JP5011697B2 - Polyimide film and printed circuit board base substrate - Google Patents

Description

The present invention relates to a polyimide film containing a high dielectric constant filler and having a dielectric property suitable as a circuit board material having a large capacitance density and excellent withstand voltage.

  In recent years, with the demand for smaller electronic devices, higher signal speeds, and larger capacities, the density of mounted circuit components has increased, resulting in increased electrical noise and data errors. It has become a problem. In order to suppress the generation of this electrical noise and operate the semiconductor device stably, it is important to supply a necessary amount of current from a position close to the semiconductor device. For this purpose, a large capacitance is directly under the semiconductor device. It is effective to arrange a capacitor.

  As a means for forming a capacitor in an inner layer, a green sheet method in a ceramic wiring board is known. In the green sheet method, a molded body made of inorganic powder and resin, a wiring material, and an insulating material are laminated, and then fired at a high temperature of 800 ° C. or higher to decompose and disperse the resin and solid-phase sinter inorganic particles. Can be formed. The ceramic in the capacitor thus obtained is densified by sintering and scattering of the resin, and becomes a material exhibiting a high relative dielectric constant of several thousands of values. However, the printed wiring board has lower heat resistance than the ceramic wiring board and cannot withstand firing at a temperature of 800 ° C. or higher. On the other hand, the method of using a composite in which a filler having a high dielectric constant and a resin are mixed for the inner layer of the printed wiring board (see Patent Document 1) can suppress the heating temperature during formation of the composite to 300 ° C. or lower. Therefore, it is effective as a method for incorporating a capacitor in a printed wiring board.

In order to increase the functionality of the composite, it is necessary to select appropriate fillers, resins, and additives. As a method for optimizing the filler, a method of mixing two or more kinds or fillers having a particle diameter has been proposed. For example, a filler having a large dielectric constant and a filler having a small temperature change of the dielectric constant are mixed and used for temperature characteristic control of the relative dielectric constant (see Patent Document 2). In some cases, two or more kinds of fillers having different particle size distributions are mixed to increase the filling of the filler in the composite to improve the dielectric constant (see Patent Document 3).
It was difficult to obtain a composite exhibiting a large relative dielectric constant and a small dielectric loss tangent in these composites. For example, when a filler having a perovskite crystal structure, which is generally known as a high dielectric constant filler, is used, a composite having a large relative dielectric constant was obtained, but the dielectric loss tangent was 1 in a frequency region of 1 MHz or higher. It was as large as -10%.
When a low dielectric loss tangent filler such as titanium oxide, silica, or alumina was used, the dielectric loss tangent was as low as 1% or less in the frequency region of 1 MHz or higher, but the relative dielectric constant was as low as about 3 to 20. An epoxy composition having a large relative dielectric constant and a small dielectric loss tangent (see Patent Document 4) has also been proposed.

JP 05-057852 A Japanese Patent Application Laid-Open No. 07-079056 Japanese Patent Laid-Open No. 53-088198 Japanese Patent Laid-Open No. 2004-363065

  In the above proposal, for example, when used for a circuit board or the like, it is often exposed to a high temperature at the time of forming a thin film such as a copper thin film or at the time of using a circuit board or the like, and has excellent dielectric properties. However, if the material itself is insufficient in heat resistance, the case of industrial use will be limited, and even when the dielectric properties of a resin having relatively excellent heat resistance such as polyimide are improved, If the coefficient of linear expansion is large, problems remain in the thermal behavior during use, affecting the life of circuits and composite elements using these materials, and adding a large amount of high-dielectric-constant filler in the resin to further improve dielectric properties. In the case where it is contained, the mechanical strength is lowered, the surface smoothness of the material is remarkably impaired, and the circuit formation and the like are hindered.

The present invention solves the above-mentioned problems, is excellent in heat resistance, has a linear expansion coefficient in a predetermined range and can be a circuit or a composite element having a long life even when used, and further maintains a mechanical strength above a certain level. It is an object of the present invention to provide a polyimide film having excellent dielectric properties that can be used effectively for circuit formation without significantly impairing the surface smoothness of the material.
That is, the present invention has the following configuration.
1. A film comprising as a main component a polyimide obtained by polycondensation of an aromatic diamine having a benzoxazole structure and an aromatic tetracarboxylic acid, wherein the film contains a high dielectric constant filler the film.
2. 2. The polyimide according to 1 above, wherein the high dielectric constant filler is one or more high dielectric constant fillers selected from titanium oxide, barium titanate, strontium titanate, barium strontium titanate, zircon titanate, boron nitride, aluminum oxide, and silica. the film.
3. 3. The polyimide film as described in 1 or 2 above, having a linear expansion coefficient of −0.1 to 10 ppm / ° C. and a tensile breaking strength of 200 MPa or more.
4). 4. A polyimide film in which a polyimide layer obtained by polycondensation of an aromatic diamine having a benzoxazole structure and an aromatic tetracarboxylic acid is formed on at least one surface of any one of the films 1 to 3.
5. A base substrate for a printed wiring board, wherein a metal layer is laminated on at least one surface of the polyimide film according to any one of 1 to 4 above.

