Electronic component mounting boards and displays

Abstract

To provide a highly reliable electronic component mounting substrate which has the sufficient resistance on the thermal shock in the time of driving in a structure in which an electronic component is reduced in size and height.SOLUTION: An electronic component mounting substrate includes an electronic component on a substrate, a conductive composite material including a resin and a conductive material between an electrode of the substrate and an electrode of the electronic component; and an insulation resin in a portion that does not have the conductive composite material between the electronic component and the substrate. When the thickness (μm) of the conductive composite material is TE, and the average diameter (μm) of the conductive material is RM, 3.0<TE / RM<20.0 is satisfied. When the insulation resin is 100 pts.wt, the content of an inorganic particle included in the insulation resin is equal to or less than 40 pts.wt.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electronic component mounting board and a display. [Background technology]

[0002] In recent years, electronic components and the electronic component mounting boards on which they are mounted have become smaller and thinner in order to meet market demands for higher integration.Currently, in the mounting of logic IC chips such as semiconductor processors and memories, the flip-chip mounting method, in which electrodes are placed under the chip and directly connected to the electrodes on the board, is widely used instead of the conventional wire bonding method in order to increase the integration level of electronic components.

[0003] Meanwhile, in the display field, structures using LED chips with sides of 100 μm or less, called μLEDs, are being actively studied. These are particularly suitable for flip-chip mounting, but because the chip size, thickness, and electrode size are significantly different from those of logic IC chips, conventional solder connection methods pose a problem of solder leaking to adjacent electrodes, causing short circuits between the electrodes. Therefore, many connection structures and methods other than soldering are being considered. A specific μLED mounting method, for example, is known to use a sheet material commonly known as ACF, which is formed on the surface of a printed wiring board and contains conductive particles with a particle size approximately equal to the thickness of the adhesive layer arranged in a fixed pattern within the adhesive layer (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 74058 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with the ACF-based construction method described in Patent Document 1, the miniaturization of electronic components is expected to result in the following reliability issues. Specifically, as shown in Figure 2, to prevent short circuits between the electrodes of electronic components, the particle size of the conductive particles used in the ACF must be smaller than the distance between the electrodes. Accordingly, the thickness of the adhesive layer must also be thinned to be approximately equal to the particle size of the conductive particles. Within such a thin adhesive layer, heat generated during circuit operation generates stress due to the thermal expansion coefficient of the adhesive layer and the conductive particles (hereinafter referred to as thermal shock), which can impair electrical connection.

[0006] Therefore, an object of the present invention is to provide a highly reliable electronic component mounting substrate that has sufficient resistance to thermal shock during operation even in a structure in which electronic components are miniaturized and low-profile. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention mainly has the following configuration. The substrate has electronic components thereon, a conductive composite material containing a resin and a conductive material is disposed between the electrode of the substrate and the electrode of the electronic component; an electronic component mounting substrate having an insulating resin in a portion between the electronic component and the substrate that does not have the conductive composite material, The thickness (μm) of the conductive composite material is T E , the average diameter (μm) of the conductive material is R M When this is done, it becomes 3.0. <T E / R M <20.0, The electronic component mounting substrate has an insulating resin containing inorganic particles in an amount of 40 parts by weight or less, based on 100 parts by weight of the insulating resin. [Effects of the Invention]

[0008] The electronic component mounting board of the present invention has sufficient thermal shock resistance. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of an electronic component mounting board according to the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing an example of the state of a joint in an electronic component mounting board using an ACF. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of an electronic component mounting board according to the present invention will be described in detail with reference to the drawings. Note that the drawings are schematic. Furthermore, the present invention is not limited to the embodiments described below.

[0011] 1 is a schematic diagram showing an example of an electronic component mounting substrate 8 according to an embodiment of the present invention. The electronic component mounting substrate 8 has an electronic component 2 on a substrate 1, a conductive composite material 3 containing a resin and a conductive material between an electrode 5a of the substrate 1 and an electrode 5b of the electronic component 2, and an insulating resin 4 in a portion between the electronic component 2 and the substrate 1 that does not have the conductive composite material 3. Each of these will be described below.

