JP2010050205A - Membrane wiring board and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane wiring board for making the specific resistance of a highly conductive film forming a circuit pattern sufficiently low, and to provide a method of manufacturing the same. <P>SOLUTION: The membrane wiring board 1 has the highly conductive film 3 formed having the desired circuit pattern by coating a surface 2a of a base 2 with highly conductive silver paste and drying the paste, and a black film 4 is formed on the highly conductive film 3, wherein the black film 4 is a conductive black film formed by applying and drying conductive ink. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a membrane wiring board and a manufacturing method thereof, and more particularly to a membrane wiring board capable of reducing the specific resistance of a high conductive film constituting a circuit pattern and a manufacturing method thereof.

Conventionally, as a printed wiring board, a conductive coating film having a desired circuit pattern is formed by printing a conductive paste such as a polymer-type silver paste on a film-like substrate such as polyethylene terephthalate (PET) by screen printing or the like. Membrane wiring boards are known.
In recent years, a membrane wiring board having a highly conductive coating film formed of a highly conductive silver paste mainly composed of silver oxide has been proposed and put into practical use as a membrane wiring board having a lower specific resistance than conventional membrane wiring boards. .

This low resistivity membrane wiring board is made by drying (baking) high-conductivity silver paste at a high temperature of about 150 ° C., thereby reducing the silver oxide particles contained therein and at the same time causing fusion between the silver oxide particles. A specific resistance of about 1.0 × 10 ⁻⁶ Ωcm is obtained.
Since this membrane wiring board has the characteristics of low specific resistance and low impedance, for example, an antenna circuit board for an RF-ID tag which has been attracting attention in recent years, or a circuit board for an IC card mounted with a coil, etc. The use is expanding. For this reason, the production volume is gradually increasing, and this field is expected to grow in the future (see, for example, Patent Documents 1 and 2).
Japanese Patent Laid-Open No. 2007-73837 Japanese Patent No. 396334

By the way, in the conventional low resistivity membrane wiring board, in order to reduce the silver oxide particles and simultaneously promote the fusion between the silver oxide particles, it is necessary to increase the drying time of the high conductive silver paste. However, since normal tunnel furnaces are not designed to take longer drying times, in order to increase the drying time of highly conductive silver paste, after passing through the tunnel furnace, it is heated again using a separate batch furnace. There is a problem that the manufacturing process becomes complicated and the process time becomes long.
In addition, for example, in an antenna circuit board for an RF-ID tag, a substrate material wound in a roll shape is used, and the completed circuit board is also delivered in a roll shape, so that heating using a batch furnace itself is required. This is not possible, and there is a problem that the characteristics of the highly conductive silver paste cannot be fully exploited.
Therefore, after passing through the tunnel furnace, a method of passing through the tunnel furnace again is conceivable, but in this case, measures such as extremely reducing the feed rate in the tunnel furnace or increasing the number of times of passage through the tunnel furnace, etc. Is necessary, impractical and not realistic.

On the other hand, a tunnel furnace using an infrared (IR) heater has a feature that drying proceeds more efficiently than a conventional hot air circulation type tunnel furnace. It is conceivable to dry the silver paste, but in this case, there are the following problems.
That is, since the highly conductive silver paste exhibits a black color derived from silver oxide, it efficiently absorbs infrared rays (IR) and advances the reduction reaction of silver oxide very efficiently. However, once the reduction reaction is completed, the coating obtained by reducing this highly conductive silver paste will exhibit a metallic luster and reflect far-infrared rays. Therefore, even if this infrared (IR) tunnel furnace is used, it is difficult to dry in a short time.

  The present invention has been made to solve the above problems, and provides a membrane wiring board capable of sufficiently reducing the specific resistance of a high conductive film constituting a circuit pattern, and a method for manufacturing the same. For the purpose.

  The membrane wiring board according to claim 1 of the present invention is a membrane wiring board in which a highly conductive film having a desired circuit pattern formed by applying and drying a highly conductive silver paste on one main surface of a substrate is formed. A black film is formed on the high conductive film.

  The membrane wiring board according to claim 2 of the present invention is the membrane wiring board according to claim 1, wherein the black film is a conductive black film formed by applying and drying conductive ink.

The membrane wiring board according to a third aspect of the present invention is the membrane wiring board according to the first or second aspect, wherein the specific resistance of the high conductive film is 1.0 × 10 ⁻⁵ Ωcm or less. .