  A film mainly comprising a polyimide obtained by polycondensation of an aromatic diamine having a benzoxazole structure of the present invention and an aromatic tetracarboxylic acid, wherein the film contains a high dielectric constant filler. The polyimide film and the high dielectric constant filler are one or more high dielectric constant fillers selected from titanium oxide, barium titanate, strontium titanate, strontium barium titanate, zircon titanate, boron nitride, aluminum oxide and silica. At least one surface of the polyimide film, the polyimide film having a linear expansion coefficient of −0.1 to 10 ppm / ° C., and any one of the films, an aromatic diamine having a benzoxazole structure, and an aromatic Is obtained by polycondensation with aliphatic tetracarboxylic acids The polyimide film formed with the polyimide layer is heat resistant, has high mechanical strength, and can easily have a linear expansion coefficient within a predetermined range. Because it is in the range, it can be used as a circuit or composite element that has a long life even when it is used, and it is effective for forming a circuit where the mechanical strength is maintained above a certain level and the surface smoothness of the material is not significantly impaired. It is a polyimide film having excellent dielectric characteristics that can be used in the present invention, and is a polyimide film having a dielectric capacity suitable as a circuit board material having a large capacity density and a high withstand voltage, and has extremely high industrial effectiveness.

A film mainly composed of polyimide obtained by polycondensation (hereinafter also referred to as polymerization) of an aromatic diamine having a benzoxazole structure and an aromatic tetracarboxylic acid according to the present invention includes, for example, an aromatic having a benzoxazole structure. A polyamic acid solution obtained by polycondensation of an aromatic diamine and an aromatic tetracarboxylic acid in a solvent is cast on a support and dried to form a self-supporting film (green film) of the polyamic acid. Or a precursor film), which is obtained by a high temperature treatment to imidize it to obtain a polyimide film.
The method of adding a high dielectric filler to the polyamic acid solution is not particularly limited, for example, adding a high dielectric filler to a solvent and adding an aromatic diamine having a benzoxazole structure and an aromatic tetracarboxylic acid It may be polycondensed, and a high dielectric filler is added to a polyamic acid solution obtained by polycondensation of aromatic diamines having a benzoxazole structure and aromatic tetracarboxylic anhydrides in a solvent. The method of making it contain may be sufficient.
Specific examples of the aromatic diamine having a benzoxazole structure used in the film of the present invention include the following.

Among these, amino (aminophenyl) benzoxazole isomers are preferable from the viewpoint of ease of synthesis. Here, “each isomer” refers to each isomer in which two amino groups of amino (aminophenyl) benzoxazole are determined according to the coordination position (eg, the above “formula 1” to “formula 4”). Each compound described in the above. These diamines may be used alone or in combination of two or more.
In the present invention, it is preferable to use 70 mol% or more of the aromatic diamine having the benzoxazole structure.

The present invention is not limited to the above items, and the following aromatic diamines may be used. Preferably, the diamines do not have the benzoxazole structure exemplified below as long as the total aromatic diamine is less than 30 mol%. Is a polyimide film using one or two or more in combination.
Examples of such diamines include 4,4′-bis (3-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, and bis [4- (3-aminophenoxy) phenyl]. Sulfide, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine,

3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfoxide, 3,4′-diaminodiphenyl sulfoxide 4,4'-diaminodiphenyl sulfoxide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 3,4'- Diaminobenzophenone, 4,4′-diaminobenzophenone, 3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, bis [4- (4-aminophenoxy) phenyl] methane, 1 , 1-Bis [4- (4-aminophen Enoxy) phenyl] ethane, 1,2-bis [4- (4-aminophenoxy) phenyl] ethane, 1,1-bis [4- (4-aminophenoxy) phenyl] propane, 1,2-bis [4- (4-aminophenoxy) phenyl] propane, 1,3-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane,

1,1-bis [4- (4-aminophenoxy) phenyl] butane, 1,3-bis [4- (4-aminophenoxy) phenyl] butane, 1,4-bis [4- (4-aminophenoxy) Phenyl] butane, 2,2-bis [4- (4-aminophenoxy) phenyl] butane, 2,3-bis [4- (4-aminophenoxy) phenyl] butane, 2- [4- (4-aminophenoxy) Phenyl] -2- [4- (4-aminophenoxy) -3-methylphenyl] propane, 2,2-bis [4- (4-aminophenoxy) -3-methylphenyl] propane, 2- [4- ( 4-aminophenoxy) phenyl] -2- [4- (4-aminophenoxy) -3,5-dimethylphenyl] propane, 2,2-bis [4- (4-aminophenoxy) -3,5-dimethylphen Le] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane,

1,4-bis (3-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) ) Biphenyl, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfoxide, bis [4- ( 4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 1,3-bis [4- (4-aminophenoxy) ) Benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (3- Aminophenoxy) benzoyl] benzene, 4,4′-bis [(3-aminophenoxy) benzoyl] benzene, 1,1-bis [4- (3-aminophenoxy) phenyl] propane, 1,3-bis [4- (3-aminophenoxy) phenyl] propane, 3,4'-diaminodiphenyl sulfide,

2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, bis [4- (3-aminophenoxy) phenyl] methane, 1,1 -Bis [4- (3-aminophenoxy) phenyl] ethane, 1,2-bis [4- (3-aminophenoxy) phenyl] ethane, bis [4- (3-aminophenoxy) phenyl] sulfoxide, 4,4 '-Bis [3- (4-aminophenoxy) benzoyl] diphenyl ether, 4,4'-bis [3- (3-aminophenoxy) benzoyl] diphenyl ether, 4,4'-bis [4- (4-amino-α) , Α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] diphenylsulfone, bis [4- 4- (4-aminophenoxy) phenoxy} phenyl] sulfone, 1,4-bis [4- (4-aminophenoxy) phenoxy-α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4- Aminophenoxy) phenoxy-α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-trifluoromethylphenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [ 4- (4-amino-6-fluorophenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-methylphenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-cyanophenoxy) -α, α-dimethylbenzyl] benzene,

