Flexible printed circuit board

Abstract

The invention provides a flexible printed circuit board. The flexible printed circuit board has at least a base material layer, an adhesive layer, a nickel-containing layer, and a conductor in this order, the adhesive layer containing a fluorine-containing rubber, and the mass of nickel per unit area in the nickel-containing layer being 100 mg / m2 or more.

Description

Technical Field

[0001] One aspect of the present invention relates to a flexible printed circuit board. Background Art

[0002] Flexible printed circuit boards are widely used as substrates for various electronic devices. In recent years, long-term use of flexible printed circuit boards in high-temperature environments such as near semiconductors in inverters has been studied (Japanese Unexamined Patent Application Publication No. 2018-195751). The long-term heat resistance temperature of a typical flexible printed circuit board is about 80°C. Therefore, when using a flexible printed circuit board in the above environment, there is a concern that the substrate layer and the conductor may be peeled off from each other due to embrittlement of the adhesive layer provided between the substrate layer and the conductor forming the circuit pattern.

[0003] In the above adhesive layer of a typical flexible printed circuit board, epoxy resin, acrylic resin, etc. are used as main components. However, they are not suitable for long-term use in high-temperature environments and cause problems such as interlayer peeling. Therefore, the development of an adhesive layer using an adhesive containing fluororubber is also underway. For example, in the technology related to a flexible printed circuit board disclosed in Japanese Unexamined Patent Application Publication No. 2021-091873, long-term heat resistance of 1000 hours was achieved by using an adhesive having a high thermal decomposition temperature containing fluorine-based rubber and a film having low oxygen permeability in a high-temperature environment. Summary of the Invention

[0004] A flexible printed circuit board having at least a substrate layer, an adhesive layer, a nickel-containing layer, and a conductor in this order, the adhesive layer containing fluororubber, and the mass of nickel per unit area in the nickel-containing layer being 100 mg / m 2 or more. Brief Description of the Drawings

[0005] Figure 1 is a schematic diagram for explaining the layer structure of a flexible printed circuit board. Figure 2 is a schematic diagram for explaining the structure of a power module. Detailed Description In the following detailed description, for the purpose of explanation, in order to provide a thorough understanding of the disclosed embodiments, many specific details are set forth. However, it is obvious that one or more embodiments can be implemented without these specific details. In other cases, well-known structures and devices are schematically shown to simplify the drawing.

[0006] If it is about 1000 hours, it can be known that the adhesive layer containing fluororubber provided on the flexible printed circuit board disclosed in Japanese Patent Laid-Open No. 2021-091873 can maintain heat resistance. However, in the long-term high-temperature environment of 3000 hours required for actual automotive parts, the peeling of the adhesive layer gradually occurs from the end of the substrate. Therefore, there are limitations in the use environment and design of this adhesive layer.

[0007] An object of the present invention is to provide a flexible printed circuit board that is less likely to cause peeling of the adhesive layer even when exposed to a high-temperature environment for a long time as compared with conventional flexible printed circuit boards.

[0008] The present inventors conducted intensive studies and as a result, found that by providing a layer containing a specific amount of nickel between the adhesive layer containing fluororubber and the conductor, the above object can be achieved, and thus completed the technology of the present invention.

[0009] That is, one aspect of the present invention is as follows. [1] A flexible printed circuit board according to one aspect of the present invention has at least a substrate layer, an adhesive layer, a nickel-containing layer, and a conductor in this order. The adhesive layer contains fluororubber, and the mass of nickel per unit area in the nickel-containing layer is 100 mg / m 2 or more. [2] In the flexible printed circuit board according to [1], the substrate layer may contain polyimide. [3] In the flexible printed circuit board according to [1] or [2], the mass of nickel per unit area in the nickel-containing layer may be 125 mg / m 2 or more and 500 mg / m 2 or less. [4] In the flexible printed circuit board according to any one of [1] to [3], the conductor may contain copper. [5] A method for manufacturing a flexible printed circuit board according to one aspect of the present invention includes: a lamination step of obtaining a laminate including at least a substrate layer, an adhesive layer, a nickel-containing layer, and a conductor layer in this order; and a circuit pattern forming step of processing the laminate to form a circuit pattern. The adhesive layer contains fluororubber, and the mass of nickel per unit area in the nickel-containing layer is 100 mg / m 2 or more. [6] In the method for manufacturing a flexible printed circuit board according to [5], the lamination step may include a step of laminating the substrate layer and a laminate including the nickel-containing layer and the conductor layer with an adhesive.

[0010] According to one aspect of the present invention, a flexible printed circuit board can be provided which is less likely to cause peeling of the adhesive layer even when exposed to a high-temperature environment for a long period compared to conventional flexible printed circuit boards.

[0011] Hereinafter, embodiments of the present invention will be described in detail. In addition, these descriptions are examples (representative examples) of the embodiments of the present invention, and the technology of the present invention is not limited to these as long as it does not exceed the gist thereof. In this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. For example, "A~B" means A or more and B or less. In addition, in this specification, a plurality of embodiments are described, but within the applicable range, various conditions of each embodiment can also be applied to other embodiments. In addition, in order to easily understand the features of the embodiments, the drawings of the present invention are schematically illustrated. Therefore, the dimensional ratios of the respective components in the drawings of the present invention are not limited to the same as the actual dimensional ratios.

[0012] <Flexible Printed Circuit Board> A flexible printed circuit board (hereinafter also simply referred to as "flexible printed circuit board") according to an embodiment of the present invention has at least a base material layer, an adhesive layer, a nickel-containing layer, and a conductor in this order. The adhesive layer contains a fluororubber, and the mass of nickel per unit area in the nickel-containing layer is 100 mg / m 2 or more.

