TWI685281B - Laminated structure - Google Patents

Abstract

Provides a structure that can meet the performance required as an insulating film of a flexible printed wiring board and is applicable even in the process of forming a bent portion and a mounted portion at one time. In addition, a flexible printed wiring board having its cured product as a protective film (for example, a cover film or a solder resist) is provided.

It has an adhesive layer (A) made of an alkali-developable resin composition, and a protective layer (B) made of a photosensitive resin composition formed above the adhesive layer (A), and the adhesive layer (A) and protection The ratio of the film thickness of the layer (B) is A/B=0.5~50, and the ratio of the development speed (a) of the subsequent layer (A) to the development speed (b) of the protective layer (B) is a/b=1.1~ The laminated structure of 100 uses the dry film and flexible printed wiring board of the laminated structure.

Description

Laminated structure

The present invention relates to a laminated structure, in particular, a laminated structure having an insulating film for a flexible printed wiring board, a dry film using the same, and a flexible printed wiring board.

In recent years, the popularization of smart phones and tablet terminals has led to the miniaturization and thinning of electronic devices, making the size of circuit boards smaller. Therefore, the applications of flexible printed wiring boards that can be folded and stored are increased, and the reliability of the flexible printed wiring boards is higher than in the past.

In contrast, currently, as an insulating film for ensuring the insulation reliability of flexible printed wiring boards, a hybrid packaging process is widely adopted, and the bent portion (bending portion) is made of a polymer having excellent mechanical properties such as heat resistance and bendability. A cover film with acetylenimine as a base (for example, refer to Patent Documents 1 and 2); and the mounting portion (non-curved portion) uses a photosensitive resin composition that is excellent in electrical insulation and the like and can be finely processed.

That is, the coating film based on polyimide with excellent mechanical properties such as heat resistance and bendability needs to be punched through the die to add Work, so it is less suitable for fine wiring. Therefore, it is necessary to partially use an alkali-developable photosensitive resin composition (solder resist) that can be processed by photolithography for a wafer mounting portion that requires fine wiring.

Prior technical literature Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 62-263692

Patent Document 2: Japanese Patent Laid-Open No. 63-110224

In this way, in the manufacturing process of the flexible printed wiring board, the mixing process of the step of attaching the cover film and the step of forming the solder resist cannot be used, so the cost and workability are poor.

In view of this, although the application of an insulating film as a solder resist or an insulating film for a covering film to both the solder resist and the covering film of a flexible printed wiring board has been discussed, materials that can fully meet the performance requirements of both But it has not yet reached practicality. Especially for flexible printed wiring boards, materials that achieve both the following characteristics are required: alkali developability required for insulating films as solder resists, and heat resistance and heat resistance required for insulating films as cover films Mechanical properties such as flexibility.

The object of the present invention here is to provide a structure that can satisfy the performance required as an insulating film of a flexible printed wiring board and can be applied even in the process of forming a bent portion and a mounted portion at one time. In addition, provide Flexible printed wiring board using its hardened material as a protective film (for example, cover film or solder resist).

In order to solve the aforementioned problems, the present invention is characterized by having an adhesive layer (A) formed of an alkali-developable resin composition, and a protective layer formed of a photosensitive resin composition formed on the adhesive layer (A) ( B), and the ratio of the thickness of the adhesive layer (A) to the protective layer (B): A/B=0.5-50; the development speed (a) of the adhesive layer (A) and the protective layer (B) The ratio of the developing speed (b): a/b=1.1~100.

It is preferable that the laminated structure of the present invention can be patterned by light irradiation regardless of the adhesive layer (A) and the protective layer (B). In addition, the laminated structure of the present invention can be applied to at least any one of the bent portion and the non-bent portion of the flexible printed wiring board; specifically, the cover film, the solder resist and the At least any one of the interlayer insulating materials is feasible.

In addition, the dry film of the present invention is characterized in that at least one side of the laminated structure of the present invention is supported or protected by a thin film.

In addition, the feature of the flexible printed wiring board of the present invention is that the laminated structure layer of the present invention is directly formed on the flexible printed wiring board, or the laminated structure layer is formed on the dry film of the present invention; Irradiation is used to pattern the pattern, and the pattern is formed once with the developer to obtain an insulating film. Furthermore, the "pattern" in the present invention refers to a hardened product of a pattern shape, that is, an insulating film.

According to the present invention, it is possible to realize a layered structure that can satisfy the performance required as an insulating film for a flexible printed wiring board, and is also suitable for a process of forming a bent portion and a mounted portion at a time, and a dry film and a dry film using the structure Flexible printed wiring board.

1‧‧‧ Flexible printed wiring substrate

2‧‧‧Copper circuit

3‧‧‧Next layer

4‧‧‧Protection layer

5‧‧‧Mask

[Fig. 1] A step diagram schematically showing an example of the manufacturing method of the flexible printed wiring board of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Laminated structure)

The laminated structure system of the present invention has an adhesive layer (A) made of an alkali-developable resin composition, and a protective layer (B) formed of a photosensitive resin composition formed on the adhesive layer (A), And the ratio of the film thickness of the adhesive layer (A) and the protective layer (B) is A/B=0.5~50, the development speed (a) of the adhesive layer (A) and the development speed of the protective layer (B) The ratio of (b) is a/b=1.1~100.

In order to use alkaline developer for patterning, the resin composition Must have alkali solubility. In the case of a laminated structure, if a resin composition excellent in heat resistance is used for the protective layer, it is difficult to impart solubility to the resin composition excellent in heat resistance, so the development speed is slow, resulting in difficulty in patterning The problem.

