JP2008280497A - Polyimide composition and flexible wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyimide composition that contains a polyimide compound high in alkali solubility and a resol resin, and is improved in its plating resistance, as well as does not cause loss of film at the time of development using an aqueous alkali solution, and to provide a flexible wiring board using the polyimide composition. <P>SOLUTION: The polyimide compound formed by polymerizing 3,3',4,4'-diphenylsulphone-tetracarboxylic acid dianhaydride with 3,3'-diamino-4,4'-dihydroxydiphenyl sulphone is high in alkali solubility, and is capable of being alkali-developed in a good state by adding a photosensitizer. Addition of a resol resin of 1-4 pts.wt. to the polyimide compound can provide the polyimide composition that can form a prescribed pattern in a good state by alkali development using the aqueous alkali solution, has plating resistance, and provides the flexible wiring board. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a flexible wiring board having a polyimide composition and a polyimide layer formed from the polyimide composition.

  In the production of insulating films and multilayer wiring boards, there is a photosensitive resin composition in which a phenol resin is added to an epoxy resin / acrylic resin as a part of the composition (see, for example, Patent Document 1). This photosensitive resin composition is improved in alkali solubility by adding a phenol resin. Among them, the resole resin increases the glass transition point by increasing the crosslinking density of the photosensitive resin composition by an acid-catalyzed self-condensation reaction, and reduces the amount of phenolic hydroxyl groups remaining. Improves plating properties.

JP 11-49847 A

  However, it is one of the phenol resins that improve alkali solubility as described above, and when a resol resin having more phenolic hydroxyl groups than phenol resin is added in a large amount to a resin that is originally highly alkali soluble, The alkali solubility becomes too high due to the phenolic hydroxyl group in the resole resin. Therefore, the resin film is reduced during alkali development, which may cause adverse effects.

  Therefore, in view of the above situation, the present invention is a polyimide composition containing a highly alkali-soluble polyimide compound and a resole resin, which improves plating resistance and does not cause film loss during development with an alkaline solution. An object is to provide a polyimide composition. And it aims at providing the flexible wiring board using the polyimide composition.

  The polyimide composition of the present invention is obtained by polymerization of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride, 3,3′-diamino-4,4′-dihydroxydiphenylsulfone, and siloxane diamine. It contains a polyimide compound to be synthesized, a resol resin in an amount of 1 to 4 parts by weight with respect to 100 parts by weight of the polyimide compound, and a photosensitizer.

  According to the polyimide composition of the present invention, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride and 3,3′-diamino-4,4′-dihydroxydiphenylsulfone are polymerized. The polyimide compound formed in (1) has improved solubility in an alkaline aqueous solution, and has good developability when irradiated with light by addition of a photosensitizer. By adding 1 part by weight to 4 parts by weight of a resole resin to this polyimide compound, the plating resistance of the polyimide composition is improved without causing film loss of the polyimide film formed by forming the polyimide composition. Can do.

  The flexible wiring board of the present invention comprises a conductor and 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride, 3,3′-diamino-4,4′-dihydroxydiphenylsulfone on the conductor and the conductor. And a polyimide layer comprising a polyimide composition containing a polyimide compound synthesized by polymerization of siloxane diamine, a resol resin of 1 part by weight to 4 parts by weight with respect to 100 parts by weight of the polyimide compound, and a photosensitizer. It is characterized by having.

  According to the flexible wiring board of the present invention, as described above, it has a polyimide layer made of a polyimide composition to which plating resistance is imparted without causing film loss due to an alkaline aqueous solution by a resol resin. Therefore, even if the resole resin is added, the flexible wiring board of this invention can form a predetermined pattern satisfactorily by exposure and alkali development with an aqueous alkali solution. Further, the adhesion between the polyimide layer and the conductor is improved by the resol resin added to the polyimide composition, and the phenomenon in which the end portion of the polyimide layer floats from the conductor can be minimized in plating after pattern formation.

