Connection structure

Abstract

A connection structure (1) in which an electrode (11) of an electronic component (10) and an electrode (21) of a substrate (20) are connected by a connection material (2 ') derived from conductive particles to which an adhesive material is attached is configured such that the area of the connection material (2') is less than 120% of the area of the electrode (11) of the electronic component (10) in plan view of a connection surface between the electrode (11) of the electronic component (10) and the electrode (21) of the substrate (20). The connection structure (1) can be obtained by disposing conductive particles (2) to which an adhesive material has been adhered on an electrode (11) of an electronic component (10) or an electrode (21) of a substrate (20) in the form of particles or a single sheet, sandwiching the conductive particles (2) to which the adhesive material has been adhered between the electrode (11) of the electronic component (10) and the electrode (21) of the substrate (20), and connecting the conductive particles (2) to the electrode (11) of the electronic component (10) and the electrode (21) of the substrate (20) by heating or pressurizing.

Description

Technical Field

[0001] The present invention relates to a connection structure for connecting electronic components such as a micro light-emitting element to a substrate using conductive particles, a method for producing the same, and a connection material used in the method for producing the same. Background Art

[0002] A μLED display, which is made by arranging μLEDs, which are tiny light-emitting elements, on a substrate, can omit the backlight required for a liquid crystal display, thereby making the display thinner. It is also expected to be a display or light source that can achieve a wide color gamut, high definition, and power saving.

[0003] As a method for producing a display in which μLEDs are arranged, Patent Document 1 describes the following: a transfer head is used to pick up red, blue, and green μLED arrays formed on a carrier substrate, and the arrays are arranged on a transfer target substrate such as a display substrate, and the μLED arrays are bonded to the transfer target substrate by melting a solder layer, and then contact lines are formed thereon using ITO or the like.

[0004] In addition, Patent Document 2 describes a method in which an anisotropic conductive film is stacked on an LED electrode formed on a wafer, the anisotropic conductive film is cut to form an LED chip, the LED chip is held on a convex embossed holding member, and the LED chip is arranged on a circuit board to manufacture a light-emitting substrate. According to this method, an anisotropic conductive film is already formed on the electrode of the LED chip, so that unnecessary anisotropic conductive film can be reduced.

[0005] Patent document 3 describes a method for mounting an LED on a substrate as follows: a bump electrode is formed on the substrate in advance, and a semi-curing adhesive layer is patterned in advance around the LED mounting portion, and then the LED is mounted on the substrate so that the bump electrode contacts the LED electrode, and the semi-curing adhesive layer around the LED is cured. According to this method, there is no adhesive between the LED electrode and the substrate electrode, so that poor contact caused by the adhesive can be avoided. Prior Art Literature Patent Literature

[0006] Patent Document 1: Japanese Patent Application No. 2015-500562 Patent Document 2: Japanese Patent Application Publication No. 2020-191419 Patent Document 3: Japanese Patent Application Publication No. 2021-9985 Summary of the invention Problems to be solved by the invention

[0007] However, as the size of μLEDs decreases for higher definition displays, the size of μLED electrodes also decreases. If the intervals between electrodes become narrower, the risk of short circuits or poor connections increases in the above-mentioned prior art.

[0008] In addition, in the method described in Patent Document 2, the LED is arranged on the substrate after being held by a convex embossed holding member, and therefore, it is not suitable for arranging LEDs over a large area from the viewpoint of productivity. In addition, since a thermosetting resin is used in the anisotropic conductive film, the LED chip cannot be arranged on the circuit substrate by being singulated by etching.

[0009] In the method described in Patent Document 3, since the bump electrodes are formed on the substrate in advance, short circuits are less likely to occur. However, the formation of the bump electrodes takes time and is not suitable for mass production. In addition, the patterning of the semi-cured adhesive layer is difficult to control.

[0010] In contrast, the present invention aims to provide a connection structure that connects electronic components such as tiny light-emitting elements to a substrate and suppresses short circuits or poor conduction, a method for manufacturing such a connection structure, and a connection material used in the manufacturing method. Solutions to Solve Problems

[0011] The inventor of the present invention completed the following idea: when installing electronic components, if conductive particles with tiny adhesive material attached to them are first arranged between the electrodes of the electronic components and the electrodes of the substrate, in this case, adjacent electrodes in the electronic components will not be buried by the conductive particles with the adhesive material, and then hot pressing or the like is performed. Even if the electronic components are miniaturized, electrical connection can be reliably performed without causing a short circuit.

