Thermosetting adhesive sheet and printed wiring board

Abstract

The present invention addresses the problem of providing: a heat-curable adhesive sheet which has a low dielectric constant, is easy to perform positioning work, and has excellent heat resistance; and a printed wiring board which contains a cured product of the heat-curable adhesive sheet. The present invention is a heat-curable adhesive sheet having an adhesive layer containing an adhesive composition, the adhesive layer containing 75-90 parts by mass of a styrene-based elastomer with respect to 100 parts by mass of the adhesive composition, the styrene-based elastomer containing at least a styrene-based elastomer (A) having a styrene ratio of 30% or more, the adhesive layer contains a polyfunctional resin having at least two reactive functional groups in the structure, and the cured product of the thermosetting adhesive sheet has a dielectric constant of 1.0-3.0 at 23 DEG C, 50% RH, and a frequency of 28 GHz.

Description

Technical Field

[0001] The present invention relates to a thermosetting adhesive sheet and a printed wiring board. Background Art

[0002] In recent years, with the realization of high-speed and large-capacity information communication, the high-frequencyization of electrical signals has been continuously developing. However, if the electrical signals are high-frequencyized, there is a tendency that the output of the electrical signals is likely to decrease and the dielectric loss increases. Therefore, for electronic devices used in high-speed communication, it is required to exhibit high output power and low dielectric properties with low loss even for high-frequencyized electrical signals. In a printed wiring board used in an electronic device for high-speed communication, the above-mentioned low dielectric properties are also required. Among them, the constituent materials of a flexible printed circuit (FPC) require characteristics such as low dielectric properties, heat resistance, and processability.

[0003] As a constituent material of a flexible printed circuit (FPC) used in high-speed communication, a thermosetting adhesive sheet having a low dielectric constant and a low dielectric loss tangent has been proposed (for example, Patent Document 1, Patent Document 2).

[0004] [Prior Art Documents] [Patent Documents] Patent Document 1: Japanese Patent Application Laid-Open No. 2019-135280 Patent Document 2: International Publication No. 2021 / 024364 Summary of the Invention

[0005] However, the thermosetting adhesive sheets disclosed in Document 1 and Document 2 have strong adhesiveness. When performing a positioning operation for confirming the attachment position of the thermosetting adhesive sheet, the thermosetting adhesive sheet adheres too strongly to the component, and it is sometimes difficult to reattach when attempting to correct the attachment position. In addition, in the solder reflow process, the cured product of the thermosetting adhesive sheet disclosed in Document 1 and Document 2 sometimes expands and flows, and the reflow heat resistance is insufficient.

[0006] Therefore, an object of the present invention is to provide a thermosetting adhesive sheet having a low dielectric constant, easy to perform a positioning operation, and excellent heat resistance, and a printed wiring board including a cured product of the thermosetting adhesive sheet.

[0007] The present invention includes the following aspects.

[0008] [1]A thermosetting adhesive sheet having an adhesive layer containing an adhesive composition, wherein, based on 100 parts by mass of the adhesive composition, the adhesive layer contains 75 to 90 parts by mass of a styrenic elastomer, the styrenic elastomer contains at least a styrenic elastomer (A) having a styrene ratio of 30% or more, the adhesive layer contains a polyfunctional resin having at least two or more reactive functional groups in its structure, and the cured product of the thermosetting adhesive sheet has a dielectric constant of 1.0 to 3.0 at 23°C, 50% RH, and a frequency of 28 GHz.

[0009] [2]The thermosetting adhesive sheet according to [1], wherein the styrenic elastomer contains a styrenic elastomer (B) having a styrene ratio of less than 30%.

[0010] [3]The thermosetting adhesive sheet according to [1] or [2], wherein, based on 100 parts by mass of the adhesive composition, the content of the styrenic elastomer (A) is 5 parts by mass or more.

[0011] [4]The thermosetting adhesive sheet according to [2] or [3], wherein, based on 100 parts by mass of the adhesive composition, the content of the styrenic elastomer (B) is 35 parts by mass or more.

[0012] [5]The thermosetting adhesive sheet according to any one of [1] to [4], containing 5 to 20 parts by mass of a modified polyphenylene ether resin having a polymerizable group at the end as the polyfunctional resin, based on 100 parts by mass of the adhesive composition.

[0013] [6]The thermosetting adhesive sheet according to any one of [1] to [5], wherein, based on 100 parts by mass of the adhesive composition, a total of 1 to 15 parts by mass of an epoxy resin is contained as the polyfunctional resin.

[0014] [7]The thermosetting adhesive sheet according to any one of [1] to [6], wherein, based on 100 parts by mass of the adhesive composition, 0.1 to 10 parts by mass of an organic peroxide is contained.

[0015] [8]The thermosetting adhesive sheet according to any one of [1] to [7], wherein the storage modulus E' of the adhesive layer at 30°C is 1×10 6 Pa to 1×10 9 Pa.

[0016] [9]The thermosetting adhesive sheet according to any one of [1] to [8], wherein the initial adhesive force of the thermosetting adhesive sheet to polyimide is 0.5 N / mm or less.

[0017]

[10] The thermosetting adhesive sheet according to any one of [1] to [9], wherein when the thermosetting adhesive sheet is attached to polyimide and cured, the T-peel adhesive force is 0.25 N / mm or more.

[0018]

[11] The thermosetting adhesive sheet according to any one of [1] to

[10] , which is used for a printed wiring board.

[0019]

[12] A printed wiring board comprising a cured product of the thermosetting adhesive sheet according to any one of [1] to

[11] .

[0020] [Effect of the Invention] According to the present invention, it is possible to provide a thermosetting adhesive sheet having a low dielectric constant, weak adhesiveness and easy positioning operation, and excellent heat resistance. Detailed Description of the Invention

[0021] Hereinafter, the thermosetting adhesive sheet of the present invention will be further described in detail based on its constituent elements.

[0022] "Thermosetting Adhesive Sheet" The thermosetting adhesive sheet of the present invention has an adhesive layer containing an adhesive composition. In the present invention, the adhesive layer containing the adhesive composition contains 75 to 90 parts by mass of a styrene-based elastomer and a polyfunctional resin having at least two or more reactive functional groups in its structure, and the styrene-based elastomer contains at least a styrene-based elastomer (A) having a styrene ratio of 30% or more. By making the adhesive composition have such a structure, it is possible to produce a thermosetting adhesive sheet having weak adhesiveness and excellent heat resistance.

[0023] <Adhesive Composition> The adhesive composition in the present invention contains 75 to 90 parts by mass of a styrene-based elastomer and a polyfunctional resin having at least two or more reactive functional groups in its structure, based on 100 parts by mass of the adhesive composition.

