Micron-sized spherical gold powder and preparation method and application thereof

Abstract

The invention discloses a micron-sized spherical gold powder and a preparation method and application thereof, belonging to the technical field of metal powders. The invention adopts a two-step method to synthesize the gold powder. In the first step, a gold salt solution is adjusted to pH 7-9 and 3-5, and the mixture is mixed with a dispersant solution and a reducing agent solution to obtain a precursor solution. In the second step, the precursor solution is mixed with the gold salt solution, the pH is adjusted to 3-5, and the mixture is mixed with a dispersant solution and a reducing agent solution to obtain the micron-sized spherical gold powder. The gold powder has a suitable particle size, a spherical surface morphology, a uniform particle size distribution, a good dispersion, and no agglomeration. The gold powder is applied to the preparation of a conductive slurry, and the performance of the conductive slurry can be effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal powders, and in particular to micron-grade spherical gold powder and a preparation method and application thereof. Background Art

[0002] Gold has high chemical stability, and its thermal and electrical conductivity are second only to silver and copper. Gold conductors have good stability in harsh environments, and gold conductors have almost no tendency to electromigrate in normal environments. Therefore, gold is increasingly widely used in the field of electronic technology.

[0003] One of the important uses of gold powder is to prepare gold paste. As the functional phase in gold conductor paste, gold powder accounts for 60% to 90% of the content in gold conductor paste. The uniformity, dispersion, surface morphology and size of its particles have a great influence on the printing performance and sintering performance of the paste. As the main filling skeleton of conductive paste, the particle size of gold powder has an important influence on the printing performance, sintering shrinkage characteristics, shielding rate, etc. of the overall paste. The particle size grading effect of gold powder is good, and the paste can obtain 1) relatively balanced leveling and thixotropy, which is conducive to different printing requirements; 2) less sintering shrinkage, avoiding the occurrence of through holes, cracks and other defects during the sintering process; 3) It is conducive to obtaining a sintering temperature that can match the co-firing of other materials, such as thick film hybrid integrated circuit substrates, LTCC substrates and other applications.

[0004] At present, conventional methods for preparing ultrafine gold powder are all through chemical reduction, where gold ions are reduced by a reducing agent in a solvent system to generate single gold powder. The current methods are all one-step preparation. The current preparation methods are difficult to obtain gold powder with a particle size above micron level, good surface morphology, and good dispersion effect, which limits its application in conductive slurries.

[0005] In view of this, this application is filed. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a micron-sized spherical gold powder and a preparation method and application thereof. The micron-sized spherical gold powder prepared by the present invention has a suitable particle size, a spherical surface morphology, a uniform particle size distribution, good dispersion, and no agglomeration phenomenon. It is applied to the preparation of conductive slurry to effectively improve the performance of the conductive slurry.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A method for preparing micron-sized spherical gold powder comprises the following steps:

[0009] (1) Add water to tetrachloroauric acid to prepare a gold salt solution; add water to a reducing agent to prepare a reducing agent solution; add water to a dispersant to prepare a dispersant solution for later use;

[0010] (2) adjusting the pH of the gold salt solution to 7-9 with an ammonia solution, and then adjusting the pH to 3-5 with a hydrochloric acid solution to obtain a first acidic mixed solution; adding the dispersant solution to the acidic mixed solution, stirring evenly, to obtain a first mixed solution; then adding the reducing agent solution, stirring evenly, centrifuging, and washing to obtain a precursor solution;

[0011] (3) Mix the precursor solution and the gold salt solution evenly, add hydrochloric acid solution to adjust the pH to 3-5, and obtain a second acidic mixed solution; then add the dispersant solution and stir evenly to obtain a second mixed solution; finally, add the reducing agent solution, stir evenly, centrifuge, wash, and dry to obtain micron-sized spherical gold powder.

[0012] The present invention creatively adopts a two-step method to synthesize gold powder. In the first step, the pH value of a gold salt solution is adjusted to 7-9 and 3-5, and the mixture is mixed with a dispersant solution and a reducing agent solution to obtain a precursor solution. In the second step, the precursor solution is mixed with the gold salt solution, the pH value is adjusted to 3-5, and the mixture is mixed with a dispersant solution and a reducing agent solution to obtain micron-sized spherical gold powder. The gold powder has a suitable particle size, a spherical surface morphology, a uniform particle size distribution, a good dispersion, and no agglomeration. The gold powder is applied to the preparation of a conductive slurry to effectively improve the performance of the conductive slurry.

