KR102632834B1 - Polyimide film - Google Patents

Abstract

[Problem] To provide a novel polyimide film that can be suitably used for metal wiring boards with wiring formed in different directions, boards with a multilayer structure, etc.
[Solution] In the first aspect, in the polyimide film, the thermal expansion coefficient in the MD direction (αT _MD ) and the thermal expansion coefficient in the TD direction (αT _TD ) are both set to 2 to 7 ppm/°C, and |αT _MD -αT _{TD _ _ _ _} Set | to 5 ppm/%RH or less. In the second aspect, in the polyimide film, the tensile modulus of elasticity in the MD direction (E _MD ) and the tensile modulus of elasticity in the TD direction (E _TD ) are both 5 to 9 GPa, and |E _MD -E _TD | is 2 GPa or less. , the in-plane anisotropy index (MT ratio) is set to 13 or less, and both the static friction coefficient and dynamic friction coefficient are set to 0.8 or less.

Description

Polyimide film {POLYIMIDE FILM}

The present invention relates to polyimide films and the like.

As electronic products become lighter, smaller, and more dense, demand for flexible printed wiring boards (FPCs) is increasing. FPC has a structure in which a circuit made of metal foil is formed on an insulating film, but polyimide film has often been used as an insulating film due to heat resistance and dimensional stability.

As mobile phones, etc. become highly functional and miniaturized, high flexibility and dimensional stability are required for FPCs, and various attempts are being made to solve these problems. As one of them, the base film and coverlay film have an elastic modulus of 4 GPa. A flexible printed wiring board using a thin polyimide film is known (see Patent Document 1). This technology controls the stiffness value of a flexible printed wiring board with a coverlay by adjusting the elastic modulus of the polyimide film, making it possible to achieve good flexibility and dimensional stability. However, with the recent development of mobile devices, the requirements for dimensional stability required for FPC have become more stringent, and conventional technologies have become unable to respond.

In addition, as the number of mounting points for electronic components increases, in order to mount a large number of electronic components in a limited space of a printed wiring board, boards suitable for three-dimensional mounting such as rigid and flex, and flexible printed wiring boards are also used as three-layer and four-layer boards. The need for multi-layering has emerged. The characteristics required for a multilayer flexible printed wiring board include being thin, freely foldable, and having a small spring back. A multilayer flexible printed wiring board is produced using a polyimide film as a core substrate and building up with an adhesive layer. However, because the dimensional stability after circuit processing was low, there were problems with positional accuracy in mounting electronic components and dimensional accuracy between layers.

Meanwhile, in the mounting of electronic components, as electronic devices such as liquid crystal TVs, notebook PCs, and smartphones become thinner, more functional, and more precise, particularly fine and high-density wiring is required for the mounting of ICs that drive displays. , To cope with this, the COF (Chip On Film) method of mounting ICs directly on a flexible wiring board has been developed and put into practical use.

Since COF requires higher dimensional accuracy than FPC, the copper-clad laminate used in COF is a two-layer type that forms a copper layer directly on the polyimide film and does not use an adhesive, which can accommodate the miniaturization of wiring. are being hired. This includes a method of forming a copper layer on a film by sputtering and plating, and a method of casting polyamic acid on copper foil and then imidizing it. However, the sputtering and plating method facilitates thinning of the copper layer and is advantageous for fine wiring. Two-layer copper-clad laminates are becoming mainstream.

However, conventional polyimide films cannot be used for flexible printed circuit boards with complicated designs that require dimensional accuracy and are not oriented in a constant manner because they require mounting of a plurality of electronic components.

For example, it is necessary to design the flexible printed circuit board separately according to the part that mounts the IC that drives the display and the part that requires complex circuit design by mounting multiple electronic devices. It became a big limitation.

Patent Document 1: Patent Publication No. 2007-208087

The purpose of the present invention is to provide a novel polyimide film.

The present inventors have repeatedly improved the properties of polyimide films in order to solve various problems in the flexible printed circuit board, etc., and as a result, it has been found that specific physical properties affect the dimensional stability of the film, and that the physical properties can be adjusted to a predetermined level. By setting this value, we discovered that excellent dimensional stability can be achieved even when used on boards with complex designs that are not limited to a specific direction, such as forming wiring in different directions, mounting multiple components, or using a multi-layer structure. , the present invention has been completed.

That is, the present invention relates to the following inventions, etc.

[1] The thermal expansion coefficient in the MD direction (αT _MD ) and the thermal expansion coefficient in the TD direction (αT _TD ) are both 2 to 7 ppm/℃, and ｜αT _MD -αT _TD ｜ is 2 ppm/℃ or less, and the A polyimide film in which the humidity expansion coefficient (αH _MD ) and the humidity expansion coefficient in the TD direction (αH _TD ) are both 3 to 16 ppm/%RH, and |αH _MD -αH _TD | is 5 ppm/%RH or less.

[2] The tensile modulus in the MD direction (E _MD ) and the tensile modulus in the TD direction (E _TD ) are both 5 to 9 GPa, ｜E _MD -E _TD ｜ is 2 GPa or less, and in-plane anisotropy ) A polyimide film with an index (MT ratio) of 13 or less and both a static friction coefficient and a dynamic friction coefficient of 0.8 or less.

[3] [1] or [2], which is at least one type of polyimide film for a substrate selected from a substrate on which wiring in different directions is formed (in multiple locations), a substrate on which a plurality of electronic components are mounted, and a substrate having a multilayer structure. ] The polyimide film described in [ ].

[4] The polyimide film according to any one of [1] to [3], which satisfies a loop rigidity of 75 mN/cm or less.

[5] An aromatic diamine component including paraphenylenediamine, and at least one acid anhydride selected from the group consisting of pyromellitic dianhydride and 3,3'-4,4'-diphenyltetracarboxylic dianhydride. The polyimide film according to any one of [1] to [4], which is composed of polyimide as a polymerization component.

[6] The polyimide film according to any one of [1] to [5] containing inorganic particles.

[7] An aromatic diamine component containing 35 mol% or more of paraphenylenediamine, and 1 selected from the group consisting of pyromellitic dianhydride and 3,3'-4,4'-diphenyltetracarboxylic dianhydride. The polyimide film according to any one of [1] to [6], which is composed of a polyimide containing at least one acid anhydride component as a polymerization component, and contains 0.05% by mass or more of inorganic particles with an average particle size of 0.03 to 1 μm.

[8] A substrate including the polyimide film and a metal layer according to any one of [1] to [7].

[9] A substrate (wiring board) including the polyimide film according to any one of [1] to [7], and wiring (metal wiring) formed on the film.

[10] The board according to [9], in which wiring (metal wiring) in different directions is formed (at multiple locations).

[11] The board according to [10], wherein wiring is formed in two directions along at least the MD and TD directions of the polyimide film.

[12] The substrate according to any one of [9] to [11], wherein the thermal expansion coefficient in the wiring transverse direction is in the range of 2 to 8 ppm/°C.

[13] A coverlay film composed of the polyimide film according to any one of [1] to [7].

[14] The coverlay film according to [13], wherein the polyimide film has a thickness of 5 to 25 ㎛.

[15] [13] or [14], which is at least one type of coverlay film for a substrate selected from a substrate on which wiring in different directions is formed (in multiple locations), a substrate on which a plurality of electronic components are mounted, and a substrate with a multilayer structure. ] Coverlay film described in [ ].

[16] An electronic component mounting substrate provided with the substrate and/or coverlay film according to any one of [8] to [15].

[17] The board described in [16] on which a plurality of electronic components are mounted.

[18] The board according to [17], which includes a substrate on which wiring is formed in two directions along at least the MD direction and the TD direction of the polyimide film, and electronic components are mounted on the wiring, respectively.

[19] A substrate having a multilayer structure including the substrate according to any one of [8] to [18] and/or a coverlay film.

In the present invention, a new polyimide film can be obtained. In particular, the present invention can provide a film with excellent dimensional stability not only in one direction but also in different directions (MD direction, TD direction, etc.) or in all directions. Additionally, the present invention can provide a polyimide film with excellent surface smoothness. Such a film has excellent handling properties, and can efficiently suppress wrinkles during winding, poor conveyance when applied to a substrate, scratches on the film surface, etc. Furthermore, the present invention can provide a polyimide film that has not only these properties but also physical properties such as bending properties.

Since the polyimide film of the present invention has good dimensional stability as described above (along with good dimensional stability, excellent surface smoothness and excellent physical properties), it can be used in different directions (e.g., film width direction and longitudinal direction). It can be suitably used for purposes such as forming wiring (particularly narrow pitch wiring), mounting a plurality of electronic components, or forming a multi-layered structure substrate.

