JP2010211095A - Photosensitive coverlay - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photosensitive coverlay which has high resolution in alkali aqueous solution, and is curable at a low temperature of 200°C or lower, and is excellent in bendability with minimized warping of a laminate with a flexible printed board after cured. <P>SOLUTION: The photosensitive coverlay contains (A) a soluble polyimide having a weight average molecular weight of 10,000 to 30,000, and has a tensile elastic modulus of 2.5 GPa or less and a tensile elongation of 5% or more after heating for 1 hour at 200°C. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a photosensitive coverlay. More specifically, the present invention relates to a photosensitive cover lay suitably used as a protective film for a flexible printed circuit board.

  In recent years, higher performance, higher functionality, lighter and shorter thicknesses of electronic devices have been increasingly advanced, and accordingly, higher-density wiring and thinning of flexible printed circuit boards have been advanced. Up to now, coverlays composed of polyimide film and adhesive have been used as protective films for flexible printed circuit boards, but it is possible to cope with fine processing by photolithography and improvement of positional accuracy. Therefore, there is an increasing demand for a photosensitive cover lay that can further reduce the thickness of the protective film.

  As a material used for the photosensitive coverlay, an unsaturated group-containing polyisocyanate which is a reaction product of an addition product of an epoxy resin (a) and an unsaturated group-containing monocarboxylic acid (b) and succinic anhydride (c). A resist ink composition for flexible printed wiring boards containing a carboxylic acid resin (A), a photopolymerization initiator (B), a diluent (C) and a curing component (D) has been proposed (see, for example, Patent Document 1). ). However, such a composition is poor in heat resistance and bendability, and there is a problem that it cannot be used for a part that requires a high solder heat resistance temperature or a part that is processed by bending. On the other hand, (A) polyamic acid, (B) (meth) acrylate having at least two photopolymerizable C═C unsaturated double bonds, (C) photopolymerization initiator, and (D) flame retardant Has been proposed (for example, see Patent Document 2). However, such a composition needs to be thermally cured at a high temperature of 250 ° C. or higher in order to imidize the polyamic acid, and there is a problem that the copper foil which is a conductor portion of the flexible printed board is oxidized. On the other hand, a photosensitive resin composition containing (A) terminal tetracarboxylic acid siloxane imide oligomer, (B) diamino compound, (C) photosensitive resin, (D) photopolymerization initiator, and (E) thermosetting resin. It has been proposed (see, for example, Patent Document 3). Although such a composition can be cured at a low temperature, there has been a problem that warpage of the laminate with the flexible printed circuit board after curing becomes large.

In addition, a photosensitive coverlay film that can be developed with an alkaline aqueous solution, has an initial elastic modulus of 1 to 100 kgf / mm ² , a 5% weight reduction rate of 275 ° C. or higher, and a thermal decomposition temperature of 350 ° C. or higher (for example, patents) Reference 4), a composition for a photosensitive coverlay film containing a soluble polyimide obtained from siloxane diamine as a raw material (see, for example, Patent Document 5), and forms a cured polyimide having a modulus of less than 2 GPa when exposed to heat. A low-temperature curable photosensitive composition (see, for example, Patent Document 6) that contains polyamic acid, an ethylenically unsaturated photosensitive monomer mixture, a photoinitiator, and a sensitizer and that can be developed in aqueous carbonate has been proposed. . However, such a composition has problems such as difficulty in developing a via having a diameter of less than 100 μm and insufficient bendability, and is a photosensitive material that achieves both high resolution and bendability after curing. A sex coverlay was needed.

JP-A-7-207211 JP 2004-29702 A JP 2008-197546 A JP 2002-174896 A JP 2002-162740 A JP 2006-146244 A

  Therefore, the present invention has a high resolution with an alkaline aqueous solution, can be cured at a low temperature of 200 ° C. or less, has a small warpage of the laminate with the cured flexible printed circuit board, and has excellent bending properties. The purpose is to provide sex coverlay.

  In order to solve the above problems, the present invention includes (A) a soluble polyimide having a weight average molecular weight of 10,000 or more and 30,000, and has a tensile modulus of 2.5 GPa or less after heat treatment at 200 ° C. for 1 hour. The photosensitive cover lay has a tensile elongation of 5% or more.

  According to the present invention, it has high resolution with an alkaline aqueous solution, can be cured at a low temperature of 200 ° C. or less, has low warpage of the laminate with the flexible printed circuit board after curing, and has excellent bendability. A photosensitive coverlay can be obtained.

  The photosensitive cover lay of the present invention is a photosensitive cover lay containing a soluble polyimide having a weight average molecular weight of 10,000 or more and 30,000 or less, and has a tensile modulus of 2 after heat treatment at 200 ° C. for 1 hour. .5 GPa or less, and the tensile elongation is 5% or more. In the present invention, the coverlay refers to a material that protects the flexible printed circuit board wiring, and is cured and used as a protective film. The shape before curing is not limited, and examples thereof include a varnish shape and a film shape.

  Said flexible printed circuit board is one in which conductor wiring is formed on an insulating resin film layer. For example, although the board | substrate with which the polyimide film and copper foil were laminated | stacked directly or via adhesives, such as an epoxy resin, and the copper foil was circuit-processed is mentioned, it is not limited to these.