[0024] (Styrene-Based Elastomer) Styrene-based elastomers refer to copolymers of styrene and olefins (e.g., conjugated dienes such as butadiene and isoprene), and / or their hydrides. Styrene-based elastomers are block copolymers with styrene as the hard segment and conjugated diene as the soft segment. As styrene-based elastomers, for example, it is preferable to use: styrene-ethylene-butene copolymers (SEB) and other styrene-based AB-type diblock copolymers; styrene-butadiene-styrene copolymers (SBS), hydrides of SBS (styrene-ethylene-butene-styrene copolymers (SEBS), styrene-butadiene-butene-styrene copolymers (SBBS)), styrene-isoprene-styrene copolymers (SIS), hydrides of SIS (styrene-ethylene-propylene-styrene copolymers (SEPS)), styrene-isobutylene-styrene copolymers (SIBS) and other styrene-based ABA-type triblock copolymers; styrene-butadiene-styrene-butadiene (SBSB) and other styrene-based ABAB-type tetrablock copolymers; styrene-butadiene-styrene-butadiene-styrene (SBSBS) and other styrene-based ABABA-type pentablock copolymers; styrene-based multi-block copolymers having AB repeating units more than them; hydrides obtained by hydrogenating the ethylenic double bonds of styrene-based random copolymers such as styrene-butadiene rubber (SBR); terminal amine-modified products obtained by amine-modifying the terminals of these copolymers; maleic anhydride-modified products obtained by maleic anhydride-modifying a part of these copolymers, etc. Commercially available products can also be used as the styrene-based elastomers. They can be used alone or in combination of two or more.

[0025] Among them, the styrene-based elastomer is at least one selected from hydrides of SBS, maleic anhydride-modified products of hydrides of SBS, and terminal amine-modified products of hydrides of SBS. In the above cases, since the tackiness of the thermosetting adhesive sheet is weak and the heat resistance can be made better, furthermore, the thermosetting adhesive sheet exhibits good low dielectric properties, so it is preferable.

[0026] The weight-average molecular weight of the styrene-based elastomer is preferably 50,000 or more, more preferably 80,000 to 1,000,000. If the weight-average molecular weight of the styrene-based elastomer is within the above preferred range, the tackiness of the thermosetting adhesive sheet is weak and the heat resistance can be made better, so it is preferable. When the adhesive composition contains two or more styrene-based elastomers as the styrene-based elastomer, the weight-average molecular weight of the vinyl-based elastomer refers to the weight-average molecular weights of the two or more styrene-based elastomers respectively.

[0027] Here, the measurement of the weight-average molecular weight of the styrene-based elastomer by the GPC method is the standard polystyrene conversion value measured using a GPC device (HLC-8329GPC, manufactured by Tosoh Corporation), and the measurement conditions are as follows.

[0028] - Measurement Conditions - · Sample concentration: 0.5 mass% (tetrahydrofuran (THF) solution) · Sample injection volume: 100 μ L · Eluent: THF · Flow rate: 1.0 mL / min · Measurement temperature: 40 °C · Main column: Two TSKgel GMHHR-H(20) · Guard column: TSKgel HXL-H · Detector: Differential refractometer · Standard polystyrene molecular weight: 10,000 - 20,000,000 (manufactured by Tosoh Corporation) The adhesive composition in the present invention contains 75 to 90 parts by mass of the styrene-based elastomer with respect to 100 parts by mass of the adhesive composition. When the adhesive composition contains two or more styrene-based elastomers as the styrene-based elastomer, the total content of the two or more styrene-based elastomers is in the above range with respect to 100 parts by mass of the adhesive composition. Among them, the content of the styrene-based elastomer is more preferably 80 to 90 parts by mass with respect to 100 parts by mass of the adhesive composition. If the content of the styrene-based elastomer is set within the above preferred range, the thermosetting adhesive sheet has weak adhesiveness and can have better heat resistance. Furthermore, the thermosetting adhesive sheet can exhibit good low dielectric properties, so it is preferred.

[0029] The styrene-based elastomer contains at least a styrene-based elastomer (A) with a styrene ratio of 30% or more. The styrene ratio of the styrene-based elastomer (A) is preferably 30% or more, more preferably 30% - 80%, and particularly preferably 30% - 70%. By having such a structure, the dielectric constant is low, the adhesiveness is weak, and the heat resistance can be better.

[0030] The content of the styrene-based elastomer (A) is preferably 5 parts by mass or more, more preferably 7 to 90 parts by mass, and further preferably 9 to 50 parts by mass with respect to 100 parts by mass of the adhesive composition. If the content of the styrene-based elastomer (A) is set within the above preferred range, the thermosetting adhesive sheet has weak adhesiveness and can have good adhesiveness after curing, so it is preferred.

[0031] The styrenic elastomer may include two or more styrenic elastomers having different styrene ratios. When the styrenic elastomer includes two or more styrenic elastomers having different styrene ratios, in addition to the styrenic elastomer (A) having a styrene ratio of 30% or more, the styrenic elastomer preferably further includes a styrenic elastomer (B) having a styrene ratio different from that of the styrenic elastomer (A). If the styrenic elastomer (B) is used in combination, the thermosetting adhesive sheet has weak tack and can provide strong adhesiveness after curing.

[0032] When the styrenic elastomer (A) and the styrenic elastomer (B) are used in combination, the styrene ratio of the styrenic elastomer (B) is preferably less than 30%, more preferably 5% to 25%, still more preferably 7% to 20%, and particularly preferably 10% to 15%. If the styrene ratio of the styrenic elastomer (B) is within the above range, the adhesiveness of the thermosetting adhesive sheet after curing can be better.

[0033] When the styrenic elastomer (A) and the styrenic elastomer (B) are used in combination, based on 100 parts by mass of the adhesive composition, the content of the styrenic elastomer (B) is preferably 35 parts by mass or more, more preferably 40 parts by mass to 80 parts by mass, and still more preferably 50 parts by mass to 75 parts by mass. If the content of the styrenic elastomer (B) is within the above preferred range, the thermosetting adhesive sheet has weak tack and can provide better heat resistance and adhesiveness after curing, so it is preferred.

[0034] When the styrenic elastomer (A) and the styrenic elastomer (B) are used in combination, the mass ratio [(A) / (B)] is not particularly limited, and is preferably in the range of 10 / 73 to 48 / 35, more preferably in the range of 17 / 65 to 48 / 35, and still more preferably in the range of 28 / 55 to 48 / 35. If the mass ratio is within the above range, the tack of the thermosetting adhesive sheet can be weakened, and the positioning operation of the thermosetting adhesive sheet when bonding to the adherend can be easily performed, so it is preferred.