[0013] In a normal flexible printed circuit board, peeling of the adhesive is likely to occur between the adhesive layer and the conductor. For example, in a high-temperature environment, copper, which is usually used as a conductor material, sometimes promotes the thermal decomposition reaction (low molecular weight formation) of the fluororubber in the adhesive layer. As a result, peeling of the adhesive occurs. On the other hand, in the above flexible printed circuit board, a nickel-containing layer having a specific nickel content is provided between the adhesive layer and the conductor. Thereby, the reaction between a metal such as copper that can be used as a conductor and the fluororubber in the adhesive layer is suppressed. Therefore, even when the flexible printed circuit board is exposed to high temperatures for a long period (especially for a period required for actual automotive parts such as 3000 hours or more), it is possible to suppress the deterioration of the adhesive and further suppress the peeling of the adhesive layer. Regarding the reaction of a metal such as copper that can be used for a conductor with a fluororubber in an adhesive layer, the thermal oxidative degradation of the fluororubber due to copper is disclosed in "Dai Takeyoshi, 'Degradation and Troubleshooting of Elastomer Products (Degradation by Residual Chlorine Water, Metal Degradation, and Ozone Degradation Caused by Global Environmental Deterioration)', Journal of the Japan Rubber Association (Dai Takeyoshi, 'Degradation and Troubleshooting of Elastomer Products (Degradation by Residual Chlorine Water, Metal Degradation, and Ozone Degradation Caused by Global Environmental Deterioration)', Journal of the Japan Rubber Association), Vol. 79, No. 19, 2006, pp. 529 - 536".

[0014] Figure 1 Shows an example of the flexible printed circuit board of the present embodiment. Figure 1 The flexible printed circuit board 100 shown has a base material layer 110, an adhesive layer 120, a nickel-containing layer 130, and a conductor 140 forming a circuit pattern in this order. The flexible printed circuit board 100 of the present embodiment only needs to have at least the above structural elements, and may also have other layers. In Figure 1 the drawing of the circuit pattern formed by the conductor 140 is omitted. Hereinafter, each component constituting the flexible printed circuit board 100 will be described.

[0015] [Base material layer] The average thickness of the base material layer 110 is not particularly limited, but is preferably 12.5 μm or more and 125 μm or less, more preferably 25 μm or more and 75 μm or less. In this specification, "average thickness" means the average value of the thicknesses measured at a plurality of portions of the target substance.

[0016] The material of the base material layer 110 is not particularly limited. For example, as the base material layer 110, a layer containing a resin film such as a polyimide film or a liquid crystal polymer film can be used. In addition, the resin film layer can be a layer containing at least one selected from the group consisting of a polyimide film and a liquid crystal polymer. The base material layer 110 may contain one film or may contain two or more films laminated on each other. In addition, a resin film on which a metal such as aluminum is vapor-deposited, that is, a metal vapor-deposited film, can also be used as the resin film layer. Specifically, as the base material layer 110, UPILEX series (polyimide film manufactured by Ube Industries) and Vecstar series (liquid crystal polymer manufactured by Kuraray) can be used. When using a liquid crystal polymer of the Vecstar series as the resin film layer, in the Vecstar series, Vecstar CTF is preferred from the viewpoint of oxygen permeability.

[0017] From the viewpoint of improving heat resistance, the base material layer 110 preferably contains polyimide and is preferably a polyimide film. When a polyimide film is used as the base material layer 110, the polyimide film preferably contains polyimide which is a polymer of a tetracarboxylic acid component and a diamine component. The tetracarboxylic acid component is not particularly limited. However, the tetracarboxylic acid component is preferably at least one selected from the group consisting of biphenyltetracarboxylic acids such as 3,3',4,4'-biphenyltetracarboxylic acid, pyromellitic acid, and their acid anhydrides and esters of their lower alcohols. The tetracarboxylic acid component more preferably contains 3,3',4,4'-biphenyltetracarboxylic acid, and further preferably contains 3,3',4,4'-biphenyltetracarboxylic dianhydride. The diamine component is not particularly limited. However, the diamine component is preferably at least one selected from the group consisting of 1,4-phenylenediamine, 1,3-phenylenediamine, 1,2-phenylenediamine, 2,4-diaminotoluene, 2,5-diaminotoluene, and 2,6-diaminotoluene.

[0018] The polyimide film more preferably contains polyimide which is a polymer of monomers as follows. That is, the monomers at least include: at least one selected from the group consisting of 1,2-phenylenediamine, 1,3-phenylenediamine, and 1,4-phenylenediamine; and 3,3',4,4'-biphenyltetracarboxylic dianhydride. Further preferably, the polyimide film contains polyimide which is a polymer of monomers as follows. That is, the monomers at least include 1,4-phenylenediamine and 3,3',4,4'-biphenyltetracarboxylic dianhydride. If the polyimide film contains the above polyimide, the unit structures of the polyimide can overlap with each other. Thus, the polyimide film becomes a structure in which oxygen is more difficult to pass through. Therefore, it is preferred that the polyimide film contains the above polyimide. As a polyimide film which is a polymer of monomers that at least include 1,4-phenylenediamine and 3,3',4,4'-biphenyltetracarboxylic dianhydride, specifically, UPILEX-S etc. can be cited.

[0019] The oxygen transmission rate of the base material layer 110 is generally 1.50×10 -10 cc·cm / cm 2 ·sec·cmHg or less, preferably 1.00×10 -10 cc·cm / cm 2 ·sec·cmHg or less, more preferably 1.00×10 -11 cc·cm / cm 2 ·sec·cmHg or less. The lower limit value of the oxygen transmission rate is not particularly limited, and the lower the better. However, for example, it can be 1.00×10 -15 cc·cm / cm 2·sec·cmHg or more. In addition, regarding the oxygen permeability of the base material layer 110, it is preferable that the oxygen permeability of the base material layer 110 at 200 °C satisfies the above-mentioned range of oxygen permeability. If the above-mentioned oxygen permeability is below the above-mentioned upper limit, oxidation deterioration of the conductor in a high-temperature environment can be suppressed, and thus it is easy to prevent a decrease in the peel strength of the base material layer 110. The oxygen permeability can be controlled by using the monomer components constituting the resin film. In addition, the oxygen permeability can also be controlled by coating an organic layer and / or an inorganic layer on the resin film, bonding an organic film and / or an inorganic film to the resin film, or adding an organic filler and / or an inorganic filler to the resin film.

[0020] The oxygen permeability of the base material layer 110 can be measured under the following conditions. Measurement method: According to Appendix 2 of JIS K7126-1 Test gas type: Oxygen Test gas flow rate: 90 ml / min Carrier gas type: Helium Carrier gas flow rate: 35 ml / min Permeation area: 15.2 cm 2 Measurement device: GTR-10AH (200 °C) or GTR-30XANO (~120 °C), both manufactured by GTR TEC Cell thermostat temperature: 25 °C, 120 °C, 200 °C Gas chromatograph calibration method: Two-point calibration at 0.0 μl and 15.3 μl

[0021] [Adhesive layer] The average thickness of the adhesive layer 120 is not particularly limited, but from the viewpoint of adhesiveness, it is preferably 5 μm or more, from the viewpoint of filling the roughness of the conductor, it is preferably 10 μm or more, and from the viewpoint of the processability of the flexible printed circuit board, it is preferably 30 μm or less. Generally, when the thickness is 10 μm or more, even if the thickness is increased, the adhesive force does not change.

