JP4371234B2 - Flexible metal foil polyimide laminate - Google Patents

Description

  The present invention relates to an all-polyimide flexible metal foil polyimide laminate obtained by laminating a metal foil on one surface of a heat-resistant polyimide film via a heat-resistant polyimide layer as an adhesive layer.

  In recent years, with the thinning and miniaturization of electronic devices such as mobile phones, flexible substrates used for them have been required to have high bending characteristics. Specifically, an IPC bending test (repeatedly bending at high temperatures) is required. Even when it is performed, high bending performance is required so that the circuit does not break.

  Conventionally, a flexible substrate is produced by directly applying a polyimide precursor resin solution onto a conductor, drying and curing, and disclosed in Japanese Patent Application Laid-Open No. 59-232455: Japanese Patent Application Laid-Open No. Sho 61-275325. : Patent Document 2, JP-A-62-212140: Patent Document 3, JP-A-7-57540: Patent Document 4. In addition, a method of applying the polyimide precursor resin solution onto the conductor in several times is also disclosed in JP-A-2-180682: Patent Document 5, JP-A-2-180679: Patent Document 6, JP-A-1- No. 245586: Patent Document 7 and Japanese Patent Application Laid-Open No. 2-12297: Patent Document 8.

  However, the method of applying once or several times so that the polyimide layer is 20 μm or more on the conductor tends to make the final polyimide layer of the flexible substrate discontinuous in both the thickness direction and the surface direction. Therefore, it was not satisfactory for bending at high temperature.

  In view of this, methods for bonding a polyimide film after forming a thermoplastic polyimide on a conductor are disclosed in Japanese Patent Application Laid-Open No. 1-224441: Patent Document 9 and Japanese Patent Application Laid-Open No. 6-190967: Patent Document 10.

  According to this method, since the thermoplastic polyimide layer is pressure-bonded, the thickness of the polyimide layer as a whole is known to be uniform. In particular, as disclosed in JP-A-6-190967: Patent Document 10, a polyimide or polyamic acid solution is applied, dried and cured to produce a thermoplastic polyimide / metal foil laminate, and its thermoplasticity. By heating and pressure-bonding the polyimide film to the polyimide side, the thermoplastic polyimide is melted by heating and the thickness is corrected. Therefore, the entire polyimide layer after being bonded to the polyimide film can have a uniform thickness. . However, in this method, it is essential to heat and pressure-bond the cured polyimide, so that a special apparatus that can be heated at a temperature equal to or higher than the glass point (Tg) of the polyimide is required, which is not economical.

  In addition, since the film characteristics (elastic modulus, elongation) of the polyimide film layer and the thermoplastic polyimide adhesive layer are inevitably different from each other in the flexible substrate obtained by this method, both of them are subjected to repeated bending of tens of thousands of times. There are inconveniences (disadvantages) such as peeling at the interface of the layers or at the interface between the metal foil and the adhesive layer, and it is not satisfactory for bending at high temperatures.

JP 59-232455 A JP-A 61-275325 JP-A-62-212140 JP-A-7-57540 Japanese Patent Laid-Open No. 2-180682 JP-A-2-180679 JP-A-1-245586 Japanese Patent Laid-Open No. 2-122697 JP-A-1-2444841 JP-A-6-190967

  The present invention has been made in view of the above circumstances, and has improved flexibility by fully utilizing the characteristics of a heat-resistant polyimide resin film having excellent heat resistance, chemical resistance, flame retardancy, bending characteristics, and the like. It aims at providing the flexible metal foil polyimide laminated board of a polyimide.

  As a result of diligent research and study on obtaining a flexible substrate having high flexibility at a high temperature so that the circuit does not break even when the IPC bending test (repeated bending at a high temperature) is performed, the present inventors have found a heat-resistant polyimide film. A flexible metal foil polyimide laminate obtained by laminating a metal foil on one side of the adhesive layer, the adhesive layer being a polyimide adhesive layer obtained by heating imidization of polyamic acid, 80 ° C., bending radius 1.5 mm The flexible metal foil polyimide laminate having an IPC flexibility of 3 million times or more sufficiently utilizes the characteristics of a heat-resistant polyimide resin film having excellent heat resistance, chemical resistance, flame retardancy, bending characteristics, Found that the flexible metal foil polyimide laminate of all polyimide with improved flexibility, and found the present invention It came to be.

