TW202027985A - Polyimide Film - Google Patents

Abstract

The present invention provides a polyimide film, a laminated polyimide film and a flexible copper-clad laminate, which are excellent in a dielectric property and a solvent-resistant property. <1> A solvent-insoluble polyimide film obtained by using a dimer diamine in an amount of more than 15 mol% and less than 50 mol% with respect to all of diamine component. <2> A laminated polyimide film comprising the solvent-insoluble polyimide film and a non-thermoplastic polyimide film. <3> A flexible copper-clad laminate comprising the laminated polyimide film and a copper foil.

Description

Polyimide film

The present invention relates to a polyimide (PI) film used for high-frequency substrates and the like with excellent dielectric properties (permittivity and loss tangent), heat resistance, dimensional stability, and electrical properties. High frequency substrates are used for printed circuits or antenna substrates for high frequency bands.

The flexible copper foil laminate (FCCL) used for high frequency substrates such as printed circuits or antenna substrates for high frequency bands is effective for improving the dielectric properties (permittivity and loss tangent) of the insulating layer formed on the copper foil. As such FCCL for high frequency substrates, Patent Document 1 discloses that a copolymerized PI film using 1 to 15 mol% dimer diamine (hereinafter sometimes referred to as "DDA") as the diamine component is formed on copper foil The FCCL. However, when the copolymerized PI film disclosed here is used as an insulating layer of FCCL for high-frequency substrates, there is a problem that it is difficult to ensure good dielectric properties.

On the other hand, Patent Documents 2 to 7 disclose copolymerized PI films that use a larger amount of DDA as a diamine component. However, although the copolymerized PI film disclosed here has excellent dielectric properties, it is solvent-soluble PI. Therefore, it has a problem of insufficient solvent resistance when used as an insulating layer of FCCL for high-frequency substrates. In addition, in a copolymerized PI film using a relatively large amount of DDA, the coefficient of linear expansion (CTE) may increase. When used as an insulating layer of FCCL for high frequency substrates, there is a problem that it is difficult to ensure good dimensional stability.

[Prior Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent No. 6422437

[Patent Document 2] Japanese Patent Application Publication No. 2018-140544

[Patent Document 3] Japanese Patent Publication No. 2015-526561

[Patent Document 4] Japanese Patent Laid-Open No. 2018-168369

[Patent Document 5] Japanese Patent Laid-Open No. 2018-168370

[Patent Document 6] Japanese Patent Laid-Open No. 2018-168371

[Patent Document 7] Japanese Patent Laid-Open No. 2018-170417

The present invention solves the above-mentioned problems and aims to provide a PI film that has good dielectric properties, excellent solvent resistance, and dimensional stability, which can be used in FCCL for high-frequency substrates.

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

The present invention has the following contents as the gist.

<1> A solvent-insoluble PI film using dimer diamine exceeding 15 mol% and less than 50 mol% relative to the total diamine component.

<2> A laminated film comprising the aforementioned solvent-insoluble PI film and a non-thermoplastic PI film.

<3> An FCCL including the above-mentioned laminated PI film and copper foil.

The PI film of the present invention has excellent dielectric properties and solvent resistance. Therefore, it can be preferably used as a PI film constituting an insulating layer of FCCL for high-frequency substrates used in printed circuits, antenna substrates, and the like.

Hereinafter, the present invention will be explained in detail.

The PI film of the present invention (hereinafter sometimes referred to as "PI-1 layer") needs to contain PI that uses more than 15 mol% and less than 50 mol% of DDA relative to the total diamine components. It is 16 mol% or more and 40 mol% or less.

In addition, the PI-1 layer needs to be solvent-insoluble. Here, the solvent insolubility means that the solubility to N-methyl-2-pyrrolidone (NMP) at 20°C is less than 5 mass%. The PI may be thermoplastic or non-thermoplastic.

