Conductive film manufacturing method

Abstract

To enable the arrangement design of conductive particles for a conductive film that is easily adaptable for connection to a mini-LED or a micro-LED substrate to be effortlessly carried out.SOLUTION: Provided is a method for designing the arrangement of conductive particles P in a conductive film when connecting a terminal in length of L1 and in width of L2 using the conductive film where the conductive particles P are held in an insulating resin layer. First, it is assumed that the conductive particles P are arranged at lattice points of a rectangular or an orthorhombic lattice, and the lattice axis is orthogonal to the longitudinal or the lateral direction of the conductive film. Then, the number density, etc., of the conductive particles P in the conductive film are set, and then, from lattice points that are at the distance of terminal length L1 or less from one lattice point A, a lattice point B is selected, where the angle that a line linking said lattice point and the lattice point A forms with the lateral direction of the film is smallest, and a rotation angle α of the lattice is found, where the lattice point A and the lattice point B overlap in the lateral direction of the film when the lattice is rotated around the lattice point A, with the inclination angle of the lattice axis of the conductive film determined by the angle α.SELECTED DRAWING: Figure 3B

Description

[Technical Field]

[0001] The present invention relates to a method for designing conductive films. [Background technology]

[0002] Conductive films, which have conductive particles held within an insulating resin layer, are widely used when mounting electronic components such as IC chips containing optical semiconductor elements like mini-LEDs and micro-LEDs onto wiring boards and the like.

[0003] The conductive film used for mounting IC chips is also called anisotropic conductive film. The conductive film in this invention also includes this anisotropic conductive film.

[0004] An anisotropic conductive film is a film interposed between the terminal rows of an electronic component and the terminal rows of a substrate to create a connection structure, where conductivity is exhibited only in the film thickness direction and not in the film surface direction. Furthermore, an anisotropic conductive connection refers to a connection between the terminal rows of an electronic component and the terminal rows of a substrate, where conductivity is present in the stacking direction of the electronic component and the substrate, but not in the direction of the terminal rows.

[0005] In anisotropic conductive films, the increasing density of electronic component mounting and the resulting finer terminal pitches necessitate enhancing the trapping ability of conductive particles at terminals while simultaneously preventing short circuits between adjacent terminals.

[0006] In response to such demands, it has been proposed to arrange the conductive particles in an anisotropic conductive film in a lattice-like arrangement, and to tilt the direction of the arrangement of the conductive particles with respect to both the longitudinal and transverse directions of the anisotropic conductive film (Patent Document 1).

[0007] Furthermore, to ensure reliable connection of electronic components even if the crimping temperature during mounting fluctuates and the terminal position shifts due to these temperature fluctuations, it is known to arrange the terminals of electronic components in a radial parallel arrangement (so-called fan-out wiring) (Patent Document 2).

[0008] In recent years, due to the demand for even finer pitches, misalignment between connecting terminals can result in a net inter-terminal space of less than 5 μm, or a width that is only slightly larger than the particle diameter of the conductive particles contained in the anisotropic conductive film (for example, 1 μm for a particle diameter of about 3 μm). Even in such cases, anisotropic conductive films are required to prevent short circuits.

[0009] Furthermore, when connecting fan-out type terminal rows using an anisotropic conductive film, if the conductive particles of the anisotropic conductive film are simply arranged in a grid, the angle between the terminal arrangement direction and the longitudinal direction of the terminals will differ sequentially in a fan-out type terminal row. Therefore, even if the grid axis is tilted with respect to the longitudinal direction of the film, the difference in the number of conductive particles captured by each terminal will be large, and the arrangement of the conductive particles captured by each terminal will differ from terminal to terminal. As a result, problems such as difficulty in determining the quality of the connection may arise.

[0010] Therefore, even when the terminal arrangement pattern is radial, and when the space between terminals is less than 5 μm or only a very small margin added to the diameter of the conductive particles contained in the anisotropic conductive film (for example, 1 μm for a particle diameter of about 3 μm), a new particle arrangement has been proposed to ensure good anisotropic conductive connection. In this particle arrangement, when the longitudinal direction of the anisotropic conductive film is divided by the terminal pitch, a first arrangement axis A1 and a second arrangement axis A2 extending in the longitudinal direction of the terminal are repeatedly arranged within the range of one terminal pitch as the arrangement axes of conductive particles, and the positional relationship between the conductive particles on the first arrangement axis A1 and the conductive particles on the second arrangement axis A2 is defined in relation to the average particle diameter of the conductive particles (Patent Document 3). [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Patent No. 6119718 [Patent Document 2] Japanese Patent Publication No. 2015-232660 [Patent Document 3] Japanese Patent Publication No. 2020-095922 [Overview of the project] [Problems that the invention aims to solve]

[0012] However, the anisotropic conductive film described in Patent Document 3 has many parameters for determining the arrangement of conductive particles in the anisotropic conductive film, making the method for determining the arrangement pattern of conductive particles practically complicated.

