TWI784065B - Polyimide membrane - Google Patents

Abstract

The present invention provides a novel polyimide film that can be favorably used for metal wiring boards, multilayer substrates, and the like on which wirings are formed in different directions. In the first aspect, in the polyimide film, the coefficient of thermal expansion in the MD direction (αT _MD ) and the thermal expansion coefficient in the TD direction (αT _TD ) are set to 2 to 7 ppm/°C, and |αT _MD - αT _TD | is set below 2 ppm/°C, the humidity expansion coefficient in the MD direction (αH _MD ) and the humidity expansion coefficient in the TD direction (αH _TD ) are both set to 3-16 ppm/%RH, and |αH _MD - αH _TD | is set to 5 ppm/%RH or less. In the second aspect, in the polyimide film, both the tensile modulus of elasticity in the MD direction (E _MD ) and the tensile modulus of elasticity in the TD direction (E _TD ) are set to 5 to 9 GPa, and the |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.

Description

Polyimide membrane

The present invention relates to a polyimide film and the like.

With the light weight, miniaturization and high density of electronic products, the demand for flexible printed wiring board (FPC) is expanding. FPC has a structure in which a circuit including metal foil is formed on an insulating film. In terms of heat resistance and dimensional stability, a polyimide film has been favored for the insulating film.

With the increase in functionality and miniaturization of mobile phones, etc., high flexibility and dimensional stability are required for FPC. In order to solve these problems, various attempts have been made in the industry. As one of them, it is known that using elastic modulus is not A polyimide film up to 4 GPa is used as a base film and a cover film for a flexible printed wiring board (refer to Patent Document 1). This technology controls the rigidity value of the flexible printed wiring board with a cover layer by adjusting the elastic modulus of the polyimide film, so as to achieve good flexibility and dimensional stability. However, with the development of mobile devices in recent years, the requirements for the dimensional stability of FPC have become increasingly stringent, and the previous technologies have gradually been unable to cope.

Also, with the increase in the number of electronic parts installed, in order to install multiple electronic parts in the limited space of the printed wiring board, it is also necessary to use rigid-flex boards (rigid-flex) and other substrates suitable for three-dimensional installation Flexible printed wiring boards are multi-layered such as 3-layer boards and 4-layer boards. As the characteristics required for multi-layer flexible printed wiring boards, it can be thin and can be bent freely, and the spring back is small. The industry has made polyimide film as the core substrate and through the adhesive layer. Multi-layer flexible printed wiring boards with build-up, but due to the low dimensional stability after circuit processing, there are problems in the positional accuracy when mounting electronic components or the dimensional accuracy between layers.

On the other hand, in the installation of electronic parts, due to the thinning, high-functioning, and high-definition of electronic equipment such as LCD TVs, notebook computers, and smart phones, ICs (Integrated Circuit, integrated circuits) that drive displays Circuits) requires extremely fine and high-density wiring. In order to cope with this, the COF (Chip On Film) method of directly mounting ICs on flexible wiring boards has been developed and put into practical use.

Compared with FPC, COF requires higher dimensional accuracy. Therefore, the copper-clad laminate used for COF adopts a double layer that can cope with the miniaturization of wiring and directly forms a copper layer on the polyimide film without using an adhesive. type. In this regard, there is a method of forming a copper layer on the film by sputtering/plating, and a method of imidizing it after casting polyamide on the copper foil. The mainstream is to easily realize the thinning of the copper layer. And it is beneficial to the double-layer copper-clad laminate formed by the sputtering/plating method of fine wiring.

However, the previous polyimide films cannot be used for complex-designed flexible printed substrates that need to mount a plurality of electronic components and require dimensional accuracy in an unstable direction.

In this way, for example, it is necessary to divide the design of the flexible printed circuit board into a part where an IC for driving a display is installed, and a part where complex circuit design is required for mounting a plurality of electronic devices, thereby greatly restricting the design of electronic devices. Prior Art Documents Patent Documents

[Patent Document 1] Japanese Patent Laid-Open No. 2007-208087

[Problem to be solved by the invention]

The object of the present invention is to provide a novel polyimide film. [Technical means to solve the problem]

The inventors of the present invention have repeatedly improved the properties of the polyimide film in order to solve various problems in the above-mentioned flexible printed circuit board, and found that specific physical properties affect the dimensional stability of the film, and by setting the physical properties is a specific value, even if it is used for a substrate with wiring in different directions, or a substrate with a plurality of parts mounted, or a multilayer structure that is not limited to a specific direction, it can achieve excellent dimensional stability, etc., thereby completing the present invention. .

That is, the present invention relates to the following inventions and the like. [1] A polyimide film, the coefficient of thermal expansion in the MD direction (αT _MD ) and the thermal expansion coefficient in the TD direction (αT _TD ) are both 2-7 ppm/°C, and |αT _MD - αT _TD | is 2 ppm/°C Below ℃, the humidity expansion coefficient in MD direction (αH _MD ) and the humidity expansion coefficient in TD direction (αH _TD ) are both 3-16 ppm/%RH, and |αH _MD -αH _TD | is below 5 ppm/%RH. [2] A 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, | E _MD - E _TD | 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. [3] The polyimide film as described in [1] or [2], which is selected from substrates on which wiring in different directions is formed (at multiple locations), substrates on which multiple electronic components are mounted, and multilayered substrates. A polyimide film for at least one of the substrates of the structure. [4] The polyimide film according to any one of [1] to [3], which satisfies a ring stiffness of 75 mN/cm or less. [5] The polyimide film according to any one of [1] to [4], comprising a polyimide having an aromatic diamine component including p-phenylenediamine, and One or more acid anhydride components selected from the group consisting of pyromellitic dianhydride and 3,3'-4,4'-biphenyltetracarboxylic dianhydride are used as polymerization components. [6] The polyimide film according to any one of [1] to [5], which contains inorganic particles. [7] The polyimide film according to any one of [1] to [6], which contains the following polyimide, and contains 0.05% by mass or more of inorganic particles with an average particle diameter of 0.03 to 1 μm, the above-mentioned Polyimide is an aromatic diamine component containing more than 35 mol% p-phenylenediamine, and is selected from pyromellitic dianhydride and 3,3'-4,4'-biphenyltetracarboxylic dianhydride One or more acid anhydride components in the formed group are used as polymerization components. [8] A substrate comprising the polyimide film and the metal layer according to any one of [1] to [7]. [9] A substrate (wiring board) comprising the polyimide film according to any one of [1] to [7] and wiring (metal wiring) formed on the film. [10] The substrate according to [9], in which wiring (metal wiring) in different directions is formed (at a plurality of locations). [11] The substrate according to [10], wherein wiring is formed in at least two directions along the MD direction and the TD direction of the polyimide film. [12] The substrate according to any one of [9] to [11], wherein the thermal expansion coefficient in the transverse direction of the wiring is in the range of 2 to 8 ppm/°C. [13] A cover film comprising the polyimide film according to any one of [1] to [7]. [14] The cover film according to [13], wherein the polyimide film has a thickness of 5 to 25 μm. [15] The cover film as described in [13] or [14], which is selected from substrates on which wirings in different directions are formed (in a plurality of locations), substrates on which a plurality of electronic components are mounted, and substrates having a multilayer structure A cover film for at least one of the substrates. [16] A substrate for mounting electronic components, comprising the substrate and/or cover film according to any one of [8] to [15]. [17] The substrate as described in [16], on which a plurality of electronic components are mounted. [18] The substrate according to [17], which includes a substrate having wiring formed in at least two directions along the MD direction and the TD direction of the polyimide film, and electronic components are respectively mounted on the wiring. [19] A substrate having a multilayer structure including the substrate and/or cover film according to any one of [8] to [18]. [Effect of Invention]

