Laminate and wiring board

Abstract

A laminate (1) comprises a resin layer (10), a first support body (20), and a second support body (30), wherein: the resin layer (10) is disposed between the first support body (20) and the second support body (30); the resin layer (10) is a cured product of a resin composition which contains a styrene-butadiene-styrene copolymer and organic peroxide; the copolymerization ratio of the styrene-butadiene-styrene copolymer is 5-20:60-90:5-20; the thickness of the resin layer (10) is 0.150-1.000 mm; the tensile elastic modulus of the resin layer (10) at 25°C is 1.0-10 MPa; and the elongation at break of the resin layer (10) at 25°C is not less than 100%.

Description

Laminate and Wiring Substrate

[0001] The present invention relates to a laminate and a wiring substrate.

[0002] In recent years, there has been a demand for electronic devices that can be deformed or bent in order to be attached to curved surfaces and uneven surfaces such as clothes. On the other hand, a flexible substrate is known as a substrate that can be repeatedly deformed, and it is known that polyimide is used for the core of the flexible substrate from the viewpoints of heat resistance and insulation.

[0003] Patent Document 1 discloses a polyimide layer-containing flexible substrate having a metal substrate and a polyimide layer formed on the metal substrate, the polyimide layer having a layer thickness of 1.5 to 100 μm and a glass transition point temperature of 300 to 450°C.

[0004] Japanese Patent Application Laid-Open No. 2018-027690

[0005] In recent years, for substrates used in antennas or radars, etc., it is required to reduce the loss during signal transmission. However, in a flexible substrate, if the thickness of the polyimide is increased, for example, to reduce transmission loss, since the rigidity of the polyimide is high, there is a risk that the polyimide substrate may break due to bending or the circuit may peel off at the interface.

[0006] The present invention has been made in view of the problems of such conventional technologies. And an object of the present invention is to provide a laminate excellent in flexibility even when the thickness of the resin layer is large and a wiring substrate using the same.

[0007] To solve the above problems, a laminate according to a first aspect of the present invention comprises a resin layer, a first support, and a second support. The resin layer is disposed between the first support and the second support. The resin layer is a cured product of a resin composition containing styrene-butadiene-styrene copolymer and an organic peroxide. The copolymerization ratio of the styrene-butadiene-styrene copolymer is 5 to 20:60 to 90:5 to 20. The thickness of the resin layer is 0.150 mm to 1.000 mm. The tensile modulus of the resin layer at 25°C is 1.0 MPa or more and 10 MPa or less. The elongation at break of the resin layer at 25°C is 100% or more. The resin composition contains 80% to 99% by mass of styrene-butadiene-styrene copolymer in its resin components. The resin composition contains 0.1% to 5% by mass of organic peroxide.

[0008] A wiring board according to a second aspect of the present invention comprises a laminate.

[0009] Figure 1 is a cross-sectional view showing an example of a laminate according to one embodiment. Figure 2 is a diagram showing the circuit pattern used for evaluating flexibility. Figure 3 is a graph showing the results of the MIT test when styrene-butadiene-styrene copolymer is used. Figure 4 is a graph showing the results of the MIT test when polyimide film is used.

[0010] This embodiment will be described in detail below with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for illustrative purposes and may differ from the actual ratios.

[0011] [Laminate] First, the laminate 1 according to this embodiment will be described with reference to Figure 1. As shown in Figure 1, the laminate 1 according to this embodiment comprises a resin layer 10, a first support 20, and a second support 30. The resin layer 10 is disposed between the first support 20 and the second support 30. In this embodiment, the resin layer 10 and the first support 20 are in direct contact. Also, the resin layer 10 and the second support 30 are in direct contact. The laminate 1 is constructed by laminating the first support 20, the resin layer 10, and the second support 30 in this order.

[0012] (Resin layer 10) The resin layer 10 is a cured product of a resin composition containing a styrene-butadiene-styrene copolymer and an organic peroxide. The styrene-butadiene-styrene copolymer is a type of elastomer and has excellent low dielectric properties, stretchability, flexibility, etc. The organic peroxide partially acts on the butadiene portion in the styrene-butadiene-styrene copolymer, causing a crosslinking reaction. As a result, the resin layer becomes stable against heat deformation, maintains its shape, and can obtain heat resistance. In this specification, a composition having such a crosslinked structure is referred to as a "cured product".

