JP5376255B2 - Firing type conductive copper paste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a calcination type conductive copper paste which has a novel structure, can be sintered at a low temperature, and enables the manufacturing of a thick calcination type conductor film having a high adhesion to a substrate surface and a high conductivity on condition that a temperature within a range of 350-450&deg;C is selected as its calcination process temperature. <P>SOLUTION: The calcination type conductive copper paste comprises: copper powder having an average particle size of 10-2 &mu;m; fine copper powder having an average particle size of 1-0.2 &mu;m; powdered glass frit having an average particle size of 1.4-0.2 &mu;m, and a softening point of 300-400&deg;C; a dispersant; an organic binder; and a dispersion solvent. In a calcination process, the calcination type conductor is manufactured by a combination of: an oxidization process for removing the dispersant and the organic binder by heating the paste to a temperature of 350-450&deg;C in an air atmosphere; and a reduction process for reducing and removing an oxide coating on the surface of the fine copper powder, and sintering the copper powder and the fine copper powder, by heating the paste to a temperature of 350-450&deg;C in a reductive atmosphere containing hydrogen gas. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a fired conductive copper paste, and more particularly to a fired conductive copper paste containing glass frit that can be fired at a temperature selected in the range of 350 ° C to 450 ° C.

  Firing-type conductive copper paste forms conductive circuit patterns by printing on substrates made of insulating inorganic materials with excellent heat resistance, such as ceramic substrates for mounting various electronic components, when manufacturing electronic devices. Widely used in applications. At that time, in order to adhere and fix the conductive layer formed of the baked conductive copper paste to the surface of the substrate made of an insulating inorganic material having excellent heat resistance, the baked conductive copper paste includes a glass frit. Is blended.

  Accordingly, the fired conductive copper paste is a paste in which copper powder as a conductive member and fine powdery glass frit are dispersed in an organic vehicle. At that time, an organic vehicle in which a binder is added to a dispersion solvent is used, and the binder is used to prepare a dispersion having a viscosity suitable for coating. High-viscosity coating film in which copper powder and fine powder-like glass frit are held by a binder after applying the baking type conductive copper paste and then drying the coating film to partially evaporate the contained dispersion solvent. It becomes. Thereafter, the copper is contained in the coating film by high-temperature treatment to evaporate the remaining dispersion solvent and binder, or to evaporate the decomposition and decomposition products and soften and fluidize the fine powdered glass frit. The powders come into contact with each other and firing proceeds. Accordingly, the softened and fluidized glass frit component causes the substrate surface made of an insulating inorganic material and the copper powder to become wet, and then the glass frit component re-vitrified during cooling causes the substrate surface and the conductor to become wet. Adhesion and fixation between layers are made.

  In the conventional fired conductive copper paste, the heating temperature during the firing process has been selected in the range of 600 ° C. or higher. At that time, the softening point of the glass frit used is selected in the range of 500 ° C. or more (see Patent Document 1, Patent Document 2, and Patent Document 3).

JP 2008-181759 A JP 2008-218022 A JP 2008-226771 A

  In the conventional fired conductive copper paste, the insulating inorganic material constituting the substrate has an excellent heat resistance that sufficiently withstands heating exceeding 600 ° C., so the heating temperature during the firing treatment is in the range of 600 ° C. or more. Is selected. At that time, the softening point of the glass frit to be used is in the range of 500 ° C. or higher. However, by selecting the heating temperature during the baking process to be 100 ° C. or higher than the softening point of the glass frit, Increases fluidity. In addition, the wettability of the softened and fluidized glass frit component to the copper powder surface of the conductive medium and the substrate material surface is increased. As a result, by using the high adhesion of the glass frit to the substrate surface, the formed fired conductor film is fixed to the substrate surface.

  On the other hand, in expanding the range of use of the firing-type conductor film, instead of the heating temperature during the firing process exceeding 600 ° C., which is required when using the conventional firing-type conductive copper paste, It is desired to develop a fired conductive copper paste that can be sintered at a low temperature and suitable for the production of a thick fired conductive film having high adhesion to the substrate surface and high conductivity even by the firing treatment.

  The present invention solves the above problems. Therefore, the object of the present invention is to increase the heating temperature during the baking treatment to a temperature significantly lower than the temperature exceeding 600 ° C., for example, in the range of 350 ° C. to 450 ° C. It is an object of the present invention to provide a fired conductive copper paste having a novel configuration and capable of low temperature sintering, which enables the production of a thick fired conductive film having high adhesion and high conductivity. In addition, a further object of the present invention is to make use of such a low temperature sinterable calcined conductive copper paste at a temperature significantly lower than the previous temperature exceeding 600 ° C., for example, 350 ° C. to 450 ° C. An object of the present invention is to provide a method for producing a thick fired conductive film having high adhesion to the substrate surface and high conductivity by selecting a heating temperature during firing treatment.

In order to solve the above-mentioned problems, the inventors change the heating temperature T _sintering at the time of the firing treatment to a temperature significantly lower than the temperature exceeding 600 ° C., for example, in the range of 350 ° C. to 450 ° C. At that time, the configuration of the conventional fired conductive copper paste and the points to be changed were examined.

First, a glass frit which is used in conventional calcination type conductive copper paste, to select the heating temperature T _Sintering at firing process in the range of above 600 ° C., a crystallization temperature _{T frit-crystallizing} of the glass frit , higher than the heating temperature T _sintering at firing process, whereas the softening point T _softening of the glass frit is lower than the heating temperature T _sintering during firing process, for example, is selected in a range of more than 500 ° C..

In contrast, the heating temperature T _Sintering during firing process, for example, even when changing the range of 350 ° C. to 450 ° C., a crystallization temperature _{T frit-crystallizing} glass frit used is higher than T _Sintering, At the same time, the softening point T _frit- softening of the glass frit is lower than T _stabilizing (T _{frit-crystallizing} > T _stabilizing > T _{frit-softening} ), and at least 20 ° C. or lower ((T _thermally- T _{frit-softening} ) ≧ 20 ° C. was found desirable.

Usually, a fired conductive copper paste is a dispersion of a copper powder equivalent to a solid component and a powdered glass frit uniformly dispersed in an organic vehicle corresponding to a dispersion medium (liquid phase). It is a form. When dried and fired, the coating film of fired conductive copper paste removes the organic vehicle and forms a fired conductor film from copper powder and powdery glass frit, which is a solid component. Is done. Considering the sum of the volume ratio of the copper powder and the powdered glass frit contained in the fired conductive copper paste, V _{solid-component} (volume%), the thickness t _{paste of the} coating film is t A fired conductive film having a thickness of about _paste · (V _{solid-component} / 100 volume%) is produced.

Therefore, when producing a thick fired conductive film, the film thickness t _paste of the fired conductive copper paste coating film is determined based on the thickness t sintered _-layer of the fired conductive film to be produced. Select about t _{sintered-layer} / (V _{solid-component} / 100 volume%). For example, when the sum of the volume ratios of the solid components contained and V _{solid-component} (volume%) is 60 volume%, it is possible to produce a thick fired conductor film as described below. When the film thickness t _paste of the fired conductive copper paste coating film is selected to be, for example, about 50 μm, the film thickness t _{sintered-layer} of the fired conductive film can be set to, for example, about 30 μm after the firing process. I came up with that.

In addition, the fired conductive film produced is composed of copper powder and glass frit. Specifically, during the firing process, softened and fluidized glass frit is infiltrated into the gap in the structure in which the copper powder is laminated, and as a result of cooling the glass frit to vitrify, the gap in the structure in which the copper powder is laminated is formed. A vitrified glass frit is filled to form a fired conductive film. At that time, when the vitrified glass frit is filled in the interface between the substrate surface and the fired conductive film, and the vitrified glass frit comes into close contact with the substrate surface, the vitrified glass frit adheres. The fired conductive film is adhered and fixed to the substrate surface. For example, when the heating temperature T _sintering during the firing process is changed to a range of 350 ° C. to 450 ° C., T _{frit-crystallizing} > T _heating > T _{frit-softening} and (T _thermally -T _{frit-softening} ) ≧ 20 ° C. When the above condition is satisfied, the fired conductive film is adhered and fixed to the substrate surface by the adhesiveness of the vitrified glass frit.

On the other hand, the average particle diameter d _particle of copper powder to be used is, relative to the thickness t _{a sintered-layer} firing type conductive film to prepare, _{typically, 1 / 3t sintered-layer ≧} d particle ≧ 1 / 20t sintered-layer , Preferably 1 / 5t _{sintered-layer} ≧ d _particle ≧ 1 / 10t _{sintered-layer} , so that the in-plane variation Δt _sintered of the thickness t _{sintered-layer} of the sintered conductive film to be produced the _-layer, it was confirmed that it is possible to be kept to less than one-tenth of the thickness t _{sintered-layer} of the target. When the film thickness t _{sintered-layer} of the fired conductive film is, for example, about 30 μm, the average particle diameter d _particle of the copper powder used is usually 10 μm ≧ d _particle ≧ 1.5 μm, preferably 6 μm ≧ It has been found that it is desirable to select d _particle ≧ 2 μm.

When the coating film of the baked conductive copper paste is formed and dried, it is converted into a dried coating film made of a solid component in which copper powder and powdery glass frit are uniformly mixed. In order to maintain the shape of the processed coating film, an organic binder is used. In the dried coating film, the copper powder and the powdery glass frit are uniformly mixed, and in particular, the powdery glass frit is uniformly inserted in the gap of the structure in which the copper powder is laminated. Found it desirable. For example, with respect to the average particle diameter d _particle of copper powder, the average particle diameter d _frit powdery glass frit, _{usually, 1 / 10d particle ≦ d frit} ≦ 1 / 2d particle, preferably, 1 / 5d _particle ≦ d _frit ≦ ((2) ^1/2 −1) By selecting so as to satisfy the condition of d _particle , it is possible to uniformly fill a powdery glass frit in a gap between copper powders. I found it.

