Adhesive-equipped metal substrate and laminate

Abstract

The present invention relates to a metal substrate with an adhesive, which has excellent transmission characteristics and can sufficiently ensure the adhesion strength between a resin substrate and a metal layer, and a laminate. More specifically, the present invention relates to a metal substrate with an adhesive, which is provided with a metal layer and an adhesive resin layer formed from an adhesive resin composition, and a laminate provided with the metal substrate with an adhesive, the adhesive resin composition contains a polyimide resin (A), a maleimide compound (B), and a radical initiator, the mass ratio of the polyimide resin (A) to the maleimide compound (B) being 10: 1 to 3: 2, and the content of the radical initiator being 1 part by mass or more and less than 25 parts by mass per 100 parts by mass of the maleimide compound (B).

Description

Technical Field

[0001] The present invention relates to a metal substrate with an adhesive and a laminate. Background Art

[0002] Copper clad laminates (hereinafter sometimes referred to as "CCL") for transmitting high-frequency signals are manufactured by laminating copper foil and resin layers.

[0003] In recent years, as the speed of transmission signals increases, CCLs are required to have further improved transmission characteristics.

[0004] For example, Patent Document 1 discloses a laminate formed by laminating a resin substrate and a metal substrate with an adhesive layer interposed therebetween. Although the adhesive layer included in the laminate disclosed in Patent Document 1 is low-frequency for 5G, it has a relative permittivity of 3.0 or less and a dielectric loss tangent of 0.02 or less at a frequency of 1 MHz.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2021-003886 Summary of the Invention

[0006] During high-frequency transmission, the higher the frequency band, the more likely the current will flow only along the surface of the metal wiring. Therefore, if the surface is not smooth, transmission losses increase. This is a well-known phenomenon known as the "skin effect." To reduce transmission losses caused by the skin effect, there is a trend to use metal foils with low surface roughness as metal substrates, for example.

[0007] As the surface roughness of the metal foil decreases, the anchor effect becomes less likely to be achieved, and the adhesion between the resin substrate and the metal foil decreases. In this case, there is a problem that circuit peeling of the printed circuit board is more likely to occur.

[0008] The present invention has been made in view of the above circumstances, and an object thereof is to provide a metal substrate with an adhesive and a laminate that are excellent in transmission characteristics and can sufficiently ensure the bonding strength between the resin substrate and the metal layer.

[0009] That is, the present invention adopts the following structure.

[0010] [1] A metal substrate with an adhesive, comprising a metal layer and an adhesive resin layer formed from an adhesive resin composition, wherein the surface roughness Rzjis of the metal layer is 1.5 μm or less, the adhesive resin composition comprises a polyimide resin (A), a maleimide compound (B) and a free radical initiator, the mass ratio of the polyimide resin (A) to the maleimide compound (B) is 10:1 to 3:2, and the content of the free radical initiator is 1 part by mass or more and less than 1 part by mass relative to 100 parts by mass of the maleimide compound (B).

[0011] [2] The metal substrate with an adhesive according to [1], wherein the metal layer is a copper foil having a surface roughness Rzjis of less than 1.0 μm.

[0012] [3] A laminate comprising a metal substrate with an adhesive as described in [1] or [2] on both sides of a prepreg, wherein the prepreg is laminated on the surface of the adhesive resin layer of the metal substrate with an adhesive opposite to the surface in contact with the metal layer, and the prepreg is one or more selected from the group consisting of a modified polyimide resin prepreg, a polyester resin prepreg, a liquid crystal polymer prepreg, a cyclic olefin resin prepreg, a polyphenylene ether resin prepreg, a polyphenylene sulfide resin prepreg, a polyetheretherketone resin prepreg, a bismaleimide resin prepreg, a triazine resin prepreg, a bismaleimide-triazine resin prepreg, a benzocyclobutene resin prepreg and a low dielectric epoxy resin prepreg.

[0013] [4] A metal substrate with an adhesive, comprising a metal layer and an adhesive resin layer formed from an adhesive resin composition, wherein the adhesive resin composition comprises a polyimide resin (A), a maleimide compound (B) and a free radical initiator, the mass ratio of the polyimide resin (A) to the maleimide compound (B) is 10:1 to 3:2, the content of the free radical initiator is 1 part by mass or more and less than 25 parts by mass relative to 100 parts by mass of the maleimide compound (B), and the thickness of the adhesive resin layer is 0.2 μm or more and 9 μm or less.

[0014] [5] The metal substrate with an adhesive according to [4], wherein the metal layer is a copper foil having a surface roughness Rzjis of 1.0 μm or less.

[0015] [6] A laminate comprising a metal substrate with an adhesive as described in [4] or [5] on both sides of a prepreg, wherein the prepreg is laminated on the surface of the adhesive resin layer of the metal substrate with an adhesive opposite to the surface in contact with the metal layer, and the prepreg is one or more selected from the group consisting of a modified polyimide resin prepreg, a polyester resin prepreg, a liquid crystal polymer prepreg, a cyclic olefin resin prepreg, a polyphenylene ether resin prepreg, a polyphenylene sulfide resin prepreg, a polyetheretherketone resin prepreg, a bismaleimide resin prepreg, a triazine resin prepreg, a bismaleimide-triazine resin prepreg, a benzocyclobutene resin prepreg and a low dielectric epoxy resin prepreg.

[0016] [7] The laminate according to [6], wherein the thickness of the adhesive resin layer is 0.2 μm to 9 μm, the thickness of the prepreg is 50 μm to 1000 μm, the thickness of the metal layer is 1 μm to 35 μm, and the laminate satisfies the following mathematical formula (1):

[0017] 0.05≤(X / Y)×100≤7···(1)

[0018] In the mathematical formula (1), X is the thickness (μm) of the adhesive resin layer, and Y is the thickness (μm) of the prepreg.

[0019] According to the present invention, a metal substrate with an adhesive and a laminate can be provided that are excellent in transmission characteristics and can sufficiently ensure the bonding strength between the resin substrate and the metal layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic cross-sectional view of an example of the metal substrate with an adhesive according to the present embodiment.

[0021] Figure 2 It is a schematic cross-sectional view of an example of the laminated body of this embodiment.

[0022] Figure 3 This is a graph showing the results of measuring the transmission loss (dB / 100 mm) of the laminates of Example 21, Comparative Example 21, and Comparative Example 22. DETAILED DESCRIPTION

[0023] <Metal substrate with adhesive>

[0024] The metal substrate with an adhesive of the present invention includes the metal substrate with an adhesive X according to the first embodiment and the metal substrate with an adhesive Y according to the second embodiment.

[0025] <<Metal Substrate X with Adhesive (First Embodiment)>>

[0026] The metal substrate X with an adhesive according to the first embodiment includes a metal layer and an adhesive resin layer formed of an adhesive resin composition.

[0027] The surface roughness Rzjis of the metal layer is less than 1.5 μm,

[0028] The adhesive resin composition comprises a polyimide resin (A), a maleimide compound (B) and a free radical initiator.