[0013] Styrene-butadiene-styrene copolymers may be unhydrogenated, partially hydrogenated, or fully hydrogenated. When hydrogen is added to a styrene-butadiene-styrene copolymer, hydrogen is added to the C=C double bond of the butadiene portion. When hydrogen is fully hydrogenated to a styrene-butadiene-styrene copolymer, styrene-ethylene-butylene-styrene copolymer (SEBS) is obtained. From the viewpoint of reactivity, it is preferable that the styrene-butadiene-styrene copolymer is unhydrogenated. Because unhydrogenated styrene-butadiene-styrene copolymers are highly reactive, they can accelerate the curing of the resin. Furthermore, from the viewpoint of thermal stability and weather resistance of the cured product, it is preferable that the styrene-butadiene-styrene copolymer is fully hydrogenated. Styrene-butadiene-styrene copolymers that possess both of these properties are preferably partially hydrogenated.

[0014] The copolymerization ratio of the styrene-butadiene-styrene copolymer is 5-20:60-90:5-20. That is, the styrene-butadiene-styrene copolymer is a copolymer of a first styrene block, a butadiene block, and a second styrene block. In the styrene-butadiene-styrene copolymer, the copolymerization ratio of the first styrene block is 5-20% by mass, the copolymerization ratio of the butadiene block is 60-90% by mass, and the copolymerization ratio of the second styrene block is 5-20% by mass. By setting the copolymerization ratio within the above range, the flexibility of the laminate 1 can be improved.

[0015] The melting point of the styrene-butadiene-styrene copolymer is preferably 70°C or higher. This configuration improves the heat resistance of the cured product. Furthermore, the resin is less likely to flow out during heating and drying, making it easier to control the film thickness. In addition, the resin is less likely to flow out from between the first support 20 and the second support 30 during heating and pressing, reducing resin loss. As a result, the manufacturing efficiency of the laminate 1 can be improved.

[0016] The number-average molecular weight Mn of the styrene-butadiene-styrene copolymer is preferably in the range of 50,000 to 100,000. When the number-average molecular weight Mn is within the above range, the flexibility of the laminate 1 can be further improved. The number-average molecular weight can be the standard polystyrene equivalent value obtained by gel permeation chromatography (GPC).

[0017] Examples of organic peroxides include α,α'-di(t-butylperoxy)diisopropylbenzene, 1,1-di(t-hexylperoxy)cyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexine, benzoyl peroxide, 3,3',5,5'-tetramethyl-1,4-diphenoquinone, chloranil, 2,4,6-tri-t-butylphenoxyl, t-butylperoxyisopropyl monocarbonate, azobisisobutyronitrile, methyl ethyl ketone peroxide, and acetylacetone peroxide. Oxide, 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(t-butylperoxy)butane, 4,4-di-(t-butylperoxy)n-butyl valerate, 2,2-di(4,4-di-(t-butylperoxy)cyclohexyl)propane, p-menthane hydroxyperoxide, diisopropylbenzene hydroxyperoxide, cumene hydroperoxide, t-butyl hydroperoxide, di(2-t-butylperoxyisopropyl)benzene, dicumyl peroxide, 2,5-dimethyl-2,5- Di(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexine, diisobutyl peroxide, di(3,5,5-trimethylhexanoyl) peroxide, dilauroyl peroxide, disuccinate peroxide, di-(3-methylbenzoyl) peroxide, benzoyl(3-methylbenzoyl) peroxide, dibenzoyl peroxide, di-n-propyl peroxydicarbonate, diisopropyl peroxide Dicarbonate, di(4-t-butylcyclohexyl)peroxycarbonate, di(2-ethylhexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate, cumylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, t-hexylperoxyneodecanoate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,Examples include 5-di(2-ethylhexanoylperoxy)hexane, t-butylperoxy-2-ethylhexanoate, t-hexylperoxyisopropyl monocarbonate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxyacetate, t-butylperoxy-3-methylbenzoate, t-butylperoxybenzoate, t-butylperoxyallyl monocarbonate, and 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone.