The PI-1 layer can be dried by coating a polyamide acid (PAA-1) solution containing more than 15 mol% and less than 50 mol% of DDA relative to the total diamine component on the substrate , Thermal curing (imidization) to obtain. Here, DDA is an aliphatic diamine derived from a dimer acid with a carbon number of 24 to 48. "Priamine 1074, Priamine 1075" (trade names manufactured by Croda Japan), "Versamine 551, Versamine 552" (Cognis Commercial products such as trade names manufactured by Japan.

For example, the PAA-1 solution can be used in a nitrogen-containing polar solvent with approximately equal moles of tetracarboxylic dianhydride and diamine (including more than 15 mole% and less than 50 mole% DDA and more than 50 mole% and The mixture of "other diamines" (less than 85 mol%) is prepared in a roughly equal molar manner, and polymerized at 10~70°C to obtain an optically uniform solution.

As the nitrogen-containing polar solvent, an amide-based solvent and a urea-based solvent are preferred. Examples of amide-based solvents include N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide, and N,N-dimethylacetamide (DMAc). Examples of urea-based solvents include tetramethylurea and dimethylethylene urea. The nitrogen-containing polar solvent may be used alone or in combination of two or more kinds. Among them, DMAc and NMP are preferred.

Specific examples of tetracarboxylic dianhydride include: pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,3,3' ,4'-Biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 4,4'-oxydiphthalic dianhydride (ODPA ), 3,3',4,4'-diphenyl tetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA), 2,2- Tetracarboxylic dianhydride such as bis[4-(3,4-dicarboxyphenoxy)phenyl]malonic anhydride (BPADA). These can be used individually or in combination of 2 or more types. In order to make PI that is solvent-insoluble, among these, BPDA, PMDA, and 6FDA are preferred.

Specific examples of the above-mentioned "other diamines" 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'-diaminodiphenyl Benzene, 4,4,-diaminodiphenylsulfide, 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]sulfonate, bis[4 -(3-Aminophenoxy)phenyl]sulfur, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane and other diamines. These can be used individually or in combination of 2 or more types. In order to make PI that is solvent-insoluble, among these, PDA, DMDB, and ODA are preferred.

In order to further improve the dimensional stability of the PI-1 layer, fillers can be formulated in the PAA-1 solution.

Examples of fillers include carbonates such as talc, calcined clay, uncalcined clay, mica, glass, titanium oxide, aluminum, boehmite, silica, calcium carbonate, magnesium carbonate, and hydromagnesium carbonate; aluminum hydroxide, hydrogen Magnesium oxide, 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, titanium Strontium acid, barium titanate, etc. These fillers may be used alone or in combination of two or more kinds. Among them, silicon oxide with excellent dielectric properties is preferred.

The average particle diameter of the filler is preferably 0.05 μm or more and 5.0 μm or less, more preferably 0.1 μm or more and 2.0 μm or less. The average particle size of the filler can be measured by a laser diffraction particle size distribution measuring device on a volume basis, and the median particle size (D50) 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 more preferably 40% by mass or more and 70.0% by mass or less relative to the mass of PI-1 of the formulated filler.

The PI-1 layer can be obtained by the following method, for example.

That is, by first coating the PAA-1 solution on the substrate and drying at 100~200℃, the formed PAA-1 film can be thermally cured at a temperature above 200℃ (thermal imidization) And get. The thickness of the PI-1 layer is not limited, but it is preferably 1 μm or more and 150 μm or less.

As the dielectric properties of the PI-1 layer, the permittivity (Dk) at 10 GHz is preferably 3.2 or less, and more preferably 3.1 or less. Furthermore, it is preferable to set the loss tangent (Df) at 10 GHz to 0.004 or less, more preferably to 0.003 or less. Set up It can ensure good dielectric properties when used as a laminated film.

The laminated PI film including the PI-1 layer is, for example, non-thermoplastic and can be obtained by integrating a PI film with excellent dimensional stability (hereinafter sometimes referred to as "PI-2 layer") and a PI-1 laminated layer.