[0035] In the adhesive composition of the present invention, in addition to the styrene-based elastomer, it also contains a polyfunctional resin having two or more reactive functional groups in its structure. As long as it is within the range that does not impair the effects of the present invention, the reactive functional groups are not particularly limited, and examples thereof include: hydroxyl group, halogen group, amino group, carboxyl group, epoxy group, functional groups containing an ethylenically unsaturated bond, etc. Among them, from the viewpoint of the heat resistance after curing of the thermosetting adhesive sheet, functional groups having an amino group, a carboxyl group, an epoxy group, or a functional group containing an ethylenically unsaturated bond are preferred. In addition, as long as it is within the range that does not impair the effects of the present invention, the polyfunctional resin is not particularly limited, and examples thereof include modified polyphenylene ether resins, epoxy resins, etc. The polyfunctional resin may contain one kind or two or more kinds. Furthermore, the adhesive composition of the present invention may contain an organic peroxide as a polymerization initiator for the modified polyphenylene ether resin, and may also contain an epoxy resin curing agent as a curing agent for the epoxy resin.

[0036] With respect to 100 parts by mass of the adhesive composition, the content of the polyfunctional resin is preferably 1 part by mass to 20 parts by mass, more preferably 2 parts by mass to 20 parts by mass, still more preferably 5 parts by mass to 20 parts by mass, and particularly preferably 10 parts by mass to 20 parts by mass. If the content of the polyfunctional resin is adjusted to the above preferred range, when the thermosetting adhesive sheet is cured, the polyfunctional resin reacts to form a crosslinked structure, thereby being able to suppress the fluidity of the cured adhesive layer at high temperatures and making the heat resistance better, so it is preferred.

[0037] (Modified polyphenylene ether resin) The adhesive composition can contain, for example, one kind or two or more kinds of modified polyphenylene ether resins as polyfunctional resins having at least two or more reactive functional groups in their structures. The modified polyphenylene ether resin preferably has a polyphenylene ether chain in the molecule and a polymerizable group at the end. The modified polyphenylene ether resin preferably has at least one of two or more epoxy groups and a functional group containing an ethylenically unsaturated bond in one molecule as the polymerizable group. In particular, from the viewpoints of compatibility with the styrene-based elastomer and dielectric properties of the adhesive composition, the modified polyphenylene ether resin preferably has at least one of an epoxy group and a functional group containing an ethylenically unsaturated bond at both ends. Examples of the functional group containing an ethylenically unsaturated bond include (meth)acryloyl group, vinylbenzyl group, etc.

[0038] Among them, the modified polyphenylene ether resin having (meth)acryloyl groups at both ends can make the heat resistance after curing of the thermosetting adhesive sheet better and impart excellent low dielectric properties, so it is preferred.

[0039] The number-average molecular weight of the modified polyphenylene ether resin is preferably from 1,000 to 10,000, more preferably from 1,000 to 3,000. If the number-average molecular weight of the modified polyphenylene ether resin is within the above-mentioned preferred range, the heat resistance and adhesiveness of the cured thermosetting adhesive sheet can be made better, and excellent low dielectric properties can be imparted, so it is preferred. It should be noted that the number-average molecular weight of the modified polyphenylene ether resin is measured in terms of standard polystyrene conversion using gel permeation chromatography (GPC). The measurement conditions are the same as those for the measurement of the weight-average molecular weight described above.

[0040] When the adhesive composition in the present invention contains a modified polyphenylene ether resin, the content of the modified polyphenylene ether resin is preferably from 5 parts by mass to 20 parts by mass, particularly preferably from 9 parts by mass to 15 parts by mass, based on 100 parts by mass of the adhesive composition. If the content of the modified polyphenylene ether resin is within the above-mentioned preferred range, the heat resistance and adhesiveness of the cured thermosetting adhesive sheet can be made better, and excellent low dielectric properties can be imparted, so it is preferred. In particular, when the thermosetting adhesive sheet is cured, the modified polyphenylene ether resin reacts to form a crosslinked structure, thereby suppressing the fluidity of the cured adhesive layer at high temperatures and making the heat resistance better, so it is preferred.

[0041] (Organic peroxide) The organic peroxide can be used as a polymerization initiator for the above-mentioned modified polyphenylene ether resin. As the organic peroxide, for example, di-tert-butyl peroxide, 2,5-bis(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-bis(tert-butylperoxy)-3-hexyne, 1,3-bis(tert-butylperoxyisopropyl)benzene, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-bis(tert-butylperoxy)valerate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butyl perbenzoate, tert-butyl isopropyl carbonate peroxide, diacetyl peroxide, lauroyl peroxide, tert-butyl peroxycumene, etc. are preferably used. The organic peroxide can be used alone or in combination of two or more.

[0042] Among them, di-tert-butyl peroxide is preferably used in terms of making the heat resistance and adhesiveness of the cured thermosetting adhesive sheet better.

[0043] When the adhesive composition in the present invention contains an organic peroxide, based on 100 parts by mass of the adhesive composition, the content of the organic peroxide is preferably 0.1 part by mass to 10 parts by mass, more preferably 0.5 part by mass to 7 parts by mass, still more preferably 1 part by mass to 5 parts by mass, and particularly preferably 1.5 parts by mass to 3 parts by mass. If the content of the organic peroxide is set within the above preferred range, the heat resistance and adhesiveness of the cured thermosetting adhesive sheet can be made better, so it is preferred. In particular, when the thermosetting adhesive sheet is cured, the organic peroxide reacts to form a crosslinked structure, thereby being able to suppress the fluidity of the cured adhesive layer at high temperatures and making the heat resistance better, so it is preferred.

[0044] (Epoxy resin) The above-mentioned adhesive composition can, for example, contain an epoxy resin as a polyfunctional resin including at least two or more reactive functional groups in its structure. As the epoxy resin, a compound having two or more epoxy groups in one molecule can be used. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin and other bisphenol type epoxy resins, their modified resins, dicyclopentadiene-phenol addition reaction type epoxy resin and other dicyclopentadiene type epoxy resins, biphenyl type epoxy resin, tetramethylbiphenyl type epoxy resin, polyhydroxynaphthalene type epoxy resin, isocyanate modified epoxy resin, 10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide modified epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, triphenylmethane type epoxy resin, tetraphenylethane type epoxy resin, phenol aralkyl type epoxy resin, naphthol novolac type epoxy resin, hexanediol type epoxy resin, naphthol aralkyl type epoxy resin, naphthol-phenol co-condensed novolac type epoxy resin, naphthol-cresol co-condensed novolac type epoxy resin, aromatic hydrocarbon formaldehyde resin modified phenolic resin type epoxy resin, biphenyl modified novolac type epoxy resin, trimethylolpropane type epoxy resin, alicyclic epoxy resin, acrylic resin having an epoxy group, polyurethane resin having an epoxy group, polyester resin having an epoxy group, flexible epoxy resin, etc. can be used. The epoxy resin can be used alone or in combination of two or more.

