JP7095880B2 - Polyimide film - Google Patents

Description

The present invention relates to a polyimide (PI) film used for a high frequency substrate or the like having excellent dielectric properties (dielectric constant and dielectric loss tangent), heat resistance, dimensional stability, electrical properties, and the like. The high frequency board is used for a printed circuit for a high frequency band, an antenna board, and the like.

In a flexible copper-clad laminate (FCCL) for a high-frequency substrate used for a printed circuit for a high-frequency band, an antenna substrate, etc., the dielectric properties (dielectric constant and dielectric loss tangent) of the insulating layer formed on the copper foil are improved. Is effective. As such an FCCL for a high-frequency substrate, Patent Document 1 describes a copolymerized PI film using 1 to 15 mol% of diaminediamine (hereinafter, may be abbreviated as "DDA") as a diamine component on a copper foil. The FCCL formed in is proposed. However, the copolymerized PI film disclosed here has a problem that it is difficult to secure good dielectric properties when used as an insulating layer of FCCL for a high frequency substrate.
On the other hand, Patent Documents 2 to 7 propose a copolymerized PI film using a relatively large amount of DDA as a diamine component. However, although the copolymerized PI film disclosed here is excellent in dielectric properties, it is a PI that is soluble in a solvent, so that there is a problem that solvent resistance is insufficient when it is used as an insulating layer of FCCL for a high frequency substrate. was there. Further, in a copolymerized PI film using a relatively large amount of DDA, the coefficient of linear expansion (CTE) may increase, and it is difficult to secure good dimensional stability when used as an insulating layer of FCCL for a high frequency substrate. There was a problem.

Japanese Patent No. 6242437 Japanese Unexamined Patent Publication No. 2018-140544 Japanese Patent Publication No. 2015-526561 Japanese Unexamined Patent Publication No. 2018-168369 Japanese Unexamined Patent Publication No. 2018-168370 Japanese Unexamined Patent Publication No. 2018-168371 JP-A-2018-170417

The present invention solves the above problems, and an object of the present invention is to provide a PI film that can be used for an FCCL for a high-frequency substrate, which has good dielectric properties, solvent resistance, and dimensional stability.

As a result of diligent research to solve the above-mentioned problems, it was found that the above-mentioned problems can be solved by using a specific PI film using DDA as a diamine component, and the present invention has been reached.

The main object of the present invention is as follows.
<1> A solvent-insoluble PI film using more than 15 mol% and less than 50 mol% of diaminediamine with respect to the total diamine component.
<2> A laminated film composed of the solvent-insoluble PI film and a non-thermoplastic PI film.
<3> FCCL composed of the laminated PI film and copper foil.

The PI film of the present invention is excellent in dielectric properties and solvent resistance. Therefore, it can be suitably used as a PI film constituting an insulating layer of FCCL for a high frequency substrate used for a printed circuit, an antenna substrate, or the like.

Hereinafter, the present invention will be described in detail.
The PI film of the present invention (hereinafter, may be abbreviated as "PI-1 layer") needs to consist of PI using DDA in an amount of more than 15 mol% and less than 50 mol% with respect to the total diamine component. It is preferably 16 mol% or more and 40 mol% or less.
And this PI-1 layer needs to be solvent insoluble. Here, solvent insoluble means that the solubility in N-methyl-2-pyrrolidone (NMP) at 20 ° C. is less than 5% by mass. This PI may be thermoplastic or non-thermoplastic.

For the PI-1 layer, a polyamic acid (PAA-1) solution containing more than 15 mol% and less than 50 mol% of DDA with respect to the total diamine component is applied onto a substrate, dried, and thermoset (imided). Can be obtained by Here, DDA is an aliphatic diamine derived from dimaic acid having 24-48 carbon atoms, and is "Priamine 1074, 1075" (trade name manufactured by Croda Japan), "Versamine 551, 552" (Cognis). Commercially available products such as (trade name) manufactured by Japan Co., Ltd. can be used.

