Conductive film, connecting structure, and method for manufacturing the same

Abstract

To provide a conductive film capable of ensuring continuity after conductive connection, suppressing the occurrence of a short circuit, and improving the reliability of a connection structure without excessively classifying solder particles having large variations in particle size.SOLUTION: In a conductive film 100, particle regions 30 of a predetermined area including a projected figure of one conductive particle 20 or a projected figure of a group of conductive particles consisting of a plurality of conductive particles 20 are regularly scattered and arranged in a plan view. When the area of any one particle region 30 is S, and the average value of the area S in a field of view of at least 100×100 μm of the conductive film 100 is SA, the maximum and minimum values of the area S are SA± within 80%.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a conductive film, a connecting structure using the same, and a method for manufacturing the same. [Background technology]

[0002] Mini-LEDs and micro-LEDs, which use light-emitting diodes (LEDs), an optical semiconductor element, as next-generation displays and light sources, are attracting attention. Micro-LEDs are still under research and development, and the method of connecting them to the substrate has not yet been fully established. On the other hand, conductive films, in which numerous conductive particles are dispersed in an insulating resin layer, are widely used for mounting electronic components such as IC chips. While conductive films enable fine-pitch connections, there are reliability issues because the connection is made via conductive particles. Furthermore, mounting micro-LEDs using conductive films requires high load and high pressure to ensure stable contact between the conductive particles and the electrodes. Generally, driver ICs (Integrated Circuits) and FPCs (Flexible Printed Circuits) are connected by pressing, but in the case of micro-LEDs, the mounting area becomes too large, which imposes constraints on the load limit of the connection device, and there are concerns that high loads will put too much stress on the substrate.

[0003] In fine pitch connection, it is also known to use solder particles as conductive particles (Patent Document 1). Since solder can be joined by an intermetallic compound, the reliability of conductive connection is high and connection with a low load is also possible. However, when applying solder particles as a non-aligned dispersed conductive film to fine pitch connection, if the particle density is too high, unintended aggregation will occur during connection. Conversely, if the particle density is too low, there is a concern that a sufficient amount of solder particles will not be sandwiched between electrodes, or the amount of solder particles required for joining will be insufficient. In particular, since the electrodes of micro LEDs are extremely small, the space between electrodes may be extremely narrow. Therefore, while it is necessary for the conductive particles to be dispersed with a certain degree or more of areal density for stable connection, if the areal density of the conductive particles is too high, the solder particles will bridge between adjacent electrodes or between the electrodes of adjacent micro LEDs, increasing the risk of short circuit.

[0004] If the solder particles are arranged in an aligned manner one by one to form a particle-aligned conductive film, the amount and arrangement of the solder particles can be appropriately controlled. However, it takes time to pre-classify the solder particles with a large variation in particle diameter, and there is a concern about an increase in the manufacturing cost of the conductive film.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Therefore, in mounting a large number of micro LEDs with a fine pitch, it has been desired to provide a conductive film in which solder particles that are not overly classified as solder particles are arranged in an aligned manner.

[0007] The object of the present invention is to provide a conductive film that can ensure conductivity after conductive connection, suppress the occurrence of short circuits, and improve the reliability of the connection structure without excessively classifying solder particles with large variations in particle size. [Means for solving the problem]

[0008] The inventors of the present invention have discovered that the above problem can be solved by aligning metal particles, such as solder particles, which have large variations in particle size, into particle regions containing one or more metal particles, and have completed the present invention.

[0009] In other words, the present invention relates to a conductive film comprising an insulating resin film and a plurality of conductive metal particles supported on the insulating resin film, In a plan view of the conductive film, particle regions of a predetermined area, including projection figures from one or more of the metal particles, are arranged in an aligned manner. Let S be the area of ​​one of the particle regions, and let S be the average value of the area S in a surface field of view of at least 100 × 100 μm of the conductive film. A In this case, the maximum and minimum values ​​of area S are S A We provide conductive films with a tolerance of ±80% or less.

[0010] Furthermore, the present invention relates to a connection structure in which a first electronic component and a second electronic component are electrically connected, The first electronic component has a plurality of first electrodes that are joined to the electrodes of the second electronic component, and a resin-filled layer of insulating resin is formed around the first electrodes. In the resin-filled layer, conductive metal particles or aggregates thereof are dispersed at multiple locations. The present invention provides a connection structure in which, in a cross-section of the resin-filled layer parallel to the bonding surface between the first electrode and the electrode of the second electronic component, the ratio of the total area SP of the figures projected from the metal particles or aggregates thereof contained in the inter-electrode region, when considered as circles, to the total area SR of the inter-electrode region demarcated by adjacent first electrodes is 35% or less. [Effects of the Invention]

[0011] The conductive film of the present invention has particle regions containing one or more metal particles arranged in an aligned manner, and because the variation in the amount of metal particles in the particle regions is small, it is possible to ensure conductivity and suppress the occurrence of short circuits while using metal particles with large variations in particle size without excessive classification. Therefore, in a connection structure using the conductive film of the present invention, it is possible to achieve both ensuring conductivity between electronic components and suppressing short circuits, thereby improving reliability. [Brief explanation of the drawing]

[0012] [Figure 1] This is a cross-sectional view of the conductive film of the present invention. [Figure 2] This is a plan view of the conductive film of the present invention. [Figure 3] This is an enlarged planar perspective view of the conductive film of the present invention. [Figure 4] This is a plan view of the conductive film of the present invention. [Figure 5] This is a cross-sectional view of the connecting structure of the present invention. [Figure 6] This is a diagram illustrating the inter-electrode region of a connecting structure. [Figure 7] This is a micrograph of the conductive film of the present invention. [Figure 8] This is an explanatory diagram of the microchip used to evaluate resin filling properties. [Figure 9] This is an explanatory diagram of the microchip used to evaluate resin filling properties. [Figure 10] This is a micrograph of the inter-electrode region of the LED chip in the example assembly, observed through a glass substrate. [Figure 11] This is a micrograph of the inter-electrode region observed through a glass substrate of an LED chip mounted as a comparative example. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the drawings as appropriate. The conductive film of the present invention is useful for mounting optical semiconductor elements such as mini-LEDs and micro-LEDs (hereinafter, these will be collectively referred to as "micro-LEDs," but this does not exclude mini-LEDs).

[0014] <Conductive film> Figure 1 shows an arbitrary cross-section in the thickness direction of a conductive film 100 according to one embodiment of the present invention. Figure 2 is a plan perspective view of the conductive film 100. As shown in Figure 1, the conductive film 100 has a plurality of conductive particles 20 arranged as metal particles on or near the surface of a single layer insulating adhesive film (binder film) 10. The insulating adhesive film 10 may be composed of multiple layers. The conductive film 100 may also be an anisotropic conductive film (ACF).

[0015] (Planar lattice patterns and particle regions) As shown in Figure 2, in the conductive film 100, when observed in a plan view (meaning observing the XY plane in Figure 2 from the Z direction), particle regions 30 of a predetermined area, each containing the projection figure of a single conductive particle 20 or the projection figure of a group of conductive particles 20, are regularly scattered and arranged. Here, "scattered" means that adjacent particle regions 30 are separated from each other without touching.

[0016] The conductive particles 20 are arranged individually or in groups of two or more within a particle region 30 of a predetermined area, centered or centroidal to a grid point P of the planar grid pattern shown by the dashed line in Figure 2. The grid point P is shown as the intersection of the dashed line in Figure 2 and is regularly arranged in accordance with the planar grid pattern. Therefore, the particle region 30 centered or centroidal to the grid point P of the planar grid pattern is also regularly arranged. In this way, by having multiple particle regions 30 arranged regularly using the planar grid pattern, it is possible to achieve both conductivity between electronic components and short-circuit suppression in a connection structure that is electrically connected using the conductive film 100.

