A copper-based pressure-sensitive chip electronic paste and a preparation method thereof

Abstract

The application relates to the technical field of electronic materials, and particularly discloses a copper-based pressure-sensitive chip electronic paste and a preparation method thereof. The paste is composed of flaky copper powder, nano copper powder, a glass bonding phase, an organic carrier and functional additives in a specific proportion. A multistage vacuum dynamic defoaming device is used in the preparation method. The device pre-defoams and releases large bubbles, and realizes full-range strong shearing and turning of the paste in a main defoaming cavity by using a dynamic stirring mechanism with revolution, rotation and reciprocating compound motion, and combines with ultrasonic cavitation effect to deeply break bubbles, so that the bubbles are efficiently and completely removed. Meanwhile, the device integrates an online viscosity monitoring and intelligent solvent vapor compensation system, and can realize real-time adjustment and stabilization of the paste rheological property. The application effectively solves the problems of incomplete bubble removal and performance fluctuation caused by solvent volatilization, and significantly improves the compactness, uniformity and production consistency of the paste product.

Description

Technical Field

[0001] This invention relates to the field of electronic materials technology, specifically to a copper-based varistor chip electronic paste and its preparation method. Background Technology

[0002] Copper-based electronic pastes are an important alternative to precious metal pastes, offering significant cost advantages in the manufacture of electronic components. However, copper-based pastes still face two major challenges in their preparation and application: first, copper powder is prone to oxidation, requiring complex process control to ensure its conductivity stability; second, in the preparation of pastes with high solid content and high viscosity, efficient degassing and stable rheological control directly determine the density and reliability of the final film.

[0003] Currently, Chinese patent application number CN201910317091.4 discloses a method for preparing a copper-based conductive paste, including the following steps: S1, dispersing a copper precursor, an inorganic chloride protective agent, and a reducing agent in a reaction solvent to obtain a reaction system; S2, reacting the reaction system at room temperature to 150°C for 10 min to 3 h to obtain a copper sol; S3, separating the copper sol into solid and liquid phases, washing, and drying to obtain dendritic copper; S4, uniformly dispersing the dendritic copper in a conductive paste solution to obtain a copper-based conductive paste. Through a specific reaction system and reaction conditions, a copper-based conductive paste based on dendritic copper was prepared, enabling large-scale production of dendritic copper. Furthermore, the size of this dendritic copper allows it to be sintered at temperatures far below the bulk melting point and to operate stably at higher temperatures for extended periods after sintering.

[0004] However, existing technologies typically employ simple static or single-stage vacuum processing for degassing during the preparation of electronic pastes. This approach suffers from problems such as low degassing efficiency, numerous dead zones, and difficulty in removing microbubbles for high-viscosity pastes. Furthermore, solvent evaporation during the degassing process can lead to rheological drift in the paste, which can negatively impact batch consistency and printing performance. Summary of the Invention

[0005] The purpose of this invention is to provide a copper-based varistor chip electronic paste and its preparation method to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] First aspect: The present invention provides a copper-based varistor chip electronic paste, which is composed of the following components by weight percentage:

[0008] Conductive phase: 50-70% flake copper powder, 5-15% nano copper powder, wherein the aspect ratio of the flake copper powder is 20:1 to 50:1 and the D50 is 3-8μm; the particle size of the nano copper powder is 50-200nm.

[0009] Glass binder phase: 5-12% lead borosilicate glass powder, with a softening point of 400-550℃;

[0010] Organic carrier: 15-30%, wherein the organic carrier is composed of solvent, resin and additives, wherein the solvent is a mixture of terpineol and diethylene glycol butyl ether acetate, the resin is ethyl cellulose, and the additives include leveling agents, thixotropic agents and coupling agents;

[0011] Functional additives: 0.5-3%, including at least one of whisker-like zinc oxide and nickel-coated graphene composite materials.

[0012] Secondly, the present invention also provides a method for preparing a copper-based varistor chip electronic paste, which includes the following steps:

[0013] S1. Preparation of organic carrier: The solvent, resin and additives are stirred and dissolved at 60-80℃ to form a uniform and transparent organic carrier, which is then cooled for later use.

[0014] S2. Premixing: The conductive phase, glass binder phase and organic carrier prepared in step S1 are initially mixed in a planetary mixer at 200-500 rpm for 10-30 minutes to obtain a premixed slurry.