[0013] The inventors of the present invention have found that the synthesis of gold powder generally consists of two processes, namely nucleation and growth. These two processes have a certain internal competitiveness, and their respective advantages and disadvantages are controlled by the synthesis conditions. The one-step method usually has a large advantage in the nucleation process, because the gold source in the solution has been consumed by the nucleation process before the gold particles grow up, and it is difficult to obtain micron-sized spherical gold powder. The two-step rule can distinguish the nucleation process from the growth process, avoid the generation of flaky gold powder during the synthesis process, reduce the tendency of agglomeration between gold powder particles, effectively improve the growth effect, obtain a suitable particle size, a spherical surface morphology, a uniform particle size distribution, a good dispersion, and no agglomeration phenomenon. It is applied to the preparation of conductive slurry, which can effectively improve the performance of the conductive slurry.

[0014] As a preferred embodiment of the present invention, in the gold salt solution, the mass ratio of tetrachloroauric acid to water is (5-10):100.

[0015] As a preferred embodiment of the present invention, in the reducing agent solution, the mass ratio of reducing agent to water is (1-20):100; and the reducing agent is vitamin C.

[0016] As a preferred embodiment of the present invention, in the reducing agent solution, the mass ratio of dispersant to water is (1-10):1000; and the dispersant is polyvinyl pyrrolidone.

[0017] As a preferred embodiment of the present invention, the average molecular weight of the polyvinyl pyrrolidone is 1000000-1500000. The inventors of the present invention have found that PVP is mainly divided into three types according to molecular weight, one type has a molecular weight of 8000-12000, one type has a molecular weight of 30000-70000, and the other type has a molecular weight of 1000000-1500000. The present invention uses PVP with a molecular weight of 1000000-1500000, which can make it evenly adsorbed on the surface of gold particles to form a more stable adsorption layer, and can form a more complex structure on the surface of gold powder, thereby increasing stability and strength, and can effectively improve the dispersibility and stability of gold powder and reduce the agglomeration tendency of gold powder.

[0018] As a preferred embodiment of the present invention, the mass ratio of the first acidic mixed solution to the dispersant solution in step (2) is 1:(0.5-2);

[0019] The mass ratio of the first mixed solution to the reducing agent solution in step (2) is 1:(0.5-2).

[0020] As a preferred embodiment of the present invention, the mass ratio of the precursor solution to the gold salt solution in step (3) is 1:(1-10).

[0021] As a preferred embodiment of the present invention, the mass ratio of the second acidic mixed solution to the dispersant solution in step (3) is 1:(0.5-2);

[0022] The mass ratio of the second mixed solution to the reducing agent solution in step (3) is 1:(0.5-2).

[0023] The present invention also provides a micron-sized spherical gold powder, which is prepared by the above-mentioned preparation method.

[0024] The invention also provides an application of micron-sized spherical gold powder in preparing conductive paste.

[0025] The beneficial effects of the present invention are as follows: the present invention adopts a two-step method to synthesize gold powder, in the first step, adjusting the pH value of a gold salt solution to 7-9, 3-5, and mixing it with a dispersant solution and a reducing agent solution to obtain a precursor solution; in the second step, mixing the precursor solution with the gold salt solution, adjusting the pH value to 3-5, and then mixing it with a dispersant solution and a reducing agent solution to obtain micron-sized spherical gold powder, the gold powder has a suitable particle size, a spherical surface morphology, a uniform particle size distribution, a good dispersion, and no agglomeration phenomenon, and is applied to the preparation of a conductive slurry to effectively improve the performance of the conductive slurry. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a scanning electron microscope image of the micron-sized spherical gold powder synthesized in Example 1. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application are described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0028] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0029] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0030] In the present application, there is no particular limitation on the specific dispersion and stirring treatment methods.

[0031] Unless otherwise specified, the components, raw materials or instruments used in the embodiments and comparative examples of the present invention are all commercially available raw materials or instruments, and the components and raw materials used in each parallel experiment are all of the same kind.

[0032] Among them, PVP-1: the average molecular weight is 1300000, which comes from McLean reagent.

[0033] PVP-2: The average molecular weight is 58,000 and is derived from McLean's reagent.

[0034] PVP-3: The average molecular weight is 10,000 and is derived from McLean's reagent.