  The photosensitive cover lay of the present invention is characterized in that the tensile modulus after heat treatment at 200 ° C. for 1 hour is 2.5 GPa or less and the tensile elongation is 5% or more. After heat treatment at 200 ° C. for 1 hour, that is, when the tensile elastic modulus after curing exceeds 2.5 GPa, the warpage of the laminate with the flexible printed board may increase. From the viewpoint of reducing tackiness after curing, 0.1 GPa or more is preferable. Examples of the means for setting the tensile elastic modulus after curing to 2.5 GPa or less include a diamine represented by the general formula (1) and a diamine residue represented by the chemical formula (2). On the other hand, when the tensile elongation after curing is less than 5%, the brittleness of the photosensitive cover lay is remarkably lowered, and the bending property may be lowered. Examples of means for setting the tensile elongation after curing to 5% or more include containing a soluble polyimide having a weight average molecular weight of 10,000 or more.

  In addition, the tensile elasticity modulus and tensile elongation after hardening of the photosensitive coverlay in this invention point out the value measured according to JISK7127 (1999) (including JISK7161 (1994) quoted in the said specification). The measurement is performed using a strip-shaped test piece of 10 mm × 150 mm at a pulling speed of 100 mm / min in an environment of a temperature of 23 ° C. and a humidity of 50% RH.

  The photosensitive coverlay of the present invention contains a soluble polyimide having a weight average molecular weight of 10,000 or more and 30,000. By using soluble polyimide, developability with an aqueous alkali solution is improved, high resolution is obtained, and curing at a low temperature of 200 ° C. or lower is possible. Here, the soluble polyimide in the present invention includes N-methylpyrrolidone, N-vinylpyrrolidone, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide and the like. Amide solvents, γ-butyl lactone, methyl monoglyme, methyl diglyme, methyl triglyme, ethyl monoglyme, ethyl diglyme, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether , 1 g or more dissolved at 25 ° C. with respect to 100 g of an organic solvent such as ethylene glycol dimethyl ether or ethylene glycol diethyl ether.

  In the present invention, it is important that the weight average molecular weight of the soluble polyimide is 10,000 or more and 30,000 or less. When two or more types of soluble polyimide are contained, at least one of the weight average molecular weights may be in the above range. When the weight average molecular weight is less than 10,000, the tensile elongation of the photosensitive cover lay may be remarkably lowered. As a result, the brittleness of the photosensitive cover lay may be remarkably lowered and the bendability may be lowered. Preferably it is 12,000 or more. On the other hand, if the weight average molecular weight exceeds 30,000, developability with an alkaline aqueous solution may be deteriorated to generate a development residue. Preferably it is 25,000 or less.

  In addition, the weight average molecular weight in this invention is measured by the gel permeation chromatography method (GPC method), and is computed by polystyrene conversion.

  The soluble polyimide is obtained by the reaction of tetracarboxylic dianhydride and diamine, and has a residue of tetracarboxylic dianhydride and a residue of diamine. In the present invention, the residue of tetracarboxylic dianhydride and the residue of diamine are preferably 1) a structure having a small number of benzene rings, 2) a large molecular weight and a bulky structure, and 3) a structure having many bending sites such as an ether bond. By having such a structure, the interaction between molecular chains is weakened, and the solubility of soluble polyimide in an organic solvent is improved.

  In the present invention, the soluble polyimide preferably contains a diamine residue represented by the following general formula (1) as a diamine residue. By having such a diamine residue, the solubility of the soluble polyimide in an organic solvent is improved, and the developability with an alkaline aqueous solution is further improved, so that high resolution is obtained. In addition, flexibility is imparted to the polyimide skeleton by an ether bond, and the tensile elastic modulus after curing of the photosensitive coverlay can be easily adjusted to 2.5 GPa or less. Moreover, the curvature of the laminated body with the flexible printed circuit board after hardening reduces.

  In the general formula (1), n is in the range of 3 to 10. When n is 3 or more, the softening effect by the ether bond is improved, the tensile modulus after curing is further reduced, and the warpage of the laminate with the flexible printed board after curing can be further reduced. More preferably, it is 4 or more. On the other hand, if n is 10 or less, the molecular chain length between imide groups is in an appropriate range, the regularity of the molecular chain is improved, and the chemical resistance and heat resistance after curing can be improved. More preferably, it is 7 or less. From the standpoint of further improving developability with an aqueous alkali solution to improve resolution and further reducing the warpage of the laminate with the cured flexible printed board, the residue of the diamine represented by the general formula (1) is all diamines. It is preferable to contain 30 mol% or more. Moreover, 60 mol% or less is preferable from a viewpoint of reducing the tackiness after hardening.

  In the present invention, the soluble polyimide preferably further has a diamine residue represented by the following chemical formula (2). By having such a diamine residue, the solubility of the soluble polyimide in an organic solvent is improved, and the developability with an alkaline aqueous solution is further improved, so that high resolution is obtained. In addition, flexibility is imparted to the polyimide skeleton by the siloxane bond, and the tensile modulus after curing of the photosensitive coverlay can be easily adjusted to 2.5 GPa or less. It is also expected to improve the adhesion between the photosensitive coverlay and the substrate.

