WO2012007992A1

WO2012007992A1 - Flexible wiring board, dry film for coverlay, and production method for flexible wiring board

Info

Publication number: WO2012007992A1
Application number: PCT/JP2010/004569
Authority: WO
Inventors: 前澤英樹; 福川弘
Original assignee: 京セラケミカル株式会社
Priority date: 2010-07-14
Filing date: 2010-07-14
Publication date: 2012-01-19
Also published as: KR20130037205A; CN102986310A

Abstract

Provided is a flexible wiring board having good flame retardant properties without the use of halogenated flame retardants, excellent resistance to bending, and minimal spring-back force. The flexible wiring board (1) is provided with: a substrate (2a) comprising a polyimide film; a circuit (2b) disposed on one main surface of the substrate (2a); and a coverlay (3) that covers the surface of the circuit (2b). The coverlay (3) is formed by a dry film for coverlays, and has a thickness of 10 to 50μm.

Description

Flexible wiring board, dry film for coverlay, and method for manufacturing flexible wiring board

The present invention relates to a flexible wiring board useful for thinning devices such as a liquid crystal display module and an imaging module, a dry film for coverlay, and a method for manufacturing a flexible wiring board.

A liquid crystal display module having a small liquid crystal display panel, for example, a TFT liquid crystal display panel, is used as a display unit of a cellular phone or the like. In such a liquid crystal display module, a semiconductor chip constituting a driver for driving each subpixel is mounted on one side of the liquid crystal display panel, and a flexible wiring board is connected for connection with a control unit. It is stored in. The flexible wiring board is bent in the vicinity of the liquid crystal display panel, and is disposed on the back side of the frame with the other end sandwiching the backlight.

Similarly, an imaging module equipped with an imaging device such as a CCD image sensor is housed in a mobile phone or the like as a camera component by bending a flexible wiring board and connecting it to a main board via a connector or the like.

¡Flexible wiring boards used in such liquid crystal display modules and imaging modules tend to have a smaller bending radius as the electronic equipment mounted becomes smaller and thinner. Generally, a flexible wiring board is covered with a cover lay film in which an adhesive is applied to a polyimide film for the purpose of protecting or insulating a wiring pattern formed on the surface of the substrate.

However, the polyimide film has a high elastic modulus, and therefore, when the flexible wiring board is bent, a repulsive force (hereinafter also referred to as a springback force) is generated on the flexible wiring board, and the liquid crystal display There is a problem that the module and the imaging module are lifted.

To solve this problem, for example, by providing a hole in the frame that houses the flexible wiring board, providing a protrusion on the flexible wiring board, and inserting the protrusion of the flexible wiring board into the hole of the frame, the flexible wiring A method of suppressing the springback force of the plate (for example, see Patent Document 1) and a method of preventing the liquid crystal panel from being lifted by the repulsive force of the flexible wiring board by forming a through hole in a portion where the bending curvature is maximized (See, for example, Patent Document 2).

In addition, for example, a method is known in which a notched portion is provided in a bent portion of an insulating substrate constituting a flexible wiring board, and a protective resin made of silicone resin or the like is applied to this portion to facilitate bending of the flexible wiring board. (For example, see Patent Document 3). Further, for example, in a flexible wiring board provided with a circuit part and a terminal forming part, a flexible piece that is convex toward the circuit part side is formed by cutting between the circuit part and the terminal forming part. A method is known in which the bent portion is eliminated by using for connection (see, for example, Patent Document 4).

From the viewpoint of thinning, it is also known to use a film made of an aramid resin as a coverlay film (see, for example, Patent Document 5).

However, none of the methods can completely eliminate the influence of the elastic modulus of the polyimide film.

Therefore, a substrate in which a cover lay is formed with an adhesive sheet that does not have a polyimide film as a supporting base has been proposed (see, for example, Patent Document 6). However, a flexible printed wiring board using a so-called dry film type coverlay material without such a supporting substrate has a problem that the folding resistance is remarkably lowered. In addition, this adhesive sheet uses an epoxy resin obtained by glycidylation of halogenated phenols in order to exhibit flame retardancy, and there is a problem in terms of environmental compatibility.

Various methods for imparting non-halogen flame retardancy have been proposed so far. Representative methods include hydrated metal compounds such as aluminum hydroxide and magnesium hydroxide, phosphorus-based flame retardants such as phosphate esters and polyphosphate compounds, and non-halogen-based compounds such as nitrogen-based flame retardants such as melamine compounds. This method uses a flame retardant. However, when these flame retardants are used, it is difficult to achieve both the properties required for the coverlay, such as electrical insulation, solder heat resistance, and bend resistance, and flame retardancy. There were problems such as bleeding out.

Also, it is desirable that the flexible wiring board used for a device that may cause a malfunction due to light leakage such as a liquid crystal display module or an imaging module has a low surface reflectance. For this reason, for example, black ink may be printed on the surface of the polyimide cover lay film, but the spring back force is further increased by this ink layer, and cracking may occur when the ink is folded.

JP 2005-338497 A JP 2008-203445 A JP-A-9-274446 JP 2007-12784 A Japanese Patent Laid-Open No. 2005-235587 JP 2003-133704 A

As described above, liquid crystal display modules and imaging element mounting modules are becoming thinner, and the flexible wiring board used therefor has a small springback force even when the bending radius is reduced, and is excellent in bending resistance. It is demanded.

The present invention has been made to solve the above problems, and provides a flexible wiring board having a small springback force, excellent bending resistance, and good flame resistance without using a halogen-based flame retardant. The purpose is to do. Moreover, this invention aims at providing the manufacturing method of the dry film for coverlays useful for manufacture of such a flexible wiring board, and a flexible wiring board.

According to one aspect of the present invention, a flexible wiring board includes a base material made of a polyimide film, a circuit provided on one main surface of the base material, and a coverlay that covers the surface of the circuit, The cover lay is formed of a cover lay dry film and has a thickness of 10 to 50 μm. A flexible wiring board is provided.

According to another aspect of the present invention, (A) an epoxy resin, (B) an epoxy resin curing agent, (C) a curing accelerator, (D) a synthetic rubber, (E) a phosphazene compound, (F) a polyphosphate Provided is a dry film for coverlay, comprising a layer made of a non-halogen flame retardant resin composition containing a compound and (G) an inorganic filler as essential components on a support film.