  According to the polyimide composition of the present invention, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride and 3,3′-diamino-4,4′-dihydroxydiphenylsulfone are polymerized. The polyimide compound formed in (1) has high alkali solubility, and good alkali development is possible by adding a photosensitizer. By adding 1 to 4 parts by weight of a resole resin to this polyimide compound, it is possible to impart plating resistance to the polyimide composition without causing film loss.

  And according to the flexible wiring board of this invention, even if a resol resin is added, a predetermined pattern can be favorably formed by exposure and alkali development by aqueous alkali solution by using this polyimide composition. Further, the adhesion between the polyimide layer and the conductor is improved by the resol resin added to the polyimide composition, and the phenomenon in which the end portion of the polyimide layer floats from the conductor can be minimized in plating after pattern formation.

  Hereinafter, the polyimide composition of this invention and the manufacturing method of a polyimide composition are demonstrated. Note that the present invention is not limited to the following description, and can be appropriately changed without departing from the spirit of the present invention.

  The polyimide composition of the present invention is obtained by adding a small amount of a resole resin to a polyimide compound having a high alkali solubility, without causing a film loss of the polyimide film formed by forming the polyimide composition with an alkaline aqueous solution, Plating resistance can be imparted. In the present invention, the plating resistance is not only the resistance of the polyimide composition itself to the plating solution, but also, for example, when plating on a conductor having a polyimide film made of a polyimide composition, such as a flexible wiring board, It also shows the property that the phenomenon that the end portion is lifted from the conductor can be suppressed and the floating can be minimized, for example, the size of the floating is about 20 μm. That is, the polyimide composition having plating resistance can form a polyimide film in which the formed polyimide film has a small float. This polyimide composition contains a polyimide compound, a photosensitizer, a resole resin, a crosslinking agent, an oxazine compound, and a rust inhibitor.

  The polyimide compound constituting the polyimide composition of the present invention includes 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride (DSDA) and 3,3′-diamino-4,4′-dihydroxydiphenyl. It can be synthesized by polymerizing sulfone (BSDA) and siloxane diamine.

  This DSDA can improve the alkali solubility of the polyimide to be synthesized. This DSDA has sulfur and oxygen atoms with high electronegativity, and these atoms reach the imide carbonyl carbon through conjugation and are susceptible to base nucleophilic attack, so that alkali solubility is improved. It is thought to be a thing.

  BSDA polymerizes with DSDA together with siloxane diamine to synthesize a polyimide compound. This BSDA has high alkali solubility by having a hydroxyl group in the molecule.

  Siloxane diamine is polymerized with DSDA together with BSDA to synthesize a polyimide compound. The siloxane diamine may be any siloxane diamine as long as it does not significantly reduce the alkali solubility of the synthesized polyimide compound. For example, the siloxane diamine has at least a dimethylsilylene skeleton in the molecule. A siloxane diamine represented by the following structural formula 1 (wherein m represents 0 or an integer of 1 or more and n represents an integer of 1 or more) is preferable.

  By having this dimethylsilylene skeleton, a polyimide film having a low elastic modulus can be formed. By using this film for a flexible wiring board, a flexible wiring board having no warpage and good flame retardancy is obtained. In particular, a siloxane diamine represented by the above structural formula 1 having a dimethylsilylene skeleton and a diphenylsilylene skeleton in the molecule (wherein m represents an integer of 1 or more and n represents an integer of 1 or more) preferable. The diphenylsilylene skeleton can further make the polyimide composition flame-retardant. That is, it is not necessary to add a flame retardant to the polyimide composition, and a polyimide composition suitable for non-halogenation and non-phosphorization can be provided. Specific examples of such siloxane diamines include KF-8010, X-22-9409 (both manufactured by Shin-Etsu Chemical Co., Ltd.) and the like.

  The polyimide composition is synthesized by polymerizing DSDA as an acid dianhydride, BSDA as a diamine, and siloxane diamine. The amounts of acid dianhydride and diamine used in this synthesis may be the same or either one may be excessive. Moreover, the ratio of BSDA which is diamine and siloxane diamine is also arbitrary. This acid dianhydride and diamine are reacted to form an amic acid (imide precursor) component, and then heated, and the imidization in the solution proceeds to close the amic acid component (solution imidization). A polyimide compound can be synthesized.

