Spherical-like copper powder and preparation method and application thereof

Abstract

The invention relates to sphere-like copper powder and a preparation method and application thereof, and relates to the field of copper powder manufacturing. According to the method, a copper salt solution is used as a raw material, and through preparation of a copper oxide intermediate, reduction precipitation and surface modification treatment, the high-purity, low-oxygen-content, spheroidic and excellent-dispersity copper powder is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of copper powder manufacturing, in particular to a kind of spheroidal copper powder and its preparation method and application. BACKGROUND

[0002] With the development of electronic components to miniaturization, high integration, multilayer ceramic capacitor (MLCC), low temperature co-fired ceramic (LTCC) and other high-performance electronic components require conductive paste increasingly. Copper powder because of its excellent conductivity, lower cost and good sinterability, become the ideal conductive material to replace precious metals (such as silver), widely used in MLCC copper paste, LTCC copper paste, film thickness conductive paste, conductive adhesive and silver-coated copper powder base powder.

[0003] However, the traditional copper powder preparation process (such as chemical reduction method, electrolysis method, atomization method, etc.) has the following technical bottlenecks: (1) poor dispersibility: copper powder is easy to agglomerate, which leads to uneven coating of the paste, affecting the electrode density and conductivity; (2) morphology is uncontrollable: irregular particles or flaky copper powder is easy to form pores in the paste, which reduces the sintering density; (3) insufficient oxidation resistance: the surface of copper powder is easy to oxidize, which increases the resistance of the paste and affects the long-term reliability; (4) wide particle size distribution: coarse particles affect the printing accuracy, and fine particles are easy to sinter and shrink unevenly, which restricts the performance of high-precision electronic components.

[0004] At present, the market demand for high dispersibility, spheroidal, low oxygen content copper powder is urgent. In the prior art, chemical reduction method combined with surface modification can improve dispersibility, but it is still difficult to balance morphology uniformity and oxidation resistance; while silver-coated copper powder can improve oxidation resistance, but the cost is high, and the coating layer is easy to break. Therefore, it is of great significance to develop a low-cost, high-dispersibility, spheroidal and oxidation-resistant copper powder preparation process to promote the development of high-performance electronic paste. SUMMARY

[0005] In view of the above problems, the present application provides a preparation method of spheroidal copper powder, which uses copper salt solution as raw material, and obtains high-purity, low-oxygen content, spheroidal and excellent dispersibility copper powder through copper oxide intermediate preparation, reduction precipitation and surface modification treatment.

[0006] In order to achieve the above purpose, the present application provides a preparation method of spheroidal copper powder, comprising the following steps:

[0007] Pre-reduction reaction: adding an alkaline precipitant to the copper salt solution, stirring to form a copper hydroxide precipitate, heating to obtain a solid-liquid mixture containing copper oxide particles;

[0008] The reducing precipitation reaction is performed by adjusting pH value of the solid-liquid mixture containing copper oxide particles, or adding a dispersant to the solid-liquid mixture containing copper oxide particles to adjust pH value, adding a reducing agent, and stirring under heating to obtain a solid-liquid mixture containing copper powder particles.

[0009] The surface modification treatment is performed by solid-liquid separation, alkali washing, water washing, and alcohol washing on the solid-liquid mixture containing copper powder particles to obtain a filter cake, adding a surface modifier, stirring, and performing vacuum freeze drying to obtain the spherical copper powder.

[0010] The dispersant can be added or not added according to the particle size of the copper powder. If the particle size of the copper powder to be prepared is relatively small, the dispersant can be added. If the particle size of the copper powder to be prepared is relatively large, the dispersant does not need to be added, and good dispersibility can be achieved by the cooperation of the above preparation process.

[0011] The copper powder, as the core conductive phase of electronic paste, needs to meet the requirements of high purity, low oxygen content, controllable morphology, and particle size distribution. The traditional preparation method has problems such as oxidation, agglomeration, or high cost, while the above new process can optimize the performance through composite reduction and surface modification technology. The copper salt solution is used as raw material, and the high-purity, low-oxygen-content, spherical, and excellent-dispersibility copper powder is obtained through the preparation of copper oxide intermediate, reducing precipitation, and surface modification treatment.

[0012] In one embodiment, the molar concentration of the alkaline precipitant is 8.0-15.0 mol / L, the molar concentration of the copper salt solution is 0.8-3.0 mol / L, the mass of the dispersant is 0-2% of the mass of the spherical copper powder, the molar concentration of the reducing agent is 1.0-5.0 mol / L, the surface modifier includes an organic component and a solvent, and the mass of the organic component is 0.01%-3% of the mass of the spherical copper powder.

[0013] In one embodiment, the alkaline precipitant in the pre-reduction reaction step includes at least one of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, and potassium carbonate.