In order to solve this problem, the inventors focused on the film thickness and development speed of the protective layer and the adhesive layer and conducted in-depth discussions. As a result, they found that by allowing the ratio of the film thickness of the protective layer and the adhesive layer and the development of the protective layer and the adhesive layer If the speed ratio falls within the aforementioned range, the aforementioned problems can be solved and the invention can be completed.

That is, it was found that a protective layer using a resin composition with a slower development speed was laminated over a subsequent layer using a resin composition with a faster development speed than the resin composition of the protective layer, and the When the ratio of the film thickness and the ratio of the development speed fall within the aforementioned ranges, even if the development speed of the protective layer is slow and it is difficult to pattern through alkali development, and even if residues are present, the development speed of the subsequent layer is fast, which results in The two are completely washed away, so that the overall development speed of the laminated structure falls within the realized range.

In order to make the mechanical properties such as alkali developability, heat resistance, and flexibility more favorable, the ratio of the aforementioned film thickness is A/B=0.5-50, preferably A/B=1.0-30, and more preferably A/B =2.0~10, and the ratio of the aforementioned development speed is a/b=1.1-100, preferably a/b=2.0-50, more preferably a/b=3.0-30.

When the ratio of the film thickness is A/B=50 or less, since the protective layer (B) having heat resistance accounts for a large proportion of the layer thickness of the laminated structure, its The developability is good and sufficient heat resistance can be obtained. Moreover, when A/B=0.5 or more, since the ratio of the adhesive layer (A) with good developability is large, it has good heat resistance and can be patterned by alkali development.

When the ratio of the development speed is a/b=1.1 or more, the development speed of the protective layer (B) and the adhesion layer (A) relative to the development difficulty is relatively fast, so that it can be patterned by alkali development. In addition, when a/b=100 or less, the solubility in the alkali aqueous solution of the adhesive layer (A) is appropriate, and the pattern shape is stable, so that various characteristics such as plating resistance are also good.

During development of the laminated structure, the time required for the protective layer and the adhesive layer to dissolve in the alkaline aqueous solution is defined as the development time [sec], and when the film thickness of each layer is determined as the film thickness [μm], the development speed is as follows Expression.

Development speed [μm/sec] = film thickness [μm] / development time [sec]

(Protective layer (B))

The composition of the photosensitive resin composition of the protective layer (B) is not particularly limited. For example, a compound containing a carboxyl group-containing resin or a carboxyl group-containing photosensitive resin and having an ethylenically unsaturated bond can be used as a solder resist composition in the past. , A photo-curable thermosetting resin composition of a photopolymerization initiator and a thermoreactive compound, and a photosensitive thermosetting resin composition containing: a carboxyl group-containing resin, a photobase generator, and a thermoreactive compound.

Among them, the protective layer (B) is preferably composed of a resin composition containing an alkali-soluble resin having an amide imide ring or an amide imide precursor skeleton, which is excellent in heat resistance and toughness.

In the present invention, the so-called alkali-soluble resin having an amide imide ring or amide imide precursor skeleton means an alkali-soluble group having a carboxyl group or an acid anhydride group, etc., and an amide imide ring or amide imide precursor skeleton. . For introducing an imide ring or an imide precursor skeleton into the alkali-soluble resin, a well-known and usual method can be used. For example, a resin obtained by allowing a carboxylic anhydride component to react with either or both of an amine component and an isocyanate component can be mentioned. The imidate can be thermally imidate or chemically imidate, or they can be used in combination.

Here, the carboxylic acid anhydride component includes tetracarboxylic acid anhydride and tricarboxylic acid anhydride, but it is not limited to these acid anhydrides, as long as it is a compound having an acid anhydride group and a carboxyl group that react with an amine group or an isocyanate group, it may contain Use its derivatives. In addition, these carboxylic anhydride components can be used alone or in combination.

Examples of the tetracarboxylic anhydride include pyromellic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 3,3',4,4'-biphenyltetracarboxylic acid. Acid dianhydride, 4,4'-oxydiphthalic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,3”,4,4”-terphenylphenyltetracarboxylic dianhydride , 3,3''',4,4'''-Tetraphenylphenyltetracarboxylic dianhydride, 3,3'''',4,4''''-Pentaphenyltetracarboxylic dianhydride , Methylene-4,4'-diphthalic dianhydride, 1,1-vinylidene-4,4'-diphthalic dianhydride, 2,2-propylene-4,4'-diphthalide Acid dianhydride, 1,2-ethylidene-4,4'-diphthalic dianhydride, 1,3-trimethylene-4,4'-diphthalic dianhydride, 1,4-tetramethylene -4,4'-diphthalic dianhydride, 1,5-pentamethylene-4,4'-diphthalic dianhydride, thio-4,4'-diphthalic dianhydride, sulfonyl- 4,4'-Diphthalic dianhydride, 1,3-bis(3,4-dicarboxyphenyl)-1,1,3,3-tetramethylsiloxane dianhydride, 1,3-bis( 3,4-dicarboxyphenyl)phthalic anhydride, 1,4- Bis(3,4-dicarboxyphenyl)phthalic anhydride, 1,3-bis(3,4-dicarboxyphenoxy)phthalic anhydride, 1,4-bis(3,4-dicarboxyphenoxy ) Phthalic anhydride, 1,3-bis[2-(3,4-dicarboxyphenyl)-2-propyl]phthalic anhydride, 1,4-bis[2-(3,4-dicarboxyphenyl )-2-propyl]phthalic anhydride, bis[3-(3,4-dicarboxyphenoxy)phenyl]methanedianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1, 2,5,6-Naphthalene tetracarboxylic dianhydride, 3,4,9,10-perylene tetracarboxylic dianhydride, 2,3,6,7-anthracene tetracarboxylic dianhydride, 1,2,7,8 -Phenanthrene tetracarboxylic dianhydride, 1,2,3,4-butane tetracarboxylic dianhydride, 1,2,3,4-cyclobutane tetracarboxylic dianhydride, cyclopentane tetracarboxylic dianhydride, Cyclohexane-1,2,3,4-tetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride, 3,3',4,4'-bicyclohexyl tetra Carboxylic dianhydride, carbonyl-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, methylene-4,4'-bis(cyclohexane-1,2-dicarboxyl Acid) dianhydride, 1,2-ethylidene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, 1,1-vinylidene-4,4'-bis( (Cyclohexane-1,2-dicarboxylic acid) dianhydride, 2,2-propylene-4,4'-bis(cyclohexane-1,2-dicarboxylic acid) dianhydride, ethylene glycol Trimellitic dianhydride, 1,2-(ethylidene)bis(trimellitic anhydride), 1,3-(trimethylene)bis(trimellitic anhydride), 1,4-(tetramethylene)bis(trimellitic anhydride), 1,5-(pentamethylene)bis(trimellitic anhydride), 1,6-(hexamethylene)bis(trimellitic anhydride), 1,7-(heptamethylene)bis(trimellitic anhydride), 1,8-( Octamethylene)bis(trimellitic anhydride), 1,9-(nonamethylene)bis(trimellitic anhydride), 1,10-(decamethylene)bis(trimellitic anhydride), 1,12-(dodecylmethylene ) Bis (trimellitic anhydride), 1,16-(hexamethylene) bis(trimellitic anhydride), 1,18-(octadecylidene) bis(trimellitic anhydride), etc.

