JPH0758428A - Flexible printed board and its manufacture - Google Patents

Abstract

PURPOSE:To provide excellent heatproof and adhesive properties by a method wherein a precursor solution of a specific thermoplastic polyimide polymer is applied to a base film layer to be made imidic, thereafter a conductive layer is superimposed thereon to be heated and pressed. CONSTITUTION:A pre cursor solution of a thermoplastic polyimide polymer represented by the formula is applied to a base film layer composed of polyimide resin in a flexible printed board. Namely, in the formula, Ar1, Ar2, Ar4, and Ar6 denote a divalent organic base and Ar3 and Ar5 denote a quadrivalent organic base. Also, l, m, and n denote a positive integer of 0 or 1 or more and also the sum of l and m is 1 or more and t denotes an integer of 1 or more. The polymer is dried and made imidic, thereafter a conductive layer is superimposed on the obtained thermoplastic polyimide layer, which is heated and pressed and adhered to each other. Thus, an adhesive layer composed of the thermoplastic polyimide polymer is excellent in a heatproof property and also in an adhesive force, and it is possible to bond to each other with enough strength by pressing for a short time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible printed circuit board and a manufacturing method thereof, and more particularly to a flexible printed circuit board using an intermediate layer made of a thermoplastic polyimide polymer and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, electronic devices have been highly functionalized and miniaturized at an extremely high speed, and electronic components used therewith have been required to be miniaturized and lightened. Further, as a wiring board on which electronic parts are mounted, a flexible printed wiring board (FPC) having flexibility is attracting attention as compared with an ordinary hard printed wiring board, and demand is rapidly increasing.

A polyimide film is mainly used as a base film of the copper clad laminate (FCCL) for the FPC, but the structure of the FCCL currently used is a polyimide film and a copper foil made of an acrylic type or an epoxy type. An FCCL having a three-layer structure attached with an adhesive or the like is generally used.

[0004]

However, these adhesives have poor heat resistance and high water absorption. For this reason, the properties such as heat resistance and dimensional stability of the obtained flexible printed circuit board are influenced by the properties of the adhesive, and there are many problems that the properties of the polyimide base film cannot be sufficiently exhibited. It was

Therefore, the present inventors have conducted diligent research with the objective of solving the above-mentioned conventional problems and providing a flexible printed circuit board excellent in heat resistance, workability and adhesiveness, and a manufacturing method thereof. As a result of the repetition, the present invention has been achieved.

[0006]

First, the gist of a flexible printed circuit board according to the present invention is that a base film layer made of a polyimide resin and a compound represented by the general formula (1)

[Chemical 8] (In the formula, Ar ₁ , Ar ₂ , Ar ₄ and Ar ₆ are divalent organic groups, A
r ₃ and Ar ₅ represent a tetravalent organic group. Further, l, m, and n are 0 or a positive integer of 1 or more, and the sum of l and m is 1.
It is above, and t represents a positive integer of 1 or more. ) Is composed of an intermediate layer made of a thermoplastic polyimide polymer and a conductor layer made of a good electrical conductor.

In such a flexible printed circuit board, the general formula (1) representing the thermoplastic polyimide polymer is given.
Ar ₁ inside becomes chemical 9

[Chemical 9] Is at least one selected from the group of divalent organic groups shown in.

Further, in such a flexible printed circuit board, Ar ₂ in the general formula (1) representing the thermoplastic polyimide polymer is

[Chemical 10] At least 1 selected from the group of divalent aromatic groups shown in
It is to be a seed.

Further, in such a flexible printed circuit board, Ar ₃ in the general formula (1) representing the thermoplastic polyimide polymer is

[Chemical 11] At least 1 selected from the group of tetravalent aromatic groups shown in
It is to be a seed.

Further, in such a flexible printed circuit board, Ar ₄ in the general formula (1) representing the thermoplastic polyimide polymer is

[Chemical 12] Is at least one selected from the group of divalent organic groups shown in.

Further, in such a flexible printed circuit board, Ar ₅ in the general formula (1) representing the thermoplastic polyimide polymer is

[Chemical 13] At least 1 selected from the group of tetravalent aromatic groups shown in
It is to be a seed.

Further, in such a flexible printed circuit board, Ar ₆ in the general formula (1) representing the thermoplastic polyimide polymer is

[Chemical 14] At least 1 selected from the group of divalent aromatic groups shown in
It is to be a seed. Next, the gist of the method for producing a flexible printed circuit board according to the present invention is that a precursor film of a thermoplastic polyimide polymer represented by the above general formula (1) is added to a base film layer made of a polyimide resin. Is applied, dried and imidized, and then a conductor layer is superposed on the obtained thermoplastic polyimide layer, and heated and pressed to adhere and laminate.

