JP5538016B2 - Conductive resin composition and electronic circuit board - Google Patents

Description

  The present invention relates to a conductive resin composition used for forming a conductive pattern on a substrate, for example, and an electronic circuit board.

  In general, a printed wiring board having a conductive pattern such as an electrode or an electronic circuit board such as a PDP substrate uses a conductive resin composition in which a conductive powder is mixed with an organic binder or the like. After pattern formation by a lithography method or the like, it is usually formed by firing at 500 ° C. or higher in the atmosphere.

  In the conductive resin composition used at this time, as the conductive powder, Ag powder that has a low resistance value even in a fine conductive pattern and can be fired in the air is preferably used. However, there is a problem that Ag powder is relatively expensive and has a high price fluctuation risk. Therefore, in order to reduce the cost of the conductive resin composition, various alternatives to other cheaper conductive powders have been studied.

  For example, use of Cu powder has been studied. Although Cu powder is cheaper than Ag powder, the surface of Cu powder is easily oxidized, and good conductivity cannot be obtained in the formed conductive pattern. Then, surface oxidation can be suppressed by coat | covering Cu powder with Ag layer as a core material. However, although it has good conductivity at low temperatures, when it is baked at 500 ° C. or higher in the atmosphere, Cu diffuses to the surface and oxidizes, so that good conductivity cannot be obtained in the formed conductive pattern. There is a problem.

  Therefore, in order to suppress the surface diffusion of Cu during firing, it has been proposed to use a multilayer coated Cu powder in which an Ag coating layer is provided via a Ni layer or the like using Cu powder as a core material (for example, Patent Documents). 1 etc.).

JP 2009-40932 A (Claims)

  By using such a multilayer coated Cu powder, surface diffusion of Cu during firing is suppressed, and good high-temperature oxidation resistance can be obtained. However, when the multilayer coated Cu powder is produced, after the Cu powder is coated with a Ni layer or the like, an Ag coating layer is further formed, which complicates the production process. Therefore, there is a problem that process costs cannot be suppressed in realizing the cost reduction of the conductive resin composition.

  Therefore, the present invention provides a conductive resin composition that has good conductivity and can reduce costs in a fine conductive pattern to be formed, and the conductivity of the conductive pattern is good. At the same time, an electronic circuit board capable of reducing the cost is provided.

In order to solve such a problem, the conductive resin composition of one embodiment of the present invention includes a core material mainly composed of Fe and Cr , and an Ag coating layer formed on the surface of the core material. It contains conductive powder and an organic binder.

  With such a configuration, the conductive powder can be formed by a simple manufacturing process, and good conductivity can be obtained in a fine conductive pattern formed using this conductive resin composition. It is possible to realize cost reduction.

  In the conductive resin composition of one embodiment of the present invention, the organic binder preferably includes any one of a dry organic binder, a thermosetting organic binder, and a photocurable organic binder. With such a configuration, it is possible to form a dry coating film or a cured coating film pattern that becomes a conductive pattern by performing drying, heating, or light irradiation before or after patterning.

Furthermore, an electronic circuit board according to an aspect of the present invention includes a conductive pattern including a conductive powder having a core material mainly composed of Fe and Cr and an Ag coating layer formed on a surface of the core material. It is characterized by that. With such a configuration, the conductivity of the conductive pattern is good and the cost can be reduced.

  According to the conductive resin composition of the present invention, a fine conductive pattern formed using the conductive resin composition has good conductivity and can be reduced in cost. Further, according to the electronic circuit board of the present invention, the conductivity of the conductive pattern is good and the cost can be reduced.

Hereinafter, embodiments of the present invention will be described.
The conductive resin composition of the present embodiment includes a core material mainly composed of Fe and Cr , a conductive powder having an Ag coating layer formed on the surface of the core material, and an organic binder. .

