JP4936142B2 - Conductive paste composition, electronic circuit, and electronic component - Google Patents

Description

  The present invention relates to a conductive paste composition for a flexible electronic circuit board comprising a mixed conductive silver powder of scaly silver powder and dendritic silver-plated copper powder, and an electronic circuit formed using the conductive paste composition, The present invention relates to an electronic component in which the electronic circuit is arranged in a pattern.

  As is well known, a conductive paste obtained by kneading a conductive powder into a resin is used to form an electronic circuit or an electrode, and a copper or silver scaly powder is generally used as the conductive powder. ing.

  Also, silver, silver-plated copper, copper, gold, nickel, baradium and their alloys, conductive fine powders such as carbon, the shape of the powder is not limited, granular, plate-like, dendritic, cage-like Electroconductive fine powder that can be used in dice, etc., saturated copolyester resin, block isocyanate compound, and conductive paste mainly composed of solvent are proposed (for example, see Patent Document 1), copper alloy powder, and silver powder Including 100 parts by weight of conductive powder composed of silver alloy powder and silver-plated copper powder, 5-40 parts by weight of binder resin is included, and the shape of the powder is dendritic, spherical, and flake (scale) A conductive resin composition that has a granular shape, a chestnut shape, a needle shape, or a mixture thereof has been proposed (for example, see Patent Document 2).

JP-A-1-159906 Japanese Patent Laid-Open No. 10-162646

  An electronic circuit formed from a conductive paste made of flaky powder has a large specific surface area of a conductive material and a low contact resistance, so that good conductivity can be ensured. In the case where an electronic circuit is formed on the flexible film, there is a problem in that the adhesion between the conductive materials and the substrate is poor, and the electronic circuit is disconnected by bending and the conductivity is impaired. Moreover, although silver is excellent in electroconductivity compared with copper, there existed a problem that the electrically conductive paste which consists of silver powder lacked practicality on a cost. Furthermore, the conductive paste (Patent Document 1) and the conductive resin composition (Patent Document 2) have a problem that the bending characteristics currently required for flexible electronic circuit boards cannot be satisfied. It was.

  Therefore, the present invention has a technical problem of obtaining a conductive paste composition that can maximize the conductive properties of silver and satisfy the bending properties required by flexible electronic circuit boards. As a result of repeated research and experimentation, if a mixed silver powder of scaly silver powder having a specific average particle diameter and specific surface area and dendritic silver-plated copper powder having a specific average particle diameter is used, the paste is applied and dried. The present inventors have achieved the above technical problem by obtaining the remarkable knowledge that the film exhibits good conductivity later and is excellent in resistance change (bending resistance) due to bending.

  The technical problem can be solved by the present invention as follows.

That is, the conductive paste composition for a flexible electronic circuit board according to the present invention is based on 100 parts by weight of flaky silver powder having an average particle size of 2.0 to 5.0 μm and a specific surface area of 2.0 to 3.0 m ² / g. The amount of plated silver is 20 to 25 parts by weight with respect to 100 parts by weight of copper powder, and the mixture is 67 to 100 parts by weight of dendritic silver plated copper powder having an average particle size of 10 to 19 μm and higher electric resistance than the scale- like silver powder A conductive powder made of silver powder, a thermosetting resin, and an organic solvent are essential components.

  Moreover, the electronic circuit according to the present invention is formed by using any one of the conductive paste compositions.

  Furthermore, an electronic component according to the present invention is obtained by arranging the electronic circuit on a flexible substrate.

  According to the present invention, since it is a conductive paste composition comprising a mixed conductive silver powder of a flaky silver powder having a specific average particle size and a specific surface area and a dendritic silver-plated copper powder having a specific average particle size, it is good. Since it is an electronic circuit formed using the said conductive paste composition, favorable electroconductivity and the outstanding bending-proof characteristic can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.

  The conductive paste composition according to the present embodiment includes a conductive powder composed of a mixed silver powder of scaly silver powder and dendritic silver-plated copper powder, a thermosetting resin, and an organic solvent as essential components. .

  Since the scaly powder has a large particle surface area and the particles are in surface contact with each other, good conductivity is obtained.Because it is a thin film, the bending performance tends to cause breakage, and the conductivity tends to decrease. The conductivity is slightly inferior because the particles are in point contact, but conversely, the powder shape is stable in the bending performance, and the conductivity does not decrease, so the mixed powder of scaly powder and dendritic powder Is used to make the conductive powder excellent in conductivity and bending performance.