[0012] <Substrate> Substrates are used to mount electronic components and are generally used to form the wiring for the electronic components. Materials include organic materials such as printed circuit boards and inorganic materials such as glass and silicon. Functionality includes, but is not limited to, those containing elements such as transistors and those functioning as interposers for reconnecting to larger substrates. When mounting low-profile electronic components using flip-chip mounting, inorganic substrates with high in-plane flatness are preferred because they minimize variations in the residual stress within the substrate surface after mounting. Furthermore, TFT substrates or silicon substrates incorporating transistor-based drive circuits within the substrate are more preferred because they can compensate for variations in the resistance values of each electrode. When the substrate is heated during processing, a temperature gradient across the substrate's thickness can cause the substrate to warp, increasing thermal shock. To prevent this, the substrate thickness is preferably 1.0 mm or less, and 0.1 mm or more is preferred from the perspective of ease of handling.

[0013] <Electronic components> The electronic component mounting board of the present invention has electronic components mounted on a substrate. Here, the term "electronic component" refers to any element mounted on a substrate with electrical connections and functioning based on the input or output of electrical signals, or both. Specific examples include, but are not limited to, semiconductor chips and interposers. The electronic component mounting board of the present invention may have multiple electronic components mounted on the substrate.

[0014] One suitable electronic component is an optical element, which includes LEDs, photoresistors, phototransistors, photodiodes, micromirrors, solar cells, etc. μLEDs with sides of 100 μm or less are particularly preferred because they can achieve particularly high reliability when used with the structure of the present invention.

[0015] The ratio of the area occupied by the electrodes of an electronic component to the total area of the surface of the electronic component having the electrodes (hereinafter sometimes referred to as the "electrode area ratio") is preferably 0.3 to 0.9. In order to prevent peeling at the interface between the electrode and the conductive composite material due to thermal shock by increasing the bonding area between the electrode and the conductive composite material, it is preferable that the electrode area is large; specifically, the electrode area ratio of an electronic component is preferably 0.3 or more. The electrode area ratio of an electronic component is more preferably 0.5 or more. On the other hand, by setting the electrode area ratio of an electronic component to 0.9 or less, short circuits between electrodes can be more easily suppressed. The electrode area ratio of an electronic component is more preferably 0.8 or less. The area of the surface of an electronic component having electrodes and the area of the electrodes can be measured by separating the electronic component from the electronic component mounting board by peeling or polishing, and then observing the electronic component with an optical microscope or a scanning electron microscope (SEM), respectively.

[0016] <Conductive composite material> The electronic component mounting board of the present invention has a conductive composite material containing a resin and a conductive material between an electrode of the board and an electrode of the electronic component.

[0017] <Resin> The resin may be one whose main component is an acrylic copolymer, an epoxy resin, a silicone resin, a polyimide resin, a phenolic resin, or the like, and preferably contains an acrylic copolymer and an epoxy resin having a carboxyl group.

[0018] <Conductive materials> The conductive material has the function of electrically connecting electrodes in contact with the conductive composite material. The conductive material may be a material that uses conductive particles (hereinafter referred to as conductive particles) and disperses the conductive particles in a resin, thereby achieving electrical connection by bringing multiple conductive particles into contact with each other. Alternatively, the conductive particles may be sintered to form a bond, thereby achieving electrical connection.

[0019] Examples of conductive particles include particles of silver, gold, copper, platinum, lead, tin, nickel, aluminum, tungsten, molybdenum, chromium, titanium, indium, magnesium, zinc, iron, and alloys thereof. Two or more of these may be contained. Among these, from the viewpoint of conductivity, particles of a metal selected from silver, gold, and copper are preferred, and from the viewpoint of cost and stability, silver particles are more preferred. Furthermore, the conductive particles may be those coated with a resin, an inorganic oxide, or the like. Metal particles are preferred because conductive particles in which the surface of resin particles or inorganic oxide particles is coated with a metal are subject to elastic repulsion by the resin particles during mounting.

[0020] The average particle diameter of the conductive particles is preferably 0.01 to 1.0 μm. When the average particle diameter of the conductive particles is 0.01 μm or more, the interaction between particles can be appropriately suppressed, and the dispersibility of the conductive particles in the resin can be improved. The average particle diameter of the conductive particles is more preferably 0.1 μm or more. On the other hand, when the average particle diameter of the conductive particles is 1.0 μm or less, the surface smoothness, pattern accuracy, and dimensional accuracy of the obtained conductive pattern can be improved.

