Connection structure

Abstract

To obtain a connection structure in which a first electronic component such as a μLED is connected to a second electronic component such as a board by low-voltage mounting using a filler array film, and suppress the reduction in luminous efficiency of the first electronic component.SOLUTION: In a connection structure 1A, an electrode 11 of a first electronic component 10 and an electrode 21 of a second electronic component 20 are connected via a filler 2; the electrode 11 is embedded in an insulating resin layer 3 on the second electronic component 20; and a top surface 13 of the first electronic component 10 is exposed from the insulating resin layer 3. The connection structure has a sloped region 4 of the insulating resin layer 3 around the first electronic component 10, is adjacent to the sloped region 4, and includes a flat region 5 of the insulating resin layer 3. 0≤B / A<1 and E≤500 μm are satisfied, where the height of the top surface 13 from an electrode surface 11a of the first electronic component 10 is A; the height of the first electronic component 10 of the portion exposed from the insulating resin layer 3 is B; and the distance between the outer edge of the sloped region 4 and the first electronic component 10 is E.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a connection structure obtained by connecting a first electronic component such as a minute light-emitting element to a second electronic component such as a substrate using a filler array film. [Background technology]

[0002] μLED displays, which consist of an array of μLEDs (micro light-emitting diodes), which are tiny light-emitting elements, on a substrate, can eliminate the need for backlights required in LCD displays, making it possible to make displays thinner. They are also expected to be a display or light source that can achieve a wider color gamut, higher resolution, and lower power consumption.

[0003] Patent document 1 describes a method for manufacturing a display with an array of μLEDs, in which red, blue, and green μLED arrays formed on a carrier substrate are picked up by a transfer head and placed on a destination substrate such as a display substrate, the μLED arrays are bonded to the destination substrate by welding a solder layer, and then contact lines are formed on top of them using ITO or the like.

[0004] Patent Document 2 also describes a method in which μLEDs formed on a wafer are placed on a substrate, connected to the substrate using an anisotropic conductive film in which conductive particles are dispersed in an adhesive component using a hydrogenated epoxy compound or the like, and then the wafer is lifted off. The method using the anisotropic conductive film described in Patent Document 2 allows multiple μLEDs to be mounted at once, making it easy to obtain a display using μLEDs.

[0005] Patent document 3 describes a two-stage connection method in which, when connecting an IC chip and an FPC using an anisotropic conductive film having a conductive particle arrangement layer in which the area occupancy rate of conductive particles in a planar view is 35% or less, a pulse heater bonder is used to increase the conductive particle capture efficiency, and in the first stage, the IC chip and FPC are pressed into the insulating resin layer of the anisotropic conductive film to temporarily fix the electrodes close to the conductive particle arrangement layer, and in the second stage, actual pressure bonding is performed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2015-500562 [Patent Document 2] Japanese Patent Application Publication No. 2017-157724 [Patent Document 3] Japanese Patent Application Publication No. 2019-216097 Summary of the Invention [Problem to be solved by the invention]

[0007] As described in Patent Document 2, the use of anisotropic conductive film makes it possible to easily manufacture displays by mounting μLEDs all at once. However, as the number of μLEDs to be mounted increases with the increase in display area and resolution, the μLED mounting tool requires a large thrust force.

[0008] To address the thrust problem, one possible solution is to thin the resin layer of the anisotropic conductive film and expose the conductive particles from the resin layer to enable low-pressure mounting. However, if the conductive particles are exposed from the resin layer of the anisotropic conductive film when aligning and mounting the μLED on the anisotropic conductive film, there is a concern that sufficient adhesive strength will not be obtained on the anisotropic conductive film, making it impossible to mount the μLED.

[0009] Furthermore, as displays become larger and more precise, the size of the μLED itself becomes smaller, and the electrode area and height also become smaller. Therefore, when μLEDs are mounted together using anisotropic conductive film (ACF), the resin of the ACF can bulge on the sides of the μLED after mounting, or the light-emitting part of the μLED can become embedded in the ACF resin, resulting in a decrease in luminous efficiency. Furthermore, when the μLED is embedded in the resin, the pressure required for mounting cannot be applied to the μLED efficiently, requiring a larger thrust force from the mounting tool, which limits the types of mounting tools that can be used.

[0010] On the other hand, in μLEDs whose light-emitting surface is not on the top surface (z-plane) opposite the electrode but on the xy-plane intersecting the base surface where the electrode is formed, it is necessary to provide a reflector structure adjacent to the light-emitting surface in order to obtain a high-brightness display.However, if the light-emitting part of the μLED is buried in the resin, it becomes difficult to provide a reflector structure adjacent to the light-emitting surface of the μLED.

[0011] In contrast to such conventional technology, the present invention aims to use an anisotropic conductive film to enable low-voltage mounting of fine light-emitting elements such as μLEDs on a substrate, and to prevent excessive reduction in light-emitting efficiency when the light-emitting element is buried in the resin of the anisotropic conductive film, and to enable a reflector structure to be provided adjacent to the light-emitting surface if necessary. [Means for solving the problem]

[0012] The inventors have conceived and completed the present invention, which proposes a connection structure in which the connection portion of a tiny first electronic component, such as an electrode of a μLED, is connected via filler to the connection portion of an electrode of a second electronic component, such as a substrate for a large-screen television, using a filler-arranged film in which fillers such as conductive particles are arranged in an insulating resin layer, wherein the electrode of the μLED and the base surface on which the electrode is formed are embedded in the insulating resin, but the top surface of the μLED is exposed from the insulating resin layer, and preferably the side surface adjacent to the top surface of the μLED is also partially exposed, and the thickness of the insulating resin layer is adjusted so that it is inclined around the first electronic component, and which can be manufactured by low-pressure mounting and which prevents the light emitted from the μLED from being blocked by the insulating resin layer.

