JP2003086906A - Flexible circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit board which is flexible so as to reduce its housing space and capable of constituting an electronic circuit in high density. SOLUTION: This flexible circuit board 6 is composed of a flexible heat- resistant film 2 and a circuit pattern formed by a process of applying circuit paste on the surface of the heat-resistant film 2, and baking the heat-resistant film 2 loaded with the circuit paste at a temperature below the endurable temperature of the film 2 and freely deformable like paper. The heat-resistant films 2 are laminated, and circuit patterns provided on the film 2 are electrically connected together, and the flexible circuit boards are laminated into a multilayer circuit board. Therefore, the heat-resistant film 2 is freely deformable, so that the flexible circuit board 6 becomes flexible like paper and can be housed in a small space. Furthermore, circuits made of circuit paste are densely printed on the heat-resistant film 2 by a screen printing technique, so that the flexible circuit board can be improved in electronic circuit density and degree of integration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible circuit board having a flexibility like paper known as electronic paper, and more specifically, a paste is applied to the surface of a heat-resistant film to be a substrate, and heat resistance is improved. TECHNICAL FIELD The present invention relates to a flexible circuit board which is flexible and has a circuit pattern formed by firing a paste at a temperature equal to or lower than the heat resistant temperature of a flexible film, and introducing high durability into the circuit pattern by the firing.

[0002]

2. Description of the Related Art Generally speaking of a circuit board, a copper foil is formed on a rigid, non-deformable bakelite board, and the copper foil is etched to form electrode wiring. (R), capacitor (C), coil (L)
2. Description of the Related Art There are known ones configured by soldering electronic components such as ICs. However, since this circuit board is a rigid body, it requires a large storage space, and since it is difficult to increase the density because it uses an existing electronic component, various improvements have been made.

As a first improvement, in order to increase the density of a circuit pattern, a conductive paste is printed on a substrate in a thick film instead of a solid circuit component, and the paste is 800-
A technique for forming an electrode pattern by firing at a high temperature of 1000 ° C. has been developed. An alumina substrate was used as the substrate to withstand this high temperature firing.

The thick film technique of the electrode pattern enables the electrode wiring to have a high density and a thin layer, and it is not necessary to etch the copper foil substrate to form the electrode pattern.
However, since it is fired at a high temperature, it takes time for heating and cooling, and it has not been possible to form the R and C parts with a conductive paste. Further, since the circuit board itself is a rigid board that cannot be deformed, the circuit board cannot be rolled or spirally formed, which makes it difficult to reduce the volume of the circuit board.

As a second improvement, it has been considered that the rigid substrate is made of a deformable resin film. However, since the resin film has extremely low heat resistance, it is difficult to fire it. For this reason, a technique has been developed in which a copper foil is plated on the entire surface of this resin film and the copper foil is etched to form an electrode pattern.

By using the deformable resin film, the circuit board can be rolled into a spiral shape, and the space for accommodating the circuit board can be reduced as compared with the rigid board. However, it is difficult to increase the density of the circuit pattern because the copper foil etching technique and the existing electronic components are used, and the copper foil etching cannot form the C component and the R component.

Therefore, a third improvement was made. That is, a technical proposal was made to combine the first improvement and the second improvement. However, when the paste is applied to the resin film and baked at a high temperature, the resin film melts and evaporates. Therefore,
A specific technique has been proposed in which a conductive adhesive is used instead of the paste, and the resin film is coated with the conductive adhesive and cured by heating. The heating temperature was set to a temperature at which the resin film was not thermally denatured.

[0008]

However, in this circuit board, although the flexibility of the resin film can be achieved,
It is difficult to increase the density by using a conductive adhesive. The cause is the thermosetting property of the conductive adhesive. Since the conductive adhesive is composed by mixing and dispersing conductive fine particles in a thermosetting adhesive, the conductive particles are in a state of being dispersed between the cured resins when heated and cured, and the cured adhesive has an insulating property. Therefore, the conductivity of the electrode wiring is likely to be insufficient.

Moreover, even if the resin film itself remains flexible, the thermoset resin loses its flexibility, so that the deformability of the resin film after heat curing is extremely small. That is, it becomes difficult to roll the resin film into a spiral shape, and a limit appears in reducing the storage space of the circuit board.

Further, even if the electrode pattern can be formed by the conductive component, it is difficult to form the R part and the C part by this conductive adhesive. In order to configure a circuit board having versatility, it is necessary not only to simply configure an electrode pattern, but also to configure electronic components such as R parts, C parts, and L parts as circuit patterns. Can only be formed.

