Paste for electromagnetic wave shield, cured product, and electronic component

Abstract

To provide a paste for electromagnetic wave shield which is excellent in coating property by a jet dispense method and has good filling property into a local region, and prevents separation of conductive particles after filling, a cured product of a paste for electromagnetic wave shield, and an electronic component including the cured product.SOLUTION: A paste for an electromagnetic wave shield contains (A) conductive particles, (B) an epoxy resin, and (C) a curing agent, and has viscosity measured under the condition of 25°C and 10 rpm by an E type viscometer of 50 Pa s or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an electromagnetic wave shielding paste, a cured product of the electromagnetic wave shielding paste, and an electronic component including the cured product. [Background technology]

[0002] With the spread of wireless devices, the amount and speed of communication in electronic devices is increasing dramatically. At the same time, electronic devices are becoming smaller and more highly integrated, and the distances between electronic components such as packages containing semiconductor ICs, baseband components, RF (Radio Frequency) components, wireless components, analog devices, and power management components are becoming shorter.

[0003] As a result, the problem of electromagnetic interference (EMI) between electronic components has become prominent, and measures to combat this problem are required. Conventional technologies have also taken measures against EMI, such as a method of removing signals that become noise by inserting an EMI suppression filter, a method of attaching an electromagnetic wave absorbing sheet to the outside (e.g., Patent Document 1), and a method of shielding electromagnetic waves by covering with a metal case.

[0004] However, these methods are difficult to apply to small electronic devices that have limitations on mounting area and weight, and in particular cannot be inserted into structures in which electronic components are in close proximity to each other, such as system-on-chip (SoC), system-in-package (SiP), and multi-chip module (MCM).

[0005] To solve this problem, a method is being considered for preventing EMI by creating trench structures such as gaps or grooves in packages or substrates on which electronic components are mounted and molded, and filling and hardening a conductive paste therein (for example, Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6461416 specification [Patent Document 2] International Publication No. 2021 / 075265 Summary of the Invention [Problem to be solved by the invention]

[0007] However, with a conventional conductive paste such as that described in Patent Document 2, there are cases where the conductive particles and the resin component contained in the conductive paste are separated when the conductive paste is filled into a trench. The present invention has been made in view of the above, and aims to provide an electromagnetic shielding paste that has excellent coatability, particularly when used by a jet dispensing method, is easy to fill into localized areas, particularly gaps and grooves, and is less likely to cause separation between the conductive particles and the resin in the paste after filling. It also aims to provide a cured product of the electromagnetic shielding paste, and an electronic component that includes the cured product. [Means for solving the problem]

[0008] As a result of extensive research, the inventors have discovered that the above-mentioned problems can be solved by setting the viscosity of an electromagnetic shielding paste containing conductive particles, an epoxy resin, and a curing agent within a specific range, and have thus completed the present invention.

[0009] The means for solving the above problems are as follows, and the present invention includes the following aspects. [1] (A) as a component, conductive particles; (B) an epoxy resin, and (C) Component: a hardener Including, The viscosity measured with an E-type viscometer at 25°C and 10 rpm is 50 Pa s or less. Paste for electromagnetic wave shielding. [2] The electromagnetic wave shielding paste according to [1], wherein the component (A) contains conductive particles having an average particle size (D50) of 0.01 to 10 μm. [3] The electromagnetic wave shielding paste according to [1] or [2], wherein the component (A) contains conductive particles treated with a hydrophilic surface treatment agent. [4] The electromagnetic shielding paste according to any one of [1] to [3], wherein the component (B) contains an epoxy resin having an aliphatic skeleton. [5] The electromagnetic shielding paste according to any one of [1] to [4], wherein the component (B) contains an epoxy resin having a viscosity of 50 Pa.s or less as measured with an HBT viscometer under conditions of 25°C and 50 rpm. [6] The paste for electromagnetic shielding according to any one of [1] to [5], wherein the content of the component (B) is 1 to 30 parts by mass per 100 parts by mass of the component (A). [7] The electromagnetic wave shielding paste according to any one of [1] to [6], wherein the component (C) contains a phenol-based resin. [8] The electromagnetic shielding paste according to any one of [1] to [7], which does not substantially contain a solvent or a diluent. [9] The electromagnetic shielding paste according to any one of [1] to [8], having a thixotropic index value, which is the viscosity at a rotation speed of 1 rpm / the viscosity at a rotation speed of 10 rpm, measured at 25°C using an E-type viscometer, of 10 or less.

[10] The electromagnetic shielding paste according to any one of [1] to [9], which is a jet-dispense type electromagnetic shielding paste.

[11] A cured product of the electromagnetic shielding paste according to any one of [1] to

[10] .

[12] An electronic part comprising the cured product according to

[11] . Effect of the Invention

[0010] According to the present invention, it is possible to provide an electromagnetic wave shielding paste which has excellent coatability, particularly when applied by a jet dispensing method, and in which separation of conductive particles is unlikely to occur after filling, a cured product of the electromagnetic wave shielding paste, and an electronic component including the cured product. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the electromagnetic shielding paste according to the present disclosure will be described based on the embodiments. However, the embodiments shown below are merely examples for embodying the technical idea of ​​the present invention, and the present invention is not limited to the electromagnetic shielding paste described below.

[0012] [Electromagnetic wave shielding paste] The electromagnetic wave shielding paste according to an embodiment of the present invention contains (A) conductive particles, (B) an epoxy resin, and (C) a curing agent, and has a viscosity of 50 Pa s or less when measured using an E-type viscometer at 25°C and 10 rpm.

[0013] It is not clear why the electromagnetic shielding paste according to the embodiment of the present invention has excellent coatability when used in a jet dispensing method (meaning the ability to be ejected from a jet dispenser, hereinafter also referred to as jet dispensability), is easy to fill into localized areas, and is less likely to cause separation of the conductive particles after filling; however, the inventors speculate as follows. The electromagnetic shielding paste according to the embodiment of the present invention has a low viscosity of 50 Pa·s or less. Therefore, it has excellent dischargeability from a dispense nozzle and can be suitably used for application using a jet dispense method. In addition, it has good filling properties in localized areas without voids being generated. It is believed that by using an epoxy resin as the resin in the electromagnetic shielding paste, it is possible to reduce the repulsive force that occurs between the resin and the substrate to which the electromagnetic shielding paste is applied. In particular, it is believed that the above-mentioned repulsive force reduction effect can be obtained when applying or filling gaps, grooves, etc. provided in the substrate, and as a result, it is possible to suppress separation of the conductive particles and the resin in the electromagnetic shielding paste after filling.