[0017] Figure 3 shows an enlarged view of the main parts of a planar perspective view of the conductive film 100 as observed from a planar perspective. In Figure 3, for example, the particle region indicated by reference numeral 30A contains the projection figure of one conductive particle 20, the particle region indicated by reference numeral 30B contains the projection figures of two conductive particles 20, and the particle region indicated by reference numeral 30C contains the projection figures of four conductive particles 20 (here, the symbols "A, B, C" in reference numerals 30A, 30B, and 30C are added for the sake of clarity and distinction).

[0018] When observing, for example, 100 particle regions 30 of the conductive film 100, it is preferable that the particle regions 30 containing conductive particle groups consisting of 3 or more conductive particles 20 are preferably in the range of 10 or more, more preferably in the range of 30 to 90, and even more preferably in the range of 40 to 80. In the present invention, while the particle regions 30 as a whole are arranged in an orderly manner, particle regions 30 in which 3 or more conductive particles 20 are aggregated or condensed to form conductive particle groups are randomly present, making it possible to secure the amount of conductive particles 20 necessary for electrode connection without excessive classification, thereby achieving both connection stability and suppression of cost increases.

[0019] In Figure 3, the diameter D of one particle region 30 and the shortest distance L between adjacent particle regions 30 are preferably set appropriately, taking into account the total volume of conductive particles 20 contained in one particle region 30. In this case, it is important to set them considering the viewpoint of ensuring conductivity by sufficiently capturing the conductive particles 20 with electrodes, and preventing short circuits by ensuring that the conductive particles 20 do not span multiple electrodes when melted. The diameter D and shortest distance L may be set according to the typical electrode layout in micro-LED mounting. For example, if the particle region 30 is circular, its diameter D is preferably smaller than the length of the space between the electrodes of the micro-LED. The diameter D is preferably in the range of 1.0 μm to 10 μm, and more preferably in the range of 1.5 μm to 4.0 μm. In this case, the shortest distance L between particle regions 30 is preferably in the range of 1.0 μm to 20 μm, and more preferably in the range of 1.5 μm to 4.0 μm. As will be described later, the particle region 30 may be a square or rectangle, or it may be a triangle or a polygon with five or more sides. In the case of a square, rectangle, or triangle, the length of one side may be within the range of 1 μm to 10 μm.

[0020] If there are multiple conductive particles 20 within each particle region 30, the multiple conductive particles 20 may be located at different positions in the thickness direction. In other words, within the particle region 30, the multiple conductive particles 20 may be located three-dimensionally in the planar direction (XY direction) and the thickness direction (Z direction) of the conductive film 100.

[0021] Furthermore, the arrangement of conductive particles 20 in the thickness direction within the particle region 30 is not particularly limited, but it is preferable that they are arranged within a range of 0.5 μm to 8 μm in the thickness (depth) direction from the surface of the conductive film 100, and more preferably within a range of 1 μm to 6 μm. From another viewpoint, it is preferable that the arrangement of conductive particles 20 in the thickness direction within the particle region 30 is within a range of 10% to 200% of the diameter D of the particle region 30.

[0022] Furthermore, within the particle region 30, it is preferable that multiple conductive particles 20 are aggregated so that they easily become one during melting. In this case, adjacent particles may be in contact or spaced apart, but contact is preferred. Also, multiple conductive particles 20 may exist in an aggregated state within the particle region 30.

[0023] The shape of the particle region 30 is not particularly limited as long as it can contain the projected figures of one or more conductive particles 20, and can take on various shapes. The shape of the particle region 30 can be, for example, a circle, a polygon such as a triangle or quadrilateral, or an amorphous shape. When the conductive particle 20 is circular (including elliptical) in a plan view, it is preferable that the shape of the particle region 30 is also a similar circle, as illustrated in Figures 2 and 3. When the shape is circular, the particle region 30 can be defined as the region enclosed by a perfect circle with a circumference that passes through the outermost part of the projected figure of the conductive particle 20, with the grid point P as the center. For this reason, when determining the particle region 30 from a film, there will be some variation in the size and shape of the particle region 30. In this case, the average value may be calculated from N=200 or more by observation with an optical microscope and used as the size of the particle region 30 (e.g., diameter D). Also, when the shape is polygonal, the particle region 30 may be considered as an inscribed circle with the grid point P as the centroid and containing the projected figure of the conductive particle 20, and treated similarly to a circle. In particular, for polygons with five or more sides, it is preferable to consider them as inscribed circles containing the polygon, similar to how circles are treated.

[0024] The planar grid pattern is not limited to a hexagonal grid; for example, a square grid as shown in Figure 4 may also be used. The grid points P are shown as the intersections of the dashed lines in Figure 4 and are arranged regularly in accordance with the planar grid pattern. Furthermore, rhombic grids, rectangular grids, parallelepiped grids, etc., may also be used. Among these, the hexagonal grid shown in Figure 2 is the most preferable from the viewpoint of ensuring conductivity between electronic components and suppressing short circuits, because the grid points P are arranged at equal intervals.

[0025] Furthermore, the regular arrangement of the multiple particle regions 30 is not limited to an aligned arrangement using a planar lattice pattern, but may be any kind of regular arrangement. When aligning the multiple particle regions 30, the lattice axis or arrangement axis of the arrangement may be parallel to the longitudinal direction Y of the conductive film 100, or to the short direction X which is perpendicular to the longitudinal direction Y, or it may intersect with the longitudinal direction Y of the conductive film 100. In addition, the aligned arrangement of the multiple particle regions 30 can be determined according to the terminal width, terminal pitch, layout, etc.

[0026] Furthermore, it is preferable for multiple particle regions 30 to be aligned in a plan view of the conductive film 100, and for the positions of one conductive particle 20 or a group of conductive particles 20 to be approximately aligned in the film thickness direction Z, in order to achieve both electrode capture stability and short-circuit suppression.

[0027] (Area variation of the particle region) In the conductive film 100, the area of ​​any one particle region 30 is defined as S, and in the conductive film 100, the average area S in a field of view (referred to as "a field of view of at least 100 × 100 μm" in this specification) that contains 20 or more particle regions 30 with a minimum area of ​​100 × 100 μm is defined as S A In this case, the maximum and minimum values ​​of area S are S A Within ±80%, S A It is preferable that the range be within ±70%. The maximum and minimum values ​​of the area S are S A Being within ±80% means that the variation in the total volume of one or more conductive particles 20 present within each particle region 30 is small, which makes it possible to ensure both conductivity and short-circuit prevention in the connection structure after mounting the microLED using the conductive film 100.

[0028] In contrast, the maximum value of area S is S A If it exceeds +80%, there is a concern that if the conductive particles 20 melt, they will spread beyond the space between adjacent electrodes or between adjacent microLEDs, causing a short circuit. The minimum value of area S is S AWhen it is less than 80%, the volume of the conductive particles 20 within one electrode area to be connected may be insufficient, making it difficult to ensure electrical conduction.

[0029] When taking the "at least 100×100 μm surface view field" as a reference, the 100×100 μm surface view field may be observed at preferably 5 or more locations (N = 100 or more), more preferably 10 or more locations (N = 200 or more), and the average may be taken.