Examples of tricarboxylic anhydrides include trimellitic anhydride and hydrogenated trimellitic anhydride.

As the amine component, aliphatic diamines and aromatic diamines can be used Diamines such as diamines and polyamines such as aliphatic polyetheramines are not limited to these amines. In addition, these amine components can also be used alone or in combination.

Examples of the diamine include p-phenylene diamine (PPD), 1,3-phenylenediamine, 2,4-toluenediamine, 2,5-toluenediamine, and 2,6-toluenediamine. Monophenyl nuclear diamines such as amines, diamino diamines such as 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether Phenyl ethers, 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4' -Diaminobiphenyl, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diamine Diphenyl nuclear diamine such as diphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 1,3-bis(3-aminophenyl sulfide)benzene, 1,3-bis (4-aminophenyl sulfide) benzene, 1,4-bis (4-aminophenyl sulfide) benzene and other triphenyl nuclear diamine, 3,3'-bis(3-aminophenoxy ) Biphenyl, 3,3'-bis(4-aminophenoxy) biphenyl, 4,4'-bis(3-aminophenoxy) biphenyl, 2,2-bis (3-(3 -Aminophenoxy)phenyl]propane, 2,2-bis[3-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy ) Phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane and other aromatic diamines such as tetraphenyl nuclear diamine; 1,2-diaminoethane , 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane and other aliphatic diamines. Examples of the aliphatic polyetheramines include ethylene glycol (and/or) propylene glycol-based polyamines and the like. In addition, amines having a carboxyl group as described below can also be used.

Examples of the amine having a carboxyl group include diaminobenzoic acids such as 3,5-diaminobenzoic acid, 2,5-diaminobenzoic acid, and 3,4-diaminobenzoic acid. 5-bis(3-aminophenoxy)benzoic acid, 3,5-bis(4-amino) (Phenoxy) benzoic acid and other amino phenoxy benzoic acids, 3,3'-diamino-4,4'-dicarboxybiphenyl and other carboxy biphenyl compounds, 3,3'-diamine -4,4'-dicarboxydiphenylmethane, 3,3'-dicarboxy-4,4'-diaminodiphenylmethane, 2,2-bis[4-amino-3-carboxybenzene Carboxyldiphenylalkanes such as propane, 3,3'-diamino-4,4'-dicarboxydiphenyl ether, 4,4'-diamino-3,3'-dicarboxydiphenyl Carboxy diphenyl ether compounds such as ethers, 3,3'-diamino-4,4'-dicarboxydiphenyl sulfone, 4,4'-diamino-3,3'-dicarboxydiphenyl ash Such as diphenyl benzene compound and so on.

As the isocyanate component, aromatic diisocyanates and their isomers or polymers, diisocyanates such as aliphatic diisocyanates, alicyclic diisocyanates and their isomers, or other general diisocyanates can be used , But not limited to these isocyanates. In addition, these isocyanate components can also be used alone or in combination.

Examples of the diisocyanate include 4,4′-diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, stubble diisocyanate, biphenyl diisocyanate, diphenyl sulfone diisocyanate, and diphenyl Aromatic diisocyanates such as ether diisocyanate and their isomers, polymers, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate and other aliphatic diisocyanates, or hydrogenated aromatics Alicyclic diisocyanates and isomers of group diisocyanates, or other commonly used diisocyanates.

As described above, the alkali-soluble resin having an amide imide ring or amide imine precursor skeleton may also contain an amide bond. It may be an amide bond obtained by the reaction of isocyanate and carboxylic acid, or may be obtained by other reactions. again Alternatively, it may have a bond formed by other additions and condensations.

In addition, as for the introduction of the amide imine ring or the amide imine precursor skeleton of the alkali-soluble resin, a well-known and commonly used alkali-soluble polymer or oligomer having either or both of a carboxyl group and an acid anhydride group is used. Polymers or monomers may also be used; for example, these well-known and commonly used alkali-soluble resins may be used alone or in combination with the above-mentioned carboxylic acid anhydride component and reacted with the above-mentioned amine/isocyanate.

