JPS61111181A - Manufacture of polyimide-metallic foil composite film - Google Patents

Abstract

PURPOSE:To manufacture the titled film without generating any curls by using a diamino compd. consisting essentially of DDBP and an aromatic tetracarboxylic acid compd. consisting essentially of 3,3',4,4'- biphenyltetracarboxylic acid dianhydride. CONSTITUTION:A polyimide precursor is obtained by allowing a diamino compd. consisting essentially of 3,3'-dimethyl-4,4'-diaminobiphenyl to react with a tetracarboxylic acid compd. consisting essentially of 3,3',4,4'- biphenyltetracarboxylic acid dianhydride or its derivative. A soln. of said polyimide precursor in an org. polar solvent is coated on metallic foil, and heated while the foil is fixed to form a polyimide thin film on the surface of the foil. Consequently, a polyimide-foil composite film can be manufactured without forming previously the film of polyimide. The composite film can be used for the substrate for a solar battery, a hybrid IC, etc. which are used under conditions where the temps. are drastically changed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] This invention relates to a method for producing a polyimide metal foil composite film.

[Background technology]

A composite film made by laminating polyimide and metal foil is used as an electric circuit board. The methods for producing this composite film include: ■ bonding a polyimide film to metal foil via an adhesive; ■ heat-sealing a polyimide film onto metal foil; and ■ applying an organic polar solvent of polyimide precursor onto metal foil. There is a method in which a solution is applied, dried, and then imidized to form a polyimide film.

Among these manufacturing methods, methods ① and ③ have the disadvantage that the process becomes complicated because the polyimide precursor must be formed into a film in advance, and method ③ in particular requires the use of an adhesive in addition to this. This has the problem of causing troubles due to On the other hand, the manufacturing method of ■ is
Since there is no need to form a film in advance as in method (1), the process can be simplified and a thin composite film can be formed, and there are no problems caused by adhesives as in method (2). however? In this method (■), the coating film shrinks when it is cooled after heating during drying or imidization, so the resulting composite film curls due to the metal foil that is difficult to follow this shrinkage, causing circuit damage. It has the disadvantage that it cannot be applied to processing or is difficult to handle during processing.

[Purpose of the invention]

An object of the present invention is to provide a method for producing a polyimide-metal foil composite film that does not substantially curl without forming the polyimide into a film in advance.

[Disclosure of the invention]

In order to achieve the above object, the method for producing a polyimide-metal foil composite film of the present invention is to provide 3,3'-dimethyl-4
, 4'-diaminobiphenyl as a main component and a tetracarboxylic acid compound containing 3.3', 4,4'-biphenyltetracarboxylic dianhydride or a derivative thereof as a main component. a step of preparing an organic polar solvent solution of a polyimide precursor, a step of applying the organic polar solvent solution of the polyimide precursor onto a metal foil, and a step of applying the organic polar solvent solution of the polyimide precursor onto a metal foil; The structure includes a step of heat-treating the metal foil in a fixed state to form a polyimide thin film on the foil surface of the metal foil.

That is, since the method of the present invention uses the above-mentioned specific diamino compound and tetracarboxylic acid compound as the diamino compound and tetracarboxylic acid compound for forming the polyimide film, the resulting polyimide film contains copper, aluminum, etc. It has a coefficient of linear expansion almost similar to that of metal foil made of . Moreover, when forming the above-mentioned polyimide film on this metal foil, the heat treatment for polyimidization is performed with the metal foil fixed, so that the stress generated in the polyimide film is relaxed, and this effect and Together with the linear expansion coefficient approximation effect described above, a polyimide-metal foil composite film that does not curl in both the length direction and the width direction can be obtained.

The diamino compound for forming the polyimide precursor (polyimide film) in the method of this invention is 3.3゛-dimethyl-
The main component is 4,4'-diaminobiphenyl (hereinafter abbreviated as rDDBPJ). Here, the term "main component" includes the case where the whole consists only of the main component. However, U containing 70 mol% or more of DDBP and 30 mol% or less of other diamines is usually used. If the proportion of DDBP is too small, the difference in linear expansion coefficient between the metal foil made of copper, aluminum, etc. and the polyimide film becomes large, which is not preferable.