In order to overcome this drawback, it is necessary to remove the resin component of the conductive adhesive by heating and form the electrode pattern only with the remaining conductive component.
Further, in order to form a circuit pattern, it is necessary to have versatility so that not only a conductive component but also a resistive component or a dielectric component can be used as a circuit forming material.

Moreover, unnecessary components are removed by heating and firing at a higher temperature than before, and only circuit-forming components such as conductive components, resistive components and dielectric components are sintered in place, and at the same heating temperature. The condition is that the resin film is not thermally modified. There is a demand for a flexible circuit board that satisfies these conditions.

Therefore, an object of the present invention is to form a circuit pattern by applying a paste such as a conductive paste or a resistive paste on a deformable heat resistant film without affecting the flexibility of the heat resistant film. It is to develop a flexible circuit board that can be baked at a temperature to remove unnecessary components and can form a circuit pattern only with circuit components.

[0014]

According to a first aspect of the present invention, a flexible heat-resistant film and a paste is applied on the surface of the heat-resistant film in a desired pattern and baked at a temperature lower than the heat-resistant temperature of the heat-resistant film. It is a flexible circuit board which is composed of a circuit pattern formed as described above and is deformable into a paper shape.

According to a second aspect of the present invention, there is provided a flexible circuit board according to the first aspect, wherein a plurality of the heat resistant films are stacked and the circuit patterns of the heat resistant films are electrically connected to each other to form a multilayer board. is there.

According to the third aspect of the present invention, a flexible heat-resistant film is coated with a conductive electrode paste in a desired pattern on the surface of the heat-resistant film and is baked at a temperature lower than the heat-resistant temperature of the heat-resistant film. The flexible circuit board is formed of the formed electrode film pattern and is deformable into a paper shape.

According to a fourth aspect of the present invention, a line-shaped electrode film for connecting the electrode films to each other is formed by firing, and wide regions and narrow regions are alternately formed on the line-shaped electrode film. The flexible circuit board according to claim 3, which constitutes an LC film that functions as an LC circuit.

According to a fifth aspect of the present invention, the spiral electrode film connecting between the electrode films is formed by firing, and the spiral electrode film forms a coil film functioning as an L circuit. It is the described flexible circuit board.

According to a sixth aspect of the present invention, a resistance paste having an electric resistance for connecting the electrode films to each other is applied,
The flexible circuit board according to claim 3, wherein the resistance paste film is fired to form the resistance film.

According to a seventh aspect of the present invention, a capacitor paste is formed by applying a dielectric paste made of a dielectric substance that connects the electrode films to each other and firing the dielectric paste film. 3 is a flexible circuit board.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have prepared a heat-resistant film and a circuit paste, which can be transformed into paper, in order to reduce the storage space and increase the circuit density. Is applied to the surface of the heat-resistant film in a desired shape using a printing technique to form a circuit pattern, and the heat-resistant film is baked at a temperature below the heat-resistant temperature to remove unnecessary components such as resin in the paste. We have come up with a technology for sintering the circuit pattern on the heat-resistant film by removing it by heating.

The heat-resistant film used as the substrate must be deformable into a spiral shape or a folded shape,
This flexibility allows the circuit board to be housed in a small space. In order to be deformable like paper, it may be formed in a film shape. Therefore, the deformable film includes not only an organic film but also an inorganic film.

Further, since this heat-resistant film is used as a circuit board, the surface on which the circuit pattern is formed needs to have electrical insulation. In general, organic films have electrical insulation properties, and many inorganic films also have electrical insulation properties. Among the inorganic films, the metal film has conductivity, but if the surface thereof is coated with an electrically insulating substance, it can be used as the heat resistant film of the present invention.

The heat-resistant organic film usable in the present invention, together with its deflection temperature under load (load of 18.6 kgf / cm ² ) and its abbreviation, is exemplified by polyether sulfone (PE).
S, 216 ° C), polyphenylene sulfide (PP
S, 260 ° C), polyamide (PA, 249 ° C), polyimide (PI, 500 ° C), polyamideimide (PA
I, 279 ° C.), polyetherimide (PEI, 214
℃).

The higher the heat-resistant temperature of the heat-resistant film, the more it can retain its deformability even if it is baked. Therefore, among the heat resistant resins, the polyimide resin has the highest heat resistant temperature and can be suitably used. However, the heat resistant temperature can be further increased by adding a heat resistant material such as glass to the resin, and various known heat resistant organic films can be used.

The heat resistance temperature of the inorganic film is generally higher than that of the organic film, and many oxide type inorganic films and metal films can be used. As described above, the metal film is used as the heat-resistant film of the present invention by forming an insulating inorganic film on the surface or adhering the heat-resistant organic film.

