Preparation method of gold powder for thick film conductive paste

Abstract

The application discloses a preparation method of gold powder for thick film conductive paste, and the method comprises the following steps: firstly, dissolving gold blocks in aqua regia, adding ammonium chloride, and evaporating to prepare ammonium chloraurate powder; secondly, mixing the ammonium chloraurate powder with ascorbic acid and ball milling to obtain uniformly mixed gold-containing precursor powder; thirdly, calcining the gold-containing precursor powder at low temperature in air to obtain nanometer gold powder; and fourthly, adding the nanometer gold powder into anhydrous ethanol to prepare nanometer gold suspension, and then performing high-temperature atomization to obtain spherical gold powder. By controlling the ball milling time of the ammonium chloraurate and ascorbic acid, combining with the control of low-temperature calcination parameters and the temperature of high-temperature atomization, the gold powder for thick film conductive paste is finally obtained, the addition and cleaning of a direct liquid-phase reduction gold powder dispersant are avoided, the spherical morphology and high purity of the gold powder are ensured, the gold powder is suitable for thick film conductive use, the preparation method is simple in process, high in product yield, large in output, green in environment protection, and easy for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy technology, specifically relating to a method for preparing gold powder for thick-film conductive paste. Background Technology

[0002] With the rapid development of modern technology, especially high-end technologies such as electronic information and aerospace, thick-film hybrid integrated circuits (HICs) have become an important component of integrated circuits. They are increasingly complementing and interpenetrating semiconductor integrated circuits, and are widely used in circuit systems. HICs can be simply referred to as thick-film hybrid circuits or thick-film circuits. They are circuit units, such as interconnected wires, resistors, and inductors, that meet specific functional requirements, created on an insulating substrate through processes like screen printing and subsequent sintering. Gold possesses excellent properties such as superior ductility, easy drawing into wires for easy wire soldering, non-reactive to air and corrosive gases under any conditions, and the ability to sinter in air at its melting point without reaction. These superior properties have led to its widespread use in electronic pastes and microelectronic components. Furthermore, gold conductors exhibit virtually no electromigration tendency in normal environments and can operate in harsh conditions. Therefore, gold pastes play a crucial role in hybrid circuits, LSIs, semiconductor packaging, and multilayer wiring circuits, especially in high-reliability military electronic technologies. Consequently, the demand for high-performance, controllable-particle-size spherical gold powder has increased dramatically. Currently, the main methods for preparing gold powder for thick-film conductive pastes are liquid-phase chemical synthesis and direct calcination. Although many types of gold powder are prepared domestically, very few can be used in high-performance thick-film hybrid integrated circuits. my country needs to import several hundred kilograms of high-performance gold powder every year. In order to break the monopoly of foreign companies, it is of great significance to develop high-performance composite thick-film hybrid integrated circuit gold powder.

[0003] Patent CN114247896A discloses a method for preparing gold powder. The process involves: 1) preparing a reducing agent solution A using sodium sulfite as a solute and deionized water as a solvent; 2) diluting a chloroauric acid solution with deionized water to obtain a gold-containing solution B; 3) adding the gold-containing solution B to the reducing agent solution A for reaction. After the reaction is complete, the precipitate is washed and dried to obtain gold powder. This method uses sodium sulfite as a reducing agent, which regulates the crystallization of the gold powder, causing small flake-like gold powder to aggregate into spherical gold powder. This spherical gold powder can better integrate with the slurry, resulting in a fast and efficient reaction, saving time and costs. It eliminates the need for dispersants, reducing production costs and preventing the introduction of additional organic matter due to dispersants, resulting in gold powder with low organic content. However, this method is difficult to control experimental conditions during preparation, leading to insufficient purity of the prepared gold powder, making it unsuitable for high-performance conductive slurries.

