Manufacturing method of LED mounting substrate

Abstract

The purpose of this invention is to provide a method for manufacturing an LED mounting substrate that improves mounting performance and subsequent connection reliability even when transferring tiny LED chips by laser etching, by capturing them at a predetermined position. This invention is a method for manufacturing an LED mounting substrate, comprising: a step of making the insulating layer forming surface of an LED mounting substrate face the electrode-containing surface of an LED transfer substrate on which an LED is attached to a transparent substrate (facing step); the LED mounting substrate comprising: a substrate with electrodes, bumps formed on the electrodes using a composite material containing organic components and conductive particles, and an insulating layer formed at least on the bumps; a step of irradiating the LED from the transparent substrate side of the LED transfer substrate towards the LED to transfer the LED to the LED mounting substrate (LED transfer step); and a step of mounting the transferred LED to the LED mounting substrate (LED mounting step).

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing an LED mounting substrate. [Previous Technology]

[0002] In recent years, there has been active development in technology for mass-mounting light-emitting diodes (LEDs) with long sides of less than 100 μm on substrates for display applications. However, the number of LED chips required for display is very large, ranging from hundreds of thousands to tens of millions, necessitating faster mass-mounting of LED chips. Therefore, mounting techniques using laser technology have been proposed (for example, see Patent Document 1). Prior art has proposed using a portion of a metal wiring or a specially formed metal pad as a drive substrate side electrode, forming an adhesive layer thereon, and then using laser etching technology to transfer LED chips onto the drive substrate side electrode using the obtained adhesive layer. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-188037 [Summary of the Invention]

[0004] [The problem that the invention aims to solve]

[0005] However, in Patent Document 1, when the metal bumps formed on the driving substrate are used as electrical connection materials, if the size of the LED chip transferred at high speed by laser etching becomes smaller, the high rigidity of the metal reduces the capture performance of the adhesive layer, making it impossible to capture at the specified position, resulting in the problem of poor installation.

[0006] In addition, the connection between the LED electrode and the metal bump is achieved through contact, and the connection is supported by the adhesive layer between the LED chip and the driving substrate. However, in thermal cycling tests, there is a problem that the connection is easily lost due to the expansion and contraction caused by the temperature change of the adhesive layer.

[0007] This invention provides a method for manufacturing an LED mounting substrate, which improves mountability by capturing the tiny LED chips at specified locations even when transferring them using laser etching, resulting in high subsequent connection reliability. [Means of the Problem]

[0008] The inventors have conducted intensive research and discovered that by using an LED transfer substrate to perform laser transfer of LED chips onto an LED mounting substrate having bumps containing organic components and conductive particles, and an insulating layer on the bumps, excellent capture performance can be achieved. After a subsequent hot-pressing step, an LED mounting substrate with high connection reliability can be manufactured, thereby completing the present invention.

[0009] That is, the present invention is as follows. (1) A method for manufacturing an LED mounting substrate, comprising: a step of making an insulating layer forming surface of an LED mounting substrate face an electrode-containing surface of an LED transfer substrate on which an LED is attached to a transparent substrate, the LED mounting substrate comprising: a substrate having electrodes, bumps formed on the electrodes of a composite material containing organic components and conductive particles, and an insulating layer formed at least on the bumps; a step of irradiating the LED from the transparent substrate side of the LED transfer substrate to the LED mounting substrate to transfer the LED to the LED mounting substrate (LED transfer step); and a step of mounting the transferred LED to the LED mounting substrate (LED mounting step). (2) The method for manufacturing an LED mounting substrate as described in (1), wherein the LED mounting step is a step of heat-pressing the transferred LED to the LED mounting substrate. (3) The method for manufacturing an LED mounting substrate as described in (1) or (2), wherein the average thickness BH of the bumps in the LED mounting substrate is 1.0 μm to 5.0 μm. (4) The method for manufacturing an LED mounting substrate as described in any one of (1) to (3), wherein the minimum distance between the bumps in the LED mounting substrate is 3 μm to 50 μm, and the thickness of the insulating layer on the bumps in the LED mounting substrate is 0.5 μm to 4 μm. (5) The method for manufacturing an LED mounting substrate as described in any one of (1) to (4), wherein the organic component contains an acrylic copolymer having carboxyl groups and an epoxy resin. (6) The method for manufacturing an LED mounting substrate as described in any one of (1) to (5), wherein the content of the conductive particles is 50% to 90% by weight of the total weight of the bumps. (7) The method for manufacturing an LED mounting substrate as described in any one of (1) to (6), wherein the area of ​​the insulating layer in the LED mounting substrate is 1.1 to 10 times the area of ​​the LED, and a pattern is formed on two bumps under the insulating layer. (8) A method for manufacturing an LED mounting substrate as described in any one of (1) to (7), wherein the insulating layer comprises an epoxy resin and a compound having a siloxane bond or a urethane bond. (9) A method for manufacturing an LED mounting substrate as described in any one of (1) to (8), comprising a step of patterning bumps in the LED mounting substrate by an exposure and development process. (10) A method for manufacturing an LED mounting substrate as described in any one of (1) to (9), comprising a step of patterning the insulating layer by an exposure and development process. [Effects of the Invention]

[0010] By means of the present invention, even when transferring tiny LED chips by laser ablation, an LED mounting substrate with improved mounting performance and high subsequent connection reliability can be obtained by capturing at a specified position.

Implementation Method

[0012] The method for manufacturing an LED mounting substrate according to the present invention comprises: a step of facing an insulating layer forming surface of an LED mounting substrate with an electrode-containing surface of an LED transfer substrate on which an LED is attached to a transparent substrate, the LED mounting substrate comprising: a substrate having electrodes, bumps formed on the electrodes using a composite material containing organic components and conductive particles, and an insulating layer formed at least on the substrate; a step of transferring the LED to the LED mounting substrate by irradiating the LED from the transparent substrate side of the LED transfer substrate (LED transfer step); and a step of mounting the transferred LED to the LED mounting substrate (LED mounting step). Preferably, the LED mounting step is a step of thermally bonding the transferred LED to the LED mounting substrate. By selecting the thermal bonding step as the LED mounting step, the insulating layer between the LED electrode and the bump is removed, allowing for a more reliable connection between the LED electrode and the bump, further improving mountability.