According to still another aspect of the present invention, a step of forming a circuit on one main surface of a substrate made of a polyimide film, and the coverlay dry film on the surface of the circuit, the non-halogen flame retardant Providing a method for manufacturing a flexible wiring board, comprising: superposing and heating the conductive resin composition layer side toward the circuit side and forming a coverlay by removing the support film Is done.

According to the present invention, it is possible to obtain a flexible wiring board having a small springback force, excellent bending resistance, and good flame resistance without using a halogen flame retardant. The obtained flexible wiring board is suitably used for devices that are required to be thin, such as liquid crystal display modules and imaging element modules.

It is sectional drawing which shows one Embodiment of the flexible wiring board of this invention. It is sectional drawing which shows an example of the connection method of a flexible wiring board and a liquid crystal display panel. It is sectional drawing which shows an example of the liquid crystal display module using the flexible wiring board of one Embodiment. It is sectional drawing which shows the manufacturing process of the flexible wiring board of one Embodiment. It is sectional drawing which shows the manufacturing process of the flexible wiring board following FIG. It is sectional drawing which shows the manufacturing process of the flexible wiring board following FIG. It is sectional drawing which shows the manufacturing process of the flexible wiring board following FIG. FIG. 8 is a cross-sectional view illustrating a manufacturing process of the flexible wiring board following FIG. 7. It is sectional drawing which shows the manufacturing process of the flexible wiring board following FIG. It is sectional drawing which shows an example of the imaging module using the flexible wiring board of other embodiment. It is sectional drawing which shows an example of the dry film for coverlays. It is a figure which shows the measurement result of the transmittance | permeability of the flexible wiring board for evaluation. It is a figure which shows the measurement result of the reflectance of the flexible wiring board for evaluation.

Hereinafter, embodiments of the present invention will be described.

FIG. 1 is a cross-sectional view showing a first embodiment of the flexible wiring board of the present invention. The flexible wiring board 1 of this embodiment has a flexible wiring board body 2 and a coverlay dry film formed on one main surface of the flexible wiring board body 2 with a thickness of 10 to 50 μm, preferably 20 to 20 μm. And a coverlay 3 of 35 μm. In the present embodiment, the other main surface of the flexible wiring board body is covered with another cover lay 4 made of a polyimide film, a photosensitive resin, or the like, and a mounting component 5 is mounted (hereinafter referred to as a cover). The lay 3 and the other cover lay 4 are referred to as a first cover lay 3 and a second cover lay 4, respectively). In addition, the material which forms the 2nd coverlay 4 is not specifically limited, Like the 1st coverlay 3, you may form with the dry film for coverlays. From the viewpoint of suppressing the springback force and improving the bending resistance, it is preferable to use a photosensitive resin or a dry film for coverlay. As will be described later, the flexible wiring board 1 is used by being bent so that the main surface side on which the first cover lay 3 is formed becomes the inner side.

The flexible wiring board body 2 connects, for example, a base material 2a made of a polyimide film,

circuits

2b and 2c provided on both main surfaces of the base material 2a, and these

circuits

2b and 2c, respectively. It has a through hole 2d and a connection terminal 2e that electrically connects the circuit 2b and the circuit 2c to the liquid crystal display panel. The first coverlay 3 is formed on substantially the entire surface of the flexible wiring board main body 2 except for the end where the connection terminal 2e is provided. On the other hand, the second coverlay 4 is formed so as to cover the circuit 2c excluding, for example, a portion where the mounting component 5 of the flexible wiring board body 2 is mounted.

Such a flexible wiring board 1 is electrically connected to a liquid crystal display panel 12 to form a liquid crystal display module 11 as shown in FIGS. For example, as shown in FIG. 2, the liquid crystal display panel 12 includes a connection terminal 13 and a semiconductor chip 14 on one main surface side. In the flexible wiring board 1, the main surface side on which the first cover lay 3 is formed, that is, the main surface side on which the connection terminals 2 e are formed faces the main surface side on which the connection terminals 13 of the liquid crystal display panel 12 are formed. The connection terminals 2e and the connection terminals 13 are electrically connected to each other. Then, as shown in FIG. 3, the flexible wiring board 1 is folded so as to enclose the liquid crystal display panel 12, that is, the flexible wiring board 1 so that the main surface side on which the first cover lay 3 is formed is inside. The liquid crystal display module 11 is configured by bending and arranging.

According to the flexible wiring board 1 of the present embodiment, since the first cover lay 3 is formed to a thickness of 10 to 50 μm using a cover lay dry film, the spring back force is suppressed as compared with the conventional one. It can be easily bent without using protrusions and tape as fixing means, and the problem of the liquid crystal display panel 12 and the liquid crystal display module 11 being lifted can be solved.

The flexible wiring board 1 of the present embodiment can be manufactured as follows, for example.

First, as shown in FIG. 4, a flexible metal-clad plate 42 in which metal foils 41 and 41 such as copper foil are bonded to both main surfaces of a base material 2a made of a polyimide film is prepared. The flexible metal tension plate 42 can be selected and used from a metal tension plate for a two-layer type flexible wiring board and a metal tension plate for a three-layer type flexible wiring board, which are generally marketed as flexible metal tension plates. As a metal-clad board for a two-layer type flexible wiring board, for example, ESPANEX (trade name, manufactured by Nippon Steel Chemical Co., Ltd.), NEOFLEX (trade name, manufactured by Mitsui Chemicals), UPISEL (trade name, manufactured by Ube Nitto Kasei Co., Ltd.), etc. Is mentioned. Examples of the three-layer type flexible wiring board metal tension plate include TLF-521 and TLF-530 (trade name, manufactured by Kyocera Chemical Co., Ltd.). In either case, copper foil is used as the metal foil.

Next, as shown in FIG. 5, through holes 2d are formed in the flexible metal-clad plate 42, and the metal foils 41 and 41 on both main surfaces are electrically connected to each other.

Next, as shown in FIG. 6, these metal foils 41, 41 are etched to form the circuit 2 b and the circuit 2 c to form the flexible wiring board main body 2, and then one of the flexible wiring board main bodies 2 (circuit The coverlay dry film 43 is overlaid and heated and pressed so as to cover the main surface of the 2b formation side. The coverlay dry film 43 includes a support film on one side, and the support film is peeled off in advance during the heating and pressurization. Thereby, the flexible wiring board main body 2 in which the 1st cover lay 3 was formed in one main surface of the flexible wiring board main body 2 as shown in FIG. 7 is obtained. The first coverlay 3 is formed on substantially the entire surface of one side of the flexible wiring board main body 2 excluding the end portion that becomes the connection terminal 2e.