For the synthesis of such an alkali-soluble resin having an alkali-soluble group and an amide imine ring or amide imine precursor skeleton, a well-known and commonly used organic solvent can be used. As the organic solvent, there is no problem as long as it does not react with carboxylic acid anhydrides, amines, and isocyanates of the raw materials, and can dissolve these raw materials, and its structure is not particularly limited. Among them, because of the high solubility of the raw materials, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylsulfoxide, Aprotic solvents such as γ-butyrolactone are preferred.

As described above, the alkali-soluble resin having an alkali-soluble group such as a carboxyl group or an acid anhydride group and an amide imide ring or amide imide precursor skeleton, in order to correspond to the photolithography step, its acid value is 20 to 200 mgKOH/g Preferably, 60~150mgKOH/g is better. When the acid value is 20 mgKOH/g or more, the solubility in alkalis increases and the developability is good. Furthermore, since the degree of crosslinking with the thermosetting component after light irradiation is high, a sufficient development contrast can be obtained. In addition, when the acid value is 200 mgKOH/g or less, the so-called hot mist can be suppressed in the PEB (POST EXPOSURE BAKE) step after light irradiation described later, and the flow margin can be increased.

In addition, after considering the developability and the characteristics of the cured coating film, the molecular weight of the alkali-soluble resin is preferably a mass average molecular weight of 1,000 to 100,000, and more preferably 2,000 to 50,000. When the molecular weight is 1,000 or more, sufficient development resistance and hardening physical properties can be obtained after exposure and PEB. In addition, when the molecular weight is 100,000 or less, the alkali solubility increases and the developability improves.

A resin composition containing an alkali-soluble resin having an amide imide ring or an amide imide precursor skeleton, when using a photobase generator, usually contains a photobase generator and a heat-reactive compound in addition to the alkali-soluble resin; When a photopolymerization initiator is used, in addition to the alkali-soluble resin, a photopolymerization initiator and a compound having an ethylenically unsaturated bond are contained. In addition, as the resin component, a carboxyl group-containing urethane resin, a carboxyl group-containing novolac resin, and the like may be used in combination.

A photobase generator is a compound that changes its molecular structure through the irradiation of light such as ultraviolet light and visible light, or by molecular cleavage, generates more than one type of alkalinity that can serve as a polymerization catalyst function for heat-reactive compounds described below substance. Examples of the basic substance system include secondary amines and tertiary amines.

Examples of the photobase generator include, for example, α-aminoacetophenone compounds, oxime ester compounds, or having an oxyimino group, N-methylated aromatic amine group, and N-acetylated aromatic Compounds having a substituent such as a family amine group, a benzylcarbamate group, an alkoxybenzylcarbamate group, etc., among which oxime ester compounds and α-aminoacetophenone compounds are preferred. The α-aminoacetophenone compound is particularly preferably one having 2 or more nitrogen atoms.

The α-aminoacetophenone compound-based molecule has a benzoin ether bond, and after being irradiated with light, it cracks inside the molecule to generate an alkaline substance (amine) that functions as a hardening catalyst. As a specific example of the α-aminoacetophenone compound, (4-morpholinobenzoyl)-1-benzyl-1-dimethylaminopropane (IRGACURE 369, trade name, BASF JAPAN Corporation) can be used System), 4-(methylthiobenzyl)-1-methyl-1-morpholinylethane (IRGACURE 907, trade name, manufactured by BASF JAPAN) or 2-(dimethylamino) -2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone (IRGACURE 379, trade name, manufactured by BASF JAPAN), etc. Commercially available compounds or their solutions.

As the oxime ester compound, any compound that can generate an alkaline substance by light irradiation can be used. As the oxime ester compound, commercially available products include CGI-325, IRGACURE-OXE01, IRGACURE-OXE02 manufactured by BASF JAPAN, N-1919, NCI-831 manufactured by ADEKA, and the like. In addition, as described in Japanese Patent No. 4344400, a compound having two oxime ester groups in the molecule can also be suitably used.

Such photobase generators may be used alone or in combination of two or more. The compounding amount of the photobase generator in the resin composition is preferably 0.1 to 40 parts by mass, more preferably 0.1 to 30 parts by mass relative to 100 parts by mass of the heat-reactive compound. At 0.1 parts by mass or more, a good contrast in development resistance of the light-irradiated portion/non-irradiated portion can be obtained. In addition, when the amount is 40 parts by mass or less, the characteristics of the cured product improve.

Thermally reactive compounds have a hardening reaction due to heat Examples of the functional group resin include epoxy resins and polyfunctional oxetane compounds.

The above-mentioned epoxy resin is a resin having an epoxy group, and any well-known epoxy resin can be used. Specifically, a bifunctional epoxy resin having two epoxy groups in the molecule, and a multifunctional epoxy resin having a large number of epoxy groups in the molecule can be given. In addition, it may be a hydrogenated bifunctional epoxy compound.

Examples of the epoxy resin include bisphenol A epoxy resin, brominated epoxy resin, novolac epoxy resin, bisphenol F epoxy resin, hydrogenated bisphenol A epoxy resin, and epoxy resin. Propylamine type epoxy resin, hydantoin type epoxy resin, alicyclic epoxy resin, trihydroxyphenylmethane type epoxy resin, bixylenol type or biphenol type epoxy resin or mixtures thereof ; Bisphenol S type epoxy resin, bisphenol A novolak type epoxy resin, tetraphenol ethane type epoxy resin, heterocyclic epoxy resin, diglycidyl phthalate resin, tetrapropylene oxide Xylenol ethane resin, epoxy resin containing naphthyl group, epoxy resin with dicyclopentadiene skeleton, epoxy methacrylate copolymer epoxy resin, cyclohexyl maleimide and methyl Copolymer epoxy resin based on glycidyl acrylate, CTBN modified epoxy resin, etc.

