Method for manufacturing structure with bumps, and substrate having bump pattern

Abstract

A method for manufacturing a structure with bumps, according to the present invention, comprises: a step (bump formation step) for forming, on a demolding layer of a transfer substrate having the demolding layer, bumps containing an organic component and conductive particles; and a step (bump transfer step) for transferring the bumps to a substrate provided with an electrode or to an electrode part of an electronic component by irradiating a laser from the reverse-surface side of the demolding layer of the transfer substrate. A substrate according to the present invention includes a bump pattern that is positioned on a demolding layer of a transfer substrate having the demolding layer and contains an organic component and conductive particles. Provided are: a method for manufacturing a structure with bumps in which bumps can be formed that have high connection reliability and excellent transfer properties even when the laser irradiation intensity is low; and a substrate having a bump pattern that is suitably for use in said method for manufacturing.

Description

Method for manufacturing structure with bumps and substrate having bump pattern

[0001] The present invention relates to a method for manufacturing a structure with bumps and a substrate having a bump pattern.

[0002] In recent years, electronic components have become increasingly miniaturized, and there has been active development of technology for manufacturing displays by arranging micro-sized LEDs. One technique being considered for mounting LEDs on TFT substrates is to form a bonding material called a "bump" on the electrodes to bond the LED electrodes to the electrodes of the TFT substrate.

[0003] As a method for manufacturing a substrate with a conductive pattern that is suitable for use as a mounting substrate for micro-LEDs, for example, a method for manufacturing a substrate with a conductive pattern has been proposed, which includes a step of forming a pattern of a composition having an organic component and conductive particles on a transfer substrate, and a step of irradiating the back side of the transfer substrate with a laser to transfer the pattern to a transfer substrate (see, for example, Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2022-55760

[0005] The manufacturing method described in Patent Document 1 allows for the formation of highly conductive conductive patterns with high positional accuracy. However, the inventors' studies have revealed that when micro-LEDs are transferred using laser irradiation, microcracks are likely to occur inside the bumps due to the impact during transfer. In particular, when the electronic component is mounted and exposed to an environment with repeated temperature changes, the microcracks can cause peeling, increasing contact resistance and other issues with connection reliability. While reducing the laser irradiation intensity is effective in mitigating the impact during transfer, the method described in Patent Document 1 made transfer difficult when the laser irradiation intensity was low.

[0006] Therefore, an object of the present invention is to provide a method for manufacturing a structure with bumps that has excellent transferability and is capable of forming bumps with high connection reliability even when the laser irradiation intensity is low, and a substrate having a bump pattern that is preferably used in the manufacturing method.

[0007] The present invention is a method for manufacturing a bumped structure, comprising: a step of forming bumps containing an organic component and conductive particles on a release layer of a transfer substrate having a release layer (bump formation step); and a step of irradiating a laser from the side opposite the release layer of the transfer substrate to transfer the bumps to an electrode-equipped substrate or an electrode portion of an electronic component (bump transfer step).

[0008] The present invention also provides a transfer substrate having a release layer, the transfer substrate having a bump pattern containing an organic component and conductive particles on the release layer.

[0009] According to the present invention, even when the laser irradiation intensity is low, a bumped structure having bumps with excellent transferability and high connection reliability can be obtained.

[0010] It is a schematic diagram showing an example of a method for manufacturing a bumped structure of the present invention. It is a schematic diagram showing an application example of the method for manufacturing a bumped structure of the present invention. It is a cross-sectional schematic diagram of a printed wiring board with bumps obtained in an example. It is a cross-sectional schematic diagram of a sample for evaluating conductivity used in an example.

[0011] The bumped structure of the present invention has bumps containing an organic component and conductive particles on an electrode-attached substrate or an electrode portion of an electronic component. As described above, the bumps serve to bond electrodes together. The bumped structure can be suitably used as a mounting substrate for electronic components such as micro LEDs.

[0012] A first aspect of the present invention, a method for manufacturing a bumped structure, includes a step of forming bumps containing an organic component and conductive particles on a release layer of a transfer substrate having a release layer (bump formation step), and a step of irradiating a laser from the side opposite the release layer of the transfer substrate to transfer the bumps to an electrode-equipped substrate or an electrode portion of an electronic component (bump transfer step). For convenience, the bumps formed on the release layer of the transfer substrate (bumps before transfer) are sometimes referred to as a bump pattern. By including an organic component and conductive particles in the bumps, impacts during the bump transfer step can be alleviated and connection reliability can be improved. Furthermore, since the transfer substrate has a release layer, transferability is excellent even when the laser irradiation intensity is low. As a result, according to the present invention, impacts during the bump transfer step can be alleviated and connection reliability can be improved.

[0013] FIG. 1 shows a schematic diagram of an example of a method for manufacturing a bumped structure of the present invention. (a) shows a bump formation step in which bumps 1 are formed on a release layer 5 on a glass substrate 2. (b) shows a bump transfer step in which a laser 3 is irradiated from the side of the glass substrate 2 opposite the release layer 5. The bumps 1, which have been peeled off from the release layer 5 by irradiation with the laser 3, are transferred to electrode portions of a transfer-receiving substrate 4. Here, the electrode portions refer to exposed connection portions of an electrode-equipped substrate or electronic component that transmit electrical signals to the substrate wiring or electronic component. For example, if bumps are formed directly on the substrate wiring, the substrate wiring is the electrode portion.

[0014] The substrate having a bump pattern according to the second aspect of the present invention has a bump pattern containing an organic component and conductive particles on the release layer of a transfer substrate having a release layer. Such a substrate can be suitably used in a method for manufacturing a structure with bumps. Specifically, a structure with bumps can be manufactured by subjecting the substrate having the bump pattern of the present invention to the bump transfer step according to the first aspect of the present invention.

[0015] Each step of the method for manufacturing a structure with bumps according to the present invention will be described below.

[0016] <Bump Forming Step> Bumps (bump pattern) containing an organic component and conductive particles are formed on the release layer of the transfer substrate having the release layer.

