JP5100716B2 - Negative photosensitive resin composition, polyimide resin film using the same, and flexible printed wiring board - Google Patents

Description

  The present invention relates to a negative photosensitive resin composition suitably used for forming a protective film of a flexible printed wiring board, a polyimide resin film using the negative photosensitive resin composition, and a flexible printed wiring board.

  Polyimide resins are used as a substrate for printed wiring boards, interlayer adhesives, coverlays (protective films) and the like because of their excellent heat resistance and good electrical insulation. Further, with the miniaturization of wiring, it has been studied to provide photosensitivity in order to finely process a polyimide resin as a protective film. After forming a coating film of a photosensitive resin composition containing a polyimide resin on the substrate on which the wiring is formed, the exposed portion is altered by irradiating ultraviolet rays or the like through a mask, so that only the exposed portion (positive type) Alternatively, only the non-exposed portion (negative type) can be removed, and the pattern can be formed.

  As a method of imparting photosensitivity to a polyimide precursor, a method of introducing a compound having a photoreactive functional group and an amino group into the polyimide precursor by ionic bonding is used. Patent Document 1 requires a polyimide precursor (polyamic acid), a compound (photopolymerizable monomer) containing a carbon-carbon double bond and an amino group or a quaternized salt thereof that can be dimerized or polymerized by actinic radiation. There is disclosed a negative photosensitive material comprising a sensitizer, a photoinitiator and a copolymerization monomer to be added according to the above. When this photosensitive material is irradiated with actinic radiation through a pattern, the photopolymerizable monomer is polymerized in the exposed area, and the amino group of the photopolymerizable monomer and the carboxyl group of the polyimide precursor are ionically bonded to form a solvent. Solubility decreases. Thereafter, the unexposed portion is dissolved and removed with a developer to form a pattern, and heated and cured to obtain a polyimide film.

  Another method for imparting photosensitivity to a polyimide precursor is to introduce a photoreactive functional group into the polyimide precursor by an ester bond. Patent Document 2 discloses such a photosensitive polyimide precursor.

  Patent Document 3 discloses a circuit board using a negative photosensitive polyimide resin as a protective film and a suspension board with circuit. The suspension board with circuit has an insulating layer on a metal foil base material such as stainless steel, and has a pattern circuit of a conductor layer made of a metal such as copper, and an insulating layer covering the insulating layer. In Patent Document 2, a negative photosensitive polyimide resin is used as an insulating layer covering the insulating layer and the conductor layer on the metal foil base material.

JP 54-145794 A Japanese Patent Publication No.55-41422 Japanese Patent Laid-Open No. 10-265572

  When using a negative photosensitive resin composition, the polyimide precursor of a non-exposed part is dissolved and removed with a developing solution. The exposed portion of the polyimide precursor remains patterned, and is cured by heating to form a polyimide film. In order to obtain good developability, it is necessary that the non-exposed part dissolves quickly without remaining undissolved, and the exposed part has little deterioration of the film due to the developing solution, and must be firmly adhered to the substrate.

  Furthermore, after the polyimide film is cured, a plating process such as gold plating may be performed on the exposed base material. However, if the adhesion between the polyimide film and the base material is not sufficient, the plating solution may be used between the polyimide film and the base material. There is a possibility that it may soak in between, deterioration of the polyimide film or peeling from the base material, and adhesion between the polyimide film and the base material is also necessary in terms of plating resistance.

  As a technique for improving the adhesion between the polyimide film and the substrate, it is conceivable to add an adhesion improver to the resin composition containing the polyimide precursor. However, by adding an adhesion improver, the adhesion between the polyimide precursor resin in the non-exposed area and the base material becomes strong, and undissolved areas (development residues) in the non-exposed area may occur during development.

  In view of the above problems, the present invention is a negative photosensitive resin composition that is excellent in solubility in a developer in a non-exposed area, has little film deterioration due to a developer in an exposed area, and has excellent adhesion to a substrate, and An object is to provide a polyimide resin film and a printed wiring board using the polyimide resin film.

The present invention is a polyimide precursor resin obtained by condensation polymerization of a carboxylic acid anhydride component containing an aromatic tetracarboxylic dianhydride having a biphenyl skeleton and a diamine component containing an aromatic diamine having a biphenyl skeleton, a photopolymerizable monomer, A negative photosensitive resin composition containing a photopolymerization initiator and an adhesion improver, wherein the adhesion improver is a compound having a thiadiazole skeleton or a triazole skeleton and a thiol group, and the adhesion improver The content is 0.2% by weight to 2.0% by weight based on the entire solid content of the negative photosensitive resin composition, and the negative photosensitive resin composition is formed into a film, and is heated and cured. A negative photosensitive resin composition characterized in that a thermal expansion coefficient of the obtained polyimide resin film is 10 ppm / ° C. or more and 30 ppm / ° C. or less .

