JP6497626B2 - Flexible printed wiring board and manufacturing method thereof - Google Patents

Description

  The present invention relates to a flexible printed wiring board and a method for manufacturing the same.

  A flexible printed wiring board including an insulating layer made of polyimide having high heat resistance is applied to various electronic devices such as portable electronic devices.

  For example, Patent Literature 1 describes a flexible printed wiring board used for manufacturing a flexible rigid printed wiring board. This flexible printed wiring board has a metal foil, a polyimide film, and an epoxy resin layer made by laminating an epoxy resin layer in this order. Furthermore, it is manufactured by removing the metal foil into a predetermined pattern shape to produce a conductor wiring.

  In recent years, there has been a demand for thin flexible printed wiring boards in order to cope with downsizing of electronic devices. For this purpose, it is required to reduce the dimension between the inner-layer conductor wiring derived from the core material and the outer-layer conductor wiring derived from the resin sheet with metal foil. This dimension is regulated by the thickness of the polyimide film.

  However, since the polyimide film has low adhesion to other members, it is necessary to subject the polyimide film to surface treatment such as corona discharge treatment in order to ensure adhesion between the polyimide film and the epoxy resin layer. If the thickness dimension of the polyimide film is small, defects such as pinholes may occur in the polyimide film due to corona discharge treatment or the like, which may cause insulation failure. For this reason, the polyimide film needs to have a thickness of at least 8 μm, which hinders the thinning of the flexible printed wiring board.

JP 2010-129610 A

  This invention is made | formed in view of the said reason, and it aims at providing the flexible printed wiring board which can achieve thickness reduction and ensuring of the insulation reliability in an insulating layer, and its manufacturing method.

  A flexible printed wiring board according to the present invention includes a bendable first insulating layer, a first conductor wiring on the first insulating layer, and the first conductor wiring on the first insulating layer. A second insulating layer; a third insulating layer on the second insulating layer; and a second conductor wiring on the third insulating layer, wherein the third insulating layer includes polyamideimide, The dimension between the conductor wiring and the second conductor wiring is in the range of 3 to 8 μm.

  In the method for producing a flexible printed wiring board according to the present invention, a third insulating layer containing polyamide-imide is produced on a metal foil, and the third insulating layer is subjected to either the plasma treatment or the discharge treatment without applying the plasma treatment and the discharge treatment. An adhesive layer is prepared by disposing a thermosetting resin composition on an insulating layer, and the adhesive layer is formed of the core material including the first insulating layer and the first conductor wiring on the first insulating layer. The method includes superposing the first conductor wiring on the first insulating layer so as to bury the first conductor wiring, and thermosetting the adhesive layer to produce a second insulating layer.

  ADVANTAGE OF THE INVENTION According to this invention, the flexible printed wiring board which can achieve thickness reduction and ensuring of the insulation reliability in an insulating layer is obtained.

It is sectional drawing of the principal part which shows one Embodiment of this invention. 2A to 2C are cross-sectional views showing an example of the manufacturing process of the flexible printed wiring board according to the present invention.

  Hereinafter, an embodiment of the present invention will be described.

  In FIG. 1, the flexible printed wiring board 1 in this embodiment is shown. The flexible printed wiring board 1 includes a first insulating layer 2, a first conductor wiring 3, a second insulating layer 4, a third insulating layer 5, and a second conductor wiring 6. The first conductor wiring 3 is on the first insulating layer 2. The first insulating layer 2 can be bent. The second insulating layer 4 is on the first insulating layer 2, and the first conductor wiring 3 is buried in the second insulating layer 4. The third insulating layer 5 is on the second insulating layer 4. The second conductor wiring 6 is on the third insulating layer 5. Hereinafter, a direction in which the first insulating layer 2, the first conductor wiring 3, the second insulating layer 4, the third insulating layer 5, and the second conductor wiring 6 are laminated is referred to as a direction D.

  In the present embodiment, the third insulating layer 5 includes polyamideimide. Furthermore, the dimension X between the first conductor wiring 3 and the second conductor wiring 6 is in the range of 3 to 8 μm. This dimension X is in the direction D between the surface 31 of the first conductor wiring 3 facing away from the first insulating layer 2 and the surface 61 of the second conductor wiring 6 facing toward the first insulating layer 2. Dimension along. When the surface 61 of the second conductor wiring 6 is a rough surface, the dimension between the first conductor wiring 3 and the second conductor wiring 6 is opposite to the first insulating layer 2 of the first conductor wiring 3. , And a dimension along the direction D between the surface 31 facing the first insulating layer 2 side of the second conductor wiring 6 and the apex of the convex portion on the surface 61 facing the first insulating layer 2 side.

  In this embodiment, since the dimension X between the first conductor wiring 3 and the second conductor wiring 6 is small, the flexible printed wiring board 1 can be thinned. Furthermore, in the present embodiment, since the third insulating layer 5 contains polyamideimide, the surface 51 of the third insulating layer 5 that is in contact with the second insulating layer 4 is not subjected to surface treatment such as plasma treatment or discharge treatment. In addition, the third insulating layer 5 has high adhesion to the second insulating layer 4. For this reason, even if the dimension X is small, no pinhole due to the surface treatment is generated in the third insulating layer 5. As a result, the flexible printed wiring board 1 is thinned and high adhesion between the second insulating layer 4 and the third insulating layer 5 is ensured, and the high height between the first conductor wiring 3 and the second conductor wiring 6 is secured. Insulation reliability can be secured.

  The withstand voltage of the third insulating layer 5 is preferably in the range of 100 to 500V. In this case, the flexible printed wiring board 1 has particularly high reliability. The withstand voltage of the third insulating layer 5 can be achieved because pinholes are unlikely to be generated in the third insulating layer 5.

  The dimension Y between the surface 51 of the third insulating layer 5 in contact with the second insulating layer 4 and the second conductor wiring 6 is preferably in the range of 3 μm or more and less than 8 μm. If this dimension Y is less than 8 μm, the dimension X between the first conductor wiring 3 and the second conductor wiring 6 can be secured sufficiently small, and the productivity in producing the third insulating layer 5 is increased. . Further, when the dimension Y is 3 μm or more, both the close contact with the conductor wiring and the stable withstand voltage are compatible. It is particularly preferred if this dimension is in the range of 3-5 μm. When the first conductor wiring 3 is in contact with the third insulating layer 5, the dimension X and the dimension Y are equal.

  The 2nd insulating layer 4 consists of hardened | cured material of a thermosetting resin composition, for example. In this case, the adhesion between the third insulating layer 5 and the second insulating layer 4 is particularly high.

  The structure of the flexible printed wiring board 1 will be described in more detail.

  The first insulating layer 2 can be bent as described above. The first insulating layer 2 is made of, for example, a highly flexible insulating material. The first insulating layer 2 is made of at least one material selected from the group consisting of polyimide resin, liquid crystal polymer, polyethylene terephthalate resin, and polyethylene naphthalate resin, for example. The thickness of the 1st insulating layer 2 exists in the range of 12-50 micrometers, for example.

