JP4766247B2 - Method for producing flexible metal foil single-sided polyimide laminate - Google Patents

Description

  The present invention relates to a method for producing a flexible metal foil single-sided polyimide laminate used for electronic components such as printed boards.

  Flexible metal foil single-sided polyimide substrate that does not have an adhesive layer and consists of a certain type of metal foil layer and heat-resistant polyimide layer. As electronic devices become smaller and more functional, finer circuit patterns and thinner laminated boards Is required.

  As a method for producing a so-called all-polyimide flexible metal foil polyimide substrate having no adhesive layer, JP 2000-103010 A (Patent Document 1) and JP 7-39161 A (Patent Document 2) can be mentioned. Such a method is disclosed in which a so-called thermoplastic polyimide having a low glass transition point is formed on a conductor or a substrate and then bonded. In such a method, since thermoplastic polyimide is used, there is a drawback that the heat resistance of the entire substrate is deteriorated.

  Further, in Japanese Patent Laid-Open No. 2001-177201 (Patent Document 3) and Japanese Patent Laid-Open No. 5-129774 (Patent Document 4), a polyimide precursor resin solution, a so-called polyamic acid solution is directly applied to a metal foil and heated imidization. The method of obtaining a flexible metal foil polyimide substrate by performing is disclosed. Japanese Patent Application Laid-Open No. 5-82925 (Patent Document 5) discloses a method of obtaining a polyimide film by applying a polyamic acid solution to a releasable film instead of a metal foil and performing heat imidization. ing. In these methods, a large-scale apparatus is required for drying, so that the equipment cost becomes high, and when a thick polyimide layer is formed, dimensional change and warping are large after removing the etched copper foil. There was a problem of becoming.

JP 2000-103010 A Japanese Patent Publication No. 7-39161 JP 2001-177201 A JP-A-5-129774 JP-A-5-82925

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a flexible metal foil single-sided polyimide substrate that is free from wrinkles and bubbles, has excellent dimensional stability, and does not warp after copper foil removal. .

As a result of intensive studies to achieve the above object, the present inventor applied polyamic acid, which becomes a heat-resistant polyimide by heating imidization, on the metal foil, and after semi-drying the solvent content , A method for producing a flexible metal foil single-sided polyimide laminate obtained by laminating a polyimide film with a heated roll press and further heating and imidizing the polyamic acid adhesive layer, and removing the residual solvent from the adhesive layer and heating imidization Is maintained at 150 ° C. to 300 ° C. and 350 ° C. to 400 ° C. for 2 hours or more at 100 Pa or less, and heated in two stages with a temperature pattern as shown in FIG. It has been found that there are no bubbles, the surface of the metal foil is kept clean, and the warp after the metal foil is removed is reduced.
Furthermore, when removing the residual solvent and heating imidization, the temperature increase rate from room temperature to 150 ° C. to 300 ° C. and the temperature increase rate from 150 ° C. to 300 ° C. to 350 ° C. to 400 ° C. are 120 ° C. / It has been found that the dimensional stability is remarkably improved by setting the time to be shorter than the time, and the present invention has been made.

Therefore, this invention provides the manufacturing method of the following flexible metal foil single-sided polyimide laminated board.
[1] A polyamic acid varnish is applied onto a metal foil, and the solvent content is semi-dried at 3O to 50% by mass at 120 ° C. or lower, and a polyimide film is laminated thereon. In the following, the first stage heating at a constant temperature of 150 ° C. to 300 ° C. and the second stage heating at a constant temperature of 330 ° C. to 420 ° C. are performed , and the heating holding time is set to 2 to 10 hours, respectively. A method for producing a flexible metal foil single-sided polyimide laminate, wherein the polyamic acid is imidized at a heating rate of 50 to 170 ° C./hour for each of the first stage heating and the second stage heating.
[2] The two-stage heating time of the heating imidization, 50-1 stage heating 0.99 ° C. to 300 ° C. in a constant temperature and the second stage heating 350 ° C. to 400 ° C. in a heating rate of Atsushi Nobori up to a constant temperature, respectively 120.degree. C./hour. The method for producing a flexible metal foil single-sided polyimide laminate according to [1].