1 is a plan view of a substrate on which wiring circuit patterns in different directions are formed on a polyimide film.
FIG. 2 is a plan view of a board with electronic components mounted on the wiring circuit pattern of the board of FIG. 1 .
Figure 3 is a cross-sectional view of the coverlay film.
Figure 4 is a cross-sectional view of a polyimide film (double-sided copper-clad laminate) provided with a metal layer on both sides.
Figure 5 is a cross-sectional view of a polyimide film (double-sided flexible printed circuit board) with wiring provided on both sides.
Figure 6 is a cross-sectional view of a polyimide film (flexible printed board with an adhesive layer) with wiring on one side and an adhesive layer on the other side.
Figure 7 is a cross-sectional view of a multilayer flexible printed board.

[Polyimide film]

The polyimide film of the present invention satisfies a specific range (value) in physical properties such as thermal expansion coefficient, humidity expansion coefficient, friction coefficient, tensile modulus, and in-plane anisotropy index. In addition, the polyimide film of the present invention may satisfy at least any of these specific ranges of physical properties, or may satisfy them in combination. In a preferred form, these are satisfied by combining them.

In addition, the polyimide film may satisfy these physical property values on at least one side of the film (one side), or may have both sides (one side and the other side).

The thermal expansion coefficient of the polyimide film is the thermal expansion coefficient (αT _MD ) in the MD direction (machine conveying direction, longitudinal direction, longitudinal direction, longitudinal direction, flow direction) and/or the TD direction (width direction, transverse direction, perpendicular to the MD direction). The coefficient of thermal expansion (αT _TD ) in the phosphorus direction (in particular, both αT _MD and αT _TD ) may be, for example, 12 ppm/°C or less (e.g., 10 ppm/°C or less), and is preferably 8. ppm/°C or less (e.g., 2 to 7 ppm/°C), more preferably 7 ppm/°C or less (e.g., 2.5 to 6.5 ppm/°C), and 6 ppm°C or less (e.g., 3 ppm/°C or less) ~6 ppm/℃) is more preferable.

In addition, in the polyimide film, |αT _MD -αT _TD , 3.5 ppm/℃ or less), more preferably 3 ppm/℃ or less (for example, 2.5 ppm/℃ or less), especially 2 ppm/℃ or less, and even more preferably 1.5 ppm/℃ or less.

By reducing the thermal expansion coefficient, it is easy to suppress dimensional changes (expansion) due to heat. Therefore, for example, expansion of the substrate at the processing temperature when mounting electronic components can be suppressed, and the risk of occurrence of mounting defects can be reduced. Furthermore, by reducing |αT _MD -αT _TD |, such dimensional changes or expansions can be uniformly suppressed in multiple directions. Therefore, for example, the mounting direction of electronic components is not limited to one direction, and the degree of freedom in circuit design increases dramatically.

In addition, the method of measuring the thermal expansion coefficient is not particularly limited, but for example, it can be measured under the conditions of a temperature range of 50 to 200°C and a temperature increase rate of 10°C/min.

The humidity expansion coefficient of the polyimide film is, for example, 20 in the humidity expansion coefficient in the MD direction (αH _MD ) and/or the humidity expansion coefficient in the TD direction (αH _TD ) (in particular, both αH _MD and αH _TD ). ppm/%RH or less (e.g., 18 ppm/%RH or less), preferably 16 ppm/%RH or less (e.g., 3 to 16 ppm/%RH), more preferably 15 ppm/%RH. It is more preferably 14 ppm/%RH or less (for example, 4 to 15 ppm/%RH), and more preferably 14 ppm/%RH or less (for example, 5 to 14 ppm/°C).

In addition, in the polyimide film, |αH _MD -αH _TD | is, for example, 6 ppm/%RH or less, preferably 5 ppm/%RH or less, more preferably 4 ppm/%RH or less, It is more preferable if it is 3 ppm/%RH or less (for example, 2.5 ppm/RH or less, 2 ppm/%RH or less).

By reducing the humidity expansion coefficient, it is easy to suppress dimensional changes due to humidity. Therefore, for example, the dimensional change of the substrate due to humidity in the process of mounting electronic components is reduced, and the risk of occurrence of mounting defects can be reduced. Furthermore, by reducing |αH _MD -αH _TD |, such dimensional changes can be suppressed without imbalance in multiple directions. Therefore, for example, the mounting direction of electronic components is not limited to one direction, and the degree of freedom in circuit design increases dramatically.

In addition, the method of measuring the humidity expansion coefficient is not particularly limited, but for example, it can be measured under the conditions of a temperature range of 25°C and a humidity range of 25 to 70 ppm/%RH.

The polyimide film has a tensile modulus in the MD direction (E _MD ) and/or a tensile modulus in the TD direction (E _TD ) (in particular, both E _MD and E _TD ) of 12 GPa or less (e.g., 10 GPa or less). ), preferably 9 GPa or less (e.g., 5 to 9 GPa), more preferably 8.5 GPa or less (e.g., 5.5 to 8.5 GPa), especially 8 GPa or less (e.g., 6 to 8 GPa) It's okay to continue. In addition, the lower limit of E _MD and/or E _TD is not particularly limited, but may be set to 3 GPa, 4 GPa, 5 GPa, etc. from the viewpoint of transportability and the like. Films that meet these E _MD and/or E _TD can reduce springback, especially springback in wiring boards, and reduce stress on connection points of electronic components when incorporated into electronic devices. easy.

In addition, in the polyimide film, the value of |E _MD -E _TD | is, for example, 3 GPa or less (for example, 2.5 GPa or less), preferably 2 GPa or less (for example, 1.8 GPa or less) ), more preferably 1.5 GPa or less (e.g., 1.2 GPa or less), and especially 1 GPa or less (e.g., 0.8 GPa or less, 0.7 GPa or less, 0.6 GPa or less, 0.5 GPa or less). A film with such a small difference between E _MD and E _TD can obtain good flexibility regardless of the bending direction, so the space of a wiring board or the like can be reduced, making it possible to cope with miniaturization of electronic devices.

In addition, the method of measuring the tensile modulus of elasticity is not particularly limited, but, for example, it can be measured under the conditions of a tensile speed of 100 mm/min.

The in-plane anisotropy index (MT ratio) of the polyimide film is, for example, 20 or less (e.g., 18 or less), preferably 15 or less (e.g., 14 or less), more preferably 13 or less, More preferably, it is 12 or less, and even more preferably, it is 10 or less (for example, 9 or less). A film having such an in-plane anisotropy index is likely to reduce warpage, especially warpage in metal laminated substrates and the like. Therefore, it becomes easy to create a wiring board with good yield.

In addition, the method of measuring the in-plane anisotropy index is not particularly limited, but can also be measured, for example, by the method described later.

The friction coefficient of the polyimide film may be 1.2 or less (for example, 1 or less) in terms of the static friction coefficient and/or the dynamic friction coefficient (especially both the static friction coefficient and the dynamic friction coefficient), and is preferably 0.8 or less ( For example, 0.1 to 0.75), more preferably 0.7 or less (for example, 0.15 to 0.65), or 0.6 or less (for example, 0.2 to 0.6).

A film that satisfies this friction coefficient has excellent handleability and can efficiently suppress the occurrence of wrinkles when wound into a roll, poor conveyance when forming a metal layer, and the occurrence of scratches.

In addition, the method of measuring the friction coefficient is not particularly limited, but for example, it can be measured under the conditions of a load of 200 g and a measurement speed of 120 mm/min.

The loop rigidity of the polyimide film is, for example, 150 mN/cm or less (e.g., 100 mN/cm or less), preferably 75 mN/cm or less, and more preferably 60 mN/cm. , it is more preferable if it is 50 mN/cm or less.

A polyimide film having such loop rigidity can reduce springback, especially springback on wiring boards, etc., and can easily reduce stress on connection points of electronic components when incorporated into electronic devices.

In addition, the method of measuring loop rigidity is not particularly limited, but can also be measured, for example, by the method described later.

The polyimide film may contain inorganic particles (or filler). The inorganic particles are not particularly limited and include, for example, oxides (e.g. titanium oxide, silica, etc.), inorganic acid salts [e.g. carbonates (e.g. calcium carbonate), phosphates (e.g. phosphoric acid calcium, calcium hydrogen phosphate, etc.].

The average particle diameter of the inorganic particles may be, for example, 0.01 to 5 μm, preferably 0.02 to 2 μm (for example, 0.03 to 1 μm), and more preferably 0.05 to 0.5 μm. In addition, the average particle size of the inorganic particles is measured, for example, in a slurry state dispersed in DMAc (N, N-dimethylacetamide) using a laser diffraction/confusion type particle size distribution measuring device LA-920 manufactured by Horiba Corporation. In the measured particle size distribution, the median diameter is defined as the average particle diameter.