[0015] S3. Fine rolling: The premixed slurry is rolled multiple times through a three-roll mill until the fineness reaches below 10μm;

[0016] S4. Vacuum dynamic degassing and viscosity adjustment: The finely rolled slurry is placed in a multi-stage vacuum dynamic degassing device for degassing treatment, and the slurry viscosity is monitored and adjusted online simultaneously.

[0017] S5. Filtration and aging: The deaerated slurry is filtered through a 300-500 mesh sieve and then aged at a constant temperature for 24-48 hours to obtain the finished slurry.

[0018] Preferably, the multi-stage vacuum dynamic degassing equipment used in step S4 of the above method includes:

[0019] A main degassing chamber has a first vacuum interface on its upper side and a discharge port at its bottom, and three support legs are locked around its bottom periphery.

[0020] A pretreatment chamber is connected to the upper sidewall of the main degassing chamber via a first controllable valve;

[0021] A recovery chamber is connected to the side of the main degassing chamber away from the pretreatment chamber via a second controllable valve, and a second vacuum interface is provided on the rear top side, with a cold trap inside.

[0022] A dynamic stirring mechanism and an ultrasonic-assisted degassing module are installed inside the main degassing chamber;

[0023] Both the first vacuum interface and the second vacuum interface are connected to an external vacuum generator through vacuum pipelines, and a solvent vapor compensation pipeline is provided through the rear side of the main degassing chamber.

[0024] Preferably, the pretreatment chamber is equipped with a preheating module and a low-speed pre-stirring device; the specific process of step S4 includes:

[0025] S4.1 Slurry pretreatment: The finely rolled slurry is first fed into the pretreatment chamber, preheated at 35-45℃ and stirred at low speed for 5-15 minutes to make the slurry temperature uniform and release some large air bubbles.

[0026] S4.2, Staged Degassing: Open the first controllable valve to introduce the preheated slurry into the main degassing chamber; start the dynamic stirring mechanism to shear and stir the slurry at a speed of 100-400 rpm; at the same time, the pressure in the main degassing chamber is reduced in two stages by an external vacuum generator: in the first stage, the pressure is reduced to -0.08 MPa to -0.09 MPa within 2-3 minutes and maintained for 3-5 minutes; in the second stage, the pressure is further reduced to -0.095 MPa to -0.1 MPa within 1-2 minutes.

[0027] S4.3, Ultrasonic-assisted debubbling: During the vacuum maintenance period in the second stage, the ultrasonic-assisted debubbling module is activated and operates in intermittent pulse mode with a working frequency of 25-40kHz and a pulse interval of 2-5 seconds.

[0028] S4.4 Microbubble Recovery and Viscosity Control: The gas carrying slurry droplets generated during the degassing process is drawn into the recovery chamber through the second controllable valve. The cold trap in the recovery chamber condenses and recovers the slurry components. At the same time, the viscosity of the slurry in the main degassing chamber is monitored in real time by an online viscometer and compared with the preset viscosity range. The control system automatically adjusts the temperature of the main degassing chamber or adds a trace amount of organic carrier vapor to the chamber to stabilize the viscosity.

[0029] Preferably, the dynamic stirring mechanism includes a partition plate fixed inside the upper part of the main degassing chamber. A first motor is locked and fixed to the rear side of the top of the partition plate. The bottom output end of the first motor is connected to the rear pulley of the pulley assembly. A fixed bevel gear is coaxially inserted inside the front pulley of the pulley assembly. The top of the fixed bevel gear is fixed to the partition plate. A first scraping structure and a second scraping structure are symmetrically arranged on both sides of the bottom of the fixed bevel gear. The first scraping structure and the second scraping structure have the same structure and size, and their tops are both fixed to the front pulley of the pulley assembly. A stirring rod is coaxially arranged at the bottom of the fixed bevel gear. The lower part of the fixed bevel gear is inserted and rotated on the top side of the protective cover, and the bottom end of the fixed bevel gear is connected to the top output end of the second motor. The second motor is fastened to the inside of the protective cover, and the protective cover is fastened to the bottom middle side of the main degassing chamber.

[0030] Preferably, a hollow groove is provided on the inner side of the partition, and the bottom of the front pulley of the pulley assembly rotates and contacts the inside of the hollow groove. A baffle is provided on the bottom of the partition near the pretreatment chamber.

