An array type anisotropic conductive adhesive film and a method for manufacturing the same
By regularly distributing conductive particles on the cross-section of the anisotropic conductive film, the problem of uneven distribution of conductive particles is solved, achieving high conductivity and low short-circuit rate, which is suitable for the preparation of array-type anisotropic conductive films.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NINGBO LIANSEN ELECTRONIC MATERIALS CO LTD
- Filing Date
- 2022-11-28
- Publication Date
- 2026-07-07
AI Technical Summary
The uneven distribution of conductive particles in existing anisotropic conductive films results in some areas having excessively high density, causing a short circuit risk, while other areas have insufficient density, causing excessively high circuit impedance or open circuits, thus affecting the effectiveness and lifespan of the circuit.
The conductive particles are regularly distributed on the cross-section of the anisotropic conductive film using an array design. The horizontal distance between two adjacent columns of conductive particles is 3 to 10 micrometers, and the vertical distance between two adjacent rows of conductive particles is 1 to 10 micrometers. The conductive particles are transferred through trapezoidal cylindrical holes on a roller press to achieve a uniform and staggered distribution.
It achieves uniform distribution of conductive particles, reduces the short-circuit rate to 0.01-0.03%, improves the conductivity and lifespan of the circuit, and the preparation process is simple, efficient, and can be mass-produced.
Smart Images
Figure CN115975517B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of anisotropic conductive adhesive technology, and relates to an array-type anisotropic conductive adhesive film and its preparation method. Background Technology
[0002] Currently, the distribution of conductive spheres / particles in anisotropic conductive films (ACF) within the anisotropic conductive adhesive layer is mostly random. When applied to precision electrode products, excessively high particle density in some areas poses a risk of short circuits between adjacent electrodes; conversely, insufficient particle density in other areas results in high circuit impedance or open circuits, ultimately leading to circuit failure. Therefore, it is necessary to find a method to achieve a uniform distribution of conductive particles within the anisotropic conductive adhesive layer to ensure effectiveness and lifespan during application.
[0003] Chinese patent application (publication number: CN110277186A) discloses a method of filling grooves in a base film by naturally rolling several conductive balls on the surface of the grooved substrate. Chinese patent application (publication number: TW201909359A) discloses a method of uniformly distributing and filling cavities with multiple anisotropic conductive balls, with the anisotropic conductive balls outside the cavities being scraped off. In other words, existing technologies have disclosed methods of controlling the position of conductive balls by creating holes, but these methods are complex and inefficient. Chinese patent application (publication number: CN109273143A) discloses a method of uniformly distributing multiple anisotropic conductive balls onto a semi-circular cavity mold using a ball-spraying machine, applying negative pressure to grasp the anisotropic conductive balls; however, this method cannot guarantee that each cavity is filled with conductive balls, easily leading to empty cavities, and the ball-spraying machine also wastes conductive balls. Summary of the Invention
[0004] The purpose of this invention is to address the aforementioned problems in the prior art by proposing an array-type anisotropic conductive film with an alternating distribution of conductive particles.
[0005] The objective of this invention can be achieved through the following technical solutions:
[0006] An array-type anisotropic conductive film, wherein conductive particles are regularly distributed in the array-type anisotropic conductive film, and on the cross-section of the array-type anisotropic conductive film, the horizontal distance between two adjacent columns of conductive particles is 3 to 10 micrometers, and the vertical distance between two adjacent rows of conductive particles is 1 to 10 micrometers; the cross-section of the array-type anisotropic conductive film has N rows of conductive particles, where N≥2.
[0007] Preferably, the cross-section of the array-type anisotropic conductive film has 2 to 6 rows of conductive particles.
[0008] Further preferably, the cross-section of the array-type anisotropic conductive film has N rows of conductive particles, and the conductive particles in the Nth row are staggered with the conductive particles in the (N-1)th row.
[0009] Preferably, the thickness of the array-type anisotropic conductive film is 10–65 micrometers.
[0010] Preferably, the diameter of the conductive particles is 2 to 18 micrometers.
[0011] Preferably, the content of conductive particles in the array-type anisotropic conductive film is 0.1% to 5%.
[0012] Preferably, the conductive particles are transferred from the trapezoidal cylindrical holes on the rollers of the roller press into a pre-made anisotropic conductive film.