[0013] Hereinafter, a method for manufacturing an LED mounting substrate according to an embodiment of the present invention will be described with reference to the accompanying drawings. Furthermore, the drawings are schematic. The present invention is not limited to the examples described below.

[0014] <Step of facing the LED mounting substrate and the LED transfer substrate> First, as shown in FIG3 (a), the insulating layer 4 forming surface of the LED mounting substrate 12 is fixed to the vacuum adsorption stage in such a way that the surface of the LED 5 with the electrode 6 of the LED transfer substrate 13 faces each other, and the stage is moved to the specified position using a positioning camera.

[0015] [LED mounting substrate] The LED mounting substrate 12 includes: a substrate 2 having an electrode 1, a bump 3 formed on the electrode, which is a composite material containing organic components and conductive particles, and an insulating layer 4 formed on the bump.

[0016] [Substrate] The substrate with electrodes is a circuit substrate on and inside a glass substrate or resin substrate, in which wiring or thin film transistors (TFTs) are arranged, and electrodes connected to LEDs are partially exposed.

[0017] [Bumps] The LED mounting substrate has bumps formed on the electrodes, which are made of a composite material containing organic components and conductive particles. Since the bumps of the composite material containing organic components and conductive particles have low rigidity, they can be captured at a specified position even when transferring tiny LED chips by laser etching, thus improving mounting performance.

[0018] Examples of methods for forming bumps on electrodes that are composite materials containing organic components and conductive particles include: pattern printing methods such as screen printing or gravure printing on photosensitive conductive paste; laser etching methods that remove unwanted parts after rough pattern printing; and photolithography methods performed by exposing and developing photosensitive conductive paste. Among these, the method of using photosensitive conductive paste and forming patterns by exposure and development processes is preferred for achieving fine patterning.

[0019] In photolithography, ultra-high pressure mercury lamps, lasers, LED i-rays (365 nm) and h-rays (405 nm) can be used as light sources during exposure.

[0020] In photolithography, the developing solution may include, for example, aqueous solutions of tetramethylammonium hydroxide, diethanolamine, diethylaminoethanol, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, triethylamine, diethylamine, methylamine, dimethylamine, dimethylaminoethyl acetate, dimethylaminoethanol, dimethylaminoethyl methacrylate, cyclohexylamine, ethylenediamine, or hexamethylenediamine.

[0021] There are no particular restrictions on the shape of the pattern. Examples of planar shapes include rectangular shapes, circular shapes, elliptical shapes, triangular shapes, polygonal shapes, and combinations thereof. The shape of the pattern can be determined based on the shape of the electrodes on the LED side.

[0022] The average thickness BH of the bumps in the LED mounting substrate is preferably 1.0 μm to 5.0 μm. By setting the average thickness BH of the bumps to 1.0 μm or more, the impact during laser transfer can be mitigated, the LED positional offset after transfer can be suppressed, and the mounting performance can be further improved. The average thickness BH of the bumps is more preferably 1.5 μm or more. Here, "mountability" refers to the state in which the two electrodes of the LED chip and the two electrodes on the LED mounting substrate side can be electrically connected respectively, which can be evaluated by applying voltage to multiple LED mounting substrates and counting the number of LEDs lit. On the other hand, by setting the average thickness BH of the bumps to 5.0 μm or less, the expansion of the bumps during installation can be suppressed, and the mounting performance can be improved by suppressing short circuits with surrounding electrodes. The average thickness BH of the bumps is more preferably 3.5 μm or less. The average thickness of the bumps can be measured by non-contact measurement using a laser microscope.

[0023] Examples of conductive particles include: particles of silver, gold, copper, platinum, lead, tin, nickel, aluminum, tungsten, molybdenum, chromium, titanium, indium, magnesium, cobalt, zinc, potassium, lithium, iron, mercury, beryllium, cadmium, rhodium, ruthenium, iridium, or alloys thereof, and carbon black. Two or more of these may be contained. From the viewpoint of conductivity, particles selected from silver, gold, and copper are preferred; from the viewpoint of cost and stability, silver particles are more preferred. Additionally, conductive particles may also coat the surface of resin or inorganic oxides. Conductive particles with a metal-coated resin particle surface exhibit elastic repulsion caused by the resin particles during transfer; therefore, metal particles are preferred.

[0024] The aspect ratio, obtained by dividing the major axis length by the minor axis length of the conductive particles, is preferably 1.1 to 2.0. Here, regarding the aspect ratio of the conductive particles, the conductive particles are observed using a scanning electron microscope (SEM) or a transmission electron microscope (TEM) at a magnification of 15,000. For one primary particle of 100 randomly selected conductive particles, the major axis length and minor axis length of each particle are measured, and the aspect ratio is calculated from the average of the two.

[0025] The average particle size of the conductive particles is preferably 0.05 μm to 1.0 μm. By having an average particle size of 0.05 μm or more, the number of conductive paths within the bump increases, further improving the reliability of the electrical connection. On the other hand, by having an average particle size of 1.0 μm or less, the surface smoothness, pattern accuracy, and dimensional accuracy of the obtained bump can be improved. Here, the average particle size of the conductive particles can be measured using a laser-irradiated particle size analyzer. The D50 value of the particle size distribution obtained by measurement is set as the average particle size (D50) of the conductive particles.

[0026] In the total weight of the bumps containing organic components and conductive particles, the proportion of conductive particles is preferably 50 wt% to 90 wt%. If the proportion of conductive particles is 50 wt% or more, the number of conductive paths formed within the bumps increases, which can further improve the reliability of electrical connections. The proportion of conductive particles is more preferably 60 wt% or more. In addition, if the proportion of conductive particles is 90 wt% or less, the rigidity of the bumps decreases and the capture ability increases, thereby improving positional accuracy and further improving mounting performance. Furthermore, by increasing the content of organic components, the contact between the bumps and the LED electrodes is improved, which can further improve connection reliability. The proportion of conductive particles is more preferably 80 wt% or less. The proportion of conductive particles in the total weight of the bumps can be calculated by removing the bumps from the substrate and analyzing the weight of the residual components after burning off the organic components using thermogravimetric analysis.

