Magnetron sputtering silver-coated conductive material powder device based on ultrasonic-electromagnetic suspension composite dispersion system and application of magnetron sputtering silver-coated conductive material powder device

Abstract

The invention relates to the technical field of magnetron sputtering, and particularly discloses a magnetron sputtering silver-coated conductive material powder device based on an ultrasonic-electromagnetic suspension composite dispersion system and application of the magnetron sputtering silver-coated conductive material powder device. In order to solve the technical problems of powder agglomeration, low target material utilization rate and poor large-scale production uniformity, a porous ceramic tool plate is used as a core carrier, and a high-frequency ultrasonic vibrator array (adjustable in 20-100kHz), a planar rectangular cathode (with an inclination angle of 0-15 degrees) and a Helmholtz coil (0.1-0.5 T rotating magnetic field) are integrated; non-contact dispersion of powder and precise coating of a silver layer are achieved through the cavitation effect, electromagnetic suspension and multi-target cooperative sputtering. The tool disc adopts a gradient aperture design, and is combined with liquid nitrogen micro-channel cooling and a modular sub-cavity structure, so that the powder dispersion uniformity (CV value lt; 5%), the silver layer porosity (llt; 1%), the target material utilization rate (52%) and the single-furnace productivity (72 kg / 8 h) are obviously optimized, and an efficient and environment-friendly industrialization solution is provided 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 silver-coated conductive material powder device based on an ultrasonic-electromagnetic suspension composite dispersion system and its application. Background Art

[0002] With the accelerating transformation of the global energy structure towards renewable energy, the market demand for electronic silver paste has exploded, leading to long-term high fluctuations in silver prices. Against this background, as a disruptive alternative material, silver-coated conductive material powder needs to reduce the silver content from 100% of traditional pure silver powder to less than 50% while maintaining electrical conductivity (resistivity ≤ 4 μΩ·cm), adhesion (≥ 5 N / mm 2 ), and printing suitability (line width accuracy ± 5 μm), which poses unprecedented technical requirements for the coating process.

[0003] Although traditional wet coating techniques (electroless plating, electroplating, etc.) have achieved small-scale production of silver-coated conductive material powder, their inherent defects have become increasingly prominent in the industrialization process. 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 one ton of powder requires 5 - 8 tons of cyanide-containing wastewater, and the treatment cost is as high as 3000 yuan / ton. Moreover, the silver layer has problems such as high porosity (5 - 8%) caused by dendritic growth and insufficient interfacial bonding strength (≤ 3 N / mm 2 ). Although the electroplating method can improve the compactness of the silver layer (porosity 3 - 5%) through a pulsed power supply, limited by the Faraday efficiency (about 85%) and edge effect, it is difficult to meet the printing requirements of MLCC electrode paste for precision circuits below 3 μm in terms of the coating uniformity (CV value > 25%) of copper core powder with a particle size < 5 μm. More severely, the thickness control accuracy of the silver layer in the wet process is limited to the level of ± 50 nm. To achieve a balance between resistivity and cost, the silver layer ratio needs to be maintained at 15 - 20%, and it is difficult to break through the technical ceiling of the 30% addition ratio.

[0004] In contrast, among the physical vapor deposition (PVD) technology routes, the magnetron sputtering method is recognized by the international materials science community as the ultimate solution for the preparation of next-generation silver-coated copper powder due to its core advantages such as atomic-level deposition accuracy (thickness deviation ±5 nm), no chemical pollution, and wide process adaptability (compatible with various substrates such as copper, nickel, and ceramics). However, there are three essential challenges for the magnetron sputtering technology to move from the laboratory to large-scale production: First, under vacuum conditions, the powder is affected by van der Waals forces (10 - 100 nN / particle) and electrostatic forces (>1 μN / particle), resulting in uncontrollable agglomeration, leading to partial uncovered coating (coverage rate < 80%) and thickness fluctuation > ±20%; Second, the shielding effect of the three-dimensional stacked powder on the plasma causes the target utilization rate to be only 10 - 15% (the theoretical utilization rate of the planar target is about 30%), and 30 - 40% of the sputtering power is converted into the powder heat load, triggering local sintering (particle size growth > 50%); Third, during the equipment scaling-up process, the strong non-linear characteristics of the flow field and plasma distribution in the magnetron sputtering furnace body result in an exponential decay of the deposition uniformity as the size of the magnetron sputtering furnace body increases (the edge rate of a 1 m diameter magnetron sputtering furnace body drops by 40% compared to the center), directly restricting the single-furnace production capacity from breaking through the 10 kg level.