The PAA-1 solution is prepared, for example, in a nitrogen-containing polar solvent with approximately equimolar tetracarboxylic acid dianhydride, diamine (more than 15 mol%, less than 50 mol% DDA, less than 85 mol%, more than 50 mol%). It can be obtained as an optically uniform solution by blending with (a mixture of "other diamines") in substantially equimolar amounts and subjecting them to a polymerization reaction at 10 to 70 ° C.
As the nitrogen-containing polar solvent, an amide-based solvent and a urea-based solvent are preferable. Examples of the amide-based solvent include N-methyl-2-pyrrolidone (NMP), N, N-dimethylformamide, and N, N-dimethylacetamide (DMAc). Examples of the urea-based solvent include tetramethylurea and dimethylethyleneurea. The nitrogen-containing polar solvents may be used alone or in combination of two or more. Of these, DMAc and NMP are preferred.

Specific examples of the tetracarboxylic acid dianhydride include pyromellitic acid dianhydride (PMDA), 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride (BPDA), 2,3,3', 4'-biphenyltetracarboxylic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride (BTDA), 4,4'-oxydiphthalic acid dianhydride (ODPA), 3,3' , 4,4'-Diphenylsulfone tetracarboxylic acid dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic acid dianhydride (6FDA), 2,2-bis [4- (3,4-dicarboxy) Phenoxy) phenyl] Tetracarboxylic acid dianhydrides such as propane dianhydride (BPADA) can be mentioned. These may be used alone or in combination of two or more. Among these, BPDA, PMDA, and 6FDA are preferable to obtain a solvent-insoluble PI.

Specific examples of the "other diamine" include p-phenylenediamine (PDA), 4,4'-diaminodiphenyl ether (ODA), 2,2-bis [4- (4-aminophenoxy) phenyl] propane (BAPP). ), M-Phenylenediamine, 2,4-diaminotoluene, 4,4'-diaminobiphenyl, 4,4'-diamino-2,2'-bis (trifluoromethyl) biphenyl (PFMB), 2,2'- Dimethyl-4,4'-diaminobiphenyl (DMDB), 3,3'-diaminodiphenylsulphon, 4,4'-diaminodiphenylsulphon, 4,4'-diaminodiphenylsulfide, 4,4'-diaminodiphenylmethane, 3, 4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) ) Benzene, 4,4'-bis (4-aminophenoxy) biphenyl, bis [4- (4-aminophenoxy) phenyl] sulphon, bis [4- (3-aminophenoxy) phenyl] sulphon, 2,2-bis [4- (4-Aminophenoxy) phenyl] Diamines such as hexafluoropropane can be mentioned. These may be used alone or in combination of two or more. Among these, PDA, DMDB, and ODA are preferable to obtain a solvent-insoluble PI.

Fila may be added to the PAA-1 solution to further improve the dimensional stability of the PI-1 layer.
Examples of the filler include carbonates such as talc, fired clay, unburned clay, mica, glass, titanium oxide, alumina, boric acid, silica, calcium carbonate, magnesium carbonate, hydrotalcite; aluminum hydroxide, magnesium hydroxide, etc. Calcium hydroxide, barium sulfate, calcium sulfate, calcium sulfite, zinc borate, barium metaborate, aluminum borate, calcium borate, sodium borate, aluminum nitride, boron nitride, silicon nitride, carbon nitride, strontium titanate, titanium Examples thereof include barium acid acid. These fillers may be used alone or in combination of two or more. Among these, silica having excellent dielectric properties is preferable.

The average particle size of the filler is preferably 0.05 μm or more and 5.0 μm or less, and more preferably 0.1 μm or more and 2.0 μm or less. For the average particle size of the filler, for example, the particle size distribution of the particles can be measured on a volume basis by a laser diffraction type particle size distribution measuring device, and the median diameter (D50) thereof can be used as the average particle size.

The content of the filler contained in the PI-1 layer is preferably 30% by mass or more and 85% by mass or less, and 40% by mass or more and 70.0% by mass or less with respect to the PI-1 mass containing the filler. More preferred.

The PI-1 layer can be obtained, for example, by the following method.
That is, it can be obtained by first applying a PAA-1 solution on a substrate, drying at 100 to 200 ° C., and then thermosetting (thermal imidizing) the formed PAA-1 film at a temperature of 200 ° C. or higher. can. The thickness of the PI-1 layer is not limited, but is preferably 1 μm or more and 150 μm or less.