The circuit pattern forming circuit paste used in the present invention includes an electrode film forming electrode paste, a capacitor film forming dielectric paste, a resistance film forming resistor paste, and the like. The electrode paste not only forms an electrode film for wiring, but in a high-frequency circuit, the electrode film is formed into a spiral shape to form an L circuit, or a line-shaped electrode film in which a wide area and a narrow area are alternately formed continuously. An LC circuit can be formed.

The circuit paste is a paste prepared by mixing a resin and an organic solvent with a circuit material to prepare a desired viscosity. When an electrode material, a dielectric material, a resistor material, or the like is selected as the circuit material, the circuit paste functions as an electrode paste, a dielectric paste, a resistor paste, or the like.

As the electrode material, ultrafine metal particles (having a particle size of 1 to 1) are used.
A metal powder composed of several tens of nm) or fine metal particles (having a particle size of several tens nm to several μm) can be used, but an organometallic compound containing an organometallic complex can also be used. When the organometallic compound is made into a paste and baked, the organic component is changed to water, carbon dioxide gas or the like and scattered and removed, and only the metallic component remains.

Examples of the metal include Bi, Cu, In and N
i, Ru, Rh, Pd, Ag, Os, Ir, Pt, Au
A wide range of noble metal and base metal elements such as metal can be used, and the metal element may be selected according to the intended electrode performance.

Of the organometallic compounds, organometallic complexes are often used, for example, balsam compounds, and more specifically, terpineol sulfide gold (C ₁₀ H ₁₈ SAuC).
l _x ), terpineol sulfide platinum (C ₁₀ H ₁₈ SPtC
l _x ), terpineol sulfide palladium (C ₁₀ H ₁₈ SP
dCl _x ) and the like are known. These compounds are generally abbreviated as gold balsam, platinum balsam, and palladium balsam, and other precious metal balsams such as rhodium balsam and ruthenium balsam are known.

From the viewpoint of environmental protection, S (sulfur)
As an organometallic complex not containing a compound of the general formula M (-C≡C-
A metal acetylide compound represented by R) _n can be used.
In this general formula, M represents a metal atom, R represents a hydrocarbon group (which may contain oxygen), and n represents the valence of the metal M.

As the hydrocarbon group R, when oxygen is contained, there is an aliphatic hydrocarbon group contained as a hydroxyl group. In this case, it may be linear or may have a side chain. Specific examples of the ligand —C≡C—R include propyne, 2-propyne-1-ol, and 1-butyne in the form of H—C≡C—R.
3-ol, 3-methyl-1-butyne-3-ol,
3,3-Dimethyl-1-butyne, 1-pentyne, 1-pentyne-3-ol, 4-pentyne-1-ol, 4-
Pentin-2-ol, 4-methyl-1-pentyne, 3
-Methyl-1-pentyne-3-ol, 3,4-dimethyl-1-pentyne-3-ol, 1-hexyne, 1-hexyne-3-ol, 5-hexyne-1-ol -Le, 5-
Methyl-1-hexyne, 5-methyl-1-hexyne-3
-Ol, 3,5-dimethyl-1-hexyne-3-ol
, 1-heptin, 1-heptin-3-ol, 5-heptin-3-ol, 3,6-dimethyl-1-heptin-3-ol, 1-octyne, 1-octyne- 3-Oh
There are such as Le.

Further, as the hydrocarbon group R, there is a hydrocarbon group containing at least a cyclic hydrocarbon which is contained as a hydroxyl group when oxygen is contained. The hydrocarbon group may have a straight chain cyclic hydrocarbon group or a side chain containing a cyclic hydrocarbon group. Of course, this also includes the case where all R are cyclic hydrocarbons. Specific examples of the ligand —C≡C—R include 1-ethynyl-1-cyclopropanol, 1-ethynyl-1-cyclobutanol, in the form of H—C≡C—R.
1-ethynyl-1-cyclopentanol, 1-ethynyl-1-cyclohexanol, 1-propyne-3-cyclopropanol, 1-propyne-3-cyclobutanol,
1-propyne-3-cyclopentanol, 1-butyne-
4-cyclopropanol, 1-butyne-4-cyclobutanol, 1-pentyne-5-cyclopropanol and the like.

As the resistor material, various metal materials from low resistivity materials to high resistivity materials, metal composition materials, and non-metal materials such as carbon-based materials can be used. As the metal, simple metals and alloys can be used. The resistor material can be freely selected according to the desired resistance value. Further, various resistors can be mixed to form an arbitrary resistor material.