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

[0006] The first-generation mechanical vibration method realizes the fluidization of the powder by driving the vibration of the sieve mesh with an eccentric motor. However, in a vacuum environment, due to the lack of air damping, the amplitude gets out of control, and the dispersion efficiency drops by more than 50% compared to normal pressure. Moreover, high-frequency vibration (>100 Hz) causes plastic deformation of the copper core (the sphericity drops from 0.95 to 0.82).

[0007] The second-generation gas-assisted method uses a vortex gas generator to suspend the powder. Although non-contact dispersion is achieved, if this method is used in a vacuum environment, it is extremely easy to deteriorate the background vacuum degree (rising from 10 -5 Pa to 10 -3 Pa), the oxygen content of the sputtered silver layer increases to more than 2000 ppm, and at the same time, the energy consumption of the circulating air pump accounts for 40% of the total system power.

[0008] The third-generation field-induced suspension method includes electroless plating combined with electric field suspension and acoustic suspension. The former cancels the gravity of the powder through a high-voltage electrostatic field (>10 kV / cm) and can achieve sub-micron-level precise positioning, but it is only applicable to conductive powders with a resistivity < 10 4 Ω·cm and a loading density < 1 kg / m 3 ; the latter uses acoustic pressure nodes (>140 dB) to suspend the powder. Although it has full material compatibility, the energy conversion efficiency < 0.1%, the actual loading capacity < 100 g / furnace, and the powder rotation speed is difficult to exceed 20 rpm, resulting in significant anisotropy in the coating layer.

[0009] The above technical routes cannot meet the industrialization requirements of magnetron sputtering dry coating due to either principle defects or insufficient economy. Summary of the Invention

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

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

[0012] A magnetron sputtering furnace body that provides a vacuum environment;

[0013] A tooling plate disposed in the magnetron sputtering furnace body to carry the conductive material powder. The surface of the tooling plate has through-holes with a gradient pore structure, where the pore diameter in the central region is smaller than that in the edge region, and the pore density in the central region is greater than that in the edge region. The pore diameter of the through-holes in the central region of the tooling plate is 8 - 15 μm, and the pore density is 1100 - 1400 holes / cm 2 , and the pore diameter of the through-holes in the edge region is 40 - 60 μm, and the pore density is 150 - 300 holes / cm 2 ;

[0014] An ultrasonic oscillator array distributed at the bottom of the tooling plate, with a working frequency of 20 - 100 kHz and a power density of 1 - 5 W / cm 2 ;

[0015] A dynamic magnetic field regulation module provided at the periphery of the tooling plate, composed of Helmholtz coils, which generates a rotating magnetic field of 0.1 - 0.5 T by passing a three-phase alternating current to drive the conductive material powder to spin at 80 - 200 rpm;

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

[0017] Optionally, the thickness of the tooling plate is 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 loading capacity of the conductive material powder is ≤15 kg / m 2 , and the leakage rate is <0.1%.

[0019] Optionally, multiple groups of the ultrasonic oscillator arrays are uniformly distributed on the bottom of the tooling plate, and each group is composed of a plurality of piezoelectric ceramic units.