As the dielectric property of the PI-1 layer, the dielectric constant (Dk) at 10 GHz is preferably 3.2 or less, and more preferably 3.1 or less. The dielectric loss tangent (Df) at 10 GHz is preferably 0.004 or less, and more preferably 0.003 or less. By doing so, it is possible to secure good dielectric properties when the laminated film is formed.

The laminated PI film including the PI-1 layer includes, for example, a PI film (hereinafter, may be abbreviated as "PI-2 layer") which is non-thermoplastic and has excellent dimensional stability, and a PI-1 layer. Can be obtained by laminating and integrating.
From the viewpoint of ensuring the rigidity of the laminated film, the tensile elastic modulus of the PI-2 layer is preferably 3 GPa or more, and more preferably 5 GPa or more. Here, as the tensile elastic modulus, a value obtained by measuring the elastic modulus in the tensile mode based on JIS K7161 is used. Further, from the viewpoint of ensuring the dimensional stability of the laminated film, the CTE of the PI-2 layer is preferably 20 ppm / K or less, and more preferably 10 ppm / K or less.

The polyamic acid (PAA-2) solution for forming the PI-2 layer is mixed, for example, in a nitrogen-containing polar solvent so that the tetracarboxylic acid dianhydride and the diamine are substantially equimolar. It can be obtained as an optically uniform solution by polymerizing at 70 ° C.
Here, as the nitrogen-containing polar solvent, the above-mentioned nitrogen-containing polar solvent can be used, and DMAc and NMP are preferable.
As the tetracarboxylic acid dianhydride, the above-mentioned tetracarboxylic acid dianhydride can be used, and BPDA, PMDA, and 6FDA are preferable.
As the diamine, the above-mentioned "other diamine" can be used, and PDA, DMDB, BAPP, ODA, and PFMB are preferable. The diamine used here is a diamine that does not contain DDA, but if it is about 5 mol% or less with respect to the total diamine component, it can be used in combination. This is preferable from the viewpoint of ensuring high rigidity and low CTE of the PI-2 layer.
In order to make the PI of the PI-2 layer non-thermoplastic, the combination of the above-mentioned tetracarboxylic acid dianhydride and diamine may be appropriately selected. Here, the non-thermoplastic PI means a PI that does not melt or soften even when heated at a temperature of 350 ° C. or lower. In addition, the non-thermoplastic PI is usually solvent-insoluble and exhibits good solvent resistance.

The laminated PI film can be obtained, for example, by the following method.
That is, first, the PAA-2 solution is applied on the substrate, dried at 100 to 200 ° C., then the PAA-1 solution is applied on the formed PAA-2 film, dried at 100 to 200 ° C., and then PAA- One film is formed, and then both films are heat-cured (thermal imidized) at a temperature of 200 ° C. or higher.
By doing so, the PI-1 layer is formed on the surface of the PI-2 layer formed on the base material, and a laminated film having excellent adhesion between the PI-2 layer and the PI-1 layer is obtained. be able to. A PI-2 layer may be further formed on the PI-1 layer. Further, the coating order may be reversed to form the PI-2 layer on the surface of the PI-1 layer, or the PI-1 layer may be further formed on the PI-2 layer.

The base material used here is not limited, and known base materials such as glass plates and copper foils can be used. When a copper foil is used as the base material, it can be a single-sided plate of FCCL on which a laminated PI film layer (insulating layer) composed of a PI-1 layer and a PI-2 layer is formed. Further, FCCL of a double-sided plate in which copper foil is arranged on both surfaces of the insulating layer can be used. In this case, the single-sided plates may be thermocompression bonded to each other using an adhesive such as PI. As this adhesive, it is preferable to use a thermoplastic PI having a low dielectric constant. The thickness of the copper foil is not limited, but it is preferably 5 μm or more and 20 μm or less. The copper foil may be chemically or physically surface treated. Examples of the chemical surface treatment include plating treatments such as nickel plating and copper-zinc alloy plating, and treatments with surface treatment agents such as aluminum alcoholate, aluminum chelate, and silane coupling agents. Among them, silane coupling agents are used. Surface treatment is preferred. As the silane coupling agent, a silane coupling agent having an amino group is preferably used. On the other hand, examples of the physical surface treatment include roughening treatment and the like.

