Conductive paste, printed wiring board, method for manufacturing printed wiring board, method for manufacturing printed circuit board

Abstract

Provided is a conductive paste capable of improving the bonding strength with an electronic component even without using an adhesive. A conductive paste containing an organic component and conductive particles, wherein the storage modulus G' at 100°C (P100) of a dried film of the conductive paste is 0.01 MPa or less, and the storage modulus G' at 25°C after heating at 140°C for 30 minutes (C25) is 0.01 MPa or more.

Description

Technical Field

[0001] This invention relates to conductive paste, printed wiring boards, methods for manufacturing printed wiring boards, and methods for manufacturing printed circuit boards. Background Technology

[0002] Previously, soldering-based methods were widely used when packaging electronic components onto printed circuit boards. However, with the miniaturization of electronic devices, packaging methods known as wire bonding or flip-chip methods have become widely known. In particular, the flip-chip method uses conductive bumps to electrically connect the electrodes of the electronic components to the electrodes of the printed circuit board, thereby enabling the packaging of even smaller electronic components.

[0003] In addition, in recent years, there has been extensive research on fine-pitch packaging for LED chips with a diameter of 50μm × 50μm or less, which are called micro LEDs. Not only flip-chip LED chips, but also conductive bumps are required to be further miniaturized.

[0004] As a packaging method for micro LEDs, for example, the following method is known: a conductive photoresist containing conductive particles is coated on the surface of a printed wiring board, and then exposed and developed, thereby forming conductive bumps on the electrodes of the printed wiring board, and then the conductive bumps are bonded to the LED electrodes by means of a conductive adhesive (for example, see Patent Document 1).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2020-92159 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, for the technology described in Patent Document 1, an adhesive is required in order to bond the conductive bumps to the LED electrodes, which results in an increase in the number of processes and poor production efficiency.

[0010] Therefore, the object of the present invention is to provide a conductive paste that enables LED encapsulation at low temperature and low pressure even without the use of additional adhesives, and that improves the bonding strength between conductive bumps and LED electrodes.

[0011] Methods for solving problems

[0012] To address the aforementioned issues, the present invention mainly comprises the following components.

[0013] A conductive paste containing organic components and conductive particles, wherein the storage modulus G'(P100) of the dried film of the aforementioned conductive paste at 100°C is less than 0.01 MPa, and the storage modulus G'(C25) at 25°C after heating at 140°C for 30 minutes is greater than 0.01 MPa.

[0014] Invention Effects

[0015] The conductive paste of the present invention can encapsulate electronic components with high bonding strength even without the use of additional adhesives at low temperature and low pressure. Attached Figure Description

[0016] [ Figure 1 [A schematic diagram illustrating an example of a method for manufacturing a printed circuit board according to the present invention.]

[0017] [ Figure 2 [A schematic diagram illustrating another example of a method for manufacturing a printed circuit board according to the present invention.]

[0018] [ Figure 3 [This is a schematic cross-sectional view of the chip shear strength test sample used in the examples.] Detailed Implementation

[0019] The conductive paste of the present invention refers to a substance obtained by dispersing conductive particles in an organic component, and also includes: a non-photosensitive conductive paste used by removing the solvent after coating it on a substrate and then thermally curing the resin; and a photosensitive conductive paste that can form a pattern by adjusting the organic component and through exposure and development processes.

[0020] <Conductive Paste>

[0021] The conductive paste of the present invention contains organic components and conductive particles. The storage modulus G'(P100) of the dried film of the aforementioned conductive paste at 100°C is 0.01 MPa or less, and the storage modulus G'(C25) at 25°C after heating at 140°C for 30 minutes is 0.01 MPa or more. Furthermore, if the storage modulus G'(P25) of the dried film of the aforementioned conductive paste at 25°C is 0.1 MPa or more, shape changes caused by contact or external pressure during the process can be suppressed, thus improving operability. Specifically, by setting the storage modulus G'(P100) of the dried film at 100°C to 0.00001–0.01 MPa, the storage modulus G'(P25) at 25°C to 0.1–50000 MPa, and the storage modulus G'(C25) at 25°C after heating at 140°C for 30 minutes to 0.01–100000 MPa, both operability and low-temperature encapsulation performance can be balanced. Furthermore, if the storage modulus G'(P100) of the dried film at 100°C is less than 1 / 10 of the storage modulus G'(P25) of the dried film at 25°C, both operability and low-temperature encapsulation performance can be further balanced.

[0022] Conductive pastes that meet the above conditions include those containing carboxyl-containing polymers, photopolymerization initiators, epoxy resins, and Novolac-type phenolic resins in their organic components. Conductive pastes containing these components not only further improve the shear strength of the packaged chip but also allow for the formation of fine bumps through exposure and development of the dried film. Furthermore, the shear strength of the chip can be further improved by using a curing catalyst containing epoxy resin to promote the curing reaction of the epoxy resin.

[0023] Furthermore, if the dried film of the conductive paste is exposed to an i-line (wavelength 365nm) at an exposure dose of 500mJ / cm 2 If the energy storage modulus G'(E100) of the exposed film at 100°C is less than 1 / 10 of the energy storage modulus G'(E25) at 25°C, then it is possible to further balance microprocessability and low-temperature encapsulation.

[0024] In the conductive paste of the present invention, the conductive paste capable of forming patterns through exposure and development is a photosensitive conductive paste containing photosensitive components and conductive particles. The aforementioned photosensitive conductive paste is dried at 100°C for 30 minutes, and the resulting dried film is exposed to an exposure dose of 500 mJ / cm at an i-line (wavelength 365 nm). 2 After exposure, the storage modulus G'(D100) of the film after being sprayed with a 0.1% sodium carbonate aqueous solution for 30 seconds is less than 0.01 MPa at 100°C. After the film is heated at 140°C for 30 minutes, the storage modulus G'(C25) of the film after exposure is greater than 0.01 MPa at 25°C.

[0025] Here, "storage modulus G'(D100)" refers to the storage modulus G' measured using a rheometer to determine the dynamic viscoelasticity (temperature dependence) of the developed film. Dynamic viscoelasticity refers to the method of analyzing the dynamic mechanical properties of a material when shear strain is applied to it at a sinusoidal frequency, resulting in shear stress at steady state. This shear stress is decomposed into a component with a phase consistent with the strain (elastic component) and a component with a phase differing from the strain by 90° (viscous component).

[0026] The storage modulus G' is obtained by dividing the stress component whose phase coincides with the shear strain by the shear strain. The storage modulus G' represents the elasticity of the material relative to dynamic strain at various temperatures and is related to the hardness of the developed film. Therefore, the storage modulus G' at each measurement temperature affects the following properties related to the developed film. Specifically, G'(D100) affects the flowability of the developed film upon heating, and G'(C25) affects the bonding strength of the cured film.

[0027] By ensuring that the G'(D100) of the developed film is less than 0.01 MPa, the bonding strength between the bumps formed using the photosensitive conductive paste and the electronic components bonded thereto is improved. This is because, after forming bumps on the electrodes of the printed wiring board, the electrodes of the electronic components are heated and pressed together with the bumps while being heated to 100°C or higher. As a result, the bumps rapidly flow and deform according to the shape of the electrodes of the electronic components, thus achieving a high adhesion force between the bumps and the electrodes. G'(D100) is more preferably 0.007 MPa or less.

[0028] There is no particular limitation on the lower limit of G'(D100). If the fluidity of the conductive bump is too high during heating and pressing, a short circuit fault may occur in the electrical connection with adjacent electronic components. Therefore, from the viewpoint of preventing this, it is preferable to be 0.002 MPa or higher.

[0029] The cured film described above has a G' (C25) of 0.01 MPa or more, more preferably 0.05 MPa or more. As a result, the fluid bumps that are heat-pressed are fixed, thereby improving the bonding strength between the electronic components and the bumps.

[0030] There is no particular limit to the upper limit of G'(C25). From the viewpoint of ease of repair when identifying the malfunction of the electronic component after it has been bonded to the printed wiring board, G'(C25) is preferably 1.0 MPa or less.

[0031] In the case of typical photosensitive conductive pastes, both G'(D100) and G'(C25) are mostly 0.01 MPa or higher. In contrast, as a method as described in this invention, where G'(C25) is 0.01 MPa or higher and G'(D100) is less than 0.01 MPa, examples include methods that include a carboxyl-containing resin having photopolymerizable groups (described later) and a carboxyl-containing resin without photopolymerizable groups in the paste.

