A magnetron sputtering device for silver-coated conductive material powder based on ultrasonic-electromagnetic suspension composite dispersion system and its application

Abstract

The present invention relates to the field of magnetron sputtering technology, and specifically discloses a magnetron sputtering silver-coated conductive material powder device based on an ultrasonic-electromagnetic suspension composite dispersion system and its application. In response to the technical difficulties of powder agglomeration, low target utilization rate and poor uniformity in large-scale production, the present invention uses a porous ceramic tooling disk as the core carrier, integrates a high-frequency ultrasonic vibrator array (adjustable at 20-100kHz), a planar rectangular cathode (tilt angle 0-15°) and a Helmholtz coil (0.1-0.5T rotating magnetic field), and realizes non-contact dispersion of powder and precise coating of silver layer through cavitation effect, electromagnetic suspension and multi-target collaborative sputtering. The tooling disk adopts a gradient aperture design, combined with liquid nitrogen microchannel cooling and modular cavity structure, so that the powder dispersion uniformity (CV value <5%), silver layer porosity (<1%), target utilization rate (52%) and single furnace production capacity (72kg / 8h) are significantly optimized, providing an efficient and environmentally friendly industrial solution for the field of electronic materials.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetron sputtering, and in particular to a magnetron sputtering device for silver-coated conductive material powder based on an ultrasonic-electromagnetic suspension composite dispersion system and applications thereof. Background Art

[0002] As the global energy structure accelerates its transition to renewable energy, the demand for electronic silver paste has exploded, causing silver prices to fluctuate at a high level for a long time. In this context, silver-coated conductive material powder, as a disruptive alternative material, needs to maintain conductivity (resistivity ≤ 4μΩ·cm), adhesion (≥5N / mm 2 ) and printability (line width accuracy ±5μm), the silver content is reduced from 100% of traditional pure silver powder to below 50%, which puts unprecedented technical requirements on the coating process.

[0003] Although traditional wet coating technologies (electroless plating, electroplating, etc.) have achieved small-scale production of silver-coated conductive material powders, their inherent defects have become increasingly prominent in the process of industrialization. Taking silver-coated copper powder (Ag / Cu) as an example, the electroless plating process relies on cyanide complexing agents (such as NaAg(CN)2) to achieve silver ion reduction. The production of a single ton of powder consumes 5-8 tons of cyanide-containing wastewater, with a treatment cost of up to 3,000 yuan / ton. In addition, the silver layer has a high porosity (5-8%) due to dendritic growth and insufficient interfacial bonding strength (≤3N / mm 2 ) and other issues. While electroplating can improve the density of the silver layer (porosity 3-5%) through pulsed power, it is limited by Faraday efficiency (approximately 85%) and edge effects. The coating uniformity (CV value > 25%) of copper core powder with a particle size of less than 5μm cannot meet the printing requirements of MLCC electrode paste for precision circuits below 3μm. Even more challenging, the wet process's silver layer thickness control accuracy is limited to ±50nm. To achieve a balance between resistivity and cost, the silver layer ratio must be maintained at 15-20%, making it difficult to break through the technical ceiling of 30% addition.

[0004] In comparison, among the physical vapor deposition (PVD) technology routes, the magnetron sputtering method is recognized by the international materials community as the ultimate solution for the preparation of the next generation of silver-coated copper powder because of its core advantages such as atomic-level deposition accuracy (thickness deviation ±5nm), no chemical pollution, and wide process adaptability (compatible with various substrates such as copper, nickel, and ceramics). However, magnetron sputtering technology faces three essential challenges in moving from laboratory to large-scale production: First, in a vacuum environment, the powder is subjected to uncontrollable agglomeration due to the van der Waals force (10-100nN / particle) and electrostatic force (>1μN / particle), resulting in partial uncovering of the coating layer (coverage <80%) and thickness fluctuations >±20%; second, the shielding effect of the three-dimensional stacked powder on the plasma results in a target material utilization rate of only 10-15% (the theoretical utilization rate of a planar target is about 30%), and 30-40% of the sputtering power is converted into powder heat load, causing local sintering (particle size growth >50%); third, the strong nonlinear characteristics of the flow field and plasma distribution in the magnetron sputtering furnace during equipment scale-up make the deposition uniformity decay exponentially with the expansion of the magnetron sputtering furnace size (the edge velocity of a 1m diameter magnetron sputtering furnace decreases by 40% compared with the center), directly restricting the single furnace production capacity from exceeding 10kg.