[0014] As a method for applying the electromagnetic wave shielding paste, various methods can be used as described below, but since the electromagnetic wave shielding paste according to the embodiment of the present invention has particularly excellent jet dispensability, it is preferable that the paste be a jet-dispense type electromagnetic wave shielding paste. The electromagnetic shielding paste according to the embodiment of the present invention is preferably used as an electromagnetic shielding paste for filling a localized region, particularly a gap or groove formed in a substrate, by a jet dispensing method. Jet dispensing is a method of applying a paste in a line or spot shape by applying pressure from a nozzle to eject the paste, and a known jet dispensing device can be used.

[0015] (viscosity) The electromagnetic wave shielding paste according to the embodiment of the present invention has a viscosity of 50 Pa s or less at 25° C. and 10 rpm as measured with an E-type viscometer. By setting the viscosity to 50 Pa s or less, excellent jet dispenseability and good filling properties into localized areas are achieved. The viscosity is preferably 25 Pa s or less, more preferably 15 Pa s or less, and even more preferably 10 Pa s or less. There is no particular lower limit, but from the viewpoint of suppressing scattering of droplets during jet dispensing, for example, a viscosity of 0.5 Pa s or more is preferable. The viscosity is preferably in the range of 0.5 to 25 Pa·s, more preferably in the range of 0.5 to 15 Pa·s, and even more preferably in the range of 0.5 to 10 Pa·s. By setting the viscosity in this range, excellent jet dispensability and good filling properties into localized areas can be achieved.

[0016] (Thixotropic index value) The electromagnetic wave shielding paste according to the embodiment of the present invention preferably has a thixotropic index (TI), which is the viscosity at a rotation speed of 1 rpm / the viscosity at a rotation speed of 10 rpm, measured with an E-type viscometer at 25° C., of no more than 10. By making the TI no more than 10, it is possible to further improve the jet dispensability and the ability to fill local areas such as gaps and grooves. The TI is preferably 10 or less, more preferably 5.0 or less, further preferably 3.5 or less, and particularly preferably 2.0 or less. The lower limit is preferably 1.0 or more, for example, from the viewpoint of suppressing scattering of droplets during jet dispensing. Furthermore, TI is preferably within the range of 1.0 to 10, more preferably within the range of 1.0 to 5.0, even more preferably within the range of 1.0 to 3.5, and particularly preferably within the range of 1.0 to 2.0. By setting it within this range, excellent jet dispensability and good filling properties in localized areas are achieved.

[0017] <(A) Component (conductive particles)> The electromagnetic wave shielding paste according to the embodiment of the present invention contains conductive particles as component (A). The conductive particles are blended to shield electromagnetic waves. The conductive particles (hereinafter sometimes referred to as "component (A)" or "conductive particles (A)") are not particularly limited, but conductive metal particles, carbon particles, and other particles can be used.

[0018] The types of metals in the metal particles include silver (Ag), gold (Au), copper (Cu), nickel (Ni), palladium (Pd), platinum (Pt), tin (Sn), and alloys thereof. Of these, silver or copper is preferred, and silver is more preferred from the viewpoint of shielding electromagnetic waves.

[0019] Examples of types of carbon particles include carbon black, ketjen black, acetylene black, carbon nanotubes, graphene, graphite, fullerenes, etc., with graphene being preferred. Graphene is a material made of pure carbon with atoms arranged in a hexagonal pattern in closely packed, one-atom-thick sheets. When the conductive resin composition contains carbon particles, the toughness of the electromagnetic shielding layer can be improved when the conductive resin composition is applied to an object to form an electromagnetic shielding layer. Commercially available carbon particles include graphite (flake graphite) (product name: CX3000) manufactured by Chuetsu Graphite Industries Co., Ltd., graphene powder (grade: XGnP-R10) manufactured by XG Science Inc., and graphene (product name: GNH-XA) manufactured by Graphene Platform Inc.

[0020] In the conductive resin composition according to the embodiment of the present invention, the conductive particles (A) may include particles in which non-conductive particles such as the carbon particles are coated with the metals described above, particles in which magnetic metal particles such as nickel are coated with non-magnetic metals such as silver and copper, etc. The conductive particles (A) may be a composite in which an organic material such as a resin or an inorganic material other than a metal is used as a core and coated with the metal component described above, or the metal component described above may be surface-treated with a surface treatment agent.

[0021] In an embodiment of the present invention, the (A) conductive particles preferably contain metal particles such as silver particles or silver-containing alloy particles, and more preferably contain silver particles. This is because silver has a higher electrical conductivity than other metals. By containing silver particles as the (A) conductive particles, a conductive resin composition that exhibits a higher electromagnetic wave shielding effect can be obtained.

[0022] The conductive particles used in the embodiment of the present invention preferably include conductive particles treated with a hydrophilic surface treatment agent. By treating the surfaces of the conductive particles with a hydrophilic surface treatment agent, the viscosity and thixotropy of the electromagnetic shielding paste can be reduced, and the jet dispensability and filling ability into localized areas can be improved.

[0023] In this specification, a surface treatment agent being hydrophilic means either a surface treatment agent having a hydrophilic group in the molecule, or a surface treatment agent that is hydrophobic but has a hydrophilic structure introduced therein by an amine salt or the like.

[0024] Examples of the hydrophilic group include an amino group, a hydroxyl group, a carboxyl group, a sulfo group, a carbamoyl group, and a sulfamoyl group. Among these, an amino group, a hydroxyl group, and a carboxyl group are preferred.

[0025] Examples of surface treatment agents having a hydrophilic group in the molecule include fatty acids, fatty acid salts, azole compounds, and derivatives thereof. Examples of fatty acids include oleic acid, stearic acid, ricinoleic acid, linoleic acid, linolenic acid, aloeuric acid, lauric acid, palmitic acid, and hydroxystearic acid. Examples of fatty acid salts include salts formed between fatty acids and metals such as lithium, sodium, and potassium. Examples of the azole compounds include imidazole, oxazole, thiazole, benzimidazole, and benzotriazole.