The content of the inorganic particles is not particularly limited as long as it does not interfere with the effect of the present invention, but for example, it is 0.05% by mass or more, preferably 0.1 to 1.5% by mass, more preferably 0.2 to 0.2% by mass, relative to the polyimide film. It may be 1.0% by mass.

The thickness of the polyimide film is not particularly limited and can be appropriately selected depending on the intended use. For example, the thickness of the polyimide film is 1 to 200 μm (e.g., 2 to 150 μm), preferably 3 to 100 μm (e.g., 4 to 90 μm), more preferably 5 to 100 μm. It may be 80 ㎛ (for example, 6-60 ㎛), 7-50 ㎛, 10-40 ㎛, etc.

The glass transition temperature of the polyimide film (or the polyimide constituting the polyimide film) is not particularly limited, but is, for example, 200°C or higher (e.g., 250 to 450°C), preferably 250°C or higher ( For example, 280 to 400°C), more preferably 300°C or more (for example, 330 to 400°C).

Polyimide films may have relatively large sizes. The length of this polyimide film is 1 m or more (e.g., 5 m or more), 10 m or more (e.g., 20 m or more), preferably 30 m or more (e.g., 40 m or more), and more preferably 50 m or more. It may be (for example, 100m or more), 200m or more, 300m or more, 500m or more, 1000m or more, 2000m or more, 3000m or more, 5000m or more, etc.

In addition, the upper limit of the length of the polyimide film is not particularly limited, and may be, for example, 30,000 m, 20,000 m, or 10,000 m.

The width of the polyimide film is not particularly limited, but is, for example, 30 mm or more (e.g., 45 mm or more), preferably 150 mm or more (e.g., 155 mm or more), more preferably 200 mm or more (e.g., For example, it may be 250 mm or more, 500 mm or more, 1000 mm or more, 1500 mm or more, etc.

In addition, the upper limit of the width of the polyimide film is not particularly limited, but may be, for example, 10000 mm, 8000 mm, 5000 mm, 4000 mm, 3000 mm, 2000 mm, 1500 mm, etc.

The polyimide film may be in a wound state, that is, in a roll shape (roll).

(Method for producing polyimide and polyimide film)

A polyimide film (or polyimide constituting a polyimide film, or polyamic acid) usually contains an aromatic diamine component and an acid anhydride component (tetracarboxylic acid component) as polymerization components. Additionally, the polymerization component may contain other polymerization components as long as it contains an aromatic diamine component and an acid anhydride component as main components. When producing a polyimide film, there is no particular limitation, but first, an aromatic diamine component and an acid anhydride component are polymerized in an organic solvent to obtain a polyamic acid (polyamic acid) solution.

The polyimide film of the present invention may preferably contain paraphenylenediamine as an aromatic diamine component. By using an aromatic diamine component containing paraphenylenediamine in this way, it is easy to efficiently obtain a polyimide film having the characteristics and physical properties described above. The aromatic diamine component may contain things other than paraphenylenediamine. Specific examples of the aromatic diamine components other than paraphenylenediamine include metaphenylenediamine, benzidine, paraxylylenediamine, 4, 4'-diaminodiphenyl ether, 3, 4'-diaminodiphenyl ether, 4 , 4'-diaminodiphenylmethane, 4, 4'-diaminodiphenylsulfone, 3, 3'-dimethyl-4, 4'-diaminodiphenylmethane, 1, 5-diaminonaphthalene, 3, 3 '-dimethoxybenzidine, 1,4-bis(3-methyl-5-aminophenyl)benzene, and amide-forming derivatives thereof. These may be used individually, or two or more types may be mixed and used. As the aromatic diamine component, a combination of paraphenylenediamine and 4,4'-diaminodiphenyl ether and/or 3,4'-diaminodiphenyl ether is preferable. Among these, the amount of diamine components such as paraphenylenediamine and 3,4'-diaminodiphenyl ether, which have the effect of increasing the tensile elastic modulus of the film, is adjusted, and the lower limit value of the tensile elastic modulus of the obtained polyimide film is adjusted (e.g. For example, it is preferable to set it to 5 GPa or more because it also improves transportability.

Specific examples of the acid anhydride component include pyromellitic acid, 3,3',4,4'-diphenyltetracarboxylic acid, 2, 3', 3, 4'-diphenyltetracarboxylic acid, 3,3' ,4,4'-benzophenonetetracarboxylic acid, 2, 3, 6, 7-naphthalenetetracarboxylic acid, 2, 2-bis(3, 4-dicarboxyphenyl)ether, pyridine-2, 3, 5 , aromatic tetracarboxylic acid anhydride components such as 6-tetracarboxylic acid and their amide-forming derivatives, pyromellitic dianhydride, 3,3',4,4'-diphenyltetracarboxylic acid Dianhydride is preferred. These may be used individually, or two or more types may be mixed and used.

Among these, a particularly preferable combination of the aromatic diamine component and the acid anhydride component is one selected from the group consisting of paraphenylenediamine, 4,4'-diaminodiphenyl ether, and 3,4'-diaminodiphenyl ether. A combination of one or more aromatic diamine components and one or more acid anhydride components selected from the group consisting of pyromellitic dianhydride and 3,3',4,4'-diphenyltetracarboxylic dianhydride can be mentioned. .

The mixing ratio of paraphenylenediamine in the aromatic diamine component is the total amount of the aromatic diamine component in order to obtain a thermal expansion coefficient in the above range and at the same time give appropriate strength to the film and prevent poor running properties. Can be selected from the range of 15 mol% or more (for example, 18 mol% or more), usually 20 mol% or more (for example, 25 mol% or more), preferably 30 mol% or more (e.g. For example, 31 mol% or more), 33 mol% or more is preferable, and 35 mol% or more is more preferable. The mixing ratio (molar ratio) of the acid anhydride component is not particularly limited as long as it does not interfere with the effect of the present invention, but for example, 3,3',4,4'-diphenyltetracarboxylic dianhydride When containing, the content of 3,3',4,4'-diphenyltetracarboxylic dianhydride is preferably 15 mol% or more, more preferably 20 mol% or more, based on the total amount of acid anhydride components, 25 mol% or more (e.g., more than 25 mol%, 26 mol% or more, 27 mol% or more, etc.) is more preferable. By using polyamic acid composed of such an aromatic diamine component and an acid anhydride component as the raw material (precursor) of the polyimide film, it is easy to easily adjust the thermal expansion coefficient of the polyimide film to the above range in both the MD and TD directions of the film. , desirable.

In addition, in the present invention, specific examples of the organic solvent used to form the polyamic acid solution include, for example, sulfoxide-based solvents such as dimethyl sulfoxide and diethyl sulfoxide, N, N-dimethylformamide, N, Formamide-based solvents such as N-diethylformamide, acetamide-based solvents such as N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2-pyrrolidone, N-vinyl- Pyrrolidone-based solvents such as 2-pyrrolidone, phenol, o-, m-, or p-cresol, xylenol, halogenated phenol, catechol, etc., or hexamethylphosphoramide, γ-butyro Examples include aprotic polar solvents such as lactone, and it is preferable to use them alone or in a mixture of two or more types, but aromatic hydrocarbons such as xylene and toluene can also be used.

The polymerization method may be carried out by any known method, for example

(1) First, the entire amount of the aromatic diamine component is placed in a solvent, and then the acid anhydride component is added in an equivalent amount (equal molar) to the entire amount of the aromatic diamine component for polymerization.

(2) First, the entire amount of the acid anhydride component is placed in a solvent, and then the aromatic diamine component is added to an equivalent amount to the acid anhydride component for polymerization.

(3) After adding the aromatic diamine component (a1) on one side to the solvent, mixing the acid anhydride component (b1) on one side in a ratio of 95 to 105 mol% with respect to the reaction components for the time required for the reaction, then adding the acid anhydride component (b1) on one side to the reaction component for the time required for the reaction. A method of polymerizing by adding the aromatic diamine component (a2) and then adding the other acid anhydride component (b2) so that the total aromatic diamine component and the total acid anhydride component are approximately equivalent.

(4) After adding the acid anhydride component (b1) on one side to the solvent, mixing the aromatic diamine component (a1) on one side in a ratio of 95 to 105 mol% with respect to the reaction components for the time required for the reaction, then adding the acid anhydride component (a1) on one side to the solvent. A method of polymerizing by adding the acid anhydride component (b2) and then adding the other aromatic diamine component (a2) so that the total aromatic diamine component and the total acid anhydride component are approximately equivalent.

