CN117616095A - Conductive sheet, wiring board, and electronic device - Google Patents

Abstract

The present disclosure provides a conductive sheet having a conductive composition excellent in metal recovery property, high adhesion and conductivity, prevention of adhesion to a protective sheet during storage, and excellent in peelability of the protective sheet, evaporation of water droplets, and reworkability, and a wiring board including the conductive composition. The conductive sheet of the present disclosure is formed only byA conductive sheet comprising a conductive composition containing a metal powder (A) and a binder (B) disposed on one surface of a protective sheet (D), wherein the conductive composition dissolves and remains a residue when immersed in a specific type of solvent composition (C) at 30 ℃ for 24 hours, the residue contains a metal element, and the mountain top point density Spd of the surface of the conductive composition not facing the protective sheet (D) is 1,000 pieces/mm ² About 500,000 pieces/mm ² 。

Description

Conductive sheet, wiring board, and electronic device

Technical Field

The present disclosure relates to a conductive composition comprising a metal powder (a) and a binder (B). Further, the present invention relates to a conductive sheet, a wiring board, and an electronic device.

Background

The printed wiring board mounted in the electronic device has flexibility, but a reinforcing plate may be disposed in a connector portion or the like for connecting components to each other to suppress deformation. The reinforcing plate is made of epoxy glass or the like, and a metal plate is used in order to provide an electromagnetic wave noise suppressing function. In connection of a printed wiring board and a metal plate, a conductive composition containing a resin as a main component is used as an adhesive.

The adhesive may be added with a filler for the purpose of conducting between the metal plate and the printed wiring board, for the purpose of controlling the elastic coefficient, or the like.

For example, patent document 1 discloses that a conductor circuit and a reinforcing plate are connected via an adhesive layer, and describes that a conductive adhesive material containing conductive particles and an adhesive agent is used as the adhesive layer. Patent document 2 discloses a conductive adhesive sheet containing a thermosetting resin (a), a curing agent (B), conductive fine particles (C), and a compound (D) having a functional group containing at least one element selected from the group consisting of nitrogen, phosphorus, and sulfur, and at least one selected from the group consisting of a silane coupling agent, a silane-based compound, phosphoric acid, and a bisphenol S-type epoxy resin.

Patent document 3 discloses a conductive composition used for electronic parts and the like, which includes: a binder comprising a resin composition comprising a resol-type phenol resin having a dimethylene ether bond and a linear polymer having a molecular weight of 1000 or more, which is compatible with the phenol resin, and metal particles comprising Cu powder, which are coated with Ag. Patent document 4 discloses a conductive paste containing a polyurethane prepolymer having an NCO value of 12% to 14% and a viscosity of 1000mpa·s to 2000mpa·s.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication No. 2005-317946

Patent document 2: japanese patent laid-open No. 2015-185717

Patent document 3: japanese patent laid-open No. 8-217955

Patent document 4: chinese patent application publication No. 109943252 specification

Disclosure of Invention

Problems to be solved by the invention

Electronic devices having printed wiring boards mounted thereon are discarded because old devices are not used any more because of their longer life and the presence of new model devices. In addition, when the conductive composition is used as a binder, it is processed into a desired shape and size to be suitable for the shape of the printed wiring board, but a lot of end materials are generated in the above-mentioned step, and these are not used any more and are discarded. In recent years, for the purpose of resource protection, the activity of recovering metal resources from these electronic devices and end materials at the time of manufacture has been active. As a method for recovering metal resources, there is a method (incineration) of burning and carbonizing organic matter at high temperature, but since the method requires a large amount of energy in the incineration, an efficient method (metal recovery) is demanded instead.

In many cases, the conductive sheet having a two-layer structure, i.e., a conductive layer and a protective sheet, is manufactured and stored in a roll. When stored in a roll form, the conductive composition adheres to the back surface of the protective sheet during use, i.e., so-called blocking (blocking resistance) is a problem.

In addition, the conductive sheet is used by adhering (temporarily adhering) the first adherend to the conductive composition, then peeling off the protective sheet, and adhering the second adherend to the exposed conductive composition. However, the strength of the protective sheet is insufficient or the adhesion of the conductive composition to the protective sheet is too strong, and thus, peeling failure (easy peeling property) such as breakage of the protective sheet occurs when the protective sheet is peeled off and removed.

In addition, when the conductive composition is stored at a high temperature, the reaction of the hardener contained therein may proceed, and the adhesion may be reduced. Therefore, the conductive composition may be stored in a refrigerated state or a frozen state. However, the conductive composition taken out from the cold storage or the frozen storage may be condensed by moisture in the air. When the bonding operation is performed in a state where water droplets (including invisible fine substances) are present on the surface of the bonding agent, a bonding failure may occur. Therefore, the adhesion work to the adherend cannot be performed until the moisture volatilizes, and this becomes a factor (instantaneity) that reduces the production efficiency.

Further, from the viewpoint of reducing the environmental load, a technique for improving the manufacturing yield of the printed wiring board is demanded. In the process of manufacturing a printed wiring board, a conductive sheet is usually temporarily stuck to the wiring board and bonded by thermocompression bonding. If the removability (reworkability) is ensured at the stage of temporarily adhering to the wiring board, the manufacturing yield can be improved, but if the removability is performed, a paste residue is generated on the adherend, and reworking may be impossible. In addition, as the thickness of the wiring board becomes thinner, the wiring board itself tends to be damaged easily, and there is a problem that reworkability is not easily ensured at the stage of temporary adhesion.

The purpose of the present disclosure is to provide a conductive sheet having a conductive composition that has excellent metal recovery properties, high adhesion and conductivity, prevents adhesion to a protective sheet during storage, and has excellent peelability of the protective sheet, evaporation properties of water droplets, and reworkability, and a wiring board including the conductive composition.

Technical means for solving the problems

The present disclosure provides the following conductive composition, conductive sheet, wiring board, and electronic device.

[1]: the conductive composition of the present disclosure is a conductive sheet in which a conductive composition containing a metal powder (A) and a binder (B) is disposed on one main surface of a protective sheet (D),

the conductive composition dissolves and remains a residue when immersed in the solvent composition (C) at 30 ℃ for 24 hours, the residue containing a metal element,

the mountain top point density Spd of the surface of the conductive composition on the non-opposite side of the protective sheet (D) is 1,000 pieces/mm ² About 500,000 pieces/mm ² ，

The solvent composition (C) contains 5 to 40% by mass of a nitrogen-containing organic solvent (C1) relative to the total mass of the solvent composition (C), and contains 5 to 40% by mass of a basic inorganic compound (C2) relative to the total mass of the solvent composition (C).

[2]: the conductive sheet according to [1], wherein the conductive composition has adhesion.

[3]: the conductive sheet according to [1] or [2], wherein the binder (B) has one or more selected from the group consisting of an ester group, an imide group, an amide group, a urethane group and a urea group.

[4]: the conductive sheet according to any one of [1] to [3], wherein the binder (B) has two or more kinds selected from the group consisting of an ester group, an imide group, an amide group, a urethane group and a urea group.

[5]: the conductive sheet according to any one of [1] to [4], wherein the spread area ratio (Sdr) of the surface of the conductive composition on the non-facing side with respect to the protective sheet (D) is 0.01 to 4.

[6]: the conductive sheet according to any one of [1] to [5], wherein the conductive composition has a maximum value (2) of the storage elastic modulus at 0℃to 30℃of 0.01GPa to 100GPa,

the value alpha obtained by dividing the highest value (2) by the highest value (1) of the storage elastic coefficient of the protective sheet (D) at 0-30 ℃ is 0.01-30.

[7]: the conductive sheet according to any one of [1] to [6], wherein the highest value of the storage elastic modulus of the protective sheet (D) at 0℃to 30℃is 0.01GPa to 1000GPa.

[8]: a wiring board comprising a metal plate, a conductive composition obtained by peeling the protective sheet (D) of the conductive sheet according to any one of [1] to [7], and a wiring circuit board,

the metal plate is fixed to the wiring circuit board via the conductive composition.