[0012] That is, the present invention provides a connection structure, which is a connection structure that connects the electrodes of opposing electronic components and the electrodes of a substrate by a connection material derived from conductive particles of an adhered adhesive material, wherein, when the connection surfaces of the electrodes of the electronic component and the electrodes of the substrate are viewed from top, the connection surface has an area of ​​the connection material that is less than 120% of the area of ​​the electrodes of the electronic component, and there is an area between adjacent electrodes in the electronic component where there is no connection material derived from conductive particles of the adhered adhesive material.

[0013] In addition, a method for manufacturing a connection structure is provided, which is the method for manufacturing a connection structure as described above, wherein conductive particles of an adhesive material are arranged in granular or monolithic form on electrodes of an electronic component or electrodes of a substrate, and areas where no conductive particles of an adhesive material are present are formed between adjacent electrodes in the electronic component or between electrodes of the substrate corresponding to these electrodes, and the conductive particles of the adhesive material are sandwiched between the electrodes of the electronic component and the electrodes of the substrate, and connection is achieved by at least heating or pressurizing.

[0014] Furthermore, a conductive particle-containing film used in the method for producing the above-mentioned connection structure is provided, wherein the conductive particles or conductive particle aggregates are retained in a film-like adhesive layer, and the conductive particles are separated from each other or the conductive particle aggregates are separated from each other.

[0015] Furthermore, there is provided a conductive particle-containing paste used in the above-mentioned method for producing a connected structure, wherein conductive particles are dispersed in a paste-like adhesive material. Effects of the Invention

[0016] The connection structure of the present invention has a connection surface where the area of ​​the connection material derived from the conductive particles attached to the adhesive material is less than 120% of the area of ​​the electrode of the electronic component when the connection surface of the electrode of the electronic component and the electrode of the substrate is viewed from above, and there is a region where the connection material derived from the conductive particles attached to the adhesive material does not exist between adjacent electrodes in the electronic component. In other words, the connection material derived from the conductive particles attached to the adhesive material is preferably accommodated between the opposing electrodes of the electronic component and the substrate in an area less than the surface of the electrode.

[0017] The connection structure is obtained by the following steps: conductive particles of adhesive material are arranged in granular or monolithic form on the electrodes of the electronic component or the electrodes of the substrate, and areas where conductive particles of adhesive material are not present are formed between adjacent electrodes in the electronic component or between electrodes of the substrate corresponding to these electrodes, and the conductive particles of adhesive material are sandwiched by the electrodes of the electronic component and the electrodes of the substrate, and connected by crimping or the like. Therefore, even if the electronic component is miniaturized, the opposing electrodes can be reliably connected. With respect to the connection structure of the present invention manufactured by this method, the adjacent electrodes in the electronic component will not be buried by conductive particles of adhesive material, and the conductive particles will not flow out from between the opposing electrodes due to the flow of resin during hot pressing, thereby reliably preventing short circuits.

[0018] In addition, according to the conductive particle-containing film of the present invention, the conductive particles are separated from each other or the conductive particle agglomerates are separated from each other and maintained in the adhesive material layer. Therefore, the conductive particles attached to the adhesive material can be separated from the conductive particle-containing film in a single sheet form and landed on the electrodes of the electronic component or the electrodes of the substrate by utilizing a laser stripping method, a transfer method using an imprinting material, etc., thereby enabling the manufacturing method of the present invention to be easily implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1A It is a cross-sectional view explaining the manufacturing process of the connection structure body of an Example. Figure 1B It is a cross-sectional view explaining the manufacturing process of the connection structure body of an Example. Figure 1C This is a plan view of the electrode portion during the manufacturing process of the connection structure of the example. Figure 2 It is a cross-sectional view explaining the manufacturing process of the connection structure body of an Example. Figure 3A It is a cross-sectional view of a connection structure according to an embodiment. Figure 3B It is a top view of the electrode portion in the connection structure of the example. DETAILED DESCRIPTION

[0020] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In addition, in each figure, the same reference numerals represent the same or equivalent components.

[0021] (Connection structure) Figure 3A is a cross-sectional view of a connection structure 1 according to an embodiment of the present invention, Figure 3B This connection structure 1 is a connection structure that connects electrodes 11 of an electronic component 10 such as a μLED and electrodes 21 of a substrate 20 on which a wiring circuit of the electronic component 10 is formed, via a connection material 2' derived from conductive particles attached to an adhesive material.

[0022] In the present invention, the electronic component 10 is not limited to a μLED having a chip side of less than 50 μm, and may be a mini LED having a chip side of about 50 μm to 200 μm.