[0018] The resin composition contains 80% to 99% by mass of styrene-butadiene-styrene copolymer in the resin components. When the content of styrene-butadiene-styrene copolymer is within the above range, the flexibility of the laminate 1 can be further improved. The content of styrene-butadiene-styrene copolymer may be 85% or more by mass, 90% or more by mass, or 95% or more by mass.

[0019] The resin composition contains 0.1% by mass or more and 5% by mass or less of organic peroxide. When the organic peroxide content is within the above range, the curing of the resin can be accelerated and the heat resistance can be improved. The organic peroxide content may be 0.5% by mass or more, or 1% by mass or more. Furthermore, the organic peroxide content may be 4% by mass or less, or 3% by mass or less.

[0020] In the resin composition, the mass ratio of the styrene-butadiene-styrene copolymer to the organic peroxide is preferably 19 to 199. That is, in the resin composition, the mass ratio of the styrene-butadiene-styrene copolymer to the organic peroxide is preferably 19:1 to 199:1. When these ratios are within the above range, the curing of the resin can be accelerated and the heat resistance can be improved.

[0021] In addition to styrene-butadiene-styrene copolymer and organic peroxides, the resin composition may also contain other resin components such as polyphenylene ether resin, epoxy resin, maleimide resin, polysiloxane resin, polybutadiene resin, acrylic resin, polystyrene resin, polyester resin, polyurethane resin, polyolefin resin, and polyamide resin. For example, when using polyphenylene ether resin, epoxy resin, or maleimide resin, it is possible to improve the tensile stress of the resin, reduce the amount of organic peroxide required, and minimize the generation of bubbles. Epoxy resins can also be used with initiators other than organic peroxides, such as imidazoles, and the combined use of epoxy resin is preferable because it improves resin strength and reduces organic peroxides. Polysiloxane resins can reduce the tensile stress of the resin, enabling the production of a flexible laminate 1. Polysiloxane resins are also components that can be cured with initiators other than organic peroxides, and they can reduce bubbles. Adding polybutadiene resin can improve tensile stress. Similar to epoxy resins and polysiloxane resins, polybutadiene resins can also have their mechanical strength improved without increasing the amount of organic peroxides required.

[0022] The resin composition may optionally contain components other than styrene-butadiene-styrene copolymer and organic peroxides. The resin composition may also contain additives such as reactive diluents such as monomers, inorganic fillers, curing agents, silane coupling agents, flame retardants, defoamers, antioxidants, heat stabilizers, antistatic agents, ultraviolet absorbers, dyes, pigments, leveling agents, adhesion improvers, dispersants, and lubricants.

[0023] The thickness of the resin layer 10 is between 0.150 mm and 1.000 mm. When the thickness of the resin layer 10 is 0.150 mm or more, transmission loss can be reduced and handling performance can be improved. When the thickness of the resin layer 10 is 1.000 mm or less, flexibility can be improved.

[0024] The tensile modulus of the resin layer 10 at 25°C is 1.0 MPa or more and 10 MPa or less. When the tensile modulus is within the above range, the flexibility of the laminate 1 can be improved. The tensile modulus of the resin layer 10 may be 2 MPa or more, or 3 MPa or more. Also, the tensile modulus of the resin layer 10 may be 8 MPa or less, or 6 MPa or less. In this embodiment, the tensile modulus is a value obtained by performing a tensile test on the cured resin composition constituting the resin layer 10 at room temperature (25°C) at a tensile speed of 25 mm / min.

[0025] The elongation at break of the resin layer 10 at 25°C is 100% or more. When the elongation at break of the resin layer 10 is 100% or more, the flexibility of the laminate 1 can be improved. The elongation at break of the resin layer 10 may be 200% or more, or 300% or more. Furthermore, the elongation at break of the resin layer 10 may be 500% or less, or 400% or less. In this embodiment, the elongation at break is obtained by performing a tensile test at room temperature (25°C) with a tensile speed of 25 mm / min, and is the elongation at which the cured product breaks.

