JPS61111180A - Manufacture of polyimide-foil composite film - Google Patents

Abstract

PURPOSE:To manufacture the titled film without generating any curls by using an 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. contg. 80-99.9mol% (A) component, as in the following, and 0.1-10mol% (B) component to react with a tetracarboxylic acid compd. consisting essentially of (C) component. A soln. of said polyimide precursor in an org. polar solvent is coated on foil, and heated to form a polyimide thin film. (A) is 3,3'- dimethyl-4,4'-diaminobiphenyl, (B) is silicon diamine expressed by the formula (R1 is a methylene group, a phenylene group, etc., R2 is a methylene group, a phenylene group, etc., X is O, a phenylene group, etc., (n) is 1 when R1 is a phenylene group or a substituted phenylene group and 3 or 4 when R1 is a methylene group), and (C) is one of 3,3',4,4'-diphenyltetracarboxylic acid dianhydride and its derivative.

Description

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

BACKGROUND ART A composite film formed by laminating polyimide and metal foil is useful as an electric circuit board. 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; ■ applying organic There is a method in which a polar solvent 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 (2), the polyimide film is directly formed on the metal foil and no adhesive is used, so depending on the composition of the polyimide precursor, the adhesive force between the produced polyimide film and the metal foil may be insufficient, and the polyimide, - It is expected that during circuit pattern formation or soldering on a metal foil composite film, floating and peeling phenomena of the conductor may occur, causing defects. In addition, in method (2), the coating film shrinks when it is cooled after heating during drying or imidization, so the resulting composite film may curl due to the metal foil, which is difficult to follow this shrinkage. It has the disadvantage that it cannot be applied to circuit processing and is difficult to handle during processing.

[Purpose of the invention]

The present invention provides a method for producing a polyimide-metal foil composite film in which a polyimide film and a metal foil are firmly bonded without substantially curling, without forming the polyimide into a film in advance. purpose.

[Disclosure of the invention]

In order to achieve the above object, the method for producing the polyimide-metal foil composite film of the present invention includes the following component (A): 80 to 9
An organic polyimide precursor obtained by reacting a diamino compound containing 9.9 mol% and 0.1 to 10 mol% of component (B) with a tetracarboxylic acid compound whose main component is the following component (C). A step of preparing a polar solvent solution, a step of applying an organic polar solvent solution of the polyimide precursor onto a metal foil, and a heating treatment of the metal foil coated with the organic polar solvent solution of the polyimide precursor in a fixed state. The method includes a step of forming a polyimide thin film on the foil surface of the metal foil.

(A) 3,3'-dimethyl-4,4''-diaminobiphenyl (B) A silicone-based diamine represented by the general formula %.

(C) At least one of 3.3', 4.4'-biphenyltetracarboxylic dianhydride and its derivatives.

That is, in the method of the present invention, the above-mentioned silicon-based diamine is used as a diamino compound for forming a polyimide film at a concentration of 0.
Since silicon atoms derived from the silicon-based diamine are introduced into the polyimide film containing 1 to 10 mol%, the polyimide film is firmly bonded to the metal foil. Moreover, as diamino compounds and tetracarboxylic acid compounds for polyimide film formation,
Since the above-mentioned specific diamino compound and tetracarboxylic acid compound are used, the resulting polyimide film has a coefficient of linear expansion almost close to that of a metal foil made of copper, aluminum, or the like. 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 Coupled with the linear expansion coefficient approximation effect described above, the I
Curls will no longer form.

The diamino compound for forming the polyimide precursor (polyimide i*) in the method of this invention is 3,3'-dimethyl-4,4°-diaminobiphenyl (rDDBPJ).
) containing 80 to 99.9 mol% and 0.1 to 10 mol% of silicone diamine represented by the above general formula,
The remainder contains other 7 diamines.

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.

