KR20020047088A - Wholly Aromatic Polyamide Fiber Paper and Laminated Sheet Therefrom - Google Patents

Abstract

The present invention provides fibrous paper made of wholly aromatic polyamide fibers formed by liquid crystal spinning. This fiber paper can be used as a substrate of an electric circuit board, and can exhibit high electrical insulation reliability at high humidity, excellent post-heating dimensional stability, and high heat resistance.

Description

Wholly Aromatic Polyamide Fiber Paper and Laminated Sheet Therefrom}

The present invention relates to wholly aromatic polyamide fiber paper comprising wholly aromatic polyamide fibers. This fiber paper can be used to make substrates of electrical circuits. The fibrous paper of the present invention is useful in the field where stringent requirements are placed on electric insulation reliability, dimensional stability, soldering heat resistance and strength at high humidity.

Summary of the Invention

The present invention mainly consists of wholly aromatic polyamide fibers which are formed by spinning from anisotropic polymer solution and can be deionized, have a crystallinity of at least 45%, and have a crystal size (ACS) of at least 50 GPa. To a substrate made of wholly aromatic polyamide fiber paper, characterized in that it has an size (Apparent Crystallinity size) (plane 110).

Omniaromatic polyamide fibers are widely used industrially and in everyday life because of their high strength, high modulus, high heat resistance and other excellent mechanical and thermal properties. Typical examples of such synthetic fibers include polyparaphenylene terephthalamide fibers and polyparaphenylene benzobisoxazole fibers.

An example using para-aromatic polyamide fibers is disclosed in Japanese Patent Application Laid-Open No. 1 [1989] -281790, wherein paraphenylene / oxydiphenylene / terephthalamide copolymer fibers (Teijin Limited) spun from an isotropic solution Ltd.) and Polyparaphenylene / terephthalamide fibers (Toray DuPont Co., Ltd.) formed by air gap spinning from anisotropic polymer solution Aromatic polyamide fiber paper consisting of para-aromatic polyamide fibers such as Kevlar) and an organic resin binder. A method for producing aromatic polyamide fiber paper is disclosed in Japanese Patent Application Laid-Open No. 2 [1990] -203589. The former para-aromatic polyamide fibers, i.e., the copolymers formed by spinning of polymer solutions with ether bonds and not anisotropic, the content of ionic material in the para-aromatic polyamide fibers formed by spinning of the anisotropic polymer solution In spite of being smaller than the content of the ionic substance in the latter para-aromatic polyamide fibers, the fibrous paper made of the former fibers is low in heat resistance and thermally contracted even at a temperature as low as about 200 ° C. Thus, using such fibrous paper as the substrate of the circuit board, the substrate will be deformed while the parts are attached onto the substrate by reflow soldering at high temperatures. In addition, the former fiber has a larger coefficient of radial thermal expansion than the latter fiber formed by spinning of the anisotropic polymer solution. When fiber paper made of the former fiber is used as the substrate of the circuit board, the rate of dimensional change in the direction of the substrate thickness increases, so that the reliability of the through-hole connection for realizing electrical conduction in the thickness direction of the substrate is achieved. Problems with In addition, as described above, an organic thermosetting resin binder is used in combination with the above-mentioned fibers in preparing the fiber paper. Since the glass transition temperature of the resin is much lower than that of para-aromatic polyamide fibers, when the pre-preg made of fiber paper is laminated under heat and pressure as a substrate of an electric circuit board, the resin bonds in the substrate I remelt, making the bonds between the fibers that make up the fiber paper unstable. As a result, significant dimensional change occurs in the laminated substrate.

In order to reduce such dimensional change, Japanese Patent Laid-Open No. 61 [1986] -160500 and US Pat. No. 4,729,921 disclose meta-aromatic polyamide fibrids having high heat resistance instead of the above-described resin binder (US patent). 3,018,091) and para-aromatic polyamide fibers are disclosed. In this case, para-aromatic polyamide fibers, such as homopolymeric para-aromatic polyamide fibers (polyparaphenylene / terephthalamide fibers (Toray DuPont), which have high heat resistance, small dimensional change and spun from anisotropic polymer solutions Preference is given to the use of Kevlar) from the company KK. Fibrous paper made from the polyamide fibers described above has high heat resistance and excellent post-heating dimensional stability. However, this fiber is produced by a spinning method in which the polymer is spun in an acidic anisotropic polymer solution and then neutralized. During the neutralization process, the ionic substances in the fibers turn into salts. The content of salt is typically 0.5 to 1% by weight after spinning, and remains the same even after the fibers have been processed into fibrous paper. Therefore, when such fiber paper is used as a substrate of an electric circuit board, a problem may arise in electrical insulation at high humidity. This is a challenge to solve.