The content of the diamine residue represented by the chemical formula (2) is preferably 5 mol% or more in the total diamine residues, and the flexibility is imparted to the polyimide, and the warpage of the laminate with the flexible printed circuit board after curing is caused. It can be further reduced. On the other hand, 15 mol% or less is preferable, moderate hydrophobicity is imparted, and developability in an alkaline aqueous solution can be further improved.
The total content of the diamine residue represented by the general formula (1) and the diamine residue represented by the chemical formula (2) is preferably 50 mol% or more in the total diamine residues, The warpage of the laminate can be further reduced.

  The soluble polyimide preferably has an alkali-soluble functional group for development with an aqueous alkali solution. The alkali-soluble functional group is a functional group having acidity, and specific examples include a phenolic hydroxyl group and a carboxyl group. In order to introduce these alkali-soluble groups into the polyimide, it is preferable to contain a diamine residue represented by the following general formula (3).

In the general formula (3), Y represents —CO—, —SO ₂ —, —O—, —S—, —CH ₂ —, —NHCO—, —C (CH ₃ ) ₂ —, —C (CF ₃ ) _2- , -COO- or a single bond is represented, and M and N represent a hydroxyl group or a carboxyl group.

  Examples of the diamine compound represented by the general formula (3) include 3,3′-diamino-4,4′-dihydroxybiphenyl, 4,4′-diamino-3,3′-dihydroxybiphenyl, and 4,4′-. Hydroxybiphenyl compounds such as diamino-2,2′-dihydroxybiphenyl, 3,3′-diamino-4,4′-dihydroxydiphenylmethane, 4,4′-diamino-3,3′-dihydroxydiphenylmethane, 4 , 4′-diamino-2,2′-dihydroxydiphenylmethane, 2,2-bis [3-amino-4-hydroxyphenyl] propane, 2,2-bis [4-amino-3-hydroxyphenyl] propane, 2, , 2-bis [3-amino-4-hydroxyphenyl] hexafluoropropane and other hydroxydiphenylalkanes Compounds, 3,3′-diamino-4,4′-dihydroxydiphenyl ether, 4,4′-diamino-3,3′-dihydroxydiphenyl ether, 4,4′-diamino-2,2′-dihydroxy Hydroxydiphenyl ether compounds such as diphenyl ether, 3,3′-diamino-4,4′-dihydroxydiphenyl sulfone, 4,4′-diamino-3,3′-dihydroxydiphenyl sulfone, 4,4′-diamino-2 A diamine compound having a phenolic hydroxyl group in a molecule such as hydroxydiphenylsulfone compounds such as 2,2'-dihydroxydiphenylsulfone, or a carboxyl group such as 3,3'-dicarboxy-4,4'-diaminodiphenylmethane The diamine compound contained in can be mentioned

  The soluble polyimide in the present invention may contain other diamine residues in addition to the above diamine residues to the extent that the effects of the present invention are not impaired. For example, diamines containing one benzene ring such as 1,4-diaminobenzene, 1,3-diaminobenzene, 2,4-diaminotoluene, 1,4-diamino-2,5-dihalogenobenzene, bis (4 -Aminophenyl) ether, bis (3-aminophenyl) ether, bis (4-aminophenyl) sulfone, bis (3-aminophenyl) sulfone, bis (4-aminophenyl) methane, bis (3- Aminophenyl) methane, bis (4-aminophenyl) sulfide, bis (3-aminophenyl) sulfide, 2,2-bis (4-aminophenyl) propane, 2,2-bis (3-aminophenyl) propane, 2 , 2-bis (4-aminophenyl) hexafluoropropane, o-dianisidine, o-tolidine, tolidinesulfonic acids and the like Diamines containing two rings, 1,4-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenyl) benzene, 1,4 -Bis (3-aminophenyl) benzene, α, α'-bis (4-aminophenyl) -1,4-diisopropylbenzene, α, α'-bis (4-aminophenyl) -1,3-diisopropylbenzene, etc. Diamines containing three benzene rings, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 2, 2-bis [4- (4-aminophenoxy) phenyl] sulfone, 4,4 ′-(4-aminophenoxy) biphenyl, 9,9-bis (4-aminophenyl) fluore And residues of diamine compounds such as diamines containing 4 or more benzene rings such as 5,10-bis (4-aminophenyl) anthracene.

  The soluble polyimide in the present invention can be obtained by the reaction of a diamine as exemplified above with tetracarboxylic dianhydride. Examples of the tetracarboxylic dianhydride include pyromellitic anhydride (PMDA), oxydiphthalic dianhydride (ODPA), 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA), 3 , 3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride (DSDA), 4,4 ′-(hexafluoro And isopropylidene) diphthalic dianhydride (6FDA) and 2,2′-bis [(dicarboxyphenoxy) phenyl] propane dianhydride (BSAA).

