Preparation method of silver-coated aluminum powder for conductive shielding

Abstract

The invention provides a preparation method of silver-coated aluminum powder for conductive shielding, and relates to the technical field of conductive and electromagnetic shielding. The preparation method of the silver-coated aluminum powder for conductive shielding comprises the following steps: step 1, replacing a target material with an Ag target material by using an ion sputtering instrument; 2, pumping the chamber to a vacuum environment by using a vacuum pump; 3, stirring the aluminum powder at a certain speed in real time by utilizing a built-in stirring and heating device, and heating to 300-600 DEG C to enable the surface of the aluminum powder to be in a semi-molten state; and fourthly, the sputtering frequency, the proper voltage and the proper beam are set, under the protection of Ar gas, Ag atoms are evenly sputtered on the semi-molten-state surface of the continuously-stirred aluminum powder at a certain speed, the Ag atoms are tightly combined with the aluminum powder, and a compact and smooth high-purity silver coating layer is formed. The obtained silver-coated aluminum powder particles are high in coating rate, low in silver consumption and good in conductivity, the silver consumption is lower than 15%, the volume resistivity can reach 10 <-4 > power and is close to the pure silver level, and the conductive effect is good.

Description

Technical Field

[0001] The invention relates to the technical field of electrical conduction and electromagnetic shielding, and in particular to a method for preparing silver-coated aluminum powder for electrical conduction and shielding. Background Art

[0002] In the prior art, the preparation of silver-coated aluminum powder mostly adopts chemical deposition method. One of them is a one-step method, which uses formaldehyde, potassium sodium tartrate or glucose as a reducing agent to reduce the oxidant with silver nitrate as the main salt and ammonia as the complexing agent, so that the silver element is reduced and deposited on the surface of the activated aluminum powder. This method has the problems of complex ingredients, many side reactions, discontinuous silver layer on the aluminum surface, low coverage, easy oxidation of the product, and poor conductivity.

[0003] The other is a two-step method, which is to pre-plating an intermediate layer such as copper or nickel on the surface of aluminum powder, and then silver plating using the silver mirror reaction. Although this method improves the coverage rate to a certain extent, it also has disadvantages such as high silver consumption, easy agglomeration of the coating on the surface, low bonding with the substrate, easy formation of hollows between the silver coating and the aluminum substrate, and easy falling off under the action of shear force.

[0004] Moreover, the particle size of aluminum silver powder prepared by the above two methods is limited to the micron level (above 20 microns), and it is impossible to coat aluminum powder below 20 microns and nanometer scale. In addition, the three wastes generated by liquid phase deposition, especially the wastewater, contain a large amount of harmful chemical products, which is not friendly to the environment and has a high treatment cost. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In view of the deficiencies in the prior art, the present invention provides a method for preparing silver-coated aluminum powder for conductive shielding, which solves the problems raised by the above-mentioned background technology.

[0007] (II) Technical solution

[0008] To achieve the above objectives, the present invention is implemented by the following technical scheme: A method for preparing silver-coated aluminum powder for conductive shielding, comprising the following steps:

[0009] Step 1: Equipment preparation:

[0010] Use an ion sputtering instrument and replace the target material with an Ag target;

[0011] Step 2: Chamber environment settings:

[0012] Use a vacuum pump to evacuate the chamber to a vacuum environment;

[0013] Step 3: Aluminum powder pretreatment:

[0014] Using the built-in stirring and heating device, the aluminum powder is stirred in real time at a certain speed and heated to 300-600℃, so that the surface of the aluminum powder is semi-molten;

[0015] Step 4: Sputtering parameter setting and deposition process:

[0016] The sputtering frequency, appropriate voltage and beam current are set, and under the protection of Ar gas, Ag atoms are evenly sputtered at a certain speed on the surface of the semi-molten aluminum powder that is constantly stirred, and are tightly combined with the aluminum powder to form a dense, smooth, high-purity silver coating layer.