[0017] The transfer substrate may be any substrate that is translucent to the wavelength of the laser described below. Examples include glass substrates, quartz substrates, sapphire substrates, etc. Among these, glass substrates are preferred because they are readily available.

[0018] Examples of methods for forming a release layer on a transfer substrate include a method of applying a release agent solution obtained by diluting a release agent with a solvent onto the transfer substrate and then removing the solvent. Examples of application methods include a coating method using a die coater and a spin coating method. Examples of solvent removal methods include heat drying.

[0019] Examples of the release agent for forming the release layer include aminoalkyd-based release agents, long-chain alkyl-based release agents, silicone-based release agents, and fluorine-based release agents. Two or more of these may be used. More specifically, aminoalkyd-based release agents such as "Tesfine (registered trademark)" 303, "Tesfine (registered trademark)" 305, and "Tesfine (registered trademark)" 314 manufactured by Showa Denko Materials Co., Ltd., silicone-based release agents such as "Tesfine (registered trademark)" 319 and TA31-209E manufactured by Showa Denko Materials Co., Ltd., and KS-702 and KS-707 manufactured by Shin-Etsu Chemical Co., Ltd., and F-6711-AL, F-6758-AL, and F-6 manufactured by AGC Seimi Chemical Co., Ltd. Examples of suitable release agents include fluorine-based release agents such as 441L-AL, EF-6521-AL, F-6811-AL, SFE-DP02H, SFE-B002H, SFE-X008, KTS-3000H, SNF-AF180E, SR-4000A, SW-930, and SWK-601, and long-chain alkyl release agents such as "Peeloil (registered trademark)" 1010, "Peeloil (registered trademark)" 1050, and "Peeloil (registered trademark)" 1070 manufactured by Lion Specialty Chemicals Co., Ltd. Among these, aminoalkyd-based release agents and fluorine-based release agents are preferred because they are less likely to adversely affect connection reliability after mounting, even if release agent transfer occurs during the bump transfer process, and because the peel force and contact angle, which will be described later, can be easily adjusted to fall within the preferred numerical ranges, which will be described later. The thickness of the release layer is preferably 50 nm or more from the viewpoint of suppressing the occurrence of pinholes, while the thickness of the release layer is preferably 1,000 nm or less from the viewpoint of suppressing the transfer of the release agent during the bump transfer step.

[0020] The peel strength of a transfer substrate having a release layer at 25°C is preferably 100 mN / 50 mm or more from the viewpoint of maintaining adequate adhesion between the bump and the release layer and increasing the process margin in the bump transfer process. On the other hand, the peel strength of a transfer substrate having a release layer at 25°C is preferably 5,000 mN / 50 mm or less from the viewpoint of increasing positional accuracy in the transfer process. Here, the peel strength of a transfer substrate in the present invention refers to the peel strength measured when an acrylic adhesive tape "31B" manufactured by Nitto Denko Corporation is applied to the release layer-formed surface of the transfer substrate using a 2 kg roller, allowed to stand for 30 minutes, and then the acrylic adhesive tape is peeled off under the following conditions: a temperature of 25°C, a peel angle of 180°, and a peel speed of 0.3 m / min. A means for adjusting the peel strength within the above range can be, for example, by selecting one of the preferred release agents exemplified above.

[0021] The water contact angle of the release layer at 25°C is preferably 80° or more, more preferably 90° or more, from the viewpoint of increasing the process margin in the bump transfer step. On the other hand, the water contact angle of the release layer at 25°C is preferably 140° or less, more preferably 110° or less, from the viewpoint of suppressing cissing and pinholes in the bump formation step and increasing the process margin in the bump transfer step. The water contact angle of the release layer can be measured in accordance with JIS R3257 (1999) using a commercially available contact angle measuring device such as "CA-Z" manufactured by Kyowa Interface Science Co., Ltd.

[0022] Examples of methods for forming a bump pattern on a release layer include pattern printing, inkjet coating, laser etching, and photolithography. The pattern printing method involves printing an organic component and conductive particles in a pattern on the release layer using screen printing, gravure printing, or the like. The laser etching method involves printing a rough pattern of the organic component and conductive particles and then removing unnecessary portions using laser etching. The photolithography method involves using a photosensitive composition as a composition containing the organic component and conductive particles, and forming a bump pattern through a process of exposing the photosensitive composition (exposure process) and a process of developing the photosensitive composition (development process). Among these, photolithography is preferred because it allows for fine patterning and improves positional accuracy in the bump transfer process.

[0023] As a light source in the exposure step, a mercury lamp or an LED emitting i-line (365 nm) or h-line (405 nm) is preferably used.

[0024] Examples of the developer used in the development step include alkaline developers such as 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, and hexamethylenediamine.

[0025] The shape of the bump pattern is not particularly limited, but examples of the shape include a rectangular, circular, elliptical, triangular, polygonal, and combinations of these in plan view.

[0026] The thickness of the bump pattern in the bump formation step is preferably 1 μm or more from the viewpoint of further suppressing the occurrence of microcracks in the bump transfer step and further improving connection reliability, while the thickness of the bump pattern is preferably 5 μm or less from the viewpoints of suppressing the spread of the bumps when an electronic component is mounted, suppressing short circuits with surrounding electrodes, and improving positional accuracy in the bump transfer step.

[0027] Here, the thickness of the bump pattern in the bump formation process refers to the average value of the heights of 10 randomly selected bumps, calculated assuming the pattern shape is rectangular. More specifically, for 10 bump patterns randomly selected from the bump patterns formed in the bump formation process, a laser microscope VK-X250 manufactured by Keyence Corporation is used to scan the surface at a magnification of 500 to 1,000 times, and the surface shape is measured. Using the analysis mode attached to the device, the heights of the bump patterns are calculated assuming the pattern shape is rectangular, and the thickness of the bump pattern can be measured by calculating the average value.

[0028] The aspect ratio of the bump pattern in the bump formation step is preferably 0.1 or more from the viewpoint of further suppressing the occurrence of microcracks in the bump transfer step and further improving connection reliability, while the aspect ratio of the bump pattern is preferably 0.4 or less from the viewpoint of further improving directionality and positional accuracy in the bump transfer step.