[0029] The mass ratio of the polyimide resin (A) to the maleimide compound (B) is 10:1 to 3:2,

[0030] The content of the radical initiator is 1 part by mass or more and less than 25 parts by mass relative to 100 parts by mass of the maleimide compound (B).

[0031] Figure 1 A schematic diagram of a cross section of a metal substrate 1 with an adhesive according to this embodiment is shown in FIG. The metal substrate 1 with an adhesive includes a metal layer 10 and an adhesive resin layer 11 .

[0032] By combining the metal substrate 1 with an adhesive and an arbitrary low-dielectric substrate and performing heat lamination, a rigid substrate for high-speed transmission can be manufactured.

[0033] If a prepreg using a polyphenylene ether resin is used as the low-dielectric base material, for example, a rigid substrate can be produced.

[0034] (Metal layer 10)

[0035] Any known conductive material that can be used for a circuit board can be used for the metal layer 10. Specifically, metal materials such as SUS, copper, aluminum, iron, steel, zinc, nickel, and alloys thereof are used.

[0036] The metal layer 10 is preferably a metal foil having a surface roughness of 1.5 μm or less, more preferably a metal foil having a surface roughness of 1.4 μm or less, further preferably a metal foil having a surface roughness of 1.3 μm or less, further more preferably a metal foil having a surface roughness of 1.0 μm or less, and particularly preferably a metal foil having a surface roughness of less than 1.0 μm.

[0037] The metal layer 10 is preferably a copper foil having a surface roughness of 1.5 μm or less, more preferably a copper foil having a surface roughness of 1.4 μm or less, further preferably a copper foil having a surface roughness of 1.3 μm or less, further more preferably a copper foil having a surface roughness of 1.0 μm or less, and particularly preferably a copper foil having a surface roughness of less than 1.0 μm.

[0038] The surface roughness in this specification refers to the ten-point average roughness (Rzjis).

[0039] The surface roughness of a metal foil such as a copper foil can be measured using, for example, a surface roughness measuring machine (model: SURFCOM 1900DX) manufactured by Tokyo Seimitsu Co., Ltd.

[0040] When the metal layer 10 is a copper foil, a rolled copper foil or an electrolytic copper foil can be used as the copper foil.

[0041] As a raw material of the copper foil, pure copper or a copper alloy obtained by adding a small amount of tin (Sn) or silver (Ag) to pure copper can be used.

[0042] The thickness of the metal layer 10 is preferably 5 μm or more, more preferably 10 μm or more, and further preferably 15 μm or more. The thickness of the metal layer 10 is preferably 50 μm or less, more preferably 45 μm or less, and further preferably 40 μm or less.

[0043] The upper and lower limits of the thickness of the metal layer 10 may be arbitrarily combined. For example, the thickness of the metal layer 10 is 5 μm to 50 μm, 10 μm to 45 μm, or 15 μm to 40 μm.

[0044] (Adhesive resin layer 11)

[0045] The adhesive resin layer 11 is formed of an adhesive resin composition described later.

[0046] According to the metal substrate 1 with an adhesive, the metal layer 10 can be bonded to any low-dielectric substrate via the adhesive resin layer 11 .

[0047] The thickness of the adhesive resin layer 11 of the metal substrate 1 with an adhesive is preferably 0.2 μm or greater, more preferably 0.5 μm or greater, even more preferably 0.6 μm or greater, even more preferably 0.7 μm or greater, particularly preferably 1.0 μm or greater, and most preferably 1.2 μm or greater. Furthermore, the thickness of the adhesive resin layer 11 is preferably 9 μm or less, more preferably 8 μm or less, even more preferably 7 μm or less, even more preferably 5 μm or less, particularly preferably 4.8 μm or less, and most preferably 4.6 μm or less.

[0048] The upper and lower limits of the thickness of the adhesive resin layer 11 may be arbitrarily combined. For example, the thickness of the adhesive resin layer 11 is 0.2 μm to 9 μm, 0.5 μm to 8 μm, or 0.7 μm to 7 μm.

[0049] When the thickness of the adhesive resin layer 11 is equal to or greater than the above lower limit, the metal layer 10 and the low-dielectric substrate can be bonded to each other.

[0050] When the thickness of the adhesive resin layer 11 is equal to or less than the above upper limit, the adhesive resin layer 11 has a low residual solvent ratio, and delamination due to volatile gas is less likely to occur during the heating step.

[0051] (Adhesive resin composition)

[0052] Hereinafter, the adhesive resin composition for forming the adhesive resin layer 11 will be described.

[0053] In this embodiment, by forming the adhesive resin layer 11 using a specific adhesive resin composition, a metal substrate and a laminate with an adhesive can be provided that can exhibit low dielectric properties in a high frequency region of 10 GHz, which is a frequency band of 6 GHz or more in the case of 5G.

[0054] Because the specific adhesive resin composition described later contains a maleimide compound, a precursor component of the polyimide resin (A), at a specific amount, the resulting adhesive resin layer 11 is believed to exhibit low dielectric properties in the high-frequency range. The maleimide groups in the maleimide compound maintain a cyclic structure even after crosslinking, and the crosslinked maleimide groups form a symmetrical structure. This is believed to suppress molecular motion, allowing the resulting adhesive resin layer 11 to exhibit low dielectric properties in the high-frequency range.

[0055] The adhesive resin composition contains a polyimide resin (A), a maleimide compound (B), and a radical initiator.

[0056] As the adhesive resin composition, the resin composition disclosed in International Publication No. 2022 / 004583 can be used.

[0057] The details are described below.

[0058] [Polyimide resin (A)]

[0059] The polyimide resin (A) is an isocyanate-modified polyimide resin (A1) or a terminal-modified isocyanate-modified polyimide resin (A2). Hereinafter, the isocyanate-modified polyimide resin (A1) is referred to as "polyimide resin (A1)", and the terminal-modified isocyanate-modified polyimide resin (A2) is referred to as "polyimide resin (A2)".

[0060] Polyimide resin (A1)

[0061] The polyimide resin (A1) is obtained by reacting a diisocyanate compound (a) with an intermediate polyimide resin. Hereinafter, the diisocyanate compound (a) is referred to as "component (a)".

[0062] The intermediate polyimide resin is a reaction product of an aliphatic diamino compound (b) (hereinafter referred to as "component (b)"), a tetrabasic acid dianhydride (c) (hereinafter referred to as "component (c)"), and an aromatic diamino compound (d) (hereinafter referred to as "component (d)").

[0063] The polyimide resin (A1) is a reaction product of one or both of the amino group and the acid anhydride group present at both terminals of the intermediate polyimide resin and the isocyanate group present in the component (a).

[0064] The reaction between the intermediate polyimide resin and component (a) is a copolymerization reaction between the amino group or acid anhydride group at the terminal of the intermediate polyimide resin and the isocyanate group of component (a). In other words, the reaction between the amino group and the isocyanate group forms a urea bond, while the reaction between the acid anhydride and the isocyanate group forms an imide bond.

[0065] Regarding the amount of component (a) used in the copolymerization reaction between the intermediate polyimide resin and the component (a), the isocyanate group of component (a) is preferably less than 1 equivalent, more preferably 0.50 to 0.99 equivalents, and even more preferably 0.67 to 0.98 equivalents, relative to 1 equivalent of the terminal functional group of the intermediate polyimide resin.

