JP2004079545A - Compound electroconductive powder, electroconductive paste, electric circuit, and manufacturing method of electric circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compound electroconductive powder of which specific-resistance is low, which has a high conductivity and with which an electroconductive paste for forming electrical circuits, of which changes of specific-resistane are small even after a cold impact test and a humid load test, is obtained, an electroconductive paste for forming the electric circuits of which specific-resistance is low, which has a high conductivity and of which changes of specific-resistance are small even after the cold impact test and humid load test, an electric circuit having a low specific-resistance, high conductivity, and superior anti-migration property, and a manufacturing method of the electric circuit having a low specific-resistance, high conductivity, and superior anti-migration property. <P>SOLUTION: The device comprises a flat silver-covered copper powder in which a covered conductor is exposed, a compound electroconductive powder containing an indefinite shaped electroconductive powder, a compound paste containing the above compound electroconductive powder, a binder , and a solvent, and an electric circuit formed on the surface of the substrate using this electroconductive paste. After the circuit patterns are formed by this electroconductive paste on the substrate, they are pressurized and cured. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a composite conductive powder, a conductive paste, an electric circuit, and a method for producing an electric circuit.

BACKGROUND ART Conventionally, as a method for forming an electric circuit (wiring conductor) such as a printed wiring board or an electronic component, a method of applying or printing a conductive paste containing silver powder having excellent conductivity as described in Non-Patent Document 1. Is generally known.
Electronic Materials, October 1994, pp. 42-46

The conductive paste containing silver powder is used for forming electric circuits and electrodes of printed wiring boards, electronic components, etc. because of its good conductivity. The volume resistivity (specific resistance) is usually 50 to 100 μΩ · cm. Even if it is excellent, it is only 30 to 40 μΩ · cm. If the length of the printed circuit is as short as several cm, it may be an obstacle. However, when it was 10 cm or more, the conduction resistance was increased, and problems were likely to occur.

導体 In order to obtain a conductor having good conduction resistance, it is sufficient to increase the amount of the silver powder, but it is not possible to stably obtain a specific resistance of 25 μΩ · cm or less. Further, if the amount of silver powder is simply increased, disadvantages such as poor balance with other properties, for example, adhesion, occur.

Further, in the method of etching a metal foil such as silver or copper, the specific resistance is several μΩ · cm with high conductivity.
However, there is a disadvantage that the cost is high due to the complicated process. Further, the conductive paste using silver powder has a drawback that when an electric field is applied in a high-temperature and high-humidity atmosphere, silver deposition called migration occurs on a wiring conductor or an electrode and a short circuit occurs between the electrodes or between the wirings. Several measures have been taken to prevent this migration, and measures such as applying a moisture-proof paint to the surface of the conductor or adding a corrosion inhibitor such as a nitrogen-containing compound to the conductive paste have been studied. A sufficient effect was not obtained.

Furthermore, in order to prevent migration, silver-palladium alloy powder may be used instead of silver powder, but such an alloy powder is more expensive than silver powder and is small in a wiring board such as a hybrid IC. However, the wiring board has not been put to practical use yet with a large-sized substrate such as a paper phenol substrate, a glass epoxy substrate, and polyethylene terephthalate. The use of silver-coated copper powder can improve migration, and if it is used, an inexpensive conductive paste can be obtained. However, if the silver coating is coated uniformly and thickly, there is no effect of improving migration. In addition, plating is an inexpensive method of coating. For example, silver plating of inexpensive spherical copper powder can be easily performed with less aggregation, but the conductive paste using this has a drawback of increasing resistance. Was.