[0013] That is, the present invention provides a connection structure in which electrodes of a first electronic component and electrodes of a second electronic component are connected via a filler, the electrodes of the first electronic component and the electrode formation base surface are embedded in an insulating resin layer on the second electronic component, and the top surface of the first electronic component is exposed from the insulating resin layer, and the connection structure has a sloped region around the first electronic component in which the thickness of the insulating resin layer changes depending on the distance from the first electronic component, and a flat region adjacent to the sloped region in which the thickness of the insulating resin layer is constant, The height of the top surface of the first electronic component from the electrode surface of the first electronic component is A, The height of the first electronic component exposed from the insulating resin layer is designated as B, When the distance between the outer edge of the inclined region and the first electronic component is E, 0≦B / A<1 and E≦500μm A connection structure is provided in which: [Effects of the Invention]

[0014] In the connection structure of the present invention, the top surface of the first electronic component is exposed from the insulating resin layer, and preferably the side surface adjacent to the top surface is also exposed from the insulating resin layer, thereby preventing the light emitted by the first electronic component from being excessively blocked by the insulating resin layer.

[0015] Furthermore, since the electrodes of the first electronic component and the base surface on which those electrodes are formed are embedded in the insulating resin layer, the first electronic component and the second electronic component are securely connected, and a sloped region is formed around the first electronic component in which the thickness of the insulating resin layer changes depending on the distance from the first electronic component. As a result, this connection structure ensures the resin layer thickness necessary for mounting the first electronic component while reducing excess resin layer thickness.

[0016] Furthermore, when the first electronic component is a light-emitting element such as a μLED, it is also easy to provide a reflector structure as needed. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view of a connection structure 1A according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view of a connection structure 1B of the embodiment. [Figure 3] FIG. 3 is a cross-sectional view of a connection structure 1C of the embodiment. [Figure 4] FIG. 4 is a cross-sectional view of a connection structure 1D of the embodiment. [Figure 5] FIG. 5 is a cross-sectional view of a filler array film. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will now be described in detail with reference to the drawings, in which the same reference numerals represent the same or equivalent components.

[0019] <Connection structure> FIG. 1 is a cross-sectional view of a connection structure 1A according to one embodiment of the present invention, which is obtained by mounting a first electronic component 10 to a second electronic component 20 using a filler-arranged film such as an anisotropic conductive film or a conductive film, thereby enabling low-voltage mounting during mounting and high luminous efficiency.

[0020] In connection structure 1A, electrode 11 of first electronic component 10 and electrode 21 of second electronic component 20 are connected via filler 2. Filler 2 is conductive particles derived from the filler-arranged film. Furthermore, electrode 11 and a formation surface 12 of electrode 11 of first electronic component 10 are embedded in insulating resin layer 3 on second electronic component 20, and top surface 13 of first electronic component 10 is exposed from insulating resin layer 3. Insulating resin layer 3 is derived from the filler-arranged film.

[0021] Here, examples of the first electronic component 10 include optical semiconductor elements such as mini LEDs and μLEDs.

[0022] Regarding the outer shape and size of the first electronic component 10, for example, if the outer shape is rectangular, the long side may be 200 μm or less, or less than 150 μm, or less than 50 μm, or less than 20 μm. More specifically, examples of the outer shape may include rectangles of 10 μm × 20 μm, 7 μm × 14 μm, and 5 μm × 5 μm. Note that the outer shape of the first electronic component 10 is not limited to a rectangle and may be, for example, a rhombus.

[0023] The preferred thickness of the first electronic component 10 varies depending on the material and strength of the first electronic component 10, the height of the electrodes, the connection conditions, etc., but for example, when the area of ​​the electrodes 11 of the first electronic component 10 is 1000 μm 2 Alternatively, if the length of the longest side of the first electronic component is 300 μm or more, the thickness can be 200 μm or less, or even 50 μm or less. If the length of the longest side is 300 μm or less, the thickness can be 50 μm or less. If the length of the longest side is 150 μm or less, the thickness can be 30 μm or less. If the length of the longest side is 50 μm or less, the thickness can be 20 μm or less, or even 15 μm or less, and particularly 10 μm or less. This is because if the ratio of the length of the longest side to the thickness of the first electronic component approaches 1, there is a concern that the first electronic component may be laterally misaligned when pressed during connection. Note that the thickness in this case does not include the height of electrodes 11.

[0024] The first electronic component 10 has an electrode 11 with an area of ​​1000 μm 2Alternatively, the electronic component may be a very small electronic component with a longest side length of 600 μm or less, 300 μm or less, 150 μm or less, or even 50 μm or less, for example, a rectangle with long sides of 5 μm to 50 μm and short sides of 3 μm to 40 μm. The lower limit of the short side of the size of electrode 11 is preferably 3 μm or more, more preferably 5 μm or more, from the viewpoint of convenience in the mounting process.

[0025] The height of the electrodes 11 of the first electronic component 10 may be substantially zero, but in order to prevent pressure from being applied to anything other than the electrodes during the pressure curing process or during a pressure process that is performed as needed after the overlapping process and before the pressure curing process, and to ensure that the conductive particles are efficiently pressed into the electrodes by pressure, it is preferable that the height of the electrodes 11 be more than one time the average particle diameter of the conductive particles. On the other hand, if the height of the electrodes 11 is excessively high, an unnecessarily large amount of resin will be filled between the electrodes, so the height of the electrodes 11 is preferably no more than three times the average particle diameter of the conductive particles, and more preferably no more than two times.

[0026] On the other hand, the second electronic component 20 to which the first electronic component 10 is connected can be made of various substrates, including transparent substrates such as glass substrates and plastic substrates, as well as opaque substrates. The second electronic component 20 may also be a ceramic substrate, a rigid resin substrate, an FPC, or other substrate.