In addition, a narrow gap exists between the copper powder and the powdery glass frit in a state where the powdery glass frit is uniformly filled in the gap of the structure in which the copper powder is laminated. When the fine copper powder is filled into the narrow gap, the fine copper powder and the powdery glass frit are uniformly and densely filled in the gap of the structure in which the copper powder is laminated. When the baking treatment is performed in that state, the glass frit is formed by vitrifying the gap between the formed copper powder and the sintered body of the fine copper powder as a result of firing with the fine copper powder filled in the narrow gap between the copper powders. It has been conceived that a dense fired conductive film filled with can be formed. In this dense fired-type conductive film, in a portion where the copper powders are in contact with each other, a narrow gap around the portion is filled with the fine copper powder, and the contact resistance at this contact portion is reduced. In order to achieve a state in which the fine copper powder is filled in a narrow gap existing around the portion where the copper powders are in contact with each other, the average particle diameter d _fine- of the fine copper powder is compared to the average particle diameter d _particle of the copper powder. It is desirable that the _particles are usually selected so as to satisfy the condition of 1 / 20d _particle ≦ d _{fine-particle} ≦ 1 / 4d _particle , preferably 1 / 10d _particle ≦ d _{fine-particle} ≦ 1 / 5d _particle. I found it.

At that time, when the average particle diameter d _{fine-particle} of the fine copper powder is 0.1 μm or less, the fine copper powder aggregates and forms an agglomerate (secondary particle). It will be a hindrance when dispersed. Therefore, it has also been found that the average particle diameter d _{fine-particle} of the fine copper powder is preferably selected to be 0.2 μm or more.

  In order to uniformly disperse the copper powder, fine copper powder, and powdery glass frit contained in the fired conductive copper paste, a dispersant, for example, a polymer surfactant of the polymer polycarboxylic acid type is used. I found it desirable. By coating the surface of copper powder, fine copper powder, and powdery glass frit with a dispersant, for example, a polymer surfactant of a polymer polycarboxylic acid type, these fine powders (fine particles) Can be prevented from agglomerating to form aggregates (secondary particles).

As a result of coating with a dispersant, these fine powders (fine particles) do not have cohesiveness. However, these fine powders (fine particles) can be obtained by using an organic binder in the dried coating film. It is possible to form an agglomerated structure composed of small particles. Thereafter, an air atmosphere, when subjected to oxidation treatment at a temperature T _Sintering selected from the range of 350 ° C. to 450 ° C., the organic binder is decomposed oxidatively and removed, at the same time, softening of the glass frit, fluidization progresses As a result, a fired body is formed. Since the oxide film is formed on the surface of the fine copper powder in the fired body formed in the oxidation treatment, the range is 350 ° C. to 450 ° C. in a reducing atmosphere in which hydrogen gas is mixed in an inert gas. subjected to reduction treatment at a temperature T _sintering be selected, as well as reducing the oxide film of the fine copper powder surface, copper powder, by advancing the firing of the fine copper powder, it is possible to form a sintered type conductive film It was confirmed.

In order to set the film thickness t _paste of the fired conductive copper paste coating film to about 50 μm, for example, a screen printing method is usually employed. When the screen printing method is applied, the liquid viscosity of the fired conductive copper paste needs to be selected in the range of 10 Pa · s to 100 Pa · s. By adding an organic binder, the viscosity of the organic vehicle in the liquid phase is increased, but by adjusting the sum of the volume ratios of the solid components contained, V _{solid-component} (volume%), the liquid of the paste It is necessary to adjust the viscosity to the above range. At that time, contained in the baking-type electroconductive copper paste, the volume of copper powder ratio V _particle, the volume ratio V _{fine-particle} of the fine copper powder, the sum of the volume ratio V _frit powdered glass frit (V _particle + V _{fine-particle} + V _frit) was also confirmed that it is desirable to select the range of 65 _{vol% ≧ (V particle + V fine} -particle + V frit) ≧ 40 % by volume.

In addition, the ratio of the volume ratio V _particle of the copper powder, the volume ratio V _{fine-particle of} the fine copper powder, and the volume ratio V _frit of the glassy glass frit (V _{fine-particle} + V _frit ), V _particle :( V _{fine-particle} + V _frit ) is selected in the range of 1: 0.40 to 1: 0.75, so that the fine copper powder and the powdered glass frit are formed in the gap between the laminated structures formed of copper powder. It was also confirmed that it can be filled.

The volume ratio V _{dispersing-agent} of the dispersing agent such as a polymeric surfactant of a polymer polycarboxylic acid type that coats the surface of copper powder, fine copper powder, powdery glass frit, and the volume ratio of the copper powder V _particle , volume ratio V _{fine-particle of} fine copper powder, sum of volume ratio V _frit of powdered glass frit (V _particle + V _{fine-particle} + V _frit ), (V _particle + V _{fine-particle} + V _frit ): By selecting V _{dispersing-agent} in a range not exceeding 1: 0.095, for example, in the range of 1: 001 to 1: 0.095, the surface of copper powder, fine copper powder, powdery glass frit is applied. It was also confirmed that an appropriate coating of the dispersant was made.

In the formed baked conductor film, when the fine copper powder is densely filled in the narrow gap around the part where the copper powder contacts, the volume ratio V _particle of the copper powder and the volume of the fine copper powder It was also confirmed that it is desirable to select the ratio V _{fine-particle} ratio, V _particle : V _{fine-particle} , in the range of 80:20 to 60:40.

Prior to the above baking treatment, a drying process is carried out in which a part of the contained dispersion solvent is evaporated, and this drying process is usually performed by heating to a _drying treatment temperature T _drying to selectively evaporate the dispersion solvent. . The drying treatment temperature T _drying is usually selected to be a temperature below the boiling point T _solvent-bp of the dispersion solvent used. On the other hand, the dispersion solvent used, the a part is transpired during the drying process, a portion which residual with organic binder, it is necessary to evaporate during heating to the firing treatment temperature T _Sintering. Therefore, the boiling point T _solvent-bp of the dispersion solvent to be used is selected so as to satisfy the condition of T _stabilizing > T _solvent-bp > T _drying . On the other hand, the organic binder must be substantially free of transpiration during the drying process. Therefore, the boiling point T _binder-bp of the organic binder is selected to be higher than the boiling point T _solvent-bp of the dispersion solvent and satisfy the condition of T _binder-bp > T _solvent-bp > T _drying . Also, for example, a dispersing agent such as a polymeric polycarboxylic acid type polymeric surfactant should not substantially evaporate during the drying process. Accordingly, the boiling point T _{dispersing-agent-bp} of the dispersing _agent is selected to be higher than the boiling point T _{solvent-bp of the dispersing solvent} and satisfy the condition of T _{dispersing-agent-bp} > T _solvent-bp > T _drying .

Furthermore, it discovered that it was also possible to add a small amount of copper nanoparticles in addition to copper powder and fine copper powder. Since the average particle diameter of the copper nanoparticles is smaller than the average particle diameter of the fine copper powder, it can be filled in a narrower gap around the portion where the copper powder contacts each other. Therefore, it discovered that the copper nanoparticle filled around the site | part which copper powder mutually contacts exhibits the function to reduce the contact resistance in this contact part. The volume ratio V _{nano-particle} of the copper nanoparticles additionally added to the fired conductive copper paste is usually set to be much lower than the volume ratio V _{fine-particle of} the fine copper powder. For example, the ratio of the volume ratio V _{nano-particle of} copper nanoparticles added additionally, the volume ratio V _particle of copper powder and the volume ratio V _{fine-particle} of fine copper powder (V _particle + V _{fine-particle} ) , (V _particle + V _{fine-particle} ): V _{nano-particle} can be selected in the range of 100: 1 to 100: 5.

Moreover, in addition to copper powder and fine copper powder, it discovered that it was also possible to add a small amount of the carboxylic acid metal salt compound which has metal cation seed | species other than copper. In the process of adding and mixing the fine powder metal carboxylate compound, the powder is uniformly distributed in the dispersion solvent, preferably dissolved in the dispersion solvent. At that time, in order to make the carboxylic acid metal salt compound uniformly distributed in the dispersion solvent, preferably dissolved in the dispersion solvent, the volume ratio V _{metal − of the} carboxylic acid metal salt compound is used. It was also confirmed that the ratio of the _carboxylate and the volume ratio V _solvent of the dispersion solvent, V _{metal -carboxylate} : V _solvent, is usually preferably selected in the range of 2: 100 to 33: 100. When the drying process is performed, the fine powdery metal carboxylate compound precipitated from the dispersion solvent is filled in the gaps in the structure where the copper powder is laminated together with the fine copper powder and the powdery glass frit. . For example, it is possible to fill a fine powdery carboxylic acid metal salt compound in a narrower gap around a portion where copper powders contact each other. Thereafter, when an oxidation treatment is performed, the carboxylic acid metal salt compound is oxidatively decomposed and converted into a metal oxide. Next, when a reduction treatment is performed, the metal oxide is also reduced to generate metal atoms. The generated metal atoms adhere to the surfaces of copper powder and fine copper powder. In particular, metal atoms derived from a fine powdery metal carboxylate compound filled in a narrow gap around a portion where copper powders contact each other fill a narrow gap in the contact portion.

  For example, when the metal cation species constituting the carboxylic acid metal salt compound is a cation species of a metal that is baser than copper, the base metal is filled in a narrower gap at the contact site than copper. . When the produced fired conductor film is oxidized, the base metal is preferentially oxidized over copper, and the oxidation of the copper surface at the portion where the copper powders are in contact with each other is suppressed. As a result, it has been found that it is possible to suppress an increase in contact resistance at the contact site due to oxidation.

At that time, the volume ratio V _metal- carboxylate of the carboxylic acid metal salt compound having a metal cation species other than copper, which is additionally added to the fired conductive copper paste, the volume ratio V _particle of the copper powder, and the fine copper powder Volume ratio of V _{fine-particle} (V _particle + V _{fine-particle} ), (V _particle + V _{fine-particle} ): V _{metal -carboxylate} can be selected in the range of 100: 1 to 100: 30 It is.

  Based on the above-described series of findings, the inventors have completed the present invention.

