JPH10338809A - Composite film comprising low-permittivity resin and p-directing polyamide, prepreg thereof and use thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composite film having low permittivity, being uniform, having uniform formation, being lightweight and having a low coefficient of thermal expansion and a flexible printed circuit board made thereof. SOLUTION: This composite film is one having a structure having a continuous phase comprising a p-directing aromatic polyamide and a phase comprising a low-permittivity resin and having a permittivity of 3.2 or below at 1 MHz or below and a coefficient of thermal expansion within ±50×10<-6> / deg.C. In this film, the part of the p-directing aromatic polyamide film is composed of fibrils having a diameter of 1 μm or below and has a structure in which the fibrils are arranged in a plane in the form a network or a nonwoven fabric. The composite film is impregnated with a thermoplastic resin and/or a thermosetting resin to obtain a prepreg, and a printed circuit board or laminate is obtained by using such prepregs.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a composite film having a low dielectric constant, a homogeneous material, and a uniform formation. The present invention also relates to a homogeneous porous composite film having a low dielectric constant. The present invention also relates to a flexible printed circuit board using such a composite film as a base material. Furthermore, the present invention relates to a prepreg made of a porous composite film, a circuit substrate and a circuit laminate using the same.

[0002]

2. Description of the Related Art In recent years, demands for high-speed signal processing and digitalization for higher functions have been further increased in electronic devices. BACKGROUND ART Laminates made of a nonwoven fabric of aromatic polyamide (hereinafter sometimes referred to as aramid) have characteristics of low dielectric constant, light weight and low coefficient of linear thermal expansion. Applications are being developed. Further, a film made of polyimide is used for a flexible substrate, but a further lowering of the dielectric constant is required for the purpose of high-speed signal processing.

Aramid is roughly classified into two types. That is, a meta-oriented aromatic polyamide (hereinafter, sometimes referred to as meta-aramid) and a para-oriented aromatic polyamide (hereinafter, sometimes referred to as para-aramid). Although the strength and tear strength of paper made of meta-aramid are practically sufficient, the coefficient of linear thermal expansion is so high that it is unsuitable as a circuit substrate. On the other hand, para-aramid fiber has excellent properties such as high strength, high rigidity, high heat resistance and low coefficient of linear thermal expansion. However, since para-aramid does not melt, para-aramid paper manufactured from para-aramid pulp has an agglutinated portion (entangled portion). Part). As a result, the para-aramid paper had low strength and was difficult to handle as a circuit substrate. For this reason, a method of applying a binder made of a heat-resistant resin to para-aramid paper or nonwoven fabric is often used.

For example, US Pat. No. 5,314,742 discloses that a nonwoven fabric comprising fibrils composed of meta-aramid and para-aramid flocs is useful as a substrate for a laminate having a low coefficient of linear thermal expansion. ing. JP-A-5-327148 describes that the coefficient of linear thermal expansion in the plane direction can be reduced by using a cloth, paper or nonwoven fabric containing 50% or more para-aramid fiber as a base material. However, in the case of a nonwoven fabric, there is a drawback in that a uniform product is difficult to obtain as a characteristic in the production method, and improvement has been desired. In addition, 1M of para-aramid
The dielectric constant at Hz is about 3.5, and it has been difficult to reduce the dielectric constant by a conventional method of simply impregnating with an epoxy resin to form a prepreg for a printed circuit board.

Several methods have been disclosed for adding a fluororesin having a low dielectric constant to a substrate for the purpose of lowering the dielectric constant.
EP-A 320 901 discloses a technique for producing a laminate made of a fluororesin reinforced with aramid woven or nonwoven fabric. However, the diameter of the fibers forming these woven and non-woven fabrics is about 15 to 20 μm, and the necessity of fine processing in the production of printed circuit boards in recent years has demanded a base material having a more uniform formation and a higher homogeneity as a material. I have.

For the purpose of lowering the dielectric constant, Japanese Patent Application Laid-Open No. 4-55437 discloses a substrate material in which a woven or nonwoven fabric made of aramid fiber is impregnated with a dispersion of a fluororesin and glass spheres. Japanese Unexamined Patent Publication (Kokai) No. 2-268486 discloses a substrate material using a base material in which a fluororesin fiber and an organic fiber are mixed. However, any of these materials has a high degree of homogeneity required for the base material when performing fine processing. Is impaired.

In Japanese Patent Publication No. 33493/1989, an aqueous dispersion of a fluororesin is applied to the surface of an aromatic polyamide film in a wet state, dried, and then heat-treated to give a fluororesin on one or both sides of the aromatic polyamide film. A method for forming a layer is shown. 6-9
No. 4206 discloses that a layer composed of a thermosetting resin and a base material includes:
JP-A-3-27395 discloses a method of manufacturing a laminate having a low dielectric constant as a whole by laminating layers each containing a fluororesin film on a layer combining a fluororesin and a fiber reinforcing material. . However, in such a form, the film as a whole is in the form of a laminate of different substances and cannot be said to be uniform. Further, it is difficult to make the printed circuit board itself thinner by a method of laminating a low dielectric layer.

[0008] As a film having a low dielectric constant, an aromatic polyester film having air bubbles therein is also a Polymer.
Preprints 37 vol. 1 (Divisio, 1996
n ofPolymer Chemistry, Inc. American Chemical
Society), page 160. According to this, it has been proposed to create air bubbles as an air phase having a low dielectric constant in order to lower the dielectric constant of an aromatic polyester having a low coefficient of linear thermal expansion. However, if bubbles are present in the film, in reality, there is a concern that the etchant may be mixed or water may flow during processing on the printed circuit board.