[0013] In contrast, the present invention aims to provide an easy way to design the arrangement of conductive particles for conductive films that can accommodate fine pitches and are suitable for connection to substrates of mini-LEDs and micro-LEDs. [Means for solving the problem]

[0014] The inventors of the present invention have conceived a method for designing the arrangement of conductive particles in a conductive film, in which conductive particles are arranged in a grid pattern on an insulating resin layer. This method involves first determining the number density of conductive particles according to the terminal pitch to be connected by the conductive film, then determining the pitch of the grid axis according to that number density, and then determining the inclination of the grid axis according to the length of the terminal to be connected by the conductive film. This method allows for the simple design of the arrangement of conductive particles for a conductive film that can accommodate connections with fine pitches, and thus the inventors have completed the present invention.

[0015] In other words, the present invention relates to a method for designing the arrangement of conductive particles in a conductive film, in which conductive particles of a predetermined particle size are held in an insulating resin layer when connecting terminals with terminal length L1 and terminal width L2 (where L1 ≥ L2), in a plan view, First, assume that the conductive particles are arranged at the lattice points of a rectangular lattice or an oblique lattice, and there is a lattice axis orthogonal to the longitudinal direction or the short-side direction of the conductive film (hereinafter also referred to as the film longitudinal direction or the film short-side direction). Set the particle density of the conductive particles in the conductive film, the pitch d1 of the conductive particles on the lattice axis in the film longitudinal direction corresponding to the particle density, and the pitch d2 of the conductive particles on the lattice axis in the film short-side direction (d2 = a·d1, where a is a coefficient). Next, among the lattice points within a distance of the terminal length L1 or less from a single lattice point A, select the lattice point B where the angle formed by the straight line connecting the lattice point and lattice point A with the film short-side direction is the smallest. Rotate the lattice around lattice point A to obtain the rotation angle α of the lattice where lattice point A and lattice point B overlap in the film short-side direction, and provide a design method for determining the inclination angle of the lattice axis of the conductive film based on the angle α.

Advantages of the Invention

[0016] According to the present invention, the capture property of the conductive particles at the terminals to be connected and the difficulty of occurrence of short circuits can be easily confirmed by simulation. In addition, since the lattice axis is angled according to the size of the terminals to be connected, short circuits can be prevented as much as possible at the set number density of the conductive particles, and the capture property of the conductive particles at each terminal can be improved.

[0017] Moreover, according to the present invention, the arrangement of the conductive particles does not become complicated. Therefore, when manufacturing a conductive film designed by the method of the present invention, it becomes easy to manufacture the master plate for determining the arrangement of the conductive particles, and the master plate can be manufactured by cutting processing in addition to laser processing.

Brief Description of the Drawings

[0018] [Figure 1] FIG. 1 is an explanatory diagram of the inclination angle α formed by the straight line connecting lattice point A where a certain conductive particle is located and lattice point B diagonally opposite to lattice point A with the lattice axis when the conductive particle is at lattice point A of a square lattice. [Figure 2] FIG. 2 is an explanatory diagram of the correspondence between a terminal having a predetermined terminal length and terminal width and the inclination angle α of the particle arrangement of the conductive particles suitable for connection to the terminal. [Figure 3A] Figure 3A is an explanatory diagram of the design method of the embodiment. [Figure 3B] Figure 3B is an explanatory diagram of the design method of the embodiment. [Figure 4A] Figure 4A is an explanatory diagram of the design method of the embodiment. [Figure 4B] Figure 4B is an explanatory diagram of the design method of the embodiment. [Figure 5] Figure 5 is a cross-sectional view of the conductive film 10A cut in the film thickness direction. [Figure 6] Figure 6 is a cross-sectional view of the conductive film 10B cut in the film thickness direction. [Figure 7A] Figure 7A is a diagram showing the particle arrangement of the connection state (i) of the conductive film of Experimental Example 1. [Figure 7B] Figure 7B is a diagram showing the particle arrangement of the connection state (ii) of the conductive film of Experimental Example 1. [Figure 8A] Figure 8A is a diagram showing the particle arrangement of the connection state (i) of the conductive film of Experimental Example 2. [Figure 8B] Figure 8B is a diagram showing the particle arrangement of the connection state (ii) of the conductive film of Experimental Example 2. [Figure 9A] Figure 9A is a diagram showing the particle arrangement of the connection state (i) of the conductive film of Experimental Example 3. [Figure 9B] Figure 9B is a diagram showing the particle arrangement of the connection state (ii) of the conductive film of Experimental Example 3. [Figure 10A] Figure 10A is a diagram showing the particle arrangement of the connection state (i) of the conductive film of Experimental Example 4. [Figure 10B] Figure 10B is a diagram showing the particle arrangement of the connection state (ii) of the conductive film of Experimental Example 4. [Figure 11A] Figure 11A is a diagram showing the particle arrangement of the connection state (i) of the conductive film of Experimental Example 5. [Figure 11B] Figure 11B is a diagram showing the particle arrangement of the connection state (ii) of the conductive film of Experimental Example 5. [Figure 12A]Figure 12A shows the particle arrangement of the connection state (i) of the conductive film in Experimental Example 6. [Figure 12B] Figure 12B shows the particle arrangement of the conductive film connection state (ii) in Experimental Example 6. [Figure 13] Figure 13 shows the particle arrangement of the conductive film connection state in Experimental Example 7. [Figure 14] Figure 14 shows the particle arrangement of the conductive film connection state in Experimental Example 8. [Modes for carrying out the invention]