[0022] The adhesive layer 120 can be a cured product of an adhesive. Hereinafter, the conditions of the adhesive will be described. The conditions of the adhesive can be regarded as the conditions of the adhesive layer 120 within the applicable range. For example, "the content of fluororubber in the adhesive" can be regarded as "the content of fluororubber in the adhesive layer".

[0023] The binder is not particularly limited as long as it contains fluororubber. As the binder, known binders can be used. The fluororubber may or may not have an unsaturated bond. However, the fluororubber preferably has an unsaturated bond. The fluororubber having an unsaturated bond can be obtained by introducing an unsaturated bond into the fluororubber by a known method. For example, as the known method, a base modification method such as modification with a water-soluble base (alkali) can be cited.

[0024] From the viewpoint of heat resistance, the material of the adhesive layer 120 is not particularly limited as long as it contains fluororubber. The material of the adhesive layer 120 may also have other components. Regarding the reason why the heat resistance can be improved if the binder contains fluororubber, the present inventors speculate as follows. It is known that the bond energy between carbon and fluorine (C-F bond) is greater than the bond energy between carbon and hydrogen (C-H bond). Therefore, by modifying the rubber with fluorine to increase the C-F bonds, it becomes difficult for the bonds between elements to be broken by heat. In addition, if the ease of rotation of the carbon-carbon (C-C) bonds in the main chain of the resin is considered, the case where fluorine modification is carried out (i.e., the case of -CF2-) is more difficult to rotate and has a larger bond energy compared to the case where fluorine modification is not carried out (i.e., the case of -CH2-). Therefore, it becomes difficult for thermal decomposition to occur, and the heat resistance can be improved. In addition, when the fluororubber has an unsaturated bond, the unsaturated bond can react with the thermosetting resin described later, so the heat resistance can be further improved.

[0025] Examples of the fluororubber include polymers or copolymers of at least one monomer selected from the group consisting of vinyl fluoride, vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene. More preferably, the fluororubber is a copolymer of at least one monomer selected from the group consisting of vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene. The copolymer is preferably a binary copolymer or a terpolymer, and more preferably a binary copolymer. In addition, examples of the fluororubber having an unsaturated bond include unsaturated bond-introduced products of the above polymers or copolymers. Within the range not impairing the technical effects of the present invention, fluorinated olefins, olefins, and vinyl compounds such as ethylene, propylene, alkyl vinyl ether, hexafluoroisobutene, and vinyl acetate can be copolymerized in the copolymer. Specifically, examples of the copolymerized substances include polytetrafluoroethylene, poly(chlorotrifluoroethylene), poly(vinyl fluoride), poly(vinylidene fluoride), vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, chlorofluoroethylene-vinylidene fluoride copolymer, and their unsaturated bond-introduced products. The copolymerized substance is preferably a vinylidene fluoride - hexafluoropropylene copolymer and an unsaturated bond-introduced product of the copolymer, more preferably an unsaturated bond-introduced product of a vinylidene fluoride - hexafluoropropylene copolymer. The copolymerization ratio (vinylidene fluoride: hexafluoropropylene) is preferably 3:7 to 9.5:0.5 by mass basis, more preferably 5:5 to 9:1. For the fluororubber, one kind can be used alone, or two or more kinds can be used in combination. In addition, a fluororubber without an unsaturated bond and a fluororubber with an unsaturated bond can be used in combination.

[0026] The Mooney viscosity (ML 1+10 (121 °C)) of the fluororubber or the fluororubber with an unsaturated bond is preferably 40 to 110. If the Mooney viscosity is within the above range, the sheet processability can be improved, and the elastic modulus and elongation can be made within an appropriate range. Therefore, the blanking processability, the adhesion at high temperature, the solder heat resistance, the adhesion after a long-term high-temperature durability test, and the processability in the B-stage state become good. The Mooney viscosity (ML 1+10 (121 °C)) is more preferably 50 to 100. The Mooney viscosity can be controlled by the molecular weight of the material, etc. For example, by increasing the molecular weight, the Mooney viscosity can be made larger. The Mooney viscosity is measured in accordance with JIS K 6300-1(2013). Using a Mooney viscometer SMV-201 (manufactured by Shimadzu Corporation), the viscosity is measured under the conditions of a temperature of 121 °C, a preheating time of 1 minute, and a rotor rotation time of 10 minutes.

[0027] If necessary, in the presence of ketone solvents such as acetone and methyl ethyl ketone, these polymers or copolymers can be treated with basic substances such as potassium hydroxide, sodium hydroxide, cesium hydroxide, calcium hydroxide, calcium carbonate, and triethylamine, preferably at a temperature of about 2 to 70 °C. Thereby, a dehydrofluorination reaction occurs, and an unsaturated bond can be formed in the molecule. The content of the unsaturated bond of the fluororubber with an unsaturated bond (-CH=CH- content) is preferably 0.1 mass% to 30 mass%, more preferably 0.5 mass% to 10 mass%. The fluororubber and the fluororubber with an unsaturated bond can use commercially available fluororubbers.

[0028] The content of the fluororubber in the adhesive is not particularly limited. For example, the content can be 40 mass% or more, and in addition, it can also be 80 mass% or less.

[0029] Within the range where the technical effects of the present invention can be obtained, the adhesive can also contain rubbers other than the fluororubber.

[0030] (Thermosetting resin) The adhesive may be an adhesive composition. The adhesive composition may contain a thermosetting resin. The thermosetting resin is preferably a thermosetting resin having a softening point of 30 °C or higher. That is, the thermosetting resin is preferably in a solid state at normal temperature (25 °C). The softening point of the thermosetting resin is more preferably 30 °C to 160 °C, further preferably 40 °C to 160 °C, still further preferably 50 °C to 150 °C, and particularly preferably 60 °C to 130 °C. In the manufacturing process of a printed wiring board such as a flexible printed circuit board, there are cases where processing such as opening holes for component mounting is performed when the adhesive composition is in the B-stage (semi-cured) state before hot pressing. By using a thermosetting resin having a softening point in the above range and being in a solid state at normal temperature as the adhesive composition, effects such as improved miscibility between fluororubber and other rubbers and increased elastic modulus of the inorganic filler described below can be obtained. Therefore, the processability in the B-stage state is further improved. The softening point of the resin can be measured by the ring and ball method of JIS K 7234. As the measuring device, for example, a METTLER softening point measuring device (FP900 calorific value analysis system) manufactured by METTLER TOLEDO can be used.