These epoxy resins can be used alone or in combination of two or more.

As the compounding amount of the heat-reactive compound, the equivalent ratio to the alkali-soluble resin (alkali-soluble group such as carboxyl group: thermally-reactive group such as epoxy group) is preferably 1:0.1 to 1:10. With such a ratio The range can be good for developing and easy to form fine patterns. The above equivalent ratio is preferably 1:0.2~1:5.

As the photopolymerization initiator system, a well-known photopolymerization initiator can be used, and examples thereof include an α-aminoacetophenone-based photopolymerization initiator, an acylphosphine oxide-based photopolymerization initiator, a benzoin compound, Acetophenone compounds, onion quinone compounds, thioxanthone compounds, ketal compounds, benzophenone compounds, tertiary amine compounds, oxyonion compounds, etc.

In addition, as the compound having an ethylenic unsaturated bond, well-known compounds such as hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate; ethylene glycol and methoxy tetra Mono- or diacrylates of glycols such as ethylene glycol, polyethylene glycol, and propylene glycol; hexanediol, trimethylolpropane, pentaerythritol, dipentaerythritol, tri-hydroxyethyl isocyanurate, etc. Polyhydric alcohols such as polyhydric alcohols or these ethylene oxide adducts or propylene oxide adducts; phenoxy acrylates, bisphenol A diacrylates, and these phenolic ethylene oxides Acrylates such as alkane adducts or propylene oxide adducts.

(Next layer (A))

As the alkali-developable resin composition constituting the adhesive layer (A), as long as it is a composition containing the following resins, both photocurable resin compositions and thermosetting resin compositions can be used: containing phenolic hydroxyl groups and sulfur One or more functional groups in alcohol group and carboxyl group, and can be developed by alkaline solution. Preferred examples include compounds containing two or more phenolic hydroxyl groups, carboxyl group-containing resins, compounds having phenolic hydroxyl groups and carboxyl groups, and two or more thiol groups As the resin composition of the compound, well-known and usual ones can be used.

Specifically, for example, a photocurable thermosetting resin composition conventionally used as a solder resist composition includes: a carboxyl group-containing resin or a carboxyl group-containing photosensitive resin, a compound having an ethylenic unsaturated bond, and photopolymerization Starter, and thermally reactive compounds. Moreover, a resin composition containing a carboxyl group-containing urethane resin, a resin having a carboxyl group, a photobase generator, and a thermosetting component can also be used. The resin composition uses an alkali generated by a photobase generator as a catalyst, and the urethane resin having a carboxyl group and a thermosetting component undergo an addition reaction by heating after exposure. The unexposed part can be added by alkali The solution is removed for development.

As various materials constituting the resin composition used for the adhesive layer (A), in addition to the well-known conventional ones, those used for the protective layer (B) can be used in the same manner.

Regarding the resin composition used for the adhesive layer (A) and the protective layer (B), a well-known and commonly used polymer resin can be formulated for the purpose of improving the flexibility and dryness of the obtained cured product. Examples of such polymer resins include cellulose-based, polyester-based, phenoxy resin-based polymers, polyvinyl acetal-based, polyvinyl butyral-based, polyamidoamine, and polyamidoamide. Binder polymer, block copolymer, elastomer, etc. The polymer resin may be used alone or in combination of two or more.

In addition, in order to suppress curing shrinkage of the cured product and improve characteristics such as adhesion and hardness, an inorganic filler may be blended into the resin composition used for the adhesive layer (A) and the protective layer (B). Examples of such inorganic fillers include barium sulfate, amorphous silica, fused silica, and spherical dioxide. Silica, talc, clay, magnesium carbonate, calcium carbonate, alumina, aluminum hydroxide, silicon nitride, aluminum nitride, boron nitride, Newcastle diatomite, etc.

In order to prepare the resin composition and adjust the viscosity when applied to the base material and the carrier film, an organic solvent can be used in the resin composition used for the adhesive layer (A) and the protective layer (B). Examples of such organic solvent systems include ketones, aromatic hydrocarbons, glycol ethers, glycol ether acetates, esters, alcohols, aliphatic hydrocarbons, and petroleum-based solvents. Such organic solvent may be used alone or in a mixture of two or more.

In the resin composition used for the adhesive layer (A) and the protective layer (B), colorants, mercapto compounds, adhesion promoters, antioxidants, ultraviolet absorbers and other components can be formulated as needed, and these can be used It is well known in the field of electronic materials. In addition, well-known and commonly used thickeners such as fine silica, hydrotalcite, organic bentonite, montmorillonite, defoamers and leveling agents such as polysilicone, fluorine, polymer, etc. Well-known and commonly used additives such as silane coupling agent and rust inhibitor.

In the laminated structure of the present invention, from the viewpoint of traceability to the copper circuit, the adhesive layer (A) is preferably thicker than the protective layer (B).

The laminated structure system of the present invention can be used for at least any one of the curved portion and the non-curved portion of a flexible printed wiring board, and ideally can be used for both, thereby allowing sufficient bending durability The flexible printed wiring board improves both cost and workability. Specifically, the laminated structure system of the present invention can be used as at least any one of a cover film, a solder resist, and an interlayer insulating material of a flexible printed wiring board.

(Manufacturing method of flexible printed wiring board)

In the present invention, the above-mentioned build-up structure layer is formed directly or through a dry film on the flexible printed wiring substrate, and then patterned by light irradiation, and then patterned by a developer to form an insulation at a time Film, a flexible printed wiring board can be obtained. Although the characteristics of the single layer of the solder resist layer in the past are not good, if a laminated structure composed of an adhesive layer (A) and a protective layer (B) is formed according to the present invention, and the thickness of the protective layer and the adhesive layer The ratio of the ratio and the development speed of the protective layer and the adhesive layer fall within the aforementioned ranges, respectively, so that the alkali developability, mechanical properties such as heat resistance and flexibility can be satisfactorily combined.