[0023] In the connection structure 1, if Figure 2As shown, by using the conductive particles 2 of the adhesive material attached to the conductive particles 3 with a small amount of adhesive material 4 formed by resin as a connecting material, a connecting material 2' derived from the conductive particles of the adhesive material is obtained. That is, the conductive particles (connecting material) 2 of the adhesive material are arranged on the opposing electrodes 11 or 21, clamped between the opposing electrodes 11, 21, and at least heated or pressurized, more specifically, pressurized, hot-pressed, reflowed, etc. are performed according to the type of the conductive particles 2 of the adhesive material to connect, thereby obtaining the connecting material 2' derived from the conductive particles of the adhesive material. The connecting material 2' has a flattened shape. The conductive particle portion 3' of the connecting material 2' between the opposing electrodes 11, 21 electrically connects the opposing electrodes 11, 21, and the adhesive material portion 4' of the connecting material 2' fixes the opposing electrodes 11, 21.

[0024] Here, in a top view of the connection surface between the electrode of the electronic component and the electrode of the substrate, the conductive particle-derived portion 3' of each electrode 11 or 21 is formed of one or more conductive particles, preferably one or more and five or less. In the case where the conductive particle-derived portion 3' is a portion formed of a plurality of conductive particles, the respective conductive particle-derived portions forming the conductive particle-derived portion 3' may be separated from each other or may be in contact with each other.

[0025] In the connection structure 1 of the present invention, the area of ​​the connection material 2' derived from the conductive particles attached to the adhesive material when the connection surface of the electrode 11 of the electronic component 10 and the electrode 21 of the substrate 20 is viewed from above is less than 120% of the area of ​​the electrode 11 of the electronic component 10, preferably less than 100%, and more preferably within 45%. Preferably, the connection material 2' does not protrude from between the opposing electrodes 11, 21, but is accommodated between the opposing electrodes 11, 21, and there is no connection material 2' between the adjacent electrodes 11 of the electronic component 10. By limiting the area or existence position of the connection material 2' in this way, short circuits can be prevented. In addition, in the case where the electronic component is an optical element such as μLED, there is no connection material 2' between adjacent electronic components 10, thereby preventing the connection material 2' from having an adverse effect on the visual recognition of the connection structure.

[0026] In the present invention, when the connection structure 1 has a plurality of connection surfaces of opposing electrodes 11, 21, it is not necessarily necessary that the area of ​​the connecting material 2' on all the connection surfaces is less than 120% of the area of ​​the electrode 11, but the area of ​​the connecting material 2' is less than 120% of the area of ​​the electrode 11 of the electronic component 10 in preferably more than 95%, more preferably more than 98% of the total number of connection surfaces, preferably less than 100%, more preferably within 45%, and it is particularly preferred that the conductive particle portion 3' exists only between the opposing electrodes 11, 21.

[0027] On the other hand, in the connection structure 1, if the connection material 2' between the opposing electrodes 11 and 21 is too little, poor conduction is likely to occur, so the area of ​​the connection material 2' is preferably 4% or more of the area of ​​the electrode 11 of the electronic component 10, more preferably 7% or more, and the area derived from the conductive particle portion 3' is preferably 4% or more of the area of ​​the electrode 11 of the electronic component 10, more preferably 5% or more, and further preferably 9% or more. On the other hand, from the viewpoint of productivity, it is preferred that the connection material 2' is not too much provided between the electrodes 11 and 21.

[0028] The area of ​​the connection material 2', the area derived from the conductive particle portion 3', and the area of ​​the electrode 11 in the top view of the connection surface can be obtained by observation using a metal microscope. Alternatively, the area can be obtained by measuring and observing the image using image analysis software (e.g., WinROOF (Mitani Shoji Co., Ltd.) or A-image (registered trademark) (Asahi Kasei Engineering Co., Ltd.).

[0029] (Conductive particles attached to adhesive material) The conductive particles 2 with adhesive material attached to the electrodes 11 or 21 before connection are composed of conductive particles 3 or conductive particle aggregates with a small amount of adhesive material 4 attached thereto, and can be in a granular or monolithic form. Here, granular means that the adhesive material is preferably attached to one conductive particle with approximately the same thickness. Monolithic means the form obtained when the conductive particle-containing film is monolithicized, and in the monolithic conductive particles with adhesive material attached thereto, the portion where the conductive particles exist is usually raised, and the surrounding portion forms an adhesive material layer of approximately uniform thickness.

[0030] The shape of the monolithic sheet containing the conductive particle film is not particularly limited, and can be appropriately set according to the shape or size of the electrode of the electronic component to be connected. Regarding the shape of the monolithic sheet, since it is expected that the quality judgment after being set on the electrode becomes easy, it can also be a rectangle (including a square) as a general electrode shape. In addition, in the case where the monolithic sheet containing the conductive particle film is set on the electrode by the laser stripping method described later, in order to suppress the occurrence of curling or defects, it is preferably selected from at least one of a polygon composed of an obtuse angle, a rounded polygon, an ellipse, an oblong, and a circle. As long as the monolithic sheet of such a shape does not hinder the connection, a part of it can also protrude from the electrode when connected.