[0029] Here, the aspect ratio of the bump pattern in the bump formation process refers to the average value of the value obtained by dividing the bump pattern thickness by the bump pattern diameter for 10 randomly selected bump patterns. If the bump is cylindrical, the diameter is taken as the bump pattern diameter, and if the bump is not cylindrical, the diameter when converted into a cylinder with the same contact area is taken as the bump pattern diameter.

[0030] In order to improve positional accuracy, the contact area between the bump pattern and the release layer in the bump formation process is set to 25 μm per bump pattern. ２On the other hand, the contact area between the bump pattern and the release layer is preferably 500 μm or more from the viewpoint of uniformly generating ablation at the contact interface during laser irradiation and improving positional accuracy. ２ The following is preferred. Here, the contact area between the bump and the release layer in the bump formation process refers to the average value of the contact area between 10 randomly selected bump patterns and the release layer. More specifically, the bump pattern is observed using an optical microscope at a magnification of 500 to 1,000 times, and the image obtained is binarized using image analysis and measurement software based on the brightness of the measurement image. The dark areas in the binarized image are considered to be the contact areas between the transfer substrate and the bump pattern, and the area of ​​the dark areas is calculated. The contact areas with the release layer for 10 randomly selected bump patterns are calculated, and the average value is taken as the contact area between the bump pattern and the release layer. Note that the contact area between the bump pattern and the release layer can be adjusted to a desired range by adjusting the dimensions of the mask, for example, when forming the bump pattern by photolithography.

[0031] The optical density (hereinafter referred to as "OD value") of the bump pattern in the bump formation process is preferably 0.5 or more, more preferably 1 or more, in the visible light range of wavelengths from 380 to 700 nm, from the viewpoint of limiting the laser light that reaches the bump pattern to the vicinity of the release layer, improving positional accuracy in the bump transfer process, and widening the process margin. On the other hand, the OD value of the bump pattern is preferably 3 or less from the viewpoint of connection reliability. Here, the OD value of the bump pattern in the present invention refers to the average value of the OD values ​​of five randomly selected bump patterns. More specifically, the OD value can be determined by measuring the transmitted light intensity at a wavelength of 532 nm using a microspectrometer for five bump patterns randomly selected from the transfer substrate, determining the OD value of each using the following relational expression (1), and calculating the average. OD value = log10(I ０ / I) (1) where I ０ denotes the incident light intensity, and I denotes the transmitted light intensity.

[0032] The bumps contain an organic component and conductive particles. When the bump pattern is formed by the photolithography method having the above-mentioned exposure step and development step, the organic component preferably contains a photosensitive organic component. Examples of the photosensitive organic component include a resin or monomer having a photoreactive group, and a photopolymerization initiator.

[0033] Examples of the organic component include acrylic copolymers, phenol novolac resins, cresol novolac resins, epoxy resins, urethane resins, polyimide resins, polyamic acids, polyamide resins, siloxane resins, etc. Among these, when used in a photosensitive composition, acrylic copolymers are preferred from the viewpoint of photosensitivity.

[0034] When the alkaline developer described above is used in the development process, examples of the organic component include a combination of a carboxyl group-containing acrylic copolymer, a compound having a photoreactive group, and a photopolymerization initiator; a combination of a phenol novolac resin or cresol novolac resin and a photoacid generator; a combination of a polyamic acid and a photoacid generator; and a combination of a polyimide resin, a compound having a photoreactive group, and a photopolymerization initiator. Among these, a combination of a carboxyl group-containing acrylic copolymer, a compound having a photoreactive group, and a photopolymerization initiator is preferred, as it facilitates the formation of bumps with high mountability and a low glass transition temperature. In such combinations, it is more preferred that the carboxyl group-containing acrylic copolymer contains a photoreactive group, which provides excellent photosensitivity and increases the crosslink density of exposed areas, thereby enhancing bump strength, further suppressing the occurrence of microcracks during the bump transfer process, and further improving connection reliability. Furthermore, it is preferable to further contain a thermosetting epoxy compound, which can enhance adhesion between electrodes and further improve connection reliability.

[0035] The carboxyl group-containing acrylic resin is produced by copolymerizing an acrylic monomer, which is a compound having a photoreactive group, with an unsaturated acid. Examples of the acrylic monomer include methyl acrylate, ethyl acrylate (hereinafter sometimes referred to as "EA"), 2-ethylhexyl acrylate, n-butyl acrylate (hereinafter sometimes referred to as "BA"), isobutyl acrylate, isopropane acrylate, glycidyl acrylate, butoxytriethylene glycol acrylate, dicyclopentanyl acrylate, dicyclopentenyl acrylate, 2-hydroxyethyl acrylate, isobornyl acrylate, 2-hydroxypropyl acrylate, isodexyl acrylate, and isooctyl acrylate. Examples of suitable unsaturated acids include methyl acrylate, ...

[0036] The content of the carboxyl group-containing acrylic resin in the organic component is preferably 20 to 70 wt % of the solid content. Here, the solid content refers to the components in the organic component other than the solvent. When the content of the carboxyl group-containing acrylic resin in the solid content of the organic component is 20 to 70 wt %, the solubility in the developer can be maintained at an appropriate level, making it possible to process fine patterns.

[0037] The compound having a photoreactive group is preferably an acrylic monomer, such as the acrylic monomers exemplified as raw materials for the carboxyl group-containing acrylic resin described above. The content of the compound having a photoreactive group in the organic component is preferably 5 to 30 wt% of the solid content. When the content of the compound having a photoreactive group is 5 wt% or more, the hardening density of the exposed area increases, thereby increasing the residual film rate after development and enabling fine patterning. On the other hand, when the content of the compound having a photoreactive group is 30 wt% or less, the formed bump pattern does not become too hard, improving adhesion to electronic components and increasing connection reliability.