  Various additives such as melamine and silane coupling agents can be mentioned as additives for improving the adhesion between the polyimide and the base material, and in the negative photosensitive polyimide, a thiadiazole skeleton or a triazole skeleton can be used as an adhesion improver. It has been found that by using a compound having a thiol group, the adhesion between the substrate and the polyimide film can be improved without degrading the developability (solubility of the developer in the non-exposed area).

The content of the adhesion improver is preferably 0.2 to 2.0% by weight with respect to the entire solid content of the negative photosensitive resin composition . When the content is less than 0.2 % by weight, there is a possibility that a sufficient adhesion improving effect cannot be obtained. On the other hand, if the content is more than 2.0% by weight, there is a possibility that undissolved portions of the non-exposed part may occur during development. The total solid content of the negative photosensitive resin composition is the total solid content of all materials including the polyimide precursor resin, the photopolymerizable monomer, the photopolymerization initiator, and other additives .

  The adhesion improver is preferably 5-amino-1,3,4-thiadiazole-2-thiol (Claim 2). 5-amino-1,3,4-thiadiazole-2-thiol is excellent in the effect of improving the adhesion between the polyimide film and the substrate, particularly when the substrate is a nickel plating layer.

  Moreover, this invention provides the polyimide resin film obtained by apply | coating one of the said photosensitive resin compositions on a base material, and heat-hardening. After application of the photosensitive resin composition, after drying the solvent, before being heated and cured, if exposed to light through a mask and developed with a developer, a polyimide resin film having an arbitrary pattern can be obtained. In this heat curing process, the polyimide precursor (polyamic acid) resin becomes a polyimide resin.

  Furthermore, the present invention provides a polyimide resin film obtained by the above production method and having a thermal expansion coefficient of 10 ppm / ° C. or more and 30 ppm / ° C. or less, and a flexible printed wiring board having the polyimide resin film as a protective film. provide.

  By setting the thermal expansion coefficient of the polyimide resin film to 10 ppm / ° C. or more and 30 ppm / ° C. or less, the thermal expansion coefficient of the polyimide resin film can be made close to metals such as stainless steel and copper, and flexible printed wiring combined with these metals. In the plate, warpage due to temperature change can be reduced. A more preferable range of the thermal expansion coefficient is 15 ppm / ° C. or more and 20 ppm / ° C. or less. Such a flexible printed wiring board is particularly preferably used as a suspension substrate used in a hard disk drive. The thermal expansion coefficient can be measured with a thermomechanical analyzer (TMA), and is an average value from 50 ° C to 150 ° C.

  According to the present invention, it is possible to obtain a negative photosensitive resin composition that is excellent in solubility in a developer in a non-exposed portion, has little film deterioration due to a developer in an exposed portion, and has excellent adhesion to a substrate. . Moreover, by using this negative photosensitive resin composition, a polyimide resin film with little film deterioration can be obtained.

  The polyimide precursor resin (polyamic acid) constituting the negative photosensitive resin composition of the present invention is obtained by condensation polymerization of an aromatic tetracarboxylic dianhydride component and a diamine component containing an aromatic diamine. This condensation polymerization reaction can be performed under the same conditions as in the conventional synthesis of polyimide.

  Examples of aromatic tetracarboxylic dianhydrides include 3,4,3 ′, 4′-biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), 3,3 ′, 4,4. '-Benzophenone tetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 3,3', 4,4'-diphenylsulfone tetracarboxylic dianhydride, bicyclo (2,2,2) -oct -7-ene-2,3,5,6-tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxylicoxyphenyl) Examples include hexafluoropropane dianhydride, 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride, and the like.

  Among them, 3,4,3 ′, 4′-biphenyltetracarboxylic dianhydride (BPDA) represented by the following formula (I) has a rigid structure having a biphenyl skeleton, and has a low thermal expansion coefficient of polyimide resin. This is preferable because it is possible. The content of BPDA is preferably 50 mol% or more based on the total amount of the aromatic tetracarboxylic dianhydride components. By setting it as such a monomer structure, content of the monomer with the biphenyl skeleton which is a rigid component can be increased, and the thermal expansion coefficient of a polyimide can be made low.

