JPS6298792A - Flexible printed circuit substrate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an improved flexible printed circuit board (hereinafter abbreviated as FPC). More specifically, polyester (hereinafter referred to as liquid crystal polyester) is a polyester that forms an optically anisotropic melt on an insulating substrate that has extremely high strength isotropically due to excellent plane orientation, and has excellent dimensional stability and soldering heat resistance. This invention relates to FPC using a film (abbreviated as ).

[Conventional technology and its problems] In recent years, supported by the deep-rooted need for smaller and lighter electronic devices, it is lighter and occupies a smaller area than normal rigid types, and allows for free three-dimensional wiring and simplified wiring. FPC
The demand for is increasing rapidly.

Conventionally, a polyimide film having high heat resistance and excellent mechanical strength has been put into practical use as a base film for FPC, but its manufacturing process is quite complicated and its cost is high, so its range of use has been significantly narrowed.

Polyester, which forms an optically anisotropic melt called liquid crystal polyester, has particularly excellent crystallinity, a high melting point, and a rigid molecular structure, so it has heat resistance and high mechanical strength, and has attracted particular attention in recent years. It is a polymeric material. %, it is an extremely promising material as an FPC material because of its high melting point and excellent strength and soldering heat resistance.

However, conventional liquid crystal polyester films have high strength and structural anisotropy, and the machine axis direction (hereinafter referred to as M
The tensile performance, for example, mechanical strength and Young's modulus in the D force direction (abbreviated) are strong, but the mechanical strength and Young's modulus in the width direction perpendicular to this (hereinafter, TD force direction abbreviated) are extremely weak, making it easy to tear. Even if this film is used as an FPC, only a product that cannot withstand practical use is obtained. Furthermore, when the solder bath was exposed to +i, undesirable phenomena such as film shrinkage, curling, and dimensional changes were observed.

Therefore, as a method for manufacturing a film that does not cause the above-mentioned drawbacks, a method is employed in which the film is simultaneously cast and stretched in the 241111 direction using the inflation method (Japanese Unexamined Patent Application Publication No. 56-46728).
(No. Publication) has been studied and reported.

However, even in this method, under conditions where the stretching ratios in the MD force direction and TD force direction are equal as shown in the examples of the publication, only a film that is excessively oriented in the MD force direction compared to the TD force direction can be obtained. The resulting films suffer from the same drawback of mechanical tensile stability of irregular ζ lances.

Furthermore, in order to improve such drawbacks, a method of applying shear stress to the molten polyester extruded from the die in a direction perpendicular to the discharge direction at the slit part, that is, a method of rotating the outer ring die in the inflation method. (
JP-A No. 56-2127) has also been proposed, but this method requires a complicated device and the resulting film solidifies without sufficiently eliminating the liquid crystal domains, making it difficult to mechanically The tensile properties are not very large, and the properties are not sufficient.

In addition, the liquid crystalline polyester films obtained by these methods have low elongation at break, probably due to the linearity of the polyester molecules, and have low resistance to crushing, so they are extremely susceptible to tearing, and are extremely susceptible to tearing in the MD force direction. It also has the disadvantage of being easily torn in the TD force direction, and as mentioned above, F
This was extremely inconvenient for use as a PC.

"Objective of the present invention/Problems to be solved" The purpose of the present invention is to improve the above-mentioned drawbacks of the conventional film obtained from polyester that forms an optically anisotropic melt, to provide high strength and high Young's modulus. FPC, which is made of polyester film with excellent tear resistance, has high strength and Young's modulus in both MD and TD, and has excellent dimensional stability.
It provides:

"Means for Solving Problems" The present invention is a polyester film that is made of polyester that forms an optically anisotropic melt and has approximately isotropic tensile performance, and has a tear propagation resistance of 100 g/mm or more. To provide a flexible printed wiring board, which is formed by using an insulating substrate as an insulating substrate, and applying IfrN to at least one side of the film.

In the present invention, the polyester 1 that forms optical anisotropy has the property of transmitting light in an optical system equipped with a polarizer crossed at 900 in a melted state in a flowable temperature range, that is, a softening point or higher. means polyester. Such polyesters include (1) one or more units of aromatic dicarboxylic acid, alicyclic dicarboxylic acid, aromatic diol, ring diol, aliphatic dicarboxylic acid, and alicyclic dicarboxylic acid;
Consisting of one or more units of diol, (2
) Those consisting of one type or two or more types of aromatic oxycarboxylic acid units, and (31) those consisting of units of (1) and units of (2) are mentioned.