[0027] (Change in thickness of insulating resin layer in connection structure) The connection structure of the present invention is characterized by a change in the thickness of the insulating resin layer 3 around the first electronic component 10, and the insulating resin layer 3 has a sloped region 4 around the first electronic component 10. The sloped region 4 is a region where the thickness of the insulating resin layer 3 changes depending on the distance from the first electronic component 10, and in this example, a side surface 14 adjacent to the top surface 13 of the first electronic component 10 is partially exposed from the insulating resin layer 3, and the sloped region 4 is formed adjacent to the side surface 14. In this sloped region 4, the thickness of the insulating resin layer 3 decreases as the distance from the first electronic component 10 increases.

[0028] In addition, in the connection structure of the present invention, a flat region 5 having a constant thickness of the insulating resin layer 3 exists adjacent to the inclined region 4, and in the connection structure 1A of this embodiment, the flat region 5 is formed adjacent to the outside of the inclined region 4.

[0029] In the connection structure of the present invention, when the height of the top surface 13 of the first electronic component 10 from the electrode surface 11a of the first electronic component 10 is A, the height of the part of the first electronic component 10 exposed from the insulating resin layer 3 (i.e., the exposed distance of the first electronic component 10 in a direction perpendicular to the electrode surface 11a) is B, and the distance between the outer edge of the inclined region 4 and the first electronic component 10 is E, the relationship "0≦B / A<1 and E≦500 μm" is satisfied.

[0030] In the above formula, "B / A=0" means that the top surface 13 of the first electronic component 10 is flush with the top surface of the insulating resin layer 3 adjacent to the first electronic component 10 around the first electronic component 10. "B / A<0" means that the top surface 13 of the first electronic component 10 is recessed relative to the top surface of the insulating resin layer 3 adjacent to the first electronic component 10. In the present invention, the top surface 13 of the first electronic component 10 preferably protrudes upward relative to the top surface of the insulating resin layer 3 adjacent to the first electronic component 10. This is because, when light is emitted from the first electronic component 10 (e.g., a μLED), blocking of the light by the insulating resin layer 3 can be suppressed. Furthermore, "B / A<1" means that the first electronic component 10 is embedded in the insulating resin layer 3. This is to fix the first electronic component 10 to the second electronic component. By making "B / A<1," the electrodes 11 and the electrode 11 formation surface 12 of the first electronic component 10 are embedded in the insulating resin layer 3 on the second electronic component 20. However, if the degree of embedding is large, the light extraction efficiency decreases if the first electronic component 10 is a μLED. Furthermore, if the degree of embedding is small (in other words, the degree of exposure of the first electronic component 10, such as a μLED, decreases), the thickness accuracy of the resulting connection structure tends to decrease when multiple first electronic components 10 are mounted on the second electronic component. Therefore, "B / A" is preferably 0.1 or more from the viewpoint of reducing the thickness tolerance of the connection structure, and is preferably 0.5 or less to avoid a decrease in light extraction efficiency.

[0031] Furthermore, E is preferably 500 μm or less, and more preferably 100 μm or less. Compared to when the thickness of insulating resin layer 3 in connection structure 1A is constant at the height of the top surface of first electronic component 10, by specifying E≦500 μm, the amount of resin constituting connection structure 1A can be reduced, and connection structure 1A can be obtained by low-pressure mounting. When mounting by reflow, it is only necessary to adjust the thickness to such a value.

[0032] <Modification of connection structure 1> The connection structure of the present invention can be modified in various ways. For example, as in connection structure 1B shown in Fig. 2, the thickness of insulating resin layer 3 in inclined region 4 may increase as the distance from first electronic component 10 increases.

[0033] As in the connection structure 1C shown in Figure 3, a flat region 5a where the thickness of the insulating resin layer 3 is constant may be provided between the first electronic component 10 and the inclined region 4, and the thickness of the insulating resin layer 3 in the flat region 5a may be set to the minimum thickness of the insulating resin layer 3 in the inclined region 4.

[0034] 4, a flat region 5a where the thickness of the insulating resin layer 3 is constant may be provided between the first electronic component 10 and the inclined region 4, and the thickness of the insulating resin layer 3 in the flat region 5a may be set to the maximum thickness of the insulating resin layer 3 in the inclined region 4. In the connection structure 1D, the height B of the part of the first electronic component 10 exposed from the insulating resin layer 3 is zero, so B / A=0. In this respect, the connection structure 1D differs from the above-described connection structures 1A, 1B, and 1C, but B / A=0 may also be satisfied depending on the application of the connection structure.

[0035] Furthermore, in connection structure 1D, flat region 5b is provided adjacent to the outside of inclined region 4, and the thickness of insulating resin layer 3 in flat region 5b is set to the minimum thickness of insulating resin layer 3 in inclined region 4.

[0036] 1 to 4, in the small region from the first electronic component 10 to the outer edge of the sloped region 4, i.e., the region from the first electronic component to the distance E, the connection structure 1D shown in Fig. 4 has the greatest amount of resin, and the connection structure 1C shown in Fig. 3 has the least, but the connection structure 1D shown in Fig. 4 has a reduced amount of resin outside the sloped region 4. Therefore, in an electronic article equipped with the connection structure of the present invention, which of the connection structures of Fig. 1 to 4 should be used can be determined appropriately depending on the application of the electronic article, etc.

[0037] <Connection structure variation 2> The above-mentioned <Modified form of connection structure No. 1> explained a modified form from the perspective of the geometric configuration of the connection structure, but <Modified form of connection structure No. 2> explains a modified form that, assuming the geometric configuration of the connection structure, focuses on using an insulating resin layer as a black matrix without excessively suppressing the luminous efficiency of the μLED.