Other diamines mentioned above include 4,4"-diaminodiphenyl ether, 4.4°-diaminodiphenylmethane, 4,4°-diaminodiphenyl sulfone,
3.3'-diaminodiphenylsulfone, p-phenylenediamine, m-phenylenediamine, 4.4'
-diaminodiphenylpropane, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 4,4°-diaminodiphenyl sulfide, 4,4"-di(m-aminophenoxy)diphenylsulfone, 3,3"-di(
m-aminophenoxy)diphenylsulfone, 4.4
'-'; Examples include (m-aminophenoxy)diphenylpropane, and one or more of these may be used as appropriate. Moreover, about several mol% of diaminosiloxane may be used.

The tetracarboxylic acid compound for forming a polyimide precursor in the present invention is mainly composed of 3.3'', 4.4'-biphenyltetracarboxylic dianhydride or its derivatives such as acid halides, diesters, and monoesters. Usually, this dianhydride or its derivatives are contained in a proportion of 70 mol% or more, and other aromatic tetracarboxylic dianhydrides or their derivatives such as acid halides, diesters, monoesters, etc. are contained in a proportion of 30 mol% or less. If the proportion of 3.3', 4.4'-biphenyltetracarboxylic dianhydride or its derivatives is too small, the coefficient of linear expansion between the metal foil made of copper, aluminum, etc. and the polyimide film will decrease. This is not preferable because problems such as an increase in the difference or an extreme decrease in film strength occur.

l Examples of the above-mentioned other aromatic tetracarboxylic dianhydrides or derivatives thereof include pyromellitic dianhydride, 3. 3', 4. Examples include acid dianhydrides or derivatives thereof such as 4°-benzophenonetetracarboxylic dianhydride and 2,3,6.7-naphthalenetetracarboxylic dianhydride, and one or more of these Used as appropriate. Among these, pyromellitic dianhydride or its derivatives, 3.3',
4.4''-benzophenonetetracarboxylic dianhydride or its derivatives are prized.The reason is that these tetracarboxylic acid compounds have excellent film strength even when reacted alone with the specific diamino compound. This is because although it is difficult to form a polyimide film, it gives a favorable result in reducing the coefficient of linear expansion and contributes to achieving the object of the present invention, which is to prevent curling.

In order to obtain a polyimide precursor by reacting the above-mentioned diamino compound and tetracarboxylic acid compound, these two compounds are mixed in approximately equal moles in an organic polar solvent at usually 0 to 90°C.
The mixture is reacted for 1 to 24 hours to form a polyimide precursor such as polyamic acid.

The above organic polar solvents include N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N.,N-dimethylformamide, dimethylsulfoxide, dimethylphosphoamide, m-cresol, p-cresol,
Examples include p-chlorophenol. Further, a portion of xylene, toluene, hexane, naphtha, etc. may be mixed therein.

The organic polar solvent solution of the polyimide precursor obtained in this way is characterized by its logarithmic viscosity (measured at 30 °C at a concentration of 0.5 g/100 ml in N-methyl-2-pyrrolidone).
is preferably in the range of 0.4 to 7.0. More preferably, it is within the range of 1.5 to 3.0. If this value is too small, the resulting polyimide film will have a low mechanical strength, which is not preferable. Moreover, if this value is too large, the coating workability on metal foil will be lowered, which is not preferable.

In the present invention, a polyimide-metal foil composite film is manufactured using the organic polar solvent solution of the polyimide precursor obtained as described above, for example, as described above. That is, first, the organic polar solvent solution of the above polyimide precursor is heated to a temperature of 80° C. or lower to lower the viscosity, and in that state, the thickness is 1 to 500 μm, preferably 10 to 100 μm.
It is particularly preferably cast onto a metal foil having a thickness of 20 to 50 μm using an appropriate means such as an applicator. In this case, if the thickness of the metal foil is less than 1 μm, the effect of preventing curling will be reduced.1. In addition, there is a possibility that problems may arise in terms of use, and conversely, if the thickness exceeds 500 μm, the composite film lacks flexibility and becomes unsuitable for uses such as electric circuit boards. Therefore, the metal foil used has a thickness of 1 to 500 μm.
Preferably, it is within the range of m.

As for the type of metal foil, copper foil, aluminum foil or stainless steel foil is preferable. When using copper foil, it is preferable to use electrolytic copper foil, rolled copper foil, or those surface-treated with a silane coupling agent or an aluminum-based coupling agent because the adhesive strength with the polyimide film will be increased.