  In the method for producing a membrane wiring board according to claim 4 of the present invention, a highly conductive silver paste is applied to one main surface of a substrate and dried to form a highly conductive coating film having a desired circuit pattern, A black ink is applied onto the highly conductive coating film, and the highly conductive coating film and the black ink are heated with infrared rays to form a highly conductive film and a black film.

  A method for manufacturing a membrane wiring board according to a fifth aspect of the present invention is the method for manufacturing a membrane wiring board according to the fourth aspect, wherein the infrared rays are far infrared rays.

  A method for manufacturing a membrane wiring board according to a sixth aspect of the present invention is the method for manufacturing a membrane wiring board according to the fourth or fifth aspect, wherein the black ink is a conductive ink.

  According to the present invention, since the black film is formed on the high conductive film obtained by applying and drying the high conductive silver paste, the specific resistance of the high conductive film constituting the circuit pattern can be sufficiently lowered. The in-plane uniformity of this specific resistance is also excellent. Therefore, it is possible to provide a membrane wiring board having a circuit pattern made of a high conductive film having excellent in-plane uniformity and low specific resistance.

  Also, a black ink is applied on a highly conductive coating film obtained by applying and drying a highly conductive silver paste, and the highly conductive coating film and black ink are heated with infrared rays to form a highly conductive film and a black film. Therefore, it is possible to easily manufacture a membrane wiring board having a circuit pattern made of a highly conductive film having excellent in-plane uniformity and low specific resistance only by adding a process of short-time infrared heating.

The best mode for carrying out the membrane wiring board and the manufacturing method thereof of the present invention will be described.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

FIG. 1 is a cross-sectional view showing a membrane wiring board according to an embodiment of the present invention.
In the figure, reference numeral 1 denotes a membrane wiring board, a base material 2, a high conductive film 3 formed on the surface (one main surface) 2 a of the base material 2, and a black color formed on the high conductive film 3. The film 4 is constituted.

  The base material 2 is made of an insulating material having flexibility, and the shape thereof can be selected and used from a sheet shape, a film shape, and a thin plate shape according to applications. In particular, in order to apply to an antenna circuit board for an RF-ID tag or a circuit board for an IC card on which a coil is mounted, a sheet or film is preferable.

As a material of the base material 2, plastics such as saturated polyester such as polyethylene terephthalate and polyethylene naphthalate, polyimide, polyphenylene sulfide, polyethylene, polypropylene, and polyamide are preferable.
Further, the thickness of the base material 2 is determined by the required specifications. For example, in the case of an antenna circuit board for an RF-ID tag, a circuit board for an IC card, etc., 25 μm to 200 μm is preferable. is there.

The high conductive film 3 is a low specific resistance film having a desired circuit pattern formed by applying and drying a high conductive silver paste, reducing the particulate silver compound into metal silver particles, and these metals. The silver particles are significantly fused by heating with infrared rays.
The average particle size of the particulate silver compound is in the range of 0.01 μm or more and 10 μm or less. can do. In particular, it is preferable to use a particulate silver compound having an average particle size of 0.5 μm or less because the speed of the reduction reaction is increased.

The specific resistance of the high conductive film 3 is preferably 1.0 × 10 ⁻⁵ Ωcm or less, and more preferably 8.0 × 10 ⁻⁶ Ωcm or less. In addition, the circuit pattern constituted by the high conductive film 3 has, for example, a thickness of 1 μm to 35 μm, a line width of 50 μm to 50 mm, and a line spacing of about 50 μm to 100 mm.

The black film 4 is a conductive black film formed by applying and drying conductive ink.
This conductive black film contains conductive particles such as carbon, carbon nanotubes, and carbon fibers, and has a specific resistance of 1.0 × 10 ⁻² Ω · cm or more.

Next, the manufacturing method of the membrane wiring board of this embodiment is demonstrated.
First, a highly conductive silver paste is applied to the surface (one main surface) 2a of the substrate 2 and dried to form a highly conductive coating film having a desired circuit pattern.

  This highly conductive silver paste is a patent application already filed by the present inventors as Japanese Patent Application No. 2001-398425, Japanese Patent Application No. 2001-335675, and Japanese Patent Application No. 2002-108178, and has a particulate silver compound as an essential component, In addition to this, a reducing agent and / or a binder and a dispersion medium are optionally contained, or a particulate silver oxide and a tertiary fatty acid silver salt are contained.