The object of the invention is made of wholly aromatic polyamide fibers formed by spinning of anisotropic polymer solutions; Can be used as a substrate of an electric circuit board; Contains a small amount of ionic material that hardly precipitates; Excellent electrical insulation at high humidity, high heat resistance and high post-heat stability; It is to provide a wholly aromatic polyamide fiber paper, characterized in that the inflection point temperature of the rate of dimensional change of the fiber paper is high.

In order to achieve the above object, the present invention uses an wholly aromatic polyamide fiber formed by spinning of an anisotropic polymer solution and having high heat resistance and excellent dimensional stability. In this case, if spinning is carried out under conditions in which the crystal size of the fiber is smaller than a certain level, the ionic material contained in the fiber can be washed off with water, and thus the fiber can be deionized. The deionized fibers of the present invention can be processed into pulp composed of short fibers or fibrils bonded with a binder having high heat resistance. In this way, the fiber paper can be heat treated at a high temperature. In addition, the degree of crystallinity, heat resistance, dimensional stability and moisture resistance of the fiber paper can be improved. The content of the ionic material and the precipitation of the ionic material can be reduced. The fiber paper of the present invention exhibits excellent electrical insulation in high humidity environments.

All wholly aromatic polyamide fibers formed by spinning of anisotropic polymer solutions can be used in the present invention.

The aromatic polyamide fibers used in the present invention are aromatic polyamides obtained by spinning of anisotropic polymer solutions. Preferred are fibers made of a polymer having a number average molecular weight of 20000 to 25000 and formed by condensation polymerization of paraphenylenediamine and terephthalic acid dichloride. Anisotropic solutions can be spun by conventional air gap spinning methods to form fibers from the polymer. In the case of para-aromatic polyamide fibers, a viscous solution in which the polymer is dissolved in a concentrated sulfuric acid solvent is spun from the spinning nozzle through the air gap and placed in a coagulating bath. In this case, the shear rate when the fiber is discharged from the spinning nozzle is preferably 25000 to 50000 sec ⁻¹ . Immediately after the end of the spinning, the sulfuric acid used as the solvent is neutralized with an aqueous sodium hydroxide solution, and the fibers are washed with water. The fibers are then dried / heat treated at 150-500 ° C. and wound up (US Pat. No. 3,767,756). The crystal size of the fibers thus obtained is usually greater than 50 mm 3 and ranges from 55 to 75 mm 3. In addition, sodium sulfate is present in the fiber as an ionic material during the neutralization process, the content of which is 0.5 to 1.0% by weight during the neutralization process.

In order to use the fibers of the present invention, it is necessary to spin the fibers under suitable drying / heat treatment conditions so that the crystal size is smaller than 50 GPa, preferably within the range of 35 to 45 GPa. If the fiber has a crystal size in the above-described range, even if the ionic material is still present in the fiber, the ionic material can be removed almost entirely from the fiber while the fiber is in contact with water or other liquid. As a result, when the fibers thus obtained are used in an electric circuit board, the electrical insulation at high humidity is improved.

The size of the aromatic polyamide fibers used in the present invention should be from 0.1 to 5 deniers, preferably from 0.3 to 3 deniers, in view of spinnability, cost effectiveness and papermaking properties during the papermaking process. do. If the fiber size is too large, the papermaking property and texture are bad. On the other hand, if the fiber size is too small, it is difficult to spin the fiber and the cost effectiveness is worse.

The length of the short fibers used to prepare the aromatic polyamide fiber paper of the present invention is preferably 1 to 50 mm, or 2 to 14 mm, when the fiber paper is produced by a wet method. If the fiber is too long, it is difficult to disperse the fiber during the papermaking process and the surface texture is not good enough that the fiber paper is used as a high quality substrate of the circuit board. On the other hand, if the fiber is too short, it is difficult to sufficiently interweave the fiber. As a result, the fiber paper strength and other mechanical properties deteriorate.