The metal foil may be made of various other materials such as silver, iron, or an alloy of nickel and chromium having the thickness described above. The length of these metal foils when applying the polyimide precursor solution is not particularly limited. However, the width is practically about 20 to 200 cm. of course,
It is acceptable to deviate from the above range. It goes without saying that the composite film obtained using the wide metal foil described above may be cut into a predetermined width in the final step and used.

Note that the organic polar solvent solution of the polyimide precursor obtained as described above may be further diluted with an organic polar solvent as necessary. As the organic polar solvent for dilution in this case, those used during the polymerization reaction of each polyimide precursor can be used.

In addition, the concentration of the polyimide precursor in the above solution is 10 to 2
It is preferable to set it to about 0% by weight.

If this concentration is too low, the surface of the polyimide film tends to become rough, while if it is too high, the viscosity increases and coating workability is impaired.The viscosity of this solution is generally The viscosity at the time of hot application is preferably 5000 voids or less.Also, in order to improve the adhesion between the metal foil and the polyimide film, a silane coupling agent is applied on the metal foil in advance. Alternatively, a silane coupling agent may be added and mixed in the above solution.

Next, after applying the solution, the metal foil is heat-treated in a fixed state. This heat treatment is usually performed at 100 to 230°C.
After drying by heating for about 30 minutes to 2 hours to remove the solvent, the temperature is further raised and finally at a temperature of 230 to 600°C for 1 minute to 6 hours, preferably at a temperature near the glass transition temperature of the polyimide to be formed. That is, heat treatment is carried out at a temperature of 250 to 350° C. for 10 minutes to 6 hours to completely carry out the imidization reaction and to relieve stress generated in the coating film during the above-mentioned solvent removal and imidization.

Note that if the heat treatment is performed at a temperature below 230° C., stress relaxation will be insufficient, and the resulting composite film will tend to curl. On the other hand, if it is carried out at a temperature exceeding 600°C, the polyimide will decompose, which is not preferable. In order to prevent such decomposition of polyimide, even if the heating temperature is 600°C or less, if the heating temperature exceeds 350°C, the heating time is
It is preferable to set it as less than 0 minutes.

Such heat treatment is performed while the metal foil coated with the polyimide precursor solution is fixed as described above. This fixing method includes fixing the metal foil in a flat plate on a glass plate using polyimide tape, etc., or fixing the metal foil by wrapping both lengthwise ends of the metal foil around a roll. Depending on the length and size of the material, various methods can be used to substantially fix the material in both the width and length directions.

After the heat treatment in this manner, it is cooled to room temperature. The above-mentioned fixation may be released at any time after the high-temperature heat treatment, but it is preferable to release it after cooling to room temperature.

Through this series of steps, a stress-relaxed polyimide film is formed on the metal foil. In this case, it is preferable to set the thickness of the polyimide film to 5 to 200 μm. More preferably, it is 10 to 100 μm, and most preferably 10 to 50 μm. If the thickness is less than 5 μm, the film properties will deteriorate, and if it exceeds 200 μm, the curl prevention effect will be reduced and the film will lack flexibility, making it unsuitable for applications such as electrical circuit boards. Therefore, the thickness of the polyimide film is 5 to 200 mm.
It is preferable to set it to pm.

The above polyimide film generally has an average linear expansion coefficient of 1.2X10-5 to 2.9X1O- at 50 to 250°C.
Although the average linear expansion coefficient is within the range of 5yc, it is possible to set the average linear expansion coefficient to be even smaller than the above value depending on the case. In contrast, metal foils in the same temperature range as above, e.g.
The average coefficient of linear expansion of ~500 μm thick metal foils ranges from 1.5 x 10-5 to 1.7 x to'yc for copper foil, and from 2.4 x 10' to 2,4 x to'yc for aluminum foil.
It is in the range of 2.6 x 10-5 yt.

As described above, in this invention, by appropriately setting the polymer composition of the polyimide film within the above-mentioned specific range and setting the thickness of the polyimide film and the metal foil within the above-mentioned range, the average line between the polyimide film and the metal foil can be adjusted. It has the characteristic that the difference in expansion coefficients can be suppressed to within 0.3 x 10-'λ.

In this specification, the coefficient of linear expansion is expressed as Δβ/1, assuming that the length of a material of length l at temperature T changes by Δl when the temperature changes by 1°C. Further, the average linear expansion coefficient is expressed as the average value of the above-mentioned linear expansion coefficients within a certain temperature range. The linear expansion coefficient was measured using a composite film with a length of 25 mm.
11 A test piece cut to a width of 3 tl was fixed with one end in the length direction facing upward, and was heated at 10°C/min in a nitrogen gas atmosphere with a load of 15 g/+u2 applied to the lower end at a chuck distance i% of 10 va. This is done by changing the temperature at a temperature increase rate and determining the above Δl/12 at this time.