  The first conductor wiring 3 is on one surface (hereinafter referred to as the first surface 21) facing the thickness direction in the first insulating layer 2. The first conductor wiring 3 may be provided on the first surface 21 of the first insulating layer 2 and on the second surface 22 of the first insulating layer 2 facing in the opposite direction to the first surface 21. . That is, the first conductor wiring 3, the second insulating layer 4, the second insulating layer 5, and the second conductor wiring 6 are laminated on the first surface 21 and the second surface 22 in the first insulating layer 2. May be.

  The first conductor wiring 3 is made of copper, for example. The thickness dimension b of the first conductor wiring 3 is preferably in the range of 10 to 30 μm. If the dimension b is 10 μm or more, the flexible printed wiring board 1 can be easily handled. Moreover, if the dimension b is 30 micrometers or less, the flexible property of the flexible printed wiring board 1 is securable.

  As described above, the second insulating layer 4 is made of, for example, a cured product of a thermosetting resin composition. The second insulating layer 4 is on the first surface 21 of the first insulating layer 2. The first conductor wiring 3 is buried in the second insulating layer 4. For this reason, the thickness dimension of the second insulating layer 4 is not less than the thickness dimension b of the first conductor wiring 3. The thickness of the second insulating layer 4 is in the range of 10 to 40 μm, for example. If the thickness dimension of the second insulating layer 4 is larger than the thickness dimension b of the first conductor wiring 3, the second insulating layer 4 covers the first conductor wiring 3 as shown in FIG. If the dimension is the same as the thickness dimension b of the first conductor wiring 3, the surface 31 of the first conductor wiring 3 is in contact with the surface 51 of the third insulating layer 5.

  The thermosetting resin composition for producing the second insulating layer 4 contains, for example, an epoxy resin and a curing agent. The thermosetting resin composition may further contain a carbodiimide-modified soluble polyamide.

  The epoxy resin contains at least one component selected from the group consisting of, for example, a glycidyl ether type epoxy resin, a glycidyl ester type epoxy resin, a glycidyl amine type epoxy resin, and an oxidation type epoxy resin. Examples of the glycidyl ether type epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak type epoxy resin, alcohol type epoxy resin and the like. The glycidyl ester type epoxy resin may include hydrophthalic acid type epoxy resin, dimer acid type epoxy resin and the like. Examples of the glycidylamine type epoxy resin include aromatic amine type epoxy resins and aminophenol type epoxy resins. An alicyclic epoxy resin is mentioned as an oxidation type epoxy resin. It is also preferable that the epoxy resin contains an epoxy resin having a naphthalene skeleton, a novolac type epoxy resin having a phenol skeleton and a biphenyl skeleton (biphenyl novolac epoxy resin), a phosphorus-modified epoxy resin (described later), and the like. The epoxy resin preferably does not contain a halogen. In particular, the epoxy resin preferably contains an epoxy resin having a naphthalene skeleton. In this case, the heat resistance, migration resistance, and chemical resistance of the flexible printed wiring board 1 are improved.

  The curing agent contains at least one component selected from the group consisting of, for example, polyamines, modified polyamines, acid anhydrides, hydrazine derivatives, and polyphenols. Examples of polyamines include aliphatic polyamines, alicyclic polyamines, and aromatic polyamines. Among these, examples of the aliphatic polyamine include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, m-xylenediamine, trimethylhexamethylenediamine, 2-methylpentamethylenediamine, and diethylaminopropylamine. Examples of the alicyclic polyamine include isophorone diamine, 1,3-bisaminomethylcyclohexane, bis (4-aminocyclohexyl) methane, norbornene diamine, 1,2-diaminocyclohexane, and laromine. Examples of the aromatic polyamine include diaminodiphenylmethane, metaphenylenediamine, and diaminodiphenylsulfone. Examples of acid anhydrides include hexahydrophthalic anhydride, methyl tetrahydro anhydride, methyl hexahydrophthalic anhydride, methyl nadic anhydride, hydrogenated methyl nadic anhydride, trialkyltetrahydrophthalic anhydride, and methylcyclohexene tetracarboxylic acid. Anhydride, trimellitic anhydride, pyromellitic acid-free, benzophenone tetracarboxylic dianhydride, aliphatic dibasic acid polyanhydride and the like can be mentioned. Examples of polyphenol-based curing agents include phenol novolak, xylene novolak, bis A novolak, triphenylmethane novolak, biphenyl novolak, dicyclopentadiene phenol novolak, and terpene phenol novolak. The curing agent may include an aminotriazine novolac resin, a novolac type phenol resin, and the like.

  In particular, the curing agent preferably contains at least one of aminotriazine novolak resin and dicyandiamide. In this case, when the thermosetting resin composition is in the B stage state, the B thermosetting resin composition is stably maintained in the B stage state for a long period of time (storage stability is improved) and flexible. The flame retardancy and chemical resistance of the printed wiring board 1 are improved.

  The content of the curing agent in the thermosetting resin composition is in the range of 10 to 45 mass% with respect to the total amount of the epoxy resin, the curing agent and the carbodiimide-modified soluble polyamide in the thermosetting resin composition. Is preferred.

  The carbodiimide-modified soluble polyamide is produced, for example, by reacting a soluble polyamide and a carbodiimide compound in the presence or absence of a solvent, for example, at a reaction temperature of 50 to 250 ° C.

  The soluble polyamide is 1 part by mass or more, preferably 5 parts by mass or more, more preferably 100 parts by mass of a mixture of alcohol and at least one of an aromatic organic solvent and a ketone organic solvent. 10 parts by mass or more is a completely soluble polyamide. The alcohol is, for example, methanol, ethanol or isopropyl alcohol. The aromatic organic solvent is, for example, benzene or toluene. The ketone-based organic solvent is, for example, cyclohexanone, 2-butanone, or cyclopentanone. The boiling points of these alcohols, aromatic solvents and ketone solvents are preferably 130 ° C. or lower.

  The soluble polyamide is obtained, for example, by subjecting a polyamide other than the soluble polyamide (polyamide before solubilization) to a treatment for solubilization. Examples of the treatment method for solubilization include a method in which a hydrogen atom in an amide group of a polyamide before solubilization is partially substituted with a methoxymethyl group. When a methoxy group is introduced into the polyamide by this method, the crystallinity of the polyamide is inhibited by losing the hydrogen bonding ability from the amide group, thereby increasing the solubility of the polyamide in the solvent. Examples of the treatment method for solubilization include a method in which a polyester or polyester is introduced into a polyamide molecule before being solubilized to form a copolymer. Examples of the polyamide before solubilization include nylon 6, nylon 66, nylon 610, nylon 11, nylon 12, nylon 46, and the like.

  Specific examples of the soluble polyamide include Zytel 61 (trade name) manufactured by DuPont, Versalon (trade name) manufactured by General Mills, Amilan CM4000 (trade name) manufactured by Toray Industries, and Amilan CM8000 manufactured by Toray Industries, Inc. (Trade name), PA-100 (trade name) manufactured by Fuji Kasei Kogyo Co., Ltd., and resin (trade name) manufactured by Nagase ChemteX Corporation.