In the present invention, in view of heat resistance and dimensional stability, it is preferable to use meta-aromatic polyamide fiber as the binder. Examples of meta-aromatic polyamide fibers are copolymers or polymer mixtures consisting of polymethphenylene isophthalamide or predominantly polymethphenylene isophthalamide. Terephthalic acid, paraphenylenediamine and the like may be copolymerized with the meta-aromatic polyamide as tertiary components, but the content of such tertiary components should be 20 mol% or less. In addition to meta-aromatic polyamide fibers, organic resins, in particular thermosetting resins such as epoxy resins, phenol resins and melamine resins, may be added as binder components within a range that does not adversely affect the object of the present invention. It may be.

When para-aromatic polyamide short fibers and meta-aromatic polyamide fibers are used in the production of the aromatic polyamide fiber paper of the present invention, the mixing ratio is based on the total weight of the aromatic polyamide fiber paper, and the para-aromatic polyamide It should be such that the amount of short fibers is 60 to 97% by weight and the amount of meta-aromatic polyamide fiber is 3 to 40% by weight. If the content of meta-aromatic polyamide fiber is too low, the strength of the fiber paper during the papermaking process and heat treatment will be low, and it will be difficult to wind the fiber paper. In addition, para-aromatic polyamide short fibers fall off, causing fluff on the fiber paper surface, which will cause problems with the fiber paper quality. The content of the binder is preferably at least 5% by weight. Meta-aromatic polyamide fibers are softened and expanded at high temperatures during heat treatment to bond with para-aromatic polyamide fibers. However, if the content of the binder is too high, the porosity of the fiber paper will be so low that the resin impregnation will worsen and the quality will be degraded. As a result, the binder content should be 30% by weight or less.

In addition to the para-aromatic polyamide short fibers, copolymer type para-aromatic polyamides such as paraphenylene / 3,4-diphenylene copolymer ether terephthalamide short fibers within a range that does not adversely affect the object of the present invention. Short fibers (Technora, manufactured by Teijin Limited) and polyparaphenylene benzobisoxazole short fibers, glass short fibers, ceramic short fibers, and the like may be added. In this case, the content of this substance should be 45% by weight or less, preferably 35% by weight or less.

Hereafter, a method of making fibrous paper from a wholly aromatic polyamide fiber produced by spinning of an anisotropic polymer solution will be described. First, para-aromatic polyamide short fibers and meta-aromatic polyamide fibers are dispersed in water in the above-described ratio to make a homogeneous papermaking slurry. At this time, the concentration of the fiber in the dispersion is maintained at 0.1 to 1.0% by weight. If the concentration of the fiber is too high, the fiber may not be dispersed well. Flat paper type paper machine, cylinder wire type paper machine, inclined wire type paper machine and the like are used to make fibrous paper from the dispersion. The ionic substance contained in the para-aromatic polyamide short fibers used in the present invention is extracted from the fibers after being ionized when contacted with water. In this way the ionic material is discharged with the water used in the papermaking process and the fibers are deionized. In this step, the content of the ionic material in the short fibers can be reduced to a level of less than 0.5% by weight. In particular, when the content of the ionic material is reduced to less than 0.2% by weight, the fiber paper made of this fiber can exhibit excellent electrical insulation even in a high humidity environment when used as an electric circuit board.

When the aromatic polyamide fibrous paper of the present invention is used as an electric circuit board, it is preferable that the fibrous paper has an influence on the manufacturing process of the substrate and the properties of the substrate, including density and strength. The density of the fiber paper is preferably 0.40 to 0.85 g / cm 3. If the density is too low, it is difficult to achieve high strength. In addition, the dimensional stability is bad. Therefore, the density of the fiber paper is preferably 0.50 g / cm 3 or more. On the other hand, if the density is too high, while the resin-impregnated prepreg is produced, it is difficult for the resin to enter the inside of the fiber paper, which adversely affects the properties of the substrate. Therefore, the density of the fiber paper is preferably 0.75 g / cm 3 or less. The strength of the fiber paper is preferably 1.5 kg / cm or more so that the paper is not easily torn in the resin-impregnation step to be described later.