[0019] The present invention will be described in detail below with reference to the drawings. In each figure, the same reference numerals represent the same or equivalent components.

[0020] <Planar arrangement of conductive particles> The present invention relates to a design method for designing the arrangement of conductive particles in a conductive film when connecting terminals with terminal length L1 and terminal width L2 (L1≧L2), using a conductive film in which conductive particles of a predetermined particle size are held at grid points of a rectangular or rhombic grid in an insulating resin layer in a plan view, and the grid axis of the grid is inclined in the longitudinal direction of the conductive film.

[0021] First, the key points of the design concept of this invention will be explained using the example of conductive particles being held at the lattice points of a square lattice. The same considerations can be applied to cases where conductive particles are held at the lattice points of a rectangular or rhombic lattice.

[0022] First, as shown in Figure 1, when conductive particles are located at lattice point A of a square lattice, consider the straight line connecting lattice point A and lattice point B, which is diagonally opposite to lattice point A. The angle (hereinafter also called the inclination angle) α that this straight line makes with the lattice axis (short side direction of the film) passing through lattice point A will be discrete because the position of lattice point B is restricted by the pitch d of the square lattice. Therefore, as shown in Figure 2, by aligning the direction of the inclination angle α with the direction of the terminal length, the optimal inclination angle α can be determined according to the terminal length and terminal width of the terminal connected by the conductive film. For example, for terminal 1x of a COG (Chip On Glass) shown by a dashed line in Figure 2, there is usually not a large difference between the terminal length L1 and the terminal width L2, so it is preferable to make the inclination angle α large in the particle arrangement of conductive particles in the conductive film for COG. On the other hand, for terminal 1y of a FOG (Film On Glass) shown by a dashed line in Figure 2, the terminal length L1 is usually long and the terminal width L2 is narrow, so it is preferable to make the inclination angle α small.

[0023] Based on the design philosophy described above, the design method of this embodiment will now be explained in detail. First, as shown in Figure 3A, we assume a particle arrangement in which conductive particles P are located at lattice points of a square lattice whose lattice axes are perpendicular to the longitudinal or short-width direction of the conductive film.

[0024] In this grid arrangement, the pitch d1 of conductive particles along the grid axis in the longitudinal direction of the film, and the pitch d2 of conductive particles along the grid axis in the short direction of the film (d2 = a·d1, where a is a coefficient) are appropriately determined according to the terminal length L1, terminal width L2 (L1 ≥ L2), and terminal arrangement pitch to be connected. For example, if the terminal arrangement pitch is twice the terminal width, the number density of conductive particles P in the conductive film is determined as follows according to the terminal length L1 and terminal width L2, and the pitch d1 and pitch d2 = a·d1 (where a is a coefficient) of conductive particles P are calculated from that number density. In this case, from the standpoint of simplifying the design, it is preferable to assume a rectangular grid by setting d1 = d2.

[0025] The number density of the conductive particles can be determined according to the intended use of the conductive film assumed from the terminal length L1 and the terminal width L2. Generally, the lower limit of the number density can be set to 500 particles / mm 2 or more in applications where a sparse state is preferred, and 20,000 particles / mm 2 or more, 40,000 particles / mm 2 or more, and further 50,000 particles / mm 2 or more. Also, for the upper limit of the number density, for the same reason, it can be set to 1,500,000 particles / mm 2 or less, 1,000,000 particles / mm 2 or less, and further 100,000 particles / mm 2 or less.

[0026] More specifically, for example, when the terminal length L1 is 50 - 100 μm and the terminal width L2 is 10 - 30 μm, the number density of the conductive particles is set within the range of 12,000 particles / mm 2 ~ 32,000 particles / mm 2 ; when the terminal length L1 is 100 - 1000 μm and the terminal width L2 is 8 - 30 μm, the number density of the conductive particles is set within the range of 4,000 particles / mm 2 ~ 20,000 particles / mm 2 ; and when the terminal length L1 is 7 - 30 μm and the terminal width L2 is 7 - 20 μm, it is preferable to set the number density of the conductive particles within the range of 20,000 particles / mm 2 ~ 100,000 particles / mm 2 .