[9]: an electronic device comprising the wiring board according to [8 ].

[10]: a conductive composition comprising a metal powder (A) and a binder (B), wherein when immersed in a solvent composition (C) comprising 5 to 40% by mass of a nitrogen-containing organic solvent (C1) and 5 to 40% by mass of a basic inorganic compound (C2) at 30 ℃ for 24 hours, a part of the composition is dissolved, a part of the composition is insoluble, and the insoluble component contains a metal element derived from the metal powder (A).

[11]: the conductive composition according to [10], which has adhesion.

[12]: the conductive composition according to [10] or [11], wherein the binder (B) has one or more selected from the group consisting of an ester group, an imide group, an amide group, a urethane group and a urea group.

[13]: the conductive composition according to any one of [10] to [12], wherein the binder (B) has two or more kinds selected from the group consisting of an ester group, an imide group, an amide group, a urethane group and a urea group.

ADVANTAGEOUS EFFECTS OF INVENTION

The present disclosure provides a conductive sheet having a conductive composition excellent in metal recovery property, high in adhesion and conductivity, capable of preventing adhesion to a protective sheet during storage, and excellent in peelability of the protective sheet, evaporation property of water droplets, and reworkability. Thus, a wiring board that can easily recover resources can be provided.

Detailed Description

The conductive composition, the conductive sheet, and the wiring board of the present disclosure will be described in order. Unless otherwise specified, the term "to" representing a numerical range includes a lower limit value and an upper limit value.

[ conductive composition ]

The conductive composition of the present disclosure comprises a metal powder (a) and a binder (B). When the conductive composition is immersed in a solvent composition (C) containing 5 to 40 mass% of a nitrogen-containing organic solvent (C1) and 5 to 40 mass% of a basic inorganic compound (C2) at 30 ℃ for 24 hours, a part of the composition is dissolved, a part of the composition is insoluble, and the insoluble component contains a metal element derived from the metal powder (A). In other words, the present conductive composition dissolves, and residues remain. The residue contains a metal element derived from the metal powder (A).

Here, dissolution in the present disclosure is defined as the following phenomenon: immersing an object in the solvent composition (C) and bringing the object into contact with the solvent composition (C), wherein a part of the object is dissolved in the solvent composition (C) and the original shape cannot be maintained. That is, the article does not need to be completely dissolved in the solvent composition (C), and an insoluble component (residue) may be present.

The metal element contained in the insoluble component (residue) when the conductive composition of the present disclosure is dissolved in the solvent composition (C) contains an element derived from the metal powder (a). The solvent composition (C) acts as an adhesive (B). The binder (B) is decomposed by the decomposition action of the solvent or the like of the solvent composition (C) and is dissolved in the solvent composition (C), and the insoluble metal powder (a) is contained in the residue, whereby the metal powder (a) in the conductive composition can be efficiently recovered. With respect to the conductive layer of the present disclosure, in the case of immersing in the solvent composition (C) at 30 ℃ for 24 hours, a residue in which the metal element derived from the metal powder (a) is contained is dissolved and remained.

[ Metal powder (A) ]

The metal powder (a) is used for the purpose of imparting conductivity to the conductive composition.

The metal powder (a) is preferably a conductive metal such as gold, platinum, silver, copper, and nickel, and an alloy thereof. Instead of the microparticles of a single composition, composite microparticles having a core body and a coating layer formed of a material having higher conductivity than the core body and coating the surface of the core body may be used. Composite microparticles are preferred from the viewpoint of cost reduction. The core is preferably a conductive metal and alloys thereof, more preferably selected from nickel, silica, copper. The coating layer may be any material having conductivity, and is preferably a conductive metal or a conductive polymer. Examples of the conductive metal include: gold, platinum, silver, tin, manganese, and indium, and alloys thereof. Among these, silver is preferable in terms of conductivity.

The metal powder (A) may be used singly or in combination of two or more.

The composite fine particles preferably have a coating layer in a proportion of 1 to 40 parts by mass, more preferably 5 to 30 parts by mass, per 100 parts by mass of the core body. When the coating is performed in an amount of 1 to 40 parts by mass, the cost can be further reduced while maintaining the conductivity. The composite microparticle is preferably such that the coating layer completely covers the core body. However, in reality, a part of the nucleus may be exposed. In this case, if the conductive material covers 70% or more of the surface area of the core body, the conductivity is easily maintained.

The shape of the metal powder (a) is not limited as long as the desired conductivity is obtained. For example, spherical, lamellar, foliated, dendritic (dendrite), plate-like, needle-like, rod-like, grape-like, and amorphous block-like are preferable. In order to efficiently form a longitudinal conduction path between the metal reinforcing plate and the wiring board, it is more preferable to be spherical and dendritic.

Regarding the average particle diameter of the metal powder (A), when the metal powder (A) is spherical, dendritic, needle-like, rod-like, grape-like, or amorphous, the average particle diameter D ₅₀ Preferably 5 to 20. Mu.m, more preferably 5.5 to 15. Mu.m, and still more preferably 6 to 10. Mu.m. By mean particle diameter D ₅₀ The adhesive force and the conductivity can be simultaneously achieved when the adhesive is 5-20 mu m. Further, the average particle diameter D ₅₀ The particle size distribution can be determined by a laser diffraction-scattering method particle size distribution measuring device.

Further, when the metal powder (a) is spherical, dendritic, needle-like, rod-like, grape-like, or amorphous block, D is preferable from the viewpoint of both adhesion and conductivity ₁₀ Is 1-15 μm, D ₉₀ Is 10-30 μm. D (D) ₁₀ 、D ₉₀ And average particle diameter D ₅₀ Similarly, the particle size distribution can be determined by a laser diffraction-scattering method particle size distribution measuring apparatus.

In the case where the metal powder (A) is spherical, dendritic, needle-like, rod-like, grape-like, or amorphous, it is preferably D ₉₀ /D ₁₀ 1.5 to less than 8.0. By being within the above range, the filled state of the metal powder (a) in the conductive composition is optimized, and the conductivity is particularly excellent.

When the metal powder (A) is in the form of flakes, leaves or plates, the average particle diameter D of the metal powder (A) ₅₀ Preferably 5 to 50. Mu.m, more preferably 6.5 to 30. Mu.m, and still more preferably 8 to 20. Mu.m. By mean particle diameter D ₅₀ The adhesive force and the conductivity can be simultaneously achieved when the adhesive is 5-50 mu m.

Further, when the metal powder (a) is in the form of a sheet, a leaf or a plate, D is preferable from the viewpoint of both adhesion and conductivity ₁₀ Is 1-25 μm, D ₉₀ Is 10-100 μm.

In addition, when the metal powder (a) is in the form of flakes, leaves, or plates, D is also preferable ₉₀ /D ₁₀ 1.5 to less than 8.0. Within the above range, the filled state of the metal powder (a) in the conductive composition is most preferable, and the conductivity is particularly excellent.

The content of the metal powder (a) in the conductive composition is preferably 40 to 90% by mass, more preferably 45 to 80% by mass, and still more preferably 50 to 70% by mass. By setting the addition amount as described above, the metal recovery property, adhesion and conductivity can be simultaneously achieved.

[ adhesive (B) ]

The binder (B) serves as a matrix of the conductive composition, and has a function of dispersing the metal powder (a). The binder (B) is preferably an organic substance because it is decomposed by the solvent composition (C). The composition and the like of the binder (B) are not particularly limited as long as the binder (B) has the above-described functions, and preferably contains the resin (B-1). The resin (b-1) in the present disclosure is defined as an organic material which is solid, semi-solid or solidified at ordinary temperature, and has a weight average molecular weight (Mw) of 5,000 or more in a softening or melting range.

The binder (B) is dissolved in the solvent composition (C) by solvent decomposition with a strong solvent. The binder (B) preferably has at least one selected from the group consisting of an ester group, an imide group, an amide group, a urethane group and a urea group. By having the above functional group in the conductive composition, the solvent composition (C) can be used more efficiently to decompose, the molecular chain of the binder (B) can be further thinned, and more binder (B) can be dissolved in the solvent composition (C), and the content of the component derived from the binder (B) contained in the residue can be reduced.