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

[0021] Optionally, the Helmholtz coils are arranged in upper and lower layers with a layer spacing of 140-160 mm, and the phase difference of the three-phase current is controlled

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

[0023] Optionally, there are multiple magnetron sputtering furnace bodies.

[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 suspension 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. This application includes combining the above device with the 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 obtained by the device and its downstream products, such as electronic silver paste materials such as photovoltaic silver paste and MLCC electrode paste. Among them, the "alloy powder" in the silver-coated alloy powder includes, but is not limited to, a mixture of multiple powders among the above 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 (8-60 μm) as the carrier substrate for the conductive material powder. The pore size is optimized according to 1 / 5-1 / 10 of the D50 of the conductive material powder, which not only allows air flow to penetrate to generate lift force but also avoids leakage of the conductive material powder;

[0027] 2. Integrate an ultrasonic oscillator array (frequency adjustable from 20-100 kHz, power density 1-5 W / cm 2 ) at the bottom of the tooling plate. Use the microjet (velocity > 100 m / s) generated by the cavitation effect to break up the agglomerates of the conductive material powder, and at the same time, the local high temperature and high pressure (5000 K, 1000 atm) during the collapse of the air bubbles can clean the surface oxides of the conductive material powder;

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

[0029] The breakthrough of the present invention lies in:

[0030] Compared with the prior art in which the powder is dispersed by jet to make the powder suspended for coating, the powder is slightly stirred and turned by vibration, and the dispersion is carried out by pure vibration, the present invention drives the powder to spin through vibration - magnetic field, and can effectively avoid insufficient film thickness caused by uneven sputtering in the coating area during the stirring process; in addition, compared with the method of large - range vibration (such as the entire conveyor belt), the method of only vibrating the tooling plate in the present invention has the characteristics of being lighter, more effective and portable, and can also effectively avoid vacuum leakage caused by large - range vibration;

[0031] Thus, the present invention realizes for the first time the stable suspension of 10 kg - level conductive material powder under a vacuum degree of 10 -5 Pa, the spatial distribution density of the conductive material powder reaches 10 4 -10 5 particles / cm 3 , the coverage rate > 95%, the coefficient of variation (CV value) of the D50 particle size distribution < 5%, which is more than 3 times higher than that of the traditional vibration method; through the multi - parameter collaborative regulation of the magnetic field - flow field - sound field, the thickness non - uniformity is compressed from ±20% to ±3%, the target utilization rate breaks through 45%, and the unit production energy consumption is reduced to less than 8 kWh / kg.

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

[0033] First, aiming at the problem of agglomeration of conductive material powder, the synergistic effect of ultrasonic cavitation and electromagnetic suspension reduces the agglomeration index from 1.5 to less than 0.3 (ISO 14887 standard), meeting the monodisperse requirements of HJT silver paste for 0.8 μm copper - core powder;

[0034] Second, through multi - target collaborative sputtering and dynamic magnetic field compensation, the non - uniformity of plasma density is improved from ±30% to ±5%, so that the thickness of the silver layer can be accurately controlled at 50 - 200 nm (adjusted according to resistivity requirements), the porosity < 1%, and the interfacial bonding strength is increased to 8 N / mm 2 ;

[0035] Third, a modular sub - chamber design is adopted, each independent sputtering unit processes 10 kg of conductive material powder, and the production capacity of a single furnace reaches 50 kg - level through parallel expansion, and the thickness fluctuation remains within ±3%, providing a technical basis for the construction of a thousand - ton - level production line. Description of the Drawings

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

[0037] Description of reference numerals:

[0038] 1. Magnetron sputtering furnace body; 2. Tooling plate; 3. Ultrasonic oscillator array; 4. Dynamic magnetic field regulation module; 5. Planar rectangular cathode. Detailed implementation manners

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

[0040] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention will be given with reference to the accompanying drawings.

[0041] In the accompanying drawings of the embodiments of the present invention, a coordinate system XYZ is set, where 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 rear, the positive direction of the Z-axis represents the upper, and the negative direction of the Z-axis represents the lower.