[0027] On the other hand, when the terminal length L1 and the terminal width L2 to be connected are specifically determined, it is preferable to determine d1 and d2 so that the following angles α and pitches d1, d2 satisfy the following relationship. Thereby, the capture ability of the conductive particles at each terminal is improved. d1·cosα ≦ L2 or d2·sinα ≦ L1

[0028] In this invention, after setting the pitches d1 and d2 of the conductive particles, in order to ensure that one or more conductive particles are present within the range of terminal length L1 in the final particle arrangement of the conductive film, a circle with terminal length L1 is considered starting from a single lattice point A (Figure 3A).

[0029] Next, among the grid points that are at a distance of terminal length L1 or less from grid point A, we select the grid point B that has the smallest angle α' (α'≠0) between the line connecting that grid point and grid point A and the short-side direction of the film.

[0030] Then, as shown in Figure 3B, the rectangular grid is rotated by an angle α (│α│=│α'│) around grid point A so that grid point A and grid point B overlap in the short direction of the film. The rotation angle α at this time is taken as the inclination angle of the grid axis of the conductive film. That is, the arrangement of conductive particles P obtained by rotating the initial rectangular grid by rotation angle α so that the line connecting grid point A and grid point B is in the short direction of the film is taken as the final particle arrangement.

[0031] When the arrangement of conductive particles is determined in this way, even if terminal 1 is minute and terminal width L2 is smaller than pitch d2, conductive particles at lattice point B within a circle of terminal length L1 will be captured by the terminal. Therefore, in a typical terminal array of an ordinary electronic component where terminals of terminal length L1 and terminal width L2 are arranged at predetermined intervals in the terminal width direction, each terminal can capture at least one conductive particle. Thus, according to the design method of the present invention, it is possible to obtain an arrangement of conductive particles in which one or more conductive particles are captured at each terminal, even in minute terminals. In other words, it is possible to obtain the longest lattice pitch necessary for one conductive particle to be captured at each terminal for that terminal length.

[0032] In the design method of the present invention, when the grid axes are inclined at an angle α as shown in Figure 3B, and adjacent axes are designated as the first array axis and the second array axis, it is preferable to set the angle α such that the conductive particles P1 on the first array axis and the conductive particles P2 on the second array axis do not overlap in the longitudinal direction of the film. This prevents conductive particles from connecting with each other between terminals and causing a short circuit.

[0033] In the design method of the present invention, even when the conductive film corresponds to the terminals of a fan-out type terminal row, as shown in Figure 4A, first a rectangular grid of conductive particles P with grid pitches d1 and d2 is set. Next, from among the grid points that are at a distance of terminal length L1 or less from one grid point A, the grid point B that has the smallest angle α' between the line connecting that grid point and grid point A and the short direction of the film is selected. As shown in Figure 4B, the rectangular grid is rotated by angle α around grid point A so that grid points A and B overlap in the short direction of the film. The arrangement of conductive particles at this time is defined as the particle arrangement of the conductive film.

[0034] In this case, it is desirable to set the grid pitches d1 and d2 such that the angle β (β = 90 - α) that the arrangement axis of the resulting particle configuration makes with the longitudinal direction of the film is smaller than the fan-out angle θ. As a result, every terminal in the fan-out type terminal row intersects with the arrangement axis of the conductive particles, making it possible to capture conductive particles at each terminal.

[0035] On the other hand, in the design method of the present invention, the particle size of the conductive particles can be appropriately determined according to the application of the conductive film of the present invention, for example, it can be 1 μm or more and 30 μm or less, more preferably 1.5 μm or more and less than 10 μm.

[0036] <Position of conductive particles in the film thickness direction> When manufacturing a conductive film in which the arrangement of conductive particles is determined according to the design method of the present invention, it is preferable that the positions of the conductive particles P in the film thickness direction are aligned. For example, Figure 5 As shown in the conductive film 10A, when conductive particles P are embedded in a laminate of a high-viscosity insulating resin layer 2 and a low-viscosity insulating resin layer 3, the amount of embedding Lb of the conductive particles P in the film thickness direction can be aligned so that the conductive particles P and the high-viscosity insulating resin layer 2 are flush. This makes it easier to stabilize the capture of conductive particles P at the terminals.

[0037] On the other hand, in a conductive film in which the arrangement of conductive particles is determined according to the design method of the present invention, the conductive particles P may be exposed from the high-viscosity insulating resin layer 2, as shown in the conductive film 10B in Figure 6. Alternatively, the conductive particles P may be completely embedded in the high-viscosity insulating resin layer 2.

[0038] Here, the embedding amount Lb refers to the distance between the tangent plane 2p in the central part between adjacent conductive particles and the deepest part of the conductive particle P on the surface of the high-viscosity insulating resin layer 2 in which the conductive particle P is embedded (the surface on which the conductive particle P is exposed, or, if the conductive particle P is completely embedded in the high-viscosity insulating resin layer 2, the surface closest to the conductive particle P).

