Composite metal powder with gold-plated surface and preparation method thereof

Abstract

The present invention provides a composite metal powder with a gold-plated surface and a preparation method thereof, and belongs to the technical field of metal powder preparation. The present invention prepares the composite metal powder by adopting a process combining aerosol powder making and liquid phase chemical plating. Among them, the aerosol powder making process can further improve the yield of fine powder products on the basis of ensuring the dispersibility and sphericity of the metal matrix powder. On the other hand, by synergistically controlling the addition method, addition order, concentration and solution pH of each component in the liquid phase chemical plating, it is possible to effectively prevent the generation of micron gold particles alone in the reaction system, thereby ensuring that the surface of the metal matrix powder is coated with a uniform and dense gold coating. The composite metal powder material prepared by the present invention has a particle size of 15 to 50 μm, and the thickness of the gold coating is less than 1 μm. It can be widely used in the preparation of conductive fillers used in semiconductor packaging, flexible circuits, sensors, thick film hybrid circuits, etc., and can further reduce the production cost of high-end electronic fillers.

Description

Technical Field

[0001] The invention relates to the technical field of metal powder and preparation thereof, in particular to a composite metal powder with gold-plated surface and a preparation method thereof. Background Art

[0002] Gold is widely used in electronics, military, aerospace, biomedicine and many other fields due to its excellent electrical conductivity, thermal conductivity and chemical stability. Among them, micro-nano gold powder can be used to prepare electromagnetic shielding, electronic packaging, target marking and other materials. However, in actual applications, due to the high cost and small reserves of gold, it is difficult to meet the demand of the high-end market. Although the metal powder materials such as silver and nickel with micron size on the market are relatively low in cost and can also be used as electronic fillers, their electrical conductivity and antioxidant properties are not comparable to gold powder, and it is difficult to meet the application requirements of high-end conductive fillers. Therefore, it is necessary to design an electronic filler with micron size, relatively low production cost, and electrical conductivity and antioxidant properties that are no less than micro-nano gold powder, so as to meet the market demand for high-end conductive fillers.

[0003] In the prior art, the patent with publication number CN104479456A discloses the application of gold-coated silver-graphene-based water-based ink and its inkjet printing transparent patterned conductive electrode. The patent first prepares nanoparticles by reducing silver nitrate, and then places it in a chloroauric acid solution to deposit a gold coating layer on its surface, thereby forming gold-coated silver nanoparticles with a particle size of less than 500nm. However, because the nano-gold-coated silver particles prepared by the patent method are too small, they have strong oil absorption and poor dispersibility in the downstream slurry, which seriously reduces the conductivity of the electronic filler and cannot be used to prepare functional materials such as electromagnetic shielding and electronic packaging.

[0004] The patent with the publication number CN115874171A discloses a method for controlling the density of a gold layer based on a cyanide-free gold plating solution. In the patent, 22 parts of a complexing agent are first mixed with 1 part of a gold salt, and then 2 parts of a reducing agent are added to prepare a cyanide-free gold plating solution. Then, nickel-plated microspheres are dispersed in ultrapure water to prepare a nickel-plated microsphere dispersion solution. The prepared cyanide-free gold plating solution is added to the prepared nickel microsphere dispersion solution. The preparation method adjusts the pH value of the cyanide-free gold plating solution to 6-13 by a pH adjusting agent to obtain gold-plated microspheres with different gold layer densities. However, this method only controls the density of the gold layer by adjusting the pH value of the gold plating solution, and does not consider the influence of other factors on the generation of micron gold particles in the reaction system, so that the utilization rate of the gold plating solution is not sufficient.

[0005] In view of this, it is necessary to design an improved composite metal powder with gold-plated surface and a preparation method thereof to solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to provide a composite metal powder with a gold-plated surface and a preparation method thereof. A composite metal powder material with a particle size of 15 to 50 μm and a gold coating thickness of less than 1 μm is prepared by a process combining gas atomization powder making and liquid phase chemical plating technology. The composite metal powder material has good sphericity and dispersibility, and the surface gold coating layer is uniform and dense. The composite metal powder material can be widely used in the preparation of conductive fillers used in semiconductor packaging, flexible circuits, sensors, thick film hybrid circuits, etc., further reducing the production cost of high-end electronic slurries.