[0009]

Under such circumstances,
An object of the present invention is to provide a composite film having a low dielectric constant, a good mechanical strength as a printed circuit board, a uniform material, a uniform formation, a low coefficient of linear thermal expansion, and such a film. To provide a base material for a flexible printed circuit board. The object of the present invention is to
It is an object of the present invention to provide a porous composite film having porosity among composite films and a prepreg obtained by impregnating such a film with a thermoplastic resin and / or a thermosetting resin (hereinafter, may be simply referred to as a resin). Another object of the present invention is to provide a printed circuit board and a laminate using such a prepreg.

[0010]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and have reached the present invention. That is, the present invention firstly provides a film having a continuous phase composed of para-oriented aromatic polyamide and a phase composed of a low dielectric constant resin, wherein the dielectric constant at 1 MHz of the film is 3.2 or less (hereinafter, referred to as The dielectric constant in this specification is 1 MHz unless otherwise specified.
And a coefficient of linear thermal expansion at 200 to 300 ° C. is within ± 50 × 10 ⁻⁶ / ° C.

Next, the present invention provides the above composite film,
Further, the present invention relates to a composite film containing short fibers and / or pulp which does not melt at a temperature of less than 230 ° C.

Next, according to the present invention, the portion of the para-oriented aromatic polyamide film is composed of fibrils having a fibril diameter of 1 μm or less, and the fibrils are arranged in a mesh or nonwoven fabric on a plane and overlapped in layers. The present invention relates to a composite film having a structure.

Further, according to the present invention, the composite film is a porous composite film having a porosity of 30-9.
It is related to a composite film of 5%.

Further, the present invention relates to a prepreg obtained by impregnating a thermoplastic resin and / or a thermosetting resin into a porous composite film having voids inside the composite film.

Further, the present invention relates to a flexible printed circuit board using the above composite film.
The present invention also relates to a printed circuit board using the prepreg, and a printed circuit board having a conductive layer made of an insulating layer and a metal foil made of the printed circuit board.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The composite film referred to in the present invention is a film having a structure in which a continuous phase composed of para-oriented aromatic polyamide and a phase composed of a low dielectric constant resin exist. Here, the continuous phase refers to a state in which the same substance is present in the same form from one surface of the film to the other surface through the inside of the film. Further, the phase made of a low dielectric constant resin means that the low dielectric constant resin is dispersed in the gaps of the continuous phase or exists in a state of filling the gaps of the continuous phase. Note that a part of the phase made of the low dielectric resin may be present on the film surface. The dielectric constant at 1 MHz of the composite film of the present invention is 3.2 or less, and the coefficient of linear thermal expansion at 200 to 300 ° C. is ± 50 × 10 ^−6.
/ ° C or less. Here, the permittivity referred to in the present invention is A
It refers to the dielectric constant measured by a method based on STM-D150.

The composite film according to the present invention is a composite film containing a low dielectric constant resin and para-aramid as main components, and the para-aramid portion is composed of para-aramid fibrils, and has a nonwoven fabric form when viewed microscopically. Have. The para-aramid phase of the composite film of the present invention preferably has a structure in which fibrils having a diameter of 1 μm or less, which are composed of para-aramid, are arranged in a network or nonwoven fabric on a plane, and are layered. Here, "disposed in a plane" means that the fibrils are disposed substantially parallel to the film surface.

The para-oriented aromatic polyamide constituting the continuous phase of the present invention is obtained by condensation polymerization of a para-oriented aromatic diamine and a para-oriented aromatic dicarboxylic acid halide, wherein the amide bond has a para-position on the aromatic ring. Or an orientation position corresponding thereto (for example, 4,4′-biphenylene, 1,5
-An alignment position extending coaxially or parallel in the opposite direction, such as -naphthalene, 2,6-naphthalene, etc.).

Specifically, poly (paraphenylene terephthalamide), poly (parabenzamide), poly (4,4)
4'-benzanilide terephthalamide), poly (paraphenylene-4,4'-biphenylenedicarboxylic amide), poly (paraphenylene-2,6-naphthalenedicarboxylic amide), poly (2-chloro-paraphenylene terephthalamide) ), Paraphenylenediamine / 2,6
And para-aramid having a para-oriented structure or a structure conforming to the para-oriented type, such as a copolymer of dichloroparaphenylenediamine / terephthalic acid dichloride.
Further, in the present invention, para-aramid whose terminal functional group is a phenolic hydroxyl group can also be used.

The term "para-aramid having a terminal functional group of a phenolic hydroxyl group" means a hydroxyl-terminated para-oriented aromatic polyamide in which part or all of the terminal functional groups of the para-oriented aromatic polyamide are hydroxyl groups. Such a hydroxyl group-terminated para-oriented aromatic polyamide is represented by a para-oriented aromatic polyamide in which an aromatic compound having a hydroxyl group at a part or the whole thereof is bonded to the molecular chain terminal of the para-oriented aromatic polyamide.

On the other hand, in the present invention, the low dielectric constant resin is preferably a resin having a dielectric constant at 1 MHz of 3.0 or less and not thermally decomposing at 300 ° C. or less. Specific examples of such a low dielectric constant resin include ethylene tetrafluoride resin, perfluoroalkoxy resin, ethylene tetrafluoride-propylene hexafluoride copolymer resin, ethylene tetrafluoride-ethylene copolymer resin, vinylidene fluoride Resins, ethylene trifluoride ethylene resin (PCTFE) and the like. Among them, ethylene tetrafluoride resin can be preferably used. When the dielectric constant at 1 MHz exceeds 3.0, the original para-aramid becomes 1
Since the dielectric constant at MHz is 3.5, the effect of reducing the dielectric constant is small, and it is difficult to obtain the effect of reduction by adding a small amount.
Further, since the printed circuit board is immersed in a solder bath in the processing step, a resin that decomposes at 300 ° C. or lower is not preferable.

