JP4694142B2 - Manufacturing method of substrate for flexible printed wiring board - Google Patents

Description

  The present invention relates to a substrate for a flexible printed wiring board and a method for producing the same, and in particular, it does not cause curling, twisting, warping, or the like after forming a circuit, and is excellent in heat resistance, dimensional stability, electrical characteristics, and the like. The present invention relates to a flexible printed wiring board substrate and a manufacturing method thereof.

  Conventionally, as a substrate for a flexible printed wiring board, an insulator made of a polyimide film and a conductor are bonded together via an adhesive such as an epoxy resin or an acrylic resin, for example, an epoxy resin on both sides of the insulator, A double-sided flexible printed wiring board substrate (hereinafter referred to as “double-sided board”) having a five-layer structure in which conductors are laminated via an adhesive such as an acrylic resin is known. However, this double-sided plate has a problem that heat resistance, flame retardancy, electrical characteristics and the like are deteriorated because an adhesive layer is present between the conductor and the insulator. In addition, there has been a problem that the rate of dimensional change is large when the conductor is etched or when the substrate is subjected to any heat treatment, which hinders subsequent processes.

  In order to solve such problems, proposals have been made to solve the above problems by using thermoplastic polyimide having thermocompression bonding as an adhesive layer when bonding a polyimide film and a conductor. (For example, Patent Documents 1 to 6) However, in this configuration, since it is a thermoplastic polymer that is in direct contact with the conductor, the rate of dimensional change when the substrate is subjected to any heat treatment is increased, The problem could not be solved sufficiently.

JP 2000-103010 A JP 2001-270033 A JP 2001-270034 A JP 2001-270035 A JP 2001-270037 A JP 2001-270039 A

  The present invention solves the above-mentioned problems, can suppress the occurrence of curling, twisting, warping, etc. due to circuit formation or heat treatment, and also has a conductor on both sides excellent in heat resistance, flame retardancy, dimensional stability, electrical characteristics, etc. It aims at providing the board | substrate for flexible printed wiring boards which has, and its manufacturing method.

  As a result of intensive studies to solve the above problems, the present inventors have formed an insulating layer having a specific thickness directly on the conductor without interposing an adhesive layer, and the insulating layers have a specific thickness. It has been found that the above-mentioned problems can be solved by integrating with an adhesive layer made of a fluororesin having the present invention, and the present invention has been achieved.

That is, in the present invention, a film made of a non-thermoplastic aromatic polyimide resin that forms an insulating layer is laminated on both surfaces of an adhesive layer made of a fluororesin, and a conductor layer is provided on the outer surface of each film, A substrate for a flexible printed wiring board is manufactured , wherein the total thickness of the insulating layers provided on both surfaces of the adhesive layer is 5 to 100 μm and 0.5 to 10 times the thickness of the adhesive layer. On the occasion
A film made of a non-thermoplastic aromatic polyimide resin, a first insulating layer having a conductor layer laminated on one side thereof, and a film made of a non-thermoplastic aromatic polyimide resin, the conductor layer being laminated on one side The gist is a method for producing a substrate for a flexible printed wiring board, wherein the film is laminated so that an adhesive film surface made of a fluororesin is disposed between the second insulating layer and pressure-bonded in a heated atmosphere. Is.

Further, a film made of a non-thermoplastic aromatic polyimide resin that forms an insulating layer is laminated on both surfaces of an adhesive layer made of a fluororesin, and a conductor layer is provided on the outer surface of each film, and the adhesive layer When the substrate for flexible printed wiring boards is manufactured, the total thickness of the insulating layers provided on both sides is 5 to 100 μm and 0.5 to 10 times the thickness of the adhesive layer. A film having a thickness of 2 to 50 μm made of a non-thermoplastic aromatic polyimide resin as a layer and having a conductor layer laminated on one side thereof, and a thickness of an adhesive film made of a fluororesin is 2 to 50 μm with the film, and laminating an adhesive layer made of a fluorine resin film between the non-thermoplastic aromatic polyimide insulating layer, to said crimping in a heated atmosphere The manufacturing method of a flexible printed circuit board substrate in which the gist.