[0039] <High-viscosity insulating resin layer> The high-viscosity insulating resin layer 2 can be formed using a curable resin composition formed from a polymerizable compound and a polymerization initiator, similar to the insulating resin layer of the anisotropic conductive film described in Japanese Patent No. 6187665. In this case, a thermal polymerization initiator may be used as the polymerization initiator, a photopolymerization initiator may be used, or both may be used in combination. For example, a cationic polymerization initiator may be used as the thermal polymerization initiator, and an epoxy resin as the thermal polymerizable compound, while a photoradical polymerization initiator may be used as the photopolymerization initiator, and an acrylate compound as the photopolymerizable compound. A thermal anionic polymerization initiator may also be used as the thermal polymerization initiator. As the thermal anionic polymerization initiator, it is preferable to use a microencapsulated latent curing agent having an imidazole modified material as a nucleus and its surface coated with polyurethane.

[0040] <Minimum melt viscosity of high-viscosity insulating resin layer> The minimum melt viscosity of the high-viscosity insulating resin layer 2 is not particularly limited, but in order to suppress the unwanted flow of conductive particles P during thermocompression bonding in the connection of electronic components using conductive films, it is preferably 1500 Pa·s or more, more preferably 2000 Pa·s or more, even more preferably 3000 to 15000 Pa·s, and particularly preferably 3000 to 10000 Pa·s. This minimum melt viscosity can be determined, for example, using a rotary rheometer (manufactured by TA instruments), maintaining a constant measurement pressure of 5g, and using a measurement plate with a diameter of 8mm. More specifically, it can be determined by setting the temperature range to 30 to 200°C, the heating rate to 10°C / min, the measurement frequency to 10Hz, and the load variation on the measurement plate to 5g. The minimum melt viscosity can be adjusted by changing the type and amount of fine solids included as a melt viscosity modifier, or by changing the adjustment conditions of the resin composition.

[0041] <Low viscosity insulating resin layer> The low-viscosity insulating resin layer 3 is a resin layer whose minimum melt viscosity in the range of 30 to 200°C is lower than that of the high-viscosity insulating resin layer 2. In a conductive film in which the particle arrangement is designed according to the present invention, the low-viscosity insulating resin layer 3 is provided as needed. By laminating the low-viscosity insulating resin layer 3 on the high-viscosity insulating resin layer 2, when electronic components facing each other are thermocompressed together via the conductive film 10A, the spaces formed by the electrodes and bumps of the electronic components can be filled with the low-viscosity insulating resin layer 3, thereby improving the adhesion between the electronic components.

[0042] Furthermore, the greater the difference between the minimum melt viscosity of the high-viscosity insulating resin layer 2 and the minimum melt viscosity of the low-viscosity insulating resin layer 3, the more the space between electronic components connected via the conductive film 10A is filled with the low-viscosity insulating resin layer 3, thus improving the adhesion between electronic components. Also, the greater this difference, the smaller the amount of movement of the high-viscosity insulating resin layer 2, which holds the conductive particles P, is relative to the low-viscosity insulating resin layer 3 during thermocompression bonding, thus improving the capture of conductive particles P at the terminals.

[0043] <Layer thickness of high-viscosity insulating resin layer and low-viscosity insulating resin layer> The thickness of the high-viscosity insulating resin layer 2 is preferably 0.3 times or more, more preferably 0.6 times or more, even more preferably 0.8 times or more, and particularly preferably 1 time or more, relative to the average particle diameter D of the conductive particles P, in order to ensure that the conductive particles P are stably pressed into the high-viscosity insulating resin layer 2 during the manufacturing process of the conductive film. Furthermore, the upper limit of the thickness of the high-viscosity insulating resin layer 2 can be determined according to the terminal shape, terminal thickness, and arrangement pitch of the electronic components to be connected, but if the layer thickness becomes too thick, the conductive particles P will be unnecessarily susceptible to the effects of resin flow during connection, so it is preferably 20 times or less, and more preferably 15 times or less, relative to the average particle diameter D of the conductive particles P.

[0044] The low-viscosity insulating resin layer 3 is provided in the conductive film as needed. When the low-viscosity insulating resin layer is provided in the conductive film, the lower limit of the thickness of the low-viscosity insulating resin layer is preferably 0.2 times or more, more preferably 1 time or more, the average particle diameter D of the conductive particles P. The upper limit of the thickness of the low-viscosity insulating resin layer 3 is preferably 50 times or less, more preferably 15 times or less, and even more preferably 8 times or less, the average particle diameter D of the conductive particles P, because if it becomes too thick, the difficulty of lamination with the high-viscosity insulating resin layer 2 increases.

