A device and method for preparing spherical silver powder for photovoltaic front-side conductive silver paste

Abstract

This invention relates to the field of conductive material production technology, specifically to a device and method for preparing spherical silver powder for photovoltaic front-side conductive silver paste. The device includes a support base and a roller. Supports are fixedly mounted at the midpoints of both ends of the top surface of the support base, and the roller is positioned between the two supports. A ball milling mechanism and an auxiliary ball milling mechanism are arranged between the support base and the roller. The roller consists of a left half and a right half arranged in a frustum shape. A feeding mechanism and a dust-free collection mechanism are respectively arranged on the outer side of the right half and the outer side of the left half of the roller. The ball milling mechanism includes an inner drive mechanism passing through the axial center line of the roller, an outer drive mechanism located on the outer side of the left half of the roller, and a sieving ball milling assembly located inside the roller. This invention can achieve rapid and thorough ball milling and dust-free collection of the milled spherical silver powder. Furthermore, the entire machine adopts a modular design, facilitating subsequent operation and maintenance.

Description

Technical Field

[0001] This invention relates to the field of conductive material production technology, specifically to a device and method for preparing spherical silver powder for photovoltaic front-side conductive silver paste. Background Technology

[0002] With the increasing depletion of non-renewable energy sources such as oil and coal, the development of renewable energy has attracted growing attention. Solar energy, as the most abundant and primary clean energy source, has received particular emphasis, making the improvement of photovoltaic power generation efficiency a key research focus. Photovoltaic silver paste, due to its excellent rheological and electrical properties, has become a primary raw material for printed solar panels. Silver powder, as the main conductive phase in solar cell silver paste, accounts for approximately 90% of the paste's mass and plays a decisive role in its rheological and electrical properties. As market demands for higher photoelectric conversion efficiency in solar cells increase, the preparation of silver powder with excellent sintering activity and printability has become a focal point.

[0003] Currently, the industrial production of two-dimensional silver powder mainly involves mechanically ball-milling spherical or near-spherical silver powder. The preparation methods for ball-milling raw materials (spherical and near-spherical silver powder) include physical methods (physical vapor deposition) and chemical methods (liquid-phase chemical reduction, precursor thermal decomposition). Among these, the liquid-phase reduction method is widely used as the primary silver powder production method due to its lower investment, lower cost, and ease of large-scale production. The preparation of two-dimensional silver powder requires ball-milling raw materials with low specific surface area and high dispersibility as ball-milling precursors. Since the characteristics of the precursor silver powder have a significant impact on the milling of two-dimensional silver powder, the reduction of the precursor silver powder should be the primary focus during the preparation process.

[0004] The prior art discloses Chinese Patent No. CN 113600825 B (IPC Classification No. H01B1 / 16): a micron-sized spherical silver powder and its preparation method, which discloses the following steps: S1, preparing a silver nitrate solution, adding trisodium citrate to the silver nitrate solution and mixing well to obtain a precursor solution; S2, preparing an ascorbic acid solution, adding gum arabic, polyvinylpyrrolidone and polyethylene glycol to the ascorbic acid solution to obtain a reducing agent solution; S3, under the condition of 20-60°C and in the dark, rapidly pouring the precursor solution into the reducing agent solution, and continuously stirring until the reaction is complete, thereby obtaining the micron-sized spherical silver powder. This silver powder has high sphericity and no irregular shapes such as flakes or dendrites.

[0005] The prior art also discloses a Chinese patent with publication number CN 110369050 B (IPC classification number B02C17): a fully sealed drum ball mill, which discloses a frame, a transverse drum on the frame, an inner liner plate on the inner wall of the drum, the inner liner plate including side plates and end plates, the side plates being composed of multiple first ceramic single plates assembled together, the cross-section of the first ceramic single plate being arc-shaped, the inner wall of the first ceramic single plate having an inward protrusion integrally formed, the end face of the protrusion being spherical, the outer wall of the first ceramic single plate having a groove integrally formed, the bottom surface of the groove being spherical, bolts being bonded and fixed in the groove, the bolt threads extending outward to the outer sleeve of the drum and a fastening nut being fitted thereon, an annular copper gasket being provided between the edge of the outer wall of the first ceramic single plate and the drum, and a first polyurethane adhesive being provided between the first ceramic plate inside the copper gasket and the drum. The structure is simple, has a long service life, high working stability, and can effectively reduce noise.

[0006] However, the existing technology still has certain defects. For example, the technical solution with publication number CN 113600825 B uses the "ascorbic acid-gum arabic silver nitrate" system to prepare precursor silver powder. Although it uses a simple liquid phase reduction, ascorbic acid is relatively expensive, and the cost of large-scale production is still high.

[0007] For example, the technical solution with publication number CN 110369050 B is not convenient for quick replacement of local parts during use, and the ball milling process relies solely on changing the trajectory of the abrasive balls to collide with the raw materials, resulting in limited collision frequency and force, and low ball milling efficiency. Summary of the Invention

[0008] The purpose of this invention is to provide an apparatus and method for preparing spherical silver powder for photovoltaic front conductive silver paste, so as to solve the problems mentioned in the background art.

[0009] The objective of this invention can be achieved through the following technical solutions:

[0010] A device for preparing spherical silver powder for photovoltaic front conductive silver paste includes a support base and a roller. The support base has brackets fixed at the middle of both ends of its top surface, and the roller is disposed between the two brackets. A ball milling mechanism and an auxiliary ball milling mechanism are disposed between the support base and the roller. The roller is composed of a left half and a right half arranged in a frustum shape. A feeding mechanism and a dust-free collection mechanism are respectively disposed on the outer side of the right half and the outer side of the left half of the roller. A feed slot and a discharge slot are respectively opened on the surface of the roller at the positions corresponding to the feeding mechanism and the dust-free collection mechanism.