As the low-resistivity metal material powder, Al, A
g, Cu, etc. Further, as the high-resistivity metal material powder, Cr, AgPd, W, Ni, NiCr, Pd, Mo, C
There are uZn, CuMn and the like. It is also possible to knead and mix both high and low to form an intermediate synthetic resistivity, and to provide an arbitrary synthetic resistivity material.

Various ceramic powders can be used as the dielectric material forming the capacitor, and among them, high dielectric ceramic materials such as barium titanate and strontium titanate are particularly preferable.

Ceramics can also be used for the construction of electronic components other than capacitors. For example, alumina and steatite can be used in electric energy storage electronic parts, piezoelectric PZT ceramics and Pb composite perovskites in electromechanical conversion electronic parts, and pyroelectric PZT system in electrothermal conversion electronic parts. Ceramics can be used.

The above electrode material powder, resistor material powder or dielectric material powder is mixed with a resin and an organic solvent to prepare a circuit paste having a desired viscosity, that is, an electrode paste, a resistor paste or a dielectric paste. . As this resin,
A resin that is dissolved / dispersed in an organic solvent is selected, and for example, ethyl cellulose, nitrocellulose, butyral, acrylic copay balsam, dammer, and related substances thereof can be used.

As the organic solvent, one in which the resin is dissolved and dispersed is selected, and examples include petroleum solvents, terpineol,
There are esters such as butyl carbitol and ethyl lactate, cellosolves, alcohols, aromatics, and DEP (diethyl phthalate).

The viscosity of these circuit pastes differs depending on the coating conditions (printing conditions) on the heat-resistant film, the firing conditions and the surface condition after firing, and a resin is mixed to adjust the viscosity. The resin is required to be easily dissolved and dispersed in an organic solvent together with the circuit material powder.

The circuit material, organic solvent and resin are mixed to produce a circuit paste. In this case, the blending amount of the components depends on the viscosity of the target paste, but 90% for the circuit material.
It is desirable to use 10 to 10 parts by weight, 5 to 85 parts by weight of organic solvent, and 3 to 30 parts by weight of resin. If necessary, additives may be added in an amount of 1 part by weight to 10 parts by weight.

The viscosity of the circuit paste produced in this range is in the range of 50 p (poise) to 5000 p (poise). When the viscosity becomes smaller than the lower limit value, the circuit paste approaches a liquid, and when the viscosity becomes large, it becomes difficult to reduce the film thickness when the circuit paste is applied to the surface of the heat resistant film.

This circuit paste is applied to a heat resistant film to form a circuit pattern. Forming a circuit pattern using a known screen printing technique has the advantages that it is possible to print with high precision while finely adjusting the line width and film thickness, and to manufacture extremely complex circuit patterns at high speed and in large quantities.

When the circuit pattern can be formed, the heat resistant film is baked. The firing temperature is lower than the heat resistant temperature of the heat resistant film, and higher than the temperature at which the organic components of the circuit paste can be burned and removed. When a heat resistant film having a high heat resistant temperature is used, the firing temperature can be easily set. Therefore,
A polyimide resin film or an inorganic film is preferably used as the heat resistant film.

The circuit pattern is a general term for electrode patterns, dielectric patterns, resistor patterns and the like. Specifically, by firing, the electrode paste film becomes an electrode film, the dielectric paste film becomes a capacitor film, the resistor paste film becomes a resistor film, and an electronic circuit of an arbitrary pattern is formed on the heat resistant film. .

It may be necessary to perform multiple screen printings and multiple firings. Resistors and capacitors are formed by connecting both ends to the electrode film, so after firing the electrode film first, screen the dielectric paste film or resistor paste film so that both ends are on the two electrode films. Printing is performed and then firing is performed to fire the resistor film and the capacitor film. Of course, conversely, the resistor film or the capacitor film may be fired first, and the electrode films may be fired on both ends thereof.

In the high frequency circuit, the spiral electrode film functions as an L circuit (coil), and the line-shaped electrode film in which wide regions and narrow regions are alternately formed functions as an LC circuit. Since the spiral electrode film and the line-shaped electrode film are formed of the same material as the electrode film serving as the wiring, these circuits can be formed at once by screen printing and baking once. Of course, it may be configured in multiple stages.

According to the present invention, since the flexible circuit board is formed by forming the film circuit on the heat resistant film, the thickness of the circuit board is extremely thin. Therefore, a multilayer flexible circuit board can be easily constructed by stacking a plurality of heat-resistant films having a film-shaped circuit and electrically connecting the heat-resistant films.