The first aspect of the present invention provides a composite conductive powder having a low specific resistance, high conductivity, and a conductive paste for forming an electric circuit having a small change in specific resistance even after a thermal shock test or a wet and medium load test. I do.
The invention according to claims 2 and 3 is a composite conductive powder which is particularly excellent in conductivity among the inventions according to claim 1 and further provides a conductive paste having excellent oxidation resistance and heat resistance in addition to the invention according to claim 1. I will provide a.
The invention according to claims 4 to 6 provides a composite conductive powder from which a conductive paste having an anchor effect can be obtained by applying pressure.
The invention according to claim 7 provides a composite conductive powder from which a conductive paste for forming an electric circuit having a low specific resistance, high conductivity and excellent migration resistance is obtained.

The invention according to claims 8 to 10 provides a conductive paste for forming an electric circuit, which has a low specific resistance, a high conductivity, and a small change in the specific resistance even after a thermal shock test or a wet and medium load test.
An eleventh aspect of the present invention provides an electric circuit having a low specific resistance, high conductivity, and excellent migration resistance.
According to a twelfth aspect of the present invention, there is provided an electric circuit which is excellent in forming a fine circuit in addition to the eleventh aspect.
The invention according to claim 13 provides a method of manufacturing an electric circuit having low specific resistance, high conductivity, and excellent migration resistance.
According to a fourteenth aspect of the present invention, in addition to the thirteenth aspect, a method of manufacturing an electric circuit which is excellent in forming a fine circuit is provided.

The present invention relates to the following items.
(1) A composite conductive powder containing a flat silver-coated copper powder (hereinafter, abbreviated as a flat silver-coated copper powder) having an exposed conductor, and an irregular-shaped conductive powder.
(2) The composite conductive powder according to the above (1), wherein the material of the irregular-shaped conductive powder is silver or a silver alloy.
(3) The composite conductive powder according to the above (2), wherein the irregular-shaped conductive powder is reduced silver powder.
(4) The composite conductive powder according to the above (2), wherein the irregular-shaped conductive powder is obtained by coating a conductor having a hardness higher than silver or a silver alloy with silver.
(5) The composite conductive powder according to the above (4), wherein the conductor having a higher hardness than silver or a silver alloy is a powder of Co, Ni, Cr, Cu, W or an alloy thereof.
(6) The composite conductive powder according to the above (5), wherein the conductor having a higher hardness than silver or silver alloy is copper powder or copper alloy powder.
(7) The composite conductive powder according to any one of the above (4) to (6), wherein the irregular-shaped conductive powder is a silver-coated copper powder or a silver-coated copper alloy powder in which the coated conductor is exposed.

(8) A conductive paste containing the composite conductive powder according to any one of (1) to (7), a binder, and a solvent.
(9) The conductive paste according to (8), wherein the composite conductive powder is contained in an amount of 85 to 93% by weight based on the solid content of the conductive paste.
(10) The composite conductive powder according to any one of (1) to (7), a binder and a solvent are contained, and the irregular shaped conductive powder 5 is contained in 95 to 50% by weight of the flat silver-coated copper powder. The conductive paste according to the above (8) or (9), comprising about 50% by weight.
(11) An electric circuit formed on the surface of the substrate using the conductive paste according to any one of (8) to (10).
(12) The electric circuit according to (11), wherein the electric circuit formed on the surface of the substrate has a specific resistance of 25 μΩ · cm or less.
(13) A method for producing an electric circuit, comprising forming a circuit pattern on the surface of a base material with the conductive paste according to any one of the above (8) to (10), followed by pressing and curing.
(14) The method for producing an electric circuit according to the above (13), wherein the electric circuit formed on the surface of the substrate has a specific resistance of 25 μΩ · cm or less.

The composite conductive powder according to the first aspect provides a conductive paste for forming an electric circuit having a low specific resistance, a high conductivity, and a small change in the specific resistance even after a thermal shock test or a wet and medium load test.
The composite conductive powder according to claims 2 and 3 is a conductive paste which is particularly excellent in conductivity among the composite conductive powders according to claim 1 and further has excellent oxidation resistance and heat resistance in addition to the composite conductive powder according to claim 1. Is obtained.
The composite conductive powder according to claims 4 to 6 is pressurized to obtain a conductive paste having an anchor effect.
According to the composite conductive powder of the present invention, a conductive paste for forming an electric circuit having low specific resistance, high conductivity and excellent migration resistance can be obtained.