[0011] The ball milling mechanism includes an inner drive mechanism that runs through the axial center line of the drum, an outer drive mechanism located on the outer side of the left half of the drum, and a sieving ball milling assembly located inside the drum.

[0012] In a preferred embodiment, the internal drive mechanism includes a drive motor fixedly installed on the opposite side of two supports. The output shaft ends of the two drive motors are each connected to a spindle, and the opposite ends of the two spindles are respectively provided with a cross block and a cross groove. The cross block is movably inserted into the cross groove. The outer circumferential surface of the two spindles located at one end of the roller is movably fitted with a positioning frame, and the bottom end face of the positioning frame is movably attached to the upper end face of the bearing seat.

[0013] In a preferred embodiment, the external drive mechanism includes a support fixed to the top of the bearing seat and a gear ring fixedly sleeved on the outer side of the left half of the roller. A second drive motor is fixedly installed at the top of the support, and a gear that meshes with the gear ring is fixedly provided at the end of the output shaft of the second drive motor.

[0014] In a preferred embodiment, the sieving ball mill assembly includes a screen sandwiched between the right half and the left half of the drum. The inner side of the right half of the drum is provided with a plurality of annularly evenly distributed flow guide strips, and the circumferential side of the mandrel on the inner side of the right half of the drum is provided with a plurality of annularly evenly distributed elastic arc plates. The flow guide strips are configured as triangular prisms, and the flow guide strips are configured in a constricted shape from the large diameter end to the small diameter end of the right half of the drum.

[0015] Multiple elastic rods are fixedly provided at the inner edge of the small diameter end of the left half of the drum, and a rigid rod is fixedly provided at the outer edge of the mandrel on the inner side of the left half of the drum. On the side opposite to the elastic rod, an arc-shaped top block with a semi-cylindrical pile structure and a triangular prism-shaped striking block are respectively provided.

[0016] Multiple T-shaped limiting grooves are provided on the large inner circumferential surface of the right half of the drum and the outer circumferential surface of the spindle on the inner side of the right half of the drum. The guide strip and the elastic arc plate are fixed with T-shaped limiting strips in the middle of the side facing the limiting groove at their respective positions, and the limiting strips are slidably connected to the inside of the limiting groove at the corresponding positions.

[0017] In a preferred embodiment, the auxiliary ball milling mechanism includes a base plate disposed at the bottom of the support seat and a through groove vertically penetrating both ends of the top surface of the support seat. A limiting guide plate is fixedly disposed at the top of the base plate corresponding to the position of the through groove. Four springs are fixedly connected between the base plate and the four corners of the opposite side of the support seat. Cams are fixedly sleeved at the positions of the limiting guide plates corresponding to the positions of the outer peripheral surfaces of the two spindles.

[0018] In a preferred embodiment, the feeding mechanism includes a hopper fixedly installed at the position of the feed inlet on the right half of the drum. A through groove is provided through the middle of the bottom of the hopper. A baffle plate that fits the outer surface of the drum is movably installed inside the through groove. A slot with the same size as the feed inlet is provided at one end of the baffle plate. Vertical plates are fixedly provided at both ends of the baffle plate. An arc rod is fixedly provided on one side of the hopper. The end of the arc rod away from the hopper movably passes through the vertical plate at the position. A spring is movably sleeved on the outer circumference of the arc rod. The two ends of the spring are fixedly connected to the hopper and the vertical plate at the corresponding position, respectively.

[0019] In a preferred embodiment, the dust-free collection mechanism includes a collar movably sleeved on the outer circumferential surface of the left half of the drum corresponding to the discharge slot. A positioning support frame connected to the discharge slot is fixedly provided on the outer circumferential surface of the collar. A channel groove is provided through one side of the positioning support frame, and a receiving box is movably inserted into the channel groove.

[0020] A sealing plate is movably inserted through the top of the channel groove cavity. Guide strips are fixedly installed in the middle of both sides of the sealing plate. Guide grooves are opened on both sides of the channel groove cavity, and the guide strips are slidably connected to the corresponding guide grooves. A vertical plate is fixedly installed at one end of the top surface of the sealing plate. A guide rod that movably passes through the vertical plate is fixedly installed in the middle of the side of the positioning support frame facing the vertical plate. A spring is movably sleeved on the outer circumference of the guide rod, and the two ends of the spring are fixedly connected to the vertical plate and the positioning support frame, respectively.

[0021] The collar corresponds to the deep end of the cross groove, and a limiting component is also provided on the positioning bracket. The limiting component includes two sets of round rods that move through both sides of the positioning bracket, and a limiting plate and a stop strip are fixed at both ends of the two sets of round rods respectively.

[0022] The top of the receiving box is movably fitted with a cover plate, and both sides of the top surface of the receiving box are provided with grooves. Straight rods are fixedly installed inside the two grooves. Slider blocks are fixedly installed on both sides of the end face of the cover plate and are movably fitted on the outside of the straight rods at their respective positions. Springs are movably fitted on the outer periphery of the two straight rods. A stop plate is fixedly installed on the top surface of the cover plate at the end corresponding to the slider.

[0023] In a preferred embodiment, both brackets include a support plate fixedly disposed on the top surface of the support seat and a buckle plate hinged to one edge of the top of the support plate. A semi-circular groove is provided in the middle of the opposite side of the support plate and the buckle plate when they are in the buckling state. A locking block is fixedly disposed in the middle of the opposite end of the two spindles. A slot is provided at the end of the output shaft of the two drive motors to match the locking block at the location. The locking block and the slot in the buckling state are both disposed inside the circular groove formed by the two semi-circular grooves at the location.