[0031] The particle size of the conductive particles 3 is not particularly limited as long as it is smaller than the electrode. The upper limit is preferably 50 μm or less, more preferably 20 μm or less, further preferably 10 μm or less, and particularly preferably 3 μm or less. The lower limit is preferably 1 μm or more. In addition, agglomerates of conductive particles with a small particle size of 0.1 μm or more and less than 1 μm can also be used.

[0032] The conductive particles 2 to which the adhesive material is attached on the electrodes 11 of the electronic component 10 or the electrodes 21 of the substrate 20 before connection by crimping or the like can change their form according to the particle diameter of the conductive particles 3 .

[0033] When the particle size of the conductive particles 3 is, for example, greater than 1 μm and less than 30 μm, and particularly greater than 1 μm and less than 10 μm, the conductive particles 2 of the adhesive material attached to the electrode 11 of the electronic component 10 or the electrode 21 of the substrate 20 before connection can be configured as conductive particles of a monolithic adhesive material attached by monolithically forming a conductive particle-containing film and depositing it on the electrode 11 or 21, wherein the conductive particle-containing film has conductive particles 3 dispersed in an adhesive material layer formed by a film-like resin.

[0034] It is also possible to attach the conductive particles 3 to the electrodes 11 of the electronic component 10 or the electrodes 21 of the substrate 20 before connection, and separate the adhesive material layer formed of a film-like resin and place it there. In the case where the conductive particles 3 are solder balls, it is sometimes useful to use this method to form a flux for melting solder or a resin material containing the flux on the electrodes 11 or 21. In addition, it is also possible to simply set the resin at a predetermined location on the substrate 20 or the electronic component 10, regardless of whether the flux is contained.

[0035] In addition, when the particle size of the conductive particles 3 is, for example, greater than 1 μm and less than 50 μm, and particularly greater than 2 μm and less than 50 μm, the conductive particles 2 of the granular attached adhesive material before connection can be set as follows: a conductive particle-containing paste in which the conductive particles 3 are dispersed in an adhesive material formed of a paste-like resin is spread on the electrode 11 of the electronic component 10 or the electrode 21 of the substrate 20 and formed in granular form by a printing method or a method using a dispenser.

[0036] The present invention includes such a conductive particle-containing film or conductive particle-containing paste.

[0037] (Contains conductive particle film, contains conductive particle paste) The content ratio of the resin in the conductive particle-containing film and the conductive particle-containing paste forming the conductive particles 2 of the adhesive material is preferably 10% by volume or more, more preferably 20% by volume or more, and preferably 80% by volume or less, and more preferably 50% by volume or less. In other words, the content ratio of the conductive particles in the conductive particle-containing film and the conductive particle-containing paste is preferably 20% by volume or more, more preferably 50% by volume or more, and preferably 90% by volume or less, and more preferably 80% by volume or less. If the proportion of the resin is too small, there is a concern that the electrode 11 of the electronic component 10 and the electrode 21 of the substrate 20 may be poorly bonded. In addition, if the content ratio of the conductive particles is too small, there is a concern that the conduction between the opposing electrodes 11 and 21 may be poor.

[0038] In addition, the conductive particle-containing film or conductive particle-containing paste of the present invention has a tendency to have a smaller volume ratio of resin to conductive particles than conventional anisotropic conductive films, and the amount of resin is therefore less. Therefore, in the present invention, the resin may be filled after connection.

[0039] The number density of conductive particles in the conductive particle-containing film and conductive particle-containing paste in the film surface field (pieces / mm 2 ) can be determined by the electrode size of the connection object and the conductive particle size, so there is no particular limitation.

[0040] In the conductive particle-containing film, each conductive particle is preferably separated from each other. For example, when the particle size of the conductive particle 3 is 1 μm or more, preferably 2 μm or more, the interparticle distance of the adjacent conductive particles is preferably set to 1 to 3 times the particle size. In addition, it is preferred that there are conductive particles in which the interparticle distance of the adjacent conductive particles is separated by more than 1 μm. Thus, by using a laser stripping device, it is easy to separate the conductive particles attached with the adhesive material from the conductive particle-containing film in a single piece and land on the electrode.