The conductive paste according to claims 8 to 10 is suitable for forming an electric circuit having a low specific resistance, high conductivity, and a small change in specific resistance even after a thermal shock test or a wet and medium load test.
The electric circuit according to claim 11 has low specific resistance, high conductivity, and excellent migration resistance.
The electric circuit according to the twelfth aspect is excellent in forming a fine circuit in addition to the electric circuit according to the eleventh aspect.
The method for manufacturing an electric circuit according to claim 13 has low specific resistance, high conductivity, and excellent migration resistance.
According to the method of manufacturing an electric circuit described in claim 14, in addition to the method of manufacturing an electric circuit described in claim 13, an electric circuit excellent in forming a fine circuit can be manufactured.

In the present invention, when the flat silver-coated copper powder and the irregular-shaped conductive powder are used in combination, the contact probability of the flat silver-coated copper powder and the irregular-shaped conductive powder can be improved, and the conductivity of the electric circuit is increased. When a circuit is printed on a substrate in a shape of a circle and the printed circuit is pressed, the conductivity can be increased.

Flat silver-coated copper powder is a silver-coated copper powder composed of fine particles that are almost flat in shape, for example, flaky silver-coated copper powder. Irregular shaped conductive powders are conductive powders having shapes other than flat, such as powders called spherical, cubic, tetrahedral, massive, and generally spherical, and powders with protrusions on the surface, such as sugary sugar. It refers to various conductive powders such as a body and a mixture thereof. Examples of the conductive powder containing various shapes of conductive powder include reduced silver powder.

In many cases, the flat silver-coated copper powder corresponds to a flat silver-coated copper powder having an aspect ratio of 6 or more, preferably about 6 to 11, and other shapes such as dendrites (also called dendrites). And these can also be used in combination. As the flat silver-coated copper powder having an aspect ratio of 6 or more, preferably 6 to 11, the aspect ratio is preferably 7 to 11, and the aspect ratio is more preferably 8 to 11 in that a highly conductive paste is obtained. Preferably, the aspect ratio is more preferably from 10 to 11. Therefore, in terms of shape and aspect ratio, flat silver-coated copper powder having an aspect ratio of 7 to 11 is more preferable in terms of high conductivity, viscosity of the conductive paste, and the like, and a flat shape having an aspect ratio of 8 to 11 is preferred. Silver-coated copper powder is more preferable, and flat silver-coated copper powder having an aspect ratio of 10 to 11 is most preferable.

か ら The average particle size of the particles of the flat silver-coated copper powder is preferably 25 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less, from the viewpoint of not deteriorating printability. Here, the average particle size can be measured by a laser scattering type particle size distribution measuring device. In the present invention, the measurement was performed using a master sizer (manufactured by Malvern) as the device.

多 く As the irregularly shaped conductive powder, most conductive powders having an aspect ratio of 5 or less correspond. As the conductive powder having an aspect ratio of 5 or less, an aspect ratio of 4 or less is preferable, an aspect ratio of 3 or less is more preferable, and an aspect ratio of 2.5 or less is more preferable in that a highly conductive paste is obtained. .

で The average particle size of the irregularly shaped conductive powder is preferably in the range of 3 to 20 μm, more preferably 3 to 10 μm, from the viewpoint of excellent printability. In addition, the average particle diameter here can be measured by a laser scattering type particle size distribution measuring device in the same manner as described above. In the present invention, the measurement was performed using a master sizer (manufactured by Malvern) as the device.