Accordingly, the present invention is a flexible metal foil polyimide laminate in which a metal foil is laminated on one side of a heat resistant polyimide film with an adhesive layer, and the polyimide film is 4,4′-diaminodiphenyl ether and pyromellitic acid. Polyimide acid that is formed by heating imidization of polyamic acid formed by reacting anhydride, and heat imidization of polyamic acid containing 50 to 90% by mass of polyamic acid that becomes polyimide having the same component as polyimide film. The thickness of the polyimide adhesive layer is less than 10% with respect to the thickness of the entire polyimide layer, the thickness of the polyimide layer comprising the heat-resistant polyimide film and the polyimide adhesive layer is 15 to 50 μm, 80 ° C., bent Flexible with an IPC flexibility with a radius of 1.5 mm of 3 million times or more A metal foil polyimide laminate is provided.

  An all-polyimide flexible metal foil polyimide laminate using the heat-resistant polyimide adhesive of the present invention can be produced under conditions of lower drying temperature and laminating temperature when the adhesive strength is high and the adhesive layer is thin. Even when a bending test (repeatedly bending at a high temperature) is performed, it has a high bending performance so that the circuit does not break.

  The flexible metal foil polyimide laminate of the present invention is a flexible metal foil polyimide laminate obtained by laminating a metal foil on one side of a heat-resistant polyimide film via a polyimide adhesive layer obtained by imidizing polyamic acid.

The heat-resistant polyimide film used in the present invention is not particularly limited, and a commercially available film can be used. However, a polyamic acid obtained by reacting 4,4′-diaminodiphenyl ether and pyromellitic anhydride is used. It is preferable to use what was obtained by thermosetting.
In this case, the reaction method of 4,4′-diaminodiphenyl ether and pyromellitic anhydride is not particularly limited, and can be performed according to a conventional method.

The heat-resistant polyimide film can be obtained by casting the polyamic acid on a metal plate, a glass plate, or a rotating drum, drying the solvent and imidizing it by heating, and then peeling it from the plate or the rotating drum. Here, in the imidization of the polyamic acid, there are no particular limitations on the heating temperature, catalyst addition, etc., so long as the film is imidized so that the film thickness becomes uniform.
Moreover, you may perform a plasma process and an etching process to the adhesion surface of a polyimide film.

  Moreover, the component which forms the adhesive bond layer used for this invention is the polyimide obtained by hardening | curing polyamic acid, As this polyamic acid, 50 masses of polyamic acids used as the polyimide of the said component and the said polyimide film are the same. % Or more, particularly 50 to 90% by mass of polyamic acid is preferable. In this case, it is possible to blend and use a polyamic acid obtained from another acid anhydride and a diamine. If the polyamic acid used as the polyimide of the same component as the polyimide film is less than 50% by mass, the heat resistance of the adhesive layer and the adhesive strength at the interface of the film-adhesive layer may not be sufficient depending on the other component polyimide to be combined, If it exceeds 90% by mass, it is difficult to adjust the curing rate of the adhesive layer to an appropriate one, and the resulting laminated board may be warped.

  Here, as the polyamic acid other than the polyamic acid obtained by reacting the above-mentioned 4,4′-diaminodiphenyl ether and pyromellitic anhydride, the following tetracarboxylic acid or its anhydride, its derivative, etc. are reacted with the following diamine. Can be mentioned.

  In addition, although illustrated here as tetracarboxylic acid, these esterified products, acid anhydrides, and acid chlorides can of course be used. That is, pyromellitic acid (except when reacted with 4,4′-diaminodiphenyl ether), 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 3,3 ′, 4,4′-benzophenonetetra Carboxylic acid, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic acid, 3,3 ′, 4,4′-diphenyl ether tetracarboxylic acid, 2,3,3 ′, 4′-benzophenone tetracarboxylic acid, 2 , 3,6,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 3,3 ′, 4,4′-diphenylmethanetetracarboxylic acid, 2,2-bis (3,4- Dicarboxyphenyl) propane, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane, 3,4,9,10-tetracarboxyperylene, 2, -Bis [4- (3,4-dicarboxyphenoxy) phenyl] propane, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] hexafluoropropane, butanetetracarboxylic acid, cyclopentanetetracarboxylic An acid etc. are mentioned. Also included are trimellitic acid and its derivatives. Furthermore, it can be modified with a compound having a reactive functional group to introduce a crosslinked structure or a ladder structure.