  According to the production method of the present invention, an all-polyimide flexible metal foil single-sided polyimide laminate using a heat-resistant polyimide adhesive having excellent dimensional stability and curling resistance can be obtained.

  In the present invention, the polyamic acid used as an adhesive preferably contains 50% by mass or more of a polyamic acid obtained by reacting 4,4′-diaminodiphenyl ether and pyromellitic anhydride. It is also possible to blend and use a polyamic acid obtained from the above acid anhydride and diamine.

Examples of acid anhydrides used for polyamic acid other than polyamic acid obtained by reacting these 4,4′-diaminodiphenyl ether and pyromellitic acid anhydride include tetracarboxylic acid anhydrides and derivatives thereof. In addition, although illustrated here as tetracarboxylic acid, these esterified products, acid anhydrides, and acid chlorides can of course be used. That is, as the tetracarboxylic acid, pyromellitic acid (except when reacted with 4,4′-diaminodiphenyl ether), 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 3,3 ′, 4 , 4′-benzophenone tetracarboxylic 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-naphthalene tetracarboxylic acid, 1,2,5,6-naphthalene tetracarboxylic acid, 3,3 ′, 4,4′-diphenylmethane tetracarboxylic acid, 2,2- Bis (3,4-dicarboxyphenyl) propane, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane, 3,4,9,10-tetracarboxyperile 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane, 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] hexafluoropropane, butanetetracarboxylic acid And cyclopentanetetracarboxylic acid. 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 diamines used for polyamic acid other than polyamic acid obtained by reacting 4,4′-diaminodiphenyl ether and pyromellitic anhydride, p-phenylenediamine, m-phenylenediamine, 2′-methoxy-4 , 4'-diaminobenzanilide, 4,4'-diaminodiphenyl ether (except when reacted with pyromellitic acid), 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, diaminodiphenyl Sulfone, diaminobenzanilide, diaminobenzoate, diami Diphenyl sulfide, 2,2-bis (p-aminophenyl) propane, 2,2-bis (p-aminophenyl) hexafluoropropane, 1,5-diaminonaphthalene, diaminotoluene, diaminobenzotrifluoride, 1,4- Bis (p-aminophenoxy) benzene, 4,4 ′-(p-aminophenoxy) biphenyl, diaminoanthraquinone, 4,4′-bis (3-aminophenoxyphenyl) diphenylsulfone, 1,3-bis (anilino) hexa Fluoropropane, 1,4-bis (anilino) octafluoropropane, 1,5-bis (anilino) decafluoropropane, 1,7-bis (anilino) tetradecafluoropropane, 2,2-bis [4- (p -Aminophenoxy) phenyl] hexafluoropropane, 2,2-bi [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-tri Fluoromethylphenoxy) benzene, 4,4′-bis (4-amino-2-trifluoromethylphenoxy) biphenyl, 4,4′-bis (4-amino-3-trifluoromethylphenoxy) biphenyl, 4,4 ′ -Bis (4-amino-2-trifluoromethylphenoxy) diphenylsulfone, 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′-hexafluorotolidine, 4,4 ″ -diaminoterphenyl, Examples include diamines such as 4,4 ′ ″-diaminoquaterphenyl, diisocyanates obtained by reaction of these diamines with phosgene, and diaminosiloxanes.

The condensation reaction for preparing the polyamic acid in the present invention is carried out in a single solution of N-methyl-2-pyrrolidone (NMP) or dimethylacetamide (DMAc) as a polar solvent, or in a mixed solution of DMAc and NMP. N _{2 in} the range of from 40 ° C. to 40 ° C., a concentration of the reaction solution of 30% or less, and a molar ratio of aromatic tetracarboxylic anhydride to aromatic diamine of 0.95: 1.00 to 1.05: 1.00. The reaction is performed under an atmosphere, and there are no particular limitations on the method of dissolving and adding the raw materials for this reaction.

  In addition, for the purpose of improving various properties, it is also possible to use a mixture of inorganic, organic or metal powders, fibers and the like. It is also possible to add an additive such as an antioxidant for the purpose of preventing oxidation of the conductor, a silane coupling agent for the purpose of improving adhesiveness, and a leveling agent for the purpose of improving the coatability.