When the coverlay dry film 3 is overlaid and pressurized and heated, at least half of the through hole 2d in the depth direction is filled with the constituent material of the thermosetting dry film coverlay 3. Is preferred. In this way, when the second cover lay 4 is formed by printing or applying a liquid photosensitive resin, for example, in the next step, the liquid photosensitive resin flows into the through hole 2d. It can suppress that the thickness of the 2nd coverlay 4 of a corner | angular part becomes thin, and can improve the insulation reliability of the flexible wiring board 1. FIG.

After the first cover lay 3 is formed, a liquid photosensitive resin 44 is applied to substantially the entire surface of the other main surface (circuit 2c forming side) of the flexible wiring board body 2 as shown in FIG. After that, the second coverlay 4 is formed so as to cover the circuit 2c excluding the mounting component mounting portion by developing and post-curing. As a result, as shown in FIG. 9, the flexible wiring 1 in which the first cover lay 3 is formed on one main surface of the flexible wiring board main body 2 and the second cover lay 4 is formed on the other main surface is obtained. . Thereafter, the mounting component 5 is mounted on the flexible wiring 1 (FIG. 2).

FIG. 10 is a cross-sectional view showing a second embodiment of the flexible wiring board of the present invention. While the first embodiment is a flexible wiring board used in a liquid crystal display module, the flexible wiring board of this embodiment is a flexible wiring board used in an imaging module. FIG. 10 shows the flexible wiring board of this embodiment. The state which connected the wiring board 10 to the imaging module is shown. In addition, in order to avoid overlapping description, description is abbreviate | omitted about the point which is common in 1st Embodiment, and only a different point is demonstrated.

The flexible wiring board 10 of the present embodiment has a thickness of 10-50 μm, preferably 20-20, formed by a flexible wiring board body 2 and a coverlay dry film on one main surface of the flexible wiring board body 2. And a coverlay 3 of 35 μm. As shown in FIG. 10, the flexible wiring board 1 is used by being bent so that the main surface side on which the cover lay 3 is formed becomes the outside.

The flexible wiring board body 2 includes, for example, a base material 2a made of a polyimide film and a circuit 2b provided on one main surface of the base material 2a. The cover lay 3 is formed on substantially the entire surface of one main surface of the flexible wiring board body 2 except for both ends where the

connection terminals

2e and 2e are provided.

Such a flexible wiring board 10 is electrically connected to the imaging module main body 15 to form an imaging module 16 as shown in FIG. The imaging module main body 15 includes a lens unit 17 and an imaging element 18. In the flexible wiring board 10, one connection terminal 2e is electrically connected to an imaging board (not shown) on which the imaging element 18 of the imaging module body 15 is mounted, and the other connection terminal 2e is a connector (not shown). Is electrically connected. Then, as shown in FIG. 10, the imaging module 16 is configured by being bent so that the main surface side on which the cover lay 3 is formed is on the outside. A reinforcing plate 19 for reinforcing the connection with the connector is provided at the end of the main surface opposite to the circuit 2b surface of the substrate 2a on the connector side.

Also in the flexible wiring board 10 of the present embodiment, since the cover lay 3 is formed to a thickness of 10 to 50 μm using a cover lay dry film, the spring back force can be suppressed as compared with the conventional one. Further, it can be easily bent without using a protrusion or a tape as a fixing means, and the problem of floating of the imaging module 16 can be solved.

Although not described with reference to the drawings, the flexible wiring board 10 of the present embodiment is, for example, a flexible metal-clad board in which a metal foil such as a copper foil (to be a circuit 2b) is bonded to one side of a base material 2a made of a polyimide film. In the same manner as in the first embodiment, the cover foil dry film is overlaid and heated and pressed so as to cover the metal foil.

Next, the coverlay dry film used in the present invention will be described.

FIG. 11 is a cross-sectional view showing an example of a dry film for a coverlay that is preferably used in the present invention.

As shown in FIG. 11, this coverlay dry film 50 has (A) an epoxy resin, (B) an epoxy resin curing agent, (C) a curing accelerator, (D) a synthetic rubber, ( A layer 52 made of a non-halogen flame retardant resin composition containing E) a phosphazene compound, (F) a polyphosphate compound, and (G) an inorganic filler as essential components is provided.

The epoxy resin of component (A) is non-halogen and has two or more epoxy groups in one molecule. Any material satisfying such conditions can be used without being limited by the molecular structure, molecular weight and the like. Specific examples include, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin, phenol novolac type resin, cresol novolac type epoxy resin, glycidyl ether type epoxy resin, and alicyclic type. Examples thereof include epoxy resins, heterocyclic epoxy resins, and glycidyl ether-based modified epoxy resins. These can be used alone or in combination of two or more.

As the (B) component epoxy resin curing agent, a phenol resin curing agent, an acid anhydride curing agent, an amine curing agent or the like generally known as an epoxy resin curing agent is used. Specific examples of the phenol resin-based curing agent include novolak type phenol resins such as phenol novolak resin and cresol novolak resin, amino-modified novolak type phenol resin, polyvinyl phenol resin, and phenol aralkyl resin. Specific examples of acid anhydride curing agents include phthalic anhydride, maleic anhydride, trimellitic anhydride, pyromellitic anhydride, hexahydrophthalic anhydride, 3-methyl-hexahydrophthalic anhydride, 4-methyl-hexahydro anhydride Examples thereof include phthalic acid, tetrahydrophthalic anhydride, and nadic anhydride. Specific examples of the amine curing agent include diethylenetriamine, triethylenetetramine, tetraethylenetetramine, tetraethylenepentamine, diethylaminopropylamine, isophoronediamine, diaminodiphenylmethane, metaphenylenediamine and the like. In addition, organic acid hydrazide, diaminomaleonitrile and derivatives thereof, melamine and derivatives thereof, polyamide resin, amine imide, polyamine salt, and the like are also used. These can be used alone or in combination of two or more.

The blending amount of the epoxy resin curing agent of the component (B) is preferably an equivalent ratio of the epoxy resin of the component (A) and the epoxy resin curing agent of the component (B) (for example, in the case of a phenol resin curing agent, the epoxy resin The molar ratio of the epoxy group and the phenolic hydroxyl group of the phenol resin-based curing agent is in the range of 0.7 to 1.3, more preferably in the range of 0.9 to 1.1. When the equivalence ratio is less than 0.7, heat resistance, chemical resistance, and the like are lowered. Conversely, when the equivalent ratio is more than 1.3, moisture resistance and the like are lowered.