  The solution imidization means may be any conditions as long as the cyclization dehydration reaction can be performed, and examples thereof include heating imidization in a solution and chemical imidization with a dehydrating agent. For example, in heat imidization, an azeotropic agent such as toluene and xylene is added to an imide precursor, and the mixture is heated and stirred at 180 ° C. or higher to perform a dehydration reaction of an amic acid component to form a ring-closed imide component. be able to. At this time, a tertiary catalyst such as triethylamine, a basic catalyst such as aromatic isoquinoline and pyridine, and an acid catalyst such as benzoic acid and parahydroxybenzoic acid may be added as a catalyst for imidization, if necessary. Further, for example, the amic acid can also be closed by a chemical imidizing agent such as acetic anhydride / pyridine or dicyclohexylcarbodiimide which is a dehydrating cyclization reagent.

  This polyimide compound is synthesized by dissolving the above acid dianhydride and diamine in a solvent such as γ-butyrolactone (GBL) and polycondensing the acid dianhydride and diamine in the solvent. Here, the solvent used is not limited to GBL. For example, an aprotic amide solvent such as triglyme (TriGL), N-methyl-2-pyrrolidone (NMP), or N, N-dimethylacetamide, or cresol. Phenol-based solvents such as can be used, but GBL, TriGL, NMP or a mixed solvent thereof is preferably used from the viewpoint of safety. Further, xylene, toluene, ethylene glycol monoethyl ether and the like may be mixed and used.

  The polyimide composition contains a photosensitizer. By containing this photosensitizer, photosensitivity can be imparted to the formed polyimide composition. Examples of the photosensitizer include a diazonaphthoquinone compound. The polyimide composition containing the diazonaphthoquinone compound changes its alkali solubility upon exposure. Before exposure, the solubility in an alkaline aqueous solution is low. On the other hand, after the exposure, the molecular structure of the diazonaphthoquinone compound changes to produce ketene, which reacts with an alkaline aqueous solution to produce carboxylic acid. The produced carboxylic acid is further reacted with water and dissolved. Therefore, the solubility in alkaline aqueous solution becomes high by irradiating light.

  By containing a diazonaphthoquinone compound as a photosensitizer, a polyimide compound having a hydroxyl group and relatively high alkali solubility has a hydrogen bond between the hydroxyl group and the diazonaphthoquinone compound. Thereby, the hydroxyl group which is easily dissolved in alkali is protected, and the alkali solubility is lowered. When the polyimide compound in this state is exposed to light, the molecular structure of the diazonaphthoquinone compound changes and alkali solubility is exhibited. Therefore, by containing a diazonaphthoquinone compound as a photosensitizer, sodium hydroxide (NaOH), potassium hydroxide, sodium carbonate, sodium bicarbonate, tetramethylammonium hydroxide (TMAH), etc. after exposure to the flexible wiring board. The pattern can be formed with an alkaline aqueous solution.

  The diazonaphthoquinone compound of the photosensitizer is not particularly limited as long as it is a compound having a diazonaphthoquinone skeleton. For example, 2,3,4-trihydroxybenzophenone o-naphthoquinonediazide-4-sulfonic acid ester, 2 3,4-trihydroxybenzophenone o-naphthoquinonediazide-5-sulfonic acid ester, 2,3,4-trihydroxybenzophenone o-benzoquinonediazide-4-sulfonic acid ester, and the like.

  The polyimide composition contains a resol resin. Since this resol resin is self-condensed, the crosslink density is increased when the polyimide composition is cured, and for example, the adhesion to the conductor can be increased. Thereby, plating resistance can be provided to a polyimide composition. That is, when the resol resin is contained in the polyimide composition of the present invention, for example, the floating of the end portion of the polyimide film provided on the conductor is reduced.