  A carbodiimide compound is a compound having one or more carbodiimide groups in one molecule. The carbodiimide compound includes at least one of a monocarbodiimide compound, for example, a polycarbodiimide compound. A carbodiimide compound is synthesized, for example, by decarboxylation condensation reaction of various polyisocyanates in a solvent-free or inert solvent at a temperature of about 70 ° C. or higher in the presence of an organophosphorus compound or organometallic compound as a catalyst. Is done.

  The monocarbodiimide compound is selected from the group consisting of, for example, dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, and di-β-naphthylcarbodiimide. At least one component. In particular, the monocarbodiimide compound preferably contains at least one of dicyclohexylcarbodiimide and diisopropylcarbodiimide from the viewpoint of industrial availability.

  The carbodiimide compound preferably contains a polycarbodiimide compound from the viewpoint of improving the reactivity and hydrolysis stability. In particular, the polycarbodiimide compound preferably contains at least one of an aliphatic polycarbodiimide compound and an alicyclic polycarbodiimide compound. The polycarbodiimide compound contains, for example, 4,4'-dicyclohexylmethane carbodiimide.

  The degree of polymerization of the polycarbodiimide compound is preferably in the range of 2-30, more preferably in the range of 2-20. When the polymerization degree is 2 or more, it is preferable in that the heat resistance of the flexible printed wiring board 1 is further improved, and when the polymerization degree is 20 or less, the compatibility between components in the thermosetting resin composition is improved. Is preferable.

  The polycarbodiimide compound is produced by various methods. For example, a polycarbodiimide compound may be prepared by a known method for producing polycarbodiimide (for example, US Pat. No. 2,941,956, J. Org. Chem. 28, 2069-2075 (1963), Chemical Review 1981, Vol. 81 No. 4). , p619-621).

  Examples of the polyisocyanate used for the production of the polycarbodiimide compound include organic diisocyanates. Examples of organic diisocyanates include aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and mixtures thereof. Specifically, 1,5-naphthalene diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyldimethylmethane diisocyanate, 1,3-phenylene diisocyanate. 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate and 2,6 A mixture of tolylene diisocyanate, hexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'- Diisocyanate, methylcyclohexane diisocyanate, tetramethylxylylene diisocyanate, 2,6-diisopropylphenyl diisocyanate 1,3,5-triisopropylbenzene-2,4-diisocyanate - DOO and the like. Among these, from the viewpoint of improving the flexibility and moisture resistance of the flexible printed wiring board 1, aliphatic (including alicyclic) organic diisocyanates are preferable, and ilophorone diisocyanate and dicyclohexyl are particularly preferable. Methane-4,4′-diisocyanate, tetramethylxylylene diisocyanate and mixtures thereof are more preferred.

  During the production of the polycarbodiimide compound, the degree of polymerization of the polycarbodiimide compound can be appropriately controlled by stopping the polymerization reaction in the middle, for example, by cooling the reaction system during the polymerization reaction of the polyisocyanate. In this case, the terminal of the molecule of the polycarbodiimide compound is an isocyanate group. In order for the degree of polymerization of the polycarbodiimide compound to be more appropriately controlled, a compound such as a monoisocyanate compound that can react with an isocyanate group (hereinafter referred to as an end-capping agent) is attached to the end of the molecule of the polycarbodiimide compound. By reacting with all or part of a certain isocyanate group, all or part of the isocyanate group of the polycarbodiimide compound may be sealed. When the polymerization degree of the polycarbodiimide compound is appropriately controlled, the compatibility between the soluble polyamide and the polycarbodiimide compound is improved, and the storage stability of the member including the second insulating layer 4 is improved.

  Monoisocyanate compounds that can be used as end-capping agents include phenyl isocyanate, tolyl isocyanate, dimethylphenyl isocyanate, cyclohexyl isocyanate, butyl isocyanate, and naphthyl isocyanate. And so on.

End capping agents other than the monoisocyanate compound may be used. Examples of the end capping agent other than the monoisocyanate compound include active hydrogen compounds capable of reacting with an isocyanate group. Examples of such active hydrogen compounds include (i) aliphatic, aromatic or alicyclic compounds having a —OH group, such as methanol, ethanol, phenol, cyclohexanol. , N-methylethanolamine, polyethylene glycol monomethyl ether, polypropylene glycol monomethyl ether, etc .; (ii) = NH3 group diethylamine, dicyclohexylamine etc. compound; (iii) —NH ₂ group (Iv) compounds such as succinic acid, benzoic acid and cyclohexane acid having a —COOH group; (v) compounds such as ethyl mercaptan, allyl mercaptan and thiophenol having a —SH group; (vi) epoxy (Vii) acetic anhydride, methyltetrahydrophthalic anhydride, methyl Kisahidoro anhydride such as phthalic anhydride, and the like.

  The decarboxylation condensation reaction of the organic diisocyanate can proceed in the presence of a suitable carbodiimidization catalyst. As the carbodiimidization catalyst, organophosphorus compounds, organometallic compounds (represented by the general formula M- (OR) n, where M is titanium (Ti), sodium (Na), potassium (K), vanadium (V), tungsten (W), Hafnium (Hf), Zirconium (Zr), Lead (Pb), Manganese (Mn), Nickel (Ni), Calcium (Ca), Barium (Ba), and other metal elements, R is carbon number 1-20 And an alkyl group or an aryl group, and n represents the valence of M).

  Among these carbodiimidization catalysts, particularly from the viewpoint of improving reaction activity, phospholene oxides are used from among organic phosphorus compounds, and alkoxides of titanium, hafnium, or zirconium from among organometallic compounds. Are preferably used. Specific examples of the phosphorene oxides include 3-methyl-1-phenyl-2-phospholene-1-oxide, 3-methyl-1-ethyl-2-phospholene-1-oxide, and 1,3-dimethyl-2. -Phospholene-1-oxide, 1-phenyl-2-phospholene-1-oxide, 1-ethyl-2-phospholene-1-oxide, 1-methyl-2-phospholene-1-oxide or their double bond isomers Is mentioned. Of these phospholene oxides, 3-methyl-1-phenyl-2-phospholene-1-oxide is preferably used in terms of industrial availability.

  A carbodiimide-modified soluble polyamide is produced by reacting a soluble polyamide and a carbodiimide compound in the presence or absence of a solvent. In this case, a reactive functional group such as a carboxyl group or amino group contained in the soluble polyamide reacts with a carbodiimide group or isocyanate group of a carbodiimide compound that can react with these.

  In order to react the soluble polyamide and the carbodiimide compound in the presence of a solvent, for example, the soluble polyamide and the carbodiimide compound are added to the solvent, and the resulting solution is stirred while heating to advance the reaction. In particular, it is preferable that the soluble polyamide is first added to a solvent, and a carbodiimide compound is further added to the resulting solution, and then this solution is heated and stirred under reflux (reflux) to advance the reaction. When the solvent is removed from the solution after the reaction under normal pressure or reduced pressure, a carbodiimide-modified soluble polyamide is obtained.

  In order to react the soluble polyamide and the carbodiimide compound in the absence of a solvent, the reaction may proceed by mixing the carbodiimide compound with the soluble polyamide melted by heating to a temperature higher than the melting point. The reaction may be allowed to proceed while melt-kneading the soluble polyamide and carbodiimide compound with a twin screw extruder.

