JP6623919B2 - Conductive composition, method for producing conductor, and method for forming wiring of electronic component - Google Patents

Description

  The present invention relates to a conductive composition, a method for manufacturing a conductor using the same, and a method for forming wiring of an electronic component.

  As one of methods for forming a circuit on a substrate of an electronic component, there is a method of forming a wiring or an electrode using a conductor obtained by firing a conductive composition containing a conductive component. At that time, gold, silver, palladium or a mixture thereof is often used as the conductive component. However, gold and palladium are precious metals, so their prices are high, and they are susceptible to price fluctuations depending on the supply and demand situation. Therefore, when these metals are used, there are problems such as an increase in the cost of the product and a change in the price. Silver is cheaper than gold and palladium, but has the problem that migration is likely to occur. As the conductive component, nickel may be used other than the noble metal, but there is a problem that the conductivity is relatively low.

  Therefore, in recent years, copper which is excellent in conductivity, excellent in migration resistance and inexpensive has been used as a conductive component. For the conductor, for example, a paste-like conductive composition (conductive paste) whose viscosity is adjusted by blending an organic vehicle is applied to a substrate by a printing method such as screen printing, and the conductive paste applied to the substrate is applied. Is formed by drying and firing. Since copper is a metal that is easily oxidized, baking of the conductive paste containing copper is generally performed in a reducing atmosphere or an inert gas atmosphere, for example, in a nitrogen gas. When calcined in the air, copper is oxidized, and the oxide formed at that time may lower the conductivity.

  The conductive composition containing copper often contains copper powder and glass frit as main components. Glass frit has an effect of bringing conductive components into close contact with each other or bringing a substrate and conductive components into close contact with each other. Conventionally, glass frit containing lead (lead glass frit) has been used in many cases. Since the lead glass frit has a low softening temperature and is excellent in wettability with a conductive component and a substrate, the conductive composition using the lead glass frit has sufficient conductivity and adhesion to the substrate.

  However, in recent years, regulations on chemical substances that are harmful to the environment are becoming stricter, and lead is a regulated substance under the RoHS Directive and the like. Therefore, a conductive composition using a glass frit that does not contain lead (lead-free glass frit) has been demanded.

  When a circuit is formed on a substrate, a resistor is formed in addition to conductors such as wiring and electrodes. The circuit is formed sequentially by, for example, applying a conductive paste or a resistive paste on the substrate by a printing method, and then baking it under appropriate conditions. After a pattern of a body or the like is continuously formed, it is formed by firing simultaneously with one heat treatment.

  The resistance paste includes, for example, ruthenium oxide and glass frit. If such a resistance paste is fired in a nitrogen atmosphere, ruthenium oxide may react with nitrogen and a desired resistance value may not be obtained. Therefore, if it is necessary to fire the conductive paste in a nitrogen atmosphere, apply a resistive paste and fire in air to form a resistor, then apply the conductive paste and fire in a nitrogen atmosphere. A method of forming a conductor by using the method has been used.

  By forming the resistor by firing beforehand as described above, the conductor can be formed in a nitrogen atmosphere. However, since the heat treatment for forming the conductor is usually performed at 800 ° C. to 1000 ° C., even if the influence of nitrogen on the resistor can be prevented, the heat history due to the heat treatment at a high temperature adversely affects the resistor. There are cases. Therefore, a conductive composition that can be fired by a heat treatment at a lower temperature, for example, 750 ° C. or lower has been demanded.

  For example, Patent Document 1 describes a copper paste composition comprising an inorganic component and an organic vehicle component containing copper powder, cuprous oxide powder, cupric oxide powder, and glass powder as main components. The article is described as being particularly suitable for low-temperature firing at 550-750 ° C. However, in the examples, only glass powder containing lead is disclosed as glass powder used in the copper paste composition.

  A lead-free glass frit containing substantially no lead tends to have poorer wettability with a substrate than a lead glass frit. Therefore, a conductive composition using a lead-free glass frit may not be able to obtain sufficient adhesion between the conductor and the substrate. In particular, the lower the heat treatment temperature at the time of firing, the more noticeable the tendency. Therefore, a conductive composition using a lead-free glass frit capable of forming a conductor having sufficient conductivity and adhesion has been demanded.

  For example, Reference 2 discloses a copper paste composition containing at least copper powder, a lead-free glass frit, and cuprous oxide, and the lead-free glass frit contains at least bismuth, boron, and each oxide of silicon, A copper paste composition having a softening start temperature of 400 ° C. or lower is disclosed. It is described that this copper paste composition has excellent adhesion to a ceramic substrate.