[0030] The maximum value, minimum value, and average value S of the area S of one particle region 30 A are not particularly limited. As an example, considering the general electrode area of a micro LED and the area of the region (space) between electrodes, for example, the maximum value of the area S is preferably within the range of 7.0 μm 2 or more and 9.0 μm 2 or less, more preferably within the range of 7.5 μm 2 or more and 8.5 μm 2 or less. Also, the minimum value of the area S is preferably within the range of 0.5 μm 2 or more and 2.5 μm 2 or less, more preferably within the range of 1.0 μm 2 or more and 2.0 μm 2 or less. Also, the average value S of the area S A is preferably within the range of 4.0 μm 2 or more and 6.0 μm 2 or less, more preferably within the range of 4.5 μm 2 or more and 5.5 μm 2 or less.

[0031] (Area ratio of the particle region) Furthermore, it is preferable that the proportion of the total area S1 of the aligned particle regions 30 in a surface field of view of at least 100 × 100 μm of the conductive film 100 is 90% or more of the total area S2 of the figures projected from all conductive particles 20. In other words, it is preferable that the proportion of the area of ​​the projected figures of conductive particles 20 that are outside the aligned particle regions 30 is less than 10% of the total S2. The fact that the proportion of the total area S1 of the particle regions 30 is 90% or more of the total area S2 of the figures projected from all conductive particles 20 means that the majority of the conductive particles 20 present in the conductive film 100 are located within the aligned particle regions 30. In the manufacturing process of the conductive film 100, when fixing the conductive particles 20 to the insulating adhesive film 10, it is possible to place most of the conductive particles 20 within the particle regions 30 by using a transfer mold. However, it is possible that some conductive particles 20 will inevitably be located outside the particle regions 30. Thus, if the proportion of conductive particles 20 that inevitably exist outside the particle region 30 becomes too large, the conductive particles 20 will approach a state of random dispersion, which may cause short circuits between adjacent electrodes or between adjacent micro-LEDs due to uneven distribution of conductive particles 20, or conversely, make it difficult to ensure conductivity at the electrodes to be connected. On the other hand, if the proportion of the total area S1 is 90% or more of the total area S2, most of the conductive particles 20 or groups of conductive particles will be arranged in an aligned state within the particle region 30 centered or centroidal of the grid point P of the planar grid pattern, making it possible to achieve both conductivity assurance and short circuit prevention. From this viewpoint, the ratio of the total area S1 to the total area S2 is more preferably in the range of 95% to 100%, and even more preferably in the range of 98% to 100%.

[0032] Furthermore, as illustrated in Figures 2 and 4, aligning the particle regions 30 using a planar grid pattern makes it easier to distinguish between conductive particles 20 located within the aligned particle regions 30 and conductive particles 20 located outside the aligned particle regions 30, and makes it easier to control the ratio of the total area S1 to the total area S2, which is preferable.

[0033] (Total area of ​​adjacent particle regions) Furthermore, in the conductive film 100, the total area S3 of two adjacent particle regions 30 located at the shortest distance from each other is 1 μm. 2 More than 20μm 2 The following range is preferred: 5 μm 2 More than 16μm 2 It is more preferable that the following ranges apply: The total area S3 of two adjacent particle regions 30 at the shortest distance is 1 μm. 2 More than 20μm 2 By staying within the following range, it is possible to ensure both conductivity and short-circuit prevention in the connection structure after mounting the microLEDs using the conductive film 100. That is, the total area S3 is 20 μm². 2 If the area exceeds this, there is a concern that if the conductive particles 20 melt, they may spread beyond the space between adjacent electrodes or between adjacent microLEDs, causing a short circuit. On the other hand, if the total area S3 is 1 μm 2 If the volume falls below this level, the volume of conductive particles 20 within the area of ​​one electrode to be connected may be insufficient, making it difficult to ensure conductivity.

[0034] (Area occupancy rate of the particle region) In a surface view of at least 100 × 100 μm of the conductive film 100, the proportion of the total area S1 of the particle region 30 (area occupancy rate) is preferably in the range of 5% to 25%, more preferably in the range of 10% to 20%. By having an area occupancy rate of 5% to 25% of the particle region 30, it is possible to ensure both conductivity and short-circuit prevention in the connection structure after mounting microLEDs using the conductive film 100. That is, if the area occupancy rate of the particle region 30 exceeds 25%, there is a concern that if the conductive particles 20 melt, they will spread beyond the space between adjacent electrodes or between adjacent microLEDs, causing a short circuit. On the other hand, if the area occupancy rate of the particle region 30 is less than 5%, the volume of conductive particles 20 will be insufficient for the electrode area to be connected, making it difficult to ensure conductivity. The area occupancy rate of the particle region 30 can be calculated using the following formula, based on a surface view of at least 100 × 100 μm.

[0035]

number

[0036] In the formula, n is the number density of particles in a particle region 30 in a surface field of at least 100 × 100 μm (unit: particles / 0.01 mm). 2 ) means, S A This represents the average area of ​​particle region 30.

[0037] While there are no particular restrictions on the number density n of the particle regions 30 in the conductive film 100 as long as the area occupancy is within the above range, if the number density n is too small, the number of conductive particles 20 captured by the electrodes will decrease, making conductive connections such as micro-LEDs difficult. If it is too large, there is a concern that a short circuit may occur. Therefore, the number density n is preferably in the range of 100 to 1500 particles, and more preferably in the range of 200 to 1000 particles, for the total number of aligned particle regions 30 in at least a 100 × 100 μm surface field of view of the conductive film 100.

[0038] In the above, the planar area S of one particle region 30 and the average area S A、 The total area S1 and number density n can be measured based on observation images of the film surface using an electron microscope such as a metallurgical microscope or a scanning electron microscope (SEM). As an example, the planar area S and number density n of the particle region 30 can be measured using observation images from an SEM for a surface field of view of at least 100 × 100 μm (preferably 5 or more locations, more preferably 10 or more locations) arbitrarily selected from the conductive film 100. If the particle region 30 is circular, a perfect circle with a circumference passing through the outermost part of the projection figure of the conductive particles 20 can be assumed, and the area of ​​the region enclosed by this perfect circle can be taken as the planar area S.

[0039] Furthermore, the total area S2 of the figures projected from all conductive particles 20 can also be measured based on observation images of the film surface using a metallurgical microscope or an electron microscope such as a scanning electron microscope (SEM). For the above measurements, image analysis software such as WinROOF (manufactured by Mitani Corporation) or A-Image-kun (registered trademark) (Asahi Kasei Engineering Corporation) may be used.

[0040] (Conductive particles) The conductive particles 20 can be any conductive particles that melt when heated, and solder particles are preferred, for example. When the conductive particles 20 are solder particles, the solder particles contain tin or a tin alloy, and as tin alloys, for example, Sn-In, Sn-Bi, Sn-Ag-Cu, Sn-Cu, etc. are preferred. Among these, those containing Cu are preferred when considering bonding strength, and Sn-Ag-Cu (for example, Sn: 96.5 mass%, Ag: 3 mass%, Cu: 0.5 mass%) are more preferred. Other than solder, for example, one or more metals such as Au, Cu, Ag, Ni, Al, Sn, Ti, or alloys of these multiple metals can be used, but Au, Cu, and Ni are preferred when considering resistance and migration.

[0041] Average particle diameter (median diameter: D) of conductive particles 20 50There are no particular restrictions on the particle size, but for example, in the case of solder particles, a range of 0.5 μm to 10 μm is preferred, and a range of 1 μm to 5 μm is more preferred. The average particle size can be measured by an image-type or laser-type particle size analyzer.