[0066] By setting the amount of component (a) used relative to the intermediate polyimide resin within the above range, the molecular weight of the polyimide resin (A1) is sufficiently increased. Furthermore, the residual rate of unreacted raw materials is reduced, and various properties of the adhesive resin composition after curing, such as heat resistance and flexibility, are improved.

[0067] In addition, the terminal functional group equivalent of the intermediate polyimide resin mentioned here refers to the value calculated from the amount of each raw material used when synthesizing the intermediate polyimide resin.

[0068] Any component (a) used in the synthesis of the polyimide resin (A1) may be used as long as it has two isocyanate groups in the molecule. Furthermore, a plurality of diisocyanate compounds may be reacted simultaneously.

[0069] Component (a) is preferably phenylene diisocyanate, toluene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, dimethylbenzidine diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, arylsulfone ether diisocyanate, allylcyano diisocyanate, N-acyl diisocyanate, trimethylhexamethylene diisocyanate, 1,3-bis(isocyanatemethyl)cyclohexane, or norbornane-diisocyanatomethyl ester. Among these, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, or isophorone diisocyanate is more preferred, as they have an excellent balance between flexibility and adhesiveness.

[0070] The reaction between the intermediate polyimide resin and the component (a) may be carried out by a known synthesis method.

[0071] Specifically, the polyimide resin (A1) can be obtained by adding the component (a) to an intermediate polyimide resin solution obtained by a synthesis method described below, and heating and stirring the mixture at a temperature of 80° C. to 150° C.

[0072] The synthesis reaction of the intermediate polyimide resin and the reaction time of the intermediate polyimide resin and component (a) are greatly affected by the reaction temperature, but the reaction is preferably carried out until the viscosity increase as the reaction proceeds reaches equilibrium and the maximum molecular weight can be obtained, usually for several tens of minutes to 10 hours.

[0073] Alternatively, the intermediate polyimide resin solution obtained above may be placed in a poor solvent such as water, methanol, or hexane, and the generated polymer may be isolated, followed by reprecipitation to obtain the solid content of the polyimide resin (A1).

[0074] Polyimide resin (A2)

[0075] The polyimide resin (A2) has either or both of an amino group and an acid anhydride group at both ends. Therefore, by reacting the ends with a compound having a functional group reactive with these functional groups, a terminal-modified isocyanate-modified polyimide resin, i.e., the polyimide resin (A2), can be prepared.

[0076] Examples of the compound capable of reacting with either or both of an amino group and an acid anhydride group include compounds having an acid anhydride group such as maleic anhydride, compounds having an alcoholic hydroxyl group such as hydroxyethyl acrylate, compounds having a phenolic hydroxyl group such as phenol, compounds having an isocyanate group such as 2-methacryloyloxyethyl isocyanate, and compounds having an epoxy group such as glycidyl methacrylate.

[0077] By modifying the terminals, both terminals of the isocyanate compound of the present invention can be converted into functional groups other than amino groups and acid anhydride groups (for example, when hydroxyethyl acrylate is used for terminal modification, the terminals of the isocyanate-modified polyimide resin can be converted into acryloyl groups). Therefore, a composition can be prepared in which a compound that reacts with functional groups other than amino groups or acid anhydride groups is combined.

[0078] Intermediate polyimide resin

[0079] The intermediate polyimide resin is a reaction product of the above-mentioned components (b), (c), and (d).

[0080] The reaction of components (b), (c), and (d) includes a step of obtaining a polyamic acid through a copolymerization reaction between the amino groups in components (b) and (d) and the anhydride groups in component (c); and a step of obtaining an intermediate polyimide resin through a dehydration cyclization reaction (imidization reaction) of the polyamic acid. These two steps can be performed separately, but it is more efficient to perform them simultaneously.

[0081] When the number of moles of the component (b) used in the copolymerization reaction is MB, the number of moles of the component (c) is MC, and the number of moles of the component (d) is MD, when the relationship MB+MD>MC is satisfied, both ends of the obtained intermediate polyimide resin become amino groups, and when the relationship MB+MD<MC is satisfied, both ends of the obtained intermediate polyimide resin become acid anhydride groups.

[0082] When the relationship MB+MD=MC is satisfied, the obtained intermediate polyimide resin theoretically has an infinite molecular weight and has one amino group and one acid anhydride group at each of its two terminals.

[0083] An example of the amount of component (b) used in the copolymerization reaction is preferably an amount in the range of 10% by mass or more and 50% by mass or less of the mass of the total mass of the components (b), (c) and (d) used in the synthesis step of the intermediate polyimide resin and the mass of the component (a) used in the synthesis step of the polyimide resin (A1) above, excluding the mass of water generated in the dehydration cyclization reaction step during the synthesis of the intermediate polyimide resin (this mass is substantially equal to the mass of the isocyanate-modified polyimide resin finally obtained).

[0084] If the amount of component (b) is below the above range, the proportion of aliphatic chains derived from component (b) in the intermediate polyimide resin is too small, resulting in increased relative dielectric constant and dielectric loss tangent. If it exceeds the above range, the proportion of aliphatic chains derived from component (b) in the intermediate polyimide resin is too high, resulting in reduced heat resistance of the cured product.

[0085] The component (b) used in the synthesis of the intermediate polyimide resin is not particularly limited as long as it is an aliphatic compound having two amino groups in one molecule, but is preferably an aliphatic diamino compound having 6 to 36 carbon atoms.

[0086] Specific examples of the component (b) include hexamethylenediamine, 1,3-bis(aminomethyl)cyclohexane, C14 branched diamine, C18 branched diamine, dimer diamine, and diaminopolysiloxane, etc. These may be used alone or in combination of two or more.

[0087] The dimer diamine described as a specific example of the component (b) in this specification is obtained by replacing two carboxyl groups of dimer acid, which is a dimer of unsaturated fatty acids such as oleic acid, with primary amino groups (see, for example, Japanese Patent Application Laid-Open No. 9-012712).

[0088] Specific examples of commercially available dimer diamines include PRIAMINE 1074 and PRIAMINE 1075 (both manufactured by Croda Japan Co., Ltd.) and Versamine 551 (both manufactured by Cognis Japan Co., Ltd.). These may be used alone or in combination of two or more.

[0089] The component (c) used for the synthesis of the intermediate polyimide resin is not particularly limited as long as it has two acid anhydride groups in one molecule.

[0090] Specific examples of the component (c) include pyromellitic dianhydride, ethylene glycol-bis(anhydrotrimellitate), glycerol-bis(anhydrotrimellitate) monoacetate, 1,2,3,4-butanetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylethertetracarboxylic dianhydride, 5-(2,5-dioxotetrahydro-3-furyl)-3-methylcyclohexane olefin-1,2-dicarboxylic anhydride, 3a,4,5,9b-tetrahydro-5-(tetrahydro-2,5-dioxo-3-furyl)-1,3-dione, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, bicyclo(2,2,2)-oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic dianhydride, and 5,5'-((propane-2,2-diylbis(4,1-phenylene))bis(oxy))bis(isobenzofuran-1,3-dione), etc.