[0026] The relative permittivity of the resin layer 10 at 10 GHz may be 3 or less. When the relative permittivity of the resin layer 10 is 3 or less, dielectric loss can be reduced compared to polyimide. The relative permittivity may also be greater than 0. The relative permittivity can be obtained by measuring it using the cavity resonator perturbation method.

[0027] The dielectric loss tangent of the resin layer 10 at 10 GHz may be 0.005 or less. When the dielectric loss tangent of the resin layer 10 is 0.005 or less, the dielectric loss can be reduced compared to polyimide. It is more preferable that the dielectric loss tangent of the resin layer 10 be 0.001 or less. The dielectric loss tangent may be greater than 0. The dielectric loss tangent can be obtained by measuring using the cavity resonator perturbation method.

[0028] (First support 20 and second support 30) The first support 20 is laminated on a first surface, which is one surface of the resin layer 10, and the second support 30 is laminated on a second surface, which is the surface opposite to the first surface. At least one of the first support 20 and the second support 30 may be a metal foil or a resin film including a release film (also called a separator). The release film is a type of resin film that has release properties.

[0029] The metal foil is not particularly limited, and any metal foil commonly used in metal-clad laminates or wiring boards can be used. Examples of metal foils include copper foil or aluminum foil for circuit formation.

[0030] The resin film is, for example, a resin with a melting point of 180°C or higher. With this configuration, even under the thermal conditions for curing the resin layer 10, the curing reaction of the resin layer 10 can be carried out appropriately while suppressing the deformation of the support itself. The melting point of the resin film is preferably 220°C or higher, and more preferably 250°C or higher.

[0031] The resin film is not particularly limited, but examples include electrically insulating films such as PI (polyimide film), PET (polyethylene terephthalate) film, PEN (polyethylene naphthalate) film, polyester film, polyparabanic acid film, polyether ether ketone film, polyphenylene sulfide film, aramid film, polycarbonate film, and polyarylate film.

[0032] In the laminate 1 of this embodiment, the thickness of the first support 20 can be appropriately set depending on the application of the laminate 1, the type of support, etc., but for example, if the first support 20 is a resin film, it is preferable that it be about 0.01 mm or more and 0.2 mm or less. From the viewpoint of handling, it is more preferable that the thickness of the first support 20 be about 0.02 mm or more and 0.1 mm or less. Furthermore, if the first support 20 is a metal foil, it is preferable that the thickness of the first support 20 be about 0.002 mm or more and 0.05 mm or less, and in particular from the viewpoint of ensuring the strength of the circuit and the flexibility of the circuit board, it is more preferable that it be 0.009 mm or more and 0.035 mm or less.

[0033] Similarly, the thickness of the second support 30 can be set appropriately. For example, if the second support 30 is a resin film, the thickness of the second support 30 is preferably 0.01 mm or more and 0.2 mm or less. From the viewpoint of handling, the thickness of the second support 30 is more preferably 0.02 mm or more and 0.1 mm or less. If the second support 30 is a metal foil, the thickness of the second support 30 is preferably 0.002 mm or more and 0.05 mm or less, and from the viewpoint of ensuring the strength of the circuit and the flexibility of the circuit board, it is more preferably 0.009 mm or more and 0.035 mm or less. The thicknesses of the first support 20 and the second support 30 may be different or the same.

[0034] The laminate 1 of this embodiment can be used for a variety of applications. For example, the laminate 1 can be used as a material for stretchable electronic devices, particularly stretchable circuit boards. In this case, at least one of the first support 20 and the second support 30 may be made of a conductive layer such as a metal foil, or the first support 20 or the second support 30 may be peeled off and a conductive layer such as a conductive paste may be provided on the resin layer 10.

[0035] The laminate 1 may be a substrate for an antenna module or a multilayer substrate. That is, it may be used as a wiring board comprising the laminate. These laminates 1 are required to particularly reduce signal loss during signal transmission. The laminate 1 according to this embodiment has excellent flexibility even when the thickness of the resin layer 10 is thick. Therefore, the laminate 1 is particularly suitable for these applications.