According to the manufacturing method of the present invention , in a flexible printed wiring board substrate of a double-sided board, an insulating layer made of non-thermoplastic aromatic polyimide is directly formed without providing an adhesive layer on the conductor layer, and the insulating layer and the insulating layer Are integrated through a specific adhesive layer, which has excellent heat resistance, flame retardancy, and electrical characteristics, good dimensional stability, and adhesion strength between insulating layers suitable as a substrate for flexible printed wiring boards. can get. In addition, by defining the thickness of the insulating layer and the adhesive layer, not only electrical insulation and adhesion between the insulating layers are improved, but mechanical properties such as dimensional stability, curl characteristics, and repeated bending resistance are further improved. It is possible to realize a good flexible printed wiring board substrate that does not curl, twist or warp even when subjected to etching treatment for circuit formation or other heat treatment.

According to the manufacturing method of the substrate for a flexible printed wiring board of the present invention, the substrate for the flexible printed wiring board can be easily realized.

  Hereinafter, the present invention will be described in detail.

In the present invention , the flexible printed wiring board substrate is formed by laminating a film made of a polyimide resin that forms an insulating layer on both sides of an adhesive layer made of a fluororesin, and a conductor layer is provided on the outer surface of each film. Need to be. By forming an insulating layer directly on the conductor layer without interposing an adhesive layer in this way, flexible printed wiring with excellent heat resistance, flame retardancy, and electrical characteristics, and good dimensional stability even in high-temperature atmospheres A board substrate can be obtained, and curling, twisting and warping can be suppressed even if etching or other heat treatment is applied to the board. Moreover, the adhesive strength of insulating layers suitable as a board | substrate for flexible printed wiring boards is obtained by integrating an insulating layer and an insulating layer with a specific contact bonding layer. Specifically, the adhesive strength between the insulating layers is preferably 5.0 N / cm or more, and more preferably 10 N / cm or more. When the adhesive strength between the insulating layers is less than 5.0 N / cm, the practicality as a substrate for a flexible printed wiring board is lacking.

The substrate for a flexible printed wiring board in the present invention, the total thickness of the insulating layer provided on both surfaces of the adhesive layer must be 5 to 100 [mu] m, and more preferably in the range of 10 to 30 [mu] m. When the total thickness of the insulating layer is less than 5 μm, the electrical insulation and the like become insufficient, and the reliability as a substrate for a flexible printed wiring board is impaired. On the other hand, when the total thickness of the insulating layer exceeds 100 μm, the mechanical properties as a flexible printed wiring board substrate including repeated bending resistance are impaired.

  The total thickness of the insulating layer needs to be 0.5 to 10 times the thickness of the adhesive layer, and preferably 2 to 5 times. When the total thickness of the insulating layer is less than 0.5 times the thickness of the adhesive layer, the coefficient of linear expansion (CTE) of the insulating layer tends to increase, and the dimensional stability decreases. When the total thickness of the insulating layer exceeds 10 times the thickness of the adhesive layer, the adhesive strength between the insulating layers decreases.

  Note that the insulating layers provided on both surfaces of the adhesive layer are not particularly limited as long as they are in the above range as a whole, but are preferably the same thickness in order to prevent curling, twisting, warping, and the like.

  As described above, since the insulating layer and the adhesive layer have specific thicknesses, not only electrical insulation and mechanical properties including repeated bending resistance are further enhanced, but also dimensional stability is further improved. Even if the conductor layer is subjected to an etching process for circuit formation or various heat treatments in the subsequent steps after the circuit formation, the occurrence of curling, twisting, warping and the like can be further suppressed. Therefore, the flexible printed wiring board substrate of the present invention can not only satisfactorily mount electronic components and the like, but also realize a high mounting density.

Examples of the fluororesin that forms the adhesive layer of the flexible printed circuit board substrate include tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer modified resin (NEOFLON ^TM PFA) Film RAF (manufactured by Daikin Industries, Ltd.) can be preferably used. By using such a fluororesin as the adhesive layer, an adhesive strength of 5.0 N / cm or more can be obtained as the adhesive strength between the insulating layers as described above.

Full lexical Bull printed circuit board substrate configured as described above can be obtained by the production method of the present invention.

The first manufacturing method in the present invention will be described.
A first insulating layer made of a polyimide resin and having a conductor layer laminated on one side thereof and a second insulating layer made of a polyimide resin and having a conductor layer laminated on one side thereof are used. And the emulsion which consists of a fluororesin is apply | coated, or the film which consists of a fluororesin is laminated | stacked on the film surface of at least one insulating layer of the 1st, 2nd insulating layer. And it laminates | stacks so that the film surface of a 1st, 2nd insulating layer may face, and is crimped | bonded and integrated in a heating atmosphere.