[0013] This invention also discloses a method for preparing an array-type anisotropic conductive adhesive film. The preparation method includes: preparing anisotropic conductive adhesive coating liquid from all raw materials except conductive particles, coating and drying to obtain a pre-made anisotropic conductive adhesive film; transferring it to a roller press via a conveyor belt, wherein an elastic layer is provided on the outer surface of the roller, and small holes are opened on the surface of the elastic layer, each containing 1 to 3 conductive particles; transferring the conductive particles in the small holes to the pre-made anisotropic conductive adhesive film by pad printing; drying again; and cutting, winding and packaging after complete drying.
[0014] Preferably, the upper roller has a three-layer structure: an inner rigid wheel layer, a middle storage layer, and an outer elastic layer; conductive particles in the storage layer are transferred in stages to the small holes in the elastic layer.
[0015] Further preferably, the elastic layer and the storage layer have openings that are connected.
[0016] Further optimization involves connecting the rigid wheel layer in the upper roller to the motor to achieve rotation; the storage layer is used to store conductive particles.
[0017] Preferably, the small hole is in the shape of a trapezoidal cylinder with a cross-section of a regular isosceles trapezoid.
[0018] Compared to conventional semi-circular structures, the trapezoidal cylinder of this invention is more conducive to the transmission and transfer printing of conductive particles.
[0019] More preferably, the diameter of the open end of the cylinder is 5 to 30 micrometers, the diameter of the other end corresponding to the open end is 5 to 20 micrometers, and the height of the cylinder is 5 to 20 micrometers.
[0020] Preferably, the elastic layer has 2 to 50 rows of small holes distributed on it, with adjacent rows staggered.
[0021] Preferably, the preparation process of the array-type anisotropic conductive film is carried out in an integrated machine, which includes a coating unit, a first drying unit, a pad printing unit, a second drying unit, and a conveying unit; wherein the first drying unit includes ovens in sections 1, 2, and 3, and the second drying unit includes ovens in sections 4 and 5.
[0022] Further optimization involves pre-fabricating anisotropic conductive adhesive film that is semi-solid with a solid content of 80-90% before entering the pad printing unit.
[0023] Preferably, the elastic layer material in the upper roller includes one or more of rubber and polyurethane.
[0024] Preferably, both the upper and lower rollers are rigid structures made of materials including stainless steel.
[0025] Compared with the prior art, the present invention has the following beneficial effects:
[0026] 1. In the array-type anisotropic conductive film of the present invention, the conductive particles are uniformly distributed in an array, and there are more than two rows of conductive particles in its cross section. The conductive particles in adjacent rows are staggered to ensure the conductivity in subsequent applications and reduce the short circuit rate to 0.01-0.03%.
[0027] 2. This invention uses trapezoidal cylindrical pores for depositing and pad printing conductive particles. Compared with conventional semi-circular structures, this method can better ensure that conductive particles are transferred to the designated positions in the anisotropic conductive film and can also prevent conductive particles from adhering to the pores and causing cavities.
[0028] 3. This invention uses an integrated machine to complete the preparation of array-type anisotropic conductive films through a production line-like equipment. The preparation process is simple, efficient, and can be mass-produced. Attached Figure Description
[0029] Figure 1 This is a schematic diagram of the cross-section of the array-type anisotropic conductive film described in Embodiment 1 of the present invention. Detailed Implementation
[0030] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.
[0031] Unless otherwise specified, the technical solution adopted in this invention is a conventional method and will not be described in detail.
[0032] The present invention employs an integrated machine, including a coating unit, a first drying unit, a pad printing unit, a second drying unit, and a conveying unit; wherein the first drying unit includes ovens in sections 1, 2, and 3, and the second drying unit includes ovens in sections 4 and 5.
[0033] All raw materials except conductive particles are made into anisotropic conductive adhesive coating liquid. The coating liquid is applied to the substrate by a coating machine and then dried in the first drying unit to obtain a pre-made anisotropic conductive adhesive film with a solid content of 80-90%. The pre-made anisotropic conductive adhesive film is then conveyed to a roller press via a conveyor belt.
[0034] The pad printing unit's roller press includes an upper roller and a lower roller made of stainless steel. The outer surface of the upper roller is also provided with an elastic layer with a thickness of 30 to 50 micrometers. Small holes are opened on the surface of the elastic layer, and adjacent rows are staggered. The small holes are trapezoidal cylinders with a cross-section of a regular isosceles trapezoid. The diameter of the open end of the cylinder is 5 to 30 micrometers, the diameter of the other end corresponding to the open end is 5 to 20 micrometers, and the height of the cylinder is 5 to 20 micrometers.