In addition, the proportion of the silicone diamine is 0 as described above.
．． It needs to be set within the range of 1 to 10 mol%, and the preferred range is 2 to 7 mol%. In other words, if the silicon-based diamine is less than 0.1 mol%, the effect of improving bonding or adhesion to metal foil cannot be obtained;
This is because if it exceeds 0 mol %, the moisture absorption rate, heat resistance, and other properties of the polyimide film will be lowered, or the coefficient of linear expansion will be increased.

Specific examples of such silicon-based diamines include:
It is as follows.

CI, Cl5 C, H, C, I (.

C,Hj-C,)lJ- CH, CH.

Other diamines mentioned above include 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, nilmethane, 4,4'-diaminodiphenylsulfone, 3.3"-diaminodiphenylsulfone, p-phenylenediamine, m-phenylenediamine, 4,4゛-diaminodiphenylpropane, 1.5-
Diaminonaphthalene, 2,6-diaminonaphthalene, 4
．． 4'-diaminodiphenylsulfide, 4,4'-di(m-aminophenoxy)diphenylsulfone,
Examples include 3.3''-di(m-aminophenoxy)diphenylsulfone, 4.4''-di(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 the polyimide precursor in this invention is 3.3',4.4°-biphenyltetracarboxylic dianhydride or its acid halide;
The main component is a derivative such as diester or monoester. Here, the term "main component" includes the case where the whole consists of only the main component. However, usually 70 mol% or more of this dianhydride or its derivatives and 3% or more of other aromatic tetracarboxylic dianhydrides or their derivatives such as acid halides, diesters, and monoesters are used.
Those containing 0 mol% or less are used. 3,3°
If the proportion of 4.4'-biphenyltetracarboxylic dianhydride or its derivatives is too small, the difference in linear expansion coefficient between the metal foil made of copper, aluminum, etc. and the polyimide film will become large, or the film strength will become extremely high. This is not preferable because it causes inconveniences such as a decrease in the temperature.

Examples of the above-mentioned other aromatic tetracarboxylic dianhydrides or derivatives thereof include pyromellitic dianhydride, 3.
Acid dianhydrides such as 3', 4,4'-benzophenonetetracarboxylic dianhydride, 2,3,6.7-sl phthaline tetracarboxylic dianhydride or derivatives thereof are mentioned; One or more of these may be used as appropriate. Among these, pyromellitic dianhydride or its derivatives, 3.3',
4. 4'-benzophenonetetracarboxylic dianhydride or its derivatives are used in practical use. The reason is,
These tetracarboxylic acid compounds are difficult to produce a polyimide film with excellent film strength even if they are reacted alone with the specific diamino compound, but they give favorable results in reducing the coefficient of linear expansion, and this invention aims to prevent curling. This is because it will contribute to achieving the objectives of

In order to obtain a polyimide precursor by reacting the above-mentioned diamino compound and tetracarboxylic acid compound, these re-compounds are mixed in approximately equimolar amounts 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, p-cresol, and p-cresol.
- Examples include chlorophenol. Further, a portion of xylene, toluene, hexane, naphtha, etc. may be mixed therein.

The organic polar solvent solution of the polyimide precursor thus obtained has a logarithmic viscosity (measured at 30°C at a concentration of 0.5 g/100 mn in N-methyl-2-pyrrolidone) of 0.4 to 7. It is preferable that it is in the range of 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 produced, for example, in the following manner using the organic polar solvent solution of the polyimide precursor obtained as described above. That is, first, the organic polar solvent/8 solution of the polyimide precursor is heated to a temperature of 80°C or less to lower the viscosity, and in that state, the thickness is 1 to 500 μm, preferably 10 to 100 μm.
It is cast onto a metal foil having a thickness of .mu.m, preferably 20 to 50 .mu.m, 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 and problems may arise in the application, while if it exceeds 500 μm, the composite film will lack flexibility. It becomes less suitable for applications such as electrical circuit boards. Therefore, the metal foil used has a thickness of 1 to 50 mm.
Preferably, the thickness is within the range of 0 μm.