[0038] Examples of the photopolymerization initiator include benzophenone derivatives, acetophenone derivatives, thioxanthone derivatives, benzil derivatives, benzoin derivatives, oxime compounds, α-hydroxyketone compounds, α-aminoalkylphenone compounds, phosphine oxide compounds, anthrone compounds, anthraquinone compounds, etc. Among these, oxime compounds having high photosensitivity are preferred. Examples of oxime compounds include 1,2-octanedione-1-[4-(phenylthio)-2-(O-benzoyloxime)], ethanone-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime), 1-phenyl-1,2-butanedione-2-(O-methoxycarbonyl)oxime, 1-phenyl-propanedione-2-(O-ethoxycarbonyl)oxime, 1-phenyl-propanedione-2-(O-benzoyl)oxime, 1,3-diphenyl-propanetrione-2-(O-ethoxycarbonyl)oxime, and 1-phenyl-3-ethoxy-propanetrione-2-(O-benzoyl)oxime. Two or more of these may be contained.

[0039] The content of the photopolymerization initiator in the organic component is preferably 1 to 10 wt % of the solid content. When the content of the photopolymerization initiator is 1 wt % or more, the hardening density of the exposed area increases, thereby increasing the residual film rate after development and enabling fine patterning. On the other hand, when the content of the photopolymerization initiator is 10 wt % or less, side edges due to excessive light absorption by the photopolymerization initiator at the top of the coated and dried film during exposure are suppressed, thereby further improving fine processability and transfer position accuracy of laser transfer.

[0040] Examples of epoxy compounds include glycidyl ethers, glycidyl amines, and epoxy resins. More specifically, examples of glycidyl ethers include methyl glycidyl ether, ethyl glycidyl ether, butyl glycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, bisphenol A diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, bisphenol fluorene diglycidyl ether, biphenol diglycidyl ether, tetramethylbiphenol glycidyl ether, trimethylolpropane triglycidyl ether, and 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate. Examples of glycidyl amines include tert-butylglycidylamine. Examples of epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, biphenyl type epoxy resins, novolac type epoxy resins, hydrogenated bisphenol A type epoxy resins, etc. Two or more of these may be used.

[0041] The content of the epoxy compound in the organic component is preferably 5 to 50 wt % of the solid content. If the content of the epoxy compound is 5 wt % or more, the adhesion between the substrate and the electronic component is improved, and the connection reliability is increased. On the other hand, if the content of the epoxy compound is 50% or less, the photocuring reaction during exposure proceeds smoothly, and the crosslinking density is increased, making it possible to form fine patterns.

[0042] In the present invention, by including conductive particles in the bumps, the conductive particles form three-dimensional conductive paths with each other after mounting, thereby achieving high conductivity. Examples of conductive particles include particles containing metals such as silver, gold, copper, platinum, lead, tin, nickel, aluminum, tungsten, molybdenum, chromium, titanium, and indium, or alloys thereof, ITO, tin oxide, antimony-doped tin oxide, and carbon black. Examples also include insulating particles such as resins and inorganic oxides, or conductive particles with a coating layer of the aforementioned metal or carbon on their surfaces. Two or more of these may be included. Among these, carbon black or metal particles with a carbon coating layer are preferred because they have an absorption range at the laser wavelength, efficiently convert energy during laser irradiation into heat, easily decompose the organic components of the bumps at the interface with the release layer, and have excellent laser transferability. Furthermore, carbon black is preferred because it can achieve stable electrical connection with molybdenum and ITO, which are considered difficult to electrically connect to.

[0043] The aspect ratio of the conductive particles is preferably 1.0 or more from the viewpoint of increasing the probability of contact between the conductive particles. On the other hand, the aspect ratio of the conductive particles is preferably 3.0 or less, more preferably 2.0 or less, from the viewpoint of suppressing the shielding of the exposure light in the exposure step and widening the development margin in the development step. Here, the aspect ratio of the conductive particles is the value obtained by dividing the major axis length by the minor axis length of the conductive particles. Using a scanning electron microscope (SEM) or a transmission electron microscope (TEM), the conductive particles are observed at a magnification of 15,000 times, and the major axis length and minor axis length of each of 100 randomly selected primary particles of the conductive particles are measured, and the number average of the aspect ratios calculated from both is defined as the aspect ratio of the conductive particles.

[0044] The particle diameter of the conductive particles is preferably 0.03 μm or more from the viewpoint of dispersibility in the photosensitive composition. On the other hand, the particle diameter of the conductive particles is preferably 1.0 μm or less, more preferably 0.2 μm or less, from the viewpoint of further improving the surface smoothness, pattern accuracy, and dimensional accuracy of the bumps, as well as the positional accuracy in the bump transfer process. Here, the particle diameter of the conductive particles can be determined by dynamic light scattering. Specifically, the particle diameter can be determined by irradiating a dispersion liquid having a conductive particle concentration of 5 to 30% by volume with light having a wavelength of 780 nm using a semiconductor laser, measuring the scattered light, and then performing frequency analysis using the FFT-heterodyne method.

[0045] The content of the conductive particles in the bump is preferably 10% by volume or more, and more preferably 15% by volume or more, from the viewpoint of improving conductivity, whereas the content of the conductive particles is preferably 40% by volume or less, and more preferably 30% by volume or less, from the viewpoints of improving positional accuracy in the bump transfer step by containing an appropriate amount of organic components, further mitigating impact in the bump transfer step and further improving connection reliability, and improving the bonding strength between the electronic component and the bumped structure.

[0046] Here, the content of conductive particles in the bumps can be measured as follows. A bump on a transfer substrate is scraped off to prepare a measurement sample. The measurement sample is held in the atmosphere at 600°C for 1 hour using a thermogravimetric analyzer to remove organic components, and the weight ratio of the remaining portion of the measurement sample (thermogravimetric analysis residue ratio) and the weight ratio of the removed portion of the measurement sample (thermogravimetric analysis reduction ratio) are determined. Using the thermogravimetric analysis residue ratio as the weight fraction of conductive particles and the thermogravimetric analysis reduction ratio as the weight fraction of organic components, the content (volume %) of conductive particles in the bumps can be calculated using the following formula [1]. Here, the density of the organic components is 1.1 g / cm ３ However, if the raw material composition ratio of the organic component and the conductive particles in the bump is known, the content (volume %) of the conductive particles in the bump can be calculated from that composition ratio.