  The polyimide film used in the present invention is also preferably obtained by heating imidization of a polyamic acid obtained by reacting 4,4′-diaminodiphenyl ether and pyromellitic anhydride. The polyamic acid can be obtained by casting it on a metal plate or glass plate, heating it to dry the solvent and imidizing it, and then peeling it off the plate.

In the imidization of the polyimide film, there is no particular limitation on the heating temperature and catalyst addition, as long as it is imidized so that the film thickness is uniform, the polyimide film can be a commercially available one, For example, Kaneka Corporation apical, Toray DuPont Kapton, manufactured by Ube Industries, Ltd. UPILEX, manufactured by Dow Chemical Company PIBO (polyimide benzoxazocin Lumpur), and the like.
Moreover, you may perform a plasma process and an etching process to a polyimide film adhesion surface.

  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 suitably used, and when the thickness of the copper foil is less than 9 μm, wrinkles during production, A problem may occur in strength and the like, and it is not preferable in terms of cost because it is necessary to use a protective material.

  The method for producing a flexible metal foil single-sided polyimide laminate comprises a polyimide layer (that is, an adhesive layer formed by heating and imidizing a polyimide film and a polyamic acid), preferably the film thickness after imidization of the polyamic acid. It is coated on a metal foil such as a copper foil so that it is less than 10%, more preferably 5 to 9% of the polyimide layer (the same applies hereinafter), and the imidization does not proceed (imidation rate is less than 5%). After drying, a polyimide film is laminated on this with a heated roll press, and a polyamic acid adhesive layer is dried with a solvent and imidized to obtain an all-polyimide flexible metal foil single-sided polyimide laminate.

  In view of the characteristics of the laminate obtained by the present invention, the thickness of the polyimide layer is preferably in the range of 15 μm to 50 μm. When the thickness of the polyimide layer is less than 15 μm, it becomes difficult or difficult to laminate the polyamic acid on the copper foil so that the film thickness after imidization of the polyamic acid is less than 10% of the polyimide layer. In some cases, the resulting laminate may have poor flexibility, and if it is thicker than 50 μm, it may be difficult to remove the solvent and imidize the polyamic acid adhesive layer by the method of the present invention. Moreover, when the film thickness after imidation of a polyamic acid is larger than 10% of the thickness of a polyimide layer, there exists a possibility that the curl of a laminated board may become large.

  In the present invention, the polyamic acid varnish is applied and dried on a treated surface of a metal foil such as copper foil. In this case, the apparatus and method are not particularly limited, and the application is a comma coater, die coater, roll coater, knife coater. , Reverse coater, lip coater, etc. may be used, and drying is performed at the time of passing through a heated roll press, and the solvent content is 3 to 50% by mass, particularly 10 to 35% by mass, and imidation does not proceed. (Imidation rate is less than 5%, especially 1% or less) The polyamic acid may be suitably dried at 120 ° C. or less for adhesion. If the solvent content exceeds 50% by mass, bubbles and blisters may occur during roll pressing, or the adhesive flow may occur and the roll may become dirty, and if the solvent content is less than 3% by mass, In particular, when laminating with a hot roll press, a high temperature and a high pressure are required, and the equipment cost is increased, which is not preferable.

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 silicon 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 DMAc used as a solvent, and the linear pressure is 5 to 100 kgf / Performed in the cm range.

  The solvent drying and imidization after lamination can be performed at a temperature equal to or higher than the boiling point of the solvent used for the varnish. As conditions for imidation, two-stage heating at 150 ° C. to 300 ° C. and 350 ° C. to 400 ° C. is performed and maintained at these temperatures for 2 hours or longer, preferably 2 to 10 hours. By heating in two stages with a temperature pattern as shown in FIG. 1, the surface of the metal foil can be kept clean and the warp after removal of the metal foil can be 5 mm or less.

By heating at 350 ° C. to 400 ° C. for 2 hours or longer, a sufficiently imidized and stable polyimide layer can be formed. Thereby, the flexible metal foil single-sided polyimide laminated board whose curl after copper foil removal is 5 mm or less can be obtained.
When the maximum heating temperature is 300 ° C. or less, the varnish is not thermally imidized into a stable polyimide layer, and thus the polyimide film after removing the copper foil is curled into a cylinder.
In this case, as a method of removing the copper foil, a method of completely removing the copper foil by etching using a ferric chloride aqueous solution is used.

