JP2009242676A - Method of manufacturing polyimide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyamide film used for a wiring substrate with fine wiring, particularly used for the wiring substrate which has not only heat resistance intrinsic to polyimides but excellent dimensional stability, and on which a chip can be mounted stably without improper connection. <P>SOLUTION: The method of manufacturing the polyimide film comprises forming a polyimide layer on a support base material and removing the support base material, wherein the base material is 5 to 50 μm thick, the difference between a temperature-increased linear expansion coefficient of the base material and a temperature-decreased linear expansion coefficient thereof is within ±3 ppm in the case of changing the temperature in the range from ambient temperature to 400°C, the difference of the linear expansion coefficient between the base material and the polyimide layer formed on the base material is within 2 to 5 ppm, a resin solution of a polyimide precursor giving the polyimide layer having the linear expansion coefficient of 15 to 25 ppm is applied onto the base material, dryed and heat-treated to form the polyimide layer, and the whole base material is removed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a polyimide film, and more particularly to a method for producing a polyimide film suitable for COF (chip-on-film) applications that require fine wiring.

  In recent years, the performance and functionality of electronic devices have been rapidly increasing, and with this, electronic components used in electronic devices and the boards on which they are mounted have become higher density and higher performance. The demand is growing. Electronic devices are becoming lighter, smaller, and thinner, and the space for storing electronic components is becoming narrower. Under these circumstances, as one of the techniques for solving these problems, a technique for mounting a semiconductor chip on a flexible wiring board is attracting attention, and its use is specially studied as a flexible wiring board for COF. Yes.

  Also in the flexible wiring board used for this so-called COF application, the pitch of the wiring is becoming narrower with the aim of further increasing the density, and the demand for fine processing is increasing. At present, COFs that have been processed to have a wiring pitch of 25 μm have already been produced, and it is estimated that the pitch will be 20 μm or less in the near future.

  Further, as the pitch of the COF substrate laminate is reduced, the required accuracy of dimensions and positions during chip mounting is also increasing. However, it is known that the dimensions of polyimide change due to heat, and due to the heat applied during circuit formation and mounting, the polyimide part in the laminate causes a dimensional change, and on the same laminate. Since the wiring pitch varies, as a result, the bump portion of the chip causes a positional shift, which leads to a decrease in electrical reliability and a decrease in yield. Therefore, it is required to reduce the thermal dimensional change rate and the variation in the film.

  The general manufacturing method of this polyimide film is as follows. That is, an organic solvent solution of polyamic acid, which is a polyimide precursor, is cast on a support, heated to evaporate the solvent until it becomes a self-supporting film, and a self-supporting polyamic acid film is formed from the support. It is manufactured by peeling and completing the removal of the remaining solvent and imidization of the polyamic acid by further heating while gripping both ends of the film. However, in this method, since the solvent contained in the film acts as a plasticizer when the self-supporting film peeled from the support is heated, the film is easily stretched by heat treatment under tension. Therefore, in order to obtain in-plane isotropic properties, when the film isolated from the support is subjected to heat treatment, the in-plane orientation is usually adjusted by controlling the stretching ratio.

  However, it is difficult to perform stretching as described above uniformly over the entire surface of the film. Usually, unevenness of heat shrinkage occurs in the film surface, resulting in a large dimensional change rate or in-plane variation. It is difficult to produce a film for use in high-definition wiring substrates by such a manufacturing method.

  Japanese Patent Application Laid-Open No. 2007-144638 (Patent Document 1) proposes a method for improving the unevenness of the heat shrinkage in the film plane. That is, an organic solvent solution of a polyimide precursor is cast-coated on a metal foil, and this is heated together with the metal foil to obtain a metal foil laminated with a polyimide film that is substantially completely imidized. This is a method for producing a polyimide film, in which the polyimide film is isolated by peeling off the foil and the polyimide film.

  However, in the contents shown in Patent Document 1, no mention has been made of the physical properties of the metal foil and the polyimide film. For this reason, if the metal foil is peeled or etched after the conductor pattern is formed, the dimensional change rate of the polyimide layer is large, and therefore, particularly when the pitch is 30 μm or less, there is a concern about poor connection during chip mounting.