[0027] In the total volume of the bump containing organic components and conductive particles, the proportion of conductive particles is preferably 10 vol% to 40 vol%. If the proportion of conductive particles is 10 vol% or more, the number of conductive paths formed within the bump increases, which can further improve the reliability of electrical connections. In addition, if the proportion of conductive particles is 40 vol% or less, the rigidity of the bump decreases and the capture ability increases, thereby improving positional accuracy and further improving installability. The proportion of conductive particles in the total volume of the bump can be calculated from the weight of the residual components obtained by thermogravimetric analysis and the true density of the conductive particles and organic components.

[0028] The organic components may include acrylic copolymers, epoxy resins, silicone resins, polyimide resins, phenolic resins, etc., but preferably acrylic copolymers and epoxy resins containing carboxyl groups. By including acrylic copolymers and epoxy resins containing carboxyl groups in the organic components, the carboxyl and epoxy groups undergo a thermosetting reaction with the organic components inside the bump and the insulating layer, which can improve the tightness of the LED electrode and the bump after thermoforming, and further improve the connection reliability.

[0029] As a carboxyl-containing acrylic copolymer, it is preferably a copolymer of an acrylic monofunctional monomer and an unsaturated acid or its anhydride.

[0030] As a monofunctional monomer of acrylic acid, examples include: methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, n-butyl acrylate, isobutyl acrylate, isopropyl acrylate, glycidyl acrylate, butoxytriethylene glycol acrylate, dicyclopentyl acrylate, dicyclopentenyl acrylate, 2-hydroxyethyl acrylate, isobornyl acrylate, 2-hydroxypropyl acrylate, isodecanyl acrylate, isoodecyl acrylate, isooctyl acrylate, lauryl acrylate, 2-methoxyethyl acrylate, methoxyethylene glycol acrylate, methoxydiethylene glycol acrylate, octafluoropentyl acrylate, phenoxyethyl acrylate, stearyl acrylate, trifluoroethyl acrylate, aminoethyl acrylate, phenyl acrylate, phenoxyethyl acrylate, 1-naphthyl acrylate, 2-naphthyl acrylate, thiophenol acrylate, benzyl mercaptan acrylate, acrylamide, N-methoxymethyl acrylamide (N-methoxyl methyl) Acrylamide), N-ethoxymethacrylamide, N-n-butoxymethacrylamide, N-isobutoxymethacrylamide, methacrylamide phenol, methacrylamide phenol, γ-acryloxypropyltrimethoxysilane, N-(2-hydroxyphenyl)acrylamide, N-(3-hydroxyphenyl)acrylamide, N-(4-hydroxyphenyl)acrylamide, o-hydroxyphenyl acrylate, m-hydroxyphenyl acrylate, p-hydroxyphenyl acrylate, o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, 2-(2-hydroxyphenyl)ethyl acrylate, 2-(3-hydroxyphenyl)ethyl acrylate, 2-(4-hydroxyphenyl)ethyl acrylate, etc. Two or more of these may also be used. Among these, ethyl acrylate, 2-hydroxyethyl acrylate, and isobornyl acrylate are preferred.

[0031] Examples of unsaturated acids or their anhydrides include: acrylic acid, methacrylic acid, itaconic acid, butenoic acid, maleic acid, fumaric acid, vinyl acetate, or their anhydrides. Two or more of these may also be used. The acid value of the carboxyl-containing acrylic copolymer can be adjusted by the copolymerization ratio of the unsaturated acids.

[0032] Examples of epoxy resins include: bisphenol A type, cresol phenolic varnish type, phenolic varnish type, bisphenol A phenolic varnish type, dicyclopentadiene type, naphthalene type, etc., among which those with a softening point of 30°C or higher and 100°C or lower are preferred. If the softening point is 30°C or higher, it can suppress the occurrence of short circuit defects with nearby bumps caused by excessive flow during heat pressing. If it is 100°C or lower, it can enable the assembly of parts at low temperatures. More specifically, examples include: EPICRON N-660, EPICRON N-670, EPICRON N-680, EPICRON N-770, EPICRON N-775, EPICRON 840, EPICRON N-865, EPICRON N-890, EPICRON HP-7200L, EPICRON HP-7200, EPICRON HP-7200H, and EPICRON HP-4700 manufactured by DIC Corporation; and KAYARAD NC-3000 and NC-3000H manufactured by Nippon Kayaku Co., Ltd. Two or more of these may also be used.

[0033] [Insulating Layer] The LED mounting substrate further has an insulating layer formed at least on the bumps. As shown in FIG1, the insulating layer 4 is formed on the substrate 2 having the electrode 1 and the bump 3 containing organic components and conductive particles.

[0034] Examples of methods for forming an insulating layer on a bump include: pattern printing methods such as screen printing or gravure printing; laser etching methods that remove unwanted parts after printing a rough pattern; and photolithography methods that are performed by exposing and developing a photosensitive paste. Among these, pattern formation by exposure and development processes is preferred for achieving fine patterning.

[0035] The insulating layer preferably contains epoxy resin and a compound having siloxane bonds or urethane bonds. If the insulating layer contains epoxy resin, the adhesion to the LED after installation can be improved, further improving connection reliability, and the insulation characteristics between electrodes can be improved. In addition, by containing compounds having siloxane bonds or urethane bonds, the elastic modulus of the insulating layer is reduced, which makes it easier to mitigate the impact during capture, thereby improving capture performance and further improving installability.

[0036] As an epoxy resin, it can be used as an organic component in the bump, for example.

[0037] The proportion of epoxy resin in the insulating layer is preferably 10 wt% to 50 wt% relative to 100 parts by weight of the acrylic copolymer with carboxyl groups.

[0038] Examples of compounds containing siloxane bonds include KUV-3433-UV, KER-4000-UV, KER-4700-UV, KER-4800-UV, KER-4700BK-UV, KER-4910-UV, FE-90-UV, KER-4301-UV, KER-4302-UV, KER-4303-UV, and KE manufactured by Shin-Etsu Chemical Co., Ltd. R-4304-UV, KER-4320-UV, SMP-7004, SMP-7014, SMP-7015, SMP-7004-3S, SMP-7014-3S, SMP-7015-3S, KER-4530, KER-4551, KER-4531, KER-4532, KER-4580, KE-4835, KE-3431, KE-3432, etc. Two or more of these may also be used.