[0047]

[0048] The bumps and the photosensitive composition used to form the bumps may contain additives such as plasticizers, leveling agents, surfactants, silane coupling agents, antifoaming agents, and pigments, to the extent that the desired properties are not impaired.

[0049] The explanations regarding the transfer substrate, release layer, and bump pattern in this step also apply to the transfer substrate, release layer, and bump pattern of the substrate having a bump pattern according to the second embodiment of the present invention. This step also corresponds to the method for manufacturing a substrate having a bump pattern according to the second embodiment of the present invention.

[0050] <Bump Transfer Step> Next, a laser is applied from the side opposite the release layer of the transfer substrate to transfer the bumps to the electrode-equipped substrate or the electrode portions of the electronic component. In this step, the organic components and conductive particles contained in the bumps are heated by the laser light that has passed through the transfer substrate, decomposing the organic components of the bumps at the interface with the release layer of the transfer substrate, and the bumps are transferred from the release layer to the electrode-equipped substrate or the electrode portions of the electronic component.

[0051] In the present invention, by having a release layer, the transferability is excellent even when the laser irradiation intensity is low, so that the decomposition of organic matter due to laser irradiation and the impact of the bump can be suppressed, and a bump with high connection reliability can be formed.

[0052] The laser to be irradiated may be any laser capable of decomposing organic components at the interface of the transfer substrate by heat generated by irradiation, and examples thereof include lasers with a wavelength range of 257 to 1900 nm. Among these, solid-state lasers with wavelengths of 355 nm or 532 nm are preferred from the viewpoint of transferability. The laser output is preferably 200 to 600 mJ. If the laser output is 200 mJ or more, the effect of variations in adhesion between the bump and the release layer is reduced, and positional accuracy in the transfer process can be improved. On the other hand, if the laser output is 600 mJ or less, impacts in the bump transfer process can be further mitigated, and connection reliability can be further improved. The laser output is more preferably 500 mJ or less.

[0053] The contact area between the bump and the electrode-attached substrate or electronic component to which the bump is to be transferred is set to an average of 20 μm per bump in order to further increase the positional accuracy in the bump transfer process. ２ On the other hand, the contact area is preferably 500 μm or more from the viewpoint of suppressing uneven temperature of the bumps due to laser irradiation and improving positional accuracy. ２ The following is preferred. Here, the contact area between the bump and the electrode-equipped substrate or electronic component in the present invention refers to the average value for 10 randomly selected bumps. An optical microscope is used to observe and photograph the electrode-equipped substrate or electronic component including the bumps at a magnification of 500 to 1,000 times, and the resulting image is binarized using image analysis and measurement software based on the brightness of the measurement image. Dark areas in the binarized image are considered to correspond to the contact areas between the electrode-equipped substrate or electronic component and the bumps, and the area of ​​the dark areas is calculated. The contact areas are calculated for 10 randomly selected bumps, and the average value is used as the contact area between the electrode-equipped substrate or electronic component and the bumps. For example, when forming bumps by photolithography, the contact area can be adjusted to a desired range by adjusting the dimensions of the mask.

[0054] The electrode-equipped substrate to which the bumps are transferred is preferably a TFT substrate having electrodes made of a material selected from molybdenum, titanium, and ITO, a printed wiring board having copper electrodes, etc. The electronic component to which the bumps are transferred is preferably an LED chip having gold electrodes, etc.

[0055] The electrodes that come into contact with the transferred bumps preferably contain a material selected from molybdenum, titanium, and ITO, because they are less susceptible to ion migration and the generation of intermetallic compounds. Electrodes containing these materials have high connection reliability with carbon black, and are therefore preferably used when carbon black is used as the conductive particles contained in the bumps.

[0056] According to the method for manufacturing a bumped structure of the present invention, bumps can be formed only in a specific narrow region on a substrate. As an example of forming bumps only in a specific narrow region on a substrate, FIG. 2 shows a schematic diagram of an application example of the method for manufacturing a bumped structure of the present invention. As shown in FIG. 2(a), after mounting a large number of electronic components 14 on a transfer substrate 13, which is an electrode-bearing substrate, by bonding bumps 10 to electrodes 15 of the electronic components, it may be found that a specific electronic component 14' is defective. In such cases, a repair process is performed in which the defective electronic component 14' is removed and a new electronic component is mounted in its place.

[0057] At this time, new bumps must be formed on the substrate in order to mount new electronic components. In this case, as shown in Figure 2(a), electronic components 14 other than the removed defective electronic component 14 are present on the substrate. Therefore, the area available for forming bumps is narrow and the unevenness on the transfer substrate 13 is large, making it difficult to form bumps by photolithography using a photosensitive composition.

[0058] On the other hand, according to the present invention, as shown in Fig. 2(b), by using a transfer substrate 11 having a release layer 5 on which bumps 10 are formed, and irradiating it with laser 12, bumps can be formed only in the missing portions of electronic components 14' as shown in Fig. 2(c). In other words, bumps can be formed on a transfer substrate 13 on which electronic components 14 are mounted, without being affected by the unevenness caused by the electronic components 14.

[0059] The method for manufacturing a structure with bumps and the substrate having a bump pattern of the present invention can be suitably used, for example, when manufacturing a substrate for mounting an LED. The substrate having a bump pattern of the present invention can be suitably used for the above-mentioned repair application.

[0060] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0061] The evaluation methods in each example are as follows.

[0062] <Contact Area Between Bump and Release Layer in Bump Formation Process> In each example and comparative example, bumps were formed on the release layer of the transfer substrate, and then 10 randomly selected bumps were photographed at a magnification of 500 to 1,000 times using a microscope VHX-5500 manufactured by Keyence Corporation. The images were then binarized using the image analysis mode based on the brightness of the measurement image. The dark areas in the binarized images were considered to correspond to the contact areas between each bump and the release layer, and the areas of the dark areas were calculated. The contact area between each bump and the release layer was determined by calculating the average area of ​​the dark areas for the 10 bumps.

