Curing agent for low dielectric resin, low dielectric resin composition, resin film, prepreg, metal-clad laminate, and method for manufacturing metal-clad laminate

Abstract

This invention provides a curing agent for low-dielectric resins, comprising an organic peroxide of general formula (a1) and an organic peroxide of general formula (a2), wherein the proportion of the organic peroxide of (a1) in the total amount of the organic peroxide of (a1) and the organic peroxide of (a2) is 5% by mass or more and 95% by mass or less. This curing agent for low-dielectric resins can achieve both low dielectric properties and heat resistance.

Description

Technical Field

[0001] This invention relates to a curing agent for low-dielectric resin, a low-dielectric resin composition, a resin film, a prepreg, a metal-coated laminate, and a method for manufacturing the metal-coated laminate. Background Technology

[0002] In mobile phones and automotive electronic devices, high-frequency, high-capacity, high-speed communication using microwaves or millimeter waves is employed. To reduce signal transmission loss, resin materials with low dielectric properties, such as low dielectric constant or loss tangent, are used in the electronic components, especially circuit boards, of these devices. Furthermore, with the miniaturization and high performance of electronic devices, the miniaturization and high-layer voltage of circuit boards necessitate low-dielectric resin materials with heat resistance.

[0003] Such circuit boards can be made by, for example, by mixing low-dielectric resins such as polyphenylene ether, copolymers of bismaleimide and triazine, and cyclic olefin copolymers with free radical polymerizable groups at the ends, and organic peroxides as thermal free radical initiators in an organic solvent, and laminating the material to be made into sheets as needed, thereby attaching metal foil to the surface, and forming a cured metal-coated laminate by hot pressing.

[0004] Patent Document 1 discloses a resin composition that yields a cured product with low dielectric properties, high heat resistance, and the ability to maintain low dielectric properties appropriately even in high humidity environments. Existing technical documents Patent documents

[0005] Patent Document 1: International Publication No. 2020 / 017399 Summary of the Invention (a) Technical problems to be solved

[0006] While studies have been conducted on methods such as using additives or mixed resins to achieve low dielectric constant and high heat resistance, these methods present technical problems that can affect the physical properties of the resin. Therefore, if low dielectric constant and high heat resistance can be achieved by using organic peroxides during curing, it offers an advantage in that these technical problems are not present.

[0007] While the addition of organic peroxides can improve heat resistance, if the amount of peroxide added increases, it can lead to a deterioration in dielectric properties.

[0008] The present invention has been carried out in view of the above circumstances, and its object is to provide a curing agent for low dielectric resin that can take into account both low dielectric properties and heat resistance.

[0009] Furthermore, the present invention aims to provide a low-dielectric resin composition comprising the above-mentioned curing agent for low-dielectric resin, a resin film, a prepreg, a metal-coated laminate, and a method for manufacturing the metal-coated laminate. (II) Technical Solution

[0010] That is, the present invention is as described in [1] to [6].

[0011] [1] A curing agent for low dielectric resin, comprising an (A) low dielectric resin curing agent containing an (a1) organic peroxide represented by general formula (1) and an (a2) organic peroxide represented by general formula (2). [Chemical Formula 1] ···(1) In general formula (1), R 1 and R 2 Each is independently an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 10 carbon atoms. [Chemical Formula 2] ···(2) In general formula (2), R 3 and R 4 Each is independently an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 10 carbon atoms. In the total amount of the (a1) organic peroxide and the (a2) organic peroxide, the proportion of the (a1) organic peroxide is more than 5% by mass and less than 95% by mass. [2] A low dielectric resin composition, wherein, relative to 100 parts by weight of (B) low dielectric resin, it comprises 0.1 to 5 parts by weight of the curing agent for the low dielectric resin and 10 to 1000 parts by weight of (C) organic solvent. [3] A resin film formed from the low dielectric resin composition. [4] A prepreg having the low dielectric resin composition and (D) fibrous substrate. [5] A metal-clad laminate comprising the resin film or the prepreg and (E) a metal foil. [6] A method for manufacturing a metal-clad laminate, comprising the following steps in sequence: Step 1: The step of impregnating (D) fibrous substrate with the low dielectric resin composition; Step 2: The step of drying the organic solvent (C) to obtain the prepreg; and Step 3: The process of laminating the prepreg and (E) metal foil and hot pressing them together. (III) Beneficial Effects