Here, the core material mainly composed of Fe and Cr constituting the conductive powder in this embodiment is an alloy of these metals , and is excellent in corrosion resistance and inexpensive stainless steel is preferably used. The core material may further contain a metal such as Ni or Mo. Specifically, SUS316 (Fe: 69, Cr: 17, Ni: 12, Mo: 2 (wt%)), SUS410 (Fe: 87, Cr: 13 (wt%)), or the like can be used.

  The average particle diameter of the core material is preferably 0.1 to 20 μm. When it is less than 0.1 μm, uniform Ag coating becomes difficult. On the other hand, if it exceeds 20 μm, the shape of the conductive pattern is affected, and it becomes difficult to form a fine pattern. More preferably, it is 0.5-10 micrometers.

  The Ag coating layer formed on the surface of such a core material is preferably formed by plating. Examples of the plating method include an electroless plating method, an electroplating method, a displacement plating method, and a vapor phase plating method. The electroless plating method is preferable because it is easy to manufacture and has excellent quality stability. Used for. The Ag coating layer thus formed may be a single layer or a multilayer, and is not particularly limited.

  The film thickness of the Ag coating layer is preferably 0.01 to 3 μm. When the film thickness is less than 0.01 μm, the resistance value increases. On the other hand, when the film thickness exceeds 3 μm, the amount of Ag increases, and it is difficult to reduce the cost. More preferably, it is 0.05-2 micrometers.

  Moreover, it is preferable that Ag amount in electroconductive powder is 10-70 mass%. If it is less than 10% by mass, the resistance value increases. On the other hand, if it exceeds 70% by mass, the amount of Ag increases, making it difficult to reduce the cost. More preferably, it is 15-50 mass%.

  The conductive powder configured as described above preferably has a substantially spherical shape because of its high conductivity. Moreover, it is preferable that the average particle diameter is 0.1-20 micrometers. When it is less than 0.1 μm, uniform Ag coating becomes difficult. On the other hand, if it exceeds 20 μm, the shape of the conductive pattern is affected, and it becomes difficult to form a fine pattern. More preferably, it is 0.5-10 micrometers.

  Such conductive powder is preferably blended at a ratio of 50 to 2,000 parts by mass with respect to 100 parts by mass of the organic binder described later. If the amount is less than 50 parts by mass, the line width shrinkage or disconnection of the conductor circuit tends to occur. On the other hand, when the amount exceeds 2,000 parts by mass, dispersibility is lowered and pasting becomes difficult. More preferably, it is 300-1500 mass parts.

  As the organic binder in this embodiment, an organic binder containing any one of a dry organic binder, a thermosetting organic binder, and a photocurable organic binder can be used.

  Among these, a dry organic binder is used with the organic solvent mentioned later, and forms a dry coating film by removing an organic solvent by heat drying. Further, the thermosetting organic binder is cured by intermolecular crosslinking under the action of heat or a catalyst to form a cured coating film.

  Examples of such dry organic binder and thermosetting organic binder include acrylic polyol, polyvinyl alcohol, polyvinyl acetal, styrene-allyl alcohol resin, olefinic hydroxyl group-containing polymer such as phenol resin, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose Cellulose derivatives such as ethylene-vinyl acetate copolymer, alkyd resin, alkyd phenol resin, butyral resin, epoxy resin, modified epoxy resin, acrylic resin, polyurethane resin, and polyester resin can be used. In particular, when a cured coating film is formed by thermosetting as the thermosetting organic binder, it is preferable to use a curing catalyst such as a peroxide or an acid catalyst or a thermal radical polymerization initiator in combination.

  In addition, the photocurable organic binder is cured by intermolecular crosslinking under the action of active energy rays such as ultraviolet rays and electron beams to form a cured coating film.

  Examples of such a photocurable organic binder include a resin having a photosensitive group such as an ethylenically unsaturated bond such as a vinyl group, an allyl group, an acryloyl group, or a methacryloyl group, or a propargyl group, for example, an ethylenically unsaturated group in a side chain. Conventionally known various photosensitive resins (photosensitive prepolymers) such as an acrylic copolymer having an unsaturated carboxylic acid, an unsaturated carboxylic acid-modified epoxy resin, or a resin further added with a polybasic acid anhydride can be used.