Here, the aromatic dicarboxylic acids include terephthalic acid,
11.4'-) Phenylenedicardic acid, 4゜4'-
triphenindicardonic acid, 2,6-naphthalene dicarboxylic acid, diphenyl ether-4,4'-dicarboxylic acid, diphenoxyethane-4,4'-,)carboxylic acid,
・Diphenoxybutane-4,4'-dicarboxylic acid, diphenylethane-4,4'-dicarboxylic acid, isophthalic acid, diphenylnyf-3,3'-dicarzeneic acid, diphenylethane-3,3'-,9carzene acids, aromatic carboxylic acids such as naphthalene, -1,6-, dicarboxylic acids, chlorterephthalic acid, dichloroterephthalic acid, bromiterephthalic acid, methylterephthalic acid,
Dimethyl terephthalic acid, ethyl terephthalic acid, methoxy 7
Examples include terephthalic acid, ethoxyterephthalic acid, and alkyl, alkoxy, or halogen-substituted derivatives of the above-mentioned aromatic dicarboxylic acids.

Examples of ring group dicarboxylic acids include ring group dicarboxylic acids such as trans-1,4-cyclohexanedicarboxylic acid and cis-1,4-cyclohexanedicarboxylic acid. 4-
Examples include alkyl, alkoxy, or halogen-substituted derivatives of the above-mentioned ring group dicarzenic acids, such as (1-methyl)cyclohexanedicarzenic acid and trans-1,4-(1-chloro)cyclohexanedicarzenic acid.

Aromatic diols include hydroquinone, resorcinol, 4-4'-dioxydiphenyl, 4-4'-2oxytriphenyl, 2,6-naphthalenediol, 44
) oxy, diphenyl ether, bis(4-oxyphenoxy)ethane, 3.3'-dioxydiphenyl, 3.3'-dioxydiphenyl ether, 1,6-naphthalenediol, 2.2-bis(4-hydroxyphenyl) Aromatic diols such as furonocane, 2,2-bis(4-hydroxyphenyl)methane, or chlorhydroquinone, methylhydroquinone, t-butylhydroquinone, phenylhydroquinone, methoxyhydroquinone, phenoxyhydroquinone, 4-chlorresorcin, Examples include alkyl, alkoxy or halogen substituted products of the above aromatic diols such as 4-methylresorcinol.

Examples of ring diols include trans-1,4-cyclohexanediol, cis-1,4-cyclohexanediol, trans-1,4-cyclohexane dimetatool,
Ring group diols such as cis-1,4-7 chlorohegisanedimethanol, trans-1,3-cyclohexanediol, cis-1,2-cyclo-\xanol, trans-1,3-cyclohexanedimetatool, or ,
Examples include trans-1,4-(1-methyl)cyclohexanediol and trans-1,4-(1-chloro)cyclohexanediol, and alkyl, alkoxy or halogen substituted products of the above aliphatic diols.

As the aliphatic diol, ethylene glycol, 1.3
- Straight chain or branched aliphatic diols such as propane diol, 1,4-butane, diol, neopentyl glycol and the like can be mentioned.

Aromatic oxycarboxylic acids include p-hydroquinebenzoic acid, m-hydroxybenzoic acid, 6-hydroxy/-2-
Aromatic oxycarboxylic acids such as naphthoic acid, 6-hydroxy-1-naphthoic acid, 3-methyl-4-hydroxybenzoic acid, 3-chloro-4-hydroxybenzoic acid,
Examples include alkyl, alkoxy or halogen substituted products of the above aromatic oxycarboxylic acids such as 3-methoxy-4-hydroxybenzoic acid.

Polyesters composed of one unit of each of the monomers (1) to (3) above may or may not form an optically anisotropic melt depending on the constituent units, the composition ratio in the polymer, and sequence distribution. However, among the polyesters mentioned above, the polyesters used in the present invention are limited to those that form optically anisotropic melts.

Further, the above polyester may be further copolymerized with a polysubstituted aromatic compound within a range that does not inhibit the formation of an optically anisotropic melt.

Examples of polysubstituted aromatic compounds include benzene-1,3゜5-
Aromatic carbenoic acids such as tricargenic acid, benzene-1,2,4,5-tetracardoic acid, and naphthalene-1,4,5,8-tetracardoic acid, and their alkyl, alkoxy, and can give.

Used in the present invention. l Realester has a softening point of 130-4
Preferably in the range of 00°C, 180-350°C
It is more preferable that it be within the range of .