[0012] According to the curing agent for low-dielectric resins of the present invention, a low-dielectric resin composition having low dielectric properties and heat resistance can be obtained. Detailed Implementation

[0013] <(A) Curing Agent for Low Dielectric Resins> The curing agent for low-dielectric resin of the present invention (A) comprises an organic peroxide represented by general formula (1) and an organic peroxide represented by general formula (2). [Chemical Formula 3] ···(1) In general formula (1), R 1 and R 2 Each is independently an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 10 carbon atoms. [Chemical Formula 4] ···(2) In general formula (2), R 3 and R 4 Each is independently an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 10 carbon atoms.

[0014] In general formula (1), R 1 and R 2 Each of the components is independently an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 10 carbon atoms, wherein methyl, ethyl, n-propyl, 2,2-dimethylpropyl, and phenyl are preferred.

[0015] In general formula (2), R 3 and R 4 Each of the components is independently an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 10 carbon atoms, wherein methyl, ethyl, n-propyl, 2,2-dimethylpropyl, and phenyl are preferred.

[0016] In general formulas (1) and (2), R is preferred. 1 R 2 R 3 and R 4 Same. By making R 1 R 2 R 3 and R 4 Similarly, during the drying process of the organic solvent in (C), the volatilization of the curing agent for the low-dielectric resin in (A) can be suppressed, and the dispersion of the curing agent for the low-dielectric resin in the low-dielectric resin composition becomes good, so that the resin can exert its effect uniformly.

[0017] Organic peroxides (a1) and (a2) generate free radicals through thermally broken peroxide bonds, thus contributing to the addition reaction catalysts of the low-dielectric resin. Both components (a1) and (a2) are bifunctional, resulting in a higher amount of free radical generation. Furthermore, the heat resistance is enhanced by the central benzene ring skeleton assisting the crosslinking structure of component (B). In particular, component (a1), due to its rigidity via the para-position of the benzene ring, significantly improves heat resistance. On the other hand, some of the residues generated from the free radical reactions of components (a1) and (a2) become alcohols. Components (a1) and (a2) are each monomers with high crystallinity, and the alcohols from their decomposition residues remain as solids within or on the surface of the low-dielectric resin. These solid alcohols are highly hygroscopic, readily absorbing moisture from the air into the resin, thus deteriorating its dielectric properties. Therefore, in this invention, since the proportion of organic peroxide (a1) in the total amount of organic peroxide (a1) and organic peroxide (a2) is set to 5% by mass or more and 95% by mass or less in the curing agent for the low-dielectric resin (A), the components (a1) and (a2) are mixed in an optimal ratio. Consequently, the crystallinity of the alcohol in the decomposition residue decreases, and it is finely dispersed in the low-dielectric resin, or easily volatilized and discharged from the system. This reduces hygroscopicity, making it less likely for moisture in the air to be absorbed into the resin, thus maintaining the dielectric properties.

[0018] In the curing agent for the low dielectric resin (A), the proportion of (a1) organic peroxide in the total amount of (a1) organic peroxide and (a2) organic peroxide is preferably 20% by mass or more and 80% by mass or less, more preferably 30% by mass or more and 70% by mass or less.