[0042] (Insulating adhesive film) It is preferable to use a thermopolymerizable resin as the material for the insulating adhesive film 10. For example, a thermopolymerizable resin containing an acrylate compound and a thermoradical polymerization initiator, a thermocationic polymerizable resin containing an epoxy compound and a thermocationic polymerization initiator, or a thermoanionic polymerizable resin containing an epoxy compound and a thermoanionic polymerization initiator can be used. In addition, the insulating adhesive film 10 may contain a silane coupling agent, pigment, antioxidant, ultraviolet absorber, etc., as appropriate.

[0043] When the conductive particles 20 are solder particles, it is preferable that the resin constituting the insulating adhesive film 10 has a curing temperature above the melting point of the solder, and it is also preferable that the temperature at which the minimum melt viscosity is reached is below the melting point of the solder.

[0044] The curing temperature of the resin constituting the insulating adhesive film 10 is above the melting point of solder. By heating, the resin melts or softens, allowing the solder particles to be sandwiched between the electrodes and then melted. Here, the curing temperature is the exothermic peak temperature measured by differential thermal analysis (DSC) using an aluminum pan weighing 5 mg or more of the sample, under conditions of a temperature range of 30 to 250°C and a heating rate of 10°C / min.

[0045] Furthermore, the minimum melt viscosity temperature of the resin constituting the insulating adhesive film 10 is preferably within the range of -10°C to -50°C above the melting point of the solder particles, more preferably within the range of -10°C to -40°C above the melting point. With such a minimum melt viscosity temperature, the minimum melt viscosity is reached before the solder particles melt, the solder particles are melted after the resin melts, and then the resin can be cured, thus enabling a good solder joint. The minimum melt viscosity temperature is determined using a rotary rheometer (TA Instruments), with a heating rate of 10°C / min, a constant measurement pressure of 5g, and a measurement plate diameter of 8mm. It is more preferable that the measurement temperature is within the measurement range of, for example, 60°C to 250°C. The measurement temperature range may be appropriately adjusted depending on the material of the insulating adhesive film 10.

[0046] Furthermore, the minimum melt viscosity of the resin constituting the insulating adhesive film 10 is preferably less than 10,000 Pa·s, and more preferably 3,000 Pa·s or less. If the minimum melt viscosity is too high, the resin may not melt properly during thermocompression bonding, which may reduce the filling ability between electrodes.

[0047] Furthermore, it is preferable that the insulating adhesive film 10 contains a flux component. The flux component may also coat the surface of the conductive particles 20. As the flux component, it is preferable to use carboxylic acids such as levulinic acid, maleic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and sebacic acid. The flux component has effects such as removing foreign matter and oxide films from the electrode surface, preventing oxidation of the electrode surface, and reducing the surface tension of the molten conductive particles 20.

[0048] The insulating adhesive film 10 can be formed by coating a coating composition containing the resin described above and drying it, or by forming it into a film using a known method.

[0049] The thickness of the insulating adhesive film 10 is preferably within the range of 1 / 5 to 3 times the diameter D of the particle region 30, although the conductive particles 20 may be exposed from the insulating adhesive film 10. Furthermore, to prevent the micro-LED chip from being buried in the insulating adhesive film 10 after mounting, the thickness is preferably 1 / 2 or less of the height of the micro-LED chip, and more preferably about 1 / 3.

[0050] Furthermore, in order to ensure the retention force of the micro-LED chip, the insulating adhesive film 10 needs to be sufficiently filled on the electrode surface side of the micro-LED chip. For this reason, the thickness of the insulating adhesive film 10 is preferably 1 / 2 or more of the electrode height of the micro-LED chip, and more preferably about the same as the electrode height. From this viewpoint, the thickness of the insulating adhesive film 10 may be, for example, in the range of 1 μm to 10 μm, and preferably in the range of 2 μm to 8 μm.

[0051] Furthermore, if necessary, insulating fillers such as silica fine particles, alumina, and aluminum hydroxide may be added to the insulating adhesive film 10. Preferably, the amount of insulating filler added is within the range of 3 parts by mass to 40 parts by mass per 100 parts by mass of the resin constituting those layers.

[0052] <Method for manufacturing conductive film> Next, a method for manufacturing the conductive film 100 will be described. Here, an example of manufacturing the conductive film 100 of the present invention using a transfer mold will be given. When using a transfer mold, for example, the conductive film 100 can be obtained by the following steps A and B.

[0053] (Process A) First, one or more conductive particles 20 are placed into the recesses of the transfer mold, which have multiple recesses formed therein.

[0054] As for the transfer molds used, inorganic materials such as silicon, various ceramics, glass, and metals such as stainless steel, or organic materials such as various resins, can be used, in which openings have been formed by known opening formation methods such as photolithography. Furthermore, the transfer molds can take the shape of a plate, roll, or other form.

[0055] Examples of the shape of the recesses in the transfer mold include prism shapes such as cylinders and rectangular prisms, and cone shapes such as frustocones, frustopyramids, cones, and square pyramids. The arrangement of the recesses is preferably a grid pattern corresponding to the particle region 30 of the planar grid pattern. The depth of the recesses can be determined so that the diameter D of the particle region 30 is of a desired size, depending on the pitch, size, and space width of the electrodes to be electrically connected, as well as the total volume and average particle diameter of the conductive particles 20. The transfer mold used in step A can be prepared using known methods.

[0056] (Process B) Next, a conductive film 100 is formed by pressing a thermopolymerizable composition containing a thermopolymerizable compound, a thermopolymerization initiator, and optionally an insulating filler onto the conductive particles 20 in the transfer mold.

[0057] By adjusting the pressing force in step B, the degree to which the conductive particles 20 are embedded in the insulating adhesive film 10 can be changed. By increasing the degree of pressing force, the degree to which the conductive particles 20 are embedded in the insulating adhesive film 10 can be increased. This results in a conductive film 100 in which the conductive particles 20 are arranged on or near the surface of the insulating adhesive film 10.

[0058] It is preferable that the variation in the total volume of conductive particles 20 contained in each particle region 30 is small. In order to average the total volume of conductive particles 20 contained in each particle region 30, it is important to make the amount of conductive particles 20 placed in the recesses of the transfer mold in step A as close to uniform as possible, and for this purpose, for example, the following a) to c): a) Pre-classify the conductive particles 20 to keep the variation in particle size within a certain range; b) Determine the amount of conductive particles 20 to be placed in the concave shape by considering the relationship between the size of the conductive particles 20 (average particle diameter, minimum particle diameter, maximum particle diameter) and the size of the concave shape (diameter and depth); c) After placing the conductive particles 20 into the concave mold, a step is provided to smooth them out, for example, with a brush or squeegee; It is preferable to implement one or more of the following.

[0059] Here, the variation in particle size of the conductive particles 20 can be calculated using an image-type particle size analyzer or the like. The particle size of the conductive particles 20 as raw material particles when not placed in the conductive film 100 can be determined, for example, using a wet flow-type particle size and shape analyzer FPIA-3000 (Malvern Panalytical).

[0060] The conductive film 100 can be preferably applied to fine-pitch conductive connections, such as when mounting micro-LEDs on a substrate. For example, the conductive film 100 can be preferably applied when making conductive or anisotropic conductive connections between first electronic components such as LED elements such as micro-LEDs and mini-LEDs, IC chips, IC modules, and FPCs, and second electronic components such as FPCs, glass substrates, rigid substrates, and ceramic substrates. The reaction rate of the conductive film is preferably 25% or less, more preferably 20% or less, and even more preferably 15% or less. This allows for stable manufacturing of the connection structure. The reaction rate is the ratio of the decrease in the amount of thermally polymerizable compound after formation to the amount of thermally polymerizable compound before formation of the conductive film, and the method for measuring the reaction rate will be described later.

