Preparation method of superfine gold powder for conductive paste

Abstract

The application discloses a preparation method of superfine gold powder for conductive paste, and the method comprises the following steps: firstly, adding chloroauric acid and ferric chloride into deionized water, then adding gelatin and heating and stirring to dissolve, and preparing a mixed solution; secondly, performing ultrasonic atomization on the mixed solution to obtain nanoscale gold-iron mist droplets, then performing calcination and decomposition, collecting gold-iron alloy nanopowder by using a hydrochloric acid solution, and soaking, filtering and drying to obtain superfine gold powder. By adding gelatin as a dispersant, more and more nanoscale gold-iron mist droplets with a more stable structure are formed, the size of the superfine gold powder is ensured, and the gelatin is utilized to prevent particle adhesion during the calcination and decomposition process, so that the gold-iron alloy nanopowder is spherical and cannot be aggregated, the gelatin decomposition is residue-free, the iron is collected and dissolved by using the hydrochloric acid, the dispersibility of the nanoscale gold particles is ensured, the superfine gold powder with a large specific surface area is obtained, the superfine gold powder is suitable for thick film conductive paste, and the method is simple in process, high in product yield, large in output, and easy for industrial production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electronic paste powder preparation, and particularly relates to a preparation method of superfine gold powder for conductive paste. BACKGROUND

[0002] Thick film conductive paste circuit, that is, a circuit with a circuit unit meeting certain functional technical requirements is made on an insulating substrate through screen printing and subsequent sintering processes, and is widely used in various communication equipment, aerospace and other fields. Gold has good corrosion resistance, oxidation resistance and good conductivity in air, and can be sintered in air reaching its melting point without reaction, and is widely used in electronic paste and microelectronic components. In addition, gold conductors have no electric migration tendency in normal environment and can work in harsh environments. Therefore, gold paste plays an important role in electronic technology applications such as hybrid circuits, LSIs, semiconductor packaging and multi-layer wiring circuits, especially in high-reliability military electronic technology. At present, the main methods for preparing gold powder for thick film conductive paste are liquid phase chemical synthesis and direct calcination. Although there are many types of gold powder prepared in China, only a few can be used in equipment, and it is of great significance to develop high-performance superfine gold powder.

[0003] The patent with the publication number CN114799198A discloses a high-dispersibility nanometer gold powder and a preparation method thereof. The preparation method of the high-dispersibility nanometer gold powder comprises the following steps: first, preparing a gold chloride solution; second, preparing a reducing agent solution; third, preparing the gold powder through a reduction reaction; and fourth, washing. The prepared nanometer gold powder has an average particle size distribution of 0.5-20 nm and a loose bulk density of 4-6 g / cm 3 . The gold powder prepared by the method has no agglomeration phenomenon, the method is simple, the process is short, and no waste liquid is generated in the preparation process. However, the nanometer gold powder prepared by the method is not suitable for preparing thick film high-performance thick film hybrid integrated circuits.

[0004] The patent with the publication number CN115625341A discloses a gold powder for LTCC, a preparation method thereof and a gold conductor paste. The method comprises the following steps: under a water bath environment, D-erythorbic acid is used as a reducing agent to reduce chloroauric acid to obtain a reaction liquid under the conditions of mechanical stirring and ultrasonic vibration; the obtained reaction liquid is centrifuged to obtain a precipitate; and the precipitate is washed and dried to obtain the gold powder. The gold powder prepared by the preparation method has good dispersibility, high purity and narrow particle size distribution. Although the method can prepare gold powder with good dispersibility, the method is not easy to scale up and is not suitable for preparing gold conductive paste.

[0005] Therefore, it is of great significance to develop high-performance superfine gold powder. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a preparation method of ultra-fine gold powder for conductive paste to solve the above problems of the prior art.

[0007] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a preparation method of ultra-fine gold powder for conductive paste, characterized in that the method comprises the following steps:

[0008] Step one: chloroauric acid and ferric chloride are added to deionized water, then gelatin is added and heated and stirred to dissolve, and a mixed solution is prepared;

[0009] Step two: the mixed solution obtained in step one is placed in an ultrasonic atomization device for ultrasonic atomization to obtain nanoscale gold-iron mist droplets, which are then sent from the top end into a vertical high-temperature tube furnace for calcination and decomposition, and hydrochloric acid solution is used to collect and soak the gold-iron alloy nanometer powder obtained by calcination and decomposition at the bottom, and the ultra-fine gold powder is obtained after filtration and drying.