[0031] From the viewpoints of reactivity and heat resistance, the thermosetting resin is preferably any one of a phenol resin and an epoxy resin, or a mixture of two or more of these. Examples of the epoxy resin include bisphenol A type epoxy resins, bisphenol F type epoxy resins, and bisphenol S type epoxy resins such as bisphenol type epoxy resins; phenol novolak type epoxy resins, cresol novolak type epoxy resins, and bisphenol A novolak type epoxy resins such as novolak type epoxy resins; alicyclic epoxy resins; aliphatic chain epoxy resins; diglycidyl ether compounds of bisphenol; diglycidyl ether compounds of naphthalene diol; diglycidyl ether compounds of phenols; diglycidyl ether compounds of alcohols; and their alkyl-substituted products or hydrogenated products. For the epoxy resin, one kind can be used alone, or two or more kinds can be used in combination.

[0032] The phenol resin is a substance obtained by reacting phenols with aldehydes using an acid or a base as a catalyst. Examples of the phenols include phenol, m-cresol, p-cresol, o-cresol, isopropylphenol, and nonylphenol. Examples of aldehydes include formaldehyde, paraformaldehyde, acetaldehyde, paraldehyde, butyraldehyde, octanal, and benzaldehyde. Formaldehyde or paraformaldehyde is usually used. In addition, vegetable oil-modified phenolic resins can also be used. The phenolic compound is reacted with a vegetable oil in the presence of an acid catalyst, and then the aldehyde is reacted in the presence of a base catalyst to obtain a vegetable oil-modified phenolic resin. Examples of the acid catalyst include p-toluenesulfonic acid. Examples of the base catalyst include amine-based catalysts such as ammonia, trimethylamine, and triethylamine. In addition, as the thermosetting resin, xylene resin, guanamine resin, diallyl phthalate resin, vinyl ester resin, unsaturated polyester resin, furan resin, polyimide resin, polyurethane resin, cyanate ester resin, maleimide resin, and benzocyclobutene resin can also be used.

[0033] The thermosetting resin preferably contains an epoxy resin and is more preferably an epoxy resin. The epoxy resin is preferably a cresol novolac type epoxy resin, and more preferably an o-cresol novolac type epoxy resin. As such an epoxy resin, commercially available epoxy resins can be used. Examples of commercially available epoxy resins include YDCN700-10 (Nippon Steel & Sumikin Chemical Co., Ltd.) and N695 (DIC Corporation). With respect to 100 parts by mass of the fluororubber, the content of the thermosetting resin is preferably 8 to 120 parts by mass. When the content of the thermosetting resin is within the above range, the blanking processability and the adhesion at high temperatures become good. The content is more preferably 8 to 110 parts by mass, and further preferably 8 to 100 parts by mass.

[0034] (Inorganic filler) The adhesive composition may contain an inorganic filler. As the inorganic filler, known materials can be used. The inorganic filler is preferably an electrically insulating inorganic filler. Examples of the inorganic filler include silica, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, calcium silicate, aluminum silicate, calcium carbonate, alumina, magnesia, antimony oxide, tin oxide, titanium oxide, manganese oxide, zirconium oxide, silicon nitride, aluminum nitride, boron nitride, talc, mica, and kaolin.

[0035] Since the fluororubber has a low elastic modulus, burrs of the adhesive and adhesion of the adhesive to the processing portion sometimes occur during processing in the B-stage state. In response to this, by making the adhesive composition contain an inorganic filler, the elastic modulus of the adhesive can be increased. As a result, the processability of the adhesive becomes good. The inorganic filler preferably has the property of coagulating to a certain extent and being easy to increase the elastic modulus, that is, thixotropy. From this point of view, the inorganic filler is preferably silica, aluminum hydroxide, talc, etc. The inorganic filler is more preferably silica. The type of silica is not particularly limited. As silica, dry silica or wet silica can be used. As silica, commercially available silica can also be used. As commercially available silica, for example, AEROSIL 200 (Nippon AEROSIL Co., Ltd.) can be cited.

[0036] The inorganic filler can also be hydrophobized. As the hydrophobization treatment, silicone oil treatment and silane coupling agent treatment can be cited. The number average particle diameter of the primary particles of the inorganic filler is preferably 10 nm to 100,000 nm, more preferably about 50 nm to 10,000 nm. Relative to 100 parts by mass of the fluororubber, the content of the inorganic filler is preferably 1 part by mass to 35 parts by mass, more preferably 1 part by mass to 30 parts by mass, and further preferably 3 parts by mass to 25 parts by mass. If the content of the inorganic filler is within the above range, in addition to the processability, the adhesiveness, solder heat resistance, and durability at high temperature for a long time also become good.

[0037] (amine compound) The adhesive composition may contain an amine compound as a curing agent. As the curing agent of the epoxy resin as a thermosetting resin, dicyandiamide with a low curing start temperature and excellent stability at room temperature is preferred. If necessary, an imidazole compound can also be used as a curing aid. In addition, from the viewpoint of curability, the amine compound as the curing agent of the fluororubber having an unsaturated bond is preferably an aromatic diamine compound. As the aromatic diamine compound, for example, the compound represented by the following formula (I) can be cited.

[0038] [Chemical formula 1]

[0039] In formula (I), R 1 , R 2 are each independently an alkyl group having 1 to 6 carbon atoms. R 3 is at least one selected from the group consisting of an alkylene group having 1 to 6 carbon atoms, an aromatic hydrocarbon group, a carbonyl group, a fluorene group, a sulfonyl group, an ether group, and a thioether group. m and n are each independently any integer from 0 to 4. As the preferred alkyl group, methyl, ethyl, and propyl can be cited. From the viewpoint of curability, the alkyl group is more preferably methyl or ethyl. Preferred alkylene groups include methylene and ethylene groups. From the perspective of curability, the alkylene group is more preferably methylene.

[0040] From the perspective of more excellent storage stability and rapid curability, it is preferred that m and n are each independently any integer from 0 to 2, more preferably 1 or 2, and still more preferably 2. In formula (I), from the perspective of curability, the configuration of -NH2 is preferably para to R 3 at the para position. If the aromatic hydrocarbon group is divalent, there is no particular limitation. Examples of the aromatic hydrocarbon group include phenylene. The aromatic hydrocarbon group may have a substituent such as a methyl group.