[0031] Preferably, the first scraping structure includes a carrier whose top is fixed to the front pulley of the pulley assembly. A movable bevel gear is rotatably connected to the side of the carrier near the stirring rod, and a grooved rod is coaxially connected to the side of the movable bevel gear away from the stirring rod. The top side of the movable bevel gear meshes with a fixed bevel gear. The middle part and the side of the grooved rod away from the movable bevel gear are rotatably connected to the carrier. A displacement block is slidably connected to the bottom of the groove of the grooved rod to drive the displacement block to perform a lateral reciprocating movement. A slider is connected to the bottom end of the displacement block, and the slider is slidably connected to the inside of the carrier. A vertical rod is integrally formed at the bottom end of the slider. A scraper is fixedly connected to the side of the vertical rod near the inside of the main degassing chamber, and horizontal columns are arranged on the side of the vertical rod near the stirring rod.

[0032] Preferably, the scraper has strip-shaped openings arranged inside, and there are no fewer than five horizontal columns, which are staggered with the stirring part of the stirring rod.

[0033] Preferably, the ultrasound-assisted defoaming module includes multiple ultrasonic transducers arranged in a ring array in the lower part of the inner wall of the main defoaming cavity, and the emitting surface of the ultrasonic transducer is conformal to the curved surface of the inner wall of the main defoaming cavity, and the direction of the ultrasonic waves emitted by the transducer is directed towards the central axis of the main defoaming cavity.

[0034] Preferably, the main degassing chamber is equipped with an online viscometer, which, based on feedback from the online viscometer, injects a controllable amount of vapor formed by the solvent components of the organic carrier into the main degassing chamber through a solvent vapor compensation pipeline, so as to accurately compensate for the solvent volatilized during the degassing process and maintain the stability of the slurry composition.

[0035] Preferably, a differential pressure sensor is provided between the recovery chamber and the main degassing chamber. When the differential pressure exceeds a set threshold, the opening of the second controllable valve is automatically adjusted to prevent excessive slurry from being drawn out.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] This invention achieves step-by-step, deep removal of bubbles from slurry by constructing a multi-level physical space comprising a pretreatment chamber, a main degassing chamber, and a recovery chamber, combined with a staged, precisely controlled vacuum program. The optimized dynamic stirring mechanism generates strong shearing and efficient agitation of the high-viscosity slurry across the entire surface and in multiple directions through a composite mechanical action of revolution, rotation, and reciprocating motion, effectively eliminating degassing dead zones. Simultaneously, the ultrasonic cavitation effect directly breaks down residual microbubbles from the inside. Through mechanical perturbation across the entire surface and ultrasonic pinpoint bubble breaking, the degassing efficiency and thoroughness are fundamentally improved, ensuring the high density of the subsequent film formation.

[0038] This invention solves the problem of slurry composition fluctuations and performance degradation caused by solvent evaporation during vacuum degassing by integrating online real-time viscosity monitoring and an intelligent solvent vapor compensation system. It can automatically sense viscosity changes and accurately replenish lost solvent components, keeping the slurry rheology highly stable throughout the degassing process, ensuring the uniformity of slurry performance in a single batch, and significantly improving the reliability and consistency of product quality.

[0039] The pretreatment, main degassing, recovery and compensation modules of this invention have clear functions and work together efficiently. The safety control mechanism such as differential pressure sensing ensures operational reliability. This method and equipment integrate the originally dispersed and manual experience-dependent degassing and viscosity adjustment processes into a one-step automated continuous process. While greatly improving production efficiency and product quality, it reduces the dependence on operator experience and raw material loss, and realizes the large-scale and standardized production of high-performance electronic pastes. Attached Figure Description

[0040] Figure 1 This is a flowchart illustrating the preparation method of the copper-based varistor chip electronic paste of the present invention.

[0041] Figure 2 This is a schematic diagram of the structure of the multi-stage vacuum dynamic degassing device of the present invention;

[0042] Figure 3 This is a schematic diagram of the internal structure of the main degassing chamber and the pretreatment chamber of the present invention;

[0043] Figure 4 This is a schematic diagram of the dynamic stirring mechanism of the present invention;

[0044] Figure 5 This is a schematic diagram of the first scraping structure of the present invention;

[0045] Figure 6 For the present invention Figure 5 Enlarged view of the local structure at point A in the middle.