[0021] The thickness of the conductive composite material is preferably 2.0 μm or more in order to obtain sufficient die shear strength, and is preferably 6.0 μm or less in order to reduce the height of the electronic component mounting board.

[0022] In the electronic component mounting substrate of the present invention, the thickness (μm) of the conductive composite material is T E , the average diameter (μm) of the conductive material is R M When this is done, it becomes 3.0. <T E / R M It is important to meet the T < 20.0. E / R M If T is 3.0 or less, the electrical connection paths formed by the conductive material are less likely to branch within the conductive composite material, and the number of connection points with the electrodes is reduced, making the material more susceptible to breakage due to thermal shock. E / R M is more preferably 5.0 or more. E / R MIf T is 20.0 or more, the diameter of the conductive material becomes too small, making it prone to breakage due to thermal shock. E / R M is more preferably 15.0 or less. E and R M R can be measured by observing a cross section perpendicular to the substrate at a location in an electronic component mounting substrate where a conductive composite material is present between the electrode of the substrate and the electrode of the electronic component. M is calculated by measuring the cross-sectional diameter of 50 randomly selected conductive materials and using the following formulas 1 and 2, which represent the average value weighted by the area and deviation. Here, the cross-sectional diameter is the distance between the two most distant points on the contour of the cross section of the conductive material, and R n represents the cross-sectional diameter measured at the nth time, and Σ is σ, where n is from 1 to 50. V ×R n 2 or σ V ×R n This means summing up R AVE is R where n is 1 to 50 n means the arithmetic mean of R M =Σ(σ V ×R n 2 ) / Σ(σ V ×R n ) (Formula 1) σ V =10 -|RAVE-Rn| (Equation 2).

[0023] <Insulating resin> The electronic component mounting board of the present invention has an insulating resin in the portion between the electronic component and the board that does not have the conductive composite material.

[0024] The insulating resin may be a resin that is generally used as an underfill material. The insulating resin may be supplied before mounting the electronic components by laminating a sheet-like resin onto the substrate, or may be filled in liquid form after mounting the electronic components to enable remounting in the event of a defect in the electronic components.

[0025] The insulating resin may be made of, for example, an acrylic polymer, an epoxy resin, and a hardening accelerator.

[0026] The acrylic polymer preferably has an average molecular weight of 3,000 or more.

[0027] Examples of epoxy resins include bisphenol A type, cresol novolac type, phenol novolac type, bisphenol A novolac type, dicyclopentadiene type, and naphthalene type. Examples of curing accelerators include imidazoles, dicyandiamide derivatives, quaternary ammonium salts, triphenylphosphine, and tetraphenylphosphonium tetraphenylborate.

[0028] The insulating resin may also contain inorganic particles. Examples of inorganic particles include silicates such as mica and glass, oxides such as titanium oxide, alumina, and silica, carbonates such as calcium carbonate and magnesium carbonate, hydroxides such as aluminum hydroxide, magnesium hydroxide, and calcium hydroxide, sulfates or sulfites such as barium sulfate, calcium sulfate, and calcium sulfite, borates such as zinc borate, barium metaborate, aluminum borate, calcium borate, and sodium borate, and nitrides such as aluminum nitride, boron nitride, and silicon nitride. Among these, silica is preferred from the standpoints of cost and dispersibility.

[0029] In the electronic component mounting substrate of the present invention, it is important that the content of inorganic particles contained in the insulating resin be 40 parts by weight or less, based on 100 parts by weight of the entire insulating resin. If the content of inorganic particles is greater than 40 parts by weight, increased stress occurs in the insulating resin when displacement occurs due to thermal shock, resulting in insufficient resistance to thermal shock. The content of inorganic particles is more preferably 30 parts by weight or less. On the other hand, while a lower content of inorganic particles improves thermal shock resistance, a content of 10 parts by weight or more is preferred from the perspective of improving heat resistance. The content of inorganic particles can be calculated by mechanically peeling the electronic components from the electronic component mounting substrate and measuring the ash content of the insulating resin remaining on the substrate using a thermogravimetric analyzer. Heat resistance can be evaluated by measuring the initial current value of the resulting electronic component mounting substrate, heating it at 230°C for 1 hour, and then measuring the current value again to determine the ratio to the initial current value.