[0038] (Reasons for focusing on using an insulating resin layer as a black matrix) In recent years, micro LED displays have been expected to have desirable characteristics such as high brightness, low power consumption, high contrast, and long life because they utilize micro LEDs with high luminous efficiency and long life to emit light themselves. In such micro LED displays, red, green, and blue LEDs are arranged at predetermined intervals on a display substrate. Because the LEDs are self-emitting, they may not use color filters separated by a black matrix. In such cases, a black matrix must be formed between the micro LEDs to prevent color mixing (see, for example, JP 2021-506108 A and WO 2021 / 060832 A1 A).

[0039] Known methods for forming a black matrix on a micro LED display include: (a) applying a composition for forming a black transfer layer to the entire surface of one side of a display substrate before mounting micro LEDs, and removing the composition for forming the black transfer layer applied to the non-black matrix area of ​​the display substrate by etching or photolithography; (b) forming a black matrix on a carrier film by screen printing, aligning and attaching the black transfer film to the display substrate before mounting micro LEDs, and peeling off the carrier film; (c) covering the display substrate on which micro LEDs are mounted with a cover glass on which a black matrix is ​​formed; and (d) applying an ink composition for a black matrix by an inkjet method between the micro LEDs of the display substrate on which micro LEDs are mounted.

[0040] However, in the method (a), it takes time to form the black matrix, in the methods (b) and (c), the positional accuracy of the black matrix is ​​not sufficient, and in the method (d), it is difficult to form a black matrix with a height sufficient to suppress color mixing of the micro LED.

[0041] Therefore, when manufacturing light-emitting devices such as image display devices and lighting devices using micro LEDs, it is necessary to form the black matrix quickly, with sufficient positional accuracy, and with a height sufficient to suppress color mixing of the micro LEDs without excessively suppressing the luminous efficiency. This need is the reason why we focused on using an insulating resin layer as the black matrix.

[0042] (Insulating resin layer that functions as a black matrix) 1 to 4, the insulating resin layer 3 is formed from an insulating resin composition containing a black pigment so that it functions as a black matrix. In other words, the insulating resin layer constituting the anisotropic conductive film or filler array film, or the insulating resin layer holding conductive particles or filler, is formed from an insulating resin composition containing a black pigment. In FIGS. 1 to 4, the surface of the first electronic component 10 (μLED) is not covered with the insulating resin layer 3 functioning as a black matrix, so there is no excessive decrease in luminous efficiency. Moreover, because at least a portion of the side surface of the first electronic component 10 is covered, the amount of light emitted in the lateral direction can be reduced, and color mixing of the μLED can be suppressed.

[0043] Known black pigments such as carbon black and titanium black can be used as black colorants for blackening the insulating resin composition. Titanium black, which has an extremely low content of impurity ions and is itself insulating, is particularly preferred. When titanium black is used as the black pigment, the titanium black content in the black resin composition for black matrices is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 40% by mass or less, and more preferably 30% by mass or less. The average particle size of these black pigments is 10 to 100 nm. It is desirable that the black pigment be smaller than the average particle size of the conductive particles.

[0044] The components of the insulating resin composition that functions as the black matrix, other than the black pigment, can be the same as the components of the insulating resin layer described below.

[0045] (Fillet shape of insulating resin layer 3 functioning as a black matrix) The insulating resin layer 3 functioning as a black matrix can have the structure shown in Figures 1 to 4. Specifically, as shown in Figure 1, when the side length in the height direction of the first electronic component is L0, the height of the portion of the first electronic component exposed from the insulating resin layer is B, and the height of the fillet formed by the insulating resin layer is "L0-B," the fillet formation rate F defined by the following formula is preferably 60% or more, more preferably 70% or more, preferably 100% or less, and more preferably 90% or less. In particular, as shown in Figure 1 or 4, a fillet shape in which the thickness of the insulating resin layer decreases in the inclined region as the distance from the first electronic component increases is preferred.

[0046]

number

[0047] <Method of manufacturing the connection structure> The manufacturing method of the connection structure 1A in FIG. 1 is roughly as follows: a filler array film is attached to the electrode 21 of the second electronic component 20; the filler array film and the first electronic component 10 are aligned and attached together; and heating and pressurizing are performed to connect the electrode 11 of the first electronic component 10 to the electrode 21 of the second electronic component 20. In this case, the first electronic component 10 may be arranged on a wafer. The heating and pressurizing method may be a two-stage heating and pressurizing method as described in Patent Document 3. Alternatively, when the filler 2 is solder particles or the like, the connection may be performed by reflow.

[0048] The temporary attachment of the filler array film, film transfer, and mounting of the μLED on the substrate can be performed using known methods such as stamp materials (see, for example, JP 2021-141160 A) or laser-based methods (laser lift-off processing methods), or methods that apply these (for example, methods described in JP 9-124020 A, JP 2011-76808 A, Japanese Patent No. 6636017 A, Japanese Patent No. 6187665 A, etc.), and there are no particular limitations on the method as long as it can achieve the effects of the present invention.

[0049] <Modifications of the manufacturing method of the connection structure> When a connection structure is produced by mounting a very small first electronic component on a second electronic component such as a wiring board, the first electronic component can be mounted by impacting the second electronic component using the laser lift-off process described above. For example, if the first electronic component is a large number of micro LEDs formed on the surface of an optically transparent substrate, a filler array film arranged in a predetermined location on the second electronic component (e.g., each electrode on the wiring board) can be irradiated with laser light from the optically transparent substrate side to each first electronic component, impacting the first electronic component, and then heating and pressurizing the first electronic component to press it into the filler array film, producing a connection structure. The laser lift-off process conditions can be determined appropriately depending on the type and constituent materials of the first electronic component, etc.