  On the other hand, as a diamine used for polyamic acid other than polyamic acid obtained by reacting 4,4′-diaminodiphenyl ether and pyromellitic anhydride, 4,4′-diaminodiphenyl ether (provided to react with pyromellitic acid) Except for the case), p-phenylenediamine, m-phenylenediamine, 2′-methoxy-4,4′-diaminobenzanilide, 4,4′-diaminodiphenyl ether, diaminotoluene, 4,4′-diaminodiphenylmethane, 3, 3'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 1,2- Bis (anilino) ethane, diaminodiphenylsulfone, diaminobenz Nilide, diaminobenzoate, diaminodiphenyl sulfide, 2,2-bis (p-aminophenyl) propane, 2,2-bis (p-aminophenyl) hexafluoropropane, 1,5-diaminonaphthalene, diaminotoluene, diaminobenzo Trifluoride, 1,4-bis (p-aminophenoxy) benzene, 4,4 ′-(p-aminophenoxy) biphenyl, diaminoanthraquinone, 4,4′-bis (3-aminophenoxyphenyl) diphenylsulfone, 1, 3-bis (anilino) hexafluoropropane, 1,4-bis (anilino) octafluoropropane, 1,5-bis (anilino) decafluoropropane, 1,7-bis (anilino) tetradecafluoropropane, 2,2 -Bis [4- (p-aminophenoxy) pheny ] Hexafluoropropane, 2,2-bis [4- (3-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis [4- (2-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) -3,5-dimethylphenyl] hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) -3,5-ditrifluoromethylphenyl] hexafluoropropane, p -Bis (4-amino-2-trifluoromethylphenoxy) benzene, 4,4'-bis (4-amino-2-trifluoromethylphenoxy) biphenyl, 4,4'-bis (4-amino-3-tri Fluoromethylphenoxy) biphenyl, 4,4'-bis (4-amino-2-trifluoromethylphenoxy) diphenyls Lufone, 4,4′-bis (4-amino-5-trifluoromethylphenoxy) diphenylsulfone, 2,2-bis [4- (4-amino-3-trifluoromethylphenoxy) phenyl] hexafluoropropane, benzidine 3,3 ′, 5,5′-tetramethylbenzidine, octafluorobenzidine, 3,3′-methoxybenzidine, o-tolidine, m-tolidine, 2,2 ′, 5,5 ′, 6,6′- Diamines such as hexafluorotolidine, 4,4 ″ -diaminoterphenyl, 4,4 ′ ″-diaminoquaterphenyl, diisocyanates obtained by reaction of these diamines with phosgene, and further diaminosiloxanes Can be mentioned.

The condensation reaction for preparing the polyamic acid in the present invention is carried out in a single solution or a mixed solution of NMP and DMAc as polar solvents, the reaction temperature is 10 to 40 ° C., the concentration of the reaction solution is 30% by mass or less, and the aromatic tetracarboxylic acid. the molar ratio of anhydride and aromatic diamine is 0.95: 1.00 to 1.05: preferably reacted under N ₂ atmosphere at 1.00 range. In addition, there is no limitation in particular in the dissolution method and addition method of the raw material in this reaction.

  In addition, for the purpose of improving various properties, it can be used by mixing inorganic, organic or metal powders, fibers, etc., and additives such as antioxidants and adhesives for the purpose of preventing conductor oxidation. It is also possible to add a silane coupling agent for the purpose of improving the coating property and a leveling agent for the purpose of improving the coatability.

  As the metal foil used in the present invention, a rolled copper foil or an electrolytic copper foil having a thickness of 9 to 35 μm is preferably used. If the thickness of the copper foil is less than 9 μm, there may be a problem in wrinkles during production, strength in the lamination process, and the like, and it is disadvantageous in cost because it is necessary to use a protective material.