[0026] Examples of surface treatment agents having a hydrophilic structure introduced by an amine salt or the like include polycarboxylate alkylamine salts, which are obtained by adding an amine salt such as an alkylamine to a carboxylic acid to introduce a hydrophilic structure.

[0027] Among the above-mentioned hydrophilic surface treatment agents, a surface treatment agent having a hydrophilic group in the molecule is preferred, and fatty acids and fatty acid salts, azole compounds and derivatives thereof are preferred, and it is preferable that the surface treatment agent contains at least one selected from the group consisting of oleic acid, ricinoleic acid, linoleic acid, linolenic acid, benzotriazole, aryl acid, and hydroxystearic acid. The surface treatment agents may be used alone or in combination of two or more kinds.

[0028] The amount of the surface treatment agent is not particularly limited, but it is preferable to set it so that the igloss value (loss on ignition) of the conductive particles falls within the preferred range described below.

[0029] As the conductive particles, commercially available products can be used. As the surface-treated silver filler, for example, oleic acid surface-treated silver filler (product name: FA-SNA-253, AG 2 1C, AG 4 1F, all manufactured by DOWA HOLDINGS CO., LTD.), ricinoleic acid / benzotriazole surface-treated silver filler (product name: AG 2 98J, manufactured by DOWA HOLDINGS CO., LTD.), benzotriazole surface-treated silver filler (product name: AG 3 11F, manufactured by DOWA HOLDINGS CO., LTD.), etc. can be used.

[0030] The conductive particles may be used alone or in combination of two or more kinds.

[0031] (shape) The (A) conductive particles may be spherical, elliptical, needle-like, flake-like, irregular, or other shapes, but from the viewpoint of jet dispensability, spherical shapes are preferred.

[0032] (particle size) (A) The size of the conductive particles can be measured by observing with a scanning electron microscope (SEM), and the average value can be calculated by measuring 50 particles randomly from the SEM image. When the particles are spherical, the average value is taken as the average particle size, and when the particles are needle-shaped, oval-spherical, flake-shaped, or irregular, the average value of the major axis is taken as the average particle size.

[0033] The (A) conductive particles preferably include conductive particles having a spherical shape. In this case, the (A) conductive particles preferably include conductive particles having an average particle size (D50) preferably in the range of 0.01 μm to 10 μm. The (A) conductive particles preferably include conductive particles having an average particle size (D50) more preferably in the range of 0.1 μm to 5 μm, and even more preferably in the range of 0.5 μm to 3 μm. By having the average particle size of the conductive particles in this range, it becomes easier to obtain an electromagnetic shielding paste that is reduced in viscosity, has excellent jet dispensability, and has good filling properties in local areas, and also contributes to reducing peeling. The (A) conductive particles are preferably composed only of conductive particles having a size in the range of 0.01 μm to 10 μm. When the conductive particles are acicular, elliptical, flake-like, or amorphous in shape, the average particle size (average major axis size) is 0.01 μm or more and 10 μm or less, and the aspect ratio is preferably in the range of 5 or more and 200 or less, and more preferably in the range of 10 or more and 150 or less.

[0034] That is, the conductive particles preferably have an average particle size of 0.01 to 10 μm. When the (A) conductive particles have an average particle size (D50) in the range of 0.01 μm to 10 μm or an average particle size (major axis average value) in the range of 0.01 μm to 10 μm, the (A) conductive particles have good dispersibility in the electromagnetic shielding paste, good jet dispenseability, and can be sufficiently filled into narrow gaps or grooves.

[0035] (BET specific surface area) The surface area per unit mass of the conductive particles measured by the BET method (BET specific surface area) is 0.35 m 2 / g or more, and 0.4m 2 / g or more is more preferable, and 0.5m 2 It is particularly preferable that the viscosity is 2.5m / g or more. 2 / g or less, and 1.2m 2 / g or less is more preferable, and 0.8m 2 It is particularly preferable that the molecular weight is not more than 1 / g. The surface area per mass of the conductive particles measured by the BET method (BET specific surface area) is preferably within the range of 0.35 to 2.5, more preferably within the range of 0.4 to 1.2, and particularly preferably within the range of 0.5 to 0.8. By setting it within the above range, the viscosity can be reduced and the jet dispensability can be improved.

[0036] (Tap density) The tap density of the conductive particles is preferably 2.0 g / ml or more, more preferably 3.0 g / ml or more, and is preferably 4.0 g / ml or less, more preferably 6.0 g / ml or less, even more preferably 5.5 g / ml or less, and particularly preferably 5.0 g / ml or less. That is, the tap density of the conductive particles is preferably 2.0 to 6.0 g / ml, more preferably 3.0 to 5.5 g / ml, and particularly preferably 4.0 to 5.0 g / ml. By setting the tap density within the above range, the specific resistance value can be reduced.

[0037] (Igross value) The ignition loss value (loss on ignition) of the conductive particles is preferably 0.1% or more, more preferably 0.2% or more, and more preferably 0.3% or more, and is preferably 1.2% or less, more preferably 1.0% or less, and particularly preferably 0.9% or less. That is, the ignition loss (ignition loss) of the conductive particles is preferably 0.1 to 1.2%, more preferably 0.2 to 1.0%, and particularly preferably 0.3 to 0.9%. By setting the ignition loss within the above range, the TI of the electromagnetic shielding paste is low, and it becomes easier to obtain an electromagnetic shielding paste that has good jet dispensability and can be sufficiently filled into narrow gaps or grooves.

[0038] The content of the conductive particles (A) relative to the total amount of the paste for electromagnetic shielding is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more, from the viewpoint of resistivity and electromagnetic shielding property, and the upper limit is preferably 99% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less, from the viewpoint of adhesion. That is, the content of the (A) conductive particles relative to the total amount of the magnetic wave shielding paste is preferably 70 to 99 mass %, more preferably 80 to 95 mass %, and particularly preferably 85 to 90 mass %.