[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0036] The following examples are provided to facilitate understanding of the present invention. These examples are not provided to limit the scope of the claims.

[0037] Example 1

[0038] A method for preparing micron-sized spherical gold powder comprises the following steps:

[0039] (1) Prepare a gold salt solution by mixing tetrachloroauric acid and water in a mass ratio of 8:100; prepare a reducing agent solution by mixing vitamin C and water in a mass ratio of 10:100; prepare a dispersant solution by mixing PVP-1 and water in a mass ratio of 5:1000; keep them for later use (the amount provided is sufficient for the following steps);

[0040] (2) adjusting the pH of the gold salt solution to 8 with a 1 mol / L ammonia solution, and then adjusting the pH to 4 with a 1 mol / L hydrochloric acid solution to obtain a first acidic mixed solution; adding the dispersant solution to the acidic mixed solution, stirring evenly, to obtain a first mixed solution; then adding the reducing agent solution, stirring evenly, centrifuging, and washing to obtain a precursor solution;

[0041] The mass ratio of the first acidic mixed solution to the dispersant solution is 1:0.5; the mass ratio of the first mixed solution to the reducing agent solution is 1:0.5;

[0042] (3) Mix the precursor solution and the gold salt solution evenly, add 1 mol / L hydrochloric acid solution to adjust the pH to 4 to obtain a second acidic mixed solution; then add the dispersant solution and stir evenly to obtain a second mixed solution; finally, add the reducing agent solution, stir evenly, centrifuge, wash, and dry to obtain micron-sized spherical gold powder.

[0043] The mass ratio of the precursor solution to the gold salt solution is 1:5; the mass ratio of the second acidic mixed solution to the dispersant solution is 1:0.5; and the mass ratio of the second mixed solution to the reducing agent solution is 1:0.5.

[0044] The scanning electron microscope image of the micron-sized spherical gold powder prepared in this embodiment is as follows: Figure 1 As shown, from Figure 1 It can be seen that the gold powder described in the present invention is micron-sized, has a spherical surface morphology, uniform particle size distribution, good dispersion, and no agglomeration. Applying it to prepare conductive paste can effectively improve the performance of the conductive paste.

[0045] Example 2

[0046] A method for preparing micron-sized spherical gold powder comprises the following steps:

[0047] (1) Prepare a gold salt solution by mixing tetrachloroauric acid and water in a mass ratio of 1:100; prepare a reducing agent solution by mixing vitamin C and water in a mass ratio of 1:100; prepare a dispersant solution by mixing PVP-1 and water in a mass ratio of 1:1000; keep them for later use (the amount provided is sufficient for the following steps);

[0048] (2) adjusting the pH of the gold salt solution to 7 with a 1 mol / L ammonia solution, and then adjusting the pH to 3 with a 1 mol / L hydrochloric acid solution to obtain a first acidic mixed solution; adding the dispersant solution to the acidic mixed solution, stirring evenly, to obtain a first mixed solution; then adding the reducing agent solution, stirring evenly, centrifuging, and washing to obtain a precursor solution;

[0049] The mass ratio of the first acidic mixed solution to the dispersant solution is 1:1; the mass ratio of the first mixed solution to the reducing agent solution is 1:1;

[0050] (3) Mix the precursor solution and the gold salt solution evenly, add 1 mol / L hydrochloric acid solution to adjust the pH to 3 to obtain a second acidic mixed solution; then add the dispersant solution and stir evenly to obtain a second mixed solution; finally, add the reducing agent solution, stir evenly, centrifuge, wash, and dry to obtain micron-sized spherical gold powder.

[0051] The mass ratio of the precursor solution to the gold salt solution is 1:5; the mass ratio of the second acidic mixed solution to the dispersant solution is 1:1; and the mass ratio of the second mixed solution to the reducing agent solution is 1:1.