  The amount of the resol resin contained in the polyimide composition is preferably 1 part by weight or more and 4 parts by weight or less with respect to 100 parts by weight of the polyimide compound. Within this range, film reduction does not occur and good alkali development is possible. The resol resin contains a lot of phenolic hydroxyl groups. Therefore, for example, if it is added to a polymer having a high alkali solubility such as the above polyimide compound, the alkali solubility is further increased, and even in a portion not exposed to light, it is dissolved by the aqueous alkali solution and patterning becomes impossible. Moreover, the polyimide layer which consists of a polyimide composition may reduce a film | membrane by the improvement of alkali solubility. However, even if a resol resin is added to the above polyimide compound, film thickness reduction does not occur as long as it is 1 part by weight or more and 4 parts by weight or less, and good development with an alkaline aqueous solution becomes possible.

  The resol resin contained in the polyimide composition is not particularly limited. For example, the resol resin itself may be solid or liquid, but is preferably liquid. If the resol resin itself is liquid, even a small amount of resol resin can be easily dispersed uniformly in the polyimide film made of the polyimide composition.

  Moreover, as a resol resin contained in a polyimide composition, it is preferable that the viscosity of the resol resin itself is 13000 mPa · s or more. When the viscosity of the resol resin is 13000 mPa · s or less, the degree of polymerization is low, and many of them remain as monomers without being polymerized. Therefore, even when a resol resin having a viscosity of 13000 mPa · s or less is contained in the polyimide composition, many monomers are dissolved in the alkaline aqueous solution during development. Accordingly, there is a possibility that the polyimide film made of the polyimide composition is reduced.

  Furthermore, when a solid resol resin whose viscosity cannot be measured is contained, it takes a long time to uniformly disperse the resol resin in the polyimide film made of the polyimide composition. For example, solid resol resin fine particles remain in the polyimide composition or on the surface of the polyimide film to be formed, making it difficult to uniformly disperse the resol resin in the polyimide film in a short time.

  The polyimide composition contains a crosslinking agent having a plurality of epoxy groups. In this crosslinking agent, a plurality of epoxy groups react with polyimide to crosslink the polyimide compound. With this cross-linking agent, for example, the adhesion between a conductor such as a copper foil and polyimide can be improved. Further, since the above-mentioned resol resin acts as a crosslinking / crosslinking promoter of the crosslinking agent, a more complicated three-dimensional structure is constructed by containing the crosslinking agent. Therefore, for example, the adhesion of the polyimide film to the conductor is improved, and the plating resistance of the polyimide composition can be further improved.

  As a quantity which makes this polyimide composition contain this crosslinking agent, it is preferable that it is 20 weight part or less with respect to 100 weight part of polyimide compounds. When the crosslinking agent is contained in an amount of 20 parts by weight or more, the stability of the polyimide composition is deteriorated and the viscosity is increased, so that the handling of the polyimide composition is deteriorated. Moreover, since photosensitivity falls, alkali development becomes difficult. Moreover, since there exists a possibility that an epoxy group may also hydrolyze with aqueous alkali solution, in order to maintain a crosslinking effect, adding 1 weight part or more is desirable.

  The crosslinking agent having an epoxy group is not particularly limited as long as it has good compatibility with the polyimide composition to be formed, and examples thereof include the following compounds. Examples of the crosslinking agent include bis-type epoxy compounds, bis-A type epoxy compounds, 3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexene carboxylate and other alicyclic epoxy compounds, sorbitol polyglycidyl ether, poly Glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether , Hydrogenated bisphenol A diglycidyl ether, polyethylene glycol glycidyl ether, polypropylene glycol diglycidyl Glycidyl ether compounds such as ether, hydroquinone diglycidyl ether, glycidyl ester compounds such as diglycidyl phthalate and glycidyl terephthalate, halogenated flame retardant epoxy compounds such as dibromoneopentylglycol glycidyl ether, cresol novolac epoxy resin And phenol novolac epoxy resins.

  The polyimide composition may contain an oxazine compound. In the oxazine compound, the oxazine skeleton in the molecule is opened by heat and cured. By containing this oxazine compound in the polyimide composition of the present invention, it acts as a crosslinking agent, and the flame retardancy and adhesion to a metal such as copper can be improved in the polyimide composition. The addition amount may be as small as 5 parts by weight or less with respect to 100 parts by weight of the polyimide compound, for example.