3,3′-diamino-4,4′-diphenoxybenzophenone, 4,4′-diamino-5,5′-diphenoxybenzophenone, 3,4′-diamino-4,5′-diphenoxybenzophenone, 3, 3'-diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzophenone, 3,4'-diamino-5'-phenoxybenzophenone, 3,3 '-Diamino-4,4'-dibiphenoxybenzophenone, 4,4'-diamino-5,5'-dibiphenoxybenzophenone, 3,4'-diamino-4,5'-dibiphenoxybenzophenone, 3,3'- Diamino-4-biphenoxybenzophenone, 4,4′-diamino-5-biphenoxybenzophenone, 3,4′-diamino-4-bipheno Cibenzophenone, 3,4'-diamino-5'-biphenoxybenzophenone, 1,3-bis (3-amino-4-phenoxybenzoyl) benzene, 1,4-bis (3-amino-4-phenoxybenzoyl) benzene 1,3-bis (4-amino-5-phenoxybenzoyl) benzene, 1,4-bis (4-amino-5-phenoxybenzoyl) benzene, 1,3-bis (3-amino-4-biphenoxybenzoyl) ) Benzene, 1,4-bis (3-amino-4-biphenoxybenzoyl) benzene, 1,3-bis (4-amino-5-biphenoxybenzoyl) benzene, 1,4-bis (4-amino-5) -Biphenoxybenzoyl) benzene, 2,6-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzonitrile and the above Some or all of the hydrogen atoms on the aromatic ring in the aromatic diamine are halogen atoms, alkyl groups having 1 to 3 carbon atoms or alkoxyl groups, cyano groups, or some or all hydrogen atoms of alkyl groups or alkoxyl groups are halogens. Examples thereof include aromatic diamines substituted with C1-C3 halogenated alkyl groups or alkoxyl groups substituted with atoms.

  The aromatic tetracarboxylic acids used in the present invention are, for example, aromatic tetracarboxylic anhydrides. Specific examples of the aromatic tetracarboxylic acid anhydrides include the following.

These tetracarboxylic dianhydrides may be used alone or in combination of two or more.
In the present invention, one or two or more non-aromatic tetracarboxylic dianhydrides exemplified below may be used in combination as long as they are less than 30 mol% of the total tetracarboxylic dianhydrides. Examples of such tetracarboxylic acid anhydrides include butane-1,2,3,4-tetracarboxylic dianhydride, pentane-1,2,4,5-tetracarboxylic dianhydride, and cyclobutanetetracarboxylic acid. Acid dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride, cyclohex-1-ene-2,3 5,6-tetracarboxylic dianhydride, 3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohexane-3 -(1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride 1-ethylcyclohexane -(1,2), 3,4-tetracarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1,3-dipropylcyclohexane- 1- (2,3), 3- (2,3) -tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ′, 4′-tetracarboxylic dianhydride,

Bicyclo [2.2.1] heptane-2,3,5,6-tetracarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1 , 3-Dipropylcyclohexane-1- (2,3), 3- (2,3) -tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ′, 4′-tetracarboxylic dianhydride, bicyclo [2.2.1] Heptane-2,3,5,6-tetracarboxylic dianhydride, bicyclo [2.2.2] octane-2,3,5,6-tetracarboxylic dianhydride, bicyclo [2.2.2] Oct-7-ene-2,3,5,6-tetracarboxylic dianhydride and the like. These tetracarboxylic dianhydrides may be used alone or in combination of two or more.

  The solvent used when polyamic acid is obtained by polycondensation (polymerization) of the aromatic diamine and aromatic tetracarboxylic acid (anhydride) dissolves both the raw material monomer and the resulting polyamic acid. Although it will not specifically limit if it carries out, A polar organic solvent is preferable, for example, N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone, N, N-dimethylformamide, N, N-diethylformamide, N, Examples thereof include N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoric amide, ethyl cellosolve acetate, diethylene glycol dimethyl ether, sulfolane, and halogenated phenols. These solvents can be used alone or in combination. The amount of the solvent used may be an amount sufficient to dissolve the monomer as a raw material. As a specific amount used, the mass of the monomer in the solution in which the monomer is dissolved is usually 5 to 40% by mass, The amount is preferably 10 to 30% by mass.

Conventionally known conditions may be applied for the polymerization reaction for obtaining the polyamic acid (hereinafter also simply referred to as “polymerization reaction”). As a specific example, in a temperature range of 0 to 80 ° C., 10 Stirring and / or mixing continuously for 30 minutes. If necessary, the polymerization reaction may be divided or the temperature may be increased or decreased. In this case, the order of adding both monomers is not particularly limited, but it is preferable to add aromatic tetracarboxylic acid anhydrides to the solution of aromatic diamines. The mass of the polyamic acid in the polyamic acid solution obtained by the polymerization reaction is preferably 5 to 40% by mass, more preferably 10 to 30% by mass, and the viscosity of the solution is measured with a Brookfield viscometer (25 ° C.). From the viewpoint of the stability of liquid feeding, it is preferably 10 to 2000 Pa · s, and more preferably 100 to 1000 Pa · s.
The reduced viscosity (ηsp / C) of the polyamic acid in the present invention is not particularly limited, but is preferably 3.0 dl / g or more, more preferably 4.0 dl / g or more, and still more preferably 5.0 dl / g or more. preferable.