  These photocurable organic binders can be used in combination with a compound having one or more ethylenically unsaturated bonds in the molecule, that is, a photopolymerizable monomer or oligomer. The photocurable organic binder is preferably used in combination with a photopolymerization initiator or a photopolymerization accelerator in order to allow the photopolymerization to proceed more efficiently.

  Moreover, these dry organic binders, thermosetting organic binders, and photocurable organic binders are not necessarily used alone, and two or more kinds can be used in combination.

  In the conductive resin composition of this embodiment, an organic solvent can be used as necessary. When the organic binder is solid, it can be applied to the substrate with a predetermined viscosity by dissolving or dispersing the organic binder in a solvent. Moreover, when the organic binder is liquid, its viscosity can be adjusted.

  Such an organic solvent is preferably blended so as to be less than 80% by mass with respect to the organic component contained in the conductive resin composition. When the blending amount of the organic solvent is 80% by mass or more with respect to the organic component, the viscosity is lowered and the coating property is deteriorated. Moreover, sedimentation etc. generate | occur | produce and the problem that storage stability falls arises.

  In the conductive resin composition of the present embodiment, when the conductive pattern is formed by baking, the low melting point glass powder is added per 100 parts by mass of the conductive powder in order to improve the strength of the conductive pattern and the adhesion to the substrate. It is preferable to mix | blend in the ratio of 1-30 mass parts.

  As such a low melting glass powder, a glass powder having a glass point transfer (Tg) of 300 to 500 ° C. and a glass softening point (Ts) of 400 to 600 ° C., for example, lead oxide, bismuth oxide, zinc oxide or oxidation A glass powder mainly composed of lithium is preferably used. The average particle diameter is preferably 0.1 to 10 μm from the viewpoint of resolution. More preferably, it is 0.5-3 micrometers.

  In the conductive resin composition of this embodiment, it is preferable to blend silica powder, particularly synthetic amorphous silica fine powder, in a range that does not adversely affect the conductive pattern in order to improve printability.

  In the conductive resin composition of the present embodiment, when a photocurable organic binder is used as the organic binder, it is preferable to use a storage stabilizer in order to prevent gelation and thickening. Specific examples of the storage stabilizer include organic acids, inorganic acids, and phosphorus-containing compounds.

  Furthermore, in the conductive resin composition of the present embodiment, if necessary, a defoaming / leveling agent such as silicone or acrylic, a dispersant, a silane coupling agent for improving the adhesion of the film, an antioxidant Various additives such as can be blended.

  The conductive resin composition of the present embodiment configured as described above is prepared by mixing and dispersing each component with a three-roll mill or a kneader, or by using a rotation and revolution stirrer after preparing each component to have a predetermined composition. It is prepared by dispersing with high-speed stirring.

  The conductive resin composition thus prepared is printed on a substrate by screen printing or the like when a dry organic binder is used, and then, for example, 100 ° C. to 150 ° C. using a hot air drying oven. The conductive pattern which consists of a dry coating film is formed by performing heat drying for 5 to 60 minutes and removing a solvent.

  Moreover, when a thermosetting organic binder is used, after conducting pattern printing on the substrate by screen printing or the like, the conductive film made of a cured coating film is heated and cured at a temperature of 120 ° C. to 180 ° C., for example. A sex pattern is formed.

  Moreover, when using a photocurable organic binder, the conductive pattern which consists of a cured coating film is formed by pattern-printing on a base material by screen printing etc., and then making it harden | cure with an active energy ray.