On the other hand, Japanese Patent Application Laid-Open No. 2007-223052 (Patent Document 2) discloses a method of reducing the dimensional change rate by controlling the cooling rate after laminating copper foil and polyimide. However, the average value of the dimensional stability of the copper-clad laminate produced by the method shown in Patent Document 2 is 0.06 to 0.10% according to the example. As stated, when used at a fine pitch of 60 μm or less, it was at a level where there was concern about poor connection during chip mounting.
JP 2007-144638 A JP 2007-223052 A

  The present invention has been made in view of the above-mentioned problems of the prior art, and as a polyimide film used for a wiring board on which fine wiring is typified by COF use, in addition to characteristics such as heat resistance inherent in polyimide. In addition, it offers superior dimensional stability compared to conventional polyimide films, and provides polyimide films that can be used for wiring boards that can be stably mounted on chips without causing poor connections even when mounted at fine pitches of 30 μm or less. The purpose is to do.

  As a result of intensive studies to achieve the above object, the present inventors have used a support base material having a small change in linear expansion coefficient before and after heating, and between the support base material layer and the insulating resin layer. The inventors have found that the above problem can be solved by controlling the difference in linear expansion coefficient, and have completed the present invention.

That is, this invention is a manufacturing method of the polyimide film obtained by forming this polyimide layer on a support base material, and removing this support base material, Comprising: The thickness of this support base material is in the range of 5-50 micrometers. The difference Δα _{1 in} the linear expansion coefficient between when the temperature is raised and when the temperature is lowered when the temperature of the supporting substrate is changed in the temperature range from room temperature to 400 ° C. is in the range of ± 3 ppm, and the supporting substrate A support base material having a linear expansion coefficient difference Δα ₂ with a polyimide layer formed thereon in the range of ₂ to 5 ppm is prepared, and the linear expansion coefficient of the polyimide layer when imidized on the support base material is 15 to A polyimide precursor resin solution having a range of 25 ppm is applied, heat treatment for drying and imidization is performed to form a polyimide layer, and then the support substrate is entirely removed to obtain a polyimide film. Manufacture of polyimide film It is the law.

  In this invention, it is preferable that the said support base material is a metal foil with a thickness of 10-40 micrometers, and has a tensile elasticity modulus of 55 GPa or more. Moreover, it is preferable to make the thickness of the said polyimide film into the range of 8-50 micrometers.

  Furthermore, the present invention is particularly useful as a method for producing a polyimide film for forming a fine wiring used for forming a fine wiring having a wiring width of 30 μm or less.

  According to the present invention, it is possible to provide a polyimide film that is excellent in heat resistance, dimensional stability, and the like, and that is particularly superior in dimensional stability to a film manufactured by another manufacturing method. Therefore, according to the present invention, as a polyimide film used for a wiring board on which fine wiring is typified by COF application, a wiring board that can be stably mounted on a chip without causing a connection failure even when mounted at a fine pitch. It is possible to provide a polyimide film to be used.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

  This invention is a manufacturing method of the polyimide film obtained by forming a polyimide layer on a support base material, and removing this support base material.

  The material of the supporting substrate is not particularly limited, but the relationship between the linear expansion coefficient before and after the heat treatment when the heat treatment is performed from room temperature to 400 ° C., and the relationship with the linear expansion coefficient with the polyimide layer formed later is It is important and it is preferable that it is a metal foil from the relationship with them. Examples of the metal foil used as the support base include metals such as copper, aluminum, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, zinc, and alloys thereof. Among these, stainless steel foil and copper foil Alternatively, an alloy copper foil containing 90% or more of copper is preferable, and a stainless steel foil is most preferable because the linear expansion coefficient (CTE) is stable.

  The thickness of the supporting base material needs to be in the range of 5 to 50 μm, more preferably in the range of 10 to 40 μm, and particularly preferably in the range of 12 to 30 μm. If the thickness of the supporting substrate is less than 5 μm, it is difficult to obtain the raw materials, handling properties at the time of manufacturing the laminate are deteriorated, and wrinkles are easily generated at the time of manufacturing the laminate. On the other hand, when the thickness of the supporting substrate exceeds 50 μm, not only the handling property at the time of producing the laminate is deteriorated, but also the productivity of the substrate removing step by chemical etching is inferior.