In particular, by forming a through hole in the heat resistant film and electrically connecting the heat resistant films through the through hole, a multilayer circuit can be easily constructed. Even if it is a multi-layer, the whole thickness is thin, and if the whole is wound in a spiral shape or in a cylindrical shape, the circuit board can be housed in a narrow space.

That is, a fine film-like circuit can be formed by screen printing to increase the density of the circuit, and moreover, it can be housed in a small space by being transformed into a spiral shape, a cylindrical shape, or a folded shape. By mounting the flexible circuit board of the present invention, miniaturization of the electronic device can be promoted.

Embodiments of the flexible circuit board according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a process drawing of a flexible circuit board having an electrode film according to the present invention. In (A), the heat resistant film 2 having a predetermined shape is arranged. This heat resistant film 2 has the flexibility of being deformed like paper. In (B), an electrode paste is screen-printed on the surface of the heat resistant film 2 and the electrode paste film 4a having a desired pattern is applied. This electrode pattern corresponds to the shape of all electrode wirings and is formed by one screen printing. The electrode paste contains an electrode material for forming wiring, that is, a conductive material as a main component.

In (C), the heat resistant film 2 is baked. The firing temperature T (° C.) is set to a temperature equal to or lower than the heat resistant temperature T _e (° C.) of the heat resistant film 2 and higher than or equal to the lowest temperature T _f (° C.) at which the organic components of the electrode paste film 4a can be burned and removed. That is, the firing temperature T is selected within the range where T _f ≤T≤T _e .

When fired at a temperature within the above range, the heat resistant film 2 does not undergo thermal transformation, and its deformability can be maintained even after firing. Further, by this firing, all the organic components of the electrode paste film 4a are burned and removed, so that the electrode film 4 is formed of only the electrode components. The electrode film 4 is firmly bonded to the heat resistant film 2 by firing and does not peel off. In this way, the electrode film 4
The flexible circuit board 6 including the heat resistant film 2 is completed.

FIG. 2 is a volume compression state diagram in which the flexible circuit board of FIG. 1 is wound in a cylindrical shape. When the flexible circuit board 6 is wound in a cylindrical shape, its volume is compressed,
It can also be housed in a small electronic device (not shown). If you wind it in a spiral, you can further reduce the volume,
Depending on the case, folding is also possible.

A back electrode film 8 is formed on the entire back surface of the heat resistant film 2. The back electrode film 8 functions as a ground conductor, and a signal flows between the front electrode film 4 and the back electrode film 8. Particularly, in a high frequency circuit, the electrode film 4 on the surface may function not only as a wiring electrode but also as a microstrip line.

FIG. 3 is a manufacturing process diagram of a flexible circuit board having electrodes and resistors according to the present invention. (A)
Then, the heat resistant film 2 having the electrode film 4 formed thereon is arranged. The heat resistant film 2 is the flexible circuit board manufactured in FIG. 1 and is used as a starting material.

In (B), a resistor paste is applied between the electrode films 4 and 4 by screen printing to form a resistor paste film 10a. This resistor paste contains a resistor material adjusted to have a desired specific resistance as a main component. When forming a plurality of resistor paste films 10a ... With different specific resistance values, they are formed by repeating screen printing a plurality of times.

In (C), the heat resistant film 2 is baked. The firing temperature T (° C.) is set to a temperature equal to or lower than the heat resistant temperature T _e (° C.) of the heat resistant film 2 and equal to or higher than the lowest temperature T _f (° C.) at which the organic component of the resistor paste film 10a can be burned and removed. The lowest temperature T _f is substantially the same as the combustion lowest temperature T _f of the electrode paste film 4a. The firing temperature T is T _f ≤
It is selected within the range of T ≦ T _e .

Even after firing, the heat resistant film 2 retains its deformability. By this firing, all the organic components of the resistor paste film 10a are burned and removed, and the resistor film 10 is made of only the resistor material. The resistor film 10 is extremely strongly bonded to the heat resistant film 2 by firing. In this way, the electrode film 4 and the resistor film 1
Flexible circuit board 6 consisting of 0 and heat resistant film 2
Is completed.

FIG. 4 is an equivalent circuit diagram of the flexible circuit board shown in FIG. The resistor film 10 has a resistance value determined by its width, length, thickness and specific resistance. Therefore, when the resistance film 10 is represented by the resistance R, a circuit in which the resistance R is bridged is formed between the electrode films 4 and 4.

FIG. 5 is a manufacturing process drawing of a flexible circuit board on which a coil and a capacitor according to the present invention are formed.
In (A), the heat resistant film 2 having the electrode film 4 formed thereon is arranged. This heat resistant film 2 is the same as the flexible circuit board manufactured in FIG. 1, and this is used as a starting material.