  Examples of the oxazine compound include bisphenol F-type benzoxazine (6,6 ′-(1-methylidene) bis [3,4-dihydro-3-phenyl-2H-1,3-benzoxazine]), bisphenol S-type. Benzoxazine (6,6′-sulfonylbis [3,4-dihydro-3-phenyl-2H-1,3-benzoxazine]), bisphenol A type benzoxazine (the following structural formula 2), phenol novolac type benzoxazine ( The following structural formula 3) and the like can be mentioned.

  The polyimide composition may contain a rust preventive agent. Examples of the rust preventive include 2,3-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] propionohydrazide (CDA-), which is a hydrazide-based metal deactivator. 10), and when used for a flexible wiring board, resin deterioration of the polyimide composition in contact with the metal can be prevented.

  Examples of rust preventives other than CDA-10 include decamethylenecarboxylic acid disalicyloyl hydrazide as hydrazide-based compounds, and 3- (N-salicyloyl) amino-1,2,4-triazole as triazole-based compounds. However, it is not limited to these.

  The polyimide composition of the present invention can be formed by adding a photosensitizer and a resole resin to a solution in which a polyimide composition synthesized by polymerization of DSDA, BSDA, and siloxane diamine is dissolved in GBL or the like. A crosslinking agent or benzoxazine may be added to this polyimide composition.

  As described above, the polyimide composition of the present invention improves the plating resistance without causing the problem of film reduction, which was thought to occur by adding a resole resin to a polyimide compound that is highly soluble in an alkaline aqueous solution. It is possible.

  This polyimide composition can be used for a flexible wiring board as shown in FIGS. In this case, a polyimide composition is applied to a conductor such as copper foil 2 by a known coating method. Then, the polyimide composition is dried to form a polyimide layer 3 on the copper foil 2 as shown in FIG.

  As shown in FIG. 2, the flexible wiring board 1 is exposed with a polyimide layer 3 provided with a mask layer 4, and then immersed in an aqueous alkali solution to perform alkali development. Thereby, a positive pattern corresponding to the mask layer 4 can be formed on the polyimide layer 3 on the copper foil 2 as shown in FIG. The polyimide layer 3 is made of the above polyimide composition, so that no film reduction occurs.

  The copper foil 2 having the polyimide layer 3 on which the positive pattern is formed is post-baked at about 200 ° C., for example, to manufacture the flexible wiring board 1 having the polyimide layer 3 having plating resistance. The manufactured flexible wiring board 1 is immersed in a plating solution for performing electroless nickel gold plating, electroless gold plating, etc., for example, and a plating layer 5 is formed on the copper foil 2 as shown in FIG.

  This polyimide layer 3 has plating resistance by being made of the above polyimide composition. Therefore, only the portion where the copper foil 2 is exposed is plated, and the floating of the end portion of the polyimide layer 3 can be minimized. That is, the plating resistance can be improved without causing the problem of film loss of the polyimide layer 3 made of the polyimide composition to which the resole resin is added.

  Specific examples of the polyimide composition to which the present invention is applied will be described based on experimental results. In this example, the polyimide composition containing the resole shown in Examples 1 to 4 was compared with the polyimide composition containing no resol resin shown in the comparative example.

  The polyimide composition of Example 1 was prepared as follows. In a 500 ml four-necked separable flask equipped with a Dean-Stark-Trap, 131.61 g (97.05 mmol) of the siloxane diamine (X22-9409), 15 .58 g (55.30 mmol) of BSDA (purity 99.5%) was added and completely dissolved with γ-butyrolactone (GBL) under a nitrogen atmosphere. 55.3 g (153.8 mmol) of DSDA (purity 99.7%) was added to the solution, and the mixture was stirred at 80 ° C. for 2 hours. Then, toluene as an azeotropic agent for removing imidized condensed water was added. 70 ml was added and refluxed for 5 hours while stirring at 180 ° C. in an oil bath to synthesize a polyimide compound.