  When a photocurable organic binder is used, a conductive pattern can be formed by a lithography method. After the entire surface is printed on the substrate by screen printing or the like, the organic solvent is evaporated by drying at 60 to 120 ° C. for 5 to 40 minutes in a hot air circulation drying furnace or a far infrared drying furnace, and a tack-free coating film Get. Furthermore, selective exposure is performed, and after development, firing is performed to form a conductive pattern made of a fired product.

  A photocurable organic binder can also be used in the state of the dry film formed into a film previously on the film. In that case, a conductive film made of a fired product is formed by laminating a dry film on a substrate, similarly performing selective exposure, and developing and firing.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this embodiment is demonstrated concretely, this invention is not limited to a following example. “Parts” and “%” are based on mass unless otherwise specified.

[Creation of conductive powder]
As shown in Table 1, an Ag coating layer is formed on two types of stainless steel powder (SUS316, SUS410) each having an average particle diameter of 6 μm by electroless plating so as to have a predetermined film thickness and plating amount. Conductive powders A and B were prepared.

[Preparation of organic binder]
(Organic binder A)
In a flask equipped with a thermometer, stirrer, dropping funnel, and reflux condenser, diethylene glycol monoethyl ether acetate as a solvent and azobisisobutyronitrile as a catalyst are added and heated to 80 ° C. in a nitrogen atmosphere. A monomer mixed with methacrylic acid: 0.4 mol and methyl methacrylate: 0.6 mol in molar ratio was added dropwise over about 2 hours, and the mixture was further stirred for 1 hour, and then the temperature was raised to 115 ° C. to deactivate. A resin solution was obtained.

  After cooling this resin solution, tetrabutylammonium bromide was used as a catalyst at 95 to 115 ° C. for 30 hours, and butyl glycidyl ether: 0.4 mol was added with an equivalent amount of the carboxyl group of the obtained resin and addition reaction. And cooled. Further, 0.26 mol of tetrahydrophthalic anhydride was added to the OH group of the obtained resin under the conditions of 95 to 105 ° C. for 8 hours, cooled and taken out to obtain an organic binder A having a solid content of 55%. It was.

[Preparation of glass slurry]
As the glass powder, Bi ₂ O ₃ : 50%, B ₂ O ₃ : 16%, ZnO: 14%, SiO ₂ : 2%, BaO: 18%, coefficient of thermal expansion α ₃₀₀ = 86 × 10 ⁻⁷ / ° C. A glass softening point of 501 ° C. was used. After roughly pulverizing the glass powder, filtering was performed with a 300 mesh screen, and 70. mass parts of the obtained glass powder and 29.16 masses of 2,2,4-trimethyl-1,3-pentanediol monobutyrate were obtained. As a dispersant, 0.14 parts by mass of BYK-410 and 0.7 parts by mass of BYK-182 were added.

Using a bead mill (SC50 manufactured by Mitsui Mining Co., Ltd.), ZrO ₂ beads with a media diameter of φ0.3 to 0.8 mm were used, and the number of revolutions was 2,000 to 3,300 rpm for 3 to 9 hours. By pulverizing, a glass slurry having a particle size of D50: 1.0 μm, Dmax: 3.9 μm and a glass powder content of 70% by mass was prepared.
The particle size measurement was performed using a Horiba laser diffraction / scattering particle size distribution analyzer LA-920.

[Preparation of conductive resin composition]
Each component was blended in a 1200 ml plastic container as shown below, and stirred with a dissolver at 500 rpm for 10 minutes. Thereafter, the mixture was kneaded twice with 7-inch ceramic three rolls to form a paste, and the conductive resin composition 1 (Examples 1 and 2, Comparative Examples 1 and 2) and the conductive resin composition 2 (Example 3). 4, Comparative Examples 3, 4) were obtained.