[0052] Example 3

[0053] A method for preparing micron-sized spherical gold powder comprises the following steps:

[0054] (1) Prepare a gold salt solution by mixing tetrachloroauric acid and water in a mass ratio of 10:100; prepare a reducing agent solution by mixing vitamin C and water in a mass ratio of 20:100; prepare a dispersant solution by mixing PVP-1 and water in a mass ratio of 10:1000; keep them for later use (the amount provided is sufficient for the following steps);

[0055] (2) adjusting the pH of the gold salt solution to 10 with a 1 mol / L ammonia solution, and then adjusting the pH to 5 with a 1 mol / L hydrochloric acid solution to obtain a first acidic mixed solution; adding the dispersant solution to the acidic mixed solution, stirring evenly, to obtain a first mixed solution; then adding the reducing agent solution, stirring evenly, centrifuging, and washing to obtain a precursor solution;

[0056] The mass ratio of the first acidic mixed solution to the dispersant solution is 1:2; the mass ratio of the first mixed solution to the reducing agent solution is 1:2;

[0057] (3) Mix the precursor solution and the gold salt solution evenly, add 1 mol / L hydrochloric acid solution to adjust the pH to 5 to obtain a second acidic mixed solution; then add the dispersant solution and stir evenly to obtain a second mixed solution; finally, add the reducing agent solution, stir evenly, centrifuge, wash, and dry to obtain micron-sized spherical gold powder.

[0058] The mass ratio of the precursor solution to the gold salt solution is 1:5; the mass ratio of the second acidic mixed solution to the dispersant solution is 1:2; and the mass ratio of the second mixed solution to the reducing agent solution is 1:2.

[0059] Example 4

[0060] A method for preparing micron-sized spherical gold powder comprises the following steps:

[0061] (1) Prepare a gold salt solution by mixing tetrachloroauric acid and water in a mass ratio of 8:100; prepare a reducing agent solution by mixing vitamin C and water in a mass ratio of 10:100; prepare a dispersant solution by mixing PVP-1 and water in a mass ratio of 5:1000; keep them for later use (the amount provided is sufficient for the following steps);

[0062] (2) adjusting the pH of the gold salt solution to 8 with a 1 mol / L ammonia solution, and then adjusting the pH to 4 with a 1 mol / L hydrochloric acid solution to obtain a first acidic mixed solution; adding the dispersant solution to the acidic mixed solution, stirring evenly, to obtain a first mixed solution; then adding the reducing agent solution, stirring evenly, centrifuging, and washing to obtain a precursor solution;

[0063] The mass ratio of the first acidic mixed solution to the dispersant solution is 1:1; the mass ratio of the first mixed solution to the reducing agent solution is 1:1;

[0064] (3) Mix the precursor solution and the gold salt solution evenly, add 1 mol / L hydrochloric acid solution to adjust the pH to 4 to obtain a second acidic mixed solution; then add the dispersant solution and stir evenly to obtain a second mixed solution; finally, add the reducing agent solution, stir evenly, centrifuge, wash, and dry to obtain micron-sized spherical gold powder.

[0065] The mass ratio of the precursor solution to the gold salt solution is 1:1; the mass ratio of the second acidic mixed solution to the dispersant solution is 1:1; and the mass ratio of the second mixed solution to the reducing agent solution is 1:1.

[0066] Example 5

[0067] A method for preparing micron-sized spherical gold powder comprises the following steps:

[0068] (1) Prepare a gold salt solution by mixing tetrachloroauric acid and water in a mass ratio of 8:100; prepare a reducing agent solution by mixing vitamin C and water in a mass ratio of 10:100; prepare a dispersant solution by mixing PVP-1 and water in a mass ratio of 5:1000; keep them for later use (the amount provided is sufficient for the following steps);

[0069] (2) adjusting the pH of the gold salt solution to 8 with a 1 mol / L ammonia solution, and then adjusting the pH to 4 with a 1 mol / L hydrochloric acid solution to obtain a first acidic mixed solution; adding the dispersant solution to the acidic mixed solution, stirring evenly, to obtain a first mixed solution; then adding the reducing agent solution, stirring evenly, centrifuging, and washing to obtain a precursor solution;

[0070] The mass ratio of the first acidic mixed solution to the dispersant solution is 1:1; the mass ratio of the first mixed solution to the reducing agent solution is 1:1;

[0071] (3) Mix the precursor solution and the gold salt solution evenly, add 1 mol / L hydrochloric acid solution to adjust the pH to 4 to obtain a second acidic mixed solution; then add the dispersant solution and stir evenly to obtain a second mixed solution; finally, add the reducing agent solution, stir evenly, centrifuge, wash, and dry to obtain micron-sized spherical gold powder.

[0072] The mass ratio of the precursor solution to the gold salt solution is 1:10; the mass ratio of the second acidic mixed solution to the dispersant solution is 1:1; and the mass ratio of the second mixed solution to the reducing agent solution is 1:1.

