JPH0448678A - Flexible printed circuit board - Google Patents

Abstract

PURPOSE:To prevent deformation caused by moisture absorption and improve dimensional stability by using a crystalline film, which is made of polyether copolymer resin at the specified composition ratio and of the specified melt viscosity, as an insulating substrate and forming a conductive layer thereon. CONSTITUTION:A polyether copolymer resin crystalline film, which is composed of cyclic units shown by formulae (I) and (II), the molar composition rate of the cyclic unit shown by formula (I), represented by (I)/{(I)+(II)}, of which is 0.15-0.40 moles, and the melt viscosity of which is 3,000-100,000 P at 400 deg.C, is used as an insulating substrate and a conductive layer is formed thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a flexible printed circuit board using a crystalline film made of a polyether copolymer as an insulating substrate. More specifically, it has excellent properties such as heat resistance and mechanical properties.

In particular, the present invention relates to a flexible printed circuit board made of an insulating substrate made of a crystalline film made of a polyether copolymer which has a low water absorption coefficient and a small coefficient of hygroscopic expansion, is free from deformation due to moisture absorption, and has excellent one-dimensional stability.

[Prior art and problems to be solved by the invention In recent years, various engineering plastics such as polyamide, polyester, polysulfone, and boimide have been developed with the aim of producing materials with excellent heat resistance, mechanical properties, and dimensional stability. Films formed using this material are used for a wide range of purposes in the electronic, electronic, and industrial fields.

Among these, polyimide film is still said to have excellent properties, but one of its problems is that it has a high expansion rate due to moisture absorption.

It is cited that it has poor dimensional stability. In other words, in flexible printed circuit boards made by laminating metal on a polyimide film, there is a large difference in humidity expansion coefficient between the resin film and the metal layer, which causes the printed circuit board to warp and deform. .

The present invention has been made based on the above-mentioned circumstances, and its object is to provide a film made of a polyether copolymer having properties on the same level as the above-mentioned polyimide products and having a small coefficient of humidity expansion. An object of the present invention is to provide a flexible printed circuit board which does not undergo deformation such as warping due to a difference in humidity expansion coefficient.

[Means to solve problems The structure of the present invention is to achieve the above object.

Consisting of a repeating unit represented by the following formula (1); and a repeating unit represented by the following formula (■); (II), the composition ratio of the repeating unit represented by the formula (1) [molar ratio )/((I)
+(II))] or 0.15 to 0-40-T, and the melt viscosity at 400°C is 3.000 to 10
This is a flexible printed circuit board characterized in that an insulating substrate is a crystalline film made of a polyether copolymer resin having a void of 0,000, and a conductive layer is provided on the insulating substrate.

This will be explained in detail below.

The flexible printed circuit board (hereinafter referred to as printed circuit board) of the present invention uses a crystalline film made of a polyether copolymer as an insulating substrate.

The crystalline film insulating substrate made of this polyether copolymer exhibits a dimensional change of 0.2% or less when the heating temperature is 250° C. and the heating time is 30 seconds during soldering. In addition, the coefficient of thermal expansion is 1.5 x 10-' ~ 2.5 x
10-', which is 2.2% of the coefficient of thermal expansion of conductive metals such as copper, nickel, and silver. The value is close to Ox 10-'.

Furthermore, this insulating substrate has a humidity expansion coefficient of 5xto-'/
%R)I (RH is relative humidity) or less, and the water absorption rate is less than 0.5%, so deformation such as warping of the substrate due to moisture absorption is unlikely to occur.

In addition, polyether copolymers exhibit sufficiently excellent electrical properties. Therefore, crystalline films made of polyether copolymers are excellent as q insulating substrates for flexible printed circuit boards. be.

The Botether copolymer, which is the basic material of this insulating substrate, will be explained below.

-Polyether copolymer- One of the important points about the polyether copolymer that is the raw material for the insulating substrate in the flexible printed circuit board of the present invention is that the polyether copolymer is the polyether copolymer or the formula (
consisting of a repeating unit represented by I) and a repeating unit represented by formula (II), and
The content ratio of repeating units expressed as [molar ratio, (I)
/((I)+(■)) is in the range of 0.15 to 0.40, and the composition ratio (molar ratio) of the repeating unit represented by the formula (■) is 0.85 to 0.60. That's true.