Examples of the highly conductive silver paste include pastes having the following four types of compositions.
(1) Highly conductive silver paste in which a particulate silver compound is dispersed in a dispersion medium The dispersant may be added to this highly conductive silver paste as necessary.
As the particulate silver compound, those having an average particle diameter of 1 μm or less and having a small particle diameter are preferable because the reduction reaction rate is increased.
The viscosity of the highly conductive silver paste varies depending on the film forming conditions, but is preferably about 30 to 300 poise.

(2) Highly conductive silver paste in which a particulate silver compound and a reducing agent are dispersed and dissolved in a dispersion medium. A dispersant may be added to this highly conductive silver paste as necessary.
In this particulate silver compound, the reduction reaction proceeds smoothly even with particles of 1 μm or more due to the presence of the reducing agent. Therefore, the average particle diameter is not limited to a small one, and there is no particular problem as long as it is in the range of 0.01 μm to 10 μm.
The viscosity of the highly conductive silver paste varies depending on the film forming conditions, but is preferably about 30 to 300 poise.

(3) Highly conductive silver paste in which a binder is further added to the above highly conductive silver paste of (1) or (2). This binder protects the obtained highly conductive film and gives flexibility. Its function is different from the binder added to the conventional conductive paste.
The viscosity of the highly conductive silver paste varies depending on the film forming conditions, but is preferably about 30 to 300 poise.

(4) Highly conductive silver paste in which a particulate silver compound and a tertiary fatty acid silver salt are dispersed and dissolved in a dispersion medium. The particle size of the particulate silver oxide is preferably 500 nm or less, and silver oxide having a larger particle size is used. In this case, it is preferable to pulverize this in the production process (kneading step) of the highly conductive silver paste so that the particle size is 500 nm or less.

Each component used for this highly conductive silver paste will be described.
The particulate silver compound is a solid particulate silver compound having the property of being reduced by simple heating or heating in the presence of a reducing agent to form metallic silver, and more specifically, first silver oxide, oxidized Secondary silver, silver carbonate, silver acetate, acetylacetone silver complex, etc. are mentioned, These may be used individually by 1 type, and may mix and use 2 or more types.

  The average particle size of the particulate silver compound is in the range of 0.01 μm or more and 10 μm or less, and is appropriately selected according to the reduction reaction conditions such as the heating temperature, the presence or absence of a reducing agent, and the reducing agent's reducing power Can do. In particular, it is preferable to use a particulate silver compound having an average particle size of 0.5 μm or less because the speed of the reduction reaction is increased. Those having an average particle size of 0.5 μm or less can be produced by a reaction between a silver compound and another compound. For example, there is a method in which an aqueous silver nitrate solution, such as sodium hydroxide, is dropped and reacted with an aqueous silver nitrate solution to obtain silver oxide. In this case, it is desirable to add a dispersion stabilizer to the solution to prevent aggregation of the precipitated particulate silver compound.

Further, the reducing agent is for reducing the above-mentioned particulate silver compound, and it is preferable that the by-product after the reduction reaction scatters as a gas or a highly volatile liquid and does not remain in the high conductive film 3. . Specific examples of such a reducing agent include ethylene glycol, formalin, hydrazine, ascorbic acid, various alcohols, and the like.
The amount of the reducing agent added is desirably 0.5 mol or more and 20 mol or less with respect to 1 mol of the particulate silver compound. In consideration of reaction efficiency and volatilization by heating, it is desirable to add more than equimolar, but even if it exceeds 20 mol at the maximum, the amount is wasted, so addition of 20 mol or more is not preferable.

The dispersion medium is a paste obtained by dispersing the particulate silver compound, and further the reducing agent and / or binder, water, alcohols such as ethanol, methanol, 2-propanol, isophorone, Organic solvents such as terpineol, triethylene glycol monobutyl ether and butyl cellosolve acetate are preferably used.
In addition, if said reducing agent is liquid and can disperse | distribute a particulate silver compound, a reducing agent can serve as a dispersion medium. Examples of such include ethylene glycol. The selection of the type of the dispersion medium and the amount of use thereof are appropriately adjusted depending on the particulate silver compound and the film forming conditions.

  Further, it is preferable to add a dispersant to disperse the particulate silver compound having an average particle diameter of 1 μm or less well to prevent secondary aggregation of the particulate silver compound. As this dispersant, hydroxypropylcellulose, polyvinylpyrrolidone, polyvinyl alcohol, or the like is used, and the amount used is preferably 0.1 parts by weight or more and 300 parts by weight or less with respect to 100 parts by weight of the particulate silver compound.