  The polyimide precursor resin is obtained by condensation polymerization of an aromatic tetracarboxylic dianhydride and two or more diamines. As the diamine or the aromatic tetracarboxylic dianhydride, 2 monomers having a biphenyl skeleton are used. The content of the monomer having at least two types and having the biphenyl skeleton is 50 mol% or more based on the total amount of the aromatic tetracarboxylic dianhydride and the diamine, and the diamine includes a tetramethyldisiloxane skeleton. It is preferable to contain 0.5 mol% or more and 5 mol% or less of diamine with diamine.

  By using two or more monomers having a biphenyl skeleton that is a rigid component and making the content 50 mol% or more, the thermal expansion coefficient can be lowered and good developability can be obtained. At the same time, by using a small amount of a diamine having a flexible tetramethyldisiloxane skeleton and introducing the disiloxane skeleton into the polymer main chain, the adhesion to the substrate can be improved, and the transparency (i-line permeability) of the polyimide resin can be improved. It can be improved. The monomer having a biphenyl skeleton may be either an aromatic tetracarboxylic dianhydride or a diamine, but a monomer having a biphenyl skeleton may be used for both the aromatic tetracarboxylic dianhydride and the diamine. preferable.

  Examples of the diamine include 2,2′-dimethyl 4,4′-diaminobiphenyl (mTBHG), 2,2′-bis (trifluoromethyl) 4,4′-diaminobiphenyl (TFMB), 2,2′-bis ( 4-Aminophenyl) hexafluoropropane (Bis-A-AF) paraphenylenediamine (PPD), 4,4′-diaminodiphenyl ether (ODA), 3,3′-dihydroxy 4,4′-diaminobiphenyl, 4, 4 Examples include '-dihydroxy 3,3'-diaminobiphenyl.

  Among these, 2,2′-dimethyl 4,4′-diaminobiphenyl (mTBHG) represented by the formula (II) and 2,2′-bis (trifluoromethyl) 4,4 represented by the formula (III) '-Diaminobiphenyl (TFMB) is a rigid structure having a biphenyl skeleton, and is preferable in that the thermal expansion coefficient of the polyimide resin can be lowered.

  The monomer having a biphenyl skeleton may be an aromatic tetracarboxylic dianhydride or a diamine, and if it is 50 mol% or more based on the entire monomer component (total amount of aromatic tetracarboxylic acid and diamine). preferable. The content of the monomer having a more preferable biphenyl skeleton is 70% or more.

  Moreover, it is necessary to contain 0.5 mol% or more and 5 mol% or less of diamine having a tetramethyldisiloxane skeleton as the diamine with respect to the entire diamine component. By containing a small amount of a diamine having a tetramethyldisiloxane skeleton, the adhesion of the polyimide resin is improved. If the amount of the diamine having a tetramethyldisiloxane skeleton is less than 0.5 mol%, the above effect cannot be obtained sufficiently. On the other hand, when it exceeds 5 mol%, the thermal expansion coefficient of the polyimide resin increases.

  A diamine having a tetramethyldisiloxane skeleton is a compound having a siloxane skeleton and two primary amino groups at its ends. For example, a product represented by the following formula (IV) is widely used.

  In addition to the above, those represented by the following structural formulas are also exemplified.

  Furthermore, it is preferable to contain a fluorinated monomer as a diamine or aromatic tetracarboxylic dianhydride in an amount of 20 mol% or more and 70 mol% or less with respect to the entire diamine component. By containing the fluorinated monomer, the transparency (light transmittance) of the polyimide resin can be improved, and the solubility is improved, so that the developability with a thick film is improved.

  Examples of the fluorinated monomer include 2,2′-bis (trifluoromethyl) 4,4′-diaminobiphenyl (TFMB) and 2,2′-bis (4-aminophenyl) represented by the formula (VI). Examples include hexafluoropropane (BIS-A-AF).

  The weight average molecular weight by GPC measurement of the polyimide precursor resin constituting the negative photosensitive resin composition of the present invention is preferably in the range of 20,000 to 400,000. When the weight average molecular weight exceeds this range, the printability of the composition is liable to be lowered, and the remaining residue during development is likely to occur. On the other hand, if the weight average molecular weight is less than this range, problems such as film deterioration during development and insufficient mechanical strength of the film may occur.

  A compound having a thiadiazole skeleton or a triazole skeleton and a thiol group is used as an adhesion improver constituting the negative photosensitive resin composition of the present invention. As a compound having a thiadiazole skeleton or a triazole skeleton and a thiol group, 5-amino-1,3,4-thiadiazole-2-thiol represented by the formula (VII), 1,3 represented by the formula (VIII) , 4-thiadiazole-2,5-thiol, 5-methyl-1,3,4-thiadiazole-2-thiol represented by formula (IX), 1H-1,3,4 represented by formula (X) -Triazole-3-thiol etc. are mentioned.