As for the type of metal foil, copper foil, aluminum foil or stainless steel foil is preferable, and in addition, those made of various materials such as silver having the thickness mentioned above, alloy of iron 2 nickel and chromium can be used. 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, you may 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 is likely to become rough, while if it is too high, the viscosity will increase and the coating workability will be impaired. From the viewpoint of coating workability, the viscosity of this solution is generally preferably 5000 voids or less, which is the viscosity at the time of hot coating.

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 t near the glass transition temperature of the polyimide to be formed. temperature, i.e. 250~
Heat treatment is carried out at a temperature of 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 above 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.

To prevent such decomposition of polyimide, the temperature is 600℃.
Even if the heating temperature is below, if the temperature exceeds 350°C, the heating time is preferably less than 10 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 above-mentioned metal foil on a glass plate etc. using polyimide tape etc. in a flat plate shape, or wrapping both lengthwise ends of the metal foil around a roll. Depending on the length and size of the foil, various methods can be used to substantially fix the foil 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 the fixation 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 be poor (on the contrary, if it exceeds 200 μm, the anti-curl effect will be reduced and the flexibility will be lacking, making it less suitable for applications such as electrical circuit boards. The thickness of the polyimide film is 5 to 200 mm.
It is preferable to set it to μm.

The polyimide film generally has an average linear expansion coefficient of 1.2 x 10' to 2.9 x 1 at 50 to 250°C.
The average linear expansion coefficient is within the range of o-'yc, but depending on the case, it is possible to set the average linear expansion coefficient to be even smaller than the above value. On the other hand, the average linear expansion coefficient of a metal foil in the same temperature range as above, for example, a metal foil with a thickness of 1 to 500 μm, is 1.5×10−′ to 1.7×10=,! H, and for aluminum foil it is 2.4 x 10'~
It is in the range of 2.6 x 109i.

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 coefficient can be suppressed to within 0.3×10'M.

In this specification, the coefficient of linear expansion is expressed as Δ2/l, assuming that a material of length l at temperature T changes in length by Δl when the temperature changes by 1°C. , and the average linear expansion coefficient is expressed as the average value of the above-mentioned linear expansion coefficients within a certain temperature range. To measure this coefficient of linear expansion, the composite film is measured with a length of 2
A test piece cut into 5 squares, 9 widths, and 3 squares was fixed with one lengthwise end facing upward, and a load of 15 g/m2 was applied to the lower end at a chuck distance of 10 squares in a nitrogen gas atmosphere for 10 minutes. This is done by changing the temperature at a heating rate of 'C/min and determining the above Δ1/It at this time.

The polyimide-metal foil composite film obtained as described above has a radius of curvature of 25 cm in both the width and length directions.
It is an excellent product with a ffi or higher and virtually no curl.

That is, the composite film usually has a radius of curvature of 50c.
M or more, preferably ■, which is excellent and has substantially no curl. In addition, the above composite film has excellent heat resistance, chemical resistance, durability, and flexibility, and also has excellent bonding conditions between the polyimide film and metal foil, so it can be used in printed wiring boards, flexible printed wiring boards, multilayer wiring boards, etc. , suitable for use as diaphragms, etc.

Note that the radius of curvature mentioned above refers to the metal foil 1 as shown in the drawing.
A composite film 3 consisting of a polyimide film 2 and a length 10
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 Pl for a test piece cut into a square lQcm square with a width of 10cm and a width of 10cIII. And this radius of curvature r
The length in the width direction (or length direction) in the curled state is 31. When the perpendicular line N is drawn from the center P to the horizontal line M connecting both ends in the width direction (or length direction), the above perpendicular line N is calculated from the intersection R.
When h is the length to the center of the film on the extension line of It can be calculated by actual measurement using the following formula.