  With respect to 100 parts by weight of the obtained polyimide compound, 15 parts by weight of diazonaphthoquinone (4NT-300) as a photosensitizer, 2 parts by weight of an epoxy resin (EP807) as a crosslinking agent, and 5 parts by weight of 6 as an oxazine compound. , 6 '-(1-methylidene) bis [3,4-dihydro-3-phenyl-2H-1,3-benzoxazine] (BF-BXZ) and 0.3 parts by weight of a rust inhibitor (CDA-10) And were added. Furthermore, 2 parts by weight of a resole resin (PS6115) obtained by pulverizing a solid resole resin was added to 100 parts by weight of a polyimide compound to prepare a polyimide composition. When the polyimide composition to which the resole resin (PS6115) was added was observed, the resole resin (PS6115) was in a state where particles were not dissolved but remained.

  And after washing | cleaning the copper foil which is a base material with 2% sulfuric acid for 30 seconds at room temperature, said polyimide composition on the copper foil after washing | cleaning so that the polyimide layer after drying may be 9-10 micrometers in thickness. The object was applied. And it pre-dried at 80 degreeC for 4 minute (s), and the test piece which has a polyimide layer on copper foil was created.

The polyimide layer of the test piece was irradiated with light (exposed) at 2500 mJ / cm ² with an ultrahigh pressure mercury lamp through a positive image mask. Thereafter, the polyimide layer on the copper foil was alkali-developed by being immersed in a 3% sodium hydroxide aqueous solution at 40 ° C., and washed with hot water at 40 ° C. for 120 seconds to form a positive pattern on the polyimide layer. . After the positive pattern was formed, the test piece was immersed in 10% sulfuric acid and further washed with water in order to neutralize the sodium hydroxide aqueous solution in the polyimide layer. After washing with water, the test piece having the polyimide layer was heated at 200 ° C. for 1 hour in a nitrogen atmosphere to crosslink the polyimide layer. After heating, the test piece is put into a plating solution for electroless nickel plating, subjected to electroless nickel plating (NPR-4) for 8 minutes, and then applied to a plating solution for electroless gold plating (TKK-51). Was introduced and electroless nickel gold plating was performed.

  In the polyimide composition of Example 2, the pulverized resol resin (PS6115) of Example 1 was replaced with a transparent solid resol resin (BRM-470), and 2 parts by weight was added to 100 parts by weight of the polyimide compound. Then, a polyimide composition was prepared. Using this polyimide composition, a test piece was prepared in the same manner as in Example 1, and exposure, development, neutralization washing, heating, electroless nickel plating and electroless nickel gold plating were performed.

  In the polyimide composition of Example 3, 2 parts by weight of the pulverized resol resin (PS6115) of Example 1 above was added to 100 parts by weight of the polyimide compound in place of the powdered resole resin (BRP-2444). A polyimide composition was prepared. Using this polyimide composition, a test piece was prepared in the same manner as in Example 1, and exposure, development, neutralization washing, heating, electroless nickel plating and electroless nickel gold plating were performed.

  In the polyimide composition of Example 4, the pulverized resol resin (PS6115) of Example 1 was replaced with a liquid resol resin (BRL-274), and 2 parts by weight was added to 100 parts by weight of the polyimide compound. A polyimide composition was prepared. The liquid resol resin (BRL-274) added here is a liquid that contains more low-molecular-weight resol resins than the above-mentioned resol resins (PS6115, BRM-470, BRP-2444), and its viscosity. Is 13000 mPa · s or more. Using this polyimide composition, a test piece was prepared in the same manner as in Example 1, and exposure, development, neutralization washing, heating, electroless nickel plating and electroless nickel gold plating were performed. The photograph which shows the mode of the edge part of this polyimide layer after electroless nickel gold plating is shown in FIG. Moreover, in order to confirm the float of the edge part of the polyimide layer of Example 4, the SEM image of an edge part cross section is shown in FIG. 6, and the enlarged SEM image is shown in FIG.