[0017] Preferably, in step 1, the main technical indicators of the ion sputtering instrument include:

[0018] (1) The operating vacuum is 1×10 -2 -1×10 -4 mbar;

[0019] (2) Sputtering current is 0-150mA;

[0020] (3) Deposition rate is 0-20 nm / min, sputtering timing is 0-4 min;

[0021] (4) The power supply voltage is 230V / 50Hz.

[0022] Preferably, in step 2, the pressure of the vacuum environment is ≤0.3-0.5Pa.

[0023] Preferably, in step three, the stirring speed is 100-300 r / min, and the heating temperature increases with the increase of the particle size of the aluminum powder.

[0024] Preferably, in step 4, the sputtering frequency is 1 minute*20 times, and the voltage and beam current increase with the increase of Ar gas intake amount.

[0025] Preferably, in step 4, the silver coating layer has uniform grain size and uniform crystal form.

[0026] (III) Beneficial effects

[0027] The present invention provides a method for preparing silver-coated aluminum powder for conductive shielding, which has the following beneficial effects:

[0028] 1. The silver-plated aluminum powder finally prepared by the present invention has the characteristics of high coverage, good bonding force, small amount of silver, uniform crystal form, silver layer not easy to fall off, stable quality, etc. At the same time, the process provided by the present invention is not limited by particle size, and silver-coated aluminum powder with a full range of scales from micron level to nanometer level can be prepared, and a large amount of wastewater and waste gas generated by liquid phase deposition method is avoided, which is in line with the concept of environmental protection.

[0029] 2. Compared with the liquid phase chemical deposition method, the silver-plated aluminum powder finally prepared by the present invention can only cover aluminum powder above 20 microns. The particle size of the silver-plated aluminum powder obtained by the physical vapor deposition method can range from tens of nanometers to hundreds of microns. The particle coverage rate is high, less silver is used, and the conductivity is good. The silver content is less than 15%, but the volume resistivity can reach 10 -4 The power is close to the level of pure silver and has good conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the preparation method of the present invention;

[0031] Figure 2 This is a schematic diagram of a photo of the silver-coated aluminum powder prepared in 30s of the present invention;

[0032] Figure 3 This is a schematic diagram of a photo of the silver-coated aluminum powder prepared in 20 minutes according to the present invention;

[0033] Figure 4 This is a schematic diagram of a photo of the finished silver-coated aluminum powder of the present invention;

[0034] Figure 5 It is a schematic diagram of the resistivity versus pressure curve of the present invention;

[0035] Figure 6 It is a schematic diagram of the conductivity variation curve with pressure of the present invention;

[0036] Figure 7 It is a schematic diagram of raw data of volume resistivity test of the present invention. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Embodiment 1:

[0039] like Figure 1 As shown, an embodiment of the present invention provides a method for preparing silver-coated aluminum powder for conductive shielding, using a PVD physical vapor deposition method, comprising the following steps:

[0040] Step 1: Equipment preparation:

[0041] Use Hitachi 1045 ion sputtering instrument to replace the target material with Ag target material; the ion sputtering instrument is debugged according to its technical indicators to ensure that the equipment can operate normally and meet the set vacuum environment, sputtering current, deposition rate and other parameter requirements. Specifically, the main technical indicators of the ion sputtering instrument include:

[0042] (1) The operating vacuum is 1×10 -2 mbar;

[0043] (2) The sputtering current is 50 mA;

[0044] (3) The deposition rate is 5 nm / min and the sputtering timing is 1 min;

[0045] (4) The power supply voltage is 230V / 50Hz

[0046] Step 2: Chamber environment settings:

[0047] Use a vacuum pump to evacuate the chamber to a vacuum environment with a pressure of 0.3 Pa;

[0048] Step 3: Aluminum powder pretreatment:

[0049] The aluminum powder is stirred in real time at a certain speed using a built-in stirring and heating device. The stirring speed is 100r / min and heated to 300°C. The heating temperature increases with the increase of the aluminum powder particle size, so that the surface of the aluminum powder is in a semi-molten state.