In (B), the line-shaped electrode paste film 12a is formed between the electrode films 4 and 4 by using the same electrode paste as the electrode film.
To form. The line-shaped electrode paste film 12a is formed as a microstrip line in a high frequency circuit. Wide areas 12b and narrow areas 12c are alternately formed on the paste film 12a.

In the microstrip line, the wide area 1
2b is the capacitor C, and the narrow region 12c is the coil L.
give. In this sense, the line-shaped electrode paste film 12a may be called an LC paste film, the wide region 12b may be called a C paste film, and the narrow region 12c may be called an L paste film. The reactance is determined by the width W _c of the wide region 12b and the width W _L of the narrow region 12c. Further, when the transmitted signal wavelength is λ _g , the reactance design becomes easy when the length of each of the regions 12b and 12c is set to λ _g / 8.

(C) shows a firing step. As described above, the firing temperature T (° C.) is equal to or lower than the heat resistant temperature T _e (° C.) of the heat resistant film 2 and is equal to or higher than the lowest temperature T _f (° C.) at which the organic components of the LC paste film 12a can be burned and removed. Is set. By firing, only the electrode components remain and the LC film 1
The flexible circuit board 6 having the number 2 is completed.

FIG. 6 is an equivalent circuit diagram of the flexible circuit board shown in FIG. LC between the electrode films 4 and 4
The membrane 12 constitutes a low pass filter LPF composed of four coils L and three capacitors C. As described above, when the electrode paste is screen-printed in a specific shape and baked, the circuit of the electrode film 4 and the LPF 12 can be formed. The electrode paste film 4a and the LC paste film 12a can be integrally formed on the heat resistant film 2 at the same time.

FIG. 7 is a manufacturing process drawing of a flexible circuit board on which a capacitor according to the present invention is formed. Particularly, in this case, the step of forming a large-capacity capacitor is shown.
In (A), the heat resistant film 2 having the electrode film 4 formed thereon is arranged. This heat resistant film 2 is the same as the flexible circuit board manufactured in FIG. 1, and this is used as a starting material.

In (B), a dielectric paste is screen-printed on one electrode 4 to form a dielectric paste film 14a. This dielectric paste contains a dielectric material adjusted to have a desired relative dielectric constant as a main component. Multiple screen printings may be repeated to adjust the final dielectric constant.

In (C), the dielectric paste film 14a is formed.
The electrode film 20 is formed so as to be overlapped with the above and to be connected to the other electrode film 4. And the state which baked this whole is shown. As described above, the firing temperature T (° C.) is equal to or lower than the heat resistant temperature T _e (° C.) of the heat resistant film 2 and is equal to or higher than the lowest temperature T _f (° C.) at which the organic component of the dielectric paste film 14a can be burned and removed. Is set to. By this firing, the capacitor film 14 in which only the dielectric component remains is formed on the heat resistant film 2, and the flexible circuit board 6 is completed.

As shown in this process diagram, the electrode paste film 4a
May be fired, and then the dielectric paste film 14a may be fired. Alternatively, the electrode paste film 4a may be applied and dried, then the dielectric paste film 14a may be applied and dried, and then baked at once to form the electrode film 4 and the capacitor film 14 at the same time.

FIG. 8 is an equivalent circuit diagram of the flexible circuit board shown in FIG. The capacitor film 14 between the electrode films 4 and 4 functions as a capacitor C having a specific electric capacity. In general, many capacitors are attached to the circuit board, so that many capacitors C may be simultaneously formed by firing.

FIG. 9 is a manufacturing process diagram of a flexible circuit board having a coil according to the present invention. In (A),
The heat resistant film 2 having the electrode film 4 formed thereon is arranged. This heat resistant film 2 is the same as the flexible circuit board manufactured in FIG. 1, and this is used as a starting material.

In (B), the electrode paste is spirally wound to form a spiral electrode film 16a by screen printing, one end is connected to the electrode film 4 on the surface, and a through hole 16b is punched at the center end. And is connected to the electrode film 4 on the back surface. The electrode paste is the same as that used to form the electrode paste film 4a. The inductance value can be adjusted by the shape of the spiral electrode film 16a. Therefore, the spiral electrode film 16a is also called a coil paste film.

(C) shows the firing step. The firing temperature T (° C.) is set to be equal to or lower than the heat resistant temperature T _e (° C.) of the heat resistant film 2 and higher than or equal to the lowest temperature T _f (° C.) at which the organic components of the coil paste film 16a can be burned and removed. By this firing, only the electrode component remains, the coil film 16 is formed on the heat resistant film 2, and the flexible circuit board 6
Is completed.