Patent Document 3 discloses that borosilicate glass frit (SiO ₂ —B ₂ O ₃ ) and barium borosilicate glass frit (BaO—SiO ₂ —B ₂ ) are used as glass frit used for a copper paste for an external electrode. A copper paste having excellent electrical properties and adhesive strength is disclosed by adding a zinc borosilicate-based glass frit containing zinc oxide at a specific ratio to a lead-free glass frit such as O ₃ ).

JP-A-03-141502 JP 2012-54113 A JP 2002-280248 A

  However, the copper pastes described in Patent Literatures 2 and 3 form conductors by firing at 900 ° C., and even when fired at a low temperature of 750 ° C. or lower, a conductor having sufficient conductivity and adhesion is obtained. Whether it can be obtained has not been considered.

  The present invention has been studied in view of such circumstances, and provides a conductive composition that can be fired even at a temperature of 750 ° C. or less, has sufficient adhesion to a substrate, and has excellent conductivity. The purpose is to:

According to a first aspect of the present invention, there is provided a conductive composition containing copper powder, cuprous oxide, and a lead-free glass frit. The lead-free glass frit contains 5 to 25 parts by mass, and the lead-free glass frit contains boron oxide, silicon oxide, zinc oxide, and optionally other components. Boron, silicon oxide and zinc oxide, zinc borosilicate glass frit, and vanadium oxide, zinc oxide, and optionally contain other components, and the top two types of oxide components having a high content are vanadium oxide and containing vanadium zinc glass frit is a zinc oxide, a, with respect to 100 mass% of lead-free glass frit, borosilicate zinc glass frit containing 90 wt% or less than 10 wt%, vanadium zinc Containing less than 10 wt% 90 wt% a Rasufuritto on the total conductive composition, the content of lead is less than 0.01 wt%, the conductive composition is provided.

Further, with respect to lead-free glass frit 100 wt%, 80 wt% to 20 wt% of borosilicate zinc glass frit or less, preferably contains a vanadium zinc glass frit less than 20 wt% 80 wt%. It is preferable that the vanadium zinc-based glass frit contains vanadium oxide in an amount of 30% by mass or more and 50% by mass or less and zinc oxide in a range of 30% by mass or more and 50% by mass or less based on the whole vanadium zinc-based glass frit . Further, it is preferable that the zinc borosilicate glass frit contains 25% by mass or more and 45% by mass or less of zinc oxide based on the whole zinc borosilicate-based glass frit . Further, it is preferable to contain the lead-free glass frit in an amount of 0.2 to 8.5 parts by mass based on 100 parts by mass of the copper powder. Further, it is preferable that cuprous oxide be contained in an amount of 5.5 parts by mass or more and 15 parts by mass or less based on 100 parts by mass of the copper powder. Preferably, the copper powder contains at least one of a spherical powder and a flake-like powder. The average particle diameter of the spherical powder is preferably 0.2 μm or more and 5 μm or less. Further, it is preferable that the organic vehicle be contained in an amount of 10% by mass or more and 50% by mass or less based on 100% by mass of the conductive composition.

  According to a second aspect of the present invention, there is provided a method for producing a conductor, comprising a step of firing the conductive composition by a heat treatment at 750 ° C. or lower.

  In a third aspect of the present invention, there is provided a method for forming a wiring of an electronic component, comprising: a step of applying the conductive composition on a substrate; and a step of firing the substrate after the application by a heat treatment at 750 ° C. or lower. Is done.

  By using the conductive composition of the present invention, a conductor excellent in conductivity and adhesion to a substrate can be formed. In addition, since the conductive composition of the present invention can be fired at a low temperature of 750 ° C. or lower, the use of the conductive composition of the present invention damages resistors and internal elements of electronic components. It is possible to form a conductor without any problems. As a result, it is possible to manufacture an electronic component having the same electrical characteristics as the conventional one without lead and with a low defect rate.

1. Conductive Composition The conductive composition of the present embodiment includes copper powder, cuprous oxide, and a lead-free glass frit. By not using a lead glass frit, the conductive composition is substantially free of lead and has excellent environmental characteristics. Note that a lead-free glass frit is a glass frit that does not contain lead or, even when it contains lead, has a very small content (for example, the content of lead is 0.1% by mass with respect to the entire glass frit). Below). Further, that the conductive composition does not substantially contain lead means, for example, a state in which the content of lead is 0.01% by mass or less with respect to the entire conductive composition.
Hereinafter, each component constituting the conductive composition will be described.