From the viewpoint of ensuring the rigidity of the laminated film, the tensile modulus of elasticity of the PI-2 layer is preferably 3 GPa or more, and more preferably 5 GPa or more. Here, the tensile modulus of elasticity uses a value measured in the tensile mode based on JIS K7161. Furthermore, from the viewpoint of ensuring the dimensional stability of the laminated film, the CTE of the PI-2 layer is preferably set to 20 ppm/K or less, more preferably 10 ppm/K or less.

The polyamide acid (PAA-2) solution used to form the PI-2 layer, for example, can be formulated in a nitrogen-containing polar solvent in such a way that tetracarboxylic dianhydride and diamine become roughly equimolar, and the temperature is 10~70℃ Then, it is polymerized and obtained as an optically uniform solution.

Here, as the nitrogen-containing polar solvent, the above-mentioned nitrogen-containing polar solvent can be used, and DMAc and NMP are preferred.

As the tetracarboxylic dianhydride, the above-mentioned tetracarboxylic dianhydride can be used, and BPDA, PMDA, and 6FDA are preferred.

As the diamine, the aforementioned "other diamines" can be used, and PDA, DMDB, BAPP, ODA, and PFMB are preferred. The diamine used here is a diamine that does not contain DDA, but it can be used in combination as long as it is about 5 mol% or less with respect to the total diamine components. In terms of ensuring the high rigidity and low CTE of the PI-2 layer, this method is better.

Furthermore, in order to make the PI of the PI-2 layer non-thermoplastic, it is only necessary to appropriately select the combination of the above-mentioned tetracarboxylic dianhydride and diamine. Here, non-thermoplastic PI refers to PI that does not melt or soften even if heated at a temperature below 350°C. In addition, non-thermoplastic PI is usually solvent-insoluble, that is, it exhibits good solvent resistance.

The laminated PI film can be obtained by the following method, for example.

That is, first coat the PAA-2 solution on the substrate and dry it at 100~200℃, then apply the PAA-1 solution on the formed PAA-2 film and dry it at 100~200℃ to form PAA- 1. After that, the two films are thermally cured (thermal imidization) at a temperature above 200°C.

Thereby, a PI-1 layer can be formed on the surface of the PI-2 layer formed on the substrate, and a laminated film with excellent adhesion between the PI-2 layer and the PI-1 layer can be made. The PI-2 layer can be further formed on the PI-1 layer. In addition, the coating sequence can be reversed, and a PI-2 layer can be formed on the surface of the PI-1 layer, or a PI-1 layer can be further formed on the PI-2 layer.

The substrate used here is not limited, and known substrates such as glass plates and copper foils can be used. In the case of using copper foil as the base material, it can be made into a single panel with FCCL formed with a laminated PI thin film layer (insulating layer) including a PI-1 layer and a PI-2 layer. In addition, it can also be made into FCCL with two panels with copper foil on both surfaces of the insulating layer. In this case, what is necessary is just to use an adhesive agent, such as PI, to thermocompression-bond the single panels. As the adhesive, it is preferable to use thermoplastic PI with low permittivity. The thickness of the copper foil is not limited, and it is preferably 5 μm or more and 20 μm or less, and the copper foil can be subjected to chemical or physical surface treatment. Examples of chemical surface treatments include plating treatments such as nickel plating, copper-zinc alloy plating, and treatments with surface treatment agents such as aluminum alkoxides, aluminum chelate compounds, and silane coupling agents. Among them, preferred are Surface treatment with silane coupling agent. As the silane coupling agent, a silane coupling agent having an amine group is preferably used. On the other hand, as physical surface treatment, roughening treatment and the like can be mentioned.

As the PI-2 layer, commercially available PI films such as "Kapton" (trade name manufactured by Toray DuPont) and "Upilex" (trade name manufactured by Ube Industries) can also be used.

These PI films contain non-thermoplastic PI.

In the case of using these PI films as the PI-2 layer, as long as the PAA-1 solution is coated on the PI film, and after drying, it is thermally cured to form a PI-1 layer on the PI-2 layer.