[0039] <Component (B) (epoxy resin)> The electromagnetic wave shielding paste according to an embodiment of the present invention contains an epoxy resin as component (B) (hereinafter, may be referred to as "component (B)", "(B) resin" or "(B) epoxy resin"). (B) Epoxy resins that can be used include cresol novolac type epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, aminophenol type epoxy resins, aromatic amine type epoxy resins, naphthalene type epoxy resins, hydrogenated bisphenol type epoxy resins, alicyclic epoxy resins, alcohol ether type epoxy resins, cyclic aliphatic epoxy resins, fluorene type epoxy resins, and siloxane type epoxy resins, and two or more of these may be mixed together.

[0040] As the (B) epoxy resin, there may be used one which contains a flexible skeleton, such as a polyethylene glycol skeleton, a polypropylene glycol skeleton, a polyether skeleton, a urethane skeleton, a polybutadiene skeleton, or a nitrile rubber skeleton, in a part of the molecule.

[0041] More specifically, the epoxy resin having a flexible skeleton may be an "epoxy resin compound in which an aromatic dihydroxy compound and a polyalkylene glycol are bonded and have an epoxy group at the terminal," which is obtained by reacting an aromatic dihydroxy compound such as bisphenol A with an alkylene oxide such as ethylene oxide or propylene oxide to synthesize a compound having a polyalkylene glycol skeleton, and further epoxidizing the terminal of the compound having the polyalkylene glycol skeleton; an "epoxy resin compound in which an alkanediol or a polyalkylene glycol is bonded to an aromatic dihydroxy compound and has an epoxy group at the terminal," which is obtained by epoxidizing an alkanediol such as propanediol or butanediol, or a polyalkylene glycol such as diethylene glycol or polypropylene glycol, and further reacting the resulting compound with an aromatic dihydroxy compound such as bisphenol A, and epoxidizing the product; Examples of such epoxy resin compounds include "epoxy resin compounds having an aliphatic skeleton or aromatic skeleton, or an alkanediol or polyalkylene glycol bonded to an aromatic dihydroxy compound and having an epoxy group at the end" obtained by divinyl etherifying an aliphatic or aromatic hydrocarbon compound, an alkanediol such as propanediol or butanediol, or a polyalkylene glycol such as diethylene glycol or polypropylene glycol, and further reacting the resulting product with an aromatic dihydroxy compound such as bisphenol A; epoxy resin compounds having an aliphatic skeleton obtained by reacting an aliphatic dicarboxylic acid such as dimer acid or sebacic acid with a bisphenol A epoxy resin or other epoxidizing agent; and epoxy resin compounds having a polyalkylene glycol structure having an epoxy group at the end obtained by epoxidizing the end of a polyalkylene glycol such as propylene oxide.

[0042] Among these, it is preferable to use an epoxy resin having an aliphatic skeleton. That is, it is preferable that the (B) component contains an epoxy resin having an aliphatic skeleton. By using an epoxy resin having an aliphatic skeleton, the epoxy resin itself has a low viscosity while imparting flexibility, and has good curing properties in a thermal environment of 180°C or less, which is preferable from the viewpoint of suppressing the volumetric shrinkage of the cured paste for electromagnetic shielding, and furthermore, suppressing peeling of the cured product after filling a local region of a substrate. The epoxy resin having an aliphatic skeleton may be a chain aliphatic type or a cyclic aliphatic type, but a chain aliphatic type epoxy resin is preferable from the viewpoint of flexibility.

[0043] As the epoxy resin having an aliphatic skeleton, a known aliphatic epoxy resin can be used, and there is no particular limitation. Specific examples of epoxy resins having an aliphatic skeleton include monofunctional aliphatic epoxy resins having one epoxy group in the molecule, such as alkyl alcohol glycidyl ethers (butyl glycidyl ether, 2-ethylhexyl glycidyl ether, etc.) and alkenyl alcohol glycidyl ethers (vinyl glycidyl ether, allyl glycidyl ether, etc.); bifunctional aliphatic epoxy resins having two epoxy groups in the molecule, such as alkylene glycol diglycidyl ether, poly(alkylene glycol) diglycidyl ether, and alkenylene glycol diglycidyl ether; and polyfunctional aliphatic epoxy resins having three or more epoxy groups in the molecule, such as polyglycidyl ethers of trifunctional or higher alcohols, such as trimethylolpropane, pentaerythritol, and dipentaerythritol (trimethylolpropane triglycidyl ether, pentaerythritol (tri- or tetra-)glycidyl ether, and dipentaerythritol (tri-, tetra-, penta- or hexa-)glycidyl ether, etc.).

[0044] The epoxy equivalent is not particularly limited, but is preferably in the range of 50 g / eq to 500 g / eq, more preferably in the range of 60 to 400 eq, and even more preferably in the range of 70 to 200 eq. When the epoxy equivalent is in this range, the curing property in a thermal environment of 180° C. or less is improved, which is preferable from the viewpoint of suppressing the volumetric shrinkage of the cured product of the paste for electromagnetic shielding, and furthermore, suppressing peeling of the cured product after filling a local region of a substrate.

[0045] As the (B) epoxy resin, a commercially available product can also be used. For example, aromatic amine type epoxy resin (product name: EP-3980S, diglycidyl orthotoluidine) manufactured by ADEKA Corporation, polypropylene glycol skeleton-containing bisphenol A type epoxy resin (product name: EP-4010L) manufactured by ADEKA Corporation, cyclic aliphatic type epoxy resin (product name: EP-4088L, dicyclopentadiene type epoxy resin) manufactured by ADEKA Corporation, alcohol ether type epoxy resin (product name: ED-503G) manufactured by ADEKA Corporation, cresol novolac type epoxy resin (product name: N-665) manufactured by DIC Corporation, bisphenol F type epoxy resin (product name: YDF8170) manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., bisphenol A type epoxy resin (product name: EXA-850CRP) manufactured by DIC Corporation, bisphenol F type epoxy resin (product name: EXA-835LV) manufactured by DIC Corporation, aminophenol type epoxy resin (product name: JER630) manufactured by Mitsubishi Chemical Corporation, and the like can be used.