The polyimide-metal foil composite film obtained as described above has a radius of curvature of 25" in both the width and length directions.
cm or more and is excellent with virtually no curls. That is, the above-mentioned composite film has an excellent curvature radius of l usually 50 cm or more, preferably a radius of curvature of 50 cm or more, and is substantially curl-free. In addition, the above composite film has excellent heat resistance, chemical resistance, durability, and flexibility, and also has an excellent bonding state between the polyimide film and metal foil, so it can be used for printed wiring boards, flexible printed wiring boards, etc.
Suitable for applications such as multilayer wiring boards and diaphragms.

Note that the radius of curvature mentioned above refers to the metal foil 1 as shown in the drawing.
Composite film 3 consisting of and polyimide film 2 has a length lQ
The degree of curvature when this test piece is curled in the width direction (or length direction) is expressed by the radius r from the center P for a test piece cut into 10 cm and 10 cm wide and 11 squares. Then, this radius of curvature r is the length of the width direction (or length direction) in the curled state. When h is the length from R to the center of the film on the extension line of the above perpendicular line N, when h≧r, measure this r, or when h<r, use the above a value for convenience. and h value can be actually measured and calculated using the following formula.

r2= (r h) 2+ (+a)"r"=r"
-2rh+h2+1a2 2rh=h2 +ia" r=JJ-h consonant/V The polyimide-metal foil composite film obtained as described above has the relationship h<r, and especially since h is small, r=25 cm or more, and preferably has substantially no curls as shown in ■.
This composite film has the advantage that it does not substantially curl after cooling even if it is subjected to a processing treatment that applies heat at 50 to 270°C. It also has the characteristics of excellent handling properties and dimensional stability.

In the above explanation, the metal foil is coated with a polyimide precursor solution and then fixed and heat-treated. Needless to say, it is okay.

〔Effect of the invention〕

As described above, the method for producing a polyimide-metal foil composite film of the present invention uses a diamino compound mainly composed of DDBP and 3.3', 4.4' as a diamine compound and a tetracarboxylic acid compound for forming a polyimide film. - By using an aromatic tetracarboxylic acid compound whose main component is biphenyltetracarboxylic dianhydride or its derivative, a polyimide film having a coefficient of linear expansion almost similar to that of the metal foil is formed on the metal foil. sell. Moreover, since the metal foil is kept in a fixed state when the polyimide film is heated and formed, stress generated in the polyimide film is alleviated. Due to these synergistic effects, the resulting polyimide-metal foil composite film is free from curling in both the length and width directions.

The composite film obtained by the method of the present invention does not substantially curl as described above, so it can be used as a substrate for producing electric circuit boards without any problems, and it is also said to have excellent handling properties during circuit processing. It has advantages. Moreover, the resulting electric circuit board has the characteristic that it does not easily curl due to temperature changes, and has excellent dimensional stability in this respect. Specific examples of applications of this composite film include applications to solar cell substrates, hybrid IC substrates, solar water heater heat collecting plates, etc. that are used under severe temperature change conditions.

Next, examples will be described together with comparative examples.

The radius of curvature and average coefficient of linear expansion in the following are measured or calculated using the method described above by cutting the composite film produced in each example and comparative example to the size of each test piece. . However, the radius of curvature is a value measured in both the length direction and the width direction (length and width) of a 10 cm square, and means that both values are substantially the same.

[Example 1] 21.2 g of DDB P in a 500 mj2 flask
(0°1 mole) and 210 g of N-methyl-2-pyrrolidone (hereinafter abbreviated as rNMPj) were added and mixed to dissolve the diamine. 3°3' while stirring the system; 4.
4'-Biphenyltetracarboxylic dianhydride 29.
4 g (0.1 mol) were added gradually. During this time, the reaction system was cooled with ice water so that the temperature did not exceed 30°C. Thereafter, the mixture was stirred for 2 hours to obtain an NMP solution of polyamic acid having a concentration of 19.4% by weight.

Logarithmic viscosity of this polyamic acid (0.5 g/10 in NMP
(measured at 30° C. at a concentration of 0 ml) was 1.48.