[0024] In a preferred embodiment, positioning blocks are fixedly provided at the center of the bottom end face of the positioning bracket and at the center of the bottom end faces of the two positioning frames. A positioning slot is provided at the top surface of the bearing seat corresponding to the position of each positioning block, and the positioning blocks are movably inserted into the positioning slots at the corresponding positions.

[0025] This invention also provides a method for preparing spherical silver powder for photovoltaic front-side conductive silver paste, specifically including the following steps:

[0026] S1: Silver powder reduction: Prepare 300 L of 100 g / L silver nitrate solution in a reaction vessel using pure water, add 2 kg of polyvinylpyrrolidone-K30, heat to 30 ℃, add the first 30% sodium hydroxide solution, adjust the pH of the silver nitrate solution to 5.0~6.0, add 10 L of 35% formaldehyde solution, stir at 100 r / min, and when the reduction reaction reaches equilibrium after 30 min, add the remaining sodium hydroxide solution in steps to promote the completion of the reaction, and age for 5 min to obtain reduced silver powder for later use;

[0027] S2: Detection of reduced silver powder: After washing and solid-liquid separation, the silver powder obtained in S1 above was dispersed with 0.7% stearic acid by weight of silver powder, placed in a tray, and dried at 70℃ for 24 h. The physical properties of the silver powder were then analyzed by scanning electron microscopy.

[0028] S3: Silver powder ball milling: Take 4 kg of silver powder from S2 above, weigh 0.5% of the silver powder mass of stearic acid and dissolve it in 500 mL of ethanol. Heat and clarify, add it to the silver powder to be ball milled and disperse it fully. Mix it with 16 kg of steel balls with a diameter of 1.5 mm and add it into the cavity enclosed by the screen and the right half of the drum through the feeding mechanism on the drum. After grinding for 12 h, sieve it and collect it using the dust-free collection mechanism for later use.

[0029] S4: Ball milled silver powder test: After the silver powder obtained in S3 above is washed with ethanol until the silver powder mass loss on ignition is constant, the physical properties of the silver powder are measured.

[0030] The beneficial effects of this invention are:

[0031] 1. This invention utilizes an auxiliary ball milling mechanism in conjunction with a sieving ball milling assembly driven by an internal drive mechanism and an external drive mechanism to ball mill the raw silver powder of the target. This not only greatly increases the collision frequency between the raw powder and the steel balls, enabling rapid and thorough ball milling of the raw powder, but also uses striking blocks to knock down qualified target silver powder accumulated on the screen, preventing blockage.

[0032] 2. This invention utilizes a dust-free collection mechanism to collect the target silver powder after ball milling in a dust-free manner, and after collection, it can be transported in a dust-free manner without causing dust pollution to the working environment.

[0033] 3. The manufacturing device of the present invention adopts a modular design, which is convenient for disassembly and assembly, and each component can be replaced independently, thereby improving the utilization rate of effective components;

[0034] 4. This invention uses inexpensive reducing agents (such as formaldehyde) to prepare precursor silver powder, breaking through the traditional "ascorbic acid-gum arabic silver nitrate" system, and has good economic benefits. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a first-view overall structural schematic diagram of the preparation device of the present invention;

[0037] Figure 2 This is a second-view overall structural schematic diagram of the preparation device of the present invention;

[0038] Figure 3 This is a top view schematic diagram of the overall structure of the preparation device of the present invention;

[0039] Figure 4 This is the present invention. Figure 3 Schematic diagram of the cross-sectional structure along the AA direction;

[0040] Figure 5 This is a schematic diagram of the right half of the drum in the preparation device of the present invention;

[0041] Figure 6 This is the present invention. Figure 5 A schematic diagram of the cross-sectional structure;

[0042] Figure 7 This is the present invention. Figure 6 Enlarged schematic diagram of section A in the middle;

[0043] Figure 8 This is a schematic diagram of the left half of the drum structure of the preparation device of the present invention;

[0044] Figure 9 This is a schematic diagram of the positioning frame and receiving box of the preparation device of the present invention.

[0045] Figure 10 This is a schematic diagram of the overall structure of the positioning frame of the preparation device of the present invention;

[0046] Figure 11 This is a schematic cross-sectional view of the receiving box structure of the preparation device of the present invention;

[0047] Figure 12 This is a schematic diagram of the support and mandrel assembly structure of the preparation device of the present invention.

[0048] The attached figures are labeled as follows: 1. Bearing seat; 2. Bracket; 21. Support plate; 22. Buckle plate; 3. Roller; 4. Ball mill mechanism; 41. Mandrel; 42. Cross block; 43. Cross groove; 44. Guide liner; 45. Elastic arc plate; 46. Elastic rod; 47. Striking block; 48. Rigid rod; 49. Arc-shaped top block; 410. Support; 411. Gear; 412. Gear ring; 413. Restriction groove; 414. Restriction strip; 415. Screen; 416. Positioning frame; 5. Dust-free collection mechanism; 51. Collar; 52. Positioning support frame; 521. Sealing plate; 522. Vertical plate one; 523. 524. Guide rod; 53. Spring 1; 54. Receiving box; 55. Cover plate; 56. Sink; 57. Slider; 58. Straight rod; 59. Spring 2; 50. Stop plate; 51. Channel groove; 62. Feeding mechanism; 63. Hopper; 64. Cover plate; 65. Vertical plate 2; 66. Arc rod; 67. Spring 3; 68. Through groove; 79. Auxiliary ball mill mechanism; 70. Base plate; 71. Cam; 72. Spring 4; 73. Through groove; 74. Restricting guide plate; 75. Round rod; 86. Limiting plate; 97. Stop bar; 10. Positioning insert; 11. Positioning slot; 12. Locking block; 13. Locking block; 14. Locking groove. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] A device and method for preparing spherical silver powder for photovoltaic front conductive silver paste, characterized by being mainly composed of metals or alloys and classified according to the properties of conductive materials, is disclosed under IPC classification number H01B1.