[0010] Compared with the traditional method of preparing gold powder by directly calcining gold precursor salt in air, the gold powder prepared by this method is flaky and severely agglomerated, or the gold powder prepared by liquid phase chemical synthesis method has the disadvantages of easy agglomeration, difficult cleaning of dispersing agent, difficult control, large amount of waste liquid, etc. In the present application, gold salt, iron salt and gelatin are dissolved in deionized water, and nanoscale gold-iron mist droplets are prepared by ultrasonic atomization. The gelatin is used as a dispersing agent to form more and more nanoscale gold-iron mist droplets with a more stable structure, to ensure that the subsequent ultra-fine gold powder is obtained, and to effectively prevent the adhesion between the nanometer particles during calcination and decomposition by using gelatin, so that the gold-iron alloy nanometer powder obtained by calcination and decomposition is spherical and does not agglomerate, avoiding the problems of agglomeration of nanoscale gold-iron mist droplets after drying and agglomeration of the powder after calcination and decomposition. At the same time, the gelatin is oxidized and decomposed at high temperature after falling into the bottom of the vertical high-temperature tube furnace, leaving no residue. By using hydrochloric acid solution to collect at the bottom, the gold-iron alloy nanometer powder obtained by calcination and decomposition falls into the hydrochloric acid solution, ensuring the dispersion of nanoscale gold particles, and the iron in the gold-iron alloy nanometer powder is completely dissolved in the acidic environment, so that the ultra-fine gold powder has a large specific surface area.

[0011] The preparation method of the superfine gold powder for the conductive paste has the following characteristics: the concentration of iron ions in the mixed solution in step one is 10wt%-25wt%, the concentration of gold ions is 1wt%-5wt%, and the concentration of gelatin is 1wt%. By controlling the concentration of each raw material, the uniform mixing of each precursor particle and gelatin is ensured.

[0012] The preparation method of the superfine gold powder for the conductive paste has the following characteristics: the power of ultrasonic atomization in step two is 50W-100W, the temperature of calcination and decomposition is 300℃-600℃, and the soaking time is 0.5h-4h. By controlling the power of ultrasonic atomization, the temperature of calcination and decomposition, and the soaking time, the one-time preparation of the superfine gold powder is ensured, and the superfine gold powder with a large specific surface area is obtained.

[0013] The preparation method of the superfine gold powder for the conductive paste has the following characteristics: the particle size of the superfine gold powder in step two is 200nm-2μm, the specific surface area is 0.1m 2 / g-5m 2 / g, the morphology is spherical, and the mass content of gold element is 99.9%. The superfine gold powder for the thick film conductive paste prepared by the method has the above-mentioned properties, has good flowability and viscosity after being made into a paste, and is suitable for thick film conductive use.

[0014] Compared with the prior art, the present application has the following advantages:

[0015] 1. By adding gelatin as a dispersant, the present application promotes the formation of more and more stable nano gold-iron mist droplets, ensures the size of the superfine gold powder, and prevents particle adhesion during calcination and decomposition by using gelatin, so that the gold-iron alloy nano powder is spherical and does not agglomerate, and the gelatin is finally decomposed without residue. Then, the iron in the gold-iron alloy nano powder is collected and dissolved by hydrochloric acid, the dispersibility of the nano gold particles is ensured, the superfine gold powder with a large specific surface area is obtained, and the superfine gold powder is suitable for thick film conductive paste.

[0016] 2. The particle size of the superfine gold powder prepared by the present application is 200nm-2μm, the specific surface area is 0.1m 2 / g-5m 2 / g, the morphology is spherical, and the mass content of gold element is 99.9%, which can meet the needs of thick film conductive paste.

[0017] 3. The preparation method of the present application stably and effectively controls the morphology and particle size of the superfine gold powder, has a simple process, high yield, and is easy to industrialize.

[0018] 4. Compared with the existing liquid phase chemical synthesis method, the preparation process of the present application is simple, no waste liquid is generated, the direct yield is nearly 100%, and the preparation cost is greatly reduced.

[0019] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a flow chart of the method for preparing ultrafine gold powder for conductive paste of the present invention.