  In the method for producing a flexible metal foil polyimide laminate in the present invention, the adhesive layer polyamic acid is cast on a metal foil such as a copper foil, and after semi-drying at a temperature at which imidization does not proceed (imidation rate is less than 5%). By laminating the polyimide film with a heated roll press, and further performing solvent drying and imidization of the adhesive layer polyamic acid, various properties such as heat resistance of the adhesive, which has been a problem in the past, are not bent and bent. An all-polyimide flexible metal foil laminate having excellent properties can be produced.

  In the manufacturing method of the flexible metal foil polyimide laminated board in this invention, the film thickness after imidation of the said adhesive layer polyamic acid is 10% of all the polyimide layers (namely, heat resistant polyimide film and polyimide adhesive layer) of a laminated board. It is preferable to apply so that it may become less than 4 to 8%. When the thickness of the adhesive layer is 10% or more of the thickness of the total polyimide resin layer, the curl of the laminated board may be increased.

  Furthermore, the thickness of the whole polyimide layer (namely, heat resistant polyimide film and polyimide adhesive layer) is preferably 15 to 50 μm, particularly preferably 15 to 30 μm in view of the characteristics of the obtained laminate. When this thickness is less than 15 μm, it is difficult to cast the polyimide adhesive layer on the copper foil with a thickness of less than 10% of the total polyimide layer, and it is difficult to laminate the polyimide film, or Flexibility may be inferior. Moreover, when it exceeds 50 micrometers, there exists a possibility that the solvent removal and imidation of the contact bonding layer by the method of this invention may become difficult.

  In the present invention, there is no particular limitation on the apparatus and method for applying and drying the polyamic acid to the treated surface of a metal foil such as copper foil, and the application is a comma coater, die coater, roll coater, knife coater, reverse coater, lip. A coater or the like may be used, and the drying is performed at the time when it is passed through a heated roll press. The polyamic acid is in a semi-dry state with a solvent content of 3 to 150% by mass and imidization does not proceed (imidation rate is less than 5%). It may be appropriately dried at a temperature of 120 ° C. or lower, preferably 40 to 100 ° C., used for adhesion.

  If the solvent content exceeds 150% by mass, bubbles or blisters may occur during roll pressing, or the adhesive may flow and soil the roll. If the solvent content is less than 3% by mass, the roll may be heated. When laminating at a high temperature and high pressure are required, equipment costs may increase. If the drying temperature exceeds 120 ° C., foaming may occur during heating lamination.

Examples of the heating method of the roll press include a method in which the roll is directly heated with oil, steam, or the like. As the roll material, a metal roll such as carbon steel, or a rubber roll made of heat-resistant NBR rubber, fluorine rubber, or silicone rubber is used.
The roll press conditions are not particularly limited, but the roll temperature is 100 to 150 ° C. which is not lower than the softening point of the polyamic acid after semi-drying and not higher than the boiling point of the solvent used, and the linear pressure is 5 to 100 kg / cm. It is preferable to perform in the range.

  Regarding the method of solvent drying and imidization after lamination, the solvent drying temperature is preferably not higher than the boiling point of the solvent used for the varnish, usually 30 to 200 ° C., and the solvent drying time is removed through the bonded polyimide film. Therefore, it is sufficient to carry out the time when the solvent runs out, usually 3 to 30 hours.

  Moreover, imidation may be continued after removing the solvent. As in the conventional method, the metal foil such as copper foil is oxidized at an oxygen concentration (2% by mass or less) under reduced pressure or in a nitrogen atmosphere at 250 to 350 ° C. It may be performed for 3 to 20 hours. The form for performing the solvent removal and imidization may be a sheet or a roll, and there is no particular limitation on how to roll the roll, and a metal foil such as a copper foil may be inside or outside, May be in the form of a roll with a spacer in between.

  In this case, in the method of the present invention, a solvent remaining after lamination and dehydration at the time of imidization are generated in solvent removal and imidization, and therefore rolls are preferably performed by loosely winding or sandwiching spacers of other materials. It is preferable to heat-process in a state.