[0051] Example 1

[0052] Refer to the instruction manual appendix Figure 1-8 and Figure 12An embodiment of the present invention provides a spherical silver powder preparation device for photovoltaic front conductive silver paste, comprising a support 1 and a roller 3. The roller 3 is composed of a left half and a right half arranged in a frustum shape. Supports 2 are fixedly provided at the middle of both ends of the top surface of the support 1, and the roller 3 is disposed between the two supports 2. A ball milling mechanism 4 and an auxiliary ball milling mechanism 7 are provided between the support 1 and the roller 3. The ball milling mechanism 4 includes an inner drive mechanism that runs through the axial center line of the roller 3, an outer drive mechanism disposed on the outer side of the left half of the roller 3, and a sieving ball milling assembly located inside the roller 3.

[0053] It should be noted that the present invention utilizes an auxiliary ball milling mechanism 7 to work in conjunction with a sieving ball milling assembly driven by an internal drive mechanism and an external drive mechanism to fully ball mill the raw silver powder.

[0054] Specifically, such as Figure 4-8 As shown, the internal drive mechanism includes a drive motor 1 fixedly installed on the opposite side of the two brackets 2. The output shaft ends of the two drive motors 1 are connected to a spindle 41, and the opposite ends of the two spindles 41 are respectively provided with a cross block 42 and a cross groove 43. The cross block 42 is movably inserted into the cross groove 43. The outer circumferential surface of the two spindles 41 located at one end of the roller 3 is movably fitted with a positioning frame 416, and the bottom end surface of the positioning frame 416 is movably attached to the upper end surface of the bearing seat 1.

[0055] The external drive mechanism includes a support 410 fixed on the top of the bearing seat 1 and a toothed ring 412 fixedly sleeved on the outer side of the left half of the roller 3. The top of the support 410 is fixedly mounted with a second drive motor, and the output shaft end of the second drive motor is fixedly provided with a gear 411 that meshes with the toothed ring 412.

[0056] The sieving ball mill assembly includes a screen 415 sandwiched between the right and left halves of the drum 3. Multiple sets of flow guide strips 44 are evenly distributed in a ring on the inner side of the right half of the drum 3. Multiple sets of elastic arc plates 45 are evenly distributed in a ring on the circumferential side of the spindle 41 on the inner side of the right half of the drum 3. The flow guide strips 44 are configured as triangular prisms and are constricted from the large diameter end to the small diameter end of the right half of the drum 3.

[0057] Multiple elastic rods 46 are fixedly provided on the inner edge of the small diameter end of the left half of the roller 3 in a ring-shaped manner, and a rigid rod 48 is fixedly provided on the outer edge of the mandrel 41 on the inner side of the left half of the roller 3. On the side opposite to the elastic rods 46, there are arc-shaped top blocks 49 with semi-cylindrical pile structure and striking blocks 47 with triangular prism structure respectively.

[0058] It should be noted that the left and right halves of the roller 3 are provided with connecting flanges on their opposite outer circumferential surfaces, and the two connecting flanges are fixed together by bolts. The left and right halves of the roller 3 are provided with annular grooves on their opposite inner circumferential surfaces, and the screen 415 is clamped inside the two annular grooves and rotates synchronously with the roller 3. In addition, the spindle 41 is set in the opposite direction of rotation to the roller 3, and the elastic arc plate 45 and the elastic rod 46 are both made of spring steel.

[0059] In this process, after the raw powder and steel balls are added to the right half of the inner cavity of the drum 3, the drive motor 1 and drive motor 2 are simultaneously started by the external controller to allow the sieving ball mill assembly inside the drum 3 to ball mill the raw powder. During this process, the mixture of raw powder and steel balls (hereinafter referred to as the mixture) initially moves towards the screen 415 along the inner circumference of the drum 3. Then, as the drum 3 rotates, it gradually moves upward under the support of the guide strip 44. After rising to a certain height, the mixture will move along the guide strip 44 towards... Its constriction direction moves, and then it separates from the guide liner 44. As the mixture moves upward with the roller 3 under the support of the guide liner 44, the elastic arc plate 45 that rotates with the spindle 41 is always rotating. The elastic arc plate that rotates with the spindle 41 can be used to impact the mixture that falls off the guide liner 44 upward. The falling mixture will once again approach the screen 415 with the help of the truncated cone structure of the roller 3. This cycle repeats, which can greatly increase the collision frequency between the raw powder and the steel ball, and realize the rapid and thorough grinding of the raw powder.

[0060] After ball milling, qualified target silver powder flows through screen 415 into the left half of drum 3. During this process, when the spindle 41 and drum 3 rotate in opposite directions, the arc-shaped top block 49, which rotates with the spindle 41, contacts the striking block 47, which rotates with the drum 3. This pushes the striking block 47 away from the screen 415, causing the elastic rod 46 connected to the striking block 47 to undergo elastic deformation. After the arc-shaped top block 49 completely passes the striking block 47, the striking block 47 is reset by the restoring force of the elastic rod 46 and strikes the screen 415. On the one hand, this can bounce the mixture gathered at the screen 415 away from the screen 415, increasing the collision frequency between the raw powder and the steel ball. On the other hand, it can knock down the qualified target silver powder accumulated on the screen 415, preventing blockage.