The support substrate used in the present invention has a linear expansion coefficient difference Δα ₁ between ± 3 ppm when the temperature is raised and lowered when the temperature of the support substrate is changed in the temperature range from room temperature to 400 ° C. There must be something. If the difference [Delta] [alpha] ₁ of the linear expansion coefficient using a large supporting substrate than this value, the variation of the dimensional change in the plane of the polyimide film produced increases. This is because when the difference between the linear expansion coefficient (dimensional change rate) during heat treatment of the support substrate and the linear expansion coefficient (dimensional change rate) during cooling is large, expansion due to heating / cooling unevenness at each location of the laminate The present inventors infer that the difference in shrinkage occurs and the difference in the amount of expansion / contraction results in variations in the dimensional change rate in the film plane.

Moreover, the support base material prepared by this invention needs to be in the range whose difference (DELTA) (alpha) ₂ of a linear expansion coefficient with the polyimide layer formed on this support base material is 2-5 ppm. The value of the difference [Delta] [alpha] ₂ of the coefficient of linear expansion, caused a large residual stress difference in the expansion coefficient at the interface between the large and the supporting substrate layer and the polyimide layer than 5ppm is increased, the dimensional change rate is large as a result Only a polyimide film can be obtained. On the other hand, when the value of the linear expansion coefficient difference Δα ₂ is smaller than ₂ , as in the case where the value of Δα ₂ is large, a large residual stress is generated and the dimensional change rate is increased. This is because the linear expansion coefficient of the support base layer is almost constant in the thickness direction, whereas the linear expansion coefficient of the polyimide layer has a gradient in the thickness direction. When the linear expansion coefficient of the base material layer is set to the same level, the linear expansion coefficient of the resin in the vicinity of the support base material layer becomes smaller than the linear expansion coefficient of the support base material layer, and as a result, the difference in expansion coefficient becomes large. Therefore, the present inventors speculate.

  The metal foil serving as the supporting substrate preferably has a tensile modulus of 55 GPa or more. In this case, the thickness of the supporting substrate is preferably in the thickness range of 10 to 40 μm. When a metal foil with a tensile modulus of elasticity of less than 55 GPa is used as the support substrate, it is easily affected by stretching due to the tension applied during the manufacturing process by the roll-to-roll method, and the dimensional change rate in the film plane The variation tends to increase.

  In the present invention, a polyimide layer is formed on the support substrate described above. The polyimide constituting this polyimide layer is generally represented by the following general formula (1), and is a known method of polymerizing in an organic polar solvent by using substantially equimolar amounts of a diamine component and an acid dianhydride component. Can be manufactured by.

In the general formula (1), Ar ₁ is a tetravalent organic group having one or more aromatic rings, and Ar ₂ is a divalent organic group having one or more aromatic rings. Ar ₁ can be referred to as an acid dianhydride residue, and Ar ₂ can be referred to as a diamine residue.

As the acid dianhydride, for example, an aromatic tetracarboxylic dianhydride represented by the general formula: O (CO) ₂ —Ar ₁ — (CO) ₂ O is preferable. What is given as Ar ₁ is exemplified.

  Such acid dianhydrides can be used alone or in admixture of two or more. Among these, pyromellitic dianhydride (PMDA), 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3 ′, 4,4′-benzophenone tetracarboxylic acid It is possible to use one selected from anhydride (BTDA), 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride (DSDA), 4,4′-oxydiphthalic dianhydride (ODPA). preferable.

Examples of the diamine include aromatic diamines represented by the general formula: H ₂ N—Ar ₂ —NH ₂ . Preferred examples of Ar ₂ include the following divalent organic groups.

  Among these diamines, diaminodiphenyl ether (DAPE), 2,2′-dimethyl-4,4′-diaminobiphenyl (m-TB), paraphenylenediamine (p-PDA), 1,3-bis (4-amino) Phenoxy) benzene (TPE-R), 1,3-bis (3-aminophenoxy) benzene (APB), 1,4-bis (4-aminophenoxy) benzene (TPE-Q), 2,2-bis [4 -(4-Aminophenoxy) phenyl] propane (BAPP) is exemplified as preferred.