[0046] In the diagram: Main degassing chamber-1, pretreatment chamber-2, recovery chamber-3, dynamic stirring mechanism-4, ultrasonic-assisted degassing module-5, solvent vapor compensation pipeline-6, first vacuum interface-11, discharge port-12, support leg-13, first controllable valve-20, preheating module-21, low-speed pre-stirrer-22, second controllable valve-30, second vacuum interface-31, partition plate-41, first motor-42, pulley assembly-43, fixed bevel gear-44, first scraping structure-45, second scraping structure-46, stirring rod-47, protective cover-48, second motor-49, carrier-451, moving bevel gear-452, grooved rod-453, shifting block-454, slider-455, upright rod-456, scraper blade-457, horizontal column-458. Detailed Implementation

[0047] To further explain the technical solution of the present invention, a detailed description is provided below through specific embodiments.

[0048] Please see Figures 1-6 This invention provides a method for preparing copper-based varistor chip electronic paste, wherein the multi-stage vacuum dynamic degassing equipment used in this method includes:

[0049] A main degassing chamber 1 has a first vacuum interface 11 on its upper side and a discharge port 12 at its bottom, and three support legs 13 are locked around its bottom periphery.

[0050] A pretreatment chamber 2 is connected to the upper side wall of the main degassing chamber 1 through a first controllable valve 20. The pretreatment chamber 2 is equipped with a preheating module 21 and a low-speed pre-stirring device 22 to make the slurry temperature uniform and the viscosity moderately reduced. The low-speed pre-stirring device 22 can gently release large air bubbles in the slurry, reduce the load for subsequent deep degassing, and improve the overall efficiency.

[0051] A recovery chamber 3 is connected to the side of the main degassing chamber 1 away from the pretreatment chamber 2 via a second controllable valve 30, and a second vacuum interface 31 is provided on the rear top side. A cold trap is provided inside to collect and condense the solvent vapor and entrained slurry droplets extracted from the main degassing chamber 1. The cold trap can effectively condense and recover valuable components, reduce raw material waste and protect the downstream vacuum generating device.

[0052] The dynamic stirring mechanism 4 and the ultrasonic-assisted degassing module 5, which are located inside the main degassing chamber 1, provide forced mechanical shearing and tumbling through the dynamic stirring mechanism 4 to promote the migration and removal of bubbles; while the ultrasonic-assisted degassing module 5 uses the cavitation effect to break up micro bubbles from the inside. The two work together to achieve all-round degassing from macro to micro.

[0053] Both the first vacuum port 11 and the second vacuum port 31 are connected to an external vacuum generator through vacuum pipelines. A solvent vapor compensation pipeline 6 is provided through the rear side of the main degassing chamber 1 to accurately replenish the evaporated solvent.

[0054] A differential pressure sensor is installed between the recovery chamber 3 and the main degassing chamber 1. When the differential pressure exceeds a set threshold, the opening of the second controllable valve 30 is automatically adjusted to prevent excessive slurry suction, ensuring the safe and stable operation of the degassing process and the slurry recovery rate. The ultrasonic-assisted degassing module 5 includes multiple ultrasonic transducers arranged in a ring array in the lower middle part of the inner wall of the main degassing chamber 1. The emitting surface of the ultrasonic transducer is conformal to the curved surface of the inner wall of the main degassing chamber 1, and the direction of the ultrasonic waves emitted is directed towards the central axis of the main degassing chamber 1. The main degassing chamber 1 is equipped with an online viscometer, which, based on the feedback from the online viscometer, injects a controllable trace amount of vapor formed by the solvent components of the organic carrier into the main degassing chamber 1 through the solvent vapor compensation pipeline 6 to accurately compensate for the solvent volatilized during the degassing process and maintain the stability of the slurry composition.