[0050] The filler array film may be disposed over the entire surface of the connection portion of the second electronic component, such as a wiring board, or may be disposed in pieces in predetermined units in part of the display unit, such as in units of one pixel (one picture element) of one set of RGB. In this case, since the insulating resin layer in the connection structure is derived from the filler array film, the insulating resin layer in the connection structure is also disposed in pieces, and the same effect as when the filler array film is used in pieces can be expected.

[0051] When the filler array film is arranged in pieces, a single piece may electrically connect (hereinafter, "connect") multiple microscopic first electronic components, such as micro LEDs. However, connecting one micro LED with one piece is preferable, and connecting one micro LED with multiple pieces is also preferable. Connecting one micro LED with a single piece makes it easier to adjust the formation of a ferrule. Connecting one micro LED with multiple pieces allows for more precise adjustment, since, for example, the P electrode and N electrode are connected with separate pieces. Multiple pieces may also be used to connect multiple micro LEDs. For example, if multiple P electrodes and N electrodes are arranged in parallel, the pieces may be arranged to correspond to the respective electrode rows. Furthermore, connecting pieces of a filler array film using a black insulating resin composition to form an insulating resin layer allows for the formation of a black matrix in the ferrule around the outer edge of the micro LEDs, enabling connection and overall color adjustment of the μLED display. Such filler array film pieces can be formed using the laser lift-off method described below, as well as screen printing, etching, inkjet printing, and other methods. The size of the piece can be determined appropriately depending on the shape and size of the first electronic component to be connected.

[0052] The method for arranging the filler array film on the display unit of the second electronic component is not particularly limited. For example, when arranging the filler array film over the entire surface of the display unit, a lamination method can be used. Furthermore, when arranging individual pieces of the filler array film in a portion of the display unit, a method using a laser lift-off (LLO) device to directly transfer and arrange the individual pieces from the base film to the second electronic component, or a method using a transfer material (stamp material) to which the individual pieces have been previously attached and transferring and arranging the individual pieces from the transfer material to the second electronic component can be used.

[0053] In addition, when a first electronic component such as a micro LED is landed by a laser lift-off process on a filler array film that has been placed at a predetermined position on a second electronic component by thermocompression bonding or on an individual piece of filler array film that has been transferred by a laser lift-off process, in order to prevent the first electronic component from being misaligned, deforming, breaking, or coming loose, it is preferable that the insulating resin layer of the filler array film contains a rubber component (e.g., acrylic rubber, silicone rubber, butadiene rubber, polyurethane-based elastomer, etc.) that provides cushioning to absorb the impact of the landing, or an inorganic filler (e.g., silica, talc, titanium oxide, calcium carbonate, etc.) that provides mechanical strength.

[0054] The insulating resin layer containing such rubber components and inorganic fillers has a durometer A hardness (according to 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 measured using a dynamic viscoelasticity tester (temperature 30°C, frequency 200 Hz; Vibron, A&D Co., Ltd.) according to JIS K7244 of preferably 60 MPa or less, more preferably 30 MPa or less, and particularly preferably 10 MPa or less.

[0055] Furthermore, the insulating resin layer preferably has a storage modulus of 100 MPa or more, and more preferably 2000 MPa or more, at 30°C, measured in a tensile mode according to JIS K7244 after curing. If the storage modulus at 30°C is too low, good conductivity cannot be obtained and connection reliability tends to decrease. The storage modulus at 30°C can be measured in a tensile mode using a viscoelasticity tester (Vibron) according to JIS K7244, for example, under measurement conditions of a frequency of 11 Hz and a heating rate of 3°C / min.

[0056] In addition, a first electronic component such as a micro LED can be transferred (landed) by laser lift-off processing to a predetermined position on a substrate made of silicone rubber such as polydimethylsiloxane (PDMS) (i.e., a position corresponding to the predetermined position of a second electronic component to which the first electronic component is to be re-transferred), and then the first electronic component side of the first electronic component placement sheet can be placed facing the second electronic component, aligned, and then transferred.

[0057] <Filler array film> The filler-arranged film used in manufacturing the connection structure 1A can be one in which conductive particles are held as a filler in a laminate of one or more insulating resin layers. When using one in which conductive particles are held in a laminate of multiple insulating resin layers, as shown in Figure 5, the insulating resin layer 31 of the filler-arranged film 30 can be made to include a high-viscosity binder resin layer 32 that holds the conductive particles 2, and an adhesive layer 33 with a lower viscosity than the high-viscosity binder resin layer 32.

[0058] In the manufacturing method of the connection structure 1A, as shown in Figure 1, the insulating resin layer 3 is formed with a sloped region 4 and a flat region 5 so as to satisfy the aforementioned formula "0≦B / A<1 and E≦500 μm". In order to do this, as the filler arranged film, when the thickness of the insulating resin layer 31 is La and the average particle diameter of the conductive particles 2 is D, La / D is preferably 0.6 or more and 8 or less, more preferably 1 or more and 2 or less, and even more preferably 1.0 or more and 1.3 or less.

[0059] The ratio La / A of the thickness La of the insulating resin layer 31 to the height A from the electrode surface 11a of the first electronic component 10 to the top surface 13 is preferably 0.1 to 1, more preferably 0.5 to 0.8.

[0060] Furthermore, to provide the above-mentioned sloped region 4 and flat region 5 in the insulating resin layer 3 of the connection structure 1A, the film thickness is preferably 1.5 times or more, preferably 7.5 times or less, and more preferably 4.5 times or less the electrode height. Furthermore, a minimum melt viscosity of 8000 to 12000 Pa s is preferable because it allows for control of the embedding state of the μLED when pressing a relatively thin film.