That is, the fired conductive copper paste according to the present invention is
A fired conductive copper paste containing glass frit,
The fired conductive copper paste comprises copper powder, fine copper powder, glass frit, a dispersant, an organic binder, and a dispersion solvent.
Using the fired conductive copper paste,
(Step 1) A coating step of coating the fired conductive copper paste to form a coating film;
(Step 2) A drying treatment step of heating to the temperature T _drying to partially evaporate the dispersion solvent contained in the coating film to form a dried coating film;
(Step 3) under an air atmosphere and heated to a temperature T _Sintering, contained in the dry treated coating film, dispersing agent, an organic binder, a dispersion solvent was removed and copper powder, oxide film on the surface of the fine copper powder Forming an baked body by softening the glass frit to form a fired body;
(Step 4) under a reducing atmosphere containing hydrogen gas in an inert gas in the range of 1 vol% to 4 vol%, and heated to a temperature T _Sintering, copper powder contained in said heat-surface of the fine copper powder A reduction treatment step of reducing the oxide film and sintering the copper powder and fine copper powder to form a fired conductor;
Using the process for producing a fired-type conductor including the steps 1 to 4, a fired-type conductor can be produced,
Wherein the temperature T _Sintering is selected in the range of _{350 ℃ ≦ T sintering ≦ 450 ℃} ,
The temperature T _drying is selected in a range of 100 ° C. ≦ T _drying <150 ° C.,
The average particle diameter d _particle of the copper powder is selected in the range of 10 μm ≧ d _particle ≧ 1.5 μm;
An average particle diameter d _{fine-particle} of the fine copper powder is selected in a range of _1/20 d _particle ≦ d _{fine-particle} ≦ 1/4 d _particle ;
The glass frit has a softening point T _{frit-softening} and a crystallization temperature T _{frit-crystallizing satisfying the following} conditions: T _{frit-crystallizing} > T _thermally > T _{frit-softening} and (T _thermally -T _{frit-softening} ) ≧ 20 ° C. A powdered glass frit formed of a filling glass frit material;
The average particle diameter d _frit of the powdery glass _frit is selected in the range of _1/10 d _particle ≦ d _frit ≦ 1/2 d _particle ,
The dispersion solvent is an organic solvent having a high boiling point, and the boiling point or decomposition point T _solvent-bp in the atmosphere satisfies the condition of T _oxidizing > T _solvent-bp > T _drying ,
The organic binder is soluble in the dispersion solvent, the boiling point T _binder-bp is to satisfy the condition of _{T binder-bp> T solvent-} bp> T drying, air atmosphere, heated to a temperature T _Sintering It is a polymer compound that can be decomposed oxidatively,
The dispersing agent, the boiling point _{T dispersing-agent-bp} satisfies the condition of _{T dispersing-agent-bp> T} solvent-bp> T drying, air atmosphere, heating to a temperature T _Sintering, oxidatively A degradable polymer surfactant,
Contained in該焼molding conductive copper paste, the volume ratio V _particle of copper powder, the volume ratio V _{fine-particle} of the fine copper powder, powdered glass frit volume ratio V _frit, the volume ratio V _Dispersing dispersant _-agent , organic binder volume ratio V _binder , and dispersion solvent volume ratio V _solvent satisfy the following conditions:
The volume of copper powder ratio V _particle, the volume ratio V _{fine-particle} of the fine copper powder, the sum of the volume ratio V _frit powdered glass frit _{(V particle + V fine-particle} + V frit) is 65 vol% ≧ (V _particle + V _{fine-particle} + V _frit ) ≧ 40% by volume;
Volume ratio V _particle of copper powder, the volume ratio V _{fine-particle} of the fine copper powder, powdered glass frit volume ratio V _frit, the sum of the volume ratio V _{Dispersing-agent} dispersant _{(V particle + V fine-particle} + V frit + V _{dispersing-agent} ), the organic binder volume ratio V _binder , and the ratio of the dispersion solvent volume ratio V _solvent (V _binder + V _solvent ), (V _particle + V _{fine-particle} + V _frit + V _{dispersing-agent} ): (V _binder + V _solvent ) is selected in the range of 1: 0.5 to 1: 1.4;
Volume ratio V _particle of copper powder, the volume ratio V _{fine-particle} of the fine copper powder, the sum of the volume ratio V _frit of powdered glass frit _{(V particle + V fine-particle} + V frit), the volume ratio V _Dispersing dispersant _-agent ratio, (V _particle + V _{fine-particle} + V _frit ): V _{dispersing-agent} is selected in a range not exceeding 1: 0.095;
The ratio of the volume ratio V _particle of the copper powder to the volume ratio V _{fine-particle} of the fine copper powder, V _particle : V _{fine-particle} is selected in the range of 80:20 to 60:40,
And the volume ratio V _particle of copper powder, the ratio of the sum of the volume ratio V _frit of the volume ratio V _{fine-particle} powdered glass frit fine copper powder _{(V fine-particle + V frit} ), V particle: (V fine- _particle + V _frit ) is selected in the range of 1: 0.40 to 1: 0.75,
Volume ratio V _particle of copper powder, the volume ratio V _{fine-particle} of the fine copper powder, powdered glass frit volume ratio V _frit, the sum of the volume ratio V _{Dispersing-agent} dispersant _{(V particle + V fine-particle} + V frit + V _{dispersing-agent} ) and organic binder volume ratio V _binder , (V _particle + V _{fine-particle} + V _frit + V _{dispersing-agent} ): V _binder should be selected in a range not exceeding 1: 0.045 Is a fired conductive copper paste.

At that time, the softening point T _frit- softening of the glass frit is preferably selected in the range of 300 ° C to 400 ° C.

The average particle diameter d _particle of the copper powder is selected in the range of 10 μm ≧ d _particle ≧ 2 μm;
The average particle diameter d _{fine-particle} of the fine copper powder is selected in the range of 1 μm ≧ d _{fine-particle} ≧ 0.2 μm;
The powdery glass _frit may have an average particle size d _frit selected in the range of 1.4 μm ≧ d _frit ≧ 0.2 μm.

The boiling point or decomposition point T _solvent-bp in the atmosphere of the dispersion solvent is preferably selected in the range of 180 ° C to 350 ° C.

  The dispersant is preferably a polymeric polycarboxylic acid type polymeric surfactant.

The organic binder is a polymer compound that can be decomposed oxidatively by heating to a temperature selected in the range of 300 ° C. to 450 ° C. in an air atmosphere,
The amount of carbon component remaining after the oxidative decomposition is preferably 5% by mass or less of the polymer compound.

The glass frit comprises an amorphous composite oxide containing vanadium pentoxide, an amorphous composite oxide containing bismuth oxide, and phosphoric acid exhibiting a softening point T _frit- softening in the range of 300 ° C. to 400 ° C. A powdery glass frit made of an amorphous composite oxide material selected from the group of amorphous composite oxides contained is desirable.

In addition, the fired conductive copper paste according to the present invention is:
In the fired conductive copper paste, in addition to copper powder, fine copper powder, glass frit, dispersant, organic binder, dispersion solvent, copper nanoparticles are contained,
The average particle diameter d _{nano-particle} of the copper nanoparticles is selected in the range of 100 nm ≧ d _{nano-particle} ≧ 50 nm,
The volume ratio V _particle of copper powder and the volume ratio V _{fine-particle} of the fine copper powder (V _particle + V _{fine-particle} ) and the volume ratio V of the copper nanoparticles contained in the fired conductive copper paste _{Nano-particle} ratio, (V _particle + V _{fine-particle} ): V _{nano-particle} may be in a form selected in the range of 100: 1 to 100: 5.

In addition, the fired conductive copper paste according to the present invention is
In the fired conductive copper paste, in addition to copper powder, fine copper powder, glass frit, dispersant, organic binder, dispersion solvent, a carboxylic acid metal salt compound having a metal cation species other than copper is contained. And
The carboxylic acid metal salt compound is contained in a state of being uniformly distributed in the dispersion solvent,
Volume ratio V _{metal-carboxylate} and the ratio of the volume ratio V _Solvent for dispersion solvent of the carboxylic acid metal salt _compound, V _{metal-carboxylate:} V _solvent is 2: 100 to 33: are selected in a range of 100,
The volume ratio V _particle of the copper powder and the volume ratio V _{fine-particle} of the fine copper powder (V _particle + V _{fine-particle} ) and metal cation species other than copper contained in the fired conductive copper paste The volume ratio V _{metal-carboxylate} of the carboxylic acid metal salt compound possessed, (V _particle + V _{fine-particle} ): V _{metal -carboxylate} may be selected in the range of 100: 1 to 100: 30. .

  The aspect in which the metal cation species contained in the carboxylic acid metal salt compound having a metal cation species other than copper can be selected as a cation species of a metal species that is baser than copper.

  In addition, it is preferable that the liquid viscosity of the baking type electroconductive copper paste concerning this invention is selected in the range of 10 Pa * s-100 Pa * s.

  Furthermore, the present invention also provides an application invention of the fired conductive copper paste according to the present invention. That is, the invention of the manufacturing method of a baking type conductor equivalent to the method of using the baking type electroconductive copper paste concerning said invention is also provided.

Therefore, the method for producing the fired conductor according to the present invention is as follows.
A method for producing a fired-type conductor using a fired-type conductive copper paste containing glass frit,
The fired conductive copper paste is a fired conductive copper paste according to the present invention described above,
The process for producing a fired-type conductor using the fired-type conductive copper paste includes the following steps 1 to 4;
(Step 1) A coating step of coating the fired conductive copper paste to form a coating film;
(Step 2) A drying treatment step of heating to the temperature T _drying to partially evaporate the dispersion solvent contained in the coating film to form a dried coating film;
(Step 3) under an air atmosphere and heated to a temperature T _Sintering, contained in the dry treated coating film, dispersing agent, an organic binder, a dispersion solvent was removed and copper powder, oxide film on the surface of the fine copper powder Forming an baked body by softening the glass frit to form a fired body;
(Step 4) under a reducing atmosphere containing hydrogen gas in an inert gas in the range of 1 vol% to 4 vol%, and heated to a temperature T _Sintering, copper powder contained in said heat-surface of the fine copper powder A reduction treatment step of reducing the oxide film and sintering the copper powder and fine copper powder to form a fired conductor;
Wherein the temperature T _Sintering is selected in the range of _{350 ℃ ≦ T sintering ≦ 450 ℃} ,
The temperature T _drying is selected from a range of 100 ° C. ≦ T _drying <150 ° C.