[0042] The embodiments of the present invention provide a magnetron sputtering silver-coated conductive material powder device based on an ultrasonic-electromagnetic suspension composite dispersion system, combined with Figure 1 as shown, including a magnetron sputtering furnace body 1 and a tooling plate 2, an ultrasonic oscillator array 3, a dynamic magnetic field regulation module 4 and a planar rectangular cathode 5 installed in the magnetron sputtering furnace body 1.

[0043] Among them, the structure of the magnetron sputtering furnace body 1 can be designed according to needs, including but not limited to a hollow rectangular column, cylinder, cone and their combinations. Preferably, it has a structure with a radial length ≥ 1000 mm and a height ≥ 400 mm. In this embodiment, a structure with a rectangular column as the main body and a cone at the top is taken as an example, and the radial length (length and width) in its cavity is 1000 mm and the height is 800 mm, and it is correspondingly equipped with an independent vacuum lock (ultimate vacuum degree 5×10 -5 Pa, pumping time ≤ 30 min). Thus, the inside of 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 plate 2 is fixedly installed in the middle of the magnetron sputtering furnace body 1 as a carrier substrate for metal powder. The tooling plate 2 is made of reaction-sintered silicon carbide (RB-SiC) material, and its surface has through-holes with a gradient pore size structure. Among them, the pore diameter of the through-holes in the central region is smaller than that in the edge region, and the pore density of the through-holes in the central region is greater than that in the edge region. This is because most of the metal powder is dispersed in the central region of the tooling plate 2. The through-holes with small pore diameters and high pore densities can effectively reduce the leakage of the conductive material powder, and at the same time help more air flow out from the central region of the tooling plate 2, providing a stirring driving force for the metal powder, thereby promoting the precise coating of the silver layer on the metal powder.

[0045] In this embodiment, it is preferred that the pore diameter of the through-holes in the central region of the tooling plate 2 is 8 - 15 μm and the pore density is 1100 - 1400 holes / cm 2 , and the pore diameter of the through-holes in the edge region is 40 - 60 μm and the pore density is 150 - 300 holes / cm 2 . At this time, the pore diameter size (8 - 60 μm) of the through-holes on the tooling plate 2 is optimized according to 1 / 5 - 1 / 10 of the D50 of the conductive material powder, which not only allows air flow to penetrate and generate lift, but also effectively reduces the leakage of the conductive material powder. Due to the relatively small pore diameter of the above through-holes, in order to ensure the precise processing of the through-holes, laser etching is used in this embodiment to achieve the gradient distribution of the through-holes. However, laser etching has certain limitations on the thickness of the tooling plate 2, and a thickness of 25 - 35 mm is preferred. This tooling plate 2 can not only meet the requirements of laser etching for processing through-holes, but also provide good support for metal powder.

[0046] To match the size of the above magnetron sputtering furnace body 1, a tooling plate 2 with a diameter of 650 mm and a plate thickness of 30 mm is selected in this embodiment. The tooling plate 2 uses the position with a diameter of 450 mm as the boundary to distinguish the central region and the edge region. Its surface is laser-etched to form a gradient pore size structure (pore diameter in the central region is 10 μm, pore diameter in the edge region is 50 μm), and the pore channel distribution density is optimized through finite element simulation (pore density in the central region is 1200 holes / cm 2 , pore density in the edge region is 200 holes / cm 2 ), so as to ensure the dynamic balance of the air flow penetration rate and the loading capacity of the conductive material powder (≤15 kg / m 2 ), and the leakage rate < 0.1%. The surface of the tooling plate 2 is also coated with a silicon nitride protective layer, which can improve the strength and wear resistance of the tooling plate 2, and effectively reduce the shedding of the ceramic components on the tooling plate 2 and their mixing into the magnetron sputtered silver-coated conductive material powder.