[0005] To address the primary bottleneck of powder dispersion, global research institutions have gone through three technological generations of exploration:

[0006] The first-generation mechanical vibration method uses an eccentric motor to drive the screen vibration to achieve powder fluidization. However, the lack of air damping in a vacuum environment causes the amplitude to lose control, and the dispersion efficiency drops by more than 50% compared with normal pressure. In addition, high-frequency vibration (>100Hz) causes plastic deformation of the copper core (the sphericity drops from 0.95 to 0.82).

[0007] The second generation of airflow assisted method uses a vortex airflow generator to suspend the powder. Although it can achieve contactless dispersion, it is very easy to cause the background vacuum to deteriorate if it is used in a vacuum environment (from 10 -5 Pa rises to 10 -3 Pa), the oxygen content of the sputtered silver layer increased to more than 2000 ppm, and the energy consumption of the circulating air pump accounted for 40% of the total power of the system.

[0008] The third generation of field-induced levitation methods includes chemical plating combined with electric field levitation and acoustic wave levitation. The former uses a high-voltage electrostatic field (>10kV / cm) to offset the gravity of the powder, which can achieve submicron precision positioning, but is only applicable to materials with a resistivity of less than 10 4 Ω·cm conductive powder with a load density of <1kg / m 3 The latter uses sound pressure nodes (>140dB) to suspend powders. Although it has full material compatibility, its energy conversion efficiency is less than 0.1%, the actual load capacity is less than 100g / furnace, and the powder rotation speed is difficult to exceed 20rpm, resulting in significant anisotropy in the coating layer.

[0009] The above technical routes cannot meet the industrialization needs of magnetron sputtering dry coating due to defects in principles or insufficient economic efficiency. Summary of the Invention

[0010] To address at least one aspect of the above-mentioned problems, the present invention provides a device for magnetron sputtering silver-coated conductive material powders based on an ultrasonic-electromagnetic levitation composite dispersion system and its application. The device achieves non-contact dispersion of conductive material powders and precise coating of silver layers through cavitation effect, electromagnetic levitation and multi-target collaborative sputtering.

[0011] In a first aspect, the present invention provides a device for magnetron sputtering silver-coated conductive material powder based on an ultrasonic-electromagnetic levitation composite dispersion system, comprising:

[0012] Magnetron sputtering furnace, providing vacuum environment;

[0013] A tooling disk is arranged in the magnetron sputtering furnace body to carry the conductive material powder, and has through holes with a gradient aperture structure on its surface. The aperture of the through holes in the central area is smaller than the aperture in the edge area, and the pore density of the through holes in the central area is greater than the pore density in the edge area. The aperture of the through holes in the central area of the tooling disk is 8-15 μm and the pore density is 1100-1400 holes / cm 2 The through holes in the edge area have a pore size of 40-60 μm and a pore density of 150-300 pores / cm 2 ;

[0014] The ultrasonic vibrator array is distributed on the bottom of the tooling plate, with an operating frequency of 20-100kHz and a power density of 1-5W / cm 2 ;

[0015] The dynamic magnetic field control module is located on the periphery of the tooling disk and is composed of a Helmholtz coil. It is connected to a three-phase alternating current to generate a 0.1-0.5T rotating magnetic field, driving the conductive material powder to spin at 80-200 rpm.

[0016] A planar rectangular cathode is arranged on the top of the magnetron sputtering furnace body. The target material is silver with a purity of ≥99.995%, the target material inclination angle is 0-15°, and the center of the target surface is 120-320 mm away from the axis of the tooling disk.

[0017] Optionally, the tooling disk has a thickness of 25-35 mm, and the gradient distribution of the through holes is achieved by laser etching.

[0018] Optionally, the surface of the tooling plate is coated with a silicon nitride protective layer, and the conductive material powder load is ≤15kg / m 2 , the loss rate is <0.1%.

[0019] Optionally, the ultrasonic vibrator array is evenly distributed in multiple groups on the bottom of the tooling plate, and each group is composed of multiple piezoelectric ceramic units.

[0020] Optionally, the sputtering power density of the planar rectangular cathode is 6-8 W / cm 2 , Edge target 3-10W / cm 2 .

[0021] Optionally, the Helmholtz coils are arranged in two layers, with a layer spacing of 140-160 mm, to control the phase difference of the three-phase current.

[0022] Optionally, a microchannel liquid nitrogen cooling interlayer is provided on the inner wall of the magnetron sputtering furnace, and a thermoelectric cooling plate is provided on the bottom of the tooling plate.

[0023] Optionally, the magnetron sputtering furnace body is provided in plurality.