[0091] Among them, 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, or 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride is preferred from the perspectives of solvent solubility, adhesion to substrates, and photosensitivity. These may be used alone or in combination of two or more.

[0092] The component (c) used in the synthesis of the intermediate polyimide resin preferably contains at least one compound selected from the group consisting of the following chemical formulas (1) to (4).

[0093] [Chemical Formula 1]

[0094]

[0095] In chemical formula (4), Y represents C(CF3)2, SO2, CO, O, a direct bond, or a divalent linking group represented by the following chemical formula (5). In addition, the two linking portions represented by chemical formula (5) are each a portion bonded to phthalic anhydride.

[0096] [Chemical Formula 2]

[0097]

[0098] The component (d) used for the synthesis of the intermediate polyimide resin is not particularly limited as long as it is an aromatic compound having two amino groups in one molecule.

[0099] Specific examples of the component (d) include metaphenylenediamine, paraphenylenediamine, metatolyldiamine, 4,4'-diaminodiphenyl ether, 3,3'-dimethyl-4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 3,3'-dimethyl-4,4'-diaminodiphenyl sulfide, 3,3'-diethoxy-4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 3,3'-dimethyl-4,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3'-dimethoxy-4,4'-diaminodiphenyl sulfide, 2,2'-bis(3-aminophenyl)propane, 2,2'-bis(4-aminophenyl)propane, 4, 4'-Diaminodiphenyl sulfoxide, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, benzidine, 3,3'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 3,3'-diaminobenzidine, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 2,2'-bis(3-aminophenoxyphenyl)propane, 2,2'-bis(4-aminophenoxyphenyl)propane, 1,3-bis(4-aminophenoxyphenyl)propane phenyl)methane, bis(4-amino-3-ethylphenyl)methane, bis(4-amino-3,5-diethylphenyl)methane, bis(4-amino-3-propylphenyl)methane, and bis(4-amino-3,5-dipropylphenyl)methane. These may be used alone or in combination of two or more.

[0100] The component (d) used in the synthesis of the intermediate polyimide resin preferably contains at least one compound selected from the group consisting of the following chemical formula (6) and chemical formula (8).

[0101] [Chemical Formula 3]

[0102]

[0103] In the chemical formula (6), R 1 represents a methyl group or a trifluoromethyl group, in the chemical formula (8), Z represents CH(CH3), SO2, CH2, O-C6H4-O, O, a direct bond or a divalent linking group represented by the above chemical formula (5), R 3 represents a hydrogen atom, a methyl group, an ethyl group, or a trifluoromethyl group. In addition, the two linking portions represented by the chemical formula (5) are portions bonded to phthalic anhydride.

[0104] The intermediate polyimide resin can be synthesized by a known method.

[0105] For example, a solvent, a dehydrating agent, and a catalyst are added to a mixture of components (b) to (d) used in the synthesis, and the mixture is heated and stirred at 100 to 300°C under an inert gas atmosphere such as nitrogen. This causes an imidization reaction (a ring-closure reaction accompanied by dehydration) via the polyamic acid to produce an intermediate polyimide resin solution. At this time, the water produced by the imidization reaction is distilled out of the system, and after the reaction is completed, the dehydrating agent and catalyst are also distilled out of the system. This allows the production of a high-purity intermediate polyimide resin without the need for washing. Examples of dehydrating agents include toluene and xylene, and examples of catalysts include pyridine and triethylamine.

[0106] Examples of solvents that can be used in the synthesis of the intermediate polyimide resin include methyl ethyl ketone, methyl propyl ketone, methyl isopropyl ketone, methyl butyl ketone, methyl isobutyl ketone, methyl n-hexyl ketone, diethyl ketone, diisopropyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone, acetylacetone, γ-butyrolactone, diacetone alcohol, cyclohexene-1-one, dipropyl ether, diisopropyl ether, dibutyl ether, tetrahydrofuran, tetrahydropyran, ethyl isoamyl ether, ethyl tert-butyl ether, ethyl benzyl ether, tolyl methyl ether, anisole, phenethyl ether, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, acetic acid The esters include, but are not limited to, amyl acetate, isoamyl acetate, 2-ethylhexyl acetate, cyclohexyl acetate, methylcyclohexyl acetate, benzyl acetate, methyl acetoacetate, ethyl acetoacetate, methyl propionate, ethyl propionate, butyl propionate, benzyl propionate, methyl butyrate, ethyl butyrate, isopropyl butyrate, butyl butyrate, isoamyl butyrate, methyl lactate, ethyl lactate, butyl lactate, ethyl isovalerate, isoamyl isovalerate, diethyl oxalate, dibutyl oxalate, methyl benzoate, ethyl benzoate, propyl benzoate, methyl salicylate, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide. These may be used alone or in combination of two or more.

[0107] [Maleimide compound (B)]

[0108] The maleimide compound (B) is not particularly limited as long as it is a compound having one or more maleimide groups in one molecule, but is preferably a compound having two or more maleimide groups in one molecule, and examples thereof include: polyfunctional maleimide compounds obtained by reacting 3,4,4'-triaminodiphenylmethane, triaminophenol, etc. with maleic anhydride; maleimide compounds obtained by reacting tris-(4-aminophenyl)-phosphate, tris(4-aminophenyl)-phosphate, tris(4-aminophenyl)-thiophosphate, etc. with maleic anhydride; trimaleimide compounds such as tris(4-maleimidephenyl)methane; bis(3,4-dimaleimidephenyl)methane, Tetramaleimide compounds such as tetramaleimide benzophenone, tetramaleimide naphthalene, maleimide obtained by the reaction of triethylenetetramine and maleic anhydride; phenol novolac-type maleimide resin, isopropylidene bis(phenoxyphenylmaleimide)phenylmaleimide aralkyl resin, and biphenyl-type phenylmaleimide aralkyl resin, etc., as commercially available products, include: MIR-3000, MIR-5000 (all manufactured by Nippon Kayaku Co., Ltd.); BMI-70, BMI-80 (all manufactured by KI Chemicals Co., Ltd.); BMI-1000, BMI-2000, BMI-3000 (all manufactured by Yamato Chemicals Co., Ltd.), etc.

[0109] Since the maleimide compound causes the maleimide groups to self-crosslink with each other due to the action of the free radical initiator, the resin composition using an isocyanate-modified polyimide resin having an amino group at the end, a maleimide compound and a free radical initiator causes the maleimide groups to self-crosslink by heating, and becomes a cured product formed by copolymerization of the polyimide resin and the maleimide resin.

[0110] [Free radical initiator]

[0111] Examples of radical initiators that can be used for self-crosslinking of maleimide groups include peroxides such as dicumyl peroxide and dibutyl peroxide, and azo compounds such as 2,2'-azobis(isobutyronitrile) and 2,2'-azobis(2,4-dimethylvaleronitrile).

[0112] The mass ratio of the polyimide resin (A) to the maleimide compound (B) in the adhesive resin composition used in the present embodiment is 10:1 to 3:2, preferably 7:1 to 5:2.