[0039] Examples of compounds having carbamate bonds include AH-600, UA-306H, UA-306T, UF-8001G, and DAUA-167 manufactured by Kyoei Chemicals, Ltd.; EBECRYL 230, EBECRYL 4858, and KRM9046 manufactured by Daicel Allnex, Ltd.; and CN963, CN964, CN965, CN980, and CN981 manufactured by Bako Industries, Ltd. Two or more of these compounds may also be used.

[0040] The content of compounds having siloxane bonds or aminocarboxylate bonds in the insulating layer is preferably 10 wt% to 50 wt% relative to 100 parts by weight of the acrylic copolymer having carboxyl groups.

[0041] Preferably, the area of ​​the insulating layer in the LED mounting substrate is 1.1 to 10 times the area of ​​the LED, and a pattern is formed on two bumps under the insulating layer. By making the area of ​​the insulating layer more than 1.1 times the area of ​​the LED, the insulating layer can easily mitigate the impact during LED capture, improving capture performance and thus further improving mountability. In addition, by making the area of ​​the insulating layer less than 10 times the area of ​​the LED, proprietary areas on the substrate can be suppressed, the degree of freedom of the isolation wall pattern formed around the LED electrodes in subsequent steps can be increased, and the effects of expansion and contraction of the insulating layer during thermal cycling tests can be reduced, thereby improving connection reliability. The area of ​​the insulating layer can be calculated by observing the exposed insulating layer under a microscope after removing the LED with a laser. Furthermore, in the calculation, even if a part of the insulating layer pattern exists directly below the LED chip, that pattern is set as the target.

[0042] The insulating layer may contain additives such as hardeners, hardening accelerators, plasticizers, leveling agents, and silane coupling agents, in order not to impair the desired properties.

[0043] Preferably, the curing agent is a compound that undergoes a curing reaction with epoxy resin. Examples of curing agents include: amine compounds, acid anhydrides, phenolic resin compounds, etc.

[0044] As a curing accelerator, it is preferably a curing accelerator that promotes the curing of epoxy resin. By containing a curing accelerator, the bonding strength between the LED and the substrate can be improved, thereby further improving the connection reliability. More specifically, examples include: imidazole derivatives, dicyandiamine derivatives, quaternary ammonium salts, triphenylphosphine, and tetraphenylphosphonium tetraphenylborate. Two or more of these may also be used.

[0045] Examples of plasticizers include: dibutyl phthalate, dioctyl phthalate, polyethylene glycol, glycerin, etc.

[0046] As a leveling agent, examples include special vinyl polymers and special acrylic polymers.

[0047] Examples of silane coupling agents include: methyltrimethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, hexamethyldisilazane, 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltrimethoxysilane, etc.

[0048] [Manufacturing Method of LED Mounting Substrate] Methods for forming bumps in a composite material containing organic components and conductive particles include: forming a pattern in a bump shape using a conductive paste prepared by dispersing conductive particles in an organic component such as a resin solution, employing a pattern printing method such as screen printing or gravure printing, or a laser etching method that removes unwanted portions after rough pattern printing; or forming a pattern in a bump shape using a photolithography method that exposes and develops a photosensitive conductive paste using a photosensitive resin solution. Preferably, the bumps are patterned on the electrodes of a substrate having electrodes using an exposure and development process.

[0049] Examples of methods for forming an insulating layer on a bump include: pattern printing methods such as screen printing or gravure printing; laser etching methods that remove unwanted parts after rough pattern printing; and photolithography methods that are performed by exposing and developing a photosensitive conductive paste. Among these, pattern formation by exposure and development processes is preferred for achieving fine patterning.

[0050] [LED transfer substrate] The LED transfer substrate 13 forms a release layer 10 on the transparent substrate 9, and the side of the LED 5 without the electrode 6 is attached to the release layer 10 by means of the adhesiveness of the release layer 10, thereby holding the LED chip.

[0051] As a transparent substrate, any substrate that allows the irradiated laser wavelength to pass through is acceptable, and a quartz substrate is preferred.

[0052] The release layer is a resin layer such as polyimide resin or acrylic resin, which absorbs the laser wavelength being irradiated.

[0053] The thickness of the release layer is preferably in the range of 1 μm to 20 μm.

[0054] <LED Transfer Step> Next, as shown in FIG3 (b), the LED 5 is transferred to the LED mounting substrate 12 by irradiating the LED 5 from the transparent substrate 9 side of the LED transfer substrate 13 with laser 11.

[0055] As the oscillator for the laser, any laser oscillator can be used as long as it is an oscillator that uses laser light to etch the release layer. Examples of such laser oscillators include: KrF excimer lasers, ArF excimer lasers, and YAG lasers. Furthermore, the laser light can be used as pulsed light, and in this case, the frequency can be approximately 0.1 kHz to 100 kHz. The energy density can be appropriately adjusted within the range of 100 mJ / cm² to 3000 mJ / cm².

[0056] The laser wavelength used for irradiation can be 366 nm as an example, but it is not limited to this and can be appropriately adjusted according to the absorption wavelength range of the release layer used.

[0057] <LED Installation Steps> Next, as shown in FIG3 (c), the transferred LED 5 is heat-pressed onto the LED mounting substrate 12 to install the LED 5.

[0058] As a method for mounting LEDs by hot-pressing them onto an LED mounting substrate, mounting can be performed using a bonding machine or a diaphragm laminator. For the purpose of enabling large-area mounting in a short time, mounting using a diaphragm laminator is preferred. The mounting temperature is preferably in the range of 90°C to 140°C, the mounting pressure is preferably in the range of 0.5 MPa to 5.0 MPa, and the mounting time is preferably in the range of 1 sec to 10 sec.

[0059] To improve the curing reaction of the organic components, the obtained LED mounting substrate 14 can be heated, for example by heating and drying using an oven, an inert oven, a heating plate, electromagnetic waves or microwaves using ultraviolet lamps, infrared heaters, halogen heaters, xenon flash lamps, etc., or vacuum drying. By heating, the reaction rate of the organic components in the bumps and insulating layer is increased, which can further improve the tightness or connection reliability.

[0060] In addition, as shown in FIG3(e), if the thickness of the insulating layer on the bump in the LED mounting substrate is in the range of 0.5 μm to 4 μm, then the LED electrode can penetrate the insulating layer and be directly mounted on the bump in the LED transfer step, which is preferred.