[0030] The insulating resin fills the space below the electronic components except for the conductive composite material, and the area of the insulating resin is preferably 0.5 or less, more preferably 0.4 or less, relative to the area of the substrate. By setting the area of the insulating resin to 0.5 or less relative to the area of the substrate, warping due to a mismatch in the linear expansion coefficients of the substrate and the insulating resin when heat is generated during circuit operation is reduced, thereby improving thermal shock resistance. Here, the "area of insulating resin" refers to the total area of all insulating resin on the substrate. It may be connected to the insulating resin filled below other electronic components as shown in Figure 1, or it may be divided into any size.

[0031] The application of the electronic component mounting substrate of the present invention is not particularly limited, but it can be suitably used in displays which are large in area and require high reliability for a large number of elements.

[0032] <Method of manufacturing an electronic component mounting board> The method for manufacturing an electronic component mounting substrate of the present invention will be exemplified below, but the present invention is not limited to the examples described below.

[0033] The conductive composite material constituting the electronic component mounting board of the present invention can be formed, for example, by kneading raw materials and applying a paste onto the board, but is not particularly limited thereto.

[0034] The paste can be produced by mixing conductive particles into an organic material that is an appropriate mixture of a thermosetting resin, a curing agent, a curing catalyst, a photopolymerization initiator, a compound having an unsaturated double bond, a solvent, and an additive.

[0035] The content of the conductive particles in the paste is preferably 30 to 90% by weight. When the content of the conductive particles is 30% by weight or more, the probability of contact between the conductive particles during heat sintering is increased, thereby improving conductivity. The content of the conductive particles is more preferably 50% by weight or more. On the other hand, when the content of the conductive particles is 90% by weight or less, the light transmittance of the coating film in the exposure step is improved, thereby improving micro-processability.

[0036] The paste is preferably photosensitive, since this improves the positional and dimensional accuracy when it is molded into protruding electrodes suitable for flip-chip mounting. Examples of photosensitive components include a photopolymerization initiator, a compound having an unsaturated double bond, and a carboxyl group-containing resin having a photopolymerizable group.

[0037] Examples of the photopolymerization initiator include benzophenone derivatives, acetophenone derivatives, thioxanthone derivatives, benzyl derivatives, benzoin derivatives, oxime compounds, α-hydroxyketone compounds, α-aminoalkylphenone compounds, phosphine oxide compounds, anthrone compounds, and anthraquinone compounds.

[0038] The term "compound having an unsaturated double bond" refers to a monomer or oligomer having an unsaturated double bond. Examples of compounds having an unsaturated double bond include bifunctional monomers such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, glycerin dimethacrylate, tripropylene glycol diacrylate, ethoxylated (4) bisphenol A diacrylate, ethoxylated (10) bisphenol A diacrylate, and acrylic acid adducts of ethylene glycol diglycidyl ether; trifunctional monomers such as pentaerythritol triacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, trimethylolpropane ethoxy triacrylate, and glycerin propoxy triacrylate; and tetrafunctional monomers such as dipentaerythritol hexaacrylate, pentaerythritol tetraacrylate, pentaerythritol ethoxy tetraacrylate, and ditrimethylolpropane tetraacrylate. Two or more of these may be contained.

[0039] Examples of carboxyl group-containing resins having a photopolymerizable group include carboxyl group-containing acrylic copolymers, carboxylic acid-modified epoxy resins, carboxylic acid-modified phenolic resins, polyamic acids, carboxylic acid-modified siloxane polymers, etc. Two or more of these may be contained.

[0040] Furthermore, the paste is preferably thermosetting because it can be mounted in a softened state by thermocompression bonding and then cured to achieve high reliability. The thermosetting component is preferably an epoxy resin, which can enhance the adhesive strength between the conductive composite material and the electrodes to be connected, and preferably contains either a curing agent or a curing catalyst, or both. The adhesive strength between an electronic component and a conductive composite material can be evaluated, for example, by die shear strength. Here, "die shear strength" is an index representing the bonding strength when a horizontal force (shear force) is applied to an adhesive member adhered to a member to be joined. Die shear strength can be measured using a general die shear strength measuring device. Examples of devices for mixing the paste include dispersers and kneaders such as a three-roller mill, a ball mill, and a planetary ball mill.