[0063] <Peel Force of Transfer Substrate Having Release Layer> An acrylic adhesive tape "31B" manufactured by Nitto Denko Corporation was attached to the release layer of the transfer substrate prepared in each of the Examples and Comparative Examples using a 2 kg roller, and after leaving it to stand for 30 minutes, the adhesive tape was peeled off under the conditions of a temperature of 25°C, a peel angle of 180°, and a peel speed of 0.3 m / min, and the peel force was measured.

[0064] <Water Contact Angle of Release Layer> The water contact angle of the release layer of the transfer substrate prepared in each example and comparative example was measured at 25°C using a contact angle measuring device "CA-Z" manufactured by Kyowa Interface Science Co., Ltd. in accordance with JIS R3257 (1999).

[0065] <OD Value of Bumps in Bump Formation Step> In each Example and Comparative Example, after bumps were formed on the release layer of the transfer substrate, five randomly selected bumps were measured for transmitted light intensity at a wavelength of 532 nm using a microspectrometer (MSV-5500 manufactured by JASCO Corporation), and the OD value of each bump was calculated from the transmitted light intensity. The average value of the five bumps was calculated and used as the OD value of the bump.

[0066] <Positional Accuracy in the Transfer Process> Ten bumps were randomly selected from the bumped glass substrates obtained in each Example and Comparative Example. The bumps were observed using an optical microscope from the side opposite to the side on which the bumps were formed, and the amount of deviation between the center of the bump and the intersection of the cross mark on the transfer target was measured. The average value for the ten bumps was calculated. Note that the smaller the difference in deviation between when irradiated with 300 mJ and when irradiated with 600 mJ, the higher the process margin.

[0067] <Conductivity> A 3 mm square silicon chip having electrodes was thermocompression bonded to the bumped printed wiring board obtained in each Example and Comparative Example at a temperature of 120°C and a pressure of 1 MPa for 5 seconds, and then heated in an oven at a temperature of 140°C for 30 minutes. This produced a silicon chip mounting substrate in which electrode 9 of silicon chip 8 was bonded to electrode 7 of printed wiring board 6 having bumps 1, as shown in Figure 4. Point a and point b of the bumped printed wiring board were then connected with a tester, and the resistance value was measured.

[0068] <Connection Reliability> The silicon chip mounting substrates prepared in the above-mentioned <Conductivity> evaluation were subjected to 500 heating and cooling cycles, each cycle consisting of leaving the substrate stationary for one hour in an environment at -55°C and one at 125°C, and then the resistance was measured in the same manner as in the above-mentioned <Conductivity>. The change in resistance before and after the heating and cooling process was calculated using the following formula to evaluate the connection reliability. The closer the change in resistance is to 1, the higher the connection reliability is. Resistance change = resistance after heating and cooling / resistance before heating and cooling.

[0069] The materials used in the examples and comparative examples are as follows. [Release Agents] Tesfine (registered trademark) 303: amino alkyd-based release agent manufactured by Showa Denko Materials Co., Ltd. Tesfine (registered trademark) 319: silicone-based release agent manufactured by Showa Denko Materials Co., Ltd. F-6711-AL: fluorine-based release agent manufactured by AGC Seimi Chemical Co., Ltd. SFE-DP02H: fluorine-based release agent manufactured by AGC Seimi Chemical Co., Ltd. SFE-X008: fluorine-based release agent manufactured by AGC Seimi Chemical Co., Ltd. KTS-3000H: fluorine-based release agent manufactured by AGC Seimi Chemical Co., Ltd. SR-4000A: fluorine-based release agent manufactured by AGC Seimi Chemical Co., Ltd. Piroil (registered trademark) 1010: long-chain alkyl-based release agent manufactured by Lion Specialty Chemicals Co., Ltd. [Conductive particles] Ag particles: Ag particles manufactured by DOWA Electronics Co., Ltd. (average particle diameter 300 nm, specific gravity 10 g / cm ３ Tin oxide particles: tin oxide particles manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd. (volume average particle diameter 300 nm, specific gravity 7.0 g / cm ３ Carbon black particles: carbon black particles manufactured by Cabot Corporation (average particle diameter 50 nm, specific gravity 1.9 g / cm ３ Carbon-coated Ag particles: carbon-coated Ag particles manufactured by Nisshin Engineering Inc. (average thickness of the surface carbon coating layer: 1 nm, average particle diameter: 40 nm, specific gravity: 9.5 g / cm ３ ) [Thermosetting Resin] EPICLON (registered trademark) N-770: Phenol novolac type epoxy resin manufactured by DIC Corporation (hereinafter referred to as N-770).

[0070] Synthesis Example 1: Organic Component Solution A-1 In a reaction vessel under a nitrogen atmosphere, 150 g of propylene glycol monomethyl ether acetate (hereinafter, "PGMEA") was charged and heated to 80°C using an oil bath. To this, a mixture consisting of 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 acrylic acid (hereinafter, "AA"), 0.8 g of 2,2'-azobisisobutyronitrile, and 10 g of PGMEA was added dropwise over 1 hour. After completion of the dropwise addition, the solution was further heated at 80°C for 6 hours to carry out a polymerization reaction. Thereafter, 0.2 g of hydroquinone monomethyl ether was added to terminate the polymerization reaction. Subsequently, 5 g of glycidyl ether was added. A mixture of methyl methacrylate, 1 g of triethylbenzylammonium chloride, and 10 g of PGMEA was added dropwise over 0.5 hours. After the completion of the dropwise addition, the mixture was heated for an additional 2 hours to carry out an addition reaction. Thereafter, the reaction vessel was returned to an air atmosphere, and 5 g of a photopolymerization initiator "Irgacure (registered trademark)" OXE03 (manufactured by BASF) and 20 g of an acrylic monomer "Aronix (registered trademark)" M-315 (manufactured by Toagosei Co., Ltd.) were added and heated to 50°C for 3 hours for dissolution, yielding an organic component solution (A-1) with a solids content of 42.8 wt%.