  Moreover, it is preferable that at least a part of the terminal of the soluble polyimide is sealed with an aniline derivative or a dicarboxylic acid anhydride. Thereby, the weight average molecular weight of soluble polyimide can be easily adjusted to an appropriate range. In addition, it is expected to suppress an increase in viscosity due to crosslinking of the terminal functional group. Examples of aniline derivatives include 2-aminobenzoic acid, 3-aminobenzoic acid, 4-aminobenzoic acid, 4-aminosalicylic acid, 5-aminosalicylic acid, 6-aminosalicylic acid, 2-aminobenzenesulfonic acid, 3-aminobenzenesulfone. Acid, 4-aminobenzenesulfonic acid, 2-aminophenol, 3-aminophenol, 4-aminophenol, 2-aminothiophenol, 3-aminothiophenol, 4-aminothiophenol and the like are preferable. Dicarboxylic acid anhydrides include maleic acid anhydride, phthalic acid anhydride, nadic acid anhydride, cyclohexanedicarboxylic acid anhydride, 5-norbornene-2,3-dicarboxylic acid anhydride, 1,2-dicarboxynaphthalene anhydride. , 3-hydroxyphthalic anhydride and the like are preferable.

  The method for synthesizing the soluble polyimide used in the present invention is not particularly limited, and is synthesized by a known method using diamine and tetracarboxylic dianhydride. For example, a method of reacting a tetracarboxylic dianhydride and a diamine compound (some of which may be substituted with an aniline derivative) at low temperature, a diester obtained by reacting a tetracarboxylic dianhydride and an alcohol, and then a diamine A method of reacting (partially with an aniline derivative) in the presence of a condensing agent, a diester is obtained by reaction of tetracarboxylic dianhydride and alcohol, and then the remaining two carboxyl groups are converted to acid chloride To obtain a polyimide precursor using a method such as a method of reacting with a diamine (a part of which may be substituted with an aniline derivative), and synthesizing it using a known imidization method. it can.

  The photosensitive coverlay of the present invention preferably contains (B) a compound having a photopolymerizable group in addition to (A) the soluble polyimide having a weight average molecular weight of 10,000 to 30,000. Thereby, the effect which improves a sensitivity, a crosslinking density, and the toughness of hardened | cured material is anticipated. Examples of the photopolymerizable group include an acrylic group, a methacryloyl group, and a vinyl group. (B) The compound having a polymerizable group is not particularly limited, and so-called polyfunctional (meth) acrylic monomers such as polyhydric alcohol acrylic ester compounds and methacrylic ester compounds generally used for photosensitive resins are used. Is possible. Here, (meth) acrylic is a generic name for acrylic and methacrylic. Polyfunctional (meth) acrylic monomers include allylated cyclohexyl di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, ethylene glycol di (meth) acrylate , Diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, ditrimethylolpropane tetra ( (Meth) acrylate, glycerol di (meth) acrylate, methoxylated cyclohexyl di (meth) acrylate, neopentyl glycol di (meth) acrylate, propylene Recall di (meth) acrylate, polypropylene glycol di (meth) acrylate, triglycerol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, bisphenol A di (meth) acrylate, di (meta) of bisphenol A-ethylene oxide adduct ) Acrylate, di (meth) acrylate of bisphenol A-propylene oxide adduct, and the like. Two or more of these may be contained.

  Among these, a polyfunctional (meth) acrylic monomer having a flexible skeleton is preferable, and the warpage of the laminate with the flexible printed circuit board after curing of the photosensitive coverlay can be further reduced. Examples of such a monomer include those having an alkylene glycol structure. Specifically, alkylene glycol (meth) acrylate esterified with (meth) acrylic acid at both ends of long-chain alkylene glycol, epoxy acrylate obtained by reacting epoxy compound modified with long-chain alkylene glycol and (meth) acrylic acid And urethane (meth) acrylate obtained by esterifying a urethane compound obtained by reacting a long-chain alkylene glycol and isocyanate with (meth) acrylic acid.

  The photosensitive coverlay of the present invention preferably further contains (C) a photopolymerization initiator. (C) As a photoinitiator, what has a sensitivity to a long wavelength is preferable, and a sensitivity can be improved. In addition, since the longer the wavelength, the harder it is to be affected by absorption and scattering, it is easy to cure the thick film. Usually, since a mercury lamp is used for exposure, it is preferable to have sensitivity up to a wavelength of 436 nm which is g line of the long wavelength emission line spectrum of the mercury lamp. Moreover, the composite initiator which gave g line sensitivity by combining the photoinitiator which has a sensitivity only in a short wavelength with a sensitizer can also be used conveniently.

  For example, initiators having sensitivity to g-line include benzophenone derivatives, acetophenone derivatives, thioxanthone derivatives, benzyl derivatives, benzoin derivatives, oxime compounds, α-hydroxyketone compounds, α-aminoalkylphenone compounds, phosphine oxides. System compounds and the like. Two or more of these may be contained. Among these, oxime compounds are desirable in terms of photosensitivity. Examples thereof include ethanone, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl]-, 1- (O-acetyloxime) (Optomer N1919, manufactured by Adeka Corporation).