[0041] One method for manufacturing an electronic component mounting substrate of the present invention includes the steps of forming a dry film of the paste on a substrate, exposing and developing the dry film to light to form a conductive composite material on electrodes of the substrate, forming an insulating resin on at least the electrodes, and heat-pressing an electronic component having an electrode onto the conductive composite material.

[0042] In the step of forming a dried film of the paste on a substrate, examples of the coating method include spin coating using a spinner, spray coating, roll coating, screen printing, and coating using a blade coater, die coater, calendar coater, meniscus coater, or bar coater.

[0043] The thickness of the dried paste film is preferably 1 to 5 μm. A dry film thickness of 1 μm or more can suppress variations in the resistance value of the conductive composite material and improve the bonding strength between the substrate and electronic components. On the other hand, a dry film thickness of 5 μm or less allows light to easily penetrate deep into the dry film during exposure, widening the development margin and preventing short circuits due to the spread of the conductive composite material during mounting. The dry film thickness is more preferably 2 to 5 μm. The thickness of the dried paste film can be measured using a stylus-type step profiler such as the "Surfcom (registered trademark)" 1400 (manufactured by Tokyo Seimitsu Co., Ltd.). More specifically, the film thickness at three random positions is measured using a stylus-type step profiler (measurement length: 1 mm, scanning speed: 0.3 mm / sec), and the average value is used as the film thickness.

[0044] Drying methods include, for example, heat drying using an oven, a hot plate, infrared rays, etc., vacuum drying, etc. The drying temperature is preferably 50 to 180° C., and the drying time is preferably 1 minute to several hours.

[0045] The dried film is then exposed and developed to form a conductive composite on the electrode on the substrate.

[0046] Examples of exposure methods include vacuum suction exposure, proxy exposure, projection exposure, and direct writing exposure, using a light source that emits i-line (wavelength 365 nm), h-line (wavelength 405 nm), or g-line (wavelength 436 nm), such as a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, or an LED.

[0047] Examples of the development method include a method in which a substrate having an exposed dry film of photosensitive conductive paste is left standing or rotated while a developer is sprayed onto the surface of the dry film, a method in which a substrate having an exposed dry film of photosensitive conductive paste is immersed in a developer, and a method in which ultrasonic waves are applied to a substrate having an exposed dry film of photosensitive conductive paste while immersing it in a developer.

[0048] The developer is preferably an alkaline aqueous solution, and after development, the film may be rinsed with a rinse solution, such as water or an aqueous solution of water to which an alcohol such as ethanol or isopropyl alcohol or an ester such as ethyl lactate or propylene glycol monomethyl ether acetate has been added.

[0049] Next, the insulating resin molded into a sheet is laminated onto the substrate. One method for molding the insulating resin is to apply a coating of the raw material dissolved in an organic solvent onto a release film and then dry it. A diaphragm laminator, roll laminator, etc. can be used to laminate the insulating resin.

[0050] Thereafter, an electronic component having electrodes is thermocompression bonded onto the conductive composite material.

[0051] In the step of thermocompression bonding an electronic component having an electrode onto a conductive composite material, the heating temperature is preferably 60°C or higher and 250°C or lower. By setting the heating temperature to 60°C or higher, the storage modulus of the conductive bumps decreases, improving the adhesion of the electronic component to the electrode. Furthermore, by setting the heating temperature to 250°C or lower, the thermal expansion and contraction of the substrate and electronic component can be reduced, thereby further improving the positional accuracy of mounting.

[0052] As a method of thermocompression bonding, a thermocompression bonding tool for a flip chip bonder or a vacuum diaphragm type laminator can be used. [Example]

[0053] EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0054] The materials used in the examples and comparative examples are as follows.