Another aspect of the method for manufacturing a flexible printed circuit board according to the present invention is that a base film layer made of a polyimide resin and a thermoplastic polyimide polymer represented by the general formula (1) described above. The film consisting of and the conductor layer are sequentially stacked, and then heated and pressed to be adhered and laminated.

[0014]

EXAMPLES Next, examples of the flexible printed circuit board and the manufacturing method thereof according to the present invention will be described.

The method for manufacturing a polyamic acid solution which is a precursor of thermoplastic polyimide used in the present invention, first, argon, in an inert gas atmosphere such as nitrogen, the general formula _{(2) H 2 N-Ar} 7 - A diamine represented by NH ₂ (2) (wherein Ar ₇ represents a divalent organic group) is dissolved or diffused in an organic solvent. In this solution, the compound of the general formula (3) 15

[Chemical 15] (In the formula, Ar ₈ represents a divalent organic group), or only the ester dianhydride represented by the formula (4)

[Chemical 16] (In the formula, Ar ₉ represents a tetravalent organic group.) A mixture with at least one kind of organic tetracarboxylic dianhydride represented by the following is added in the form of a solid or a solution prepared by dissolving it in an organic solvent, A polyamic acid solution that is a precursor of the thermoplastic polyimide can be obtained.

Further, in the method for producing a polyamic acid solution which is a precursor of another thermoplastic polyimide used in the present invention, first, the compound represented by the general formula (5) is prepared in an atmosphere of an inert gas such as argon or nitrogen.

[Chemical 17] (In the formula, Ar ₁₀ represents a divalent organic group.) Only an ester diamine represented by the formula, or a mixture of the ester diamine and at least one diamine represented by the general formula (2) is used as an organic solvent. Dissolve or diffuse in. In this solution, only the ester acid dianhydride represented by the general formula (3), or at least one organic tetracarboxylic acid dianhydride represented by the general formula (4), or these ester acids is used. A mixture of a dianhydride and an organic tetracarboxylic dianhydride can be added in the form of a solution with a solid or an organic solvent to obtain a polyamic acid solution which is a precursor of a thermoplastic polyimide.

In this reaction, contrary to the above, first, the ester dianhydride represented by the general formula (3) or at least one organic tetracarboxylic dianhydride represented by the general formula (4) is used. Or a solution of a mixture of these ester acid dianhydrides and organic tetracarboxylic acid dianhydrides is prepared, and the solution of the ester diamine represented by the general formula (5) or the general formula (2) is prepared in the solution. A solution or slurry of at least one diamine represented by itself or a mixture of the ester diamine and at least one diamine represented by the general formula (2) in a solid or organic solvent may be added.

The reaction temperature at this time is -10 to 50 ° C, more preferably -5 to 20 ° C. The reaction time is 3
It is 0 minutes to 3 hours. By the reaction, the general formula (1)
18

[Chemical 18] Thus, a polyamic acid polymer which is a precursor of the thermoplastic polyimide polymer represented by is produced.

Next, in order to obtain a polyimide polymer from the polyamic acid polymer solution which is the precursor, it is necessary to use a thermal and / or
Alternatively, a method of chemically performing dehydration ring closure may be used.

Explaining by way of example, in the method of thermal dehydration ring closure (imidization), the solution of the polyamic acid polymer is applied onto a support plate, an organic film such as PET, or a support such as a drum or an endless belt. After casting or coating to form a film and drying, a film having self-supporting property is obtained. Drying is preferably performed at a temperature of 150 ° C. or lower for about 5 to 90 minutes. Next, this is further heated and dried to be imidized to obtain a polyimide film made of a thermoplastic polyimide polymer. The temperature during heating is preferably in the range of 150 to 350 ° C, particularly preferably 250 to 300 ° C. There is no limitation on the rate of temperature increase during heating, but it is preferable that the maximum temperature reaches the above temperature by gradually heating. Although the heating time varies depending on the film thickness and the maximum temperature, it is generally preferably in the range of 10 seconds to 10 minutes after the maximum temperature is reached. When heating a self-supporting film,
Peeling off from the support, fixing the ends in this state and heating is preferred because a polymer having a small linear expansion coefficient can be obtained.

