Preparation method of superfine gold powder for conductive paste

Abstract

The invention discloses a preparation method of superfine gold powder for conductive paste, which comprises the following steps: 1, adding chloroauric acid and ferric chloride into deionized water, then adding gelatin, heating, stirring and dissolving to prepare a mixed solution; and 2, the mixed solution is subjected to ultrasonic atomization to obtain nano-scale gold-iron fog drops, then the nano-scale gold-iron fog drops are calcined and decomposed, gold-iron alloy nano-powder is collected through a hydrochloric acid solution and soaked, filtering and drying are conducted, and the superfine gold powder is obtained. Gelatin is added to serve as a dispersing agent, more nano gold-iron fog drops with firmer structures are promoted to be formed, the size of superfine gold powder is guaranteed, the gelatin is used for preventing particle adhesion in the calcination decomposition process, the gold-iron alloy nano powder is spherical and does not agglomerate, the gelatin is free of residues after being decomposed, and then dissolved iron is collected through hydrochloric acid, so that the gold powder is obtained. The preparation method is simple in process, high in yield, large in yield and easy for industrial production, and the superfine gold powder with the large specific surface area is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic paste powder preparation, and in particular relates to a method for preparing ultrafine gold powder for conductive paste. Background Art

[0002] Thick film conductive paste circuits, that is, interconnected wires are made on insulating substrates through processes such as screen printing and subsequent sintering. They have circuit units that meet certain functional and technical requirements and are widely used in various communication equipment, aerospace and other fields. Gold fittings have good corrosion resistance, oxidation resistance and good conductivity in the air, and can be sintered in air that reaches its melting point without reacting. They are widely used in electronic pastes and microelectronic components. In addition, since gold conductors have basically no electromigration tendency in normal environments and can work in harsh environments. Therefore, gold paste plays a very important role in electronic technology applications such as hybrid circuits, LSI, semiconductor packaging and multi-layer wiring circuits, especially in high-reliability military electronic technology. At present, the methods for preparing gold powder for thick film conductive paste are mainly liquid phase chemical synthesis and direct calcination. Although there are many varieties of gold powder prepared in China, very few can be used in equipment. It is of great significance to develop high-performance ultrafine gold powder.

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

[0004] The patent with publication number CN115625341A discloses a gold powder for LTCC and a preparation method and a gold conductor slurry. The method comprises the following steps: in a water bath environment, using D-isoascorbic acid as a reducing agent, reducing chloroauric acid under mechanical stirring and ultrasonic vibration conditions to obtain a reaction solution; centrifuging the obtained reaction solution to obtain a precipitate; washing and drying the precipitate to obtain gold powder. The gold powder prepared by the preparation method of the invention 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 slurry.

[0005] Therefore, it is of great significance to develop high-performance ultrafine gold powder. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing ultrafine gold powder for conductive paste in view of the shortcomings of the above-mentioned prior art. The method promotes the formation of more nano-gold-iron droplets with a stronger structure by adding gelatin as a dispersant, ensures the size of ultrafine gold powder, and uses gelatin to prevent particle adhesion during calcination and decomposition, so that the gold-iron alloy nanopowder is spherical and will not agglomerate, and the gelatin is finally decomposed without residue, and then the iron in the gold-iron alloy nanopowder is collected and dissolved by hydrochloric acid to ensure the dispersibility of nano-gold particles, and obtain ultrafine gold powder with a large specific surface area, which solves the problem that the existing nano-gold powder preparation process is not easy to scale up and it is difficult to obtain high-performance gold powder.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing ultrafine gold powder for conductive paste, characterized in that the method comprises the following steps:

[0008] Step 1, adding chloroauric acid and ferric chloride into deionized water, then adding gelatin and heating and stirring to dissolve, to prepare a mixed solution;

[0009] Step 2: Place the mixed solution obtained in step 1 into an ultrasonic atomization device for ultrasonic atomization to obtain nano-scale gold-iron droplets, and then send the nano-scale gold-iron droplets from the top into a vertical high-temperature tubular furnace for calcination and decomposition, collect the gold-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.

[0010] Compared with the traditional method of preparing gold powder, the gold powder prepared by directly calcining the gold precursor salt in the air is flaky and seriously agglomerated, or the gold powder prepared by adding a reducing agent and a dispersant to the gold salt by the liquid phase chemical synthesis method has the disadvantages of easy agglomeration, difficult to clean the dispersant, difficult to control, and a large amount of waste liquid. In the present invention, the gold salt, the iron salt and the gelatin are first dissolved in deionized water, and nano-scale gold-iron droplets are prepared by ultrasonic atomization. The gelatin is used as a dispersant, so that more nano-gold-iron droplets with a stronger structure are formed during the ultrasonic atomization process to ensure that the ultra-fine size of the gold powder is obtained later, and the gold powder is decomposed during the calcination process. In the process, gelatin is used to effectively prevent the adhesion between nanoparticles, ensuring that the gold-iron alloy nanopowders obtained by calcination and decomposition are spherical and will not agglomerate, avoiding the agglomeration of nano-gold-iron droplets after drying and the aggregation of powders after calcination and decomposition. At the same time, after falling into the bottom of the vertical high-temperature tubular furnace, the gelatin will be oxidized and decomposed at high temperature without residue. By using hydrochloric acid solution to collect at the bottom, the gold-iron alloy nanopowders obtained by calcination and decomposition fall into the hydrochloric acid solution, ensuring the dispersibility of the nano-gold particles, and the iron in the gold-iron alloy nanopowders is completely dissolved in an acidic environment, so that the ultrafine gold powder has a larger specific surface area.

