conductive coating. Conductive glue is mainly used for the packaging of precision instruments, such as chips and PCB boards. Conductive coating is mainly used for the external coating of electrodes and electric heating films to eliminate static interference.

[0049] The following is a more specific example:

[0050] Example 1

[0051] A method for efficiently preparing micron-sized silver-plated copper powder comprises the following steps:

[0052] S1, preparation of silver plating solution

[0053] S11, prepare solution A: weigh 1 g of 5-5-dimethylhydantoin, 75 g of EDTA-2Na, 1 g of polyethylene glycol-2000, 80 mL of ammonium chloride, 240 mL of ammonia water, 1 g of butynediol and 0.5 g of polyvinyl pyrrolidone solid powder in a beaker, add 1 L of deionized water and stir evenly;

[0054] S12, prepare solution B: dissolve 15 g of silver nitrate in 1 L of deionized water to prepare a silver nitrate solution, then add 15 mL / L of ammonia water dropwise and stir until the precipitate is completely dissolved to form a transparent and colorless mixed solution;

[0055] S13, preparing liquid C: dissolving 20 g of glucose in 1 L of deionized water, and then adding 15 mL / L of ammonia water dropwise while stirring;

[0056] S2, taking the liquid A prepared in step S11 and charging it into a container, adding the ball-milled copper powder therein, and ultrasonically stirring in an ultrasonic constant temperature water bath at 40° C. for 20 min, wherein the volume mass ratio of the liquid A to the copper powder is 1 L: (50) g;

[0057] S3, after the ultrasound is finished, continue to drop 1L of liquid B into the container, wherein liquid B is added dropwise using a peristaltic pump at a dropping rate of 5 mL / min, and slowly stirred during the dropping process;

[0058] S4, when liquid B is added to 20-30% of the remaining amount, 500 mL of liquid C is added to the container. After all liquid C is added, stirring is continued for 0.5-1 h. Liquid C is added by a peristaltic pump at a dropping rate of 10 mL / min.

[0059] S5, after taking out the obtained mixture from the container, repeatedly washing it with deionized water and anhydrous ethanol for multiple times, and drying it under nitrogen protection or vacuum conditions to obtain silver-plated copper powder, wherein the drying temperature is 40° C. and the drying time is 100 minutes.

[0060] Example 2

[0061] A method for efficiently preparing micron-sized silver-plated copper powder, the preparation steps are basically the same as those in Example 1, except that in step S2, flaky copper powder is added to liquid A to prepare the silver-plated copper powder.

[0062] The D50 average particle size, spheroidization rate and volume resistivity values ​​of the prepared silver-plated copper powder are shown in Table 1 below.

[0063] Example 3

[0064] A method for efficiently preparing micron-sized silver-plated copper powder, the preparation steps are basically the same as those in Example 1, except that in step S2, dendritic copper powder is added to liquid A to prepare the silver-plated copper powder.

[0065] The microscopic morphology of the surface of the silver-plated copper powder prepared in Examples 1 to 3 was observed using a scanning electron microscope. The observation results are as follows: Figure 1 As shown, (a) corresponds to Example 1, (b) corresponds to Example 2, and (c) corresponds to Example 3. Figure 1 Comparing the three figures, it can be seen that the method of the present invention can form a dense silver plating layer on the surface of copper powder in different forms. This is because the silver plating solution A of the present invention does not use a single copper complexing agent EDTA-2Na, but also adds ammonia water and ammonium chloride. The ammonia ion source provided by the ammonia water can undergo a replacement reaction with CuO, and the strong alkalinity of the ammonia water can effectively activate the surface of spherical, flaky, dendritic and other copper powders. The chloride ions in the ammonium chloride can be well complexed with the free silver ions to control the rate at which they form particles. In addition, the addition of the silver complexing agent (5,5-dimethylhydantoin) can effectively regulate the replacement reaction rate of copper and silver, so that copper can more fully replace silver ions with silver elements to ensure that the reduced silver plating layer is denser. The present invention first uses silver plating solution A to remove oil stains and degreasing activation on the surface of the copper powder, then uses silver plating solution B to carry out a chemical replacement reaction to replace the copper on the surface of the copper powder, and finally uses silver plating solution C to carry out a chemical reduction reaction so that the silver ions are reduced and evenly attached to the copper powder. The reaction mechanism of the present invention is as follows Figure 2 shown.