[0046] The epoxy resin (B) is preferably liquid at room temperature (25°C). When a plurality of epoxy resins are used in combination, the epoxy resin (B) is preferably composed of only an epoxy resin that is liquid at room temperature (25°C). The epoxy resin (B) preferably contains an epoxy resin having a viscosity of 50 Pa·s or less as measured by an HBT viscometer at 25°C and a rotation speed of 50 rpm, and is preferably an epoxy resin having a viscosity of 50 Pa·s or less. By making the viscosity 50 Pa·s or less, the jet dispensability is improved even when the paste for electromagnetic shielding does not substantially contain a solvent or a diluent, as described later. The viscosity is more preferably 10 Pa·s or less, even more preferably 5 Pa·s or less, and particularly preferably 1 Pa·s or less. The lower limit is not particularly limited, but is preferably 10 mPa·s or more from the viewpoint of suppressing scattering of droplets.

[0047] When a plurality of epoxy resins are used in combination, the epoxy resin preferably has a viscosity of 50 Pa·s or less, more preferably 10 Pa·s or less.

[0048] The content of the (B) epoxy resin is preferably 1 to 40 parts by mass, more preferably 5 to 35 parts by mass, further preferably 7 to 30 parts by mass, and particularly preferably 10 to 25 parts by mass, relative to 100 parts by mass of the (A) conductive particles. By setting the content within the above range, the jet dispensability becomes good, and the paste for electromagnetic shielding can be filled without forming voids in localized regions, particularly in narrow gaps or grooves. The content of the (B) epoxy resin is preferably 1 part by mass or more, more preferably 5 parts by mass or more, even more preferably 7 parts by mass or more, and particularly preferably 10 parts by mass or more, relative to 100 parts by mass of the (A) conductive particles, and is preferably 40 parts by mass or less, more preferably 35 parts by mass or less, even more preferably 30 parts by mass or less, and particularly preferably 25 parts by mass. The content of the (B) component may be 1 to 30 parts by mass per 100 parts by mass of the (A) component.

[0049] The content of the epoxy resin (B) relative to the total amount of the paste for electromagnetic shielding is preferably 1 to 30 mass%, more preferably 5 to 20 mass%, and even more preferably 10 to 15 mass%, from the viewpoint of adhesion. The content of the epoxy resin (B) is 1 mass% or more, more preferably 5 mass% or more, and even more preferably 10 mass% or more. Furthermore, the upper limit is preferably 30 mass% or less, more preferably 20 mass% or less, and even more preferably 15 mass% or less, from the viewpoint of electrical conductivity. If the content of the epoxy resin (B) relative to the total amount of the paste for electromagnetic shielding is within this range, the paste for electromagnetic shielding has excellent jet dispensability even when the paste for electromagnetic shielding does not substantially contain a solvent or diluent, as described below. In addition, the paste can maintain a viscosity that allows it to be filled into localized areas, particularly narrow gaps or grooves, and the paste has good handleability during production.

[0050] <Component (C) (hardening agent)> The electromagnetic shielding paste according to the embodiment of the present invention contains a curing agent (hereinafter, may be referred to as "component (C)" or "curing agent (C)") as the component (C) that cures the above-mentioned epoxy resin (B). Note that the curing agent in this application may be any agent that cures an epoxy resin, and curing accelerators are also included as curing agents. (C) As the curing agent, phenol-based curing agents, amine-based curing agents such as aliphatic amines and aromatic amines, acid anhydride-based curing agents, polymercaptan-based curing agents, polyaminoamide-based curing agents, isocyanates, blocked isocyanates, etc. can be used.

[0051] Examples of phenol-based curing agents that can be used include bisphenols such as bisphenol F, bisphenol A, bisphenol S, tetramethyl bisphenol A, tetramethyl bisphenol F, tetramethyl bisphenol S, dihydroxydiphenyl ether, dihydroxybenzophenone, tetramethyl biphenol, ethylidene bisphenol, methyl ethylidene bis(methylphenol), cyclohexylidene bisphenol, and biphenol, and derivatives thereof; trifunctional phenols such as tri(hydroxyphenyl)methane and tri(hydroxyphenyl)ethane, and derivatives thereof; and compounds obtained by reacting phenols such as phenol novolac and cresol novolac with formaldehyde and derivatives thereof.

[0052] Examples of aliphatic amines that can be used include aliphatic polyamines such as diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, trimethylhexamethylenediamine, m-xylenediamine, and 2-methylpentamethylenediamine; alicyclic polyamines such as isophoronediamine, 1,3-bisaminomethylcyclohexane, bis(4-aminocyclohexyl)methane, norbornenediamine, and 1,2-diaminocyclohexane; and piperazine-type polyamines such as N-aminoethylpiperazine and 1,4-bis(2-amino-2-methylpropyl)piperazine. As the aromatic amine, an aromatic polyamine such as diaminodiphenylmethane, m-phenylenediamine, diaminodiphenylsulfone, diethyltoluenediamine, trimethylenebis(4-aminobenzoate), polytetramethyleneoxide-di-p-aminobenzoate, or the like can be used.

[0053] Examples of acid anhydride-based curing agents that can be used include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, dodecenylsuccinic anhydride, a reaction product of maleic anhydride and polybutadiene, and a copolymer of maleic anhydride and styrene.

[0054] As the curing agent, commercially available products can be used. Specifically, a phenol-based curing agent manufactured by Meiwa Kasei Co., Ltd. (product name: MEH-8005, allylphenol resin), a curing accelerator manufactured by Shikoku Kasei Co., Ltd. (product name: 2P4MZ (4-methyl-2-phenylimidazole)), a phenol-based curing agent manufactured by Gun-ei Chemical Industry Co., Ltd. (product name: PSM4324), an amine-based curing agent manufactured by ALBEMARLE Co., Ltd. (containing 3,5-diethyltoluene-2,4-diamine and 3,5-diethyltoluene-2,6-diamine) (product name: Ethacure 100), an amine-based curing agent manufactured by Nippon Kayaku Co., Ltd. (4,4'-diamino-3,3'-diethyldiphenylmethane) (product name: HDAA), an acid anhydride-based curing agent manufactured by Mitsubishi Chemical Co., Ltd. (product name: YH307), etc. can be used.

[0055] These curing agents may be used alone or in combination of two or more kinds. Also, known curing accelerators may be used in combination as appropriate.