In the following, in one example of the method for manufacturing the flexible printed wiring board of the present invention from the laminated structure of the present invention, both the adhesive layer (A) and the protective layer (B) contain a photobase generator and a heat-reactive compound. The case of the resin composition is explained based on the step diagram shown in FIG. In addition, photocurable thermosetting using a carboxyl group-containing resin or a carboxyl group-containing photosensitive resin, a compound having an ethylenic unsaturated bond, a photopolymerization initiator, and a heat-reactive compound conventionally used as a solder resist composition In the case of a reactive resin composition, the same steps as the solder resist can be taken.

[Stacking steps]

The layering step is a step of forming the layered structure of the present invention on the substrate. The lamination step in FIG. 1 shows the state of forming a laminated structure composed of the adhesive layer 3 and the protective layer 4 on the flexible printed wiring substrate 1 on which the copper circuit 2 has been formed. The adhesive layer 3 is made of alkali The development type resin composition.

Here, the layers constituting the laminated structure can be formed, for example, by directly coating and drying the resin composition constituting the adhesive layer 3 and the protective layer 4 on the substrate to form the adhesive layer 3 and the protective layer 4 directly Or, the resin composition constituting the adhesive layer 3 and the protective layer 4 are each formed by sequentially laminating on the substrate in the form of a dry film. Alternatively, it may be formed by a method of laminating a laminated structure having a two-layer structure in the form of a dry film on a substrate. In this case, at least one side of the laminated structure is supported or protected by a thin film. As the used film system, a plastic film that can be peeled off from the laminated structure can be used. Although the thickness of the film is not particularly limited, it is generally appropriately selected in the range of 10 to 150 μm. From the viewpoint of the strength of the coating film, the interfaces between the layers can also be fused.

The coating method of the resin composition to the base material may be a well-known method such as a blade coater, a lip coater, a comma coater, and a film coater. In addition, the drying method is a method using a hot air circulation type drying furnace, an IR furnace, a heating plate, a convection oven, etc., having a heat source using steam as a heating method, and making it contact the hot air in the dryer countercurrent, and spraying the support with a nozzle Known methods.

Here, the base material is a flexible printed wiring base material in which circuits have been previously formed. In addition, in order to obtain effects other than the expected effects, an additional layer may be provided between the adhesive layer 3 and the protective layer 4.

[Light irradiation steps]

The light irradiation step is a step of activating the photobase generator contained in the resin composition by irradiating the negative pattern shape with light to harden the light irradiation portion. In this light irradiation step, by disposing the mask 5 on the protective layer 4 and irradiating the negative pattern shape with light, the photobase generator contained in the resin composition is activated to harden the light irradiation portion .

In this step, the photobase generator is unstable due to the base generated in the light irradiation section, and an alkaline substance derived from the photobase generator (hereinafter sometimes simply referred to as "base") is generated. The generated base will make the photobase generator unstable, and then the base will be regenerated. By generating alkali in this way and chemically propagating deep into each layer, it is considered to be sufficiently hardened to the depth of each layer. In the subsequent thermal hardening, since this base is used as an addition reaction catalyst for the alkali-developable resin and the heat-reactive compound, it also undergoes an addition reaction, so each layer in the light irradiation section is sufficiently thermally hardened Deep. Since the hardening of the resin composition in this case is, for example, the ring-opening reaction of the epoxy by thermal reaction, the strain or hardening shrinkage can be suppressed more than in the case of the photo reaction.

As a light irradiator used in light irradiation, a direct drawing device (for example, a laser direct imaging device that directly draws an image with a laser using CAD data from a computer), light equipped with a metal halogen lamp Direct drawing device for irradiation machine, light irradiation machine equipped with (ultra) high-pressure mercury lamp, light irradiation machine equipped with mercury short-arc lamp, or ultraviolet lamp using (ultra) high pressure mercury lamp. The pattern-shaped light irradiation mask is a negative mask.

As the active energy ray system, it is preferable to use laser light or scattered light with a maximum wavelength in the range of 350 to 410 nm. By allowing the maximum wavelength to fall within this range, the photobase generator can be efficiently activated. As long as the laser light in this range is used, the type of laser can be either a gas laser or a solid laser. In addition, although the amount of light irradiation varies depending on the film thickness and the like, it is generally 100 to 1500 mJ/cm ² , preferably 300 to 1500 mJ/cm ² .

[Heating step]

The heating step refers to hardening the light irradiated part by heating, and can be hardened to the depth by the alkali generated in the light irradiation step. This heating step is a step called the "PEB (POST EXPOSURE BAKE) step" by heating the adhesive layer 3 and the protective layer 4 after the light irradiation step to harden the light irradiation part. According to this, each layer is sufficiently hardened to the depth by the alkali generated in the light irradiation step, and a patterned layer excellent in hardening characteristics can be obtained.

For example, the heating step is preferably performed at a temperature lower than the heat generation start temperature or heat generation peak temperature of the unirradiated resin composition and higher than the heat generation start temperature or heat generation peak temperature of the resin composition that has been irradiated with light. By such heating, only the light irradiation part can be selectively hardened.

The heating temperature at this time is preferably a temperature at which the light-irradiated portion in the resin composition is thermally cured, but the unirradiated portion is not thermally cured. The heating temperature is, for example, 80 to 140°C. By setting the heating temperature to 80°C or higher, the light irradiation portion can be sufficiently hardened. On the other hand, by setting the heating temperature to 140° C. or lower, only the light irradiated portion can be selectively cured. The heating time is, for example, 10 to 100 minutes. The heating method is the same as the drying method described above. In addition, since no alkali is generated from the photobase generator in the unirradiated portion, thermal hardening is suppressed.