To determine the softening point, the film is sandwiched between Katzu glasses and heated at a heating rate of 30°C/min while being observed with a polarizing microscope on a hot stage. shall be.

Preferred polyesters used in the present invention include (1)
At least one unit selected from the following units: terephthalic acid, diphenyl ether-4,4'-dicarzenic acid, diphenoxyethane-4,4'-,9carzenic acid, and 2,6-naphthaleneccarzenic acid. and hydroquinone, chlorohydroquinone, methylhydroquinone,
A copolyester comprising at least one unit selected from methoxyhydroquinone units.

(2) Terephthalic acid, diphenyl ether-4,4
'-dicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, and at least one unit selected from 2,6-naphthalene dicarboxylic acid units, and each of hydroquinone, methylhydroquinone, and methoxyhydroquinone. A copolyester composed of at least one unit selected from among the units and p-hydroxybenzoic acid.

(3) f-phthalic acid, diphenyl ether-4,4
'-2carzenic acid, diphenoxyethani/-4,4'-
1) At least one unit selected from carboxylic acid and 2,6-naphthalene dicarboxylic acid units, and at least one unit selected from hydroquinone, chlorohydroquinone, methylhydroquinone, and methoxyhydroquinone. A copolyester comprising seed units, ethylene glycol units, and p-hydroxybenzoic acid units.

(4) f-phthalic acid, diphenyl ether-4,4
'-dicarboxylic acid, diphenoxyethane-4,4'-dicarginic acid, and at least one unit selected from the units of 2,6-natutaledicarginic acid, hydroquinone, methylhydroquinone A copolyester comprising at least one unit selected from , methoxyhydroquinone units, and ethylene glycol units.

(5) f-phthalic acid, diphenyl ether-4,4
'-dicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, and 2,6-naphthalene dicarboxylic acid units, an ethylene glycol unit, and p-hydroxybenzoic acid. A copolyester composed of acid units.

etc. can be mentioned.

The polyester used in the present invention can be produced by a known method from dicarboxylic acids, diols, oxycarboxylic acids, derivatives thereof, etc. corresponding to the above-mentioned structural units.

For example, (1) mixing and heating at least one selected from aromatic dicarboxylic acids and aliphatic dicarboxylic acids and at least one selected from aromatic diols and aliphatic diols such as ethyl acetate; A method of stirring and performing acetic acid removal polycondensation reaction. (2) At least 1fI selected from aromatic, ) cardanic acid and aliphatic dicarboxylic acid, and at least one selected from aromatic diol and acetate ester of) aliphatic,) A method in which oxycarboxylic acid and acetate are mixed, heated, and stirred to perform acetic acid depolycondensation reaction. (3) mixing at least one selected from aromatic dicarboxylic acid and phenyl ester of cardanic acid and at least one selected from aromatic diol and aliphatic diol;
A method of heating and stirring to perform a phenol-free polycondensation reaction.

(4) At least one selected from aromatic dicarboxylic acids and phenyl esters of aliphatic dicarboxylic acids, at least one selected from aromatic diols and aliphatic diols, and aromatic oxycardoic acids. A method in which phenyl esters are mixed, heated, and stirred to perform a phenol-free polycondensation reaction. (5) A polyester obtained by ordinary melt polycondensation from at least 14 selected from aromatic dicarboxylic acids and aliphatic carboxylic acids and an aliphatic diol, such as polyethylene phthalate, polybutylene terephthalate, poly(ethylene- 1,2-bis-diphenoxyethane-1)l p'-dicarxylate)
(a) mixing at least one selected from aromatic dicarboxylic acids and alicyclic dicarboxylic acids and at least one selected from acetic esters of aromatic diols and ring diols; A method of heating and stirring to perform acidolysis reaction and deacetic acid polycondensation reaction. (bl) A method in which aromatic oxene dicarboxylic acid acetate is mixed, heated, and stirred to perform acidolysis reaction and acetic acid removal polycondensation reaction. At least one Φ, at least one selected from the acetate esters of aromatic diols and ring diols, and the acetate ester of aromatic oxycarboxylic acid are mixed, heated, and stirred to perform an acidolysis reaction and a desorption reaction. It can be produced by a method such as carrying out an acetic acid polycondensation reaction.

The polycondensation reaction is usually carried out at a temperature range of 150 to 400°C and at normal pressure to
It is carried out in the molten state at a pressure range of 0.01 torr, and in the final stage of the reaction, a pressure of 10 torr is applied.
It is carried out under reduced pressure of ˜0.01 torr.