[0061] Since the two spindles 41 are connected by a matching cross block 42 and cross slot 43, and the two spindles 41 are driven by their respective corresponding drive motors, the spindles 41 are easy to connect while improving their durability.

[0062] Furthermore, multiple T-shaped limiting grooves 413 are provided on the large inner circumferential surface of the right half of the roller 3 and the outer circumferential surface of the spindle 41 on the inner side of the right half of the roller 3. T-shaped limiting strips 414 are fixedly provided on the middle of the side of the flow guide strip 44 and the elastic arc plate 45 facing the limiting groove 413 at their respective positions, and the limiting strips 414 are slidably connected to the inside of the limiting groove 413 at the corresponding positions.

[0063] It should be noted that the T-shaped limiting strip 414 and the T-shaped limiting groove 413 ensure stable insertion of the guide strip 44 and the elastic arc plate 45. After the left and right halves of the drum 3 are connected and installed, the screen 415 can be used to check the position of the guide strip 44 and the elastic arc plate 45. The limiting groove 413 is sealed by the side of the guide strip 44 that contacts the inner surface of the drum 3 and the side of the elastic arc plate 45 that contacts the outer surface of the spindle 41. This can prevent small-diameter particles from getting stuck in the gaps formed during the ball milling process. At the same time, it also facilitates the quick replacement of the guide strip 44 and the elastic arc plate 45 in the later stage.

[0064] Specifically, such as Figure 1 and Figure 4 As shown, the auxiliary ball milling mechanism 7 includes a base plate 71 disposed at the bottom of the support seat 1 and a through groove 74 vertically penetrating both ends of the top surface of the support seat 1. A limiting guide plate 75 is fixedly disposed at the top of the base plate 71 corresponding to the position of the through groove 74. Springs 73 are fixedly connected between the four corners of the base plate 71 and the support seat 1 on opposite sides. Cams 72 are fixedly sleeved on the outer circumference of the two spindles 41 corresponding to the positions of the limiting guide plates 75.

[0065] It should be noted that the top of the limiting guide plate 75 is designed with a semi-circular structure, which can facilitate the quick passage of the top of the limiting guide plate 75 through the slot 74 on the bearing seat 1, and guide the bearing seat 1 to move upward after contacting the rotating cam 72. During the ball milling of the raw powder, as the spindle 41 rotates, the cam 72 will rotate synchronously with the spindle 41. The rotating cam 72 will intermittently contact the arc section of the limiting guide plate 75, allowing the bearing seat 1 to move upward along the limiting guide plate 75 and stretching the spring 4 73. When the cam 72 disengages from the limiting guide plate 75, the spring 4 73 will drive the bearing seat to reset and generate up-and-down vibration, thereby causing the entire ball mill to move up and down, accelerating the collision frequency between the raw powder and the steel balls and the sieving of qualified target silver powder.

[0066] Specifically, such as Figure 1-2 and Figure 12As shown, both brackets 2 include a support plate 21 fixedly mounted on the top surface of the support base 1 and a buckle plate 22 hinged to the edge of the top end of the support plate 21. The support plate 21 and the buckle plate 22 are respectively provided with a semi-circular groove in the middle of their opposite sides when they are in the buckling state. The two spindles 41 are respectively provided with a locking block 13 fixedly mounted in the middle of their opposite ends. The output shaft ends of the two drive motors are respectively provided with a slot 14 that matches the locking block 13 at the position. The locking block 13 and the slot 14 in the buckling state are respectively located inside the circular groove formed by the two semi-circular grooves at the position.

[0067] It should be noted that the drive motor is fixed on the outside of the support plate 21 on the bracket 2 at the location. During the assembly of the preparation device, after the left half and right half of the roller 3 are connected, the two positioning frames 416 are placed on the top of the support seat 1. The slots 14 of the two spindles 41 extending to the outside of the roller 3 are located inside the semi-circular groove at the location and are locked on the outside of the locking block 13 at the end of the output shaft of the drive motor at the location. Then, the buckle plate 22 is fastened to the top of the support plate 21 and fixed with locking bolts, which greatly improves the convenience of assembly.

[0068] Example 2

[0069] Refer to the instruction manual appendix Figure 1-5 and Figure 9-11 An embodiment of the present invention provides a spherical silver powder preparation device for photovoltaic front conductive silver paste, comprising a support base 1 and a roller 3. The roller 3 is composed of a left half and a right half arranged in a frustum-shaped structure. A feeding mechanism 6 and a dust-free collection mechanism 5 are respectively arranged on the outer side of the right half and the outer side of the left half of the roller 3. A feeding slot and a discharging slot are respectively opened on the surface of the roller 3 at the positions corresponding to the feeding mechanism 6 and the dust-free collection mechanism 5.

[0070] Specifically, such as Figure 5 As shown, the feeding mechanism 6 includes a hopper 61 fixedly installed at the position of the feed trough on the right half of the roller 3. A through groove 66 is provided through the middle of the bottom of the hopper 61. A cover plate 62 that fits the outer surface of the roller 3 is movably installed inside the through groove 66. A slot with the same size as the feed trough is provided at one end of the cover plate 62. Vertical plates 63 are fixedly provided at both ends of the cover plate 62. An arc rod 64 is fixedly provided on one side of the hopper 61. The end of the arc rod 64 away from the hopper 61 movably passes through the vertical plate 63 at its position. A spring 65 is movably sleeved on the outer circumference of the arc rod 64. The two ends of the spring 65 are fixedly connected to the hopper 61 and the vertical plate 63 at the corresponding position, respectively.