[0045] Among them, from the aspect of making the heat resistance and adhesiveness of the cured thermosetting adhesive sheet better, it is preferred to use dicyclopentadiene type epoxy resins such as dicyclopentadiene-phenol addition reaction type epoxy resin, biphenyl type epoxy resin, tetramethylbiphenyl type epoxy resin, and polyhydroxynaphthalene type epoxy resin.

[0046] When the adhesive composition in the present invention contains an epoxy resin, the content of the epoxy resin is preferably 1 to 15 parts by mass, more preferably 2 to 10 parts by mass, relative to 100 parts by mass of the adhesive composition. If the content of the epoxy resin is within the above preferred range, the heat resistance after curing of the thermosetting adhesive sheet can be made better, and excellent low dielectric properties can be imparted, so it is preferred. In particular, when the thermosetting adhesive sheet is cured, the epoxy resin reacts to form a crosslinked structure, thereby suppressing the fluidity of the cured adhesive layer at high temperatures and making the heat resistance better, so it is preferred.

[0047] (Epoxy resin curing agent) The epoxy resin curing agent can be used as a catalyst to promote the curing reaction of the above epoxy resin. As the epoxy resin curing agent, for example, imidazole-based, phenol-based, amine-based, acid anhydride-based, organic peroxide-based, etc. can be used. In particular, from the viewpoint of the storage stability of the adhesive composition at room temperature, the epoxy resin curing agent is preferably a latent curing agent, and more preferably a capsuleized imidazole-based latent curing agent. By improving the storage stability at room temperature, the supply and management during the use of the adhesive composition can be made more convenient. Specifically, as the epoxy resin curing agent, a microcapsule-type latent curing agent in which a latent imidazole modifier is used as the core and its surface is coated with polyurethane can be used. The epoxy resin curing agent can be used alone or in combination of two or more.

[0048] When the adhesive composition in the present invention contains an epoxy resin curing agent, the content of the epoxy resin curing agent is preferably 1 to 10 parts by mass, more preferably 1 to 7 parts by mass, further preferably 2 to 5 parts by mass, and particularly preferably 2 to 3 parts by mass, relative to 100 parts by mass of the adhesive composition. If the content of the epoxy resin curing agent is within the above preferred range, the good curability during heating and the heat resistance after curing of the thermosetting adhesive sheet can be made better, so it is preferred. In particular, when the thermosetting adhesive sheet is cured, the epoxy resin curing agent reacts to form a crosslinked structure, thereby suppressing the fluidity of the cured adhesive layer at high temperatures and making the heat resistance better, so it is preferred.

[0049] (Other components) Within the scope that does not impair the effects of the present invention, the adhesive composition in the present invention may further contain other components. As the other components, for example, the following can be mentioned: tackifying resins; additives such as crosslinking agents, anti-aging agents, ultraviolet absorbers, polymerization inhibitors, surface conditioners, antistatic agents, foaming agents, defoaming agents, viscosity modifiers, light stabilizers, weather stabilizers, heat stabilizers, antioxidants, leveling agents, conductive particles, organic pigments, inorganic pigments, pigment dispersants, silica beads, organic beads, etc.; fillers such as silica, alumina, titanium oxide, zirconium oxide, antimony pentoxide, etc. They can be used alone or in combination of two or more.

[0050] Within the scope that does not impair the effects of the present invention, the content of the above-mentioned other components can be appropriately selected.

[0051] <Adhesive layer> The adhesive layer in the present invention can be a single-layer structure or a multi-layer structure of two or more layers.

[0052] The thickness of the adhesive layer in the present invention is not particularly limited as long as it is within the scope that does not impair the effects of the present invention, and is preferably 10 μ μm to 75 μ μm, more preferably 15 μ μm to 50 μ μm, still more preferably 15 μ μm to 25 μ μm. If the thickness of the adhesive layer is set within the above-mentioned preferred range, the heat resistance and adhesiveness after curing of the thermosetting adhesive sheet can be maintained well, and at the same time, the components of the cured product including the thermosetting adhesive sheet such as printed wiring boards can be made thinner, so it is preferred.

[0053] The storage modulus E' of the adhesive layer in the present invention at 30°C is preferably 1×10 6 Pa to 1×10 9 Pa, more preferably 2×10 6 Pa to 5×10 8 Pa, still more preferably 1×10 7 Pa to 5×10 8 Pa. If the storage modulus E' of the adhesive layer is set within the above-mentioned preferred range, the viscosity of the thermosetting adhesive sheet can be weakened, and the positioning operation of the thermosetting adhesive sheet when bonding to the adherend can be easily performed.

[0054] The storage modulus E' of the adhesive layer at 30°C can be adjusted to the above-mentioned preferred range, for example, by adjusting the types, styrene ratios, and contents of the styrene-based elastomer (A) and styrene-based elastomer (B) contained in the adhesive layer.

[0055] The storage modulus E' of the adhesive layer can be measured by the following method.

[0056] Overlap the adhesive layers in the present invention to make an adhesive layer with a thickness of 100 mm. Then, use a dumbbell cutter to punch the adhesive layer into the shape of test piece type 5 of JIS K 7127, and use it as a test piece. Then, use a tensile viscoelasticity tester (manufactured by Rheometrics, trade name: RSA-II)) to measure under the following conditions.

[0057] · Loading mode: sine wave (loading change frequency 3.5 Hz) · Tensile strain: 0.1% · Heating rate: 5 °C / minute The curing rate of the cured product of the adhesive layer in the present invention after heating the cured product of the adhesive layer at 290 °C for 10 minutes is preferably 10% - 100%, more preferably 15% - 95%, and further preferably 30% - 90%. If the curing rate after heating the cured product of the adhesive layer at 290 °C for 10 minutes is within the above preferred range, the fluidity of the cured adhesive layer at high temperature can be suppressed, and the heat resistance can be better.

[0058] The curing rate of the cured product of the adhesive layer after heating at 290 °C for 10 minutes can be adjusted to the above preferred range by adjusting, for example, the type and content of the polyfunctional resin and the type and content of the organic peroxide contained in the adhesive layer.

[0059] The curing rate of the cured product of the adhesive layer after heating at 290 °C for 10 minutes is represented by the gel fraction and can be measured by the following method.

[0060] Heat the adhesive layer in the present invention at 180 °C for 60 minutes to make a cured product, and then heat the cured product at 290 °C for 10 minutes to make a test piece. Then, immerse the test piece in a toluene solution adjusted to 23 °C for 24 hours, and use the mass of the dried test piece remaining in the solvent and the mass of the test piece before toluene impregnation and calculate the value based on the following calculation formula.