More preferably, the adhesive (B) has two or more kinds selected from the group consisting of an ester group, an imide group, an amide group, a urethane group and a urea group. By having two or more kinds, multiple effects can be exerted, and the adhesive (B) can be decomposed more efficiently. Preferable examples include a combination of at least one member selected from the group consisting of an ester group, an imide group, an amide group, a urea group and an ester group and a urethane group.

[ resin (b-1) ]

The resin (b-1) is not particularly limited in composition, molecular structure, and the like other than the weight average molecular weight (Mw) described above, and is preferably a resin having one or more chemical bonds selected from the group consisting of imide bonds, amide bonds, urethane bonds, and urea bonds.

Further, the resin (b-1) is preferably a thermosetting resin, a thermoplastic resin, a photocurable resin such as an ultraviolet curable resin, a natural resin, or an elastomer in view of exhibiting the function of dispersing the supported metal powder (a), and the resin (b-1) is preferably a thermosetting resin (b-2) in view of imparting excellent adhesion to the conductive composition.

[ thermosetting resin (b-2) ]

The thermosetting resin (b-2) is a resin having thermosetting properties among the resins (b-1). Thermosetting is defined as "polymerization and/or crosslinking reactions due to heat, the elastic modulus increases irreversibly".

In the case where the thermosetting resin (b-2) has a reactive functional group, the thermosetting resin may be represented by the reaction of the reactive functional groups with each other, or may be represented by the reaction of the thermosetting resin (b-2) with reactive functional groups incorporated in a curing agent (H) described later.

Examples of the thermosetting resin (b-2) include: epoxy resin, phenol resin, polyacrylic resin, polyester resin, polyurethane resin, polyamide resin, polyimide resin, polyamideimide resin, urea resin, polyurethane urea resin, melamine resin, polyolefin resin. Of these, the thermosetting resin (b-2) preferably has one or more selected from the group consisting of an ester group, an imide group, an amide group, a urethane group and a urea group. Imide bonds, amide bonds, urethane bonds, and urea bonds can achieve firm adhesion by the interaction of non-covalent electron pairs of nitrogen atoms contained in the bonds with an adherend. The effect of improving the adhesion described above can be further improved by the thermosetting resin (b-2) having two or more kinds selected from the group consisting of an ester group, an imide group, an amide group, a urethane group and a urea group.

The binder (B) may also contain a hardener (H). The hardener (H) in the present disclosure is a substance that promotes or regulates a hardening reaction, and is defined as a substance having a molecular weight or weight average molecular weight (Mw) of less than 5,000. The hardening reaction is defined as "polymerization and/or crosslinking of the prepolymer or the polymerization composition by means of heat, radiation, catalyst, etc., to irreversibly raise the modulus of elasticity". In the adhesive (B), the adhesive (B) of the present disclosure preferably contains a hardener (H) in view of forming polymerization and/or crosslinking by stimulation such as heat, and making the conductive composition exhibit firm adhesion.

The curing agent (H) may be appropriately selected from known compounds which exhibit curing properties by combination with the thermosetting resin (b). Examples of the curing agent (H) include: epoxy compound, oxetane compound, episulfide compound, aziridine compound, isocyanate compound, amine compound, isocyanate compound, imidazole compound and acid anhydride.

Examples of the epoxy compound include glycidyl ether type epoxy compounds, glycidyl amine type epoxy compounds, glycidyl ester type epoxy compounds, and cyclic aliphatic (alicyclic) epoxy compounds.

Examples of the glycidyl ether type epoxy compound include: bisphenol A type epoxy compound, bisphenol F type epoxy compound, bisphenol S type epoxy compound, bisphenol AD type epoxy compound, cresol novolak type epoxy compound, phenol novolak type epoxy compound, a-1-naphthol novolak type epoxy compound, bisphenol A type novolak type epoxy compound, dicyclopentadiene type epoxy compound, tetrabromobisphenol A type epoxy compound, brominated phenol novolak type epoxy compound, tris (glycidoxyphenyl) methane, tetrakis (glycidoxyphenyl) ethane.

Examples of the glycidylamine-type epoxy compound include: tetraglycidyl diaminodiphenylmethane, triglycidyl para-aminophenol, triglycidyl meta-aminophenol, tetraglycidyl meta-xylylenediamine.

Examples of the glycidyl ester type epoxy compound include: diglycidyl phthalate, diglycidyl hexahydrophthalate, diglycidyl tetrahydrophthalate.

Examples of the cyclic aliphatic (alicyclic) epoxy compound include: epoxycyclohexylmethyl-epoxycyclohexane carboxylate and bis (epoxycyclohexyl) adipate.

Examples of oxetane compounds include: 1, 4-bis { [ (3-ethyloxetan-3-yl) methoxy ] methyl } benzene, 3-ethyl-3- { [ (3-ethyloxetan-3-yl) methoxy ] methyl } oxetan, 1, 3-bis [ (3-ethyloxetan-3-yl) methoxy ] benzene, 4' -bis [ (3-ethyl-3-oxetan) methoxymethyl ] biphenyl, an esterified product of (2-ethyl-2-oxetan) ethanol and terephthalic acid, an esterified product of (2-ethyl-2-oxetan) ethanol and a phenol novolac resin, and an esterified product of (2-ethyl-2-oxetan) ethanol and a polycarboxylic acid compound.

Examples of the episulfide compound include: bis (1, 2-cyclothioethyl) sulfide, bis (1, 2-cyclothioethyl) disulfide, bis (2, 3-cyclothiopropyl) sulfide, bis (2, 3-cyclothiopropyl) methane, bis (2, 3-cyclothiopropyl) disulfide, bis (2, 3-cyclothiopropyl dithio) methane, bis (2, 3-cyclothiopropyl dithio) ethane, bis (6, 7-cyclothio-3, 4-dithioheptyl) sulfide, bis (6, 7-cyclothio-3, 4-dithioheptyl) disulfide, 1, 4-dithiane-2, 5-bis (2, 3-cyclothiopropyl dithiomethyl) benzene, 1, 3-bis (2, 3-cyclothiopropyl dithiomethyl) -2- (2, 3-cyclothiopropyl dithioethylthio) -4-thiohexane, 1,2, 3-tris (2, 3-cyclothiopropyl) dithiopropane.

Examples of the aziridine compound include: trimethylolpropane-tri-a-2-aziridinyl propionate, tetramethylolmethane-tri-a-2-aziridinylpropionate, N ' -diphenylmethane-4, 4' -bis (1-aziridinecarboxamide), N ' -hexamethylene-1, 6-bis (1-aziridinecarboxamide).

Examples of the amine compound include: diethylenetriamine, triethylenetetramine, methylenebis (2-chloroaniline), methylenebis (2-methyl-6-methylaniline), 1, 5-naphthalene diisocyanate, n-butylbenzyl phthalate.

Examples of the isocyanate compound include: toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, dicyclohexylmethane diisocyanate, 1, 5-naphthalene diisocyanate, tetramethylxylylene diisocyanate, trimethylhexamethylene diisocyanate.

Examples of the imidazole compound include: 2-methylimidazole, 2-heptadecylimidazole, 2-phenyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate.

Anhydrides can be mentioned: tetrahydrophthalic anhydride, dodecenyl succinic anhydride, methyl-resistant anhydride, trimellitic anhydride, pyromellitic dianhydride, and the like.

When the thermosetting resin (b-2) is 100 parts by mass, the content of the curing agent (H) is preferably 1 to 70 parts by mass, more preferably 3 to 50 parts by mass, and still more preferably 3 to 30 parts by mass.

The conductive composition can be set to a B-stage cured state by setting the content of the curing agent (H) to 1 part by mass or more. The B-stage curing is a method in which the conductive composition is heated at a predetermined temperature for a predetermined time to partially cause the curing agent (H) contained therein to undergo a curing reaction. By performing the B-stage hardening, strength can be improved while maintaining adhesion of the conductive composition, and by improving elasticity of the conductive composition, blocking resistance can be improved. In addition, the content of the hardener (H) is 70 parts by mass or less, whereby formation of an excessive crosslinked structure at the time of hardening the conductive composition can be suppressed, and the solubility of the binder (B) in the solvent composition (C) can be improved.