[0024] In a second aspect, the present invention provides an application of a magnetron sputtering silver-coated conductive material powder device based on an ultrasonic-electromagnetic levitation composite dispersion system in the preparation of silver-coated copper powder, silver-coated nickel powder, silver-coated aluminum powder, silver-coated graphite powder, silver-coated carbon nanotube powder, and silver-coated alloy powder. The application includes combining the above-mentioned device with processing equipment for silver-coated copper powder, silver-coated nickel powder, silver-coated aluminum powder, silver-coated graphite powder, silver-coated carbon nanotube powder, and silver-coated alloy powder, and also includes the product itself and its downstream products prepared by the device, such as photovoltaic silver paste, MLCC electrode paste, and other electronic silver paste materials. Among them, the "alloy powder" in the silver-coated alloy powder includes but is not limited to a mixture of multiple powders of the above-mentioned copper powder, nickel powder, aluminum powder, graphite powder, and carbon nanotube powder.

[0025] Compared with the prior art, the core innovation of the present invention lies in:

[0026] 1. Design a tooling plate with a gradient pore size distribution (8-60μm) as the base for the conductive material powder. The pore size is optimized to 1 / 5-1 / 10 of the conductive material powder's D50, allowing airflow to penetrate and generate lift while preventing conductive material powder from leaking.

[0027] 2. Integrate ultrasonic vibrator array at the bottom of the tooling plate (frequency 20-100kHz adjustable, power density 1-5W / cm 2 ) uses the micro jet (speed > 100m / s) generated by the cavitation effect to break up the agglomerates of the conductive material powder. At the same time, the local high temperature and high pressure (5000K, 1000atm) when the cavitation bubble collapses can clean the oxides on the surface of the conductive material powder.

[0028] 3. Arrange the Helmholtz coil along the circumference of the tooling disk and adjust the current phase difference in real time Generate a rotating magnetic field (0.1-0.5T) to make the conductive material powder spin at 50-200rpm driven by the Coriolis force, ensuring that silver atoms are uniformly deposited along the surface normal of the conductive material powder.

[0029] The breakthrough of the present invention is:

[0030] Compared to conventional techniques that disperse powders through jets to suspend them for coating, stir the powders slightly through vibration, or disperse them through pure vibration, the present invention uses a vibration-magnetic field to drive the powders to spin, effectively avoiding insufficient film thickness in the coating area due to uneven sputtering during the stirring process. Furthermore, compared to methods that vibrate over a large area (such as an entire conveyor belt), the present invention only requires vibrating the tooling tray, making it lighter, more efficient, and more portable. It also effectively avoids vacuum leaks caused by large-scale vibration.

[0031] Therefore, the present invention realizes for the first time the 10kg level conductive material powder in 10 -5 Pa vacuum stable suspension, the conductive material powder spatial distribution density reaches 10 4 -10 5 Particles / cm 3 , coverage rate > 95%, D50 particle size distribution coefficient of variation (CV value) < 5%, which is more than 3 times higher than the traditional vibration method; through the multi-parameter coordinated control of magnetic field-flow field-acoustic field, the thickness unevenness is compressed from ± 20% to ± 3%, the target material utilization rate exceeds 45%, and the energy consumption per unit production capacity is reduced to below 8kWh / kg.

[0032] The technical solution of the present invention successfully overcomes three major industrialization obstacles:

[0033] First, to address the problem of conductive material powder agglomeration, the synergistic effect of ultrasonic cavitation and electromagnetic levitation reduces the agglomeration index (Agglomeration Index) from 1.5 to below 0.3 (ISO 14887 standard), meeting the monodisperse requirements of HJT silver paste for 0.8μm copper core powder.

[0034] Secondly, through multi-target coordinated sputtering and dynamic magnetic field compensation, the plasma density non-uniformity is improved from ±30% to ±5%, so that the silver layer thickness can be precisely controlled within 50-200nm (adjusted according to resistivity requirements), the porosity is less than 1%, and the interface bonding strength is increased to 8N / mm 2 ;

[0035] Third, a modular chamber design is adopted, with each independent sputtering unit processing 10kg of conductive material powder. Through parallel expansion, a single furnace production capacity of 50kg is achieved, and the thickness fluctuation is kept within ±3%, providing a technical foundation for the construction of a thousand-ton production line. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of a single magnetron sputtering furnace structure of a magnetron sputtering device for silver-coated conductive material powder based on an ultrasonic-electromagnetic levitation composite dispersion system according to an embodiment of the present invention.

[0037] Description of reference numerals:

[0038] 1. Magnetron sputtering furnace; 2. Tooling tray; 3. Ultrasonic vibrator array; 4. Dynamic magnetic field control module; 5. Planar rectangular cathode. DETAILED DESCRIPTION

[0039] The present invention aims to solve the core pain points of conductive material powder agglomeration, uneven dispersion and low target material utilization in the vacuum magnetron sputtering dry coating process, and proposes an innovative technical solution. Specifically, with the tooling disk as the core carrier, an ultrasonic-electromagnetic suspension composite dispersion system is constructed, which covers three dimensions: precision structural design, multi-physical field coupling and adaptability to large-scale production.