[0071] Synthesis Example 2: Organic Component Solution A-2 A reaction vessel under a nitrogen atmosphere was charged with 150 g of PGMEA, and the temperature was raised to 80°C using an oil bath. To this was added dropwise a mixture of 20 g of EA, 20 g of 2-EHMA, 20 g of BA, 5 g of methylol acrylamide, 25 g of AA, 0.8 g of 2,2'-azobisisobutyronitrile, and 10 g of PGMEA over 1 hour. After completion of the dropwise addition, the mixture was further heated at 80°C for 6 hours to carry out the polymerization reaction. Thereafter, 0.2 g of hydroquinone monomethyl ether was added to terminate the polymerization reaction. After the atmosphere inside the reaction vessel was replaced with air, 5 g of a photopolymerization initiator "Irgacure" OXE03 (manufactured by BASF) and 20 g of an acrylic monomer "Aronix (registered trademark)" M-315 (manufactured by Toagosei Co., Ltd.) were added and dissolved by heating at 50°C for 3 hours, thereby obtaining an organic component solution (A-2) with a solids content of 42.0 wt%.

[0072] Synthesis Example 3 Carbon Black Dispersion B-1 13.7 g of carbon black particles, 4 g of a dispersant "DISPERBYK (registered trademark)"-21116 (manufactured by BYK-Chemie), and 200 g of PGMEA were mixed and subjected to a mixing treatment using a homogenizer at 1,200 rpm for 30 minutes. This was followed by further dispersion treatment using a high-pressure wet media-less atomization device "Nanomizer" (Nanomizer Co., Ltd.), yielding carbon black dispersion B-1 having an average particle size of 0.15 μm and a conductive particle content of 6.3 wt %.

[0073] Synthesis Example 4: Ag particle dispersion B-2 80 g of Ag particles, 4 g of a dispersant "DISPERBYK (registered trademark)"-21116 (manufactured by BYK-Chemie), and 200 g of PGMEA were mixed and subjected to a mixing treatment using a homogenizer at 1,200 rpm for 30 minutes. Thereafter, a further dispersion treatment was performed using a high-pressure wet media-less atomization device "Nanomizer" (Nanomizer Co., Ltd.), to obtain Ag particle dispersion B-2 having an average particle size of 0.6 μm and a conductive particle content of 28.2 wt %.

[0074] Synthesis Example 5 Carbon-Coated Ag Dispersion B-3 80 g of carbon-coated Ag particles, 4 g of a dispersant "DISPERBYK (registered trademark)"-21116 (manufactured by BYK-Chemie), and 200 g of PGMEA were mixed and subjected to a mixing treatment using a homogenizer at 1,200 rpm for 30 minutes. Thereafter, the mixture was further dispersed using a high-pressure wet media-less atomization device "Nanomizer" (Nanomizer Co., Ltd.) to obtain carbon-coated Ag Dispersion B-3 having an average particle size of 0.2 μm and a conductive particle content of 28.2 wt %.

[0075] Synthesis Example 6 Tin Oxide Dispersion B-4 40 g of tin oxide particles, 4 g of a dispersant "DISPERBYK (registered trademark)"-21116 (manufactured by BYK-Chemie KK), and 200 g of PGMEA were mixed and subjected to a mixing treatment using a homogenizer at 1200 rpm for 30 minutes. Thereafter, the mixture was further dispersed using a high-pressure wet media-less atomization device "Nanomizer" (Nanomizer Co., Ltd.) to obtain tin oxide dispersion B-4 having an average particle size of 0.2 μm and a conductive particle content of 16.4 wt %.

[0076] Example 1 A 5 wt % toluene solution of silicone release agent "Tesfine (registered trademark)" 303 was applied to a glass substrate using a spin coater at a rotation speed of 2,000 rpm, and then heated in a drying oven at 140°C for 30 minutes to produce a transfer substrate 1 having a release layer.

[0077] 10 g of the organic component solution A-1 obtained in Synthesis Example 1, 1.07 g of thermosetting resin N-770, and 36.8 g of the carbon black dispersion B-1 obtained in Synthesis Example 3 were mixed using a rotation-revolution vacuum mixer "Awatori Rentaro" (registered trademark) ARE-310 (manufactured by Thinky Corporation) to obtain a photosensitive composition 1 having a conductive particle content of 30.2 wt % (20.0 vol %) in the solid content. Here, the solid content refers to the components in the photosensitive composition other than the solvent.

[0078] Next, the photosensitive composition 1 was applied to the transfer substrate 1 obtained by the above-mentioned method using an inkjet coating device in a pattern with a diameter of 100 μm and a thickness of 2 μm after drying to form a bump pattern. A total of 100 bump patterns were prepared, 10 in each direction, within a 3 mm square area on the transfer substrate 1. Thereafter, the bump patterns were dried at 100° C. for 10 minutes using a drying oven. The contact area with the transfer substrate 1 per bump pattern was 7,850 μm. ２ It was.

[0079] Next, the transfer substrate 1 on which the bump pattern was formed and a receiving glass substrate with cross marks previously attached at desired positions were placed face to face with a distance of 50 μm between the substrates, and the substrates were aligned so that the intersections of the cross marks on the receiving glass substrate overlapped the centers of the bumps. Laser irradiation was then performed from the backside of the transfer substrate 1. The laser had a wavelength of 532 nm, a beam size 1.5 times the size of the bumps, and two energy levels of 300 mJ and 600 mJ were used. This resulted in the bumps on the transfer substrate 1 being transferred to the receiving glass substrate, yielding a glass substrate with bumps. The resulting glass substrate with bumps was used to evaluate positional accuracy using the method described above.

[0080] Similarly, ten 100 μm diameter bumps were formed in a row at 100 μm intervals within a 3 mm square area on transfer substrate 1, and then the bumps were transferred onto Au electrodes on a printed wiring board (another transfer substrate) by laser irradiation. The laser had a wavelength of 532 nm, a beam size 1.2 times the size of the bumps, and an energy amount of 300 mJ. This resulted in a bumped printed wiring board having bumps 1 on electrodes 7 of printed wiring board 6, as shown in FIG. 3. The resulting bumped printed wiring board was used to evaluate conductivity and connection reliability using the methods described above.