  Examples of the solvent used for polymerization include dimethylacetamide, n-methylpyrrolidinone, 2-butanone, diglyme, xylene, and the like. These can be used alone or in combination of two or more. The resin viscosity of the polyamic acid (polyimide precursor) obtained by polymerization is preferably in the range of 500 cps to 35000 cps.

  The polyimide layer formed on the support substrate may be composed of a single layer or a plurality of layers. However, the dimensional stability and curl of the produced film are reduced, and the laminate substrate. In order to make the adhesive strength with the copper foil excellent when used for applications, it is preferable to have a plurality of layers. In the case where a plurality of polyimide layers are used, the main polyimide layer is a low linear expansion polyimide layer (B) having a linear expansion coefficient (CTE) of 30 ppm [1 / K] or less, preferably in the range of 1 to 30 ppm [1 / K]. It is preferable to provide the thermoplastic polyimide layer (A) on one side or both sides.

  Here, the thermoplastic polyimide layer (A) refers to a layer having a linear expansion coefficient (CTE) exceeding 30 ppm [1 / K] and a glass transition temperature of 330 ° C. or lower. The linear expansion coefficient of a preferable thermoplastic polyimide layer is 30 to 60 ppm [1 / K], and the glass transition temperature is in the range of 200 to 330 ° C. When the linear expansion coefficient of the low linear expansion polyimide layer (B) is larger than 30 ppm [1 / K], curling tends to become severe when a copper clad laminate is formed, and dimensional stability tends to decrease. Therefore, it is not preferable as a product. The thickness of the low linear expansion polyimide layer (B) is preferably 50% or more of the total polyimide resin layer thickness, and more preferably 70 to 95%.

  Thus, although a polyimide layer can be comprised, it is necessary to make the linear expansion coefficient of the polyimide layer formed on a support base material into the range of 15-25 ppm. In order to set the linear expansion coefficient of the polyimide resin layer within this range, the raw material monomer constituting the low thermal expansion coefficient is appropriately selected, and when a plurality of polyimide layers are used, the low linear expansion polyimide layer (B) and thermoplasticity It can be easily adjusted by appropriately controlling the layer structure and thickness with the polyimide layer (A) and the curing conditions during imidization.

  Although the method for forming the polyimide layer is not particularly limited, for example, the following method is preferable. That is, a polyamide acid resin solution, which is a precursor of polyimide, is directly applied onto a support substrate, and the solvent contained in the resin solution is removed to some extent at a temperature of 150 ° C. or lower. The solvent is removed and imidized by performing a heat treatment in a temperature range of preferably 300 to 450 ° C. for about 5 to 40 minutes. When the polyimide layer is provided in two or more layers, the first polyamic acid resin solution is applied and dried, and then the second polyamic acid resin solution is applied and dried. After sequentially applying and drying the resin solutions, it is preferable to perform imidization by collectively performing a heat treatment at a temperature range of 300 to 450 ° C. for about 5 to 40 minutes. If the temperature of the heat treatment is lower than 100 ° C., the dehydration ring-closing reaction of polyimide does not proceed sufficiently. On the other hand, if it exceeds 450 ° C., the polyimide resin layer tends to deteriorate due to oxidation or the like.

  The thickness of the polyimide layer is preferably in the range of 8 to 50 μm, and more preferably in the range of 9 to 40 μm. If the thickness of the resin layer is less than 8 μm, there is a tendency to cause problems such as wrinkling during transportation after removing the supporting base material. On the other hand, if the thickness exceeds 50 μm, it will be bent when used as a flexible wiring board. Tend to be low.

  In this invention, after forming the said polyimide layer on the said support base material, a polyimide film can be obtained by removing a support base material by arbitrary methods. Examples of the method for removing the supporting substrate include a method for peeling the polyimide film and a method for removing the supporting substrate by chemical etching. However, the dimensional stability is improved by not applying excessive stress to the polyimide film. Since a polyimide film can be obtained, a method of removing by chemical etching is advantageous. For example, when a copper foil is used for the support base material layer, it can be removed by using a known etching solution such as a ferric chloride aqueous solution.