The method of chemically dehydrating ring closure (imidization) is the same as the method of thermally dehydrating by adding a stoichiometric or more stoichiometric dehydrating agent and a catalytic amount of a tertiary amine to the solution of the polyamic acid polymer. The desired polyimide polymer can be obtained by treating with the above method.

Comparing the method of thermal imidization and the method of chemical imidation, the chemical method has a higher mechanical strength of polyimide and a smaller coefficient of linear expansion. In general, a chemical method and a thermal method are often used together.

The polyimide polymer represented by the general formula (1) is produced by imidizing the polyamic acid polymer by such a thermal and / or chemical method.

Here, as the ester dianhydride represented by the above general formula (3) used in the present invention, ester dianhydrides having any structure can be used. The Ar ₈ group of is preferably a divalent organic group. A concrete example of this Ar ₈ group is:

[Chemical 19] Can be mentioned. More specifically, in terms of the balance of various characteristics,

[Chemical 20] It is preferable to have as a main component.

As the ester diamine represented by the above general formula (5) used in the present invention, ester diamines having any structure can be used, but the Ar ₁₀ group in the general formula (5) is divalent. It is preferable that the organic group is A concrete example of this Ar ₁₀ is:

[Chemical 21] Can be mentioned. More specifically, from the viewpoint of the balance of various characteristics,

[Chemical formula 22] It is preferable to have as a main component.

As the organic tetracarboxylic dianhydride, organic tetracarboxylic dianhydrides having any structure can be used, but the Ar ₉ group in the above general formula (4) is a tetravalent organic group. Yes, and particularly preferably an aromatic group.
Specific examples of the Ar ₉ group include chemical formulas 23 and 24

[Chemical formula 23]

[Chemical formula 24] Can be mentioned. These organic tetracarboxylic dianhydrides may be used alone or in combination of two or more. More specifically, in terms of the balance of various characteristics,

[Chemical 25] It is preferable that at least one of the above is a main component.

Further, Ar ₇ in the diamine compound represented by the general formula (2) may be essentially any divalent organic group, but an aromatic group is particularly desirable and There are 26 and 27

[Chemical formula 26]

[Chemical 27] Etc., but more specifically,

[Chemical 28] It is preferable that at least one of the above is a main component.

Next, the number of repeating block units l, m, n in the thermoplastic polyimide polymer represented by the general formula (1) is 0 or a positive integer of 1 or more, and l and m are The sum may be 1 or more, but especially the repetition number l,
Both m and n are preferably 15 or less. Because, for the sum of the number of repetitions l and m, the number of repetitions n is 15
This is because if it exceeds twice, the copolymerization ratio is biased and the effect of polymerization is reduced, and specifically, low temperature adhesiveness is difficult to be recognized. Further, in one molecule of the polymer, l, m, n
There may be units with different values of, but especially l,
It is preferable that the values of m and n are constant.

The number of block repetitions t may be a positive integer of 1 or more, and the molecular weight of this polyimide polymer is not particularly limited, but in order to maintain the strength of the produced polyimide polymer. Has a number average molecular weight of 1
10,000 or more is preferable.

It is often difficult to directly measure the molecular weight of a polyimide polymer. In such a case, an indirect method is used to make a speculative measurement. For example, when a polyimide polymer is synthesized from polyamic acid, the value corresponding to the molecular weight of polyamic acid is the molecular weight of polyimide.

Examples of the organic solvent used in the reaction for producing the polyamic acid solution include sulfoxide-based solvents such as dimethyl sulfoxide and diethyl sulfoxide, and N, N-.
Examples thereof include formamide solvents such as dimethylformamide and N, N-diethylformamide, acetamide solvents such as N, N-dimethylacetamide and N, N-diethylacetamide. These may be used alone or as a mixed solvent of two or three or more. Further, it can be used as a mixed solvent with a non-solvent of polyamic acid such as acetone, methanol, ethanol, isopropanol, and benzenemethylcellosolve together with these polar solvents.

The film-like thermoplastic polyimide polymer thus obtained is used in combination with a polyimide film such as Apical (registered trademark: manufactured by Kanegafuchi Chemical Industry Co., Ltd.) and a conductor layer such as a copper foil. The desired flexible printed circuit board is obtained by inserting it in between, stacking it in three layers, and thermocompression bonding. In addition, another method for manufacturing a flexible printed circuit board is, in which a polyamic acid solution, which is a precursor of a thermoplastic polyimide polymer, is cast and applied on a polyimide film, then imidized, and then thermocompression bonded with a conductor layer. You can also get Furthermore, another method for producing a flexible printed circuit board is a polyimide film, a film-shaped thermoplastic polyimide polymer obtained by the method described above, and a release paper is overlaid and thermocompression-bonded, then the release paper is peeled off, and then a conductor layer is formed. It can also be obtained by thermocompression bonding.