[0004] Patent CN114799198A discloses highly dispersed nano-gold powder and its preparation method. This invention proposes a method for preparing highly dispersed nano-sized gold powder, comprising: first, preparing a gold chloride solution; second, preparing a reducing agent solution; third, performing a reduction reaction to prepare gold powder; and fourth, washing. The prepared nano-sized gold powder has an average particle size distribution of 0.5–20 nm and a loose packing density of 4–6 g / cm³. 3 The gold powder prepared using this method exhibits no agglomeration, and the method is simple, has a short process, and does not generate waste liquid. However, the gold nanoparticles prepared by this method are not suitable for fabricating high-performance thick-film hybrid integrated circuits.

[0005] Patent CN115625341A discloses a gold powder for LTCC, its preparation method, and a gold conductor paste. The method includes the following steps: reducing chloroauric acid in a water bath environment using D-isoascorbic acid as a reducing agent under mechanical stirring and ultrasonic vibration to obtain a reaction solution; centrifuging the obtained reaction solution to collect the precipitate; and washing and drying the precipitate to obtain gold powder. The gold powder prepared by the method of this invention has good dispersibility, high purity, and narrow particle size distribution. Although this method can prepare well-dispersed gold powder, it is not easily scaled up and is not suitable for preparing high-performance thick-film hybrid integrated circuits.

[0006] Therefore, there is an urgent need for a method for preparing gold powder for high-performance composite thick-film hybrid integrated circuits. Summary of the Invention

[0007] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a method for preparing gold powder for thick-film conductive pastes. This method involves dissolving high-purity gold ingots in aqua regia, adding ammonium chloride to precipitate gold salts, then mixing ammonium chloroaurate and ascorbic acid (a reducing agent) and ball milling the mixture. The mixture is then calcined and decomposed at low temperature in a tube furnace to prepare gold nanoparticles. Finally, the gold nanoparticles are added to anhydrous ethanol and atomized at high temperature to prepare spherical gold powder. This process ensures that the atomized gold nanoparticles are instantly dried and grow into individual micron-sized gold powders within a single droplet. The prepared gold powder has a uniform spherical morphology, a micron-sized particle size, and a narrow particle size distribution, making it suitable for use in thick-film conductive pastes.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing gold powder for thick-film conductive paste, characterized in that the method includes the following steps:

[0009] Step 1: Dissolve the gold nugget in aqua regia and remove the nitrate, then add ammonium chloride and evaporate to dryness to obtain ammonium chloroaurate powder;

[0010] Step 2: Mix and ball-mill the ammonium chloroaurate powder obtained in Step 1 with ascorbic acid to obtain a uniformly mixed gold-containing precursor powder;

[0011] Step 3: Calcining the gold-containing precursor powder obtained in Step 2 in air at a low temperature to obtain nano-gold powder;

[0012] Step 4: Add the nano-gold powder obtained in Step 3 to anhydrous ethanol to prepare a nano-gold suspension, and then atomize it at high temperature to obtain gold powder for thick film conductive paste.

[0013] Compared to traditional methods for preparing gold powder, gold powder prepared by directly calcining gold precursor salts in air is flake-shaped and has severe agglomeration. Alternatively, gold powder prepared by adding reducing agents and dispersants to gold salts through liquid-phase chemical synthesis has disadvantages such as easy agglomeration, difficulty in cleaning dispersants, difficulty in control, and large waste volume. This invention first dissolves gold nuggets in aqua regia, then removes the nitrate to prepare a high-purity chloroauric acid solution. Ammonium chloride is then added to precipitate the gold salt, ultimately yielding ammonium chloroaurate. This process ensures the purity and quality of the ammonium chloroaurate. Next, the ammonium chloroaurate is mixed with the reducing agent ascorbic acid and ball-milled to achieve atomic-level mixing, ensuring sufficient contact between the gold salt and the reducing agent. The uniformly mixed gold precursor is then calcined and decomposed at low temperature in a tube furnace to prepare gold nanoparticles. Because this reaction is a solid-state reaction and carried out at low temperature, it is beneficial to control the reaction rate, ensuring the morphology and dispersibility of the obtained gold nanoparticles. Finally, the gold nanoparticles are added to anhydrous ethanol to form a suspension, which is then atomized at high temperature to prepare spherical gold powder. This process ensures the instantaneous drying of the atomized gold nanoparticles and their growth into individual micron-sized gold powders within a single droplet. This process guarantees the spherical morphology and high purity of the gold powder, making it suitable for thick-film conductive applications. Furthermore, this preparation method is simple, has a high yield, large production volume, is environmentally friendly, and is easy to industrialize. Since the application of thick-film conductive gold paste requires gold to be made into a paste, and the paste made of spherical powder has good fluidity and viscosity, which is beneficial to the application of the paste, the micron-sized spherical gold powder obtained by the preparation method of the present invention is suitable for use in thick-film conductive paste.