As the (C) component curing accelerator, those generally known as epoxy resin curing accelerators are used. Specific examples include 2-heptadecylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 4-methylimidazole, 4-ethylimidazole, 2-phenyl. -4-hydroxymethylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole 2-undecylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyano Tyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 2,4-diamino-6- [2'-methylimidazolyl- (1 ') ] -Ethyl-s-triazine, 2,4-diamino-6- [2'-undecylimidazolyl- (1 ')]-ethyl-s-triazine, 2,4-diamino-6- [2'-ethyl- 4'-methylimidazolyl- (1 ')]-ethyl-s-triazine, 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl-s-triazine, 2-phenylimidazole isocyanur Acid adducts, 2-methylimidazole isocyanuric acid adducts, imidazoles such as 2-phenylimidazoline; 1,8-diazabicyclo [5, , 0] undecene-7 (DBU), 1,5-diazabicyclo [4,3,0] nonene, 5,6-dibutylamino-1,8-diazabicyclo [5,4,0] undecene-7 Tertiary amines such as triethylamine, triethylenediamine, benzyldimethylamine, α-methylbenzyldimethylamine, triethanolamine, dimethylaminoethanol, 2,4,6-tris (dimethylaminomethyl) phenol; trimethylphosphine, triethylphosphine , Tributylphosphine, triphenylphosphine, tri (p-methylphenyl) phosphine, tri (nonylphenyl) phosphine, methyldiphenylphosphine, dibutylphenylphosphine, tricyclohexylphosphine, bis (diphenylphosphino Methane, 1,2-bis (diphenylphosphino) ethane, tetraphenyl phosphonium tetraphenyl borate, triphenyl phosphine tetraphenyl borate, organic phosphine compounds such as triphenylphosphine triphenyl borane, and the like. These can be used alone or in combination of two or more.

The blending amount of the curing accelerator of component (C) is preferably 0.01 with respect to 100 parts by mass of the epoxy resin of component (A) from the viewpoint of the balance between curing acceleration and physical properties of the resin after curing. Is 5 parts by mass, and more preferably 0.3-2 parts by mass.

Examples of the synthetic rubber (D) include acrylic rubber, acrylonitrile butadiene rubber, styrene butadiene rubber, butadiene methyl acrylate acrylonitrile rubber, butadiene rubber, carboxyl group-containing acrylonitrile butadiene rubber, vinyl group-containing acrylonitrile butadiene rubber, silicone rubber, urethane. Rubber, polyvinyl butyral, etc. are used. These can be used alone or in combination of two or more.

The blending amount of the synthetic rubber of the component (D) is preferably 10 to 30% by mass, more preferably 15 to 25% by mass with respect to the total components (A) to (D). If the blending amount is less than 10% by mass, there is a possibility that sufficient adhesion with a substrate made of a polyimide film may not be obtained. Conversely, if it exceeds 30% by mass, the electrical characteristics and the like deteriorate.

The phosphazene compound as the component (E) is used without particular limitation as long as it has substantially no halogen. From the viewpoint of flame retardancy, heat resistance, moisture resistance, chemical resistance, etc., those having a melting point of 80 ° C. or higher are preferred, and those having a melting point of 90 ° C. or higher are more preferred. Specific examples of preferred phosphazene compounds include phosphazene compounds represented by the following general formula (1) or (2).

In formulas (1) and (2), X ¹ is a group —N═P (OPh) ₃ or a group —N═P (O) OPh, and Y ¹ is a group —N═P (OPh) ₄ or a group— N = P (O) (OPh) ₂ Ph is a phenyl group, m is an integer of 3 to 25, and n is an integer of 3 to 10,000. These phosphazene compounds can be used singly or in combination of two or more.

The blending amount of the phosphazene compound as the component (E) is preferably 3 to 10 parts by mass, more preferably 5 to 7 parts by mass with respect to 100 parts by mass of the total amount of the components (A) to (D). . If the blending amount is less than 3 parts by mass, the desired flame retardancy may not be obtained. Conversely, if it exceeds 10 parts by mass, bleeding may occur on the surface of the dry film or coverlay.

Examples of the (F) component polyphosphate compound include amine salts and ammonium salts of polyphosphoric acid. Examples of polyphosphoric acid include linear condensed phosphoric acid represented by the general formula: HO (HPO3) nH (wherein n is an integer of 2 or more) (for example, pyrophosphoric acid, tripolyphosphoric acid, tetrapolyphosphoric acid). , Pentapolyphosphoric acid, etc.), cyclic condensed phosphoric acid (trimetaphosphoric acid, tetrametaphosphoric acid, hexametaphosphoric acid, etc.) represented by the general formula: (HPO3) m (where m is an integer of 2 or more), etc. It is done.

As the polyphosphate compound of component (F), melamine polyphosphate, melam polyphosphate, and melem polyphosphate are particularly preferable. Incidentally, melam is a 1,3,5-triazine derivative in which one molecule of ammonia is desorbed from two melamine molecules, and melem is a 1,3,5-triazine derivative in which two molecules of ammonia are desorbed and condensed. It is a triazine derivative. These polyphosphate compounds can be used alone or in combination of two or more.

The blending amount of the polyphosphate compound of the component (F) is preferably 5 to 30 parts by weight, more preferably 15 to 25 parts by weight with respect to 100 parts by weight of the total amount of the components (A) to (D). It is. If the blending amount is less than 5 parts by mass, the desired flame retardancy may not be obtained. Conversely, if it exceeds 30 parts by mass, the bending resistance of the dry film or coverlay may be reduced.

As the inorganic filler of component (G), any conventional filler used in coverlays can be used without any particular limitation. Specific examples include metal hydrates such as aluminum hydroxide and magnesium hydroxide, talc, silica, alumina and the like. These inorganic fillers can be used alone or in combination of two or more. Further, these inorganic fillers preferably have an average particle diameter of 0.1 to 10 μm, more preferably 0.5 to 5 μm, from the viewpoint of crack resistance during bending. The average particle diameter of the inorganic filler can be measured using, for example, a laser diffraction / scattering particle size distribution apparatus.

The blending amount of the inorganic filler as the component (G) is preferably in the range of 5 to 30% by mass, more preferably in the range of 10 to 20% by mass based on the total solid content in the composition. If the blending amount is less than 5% by mass, sufficient flame retardancy may not be obtained. Conversely, if it exceeds 30% by weight, crack resistance may decrease.