The conductor layer used here is
Any conductor such as aluminum, iron, nickel may be used,
Copper foil is particularly preferable. Further, this thermoplastic polyimide polymer is most suitable as an intermediate layer of a flexible printed circuit board, but other uses are not particularly limited.

The flexible printed circuit board of the present invention obtained as described above has excellent heat resistance, processability and low water absorption. In particular, the thermoplastic polyimide polymer used as the intermediate layer of the flexible printed circuit board of the present invention has a composition of 150 ° C to 350 ° C.
By having a clear glass transition point between 0 ° C. and laminating at a temperature close to the glass transition point, the base film made of a polyimide resin and a conductor layer such as a copper foil can be easily bonded. Therefore, the copper clad laminate can be manufactured relatively easily. Further, the thermoplastic polyimide polymer used as the intermediate layer of the flexible printed circuit board of the present invention has a low water absorption rate of about 1% when immersed in pure water at 20 ° C. for 24 hours. An excellent flexible printed circuit board can be provided.

Although the embodiments of the flexible printed circuit board and the method of manufacturing the same according to the present invention have been described above, the present invention is not limited to these embodiments, and the present invention is within the scope of the present invention. Therefore, it can be implemented in various modified, changed, and modified modes based on the knowledge of those skilled in the art.

The present invention will be further described below with reference to examples, but the present invention is not limited to these examples.

Example 1 In a 50 ml volumetric flask (1), 2,2-bis [4- (4-
Aminophenoxy) phenyl] propane (hereinafter, BAP
It is called P. ) 16.9 g and dimethylformamide (hereinafter, referred to as DMF) 25.4 g were taken, stirred with a stirrer and sufficiently dissolved. In another 50 ml volumetric flask (2), 1.0 g of BAPP and 10.0 g of DMF.
Was taken, and similarly melted sufficiently. On the other hand, in a 500 ml three-necked flask equipped with a stirrer, 2,2-bis (4-hydroxyphenyl) propanedibenzoate-2,2 ′, 3
3'-Tetracarboxylic acid dianhydride (hereinafter referred to as ESDA) 29

[Chemical 29] 11.9 g and pyromellitic dianhydride (PMDA) 4.
5 g of DMF and 25.0 g of DMF were added, and the mixture was sufficiently dissolved by cooling with ice water and stirring while replacing the atmosphere in the flask with nitrogen.

Then, 500 ml of the BAPP solution in the 50 ml volumetric flask (1) obtained in advance was stirred while stirring.
Immediately charged into a three-necked flask. After standing for about 30 minutes with stirring, BA in a 50 ml volumetric flask (2)
The PP solution was gradually charged into the three-necked flask while paying attention to the viscosity of the solution in the three-necked flask. After reaching the maximum viscosity, the addition of the BAPP solution in the 50 ml volumetric flask (2) was completed, and the mixture was left for 1 hour with stirring. Then DM
78.2 g of F was added and stirred to obtain a polyamic acid solution.

This polyamic acid solution was applied onto a polyimide film (Kanefuchi Chemical Industry Co., Ltd.) and the temperature was adjusted to 25 at 80 ° C.
After heating for 150 minutes, 150 ℃, 200 ℃, 250 ℃, 30
Each was heated in the order of 0 ° C. for 5 minutes for imidization to obtain a polyimide film having a thermoplastic polyimide polymer layer formed thereon. Further, the surface of the thermoplastic polyimide polymer layer of the obtained polyimide film was overlaid with a copper foil (thickness of 35 μm) and laminated at 300 ° C. at a speed of 2.2 cm / min to obtain a flexible printed board.

In order to investigate the properties of the obtained flexible printed circuit board, the glass transition point (° C.) and water absorption rate (%) of the thermoplastic polyimide polymer, which is the intermediate layer, and the peel strength (kg / cm) of the flexible printed circuit board. ). The glass transition point was examined by TMA, the peel strength was examined by JIS K6481, and the water absorption rate was examined by ASTM D-570. The results are shown in Table 1.
Shown in.