[0045] Furthermore, the total thickness of the high-viscosity insulating resin layer 2 and the low-viscosity insulating resin layer 3 is preferably thinner in terms of suppressing unnecessary flow of conductive particles P when connecting electronic components, accommodating the reduction of bumps in the connected electronic components, suppressing resin overflow and blocking when the conductive film is wound into a coil, and increasing the film length per unit weight of the conductive film. However, if it becomes too thin, the handling of the conductive film deteriorates. Also, it becomes difficult to adhere the conductive film to the electronic components, and there is a risk that the necessary adhesive strength cannot be obtained during temporary bonding when connecting electronic components, and there is a risk that the necessary adhesive strength cannot be obtained during final bonding due to insufficient resin. For this reason, the lower limit of the total thickness is preferably 0.6 times or more, more preferably 0.8 times or more, even more preferably 1 time or more, and particularly preferably 1.2 times or more, relative to the average particle diameter D of the conductive particles P.

[0046] On the other hand, if the total thickness becomes too thick, the conductive particles P become unnecessarily susceptible to the effects of resin flow when the conductive film is heat-pressed onto the electronic components. Also, if fillers are included in these resin layers for viscosity adjustment or other reasons, the absolute amount of fillers may increase, potentially hindering the heat-pressing of the electronic components. Therefore, the upper limit of the total thickness of the resin layer is preferably 50 times or less, more preferably 15 times or less, and even more preferably 8 times or less, the average particle diameter D of the conductive particles P. Furthermore, to prevent the thrust required for the pressing tool from becoming too high during heat-pressing, the total thickness of the resin layer is preferably 4 times or less, more preferably 3 times or less, even more preferably 2 times or less, even more preferably 1.8 times or less, and particularly 1.5 times or less, the average particle diameter D of the conductive particles P. The ratio of the thickness of the high-viscosity insulating resin layer 2 to the low-viscosity insulating resin layer 3 can be appropriately adjusted based on the relationship between the average particle diameter D of the conductive particles P, the bump height, and the required adhesive strength.

[0047] <Conductive film winding assembly> The conductive film in which the arrangement of conductive particles is determined according to the present invention can be in the form of a winding. There are no particular restrictions on the length of the winding, but from the viewpoint of handling the shipped product, it is preferably 5000m or less, more preferably 1000m or less, and even more preferably 500m or less. On the other hand, from the viewpoint of mass production of the winding, it is preferable to have a length of 5m or more.

[0048] There are no particular restrictions on the film width in the winding assembly, but it is preferable to have a film width of 0.3 mm or more from the perspective of the lower limit of the slit width when manufacturing a winding assembly by slitting a wide conductive film, and more preferably 0.5 mm or more from the perspective of stabilizing the slit width. There are no particular restrictions on the upper limit of the film width, but from the viewpoint of portability and handling, it is preferable to have a film width of 700 mm or less, and more preferably 600 mm or less. From the viewpoint of practical handling of the conductive film, it is preferable to select a film width between 0.3 and 400 mm. That is, when the conductive film is used at the edge of the electronic components to be connected, the film width is often a few mm or less, and when it is used by directly attaching it to relatively large electronic components (such as substrates with electrode wiring and mounting parts on one surface or wafers before cutting), a film width of about 400 mm may be required. In general, conductive films are often used with a film width of 0.5 to 5 mm.

[0049] <Method for manufacturing conductive film> The method for manufacturing a conductive film in which conductive particles are arranged according to the present invention is not particularly limited. For example, in order to arrange the conductive particles in a predetermined arrangement, a transfer mold is first manufactured. The method for manufacturing the transfer mold will be described later.

[0050] Next, conductive particles are filled into the recesses of the transfer mold, and a high-viscosity insulating resin layer formed on a release film is placed over them and pressure is applied to push the conductive particles into the high-viscosity insulating resin layer, thereby transferring the conductive particles to the high-viscosity insulating resin layer, or a low-viscosity insulating resin layer is further laminated on top of the conductive particles to produce a conductive film.

[0051] Alternatively, a conductive film may be manufactured by filling the recesses of a transfer mold with conductive particles, covering them with a high-viscosity insulating resin layer, transferring the conductive particles from the transfer mold to the surface of the high-viscosity insulating resin layer, and pressing the conductive particles into the high-viscosity insulating resin layer.

[0052] In addition to the type in which conductive particles are filled into the recessed areas, a type in which a slight adhesive is applied to the top surface of the convex area so that the conductive particles adhere to that surface may also be used as a transfer type.

[0053] Furthermore, as a method for arranging conductive particles in a predetermined configuration, instead of using a transfer mold, a method of passing conductive particles through holes provided in a predetermined configuration may be used.

[0054] <Manufacturing method for transfer molds> Transfer molds can be manufactured by known methods. For example, first, a metal plate such as a nickel plate is subjected to known cutting or laser processing to form a pattern of conductive particles as recesses or protrusions on the metal plate, thereby creating a transfer mold master. The metal master may also be manufactured by patterning using techniques such as photolithography or printing.

[0055] Next, a transfer mold can be produced by applying a curable resin composition to a transfer mold master disc, curing it, and then separating it from the master disc.