[0041] R 3 may be a substituent combining an aromatic hydrocarbon group and an alkylene group. In this case, the combination of the aromatic hydrocarbon and the alkylene group is not particularly limited. Examples of such a substituent include an alkylene group having an aromatic hydrocarbon group. As possible modes, specifically, for example, there are modes in which two alkylene groups are bonded through an aromatic hydrocarbon, a mode in which an aromatic hydrocarbon is bonded as a side chain of an alkylene group, and a mode in which the aromatic hydrocarbon groups and alkylene groups bonded to each other are respectively bonded to the two benzene rings shown in formula (I). Examples of the aromatic hydrocarbon include benzene rings and naphthalene. The aromatic hydrocarbon may have a substituent such as a methyl group. Among the compounds shown in formula (I), 4,4'-methylenebis(2-ethyl-6-methylaniline) is particularly preferred. Relative to 100 parts by mass of the fluororubber, the content of the amine compound is preferably 0.1 part by mass to 20 parts by mass, more preferably 1 part by mass to 10 parts by mass. In addition, relative to 100 parts by mass of the epoxy resin, a content of the amine compound of 0.5 part by mass to 30 parts by mass is also a preferred mode.

[0042] (Adhesive composition) By mixing the fluororubber with other additives such as a thermosetting resin, an inorganic filler, and a curing agent as needed, the above-mentioned adhesive composition can be obtained. When performing the mixing, an organic solvent can be used as needed. The above-mentioned adhesive or adhesive composition is preferably used for the manufacture of flexible printed boards. For example, an adhesive film using the adhesive or adhesive composition can be obtained, and this adhesive film is used for the manufacture of flexible printed boards.

[0043] The elastic modulus of the adhesive layer (or the elastic modulus when the adhesive composition is in the B-stage state (semi-cured state)) measured according to the test method for tensile properties of JIS K 7127 is preferably 15 MPa or more. This elastic modulus is more preferably 20 MPa or more. There is no particular limitation on the upper limit of this elastic modulus, and it is preferably 3000 MPa or less, more preferably 1000 MPa or less, and further preferably 100 MPa or less. In addition, the elongation at break of the adhesive layer (or the elongation at break when the adhesive composition is in the B-stage state (semi-cured state)) measured according to the test method for tensile properties of JIS K 7127 (1999) is preferably less than 400%. This elongation at break is more preferably less than 300%, and further preferably less than 200%. There is no particular limitation on the lower limit of this elongation at break, but it is preferably 50% or more, and more preferably 100% or more. By making the elastic modulus and the elongation at break within the above ranges, the processability becomes good. The elastic modulus and the elongation at break can be controlled by using the softening point of the thermosetting resin, the Mooney viscosity of the fluororubber, the content of the inorganic filler, etc.

[0044] The adhesive layer 120 can be manufactured by a known method. For example, an organic solvent solution of the above adhesive composition is prepared, and this organic solvent solution is coated on a resin film layer such as polyimide, thereby forming a pre-adhesive layer. Moreover, for example, the pre-adhesive layer is dried at 50°C to 160°C for 1 minute to 15 minutes to make the pre-adhesive layer in the B-stage state, thereby obtaining the adhesive layer 120. Thereafter, the obtained adhesive layer 120 can be bonded to the adherend and heat-cured. In the manufacture of the flexible printed circuit board 100, when the above adhesive composition is used for bonding a cover layer or the like, the same bonding is also carried out, whereby a flexible printed circuit board 100 having an adhesive layer containing a cured product of the adhesive composition can be obtained. During the period from the B-stage state of the adhesive layer to being heat-cured, if necessary, opening processing or the like can also be carried out.

[0045] The method for obtaining the adhesive composition in the B-stage state is not particularly limited, and a known method including the method of heat-drying as described above can be adopted. As the organic solvent, there is no particular limitation, and known organic solvents can be used. As the organic solvents that can be used, for example, acetone, methyl ethyl ketone, tetrahydrofuran, chloroform, dimethylformamide, methyl isobutyl ketone, etc. can be cited. The amount of the organic solvent used is not particularly limited. As long as the solid content amount contained in the adhesive composition is made to be preferably in the range of 10% by mass to 70% by mass, more preferably 20% by mass to 40% by mass, the organic solvent can be used.

[0046] The heat 3% mass reduction temperature of the adhesive is preferably 320 °C or higher, more preferably 350 °C or higher, and further preferably 370 °C or higher. The upper limit value of the heat 3% mass reduction temperature is not particularly limited, and from the viewpoint of laser processability, it is preferably 600 °C or lower. The heat 3% mass reduction temperature can be controlled by optimizing the molecular structure, crosslinking density, etc.

[0047] As the adhesive layer 120, an adhesive layer obtained by laminating two or more resins can also be used. In the case of using a laminate obtained by laminating two or more layers as the adhesive layer 120, the laminate is regarded as one adhesive layer.

[0048] [Nickel-containing layer] As long as the mass per unit area of nickel in the nickel-containing layer 130 is 100 mg / m 2 or more, the nickel-containing layer 130 is not particularly limited. By disposing this layer between the adhesive layer 120 and the conductor 140, even when the flexible printed circuit board 100 is exposed to high temperatures for a long period of time, it is possible to suppress the deterioration of the adhesive and further suppress the peeling of the adhesive layer 120. The mass per unit area of nickel in the nickel-containing layer only needs to be 100 mg / m 2 or more, preferably 125 mg / m 2 or more and 500 mg / m 2 or less. By making this mass the lower limit (100 mg / m 2 or 125 mg / m 2 ) or more of this range, a sufficient effect of suppressing peeling can be obtained. In addition, by making this mass the upper limit (500 mg / m 2 ) or less of this range, the substrate can be manufactured well. For example, the etching process for forming wiring becomes easy. The average thickness of the nickel-containing layer 130 is not particularly limited. For example, it can be or more, and can also be or less. The average thickness can be calculated based on the area of the nickel-containing layer, the amount of components in the nickel-containing layer, and the specific gravity of each component.