The composition ratio of the reversing unit represented by the formula (I) is 0.
If it is less than 15, the glass transition temperature of the polyether copolymer will be low, resulting in a decrease in heat resistance, or the melting point will be high, leading to deterioration in moldability. On the other hand, when it exceeds 0.40, the crystallinity of the polyether polymer is lost, resulting in a decrease in heat resistance and oxidation properties.

Further, in the polyether copolymer used in the present invention, it is important that the melt viscosity (zero shear viscosity) at a temperature of 400°C is 3,000 to 100,000 poise.

This is because a low molecular weight polyether copolymer having a melt viscosity of less than 3,000 voids cannot achieve sufficient heat resistance and mechanical strength.

Moreover, when the melt viscosity exceeds 100,000 voids, the moldability such as forming into a film deteriorates.

The polyether copolymer used in the present invention has, for example, a crystal melting point of about 330 to 400°C, which allows for high crystallinity, has a sufficiently high molecular weight, exhibits sufficient heat resistance, and Excellent solvent resistance and mechanical strength.
For example, it can be suitably used as a new material in the electrical/electronic equipment field, mechanical field, etc.

Such a polyether copolymer can be produced as follows.

-Production method of polyether copolymer-Polyether copolymer is produced by reacting dihalogenobenzonitrile, 4,4'-biphenol, and an alkali metal compound in the presence of a neutral polar solvent in a specific usage ratio. After that, the reaction product can be produced by carrying out a copolymerization reaction with a specific amount of 4,4'-dihalogenobenzophenone.

Specific examples of the dihalogenobenzonitrile that can be used include the following formula.

Examples thereof include 2,6-dihalogenobenzonitrile and 2,4-dihalogenobenzonitrile represented by N (wherein, X is a halogen atom).

Among these, 2,6-dichlorobenzonitrile, 2,6-cyfluoropenzonitrile, 2,4
-dichlorobenzonitrile, 2°4-cyfluoropenzonitol, and 2,6-dichlorobenzonitrile is particularly preferred.

The dihalogenobenzonitrile and 4 represented by the following formula;
, 4'-biphenol in the presence of an alkali metal compound and a neutral polar solvent.

The alkali metal compound to be used is as described in 4.4 above.
Any substance that can convert '-biphenol into an alkali gold Ji salt may be used, and there are no particular restrictions, but alkali metal carbonates and alkali metal hydrogen carbonates are preferred.

Examples of the alkali gold carbonate include charcoal lithium, sodium carbonate, potassium carbonate, rubidium carbonate,
Examples include cesium carbonate.

Among these, preferred are sodium carbonate and potassium carbonate.

Examples of the alkali metal hydrogen carbonate include lithium hydrogen carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate,
Examples include rubidium hydrogen carbonate and cesium hydrogen carbonate.

Among these, preferred are sodium hydrogen carbonate and potassium hydrogen carbonate.

Examples of the neutral polar solvent include N,N-dimethylformamide N, N-diethylformamide, N,N-
Dimethylacetamide, N.

N-diethylacetamide, N,N-dipropylacetamide, N,N-dimethylbenzoic acid amide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-
Isopropyl-2-pyrrolidone, N-isobutyl-2-
Pyrrolidone, N-n-propyl-2-pyrrolidone, N-
n-phthyl-2-pyrrolidone, N-cyclohexyl-2
Pyrrolidone, N-methyl-3-methyl-2-hypersoton, N-ethyl-3-methyl-2-pyrrolidone, N-methyl-3,4,5-hysomethyl-2-pyrrolidone, N-
Methyl-2-piperitone, N-ethyl-2-piperitone, N,-isopropyl-2-piperitone, N-methyl-
6-Methyl-2-piperitone, N-methyl-3-ethylpiperitone, dimethyl sulfoxide, diethyl sulfoxide, l-methyl-1-oxosulfolane, 1-ethyl-1-oxosulfolane, l-7enyl-1-year-old xosulfolane, N , N'-dimethylimidazolidinone, diphenyl sulfone and the like.

As an example of the production method, the reaction product obtained by reacting the dihalogenobenzonitrile with the 4.4'-biphenol in the presence of the alkali metal compound and the neutral polar solvent, and the reaction product obtained in 4. React with 4'-dihalogenobenzophenone.

The 4,4'-dihalogenobenzophenone used is a compound represented by the following formula: (wherein, X has the same meaning as above), and in the present invention, the 4,4'-dihalogenobenzophenone Difluorobenzophenone and 4,4-dichlorobenzophenone are particularly preferably used.