[0040] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0041] A coordinate system XYZ is provided in the drawings of the embodiments of the present invention, wherein the positive direction of the X axis represents the left, the negative direction of the X axis represents the right, the positive direction of the Y axis represents the front, the negative direction of the Y axis represents the back, the positive direction of the Z axis represents the top, and the negative direction of the Z axis represents the bottom.

[0042] The embodiment of the present invention provides a device for magnetron sputtering silver-coated conductive material powder based on an ultrasonic-electromagnetic suspension composite dispersion system, combined with Figure 1 As shown, it includes a magnetron sputtering furnace body 1 and a tooling plate 2, an ultrasonic vibrator array 3, a dynamic magnetic field control module 4 and a planar rectangular cathode 5 installed in the magnetron sputtering furnace body 1.

[0043] The structure of the magnetron sputtering furnace body 1 can be designed as needed, including but not limited to hollow rectangular columns, cylinders, cones, and combinations thereof. Preferably, the structure has a radial length ≥ 1000 mm and a height ≥ 400 mm. This embodiment takes a structure with a rectangular column as the main body and a cone at the top as an example. The radial length (length and width) of the cavity is 1000 mm and the height is 800 mm. It is equipped with an independent vacuum lock (maximum vacuum degree 5×10 -5 Pa, pumping time ≤ 30 min), thereby the magnetron sputtering furnace body 1 is in a relatively vacuum state, providing a good reaction space for magnetron sputtering and reducing the oxidation of the planar rectangular cathode and the corresponding metal powder.

[0044] Optionally, the tooling disk 2 is fixedly installed in the middle of the magnetron sputtering furnace body 1 as a supporting base for the metal powder. The tooling disk 2 is made of reaction-bonded silicon carbide (RB-SiC) material, and its surface has through holes with a gradient aperture structure. Among them, the aperture of the through holes in the central area is smaller than the aperture in the edge area, and the pore density of the through holes in the central area is greater than the pore density in the edge area. This is based on the fact that most of the metal powder is dispersed in the central area of the tooling disk 2. The through holes with small aperture and high pore density can effectively reduce the leakage of conductive material powder, and at the same time help more air flow to flow out from the central area of the tooling disk 2, which has a stirring driving force on the metal powder, thereby promoting the silver layer to accurately coat the metal powder.

[0045] In this embodiment, the aperture of the through holes in the center area of the tooling plate 2 is preferably 8-15 μm, and the hole density is 1100-1400 holes / cm 2 The through holes in the edge area have a pore size of 40-60 μm and a pore density of 150-300 pores / cm 2 At this time, the aperture size (8-60μm) of the through-holes on the tooling plate 2 is optimized to 1 / 5-1 / 10 of the D50 of the conductive material powder, allowing airflow to penetrate and generate lift while effectively reducing the loss of the conductive material powder. Due to the relatively small aperture of the above-mentioned through-holes, in order to ensure the precise processing of the through-holes, this embodiment uses laser etching to achieve a gradient distribution of the through-holes. However, laser etching has certain limitations on the thickness of the tooling plate 2, with a thickness of 25-35mm being preferred. This tooling plate 2 can both meet the requirements of laser etching through-hole processing and provide good support for the metal powder.

[0046] In order to match the size of the magnetron sputtering furnace body 1, this embodiment uses a tooling plate 2 with a diameter of 650 mm and a plate thickness of 30 mm. The tooling plate 2 is divided into a central area and an edge area at a position of 450 mm in diameter. The surface of the tooling plate is laser etched to form a gradient aperture structure (the aperture of the central area is 10 μm and the edge area is 50 μm). The pore distribution density is optimized by finite element simulation (the pore density in the central area is 1200 holes / cm 2 、Edge area hole density 200 holes / cm 2 ), in order to ensure the air flow penetration rate and the conductive material powder load (≤15kg / m 2 ) dynamic balance, with a leakage rate of <0.1%. The surface of the tooling disk 2 is also coated with a silicon nitride protective layer, which can improve the strength and wear resistance of the tooling disk 2 and effectively prevent the ceramic components on the tooling disk 2 from falling off and mixing with the magnetron sputtering silver-coated conductive material powder.