Moreover, the desired amount of conductive powder needs to those of the silver-plated, but since plating shape silver plating scaly copper powder is not good conductivity is obtained becomes uneven, flaky powder Is a silver powder, and the dendritic powder is a silver-plated copper powder that is silver-plated using copper powder. By this combination with the scaly silver powder, the long dendritic branches of the dendritic silver-plated copper powder act on the thin scaly silver powder to obtain the best folding performance.

The flaky silver powder has an average particle size of 2.0 to 5.0 μm and a specific surface area of 2.0 to 3.0 m ² / g. If the average particle size is less than 2.0 μm, the silver powder tends to agglomerate in the paste, which is not preferable, and if it exceeds 5.0 μm, the bending resistance is deteriorated. Further, if the specific surface area is less than 2.0 m ² / g, the conductivity is deteriorated, which is not preferable, and if it exceeds 3.0 m ² / g, the bending resistance is deteriorated, which is not preferable.

  The dendritic silver-plated copper powder has an average particle size of 10 to 19 μm. If the average particle size is less than 10 μm, the conductivity is deteriorated, which is not preferable, and if it is 20 μm or more, the bending resistance is deteriorated, it is not preferable. In particular, a mixed silver powder of flaky silver powder having an average particle diameter of 2.0 to 5.0 μm and an average particle diameter of 10 to 15 μm of dendritic silver-plated copper powder is preferable.

  The mixing ratio of scaly silver powder and dendritic silver-plated copper powder is preferably 67-100 parts by weight of dendritic silver-plated copper powder with respect to 100 parts by weight of scaly silver powder, and more preferable dendritic silver-plated copper powder The mixing ratio is 82 parts by weight with respect to 100 parts by weight of the flaky silver powder. If the blending ratio of the dendritic silver-plated copper powder is less than 67 parts by weight, the blending ratio of the silver powder will increase and the cost will be unfavorable. If the blending ratio exceeds 100 parts by weight, the conductivity and the bending resistance will decrease. It is not preferable.

  The plating silver amount of the dendritic silver-plated copper powder is preferably 20 to 25 parts by weight with respect to 100 parts by weight of the copper powder. If the amount of plated silver is less than 20 parts by weight, it is not preferable because appropriate conductivity cannot be obtained, and 25 parts by weight is a substantially upper limit value for silver plating. The silver-plated copper powder may be produced by a general method such as electroplating or electroless plating, and may be plated with a base such as Ni or Au for the purpose of preventing oxidation or improving adhesion.

  As the thermosetting resin, phenol resin, epoxy resin, polyester resin, alkyl resin, polyurethane, polyimide, and the like can be used. The resin is not limited to these resins, and a polyester resin excellent in flexibility is more preferable. . The mixing ratio of the conductive powder and the thermosetting resin should be 5 to 20 parts by weight of the thermosetting resin with respect to 100 parts by weight of the conductive powder. Since it cannot be applied, it is not preferable, and if it exceeds 20 parts by weight, the conductivity is lowered and the coating film performance is inferior (sagging or bleeding occurs), which is not preferable.

  As the organic solvent, ordinary ester solvents, ketone solvents, ether ester solvents, ether glycol solvents and the like may be used. In the case of coating by screen printing, it is preferable to use a solvent having a boiling point of 180 ° C. or higher, such as ester glycol type, ester type, and ketone type.

Embodiment 2. FIG.

  The conductive powder and the thermosetting resin in Embodiment 1 are blended at a ratio of 5 to 20 parts by weight of the thermosetting resin with respect to 100 parts by weight of the conductive powder, and further, a desired organic solvent is added and mixed. Then, the conductive paste composition is prepared.

  Next, the pattern circuit shown in FIG. 1 is printed on the circuit board film using the conductive paste composition, and then dried with hot air to form an electronic circuit.

Examples 1 to 5: A scaly silver powder and dendritic silver-plated copper powder having the respective powder characteristics shown in Table 1, and a polyester resin and a vinyl resin are mixed at a ratio shown in Table 2 and mixed with a stirring crusher. Premixing was performed for ˜15 minutes, and thereafter, dispersion treatment was performed twice using a three-roll mill. Subsequently, using a bisco tester (manufactured by Rion Co., Ltd .: Model: VT-04), the viscosity is adjusted with an ethyl carbitol acetate solvent so that the viscosity becomes a value of 200 to 300 ps (at a temperature of 25 ° C.). A paste composition was obtained (Examples 1 to 5).