(5) The polyamic acid solution (A) is prepared by reacting one aromatic diamine component and the acid anhydride component in a solvent so that either side becomes excessive, and the other aromatic diamine component and the acid anhydride component in the other solvent are reacted so that either side becomes excessive. The polyamic acid solution (B) is adjusted by reacting to excess. A method of completing polymerization by mixing the polyamic acid solutions (A) and (B) obtained in this way. At this time, when adjusting the polyamic acid solution (A), if the aromatic diamine component is excessive, the acid anhydride component is excessive in the polyamic acid solution (B), and if the acid anhydride component is excessive in the polyamic acid solution (A), poly In the acid solution (B), the aromatic diamine component is in excess, and the polyamic acid solutions (A) and (B) are mixed and adjusted so that the total aromatic diamine component and the total acid anhydride component used in these reactions are approximately equivalent. In addition, the polymerization method is not limited to these, and other known methods can also be used.

The polyamic acid solution obtained in this way usually contains 5 to 40% by weight of solid content, and preferably contains 10 to 30% by weight of solid content. Additionally, the viscosity is usually 10 to 2000 Pa·s as measured by a Brookfield viscometer, and is preferably 100 to 1000 Pa·s for stable liquid delivery. Additionally, polyamic acid in an organic solvent solution may be partially imidized.

Next, the manufacturing method of the polyimide film is explained. Methods for forming a polyimide film include a method of casting a polyamic acid (polyamic acid) solution into a film form and thermal decyclization and desolvation to obtain a polyimide film, and a method of mixing a polyamic acid solution with a cyclization catalyst and a dehydrating agent to obtain a polyimide film. There is a method of producing a gel film by decyclization and heating and desolvating the gel film to obtain a polyimide film. However, the latter method is preferable because the thermal expansion coefficient and humidity expansion coefficient of the obtained polyimide film can be suppressed low.

In the chemical decyclization method, the polyamic acid solution is first prepared. In addition, in the present invention, the polyamic acid solution can usually contain inorganic particles as described above.

The polyamic acid solution used here may be a polyamic acid solution that has been polymerized in advance, or may be one that has been polymerized sequentially when containing inorganic particles.

The polyamic acid solution may contain a cyclization catalyst (imidization catalyst), a dehydrating agent, a gelation retardant, etc.

As cyclization catalysts, amines, such as aliphatic tertiary amines (trimethylamine, triethylenediamine, etc.), aromatic tertiary amines (dimethylaniline, etc.), heterocyclic tertiary amines (e.g. isoquinoline, pyridine, β-picoline, etc.). These may be used individually, or two or more types may be mixed and used.

Examples of the dehydrating agent include acid anhydrides, such as aliphatic carboxylic acid anhydrides (e.g., acetic anhydride, propionic anhydride, butyric acid anhydride, etc.), and aromatic carboxylic acid anhydrides (e.g., benzoic anhydride, etc.). . These may be used individually, or two or more types may be mixed and used. The gelation retardant is not particularly limited, and acetylacetone and the like can be used.

As a method of producing a polyimide film from a polyamic acid solution, a polyamic acid solution (particularly, a polyamic acid solution containing a cyclization catalyst and a dehydrating agent) is flow casted on a support to form a film, and the polyamic acid solution (particularly, a polyamic acid solution containing a cyclization catalyst and a dehydrating agent) is molded into a film by flow casting on a support. An example is a method in which the gel film is partially deformed to form a self-supporting gel film, then peeled from the support, heated and dried/imidized, and then heat treated.

Examples of the support include a rotating drum made of metal or an endless belt, but there is no particular limitation as long as it is made of a uniform material.

The gel film is heated to usually 20 to 200°C, preferably 40 to 150°C, by hydrothermal heat from the support and/or hydrothermal heat from a heat source such as hot air or an electric heater to undergo a ring-closure reaction, and volatile matter such as an advantageous organic solvent is heated to 40 to 150°C. By drying, it becomes self-supporting and is peeled off from the support.

The gel film peeled from the support may be stretched. As a stretching process, the apparatus and method are not limited as long as it is possible to combine stretching in the transport direction (MD) and stretching in the width direction (TD) at a predetermined magnification. The stretch ratio for creating a film having the effect of the present invention is usually 1.05 to 1.9 times the stretch ratio in the MD direction (MDX) at a temperature of 200° C. or higher, and preferably 1.1 to 1.6. It may be 1.1 to 1.3 times more preferably 1.1 to 1.3 times. The draw ratio (TDX) of TD is usually 1.05 to 1.3 times the draw ratio (MDX) of MD, preferably 1.1 to 1.25 times, and more preferably 1.1 to 1.2 times.

The film may be heat treated at a temperature of 250 to 500° C. for 15 seconds to 30 minutes using hot air and/or an electric heater.

The thickness of the film is determined by adjusting the solid content concentration, viscosity, and the amount of polymer flexible to the support so that it has a predetermined thickness (e.g., 7 to 75 ㎛, preferably 10 to 50 ㎛, more preferably 10 to 40 ㎛). It is advisable to adjust.

It is preferable to perform annealing treatment again on the polyimide film obtained in this way. By doing so, thermal relaxation of the film occurs and the heat shrinkage rate can be suppressed. The temperature of the annealing treatment is not particularly limited, but is preferably 200°C or more and 500°C or less, more preferably 200°C or more and 370°C or less, and particularly preferably 210°C or more and 350°C or less. Due to thermal relaxation from the annealing treatment, the heat shrinkage rate at 200°C can be suppressed within the above range, which is desirable because the dimensional accuracy is further increased.

In addition, in order to provide adhesiveness to the obtained polyimide film, the film surface may be subjected to electrical treatment such as corona treatment or plasma treatment, or physical treatment such as blast treatment, and such physical treatment may be performed according to a conventional method. You can. The atmospheric pressure when performing plasma treatment is not particularly limited, but is usually preferably in the range of 13.3 to 1330 kPa, 13.3 to 133 kPa (100 to 1000 Torr), and 80.0 to 120 kPa (600 to 900 Torr). ) range is more preferable.

The atmosphere in which the plasma treatment is performed contains at least 20 mol% of inert gas, preferably 50 mol% or more, more preferably 80 mol% or more, and 90 mol% or more. Most desirable. The inert gas includes He, Ar, Kr, Xe, Ne, Rn, N ₂ and mixtures of two or more of these. A particularly preferred inert gas is Ar. Furthermore, oxygen, air, carbon monoxide, carbon dioxide, carbon tetrachloride, chloroform, hydrogen, ammonia, tetrafluoromethane (carbon tetrafluoride), trichlorofluoroethane, trifluoromethane, etc. can be mixed with the above inert gas. . Preferred mixed gas combinations used as an atmosphere for the plasma treatment of the present invention include argon/oxygen, argon/ammonia, argon/helium/oxygen, argon/carbon dioxide, argon/nitrogen/carbon dioxide, argon/helium/nitrogen, and argon/helium. /nitrogen/carbon dioxide, argon/helium, helium/air, argon/helium/monosilane, argon/helium/disilane, etc.

The processing power density when applying plasma treatment is not particularly limited, but is preferably 200 W·min/m ² or more, more preferably 500 W·min/m ² or more, and 1000 W·min/m ² or more. Most desirable. The plasma irradiation time for performing plasma treatment is preferably 1 second to 10 minutes. By setting the plasma irradiation time within this range, the effect of plasma treatment can be fully exhibited without deterioration of the film. The gas type, gas pressure, and processing density of plasma processing are not limited to the above conditions, and may be performed in the air.

In addition, the polyimide film of the present invention has specific characteristics and physical properties as described above, but these aspects can be adjusted by appropriately selecting the above conditions, etc.

For example, the friction coefficient can be optimized to a predetermined range by adjusting the content of inorganic particles (or filler) and changing the surface roughness of the polyimide film. For example, it is easy to obtain efficiently by using a method of adding 0.3 to 1.0% by mass of inorganic particles with an average particle diameter of 0.05 to 0.5 μm relative to the polyimide film.

Regarding the tensile modulus, thermal expansion coefficient, humidity expansion coefficient, and anisotropy index, for example, the content of paraphenylenediamine and 3,3',4,4'-diphenyltetracarboxylic dianhydride in the polymerization process of polyamic acid. By adjusting to a predetermined range and further adjusting the draw ratios of MD and TD to a predetermined range in the film forming process, it can be within the scope of the present invention. For example, the mixing ratio of paraphenylenediamine in the aromatic diamine component is 30 mol% or more, and the content of 3,3',4,4'-diphenyltetracarboxylic dianhydride is 30 mol% or more based on the total amount of aromatic diamine component. , 20 mol% or more based on the total amount of the acid anhydride component, and the stretching ratio is 1.05 to 1.9 times the MD direction and 1.10 to 1.20 times the MD magnification in the TD direction at a temperature of 200°C or higher.