  When the soluble polyamide reacts with the carbodiimide compound, the ratio of the carbodiimide compound to 100 parts by mass of the soluble polyamide is preferably in the range of 0.5 to 20 parts by mass, and more preferably 1 to 10 parts by mass. In this case, the moisture resistance and heat resistance of the flexible printed wiring board 1 are sufficiently improved, and the plasticity of the flexible printed wiring board 1 is hardly increased or the impact resistance is not easily lost. That is, when the ratio of the carbodiimide compound is 0.5 parts by mass or more, the moisture resistance and heat resistance of the flexible printed wiring board 1 are sufficiently improved. On the other hand, when the ratio is 20 parts by mass or less, the plasticity of the flexible printed wiring board 1 becomes too high and the impact resistance is hardly deteriorated.

  During the reaction between the soluble polyamide and the carbodiimide compound, it is preferable that the reaction system does not contain a compound that inhibits the modification of the soluble polyamide. In particular, the reaction system contains only the carbodiimide compound, the soluble polyamide and the solvent used as necessary. It is preferable. Specific examples of the compound that inhibits the modification of the soluble polyamide include an epoxy resin, an amine resin, a melamine resin, and a phenol resin.

  The reaction time of the soluble polyamide with the carbodiimide compound is appropriately set according to the type of the soluble polyamide or carbodiimide compound, the reaction method, the reaction temperature, etc., but is preferably in the range of 1 to 500 minutes, preferably 5 to 200 minutes. If it is the range, it is still more preferable.

  The temperature of the reaction system during the reaction between the soluble polyamide and the carbodiimide compound is also appropriately set according to the type of the soluble polyamide or carbodiimide compound, the reaction method, the reaction temperature, etc., but is preferably in the range of 50 to 250 ° C. . In particular, when the soluble polyamide and the carbodiimide compound react in the presence of a solvent, the temperature of the reaction system is preferably in the range of 50 to 150 ° C, more preferably in the range of 70 to 130 ° C. On the other hand, when the soluble polyamide and the carbodiimide compound react in the absence of a solvent, the temperature of the reaction system is preferably in the range of 130 to 250 ° C, more preferably 150 to 220 ° C. When the temperature of this reaction system is 50 ° C. or higher, the reaction between the soluble polyamide and the carbodiimide compound is sufficiently fast and the modification of the soluble polyamide occurs rapidly, which is preferable from an industrial viewpoint. Furthermore, it is preferable that the temperature of the reaction system is 250 ° C. or less because the product is hardly deteriorated due to decomposition of the resin or the like.

  Thus, when soluble polyamide and a carbodiimide compound react, soluble polyamide will modify and it will become carbodiimide modified soluble polyamide. As this reaction proceeds, the carbodiimide group of the carbodiimide compound decreases accordingly. For this reason, when each of the raw material and the product is measured by infrared spectroscopy, the peak attributed to the carbodiimide group decreases in the infrared absorption spectrum measured for the product. Furthermore, when differential thermogravimetric analysis of the raw material and the product is performed, a plurality of absorption peaks such as an absorption peak caused by an amide resin and an absorption peak caused by a carbodiimide resin are observed in the raw material. In the product, endothermic peaks are combined into one. These confirm that the soluble polyamide has been modified.

  A composition containing a carbodiimide-modified soluble polyamide is excellent in storage stability as compared with a composition containing a soluble polyamide and a carbodiimide compound. That is, a composition containing a soluble polyamide and a carbodiimide compound thickens when it is made into a solution, and becomes easier to gel, whereas a composition containing a carbodiimide-modified soluble polyamide is less susceptible to changes such as thickening, Long-term storage is possible.

  The content of the carbodiimide-modified soluble polyamide in the thermosetting resin composition is 20 to 70% by mass with respect to the total amount of the epoxy resin, the curing agent, and the carbodiimide-modified soluble polyamide in the thermosetting resin composition. It is preferable that it is the range of these. When the content of the carbodiimide-modified soluble polyamide is 20% by mass or more, the flexibility of the flexible printed wiring board 1 is improved, and when the content is 70% by mass or less, the flame retardancy and heat resistance of the flexible printed wiring board 1 are improved. Improves.

  The thermosetting resin composition may contain a curing accelerator such as 2-ethyl-4-methylimidazole as necessary.

  It is preferable that the thermosetting resin composition further contains a phenoxy resin. In this case, the flexibility of the flexible printed wiring board 1 is further improved. The phenoxy resin may include bisphenol A type phenoxy resin, bisphenol A / bisphenol F type copolymer type phenoxy resin, phosphorus-modified phenoxy resin (described later), and the like. The content of the phenoxy resin in the thermosetting resin composition is preferably in the range of 5 to 30% by mass with respect to the total amount of the thermosetting resin composition.

  The thermosetting resin composition preferably also contains at least one of a phosphorus-based flame retardant such as a phosphorus-modified epoxy resin, a phosphorus-modified phenoxy resin, and phosphazene. In this case, the flame retardancy of the flexible printed wiring board 1 is further improved. The ratio of the total content of the phosphorus-modified epoxy resin, phosphorus-modified phenoxy resin and phosphorus flame retardant to the total amount of the thermosetting resin composition is preferably in the range of 10 to 40% by mass.

  The phosphorus-modified epoxy resin can be obtained, for example, by reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with 1,4-naphthoquinone and further reacting with cresol novolac resin. .

  The main molecular skeleton of the phosphorus-modified phenoxy resin is composed of a phenoxy resin, and one mole of the phosphorus-modified phenoxy resin contains, for example, several phosphorus elements (about 1 to 5).

  Examples of phosphorus flame retardants include phosphazenes, monomeric phosphate esters, condensed phosphate esters, reactive phosphorus flame retardants, phosphates, and phosphazene compounds. Specific examples of the monomer type phosphate ester include triphenyl phosphate, tricresyl phosphate, trixinyl phosphate, triethyl phosphate, cresyl diphenyl phosphate, xylyl. Examples thereof include diphenyl phosphate, cresyl bis (di-2,6-xylenyl) phosphate, 2-ethylhexyl diphenyl phosphate, and the like. Specific examples of condensed phosphates include resorcinol bis (diphenyl) phosphate, bisphenol A bis (diphenyl) phosphate, bisphenol A bis (dicresyl) phosphate, resorcinol bis (di-). -2,6-xylenyl) phosphate and the like. Specific examples of reactive phosphorus flame retardants include bisphenol A bisphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphenanthrene-10-oxide, 2- (diphenylphosphini E) Hydroquinone and the like. Specific examples of the phosphate include melamine phosphate, dimelamine phosphate, melamine pyrophosphate, dimelamine pyrophosphate, melamine polyphosphate, ethylenediamine phosphate, and the like. Specific examples of the phosphazene compound include phosphonitrile acid phenyl ester, cyanophenol / phenol mixed substituted cyclophosphazene, phosphonitrile chloride / hydroquinone / phenol condensate, and the like.

  The thermosetting resin composition preferably does not contain a filler. In general, fillers such as aluminum hydroxide and magnesium hydroxide are sometimes used as flame retardants, but such fillers are preferably not used. In this case, even if the flexible printed wiring board 1 is bent, fine cracks are unlikely to occur in the second insulating layer 4, and deterioration of the appearance of the flexible printed wiring board 1 is suppressed, and high insulation reliability is provided by the second insulating layer 4. Sex is maintained.