[0007] To achieve the above-mentioned purpose, the present invention provides a composite metal powder with gold-plated surface and a preparation method thereof, comprising the following steps:

[0008] S1. Prepare the first micron metal powder from pure metal raw material by gas atomization powder making process;

[0009] S2. The first micron metal powder prepared in step S1 is sieved to obtain a second micron metal powder;

[0010] S3. Liquid phase chemical plating: The second micron metal powder obtained in step S2 is added to an alkali solution for alkalization, and then a chloroauric acid solution and a glucose solution are added in sequence, and a pH regulator is added during the reaction to control the pH value of the reaction system to 8 to 12, and a third micron metal powder is obtained after sufficient reaction;

[0011] S4. The third micron metal powder obtained in step S3 is subjected to solid-liquid separation, washing and drying to obtain a composite metal powder with a gold-plated surface.

[0012] As a further improvement of the present invention, in step S3, the mass concentration of the chloroauric acid solution is 20 g / L~50 g / L, and the mass fraction of the glucose solution is 10%~20%.

[0013] As a further improvement of the present invention, in step S3, the chloroauric acid is added by pouring it all at once, and the glucose solution is added by dropping it at a dropping speed of 10 mL / min to 50 mL / min.

[0014] As a further improvement of the present invention, in step S3, the time interval between adding the chloroauric acid solution and the glucose solution is 5 to 15 minutes.

[0015] As a further improvement of the present invention, in step S3, the alkali solution is a sodium hydroxide solution or a potassium hydroxide solution, and the concentration of the alkali solution is 0.005-0.015 mol / L.

[0016] As a further improvement of the present invention, in step S1, the aerosol powder making process comprises the following steps:

[0017] The pure metal raw material is placed in a crucible for electromagnetic induction heating and melting. When it reaches the atomization temperature, it flows out along the guide tube and is broken into fine droplets under a certain atomization pressure and the impact of high-purity inert gas flow. It is then spheroidized and condensed to form the first micron metal powder.

[0018] As a further improvement of the present invention, the atomization temperature is 150°C to 400°C higher than the melting point of the pure metal raw material, the inert gas flow is helium or argon with a purity of more than 99.999%, and the atomization pressure is 4MPa to 8MPa.

[0019] As a further improvement of the present invention, in step S1, the purity of the pure metal raw material is above 99.99%, and the pure metal raw material is any one of silver, copper, nickel and aluminum.

[0020] As a further improvement of the present invention, in step S2, the screening process uses a 300-mesh ultrasonic vibration screen.

[0021] The present invention also provides a composite metal powder with a gold-plated surface, which is prepared by the above-mentioned method for preparing the composite metal powder with a gold-plated surface, and comprises a metal base powder and a gold coating coated on the surface of the metal base powder; the particle size of the composite metal powder with a gold-plated surface is 15~50μm, the gold content is 1%~5%, and the thickness of the gold coating is less than 1μm.

[0022] The beneficial effects of the present invention are:

[0023] 1. The present invention adopts a gas atomization powder making process to prepare pure metal micron powder. By controlling the process conditions such as the superheat of the molten metal, the type of atomizing gas and the pressure, the atomization efficiency and the fine powder yield can be further improved on the basis of ensuring the dispersibility of the metal matrix powder. In addition, compared with the liquid phase chemical reduction method, the gas atomization powder making process adopted by the present invention is simple, the production cost is low, and the powder sphericity and surface morphology are good, which is conducive to the secondary plating of the powder surface, so as to be applied to the preparation of conductive fillers.

[0024] 2. The present invention adopts a liquid phase chemical plating method to prepare a composite metal powder with a gold-plated surface. By synergistically controlling the addition method, addition order, concentration and solution pH value of each component in the liquid phase chemical plating, it can effectively prevent the generation of micron gold particles alone in the reaction system, thereby ensuring that the surface of the metal matrix powder is coated with a uniform and dense gold coating, thereby greatly improving the utilization rate of the gold plating solution.