[0021] Figure 2 This is the SEM image of the ultrafine gold powder prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0022] Example 1

[0023] like Figure 1 As shown, this embodiment includes the following steps:

[0024] Step 1: Add 5 g of chloroauric acid and ferric chloride in total to deionized water, then add gelatin and heat and stir to dissolve to prepare a mixed solution; the concentration of iron ions in the mixed solution is 10 wt%, the concentration of gold ions is 1 wt%, and the concentration of gelatin is 1 wt%;

[0025] Step 2: Place the mixed solution obtained in step 1 into an ultrasonic atomization device for ultrasonic atomization at a power of 80W to obtain nano-scale gold and iron droplets, and then send the nano-scale gold and iron droplets from the top into a vertical high-temperature tubular furnace for calcination and decomposition. The calcination and decomposition temperature is 500°C, and a 37% mass fraction hydrochloric acid solution is used to collect the gold-iron alloy nanopowder obtained by calcination and decomposition at the bottom and soak it for 2 hours. After filtering and drying, ultrafine gold powder is obtained.

[0026] The ultrafine gold powder prepared in this embodiment has a particle size of 200nm to 500nm and a specific surface area of ​​2m 2 / g~5m 2 / g, the shape is spherical, such as Figure 2 As shown, the gold element mass content is 99.9%.

[0027] Example 2

[0028] like Figure 1 As shown, this embodiment includes the following steps:

[0029] Step 1: Add 5 g of chloroauric acid and ferric chloride in total to deionized water, then add gelatin and heat and stir to dissolve to prepare a mixed solution; the concentration of iron ions in the mixed solution is 25 wt%, the concentration of gold ions is 3 wt%, and the concentration of gelatin is 1 wt%;

[0030] Step two, the mixed solution obtained in step one is put into an ultrasonic atomization device for ultrasonic atomization, the power of the ultrasonic atomization is 50W, nanoscale gold-iron mist droplets are obtained, then the nanoscale gold-iron mist droplets are sent into a vertical high-temperature tubular furnace from the top end for calcination and decomposition, the temperature of the calcination and decomposition is 300℃, gold-iron alloy nanometer powder obtained by the calcination and decomposition is collected at the bottom by using a 37% hydrochloric acid solution and soaked for 0.5h, after filtration and drying, superfine gold powder is obtained.

[0031] It is detected that the particle size of the superfine gold powder prepared in the embodiment is 200nm-2μm, the specific surface area is 1m 2 / g-3m 2 / g, the morphology is spherical, and the mass content of gold element is 99.9%.

[0032] Embodiment 3

[0033] As shown in the figure, the embodiment includes the following steps: Figure 1

[0034] Step one, 5g of chloroauric acid and ferric chloride in total is added into deionized water, then gelatin is added and heated and stirred to dissolve, so that a mixed solution is prepared; the concentration of iron ions in the mixed solution is 20wt%, the concentration of gold ions is 5wt%, and the concentration of gelatin is 1wt%;

[0035] Step two, the mixed solution obtained in step one is put into an ultrasonic atomization device for ultrasonic atomization, the power of the ultrasonic atomization is 100W, nanoscale gold-iron mist droplets are obtained, then the nanoscale gold-iron mist droplets are sent into a vertical high-temperature tubular furnace from the top end for calcination and decomposition, the temperature of the calcination and decomposition is 600℃, gold-iron alloy nanometer powder obtained by the calcination and decomposition is collected at the bottom by using a 37% hydrochloric acid solution and soaked for 4h, after filtration and drying, superfine gold powder is obtained.

[0036] It is detected that the particle size of the superfine gold powder prepared in the embodiment is 200nm-2μm, the specific surface area is 0.1m 2 / g-2m 2 / g, the morphology is spherical, and the mass content of gold element is 99.9%.

[0037] Embodiment 4

[0038] As shown in the figure, the embodiment includes the following steps: Figure 1

[0039] Step one, 5g of chloroauric acid and ferric chloride in total is added into deionized water, then gelatin is added and heated and stirred to dissolve, so that a mixed solution is prepared; the concentration of iron ions in the mixed solution is 20wt%, the concentration of gold ions is 5wt%, and the concentration of gelatin is 1wt%;

[0040] ​​Step two, the mixed solution obtained in step one is put into an ultrasonic atomization device for ultrasonic atomization, the power of the ultrasonic atomization is 70W, nanoscale gold-iron mist droplets are obtained, then the nanoscale gold-iron mist droplets are sent into a vertical high-temperature tubular furnace from the top end for calcination and decomposition, the temperature of the calcination and decomposition is 400℃, gold-iron alloy nanometer powder obtained by the calcination and decomposition is collected at the bottom by using a 37% hydrochloric acid solution and soaked for 3h, after filtration and drying, superfine gold powder is obtained.