[0061] The resins constituting the high-viscosity binder resin layer 32 and adhesive layer 33 of the insulating resin layer 31 of the filler-arranged film 30 can be, for example, the same as the binder and adhesive layer constituting the insulating resin layer described in Patent Document 3. Different fillers may be arranged in different layers and laminated.

[0062] The insulating resin layer 31 may contain rubber components, inorganic fillers, silane coupling agents, diluting monomers, bulking agents, softeners, colorants, flame retardants, thixotropic agents, and the like, as required.

[0063] A rubber component may be blended to prevent warping or distortion of the connection structure. The rubber component is not particularly limited as long as it is an elastomer with high cushioning properties (shock absorption), and specific examples include acrylic rubber, silicone rubber, butadiene rubber, and polyurethane resin (polyurethane-based elastomer).

[0064] The conductive particles 2 in the filler array film 30 may be arranged randomly or regularly, but a planar lattice pattern having one or more arrangement axes in which the conductive particles are arranged in a predetermined direction at a predetermined pitch is preferred to improve the capture of the conductive particles in each electrode 11, 21. Examples include an oblique lattice, a hexagonal lattice, a square lattice, a rectangular lattice, and a parallelepiped lattice. Also, there may be regions with different planar lattice patterns.

[0065] In the filler arranged film 30, the average particle diameter D of the conductive particles 2 is preferably 1 μm or more and 50 μm or less, and more preferably 1 μm or more and 2 μm or less.

[0066] The average particle size can be a value measured using an imaging particle size distribution analyzer (for example, FPIA-3000, manufactured by Malvern Panalytical). At the time of measurement, the number of particles is preferably 1,000 or more, and more preferably 2,000 or more.

[0067] The hardness of the conductive particles 2 is preferably 2000 N / mm 2 More than 25000N / mm 2 Less than or equal to 5000N / mm 2 More than 10000N / mm 2 The following is the result.

[0068] The number density of the conductive particles 2 in the filler array film 30 is 30 particles / mm 2 More than 500000 pieces / mm 2 The number of particles per mm can be set to 120,000 or less, and preferably 120,000 particles per mm 2 More than 350000 pieces / mm 2 Less than or equal to 150,000 pieces / mm 2 More than 300000 pieces / mm 2 It is preferable to do the following:

[0069] The number density of the conductive particles 2 may be determined by observation using a metallurgical microscope or by measuring an observed image using image analysis software (for example, WinROOF (Mitani Corporation) or Azokun (registered trademark) (Asahi Kasei Engineering Corporation)). The number of conductive particles is measured by counting the number observed on the filler array film.

[0070] The type of conductive particles 2 can be appropriately selected from conductive particles used in known anisotropic conductive films. Examples of conductive particles include metal particles such as nickel, cobalt, silver, copper, gold, and palladium; alloy particles such as solder; metal-coated resin particles; and metal-coated resin particles with insulating fine particles attached to their surfaces. Two or more types can also be used in combination. Among these, metal-coated resin particles are preferred because they facilitate maintaining contact with the terminals by repulsion of the resin particles after connection, thereby stabilizing electrical conductivity. Furthermore, the surfaces of the conductive particles may be subjected to an insulating treatment using known techniques that does not impair electrical conductivity.

[0071] In addition, the filler in the filler array film is appropriately selected from inorganic fillers (metal particles, metal oxide particles, metal nitride particles, etc.), organic fillers (resin particles, rubber particles, etc.), and fillers that are a mixture of organic and inorganic materials (for example, particles whose core is formed from a resin material and whose surface is metal-plated (metal-coated resin particles), conductive particles with insulating fine particles attached to the surface, conductive particles with an insulating treatment applied to the surface, etc.) depending on the performance required for the application, such as hardness and optical performance.

[0072] For example, when the filler array film is used for adjusting the color of micro-optical elements such as μLEDs or as a black matrix in a color display, it may contain known dyes, pigments, light-scattering particles, etc. as fillers.

[0073] <Manufacturing method of filler array film> The filler array film 30 can be manufactured in the same manner as known anisotropic conductive films, except that the minimum melt viscosity and thickness are adjusted so that the insulating resin layer 31 in the connection structure 1A has the inclined region 4 and flat region 5 shown in Figure 1.

[0074] For example, similar to the method for producing an anisotropic conductive film described in Patent Document 3, a mold having recesses formed therein corresponding to the arrangement pattern of the conductive particles is first prepared, the mold is filled with conductive particles 2, a high-viscosity binder resin layer 32 formed on a release film is attached thereto, the conductive particles 2 are pressed into the high-viscosity binder resin layer 32 and transferred, and an adhesive layer 33 is laminated on the transferred surface. Here, in order to change the thickness of the insulating resin layer 31 as shown in Figure 1, the minimum melt viscosity and thickness may be adjusted, and an insulating resin layer may be further laminated.

[0075] <Example of use of filler array film> The filler array film may be individual pieces of a predetermined unit, such as one pixel unit (one pixel unit) of one RGB set. The individual pieces may be spaced apart according to the electrodes on the substrate corresponding to each electrode of the micro LED. That is, the filler array film may be in the form of individual pieces. The shape of the individual pieces is not particularly limited and can be appropriately set according to the dimensions of the electronic components to be connected. When the individual pieces of the filler array film are formed on the base film by a laser lift-off processing method (see JP 2017-157724 A) using an LLO device (e.g., product name: Invisi LUM-XTR, Shin-Etsu Chemical Co., Ltd.), in order to prevent the occurrence of curling or chipping, the shape of the individual pieces is preferably at least one selected from a polygon with obtuse angles, a polygon with rounded corners, an ellipse, an oval, and a circle. The connection structure of the present invention may be a combination of a filler array film for connection consisting of pieces of such a shape and a micro LED, and also includes an embodiment in which the micro LED is embedded in the piece by adjusting the thickness, viscosity, etc. of the film that becomes the piece. The shape of the piece may be at least one selected from a polygon with obtuse angles, a polygon with rounded corners, an ellipse, an oval, and a circle, and the pieces may be individually placed separately only on the electrodes on the substrate, and the electrodes of the micro LEDs may be connected to each other at the separated pieces.