[0055] The dynamic stirring mechanism 4 includes a partition 41 fixed inside the upper part of the main degassing chamber 1. A first motor 42 is locked and fixed to the rear side of the top of the partition 41. The bottom output end of the first motor 42 is connected to the rear pulley of the pulley group 43. A fixed bevel gear 44 is coaxially passed through the front pulley of the pulley group 43. The top of the fixed bevel gear 44 is fixed to the partition 41. A first scraping structure 45 and a second scraping structure 46 are symmetrically arranged on both sides of the bottom of the fixed bevel gear 44. The first scraping structure 45 and the second scraping structure 46 have the same structure and size, and their tops are both fixed to the front pulley of the pulley group 43. The two symmetrically arranged scraping structures can balance the force and obtain the power to revolve around the fixed bevel gear 44 through the fixed connection with the front pulley of the pulley group 43.

[0056] A stirring rod 47 is coaxially mounted on the bottom of the fixed bevel gear 44. The lower part of the fixed bevel gear 44 is inserted into and rotates on the top side of the protective cover 48. The bottom end of the fixed bevel gear 44 is connected to the top output end of the second motor 49. The second motor 49 is fastened to the inside of the protective cover 48, and the protective cover 48 is fastened to the bottom middle side of the main degassing chamber 1. The stirring rod 47 is driven by an independent second motor 49, which can achieve high-speed rotation and perform strong shearing on the central area of ​​the slurry. The protective cover 48 protects the lower transmission components from slurry intrusion.

[0057] The partition 41 has a hollow groove in the middle, and the bottom of the front pulley of the pulley assembly 43 rotates and contacts the inside of the hollow groove. The hollow groove provides stable rotation support and positioning for the front pulley of the pulley assembly 43, reducing shaking during operation. A baffle is provided on the bottom of the partition 41 near the pretreatment chamber 2, which can guide the flow of slurry flowing from the pretreatment chamber 2 and prevent the slurry from directly washing or splashing onto the transmission components on the upper part of the dynamic stirring mechanism 4.

[0058] The first scraping structure 45 includes a carrier 451 whose top is fixed to the front pulley of the pulley group 43. A movable bevel gear 452 is rotatably connected to the side of the carrier 451 near the stirring rod 47, and a grooved rod 453 is coaxially connected to the side of the movable bevel gear 452 away from the stirring rod 47. The top side of the movable bevel gear 452 meshes with a fixed bevel gear 44. When the carrier 451 drives the movable bevel gear 452 to revolve, the movable bevel gear 452 will simultaneously rotate due to meshing with the fixed bevel gear 44, thereby converting the kinetic energy of the revolution into the rotational power of the grooved rod 453.

[0059] The middle part of the groove rod 453 and the side away from the moving bevel gear 452 are rotatably connected to the carrier 451. The bottom of the groove of the groove rod 453 is slidably connected to the displacement block 454, which is used to drive the displacement block 454 to perform a lateral reciprocating movement. The bottom end of the displacement block 454 is connected to the slider 455, and the slider 455 is slidably connected to the inside of the carrier 451. The bottom end of the slider 455 is integrally formed with a vertical rod 456. Under the guidance of the carrier 451 and the movement of the displacement block 454, the slider 455 performs a stable reciprocating linear motion, thereby driving the vertical rod 456 and the scraper 457 to move synchronously.

[0060] A scraper 457 is fixedly connected to the side of the upright rod 456 near the inside of the main degassing chamber 1, and horizontal columns 458 are arranged on the side of the upright rod 456 near the stirring rod 47. The scraper 457 has strip-shaped openings inside. During the reciprocating motion of the scraper 457, it can effectively scrape off the slurry and air bubbles adhering to the inner wall of the main degassing chamber 1, preventing the formation of degassing dead zones. The strip-shaped openings can reduce the resistance when the scraper 457 moves and allow some slurry to flow through, avoiding excessive dragging and squeezing, making the mixing more gentle and efficient. There are no fewer than five horizontal columns 458, and they are staggered with the stirring points of the stirring rod 47, increasing the contact and shearing points with the slurry. This results in strong interactive convection and turbulence between the central and outer areas of the slurry, greatly improving the overall mixing and air bubble removal effect.

[0061] Example 1: Composition of copper-based varistor chip electronic paste:

[0062] A copper-based varistor chip electronic paste, by weight percentage, comprises the following components:

[0063] Flake copper powder (aspect ratio of 35:1, D50 of 5μm): 65%;

[0064] Nano copper powder (particle size 100nm): 8%;

[0065] Lead borosilicate glass powder (softening point 480℃): 8%;

[0066] Organic carrier: 18.5%;

[0067] Functional additive (whisker-like zinc oxide): 0.5%;

[0068] The organic carrier is composed of the following components (percentage of total weight of slurry): 10% terpineol, 5% diethylene glycol butyl ether acetate, 2.5% ethyl cellulose, 0.3% leveling agent (polyether modified polydimethylsiloxane), 0.5% thixotropic agent (hydrogenated castor oil), and 0.2% coupling agent (silane coupling agent KH-550).