In addition to the above components (A) to (G), the non-halogen flame retardant resin composition contains (H) colorants such as inorganic pigments, organic pigments, organic dyes, etc., for coloring the coverlay. Can be blended.

Examples of inorganic pigments include carbon black, cobalt dyes, iron dyes, chromium dyes, titanium dyes, vanadium dyes, zirconium dyes, molybdenum dyes, ruthenium dyes, platinum dyes, ITO (indium) Tin oxide) dyes, ATO (antimony tin oxide) dyes, and the like. Examples of organic pigments and organic dyes include aminium dyes, cyanine dyes, merocyanine dyes, croconium dyes, squalium dyes, azurenium dyes, polymethine dyes, naphthoquinone dyes, pyrylium dyes, and phthalocyanine dyes. Dye, Naphthalocyanine dye, Naphlactam dye, Azo dye, Condensed azo dye, Indigo dye, Perinone dye, Perylene dye, Dioxazine dye, Quinacridone dye, Indanthrene blue dye, Isoindolinone Dyes, watching dyes, permanent dyes, quinophthalone dyes, pyrrole dyes, thioindigo dyes, metal complex dyes, dithiol metal complex dyes, indolephenol dyes, triallylmethane dyes, anthraquinone dyes, Dioqui Jin dyes, naphthol dyes, azomethine dyes, benzimidazolone pigments, pyranthrone pigments and threne pigments, and the like.

These colorants can be used by appropriately selecting one or more kinds in order to adjust to a target hue. For example, carbon black, etc. for black coloring, phthalocyanine dyes, indanthrene blue dyes, etc. for blue coloring, quinacridone dyes, watching dyes, permanent dyes, anthraquinone dyes for red coloring, etc. Perylene dyes, condensed azo dyes, and the like are used.

In particular, for applications requiring light shielding properties such as liquid crystal display modules and imaging modules, it is preferable to use a black pigment as the (H) colorant. Specific examples of preferable black pigments include, for example, carbon black, aniline black, carbon black, titanium black, inorganic pigment hematite, perylene black, or a mixture of two or more thereof. Among these, carbon black, titanium black, or a mixture thereof is more preferable. As carbon black, furnace black, channel black, acetylene black, etc. can be used. Carbon black having a small primary particle diameter is suitable because it generally has excellent blackness and coloring power. Specifically, the primary particle diameter is preferably 1 μm or less, preferably 0.5 μm or less. Is more preferable. However, if the primary particle diameter is smaller than 10 nm, the particles are aggregated, and therefore it is preferably 10 nm or more. Titanium black is obtained by oxidation of titanium or reduction of titanium dioxide. For example, titanium black is a black pigment containing titanium dioxide and titanium monoxide and / or titanium nitride as constituent components.

The blending amount of the colorant as the component (H) is preferably in the range of 0.1 to 10% by mass, more preferably in the range of 0.5 to 3% by mass, based on the total solid content in the composition. If the blending amount is less than 0.1% by mass, a sufficient coloring effect may not be obtained. Conversely, if it exceeds 10% by weight, the adhesion with the flexible wiring board may be reduced. In addition, when mix | blending a pigment, it is preferable that the pigment is disperse | distributed with the dispersing agent. As the dispersant, for example, a silane coupling agent, a titanium coupling agent, a resin into which various functional groups are introduced, or the like is used.

A flexible wiring board using a dry film for coverlay using a non-halogen flame retardant resin composition containing a black pigment is used for a liquid crystal display module, an imaging module, etc. where light shielding properties are required. The printing process of the black ink for light shielding after formation can be omitted. As a result, the productivity and environmental compatibility are excellent, and the plate thickness can be reduced, which leads to a reduction in springback force and good bending properties.

In addition to the components (A) to (H) described above, the non-halogen flame retardant resin composition includes various additives, such as organic fillers, deterioration, as necessary and within the range not impairing the effects of the present invention. An inhibitor or the like can be further blended.

Further, a solvent can be added to the non-halogen flame retardant resin composition in order to obtain a viscosity suitable for the processing method. Examples of the solvent include alcohol solvents such as methanol, ethanol and isopropanol, ketone solvents such as acetone and methyl ethyl ketone, aromatic hydrocarbon solvents such as benzene, toluene and xylene, 1,4-dioxane and 1,3-dioxane. And ether solvents such as propylene glycol monomethyl ether, N-methylpyrrolidone, dimethylformamide and the like. These can be used alone or in combination of two or more.

The non-halogen flame retardant resin composition can be prepared by applying a known method. For example, the above components (A) to (G) and various components to be blended as necessary are mixed using a known kneader such as a pot mill, a ball mill, a bead mill, a roll mill, a homogenizer, a super mill, or a reika machine. It can be prepared by kneading at room temperature or under heating. Among the blended components, the component insoluble in the solvent, at least the polyphosphate compound of component (F), is to have a particle size of 10 μm or less by kneading from the viewpoint of preventing a decrease in crack resistance. Is preferred.

The dry film for coverlay 50 is obtained by applying the non-halogen flame retardant resin composition, which is adjusted to an appropriate viscosity with a solvent as required, onto the support film 51 by a known method and drying. Specifically, it is applied onto the support film 51 by a known coating method such as a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, or a gravure coating method, followed by drying treatment, and a semi-cured state. Is obtained. As the support film 51, a plastic film such as polyethylene, polypropylene, polyester, polycarbonate, polyarylate, polyacrylonitrile, etc., having a release agent layer on one side is used. The thickness of the support film 51 is usually 10 to 50 μm, preferably 25 to 38 μm, from the viewpoint of handling properties.

The non-halogen flame retardant resin composition is preferably applied so that the thickness after drying is 10 to 50 μm. More preferably, it is 20 to 35 μm.

Further, the non-halogen flame retardant resin composition coated surface side of the support film 51 may have a surface roughness (Ra: arithmetic average roughness) of 0.3 to 5.0 μm by surface treatment. Preferably, the thickness is 0.5 to 3.0 μm. As the surface treatment method, for example, methods such as sand blast treatment, chemical mat treatment, kneading mat treatment and the like can be used.

The non-halogen flame retardant resin composition is applied onto the support film 51 having a surface roughness (Ra) of 0.3 to 5.0 μm as described above and a release agent layer provided on the surface, and dried. Using the coverlay dry film 50 obtained by the treatment, a coverlay is formed by a method as described later, and then the support film 51 is peeled off, whereby the surface roughness (Ra) of the support film 51 is increased. A transferred coverlay surface can be obtained.