[0041]

[Table 1]

Example 2 1.0 g ESDA and DMF1 in a 50 ml volumetric flask.
0.0 g was taken and sufficiently dissolved by stirring using a stirrer. On the other hand, a 500 ml three-necked flask equipped with a stirrer was used. 3
0

[Chemical 30] 1,2-bis (4-aminobenzyloxyphenyl) propane (hereinafter referred to as BABPP) represented by
2.9 g and DMF 38.7 g were put, and the atmosphere in the 500 ml three-necked flask was agitated while substituting the atmosphere with nitrogen and sufficiently dissolved. Next, add ESDA14.9 to a 100 ml eggplant flask.
g was taken and added as a solid in the BABPP solution. Further, the ESDA remaining on the wall surface of the 100 ml eggplant-shaped flask was poured into a three-necked flask with 37.7 g of DMF. After leaving it for about 1 hour with stirring, 50
The ESDA solution in the ml volumetric flask was gradually charged into the three-necked flask while paying attention to the viscosity of the solution in the three-necked flask. After reaching the maximum viscosity, the addition of the ESDA solution was terminated, and the mixture was allowed to stand with stirring for 1 hour to obtain a polyamic acid solution.

This polyamic acid solution was coated on a PET film, then heated at 80 ° C. for 25 minutes and dried to the extent that it had a self-supporting property. Thereafter, the polyamic acid film was peeled off from the PET film, fixed on a metal support, and then heated at 150 ° C., 200 ° C., 250 ° C., and 300 ° C. for 5 minutes in order to imidize the thermoplastic polyimide polymer. I got a film. Furthermore, a polyimide film (Kanefuchi Chemical Industry Co., Ltd., Apical (registered trademark)), a film of the thermoplastic polyimide polymer obtained above, and a copper foil (35 μm thick) are overlaid, and the temperature is 300 ° C.
A flexible printed circuit board was obtained by laminating at a speed of 2.2 cm / min.

To examine the characteristics of the obtained flexible printed circuit board, the glass transition point (° C.) and water absorption rate (%) of the thermoplastic polyimide polymer and the peel strength of the flexible printed circuit board were measured in the same manner as in Example 1. (k
g / cm). The results are shown in Table 1.

Comparative Example 1 (Intermediate Layer Made of Thermoplastic Polyimide Using BTDA and BAPP) First, in a 50 ml volumetric flask, 3, 3 ',
4,4'-benzophenone tetracarboxylic dianhydride (BTDA) 1.94 g, DMF 30.0
g was taken and melted sufficiently. 500ml with a stirrer
In a three-necked flask, 51.8 g of BAPP and 310.
0 g was taken and stirred while cooling with ice water and while replacing the atmosphere in the three-neck flask with nitrogen. next,
Collect 38.8g of BTDA in a 100ml eggplant flask,
It was added as a solid in the BAPP solution. Furthermore, this 10
1 BTDA remaining on the wall in a 0 ml eggplant flask
Pour into a three necked flask with 0.0 g DMF. After allowing to stand for about 30 minutes with stirring, the BTDA solution in a 50 ml volumetric flask was gradually charged into the three-necked flask while paying attention to the viscosity of the solution in the three-necked flask. After reaching the maximum viscosity, the addition of the BTDA solution was completed, and the mixture was left for 1 hour with stirring. Then, DMF was added so that the sample amount would be 500 g, and the mixture was stirred to obtain a polyamic acid solution.

This polyamic acid solution was applied onto a polyimide film (Kanefuchi Chemical Industry Co., Ltd.) and the temperature was adjusted to 25 at 80 ° C.
After heating for 150 minutes, 150 ℃, 200 ℃, 250 ℃, 30
Each was heated in the order of 0 ° C. for 5 minutes for imidization to obtain a polyimide film having a thermoplastic polyimide layer formed thereon. Further, the surface of the thermoplastic polyimide layer of the obtained polyimide film and a copper foil (thickness of 35 μm) were overlaid, and the conditions were the same as those in Example 1 and Example 2 at 300 ° C. and 2.2 cm.
A flexible printed circuit board was obtained by laminating at a speed of / min.

Regarding the obtained flexible printed circuit board, the glass transition point (° C.) and water absorption rate (%) of the thermoplastic polyimide polymer and the peel strength (kg / cm) of the flexible printed circuit board were obtained in the same manner as in Example 1. I checked about.
The results are shown in Table 1. As shown in Table 1, the copper foil was not adhered.