Regarding loop rigidity, for example, the content of paraphenylenediamine and 3,3',4,4'-diphenyltetracarboxylic dianhydride in the polyamic acid polymerization process, and MD and TD in the film forming process. When the draw ratio is within the above range, it can be adjusted to a predetermined range by setting the polyimide film to a predetermined thickness (for example, 60 μm or less).

The polyimide film obtained in this way has the above-mentioned characteristics. Therefore, it has excellent dimensional stability, surface smoothness, bending characteristics, etc. and, as described later, can be used for various purposes, especially substrates on which wiring (patterns) in different directions are formed, substrates on which a plurality of electronic components are mounted, and multilayer structures. It is desirable for forming a substrate having .

[Metal laminate, metal wiring board]

The polyimide film of the present invention can be preferably used to form a substrate (metal laminate (metal laminate, metal laminate substrate)) by laminating it with a metal layer (metal foil). In particular, the polyimide film of the present invention is suitable as a film for circuit boards, especially flexible printed circuit boards (FPC).

Therefore, the present invention includes a substrate provided with (using) the polyimide film. That is, this substrate (metal laminate) includes the polyimide film and the metal layer.

There is no particular limitation on the type of metal constituting the metal layer (metal foil), but examples include copper (copper alone, copper alloy, etc.), stainless steel and its alloys, nickel (nickel alone, nickel alloy, etc.), Aluminum (aluminum, aluminum alloy, etc.) can be mentioned.

The metal is preferably copper. By laminating such a metal layer and a polyimide film, a metal laminate substrate can be obtained. Additionally, those formed on the surface of these metals with a waterproof layer, a heat-resistant layer (for example, plating treatment with chrome, zinc, etc.), a silane coupling agent, etc. can also be used. Preferably it contains copper and/or at least one component selected from nickel, zinc, iron, chromium, cobalt, molybdenum, tungsten, vanadium, beryllium, titanium, tin, manganese, aluminum, phosphorus, silicon, etc. It is a copper alloy, and they are preferred for circuit processing. Particularly preferable metal layers include copper formed by rolling or electrolytic plating.

Additionally, the metal layer may be formed on at least one side of the polyimide film, or may be formed on both sides of the polyimide film.

In a metal laminate substrate, the thickness of the metal layer is not particularly limited, but may be, for example, about 1 to 150 ㎛ (e.g., 1.5 to 100 ㎛, 2 to 80 ㎛, 3 to 50 ㎛, etc.), 2 It may be about ~12 ㎛.

As long as the metal laminated substrate includes a polyimide film and a metal layer, the form of the lamination is not particularly limited and depends on the purpose of use of the polyimide film, etc., but for example, the polyimide film and the metal layer may be directly laminated. Also, the polyimide film and metal foil may be laminated (joined) through an adhesive layer (adhesive layer).

The adhesive component constituting the adhesive layer is not particularly limited, and may be, for example, either a thermosetting resin or a thermoplastic resin.

The manufacturing method of such a metal laminated substrate is not particularly limited, and it can be manufactured according to a conventionally known manufacturing method depending on the shape of the metal laminated substrate, etc. For example, a common method is to laminate a layer containing copper as a main component by electroplating on one or both sides of a polyimide film on a metal layer mainly containing nickel chromium formed by a sputtering method. A representative metal laminated substrate (copper clad laminate, copper clad laminate) of the present invention is, for example, a nickel chromium alloy layer provided on both sides of a polyimide film, and a layer of nickel chromium alloy is formed on this layer to a predetermined thickness (for example, thickness 2 to 2). It can be obtained by forming copper of 12 ㎛) according to the electroplating method.

In a metal laminate substrate, desired wiring (metal wiring, wiring pattern) can be formed by etching the metal layer.

Therefore, the present invention also includes a substrate (metal wiring board, metal wiring board) provided with the polyimide film and wiring (metal wiring) formed on the film. Such a metal wiring board may usually be a flexible printed board.

Additionally, wiring (wiring circuit, metal wiring) may be formed on at least one side of the polyimide film, or may be formed on both sides of the polyimide film.

In such a metal wiring board, wiring (for example, wiring on the same film surface) may be formed at one location or multiple locations, and when formed at multiple locations, the wiring may be formed in the same direction or in different directions. .

In particular, in the present invention, wiring can be formed in different directions (different directions at multiple locations). The form of forming in different directions is not particularly limited, but for example, wiring may be formed in at least two directions along the MD and TD directions of the polyimide film. That is, the polyimide film is provided with at least wiring along the MD direction of the polyimide film (wiring with the wiring crossing direction in the TD direction) and wiring along the TD direction of the polyimide film (wiring with the wiring crossing direction in the MD direction). It can also be formed.

Additionally, the size (pitch) of the wiring is not particularly limited, but can be formed efficiently even if it is a narrow pitch. The size of such wiring may be, for example, a line width of 30 μm or less (e.g., 20 μm or less, 15 μm or less, 10 μm or less), and a line-to-line (line spacing) of 40 μm or less (e.g., It may be about 20㎛ or less, 15㎛ or less, 10㎛ or less).

In a metal wiring board (polyimide film constituting the metal wiring board), the coefficient of thermal expansion in the transversal direction of the wiring is often small, reflecting the thermal expansion coefficient of the polyimide film, for example, 12 ppm/°C or less (e.g. For example, it may be 10 ppm/°C or less), preferably 8 ppm/°C or less (e.g., 2 to 8 ppm/°C), more preferably 7 ppm/°C or less (e.g., 3 to 7 ppm/°C). ppm/°C), and it is more preferable if it is 6 ppm°C or less (for example, 3 to 6 ppm/°C).

In addition, when forming wiring at multiple locations or in different directions, it is preferable that all of them satisfy the above-mentioned thermal expansion coefficient. For example, when forming wiring along the MD direction and the TD direction, it is desirable that the thermal expansion coefficients of these wiring transversal directions (i.e., TD direction and MD direction) both satisfy the above-mentioned thermal expansion coefficients.

Additionally, when forming wiring at multiple locations or in different directions, it is desirable that the coefficient of thermal expansion is small at all locations or in the transverse direction of the wiring and that their deviation is small. For example, when forming wiring along the MD direction and TD direction (i.e., when the wiring crossing direction is in the TD direction and MD direction), in a metal wiring board (polyimide film constituting the metal wiring board) |αT _MD -αT _TD | It may be 5 ppm/℃ or less (e.g., 4.5 ppm/℃ or less), more preferably 4 ppm/℃ or less (e.g., 3.5 ppm/℃ or less), especially 3 ppm/℃ or less, and 2.5 ppm/℃ or less. It is more preferable if it is ℃ or less, 2 ppm/℃ or less, 1.5 ppm/℃ or less, etc. In addition, the value _of |αT _{MD -αT TD} For example, when wiring A with the MD direction as the wiring crossing direction and wiring B with the TD direction as the wiring crossing direction are formed, |αT in wiring A _MD -αT _TD | or |αT in wiring B _{MD - αT TD _} αT _TD ｜ can also be obtained.

By reducing the thermal expansion coefficient, it is easy to suppress dimensional changes (expansion) due to heat. Therefore, for example, expansion of the substrate at the processing temperature when mounting electronic components can be suppressed, and the risk of occurrence of mounting defects can be reduced. Furthermore, by reducing |αT _MD -αT _TD |, such dimensional changes or expansions can be suppressed in multiple directions. Therefore, for example, the mounting direction of electronic components is not limited to one direction, and the degree of freedom in circuit design increases dramatically.

The manufacturing method of the metal wiring board (flexible printed board) is not particularly limited, and known methods can be used, but in particular, it can be manufactured according to a semiadditive method or a subtractive method. .

In a more specific form, wiring (wiring circuit) is patterned on a copper clad laminate (for example, a copper clad laminate with a copper thickness of about 1 to 3 μm) using the photolithography method, and the wiring is patterned at the location where wiring is to be formed. After peeling off the resist layer, wiring (for example, wiring with a copper thickness of 7 to 10 ㎛) is formed on the exposed thin copper layer by electrolytic copper plating, and then the resist layer and thin copper layer are formed. It can be manufactured by removing the underlying metal layer (semi-additive method), or by using a photolithography method on a copper-clad laminate (for example, a copper-clad laminate with a copper thickness of 7 to 10 ㎛). It can also be manufactured by patterning a wiring circuit, removing the copper layer and base metal layer in areas where wiring is not formed by etching, and then peeling off the resist layer (subtractive method).