The molar ratio of the total amount of dihalogenobenzonitrile and 4,4°-dihalogenobenzophenone to the amount of 4,4'-biphenol used is usually 0.98 to 1.02.
．． Preferably, l is 00 to 1.01. The molar ratio of the alkali metal compound to 4.4′-biphenol is
Usually 1.03-2.50, preferably 1.05-2.50
It is 1.25.

There is no particular restriction on the amount of the neutral polar solvent used, but usually the total amount of the dihalogenobenzonitrile, the 4゜4゛-biphenol, and the alkali metal compound is used per 200 ml of the neutral polar solvent. The amount is adjusted to 0.05 to 1 mole.

To obtain the polyether copolymer, for example, the dihalogenobenzonitrile, the 4.4°-biphenol, and the alkali metal compound are added simultaneously to the neutral polar solvent.

After the reaction between the dihalogenobenzonitrile and the 4.4'biphenol, the 4.4°-dihalogenobenzophenone is further added, usually to a concentration of 150 to 38
A series of reactions is carried out at a temperature in the range of 0°C, preferably 180 to 330°C.If the reaction temperature is less than 150°C, the reaction rate is too slow to be practical.
If the temperature exceeds 0°C, side reactions may occur.

In addition, the reaction time of this series of reactions is usually 0.1 to 10
The time is preferably 0.5 to 5 hours.

After completion of the reaction, the polyether copolymer is separated and purified from the resulting neutral polar solvent solution containing the polyether copolymer according to a known method to obtain a botether copolymer. It comes.

In addition, the polyether copolymer used in the present invention is
It can also be obtained by simultaneously adding dihalogenobenzonitrile, biphenol, alkali metal salt, and dihalogenobenzophenone to a neutral polar solvent.

The polyether copolymer used in the present invention is 4
Melt viscosity at 00°C 3,000~too,000
It has a crystalline melting point of 330-400°C.

In the present invention, the content of the alkali metal salt contained in the polyether copolymer, which is the raw material for the insulating substrate, is as low as possible, particularly 50 pp or less. desirable.

This is because if a polyether copolymer contains more than 50 ppm of alkali metal salt, a flexible printed circuit board having an insulating substrate formed from such a polyether copolymer may be damaged for a long period of time. This is because when used, it may corrode the metal parts of peripheral devices.

In order to reduce the alkali metal salt in the polyether copolymer after completion of polymerization, the polyether copolymer is treated with an acidic aqueous solution containing an organic acid or no acid and adjusted to pH 3.5 or less, Should I wash it?

Examples of the organic acids include monocarboxylic acids such as formic acid, acetic acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, and propionic acid, and dicarboxylic acids such as oxalic acid and malonic acid. Among these, dicarboxylic acids such as oxalic acid are preferred, and oxalic acid is particularly preferred. Incidentally, these organic acids can be used alone, or they can be used alone. The above can also be used together.

Examples of the inorganic acid include hydrochloric acid, sulfuric acid, and phosphoric acid. Among these, hydrochloric acid is preferred.

It is preferable to adjust the concentration of the solution containing these acids so that the pH is 3.5 or less, or to determine the type of acid.

The time for washing the polyether copolymer with the acidic aqueous solution is sufficient for the content of the alkali metal salt in the polyether copolymer to be 50 pp1 or less. In addition,
In order to promote the desalination effect by washing, the mixture of the acidic aqueous solution and the polyether copolymer may be heated or heated under pressure during washing.

After washing with an acidic aqueous solution, it is recommended to wash thoroughly with pure water, ion-exchanged water, distilled water, etc. in order to remove the acid from the polyether copolymer.

Next, the insulating substrate in the present invention can be formed from the polyether copolymer, preferably the polyether copolymer that has been sufficiently desalted; It can also be formed from a polyether copolymer resin composition in which a copolymer and an inorganic filler are mixed.

The polyether copolymer resin composition contains the polyether copolymer and the inorganic filler, and the content of the inorganic filler is less than 10% by weight, preferably less than 10% by weight, based on the polyether copolymer. By setting o, oos to 5% by weight, the slipperiness of the surface of the insulating substrate is improved, and by setting the content to 10 to 50% by weight, preferably 15 to 40% by weight, the coefficient of thermal expansion is small. It is possible to obtain an insulating substrate.