[0041] It is detected that the particle size of the superfine gold powder prepared in the embodiment is 200nm-2μm, the specific surface area is 0.5m 2 / g-2m 2 / g, the morphology is spherical, and the mass content of gold element is 99.9%.

[0042] Embodiment 5

[0043] As shown in the embodiment, the following steps are included: Figure 1

[0044] Step one, 5g of chloroauric acid and ferric chloride in total is added into deionized water, then gelatin is added and heated and stirred to dissolve, so that a mixed solution is prepared; the concentration of iron ions in the mixed solution is 15wt%, the concentration of gold ions is 3wt%, and the concentration of gelatin is 1wt%;

[0045] Step two, the mixed solution obtained in step one is put into an ultrasonic atomization device for ultrasonic atomization, the power of the ultrasonic atomization is 90W, nanoscale gold-iron mist droplets are obtained, then the nanoscale gold-iron mist droplets are sent into a vertical high-temperature tubular furnace from the top end for calcination and decomposition, the temperature of the calcination and decomposition is 500℃, gold-iron alloy nanometer powder obtained by the calcination and decomposition is collected at the bottom by using a 37% hydrochloric acid solution and soaked for 1h, after filtration and drying, superfine gold powder is obtained.

[0046] It is detected that the particle size of the superfine gold powder prepared in the embodiment is 400nm-2μm, the specific surface area is 1m 2 / g-4m 2 / g, the morphology is spherical, and the mass content of gold element is 99.9%.

[0047] Embodiment 6

[0048] As shown in the embodiment, the following steps are included: Figure 1

[0049] Step one, 5g of chloroauric acid and ferric chloride in total is added into deionized water, then gelatin is added and heated and stirred to dissolve, so that a mixed solution is prepared; the concentration of iron ions in the mixed solution is 25wt%, the concentration of gold ions is 2wt%, and the concentration of gelatin is 1wt%;

[0050] ​​Step two, the mixed solution obtained in step one is put into an ultrasonic atomization device for ultrasonic atomization, the power of the ultrasonic atomization is 100W, and nanoscale gold-iron mist droplets are obtained, then the nanoscale gold-iron mist droplets are sent from the top end into a vertical high-temperature tubular furnace for calcination and decomposition, the temperature of the calcination and decomposition is 600℃, a 37% hydrochloric acid solution by mass fraction is used to collect the gold-iron alloy nanometer powder obtained by the calcination and decomposition at the bottom and soak for 1h, the gold-iron alloy nanometer powder is filtered and dried to obtain superfine gold powder.

[0051] It is detected that the particle size of the superfine gold powder prepared in the embodiment is 800nm-2μm, the specific surface area is 0.5m 2 / g-2m 2 / g, the morphology is spherical, and the mass content of gold element is 99.9%.

[0052] The above is only a preferred embodiment of the present application, and does not limit the present application. Any simple modification, change and equivalent change of the above embodiment according to the technical essence of the present application are still within the protection scope of the technical scheme of the present application.

Claims

1. A method for preparing ultrafine gold powder for conductive paste, characterized in that: The method comprises the following steps: Step 1: Add chloroauric acid and ferric chloride to deionized water, then add gelatin and heat and stir to dissolve to prepare a mixed solution; the concentration of iron ions in the mixed solution is 10wt%~25wt%, the concentration of gold ions is 1wt%~5wt%, and the concentration of gelatin is 1wt%; Step 2: Place the mixed solution obtained in step 1 into an ultrasonic atomization device for ultrasonic atomization to obtain nano-scale gold and iron droplets, and then send the nano-scale gold and iron droplets from the top into a vertical high-temperature tubular furnace for calcination and decomposition, collect the gold and iron alloy nanopowder obtained by calcination and decomposition at the bottom with hydrochloric acid solution and soak it, filter and dry it to obtain ultrafine gold powder; the power of the ultrasonic atomization is 50W~100W, the temperature of the calcination and decomposition is 300℃~600℃, and the soaking time is 0.5h~4h; the particle size of the ultrafine gold powder is 200nm~2μm, and the specific surface area is 0.1m 2 / g~5m 2 / g, the shape is spherical, and the gold element mass content is 99.9%.

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