[0061] Furthermore, as shown in FIG3(e), if the minimum distance between the bumps in the LED mounting substrate is 3 μm or more, the discharge of the insulating layer will not be hindered during the LED transfer step, further improving the connectivity between the LED electrode and the bumps, thus further improving the mounting performance and connection reliability. On the other hand, if the minimum distance between the bumps is 50 μm or less, the shrinkage difference generated during thermal cycling can be suppressed, further improving the connection reliability. [Example]

[0062] The present invention will be described in detail below with reference to examples and comparative examples, but the form of the present invention is not limited to these.

[0063] The evaluation methods in each embodiment are as follows.

[0064] <Minimum distance between bumps> The distance between a pair of bumps formed on a circuit board at ten locations was randomly measured using a digital microscope (VHX-6000; manufactured by Keyence, Inc.), and the minimum value was set as the minimum distance between bumps.

[0065] <Average thickness of bumps> The average thickness of ten bumps randomly selected from 200 bumps formed on the circuit board was measured using a laser microscope (VK-X1000 / 1100; manufactured by Keyence, Inc.), and the average value was set as the average thickness of the bumps.

[0066] <Thickness of insulating layer on bump> The thickness of insulating layer from circuit board to bump at ten locations was randomly measured using a laser microscope (VK-X1000 / 1100; manufactured by Keyence (stock)). The average thickness of the insulating layer on bump was taken as the average value minus the average thickness of the bump.

[0067] <Area Ratio of Insulating Layer> The insulating layer pattern formed on the bump is imaged and its area is calculated using a digital microscope (VHX-6000; manufactured by Keyence, Inc.). The area of ​​the insulating layer is then divided by the light-emitting area of ​​the installed LED and set as the area ratio of the insulating layer.

[0068] <Installation Evaluation> Apply voltage to the LED mounting substrate with 100 LED chips mounted on 200 bumps obtained in the embodiments and comparative examples, count the number of LEDs lit, and use the number as the installation evaluation result.

[0069] <Connectivity Reliability Evaluation (Thermal Cycling Test)> For the LED mounting substrates obtained in the Examples and Comparative Examples, 300 cycles were performed at -40°C and 85°C for 1 hour each. The subsequent LED illumination rate was calculated according to the following formula and used as the connectivity reliability evaluation result. Connectivity Reliability Evaluation = Number of LEDs lit after the test / Number of LEDs lit before the test × 100.

[0070] The materials used in the examples and comparative examples are as follows.

[0071] [Photosensitive Components] (Synthesis Example) An acrylic copolymer (A) containing carboxyl groups with unsaturated double bonds was charged with 150 g of diethylene glycol monobutyl ether (hereinafter "DGME") in a reaction vessel under nitrogen atmosphere, and heated to 80°C using an oil bath. Over a period of 1 hour, a mixture comprising 20 g of ethyl acrylate (hereinafter "EA"), 40 g of 2-ethylhexyl methacrylate (hereinafter "2-EHMA"), 20 g of n-butyl acrylate (hereinafter "BA"), 15 g of N-hydroxymethyl acrylamide (hereinafter "MAA"), 0.8 g of 2,2'-azobisisobutyronitrile, and 10 g of DGME was added dropwise. After the dropwise addition was complete, the mixture was heated at 80°C for 6 hours to carry out the polymerization reaction. Then, 1 g of hydroquinone monomethyl ether was added, and the polymerization reaction was stopped. Subsequently, a mixture containing 5 g of glycidyl methacrylate (hereinafter "GMA"), 1 g of triethylbenzylammonium chloride, and 10 g of DGME was added dropwise over 0.5 hours. After the addition was completed, the mixture was heated for 2 hours to carry out the addition reaction. Unreacted impurities were removed by purifying the obtained reaction solution with methanol, and then the solution was vacuum dried for 24 hours to obtain a carboxyl-containing acrylic copolymer (A) with a copolymer ratio (mass basis) of EA / 2-EHMA / BA / GMA / AA = 20 / 40 / 20 / 5 / 15.

[0072] [Photopolymerization initiator] · "IRGACURE" OXE04 (manufactured by BASF Japan) (hereinafter referred to as OXE04).

[0073] [Compounds with unsaturated double bonds] · "Light Acrylate (registered trademark)" BP-4EA (manufactured by Kyoei Chemical Co., Ltd.) (hereinafter referred to as BP-4EA).

[0074] [Conductive Particles] • Ag particles with a particle size (D50) of 0.5 μm and an aspect ratio of 1.1 (hereinafter referred to as Ag particles) • Resin-core Ag-coated particles with a particle size (D50) of 0.5 μm and an aspect ratio of 1.1 (average particle size of resin core particles is 0.35 μm). (True density 7.24 g / cm 3) [Epoxy Resin] • "EPICRON" 840 (manufactured by DIC) (hereinafter referred to as "840"), epoxy equivalent 185 g / eq, liquid • "EPICRON" HP-7200L (manufactured by DIC) (hereinafter referred to as HP-7200L), epoxy equivalent 250 g / eq, softening point 55°C.

[0075] [Hardening Accelerator] · "Curezol (registered trademark)" C11Z-A (manufactured by Shikoku Chemical Co., Ltd.) (hereinafter referred to as C11Z-A).

[0076] [Hardening agent] ·Phenolic varnish type phenolic resin H-4 (manufactured by Meiwa Kasei Corporation) (hereinafter referred to as H-4), hydroxyl equivalent 105 g / eq, softening point 72℃.

[0077] [Compounds with siloxane bonds] ·KER-4910-UV (manufactured by Shin-Etsu Chemical Co., Ltd.) ·SMP-7004 (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0078] [Compounds with carbamate bonds] · EBECRYL 230 (manufactured by Daicel Allnex (stock)).

[0079] (Synthesis Example 1) <Materials for bump formation> 15.00 g of an acrylic copolymer (A) containing carboxyl groups with unsaturated double bonds, 0.66 g of OXE04, 1.5 g of BP-4EA, 3.82 g of "840", 2.17 g of H-4, and 5.78 g of DGME were placed in a 100 ml clean bottle and mixed using a rotary-revolution vacuum mixer "Defoaming Stirring Taro (registered trademark)" ARE-310 (manufactured by Thinky Co., Ltd.) to obtain a resin solution of 28.94 g.