[0014] The method for preparing gold powder for thick-film conductive paste described above is characterized in that the mass of ammonium chloride added in step one is 3 to 6 times the mass of the gold ingot. This invention ensures the purity and quality of ammonium chloroaurate by controlling the amount of ammonium chloride.

[0015] The above-mentioned method for preparing gold powder for thick-film conductive paste is characterized in that, in step two, the mass ratio of ammonium chloroaurate powder to ascorbic acid is 1-3:1, and the ball milling speed is 300 r / min-600 r / min for 0.5 h-2 h. This invention ensures sufficient contact between the gold salt and the reducing agent by controlling the mass ratio of ammonium chloroaurate powder and ascorbic acid and the ball milling parameters, thus guaranteeing the subsequent low-temperature calcination.

[0016] The method for preparing gold powder for thick-film conductive paste described above is characterized in that the low-temperature calcination process in step three involves placing the gold-containing precursor powder in a tube furnace and heating it to 130°C–200°C in an air atmosphere, followed by holding at that temperature for 0.5–2 hours. In this invention, since the calcination of the gold-containing precursor powder is a solid-phase reaction and is carried out at a low temperature, it is beneficial to control the reaction rate and ensure the morphology and dispersibility of the obtained nano-gold powder.

[0017] The above-mentioned method for preparing gold powder for thick-film conductive paste is characterized in that the high-temperature atomization process in step four is as follows: 1g of nano-gold powder is dissolved in 200mL to 1000mL of anhydrous ethanol, and then atomized at 250℃ to 500℃. This invention, by controlling the high-temperature atomization process, enables the nano-gold powder to dry instantaneously and grow into individual micron-sized gold powders within a single droplet.

[0018] The above-mentioned method for preparing gold powder for thick-film conductive paste is characterized in that the gold powder for thick-film conductive paste in step four has a particle size of 0.5 μm to 4 μm and a specific surface area of ​​less than 3 m². 2 The gold powder, with a spherical morphology and a purity greater than 99.9%, is prepared by this invention to obtain a gold powder for thick-film conductive paste with the above-mentioned properties. After being made into a paste, it has good flowability and viscosity, making it suitable for thick-film conductive applications.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. This invention involves dissolving high-purity gold ingots in aqua regia, adding ammonium chloride to precipitate gold salts, mixing ammonium chloroaurate and ascorbic acid as a reducing agent and ball milling the mixture, followed by low-temperature calcination and decomposition in a tube furnace to prepare nano-gold. Finally, the nano-gold powder is added to anhydrous ethanol and atomized at high temperature to prepare spherical gold powder. This process ensures that the atomized nano-gold powder dries instantly and grows into individual micron-sized gold powders within a single droplet. The prepared gold powder has a uniform spherical morphology, a micron-sized particle size, and a narrow particle size distribution, making it suitable for use in thick-film conductive pastes.

[0021] 2. This invention obtains gold powder for thick-film conductive paste by controlling the ball milling time of ammonium chloroaurate and ascorbic acid, combined with controlling the low-temperature calcination parameters and the high-temperature atomization temperature. This avoids the need for adding and cleaning the gold powder dispersant in direct liquid-phase reduction, ensuring the spherical morphology and high purity of the gold powder, making it suitable for thick-film conductive applications. At the same time, this preparation method is simple, has a high yield, large output, is green and environmentally friendly, and is easy to industrialize. It solves the problems of poor performance, easy agglomeration, and high pollution associated with direct liquid-phase reduction of gold powder.