As will be apparent from the examples described later, the coverlay having such a roughened surface has a significantly lower light reflectance than a coverlay having a smooth surface (see FIG. 13). . Therefore, the dry film for coverlay 50 having the support film 51 that is black and has a surface roughness (Ra) of 0.3 to 5.0 μm is very large due to light leakage from a liquid crystal display module, an imaging module, or the like. It is suitable for the use of the flexible wiring board of the affected electronic component module. The reason why the reflectance of light is greatly reduced by roughening is that incident light is absorbed and diffusely reflected on the coverlay surface, and as a result, the amount of light reflected from the coverlay surface and returning to the light receiving portion is small. It is thought that it became. On the other hand, the effect of roughening is hardly observed on the light transmittance (see FIG. 12).

The flexible wiring board of the present invention can be manufactured by forming a coverlay using the above-mentioned dry film for coverlay. Specifically, for example, the above-mentioned coverlay in which a metal foil such as a copper foil is bonded to one side or both sides of a polyimide film with a hot roll to form a circuit, and then a hole is previously drilled in a predetermined place on the circuit forming surface. The dry film is overlaid with the non-halogen flame retardant resin composition layer side facing the circuit forming surface, and by hot pressing, a temperature of 130 to 180 ° C., preferably 150 to 170 ° C., and 5 to 50 MPa, preferably 15 Heat and pressurize at a pressure of ~ 35 MPa. Thereby, the flexible wiring board by which the coverlay which consists of the said dry film for coverlays was formed on the circuit is obtained.

In addition, a flexible printed wiring board with a reinforcing plate can be produced by a normal method of superposing a reinforcing plate on the flexible wiring board via a thermosetting resin composition and performing heat-press molding.

Furthermore, a flexible copper-clad laminate and the like are superimposed on the flexible wiring board of the present invention via a thermosetting resin composition, heated and pressed, formed through-holes, plated through-holes, A multilayer flexible printed wiring board can be manufactured by the usual method of forming a circuit.

Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the following description, “parts” and “%” indicate “parts by mass” and “% by mass”, respectively, unless otherwise specified.

(Manufacture of dry film for coverlay)
Production Example 1
200 parts of Nipol 1072 (trade name, manufactured by Nippon Zeon Co., Ltd., nitrile content 27%) as carboxyl group-containing acrylonitrile butadiene rubber, 320 parts of Epicoat 1001 (trade name, manufactured by Yuka Shell Co., Ltd., epoxy equivalent 470) as bisphenol A type epoxy resin, cresol 147 parts of YDCN-703P (trade name, epoxy equivalent 210, manufactured by Toto Kasei Co., Ltd.) as a novolac epoxy resin, 146 parts of BRG558 (trade name, hydroxyl value 106, manufactured by Showa Polymer Co., Ltd.) as a phenol novolac resin, SPB-100 as a phenoxyphosphazene oligomer (Product name, phosphorus content 13%, manufactured by Otsuka Chemical Co., Ltd.) 65 parts by mass, PHOSMEL200 as a melamine polyphosphate (product name, phosphorus content 12%, manufactured by Nissan Chemical Co., Ltd.) 163 parts, Antage BHT (kawa 1 part by Chemical Industry Co., Ltd.), 100 parts H-42I (trade name by Showa Denko) as aluminum hydroxide, CAB-LX905 (trade name by Toyo Ink Co., Ltd.) as black pigment, 5% carbon content, average primary A mixture of 450 parts of a particle size of 0.25 μm) and 0.5 part of 2-ethyl-4-methylimidazole as a curing accelerator was mixed with propylene glycol monomethyl ether (PGM) and methyl ethyl ketone (mixing mass ratio 30:70) as a solvent. In addition, a resin composition having a solid content of 40% was prepared.

The resin composition is kneaded with three rolls and prepared so that the particle size of the component insoluble in the solvent is 10 μm or less, and then this preparation is formed into a single-side matte type 25 μm thick biaxially oriented polypropylene. Roll on the mat (surface treatment) side of the film, Treffan YM17S (trade name, surface roughness (Ra) = 0.8 to 1.2 μm, manufactured by Toray Industries Inc.) so that the thickness after drying is 25 μm It was applied with a coater and dried by heating to prepare a dry film A for coverlay.

Production Example 2
A resin composition was prepared in the same manner as in Production Example 1, except that 65 parts of SPE-100 (trade name, phosphorous content 13%, manufactured by Otsuka Chemical Co., Ltd.) was used as the phenoxyphosphazene oligomer instead of SPB-100 (trade name). Further, using this, a coverlay dry film B having a thickness of 25 μm was produced.

Production Example 3
A resin composition was prepared in the same manner as in Production Example 1 except that the blending amount of PHOSMEL 200 (trade name) of melamine polyphosphate was 200 parts and SPB-100 (trade name) of phenoxyphosphazene oligomer was not blended. Further, using this, a coverlay dry film C having a thickness of 25 μm was produced.

Production Example 4
A resin composition was prepared in the same manner as in Production Example 1 except that 163 parts of MPP-B (trade name, phosphorous content 13%, manufactured by Sanwa Chemical Co., Ltd.) was used as melamine polyphosphate instead of PHOSMEL200 (trade name). Further, using this, a dry film D for coverlay having a thickness of 25 μm was produced.

Production Example 5
A resin composition was prepared in the same manner as in Production Example 1, except that the amount of SPB-100 (trade name) of the phenoxyphosphazene oligomer was 200 parts and PHOSMEL 200 (trade name) of melamine polyphosphate was not blended. Further, using this, a coverlay dry film E having a thickness of 25 μm was produced.

Production Example 6
The black pigment CAB-LX905 (trade name) is not blended, and instead of Trefan YM17S (trade name), a biaxially stretched polypropylene film with a thickness of 25 μm on one side, a release agent layer on one side 38E-CTR2 (trade name, surface roughness (Ra) = 0.2 μm or less, manufactured by Fujimori Kogyo Co., Ltd.) which is a 38 μm thick polyethylene terephthalate (PET) film with a release agent provided with A resin composition was prepared in the same manner as in Example 1, and a coverlay dry film F having a thickness of 25 μm was prepared using the resin composition.