The step of heating the conductive composition and then attaching it to the adherend is preferably heat pressing. By applying the pressing treatment, the adhesion to the adherend is improved. The conditions for heating and pressing can be appropriately selected depending on the composition of the conductive composition and the material, size, and shape of the adherend. For example, it is preferable that the temperature is 130 to 200 ℃, the pressure is 1 to 10MPa, and the time is 3 to 60 minutes.

In terms of excellent adhesion to the metal plate and the wiring circuit board, the content of the binder (B) is preferably 10 to 60 mass% of the total solid content of the conductive composition.

The conductive composition of the present disclosure preferably has voids. By the presence of voids in the conductive composition, permeation of the solvent composition (C) is promoted, and the metal recovery is improved. The method of adjusting the presence or absence of voids or the void ratio can be any known method, and by using a dendritic metal powder as the metal powder (a), voids can be relatively easily set.

The void ratio of the conductive composition is preferably 0.5% to 60%. By setting the void ratio to 0.5% or more, permeation of the solvent composition (C) is promoted, metal recovery is improved, evaporation of dew condensation generated when taking out from the freeze storage is promoted, and instantaneity is improved. Further, by setting the void ratio to 60% or less, accumulation of excessive dew condensation can be suppressed, and instantaneity can be improved. The porosity is more preferably 1.0% to 30%.

In the present specification, "void ratio" refers to the area ratio of voids derived from a microscopic image of a cross section of the cut conductive composition. The specific calculation method is as follows. The cut surface of the conductive composition is preferably observed by a microscope such as a scanning electron microscope (Scanning Electron Microscope, SEM) or a laser microscope. When the cut surface is observed from the vertical direction by a microscope, a contrast difference is generated between the conductive composition and the void, and the shape of the void can be recognized. For the cross-sectional image in which the conductive composition was cut, the portions of the conductive composition and the portions of the voids were binarized into black and white using image analysis software "GIMP2.10.6". Then, by counting the number of pixels of black and white, the ratio of the area of the void is calculated from the ratio of the number of pixels.

The porosity of the conductive composition can be suitably controlled according to the shape or content of the metal powder (a), by using a known method such as a foaming agent that foams and generates voids by arbitrary triggering such as heat. In the case where the metal powder (a) is particularly dendritic (dendrite-like) having a high volume, voids which are exhibited by the effect of the present disclosure are easily formed, and are preferable to other metal powders. In addition, as the content of the metal powder (a) increases, voids tend to increase.

[ solvent composition (C) ]

The solvent composition (C) of the present disclosure comprises a nitrogen-containing organic solvent (C1) and a basic inorganic compound (C2). From the viewpoint of effectively acting the solubility effect of the solvent composition (C) on the binder (B), the solvent composition (C) contains 5 to 40 mass% of the nitrogen-containing organic solvent (C1) relative to the total mass of the solvent composition (C). The content of the nitrogen-containing organic solvent (c 1) is more preferably 10 to 30% by mass. The nitrogen-containing organic solvent (c 1) may be used without any particular limitation as long as it contains a nitrogen atom in the molecule. Specifically, N-methyl-2-pyrrolidone, N-propyl bromide, gamma-butyrolactone, monoethanolamine, diethanolamine, triethanolamine, and the like can be used, and the type can be appropriately selected according to the content of the dissolved binder (B).

In terms of making the solvent composition (C) alkaline and promoting the decomposition of the binder (B) by the solvent, the solvent composition (C) contains 5 to 40 mass% of the basic inorganic compound (C2) relative to the total mass of the solvent composition (C). The basic inorganic compound (c 2) may be used without particular limitation as long as it exhibits the above-mentioned function, and examples thereof include at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium hydrogencarbonate, sodium dihydrogen phosphate, disodium phosphate, trisodium phosphate, potassium dihydrogen phosphate and tripotassium phosphate. The content of the basic inorganic compound (C2) is more preferably 10 to 30% by mass in terms of imparting preferable solubility to the solvent composition (C).

In the solvent composition (C), an organic solvent for dilution, an additive for promoting decomposition of the binder (B), or the like may be suitably added from the viewpoint of imparting fluidity. From the viewpoint of facilitating the handling of the solvent composition (C), it is preferable to use glycerin having low volatility.

[ conductive sheet ]

The conductive sheet of the present embodiment is a conductive sheet in which a conductive composition containing a metal powder (a) and a binder (B) is disposed on one main surface (only one surface) of a protective sheet (D). In other words, the present conductive sheet is a sheet-like article having the conductive composition on the protective sheet (D). The conductive composition included in the conductive sheet is a solid that is not flowable at room temperature, and is formed in a layer shape having a certain thickness, which is also called a conductive layer. The conductive layer dissolves and remains a residue including a metal element when immersed in the solvent composition (C) at 30 ℃ for 24 hours.

[ protective sheet (D) ]

The protective sheet (D) may be suitably used if it is a film having been subjected to mold release treatment on one or both surfaces.

Examples of the base material of the protective sheet (D) include: plastic sheets of polyethylene terephthalate, polyethylene naphthalate, polyvinyl fluoride, polyvinylidene fluoride, rigid polyvinyl chloride, polyvinylidene chloride, nylon, polyimide, polystyrene, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polycarbonate, polyacrylonitrile, polybutylene, soft polyvinyl chloride, polyvinylidene fluoride, polyethylene, polypropylene, polyurethane, ethylene vinyl acetate copolymer, polyvinyl acetate, and the like; papers such as cellophane, woodfree paper (woodfree paper), kraft paper, and coated paper; various nonwoven fabrics, synthetic papers, metal foils, or composite films combining these. Among these, polyethylene terephthalate and polyethylene naphthalate are preferable from the viewpoint of improving the peeling easiness.

The surface of the protective sheet (D) may be subjected to a matting treatment as needed. The matting treatment may be exemplified by: sand matting, etching matting, coating matting, chemical matting, kneading matting, and the like.

The protective sheet (D) can be obtained by, for example, coating a release agent on a substrate. As the release agent, use can be made of: hydrocarbon resins such as polyethylene and polypropylene, higher fatty acids and metal salts thereof, higher fatty acid soaps, waxes, animal and vegetable oils and fats, mica, talc, silicone surfactants, silicone oils, silicone resins, fluorine surfactants, fluorine resins, fluorine-containing silicone resins, melamine resins, acrylic resins, and the like. The application method of the release agent can be performed by a conventionally known method such as gravure coating method, kiss coating method, die coating method, lip coating method, unfilled corner coating method, blade coating method, roll coating method, knife coating method, spray coating method, bar coating method, spin coating method, dip coating method.

The highest value (1) of the storage modulus of elasticity of the protective sheet (D) at 0℃to 30℃is preferably 0.01GPa to 1000GPa, more preferably 0.1GPa to 100GPa. When the protective sheet (D) is peeled off from the conductive composition after heat lamination, the protective sheet (D) is easily peeled off without being elongated or broken by setting the highest value (1) of the storage elastic modulus at 0 to 30 ℃ of the protective sheet (D) to 0.01 to 1000 GPa.

The highest value (2) of the storage modulus of elasticity of the conductive composition (conductive layer) at 0℃to 30℃is preferably 0.01GPa to 100GPa, more preferably 1GPa to 10GPa. When the protective sheet (D) is peeled off from the conductive composition after heat lamination, the conductive composition is easily peeled off without being elongated or broken by the fact that the highest value (2) of the storage modulus of elasticity of the conductive composition at 0 to 30 ℃ is within the above-mentioned range. The storage modulus of elasticity of the conductive composition and the protective sheet (D) can be determined by using a dynamic viscoelasticity measuring device.