In the present invention, a novel polyimide film can be obtained. In the present invention, it is possible to provide a film excellent in dimensional stability not only in one direction but in different directions (MD direction, TD direction, etc.) or all directions. Also, in the present invention, a polyimide film excellent in surface smoothness can be provided. Such a film is excellent in handleability, and can efficiently suppress the occurrence of wrinkles during winding, etc., the occurrence of poor transport when applied to a substrate, and the occurrence of scratches on the film surface. Furthermore, in the present invention, it is also possible to provide a polyimide film having not only the above-mentioned characteristics but also physical properties such as bending characteristics.

This kind of polyimide film of the present invention especially because possesses above-mentioned good dimensional stability (and then, good dimensional stability and excellent surface smoothness or excellent physical properties complement each other), so can be well used for forming different Direction (such as the width direction and length direction of the film) wiring (especially narrow-pitch wiring), or mounting multiple electronic components, or forming a substrate with a multilayer structure, etc.

[Polyimide Film] The polyimide film of the present invention satisfies specific ranges (values) in physical properties such as thermal expansion coefficient, humidity expansion coefficient, friction coefficient, tensile elastic modulus, and in-plane anisotropy index. In addition, the polyimide film of this invention should just satisfy at least any one of the physical properties of the said specific range, and these may be combined and satisfied. In a preferable aspect, these are combined and are satisfied.

In addition, the polyimide film only needs to satisfy such physical property values on at least one side (single side) of the film, and may have such physical property values on both sides (one side and the other side).

Regarding the thermal expansion coefficient of the polyimide film, the thermal expansion coefficient (αT _MD ) in the MD direction (machine conveying direction, longitudinal direction, longitudinal direction, longitudinal direction, and traveling direction) and/or the TD direction (width direction, transverse direction, and MD direction) Vertical direction) thermal expansion coefficient (αT _TD ) (especially both αT _MD and αT _TD ) can be, for example, 12 ppm/°C or less (eg, 10 ppm/°C or less), preferably 8 ppm/°C or less (eg, 2 ~7 ppm/°C), more preferably 7 ppm/°C or less (for example, 2.5 to 6.5 ppm/°C), and even more preferably 6 ppm or less (for example, 3 to 6 ppm/°C).

Also, in the polyimide film, |αT _MD -αT _TD | can be, for example, 6 ppm/°C or less (eg, 5 ppm/°C or less), preferably 4 ppm/°C or less (eg, 3.5 ppm/°C or less) , and more preferably 3 ppm/°C or less (for example, 2.5 ppm/°C or less), especially 2 ppm/°C or less, and even more preferably 1.5 ppm/°C or less.

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

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

Regarding the humidity expansion coefficient of the polyimide film, 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 ) is, for example, 20 ppm/ Below %RH (such as below 18 ppm/%RH), preferably below 16 ppm/%RH (such as 3-16 ppm/%RH), more preferably below 15 ppm/%RH (such as 4-15 ppm/% RH), it is more preferable if it is 14 ppm/%RH or less (for example, 5-14 ppm/°C).

Also, 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, and if it is 3 ppm /%RH or less (for example, 2.5 ppm/%RH or less, 2 ppm/%RH or less) is still more preferable.

By reducing the coefficient of humidity expansion, it is easy to suppress dimensional changes caused by humidity. Therefore, for example, the dimensional change of the substrate due to the humidity in the step of mounting electronic components can be reduced, and the risk of occurrence of mounting failure can be reduced. Also, by reducing |αH _MD −αH _TD |, such dimensional changes can be suppressed in a balanced manner in multiple directions. Therefore, for example, the mounting direction of electronic components is not limited to one direction, and the degree of freedom of circuit design is greatly improved.

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

The tensile modulus of elasticity in the MD direction (E _MD ) and/or the tensile modulus of elasticity in the TD direction (E _TD ) of the polyimide film (especially both E _MD and E _TD ) may be 12 GPa or less ( For example, 10 GPa or less), preferably 9 GPa or less (for example, 5-9 GPa), more preferably 8.5 GPa or less (for example, 5.5-8.5 GPa), especially 8 GPa or less (for example, 6-8 GPa). Also, the lower limit of E _MD and/or E _TD is not particularly limited, and may be 3 GPa, 4 GPa, 5 GPa, etc. from the viewpoint of transportability or the like. A film that satisfies such _EMD and/or _ETD can reduce resilience, especially the resilience of a wiring substrate, and easily relieve the stress on the connection part when electronic components are assembled into electronic equipment.

In addition, in the polyimide film, the value of |E _MD - E _TD | can be, 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), and more preferably 1.5 GPa or less. GPa or less (eg, 1.2 GPa or less), especially 1 GPa or less (eg, 0.8 GPa or less, 0.7 GPa or less, 0.6 GPa or less, 0.5 GPa or less). Such a film with a small difference between _EMD and _ETD can obtain good flexibility regardless of the bending direction, so it can reduce the space of a wiring board and the like, and can also cope with the miniaturization of electronic equipment.

Furthermore, the method for measuring the tensile elastic modulus is not particularly limited, for example, it can be measured under the condition 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 (eg, 18 or less), preferably 15 or less (eg, 14 or less), more preferably 13 or less, and more preferably 12 or less, It is still more preferable if it is 10 or less (for example, 9 or less). A film having such an in-plane anisotropy index tends to reduce warpage, especially warpage of metal laminated substrates and the like. Therefore, it is easy to produce a wiring board with good yield.

In addition, the measuring method of an in-plane anisotropy index is not specifically limited, For example, it can measure by the method described below.

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

A film that satisfies such a coefficient of friction is excellent in handleability, and can efficiently suppress occurrence of wrinkles when winding up into a roll, etc., and occurrence of poor transport or damage when forming a metal layer.

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

The ring stiffness of the polyimide film is, for example, 150 mN/cm or less (for example, 100 mN/cm or less), preferably 75 mN/cm or less, more preferably 60 mN/cm or less, and if it is 50 mN/cm or less then And then even better.

The polyimide film with such ring rigidity can reduce the resilience, especially the resilience of the wiring board, etc., and it is easy to reduce the stress on the connection part when the electronic parts are assembled into the electronic machine.

In addition, the measuring method of ring stiffness is not specifically limited, For example, it can measure by the method described below.

The polyimide film may contain inorganic particles (or fillers). The inorganic particles are not particularly limited, and examples include: oxides (such as titanium oxide, silicon dioxide, etc.), inorganic acid salts [such as carbonates (such as calcium carbonate), phosphates (such as calcium phosphate, calcium hydrogen phosphate) Wait].

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

The content of the inorganic particles is not particularly limited as long as the effects of the present invention are not impaired. For example, it may be 0.05% by mass or more, preferably 0.1 to 1.5% by mass, and more preferably 0.2 to 1.0% by mass relative to the polyimide film. .