[0022] 3. The gold powder used in the thick-film conductive paste prepared by this invention is spherical with a particle size range of 0.5μm to 4μm and a specific surface area of ​​less than 3m². 2 / g, with a purity greater than 99.9%, meeting the requirements for thick-film conductive paste.

[0023] 4. The preparation method of the present invention can stably and effectively control the morphology of gold powder, the process is simple, the yield is high, the output is large, it is green and environmentally friendly, and it is easy to industrialize.

[0024] 5. Compared with existing liquid-phase chemical synthesis methods, the preparation process of this invention is simple, generates no waste liquid, and has a direct recovery rate of nearly 100%, making it more green and environmentally friendly.

[0025] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the preparation process of gold powder for the thick-film conductive paste of the present invention.

[0027] Figure 2 This is a SEM image of the gold powder used in the thick-film conductive paste prepared in Example 1 of the present invention. Detailed Implementation

[0028] Figure 1 This is a flowchart illustrating the preparation process of gold powder for the thick-film conductive paste of this invention. Figure 1 As can be seen from the present invention, gold nuggets are dissolved in aqua regia and denitrated, then ammonium chloride is added and evaporated to dryness to obtain ammonium chloroaurate powder. The ammonium chloroaurate powder and ascorbic acid are mixed and ball-milled to obtain a uniformly mixed gold precursor powder. The gold precursor powder is calcined in air at low temperature to obtain nano gold powder. The nano gold powder is added to anhydrous ethanol to prepare a nano gold suspension, and then atomized at high temperature to obtain gold powder for thick film conductive paste.

[0029] Example 1

[0030] This embodiment includes the following steps:

[0031] Step 1: Add 50g of gold nugget to 500mL of aqua regia, heat to 70℃ and dissolve for 4 hours. After complete dissolution, remove the nitrate and fix the solution volume at 250mL. Then add ammonium chloride with a mass of 3 times that of the gold nugget and evaporate and dry at 80℃ for 12 hours to obtain ammonium chloroaurate powder.

[0032] Step 2: Place the ammonium chloroaurate and ascorbic acid obtained in Step 1 into a ball mill jar at a mass ratio of 1:1, and ball mill at a speed of 300 r / min for 0.5 h to obtain a uniformly mixed precursor gold powder.

[0033] Step 3: Place the precursor gold powder obtained in Step 2 into a tube furnace, heat it to 130°C in an air atmosphere, and hold it at that temperature for 0.5 hours for low-temperature calcination to obtain nano gold powder.

[0034] Step 4: Add 1g of the gold nanoparticles obtained in Step 3 to 200mL of anhydrous ethanol to prepare a gold nanoparticle suspension, and then perform high-temperature atomization at 250℃ to obtain gold powder for thick film conductive paste.

[0035] Testing revealed that the gold powder used in the thick-film conductive paste prepared in this embodiment has a particle size of 0.5 μm to 4 μm, a spherical morphology, and a specific surface area of ​​less than 3 m². 2 / g, with a purity greater than 99.9%.

[0036] Figure 2 This is a SEM image of the gold powder used in the thick-film conductive paste prepared in this embodiment. Figure 2 It can be seen that the gold powder used in the thick film conductive paste prepared in this embodiment has a spherical powder morphology and a uniform particle size distribution with a particle size of less than 4μm.

[0037] Example 2

[0038] This embodiment includes the following steps:

[0039] Step 1: Add 50g of gold nugget to 500mL of aqua regia, heat to 70℃ and dissolve for 4 hours. After complete dissolution, remove the nitrate and fix the final solution volume at 250mL. Then add ammonium chloride in an amount three times the weight of the gold nugget and evaporate and dry at 80℃ for 12 hours to obtain ammonium chloroaurate powder.

[0040] Step 2: Place the ammonium chloroaurate and ascorbic acid obtained in Step 1 into a ball mill jar at a mass ratio of 1:1, and ball mill at a speed of 300 r / min for 0.5 h to obtain a uniformly mixed precursor gold powder.