[0036] The laminate 1 described above can be applied to electronic devices and the like. For example, an electronic device may comprise the laminate 1 and electronic components mounted on the laminate 1. The electronic components are not particularly limited, but examples include resistors, transistors, signal-emitting elements, light-emitting elements, solar power generation elements, diodes, switching elements, capacitors, coils, liquid crystals, wireless modules such as Bluetooth®, various sensors such as acceleration sensors, humidity sensors, and temperature sensors, and chip components used in RFID, etc.

[0037] Electronic components can be mounted, for example, by mounting methods using conductive adhesives or glues, or by mounting methods using solder and reflow soldering. Alternatively, instead of solder, the elements can be printed onto the resin layer 10 of the laminate or onto the support.

[0038] [Method for Manufacturing the Laminate] Next, the method for manufacturing the laminate 1 of this embodiment will be described. The method for manufacturing the laminate 1 of this embodiment includes laminating the resin layer 10, the first support 20, and the second support 30, and heating under pressure.

[0039] First, a resin varnish, which will be the raw material for the resin layer 10, is applied to the surface of the first support 20 to a desired thickness. Methods for applying the resin varnish include bar coaters, comma coaters, die coaters, roll coaters, and gravure coaters.

[0040] The resin varnish is prepared, for example, as follows: First, the raw materials containing styrene-butadiene-styrene copolymer and organic peroxide are dissolved in an organic solvent. The organic solvent may be heated if necessary. Then, if necessary, components that do not dissolve in the organic solvent, such as inorganic fillers, are added to the organic solvent, and the mixture is dispersed using a ball mill, bead mill, planetary mixer, or roll mill until a predetermined dispersion state is reached, thereby preparing the resin varnish.

[0041] The organic solvent is not particularly limited, and examples thereof include toluene, methyl ethyl ketone, cyclohexanone, and propylene glycol monomethyl ether acetate. These organic solvents may be used alone or in combination of two or more. Further, part or all of the organic solvent may be replaced with a reactive diluent. Specific examples of the reactive diluent include styrene, butyl acrylate, butyl methacrylate, butyl glycidyl ether, and 1,2-dodecene.

[0042] Thereafter, the applied resin varnish is dried by heating under desired heating conditions, for example, at 50°C or higher and 180°C or lower for about 1 minute or longer and 60 minutes or shorter. By heating, the solvent is volatilized from the resin varnish, and the solvent is reduced or removed to form a resin composition in a pre-cured (A stage) or semi-cured state (B stage).

[0043] Next, the second support 30 is laminated on the resin composition in a pre-cured or semi-cured state. The second support 30 may be laminated by a vacuum lamination method. Then, the resin composition in a pre-cured or semi-cured state is cured and integrated by heat and pressure molding to form a laminate including the first support 20, the resin layer 10, and the second support 30. At this time, the resin composition in a pre-cured or semi-cured state is sandwiched between the first support 20 and the second support 30 and heated and pressurized, and by setting the pressure during the pressurization to 0.3 MPa or higher and 10 MPa or lower, the generation of bubbles and openings in the resin layer 10 can be suppressed. Further, the temperature during heat and pressure molding is preferably about 130 to 230°C, and the heat and pressure molding time can be about 5 to 120 minutes. When performing heat and pressure molding, if the resin layer 10 protrudes outside the first support 20 and the second support 30, the protruding resin layer 10 may be removed by cutting with a cutter, a slitter, a guillotine cutter, or the like. <000​​​​​​(Technology 1) A laminate comprising a resin layer, a first support, and a second support, wherein the resin layer is disposed between the first support and the second support, the resin layer is a cured product of a resin composition containing a styrene-butadiene-styrene copolymer and an organic peroxide, the copolymerization ratio of the styrene-butadiene-styrene copolymer is 5 to 20:60 to 90:5 to 20, the thickness of the resin layer is 0.150 mm to 1.000 mm, the tensile modulus of the resin layer at 25°C is 1.0 MPa or more and 10 MPa or less, the elongation at break of the resin layer at 25°C is 100% or more, the resin composition contains 80% by mass or more and 99% by mass or less of the styrene-butadiene-styrene copolymer in the resin component, and the resin composition contains 0.1% by mass or more and 5% by mass or less of the organic peroxide.