Further, a polycondensation catalyst of Sb and Ge compounds, a stabilizer such as a phosphorus compound, a coloring agent, an antioxidant, etc. can be added at any time from the start to the end of the reaction, if necessary.

In the film used in the present invention, the die temperature during film formation is equal to or higher than the softening point of the stream ester, preferably higher than the softening point by filO°C or more and equal to or lower than 400°C.

In forming the film used in the present invention, the preferred apparent viscosity (η., is 20～
It is in the range of 1oooo voices. This apparent viscosity depends on the degree of polymerization, temperature, and shear rate of the polyester, but if η□ is low, the resulting film will have poor mechanical properties, and if it is too high, the stringability of the melt will decrease. It becomes difficult to increase the stretching ratio and it becomes difficult to obtain a uniform film.

Here, the apparent viscosity is given by the following formula (1), and the shear rate is given by the following formula (2), and is determined by measurement using a Koka type flow tester.

η□=πPr' /8LQ == (1) γ□=4Q
/πr ・・・・・・(2) Q: Discharge amount [-/sec] L2 nozzle length [α] P: Pressure loss when extruding through the nozzle [dyne (d y
n cap]r: radius of nozzle [α] In order to obtain the film used in the present invention, a polyester that forms an optically anisotropic melt as a film before heat treatment has excellent strength not only in the MD force direction but also in the TD force direction. It is essential to use a film having a Young's modulus of , that is, a uniform tensile performance.

Here, approximately equal tensile performance means that when the film is tensile tested as described above, the MD force direction breaking strength and the TD
This means that the ratio of the strength at break in the force direction is close to 1, specifically in the range of 0.8 to 1.25. Similarly, regarding the Young's modulus, it is preferable that the ratio of the Young's modulus in the MD force direction to the Young's modulus in the TD force direction is in the range of 0.8 to 1.25.

In the film used in the present invention, the polyester film having almost uniform tensile properties obtained by K is further reduced in pressure and the softening point is lowered from a temperature 100°C lower than the softening point under fc'' or an inert gas atmosphere. Preferably, the heat treatment is carried out at a temperature in the range up to .

The film used in the present invention may be heat-treated under no tension or while being stretched by 2% or less, preferably 1% or less using a biaxial film stretching machine, heated stretching roll, metal frame with a large coefficient of thermal expansion, etc. However, it is not preferable to carry out the process under such high tension that structural destruction of the film occurs.

In addition, in order to prevent the polyester from decomposing due to oxygen, heat treatment is performed under reduced pressure of 10 torr or less or with N2 at an oxygen concentration of 5% or less, preferably 2% or less.
．． It is preferable to carry out under an inert gas atmosphere such as Ar.

The heat treatment temperature should be in the range from 100°C below the softening point of the film to the softening point, but it is more preferable to range from 40°C below the softening point to the softening point. Since the softening point of the film usually increases as the heat treatment progresses, the heat treatment temperature can also be increased stepwise.

The heat treatment temperature can be carried out within a range of several seconds to about 24 hours, but from an industrial practical standpoint, it is preferable that the heat treatment be as short as possible.

IJO during heat treatment? Furnace A (temperature, 10 torr)
A commonly used electric furnace can be used as is, as long as it can guarantee a reduced pressure below or an inert gas atmosphere with an oxygen concentration of 5 inches or below, or if it is an oven made specifically for heat treatment. Both Nototsuchi type and continuous type are one of them! Needless to say, you can use it.

Further, the heating means is not limited to an electric heater, but any type of heater, dielectric heating, etc. can be used as long as a desired temperature can be maintained.

The heat treatment may be carried out with a heat treatment accelerator such as KCI or KI attached to the film, or may be carried out without attachment.

Furthermore, the heat treatment rate can be increased by attaching a polyfunctional epoxy compound as reported in JP-A-59-163479.

By using the liquid crystal polyester film obtained by the above method as an insulating substrate, for the first time, it has extremely high mechanical strength in both the MD force direction and the TD force direction, which is the object of the present invention, and also has excellent soldering heat resistance. , F with dimensional stability
You can get a PC. However, in order to fully demonstrate the performance of this substrate film, it is necessary to pay sufficient attention when laminating copper.

The method of laminating copper for the body is to glue electrolytic steel foil or rolled copper foil together using an adhesive with excellent heat resistance! ! This method is generally used. The selection of adhesive and the bonding method are important points.