(1) Copper powder The conductive composition of the present embodiment contains copper powder as a conductive component. Copper powder has excellent conductivity and migration resistance and is inexpensive. Since copper powder is easily oxidized, when heat-treating the conductive composition, it is usually heat-treated in a nitrogen atmosphere.

  The method for producing the copper powder is not particularly limited, and a conventionally known method, for example, an atomizing method, a wet reduction method, an electrolysis method, or the like can be used. For example, when the atomizing method is used, the residual concentration of impurities in the obtained copper powder can be reduced, and the number of pores extending from the surface to the inside of the obtained copper powder particles can be reduced. Oxidation can be suppressed.

  The shape and particle size of the copper powder are not particularly limited, and can be appropriately selected according to the target electronic component. As the shape of the copper powder, for example, spherical or flake-like copper powder or a mixture thereof can be used. The copper powder contains, for example, flake-shaped copper powder, so that the contact area between the copper powders becomes large and the copper powder may be excellent in conductivity.

  When a spherical copper powder and a flake-like mixture are used as the copper powder, the mixing ratio of the spherical copper powder and the flake-like can be appropriately selected according to the application. The mixing ratio can be, for example, 10 parts by mass or more and 90 parts by mass or less of the spherical copper powder and 90 parts by mass or less and 10 parts by mass or more of the flaky copper powder with respect to 100 parts by mass of the entire copper powder.

  For example, in the case of spherical copper powder, the average particle size of the copper powder can be about 0.2 μm or more and 5 μm or less. For example, in the case of flake-shaped copper powder, the flat elongated particle diameter can be set to be about 3 μm or more and about 30 μm or less. When the particle size is in the above range, the applicability to miniaturized electronic components is excellent. The average particle diameter is a median diameter (D50) and can be measured by a particle size distribution measuring device based on a laser diffraction / scattering method. The copper powder may be a powder having the same particle size or a mixture of two or more powders having different particle sizes.

  In general, firing can be facilitated by reducing the particle size of the conductive powder.For example, when the average particle size of the spherical copper powder is set to less than 0.2 μm, the copper powder is oxidized. In addition, not only sintering failure may occur, but also problems such as insufficient capacity and change in paste viscosity with time may occur. The conductive composition of the present embodiment, for example, even if the particle size of the copper powder is 1 μm or more, by including a specific component described later, for example, even a low-temperature heat treatment of 750 ° C. or less, enough, The copper powder can be fired.

(2) Lead-free glass frit The conductive composition of the present embodiment contains zinc borosilicate glass frit and vanadium zinc glass frit as lead-free glass frit. Since the conductive composition contains a glass frit in which the above two types are combined, even when a lead-free glass frit is used, the wettability to the copper powder and the substrate is excellent in a well-balanced manner. Further, even when this conductive composition is fired at 750 ° C. or lower, a conductor having extremely excellent conductivity and adhesion can be obtained.

The zinc borosilicate glass frit includes boron oxide (B ₂ O ₃ ), silicon oxide (SiO ₂ ), zinc oxide (ZnO), and optionally other components, and is the top three oxide components having a high content. It is a glass frit whose type is B ₂ O ₃ , SiO ₂ and ZnO. The zinc borosilicate-based glass frit has a ZnO content of 25% by mass to 45% by mass, a SiO ₂ content of 5% by mass to 15% by mass, and a B ₂ O ₃ of 35% by mass with respect to 100% by mass of the zinc borosilicate-based glass frit. % Or more and 55% by mass or less.

The composition of the zinc borosilicate glass frit may include one or more other components other than the above, and may include, for example, an oxide of an alkali metal such as Na ₂ O or Al ₂ O _3. it can. It is preferable that the addition amounts of these other components are respectively 0.5% by mass or more and 10% by mass or less.

  The particle size of the zinc borosilicate glass frit is not particularly limited, but is, for example, 1 μm or more and 10 μm or less, preferably 1 μm or more and 5 μm or less. When the particle size is within the above range, excellent fluidity is obtained even during low-temperature firing. The average particle size is a value measured by a laser diffraction / scattering type particle size / particle size distribution measuring device (microtrack method).