  These adhesion improvers are excellent in the effect of improving the adhesion between the substrate and the polyimide film without impairing the developability. In particular, when the base material is nickel, the effect of improving the adhesion is high.

  The photopolymerizable monomer constituting the negative photosensitive resin composition of the present invention is a monomer having a photoreactive functional group that is crosslinked by irradiation (exposure) with X-rays, electron beams, ultraviolet rays, or the like. In the present invention, it is preferable to use a compound having a photoreactive functional group such as an unsaturated double bond and an amino group as the photopolymerizable monomer. Such compounds include N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminoethyl acrylate, N, N-diethylaminoethyl methacrylate, N, N-diethylaminoethyl acrylate, N, N-methacrylate. Dimethylaminomethyl, N, N-dimethylaminopropyl methacrylate, N, N-dimethylaminomethyl acrylate, N, N-dimethylaminopropyl acrylate, acrylamide, methacrylamide, N-methylmethacrylamide, N-methylacrylamide, N-ethyl methacrylamide, N-ethyl acrylamide, N-isopropyl methacrylamide, N-isopropyl acrylamide, N-butyl methacrylamide, N-butyl acrylamide, diacetone acrylamide, diacetone methacrylamide N-cyclohexylmethacrylamide, N-cyclohexylacrylamide, N-methylacrylamide, acryloylmorpholine, methacryloylmorpholine, acryloylpiperidine, methacryloylpiperidine, crotonamide, N-methylcrotonamide, N-isopropylcrotonamide, N-butyl Examples include crotonamide, acetic acid allylamide, propionic acid allylamide, and the like. The photopolymerizable monomer is preferably blended in the range of 1 to 1.5 equivalents relative to the carboxyl group of the polyimide precursor resin.

  Furthermore, in the present invention, a small amount of a compound having a photoreactive functional group and a glycidyl group may be added as a photopolymerizable monomer. As the compound having a photoreactive functional group and a glycidyl group, glycidyl (meth) acrylate such as glycidyl methacrylate and glycidyl acrylate can be used. In addition, compounds such as 4-hydroxybutyl acrylate glycidyl ether and allyl glycidyl ether can also be used.

  The photopolymerization initiator constituting the photosensitive resin composition of the present invention includes an α-aminoketone type as the i-line (wavelength 365 nm) absorption type and a metallocene such as a titanocene compound as the g-line (wavelength 436 nm) absorption type. Those of the system are preferably used. When any initiator is blended in an amount of 0.1 to 10% by weight based on the solid content of the polyimide precursor resin, good developability can be obtained. In the case of forming a thick film, it is desirable to use a g-line absorption type photopolymerization initiator because the low CTE polyimide precursor has absorption on the long wavelength side.