As the PI-2 layer, PI films commercially available such as "Kapton" (trade name manufactured by Toray DuPont) and "UPIREX" (trade name manufactured by Ube Kosan Co., Ltd.) can also be used.
These PI films are made of non-thermoplastic PI.
When these PI films are used as the PI-2 layer, the PAA-1 solution may be applied onto the PI film, dried, and then thermoset to form the PI-1 layer on the PI-2 layer. ..
These PI films may be chemically or physically surface-treated to improve their adhesion to the PI-1 layer. Examples of the chemical surface treatment include surface treatment with a silane coupling agent, aluminum alcoholate and the like. On the other hand, examples of the physical surface treatment include roughening treatment, plasma treatment, and the like.

The total thickness of the laminated film composed of the PI-1 layer and the PI-2 layer is not limited, but is preferably 5 μm or more and 200 μm or less.
The thickness ratio between the PI-1 layer and the PI-2 layer is not limited, but the thickness of the PI-1 layer is preferably 10 to 80%, preferably 30 to 70% of the entire laminated film. Is more preferable.

As the dielectric property of the laminated film of the present invention, the dielectric constant (Dk) at 10 GHz is preferably 3.3 or less, and more preferably 3.2 or less. The dielectric loss tangent (Df) at 10 GHz is preferably 0.005 or less, and more preferably 0.004 or less. By doing so, it is possible to secure good dielectric properties when the laminated film is used as an insulating layer of FCCL for a high frequency substrate.
Further, the CTE of the laminated film of the present invention is preferably 40 ppm / K or less, more preferably 30 ppm / K or less.
By doing so, good dimensional stability can be ensured when the laminated film is used as an insulating layer of FCCL for a high frequency substrate.

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In the following examples and comparative examples, the method for measuring the characteristic value is as follows.

<Dielectric property>
Using a sufficiently dried film as a sample, a disk resonator was prepared on one side, and a dielectric constant (Dk) and a dielectric loss tangent (Df) were measured at 10 GHz using a network analyzer (manufactured by Agilent Technologies). The measurement was performed three times for the same sample, and the average value was used as the measured value.

<CTE>
Using a sufficiently dried film as a sample, using a thermomechanical property analyzer (TMA, TMA2940 manufactured by TA Instruments), a constant rate temperature rise of 5 ° C / min and a tension mode of 30 mN from 20 ° C in nitrogen. It was calculated by raising the temperature and measuring the amount of dimensional change between 100 ° C and 250 ° C.

<Example 1>
In a glass reaction vessel, under a nitrogen gas atmosphere, as a diamine component, PDA: 0.42 mol, DDA ("Priamine 1075" manufactured by Croder Japan Co., Ltd., molecular weight: 549): 0.18 mol, tetracarboxylic acid dianhydride BPDA: 0.6 mol as a component and NMP as a solvent were charged and reacted at 60 ° C. for 3 hours with stirring to obtain a uniform PAA-1 solution having a solid content concentration of 18% by mass.
A PAA-1 solution is applied onto a glass plate so that the thickness of the cured PI-1 layer is 20 μm, and then dried in a nitrogen gas atmosphere at 130 ° C. for 20 minutes on a copper foil. A coating of PAA-1 was formed.
The film thus obtained was gradually heated in a nitrogen gas atmosphere, treated at 350 ° C. for 60 minutes, and heat-cured to convert the PAA-1 film into a PI film. After that, the PI film (A-1) was obtained by peeling the PI film from the glass plate.
Various characteristics of the obtained PI film were measured according to the above-mentioned method, and the results are shown in Table 1. When the obtained PI film was solvent-insoluble, it was indicated by "◯", and when it was soluble, it was indicated by "x".

<Example 2>
A PI film (A-2) was obtained in the same manner as in Example 1 except that the diamine composition in the PAA-1 solution was PDA: 0.45 mol and DDA: 0.15 mol. Table 1 shows various characteristics of the obtained PI film.

<Example 3>
A PI film (A-3) was obtained in the same manner as in Example 1 except that the diamine composition in the PAA-1 solution was PDA: 0.36 mol and DDA: 0.24 mol. Table 1 shows various characteristics of the obtained PI film.

<Example 4>
A PI film (A-4) was obtained in the same manner as in Example 1 except that the diamine composition in the PAA-1 solution was PDA: 0.50 mol and DDA: 0.10 mol. Table 1 shows various characteristics of the obtained PI film.