The amount of the low dielectric resin to be added is not particularly limited, but is preferably 20 to 80% by weight when the total weight of the composite film of the present invention is 100% by weight. If it is less than 20% by weight, the effect of lowering the dielectric constant is not sufficient, and if it exceeds 80% by weight, dimensional stability important as a printed circuit board is impaired. In particular, from the viewpoint of dimensional stability, in the case of the above-mentioned fluororesin, since the elastic modulus is nearly one order of magnitude smaller than that of para-aramid, the thermal expansion coefficient of para-aramid becomes dominant, resulting in excellent dimensional stability. Material.

In the present invention, the film can be reinforced with high heat-resistant short fibers and / or pulp in order to improve the handleability of the film, specifically, to improve the tear energy. In the present invention, a high heat-resistant short fiber is
An aspect ratio (fiber length / fiber diameter) of 50 or more;
The coefficient of linear thermal expansion at 00 to 300 ° C is ± 50 × 10 ^-6 / ° C.
And preferably within ± 25 × 10 ⁻⁶ / ° C. and having a temperature of less than 230 ° C., preferably less than 250 ° C., and short fibers composed of fibers that do not melt. Specific examples of the organic fiber used as a raw material of the short fiber of the present invention include aromatic polyamides such as polyparaphenylene terephthalamide and polyparabenzamide; polyesters such as polyparabenzoate, polyparaphenylene terephthalate and polyethylene terephthalate. Organic fibers made of aromatic heterocyclic polymers such as polyparaphenylenebenzobisthiazole and polyparaphenylenebisoxazole. Among these, organic fibers made of aromatic polyamides are preferable, and organic fibers made of polyparaphenylene terephthalamide are particularly preferably used because they have good compatibility with the porous film.

In the present invention, the high heat-resistant pulp is a pulp made of fibers that do not melt at a temperature of less than 230 ° C., preferably less than 250 ° C. The pulp is 200-3
It is preferably manufactured from a raw material fiber having a coefficient of linear thermal expansion at 00 ° C. within ± 50 × 10 ⁻⁶ / ° C.
Specific examples of the organic fiber used as a raw material of the pulp of the present invention include aromatic polyamides such as polyparaphenylene terephthalamide and polyparabenzamide; polyesters such as polyparabenzoate, polyparaphenylene terephthalate and polyethylene terephthalate; Organic fibers made of aromatic heterocyclic polymers such as polyparaphenylene benzobisthiazole and polyparaphenylene bisoxazole are exemplified. Among them, organic fibers made of aromatic polyamides are preferable, and organic fibers made of polyparaphenylene terephthalamide are particularly preferably used because they are well compatible with the composite film.

The amount of the short fibers or pulp added is not particularly limited, but is preferably 5 to 50% when the para-oriented aromatic polyamide is 100%. If it is less than 5%, the reinforcing effect is not sufficient, and if it exceeds 50%, irregularities of the film due to short fibers and / or pulp are exposed and the smoothness of the film is impaired.

Also, in the process of manufacturing a multilayer printed circuit board, which is one of the uses of the prepreg of the present invention, it is not suitable when a laser is used to form a circuit between insulating layers, but inorganic fibers can also be used. . Whisker and the like are included in the inorganic fiber, and specific examples of the fiber include glass fiber, boron fiber, and alumina fiber.

In the composite film of the present invention reinforced with short fibers and / or pulp, the short fibers are arranged in the film substantially parallel to the film surface. Also, the pulp has a structure arranged in a state of being uniformly dispersed in the film, and more desirably has a structure arranged in a state where the fibrils are opened,
The tear energy is particularly improved. That is, the composite film alone has a resistance to the initiation of tearing, but once cut, the crack easily propagates. However, if the short fibers are arranged in parallel with the film surface or the pulp is arranged in a uniformly dispersed state, the propagation of cracks can be effectively prevented, and the tear resistance is improved. Further, the composite film of the present invention may be coated with a thermoplastic resin and / or a thermosetting resin for the purpose of various modifications. In particular, it is effective to apply an epoxy resin even among thermosetting resins in order to improve the adhesive strength with a copper foil used for forming an electronic circuit on a flexible printed circuit board.

The composite film of the present invention includes the following porous composite films having voids. That is, the porous composite film referred to in the present invention is a porous film obtained from a low dielectric constant resin and para-aramid, and the film is formed from para-aramid fibrils, and has a nonwoven fabric form when viewed microscopically. doing. The porous composite film of the present invention has a structure in which fibrils having a diameter of 1 μm or less, which are made of para-aramid, are arranged in a mesh or nonwoven fabric on a plane, and are layered. Here, being arranged in a plane means that the fibrils are arranged in parallel to the film surface.