[0019] <Low Dielectric Resin Composition> The low-dielectric resin composition of the present invention is a resin varnish, which, relative to 100 parts by weight of (B) low-dielectric resin, comprises 0.1 to 5 parts by weight of the curing agent for the low-dielectric resin and 10 to 1000 parts by weight of (C) organic solvent. If the curing agent for (A) low-dielectric resin is less than 0.1 parts by weight, the reaction of (B) low-dielectric resin will become insufficient, and sufficient heat resistance cannot be obtained. On the other hand, if the curing agent for (A) low-dielectric resin is more than 5 parts by weight, the dielectric properties will deteriorate. If the organic solvent for (C) is less than 10 parts by weight, the (B) low-dielectric resin will not dissolve, and the mixing with the curing agent for (A) low-dielectric resin will become insufficient. On the other hand, if the organic solvent for (C) is more than 1000 parts by weight, the organic solvent for (C) cannot be sufficiently removed during the drying and hot pressing processes, resulting in stickiness or a decrease in physical properties in the cured metal-coated laminate, which is unsuitable. In the low dielectric resin composition, the curing agent for the low dielectric resin (A) is preferably 0.3 parts by mass and 3 parts by mass or less, more preferably 0.5 parts by mass and 2 parts by mass or less, relative to 100 parts by mass of the low dielectric resin (B).

[0020] <(B) Low Dielectric Resin> (B) Low dielectric resins are not particularly limited as long as they exhibit the target performance when used in this application. Examples include polyphenylene ethers with free radical reactive groups, copolymers of bismaleimide and triazine, cyclic olefin copolymers, etc. These ingredients can also be commercially available products, such as Noryl SA9000 manufactured by SABIC INNOVATIVE PLASTICS JAPAN LLC., OPE-2St and other polyphenylene ethers manufactured by MITSUBISHI GAS CHEMICAL COMPANY, INC., BMI series manufactured by DAIWA KASEI INDUSTRIAL CO., LTD., MIR-3000-70MT manufactured by Nippon Kayaku Co., Ltd., COMPIMIDE and other bismaleimides manufactured by Evonik Degussa Co., Ltd., ZEONEX manufactured by ZEONCORPORATION, APEL manufactured by Mitsui Chemicals, Inc., and TOPAS and other cyclic olefin copolymers manufactured by Polyplastics Co., Ltd.

[0021] In addition to the above-mentioned components, polybutadiene resin or styrene-ethylene-butene-styrene (SEBS) resin can be appropriately blended. These resins impart flexibility to the low-dielectric resin composition and prevent the laminate from cracking during processing. (B) One or more low-dielectric resins can be used.

[0022] <(C) Organic Solvents> (C) The organic solvent is used to dissolve and mix the curing agent for (A) and (B) low-dielectric resin. It is not particularly limited to any solvent capable of dissolving both components (A) and (B). The organic solvent (C) is preferably a solvent that easily evaporates and is removed during drying and hot pressing in the subsequent steps. Furthermore, to reduce dielectric properties, the organic solvent (C) preferably does not contain water. Examples of preferred organic solvents (C) include toluene, xylene, ethylbenzene, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, and vinyl acetate. Toluene is particularly preferred. Furthermore, the low-dielectric resin (B) can be a resin pre-dissolved in the organic solvent (C). One or more organic solvents (C) can be used.

[0023] <Other Ingredients> Within the scope of not impairing the effects of the present invention, the low dielectric resin composition may be incorporated into other components such as crosslinking aids, silane coupling agents, inorganic fillers, flame retardants, etc.

[0024] In preparing the low-dielectric resin composition, components (A), (B), and (C), along with other components as needed, are placed in a container and dissolved or dispersed using conventional methods such as a ball mill, bead mill, planetary mixer, or roller mill. Heating may be performed as needed. When dissolving the low-dielectric resin (B) in the organic solvent (C) by heating, unnecessary gelation can be suppressed by adding a curing agent for the low-dielectric resin (A) after cooling to below 50°C. Furthermore, filtration may be performed using a sieve or membrane filter as needed.

[0025] <Resin Film> The resin film of the present invention is a cured product formed from a low-dielectric resin composition. While the resin film may contain the low-dielectric resin composition before curing, a portion of the low-dielectric resin composition may already be cured. The resin film can be obtained, for example, by drying the low-dielectric resin composition separately, or by coating a support such as a support film with the low-dielectric resin composition and then drying it. (C) Drying and removal of organic solvents is performed, for example, using a hot air dryer at 20°C to 180°C, preferably at 80°C to 150°C.