[0014] The solute of the copper salt solution includes at least one of copper sulfate, copper nitrate, and copper chloride.

[0015] In one embodiment, the dispersant in the reducing precipitation reaction step includes at least one of gum arabic, gelatin, polyethylene glycol, polyvinyl alcohol, and polyvinylpyrrolidone.

[0016] The reducing agent includes at least one of hydroquinone, ascorbic acid, hydrazine hydrate, sodium sulfite, sodium borohydride, and hydroxylamine sulfate.

[0017] In one embodiment, the organic component includes at least one of alkyl phenol polyoxyethylene ether, nonyl phenol polyoxyethylene ether, unsaturated fatty acid, and saturated fatty acid.

[0018] In one embodiment, the solvent includes anhydrous ethanol, and the mass fraction of the organic component in the surface modifier is less than or equal to 10%.

[0019] In one embodiment, in the pre-reduction reaction step, the heating temperature is 60-80°C.

[0020] In one embodiment, in the reduction precipitation reaction step, the pH value is adjusted to 10-12, and the heating temperature is 60-85°C.

[0021] In one embodiment, the preparation method is as follows:

[0022] Step 1: pre-reduction reaction

[0023] A basic precipitant is added to a copper salt solution to generate a copper hydroxide precipitate, which is decomposed into copper oxide by heating (60-80°C);

[0024] The copper oxide particles generated in this step have controllable morphology, providing a uniform reaction interface for subsequent reduction;

[0025] Step 2: reduction precipitation reaction

[0026] Under heating and stirring, a dispersant solution, a lye, and a reducing agent solution are added, the pH range is adjusted to 10-12, and the reaction is stirred at 60-80°C to generate copper powder particles;

[0027] This step controls the copper powder particle size (0.5-3 μm) and morphology (spherical) by adjusting the reducing agent concentration, pH (10-12), and reaction time, and can also improve the dispersibility of the copper powder by adding a dispersant;

[0028] Step 3: surface modification treatment

[0029] The solid-liquid mixture obtained from the reduction precipitation reaction in Step 2 is separated, washed with lye, water, and alcohol to obtain a filter cake, and then a surface modification solution is added to the filter cake for stirring and coating treatment. After uniform dispersion, the obtained solid-liquid mixture is vacuum freeze-dried, and then mechanically dispersed to obtain high-dispersibility copper powder;

[0030] In this step, after alcohol washing, a surface modification solution containing an organic component (such as oleic acid) is added to the copper powder, forming a protective layer on the surface of the copper powder through adsorption or chemical reaction, which can effectively prevent oxidation and agglomeration.

[0031] The application also provides the spheroid copper powder prepared by the preparation method.

[0032] The application also provides an electronic paste prepared by the spheroid copper powder.

[0033] The application also provides the application of the spheroid copper powder in the preparation of an electronic paste or conductive material.

[0034] In one embodiment, the electronic paste comprises at least one of MLCC copper paste, LTCC copper paste and film-thickness conductive paste.

[0035] In one embodiment, the conductive material comprises at least one of conductive adhesive or base powder of silver-coated copper powder.

[0036] Compared with the prior art, the application has the following beneficial effects:

[0037] The spheroid copper powder, the preparation method and the application thereof can meet the strict requirements of the fields of MLCC, LTCC and the like for high-performance copper-based conductive materials by optimizing a reduction system, controlling nucleation and growth kinetics and a surface modification technology to prepare high-dispersibility spheroid copper powder suitable for high-end electronic paste. The preparation method and the copper powder prepared by the method have the following advantages: 1. high dispersibility: uniform nucleation sites are provided by copper oxide precursors, and agglomeration is significantly reduced by surface modification; 2. spheroid morphology: reduction process kinetics control makes the copper powder close to spherical shape, and improves the flowability and printing performance of the paste; 3. low oxygen content: surface modification and inert atmosphere treatment make the oxygen content less than 0.5% (wt.%); 4. controllable process: by adjusting the type of reducing agent, the amount of modifier and the like, different application scenarios can be adapted. The preparation method is simple and low in cost, and the copper powder is suitable for high-precision electronic paste, and especially meets the strict requirements of MLCC, LTCC and the like for conductive materials. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 It is the copper powder electron microscope picture of embodiment 1 of the application;

[0039] Figure 2 It is the copper powder electron microscope picture of embodiment 2 of the application;

[0040] Figure 3 It is the copper powder electron microscope picture of embodiment 3 of the application;

[0041] Figure 4 It is the copper powder electron microscope picture of comparative example 1 of the application;

[0042] Figure 5 It is the copper powder electron microscope picture of comparative example 2 of the application. DETAILED DESCRIPTION