And, the porous composite film of the present invention
It has many voids, and its porosity is preferably 30
~ 95%, more preferably 35 ~ 90%. If the porosity is less than 30%, the varnish obtained by dissolving a thermoplastic resin and / or a thermosetting resin in a solvent is insufficient when a prepreg to be described later is obtained because the porosity is not substantially porous. . On the other hand, if it exceeds 95%, the strength of the porous composite film becomes insufficient and handling becomes difficult. Here, the porosity means a value obtained by the following method. Porosity: Cut the porous composite film into a square shape (length of one side L: cm), weight (W: g), thickness (D: cm)
Is measured. Assuming that the content of the low dielectric constant resin contained in the film is A (% by weight), the content weight Wf (g) of the low dielectric constant resin in the film is represented by the following equation. Wf = (W × A / 100) Assuming that the true specific gravity of the low dielectric constant resin is σ (g / cm ³ ), the volume (Vf: cm ³ ) occupied by the low dielectric constant resin is expressed by the following equation. Vf = Wf / σ Assuming that the true specific gravity of para-aramid is 1.45 g / cm ³ , the volume Va occupied by aramid is represented by the following equation. Va = (W−Wf) /1.45 From the above values, the porosity (volume%) is obtained by the following equation. Porosity (volume%) = 100−100 × (Va + Vf) /
(L ² × D)

Further, the porous film of the present invention has a thickness of 200
The coefficient of linear thermal expansion (up to 300 ° C) (± 50 × 1)
Within 0 ^-6 / ° C, preferably within ± 25 × 10 ^-6 / ° C. The small coefficient of linear thermal expansion indicates good dimensional stability in the planar direction.

Hereinafter, an example of the method for producing the composite film of the present invention will be described in detail. These are merely examples and do not limit the present invention in any way. Representative examples of the method for producing a composite film and a porous composite film of the present invention include the following steps (a) to (d). (A) 1 to 10% by weight of a para-oriented aromatic polyamide having an intrinsic viscosity of 1.0 to 2.8 dl / g in a polar amide-based solvent or a polar urea-based solvent, Forming a film from a solution containing 1 to 10% by weight of a substance and a low dielectric constant resin. (B) maintaining the film at a temperature of 20 ° C. or more and 5 ° C. or less to precipitate para-oriented aromatic polyamide from the film. (C) The film obtained in step (b) is immersed in an aqueous solution or an alcoholic solution to elute the solvent and the alkali metal or alkaline earth metal chloride, and then dried to obtain a porous composite film. Process. (D) rolling the porous composite film obtained in step (c) to obtain a composite film; Also, a prepreg described later can be manufactured at the same time. That is, before rolling, the thermoplastic resin and / or the thermosetting resin is impregnated into a dried porous composite film as a varnish dissolved in a solvent, and a step of evaporating and removing the solvent is performed. And / or a prepreg comprising a porous composite film impregnated with a thermosetting resin can be produced.

The para-aramid solution used in the step (a) can be suitably produced, for example, by the following operation. That is, in a polar amide solvent or a polar urea solvent in which 1 to 10% by weight of an alkali metal or alkaline earth metal chloride is dissolved, para-oriented aromatic diamine 1.
With respect to 0 mol, 0.94 to 0.99 mol of para-oriented aromatic dicarboxylic acid halide is added, and the temperature is -20 ° C to 5 ° C.
Condensation polymerization at 0 ° C. produces a para-aramid solution having a para-aramid concentration of 1 to 10% by weight. When producing hydroxyl-terminated para-aramid, a part of the para-oriented aromatic diamine is replaced with an aromatic compound having an amino group and a hydroxyl group, and the carboxylic acid halide is equimolar to 1 mol of the total amino group. An oriented aromatic dicarboxylic acid halide is added. A predetermined amount of a low-permittivity resin is mixed with the para-aramid solution thus produced to produce a raw material solution for forming a film. In this step, short fibers for reinforcement can be blended.

The porous composite film according to the present invention can be used as a so-called prepreg by impregnating a thermoplastic resin and / or a thermosetting resin for various purposes. In particular, it is effective to impregnate an epoxy resin among thermosetting resins in order to improve the adhesive strength with a copper foil used for forming an electronic circuit on a printed circuit board. The impregnation amount of the thermoplastic resin and / or the thermosetting resin is preferably 5 to 60%. If it is less than 5%, a sufficient adhesive force to the copper foil cannot be obtained, and if it exceeds 60%, the coefficient of linear thermal expansion becomes high, and the characteristic of the present invention having a low dielectric constant is lost.

The thermoplastic resin is not particularly limited as long as it is a resin having thermoplasticity, but is preferably a thermoplastic resin having a melting point of 150 ° C. or higher. When a prepreg according to the present invention is intended for a printed circuit laminate which is considered to be a main use, a prepreg preferably has sufficient adhesiveness to a material for forming an electronic circuit. Such thermoplastic resins include polyethersulfone, polysulfone, polyetherimide, polysulfidesulfone, polycarbonate,
Examples include polyimide, polyamide imide or polyether ketone. These can be used alone or in appropriate combination.

On the other hand, examples of the thermosetting resin include, but are not particularly limited to, an epoxy resin, a bismaleimide-triazine resin, a polyimide resin, a diallyl phthalate resin, an unsaturated polyester resin, a cyanate resin, and an aryl-modified polyphenylene ether resin. Can be. These can be used alone or in appropriate combination.

The prepreg of the present invention can be made thinner by reducing its thickness. However, if the film thickness is less than 10 μm, it is not preferable because wrinkles are easily formed and handling is difficult. Specifically, the thickness of the para-aramid film is 1
It is preferably from 0 to 150 μm, more preferably from 30 to 150 μm.
100 μm. Although the upper limit of the thickness of the film is not particularly specified, it is not preferable that the thickness exceeds 150 μm because important light and thin characteristics of the laminate are lost.