When using aromatic polyamide fibrous paper having the above-mentioned composition as an electric circuit board, in order for the fibrous paper to exhibit sufficient heat resistance, post-heating dimensional stability and post-humidification stability, these properties of the fibrous paper must be within the aforementioned ranges, respectively. It is necessary to heat-treat and then process the paper properly. For example, a calender machine may be used to process fibrous paper and to control temperature and pressure. In this case, the fiber paper is passed between calender rolls composed of single or multi-stage metal rolls under heat and pressure. When meta-aromatic polyamide fiber is used as the binder, the temperature and pressure for softening the binder are 140 to 400 ° C. and 30 kg / cm or more, respectively. If the temperature and pressure are not kept in the above-mentioned range, fine fiber paper structure cannot be obtained, and the strength of the fiber paper is hard to reach the above-mentioned range. Further, the heat treatment conditions should be appropriately set so that the crystallinity of the aromatic polyamide fiber paper of the present invention is 45 or more and the crystal size (ACS: Apparent Crystallinity Size (plane 110)) is 50 kPa or more. When fiber paper is used as an electric circuit board, it is possible to suppress the ionization of a small amount of ionic material remaining in the aromatic polyamide fiber at high humidity by promoting the degree of crystallinity of the fiber paper. By forming a fine aromatic polyamide fiber crystal structure, the heat resistance, dimensional stability and moisture resistance of the fiber paper used as a substrate of an electric circuit board can be remarkably improved.

The present invention will now be described in more detail with reference to application embodiments. However, the invention is not limited to this application embodiment.

Test Methods

1. Crystallinity and Size

The diffraction intensity of the fibrous paper sample cut to about 3 cm x 4 cm was measured using an X-ray diffractometer (PW1075 / 00, manufactured by Philips Co.) and reflecting conditions of 40 kv and 40 mA. Measure in mode. The crystal size (ACS: Apparent Crystallinity Size) is consistent with the diffraction intensity at the scanning angle of 20 to 21 °. Using half the width of the diffraction peak of plane 110, the crystal size is calculated according to the following equation:

ACS = (Kx) / βcosTH

Where K is 1, x is the wavelength of X-rays (1.5418 GHz in this case), β is the correction factor, and TH is half the Bragg angle of the plane 110 obtained in the diffraction pattern. Value (half the scattering angle).

The crystallinity (CI: crystallization index) is calculated according to the following equation:

CI = [(A-C) × 100] / A

Where A is the diffraction peak intensity of plane 200 at about 23 ° and C is the lowest diffraction intensity at about 22 °.

In the case of the fibers of the present invention, the crystal size and crystallinity thereof are followed in the same manner as described above, except that the fiber paper sample having a length of 4 cm and a weight of 20 mg is fixed with a collodion solution before measurement. Calculate

2. Content of ionic substances in fiber paper

About 0.3 g of fiber paper is placed on a platinum plate. This fiber paper sample is dissolved in sulfuric acid and then burned in a gas burner or electric oven to make ash. The ash is pyrolyzed in sulfuric acid, nitric acid or hydrofluoric acid and dissolved in dilute nitric acid to form a solution. The amount of cationic material in this solution is measured by atomic absorption method.

3. Density of fiber paper

The density of the fiber paper is measured according to JIS P-8118.

4. Rate of change of fiber paper during heating

The change in length of the fiber paper sample 200 mm long and 30 mm wide was measured. The length of the fiber paper sample before heating the fiber paper sample and after heating at 300 ° C. for 10 minutes is measured with an X-Y coordinate measuring device. After heating the fiber paper sample, the percent dimensional change in both longitudinal (MD) and transverse (CD) is calculated according to the following equation:

Dimensional rate of change (%) = 100 × (length measured after heating-length measured before heating) / (length measured before heating)

5. Inflection point temperature of dimensional change of fiber paper during heating

The temperature at which the dimensional change of the fibrous paper samples 5 mm long and 2 mm wide is significantly increased is measured. Measurements are made using a TMA (Thermotechnic Analyzer: TA Instrument Co.). The temperature is raised from room temperature to 150 ° C. at a heating rate of 10 ° C./min under a load of 2 g, then the temperature is dropped and again at a rate of 10 ° C./min. The fiber paper sample is heated to 350 ° C. As the temperature rises, the temperature at which the constant rate of change of dimensional changes significantly is taken as the polarization point temperature of the dimensional change.