[0113] When the mass ratio of the polyimide resin (A) to the maleimide compound (B) is within the above range, the metal substrate or laminate with the adhesive exhibits low dielectric properties in the high-frequency region. Furthermore, the adhesive easily adheres to metal foils with a surface roughness of 1.5 μm or less, and exhibits high adhesive strength.

[0114] The content of the radical initiator in the adhesive resin composition used in the present embodiment is 1 part by mass or more and less than 25 parts by mass, preferably 5 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of the maleimide compound (B).

[0115] If the content of the radical initiator falls within the above range, the metal substrate or laminate with adhesive can achieve sufficient bonding strength between the resin film and the metal layer. In particular, it is easy to adhere even to metal foils with a surface roughness of 1.5 μm or less, and thus exhibit high bonding strength.

[0116] The adhesive resin composition used in this embodiment may contain an organic solvent.

[0117] Specific examples of organic solvents include: γ-butyrolactones; amide solvents such as N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide and N,N-dimethylimidazolidinone; sulfones such as tetramethylene sulfone; ether solvents such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl ether monoacetate and propylene glycol monobutyl ether; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone and cyclohexanone; and aromatic solvents such as toluene and xylene.

[0118] The organic solvent is used in such a proportion that the solid content concentration in the adhesive resin composition after removing the organic solvent is generally 5% by mass or more and 80% by mass or less, preferably 10% by mass or more and 70% by mass or less.

[0119] The adhesive resin composition can be produced by adding a main component containing a polyimide resin (A) and a maleimide compound (B) to an organic solvent, and further adding a radical initiator.

[0120] <Laminated body>

[0121] The laminated body of the present embodiment includes the metal substrate with an adhesive of the present embodiment described above on both surfaces of a prepreg.

[0122] exist Figure 2 Schematic diagram of a cross section of a laminate 2 according to this embodiment is shown in FIG. The laminate 2 includes a metal substrate 1 with an adhesive on both surfaces of a prepreg 12 .

[0123] The prepreg 12 is laminated on a surface 11 a of the adhesive resin layer 11 of the metal substrate 1 with an adhesive, the surface 11 a being opposite to the surface in contact with the metal layer 10 .

[0124] That is, the laminate 2 is stacked in the order of metal layer 10 / adhesive resin layer 11 / prepreg 12 / adhesive resin layer 11 / metal layer 10 .

[0125] (Prepreg)

[0126] The prepreg 12 is preferably one or more selected from the group consisting of modified polyimide resin prepreg, polyester resin prepreg, liquid crystal polymer prepreg, cyclic olefin resin prepreg, polyphenylene ether resin prepreg, polyphenylene sulfide resin prepreg, polyetheretherketone resin prepreg, bismaleimide resin prepreg, triazine resin prepreg, bismaleimide-triazine resin prepreg, benzocyclobutene resin prepreg and low dielectric epoxy resin prepreg.

[0127] In the laminate 2 including the metal substrate X with adhesive according to the first embodiment, it is preferable that the thickness of the adhesive resin layer 11 is 0.2 μm to 9 μm, and the thickness of the metal layer 10 is 5 μm to 50 μm.

[0128] An example of the laminate 2 is a copper-clad laminate.

[0129] <<Metal Substrate Y with Adhesive (Second Embodiment)>>

[0130] The metal substrate X with adhesive involved in the first embodiment described above is characterized in that the surface roughness Rzjis of the metal layer possessed by the metal substrate with adhesive is less than 1.5 μm, and the metal substrate Y with adhesive involved in the second embodiment is characterized in that the thickness of the adhesive resin layer possessed by the metal substrate with adhesive is greater than 0.2 μm and less than 9 μm.

[0131] Specifically, the metal substrate Y with an adhesive according to the second embodiment includes a metal layer and an adhesive resin layer formed of an adhesive resin composition.

[0132] The adhesive resin composition comprises a polyimide resin (A), a maleimide compound (B) and a free radical initiator.

[0133] The mass ratio of the polyimide resin (A) to the maleimide compound (B) is 10:1 to 3:2,

[0134] The content of the radical initiator is 1 part by mass or more and less than 25 parts by mass relative to 100 parts by mass of the maleimide compound (B).

[0135] The adhesive resin layer has a thickness of 0.2 μm or more and 9 μm or less.

[0136] The metal substrate with adhesive Y according to the second embodiment is similar to the metal substrate with adhesive X according to the first embodiment, except that the thickness of the adhesive resin layer is within a specific range as described above, and a detailed description thereof will be omitted. However, in the laminate 2 including the metal substrate with adhesive Y according to the second embodiment, it is preferred that the thickness of the adhesive resin layer 11 be 0.2 μm to 9 μm, the thickness of the metal layer 10 be 1 μm to 35 μm, and the thickness of the prepreg be 50 μm to 1000 μm.

[0137] Furthermore, the laminate 2 including the metal substrate Y with an adhesive according to the second embodiment preferably satisfies the mathematical formula (1).

[0138] 0.01≤(X / Y)×100≤7···(1)

[0139] [In mathematical formula (1), X is the thickness of the adhesive resin layer (μm), and Y is the thickness of the prepreg (μm).]

[0140] The above-mentioned mathematical formula (1) is preferably any one of the following mathematical formulas (1)-1 to (1)-3.

[0141] 0.05≤(X / Y)×100≤7···(1)-1

[0142] 0.2≤(X / Y)×100≤6.5···(1)-2

[0143] 0.4≤(X / Y)×100≤6···(1)-3

[0144] Example

[0145] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[0146] <<Metal substrate X with adhesive and laminate thereof>>

[0147] <Preparation of Adhesive Resin Composition>

[0148] A polyimide resin (A) and a maleimide compound (B) were mixed at a mass ratio of 4:1 to prepare a base resin, which was then dissolved in anisole. Next, 17 parts by mass of dicumyl peroxide (manufactured by Sigma Aldrich) was added to 100 parts by mass of the maleimide compound (B), and the mixture was diluted with an organic solvent (anisole:toluene = 9:1) to prepare an adhesive resin composition 1 having a solids concentration of 11% by mass.

[0149] <Manufacturing of Metal Substrate X with Adhesive>

[0150] (Example 1)

[0151] The obtained adhesive resin composition 1 was applied to an electrolytic copper foil (manufactured by Fukuda Metal Foil Powder Co., Ltd., CF-T9DA-SV) having a surface roughness Rzjis of 0.85 μm and a thickness of 18 μm as a metal layer using a rod coater so that the thickness of the adhesive resin layer after drying was 6 μm. The metal substrate with an adhesive of Example 1 was then dried at 140°C for 1 minute until the residual solvent content became 1%.

[0152] (Comparative Example 1)

[0153] A metal substrate with an adhesive of Comparative Example 1 was produced in the same manner as in Example 1 except that the metal layer was changed to an electrolytic copper foil having a surface roughness Rzjis of 1.6 μm and a thickness of 9 μm (CF-T4X-SV-9 manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd.).