In the present invention, the method of impregnating the porous composite film with a thermoplastic resin and / or a thermosetting resin is not particularly limited, and a conventionally known method of impregnating a paper or glass cloth with a thermosetting resin. Etc. can be applied. For example, a varnish in which a composition comprising a thermoplastic resin and a thermosetting resin is dissolved in a solvent is prepared, applied to the composite film and impregnated, and then the solvent is evaporated to produce a prepreg.

The above prepreg has a low coefficient of linear thermal expansion,
Since it has excellent mechanical strength and good adhesion to metal foil, it can be suitably used as a printed circuit board and a laminate. In particular, it is useful as a flexible printed circuit board. Such a printed circuit board and a laminated board can be formed by a commonly used method (for example, “all of printed wiring boards”).
(Electronic technology, 1986 edition, separate volume). That is, using the prepreg of the present invention as an insulating layer,
Further, a conductor layer made of metal foil is laminated to produce a printed circuit laminate. Gold, silver, copper, nickel, aluminum, or the like can be used as the metal foil.

[0039]

The present invention will be described below in detail with reference to examples. These are merely examples and do not limit the present invention in any way. In addition, the test, the evaluation method, or the criterion in Examples and Comparative Examples are as follows.

(1) Intrinsic viscosity 96 to 98% sulfuric acid 100 ml in 100 ml of para-aramid polymer.
For a solution of 5 g and 96-98% sulfuric acid,
The flow time was measured at 30 ° C. using a capillary viscometer, and the intrinsic viscosity was determined from the ratio of the determined flow times according to the following equation. Intrinsic viscosity = ln (T / T ₀ ) / C [unit: dl / g] Here, T and T _O are the flow times of the para-aramid sulfate solution and sulfuric acid, respectively, and C indicates the para-aramid concentration (g / dl) in the para-aramid sulfate solution.

(2) Tensile test A test piece was punched out from a composite film, a prepreg or a sheet obtained by curing the prepreg with a dumbbell cutter manufactured by Dumbbell Co., Ltd., and JIS K was applied using an Instron universal tensile tester model 4301 manufactured by Instron Japan. −71
The tensile strength was determined according to No. 27.

(3) Peel strength with copper foil Measured according to JIS C-6481.

(4) Coefficient of linear thermal expansion Measured using a thermal analyzer TMA120 manufactured by Seiko Electronics Co., Ltd. according to ASTM D696, and calculated by the following equation. However, as for the measurement specimen which was not annealed before the measurement, the specimen was once heated to 300 ° C. in the apparatus and then re-measured. α1 = ΔL / L ₀ · ΔT where, [alpha] 1: linear thermal expansion coefficient (/ ℃) ΔL: change in specimen length L ₀ : Specimen length before test ΔT: Temperature difference (° C)

(5) Dielectric constant Except for Example 1, the dielectric constant was measured according to ASTM-D150. That is, precision LCR meter HP-4284 manufactured by Yokogawa Hewlett-Packard Co., Ltd.
A was measured using A and SE-70 manufactured by Ando Electric Co., Ltd. The test piece was cut into a 5 cm square, and silver paint was applied to both sides. After drying at 120 ° C. for 2 hours,
After adjusting the condition at 2 ° C. and 60% RH for 90 minutes, the measurement was performed at 1 MHz. The dielectric constant described in Example 1 is JIS K
It was measured by the gap method according to 6911. That is, Yokogawa
Precision LC manufactured by Hewlett-Packard Co., Ltd.
R meter HP-4285A and electrodes as electrodes, HP
It measured using 16451B. As a test piece, a composite film was cut into a 5 cm square, and silver paint was applied to both sides.
After drying at 120 ° C. for 2 hours,
After conditioning for 90 minutes under% RH, the measurement was performed at 1 MHz. Generally, the result of the dielectric constant obtained in accordance with JIS K6911 is almost the same as the result of ASTM-D150.

(6) Water Absorption Ratio A prepreg was cut into a 70 mm square, and a cured sheet was used as a test piece.
The sample was allowed to stand for 24 hours under the condition of a relative humidity of 65%, and the change in weight was measured.

(7) Tear energy A porous film, a prepreg or a sheet obtained by curing a prepreg is subjected to JIS K-7128- manufactured by Dumbbell Co., Ltd.
A test piece was punched out with a dumbbell cutter for the 1991C method (right angle tearing method), and JIS K was used using an Instron universal tensile tester model 4301 manufactured by Instron Japan.
The tear strength was determined according to -7128-1991C. A chart showing the measurement results of the tear strength (the vertical axis indicates the load (kg /
mm) and the horizontal axis is the displacement (mm), and the area surrounded by the measured SS curve, the line with no load, and the vertical line indicating the fracture was defined as the tear energy (unit kg / mm × mm).

Example 1 1) Synthesis of hydroxyl-terminated poly (paraphenylene terephthalamide) A hydroxyl-terminated poly (paraphenylene terephthalamide) was prepared using a 3-liter (l) separable flask having a stirring blade, a thermometer, a nitrogen inlet tube and a powder addition port. Poly (paraphenylene terephthalamide) (hereinafter abbreviated as hydroxyl-terminated PPTA) was synthesized. The flask was sufficiently dried and charged with 2220 g of N-methyl-2-pyrrolidone (hereinafter sometimes abbreviated as NMP).
149.2 g of calcium chloride dried at 200 ° C. for 2 hours
Was added and the temperature was raised to 100 ° C. After the calcium chloride is completely dissolved, the temperature is returned to room temperature, and 67.2 g of paraphenylenediamine (hereinafter may be abbreviated as PPD) and 4-aminomethcresol (hereinafter may be abbreviated as 4-AMC). 6.7 g was added and completely dissolved. While keeping this solution at 20 ± 2 ° C., 130.7 g of terephthalic acid dichloride (hereinafter, sometimes abbreviated as TPC) was added in 1 part.
It was added in about 0 minutes and added about every 5 minutes. Then the solution was
The mixture was aged for 1 hour while maintaining at 2 ° C., and stirred under reduced pressure for 30 minutes to remove bubbles. The resulting polymerization solution (polymer dope)
It showed optical anisotropy. A part is sampled, reprecipitated with water, taken out as a polymer, and the obtained hydroxyl terminal P
The intrinsic viscosity of PTA was measured and found to be 2.11 dl / g.