The thickness of the polyimide film is not particularly limited, and can be appropriately selected according to applications and the like. The thickness of the polyimide film can be, for example, 1-200 μm (such as 2-150 μm), preferably 3-100 μm (such as 4-90 μm), and more preferably 5-80 μm (such as 6-60 μm). μm), or 7-50 μm, 10-40 μm, etc.

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

Polyimide films can have relatively large dimensions. The length of this polyimide film can be more than 1 m (for example, more than 5 m), more than 10 m (for example, more than 20 m), preferably more than 30 m (for example, more than 40 m), and more preferably 50 m More than (for example, 100 m or more), 200 m or more, 300 m or more, 500 m or more, 1000 m or more, 2000 m or more, 3000 m or more, 5000 m or more, etc.

Furthermore, the upper limit of the length of the polyimide film is not particularly limited, for example, it may be 30000 m, 20000 m, 10000 m or the like.

The width of the polyimide film is not particularly limited. For example, it can be more than 30 mm (for example, more than 45 mm), preferably more than 150 mm (for example, more than 155 mm), and more preferably more than 200 mm (for example, more than 250 mm). ), it can also be more than 500 mm, more than 1000 mm, more than 1500 mm, etc.

Furthermore, the upper limit of the width of the polyimide film is not particularly limited, for example, it may be 10000 mm, 8000 mm, 5000 mm, 4000 mm, 3000 mm, 2000 mm, 1500 mm and the like.

The polyimide film may be rolled up, that is, in the form of a roll (roll).

(Manufacturing method of polyimide and polyimide film) Polyimide film (or polyimide or polyamic acid constituting polyimide film) is usually made of aromatic diamine component and acid anhydride Component (tetracarboxylic acid component) as a polymerization component. In addition, as long as the polymerization component has an aromatic diamine component and an acid anhydride component as a main component, it may contain other polymerization components. There are no particular limitations on the production of the polyimide film. First, a polyamic acid solution is obtained by polymerizing the aromatic diamine component and the acid anhydride component in an organic solvent.

Particularly preferably, the polyimide film of the present invention may contain p-phenylenediamine as an aromatic diamine component. By using the aromatic diamine component containing p-phenylenediamine in this way, it becomes easy and efficient to obtain the polyimide film which has the above-mentioned characteristics and physical properties. The aromatic diamine component may also contain things other than p-phenylenediamine. Specific examples of the aforementioned aromatic diamine components other than p-phenylenediamine include m-phenylenediamine, benzidine, p-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4 '-Diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylene, 3,3'-dimethyl-4,4'-diamino Diphenylmethane, 1,5-diaminonaphthalene, 3,3'-dimethoxybenzidine, 1,4-bis(3-methyl-5-aminophenyl)benzene and their amides Formative derivatives. These may be used individually by 1 type, and may mix and use 2 or more types. The aromatic diamine component is preferably a combination of p-phenylenediamine, 4,4'-diaminodiphenyl ether and/or 3,4'-diaminodiphenyl ether. Among them, adjusting the amount of diamine components of p-phenylenediamine and 3,4'-diaminodiphenyl ether, which have the effect of improving the tensile elastic modulus of the film, adjusts the tensile strength of the polyimide film obtained. The lower limit of the modulus of elongation (for example, 5 GPa or more) is preferable since the transferability will also be good.

Specific examples of the above-mentioned acid anhydride components include pyromellitic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3',3,4'-biphenyltetracarboxylic acid, 3, 3',4,4'-benzophenone tetracarboxylic acid, 2,3,6,7-naphthalene tetracarboxylic acid, 2,2-bis(3,4-dicarboxyphenyl)ether, pyridine-2, Aromatic tetracarboxylic anhydride components such as 3,5,6-tetracarboxylic acid and their amide-forming derivatives, preferably pyromellitic dianhydride, 3,3',4,4'-biphenyltetra Carboxylic dianhydride. These may be used individually by 1 type, and may mix and use 2 or more types.

Among them, as a particularly preferable combination of the aromatic diamine component and the acid anhydride component, there are selected from the group consisting of p-phenylenediamine, 4,4'-diaminodiphenyl ether and 3,4'-diaminodiphenyl ether. One or more aromatic diamine components in the group and one or more kinds selected from the group consisting of pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride A combination of anhydride components.

Regarding the blending ratio of p-phenylenediamine in the above-mentioned aromatic diamine component, in terms of obtaining the thermal expansion coefficient in the above-mentioned range, imparting appropriate strength to the film, and preventing poor migration, etc. , can be selected in the range of more than 15 mol% (for example, more than 18 mol%), usually more than 20 mol% (for example, more than 25 mol%), preferably more than 30 mol% (for example, 31 mol%) % or more), preferably more than 33 mol%, more preferably more than 35 mol%. The compounding ratio (molar ratio) of the above-mentioned acid anhydride components is not particularly limited as long as the effect of the present invention is not impaired. For example, when 3,3',4,4'-biphenyltetracarboxylic dianhydride is included, Relative to the total amount of anhydride components, the content of 3,3',4,4'-biphenyltetracarboxylic dianhydride is preferably at least 15 mol%, more preferably at least 20 mol%, even more preferably 25 mol% More than mol% (for example, more than 25 mol%, more than 26 mol%, more than 27 mol%, etc.). By using such polyamic acid containing aromatic diamine components and acid anhydride components as the raw material (precursor) of the polyimide film, it is easy to make the thermal expansion coefficient of the polyimide film equal to the MD direction and TD direction of the film Both are adjusted to the above-mentioned range, so it is preferable.

In addition, in the present invention, specific examples of the organic solvent used to form the polyamic acid solution include, for example, dimethyl sulfide, diethyl sulfide, and other sulfide-based solvents, N,N-dimethyl N, N-dimethylacetamide, N, N-diethylacetamide and other formamide solvents, Pyrrolidone-based solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone, phenol, o/m/p-cresol, xylenol, halogenated phenol, catechol, etc. Phenolic solvents, or aprotic polar solvents such as hexamethylphosphamide and γ-butyrolactone, which are preferably used alone or as a mixture of two or more, and xylene, toluene, etc. can also be used Aromatic hydrocarbons.