  The fired conductive copper paste of the present invention is a copper powder having an average particle diameter of 10 μm to 2 μm, a fine copper powder having an average particle diameter of 1 μm to 0.2 μm, and a powder form having an average particle diameter of 1.4 μm to 0.2 μm. Glass frit, a dispersant, an organic binder, and a dispersion solvent are used, and a glass frit having a softening point in the range of 300 ° C. to 400 ° C. is applied, and the fired conductive copper paste is applied and dried. The dried coating film was heated to 350 ° C. to 450 ° C. in an air atmosphere to remove the dispersant and the organic binder, and 350 ° C. to 350 ° C. in a reducing atmosphere containing hydrogen gas. High adhesion to the substrate surface by heating in a range of 450 ° C, reducing and removing the oxide film on the surface of the fine copper powder, and combining the reduction treatment to sinter copper powder and fine copper powder Thick film with high conductivity and high conductivity Thereby enabling the fabrication of conductive films.

  Hereinafter, the fired conductive copper paste according to the present invention will be described in more detail.

Conventional calcination type conductive copper paste, the heating temperature T _Sintering during firing process, whereas adopts a configuration suitable for when setting above 600 ° C., cermet type conductive copper paste of the present invention The heating temperature T _sintering at the time of the firing process is characterized in that a suitable configuration is adopted when selecting in the range of 350 ° C to 450 ° C. The baking-type electroconductive copper paste of the present invention, for selecting the heating temperature T _Sintering at firing process in the range of 350 ° C. to 450 ° C., the glass frit to be used, the crystallization temperature T and its softening point T _{frit-Softening The frit-crystallizing} is a powdered glass frit formed of a glass frit material that satisfies the following conditions: T _{frit-crystallizing} > T _fisting > T _{frit-softening} and (T _annealing -T _{frit-softening} ) ≧ 20 ° C. On the other hand, when selecting the heating temperature T _Sintering at firing process in the range of 350 ° C. to 450 ° C., to produce a sintered type conductive film having high adhesion and high electrical conductivity to the substrate surface,該焼molded conductive An oxidation treatment for removing the dispersant and the organic binder by heating in a range of 350 ° C. to 450 ° C. in an air atmosphere with respect to the dried coating film that has been coated with a conductive copper paste and subjected to a drying treatment; and hydrogen Firing in a reducing atmosphere containing gas, combined with a reduction treatment in which the oxide film on the surface of the fine copper powder is reduced and removed, and sintering of the copper powder and the fine copper powder is performed by heating in a range of 350 ° C to 450 ° C. A form to be processed is selected. Therefore, the fired conductive copper paste of the present invention employs a firing treatment that includes copper powder, fine copper powder, glass frit, a dispersant, an organic binder, and a dispersion solvent, and combines the oxidation treatment and the reduction treatment. Along with this, a composition suitable for the baking treatment is selected.

  Each of the six components of copper powder, fine copper powder, glass frit, dispersant, organic binder, and dispersion solvent contained in the fired conductive copper paste of the present invention will be described below.

First, the fired conductive copper paste of the present invention needs to be adapted for use in producing a thick fired conductive film. Specifically, the thickness t _{sintered-layer} of the fired conductive film to be produced is usually selected in the range of 10 μm to 30 μm. The fired conductor film is composed of copper powder, fine copper powder, and glass frit. Actually, as a result of the firing treatment, the copper powder and the fine copper powder are sintered to form a conductor structure in a state in which the fine copper powder and the softened glass frit are filled in the gap between the structures in which the copper powder is laminated. The softened and fluidized glass frit is infiltrated into the gap between the conductor structures. Next, upon cooling, the glass frit is re-glassed, and the surface of the conductor structure formed by sintering copper powder and fine copper powder is covered with the re-glassed glass frit, and the adhesiveness of the glass frit is utilized. Then, the fired conductive film is adhered and fixed to the substrate surface.

Therefore, the thickness t _{sintered-layer} of the fired conductive film to be produced is determined by the thickness of the structure in which the copper powder is laminated. The in _- plane variation Δt _{sintered-layer} of the thickness t _{sintered-layer} of the fired conductive film is caused by the variation in the thickness of the structure in which the copper powder is laminated, and the average particle diameter d of the copper powder used It becomes about 1/2 of the _particle . Further, irregularities resulting from the outer shape of the copper powder used are present on the surface of the fired conductive film. This surface irregularity δt _{sintered-layer} is about ¼ of the average particle diameter d _particle of the copper powder used.

The ratio of the in _- plane variation Δt _{sintered-layer to} the film thickness t _{sintered-layer} of the sintered conductive film, (Δt _{sintered-layer} / t _{sintered-layer} ), is usually (Δt _{sintered-layer} / t _{sintered-layer).} ) <1/5, preferably (Δt _{sintered-layer} / t _{sintered-layer} ) ≦ _1/10 . Therefore, (Δt _{sintered-layer} / t _{sintered-layer} ) _≈1 / 2 (d _particle / t _{sintered-layer} ) <1/5, preferably 1/2 (d _particle / t _{sintered-layer} ) ≦ 1/10 It is desirable to be in the range.

On the other hand, the resistivity ρ _{conductive-layer} of the fired conductive film is approximated by the sum of the sum Σρ _contact of the contact resistance of the portions where the copper powders are in _contact with the sum Σρ _particle of the resistance of the copper powder itself (ρ _{conductive-layer layer} ≒ Σρ _contact + Σρ _particle ). When the average particle diameter d _particle of the copper powder to be used is reduced, the density of the portions where the copper powders are in contact with each other increases, and the total contact resistance Σρ _contact of the portions where the copper powders are in contact with each other relatively increases. Considering this point, the average particle diameter d _particle of the copper powder to be used is usually (d _particle / t _{sintered-layer} ) ≧ _{1/20 with} respect to the film thickness t _{sintered-layer} of the fired conductive film. Preferably, it is desirable to select a range of (d _particle / t _{sintered-layer} ) ≧ _1/10 .

Therefore, in the fired conductive copper paste of the present invention, the average particle diameter d _particle of the copper powder used is usually _1/3 t _{sintered-layer} relative to the film thickness t _{sintered-layer of} the fired conductive film to be _{produced. The range of layer} ≧ d _particle ≧ _1/20 t _{sintered-layer} , preferably _1/5 t _{sintered-layer} ≧ d _particle ≧ _1/10 t _{sintered-layer} is selected. By the above selection, the in-plane variation Δt _{sintered-layer} of the film thickness t _{sintered-layer} of the fired conductive film to be manufactured can be kept to 1/10 or less of the target film thickness t _{sintered-layer.} . In particular, when the thickness t- _{sintered-layer} of the sintered conductor film is selected in the range of, for example, 10 μm to 30 μm, the average particle diameter d _particle of the copper powder to be used is at least 10 μm ≧ d _particle ≧ 1.5 μm. For example, it is desirable to select a range of 10 μm ≧ d _particle ≧ 2 μm, preferably a range of 6 μm ≧ d _particle ≧ 2 μm.

In the fired conductive copper paste of the present invention, a fine copper powder is used in addition to the copper powder to form a gap in a structure in which the copper powder is laminated, particularly around a portion where the copper powder contacts each other. The gap is filled with fine copper powder. The fine copper powder filled in the gap formed around the portion where the copper powders are in contact with each other is in electrical contact with two adjacent copper powders when sintered. As a result, the effective contact resistance ρ _{contact-eff. Of} the part where the copper powders are in contact with each other is the contact resistance ρ _{contact of the} part where the copper powders are in contact with each other and the fine copper powder filled in the gap formed around it. (1 / ρ _contact-eff ) = (1 / ρ _contact ) + (1 / ρ _{bypass-contact} ) using the effective resistance ρ _{bypass-contact of} the conduction path via That is, as a result of the formation of a conduction path through the fine copper powder, the effective contact resistance ρ _{contact-eff. Of} the portion where the copper powder contacts is reduced.

In order to efficiently fill the fine copper powder in the gap formed around the part where the copper powders are in contact with each other, the average particle diameter d _{fine-particle} of the _fine copper powder is set to the average particle diameter d _particle of the copper powder. Usually, it is desirable to select 1 / 20d _particle ≦ d _{fine-particle} ≦ 1 / 4d _particle , preferably 1 / 10d _particle ≦ d _{fine-particle} ≦ 1 / 5d _particle .

On the other hand, when the average particle diameter d _{fine-particle} of the fine copper powder is 0.1 μm or less, the fine copper powder aggregates and forms an agglomerate (secondary particle). It becomes a hindrance when dispersing. Therefore, the average particle diameter d _{fine-particle} of the fine copper powder is usually preferably selected to be 0.2 μm or more.

Considering the two conditions above, the average particle diameter d _particle of copper powder to be used, for example, the range of 10μm ≧ d _particle ≧ 2μm, preferably, when selecting the range of 6μm ≧ d _particle ≧ 2μm, fine copper The average particle diameter d _{fine-particle} of the powder is, for example, desirably selected in the range of 1 μm ≧ d _particle ≧ 0.2 μm, preferably in the range of 0.6 μm ≧ d _particle ≧ 0.2 μm.

At that time, since the fine copper powder is preferably filled in the gap of the structure in which the copper powder is laminated, the volume ratio V _particle of the copper powder and the fine copper contained in the fired conductive copper paste of the present invention. The powder volume ratio V _{fine-particle} ratio, V _particle : V _{fine-particle,} is preferably selected in the range of 80:20 to 60:40, and preferably in the range of 80:20 to 65:35.

  Both the copper powder and the fine copper powder are preferably spherical in shape. In other words, when spherical copper powder is used, the distribution of the size of the gap formed around the part where the copper powders are in contact with each other is substantially the same in both the in-plane direction and the film thickness direction in the laminated structure of copper powder. Shows the same distribution. At that time, by using spherical fine copper powder, the fine copper powder can be efficiently filled into the gap.

  In the fired-type conductor film to be formed, the surface of the conductor structure formed by sintering copper powder and fine copper powder is covered with re-glassified glass frit, and the adhesiveness of the glass frit is utilized. Then, the fired conductive film is adhered and fixed to the substrate surface. Therefore, it is desirable that the re-glassified glass frit fills the gap inside the conductor structure formed by sintering copper powder and fine copper powder and the gap left at the interface between the fired-type conductor film and the substrate surface. . For that purpose, prior to the firing treatment, the coating film of the firing type conductive copper paste is subjected to a drying treatment, and when the dried coating film is produced, the gap formed in the structure in which the copper powder is laminated is finely formed. It is desirable that the copper powder and the powdered glass frit are uniformly filled.