[0055] [Photosensitive component] (Synthesis Example) Carboxyl-containing acrylic copolymer (A) having unsaturated double bonds A reaction vessel under nitrogen was charged with 150 g of diethylene glycol monobutyl ether (DGME) and heated to 80°C using an oil bath. A mixture consisting of 20 g of ethyl acrylate (EA), 40 g of 2-ethylhexyl methacrylate (2-EHMA), 20 g of n-butyl acrylate (BA), 15 g of N-methylolacrylamide (MAA), 0.8 g of 2,2'-azobisisobutyronitrile, and 10 g of DGME was added dropwise over 1 hour. After the addition was complete, the mixture was heated at 80°C for an additional 6 hours to allow the polymerization reaction to proceed. The polymerization reaction was then terminated by the addition of 1 g of hydroquinone monomethyl ether. Subsequently, a mixture consisting of 5 g of glycidyl methacrylate (GMA), 1 g of triethylbenzylammonium chloride, and 10 g of DGME was added dropwise over 0.5 hours. After the dropwise addition was completed, the mixture was heated for an additional 2 hours to carry out the addition reaction. The resulting reaction solution was purified with methanol to remove unreacted impurities, and then vacuum dried for 24 hours to obtain a carboxyl-containing acrylic copolymer (A) having unsaturated double bonds with a copolymerization ratio (by mass): EA / 2-EHMA / BA / GMA / AA = 20 / 40 / 20 / 5 / 15.

[0056] [Photopolymerization initiator] "IRGACURE" OXE04 (manufactured by BASF Japan Ltd.) (hereinafter referred to as OXE04).

[0057] [Compounds with unsaturated double bonds] "Light Acrylate" BP-4EA (manufactured by Kyoeisha Chemical Co., Ltd.) (hereinafter referred to as BP-4EA).

[0058] [Conductive materials] Silver particles with a particle size (D50) of 0.3 μm Silver particles with a particle size (D50) of 0.5 μm Silver particles with a particle size (D50) of 1.0 μm -Silver particles with a particle size (D50) of 2.0 μm.

[0059] [Epoxy resin] "EPICLON" HP-7200L (manufactured by DIC Corporation) (hereinafter referred to as HP-7200L) "EPICLON" N-865 (manufactured by DIC Corporation) (hereinafter referred to as N-865) "jER" YL-980 (manufactured by Mitsubishi Chemical Corporation) (hereinafter referred to as YL-980).

[0060] [Novolac phenolic resin] MEH-7600-4H (manufactured by Meiwa Kasei Co., Ltd.) (hereinafter referred to as MEH-7600).

[0061] [Curing accelerator] "Curezol" C11Z-A (manufactured by Shikoku Kasei Co., Ltd.) (hereinafter referred to as C11Z-A) "Curesol" C11Z-CN (manufactured by Shikoku Chemicals Co., Ltd.) (hereinafter referred to as C11Z-CN).

[0062] [Insulating resin] XER-32C (manufactured by JSR Corporation).

[0063] [Inorganic particles] "Admanano" Y50-SP-AL1 (manufactured by Admatechs Co., Ltd.) (hereinafter referred to as Y50-SP-AL1).

[0064] <Preparation of insulating resin sheet> An insulating resin solution was prepared by dissolving 5 parts by weight of XER-32C, 15 parts by weight of N-865, 20 parts by weight of YL-980, and 2 parts by weight of C11Z-CN in PGMEA and mixing them. Y50SP-AL1 was then added to the solution so that the content of inorganic particles in the insulating resin was the value listed for each Example and Comparative Example in Table 1. Here, the "content of inorganic particles in the insulating resin" refers to the weight ratio of inorganic particles to 100 parts by weight of the insulating resin in the insulating resin of the electronic component mounting substrate obtained in each Example and Comparative Example. The insulating resin solution was applied to a release film PET25AL-5 (trade name, PET film, thickness 25 μm, manufactured by Lintec Corporation) using a comma coater to a film thickness of 5 μm after drying, and then dried at 100°C for 5 minutes to obtain an insulating resin sheet corresponding to each Example and Comparative Example in Table 1.

[0065] <Preparation of conductive composite paste> A conductive composite material paste was obtained by mixing 30 parts by weight of the acrylic copolymer (A), 20 parts by weight of BP-4EA, 3 parts by weight of OXE04, 15 parts by weight of HP-7200L, 5 parts by weight of MEH-7600, and 0.2 parts by weight of C11Z-A into a resin paste so that the content of the conductive material in the conductive composite material would be the value shown for each Example and Comparative Example in Table 1. Here, the "content of the conductive material in the conductive composite material" refers to the weight ratio of the conductive material when the weight of the conductive composite material obtained by drying the conductive composite material paste is taken as 100 parts by weight.