  The polyimide film produced according to the present invention is suitably used for forming fine wiring, but the method of providing a conductive metal layer on the polyimide film is not particularly limited. For example, the polyimide film surface is conductive by sputtering. A sputter plating method in which a conductor layer is formed by electroplating after the layer is formed is preferably employed. In addition, a copper foil may be laminated under heat and pressure.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example. In the following Examples, various evaluations are as follows unless otherwise specified.

[Measurement of linear expansion coefficient (CTE): measurement of linear expansion coefficient (CTE) of support base material and polyimide film]
Using a supporting substrate or a polyimide film (3 mm × 15 mm) as a measurement sample, the temperature was increased from 25 ° C. to 400 ° C. at a temperature increase rate of 20 ° C./min while applying a 5.0 g load with a thermomechanical analysis (TMA) apparatus. Then, after holding for 60 minutes, the temperature was lowered to 25 ° C. at a rate of 5 ° C./min. The linear expansion coefficient was measured from the expansion and contraction (shrinkage amount) of the measurement sample with respect to the temperature change in the temperature lowering process.

[Measurement of the difference Δα _{1 in} linear expansion coefficient between when the temperature is raised and when the temperature of the supporting substrate is changed in the temperature range from room temperature to 400 ° C.]
Using a supporting substrate (3 mm × 15 mm) as a measurement sample, the temperature was raised from 25 ° C. to 400 ° C. at a temperature rising rate of 20 ° C./min while applying a 5.0 g load with a thermomechanical analysis (TMA) apparatus. After holding for a minute, the temperature was lowered to 25 ° C. at a rate of 5 ° C./min. The value of the linear expansion coefficient (α _h ) in the temperature rising process and the value of the linear expansion coefficient (α _L ) in the temperature lowering process measured at this time are measured, and the difference is measured from room temperature (25 ° C.) to 400 ° C. The difference in linear expansion coefficient Δα ₁ between when the temperature was raised and when the temperature was lowered when the temperature was changed in the temperature range was set.

[Measurement of etching dimensional change rate]
In accordance with the method described in IPC-TM-650, Section 2.2.4 B, a test piece in which a mark for measurement was formed at an arbitrary position of a laminate (polyimide film) cut into a width of 250 mm and a length of 250 mm. The dimensional change rate before and after etching was determined.

(Synthesis Example 1)
N, N-dimethylacetamide was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 2,2′-Dimethyl-4,4′-diaminobiphenyl (m-TB) was dissolved in this reaction vessel with stirring. Next, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and pyromellitic dianhydride (PMDA) were added. The total amount of monomers charged was 15 wt%, and the molar ratio of each acid anhydride (BPDA: PMDA) was 20:80. Thereafter, stirring was continued for 3 hours to obtain a resin solution a of polyamic acid. The solution viscosity of the polyamic acid resin solution a was 20,000 cps.

(Synthesis Example 2)
N, N-dimethylacetamide was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 2,2-bis [4- (4-aminophenoxy) phenyl] propane was dissolved in the reaction vessel with stirring. Next, pyromellitic dianhydride was added so that the total amount of monomers was 12 wt%. Thereafter, stirring was continued for 3 hours to obtain a resin solution b of polyamic acid. The solution viscosity of the polyamide acid resin solution b was 3,000 cps.

Example 1
The stainless steel foil 1 having the characteristics shown in Table 1 was used as a supporting base, and the polyamic acid resin solution b prepared in Synthesis Example 2 was applied onto the supporting base so that the thickness after curing was 2 μm. Next, the polyamic acid resin solution a prepared in Synthesis Example 1 was applied so that the thickness after curing was 33 μm, dried, and finally subjected to heat treatment at 300 ° C. or higher for about 10 minutes. A laminate having a polyimide layer thickness of 35 μm was obtained. The entire surface of the support substrate of this laminate was etched with an aqueous ferric chloride solution, and all of the support substrate layer was removed from the laminate. The resulting polyimide film had a linear expansion coefficient of 21 ppm, and the difference Δα _{2 in} linear expansion coefficient between the laminate and the polyimide film was 3 ppm. Further, the dimensional change rate before and after etching was 0.012% in the MD direction and -0.009% in the TD direction. The evaluation results are shown in Table 1.