[0066] Example 4

[0067] A method for efficiently preparing micron-sized silver-plated copper powder comprises the following steps:

[0068] S1, preparation of silver plating solution

[0069] S11, prepare solution A: weigh 1.2 g of 5-5-dimethylhydantoin, 90 g of EDTA-2Na and 2 g of polyethylene glycol-2000 in a beaker, add 1 L of deionized water and stir evenly;

[0070] S12, prepare solution B: dissolve 10 g of silver nitrate in 1 L of deionized water to prepare a silver nitrate solution, then add 15 mL / L of ammonia water dropwise and stir until the precipitate is completely dissolved to form a transparent and colorless mixed solution;

[0071] S13, preparing liquid C: adding a 30 g / L sodium hypophosphite solution dropwise into 10 mL / L ammonia water and stirring;

[0072] S2, taking the liquid A prepared in step S11 and charging it into a container, adding copper powder therein, and ultrasonically stirring in an ultrasonic constant temperature water bath at 40°C for 10 minutes, wherein the volume mass ratio of the liquid A to the copper powder is 1L:(80)g;

[0073] S3, after the ultrasound is finished, continue to drop 1L of liquid B into the container, wherein liquid B is added dropwise using a peristaltic pump at a dropping rate of 5 mL / min, and slowly stirred during the dropping process;

[0074] S4, when liquid B is added to 20-30% of the remaining amount, continue to add 500 mL of liquid C to the container. After all liquid C is added, continue to stir for 0.5-1 h. Liquid C is added by a peristaltic pump with a drop rate of 6 mL / min.

[0075] S5, after taking out the obtained mixture from the container, repeatedly washing it with deionized water and anhydrous ethanol for multiple times, and drying it under nitrogen protection or vacuum conditions to obtain silver-plated copper powder, wherein the drying temperature is 50° C. and the drying time is 60 minutes.

[0076] The D50 average particle size, spheroidization rate and volume resistivity values ​​of the prepared silver-plated copper powder are shown in Table 1 below.

[0077] Example 5

[0078] A method for efficiently preparing micron-sized silver-plated copper powder comprises the following steps:

[0079] S1, preparation of silver plating solution

[0080] S11, prepare solution A: weigh 1 g of 5-5 dimethyl hydantoin, 120 mL of ammonium chloride, 200 mL of ammonia water, 1.2 g of butynediol and 1 g of polyvinyl pyrrolidone solid powder into a beaker, add 1 L of deionized water and stir evenly;

[0081] S12, preparing solution B: dissolving 10 g of silver nitrate in 1 L of deionized water to prepare a silver nitrate solution, then adding 10 mL / L of ammonia water dropwise and stirring until the precipitate is completely dissolved to form a transparent and colorless mixed solution;

[0082] S13, preparing liquid C: adding a 20 g / L formaldehyde solution dropwise into 10 mL / L ammonia water and stirring;

[0083] S2, taking the liquid A prepared in step S11 and charging it into a container, adding copper powder therein, and ultrasonically stirring in an ultrasonic constant temperature water bath at 50° C. for 20 minutes, wherein the volume mass ratio of the liquid A to the copper powder is 1 L: (100) g;

[0084] S3, after the ultrasound is finished, continue to drop 1L of liquid B into the container, wherein liquid B is added dropwise using a peristaltic pump at a dropping rate of 6 mL / min, and slowly stirred during the dropping process;

[0085] S4, when liquid B is added to 20-30% of the remaining amount, continue to add 500 mL of liquid C to the container. After all liquid C is added, continue to stir for 0.5-1 h. Liquid C is added by a peristaltic pump with a drop rate of 6 mL / min.

[0086] S5, after taking out the obtained mixture from the container, repeatedly washing it with deionized water and anhydrous ethanol for multiple times, and drying it under nitrogen protection or vacuum conditions to obtain silver-plated copper powder, wherein the drying temperature is 100° C. and the drying time is 100 min.