<Example 5>
A PI film (A-5) was obtained in the same manner as in Example 1 except that the composition of the tetracarboxylic acid dianhydride in the PAA-1 solution was BPDA: 0.48 mol and PMDA: 0.12 mol. rice field. Table 1 shows various characteristics of the obtained PI film.

<Example 6>
Except that the diamine composition in the PAA-1 solution was PDA: 0.45 mol and DDA: 0.15 mol, and the tetracarboxylic acid dianhydride composition was BPDA: 0.48 mol and 6FDA: 0.12 mol. Obtained a PI film (A-6) in the same manner as in Example 1. Table 1 shows various characteristics of the obtained PI film.

<Example 7>
Except that the diamine composition in the PAA-1 solution was PDA: 0.48 mol and DDA: 0.12 mol, and the tetracarboxylic acid dianhydride composition was BPDA: 0.48 mol and PMDA: 0.12 mol. Obtained a PI film (A-7) in the same manner as in Example 1. Table 1 shows various characteristics of the obtained PI film.

<Example 8>
A PI film (A-8) was obtained in the same manner as in Example 1 except that the diamine composition in the PAA-1 solution was DMDB: 0.42 mol and DDA: 0.18 mol. Table 1 shows various characteristics of the obtained PI film.

<Comparative Example 1>
A PI film (B-1) was obtained in the same manner as in Example 1 except that the diamine in the PAA-1 solution was PDA: 0.60 mol. Table 1 shows various characteristics of the obtained PI film.

<Comparative Example 2>
A PI film (B-2) was obtained in the same manner as in Example 1 except that the diamine composition in the PAA-1 solution was PDA: 0.54 mol and DDA: 0.06 mol. Table 1 shows various characteristics of the obtained PI film.

<Comparative Example 3>
A PI film (B-3) was obtained in the same manner as in Example 1 except that the diamine composition in the PAA-1 solution was DMDB: 0.54 mol and DDA: 0.06 mol. Table 1 shows various characteristics of the obtained PI film.

<Comparative Example 4>
The PI film (B) was the same as in Example 1 except that the diamine composition in the PAA-1 solution was ODA: 0.3 mol and DDA: 0.3 mol, and the tetracarboxylic acid dianhydride was BPADA. -4) was obtained. Table 1 shows various characteristics of the obtained PI film.

<Comparative Example 5>
The PI film (B) was the same as in Example 1 except that the diamine composition in the PAA-1 solution was ODA: 0.3 mol and DDA: 0.3 mol, and the tetracarboxylic acid dianhydride was ODPA. -5) was obtained. Table 1 shows various characteristics of the obtained PI film.

As shown in Table 1, it can be seen that the PI films A-1 to A-8 according to the present invention obtained in Examples have good dielectric properties and are solvent-insoluble. On the other hand, it can be seen that the PI films obtained in Comparative Examples 1 to 3 are solvent-insoluble but have poor dielectric properties. Further, it can be seen that the PI films obtained in Comparative Examples 4 and 5 have good dielectric properties, but are solvent-soluble and lack solvent resistance.

<Example 9>
In a glass reaction vessel, under a nitrogen gas atmosphere, PDA: 0.48 mol, ODA: 0.12 mol, BPDA: 0.6 mol as a tetracarboxylic acid dianhydride component, and NMP as a solvent were charged. By reacting at 60 ° C. for 3 hours with stirring, a uniform PAA-2 solution having a solid content concentration of 18% by mass was obtained.
A PAA-2 solution is applied onto a copper foil having a thickness of 18 μm so that the thickness of the cured PI-2 layer is 5 μm, and then the copper is dried at 130 ° C. for 20 minutes in a nitrogen gas atmosphere. A PAA-2 film was formed on the foil. Next, the PAA-1 solution obtained in Example 1 was applied onto the PAA-2 coating so that the thickness of the cured PI-1 layer was 15 μm, and then under a nitrogen gas atmosphere. A PAA-1 film was formed on the PAA-2 film by drying at 130 ° C. for 20 minutes. Further, a PAA-2 solution is applied onto the PAA-1 film so that the thickness of the PI-2 layer after curing is 5 μm, and then dried in a nitrogen gas atmosphere at 130 ° C. for 20 minutes. , A PAA-2 film was formed on the PAA-1 film.
The three-layered laminated film thus obtained was gradually heated in a nitrogen gas atmosphere and then heat-cured at 350 ° C. for 60 minutes to convert PAA-1 and PAA-2 into PI. Then, a laminate in which the PI-2 layer, the PI-1 layer, and the PI-2 layer were formed in this order on the copper foil was obtained. By etching and removing the copper foil from this laminated body, a laminated film (L-1) composed of three layers of PI was obtained. Table 1 shows various characteristics of the obtained laminated PI film.
On the other hand, the PI-2 film obtained by applying the PAA-2 solution to a glass plate so that the thickness of the PI-2 layer after curing is 10 μm, drying and heat-curing under the same conditions as described above. Was peeled off from the glass plate to obtain a PI-2 film. This film was non-thermoplastic and its CTE was 16.5 ppm / K.