[0071] It should be noted that when spring 65 is in its natural state, the trough on the baffle 62 is completely offset from the feed inlet and is located on the side of the hopper 61 away from the arc rod 64. When adding the mixture, pull the vertical plate 63 on the baffle 62 corresponding to the side of the arc rod 64 along the direction of the arc rod 64 to connect the trough with the feed inlet on the roller 3. After the feeding is completed, remove the force on the vertical plate 63. The baffle 62 returns to its initial state under the restoring force of spring 65 and seals the feed inlet. The operation is convenient.

[0072] Specifically, such as Figure 4 and Figure 9-11 As shown, the dust-free collection mechanism 5 includes a collar 51 that is movably sleeved on the outer circumferential surface of the left half of the roller 3 corresponding to the discharge slot. A positioning frame 52 that communicates with the discharge slot is fixedly provided on the outer circumferential surface of the collar 51. A channel groove 54 is provided through one side of the positioning frame 52. A receiving box 53 is movably inserted into the channel groove 54.

[0073] A sealing plate 521 is movably inserted through the top of the inner cavity of the channel groove 54. Guide strips are fixedly installed in the middle of both sides of the sealing plate 521. Guide grooves are opened on both sides of the inner cavity of the channel groove 54, and the guide strips are slidably connected to the corresponding guide grooves. A vertical plate 522 is fixedly installed at one end of the top surface of the sealing plate 521. A guide rod 523 that movably passes through the vertical plate 522 is fixedly installed in the middle of the side of the positioning support frame 52 facing the vertical plate 522. A spring 524 is movably sleeved on the outer circumference of the guide rod 523, and the two ends of the spring 524 are fixedly connected to the vertical plate 522 and the positioning support frame 52, respectively.

[0074] The collar 51 corresponds to the deep end of the cross groove 43, and the positioning frame 52 is also provided with a limiting component. The limiting component includes two sets of round rods 8 that move through both sides of the positioning frame 52. The two sets of round rods 8 are respectively fixed with a limiting plate 9 and a stop strip 10 at both ends.

[0075] The top of the receiving box 53 is movably fitted with a cover plate 531, and both sides of the top surface of the receiving box 53 are provided with sink grooves 532. Straight rods 534 are fixedly installed inside the two sink grooves 532. Slider blocks 533 are fixedly installed on both sides of the end face of the cover plate 531 and are movably sleeved on the outside of the straight rods 534. Springs 535 are movably sleeved on the outer periphery of the two straight rods 534. A stop plate 536 is fixedly installed on the top surface of the cover plate 531 corresponding to the end of the slider 533.

[0076] It should be noted that in the initial state, the sealing plate 521 completely seals the discharge slot under the restoring force of the spring 524. Specifically, during real-time dust-free collection of the target spherical silver powder, simply insert the corresponding end of the stop plate 536 of the receiving box 53 into the channel slot 54. During this process, the stop plate 536 is blocked by the positioning bracket 52. As the receiving box 53 is gradually pushed in, the cover plate 531 is pushed open by the positioning bracket 52 and compresses the spring 524 along the direction of the guide rod 523, while the sealing plate 521 is pushed into the receiving box. 53 is pushed open, and spring 535 is compressed along the direction of straight rod 534, gradually releasing the blockage of the discharge trough, allowing the qualified target spherical silver powder after screening to fall into the receiving box 53. Since the discharge trough is in motion, the receiving process is intermittent. After the sealing plate 521 is fully pushed open, the stop bar 10 can be moved to fasten the end of the receiving box 53 located outside the channel groove 54, and the restoring force of spring 524 and spring 535 is used to limit the stop bar in the fastened state, thereby locking the position of the receiving box 53.

[0077] Conversely, during the process of removing the receiving box 53 after collection, the sealing plate 521 will automatically reset under the restoring force of the spring 524, thus sealing the outlet. As the receiving box 53 gradually separates from the channel 54, the cover plate 531 will automatically seal the receiving box 53 under the restoring force of the spring 535, achieving dust-free transfer.

[0078] Furthermore, positioning blocks 11 are fixedly provided at the center of the bottom end face of the positioning bracket 52 and at the center of the bottom end face of the two positioning frames 416. Positioning slots 12 are provided at the top end face of the bearing seat 1 corresponding to the position of each positioning block 11, and the positioning blocks 11 are movably inserted into the corresponding positioning slots 12.

[0079] It should be noted that during the assembly of the preparation device, after the docking between the left and right halves of the roller 3 is completed, the positioning frame 416 and the positioning block 11 at the bottom of the positioning bracket 52 can be inserted into the positioning slot 12 at the corresponding position on the top of the support seat 1. This can enhance the support of the roller 3 and ensure the real-time stability of the material receiving process.

[0080] This invention also provides a method for preparing spherical silver powder for photovoltaic front-side conductive silver paste, specifically including the following steps:

[0081] S1: Silver powder reduction: Prepare 300 L of 100 g / L silver nitrate solution in a reactor using pure water, add 2 kg of polyvinylpyrrolidone (PVP)-K30, heat to 30 ℃, add the first 30% sodium hydroxide solution, adjust the pH of the silver nitrate solution to 5.0~6.0, add 10 L of 35% formaldehyde solution, stir at 100 r / min, and wait for the reduction reaction to reach equilibrium after 30 min. Then add the remaining sodium hydroxide solution in steps to promote the completion of the reaction and age for 5 min to obtain reduced silver powder for later use.

[0082] S2: Detection of reduced silver powder: After washing and solid-liquid separation, the silver powder obtained in S1 above was dispersed with 0.7% stearic acid by weight of silver powder, placed in a tray, and dried at 70℃ for 24 h. The physical properties of the silver powder were then analyzed by scanning electron microscopy.