The polymerization method can be carried out by any known method, such as the following method: (1) Add the entire amount of aromatic diamine components to the solvent first, and then add the aromatic diamine components in an equivalent amount to the total amount of the aromatic diamine components (e.g. Mole) way to add acid anhydride components, polymerization. (2) The entire amount of the acid anhydride component is added to the solvent, and then the aromatic diamine component is added so as to be equivalent to the acid anhydride component, and polymerized. (3) After adding an aromatic diamine component (a1) to the solvent, mix and react an acid anhydride component (b1) at a ratio of 95 to 105 mol% relative to the reaction component for the required time, then add another aromatic diamine component (a1) The aromatic diamine component (a2), and then another acid anhydride component (b2) is added so that the whole aromatic diamine component and the whole acid anhydride component become substantially equivalent, and it superposes|polymerizes. (4) After adding one acid anhydride component (b1) to the solvent, mix one aromatic diamine component (a1) at a ratio of 95 to 105 mol% relative to the reaction components and react for the required time, then add another acid anhydride Component (b2) and another aromatic diamine component (a2) are added so that all the aromatic diamine components and all the acid anhydride components may become substantially equivalent, and it superposes|polymerizes. (5) Make an aromatic diamine component and an acid anhydride component react in a solvent in an excess of one of them to prepare a polyamic acid solution (A), and make another aromatic diamine component and an acid anhydride component use a certain one The excess is reacted in another solvent to prepare polyamic acid solution (B). The respective polyamic acid solutions (A) and (B) thus obtained are mixed to complete the polymerization. At this time, when the aromatic diamine component is excessive when preparing the polyamic acid solution (A), the acid anhydride component is set to be excessive in the polyamic acid solution (B), and the polyamic acid solution ( When the acid anhydride component in A) is excessive, make the aromatic diamine component excessive in the polyamic acid solution (B), mix the polyamic acid solution (A) and (B), and react All the aromatic diamine components and all the acid anhydride components used were adjusted so that it might become substantially equivalent. In addition, the polymerization method is not limited to these, and other well-known methods can also be used.

The polyamic acid solution thus obtained generally contains 5 to 40% by weight of solid content, preferably 10 to 30% by weight of solid content. In addition, the viscosity measured by a Brookfield viscometer is usually 10 to 2000 Pa·s, preferably 100 to 1000 Pa·s in order to ensure stable liquid delivery. Also, polyamic acid in an organic solvent solution can be partially imidized.

Next, a method for producing the polyimide film will be described. As a method for manufacturing a polyimide film, the following methods can be enumerated: polyamic acid (polyamic acid) solution is cast into a film shape, and a polyimide film is obtained by thermal decyclization and desolventization; A cyclization catalyst and a dehydrating agent are mixed in an amine acid solution, and chemically decyclized to form a gel film, which is heated to remove the solvent, thereby obtaining a polyimide film. The latter is preferable since the thermal expansion coefficient or the humidity expansion coefficient of the obtained polyimide film can be suppressed low.

In the method of chemical decyclization, the above-mentioned polyamic acid solution is first prepared. Furthermore, in the present invention, the polyamic acid solution may generally contain the above-mentioned inorganic particles.

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

The polyamic acid solution may contain a cyclization catalyst (imidization catalyst), a dehydrating agent, a gelling retarder, and the like.

As the cyclization catalyst, amines such as aliphatic tertiary amines (trimethylamine, triethylenediamine, etc.), aromatic tertiary amines (dimethylaniline, etc.), heterocyclic tertiary amines (such as isoquinoline, pyridine, β-picoline, etc.), etc. These may be used individually by 1 type, and may mix and use 2 or more types.

Examples of the dehydrating agent include acid anhydrides such as aliphatic carboxylic anhydrides (eg, acetic anhydride, propionic anhydride, butyric anhydride, etc.), aromatic carboxylic anhydrides (eg, benzoic anhydride, etc.), and the like. These may be used individually by 1 type, and may mix and use 2 or more types. The gelling retardant is not particularly limited, and acetylacetone or the like can be used.

As a method for producing a polyimide film from a polyamic acid solution, the following method can be cited: casting a polyamic acid solution (especially a polyamic acid solution containing a cyclization catalyst and a dehydrating agent) on a support It is formed into a film, and a part of the imidization is carried out on the support to form a self-supporting gel film, which is peeled off from the support, heat-dried/imidized, and then heat-treated.

Examples of the above-mentioned so-called support include a metal drum or an endless belt, and there are no particular limitations as long as the material is uniform.

The above-mentioned gel film is usually heated to 20-200°C, preferably 40-150°C by heating from the support and/or heat from a heat source such as a hot air or an electric heater, so that the free organic solvent Wait for the volatile components to dry, thereby becoming self-supporting and peeling off from the support.

The above-mentioned gel film peeled off from the support can be stretched. As the stretching process, the apparatus and method are not limited as long as stretching in the conveyance direction (MD) and stretching in the width direction (TD) can be combined at a specific magnification. Regarding the stretching ratio used to make the film having the effect of the present invention, usually at a temperature above 200° C., for example, the stretching ratio (MDX) in the MD direction is usually 1.05 to 1.9 times, preferably 1.1 to 1.6 times, and then Preferably it is 1.1 to 1.3 times. The elongation ratio (TDX) of TD is usually 1.05 to 1.3 times the elongation 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 250-500° C. for 15 seconds to 30 minutes by hot air and/or an electric heater.

Regarding the thickness of the film, it is preferable to adjust the solid content concentration, viscosity, and flow on the support so that it becomes a specific thickness (for example, 7 to 75 μm, preferably 10 to 50 μm, and more preferably 10 to 40 μm). Extend the amount of polymer.

It is preferable to further anneal the polyimide film thus obtained. Thereby, thermal relaxation of the film can be induced and the heat shrinkage rate can be suppressed to be small. The temperature of the annealing treatment is not particularly limited, but is preferably 200°C to 500°C, more preferably 200°C to 370°C, and particularly preferably 210°C to 350°C. The heat shrinkage rate at 200° C. can be suppressed within the above-mentioned range by the thermal relaxation caused by the annealing treatment, so that the dimensional accuracy becomes higher, which is preferable.

Also, in order to make the obtained polyimide film have adhesiveness, electrical treatment such as corona treatment or plasma treatment, or physical treatment such as sandblasting can be carried out on the surface of the film. Such physical treatment can be based on conventional method. The pressure of the atmosphere in the case of plasma treatment is not particularly limited, usually in the range of 13.3 to 1330 kPa, preferably in the range of 13.3 to 133 kPa (100 to 1000 Torr), more preferably in the range of 80.0 to 120 kPa (600 Torr) ~900 Torr).

The atmosphere for plasma treatment contains at least 20 mole % of inert gas, preferably more than 50 mole % of inert gas, more preferably more than 80 mole %, most preferably more than 90 mole %. The above-mentioned inert gases include 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 (tetrafluoromethane), trichlorofluoroethane, trifluoromethane, etc. may be mixed with the inert gas. As the combination of the preferred mixed gas that can be used as the atmosphere of plasma treatment of the present invention, can enumerate: argon/oxygen, argon/ammonia, argon/helium/oxygen, argon/carbon dioxide, argon/ Nitrogen/Carbon Dioxide, Argon/Helium/Nitrogen, Argon/Helium/Nitrogen/Carbon Dioxide, Argon/Helium, Helium/Air, Argon/Helium/Monosilane, Argon/Helium/Disilane Wait.

There is no particular limitation on the treatment power density when performing plasma treatment, but it is preferably at least 200 W·min/m ² , more preferably at least 500 W·min/m ² , most preferably at least 1000 W·min/m ² . The plasma irradiation time for plasma treatment is preferably 1 second to 10 minutes. By setting the plasma irradiation time within this range, the effect of the plasma treatment can be fully exerted without accompanying deterioration of the film. The gas type, gas pressure, and processing density of plasma treatment are not limited to the above conditions, and may be performed in the atmosphere.

Furthermore, the polyimide film of the present invention has specific characteristics and physical properties as described above, and such aspects can be adjusted by appropriately selecting the above-mentioned conditions and the like.