[0056] <Method for connecting electronic components using conductive film> The present invention provides a method for connecting electronic components using a conductive film in which conductive particles are arranged. For example, one electronic component is placed on a stage, another electronic component is placed on top of it via the conductive film, and the connected structure is manufactured by heating and pressing with a crimping tool. In this case, the electronic component placed on the stage is a second electronic component such as a light-emitting element like a mini-LED or micro-LED, an IC chip, an IC module, an FPC, a glass substrate, a plastic substrate, a rigid substrate, or a ceramic substrate, and the electronic component that is heated and pressed with the crimping tool is a first electronic component such as an FPC, an IC chip, an IC module, or a light-emitting element. In a more detailed method, the conductive film is temporarily attached to the second electronic component such as various substrates and temporarily crimped, and the first electronic component such as an IC chip is placed on the temporarily crimped conductive film and heat-pressed to manufacture the connected structure. It is also possible to manufacture the connected structure by temporarily attaching the conductive film to the first electronic component instead of the second electronic component. Furthermore, the crimping method in the connection method is not limited to heat-pressing; crimping using light curing or crimping using both heat and light may also be performed.

[0057] The conductive film with conductive particles arranged according to the present invention is highly significant because (i) it can effectively suppress short circuits between terminals when the terminal rows to be connected are fine-pitch, such as when connecting micro-LEDs to a display substrate, and (ii) it is highly significant when at least one of the first and second electronic components is made of a material that easily expands with heat, such as an FPC or plastic substrate. Specifically, it is preferable when using FOP (Flex On Plastic), FOG (Flex On Glass), COG (Chip On Glass), or COP (Chip On Plastic) connections, as it satisfies one or both of the above conditions (i) and (ii). Furthermore, the significance of the present invention is even greater when the terminal rows to be connected are of the fan-out type. Note that the fan-out arrangement is not limited to a configuration in which the terminal rows exist on only one of the components. The conductive film with conductive particles arranged according to the present invention can also be applied to known arrangements such as peripheral arrangements. [Examples]

[0058] The present invention will be described in detail below with reference to experimental examples. Experimental Examples 1-6 A conductive film was manufactured with the specifications shown in Table 1. In this conductive film, the particle size of the conductive particles was set to 3 μm. The conductive particles were arranged at the grid points of a square grid, and the angle (inclination angle) α between the grid axis and the short side of the conductive film was set to the value shown in Table 1. These particle arrangements are shown in Figures 7A, 7B to 12A, and 12B.

[0059] Using the conductive film of each experimental example, when connecting a first electronic component having a terminal row with a terminal length of 100 μm, a terminal width of 10 μm, and a terminal distance of 10 μm to a second electronic component having a similar terminal row, the connection state (i) was considered as the case where the opposing terminals of the first and second electronic components did not shift in the terminal width direction. As a performance evaluation in that case, the following were investigated by simulation: (a) the minimum number of conductive particles captured at each terminal, (b) the maximum number of particles per terminal, and (c) the maximum particle occupancy rate per terminal.

[0060] Furthermore, as connection state (ii), we considered the case where the opposing terminals of the first electronic component and the second electronic component were offset by 4 μm in the terminal width direction, and similarly investigated the performance evaluation in that case.

[0061] Furthermore, to determine the performance of connection states (i) and (ii), the conductivity was predicted from the minimum number of conductive particles captured at each terminal obtained in (d) simulation and evaluated as follows: a rating of C or higher was considered a pass, and a rating of D was considered a fail.

[0062] (d) Continuity and connectivity Rating A: 5 or more Rating B: 3-4 items Rating C: 1-2 items Rating D: 0 items

[0063] Furthermore, to determine the performance of connection states (i) and (ii), the likelihood of short circuits was predicted from the maximum number of conductive particles between terminals obtained in (e) simulation and evaluated as follows: a rating of C or higher was considered a pass, and a rating of D was considered a fail. Specifically, the maximum number of conductive particles between terminals and the area between terminals are used to calculate the particle occupancy rate between terminals by applying them to the following formula. Particle occupied area ratio between terminals = (maximum number of particles between terminals × particle area) / area between terminals × 100

[0064] (e) Difficulty of cutting Rating A: Less than 10% Rating B: 10% or higher, less than 18% Rating C: 18% or higher, less than 26% Rating D: 26% or higher

[0065] The results are shown in Table 1.

[0066] [Table 1]

[0067] Table 1 shows that by using a square lattice for the particle arrangement and tilting the inclination angle α at discrete magnitudes as shown in Figure 2, the performance evaluation and determination of the conductive film can be easily confirmed through simulation.