[0061] <Deformation patterns of conductive film> When the conductive film is used for minute components such as micro-LEDs, it may be in the form of individual pieces in predetermined units, such as one pixel (one pixel unit) for one set of RGB. Individual pieces may be provided according to each electrode on the substrate side that corresponds to each electrode of the micro-LED. The shape of the individual pieces is not particularly limited and can be set appropriately according to the dimensions of the electronic component to be connected. When the individual pieces of conductive film are formed on a substrate film by a laser lift-off processing method using a laser lift-off (LLO) device (for example, product name: Invisi LUM-XTR, Shin-Etsu Chemical Co., Ltd.) (see Japanese Patent Publication No. 2017-157724), it is preferable that the shape of the individual pieces be at least one selected from obtuse-angled polygons, rounded-corner polygons, ellipses, oblongs, and circles in order to suppress the occurrence of peeling and chipping. At least one individual piece selected from such shapes may be provided individually spaced apart on the substrate side electrodes, and the electrodes of the micro-LED may be connected by different individual pieces.

[0062] The dimensions (length × width) of each piece of conductive film are appropriately set according to the dimensions of the electronic component to be connected, and the ratio of the area of ​​each piece to the area of ​​the electronic component is preferably 2 or more, more preferably 4 or more, and even more preferably 5 or more. The thickness of each piece is the same as the thickness of the conductive film, preferably 1 to 4 μm, particularly preferably 1 to 2 μm added to the average particle size of the conductive particles, preferably 1 μm to 10 μm, more preferably 1 μm to 6 μm, and even more preferably 2 μm to 4 μm.

[0063] Furthermore, the distance between individual pieces on the base film is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. The upper limit of the distance between individual pieces is preferably 3000 μm or less, more preferably 1000 μm or less, and even more preferably 500 μm or less. If the distance between individual pieces is too small, it becomes difficult to transfer the pieces by LLO, and if the distance between individual pieces is too large, a method of attaching the pieces becomes preferable. The distance between individual pieces can be measured using microscopic observation (optical microscope, metallurgical microscope, electron microscope, etc.).

[0064] <Method for manufacturing a deformed conductive film> The conductive film pieces may be formed by slitting or half-cutting, or by using a laser lift-off device. When forming pieces using an LLO device, the base film only needs to be transparent to laser light, and is preferably quartz glass having high light transmittance across all wavelengths.

[0065] When forming individual pieces of conductive film using an LLO (Laser Laser Oscillator) device, laser light is irradiated onto the conductive film provided on the base film from the base film side, and the conductive film in the irradiated area is removed, thereby forming individual pieces of conductive film of a predetermined shape on the base film.

[0066] For example, by using a mask with a square-shaped opening window and removing the unnecessary portion of the conductive film from the base film, individual pieces of a predetermined shape can be formed from the remaining portion of the conductive film. Alternatively, for example, by using a mask with a predetermined-shaped light-shielding portion formed within the opening window and removing the unnecessary portion of the conductive film around the individual pieces from the base film, individual pieces of a predetermined shape can be formed from the remaining portion of the conductive film.

[0067] Furthermore, when individual pieces are prepared using a laser lift-off device, the reaction rate of the individual pieces is 25% or less, preferably 20% or less, and more preferably 15% or less. This allows for excellent transferability. The reaction rate of the curable resin film before laser irradiation and the individual pieces obtained after laser irradiation can be determined, for example, by measuring the rate of decrease of reactive groups using FT-IR. For example, in the case of a curable resin film utilizing the reaction of an epoxy compound, the IR spectrum is measured by irradiating the sample with infrared light, and the methyl group (2930cm²) in the IR spectrum is determined. -1 (Nearby) and epoxy group (914cm) -1 The peak heights in the vicinity can be measured and calculated as the ratio of the peak height of the epoxy group to the peak height of the methyl group before and after the reaction (for example, before and after laser irradiation), as shown in the formula below.

[0068]

number

[0069] In the above formula, A is the peak height of the epoxy group before the reaction, B is the peak height of the methyl group before the reaction, a is the peak height of the epoxy group after the reaction, and b is the peak height of the methyl group after the reaction. If other peaks overlap with the epoxy group peak, the peak height of the fully cured (100% reaction rate) sample should be set to 0%.

[0070] <Utilization of conductive film (connecting structure, manufacturing method thereof)> The conductive film of the present invention can be used by laminating it to an article, similar to conventional conductive films, and there are no particular restrictions on the article to which it is laminated. Therefore, a connection structure in which a first member and a second member are connected via a conductive film, and a method for manufacturing a connection structure by arranging and connecting a conductive film between a first member and a second member are also part of the present invention. For example, when the conductive film is configured as an anisotropic conductive film by employing conductive particles as a filler, the anisotropic conductive film can be used with a thermocompression bonding tool to make anisotropic conductive connections between first electronic components such as semiconductor elements (power generation elements such as solar cells, image sensors such as CCDs, light-emitting elements such as mini-LEDs with a chip side length of about 50 μm to 200 μm and micro-LEDs with a chip side length of less than 50 μm, Peltier elements), various other semiconductor elements, IC chips, IC modules, FPCs, etc., and second electronic components such as FPCs, glass substrates, plastic substrates, rigid substrates, ceramic substrates, etc. This conductive film can also be used as a conductive film in electronic components for applications other than anisotropic conductive connections. The surface of the article to which the conductive film is bonded may be smooth, or it may have stepped or convex shapes.

[0071] As for specific methods of using conductive film, for example, when the first electronic component is a micro-LED, IC chip, or FPC containing semiconductor elements, and the second electronic component is a substrate, the first electronic component is generally placed on the side of the pressure tool, and the second electronic component is placed on the stage opposite the first electronic component. The conductive film, preferably individual pieces thereof, is pre-attached to the second electronic component by a laser lift-off process or the like, and the first and second electronic components are thermally bonded using a pressure tool. In this case, the individual pieces of conductive film may be pre-attached to the first electronic component instead of the second electronic component, and the first electronic component is not limited to an IC chip or FPC containing semiconductor elements. When the first or second electronic component is a substrate, it may have, for example, a silicone rubber layer. The silicone rubber layer may be polydimethylsiloxane (PDMS).

[0072] <Connection Structure> Figure 5 is a cross-sectional view showing an example of the configuration of a connection structure obtained using the conductive film 100. This connection structure 200 is a micro-LED mounting body in which a micro-LED element 50 as a first electronic component and a substrate 60 as a second electronic component are electrically connected or anisotropically connected using the conductive film 100. Here, we will describe the case in which the conductive particles 20 in the conductive film 100 are solder particles.

[0073] As shown in Figure 5, the connecting structure 200 comprises a micro-LED element 50, a substrate 60, and a resin filling layer 101 filled between the micro-LED element 50 and the substrate 60. In Figure 5, the plane direction parallel to the bonding surface between the electrodes 51, 52 of the micro-LED element 50 and the electrodes 61, 62 of the substrate 60 is defined as the XY plane, with mutually orthogonal X-axis and Y-axis directions, and the crimping direction of the first and second electronic components perpendicular to this XY plane is defined as the Z-axis direction.