ア ス ペ ク ト The aspect ratio described above refers to the ratio of the major axis to the minor axis (major axis / minor axis) of the particles of the flat silver-coated copper powder or conductive powder. In the present invention, the particles of the flaky silver-coated copper powder or conductive powder are mixed well in a low-viscosity curable resin, and the resin is cured as it is, allowing the particles to settle by standing, and the resulting cured product is cured. It is cut in the vertical direction, the shape of the particles appearing on the cut surface is enlarged and observed with an electron microscope, and the major axis / minor axis of each particle is obtained for at least 100 particles. I do.

Here, the minor axis is defined as a combination of two parallel lines that are in contact with the outside of the particle so that the particle appears on the cut surface so as to sandwich the particle. Distance. On the other hand, the major axis is two parallel lines perpendicular to the parallel line that determines the minor axis, and is the distance between the two parallel lines that are the longest among the combinations of the two parallel lines that contact the outside of the particle. is there. The rectangle formed by these four lines is sized to fit the particle exactly inside it.
The specific method used in the present invention will be described later.

As the material of the irregularly shaped conductive powder, silver or a silver alloy is preferable in terms of conductivity and oxidation resistance.
As the silver alloy, it is preferable to use an alloy with palladium (for example, about 1 to 5% by weight in a silver alloy), platinum (for example, about 1% by weight in a silver alloy), or the like.
One of the methods for producing the silver powder is a submerged reduction method. The silver powder produced by this method is a fine powder having an average particle size of several μm, and is widely used as an industrial production method. I have. The in-liquid reduction method is a method in which silver is dissolved in an acid, then neutralized with an alkali, and then a reducing agent such as formalin or starch is added thereto and reduced in the liquid to form a fine powder. The resulting powder is called reduced silver powder, and its shape is close to a lump but is not a fixed shape but an irregular shape. This reduced silver powder can be used as an irregularly shaped conductive powder in the present invention.
The irregular-shaped conductive powder may be a silver-coated conductive powder in which a conductor other than silver or a silver alloy is coated with silver or a silver alloy.

As described above, the irregular-shaped conductive powder may be a silver-coated conductive powder, but the conductive material to be coated is preferably a conductive material having a higher hardness than silver or a silver alloy. As such a conductor, for example, metal powder of Co, Ni, Cr, Cu, W or the like or an alloy powder thereof can be used, and among them, copper powder or copper alloy powder is preferably used.
The use of this is preferable because when the electric circuit is pressurized, the conductive powder of the irregular shape is embedded in the flat silver-coated copper powder to increase the conductivity of the electric circuit.
As the copper alloy powder, for example, an alloy powder of copper and tin, copper and zinc, or the like is used.

There are methods such as displacement plating, electroplating, and electroless plating to cover the surface of copper powder or irregular-shaped conductive powder with silver. The adhesion between copper powder or irregular-shaped conductive powder and silver is high and running. Since the cost is low, it is preferable to coat by a displacement plating method. The amount of silver coated on the surface of the copper powder or the irregularly shaped conductive powder is preferably in the range of 3 to 50% by weight based on the copper powder or the irregularly shaped conductive powder from the viewpoints of cost, effect of suppressing electrolytic corrosion, and the like. A range of 20% by weight is more preferred.

It is preferable to use any of the above-described silver-coated copper powder or silver-coated conductor powder because of excellent migration resistance. As the silver-coated copper powder or the silver-coated conductor powder, a powder in which a part of the copper powder or the conductor is exposed can be used. These can be used for each of the flat silver-coated copper powder and the irregular-shaped conductive powder.
The exposed area of the copper powder or conductive powder is preferably 50% or less, more preferably 20% or less, in order to obtain good conductivity.

抵抗 The resistance of the spherical silver-coated copper powder after displacement plating is likely to be high because of few contact points. Therefore, the spherical silver-coated copper powder after the displacement plating may be impacted to deform the particles into a flat shape. Specifically, it can be deformed by a method such as a ball mill and a vibration mill.