〔Development steps〕

In the development step, the non-irradiated portion is removed by alkali development to form a negative pattern layer. The development step in FIG. 1 shows the step of developing the adhesion layer 3 and the protective layer 4 with an alkaline aqueous solution to remove unirradiated portions and form a negative pattern layer. As the development method, well-known methods such as a dipping method, a shower method, a spray method, and a brush coating method can be used. In addition, as the developer, amines such as potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, sodium silicate, ammonia, ethanolamine, and tetramethylammonium hydroxide aqueous solution (TMAH) can be used. An aqueous solution or a mixture of these.

[Second light irradiation step]

After the development step, it is preferable to include the second light irradiation step. This second light irradiation step is a step of irradiating ultraviolet rays as needed to activate the residual photobase generator that has not been activated in the pattern layer of the light irradiation step and generate alkali. The ultraviolet wavelength and light irradiation amount (exposure amount) in the second light irradiation step may be the same as or different from the light irradiation step described above. The light irradiation amount (exposure amount) is, for example, 150 to 2000 mJ/cm ² .

[Thermosetting step]

After the development step, it is preferable to further include a thermal curing step (post-curing). This thermal hardening step is a step of performing thermal hardening (post-hardening) as necessary in order to sufficiently thermally harden the pattern layer. In the case where both the second light irradiation step and the heat curing step are performed after the development step, the heat curing step is preferably performed after the second light irradiation step.

In this thermal hardening step, the pattern layer is sufficiently thermally hardened by the base generated by the photobase generator due to the light irradiation step or the light irradiation step and the second light irradiation step. Since the non-irradiated portion has been removed at the time of the thermal curing step, the thermal curing step can be performed at a temperature above the curing reaction start temperature of the unirradiated resin composition, whereby the patterned layer can be sufficiently thermally cured. The heating temperature is, for example, 150°C or higher.

Examples

The present invention is explained in more detail below using examples.

(Synthesis Example 1)

<Synthesis of alkali-soluble resin with amide imine ring>

In a separable three-necked flask equipped with a stirrer, nitrogen introduction tube, fractionation ring and cooling ring, add 3,5-diaminobenzoic acid 12.5g, 2,2'-bis[4-(4-aminobenzene Oxy)phenyl]propane 8.2g, NMP 30g, γ-butyrolactone 30g, 4,4'-oxydiphthalic anhydride 27.9g, trimellitic anhydride 3.8g, and stirred at room temperature and 100rpm under a nitrogen atmosphere 4 hours. Next, 20 g of toluene was added, and toluene and water were distilled off at a silicon bath temperature of 180° C. and 150 rpm while stirring for 4 hours to obtain an alkali-soluble resin solution containing an imidate ring. Thereafter, γ-butyrolactone was added so that the solid content became 30% by mass. The resulting resin solution had a solid content acid value of 86 mgKOH/g and Mw10000.

(Synthesis Example 2)

<Synthesis of urethane resin containing carboxyl group>

A polycarbonate diol derived from 1,5-pentanediol and 1,6-hexanediol (Asahi Kasei Chemicals Co., Ltd. product, T5650J, number The average molecular weight is 800) 2400 g (3 mol), dimethylol propionic acid 603 g (4.5 mol), and 238 g (2.6 mol) of 2-hydroxyethyl acrylate as a monohydroxy compound. Then put in 1887g (8.5 moles) of isophorone diisocyanate as polyisocyanate, stir and heat to 60°C, then stop, then reheat when the temperature in the reaction vessel begins to drop, and continue stirring at 80°C, then After confirming the absorption spectrum (2280 cm ^-1 ) of the isocyanate group by infrared absorption spectrum, the reaction was terminated. Thereafter, carbitol acetate was added so that the solid content became 50% by mass, and the solid content acid value of the resulting carboxyl group-containing urethane resin was 50 mg KOH/g.

<Preparation of resin composition constituting each layer>

The materials described in the examples and comparative examples were prepared according to the blending methods described in Tables 1 and 2 below, and mixed in advance with a blender, and then kneaded with a three-roll mill to prepare the adhesive layer and protection. The resin composition of the layer. Unless otherwise specified, the values in the table are parts by mass.

<Formation of Adhesive Layer (A)>

Prepare a flexible printed wiring substrate on which a circuit with a copper thickness of 18 μm has been formed, and use CB-801Y manufactured by MEC Corporation for pretreatment. After that, on the flexible printed wiring substrate that has been pre-treated, each adhesive layer is applied so that the film thickness after drying becomes the film thickness shown in Tables 1 and 2 below The resin composition. Thereafter, it was dried at 80°C/30 minutes in a hot-air circulation type drying furnace to form an adhesive layer (A) made of a resin composition. In addition, in Comparative Example 1, no adhesive layer was formed.

<Formation of protective layer (B)>

On the adhesive layer (A), the resin composition for each protective layer was applied so that the film thickness after drying became the film thickness shown in Table 1 and Table 2 below. Thereafter, it was dried at 80°C/30 minutes in a hot-air circulation type drying furnace to form a protective layer (B) made of a resin composition.

The total film thickness of the next layer (A) and the protective layer (B) is all 20 μm.

<Measurement of film thickness>

The film thickness was measured using a micrometer MDC-25MX manufactured by Mitutoyo Corporation.