[0047] The ultrasonic oscillator array 3 is fixedly distributed at the bottom of the tooling plate 2, and the distribution quantity can be adjusted according to the design requirements. Each group of oscillators is composed of multiple piezoelectric ceramic units. In this embodiment, 12 groups of high-frequency ultrasonic oscillator arrays 3 are specifically shown as an example. They are embedded in the bottom of the tooling plate 2 in a hexagonal close-packed manner. Each group of oscillators is composed of 6 piezoelectric ceramic units (PZT-8 material, diameter 20 mm), which helps the compact connection of each structure and improves the space utilization rate. The working frequency of the ultrasonic oscillator array 3 is controlled at 20 - 100 kHz, and the power density is 1 - 5 W / cm 2 , and the above-mentioned multiple piezoelectric ceramic units help to configure the ultrasound with appropriate power density according to the regional configuration (central area, transition area, and edge area).

[0048] In order to more precisely suspend the metal powder, in this embodiment, the working frequency is divided into three adjustable gears (low frequency 20 kHz, medium frequency 60 kHz, high frequency 100 kHz), and the power density is configured differently according to the region (for example, 5 W / cm in the central area 2 , 3 W / cm in the transition area 2 , 1 W / cm in the edge area 2 , and this power density can be appropriately adjusted according to needs). The micro-jet (peak velocity 160 m / s) generated by the cavitation effect is used to directionally depolymerize the agglomeration of the conductive material powder, and at the same time, the local high temperature (instantly reaching 6000 K) of the cavitation bubble collapse is used to remove the oxide layer on the nuclear surface of the metal powder (the oxygen content is reduced from 800 ppm to less than 50 ppm).

[0049] The dynamic magnetic field regulation module 4 is arranged on the periphery of the tooling plate 2 and is composed of Helmholtz coils. By adjusting the current phase difference in real time , a rotating magnetic field (0.1 - 0.5 T) is generated, so that the conductive material powder spins at 80 - 200 rpm under the drive of the Coriolis force, ensuring the uniform deposition of silver atoms along the normal direction of the surface of the conductive material powder. In order to ensure the stability of the magnetic field on the upper and lower layers of the tooling plate 2, the Helmholtz coils are arranged in two layers, and the layer spacing is 140 - 160 mm. Among them, the number of Helmholtz coils can also be increased or decreased according to needs. In this embodiment, it is specifically composed of 24 groups of Helmholtz coils (coil inner diameter 700 mm, wire diameter 5 mm, number of turns 120), and they are arranged in two layers (spacing 150 mm) to form an axisymmetric magnetic field. The coils are energized with three-phase alternating current (frequency adjustable from 0.1 - 10 Hz, current peak value 200 A), and a rotating magnetic field is generated through phase difference control , driving the conductive material powder to spin and generating the Coriolis effect, so that silver atoms are deposited along the normal direction of the surface of the conductive material powder (the incident angle deviation < 5°). The magnetic field module works in cooperation with the top planar cathode, using the Lorentz force to deflect the secondary electrons in the plasma, and increasing the target utilization rate from 25% of the traditional planar target to 52%.

[0050] The planar rectangular cathode 5 is fixedly arranged at the top of the magnetron sputtering furnace body 1 and is located 10 - 50 mm above the tooling plate 2. The target material is silver with a purity of ≥99.995%, the inclination angle of the target surface (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 plate 2. The number of the arranged planar rectangular cathodes 5 can be adjusted according to the target material consumption. In this embodiment, four planar rectangular cathodes 5 (with dimensions of 850 mm × 120 mm) are set, and they are arranged in a circular pattern with an inclination angle of 15° (the center of the target surface is 320 mm away from the axis of the tooling plate 2), and the sputtering power density is optimized according to the plasma distribution (the central target is 6 - 8 W / cm 2 , and the edge target is 3 - 10 W / cm 2 ). A closed magnetic field (the magnetic flux density on the target surface is 600 - 800 Gs) is generated by the magnetron to confine electrons near the target surface to improve the ionization rate (Ar + density ≥5 × 10 13 cm -3 ).