FIG. 10 is an equivalent circuit diagram of the flexible circuit board shown in FIG. The coil film 16 between the electrode films 4 and 4 functions as a coil L having a specific inductance. Generally, many coils are attached to the circuit board, so that many coils L can be simultaneously formed by firing.

FIG. 11 is a manufacturing process diagram of a flexible circuit board on which an arbitrary circuit pattern according to the present invention is formed.
In this manufacturing process diagram, the various circuits shown in FIGS. 1 to 10 are formed by firing one heat resistant film 2. However, the capacitor is shown as a small-capacity capacitor.

In (A), the heat resistant film 2 having a predetermined shape
To place. In (B), the electrode paste film 4 is formed by screen-printing an electrode paste on the surface of the heat resistant film 2.
a, LC paste film 12a and coil paste film 16a
Are formed at the same time. In (C), this heat resistant film 2
Is fired to burn and remove all unnecessary organic substances while maintaining the deformability of the heat resistant film 2 to form the electrode film 4, the LC film 12 and the coil film 16 composed of only the electrode components at a stretch.

In (D), a resistor paste and a dielectric paste are screen-printed between the electrode films 4 and 4 in a predetermined shape to form a resistor paste film 10a and a dielectric paste film 14a.
To form. Since the electrode film covering the dielectric paste film 14a is not formed, it corresponds to a small capacity capacitor. In (E), the heat-resistant film 2 is fired to burn and remove all unnecessary organic substances while maintaining the deformability of the heat-resistant film 2, thereby forming the resistor film 10 and the capacitor film 14.
Are formed at the same time. In this way, the final purpose, the flexible circuit board 6, is completed.

Although the firing is performed twice in the above description, the flexible circuit board 6 can be completed by performing the firing once as follows. That is, in (B), the electrode paste film 4a, the LC paste film 12a, and the coil paste film 16 are formed.
A is screen-printed and dried, and then the resistor paste film 10a and the dielectric paste film 14a of (D) are screen-printed. When all the paste films are dried and then finally baked, the flexible circuit board 6 of (E) is completed.

FIG. 12 is an equivalent circuit diagram of the flexible circuit board shown in FIG. A resistor R, a capacitor C, a coil and a low-pass filter L are provided between the electrode films 4 and 4.
The PF is formed. As described above, an arbitrary circuit pattern is freely formed on the flexible circuit board 6 of the present invention.

The present invention is not limited to the above-described embodiments, but includes various modifications, design changes and the like within the technical scope thereof without departing from the technical idea of the present invention.

[0083]

According to the invention of claim 1, a circuit paste is applied to the surface of a flexible heat-resistant film, and the heat-resistant film is baked at a temperature not higher than the heat-resistant temperature to form a circuit pattern. Therefore, various electronic components can be formed into a high-density film with a circuit paste, and the heat-resistant film can be freely deformed into a spiral shape, so that the circuit board storage space can be miniaturized. Therefore, it is possible to provide a flexible circuit board that is most suitable for electronic devices that are becoming smaller and higher in density.

According to the invention of claim 2, a plurality of heat-resistant films having a circuit pattern formed thereon are laminated, and the circuit patterns of the heat-resistant film are electrically connected to each other through through holes or the like. It is possible to realize a flexible circuit board, and to achieve ultra high density of the circuit board.

According to the third aspect of the present invention, since an electrode film having an arbitrary pattern can be formed on the surface of the heat resistant film by the paste technique, a high density electrode film pattern can be formed with high precision, and the heat resistant film is deformed. The flexibility allows the storage space of the circuit board to be miniaturized, which contributes to higher density of electronic devices.

According to the invention of claim 4, an electrode film having an arbitrary pattern can be formed on the surface of the heat resistant film, and the line-shaped electrode film can be baked between the electrode films to form an LC circuit. It is possible to provide a flexible circuit board in which a high-frequency circuit can be freely formed with high density and the heat-resistant film can be freely deformed to occupy a small storage space.

According to the fifth aspect of the present invention, an L circuit can be formed by forming an electrode film having an arbitrary pattern on the surface of the heat resistant film and forming a spiral electrode film between the electrode films. It is possible to provide a flexible circuit board that can miniaturize the storage space while increasing the density of L circuits.

According to the sixth aspect of the present invention, an R film is formed by forming an electrode film having an arbitrary pattern on the surface of the heat resistant film and further forming a resistor film having an arbitrary pattern between the electrode films. Thus, it is possible to provide a flexible circuit board that can miniaturize the storage space while increasing the density of the R circuit.