<Measurement of development speed>

Each resin composition was coated on the flexible printed wiring substrate on which a circuit with a copper thickness of 18 μm had been formed, and dried at 80° C./30 minutes in a hot-air circulation type drying furnace. After that, the substrate was immersed in a 30°C‧1% by mass sodium carbonate aqueous solution, and the time until the coating film was dissolved was measured. When the time until the coating film is dissolved is defined as the development time [sec] and the film thickness is defined as the film thickness [μm], the development speed is expressed by the following formula.

Development speed [μm/sec] = film thickness [μm]/development time [sec].

<Alkali developability, solder heat resistance and gold plating resistance>

With respect to the base material provided with the laminated structure obtained as described above, a negative pattern shape was irradiated with an exposure amount of 500 mJ/cm ² by HMW 680GW (metal halide lamp, scattered light) manufactured by ORC Corporation. Next, heat treatment at 90°C was performed for 60 minutes. Thereafter, the base material was immersed in a 30°C‧1% by mass sodium carbonate aqueous solution for development for 3 minutes to evaluate whether alkali developability was possible. The evaluation is carried out visually and is evaluated using the following criteria.

○: No residue can be developed

×: Development residue

Next, a hot air circulation type drying furnace was used to perform heat treatment at 150°C/60 minutes to obtain a pattern-shaped cured coating film. For the obtained cured coating film, apply a rosin-based flux on the evaluation substrate, and immerse it in a solder bath set at 260°C for 20 seconds (10 seconds × 2 times), and then wash the flux with isopropyl alcohol After that, a peel test was performed with cellophane adhesive tape, and the following criteria were evaluated for swelling, peeling, discoloration, etc.

○: No change found at all

×: Those who swell or peel off

In addition, for the obtained cured coating film, a commercially available electroless nickel plating plating bath and electroless gold plating bath were used, and plating was performed under the conditions of 80 to 90° C., nickel 5 μm, and gold 0.05 μm. The plated evaluation substrate was visually evaluated for plating penetration.

○: No infiltrator

×: Infiltration is confirmed between the substrate and the coating film

The results obtained are shown in Tables 1 and 2 below.

※5：二環戊二烯型環氧樹脂(DIC(股)製)※6：雙酚A型環氧樹脂(分子量400)(三菱化學(股)製)※7：肟型光鹼產生劑(BASF JAPAN公司製)※8：2-(二甲基胺基)-2-〔(4-甲基苯基)甲基〕-1-〔4-(4-嗎啉基)苯基〕-1-丁酮(BASF JAPAN公司製)※9：雙酚F型酸改質環氧丙烯酸酯(日本化藥(股)製)※10：硫酸鋇(堺化學(股)製)

※5: Dicyclopentadiene-type epoxy resin (DIC (product)) ※6: Bisphenol A-type epoxy resin (molecular weight 400) (Mitsubishi Chemical (product)) ※7: Oxime-type photobase generator (Manufactured by BASF JAPAN) ※8: 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]- 1-Butanone (manufactured by BASF JAPAN) ※9: Bisphenol F-type acid-modified epoxy acrylate (manufactured by Nippon Kayaku Co., Ltd.) ※10: barium sulfate (manufactured by Sakai Chemical Co., Ltd.)

As is clear from the evaluation results shown in Tables 1 and 2 above, it was confirmed that the flexible printed wiring boards of Examples showed good developability and heat resistance. On the other hand, it is understood that Comparative Example 1 is composed only of the protective layer of the resin composition having an amide imide ring, so although its heat resistance is good, the developability is not good, and development using general sodium carbonate is impossible. Also, in Comparative Example 2, since the adhesive layer is thin, and the ratio of the thickness of the adhesive layer to the protective layer Deviating from the scope of the present invention, although its heat resistance is good, the result is that the developability is deteriorated. Furthermore, in Comparative Example 3, since the ratio of the thickness of the adhesive layer to the protective layer is still out of the scope of the present invention, although the developability is good, the heat resistance is deteriorated as a result. In Comparative Example 4, although the ratio of the film thickness is within the scope of the present invention, since the development speed of the adhesive layer and the protective layer are the same, the ratio of the development speed of the two exceeds the scope of the present invention, so the result is that the developability changes difference. In Comparative Example 5, since the ratio of the development speed deviates from the scope of the present invention, although the development property is good, the heat resistance is deteriorated as a result.

1‧‧‧ Flexible printed wiring substrate

2‧‧‧Copper circuit

3‧‧‧Next layer

4‧‧‧Protection layer

5‧‧‧Mask

Claims (6)

A laminated structure characterized by having an adhesive layer (A) made of an alkali-developable resin composition and a precursor skeleton formed on the adhesive layer (A) containing an imide ring or an imide precursor The protective layer (B) of the photosensitive resin composition of the alkali-soluble resin, the ratio of the thickness of the adhesive layer (A) to the protective layer (B) is A/B=0.5~50, the adhesive layer The ratio of the development speed (a) of (A) to the development speed (b) of the aforementioned protective layer (B) is a/b=1.1~100. The laminated structure according to claim 1, wherein both the adhesive layer (A) and the protective layer (B) can be patterned by light irradiation. The laminated structure according to claim 1, which is used for at least any one of the curved portion and the non-curved portion of the flexible printed wiring board. The laminated structure according to claim 1, which is used for at least any one of the covering layer, the solder resist, and the interlayer insulating material of the flexible printed wiring board. A dry film characterized in that at least one side of the laminated structure according to any one of claims 1 to 4 is supported or protected by a film. A flexible printed wiring board is characterized by having an insulating film formed by directly forming a layered structure of any one of claims 1 to 4 on the flexible printed wiring board, or After the dry film of claim 5 is formed into a layered structure, the pattern is patterned by light irradiation, and then the pattern is formed once with a developer to form the pattern.

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