  The negative photosensitive resin composition of this invention can be obtained by mixing said polyimide precursor resin, a photopolymerizable monomer, and a polymerization initiator. Moreover, the photosensitive resin composition of this invention may contain various additives as needed. Additives include dyes for improving visibility during development, and pigments include phenolphthalein, phenol red, neil red, pyrogallol red, pyrogallol billet, disperse thread 1, disper thread 13, disper thread 19, disperse orange 1, disperse orange 3, disperse orange 13, disperse orange 25, disperse blue 3, disperse blue 14, eosin B, rhodamine B, quinalizarin, 5- (4-dimethylaminobenzylidene) rhodanine, aurin tricarboxyacid , Aluminone, alizarin, pararosaniline, emodin, thionine, methylene violet, pigment blue, pigment red and the like. Further, as an additive for improving the dissolution promotion of the non-exposed portion, benzenesulfonamide, N-methylbenzenesulfonamide, N-ethylbenzenesulfonamide, N, N-dimethylbenzenesulfonamide, Nn-butylbenzenesulfonamide, Nt-butylbenzenesulfonamide, N, N-di-n-butylbenzenesulfonamide, benzenesulfonanilide, N, N-diphenylbenzenesulfonamide, Np-tolylbenzenesulfonamide, N-o-tolylbenzene Sulfonamide, Nm-tolylbenzenesulfonamide, N, N-di-p-tolylbenzenesulfonamide, p-toluenesulfonamide, N-methyl-p-toluenesulfonamide, N-ethyl-p-toluenesulfonamide N, N-dimethyl-p-tolu Sulfonamide, Nn-butyl-p-toluenesulfonamide, Nt-butyl-p-toluenesulfonamide, N, N-di-n-butyl-p-toluenesulfonamide, N-phenyl-p- Toluenesulfonamide, N, N-diphenyl-p-toluenesulfonamide, Np-tolyl-p-toluenesulfonamide, Nm-tolyl-p-toluenesulfonamide, N, N-di-p-tolyl- p-toluenesulfonamide, N, N-di-m-tolyl-p-toluenesulfonamide, o-toluenesulfonamide, N-methyl-o-toluenesulfonamide, N-ethyl-o-toluenesulfonamide, N, N-dimethyl-o-toluenesulfonamide, Nn-butyl-o-toluenesulfonamide, Nt-butyl-o-tolue Sulfonamide, N, N-di-n-butyl-o-toluenesulfonamide, N-phenyl-o-toluenesulfonamide, N, N-diphenyl-o-toluenesulfonamide, Np-tolyl-o-toluene Sulfonamide, Nm-tolyl-o-toluenesulfonamide, N, N-di-p-tolyl-o-toluenesulfonamide, N, N-di-m-tolyl-o-toluenesulfonamide, naphthalenesulfonamide N-methylnaphthalenesulfonamide, N-ethylnaphthalenesulfonamide, N, N-dimethylnaphthalenesulfonamide, Nn-butylnaphthalenesulfonamide, Nt-butylnaphthalenesulfonamide, N, N-di-n- Butylnaphthalenesulfonamide, N-phenylnaphthalenesulfonamide, N, N-di Phenylnaphthalenesulfonamide, Np-tolylnaphthalenesulfonamide, No-tolylnaphthalenesulfonamide, Nm-tolylnaphthalenesulfonamide, N, N-di-p-tolylnaphthalenesulfonamide, N, N-di -M-Tolylnaphthalenesulfonamide, 2,3-dimethylbenzenesulfonamide, N-methyl-2,3-dimethylbenzenesulfonamide, Nn-butyl-2,3-dimethylbenzenesulfonamide, p-ethylbenzenesulfonamide N-methyl-p-ethylbenzenesulfonamide, N-ethylbenzenesulfonamide, N, N-dimethylbenzenesulfonamide, Nn-butyl-p-ethylbenzenesulfonamide and the like.

  A step of applying the negative photosensitive resin composition on a substrate, a step of heating the obtained film to remove the solvent, a step of exposing the film from which the solvent has been removed through a mask, and a developer A polyimide resin film is obtained by the step of developing using and the step of heat-curing the film after development.

  For the application of the photosensitive resin composition, a general method such as screen printing or spin coating can be used. Moreover, it can carry out similarly to the case where the conventional negative photosensitive resin composition is used also about a subsequent process.

  The polyimide resin film thus obtained can be formed into a thick film, and the film thickness during development can be 20 μm or more. Further, the thermal expansion coefficient can be 10 ppm / ° C. or more and 30 ppm / ° C. or less. Since the thermal expansion coefficient of stainless steel is about 17 ppm / ° C and the thermal expansion coefficient of copper is about 19 ppm / ° C, the thermal expansion coefficient of the polyimide resin film is 10 ppm / ° C to 30 ppm / ° C, more preferably 15 ppm / ° C to 20 ppm. By setting the temperature to / ° C. or less, the thermal expansion coefficient of the polyimide resin film can be made closer to the thermal expansion coefficient of the metal, and when both are combined, a product with less warpage due to temperature change can be obtained.

  In addition, a thermal expansion coefficient can be measured with a thermomechanical analyzer (TMA), and is made into the average value from 50 degreeC to 150 degreeC here.

  Moreover, this invention provides the flexible printed wiring board which has said polyimide resin film as a protective film. For example, a single-sided flexible printed wiring board having conductor wiring made of a metal such as copper on one side of a polyimide base material and having the polyimide resin film as a coverlay film (protective film) on the conductor wiring can be exemplified. In addition, an insulating layer such as polyimide is provided on a metal foil base material such as stainless steel, conductor wiring (circuit) made of metal such as copper is provided thereon, and the polyimide resin film is protected on the conductor wiring. Examples of the suspension board with circuit included in FIG. The conductor wiring (circuit) may be used after being nickel-plated, and in this case, the adhesion between the polyimide film and the conductor wiring is particularly improved. Moreover, it is also possible to use said polyimide resin film as an insulating layer on a metal foil base material. This suspension board with circuit is used as a suspension board used in a hard disk drive.

  Next, the best mode for carrying out the invention will be described by way of examples. The examples are not intended to limit the scope of the invention.