[0056] The curing agent preferably contains a phenol-based curing agent, and from the viewpoint of resistivity, more preferably contains a phenol-based resin.

[0057] The blending ratio of these curing agents to the epoxy resin can be the same as when these curing agents are usually used. From the viewpoint of expressing the curing action of the epoxy resin, it is preferably 1 mass or more, more preferably 3 mass parts or more, and even more preferably 5 mass parts or more, relative to the (B) epoxy resin. Also, from the viewpoint of improving the jet dispensability, the upper limit is preferably 30 mass parts or less, more preferably 15 mass parts or less.

[0058] <Additives> The electromagnetic shielding paste according to the embodiment of the present invention may contain additives in addition to the above-mentioned (A) conductive particles, (B) epoxy resin, and (C) curing agent, such as (D) initiator, (E) dispersant, silane coupling agent, and defoamer.

[0059] The dispersant (E) is blended in order to disperse the conductive particles in the electromagnetic shielding paste, and a dicarboxylic acid-based, phosphoric acid ester-based, or other dispersant can be used. Specifically, a dicarboxylic acid weak anionic dispersant manufactured by CRODA Corporation (product name: Hypermer KD-57), a phosphate ester dispersant manufactured by CRODA Corporation (product name: CRODAFOS O3A), and a product manufactured by BYK Japan K.K. (product names: DISPERBYK-164, 167, 111) can be used.

[0060] The silane coupling agent is blended to enhance the heat resistance and adhesive strength of the electromagnetic wave shielding paste, and various silane coupling agents can be used, such as epoxy-based, amino-based, vinyl-based, methacryl-based, acrylic-based, mercapto-based, etc. Among these, epoxy-based silane coupling agents having an epoxy group and methacryl-based silane coupling agents having a methacryl group are preferred. Specifically, an epoxy-based silane coupling agent (3-glycidoxypropyltrimethoxysilane) (product name: KBM403) manufactured by Shin-Etsu Chemical Co., Ltd., a methacryl-based silane coupling agent (3-methacryloxypropyltrimethoxysilane) (product name: KBM503) manufactured by Shin-Etsu Chemical Co., Ltd., and the like can be used.

[0061] The antifoaming agent is added to prevent the generation of bubbles in the electromagnetic shielding paste, and for example, silicone-based and fluorosilicone-based antifoaming agents can be used. Specifically, a silicone-based defoaming agent manufactured by Wacker Asahi Kasei Silicone Co., Ltd. (product name: WACKER AF98 / 1000) can be used.

[0062] The content of the additive in the electromagnetic shielding paste according to the embodiment of the present invention is preferably 0.05 parts by mass or more and 10 parts by mass or less relative to the total amount of the electromagnetic shielding paste.

[0063] <(F) Solvent or diluent> The electromagnetic shielding paste according to an embodiment of the present invention may contain, in addition to the above-mentioned (A) conductive particles, (B) epoxy resin, and (C) curing agent, (F) a solvent or diluent (hereinafter, sometimes referred to as "(F) component", "(F) solvent", or "(F) solvent or diluent").

[0064] Examples of the solvent or diluent (F) according to the embodiment of the present invention include water, methanol, ethanol, propanol, butanol, ethylene glycol, propyl acetate, butyl acetate, dibasic acid ester, ethyl proxitol ethoxypropanol, carbitol acetate, 2-methoxy-1-methylethyl acetate, carbitol acetate, 2-methoxy-1-methylethyl acetate, dipropylene glycol methyl ether (DNP), ethylene glycol monobutyl ether acetate (BG), methyl isobutyl ketone (MIBK), 2-butoxyethanol, diethylene glycol monobutyl ether Examples of suitable esters include ethyl acetate (ECA), 4-methyl-1,3-dioxolan-2-one, dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), diethylene glycol monobutyl ether (BC), triethylene glycol monomethyl ether, diethylene glycol ethyl ether acetate, diethylene glycol monoethyl ether (EC), diethylene glycol monomethyl ether, phenol, terpineol (TEL), γ-butyrolactone methyl succinate and ester mixtures including methyl glutarate and dimethyl adipate, butyl glycol acetate and mixtures thereof.

[0065] On the other hand, it is preferable that the electromagnetic shielding paste according to the embodiment of the present invention is substantially free of (F) solvent or diluent from the viewpoint of reducing voids during heat curing of the electromagnetic shielding paste. In this specification, "substantially free of solvent or diluent" means that a solvent or diluent is not intentionally added to the electromagnetic shielding paste. The (A) conductive particles, (B) epoxy resin, or (C) curing agent contained in the electromagnetic shielding paste may already contain the (F) solvent or diluent. Since it is difficult to remove the (F) solvent or diluent contained in the (A) conductive particles, (B) epoxy resin, or (C) curing agent used in the electromagnetic shielding paste, the solvent or diluent that is inevitably contained in the (A) conductive particles, (B) epoxy resin, or (C) curing agent may be contained in the electromagnetic shielding paste.

[0066] That the electromagnetic shielding paste is substantially free of solvent or diluent specifically means that the solvent or diluent contained in the electromagnetic shielding paste is less than 5 mass% relative to the total amount of the electromagnetic shielding paste, and may be 3 mass% or less, 2 mass% or less, or 1 mass% or less.

[0067] Moreover, from the viewpoint of reducing viscosity, it is preferable that the electromagnetic shielding paste according to the embodiment of the present invention is substantially free of thermoplastic resin. In this specification, "substantially free of thermoplastic resin" means that no thermoplastic resin is intentionally added to the electromagnetic shielding paste. The thermoplastic resin inevitably contained in the (A) conductive particles, the (B) epoxy resin, or the (C) curing agent may be contained in the electromagnetic shielding paste.

[0068] That the electromagnetic shielding paste is substantially free of thermoplastic resin specifically means that the thermoplastic resin contained in the electromagnetic shielding paste is less than 5 mass% relative to the total amount of the electromagnetic shielding paste, and may be 3 mass% or less, 2 mass% or less, or 1 mass% or less.