[0025] 3. The present invention combines the aerosol powder making process with the liquid phase chemical plating technology to prepare composite metal powder materials such as gold-coated silver, gold-coated nickel, gold-coated copper, and gold-coated aluminum with a particle size of 15 to 50 μm. Due to its good dispersibility and conductivity, it can be widely used in the preparation of conductive fillers used in semiconductor packaging, flexible circuits, sensors, thick film hybrid circuits, etc. The gold coating with a thickness of less than 1 μm in the composite metal powder material can significantly improve the conductivity of the metal matrix material and effectively prevent the oxidation of the metal matrix powder, thereby improving the stability of the powder product. Moreover, since the gold content in the composite metal powder is very low, the cost of the conductive filler prepared based on the composite metal powder is significantly reduced compared to using gold powder alone. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the SEM image of the gold-plated composite nickel powder prepared in Example 1.

[0027] Figure 2 This is the SEM image of the gold-plated composite nickel powder prepared in Example 4.

[0028] Figure 3 This is the SEM image of the gold-plated composite nickel powder prepared in Example 5.

[0029] Figure 4 This is the SEM image of the gold-plated composite nickel powder prepared in Comparative Example 1.

[0030] Figure 5 This is the SEM image of the gold-plated composite nickel powder prepared in Comparative Example 2.

[0031] Figure 6 This is a SEM image of the surface morphology of a single particle of composite nickel powder with gold plating on the surface prepared in Comparative Example 3. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the scheme of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0034] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0035] The present invention provides a method for preparing a composite metal powder with a gold-plated surface, comprising the following steps:

[0036] S1. Prepare the first micron metal powder from pure metal raw material by gas atomization powder making process;

[0037] S2. The first micron metal powder prepared in step S1 is sieved to obtain a second micron metal powder;

[0038] S3. Liquid phase chemical plating: under stirring conditions, the second micron metal powder obtained in step S2 is added to an alkali solution for alkalization, and then a chloroauric acid solution and a glucose solution are added in sequence, and a pH regulator is added during the reaction to control the pH value of the reaction system to 8 to 12, and a third micron metal powder is obtained after sufficient reaction;

[0039] S4. The third micron metal powder obtained in step S3 is subjected to solid-liquid separation, washing and drying to obtain a composite metal powder with a gold-plated surface.

[0040] Through the above method, the present invention can coat the surface of the metal matrix powder with a uniform and dense gold coating, while effectively preventing the generation of micron gold particles alone in the reaction system, thereby preparing a composite metal powder with excellent conductive properties at a relatively low cost.

[0041] Preferably, in step S1, the gas atomization powder making process specifically includes: placing any one of the pure metal raw materials of silver, copper, nickel, and aluminum with a purity of more than 99.99% in a crucible for electromagnetic induction heating and melting, and when it reaches the atomization temperature, that is, 150°C to 400°C higher than the melting point of the pure metal raw material, the pure metal raw material flows out along the guide tube, and under the atomization pressure of 4MPa to 8MPa, it is broken into fine droplets by the impact of helium or argon gas flow with a purity of more than 99.999%, and the first micron metal powder is formed by spheroidization and condensation. In the above manner, the particle size of the metal matrix powder can be regulated to obtain a micron-level metal matrix powder, and the yield of the fine powder product can be further improved on the basis of ensuring the dispersibility and sphericity of the metal matrix powder.

[0042] In step S2, an ultrasonic vibration screen with a screen size of 300 mesh is preferably used for screening.

[0043] In step S3, the alkali solution is preferably a sodium hydroxide solution or a potassium hydroxide solution, the concentration of the alkali solution is preferably 0.005-0.015 mol / L, the solid content of the second micron metal powder in the alkali solution is preferably 100-500 g / L, and the alkalization treatment time is 5-15 min. Wherein, if the concentration of the alkali solution is too high, the surface of the second micron metal powder will be destroyed, thereby significantly reducing its surface coating effect; if the concentration of the alkali solution is too low, the alkalization is incomplete, and it is difficult to achieve the desired alkalization effect, thereby affecting the plating effect of gold on its surface, resulting in poor density and uniformity of the gold coating. The present invention can alkalize the surface of the second micron metal powder by adding the second micron metal powder to the above-mentioned alkali solution for alkalization treatment, provide a good growth environment for the subsequent plating of the gold layer, promote the surface growth of the gold coating on the second micron metal powder, and prevent the generation of micron gold particles alone in the reaction system, thereby forming a uniform and dense gold coating on the surface of the second micron metal powder.