[0068] Experimental Examples 7 and 8 To confirm that changing the inclination angle α alters the minimum number of conductive particles captured at each terminal, we simulated the case where terminals with a terminal length L1 of 30 μm, a terminal width L2 = effective connection terminal width L3 = 5 μm, and a conductor distance L5 = 5 μm in the direction between terminals are connected with the following conductive particle arrangement. Particle size of conductive particles: 2 μm Particle density of conductive particles: 12,000 particles / mm 2 Particle arrangement interstitial distance: 9.1 μm

[0069] In this case, the inclination angle α was set to 14° in Experimental Example 7, and to 9.5° in Experimental Example 8. The results are shown in Figures 13 and 14 and Table 1.

[0070] In this experimental example, when conductive particles with a particle size of 2 μm are placed in a square grid with an interlattice distance of 9.1 μm for the terminals, it can be seen that at least one conductive particle is trapped in each terminal when the tilt angle α is 14° (Figure 13), and when the tilt angle α is 9.5° (Figure 14), it can be seen that terminals that do not trap conductive particles appear. [Explanation of symbols]

[0071] Terminals 1, 1x, 1y 2. High-viscosity insulating resin layer 3. Low-viscosity insulating resin layer 10A, 10B conductive film P conductive particles

Claims

1. A method for designing an arrangement of conductive particles in a conductive film in a case where a terminal having a terminal length L1 and a terminal width L2 (where L1 ≧ L2) is connected using a conductive film in which conductive particles having a predetermined particle diameter are held in an insulating resin layer in a plan view, the method comprising the steps of: First, the conductive particles are arranged at the lattice points of a rectangular lattice or an oblique lattice, and have a lattice axis perpendicular to the longitudinal direction or the transverse direction of the conductive film (hereinafter also referred to as the film longitudinal direction or the film transverse direction), and a number density of the conductive particles in the conductive film, a pitch d of the conductive particles on the lattice axis in the film longitudinal direction corresponding to the number density, and a pitch d of the conductive particles on the lattice axis in the film transverse direction (d = a d, a is a coefficient) are set; Next, among the lattice points located at a distance equal to or less than the terminal length L1 from one lattice point A, lattice point B is selected which has the smallest angle between the straight line connecting that lattice point and lattice point A and the short-side direction of the film; the lattice is rotated around lattice point A to determine the rotation angle α of the lattice where lattice point A and lattice point B overlap in the short-side direction of the film; and the inclination angle of the lattice axis of the conductive film is determined based on this angle α.

2. 2. The design method according to claim 1, wherein the lattice is a square lattice.

3. When the terminal length L1 and terminal width L2 are 7 to 1000 μm, the conductive particle density is 500 particles / mm 2 ~1500000 pieces / mm 2 3. The design method according to claim 1, wherein the range is set as follows:

4. 4. The design method according to claim 1, wherein the particle diameter of the conductive particles is 1.0 to 30 μm.

5. The design method according to any one of claims 1 to 4, wherein when lattice axes inclined at an angle α with respect to the short direction of the film are defined as a first arrangement axis and a second arrangement axis which are adjacent to each other, the angle α is determined so that the conductive particles on the first arrangement axis and the conductive particles on the second arrangement axis do not overlap in the longitudinal direction of the film.

6. d1 · cosα≦L2 or d2 sinα≦L1 6. The design method according to claim 1, wherein the pitches d1 and d2 of the conductive particles are determined so that the following is satisfied:

7. A method for manufacturing a transfer mold used for transferring conductive particles in a predetermined arrangement pattern to an insulating resin layer, the method comprising a step of processing the predetermined arrangement pattern designed by the method according to any one of claims 1 to 6 into a metal plate as recesses or protrusions.

8. 8. The method according to claim 7, wherein the metal plate is processed by cutting.

9. A conductive film in which, in a plan view, conductive particles having a predetermined particle diameter are held in an insulating resin layer, When connecting a terminal having a terminal length L1 and a terminal width L2 (where L1≧L2), the conductive particles in the conductive film are arranged at lattice points of a rectangular lattice or an oblique lattice, and have a lattice axis perpendicular to the longitudinal direction or transverse direction of the conductive film (hereinafter also referred to as the film longitudinal direction or the film transverse direction), and the number density of the conductive particles in the conductive film, the pitch d1 of the conductive particles on the lattice axis in the film longitudinal direction which is dependent on the number density, and the pitch d2 of the conductive particles on the lattice axis in the film transverse direction have a relationship of d2=a·d1 (a is a coefficient), A conductive film in which, among lattice points A located at a distance equal to or less than the terminal length L1, lattice point B is selected which has the smallest angle between the straight line connecting lattice point A and the short-side direction of the film; the lattice is rotated around lattice point A to determine the rotation angle α of the lattice where lattice point A and lattice point B overlap in the short-side direction of the film; and the inclination angle of the lattice axis of the conductive film is determined by the angle α.

10. A connection structure in which a first electronic component and a second electronic component are connected via the conductive film described in claim 9.

11. A method for manufacturing a connection structure, connecting a first electronic component and a second electronic component via the conductive film described in claim 9.

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