[0041] On the other hand, in the conductive particle-containing film, a plurality of conductive particles may also form a unit or an aggregate. For example, a unit in which 2 to 5, preferably 2 to 3 conductive particles are close to or in contact may be formed. In this case, it is preferred that the aggregates are separated from each other or the units are separated from each other. Thus, a single sheet of conductive particles with a small amount of adhesive material attached to the aggregate or unit of the conductive particles can be arranged on the electrode, and conduction can be ensured without worrying about short circuits. In addition, a plurality of conductive particles form a unit, so that the electrode is supported by a plurality of conductive particles, and it is easy to prevent the electrode from tilting. In a tiny electronic component such as a μLED having two electrodes in one electronic component, the clamping or bonding state of the conductive particles is sometimes directly related to the quality after connection, so it can be said that it is useful to arrange a unit composed of a plurality of conductive particles on the electrode surface.

[0042] The arrangement of the conductive particles or conductive particle aggregates in the conductive particle-containing film in the film surface direction (the arrangement of the conductive particles observed in the film surface field) may be arranged in a regular arrangement or may be random.

[0043] The arrangement of the conductive particles in the conductive particle-containing film in the film thickness direction is not particularly limited. From the viewpoint of improving the size or position accuracy when a single piece of the conductive particle-containing film is landed on an electrode using a laser lift-off device, the conductive particles are preferably aligned in the film thickness direction.

[0044] When the conductive particle-containing film of the present invention is monolithic and used in the connection of electrodes of a tiny electronic component, the number of conductive particles is reduced by locally setting a minimum number of conductive particles on the electrode, and the number of conductive particles is reduced by making the conductive particles present between the electrodes close to zero, thereby preventing short circuits and ensuring stable conduction. However, when the conductive particle-containing film of the present invention is used as a general anisotropic conductive film, the amount of resin is insufficient, so it is difficult to obtain sufficient adhesion except for tiny components, which is different from the general anisotropic conductive film. More specifically, when the conductive particle-containing film of the present invention is arranged between an electronic component having an electrode pattern in which long strip electrodes (electrode height 8 μm) with a width of 10 μm are arranged at a pitch of 20 μm (L / S=1 / 1) and a glass substrate having a corresponding electrode pattern, unlike the case of performing the same thermal compression bonding using a conventional general anisotropic conductive film, conductive particles with an adhesive material attached are provided only in a portion of the rectangular electrode in the longitudinal direction. Therefore, even if the performance of preventing short circuit is satisfied, the adhesive force cannot be satisfied. In this respect, the conductive particle-containing film of the present invention is different from the conventional anisotropic conductive film. In addition, if the conductive particle-containing film of the present invention is used as a general anisotropic conductive film, the area occupancy of the conductive particles in the electrode may become insufficient, and there is a concern that the conduction resistance between the electrodes becomes more than 2Ω and cannot show sufficient anisotropic conduction characteristics.

[0045] Regarding the film thickness of the conductive particle-containing film, if the film thickness is too thin, when the conductive particles 2 of the attached adhesive material are provided on the electrode in a single sheet shape, the bonding force between the opposing electrodes 11 and 21 will be insufficient. If the film thickness is too thick, there will be concerns about the occurrence of a short circuit or a decrease in the conductive characteristics between the electrodes 11 and 21 due to the positional displacement of the conductive particles 2 of the attached adhesive material during the crimping step in the manufacturing process of the connection structure. Therefore, the film thickness is preferably 0.8 times or more of the particle size of the conductive particles 3, more preferably 1 times or more, and preferably 3 times or less, more preferably 2.5 times or less, and further preferably 1.5 times or less.

[0046] (Type of conductive particles) The type of conductive particles 3 is not particularly limited as long as it is a metal that can achieve conduction between the electrodes 11 and 21, and Au, Ni, Ag, Cu, Sn-based solders, etc. can be preferably listed. In addition, metal-coated resin core particles can also be used. The type of conductive particles between the electrodes 11 and 21 can be set to a single type or multiple types.

[0047] (Type of adhesive material) As the adhesive material of the conductive particles 2 to which the adhesive material is attached, an adhesive material used as an insulating resin in a known anisotropic conductive film (for example, Japanese Patent 6187665, Japanese Patent Gazette No. 2018-090768, etc.) can be used. A curable resin can be used as an insulating resin. In this case, it can also be either a thermosetting resin or a photocurable resin. If a curable resin is used, the adhesiveness before curing can be used to easily temporarily fix the electronic components to the substrate, and after curing, the opposing electrodes 11 and 21 can be firmly fixed. In addition, a thermoplastic resin can also be used as an insulating resin.

[0048] The insulating resin may also be mixed with a rubber component having a cushioning property. The rubber component is not particularly limited as long as it is an elastomer having a high cushioning property (impact absorption), and specific examples thereof include acrylic rubber, silicone rubber, butadiene rubber, polyurethane resin (polyurethane elastomer), etc.