  The photosensitive coverlay of the present invention may contain an organic solvent. The organic solvent is not particularly limited as long as it dissolves components contained in the photosensitive coverlay. Specifically, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl Ethers such as ethyl ether, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, propyl acetate, butyl acetate, isobutyl acetate, 3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, methyl lactate, ethyl lactate , Lactic acid Acetates such as chill, acetylacetone, methyl propyl ketone, methyl butyl ketone, methyl isobutyl ketone, cyclopentanone, ketones such as 2-heptanone, butyl alcohol, isobutyl alcohol, pentanol, 4-methyl-2-pentanol, Alcohols such as 3-methyl-2-butanol, 3-methyl-3-methoxybutanol and diacetone alcohol, aromatic hydrocarbons such as toluene and xylene, and others, γ-butyrolactone, N-methylpyrrolidone, N, N -Dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide and the like. Two or more of these may be contained.

  When the photosensitive cover lay is used for the purpose of printing by screen printing such as a protective film for flexible printed circuit board wiring and drying at a low temperature, the boiling point of the organic solvent under atmospheric pressure is preferably 130 ° C. or higher and 250 ° C. or lower. A boiling point of 130 ° C. or higher is suitable for screen printing, and 160 ° C. or higher is more preferable. On the other hand, if it is less than 250 degreeC, it is suitable for low temperature drying, and less than 220 degreeC is more preferable.

  The photosensitive coverlay of the present invention may contain a filler. In particular, when the photosensitive cover lay of the present invention is applied onto a flexible substrate wiring by screen printing, it is possible to improve the printability by imparting appropriate viscosity and thixotropy to the screen printing. As the filler, commonly used ones can be used without particular limitation. Examples thereof include silica, barium sulfate, aluminum hydroxide, talc and the like.

  The photosensitive coverlay of the present invention may further have a colorant. When a photosensitive coverlay is used as a wiring protective film on a flexible printed circuit board, it is generally colored blue or green to confirm pattern processing and improve the visibility of wiring inspection after forming the protective film. is there. Examples of the colorant used in the present invention include dyes, thermochromic dyes, inorganic pigments, and organic pigments. Two or more of these dyes or pigments may be contained, or a combination of a dye and a pigment may be contained.

  Furthermore, the photosensitive coverlay of this invention may contain surfactant as needed, and can improve the coating property with a board | substrate. Moreover, you may contain 0.5 to 10weight% of silane coupling agents, such as methylmethacryloxy dimethoxysilane and 3-aminopropyl trimethoxysilane, a titanium chelating agent, etc. in a photosensitive coverlay.

  Next, a method for forming a wiring protective film on a wiring board using the photosensitive cover lay of the present invention will be described. First, a photosensitive cover lay is applied on the substrate. Examples of the material for the substrate include polyimide films, epoxy resins and ceramics, silicon wafers, glass substrates, and gallium arsenide.

  Examples of the coating method include spin coating using a spinner, spray coating, roll coating, and screen printing coating. The coating film thickness varies depending on the coating method, the solid content concentration of the photosensitive coverlay, the viscosity, and the like, but is usually applied so that the film thickness after drying becomes 1 to 150 μm.

  Next, the substrate coated with the photosensitive coverlay is dried. Drying is generally performed using an oven, a hot plate, infrared rays, or the like at 50 to 150 ° C. for 1 minute to several hours.

Next, exposure is performed through a mask having a predetermined pattern. For the exposure, an exposure apparatus using a light source with high brightness that generates abundant ultraviolet rays, such as a low-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, or a mercury xenon lamp, is preferably used. The exposure dose is preferably in the range of 200 to 1000 mJ / cm ² . After the exposure, development is performed using an alkaline aqueous solution. As the alkaline aqueous solution, an aqueous sodium carbonate solution or an aqueous tetramethylammonium hydroxide (TMAH) solution is preferably used.

  Next, a curing treatment is performed to obtain a wiring protective film having excellent heat resistance and mechanical properties. The curing treatment is generally performed in the range of 150 to 300 ° C. for 1 minute to several hours. Examples of the heating means include a hot plate, a hot air circulating furnace, a far-infrared heating furnace, and the like, but are not particularly limited, and can be selected depending on the size of the base material and the amount of curing treatment.

  As an example, a method of forming a protective film for flexible printed circuit board wiring using the photosensitive coverlay of the present invention will be described. First, a photosensitive coverlay is applied on a substrate and dried. Usually, a polyimide film on which a metal wiring pattern such as copper is formed is used as a base material of a flexible printed board. The coating method is preferably a screen printing method. The film thickness after drying of the photosensitive cover lay is generally not less than the thickness of the wiring pattern of the flexible printed board and not more than twice the wiring pattern. The thickness of the wiring pattern is usually 9 to 18 μm, and the thickness of the wiring protective film is preferably 10 to 20 μm.

  Next, it exposes through the mask of a predetermined pattern. An ultrahigh pressure mercury lamp is preferably used for exposure. Further, development and curing are performed to obtain a wiring protective film.

  The photosensitive coverlay of the present invention has a high resolution with an alkaline aqueous solution and can be cured at a low temperature of 200 ° C. or lower. Furthermore, since the curvature of the laminated body with the cured flexible printed circuit board is small, and it is excellent in bending property and heat resistance, it is suitable as a wiring protective film of a flexible printed circuit board. Other than that, it is used for an interlayer insulating film of a circuit board, a photosensitive heat-resistant adhesive, a semiconductor protective film, and the like.