In this case, it is preferable that the temperature increase rate in the temperature increase process is 170 ° C./hour or less, more preferably 120 ° C./hour or less. In particular, the rate of temperature increase is preferably 70 ° C./hour or less. In addition, the rate of temperature increase in the temperature increasing process is preferably 5 ° C./hour or more.
By increasing the rate of temperature rise preferably 120 ° C./hour or less, more preferably 70 ° C./hour or less, volatilization of the solvent contained in the varnish is slowed and bubbles are formed between the copper foil and the polyimide film. If the rate of temperature rise exceeds 170 ° C./hour, the solvent contained in the varnish may be vaporized by rapid heating, forming bubbles between the copper foil and the polyimide film, and may swell.

  By performing imidization under such conditions, the dimensional change rate after heating is within ± 0.1%, particularly within ± 0.05%, particularly −0.03 to 0.04%, and good dimensional stability is obtained. be able to. This is thought to be because the shrinkage proceeds gently when the varnish changes to polyimide.

  Further, the solvent drying and imidization are performed under a reduced pressure of 100 Pa or less, preferably 10 Pa or less, in order to promote the volatilization of the solvent and prevent the metal foil surface from being contaminated by the volatile solvent. If it exceeds 100 Pa, the copper foil surface is corroded and discolored or oxidized by the solvent gas released through the film by heating, so that the value as a product is remarkably impaired.

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

[Synthesis Example 1] Synthesis of polyamic acid varnish 200.5 g of 4,4′-diaminodiphenyl ether was dissolved in 2 kg of N, N-dimethylacetamide, stirred in an N ₂ atmosphere, and maintained at 10 ° C. 218.5 g of merit acid 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 mixture was further stirred at room temperature for 6 hours and reacted to obtain a polyamic acid varnish.

《Preparation of flexible metal foil single-sided polyimide laminate》
The polyamic acid varnish shown in the synthesis example was applied to a rolled copper foil manufactured by Nikko Materials Co., Ltd. with a thickness of 60 μm with an applicator, and dried at 120 ° C. for 3 minutes with an air dryer. The polyamic acid varnish layer after drying has a solvent content of 10% by mass and a thickness of 6 μm, and this is linear pressure with a polyimide film (Apical NPI, thickness 24 μm) manufactured by Kaneka Chemical Industry Co., Ltd. and a roll heated to 120 ° C. Laminate at 15 kgf / cm, speed 4 m / min, heat imidize polyamic acid using a vacuum heating furnace under the conditions shown in Table 1, cool to 30 ° C. or less in a nitrogen atmosphere, one side of flexible metal foil A polyimide laminate was obtained.
The heating imidization conditions in Examples and Comparative Examples will be described below.

[Example 1]
The temperature was raised from room temperature (20 ° C.) to 250 ° C. at 100 ° C./hour, held at 250 ° C. for 6 hours, then heated from 250 ° C. to 350 ° C. at 50 ° C./hour, and held at 350 ° C. for 10 hours.

[Example 2]
The temperature was raised from room temperature (20 ° C.) to 300 ° C. at 100 ° C./hour, held at 300 ° C. for 6 hours, then heated from 300 ° C. to 370 ° C. at 100 ° C./hour and held at 370 ° C. for 2 hours.

[Example 3]
The temperature was raised from room temperature (20 ° C.) to 200 ° C. at 100 ° C./hour, held at 200 ° C. for 2 hours, then heated from 200 ° C. to 350 ° C. at 100 ° C./hour, and held at 350 ° C. for 2 hours.

[Example 4]
The temperature was raised from room temperature (20 ° C.) to 280 ° C. at 100 ° C./hour and held at 280 ° C. for 10 hours, then heated from 280 ° C. to 380 ° C. at 100 ° C./hour and held at 380 ° C. for 10 hours.

[Example 5]
The same procedure as in Example 4 was performed except that the heating imidization was performed at a first stage temperature increase rate of 150 ° C./hour.