[0047] Thus, in the laminate according to this embodiment, even if the thickness of the resin layer is large, the flexibility is high. Therefore, even when the laminate is deformed into an arbitrary shape, the followability is high, so that when the laminate is used as a stretchable circuit board material, the laminate and its circuit layer are not easily damaged.

[0048] (Technology 2) The laminate according to Technology 1, wherein at least a part of the styrene-butadiene-styrene copolymer is hydrogenated. With such a configuration, the thermal stability and weather resistance of the resin layer can be improved.

[0049] (Technology 3) The laminate according to Technology 1 or 2, wherein the melting point of the styrene-butadiene-styrene copolymer is 70°C or higher. With such a configuration, the heat resistance of the cured product is improved. Also, the resin is less likely to flow out during heat drying, making it easier to control the film thickness. Furthermore, the resin is less likely to flow out during heat press molding, reducing resin loss. Therefore, the manufacturing efficiency of the laminate can be improved.

[0050] (Technology 4) The laminate according to any one of Technologies 1 to 3, wherein the number average molecular weight Mn of the styrene-butadiene-styrene copolymer is in the range of 50,000 to 100,000. With such a configuration, the flexibility of the laminate can be further improved.

[0051] (Technical 5) The laminate according to any one of Technical 1 to 4, wherein the mass ratio of the styrene-butadiene-styrene copolymer to the organic peroxide in the resin composition is 19:1 to 199:1. With such a configuration, the curing of the resin can be accelerated and the heat resistance can be improved.

[0052] (Technical 6) A laminate according to any one of Technical 1 to 5, wherein the first support is a metal foil, the second support is a metal foil or a resin film, and the resin film is a resin with a melting point of 180°C or higher. With such a configuration, a laminate suitable as a substrate for circuit formation can be provided.

[0053] (Technical 7) A wiring board comprising a laminate as described in any one of Technical 1 to 6. The laminate according to the above embodiment has high flexibility even when the resin layer is thick, making it possible to reduce signal loss during transmission. For this reason, a wiring board comprising the laminate is particularly suitable for these applications.

[0054] The present disclosure will be described in further detail below with reference to examples, comparative examples, and reference examples, but the present disclosure is not limited to these examples. In the examples and comparative examples, "core component" refers to the main component that constitutes the resin layer in the laminate.

[0055] (Reference Example 1) First, the following materials were prepared: (1) Styrene-butadiene-styrene copolymer: "ToughTec® P1083" manufactured by Asahi Kasei Corporation, styrene block:butadiene block:styrene block = 10:80:10 (mass ratio), partially hydrogenated (2) Organic peroxide: 1,3-bis(butylperoxyisopropyl)benzene, "Perbutyl® P" (manufactured by NOF Corporation) (3) First support: copper foil ("CF-S9V-SV" manufactured by Fukuda Metal Copper Powder Co., Ltd., melting point over 1000℃, thickness: 18μm) (4) Second support: copper foil ("CF-S9V-SV" manufactured by Fukuda Metal Copper Powder Co., Ltd., melting point over 1000℃, thickness: 18μm)

[0056] Next, a styrene-butadiene-styrene copolymer was dissolved in toluene to a solid content concentration of 33% by mass to prepare a toluene solution of the styrene-butadiene-styrene copolymer. Then, the toluene solution and organic peroxide were mixed so that the mass ratio of the styrene-butadiene-styrene copolymer solid content to the organic peroxide was 98:2 to prepare a resin varnish.

[0057] The resin varnish prepared as described above was applied to the first support to a thickness of 0.050 mm after drying, and dried at 80°C for 10 minutes to form an uncured resin composition. Next, copper foil was laminated on top of the resin composition as a second support, and vacuum lamination was performed (vacuum time 20 seconds, pressure 0.3 MPa, pressurization time 1 minute, temperature 80°C). After that, the resin composition was cured by heating and pressurizing at a temperature of 180°C and a pressure of 4 MPa for 30 minutes, obtaining a laminate in which the first support, resin layer, and second support were laminated in this order.