[0049] In addition, when the laser lift-off method is used before the process of connecting the electrode 11 of the electronic component 10 and the electrode 21 of the substrate 20, the adhesive material is preferably an adhesive material having a durometer A hardness of preferably 20 to 40, more preferably 20 to 35, and particularly preferably 20 to 30 according to JIS K6253 before laser irradiation (state before curing), and preferably an adhesive material having a storage modulus of 60 MPa or less at a temperature of 30° C. and a frequency of 200 Hz based on a dynamic viscoelasticity test (Vibron, A&D Co., Ltd.) according to JIS K7244. The shape of the adhesive material can be measured as long as it is in a film shape.

[0050] On the other hand, with respect to the adhesive material, the storage modulus at a temperature of 30°C measured in a tensile mode according to JIS K7244 after curing (after connection) is preferably 100 MPa or more, and more preferably 2000 MPa or more. When the storage modulus at a temperature of 30°C is too low, there is a tendency that good conductivity cannot be obtained and the connection reliability also decreases. The storage modulus at a temperature of 30°C can be measured under the tensile mode according to JIS K7244 and using a viscoelasticity tester (Vibron, A&D Co., Ltd.), for example, under the measurement conditions of a frequency of 11 Hz and a heating rate of 3°C / minute. With respect to the shape of the adhesive material, it is sufficient to measure it as long as it is set in a film-like shape.

[0051] In addition, when the laser lift-off method is used before the connection process between the electrode 11 of the electronic component 10 and the electrode 21 of the substrate 20, it is preferred that the reaction rate of the adhesive material after transfer is preferably 25% or less, more preferably 20% or less, and further preferably 15% or less. In order to meet this requirement, the type of resin constituting the adhesive material and the concentration of the polymerization initiator are preferably selected. In this way, excellent transferability can be obtained. Regarding the determination of the reaction rate, for example, FT-IR can be used to measure the epoxy group (914cm -1 Nearby), (meth)acryloyl (1635cm -1 The peak heights of reactive groups such as A, a and methyl (2930 cm -1 The reduction rate of the reactive groups was obtained by the following formula using the reference peak heights B and b) and the like.

[0052] Reaction rate (%) = {1-(a / b) / (A / B)}×100 In the formula, A is the peak height of the reactive group before laser irradiation, B is the reference peak height before laser irradiation, a is the peak height of the reactive group after laser irradiation, and b is the reference peak height after laser irradiation.

[0053] When other peaks overlap with the peak of the epoxy group, the peak height of the completely cured sample (reaction rate 100%) may be set to 0%.

[0054] (Method for producing conductive particle-containing film and conductive particle-containing paste) The conductive particle-containing film and the conductive particle-containing paste of the present invention can be produced by a known method, for example, by the method described in Japanese Patent No. 6187665, Japanese Patent Application Laid-Open No. 2022-75723, and the like.

[0055] In the conductive particle-containing film of the present invention, units in which every 2 to 5 conductive particles, preferably every 2 to 3 conductive particles are close to or in contact may be formed. In this case, the conductive particle-containing film can be manufactured according to the anisotropic conductive film described in Japanese Patent Application Laid-Open No. 2016-85983, for example.

[0056] (Method for manufacturing a connected structure) Regarding the method for manufacturing the connection structure 1, generally, first Figure 1A As shown, conductive particles 2 with adhesive material attached are arranged on electrodes 11 of electronic component 10, and regions 5 without conductive particles 2 with adhesive material attached are formed between adjacent electrodes 11a and 11b in electronic component 10, or as shown in FIG. Figure 1B As shown, conductive particles 2 with adhesive material attached are arranged on electrodes 21a and 21b of substrate 20 corresponding to electrodes 11a and 11b of electronic component 10, and a region 5 without conductive particles 2 with adhesive material attached is formed between the electrodes 21a and 21b of the substrate.

[0057] Then, if Figure 2 As shown, the electrodes 11 of the electronic component 10 and the electrodes 21 of the substrate 20 facing each other are aligned, and the facing electrodes 11 and 21 are connected by thermocompression bonding or the like.

[0058] The preferred amount of conductive particles 2 of the adhesive material attached to the electrode 11 of the electronic component 10 or the electrode 21 of the substrate 20 can be determined according to the area of ​​the electrode 11 or the particle size of the conductive particles 3, but for each electrode 11, it is preferably more than 1 and less than 5, and may also be less than 4, less than 3, or less than 2.

[0059] Thus, in the present invention, by providing a minimum number of conductive particles on tiny electrodes, unnecessary conductive particles in electrical connection are reduced, and short circuits between electrodes are suppressed. Thus, cost reduction and defect rate reduction in the manufacture of electronic devices such as displays equipped with many extremely tiny connection structures are achieved.