  The thermosetting resin composition is prepared by blending the above components. Furthermore, the thermosetting resin composition may contain an organic solvent for viscosity adjustment, if necessary.

  When the thermosetting resin composition thus obtained contains the carbodiimide-modified soluble polyamide, the storage stability, adhesiveness, flexibility and fillability of the thermosetting resin composition are increased. That is, the carbodiimide-modified soluble polyamide is produced by a reaction between a reactive functional group such as a carboxyl group or amino group that the soluble polyamide has, and a carbodiimide group or isocyanate group of a carbodiimide compound that can react with these, Difficult to react with epoxy resin at low temperatures. Therefore, the storage stability of the thermosetting resin composition is increased, and the storage stability and press moldability of a member including the adhesive layer 11 produced from the thermosetting resin composition are increased. Furthermore, the handleability and workability (storage stability and press formability) of the thermosetting resin composition and the adhesive layer 11 and various characteristics (adhesiveness, flexibility, fillability, etc.) of the flexible printed wiring board 1 are compatible. You can get it.

  Furthermore, when the thermosetting resin composition contains the carbodiimide-modified soluble polyamide, the insulation reliability of the second insulating layer 4 is improved and the flame retardancy, heat resistance and chemical resistance are further improved.

  The adhesive layer 11 obtained by semi-curing the thermosetting resin composition has a high resin flow. The resin flow of the adhesive layer 11 is easily adjusted by adjusting the heating temperature and the heating rate when the adhesive layer 11 is produced by heating and drying the coating film of the thermosetting resin composition. Can be done.

  The third insulating layer 5 contains polyamideimide. For this reason, as described above, the third insulating layer 5 has high adhesion to the second insulating layer 4 even if the third insulating layer 5 is not subjected to surface treatment.

  The third insulating layer 5 is produced, for example, by drying a liquid composition containing polyamideimide and a solvent.

  For example, the polyamideimide includes at least one of a first structural unit represented by the following structural formula (1) and a second structural unit represented by the following structural formula (2). It is more preferable if the polyamideimide has both the first structural unit and the second structural unit.

  The second structural unit is preferably in the range of 5 to 35 mol% with respect to the total of the first structural unit and the second structural unit in the polyamide resin. When the second structural unit is 35 mol% or less (that is, the first structural unit is 65 mol% or more), the heat resistance of the third insulating layer 5 is particularly improved. Further, when the second structural unit is 5 mol% or more (that is, the first structural unit is 95 mol% or less), the adhesion between the third insulating layer 5 and the second conductor wiring 6 is particularly high. Further, when the second structural unit is 5 mol% or more, the solubility of polyamideimide in the solvent is improved when preparing the liquid composition for producing the third insulating layer 5, and thus the third Molding defects when producing the insulating layer 5 are suppressed. The second structural unit is preferably 10 mol% or more, preferably 30 mol% or less, and preferably within the range of 10 to 30 mol% with respect to the total of the first structural unit and the second structural unit. Particularly preferred.

  The structural unit in the polyamideimide may be only the first structural unit and the second structural unit. Moreover, units other than the first structural unit and the second structural unit (hereinafter referred to as additional structural units) may be included in the structural unit in the polyamideimide. It is preferable that an additional structural unit is 20 mol% or less with respect to all the structural units in a polyamideimide, and it is still more preferable if it is 10 mol% or less.

  The additional structural unit includes, for example, a third structural unit represented by the following structural formula (3). That is, the polyamide resin may include a third structural unit.

  “A” in the structural formula (3) is an aromatic residue. “A” is not particularly limited, but may include at least one of the structures listed in [Chemical Formula 3] below.

Each of R ¹ and R ² in [Chemical Formula 3] is selected from hydrogen, an alkyl group having 1 to 3 carbon atoms, and an allyl group. However, the same structure as the first structural unit and the second structural unit is excluded from the additional structural unit.

  The method for synthesizing the polyamideimide is, for example, an isocyanate method or an amine method. The amine method is, for example, an acid chloride method, a low temperature solution polymerization method, or a room temperature solution polymerization method. Of these, the isocyanate method is preferably employed.

  When synthesizing polyamideimide by the isocyanate method, for example, trimellitic acid or a derivative thereof such as anhydride or halide and an aromatic diisocyanate for introducing an aromatic residue are added to an organic solvent. Further, a reactive solution is obtained by adding a catalyst as necessary. This reactive solution is preferably heated at a temperature of 10 to 200 ° C. for 1 to 24 hours to be reacted to synthesize polyamideimide.

  Aromatic diisocyanates for introducing aromatic residues include, for example, 4,4'-diisocyanato-3,3'-dimethylbiphenyl and tolylene 2,4-diisocyanate. In this case, by adjusting the molar ratio of 4,4′-diisocyanato-3,3′-dimethylbiphenyl and tolylene 2,4-diisocyanate, the moles of the first structural unit and the second structural unit in the polyamideimide are adjusted. The ratio can be adjusted. In addition, an additional structural unit is introduced into the polyamideimide by further adding components other than 4,4′-diisocyanato-3,3′-dimethylbiphenyl and tolylene 2,4-diisocyanate to the aromatic diisocyanate. You can also

  One specific example of polyamideimide is Toyobo Co., Ltd. product number HR-16NN.

  Examples of the organic solvent in the reactive solution include N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, tetramethylurea, sulfolane, Contains one or more components selected from the group consisting of dimethyl sulfoxide, γ-butyrolactone, cyclohexanone, and cyclopentanone, or further includes hydrocarbon organic solvents such as toluene and xylene, diglyme, triglyme, tetrahydrofuran, and the like. -It contains at least one component selected from the group consisting of tellurium organic solvents and ketone organic solvents such as methyl ethyl ketone and methyl isobutyl ketone.

  Examples of the catalyst include tertiary amines, alkali metal compounds, and alkaline earth metal compounds.

  When synthesizing polyamideimide by the amine method, for example, trimellitic acid or its anhydride, halide and other derivatives and an aromatic diamine for introducing an aromatic residue are added to an organic solvent and further required. A reactive solution is prepared by adding the catalyst accordingly. The polyamideimide can be synthesized by heating and reacting this reactive solution at a temperature of preferably 0 to 200 ° C. for 1 to 24 hours.

  The number average molecular weight of the polyamideimide is preferably in the range of 10,000 to 40,000 in order to impart good solvent solubility to the polyamideimide. This number average molecular weight is a value measured by gel permeation chromatography.

  The third insulating layer 5 preferably contains bismaleimide. For that purpose, it is preferable that the liquid composition for producing the third insulating layer 5 contains bismaleimide. In this case, the heat resistance of the third insulating layer 5 is further improved. The bismaleimides are 4,4′-diphenylmethane bismaleimide, bisphenol A diphenyl ether bismaleimide, 3,3′-dimethyl-5,5′-diethyl-4,4′-diphenylmethane bismaleimide, and 1, It is preferable to contain one or more components selected from the group consisting of 6′-bismaleimide- (2,2,4-trimethyl) hexane.