[0087] The D50 average particle size, spheroidization rate and volume resistivity values ​​of the prepared silver-plated copper powder are shown in Table 1 below.

[0088] Example 6

[0089] A method for efficiently preparing micron-sized silver-plated copper powder comprises the following steps:

[0090] S1, preparation of silver plating solution

[0091] S11, prepare solution A: weigh 2.5 g of 5-5 dimethyl hydantoin into a beaker, add 1 L of deionized water and stir evenly;

[0092] S12, prepare solution B: dissolve 30 g of silver nitrate in 1 L of deionized water to prepare a silver nitrate solution, then add 10 mL of ammonia water dropwise and stir until the precipitate is completely dissolved to form a transparent and colorless mixed solution;

[0093] S13, preparing liquid C: adding 20 g / L hydrazine hydrate solution and 10 g / L glucose solution dropwise into 10 mL / L ammonia water and stirring;

[0094] S2, taking the liquid A prepared in step S11 and charging it into a container, adding copper powder therein, and ultrasonically stirring in an ultrasonic constant temperature water bath at 50°C for 30 minutes, wherein the volume mass ratio of the liquid A to the copper powder is 1L:(50)g;

[0095] S3, after the ultrasound is finished, continue to drop 1L of liquid B into the container, wherein liquid B is added dropwise using a peristaltic pump at a dropping rate of 7 mL / min, and slowly stirred during the dropping process;

[0096] S4, when liquid B is added to 20-30% of the remaining amount, continue to add 500 mL of liquid C to the container. After all liquid C is added, continue stirring for 0.5-1 h. Liquid C is added using a peristaltic pump with a drop rate of 5 mL / min.

[0097] S5, after taking out the obtained mixture from the container, repeatedly washing it with deionized water and anhydrous ethanol for multiple times, and drying it under nitrogen protection or vacuum conditions to obtain silver-plated copper powder, wherein the drying temperature is 60° C. and the drying time is 120 min.

[0098] The D50 average particle size, spheroidization rate and volume resistivity values ​​of the prepared silver-plated copper powder are shown in Table 1 below.

[0099] Example 7

[0100] A method for efficiently preparing micron-sized silver-plated copper powder comprises the following steps:

[0101] S1, preparation of silver plating solution

[0102] S11, prepare solution A: weigh 1.8 g of 5-5-dimethylhydantoin, 2 g of butynediol and 0.5 g of polyvinylpyrrolidone solid powder into a beaker, add 1 L of deionized water and stir evenly;

[0103] S12, prepare solution B: dissolve 30 g of silver nitrate in 1 L of deionized water to prepare a silver nitrate solution, then add 20 mL of ammonia water dropwise and stir until the precipitate is completely dissolved to form a transparent and colorless mixed solution;

[0104] S13, preparing liquid C: adding 30 g / L sorbitol solution and 10 g / L sodium hypophosphite solution dropwise into 20 mL / L ammonia water and stirring;

[0105] S2, taking the liquid A prepared in step S11 and charging it into a container, adding copper powder therein, and ultrasonically stirring in an ultrasonic constant temperature water bath at 40°C for 20 minutes, wherein the volume mass ratio of the liquid A to the copper powder is 1L:(30)g;

[0106] S3, after the ultrasound is finished, continue to drop 1L of liquid B into the container, wherein liquid B is added dropwise using a peristaltic pump at a dropping rate of 8 mL / min, and slowly stirred during the dropping process;

[0107] S4, when liquid B is added to 20-30% of the remaining amount, continue to add 500 mL of liquid C to the container. After all liquid C is added, continue stirring for 0.5-1 h. Liquid C is added using a peristaltic pump with a drop rate of 5 mL / min.

[0108] S5, after taking out the obtained mixture from the container, repeatedly washing it with deionized water and anhydrous ethanol for multiple times, and drying it under nitrogen protection or vacuum conditions to obtain silver-plated copper powder, wherein the drying temperature is 40° C. and the drying time is 80 minutes.

[0109] The D50 average particle size, spheroidization rate and volume resistivity values ​​of the prepared silver-plated copper powder are shown in Table 1 below.