  The polyimide composition of the comparative example was prepared without adding the resole resin added in Examples 1 to 4 above. And using this polyimide composition, the test piece was created similarly to Example 1, and exposure, image development, neutralization washing | cleaning, heating, electroless nickel plating, and electroless nickel gold plating were performed. The photograph which shows the mode of the edge part of this polyimide layer after electroless nickel gold plating is shown in FIG.

  Resistance to electroless nickel plating and electroless nickel gold plating in Examples 1 to 4 and Comparative Example, that is, electroless resistance from the viewpoint of floating and discoloration of the end of the polyimide layer by electroless nickel plating and electroless nickel gold plating The plating properties were evaluated and are shown in the following table. In the electroless nickel plating column, o indicates that the color change of the polyimide layer of the test piece was 20 μm or less, and the float at the end was 20 μm or less. Further, x in the column of electroless nickel plating indicates that the discoloration of the polyimide layer of the test piece was confirmed to be 50 μm or more, or a large float of 50 μm or more was confirmed at the end. The electroless nickel gold plating column is also the same as the electroless nickel plating, where ◯ indicates that the color change of the polyimide layer is 20 μm or less and the float at the end thereof is 20 μm or less, and × indicates the color change of the polyimide layer is 50 μm. It has been confirmed above, or a large float of 50 μm or more has been confirmed at the end.

  In each of Examples 1 to 4 and the comparative example, each polyimide layer was able to be well developed with an alkaline aqueous solution without causing film loss in which the thickness of the polyimide layer before development was reduced. Further, in the electroless nickel plating in Examples 1 to 4 and the comparative example, no floating or discoloration was confirmed at the end of each polyimide layer. In Example 3, no floating or discoloration was confirmed, but fine particles of resole resin were confirmed on the surface of the polyimide layer. Furthermore, in the electroless nickel gold plating in Examples 1 to 4, no floating or discoloration was observed at the end of each polyimide layer. In the comparative example, as shown in FIG. 8, a 120 μm discoloration region was confirmed at the end of the polyimide layer.

  First, the alkali developability of Examples 1 to 4 will be examined. The polyimide layer made of the polyimide composition having the composition shown in the comparative example can be satisfactorily developed with an alkaline aqueous solution. Since the polyimide composition contains a resole resin having a phenolic hydroxyl group, the polyimide layer was expected to be reduced by an alkaline developer. In particular, the liquid resol resin (BRL-274) having a low molecular weight was expected to have a prominent tendency due to the presence of more phenolic hydroxyl groups. However, in the polyimide compositions such as the compositions shown in Examples 1 to 4, no film loss of the polyimide layer was confirmed. That is, it was found that even when 2 parts by weight of a resole resin was added to a polyimide composition having DSDA, BSDA, or diaminosiloxane as a main skeleton, there was no decrease in alkali developability.

  Next, the plating resistance of Examples 1 to 4 will be examined. As described above, in the comparative example to which no resol resin is added, the polyimide composition having the composition shown in the comparative example is obtained by confirming a discoloration region having a width of 120 μm as shown in FIG. 8 at the end of the polyimide layer. It was found that the resistance to electroless nickel gold plating is low.

  As shown in FIG. 6, the polyimide composition having the composition of Example 4 cannot confirm discoloration at the end of the polyimide layer on the copper foil even after electroless nickel gold plating. Further, as shown in FIGS. 7 and 8, the floating of the polyimide layer was about 20 μm, and the phenomenon of plating insertion in which the polyimide layer and the copper foil were plated was not confirmed. The polyimide composition having the composition shown in Example 4 has no discoloration as in the comparative example and has very little floating. That is, the polyimide composition having the composition shown in Example 4 has dramatically improved floating due to electroless nickel gold plating as compared with the comparative example, and is resistant to electroless nickel plating and electroless nickel gold plating. It was found that can be improved. In addition, by using a test piece in which the polyimide composition of Example 4 was applied to both sides with a thickness of 20 μm on a 25 μm-thick raw fabric polyimide satisfying UL94-V-0, the UL standard (UL94 “flammability test of plastic material for equipment parts” was used. According to the method "), a flammability test was conducted, and it was found that the VTM-0 standard was satisfied.