<Example 10>
In a glass reaction vessel, DMDB: 0.6 mol as a diamine component, BPDA: 0.6 mol as a tetracarboxylic dianhydride component, and NMP as a solvent were charged under a nitrogen gas atmosphere at 60 ° C. under stirring. By reacting for a time, a uniform PAA-2 solution having a solid content concentration of 18% by mass was obtained.
A PAA-2 solution is applied onto a copper foil having a thickness of 18 μm so that the thickness of the cured PI-2 layer is 4 μm, and then the copper is dried at 130 ° C. for 20 minutes in a nitrogen gas atmosphere. A PAA-2 film was formed on the foil. Next, the PAA-1 solution obtained in Example 1 was applied onto the PAA-2 coating so that the thickness of the cured PI-1 layer was 18 μm, and then under a nitrogen gas atmosphere. A PAA-1 film was formed on the PAA-2 film by drying at 130 ° C. for 20 minutes. Further, a PAA-2 solution is applied onto the PAA-1 film so that the thickness of the PI-2 layer after curing is 4 μm, and then dried in a nitrogen gas atmosphere at 130 ° C. for 20 minutes. , A PAA-2 film was formed on the PAA-1 film.
The three-layered laminated film thus obtained was gradually heated in a nitrogen gas atmosphere, treated at 350 ° C. for 60 minutes, and heat-cured to convert PAA-1 and PAA-2 into PI. Then, a laminate in which the PI-2 layer, the PI-1 layer, and the PI-2 layer were formed in this order on the copper foil was obtained. The copper foil was removed by etching from this laminated body to obtain a laminated film (L-2) composed of three layers of PI. Table 1 shows various characteristics of the obtained laminated PI film.
On the other hand, the PI-2 film obtained by applying the PAA-2 solution to a glass plate so that the thickness of the PI-2 layer after curing is 10 μm, drying and heat-curing under the same conditions as described above. Was peeled off from the glass plate to obtain a PI-2 film. This film was non-thermoplastic and its CTE was 8.3 ppm / K.

As shown in Table 2, it can be seen that the laminated PI film according to the present invention exhibits good dielectric properties.
Further, since the CTE is as low as 30 ppm or less, it can be seen that the dimensional stability is good.

The PI film of the present invention is excellent in dielectric properties, solvent resistance, and dimensional stability. Therefore, it can be suitably used as a PI film constituting an insulating layer of FCCL for a high frequency substrate used for a printed circuit, an antenna substrate, or the like.

Claims (3)

A solvent-insoluble polyimide film that satisfies the following 1) and 2).
1) The polyimide is 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride (BPDA), pyromellitic acid dianhydride (PMDA), or 4,4'-(hexafluoroisopropylidene) diphthal. It contains a tetracarboxylic acid dianhydride component selected from acid dianhydride (6FDA) and has at least 80 mol% BPDA relative to the total tetracarboxylic acid dianhydride component.
2) The polyimide contains diaminediamine and p-phenylenediamine (PDA) as diamine components, and the diaminediamine is more than 15 mol% and less than 50 mol% with respect to the total diamine component . The solvent-insoluble polyimide film (PI-1) and the non-thermoplastic polyimide film (PI-2) according to claim 1 are laminated in the order of PI-2, PI-1, PI-2, and have a linear expansion coefficient (PI-2). A laminated polyimide film having a CTE) of 40 ppm / K or less . A flexible copper-clad laminate made of the laminated polyimide film according to claim 2 and a copper foil.