  In this method, the first insulating layer and the second insulating layer may have a total thickness of 5 to 100 μm, and the thickness of each insulating layer may be the same or different. The thickness of the fluororesin layer is not particularly limited as long as the thickness of the entire insulating layer is 0.5 to 10 times the thickness of the adhesive layer obtained after drying.

  Here, the fluororesin layer applied or laminated on the surface of the insulating layer film only needs to be applied to at least one side of each insulating layer, and may be applied to both. When the fluororesin layer is formed on both insulating layers, the thickness may be the same or different.

Next, the 2nd manufacturing method in this invention is demonstrated.
As the insulating layer, one having a conductor layer laminated on one side of a film made of polyimide resin and having a thickness of 2 to 50 μm is used. When the thickness of the film is less than 2 μm, the electrical insulation and the like are insufficient, and the reliability as a flexible printed wiring board substrate is impaired. Moreover, when the thickness of an insulating layer exceeds 50 micrometers, the mechanical characteristic as a board | substrate for flexible printed wiring boards including repeated bending tolerance will be impaired. The thickness of the film is more preferably in the range of 5 to 15 μm.

Next, a fluororesin film having a thickness of 2 to 50 μm is laminated between the two laminated films composed of the conductor layer and the insulating layer so that the fluororesin film faces the polyimide film that is the insulating layer, and is heated. in crimping, full lexical Bull PWB substrate ing a laminated film of five-layer structure consisting of constituting the adhesive layer conductor layer / insulating layer / adhesive layer / insulating layer / conductive layer is obtained by integrating. At this time, when the thickness of the adhesive layer is less than 5 μm, when the laminated films are bonded to each other as described later, sufficient adhesive force between the insulating layers cannot be obtained, and the thickness of the adhesive layer is the thickness of the insulating layer. When the thickness exceeds 50 μm, the dimensional stability of the substrate is impaired.

In the present invention , the conductor constituting the conductor layer of the flexible printed wiring board substrate is a metal foil made of a conductive material such as copper, aluminum, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, or an alloy thereof. Copper foil is most suitable.

  The surface of the conductor layer on which the insulating layer is formed may be subjected to chemical or mechanical surface treatment in order to improve the adhesion with the insulating layer. Examples of the chemical surface treatment include plating treatment such as nickel plating and copper-zinc alloy plating, treatment with a surface treatment agent such as aluminum alcoholate, aluminum chelate, and silane coupling agent. Surface treatment is preferred. As the silane coupling agent, a silane coupling agent having an amino group can be suitably used. On the other hand, examples of the mechanical surface treatment include a roughening treatment.

  Although the thickness of a conductor layer is not specifically limited, The thing of 5 micrometers or more and 30 micrometers or less is preferable.

As the insulating layer , it is necessary to use a film made of a non-thermoplastic aromatic polyimide having a glass transition temperature of 300 ° C. or higher measured by a thermomechanical property analyzer (TMA). Examples of the aromatic polyimide having such thermal characteristics include those having a structure represented by the following structural formula (1).

Here, R ₁ represents a tetravalent aromatic residue, and R ₂ represents a divalent aromatic residue.

A conductor layer is directly laminated on the film forming the insulating layer. Such a film can be produced by coating a polyimide precursor solution on the conductor, followed by drying and thermosetting. Here, the polyimide precursor is the one that becomes the above structural formula (1) after being thermally cured, and any compound can be used as long as it is such a compound. As a polyimide precursor, the polyamic acid shown by following Structural formula (2) or its ester is mentioned, for example. The polyimide precursor solution usually consists of a polyamic acid and a solvent.

Here, R ₃ is a hydrogen atom or an alkyl group.

  The polyimide precursor solution is usually formed by mixing a polyamic acid and a solvent. Examples of the solvent to be used include aprotic polar solvents, ether compounds, and water-soluble alcohol compounds.

  Examples of the aprotic polar solvent include N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoramide and the like.