[0051] Furthermore, the magnetron sputtering silver-coated conductive material powder device of this embodiment also integrates a double-cycle thermal management mechanism: one is to set a micro-channel liquid nitrogen cooling interlayer (the channel diameter is 2 mm, and the flow rate is 5 - 8 L / min) on the inner wall of the magnetron sputtering furnace body 1 to control the temperature of the conductive material powder below 120°C (reducing by 180°C compared with no cooling), and inhibit the particle size growth caused by the recrystallization of metal nuclei (the D50 fluctuation <0.5%); the other is to embed a thermoelectric cooler (TEC1-12706 type, with a refrigeration power of 60 W) at the bottom of the tooling plate 2, and combine with infrared temperature measurement feedback (accuracy ±1°C) to achieve dynamic temperature control of local hot spots (the temperature difference <3°C).

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

[0053] 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 detailed description is made in combination with application examples. Application Example 1

[0054] This application example discloses the preparation of silver-coated copper powder for photovoltaic silver paste, and its preparation method includes the following steps:

[0055] Step 1: Powder pretreatment

[0056] Select spherical copper powder with D50 = 0.8μm (purity ≥ 99.9%), remove the surface oxide layer (oxygen content < 50ppm) by hydrofluoric acid cleaning, and after drying, stack it in the central area of the porous ceramic tooling plate 2 (diameter 650mm) with a stacking thickness of 3mm (total loading amount 12kg);

[0057] Step 2: System parameter setting

[0058] Ultrasonic oscillator array 3: Activate four groups of oscillators in the central area (frequency 100kHz, power 5W / cm 2 ) and eight groups of oscillators in the edge area (frequency 60kHz, power 1W / cm 2 ), with a cavitation micro-jet velocity of 160m / s;

[0059] Dynamic magnetic field regulation module 4: Pass in three-phase alternating current (frequency 2Hz, current 200A, phase difference ), generate a 0.3T rotating magnetic field, and drive the copper powder to spin at 120rpm;

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

[0061] Step 3: Dynamic deposition and thermal management

[0062] During the sputtering process, the micro-channel liquid nitrogen cooling system maintains a flow rate of 5L / min, and the surface temperature of the tooling plate 2 ≤ 115°C; the thermoelectric cooler compensates for local hot spots in real time (temperature difference < 3°C);

[0063] Deposition time is 120 minutes, silver layer thickness is 180 ± 5nm (weight gain 15%), and porosity is 0.7%;

[0064] Step 4: Performance testing

[0065] The resistivity of the silver-coated copper powder is 3.1 μΩ·cm. Add it to the photovoltaic silver paste (mass ratio 48%), print the fine grid of the HJT battery (line width 28μm ± 1.2μm), the sheet resistance is 3.2 μΩ·cm, the photoelectric conversion efficiency is 26.45%, and the single-piece silver consumption is 48mg.

[0066] Application example 2

[0067] This application example discloses the preparation of silver-coated nickel powder for MLCC electrodes, and its preparation method includes the following steps:

[0068] Step 1: Powder pretreatment

[0069] Select flaky nickel powder with D50 = 2.5 μm (aspect ratio 3:1), activate it by plasma (power 500 W, Ar / H 2 = 4:1) to improve surface activity, and the loading amount is 10 kg (bulk density 2.5 g / cm 3 );

[0070] Step 2: System parameter setting

[0071] Ultrasonic oscillator array 3: Enable 60 kHz intermediate frequency (power 3 W / cm 2 ) in the whole area to avoid damage to the flaky powder structure;

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

[0073] Planar rectangular cathode 5: Increase the edge target power to 10 W / cm 2 (center target 6 W / cm 2 ), substrate bias -30 V, argon gas pressure 0.5 Pa;