  Each of the conductive paste compositions was heat-treated at 150 ° C. for 30 minutes, and each test (shown in FIG. 1) using a 180 mesh Tetron plate (emulsion thickness 15 μm) on each PET (polyethylene terephthalate) film having a thickness of 100 μm. A pattern circuit was printed and applied. And after printing, it was made to harden | cure by predetermined conditions (implemented at 120 degreeC and 150 degreeC for 30 minutes) with the hot air circulation type dryer, and each pattern circuit was formed (Examples 1-5).

  In each pattern circuit, the pattern wiring between A and B was 1 mm wide × 1000 mm long, and the square pattern surface indicated by C was 1 cm × 1 cm.

  The resistance of the pattern wiring between A and B of each pattern circuit was measured using a digital multimeter (manufactured by Yokogawa Electric Corporation). Each measurement result is shown in Table 3 as an initial resistance value.

  Next, the film substrate on which the pattern circuit is formed with the DE line as the folding line in FIG. 1 is bent at 180 ° C. so that the pattern circuit surface is on the inside, and the bent part of the DE line is pressed with a fingertip. The -E line was folded in the same way on the opposite side, and this operation was carried out twice, and the resistance of the pattern wiring between A and B was measured using a digital multimeter. Each measurement result is shown in Table 3 as a resistance value after bending.

In Table 3, the resistance change rate (%) is calculated by the formula ((resistance value after bending) − (initial resistance value)) / (initial resistance value) × 100, and the resistance evaluation “◯” is 100Ω. “Δ” indicates 100 to less than 120Ω, and “X” indicates 120Ω or more. Further, the bending property “◯” indicates a resistance change rate of less than 40%, and “x” indicates 40% or more.

Comparative Examples 1-5: Comparative Example 1 uses only scaly silver powder, Comparative Example 2 uses only dendritic silver-plated copper powder, and Comparative Example 3 uses scaly silver-plated copper powder. Each paste composition was adjusted by mixing for each particle shape shown in Table 1 and the ratio shown in Table 2 in the same manner as in 1-5, and each pattern circuit was formed (Comparative Examples 1-5). In Comparative Example 2, resistance after bending could not be measured due to lack of conductivity.

Example 6 In the same manner as in Example 1, an actual keyboard pattern circuit was formed on a film to obtain an electronic component of a flexible substrate. FIG. 2 is a schematic view of an electronic component obtained by printing an actual keyboard pattern circuit on a film.

  The electronic component was subjected to an adhesion test, a cross cut test, a hardness test, and a bending test.

Adhesion test: Adhesive tape (No. 600 tape: manufactured by Sumitomo 3M Co., Ltd.) was adhered to the pattern circuit surface in a close contact state, and then the adhesive tape was peeled off, but the paste did not peel off.
Cross cut test: The adhesion test was conducted at intervals of 2 mm using the adhesive tape, but the paste did not peel off.
Hardness test: A 2H pencil was applied to the pattern circuit surface at an angle of 45 ° and the pencil was run with a force of 1 kg, but the paste did not peel off.
Bending test: The resistance change rate was measured after bending 10 times in one direction with a load of 2 kg. The rate of change in resistance was 35%, which was well below the standard of 300% or less.

  According to the present invention, since the manufacturing cost is low compared with the conductive paste composition composed of silver powder, it has excellent conductivity after coating and drying, and also has excellent bending resistance. It can be suitably used as a material for forming an electronic circuit or the like of a film-like electronic component that requires bending characteristics.

  Therefore, it can be said that the industrial applicability of the present invention is very high.

It is a pattern circuit diagram. It is the schematic of the electronic component formed by printing the actual machine pattern circuit for keyboards on a film.

Explanation of symbols

A, B Pattern wiring C Pattern surface 1 Electronic parts

Claims (3)

The amount of plated silver is 20 to 25 parts by weight with respect to 100 parts by weight of copper powder with respect to 100 parts by weight of flaky silver powder having an average particle size of 2.0 to 5.0 μm and a specific surface area of 2.0 to 3.0 m ² / g. And a conductive powder composed of 67 to 100 parts by weight of mixed silver powder having an average particle diameter of 10 to 19 μm and an electric resistance higher than that of the flaky silver powder, a thermosetting resin, and an organic solvent are essential. A conductive paste composition for flexible electronic circuit boards as a component. An electronic circuit formed by using the conductive paste composition according to claim 1 . An electronic component comprising the electronic circuit according to claim 2 arranged on a flexible substrate.

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