2) Preparation of Composite Film Consisting of Hydroxyl-Terminal PPTA and Low Dielectric Resin Resin Hydroxyl-terminated PPTA and low dielectric constant resin (polytetrafluoroethylene fine particles (hereinafter abbreviated as PTFE fine particles; Lubron L- manufactured by Daikin Industries, Ltd.) 5F)) and a composite film comprising aramid short fibers for reinforcement were prepared from the polymerization solution of the above item 1). That is, 1.2 g of aramid short fiber having a fiber length of 1 mm and 8.7 g of PTFE fine particles having a dielectric constant of 2.2.
With a stirring blade, a nitrogen injection tube and a liquid addition port.
The mixture was weighed in a 0 ml separable flask, 100 g of the polymerization solution of item 1) was added, and the mixture was stirred in a nitrogen stream. Since aramid short fibers and PTFE fine particles were sufficiently dispersed, NMP20
0 g was added for dilution. Using the obtained solution, a film-like material of the solution was prepared on a glass plate using a bar coater (1.2 mm in thickness) manufactured by Tester Sangyo Co., Ltd., and placed in an aluminum pad with a lid. About 10 in a heating oven
Hold for minutes. The aluminum pad used was a mop which had been wetted with pure water in advance and placed in an oven at 80 ° C. During this time, hydroxyl-terminated PPTA was precipitated, and a film was obtained. The film was immersed in ion-exchanged water. After 5 minutes, the film was peeled from the glass plate. After sufficient washing with flowing ion-exchanged water, a wet film was taken out of the water and free water was wiped off. This film was sandwiched between felts made of aramid and further sandwiched between glass cloths. An aluminum plate was placed with the film material sandwiched between filter paper and glass cloth, a nylon film was placed on the aluminum plate, the nylon film and the aluminum plate were sealed with gum, and a conduit for decompression was provided. The whole was put in a hot oven and dried at 120 ° C. while reducing the pressure to obtain a porous composite film. Further, the obtained porous composite film was sandwiched between aluminum plates having a thickness of 0.8 mm, and subjected to hot rolling with a small rolling mill manufactured by Daito Seisakusho Co., Ltd. The roll temperature at this time was 165 ° C., and the linear pressure was 80 kg / cm. This composite film was immersed in water and subjected to ultrasonic wave for 10 minutes. The weight of the composite film before and after this operation was measured, but there was no significant difference. However, when the same operation was performed on the dried porous composite film before hot rolling, a weight increase of 22.6% was observed. From this result, it was confirmed that voids existed in the porous composite film before the hot rolling step, and it was confirmed that the voids in the film disappeared in the hot rolling step.

Example 2 In the section 2) of Example 1, the added amount of the PTFE fine particles was 10.4.
A composite film was produced in the same manner as in 2), except that g was used. Each of the dried porous composite film and the fired composite film at 350 ° C. was slightly torn, and the torn portions were observed with a scanning electron microscope. The results are shown in FIGS. Fig. 1 is magnification 1
FIGS. 3 and 5 are photographs at 50 × magnification and 200 × magnification.
A part of the torn fracture surface in FIGS.
Scanning electron micrographs at × 2 magnification are shown in FIGS.
Shown in In FIG. 1, it was observed that the aramid short fibers were exposed from the torn composite film, and it was observed that the agglomerated particles of PTFE fine particles were covered with the hydroxyl-terminated PPTA on the film surface. . In the center of the photograph in FIG. 2, aggregated particles of PTFE incorporated in the layer structure composed of hydroxyl-terminated PPTA can be seen. In FIG. 3, it can be seen that the agglomerated particles of PTFE are crushed by rolling to form a smooth surface. In FIG.
It is observed that the primary particles forming the PTFE aggregated particles are almost completely adhered. In FIG. 6, as a result of baking the PTFE portion, when the composite film is torn, a part of the fibrous portion is torn off in a fibrous form, which is observed in the broken surface. In each of the photographs, the hydroxyl group-terminated PPTA portion has multiple layers of fibrils overlapping each other, and it is clear that each layer has fibrils spread in a plane.

Next, the physical properties of the composite film were measured. The dielectric constant at 1 MHz was 2.6. Table 1 shows the measurement results of the tensile strength. The water absorption of the composite film was 0.9%.