[0074] Step 3: Gradient deposition and interface strengthening

[0075] Deposit in two stages: Low power (6 W / cm 2 ) for the first 60 minutes to form a 50 nm silver seed layer; High power (10 W / cm 2 ) for the next 60 minutes to thicken to 100 nm, and the thickness of the interface transition zone < 5 nm;

[0076] Liquid nitrogen system controls the temperature ≤ 100 °C to inhibit nickel diffusion (interface resistance ≤ 0.8 mΩ·cm 2 );

[0077] Step 4: Performance test

[0078] The silver-coated nickel powder is sintered at 950 °C (N 2 / H 2 atmosphere), the silver layer is continuous and crack-free, suitable for 01005 type MLCC inner electrodes (line width 3 μm ± 0.3 μm), the capacitance deviation is ±2.8%, and the resistance drift of the high-temperature storage life (150 °C / 1000 h) is < 5%.

[0079] To intuitively understand the technical effects of Application Example 1 and Application Example 2, the present invention summarizes the above technical effects, as shown in Table 1 below for details.

[0080] Table 1 Comparison table of technical effects of Application Example 1 and 2

[0081] Index Application Example 1 (Copper-coated Silver Powder) Application Example 2 (Nickel-coated Silver Powder) Powder Type 0.8μm Spherical Copper Core 2.5μm Flaky Nickel Core Silver Layer Thickness 180±5nm 100nm (Gradient Deposition) Resistivity 3.1μΩ·cm <![CDATA[Interface resistance 0.8 mΩ·cm 2 > Addition Ratio 48％ 35% (MLCC Electrode) Terminal Application Performance HJT Cell Efficiency Loss 0.25% MLCC Capacitance Deviation ±2.8% Production Cost Reduced by 52% Reduced by 40%

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

[0083] In Application Example 1, spherical copper core powder with D50 = 0.8 μm (15% increase in silver layer weight) was used. The addition ratio of the prepared silver-coated copper powder reached 48%. The sheet resistance of the paste was 3.1 μΩ·cm (only a 24% increase compared to 2.5 μΩ·cm of pure silver paste), which was suitable for 12BB fine grid printing of HJT cells (line width 28 μm ± 1.2 μm). The loss of photoelectric conversion efficiency was 0.25% (26.5% → 26.45%), and the silver consumption per single piece decreased to 48 mg (cost reduction of 52%). In terms of economic benefits, calculated based on a production line of 1000 tons of silver-coated copper powder per year, 500 tons of silver usage can be reduced per year. Calculated at a silver price of 6000 yuan / kg, the direct material cost can be saved by 3 billion yuan. At the social benefit level, cyanide pollution was completely eliminated, 1.2 million tons of toxic wastewater was reduced annually, the photovoltaic LCOE was reduced by 0.02 yuan / kWh, and each production line could support the production of 10 GW HJT modules on average annually, with a reduction of 1.8 million tons of carbon dioxide emissions.

[0084] In Application Example 2, nickel core powder with D50 = 2.5 μm (silver layer thickness 80 nm) was used. After sintering at 950 °C, the interface resistance ≤ 0.8 mΩ·cm 2 , which was suitable for printing with a 3 μm line width of 01005 type components, and the capacitance deviation was compressed from ±10% to ±3%.

[0085] Therefore, the structural innovation and process breakthrough of the present invention provide a complete technical path from laboratory to industrialization for the electronic materials industry.

[0086] To facilitate further comparison of the differences between the present invention and traditional processes, the technical indicators of the present invention are now quantified, as shown in Table 2 below.