[0011] The above-mentioned method for preparing ultrafine gold powder for conductive paste is characterized in that the concentration of iron ions in the mixed solution in step 1 is 10wt% to 25wt%, the concentration of gold ions is 1wt% to 5wt%, and the concentration of gelatin is 1wt%. By controlling the concentration of each raw material, it is ensured that each precursor particle and gelatin are uniformly mixed.

[0012] The above-mentioned method for preparing ultrafine gold powder for conductive paste is characterized in that the power of the ultrasonic atomization in step 2 is 50W to 100W, the temperature of the calcination and decomposition is 300°C to 600°C, and the soaking time is 0.5h to 4h. By controlling the power of ultrasonic atomization, the temperature of calcination and decomposition, and the soaking time, the one-time preparation of ultrafine gold powder is ensured, and ultrafine gold powder with a large specific surface area is obtained.

[0013] The above-mentioned method for preparing ultrafine gold powder for conductive paste is characterized in that the particle size of the ultrafine gold powder in step 2 is 200nm-2μm and the specific surface area is 0.1m 2 / g~5m 2 / g, spherical in shape, and 99.9% in mass content of gold element. The invention prepares ultrafine gold powder for thick film conductive paste with the above properties, which has good fluidity and viscosity after being made into paste, and is suitable for thick film conductive paste.

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

[0015] 1. The present invention promotes the formation of more nano-gold-iron droplets with a firmer structure by adding gelatin as a dispersant, ensures the size of ultrafine gold powder, and uses gelatin to prevent particle adhesion during calcination and decomposition, so that the gold-iron alloy nano-powder is spherical and will not agglomerate, and the gelatin is finally decomposed without residue, and then the iron in the gold-iron alloy nano-powder is collected and dissolved by hydrochloric acid to ensure the dispersibility of nano-gold particles, and obtain ultrafine gold powder with a large specific surface area, which is suitable for thick film conductive slurry.

[0016] 2. The particle size of the ultrafine gold powder prepared by the present invention is 200nm~2μm, and the specific surface area is 0.1m 2 / g~5m 2 / g, the shape 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 invention can stably and effectively control the morphology and particle size of ultrafine gold powder, has simple process, high yield, large output, and is easy for industrial production.

[0018] 4. Compared with the existing liquid phase chemical synthesis method, the preparation process of the present invention 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 The present invention is a flow chart of the method for preparing ultrafine gold powder for conductive paste.

[0021] Figure 2 This is a 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, adding 5 g of chloroauric acid and ferric chloride in total to deionized water, then adding gelatin and heating and stirring to dissolve to prepare a mixed solution; the concentration of iron ions in the mixed solution is 10wt%, the concentration of gold ions is 1wt%, and the concentration of gelatin is 1wt%;

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

[0026] After testing, the particle size of the ultrafine gold powder prepared in this embodiment is 200nm~500nm, and the specific surface area is 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, adding 5 g of chloroauric acid and ferric chloride in total to deionized water, then adding gelatin and heating and stirring to dissolve to prepare a mixed solution; the concentration of iron ions in the mixed solution is 25wt%, the concentration of gold ions is 3wt%, and the concentration of gelatin is 1wt%;

[0030] Step 2: Place the mixed solution obtained in step 1 into an ultrasonic atomization device for ultrasonic atomization at a power of 50 W to obtain nano-scale gold-iron droplets, and then send the nano-scale gold-iron droplets from the top into a vertical high-temperature tubular furnace for calcination and decomposition at a temperature of 300° C. Use a 37% by mass hydrochloric acid solution to collect the gold-iron alloy nanopowder obtained by calcination and decomposition at the bottom and soak it for 0.5 h, filter and dry it to obtain ultrafine gold powder.

[0031] The ultrafine gold powder prepared in this embodiment has a particle size of 200nm-2μm and a specific surface area of ​​1m 2 / g~3m 2 / g, the shape is spherical, and the mass content of gold element is 99.9%.

[0032] Example 3

[0033] like Figure 1 As shown, this embodiment includes the following steps:

[0034] Step 1, adding 5 g of chloroauric acid and ferric chloride in total to deionized water, then adding gelatin and heating and stirring to dissolve to prepare a mixed solution; the concentration of iron ions in the mixed solution is 20 wt%, the concentration of gold ions is 5 wt%, and the concentration of gelatin is 1 wt%;

[0035] Step 2: Place the mixed solution obtained in step 1 into an ultrasonic atomization device for ultrasonic atomization at a power of 100 W to obtain nano-scale gold-iron droplets, and then send the nano-scale gold-iron droplets from the top into a vertical high-temperature tubular furnace for calcination and decomposition at a temperature of 600° C. Use a 37% by mass hydrochloric acid solution to collect the gold-iron alloy nanopowder obtained by calcination and decomposition at the bottom and soak it for 4 hours, filter and dry it to obtain ultrafine gold powder.