  The softening point of the zinc borosilicate glass frit is preferably 600 ° C. or lower, more preferably 400 ° C. or higher and 600 ° C. or lower, and further preferably 500 ° C. or higher and 600 ° C. or lower. When the softening point is in the above range, a conductor excellent in conductivity and adhesion can be obtained even when fired at a low temperature. The softening point can be controlled, for example, by appropriately adjusting the composition and particle size of the glass frit.

The vanadium zinc-based glass frit includes vanadium oxide (V ₂ O ₅ ), zinc oxide (ZnO), and optionally other components, and the top two oxide components having a high content are V ₂ O ₅ and ZnO. Is a glass frit. The vanadium zinc-based glass frit preferably contains ZnO in a range of 30% by mass to 50% by mass and V ₂ O _{5 in a range} of 30% by mass to 50% by mass. By containing V ₂ O ₅ , the vanadium zinc-based glass frit can obtain a conductive composition having excellent fluidity even when heat-treated at a low temperature, and having excellent permeability to a substrate.

The composition of the vanadium zinc-based glass frit can include one or more components other than those described above. For example, alkali metal oxides such as CaO, B ₂ O ₃ , Bi ₂ O ₃ , and Al ₂ O _{3 and the} like can be included. It is preferable that the addition amount of these other components is respectively 0% by mass or more and 10% by mass or less.

  The particle size of the vanadium zinc-based glass frit is not particularly limited, but is, for example, 1 μm or more and 10 μm or less, preferably 1 μm or more and 5 μm or less. When the particle size is within the above range, excellent fluidity is obtained even during low-temperature firing. The average particle size is a value measured by the microtrack method.

  The vanadium zinc-based glass frit has a softening point of preferably 600 ° C. or less, more preferably 300 ° C. or more and 500 ° C. or less, and more preferably 350 ° C. or more and 450 ° C. or less. When the softening point is in the above range, a conductive composition having excellent fluidity can be obtained. The softening point can be controlled, for example, by appropriately adjusting the composition and particle size of the glass frit.

  Further, the softening point of the zinc borosilicate glass frit can be selected to be higher than the softening point of the vanadium zinc glass frit. Since the conductive composition contains glass frit having different softening points, the conductive composition is excellent in fluidity and excellent in wettability to the conductive component and the substrate in a well-balanced manner. In addition, ZnO contained in these glass frit is reduced by residual char (soot, carbon) derived from an organic vehicle into zinc during a drying or baking step, and this zinc suppresses oxidation of copper powder. it can. The function of ZnO in the glass frit is not limited to the above.

  The content of the lead-free glass frit can be appropriately selected from, for example, the electronic component to be coated, the type of the glass frit to be used, the characteristics obtained by the content of the copper powder, and the like. The content of the lead-free glass frit is, for example, the lower limit thereof is 0.2 parts by mass or more, preferably 1 part by mass or more, more preferably 2 parts by mass or more based on 100 parts by mass of the copper powder. . When the lower limit of the content of the lead-free glass frit is within the above range, the adhesion to the substrate is more excellent. Although the upper limit of the content of the lead-free glass frit is not particularly limited, for example, the upper limit is 15 parts by mass or less based on 100 parts by mass of the copper powder. When the conductive composition of the present embodiment is used for forming a conductive pattern, the upper limit is preferably 9 parts by mass or less, more preferably 6 parts by mass or less, and even more preferably 5 parts by mass or less. When the upper limit of the content of the lead-free glass frit is in the above range, the formed electrode is more excellent in solder jointability. If the content of the lead-free glass frit is too large, excess glass is extruded to the outside of the conductor during sintering, so that excess glass remains on the surface of the electrode, resulting in poor solder jointability.

  Further, the content of the lead-free glass frit can be, for example, in the range of 0.5% by mass or more and 10% by mass or less with respect to the entire conductive paste, and particularly preferably 2% by mass or more and 8% by mass or less. .

  The content of the vanadium zinc-based vitreous frit is, for example, 10% by mass or more and 90% by mass or less, preferably 20% by mass or more and 80% by mass or less, more preferably 40% by mass or more based on the whole lead-free glass frit. It is 60% by mass or less. In the present embodiment, when the content of the vanadium zinc-based vitreous frit is in the above range, the formed conductor is excellent in conductivity and adhesion to the substrate in a well-balanced manner.

  The content of the zinc borosilicate glass frit is, for example, 90% by mass or less and 10% by mass or more, preferably 80% by mass or less and 20% by mass or more, more preferably 60% by mass, based on the whole lead-free glass frit. Below, it is 40% by mass or more. In this embodiment, when the content of the zinc borosilicate glass frit is in the above range, the formed conductor is excellent in conductivity and adhesion to the substrate in a well-balanced manner.