[0080] The obtained 28.94 g of resin solution was mixed with 54.02 g of Ag particles with a particle size (D50) of 0.5 μm and an aspect ratio of 1.1, and kneaded using a three-roll mill (EXAKT M-50; manufactured by EXAKT Corporation) to obtain 82.96 g of bump-forming paste. The composition of the bump-forming paste is shown in Table 1-a.

[0081] <Bump Forming Substrate Fabrication> The obtained bump forming paste is applied to a circuit board with substrate electrodes having a substrate thickness of 0.7 mm, and heated in a drying oven at 100°C for 5 minutes.

[0082] Using a direct-line exposure apparatus (MX-1201; manufactured by Dai Nippon Research, Ltd.), taking into account the increase in line thickness of the exposed section, 200 ϕ10 μm bump patterns were exposed at an exposure dose of 300 mJ / cm 2 (wavelength converted to 375 nm).

[0083] After exposure, a 0.1% by weight Na2CO3 aqueous solution is used for spray development for 20 seconds, followed by rinsing with ultrapure water to create a bump-forming substrate.

[0084] <Insulating Layer Material> 15.00 g of an acrylic copolymer (A) containing carboxyl groups with unsaturated double bonds, 0.30 g of OXE04, 3.00 g of "840", 0.015 g of C11Z-A, and 4.579 g of DGME were placed in a 100 ml clean bottle and mixed using a rotary-revolutionary vacuum mixer "Defoaming Stirring Taro (registered trademark)" ARE-310 (manufactured by Thinky Co., Ltd.) to obtain a resin solution of 22.89 g. The composition of the insulating layer material is shown in Table 1-b.

[0085] <Preparation of LED mounting substrate> The obtained insulating layer material is coated onto the bump forming substrate in such a way that it becomes the desired dry thickness, and the insulating layer area is made the same as the light-emitting area of ​​the LED used, 800 μm 2, using a direct-line exposure apparatus (MX-1201; manufactured by Dai Nippon Research, Ltd.) with an exposure dose of 100 mJ / cm 2 (wavelength converted to 375 nm).

[0086] After exposure, a 0.1% by weight Na₂CO₃ aqueous solution is used for spray development for 20 seconds, followed by rinsing with ultrapure water to fabricate an LED mounting substrate. The average thickness of the bumps on the obtained LED mounting substrate is evaluated using the method described above.

[0087] <Preparation of LED Transfer Substrate> As shown in Figure 2, on an LED substrate 15 on which LED chips with an area of ​​20 μm × 40 μm and an LED electrode 6 of 18 μm × 13 μm are arranged on a sapphire substrate 8 and a sacrificial layer 7 which is decomposed by laser energy, a polyimide layer 10 with a thickness of 10 μm is formed on a 0.5 mm quartz substrate 9. The substrate is then hot-pressed at 500 N and 200 °C for 10 minutes. A KrF excimer laser with a wavelength of 248 nm is then irradiated from the sapphire substrate 8 at 300 mJ / cm². Afterwards, the sapphire substrate 8 is separated to obtain the LED transfer substrate 13.

[0088] (Example 1) As shown in Figure 3(a), an LED mounting substrate and an LED transfer substrate were vacuum-adsorbed onto a stage and a transport tool. While confirming the position using a camera, the stage was moved to directly below the electrodes of the LED chips with overlapping bumps, facing each other with the insulating layer and LED electrodes spaced 50 μm apart. Then, as shown in Figure 3(b), 100 LED chips were transferred onto the insulating layer of the mounting substrate by irradiating a 366 nm wavelength laser at 300 mJ / cm² from the quartz substrate (transparent substrate) side of the LED transfer substrate. Afterwards, as shown in Figure 3(c), a diaphragm laminator (MVLP600; manufactured by Nippon Steel Co., Ltd.) was used for hot pressing at 120°C, 1 MPa, and 30 sec to obtain the LED mounting substrate. The mounting performance and connection reliability of the obtained LED mounting substrate were evaluated using the above method. The evaluation results are shown in Table 2.

[0089] (Examples 2 to 17) The bump forming material and insulating layer material with the compositions shown in Tables 1-a and 1-b were prepared using the same method as in Example 1, and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0090] (Example 18) As shown in Figure 3(a), an LED mounting substrate and an LED transfer substrate were vacuum-adsorbed onto a stage and a transport tool. While confirming the position using a camera, the stage was moved to directly below the electrodes of the LED chips with overlapping bumps, facing each other with the insulating layer and LED electrodes spaced 50 μm apart. Then, as shown in Figure 3(b), a 366 nm wavelength laser was irradiated from the quartz substrate (transparent substrate) side of the LED transfer substrate with 300 mJ / cm² to transfer 100 LED chips onto the insulating layer of the mounting substrate, thereby obtaining an LED mounting substrate. The mounting performance and connection reliability of the obtained LED mounting substrate were evaluated using the above method. The evaluation results are shown in Table 2.