[0032] The bonding strength between electronic components and bumps can be evaluated, for example, by measuring chip shear strength. Here, "chip shear strength" refers to the bonding strength when a horizontal force (a shear force) is applied to the bonding member bonded to the bonded component. Chip shear strength can be measured using a standard chip shear strength measuring device.

[0033] <Photosensitive components>

[0034] The conductive paste of the present invention preferably contains a photosensitive component. By containing a photosensitive component, fine conductive bumps can be formed on the electrodes of the printed wiring board with high positional precision. Examples of photosensitive components include photopolymerization initiators, compounds having unsaturated double bonds, and carboxyl-containing resins having photopolymerizable groups.

[0035] <Photopolymerization Initiator>

[0036] The conductive paste of the present invention preferably contains a photopolymerization initiator. Examples of photopolymerization initiators include benzophenone derivatives, acetophenone derivatives, thioxanone derivatives, benzoyl derivatives, benzoin derivatives, oxime compounds, α-hydroxyketone compounds, α-aminoalkylphenyl ketone compounds, phosphine oxide compounds, anthrone compounds, and anthraquinone compounds.

[0037] Regarding the content of the photopolymerization initiator in the conductive paste of the present invention, it is preferably 0.05 to 30 parts by weight relative to 100 parts by weight of the carboxyl-containing resin having photopolymerizable groups. When the content of the photopolymerization initiator is 0.05 parts by weight or more, the curing density of the exposed section increases, which can improve the residual film yield after development. On the other hand, when the content of the photopolymerization initiator is 30 parts by weight or less, it can suppress the coarsening of the wiring pattern caused by excessive light absorption of the photopolymerization initiator on the upper part of the coating film obtained by coating the photosensitive conductive paste, thereby further improving the microprocessability.

[0038] <Compounds with unsaturated double bonds>

[0039] The conductive paste of the present invention preferably contains a compound having unsaturated double bonds. Here, "a compound having unsaturated double bonds" refers to a monomer having unsaturated double bonds. By containing unsaturated double bonds, the crosslinking density of the exposed portion can be increased during exposure, the development margin can be widened, and the microprocessability can be further improved.

[0040] Examples of compounds containing unsaturated double bonds include, for instance, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, neopentyl glycol dimethacrylate, glycerol dimethacrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, dimethyloltricyclodecane dimethacrylate, tripropylene glycol diacrylate, and dioxanediol diacrylate. Two functional monomers, including glycol diacrylate, cyclohexanedimethyl dimethacrylate, tricyclodecanedimethyl dimethacrylate, ethoxylated (4) bisphenol A diacrylate, ethoxylated (10) bisphenol A diacrylate, acrylate adducts of ethylene glycol diglycidyl ether, and acrylate adducts of neopentyl glycol diglycidyl ether; three functional monomers, including pentaerythritol triacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, trimethylolpropane ethoxytriacrylate, and glycerol propoxytriacrylate; and four functional monomers, including dipentaerythritol hexaacrylate, pentaerythritol tetraacrylate, pentaerythritol ethoxytetraacrylate, and di(trimethylolpropane)tetraacrylate. It may contain two or more of these.

[0041] Regarding the content of the compound having unsaturated double bonds in the conductive paste of the present invention, it is preferably 1 to 100 parts by weight relative to 100 parts by weight of the carboxyl-containing resin having photopolymerizable groups. If the content of the compound having unsaturated double bonds is 1 part by weight or more, the crosslinking density of the exposed portion increases, which can increase the solubility difference between the unexposed portion and the exposed portion in the developer, thereby improving microprocessability. On the other hand, if the content of the compound having unsaturated double bonds is 100 parts by weight or less, G'(D100) can be further reduced.

[0042] <Carboxyl-containing resins with photopolymerizable groups>

[0043] The conductive paste of the present invention preferably contains a carboxyl-containing resin with photopolymerizable groups as a photosensitive component. By including carboxyl groups in this resin, alkaline developability and microprocessability based on photolithography can be improved. Furthermore, since this resin has photopolymerizable groups, it remains as an organic component in the developed film. Therefore, the phenomenon that the proportion of conductive particles in the film increases due to film loss during development (reduction of organic components), thereby increasing G'(D100), can be suppressed.

[0044] Examples of carboxyl-containing resins with photopolymerizable groups include, for example, acrylic copolymers containing carboxyl groups, carboxylic acid-modified epoxy resins, carboxylic acid-modified phenolic resins, polyamic acid, and carboxylic acid-modified siloxane polymers. Two or more of these may be contained. Among the above, acrylic copolymers containing carboxyl groups or carboxylic acid-modified epoxy resins with high ultraviolet light transmittance are preferred, and carboxylic acid-modified epoxy resins are more preferred.

[0045] As an acrylic copolymer containing a carboxyl group, a copolymer of an acrylic monofunctional monomer and an unsaturated acid or its anhydride is preferred.

[0046] Examples of acrylic monofunctional monomers include, for example, methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, n-butyl acrylate, isobutyl acrylate, isopropyl acrylate, glycidyl acrylate, butoxytriethylene glycol acrylate, dicyclopentyl acrylate, dicyclopentenyl acrylate, 2-hydroxyethyl acrylate, isobornyl acrylate, 2-hydroxypropyl acrylate, isodecanyl acrylate, isoodecyl acrylate, isooctyl acrylate, lauryl acrylate, 2-methoxyethyl acrylate, methoxyethylene glycol acrylate, methoxydiethylene glycol acrylate, octafluoropentyl acrylate, phenoxyethyl acrylate, stearyl acrylate, trifluoroethyl acrylate, aminoethyl acrylate, phenyl acrylate, phenoxyethyl acrylate, 1-naphthyl acrylate, and 2- Naphthalene ester, thiophenol acrylate, benzyl thiol acrylate, acrylamide, N-methoxymethylacrylamide, N-ethoxymethylacrylamide, N-n-butoxymethylacrylamide, N-isobutoxymethylacrylamide, phenol methacrylate, methacrylamide phenol, γ-acryloyloxypropyltrimethoxysilane, N-(2-hydroxyphenyl)acrylamide, N-(3-hydroxyphenyl)acrylamide, N-(4-hydroxyphenyl)acrylamide, o-hydroxyphenyl acrylate, m-hydroxyphenyl acrylate, p-hydroxyphenyl acrylate, o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, 2-(2-hydroxyphenyl)ethyl acrylate, 2-(3-hydroxyphenyl)ethyl acrylate, 2-(4-hydroxyphenyl)ethyl acrylate, etc. Two or more of these can be used. Among the above, ethyl acrylate, 2-hydroxyethyl acrylate, and isobornyl acrylate are preferred.

[0047] Examples of unsaturated acids or their anhydrides include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, vinyl acetate, and their anhydrides. Two or more of these can be used. The acid value of the carboxyl-containing acrylic copolymer can be adjusted by the copolymerization ratio of the unsaturated acids.

[0048] As a carboxylic acid-modified epoxy resin, the preferred options are epoxy compounds and reactants with unsaturated acids or unsaturated acid anhydrides. Here, carboxylic acid-modified epoxy resin refers to a resin obtained by modifying the epoxy groups of an epoxy compound with carboxylic acid or carboxylic anhydrides, and does not contain epoxy groups.

[0049] Examples of epoxy compounds include, for example, glycidyl ethers, glycidyl amines, and epoxy resins. More specifically, examples of glycidyl ethers include, for example, 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-epoxycyclohexane carboxylate. Examples of glycidylamines include, for example, tert-butyl glycidylamine. Examples of epoxy resins include, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin, Novolac type epoxy resin, hydrogenated bisphenol A type epoxy resin, etc. Two or more of these can be used.

[0050] Unsaturated double bonds can be introduced by reacting compounds with unsaturated double bonds, such as glycidyl (meth)acrylate, with the aforementioned carboxyl-containing acrylic copolymers and carboxylic acid-modified epoxy resins. By introducing unsaturated double bonds into carboxyl-containing resins, the crosslinking density of the exposed portion can be increased during exposure, the development margin can be widened, and the microprocessability can be further improved.