[0035] The elastic layer material includes one or more of rubber and polyurethane.
[0036] Each small hole contains 1 to 3 conductive particles, which are transferred from the intermediate storage layer in the upper roller to the small holes in the elastic layer in stages.
[0037] Keeping the lower roller stationary, rotate the upper roller to transfer the conductive particles in the regularly distributed small holes to the pre-made anisotropic conductive film by pad printing. Repeat 2 to 6 times to obtain an array of anisotropic conductive films with 2 to 6 rows of conductive particles in the vertical direction (cross-section of the anisotropic conductive film).
[0038] Then rotate the lower roller and repeat the above pad printing process.
[0039] Then it enters the second drying unit, where the arrayed anisotropic conductive film is dried, cut, rolled up, and packaged.
[0040] Example 1
[0041] In this embodiment, the elastic layer surface of the rollers on the roller press has multiple rows of small holes, with adjacent rows staggered. The small holes are trapezoidal cylinders with a cross-section of a regular isosceles trapezoid. The diameter of the open end of the cylinder is 9 micrometers, and the diameter of the other end corresponding to the open end is 7 micrometers. The height of the cylinder is 10 micrometers. Each small hole contains one conductive particle with a diameter of 3 micrometers. The thickness of the pre-fabricated anisotropic conductive film is 50 micrometers.
[0042] All raw materials except conductive particles are made into anisotropic conductive adhesive coating liquid. The coating liquid is applied to the substrate by a coating machine and then dried in the first drying unit to obtain a pre-made anisotropic conductive adhesive film with a solid content of 82%. The pre-made anisotropic conductive adhesive film is then conveyed to the roller press by a conveyor belt.
[0043] After reaching the set position, keep the lower roller stationary and rotate the upper roller to transfer the conductive particles in the rows of holes to the pre-made anisotropic conductive film through pressure transfer printing. Adjust the transfer printing pressure and repeat 5 times to obtain an array-type anisotropic conductive film with 5 rows of conductive particles in the vertical direction (cross-section of the anisotropic conductive film). The schematic diagram of this cross-section is shown below. Figure 1 As shown.
[0044] In the cross-section of the anisotropic conductive film, it can be observed that the conductive particles in rows 1, 3, and 5 are interspersed with the conductive particles in rows 2 and 4; in the horizontal direction, the distance between two adjacent conductive particles is 9 micrometers, and in the vertical direction, the vertical distance between two adjacent conductive particles is 3 micrometers; in the same vertical direction, the vertical distance between the conductive particles in rows 1 and 3 is 9 micrometers.
[0045] Rotate the lower roller until it reaches the next set position, then repeat the above pad printing operation.
[0046] The anisotropic conductive film is conveyed to the second drying unit. After the array-type anisotropic conductive film is dried (solid content 98%), it is cut, wound up, and packaged.
[0047] The prepared array-type anisotropic conductive film was subjected to performance testing, and the conductivity failure rate (short circuit rate) was 0.01%.
[0048] Example 2
[0049] In this embodiment, the elastic layer surface of the rollers on the roller press has multiple rows of small holes, with adjacent rows staggered. The small holes are trapezoidal cylinders with a cross-section of a regular isosceles trapezoid. The diameter of the open end of the cylinder is 25 micrometers, and the diameter of the other end corresponding to the open end is 18 micrometers. The height of the cylinder is 15 micrometers. Each small hole contains one conductive particle with a diameter of 11 micrometers. The thickness of the pre-fabricated anisotropic conductive film is 50 micrometers.
[0050] All raw materials except conductive particles are made into anisotropic conductive adhesive coating liquid. The coating liquid is applied to the substrate by a coating machine and then dried in the first drying unit to obtain a pre-made anisotropic conductive adhesive film with a solid content of 81%. The pre-made anisotropic conductive adhesive film is then conveyed to the roller press by a conveyor belt.
[0051] After reaching the set position, keep the lower roller stationary and rotate the upper roller to transfer the conductive particles in the row holes to the pre-made anisotropic conductive film by pad printing. Repeat twice to obtain an array of anisotropic conductive films with two rows of conductive particles in the vertical direction (cross-section of the anisotropic conductive film).
[0052] In the cross-section of the anisotropic conductive film, it can be observed that the conductive particles in the first row and the conductive particles in the second row are distributed alternately.