If necessary, 0.1 to 0.5 μm of tin or gold may be formed on wiring (copper wiring, etc.) using an electroless plating method.

Additionally, for circuit protection, solder resist may be laminated on necessary areas or a coverlay film may be laminated. Alternatively, it is also possible to combine solder resist and coverlay film to protect each necessary location.

[Coverlay Film]

The polyimide film of the present invention can also constitute a cover film. Therefore, the present invention also includes a coverlay film made of the polyimide film.

Such a coverlay film is, in particular, a substrate on which wiring in different directions is formed (the metal wiring board, a metal wiring board in which the polyimide film is not the polyimide film, etc.), a substrate on which a plurality of components are mounted. It may be at least one type of coverlay film for a substrate selected from (such as a mounting substrate described later) and a substrate having a multilayer structure (such as a substrate described later).

Since the coverlay film covers wiring and components (electronic components), the dimensional stability of the coverlay film may also affect the formed wiring or mounted components. Therefore, in the coverlay film, it becomes important to exhibit excellent dimensional stability, etc.

The coverlay film may be composed of only a polyimide film, or may be composed of a polyimide film and an adhesive layer (adhesive layer).

The thickness of the coverlay film (or the polyimide film constituting the coverlay film) is not particularly limited, but is, for example, 1 to 100 ㎛, preferably 3 to 50 ㎛, more preferably 5 to 25 ㎛. It's okay too. Additionally, in the coverlay film, the thickness of the adhesive layer is not particularly limited, but is, for example, 1 to 300 μm (e.g., 2 to 200 μm), preferably 3 to 150 μm (e.g., 5 to 150 μm). ~100 ㎛) may be sufficient, and may be 1-80 ㎛ (for example, 3-60 ㎛, preferably 5-50 ㎛, more preferably 10-30 ㎛).

Additionally, a coverlay film is used, for example, to cover the metal layer of a metal wiring board (wiring of a metal wiring board). This metal wiring board (metal wiring board) is composed of a base film (base film) and a metal layer (wiring). The base film may be the polyimide film, or may be a polyimide film other than the polyimide film. In particular, both the coverlay film and the base film may be the polyimide film. In this way, in both the coverlay film and the base film of the metal wiring board, excellent dimensional stability, etc. can be efficiently exhibited by combining the polyimide film.

[Mounting board]

The present invention also includes the metal wiring board (metal wiring board) and/or a mounting board (electronic component mounting board) provided with the coverlay film. Such a mounting substrate may be, for example, a chip-on-film (COF) substrate.

In such a mounting board, the number of components (electronic components) to be mounted may be one or more, and in particular, more than one may be used. In the present invention, even when multiple components are mounted, excellent dimensional stability, etc. can be efficiently achieved. Therefore, high-precision mounting is possible even for multiple components.

In a representative form, components may be mounted on the wiring of a board with wiring formed in different directions. A more specific mounting board includes a board (metal wiring board) on which wiring (metal wiring) is formed in at least two directions along the MD and TD directions of the polyimide film, and electronic components may be mounted on these wiring, respectively. .

Additionally, the components (electronic components) can be selected depending on the application and are not particularly limited, and examples include IC chips, condensers, transistors, memories, and inductors. These parts can be used individually or in combination of two or more.

[Substrate with multilayer structure]

The polyimide film of the present invention is also suitable as a film constituting a substrate having a multilayer structure.

The substrate having such a multilayer structure may typically be a substrate having a multilayer structure provided at least with the metal wiring board and/or the coverlay film. According to a substrate having such a multilayer structure, despite having a multilayer structure, excellent dimensional stability, etc. can be exhibited, and a substrate with a multilayer structure can be formed with high precision. In particular, interlayer connection is required in a multi-layer structure substrate, but according to the polyimide film of the present invention, interlayer connection through via holes can be made possible with high positioning accuracy.

For example, a board with a multilayer structure (e.g., a multilayer flexible printed board) usually covers a plurality of stacked metal wiring boards and the metal wiring board (or wiring of the metal wiring board) in the outermost layer thereof. Although it is composed of a coverlay film, at least one of the plurality of metal wiring boards (base films) and/or coverlay films may be the polyimide film.

In particular, in a substrate having a multilayer structure, it is preferable that both the base film and the coverlay film constituting the metal wiring board (or all polyimide films constituting the substrate having a multilayer structure) are the polyimide films. do.

The present invention includes various combinations of the above structures within the technical scope of the present invention as long as the effect of the present invention is achieved.

[ Example ]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Additionally, in the examples, PPD represents paraphenylenediamine, 4,4'-ODA represents 4,4'-diaminodiphenyl ether, PMDA represents pyromellitic dianhydride, and BPDA represents 3,3 It represents ',4,4'-diphenyltetracarboxylic dianhydride, and DMAc represents N and N-dimethylacetamide, respectively.

[ Example 1~3]

(Preparation of polyimide film)

PPD (molecular weight 108.14), 4, 4'-ODA (molecular weight 200.24), BPDA (molecular weight 294.22), and PMDA (molecular weight 218.12) were prepared at a molar ratio of 40/60/30/70 and dissolved as a 20 wt% solution in DMAc. By polymerization, a polyamic acid solution of 3500 poise was obtained. To this, 0.3% by weight of DMAc slurry of silica with an average particle diameter of 0.3 μm was added per weight of the resin, and stirred sufficiently to disperse. Acetic anhydride (molecular weight 102.09) and β-picoline were mixed in this solution at a ratio of 17% by weight each and stirred. The resulting mixture was casted and peeled on a stainless steel drum rotating at 75°C using a T-shaped slit die to obtain a self-supporting gel film with a residual volatile component of 55% by weight and a thickness of approximately 0.05 mm. This gel film was stretched 1.25 times in the conveyance direction at 65°C, then stretched 1.45 times in the direction perpendicular to the conveyance direction in a heating furnace, and continuously heat treated at 250°C for 50 seconds and at 400°C for 75 seconds. It was carried out. By adjusting the conveyance speed, polyimide films with thicknesses of 13 μm, 25 μm, and 35 μm were obtained.

[ Example 4]

A polyimide film with a thickness of 50 μm was obtained in the same manner as in Examples 1 to 3, except that a DMAc slurry of silica with an average particle diameter of 0.1 μm was used.

[ Example 5, 6]

PPD, 4,4'-ODA, BPDA, and PMDA were used in a molar ratio of 20/80/35/65, and the same procedures as in Examples 1 to 3 were used, except that silica with an average particle diameter of 0.1 μm was used, and a thickness of 13 μm was used. , a 25㎛ polyimide film was obtained.

[ Comparative example One]

PPD, 4, 4'-ODA, BPDA, and PMDA were used in a molar ratio of 35/65/30/70, no particles were added, and stretching was carried out 1.20 times in the conveyance direction and 1.45 times in the direction perpendicular to the conveyance direction. A polyimide film with a thickness of 25 ㎛ was obtained in the same manner as in Examples 1 to 3 except that it was carried out.

[ Comparative example 2]

Example 1 except that PPD, 4,4'-ODA, BPDA, and PMDA were used in a molar ratio of 30/70/25/75, and stretching was carried out 1.15 times in the conveyance direction and 1.40 times in the direction perpendicular to the conveyance direction. Following the same procedure as in ~3, a polyimide film with a thickness of 38 μm was obtained.

For these films, the following characteristic evaluation was performed, and the results are shown in Table 1. Unless otherwise specified, each evaluation was conducted in an environment of 25°C and 60%RH.

(1) Tensile modulus

Measurement was performed using RTM-250 (A&D) under the condition of tensile speed: 100 mm/min.

(2) Coefficient of thermal expansion (CTE)

Measurement was performed using TMA-60 (manufactured by Shimadzu Corporation) under the conditions of a measurement temperature range of 50 to 200°C and a temperature increase rate of 10°C/min.

(3) Humidity expansion coefficient (CHE)

TM-9400 (Albak Coje) was used to measure temperature at 25°C and measurement humidity range: 25 to 70%RH.

(4) Friction coefficient

The support surface and the non-support surface of the sample were polymerized and fixed on a slip tester (manufactured by Techno Niz), and the static friction coefficient and dynamic friction coefficient were measured at a load of 200 g and a measurement speed of 120 mm/min.

(5) Anisotropy index (MT ratio)

Using SST-2500 (Sonic Sheet Tester manufactured by Nomura Shoji), measure the ultrasonic pulse propagation speeds V _MD and V _TD in the MD and TD directions and calculate the anisotropy index (MT ratio) defined by the following equation 1: did.