[0051] Regarding the acid value of carboxyl-containing resins with photopolymerizable groups, for example, in the case of an acrylic copolymer containing carboxyl groups, the desired range can be adjusted by the proportion of unsaturated acids in the constituent components. In the case of a carboxylic acid-modified epoxy resin, the desired range can be adjusted by reacting a polyacid anhydride. In the case of a carboxylic acid-modified phenolic resin, the desired range can be adjusted by the proportion of polyacid anhydrides in the constituent components.

[0052] <Epoxy Resin>

[0053] The conductive paste of the present invention preferably contains epoxy resin. By containing epoxy resin, the bonding strength between conductive bumps and electronic components such as LED electrodes can be improved. Examples of epoxy resins include bisphenol A type, cresol Novolac type, phenol Novolac type, bisphenol A Novolac type, dicyclopentadiene type, and naphthalene type, among which epoxy resins with a softening point of 30°C or higher and 100°C or lower are preferred. If the softening point is 30°C or higher, short-circuit faults with nearby bumps caused by excessive flow during heat pressing can be suppressed; if it is 100°C or lower, component encapsulation at low temperatures can be achieved. More specifically, examples include EPICRON N-660 (softening point 61-69℃), EPICRON N-670 (softening point 68-76℃), EPICRON N-680 (softening point 80-90℃), EPICRON N-770 (softening point 65-75℃), EPICRON N-775 (softening point 70-80℃), EPICRON N-865 (softening point 64-72℃), EPICRON N-890 (softening point 75-90℃), EPICRON HP-7200L (softening point 50-60℃), EPICRON HP-7200 (softening point 57-68℃), EPICRON HP-7200H (softening point 75-90℃), and EPICRON products manufactured by DIC Co., Ltd. HP-4700 (softening point 85-98℃), KAYARADNC-3000 (softening point 53-63℃), NC-3000H (softening point 65-75℃) manufactured by Nippon Kayaku Co., Ltd., etc. Two or more of these can be used.

[0054] <Novolac type phenolic resin>

[0055] The conductive paste of the present invention preferably contains a Novolac-type phenolic resin. By containing a Novolac-type phenolic resin, the bonding strength between the conductive bumps and electronic components such as LED electrodes can be improved. The softening point is preferably 30°C or higher and 100°C or lower. If the softening point is 30°C or higher, short-circuit faults with nearby bumps caused by excessive flow during heat pressing can be suppressed; if it is 100°C or lower, component encapsulation at low temperatures can be achieved. More specifically, examples include KAYARAD GPH-65 (softening point 63-69°C) and KAYARAD... (the text abruptly ends here, so the translation stops here as well.) GPH-103, Meiwa Kasei Corporation H-4 (softening point 67-75℃), HF-1M (softening point 82-86℃), HF-3M (softening point 94-98℃), MEHC-7800-4S (softening point 61-65℃), MEHC-7800SS (softening point 63-67℃), MEHC-7800S (softening point 72-78℃), MEHC-7800M (softening point 78-84℃), MEHC-7851-SS (softening point 64-69℃), MEHC-7851-S (softening point 70-75℃), MEHC-7851-M (softening point 74-79℃), MEHC-7851-H (softening point 80-85℃), MEHC-7841 (softening point 58-65℃), etc. Two or more of these can be used.

[0056] The total amount of epoxy resin and Novolac-type phenolic resin added in this invention is preferably 1 to 100 parts by weight relative to 100 parts by weight of the carboxyl-containing polymer. If the total amount of epoxy resin and Novolac-type phenolic resin added is 1 part by weight or more, the bonding strength between conductive bumps and electronic components such as LED electrodes can be improved; if it is 100 parts by weight or less, the solubility during development can be improved, enabling high-resolution patterning. The ratio of epoxy resin to Novolac-type phenolic resin is preferably consistent with the ratio of the epoxy equivalent of the epoxy resin used to the hydroxyl equivalent of the Novolac-type phenolic resin.

[0057] <Curing Accelerator>

[0058] The conductive paste of the present invention preferably contains a curing accelerator that promotes the curing of epoxy resin and Novolac-type phenolic resin. By containing a curing accelerator, the bonding strength between the conductive bumps and electronic components such as LED electrodes can be improved. More specifically, imidazole derivatives, dicyandiamide derivatives, quaternary ammonium salts, triphenylphosphine, and tetraphenylphosphonium tetraphenylborate are examples. Two or more of these can be used.

[0059] The amount of curing accelerator added in this invention is preferably 0.01 to 5 parts by weight relative to 100 parts by weight of epoxy resin. If the amount of curing accelerator added is 0.01 parts by weight or more, the bonding strength between the conductive bump and electronic components such as LED electrodes can be improved. If it is 5 parts by weight or less, the curing reaction will not be excessive during heat pressing, and the temperature margin during heat pressing can be widened.

[0060] <Carboxyl-containing resins without photopolymerizable groups>

[0061] The conductive paste of the present invention preferably contains a carboxyl-containing resin that does not have photopolymerizable groups. By containing a carboxyl-containing resin that does not have photopolymerizable groups, the flexibility of the developed film during heating can be improved while maintaining alkaline developability. As a result, it is easy to prepare the paste in a manner that simultaneously maintains G'(C25) at 0.01 MPa or higher and reduces G'(D100) to less than 0.01 MPa.

[0062] Examples of carboxyl-containing resins that do not have photopolymerizable groups include, for example, oligomers containing carboxyl groups. More specifically, examples include solid JONCRYL 67 (glass transition temperature 73°C), JONCRYL 678 (glass transition temperature 85°C), JONCRYL 611 (glass transition temperature 50°C), JONCRYL 693 (glass transition temperature 84°C), JONCRYL 682 (glass transition temperature 56°C), JONCRYL 690 (glass transition temperature 102°C), JONCRYL 819 (glass transition temperature 57°C), JONCRYL JDX-C3000A (glass transition temperature 65°C), JONCRYL JDX-C3080 (glass transition temperature 134°C) manufactured by BASF JAPAN Co., Ltd.; JONCRYL 52J (glass transition temperature 56°C), JONCRYL PDX-6157 (glass transition temperature 84°C), and JONCRYL 60J (glass transition temperature 85°C) dissolved in alkaline water. The following are glass transition temperature (GLT) products: JONCRYL 63J (GLT 73℃), JONCRYL 70J (GLT 102℃), JONCRYL JDX-6180 (GLT 134℃), JONCRYL HPD-196 (GLT 85℃), JONCRYL HPD-96J (GLT 102℃), JONCRYL PDX-6137A (GLT 102℃), JONCRYL 6610 (GLT 85℃), JONCRYL JDX-6500 (GLT 65℃), and JONCRYL PDX-6102B (GLT 19℃). Two or more of these can be used.

[0063] Of the above, from the viewpoint of reducing G'(D100), a material with a glass transition temperature of 110°C or lower is preferred. Furthermore, a solid oligomer containing carboxyl groups is preferred.

[0064] It should be noted that the glass transition temperature can be measured, for example, by differential scanning calorimetry (DSC) using a differential scanning calorimeter (DSC-60Aplus; manufactured by Shimadzu Corporation).

[0065] Regarding the content of the carboxyl-containing resin without photopolymerizable groups in the conductive paste of the present invention, it is preferably 1 to 50 parts by weight relative to 100 parts by weight of the carboxyl-containing resin with photopolymerizable groups. When the content of the carboxyl-containing resin without photopolymerizable groups is 1 part by weight or more, the aforementioned G'(D100) can be further reduced, the adhesion between the electronic component and the conductive bump can be improved, and the bonding strength of the cured film can be increased. If the content of the carboxyl-containing resin without photopolymerizable groups is 50 parts by weight or less, pattern peeling during development can be suppressed. The content of the carboxyl-containing resin without photopolymerizable groups is more preferably 5 to 40 parts by weight.

[0066] <Conductive particles>

[0067] The conductive paste of the present invention contains conductive particles. Examples of conductive particles include those of silver, gold, copper, platinum, lead, tin, nickel, aluminum, tungsten, molybdenum, chromium, titanium, indium, magnesium, cobalt, zinc, potassium, lithium, iron, mercury, beryllium, cadmium, rhodium, ruthenium, iridium, and their alloys. Two or more of these particles may be contained. From the viewpoint of conductivity, particles selected from silver, gold, and copper are preferred; from the viewpoint of cost and stability, silver particles are more preferred. Alternatively, conductive particles may be obtained by coating the surface of resin, inorganic oxides, etc. Conductive particles obtained by coating the surface of resin particles or inorganic oxide particles with metal exhibit elastic repulsion caused by the resin particles during encapsulation; therefore, metal particles are preferred.