6. Coefficient of thermal expansion in the thickness direction of fiber paper

The coefficient of thermal expansion of the fibrous paper sample cut into the size of 10 mm x 10 mm is measured. Measurements are made using TMA (Thermotechnic Analyzer: TAI Instruments Co., Ltd.). The temperature is raised from room temperature to 150 ° C. at a heating rate of 10 ° C./min under a load of 2 g, followed by a temperature drop and then to 350 ° C. at a rate of 10 ° C./min. The average coefficient of thermal expansion is calculated within the range of room temperature to 250 ° C.

7. Tensile Strength of Fiber Paper

Tensile strength of the fiber paper is measured according to JIS P-8113.

8. Electrical Conductivity of Extraction of Fiber Paper

By evaluating the extraction state of the ionic substance as ions, the insulation reliability at high humidity of the fiber paper used as the electric circuit board is determined. The ionic material is extracted by the following method. About 5 g of the fiber paper sample is cut out and weighed accurately. A fibrous paper sample is placed in a flask and about 180 ml of ion exchanged water is added. The flask is heated for 24 hours to extract ions into water. After cooling it, the electrical conductivity of the extracted liquid is measured with an conductivity meter and calculated for 5 g of sample.

Characteristics of Electrical Circuit Boards

9. Insulation reliability after moisture absorption

An epoxy resin composition is prepared by adding dicyandiamide as a curing agent and benzylmethylamine as a curing accelerator to a cresol novolak epoxy resin and a bisphenol A epoxy resin used as an epoxy resin impregnated with an aromatic polyamide fiber paper. Varnish prepared by dissolving this epoxy resin composition in a methyl ethyl ketone solution is impregnated with an aromatic polyamide fiber paper, and the fiber paper is dried to obtain a B-stage prepreg containing 53% by weight of resin. A laminate is obtained by abutting a copper foil having a thickness of 18 µm on both sides of the prepreg and pressing the prepreg for 60 minutes at a pressure of 30 kg / cm 2 at 170 ° C with a vacuum heated press. On one side of the laminate, a comb-shaped electrode pattern was formed by etching lines of 200 mu m intervals and widths. Another laminate is then obtained by abutting the B-staged prepreg impregnated with the resin described above on both sides of the laminate and pressing it for 60 minutes at a pressure of 30 kg / cm 2 at 170 ° C. with a vacuum heated press. The substrate is allowed to stand for 500 hours and 1000 hours at 110 DEG C and 85% RH while applying a DC voltage of 20V. The substrate is taken out of the above-described high temperature and high humidity environment and left at 20 ° C. and 60% RH to recover the steady state. Subsequently, a DC voltage of 35 V is applied between the comb-shaped electrodes for 60 seconds, and the insulation resistance of the substrate is measured after treatment in a high humidity environment. The minimum resistance of each comb-shaped electrode is used as a measured value.

10. Dimensional stability

Sheets were made by superimposing five B-staged resin-impregnated prepregs obtained in item 9 above. Each side of this sheet was abutted with a copper foil having a thickness of 18 µm, and pressurized for 60 minutes at a pressure of 30 kg / cm 2 at 180 ° C. with a vacuum heated press to obtain a laminate. The copper foil laminate is cut to 250 mm × 250 mm. Four such laminate samples are made. The longitudinal and lateral dimensions of each substrate are measured every 200 mm x 200 mm. It is measured after a steady state (measurement 1), after copper foil etching (measurement 2) and after heat treatment (measurement 3). The rate of dimensional change from the steady state is calculated from the maximum and minimum changes.

11. Soldering heat resistance

The soldering heat resistance of the copper foil laminate obtained in the ninth item is measured according to JIS C-6481.

12. Coefficient of thermal expansion in the thickness direction

After the copper foil on each side of the copper foil laminate obtained in the ninth item is removed by etching, a sample having a size of 10 mm x 10 mm is cut from the substrate. The coefficient of thermal expansion in the thickness direction of this sample is measured using TMA (Thermotechnical Analysis Apparatus: manufactured by TA Instruments Co., Ltd.). The temperature is raised from room temperature to 150 ° C. at a heating rate of 10 ° C./min under a load of 2 g, followed by a temperature drop and then to 300 ° C. at a rate of 10 ° C./min. The average coefficient of thermal expansion is calculated within the range of room temperature to 250 ° C.