That is, suitable examples of the adhesive include polyimide compounds and epoxy compounds that have excellent heat resistance. Adhesives are generally applied in the form of a solution, and when selecting a solvent, it is of course possible to dissolve the adhesive, but it must not attack the base film. In this respect, liquid crystal polyester film is not affected at all by almost all of these solvents and can be said to be an optimal base film.

"Actions and Effects of the Invention" Conventional liquid crystal polyester films, such as JP-A-56-
The films obtained in JP-A No. 46728 and JP-A No. 56-2127 have high strength and high Young's modulus in the MD force direction, but are anonymous films with low these properties in the TD force direction. However, it still has low elongation and is extremely easy to tear, making K used as FPc extremely inconvenient.

On the other hand, the film used as the base material of the FPC of the present invention is
It has excellent mechanical properties in both the MD and TD directions, and by heat treatment, it has more than twice the elongation and more than twice the tear propagation resistance than before heat treatment without losing its high breaking strength and high Young's modulus. In addition, it has a low moisture content, good heat resistance, and good humidity dimensional stability.
Extremely excellent as a base material for PCs.

The FPC of the present invention has good mechanical properties supported by the liquid crystal polyester film as a Luhes film with the above-mentioned excellent properties, and has various properties required for FPc, such as solder heat resistance. It exhibits excellent properties in terms of hardness, thermal dimensional stability, flexibility, chemical resistance, and electrical properties.

"Examples" The present invention will be described in more detail below with reference to Examples. It will be readily understood by those skilled in the art that the components, proportions, order of operations, etc. shown herein may be changed without departing from the spirit of the invention.

Therefore, the invention should not be limited to the following examples.

Example 1 Biphenol diacetate + 62 g (o, 6 mol), terephthalic acid 50 g (0,3 mol), isophthalic acid sog
(o3 mol), p-acetoquine benzoic acid 324 g (1,
8 mol) was charged into a polymerization reactor equipped with a stirrer and a pressure reducing device, and while stirring in a nitrogen stream, the temperature was raised to 330°C for 60 minutes, and the pressure was gradually reduced over 5'5+ to 1. The reaction was carried out for 60 minutes at Thor. After the reaction is complete,
After introducing nitrogen and returning the system to normal pressure, the polyester melt was taken out, allowed to cool naturally to solidify, and then crushed using a crusher.

The softening point of the obtained polyester film was 300°C, and the melt viscosity at 320°C was 3187 poise at a shear rate of 58000 sec-1.

This polyester was heated at 340℃ with a diameter of 5 mm and a slit width of 0.
．． The tubular film was extruded through a 25 m annular slit at a speed of 267 cm/min, nitrogen was injected into the hollow part of the tubular film to expand the diameter by 8.2 times, and the tubular film was wound up at a speed of 370 tM/min.

The obtained film was a glossy film with a thickness of 22 μm, where the TD force direction stretch ratio was 59 times that of the MD force direction stretch ratio, and the MD force direction tensile strength, Young's modulus, and elongation were each 20.3 K9. /rrn2.996 2.3.5% between K97, TD force direction tensile strength, Young's modulus, and groaning index are each 19.2 Kq/ws2.863 Kq/m2.
It had a tensile strength of 4.1 inches.

Next, this film was stretched by 0.5% for 7 days in a high temperature dryer at 260°C with an oxygen concentration of 0.4 while flowing nitrogen gas.
The sample was heat-treated for 10 minutes.

The obtained film had MD force direction tensile strength, Young's modulus,
The elongation is 2z9Fg/Y2.982Kv/Easy 2.
5.6%, TD force direction tensile strength, Young's modulus, and elongation are respectively 20.2 K9/K2, s 2 Kq/K2.
7.4ch and MD.

The tear propagation resistance in the TD force direction was 6 before heat treatment.
0 g/wn and 60 g/mm, but after heat treatment they were 220 g/mm and 290 g/m, respectively, which was excellent not only in tensile strength and Young's modulus but also in elongation and tear propagation resistance. Met.

The above film and 35 μm electrolytic steel foil were heat-pressed at 280° C. using an adhesive represented by the following structural formula.

Table 1 shows the characteristics of the FPC thus obtained.

Example 2 293 g (1,6 mol) of p-acetoxybenzoic acid, 6-
Acetoxy-2-naphthoic acid s, ig (o, z mol),
168 g (0.6 mol) of biphenol diacetate, 103 g (0.6 mol) of terephthalic acid, a stirrer,
It was charged into a polymerization reactor equipped with a pressure reduction device, and heated to 330CK in 60 minutes while stirring in a nitrogen stream.
The pressure was gradually reduced over a period of minutes, and the reaction was carried out at 1 torr for 60 minutes. After the reaction was completed, nitrogen was introduced to return the system to normal pressure, and the polyester melt was taken out, allowed to cool naturally to solidify, and then pulverized using a crusher.