[0041] Step 3: Place the precursor gold powder obtained in Step 2 into a tube furnace, heat it to 130°C in an air atmosphere, and hold it at that temperature for 0.5 hours for low-temperature calcination to obtain nano gold powder.

[0042] Step 4: Add 1g of the gold nanoparticles obtained in Step 3 to 200mL of anhydrous ethanol to prepare a gold nanoparticle suspension, and then perform high-temperature atomization at 300℃ to obtain gold powder for thick film conductive paste.

[0043] Testing revealed that the gold powder used in the thick-film conductive paste prepared in this embodiment has a particle size of 0.5 μm to 4 μm, a spherical morphology, and a specific surface area of ​​less than 3 m². 2 / g, with a purity greater than 99.9%.

[0044] Comparing the test results of the gold powder prepared in this embodiment with those in Example 1, it can be seen that the particle size and dispersibility of the gold powder do not change significantly.

[0045] Example 3

[0046] This embodiment includes the following steps:

[0047] Step 1: Add 50g of gold nugget to 500mL of aqua regia, heat to 70℃ and dissolve for 4 hours. After complete dissolution, remove the nitrate and fix the final solution volume at 250mL. Then add ammonium chloride in an amount three times the weight of the gold nugget and evaporate and dry at 80℃ for 12 hours to obtain ammonium chloroaurate powder.

[0048] Step 2: Place the ammonium chloroaurate and ascorbic acid obtained in Step 1 into a ball mill jar at a mass ratio of 1:1, and ball mill at a speed of 400 r / min for 0.5 h to obtain a uniformly mixed precursor gold powder.

[0049] Step 3: Place the precursor gold powder obtained in Step 2 into a tube furnace, heat it to 130°C in an air atmosphere, and hold it at that temperature for 0.5 hours for low-temperature calcination to obtain nano gold powder.

[0050] Step 4: Add 1g of the gold nanoparticles obtained in Step 3 to 200mL of anhydrous ethanol to prepare a gold nanoparticle suspension, and then perform high-temperature atomization at 400℃ to obtain gold powder for thick film conductive paste.

[0051] Testing revealed that the gold powder used in the thick-film conductive paste prepared in this embodiment has a particle size of 0.5 μm to 4 μm, a spherical morphology, and a specific surface area of ​​less than 3 m². 2 / g, with a purity greater than 99.9%.

[0052] Comparing the test results of the gold powder prepared in this embodiment with those in Example 1, it can be seen that the particle size distribution and size of the gold powder did not change much, and the surface of the single powder became smoother. This indicates that when the atomization temperature was increased to 400℃ in step four of this embodiment, surface sintering occurred while the gold particles were regrowing, and a sintering phenomenon was formed on the surface.

[0053] Example 4

[0054] This embodiment includes the following steps:

[0055] Step 1: Add 50g of gold nugget to 500mL of aqua regia, heat to 70℃ and dissolve for 4 hours. After complete dissolution, remove the nitrate and fix the final solution volume at 250mL. Then add ammonium chloride in an amount three times the weight of the gold nugget and evaporate and dry at 80℃ for 12 hours to obtain ammonium chloroaurate powder.

[0056] Step 2: Place the ammonium chloroaurate and ascorbic acid obtained in Step 1 into a ball mill jar at a mass ratio of 3:1, and ball mill at a speed of 300 r / min for 2 hours to obtain a uniformly mixed precursor gold powder.

[0057] Step 3: Place the precursor gold powder obtained in Step 2 into a tube furnace, heat it to 150°C in an air atmosphere, and then hold it at that temperature for 2 hours for low-temperature calcination to obtain nano gold powder.

[0058] Step 4: Add 1g of the gold nanoparticles obtained in Step 3 to 500mL of anhydrous ethanol to prepare a gold nanoparticle suspension, and then perform high-temperature atomization at 300℃ to obtain gold powder for thick film conductive paste.