[0047] The ultrasonic vibrator array 3 is fixedly distributed on the bottom of the tooling plate 2. The number of its distribution can be adjusted according to the design requirements. Each group of vibrators is composed of multiple piezoelectric ceramic units. This embodiment specifically takes 12 groups of high-frequency ultrasonic vibrator arrays 3 as an example. They are embedded in the bottom of the tooling plate 2 in a hexagonal close-packed manner. Each group of vibrators is composed of 6 piezoelectric ceramic units (PZT-8 material, diameter 20mm), which helps to compactly connect the various structures and improve space utilization. The operating frequency of the ultrasonic vibrator array 3 is controlled at 20-100kHz, and the power density is 1-5W / cm 2 The above-mentioned multiple piezoelectric ceramic units are helpful to design ultrasound with appropriate power density according to regional configuration (central area, transition area and edge area).

[0048] In order to achieve more precise suspension of metal powder, this embodiment divides the operating frequency into three adjustable levels (low frequency 20kHz, medium frequency 60kHz, high frequency 100kHz), and the power density is configured according to regional differences (for example, 5W / cm in the center area). 2 , transition zone 3W / cm 2 , edge area 1W / cm 2 The power density can be adjusted appropriately as needed). The microjets (peak velocity 160m / s) generated by the cavitation effect are used to directionally deagglomerate the conductive material powder agglomerates. Simultaneously, the local high temperature (instantaneously reaching 6000K) caused by the collapse of the cavitation bubbles is used to remove the oxide layer on the core surface of the metal powder (the oxygen content is reduced from 800ppm to below 50ppm).

[0049] The dynamic magnetic field control module 4 is located on the periphery of the tooling disk 2 and is composed of a Helmholtz coil. Generate a rotating magnetic field (0.1-0.5T) to make the conductive material powder spin at 80-200rpm driven by the Coriolis force, ensuring that the silver atoms are uniformly deposited along the normal direction of the conductive material powder surface. In order to ensure the stability of the upper and lower magnetic fields of the tooling disk 2, the Helmholtz coils are arranged in two layers, with an interlayer spacing of 140-160mm. Among them, the number of Helmholtz coils can also be increased or decreased as needed. This embodiment is specifically composed of 24 groups of Helmholtz coils (coil inner diameter 700mm, wire diameter 5mm, number of turns 120), which are divided into two layers (spacing 150mm) to form an axially symmetric magnetic field. The coil is passed through a three-phase alternating current (frequency 0.1-10Hz adjustable, current peak 200A), and the phase difference is controlled A rotating magnetic field is generated, driving the spin of the conductive material powder and generating the Coriolis effect, causing silver atoms to deposit along the surface of the conductive material powder (with an incident angle deviation of less than 5°). The magnetic field module works in conjunction with the top planar cathode to deflect secondary electrons in the plasma using the Lorentz force, increasing target utilization from 25% for traditional planar targets to 52%.

[0050] The planar rectangular cathode 5 is fixedly arranged on the top of the magnetron sputtering furnace body 1 and is located 10-50 mm above the tooling disk 2. The target material is silver with a purity of ≥99.995%. The target surface inclination angle (the inclination angle relative to the horizontal plane) is 0-15°, and the center of the target surface is 120-320 mm away from the axis of the tooling disk 2. The number of planar rectangular cathodes 5 can be adjusted according to the amount of target material used. In this embodiment, four planar rectangular cathodes 5 (size 850 mm × 120 mm) are arranged in a ring with an inclination angle of 15° (the center of the target surface is 320 mm away from the axis of the tooling disk 2). The sputtering power density is optimized according to the plasma distribution (6-8 W / cm2 at the center target). 2 , Edge target 3-10W / cm 2 ), a closed magnetic field is generated by a magnetron (the magnetic flux density on the target surface is 600-800Gs), which confines the electrons near the target surface to increase the ionization rate (Ar + Density ≥5×10 13 cm -3 ).

[0051] Furthermore, the magnetron sputtering device for silver-coated conductive material powder in this embodiment also integrates a dual-circulation thermal management mechanism: first, a microchannel liquid nitrogen cooling interlayer (channel diameter 2 mm, flow rate 5-8 L / min) is set on the inner wall of the magnetron sputtering furnace body 1 to control the temperature of the conductive material powder below 120°C (180°C lower than when there is no cooling), thereby suppressing the particle size growth caused by metal core recrystallization (D50 fluctuation <0.5%); second, a thermoelectric cooling plate (TEC1-12706 model, cooling power 60W) is embedded in the bottom of the tooling tray 2, combined with infrared temperature measurement feedback (accuracy ±1°C), to achieve dynamic temperature control of local hotspots (temperature difference <3°C).