[0060] The method of arranging the conductive particles 2 to which the adhesive material is attached on the electrode 11 or the electrode 21 can be selected according to the form of the conductive particles 2 to which the adhesive material is attached.

[0061] For example, in the case where a monolithic conductive particle-containing film is arranged as conductive particles 2 of an adhesive material on an electrode 11 of an electronic component 10 or an electrode 21 of a substrate 20, or as a method for aligning the electrode 11 of an electronic component 10 and arranging the conductive particles 2 of an adhesive material on an electrode 21 of a substrate 20, a known laser stripping method (for example, Japanese Patent Publication No. 2017-157724) or a method in accordance with the laser stripping method can be performed. For example, a laser can be irradiated to a conductive particle-containing film so that a monolithic film of an area corresponding to the electrode 11 or 21 is detached from the conductive particle-containing film and landed on the electrode 11 or 21. In the case where the electronic component 10 is landed on the substrate 20 by the laser stripping method, a silicone rubber layer can also be provided on the substrate 20. The silicone rubber layer can be formed by polydimethylsiloxane (PDMS) or the like. Alternatively, the electronic component 10 may be placed on the silicone sheet by laser lift-off, and the electrodes 11 of the electronic component 10 and the electrodes 21 of the substrate 20 may be overlapped with each other in a state where the electronic component 10 is placed on the silicone sheet.

[0062] The laser lift-off method can be performed using a commercially available laser lift-off apparatus (for example, a laser lift-off apparatus manufactured by Shin-Etsu Chemical Co., Ltd., trade name “Invisi LUM-XTR”).

[0063] Alternatively, the conductive particle-containing film may be transferred onto the electrode 11 of the electronic component 10 or onto the electrode 21 of the substrate 20 by a transfer method using a known imprint material (for example, Japanese Patent Application Laid-Open No. 2021-141160).

[0064] On the other hand, when the conductive particles 2 dispersed with the conductive particle-containing paste as an adhesive material are arranged on the electrodes 11 of the electronic component 10 or the electrodes 21 of the substrate 20, the arrangement method may be a printing method such as inkjet or screen printing.

[0065] In addition, when the particle size of the conductive particles 3 of the conductive particles 2 attached with the adhesive material is greater than 1 μm, preferably greater than 2 μm, a conductive particle-containing paste having a low concentration of the conductive particles 3 can also be prepared and applied to the surface of the electrode 11 of the electronic component 10 or the surface of the electrode 21 of the substrate 20 in such a manner that the number of conductive particles becomes 1 to 5.

[0066] When a plurality of conductive particles 3 having a particle size of 1 μm or more and conductive particles 2 attached with a binder material are arranged on the electrode 11 or the electrode 21, a plurality of conductive particles having different melt viscosities may be arranged and reflow bonding may be performed.

[0067] Furthermore, in order to easily satisfy both initial conductivity and conductivity reliability after connection, two types of conductive particles having different hardness, resilience, particle size, etc. may be used.

[0068] When the particle size of the conductive particles 3 of the conductive particles 2 attached with the adhesive material is about 10 μm to 50 μm, spherical solder particles can also be used as the conductive particles 3, and the spherical solder particles coated with the adhesive material can be placed on the electrode 11 or the electrode 21 according to the well-known BGA (ball grid array) method of loading electrodes.

[0069] After the conductive particles 2 with adhesive material attached are arranged on the electrode 11 of the electronic component 10 or the electrode 21 of the substrate 20, the electrode 11 or 21 with the conductive particles 2 with adhesive material attached is aligned with the electrode 21 or 11 opposite thereto by a common method, such as Figure 2 As shown, conductive particles 2 to which an adhesive material is attached are sandwiched between opposing electrodes 11 and 21, and the electrodes 11 and 21 are connected by crimping or the like.

[0070] After the electrodes 11 of the electronic component 10 and the electrodes 21 of the substrate 20 are aligned via the conductive particles 2 of the adhesive material, the connection conditions can be appropriately determined according to the type of conductive particles 3 or adhesive material 4 constituting the conductive particles 2 of the adhesive material. That is, it is also possible to heat cure, light cure, or heat and pressurize according to the type of resin forming the adhesive material. It is also possible to heat and connect the opposing electrodes 11 and 21 by reflow soldering according to the type or particle size of the conductive particles.