Hereinafter, the present invention will be described with reference to examples and techniques, but the present invention is not limited to these examples. In addition, the detail of the raw material shown by the abbreviation in each Example is shown below.
PMDA: pyromellitic anhydride (manufactured by Daicel Chemical Industries)
OPDA: 4,4′-oxydiphthalic dianhydride (manac)
SiDA: Bis (3-aminopropyl) tetramethyldisiloxane (manufactured by Shin-Etsu Chemical Co., Ltd.)
BAPP: 2,2-bis [4- (4-aminophenoxy) phenyl] propane (Wakayama Seika Kogyo Co., Ltd.)
DAPE: 4,4′-diaminodiphenyl ether (Wakayama Seika Kogyo Co., Ltd.)
MBAA: [Bis (4-amino-3-carboxy) phenyl] methane (manufactured by Wakayama Seika Kogyo Co., Ltd.)
MAP: 3-aminophenol (manufactured by Tokyo Chemical Industry Co., Ltd.)
D-400: Polyoxypropylene diamine (Mitsui Chemicals Fine Co., Ltd., trade name “Jeffamine” D-400, n = 5.6 in the general formula (1))
Photopolymerizable compound CN981: Urethane acrylate oligomer (manufactured by Sartomer)
M-245: Polyethylene glycol diacrylate (trade name “Aronix” M-245, manufactured by Toagosei Co., Ltd.)
MOI-BP: 2-isocyanate ethyl methacrylate block ("Karenz (registered trademark)" MOI-BP manufactured by Showa Denko KK)
EBE3708: Epoxy acrylate oligomer (manufactured by Daicel Cytec Co., Ltd., trade name “EBECRYL3708”)
ATM-35E: ethoxylated pentaerythritol tetraacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.)
Photopolymerization initiator N1919: Photoradical polymerization initiator (manufactured by Adeka Co., Ltd., trade name “Optomer N1919”)
Thermal polymerization inhibitor HQME: Hydroquinone monomethyl ether filler SG-95: Talc fine particles Average particle size 2.5 μm (manufactured by Nippon Talc)
Surfactant L1983: “Disparon (registered trademark)” L1983 (manufactured by Enomoto Kasei Co., Ltd.)
Colorant PB4920: Blue pigment solvent NMP: N-methylpyrrolidone.

  The evaluation method in each example and comparative example is shown below.

(1) Measurement of weight average molecular weight of polyimide A solution in which polyimide is dissolved in NMP to a solid content concentration of 0.1% by weight is measured with a GPC apparatus Waters 2690 (manufactured by Waters Co., Ltd.), and the weight average molecular weight is calculated in terms of polystyrene. Calculated. GPC measurement conditions were such that the moving bed was NMP in which LiCl and phosphoric acid were each dissolved at a concentration of 0.05 mol / L, and the development rate was 0.4 ml / min.

(2) Evaluation of Resolution of Photosensitive Coverlay Screen printer MEC-2400 (manufactured by Mitani Electronics Co., Ltd.), SUS 200 mesh, emulsion thickness 20 μm, 50 mm × 50 mm screen plate having a thickness of 25 μm The obtained photosensitive resin composition was applied on a polyimide film “Kapton (registered trademark)” 100EN (manufactured by Toray DuPont Co., Ltd.) so that the film thickness after drying was 20 μm. Subsequently, heat treatment was performed at 100 ° C. for 30 minutes using a hot air oven INH-21CD (manufactured by Koyo Thermo System Co., Ltd.). Then, a negative photomask in which vias of 50 to 100 μm were arranged at a pitch of 100 μm with an area of 50 × 50 mm was arranged, and exposure was performed at 200 mJ / cm ^{2 in} terms of i-line integrated exposure measurement. Thereafter, using a developing device AD-3000 (manufactured by Mikasa), development was performed in a TMAH 2.38 wt% aqueous solution as a developing solution for 1 minute of shower development and 1 minute of washing with water. Subsequently, heat treatment was performed at 200 ° C. for 60 minutes using a hot air oven INH-21CD (manufactured by Koyo Thermo System Co., Ltd.).

  The surface of the photosensitive cover lay obtained by the above method is observed with an optical microscope at a magnification of 100 times, a clear pattern is drawn on the surface, and the minimum via diameter with no residual development at the bottom of the via is defined as the resolution. did. Even if a 100 μm diameter via is left undeveloped, it was marked as x.

(3) Measurement of tensile elastic modulus and tensile elongation On the copper foil NA-DFF (Mitsui Metal Mining Co., Ltd.) having a thickness of 12 μm, the photosensitive resin composition was applied so that the thickness after curing was 20 μm. . The entire surface was exposed to 200 mJ / cm ² and subjected to heat treatment at 200 ° C. for 60 minutes using a hot air oven, and then the copper foil was etched away with an aqueous ferric chloride solution to obtain a photosensitive coverlay film. Tensile elongation and tensile modulus were measured according to JIS K7127 (1999) “Plastic film and sheet tensile test method” (including JIS K7161 (1994) cited in the standard). The measurement was performed on a 10 mm × 150 mm strip test piece in an environment of a temperature of 23 ° C. and a humidity of 50% RH at a pulling rate of 100 mm / min, and the average value of N = 10 tests was used.