[0076] The dimensions (length x width) of the filler-arranged film pieces are appropriately set according to the dimensions of the electronic components to be connected, and the ratio of the area of ​​the pieces to the area of ​​the electronic components is preferably 2 or more, more preferably 4 or more, and even more preferably 5 or more. The thickness of the pieces, like the thickness of the filler-arranged film, is preferably the average particle diameter of the conductive particles plus 1 to 4 μm, particularly preferably 1 to 2 μm, and is preferably 1 μm to 10 μm, more preferably 1 μm to 6 μm, and even more preferably 2 μm to 4 μm. Such filler-arranged film pieces may be provided only on the electronic components or only on the electrodes of the electronic components. To achieve an appropriate resin embedding state, multiple pieces may be transferred to achieve a predetermined resin thickness. The present invention also encompasses a method for producing such a connection structure.

[0077] The distance between the 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 the 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 the pieces is too small, it becomes difficult to transfer the pieces by LLO. If the distance between the pieces is large, a method of bonding the pieces becomes preferable. The distance between the pieces can be measured using a microscope (optical microscope, metallographic microscope, electron microscope, etc.).

[0078] <Manufacturing method for individual filler-arranged film> The individual pieces of the filler array film may be formed by slitting or half-cutting, or may be formed using an LLO apparatus. When forming the individual pieces using an LLO apparatus, the substrate film may be any film that is transparent to laser light, and is preferably quartz glass, which has high light transmittance over all wavelengths.

[0079] When forming individual pieces of filler array film using an LLO device, laser light is irradiated from the base film side onto the filler array film provided on the base film, and the irradiated parts of the filler array film are removed, thereby forming individual pieces of filler array film of a predetermined shape on the base film.

[0080] For example, by using a mask with a rectangular opening window to remove unnecessary portions of the filler array film from the base film, it is possible to form individual pieces of a predetermined shape with the remaining portions of the filler array film.Also, by using a mask with a predetermined shaped light-shielding portion formed in the opening window to remove unnecessary portions of the filler array film around the individual pieces from the base film, it is possible to form individual pieces of a predetermined shape with the remaining portions of the filler array film.

[0081] Furthermore, when individual pieces are produced using an LLO 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 or the individual pieces obtained after laser irradiation can be determined from the reduction rate of reactive groups using, for example, FT-IR. For example, in the case of a curable resin film utilizing the reaction of an epoxy compound, infrared rays are irradiated onto the sample to measure the IR spectrum, and the methyl group (2930 cm) in the IR spectrum is measured. -1 around 914cm -1 The peak heights of the epoxy groups (near the peak height of the methyl group) are measured, and the ratio of the peak height of the epoxy group before and after the reaction (for example, before and after laser irradiation) to the peak height of the methyl group can be calculated as shown in the following formula.

[0082]

number

[0083] 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. Note that if other peaks overlap the epoxy group peak, the peak height of the fully cured sample (100% reaction rate) should be taken as 0%. [Example]

[0084] <Preparation of particle-aligned black anisotropic conductive film> The black insulating resin compositions (i), (ii), and (iii) in Table 1 were mixed, respectively, and the resulting mixture was applied to a release substrate and dried at 60°C for 3 minutes to obtain black insulating resin films with a thickness of 4 μm or 6 μm, respectively.

[0085] Thereafter, conductive particles (Micropearl AU, Sekisui Chemical Co., Ltd.) were deposited at a particle density of 58,000 particles / mm by the conductive particle regular array treatment described in paragraphs 0111 to 0112 and FIG. 1A of Japanese Patent No. 6187665. 2 After the particles were regularly arranged so as to form a black insulating resin film, they were transferred onto a black insulating resin film to obtain a particle-aligned black anisotropic conductive film A from the black insulating resin composition (i), a black anisotropic conductive film B from the particle-aligned black insulating resin composition (ii), and a black anisotropic conductive film C from the particle-aligned black insulating resin composition (iii).

[0086] [Table 1]

[0087] <Creating an implementation sample> The black anisotropic conductive films of Examples 1 to 4 were temporarily fixed to an evaluation substrate, and an evaluation LED chip was placed on the adherend and pressure-bonded at 200°C, 10 MPa, and 30 seconds to obtain a mounted assembly. The resulting mounted assembly was tested and evaluated for "degree of color mixing," "fillet formation rate F," and "conduction resistance" as described below. The results are shown in Table 2.

[0088] <Degree of color mixing> In Examples 1 to 4, the mounting body was placed in a dark room, the evaluation LED chip was made to emit light, the contour of the scattered light was measured with a metallurgical microscope, and the color mixing ability was evaluated based on the maximum value.

[0089] (Color mixing evaluation) Evaluation Rank Criteria AA: Less than 5 μm A: 5 μm or more and less than 15 μm B: 15 μm or more and less than 25 μm C: 25μm or more

[0090] <Fillet formation rate F> The fillet shape of the mounting body was observed with a laser microscope to determine the side length L0 of the LED in the height direction and the height B of the LED part exposed from the insulating resin layer, and the fillet formation rate F was calculated according to the following formula. For practical purposes, it is preferable that the fillet formation rate F is 60% or more and 100% or less.

[0091]

number

[0092] <Conduction resistance> Two pairs of 10 x 10 μm electrodes were attached to the evaluation LED chip of this package, and the conduction resistance was measured through the conductive wiring on the substrate side. Measurements were made at a total of 30 locations, and the obtained average conduction resistance was evaluated according to the following criteria.