  Examples of ether compounds include 2-methoxyethanol, 2-ethoxyethanol, 2- (methoxymethoxy) ethoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol, tetrahydrofurfuryl alcohol, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl. Ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monoethyl ether, tetraethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol Monoethyl ether, tripropylene glycol monomethyl ether, polyethylene Glycol, polypropylene glycol, tetrahydrofuran, dioxane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether.

  Examples of water-soluble alcohol compounds include methanol, ethanol, 1-propanol, 2-propanol, tert-butyl alcohol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, , 4-butadiol, 2,3-butanediol, 1,5-pentanediol, 2-butene-1,4-diol, 2-methyl-2,4-pentanediol, 1,2,6-hexanetriol, di Acetone alcohol etc. are mentioned.

  These solvents may be used as a mixture of two or more. Among these solvents, particularly preferred examples include N, N-dimethylacetamide and N-methyl-2-pyrrolidone as the sole solvent, and examples of the mixed solvent include N, N-dimethylacetamide and N- Examples thereof include a combination of methyl-2-pyrrolidone, N-methyl-2-pyrrolidone and methanol, N-methyl-2-pyrrolidone and 2-methoxyethanol.

Next, the manufacturing method of a polyimide precursor is demonstrated.
First, a solution comprising a polyamic acid is prepared by mixing an aromatic tetracarboxylic dianhydride represented by the following structural formula (3) and an aromatic diamine represented by the following structural formula (4) with the above-described solvent, for example, aprotic polarity. It can manufacture by making it react in a solvent.

Here, R ₁ represents a tetravalent aromatic residue, and R ₂ represents a divalent aromatic residue.

  In the above reaction, the ratio of aromatic tetracarboxylic dianhydride and aromatic diamine is in the range of 1.03 to 0.97 mol of aromatic tetracarboxylic dianhydride with respect to 1 mol of aromatic diamine. It is preferable that the aromatic tetracarboxylic dianhydride is 1.01 to 0.99 mol with respect to 1 mol of the aromatic diamine. Moreover, -30-60 degreeC is preferable and, as for reaction temperature, -20-40 degreeC is more preferable.

  In the above reaction, the order of mixing the monomer and solvent is not particularly limited, and may be any order. When a mixed solvent is used as a solvent, a solution composed of polyamic acid can also be obtained by dissolving or suspending separate monomers in each solvent, mixing them, and reacting at a predetermined temperature and time with stirring. Is obtained. Two or more kinds of polyimide resin precursor solutions may be mixed and used.

  Specific examples of the aromatic tetracarboxylic dianhydride represented by the structural formula (3) include pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 3,3 ′, 4,4 ′. -Benzophenone tetracarboxylic acid, 3,3 ', 4,4'-diphenylsulfone tetracarboxylic acid, 2,3,3', 4'-diphenyl ether tetracarboxylic acid, 2,3,3 ', 4'-benzophenone tetracarboxylic acid Acid, 2,3,6,7-naphthalenetetracarboxylic acid, 1,4,5,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 3,3 ', 4,4' -Diphenylmethanetetracarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) propane, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane, 3,4, , 10-tetracarboxyperylene, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] hexafluoropropane And the dianhydrides. These aromatic tetracarboxylic dianhydrides can be used in combination of two or more. In the present invention, pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid or a mixture thereof can be particularly preferably used.

  Specific examples of the aromatic diamine represented by the structural formula (4) include p-phenylene diamine, m-phenylene diamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane. 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 1,2-bis (anilino) ethane, diaminodiphenylsulfone, diaminobenz Anilide, diaminobenzoate, diaminodiphenyl sulfide, 2,2-bis (p-aminophenyl) propane, 2,2-bis (p-aminophenyl) hexafluoropropane, 1,5-diaminonaphthalene, diaminotoluene, diaminobenzotrifluor Ride, 1,4-bis (p- Minophenoxy) benzene, 4,4′-bis (p-aminophenoxy) biphenyl, diaminoanthraquinone, 4,4′-bis (3-aminophenoxyphenyl) diphenyl sulfone, 1,3-bis (anilino) hexafluoropropane, Examples thereof include 1,4-bis (anilino) octafluorobutane, 1,5-bis (anilino) decafluoropentane, 1,7-bis (anilino) tetradecafluoroheptane and the like. These aromatic diamines can be used in combination of two or more. In the present invention, p-phenylenediamine, 4,4′-diaminodiphenyl ether or a mixture thereof is particularly preferable.