[0051]

Table 1 Example / Comparative Example Tensile Strength Tensile Elongation kg / mm ² % Composite Film of Example 2 7.3 2.8 Composite Film Fired 7.2 2.1 Example 3 Cured Product 9 1 3.1

Example 3 In the same manner as in Example 2, hydroxyl-terminated PPTA and PTF
A film composed of E fine particles and reinforcing aramid short fibers wetted in water was obtained, and then the film was dried to produce a porous composite film. Next, a prepreg, a printed circuit board, and a laminate were prepared. (1) Preparation of Varnish A solvent (methyl ethyl ketone, hereinafter abbreviated as MEK) was added to a mixture having the following composition, and a 300 m
In a 1 Erlenmeyer flask, the mixture was heated and refluxed for 90 minutes while stirring with a magnetic stirrer to obtain a varnish. Varnish composition: (parts by weight) Main agent: Sumiepoxy ESB-400 (Sumitomo Chemical Co., Ltd.) 44 Sumiepoxy ESCN-195 (Sumitomo Chemical Co., Ltd.) 28 Curing agent: Phenol novolak (Gunei Chemical Co., Ltd.) 28 Catalyst: 2-methyl- 4-ethylimidazole (manufactured by Shikoku Chemicals, Cureazole 2E4MZ) 0.4

(2) Preparation of Prepreg The above-described porous composite film was sandwiched between aramid papers, and further sandwiched between aluminum plates having a thickness of 0.2 mm. This is further sandwiched between aramid felt and a 1 mm thick aluminum plate,
It was annealed by pressing at 10 kg / cm ² for 10 minutes.
Cut this porous composite film into 100 mm square,
The varnish prepared in (1) was applied to both sides. During the impregnation of the varnish, the varnish was uniformly spread by sandwiching it between fluorine films (trade name: TOYOFLON 50F, manufactured by Toray Industries, Inc.) so that the solvent would not evaporate. Leave for 10 minutes,
After uniformly impregnating the film with a varnish, a glass cloth (product code: YES-2101, Nippon Sheet Glass Fiber Co., Ltd.)
Was heated at 150 ° C. for 3 minutes to remove the solvent, and the epoxy resin was semi-cured to prepare a prepreg. In order to reduce the impregnation amount of the epoxy resin, it is possible to squeeze out the epoxy resin by rolling at room temperature before semi-curing. However, in this experiment, the prepreg was simply semi-cured to obtain a prepreg.

(3) Hardening of the prepreg alone, lamination hardening with copper foil and measurement of physical properties The prepreg of the above item (2) was placed in a gap between 45 μm spacers, sandwiched between Teflon sheets, and press-cured at 175 ° C. The prepreg sandwiched between copper foils having a thickness of 35 μm was placed in a gap between 115 μm spacers, and press-cured at 175 ° C. The cured product of prepreg alone has a water absorption of 0.9% and a coefficient of linear thermal expansion of 24 × 10
⁻⁶ / ° C. The tensile strength of this cured product is also shown in Table 1. The peel strength with the copper foil is 0.7 kg / c.
m.

Example 4 Hydroxyl-terminated PPT synthesized in the same manner as in Example 1 (1)
13.92 g of aramid short fibers having an average fiber length of 1 mm in 1237 g of the A polymerization liquid 4.64 mm of aramid short fibers 4.64
g and 2474 g of NMP were added, and a polymer solution stirred and defoamed under a nitrogen stream was prepared. 1000 g of the polymer solution
Was transferred to another stirring device, and 20 g of PTFE fine particles were added to the solution to prepare a polymer solution for coating. The solution was applied to the polymer solution using a tester industry coating machine,
It was coated on a PET film, and the obtained film was washed with water and dried in the same manner as in item 2) of Example 1 to obtain a porous composite film. The film was impregnated with the same thermosetting resin varnish as in Example 3 to obtain a prepreg, which was further cured. The coefficient of linear expansion of the cured product, the dielectric constant at 1 MHz, and the water absorption were measured. Table 2 shows the results.

Comparative Example 1 The dielectric constant at 1 MHz of a commercially available polyimide film, Kapton (manufactured by Toray DuPont) was measured.
Met.

Comparative Example 2 A cured product was obtained in the same manner as in Example 4 except that no PTFE fine particles were contained. The coefficient of linear expansion, the dielectric constant at 1 MHz, and the water absorption were measured. Table 2 shows the results.

[0058]

Table 2 Example / comparative example Dielectric constant Linear expansion coefficient (100 to 200 ° C) Water absorption (× 10 ⁻⁶ / ° C) (%) Example 4 3.39 11.4 1.0 Comparative example 2 4.11 8.9 1.5

Reference Example 1 In a 3000 ml separable flask under a nitrogen stream, 1,283 g of NMP for dilution, 8.25 g of aramid short fibers having an average fiber length of 1 mm, and aramid short fibers having an average fiber length of 3 mm.
75 g was added and stirred. To this fiber dispersion was added a hydroxyl-terminated PPTA solution prepared in the same manner as in item 1) of Example 1 to 9
17 g was further added and stirred. After homogenization, the mixture was defoamed to obtain a coating polymer solution. The polymer solution was coated on a PET film using a coating machine manufactured by Tester Sangyo, and the resulting film was washed with water and dried in the same manner as in item 2) of Example 1. The film was measured for tensile strength. The tear strength was measured, and the tear energy was calculated. Table 3 shows the results. Reference Example 2 A porous film was produced in the same manner as in Reference Example 1, except that aramid short fibers were not added when preparing the coating polymer solution. The film was measured for tensile strength. The tear strength was measured, and the tear energy was calculated. Table 3 shows the results.

[0060]

Table 3 Table 3 Aramid short fibers Tensile strength Tensile elongation Tear energy kg / mm ² % kg / mmxmm Reference example 1 Yes 5.8 2.1 9.2 Reference example 2 None 10.8 6.6 3.2 Above As shown in Table 3, in the composite film containing no PTFE fine particles, the tensile strength was decreased but the tear energy was increased by reinforcing with the aramid short fiber. From this, the same effect can be expected by the short fiber reinforcement in the composite film containing the PTFE fine particles of the present invention.