[0058] (Reference Example 2) A laminate was fabricated in the same manner as in Reference Example 1, except that the thickness of the resin layer was set to 0.100 mm.

[0059] (Example 1) A laminate was prepared in the same manner as in Reference Example 1, except that the thickness of the resin layer was 0.150 mm.

[0060] (Example 2) A laminate was prepared in the same manner as in Reference Example 1, except that the thickness of the resin layer was 0.200 mm.

[0061] (Comparative Example 1) A polyimide film (manufactured by Panasonic Industries, Ltd., R-F775) was used as the resin layer, and a laminate was prepared to have the same configuration as in Reference Example 1.

[0062] (Comparative Example 2) A laminate was prepared in the same manner as in Comparative Example 1, except that the thickness of the resin layer was 0.075 mm.

[0063] (Comparative Example 3) A laminate was prepared in the same manner as in Comparative Example 1, except that the thickness of the resin layer was 0.100 mm.

[0064] (Comparative Example 4) A laminate was prepared in the same manner as in Comparative Example 1, except that the thickness of the resin layer was 0.125 mm.

[0065] (Comparative Example 5) A laminate was prepared in the same manner as in Comparative Example 1, except that the thickness of the resin layer was 0.150 mm.

[0066] (Comparative Example 6) A laminate was prepared in the same manner as in Reference Example 1, except that an LCP (liquid crystal polymer) film (manufactured by Panasonic Industries, Ltd., R-F705) was used as the resin layer.

[0067] (Comparative Example 7) A laminate was prepared in the same manner as in Comparative Example 6, except that the thickness of the resin layer was 0.100 mm.

[0068] (Comparative Example 8) A laminate was prepared in the same manner as in Comparative Example 6, except that the thickness of the resin layer was 0.125 mm.

[0069] (Comparative Example 9) A laminate was prepared in the same manner as in Comparative Example 6, except that the thickness of the resin layer was 0.150 mm.

[0070] (Comparative Example 10) A laminate was prepared in the same manner as in Reference Example 2, except that a fluorine-based film (PTFE film manufactured by Panasonic Industries, Ltd.) was used as the resin layer.

[0071] (Comparative Example 11) A laminate was prepared in the same manner as in Comparative Example 10, except that the thickness of the resin layer was 0.150 mm.

[0072] [Evaluation] (Tensile modulus and elongation at break) First, No. 6 dumbbell test specimens, as specified in JIS K6251:2023, were taken from the 100 μm thick resin layers obtained in Reference Example 2, Comparative Example 3, Comparative Example 7, and Comparative Example 10. Next, tensile tests were performed on each of the obtained test specimens using an Autograph (AGS-X) manufactured by Shimadzu Corporation under the following conditions: Temperature: 25°C Load cell: 50 N Initial grip distance: 35 mm Tensile speed: 25 mm / min

[0073] The tensile modulus of the film was calculated by determining the slope of r-σ using the least squares method from all stress (σ) data corresponding to strain (r) from 0.01 to 0.05. Strain (r) and stress (σ) are expressed by the following equations: Strain (r) = x / 35 (x is the distance traveled by the grip) Stress (σ) = F / (d・l) (F is the test force, d is the film thickness, and l is the width of the test specimen)

[0074] The film's elongation at break (%) was calculated using the distance the gripper moved at the time of break, using the following formula: Film elongation at break (%) = x / 35 × 100

[0075] (Relative permittivity Dk and dielectric loss tangent Df) The relative permittivity and dielectric loss tangent at 10 GHz of the 100 μm thick resin layers obtained in Reference Example 2, Comparative Example 3, Comparative Example 7, and Comparative Example 10 were measured using a network analyzer (N5230A manufactured by Agilent Technologies, Inc.) by the cavity resonator perturbation method.