[0110] Example 8

[0111] A method for efficiently preparing micron-sized silver-plated copper powder comprises the following steps:

[0112] S1, preparation of silver plating solution

[0113] S11, prepare solution A: weigh 5 g of polyethylene glycol-2000, 150 mL of ammonium chloride, 200 mL of ammonia water, 0.8 g of butynediol and 0.5 g of polyvinyl pyrrolidone solid powder into a beaker, add 1 L of deionized water and stir evenly;

[0114] S12, prepare solution B: dissolve 25 g of silver nitrate in 1 L of deionized water to prepare a silver nitrate solution, then add 20 mL / L of ammonia water dropwise and stir until the precipitate is completely dissolved to form a transparent and colorless mixed solution;

[0115] S13, preparing liquid C: adding a 15 g / L potassium sodium tartrate solution dropwise into 20 mL / L ammonia water and stirring;

[0116] S2, taking the liquid A prepared in step S11 and charging it into a container, adding copper powder therein, and ultrasonically stirring in an ultrasonic constant temperature water bath at 30°C for 10 minutes, wherein the volume mass ratio of the liquid A to the copper powder is 1L:(30)g;

[0117] S3, after the ultrasound is finished, continue to drop 1L of liquid B into the container, wherein liquid B is added dropwise using a peristaltic pump at a dropping rate of 10 mL / min, and slowly stirred during the dropping process;

[0118] S4, when liquid B is added to 20-30% of the remaining amount, 500 mL of liquid C is added to the container. After liquid C is completely added, stirring is continued for 0.5-1 h. Liquid C is added using a peristaltic pump with a drop rate of 8 mL / min.

[0119] S5, after taking out the obtained mixture from the container, repeatedly washing it with deionized water and anhydrous ethanol for multiple times, and drying it under nitrogen protection or vacuum conditions to obtain silver-plated copper powder, wherein the drying temperature is 50° C. and the drying time is 30 minutes.

[0120] The D50 average particle size, spheroidization rate and volume resistivity values ​​of the prepared silver-plated copper powder are shown in Table 1 below.

[0121] The D50 average particle size, spheroidization rate and volume resistivity values ​​of the prepared silver-plated copper powder are shown in Table 1 below.

[0122] Comparative Example 1

[0123] A method for preparing silver-plated copper powder, the preparation steps are basically the same as those in Example 1, except that no 5-5-dimethylhydantoin is added to the raw materials for preparing liquid A in step S11.

[0124] Comparative Example 2

[0125] A method for preparing silver-plated copper powder, the preparation steps are basically the same as those in Example 1, except that no ammonia water is added to the raw materials for preparing liquid A in step S11.

[0126] Comparative Example 3

[0127] A method for preparing silver-plated copper powder, the preparation steps are basically the same as those in Example 1, except that ammonium chloride is not added to the raw materials for preparing liquid A in step S11.

[0128] In order to detect the D50 average particle size, spheroidization rate and volume resistivity values ​​of each silver-plated copper powder obtained in Examples 1 to 8 and Comparative Examples 1 to 3, the particle size of the obtained powder was measured by a BECKMAN COULTER particle size analyzer, and the average value of D50 was calculated. The obtained data is the average particle size of the powder, the spheroidization rate of the powder was detected by a KARLDEUTSCH sound velocity meter, and the powder volume resistivity tester FT-301B was used and tested according to JB / T13537-2018 (the test amount was 1.5 g, the pressure was 0-22 MPa, and the lowest volume resistivity value was taken).