Moreover, as said binder, the polyhydric phenol compound, a phenol resin, an alkyd resin, unsaturated polyester resin, 1 type, or 2 or more types of mixtures of thermosetting resins, such as an epoxy resin, are used.
Among these resins and compounds, this binder is preferably one that itself has a reducing action, in other words, one that has oxidative polymerizability and that reduces the particulate silver compound upon heating and polymerizes itself. By selecting such a binder, the amount of the reducing agent added can be reduced, or the reducing agent can be made unnecessary. Examples of the binder having such a reducing action include polyhydric phenol compounds, phenol resins, alkyd resins, and the like.

In the case of using a thermosetting resin, an uncured resin and a curing agent, a catalyst, or the like for curing the uncured resin are used.
The compounding quantity of a binder is 1-20 mass parts with respect to 100 mass parts of particulate silver compounds, Preferably it is 1-5 mass parts. The reason is that when the amount is less than 1 part by mass, the blending effect cannot be obtained, and when the amount exceeds 20 parts by mass, the volume resistivity of the resulting high conductive film increases, resulting in poor thermal shock characteristics and mechanical characteristics.

  Furthermore, the tertiary fatty acid silver salt is a silver salt of a tertiary fatty acid having a total carbon number of 5 to 30, preferably 10 to 30. This tertiary fatty acid silver salt plays the role of a lubricant. When kneading silver oxide and tertiary fatty acid silver salt into a paste, the silver oxide is pulverized to promote micronization and silver oxide. It exists around the grains to suppress reaggregation of silver oxide grains and improve dispersibility. For this reason, it can be made into a paste without adding a binder.

  Moreover, this tertiary fatty acid silver salt precipitates silver at the time of heating, and fuses silver particles produced by reduction from silver oxide. Specific examples of such tertiary fatty acid silver salts include silver pivalate, silver neoheptanoate, silver neononanoate, and silver neodecanoate. The production of the tertiary fatty acid silver salt is carried out, for example, by neutralizing the tertiary fatty acid with an alkali compound in water and reacting this with silver nitrate.

The blending ratio of the particulate silver oxide and the tertiary fatty acid silver salt in the highly conductive silver paste containing the particulate silver compound and the tertiary fatty acid silver salt is such that the mass of the silver oxide is A and the mass of the tertiary fatty acid silver salt is When B, the mass ratio (A / B) is preferably ¼ to 3/1.
Moreover, in this highly conductive silver paste, a solvent is contained in addition to silver oxide and tertiary fatty acid silver salt. The solvent is not particularly limited as long as it does not react with silver oxide and the tertiary fatty acid silver salt and can disperse them satisfactorily.

As such a highly conductive silver paste, for example, a highly conductive silver paste XA-9053 (Fujikura Kasei) containing silver oxide having an average particle size of 500 μm or less is available.
Next, this highly conductive silver paste is applied to the surface (one main surface) 2a of the substrate 2 by screen printing or the like, and heated and dried. The heating / drying temperature is 140 to 160 ° C. when the reducing agent is contained in the highly conductive silver paste, and 180 to 200 ° C. when the reducing agent is not contained in the highly conductive silver paste. The heating time is about 10 seconds to 120 minutes for both.
As a result, the particulate silver compound in the highly conductive silver paste is reduced to produce metallic silver fine particles, and the reducing agent, binder, dispersion medium, etc. contained in the highly conductive silver paste are decomposed or melted and scattered. As a result, a highly conductive coating film is formed on the surface 2 a of the substrate 2.

Next, black ink is applied onto the highly conductive coating film by screen printing or the like.
As the black ink, a conductive ink is preferably used.
The conductive ink is a black ink containing carbon that is conductive black particles. For example, FC-415 (Fujikura Kasei) or the like is available.

The black ink and highly conductive coating are then heated by infrared (IR), preferably far infrared.
Examples of the infrared (IR) heating means include an infrared (IR) firing furnace and an infrared (IR) drying furnace.
By this infrared heating, the fusion of metallic silver fine particles in the highly conductive coating film proceeds remarkably, and the highly conductive film 3 having a specific resistance of 1.0 × 10 ⁻⁵ Ωcm or less is obtained.
Further, the black ink also becomes a conductive black film having a specific resistance of 1.0 × 10 ⁻² Ω · cm or less by scattering the dispersion medium or the like by infrared heating.