[0044] After the alkalization treatment is completed, it is preferred to add chloroauric acid solution to the alkali solution in a one-time pouring manner, the concentration of the chloroauric acid solution is preferably 20g / L~50g / L, and the ratio of the chloroauric acid solution to the second micron metal powder is preferably 1.5mL / g; after a period of time, it is preferred to add glucose solution to the alkali solution in a dropwise manner, the mass fraction of the glucose solution is preferably 10%~20%, the dripping speed of the glucose solution is preferably 10mL / min~50mL / min, the ratio of the glucose solution to the second micron metal powder is preferably 0.2mL / g, and the time interval between the addition of the chloroauric acid solution and the glucose solution is preferably 5~15min. Among them, when the concentration of chloroauric acid solution is too low, the coating efficiency will be low. When the concentration of chloroauric acid is too high, the deposition rate is fast, which may cause the gold plating layer to be rough, and the plating solution system is unstable, which will affect the plating effect of the gold plating layer. When the glucose solution is added too quickly and the addition interval is too short, the concentration of the reducing agent in the gold plating solution increases instantly, and the gold reduction rate is too fast, which will cause the gold dendrites to be coarse and the coating uniformity and density to be poor.

[0045] By synergistically controlling the addition method, addition order, concentration and solution pH of each component in liquid phase chemical plating, the reaction rate and stability of the gold plating solution can be controlled, which can effectively prevent the generation of micron gold particles alone in the reaction system and form a uniform and dense gold coating on the surface of the metal matrix powder.

[0046] S4. The third micron metal powder obtained in step S3 is subjected to solid-liquid separation, washing and drying to obtain micron composite metal powder.

[0047] The present invention also provides a composite metal powder with a gold-plated surface, which is prepared by the above-mentioned method for preparing the composite metal powder with a gold-plated surface. The particle size of the composite metal powder with a gold-plated surface is about 15-50 μm, the gold content is 1%-5%, and the thickness of the gold coating is less than 1 μm.

[0048] The present invention is described in detail below with reference to specific embodiments.

[0049] Example 1

[0050] This embodiment provides a method for preparing a composite metal powder with a gold-plated surface, comprising the following steps:

[0051] S1. Place 99.99% pure nickel raw material in a crucible for electromagnetic induction heating and melting. When its temperature is 300°C higher than the melting point of the pure nickel raw material, it flows out along the guide tube. Under the condition of an atomization pressure of 6MPa, it is impacted by 99.999% pure helium to break it into fine droplets, which are then spheroidized and condensed to form the first micron nickel powder.

[0052] S2. The first micron nickel powder prepared in step S1 is placed in an ultrasonic vibration screen for classification, and the metal powder under the 300-mesh screen is the second micron nickel powder.

[0053] S3. Add 100g of the second micron nickel powder into 1L of 0.01mol / L sodium hydroxide solution and stir for 10min for alkalization. Then pour in 150mL of 25g / L chloroauric acid solution at one time. After mixing for 10min, add 20mL of 10% glucose solution at a rate of 20mL / min. At the same time, add sodium hydroxide solution as a pH adjuster to control the pH value of the reaction system to 10. After the reaction, the third micron nickel powder is obtained.

[0054] S4. The third micron nickel powder obtained in step S3 is subjected to solid-liquid separation, and washed three times with deionized water. After drying, a composite nickel powder with a gold-plated surface can be obtained.

[0055] The SEM image of the gold-plated composite nickel powder prepared in this embodiment is as follows: Figure 1 As shown. Figure 1 It can be seen that the obtained surface-gold-plated composite nickel powder has good sphericity and dispersibility, the particle size is about 15~50μm, and the gold content of the powder is 1.78%.