[Example 6]
The same procedure as in Example 4 was performed except that the heating imidization was performed at a second stage temperature increase rate of 150 ° C./hour.

[Example 7]
The same procedure as in Example 4 was performed, except that the heating imidization was performed at the first and second stage heating rates of 150 ° C./hour.

[Example 8]
The temperature was raised from room temperature (20 ° C.) to 150 ° C. at 50 ° C./hour, held at 150 ° C. for 5 hours, then heated from 150 ° C. to 380 ° C. at 50 ° C./hour, and kept at 380 ° C. for 5 hours.

[Example 9]
After raising the temperature from room temperature (20 ° C.) to 200 ° C. at 100 ° C./hour and holding 200 ° C. for 5 hours, the temperature was raised from 200 ° C. to 400 ° C. at 50 ° C./hour and kept at 400 ° C. for 5 hours.

[Comparative Example 1]
The same procedure as in Example 1 was performed except that heating imidization was performed in a nitrogen atmosphere of 10 ⁵ Pa.

[Comparative Example 2]
The same procedure as in Example 1 was performed except that the heating imidization was performed at an internal pressure of 10 ⁴ Pa to 10 ³ Pa.

[Comparative Example 3]
The same operation as in Example 2 was performed except that the second stage temperature increase was not performed.

[Comparative Example 4]
The same operation as in Example 3 was performed except that the second stage reached temperature holding time was 1 hour.

[Comparative Example 5]
The same procedure as in Example 9 was performed, except that the heating imidization was performed with the first stage temperature maintenance time set to 0 hour.

  Using the flexible metal foil single-sided polyimide laminates of the above Examples and Comparative Examples, measurement of dimensional stability, observation of copper foil stains, and measurement of curl were performed by the following methods. These results are also shown in Table 1.

<Measurement of dimensional stability>
In accordance with IPC FC241, the copper foil of the produced laminate was completely removed by etching with an aqueous ferric chloride solution to make only a polyimide layer composed of a polyimide film and a polyimide adhesive layer. A heat treatment was performed at 30 ° C. for 30 minutes, and the dimensional change rate was obtained from the dimensions of the polyimide layer before and after the heat treatment using the following formula.
Dimensional change rate = {(size before heat treatment−size after heat treatment) / size before heat treatment} × 100%
Positive value: Elongation, Negative value: Shrinkage The dimensional change rate is preferably within ± 0.1%, and more preferably within ± 0.05%.

<< Observation of copper foil dirt >>
The flexible metal foil single-sided polyimide laminated board after heat imidation was cut out as a 1-m sample in the winding length direction, and the dirt on the copper foil surface was visually observed.

<Measurement of curl>
After removing the copper foil of the produced laminate by etching using a ferric chloride aqueous solution, it was cut into 12 × 12 cm, and heat-treated for 30 minutes in an air dryer set at 150 ° C., and a polyimide film and a polyimide adhesive layer A test piece having only a polyimide layer made of The test piece was left on a horizontal plane, and when both ends of the test piece were lifted, the height from the horizontal plane was measured.

It is a two-step temperature rising schematic diagram at the time of solvent drying and imidation of polyamic acid in the present invention.

Claims (2)

A polyamic acid varnish is applied onto a metal foil, and the solvent content is semi-dried to 3 to 50% by mass at 120 ° C. or lower, and a polyimide film is laminated thereon. 0.99 ° C. to 300 was two-step heating of the second stage heating with constant temperature of the first stage heating and 330 ° C. to 420 ° C. with a constant temperature of ° C., and the first stage while the heat holding time, respectively 2 to 10 hours A method for producing a flexible metal foil single-sided polyimide laminate, wherein the polyamic acid is imidized at a heating rate of 50 to 170 ° C./hour each until heating and the second stage heating. In the two-stage heating at the time of heating imidization, the heating rate of heating to the constant temperature of the first stage heating 150 ° C. to 300 ° C. and the constant temperature of the second stage heating 350 ° C. to 400 ° C. is 50 to 120 ° C. / 2. The method for producing a flexible metal foil single-sided polyimide laminate according to claim 1, wherein time is used.

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