[0069] Example 2: Preparation method and equipment operation of copper-based varistor chip electronic paste:

[0070] Using the formulation of Example 1, utilizing as Figure 2-6 The multi-stage vacuum dynamic degassing equipment shown is based on... Figure 1 The slurry is prepared using the process shown.

[0071] Step S1, Organic carrier preparation: Add terpineol, diethylene glycol butyl ether acetate, ethyl cellulose, leveling agent, thixotropic agent and coupling agent to a container equipped with heating and stirring functions in proportion, stir at medium speed at 75°C for about 60 minutes until completely dissolved into a homogeneous transparent liquid, and cool to room temperature for later use.

[0072] Step S2, Premixing: Weigh the flake copper powder, nano copper powder, glass powder, and functional additives, and add them together with about two-thirds of the organic carrier obtained in step S1 into the hopper of a planetary mixer. Mix for 20 minutes at a revolution speed of 300 rpm and a rotation speed of 500 rpm to obtain a uniform paste-like premixed slurry.

[0073] Step S3, Fine Rolling: Transfer the premixed slurry to a three-roll mill, adjust the gap between the rolls, and roll repeatedly 5-8 times. Take a sample and test it with a scraper fineness gauge until the fineness is ≤8μm.

[0074] Step S4, Vacuum dynamic degassing and viscosity adjustment:

[0075] S4.1 Slurry pretreatment: Pump the rolled slurry into the pretreatment chamber 2 through the feed port, then close the feed port, start the preheating module 21 and the low-speed pre-mixer 22, maintain the slurry temperature at 40℃, and slowly stir at 50rpm for 10 minutes. At this time, some large air bubbles that are not tightly wrapped will rise and burst.

[0076] S4.2, Degassing: Open the first controllable valve 20, and the preheated slurry flows into the main degassing chamber 1 under gravity. Start the first motor 42 and the second motor 49 of the dynamic stirring mechanism 4. The first motor 42 drives the first scraping structure 45 and the second scraping structure 46 to revolve around the fixed bevel gear 44 (e.g., 30 rpm) through the pulley group 43. At the same time, since the moving bevel gear 452 meshes with the fixed bevel gear 44, the revolution drives the moving bevel gear 452 to rotate, which in turn drives the groove rod 453 to rotate. The groove rod 453, through its sliding groove and the cooperation with the displacement block 454, converts the rotational motion into the lateral reciprocating motion of the displacement block 454, the slider 455, the upright rod 456 and the scraper 457. Meanwhile, the second motor 49 drives the stirring rod 47 to rotate at high speed (e.g., 400 rpm). The horizontal column 458 interacts with the high-speed rotating stirring rod 47 to further break up the slurry clumps.

[0077] Simultaneously, the external vacuum generator is activated, and the main degassing chamber 1 is evacuated through the first vacuum interface 11. The vacuum level is controlled in two stages using the control system: in the first stage, the pressure inside the chamber is steadily reduced from atmospheric pressure to -0.085 MPa within 2.5 minutes and maintained for 4 minutes; in the second stage, the pressure is further reduced to -0.098 MPa within 1.5 minutes.

[0078] S4.3, Ultrasonic-assisted defoaming: During the second stage of vacuum maintenance, the ultrasonic-assisted defoaming module 5 is activated. Multiple ultrasonic transducers emit ultrasonic waves at a frequency of 30kHz in pulse mode (working for 2 seconds, with a 3-second interval) to act on the deep layer of the slurry.