[0129] The test results are shown in Table 1 below:

[0130] Table 1

[0131] D50 average particle size (μm) Spheroidization rate (%) Volume resistivity (mΩ·mm) Example 1 5.2 94.8 2.7 Example 2 8.8 91.7 3.1 Example 3 10.0 90.0 1.55 Example 4 6.7 93.0 6.8 Example 5 5.5 94.2 7.7 Example 6 6.1 95.0 8.0 Example 7 7.4 92.6 7.6 Example 8 7.5 94.5 5.9 Comparative Example 1 25.3 83.2 11.2 Comparative Example 2 26.4 77.9 10.5 Comparative Example 3 33.0 72.4 11.3

[0132] As can be seen from the above table, the present invention adds 5-5 dimethylhydroxylamine as a complexing agent, EDTA-2Na, ammonia and ammonium chloride, etc. in the silver plating solution, and the components cooperate with each other to effectively regulate the replacement reaction rate of copper and silver, so that copper can more fully replace silver ions with silver elements to ensure that the reduced silver-plated layer is more dense. And the prepared silver-plated copper powder product has a higher spheroidization rate, which is beneficial to have better fluidity when preparing materials such as conductive adhesives in the later stage. The D50 average particle size is small, the specific surface area is large, but the volume resistivity is lower, indicating that the silver-plated copper powder prepared by the present invention has good conductivity, further proving that the surface of the copper powder is well coated with a dense silver plating layer.

[0133] The silver-plated copper powder prepared by the method of Example 1 is further used to prepare a shielding film material with a thickness of 200 μm, such as Figure 3 As shown, the electromagnetic shielding performance of the shielding film material is tested with two commercially available shielding film materials made of silver-plated copper powder with the same thickness of 200 μm. Figure 4 As shown, from the comparison of the three, the shielding film prepared by the present invention has the best electromagnetic shielding performance. When the frequency reaches 18 GHz, the electromagnetic shielding performance reaches 75.1 dB, which is much higher than the commercially available products.

[0134] The specific surface area, resistivity and whiteness performance parameters of the dendritic silver-plated copper powder prepared in Example 3 and a competing product (silver-plated copper powder) sold by a foreign company are shown in Table 2 below:

[0135] Table 2

[0136] Performance parameters Embodiment 3 of the present invention A foreign competitor <![CDATA[Specific surface area (m 2 / g)]]> 0.5033 0.1355 Volume resistivity (mΩ·mm) 1.55 1.5 Whiteness (%) 36.1 40.2

[0137] The photos of Example 3 of the present invention and the competing products are as follows Figure 5 As shown in the figure, the EDS scan photos of the two are as follows Figure 6 As shown, from the comparison between the two, it can be seen that the blue area in the product photo of the present invention is more, indicating that the Ag element accounts for a large proportion, while the yellow area is smaller, that is, the Cu element accounts for a small proportion, which shows that the silver plating layer of the present invention is denser and realizes effective coating of the copper powder.

[0138] The preparation method of the invention is simple, and no waste liquid is generated in the whole preparation process; the adopted silver plating solution does not use strong acid or cyanide, which meets the requirements of green environmental protection; the prepared silver-plated copper powder has denser silver particles generated by surface replacement and smaller volume resistivity, and has considerable application prospects.

Claims

1. A method for efficiently preparing micron-sized silver-plated copper powder, characterized in that: The copper powder is directly added to a container containing liquid A, and after ultrasonic stirring in an ultrasonic constant temperature water bath at 30-50°C, liquid B is added dropwise to the container. When the remaining amount of liquid B is 20-30%, liquid C is added dropwise, and liquid B is continued to be added dropwise until the addition is complete. After all liquid C is added dropwise, stirring is continued for at least 0.5h. After taking out, it is repeatedly washed with deionized water and anhydrous ethanol for several times, and then dried under nitrogen protection or vacuum conditions to obtain silver-plated copper powder. Among them, the main components of the A liquid include one or more of 5-5 dimethyl hydantoin, EDTA-2Na, polyethylene glycol-2000, ammonium chloride, ammonia water, butynediol and polyvinyl pyrrolidone; the main components of the B liquid include silver nitrate and ammonia water; the main components of the C liquid include a reducing agent and ammonia water, and the reducing agent is one or more of glucose, sodium hypophosphite, formaldehyde, hydrazine hydrate, sorbitol or potassium sodium tartrate.