[0068] The aspect ratio, obtained by dividing the major axis length by the minor axis length of the conductive particle, is preferably 1.1 to 2.0. Here, regarding the aspect ratio of the conductive particles, a scanning electron microscope (SEM) or a transmission electron microscope (TEM) can be used to observe the conductive particles at a magnification of 15,000. For 100 randomly selected primary conductive particles, the major axis length and minor axis length of each particle are measured, and the aspect ratio is calculated based on the average of the two.

[0069] The average particle size of the conductive particles is preferably 0.05 to 5.0 μm. By making the average particle size of the conductive particles 0.05 μm or more, the interaction between particles can be moderately suppressed, thereby improving the dispersibility of the conductive particles in the photosensitive conductive paste. The average particle size of the conductive particles is more preferably 0.1 μm or more. On the other hand, by making the average particle size of the conductive particles 5.0 μm or less, the surface smoothness, pattern accuracy, and dimensional accuracy of the obtained conductive pattern can be improved. The average particle size of the conductive particles is more preferably 2.0 μm or less. Here, the average particle size of the conductive particles can be measured using a laser-irradiated particle size analyzer. The D50 value of the particle size distribution obtained by measurement is taken as the average particle size (D50) of the conductive particles.

[0070] The conductive particles in the conductive paste of the present invention are preferably 30 to 90% by weight of the total solid components. If the content of conductive particles is 30% by weight or more, the probability of contact between the conductive particles during heating and sintering is increased, thereby improving conductivity. The content of conductive particles is more preferably 50% by weight or more. On the other hand, if the content of conductive particles is 90% by weight or less, the light transmittance of the coating film during the exposure process is improved, thereby improving microprocessability. Here, the total solid components refer to all components of the conductive paste except for the solvent.

[0071] <Solvent>

[0072] The conductive paste of the present invention may contain a solvent. Examples of solvents include N,N-dimethylacetamide (boiling point 165°C), N,N-dimethylformamide (boiling point 153°C), N-methyl-2-pyrrolidone (boiling point 204°C), dimethylimidazolinone (boiling point 225°C), dimethyl sulfoxide (boiling point 189°C), γ-butyrolactone (boiling point 204°C), ethyl lactate (boiling point 154°C), 1-methoxy-2-propanol (boiling point 120°C), 1-ethoxy-2-propanol (boiling point 132°C), and so on. Acetone alcohol (boiling point 166℃), tetrahydrofurfuryl alcohol (boiling point 178℃), propylene glycol monomethyl ether acetate (boiling point 146℃), diethylene glycol monoethyl ether acetate (boiling point 217℃), diethylene glycol monomethyl ether (boiling point 194℃), diethylene glycol monobutyl ether (boiling point 230℃), diethylene glycol (boiling point 245℃), diethylene glycol monobutyl ether acetate (boiling point 247℃), 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (boiling point 253℃), etc. It may contain two or more of these.

[0073] Particularly preferred are solvents containing a solubility of 80g or more in 100g of water at 20°C and a boiling point of 200°C or higher. Specifically, N-methyl-2-pyrrolidone, dimethylimidazolinone, γ-butyrolactone, diethylene glycol monobutyl ether, and diethylene glycol are preferred. If the solvent has a solubility of 80g or more in 100g of water at 20°C, the residual solvent in the dried film of the photosensitive conductive paste is easily replaced by the developer during development, reducing the residual solvent in the developed film and preventing the evaporation of residual solvent during heat pressing, thereby further improving the adhesion strength between electronic components and conductive bumps. In addition, when the boiling point is 200°C or higher, solvent evaporation is suppressed, which can inhibit the thickening of the photosensitive conductive paste.

[0074] The solvent content in the conductive paste of the present invention is preferably 3 to 30% by weight of the total paste composition. When the solvent content is 3 to 30% by weight, the viscosity of the conductive paste can be kept within a range suitable for coating such as printing, and good coatability can be obtained.

[0075] <Other Ingredients>

[0076] The conductive paste of the present invention may contain additives such as plasticizers, leveling agents, surfactants, silane coupling agents, defoamers, and pigments, as long as they are within the range that do not impair the desired properties.

[0077] Examples of plasticizers include dibutyl terephthalate, dioctyl phthalate, polyethylene glycol, and glycerol.

[0078] As leveling agents, examples include special vinyl polymers and special acrylic polymers.

[0079] Examples of silane coupling agents include methyltrimethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, hexamethyldisilazane, 3-methacryloyloxypropyltrimethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, vinyltrimethoxysilane, etc.

[0080] Printed wiring boards

[0081] The printed wiring board of the present invention comprises a dried film of the conductive paste of the present invention, or a film after the dried film has been exposed and developed. Thus, it becomes flexible when heated and cures after heating, thereby improving the bonding strength with electronic components after curing, even without the use of additional adhesives, when bonding electronic components.

[0082] <Methods for manufacturing conductive pastes and photosensitive conductive pastes>

[0083] The conductive paste of the present invention can be manufactured by mixing conductive particles into an organic compound that appropriately contains thermosetting resin components such as epoxy resin and Novolac-type phenolic resin, a photopolymerization initiator that reacts under exposure light, a compound having unsaturated double bonds, a carboxyl-containing polymer, a carboxyl-containing resin without photopolymerizable groups, a solvent, and additives. Examples of mixing devices include dispersers such as three-roll mills, ball mills, and planetary ball mills, as well as mixers.

[0084] <Printed Circuit Board Manufacturing Method>

[0085] Hereinafter, an example of a method for manufacturing a printed circuit board according to the present invention will be described with reference to the accompanying drawings. It should be noted that the drawings are schematic. Furthermore, the present invention is not limited to the examples described below.

[0086] One method for manufacturing a printed circuit board according to the present invention includes the following steps: forming a dried film of the conductive paste of the present invention on a printed wiring board; exposing and developing the dried film to form conductive bumps on the electrodes of the printed wiring board; and heating and pressing an electronic component having electrodes onto the conductive bumps.

[0087] Figure 1 A process diagram illustrating an example of a method for manufacturing a printed circuit board according to the present invention. First, as... Figure 1 As shown in (a), a dry film 1 of the conductive paste of the present invention is formed on the printed wiring board 2.

[0088] In the process of forming a dry film of the conductive paste of the present invention on a printed wiring board, the coating method may include, for example, spin coating using a spin coater, spray coating, roller coating, screen printing, coating using a doctor blade coater, die coater, calender coater, meniscus coater, or bar coater.

[0089] The thickness of the dried film of the photosensitive conductive paste is preferably 1 to 10 μm. If the film thickness is 1 μm or more, it can suppress uneven resistance of the conductive bumps and improve the bonding strength between the printed circuit board and the electronic components. On the other hand, if the film thickness is 10 μm or less, the exposure time can easily reach the depth of the dried film, thus widening the development margin. Furthermore, it can suppress short circuits caused by the wetting and expansion of the conductive bumps during encapsulation. The film thickness is more preferably 2 to 5 μm. It should be noted that the film thickness of the dried film of the photosensitive conductive paste can be measured using a stylus height difference meter, such as the Surfcom 1400 (Tokyo Seimitsu Co., Ltd.). More specifically, the film thickness is measured at three random locations using a stylus height difference meter (measuring length: 1 mm, scanning speed: 0.3 mm / s), and the average value is taken as the film thickness.

[0090] Examples of drying methods include heating drying using an oven, heating plate, infrared radiation, and vacuum drying. The preferred drying temperature is 50–180°C, and the preferred drying time is 1 minute to several hours.

[0091] Next, as Figure 1 As shown in (b), the dry film 1 is exposed and developed to form conductive bumps 4 on the electrodes 3 of the printed wiring board 2.