r" = (r-h)" + (ia) 2r2=r'
-2rh+h" 11a22r h=h2+ia" r=Shirijushi・r The polyimide-metal foil composite film obtained as described above has a relationship of her, and in particular, because h is small, r=25cn+ or more and preferably has substantially no curls such as frizz. Additionally, 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, and in this respect it is suitable for the various uses listed above. It is also characterized by excellent handling properties and two-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 containing DDBP as a main component and 3.3', 4.4' as the diamino compound and 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. However, 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 does not curl in both the length and width directions. Moreover, in order to make the diamino compound contain 0.1 to 10 mol% of silicon diamine represented by the general formula, silicon atoms derived from the silicon diamine are introduced into the resulting polyimide film. As a result, the produced polyimide film is firmly bonded to the metal foil. As a result, during the formation of a circuit pattern on a polyimide-metal foil composite film, floating and peeling phenomena of the conductor do not occur, and the occurrence of defects caused by these is significantly reduced.

The composite film obtained by the method of this invention has the polyimide film and the metal foil firmly bonded together as described above, and substantially does not curl, so it can be used as a substrate for producing electric circuit boards. It also has the advantage of being easy to handle during circuit processing.Furthermore, the resulting electrical circuit board has the characteristic that it is less prone to curling due to temperature changes, and in this respect, it has the advantage of being easy to handle during circuit processing. It has excellent stability. Specific examples of applications of this composite film include substrates for solar cells used under severe temperature change conditions, substrates for hybrid l-ICs, and heat collector plates for solar water heaters. There are many applications.

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] 20.2 g of DDEP (0°0
95 mol) and bis(3
-aminopropyl)tetramethyldisilo I
1.24 g (0,005 mol) of xane and N
-Methyl-2-pyrrolidone (hereinafter abbreviated as rNMPJ) 2
10 g was added and mixed to dissolve the diamine.

Next, while stirring this system, 3.3°, 4,4゛ −
Biphenyltetracarboxylic dianhydride 29.4g (0,
1 mol) was added gradually. During this time, the temperature of the reaction system was 30
It was cooled with ice water so that the temperature did not exceed ℃. Thereafter, the mixture was stirred for 2 hours to obtain an NMP melt of polyamic acid having a concentration of 19.5% by weight (hereinafter abbreviated as "%"). The logarithmic viscosity of this polyamic acid (30 with a degree of 0.5 g/100 mj in NMP)
℃) was 1.83. Further, the viscosity of this NMP melt was 3510 poise (30°C).

This NMP solution of polyamic acid was heated in advance to reduce the viscosity to 1.
000 poise or less, and cast this 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 measuring 30 cffi length x 20 cm width. 30 at 150℃
The mixture was heated at 200°C for 60 minutes, and further heated at 280°C for 2 hours. Thereafter, it was cooled to room temperature, and the fixation of the copper foil was released to obtain a polyimide-metal foil composite film. The resulting polyimide-copper foil composite film had a polyimide coating thickness of 25 μm, a radius of curvature of 75 cm, and was substantially curl-free.

In addition, the 90" peel strength between the polyimide film and the copper foil in this composite film is 2.20 kg/10 fl under normal conditions, and the 90 degree peel strength after immersing it in a 260°C solder bath for 30 seconds is 2.161 qr/Low. there were.

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 between 50 and 250°C was 1.68x1.
0-', l'i, which was almost equal to the average linear expansion coefficient (1,60×10-'h) of copper foil in the same temperature range.

[Comparative Example 1] In place of DDBP in Example 1, 20.0 g (0.1 mol) of 4.4'-diaminodiphenyl ether was used. Other than that, the procedure was the same as in Example 1 to obtain an NMP solution of polyamic acid having a concentration of 19.0%. The logarithmic viscosity of this polyamic acid (measured at 30 °C at a concentration of 0.5 g/100 m in NMP) was 2.12, and the viscosity of this NMP solution was 2.040 voids (at 30 °C). .