[0154] (Reference Example 1)

[0155] As Reference Example 1, an electrolytic copper foil having a surface roughness Rzjis of 1.0 μm and a thickness of 18 μm (manufactured by Fukuda Metal Foil & Powder Co., Ltd., CF-T4X-SV-18) was used.

[0156] (Reference Example 2)

[0157] As Reference Example 2, an electrolytic copper foil having a surface roughness Rzjis of 0.85 μm and a thickness of 18 μm (manufactured by Fukuda Metal Foil & Powder Co., Ltd., CF-T9DA-SV) was used.

[0158] (Reference Example 3)

[0159] As Reference Example 3, an electrolytic copper foil having a surface roughness Rzjis of 1.5 μm and a thickness of 18 μm (HS1-VSP, manufactured by Mitsui Mining & Smelting Co., Ltd.) was used.

[0160] <Manufacturing of Laminated Body>

[0161] (Type of prepreg)

[0162] Five types of polyphenylene ether resin prepregs and two types of bismaleimide-triazine resin prepregs were used as prepregs. Hereinafter, the polyphenylene ether resin prepregs will be referred to as "PPE-based prepregs," and the bismaleimide-triazine resin prepregs will be referred to as "BT-based prepregs."

[0163] (PPE-based prepreg)

[0164] PPE-based prepreg 1 (PPE1): manufactured by AGC Corporation, Meteorwave (registered trademark) 4000, thickness: 110.3 μm

[0165] PPE-based prepreg 2 (PPE2): manufactured by Panasonic Corporation, MEGTRON (registered trademark), thickness: 100.5 μm

[0166] PPE-based prepreg 3 (PPE3): manufactured by Panasonic Corporation, MEGTRON (registered trademark) 6, thickness: 130.3 μm

[0167] PPE-based prepreg 4 (PPE4): manufactured by Panasonic Corporation, MEGTRON (registered trademark) 7, thickness: 140.5 μm

[0168] PPE-based prepreg 5 (PPE5): Commercially available prepreg with a relative permittivity of 3.6 and a dielectric loss tangent of 0.0041 at 10 GHz, thickness: 100 μm

[0169] (BT-based prepreg)

[0170] BT prepreg 1 (BT1): manufactured by AGC Corporation, N5000, thickness: 30 μm

[0171] BT prepreg 2 (BT2): GHPL-970LF, manufactured by Mitsubishi Gas Chemical Co., Ltd., thickness: 45 μm

[0172] The metal substrates with adhesive of Example 1 and Comparative Example 1 were laminated on both surfaces of each prepreg in the order of copper foil (metal layer) / adhesive resin layer / prepreg / adhesive resin layer / copper foil (metal layer).

[0173] When the metal substrates of Reference Examples 1 and 2 were used, lamination was performed in the order of copper foil (metal layer) / prepreg / copper foil (metal layer).

[0174] Lamination conditions differ depending on the type of prepreg, but lamination was performed under the conditions described in Table 1 below.

[0175] [Table 1]

[0176]

[0177] Thus, laminates 1A to 1D, 2A to 2D, 3A to 3D, 4A to 4D, 5A, 5D, 6A to 6D, and 7A to 7D are manufactured.

[0178] <Measurement of Adhesive Strength>

[0179] The bond strength between the copper foil (metal layer) and the prepreg was measured for the resulting laminate. The laminate was cut into 10 mm wide test pieces, and the prepreg side was attached to the center of a ring with a diameter of 11 cm. The copper foil (metal layer) portion was stretched at a speed of 50 mm / min to perform a 90° peel test.

[0180] In this measurement, a bonding strength of 0.60 N / mm or more (3.4 lbs / inch or more) was evaluated as “sufficient bonding strength was ensured.” Table 2 shows the bonding strengths of the produced laminates.

[0181] Furthermore, as an indicator of the bonding strength between the prepreg and the metal layer, a bonding strength of 0.60 N / mm or greater (3.4 lbs / inch or greater) is required to prevent delamination of the metal layer during the manufacturing process. Therefore, a value of 0.60 N / mm or greater (3.4 lbs / inch or greater) is considered acceptable.

[0182] <Solder Heat Resistance>

[0183] The resulting laminate was placed in a constant temperature chamber at 23°C and 50% humidity for 24 hours and then floated in a 288°C solder bath. The time until deformation and blistering occurred was measured to evaluate heat resistance. The results are shown in Table 2. A laminate was considered acceptable if no deformation or blistering occurred after 300 seconds.

[0184] <Measurement of Dielectric Properties>

[0185] The copper foil (metal layer) of the resulting laminate was removed by etching, and a test piece (50 mm wide, 100 mm long) was prepared in which the adhesive resin layer / prepreg / adhesive resin layer was laminated in this order. The test piece was dried at 135°C for 1 hour and designated as the "dried" test piece. Separately, the test piece, after drying, was further allowed to stand at 23°C and 50% humidity for 24 hours and designated as the "humidified" test piece. The dielectric properties of each test piece were measured.

[0186] Regarding dielectric properties, the relative permittivity and dielectric loss tangent were measured at a frequency of 10 GHz using a resonator manufactured by QWED Corporation by a split dielectric resonator method.

[0187] For stacks 1A to 1D, stacks 2A to 2D, stacks 3A to 3D, stacks 4A to 4D, stacks 5A to 5D, stacks 6A to 6D, and stacks 7A to 7D, the type of metal substrate with adhesive, the type of prepreg, bonding strength, solder heat resistance, and dielectric properties are recorded in Table 2.

[0188] [Table 2]

[0189]

[0190] As shown in Table 2, in each laminate, when Reference Examples 1 and 2 are compared with Example 1, Example 1 has higher adhesive strength than Reference Examples 1 and 2.

[0191] In addition, in each laminated body, when Example 1 is compared with Comparative Example 1, Example 1 is superior to Comparative Example 1 in both adhesive strength and transmission characteristics.

[0192] <<Metal substrate Y with adhesive and laminate thereof>>

[0193] <Preparation of Adhesive Resin Composition>

[0194] A polyimide resin (A) and a maleimide compound (B) were mixed at a mass ratio of 4:1 to prepare a base resin, which was then dissolved in anisole. Next, 17 parts by mass of dicumyl peroxide (manufactured by Sigma Aldrich) was added to 100 parts by mass of the maleimide compound (B), and the mixture was diluted with an organic solvent (anisole:toluene = 9:1) to prepare an adhesive resin composition 2 having an adjusted solids concentration.

[0195] The solid content concentration was adjusted to the following concentrations depending on the thickness of the adhesive resin layer.

[0196] The thickness of the adhesive resin layer is 1 to 6 μm: the solid content concentration is adjusted to 11% by mass, and coating is performed using a bar coater.

[0197] When the thickness of the adhesive resin layer exceeds 10 μm: the solid content concentration is adjusted to 11% by mass and the layer is coated using a coater.

[0198] The thickness of the adhesive resin layer is less than 0.1 μm: The solid content concentration is adjusted to 1% by mass, and coating is performed using a bar coater.