[Equation 1]

MT ratio=｜(V _MD ² -V _TD ² )/[(V _MD ² ＋V _TD ² )/2]×100｜

(6) Loop stiffness

Measurements were made using a loop rigidity tester DA (manufactured by Toyo Seiki Seisakusho) under the conditions of a sample width of 20 mm, a loop length of 50 mm, and a compression distance of 20 mm.

As revealed from the results in Table 1, the polyimide film of the example was found to be within a predetermined range in terms of specific physical properties. Therefore, it is necessary to confirm that there is a polyimide film that has excellent surface smoothness (and thus handling properties) or has excellent dimensional stability in both the MD and TD directions (and thus has excellent dimensional stability regardless of the direction of the film). I was able to.

(Creation of copper clad laminate)

A nickel chromium layer (Ni:Cr=80:20, thickness 25 nm) and a copper layer (thickness 100 nm) were formed on the support surface of the polyimide film shown in Table 2 by sputtering, followed by electrolytic plating using a copper sulfate plating solution. A copper layer with a thickness of 8㎛ was formed.

The following items were evaluated for the obtained copper-clad laminate. The results are shown in Table 2. In addition, in Table 2, “Example 1” in the term “polyimide film” means “polyimide film obtained in Example 1” (other matters are the same).

(7) Bending

The copper-clad laminate was cut to a size of 70 mm x 70 mm, the ends were fixed at 5 mm, and the amount of sagging was measured with a JIS 1 grade rectangular ruler.

As revealed from the results in Table 2 above, in the films obtained in Examples, warping in the copper-clad laminate could be suppressed to a relatively small extent.

(Creation of flexible printed board for evaluation)

A negative resist with a film thickness of 5 μm was created on the copper layer of the copper-clad laminate obtained above using a liquid resist according to a conventional method, and the copper layer and nickel chromium layer were removed by etching, and then the resist was peeled. Next, it was immersed in an electroless tin plating solution (tin plating solution TINPOSIT LT-34 manufactured by Seaplay Feist) at 70°C for 5 minutes to form a plating film with a thickness of 0.5 ㎛, and then plated on a substrate (polyimide film) (1) as shown in Figure 1. ), a flexible printed circuit board for evaluation was created having two electronic component connection portions (wiring) 2 at a 30 ㎛ pitch (15 ㎛ line width, 15 ㎛ between lines) with the MD direction and TD direction as the wiring transversal direction. did. The obtained flexible printed circuit board was evaluated for the following items, and the results are shown in Table 3.

(8) Coefficient of thermal expansion (CTE)

Measurement was performed using TMA-60 (manufactured by Shimadzu Corporation) under the conditions of measurement temperature range: 50 to 200°C and temperature increase rate: 10°C/min. In addition, the thermal expansion coefficient is measured as the coefficient of thermal expansion in the MD direction (αTMD) for pitches with the MD direction as the wiring transversal direction, and the coefficient of thermal expansion in the TD direction (αTMD) for pitches with the TD direction as the wiring transversal direction. These thermal expansion coefficients were used to calculate the absolute value of the difference in thermal expansion coefficient (｜αT _MD -αT _TD ｜, in the table, ｜MD-TD｜).

(9) Dimensional stability

Semiconductor chips (ICs) for evaluation were placed on two electronic component connection portions of the flexible printed circuit board for evaluation obtained above, and were bonded using a flip chip bonder at a stage temperature of 150°C and a tool temperature of 360°C. By pressing for 1 second, a substrate on which the semiconductor chip 3 was mounted as shown in FIG. 2 was obtained. After that, the external dimension (L4) of the wiring portion at the mounting location was measured, the elongation was calculated from the measured value (L3) before compression using the following equation (2), the standard deviation of 30 samples was obtained, and dimensional stability was evaluated.

(Equation 2)

Elongation rate (%)={(L4-L3)/L3}×100

As revealed from the results in Table 3 above, in the examples, the CTE values of the polyimide films obtained in Examples 1 to 4 can be efficiently reflected, and low dimensional stability can be realized or the imbalance in dimensional stability can be reduced. I was able to.

(Preparation of coverlay film for evaluation)

Polyamide-imide resin (Toyobo, Viromax HR16-NN) 70 parts by weight, liquid epoxy resin (Mitsubishi Chemical, jER828, epoxy equivalent 190) 50 parts by weight, solid epoxy resin (Mitsubishi Chemical, jER1001, epoxy equivalent 480) ) 50 parts by weight, 60 parts by weight of alumina (AA04, made by Sumitomo Chemical, average particle diameter 0.4㎛), 8 parts by weight of curing agent (4, 4'-diaminodiphenylsulfone), N-methyl-2-pyrrolidone Resin composition A with a solid content of 40% by mass was prepared using as a solvent. This resin composition was applied to the polyimide film (1) shown in Table 4 using a bar coater, dried at 150°C for 30 minutes, and a polyimide film with a B stage adhesive (4) having a thickness after drying of 15 μm was created, It was used as a coverlay film (Figure 3).

(Creation of multilayer flexible printed board for evaluation)

After forming a nickel chromium layer (Ni:Cr=95:5, thickness 10 nm) and a copper layer (thickness 100 nm) on the support surface of the polyimide film 1 shown in Table 4 by the sputtering method, A nickel chrome layer and a copper layer (2') were also formed on the body surface. Subsequently, a copper layer (2') with a thickness of 8 μm was formed on both sides by electrolytic plating using a copper sulfate plating solution, and a double-sided copper clad laminate (FIG. 4) was created. In addition, a negative resist with a film thickness of 5 μm was created using a liquid resist according to a conventional method, the copper layer and the nickel chrome layer were removed by etching, and then the resist was peeled off to form the copper wiring 2 as shown in FIG. 5 on both sides. A double-sided flexible printed board was created, and this was used as an inner layer board. Next, a single-sided flexible printed circuit board was created in the same manner as the double-sided flexible printed circuit board, except that the copper wiring 2 was formed on only one side using the polyimide film 1 shown in Table 4. And, 70 parts by weight of acrylonitrile butadiene rubber (made by Japan Zeon, Nipol 1043, nitrile content 29%), 50 parts by weight of liquid epoxy resin (made by Mitsubishi Chemical, jER828, epoxy equivalent 190), and solid epoxy resin (made by Mitsubishi Chemical, jER1001, epoxy equivalent weight 480), 50 parts by weight, 60 parts by weight of alumina (Sumitomo Chemical, AA04, average particle diameter 0.4㎛), 8 parts by weight of curing agent (4, 4'-diaminodiphenyl sulfone), methyl isobutyl ketone Resin composition B with a solid content of 40% by mass was prepared using as a solvent. This resin composition was applied to the film surface of the single-sided flexible printed circuit board obtained above using a bar coater, dried at 150°C for 10 minutes, and an adhesive-attached single-sided flexible printed circuit board with a thickness of 15 μm after drying was formed (Figure 6). was created and used as an outer layer substrate. Subsequently, the outer layer substrate and the coverlay film were overlapped side by side in the MD and TD directions on both sides of the inner layer substrate obtained above, in the order of A flexible printed board was created. The following items were evaluated for the obtained multilayer flexible printed board. The results are shown in Table 4.

(10) Bending (Method B)

The multilayer flexible printed circuit board was cut to a size of 70 mm x 70 mm and placed on a flat plate. The heights at four points from the flat plate were measured with a JIS 1 class right angle ruler, and the maximum value was adopted.

As revealed from the results in Table 4 above, by using the polyimide film obtained in the Example, warping could be suppressed to a small extent even if the substrate had a multilayer structure.

The polyimide film of the present invention is excellent in dimensional stability and handleability. In addition, the polyimide film of the present invention can also provide bending properties and the like. In particular, the polyimide film of the present invention has excellent dimensional stability not only in one direction but also in different directions, so that wiring in different directions (for example, MD direction and TD direction) can be installed at a narrow pitch or , it can be suitably used as a polyimide film used for purposes such as mounting a plurality of electronic components or forming a multilayer structure.