In addition, the viscosity of this NMP solution is 19.900 bois (3
0'c).

This NMP solution of polyamic acid was heated in advance to a viscosity of about 1500 poise, and this was placed in a 30 cm long x 20 cm wide area.
It was cast using an applicator onto a 35 μm thick copper foil (dimensions are the same as the above glass plate) whose entire circumference was fixed with a polyimide film on a glass plate.
It was heated at 0°C for 60 minutes and further heated at 300°C for 1 hour. Thereafter, it was cooled to room temperature, and the fixation of the copper foil was released to obtain a polyimide-metal foil composite film. Obtained polyimide
The copper foil composite film has a polyimide coating thickness of 28 μm.
The radius of curvature was 76 marks, and there was virtually no curl.

In addition, the 90' peel strength between the polyimide film and the copper foil in this composite film is 1.20 kg/1011 under normal conditions.
1 and 9 after immersion in a 260°C solder bath for 30 seconds.
The 0° peel strength was 1.15 kg/10 mm.

The linear expansion coefficient of the polyimide membrane in this composite film was measured using a thermomechanical analyzer (hereinafter referred to as rTMAJ), and the average linear expansion coefficient at 50 to 250°C was 1.68X.
10-', l'i, which was almost equal to the average coefficient of linear expansion of copper foil (1,60 x 10''yc) in the same temperature range.

[Examples 2 to 5] The NMP solution of polyamic acid obtained in Example 1 was fixed on a glass plate of the same size as in Example 1 in the same manner as in Example 1. is the same as a glass plate)
The top was cast by the same means as in Example 1, and then heated at 150°C for 30°C.
After heating at 200'C for 60 minutes, the mixture was further heated under the conditions shown in Table 1 below, and then cooled to obtain a polyimide-copper foil composite film having a polyimide film thickness of 28 μm. The radius of curvature of the resulting composite film was as shown in Table 1 below. For reference, Example 1
The composite films obtained in the above are also shown in Table 1.

[Comparative Example 1] 21.2 g (0.1 mol) of DDBP was replaced with 20.0 g (0.1 mol) of 4,4'-diaminodiphenyl ether. Other than that, the same procedure as in Example 1 was carried out. 19.0
An NMP solution of polyamic acid at a concentration of % by weight was obtained. Logarithmic viscosity of this polyamic acid (0.5 g/100 mj in NMP
! (measured at 30° C.) was 2°12, and the viscosity of this NMP solution was 2.040 voids (at 30° C.).

This NMP solution of polyamic acid was fixed on a glass plate of the same size as in Example 1 in the same manner as in Example 1.
Example 1
It was cast in the same manner as in Example 1, heated under the same conditions as in Example 1, and then cooled to room temperature to release the fixation of the copper foil.

The thickness of the polyimide film in the obtained polyimide-metal foil composite film was 28 μm, the radius of curvature of this composite film was 1.1 cm, and the curl was large.

The average linear expansion coefficient of the polyimide membrane in this composite film at 50 to 250'C measured by TMA is 3.4X10-8. H, which was larger than the average linear expansion coefficient of copper foil in the same temperature range. For this reason, it is thought that even if stress relaxation is performed during polyimide film formation, curling will occur when the polyimide film is cooled to room temperature.

[Comparative Example 2] In Comparative Example 1, an NMP solution of polyamic acid was cast on a copper foil, and then, as in Example 1, it was heated at 150°C for 30 minutes and then at 200°C.
This heat treatment was repeated at 150°C for 30 minutes, 200°C for 60 minutes, and then heated at 300°C for 1 hour.
The temperature was changed to 20°C for 0.5 hours. A polyimide-copper foil composite film was obtained in the same manner as in Comparative Example 1 except for the above. The thickness of the polyimide film in the obtained polyimide-copper foil composite film was 24 μm, and the radius of curvature of this composite film was 1
．． It was 3 cm long and had large curls.

[Go to Example 6/9. Comparative Examples 3 to 6] The solvent shown in Table 2 and the diamino compound were placed in a 500 ml flask, and the diamino compound was dissolved. in this case,
The amount of the solvent used was set so that the concentration of the diamino compound and the aromatic tetracarboxylic acid compound in the 7-mer preparation was 15% by weight.

Next, the aromatic tetracarboxylic acid compounds shown in Table 2 were gradually added to the above system while stirring.