2. The method for efficiently preparing micron-sized silver-plated copper powder according to claim 1, characterized in that: The main components of the A solution include one or more of a 5-5 dimethylhydantoin ethanol solution with a concentration of 1-3 g / L, an EDTA-2Na aqueous solution with a concentration of 50-100 g / L, a polyethylene glycol-2000 aqueous solution with a concentration of 1-5 g / L, an ammonia chloride aqueous solution with a concentration of 50-150 ppm, an ammonia solution with a concentration of 150-300 mL / L, a butynediol aqueous solution with a concentration of 0.5-2 g / L, and a polyvinylpyrrolidone aqueous solution with a concentration of 0.5-1 g / L; the main components of the B solution include a silver nitrate aqueous solution with a concentration of 10-30 g / L and an ammonia solution with a concentration of 10-20 mL / L; the main components of the C solution include a reducing agent with a concentration of 10-30 g / L and an ammonia solution with a concentration of 10-20 mL / L.

3. The method for efficiently preparing micron-sized silver-plated copper powder according to claim 1, characterized in that: The mass volume ratio of the copper powder to the A liquid is (30-100) g:1 L, and the volume ratio of the added amounts of the A liquid, the B liquid, and the C liquid is 2:2:

1.

4. The method for efficiently preparing micron-sized silver-plated copper powder according to claim 1, characterized in that: The ultrasonic stirring time is 10-30 min, and the B solution and the C solution are added dropwise within 2-3 h.

5. The method for efficiently preparing micron-sized silver-plated copper powder according to claim 1, characterized in that: The B solution and the C solution are added dropwise at a uniform speed, and the dropwise addition rate is 5-10 mL / min.

6. The method for efficiently preparing micron-sized silver-plated copper powder according to claim 1, characterized in that: The B solution and the C solution are added dropwise using a peristaltic pump.

7. A method for efficiently preparing micron-sized silver-plated copper powder according to any one of claims 1 to 6, characterized in that: The steps include: S1, preparation of silver plating solution S11, prepare solution A: weigh one or more of 1-3 g of 5-5-dimethylhydantoin, 50-100 g of EDTA-2Na, 1-5 g of polyethylene glycol-2000, 50-150 mL of ammonium chloride, 150-300 mL of ammonia water, 0.5-2 g of butynediol, and 0.5-1 g of polyvinylpyrrolidone in a beaker, add to 1 L of deionized water and stir evenly; S12, prepare solution B: dissolve 10-30 g of silver nitrate in 1 L of deionized water to prepare a silver nitrate solution, then add 10-20 mL of ammonia water dropwise and stir until the precipitate is completely dissolved to form a transparent and colorless mixed solution; S13, preparing liquid C: dissolving 10-30 g of one or more of glucose, sodium hypophosphite, formaldehyde, hydrazine hydrate, sorbitol or potassium sodium tartrate in 1 L of deionized water, and then adding 10-20 mL / L of ammonia water dropwise and stirring; S2, taking the liquid A prepared in step S11 and putting it into a container, adding copper powder therein, and ultrasonically stirring in an ultrasonic constant temperature water bath at 30-50° C. for 10-30 minutes, wherein the volume mass ratio of the liquid A to the copper powder is 1L: (30-100) g; S3, after the ultrasound is finished, continue to drop 1L of liquid B into the container, wherein liquid B is added dropwise using a peristaltic pump at a rate of 5-10 mL / min, and slowly stirred during the dropping process; S4, when liquid B is added to 20-30% of the remaining amount, start to add 0.5L of liquid C to the container, and continue to add liquid B until the addition is complete. After liquid C is completely added, continue to stir for at least 0.5h, wherein liquid C is added using a peristaltic pump with a drop rate of 5-10 mL / min; S5, after taking out the obtained mixture from the container, repeatedly washing it with deionized water and anhydrous ethanol for multiple times, and drying it under nitrogen protection or vacuum conditions to obtain silver-plated copper powder, wherein the drying temperature is 40-100° C. and the drying time is 30-120 min.

8. A silver-plated copper powder, characterized in that: The silver-plated copper powder is prepared by the method according to claim 7, and the silver-plated copper powder has an average particle size D50 of 5 to 10 μm and a volume resistivity of 1.55 to 8 mΩ·mm.

9. An application of the silver-plated copper powder as claimed in claim 8, characterized in that: The silver-plated copper powder prepared according to claim 8 is used to prepare conductive adhesive, conductive coating or shielding film material.

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