Production Example 7
Polyethylene terephthalate (PET) with a release agent of 38 μm thickness with a release agent layer provided on one side instead of Trefan YM17S (trade name) which is a biaxially stretched polypropylene film with a thickness of 25 μm on one side. A resin composition was prepared in the same manner as in Production Example 1 except that 38E-CTR2 (trade name, manufactured by Fujimori Kogyo Co., Ltd., surface roughness (Ra) = 0.2 μm or less), which was a film, was used. A dry film G for coverlay having a thickness of 25 μm was produced.

Production Example 8
A resin composition prepared in the same manner as in Production Example 1 was added to Trefan YM17S (trade name, surface roughness (Ra) = 0.8, manufactured by Toray Industries, Inc.), which is a one-side matte type biaxially oriented polypropylene film with a thickness of 25 μm. A dry film H for coverlay was prepared by applying the film to a mat (surface treatment) surface of (˜1.2 μm) with a roll coater so that the thickness after drying was 75 μm, and drying by heating.

Table 1 shows the compositions (excluding the solvent) of the resin compositions used in the production of the coverlay dry films of Production Examples 1 to 8.

Example 1
A flexible double-sided copper-clad Espanex MB 18-25-18 FRG (trade name, manufactured by Nippon Steel Chemical Co., Ltd.) with a 18 μm thick copper foil on both sides of a 25 μm thick polyimide film is used to form circuits on both sides. After that, the coverlay dry film A and the coverlay dry film F previously produced are superimposed on each circuit formation surface (first and second circuit formation surfaces), respectively, and heated at 160 ° C. under pressure. Adhesion was performed by heating and pressing at 4 MPa for 1 hour to produce a flexible wiring board for evaluation.

Example 2
A flexible wiring board for evaluation was produced in the same manner as in Example 1 except that the coverlay dry film B was superposed on one circuit forming surface instead of the coverlay dry film A.

Example 3
A flexible wiring board for evaluation was produced in the same manner as in Example 1 except that the coverlay dry film C was superposed on one circuit formation surface instead of the coverlay dry film A.

Example 4
A flexible wiring board for evaluation was produced in the same manner as in Example 1 except that the coverlay dry film D was superposed on one circuit forming surface instead of the coverlay dry film A.

Example 5
A flexible wiring board for evaluation was produced in the same manner as in Example 1 except that the coverlay dry film E was superposed on one circuit formation surface instead of the coverlay dry film A.

Example 6
After using Epanex MB 18-25-18 FRG (trade name), a flexible double-sided copper-clad board, after forming circuits on both sides, overlay the coverlay dry film A on one circuit-forming surface, Adhesion was carried out by heating and pressing at a temperature of 160 ° C. and a pressure of 4 MPa for 1 hour. Next, a photosensitive liquid coverlay KSR-800 (trade name, manufactured by Kyocera Chemical Co., Ltd.) was applied to the other circuit formation surface by screen printing using a 150 mesh polyester screen to a thickness of 20 to 30 μm, and 80 ° C. A coating film was formed by drying with a hot air dryer for 30 minutes.

A negative film of a resist pattern was brought into contact with this coating film and irradiated with ultraviolet rays using an ultraviolet irradiation exposure apparatus (exposure amount: 400 mJ / cm ² ), and then a 1% sodium carbonate aqueous solution was added at about 0.10 to 0.15 MPa. The film was developed by spraying for 1 minute at a pressure of 1 to dissolve and remove the unexposed portion, and further thermally cured at 150 ° C. for 60 minutes to form a photosensitive resin layer, and a flexible wiring board for evaluation was produced.

Example 7
After using Epanex MB 18-25-18 FRG (trade name), a flexible double-sided copper-clad board, after forming circuits on both sides, overlay the coverlay dry film A on one circuit-forming surface, Adhesion was carried out by heating and pressing at a temperature of 160 ° C. and a pressure of 4 MPa for 1 hour. Next, a polyimide film coverlay TFA-560-1215 (trade name, manufactured by Kyocera Chemical Co., Ltd.) was laminated on the other circuit forming surface and integrated to produce a flexible wiring board for evaluation.

Example 8
A flexible wiring board for evaluation was produced in the same manner as in Example 1 except that the coverlay dry film G was superposed on one circuit formation surface instead of the coverlay dry film A.

Example 9
A flexible wiring board for evaluation was produced in the same manner as in Example 1 except that the coverlay dry film F was superposed on one circuit formation surface instead of the coverlay dry film A.

Comparative Example 1
A flexible wiring board for evaluation was produced in the same manner as in Example 7, except that the coverlay dry film H was superposed on one circuit formation surface instead of the coverlay dry film A.

Comparative Example 2
A flexible double-sided copper-clad Espanex MB 18-25-18 FRG (trade name) was used to form circuits on both sides, and polyimide film coverlay TFA-560-1215 (manufactured by Kyocera Chemical Co., Ltd.) Product name) were laminated and integrated to produce a flexible wiring board for evaluation.

Comparative Example 3
Except for laminating polyimide film coverlay TFA-560-1215 (trade name) and further printing thermosetting printing ink black ink CCR-1200B (trade name, manufactured by Asahi Kaken Co., Ltd.) to a thickness of 15 μm, A flexible wiring board for evaluation was produced in the same manner as in Comparative Example 2.

Comparative Example 4
A polyimide film coverlay TFA-560-1215 (trade name) is laminated, and a thermosetting printing ink black ink CCR-1200B (trade name, manufactured by Asahi Kaken Co., Ltd.) is further printed to a thickness of 15 μm. Instead of laminating polyimide film cover lay TFA-560-1215 (trade name) on the circuit forming surface, photosensitive liquid cover lay KSR-800 (trade name) 20 to 20 by screen printing using a 150 mesh polyester screen. The whole surface is applied to a thickness of 30 μm, dried with a hot air dryer at 80 ° C. for 30 minutes to form a coating film, a negative film of a resist pattern is brought into contact with this coating film, and ultraviolet irradiation is performed using an ultraviolet irradiation exposure apparatus. the (exposure dose 400 mJ / cm ²⁾ after 1% strength aqueous sodium carbonate about 0.10 ~ 0.15MP Evaluation was conducted in the same manner as in Comparative Example 2 except that the photosensitive resin layer was formed by spray development for 1 minute at a pressure of 150 ° C., dissolving and removing unexposed portions, and further thermosetting at 150 ° C. for 60 minutes. A flexible wiring board was prepared.

About flexible wiring boards obtained in the above examples and comparative examples, bleeding out resistance, stiffness resistance, bending resistance, MIT folding resistance, transmittance and reflectance, surface roughness (Ra), mounting on glass substrate And flame retardancy were evaluated based on the following methods and criteria. These results are shown in Table 2.