[0026] Examples of supports for resin films include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polyethylene, polypropylene, and polyvinyl chloride, polycarbonate, polyimide, ethylene-tetrafluoroethylene copolymer, metal foils such as copper foil and aluminum foil, and release paper. Materials obtained by coating a low-dielectric resin composition onto a metal foil and then drying and removing the organic solvent (C) using a hot air dryer are also called resin-coated metal foils. Furthermore, the support can undergo chemical or physical treatments such as matte finishing, corona treatment, and release treatment.

[0027] Resin films are suitable as interlayer insulating sheets and adhesive films for multilayer printed circuit boards and other laminates.

[0028] <Prepreg> The prepreg of the present invention is a composite comprising a low-dielectric resin composition and a (D) fibrous substrate. While the prepreg contains the low-dielectric resin composition before curing, it may also contain a portion of the low-dielectric resin composition that has already been cured. The prepreg is preferably a composite of a (D) fibrous substrate and a low-dielectric resin composition impregnated or coated onto the (D) fibrous substrate. Even when a layer is formed by coating the low-dielectric resin composition onto the surface of the (D) fibrous substrate, a structure in which the cured low-dielectric resin composition is impregnated into the substrate can be obtained by pressure molding for curing the prepreg. The prepreg can be obtained, for example, by impregnating or coating a resin varnish, which is a mixture of the low-dielectric resin composition and a solvent, onto a substrate such as glass cloth, and then drying to remove the solvent. Furthermore, the impregnation or coating can be repeated multiple times. Furthermore, the final desired impregnation amount can be adjusted by repeatedly impregnating or coating with various low-dielectric resin compositions of different concentrations or compositions. Solvent removal by drying can be performed, for example, using a hot air dryer at a temperature of 20°C to 180°C. The drying temperature is preferably 50°C to 160°C, and more preferably 80°C to 150°C.

[0029] Examples of (D) fibrous substrates include glass cloth, aramid cloth, polyester cloth, glass nonwoven fabric, aramid nonwoven fabric, pulp paper, and cotton linter paper. Among these, glass cloth is preferred due to the excellent physical strength of printed circuit boards, and glass cloth that has undergone a flattening process is even more preferred. These (D) fibrous substrates can be used alone or in combination of two or more. Furthermore, the thickness of the (D) fibrous substrate can be, for example, 1 to 300 μm.

[0030] In the solid components of the prepreg, the proportion of the low-dielectric resin composition is preferably 30 to 80% by mass, more preferably 40 to 70% by mass. If the above proportion is less than 30% by mass, the insulation reliability tends to deteriorate when the prepreg is used for electronic substrates, etc. Furthermore, if the above proportion is more than 80% by mass, physical properties such as flexural modulus tend to deteriorate when used for electronic substrates, etc.

[0031] <Metal-coated laminate> The metal-clad laminate of the present invention is a laminate comprising a resin film or prepreg and an (E) metal foil. The laminate can be manufactured by stacking one or more sheets of resin film and / or prepreg with a substrate such as an (E) metal foil, followed by pressure molding to cure the low-dielectric resin composition and form an insulating layer. A resin-coated metal foil can also be used instead of a metal foil. Heat molding can be performed, for example, at a temperature of 150°C to 250°C, a heating time of 10 minutes to 150 minutes, and a temperature of 20 kgf / cm². 2 ~40kgf / cm 2 The surface pressure is applied. The manufacturing method of the metal-coated laminate of the present invention includes, for example, the following steps in sequence: step 1: impregnating the low dielectric resin composition into (D) a fibrous substrate; step 2: drying the (C) organic solvent to obtain a prepreg; and step 3: laminating the prepreg and (E) metal foil and hot pressing them together.