In order to improve the adhesion of the PI films to the PI-1 layer, chemical or physical surface treatments can be implemented. Examples of chemical surface treatments include surface treatments with silane coupling agents, aluminum alcoholates, and the like. On the other hand, as a physical surface treatment, roughening treatment, plasma treatment, etc. are mentioned.

The total thickness of the laminated film including the PI-1 layer and the PI-2 layer is not limited, but it can preferably be 5 μm or more and 200 μm or less.

In addition, the thickness ratio of the PI-1 layer to the PI-2 layer is not limited, but the thickness of the PI-1 layer can preferably be set to 10 to 80% of the entire laminated film, more preferably 30 to 70%.

As the dielectric properties of the laminated film of the present invention, the permittivity (Dk) at 10 GHz can be preferably set to 3.3 or less, more preferably 3.2 or less. And it is preferable to set the loss tangent (Df) at 10 GHz to 0.005 or less, more preferably 0.004 or less. This can ensure good dielectric properties when the laminated film is used as the insulating layer of the FCCL for high-frequency substrates.

In addition, the CTE of the laminated film of the present invention is preferably set to 40 ppm/K or less, more preferably set to 30 ppm/K or less.

This can ensure good dimensional stability when the laminated film is used as the insulating layer of the FCCL for high-frequency substrates.

[Example]

The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. Furthermore, in the following examples and comparative examples, the measurement of characteristic values Methods as below.

<Dielectric Properties>

Using the fully dried film as a sample, a disc resonator was fabricated on one side, and a network analyzer (manufactured by Agilent Technologies) was used to measure the permittivity (Dk) and loss tangent (Df) at 10 GHz. The measurement was performed 3 times on the same sample, and the average value was used as the measurement value.

<CTE>

A fully dried film was used as a sample, and a thermomechanical characteristic analyzer (TMA, TMA2940 manufactured by TA Instrument) was used to measure the temperature at a constant rate of 5°C/min and a tensile mode of 30mN in nitrogen to increase the temperature from 20°C And calculate the dimensional change between 100℃ and 250℃.

<Example 1>

Add PDA as a diamine component to a glass reaction vessel under nitrogen atmosphere: 0.42 mol, DDA ("Priamine 1075" manufactured by Croda Japan Co., Ltd., molecular weight: 549): 0.18 mol, as tetracarboxylic dianhydride Composition BPDA: 0.6 mol, NMP as a solvent, and reacted at 60°C for 3 hours with stirring, thereby obtaining a uniform PAA-1 solution with a solid concentration of 18% by mass.

The PAA-1 solution was coated on the glass plate so that the thickness of the cured PI-1 layer became 20μm, and then dried at 130°C for 20 minutes in a nitrogen atmosphere, thereby forming PAA-1 on the copper foil The envelope.

The film obtained in this way was slowly heated in a nitrogen atmosphere, and then treated at 350° C. for 60 minutes for thermal curing, thereby converting 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.

The properties of the obtained PI film were measured according to the above-mentioned method, and the results are shown in Table 1. In addition, the case where the obtained PI film is solvent-insoluble is marked as "○", and the case where the obtained PI film is soluble is marked as "×".

<Example 2>

Except that the diamine composition in the PAA-1 solution was set to PDA: 0.45 mol and DDA: 0.15 mol, the PI film (A-2) was obtained in the same manner as in Example 1. The properties of the obtained PI film are shown in Table 1.

<Example 3>

Except for setting the diamine composition in the PAA-1 solution to PDA: 0.36 mol and DDA: 0.24 mol, the PI film (A-3) was obtained in the same manner as in Example 1. The properties of the obtained PI film are shown in Table 1.

<Example 4>

Except for setting the diamine composition in the PAA-1 solution to PDA: 0.50 mol and DDA: 0.10 mol, the PI film (A-4) was obtained in the same manner as in Example 1. The properties of the obtained PI film are shown in Table 1.