For example, the coefficient of friction can be optimized to a specific range by adjusting the content of inorganic particles (or fillers) and changing the surface roughness of the polyimide film. For example, it can be achieved easily and efficiently by employing a method of adding 0.3 to 1.0% by mass of inorganic particles having an average particle diameter of 0.05 to 0.5 μm to a polyimide film.

Regarding tensile elastic modulus, coefficient of thermal expansion, coefficient of humidity expansion, and anisotropy index, for example, in the polymerization step of polyamic acid, p-phenylenediamine and 3,3',4,4'-biphenyl The content of the tetracarboxylic dianhydride is adjusted to a specific range, and further, in the film forming step, the stretch ratios of MD and TD are adjusted to a specific range, and can be set as the range of the present invention. For example, the blending ratio of p-phenylenediamine in the aromatic diamine component is 30 mol% or more relative to the total amount of the aromatic diamine component, and the ratio of 3,3',4,4'-biphenyltetracarboxylic dianhydride The content is more than 20 mol% relative to the total amount of anhydride components, and the elongation ratio in the MD direction is 1.05 to 1.9 times at a temperature above 200°C, and the elongation ratio in the TD direction is 1.10 to 1.20 times the MD ratio.

Regarding ring stiffness, for example, the content of p-phenylenediamine and 3,3',4,4'-biphenyltetracarboxylic dianhydride in the polyamic acid polymerization step, and MD and TD in the film forming step When the elongation ratio is in the above range, it can be adjusted to a specific range by making the polyimide film a specific thickness (for example, 60 μm or less).

The polyimide film thus obtained has the properties described above. Therefore, it has excellent dimensional stability, surface smoothness, bending characteristics, etc., and is suitable for various purposes as follows, especially suitable for forming: substrates with wiring (patterns) in different directions, substrates with multiple electronic components mounted Substrates, substrates with multilayer structures, etc.

[Metal Laminate, Metal Wiring Board] The polyimide film of the present invention can be favorably used for laminating with a metal layer (metal foil) to form a substrate [metal laminate (metal laminate, metal laminate substrate)]. The polyimide film of the present invention is particularly suitable as a film for circuit boards, especially for flexible printed circuit boards (FPC), and the like.

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

The type of metal constituting the metal layer (metal foil) is not particularly limited, for example, copper (copper element, copper alloy, etc.), stainless steel and its alloys, nickel (nickel element, nickel alloy, etc.), aluminum (aluminum element, Aluminum alloy, etc.) etc.

The metal is preferably copper. A metal laminated substrate is obtained by laminating such a metal layer and a polyimide film. In addition, it can also be used for the metal surface formed with a rust-proof layer or a heat-resistant layer (such as chrome plating, zinc plating, etc.), silane coupling agent, and the like. Preferably copper and/or copper containing at least one of nickel, zinc, iron, chromium, cobalt, molybdenum, tungsten, vanadium, beryllium, titanium, tin, manganese, aluminum, phosphorus, silicon, etc. and copper Alloys, which are well used in circuit processing. Copper formed by rolling or electrolytic plating is mentioned as a particularly preferable metal layer.

In addition, the metal layer only needs to be formed on at least one side of the polyimide film, and may be formed on both sides of the polyimide film.

In metal laminate substrates, the thickness of the metal layer is not particularly limited, and may be, for example, about 1 to 150 μm (for example, 1.5 to 100 μm, 2 to 80 μm, 3 to 50 μm, etc.), or about 2 to 12 μm.

As long as the metal-laminated substrate has a polyimide film and a metal layer, the lamination form is not particularly limited. According to the purpose of the polyimide film, for example, the polyimide film and the metal layer can be directly laminated, or through The polyimide film and the metal foil are laminated (laminated) next to the layer (adhesive layer).

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

The manufacturing method of such a metal laminated board is not specifically limited, According to the form etc. of a metal laminated board, it can manufacture according to the conventionally well-known manufacturing method. Generally, the method is as follows: For example, a metal layer mainly composed of nickel and chromium is formed on one or both sides of the polyimide film by sputtering, and a layer mainly composed of copper is deposited on the metal layer by electrolytic plating. . A representative metal laminate substrate (copper-clad laminate, copper-clad laminate) of the present invention is, for example, provided with a nickel-chromium alloy layer on both sides of a polyimide film, on which a specific thickness (such as a thickness 2~12 μm) of copper.

In the metal build-up 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) including the above-mentioned polyimide film and wiring (metal wiring) formed on the film. Such metal wiring substrates are generally flexible printed substrates.

Furthermore, wiring (wiring circuit, metal wiring) may be formed on at least one side of the polyimide film, and 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) can be formed in one location or in multiple locations, and when formed in a plurality of locations, wiring can be formed in the same direction or in different directions.

In the present invention, in particular, wiring can be formed in different directions (different directions at a plurality of locations). The mode of forming in different directions is not particularly limited. For example, wiring may be formed in at least two directions along the MD direction and the TD direction of the polyimide film. That is, wiring along the MD direction of the polyimide film can be formed at least on the polyimide film (taking the wiring transverse direction as the wiring in the TD direction) and wiring along the TD direction of the polyimide film (taking the wiring transverse direction as the wiring in the TD direction) The disconnecting direction is regarded as the wiring in the MD direction).

In addition, the size (pitch) of wiring is not specifically limited, Even if it is a narrow pitch, it can form efficiently. Regarding the size of such wiring, for example, the line width can be about 30 μm or less (for example, 20 μm or less, 15 μm or less, 10 μm or less), and the line (line spacing) can be 40 μm or less (for example, 20 μm or less, 15 μm less than 10 μm) or so.

In metal wiring boards (polyimide films that make up metal wiring boards), the thermal expansion coefficient in the cross-sectional direction of the wiring mostly reflects the thermal expansion coefficient of the polyimide film and is relatively small, for example, it can be below 12 ppm/°C (for example 10 ppm/°C or less), preferably 8 ppm/°C or less (for example, 2-8 ppm/°C), more preferably 7 ppm/°C or less (for example, 3-7 ppm/°C), if it is 6 ppm or less ( For example, 3 to 6 ppm/°C) is even more preferable.

Furthermore, when wiring is formed in a plurality of places or in different directions, it is preferable that all of them satisfy the above-mentioned coefficient of thermal expansion. For example, when the wiring is formed along the MD direction and the TD direction, it is preferable that the thermal expansion coefficients of the wiring transverse directions (that is, the TD direction and the MD direction) all satisfy the above-mentioned thermal expansion coefficients.

Also, when wiring is formed in a plurality of locations or in different directions, it is preferable that the coefficient of thermal expansion is small in all the locations or in the transverse direction of the wiring, so that the difference is small. For example, when the wiring is formed along the MD direction and the TD direction (that is, when the wiring transverse direction is set to the TD direction and the MD direction), the metal wiring board (polyimide film constituting the metal wiring board) | αT _MD －αT _TD ｜Most will reflect the above-mentioned value in the polyimide film and be smaller, such as 7 ppm/°C or less (eg, 6 ppm/°C or less), preferably 5 ppm/°C or less (eg, 4.5 ppm /°C or less), more preferably 4 ppm/°C or less (for example, 3.5 ppm/°C or less), especially 3 ppm/°C or less, if it is 2.5 ppm/°C or less, 2 ppm/°C or less, 1.5 ppm/°C or less The following are even better. In addition, the value of |αT _MD - αT _TD | may be a value (or an average value thereof) in each wiring, and may be calculated using αT _MD and αT _TD in different wirings. For example, when forming the wiring A with the MD direction as the wiring transverse direction and the wiring B with the TD direction as the wiring transverse direction, you can use |αT _MD - αT _TD | in the wiring A or |αT in the wiring B _MD - αT _TD | (or their average value) can also be obtained from the values of αT _MD in wiring A (in the transverse direction) and αT _TD in wiring B (in the transverse direction) as the above value | αT _MD - αT _TD |.