[0052] In order to break through the bottleneck of large-scale production, the present invention also adopts a chamber-type modular design, that is, multiple magnetron sputtering furnace bodies 1 are set up. Each magnetron sputtering furnace body 1 cooperates with the above-mentioned tooling plate 2, ultrasonic vibrator array 3, flat rectangular cathode 5 and dynamic magnetic field control module 4 to form an independent module. Each module processes a powder volume ≥12kg (stacking thickness 3mm). By connecting 6 cavities in parallel, a single batch production capacity of ≥72kg is achieved, which helps to control the thickness non-uniformity within ±3% (measured data: the silver layer thickness in the center area is 185nm±4nm, and the edge area is 180nm±6nm). After 120 hours of continuous operation test, the system stability reached 99.8%, the powder breakage rate was <0.05%, and the target consumption rate was reduced to 0.8g / kWh (the traditional process is 2.5g / kWh).

[0053] In order to further verify the operability of the above-mentioned magnetron sputtering silver-coated conductive material powder device based on the ultrasonic-electromagnetic suspension composite dispersion system, the following is a detailed description combined with an application example. Application Example 1

[0054] This application example discloses a method for preparing silver-coated copper powder for photovoltaic silver paste, the preparation method comprising the following steps:

[0055] Step 1: Powder pretreatment

[0056] Spherical copper powder with a D50 of 0.8 μm (purity ≥ 99.9%) was selected, cleaned with hydrofluoric acid to remove the surface oxide layer (oxygen content < 50 ppm), and then dried and deposited in the center of a porous ceramic tooling plate 2 (diameter 650 mm) to a thickness of 3 mm (total loading capacity 12 kg).

[0057] Step 2: System parameter settings

[0058] Ultrasonic vibrator array 3: activate the four groups of vibrators in the central area (frequency 100kHz, power 5W / cm 2 ), eight groups of oscillators in the edge area (frequency 60kHz, power 1W / cm 2 ), cavitation microjet velocity 160m / s;

[0059] Dynamic magnetic field control module 4: three-phase AC power (frequency 2Hz, current 200A, phase difference ), generating a 0.3T rotating magnetic field to drive the copper powder to spin at 120 rpm;

[0060] Planar rectangular cathode 5: Open four sets of cathode targets (power density: central target 8W / cm 2 , edge target 10W / cm 2 ), argon working pressure 0.3Pa, substrate bias -50V;

[0061] Step 3: Dynamic Deposition and Thermal Management

[0062] During the sputtering process, the microchannel liquid nitrogen cooling system maintained a flow rate of 5L / min and the surface temperature of the tooling plate 2 was ≤115°C. The thermoelectric cooling chip compensated for local hot spots in real time (temperature difference <3°C).

[0063] The deposition time was 120 min, the silver layer thickness was 180 ± 5 nm (weight gain 15%), and the porosity was 0.7%;

[0064] Step 4: Performance Testing

[0065] The resistivity of silver-coated copper powder is 3.1μΩ·cm. When added to photovoltaic silver paste (mass ratio 48%), HJT cell fine grid (line width 28μm±1.2μm) is printed, the square resistance is 3.2μΩ·cm, the photoelectric conversion efficiency is 26.45%, and the single-chip silver consumption is 48mg.

[0066] Application Example 2

[0067] This application example discloses a method for preparing silver-coated nickel powder for MLCC electrodes, the preparation method comprising the following steps:

[0068] Step 1: Powder pretreatment

[0069] Nickel powder with D50=2.5μm flakes (aspect ratio 3:1) was selected and activated by plasma (power 500W, Ar / H2=4:1) to enhance the surface activity. The loading amount was 10kg (bulk density 2.5g / cm 3 );

[0070] Step 2: System parameter settings

[0071] Ultrasonic vibrator array 3: 60kHz intermediate frequency (power 3W / cm2) is enabled in the entire area 2 ) to avoid damage to the flaky powder structure;

[0072] Dynamic magnetic field control module 4: lower the magnetic field intensity to 0.2T (frequency 5Hz, current 150A), and spin the powder at 80rpm to ensure normal deposition on the flake surface;

[0073] Planar rectangular cathode 5: Edge target power increased to 10W / cm 2 (Center target 6W / cm 2 ), substrate bias -30 V, argon pressure 0.5 Pa;

[0074] Step 3: Gradient deposition and interface strengthening

[0075] Deposition was performed in two stages: the first 60 minutes were at low power (6 W / cm 2 ) to form a 50nm silver seed layer; after 60 minutes of high power (10W / cm 2 ) thickened to 100 nm, and the thickness of the interface transition zone was <5 nm;

[0076] Liquid nitrogen system temperature control ≤ 100 ℃, inhibit nickel diffusion (interface resistance ≤ 0.8mΩ·cm 2 );

[0077] Step 4: Performance Testing

[0078] Silver-coated nickel powder is sintered at 950°C (N2 / H2 atmosphere), and the silver layer is continuous without cracks. It is suitable for the inner electrode of 01005 type MLCC (line width 3μm±0.3μm), with a capacity deviation of ±2.8% and a resistance drift of <5% during high-temperature storage life (150°C / 1000h).