Example 1
2,5′-dimethyl 4,4′-diaminobiphenyl (mTBHG) 35.5 g (120 mmol) and p-phenylenediamine (PPD) 19.4 g (180 mmol) were dissolved in 700 g of N-methylpyrrolidone, Add 44.2 g (150 mmol) of 4,3 ′, 4′-biphenyltetracarboxylic dianhydride (BPDA) and 32.7 g (150 mmol) of pyromellitic dianhydride (PMDA) for 1 hour at room temperature in a nitrogen atmosphere. Stir. Thereafter, the reaction was completed by stirring at 60 ° C. for 20 hours. The synthesized copolymer varnish had a solid content of 16.5% and a viscosity at 24 ° C. of 20,000 cps (measured with a B-type viscometer). The varnish was mixed with 0.5% by weight of 5-amino-1,3,4-thiadiazole-2-thiol as an adhesion improver based on the total solid content of the varnish, and methacrylic acid N, which is a photopolymerizable monomer. , N-dimethylaminoethyl with respect to carboxylic acid of polyamic acid, 1.2 equivalent, 2-benzyl 2- (dimethylamino) -1- [4- (4-morpholinyl) phenyl] -1-butanone as a polymerization initiator And bis (cyclopentadienyl) -bis [2,6-difluoro-3- (py-1-yl) phenyl] titanium are mixed in an amount of 4% and 2%, respectively, based on the total varnish solid content, and further benzenesulfonanilide. Was mixed with 5% of the entire solid content of the varnish to prepare a negative photosensitive resin composition.

The negative photosensitive resin composition was applied onto a copper foil having a thickness of 40 μm by a spin coating method, followed by heating and drying at 90 ° C. for 30 minutes to form a film of a photosensitive polyimide precursor having a thickness of 20 μm. Next, ultraviolet light was irradiated through a negative test pattern at an exposure amount of 500 mJ / cm ² and then post-baked at 105 ° C. for 10 minutes. Subsequently, development processing was performed at 30 ° C. using an organic solvent-based developer, washed thoroughly with distilled water, and then forced-air dried with a nitrogen stream. Then, when the polyimide precursor was imidized by performing heat treatment at 120 ° C. for 30 minutes, 220 ° C. for 30 minutes, and 340 ° C. for 60 minutes in a nitrogen atmosphere, a good development pattern was maintained with almost no film loss. A polyimide resin film was obtained. The obtained cured polyimide film had a thermal expansion coefficient of 17 ppm / ° C. and a residual film ratio of 85%. The thermal expansion coefficient is measured by TMA measurement (tensile test) using a thermal stress strain measuring device “TMA / SS120C” manufactured by Seiko Instruments Inc., and the temperature rise is −50 ° C. → 200 ° C. → −50 ° C. The average value in the temperature range from 50 ° C. to 150 ° C. was determined by measuring both in descending. The obtained sample was cut to a width of 5.0 mm, subjected to a 180 ° peel test, and the adhesion between copper and the polyimide film was measured. The adhesion to copper was 0.9 kgf / cm.

  The negative photosensitive resin composition is applied onto a base material plated with electroless nickel on a copper foil by a spin coating method and then treated under the same conditions as above to increase the adhesion between nickel and the polyimide film. It was measured. The adhesion strength to nickel was 0.7 kgf / cm.

(Comparative Example 1)
On copper foil and electroless nickel-plated copper foil by performing the same operation as in Example 1 except that 5-amino-1,3,4-thiadiazole-2-thiol as an adhesion improver was not added A polyimide film having a thickness of 20 μm after pre-baking was prepared. A polyimide resin film having a good development pattern with almost no film loss was obtained. However, when the adhesive strength with copper and nickel was evaluated, the adhesive strength with respect to copper was 0.5 kgf / cm, and the adhesive strength with respect to nickel was 0. .3 kgf / cm, which is lower in adhesion than Example 1.

(Example 2)
2,2′-bis (trifluoromethyl) 4,4′-diaminobiphenyl (TFMB) 43.2 g (135 mmol), 2,2′-dimethyl4,4′-diaminobiphenyl (mTBHG) 33.8 g (159 mmol) 1,3-bis (3-aminopropyl) tetramethyldisiloxane (APDS) 1.49 g (6.0 mmol) was dissolved in 700 g of N-methylpyrrolidone, and then 3,4,3 ′, 4′-biphenyl was dissolved. Tetracarboxylic dianhydride (BPDA) 44.2 g (150 mmol) and pyromellitic dianhydride (PMDA) 32.7 g (150 mmol) were added, and the mixture was stirred at room temperature for 1 hour in a nitrogen atmosphere. Thereafter, the reaction was completed by stirring at 60 ° C. for 20 hours. The synthesized copolymer varnish had a solid content of 18.2% and a viscosity at 24 ° C. of 24,000 cps (measured with a B-type viscometer). In this varnish, 5-amino-1,3,4-thiadiazole-2-thiol was mixed as an adhesion improver in an amount of 0.27% by weight based on the entire solid content of the varnish, and a photopolymerizable monomer, methacrylic acid N, 1.2 equivalents of N-dimethylaminoethyl to carboxylic acid of polyamic acid, and 2-benzyl 2- (dimethylamino) -1- [4- (4-morpholinyl) phenyl] -1-butanone as a polymerization initiator Bis (cyclopentadienyl) -bis [2,6-difluoro-3- (py-1-yl) phenyl] titanium is mixed with 4% and 2% of the total varnish solid content, respectively, and benzenesulfonanilide is further added. 5% of the solid content of the varnish was mixed to prepare a negative photosensitive resin composition.