[0053] The anisotropic conductive film is conveyed to the second drying unit, and after the array of anisotropic conductive films is dried, it is cut, rolled up, and packaged.
[0054] The prepared array-type anisotropic conductive film was subjected to performance testing, and the conductivity defect rate was 0.01%.
[0055] Example 3
[0056] Compared with Example 2, the difference is that the shape of the small hole is a trapezoidal cylinder with a cross-section of a regular isosceles trapezoid. The diameter of the open end of the cylinder is 16 micrometers, the diameter of the other end corresponding to the open end is 13 micrometers, and the height of the cylinder is 10 micrometers. Each small hole contains 2 conductive particles (called a group), and the diameter of the conductive particles is 6 micrometers. The thickness of the pre-fabricated anisotropic conductive film is 50 micrometers.
[0057] In the cross-section of the prepared array-type anisotropic conductive film, it can be observed that the conductive particles in the first row and the conductive particles in the second row are distributed alternately.
[0058] The prepared array-type anisotropic conductive film was subjected to performance testing, and the conductivity defect rate was 0.01%.
[0059] Example 4
[0060] Compared with Example 2, the difference is that the shape of the small hole is a trapezoidal cylinder with a cross-section of a regular isosceles trapezoid. The diameter of the open end of the cylinder is 22 micrometers, the diameter of the other end corresponding to the open end is 15 micrometers, and the height of the cylinder is 10 micrometers. Each small hole contains 2 conductive particles (called a group), and the diameter of the conductive particles is 7 micrometers. The thickness of the pre-fabricated anisotropic conductive film is 50 micrometers.
[0061] In the cross-section of the prepared array-type anisotropic conductive film, it can be observed that the conductive particles in the first row and the conductive particles in the second row are distributed alternately.
[0062] The prepared array-type anisotropic conductive film was subjected to performance testing, and the conductivity defect rate was 0.02%.
[0063] Example 5
[0064] Compared with Example 2, the difference is that the solid content of the pre-made anisotropic conductive film is 92%.
[0065] Performance testing revealed a conductivity defect rate of 0.11%.
[0066] This is because the solid content of the pre-made anisotropic conductive film is too high, resulting in a short vertical distance between two adjacent groups of conductive particles; the conductive particles cannot reach the set position.
[0067] Example 6
[0068] Compared with Example 2, the difference is that the solid content of the pre-made anisotropic conductive film is 75%.
[0069] Performance testing revealed a conductivity defect rate of 0.25%.
[0070] This is because the solid content of the pre-made anisotropic conductive adhesive film is too low, causing the conductive particles to shift in the anisotropic conductive adhesive and fail to maintain an array.
[0071] Example 7
[0072] Compared with Example 2, the difference is that the elastic layer surface of the upper roller has small holes, which are hemispherical with an opening diameter of 13 micrometers; the diameter of the conductive particles is 6 micrometers.
[0073] Performance testing revealed a conductivity defect rate of 0.24%.
[0074] This is because the aperture is hemispherical, which makes it impossible for conductive particles to remain stably inside the aperture, causing some to fall out and form a cavity.
[0075] Example 7
[0076] Compared with Example 2, the difference is that a ball spraying machine is used to directly place conductive particles into the small holes on the surface of the elastic layer, and an air blowing method is used to remove excess conductive particles.
[0077] Performance testing revealed a conductivity defect rate of 0.35%.
[0078] The ball spraying machine caused cavities in some of the small holes, and the number of conductive particles in the small holes could not be stably controlled, resulting in poor conductivity.
[0079] Comparative Example 1
[0080] The elastic layer surface of the rollers used in this comparative example has multiple rows of small holes, with adjacent rows staggered. The small holes are trapezoidal cylinders with a cross-section of a regular isosceles trapezoid. The diameter of the open end of the cylinder is 6 micrometers, and the diameter of the other end corresponding to the open end is 5 micrometers. The height of the cylinder is 6 micrometers. Each small hole contains one conductive particle with a diameter of 3 micrometers. The thickness of the pre-fabricated anisotropic conductive film is 20 micrometers.
[0081] All raw materials except conductive particles are made into anisotropic conductive adhesive coating liquid. The coating liquid is applied to the substrate by a coating machine and then dried in the first drying unit to obtain a pre-made anisotropic conductive adhesive film with a solid content of 83%. The pre-made anisotropic conductive adhesive film is then conveyed to the roller press by a conveyor belt.