The softening point of the obtained polyester film was 305°C, and the melt viscosity at 320°C was 27 poise at a shear rate of 50,000 sec-1.

This polyester was heated to 340°C with a diameter of 5 cm and a slit width of 0.
．． It is extruded through a 25m+ annular slit at a speed of 267c111/min, and nitrogen is injected into the hollow part of the tubular film to expand the diameter of the tubular film 8.9 times to 420cr.
It was wound up at a speed of n/min.

The obtained film is a glossy film with a thickness of 18 μm and a TD force direction stretching ratio of 5.6 times that of MD force direction stretching ratio, and MD force direction tensile strength, Young's modulus, and elongation of 27. .5 Kg/1m2.1103 to 9/
The tensile strength in the TD force direction, Young's modulus, and elongation are each 24.9K/-1974K9/S2.6
．． It had a tensile strength of 8.

Next, this film was heat-treated in a high-temperature dryer at 260° C. with an oxygen concentration of 0.4 while flowing nitrogen gas while being stretched by 0.5 inch.

The obtained film had MD force direction tensile strength, Young's modulus,
The elongation is 30.2 Kg/mn2.976 K9
/fTrM2.8.3%, TD force direction tensile strength, Young's modulus, and elongation are each 26.7 Kq/=2.892 K
rt/w is 2.8.6%, and the tear propagation resistance in the MD and TD force directions is 50 g/an and 6 before heat treatment, respectively.
The tensile strength was 0 g/ran, but after heat treatment, the tensile strength was 180 g/wn and 220 g/yra, respectively.
It was excellent not only in Young's modulus but also in elongation and tear propagation resistance.

Table 1 shows the properties of F''PC obtained by using the above film and a 35μ electrolytic copper foil in the following structure.

Comparative Example 1 The polyester obtained in 1 was heated to 340°C and made into an annular slit with a diameter of 5 cm and a slit width of 0.25+n (F) 267 cn.
The tubular film was extruded at a speed of T/min, nitrogen was pressurized into the hollow part of the tubular film, the diameter of the tubular film was expanded to 2 times the diameter at about 2 degrees below the die, and the film was wound up at a speed of 600σ/min.

The obtained film was a glossy film with a thickness of 21 μm, where the TD force direction stretching ratio was 13 times that of the MD force direction stretching ratio, and the MD force direction tensile strength, Young's modulus, and elongation were each 53.8 Kq/ 2.1867 to 9/m+”
, 5.1 Chi, TD force direction tensile strength, Young's modulus, and elongation are each 9.3 Kq/bu 2.464 and 4/fu 2.7.1
% and the MD force direction have very good tensile properties, but the TD force direction shows an uncharted film with extremely poor tensile properties.

Next, this film was heat-treated in a high-temperature dryer at 260°C with an oxygen concentration of 0.4% while flowing nitrogen gas, and was stretched by 0.5 times.The resulting film had a tensile strength in the MD force direction, Young's modulus,
The elongation is 59.6 Kt)7mm2.1832 9/2.64%, and the TD force direction tensile strength, Young's modulus, and elongation are 9.4Ka/wn2.458Kq/B2.
The tear propagation resistance in the MD and TD force directions was 10 g/rtan and 50 g/rtan, respectively, before heat treatment.
rm, but after heat treatment it was 10g/w, respectively.
, 60 g/rum.

Although this film was easily torn in the MD force direction and difficult to handle, it was made into an FPC by laminating copper in the same manner as in Example 1. However, when this FPC was immersed in a 260° C. solder bath and pulled up, it curled and could not be used as an FPC.

As shown in the examples above, the FPC of the present invention has an extremely smooth balance in the MD force direction and TD force direction, and also has a liquid crystal ester film as a base film that has high strength and Young's modulus not found in commercially available films. In addition, it exhibits excellent mechanical properties in many respects, such as soldering heat resistance, thermal dimensional stability, willowability, chemical resistance, and electrical properties. Demonstrates unique characteristics.

(Hereafter (3)

Claims (1)

[Claims] An insulating substrate is a polyester film that is made of polyester that forms an optically anisotropic melt and has approximately isotropic tensile performance and has a tear propagation resistance of 100 g/mm or more. Flexible printed wiring board made of laminated copper