By reducing the coefficient of thermal expansion, it is easy to suppress dimensional change (expansion) due to heat. Therefore, it is possible to suppress the expansion of the substrate at the processing temperature when mounting electronic components, for example, and reduce the risk of defective mounting. Furthermore, by reducing |αT _MD −αT _TD |, it is possible to suppress such a dimensional change or expansion in multiple directions. Therefore, for example, the mounting direction of electronic components is not limited to one direction, and the degree of freedom of circuit design is greatly improved.

The method of manufacturing the metal wiring board (flexible printed circuit board) is not particularly limited, and known methods can be used, especially semi-additive or subtractive methods.

In a more specific aspect, it can be manufactured by the following method (semi-additive method): use photolithography to pattern a copper-clad laminate (such as a copper-clad laminate with a copper thickness of about 1-3 μm) Wiring (wiring circuit), after peeling off the resist layer of the part where the wiring is to be formed, the wiring is formed on the exposed thin copper layer by electrolytic copper plating (such as wiring with a copper thickness of 7-10 μm), and then removed Resist layer, thin copper layer, base metal layer; or can be manufactured by the following method (subtractive method): using photolithography on copper-clad laminates (such as copper-clad laminates with a copper thickness of 7-10 μm) The wiring circuit is patterned on the top, and the copper layer and the base metal layer in the parts where no wiring is formed are removed by etching, and the resist layer is peeled off.

If necessary, 0.1 to 0.5 μm of tin or gold can be formed on wiring (copper wiring, etc.) by electroless plating.

Moreover, in order to protect a circuit, a solder resist may be laminated|stacked on the necessary part, and a cover film may be laminated|stacked. Alternatively, a solder resist and a cover film can be combined to separately protect necessary parts.

[Cover Film] The polyimide film of the present invention can also constitute a cover film. Therefore, the present invention also includes a cover film comprising the above-mentioned polyimide film.

In particular, such a cover film can be selected from substrates on which wirings in different directions are formed (the above-mentioned metal wiring substrates, metal wiring substrates in which the polyimide film in the above-mentioned metal wiring substrates is not the above-mentioned polyimide film, etc.), A cover film for at least one of substrates with multiple parts (mounting substrates described below, etc.) and substrates with a multilayer structure (substrates described below, etc.).

The cover film covers wiring or parts (electronic parts), therefore, the dimensional stability of the cover film also affects the formed wiring or mounted parts. Therefore, it is important to make the cover film exhibit excellent dimensional stability and the like.

The cover 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 cover film (or the polyimide film constituting the cover film) is not particularly limited, and may be, for example, 1-100 μm, preferably 3-50 μm, and more preferably about 5-25 μm. In addition, in the cover film, the thickness of the adhesive layer is not particularly limited, for example, it can be 1-300 μm (for example, 2-200 μm), preferably 3-150 μm (for example, 5-100 μm), and it can also be 1-300 μm. 80 μm (for example, 3-60 μm, preferably 5-50 μm, more preferably 10-30 μm).

In addition, a cover film is used for covering the metal layer (wiring of a metal wiring board) of a metal wiring board, for example. Such a metal wiring board (metal wiring board) includes a base film (base film) and a metal layer (wiring). The base film may be the above-mentioned polyimide film or a polyimide film other than the above-mentioned polyimide film. In particular, both the cover film and the base film may be the above-mentioned polyimide film. By combining the above-mentioned polyimide film on both the cover film and the base film of the metal wiring board in this way, excellent dimensional stability and the like can be efficiently exhibited.

[Mounting board] The present invention also includes a mounting board (electronic component mounting board) including the above-mentioned metal wiring board (metal wiring board) and/or the above-mentioned cover film. Such a mounting substrate may be, for example, a chip-on-film (COF) substrate.

In such a mounting substrate, the mounting component (electronic component) may be one, or plural, especially plural. In the present invention, even when a plurality of components are mounted, excellent dimensional stability and the like can be efficiently exhibited. Therefore, high-precision mounting can be realized even with a plurality of parts.

In a representative aspect, components can be mounted on wiring of a substrate on which wiring is formed in different directions. In a more specific mounting substrate, there is provided a substrate (metal wiring substrate) on which wiring (metal wiring) is formed in at least two directions along the MD direction and the TD direction of the polyimide film, and can be separately mounted on the wiring. electronic parts.

In addition, as a component (electronic component), it can be selected according to a use, and it is not specifically limited, For example, an IC chip, a capacitor, a transistor, a memory, an inductor, etc. are mentioned. These components may be used alone or in combination of two or more.

[Substrate having a multilayer structure] The polyimide film of the present invention is also suitably used as a film constituting a substrate having a multilayer structure.

Typically, such a substrate having a multilayer structure may be a substrate having a multilayer structure including at least the above-mentioned metal wiring board and/or the above-mentioned cover film. According to such a substrate having a multilayer structure, excellent dimensional stability and the like can be exhibited despite having a multilayer structure, and a high-precision multilayer structure substrate can be formed. Especially in multi-layer structure substrates, interlayer connections must be made. According to the polyimide film of the present invention, interlayer connections can be realized by using guide holes with high positional accuracy.

For example, a substrate with a multilayer structure (such as a multilayer flexible printed circuit board) usually includes a multi-layer metal wiring substrate laminated and a cover film covering the outermost metal wiring substrate (or wiring of the metal wiring substrate). At least one of the wiring board (base film) and/or the cover film may be the aforementioned polyimide film.

In the substrate having a multilayer structure, it is preferable that all of the base film and cover film constituting the metal wiring substrate (or the polyimide film constituting the entirety of the substrate having a multilayer structure) be the polyimide film described above.

As long as the effects of the present invention are exhibited, the present invention includes various combinations of the above-mentioned constitutions within the technical scope of the present invention. [Example]

Next, the present invention will be described concretely by giving examples, but the present invention is not limited by these examples.

Furthermore, in the examples, PPD represents p-phenylenediamine, 4,4'-ODA represents 4,4'-diaminodiphenyl ether, PMDA represents pyromellitic dianhydride, BPDA represents 3,3', 4,4'-biphenyltetracarboxylic dianhydride, DMAc means N,N-dimethylacetamide.