[0071] For example, when the particle size of the conductive particles 3 of the conductive particles 2 with adhesive material is set as large as about 10 μm to 50 μm, spherical solder particles can be used as the conductive particles 3, and the conductive particles 2 with adhesive material can be set in a form in which the adhesive material is attached to the spherical solder particles. In this case, in the manufacturing process of the connection structure ( Figure 2 ), the electronic component 10 can be mounted on the substrate 20 by heating (reflow soldering) in much the same way as a BGA (ball grid array). In the case of conductive particles attached with an adhesive material, it can be expected that the electrodes of tiny electronic components can be easily and accurately obtained in much the same way as a BGA (ball grid array).

[0072] In this way, we can get Figure 3A The connection structure 1 shown.

[0073] In the connection structure 1, sealing may be performed by underfill etc. as needed after connection. Also, the same effect as underfill may be obtained by simply providing an insulating resin layer before or after providing conductive particles or monoliths with adhesive material on electrodes.

[0074] According to the manufacturing method of the connection structure of the present invention, in order to install the electronic component 10 on the substrate 20, there is no need to pattern the resin or metal constituting the connecting material 2'. It is only necessary to arrange the conductive particles 2 with the adhesive material attached on the electrode surfaces of the opposing electrodes 11 and 21 and connect the opposing electrodes 11 and 21 by crimping, etc., so that regardless of the size of the electrodes 11 and 21, the best installation can be achieved.

[0075] In the case where a single piece containing a conductive particle film is set at an electrode on a substrate by the above method, the shape of the single piece can be at least one selected from a polygon composed of obtuse angles, a polygon with rounded corners, an ellipse, an oblong, and a circle. Single pieces of such shapes can also be set at each electrode of the substrate, and the micro-LED is connected in a manner that spans each of two single pieces. These single pieces or conductive particles of an adhesive material may also be pre-set at the electrodes of the micro-LED. The electrodes and single pieces sometimes appear as if parts of each are repeated. It may also be a state where the electrodes of the substrate or the electrodes of the micro-LED exist at the ends of the single piece. In the case where the insulating resin or conductive particles are insufficient, the present invention also includes the case where an additional single piece is set or the insulating resin or conductive particles are added to the original single piece.

[0076] The electronic component mounting method is very convenient to use and has excellent mass productivity. The mounted electronic component may be an electronic component other than μLED, and the method for manufacturing a connection structure of the present invention can be applied to the manufacture of a transparent display. Description of Reference Numerals

[0077] 1 Connecting structures 2 Conductive particles and connecting materials attached to adhesive materials 2' Connecting materials in the connecting structure 3 Conductive particles 3' from the conductive particles 4. Adhesive Materials 4' from the adhesive material part 10Electronic components, μLED 11 electrodes 20 substrates 21 electrodes

Claims

1. A connection structure, wherein an electrode of an electronic component and an electrode of a substrate facing each other are connected by a connection material derived from conductive particles of an adhesive material, wherein, when the connection surface of the electrode of the electronic component and the electrode of the substrate is viewed from above, the area of ​​the connection material is less than 120% of the area of ​​the electrode of the electronic component, and there is an area between adjacent electrodes in the electronic component where there is no connection material derived from conductive particles of an adhesive material.

2. The connection structure according to claim 1, wherein: The connection structure has a plurality of connection surfaces, which are connection surfaces between the electrodes of the electronic component and the electrodes of the substrate, and the area of ​​the connection material derived from the conductive particles attached with the adhesive material in more than 95% of the total number of connection surfaces is less than 120% of the area of ​​the electrodes of the electronic component.

3. The connection structure according to claim 1 or 2, wherein: In a plan view of the connection surface between the electrode of the electronic component and the electrode of the substrate, there are 1 or more and 5 or less portions derived from the conductive particles to which the adhesive material is attached per electrode of the electronic component.

4. A method for manufacturing a connected structure, which is the method for manufacturing a connected structure according to claim 1, wherein conductive particles of an adhesive material are arranged in granular or monolithic form on electrodes of an electronic component or electrodes of a substrate, and areas where no conductive particles of an adhesive material are present are formed between adjacent electrodes in the electronic component or between electrodes of the substrate corresponding to these electrodes, and the conductive particles of the adhesive material are sandwiched between the electrodes of the electronic component and the electrodes of the substrate, and connection is performed by at least heating or pressurizing.

5. The manufacturing method according to claim 4, wherein: The ratio of the resin in the conductive particles to which the binder material is attached is 10% by volume or more and 80% by volume or less. 6 . A conductive particle-containing paste used in the method for producing a connected structure according to claim 4 , wherein conductive particles are dispersed in a paste-like adhesive material.

7. A conductive particle-containing film used in the method for manufacturing a connected structure according to claim 4 or 5, wherein the conductive particle-containing film holds conductive particles or conductive particle aggregates in a film-like adhesive layer, and the conductive particles are separated from each other or the conductive particle aggregates are separated from each other.

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