<Example 5>

The composition of the tetracarboxylic dianhydride in the PAA-1 solution was set to BPDA: 0.48 mol and PMDA: 0.12 mol, except that the PI film (A-5) was obtained in the same manner as in Example 1. The properties of the obtained PI film are shown in Table 1.

<Example 6>

The diamine composition in the PAA-1 solution is set to PDA: 0.45 mol, DDA: 0.15 mol, the tetracarboxylic dianhydride composition is set to BPDA: 0.48 mol, 6FDA: 0.12 mol, in addition to The PI film (A-6) was obtained in the same manner as in Example 1. The properties of the obtained PI film are shown in Table 1.

<Example 7>

The diamine composition in the PAA-1 solution is set to PDA: 0.48 mol, DDA: 0.12 mol, and the tetracarboxylic dianhydride composition is set to BPDA: 0.48 mol, PMDA: 0.12 mol, in addition to The PI film (A-7) was obtained in the same manner as in Example 1. The properties of the obtained PI film are shown in Table 1.

<Example 8>

Except for setting the diamine composition in the PAA-1 solution to DMDB: 0.42 mol and DDA: 0.18 mol, the PI film (A-8) was obtained in the same manner as in Example 1. The properties of the obtained PI film are shown in Table 1.

<Comparative Example 1>

Except that the diamine in the PAA-1 solution was set to PDA: 0.60 mol, a PI film (B-1) was obtained in the same manner as in Example 1. The properties of the obtained PI film are shown in Table 1.

<Comparative Example 2>

Except that the diamine composition in the PAA-1 solution was set to PDA: 0.54 mol and DDA: 0.06 mol, the PI film (B-2) was obtained in the same manner as in Example 1. The properties of the obtained PI film are shown in Table 1.

<Comparative Example 3>

Except for setting the diamine composition in the PAA-1 solution to DMDB: 0.54 mol and DDA: 0.06 mol, the PI film (B-3) was obtained in the same manner as in Example 1. The properties of the obtained PI film are shown in Table 1.

<Comparative Example 4>

The diamine composition in the PAA-1 solution was set to ODA: 0.3 mol, DDA: 0.3 mol, and tetracarboxylic dianhydride was set to BPADA, except that the PI film was obtained in the same manner as in Example 1 ( B-4). The properties of the obtained PI film are shown in Table 1.

<Comparative Example 5>

The diamine composition in the PAA-1 solution was set to ODA: 0.3 mol, DDA: 0.3 mol, and tetracarboxylic dianhydride was set to ODPA, except that the PI film was obtained in the same manner as in Example 1 ( B-5). The properties of the obtained PI film are shown in Table 1.

[Table 1]

As shown in Table 1, it can be seen that the PI films A-1 to A-8 obtained by the present invention obtained in the examples ensure good dielectric properties and are solvent-insoluble. In contrast, it can be seen that the PI films obtained in Comparative Examples 1 to 3 are solvent-insoluble, but have poor dielectric properties. In addition, it can be seen that the PI films obtained in Comparative Examples 4 and 5 have good dielectric properties, but are solvent-soluble and have insufficient solvent resistance.

<Example 9>

Add PDA as a diamine component: 0.48 mol, ODA: 0.12 mol, BPDA as a tetracarboxylic dianhydride component: 0.6 mol, and NMP as a solvent to a glass reaction vessel under a nitrogen atmosphere, and stir The reaction was carried out at 60° C. for 3 hours, thereby obtaining a uniform PPA-2 solution with a solid concentration of 18% by mass.

Coat the PAA-2 solution on a copper foil with a thickness of 18μm so that the thickness of the hardened PI-2 layer becomes 5μm, and then dry it at 130°C for 20 minutes in a nitrogen atmosphere, thereby forming PAA on the copper foil -2 of the film. Next, the PAA-2 film was coated with the layer obtained in Example 1 so that the thickness of the cured PI-1 layer became 15 μm The PAA-1 solution was then dried under a nitrogen atmosphere at 130° C. for 20 minutes, thereby forming a PAA-1 film on the PAA-2 film. Furthermore, the PAA-2 solution was coated on the PAA-1 film so that the thickness of the cured PI-2 layer became 5μm, and then dried under a nitrogen atmosphere at 130°C for 20 minutes, thereby, the PAA-1 A PAA-2 film is formed on the film.