[0061] Gel fraction (mass%) = { (mass of the dried test piece remaining undissolved after immersion in toluene) / (mass of the test piece before toluene impregnation)} × 100 The dielectric constant (Dk) of the cured adhesive layer is preferably 1.0 to 3.0, more preferably 1.0 to 2.8. In addition, the tangent of the dielectric loss angle (Df) of the cured adhesive layer is preferably 0.01 or less, more preferably 0.0001 to 0.01, further preferably 0.0001 to 0.005, and particularly preferably 0.0001 to 0.003. By setting the dielectric constant (Dk) and / or the tangent of the dielectric loss angle (Df) of the cured adhesive layer within the above preferred ranges, the cured adhesive layer can exhibit good low dielectric properties.

[0062] The dielectric constant (Dk) and the tangent of the dielectric loss angle (Df) of the cured adhesive layer can be adjusted within the above preferred ranges, for example, by adjusting the types, styrene ratios, and contents of the styrene-based elastomer (A) and the styrene-based elastomer (B) contained in the adhesive layer.

[0063] The dielectric constant (Dk) and the tangent of the dielectric loss angle (Df) can be measured by the following method.

[0064] The adhesive layer is cut into a size of 35 mm × 50 mm and cured at 180 °C for 1 hour to produce a test piece for evaluation. For this test piece for evaluation, using a dielectric constant measuring device (manufactured by Keysight Technologies, split cylinder resonator), the dielectric constant (Dk) and the tangent of the dielectric loss angle (Df) at a measurement frequency of 28 GHz are obtained in an environment with a measurement temperature of 23 °C and 50% RH.

[0065] <Thermosetting adhesive sheet> The thermosetting adhesive sheet of the present invention has an adhesive layer containing the above adhesive composition. The thermosetting adhesive sheet of the present invention can use an adhesive sheet composed of a single adhesive layer, and can also use an adhesive sheet formed by laminating two or more adhesive layers that are the same or different.

[0066] The thermosetting adhesive sheet of the present invention can be a substrate-free adhesive sheet in which both sides of the adhesive layer are adhesive surfaces of the thermosetting adhesive sheet, or a substrate can be laminated on the adhesive layer. In the case where a substrate is laminated, the thermosetting adhesive sheet of the present invention can be a single-sided adhesive sheet in which the adhesive layer is laminated on a single surface of the substrate, or can also be a double-sided adhesive sheet in which the adhesive layer is laminated on both surfaces of the substrate.

[0067] As the base material, a resin film, a foam film, paper, cloth, a metal foil, a composite thereof, etc. can be used. Examples of the resin film include: polyolefin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyester films such as PET; vinyl chloride resin films; vinyl acetate resin films; polyimide resin films; polyamide resin films; fluororesin films; cellophane (Japanese: セロハン), etc. Examples of the paper include: Japanese paper, kraft paper, glassine paper, high-quality paper, synthetic paper, top coat, etc. Examples of the cloth include woven fabrics and non-woven fabrics based on various fibrous materials alone or blended, etc. Examples of the fibrous material include: cotton, staple fiber (Japanese: スフ), Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, polyolefin fiber, etc. Examples of the rubber sheet include: natural rubber sheet, butyl rubber sheet, etc. Examples of the foam sheet include: foamed polyurethane sheet, foamed polychloroprene rubber sheet, etc. Examples of the metal foil include: aluminum foil, copper foil, etc.

[0068] The thermosetting adhesive sheet of the present invention is not particularly limited in terms of its shape and size. For example, it includes an adhesive sheet having a shape and size suitable for attaching to a specified adherend (for example, an adhesive sheet in a state after stamping), and a long strip-shaped adhesive sheet (for example, an adhesive sheet before being processed into a specific shape).

[0069] The thickness of the thermosetting adhesive sheet of the present invention is not particularly limited as long as it is within a range that does not impair the effects of the present invention, and is preferably 10 μ μm to 150 μ μm, preferably 10 μ μm to 100 μ μm, more preferably 10 μ μm to 75 μ μm, further preferably 15 μ μm to 50 μm, particularly preferably 15 μ μm to 25 μ μm. If the thickness of the thermosetting adhesive sheet is set within the above preferred range, the heat resistance and adhesiveness of the thermosetting adhesive sheet after curing can be maintained well, and at the same time, the printed wiring board including the cured product of the thermosetting adhesive sheet can be made thinner, so it is preferred.

[0070] The thermosetting adhesive sheet of the present invention is firmly adhered to the adherend by curing it after being attached to the adherend. The curing conditions of the thermosetting adhesive sheet of the present invention are not particularly limited, and can be appropriately selected from known methods.

[0071] The curing conditions can be appropriately set according to the type of the adhesive composition, etc. The curing temperature is, for example, preferably 100°C to 220°C, more preferably 120°C to 200°C, and still more preferably 150°C to 180°C. The curing time is, for example, preferably 1 minute to 180 minutes, more preferably 15 minutes to 120 minutes, and still more preferably 30 minutes to 60 minutes. If the curing conditions are set within the above-mentioned preferred ranges, firm adhesion to the adherend can be achieved after curing, which is preferred.

[0072] The dielectric constant (Dk) of the cured thermosetting adhesive sheet of the present invention is preferably 1.0 to 3.0, more preferably 1.0 to 2.8. If the dielectric constant (Dk) of the cured thermosetting adhesive sheet is set within the above-mentioned preferred ranges, the cured thermosetting adhesive sheet exhibits good low dielectric properties and can exhibit better transmission characteristics when used in components for high-frequency applications.

[0073] The dielectric constant (Dk) of the cured thermosetting adhesive sheet can be adjusted to the above-mentioned preferred range, for example, by adjusting the types, styrene ratios, and contents of the styrene-based elastomer (A) and the styrene-based elastomer (B) contained in the adhesive layer.

[0074] The dielectric loss tangent (Df) of the cured thermosetting adhesive sheet of the present invention is preferably 0.01 or less, more preferably 0.0001 to 0.01, still more preferably 0.0001 to 0.005, and particularly preferably 0.0001 to 0.003. If the dielectric loss tangent (Df) of the cured thermosetting adhesive sheet is set within the above-mentioned preferred ranges, the cured thermosetting adhesive sheet exhibits good low dielectric properties and can exhibit good transmission characteristics when used in components for high-frequency applications.

[0075] The dielectric loss tangent (Df) of the cured thermosetting adhesive sheet can be adjusted to the above-mentioned preferred range, for example, by adjusting the types, styrene ratios, and contents of the styrene-based elastomer (A) and the styrene-based elastomer (B) contained in the adhesive layer.

[0076] The dielectric constant (Dk) and the dielectric loss tangent (Df) can be measured by the following method.

[0077] The thermosetting adhesive sheet is cut into a size of 35 mm × 50 mm to produce a test piece. This test piece is cured at 180°C for 1 hour to produce a test piece for evaluation. Using a dielectric constant measuring device (manufactured by Keysight Technologies, split cylindrical resonator), the dielectric constant (Dk) and the dielectric loss tangent (Df) at a measurement frequency of 28 GHz are obtained in an environment with a measurement temperature of 23°C and 50% RH.