  The bismaleimide is preferably in the range of 3 to 30% by mass with respect to the total of polyamideimide and bismaleimide. When the bismaleimide is 3% by mass or more, particularly high heat resistance is imparted to the third insulating layer 5. When the bismaleimide is 30% by mass or less, the flexibility of the third insulating layer 5 is good. It is particularly preferable if the bismaleimide is in the range of 3 to 20% by mass.

  The liquid composition for producing the third insulating layer 5 preferably contains an epoxy compound instead of or together with bismaleimide. Also in this case, the heat resistance of the third insulating layer 5 is improved. The epoxy compound is preferably a polyfunctional epoxy resin having a naphthalene skeleton. Examples of the polyfunctional epoxy resin having a naphthalene skeleton include novolak type epoxy resins, trifunctional type epoxy resins, aralkyl type epoxy resins, and cresol type cocondensation type epoxy resins. Besides these, as the polyfunctional epoxy compound, bisphenol A type epoxy resin, polyphenol type epoxy resin, polyglycidylamine type epoxy resin, alcohol type epoxy resin, alicyclic epoxy resin, phenol skeleton And a novolac type epoxy resin having a biphenyl skeleton.

  It is preferable that an epoxy compound exists in the range of 3-30 mass% with respect to the sum total of a polyamideimide and an epoxy compound. When the epoxy compound is 3% by mass or more, the heat resistance of the third insulating layer 5 is particularly improved. Moreover, the softness | flexibility of the 3rd insulating layer 5 is favorable in an epoxy compound being 30 mass% or less. Moreover, it is especially preferable if an epoxy compound exists in the range of 3-20 mass%.

  The third insulating layer 5 may contain an inorganic filler. For that purpose, the liquid composition for producing the third insulating layer 5 may contain an inorganic filler.

  The inorganic filler can contain, for example, silica. When the inorganic filler contains silica, that is, when the third insulating layer 5 contains silica, the silica can impart high thermal conductivity to the third insulating layer 5. Therefore, when the third insulating layer 5 is subjected to laser processing for drilling through holes, the generation of resin residues on the inner surface of the holes formed in the third insulating layer 5 and the hole Formation of irregularities on the inner surface is suppressed. Moreover, even if the desmear process which uses desmear liquids, such as an alkaline permanganate solution, is given to the inner surface of a hole, formation of the unevenness | corrugation of the inner surface of a hole is suppressed. For this reason, when the plating treatment is performed on the inner surface of the hole for forming the through hole, the plating layer is easily formed uniformly. Thereby, high conduction stability is imparted to the through hole.

  The average particle size of silica is preferably in the range of 5 to 200 nm. The maximum particle size of silica is preferably 500 nm or less. In these cases, silica is unlikely to hinder the flexibility of the third insulating layer 5. The silica in the third insulating layer 5 is preferably in the range of 2 to 20 phr. The average particle size and the maximum particle size of silica are measured by a dynamic light scattering method. The silica is preferably spherical silica. In this case, the filling property of silica in the third insulating layer 5 is improved.

  The second conductor wiring 6 is made of, for example, copper. The thickness dimension a of the second conductor wiring 6 is in the range of 10 to 40 μm, for example.

  It is preferable that the surface 61 facing the first insulating layer 2 side in the second conductor wiring 6 is a rough surface having an appropriate roughness. In this case, the second conductor wiring 6 and the third insulating layer 5 have particularly high adhesion. The ten-point average roughness Rz of the surface 61 according to JIS B0601 1994 is, for example, in the range of 1.0 to 2.5 μm.

  In order to reduce the thickness of the flexible printed wiring board 1, the interface 7 between the first insulating layer 2 and the second insulating layer 4, and the surface 62 facing the opposite side of the first insulating layer 2 of the second conductor wiring 6, The dimension T between is preferably in the range of 20 to 80 μm. Note that the dimension X, the dimension a, the dimension b, and the dimension T satisfy the relationship X = T−a−b.

  The manufacturing method of the flexible printed wiring board 1 in this embodiment is demonstrated with reference to FIG. 2A-FIG. 2C.

  When manufacturing the flexible printed wiring board 1, for example, the third insulating layer 5 containing polyamideimide is produced on the metal foil 10. The adhesive layer 11 is produced by disposing the thermosetting resin composition on the third insulating layer 5 without performing any plasma treatment or discharge treatment on the third insulating layer 5. This adhesive layer 11 is formed on the first insulating layer 2 of the core material 8 including the first insulating layer 2 and the first conductor wiring 3 on the first insulating layer 2. Overlay to fill. The second insulating layer 4 is produced by thermally curing the adhesive layer 11. A second conductor wiring 6 is produced on the second insulating layer 4 by an appropriate method.

  An example of the manufacturing method of the flexible printed wiring board 1 will be described more specifically.

  As shown in FIG. 2A, a core material 8 including a first insulating layer 2 and a first conductor wiring 3 on the first insulating layer 2 is prepared. In this example, the first conductor wiring 3 is provided on each of the first surface 21 and the second surface 22 of the first insulating layer 2. For example, the core material 8 is laminated by bonding or fusing a metal foil on the first insulating layer 2, and then the metal foil is patterned by an etching process or the like to produce the first conductor wiring 3. ,can get. A through hole may be formed on the core material 8 as required.

  As shown in FIG. 2A, a resin sheet 9 with a metal foil including an adhesive layer 11, a third insulating layer 5 on the adhesive layer 11, and a metal foil 10 on the third insulating layer 5 is also prepared. The surface of the metal foil 10 in contact with the third insulating layer 5 is a rough surface. Rz of this surface is preferably in the range of 1.0 to 2.5 μm, similarly to the surface facing the first insulating layer 2 side in the second conductor wiring 6.

  When producing the resin sheet 9 with metal foil, for example, the third insulating layer 5 containing polyamideimide is first produced on the metal foil 10. For that purpose, for example, after applying a liquid composition containing polyamideimide and a solvent on the rough surface of the metal foil 10, for example, the conditions within a heating temperature range of 240 to 270 ° C. and a heating time range of 1 to 10 minutes The third insulating layer 5 is produced by heating at. Thereby, the single-sided flexible metal-clad base material provided with the 3rd insulating layer 5 and the metal foil 10 is obtained.

  Next, the adhesive layer 11 is produced by disposing the thermosetting resin composition on the third insulating layer 5 without performing any plasma treatment or discharge treatment on the third insulating layer 5 in the single-sided flexible metal-clad substrate. . For this purpose, for example, a thermosetting resin composition is applied on the third insulating layer 5 and then heated under the conditions of a heating temperature of 120 to 160 ° C. and a heating time of 2 to 10 minutes. The adhesive layer 11 is produced by curing.

  The core material 8 and the resin sheet 9 with metal foil are overlapped so that the insulating layer in the core material 8 and the first conductor wiring 3 are covered with the adhesive layer 11 in the resin sheet 9 with metal foil. In this state, the core material 8 and the resin sheet 9 with metal foil are heated and pressed. The heating temperature at the time of hot pressing is, for example, in the range of 160 to 190 ° C., and the pressing pressure is in the range of 1.0 to 3.0 MPa. As a result, the adhesive layer 11 is first softened and deformed so as to follow the shape of the first conductor wiring 3, and then thermally cured, whereby the second insulating layer 4 is produced. Thereby, as shown to FIG. 2B, the double-sided metal-clad flexible multilayer board 12 is obtained.