[0056] Embodiment 2-3

[0057] Embodiments 2 and 3 respectively provide a method for preparing a composite metal powder with a gold-plated surface. Compared with Embodiment 1, the difference is that the pure metal raw material used in step S1 is changed. In Embodiment 2, the pure nickel raw material with a purity of 99.99% is changed to a pure silver raw material with a purity of 99.99%, and in Embodiment 3, the pure silver raw material with a purity of 99.99% is changed to a pure copper raw material with a purity of 99.99%. The other steps are substantially the same as those in Embodiment 1 and are not described in detail here.

[0058] The appearance morphology and particle size of the surface gold-plated composite silver powder and surface gold-plated composite copper powder prepared in Example 2 and Example 3, respectively, are similar to those in Example 1, indicating that the method provided by the present invention can perform surface gold plating on different types of metal matrix powders and has a wide range of applications.

[0059] Embodiment 4-5

[0060] Embodiments 4 and 5 respectively provide a method for preparing a composite metal powder with a gold-plated surface. Compared with Embodiment 1, the difference is that the concentration of the sodium hydroxide solution used in the alkalization treatment in step S3 is changed. In Embodiment 4, the sodium hydroxide solution with a concentration of 0.01 mol / L is changed to a sodium hydroxide solution with a concentration of 0.005 mol / L, and in Embodiment 5, the sodium hydroxide solution with a concentration of 0.01 mol / L is changed to a sodium hydroxide solution with a concentration of 0.015 mol / L. The other steps are substantially the same as in Embodiment 1 and are not repeated here.

[0061] The microscopic morphologies of the gold-plated composite nickel powders prepared in Example 4 and Example 5 are as follows: Figure 2 As shown in 3, the gold contents of the powders are 1.76% and 1.85% respectively, and the particle size is basically the same as that of the powder prepared in Example 1. It can be seen that when the concentration of the alkali solution changes within the range of 0.005-0.015 mol / L, the reduction plating effect of gold on the surface of the base nickel powder can be achieved.

[0062] Comparative Example 1

[0063] This comparative example provides a method for preparing a composite metal powder with a gold-plated surface. Compared with Example 1, the difference is that in step S3, the second micron nickel powder is not subjected to alkalization treatment, but the second micron nickel powder is directly added to a 25g / L chloroauric acid solution. The other steps are roughly the same as those in Example 1 and are not repeated here.

[0064] The microscopic morphology of the composite metal powder prepared in this comparative example is as follows Figure 4As shown in the figure, since the second micron nickel powder was not first added to the sodium hydroxide solution for treatment, the surface of the nickel powder was not alkalized, resulting in the generation of micron gold particles in the reaction system alone, which appeared in the base nickel powder particles in the form of doping or adsorption, resulting in the failure to effectively coat the surface of the second micron nickel powder with gold.

[0065] Comparative Example 2

[0066] This comparative example provides a method for preparing a composite metal powder with a gold-plated surface. Compared with Example 1, the difference is that in step S3, no pH regulator is added to adjust the pH value of the reaction. The other steps are roughly the same as Example 1 and will not be repeated here.

[0067] The microscopic morphology of the composite metal powder prepared in this comparative example is as follows Figure 5 As shown in the figure, since the aldehyde group of glucose has strong reducing property, if the pH value of the reaction system is not regulated, the gold will be reduced into individual micron spherical particles existing in the solution, thus affecting the gold plating effect on the surface of the nickel powder.

[0068] Comparative Example 3

[0069] This comparative example provides a method for preparing a composite metal powder with a gold-plated surface. Compared with Example 1, the difference is that in step S3, the order of adding the chloroauric acid solution and the glucose solution is swapped, that is, the glucose solution is added first, and then the chloroauric acid solution is added. The other steps are roughly the same as Example 1 and will not be repeated here.

[0070] The surface morphology of the single particle of composite metal powder prepared in this comparative example is as follows Figure 6 As shown. Figure 6 It can be seen that adding glucose to the sodium hydroxide solution first will not only reduce the stability of chloroauric acid during the reaction, but the glucose in the base solution will significantly increase the reduction rate of gold, thereby affecting the uniformity and density of the gold plating on the surface of the nickel powder.