[0076] (Heat Resistance) The solder heat resistance tests of the laminates obtained in each example were conducted in accordance with JIS C6481-1996 to evaluate the heat resistance of the laminates. Laminates that bulged were evaluated as NG, and those that did not bulge were evaluated as OK. The solder bath temperature was 260°C, and the float time was 3 minutes.

[0077] (Flexibility) A copper circuit pattern, as shown in Figure 2, was formed on one side of the resin layer in each example, and a coverlay was applied thereon. Then, an MIT test was performed using an MIT folding fatigue tester manufactured by Toyo Seiki Seisakusho Co., Ltd., and the number of bends until the circuit broke was evaluated as flexibility. The measurement conditions were a bending radius of 0.38 mm, a bending angle of 135 degrees, a rotation speed of 175 rotations / min, and a tensile load of 500 g.

[0078]

[0079]

[0080]

[0081]

[0082] As shown in Table 1 and Figure 3, the laminates according to Example 1 and Example 2 contain a cured resin layer made from a resin composition containing a styrene-butadiene-styrene copolymer and an organic peroxide. The tensile modulus of the resin layer is 1.0 MPa or more and 10 MPa or less, and the elongation at break of the resin layer is 100% or more. Therefore, the laminates according to Example 1 and Example 2 maintained high flexibility even with a thicker resin layer compared to Reference Examples 1 and 2.

[0083] On the other hand, the laminates of Comparative Examples 1 to 5 used polyimide for the resin layer, the laminates of Comparative Examples 6 to 9 used LCP film for the resin layer, and the laminates of Comparative Examples 10 to 11 used fluorine-based film for the resin layer. As shown in Tables 2 to 4, the resin layers of Comparative Examples 1 to 11 had high tensile modulus, while the resin layers of Comparative Examples 1 to 9 had low elongation at break. Therefore, as shown in Tables 2 to 4 and Figure 4, increasing the thickness of the resin layer reduced the number of MIT tests required and decreased flexibility.

[0084] From the above results, it can be seen that the laminates according to Example 1 and Example 2 have higher flexibility even with a thicker resin layer compared to the laminate according to the comparative example.

[0085] The entire contents of Japanese Patent Application No. 2025-015261 (Filing Date: January 31, 2025) are incorporated herein by reference.

[0086] Although this embodiment has been described above, this embodiment is not limited to these, and various modifications are possible within the scope of the gist of this embodiment.

[0087] According to this disclosure, it is possible to provide a laminate with excellent flexibility even when the resin layer is thick, and a wiring board using the same.

[0088] 1 Laminate 10 Resin layer 20 First support 30 Second support

Claims

1. A laminate comprising a resin layer, a first support, and a second support, wherein the resin layer is disposed between the first support and the second support, the resin layer is a cured product of a resin composition containing styrene-butadiene-styrene copolymer and an organic peroxide, the copolymerization ratio of the styrene-butadiene-styrene copolymer is 5 to 20:60 to 90:5 to 20, the thickness of the resin layer is 0.150 mm to 1.000 mm, the tensile modulus of the resin layer at 25°C is 1.0 MPa or more and 10 MPa or less, the elongation at break of the resin layer at 25°C is 100% or more, the resin composition contains 80% to 99% by mass of the styrene-butadiene-styrene copolymer in its resin components, and the resin composition contains 0.1% to 5% by mass of the organic peroxide.

2. The laminate according to claim 1, wherein at least a portion of the styrene-butadiene-styrene copolymer is hydrogenated.

3. The laminate according to claim 1 or 2, wherein the melting point of the styrene-butadiene-styrene copolymer is 70°C or higher.

4. The laminate according to any one of claims 1 to 3, wherein the number average molecular weight Mn of the styrene-butadiene-styrene copolymer is in the range of 50,000 to 100,000.

5. The laminate according to any one of claims 1 to 4, wherein the mass ratio of the styrene-butadiene-styrene copolymer to the organic peroxide in the resin composition is 19:1 to 199:

1.

6. The laminate according to any one of claims 1 to 5, wherein the first support is a metal foil, the second support is a metal foil or a resin film, and the resin film is a resin having a melting point of 180°C or higher.

7. A wiring board comprising a laminate according to any one of claims 1 to 6.

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