  The content of ZnO is preferably 30% by mass or more and 50% by mass or less, more preferably 35% by mass or more and 40% by mass or less based on the entire lead-free glass frit. When the content of ZnO is in the above range, the adhesion to the substrate is more excellent.

In addition, the content of V ₂ O ₅ is preferably 5% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 30% by mass or less, and further preferably 10% by mass or less with respect to the entire lead-free glass frit. It is at least 25 mass%. When the V ₂ O ₅ content is in the above range, the adhesion to the substrate is more excellent.

In addition, the content of B ₂ O ₃ is preferably 3% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 45% by mass or less, and further preferably 20% by mass or less, based on the entire lead-free glass frit. Not less than 40% by mass. Further, the content of SiO ₂ is preferably 2% by mass or more and 10% by mass or less based on the entire lead-free glass frit.

(3) Cuprous oxide The conductive composition of the present embodiment contains cuprous oxide (copper (I) oxide: Cu ₂ O) as an inorganic binder, so that the copper powders of the copper conductive paste for low-temperature firing can be used. Can be promoted.

  The content of cuprous oxide can be, for example, preferably from 5.5 parts by mass to 25 parts by mass, more preferably from 6 parts by mass to 25 parts by mass, based on 100 parts by mass of copper powder. Preferably it is 7 to 15 parts by mass. When the content of copper oxide is in the above range, sintering of copper powders is promoted, and excellent conductivity and adhesion to a substrate are obtained. If the content of cuprous oxide is too large, excess copper oxide that does not contribute to sintering of copper becomes a resistance, and the conductivity may be insufficient.

  When baked in a non-oxygen atmosphere (for example, in a nitrogen gas atmosphere), the lead-free glass frit tends to have insufficient adhesion to a substrate. However, when a conductive composition containing a lead-free glass frit and cuprous oxide is heat-treated in a non-oxygen atmosphere, for example, after being adjusted to a paste, a small amount of oxygen is converted from cuprous oxide into a firing atmosphere during the heat treatment. By being introduced, the adhesion to the substrate can be improved. According to the conductive composition of the present embodiment, by combining a zinc borosilicate glass frit, a vanadium zinc glass frit, and cuprous oxide, a conductor having significantly improved conductivity and adhesion to a substrate Can be obtained. Note that the conductive composition of the present embodiment may contain a small amount of cupric oxide (copper (II) oxide: CuO) as long as the above-described effects are not impaired. Cupric oxide can be contained, for example, in an amount of 0 to 5 parts by mass with respect to 100 parts by mass of the copper powder.

(4) Organic Vehicle The conductive composition of the present embodiment may contain an organic vehicle. The organic vehicle can adjust the viscosity of the conductive composition to be a paste-like composition having appropriate printability.

  The composition of the organic vehicle is not particularly limited, and a known composition used for a conductive paste can be used. The organic vehicle contains, for example, a resin component and a solvent. As the resin component, for example, a cellulose resin or an acrylic resin can be used. As the solvent, for example, terpene-based solvents such as terpineol and dihydroterpineol, and ether-based solvents such as ethyl carbitol and butyl carbitol can be used alone or in combination.

  Since the organic vehicle is a component that volatilizes or burns when the conductive composition is dried or fired, the content of the organic vehicle in the conductive composition is not particularly limited. The organic vehicle may be added so that the conductive composition has appropriate viscosity and applicability, and the content thereof can be appropriately adjusted depending on the use and the like. For example, the organic vehicle can be contained in an amount of 10% by mass or more and 50% by mass or less based on 100% by mass of the paste-like conductive composition (conductive paste).

  Note that the conductive composition of the present embodiment may contain other components as long as the effects of the present invention are exhibited. For example, as such other components, an antifoaming agent, a dispersant, a coupling agent, and the like may be appropriately added to the conductive composition.

(5) Characteristics of Conductive Composition The conductive composition of the present embodiment is very excellent in conductivity of a conductor after firing and adhesion to a substrate, and thus can be suitably used for forming a conductor. In addition, the conductive composition of the present embodiment can be fired by a heat treatment of 750 ° C. or lower, and can be fired by a heat treatment of 600 ° C. or lower. And an adhesive property with the substrate. Therefore, the conductive composition of the present embodiment can be suitably used as a conductive paste for low-temperature firing.