[0092] As an exposure method, examples include using light sources such as high-pressure mercury lamps, ultra-high-pressure mercury lamps, and LEDs that emit i-lines (wavelength 365nm), h-lines (wavelength 405nm), or g-lines (wavelength 436nm), as well as various exposure methods such as vacuum adsorption exposure, proximity exposure, projection exposure, and direct tracing exposure.

[0093] Furthermore, the illuminance ratio of the exposure light during exposure (illuminance at a wavelength of 365 nm) to (illuminance at a wavelength of 405 nm) is preferably 1.1 to 1.9. When the illuminance ratio is 1.1 or higher, excessive photoreaction will not occur, and electronic components can be heated and pressed under low temperature and low pressure conditions. When the illuminance ratio is 1.9 or lower, the photoreaction of the exposed part can be carried out effectively, and the process margin during development can be widened.

[0094] Examples of developing methods include: spraying developer onto the surface of a dried film while the substrate having the exposed photosensitive conductive paste dried film is left to stand or rotate; immersing the substrate having the exposed photosensitive conductive paste dried film in developer; and applying ultrasound while immersing the substrate having the exposed photosensitive conductive paste dried film in developer.

[0095] As the developer, an alkaline aqueous solution is preferred. Examples include 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. Two or more of these can be used. Additionally, depending on the situation, one or more of the following can be added to the above aqueous solution: polar solvents such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and γ-butyrolactone; alcohols such as methanol, ethanol, and isopropanol; esters such as ethyl lactate and propylene glycol monomethyl ether acetate; ketones such as cyclopentanone, cyclohexanone, isobutyl ketone, and methyl isobutyl ketone; and surfactants.

[0096] After development, a rinsing process based on a rinsing solution can be performed. Examples of rinsing solutions include water, or aqueous solutions of water containing alcohols such as ethanol and isopropanol, or esters such as ethyl lactate and propylene glycol monomethyl ether acetate.

[0097] Next, as Figure 1 As shown in (c), an electronic component 5 having an electrode 6 is heated and pressed onto a conductive bump 4.

[0098] In the process of heat-pressing electronic components with electrodes onto conductive bumps, the heating temperature is preferably 60°C to 250°C, more preferably 60°C to 160°C. By setting the heating temperature to 60°C or higher, it becomes easier to design a photosensitive conductive paste that increases the difference between the storage modulus G' of the conductive bump at room temperature and the storage modulus G' of the conductive bump during encapsulation. Furthermore, by setting the heating temperature to 250°C or lower, the thermal expansion and contraction of the printed circuit board and electronic components can be reduced, thereby further improving the positioning accuracy of the encapsulation.

[0099] As a heat-pressing method, heat-pressing tools for flip chip bonding, vacuum diaphragm laminators, etc., can be used. During heat-pressing, the pattern can be irradiated with ultrasonic waves. Irradiation with ultrasonic waves further improves the bonding strength between the conductive bumps and the cured films of each electrode. During heat-pressing, the pattern can be irradiated with a laser. Irradiation with a laser allows for the sintering of the conductive bumps in a short time, improving production efficiency. There are no particular limitations on the laser source; it can be appropriately selected based on the wavelength matched to the absorption band of the metal. Examples of laser source sources include solid-state lasers (ruby, glass, YAG, etc.), semiconductor lasers (GaAs, InGaAsP, etc.), liquid lasers (pigment lasers, etc.), and gas lasers (He-Ne, Ar, CO2, excimer lasers, etc.).

[0100] Examples of electronic components include LED chips, MiniLED chips, μLED chips, IC chips, LSI chips, resistor chips, capacitor chips, and other chip-type electronic components having at least one connection terminal. Printed circuit boards encapsulating μLEDs exhibit high brightness, energy efficiency, high response speed, and excellent display characteristics. Furthermore, it is preferable that the electrode surface of the electronic component having electrodes has an unevenness of 0.5 μm or more. By having an unevenness of 0.5 μm or more, the uneven portion is embedded in the conductive bump during encapsulation, resulting in high adhesion and improved bonding strength of the cured film.

[0101] One method for manufacturing a printed circuit board according to the present invention includes the following steps: forming a dried film of the conductive paste of the present invention on the surface of an electronic component having electrodes; exposing and developing the dried film to form conductive bumps on the electrodes of the electronic component having electrodes; and heating and pressing the electronic component having electrodes onto the conductive bumps.

[0102] Figure 2 A process diagram illustrating an example of a method for manufacturing a printed circuit board according to the present invention. First, as... Figure 2As shown in (a), a dried film 1 of the conductive paste of the present invention is formed on the surface of the electronic component 5 having electrodes where the electrodes 6 are located. The same method as described above can be used as a method for forming the dried film of the photosensitive conductive paste.

[0103] Next, as Figure 2 As shown in (b), the dried film 1 is exposed and developed to form conductive bumps 4 on the electrode 6 of the aforementioned electronic component 5 having electrode 6. The same method as described above can be used as a method for forming the conductive bumps.

[0104] Next, as Figure 2 As shown in (c), conductive bumps 4 are heat-pressed onto the electrodes 3 of the printed wiring board 2. The same method as described above can be used as a method for heat-pressing them.

[0105] Example

[0106] The present invention is illustrated in detail below with examples and comparative examples, but the invention is not limited to these.

[0107] The evaluation methods for each embodiment are described below.

[0108] <Methods for determining the storage modulus G'(P25) and G'(P100) of the dry film (1)>

[0109] The conductive pastes obtained in Examples 1 to 21 and Comparative Example 1 were coated onto a glass substrate with a film thickness of 1 mm after drying to a film thickness of 4 μm. The coated film was dried in a drying oven at 100°C for 10 minutes to form a dried film on the glass substrate. The storage modulus at 25°C and 100°C was measured using the following apparatus.

[0110] Measurement apparatus: Triboindenter TI950 (manufactured by Hysitron)

[0111] Measurement method: Nanoindentation

[0112] Determination mode: Continuous synthesis assay

[0113] Measurement frequency 100Hz

[0114] Indenter used: Sapphire triangular hammer indenter (Berkovich indenter)

[0115] Measurement temperatures: 25℃, 100℃.

[0116] <Methods for determining the storage modulus G'(E25) and G'(E100) of the film after exposure (2)>

[0117] The photosensitive conductive pastes obtained in Examples 3-21 and Comparative Example 1 were coated onto a glass substrate with a film thickness of 1 mm to a dried film thickness of 4 μm. The coated film was dried in a drying oven at 100°C for 10 minutes to obtain a dried film. The film was then further exposed at an exposure dose of 500 mJ / cm² (wavelength 365 nm). 2 Exposure is performed to form an exposure film on a glass substrate. The storage modulus at 25°C and 100°C is measured using the following apparatus.

[0118] Measurement apparatus: Triboindenter TI950 (manufactured by Hysitron)

[0119] Measurement method: Nanoindentation

[0120] Determination mode: Continuous synthesis assay

[0121] Measurement frequency 100Hz

[0122] Indenter used: Sapphire triangular hammer indenter (Berkovich indenter)

[0123] Measurement temperatures: 25℃, 100℃.

[0124] <Methods for determining the storage modulus G'(D100) of the film after development and the storage modulus G'(C25) after curing (3)>

[0125] Using a die-coating machine, the photosensitive conductive paste obtained in Examples 3-21 and Comparative Example 1 was applied to the release surface of a 75 μm thick PET film "Cerapeel (registered trademark)" (manufactured by Toray Industries, Inc.) with a dried film thickness of 50 μm. The coated film was dried in a drying oven at 100°C for 30 minutes to form a dried film on the PET film.

[0126] Then, using an exposure apparatus equipped with an ultra-high pressure mercury lamp (PEM-6M; manufactured by Union Optical Co., Ltd.), the entire surface of the dried film on the PET film was exposed at an i-line (wavelength 365nm) with an exposure dose of 500mJ / cm. 2 To expose it.

[0127] After exposure, the film was developed by spraying with a 0.1% by weight Na2CO3 aqueous solution for 30 seconds, followed by rinsing with ultrapure water. Then, the developed film was peeled off, and a circle with a diameter of 18 mm was cut out. The storage modulus G'(D100) of the developed film was measured using the following apparatus.