  In the present invention, when a polyimide precursor solution is produced, an amine, diamine, dicarboxylic acid, tricarboxylic acid, or tetracarboxylic acid derivative having a polymerizable unsaturated bond is added to form a crosslinked structure during thermosetting. be able to. Specifically, maleic acid, nadic acid, tetrahydrophthalic acid, ethynylaniline and the like can be used.

  In addition, there is no particular problem even if the polyimide resin precursor is partially imidized due to the synthesis conditions, drying conditions, and other reasons of the polyimide resin precursor.

  Moreover, when manufacturing the solution of these polyimide resin precursors, you may mix other heat resistant resins, such as a polyimide resin soluble in the said solvent, a polyamideimide resin. Furthermore, in order to improve adhesiveness (adhesiveness) and film properties, a silane coupling agent and various surfactants can be added in minute amounts.

In this invention , the film which consists of a polyimide resin by which the conductor was laminated | stacked on the single side | surface which comprises the board | substrate for flexible printed wiring boards is manufactured in the following procedures.

  The polyimide precursor solution described above is applied onto a conductor, dried to form a precursor layer, and further thermoset and imidized to form a polyimide resin film. Specifically, the polyimide precursor solution described above is applied on a conductor having a predetermined thickness whose surface is roughened so that the film thickness after thermosetting is 5 μm or more, and is subjected to a drying treatment to obtain a polyimide precursor. Form a body coat. The drying temperature is preferably 200 ° C. or lower, and more preferably 150 ° C. or lower. Next, heat treatment is performed at a temperature of 150 ° C. or higher and 500 ° C. or lower, and the precursor film is thermoset to complete imidization. Thereby, a film made of a non-thermoplastic polyimide resin having a conductor laminated on one side is obtained.

  The polyimide precursor solution may be applied in a plurality of times and finally thermally cured. Moreover, it is good also as a film which consists of two or more layers of polyimides using two or more types of polyimide precursor solutions. In addition, although polyamic acid was described here as a polyimide precursor, the non-thermoplastic polyimide film by which the conductor was laminated | stacked on the single side | surface similarly was obtained also about another polyimide precursor.

  When applying a polyimide precursor solution to a conductor, industrially, a die coater, a multilayer die coater, a gravure coater, a comma coater, a reverse roll coater, a doctor blade coater, etc. can be used as a coating machine. The curing can be performed by a method in which the precursor is applied and the copper foil is wound up in a roll shape and heated in a furnace in an inert gas atmosphere, a method in which a heating zone is provided in the production line, or the like.

The adhesive layer which consists of a fluororesin film is formed in the film surface of the polyimide film produced as mentioned above. The fluororesin is not particularly limited, but is a tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP), a modified resin of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (NEOFLON ^TM PFA film RAF: Daikin Industries, Ltd.) is preferably used. As a method of forming an adhesive layer made of a fluororesin film on the film surface of the polyimide film, a method of curing after coating the fluororesin emulsion on the polyimide precursor state or a cured polyimide film on the fluororesin emulsion The method of coating may be used.

  In the case of using a pre-filmed fluororesin film as the adhesive layer, a neat film or a fluororesin film reinforced with inorganic fibers can be used.

Neat films include neoflon films PFA, FEP, ETFE, PCTFE
NEOFLON ^TM PFA film RAF (manufactured by Daikin Industries, Ltd.), etc., as a fluororesin film reinforced with inorganic fibers, melted neat film into glass fiber fabric using E glass fiber, S glass fiber, quartz fiber, etc. There are fluororesin films that are impregnated and reinforced, and fluororesin films that are reinforced by impregnating a glass fiber fabric with a fluororesin dispersion. The fluororesin dispersion impregnated into the glass fiber fabric is not particularly limited, such as PTFE, PFA, FEP, ETFE, PCTFE.

  EXAMPLES Next, although this invention is demonstrated concretely based on an Example, this invention is not limited only to these Examples. In the following examples and comparative examples, methods for measuring various physical properties and raw materials are as follows.