[Examples 1-3] (Preparation of polyimide film) PPD (molecular weight 108.14), 4,4'-ODA (molecular weight 200.24), BPDA (molecular weight 294.22), PMDA (molecular weight 218.12), made into a 20% by weight solution in DMAc, and polymerized to obtain a polyamic acid solution of 3500 poise. A DMAc slurry of silicon dioxide with an average particle diameter of 0.3 μm was added thereto at 0.3% by weight relative to the weight of the resin, and stirred sufficiently to disperse it. In this solution, acetic anhydride (molecular weight: 102.09) and (beta)-picoline were mixed and stirred at the ratio of 17 weight%. The obtained mixture was flow-cast from a T-shaped slit die to a rotating stainless steel drum at 75°C, and peeled off to obtain a self-supporting gel with a residual volatile content of 55% by weight and a thickness of about 0.05 mm. film. After stretching the gel film 1.25 times in the direction of conveyance at 65°C, heat treatment at 250°C for 50 seconds and 400°C for 75 seconds in a heating furnace while stretching 1.45 times in a direction perpendicular to the direction of conveyance . By adjusting the transport speed, polyimide films with a thickness of 13 μm, 25 μm, and 35 μm were obtained.

[Example 4] A polyimide film having a thickness of 50 μm was obtained by the same procedure as in Examples 1 to 3 except that a DMAc slurry of silica having an average particle diameter of 0.1 μm was used.

[Examples 5 and 6] PPD, 4,4'-ODA, BPDA, and PMDA were set to a molar ratio of 20/80/35/65, and silica with an average particle size of 0.1 μm was used. In addition, Polyimide films with a thickness of 13 μm and 25 μm were obtained by the same procedure as in Examples 1-3.

[Comparative Example 1] Set PPD, 4,4'-ODA, BPDA, and PMDA to a molar ratio of 35/65/30/70, without adding particles, extend 1.20 times along the conveying direction, and extend along the direction perpendicular to the conveying direction Except that the direction was stretched 1.45 times, a polyimide film having a thickness of 25 μm was obtained by the same procedure as in Examples 1 to 3.

[Comparative Example 2] Set PPD, 4,4'-ODA, BPDA, and PMDA to a molar ratio of 30/70/25/75, extend 1.15 times along the conveying direction, and extend 1.40 times along the direction perpendicular to the conveying direction , except that, a polyimide film having a thickness of 38 μm was obtained by the same procedure as in Examples 1 to 3.

These films were evaluated for the following characteristics, and the results are shown in Table 1. Unless otherwise specified, each evaluation was carried out in an environment of 25° C. and 60% RH.

(1) Tensile modulus of elasticity was measured using RTM-250 (manufactured by A & D) under the condition of tensile speed: 100 mm/min.

(2) Coefficient of thermal expansion (CTE) Using TMA-60 (manufactured by Shimadzu Corporation), it was measured under the conditions of a measurement temperature range: 50°C to 200°C, and a temperature increase rate: 10°C/min.

(3) Humidity expansion coefficient (CHE) Using TM-9400 (manufactured by ULVAC Riko), it was measured at a temperature of 25° C. and a measurement humidity range of 25 to 70% RH.

(4) Coefficient of friction Overlap the support surface and the non-support surface of the sample and fix them on a sliding tester (manufactured by Techno Needs Co., Ltd.), and measure the coefficient of static friction and coefficient of dynamic friction at a speed of 120 mm/min under a load of 200 g.

(5) Anisotropy index (MT ratio) Using SST-2500 (Sonic Sheet Tester manufactured by Nomura Corporation), measure the ultrasonic pulse propagation speed V _MD and V _TD in the MD direction and TD direction, and calculate the value defined by the following formula 1 Anisotropy index (MT ratio). (Formula 1): MT ratio = |(V _MD ² -V _TD ² )/((V _MD ² +V _TD ² )/2)×100|

(6) Ring stiffness Using a ring stiffness tester DA (manufactured by Toyo Seiki Seisakusho), it was measured under the conditions of a sample width of 20 mm, a ring length of 50 mm, and a compression distance of 20 mm.

[Table 1]

According to the results in the above table, it can be seen that the polyimide film of the embodiment is in a specific range in terms of specific physical properties. Therefore, it can be confirmed that the polyimide film is excellent in surface smoothness (and thus handleability), and excellent in dimensional stability in both MD and TD directions (and also excellent in dimensional stability regardless of the direction of the film). .

(Manufacturing of copper-clad laminates) 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. nm), a copper layer with a thickness of 8 μm was formed by electrolytic plating using a copper sulfate plating solution.

The following items were evaluated for the obtained copper-clad laminates. The results are shown in Table 2. Furthermore, in Table 2, "Example 1" in the item "polyimide film" means "the polyimide film obtained in Example 1" (others are also the same).

(7) Warpage Cut the copper-clad laminate into a size of 70 mm x 70 mm, fix the end 5 mm, and measure the sag with a JIS class 1 curved ruler.

[Table 2]

From the results in Table 2 above, it can be seen that the warpage of the copper-clad laminate can be suppressed relatively small by the films obtained in Examples.

(Fabrication of flexible printed circuit boards for evaluation) According to the conventional method, a negative resist with a film thickness of 5 μm was prepared on the copper layer of the copper-clad laminate obtained above using a liquid resist, and the copper was removed by etching layer and NiCr layer, the resist is stripped. Then, immerse in an electroless tin plating solution (TINPOSIT LT-34 manufactured by Shipley Far East) at 70°C for 5 minutes to form a coating film with a thickness of 0.5 μm, as shown in Figure 1. A flexible printed circuit board for evaluation with two electronic component connection parts (wiring) 2 on the amine film) 1 with the MD direction and the TD direction as the wiring transverse direction and a pitch of 30 μm (15 μm in line width and 15 μm in between lines) . The following items were evaluated about the obtained flexible printed circuit board, and the result is shown in Table 3.

(8) Coefficient of thermal expansion (CTE) Using TMA-60 (manufactured by Shimadzu Corporation), it was measured under the conditions of a measurement temperature range: 50° C. to 200° C., and a temperature increase rate: 10° C./min. Furthermore, regarding the thermal expansion coefficient, the thermal expansion coefficient in the MD direction (αT MD ) was measured for the MD direction as the distance between the wiring transverse directions, and the thermal expansion coefficient in the TD direction (αT _MD ) was measured for the TD direction as the distance in the wiring transverse direction. _TD ), using these coefficients of thermal expansion to calculate the absolute value of the difference in coefficient of thermal expansion (|αT _MD −αT _TD |, in the table, |MD−TD|).

(9) Dimensional stability Place semiconductor chips (ICs) for evaluation on the two electronic component connection parts of the flexible printed circuit board for evaluation obtained above, and use a flip-chip bonding machine at a stage temperature of 150°C and a tool temperature Press bonding at 360° C. for 1 second to obtain a substrate mounted with a semiconductor chip 3 as shown in FIG. 2 . Afterwards, measure the external dimension (L4) of the wiring part of the mounting part, and calculate the elongation rate based on the following formula from the measured value (L3) before crimping, and calculate the standard deviation of 30 samples to evaluate the dimensional stability. Elongation (%)={(L4－L3)/L3}×100

[table 3]

According to the results in Table 3 above, it can be seen that in the examples, the CTE values of the polyimide films obtained in Examples 1 to 4 can be efficiently reflected, higher dimensional stability can be achieved, and dimensional stability can be reduced. gender differences.