[0061]

According to the present invention, a low dielectric constant, good mechanical strength as a printed circuit board, uniform material, uniform formation (indicating that the film surface is smooth), and light weight. Provided are a composite film having a low coefficient of linear thermal expansion and a material useful as a substrate for a flexible printed circuit board using such a film. Further, a composite film containing short fibers and / or pulp having high heat resistance has a large tear energy and is excellent in handleability. Further, the present invention provides a porous composite film and a prepreg obtained by impregnating such a film with a thermoplastic resin and / or a thermosetting resin. Further, according to the present invention, there is provided a printed circuit board and a laminate using the prepreg.

[Brief description of the drawings]

FIG. 1 shows the fibril shape of the composite film obtained in Example 2 (the structure of the portion where the porous composite film is torn).
Is shown. Photograph substitute for drawing (scanning electron micrograph at 150x magnification)

FIG. 2 shows the shape of fibrils of the composite film obtained in Example 2 (the structure of the fracture surface at the portion where the porous composite film was torn). Photograph substitute for drawing (scanning electron micrograph at 2000x magnification)

FIG. 3 shows the shape of fibrils of a composite film obtained in Example 2 (the structure of a portion where the composite film is torn). Photograph substitute for drawing (scanning electron micrograph at 200x magnification)

FIG. 4 shows the shape of fibrils (structure of a portion where the composite film is torn) of the composite film obtained in Example 2. Photograph substitute for drawing (scanning electron micrograph at 2000x magnification)

FIG. 5 shows the shape of fibrils of the composite film obtained in Example 2 (the structure of a portion where the composite film is torn). Photograph substitute for drawing (scanning electron micrograph at 200x magnification)

FIG. 6 shows the shape of fibrils (structure of a portion where the composite film is torn) of the composite film obtained in Example 2. Photograph substitute for drawing (scanning electron micrograph at 2000x magnification)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H05K 1/00 H05K 1/00 // B29K 105: 06

Claims (15)

[Claims] 1. A film having a continuous phase comprising a para-oriented aromatic polyamide and a phase comprising a low dielectric constant resin, wherein the dielectric constant of the film at 1 MHz is 3.2 or less, and 200 to 300 ° C. ± 50 × linear thermal expansion coefficient
A composite film having a temperature within 10 ^-6 / ° C. 2. The composite film according to claim 1, further comprising a high heat-resistant short fiber and / or pulp that does not melt at a temperature lower than 230 ° C. 3. A continuous phase comprising a para-oriented aromatic polyamide, comprising fibrils having a fibril diameter of 1 μm or less, having a structure in which the fibrils are arranged in a network or a non-woven fabric on a plane and layered. The composite film according to claim 1, wherein: 4. The composite according to claim 1, wherein the low dielectric resin does not thermally decompose at a temperature of 300 ° C. or less and has a dielectric constant at 1 MHz of 3.0 or less. the film. 5. The low dielectric constant resin is a tetrafluoroethylene resin, a perfluoroalkoxy resin, or a tetrafluoroethylene resin.
It is a propylene hexafluoride copolymer resin, an ethylene tetrafluoride-ethylene copolymer resin, a vinylidene fluoride resin or an ethylene trifluoride ethylene resin.
5. The composite film according to any one of 4. 6. The composite film according to claim 1, wherein a ratio of the low dielectric resin is 20 to 80% by weight of the composite film.
The composite film according to any one of the above. 7. The para-oriented aromatic polyamide is poly (paraphenylene terephthalamide), poly (parabenzamide), poly (4,4′-benzanilide terephthalamide), poly (paraphenylene-4,4′-biphenylene). Dicarboxylic acid amide), poly (paraphenylene-)
2,6-naphthalenedicarboxylic acid amide), poly (2-
The composite film according to any one of claims 1 to 6, wherein the composite film is a copolymer composed of (chloro-paraphenyleneterephthalamide) or paraphenyleneamine / 2,6-dichloroparaphenylenediamine / terephthalic acid dichloride. 8. The composite film according to claim 2, wherein
Short fiber aspect ratio of 50 or more and 200 to 300
The coefficient of linear thermal expansion at ℃ is within ± 50 × 10 ^-6 / ° C,
The staple fibers have a structure present in the film and arranged parallel to the film surface, and the pulp is at 200 to 300 ° C.
Manufactured from raw material fibers having a coefficient of linear thermal expansion within ± 50 × 10 ⁻⁶ / ° C., wherein the pulp is present in the film and has a structure in which the pulp is uniformly dispersed in the film. A composite film comprising: 9. The composite film according to claim 1, wherein the composite film is a porous composite film, and has a porosity of 30 to 95%. 10. A flexible printed circuit board comprising the composite film according to claim 1 as a substrate. 11. A prepreg, wherein the porous composite film according to claim 9 is impregnated with a thermoplastic resin and / or a thermosetting resin. 12. The prepreg according to claim 11, wherein the thermoplastic resin is polyethersulfone, polysulfone, polyetherimide, polysulfidesulfone or polycarbonate. 13. The thermosetting resin according to claim 11, wherein the thermosetting resin is an epoxy resin, a bismaleimide-triazine resin, a polyimide resin, a diallyl phthalate resin, an unsaturated polyester resin, a cyanate resin or an aryl-modified polyphenylene ether resin. The prepreg described. 14. A printed circuit board comprising the prepreg according to claim 11. Description: 15. A printed circuit laminate, comprising: an insulating layer comprising the printed circuit board base according to claim 14; and a conductive layer comprising a metal foil.