The value α obtained by dividing the highest value (2) of the storage elastic modulus of the conductive composition (conductive layer) at 0 to 30 ℃ by the highest value (1) of the storage elastic modulus of the protective sheet (D) at 0 to 30 ℃ is preferably 0.01 to 30, more preferably 0.1 to 15. When α is 0.01 to 30, the protective sheet (D) is easily peeled from the conductive composition after heat lamination.

[ mountain top Point Density Spd and spread area ratio Sdr ]

In the conductive sheet of the present disclosure, the mountain top point density Spd of the surface of the conductive composition (conductive layer) not facing (not facing side) the protective sheet (D) is 1,000 pieces/mm ² About 500,000 pieces/mm ² . When the mountain top point density Spd of the surface is within the above range, the contact point with the adherend is set to an appropriate range, and excessive adhesion to the adherend is suppressed, whereby reworkability can be improved. The mountain top point density Spd is preferably 10,000 pieces/mm ² About 300,000 pieces/mm ² Further preferably 25,000 pieces/mm ² About 250,000 pieces/mm ² 。

The mountain top point density Spd (hereinafter, may be abbreviated as Spd) of the interface is defined in international organization for standardization (International Standardization Organization, ISO) 25178-2:2012, the mountain top point density, which represents the number of mountain top points per defined area (unit area).

In view of both adhesion and blocking resistance, the conductive sheet of the present disclosure preferably has an expanded area ratio Sdr of 0.01 to 4 on the surface of the conductive composition (conductive layer) that is a non-facing surface that does not face the protective sheet (D). The conductive sheet is stored in a state of being wound into a roll, or is transported or the like. When the conductive sheet is wound out from the wound conductive sheet, a blocking phenomenon may occur in which the conductive sheet adheres to the back surface of the protective sheet (D). By setting the Sdr on the surface of the conductive layer to the specific range, the irregularities of each defined region can be densified. Thus, the contact area between the surface of the conductive composition in the roll and the back surface of the protective sheet (D) can be reduced, and both adhesion and blocking resistance can be achieved.

The interfacial expansion area ratio Sdr (hereinafter, abbreviated as Sdr) is set at ISO 25178-2:2012 is an index indicating how much the developed area (surface area) of the defined area is increased relative to the area of the defined area. Furthermore, the Sdr of the flat surface is 0 (zero).

In the present disclosure, mountain top point density Spd and expansion area ratio Sdr are used according to ISO 25178-2:2012, measuring the obtained value. Specifically, it can be calculated as follows: measurement data was acquired using a laser microscope (manufactured by ken corporation, VK-X100), and the acquired measurement data was incorporated into analysis software (analysis application program "VK-H1XA", including ISO 25178-2:2012 surface texture measurement module "VK-H1XR", all manufactured by ken corporation), and ISO 25178-2 was executed: 2012 surface texture measurement.

The inventors have further found that: the water droplets are easily evaporated by the surface of the conductive composition having a non-facing surface with respect to the protective sheet (D) having an area ratio Sdr of 0.01 to 4.0. The water droplets are easily evaporated, so that the evaporation waiting time of dew condensation generated when taking out from the freezing storage can be shortened. As a result, the waiting time (hereinafter, also referred to as immediacy) for the bonding operation to the adherend can be shortened, and the work efficiency can be improved. The spread area ratio Sdr is preferably 0.1 to 3.0, more preferably 0.25 to 2.0, from the viewpoint of improving the instantaneity.

[ control method of Spd and Sdr ]

The method of controlling the mountain top point density Spd and the spread area ratio Sdr of the conductive sheet surface of the present disclosure may be applied to a conventionally known method as a method of adjusting the surface shape of an object. Spd and Sdr may be different methods or a common method may be used. Examples include: a method of polishing a surface using a polishing pad paper; a shot blasting method in which a polishing material is blown onto the surface of the conductive composition by compressed air; a method in which a conductive composition is formed on a film having a predetermined mountain top density Spd and a developed area ratio Sdr, and after a protective sheet is laminated, the film is removed and irregularities on the film surface are transferred; a method of pressure-bonding a film having a predetermined mountain top density Spd and a developed area ratio Sdr to a conductive composition to transfer the irregularities on the surface of the film; a method for controlling surface irregularities by incorporating a particulate material into a conductive composition.

The thickness of the conductive composition (conductive layer) in the conductive sheet is preferably 5 μm to 200 μm, more preferably 10 μm to 100 μm, and even more preferably 30 μm to 70 μm, from the viewpoint of both the film property and the conductivity.

[ method for producing conductive sheet ]

The conductive sheet of the present disclosure can be obtained, for example, by applying the conductive composition onto the protective sheet (D), drying, and then B-stage hardening as needed. The application method may be appropriately selected from known methods in consideration of the film thickness of the adhesive agent and the like. Specific examples of the coating method include: gravure coating mode, kiss coating mode, die coating mode, lip coating mode, unfilled corner coating mode, blade coating mode, roll coating mode, knife coating mode, spray coating mode, bar coating mode, spin coating mode, dip coating mode.

[ method for producing Wiring Board ]

As an example, the method for manufacturing the present wiring board includes the following methods: a method of laminating a wiring circuit board for a printed wiring board, a conductive composition and a metal plate, bonding them by pressure bonding, and then mounting an electronic component on the substrate. An example of a method for manufacturing the wiring board is described below.

First, a conductive composition varnish is applied to a protective sheet (D), and dried to prepare a conductive sheet (step a). Then, the exposed surface of the conductive layer (the non-facing surface of the protective sheet (D) of the conductive layer) is thermally laminated in a state of being in contact with the metal plate, and the conductive sheet is laminated on the metal plate (step b). Then, the protective sheet (D) is peeled off (step c), and the exposed conductive composition is thermally laminated in a state of being brought into contact with the wiring circuit board (step D), and thereafter, the conductive composition is cured by heating and pressing or the like, whereby a wiring board having a metal plate fixed to the wiring circuit board is obtained via the conductive composition (step e).

[ electronic device ]

The present patch panel can be applied to all of the products known in the prior art using printed patch panels. Specifically, the present invention is applicable to electronic devices such as mobile phones, smart phones, notebook personal computers (Personal Computer, PCs), digital cameras, and liquid crystal displays. It can be preferably used for transportation equipment such as automobiles, electric cars, ships, airplanes and the like.

Examples

The present disclosure will be specifically described below with reference to examples and comparative examples, but the present disclosure is not limited to these examples. The blending ratio represents a value calculated by solid component conversion excluding the solvent. In addition, "parts" means "parts by mass".

[ D of Metal powder (A) ] ₁₀ 、D ₅₀ 、D ₉₀ Average particle diameter]

D ₅₀ The average particle diameter was measured by a laser diffraction-scattering particle size distribution measuring apparatus LS13320 (manufactured by Beckman Coulter). Is a value obtained by measuring the conductive filler by a cyclone-dried powder sample module (tornado dry powder sample module), and is a particle diameter in which the cumulative value in the cumulative particle diameter distribution is 50%. The refractive index was set to 1.6.D (D) ₁₀ 、D ₉₀ Is the accumulation in the cumulative particle size distributionThe average particle diameter of the particles having a product value of 10% and 90% was measured in the same manner as described above.

[ acid value of thermosetting resin (b-2) ]

The acid value (mgKOH/g) was obtained by converting the solid content according to the neutralization titration method of Japanese Industrial Standard (Japanese Industrial Standards, JIS) K0070. About 1g of the sample was precisely measured in a co-stopper Erlenmeyer flask, and 100mL of a tetrahydrofuran/ethanol (volume ratio: tetrahydrofuran/ethanol=2/1) mixture was added thereto and dissolved. A phenolphthalein reagent was added thereto as an indicator, and titration was performed with a 0.1N alcoholic potassium hydroxide solution, ending at the point when the indicator remained pale red for 30 seconds. The acid value was determined by the following formula (unit: mgKOH/g).