(Preparation of cover film for evaluation) A preparation containing 70 parts by weight of polyamide imide resin (manufactured by Toyobo, VYLOMAX HR16-NN) and 50 parts by weight of liquid epoxy resin (manufactured by Mitsubishi Chemical, jER828, epoxy equivalent 190) , Solid epoxy resin (manufactured by Mitsubishi Chemical, jER1001, epoxy equivalent 480) 50 parts by weight, alumina (manufactured by Sumitomo Chemical, AA04, average particle diameter 0.4 μm) 60 parts by weight, hardener (4,4'-diamine 8 parts by weight of base diphenyl (diphenylsulfone), and use N-methyl-2-pyrrolidone as the resin composition A of 40% by mass of the solid content of the solvent. Use a bar coater to coat the resin composition on the polyimide film 1 shown in Table 4, and dry it at 150°C for 30 minutes to prepare a B-stage adhesive 4 with a thickness of 15 μm after drying. A polyimide film was used as a cover film (Figure 3).

(Fabrication of Multilayer Flexible Printed Boards for Evaluation) On the support surface of the polyimide film 1 shown in Table 4, a nickel-chromium layer (Ni:Cr=95:5, thickness 10 nm) was formed by sputtering and After the copper layer (thickness 100 nm), a nickel-chromium layer and a copper layer 2' were also formed on the non-support surface in the same manner. Next, a copper layer 2' having a thickness of 8 μm was formed on both sides by electrolytic plating using a copper sulfate plating solution, thereby producing a double-sided copper-clad laminate (FIG. 4). Furthermore, according to the conventional method, a negative resist with a film thickness of 5 μm was prepared using a liquid resist, and after the copper layer and the nickel-chromium layer were removed by etching, the resist was peeled off, and the two-sided resist as shown in FIG. 5 was produced. A double-sided flexible printed circuit board with copper wiring 2 is used as an inner layer substrate. Next, using the polyimide film 1 shown in Table 4, except that the copper wiring 2 was formed only on one side, a single-sided flexible printed circuit board was produced in the same manner as the double-sided flexible printed circuit board. Further, 70 parts by weight of acrylonitrile-butadiene rubber (manufactured by Nippon Zeon, Nipol 1043, nitrile content 29%), 50 parts by weight of liquid epoxy resin (manufactured by Mitsubishi Chemical, jER828, epoxy equivalent 190) were prepared, Solid epoxy resin (manufactured by Mitsubishi Chemical, jER1001, epoxy equivalent 480) 50 parts by weight, alumina (manufactured by Sumitomo Chemical, AA04, average particle size 0.4 μm) 60 parts by weight, hardener (4,4'-diamine Resin composition B with 8 parts by weight of diphenylsulfone and 40% by mass of solid content using methyl isobutyl ketone as a solvent. The resin composition was coated on the film surface of the single-sided flexible printed substrate obtained above using a bar coater, and dried at 150°C for 10 minutes to prepare a film with an adhesive with a thickness of 15 μm after drying. Single-sided flexible printed substrate (Figure 6), as the outer substrate. Then, on both sides of the inner substrate obtained above, the MD and TD directions were sequentially stacked with the outer substrate and the cover film, and thermocompression bonding was carried out at 150°C and 3 MPa for 30 minutes to produce the substrate shown in Figure 7. Multilayer flexible printed substrates for evaluation. The following items were evaluated about the obtained multilayer flexible printed circuit board. The results are shown in Table 4. (10) Warpage (Method B) Cut the multi-layer flexible printed substrate into a size of 70 mm×70 mm, place it on a flat plate, use a JIS class 1 curved ruler to measure the height between 4 points and the flat plate, and adopt the maximum value.

[Table 4]

From the results in Table 4 above, it can be seen that warpage can be suppressed to be small even if it is a multilayer substrate by using the polyimide film obtained in the examples. [Industrial availability]

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 impart bending properties and the like. In particular, the polyimide film of the present invention is excellent in dimensional stability not only in one direction, but also in different directions, and no matter in which direction, it is excellent in dimensional stability. Polyimide film for wiring in different directions (such as MD direction and TD direction), or for mounting multiple electronic components, or for multi-layer structure.

1‧‧‧polyimide film 2‧‧‧wiring (pattern) 2'‧‧‧metal layer (copper layer) 3‧‧‧electronic parts (semiconductor chip, etc.) 4‧‧‧adhesive layer (adhesive)

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

Claims (20)

A polyimide film, the coefficient of thermal expansion in the MD direction (αT _MD ) and the thermal expansion coefficient in the TD direction (αT _TD ) are both 2~7ppm/℃, |αT _MD -αT _TD | is below 2ppm/℃, and the MD direction The coefficient of humidity expansion (αH _MD ) and the coefficient of humidity expansion in TD direction (αH _TD ) are both 3~14ppm/%RH, and |αH _MD -αH _TD | is below 5ppm/%RH. A 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 less than 2 GPa, 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. The polyimide film according to claim 1 or 2, which is polyamide for at least one substrate selected from substrates with wiring in different directions, substrates with a plurality of electronic components mounted thereon, and substrates with a multilayer structure imine film. The polyimide membrane according to claim 1 or 2, which satisfies the ring stiffness of 75mN/cm or less. The polyimide film as claimed in claim 1 or 2, which comprises the following polyimide: an aromatic diamine component comprising p-phenylenediamine, and an aromatic diamine component selected from pyromellitic dianhydride and 3,3'-4 , One or more acid anhydride components in the group consisting of 4'-biphenyltetracarboxylic dianhydride are polymerized components. The polyimide film according to claim 1 or 2, which comprises the following polyimide: an aromatic diamine component containing 15-40 mol % of p-phenylenediamine as a polymerization component. The polyimide film according to claim 1 or 2, which contains inorganic particles. The polyimide film according to claim 1 or 2, which includes the following polyimide, and contains 0.05% by mass or more of inorganic particles with an average particle diameter of 0.03-1 μm, and the above-mentioned polyimide contains 35 mol% or more The aromatic diamine component of p-phenylenediamine, and one or more acid anhydrides selected from the group consisting of pyromellitic dianhydride and 3,3'-4,4'-biphenyltetracarboxylic dianhydride Components act as aggregated components. A substrate, which is provided with the polyimide film and metal layer according to any one of claims 1 to 8. A substrate comprising the polyimide film according to any one of claims 1 to 8 and wiring formed on the film. As the substrate of claim 10, wirings in different directions are formed on it. In the substrate according to claim 11, wirings are formed in at least two directions along the MD direction and the TD direction of the polyimide film. As for the substrate according to any one of claims 10 to 12, the coefficient of thermal expansion in the transverse direction of the wiring is in the range of 2-8ppm/°C. A cover film comprising the polyimide film according to any one of claims 1 to 8. The cover film as claimed in item 14, wherein the thickness of the polyimide film is 5-25 μm. The cover film according to Claim 14 or 15, which is a cover film for at least one substrate selected from substrates on which wirings in different directions are formed, substrates on which a plurality of electronic components are mounted, and substrates with a multilayer structure. An electronic component mounting substrate comprising the substrate and/or cover film according to any one of claims 9 to 16. As the substrate of claim 17, a plurality of electronic components are mounted on it. The board|substrate of claim 18 which has the board|substrate in which the wiring was formed at least in two directions along the MD direction and the TD direction of a polyimide film, and electronic components are respectively mounted on this wiring. A substrate having a multilayer structure comprising the substrate and/or cover film according to any one of claims 9 to 19.

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