[0073] Example 6

[0074] A method for preparing micron-sized spherical gold powder comprises the following steps:

[0075] (1) Prepare a gold salt solution by mixing tetrachloroauric acid and water in a mass ratio of 8:100; prepare a reducing agent solution by mixing vitamin C and water in a mass ratio of 10:100; prepare a dispersant solution by mixing PVP-2 and water in a mass ratio of 5:1000; keep them for later use (the amount provided is sufficient for the following steps);

[0076] (2) adjusting the pH of the gold salt solution to 8 with a 1 mol / L ammonia solution, and then adjusting the pH to 4 with a 1 mol / L hydrochloric acid solution to obtain a first acidic mixed solution; adding the dispersant solution to the acidic mixed solution, stirring evenly, to obtain a first mixed solution; then adding the reducing agent solution, stirring evenly, centrifuging, and washing to obtain a precursor solution;

[0077] The mass ratio of the first acidic mixed solution to the dispersant solution is 1:0.5; the mass ratio of the first mixed solution to the reducing agent solution is 1:0.5;

[0078] (3) Mix the precursor solution and the gold salt solution evenly, add 1 mol / L hydrochloric acid solution to adjust the pH to 4 to obtain a second acidic mixed solution; then add the dispersant solution and stir evenly to obtain a second mixed solution; finally, add the reducing agent solution, stir evenly, centrifuge, wash, and dry to obtain micron-sized spherical gold powder.

[0079] The mass ratio of the precursor solution to the gold salt solution is 1:5; the mass ratio of the second acidic mixed solution to the dispersant solution is 1:0.5; and the mass ratio of the second mixed solution to the reducing agent solution is 1:0.5.

[0080] Example 7

[0081] A method for preparing micron-sized spherical gold powder comprises the following steps:

[0082] (1) Prepare a gold salt solution by mixing tetrachloroauric acid and water in a mass ratio of 8:100; prepare a reducing agent solution by mixing vitamin C and water in a mass ratio of 10:100; prepare a dispersant solution by mixing PVP-3 and water in a mass ratio of 5:1000; keep them for later use (the amount provided is sufficient for the following steps);

[0083] (2) adjusting the pH of the gold salt solution to 8 with a 1 mol / L ammonia solution, and then adjusting the pH to 4 with a 1 mol / L hydrochloric acid solution to obtain a first acidic mixed solution; adding the dispersant solution to the acidic mixed solution, stirring evenly, to obtain a first mixed solution; then adding the reducing agent solution, stirring evenly, centrifuging, and washing to obtain a precursor solution;

[0084] The mass ratio of the first acidic mixed solution to the dispersant solution is 1:0.5; the mass ratio of the first mixed solution to the reducing agent solution is 1:0.5;

[0085] (3) Mix the precursor solution and the gold salt solution evenly, add 1 mol / L hydrochloric acid solution to adjust the pH to 4 to obtain a second acidic mixed solution; then add the dispersant solution and stir evenly to obtain a second mixed solution; finally, add the reducing agent solution, stir evenly, centrifuge, wash, and dry to obtain micron-sized spherical gold powder.

[0086] The mass ratio of the precursor solution to the gold salt solution is 1:5; the mass ratio of the second acidic mixed solution to the dispersant solution is 1:0.5; and the mass ratio of the second mixed solution to the reducing agent solution is 1:0.5.

[0087] Comparative Example 1

[0088] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 is synthesized by a one-step method.

[0089] A method for preparing gold powder comprises the following steps:

[0090] (1) Prepare a gold salt solution by mixing tetrachloroauric acid and water in a mass ratio of 8:100; prepare a reducing agent solution by mixing vitamin C and water in a mass ratio of 10:100; prepare a dispersant solution by mixing PVP-1 and water in a mass ratio of 5:1000; keep them for later use (the amount provided is sufficient for the following steps);

[0091] (2) Add 1 mol / L hydrochloric acid solution to the gold salt solution to adjust the pH to 4 to obtain a second acidic mixed solution; then add the dispersant solution and stir evenly to obtain a second mixed solution; finally add the reducing agent solution, stir evenly, centrifuge, wash, and dry to obtain micron-sized spherical gold powder.

[0092] The mass ratio of the second acidic mixed liquid to the dispersant solution is 1:0.5; the mass ratio of the second mixed liquid to the reducing agent solution is 1:0.5.