Vacuum defoaming during the polymerization reaction is effective for producing a high-quality polyamic acid organic solvent solution. Moreover, you may perform superposition | polymerization by adding a small amount of terminal blockers to aromatic diamines before a polymerization reaction. Examples of the end capping agent include compounds having a carbon-carbon double bond such as maleic anhydride. The amount of maleic anhydride used is preferably 0.001 to 1.0 mol per mol of aromatic diamine.
In order to form a polyimide film from the polyamic acid solution obtained by the polymerization reaction, a green film is obtained by coating the polyamic acid solution on a support and drying, and then subjecting the green film to a heat treatment. The method of imidating reaction is mentioned.

  The support on which the polyamic acid solution is applied is only required to have smoothness and rigidity sufficient to form the polyamic acid solution into a film, and a drum or belt whose surface is made of metal, plastic, glass, porcelain, etc. And the like. Among them, the surface of the support is preferably a metal, more preferably stainless steel that does not rust and has excellent corrosion resistance. The surface of the support may be plated with metal such as Cr, Ni, or Sn. The surface of the support can be mirror-finished or processed into a satin finish as required. Application of the polyamic acid solution to the support includes, but is not limited to, casting from a slit base, extrusion through an extruder, squeegee coating, reverse coating, die coating, applicator coating, wire bar coating, etc. Conventionally known solution coating means can be appropriately used.

  The support on which the polyamic acid solution is applied is only required to have smoothness and rigidity sufficient to form the polyamic acid solution into a film, and a drum or belt whose surface is made of metal, plastic, glass, porcelain, etc. And the like. A method using a polymer film having moderate rigidity and high smoothness is also a preferred embodiment. Among them, the surface of the support is preferably a metal, more preferably stainless steel that does not rust and has excellent corrosion resistance. The surface of the support may be plated with metal such as Cr, Ni, or Sn. The surface of the support can be mirror-finished or processed into a satin finish as required. Application of the polyamic acid solution to the support includes, but is not limited to, casting from a slit base, extrusion through an extruder, squeegee coating, reverse coating, die coating, applicator coating, wire bar coating, etc. Conventionally known solution coating means can be appropriately used.

As an imidization method by high-temperature treatment, a conventionally known imidation reaction can be appropriately used. For example, using a polyamic acid solution that does not contain a ring-closing catalyst or a dehydrating agent, the imidization reaction proceeds by subjecting it to a heat treatment (so-called thermal ring-closing method), or the polyamic acid solution contains a ring-closing catalyst and a dehydrating agent. In order to obtain a polyimide film in which the difference in surface orientation between the front and back surfaces of the polyimide film is small, a chemical ring closing method can be mentioned in which an imidization reaction is performed by the action of the above ring closing catalyst and dehydrating agent. The thermal ring closure method is preferred.
100-500 degreeC is illustrated as a heating maximum temperature of a thermal ring closure method, Preferably it is 200-480 degreeC. When the maximum heating temperature is lower than this range, it is difficult to close the ring sufficiently, and when it is higher than this range, deterioration proceeds and the film tends to become brittle. A more preferable embodiment includes a two-stage heat treatment in which treatment is performed at 150 to 250 ° C. for 3 to 20 minutes and then treatment is performed at 350 to 500 ° C. for 3 to 20 minutes.
In the chemical ring closure method, after the polyamic acid solution is applied to a support, the imidization reaction is partially advanced to form a self-supporting film, and then imidization can be performed completely by heating. In this case, the condition for partially proceeding with the imidization reaction is preferably a heat treatment for 3 to 20 minutes at 100 to 200 ° C., and the condition for allowing the imidization reaction to be completely performed is preferably 200 to 400 ° C. For 3 to 20 minutes.

The timing for adding the ring-closing catalyst to the polyamic acid solution is not particularly limited, and may be added in advance before the polymerization reaction for obtaining the polyamic acid. Specific examples of the ring-closing catalyst include aliphatic tertiary amines such as trimethylamine and triethylamine, and heterocyclic tertiary amines such as isoquinoline, pyridine, and betapicoline. Among them, heterocyclic tertiary amines are mentioned. At least one amine selected from is preferred. Although the usage-amount of a ring-closing catalyst with respect to 1 mol of polyamic acids does not have limitation in particular, Preferably it is 0.5-8 mol.
The timing of adding the dehydrating agent to the polyamic acid solution is not particularly limited, and may be added in advance before the polymerization reaction for obtaining the polyamic acid. Specific examples of the dehydrating agent include aliphatic carboxylic acid anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride, and aromatic carboxylic acid anhydrides such as benzoic anhydride. Among them, acetic anhydride, benzoic anhydride, etc. Acids or mixtures thereof are preferred. Moreover, the usage-amount of the dehydrating agent with respect to 1 mol of polyamic acids is not particularly limited, but is preferably 0.1 to 4 mol. When a dehydrating agent is used, a gelation retarder such as acetylacetone may be used in combination.

Whether it is a thermal cyclization reaction or a chemical cyclization method, the polyimide film precursor film (green film) formed on the support may be peeled off from the support prior to complete imidization, You may peel after imidation.
Although the thickness of a polyimide film is not specifically limited, When considering using it for the base substrate for printed wiring boards mentioned later, it is 1-150 micrometers normally, Preferably it is 3-50 micrometers. This thickness can be easily controlled by the amount of the polyamic acid solution applied to the support and the concentration of the polyamic acid solution.