[0032] There are no particular limitations on the metal foil; examples include aluminum foil and copper foil, with copper foil being preferred due to its lower resistance. For the thickness of the metal foil, for example, metal foils ranging from 1 μm to 50 μm can be used.

[0033] The resin film and prepreg combined with the metal foil can be a single sheet or multiple sheets, with the metal foil stacked on one or both sides depending on the application, thus forming a laminate. Metal-coated laminates are particularly suitable for use as printed circuit boards.

[0034] Printed Circuit Boards The printed circuit board of the present invention can be obtained by removing a portion of the metal foil on the surface of a metal-clad laminate through etching or other processes to form circuitry, thereby forming a circuit on the surface of a resin film or prepreg. Due to the inclusion of a low-dielectric resin composition, the printed circuit board exhibits excellent dielectric properties such as dielectric constant and loss tangent, as well as superior formability and heat resistance.

[0035] In addition, low-dielectric resin compositions can be used in applications such as molding, lamination, adhesives, and composite materials such as copper-clad laminates. Particularly, when isocyanates or epoxy compounds are used alone or in combination, representative examples include prepregs formed by semi-curing the resin and laminates formed by curing the prepreg. Furthermore, when epoxy compounds are used, representative examples include applications in semiconductor sealing materials. Example

[0036] The present invention is illustrated below by way of examples, but the scope of the present invention is not limited thereto.

[0037] <(A) Preparation of curing agent for low dielectric resin> <Example 1> 50 parts by weight of 1,4-bis(α,α'-dihydroxyisopropyl)benzene, 40 parts by weight of glacial acetic acid, and 60 parts by weight of tert-butyl hydroperoxide were placed in a flask, and the temperature was raised to 30°C. A solution of 10 parts by weight of glacial acetic acid and 1 part by weight of perchloric acid, prepared separately, was added dropwise over 60 minutes at 30°C, and the mixture was kept in this state to allow the reaction to continue for 120 minutes. The temperature was raised to 60°C and allowed to stand. The aqueous layer was discarded, and the oil layer was washed with a 2% by weight sodium hydroxide aqueous solution at 60°C. After further standing, separation was performed. After washing twice with warm water at 60°C, the oil layer was crystallized using methanol at 10°C to obtain 100 parts by weight of (a1-1) organic peroxide (in general formula (1), R...). 1 R 2 (All are methyl).

[0038] Except for using 1,3-bis(α,α'-dihydroxyisopropyl)benzene in the raw materials, the same operation as described above is performed to obtain (a2-1) organic peroxide (in general formula (2), R 3 R 4 (All are methyl).

[0039] Using a rotary drum mixer, 5 parts by weight of the above-obtained (a1-1) organic peroxide and 95 parts by weight of (a2-1) organic peroxide were mixed for 5 minutes to obtain the curing agent for the low dielectric resin of Example 1.

[0040] <Examples 2-3, Comparative Examples 1-2> Except for changing the blending amounts of (a1) organic peroxide and (a2) organic peroxide to the ratio shown in Table 1, the same operation as in Example 1 was performed, thereby obtaining the low dielectric resin curing agents of Examples 2 to 3 and Comparative Examples 1 to 2.

[0041] <Example 4> In addition to replacing tert-butyl hydrogen peroxide with tert-hexyl hydrogen peroxide, we obtain (a1-2) organic peroxides (in general formula (1), R 1 R 2 All are n-propyl) and (a2-2) organic peroxides (in general formula (2), R 3 R 4 Except for n-propyl, the same operation as in Example 2 was performed to obtain the low dielectric resin curing agent of Example 4.

[0042] <Example 5> In addition to replacing tert-butyl hydroperoxide with cumene hydroperoxide, (a1-3) organic peroxides (in general formula (1), R) are obtained. 1 R 2 All are phenyl) and (a2-3) organic peroxides (in general formula (2), R 3 R 4 Except for phenyl groups, the same operation as in Example 2 was performed to obtain the low dielectric resin curing agent of Example 5.