[0093] Comparative Example 2

[0094] The difference between Comparative Example 2 and Example 1 is that the dispersant in Comparative Example 2 is sodium dodecyl sulfate, and the other contents are the same.

[0095] A method for preparing micron-sized spherical gold powder comprises the following steps:

[0096] (1) Prepare a gold salt solution by mixing tetrachloroauric acid and water in a mass ratio of 8:100; prepare a reducing agent solution by mixing vitamin C and water in a mass ratio of 10:100; prepare a dispersant solution by mixing sodium dodecyl sulfate and water in a mass ratio of 5:1000; keep aside (the amount provided is sufficient for the following steps);

[0097] (2) adjusting the pH of the gold salt solution to 8 with a 1 mol / L ammonia solution, and then adjusting the pH to 4 with a 1 mol / L hydrochloric acid solution to obtain a first acidic mixed solution; adding the dispersant solution to the acidic mixed solution, stirring evenly, to obtain a first mixed solution; then adding the reducing agent solution, stirring evenly, centrifuging, and washing to obtain a precursor solution;

[0098] The mass ratio of the first acidic mixed solution to the dispersant solution is 1:0.5; the mass ratio of the first mixed solution to the reducing agent solution is 1:0.5;

[0099] (3) Mix the precursor solution and the gold salt solution evenly, add 1 mol / L hydrochloric acid solution to adjust the pH to 4 to obtain a second acidic mixed solution; then add the dispersant solution and stir evenly to obtain a second mixed solution; finally, add the reducing agent solution, stir evenly, centrifuge, wash, and dry to obtain micron-sized spherical gold powder.

[0100] The mass ratio of the precursor solution to the gold salt solution is 1:5; the mass ratio of the second acidic mixed solution to the dispersant solution is 1:0.5; and the mass ratio of the second mixed solution to the reducing agent solution is 1:0.5.

[0101] Comparative Example 3

[0102] The difference between Comparative Example 3 and Example 1 is that the mass ratio of the precursor solution to the gold salt solution is not within the scope of the present invention, and the others are the same.

[0103] A method for preparing micron-sized spherical gold powder comprises the following steps:

[0104] (1) Prepare a gold salt solution by mixing tetrachloroauric acid and water in a mass ratio of 8:100; prepare a reducing agent solution by mixing vitamin C and water in a mass ratio of 10:100; prepare a dispersant solution by mixing PVP-1 and water in a mass ratio of 5:1000; keep them for later use (the amount provided is sufficient for the following steps);

[0105] (2) adjusting the pH of the gold salt solution to 8 with a 1 mol / L ammonia solution, and then adjusting the pH to 4 with a 1 mol / L hydrochloric acid solution to obtain a first acidic mixed solution; adding the dispersant solution to the acidic mixed solution, stirring evenly, to obtain a first mixed solution; then adding the reducing agent solution, stirring evenly, centrifuging, and washing to obtain a precursor solution;

[0106] The mass ratio of the first acidic mixed solution to the dispersant solution is 1:0.5; the mass ratio of the first mixed solution to the reducing agent solution is 1:0.5;

[0107] (3) Mix the precursor solution and the gold salt solution evenly, add 1 mol / L hydrochloric acid solution to adjust the pH to 4 to obtain a second acidic mixed solution; then add the dispersant solution and stir evenly to obtain a second mixed solution; finally, add the reducing agent solution, stir evenly, centrifuge, wash, and dry to obtain micron-sized spherical gold powder.

[0108] The mass ratio of the precursor solution to the gold salt solution is 1:0.05; the mass ratio of the second acidic mixed solution to the dispersant solution is 1:0.5; and the mass ratio of the second mixed solution to the reducing agent solution is 1:0.5.

[0109] Comparative Example 4

[0110] The difference between Comparative Example 4 and Example 1 is that the mass ratio of the precursor solution to the gold salt solution is not within the scope of the present invention, and the others are the same.