  In the conductive composition of the present embodiment, the area resistance of the conductor fired at 600 ° C. in terms of a film thickness of 10 μm is preferably 10 mΩ or less, more preferably 5 mΩ or less. The sheet resistance is a value measured by a method described in Examples described later.

  In the conductive composition of the present embodiment, the peel strength of the conductor fired at 600 ° C. is preferably 20 N or more, more preferably 25 N or more. Further, by adjusting the mixing ratio of each component of the conductive composition, it can be made 30N or more, and furthermore, 40N or more. The peel strength is determined, for example, by attaching a Sn-plated Cu wire having a diameter of 0.6 mm to a copper conductor prepared by sintering the conductive composition at 600 ° C. with 3Ag-0.5Cu-Sn solder, It is a value measured when the plated Cu wire is pulled and broken, and is a value for evaluating the adhesion between the substrate of the electronic component and the conductor.

  Note that the conductive composition of the present embodiment can be used for other than conductors such as wiring and electrodes formed on the surface of an electronic component. A chip component such as an element may be adhered to a lead frame or various substrates and used as a material for electrically or thermally conducting.

2. Hereinafter, a method for forming a conductor according to the present embodiment will be described.
First, a conductive composition is produced by mixing copper powder, cuprous oxide, lead-free glass frit, and an organic vehicle. The lead-free glass frit contains a zinc borosilicate glass frit and a vanadium zinc glass frit. The conductive composition forms a paste (conductive paste) whose viscosity is appropriately adjusted by the solvent in the organic vehicle. The composition, mixing ratio, and the like of each component in the conductive paste are as described above.

  Next, the conductive paste is fired to form a conductor. The firing is generally performed by a heat treatment at 800 ° C. or more and 1000 ° C. or less. The conductive paste of the present embodiment can be sufficiently fired even at a heat treatment of less than 800 ° C., for example, can be fired even at a heat treatment of 750 ° C. or less, and can be fired at a heat treatment of 650 ° C. or less. Further, according to the conductive paste of the present embodiment, as shown in the examples described below, even when baked by a heat treatment at 600 ° C., it is possible to obtain a conductor having extremely excellent conductivity and adhesion to a substrate. it can.

  The lower limit of the heat treatment temperature for firing is not particularly limited, but is, for example, 400 ° C. or higher. The firing time is, for example, 5 minutes or more and 20 minutes or less at the peak temperature.

  Further, drying may be performed before firing. The drying conditions are not particularly limited, but for example, the drying can be performed at 50 ° C. to 150 ° C. for about 5 minutes to 15 hours. Further, the oxygen concentration in the burnout zone in the firing furnace is not particularly limited, but may be, for example, about 100 ppm.

  By applying the conductive paste on the electronic component and firing the applied electronic component, an electronic component having a circuit formed thereon can be manufactured. Further, by applying the conductive paste on a substrate and baking the substrate after the application, an electronic component having wiring formed thereon can be manufactured. In the method for manufacturing an electronic component, if the conductive composition of the present embodiment is used, it can be fired by a heat treatment at 750 ° C. or less, so that damage to resistors, internal elements, and the like can be reduced. In addition, the heat treatment can be performed at 650 ° C. or lower, and can be performed at 600 ° C. or lower. The conductor formed by this manufacturing method is very excellent in conductivity and adhesion to a substrate.

Next, the present invention will be described using examples and comparative examples, but the present invention is not limited to these examples.
1. Raw material (1) Copper powder (spherical): Spherical copper powder having an average particle diameter of 0.3 μm, 1.0 μm, and 2.5 μm manufactured by an atomizing method was used.
(2) Copper powder (flake shape): The spherical copper powder produced by the above method was used as a raw material and flaked by a wet ball mill method, and a flake copper powder having an average particle size of 10 μm was used.

(3) lead-free glass frit borosilicate zinc glass frit: a _ZnO-SiO 2 _-B 2 _{O 3} based glass frit having a softening point of 520 to 570 ° C., ZnO 36 wt%, a SiO ₂ 10 wt%, B _{The one} containing 45% by mass of ₂ O _{3 and} having an average particle size of 1.5 μm was used.
Vanadium zinc glass frit: a _ZnO-V 2 _{O 5} based glass frit having a softening point of three hundred eighty to four hundred thirty ° C., ZnO 41 _wt%, the V 2 _{O 5} contained 39.5 wt%, average particle size 3 0.5 μm was used.
· Borosilicate bismuth glass frit: as _{Bi 2 O 3 -SiO 2 -B 2} O 3 based glass frit having a softening point of five hundred and sixty-five to five hundred ninety-five ° C., the _Bi 2 _{O 3} 34.1 _wt%, B 2 _{O 3} 24 A material containing 0.4% by mass and 17% by mass of SiO _{2 and} having an average particle size of 1.5 μm was used.
Table 1 shows the composition of each lead-free glass frit used.