[0081] (Example 2) The photosensitive composition 1 prepared in Example 1 was applied onto the transfer substrate 1 prepared in Example 1 so that the film thickness after drying would be 2 μm, and the applied film was dried at 100° C. for 10 minutes using a drying oven. Thereafter, the applied film was exposed to light at an exposure dose of 1,000 mJ / cm using an exposure machine through a mask corresponding to the pattern described below. ２ The bump patterns were exposed to light and developed with an alkali to form a bump pattern. Each bump pattern had a diameter of 100 μm, and 10 bumps were formed vertically and horizontally in a 3 mm square area on the transfer substrate 1, for a total of 100 bump patterns. The contact area with the transfer substrate 1 per bump pattern was 7,850 μm. ２ It was.

[0082] Using the transfer substrate 1 on which the bump pattern obtained by the above method was formed, a glass substrate with bumps and a printed wiring board with bumps were produced in the same manner as in Example 1 and evaluated.

[0083] Examples 3 to 6 Glass substrates with bumps and printed wiring boards with bumps were produced and evaluated in the same manner as in Example 2, except that the diameter of the bumps was changed to change the contact area per bump with the release layer as shown in Table 1.

[0084] Example 7 A glass substrate with bumps and a printed wiring board with bumps were produced in the same manner as in Example 4, except that the thickness of the bumps was changed as shown in Table 1, and were evaluated.

[0085] Examples 8 to 14 Glass substrates with bumps and printed wiring boards with bumps were produced and evaluated in the same manner as in Example 4, except that a release layer was formed on a glass substrate using the material shown in Table 1 instead of the silicone-based release agent "Tesfine (registered trademark)" 303.

[0086] Examples 15 to 17 Glass substrates with bumps and printed wiring boards with bumps were produced and evaluated in the same manner as in Example 4, except that the carbon black dispersion B-1 obtained in Synthesis Example 3 was replaced with the Ag particle dispersion B-2, the carbon-coated Ag dispersion B-3, and the tin oxide dispersion B-4 obtained in Synthesis Examples 4 to 6, respectively.

[0087] Example 18 A glass substrate with bumps and a printed wiring board with bumps were produced and evaluated in the same manner as in Example 4, except that the organic component solution A-2 obtained in Synthesis Example 2 was used instead of the organic component solution A-1 obtained in Synthesis Example 1.

[0088] Examples 19 to 24 Glass substrates with bumps and printed wiring boards with bumps were produced and evaluated in the same manner as in Example 4, except that the content of conductive particles in the carbon black dispersion B-1 and the content of thermosetting resin in the organic component solution A-1 were changed as shown in Table 2.

[0089] Examples 25 and 26 Glass substrates with bumps and printed wiring boards with bumps were produced in the same manner as in Example 15, except that the electrodes of the printed wiring board were changed as shown in Table 2, and then evaluated.

[0090] Examples 27 and 28 Glass substrates with bumps and printed wiring boards with bumps were produced in the same manner as in Example 4, except that the electrodes of the printed wiring board were changed as shown in Table 2, and then evaluated.

[0091] (Example 29) A silicon chip with electrodes for evaluating conductivity was mounted on a printed wiring board fabricated in the same manner as in Example 4, and then a new printed wiring board with bumps was fabricated next to the mounted silicon chip in the same manner as in Example 4 and evaluated.

[0092] Comparative Example 1 A glass substrate with bumps and a printed wiring board with bumps were produced and evaluated in the same manner as in Example 23, except that no release layer was provided.

[0093] Comparative Examples 2 and 3 A glass substrate with bumps and a printed wiring board with bumps were produced and evaluated in the same manner as in Example 28 and Example 26, respectively, except that no release layer was provided.

[0094] The main configurations and evaluation results of each of the examples and comparative examples are shown in Tables 1 to 3.

[0095]

[0096]

[0097]

[0098] 1: Bump 2: Glass substrate 3: Laser 4: Transferred substrate 5: Release layer 6: Printed wiring board 7: Electrode of printed wiring board 8: Silicon chip 9: Electrode of silicon chip 10: Bump 11: Transferred substrate 12: Laser 13: Transferred substrate 14, 14': Electronic component 15: Electrode of electronic component

Claims

1. A transfer substrate having a release layer, wherein the release layer has a bump pattern containing organic components and conductive particles, and the transfer substrate having the release layer has a peeling force of 100 to 5,000 mN / 50 mm at 25°C.

2. The substrate according to claim 1, wherein the water contact angle of the release layer at 25°C is 90 degrees or more.

3. The substrate according to claim 1 or 2, wherein the content of conductive particles in the bump pattern is 10 to 40 volume percent.

4. The substrate according to claim 1 or 2, wherein the OD value of the bump pattern is 0.5 to 3.

5. The aspect ratio of the bump pattern is 0.1 to 0.4, and the contact area with the release layer per bump pattern is 25 to 500 μm². ２ The substrate according to claim 1 or 2.

6. The substrate according to claim 1 or 2, wherein the conductive particles include metal particles having a carbon black and / or carbon coating layer.

7. A circuit board according to claim 1 or 2, which is for repair purposes.

8. A method for manufacturing a substrate according to claim 1 or 2, comprising the steps of exposing a photosensitive composition containing organic components and conductive particles (exposure step) and developing it (development step).

9. A method for manufacturing a bumped structure, comprising the step of transferring bumps to an electrode-equipped substrate or an electrode portion of an electronic component by irradiating a laser from the opposite side of the release layer of the substrate according to claim 1 or 2 (bump transfer step).

10. The method for manufacturing a bumped structure according to claim 9, wherein the electrode-equipped substrate is an electrode-equipped substrate on which electronic components are mounted.

11. A method for manufacturing a bumped structure, comprising the steps of forming bumps containing organic components and conductive particles on the release layer of a transfer substrate having a release layer (bump formation step), and transferring the bumps to an electrode-equipped substrate or an electrode portion of an electronic component by irradiating the transfer substrate with a laser from the opposite side of the release layer (bump transfer step), wherein the peeling force of the transfer substrate having a release layer at 25°C is 100 to 5,000 mN / 50 mm.

12. The method for manufacturing a bumped structure according to claim 11, wherein the water contact angle of the release layer at 25°C is 90 degrees or more.