For example, when spherical copper powder having an average particle diameter d _particle forms a cubic close-packed structure, the interval size of the gap surrounded by eight spherical copper powders is about ((3) ^1/2 −1) d _particle. It has become. Also. The interval size of the gap (opening) formed between the four spherical copper powders is about ((2) ^1/2 −1) d _particle . Therefore, when the average particle diameter d _frit of the powdery glass frit is selected within the range of d _frit ≦ ((3) ^1/2 −1) d _particle , the powdery glass frit has a powdery shape when forming a laminated structure of copper powder. The glass frit can be filled in a gap surrounded by eight spherical copper powders. In particular, when d _frit ≦ ((2) ^1/2 −1) d _particle is selected, the powdery glass frit can pass through a gap (opening) formed between four spherical copper powders, and the gap It becomes possible to fill the gap surrounded by the spherical copper powder with the powdered glass frit via (opening).

On the other hand, when the average particle diameter d _frit of the powdery glass frit is smaller than the average particle diameter d _{fine-particle} of the fine copper powder, the fine copper powder is formed in the gap formed around the portion where the copper powder contacts each other. Instead, the probability that the powdered glass frit is filled increases rapidly. In order to avoid an abrupt increase in the probability, it is desirable that the average particle diameter d _frit of the powdered glass frit is larger than the average particle diameter d _{fine-particle of the} fine copper powder.

Therefore, the average particle diameter d _frit of the powdery glass _frit is such that d _frit ≦ ((3) ^1/2 −1) d _particle and d _{fine-particle} ≦ d _frit , preferably d _frit ≦ ((2 ) ^{1 /} 2-1) It is desirable to select so as to satisfy the conditions of d _particle and 2d _{fine-particle} ≦ d _frit . For example, with respect to the average particle diameter d _particle of copper powder, the average particle diameter d _frit powdery glass frit, _{usually, 1 / 10d particle ≦ d frit} ≦ 1 / 2d particle, preferably, 1 / 5d _particle ≦ It is desirable to select d _frit ≦ ((2) ^1/2 −1) d _particle . When the average particle diameter d _frit of the powdery glass frit is selected within the above range, it is possible to uniformly fill the mixture of the powdered glass frit and fine copper powder into the gaps in the structure in which the copper powder is laminated. .

For example, when the condition of 2d _{fine-particle} ≦ d _frit ≦ ((2) ^1/2 −1) d _particle is satisfied, the powdery glass frit is uniformly filled in the gap of the structure in which the copper powder is laminated. In the state, a narrow gap exists between the copper powder and the powdery glass frit. This narrow gap can be efficiently filled with fine copper powder having an average particle diameter d _{fine-particle} of _1/5 d _particle or less.

Considering the above conditions, the average particle diameter d _particle of the copper powder to be used is selected, for example, in the range of 10 μm ≧ d _particle ≧ 2 μm, preferably in the range of 6 μm ≧ d _particle ≧ 2 μm. When the particle size d _{fine-particle} is selected, for example, in the range of 1 μm ≧ d _particle ≧ 0.2 μm, preferably in the range of 0.6 μm ≧ d _particle ≧ 0.2 μm, the average particle size d _{fine- of the} glass frit is selected. For example, it is desirable to select the _particles in the range of 1.4 μm ≧ d _frit ≧ 0.2 μm, and preferably in the range of 1.2 μm ≧ d _frit ≧ 0.4 μm.

  The fired conductive copper paste according to the present invention usually contains a dispersant, and the copper powder, fine copper powder, and powdery glass frit are covered with the dispersant. Thus, it is uniformly dispersed in a liquid phase (organic vehicle) comprising an organic binder and a dispersion solvent.

  When a coating film of a fired conductive copper paste is formed and dried, a part of the dispersion solvent is evaporated and a structure in which copper powder is laminated is formed. The glass frit is uniformly mixed, and the dispersion liquid dispersed in the liquid phase composed of the organic binder and the remaining dispersion solvent is infiltrated. In the dry-processed coating film to be formed, the gap existing in the structure in which the copper powder is laminated is densely filled with the fine copper powder, the powdery glass frit, and the fluid mixture containing the organic binder. Become. At this time, an organic binder is used in order to maintain the shape of the dried coating film.

When converted into the dried coating film, it is desirable that the gap between the structures in which the copper powder is laminated is filled with fine copper powder and powdered glass frit. Therefore, the sum of the volume ratio V _particle of the copper powder, the volume ratio V _{fine-particle of} the fine copper powder, and the volume ratio V _frit of the powdered glass frit contained in the fired conductive copper paste of the present invention ( V _{fine-particle} + V _frit ), V _particle : (V _{fine-particle} + V _frit ), usually in the range of 1: 0.40 to 1: 0.75, preferably 1: 0.45 to 1: It is desirable to select in the range of 0.70, more preferably in the range of 1: 0.50 to 1: 0.65.

On the other hand, in the finally produced sintered conductor film, the gap existing in the sintered body layer made of copper powder and fine copper powder, and the sintered body layer made of copper powder and fine copper powder and the substrate surface It is necessary that the gap existing at the interface is filled with re-glazed glass frit. Therefore, the sum of the volume ratio V _particle of copper powder and the volume ratio V _{fine-particle} of fine copper powder (V _particle + V _{fine-particle} ) contained in the fired conductive copper paste and the powdered glass frit Volume ratio V _frit ratio, (V _particle + V _{fine-particle} ): V _frit is in the range of 1: 0.05 to 1: 0.15, preferably in the range of 1: 0.05 to 1: 0.12. More preferably, it is desirable to select in the range of 1: 0.06 to 1: 0.095.

In order to make the surface of the copper powder and fine copper powder and the powdered glass frit coated with the dispersant, the volume ratio V _{particle of} the copper powder contained in the fired conductive copper paste, volume ratio V _{fine-particle} of the fine copper powder, the sum of the volume ratio V _frit of powdered glass frit _{(V particle + V fine-particle} + V frit), the ratio of the volume ratio V _{dispersing-agent} of the dispersing agent, (V _particle + V _{fine-particle} + V _frit ): V _{dispersing-agent} is selected in a range not exceeding 1: 0.095. When the dispersant is added, for example, a range of 1: 0.001 to 1: 0.095, preferably a range of 1: 0.003 to 1: 0.095, more preferably 1: 0. The range of 01 to 1: 0.07, more preferably, the range of 1: 0.015 to 1: 0.045 can be selected.

The fired-type conductor film to be produced is composed of copper powder, fine copper powder, and glass frit from which the dispersant, the organic binder, and the dispersion solvent are removed during the drying process and the firing process. Incidentally, contained in cermet type conductive copper paste, the volume ratio V _particle of copper powder, the volume ratio V _{fine-particle} of the fine copper powder, the sum of the volume ratio V _frit powdered glass frit (V _particle + V _{fine -particle} + V _frit ) is a solid component volume ratio V _{solid-component} (volume%), the ratio of the thickness t _{sintered-layer} of the fired conductive film to the film thickness t _paste of the coating film, (T _{sintered-layer} / t _paste ) is about a solid component volume ratio V _{solid-component} (volume%).

In the fired conductive copper paste of the present invention, the volume ratio V _{particle of} the copper powder, the volume ratio V _{fine-particle of} the fine copper powder, and the volume of the powdered glass frit contained in the fired conductive copper paste. The sum of the ratios V _frit (V _particle + V _{fine-particle} + V _frit ) is usually in the range of 65 vol% ≧ (V _particle + V _{fine-particle} + V _frit ) ≧ 40 vol%, preferably 60 vol% ≧ (V _particle + V _{fine-particle} + V _frit ) ≧ 45 vol%. For example, if the sum of the volume ratios of the solid components and V _{solid-component} (volume%) is 60 volume%, the film thickness t _paste of the fired conductive copper paste coating film is selected to be, for example, about 50 μm. After the firing treatment, the thickness t _{sintered-layer} of the fired conductive film can be set to about 30 μm.

Copper powder, fine copper powder, and powdery glass frit are uniformly dispersed in a liquid phase (organic vehicle) composed of an organic binder and a dispersion solvent in a state where the surface is coated with a dispersant. At that time, contained in the baking-type electroconductive copper paste, copper powder volume ratio V _particle, the volume ratio V _{fine-particle} of the fine copper powder, powdered glass frit volume ratio V _frit, the volume ratio of the dispersing agent The ratio of the sum of V _{dispersing-agent} (V _particle + V _{fine-particle} + V _frit + V _{dispersing-agent} ), the organic binder volume ratio V _binder , and the dispersion solvent volume ratio V _solvent (V _binder + V _solvent ), (V _particle + V _{fine-particle} + V _frit + V _{dispersing-agent} ) :( V _binder + V _solvent ) is usually in the range of 1: 0.5 to 1: 1.4, preferably 1: 0.55 to 1: 1. It is desirable to select a range of 3, more preferably, a range of 1: 0.6 to 1: 1.2.

At that time, the volume ratio V _particle of copper powder, the volume ratio V _{fine-particle} of the fine copper powder, powdered glass frit volume ratio V _frit, the sum of the volume ratio V _{Dispersing-agent} dispersant _{(V particle} + V fine- _particle + V _frit + V _{dispersing-agent} ) and organic binder volume ratio V _binder , (V _particle + V _{fine-particle} + V _frit + V _{dispersing-agent} ): V _binder does not exceed 1: 0.045, for example, The range is 1: 0 to 1: 0.045, preferably 1: 0.015 to 1: 0.045. The organic binder has a function of adjusting the viscosity of the baked conductive copper paste to a target range by dissolving in the dispersion solvent to be used. Therefore, depending on the fluidity of the dispersion solvent itself, The content ratio is adjusted within the range.

  When producing a fired conductive film using the fired conductive copper paste of the present invention, a production process including the following steps 1 to 4 is utilized.