  Next, the metal foil 10 in the double-sided metal-clad flexible multilayer board 12 (that is, the metal foil 10 derived from the resin sheet 9 with metal foil) is patterned by etching or the like to produce the second conductor wiring 6. . Thereby, the flexible printed wiring board 1 is obtained.

  In the above example, the flexible printed wiring board 1 is manufactured using the resin sheet 9 with metal foil. However, the flexible printed wiring board 1 may be manufactured without using the resin sheet 9 with metal foil. . For example, a resin sheet including the third insulating layer 5 and the adhesive layer 11 and not including the metal foil 10 is used, and this is overlaid on the core material 8 in the same manner as in the case of the resin sheet 9 with metal foil. The second conductor wiring 6 may be produced on the third insulating layer 5.

  In order to describe a more specific configuration of the present invention, the following examples and comparative examples are given as test examples. In addition, this invention is not restrict | limited only to the following Example.

[Synthesis of carbodiimide compounds]
590 g of 4,4′-dicyclohexylmethane diisocyanate, 62.6 g of cyclohexylisocyanate and 6.12 g of carbodiimidization catalyst (3-methyl-1-phenyl-2-phospholene-1-oxide) were blended, The reaction was allowed to proceed by heating the resulting mixture at 180 ° C. for 48 hours. As a result, 4,4′-dicyclohexylmethanecarbodiimide resin (degree of polymerization = 10) was synthesized.

[Synthesis of carbodiimide-modified soluble polyamide]
In a 1-liter separable flask, 50.0 g of ester copolymerized amide resin (trade name CM8000, manufactured by Toray Industries, Inc.) and 450.0 g of a mixed solvent of isopropyl alcohol and toluene (mass mixing ratio 4: 6) Were added and dissolved by stirring. To the solution in the separable flask thus obtained, 5.0 g of a carbodiimide compound (4,4′-dicyclohexylmethanecarbodiimide resin) was added. Subsequently, this separable flask was immersed in an oil bath at 120 ° C., the solution in the separable flask was heated and stirred for 3 hours under reflux, and then the solvent was removed by drying under reduced pressure. Thereby, a solution containing a carbodiimide-modified soluble polyamide was obtained.

When infrared spectrophotometry was performed on this carbodiimide-modified soluble polyamide, an absorption peak indicating the presence of a carbodiimide group was observed at 2120 cm ⁻¹ . Further, when differential scanning calorimetry was performed on the carbodiimide-modified soluble polyamide, one endothermic peak was observed. The carbodiimide-modified soluble polyamide had a glass transition temperature (Tg) of 120 ° C., a 5% weight loss temperature of 320 ° C., and a solution viscosity of 860 mPa · s.

[Preparation of thermosetting resin composition]
Epoxy resin (epoxy resin having a naphthalene skeleton, Nippon Kayaku Co., Ltd., product number NC-7000L) 27.2% by mass, curing agent (aminotriazine novolac resin, methyl ethyl ketone solution having a resin solid content of 60% by mass, manufactured by DIC Corporation , Part number LA-7052) 17.2% by weight, 36.4% by weight carbodiimide-modified soluble polyamide synthesized as described above, curing accelerator (Shikoku Kasei Kogyo Co., Ltd., part number 2E4MZ) 0.1% by weight, phosphorus system A thermosetting resin composition having a solid content of 33% by mass was obtained by mixing 19.0% by mass of a flame retardant (manufactured by Otsuka Chemical Co., Ltd., product number SPB-100) in a container.

[Example 1]
194 g of trimellitic anhydride (manufactured by Nacalai Tesque), 211 g of 4,4′-diisocyanato-3,3′-dimethylbiphenyl, 35 g of tolylene 2,4-diisocyanate, 1 g of diazabicycloundecene (manufactured by San Apro) , And N, N-dimethylacetamide (DMAC, manufactured by Nacalai Tesque Co., Ltd.) 2482 g to adjust the polymer concentration to 15% by mass and heat the resulting mixture to 100 ° C. over 1 hour. The reaction was allowed to proceed by raising the temperature and then maintaining the mixture at 100 ° C. for 6 hours.

  The polymer concentration was then adjusted to 10 wt% by adding an additional 1460 g of DMAC to the mixture, and then the mixture was cooled to room temperature. As a result, a liquid composition in which polyamideimide was dissolved was obtained. This liquid composition is a yellowish brown transparent liquid, and it is thus confirmed that the polyamideimide is sufficiently dissolved.

  As a metal foil, a copper foil having a thickness of 12 μm and a rough surface of Rz = 1 μm was prepared. The liquid composition is applied on the rough surface of the metal foil using a comma and a dryer connected thereto, and then the liquid composition is heated at 200 ° C. for 4 minutes, and then the dryer is used. And heated at 250 ° C. for 10 minutes and dried. This produced the 3rd insulating layer on metal foil. This obtained the single-sided flexible metal-clad base material provided with metal foil and a 3rd insulating layer. The dimension between the top of the convex portion on the rough surface of the metal foil and the outer surface of the third insulating layer was 3 μm.

  Next, without applying any surface treatment to the third insulating layer in the single-sided flexible metal-clad base material, the thermosetting resin composition is applied on the third insulating layer using a comma coater and a dryer connected thereto. Then, this thermosetting resin composition was heated at 150 ° C. for 3 minutes. Thus, an adhesive layer in a B stage state having a thickness of 10 μm was produced. This obtained the resin sheet with metal foil provided with metal foil, a 3rd insulating layer, and an adhesion layer.

  A double-sided metal-clad laminate (product number R-F775, manufactured by Panasonic Corporation) comprising a first insulating layer made of polyimide and having a thickness of 25 μm and a metal foil made of copper (copper foil) having a thickness of 18 μm on the first insulating layer. Prepared. The metal foil in the double-sided metal-clad laminate was subjected to a pattern etching process to produce a first conductor wiring including a comb-shaped electrode. Thereby, the core material provided with the 1st insulating layer and the 1st conductor wiring in each on both surfaces was obtained.

  This core material and two resin sheets with metal foil are overlapped so that each first insulating layer and first conductor wiring in the core material are covered with an adhesive layer in each resin sheet with metal foil, and this state Then, the core material and the resin sheet with metal foil were hot pressed under the conditions of a heating temperature of 180 ° C., a pressing pressure of 1.5 MPa, and a processing time of 1 hour. Thereby, a double-sided metal-clad flexible multilayer board was obtained.

  The metal foil in this double-sided metal-clad flexible multilayer board was subjected to a pattern etching process to produce a second conductor wiring including a comb-shaped electrode. This obtained the flexible printed wiring board.

  When the flexible printed wiring board was cut, the dimension a, dimension b, dimension X, dimension Y and dimension T appearing in the cross section were as shown in Table 2.

[Example 2]
A single-sided flexible metal-clad substrate, a resin sheet with metal foil, a double-sided metal-clad flexible multilayer board and a flexible printed wiring board were obtained in the same manner as in Example 1 except that the thickness of the adhesive layer was 12 μm.