[0128] Similar to the method described above, the conductive pastes obtained in Examples 1-21 and Comparative Example 1 were applied to the release surface of a 75 μm thick PET film "Cerapeel" with a dried film thickness of 50 μm, and then dried, exposed, and developed. The developed film was then heated in a drying oven at 140°C for 30 minutes to form a cured film. The cured film was then peeled off, and a circle with a diameter of 18 mm was cut. The storage modulus G'(C25) of the cured film at 25°C was measured using the following apparatus.

[0129] Measuring apparatus: HAAKE MARSIII viscosity-viscoelasticity measuring apparatus (Thermo Fisher Scientific)

[0130] Measurement conditions: OSC temperature-dependent determination

[0131] Geometry: Parallel circular plate type (20mm)

[0132] Angular frequency: 1Hz

[0133] Angular velocity: 6.2832 rad / s

[0134] Temperature range: 25~150℃ (set to 25℃ for determining the storage modulus of the film after development) Heating rate: 0.08333℃ / second (set only for determining the storage modulus of the cured film)

[0135] Sample shape: Circular (18mm in diameter)

[0136] Sample thickness: 50 μm.

[0137] <Methods for Determining Chip Shear Strength>

[0138] Using screen printing, the conductive paste obtained in Examples 1-2 was coated onto a glass substrate with a dried film thickness of 3 μm. The coated film was then dried in a drying oven at 100°C for 10 minutes to form a dried film on the glass substrate.

[0139] Then, wafer chips obtained by slicing 0.7mm thick silicon wafers into 2mm squares are placed on a conductive film, encapsulated using a vacuum diaphragm laminator (MVLP500 / 600; manufactured by Meiki Prototype Co., Ltd.), and heated in a drying oven at 140°C for 30 minutes to obtain... Figure 3 The chip shear strength test sample is shown. The packaging conditions were set to a temperature of 120°C, a pressure of 1 MPa, and a pressure duration of 60 seconds. The chip shear strength was then measured using a chip shear strength tester (Dage series 4000; manufactured by Dage Corporation). The measurement was performed at 25°C and a shear rate of 200 μm / s.

[0140] The photosensitive conductive paste obtained in Examples 3-21 and Comparative Example 1 was screen-printed onto a glass substrate with a dried film thickness of 3 μm. The coated film was then dried in a drying oven at 100°C for 10 minutes to form a dried film on the glass substrate.

[0141] Then, using an exposure apparatus equipped with an ultra-high pressure mercury lamp (PEM-6M; manufactured by Union Optical Co., Ltd.), the entire surface of the dried film on the glass substrate was exposed at an exposure dose of 500 mJ / cm at an i-line (wavelength 365 nm). 2 To expose it.

[0142] After exposure, a 0.1% by weight Na2CO3 aqueous solution is sprayed for development for 30 seconds, followed by rinsing with ultrapure water to form a conductive film on the glass substrate.

[0143] Then, wafer chips obtained by slicing 0.7mm thick silicon wafers into 2mm squares are placed on a conductive film, encapsulated using a vacuum diaphragm laminator (MVLP500 / 600; manufactured by Meiki Prototype Co., Ltd.), and heated in a drying oven at 140°C for 30 minutes to obtain... Figure 3 The chip shear strength test sample is shown. The packaging conditions were set to a temperature of 120°C, a pressure of 1 MPa, and a pressure duration of 60 seconds. The chip shear strength was then measured using a chip shear strength tester (Dage series 4000; manufactured by Dage Corporation). The measurement was performed at 25°C and a shear rate of 200 μm / s.

[0144] Figure 3 This is a schematic diagram of the cross-section of a sample used for chip shear strength measurement. Figure 3 In this process, a wafer chip 10 is bonded to a conductive film 9 formed on a glass substrate 8.

[0145] <Method for determining the sealable temperature>

[0146] Using screen printing, the conductive pastes of Examples 1 and 2 were coated onto a glass substrate with a dried film thickness of 3 μm. The coated film was then dried in a drying oven at 100°C for 10 minutes to form a dried film on the glass substrate.

[0147] Then, wafer chips obtained by slicing 0.7mm thick silicon wafers into 2mm squares are placed on a dry film and packaged using a vacuum diaphragm laminator (MVLP500 / 600; manufactured by Meiki Prototype Co., Ltd.) to obtain... Figure 3The sample used for chip shear strength testing is shown. Regarding packaging conditions, the pressure was 1 MPa, the pressure time was 60 seconds, and the heating temperature was 70°C, 80°C, 90°C, 100°C, 110°C, and 120°C. The resulting substrate was heated in a drying oven at 140°C for 30 minutes, and the chip shear strength was measured using a chip shear strength measuring device (Dage series 4000; manufactured by Dage Corporation). The measurement was performed at 25°C and a shear rate of 200 μm / s. The chip shear strength value is 5 N / mm². 2 The minimum heating temperature mentioned above is used as the sealing temperature.

[0148] The photosensitive conductive paste obtained in Examples 3-21 and Comparative Example 1 was coated by screen printing with a film thickness of 3 μm after drying. The coated film was dried in a drying oven at 100°C for 10 minutes to form a dried film on a glass substrate.

[0149] Then, using an exposure apparatus equipped with an ultra-high pressure mercury lamp (PEM-6M; manufactured by Union Optical Co., Ltd.), the entire surface of the dried film on the glass substrate was exposed at an exposure dose of 500 mJ / cm at an i-line (wavelength 365 nm). 2 To expose it.

[0150] After exposure, a 0.1% by weight Na2CO3 aqueous solution is sprayed for development for 30 seconds, which facilitates rinsing with ultrapure water to form a post-development film on the glass substrate.

[0151] Then, the 0.7mm thick silicon wafers, cut into 2mm square wafer chips, are placed on the developed film and packaged using a vacuum diaphragm laminator (MVLP500 / 600; manufactured by Meiki Prototype Co., Ltd.) to obtain... Figure 3 The sample used for chip shear strength testing is shown. Regarding packaging conditions, the pressure was 1 MPa, the pressure time was 60 seconds, and the heating temperature was 70°C, 80°C, 90°C, 100°C, 110°C, and 120°C. The resulting substrate was heated in a drying oven at 140°C for 30 minutes, and the chip shear strength was measured using a chip shear strength measuring device (Dage series 4000; manufactured by Dage Corporation). The measurement was performed at 25°C and a shear rate of 200 μm / s. The chip shear strength value is 5 N / mm². 2 The minimum heating temperature mentioned above is used as the sealing temperature.

[0152] The materials used in the examples and comparative examples are described below.

[0153] [Photosensitive ingredient]

[0154] (Synthetic Example) Acrylic copolymer containing carboxyl groups with unsaturated double bonds (A)

[0155] 150 g of diethylene glycol monobutyl ether (hereinafter referred to as "DGME") was charged into a reaction vessel under a nitrogen atmosphere, and the temperature was raised to 80°C using an oil bath. A mixture containing 20 g of ethyl acrylate (hereinafter referred to as "EA"), 40 g of 2-ethylhexyl methacrylate (hereinafter referred to as "2-EHMA"), 20 g of n-butyl acrylate (hereinafter referred to as "BA"), 15 g of N-hydroxymethylacrylamide (hereinafter referred to as "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 further heated at 80°C for 6 hours to carry out the polymerization reaction. Then, 1 g of hydroquinone monomethyl ether was added to stop the polymerization reaction. Next, a mixture containing 5 g of glycidyl methacrylate (hereinafter referred to as "GMA"), 1 g of triethylbenzyl ammonium chloride, and 10 g of DGME was added dropwise over 0.5 hours. After the addition was completed, the mixture was heated for another 2 hours to carry out the addition reaction. The resulting reaction solution was purified with methanol to remove unreacted impurities, and then dried under vacuum for 24 hours to obtain an acrylic copolymer (A) containing carboxyl groups and unsaturated double bonds with a copolymerization ratio (mass basis) of EA / 2-EHMA / BA / GMA / AA = 20 / 40 / 20 / 5 / 15.

[0156] [Carboxyl-containing resins that do not possess photopolymerizable groups]

[0157] ·JONCRYL 67 (manufactured by BASF JAPAN Co., Ltd.)

[0158] ·JONCRYL 678 (manufactured by BASF JAPAN Co., Ltd.)

[0159] ·JONCRYL 611 (manufactured by BASF JAPAN Co., Ltd.)

[0160] ·JONCRYL 693 (manufactured by BASF JAPAN Co., Ltd.)