[0043] [Table 1]

[0044] <Preparation of Low Dielectric Resin Compositions> The (B) low-dielectric resin and (C) organic solvent used in the following examples and comparative examples are shown below. (B1) Polyphenylene ether oligomer (NorylSA9000 manufactured by SABIC INNOVATIVE PLASTICS JAPAN LLC.) (B2) Bismaleimide resin (MIR-3000-70MT manufactured by Nippon Kayaku Co., Ltd.) (C1) Toluene (C2) Methyl ethyl ketone

[0045] <Example 6> 100 parts by weight of toluene were added to a 500 ml four-necked flask. The liquid temperature was maintained at 30°C. Using a 75 mm crescent blade made of PTFE, the mixture was stirred at 300 rpm. 100 parts by weight of Noryl SA9000 and 1 part by weight of the curing agent for the low-dielectric resin of Example 1 were slowly added until completely dissolved to obtain a low-dielectric resin composition. The obtained low-dielectric resin composition was transferred to a dish and dried in an explosion-proof oven at 130°C for 60 minutes, followed by vacuum drying at 40°C for 120 minutes to reduce the toluene content to less than 1 part by weight. The obtained solid components were pulverized using a ball mill. To ensure uniform powder thickness, the powder was spread on a PTFE sheet to a diameter of approximately 6 cm. The powder was then held in place by a PTFE sheet and pressurized at 200°C for 60 minutes to obtain a resin film (cured product) of the low-dielectric resin composition with a film thickness of approximately 100 μm.

[0046] <Appearance Evaluation> The obtained resin film was confirmed through visual inspection and tactile evaluation. The evaluation criteria are as follows. ○: When observed with the naked eye using a magnifying glass, there are no pores, cracks, foreign objects, or areas with a film thickness of less than 50μm except at the ends, and no roughness or stickiness can be felt when touched. ×: When observed with the naked eye using a magnifying glass, there are pores, cracks, foreign objects, or areas with a film thickness of less than 50μm except at the ends, or the surface feels rough or sticky when touched.

[0047] <Evaluation of Low Dielectric Properties (Determination of Loss Tangent (Df))> The loss tangent of the obtained resin film was measured using a network analyzer MS46122B manufactured by ANRITSU CORPORATION and a 10 GHz cavity resonator manufactured by AET, INC. The average value of three measurements was taken as the value of Df. [Judgment Criteria] ◎: Below 0.0020, ○: 0.0021~0.0027, △: 0.0028~0.0035, ×: Above 0.0035

[0048] <Evaluation of heat resistance (determination of glass transition temperature (Tg))> Using a DMA7100 manufactured by Hitachi High-Tech Science CORPORATION, measurements were taken in tensile mode at a rate of 2°C / min from 30°C to 300°C. The peak value of tanδ (=loss modulus (E'') / storage modulus (E')) was recorded and used as the Tg value. The test method was based on JIS K7244-4. [Judgment Criteria] ○: Above 216℃, △: Above 205℃ but below 216℃, ×: Below 205℃

[0049] <Examples 7 to 14 and Comparative Examples 3 to 5> Except for changing the blending amounts of each component to the ratios shown in Table 2, the same operation as in Example 6 was performed to obtain resin films (cured products) of the low dielectric resin compositions of Examples 7 to 14 and Comparative Examples 3 to 5.

[0050] [Table 2]

[0051] <Evaluation Results> Examples 6 through 14 all showed good appearance and low Df, resulting in cured products with high Tg. Comparative Example 3 did not contain (A) a low-dielectric resin curing agent, so the resin was not cured. Comparative Example 4, due to the use of a curing agent that is only a low dielectric resin (a1), showed decomposition residue as a foreign object, with an appearance of ×, and Df also deteriorated. Comparative Example 5, due to the use of a curing agent that is only for the low dielectric resin of (a2), has a good appearance but a worse Df.