[0074] The micro-LED element 50 includes electrodes 51 and 52. When a voltage is applied between electrodes 51 and 52, carriers concentrate in the active layer within the element and recombine to produce light. The heights of electrodes 51 and 52 can be appropriately set according to the size of the micro-LED element 50, and are preferably in the range of 0 μm to 10 μm, more preferably in the range of 0 μm to 7 μm, and even more preferably in the range of 0 μm to 5 μm.

[0075] The length of the space between electrode 51 and electrode 52 (inter-electrode space) can be appropriately set according to the size of the micro LED element 50, and is preferably in the range of 3 μm to 15 μm, more preferably in the range of 3 μm to 12 μm, and even more preferably in the range of 5 μm to 10 μm.

[0076] The substrate 60 has electrodes 61 and 62 on the substrate. Electrodes 61 and 62 are positioned at locations corresponding to electrodes 51 and 52 of the micro-LED element 50, respectively. Examples of substrates 60 include printed circuit boards, glass substrates, flexible substrates, ceramic substrates, plastic substrates, and semiconductor substrates (IC chips).

[0077] The resin-filled layer 101 is formed when the conductive film 100 becomes a film after bonding. The resin-filled layer 101 is filled between the micro-LED element 50 and the substrate 60 around the solder joint 21 that joins the electrodes 51 and 52 of the micro-LED element 50 to the electrodes 61 and 62 of the substrate 60. Conductive particles 20 that did not participate in the bonding are dispersed in the resin-filled layer 101 between the micro-LED element 50 and the substrate 60 in the form of one or more aggregates.

[0078] In the connection structure 200, electrodes 51 and 52, which are terminals on the micro-LED element 50 side, and electrodes 61 and 62, which are terminals on the substrate 60, are joined at solder joints 21. In other words, after the solder particles, which are conductive particles 20 in the conductive film 100, melt and solidify, an alloy (intermetallic compound) is formed between them and the electrode material. Electrical conductivity is achieved between the electrode 51 of the micro-LED element 50 and the electrode 61 of the substrate 60, and between the electrode 52 of the micro-LED element 50 and the electrode 62 of the substrate 60, through the solder joints 21.

[0079] <Method for manufacturing a connecting structure> The connecting structure 200 can be manufactured by placing a conductive film 100 between the micro LED element 50 and the substrate 60 and then thermocompressing them. The solder particles, which are conductive particles 20 in the conductive film 100, melt and solidify during thermocompression to form a solder joint 21. Alternatively, the connecting structure 200 may be manufactured by placing the conductive film 100 between the micro LED element 50 and the substrate 60 and then melting the solder particles by heat treatment (reflow). The reflow may be atmospheric pressure reflow or vacuum reflow, but vacuum reflow is preferred.

[0080] Figure 6 shows a cross-section of the resin filling layer 101 parallel to the bonding surface between the electrodes 51 and 52 of the micro-LED element 50 and the electrodes 61 and 62 of the substrate 60 in the connection structure 200. Here, the "cross-section of the resin filling layer 101 parallel to the bonding surface" is a hypothetical surface, but it may be a polished cross-section obtained by polishing after connection, for example. Since the thickness (height in the Z direction) of the connection structure 200 using the micro-LED element 50 is very small, if the electrodes 51 and 52 of the micro-LED element 50 can be seen through from the substrate 60 side, the plane observed through the substrate 60 in the Z direction can also be viewed as the same as the above cross-section. Furthermore, the peeled surface when the micro-LED element 50 is peeled off from the substrate 60 after connection can also be viewed as the same as the above cross-section. In such a cross-section, the connecting structure 200 has a total area SP (area occupancy rate) that is 35% or less, preferably 30% or less, of the area SR of the inter-electrode region R (inter-electrode space) demarcated by the adjacent electrodes 51 and 52, and is projected from the conductive particles 20 (solder particles or aggregates thereof) contained in the inter-electrode region R. If the ratio of the total area SP to the area SR exceeds 35%, there is a concern that a short circuit may occur between adjacent electrodes (i.e., electrodes 51 and 52). Here, the total area SP can be determined by summing the areas when the figures projected from each conductive particle 20 (solder particles or aggregates thereof) contained in the inter-electrode region R are considered to be circles. In this case, from the "area of ​​the figure projected from the conductive particle 20 (solder particles or aggregates thereof)", a perfect circle with a circumference passing through the outermost part of the projected figure is assumed, and the areas enclosed by this perfect circle are summed up. The total area SP can be measured by observing the cross-section (or delamination surface) of the inter-electrode region R using observation techniques such as a metallurgical microscope or an electron microscope such as a scanning electron microscope (SEM). Any software may be used to measure the total area SP.

[0081] Furthermore, since a conductive film 100 in which particle regions 30 are arranged in an aligned manner is used, if the ratio of the total area SP to the area SR is too small, there may not be a sufficient amount of solder particles between the electrodes to be connected (electrode 51 and electrode 61, electrode 52 and electrode 62), and sufficient conductivity may not be ensured. For this reason, the lower limit of the ratio of the total area SP to the area SR is preferably 0.5% or more, and more preferably 1.0% or more.

[0082] <Modified Method of Manufacturing a Connecting Structure> Furthermore, when mounting extremely small first electronic components onto second electronic components such as wiring boards, mounting can also be performed by projecting the first electronic components onto the second electronic components using the laser lift-off processing method described above. For example, if the first electronic components are a vast number of micro-LEDs formed on the surface of a light-transmitting substrate, the first electronic components can be mounted by irradiating each individual first electronic component with laser light onto a conductive film or transferred individual pieces of the conductive film placed at predetermined locations on the second electronic component (e.g., each electrode of the wiring board), thereby projecting the first electronic components. The laser lift-off processing conditions can be appropriately determined depending on the type and constituent materials of the first electronic component. Note that placing the conductive film at predetermined locations on the second electronic component (e.g., each electrode of the wiring board) or transferring individual pieces of the conductive film can be done by thermocompression bonding or the laser lift-off processing method.

[0083] Furthermore, when a first electronic component such as a micro-LED is placed on a conductive film positioned at a predetermined location on a second electronic component by thermocompression bonding, or when a piece of conductive film transferred by a laser lift-off processing method is projected onto the conductive film using a laser lift-off processing method, it is preferable that the insulating adhesive film of the conductive film contains rubber components (e.g., acrylic rubber, silicone rubber, butadiene rubber, polyurethane elastomer, etc.) that provide cushioning to mitigate the impact of the projectile, and inorganic fillers (e.g., silica, talc, titanium dioxide, calcium carbonate, etc.) that provide mechanical strength.

[0084] Such insulating adhesive films containing rubber components and inorganic fillers have a durometer A hardness (in accordance with JIS K6253) of preferably 20 to 40, more preferably 20 to 35, and particularly preferably 20 to 30 before laser irradiation, and a storage modulus of elasticity obtained by a dynamic viscoelasticity tester (temperature 30°C, frequency 200Hz; Vibron, A&D Co., Ltd.) in accordance with JIS K7244 is preferably 60 MPa or less, more preferably 30 MPa or less, and particularly preferably 10 MPa or less.

[0085] Furthermore, the insulating adhesive film preferably has a storage modulus of 100 MPa or higher, and more preferably 2000 MPa or higher, at a temperature of 30°C, measured in tensile mode according to JIS K7244 after curing (after connection). If the storage modulus of 30°C is too low, good conductivity cannot be obtained, and connection reliability tends to decrease. The storage modulus of 30°C can be measured in tensile mode using a viscoelasticity tester (vibron) in accordance with JIS K7244, for example, under measurement conditions of a frequency of 11 Hz and a heating rate of 3°C / min.