[0078] The initial adhesion of the thermosetting adhesive sheet of the present invention to polyimide is preferably 0.5 N / mm or less, more preferably 0.46 N / mm or less, further preferably 0.1 N / mm or less, and particularly preferably 0.05 N / mm or less. If the initial adhesion of the thermosetting adhesive sheet to the polyimide is within the above preferred range, the viscosity is weak, and it is easy to perform the positioning operation when attaching the thermosetting adhesive sheet to the adherend.

[0079] The initial adhesion refers to the 90-degree peel adhesion of the thermosetting adhesive sheet before curing to polyimide, and it can be measured according to the method described below.

[0080] In an environment of 23°C and 50% RH, both sides of the thermosetting adhesive sheet are attached to a polyimide film (manufactured by Toray-DuPont, Kapton 100H, thickness 0.025 mm) to produce a test piece. The test piece is cut into a size of 20 mm × 70 mm and pressed back and forth once with a 2 kg roller, and aged for 1 hour in an environment of 23°C and 50% RH. One side of the polyimide film of the test piece is fixed to a SUS plate (30 mm × 130 mm). The end of the polyimide film of the test piece that is not fixed to the SUS plate is clamped by a tensile testing machine (RTH-1310 manufactured by A&D Company, Limited), and a tensile test is performed in the 90-degree direction at a test speed of 50 mm / min using the tensile testing machine. The value obtained at this time can be used as the initial adhesion of the thermosetting adhesive sheet.

[0081] When the thermosetting adhesive sheet of the present invention is attached to polyimide, the T-peel adhesion after curing of the thermosetting adhesive sheet of the present invention is preferably 0.25 N / mm or more, preferably 0.25 N / mm to 4.00 N / mm, more preferably 0.35 N / mm to 4.00 N / mm, and further preferably 0.50 N / mm to 4.00 N / mm. If the T-peel adhesion after curing of the thermosetting adhesive sheet to the polyimide is within the above preferred range, the close contact between the cured thermosetting adhesive sheet and the adherend becomes good, and good transmission characteristics can be exhibited when used in high-frequency components, and excellent adhesion performance can be exhibited at the same time.

[0082] The T-peel adhesion force after curing of the heat-curable adhesive sheet for the polyimide can be measured by the method described below.

[0083] In an environment of 23°C and 50% RH, both sides of the heat-curable adhesive sheet are bonded to a polyimide film (manufactured by Toray-DuPont, Kapton 100H, thickness 0.025 mm) to produce a test piece. For the test piece, a hot press is used to heat at 180°C while applying a pressure of 4.0 MPa for 10 minutes. Then, it is heated with a dryer at 180°C for 50 minutes to cure the test piece, thereby producing an evaluation test piece. The evaluation test piece is cut into a size of 10 mm × 100 mm, and the ends of the polyimide films bonded to both sides of the evaluation test piece are respectively clamped using a tensile testing machine (RTH-1310 manufactured by A&D Company, Limited). The tensile test is carried out in the T-shaped direction at a test speed of 300 mm / min using the tensile testing machine. The value obtained at this time can be used as the T-peel adhesion force after curing of the heat-curable adhesive sheet.

[0084] "Another form of the heat-curable adhesive sheet" The storage modulus E' at 30°C of the adhesive layer of another form of the heat-curable adhesive sheet of the present invention is 1×10 6 Pa to 1×10 9 Pa, the initial adhesion force of the heat-curable adhesive sheet to the polyimide is 0.5 N / mm or less, and the dielectric constant of the cured product of the heat-curable adhesive sheet at 23°C, 50% RH, and a frequency of 28 GHz is 1.0 to 3.0.

[0085] It should be noted that the adhesive layer containing 75 to 90 parts by mass of a styrene-based elastomer with respect to 100 parts by mass of the adhesive composition, which has been described, is sometimes referred to as an adhesive layer mainly composed of a styrene-based elastomer for description.

[0086] The heat-curable adhesive sheet of the present embodiment is easy to perform positioning operations when attaching to the adherend and can be reattached, and can be firmly bonded to the adherend by curing after attachment. In addition, the heat-curable adhesive sheet of the present embodiment has a low dielectric constant and can exhibit good transmission characteristics when used for high-frequency components, and furthermore, has excellent heat resistance, so it is possible to suppress the occurrence of adverse conditions such as expansion caused by exposure to high temperatures in the manufacturing process of such components, such as the reflow process.

[0087] In the heat-curable adhesive sheet of the present embodiment, the storage modulus E' at 30°C of the adhesive layer can be set to the same preferred range as the storage modulus E' at 30°C of the adhesive layer mainly composed of a styrene-based elastomer that has been described.

[0088] The adhesive composition constituting the adhesive layer in the present embodiment is not particularly limited as long as it can exhibit desired physical properties, and is not limited to the above-described adhesive composition mainly composed of a styrene-based elastomer. For example, epoxy resins, olefin resins, polyester resins, etc. can be cited.

[0089] Other detailed contents of the adhesive layer mainly composed of a styrene-based elastomer described in this specification can also be applied to the above-mentioned adhesive layer in the present embodiment.

[0090] The initial adhesion of the thermosetting adhesive sheet of the present embodiment to polyimide can be set to the same preferred range as the initial adhesion of the thermosetting adhesive sheet having an adhesive layer mainly composed of a styrene-based elastomer described above.

[0091] The dielectric constant of the cured product of the thermosetting adhesive sheet of the present embodiment at 23°C, 50% RH, and a frequency of 28 GHz can be set to the same preferred range as the dielectric constant of the cured product of the thermosetting adhesive sheet having an adhesive layer mainly composed of a styrene-based elastomer described above in an environment of 23°C, 50% RH, and a frequency of 28 GHz.

[0092] Other detailed contents of the thermosetting adhesive sheet having an adhesive layer mainly composed of a styrene-based elastomer described in this specification can also be applied to the thermosetting adhesive sheet of the present embodiment.

[0093] "Method for manufacturing a thermosetting adhesive sheet" The method for manufacturing the thermosetting adhesive sheet of the present invention is not particularly limited and can be appropriately selected from known methods.

[0094] The thermosetting adhesive sheet of the present invention can be manufactured, for example, by forming an adhesive layer containing the above-mentioned adhesive composition into a sheet shape on a release liner. The sheet-shaped adhesive layer can be manufactured, for example, by diluting the adhesive composition with a solvent, coating it on the surface of the release liner, and drying it, etc.

[0095] It should be noted that the thickness and physical properties of the thermosetting adhesive sheet are the thickness and physical properties after removing the release liner.