[0083] S3: Silver powder ball milling: Take 4 kg of silver powder from S2 above, weigh 0.5% of the silver powder mass of stearic acid and dissolve it in 500 mL of ethanol, heat and clarify, add it to the silver powder to be ball milled and disperse it fully, mix it with 16 kg of steel balls with a diameter of 1.5 mm and add it into the cavity formed by the screen 415 and the right half of the drum 3 through the feeding mechanism 6 on the drum 3. After grinding for 12 h, sieve it and collect it using the dust-free collection mechanism 5 for later use.

[0084] S4: Ball milled silver powder test: After the silver powder obtained in S3 above is washed with ethanol until the silver powder mass loss on ignition is constant, the physical properties of the silver powder are measured.

[0085] In the above steps, it should be noted that the silver nitrate, sodium hydroxide, stearic acid, and ethanol involved are all analytical grade raw materials. Sodium hydroxide reacts with silver nitrate to form a white silver hydroxide precipitate. However, since silver hydroxide precipitate is extremely unstable in water, it decomposes into a gray silver oxide precipitate. Formaldehyde is then used to reduce the silver oxide to prepare silver powder. The relevant reaction formula is as follows:

[0086] AgNO3+NaOH = AgOH↓+NaNO3 (1)

[0087] 2AgOH = Ag2O↓ + H2O (2)

[0088] Ag2O+HCHO=2Ag↓+HCOOH (3)

[0089] HCOOH+Ag2O=2Ag↓+CO2↑+H2O (4)

[0090] In the above technical solutions, the circuits, electronic components and control modules involved are all existing technologies, which can be fully implemented by those skilled in the art, and need not be elaborated. The content to be protected by this invention does not involve any improvement to the software and methods.

[0091] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

[0092] Finally, the following points should be noted: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installation", "connection", and "linkage" should be interpreted broadly, and can be mechanical or electrical connections, or internal connections between two components, or direct connections. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may change.

[0093] Secondly: The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

Claims

1. A device for preparing spherical silver powder for photovoltaic front-side conductive silver paste, comprising a support (1) and a roller (3), characterized in that, The top surface of the bearing seat (1) is fixed with brackets (2) at both ends and the middle of the top surface. The roller (3) is located between the two brackets (2). A ball milling mechanism (4) and an auxiliary ball milling mechanism (7) are provided between the bearing seat (1) and the roller (3). The roller (3) is composed of a left half and a right half with a frustum-shaped structure. A feeding mechanism (6) and a dust-free collection mechanism (5) are respectively provided on the outer side of the right half and the outer side of the left half of the roller (3). A feed trough and a discharge trough are respectively opened on the surface of the roller (3) at the positions corresponding to the feeding mechanism (6) and the dust-free collection mechanism (5). The ball milling mechanism (4) includes an inner drive mechanism that runs through the axial center line of the drum (3), an outer drive mechanism located on the outer side of the left half of the drum (3), and a sieving ball milling assembly located inside the drum (3). The internal drive mechanism includes a drive motor fixedly installed on the opposite side of the two supports (2). The output shaft ends of the two drive motors are connected to a spindle (41). The opposite ends of the two spindles (41) are respectively provided with a cross block (42) and a cross groove (43). The cross block (42) is movably inserted into the cross groove (43). The outer circumferential surface of the two spindles (41) located at one end of the roller (3) is movably fitted with a positioning frame (416). The bottom end surface of the positioning frame (416) is movably attached to the upper end surface of the bearing seat (1). The external drive mechanism includes a support (410) fixed on the top of the bearing seat (1) and a toothed ring (412) fixedly sleeved on the outer side of the left half of the roller (3). The top of the support (410) is fixedly installed with a second drive motor, and the output shaft end of the second drive motor is fixedly provided with a gear (411) that meshes with the toothed ring (412). The sieving ball mill assembly includes a screen (415) sandwiched between the right half and the left half of the drum (3). The inner side of the right half of the drum (3) is provided with multiple sets of flow guide strips (44) evenly distributed in a ring. The outer side of the mandrel (41) on the inner side of the right half of the drum (3) is provided with multiple sets of elastic arc plates (45) evenly distributed in a ring. The flow guide strips (44) are configured as triangular prisms and the flow guide strips (44) are constricted from the large diameter end to the small diameter end of the right half of the drum (3). Multiple elastic rods (46) are fixedly arranged in a ring evenly distributed position on the inner edge of the small diameter end of the left half of the roller (3), and a rigid rod (48) is fixedly arranged on the outer edge of the mandrel (41) on the inner side of the left half of the roller (3). On the side opposite to the elastic rod (46), a semi-cylindrical pile structure arc-shaped top block (49) and a triangular prism structure striking block (47) are respectively provided. Multiple T-shaped limiting grooves (413) are provided on the large inner circumferential surface of the right half of the roller (3) and the outer circumferential surface of the spindle (41) on the inner side of the right half of the roller (3). The guide strip (44) and the elastic arc plate (45) are fixedly provided with T-shaped limiting strips (414) on the middle of the side facing the limiting groove (413) at their respective positions, and the limiting strips (414) are slidably connected to the inside of the limiting groove (413) at the corresponding position. The auxiliary ball milling mechanism (7) includes a base plate (71) disposed at the bottom of the support seat (1) and a through groove (74) vertically penetrating both ends of the top surface of the support seat (1). A limiting guide plate (75) is fixedly provided at the top of the base plate (71) corresponding to the position of the through groove (74). Springs (73) are fixedly connected between the four corners of the base plate (71) and the support seat (1) on opposite sides. Cams (72) are fixedly sleeved on the outer peripheral surfaces of the two spindles (41) corresponding to the positions of the limiting guide plates (75). The dust-free collection mechanism (5) includes a collar (51) that is movably sleeved on the outer circumferential surface of the left half of the roller (3) corresponding to the discharge slot. A positioning frame (52) that communicates with the discharge slot is fixedly provided on the outer circumferential surface of the collar (51). A channel groove (54) is provided through one side of the positioning frame (52). A receiving box (53) is movably inserted into the channel groove (54). A sealing plate (521) is movably inserted through the top of the inner cavity of the channel groove (54). Guide strips are fixedly provided in the middle of both sides of the sealing plate (521). Guide grooves are opened on both sides of the inner cavity of the channel groove (54), and the guide strips are slidably connected to the corresponding guide grooves. A vertical plate (522) is fixedly provided at one end of the top surface of the sealing plate (521). A guide rod (523) that movably passes through the vertical plate (522) is fixedly provided in the middle of the side of the positioning bracket (52) facing the vertical plate (522). A spring (524) is movably sleeved on the outer circumference of the guide rod (523), and the two ends of the spring (524) are fixedly connected to the vertical plate (522) and the positioning bracket (52) respectively. The collar (51) corresponds to the deep end of the cross groove (43), and a limiting component is also provided on the positioning bracket (52). The limiting component includes two sets of round rods (8) that move through both sides of the positioning bracket (52). The two sets of round rods (8) are respectively fixed with a limiting plate (9) and a stop strip (10) at both ends. The top of the receiving box (53) is movably fitted with a cover plate (531), and both sides of the top surface of the receiving box (53) are provided with sink grooves (532). Straight rods (534) are fixedly installed inside the two sink grooves (532). Slider blocks (533) are fixedly installed on both sides of the end face of the cover plate (531) and are movably sleeved on the outside of the straight rods (534) at their respective positions. Springs (535) are movably sleeved on the outer periphery of the two straight rods (534). A stop plate (536) is fixedly installed on the top surface of the cover plate (531) at one end corresponding to the slider (533).