Description of the Preferred Embodiments

Application Example 1

The para-aromatic polyamide short fibers used for the wholly aromatic polyamide fibers formed by spinning of the anisotropic polymer solution were made of polyparaphenylene terephthalamide. The content of the ionic substance contained in the short fibers after spinning was 0.36% by weight, and the short fibers were appropriately processed so that the crystal size in the plane 110 was 40 kPa. The size of the short fiber was 1.5 denier and the length was 3 mm. The polymetaphenylene isophthalamide solution was precipitated in a coagulating solution under high shear conditions to give a meta-aromatic polyamide fiber. Short fibers and fibers were homogeneously dispersed in water as a dispersant to obtain a papermaking slurry having a fiber concentration of 0.2% by weight. Short fibers accounted for 90% by weight of the total weight of short fibers and fibers. The slurry was processed with a TAPPI type square sheet machine and dehydrated to obtain aromatic polyamide fiber paper having a basis weight of 70 g / cm 2. The paper was then calendered under linear pressure of 60 kg / cm 2 using a calender made of a pair of metal rolls heated to 300 ° C. The paper was then heated at 300 ° C. for about 2 minutes in a hot blast stove. The fiber paper thus obtained was made into a resin-impregnated prepreg according to the method described above. The prepreg thus obtained was used to make a substrate for an electric circuit. The properties of the wholly aromatic synthetic fiber paper and the properties of the substrate for the electric circuit are recorded in Table I.

Application Example 2

The para-aromatic polyamide short fibers used for the wholly aromatic polyamide fibers formed by liquid crystal spinning were made of polyparaphenylene terephthalamide. The content of the ionic substance contained in the short fibers after spinning was 0.36% by weight, and the short fibers were appropriately processed so that the crystal size in the plane 110 was 40 kPa. The size of the short fiber was 1.5 denier and the length was 3 mm. Para-aromatic polyamide fiber paper is prepared in the same manner as in Application Example 1, except that the fiber paper is coated with an aqueous solution of a bisphenol-type water-dispersible epoxy resin instead of the meta-aromatic polyamide fiber, and then the epoxy attached to the fiber paper. It processed suitably so that the quantity of resin might be 10 weight%. The content of short fibers in the coated fiber paper was 90% by weight. The fiber paper thus obtained was made into a resin-impregnated prepreg according to the method described above. The prepreg thus obtained was used to make a substrate for an electric circuit. The properties of the wholly aromatic polyamide fiber paper and the properties of the substrate for the electric circuit are recorded in Table I.

Comparative Example 1

Para-aromatic polyamide fiber paper was made using the same method as described in Application Example 1, but using different types of short fibers. In this case, the para-aromatic polyamide short fibers (Kevlar, product of Toray Dupont Limited) used for the wholly aromatic polyamide fibers formed by spinning of the anisotropic polymer solution were made of polyparaphenylene terephthalamide. After spinning and drying by heat treatment, the content of the ionic substance was 0.5% by weight. The crystal size in the plane 110 was 55 mm 3. The size of the short fiber was 1.5 denier and the length was 3 mm. The content of the short fibers in the prepared fiber paper was 90% by weight of the total weight of the short fibers and the fiber. The fiber paper was made of resin-impregnated prepreg according to the method described above. The prepreg thus obtained was used to make a substrate for an electric circuit. The properties of the wholly aromatic polyamide fiber paper and the properties of the substrate for the electric circuit are recorded in Table I.

Comparative Example 2

Para-aromatic polyamide fiber paper was made using the same method as described in Application Example 1, but using different types of short fibers. The para-aromatic polyamide short fibers used in this comparative example were prepared by methods other than spinning of the anisotropic polymer solution. This short fiber was made from a paraphenylene / 3,4-oxydiphenylene / terephthalamide copolymer (Technora, a product of Teijin Limited). The size of the short fiber was 1.5 denier and the length was 3 mm. The content of the short fibers in the prepared fiber paper was 90% by weight of the total weight of the short fibers and the fiber. The fiber paper was made of resin-impregnated prepreg according to the method described above. The prepreg thus obtained was used to make a substrate for an electric circuit. The properties of the wholly aromatic polyamide fiber paper and the properties of the substrate for the electric circuit are recorded in Table I.