[0043] For the purposes of promoting an understanding of the principles of the application, the application will now be described with reference to the accompanying drawings. The preferred embodiments are illustrated in the drawings, wherein like reference numerals designate corresponding parts throughout the several views. The application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the application to those skilled in the art.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0045] Example 1

[0046] I. Preparation method of spheroid copper powder

[0047] Step 1: Pre-reduction reaction

[0048] Weigh 268g of sodium hydroxide into 0.5L of water and keep it at 60°C; dissolve 500g of copper nitrate trihydrate into 1L of deionized water and keep it at 60°C in a 5L three-necked flask; under mechanical stirring (400rpm), add the NaOH solution (alkaline precipitant) into the copper salt solution (copper salt solution) at a speed of 80mL / min through peristaltic pump 1#; after the addition is completed, raise the temperature of the reaction system to 80°C (water bath temperature control) and maintain stirring for 10min to obtain a solid-liquid mixture containing copper oxide particles. In this example, the molar concentration of the alkaline precipitant is 13.40mol / L and the molar concentration of the copper salt solution is 2.07mol / L.

[0049] Step 2: Reduction precipitation reaction

[0050] Dissolve 1.4g of PVP-K30 powder (dispersant) into 200ml of water and adjust it to 80°C; add the lye and adjust the pH value to 10-12; add the solid-liquid mixture containing copper oxide particles from Step 1 in one go and continue stirring for 10min; dissolve 400g of ascorbic acid (reducing agent) into 0.8L of water and adjust it to 80°C; add the ascorbic acid solution into the copper oxide solution at a speed of 50mL / min through peristaltic pump 2#; adjust the temperature to be stable within the range of 80±2°C during the addition process; after the addition is completed, keep it at temperature and stir for 10min to obtain a solid-liquid mixture containing copper powder particles. In this example, the amount of dispersant is 1.06% of the mass of spheroid copper powder and the molar concentration of the reducing agent is 2.84mol / L.

[0051] Step 3: Washing and surface modification treatment

[0052] Washing: The solid-liquid mixture obtained in step 2 was subjected to solid-liquid separation using a Buchner funnel, and was sequentially subjected to alkali washing, water washing, and alcohol washing.

[0053] Alkali washing: 0.5 L of 0.1 mol / L NaOH solution was added to the filter cake obtained by suction filtration, and stirring washing was performed for 5 min. After washing, the filter cake was subjected to suction filtration, and the above step was repeated twice. Water washing: The filter cake obtained by suction filtration after alkali washing was stirred and washed with 0.5 L of deionized water for 5 min. After washing, the filter cake was subjected to suction filtration, and the above step was repeated until the conductivity was less than 20 us / cm, and then suction filtration was performed. Alcohol washing: 400 g of electronic grade anhydrous ethanol was added to the filter cake obtained by suction filtration after water washing, and stirring washing was performed for 10 min. After washing, the filter cake was subjected to suction filtration.

[0054] Surface modification and drying and dispersion treatment: The filter cake obtained by suction filtration after alcohol washing was added to a high-speed disperser, and then 20 g of an ethanolic solution of oleic acid (surface modifier) was added, wherein the mass of oleic acid contained was 1.3 g (the mass percentage of oleic acid in the surface modifier was 6.5%). The high-speed disperser was operated at a speed of 5000 rpm, and the obtained solid-liquid mixture was dispersed for 5 min. The dispersed solid-liquid mixture was transferred into a quartz tray and placed in a vacuum drying oven for drying for 16 h. Finally, mechanical dispersion treatment was performed, and the product was passed through a 300-mesh sieve under ultrasonic vibration. In this embodiment, the amount of oleic acid used was 0.98% of the mass of the spherical copper powder.

[0055] II. Performance test

[0056] 1. Product test: Morphology analysis: SEM showed that the copper powder was regular spherical Figure 1 ).

[0057] 2. TG test residual mass (medium nitrogen, temperature rise rate 5℃ / min, temperature range 0℃-1200℃).

[0058] 3. Particle size distribution: Malvern 3000 laser particle size analyzer was used to determine D10, D50, and D90 with anhydrous ethanol as the solvent.

[0059] 4. Specific surface area: nitrogen adsorption method; bulk density and tap density were determined according to national standards GB / T 1479.2-2011 and GB / T 5162-2021, respectively.

[0060] The performance test data of Example 1 are shown in Table 1.

[0061] Example 2

[0062] In this embodiment, 400 g of ascorbic acid in step 2 of Example 1 was replaced with 150 g of 50% hydrazine hydrate (AR grade), and other conditions were the same as in Example 1. In this embodiment, the molar concentration of the reducing agent hydrazine hydrate was 3.15 mol / L.

[0063] Test Results: Morphology Analysis: SEM showed that the copper powder was in the form of regular spherical shapes. Figure 2 The remaining test conditions are the same as in Example 1, and the test data are shown in Table 1.