The 3-layer laminate film obtained in this way is slowly heated in a nitrogen atmosphere, and then treated at 350°C for 60 minutes for thermal curing, thereby converting PAA-1 and PAA-2 into PI, and obtaining it on copper foil A laminate of PI-2 layer, PI-1 layer, and PI-2 layer is sequentially formed on the top. The copper foil was removed by etching from the laminate, thereby obtaining a laminate film (L-1) containing three layers of PI. Table 1 shows the characteristics of the obtained laminated PI film.

On the other hand, the PAA-2 solution is applied to the glass plate so that the thickness of the cured PI-2 layer becomes 10μm, and it is dried and thermally cured under the same conditions as the above conditions to obtain a PI-2 film , The PI-2 film was peeled from the glass plate to obtain a PI-2 film. The film is non-thermoplastic and its CTE is 16.5 ppm/K.

<Example 10>

Add DMDB as a diamine component: 0.6 mol, BPDA as a tetracarboxylic dianhydride component: 0.6 mol, and NMP as a solvent to a glass reaction vessel under a nitrogen atmosphere, and react with stirring at 60°C For 3 hours, a uniform PAA-2 solution with a solid content concentration of 18% by mass was obtained.

The PAA-2 solution was coated on a copper foil with a thickness of 18μm so that the thickness of the hardened PI-2 layer became 4μm, and then dried at 130°C in a nitrogen atmosphere for 20 minutes, thereby forming PAA- on the copper foil 2 of the film. Next, the PAA-2 film was coated with the layer obtained in Example 1 so that the thickness of the cured PI-1 layer became 18 μm The PAA-1 solution was then dried under a nitrogen atmosphere at 130° C. for 20 minutes, thereby forming a PAA-1 film on the PAA-2 film. Furthermore, the PAA-2 solution was coated on the PAA-1 film so that the thickness of the cured PI-2 layer became 4μm, and then dried at 130°C in a nitrogen atmosphere for 20 minutes, thereby, the PAA-1 film A PAA-2 film is formed on it.

The three-layer laminated film obtained in this way is slowly heated in a nitrogen atmosphere, and then treated at 350°C for 60 minutes for thermal curing, thereby converting PAA-1 and PAA-2 into PI, and obtaining copper A laminate of PI-2 layer, PI-1 layer, and PI-2 layer is sequentially formed on the foil. The copper foil was etched and removed from the laminate to obtain a laminate film (L-2) containing three layers of PI. Table 1 shows the characteristics of the obtained laminated PI film.

On the other hand, the PAA-2 solution is applied to the glass plate so that the thickness of the cured PI-2 layer becomes 10μm, and it is dried and thermally cured under the same conditions as the above conditions to obtain a PI-2 film , The PI-2 film was peeled from the glass plate to obtain a PI-2 film. The film is non-thermoplastic and its CTE is 8.3 ppm/K.

[Table 2]

As shown in Table 2, it can be seen that the laminated PI film obtained by the present invention exhibits good dielectric properties.

In addition, it can be seen that since the CTE is as low as 30 ppm or less, dimensional stability is good.

(Industrial availability)

The PI film of the present invention has excellent dielectric properties, solvent resistance and dimensional stability. Therefore, it can be preferably used as a PI film constituting an insulating layer of FCCL for high-frequency substrates used in printed circuits, antenna substrates, and the like.

Claims (3)

A solvent-insoluble polyimide film that uses more than 15 mol% and less than 50 mol% of dimeric diamine relative to the total diamine component. A laminated polyimide film includes the solvent-insoluble polyimide film and the non-thermoplastic polyimide film. A flexible copper foil laminated board comprising the above-mentioned laminated polyimide film and copper foil.