[0066] The evaluation methods in each example are as follows.

[0067] <Die shear strength> The conductive composite paste was applied to a glass substrate by screen printing, and the applied film was dried in a drying oven at 100 °C for 10 minutes to form a dry film on the glass substrate. Then, using an exposure device (PEM-6M; manufactured by Union Optical Co., Ltd.) equipped with an ultra-high pressure mercury lamp, the entire surface of the dried film on the MAM substrate was exposed to i-line light (wavelength 365 nm) at a dose of 2000 mJ / cm. 2 The exposure was carried out.

[0068] Next, a 0.525 mm thick silicon wafer cut into 2 mm squares was placed on the dried film and thermocompressed using a vacuum diaphragm laminator (MVLP500 / 600; manufactured by Meiki Shisakusho Co., Ltd.). The resulting sample was then heated in a drying oven at 140°C for 60 minutes to obtain a die shear strength measurement sample. The mounting conditions were a temperature of 100°C, a pressure of 0.5 MPa, and a pressure time of 30 seconds. The die shear strength was then measured using a die shear strength measurement device (Dage Series 4000; manufactured by Dage). Measurements were performed at 25°C and a shear rate of 200 μm / s. A die shear strength of 20 MPa or greater was rated as A, and a die shear strength of less than 20 MPa was rated as B. The die shear strengths obtained here are believed to be equivalent to those of the electronic component mounting substrates fabricated in the examples and comparative examples.

[0069] <Thermal shock resistance> The current value when 3.0 V was applied to an electronic component mounting board prepared by the method described in the following Examples and Comparative Examples was defined as the initial current value. After measuring the initial current value, the board was subjected to 300 cycles using a thermal shock tester, moving between chambers at -40°C and 85°C every 30 minutes, and the current value measured in the same manner was defined as the post-thermal cycle current value. At this time, a ratio of the post-thermal cycle current value to the initial current value was rated as A if it was 0.95 or more, B if it was less than 0.95 and 0.90 or more, C if it was less than 0.90 and 0.85 or more, and D if it was less than 0.85.

[0070] <Film thickness of conductive composite material> The electronic component mounting substrates obtained in the examples and comparative examples were cut along a plane passing through the center of the μLED chip, and the cross section was observed using an SEM to measure the thickness T of the conductive composite material between the electrode on the μLED chip and the electrode on the wiring substrate. E was measured.

[0071] <Insulating resin area ratio> The ratio of the area of the insulating resin to the area of the substrate was calculated. In Examples 10 and 11, the area of the insulating resin was calculated by dividing the area where the insulating resin sheet was laminated by the total area of the conductive composite material. The total area of the conductive composite material was calculated by multiplying the average area of 30 randomly selected conductive composite materials by the total number of conductive composite materials. In Examples and Comparative Examples other than those described above, the area of the insulating resin was calculated by multiplying the average area of the insulating resin below 30 randomly selected μLED chips by the total number of μLED chips.

[0072] <Electrode area ratio of electronic components> The ratio of the total area of the electrodes formed on the μLED chip to the total area of the electrode-bearing surface of the μLED chip was calculated by SEM measurement. The area of the μLED chip and its electrodes was calculated using the average value measured on 30 randomly selected μLED chips.

[0073] <Heat resistance> The current value when 3.0 V was applied to an electronic component mounting substrate produced by the method described in the following Examples and Comparative Examples was defined as the initial current value. The sample was heated at 230°C for 1 hour and then the current value was measured in the same manner as above. A ratio of the current value after heating to the initial current value of 0.9 or more was rated as A, and a ratio of less than 0.90 was rated as B.

[0074] Example 1 An insulating resin sheet was prepared by the method shown in <Preparation of insulating resin sheet>, and a conductive composite material paste was prepared by the method shown in Method for preparing conductive composite material paste. Using a 0.73 mm thick wiring board having wiring in which 0.05 μm of chromium and 0.2 μm of gold were laminated in this order on a glass substrate by sputtering, the conductive composite material paste was dried to form a dry film on the surface of the wiring board in the same manner as described in Method for measuring die shear strength.