Acid value (mgKOH/g) = (5.611 ×a×f)/S

Wherein,

s: sample collection amount (g)

a: consumption of 0.1N alcoholic potassium hydroxide solution (mL)

F: force value of 0.1N alcoholic potassium hydroxide solution

[ weight average molecular weight (Mw) of thermosetting resin (b-2) ]

Mw was measured by gel permeation chromatography (Gel Permeation Chromatograph, GPC) "HPC-8020" (manufactured by Tosoh Corp.). GPC is a liquid chromatograph that separates and quantifies substances dissolved in a solvent (THF: tetrahydrofuran) based on differences in molecular size. The measurement was performed using 2 "LF-604" (manufactured by Showa electric company; quick analysis GPC column: 6 mmID. Times.150 mm size) columns connected in series at a flow rate of 0.6mL/min and a column temperature of 40 ℃. The Mw was determined by conversion to polystyrene.

< preparation of conductive composition >

The raw materials used for producing each conductive composition are shown below.

< raw materials >

Metal powder (A)

A1: silver-coated copper powder: d (D) ₅₀ ＝5.7μm、D ₁₀ ＝2.1μm、D ₉₀ =12.8 μm, dendritic (three-well metal miningManufacturing a bag

A2: silver-coated copper powder: d (D) ₅₀ ＝31.2μm、D ₁₀ ＝12.9μm、D ₉₀ =44.6 μm, dendritic (three-well metal mining manufacturing)

A3: silver-coated copper powder: d (D) ₅₀ ＝10.8μm、D ₁₀ ＝3.2μm、D ₉₀ =29.5 μm, spherical (manufactured by Zhaoya electrical material)

A4: silver-coated copper powder: d (D) ₅₀ ＝7.5μm、D ₁₀ ＝1.5μm、D ₉₀ =11.3 μm, spherical (manufactured by Zhaoya electrical material)

A5: silver-coated copper powder: d (D) ₅₀ ＝11.3μm、D ₁₀ ＝3.8μm、D ₉₀ =29.5 μm, sheet-like (manufactured by DOWA holders)

Adhesive (B)

Thermosetting resin (b-2)

P1: polyester resin (thermosetting resin having ester group): acid value 36mgKOH/g, mw=27,000 (manufactured by TOYO CHEM)

P2: polyimide resin (thermosetting resin having imide group): acid value=22 mgKOH/g, mw=55,000 (manufactured by TOYO chemical industry (TOYO CHEM))

P3: polyamide resin (thermosetting resin having amide group): acid value=28 mgKOH/g, mw=49,000 (manufactured by eastern chemical industry (TOYO CHEM))

P4: polymaleimide resin (thermosetting resin having imide groups): acid value=13 mgKOH/g, mw=98,000 (manufactured by eastern chemical industry (TOYO CHEM))

P5: polyurethane imide resin (thermosetting resin having urethane group and imide group): acid value=11 mgKOH/g, mw=100,000 (manufactured by TOYO chemical industry (TOYO CHEM))

P6: polyacrylic resin (thermosetting resin not having any of ester group, imide group, amide group, urethane group and urea group): acid value=17 mgKOH/g, mw=120,000 (manufactured by TOYO chemical engineering (TOYO CHEM))

P7: polyolefin resin (thermosetting resin not having any of ester group, imide group, amide group, urethane group and urea group): acid value=26 mgKOH/g, mw=85,000 (manufactured by TOYO chemical industry (TOYO CHEM))

Hardening agent (H)

H1: bisphenol a epoxy compound (jER 834, molecular weight=470, mitsubishi chemical manufacturing method)

Protective sheet (D)

D1: protective sheet coated with silicone release agent and obtained by matting 50 μm polyethylene terephthalate (Polyethylene Terephthalate, PET) film by sand blasting

D2: protective sheet coated with silicone release agent and obtained by matting 50 μm polyethylene naphthalate (Polyethylene naphthalate, PEN) film by sand blasting

D3: protective sheet coated with silicone release agent by matting a 38 μm Polypropylene (PP) film by sand blasting

Conductive composition and production of conductive sheet

Example 1

100 parts by mass of a polyurethane imide resin (P5) as a thermosetting resin (b-2) and 225 parts by mass of a dendritic metal powder (A1) as a metal powder (A) were put into a container, 20 parts by mass of an epoxy compound (H1) as a hardener (H) was added, and methyl ethyl ketone (Methyl Ethyl Ketone, MEK) was added so that the nonvolatile content concentration became 45% by mass, and mixed. The conductive composition varnish was prepared by stirring for 10 minutes with a stirrer.

Next, the prepared electroconductive composition varnish was applied to the release treated surface (only one surface) of the protective sheet (D1) using a doctor blade so that the thickness of the dried electroconductive composition (electroconductive layer) became 60 μm, and dried in an electric oven at 120 ℃ for 2 minutes, whereby a laminate sheet of electroconductive sheet (protective sheet (D1)/electroconductive layer) was obtained.

Examples 2 to 27 and comparative examples 1 to 3

Conductive sheets of examples 2 to 27 and comparative examples 1 to 3 were obtained in the same manner as in example 1, except that the types and the amounts of the components to be blended were as shown in tables 1 to 4. In examples 16 to 21, the surface of the conductive composition was polished and ground after drying by an electric oven, so that Spd and Sdr were adjusted to desired values.

Method for confirming solubility

Whether the conductive composition (conductive layer) was dissolved in the solvent composition (C) and whether the residue contained metal (solubility) was confirmed by the following method. The conductive sheet was cut into pieces of 45mm in width and 100mm in length, and the protective sheet (D) was peeled off, and the obtained conductive composition was immersed in 100g of a solvent composition (C) (containing 20 mass% of monoethanolamine as a nitrogen-containing organic solvent (C1), 15 mass% of potassium hydroxide as a basic inorganic compound (C2), and 65 mass% of glycerin), and then subjected to ultrasonic treatment for 2 hours, and left standing for 22 hours, and when the conductive composition was thinned as compared with the shape before immersion, it was judged as "dissolved", and whether or not the insoluble component (residue) contained metal was confirmed. If the shape is unchanged from that before immersion, it is determined as "insoluble". In addition, when the shape change was not visually recognized, the mass of the sample before and after immersion was compared, and the case where the mass loss was less than 5% was determined as "insoluble".

The determination of whether or not the residue contains metal was performed by qualitative analysis using an inductively coupled plasma (Inductively Coupled Plasma, ICP) emission spectrometry device (manufactured by Ameterk (AMETEK) company, "SPECTRO ARCOS) (registered trademark): FHS 12") for the residue. By the analysis, whether or not the metal element is contained is confirmed, and when the metal element is contained, it is determined as "contained".

Method for measuring mountain top point density Spd and expansion area ratio Sdr

The mountain top point density Spd and the developed area ratio Sdr of the conductive composition (conductive layer) and the protective sheet (D) on the non-facing surface were measured by the following methods. After measurement data acquisition was performed on the surface of the conductive composition using a laser microscope (manufactured by ken corporation, VK-X100), the acquired measurement data was incorporated into analysis software (including analysis application program "VK-H1XA" of ISO 25178-2:2012 surface texture measurement module "VK-H1XR", all manufactured by ken corporation), and ISO 25178-2 was executed: 2012 surface texture measurement. The condition is set as S-filter: 1 μm, L-filter: 0.2mm.

< measurement of maximum value of storage elastic coefficient at 0℃to 30℃of conductive composition (conductive layer) and protective sheet (D) >)

The highest value of the storage modulus of elasticity of each of the conductive composition and the protective sheet (D) at 0℃to 30℃was measured by the following method. The thickness of the conductive layer was 60 μm, and the thickness of the protective sheet was the value described in the raw material.

First, a measurement sample having a width of 5mm and a length of 30mm was prepared, and the sample was placed in a dynamic viscoelasticity measuring apparatus (dynamic viscoelasticity measuring apparatus DVA-200, manufactured by it measurement control company) at a temperature increase rate: 10 ℃/min, measurement frequency: 1Hz, strain: and (3) carrying out dynamic viscoelasticity measurement under the condition of 0.08%, and reading the storage elasticity coefficient E' at the temperature of 0-30 ℃ according to the obtained dynamic viscoelasticity curve to obtain the highest value.