[0161] ·JONCRYL 682 (manufactured by BASF JAPAN Co., Ltd.)

[0162] ·JONCRYL 819 (manufactured by BASF JAPAN Co., Ltd.)

[0163] ·JONCRYL JDX-C3000A (manufactured by BASF JAPAN Co., Ltd.)

[0164] ·JONCRYL JDX-C3080 (manufactured by BASF JAPAN Co., Ltd.).

[0165] [Photopolymerization initiator]

[0166] • “IRGACURE” OXE04 (manufactured by BASF JAPAN Co., Ltd.) (hereinafter referred to as OXE04).

[0167] [Compounds containing unsaturated double bonds]

[0168] • "Light acrylate (registered trademark)" BP-4EA (manufactured by Kyoei Chemical Co., Ltd.) (hereinafter referred to as BP-4EA).

[0169] [Conductive particles]

[0170] • Ag particles with a diameter (D50) of 0.7 μm and an aspect ratio of 1.1 (hereinafter referred to as Ag particles)

[0171] • Resin-core Ag-coated particles with a particle size (D50) of 0.7 μm and an aspect ratio of 1.1 (average particle size of resin core particles is 0.65 μm).

[0172] [Epoxy Resin]

[0173] • "EPICLON (registered trademark)" 840 (manufactured by DIC Co., Ltd.) (hereinafter referred to as "840"), epoxy equivalent 185g / eq, liquid

[0174] • "EPICLON" HP-7200L (manufactured by DIC Corporation) (hereinafter referred to as HP-7200L), epoxy equivalent 250g / eq, softening point 55℃.

[0175] [Novolac type phenolic resin]

[0176] • Standard type H-4 (manufactured by Meiwa Kasei Corporation) (hereinafter referred to as H-4), hydroxyl equivalent 105 g / eq, softening point 72℃

[0177] • High heat resistance and high rigidity MEH-7600-4H (manufactured by Meiwa Kasei Corporation) (hereinafter referred to as MEH-7600), hydroxyl equivalent 100g / eq, softening point 155℃.

[0178] [Curing Accelerator]

[0179] • "Curezol (registered trademark)" C11Z-A (Shikoku Chemical Co., Ltd.) (hereinafter referred to as C11Z-A).

[0180] (Example 1)

[0181] Add 15g of "840", 8.51g of H-4, 5g of JONCRYL 67 and 6g of DGME to a 100mL clean bottle, and mix using an "Awatori Rentaro (registered trademark)" ARE-310 (manufactured by Thinky Co., Ltd.) to obtain 34.51g of resin solution.

[0182] The obtained 34.51 g of resin solution was mixed with 66.52 g of Ag particles and kneaded using a three-roll mill (EXAKT M-50; manufactured by EXAKT Corporation) to obtain 101.03 g of conductive paste. The composition of the conductive paste is shown in Table 1.

[0183] Using the obtained conductive paste, the energy storage modulus G', encapsulation temperature, and chip shear strength were evaluated using the methods described above. The evaluation results are shown in Table 2.

[0184] (Example 2)

[0185] Add 15g of "840", 8.51g of H-4, 5g of JONCRYL 67, 1.18g of C11Z-A, and 6g of DGME to a 100mL clean bottle, and mix using an "Awatori Rentaro (registered trademark)" ARE-310 (manufactured by Thinky Co., Ltd.) to obtain 35.69g of resin solution.

[0186] The obtained 35.69 g of resin solution was mixed with 69.28 g of Ag particles and kneaded using a three-roll mill (EXAKT M-50; manufactured by EXAKT Corporation) to obtain 104.97 g of conductive paste. The composition of the conductive paste is shown in Table 1.

[0187] Using the obtained conductive paste, the energy storage modulus G', encapsulation temperature, and chip shear strength were evaluated using the methods described above. The evaluation results are shown in Table 2.

[0188] (Example 3)

[0189] 13.59 g of an acrylic copolymer (A) containing carboxyl groups with unsaturated double bonds, 4.08 g of JONCRYL 67, 0.60 g of OXE04, 2.00 g of BP-4EA, and 5.66 g of DGME were added to a 100 mL clean bottle and mixed using an Awatori Rentaro ARE-310 (manufactured by Thinky Co., Ltd.) to obtain a resin solution of 25.93 g.

[0190] The obtained 25.93g resin solution was mixed with 60.46g Ag particles and kneaded using a three-roll mill to obtain 86.39g of photosensitive conductive paste. Table 1 shows the composition of the photosensitive conductive paste.

[0191] Using the obtained photosensitive conductive paste, the storage modulus G', encapsulation temperature, and chip shear strength were evaluated using the methods described above. The evaluation results are shown in Table 2.

[0192] (Examples 4-10)

[0193] The photosensitive conductive paste with the composition shown in Table 1 was prepared using the same method as in Example 1, and evaluated in the same manner as in Example 3. The evaluation results are shown in Table 2.

[0194] (Example 11)

[0195] 13.59 g of an acrylic copolymer (A) containing carboxyl groups with unsaturated double bonds, 0.68 g of JONCRYL 819, 0.60 g of OXE04, 2.00 g of BP-4EA, and 4.93 g of DGME were added to a 100 mL clean bottle and mixed using an Awatori Rentaro ARE-310 (manufactured by Thinky Co., Ltd.) to obtain a resin solution of 21.80 g.

[0196] The obtained 21.80 g of resin solution was mixed with 50.79 g of Ag particles and kneaded using a three-roll mill (EXAKT M-50; manufactured by EXAKT Corporation) to obtain 72.59 g of photosensitive conductive paste. The obtained photosensitive conductive paste was evaluated in the same manner as in Example 3. The evaluation results are shown in Table 2.

[0197] (Example 12)

[0198] 13.59 g of an acrylic copolymer (A) containing carboxyl groups with unsaturated double bonds, 2.04 g of JONCRYL 819, 0.60 g of OXE04, 2.00 g of BP-4EA, and 5.23 g of DGME were added to a 100 mL clean bottle and mixed using an Awatori Rentaro ARE-310 (manufactured by Thinky Co., Ltd.) to obtain a resin solution of 23.46 g.

[0199] The obtained 23.46 g of resin solution was mixed with 54.73 g of Ag particles and kneaded using a three-roll mill (EXAKT M-50; manufactured by EXAKT Corporation) to obtain 78.18 g of photosensitive conductive paste. The obtained photosensitive conductive paste was evaluated in the same manner as in Example 3. The evaluation results are shown in Table 2.

[0200] (Example 13)

[0201] 13.59 g of an acrylic copolymer (A) containing carboxyl groups with unsaturated double bonds, 4.08 g of JONCRYL 819, 0.60 g of OXE04, 2.00 g of BP-4EA, and 5.66 g of diethylene glycol monobutyl ether acetate (solubility in 100 g of water at 20°C is 6.5 g) were added to a 100 mL clean bottle and mixed using an Awatori Rentaro ARE-310 (manufactured by Thinky Co., Ltd.) to obtain a resin solution of 25.93 g.

[0202] The obtained 25.93 g of resin solution was mixed with 60.46 g of Ag particles and kneaded using a three-roll mill (EXAKT M-50; manufactured by EXAKT Corporation) to obtain 86.39 g of photosensitive conductive paste. The obtained photosensitive conductive paste was evaluated in the same manner as in Example 3. The evaluation results are shown in Table 2.

[0203] (Example 14)

[0204] Using an optical filter, an exposure dose of 500 mJ / cm² was achieved at the i-line (wavelength 365 nm). 2 The exposure dose for the h-line (wavelength 405nm) during exposure was 2000 mJ / cm². 2 The exposure conditions of Example 13 were adjusted in the same manner as in Example 3, and the evaluation was performed accordingly. The evaluation results are shown in Table 2. By adjusting the spectral characteristics as described above, the exposure section can perform photoreaction appropriately, the storage modulus G'(D100) of the developed film can be suppressed to a low level, the encapsulation performance can be improved, and the encapsulation temperature can be reduced.

[0205] (Example 15)

[0206] Add 15.00g of an acrylic copolymer (A) containing carboxyl groups with unsaturated double bonds, 0.66g of OXE04, 3.82g of "840", 2.17g of H-4, and 1.53g of DGME to a 100ml clean bottle, and mix using an Awatori Rentaro ARE-310 (manufactured by Thinky Co., Ltd.) to obtain a resin solution of 23.18g.