[0050] Step 4: Sputtering parameter setting and deposition process:

[0051] The sputtering frequency, appropriate voltage and beam current were set. Specifically, the sputtering frequency was 1 minute * 20 times. The voltage and beam current increased with the increase of the Ar gas intake. Under the protection of Ar gas, Ag atoms were evenly sputtered at a certain speed on the surface of the semi-molten aluminum powder that was constantly stirred, and were tightly combined with the aluminum powder to form a dense, smooth, high-purity silver coating layer. The grain size of the silver coating layer was uniform and the crystal shape was unified.

[0052] Embodiment 2:

[0053] like Figure 1 As shown, an embodiment of the present invention provides a method for preparing silver-coated aluminum powder for conductive shielding, using a PVD physical vapor deposition method, comprising the following steps:

[0054] Step 1: Equipment preparation:

[0055] Use Hitachi 1045 ion sputtering instrument to replace the target material with Ag target material; the ion sputtering instrument is debugged according to its technical indicators to ensure that the equipment can operate normally and meet the set vacuum environment, sputtering current, deposition rate and other parameter requirements. Specifically, the main technical indicators of the ion sputtering instrument include:

[0056] (1) The operating vacuum is 1×10 -3 mbar;

[0057] (2) Sputtering current is 100 mA;

[0058] (3) The deposition rate is 10 nm / min and the sputtering timing is 2 min;

[0059] (4) The power supply voltage is 230V / 50Hz

[0060] Step 2: Chamber environment settings:

[0061] Use a vacuum pump to evacuate the chamber to a vacuum environment with a pressure of 0.4 Pa;

[0062] Step 3: Aluminum powder pretreatment:

[0063] The aluminum powder is stirred in real time at a certain speed using a built-in stirring and heating device. The stirring speed is 200r / min and heated to 400°C. The heating temperature increases with the increase of the aluminum powder particle size, so that the surface of the aluminum powder is in a semi-molten state.

[0064] Step 4: Sputtering parameter setting and deposition process:

[0065] The sputtering frequency, appropriate voltage and beam current were set. Specifically, the sputtering frequency was 1 minute * 20 times. The voltage and beam current increased with the increase of the Ar gas intake. Under the protection of Ar gas, Ag atoms were evenly sputtered at a certain speed on the surface of the semi-molten aluminum powder that was constantly stirred, and were tightly combined with the aluminum powder to form a dense, smooth, high-purity silver coating layer. The grain size of the silver coating layer was uniform and the crystal shape was unified.

[0066] Embodiment three:

[0067] like Figure 1 As shown, an embodiment of the present invention provides a method for preparing silver-coated aluminum powder for conductive shielding, using a PVD physical vapor deposition method, comprising the following steps:

[0068] Step 1: Equipment preparation:

[0069] Use Hitachi 1045 ion sputtering instrument to replace the target material with Ag target material; the ion sputtering instrument is debugged according to its technical indicators to ensure that the equipment can operate normally and meet the set vacuum environment, sputtering current, deposition rate and other parameter requirements. Specifically, the main technical indicators of the ion sputtering instrument include:

[0070] (1) The operating vacuum is 1×10 -4 mbar;

[0071] (2) Sputtering current is 150mA;

[0072] (3) The deposition rate is 20 nm / min and the sputtering time is 4 min;

[0073] (4) The power supply voltage is 230V / 50Hz

[0074] Step 2: Chamber environment settings:

[0075] Use a vacuum pump to evacuate the chamber to a vacuum environment with a pressure of 0.5 Pa;

[0076] Step 3: Aluminum powder pretreatment:

[0077] The aluminum powder is stirred in real time at a certain speed of 300r / min by using the built-in stirring and heating device, and heated to 600°C. The heating temperature increases with the increase of the aluminum powder particle size, so that the surface of the aluminum powder is in a semi-molten state.

[0078] Step 4: Sputtering parameter setting and deposition process:

[0079] The sputtering frequency, appropriate voltage and beam current were set. Specifically, the sputtering frequency was 1 minute * 20 times. The voltage and beam current increased with the increase of the Ar gas intake. Under the protection of Ar gas, Ag atoms were evenly sputtered at a certain speed on the surface of the semi-molten aluminum powder that was constantly stirred, and were tightly combined with the aluminum powder to form a dense, smooth, high-purity silver coating layer. The grain size of the silver coating layer was uniform and the crystal shape was unified.