(4) Evaluation of warpage In order to modelly evaluate the warpage of the laminate of the photosensitive coverlay after curing and the flexible printed circuit board, the warpage of the laminate of the photosensitive coverlay after curing and the polyimide film was evaluated. .

A 25 μm-thick polyimide film “Kapton” 100EN (manufactured by Toray DuPont Co., Ltd.) is cut to a size of 50 mm × 50 mm, and the photosensitive resin composition is dried on this and coated to a thickness of 20 μm. Dry at 30 ° C. for 30 minutes. Subsequently, it exposed to 200 mJ / cm < ² > with the ultra high pressure mercury lamp, and heat-processed for 60 minutes at 200 degreeC using the hot air oven. The laminate after the heat treatment was placed on a flat place so that the top was convex, and the height of the warp was measured. In the case where the warp was large and the laminate was wound more than once, it was evaluated as x without measuring the height of the warp.

(5) Evaluation of folding resistance A laminate after heat treatment was obtained by the method described in (4) above. The obtained laminate was cut into a strip having a width of 10 mm and a length of 50 mm, bent 10 times at 180 ° at a length of 25 mm, and visually observed for cracks. When a crack was observed, the number of bending at that time was regarded as bending resistance.

(6) Solder heat resistance By the method described in (2) above, a photosensitive cover lay subjected to patterning and heat treatment was obtained. After being left for 24 hours in an atmosphere at a temperature of 23 ° C. and a humidity of 50% RH, it was immersed in a solder bath completely dissolved at 300 ° C. for 10 seconds. Thereafter, the sample pulled up was visually observed. The case where cracks, peeling, and swelling occurred on the photosensitive coverlay was evaluated as x, and the case where none occurred was evaluated as o.

Example 1
(Polyimide synthesis)
A 300 ml four-necked flask was equipped with a stirrer, thermometer, nitrogen inlet tube and dropping funnel, and under a nitrogen atmosphere, 103.31 g of NMP and 34.12 g of ODPA were charged and dissolved by stirring at 60 ° C. Then, MAP2.40g, SiDA3.06g, D-400 16.17g, MBAA 10.64g, DAPE2.47g was added and stirred for 1 hour, stirring at 60 degreeC. Thereafter, the temperature was raised to 180 ° C. and stirred for 2 hours, and then cooled to room temperature to obtain a soluble polyimide solution A (solid content concentration 40.0% by weight). As a result of measuring the weight average molecular weight of the soluble polyimide by size exclusion chromatography, it was 16,200.

(Synthesis of photosensitive resin composition)
To the soluble polyimide solution A10.3 g obtained by the method described above, 1.8 g of CN981, 0.8 g of M245, 0.3 g of MOI-BP, 0.1 g of N1919, and 0.02 g of HQME were added. Mixing and stirring were performed to obtain a photosensitive coverlay (hereinafter referred to as a photosensitive resin composition) which is a viscous liquid.

Example 2
To 10.3 g of the soluble polyimide solution A obtained in Example 1, 1.5 g of EBE3708, 0.5 g of ATM-35E, 0.5 g of MOI-BP, N1919. 1 g and 0.02 g of HQME were added and mixed and stirred to obtain a photosensitive resin composition that was a viscous liquid.

Example 3
To the soluble polyimide solution A10.3 g obtained in Example 1, 1.8 g of CN981, 0.8 g of M245, 0.3 g of MOI-BP, 0.1 g of N1919, and HQME. 0.02 g, 1.2 g of SG95, 0.16 g of L1983, and 0.02 g of PB4920 were added and stirred, and then kneaded five times with a three-roll mill to obtain a photosensitive resin composition that was a viscous liquid.

Example 4
Soluble polyimide solution B (solid content concentration 40.0) was changed in the same manner as in Example 1 except that 103.31 g of NMP was changed to 107.65 g, 16.17 g of D-400 was changed to 21.53 g, and DAPE was not added. % By weight). It was 18,550 as a result of measuring the weight average molecular weight of soluble polyimide by size removal chromatography. A photosensitive resin composition that is a viscous liquid was obtained in the same manner as in Example 1 except that the soluble polyimide solution B was used in place of the soluble polyimide solution A.

Example 5
Example except that NMP 107.65g was changed to 145.95g, SiDA 3.06g was changed to 5.47g, D-400 21.53g was changed to 11.96, and MBAA 10.64g was changed to 14.17g In the same manner as in Example 4, a soluble polyimide solution C (solid content concentration: 40.0% by weight) was obtained. It was 21800 as a result of measuring the weight average molecular weight of soluble polyimide by size removal chromatography. A photosensitive resin composition that is a viscous liquid was obtained in the same manner as in Example 1 except that the soluble polyimide solution C was used instead of the soluble polyimide solution A.