[0091] (Comparative Example 1) A bump forming material with the composition shown in Tables 1-a and 1-b was prepared using the same method as in Example 1. A bump forming substrate was formed using the same method as in Example 1, but no insulating layer was formed on the bumps. The evaluation was performed in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0092] (Comparative Examples 2 to 5) Indium plating was performed on a circuit board having substrate electrodes with a substrate thickness of 0.7 mm to obtain a bump-forming substrate with indium bumps having a thickness of 4.0 μm formed on the substrate electrodes. The substrates were fabricated using the insulating layer materials shown in Table 1-b and using the same method as in Example 1, and were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0093] (Comparative Example 6) Indium plating was performed on a circuit board having substrate electrodes with a substrate thickness of 0.7 mm to obtain a bump-forming substrate with indium bumps of 0.5 μm thickness formed on the substrate electrodes. The substrate was fabricated using the insulating layer materials shown in Table 1-b and the same method as in Example 1, and was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0094] (Comparative Example 7) Indium plating was performed on a circuit board having substrate electrodes with a substrate thickness of 0.7 mm to obtain a bump-forming substrate with indium bumps of 3.0 μm thickness formed on the substrate electrodes. The substrate was fabricated using the insulating layer materials shown in Table 1-b and the same method as in Example 1, and was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0095] (Comparative Example 8) Indium plating was performed on a circuit board having substrate electrodes with a substrate thickness of 0.7 mm to obtain a bump-forming substrate with indium bumps of 3.0 μm thickness formed on the substrate electrodes. The substrate was fabricated using the insulating layer materials shown in Table 1-b and the same method as in Example 18, and was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0096] [Table 1-a] [Table 1-a] Bumps in composite materials containing organic components and metal particles Acrylic acid copolymers with carboxyl groups Photopolymerization initiator Epoxy resin Compounds with unsaturated double bonds conductive particles Hardener / hardening accelerator solvent type type content (*1) type content (*1) type content (*1) type content (*2) content (*3) type content (*1) type content (*4) Example 1 A OXE04 4.4 840 25.47 BP-4EA 10 Ag particles 45 7.2 H-4 14.47 DGME 20 Example 2 A OXE04 4.4 840 25.47 BP-4EA 10 Resin core Ag-coated particles 45 10.2 H-4 14.47 DGME 20 Example 3 A OXE04 4.4 840 25.47 BP-4EA 10 Ag particles 45 7.2 H-4 14.47 DGME 20 Example 4 A OXE04 4.4 840 25.47 BP-4EA 10 Ag particles 45 7.2 C11Z-A 0.1 DGME 20 Example 5 A OXE04 4.4 HP-7200L 25.47 BP-4EA 10 Ag particles 45 7.2 C11Z-A 0.1 DGME 20 Example 6 A OXE04 4.4 HP-7200L 25.47 BP-4EA 10 Ag particles 95 64.4 C11Z-A 0.1 DGME 20 Example 7 A OXE04 4.4 HP-7200L 25.47 BP-4EA 10 Ag particles 70 18.2 C11Z-A 0.1 DGME 20 Example 8 A OXE04 4.4 HP-7200L 25.47 BP-4EA 10 Ag particles 70 18.2 C11Z-A 0.1 DGME 20 Example 9 A OXE04 4.4 HP-7200L 25.47 BP-4EA 10 Ag particles 70 18.2 C11Z-A 0.1 DGME 20 Example 10 A OXE04 4.4 HP-7200L 25.47 BP-4EA 10 Ag particles 70 18.2 C11Z-A 0.1 DGME 20 Example 11 A OXE04 4.4 HP-7200L 25.47 BP-4EA 10 Ag particles 70 18.2 C11Z-A 0.1 DGME 20 Example 12 A OXE04 4.4 HP-7200L 25.47 BP-4EA 10 Ag particles 70 18.2 C11Z-A 0.1 DGME 20 Example 13 A OXE04 4.4 HP-7200L 25.47 BP-4EA 10 Ag particles 70 18.2 C11Z-A 0.1 DGME 20 Example 14 A OXE04 4.4 HP-7200L 25.47 BP-4EA 10 Ag particles 70 18.2 C11Z-A 0.1 DGME 20 Example 15 A OXE04 4.4 HP-7200L 25.47 BP-4EA 10 Ag particles 70 18.2 C11Z-A 0.1 DGME 20 Example 16 A OXE04 4.4 HP-7200L 25.47 BP-4EA 10 Ag particles 70 18.2 C11Z-A 0.1 DGME 20 Example 17 A OXE04 4.4 HP-7200L 25.47 BP-4EA 10 Ag particles 70 18.2 C11Z-A 0.1 DGME 20 Example 18 A OXE04 4.4 HP-7200L 25.47 BP-4EA 10 Ag particles 70 18.2 C11Z-A 0.1 DGME 20 Comparative Example 1 A OXE04 4.4 840 25.47 BP-4EA 10 Ag particles 45 7.2 H-4 14.47 DGME 20 Comparative Example 2 - - - - - - - - - - - - - - Comparative Example 3 - - - - - - - - - - - - - - Comparative Example 4 - - - - - - - - - - - - - - Comparative Example 5 - - - - - - - - - - - - - - Comparative Example 6 - - - - - - - - - 0 - - - - Comparative Example 7 - - - - - - - - - - - - - - Comparative Example 8 - - - - - - - - - - - - - - *1: Parts by weight relative to 100 parts by weight of the acrylic copolymer containing carboxyl groups *2: Weight % of solids *3: Volume % of solids *4: Weight % of paste composition

[0097] [Table 1-b] [Table 1-b] Insulation layer Acrylic acid copolymers with carboxyl groups Photopolymerization initiator Epoxy resin Compounds containing siloxane bonds or urethane bonds Hardening accelerator / hardener solvent type type content (*1) type content (*1) type content (*1) type content (*1) type content (*3) Example 1 A OXE04 2 840 20 - - C11Z-A 0.1 DGME 20 Example 2 A OXE04 2 840 20 - - C11Z-A 0.1 DGME 20 Example 3 A OXE04 2 840 20 - - C11Z-A 0.1 DGME 20 Example 4 A OXE04 2 840 20 - - C11Z-A 0.1 DGME 20 Example 5 A OXE04 2 HP-7200L 20 - - C11Z-A 0.1 DGME 20 Example 6 A OXE04 2 HP-7200L 20 - - C11Z-A 0.1 DGME 20 Example 7 A OXE04 2 HP-7200L 20 - - C11Z-A 0.1 DGME 20 Example 8 A OXE04 2 HP-7200L 20 - - C11Z-A 0.1 DGME 20 Example 9 A OXE04 2 HP-7200L 20 - - C11Z-A 0.1 DGME 20 Example 10 A OXE04 2 HP-7200L 20 - - C11Z-A 0.1 DGME 20 Example 11 A OXE04 2 HP-7200L 20 - - C11Z-A 0.1 DGME 20 Example 12 A OXE04 2 HP-7200L 20 KER-4910-UV 20 C11Z-A 0.1 DGME 20 Example 13 A OXE04 2 HP-7200L 20 SMP-7004 20 C11Z-A 0.1 DGME 20 Example 14 A OXE04 2 HP-7200L 20 EBECRYL 230 20 C11Z-A 0.1 DGME 20 Example 15 A OXE04 2 HP-7200L 20 EBECRYL 230 20 C11Z-A 0.1 DGME 20 Example 16 A OXE04 2 HP-7200L 20 EBECRYL 230 20 C11Z-A 0.1 DGME 20 Example 17 A OXE04 2 HP-7200L 20 EBECRYL 230 20 C11Z-A 0.1 DGME 20 Example 18 A OXE04 2 HP-7200L 20 EBECRYL 230 20 C11Z-A 0.1 DGME 20 Comparative Example 1 - - - - - - - - - - - Comparative Example 2 A OXE04 2 840 20 - - C11Z-A 0.1 DGME 20 Comparative Example 3 A OXE04 2 HP-7200L 20 KER-4910-UV 20 C11Z-A 0.1 DGME 20 Comparative Example 4 A OXE04 2 - - - - - - - - Comparative Example 5 A OXE04 2 - - - - - - - - Comparative Example 6 A OXE04 2 - - - - - - - - Comparative Example 7 A OXE04 2 - - - - - - - - Comparative Example 8 A OXE04 2 - - - - - - - - *1: Parts by weight relative to 100 parts by weight of the acrylic copolymer containing carboxyl groups *3: Weight % of the ointment composition