[0093] (Conductive resistance evaluation) Evaluation Rank Criteria A: 50Ω or less B: More than 50Ω but less than 100Ω C: More than 100Ω but less than 200Ω D(NG): Over 200Ω

[0094] [Table 2]

[0095] <Discussion of results> The degree of color mixing was evaluated as A in Examples 1 to 3, where the fillet formation rate F was 60%. In Example 4, where the fillet formation rate F was 100%, the degree of color mixing was even better than in Examples 1 to 3, where the fillet formation rate was 60%, and was evaluated as AA. This is thought to be because Example 4 was able to block more light emitted from the side surfaces of the LED. In addition, in Examples 1 to 4, the conduction resistance was evaluated as A, which means that there is no problem in practical use. [Industrial Applicability]

[0096] In the connection structure of the present invention, the top surface of the first electronic component is exposed from the insulating resin layer, and preferably the side surface adjacent to the top surface is also exposed from the insulating resin layer, thereby preventing excessive blocking of light emitted by the first electronic component by the insulating resin layer. Furthermore, the electrodes of the first electronic component and the base surface on which those electrodes are formed are embedded in the insulating resin layer, ensuring a reliable connection between the first electronic component and the second electronic component. Furthermore, a gradient region is formed around the first electronic component in which the thickness of the insulating resin layer varies depending on the distance from the first electronic component. This connection structure ensures the resin layer thickness necessary for mounting the first electronic component while reducing excess resin layer thickness. Furthermore, using a black insulating resin composition to form the insulating resin layer can shorten the process and reduce costs for connecting LEDs and forming a black matrix. [Explanation of symbols]

[0097] 1A, 1B, 1C, 1D Connection structure 2 Filler, conductive particles 3. Insulating resin layer 4 Slope area 4a Outer edge of the sloped area 5, 5a, 5b flat area 10 First Electronic Components, μLED 11 electrodes 11a Electrode surface 12 Electrode formation base surface 13 Top 14 Side 20 Second electronic component, board 21 electrodes 30 Filler array film 31 Insulating resin layer 32 High viscosity binder resin layer 33 Adhesive layer A: Height from the electrode surface of the first electronic component to the top surface of the first electronic component B: Height of the part of the first electronic component exposed from the insulating resin layer E: Distance between the outer edge of the sloped area and the first electronic component D Average particle size of conductive particles La Thickness of insulating resin layer L0: Side length of the first electronic component

Claims

1. A connection structure in which the electrodes of a first electronic component and the electrodes of a second electronic component are connected via a filler, and the electrodes and electrode formation base surface of the first electronic component are embedded in an insulating resin layer on the second electronic component, with the top surface of the first electronic component exposed from the insulating resin layer, The first electronic component has a sloped region where the thickness of the insulating resin layer changes according to the distance from the first electronic component, and adjacent to the sloped region, there is a flat region where the thickness of the insulating resin layer is constant. When A is the height of the top surface of the first electronic component from the electrode surface of the first electronic component, B is the height of the portion of the first electronic component exposed from the insulating resin layer, and E is the distance between the outer edge of the inclined region and the first electronic component, 0 ≤ B / A < 1 and E ≤ 500 μm A connection structure.

2. The connection structure according to claim 1, wherein the side surface adjacent to the top surface of the first electronic component is partially exposed from the insulating resin layer.

3. The connection structure according to claim 1 or 2, wherein the thickness of the insulating resin layer decreases as the distance to the first electronic component increases in the inclined region.

4. The connection structure according to claim 1 or 2, wherein the thickness of the insulating resin layer increases as the distance to the first electronic component increases in the inclined region.

5. The connecting structure according to claim 1 or 2, wherein a flat region is formed outside the inclined region.

6. The connection structure according to claim 1, wherein the filler connecting the electrode of the first electronic component and the electrode of the second electronic component is derived from a filler array film in which the filler is held in a single insulating resin layer or a laminate of multiple insulating resin layers.

7. The connection structure according to claim 4, wherein there is a flat region between the first electronic component and the inclined region in which the thickness of the insulating resin layer is constant, and the thickness of the insulating resin layer in the flat region is the minimum thickness of the insulating resin layer in the inclined region.

8. The connection structure according to claim 3, wherein there is a flat region between the first electronic component and the inclined region in which the thickness of the insulating resin layer is constant, and the thickness of the insulating resin layer in the flat region is the maximum thickness of the insulating resin layer in the inclined region.

9. The connecting structure according to claim 1, wherein the insulating resin layer is a single piece.

10. The connecting structure according to claim 3, wherein the insulating resin layer is formed from a black resin composition for black matrices.

11. The connecting structure according to claim 10, wherein the black resin composition for the black matrix contains 5% by mass or more and 40% by mass or less of titanium black.

12. The side length in the height direction of the first electronic component is L. ０ Let B be the height of the first electronic component in the portion exposed from the insulating resin layer, and L be the height of the fillet formed by the insulating resin layer. ０ When we set it to -B'', the following equation [Math 1] The connection structure according to claim 10, wherein the fillet formation rate F, as defined by [formula], is 60% or more and 100% or less.

13. A method for manufacturing a connecting structure according to Claim 1, A method for manufacturing a connection structure, comprising attaching a filler array film to the electrodes of a second electronic component, aligning and bonding the filler array film with the first electronic component, and then heating and pressurizing to connect the electrodes of the first electronic component with the electrodes of the second electronic component.

14. A method for manufacturing a connecting structure according to Claim 1, A method for manufacturing a connecting structure, comprising irradiating a first electronic component formed on the surface of a light-transmitting substrate with laser light from the light-transmitting substrate side, thereby causing the first electronic component to land on a filler array film positioned at a predetermined location on the second electronic component.

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