< evaluation >

With respect to each of the obtained conductive compositions, metal recovery, adhesion, conductivity, blocking resistance, easy peeling, instantaneity and reworkability were evaluated according to the following methods. The evaluation results are shown in table 5.

[ Metal recovery Property ]

The metal recovery property was evaluated by a ratio of a metal component (M1) remaining after carbonization and decomposition of the binder (B) by exposing the conductive composition (conductive layer) to high temperature and a residue (M2) obtained after decomposition of the binder (B) by immersing the conductive composition (conductive layer) in the solvent composition (C).

The conductive sheet produced in each of examples and comparative examples was cut into pieces of 45mm in width and 100mm in length, the protective sheet (D) was peeled off, the obtained conductive composition was allowed to stand in an electric furnace at 600℃for 10 hours, and the mass of the metal component (M1) was measured after removal.

The conductive sheet was cut into pieces of 45mm in width and 100mm in length, and the protective sheet (D) was peeled off, and the obtained conductive composition was immersed in 100g of a solvent composition (C) (containing 20% by mass of monoethanolamine as a nitrogen-containing organic solvent (C1), 15% by mass of potassium hydroxide as a basic inorganic compound (C2), and 65% by mass of glycerin) at 30 ℃ and then subjected to ultrasonic treatment for 2 hours, and left standing for 22 hours to settle the residue. Then, the solvent composition (C-1) of the supernatant was replaced with isopropyl alcohol, and after standing again for 5 hours, the supernatant was removed, and after air-drying for 3 days, the quality of the obtained residue (M2) was measured. The value of M1 divided by M2 was obtained, and the metal recovery was evaluated according to the following criteria.

+++: is very excellent (M1/M2 is more than 0.95).

++: excellent (M1/M2 is 0.80 or more and less than 0.95).

+: practical (M1/M2 is more than 0.50 and less than 0.80).

NG: it is not practical (M1/M2 is less than 0.50).

[ adhesive force ]

The conductive sheets produced in each of examples and comparative examples were cut to a size of 25mm in width and 100mm in length, and the conductive sheets were stacked on a stainless steel (SUS) plate (a nickel layer having a thickness of 2 μm was formed on the surface of a commercially available SUS304 plate having a thickness of 0.2 mm) such that the exposed surface of the conductive composition (conductive layer) was in contact with the SUS plate having a width of 30mm and a length of 150 mm. Then, a roll laminator was used at 130℃and 3kgf/cm ² After roll-laminating the conductive sheet and the SUS plate at 0.5m/min, the protective sheet (D) was peeled off, and a gold-plated copper foil (Jin Tongbo obtained by subjecting a copper foil having a thickness of 25 μm to gold plating treatment) was laminated on the exposed surface of the conductive composition, and the laminate was laminated at 130℃and 3kgf/cm using a roll laminator ² The conductive composition and the gold-plated copper foil were roll-laminated under a condition of 0.5m/min to obtain a laminate before pressing. Then, after the laminate was heated and pressed at 150 ℃ and 2MPa, it was left to stand (cure) for 30 minutes at 180 ℃ to obtain a sample for evaluation (SUS plate with conductive adhesive).

Then, the adhesion was evaluated by using a tensile tester (manufactured by Shimadzu corporation, small-sized bench TEST) at a tensile speed of 50mm/min, using the adhesion strength of the conductive composition of the evaluation sample in the 90 ° peel TEST to the gold-plated surface as an index, according to the following evaluation criteria.

+++: is excellent (adhesive strength is 3N/cm or more).

++: excellent (adhesion strength of 2N/cm or more and less than 3N/cm).

+: it is practical (the bonding strength is 1N/cm or more and less than 2N/cm).

NG: it is not practical (adhesive strength less than 1N/cm).

[ conductivity ]

The conductive sheets (20 mm in width and 20mm in length) produced in each of examples and comparative examples were stacked on SUS plates (0.1 mm thick commercial SUS304 plates) such that the exposed surfaces of the conductive compositions were in contact with the SUS plates (2 μm thick nickel layers were formed on the surfaces of the SUS plates). Then, a roll laminator was used at 90℃and 3kgf/cm ² The conductive sheet and the SUS plate were roll laminated under a condition of 1m/min to obtain a SUS plate with a conductive sheet.

Next, after the protective sheet (D) was peeled off from the SUS plate with conductive sheet, a square having 1 side of 10mm was punched out by a punching machine. Then, an SUS plate with a conductive composition (hereinafter, referred to as "SUS plate with a conductive composition") was obtained. Then, the exposed surface of the conductive composition (non-facing surface of the conductive composition and the SUS plate) of the SUS plate with the conductive composition was superimposed on a wiring circuit board (flexible printed wiring board) prepared separately, and the wiring circuit board was laminated at 130℃and 3kgf/cm using a roll laminator ² And adhering the SUS plate with the conductive composition to the flexible printed wiring board under the condition of 1 m/min. These were then thermally pressed at 170℃and 2MPa for 5 minutes, and then heated at 160℃for 60 minutes using an electric oven, whereby an evaluation sample was obtained. Further, in the wiring circuit board, copper foil circuits each having a thickness of 32 μm were formed on both sides of a polyimide film having a thickness of 75 μm, and a square having a side of 0.7mm and an opening area of 0.49mm were laminated on the copper foil circuits ² Adhesive tape having a thickness of 37.5 μm in through-holes (openings) of (a) aAn insulating cover film of the above (C). Further, an insulating cover film (the copper foil circuit and the cover film are arranged symmetrically with respect to the polyimide film so that the wiring circuit board does not warp) having a thickness of 37.5 μm with an adhesive without a through hole is laminated on the other copper foil circuit.

Then, the resistance (connection resistance value) between the SUS plate and the copper foil circuit of the sample for evaluation was measured using a resistance value measuring instrument and a BSP probe (model: MCP-TP05P, manufactured by Mitsubishi chemical analysis technique), and the conductivity was evaluated based on the measurement value as an index.

+++: good (connection resistance value less than 20mΩ).

++: practical (the connection resistance value is 20mΩ or more and less than 100mΩ).

+: practical (the connection resistance value is more than 100mΩ and less than 300mΩ).

NG: it is not practical (the connection resistance value is 300mΩ or more).

[ blocking resistance ]

2 conductive sheets (width 50mm, length 50 mm) prepared in each example and comparative example were prepared. Then, the conductive sheets were stacked so that the surface of the conductive sheet where the conductive composition was exposed was brought into contact with the surface of the other conductive sheet where the protective sheet (D) was exposed (i.e., the surface where the release agent was not applied), and after placing a weight of 2kg, the conductive sheets were allowed to stand at 40 ℃ under atmospheric pressure for 3 days. Then, when the weight was removed and each conductive sheet was pulled apart, the blocking resistance was evaluated based on the following evaluation criteria, using the area of the conductive composition transferred to the protective sheet (D) as an index.

+++: good (transfer area less than 5%).

++: practical (transfer area is 5% or more and less than 10%).

+: practical (transfer area is 10% or more and less than 20%).

NG: it is not practical (transfer area is 20% or more).

[ easy peelability ]

The conductive sheets produced in each of the examples and comparative examples were cut into pieces having a width of 25mm and a length of 100mm, and the conductive sheets were used as the conductive sheets The exposed surface of the conductive composition was brought into contact with an SUS plate having a width of 30mm and a length of 150mm (a nickel layer having a thickness of 2 μm was formed on the surface of a commercially available SUS304 plate having a thickness of 0.2 mm), and the conductive sheet was superimposed on the SUS plate. Then, a roll laminator was used at 130℃and 3kgf/cm ² The conductive sheet and the SUS plate were roll laminated under a condition of 0.5m/min to obtain a sample for evaluation.

Then, using a tensile tester (small-sized bench TEST machine EZ-TEST, manufactured by Shimadzu corporation), the peeling property was evaluated according to the following evaluation criteria under the condition that the tensile speed was 50mm/min, using the peel strength of the protective sheet (D) of the TEST sample for evaluation in the 90 DEG peeling TEST with respect to the conductive composition as an index.