  As in the composition of Example 4, the polyimide compositions having the compositions shown in Examples 1 to 3 were confirmed to be discolored and floated at the ends of the polyimide layer by electroless nickel plating and electroless nickel gold plating. There wasn't. Therefore, the polyimide composition having the composition shown in Examples 1 to 3 as in Example 4 has dramatically improved floating due to electroless nickel gold plating compared to the comparative example, and electroless nickel plating and electroless It was found that the plating resistance against nickel gold plating can be improved.

  In response to this result, the amount of the resole resin used in Examples 1 to 4 was changed, and test pieces were prepared in the same manner as in Example 1, and exposure, development, neutralization washing, heating, electroless nickel plating and Electroless nickel gold plating was performed. The amount of the resole resin added is 1 part by weight or 4 parts by weight with respect to 100 parts by weight of the polyimide compound.

  In any of the examples, it was possible to develop well with an alkaline aqueous solution. Also, even when electroless nickel plating and electroless nickel gold plating are performed, the end of the polyimide layer is not lifted or discolored, and the resistance to electroless nickel plating and electroless nickel gold plating is improved compared to the comparative example. I found out that That is, by adding the resol resin in the range of 1 part by weight or more and 4 parts by weight or less with respect to 100 parts by weight of the polyimide compound, the plating resistance can be improved without deteriorating the developability with the alkaline aqueous solution.

  As described above, Example 1 was in a state where fine particles of the resole resin remained in the polyimide composition. In Example 3, when the polyimide layer was observed after electroless nickel plating, fine particles of resole resin were confirmed. On the other hand, since Example 4 was liquid, it could be uniformly dispersed in the polyimide composition. Therefore, the resole resin could be uniformly dispersed in the polyimide layer. Therefore, as in Example 4, the resole resin itself has a viscosity of 13000 mPa · s or more and is in a liquid state, so that the resole resin can be easily dispersed in the polyimide layer, and the handling becomes easy.

It is sectional drawing of the flexible wiring board of this invention. It is a figure which shows the flexible wiring board of this invention at the time of exposure. It is a figure which shows the flexible wiring board of this invention after image development by alkaline aqueous solution. It is a figure which shows the flexible wiring board of this invention after plating. It is a photograph which shows the edge part of the polyimide layer after the electroless nickel gold plating in Example 4. FIG. It is a SEM image of the cross section of the edge part of the polyimide layer after the electroless nickel gold plating in Example 4. FIG. It is an enlarged SEM image of FIG. It is a photograph which shows the edge part of the polyimide layer after the electroless nickel gold plating in a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flexible wiring board 2 Copper foil 3 Polyimide layer 4 Mask layer 5 Plating layer

Claims (8)

3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride, 3,3′-diamino-4,4′-dihydroxydiphenylsulfone, and a polyimide compound synthesized by polymerization of siloxane diamine,
1 to 4 parts by weight of a resole resin with respect to 100 parts by weight of the polyimide compound;
A polyimide composition comprising a photosensitizer.   2. The polyimide composition according to claim 1, wherein the resol resin has a viscosity of 13000 mPa · s or more.   The polyimide composition according to claim 1, wherein the resol resin itself is in a liquid state. The siloxane diamine has the following structural formula 1
2. The polyimide composition according to claim 1, wherein the polyimide composition is a siloxane diamine represented by (wherein m in the structural formula 1 is 0 or an integer of 1 or more and n is an integer of 1 or more).   The polyimide composition according to claim 4, wherein m in the structural formula 1 is an integer of 1 or more.   The polyimide composition according to claim 1, wherein the polyimide composition contains an oxazine compound.   The polyimide composition according to claim 1, wherein the polyimide composition contains a crosslinking agent having a plurality of epoxy groups. Conductors,
Synthesized by polymerization of 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride, 3,3′-diamino-4,4′-dihydroxydiphenylsulfone, and siloxane diamine on the conductor. A flexible wiring board comprising: a polyimide compound; a polyimide layer comprising a polyimide composition containing 1 to 4 parts by weight of a resole resin with respect to 100 parts by weight of the polyimide compound; and a photosensitive agent. .