The mixing ratio of the flat silver-coated copper powder and the irregular-shaped conductive powder is such that the irregular-shaped conductive powder is in the range of 5 to 50% by weight with respect to the flat silver-coated copper powder of 95 to 50% by weight to enhance the conductivity. It is more preferable if the flat silver-coated copper powder is in the range of 80 to 60% by weight and the irregularly shaped conductive powder is in the range of 20 to 40% by weight.

The conductive paste contains these composite conductive powder, binder and solvent. In this conductive paste, the content of the composite conductive powder is preferably 85 to 93% by weight, and more preferably 87 to 90% by weight with respect to the solid content of the conductive paste in view of the resistance, economy and adhesiveness of the conductor. Is more preferred.

有機 As the binder, an organic adhesive component such as a liquid epoxy resin, a phenol resin, or an unsaturated polyester resin is used. As the solvent, terpineol, ethyl carbitol, carbitol acetate, butyl cellosolve, or the like is used. In addition to the above-mentioned materials, the conductive paste is added with a curing agent of an organic adhesive component such as 2-ethylmethylimidazole, a corrosion inhibitor such as benzothiazole and benzimidazole as required, and fine graphite powder, and uniformly mixed. Obtained.

The content of the binder and the solvent is preferably in the range of 7 to 15% by weight of the binder and 10 to 35% by weight of the solvent with respect to the conductive paste in view of conductivity, adhesiveness and printability. More preferably, the agent is in the range of 7 to 12% by weight and the solvent is in the range of 15 to 25% by weight. The content of the curing agent is preferably in the range of 0.5 to 10 parts by weight, more preferably in the range of 1 to 8 parts by weight, based on 100 parts by weight of the binder from the viewpoint of workability. The corrosion inhibitor and the fine graphite powder are added as necessary, but if added, the content should be in the range of 0.1 to 3 parts by weight of the corrosion inhibitor with respect to 100 parts by weight of the binder. Is preferred. The fine graphite powder is preferably in the range of 1 to 10% by weight based on the conductive paste.

The method for forming the electric circuit is not particularly limited, and the electric circuit can be formed by a known method, for example, screen printing of a conductive paste or a drawing machine controlled by a computer.
As the substrate, a polyethylene terephthalate film, a polyimide film, a polyamideimide film, a paper phenol laminate, an epoxy resin glass cloth substrate laminate, a polyimide resin glass cloth substrate laminate, or the like is used.

In the present invention, the specific resistance of the electric circuit is preferably 25 μΩcm or less, more preferably 15 μΩcm or less, and if it exceeds 25 μΩcm, the conductivity tends to decrease. It becomes difficult to make a fine electric circuit. Note that it is particularly preferable that the specific resistance of the electric circuit be 10 μΩ · cm or less, since the electric circuit can be used for a fine electric circuit having a long wire such as a coiled planar antenna.

The specific resistance of the electric circuit can be reduced to 25 μΩ · cm or less by forming a circuit pattern on the surface of the base material using the above-mentioned conductive paste and then pressurizing the circuit pattern with a press, for example, to densify the circuit pattern. As a pressing method, a method of applying pressure using a surface plate, a method of pressing with a roll, or the like is applied, as long as the contact efficiency between powders in a conductive layer formed of a conductive paste can be increased. Note that the binder in the conductive layer is preferably softened during pressing, and if the binder is in a semi-cured state or is cured, it is preferably used after being softened by heating. The binder may be cured after pressing or may be cured during pressing.
Hereinafter, examples of the present invention will be described.

60 parts by weight of a bisphenol A type epoxy resin (trade name: Epicoat 834, manufactured by Yuka Shell Epoxy Co., Ltd.) and 40 parts by weight of bisphenol A type epoxy resin (trade name: Epicoat 828, manufactured by Yuka Shell Epoxy Co., Ltd.) are added in advance. After dissolving in warm water and then cooling to room temperature, 5 parts by weight of 2-ethyl 4-methylimidazole (manufactured by Shikoku Chemicals Co., Ltd.), 20 parts by weight of ethyl carbitol and 20 parts by weight of butyl cellosolve were added and uniformly mixed to obtain a resin composition. Things.