[1] Measuring method (1) Adhesive strength (N / cm): The adhesive strength between insulating layers on a substrate was measured using a Tensilon tester (manufactured by Intesco, precision universal material testing machine 2020). In the measurement, the substrate was cut into a width of 10 mm and a length of 100 mm to prepare a test piece, and one conductor layer surface of the test piece was fixed to an aluminum plate using a double-sided pressure-sensitive adhesive tape coated with an adhesive on both sides. . Then, the insulating layer provided with the conductor layer on the side not fixed to the aluminum plate was pulled at a rate of 50 mm / min in the direction of 180 ° and peeled from the other insulating layer to determine the adhesive strength.

(2) Linear expansion coefficient [CTE] (ppm) and glass transition temperature [Tg] (° C.): The prepared substrate is immersed in an aqueous ferric chloride solution, and the copper foil as the conductor layer is immersed in the aqueous ferric chloride solution. The entire surface was etched to remove all the conductor layer from the substrate. The linear expansion coefficient and glass transition temperature Tg of the insulating layer obtained after the etching were determined using a thermomechanical analyzer (TMA: manufactured by TA Instruments, TMA2940 type).

(3) Dimensional change rate (%): A test piece having a width of 10 mm and a length of 200 mm was prepared, and this test piece was immersed in an aqueous ferric chloride solution to etch the entire surface of the copper foil as a conductor layer. All conductor layers were removed. And the dimensional change rate was calculated | required from the dimension of the test piece after performing the heat processing after 150 degreeC * 30 minute (s) after etching and the after-etching and the dimension of the test piece measured before the etching. In addition, the dimension measurement of the test piece was performed using the digital reading microscope (the Nihon Kogyo company make, NRM-D-2XZ type | mold).

(4) Curl characteristics: A test piece having a length of 100 mm and a width of 100 mm was prepared, and the copper foil as a conductor layer was etched on the entire surface by immersion in a test piece not subjected to etching treatment and ferric chloride aqueous solution. The test piece from which all the conductor layers were removed from the substrate and the test piece subjected to the heat treatment at 150 ° C. for 30 minutes after the etching treatment were left in an atmosphere of 23 ° C. and 60% RH for 24 hours, respectively, and then the curvature was obtained. The radius was measured and evaluated as follows.
◎: 80 mm or more ○: 50 mm or more and less than 80 mm △: 20 mm or more and less than 50 mm ×: less than 20 mm

(5) Folding strength: an index of repeated bending resistance. According to the method described in JIS C-5016, the bending strength of the bent surface is measured at a radius of curvature of 0.8 mm. It was evaluated as follows.
○: 400 times or more Δ: 200 to 399 times ×: 0 to 199 times

[2] Method for producing polyimide precursor solution A polyimide precursor solution for forming an insulating layer was synthesized. The terms used in the following description are as follows.
(Reaction component)
BPDA: 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride PMDA: pyromellitic dianhydride ODA: 4,4′-oxydianiline PDA: p-phenylenediamine (solvent)
DMAc: N, N-dimethylacetamide NMP: N-methyl-2-pyrrolidone

A. Synthesis Example of Polyimide Precursor Solution a Under a nitrogen gas stream, 30.03 g (0.15 mol) of ODA, 91.92 g (0.85 mol) of PDA, 2330 g of DMAc, and 999 g of NMP were collected in a three-necked flask. The contents were stirred for 30 minutes. Next, 294.22 g (1.00 mol) of BPDA was added, and the mixture was stirred in a hot water bath at 40 ° C. for 1 hour to obtain a uniform solution composed of polyamic acid. This is referred to as polyimide precursor solution a.

B. Synthesis Example of Polyimide Precursor Solution b 18.38 g (62.5 mmol) of BPDA was collected in a three-necked flask under a nitrogen gas stream, and 122.5 g of DMAc was added and dissolved. To this, 6.62 g (61.2 mmol) of PDA and 52.5 g of NMP were added and stirred overnight at room temperature to obtain a uniform solution composed of polyamic acid having a solid content concentration of 12.5% by mass. This is referred to as a polyimide precursor solution b.

[3] Production example of fluororesin film reinforced with glass fiber fabric Example of production of fluororesin film a FEP resin dispersion (product name: NEOFLON ND-1: product made by Daikin Industries) is applied to a woven fabric (product name: E02Z 2W 127B: manufactured by Unitika Glass Fiber Co., Ltd.) made of E glass fiber and having a thickness of 15 μm. After coating twice, it was dried at 90 ° C. for 10 minutes and then baked at 380 ° C. for 10 minutes. A glass fiber reinforced fluororesin film was prepared by adjusting the solid content of the dispersion so that the thickness after application of the FEP resin was 20 μm. This is designated as a fluororesin film a.