Example 6
To 10.3 g of the soluble polyimide solution A obtained in Example 1, 1.5 g of EBE3708, 1.0 g of ATM-35E, 0.1 g of N1919, and 0.02 g of HQME were added and stirred, mixed and stirred. A photosensitive resin composition that was a viscous liquid was obtained.

Example 7
Soluble polyimide solution D (in the same manner as in Example 1 except that NMP 103.31 g was changed to 145.95 g, D-400 16.17 g was changed to 10.77 g, and MBAA 10.64 g was changed to 14.17 g. Solid content concentration 40.0% by weight) was obtained. It was 23,250 as a result of measuring the weight average molecular weight of soluble polyimide by size removal chromatography. A photosensitive resin composition that is a viscous liquid was obtained in the same manner as in Example 6 except that the soluble polyimide solution D was used instead of the soluble polyimide solution A.

Example 8
A stirrer, a thermometer, a nitrogen introducing tube and a dropping funnel were placed in a 300 ml four-necked flask, and NMP145.95 g, ODPA27.3 g and PMDA4.8 g were charged in a nitrogen atmosphere and dissolved at 60 ° C. with stirring. Thereafter, 2.40 g of MAP, 6.15 g of SiDA, 16.17 g of D-400 and 10.64 g of MBAA were added while stirring at 60 ° C., and the mixture was stirred for 1 hour. Thereafter, the temperature was raised to 180 ° C. and stirred for 2 hours, followed by cooling to room temperature to obtain a soluble polyimide solution E (solid content concentration 40.0% by weight). It was 14,865 as a result of measuring the weight average molecular weight of soluble polyimide by size removal chromatography. A photosensitive resin composition that is a viscous liquid was obtained in the same manner as in Example 1 except that the soluble polyimide solution E was used instead of the soluble polyimide solution A.

Comparative Example 1
NMP 103.31g was changed to 145.95g, MAP 2.40g to 1.20g, SiDA 3.06g to 3.23g, D-400 16.17g to 17.08g, MBAA 10.64g to 11.24g, A soluble polyimide solution F (solid content concentration: 40.0% by weight) was obtained in the same manner as in Example 1 except that 2.47 g of DAPE was changed to 2.60 g. It was 35,536 as a result of measuring the weight average molecular weight of soluble polyimide by size removal chromatography. A photosensitive resin composition that is a viscous liquid was obtained in the same manner as in Example 3 except that the soluble polyimide solution F was used instead of the soluble polyimide solution A.

Comparative Example 2
NMP 103.31g was changed to 101.50g, MAP 2.40g to 4.80g, SiDA 3.06g to 2.73g, D-400 16.17g to 14.36g, MBAA 10.64g to 9.45g, A soluble polyimide solution G (solid content concentration 40.0% by weight) was obtained in the same manner as in Example 1 except that 2.47 g of DAPE was changed to 2.20 g. It was 9,277 as a result of measuring the weight average molecular weight of soluble polyimide by size removal chromatography. A photosensitive resin composition that is a viscous liquid was obtained in the same manner as in Example 3 except that the soluble polyimide solution G was used instead of the soluble polyimide solution A.

Comparative Example 3
NMP 101.50 g was changed to 93.69 g, SiDA 2.73 g was changed to 10.93 g, MBAA 9.45 g was changed to 12.60, and D-400 and DAPE were not added, and the same as Comparative Example 2 A soluble polyimide solution H (solid content concentration 40.0% by weight) was obtained. As a result of measuring the weight average molecular weight of the soluble polyimide by size removal chromatography, it was 10,350. A photosensitive resin composition that is a viscous liquid was obtained in the same manner as in Example 2 except that the soluble polyimide solution H was used instead of the soluble polyimide solution A.

  The compositions of Examples 1 to 7 and Comparative Examples 1 to 3 are shown in Table 1, and the evaluation results are shown in Table 2.

Claims (5)

(A) Contains a soluble polyimide having a weight average molecular weight of 10,000 or more and 30,000 or less, has a tensile elastic modulus of 2.5 GPa or less after heat treatment at 200 ° C. for 1 hour, and has a tensile elongation of 5% or more. A photosensitive cover lay characterized by the above. The soluble polyimide (A) having a weight average molecular weight of 10,000 or more and 30,000 or less contains a diamine residue represented by the following general formula (1) in an amount of 30 mol% or more of all diamine residues. Item 2. A photosensitive cover lay according to item 1.

(In said general formula (1), n shows the range of 3-10.) The (A) soluble polyimide having a weight average molecular weight of 10,000 or more and 30,000 or less contains a diamine residue represented by the following chemical formula (2) in an amount of 5 mol% to 15 mol% in all diamine residues. The photosensitive cover lay according to claim 1 or 2.

The soluble polyimide (A) having a weight average molecular weight of 10,000 to 30,000 contains a diamine residue represented by the general formula (1) and a diamine residue represented by the chemical formula (2), The total content is 50 mol% or more in all diamine residues, The photosensitive coverlay of Claim 2 or 3 characterized by the above-mentioned. The photosensitive coverlay according to any one of claims 1 to 4, further comprising (B) a compound having a photopolymerizable group and (C) a photopolymerization initiator.