(Step 1) A coating step of coating the fired conductive copper paste to form a coating film;
(Step 2) A drying treatment step of heating to the temperature T _drying to partially evaporate the dispersion solvent contained in the coating film to form a dried coating film;
(Step 3) under an air atmosphere and heated to a temperature T _Sintering, contained in the dry treated coating film, dispersing agent, an organic binder, a dispersion solvent was removed and copper powder, oxide film on the surface of the fine copper powder Forming an baked body by softening the glass frit to form a fired body;
(Step 4) inert gas 1 vol% to 4 vol% in the range of hydrogen gas into, preferably, under a reducing atmosphere containing in the range of 2 vol% to 4 vol%, and heated to a temperature T _Sintering, the Reduction treatment process for reducing the oxide film on the surface of the copper powder and fine copper powder contained in the fired body and sintering the copper powder and fine copper powder to form a fired conductor. calcination treatment at a heating temperature T _sintering that combines typically, 350 ° C. ≦ T range _sintering ≦ 450 ° C., preferably, selected within the range of _{400 ℃ ≦ T sintering ≦ 450 ℃} . In addition, the heating temperature T _drying at the time of the drying process of step 2 is preferably selected in the range of 100 ° C. ≦ T _drying <150 ° C., preferably in the range of 100 ° C. ≦ T _drying ≦ 130 ° C.

  A part of the dispersion solvent is evaporated in the drying treatment step of Step 2, but a part of the dispersion solvent remains, and it is necessary to maintain a liquid phase composed of the organic binder and the remaining dispersion solvent. On the other hand, it is necessary that the organic binder and the dispersant do not evaporate at the stage of the drying process of Step 2.

  On the other hand, it is necessary to remove the dispersant, the organic binder, and the remaining dispersion solvent during the oxidation treatment step of step 3.

Therefore, an organic solvent having a high boiling point is used as the dispersion solvent. The boiling point of the organic solvent having a high boiling point is higher than the temperature T _drying , and on the other hand, it is necessary to be easily evaporated or decomposed and removed by heating to the temperature T _annealing in an air atmosphere. That is, the boiling point or decomposition point T _Solvent-bp in the atmosphere satisfies the condition of _{T sintering> T solvent-bp>} T drying, the organic solvent is selected in the dispersion solvent. For example, an organic solvent whose boiling point or decomposition point T _solvent-bp in the atmosphere is in the range of 350 ° C. ≧ T _solvent-bp ≧ 180 ° C., more preferably in the range of 300 ° C. ≧ T _solvent-bp ≧ 200 ° C. It is desirable to select a dispersion solvent.

The dispersion solvent needs to form a uniform liquid phase with the organic binder. For example, when an organic binder such as cellulose such as ethyl cellulose or a (meth) acrylic resin is used, as a dispersion solvent, terpineol (α-terpineol, melting point 31-35 ° C., boiling point 217-218 ° C.), glycol ethers, diol An organic _solvent having a boiling point T _{solvent-bp in} the range of 180 ° C. to 350 ° C. that is excellent in solubility of the organic binder, such as glycerin (boiling point: 290.5 ° C. decomposition). Furthermore, polymer-type organic solvents having a decomposition point in the range of 180 ° C. to 350 ° C., such as polyalkylene glycol, polyalkylene glycol derivatives, and polyether (polyethylene series manufactured by NOF Corporation) may be used as the dispersion solvent. it can.

On the other hand, the organic binder is soluble in the dispersion solvent, the boiling point T _binder-bp satisfies the condition of _{T binder-bp> T solvent-} bp> T drying, air atmosphere, heating to a temperature T _Sintering By doing so, a polymer compound that can be decomposed oxidatively can be used. For example, by heating to a temperature in the range of 300 ° C. to 450 ° C. in an air atmosphere, the carbon component that is oxidatively decomposed and remains after the decomposition is 5% by mass or less with respect to the polymer compound. It is preferable to use a polymer compound. For example, ethyl cellulose and (meth) acrylic resin can be suitably used as the organic binder.

The dispersing agent, the boiling point _{T dispersing-agent-bp} satisfies the condition of _{T dispersing-agent-bp> T} solvent-bp> T drying, air atmosphere, heating to a temperature T _Sintering, oxidatively Degradable polymeric surfactants can be used. For example, it is preferable to use a polymeric surfactant of a polymeric polycarboxylic acid type as a dispersant. As a polymeric polycarboxylic acid type polymeric surfactant that can be used as a dispersant, NOF's Marialim AKM-0531, Marialim AFB-1521, Mariarim AWS-0851, Marialim AEM-3511, Marialim AAB-0851, Mariarim Examples include AFB-0561, Marialim AKM-1511-60, DEMO EP made by Kao, Poise 520, Poise 521, Poise 530, Poise 532A, Homogenol L-18, and Homogenol L-1820.

The baking-type electroconductive copper paste of the present invention, for selecting the heating temperature T _Sintering at firing process in the range of 350 ° C. to 450 ° C., the glass frit to be used, the crystallization temperature T and its softening point T _{frit-Softening frit-crystallizing is, T frit-crystallizing> T sintering} > T frit-softening and _{(T sintering -T frit-softening)} ≧ 20 ℃, _{preferably, 60 ℃ ≧ (T sintering -T} frit-softening) ≧ 40 ℃ It is a powdery glass frit formed of a glass frit material that satisfies the conditions.

For example, an amorphous composite oxide containing vanadium pentoxide, an amorphous composite oxide containing bismuth oxide having a softening point T _frit- softening of 400 ° C. ≧ T _{frit-softening} ≧ 300 ° C. A powdery glass frit made of an amorphous composite oxide material selected from the group of amorphous composite oxides containing phosphoric acid can be suitably used. Amorphous composite selected from the group of available amorphous composite oxides containing vanadium pentoxide, amorphous composite oxides containing bismuth oxide, and amorphous composite oxides containing phosphoric acid As a powdery glass frit made of an oxide material, for example, Japanese Patent No. 4299021 (V ₂ O ₅ —ZnO—BaO—TeO ₂ glass frit), Japanese Patent Application Laid-Open No. 2010-184852 (V ₂ O ₅ − P ₂ O ₅ —TeO ₂ —Fe ₂ O ₃ glass frit), JP 2010-70426 (B ₂ O ₃ —Bi ₂ O ₃ glass frit), JP 2002-326838 A (P ₂ O ₅ -SnO glass frit, P ₂ O ₅ -SnO-B ₂ O ₃ glass frit, P ₂ O ₅ -SnO-SiO ₂ glass frit) and prepared by the method described It is possible to use a powdered glass frit.

Specifically, as an example of a glass frit made of an amorphous composite oxide containing vanadium pentoxide having a softening point T _frit- softening of 400 ° C. ≧ T _{frit-softening} ≧ 300 ° C., V ₂ Examples thereof include O ₅ —ZnO—BaO—TeO ₂ glass frit and V ₂ O ₅ —P ₂ O ₅ —TeO ₂ —Fe ₂ O ₃ glass frit. As an example of the composition of the glass frit of the V ₂ O ₅ —ZnO—BaO—TeO ₂ system in which the softening point T _{frit-softening} is in the range of 400 ° C. ≧ T _{frit-softening} ≧ 300 ° C., 16-80% by mass A glass composition composed of V ₂ O ₅ , 6-40% by mass of ZnO, 4-50% by mass of BaO, 10-60% by mass of TeO ₂ can be exemplified (for example, see Japanese Patent No. 4299021). In Example 1 described later, a glass frit of V ₂ O ₅ —ZnO—BaO—TeO ₂ (softening point 311 ° C., crystallization temperature 444 ° C.) is used.

Further, an example of the composition of a glass frit of V ₂ O ₅ —P ₂ O ₅ —TeO ₂ —Fe ₂ O ₃ in which the softening point T _{frit-softening} is in the range of 400 ° C. ≧ T _{frit-softening} ≧ 300 ° C. As
The content of V ₂ O ₅ is 45 to 65% by mass, the content of P ₂ O ₅ is 10 to 20% by mass, the content of TeO ₂ is 10 to 25% by mass, and the content of Fe ₂ O ₃ is 5 to 5%. A glass composition selected in the range of 15% by mass and the other subcomponents, MnO ₂ , ZnO, WO ₃ , MoO ₃ , and BaO, being selected to be 10% by mass or less in total;
The content of V ₂ O ₅ is 40 to 55% by mass, the content of P ₂ O ₅ is 5 to 15% by mass, the content of TeO ₂ is 20 to 30% by mass, and the content of BaO is 2 to 10% by mass. The content of WO ₃ is 15% by mass or less, the content of MoO ₃ is 15% by mass or less, the content of Fe ₂ O ₃ is 8% by mass or less, and the content of R ₂ O (R: alkali metal) The amount is selected in the range of 5% by mass or less, in which case the sum of the contents of P ₂ O ₅ and TeO ₂ is 30 to 40% by mass, and the sum of the contents of WO ₃ and MoO ₃ is 5 to 15% by mass. The sum of the contents of Fe ₂ O ₃ and R ₂ O can be exemplified by a glass composition or the like adjusted in the range of 2 to 8% by mass (see JP 2010-184852 A).

As an example of a glass frit made of an amorphous composite oxide containing bismuth oxide having a softening point T _frit- softening of 400 ° C. ≧ T _{frit-softening} ≧ 300 ° C., B ₂ O ₃ —Bi ₂ O An example is a ₃ series glass frit. As an example of the composition of a B ₂ O ₃ -Bi ₂ O ₃ glass frit having a softening point T _frit- softening of 400 ° C. ≧ T _{frit-softening} ≧ 300 ° C.
The content of B ₂ O ₃ is selected in the range of 4 to 12% by mass and the content of Bi ₂ O ₃ is selected in the range of 83 to 93% by mass. The other secondary components are selected from R ₂ O (Li ₂ O, Na The total content of one or more selected from ₂ O and K ₂ O is selected in the range of 0.1 to 6% by mass, and the content of Al ₂ O ₃ is selected in the range of 0.1 to 5% by mass. The glass composition which can be illustrated can be illustrated (refer Unexamined-Japanese-Patent No. 2010-70426). In Example 5 described later, a B ₂ O ₃ —Bi ₂ O ₃ -based glass frit (softening point: 390 ° C., crystallization temperature: 460 ° C.) is used.

As an example of a glass frit made of an amorphous complex oxide containing phosphoric acid having a softening point T _frit- softening in the range of 400 ° C. ≧ T _{frit-softening} ≧ 300 ° C., a P ₂ O ₅ —SnO system Examples thereof include a glass frit, a P ₂ O ₅ —SnO—B ₂ O ₃ glass frit, and a P ₂ O ₅ —SnO—SiO ₂ glass frit (see JP 2002-326838 A). In addition, a P ₂ O ₅ —ZnO—SnO-based glass frit (softening point of 340 ° C.) that satisfies the above softening point range can also be used.