[0049] The nickel content in the nickel-containing layer 130 can be measured by the following method. First, hydrochloric acid and nitric acid are mixed at a volume ratio of hydrochloric acid:nitric acid = 3:1 to obtain a first mixed solution (aqua regia). In addition, water and aqua regia are mixed at a volume ratio of water:aqua regia = 3:2 (by adding aqua regia to water to mix them) to obtain a second mixed solution. The laminate of the conductor (conductor layer) 140 and the nickel-containing layer 130 in the flexible printed circuit board 100 is immersed in the second mixed solution for extraction. Using the obtained extraction solution, ICP emission analysis is performed to determine the amount of nickel. Finally, based on the obtained amount of nickel and the mass of the nickel-containing layer 130, the nickel content in the nickel-containing layer 130 can be calculated. In addition, there are cases where it is difficult to remove the nickel-containing layer 130 from the flexible printed circuit board 100. In such cases, the flexible printed circuit board 100 or a part thereof is immersed in a solvent that dissolves the nickel-containing layer 130. Moreover, ICP emission analysis is performed on the obtained solution, whereby the nickel content in the nickel-containing layer 130 can be evaluated. In addition, as described above, the object to be immersed in the second mixed solution (the object to be extracted) is preferably the laminate of the conductor 140 and the nickel-containing layer 130 in the flexible printed circuit board 100. However, the object to be extracted may also be the flexible printed circuit board 100. By dividing the nickel content in the nickel-containing layer by the area in the planar direction of the nickel-containing layer, the mass per unit area of nickel in the nickel-containing layer can be determined.

[0050] The components other than nickel constituting the nickel-containing layer 130 are not particularly limited. Examples of such components include Co, Mo, Zn, and Cr.

[0051] [Conductor] The material of the conductor 140 is not particularly limited, and known materials can be used. Examples of the material of the conductor 140 include copper, silver, gold, tin, aluminum, indium, and their alloys. The conductor 140 is preferably made of a material containing copper, and more preferably a copper foil. The average thickness of the conductor 140 is not particularly limited, and is preferably 5 μm or more and 500 μm or less, and more preferably 12 μm or more and 500 μm or less. The circuit pattern formed by the conductor 140 is not particularly limited and can be appropriately designed according to the use.

[0052] [Other Layers] The flexible printed circuit board 100 may also have layers other than the above-described base material layer 110, adhesive layer 120, nickel-containing layer 130, and conductor 140 (other layers).

[0053] [Peel Strength] There is no particular limitation on the peel strength of the conductor relative to the base material layer. According to the JPCA standard JPCA-DG 02-2006, it is preferably 0.49 N / mm or more. Additionally, from the perspective of achieving the strength required when the flexible printed circuit board 100 is used as an automotive part, it is preferred that after the flexible printed circuit board 100 is exposed to an environment of 225 °C for 3000 hours, the peel strength is 0.49 N / mm or more. The peel strength can be evaluated according to IPC TM 650 2.4.9 (free rotating drum method).

[0054] <Manufacturing method of flexible printed circuit board> There is no particular limitation on the method for manufacturing the above flexible printed circuit board 100. Known methods or a combination of multiple known methods can be used to manufacture the flexible printed circuit board 100. The manufacturing method of the flexible printed circuit board 100 may include, for example: a lamination process to obtain a laminate including at least a base material layer, an adhesive layer, a nickel-containing layer, and a conductor layer in sequence; and a circuit pattern forming process to process the laminate to form a circuit pattern. The adhesive layer may contain fluororubber, and the mass per unit area of nickel in the nickel-containing layer may be 100 mg / m 2 or more. In particular, the lamination process preferably includes a process of laminating the base material layer and a laminate including the nickel-containing layer and the conductor layer with an adhesive.

[0055] There is no particular limitation on the method for forming the nickel-containing layer. As this method, for example, a method of providing a nickel-containing layer by plating nickel on the surface of a conductor can be cited. In this method, known methods such as wet plating or dry plating can be applied. Specifically, methods such as electroplating, electroless plating, vacuum evaporation plating, or sputtering can be applied in this method.

[0056] <Uses of flexible printed circuit board> There is no particular limitation on the uses of the above flexible printed circuit board 100. For example, the flexible printed circuit board 100 can be used as a substrate for automotive, printed wiring boards, liquid crystal displays, robots, televisions, automotive navigation devices, game consoles, mobile phones, digital cameras, personal computers, printers, light-emitting diode illuminators, or wearable devices, etc. Among them, from the perspective of long-term exposure at high temperatures, the flexible printed circuit board 100 is preferably used as an automotive component (part).

[0057] The usage mode of the flexible printed circuit board 100 is not particularly limited. The flexible printed circuit board 100 can be used as, for example, the substrate of a power module. The form of the power module is not particularly limited. The power module can include, for example, a substrate, a SiC semiconductor element electrically connected to a conductor provided on the substrate, and a flexible printed circuit board connected to the SiC semiconductor element. In this case, the flexible printed circuit board has a conductor layer electrically connected to the SiC semiconductor element and is the flexible printed circuit board 100 of the above-described embodiment. Figure 2 This shows an example of the power module.

[0058] Refer to Figure 2 An example of the power module 200 will be described. The power module 200 includes a resin housing 310 and a heat sink 320 for releasing heat inside the module. In addition, the power module 200 includes a DBC substrate 400, a plurality of SiC semiconductor elements 500 fixed to the DBC substrate 400, and the flexible printed circuit board of the above-described embodiment (hereinafter referred to as "FPC100"). In addition, Figure 2 two SiC semiconductor elements 500 are provided, but the number of SiC semiconductor elements is not limited to two. In Figure 2 the circuit pattern formed by the conductor 140 is omitted.

[0059] The DBC substrate 400 includes an insulating base material 410 and a first conductor layer 421 and a second conductor layer 422 provided on both sides of the base material 410, respectively. The base material 410 is made of a ceramic material or the like. Moreover, the first conductor layer 421 is connected to and fixed to the heat sink 320. In addition, an external connection terminal 430 electrically connected to an external device is electrically connected to the second conductor layer 422.

[0060] The plurality of SiC semiconductor elements 500 are electrically connected to the second conductor layer 422 through a bonding member 511 including sintered silver or solder.

[0061] In the FPC100, an adhesive layer 120, a nickel-containing layer 130, and a conductor 140 are sequentially laminated on one surface of the base material layer 110. In addition, an adhesive layer 122, a nickel-containing layer 132, and a conductor 141 are sequentially laminated on the other surface of the base material layer 110.

[0062] Moreover, the conductor 140 is electrically connected to the SiC semiconductor element 500 through a bonding member 512 including sintered silver or solder. In addition, the conductor 140 is also electrically connected to the second conductor layer 422 of the DBC substrate 400 through a bonding member 600 including sintered silver or solder. In addition, according to the desired electrical circuit, the conductor layers can be electrically connected through vias or through-holes.