  In the present invention, a high dielectric constant filler is used. The high dielectric constant filler in the present invention is not particularly limited as long as it exhibits high dielectric properties, but a material having a relative dielectric constant of 5 or more, preferably 7 or more, and more preferably 12 or more is used. The upper limit of the relative dielectric constant is not particularly limited, but generally does not exceed 5000 practically. As the high dielectric constant filler, an inorganic filler is preferable, and titanate, zirconate and the like are particularly preferable. The high dielectric filler to be added to the polyimide film of the present invention is preferably titanium oxide, barium titanate, strontium titanate, barium titanate, zircon titanate, barium zirconate, barium zirconate titanate, boron nitride , One or more selected from aluminum oxide and silica. The particle size of the filler is 0.3 to 200 μm, preferably 0.7 to 120 μm, more preferably 1.2 to 80 μm, and still more preferably 1.2 to 30 μm. Here, the particle diameter is a volume average molecular weight. If the particle size is less than this range, sufficient dielectric properties may not be expressed. On the other hand, when the particle diameter exceeds this range, the film has many defects and the mechanical strength of the film is lowered.

  Moreover, the compounding quantity of the high dielectric constant filler in this invention is 5-70 mass% with respect to the whole film, Preferably it is 7-55 mass%, More preferably, it is 9-45 mass%. If the addition amount is less than this range, sufficient dielectric properties cannot be obtained. On the other hand, if the amount added exceeds this range, the strength of the film is remarkably lowered and handling becomes difficult.

The polyimide film of the present invention is usually an unstretched film, but may be stretched uniaxially or biaxially. Here, the unstretched film refers to a film obtained without intentionally applying a mechanical external force in the surface expansion direction of the film by tenter stretching, roll stretching, inflation stretching, or the like.
The polyimide layer obtained by polycondensation of aromatic diamines having a benzoxazole structure formed on at least one surface of the polyimide film of the present invention and aromatic tetracarboxylic acid anhydrides is a high layer in the polyimide film described above. It is a polyimide layer that does not contain a dielectric filler, and the multilayering (lamination) method is not particularly limited as long as there is no problem in adhesion between the two layers, and other layers such as an adhesive layer may be used. It is only necessary to be in close contact without intervening, for example, a method by coextrusion, a method in which the other polyamic acid solution is cast on a polyimide film as one layer and imidized, and a high dielectric filler is included. A polyimide layer (hereinafter also referred to as (a) layer) containing no high dielectric filler on a film (hereinafter also referred to as (b) layer). And a method of imidation by applying a de-acid solution at a spray coating and the like.
The multi-layer structure is sufficient if at least the (a) layer and the (b) layer are laminated, but the (a) layer is laminated on the (b) layer, (a) / (b) / (a The layer (a) is preferably laminated on both sides of the layer (b).
The ratio of the thickness of (a) / (b) in the multilayer polyimide film of the present invention is not particularly limited, but the ratio of the thickness of (a) / (b) (in the case of a three-layer structure) from the gist of the present invention (A) is a calculation in a single layer) is 0.001 to 0.5 or less, more preferably 0.3 or less. If the thickness ratio of (a) / (b) exceeds 0.5, the mechanical strength may be insufficient or the linear expansion coefficient may be too large. On the other hand, if it is less than 0.001, the effect of improving surface characteristics, particularly surface smoothness, may be insufficient.
The thickness of the multilayer polyimide film of the present invention is not particularly limited, but when used as a substrate of a flexible printed circuit board, it is preferable that the thickness of the (b) layer mainly responsible for mechanical strength is 3 to 60 μm. is there.

  The film in the present invention has excellent tensile breaking strength and tensile elastic modulus, and has a relatively low value of linear expansion coefficient, but has a tensile breaking strength of 300 MPa or more and a linear expansion coefficient of −1 to 1. The film is +10 ppm / ° C. When the linear expansion coefficient is out of the range of −1 to +10 ppm / ° C., when the metal layer is formed, the thermal expansion behavior with the metal layer is deviated, causing peeling or warping, which is a problem in industrial use. Happens. Similarly, if the high dielectric filler is excessively added and the capacity density and the withstand voltage are improved too much, if the tensile rupture strength of the film is less than 300 MPa, a problem occurs in industrial use. It is preferable that a high dielectric filler is added and the tensile strength at break is 300 MPa or more.

The linear expansion coefficient in the present invention is measured as follows.
<Measurement of linear expansion coefficient of polyimide film>
For the polyimide film to be measured, the stretch rate in the MD direction and TD direction is measured under the following conditions, and the stretch rate / temperature at intervals of 90 ° C. to 100 ° C., 100 ° C. to 110 ° C.,. This measurement was performed up to 400 ° C., and the average value of all measured values from 100 ° C. to 350 ° C. was calculated as CTE (average value). The meanings of the MD direction and the TD direction indicate the flow direction (MD direction; the length direction of the long film) and the width direction (TD direction; the width direction of the long film).
Device name: manufactured by MAC Science, TMA4000S
Sample length; 10mm
Sample width: 2 mm
Temperature rise start temperature: 25 ° C
Temperature rising end temperature: 400 ° C
Temperature increase rate: 5 ° C / min
Atmosphere: Argon

Measurements of tensile strength at break, tensile modulus, and tensile elongation at break are as follows.
<Measurement of Tensile Breaking Strength, Tensile Elastic Modulus, and Tensile Breaking Elongation of Polyimide Film>
A test piece was prepared by cutting a polyimide film to be measured into a strip of 100 mm × 10 mm in the MD direction and the TD direction, respectively. Using a tensile tester (manufactured by Shimadzu Corp., Autograph (registered trademark) model name AG-5000A) under the conditions of a tensile speed of 50 mm / min and a distance between chucks of 40 mm, the tensile modulus and tension in each of the MD and TD directions. The breaking strength and tensile breaking elongation were measured.