[0098] [Table 2] [Table 2] Average thickness B of the bump H [μm] Minimum distance between bumps [μm] The ratio of the area of ​​the insulating layer to the area of ​​the LED. Insulating layer thickness on the bump [μm] Installation performance evaluation [indivual] Connection reliability evaluation [%) Example 1 8.0 10.0 1.0 5.0 77 84.4 Example 2 8.0 10.0 1.0 5.0 56 69.6 Example 3 0.8 10.0 1.0 5.0 73 75.3 Example 4 4.0 10.0 1.0 5.0 91 75.8 Example 5 4.0 10.0 1.0 5.0 90 77.8 Example 6 8.0 10.0 1.0 5.0 50 72.4 Example 7 4.0 10.0 1.0 5.0 92 96.7 Example 8 4.0 10.0 1.0 5.0 90 97.8 Example 9 4.0 10.0 15.0 5.0 95 89.5 Example 10 4.0 10.0 2.0 5.0 96 96.9 Example 11 4.0 10.0 2.0 5.0 98 98.0 Example 12 4.0 10.0 2.0 5.0 100 100.0 Example 13 4.0 10.0 2.0 5.0 100 100.0 Example 14 4.0 10.0 2.0 5.0 100 100.0 Example 15 4.0 10.0 1.0 2.0 75 80.0 Example 16 4.0 10.0 2.0 2.0 100 100.0 Example 17 4.0 10.0 2.0 0.3 56 89.3 Example 18 4.0 10.0 1.0 2.0 70 97.1 Comparative Example 1 4.0 10.0 - - LED cannot be transferred - Comparative Example 2 4.0 10.0 1.0 5.0 LED cannot be transferred - Comparative Example 3 4.0 10.0 1.0 5.0 10 0.0 Comparative Example 4 3.0 2.0 1.3 5.0 67 0.0 Comparative Example 5 3.0 60.0 1.3 5.0 30 40.0 Comparative Example 6 0.5 10.0 1.3 5.0 60 50.0 Comparative Example 7 3.0 10.0 1.3 5.0 65 50.0 Comparative Example 8 3.0 10.0 1.3 5.0 0 0.0 [Simplified Explanation of the Diagram]

[0011] FIG1 is a schematic diagram showing the manufacturing method of the LED mounting substrate used in the present invention. FIG2 is a schematic diagram showing the manufacturing method of the LED transfer substrate used in the embodiment. FIG3(a) to FIG3(f) are schematic diagrams showing the manufacturing method of the LED mounting substrate of the present invention.

Claims

1. A method for manufacturing a light-emitting diode (LED) mounting substrate, comprising: a step of making an insulating layer forming surface of an LED mounting substrate face an electrode-containing surface of an LED transfer substrate on which an LED is attached to a transparent substrate, the insulating layer forming surface of the LED mounting substrate comprising: a substrate having electrodes, bumps formed on the electrodes of a composite material containing organic components and conductive particles, and an insulating layer formed at least on the bumps; a step of irradiating the LED from the transparent substrate side of the LED transfer substrate to the LED to transfer the LED to the LED mounting substrate (LED transfer step); and a step of mounting the transferred LED to the LED mounting substrate (LED mounting step).

2. The method for manufacturing a light-emitting diode mounting substrate as claimed in claim 1, wherein the light-emitting diode mounting step is a step of thermally bonding a transferred light-emitting diode to a light-emitting diode mounting substrate.

3. A method for manufacturing a light-emitting diode mounting substrate as described in claim 1 or claim 2, wherein the average thickness BH of the bumps in the light-emitting diode mounting substrate is 1.0 μm to 5.0 μm.

4. A method for manufacturing a light-emitting diode mounting substrate as described in claim 1 or claim 2, wherein the minimum distance between bumps in the light-emitting diode mounting substrate is 3 μm to 50 μm, and the thickness of the insulating layer on the bumps in the light-emitting diode mounting substrate is 0.5 μm to 4 μm.

5. A method for manufacturing a light-emitting diode mounting substrate as described in claim 1 or claim 2, wherein the organic component comprises an acrylic copolymer having carboxyl groups and an epoxy resin.

6. A method for manufacturing a light-emitting diode mounting substrate as claimed in claim 1 or claim 2, wherein the content of the conductive particles is 50% to 90% by weight of the total weight of the bumps.

7. A method for manufacturing a light-emitting diode mounting substrate as described in claim 1 or claim 2, wherein the area of ​​the insulating layer in the light-emitting diode mounting substrate is 1.1 to 10 times the area of ​​the light-emitting diode, and a pattern is formed on two bumps under the insulating layer.

8. A method for manufacturing a light-emitting diode mounting substrate as claimed in claim 1 or claim 2, wherein the insulating layer comprises an epoxy resin and a compound having siloxane bonds or urethane bonds.

9. A method for manufacturing a light-emitting diode mounting substrate as described in claim 1 or claim 2, comprising a step of patterning bumps in the light-emitting diode mounting substrate by means of an exposure and development process.

10. A method for manufacturing a light-emitting diode mounting substrate as described in claim 1 or claim 2, comprising a step of patterning the insulating layer by an exposure and development process.

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