[0063] In addition, the conductor 140 serving as the element-side conductor layer is configured to have an average thickness of 70 μm or more and 500 μm or less. The element-side conductor layer is electrically connected to the SiC semiconductor element 500 and is disposed closest to the side where the SiC semiconductor element 500 is arranged. Similarly, the conductor 141 is also configured to have an average thickness of 70 μm or more and 500 μm or less. Further, the conductor 141 can also be electrically connected to the SiC semiconductor element 500 through the conductor 140 and vias or through-holes.

[0064] Furthermore, the FPC 100 has the following heat resistance: at the time point after 3000 hours in an environment of 225°C, the conductor 140 serving as the element-side conductor layer is substantially not peeled off from the base material layer 110. In addition, the FPC 100 has the following heat resistance: at the time point after 3000 hours in an environment of 225°C, the conductor 140 is substantially not peeled off from the cover layer. Here, the cover layer is an element-side film provided on the side closer to the SiC semiconductor element 500 than the conductor 140 serving as the element-side conductor layer through an adhesive layer. Moreover, the FPC 100 has the following heat resistance: for all the films and adhesive layers, at the time point after 3000 hours in an environment of 225°C, the film is not peeled off from the conductor layer.

[0065] In addition, inside the housing 310, a DBC substrate 400, a plurality of SiC semiconductor elements 500, the FPC 100, and a part of the external connection terminals 430 are embedded in a resin material 330 formed by filling and curing.

[0066] In the power module 200, by adopting the FPC 100, the wiring line length can be shortened. That is, by arranging the FPC 100 along the surface of the DBC substrate 400 through a plurality of SiC semiconductor elements 500, the wiring line length can be shortened compared with the case of adopting the wire bonding method. Thereby, the parasitic inductance can be reduced, and thus the surge voltage can be suppressed. In addition, by adopting the FPC 100 which originally has flexibility, the FPC 100 can be arranged along the surface of the DBC substrate 400 imitating a plurality of SiC semiconductor elements 500. Therefore, the module can also be miniaturized compared with the case of adopting a rigid substrate. [Embodiment]

[0067] Hereinafter, the embodiments of the present invention will be described more specifically using examples. However, the technology of the present invention is not construed as being limited to the following examples.

[0068] <Fabrication of Flexible Printed Circuit Board> [Example 1] · Unsaturated modified product of double bond modified fluorine rubber (copolymer of vinylidene fluoride and hexafluoropropylene (copolymerization ratio: vinylidene fluoride / hexafluoropropylene = 8 / 2), Mooney viscosity (ML 1+10 (121°C)): 98, double bond content: 4% by mass, 100 parts by mass Silica (fumed silica: AEROSIL 200 (Japan AEROSIL Industries)) 15 parts by mass Epoxy resin (solid softening point 95°C) o-cresol novolac type epoxy resin (N695 (DIC Corporation)) 20 parts by mass · Amine compound (4,4'-methylenebis(2-ethyl-6-methylaniline): CUREHARDMED-J manufactured by KUMIAI Chemical Industry Co., Ltd.) 5 parts by mass The solid content was dissolved using methyl ethyl ketone so that the solid content was 30% by mass. Thus, an adhesive composition containing fluorine rubber was obtained. The 3% thermal mass loss temperature of the obtained adhesive composition was 373° C. In addition, silica was dispersed using a bead mill. In addition, the obtained adhesive composition solution was applied to a polyimide film (UPILEX-S, a polyimide film manufactured by Ube Industries, Ltd., with a thickness of 25 μm) so that the average thickness after drying was 25 μm, and dried at 140° C. for 3 minutes using a hot air dryer. Thus, an adhesive film in a B-stage state (semi-cured state) was obtained. The adhesive coated surface of the adhesive film was pressed against a first laminate sheet having a nickel alloy layer laminated on one surface of a copper foil (CF-T4M-HD manufactured by Fukuda Metal Co., Ltd., electrolytic copper foil, average thickness 35 μm, mass per unit area of ​​nickel in the nickel alloy layer 150 mg / m2) using a vacuum laminator at 160° C., 3 MPa, and reduced pressure for 30 seconds. 2 ) nickel alloy layer was thermally pressed. Then, heat curing was performed at 160°C for 10 hours to obtain a sheet-shaped test sample (area in the plane direction: 100 cm 2 The following evaluations were performed using the obtained test samples. Table 1 shows the evaluation results. In addition, the mass per unit area of ​​the metal element other than Ni contained in the nickel alloy layer in this example is Zn: 7 mg / m 2 and Cr: 7mg / m 2 .

[0069] [Example 2] In addition to changing the mass per unit area of ​​nickel in the nickel alloy layer to 239 mg / m 2 A flexible printed circuit board was obtained by the same method as in Example 1 except for the above. In addition, the mass per unit area of the metal elements other than Ni contained in the nickel alloy layer in this embodiment is Zn: 6 mg / m 2 and Cr: 6 mg / m 2 .

[0070] [Example 3] Except that the first laminate was changed to a second laminate obtained by laminating a nickel alloy layer on one surface of a copper foil (RCF foil manufactured by Fukuda Metal Co., Ltd., rolled copper foil, average thickness 35 μm, mass per unit area of nickel in the nickel alloy layer 150 mg / m 2 ), a flexible printed circuit board was obtained by the same method as in Example 1. In addition, the mass per unit area of the metal elements other than Ni contained in the nickel alloy layer in this embodiment is Zn: 7 mg / m 2 and Cr: 7 mg / m 2 .

[0071] [Comparative Example 1] Except that the mass per unit area of nickel in the nickel alloy layer was changed to 63 mg / m 2 , a flexible printed circuit board was obtained by the same method as in Example 1. In addition, the mass per unit area of the metal elements other than Ni contained in the nickel alloy layer in this comparative example is Zn: 7 mg / m 2 and Cr: 7 mg / m 2 .

[0072] [Comparative Example 2] Except that the first laminate was changed to a third laminate obtained by laminating a nickel alloy layer on one surface of a copper foil (BHY-82F-HA-V2 manufactured by JX Metals Co., Ltd., average thickness 35 μm, mass per unit area of nickel in the nickel alloy layer 70 mg / m 2 ), a flexible printed circuit board was obtained by the same method as in Example 1. In addition, the mass per unit area of the metal elements other than Ni contained in the nickel alloy layer in this comparative example is Co: 169 mg / m 2 , Zn: 39 mg / m 2 and Cr: 6 mg / m 2 .