A base substrate for a printed wiring board will be described as an example in which a metal layer is formed on at least one surface of the polyimide film of the present invention, which is a preferred embodiment of the present invention.
Here, the “base substrate for a printed wiring board” is a substantially flat substrate having a structure in which a metal layer is laminated on at least one surface of an insulating plate. The metal layer to be laminated may be a metal layer for a circuit that is intended to form a circuit by processing such as etching or the like. It may be a metal layer used for the purpose.
As the application of “base substrate for printed wiring board”, FPC, TAB carrier tape, COF base material, CSP base material and the like are preferable.
The metal laminated on at least one surface of the polyimide film is not particularly limited, and preferably copper, aluminum, stainless steel, or the like. The lamination means is not particularly limited, and the following means are exemplified.
・ Means for attaching a metal plate to a polyimide film using an adhesive,
-Means for forming a metal layer on a polyimide film using vacuum coating techniques such as vapor deposition, sputtering, and ion plating,
A means for forming a metal layer on a polyimide film by a wet plating method such as electroless plating or electroplating.
A metal layer can be laminated on at least one side of a polyimide film by combining these means alone or in combination.
Especially, as a method of laminating a metal layer, a method of forming a base metal layer by sputtering and thickening by electroplating is preferable.
In this case, the base metal may be a simple substance or an alloy such as Cu, Ni, Cr, Mo, Zn, Ti, Ag, Au, and Fe. Further, a good conductor such as Cu may be further deposited as a conductive layer on the base metal by sputtering.
The thickness of the underlayer and the conductive layer is preferably 100 to 5000 mm.
Cu is preferable as the metal to be electroplated.

The thickness of the metal layer is not particularly limited, but when the metal layer is used for a circuit (conductive), the thickness of the metal layer is preferably 1 to 175 μm, more preferably 3 to 105 μm. is there. When using the polyimide film which bonded the metal layer as a thermal radiation board, the thickness of a metal layer becomes like this. Preferably it is 50-3000 micrometers. The surface roughness of the surface of the metal layer bonded to the polyimide is not particularly limited, but the center line average roughness (hereinafter referred to as Ra) and ten points in JIS B 0601 (definition and display of surface roughness). A value represented by average roughness (hereinafter referred to as Rz) is preferably 0.1 μm or less for Ra and 1.00 μm or less for Rz because the effect of improving the adhesion between the film and the metal layer is great. . Of these, those satisfying these conditions are preferred. Although Ra and Rz are preferably as small as possible, the lower limit of Ra is 0.0001 μm and the lower limit of Rz is 0.001 μm because of ease of acquisition and processing.
An inorganic coating film such as a single metal or a metal oxide may be formed on the surface of the metal layer used in the present invention. Further, the surface of the metal layer may be subjected to treatment with a coupling agent (aminosilane, epoxysilane, etc.), sand plast treatment, hole treatment, corona treatment, plasma treatment, etching treatment, and the like. Similarly, the surface of the polyimide film may be subjected to honing treatment, corona treatment, plasma treatment, etching treatment, and the like.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited by a following example. The physical property evaluation methods in the following examples are as follows except for the above.

1. Reduced viscosity of polyamic acid (ηsp / C)
A solution dissolved in N-methyl-2-pyrrolidone (or N, N-dimethylacetamide) so that the polymer concentration was 0.2 g / dl was measured at 30 ° C. with an Ubbelohde type viscosity tube. (When the solvent used for preparing the polyamic acid solution was N, N-dimethylacetamide, the polymer was dissolved using N, N-dimethylacetamide and measured.)
2. The thickness of the polyimide film The thickness was measured using a micrometer (Millitron 1254D manufactured by Fine Reef).

[Reference Example 1]
(Preliminary dispersion of high dielectric constant particles)
975 parts by weight of barium titanate (manufactured by Sakai Chemical Industry Co., Ltd., trade name BT-05), 2210 parts by weight of N-methyl-2-pyrrolidone, the wetted part of the container, and the pipe for infusion are austenitic stainless steel SUS316L The mixture was placed in a container and stirred with a homogenizer T-25 basic (manufactured by IKA Labortechnik) at 1000 rpm for 1 minute to obtain a preliminary dispersion.
(Preparation of polyamic acid solution)
A nitrogen inlet tube, a thermometer, a liquid contact part of a container equipped with a stirring rod, and a pipe for infusion were substituted with nitrogen in the reaction container made of austenitic stainless steel SUS316L, and then 223 parts by mass of 5-amino-2- ( p-Aminophenyl) benzoxazole (also referred to as DAMBO) was added. Next, after 2210 parts by mass of N-methyl-2-pyrrolidone was added and completely dissolved, 2210 parts by mass and 217 parts by mass of pyromellitic dianhydride (also referred to as PMDA) were obtained in advance. And stirred for 24 hours at 25 ° C., a white brown viscous high dielectric constant filler-dispersed polyamic acid solution A was obtained. The reduced viscosity (ηsp / C) was 3.9 dl / g.