(Example 2)
A polyimide film having a thickness of 40 μm was obtained in the same manner as in Example 1 using the copper foil 1 having the characteristics shown in Table 1 as a supporting substrate. At this time, the thickness of the polyimide layer obtained using the polyamic acid resin solution b prepared in Synthesis Example 2 was 2 μm, and was obtained using the polyamic acid resin solution a prepared in Synthesis Example 1. The thickness of the polyimide layer was 38 μm. The resulting polyimide film had a linear expansion coefficient of 21 ppm, and the difference Δα _{2 in} linear expansion coefficient between the laminate and the polyimide film was 4 ppm. The etching dimensional change rate was 0.014% in the MD direction and -0.005% in the TD direction. The evaluation results are shown in Table 1.

(Comparative Example 1)
A polyimide film having a thickness of 35 μm was obtained in the same manner as in Example 1 using the stainless steel foil 2 having the characteristics shown in Table 1 as a supporting substrate. The resulting polyimide film had a linear expansion coefficient of 21 ppm, and the difference Δα _{2 in} linear expansion coefficient between the laminate and the polyimide film was 6 ppm. The etching dimensional change rate was -0.023% in the MD direction and -0.022% in the TD direction. The evaluation results are shown in Table 1.

(Comparative Example 2)
A polyimide film having a thickness of 40 μm was obtained in the same manner as in Example 2 using the copper foil 2 having the characteristics shown in Table 1 as a supporting substrate. The resulting polyimide film had a linear expansion coefficient of 20 ppm, and the difference Δα _{2 in} linear expansion coefficient between the laminate and the polyimide film was 3.0 ppm. The etching dimensional change rate was 0.032% in the MD direction and 0.023% in the TD direction.

(Comparative Example 3)
A polyimide film having a thickness of 40 μm was obtained in the same manner as in Example 2 using the copper foil 3 having the characteristics shown in Table 1 as a supporting substrate. The resulting polyimide film had a linear expansion coefficient of 17 ppm, and the difference Δα _{2 in} linear expansion coefficient between the laminate and the polyimide film was 0 ppm. The etching dimensional change rate was 0.103% in the MD direction and 0.081% in the TD direction.

  As is clear from the results shown in Table 1, the polyimide films produced by the method of the present invention (Examples 1 and 2) are polyimide films produced by the method not satisfying the conditions of the present invention (Comparative Examples 1 and 2). Compared with 3), it was confirmed that the dimensional stability was very excellent.

  As described above, according to the present invention, as a polyimide film used for a wiring board formed with fine wiring represented by COF applications, in addition to the characteristics such as heat resistance inherent in polyimide, Compared to this, it is possible to provide a polyimide film that is more excellent in dimensional stability and used for a wiring board that can be stably mounted on a chip without causing a connection failure even when mounted at a fine pitch of 30 μm or less.

  Therefore, the present invention is particularly useful as a method for producing a fine wiring forming polyimide film used for forming a fine wiring having a wiring width of 30 μm or less.

Claims (4)

A method for producing a polyimide film obtained by forming a polyimide layer on a supporting substrate and then removing the supporting substrate, wherein the thickness of the supporting substrate is in the range of 5 to 50 μm, and the supporting substrate The difference in linear expansion coefficient Δα ₁ between when the temperature is raised and when the temperature is lowered when the temperature is changed in the temperature range from room temperature to 400 ° C. is in the range of ± 3 ppm, and the polyimide layer formed on the support substrate A polyimide having a linear expansion coefficient of 15 to 25 ppm in the case of preparing a support base material having a linear expansion coefficient difference Δα ₂ in the range of ₂ to 5 ppm and imidizing on the support base material A method for producing a polyimide film, comprising: applying a resin solution of a precursor; performing heat treatment for drying and imidization to form a polyimide layer; and then removing the entire support substrate to obtain a polyimide film.   2. The method for producing a polyimide film according to claim 1, wherein the support base is a metal foil having a thickness of 10 to 40 μm and a tensile elastic modulus of 55 GPa or more.   The thickness of the said polyimide film exists in the range of 8-50 micrometers, The manufacturing method of the polyimide film of Claim 1 or 2 characterized by the above-mentioned.   The method for producing a polyimide film according to any one of claims 1 to 3, wherein the polyimide film is used for forming a fine wiring having a wiring width of 30 µm or less.