This N M P /8 solution of polyamic acid was placed on a 35 μm thick copper foil (the dimensions are the same as the glass plate) fixed in the same manner as in Example 1 on a glass plate of the same size as in Example 1. The copper foil was cast by the same means as in Example 1, heated under the same conditions as in Example 1, and then cooled to room temperature to release 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 0.8 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-')'C, which was larger than the average linear expansion coefficient of copper foil in the same temperature range. Furthermore, the 90° peel strength between the polyimide film and copper foil was measured and was 1.0.
The weight was 5 kg/10x■, which was a somewhat insufficient value for an electric circuit board.

[Examples 2 to 5] NMP and the diamino compounds shown in Table 1 below were placed in a 500mj+ flask to dissolve the diamino compounds.

In this case, the amount of NMP used was set so that the concentration of the diamino compound and the aromatic tetracarboxylic acid compound to be described later was 15%.

Next, the aromatic tetracarboxylic acid compounds shown in Table 1 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 1 (at a concentration of 0.5 g/100 ml in NMP is 30
An NMP solution of polyimide acid was obtained.

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.
It was cast onto a foil (same dimensions as the glass plate, thickness as shown in Table 1) using the same method as in Example 1, heated at 150°C for 30 minutes, at 200°C for 60 minutes, and then at 300°C for 2 hours. Heated. 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 metal foil composite film were as shown in Table 1. In addition, 5% of the polyimide film in this composite film was measured by TMA.
Table 1 also shows the difference in average coefficient of linear expansion at 0 to 250°C and the 90' peel strength in normal conditions between the polyimide film and the copper foil.

[Comparative Examples 2 to 5] Using the diamine compounds and aromatic tetracarboxylic acid compounds shown in Table 1, the first
An NMP solution of polyimide acid having the logarithmic viscosity shown in the table (measured at 30° C. at a concentration of 0.5 g/100 mj+ in NMP) was obtained.

Using this NMP solution of polyamic acid, the above Example 2
A polyimide-metal foil composite film was produced in the same manner as in 5. The radius of curvature of this composite film, the thickness of the copper foil and polyimide film, and the 50-2
Table 1 shows the difference between the average linear expansion coefficient of the polyimide film and the average linear expansion coefficient of the copper foil at 50°C, and also shows the 90° peel strength between the polyimide film and the copper foil in normal conditions. Ta.

(Left below) In Table 1, DADE is 4,4'-diaminodiphenyl ether, DADM is 4,4'-diaminodiphenylmethane, (a) and (f) are silicon-based diamines with the above structural formula, and 5-BPDA is 4,4'-diaminodiphenyl ether. 3,3”, 4.4
'-Biphenyltetracarboxylic dianhydride, PMD
A is pyromellitic dianhydride, BTDA is 3. 3'
, 4. It shows 4'-benzophenonetetracarboxylic dianhydride.

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 can be obtained in which the polyimide film and the copper foil are firmly bonded and virtually curl-free.

[Brief explanation of the drawing]

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

Claims (5)

[Claims] (1) 80 to 99.9 mol% of component (A) below and (
B) A step of preparing an organic polar solvent solution of a polyimide precursor obtained by reacting a diamino compound containing 0.1 to 10 mol% of component with a tetracarboxylic acid compound whose main component is component (C) below. and a step of applying an organic polar solvent solution of the polyimide precursor onto a metal foil, and heating the metal foil coated with the organic polar solvent solution of the polyimide precursor in a fixed state to heat the foil surface of the metal foil. 1. A method for producing a polyimide-metal foil composite film, comprising the step of forming a polyimide thin film. (A) 3,3'-dimethyl-4,4'-diaminobiphenyl (B) General formula ▲ Numerical formulas, chemical formulas, tables, etc. are available ▼ [In the formula, R_1 is a methylene group, phenylene group or substituted phenylene group, R_2 is methylene group, phenyl group or substituted phenyl group; ] Silicon-based diamine represented by. (C) At least one of 3,3',4,4'-biphenyltetracarboxylic dianhydride and its derivatives. (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 .