[Reference Example 2]
Nitrogen introduction tube, thermometer, vessel wetted part equipped with stirring rod, and infusion pipe were replaced with nitrogen in the reaction vessel of austenitic stainless steel SUS316L, and then 5-amino-2- (p-aminophenyl) ) After adding 223 parts by mass of benzoxazole and 4416 parts by mass of N, N-dimethylacetamide and completely dissolving them, Snowtex DMAC-ST30 (manufactured by Nissan Chemical Industries, Ltd.) 40 in which colloidal silica is dispersed in dimethylacetamide .5 parts by mass (including 8.1 parts by mass of silica) and 217 parts by mass of pyromellitic dianhydride are added and stirred at a reaction temperature of 25 ° C. for 36 hours to obtain a brown and viscous polyamic acid solution b. It was. Ηsp / C of this product was 5.2 dl / g.
To the obtained polyamic acid solution B, 975 parts by mass of barium titanate (product name BT-05, manufactured by Sakai Chemical Industry Co., Ltd.) was added, and the stirring was continued for 12 hours. A dispersed polyamic acid solution B was obtained.

[Reference Example 3]
(Preliminary dispersion of high dielectric constant filler)
924 parts by mass of barium titanate (manufactured by Sakai Chemical Industry Co., Ltd., trade name BT-05), 2000 parts by mass of N-methyl-2-pyrrolidone, and the infusion pipe are austenitic stainless steel SUS316L And stirred with a homogenizer T-25 Basic (manufactured by IKA Labortechnik) for 1 minute at a rotational speed of 1000 revolutions / minute to obtain a preliminary dispersion.
(Preparation of polyamic acid solution)
A nitrogen inlet tube, a thermometer, a wetted part of a container equipped with a stirring rod, and an infusion pipe were replaced with nitrogen in the reaction vessel made of austenitic stainless steel SUS316L, and then 200 parts by mass of diaminodiphenyl ether (also referred to as DADPE). Put. Next, after 2190 parts by mass of N-methyl-2-pyrrolidone was added and completely dissolved, the preliminary dispersion obtained above and 217 parts by mass of pyromellitic dianhydride were added, and the mixture was stirred at 25 ° C. for 5 minutes. When stirred for a while, white brown viscous high dielectric constant filler-dispersed polyamic acid solution C was obtained. The reduced viscosity (ηsp / C) was 3.2 dl / g.

[Reference Example 4]
(Preliminary dispersion of high dielectric constant filler)
Barium titanate (manufactured by Sakai Chemical Industry Co., Ltd., trade name BT-05) 887 parts by mass, N-methyl-2-pyrrolidone 420 parts by mass, and the infusion part of the container is austenitic stainless steel SUS316L And stirred with a homogenizer T-25 Basic (manufactured by IKA Labortechnik) for 1 minute at a rotational speed of 1000 revolutions / minute to obtain a preliminary dispersion.
(Preparation of polyamic acid solution)
A nitrogen inlet tube, a thermometer, a wetted part of a container equipped with a stirring bar, and an infusion pipe were replaced with nitrogen in the reaction vessel made of austenitic stainless steel SUS316L, and then 108 parts by mass of phenylenediamine (also referred to as PDA). Put. Next, after 3600 parts by mass of N-methyl-2-pyrrolidone was added and completely dissolved, 420 parts by mass and 292.5 parts by mass of diphenyltetracarboxylic dianhydride (BPDA) were obtained. When the mixture was stirred at 25 ° C. for 12 hours, a white brown viscous high dielectric constant filler-dispersed polyamic acid solution D was obtained. The reduced viscosity (ηsp / C) was 3.8 dl / g.

<Comparative Examples 1-4>
The high dielectric constant filler-dispersed polyamic acid solution obtained in Reference Examples 1 to 4 was degassed under reduced pressure for 24 hours, and then a metered gear pump was used on the non-slip material surface of polyethylene terephthalate film A-4100 (manufactured by Toyobo). After transporting and coating using a comma coater (gap: 350 μm, coating width: 1240 mm), it was dried at 110 ° C. for 30 minutes. The polyamic acid film which became self-supporting after drying was peeled off from the support and cut at both ends to obtain respective green films having a thickness of 43 μm and a width of 1200 mm.
These green films thus obtained were passed through a pin tenter, the first stage was heated at 200 ° C. for 5 minutes, and the temperature was raised at a heating rate of 4 ° C./second, and the second stage was performed at 450 ° C. for 5 minutes. Heating was applied to advance the imidization reaction. The maximum wind speed in the heat treatment furnace was 2.5 m / second on the film surface (approximately 3 cm above the surface) just below the blow nozzle.
The wind speed was measured using “Anemo Master (registered trademark) 24-6111” (manufactured by Nippon Kanomax Co., Ltd.) with the anemometer detection unit placed directly under the wind outlet. (In addition, the measurement of the wind speed is a value obtained by applying the value measured with the air blowing system and the drive system in the operating state at normal temperature, because this is a problem in use at high temperatures due to the heat resistance of the wind speed detection unit, The control of the air blowing system is controlled in accordance with the control at the time of normal temperature measurement, and the actual wind speed is assigned with the value from the air blow system control value at the time of normal temperature measurement.
Table 1 shows the properties of the obtained film and the state during film formation.