2. The apparatus for preparing spherical silver powder for photovoltaic front-side conductive silver paste according to claim 1, characterized in that, The feeding mechanism (6) includes a hopper (61) fixedly installed on the right half of the roller (3) at the position corresponding to the feed inlet. A through groove (66) is provided through the middle of the bottom of the hopper (61). A cover plate (62) that fits the outer surface of the roller (3) is movably installed inside the through groove (66). A slot with the same size as the feed inlet is provided at one end of the cover plate (62). Vertical plates (63) are fixedly provided at both ends of the cover plate (62). An arc rod (64) is fixedly provided on one side of the hopper (61). The end of the arc rod (64) away from the hopper (61) movably passes through the vertical plate (63) at its position. A spring (65) is movably sleeved on the outer circumference of the arc rod (64). The two ends of the spring (65) are fixedly connected to the hopper (61) and the vertical plate (63) at the corresponding position, respectively.

3. The apparatus for preparing spherical silver powder for photovoltaic front-side conductive silver paste according to claim 1, characterized in that, Both brackets (2) include a support plate (21) fixed on the top surface of the support base (1) and a buckle plate (22) hinged to the top edge of the support plate (21). The support plate (21) and the buckle plate (22) are in a buckling state with a semi-circular groove in the middle of their opposite sides. The two spindles (41) are fixed with a locking block (13) at the middle of their opposite ends. The output shaft ends of the two drive motors are provided with a slot (14) that matches the locking block (13) at their respective positions. The locking block (13) and the slot (14) in the buckling state are both located inside the circular groove formed by the two semi-circular grooves at their respective positions.

4. The apparatus for preparing spherical silver powder for photovoltaic front-side conductive silver paste according to claim 1, characterized in that, Positioning blocks (11) are fixedly provided at the center of the bottom end face of the positioning bracket (52) and at the center of the bottom end face of the two positioning frames (416). Positioning slots (12) are provided at the top end face of the bearing seat (1) corresponding to the position of each positioning block (11), and the positioning blocks (11) are movably inserted into the corresponding positioning slots (12).

5. A method for preparing spherical silver powder for photovoltaic front-side conductive silver paste, relating to the apparatus for preparing spherical silver powder for photovoltaic front-side conductive silver paste according to any one of claims 1-4, characterized in that, The specific steps include the following: S1: Silver powder reduction: Prepare a 300 L silver nitrate solution with a mass concentration of 100 g / L in a reaction vessel using pure water, add 2 kg of polyvinylpyrrolidone-K30, heat to 30 ℃, add the first part of a 30% sodium hydroxide solution, adjust the pH of the silver nitrate solution to 5.0~6.0, add 10 L of a 35% formaldehyde solution, stir at 100 r / min, and when the reduction reaction reaches equilibrium after 30 min, add the remaining sodium hydroxide solution in steps to promote the completion of the reaction, and age for 5 min to obtain reduced silver powder for later use; S2: Detection of reduced silver powder: After washing and solid-liquid separation, the silver powder obtained in S1 above was dispersed with 0.7% stearic acid by weight of silver powder, placed in a tray, and dried at 70℃ for 24 h. The physical properties of the silver powder were then analyzed by scanning electron microscopy. S3: Silver powder ball milling: Take 4 kg of silver powder from S2 above, weigh 0.5% of the silver powder mass of stearic acid, dissolve it in 500 mL of ethanol, heat and clarify, add it to the silver powder to be ball milled and disperse it fully, mix it with 16 kg of steel balls with a diameter of 1.5 mm, and add it from the feeding mechanism (6) on the drum (3) into the cavity enclosed by the screen (415) and the right half of the drum (3). After grinding for 12 h, sieve it and collect it using the dust-free collection mechanism (5) for later use. S4: Ball milled silver powder test: After the silver powder obtained in S3 above is washed with ethanol until the silver powder mass loss on ignition is constant, the physical properties of the silver powder are measured.

Images