[0059] Testing revealed that the gold powder used in the thick-film conductive paste prepared in this embodiment has a particle size of 0.5 μm to 4 μm, a spherical morphology, and a specific surface area of ​​less than 3 m². 2 / g, with a purity greater than 99.9%.

[0060] Comparing the test results of the gold powder prepared in this embodiment with those in Example 1, it can be seen that the particle size of the gold powder is smaller. This is because 1g of gold powder is dissolved in 500mL of aqueous solution containing ethanol, the solution concentration is reduced, the number of gold nanoparticles in the atomized droplets is reduced, resulting in a reduction in the number of gold particles grown in a single droplet at high temperature, and ultimately a smaller volume and particle size.

[0061] Example 5

[0062] This embodiment includes the following steps:

[0063] Step 1: Add 50g of gold nugget to 500mL of aqua regia, heat to 70℃ and dissolve for 4 hours. After complete dissolution, remove the nitrate and fix the final solution volume at 250mL. Then add ammonium chloride in an amount three times the weight of the gold nugget and evaporate and dry at 80℃ for 12 hours to obtain ammonium chloroaurate powder.

[0064] Step 2: Place the ammonium chloroaurate and ascorbic acid obtained in Step 1 into a ball mill jar at a mass ratio of 1:1, and ball mill at a speed of 300 r / min for 0.5 h to obtain a uniformly mixed precursor gold powder.

[0065] Step 3: Place the precursor gold powder obtained in Step 2 into a tube furnace, heat it to 200°C in an air atmosphere, and then hold it at that temperature for 2 hours for low-temperature calcination to obtain nano gold powder.

[0066] Step 4: Add 1g of the gold nanoparticles obtained in Step 3 to 200mL of anhydrous ethanol to prepare a gold nanoparticle suspension, and then perform high-temperature atomization at 500℃ to obtain gold powder for thick film conductive paste.

[0067] Testing revealed that the gold powder used in the thick-film conductive paste prepared in this embodiment has a particle size of 0.5 μm to 4 μm, a spherical morphology, and a specific surface area of ​​less than 1 m². 2 / g, with a purity greater than 99.9%.

[0068] Comparing the test results of the gold powder prepared in this embodiment with those in Example 1, it can be seen that the particle size distribution and size of the gold powder did not change much, and the surface of the single powder became smoother. This indicates that when the atomization temperature was increased to 500℃ in step four of this embodiment, surface sintering occurred while the gold particles were regrowing, and a sintering phenomenon was formed on the surface. At the same time, the specific surface area decreased because a severe sintering phenomenon occurred on the gold surface, thus the specific surface area decreased.

[0069] Example 6

[0070] This embodiment includes the following steps:

[0071] Step 1: Add 50g of gold nugget to 500mL of aqua regia, heat to 70℃ and dissolve for 4 hours. After complete dissolution, remove the nitrate and fix the final solution volume at 250mL. Then add ammonium chloride in an amount equal to 6 times the weight of the gold nugget, and evaporate and dry at 80℃ for 12 hours to obtain ammonium chloroaurate powder.

[0072] Step 2: Place the ammonium chloroaurate and ascorbic acid obtained in Step 1 into a ball mill jar at a mass ratio of 2:1, and ball mill at a speed of 300 r / min for 1 hour to obtain a uniformly mixed precursor gold powder.

[0073] Step 3: Place the precursor gold powder obtained in Step 2 into a tube furnace, heat it to 160°C in an air atmosphere, and then hold it at that temperature for 1 hour for low-temperature calcination to obtain nano gold powder.

[0074] Step 4: Add 1g of the gold nanoparticles obtained in Step 3 to 200mL of anhydrous ethanol to prepare a gold nanoparticle suspension, and then perform high-temperature atomization at 250℃ to obtain gold powder for thick film conductive paste.

[0075] Testing revealed that the gold powder used in the thick-film conductive paste prepared in this embodiment has a particle size of 0.5 μm to 4 μm, a spherical morphology, and a specific surface area of ​​less than 3 m². 2 / g, with a purity greater than 99.9%.