[0096] As the release liner, there is no particular limitation, and it can be appropriately selected according to the purpose. For example, it can include: papers such as kraft paper, cellophane, and high-quality paper; resin films such as polyethylene, polypropylene (biaxially oriented polypropylene (OPP)), uniaxially oriented polypropylene (CPP), and polyethylene terephthalate (PET); laminated papers formed by laminating the above-mentioned paper and resin film, papers obtained by performing caulking treatment on the above-mentioned paper with clay, polyvinyl alcohol, etc.; papers obtained by performing release treatment such as silicone-based resin on one or both sides of these papers, etc. These papers can be used alone or in combination of two or more.

[0097] "Use of the thermosetting adhesive sheet" As described above, the thermosetting adhesive sheet of the present invention has weak tack before curing. Therefore, when the thermosetting adhesive sheet is attached to the adherend in the manufacturing process, the positioning operation is easy, and the cured product of the thermosetting adhesive sheet has low dielectric constant and dielectric loss tangent, and further has excellent heat resistance when exposed to a very high temperature. Therefore, for example, it can be applied to uses such as interlayer adhesives for printed wiring boards and bonding and fixing of terminal portions of printed wiring boards and connection substrates for supporting them. In addition, in addition to printed wiring boards, the thermosetting adhesive sheet of the present invention can also be used for components in high-frequency applications such as flexible flat cables and various high-speed communication corresponding components.

[0098] "Printed wiring board" The printed wiring board of the present invention can be manufactured by including the cured product of the thermosetting adhesive sheet. The printed wiring board can be a printed circuit board connected with a circuit by circuit components such as printed components and mounted components, and can also be a printed wiring board having a wiring before forming circuit components. The printed wiring board of the present invention can be a rigid printed wiring board having a rigid insulating substrate, and can also be a flexible printed wiring board having a flexible insulating substrate. Further, the insulating substrate can also be a flexible-rigid printed wiring board having a rigid part and a flexible part.

[0099] Examples Next, examples are given to further illustrate the present invention in detail, but the present invention is not limited to these examples. Each material used in the examples and comparative examples is as follows.

[0100] <Component A: Styrene-based elastomer> A-1: Hydrogenated styrene-based elastomer modified with amine (Tuftec MP10, styrene ratio 30%, manufactured by Asahi Kasei Corporation) A-2: Hydrogenated styrene-based elastomer modified with maleic acid (Tuftec M1913, styrene ratio 30%, manufactured by Asahi Kasei Corporation) A-3: Hydrogenated styrene-based elastomer (Tuftec H1221, styrene ratio 12%, manufactured by Asahi Kasei Corporation) A-4: Hydrogenated styrene-based elastomer (Tuftec H1041, styrene ratio 30%, manufactured by Asahi Kasei Corporation) A-5: Hydrogenated styrene-based elastomer (Tuftec H1043, styrene ratio 67%, manufactured by Asahi Kasei Corporation) <Component B: Modified polyphenylene ether resin> B-1: Modified polyphenylene ether resin with methacryloyl groups at both ends (NORYL SA9000, number average molecular weight 2300, glass transition temperature 160 °C, manufactured by SABIC) <Component C: Epoxy resin> C-1: Naphthalene-type epoxy resin (HP4032D, epoxy equivalent 136 g / eq to 148 g / eq, liquid or crystalline, manufactured by DIC) <Component D: Organic peroxide> D-1: Dicumyl peroxide (Permicle D, decomposition temperature for a half-life of 1 minute is 175 °C, manufactured by NOF Corporation) [Preparation of adhesive composition] According to the parts by mass shown in Table 1, dissolve Component A shown in Table 1 in toluene solvent so that the concentration becomes 25%. Then, prepare the adhesive composition by uniformly mixing the other components B - D shown in Table 1 according to the parts by mass shown in Table 1.

[0101] [Manufacture of thermosetting adhesive sheet] Coat the obtained adhesive composition on a release liner so that the thickness after drying becomes 25 μ μm. Then dry it with a dryer at 85 °C for 2 minutes to obtain an adhesive layer with a thickness of 25 μ μm. Then, laminate a release liner on the surface where the adhesive layer is exposed to manufacture a thermosetting adhesive sheet.

[0102] The measurement and evaluation of the physical properties of the adhesive layer and the thermosetting adhesive sheet manufactured by the above method are carried out based on the following method. It should be noted that unless otherwise specified, the measurement of the thermosetting adhesive sheet is carried out by peeling the laminated release liner.

[0103] <Dielectric constant (Dk)> The thermosetting adhesive sheets produced in the examples and comparative examples were cut into a size of 35 mm × 50 mm and cured at 180°C for 1 hour to produce test pieces for evaluation. For these test pieces for evaluation, a dielectric constant measuring device (manufactured by Keysight Technologies, split cylindrical resonator) was used to determine the dielectric constant (Dk) at a measuring frequency of 28 GHz in an environment with a measuring temperature of 23°C and 50% RH. The results are shown in Table 1.

[0104] <Dielectric loss tangent (Df)> Using the same method as the measurement of the above dielectric constant (Dk), the dielectric loss tangent (Df) was determined for the test pieces for evaluation. The results are shown in Table 1.

[0105] <Storage modulus E'> The adhesive layers produced in the examples and comparative examples were overlapped to produce an adhesive layer with a thickness of 100 mm. Then, a dumbbell cutter was used to punch the adhesive layer into the shape of test piece type 5 of JIS K 7127, and it was used as a test piece. For the obtained test pieces, a tensile viscoelasticity tester (manufactured by Rheometrics, trade name: RSA-II) was used to measure the storage modulus E' under the following conditions. The results are shown in Table 1.

[0106] · Load mode: sine wave (load change frequency 3.5 Hz) · Tensile strain: 0.1% · Heating rate: 5°C / min <Initial adhesion to polyimide> In an environment of 23°C and 50% RH, both sides of the thermosetting adhesive sheets produced in the examples and comparative examples were adhered to a polyimide film (manufactured by Toray-DuPont, Kapton 100H) to produce test pieces. The test pieces were cut into a size of 20 mm × 70 mm and pressed back and forth once with a 2 kg roller, and cured for 1 hour in an environment of 23°C and 50% RH, and used as test pieces for evaluation.

[0107] One side of the polyimide film of the test piece for evaluation was fixed to a SUS plate (30 mm × 130 mm). The end of the polyimide film of the test piece for evaluation that was not fixed to the SUS plate was clamped using a tensile testing machine (RTH-1310 manufactured by A&D Company, Ltd.), and a tensile test was performed in the 90-degree direction at a test speed of 50 mm / min using the tensile testing machine. The value obtained at this time was used as the initial adhesion of the thermosetting adhesive sheet. The results are shown in Table 1.