Next, after coating 25% by weight of silver on a spherical copper powder (SF-Cu, manufactured by Nippon Atomize Processing Co., Ltd.) having an average particle diameter of 6.2 μm, the zirconia ball and the ball mill were rotated 60 times per minute after being coated with 25% by weight of silver. Is rotated for 30 minutes under the conditions described above to deform the shape, and the average particle diameter of the major axis is 10.3 μm, the aspect ratio is 6, and the exposed area of copper is in the range of 3 to 18%. A coated copper powder was obtained.

Separately from the above, the same copper powder as described above was coated with 25% by weight of silver by displacement plating, and then rotated together with a glass ball by a ball mill at a rate of 60 rotations per minute for 20 minutes to deform the shape. The average particle size was 7.5 μm, the aspect ratio was 2, and the exposed area of copper was in the range of 2 to 7% to obtain an irregularly shaped silver-coated copper powder having an average of 3%.

Next, 410 parts by weight (66.7% by weight) of flaky silver-coated copper powder and 205 parts by weight (33.3% by weight) of irregularly shaped silver-coated copper powder were added to 145 parts by weight of the resin composition obtained above. The resulting mixture was uniformly mixed and dispersed with a stirrer and a three-roll mill to obtain a conductive paste. The content of the flaky silver-coated copper powder and the irregular-shaped silver-coated copper powder was 86% by weight based on the solid content of the conductive paste.

露出 The above exposed copper area was determined as follows. That is, a SEM photograph of the silver-coated copper powder is taken with a scanning electron microscope (SEM), and 20 particles of the silver-coated copper powder are randomly selected from the SEM photograph, and the surface analysis of silver and copper is performed using an X-ray microanalyzer. Then, the ratio of exposed copper was calculated from the area ratio of the portion covered with silver and the portion where copper was exposed, and the average value was obtained. The average value was defined as the coating area. In the following Examples and Comparative Examples, the copper covering area was calculated in the same manner as described above.

Thereafter, using the conductive paste obtained above, a silver conductor circuit 1 shown in FIGS. 1 and 2 was printed on a 125 μm-thick polyethylene terephthalate film at 80 ° C. for 30 minutes in the air and at 100 ° C. Using a press heated at a pressure of 5 MPa for 2 minutes, a heat treatment was performed at 145 ° C. for 30 minutes to obtain an electric circuit. 1 and 2, reference numeral 2 denotes a polyethylene terephthalate film, and the dimension of A in FIG. 2 is 100 μm.

Next, when the specific resistance of the obtained electric circuit shown in FIG. 1 was measured, it was 11.5 μΩ · cm. In addition, as a result of performing a thermal shock test on the electric circuit, the rate of change in specific resistance was 5%. Further result of the medium load test wet comb the electric circuit shown in FIG. 2, the insulation resistance between wires was at least 10 ⁸ Omega. The cooling / heating test conditions were 100 cycles of 125 ° C. for 30 minutes to −65 ° C. for 30 minutes, and the humidity and load test was carried out by applying a voltage of 50 V between adjacent lines at 40 ° C. and 90% RH for 2000 hours.

Note that a specific method of measuring the aspect ratio in this example is described below. 8 g of a base material (No. 20-8130) of a low-viscosity epoxy resin (manufactured by Buehler Co.) and 2 g of a curing agent (No. 20-8132) are mixed, and 2 g of conductive powder is mixed and dispersed well, and the mixture is left as it is. After degassing in vacuo at ℃, the particles were allowed to stand at 30 ℃ for 6 to 8 hours to settle and harden the particles. Thereafter, the obtained cured product was cut in the vertical direction, and the cut surface was magnified 2000 times with an electron microscope to determine the major axis / minor axis for 100 particles appearing on the cut surface. Ratio.