  The flexible metal foil polyimide laminate thus obtained has a bending property of 80 ° C. and an IPC flexibility with a bending radius of 1.5 mm of 3 million times or more, preferably 3.3 million times or more, more preferably 30.8 million times or more. It has excellent bending performance so that the circuit is not broken. As described above, the laminated plate that gives such a high bending performance is a polyimide film component, a polyimide adhesive layer component, a metal foil component, a polyimide adhesive layer thickness, a total polyimide layer thickness, a metal foil thickness, etc. Can be obtained by appropriately selecting.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Examples 1 and 2]
Synthesis of polyamic acid A 202.5 g of 4,4′-diaminodiphenyl ether was dissolved in 1.5 kg of N, N-dimethylacetamide, stirred in an N ₂ atmosphere, and maintained at 10 ° C. 218.5 g of the product was gradually added so that the internal temperature did not exceed 15 ° C. After reacting at 10 to 15 ° C. for 2 hours, the reaction was further performed at room temperature for 6 hours.

Synthesis of polyamic acid B 108.5 g of p-phenylenediamine was dissolved in 2 kg of N, N-dimethylacetamide, stirred in an N ₂ atmosphere and kept at 10 ° C., 3, 3 ′, 4, 4 ′. -295.7 g of biphenyltetracarboxylic anhydride was gradually added so that the internal temperature did not exceed 15 ° C. After reacting at 10 to 15 ° C. for 2 hours, the reaction was further performed at room temperature for 6 hours.

Polyimide film production Polyamic acid A was cast on an SUS plate with a mirror finish to a thickness of 130 μm and 200 μm using an applicator, dried at 110 ° C. for 10 minutes, and then peeled off from the SUS plate. fixed to at N ₂ inert oven, 250 ° C. × 3 hours, subjected to 350 ° C. × 3 hours continuously heated imidization, over 5 hours and cooled to 100 ° C. or less, a polyimide film having a thickness of 25μm and 38μm Obtained.

Preparation of laminated plate Coated with an applicator so that the mixed thickness of the polyamic acid A and B shown in Table 1 is 30 μm, and the thickness of the liquid is 30 μm. Was dried at 120 ° C. for 2 minutes. This was overlaid with a polyimide film having a thickness shown in Table 1 cut to 30 cm × 25 cm and laminated with a test roll laminator manufactured by Nishimura Machinery Co., Ltd. at 120 ° C. × 15 kg / cm × 4 m / min. This was heat-treated continuously in an N ₂ inert oven at 160 ° C. for 4 hours, 250 ° C. for 1 hour, and 350 ° C. for 1 hour.

[Comparative Examples 1-3]
The same procedure as in Example was performed except that the polyimide layer shown in Table 1 was formed, laminated, and cured.

  Using the laminates of Examples 1 and 2 and Comparative Examples 1 to 3, IPC flexibility was measured by the following method. The results are also shown in Table 1.

IPC Flexibility A circuit pattern defined in IPC FC 241 was formed and formed on the copper foil layer of the obtained laminate. Coverlay (trade name: CN261, manufactured by Shin-Etsu Chemical Co., Ltd.) was hot-pressed at 160 ° C. and 4.9 MPa for 30 minutes on the circuit pattern forming surface (circuit pattern copper foil surface), and further after-curing at 160 ° C. for 4 hours. The IPC flexibility test piece was prepared. Using this IPC bendability test piece, repeated bending was performed at a temperature of 80 ° C., a bending radius of 1.5 mm, a bending speed of 1500 times / minute, and a stroke of 20 mm, and the circuit resistance value exceeded 10% or the circuit was broken. The number of bendings was defined as the number of bendings.

Claims (2)

A flexible metal foil polyimide laminate in which a metal foil is laminated on one side of a heat-resistant polyimide film via an adhesive layer, the polyimide film reacting 4,4'-diaminodiphenyl ether and pyromellitic anhydride comprising a polyamic acid are those formed by thermal imidization, the adhesive layer is a polyimide adhesive layer heated imidized polyamic acid containing 50 to 90 wt% of the polyamic acid as a polyimide of the polyimide film and the same component, polyimide adhesive The thickness of the layer is less than 10% with respect to the total thickness of the polyimide layer, the thickness of the polyimide layer composed of the heat-resistant polyimide film and the polyimide adhesive layer is 15 to 50 μm, and the IPC has a bending radius of 1.5 mm at 80 ° C. Flexible metal foil polyimide characterized in that the flexibility is 3 million times or more Laminated board. Flexible metal foil polyimide laminate according to claim 1, wherein the metal foil is a rolled copper foil or electrolytic copper foil having a thickness of 9～35Myuemu.