[0087] Table 2 Quantified technical indicator table of traditional process and the present invention

[0088]

[0089] It can be seen that the above Application Example 1 and Application Example 2 can fully reflect the versatility and engineering value of a magnetron sputtering silver-coated conductive material powder device based on an ultrasonic-electromagnetic suspension composite dispersion system of the present invention in the field of electronic materials, and provide a quantifiable and replicable technical path for precious metal reduction, including but not limited to the following advantages:

[0090] 1. Stronger process adaptability. In Application Example 1, the high-silver layer thickness and low resistivity are mainly optimized for the requirements of photovoltaic silver paste. In Application Example 2, the focus is on the 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 - 100 kHz) and power density (1 - 5 W / cm 2 ) of the ultrasonic oscillator, the intensity of the dynamic magnetic field (0.1 - 0.5 T), the target tilt angle (0 - 15°), and the sputtering power (6 - 8 W / cm 2 for the central target and 3 - 10 W / cm 2 for the edge target), different powder morphologies (spherical / flaky) and coating requirements can be adapted.

[0092] 3. It can withstand industrial verification. The data of Application Example 1 is based on the continuous 10 - furnace test with 72 kg per batch, and the standard deviation of thickness fluctuation σ = 2.1 nm. Application Example 2 verifies the long-term stability through a 1000 - hour aging test.

[0093] In the description of the present disclosure, it should be understood that the orientation or positional relationship indicated by terms such as "center", "edge", "thickness", "upper", "lower", "top", "bottom", "inner", "outer", "axial", etc. is based on the orientation or positional relationship shown in the drawings. It is 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 construed as a limitation to the present disclosure.

[0094] Equivalently, the components included in the "device", "module", "mechanism", etc. of the present disclosure can also be flexibly combined. That is, they can be modularly produced according to the actual situation and assembled as an independent module; they can also be assembled separately to form a module in this device. The division of the above components in the present disclosure is only one embodiment for the convenience of reading, rather than a limitation to the protection scope of the present disclosure. As long as the above components are included and have the same function, they should be understood as equivalent technical solutions of the present disclosure.

[0095] In the present disclosure, unless otherwise clearly specified and limited, terms such as "set", "distributed", "arranged", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. It can be the internal communication of two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present disclosure can be understood according to the specific circumstances.

[0096] In this disclosure, unless otherwise clearly defined and limited, a first feature being "on" or "under" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact via an intermediate medium. Moreover, a first feature being "above", "over" and "on top of" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature has a higher horizontal height than the second feature. A first feature being "under", "below" and "beneath" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature has a lower horizontal height than the second feature.

[0097] It should be noted that when an element is referred to as being "fixed to", "disposed on", "secured to" or "mounted on" another element, it may be directly on the other element or there may also 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. Further, when an element is considered to be "fixedly connected" to another element, the two may be fixed in a detachable connection manner or a non-detachable connection manner, such as socket connection, snap connection, integral molding fixation, welding, etc., which can be achieved in the prior art and will not be elaborated here.

[0098] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, 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, it should be considered as the scope described in this specification.

[0099] The above embodiments only represent several implementation manners of the present disclosure, and the description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the inventive concept of the present disclosure, several modifications and improvements can still be made, and these all belong to the protection scope of the present disclosure.

Claims

1. A device for magnetron sputtering 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 plate (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 of the through holes in the edge region, and the pore density of the through holes in the central region is greater than the pore density of the through holes in the edge region, and the aperture of the through holes in the central region of the tooling plate (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), has an operating frequency of 20-100 kHz, and a power density of 1-5 W / 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, through which a three-phase alternating current is passed to generate a 0.1-0.5T rotating magnetic field, driving 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 center of the target surface is 120-320 mm away from the axis of the tooling disk (2).

2. The device for magnetron sputtering 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 device for magnetron sputtering 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 leakage rate is <0.1%.

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

5. The device for magnetron sputtering silver-coated conductive material powder according to claim 1, characterized in that: The Helmholtz coils are arranged in two layers, upper and lower, 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 device for magnetron sputtering 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 / cm for the central target. 2 , Edge target 3-10W / cm 2 .

7. The device for magnetron sputtering 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 sheet.

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. Application of the magnetron sputtering silver-coated conductive material powder device based on ultrasonic-electromagnetic suspension 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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