[0111] A method for preparing micron-sized spherical gold powder comprises the following steps:

[0112] (1) Prepare a gold salt solution by mixing tetrachloroauric acid and water in a mass ratio of 8:100; prepare a reducing agent solution by mixing vitamin C and water in a mass ratio of 10:100; prepare a dispersant solution by mixing PVP-1 and water in a mass ratio of 5:1000; keep them for later use (the amount provided is sufficient for the following steps);

[0113] (2) adjusting the pH of the gold salt solution to 8 with a 1 mol / L ammonia solution, and then adjusting the pH to 4 with a 1 mol / L hydrochloric acid solution to obtain a first acidic mixed solution; adding the dispersant solution to the acidic mixed solution, stirring evenly, to obtain a first mixed solution; then adding the reducing agent solution, stirring evenly, centrifuging, and washing to obtain a precursor solution;

[0114] The mass ratio of the first acidic mixed solution to the dispersant solution is 1:0.5; the mass ratio of the first mixed solution to the reducing agent solution is 1:0.5;

[0115] (3) Mix the precursor solution and the gold salt solution evenly, add 1 mol / L hydrochloric acid solution to adjust the pH to 4 to obtain a second acidic mixed solution; then add the dispersant solution and stir evenly to obtain a second mixed solution; finally, add the reducing agent solution, stir evenly, centrifuge, wash, and dry to obtain micron-sized spherical gold powder.

[0116] The mass ratio of the precursor solution to the gold salt solution is 1:20; the mass ratio of the second acidic mixed solution to the dispersant solution is 1:0.5; and the mass ratio of the second mixed solution to the reducing agent solution is 1:0.5.

[0117] Test Case

[0118] Gold powder, glass powder, PVB resin and diethylene glycol butyl ether acetate were prepared into a conductive paste in a mass ratio of 82.5:2.5:15 for testing, wherein the gold powder was the gold powder of the embodiment and the comparative example, and the glass powder had the following composition ratios by mass percentage: 52% silicon dioxide, 24% boron oxide, 18% bismuth oxide, 5% sodium oxide, 0.9% zirconium oxide and 0.1% titanium dioxide.

[0119] 1. The conductive paste is screen-printed on the ceramic substrate, baked at 130°C, and then sintered at 950°C. After sintering, the performance is tested and placed at 85°C for 72 hours to test the resistivity change rate. The resistivity change rate = (resistivity after high temperature - initial resistivity) / initial resistivity * 100%.

[0120] 2. Test the viscosity of the conductive paste. After placing it for 1 month, test the viscosity change rate. The viscosity change rate = (viscosity before placement - viscosity after placement) / viscosity before placement * 100%.

[0121] Table 1

[0122]

[0123] It can be seen from Table 1 that the gold powder of the present invention has uniform particle size distribution, good dispersion, and no agglomeration. Applying it to prepare conductive paste can effectively improve the performance of the conductive paste.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing micron-sized spherical gold powder, characterized in that: The following steps are involved: (1) Add water to tetrachloroauric acid to prepare a gold salt solution; add water to a reducing agent to prepare a reducing agent solution; add water to a dispersant to prepare a dispersant solution for later use; In the gold salt solution, the mass ratio of tetrachloroauric acid to water is (5-10):100; In the reducing agent solution, the mass ratio of reducing agent to water is (1-20):100; the reducing agent is vitamin C; In the dispersant solution, the mass ratio of dispersant to water is (1-10): 1000; (2) adjusting the pH of the gold salt solution to 7-9 with an ammonia solution, and then adjusting the pH to 3-5 with a hydrochloric acid solution to obtain a first acidic mixed solution; Adding the dispersant solution to the first acidic mixed solution, stirring evenly to obtain a first mixed solution; then adding the reducing agent solution, stirring evenly, centrifuging, washing, and obtaining a precursor solution; The mass ratio of the first acidic mixed solution to the dispersant solution is 1:(0.5-2); The mass ratio of the first mixed solution to the reducing agent solution is 1:(0.5-2); (3) Mix the precursor solution and the gold salt solution evenly, add hydrochloric acid solution to adjust the pH to 3-5, and obtain a second acidic mixed solution; then add the dispersant solution and stir evenly to obtain a second mixed solution; finally add the reducing agent solution, stir evenly, centrifuge, wash, and dry to obtain micron-sized spherical gold powder; The dispersant is polyvinyl pyrrolidone, and the average molecular weight of the polyvinyl pyrrolidone is 1000000-1500000; The mass ratio of the precursor solution to the gold salt solution in step (3) is 1:(1-10); The mass ratio of the second acidic mixed solution to the dispersant solution is 1:(0.5-2); The mass ratio of the second mixed solution to the reducing agent solution is 1:(0.5-2).

2. A micron-sized spherical gold powder, characterized in that: The preparation method according to claim 1 is used for preparation.

3. Use of the micron-sized spherical gold powder according to claim 2 in preparing conductive paste.

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