[0075] Thereafter, an exposure device (PEM-6M; manufactured by Union Optical Co., Ltd.) having an ultra-high pressure mercury lamp was used to expose the entire surface of the dried film on the wiring substrate to i-line light (wavelength 365 nm) at a dose of 2000 mJ / cm. 2After exposure, the film was shower-developed for 50 seconds using a 0.1% by weight Na2CO3 aqueous solution and rinsed with ultrapure water to form a 20μm square conductive bump array made of conductive composite material at the positions corresponding to the μLED electrodes that would be mounted on the wiring board later. The conductive bump array consisted of pairs corresponding to the μLED anode / cathode electrodes, and was a 120μm pitch pattern of 125 rows x 60 columns.

[0076] Next, the insulating resin sheet was laminated at 80°C and 0.6 MPa on the surface of the wiring board with the conductive bump array using a vacuum diaphragm laminator (MVLP500 / 600; manufactured by Meiki Shisakusho Co., Ltd.) to form an insulating resin. A μLED chip (short side 30 μm, long side 60 μm, electrode spacing 18 μm) was then mounted on the conductive bumps laminated with the insulating resin using a flip-chip bonder (manufactured by Toray Engineering Co., Ltd., FC-3000WS) under the following conditions: stage temperature 40°C, head temperature 150°C, load 24 N, 10 seconds of pressure, followed by 20 seconds of cooling until the head temperature reached 40°C, and then the load was released. The insulating resin outside the μLED chip was then removed using plasma treatment.

[0077] The substrate was then cured for 60 minutes in a drying oven at 140°C to obtain a substrate mounted with electronic components. The obtained substrate was evaluated as described above. The results are shown in Tables 1 and 2.

[0078] (Examples 2 to 9 and Comparative Examples 1 to 6) An electronic component mounting board was produced in the same manner as in Example 1, except that the conductive composite material and insulating resin were changed as shown in Tables 1 and 2.

[0079] Example 10 An electronic component mounting substrate was produced in the same manner as in Example 1, except that the area ratio of the insulating resin was set to 0.67 by not performing plasma treatment after mounting the μLED chip.

[0080] Example 11 An electronic component mounting substrate was produced in the same manner as in Example 1, except that the electrode area ratio of the electronic component was set to 0.25 by setting the inter-electrode distance of the μLED chip to 45 μm.

[0081] [Table 1]

[0082] [Table 2]

[0083] In Examples 1 to 11, the value was 3.0 <T E / R M <20.0, and the content of inorganic particles contained in the insulating resin was 40 parts by weight or less when the insulating resin was taken as 100 parts by weight, so that the insulating resin exhibited high thermal shock resistance. On the other hand, in Comparative Examples 1 and 2, the content of inorganic particles in the insulating resin was 50 parts by weight, and the thermal shock resistance was low. In Comparative Examples 3 to 5, all of T E / R M In Comparative Example 6, T E / R M These exceeded 20.0, and had poor thermal shock resistance. [Explanation of symbols]

[0084] 1: Circuit board 2: Electronic components 3: Conductive composite material 4: Insulating resin 5b: Electrodes on electronic components 5a: Electrodes on the substrate 6: Conductive particles in ACF 7: Short circuit between adjacent electrodes 8: Electronic component mounting board

Claims

1. The substrate has electronic components thereon, a conductive composite material containing a resin and a conductive material is disposed between the electrode of the substrate and the electrode of the electronic component; an electronic component mounting substrate having an insulating resin in a portion between the electronic component and the substrate that does not have the conductive composite material, The thickness (μm) of the conductive composite material is T Ｅ , the average diameter (μm) of the conductive material is R Ｍ When this is the case, 3.0<T Ｅ / R Ｍ <20.0, The electronic component mounting substrate has an insulating resin containing inorganic particles in an amount of 40 parts by weight or less, based on 100 parts by weight of the insulating resin.

2. 2. The electronic component mounting board according to claim 1, wherein the ratio of the area occupied by the electrodes of the electronic component to the total area of the surface having the electrodes of the electronic component is 0.3 to 0.

9.

3. 3. The electronic component mounting board according to claim 1, wherein the area of the insulating resin is 0.5 or less relative to the area of the board.

4. 4. The electronic component mounting board according to claim 1, wherein the electronic component is an optical element.

5. The electronic component mounting board according to claim 4 , wherein the optical element is a μLED.

6. A display comprising the electronic component mounting substrate according to any one of claims 1 to 5.

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