(4) Cuprous oxide: Cu ₂ O having an average particle size of 1 μm to 5 μm was used.

2. Production of conductive paste (production of organic vehicle)
Ethyl cellulose (18 parts by mass) and acrylic resin (2 parts by mass) were added to terpineol (80 parts by mass) and lightly dispersed to obtain a dispersion. Thereafter, the dispersion was heated to 60 ° C. while being stirred by an air motor to produce a transparent and viscous organic vehicle.

(Preparation of conductive paste)
Copper powder, glass frit, cuprous oxide, and the organic vehicle prepared as described above were mixed with a mixer to obtain a mixture. Table 2 shows the mixing ratio of each component. This mixture was kneaded with a three-roll mill to produce a conductive paste.

3. Formation of Conductor for Evaluation (1) Sample for Evaluation of Area Resistance A gold paste was printed on an alumina substrate and baked to prepare an alumina substrate on which a gold (Au) electrode having a distance between electrodes of 50 mm was formed. The obtained conductive paste was printed between Au electrodes using a pattern having a width of 0.5 mm and a distance between electrodes of 50 mm on the surface of the substrate so that the thickness after firing was 10 μm to 13 μm. The printed alumina substrate was heat-treated at 120 ° C. to dry the conductive paste. The dried alumina substrate was heat-treated in a nitrogen atmosphere belt furnace with a peak temperature of 600 ° C., a peak temperature duration of 10 minutes, and a profile of 60 minutes from the entrance to the exit of the furnace, and the conductive paste was fired. The oxygen concentration in the firing zone in the furnace was 5 ppm, and dry air was introduced into the burnout zone provided in the first half of the furnace (from the furnace entrance to the zone at 600 ° C.) to reduce the oxygen concentration to 200 ppm, 400 ppm and 600 ppm. Each concentration was set. The oxygen concentration was measured using a zirconia oxygen concentration meter (manufactured by Toray: Model LC-750) and adjusted to each concentration.
(2) Sample for Adhesion Evaluation The above-mentioned copper conductive paste for low-temperature firing was printed on an alumina substrate in a pattern of 2 mm × 2 mm, and fired under the same conditions as the above-mentioned sheet resistance evaluation sample preparation conditions. A sample (thickness after firing: 10 μm) for evaluating adhesion was prepared.

(3) Characteristic evaluation of formed conductor 3-1) Area resistance value A resistance measuring probe of a digital multimeter (manufactured by Advantest Co., Ltd.) is brought into contact between the Au electrodes of the sample for evaluation of area resistance obtained above. Then, the resistance R [t] of the conductor was measured. Subsequently, the resistance value R [t] was converted to a sheet resistance value Rs [t] (= R (t) × W / L). Using this value, the sheet resistance Rs0 (= Rs [t] × t / 10) (Ω / □) when the thickness of the conductor was 10 μm was calculated. Note that t represents the thickness of the conductor, W represents the width of the conductor, and L represents the length of the conductor. Table 2 shows the results.

3-2) Adhesion to Substrate A copper conductor of the obtained adhesion evaluation sample was coated with a Sn-plated Cu wire having a diameter of 0.6 mm by using 96.5% by mass Sn-3% by mass Ag-0.5% by mass. Peeling strength when the conductor is peeled off from the substrate by soldering with a Cu composition solder, pulling the conductor in a vertical direction at a speed of 80 mm / min using a load measuring device (Model 2152HTP, manufactured by Aiko Engineering Co., Ltd.) Was measured at 20 points and evaluated by the average value.

[Evaluation results]
As shown in Table 2, according to the conductive composition of the example, a conductor having sufficient adhesion to the substrate and having sufficient conductivity can be obtained. In the conductive compositions of Examples 1 to 12, the content of the vanadium zinc-based glass frit was 10% to 90% by mass with respect to the entire glass frit (100% by mass). Excellent in both properties and adhesion. Above all, in Examples 3 to 7 and 10 to 12 in which the content of the vanadium zinc-based glass frit is 40% by mass to 60% by mass, the adhesion is extremely excellent. In addition, Examples 13 to 23 using the spherical copper powder (average particle diameter of 1.0 μm or 2.5 μm) and the flake-shaped copper powder also had good results, and tended to have excellent conductivity.