[0052] <Manufacturing of Metal-Clad Laminates> <Reference Example 1> The low-dielectric resin composition of Example 6 was made into a varnish, which was then impregnated with (D) glass cloth to achieve impregnation. The varnish was dried at 130°C for 15 minutes to obtain a prepreg. Six sheets of the obtained prepreg were stacked together, and a copper foil with a thickness of 30 μm was stacked on top as (E) metal foil. The layers were then pressed at 200°C for 60 minutes to obtain the metal-coated laminate of Reference Example 1.

[0053] <Evaluation of Metal-Clad Laminates> <Metal Foil Adhesion> The metal-clad laminate was cut into 1.5cm × 10cm pieces. For each cut specimen, the adhesive strength was determined according to "JIS C 6471 Test Method for Copper-Clad Laminates for Flexible Printed Circuit Boards". Specifically, the adhesive strength of a 1mm wide metal foil was measured using a tensile-compression testing machine (EZ-TEST, SHIMADZUCORPORATION) at a test speed of 50mm / min and a peel direction of 90°. The obtained values ​​were evaluated using the following criteria. [Judgment Criteria] ○: Above 1.0 kN / m ×: Less than 1.0 kN / m

[0054] <Heat resistance after molding> After immersing the metal-clad laminate in a solder bath heated to 260°C for 30 seconds, its deformation was observed visually, and the deformation and expansion were evaluated using the following criteria. Less deformation and expansion of the sample indicates higher solder heat resistance. [Judgment Criteria] ○: Neither deformation nor expansion occurred. ×: At least one of deformation and expansion has occurred.

[0055] <Processability> When cutting the metal-clad laminate into 50mm×50mm pieces, visual inspection is used to confirm whether any abnormalities such as cracks, defects, peeling of metal foil, wrinkles, or expansion are observed in the metal-clad laminate. [Judgment Criteria] ○: No abnormalities ×: An anomaly exists.

[0056] <Insulation> After cutting the metal-clad laminate into 50mm × 50mm pieces and immersing it in an etching solution (product name "H-1000A", manufactured by Sunhayato Corp.) for 10 minutes, the loss tangent (Df) of the material with the copper foil removed was measured using the same method as described above. [Judgment Criteria] ○: Df is below 0.0030 ×: Df is higher than 0.0030

[0057] <Refer to Example 2 and compare with Examples 3 to 4> Except for changing the blending amount of each component to the ratio shown in Table 3, the same operation as in Reference Example 1 was performed to obtain the metal-coated laminates of Reference Example 2 and Comparative Reference Examples 3 to 4.

[0058] [Table 3]

Claims

1. A curing agent for a low dielectric resin, which is (A) a curing agent for a low dielectric resin comprising (al) an organic peroxide represented by the following general formula (1) and (a2) an organic peroxide represented by the following general formula (2), [Chemical Formula 1] ···(1)， In General Formula (1), R 1 and R 2 each independently is an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 10 carbon atoms, [Chemical Formula 2] ···(2)， In General Formula (2), R 3 and R 4 each independently is an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 10 carbon atoms, The proportion of the (al) organic peroxide in the total amount of the (al) organic peroxide and the (a2) organic peroxide is 5 mass% or more and 95 mass% or less.

2. A low dielectric resin composition, wherein, It comprises 0.1 to 5 parts by mass of the curing agent for a low dielectric resin according to claim 1, and 10 to 1000 parts by mass of (C) an organic solvent, with respect to 100 parts by mass of (B) a low dielectric resin.

3. A resin film formed from the low dielectric resin composition according to claim 2.

4. A prepreg having the low dielectric resin composition according to claim 2 and (D) a fibrous base material.

5. A metal-clad laminate provided with the resin film according to claim 3 or the prepreg according to claim 4, and (E) a metal foil.

6. A method for producing a metal-clad laminate, which successively comprises the following steps: Step 1: a step of impregnating (D) a fibrous base material with the low dielectric resin composition according to claim 2; Step 2: a step of drying the (C) organic solvent to obtain a prepreg; and Step 3: a step of laminating the prepreg and (E) a metal foil and performing hot pressing.

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