[0080] Product testing and analysis

[0081] The prepared silver-coated aluminum powder is tested, including observing its microstructure (through an electron microscope and other equipment) and measuring its electrical properties (such as resistivity and conductivity).

[0082] Combination Figure 2-Figure 7 , according to the resistivity / conductivity curve and volume resistivity test raw data provided in the attached figure, analyze whether the product meets the expected performance indicators.

[0083] The measured volume resistivity of the silver-coated aluminum powder is consistent with the expected 10 -4It is about the power of one, which means the product has good conductivity.

[0084] In summary, the present invention overcomes many defects of the existing chemical deposition method for preparing silver-coated aluminum powder by adopting PVD physical vapor deposition method, and provides a high-efficiency, environmentally friendly and high-performance method for preparing silver-coated aluminum powder, which has broad application prospects in the fields of conductivity and electromagnetic shielding.

[0085] The silver-plated aluminum powder finally prepared by the present invention has the characteristics of high coverage, good bonding force, small amount of silver, uniform crystal form, silver layer not easy to fall off, stable quality, etc. At the same time, the process provided by the present invention is not limited by particle size, and silver-plated aluminum powder with a full range of scales from micron level to nanometer level can be prepared, and a large amount of wastewater and waste gas generated by liquid phase deposition method is avoided, which is in line with the concept of environmental protection.

[0086] Compared with the liquid phase chemical deposition method, the silver-plated aluminum powder finally prepared by the present invention can only coat aluminum powder of more than 20 microns. The particle size of the silver-coated aluminum powder obtained by the physical vapor deposition method can range from tens of nanometers to hundreds of microns. The particle coverage rate is high, the silver content is small, the conductivity is good, the silver content is less than 15%, but the volume resistivity can reach 10 -4 The power is close to the level of pure silver and has good conductivity.

[0087] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing silver-coated aluminum powder for conductive shielding, characterized in that: The following steps are involved: Step 1: Equipment preparation: Use an ion sputtering instrument and replace the target material with an Ag target; Step 2: Chamber environment settings: Use a vacuum pump to evacuate the chamber to a vacuum environment; Step 3: Aluminum powder pretreatment: Using the built-in stirring and heating device, the aluminum powder is stirred in real time at a certain speed and heated to 300-600℃, so that the surface of the aluminum powder is semi-molten; Step 4: Sputtering parameter setting and deposition process: The sputtering frequency, appropriate voltage and beam current are set, and under the protection of Ar gas, Ag atoms are evenly sputtered at a certain speed on the surface of the semi-molten aluminum powder that is constantly stirred, and are tightly combined with the aluminum powder to form a dense, smooth, high-purity silver coating layer.

2. The method for preparing silver-coated aluminum powder for conductive shielding according to claim 1, characterized in that: In step 1, the main technical indicators of the ion sputtering instrument include: (1) The operating vacuum is 1×10 -2 -1×10 -4 mbar; (2) Sputtering current is 0-150mA; (3) Deposition rate is 0-20 nm / min, sputtering timing is 0-4 min; (4) The power supply voltage is 230V / 50Hz.

3. The method for preparing silver-coated aluminum powder for conductive shielding according to claim 1, characterized in that: In step 2, the pressure of the vacuum environment is ≤0.3-0.5Pa.

4. The method for preparing silver-coated aluminum powder for conductive shielding according to claim 1, characterized in that: In step three, the stirring speed is 100-300 r / min, and the heating temperature increases with the increase of the particle size of the aluminum powder.

5. The method for preparing silver-coated aluminum powder for conductive shielding according to claim 1, characterized in that: In step 4, the sputtering frequency is 1 minute*20 times, and the voltage and beam current increase with the increase of the Ar gas intake amount.

6. The method for preparing silver-coated aluminum powder for conductive shielding according to claim 1, characterized in that: In step 4, the silver coating layer has uniform grain size and uniform crystal form.

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