[0199] <Manufacturing of Metal Substrate Y with Adhesive>

[0200] (Example 11)

[0201] The adhesive resin composition 2 obtained was applied to an electrolytic copper foil (manufactured by Fukuda Metal Foil Powder Co., Ltd., CF-T9DA-SV) having a surface roughness Rzjis of 0.85 μm and a thickness of 18 μm as a metal layer using a coater or a rod coater so that the thickness of the adhesive resin layer after drying was 6 μm. The metal substrate with an adhesive of Example 11 was then dried at 140°C for 1 minute until the residual solvent content became 1%.

[0202] (Examples 12 to 16, Comparative Examples 11 and 12)

[0203] Adhesive-attached metal substrates of Examples 12 to 16 and Comparative Examples 11 and 12 were produced in the same manner as in Example 11, except that the thickness of the adhesive resin layer was changed to the thickness shown in Table 3 below.

[0204] [Table 3]

[0205] Thickness of adhesive resin layer (μm) Residual solvent rate (%) Example 11 6.0 0.65 Example 12 5.0 Example 13 3.0 0.55 Example 14 2.0 Example 15 1.0 Example 16 0.5 Comparative Example 11 10.0 0.85 Comparative Example 12 0.1

[0206] Processability Evaluation

[0207] As evaluation of processability, the residual solvent ratio and processing speed were evaluated.

[0208] (Residual solvent rate)

[0209] An adhesive resin layer having the same thickness as in Examples 11, 13, and Comparative Example 11 was formed on a polyimide sheet and dried at 120° C. for 10 minutes, and then the residual rate of the organic solvent was measured using TG / DTA.

[0210] The results are shown in Table 3. As shown in Table 3, the residual solvent ratio of Comparative Example 11, in which the adhesive resin layer had a thickness of 10.0 μm, was as high as 0.85%. A high residual solvent ratio can cause gas volatilization from the adhesive resin layer during the heating step, leading to delamination.

[0211] On the other hand, it was found that the residual solvent ratios in Examples 11 and 13, in which the thickness of the adhesive resin layer was 6.0 μm or 3.0 μm, were low, and the possibility of delamination due to gas generation was low.

[0212] (Processing speed)

[0213] A coater test was conducted assuming an adhesive coating process with the copper foil in a roll state. The processing speed was measured under the same drying conditions (a drying oven (8 zones, each 1 m) set at 70°C to 140°C) to achieve the same residual solvent content (0.7% or less).

[0214] Changing the drying conditions to high temperatures or long periods of time to reduce the residual solvent content is not done because it makes the curing reaction difficult to proceed. Therefore, in order to reduce the residual solvent content of the formed adhesive resin layer, the drying process is carried out at a reduced processing speed. However, if the processing speed is too slow, productivity decreases, which is not preferred.

[0215] As shown in the results in Table 4, when the thickness of the adhesive resin layer is 1.5 to 6 μm, processing can be performed at a processing speed of approximately 3 to 5 m / min, maintaining productivity. On the other hand, when the thickness of the adhesive resin layer is 9 μm, the processing speed is 1 m / min, which may lead to a decrease in productivity.

[0216] [Table 4]

[0217] Thickness of adhesive resin layer Processing speed 9μm 1m / min 6μm 3m / min 1.5μm 5m / min

[0218] (Reference Example 11)

[0219] As Reference Example 11, an electrolytic copper foil having a surface roughness Rzjis of 0.85 μm and a thickness of 18 μm (manufactured by Fukuda Metal Foil & Powder Co., Ltd., CF-T9DA-SV) was used.

[0220] (Reference Example 12)

[0221] As Reference Example 12, an electrolytic copper foil having a surface roughness Rzjis of 1.5 μm and a thickness of 18 μm (HS1-VSP, manufactured by Mitsui Mining & Smelting Co., Ltd.) was used.

[0222] <Manufacturing of Laminated Body>

[0223] (Type of prepreg)

[0224] Four types of polyphenylene ether resin prepregs were used as prepregs. These polyphenylene ether resin prepregs are referred to as "PPE-based prepregs."

[0225] (PPE-based prepreg)

[0226] PPE-based prepreg 11 (PPE11): manufactured by AGC Corporation, Meteorwave (registered trademark) 4000, thickness: 110.3 μm

[0227] PPE-based prepreg 12 (PPE12): manufactured by Panasonic Corporation, MEGTRON (registered trademark) 6, thickness: 130.3 μm

[0228] PPE-based prepreg 13 (PPE13): manufactured by Panasonic Corporation, MEGTRON (registered trademark) 7, thickness: 140.5 μm

[0229] PPE-based prepreg 14 (PPE14): Commercially available prepreg with a relative permittivity of 3.6 and a dielectric loss tangent of 0.0041 at 10 GHz, thickness: 100 μm

[0230] The metal substrates with adhesive of Examples 11 to 16 and Comparative Examples 11 and 12 were laminated on both surfaces of each prepreg in the order of copper foil (metal layer) / adhesive resin layer / prepreg / adhesive resin layer / copper foil (metal layer).

[0231] When the metal substrate of Reference Example 11 was used, lamination was performed in the order of copper foil (metal layer) / prepreg / copper foil (metal layer).

[0232] Lamination conditions differed depending on the type of prepreg, but lamination was performed under the conditions described in Table 5 below.

[0233] [Table 5]

[0234]

[0235] In this manner, the stacked bodies 11A to 11I, the stacked bodies 12A to 12I, and the stacked bodies 13A to 13I are manufactured.

[0236] <Measurement of Adhesive Strength>

[0237] The bond strength between the copper foil (metal layer) and the prepreg was measured for the resulting laminate. The laminate was cut into 10 mm wide test pieces, and the prepreg side was attached to the center of a ring with a diameter of 11 cm. The copper foil (metal layer) portion was stretched at a speed of 50 mm / min to perform a 90° peel test.

[0238] In this measurement, a bonding strength of 0.60 N / mm or more (3.4 lbs / inch or more) was evaluated as “sufficient bonding strength was ensured.” The bonding strengths of the produced laminates are shown in Table 5.

[0239] Furthermore, as an indicator of the bonding strength between the prepreg and the metal layer, a bonding strength of 0.60 N / mm or greater (3.4 lbs / inch or greater) is required to prevent delamination of the metal layer during the manufacturing process. Therefore, a value of 0.60 N / mm or greater (3.4 lbs / inch or greater) is considered acceptable.

[0240] <Solder Heat Resistance>

[0241] The resulting laminate was placed in a constant temperature chamber at 23°C and 50% humidity for 24 hours and then floated in a 288°C solder bath. The time until deformation and blistering occurred was measured to evaluate heat resistance. The results are shown in Tables 6 to 8. A laminate was considered acceptable if no deformation or blistering occurred after 300 seconds.

[0242] <Measurement of Dielectric Properties>

[0243] The copper foil (metal layer) of the resulting laminate was removed by etching, and a test piece (50 mm wide, 100 mm long) was prepared in which the adhesive resin layer / prepreg / adhesive resin layer was laminated in this order. The test piece was dried at 135°C for 1 hour and designated as the "dried" test piece. Separately, the test piece, after drying, was further allowed to stand at 23°C and 50% humidity for 24 hours and designated as the "humidified" test piece. The dielectric properties of each test piece were measured.