Comparative Example 3

Para-aromatic polyamide fiber paper was made according to the same method as described in Application Example 1, except as follows. The para-aromatic polyamide short fibers used in this comparative example were prepared by methods other than spinning of the anisotropic polymer solution. This short fiber was made from a paraphenylene / 3,4-oxydiphenylene / terephthalamide copolymer (Technora, a product of Teijin Limited). The size of the short fiber was 1.5 denier and the length was 3 mm. The content of the short fibers in the prepared fiber paper was 90% by weight of the total weight of the short fibers and the fiber. The fibrous paper was applied with an aqueous solution of a bisphenol-type water-dispersible epoxy resin instead of the meta-aromatic polyamide, and then appropriately processed so that the amount of the epoxy resin attached to the fibrous paper was 10% by weight. The fiber paper was made of resin-impregnated prepreg according to the method described above. The prepreg thus obtained was used to make a substrate for an electric circuit. The properties of the wholly aromatic polyamide fiber paper and the properties of the substrate for the electric circuit are recorded in Table I.

Characteristics of fiber paper Characteristics of Electrical Circuit Boards Crystallinity (%) Crystal Size (Flat 110) Ionic substance content (wt%) Density (g / cm 3) Dimensional change rate during heating (%) Change point of dimensional change (℃) Thermal expansion coefficient in the thickness direction (ppm / ℃) Strength of fiber paper (kg / cm) Extraction Conductivity (μs / cm) Insulation reliability at high humidity (minimum value) Dimensional stability Solder Heat Resistance (sec) Thermal expansion coefficient in the thickness direction (ppm / ℃) 500 hours (Ω) 1000 hours (Ω) After molding (%) After etching (%) Application Example 1 52.9 73.0 0.03 0.53 0.030 275 140 4.4 3 3.7 × 10 ¹¹ 6.7 × 10 ¹¹ 0.08 0.15 1500 160 Application Example 2 53.0 70.0 0.03 0.53 0.030 170 340 8.0 3 3.7 × 10 ¹¹ 6.7 × 10 ¹¹ 0.08 0.15 1500 180 Comparative Example 1 54.0 74.0 0.50 0.53 0.036 275 150 4.2 40 7.3 × 10 ⁸ paragraph 0.07 0.17 1400 160 Comparative Example 2 Not measurable 50 or less 0.02 0.47 0.046 255 170 6.0 4 6.4 × 10 ¹¹ 2.2 × 10 ¹⁰ 0.12 0.35 500 230 Comparative Example 3 Not measurable 50 or less 0.02 0.47 0.046 170 1200 9.7 5 1.0 × 10 ¹¹ 3.5 × 10 ¹¹ 0.15 0.33 500 250

Claims (9)

60 to 97% by weight of wholly aromatic polyamide fibers and 3 to 40% by weight binder; The content of ionic material in the fiber paper is less than 0.5% by weight; The crystallinity of the aromatic polyamide fibers is at least 45%; A wholly aromatic polyamide fiber paper characterized in that the crystal size (ACS: Apparent Crystallinity Size (ACS) (plane 110)) of the aromatic polyamide fiber is at least 50 mm 3. The wholly aromatic polyamide fiber paper of claim 1, wherein the wholly aromatic polyamide fiber is polyparaphenylene terephthalamide. The wholly aromatic polyamide fiber paper as claimed in claim 1, wherein the wholly aromatic polyamide fiber has a length of 2 to 14 mm. The wholly aromatic polyamide fiber paper as claimed in claim 1, wherein the density is 0.45 to 0.85 g / cm 3. The wholly aromatic polyamide fiber paper according to claim 1, wherein the dimensional change after heating at 300 DEG C for 10 minutes is 0.03% or less. The wholly aromatic polyamide fiber paper according to claim 1, wherein the coefficient of thermal expansion in the thickness direction is 50 to 400 ppm / 占 폚. The wholly aromatic polyamide fiber paper according to claim 1, wherein the extraction conductivity is 10 µS / cm or less. The wholly aromatic polyamide fiber paper according to claim 1, wherein the tensile strength is 1.5 kg / cm or more. A laminated sheet comprising at least one layer of the fibrous paper of claim 1 impregnated with a thermosetting resin, having a thermal expansion coefficient of 200 ppm / 占 폚 or less.