[0086] Furthermore, it is also possible to transfer (impact) a first electronic component, such as a micro-LED, onto a silicone rubber sheet such as polydimethylsiloxane (PDMS) at a predetermined position (i.e., a position corresponding to the predetermined position of the second electronic component to which the first electronic component should be retransferred) using a laser lift-off processing method, then align the first electronic component side of the sheet with the second electronic component, and transfer it after alignment. [Examples]

[0087] The present invention will be described in detail below with reference to examples.

[0088] [Preparation of thermopolymerizable compositions] A thermopolymerizable composition containing the following compounds (in parts by mass) was prepared by mixing phenoxy resin [Nippon Steel Chemical & Material Co., Ltd., YP-50], epoxy resin A [Nippon Steel Chemical & Material Co., Ltd., YD-019 (Bisphenol A type epoxy resin)], epoxy resin B [Mitsubishi Chemical Corporation, YL-980 (Liquid epoxy resin)], epoxy resin C [Mitsubishi Chemical Corporation, YX-8000 (Liquid hydrogenated epoxy resin)], flux compound [Adipic acid, Tokyo Chemical Industry Co., Ltd.], and curing agent [NovaCure, Asahi Kasei Corporation, HX-3941], as shown in Table 1.

[0089] [Table 1]

[0090] [Preparation of binder film] The obtained thermopolymerizable composition was applied to a substrate using a bar coater, dried at 60°C for 3 minutes, and then peeled off to form binder films 1 and 2 having the thicknesses shown in Table 2. Furthermore, solder particles (composition Sn) were added to the thermopolymerizable composition. 42 Bi 58 ; Mitsui Mining & Smelting Co., Ltd. ST-3, particle size distribution D 10 ;1.7μm, D 50 ;3.1μm, D 90 Binder films 3 and 4 having the thicknesses shown in Table 2 were prepared in the same manner except that a 5.0 μm layer was added and mixed. Binder films 3 and 4 are non-aligned anisotropic conductive films (hereinafter referred to as "ACF") in which solder particles are randomly dispersed in an insulating resin film.

[0091] [Table 2]

[0092] [Preparation of ACF: Examples 1-6, Comparative Examples 1 and 2] A mold was created with an arrangement pattern of protrusions corresponding to a hexagonal lattice pattern. Molten transparent resin pellets (polycarbonate-based) were poured into the mold and cooled to solidify, thereby producing three types of resin transfer molds with recesses in a hexagonal lattice pattern. Solder particles (composition Sn) were placed in the recesses of each transfer mold. 42 Bi 58 ; Mitsui Mining & Smelting Co., Ltd. ST-3, particle size distribution D 10 ;1.7μm, D 50 ;3.1μm, D 90 A 5.0 μm particle was packed into the cavity.

[0093] Using binder film 1 from Table 2, an elastic roller was used to press the solder particle-containing surface of each transfer mold under the conditions of a pressing temperature of 50°C and a pressing pressure of 0.5 MPa, thereby forming a binder film onto which solder particles were transferred. By peeling the binder film onto which solder particles were transferred from the transfer mold, aligned ACFs for Examples 1 to 4 were prepared. The ACFs for Examples 1 to 4 are identified by the combination of binder films 1 and 2 from Table 2 and aligned arrangement configurations 1 to 3 from Table 3. Binder films 3 and 4 from Table 2 were used as ACFs for Comparative Examples 1 and 2. An overview of the above is shown in Table 4.

[0094] [Table 3]

[0095] [Table 4]

[0096] The ACF obtained in Examples 1-4 was observed using a scanning electron microscope (SEM). As a result, if S is the area of ​​an arbitrary particle region, the average value of the area S in a field of view of at least 100 × 100 μm was defined as S. A In this case, the average value of the maximum and minimum values ​​of area S is S. A Ratio to S A (Written as "ratio"), each is S A It was confirmed that the result falls within ±80%.

[0097] As an example, the average area S of 20 particle regions in a field of view of at least 100 × 100 μm in Example 1. A is 5.1 μm 2 The maximum value is 8.0 μm 2 against S A The ratio was 157%, and the minimum value was 1.5 μm. 2 against S A The ratio is 29%, and the mean value is S A It was within ±80% of the standard. A The percentage results are also shown in Table 4. As a representative example, the SEM image of the ACF obtained in Example 1 is shown in Figure 7.

[0098] Furthermore, it was confirmed that the ACF obtained in Examples 1 to 4 had a ratio (S1 / S2 ratio; %) of 90% or more of the total area S1 of aligned particle regions relative to the total area S2 projected from all solder particles in a field view of at least 100 × 100 μm. The results for the S1 / S2 ratio [%] are also shown in Table 4.

[0099] Furthermore, in the ACF obtained in Examples 1-4, the total area S3 of two adjacent particle regions at the shortest distance is 1 μm. 2 More than 20μm 2 It was confirmed that the total area was within the following range: Total area S3 [μm²] 2 The results for [ ] are also shown in Table 4. Note that the total area S3 in the table is the average value of 10 pairs of particle regions adjacent by the shortest distance.

[0100] Furthermore, in the ACF obtained in Examples 1 to 4, the total number of aligned particle regions (number density of particle regions) in a field of view of at least 100 × 100 μm was in the range of 100 to 1500. Number density of particle regions [particles / 0.01 mm] 2 The results for [ ] are also shown in Table 4.

[0101] Furthermore, in the ACF obtained in Examples 1 to 4, it was confirmed that the proportion of the total area S1 of the particle region area S within a field of view of at least 100 × 100 μm (area occupancy rate) was within the range of 5% to 25%. The results of the area occupancy rate [%] of the total area S1 are also shown in Table 4. Note that the area occupancy rate in the table is the average value across a total of 10 field of view locations.

[0102] [Evaluation of conductivity resistance and insulation properties] The ACFs of Examples 1-3 and Comparative Examples 1 and 2 were attached to glass substrates on which Cr-Au electrode patterns were formed. An IC chip (chip size: 1.5 × 1.5 cm) having an electrode pattern mimicking the electrodes of a micro-LED element was placed on top of the ACF, and the two were thermocompressed under conditions of a maximum temperature of 150°C, a pressure of 1 MPa, and 30 seconds to obtain micro-LED mounting bodies, specifically mounting bodies 1-6 of the Examples and comparative mounting bodies 1 and 2 of the Comparative Examples. The IC chips had square electrodes in plan view, forming an electrode pattern with the electrode size, inter-electrode space length, and inter-electrode space area shown in Table 5. Three different evaluation components, 1 to 3, were fabricated and used.

[0103] [Table 5]

[0104] Table 6 shows the evaluation results for the conductivity resistance and insulation properties of micro-LED mountings bonded using ACF in Examples 1-3 and Comparative Examples 1 and 2. The evaluation criteria are as follows.

[0105] Criteria for determining conductivity resistance: Grades A through C were judged as passing, while grades D and E were judged as failing. A: 30Ω or less B: 31~100Ω C: 101~300Ω D: 301Ω or more E: There is one or more locations where measurement is not possible.