[0244] Regarding dielectric properties, the relative permittivity and dielectric loss tangent were measured at a frequency of 10 GHz using a resonator manufactured by QWED Corporation by a split dielectric resonator method.

[0245] For stacks 11A to 11I, stacks 12A to 12I, and stacks 13A to 13I, the type of metal substrate with adhesive, the type of prepreg, bonding strength, solder heat resistance, X / Y (X is the thickness of the adhesive resin layer (μm), Y is the thickness of the prepreg (μm)), and dielectric properties are recorded in Tables 6 to 8.

[0246] [Table 6]

[0247]

[0248] [Table 7]

[0249]

[0250] [Table 8]

[0251]

[0252] As shown in Tables 6 to 8, in each laminate, when Reference Example 11 is compared with each Example, the adhesive strength of the Example is higher than that of Reference Example 11.

[0253] Furthermore, in each laminate, the adhesive strength was comparable when comparing Example 11 with Comparative Example 11. In Comparative Example 11, where the adhesive resin layer had a thickness of 10.0 μm, delamination was a concern based on the processing speed evaluation results. Therefore, the superiority of setting the adhesive resin layer thickness to 0.2 μm or more and 9 μm or less was confirmed.

[0254] In addition, when Example 11 and Comparative Example 12 were compared in each laminate, the adhesive strength of Comparative Example 12 was NG or lower than that of the Examples.

[0255] In addition, for the laminate, when the dielectric properties of the prepreg are inferior to those of the adhesive resin layer, if the embodiment is compared with Comparative Example 11, it can be predicted that the transmission loss of Comparative Example 11 is better than that of the embodiment. However, when the dielectric properties of the prepreg are better than those of the adhesive resin layer, it can be predicted that the excess thickness of the adhesive resin layer affects the transmission loss. Therefore, the thickness of the adhesive resin layer is preferably 9 μm or less, taking other properties into consideration.

[0256] Furthermore, when Example 11 is compared with Reference Example 11, the bonding strength of Reference Example 11 is evaluated as "NG", and the relative dielectric constant of Example is lower than that of Reference Example 11. Therefore, it can be confirmed that both the bonding strength and the transmission characteristics of Example are superior to those of Reference Example 11.

[0257] <Measurement of transmission characteristics>

[0258] The laminated bodies of Example 21, Comparative Example 21, and Comparative Example 22 shown in Table 9 below were produced.

[0259] [Table 9]

[0260]

[0261] The transmission loss (dB / 100 mm) of the laminates of Example 21, Comparative Example 21, and Comparative Example 22 was measured using the following apparatus. The results are shown in FIG. Figure 3 middle.

[0262] [Installation]

[0263] KEISIGHT TECHNOLOGIES

[0264] 10MHz-67GHz: Network Analyzer

[0265] PNA Series N5227B

[0266] 55GHZ-95GHz: Frequency extender for WR12 signal analyzer

[0267] N9029AV12

[0268] like Figure 3 As shown in Table 9, even at high frequencies, Example 21 has a lower transmission loss than Comparative Examples 21 and 22. Furthermore, as shown in Table 9, Example 21 also has high bonding strength.

[0269] On the other hand, in Comparative Example 21, since the surface roughness Rzjis was as high as 1.5 μm, although the adhesive strength was exhibited, the transmission loss increased as the frequency became higher.

[0270] Comparative Example 22 had a surface roughness Rzjis of 0.85 μm, and thus had a smaller transmission loss than Comparative Example 21. However, since the adhesive resin layer was not included, the adhesive strength was low.

[0271] (Explanation of Reference Numerals)

[0272] 1: Metal substrate with adhesive, 2: Laminated body, 10: Metal layer, 11: Adhesive resin layer, 12: Prepreg

Claims

1. A metal substrate with an adhesive, comprising a metal layer and an adhesive resin layer formed from an adhesive resin composition, wherein: The surface roughness Rzjis of the metal layer is less than 1.5 μm, The adhesive resin composition comprises a polyimide resin (A), a maleimide compound (B) and a free radical initiator. The mass ratio of the polyimide resin (A) to the maleimide compound (B) is 10:1 to 3:2, The content of the radical initiator is 1 part by mass or more and less than 25 parts by mass relative to 100 parts by mass of the maleimide compound (B).

2. The metal substrate with adhesive according to claim 1, wherein The metal layer is a copper foil with a surface roughness Rzjis less than 1.0 μm.

3. A laminate comprising the metal substrate with an adhesive according to claim 1 or 2 on both sides of a prepreg, wherein: The prepreg is laminated on the surface of the adhesive resin layer of the metal substrate with adhesive, which surface is opposite to the surface in contact with the metal layer. The prepreg is one or more selected from the group consisting of modified polyimide resin prepreg, polyester resin prepreg, liquid crystal polymer prepreg, cyclic olefin resin prepreg, polyphenylene ether resin prepreg, polyphenylene sulfide resin prepreg, polyetheretherketone resin prepreg, bismaleimide resin prepreg, triazine resin prepreg, bismaleimide-triazine resin prepreg, benzocyclobutene resin prepreg and low dielectric epoxy resin prepreg.

4. A metal substrate with an adhesive, comprising a metal layer and an adhesive resin layer formed from an adhesive resin composition, wherein: The adhesive resin composition comprises a polyimide resin (A), a maleimide compound (B) and a free radical initiator. The mass ratio of the polyimide resin (A) to the maleimide compound (B) is 10:1 to 3:2, The content of the radical initiator is 1 part by mass or more and less than 25 parts by mass relative to 100 parts by mass of the maleimide compound (B). The adhesive resin layer has a thickness of 0.2 μm or more and 9 μm or less.

5. The metal substrate with adhesive according to claim 4, wherein The metal layer is a copper foil having a surface roughness Rzjis of 1.0 μm or less.

6. A laminate comprising the metal substrate with an adhesive according to claim 4 or 5 on both sides of a prepreg, wherein: The prepreg is laminated on the surface of the adhesive resin layer of the metal substrate with adhesive, which surface is opposite to the surface in contact with the metal layer. The prepreg is one or more selected from the group consisting of modified polyimide resin prepreg, polyester resin prepreg, liquid crystal polymer prepreg, cyclic olefin resin prepreg, polyphenylene ether resin prepreg, polyphenylene sulfide resin prepreg, polyetheretherketone resin prepreg, bismaleimide resin prepreg, triazine resin prepreg, bismaleimide-triazine resin prepreg, benzocyclobutene resin prepreg and low dielectric epoxy resin prepreg.

7. The laminate according to claim 6, wherein The thickness of the adhesive resin layer is 0.2 μm or more and 9 μm or less. The thickness of the prepreg is 50 μm or more and 1000 μm or less, The thickness of the metal layer is not less than 1 μm and not more than 35 μm, The laminate satisfies the following mathematical formula (1): 0.05≤(X / Y)×100≤7 ··· (1) In the mathematical formula (1), X is the thickness of the adhesive resin layer in μm, and Y is the thickness of the prepreg in μm.

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