  When the flexible printed wiring board was cut, the dimension a, dimension b, dimension X, dimension Y and dimension T appearing in the cross section were as shown in Table 2.

[Example 3]
A single-sided flexible metal-clad substrate, a resin sheet with a metal foil, a double-sided metal-clad flexible multilayer board and a flexible printed wiring board were obtained in the same manner as in Example 1 except that the thickness of the adhesive layer was 15 μm.

  When the flexible printed wiring board was cut, the dimension a, dimension b, dimension X, dimension Y and dimension T appearing in the cross section were as shown in Table 2.

[Example 4]
Single-sided flexible as in Example 1 except that the dimension between the top of the convex portion on the rough surface of the copper foil in the single-sided flexible metal-clad base and the outer surface of the third insulating layer was 5 μm and the thickness of the adhesive layer was 12 μm. A metal-clad substrate, a resin sheet with a metal foil, a double-sided metal-clad flexible multilayer board and a flexible printed wiring board were obtained.

  When the flexible printed wiring board was cut, the dimension a, dimension b, dimension X, dimension Y and dimension T appearing in the cross section were as shown in Table 2.

[Examples 5 and 6]
In Example 1, the molar ratio of trimellitic anhydride, 4,4′-diisocyanato-3,3′-dimethylbiphenyl, and tolylene 2,4-diisocyanate for preparing the liquid composition is shown in Table 1 below. It was changed as follows. Otherwise, a single-sided flexible metal-clad base, a resin sheet with a metal foil, and a double-sided metal-clad flexible multilayer board were obtained under the same conditions as in Example 1.

[Comparative Example 1]
A liquid composition was obtained by diluting a thermoplastic polyimide varnish (manufactured by Shin Nippon Rika Co., Ltd., product number PN-20) twice with N-methyl-2-pyrrolidone.

  A copper foil having a rough surface with a thickness of 12 μm and Rz = 1 μm was prepared at the time of producing the single-sided flexible metal-clad base material. The liquid composition was applied on the copper foil with a comma coater, and then the liquid composition was heated at 200 ° C. for 2 minutes and then heated at 200 ° C. for 15 minutes. This produced a 3 μm thick third insulating layer on the first metal foil.

  Except that, a single-sided flexible metal-clad substrate, a resin sheet with metal foil, a double-sided metal-clad flexible multilayer board and a flexible printed wiring board were obtained in the same manner as in Example 1.

  When the flexible printed wiring board was cut, the dimension a, dimension b, dimension X, dimension Y and dimension T appearing in the cross section were as shown in Table 2.

[Comparative Example 2]
Before producing the adhesive layer on the third insulating layer, the third insulating layer was subjected to corona treatment under the condition of a discharge amount of 250 W · min / m ² . Except that, a single-sided flexible metal-clad substrate, a resin sheet with metal foil, a double-sided metal-clad flexible multilayer board and a flexible printed wiring board were obtained in the same manner as in Example 1.

  When the flexible printed wiring board was cut, the dimension a, dimension b, dimension X, dimension Y and dimension T appearing in the cross section were as shown in Table 2.

[Comparative Example 3]
A single-sided flexible metal-clad substrate, metal, as in Comparative Example 1, except that the thickness of the adhesive layer 11 is 12 μm and the dimension between the top of the convex portion on the rough surface of the copper foil and the outer surface of the third insulating layer is 10 μm. A resin sheet with foil, a double-sided metal-clad flexible multilayer board and a flexible printed wiring board were obtained.

  When the flexible printed wiring board was cut, the dimension a, dimension b, dimension X, dimension Y and dimension T appearing in the cross section were as shown in Table 2.

[Appearance evaluation of third insulation layer]
In each of the examples and comparative examples, the appearance of the third insulating layer was observed with a stereomicroscope to confirm the presence or absence of pinholes.

[Adhesion evaluation]
The resin sheet with metal foil obtained in each Example and Comparative Example was overlaid on each of both surfaces of a polyimide film having a thickness of 25 μm, and these were heated and pressed at 180 ° C. for 1 hour to prepare a sample. . The peeling strength when the copper foil in this sample was peeled off in the 90 ° direction together with the third insulating layer was measured. The value obtained by this was used as an index of adhesion between the third insulating layer and the second insulating layer.

[Insulation voltage evaluation]
The withstand voltage of the third insulating layer was measured as follows. A metal plate was disposed on each of both surfaces of the single-sided flexible metal-clad substrate obtained in each of the examples and comparative examples, and a voltage was applied between the metal plates. The voltage was increased until dielectric breakdown occurred, and the voltage when the voltage breakdown occurred was measured.

[Insulation reliability evaluation]
The electrical resistance value between the first conductor wiring and the second conductor wiring in the flexible printed wiring board obtained in each example and comparative example was measured.

[Migration resistance]
While exposing the flexible printed wiring board obtained in each Example and Comparative Example in an environment of 85 ° C./85% RH, a voltage of 10 V was applied between the first conductor wiring and the second conductor wiring for 250 hours. . Then, the flexible printed wiring board was cut | disconnected and the cross section was observed and the presence or absence of the migration between 1st conductor wiring and 2nd conductor wiring was confirmed.

  The above evaluation results are shown in Table 2 below.

DESCRIPTION OF SYMBOLS 1 Flexible printed wiring board 2 1st insulating layer 3 1st conductor wiring 4 2nd insulating layer 5 3rd insulating layer 6 2nd conductor wiring 7 interface 8 core material 9 resin sheet with metal foil 10 metal foil 11 adhesive layer

Claims (6)

A bendable first insulating layer;
A first conductor wiring on the first insulating layer;
A second insulating layer on the first insulating layer and embedded with the first conductor wiring;
A third insulating layer on the second insulating layer;
A second conductor wiring on the third insulating layer,
The third insulating layer comprises polyamideimide;
The flexible printed wiring board whose dimension between said 1st conductor wiring and said 2nd conductor wiring exists in the range of 3-8 micrometers. The flexible printed wiring board according to claim 1, wherein the withstand voltage of the third insulating layer is in a range of 100 to 500V. 3. The flexible printed wiring board according to claim 1, wherein a dimension between an interface between the second insulating layer and the third insulating layer and the second conductor wiring is in a range of 3 μm or more and less than 8 μm. The flexible printed wiring board according to any one of claims 1 to 3, wherein the second insulating layer is made of a cured product of a thermosetting resin composition. 5. The flexible printed wiring board according to claim 1, wherein neither plasma treatment nor discharge treatment is applied to a surface of the third insulating layer that contacts the second insulating layer. A method for producing the flexible printed wiring board according to any one of claims 1 to 5,
Create a third insulating layer containing polyamideimide on the metal foil,
Without performing any of plasma treatment and discharge treatment on the third insulating layer, an adhesive layer is prepared by disposing a thermosetting resin composition on the third insulating layer,
The adhesive layer is overlaid on the first insulating layer of a core material including a first insulating layer and a first conductor wiring on the first insulating layer so as to bury the first conductor wiring in the adhesive layer. ,
The manufacturing method of a flexible printed wiring board including producing a 2nd insulating layer by thermosetting the said contact bonding layer.