[0207] The obtained 23.18 g of resin solution was mixed with 50.52 g of Ag particles with a particle size (D50) of 0.7 μm and an aspect ratio of 1.1, and the mixture was kneaded using a three-roll mill (EXAKT M-50; manufactured by EXAKT Corporation) to obtain 73.70 g of photosensitive conductive paste. The obtained photosensitive conductive paste was evaluated in the same manner as in Example 3. The evaluation results are shown in Table 2.

[0208] (Examples 16-21)

[0209] The photosensitive conductive paste with the composition shown in Table 1 was prepared using the same method as in Example 1, and evaluated in the same manner as in Example 3. The evaluation results are shown in Table 2.

[0210] (Comparative Example 1)

[0211] 13.59 g of an acrylic copolymer (A) containing carboxyl groups with unsaturated double bonds, 0.60 g of OXE04, 2.00 g of BP-4EA, and 4.78 g of DGME were added to a 100 mL clean bottle and mixed using an Awatori Rentaro ARE-310 (manufactured by Thinky Co., Ltd.) to obtain a resin solution of 20.96 g.

[0212] The obtained 20.96 g of resin solution was mixed with 48.97 g of Ag particles with a particle size (D50) of 0.7 μm and an aspect ratio of 1.1, and the mixture was kneaded using a three-roll mill (EXAKT M-50; manufactured by EXAKT Corporation) to obtain 69.93 g of photosensitive conductive paste. The obtained photosensitive conductive paste was evaluated in the same manner as in Example 3. The evaluation results are shown in Table 2.

[0213] [Table 1-1]

[0214]

[0215] [Table 1-2]

[0216]

[0217] *1 is a part by weight relative to 100 parts by weight of a carboxyl-containing resin having photopolymerizable groups. For Examples 1 and 2, it is a part by weight relative to 100 parts by weight of a carboxyl-containing resin not having photopolymerizable groups.

[0218] *2% by weight of solid components

[0219] *3% by weight of the paste composition

[0220] *4 parts by weight relative to 100 parts by weight of epoxy resin

[0221] [Table 2]

[0222]

[0223] The storage modulus G'(P100) of the dried films in Examples 1-21 at 100°C was all below 0.01 MPa. The adhesion between the conductive film and the wafer chip during heat pressing was improved, and the bonding strength of the cured film was also improved. As a result, the chip shear strength was good, at 6.0 N / mm². 2 That's all. In Example 10, a carboxyl-containing resin without photopolymerizable groups was used, and a material with a high glass transition temperature was used. Although this resulted in a decrease in the chip shear strength, it was within acceptable limits.

[0224] In Examples 3-21, the G'(D100) of the developed films was less than 0.01 MPa. The adhesion between the conductive film and the wafer chip during heat pressing was improved, and the bonding strength of the cured film was also improved. As a result, the chip shear strength was good, at 6.0 N / mm². 2 above.

[0225] In Comparative Example 1, G'(D100) was not less than 0.01 MPa, resulting in poor adhesion between the conductive film and the wafer chip. Consequently, compared with Examples 3 to 21, the chip shear strength decreased significantly.

[0226] Explanation of reference numerals in the attached figures

[0227] 1: Dry film of conductive paste

[0228] 2: Printed wiring board

[0229] 3: Electrodes of printed wiring boards

[0230] 4: Conductive bumps

[0231] 5: Electronic components

[0232] 6: Electrodes of electronic components

[0233] 7: Printed Circuit Board

[0234] 8: Glass substrate

[0235] 9: Conductive film

[0236] 10: Chip

Claims

1. A conductive paste containing organic components and conductive particles, wherein the storage modulus G'(P100) of the dried film of the conductive paste at 100°C is less than 0.01 MPa, and the storage modulus G'(C25) at 25°C after heating at 140°C for 30 minutes is greater than 0.01 MPa. The dried film of the conductive paste was exposed to an i-line at a wavelength of 365 nm with an exposure dose of 500 mJ / cm. 2 The storage modulus G'(E100) of the exposed film at 100°C is less than 1 / 10 of the storage modulus G'(E25) at 25°C. The conductive paste contains an acrylic copolymer (A) with unsaturated double bonds and containing carboxyl groups as a photosensitive component, and also contains monomers with unsaturated double bonds.

2. A conductive paste containing organic components and conductive particles, wherein the storage modulus G'(P100) of the dried film of the conductive paste at 100°C is less than 0.01 MPa, and the storage modulus G'(C25) at 25°C after heating at 140°C for 30 minutes is greater than 0.01 MPa. The dried film of the conductive paste was exposed to an i-line at a wavelength of 365 nm with an exposure dose of 500 mJ / cm. 2 The storage modulus G'(E100) of the exposed film at 100°C is less than 1 / 10 of the storage modulus G'(E25) at 25°C. The conductive paste contains a carboxyl-containing resin with a glass transition temperature below 110°C and no photopolymerizable groups.

3. The conductive paste as described in claim 1 or 2, wherein, The storage modulus G' (P25) of the dried film of the conductive paste at 25°C is above 0.1 MPa.

4. The conductive paste as described in claim 1 or 2, wherein, The storage modulus G' (P100) of the dried film of the conductive paste at 100°C is 0.00001 to 0.01 MPa, the storage modulus G' (P25) at 25°C is 0.1 MPa to 50000 MPa, and the storage modulus G' (C25) at 25°C after heating at 140°C for 30 minutes is 0.01 MPa to 100000 MPa.

5. The conductive paste as described in claim 1 or 2, wherein, The organic components include carboxyl-containing polymers, photopolymerization initiators, epoxy resins, and Novolac-type phenolic resins.

6. The conductive paste as described in claim 5, wherein it contains an epoxy resin curing accelerator.

7. The conductive paste according to claim 1 or 2, wherein, The storage modulus G' (P100) of the dried film of the conductive paste at 100°C is less than 1 / 10 of the storage modulus G' (P25) at 25°C.

8. The conductive paste as described in claim 1 or 2, wherein, The organic component is a photosensitive component. The conductive paste is dried at 100°C for 30 minutes, and the resulting dried film is exposed to an i-line at a wavelength of 365 nm with an exposure dose of 500 mJ / cm. 2 After exposure and development by spraying with a 0.1% sodium carbonate aqueous solution for 30 seconds, the storage modulus G' (D100) of the film at 100°C is less than 0.01 MPa. After heating the developed film at 140°C for 30 minutes, the storage modulus G' (C25) at 25°C is greater than 0.01 MPa.

9. The conductive paste of claim 8, wherein a carboxyl-containing resin having photopolymerizable groups is used as the photosensitive component.

10. A printed wiring board comprising a film after exposure and development of a dried film of the conductive paste according to any one of claims 1 to 9.

11. A method for manufacturing a printed wiring board with conductive bumps, comprising: The process of forming a dried film of the conductive paste according to any one of claims 1 to 9 on a printed wiring board; and The process of exposing and developing the dried film to form conductive bumps on the electrodes of the printed wiring board. in, The illuminance ratio of the exposure light during the exposure (illuminance of the exposure light at a wavelength of 365 nm) to (illuminance of the exposure light at a wavelength of 405 nm) is 1:1 to 1:

9.

12. A method for manufacturing printed circuit boards, which has the following characteristics: The process of forming a dried film of the conductive paste according to any one of claims 1 to 9 on a printed wiring board; The process of exposing and developing the dried film to form conductive bumps on the electrodes of the printed wiring board; and The process of heating and pressing an electronic component with electrodes onto the conductive bump.

13. A method for manufacturing printed circuit boards, which has the following characteristics: The process of forming a dried film of the conductive paste according to any one of claims 1 to 9 on the surface where the electrodes are present in an electronic component having electrodes; The process of exposing and developing the dried film to form conductive bumps on the electrodes of the electronic component having electrodes; and The process of heating and pressing a printed wiring board onto the conductive bumps.

14. The method for manufacturing a printed circuit board as described in claim 12 or 13, wherein, The electrode surface of the electronic component having electrodes has an unevenness of 0.5 μm or more.

15. The method of manufacturing a printed circuit board as described in claim 12 or 13, wherein, The electronic component with electrodes is a μLED.

Images