According to this embodiment, since the black film 4 is formed on the high conductive film 3 formed by applying and drying the high conductive silver paste, the specific resistance of the high conductive film 3 constituting the circuit pattern is sufficiently lowered. And the in-plane uniformity of this specific resistance is also excellent.
In addition, a black ink is applied on a highly conductive coating film obtained by applying and drying a highly conductive silver paste, and the highly conductive coating film and the black ink are heated with infrared rays so that the highly conductive film 3 and the black film 4 are heated. Therefore, it is possible to easily manufacture a membrane wiring board having a circuit pattern made of the high conductive film 3 having excellent in-plane uniformity and low specific resistance.

Hereinafter, although an example and a comparative example explain the present invention, the present invention is not limited to these examples.
(Examples 1-3)
A polyester-based Lumirror S10 (thickness 75 μm: manufactured by Toray Industries, Inc.) is used as the base material 2, and a primer for high-conductivity silver paste is primed on the surface of the base material 2, and high-conductivity silver is coated on the primer for high-conductivity silver paste. Paste XA-9053 (Fujikura Kasei) was applied and dried using an IR furnace under the conditions listed in Table 1 (150 ° C. for 3 minutes, predetermined number of passes) to form a highly conductive coating film having a desired circuit pattern. Formed.

Next, the black ink listed in Table 1 was applied onto this highly conductive coating film, and these highly conductive coating film and black ink were subjected to the conditions listed in Table 1 using an IR furnace (150 ° C. for 3 minutes, predetermined pass). Example 1 in which the high conductive film 3 and the black film 4 were laminated on the base material 2 by drying under the conditions shown in Table 1 (60 minutes at 150 ° C.) using a BOX furnace. -3 membrane wiring boards were produced.
Subsequently, the specific resistance of the high conductive film of each of the membrane wiring boards of Examples 1 to 3 was measured.
Table 1 shows the measurement results of these conditions and specific resistance.

(Comparative Examples 1-3)
A polyester-based Lumirror S10 (thickness 75 μm: manufactured by Toray Industries, Inc.) is used as the base material 2, and a primer for high-conductivity silver paste is primed on the surface of the base material 2, and high-conductivity silver is coated on the primer for high-conductivity silver paste. Paste XA-9053 (Fujikura Kasei) was applied and dried under the conditions listed in Table 1 using an IR furnace (3 minutes at 150 ° C., predetermined number of passes), or conditions listed in Table 1 using a BOX furnace The membrane wiring board of Comparative Examples 1-3 in which the highly conductive film was formed on the base material 2 was produced by drying at 150 ° C. for 60 minutes.
Subsequently, the specific resistance of the high conductive film of each of the membrane wiring boards of Comparative Examples 1 to 3 was measured.
Table 2 shows the measurement results of each of these conditions and specific resistance.

According to these results, it was found that the membrane wiring boards of Examples 1 to 3 can obtain a high conductive film having a low specific resistance by a small IR heating (thermal history).
On the other hand, in the membrane wiring boards of Comparative Examples 1 to 3, if the IR heating (thermal history) by the IR furnace is increased or the BOX furnace is not used, the high electrical conductivity having the same low resistivity as in Examples 1 to 3 is used. It was found that no film was obtained.
Thereby, it turned out that the membrane wiring board of Examples 1-3 has improved production efficiency compared with Comparative Examples 1-3.

It is sectional drawing which shows the membrane wiring board of one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Membrane wiring board, 2 ... Base material, 3 ... High conductive film, 4 ... Black film.

Claims (6)

In a membrane wiring board in which a highly conductive film having a desired circuit pattern formed by applying and drying a highly conductive silver paste on one main surface of a substrate is formed,
A membrane wiring board comprising a black film formed on the high conductive film.   2. The membrane wiring board according to claim 1, wherein the black film is a conductive black film formed by applying and drying conductive ink. 3. The membrane wiring board according to claim 1, wherein a specific resistance of the high conductive film is 1.0 × 10 ⁻⁵ Ωcm or less. A highly conductive silver paste is applied to one main surface of the substrate and dried to form a highly conductive coating film having a desired circuit pattern,
Next, a black ink is applied on the highly conductive coating film, and the highly conductive coating film and the black ink are heated with infrared rays to form a highly conductive film and a black film.   The method for manufacturing a membrane wiring board according to claim 4, wherein the infrared rays are far infrared rays.   6. The method for manufacturing a membrane wiring board according to claim 4, wherein the black ink is a conductive ink.

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