[0069] [Method of manufacturing electromagnetic wave shielding paste] The electromagnetic wave shielding paste is prepared by blending (A) conductive particles, (B) epoxy resin, (C) curing agent, and additives as necessary, so that each component falls within the aforementioned content range. The electromagnetic shielding paste can be produced, for example, by blending and stirring raw materials consisting of (A) conductive particles, (B) epoxy resin, and (C) curing agent. Specifically, the electromagnetic shielding paste can be produced by stirring and mixing (A) conductive particles, (B) epoxy resin, and (C) curing agent using a known device. Examples of known devices that can be used include a Henschel mixer, a roll mill, and a triple roll mill. The (A) conductive particles, (B) epoxy resin, and (C) curing agent may be simultaneously charged into the device and mixed, or a portion of them may be charged into the device first and mixed, and the remainder may be charged into the device later and mixed.

[0070] [Electronic Components] The present disclosure also relates to a cured product of the electromagnetic shielding paste according to the embodiment of the present invention. The present disclosure also relates to an electronic component including the cured product. Examples of electronic components using the cured product include power amplifiers, Wi-Fi / Bluetooth modules, and flash memories used in electronic devices such as mobile phones, smartphones, notebook computers, and tablet terminals.

[0071] A cured product formed from the electromagnetic shielding paste has an electromagnetic shielding effect of preferably 30 dB or more, more preferably 35 dB or more, and even more preferably 40 dB or more when measured at a measurement frequency of 500 MHz to 18 GHz. By having such a shielding effect, electromagnetic waves can be effectively shielded. This electromagnetic shielding effect can be measured in accordance with ASTM D4935.

[0072] [Electronic component manufacturing] The obtained paste for electromagnetic shielding can be applied to a substrate or the like and cured to form an electronic component having a cured product with electromagnetic shielding effect. Coating methods include inkjet method, super inkjet method, screen printing method, gravure printing method, offset printing method, gravure offset printing method, flexographic printing method, spray coating method, dispense coating method, jet dispensing method, etc. In particular, the jet dispensing method can be preferably used from the viewpoint of expressing the effect of the present invention, which is good jet dispensability.

[0073] As described above, the electromagnetic shielding paste according to the embodiment of the present invention is preferably used as an electromagnetic shielding paste for filling a local region, in particular, a gap or groove formed in a substrate. Examples of gaps or grooves that are preferably filled by the jet dispensing method include narrow gaps or grooves with a width of 50 μm to 1,000 μm and a depth of 100 μm to 1,000 μm, and gaps or grooves with an aspect ratio of 1 to 15.

[0074] Examples of a method for curing the paste for electromagnetic shielding include a heat treatment, an ultraviolet ray irradiation treatment, etc. The conditions for the heat treatment are not particularly limited, but the heating temperature can be, for example, 120 to 200° C. The heating time can be 30 to 180 minutes. EXAMPLES

[0075] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0076] The following raw materials were used to prepare the electromagnetic shielding pastes of the Examples and Comparative Examples.

[0077] (A) Component (conductive particles) The materials A1 to A6 shown in Table 1 below were used.

[0078] [Table 1]

[0079] (A) The average particle size of the conductive particles was measured by observing the particles with a scanning electron microscope (SEM) and calculating the average value of 50 particles randomly selected from the SEM image. When the particles were spherical, the average value was used as the average particle size, and when the particles were needle-like, oval-spherical, flake-like, or irregular, the average value of the major axis was used as the average particle size.

[0080] The surface area per mass of conductive particles measured by the BET method (BET specific surface area) (m 2 The specific surface area (g) was measured using a fully automatic specific surface area measuring device Macsoeb (manufactured by MOUNTEC Co., Ltd.) After preliminary drying at 100° C. and flowing nitrogen gas for 10 minutes, the specific surface area (g) was measured by the BET one-point method using nitrogen gas adsorption. The TAP density (g / ml) of the conductive particles was measured as follows: A tap density measuring device (Kuramochi Scientific Instruments Co., Ltd.) was used. 10 g of the sample was weighed into a 10 mL sedimentation tube, and tapped 400 times with a stroke length of 15 mm, and the density at that time was taken as the TAP density. The ignition loss value (%) of the conductive particles was calculated from the mass of the residue after the conductive particles were fired at 800° C. for 30 minutes.

[0081] (B) Component B1: Aminophenol type epoxy resin (product number: JER630, manufactured by Mitsubishi Chemical Corporation, viscosity 1 Pa·s or less) epoxy equivalent 95g / eq. B2: Aromatic amine epoxy resin (product number: EP-3980S, manufactured by ADEKA Corporation, diglycidyl orthotoluidine, viscosity 1 Pa·s or less) epoxy equivalent 115g / eq. B3: Polypropylene glycol skeleton-containing bisphenol A type epoxy resin (product number: EP-4010L, manufactured by ADEKA Corporation, viscosity 50 Pa·s) epoxy equivalent 350 g / eq. B4: Cycloaliphatic epoxy resin (product number: EP-4088L, manufactured by ADEKA Corporation, dicyclopentadiene type epoxy resin, viscosity 1 Pa·s or less) Epoxy equivalent 165g / eq. B5: Alcohol ether type epoxy resin (product number: ED-503G, manufactured by ADEKA Corporation, viscosity 1 Pa·s or less) epoxy equivalent 135g / eq. B'6: Bisphenol acrylate resin (product number: SR601, manufactured by Sartomer Co., Ltd., viscosity 1.1 Pa·s) B'7: Aliphatic acrylate resin (product number: CN2270, manufactured by Sartomer Co., Ltd., viscosity 0.035 Pa s)

[0082] The viscosity of the resin is measured using an HBT viscometer manufactured by Brookfield Corporation at 25° C. and a rotation speed of 50 rpm.

[0083] The structural formulae of B1 to B5 are shown below. In B3, m is 2 or more, and n is 2 or more.

[0084] [ka]

[0085] (C) Hardener C1: 2-phenyl-4-methylimidazole (product number: 2P4MZ, manufactured by Shikoku Kasei Co., Ltd.) C2: Allylphenol resin (product number: MEH8005, manufactured by Meiwa Kasei Co., Ltd.)

[0086] (D) Initiator D1: t-Butyl-peroxybenzoate (product name: Perbutyl Z, manufactured by Nippon Oil & Fats Co., Ltd.)

[0087] (E) Dispersant E1: Phosphate polyester dispersant (product number: DISPERBYK-111, manufactured by BYK Japan Co., Ltd.)