Examples of the inorganic filler include carbonates such as calcium carbonate, magnesium carbonate, and dolomite, sulfates such as calcium sulfate and magnesium sulfate, sulfites such as calcium sulfite, talc, clay, mica, asbestos, glass fiber, and glass. In the present invention, preferred examples include silicates such as carbon dioxide, calcium silicate, montmorillonite bentonite, silicon dioxide, alumina, silicon carbide, silicon nitride, ceramics such as silicon nitride, and their whiskers. Calcium carbonate, silicon dioxide, alumina clay (kaolin, bentonite, clay, etc.), talc, metal oxides (MgO, ZnO,
Ti02) etc.

The non-41-hole filler may be in the form of granules, plates, or fibers, and in this invention, the particle size is 5 μm.
It is sufficient if it is less than m, and preferably a finer one is used.

These inorganic fillers may be used alone or in combination of two or more.

The polyether copolymer resin composition is prepared by adding 50% by weight or less of an appropriately selected inorganic filler to the polyether copolymer paratar obtained by the above-mentioned polyether copolymer manufacturing method. It can be obtained by mixing proportions, heating, kneading in an extruder, and pelletizing.

Furthermore, a botether copolymer composition can also be obtained by employing a method of producing a botether copolymer in the presence of an inorganic filler.

- Creation of an insulating substrate - In the present invention, a crystallized film is created from the obtained polyether copolymer or the polyether copolymer resin composition, and an insulating substrate is created from it.

In order to obtain a crystallized film, first, a polyether copolymer or the polyether copolymer resin composition is formed into a film.

Forming into a film is performed using a conventional method such as extrusion molding or press molding at a temperature of 10 to 100°C higher than the crystal melting point, preferably 30 to 70°C higher than the crystal melting point, and then rapidly cooled. By this method, a non-grade film with good transparency can be obtained.

For example, the polyether copolymer or polyether copolymer resin composition is supplied to an extruder, the resin temperature is set at 350 to 450°C, the molten state is extruded through a slit-shaped die, and the mixture is cooled and solidified. Accordingly, it is possible to produce an unstretched, non-quality film of a polyether copolymer or a polyether copolymer resin composition.

Or press at a temperature of 350 to 450 using a heat press machine.
By producing a press film at .degree. C., it is possible to obtain an unstretched, unstretched film of a polyether copolymer or a polyether copolymer resin composition.

Then, a stretched film can be produced by uniaxially or biaxially stretching and orienting these unstretched films.

The stretching method may be either simultaneous biaxial stretching or sequential stretching on each axis.

The stretching temperature is a temperature between the glass transition temperature and the crystal melting point,
For example, it is carried out at 180-250°C.

The stretching ratio is preferably 1.2 to 3 times, particularly preferably 1.3 to 2.5 times.

If the stretching ratio is less than 1.2 times, sufficient stretching effect (improving effect on film properties such as tensile strength and tensile modulus) may not be achieved, and even if the stretching ratio is more than 3 times, The stretching effect may not be further improved.

Furthermore, by heat-treating the film before stretching or the stretched film after stretching, it is possible to obtain a heat-treated film with significantly improved heat resistance.

Heat treatment is carried out by heating at a temperature between the crystallization temperature and the crystal melting point, resulting in a crystallized film.

Regardless of the stretching, the heat treatment is performed under tension, and the crystallization temperature is higher than the temperature at which the film-formed and amorphous polymer crystallizes by heat treatment (temperature elevation) and lower than the crystal melting point. For example, it is carried out at 190-370°C.

As a preferred example, the stretched film may be fixed with a metal frame or the like, and heat treated under tension while heating at 190 to 370°C for 1 to 600 sheets.

There are no particular restrictions on the heating method, and various means can be employed.

Furthermore, the heat-treated film obtained by this heat treatment is
The heat treatment may be performed again at around the heat treatment temperature.

This reheat treatment is preferably carried out under tension or without tension as required, and at a temperature between the glass transition temperature of the polyether copolymer resin composition and the heat treatment temperature.

By performing this reheat treatment, the heat shrinkage rate of the heat-treated film is reduced, and a film with excellent dimensional stability can be obtained.

- Preparation of flexible printed circuit board - The flexible printed circuit board of the present invention is produced by applying electrically conductive material to the surface of the crystallized film made of a polyether copolymer and wiring based on electrical design. It can be obtained by forming a pattern.

Examples of the conductive material include commonly used metal foils such as copper foil, aluminum foil, and silver foil. Among these, copper foil is preferable.
Electrolytic copper foil or rolled copper foil of pm, 3 Spm, 70 gm is used.