700 parts by weight (87.5% by weight) of the flaky silver-coated copper powder obtained in Example 1 and 100 parts by weight (12.5% by weight) of the irregularly shaped silver-coated copper powder obtained in Example 1 were used. The mixture was added to 145 parts by weight of the resin composition obtained in Example 1, and uniformly mixed and dispersed with a stirrer and a three-roll mill to obtain a conductive paste. The content of the flaky silver-coated copper powder and the irregular-shaped silver-coated copper powder was 89% by weight based on the solid content of the conductive paste. Hereinafter, an electric circuit was manufactured through the same steps as in Example 1, and its characteristics were evaluated. As a result, the specific resistance of the electric circuit was 9.5 μΩ · cm. As a result of performing a thermal shock test on the electric circuit, the rate of change in specific resistance was 4%, and the insulation resistance between the wirings was 10 ⁸ Ω or more in a wet / medium load test on the comb-type electric circuit.

750 parts by weight (83.3% by weight) of the flaky silver-coated copper powder obtained in Example 1 and 10% by weight of silver were coated on the surface of the copper powder used in Example 1 by displacement plating. Amorphous silver-coated copper powder having an average major particle diameter of 6.0 μm, an aspect ratio of 2 and an exposed area of copper of 3 to 13%, and an average of 7%, and having an average of 7%, obtained by the same process as in Example 1 150 weight Parts (16.7% by weight) was added to 145 parts by weight of the resin composition obtained in Example 1, and the mixture was uniformly mixed and dispersed with a stirrer and a three-roll mill to obtain a conductive paste. The content of the flaky silver-coated copper powder and the irregular-shaped silver-coated copper powder was 89% by weight based on the solid content of the conductive paste. Hereinafter, an electric circuit was produced through the same steps as in Example 33 except that the pressing pressure was set to 20 MPa, and its characteristics were evaluated. As a result, the specific resistance of the electric circuit was 8.3 μΩ · cm. In addition, as a result of performing a thermal shock test of the electric circuit, the rate of change of the specific resistance was 5%, and the insulation resistance between the wirings was 10 ⁸ Ω or more in the wet and medium load test of the comb-type electric circuit.

Using the conductive paste obtained in Example 3, an electric circuit was manufactured through the same steps as in Example 1, and then the printed circuit was densified by heating and pressing under the conditions of a hot roll, a temperature of 100 ° C. and a pressure of 10 MPa. The properties were evaluated. As a result, the specific resistance of the densified electric circuit was 8.4 μΩ · cm. In addition, as a result of performing a thermal shock test on the densified electric circuit, the rate of change in specific resistance was 4%, and the insulation resistance between the wirings was 10 ⁸ Ω or more in a wet / medium load test of the comb-type electric circuit. .

Comparative Example 1
400 parts by weight of the flaky silver-coated copper powder obtained in Example 1 was added to 145 parts by weight of the resin composition obtained in Example 1, and the mixture was uniformly mixed and dispersed with a stirrer and a three-roll mill. A paste was obtained. Next, an electric circuit was manufactured through the same steps as in Example 1 except for the step of heating and pressing with a press, and its characteristics were evaluated. As a result, the specific resistance of the electric circuit was 62 μΩ · cm. In addition, as a result of performing a thermal shock test on the electric circuit, the rate of change of the specific resistance was 10%, and the insulation resistance between the wirings was 10 ⁸ Ω or more in the wet and medium load test of the comb-type electric circuit.