[0082] After reaching the set position, the upper and lower rollers are rotated simultaneously to transfer the conductive particles in the upper roller to the horizontal surface of the anisotropic conductive film in sequence, thereby obtaining an array of anisotropic conductive films with one row of conductive particles in the vertical direction (cross-section of the anisotropic conductive film); the upper and lower rollers are rotated to continue the transfer printing in the horizontal direction of the array of anisotropic conductive films.
[0083] The prepared array-type anisotropic conductive film was subjected to performance testing. The low number of conductive particles resulted in poor conductivity, and the conductivity defect rate was 0.05%.
[0084] Comparative Example 2
[0085] Compared with Example 1, the difference is that the 5 rows of conductive particles are not staggered, but the vertical distance between the conductive particles in adjacent rows remains unchanged.
[0086] The prepared array-type anisotropic conductive film was subjected to performance testing, and the conductivity failure rate was 0.08%.
[0087] In summary, this invention transfers conductive particles from the trapezoidal cylindrical holes on the rollers of a roller press into a pre-made anisotropic conductive film, resulting in a uniformly distributed array of anisotropic conductive films with at least two rows of conductive particles on its cross-section. The adjacent rows of conductive particles are staggered, ensuring conductivity in subsequent applications and reducing the short-circuit rate to 0.01-0.03%.
[0088] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.
Claims
1. A method for preparing an array-type anisotropic conductive adhesive film, characterized in that, The preparation process of the array-type anisotropic conductive adhesive film is carried out in an integrated machine, which includes a coating unit, a first drying unit, a pad printing unit, a second drying unit, and a conveying unit. The first drying unit includes ovens sections 1, 2, and 3, and the second drying unit includes ovens sections 4 and 5. The preparation method includes: All raw materials except conductive particles are made into anisotropic conductive adhesive coating liquid. The coating liquid is applied to the substrate by a coating machine and then dried in the first drying unit to obtain a pre-made anisotropic conductive adhesive film with a solid content of 80-90%. The pre-made anisotropic conductive adhesive film is then conveyed to the roller press via a conveyor belt. The pad printing unit's roller press includes upper and lower rollers made of stainless steel. The upper roller has a three-layer structure: an inner rigid wheel layer, a middle material storage layer, and an outer elastic layer. The elastic layer is connected to the storage layer through openings; Each small hole contains 1 to 3 conductive particles, which are transferred from the intermediate storage layer in the upper roller to the small holes in the elastic layer in stages. The surface of the elastic layer has small holes, which are distributed alternately in two adjacent rows; the shape of the small holes is a trapezoidal cylinder with a cross-section of a regular isosceles trapezoid. Keeping the lower roller stationary, rotate the upper roller to transfer the conductive particles in the regularly distributed small holes to the pre-made anisotropic conductive film by pad printing. Then rotate the lower roller and repeat the above pad printing process; Then it enters the second drying unit. After the array-type anisotropic conductive film is dried, it is cut, rolled up, and packaged to obtain the array-type anisotropic conductive film. The cross-section of the array-type anisotropic conductive film has N rows of conductive particles, with the conductive particles in the Nth row and the conductive particles in the (N-1)th row arranged alternately; N≥2; The horizontal distance between two adjacent columns of conductive particles is 3 to 10 micrometers, and the vertical distance between two adjacent rows of conductive particles is 1 to 10 micrometers.
2. The method for preparing an array-type anisotropic conductive film according to claim 1, characterized in that, The thickness of the array-type anisotropic conductive film is 10-65 micrometers; the diameter of the conductive particles is 2-18 micrometers.
3. The method for preparing an array-type anisotropic conductive film according to claim 1, characterized in that, The content of conductive particles in the array-type anisotropic conductive film is 0.1-5%.
4. The method for preparing an array-type anisotropic conductive film according to claim 1, characterized in that, The diameter of the open end of the trapezoidal cylinder is 5-30 micrometers, the diameter of the other end corresponding to the open end is 5-20 micrometers, and the height of the trapezoidal cylinder is 5-20 micrometers.
5. The method for preparing an array-type anisotropic conductive film according to claim 1, characterized in that, The elastic layer has 2 to 50 rows of small holes distributed on it, with adjacent rows staggered.
6. The method for preparing an array-type anisotropic conductive film according to claim 1, characterized in that, The elastic layer material includes one or more of rubber and polyurethane.