+++: is very excellent (peel strength less than 50g/50 mm).

++: excellent (peel strength of 50g/50mm or more and less than 100g/50 mm).

+: it is practical (peel strength of 100g/50mm or more and less than 400g/50 mm).

NG: it is not practical (peel strength of 400g/50mm or more).

[ instantaneity ]

The conductive sheets produced in each of examples and comparative examples were cut into pieces having a width of 25mm and a length of 100mm, left standing in a freezer (-15 ℃) for 10 hours, taken out, and left standing in an atmosphere of 50% RH at 23℃for 3 minutes. Then, the conductive sheet was overlapped on the SUS plate so that the exposed surface of the conductive composition (conductive layer) was in contact with a SUS plate having a width of 30mm and a length of 150mm (a nickel layer having a thickness of 2 μm was formed on the surface of a commercially available SUS304 plate having a thickness of 0.2 mm). Then, a roll laminator was used at 90℃and 3kgf/cm ² After roll-laminating the conductive sheet and the SUS plate under a condition of 0.5m/min, the protective sheet was peeled off from the conductive sheet to obtain a SUS plate with a conductive layer.

Then, a gold plating surface of an electroless gold plating sheet (manufactured by Taiyang industries Co., ltd.) cut to a width of 30mm and a length of 200mm was bonded to the exposed surface of the conductive layer of the SUS plate with the conductive layer, and roll lamination was performed under the same conditions as described above. These were then thermally pressed at 170℃under 2MPa for 3 minutes, respectively, and then heated at 160℃for 60 minutes using an electric oven, thereby obtaining samples for evaluation. The results were classified (expansion evaluation) by a to d to such an extent that the appearance was poor (expansion due to evaporation of water droplets on the conductive layer) when the conductive layer of the obtained evaluation sample was observed from the electroless gold plating sheet side.

a: the area of expansion is 5% or more and less than 10% relative to the area of the conductive layer.

b: the area of expansion is 10% or more and less than 15% relative to the area of the conductive layer.

c: the area of expansion is 15% or more and less than 20% relative to the area of the conductive layer.

d: the expanded area is less than 5% relative to the area of the conductive layer.

For each of the evaluation samples obtained above, a tensile tester (manufactured by Shimadzu corporation, small-sized bench TEST) was used, and a portion to which the SUS plate was not attached was mounted on the tensile tester, and the adhesion strength of the conductive layer of the evaluation sample in the 180 DEG peel TEST to the electroless gold plating surface was measured under the condition that the tensile speed was 50mm/min, and the results were classified by a to d (adhesion strength).

a: the adhesive strength is 6N/cm or more.

b: the adhesion strength is 3N/cm or more and less than 6N/cm.

c: the adhesive strength is 1N/cm or more and less than 3N/cm.

d: the adhesive strength is less than 1N/cm.

Further, the adhesion was evaluated based on the following evaluation criteria, using the results as indicators.

+++: expansion evaluation and adhesive strength were all a (very excellent)

++: either one of the expansion evaluation and the adhesive strength was a and the other was b, or both were b (excellent)

+: either expansion evaluation or adhesion strength was c and d-free (practical)

NG: either or both of the expansion evaluation and the adhesive strength were d (not practical)

[ reworkability ]

Reworkability was evaluated by the paste residual area and arithmetic average height of the conductive layer when the conductive layer temporarily stuck to polyimide was peeled off. The exposed surface of the conductive layer of the conductive sheet cut out to have a width of 50mm and a length of 50mm was bonded to a polyimide film (Kapton) 300H cut out to have a width of 70mm and a length of 70mm, and a roll laminator (transport speed: 1 m/min, temperature: 90 ℃ C., pressure: 3 kgf/cm) ² ) Temporary pasting is performed by the method. The conductive layer in the obtained temporary adhesive laminate was peeled off from the end, and the area of the conductive layer remaining on the polyimide was divided by the area of the conductive layer before lamination, thereby calculating the paste residual ratio. Then, an arbitrary 5-point was selected from the paste residue, measurement data acquisition was performed on the surface using a laser microscope (manufactured by ken corporation, VK-X100), the acquired measurement data was incorporated into analysis software (including an analysis application program "VK-H1XA" of the ISO25178 surface texture measuring module "VK-H1XR", manufactured by ken corporation), and the ISO25178 surface texture measurement was performed to calculate an arithmetic average height (the conditions were set to S-filter: 1 μm, L-filter: 0.2 mm). Using the paste residue ratio and the arithmetic average height thus obtained, evaluation was performed on the following basis.

+++: when the paste residue ratio is 5% or less and a paste residue portion is present, the arithmetic average height thereof is less than 20% of the thickness of the adhesive layer. Is extremely good.

++: the paste residue ratio exceeds 5% and is 15% or less, and the arithmetic average height thereof is less than 20% of the thickness of the adhesive layer. Good.

+: the paste residue ratio is 15% or less, and the arithmetic average height of the paste residue portion is 20% to 50% of the thickness of the adhesive layer. Is practical.

NG: the paste residue ratio is greater than 15%, and/or the arithmetic average height of the paste residue portion is greater than 50% of the thickness of the adhesive layer. It is not practical.

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Comparative example 1, which is insoluble in the solvent composition (C), has problems in terms of metal recovery. In addition, comparative examples 2 and 3, in which Spd is outside the range of 1000 to 500,000, have problems in terms of reworkability. In contrast, by having a conductive layer with Spd at 1,000 pieces/mm 2[ mm ] ² ]500,000 pieces/mm 2[ mm ] ² ]The conductive sheets of examples 1 to 27, which were dissolved in the solvent composition (C) and contained the conductive layer containing the metal element in the residue, were found to be excellent in metal recovery, adhesion, conductivity, blocking resistance, easy peeling, instantaneity and reworkability.

The present application claims priority based on japanese patent application publication No. 2022-70493, filed at 22 at 4/2022, the disclosure of which is incorporated herein in its entirety.

Claims (9)

1. A conductive sheet comprising a protective sheet (D) and a conductive composition comprising a metal powder (A) and a binder (B) disposed on one main surface of the protective sheet,

the conductive composition dissolves and remains a residue when immersed in the solvent composition (C) at 30 ℃ for 24 hours, the residue containing a metal element,

The mountain top point density Spd of the surface of the conductive composition on the non-opposite side of the protective sheet (D) is 1,000 pieces/mm ² About 500,000 pieces/mm ² ，

The solvent composition (C) contains 5 to 40% by mass of a nitrogen-containing organic solvent (C1) relative to the total mass of the solvent composition (C), and contains 5 to 40% by mass of a basic inorganic compound (C2) relative to the total mass of the solvent composition (C).

2. The conductive sheet according to claim 1, wherein the conductive composition has adhesion.

3. The conductive sheet according to claim 1, wherein the binder (B) has one or more selected from the group consisting of an ester group, an imide group, an amide group, a urethane group and a urea group.

4. The conductive sheet according to claim 1, wherein the binder (B) has two or more kinds selected from the group consisting of an ester group, an imide group, an amide group, a urethane group and a urea group.

5. The conductive sheet according to claim 1, wherein the surface of the conductive composition on the non-facing side of the protective sheet (D) has an expanded area ratio Sdr of 0.01 to 4.

6. The conductive sheet according to claim 1, wherein the conductive composition has a maximum value (2) of the storage elastic modulus at 0 to 30℃of 0.01 to 100GPa,

The value alpha obtained by dividing the highest value (2) by the highest value (1) of the storage elastic coefficient of the protective sheet (D) at 0-30 ℃ is 0.01-30.

7. The conductive sheet according to claim 1, wherein the highest value of the storage elastic modulus of the protective sheet (D) at 0 to 30 ℃ is 0.01 to 1000GPa.

8. A wiring board comprising a metal plate, a conductive composition obtained by peeling the protective sheet (D) of the conductive sheet according to any one of claims 1 to 7, and a wiring circuit board,

the metal plate is fixed to the wiring circuit board via the conductive composition.

9. An electronic device comprising the patch panel of claim 8.