Comparative Example 2
To 145 parts by weight of the resin composition obtained in Example 1, 400 parts by weight of flaky silver powder (manufactured by Tokurika Chemical Laboratory, trade name: TCG-1) having an aspect ratio of 8 and a long average particle diameter of 8 μm were added. The mixture was uniformly mixed and dispersed with a stirrer and a three-roll mill to obtain a conductive paste. Next, an electric circuit was manufactured through the same steps as in Example 1 except for the step of heating and pressing with a press, and its characteristics were evaluated. As a result, the specific resistance of the electric circuit was 62 μΩ · cm. In addition, as a result of performing a thermal shock test on the electric circuit, the rate of change of the specific resistance was 10%. In a wet and medium load test of the comb-type electric circuit, the insulation resistance between the wirings was reduced to 10 ⁸ Ω or less in a test time of 370 hours. And migration of silver occurred between wirings.

Comparative Example 3
Copper powder coated with 145 parts by weight of the resin composition obtained in Example 1 and coated with silver before the scaly shape obtained in Example 1 (exposed area of copper is less than 1%, almost 0%) Was added, and the mixture was uniformly mixed and dispersed with a stirrer and a three-roll mill to obtain a conductive paste. Next, an electric circuit was manufactured through the same steps as in Example 1 except for the step of heating and pressing with a press, and its characteristics were evaluated. As a result, the specific resistance of the electric circuit was 65 μΩ · cm. In addition, as a result of performing a thermal shock test of the electric circuit, the rate of change of the specific resistance was 12%. In a wet and medium load test of the comb-type electric circuit, the insulation resistance between the wirings was reduced to 10 ⁸ Ω or less in a test time of 530 hours. And migration of silver occurred between wirings.

It is a top view showing the state where a silver conductor circuit was printed on a polyethylene terephthalate film. FIG. 3 is a plan view showing a state in which silver conductor circuits are printed in a comb shape on a polyethylene terephthalate film.

Explanation of reference numerals

1 silver conductor circuit 2 polyethylene terephthalate film

Claims (14)

複合 Composite conductive powder containing flat silver-coated copper powder with exposed conductors and irregular-shaped conductive powder. The composite conductive powder according to claim 1, wherein the material of the irregularly shaped conductive powder is silver or a silver alloy. 3. The composite conductive powder according to claim 2, wherein the irregular-shaped conductive powder is a reduced silver powder. (3) The composite conductive powder according to (2), wherein the irregular-shaped conductive powder is obtained by coating a conductor having a hardness higher than silver or a silver alloy with silver. 5. The composite conductive powder according to claim 4, wherein the conductor having a higher hardness than silver or a silver alloy is a powder of Co, Ni, Cr, Cu, W or an alloy thereof. 6. The composite conductive powder according to claim 5, wherein the conductor having a higher hardness than silver or a silver alloy is copper powder or copper alloy powder. The composite conductive powder according to any one of claims 4 to 6, wherein the irregular-shaped conductive powder is a silver-coated copper powder or a silver-coated copper alloy powder from which the coated conductor is exposed. A conductive paste comprising the composite conductive powder according to claim 1, a binder, and a solvent. The conductive paste according to claim 8, wherein the composite conductive powder is contained in an amount of 85 to 93% by weight based on the solid content of the conductive paste. A flat silver-coated copper powder containing the composite conductive powder according to any one of claims 1 to 7, a binder, and a solvent and exposing the coated conductor, based on 95 to 50% by weight. 10. The conductive paste according to claim 8, comprising 5 to 50% by weight of the irregularly shaped conductive powder. An electric circuit formed on the surface of a substrate using the conductive paste according to any one of claims 8 to 10. 12. The electric circuit according to claim 11, wherein a specific resistance of the electric circuit formed on the surface of the base material is 25 μΩ · cm or less. (11) A method for producing an electric circuit, comprising: forming a circuit pattern on the surface of a substrate with the conductive paste according to any one of claims 8 to 10; 14. The method for manufacturing an electric circuit according to claim 13, wherein the specific resistance of the electric circuit formed on the surface of the base material is 25 μΩ · cm or less.

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