According to the invention of claim 7, a C circuit can be formed by forming an electrode film of an arbitrary pattern on the surface of the heat resistant film and further forming a capacitor film of an arbitrary pattern between the electrode films. , A flexible circuit board which can miniaturize the storage space as well as the density of C circuits can be provided.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram of a flexible circuit board having an electrode film according to the present invention.

FIG. 2 is a volume compression state diagram in which the flexible circuit board of FIG. 1 is wound into a cylindrical shape.

FIG. 3 is a manufacturing process diagram of a flexible circuit board on which electrodes and resistors according to the present invention are formed.

FIG. 4 is an equivalent circuit diagram of the flexible circuit board shown in FIG.

FIG. 5 is a manufacturing process diagram of a flexible circuit board on which a coil and a capacitor according to the present invention are formed.

6 is an equivalent circuit diagram of the flexible circuit board shown in FIG.

FIG. 7 is a manufacturing process diagram of a flexible circuit board on which a capacitor according to the present invention is formed.

8 is an equivalent circuit diagram of the flexible circuit board shown in FIG.

FIG. 9 is a manufacturing process diagram of a flexible circuit board having a coil according to the present invention.

10 is an equivalent circuit diagram of the flexible circuit board shown in FIG.

FIG. 11 is a manufacturing process diagram of a flexible circuit board on which an arbitrary circuit pattern according to the present invention is formed.

12 is an equivalent circuit diagram of the flexible circuit board shown in FIG.

[Explanation of symbols]

2 is a heat resistant film, 4a is an electrode paste film, 4 is an electrode film, 6 is a flexible circuit board, 8 is a back electrode film, 10
a is a resistor paste film, 10 is a resistor film, 12a is a line-shaped electrode paste film (LC paste film), 12b is a wide region (C paste film), 12c is a narrow region (L paste film), and 12 is a line. Electrode film (LC film), 14a is a dielectric paste film, 14 is a capacitor film, 16a is a spiral electrode paste film (coil paste film), 16b is a through hole, 20 is an electrode film, C is a capacitor, L is a coil , L
PF is a low pass filter and R is a resistor.

Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05K 3/46 H05K 3/46 N Q T (72) Inventor Akio Harada 2-7, Tadashi Nishi, Joto-ku, Osaka City, Osaka Prefecture No. 19 F-term in Daiken Chemical Co., Ltd. (reference) 4E351 AA04 BB01 BB03 BB05 BB09 BB22 BB31 CC11 DD04 DD05 DD10 DD17 DD19 DD20 DD22 DD23 DD43 DD52 EE12 GG20 5E338 AA01 AA03 AA05 AA12 AA16 EE23 EE24 BB23 A25 A33 AA02 A18 BB38 BB39 BB40 BB44 BB52 BB62 BB75 DD02 ER35 GG20 5E346 AA12 AA13 AA14 AA15 AA43 CC02 CC10 CC32 CC34 CC35 CC36 CC37 CC39 DD34 EE04 EE08 FF18 GG15 GG19 GG28 HH24 HH25

Claims (7)

[Claims] 1. A flexible heat-resistant film, and a circuit pattern formed by applying a circuit paste on the surface of the heat-resistant film and baking the paste at a temperature not higher than the heat-resistant temperature of the heat-resistant film. A flexible circuit board that can be deformed into a shape. 2. The flexible circuit board according to claim 1, wherein a plurality of the heat resistant films are stacked and the circuit patterns of the heat resistant films are electrically connected to each other to form a multilayer board. 3. A flexible heat-resistant film, and an electrode film pattern formed by applying a conductive electrode paste on the surface of the heat-resistant film and firing it at a temperature lower than the heat-resistant temperature of the heat-resistant film. The flexible circuit board is characterized by being deformed into a paper shape. 4. A line-shaped electrode film for connecting between the electrode films is formed by firing, and a wide region and a narrow region are alternately formed on the line-shaped electrode film to function as an LC circuit. The flexible circuit board according to claim 3, which constitutes an LC film. 5. The flexible circuit board according to claim 3, wherein a spiral electrode film connecting between the electrode films is formed by firing, and the spiral electrode film forms a coil film functioning as an L circuit. . 6. The flexible circuit board according to claim 3, wherein a resistance paste having electrical resistance for connecting between the electrode films is applied and the resistance paste film is fired to form the resistance film. 7. The flexible film according to claim 3, wherein a dielectric paste made of a dielectric material that connects the electrode films to each other is applied, and the dielectric paste film is baked to form a capacitor film. Circuit board.