[0071] In summary, the present invention combines the aerosol powder making process with the liquid phase chemical plating technology to prepare composite metal powder materials such as gold-coated silver, gold-coated nickel, gold-coated copper, and gold-coated aluminum with a particle size of about 15 to 50 μm, which can be widely used in the preparation of conductive fillers used in semiconductor packaging, flexible circuits, sensors, thick film hybrid circuits, etc. The gold coating with a thickness of less than 1 μm in the composite metal powder material can significantly improve the conductivity of the metal matrix material, and can effectively prevent the oxidation of the metal matrix powder, thereby improving the stability of the powder product, and because the gold content of the plating layer is very low, the cost of the conductive slurry is significantly reduced compared to the use of gold powder alone. On the other hand, the present invention can further improve the yield of fine powder products on the basis of ensuring the dispersibility and sphericity of the metal matrix powder by controlling the process conditions such as the superheat of the metal liquid, the type of atomizing gas, and the pressure. In addition, by synergistically controlling the addition method, addition order, concentration, and solution pH of each component in the liquid phase chemical plating, it can effectively prevent the generation of micron gold particles alone in the reaction system, thereby ensuring that a uniform and dense gold coating layer is formed on the surface of the metal matrix particles.

[0072] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. 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 may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a composite metal powder with a gold-plated surface, characterized in that: The steps include: S1. preparing a first micron metal powder from a pure metal raw material by a gas atomization powder making process, wherein the pure metal raw material is any one of silver, copper, nickel, and aluminum; S2. The first micron metal powder prepared in step S1 is sieved to obtain a second micron metal powder; S3. Liquid phase chemical plating: The second micron metal powder obtained in step S2 is added to an alkali solution with a concentration of 0.005-0.015 mol / L for alkalization treatment, and then a chloroauric acid solution with a mass concentration of 20 g / L-50 g / L and a glucose solution with a mass fraction of 10%-20% are added in sequence, and a pH regulator is added during the reaction to control the pH value of the reaction system at 8-12, and a third micron metal powder is obtained after sufficient reaction; S4. The third micron metal powder obtained in step S3 is subjected to solid-liquid separation, washing and drying to obtain a composite metal powder with a gold-plated surface.

2. The method for preparing a composite metal powder with a gold-plated surface according to claim 1, characterized in that: In step S3, the chloroauric acid solution is added by pouring it all at once, and the glucose solution is added by dropping at a speed of 10 mL / min to 50 mL / min.

3. The method for preparing a composite metal powder with a gold-plated surface according to claim 1, characterized in that: In step S3, the time interval between adding the chloroauric acid solution and the glucose solution is 5 to 15 minutes.

4. The method for preparing a composite metal powder with a gold-plated surface according to claim 1, characterized in that: In step S3, the alkali solution is a sodium hydroxide solution or a potassium hydroxide solution.

5. The method for preparing a composite metal powder with a gold-plated surface according to claim 1, characterized in that: In step S1, the gas atomization powder making process comprises the following steps: The pure metal raw material is placed in a crucible for electromagnetic induction heating and melting. When it reaches the atomization temperature, it flows out along the guide tube and is broken into fine droplets under the impact of the predetermined atomization pressure and high-purity inert gas flow. It is then spheroidized and condensed to form the first micron metal powder.

6. The method for preparing a composite metal powder with a gold-plated surface according to claim 5, characterized in that: The atomization temperature is 150° C. to 400° C. higher than the melting point of the pure metal raw material, the inert gas flow is helium or argon with a purity of more than 99.999%, and the atomization pressure is 4 MPa to 8 MPa.

7. The method for preparing a composite metal powder with a gold-plated surface according to claim 1, characterized in that: In step S1, the purity of the pure metal raw material is above 99.99%.

8. The method for preparing a composite metal powder with a gold-plated surface according to claim 1, characterized in that: In step S2, the screening process uses a 300-mesh ultrasonic vibration screen.

9. A composite metal powder with gold-plated surface, characterized in that: The composite metal powder with gold plating on the surface is prepared by the preparation method of any one of claims 1 to 8, comprising a metal base powder and a gold coating coated on the surface of the metal base powder; the particle size of the composite metal powder with gold plating on the surface is 15 to 50 μm, the gold content is 1% to 5%, and the thickness of the gold coating is less than 1 μm.

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