Softening point T _{frit-Softening} is in the range of _{400 ℃ ≧ T frit-softening ≧} 300 ℃, as an example of the P ₂ O ₅ -SnO-based glass frit, 25～50Mol% content of P ₂ O _5, SnO of the content selected in the range of 40~70mol%, the other secondary components, 0 to 20 mol% of the content of ZnO, 0-10 mol% and the content of Li ₂ O, content of Al ₂ O ₃ amount of 0-10 mol%, the content of SiO ₂ in the range of 0-10 mol%, can be exemplified glass compositions are respectively selected.

As an example of a P ₂ O ₅ —SnO—B ₂ O ₃ glass frit having a softening point T _frit- softening of 400 ° C. ≧ T _{frit-softening} ≧ 300 ° C., the content of P ₂ O ₅ is 15 ~35mol%, 40~65mol the content of SnO%, B content of ₂ O ₃ selected in the range of 15 to 25%, for the other secondary components, 0~15mol% content of ZnO, Examples of the glass composition selected include the Li ₂ O content of 0 to 10 mol%, the Al ₂ O ₃ content of 0 to 10 mol%, and the SiO ₂ content of 0 to 5 mol%. .

Softening point T _{frit-Softening} is in the range of _{400 ℃ ≧ T frit-softening ≧} 300 ℃, as an example of the P ₂ O ₅ -SnO-SiO ₂ based glass frit, 10-50 mol content of P ₂ O ₅ %, 40~80mol the content of SnO%, select the content of SiO ₂ in the range of 5.5~20mol%, the other secondary components, 0~15mol% content of ZnO, Li ₂ O 0-10 mol% of the content of the content of Al ₂ O ₃ in the range of 0-10 mol%, can be exemplified glass compositions are respectively selected.

  The amorphous composite oxide containing vanadium pentoxide, the amorphous composite oxide containing bismuth oxide, and the amorphous composite oxide containing phosphoric acid are composed of a glass material, an oxide ceramic, and silicon. High adhesion to the surface of the substrate. Therefore, by using the glass frit made of these amorphous composite oxides, it is possible to produce a fired conductive film that exhibits high adhesion to the substrate surface made of glass material, oxide ceramics, and silicon. It becomes possible.

  In the third form of the fired conductive copper paste of the present invention, a small amount of copper nanoparticles are added to the fired conductive copper paste in addition to the copper powder and fine copper powder.

The average particle diameter d _{nano-particle} of the copper nanoparticles to be added is selected in the range of 100 nm ≧ d _{nano-particle} ≧ 50 nm. Since the average particle diameter d _{fine-particle} of fine copper powder is usually selected to be 0.2 μm or more, the average particle diameter d _{nano-particle} of copper nanoparticles is larger than the average particle diameter d _{fine-particle of} fine copper powder. Since it is significantly small, it is possible to fill the copper nanoparticles in a narrower gap around the portion where the copper powders are in contact with each other, which is difficult to fill with the fine copper powder.

When the drying treatment is performed, the gaps in the structure in which the copper powder is laminated are filled with the copper nanoparticles as well as the fine copper powder and the powdery glass frit. The average particle diameter d _{nano-particle} of copper nanoparticles have an average particle size d _{fine-particle} of the fine copper powder, but significantly smaller than the average particle diameter d _frit powdery glass frit, fine copper powder, powdered glass Since the size of the gap between the frit is about the same, the narrower gap around the portion where the copper powder contacts is preferentially filled. Specifically, during the drying process, a liquid phase (organic vehicle) composed of a dispersion solvent and an organic binder is supplied to a narrower gap around the portion where the copper powders are in contact with each other by capillary action. Since the copper nanoparticles are dispersed in a liquid phase (organic vehicle) composed of a dispersion solvent and an organic binder, the copper nanoparticles are supplied together with the liquid phase to a narrower gap around the portion where the copper powders are in contact with each other. To fill a narrow gap.

  When the sintered conductor film is prepared, the copper nanoparticles filled in the narrower gap around the part where the copper powders are in contact with each other are in electrical contact with the two copper powders. In addition to the conduction path through the fine copper powder filled in the gap formed around, a conduction path through the copper nanoparticles filled in the narrower gap is added.

As a result, the effective contact resistance ρ _{contact-eff. Of} the part where the copper powders are in contact with each other is the contact resistance ρ _{contact of the} part where the copper powders are in contact with each other and the fine copper powder filled in the gap formed around it. Using the effective resistance ρ _{bypass-contact of} the conduction path via the, and the effective resistance ρ _{nano-bypass-contact of} the conduction path via the copper nanoparticles filled in the narrower gap, (1 / ρ _{contact -eff} ) = (1 / ρ _contact ) + (1 / ρ _{bypass-contact} ) + (1 / ρ _{nano-bypass-contact} ). In other words, as a result of the formation of a conduction path via the fine copper powder and a conduction path via the copper nanoparticles, the effective contact resistance ρ _{contact-eff. Of} the portion where the copper powder contacts each other is further reduced.

At that time, filling with fine copper powder is difficult, but filling with copper nanoparticles is possible, and the volume of narrower gaps formed around the part where the copper powder contacts each other is filled with fine copper powder Compared to the possible gap volume, it is much smaller. Considering this point, the volume ratio V _{nano-particle} of the copper nanoparticles additionally added to the fired conductive copper paste is usually much lower than the volume ratio V _{fine-particle of} the fine copper powder. Set. For example, the ratio of the volume ratio V _{nano-particle of} copper nanoparticles added additionally, the volume ratio V _particle of copper powder and the volume ratio V _{fine-particle} of fine copper powder (V _particle + V _{fine-particle} ) , (V _particle + V _{fine-particle} ): V _{nano-particle} is selected in the range of 100: 1 to 100: 5, preferably in the range of 100: 2 to 100: 4.

In order to prevent the copper nanoparticles from aggregating with each other and forming an aggregate (secondary particle), it is desirable to form a coating agent molecular layer on the surface in advance. The coating agent molecular layer covering the surface of the copper nanoparticles is also removed in the oxidation treatment step of step 3 as in the case of the dispersant. As a result, an oxide film is also generated on the surface of the copper nanoparticle, but the oxide film on the surface of the copper nanoparticle is also reduced and removed during the reduction treatment step of Step 4. That is, in the range of the heating temperature T _drying and the _drying temperature of 100 ° C. ≦ T _drying <150 ° C. in the step 2 above, the removal of the coating agent molecular layer does not substantially proceed. in step, by heating in the range of heating temperature _{T sintering, 350 ℃ ≦ T sintering} ≦ 450 ℃, removal of the covering agent molecule layer progresses. Therefore, the boiling point or decomposition point T _{coating-molecule-bp} covering agent molecules forming a coating agent molecule layer is higher than the heating temperature T _Drying of the drying process, lower than the heating temperature T _Sintering of the oxidation treatment process, i.e., It is necessary to satisfy the condition of T _blocking > T _{coating-molecule-bp} > T _drying .

As a coating agent molecule forming this coating agent molecular layer, as a group capable of coordinative bonding with a metal copper atom constituting a copper nanoparticle, nitrogen or an oxygen atom is contained, and the nitrogen or oxygen atom has An organic compound having a group capable of coordinative bonding to a metal copper atom by a lone electron pair can be used. At that time, as the coating agent molecules for coating the surface of the copper nanoparticles, those having a hydrocarbon chain having an affinity for the organic solvent used as the dispersion solvent are selected. As an organic compound having a group capable of coordinative bonding to a metal copper atom by a lone pair of electrons of nitrogen or oxygen atoms, examples of a group capable of coordinating bond to the metal copper atom include amino An amine compound having a group, preferably a saturated or unsaturated aliphatic amine, more preferably an alkylamine can be used. In addition, a copper carboxylate compound having a carboxylate group (—COO ⁻ ) capable of forming a coating agent molecular layer in the form of a carboxylate copper salt (—COOCu) on the surface of the copper nanoparticles, Preferably, saturated or unsaturated fatty acid copper salts can be used.

  A saturated or unsaturated aliphatic amine, particularly an alkylamine, used as the coating agent molecule has a boiling point in the range of 180 ° C. to 350 ° C., preferably in the range of 200 ° C. to 350 ° C. desirable.

  The carboxylic acid copper salt compound used as the coating agent molecule is removed by being decomposed by heating. In the drying treatment step, a carboxylic acid copper salt compound, for example, a saturated or unsaturated fatty acid copper salt is used in which the thermal decomposition does not proceed but the thermal decomposition proceeds by heating during the oxidation treatment step. Therefore, the decomposition temperature at which decomposition of the carboxylic acid copper salt compound starts is desirably in the range of 180 ° C to 350 ° C, and preferably in the range of 200 ° C to 350 ° C.

  Furthermore, as the polymer surfactant of the polymer polycarboxylic acid type used as the coating agent molecule, the polymer surfactant of the polymer polycarboxylic acid type used in the dispersant is used. Can do.

  In the second form of the fired conductive copper paste of the present invention, in addition to the copper powder and fine copper powder, a small amount of a metal carboxylate compound having a metal cation species other than copper is contained in the fired conductive copper paste. Added. In the process of adding and mixing the carboxylic acid metal salt compound, the carboxylic acid metal salt compound is uniformly distributed in the dispersion solvent, preferably dissolved in the dispersion solvent. Accordingly, when preparing the fired conductive copper paste, the carboxylic acid metal salt compound to be added is previously dissolved in a dispersion solvent and then mixed with copper powder, fine copper powder, and glass frit. A form can be adopted.

At that time, to a state in which the carboxylic acid metal salt compound is uniformly distributed in the dispersion solvent, and the volume ratio _{V metal} -carboxylate of the carboxylic acid metal salt compound, the ratio of the volume ratio V _Solvent for dispersion solvent, V _{metal -carboxylate} : V _solvent is usually selected in the range of 2: 100 to 33: 100, preferably in the range of 2.2: 100 to 33: 100.