  Using the obtained negative photosensitive resin composition, the same operation as in Example 1 was performed to create a polyimide film having a thickness after pre-baking of 20 μm on the copper foil and the electroless nickel-plated copper foil. . A polyimide resin film having almost no film reduction and maintaining a good development pattern was obtained. The obtained cured polyimide film had a thermal expansion coefficient of 17 ppm / ° C. and a residual film ratio of 85%. When the adhesive strength with copper and nickel was evaluated, the adhesive strength with respect to copper was 1.0 kgf / cm, the adhesive strength with respect to nickel was 0.7 kgf / cm, and the adhesion to the substrate was good as in Example 1. It is.

( Reference Examples 1-2 , Examples 5-6 , Comparative Example 2)
Except that the addition amount of 5-amino-1,3,4-thiadiazole-2-thiol was changed to the amount shown in Table 1, the same operation as in Example 2 was performed, and the thickness after pre-baking on nickel was 20 μm. A polyimide film was prepared and evaluated for adhesion with nickel. The results are shown in Table 1.

Compared to Comparative Example 2 in which 5-amino-1,3,4-thiadiazole-2-thiol was not added, 0.07% by weight of 5-amino-1,3,4-thiadiazole-2-thiol was added. In Reference Example 1 , the adhesive force is improved although the adhesive force is as small as 0.44 kgf / cm. Example 2 in which the adhesion to nickel is improved as the addition amount of 5-amino-1,3,4-thiadiazole-2-thiol increases, and the addition amount is in the range of 0.2 wt% to 1.0 wt%. In Examples 5 and 6, the adhesive strength is 0.6 kgf / cm, and it can be seen that it is particularly preferable to set the addition amount within this range. In addition, in the varnish of the comparative example 2, the adhesive force with respect to copper was also evaluated, and the result was 0.52 kgf / cm.

(Example 7)
2,2′-bis (trifluoromethyl) 4,4′-diaminobiphenyl (TFMB) 48.0 g (150 mmol) and p-phenylenediamine (PPD) 16.2 g (150 mmol) were dissolved in N-methylpyrrolidone 700 g. Thereafter, 88.3 g (300 mmol) of 3,4,3 ′, 4′-biphenyltetracarboxylic dianhydride (BPDA) was added and stirred at room temperature for 1 hour under a nitrogen atmosphere. Thereafter, the reaction was completed by stirring at 60 ° C. for 20 hours. The synthesized copolymer varnish had a solid content of 16.2% and a viscosity at 24 ° C. of 24,000 cps (measured with a B-type viscometer). While mixing 0.7 wt% of 5-amino-1,3,4-thiadiazole-2-thiol as an adhesion improver to the varnish with respect to the entire solid content of the varnish, methacrylic acid N, which is a photopolymerizable monomer, 1.2 equivalents of N-dimethylaminoethyl to carboxylic acid of polyamic acid, and 2-benzyl 2- (dimethylamino) -1- [4- (4-morpholinyl) phenyl] -1-butanone as a polymerization initiator And bis (cyclopentadienyl) -bis [2,6-difluoro-3- (py-1-yl) phenyl] titanium are mixed in an amount of 1% and 3%, respectively, with respect to the entire varnish solid content, and further benzenesulfonanilide. Was mixed 6% with respect to the whole varnish solid content, and the negative photosensitive resin composition was produced.

  Using the obtained negative photosensitive resin composition, the same operation as in Example 1 was performed to create a polyimide film having a thickness after pre-baking of 20 μm on the copper foil and the electroless nickel-plated copper foil. . A polyimide resin film having almost no film reduction and maintaining a good development pattern was obtained. The obtained cured polyimide film had a thermal expansion coefficient of 16 ppm / ° C. and a residual film ratio of 85%. When the adhesive strength with copper and nickel was evaluated, the adhesive strength with respect to copper was 0.71 kgf / cm, the adhesive strength with respect to nickel was 0.73 kgf / cm, and the adhesion to the substrate was good as in Example 1. It is.