<Example 1>
The polyamic acid solution b obtained in Reference Example 2 was applied and dried on the surface of the green film obtained in Comparative Example 4 using a comma coater so that the dry thickness was 7 μm, and then the green film was peeled off from the support. Similarly, the polyamic acid solution b was applied and dried on the peeled surface so that the dry thickness was 7 μm.
The obtained green film has a structure in which a 43 μm-thick green film containing a high dielectric filler is sandwiched by a 7 μm thick polyamic acid layer not containing a high dielectric. The green film was further heat-treated under the same conditions as in Example 2 to obtain a high dielectric filler-containing film with a smooth surface. Table 1 shows the properties of the obtained film and the state during film formation.

<Comparative Example 5>
The same operation was performed except that the comma coater gap was 170 microns and the drying time was 20 minutes in Comparative Example 3 , and a thin high dielectric filler-containing film was obtained. Table 1 shows the properties of the obtained film and the state during film formation.

<Evaluation of high dielectric constant filler-containing film>
The high dielectric constant filler-containing film obtained in the examples was set in a vacuum apparatus equipped with an unwinding device, a winding device, and a plasma processing device, and then plasma processing was performed on the front and back surfaces of the film. The plasma treatment conditions were as follows: oxygen gas, frequency 13.56 MHz, power 80 W, gas pressure 0.9 Pa. The temperature during the treatment was 24 ° C. and the residence time in the plasma atmosphere was about 45 seconds. Next, the film after the plasma treatment is set in a vacuum apparatus having a winding apparatus, a winding apparatus, and a sputtering area, and the conditions of frequency 13.56 MHz, output 400 W, gas pressure 0.8 Pa, nickel-chromium ( A 150% nickel-chromium alloy coating was formed on both sides of the film by RF sputtering under a xenon atmosphere using a 7% chromium) target.
Next, a copper thin film having a thickness of 3000 mm was formed on both sides of the film by sputtering using a copper target, and a thick copper plating layer having a thickness of 8 μm was formed on both sides of the film using a copper sulfate plating bath.
Subsequently, on the first electrode layer, a titanium oxide layer as a barrier layer is 1000 angstroms,
Table 1 shows the capacity density and the withstand voltage of the obtained double-sided copper-clad high dielectric constant filler-containing film.
In the same manner, films 2 to 6 were used as base materials in the same manner to obtain double-sided copper-clad high dielectric constant filler-containing films. The characteristics of each film are shown in Table 1.

<Trial manufacture of capacitor built-in multilayer substrate using double-sided copper-clad high dielectric constant filler-containing film>
(Patterning)
The copper foils on both sides of the double-sided copper-clad high dielectric constant filler-containing film obtained in Example 1 were etched using a normal subtractive method to form a predetermined pattern to be a built-in capacitor.
Using an alumina ceramic substrate as the core layer, a patterned high dielectric constant filler-containing film, copper foil, and prepreg are layered together, and then layered patterning is repeated in a build-up manner, stacked and multilayered, as shown in FIG. A multilayer substrate sheet containing 30 elements was produced. In FIG. 1, only one side is schematically shown for convenience, but in practice, the same number of build-up layers is laminated on both sides according to a standard method. Laser processing was used for drilling via holes, and filled via plating was used for interlayer connection of via holes.
When a voltage of 50 V was applied to each capacitor of the obtained multilayer substrate with built-in capacitor and the presence or absence of leakage was examined, no abnormality was found. Next, 10 prototype multilayer boards were evaluated for leaks again after exposure to 500 cycles of a heat cycle test from -55 ° C to 80 ° C. Got.
Table 1 shows the results of evaluation conducted in the same manner using films 2 to 6 as the base material.

As described above, the high-dielectric-constant filler-containing film of the present invention is useful as a basic material for a thin film capacitor. In particular, it is possible to incorporate a capacitor in a build-up layer of a multilayer board, and particularly high-density mounting is possible. It is useful as a substrate material for mounting required high-speed arithmetic devices, graphic controllers, display controllers, high-capacity memory modules, system-in-packages, and the like.
Since the high dielectric constant filler-containing film according to the present invention includes a high-quality dielectric layer with a small leakage current as a built-in capacitor element, it can be advantageously used in various applications as a capacitor. The capacitor element of the present invention can exert its excellent function particularly when it is incorporated as a capacitor in a printed circuit board. The basic structure of the printed circuit board of the present invention can be the same as that of the conventional circuit board except for the difference in which the thin film capacitor element of the present invention is incorporated therein. A substrate can be included. The printed circuit board of the present invention is particularly preferably a printed circuit board having a built-up structure used for a semiconductor package.

Claims (4)

A film comprising as a main component a polyimide obtained by polycondensation of an aromatic diamine having a benzoxazole structure and an aromatic tetracarboxylic acid, wherein the film contains a high dielectric constant filler A multilayer polyimide film obtained by forming, on at least one surface of a film, a polyimide layer that is obtained by polycondensation of an aromatic diamine having a benzoxazole structure and an aromatic tetracarboxylic acid and does not contain a high dielectric constant filler. The high dielectric constant filler is one or more high dielectric constant fillers selected from titanium oxide, barium titanate, strontium titanate, barium titanate, zircon titanate, boron nitride, aluminum oxide, and silica. Multilayer polyimide film. The multilayer polyimide film according to claim 1, wherein the linear expansion coefficient is −0.1 to 10 ppm / ° C., and the tensile strength at break is 200 MPa or more. The base substrate for printed wiring boards by which a metal layer is laminated | stacked on the at least single side | surface of the multilayer polyimide film in any one of Claims 1-3.