[0088] (F) Solvent F1: Diethylene glycol monobutyl ether (product name: Butyl Carbitol, manufactured by Taishin Chemical Co., Ltd.)

[0089] [Examples 1 to 14, Comparative Examples 1 to 4] Electromagnetic shielding pastes were produced by mixing and dispersing the raw materials using a three-roll mill so as to obtain the blending ratios shown in the following Tables 2 to 4. The electromagnetic shielding pastes of Examples 1 to 14 and Comparative Examples 1 to 4 did not substantially contain a solvent or diluent. In addition, the electromagnetic shielding pastes of Examples 1 to 14 did not substantially contain a thermoplastic resin. In Tables 2 to 4, the numerical values ​​for each raw material represent parts by mass.

[0090] 〔evaluation〕 <Viscosity of electromagnetic wave shielding paste> The viscosity of each of the electromagnetic shielding pastes in the Examples and Comparative Examples was measured using an E-type viscometer manufactured by Tokimec Inc., as a viscosity (Pa·s) at 10 rpm and 25°C.

[0091] <Thixotropic index> Viscosity measurements were performed at 1 rpm and 10 rpm at 25° C. using an E-type viscometer manufactured by Tokimec Inc. Using these measured values, a thixotropic index value (TI) expressed as viscosity at 1 rpm / viscosity at 10 rpm was calculated.

[0092] <Jet dispensability> Using a jet dispenser SUPER JET (registered trademark) manufactured by Musashi Engineering Co., Ltd., each of the electromagnetic shielding pastes from the Examples and Comparative Examples was continuously dispensed in a dot shape 20 times, the dispensed diameter was measured, and the results were evaluated using the following indexes. ○: The difference between the maximum and minimum diameters is less than 20% △: The difference between the maximum and minimum diameters is 20% or more ×: Discharge becomes impossible midway

[0093] <Separation and peeling of the cured product> After the jet dispensability was confirmed, the test piece was heated at 175° C. for 1 hour to harden the paste for electromagnetic shielding. After hardening, the cross section was polished and visually observed, and the presence or absence of separation of the hardened product and peeling of the hardened product from the trench were evaluated using the following indexes. (separation) ○: Separation is observed ×: No separation observed (peeling) ○: No peeling △: Partial peeling ×: Full peeling

[0094] <Electromagnetic wave shielding effect> The electromagnetic shielding effect was measured in accordance with ASTM D4935. More specifically, a dispenser bubble (name: Dispense Jet, model number: DJ-2200, manufactured by Nordson Asymtek) was attached to a precision dispenser device (name: Spectrum II dispenser, model number: S2-920P, manufactured by Nordson Asymtek), and each of the electromagnetic shielding pastes of the Examples and Comparative Examples was applied onto a 5 mm square polyimide substrate (thickness: 1 mm), and heated at 175°C for 1 hour to harden the electromagnetic shielding paste. Each of the polyimide substrates on which the electromagnetic shielding paste had been hardened was measured using a "coaxial tube type shielding effect measurement system (500 MHz to 18 GHz)" (shielding effect measurement kit S-GPC7, manufactured by Keycom Co., Ltd.). When the electromagnetic shielding effect was 40 dB or more, it was rated as "excellent", when it was between 30 dB and 40 dB, it was rated as "good", and when it was between 20 dB and 30 dB, it was rated as "fair".

[0095] [Table 2]

[0096] [Table 3]

[0097] [Table 4]

[0098] As shown in Tables 2 to 4, the electromagnetic shielding pastes of Examples 1 to 14 had excellent jet dispensability, good filling properties into trenches, and no separation between the conductive particles and the resin was observed after filling. The electromagnetic shielding effect was 20 dB or more, which was a good result. Among them, the example using conductive particles surface-treated with a hydrophilic surface treatment agent and a low-viscosity epoxy resin gave better results. Note that in example 2, which contained a solvent component, voids were generated during heat curing, making it impossible to measure the electromagnetic wave shielding effect.

[0099] On the other hand, separation of the conductive particles and the resin was observed in the cured products of the electromagnetic shielding pastes of Comparative Examples 1 and 2. Furthermore, the electromagnetic shielding pastes of Comparative Examples 3 and 4 had poor jet dispensability, and a phenomenon occurred in which they became unable to be discharged midway through continuous dispensing.

Claims

1. As the component (A), conductive particles, Component (B) is an epoxy resin, and (C) Component: a curing agent Including, The viscosity measured using an E-type viscometer at 25°C and 10 rpm is 50 Pa s or less. Electromagnetic wave shielding paste.

2. 2. The electromagnetic wave shielding paste according to claim 1, wherein the component (A) contains conductive particles having an average particle size (D50) of 0.01 to 10 μm.

3. 3. The electromagnetic wave shielding paste according to claim 1, wherein the component (A) comprises conductive particles treated with a hydrophilic surface treatment agent.

4. 3. The electromagnetic wave shielding paste according to claim 1, wherein the component (B) comprises an epoxy resin having an aliphatic skeleton.

5. 3. The electromagnetic wave shielding paste according to claim 1, wherein the component (B) comprises an epoxy resin having a viscosity of 50 Pa.s or less as measured with an HBT viscometer at 25°C and 50 rpm.

6. 3. The electromagnetic wave shielding paste according to claim 1, wherein the content of the component (B) is 1 to 30 parts by mass per 100 parts by mass of the component (A).

7. 3. The electromagnetic wave shielding paste according to claim 1, wherein the component (C) comprises a phenolic resin.

8. 3. The electromagnetic wave shielding paste according to claim 1, which is substantially free of a solvent or a diluent.

9. 3. The electromagnetic wave shielding paste according to claim 1, wherein the paste has a thixotropic index value, which is the ratio of viscosity at 1 rpm to viscosity at 10 rpm, measured at 25°C using an E-type viscometer, of 10 or less.

10. 3. The electromagnetic wave shielding paste according to claim 1, wherein the electromagnetic wave shielding paste is a jet-dispense type electromagnetic wave shielding paste.

11. A cured product of the electromagnetic wave shielding paste according to claim 1 or 2.

12. An electronic component comprising the cured product according to claim 11.