[0079] S4.4 Microbubble Recovery and Viscosity Control: During the entire degassing process, the solvent volatilized in the main degassing chamber 1 and the small amount of entrained slurry droplets are drawn into the recovery chamber 3 through the second controllable valve 30 under the action of pressure difference. The cold trap (temperature set at -10℃) in the recovery chamber 3 condenses and recovers these gaseous substances. At the same time, the online viscometer installed on the inner wall of the main degassing chamber 1 transmits the viscosity data to the control system in real time. In this embodiment, the target viscosity is set to 25 Pa·s ± 2 Pa·s. When the control system detects that the viscosity has risen to 27 Pa·s, it determines that there is a loss of solvent. Then, it controls the precision metering evaporator connected to the solvent vapor compensation pipeline 6 to inject a small amount of vapor mixed with terpineol and diethylene glycol butyl ether acetate in the carrier ratio into the main degassing chamber 1 until the viscosity drops back to 25 Pa·s. The entire S4 step takes about 15-25 minutes.

[0080] Step S5, Filtration and Aging: After the preset degassing time and viscosity requirements are met, the vacuum is broken, the discharge port 12 at the bottom of the main degassing chamber 1 is opened, and the slurry is released and filtered through a 400-mesh stainless steel screen to remove any possible trace amounts of impurities or large particles; the filtered slurry is placed in a sealed container and aged in a constant temperature environment of 25°C for 36 hours to release the internal stress of the slurry and achieve optimal and stable rheological properties, thus obtaining the finished copper-based varistor chip electronic slurry.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a copper-based varistor chip electronic paste, characterized in that, The electronic paste consists of the following components by weight percentage Composition: Conductive phase: 50-70% flake copper powder, 5-15% nano copper powder, wherein the aspect ratio of the flake copper powder is 20:1 to 50:1 and the D50 is 3-8μm; the particle size of the nano copper powder is 50-200nm; Glass binder phase: 5-12% lead borosilicate glass powder, with a softening point of 400-550℃; Organic carrier: 15-30%, wherein the organic carrier is composed of solvent, resin and additives, wherein the solvent is a mixture of terpineol and diethylene glycol butyl ether acetate, the resin is ethyl cellulose, and the additives include leveling agents, thixotropic agents and coupling agents; Functional additives: 0.5-3%, including at least one of whisker-like zinc oxide and nickel-coated graphene composite material; The preparation method includes the following steps: S1. Preparation of organic carrier: The solvent, resin and additives are stirred and dissolved at 60-80℃ to form a uniform and transparent organic carrier, which is then cooled for later use. S2. Premixing: The conductive phase, glass binder phase and organic carrier prepared in step S1 are initially mixed in a planetary mixer at 200-500 rpm for 10-30 minutes to obtain a premixed slurry. S3. Fine rolling: The premixed slurry is rolled multiple times through a three-roll mill until the fineness reaches below 10μm; S4. Vacuum dynamic degassing and viscosity adjustment: The finely rolled slurry is placed in a multi-stage vacuum dynamic degassing device for degassing treatment, and the slurry viscosity is monitored and adjusted online simultaneously. S5. Filtration and aging: The deaerated slurry is filtered through a 300-500 mesh sieve and then aged at a constant temperature for 24-48 hours to obtain the finished slurry. The multi-stage vacuum dynamic degassing device described in step S4 includes: a main degassing chamber with a first vacuum interface on its upper side, a discharge port at its bottom, and three support legs locked around its bottom periphery; a pretreatment chamber connected to the upper sidewall of the main degassing chamber via a first controllable valve; a recovery chamber connected to the side of the main degassing chamber away from the pretreatment chamber via a second controllable valve, with a second vacuum interface on its rear top side and a cold trap inside; a dynamic stirring mechanism and an ultrasonic-assisted degassing module disposed inside the main degassing chamber; both the first and second vacuum interfaces are connected to an external vacuum generator via vacuum pipelines; a solvent vapor compensation pipeline is provided through the rear side of the main degassing chamber; and a preheating module and a low-speed pre-stirrer are disposed inside the pretreatment chamber. The specific process of step S4 includes: S4.1 Slurry pretreatment: The finely rolled slurry is first fed into the pretreatment chamber, preheated at 35-45℃ and stirred at low speed for 5-15 minutes to make the slurry temperature uniform and release some large air bubbles. S4.2, Staged Degassing: Open the first controllable valve to introduce the preheated slurry into the main degassing chamber; start the dynamic stirring mechanism to shear and stir the slurry at a speed of 100-400 rpm; at the same time, the pressure in the main degassing chamber is reduced in two stages by an external vacuum generator: in the first stage, the pressure is reduced to -0.08 MPa to -0.09 MPa within 2-3 minutes and maintained for 3-5 minutes; in the second stage, the pressure is further reduced to -0.095 MPa to -0.1 MPa within 1-2 minutes. S4.3, Ultrasonic-assisted debubbling: During the vacuum maintenance period in the second stage, the ultrasonic-assisted debubbling module is activated and operates in intermittent pulse mode with a working frequency of 25-40kHz and a pulse interval of 2-5 seconds. S4.4 Microbubble Recovery and Viscosity Control: The gas carrying slurry droplets generated during the degassing process is drawn into the recovery chamber through the second controllable valve. The cold trap in the recovery chamber condenses and recovers the slurry components. At the same time, the viscosity of the slurry in the main degassing chamber is monitored in real time by an online viscometer and compared with the preset viscosity range. The control system automatically adjusts the temperature of the main degassing chamber or adds a trace amount of organic carrier vapor to the chamber to stabilize the viscosity.