[0079] In order to intuitively understand the technical effects of Application Example 1 and Application Example 2, the present invention summarizes the above technical effects, please refer to Table 1 below for details.

[0080] Table 1 Comparison of technical effects of application examples 1 and 2

[0081] index Application Example 1 (Silver-coated copper powder) Application Example 2 (Silver-coated Nickel Powder) Powder type 0.8μm spherical copper core 2.5μm flake nickel core Silver layer thickness 180±5nm 100nm (gradient deposition) Resistivity 3.1μΩ·cm <![CDATA[Interface resistance 0.8 mΩ·cm 2 > Add Scale 48％ 35% (MLCC electrode) Terminal application performance HJT cell efficiency loss of 0.25% MLCC capacity deviation ±2.8% production costs 52% reduction 40% reduction

[0082] As can be seen from Table 1 above, the magnetron sputtering silver-coated conductive material powder device based on the ultrasonic-electromagnetic suspension composite dispersion system of the present invention has achieved breakthrough applications in the field of photovoltaic silver paste and in the field of MLCC internal electrodes.

[0083] Application Example 1 uses D50=0.8μm spherical copper core powder (silver layer weight gain 15%), and the prepared silver-coated copper powder addition ratio reaches 48%, the slurry square resistance is 3.1μΩ·cm (only 24% higher than the pure silver paste 2.5μΩ·cm), suitable for HJT battery 12BB fine grid printing (line width 28μm±1.2μm), the photoelectric conversion efficiency loss is 0.25% (26.5%→26.45%), and the single-piece silver consumption is reduced to 48mg (cost reduction 52%). In terms of economic benefits, based on an annual production line of 1,000 tons of silver-coated copper powder, the use of silver can be reduced by 500 tons / year. Calculated at a silver price of 6,000 yuan / kg, direct material costs can be saved by 3 billion yuan. In terms of social benefits, cyanide pollution can be completely eliminated, toxic wastewater emissions can be reduced by 1.2 million tons annually, and the photovoltaic LCOE can be reduced by 0.02 yuan / kWh. A single production line can support the production of 10GWHJT modules annually and reduce carbon dioxide emissions by 1.8 million tons.

[0084] Application Example 2: Using D50 = 2.5 μm nickel core powder (silver layer thickness 80 nm) sintered at 950 ° C, the interface resistance is ≤ 0.8 mΩ·cm 2 , suitable for 3μm line width printing of 01005 type components, and the capacity deviation is compressed from ±10% to ±3%.

[0085] It can be seen that the structural innovation and process breakthrough of the present invention provide the electronic materials industry with a complete technical path from laboratory to industrialization.

[0086] In order to facilitate further comparison of the differences between the present invention and the traditional process, the technical indicators of the present invention are quantified, as shown in Table 2 below.

[0087] Table 2 Quantitative technical indicators of traditional process and the present invention

[0088]

[0089] Thus, the above-mentioned Application Examples 1 and 2 can fully demonstrate the versatility and engineering value of the magnetron sputtering silver-coated conductive material powder device based on the ultrasonic-electromagnetic levitation composite dispersion system of the present invention in the field of electronic materials, and provide a quantifiable and replicable technical path for the reduction of precious metals, including but not limited to the following advantages:

[0090] 1. Strong process adaptability. Application Example 1 mainly optimizes the high silver layer thickness and low resistivity required for photovoltaic silver paste, while Application Example 2 focuses on thin-layer interface control and high-temperature reliability of MLCC electrodes;

[0091] 2. Parameters can be adjusted according to different materials by adjusting the working frequency (20-100kHz) and power density (1-5W / cm 2 ), the intensity of the dynamic magnetic field (0.1-0.5T), the target inclination angle (0-15°), and the sputtering power (center target 6-8W / cm 2 , Edge target 3-10W / cm 2 ) to adapt to different powder forms (spherical / flake) and coating requirements;

[0092] 3. Able to withstand industrial verification. The data of Application Example 1 is based on 10 consecutive furnace tests with 72kg / batch, with a thickness fluctuation standard deviation σ=2.1nm; Application Example 2 verifies long-term stability through a 1000-hour aging test.

[0093] In the description of the present disclosure, it should be understood that the terms "center", "edge", "thickness", "up", "down", "top", "bottom", "inside", "outside", "axial", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present disclosure and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present disclosure.

[0094] Equivalently, the components included in the "device," "module," and "mechanism" of the present disclosure can also be flexibly combined. They can be modularly produced according to actual conditions and assembled as a separate module; or they can be assembled separately to form a module in the present device. The division of the above components in the present disclosure is only one embodiment, for ease of reading, and not to limit the scope of protection of the present disclosure. As long as the above components are included and have the same functions, they should be understood as equivalent technical solutions of the present disclosure.