In addition, Example 1 as an example in which a roughened black coverlay is arranged on the light incident surface side, Example 8 as an example in which a smooth black coverlay is arranged, and an example in which a polyimide film coverlay is further arranged Comparative Example 2 was prepared as above, and the results of measuring the transmittance and the reflectance with respect to the incident light are shown in FIGS.

[Bleed-out resistance]
After the flexible wiring board for evaluation was exposed to a super accelerated high temperature and high humidity life test (HAST) bath at 121 ° C. and 85% RH for 100 hours, the surface of each wiring board was observed with an optical microscope (100 times), The presence or absence of bleed was examined and evaluated according to the following criteria.
○… No bleed, ×… Bleed

[Stiffness]
Cut out a measurement sample of 1cm x 10cm from the flexible wiring board for evaluation, fold it back in half with respect to the length direction, and push and pull the repulsive load when the vertical distance 5mm inside from the end is 2mm. Measured with a gauge.

[Bending resistance]
The evaluation flexible wiring board was repeatedly bent 180 ° by goby folding, and the number of times until a crack was generated in the coverlay by visual observation and observation with an optical microscope (200 times) was measured.

[MIT folding resistance]
In accordance with JIS C 6471 8.2, the number of times until the sample broke at an R (curvature radius) of 0.38 mm and a load of 4.9 N was measured by an MIT folding resistance tester and evaluated according to the following criteria.
○ ... 300 times or more, Δ ... 100 times or more and less than 300 times, × ... less than 100 times

[Transmissivity, reflectivity]
The light transmittance of 500 nm (visible light region) was measured by U-best V-570 (manufactured by JASCO). Moreover, the reflectance of light of 500 nm was similarly measured about the sample whose transmittance | permeability is 10% or less.

[Surface roughness (Ra)]
Using a surface roughness measuring machine SE-3300 (manufactured by Kosaka Laboratories), the surface roughness (Ra) of the coverlay formed by the coverlay dry film was measured.

[Mountability on glass substrate]
One end of the flexible wiring board for evaluation and one side of the glass substrate were fixed, bent so that the first circuit forming surface side was inside, and fixed to the back surface of the glass substrate with double-sided tape. The front and back sides of the glass substrate to which the flexible wiring board is fixed are fixed with metal plates, and a temperature cycle test (−25 ° C./125° C., held for 30 minutes each) is carried out for 1000 cycles. It checked visually and evaluated by the following reference | standard.
○… No bulge or deflection × ×: bulge or deflection occurs

[Flame retardance]
Flame retardancy was measured according to the UL94VTM-0 flame retardancy standard and evaluated according to the following criteria.
○… Satisfies the UL94VTM-0 standard ×… Does not meet the UL94VTM-0 standard (sample burns)

The flexible wiring board of the present invention is excellent in flexibility and folding resistance, and is particularly suitable for the use of a flexible wiring board that is required to be thin and have low springback properties.

DESCRIPTION OF

SYMBOLS

1, 10 ... Flexible wiring board, 2 ... Flexible wiring board main body, 2a ... Base material, 2b, 2c ... Circuit, 3 ... (1st) coverlay, 4 ... (2nd) coverlay, 5 ... Mounting components, 11 DESCRIPTION OF SYMBOLS ... Liquid crystal display module, 12 ... Liquid crystal display panel, 16 ... Imaging module, 50 ... Dry film for coverlays, 51 ... Support film, 52 ... Layer which consists of a non-halogen flame-retardant resin composition.

Claims

A substrate made of a polyimide film, a circuit provided on one main surface of the substrate, and a coverlay covering the surface of the circuit,
The flexible printed circuit board, wherein the coverlay is formed of a dry film for coverlay and has a thickness of 10 to 50 μm.
The coverlay dry film comprises (A) an epoxy resin, (B) an epoxy resin curing agent, (C) a curing accelerator, (D) a synthetic rubber, (E) a phosphazene compound, (F) a polyphosphate compound, and ( The flexible wiring board according to claim 1, comprising G) a non-halogen flame-retardant resin composition containing an inorganic filler as an essential component.
3. The flexible wiring board according to claim 2, wherein the component (D) is contained in an amount of 10 to 30% by mass with respect to the entire components (A) to (D).
4. The flexible wiring board according to claim 2, wherein the component (E) is contained in an amount of 3 to 10 parts by mass with respect to 100 parts by mass of the total amount of the components (A) to (D).
The component (F) is contained in an amount of 5 to 30 parts by mass with respect to 100 parts by mass of the total amount of the components (A) to (D). Flexible wiring board.
The flexible wiring board according to claim 2, wherein the component (E) includes a phosphazene compound represented by the following general formula (1) or (2).

(In the formula, Ph represents a phenyl group, and m represents an integer of 3 to 25.)

Wherein X 1 represents a group —N═P (OPh) 3 or a group —N═P (O) OPh, and Y 1 represents a group —N═P (OPh) 4 or a group —N═P (O ) (OPh) 2 (where Ph represents a phenyl group), Ph represents a phenyl group, and n represents an integer of 3 to 10,000. )
The flexible wiring board according to any one of claims 2 to 6, wherein the component (F) includes at least one selected from the group consisting of melamine polyphosphate, melam polyphosphate, and melem polyphosphate.
The flexible wiring board according to any one of claims 2 to 7, wherein the non-halogen flame retardant resin composition further contains (H) a colorant.
The flexible wiring board according to any one of claims 2 to 8, wherein the component (H) is carbon black having a primary particle diameter of 0.01 to 1 µm.
10. The flexible wiring board according to claim 1, wherein the coverlay has a surface roughness (Ra) of 0.3 to 5.0 μm.
(A) epoxy resin, (B) epoxy resin curing agent, (C) curing accelerator, (D) synthetic rubber, (E) phosphazene compound, (F) polyphosphate compound and (G) inorganic filler as essential components A dry film for coverlays comprising a layer comprising a non-halogen flame retardant resin composition as defined above on a support film.
12. The support film has a surface having a surface roughness (Ra) of 0.3 to 5.0 μm, and a layer made of the non-halogen flame retardant resin composition is provided on the surface. The dry film for coverlay as described.
Forming a circuit on one main surface of the substrate made of polyimide film;
The coverlay dry film according to claim 11 or 12 is superimposed and heated on the surface of the circuit with the non-halogen flame-retardant resin composition layer side facing the circuit side, and the support film is And a step of forming a coverlay to remove the flexible wiring board.