[0108] <T-peel adhesion of the thermosetting adhesive sheet after curing> Under the environment of 23°C and 50% RH, test pieces were fabricated by laminating both sides of the thermosetting adhesive sheets prepared in the examples and comparative examples onto a polyimide film (manufactured by Toray-DuPont, Kapton 100H). For the test pieces, using a hot press, heating was carried out at 180°C while applying a pressure of 4.0 MPa for 10 minutes. Then, the test pieces were cured by heating in a dryer at 180°C for 50 minutes to fabricate test pieces for evaluation.

[0109] The test pieces were cut into a size of 10 mm × 100 mm. The ends of the polyimide films laminated on both sides of the test pieces were respectively clamped using a tensile testing machine (RTH-1310 manufactured by A&D Company, Limited), and a tensile test was carried out in the T-shaped direction at a test speed of 300 mm / min using the tensile testing machine. The value obtained at this time was used as the T-shaped peel adhesion force after curing of the thermosetting adhesive sheet. The results are shown in Table 1.

[0110] <Curing Rate> The curing rate of the cured product of the adhesive layer prepared in the examples and comparative examples was represented by the gel fraction and could be measured according to the following method.

[0111] The adhesive layers prepared in the examples and comparative examples were heated at 180°C for 60 minutes to obtain cured products. Then, the cured products were heated at 290°C for 10 minutes to fabricate test pieces. The test pieces were immersed in a toluene solution adjusted to 23°C for 24 hours, and the value calculated based on the following calculation formula using the mass of the dried test pieces remaining in the solvent and the mass of the test pieces before toluene impregnation was used.

[0112] Gel fraction (mass %) = {(mass of the dried test pieces remaining undissolved after toluene impregnation) / (mass of the adhesive layer before toluene impregnation)} × 100 The results are shown in Table 1.

[0113] <Positioning Property> The release liner on one side of the thermosetting adhesive sheets prepared in the examples and comparative examples was peeled off and placed on the polyimide film. Then, in the state where the release liner was laminated on one side of the thermosetting adhesive sheet, the following criteria were used for evaluation: whether the thermosetting adhesive sheet could be positioned by sliding or re-peeling relative to the polyimide film. The results are shown in Table 1.

[0114] ○: Does not adhere to the polyimide film, can slide, and can be positioned.

[0115] △: Adheres to the polyimide film, cannot slide, but can be positioned without residual adhesive when peeled off.

[0116] ×: With respect to bonding to the polyimide film, it cannot slide, there is residual glue during peeling, so it is not suitable for positioning.

[0117] <Reflow heat resistance> Bond both sides of the thermosetting adhesive sheets prepared in the examples and comparative examples to polyimide or copper foil, and heat at 180 °C for 60 minutes to prepare a cured product. Then, heat the cured product at 260 °C or 290 °C for 15 minutes to make a test piece. Confirm the appearance of the test piece and evaluate it visually according to the following criteria. The results are shown in Table 1.

[0118] ○: The appearance of the test piece has not changed. △: The test piece expands. ×: The test piece has resin flow. Based on the results of the reflow heat resistance, judge whether the reflow heat resistance is qualified according to the following criteria. The results are shown in Table 1.

[0119] Qualified: Before and after heating at 260 °C and 290 °C, the test piece does not expand or have resin flow. Or, before and after heating at 260 °C, the test piece does not expand or have resin flow, but after heating at 290 °C, the test piece expands or has resin flow.

[0120] Unqualified: Before and after heating at 260 °C and 290 °C, the test piece expands and has resin flow.

[0121] [Table 1]

[0122] From the results shown in Table 1, it can be seen that: the thermosetting adhesive sheet of the example has good positioning properties, and good adhesiveness and reflow heat resistance after thermosetting.

[0123] From the results of Comparative Example 1 and Comparative Example 2, it can be seen that: the thermosetting adhesive sheet without the styrene-based elastomer (A) with a styrene ratio of 30% or more has a higher initial adhesion to polyimide, and the positioning property deteriorates.

[0124] From the results of Comparative Example 2, it can be seen that: the thermosetting adhesive sheet without the polyfunctional resin such as polyphenylene ether resin and epoxy resin, which includes at least two or more reactive functional groups in the structure, has a higher resin fluidity in a high-temperature environment above 260 °C and is difficult to maintain heat resistance.

Claims

1. A thermosetting adhesive sheet, characterized in that, It has an adhesive layer containing an adhesive composition. Relative to 100 parts by mass of the adhesive composition, the adhesive layer contains 75 to 90 parts by mass of a styrenic elastomer. The styrenic elastomer contains at least a styrenic elastomer (A) with a styrene ratio of 30% or more. The adhesive layer contains a polyfunctional resin having at least two or more reactive functional groups in its structure. The cured product of the thermosetting adhesive sheet has a dielectric constant of 1.0 to 3.0 at 23°C, 50% RH, and a frequency of 28 GHz.

2. The thermosetting adhesive sheet according to claim 1, wherein, The styrenic elastomer contains a styrenic elastomer (B) with a styrene ratio of less than 30%.

3. The thermosetting adhesive sheet according to claim 1 or 2, wherein, Relative to 100 parts by mass of the adhesive composition, the content of the styrenic elastomer (A) is 5 parts by mass or more.

4. The thermosetting adhesive sheet according to claim 2, wherein, Relative to 100 parts by mass of the adhesive composition, the content of the styrenic elastomer (B) is 35 parts by mass or more.

5. The thermosetting adhesive sheet according to claim 1 or 2, wherein, Relative to 100 parts by mass of the adhesive composition, 5 to 20 parts by mass of a modified polyphenylene ether resin having a polymerizable group at its end is contained as the polyfunctional resin.

6. The thermosetting adhesive sheet according to claim 1 or 2, wherein Relative to 100 parts by mass of the adhesive composition, 1 to 15 parts by mass of an epoxy resin is contained as the polyfunctional resin.

7. The thermosetting adhesive sheet according to claim 1 or 2, wherein, Relative to 100 parts by mass of the adhesive composition, 0.1 to 10 parts by mass of an organic peroxide is contained.

8. The thermosetting adhesive sheet according to claim 1 or 2, wherein, The storage modulus E' of the adhesive layer at 30°C is 1×10 6 Pa to 1×10 9 Pa.

9. The thermosetting adhesive sheet according to claim 1 or 2, wherein, The initial adhesive force of the thermosetting adhesive sheet to polyimide is 0.5 N / mm or less.

10. The thermosetting adhesive sheet according to claim 1 or 2, wherein, The T-peel adhesive force after attaching the thermosetting adhesive sheet to polyimide and curing it is 0.25 N / mm or more.

11. The thermosetting adhesive sheet according to claim 1 or 2, wherein, The thermosetting adhesive sheet is used for printed wiring boards.

12. A printed wiring board, characterized in that, It contains the cured product of the thermosetting adhesive sheet according to claim 1 or 2.

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