(Conductive resin composition 1)
Novolac-type phenol resin: 100.0 parts Tripropylene glycol monomethyl ether: 120.0 parts Leveling / antifoaming agent (manufactured by Monsanto, trade name: Modaflow): 5.0 parts Dispersant (manufactured by BYK-chemie, trade name: BYK-182): 5.0 parts Hexamethylenetetramine: 10.0 parts Conductive powder: 700.0 parts

(Conductive resin composition 2)
Organic binder A: 180.0 parts Tripropylene glycol monomethyl ether: 85.0 parts Leveling / antifoaming agent (manufactured by Monsanto, trade name: Modaflow) 5.0 parts Phosphate ester 4.0 parts Glass slurry 98.0 parts Organic solvent (ExxonMobil Corporation, trade name: Solvesso 200) 10.0 parts Conductive powder: 730.0 parts

  In addition, as the conductive powder, the obtained conductive powders A and B and, as a comparative example, Cu powder and Ag-plated Cu powder were used.

[Evaluation of conductive resin composition]
The obtained conductive resin composition was evaluated as follows.
(Production of test substrate)
A test substrate was produced using each of the obtained conductive resin compositions.

Preparation of test substrate 1:
The conductive resin composition 1 in which each conductive powder is mixed is pattern-printed on a glass substrate so as to form a line pattern of 0.1 cm × 5 cm with a film thickness of about 25 to 30 μm, and at 90 ° C. for 30 minutes. It dried and obtained the dry coating film.
Next, the obtained dried coating film was cured at 150 ° C. for 30 minutes to obtain a test substrate 1 having conductive patterns to be Examples 1 and 2 and Comparative Examples 1 and 2.

Preparation of test substrate 2:
The conductive resin composition 2 in which each conductive powder is mixed is pattern-printed on a glass substrate so as to form a 0.1 cm × 5 cm line pattern with a film thickness of about 25 to 30 μm, and at 90 ° C. for 30 minutes. It dried and obtained the dry coating film.
Next, the obtained dried coating film was heated at 20 ° C./min in the atmosphere and baked at 600 ° C. for 20 minutes, whereby conductive patterns to be Examples 3 and 4 and Comparative Examples 3 and 4 were obtained. A test substrate 2 having the following characteristics was obtained.

The line resistance value and specific resistance value of the obtained conductive pattern were evaluated as follows.
(Measurement of resistance value)
With respect to the evaluation substrates 1 and 2 having a conductive pattern of 0.1 cm × 5 cm produced as described above, the line resistance value of the conductive pattern was measured using a HIOKI 3540 mΩ HiTester manufactured by HIOKI Corporation. Further, the specific resistance value was calculated from the line resistance value as follows.
Specific resistance (Ω · cm)
= Line resistance (Ω) x film thickness (cm) x line width (cm) / line length (cm)
These results are shown in Table 2.
In Table 2, “not measurable” indicates that the upper limit of measurement by the high tester is exceeded.

  As shown in Table 2, in Comparative Examples 1 to 4 in which the Ag plating Cu powder and Cu powder are used for the core material, it is understood that good conductivity cannot be obtained. In Comparative Examples 1 and 2 which are non-fired patterns, both the line resistance value and the specific resistance value are slightly higher than those in Examples 1 and 2. Moreover, in the comparative examples 3 and 4 which are a baking pattern, it cannot measure and it turns out that favorable electroconductivity is not acquired by the spreading | diffusion and oxidation of Cu at the time of baking.

  On the other hand, in Examples 1 to 4 using stainless steel as the core material, good line resistance values and specific resistance values are obtained in both Examples 1 and 2 which are non-fired patterns and Examples 3 and 4 which are fired patterns. I can see that

Claims (3)

A conductive powder having a core material mainly composed of Fe and Cr , and an Ag coating layer formed on the surface of the core material;
An organic binder,
The conductive resin composition characterized by including.   The conductive resin composition according to claim 1, wherein the organic binder includes any one of a dry organic binder, a thermosetting organic binder, and a photocurable organic binder. An electronic circuit board comprising a conductive pattern including a conductive powder having a core material mainly composed of Fe and Cr and an Ag coating layer formed on a surface of the core material.