[0076] Comparing the test results of the gold powder prepared in this embodiment with those in Example 1, it can be seen that the particle size and dispersibility of the gold powder do not change significantly.

[0077] Example 7

[0078] This embodiment includes the following steps:

[0079] Step 1: Add 50g of gold nugget to 500mL of aqua regia, heat to 70℃ and dissolve for 4 hours. After complete dissolution, remove the nitrate and fix the final solution volume at 250mL. Then add ammonium chloride in an amount four times the weight of the gold nugget, and evaporate and dry at 80℃ for 12 hours to obtain ammonium chloroaurate powder.

[0080] Step 2: Place the ammonium chloroaurate and ascorbic acid obtained in Step 1 into a ball mill jar at a mass ratio of 1:1, and ball mill at a speed of 600 r / min for 0.5 h to obtain a uniformly mixed precursor gold powder.

[0081] Step 3: Place the precursor gold powder obtained in Step 2 into a tube furnace, heat it to 130°C in an air atmosphere, and hold it at that temperature for 0.5 hours for low-temperature calcination to obtain nano gold powder.

[0082] Step 4: Add 1g of the gold nanoparticles obtained in Step 3 to 1000mL of anhydrous ethanol to prepare a gold nanoparticle suspension, and then perform high-temperature atomization at 250℃ to obtain gold powder for thick film conductive paste.

[0083] Testing revealed that the gold powder used in the thick-film conductive paste prepared in this embodiment has a particle size of 0.5 μm to 2 μm, a spherical morphology, and a specific surface area of ​​less than 3 m². 2 / g, with a purity greater than 99.9%.

[0084] Comparing the test results of the gold powder prepared in this embodiment with those in Example 1, it can be seen that the particle size of the gold powder is smaller. This is because 1g of gold powder is dissolved in 1000mL of aqueous solution containing ethanol, the solution concentration is reduced, the number of gold nanoparticles in the atomized droplets is reduced, resulting in a reduction in the number of gold particles grown in a single droplet at high temperature, and ultimately a smaller volume and smaller particle size.

[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing gold powder for thick-film conductive paste, characterized in that, The method includes the following steps: Step 1: Dissolve the gold nugget in aqua regia and remove the nitrate, then add ammonium chloride and evaporate to dryness to obtain ammonium chloroaurate powder; Step 2: Mix and ball-mill the ammonium chloroaurate powder obtained in Step 1 with ascorbic acid to obtain a uniformly mixed gold-containing precursor powder; Step 3: Calcining the gold-containing precursor powder obtained in Step 2 in air at a low temperature to obtain nano-gold powder; Step 4: Add the gold nanoparticles obtained in Step 3 to anhydrous ethanol to prepare a gold nanoparticle suspension, and then atomize it at high temperature to obtain gold powder for thick film conductive paste; the high temperature atomization process is as follows: dissolve 1g of gold nanoparticles in 200mL~1000mL of anhydrous ethanol, and then atomize it at 250℃~500℃.

2. The method for preparing gold powder for thick-film conductive paste according to claim 1, characterized in that, The amount of ammonium chloride added in step one is 3 to 6 times the mass of the gold nugget.

3. The method for preparing gold powder for thick-film conductive paste according to claim 2, characterized in that, In step two, the mass ratio of ammonium chloroaurate powder to ascorbic acid is 1~3:1, the ball milling speed is 300r / min~600r / min, and the time is 0.5h~2h.

4. The method for preparing gold powder for thick-film conductive paste according to claim 3, characterized in that, The low-temperature calcination process described in step three is as follows: the gold-containing precursor powder is placed in a tube furnace and heated to 130℃~200℃ in an air atmosphere, and then held at that temperature for 0.5h~2h.

5. The method for preparing gold powder for thick-film conductive paste according to claim 4, characterized in that, The gold powder used in the thick-film conductive paste described in step four has a particle size of 0.5μm~4μm and a specific surface area of ​​less than 3m². 2 / g, spherical in shape, with a mass purity greater than 99.9%.

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