[0064] Example 3

[0065] The difference from Example 1 is that the step 2 in Example 1, "1.4g of PVP-K30 powder is dissolved in 200ml of water", is omitted, that is, the amount of PVP-K30 added is 0g, and other conditions are the same as in Example 1.

[0066] Test Results: Morphology Analysis: SEM showed that the copper powder was in the form of regular spherical shapes. Figure 3 The remaining test conditions are the same as in Example 1, and the test data are shown in Table 1.

[0067] Comparative Example 1

[0068] In Example 1, step two, the amount of PVP-K30 added in the step of "dissolving 1.4g of PVP-K30 powder in 200ml of water" was increased from 1.4g to 5g, while other conditions remained the same as in Example 1. In this comparative example, the amount of dispersant PVP-K30 was 3.78% of the mass of the spherical copper powder.

[0069] Test Results: Morphology Analysis: SEM showed that the copper powder was in the form of regular spherical shapes. Figure 4 The remaining test conditions are the same as in Example 1, and the test data are shown in Table 1.

[0070] Results: The copper powder had a small particle size and irregular morphology, and the residual mass was low according to TG test.

[0071] Comparative Example 2

[0072] In Example 1, step two, 400g of ascorbic acid was replaced with 400g of glucose (AR grade), with no other changes. In this comparative example, the molar concentration of the reducing agent glucose was 2.78 mol / L.

[0073] Test Results: Morphology Analysis: SEM showed that the copper powder was in the form of regular spherical shapes. Figure 5 The remaining test conditions are the same as in Example 1, and the test data are shown in Table 1.

[0074] Results: The copper powder had an irregular morphology and varied in size, with a particle size distribution D50 > 3 μm.

[0075] Table 1. Performance test results of copper powder prepared in each embodiment and comparative example.

[0076]

[0077]

[0078] Any combination of the technical features in the above-described embodiments can be made, and for the sake of brevity, not all possible combinations are described, however, as long as there is no conflict, any combination of the technical features should be considered within the scope of the present disclosure.

[0079] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the scope of protection of the patent of the present application should be subject to the appended claims.

Claims

1. A method for preparing a spheroid-like copper powder, characterized by, The method comprises the following steps: a pre-reduction reaction, in which a basic precipitant is added to a copper salt solution, stirred to form a copper hydroxide precipitate, and heated to obtain a solid-liquid mixture containing copper oxide particles; a reduction precipitation reaction, in which the pH value of the solid-liquid mixture containing copper oxide particles is adjusted, or a dispersant is added to the solid-liquid mixture containing copper oxide particles to adjust the pH value, and a reducing agent is added and stirred under heating to obtain a solid-liquid mixture containing copper powder particles; a surface modification treatment, in which the solid-liquid mixture containing copper powder particles is subjected to solid-liquid separation, alkaline washing, water washing, alcohol washing to obtain a filter cake, a surface modifier is added, stirred, and vacuum freeze-dried to obtain spherical copper powder.

2. The production method according to claim 1, characterized by, The molar concentration of the basic precipitant is 8.0-15.0 mol / L, the molar concentration of the copper salt solution is 0.8-3.0 mol / L, the mass of the dispersant is 0-2% of the mass of the spherical copper powder, the molar concentration of the reducing agent is 1.0-5.0 mol / L, and the surface modifier comprises an organic component and a solvent, and the mass of the organic component is 0.01%-3% of the mass of the spherical copper powder.

3. The production method according to claim 1, characterized by, In the pre-reduction reaction step, the basic precipitant comprises at least one of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, and potassium carbonate. The solute of the copper salt solution comprises at least one of copper sulfate, copper nitrate, and copper chloride.

4. The method of claim 1, wherein, In the reduction precipitation reaction step, the dispersant comprises at least one of gum arabic, gelatin, polyethylene glycol, polyvinyl alcohol, and polyvinylpyrrolidone. The reducing agent comprises at least one of hydroquinone, ascorbic acid, hydrazine hydrate, sodium sulfite, sodium borohydride, and hydroxylamine sulfate.

5. The preparation method according to claim 1, characterized in that, The organic component comprises at least one of alkylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether, unsaturated fatty acid, and saturated fatty acid.

6. The production method according to any one of claims 1 to 5, characterized by, In the pre-reduction reaction step, the heating temperature is 60-80℃.

7. The production method according to claim 6, wherein In the reduction precipitation reaction step, the pH value is adjusted to 10-12, and the heating temperature is 60-85℃.

8. The spherical copper powder obtained by the preparation method of any one of claims 1-7.

9. An electronic paste characterized by, The spherical copper powder is prepared by the method of claim 8.

10. The use of the spherical copper powder of claim 8 in the preparation of electronic paste or conductive material.

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