1: Polyimide film
2': metal layer (copper layer)
2: Wiring (pattern)
3: Electronic components (semiconductor chips, etc.)
4: Adhesive layer (adhesive)

Claims (24)

The thermal expansion coefficient in the MD direction (αTMD) and the thermal expansion coefficient in the TD direction (αTTD) are both 2 to 7 ppm/℃, |αTMD-αTTD| is less than 2 ppm/℃, the humidity expansion coefficient in the MD direction (αHMD), The humidity expansion coefficients (αHTD) in the TD direction are all 3 to 14 ppm/%RH, and ｜αHMD-αHTD｜ is 5 ppm/%RH or less,
The tensile modulus in the MD direction (E _MD ) and the tensile modulus in the TD direction (E _TD ) are both 5 to 8 GPa,
Contains more than 0.05% by mass of silica with an average particle diameter of 0.03 to 1 ㎛,
For a board on which wiring in different directions is formed, a board with a multilayer structure, or a board on which wiring in different directions is formed and has a multilayer structure,
Polyimide film. The polyimide film according to claim 1, wherein |E _MD -E _TD | is 2 GPa or less, the in-plane anisotropy index (MT ratio) is 13 or less, and both the static friction coefficient and the dynamic friction coefficient are 0.8 or less. . delete The polyimide film according to claim 1 or 2, which satisfies a loop stiffness of 75 mN/cm or less. The method according to claim 1 or 2, wherein 1 selected from the group consisting of an aromatic diamine component including paraphenylenediamine, pyromellitic dianhydride, and 3,3'-4,4'-diphenyltetracarboxylic dianhydride. A polyimide film composed of polyimide containing one or more types of acid anhydride components as polymerization components. delete The group according to claim 1 or 2, comprising an aromatic diamine component containing 35 mol% or more of paraphenylenediamine, pyromellitic dianhydride, and 3,3'-4,4'-diphenyltetracarboxylic dianhydride. A polyimide film composed of a polyimide containing as a polymerization component one or more acid anhydride components selected from the following. The polyimide according to claim 1 or 2, which is composed of a polyimide containing as polymerization components an aromatic diamine component containing 50 to 100 mol% of paraphenylenediamine and an aromatic acid anhydride component containing 50 to 100 mol% of pyromellitic dianhydride. A polyimide film, except that it is a polyimide film. The thermal expansion coefficient in the MD direction (αTMD) and the thermal expansion coefficient in the TD direction (αTTD) are both 2 to 7 ppm/℃, |αTMD-αTTD| is less than 2 ppm/℃, the humidity expansion coefficient in the MD direction (αHMD), The humidity expansion coefficients (αHTD) in the TD direction are all 3 to 14 ppm/%RH, and ｜αHMD-αHTD｜ is 5 ppm/%RH or less,
The tensile modulus in the MD direction (E _MD ) and the tensile modulus in the TD direction (E _TD ) are both 5 to 8 GPa,
A substrate comprising a polyimide film containing 0.05% by mass or more of silica with an average particle diameter of 0.03 to 1 ㎛ and a metal layer,
The substrate has a multilayer structure. The method of claim 9, wherein |E _MD -E _TD | of the polyimide film is 2 GPa or less, the in-plane anisotropy index (MT ratio) is 13 or less, and both the static friction coefficient and the dynamic friction coefficient are 0.8 or less. , Board. The thermal expansion coefficient in the MD direction (αTMD) and the thermal expansion coefficient in the TD direction (αTTD) are both 2 to 7 ppm/℃, |αTMD-αTTD| is less than 2 ppm/℃, the humidity expansion coefficient in the MD direction (αHMD), The humidity expansion coefficients (αHTD) in the TD direction are all 3 to 14 ppm/%RH, and ｜αHMD-αHTD｜ is 5 ppm/%RH or less,
The tensile modulus in the MD direction (E _MD ) and the tensile modulus in the TD direction (E _TD ) are both 5 to 8 GPa,
A substrate having a polyimide film containing 0.05% by mass or more of silica with an average particle diameter of 0.03 to 1 ㎛ and wiring formed on the film,
The substrate is formed with wiring in different directions, has a multi-layer structure, or has wiring in different directions and has a multi-layer structure. The method of claim 11, wherein |E _MD -E _TD | of the polyimide film is 2 GPa or less, the in-plane anisotropy index (MT ratio) is 13 or less, and both the static friction coefficient and the dynamic friction coefficient are 0.8 or less. , Board. delete The substrate according to claim 11 or 12, wherein wiring is formed in at least two directions along the MD and TD directions of the polyimide film. The substrate according to claim 11 or 12, wherein the thermal expansion coefficient in the wiring transverse direction is in the range of 2 to 8 ppm/°C. The thermal expansion coefficient in the MD direction (αTMD) and the thermal expansion coefficient in the TD direction (αTTD) are both 2 to 7 ppm/℃, |αTMD-αTTD| is less than 2 ppm/℃, the humidity expansion coefficient in the MD direction (αHMD), The humidity expansion coefficients (αHTD) in the TD direction are all 3 to 14 ppm/%RH, and ｜αHMD-αHTD｜ is 5 ppm/%RH or less,
The tensile modulus in the MD direction (E _MD ) and the tensile modulus in the TD direction (E _TD ) are both 5 to 8 GPa,
A coverlay film composed of a polyimide film containing 0.05 mass% or more of silica with an average particle diameter of 0.03 to 1 ㎛,
A coverlay film for a substrate on which wiring in different directions is formed, a substrate with a multilayer structure, or a substrate on which wiring in different directions is formed and has a multilayer structure. The method of claim 16, wherein |E _MD -E _TD | of the polyimide film is 2 GPa or less, the in-plane anisotropy index (MT ratio) is 13 or less, and both the static friction coefficient and the dynamic friction coefficient are 0.8 or less. , coverlay film. The coverlay film according to claim 16 or 17, wherein the polyimide film has a thickness of 5 μm to 25 μm. delete The thermal expansion coefficient in the MD direction (αTMD) and the thermal expansion coefficient in the TD direction (αTTD) are both 2 to 7 ppm/℃, |αTMD-αTTD| is less than 2 ppm/℃, the humidity expansion coefficient in the MD direction (αHMD), The humidity expansion coefficients (αHTD) in the TD direction are all 3 to 14 ppm/%RH, |αHMD-αHTD| is less than 5 ppm/%RH, the tensile modulus in the MD direction (E _MD ), and the tensile modulus in the TD direction ( A substrate having a polyimide film (E _TD ) of 5 to 8 GPa and containing 0.05% by mass or more of silica with an average particle diameter of 0.03 to 1 ㎛ and wiring formed on the film, and/or
The thermal expansion coefficient in the MD direction (αTMD) and the thermal expansion coefficient in the TD direction (αTTD) are both 2 to 7 ppm/℃, |αTMD-αTTD| is less than 2 ppm/℃, the humidity expansion coefficient in the MD direction (αHMD), The humidity expansion coefficient (αHTD) in the TD direction is all 3 to 14 ppm/%RH, |αHMD- _αHTD | (E _TD ) is all 5 to 8 GPa, and is provided with a coverlay film composed of a polyimide film containing 0.05% by mass or more of silica with an average particle diameter of 0.03 to 1 ㎛,
The board with the wiring is an electronic component mounting board in which wiring is formed in two directions along the MD direction and the TD direction. The method of claim 20, wherein |E _MD -E _TD | of the polyimide film is 2 GPa or less, the in-plane anisotropy index (MT ratio) is 13 or less, and both the static friction coefficient and the dynamic friction coefficient are 0.8 or less. , Board. The board according to claim 20 or 21, wherein a plurality of electronic components are mounted. delete The thermal expansion coefficient in the MD direction (αTMD) and the thermal expansion coefficient in the TD direction (αTTD) are both 2 to 7 ppm/℃, |αTMD-αTTD| is less than 2 ppm/℃, the humidity expansion coefficient in the MD direction (αHMD), The humidity expansion coefficients (αHTD) in the TD direction are all 3 to 14 ppm/%RH, |αHMD-αHTD| is less than 5 ppm/%RH, the tensile modulus in the MD direction (E _MD ), and the tensile modulus in the TD direction ( A substrate having a polyimide film (E _TD ) of 5 to 8 GPa and containing 0.05% by mass or more of silica with an average particle diameter of 0.03 to 1 ㎛ and wiring formed on the film, and/or
The thermal expansion coefficient in the MD direction (αTMD) and the thermal expansion coefficient in the TD direction (αTTD) are both 2 to 7 ppm/℃, |αTMD-αTTD| is less than 2 ppm/℃, the humidity expansion coefficient in the MD direction (αHMD), The humidity expansion coefficients (αHTD) in the TD direction are all 3 to 14 ppm/%RH, |αHMD-αHTD| is less than 5 ppm/%RH, the tensile modulus in the MD direction (E _MD ), and the tensile modulus in the TD direction ( E _TD ) is all 5 to 8 GPa and is provided with a coverlay film composed of a polyimide film containing 0.05% by mass or more of silica with an average particle diameter of 0.03 to 1 ㎛,
The board with the wiring has a multilayer structure in which the wiring is formed in two directions along the MD direction and the TD direction.