[0073] [Comparative Example 3] Except that the adhesive composition was changed to EPOX AH 357 manufactured by Printec Co., Ltd., a flexible printed circuit board was obtained by the same method as in Example 3. At this time, the solution of the adhesive composition was applied to the polyimide film so that the average thickness after drying of the adhesive composition became 25 μm. In addition, the mass per unit area of the metal elements other than Ni contained in the nickel alloy layer in this comparative example was Zn: 7 mg / m 2 and Cr: 7 mg / m 2 .

[0074] [Comparative Example 4] A flexible printed circuit board was obtained by the same method as in Example 1, except that the nickel-containing alloy layer of the first laminate was changed to a nickel-free alloy layer and the adhesive composition was changed to EPOX AH 357 manufactured by Printec Co., Ltd. At this time, the solution of the adhesive composition was applied to the polyimide film so that the average thickness after drying of the adhesive composition became 25 μm. In addition, the mass per unit area of the metal elements contained in the nickel-free alloy layer in this comparative example was Co: 33 mg / m 2 , Mo: 26 mg / m 2 , Zn: 17 mg / m 2 and Cr: 12 mg / m 2 .

[0075] <Evaluation> [Nickel content] A first mixed solution (aqua regia) was obtained by mixing hydrochloric acid and nitric acid at a ratio of hydrochloric acid: nitric acid = 3:1 (volume ratio). In addition, a second mixed solution was obtained by mixing water and aqua regia at a ratio of water: aqua regia = 3:2 (volume ratio) (by adding aqua regia to water to mix them). The above-mentioned first laminate, second laminate, or third laminate was immersed in the second mixed solution for extraction. ICP emission analysis was performed using the obtained extract to determine the amount of nickel. Finally, the mass per unit area of nickel in the nickel-containing layer was calculated by dividing the content of nickel in the nickel-containing layer by the area in the planar direction of the nickel-containing layer. Table 1 shows the evaluation results.

[0076] Based on the area of the nickel-containing layer, the mass per unit area of the metal elements contained in the nickel-containing layer, and the specific gravity of each metal element, the thickness of the nickel-containing layer was calculated. Table 1 shows the calculated results.

[0077] [Peel strength] After storing each flexible printed circuit board at 225 °C for the time shown in Table 1, the peel strength was evaluated in accordance with IPC TM 650 2.4.9 (free-rotating drum method). In addition, the initial (0 hour) peel strength was the peel strength evaluated before storage. At this time, for each flexible printed circuit board, three evaluation samples were prepared, and these evaluation samples were used for evaluation, and the average value of the evaluation results was adopted. Table 1 shows the evaluation results.

[0078] [Oxygen Permeability Rate] Under the following measurement conditions, the oxygen permeability rate of the polyimide film (UPILEX-S) was measured. The measurement results were 5.93×10 -14 cc·cm / cm 2 ·sec·cmHg at 25°C, and 1.67×10 -12 cc·cm / cm 2 ·sec·cmHg at 120°C, and 8.72×10 -12 cc·cm / cm 2 ·sec·cmHg at 200°C. (Measurement Conditions for Oxygen Permeability Rate) Measurement method: In accordance with Appendix 2 of JIS K7126-1 Test gas type: Oxygen Test gas flow rate: 90 ml / min Carrier gas type: Helium Carrier gas flow rate: 35 ml / min Permeation area: 15.2 cm 2 Measurement device: GTR-30XANO (25°C, 120°C), GTR-10AH (200°C); both are manufactured by GTR TEC Cell thermostat temperature: 25°C, 120°C, 200°C Gas chromatograph calibration method: Two-point calibration with 0.0 μl and 15.3 μl

[0079] [Table 1]

[0080] From the comparison of Comparative Examples 3-4 with other comparative examples and examples, it can be seen that by using an adhesive containing fluororubber as the adhesive, a flexible printed circuit board can be obtained in which the peeling of the adhesive layer hardly occurs even at a high temperature of 225°C. In addition, from the comparison of Examples 1-3 with Comparative Examples 1-2, it can be seen that by making the mass per unit area of nickel in the nickel-containing layer 100 mg / m 2 or more, a flexible printed circuit board can be obtained in which the peeling of the adhesive layer hardly occurs even in a high-temperature environment of 225°C for a long period of 3000 hours.

[0081] From the above description, it can be seen that according to the embodiments of the present invention, a flexible printed circuit board can be provided which is less likely to have peeling of the adhesive layer even when exposed to a high-temperature environment for a long period compared with conventional flexible printed circuit boards. The detailed description has been given for purposes of illustration and example. Many variations and modifications are possible in light of the above teachings. The detailed description is not without omissions or intended to limit the subject matter described herein. Although the subject matter has been described in terms of particular structural features and / or methodological processes, it is to be understood that the subject matter defined in the claims is not necessarily limited to the specific features or specific processes described. Rather, the specific features and specific processes are described as examples for implementing the claims.

Claims

1. A flexible printed substrate, characterized in that: The flexible printed substrate comprises at least a base material layer, an adhesive layer, a nickel-containing layer and a conductor in sequence. The adhesive layer contains fluorine-containing rubber, The mass per unit area of ​​nickel in the nickel-containing layer is 100 mg / m 2 above.

2. The flexible printed circuit board according to claim 1, characterized in that: The substrate layer includes polyimide.

3. The flexible printed circuit board according to claim 1 or 2, characterized in that: The mass per unit area of ​​nickel in the nickel-containing layer is 125 mg / m 2 Above and 500mg / m 2 the following.

4. The flexible printed substrate according to claim 1 or 2, characterized in that: The conductor includes copper.

5. A method for manufacturing a flexible printed substrate, characterized in that: include: A lamination step to obtain a laminated body comprising at least a substrate layer, an adhesive layer, a nickel-containing layer and a conductor layer in sequence; as well as a circuit pattern forming step of processing the laminate to form a circuit pattern, The adhesive layer contains fluorine-containing rubber, The mass per unit area of ​​nickel in the nickel-containing layer is 100 mg / m 2 above.

6. The method for manufacturing a flexible printed circuit board according to claim 5, characterized in that: The lamination step includes a step of bonding the base material layer and a laminate layer including the nickel-containing layer and the conductor layer with an adhesive.

Images