There are no particular restrictions on the specific means for bonding or shaping the metal foil. For example, the so-called subtractive method, in which metal foil such as copper foil is pasted onto an insulating substrate, and then pattern-etched on the metal foil; An additive method in which copper or the like is plated in a pattern, a stamping foil method in which copper foil or the like punched out in a pattern is bonded to an insulating substrate, etc. can be used.

[Examples] Next, the present invention will be explained in more detail based on examples.

(Example 1) 32.34 g of 2,6-cyclopenzonitrile was placed in a reactor with an internal volume of 5 fL equipped with a Dean-Starck trap filled with toluene, a stirring device, and an argon gas blowing tube.
(0,i88 mol), 4,4'-biphenol 139
．． 66 g (0.75 mol), potassium carbonate 124.3
9 g (0.9 mol) and 1.5 moles of N-methyl-2-pyrrolidone were added, and the temperature was raised from room temperature to 195°C over 1 hour while blowing argon gas.

After the temperature was raised, a small amount of toluene was added and the resulting water was removed with a sieve.

Next, after carrying out the reaction at a temperature of 195°C for 30 minutes, 4,4'-difluorobenzophenone 122
．． A solution of 85 g (0,563 mol) dissolved in 1.5 g of N-methyl-2-pyrrolidone was added, and the reaction was continued for an additional hour.

After the reaction, the product was pulverized with a blender (manufactured by Warninck), washed with acetone, methanol, water, and acetone in that order, and dried to obtain 259.36 g of a white powdery copolymer (yield 98%).

When the properties of this polyether copolymer were measured, the melt viscosity (ηm) (zero shear viscosity) at a temperature of 400°C was 13.000 voids, and the glass transition temperature (Tg) was 182°C1 crystal melting point (TI) 379°C
1 Crystallization temperature (Tcc) 241°C Thermal decomposition start temperature (
Td) and 562°C (5% weight loss in air).

This polyether copolymer was found to have the following repeating unit from its infrared absorption spectrum analysis.

N (ab) (Ia) / ((Ia) + (II
b) ) =0.25 This polymer was formed into a film by hot pressing (400°C) and heat treated at 250°C to obtain a crystallized film with a thickness of 25 μm.

Electrolytic copper foil was attached to the surface of this film using an epoxy resin adhesive, and the temperature was 120°C5kg/C■2
A flexible printed circuit board (FPC) was fabricated by heat-pressing and etching a test pattern. The various properties shown in Table 1 were measured for this FPC.

(Example 2) The proportion of repeating units represented by formula (Ia) or (Ia
)/((Ia)+(nb))=OJ A polyether copolymer was produced in the same manner as in Example 1, except that the amount of raw materials charged was changed so that the melt viscosity [η
m] or 16,000 voids, and the glass transition temperature [T
g] is 185°C, and the crystal melting point [Tm] is 348°C.
A polymer having a crystallization temperature [Tcc] of 250°C and a thermal decomposition onset temperature [Td] of 560°C was obtained.

This polymer was formed into a film and crystallized in the same manner as in Example 1, and then an FPC was created using electrolytic copper foil and various properties were measured.

(Comparative example) Using a commercially available polyimide film (manufactured by DuPont, trade name "Kapton J 200H"), an FPC was created using electrolytic copper foil in the same manner as in Example 1, and various characteristics were similarly measured. Comparisons are shown in Table 1.

Table 1 shows that the EPC of the present invention is superior to the FPC using "Kapton" in terms of water absorption and humidity expansion coefficient.

4. Effects of the invention According to the present invention, it has excellent properties such as thermal properties and mechanical properties, and has particularly low water absorption and hygroscopic expansion.
It is possible to provide a flexible flexible circuit board made of an insulating substrate made of a crystalline film made of a polyether copolymer that does not undergo deformation due to moisture absorption and has excellent dimensional stability.

Claims (1)

[Claims] (1) The following formula (I); ▲There are mathematical formulas, chemical formulas, tables, etc.▼ The repeating unit represented by (I) and the following formula (II); ▲There are mathematical formulas, chemical formulas, tables, etc.▼ Represented by (II) The composition ratio of the repeating units represented by the above formula (I) [molar ratio: (I)/{(
I)+(II)}] is 0.15 to 0.40 mol, and the melt viscosity at 400°C is 3,000 to 10
1. A flexible printed circuit board, characterized in that the insulating substrate is a crystalline film made of a polyether copolymer resin having a poise of 0,800, and a conductive layer is provided on the insulating substrate.