(Comparative Examples 3 to 11)
The thickness after pre-baking on the copper foil and the electroless nickel-plated copper foil is 20 μm by performing the same operation as in Example 7 except that the type and amount of adhesion improver are changed to those shown in Table 2. A polyimide film was prepared and evaluated for adhesion to copper and nickel. The results are shown in Table 2.

(* 1) (Nippon Cytec Industries, Inc., Cymel (registered trademark) 303: Hexamethoxymelamine)
(* 2) Shin-Etsu Chemical Co., Ltd., KBM-573
(* 3) (Cipro Kasei Co., Ltd., SEETEC BT-R)

  The evaluation criteria are an adhesive strength to copper of 0.7 kgf / cm or higher and an adhesive strength to nickel of 0.4 kgf / cm or higher. In Examples 1 to 3 using 5-amino-1,3,4-thiadiazole-2-thiol as an adhesion improver, both satisfy the evaluation criteria. In Comparative Examples 4 and 5 using a melamine compound as an adhesion improver, the adhesion to copper is slightly improved as compared to Comparative Example 3 in which no adhesion improver is added, but the adhesion to nickel is almost unchanged. . In Comparative Example 7 in which the addition amount was 0.70% by weight using a silane coupling agent, the adhesion strength to nickel was slightly improved, but conversely, the adhesion strength to copper was low and did not satisfy the evaluation criteria. In Comparative Examples 8 and 9 using benzotriazole, no effect of improving the adhesive strength is observed for both copper and nickel. From these results, it can be seen that the use of 5-amino-1,3,4-thiadiazole-2-thiol, which is a compound having a thiadiazole skeleton and a thiol group, has a remarkable effect of improving adhesive strength.

Example 4
After preparing a SUS / low CTE polyimide / copper fine wiring (minimum L / S 20 μm pitch) base material and electroless nickel-plating the copper fine wiring, spin the negative photosensitive resin composition used in Example 2 After coating by a coating method, it was dried by heating at 90 ° C. for 30 minutes to form a photosensitive polyimide precursor film having a thickness of 20 μm. Next, ultraviolet light was irradiated at an exposure amount of 1000 mJ / cm ² through a negative test pattern, and then post-baked at 105 ° C. for 20 minutes. Subsequently, development processing was performed at 30 ° C. using an organic solvent-based developer, washed thoroughly with distilled water, and then forced-air dried with a nitrogen stream. Thereafter, the temperature was raised while gradually heating in a nitrogen atmosphere, and finally a heat treatment was performed at 350 ° C. for 2 hours to imidize the polyimide precursor. As a result, a good development pattern was maintained with almost no film loss. A polyimide resin film was obtained. After this, when the exposed conductor (nickel-plated copper) was gold-plated, gold plating was possible without any problem, soaking of the plating solution into the polyimide film or peeling of the polyimide film was observed. There wasn't.

  The same operation as in Example 4 was performed using the negative photosensitive resin composition of Comparative Example 2 in which no adhesion improver was added. The sample after gold plating was found to have poor plating resistance due to seeping of a plating solution in a part of the polyimide film.

  From the above results, the negative photosensitive resin compositions of Examples 1 to 3 using a thiadiazole skeleton or a compound having a triazole skeleton and a thiol group as an adhesion improver have high adhesion to copper and nickel, and further implemented. It can be seen that the formulation of Example 2 also has good resistance to gold plating.

Claims (5)

Polyimide precursor resin, photopolymerizable monomer, photopolymerization initiator obtained by condensation polymerization of a carboxylic anhydride component containing an aromatic tetracarboxylic dianhydride having a biphenyl skeleton and a diamine component containing an aromatic diamine having a biphenyl skeleton And a negative photosensitive resin composition containing an adhesion improver,
The adhesion improver is a compound having a thiadiazole skeleton or a triazole skeleton and a thiol group, and the content of the adhesion improver is 0.2% by weight to the total solid content of the negative photosensitive resin composition The thermal expansion coefficient of the polyimide resin film obtained by forming the negative photosensitive resin composition and heat-curing the film is 1.0 wt% to 30 ppm / ° C. A negative photosensitive resin composition.   The negative photosensitive resin composition according to claim 1, wherein the adhesion improver is 5-amino-1,3,4-thiadiazole-2-thiol. A polyimide resin film obtained by forming the negative photosensitive resin composition according to claim 1 or 2 and heating and curing it. A flexible printed wiring board having the polyimide resin film according to claim 3 as a protective film. The flexible printed wiring board according to claim 4 , wherein the flexible printed wiring board is used as a substrate for a suspension used in a hard disk drive.