B. Example of production of fluororesin film b E glass fiber with a thickness of 15 μm (product name: E02Z 2W 127B: manufactured by Unitika Glass Fiber Co., Ltd.) A 12 μm thick PFA film (product name: NEOFLON PFA film RAF: manufactured by Daikin Industries) The glass fiber reinforced fluororesin film having a thickness of 20 μm was formed by overlapping and heating and molding under pressure. Molding was performed under the following conditions.
(1) Pressure 50 N / cm ² 200 ° C. × 30 minutes (2) Pressure 300 N / cm ² 200 ° C. → 350 ° C./20 minutes (3) Pressure 300 N / cm ² 350 ° C. × 30 minutes (4) Pressure 300 N / cm ² This is taken out at a temperature of 150 ° C. or lower, and is designated as a fluororesin film b.

Example 1
The polyimide precursor solution a was applied onto a copper foil having a thickness of 18 μm obtained by electrolysis with a bar coater so that the thickness of the heat-cured film became 7 μm, and dried at 130 ° C. for 10 minutes. Next, after fixing to a metal frame and raising the temperature from 100 ° C. to 360 ° C. in a nitrogen atmosphere over 2 hours, heat treatment was performed at 360 ° C. for 2 hours, the polyimide precursor was thermoset and imidized, and the copper foil was laminated. A polyimide film was obtained.
Next, a fluororesin emulsion (Neoflon FEP, product number ND-2, manufactured by Daikin Industries) was applied to the film surface of the polyimide film on which the copper foil was laminated to form an adhesive layer. Then, two laminated films having a three-layer structure composed of the conductor layer / insulating layer / adhesive layer are laminated so that the adhesive layers face each other, and are integrally bonded under the same conditions as the molding conditions described in the production example of the fluororesin film b. Turned into.
The resulting laminated film having a five-layer structure of conductor layer / insulating layer / adhesive layer / insulating layer / conductor layer has a conductor layer thickness of 18 μm and an insulating layer provided on both sides of the entire thickness of 14 μm. The thickness was 6 μm, and the total thickness was 56 μm.
Table 1 shows the configuration of each layer of the flexible printed wiring board substrate, and Table 2 shows the measured physical properties.

Example 2
Instead of the polyimide precursor solution a used in Example 1, a polyimide precursor solution b was used. And otherwise, it carried out similarly to Example 1, and obtained the board | substrate for flexible printed wiring boards with thickness of 56 micrometers.
The structure of each layer of the obtained flexible printed wiring board substrate is shown in Table 1, and the measured physical properties are shown in Table 2.

Example 3
A polyimide that is an insulating layer made of a 12 μm-thick fluororesin film (Neoflon PFA film RAF manufactured by Daikin Industries) between two polyimide films laminated with a copper foil, prepared using the polyimide precursor solution a in Example 1. It laminated so that it might face a film, and the laminated | multilayer film was obtained by crimping | bonding and integrating on the same conditions as the molding conditions as described in the manufacture example of the fluororesin film b. The resulting laminated film having a five-layer structure composed of conductor layer / insulating layer / adhesive layer / insulating layer / conductor layer has a conductor layer thickness of 18 μm, the entire insulating layer provided on both sides has a thickness of 14 μm, The thickness was 12 μm, and the overall thickness was 62 μm.
The structure of each layer of the obtained flexible printed wiring board substrate is shown in Table 1, and the measured physical properties are shown in Table 2.

Example 4
A laminated film having a five-layer structure comprising conductor layer / insulating layer / adhesive layer / insulating layer / conductor layer was obtained in the same manner as in Example 3 except that the fluororesin film a was used for the adhesive layer. In the obtained laminated film, the thickness of the conductor layer was 18 μm, the thickness of the entire insulating layer provided on both sides was 14 μm, the thickness of the adhesive layer was 20 μm, and the total thickness was 70 μm.
Table 1 shows the configuration of each layer of the flexible printed wiring board substrate, and Table 2 shows the measured physical properties.