[0095] In this disclosure, unless otherwise expressly specified or limited, terms such as "disposed," "distributed," "arranged," and "fixed" should be understood in a broad sense. For example, they may refer to fixed or detachable connections, or integration; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two elements or interaction between two elements, unless otherwise expressly limited. Those skilled in the art will understand the specific meanings of the above terms in this disclosure based on specific circumstances.

[0096] In this disclosure, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0097] It should be noted that when an element is referred to as being “fixed to,” “disposed on,” “fixed on,” or “installed on” another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be “connected to another element,” it may be directly connected to the other element or there may be an intermediate element at the same time. Furthermore, when an element is considered to be “fixedly connected” to another element, the two may be fixed in a detachable connection manner or in a non-detachable connection manner, such as socketing, snap-fitting, integral molding, welding, etc., which can be achieved in traditional technologies and will not be repeated here.

[0098] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0099] The above embodiments merely illustrate several implementations of the present disclosure, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the inventive concept of the present disclosure, and all such variations and improvements fall within the scope of protection of the present disclosure.

Claims

1. A magnetron sputtering device for silver-coated conductive material powder based on an ultrasonic-electromagnetic suspension composite dispersion system, characterized in that: include: A magnetron sputtering furnace (1) provides a vacuum environment; A tooling disk (2) is arranged in the magnetron sputtering furnace body (1) to carry conductive material powder, and has through holes with a gradient aperture structure on its surface, wherein the aperture of the through holes in the central region is smaller than the aperture in the edge region, and the pore density of the through holes in the central region is greater than the pore density in the edge region, and the aperture of the through holes in the central region of the tooling disk (2) is 8-15 μm and the pore density is 1100-1400 holes / cm 2 The through holes in the edge area have a pore size of 40-60 μm and a pore density of 150-300 pores / cm 2 ; The ultrasonic vibrator array (3) is distributed on the bottom of the tooling plate (2), with an operating frequency of 20-100kHz and a power density of 1-5W / cm 2 ; A dynamic magnetic field control module (4) is arranged on the periphery of the tooling disk (2), and is composed of a Helmholtz coil, which generates a 0.1-0.5T rotating magnetic field by passing a three-phase alternating current, and drives the conductive material powder to spin at 80-200 rpm; A planar rectangular cathode (5) is arranged on the top of the magnetron sputtering furnace (1); the target material is silver with a purity of ≥99.995%, the target material inclination angle is 0-15°, and the distance between the center of the target surface and the axis of the tooling disk (2) is 120-320 mm.

2. The magnetron sputtering device for silver-coated conductive material powder according to claim 1, characterized in that: The tooling disc (2) has a disc body thickness of 25-35 mm, and the gradient distribution of the through holes is achieved by laser etching.

3. The magnetron sputtering device for silver-coated conductive material powder according to claim 1, characterized in that: The surface of the tooling plate (2) is coated with a silicon nitride protective layer, and the conductive material powder carrying capacity is ≤15kg / m 2 , the loss rate is <0.1%.

4. The magnetron sputtering device for silver-coated conductive material powder according to claim 1, characterized in that: The ultrasonic vibrator array (3) comprises multiple groups evenly distributed on the bottom of the tooling plate (2), and each group is composed of multiple piezoelectric ceramic units.

5. The magnetron sputtering device for silver-coated conductive material powder according to claim 1, characterized in that: The Helmholtz coils are arranged in two layers, with a layer spacing of 140-160 mm, and the phase difference of the three-phase current is controlled to be Δφ=120°.

6. The magnetron sputtering device for silver-coated conductive material powder according to claim 1, characterized in that: The sputtering power density of the planar rectangular cathode (5) is 6-8 W / cm2 for the central target. 2 , Edge target 3-10W / cm 2 .

7. The magnetron sputtering device for silver-coated conductive material powder according to claim 1, characterized in that: The inner wall of the magnetron sputtering furnace body (1) is provided with a microchannel liquid nitrogen cooling interlayer, and the bottom of the tooling plate (2) is provided with a thermoelectric cooling plate.

8. The device for magnetron sputtering silver-coated conductive material powder according to claim 1, characterized in that: The magnetron sputtering furnace body (1) is provided with a plurality of them.

9. Use of the magnetron sputtering silver-coated conductive material powder device based on the ultrasonic-electromagnetic levitation composite dispersion system according to any one of claims 1 to 8 in the preparation of silver-coated copper powder, silver-coated nickel powder, silver-coated aluminum powder, silver-coated graphite powder, silver-coated carbon nanotube powder, and silver-coated alloy powder.

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