  On the other hand, in Comparative Example 1 using only a zinc borosilicate glass frit as the glass frit, the adhesion was extremely poor, and a stable conductor could not be formed. In Comparative Example 2, in which only a vanadium zinc-based glass frit was used as the glass frit, the glass component permeated too much into the substrate, so that the shape of the conductor (wiring shape) could not be maintained, and the adhesion could be evaluated. Did not. Further, in Comparative Example 3 using a zinc borosilicate glass frit and a bismuth borosilicate glass frit as the glass frit, it was confirmed that the glass was not sufficiently melted and the adhesion was poor. In Comparative Examples 4 and 5, in which the content of cuprous oxide was less than 5.5 parts by mass, the adhesion was extremely poor, and a stable conductor could not be formed.

  From the above results, by using the conductive composition of the present embodiment, a conductive pattern having extremely excellent conductivity and adhesion to a substrate when fired at a low temperature of 750 ° C. or less, for example, about 600 ° C. It is clear that can be formed.

Since the conductive composition of the present embodiment contains copper powder, a specific lead-free glass frit, and cuprous oxide, the conductivity and the adhesive strength with the substrate are extremely excellent, and thus the conductive composition is used for forming circuits such as wiring. It can be suitably used. Further, the conductive composition of the present embodiment can also be used as an internal electrode or an external electrode of an electronic component, a solder substitute, or the like.

Claims (11)

A conductive composition containing copper powder, cuprous oxide, and lead-free glass frit,
The cuprous oxide contains 5.5 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the copper powder,
The lead-free glass frit,
It contains boron oxide, silicon oxide, zinc oxide, and optionally other components, and the top three types of oxide components having a high content are boron oxide, silicon oxide and zinc oxide, and a zinc borosilicate glass frit. ,
Containing vanadium oxide, zinc oxide, and optionally other components, and a vanadium zinc-based glass frit in which the top two types of oxide components having a high content are vanadium oxide and zinc oxide,
Based on 100% by mass of the lead-free glass frit, the zinc borosilicate-based glass frit is contained in an amount of 10% by mass to 90% by mass, and the vanadium zinc-based glass frit is contained in an amount of 90% by mass or less and 10% by mass or more,
The content of lead is 0.01% by mass or less with respect to the entire conductive composition.
A conductive composition characterized by the above-mentioned.   The zinc-borosilicate glass frit is contained in an amount of 20% by mass or more and 80% by mass or less, and the vanadium zinc-based glass frit is 80% by mass or less and 20% by mass or more with respect to 100% by mass of the lead-free glass frit. The conductive composition according to claim 1.   The vanadium-zinc-based glass frit contains vanadium oxide in an amount of 30% by mass or more and 50% by mass or less and zinc oxide in an amount of 30% by mass or more and 50% by mass or less based on the whole vanadium-zinc-based glass frit. The conductive composition according to claim 1. The zinc borosilicate-based glass frit contains zinc oxide in an amount of 25% by mass or more and 45% by mass or less with respect to the whole of the zinc borosilicate-based glass frit, according to any one of claims 1 to 3 , wherein The conductive composition as described in the above. The conductive material according to any one of claims 1 to 4 , wherein the lead-free glass frit is contained in an amount of 0.2 to 8.5 parts by mass with respect to 100 parts by mass of the copper powder. Composition. The conductive material according to any one of claims 1 to 5 , wherein the cuprous oxide is contained in an amount of 5.5 parts by mass or more and 15 parts by mass or less based on 100 parts by mass of the copper powder. Composition. The conductive composition according to any one of claims 1 to 6 , wherein the copper powder contains at least one of a spherical powder and a flaky powder. The conductive composition according to claim 7 , wherein an average particle diameter of the spherical powder is 0.2 μm or more and 5 μm or less. The conductive composition according to any one of claims 1 to 8 , wherein the organic vehicle is contained in an amount of 10% by mass or more and 50% by mass or less based on 100% by mass of the conductive composition. The conductive composition according to any one of claims 1 to 9 , wherein the conductive composition is 750.
A method for producing a conductor, comprising a step of firing by heat treatment at a temperature of not more than ° C. An electronic device comprising: a step of applying the conductive composition according to claim 1 on a substrate; and a step of firing the substrate after the application by a heat treatment at 750 ° C. or lower. The method of forming wiring for parts.