Example 5
In place of the polyimide precursor solution a used in Example 4, a polyimide precursor solution b was used, and a fluororesin film b was used. And otherwise, it carried out similarly to Example 4, and obtained the board | substrate for flexible printed wiring boards with thickness of 70 micrometers.
The structure of each layer of the obtained flexible printed wiring board substrate is shown in Table 1, and the measured physical properties are shown in Table 2.

Example 6
The thickness of the insulating layer in one laminated film used in Example 5 was 14 μm. And otherwise, it carried out similarly to Example 5, and obtained the board | substrate for flexible printed wiring boards with thickness of 77 micrometers.
The structure of each layer of the obtained flexible printed wiring board substrate is shown in Table 1, and the measured physical properties are shown in Table 2.

  In each of Examples 1 to 6, the film surfaces of the insulating layer provided with the conductor layer on one side were integrated by a specific adhesive layer, and the thickness of the insulating layer was within the scope of the present invention. The adhesive strength was excellent. In addition, a flexible printed wiring board substrate having a small CTE, a small dimensional change rate, excellent dimensional stability, and excellent curling characteristics and bending resistance was obtained.

Comparative Example 1
The thickness of the insulating layer in the laminated film having a three-layer structure was 14 μm, and the thickness of the adhesive layer was 1 μm. And otherwise, it carried out similarly to Example 1, and obtained the board | substrate for flexible printed wiring boards with thickness of 66 micrometers.
The structure of each layer of the obtained flexible printed wiring board substrate is shown in Table 1, and the measured physical properties are shown in Table 2.

Comparative Example 2
The thickness of the adhesive layer in the laminated film having a three-layer structure was 16 μm. And otherwise, it carried out similarly to Example 1, and obtained the board | substrate for flexible printed wiring boards with thickness of 82 micrometers.
The structure of each layer of the obtained flexible printed wiring board substrate is shown in Table 1, and the measured physical properties are shown in Table 2.

Comparative Example 3
A flexible printed wiring board substrate having a thickness of 64 μm was obtained in the same manner as in Example 5 except that a laminated polyimide film having an insulating layer thickness of 4 μm was used.
The structure of each layer of the obtained flexible printed wiring board substrate is shown in Table 1, and the measured physical properties are shown in Table 2.

In Comparative Example 1, since the ratio of the thickness of the insulating layer to the adhesive layer was too high, the adhesive strength between the insulating layers was low, and the bending strength was inferior.
In Comparative Examples 2 and 3, since the ratio of the thickness of the insulating layer to the adhesive layer was too low, the dimensional stability, curl characteristics, and bending strength were inferior.

Claims (3)

A film made of a non-thermoplastic aromatic polyimide resin that forms an insulating layer is laminated on both sides of an adhesive layer made of a fluororesin, and a conductor layer is provided on the outer surface of each film. In manufacturing a flexible printed wiring board substrate , the total thickness of the insulating layer provided on the substrate is 5 to 100 μm and 0.5 to 10 times the thickness of the adhesive layer .
A film made of a non-thermoplastic aromatic polyimide resin, a first insulating layer having a conductor layer laminated on one side thereof, and a film made of a non-thermoplastic aromatic polyimide resin, the conductor layer being laminated on one side A method for producing a substrate for a flexible printed wiring board, comprising: laminating an adhesive film surface made of a fluororesin between the second insulating layer and press-bonding in a heated atmosphere. A film made of a non-thermoplastic aromatic polyimide resin that forms an insulating layer is laminated on both sides of an adhesive layer made of a fluororesin, and a conductor layer is provided on the outer surface of each film. In manufacturing a flexible printed wiring board substrate, the total thickness of the insulating layer provided on the substrate is 5 to 100 μm and 0.5 to 10 times the thickness of the adhesive layer.
A film having a thickness of 2 to 50 μm made of a non-thermoplastic aromatic polyimide resin as an insulating layer and having a conductor layer laminated on one side thereof, and a thickness of an adhesive film made of a fluororesin is 2 to 2 with 50μm of film, the fluorine adhesive film laminated consisting of a resin, a flexible printed circuit board substrate, wherein the crimping under heating atmosphere during the non-thermoplastic aromatic polyimide film as an insulating layer Manufacturing method. The method for producing a substrate for a flexible printed wiring board according to claim 1 or 2 , wherein the adhesive film made of a fluororesin is reinforced with an inorganic fiber fabric.