[0036] The ultrafine gold powder prepared in this embodiment has a particle size of 200 nm to 2 μm and a specific surface area of ​​0.1 m 2 / g~2m 2 / g, the shape is spherical, and the mass content of gold element is 99.9%.

[0037] Example 4

[0038] like Figure 1 As shown, this embodiment includes the following steps:

[0039] Step 1, adding 5 g of chloroauric acid and ferric chloride in total to deionized water, then adding gelatin and heating and stirring to dissolve to prepare a mixed solution; the concentration of iron ions in the mixed solution is 15wt%, the concentration of gold ions is 4wt%, and the concentration of gelatin is 1wt%;

[0040] Step 2: Place the mixed solution obtained in step 1 into an ultrasonic atomization device for ultrasonic atomization at a power of 70 W to obtain nano-scale gold-iron droplets, and then send the nano-scale gold-iron droplets from the top into a vertical high-temperature tubular furnace for calcination and decomposition at a temperature of 400° C. Use a 37% by mass hydrochloric acid solution to collect the gold-iron alloy nanopowder obtained by calcination and decomposition at the bottom and soak it for 3 hours, filter and dry it to obtain ultrafine gold powder.

[0041] The ultrafine gold powder prepared in this embodiment has a particle size of 200 nm to 2 μm and a specific surface area of ​​0.5 m 2 / g~2m 2 / g, the shape is spherical, and the mass content of gold element is 99.9%.

[0042] Example 5

[0043] like Figure 1 As shown, this embodiment includes the following steps:

[0044] Step 1, adding 5 g of chloroauric acid and ferric chloride in total to deionized water, then adding gelatin and heating and stirring to dissolve to prepare a mixed solution; 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 2: Place the mixed solution obtained in step 1 into an ultrasonic atomization device for ultrasonic atomization at a power of 90 W to obtain nano-scale gold-iron droplets, and then send the nano-scale gold-iron droplets from the top into a vertical high-temperature tubular furnace for calcination and decomposition at a temperature of 500° C. Use a 37% by mass hydrochloric acid solution to collect the gold-iron alloy nanopowder obtained by calcination and decomposition at the bottom and soak it for 1 hour, filter and dry it to obtain ultrafine gold powder.

[0046] The ultrafine gold powder prepared in this embodiment has a particle size of 400nm-2μm and a specific surface area of ​​1m 2 / g~4m 2 / g, the shape is spherical, and the mass content of gold element is 99.9%.

[0047] Example 6

[0048] like Figure 1 As shown, this embodiment includes the following steps:

[0049] Step 1, adding 5 g of chloroauric acid and ferric chloride in total to deionized water, then adding gelatin and heating and stirring to dissolve to prepare a mixed solution; 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 2: Place the mixed solution obtained in step 1 into an ultrasonic atomization device for ultrasonic atomization at a power of 100 W to obtain nano-scale gold-iron droplets, and then send the nano-scale gold-iron droplets from the top into a vertical high-temperature tubular furnace for calcination and decomposition at a temperature of 600° C. Use a 37% by mass hydrochloric acid solution to collect the gold-iron alloy nanopowder obtained by calcination and decomposition at the bottom and soak it for 1 hour, filter and dry it to obtain ultrafine gold powder.

[0051] After testing, the particle size of the ultrafine gold powder prepared in this embodiment is 800nm~2μm, and the specific surface area is 0.5m 2 / g~2m 2 / g, the shape is spherical, and the mass content of gold element is 99.9%.

[0052] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing ultrafine gold powder for conductive paste, characterized in that: The method comprises the following steps: Step 1, adding chloroauric acid and ferric chloride into deionized water, then adding gelatin and heating and stirring to dissolve, to prepare a mixed solution; Step 2: Place the mixed solution obtained in step 1 into an ultrasonic atomization device for ultrasonic atomization to obtain nano-scale gold-iron droplets, and then send the nano-scale gold-iron droplets from the top into a vertical high-temperature tubular furnace for calcination and decomposition, collect the gold-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.

2. The method for preparing ultrafine gold powder for conductive paste according to claim 1, characterized in that: In the mixed solution in step 1, the concentration of iron ions is 10wt% to 25wt%, the concentration of gold ions is 1wt% to 5wt%, and the concentration of gelatin is 1wt%.

3. The method for preparing ultrafine gold powder for conductive paste according to claim 1, characterized in that: The power of the ultrasonic atomization in step 2 is 50W to 100W, the temperature of the calcination decomposition is 300° C. to 600° C., and the soaking time is 0.5h to 4h.

4. The method for preparing ultrafine gold powder for conductive paste according to claim 1, characterized in that: The particle size of the ultrafine gold powder in step 2 is 200nm-2μm, and the specific surface area is 0.1m 2 / g~5m 2 / g, the shape is spherical, and the mass content of gold element is 99.9%.

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