Comparative Example 2 The polyimide film having the intermediate layer made of the thermoplastic polyimide polymer obtained in Comparative Example 1 was used again,
Laminated with copper foil under different conditions. That is, as a laminating condition, at the same heating temperature of 300 ° C.,
When laminated at a speed of 0.3 cm / min, the copper foil adhered to the thermoplastic polyimide layer.

The peel strength (kg / cm) of the obtained flexible printed circuit board was examined in the same manner as in Example 1. The results are shown in Table 1. As shown in Table 1, the peel strength was 0.3 kg / cm 2, and sufficient strength could not be obtained.

[0050]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, by using the flexible printed circuit board using the thermoplastic polyimide polymer represented by the general formula (1), excellent heat resistance,
Adhesiveness can be realized. That is, since the epoxy adhesive is inferior in heat resistance, the excellent heat resistance of the polyimide film as the base film cannot be utilized. On the other hand, the conventional adhesive made of a thermoplastic polyimide polymer needs to be heated / pressurized for a long time using a press or the like in order to be bonded, and the productivity is very poor,
Moreover, the adhesive strength was low, and sufficient adhesive strength could not be obtained. On the other hand, in the flexible printed circuit board of the present invention, the adhesive layer made of the thermoplastic polyimide polymer represented by the general formula (1) not only has excellent heat resistance,
The adhesive strength is excellent, and since it is possible to bond with sufficient strength by applying pressure for a short time, it is possible to manufacture a flexible printed circuit board with high productivity. Further, it was confirmed that the base film layer made of a polyimide resin and the intermediate layer made of the thermoplastic polyimide polymer represented by the general formula (1) have excellent radiation resistance, and thus the obtained flexible printed circuit board is It can also be used for equipment that may be exposed to radiation.

Claims (9)

[Claims] 1. A base film layer made of a polyimide resin, and a compound represented by the general formula (1): (In the formula, Ar ₁ , Ar ₂ , Ar ₄ and Ar ₆ are divalent organic groups, A
r ₃ and Ar ₅ represent a tetravalent organic group. Further, l, m, and n are 0 or a positive integer of 1 or more, and the sum of l and m is 1.
It is above, and t represents a positive integer of 1 or more. ) A flexible printed circuit board comprising an intermediate layer made of a thermoplastic polyimide polymer represented by the formula (4) and a conductor layer made of a good electrical conductor. 2. Ar ₁ in the general formula (1) representing the thermoplastic polyimide polymer is represented by the following formula: The flexible printed board according to claim 1, wherein the flexible printed board is at least one selected from the group of divalent organic groups shown in. 3. Ar ₂ in the general formula (1) representing the thermoplastic polyimide polymer is represented by the following formula: At least 1 selected from the group of divalent aromatic groups shown in
The flexible printed circuit board according to claim 1 or 2, wherein the flexible printed circuit board is a type. 4. Ar ₃ in the general formula (1) representing the thermoplastic polyimide polymer is represented by the following formula: At least 1 selected from the group of tetravalent aromatic groups shown in
The flexible printed circuit board according to any one of claims 1 to 3, which is a kind. 5. Ar ₄ in the general formula (1) representing the thermoplastic polyimide polymer is represented by the following formula: It is at least 1 sort (s) selected from the group of the bivalent organic group shown in Claim 4, The flexible printed circuit board in any one of Claim 1 thru | or 4. 6. Ar ₅ in the general formula (1) representing the thermoplastic polyimide polymer is represented by the following formula: At least 1 selected from the group of tetravalent aromatic groups shown in
The flexible printed circuit board according to any one of claims 1 to 5, which is a kind. 7. Ar ₆ in the general formula (1) representing the thermoplastic polyimide polymer is represented by the following formula: At least 1 selected from the group of divalent aromatic groups shown in
The flexible printed circuit board according to any one of claims 1 to 6, which is a kind. 8. A base film layer made of a polyimide resin is coated with a precursor solution of a thermoplastic polyimide polymer represented by the general formula (1) according to any one of claims 1 to 7, A method for manufacturing a flexible printed circuit board, which comprises drying and imidizing, and then superposing a conductor layer on the obtained thermoplastic polyimide layer, heating and pressurizing and laminating. 9. A base film layer made of a polyimide resin, a film made of the thermoplastic polyimide polymer represented by the general formula (1) according to any one of claims 1 to 7, and a conductor layer. A method for manufacturing a flexible printed circuit board, which comprises stacking the layers in order and then applying heat and pressure to laminate the layers.