2. The method for preparing a copper-based varistor chip electronic paste according to claim 1, characterized in that, The dynamic stirring mechanism includes a partition plate fixed inside the upper part of the main degassing chamber. A first motor is locked and fixed to the rear side of the top of the partition plate. The bottom output end of the first motor is connected to the rear pulley of the pulley assembly. A fixed bevel gear is coaxially inserted inside the front pulley of the pulley assembly. The top of the fixed bevel gear is fixed to the partition plate. A first scraping structure and a second scraping structure are symmetrically arranged on both sides of the bottom of the fixed bevel gear. The first scraping structure and the second scraping structure have the same structure and size, and their tops are both fixed to the front pulley of the pulley assembly. A stirring rod is coaxially arranged at the bottom of the fixed bevel gear. The lower part of the fixed bevel gear is inserted and rotated on the top side of the protective cover, and the bottom end of the fixed bevel gear is connected to the top output end of the second motor. The second motor is fastened to the inside of the protective cover, and the protective cover is fastened to the bottom middle side of the main degassing chamber.

3. The method for preparing a copper-based varistor chip electronic paste according to claim 2, characterized in that, The partition has a hollowed-out groove in the middle, and the bottom of the front pulley of the pulley assembly rotates and contacts the inside of the hollowed-out groove. A baffle is provided on the bottom of the partition near the pretreatment chamber.

4. The method for preparing a copper-based varistor chip electronic paste according to claim 2, characterized in that, The first scraping and stirring structure includes a carrier fixed at the top to the front pulley of the pulley assembly. A movable bevel gear is rotatably connected to the side of the carrier near the stirring rod, and a grooved rod is coaxially connected to the side of the movable bevel gear away from the stirring rod. The top side of the movable bevel gear meshes with a fixed bevel gear. The middle part and the side of the grooved rod away from the movable bevel gear are rotatably connected to the carrier. A displacement block is slidably connected to the bottom of the groove of the grooved rod to drive the displacement block to perform a lateral reciprocating movement. A slider is connected to the bottom end of the displacement block, and the slider is slidably connected to the inside of the carrier. A vertical rod is integrally formed at the bottom end of the slider. A scraper is fixedly connected to the side of the vertical rod near the inside of the main degassing chamber, and horizontal columns are arranged on the side of the vertical rod near the stirring rod.

5. The method for preparing a copper-based varistor chip electronic paste according to claim 4, characterized in that, The scraper blade has strip-shaped openings inside, and there are no fewer than five horizontal columns, which are staggered with the stirring part of the stirring rod.

6. The method for preparing a copper-based varistor chip electronic paste according to claim 1, characterized in that, The ultrasonic-assisted defoaming module includes multiple ultrasonic transducers arranged in a ring array in the lower part of the inner wall of the main defoaming cavity. The emitting surface of the ultrasonic transducer is conformal to the curved surface of the inner wall of the main defoaming cavity, and the ultrasonic waves emitted by it point towards the central axis of the main defoaming cavity.

7. The method for preparing a copper-based varistor chip electronic paste according to claim 1, characterized in that, The main degassing chamber is equipped with an online viscometer, which, based on feedback from the online viscometer, injects a controllable amount of vapor formed by the solvent components of the organic carrier into the main degassing chamber through a solvent vapor compensation pipeline. This accurately compensates for the solvent volatilized during the degassing process and maintains the stability of the slurry composition.

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