[0106] Criteria for determining insulation properties: Check the space between each electrode at 100 locations, 10 3A value below Ω was treated as a short circuit, and grades A through C were judged as passing, while grade D was judged as failing. A: No short B: One short circuit C: Two short circuits D: Short 3 locations

[0107] [Table 6]

[0108] [Evaluation of resin filling properties] As shown in Figures 8 and 9, a microchip 50A (chip size: 15 × 30 μm, chip thickness: 10 μm) modeled after a micro-LED element was fabricated. Three types of electrodes 51A and 52A were fabricated with heights of H: flat (0 μm), 2.5 μm, and 5 μm. After temporarily attaching the ACFs of Examples 1 and 4 to a glass substrate, the fabricated microchips were arranged in a 1.5 × 1.5 cm area so that they corresponded to 110 ppi. Then, the assembly bodies 7 to 12 shown in Table 7 were obtained by pressing them under conditions of a maximum temperature of 150°C, a pressure of 1 MPa, and a duration of 30 seconds. The resin-filling properties of the obtained assembly bodies 7 to 12 were evaluated. The evaluation criteria are as follows. The results are also shown in Table 7.

[0109] Criteria for determining resin-fillability: As described below, the evaluation was based on the chip side, electrode height, and chip top surface, and only A was judged as passing. A: The resin is filled up to the sides of the tip, but not to the top surface of the tip. B: The electrode height is not completely filled. C: The resin has flowed up to the top surface of the tip (the entire tip is embedded in the resin).

[0110] The ranges exceeding the chip side (A), the electrode height (B), and the top surface of the chip (C), which were used as the judgment criteria, are shown in Figure 8 with symbols A to C.

[0111] [Table 7]

[0112] [Evaluation of area occupancy rate after implementation] For mountings 1-6 and comparative mountings 1 and 2, the area occupancy rate of solder particles in the inter-electrode space (inter-electrode region) was confirmed. The inter-electrode space refers to the inter-electrode region R enclosed by the dashed line in Figure 6. For each mounting, a cross-section parallel to the joint surface was observed (here, the IC chip of the mounting is observed from the glass substrate side, through the glass substrate, but this can be considered equivalent to a cross-sectional observation). By checking the inter-electrode space at any 10 locations for one mounting, the total area SP of the solder particles was measured, and the area occupancy rate (%) relative to the total area SR of the inter-electrode space was calculated. Here, the total area SP of the solder particles was determined by summing the areas when the figures projected from the solder particles or aggregates contained in the inter-electrode space were considered as circles. In this case, a perfect circle with a circumference passing through the outermost part of the projected figure was assumed from the figure projected from the solder particles or aggregates, and the area enclosed by this perfect circle was summed. The total area SP was measured using a metallurgical microscope. The results are shown in Table 8.

[0113] As representative examples, Figure 10 shows a metallurgical microscope image of the inter-electrode space of assembly 1, and Figure 11 shows a metallurgical microscope image of comparative assembly 1.

[0114] [Table 8]

[0115] Table 8 confirms that by using the aligned ACF of Examples 1 to 3, it is possible to fabricate highly reliable micro-LED mounting structures (connection structures) in which the area occupancy rate of solder particles in the space between electrodes is 35% or less, and the occurrence of short circuits between adjacent electrodes is suppressed.

[0116] On the other hand, in the micro-LED packaging materials fabricated using the dispersed ACF of Comparative Examples 1 and 2, Comparative Packaging 1 showed significant variation in the area occupancy rate of solder particles in the space area, with some exceeding 35%. This suggests a bias in the distribution of solder particles, raising concerns about poor conductivity or short circuits. Comparative Packaging 2 also showed excessively high area occupancy rates, raising concerns about short circuits.

[0117] Furthermore, Figure 10 shows that in assembly 1, solder particles were present in the space between electrodes, but no bridging was observed. On the other hand, Figure 11 shows that in comparative assembly 1, solder particles fused in the space between electrodes, and bridging was observed.

[0118] From the above results, it was confirmed that by using the aligned ACF of the embodiment, it is possible to achieve both ensuring conductivity and preventing short circuits in the micro-LED mounting body (connection structure), and that the resin filling properties are also good. [Industrial applicability]

[0119] The conductive film of the present invention is useful for conductive connections or anisotropic conductive connections of electronic components such as micro-LEDs to wiring boards. Although embodiments of the present invention have been described in detail for illustrative purposes, the present invention is not limited to the above embodiments. [Explanation of symbols]

[0120] 10…Insulating adhesive film 20... Conductive particles 21...Solder joint 30…Particle region 50... Micro LED elements 50A…Microchip 51,51A,52,52A…electrode 60... Circuit board 61,62...electrode 100... Conductive film 101…Resin filled layer 200...Connection structure D...Diameter of the particle region L...shortest distance between particle regions H... electrode height P…lattice point R…Inter-electrode area

Claims

1. Insulating resin film and Multiple conductive metal particles, which are supported on the insulating resin film, A conductive film comprising, In a plan view of the conductive film, particle regions of a predetermined area, including projection figures from one or more of the metal particles, are arranged in an aligned manner. Let S be the area of ​​one of the particle regions, and let S be the average value of the area S in a surface field of view of at least 100 × 100 μm of the conductive film. Ａ In this case, the maximum and minimum values ​​of area S are S Ａ Within ±80% A conductive film characterized in that, within a particle region where the particle regions as a whole are aligned, there are randomly present particle regions in which three or more conductive particles are gathered or aggregated to form conductive particle groups.

2. The conductive film according to claim 1, wherein there is variation in the size or shape of the particle regions.

3. The conductive film according to claim 1, wherein the number of conductive particles in the particle region is multiple, and the multiple conductive particles are located at different positions in the thickness direction of the conductive film.

4. The conductive film according to claim 1, wherein, in a surface field of view of the conductive film of at least 100 × 100 μm, the total area S1 of the aligned particle regions is 90% or more of the total area S2 projected from all metal particles.

5. The sum of the areas of two adjacent particle regions at the shortest distance is 1 μm. ２ 20 μm or more ２ The conductive film according to claim 1, wherein the conductive film is within the following range.

6. The conductive film according to claim 1, wherein the total number of aligned particle regions in a surface field of at least 100 × 100 μm of the conductive film is within the range of 100 to 1500.

7. The conductive film according to claim 1, wherein the proportion of the total area S1 in a surface field of view of at least 100 × 100 μm of the conductive film is within the range of 5% to 25%.

8. The conductive film according to claim 1, wherein the particle regions are aligned and superimposed on the grid points of any planar grid pattern, such as a hexagonal grid, a square grid, an orthorhombic grid, a rectangular grid, or a parallelepiped grid.

9. The conductive film according to claim 1, wherein the shape of the particle region is circular or polygonal.

10. The conductive film according to claim 1, wherein the conductive particles are circular in plan view, and the shape of the particle region is also a similar circular shape.

11. The conductive film according to claim 1, wherein the metal particles are solder particles.

12. The conductive film according to claim 1, wherein the reaction rate of the film is 25% or less.

13. A connection structure in which a first electronic component and a second electronic component are electrically connected via a conductive film according to any one of claims 1 to 12, The first electronic component has a plurality of first electrodes joined to the electrodes of the second electronic component, and a resin-filled layer of insulating resin is formed around the first electrodes. In the resin-filled layer, conductive metal particles or aggregates thereof are dispersed at multiple locations. A connection structure characterized in that, in a cross-section of the resin-filled layer parallel to the bonding surface between the first electrode and the electrode of the second electronic component, the ratio of the total area SP of the figures projected from the metal particles or aggregates thereof contained in the inter-electrode region, when considered as circles, to the total area SR of the inter-electrode region demarcated by adjacent first electrodes is 35% or less.

14. The connection structure according to claim 13, wherein the ratio of the total area SP of the circles to the total area SR of the inter-electrode region is 0.5% or more.

15. A method for manufacturing a connection structure, comprising electrically connecting the electrode of a first electronic component and the electrode of a second electronic component using a conductive film according to any one of claims 1 to 12.

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