During this time, the reaction system was cooled with ice water so that the temperature did not exceed 30°C. After that, the logarithmic viscosity shown in Table 2 (0.5 g/100 ml in NMP at 30°C) was stirred for a predetermined time.
A solution of polyamic acid was obtained with a polyamic acid (determined below).

This polyamic acid solution was fixed in the same manner as in Example 1 on a glass plate of the same size as in the example. Example 1
Casting in the same manner as above, 30 minutes at 150℃, 200℃
The mixture was further heated at 320° C. for 0.5 hour. Thereafter, it was cooled to room temperature and the copper foil was released. The thickness of the polyimide film and the radius of curvature of the composite film in the obtained polyimide-copper foil composite film were as shown in Table 2. Further, Table 2 shows the difference between the average linear expansion coefficient of the polyimide film in this composite film at 50 to 250°C measured by TMA and the average linear expansion coefficient of the copper foil.

(Left below) In Table 2, p-PDA is p-phenylenediamine, DADE is 4,4'-diaminodiphenyl ether, DADM is 4,4'-diaminodiphenylmethane, and 5-BPDA is 3.3'.

4.4”-biphenyltetracarboxylic dianhydride, P
MDA is pyromellitic dianhydride, BTDA.

represents 3,3",4.4"-benzophenonetetracarboxylic dianhydride, and DMF represents N,N-dimethylformamide.

C Example 10) As a diamino compound, DDBP 19.1 g (
0.09 mol) and 2.0 g (0.01 mol) of 4,4'-diaminodiphenyl ether. Other than that, the procedure was the same as in Example 1 to obtain an NMP solution of polyamic acid.

Logarithmic viscosity of this polyamic acid solution (0.5 g/in NMP)
(measured at 30° C. at a concentration of 100 mA) was 2.0.

Next, this NMP solution of polyamic acid was placed on a 50 μm thick aluminum foil (the dimensions are the same as the glass plate) that was fixed in the same manner as in Example 1 on a glass plate of the same size as in Example 1. Casting was carried out using the same method as in 1, and 3 was cast at 150°C.
After heating at 180°C for 60 minutes, further heating at 290°C.
The mixture was heated at C for 2 hours. Thereafter, it was cooled to room temperature, and the aluminum foil was released to obtain a polyimide-aluminum foil composite film. The obtained polyimide-aluminum foil composite film had a polyimide film thickness of 26 μm,
The radius of curvature was 85 cm.

In addition, the TMA of the polyimide film in this composite film
The average linear expansion coefficient at 50 to 250°C measured by
was almost equal.

As is clear from the above Examples and Comparative Examples, according to the method for producing a polyimide-metal foil composite film of the present invention, a composite film substantially free from curling can be obtained.

[Brief explanation of drawings]

The drawing is an explanatory diagram illustrating the radius of curvature of a polyimide-metal foil composite film.

Claims (5)

[Claims] (1) Diamino compound mainly composed of 3,3'-dimethyl-4,4'-diaminobiphenyl and 3,3',4,4
A step of preparing an organic polar solvent solution of a polyimide precursor obtained by reacting with a tetracarboxylic acid compound containing ′-biphenyltetracarboxylic dianhydride or a derivative thereof as a main component, and determining the organic polarity of the polyimide precursor. The process comprises a step of applying a solvent solution onto the metal foil, and a step of heating the metal foil coated with the organic polar solvent solution of the polyimide precursor in a fixed state to form a polyimide thin film on the foil surface of the metal foil. A method for producing a polyimide-metal foil composite film characterized by: (2) The method for producing a polyimide-metal foil composite film according to claim 1, wherein the metal foil has a thickness of 1 to 500 μm and the polyimide thin film has a thickness of 5 to 200 μm. (3) Logarithmic viscosity of polyimide precursor (N-methyl-2-
2. The method for producing a polyimide-metal foil composite film according to claim 1, wherein the polyimide-metal foil composite film has a polyimide-metal foil composite film of 0.4 to 7.0 (measured at 30° C. at a concentration of 0.5 g/100 ml in pyrrolidone). (4) The method for producing a polyimide-metal foil composite film according to any one of claims 1 to 3, wherein the metal foil is copper foil, aluminum foil, or stainless steel foil. (5) Any one of claims 1 to 4, wherein the difference in average linear expansion coefficient between the metal foil and the polyimide film at 50 to 250°C is within 0.3 x 10^-^5l/°C. A method for producing a polyimide-metal foil composite film as described in .