Density of metal carboxylate having a metal cation species other than copper d _{metal -carboxylate}
(G / cm ^3), considering the density of the dispersion solvent d _Solvent (g / cm ^3), wherein the volume ratio, in terms of mass _{ratio, (d metal -carboxylate / d solvent} ) · V metal -carboxylate: V It becomes _solvent . Therefore, the dispersion solvent is selected so that the solubility of the carboxylic acid metal salt compound in the dispersion solvent is not less than (d _{metal -carboxylate} / d _solvent ) · V _{metal-carboxylate} / V _solvent (g / g). There is a need.

  At the time of preparation of the fired conductive copper paste, the carboxylic acid metal salt compound is dissolved in the dispersion solvent in advance, or a high concentration carboxylic acid dissolved in advance in an organic solvent in which the solubility of the carboxylic acid metal salt compound is high A solution of the metal salt compound is prepared and mixed in the dispersion solvent, whereby the carboxylic acid metal salt compound is dissolved in the dispersion solvent. As an example of an organic solvent that can be used for preparing a high-concentration carboxylic acid metal salt compound solution, toluene (boiling point 110.6 ° C.), xylene (for example, p-xylene, boiling point 138.35 ° C.), mineral spirit (boiling range) 130 ° C to 180 ° C), terpineol, 2-ethylhexanoic acid (boiling point 227 ° C), and the like.

  When the drying treatment is performed, a substantial part of the dispersion solvent is evaporated, and as a result, a substantial part of the carboxylic acid metal salt compound dissolved in the dispersion solvent is precipitated in the form of a fine powder. Therefore, when the drying treatment is performed, the fine powdery carboxylic acid metal salt compound that has precipitated is filled together with the fine copper powder and the powdery glass frit in the gaps in the structure in which the copper powder is laminated. For example, it is possible to fill a fine powdery carboxylic acid metal salt compound in a narrower gap around a portion where copper powders contact each other.

  Thereafter, when an oxidation treatment is performed, the carboxylic acid metal salt compound is oxidatively decomposed and converted into a metal oxide. Next, when a reduction treatment is performed, the metal oxide is also reduced to generate metal atoms. The generated metal atoms adhere to the surfaces of copper powder and fine copper powder. In particular, metal atoms derived from a fine powdery metal carboxylate compound that has been filled in a narrow gap around a portion where copper powders contact each other fill a narrower gap in the contact portion.

  For example, when the metal cation species constituting the carboxylic acid metal salt compound is a cation species of a metal that is baser than copper, the base metal is filled in a narrower gap at the contact site than copper. . When the produced fired conductor film is oxidized, the base metal is preferentially oxidized over copper, and the oxidation of the copper surface at the portion where the copper powders are in contact with each other is suppressed. As a result, it is possible to suppress an increase in contact resistance at the contact site due to oxidation.

The volume ratio V _metal- carboxylate of the carboxylic acid metal salt compound having a metal cation species other than copper that is additionally added to the fired conductive copper paste, the volume ratio V _particle of the copper powder, and the volume ratio of the fine copper powder the ratio of the sum of _{V fine-particle (V particle +} V fine-particle), (V particle + V fine-particle): V metal -carboxylate is 100: 1 to 100: 30 range, preferably 100: 1.5 It is desirable to select in the range of ˜100: 30. As a result of selecting the above range, the volume ratio V _{metal-atom of the metal} derived from the carboxylic acid metal salt compound having a metal cation species other than copper, which is additionally added to the fired conductive copper paste, and copper powder The ratio of the volume ratio V _particle to the fine copper powder volume ratio V _{fine-particle} (V _particle + V _{fine-particle} ), (V _particle + V _{fine-particle} ): V _metal-atom is 100: 0.05 ~ The range is 100: 1, preferably 100: 0.06 to 100: 0.8.

  The metal cation species contained in the carboxylic acid metal salt compound having a metal cation species other than copper is desirably a cation species of a base species that is lower than copper. As a carboxylic acid metal salt compound having a metal cation species other than copper, which can be suitably used, nickel (II) 2-ethylhexanoate (decomposition point 250 to 300 ° C.), manganese (II) 2-ethylhexanoate (decomposition) Point 250-300 ° C.) and cobalt (II) 2-ethylhexanoate (decomposition point 250-300 ° C.).

Note that the resistivity ρ _Ni of metallic nickel is 6.84 μΩ · cm, the resistivity ρ _Mn of metallic manganese is 185.0 μΩ · cm (20 ° C.), and the resistivity ρ _Co of metallic cobalt is 6.24 μΩ · cm. The resistivity ρ _Cu of metallic copper is higher than 1.673 μΩ · cm (20 ° C.). Metal nickel, metal manganese, and metal cobalt are all base metals rather than metal copper.

  The carboxylic acid metal salt compound having a metal cation species other than copper needs to be capable of decomposing and producing a base metal atom that is lower than copper when performing the baking treatment. In addition, when preparing a fired conductive copper paste, it is necessary to dissolve in a dispersion solvent and to be contained as a solution. The carboxylic acid metal salt compound containing the divalent cation species of nickel, manganese and cobalt is suitably used as a carboxylic acid metal salt compound having a metal cation species other than copper that satisfies the above two conditions. .

In order to set the film thickness t _paste of the fired conductive copper paste coating film to about 50 μm, for example, a screen printing method is usually employed. When the screen printing method is applied, the liquid viscosity of the fired conductive copper paste is selected in the range of 10 Pa · s to 100 Pa · s, preferably in the range of 20 Pa · s to 80 Pa · s. By adding an organic binder, the viscosity of the organic vehicle in the liquid phase is increased, but by adjusting the sum of the volume ratios of the solid components contained, V _{solid-component} (volume%), the liquid of the paste The viscosity can also be adjusted to the above range.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, although the Example shown here is an example of the best embodiment concerning this invention, this invention is not limited to the form shown to this specific example.

Example 1
The fired conductive copper paste of Example 1 is prepared by the following procedure.

To 70 parts by mass of spherical copper powder having an average particle diameter d _{particle of} 4 μm and 30 parts by mass of spherical fine copper powder having an average particle diameter d _{fine-particle of} 0.4 μm, Marialim AFB-0851 (manufactured by NOF Corporation) 2 parts by weight, 10 parts by weight of terpineol (boiling point 217 ° C.) as a dispersion solvent, 0.5 parts by weight of ethyl cellulose, V ₂ O ₅ —ZnO—BaO—TeO ₂ glass frit (softening point 311 ° C., crystallization temperature 444 ° C. , Average particle diameter d _frit 0.95 μm) was mixed with 4.5 parts by mass. This mixture was kneaded with a three-roll kneader to prepare a copper paste.

In the copper paste, the volume ratio V _particle of spherical copper powder is 33.2% by volume; the volume ratio V _{fine-particle} of spherical fine copper powder is 14.2% by volume; the volume ratio V _frit of glass _frit is 4 Dispersing agent volume ratio V _{dispersing-agent} is 0.9 vol%; organic binder volume ratio V _binder is 1.9 vol%; dispersing solvent volume ratio V _solvent is 45.4 vol. %.

  Marialim AFB-0851 is a high molecular weight polycarboxylic acid type surfactant suitable for an oil-based dispersant, but decomposes when heated to 350 ° C. or higher for 10 minutes in an air atmosphere. Ethyl cellulose used as an organic binder component is decomposed when heated to 350 ° C. or higher for 10 minutes in an air atmosphere. The used spherical copper powder and spherical fine copper powder are produced by a wet method, and the surface thereof is covered with a very thin oxide film. The surfaces of spherical copper powder, spherical fine copper powder, and glass frit are coated with Mariarim AFB-0851, which is a polymer polycarboxylic acid type surfactant, and are uniformly dispersed in a liquid phase composed of ethyl cellulose and terpineol. ing.

  The viscosity of the prepared copper paste was 30 Pa · s.

Spherical copper powder having a volume ratio V _particle contained in the copper paste, the volume ratio V _{fine-particle} spherical fine copper powder, the sum of the volume ratio V _frit glass frit _{(V particle + V fine-particle} + V frit) is This corresponds to 51.9% by volume. Moreover, the volume ratio V _particle of the spherical copper powder, the ratio of the sum of the volume ratio V _frit of the volume ratio V _{fine-particle} glass frit spherical fine copper powder _{(V fine-particle + V frit} ), V particle: (V fine _-particle + V _frit ) is 1: 0.56. The ratio of the volume ratio V _{dispersing-agent of} Marialim AFB-0851 which is a dispersant to the sum (V _particle + V _{fine-particle} + V _frit ), (V _particle + V _{fine-particle} + V _frit ): V _{dispersing-agent} is 1: It is 0.02. The average particle diameter d _{frit of} 0.95 μm of the glass frit satisfies the relationship of d _frit <((2) ^1/2 −1) d _particle with respect to the average particle diameter d _{particle of} 4 μm of the spherical copper powder. Therefore, for example, when spherical copper powders are stacked in a cubic close-packed state, it is possible to have a state in which fine copper powder and glass frit are filled in the gaps between the spherical copper powders.

This copper paste was screen-printed on a glass substrate to produce a 3 mm × 20 mm strip pattern coating film. The produced coating film had an average film thickness t _paste of 30 μm. The coating film was dried at 120 ° C. for 1 minute and baked at 400 ° C. for 10 minutes in an air atmosphere using an electric furnace. The fired film taken out from the electric furnace was subjected to reduction treatment at 400 ° C. for 10 minutes in an infrared firing furnace in which nitrogen-4% hydrogen gas was passed.

The average film thickness t _{sintered-layer} of the fired film after the reduction treatment was 25 μm. Assuming that the conductor film has a uniform average film thickness, the volume resistivity of the reduced fired film was measured with a four-end needle probe. The measured volume resistivity was 8.8 μΩ · cm. The average film thickness t _{sintered-layer} of the fired film after reduction treatment is about 1.61 times that of t _paste × (V _particle + V _{fine-particle} + V _frit ) / 100 volume% ≈15.6 μm. The resistivity ρ _Cu of metallic copper is 1.673 μΩ · cm (20 ° C.), and 8.8 μΩ · cm is about 5.26 times that.

The reduction-treated fired film was left in an oven at 125 ° C. for 48 hours in an air atmosphere to be oxidized. Thereafter, assuming that the conductor film has a uniform average thickness t _{sintered-layer} , the volume resistivity of the fired film subjected to the oxidation treatment was measured with a four-end needle probe. The measured volume resistivity was 13.2 μΩ · cm. Therefore, the change rate of the volume resistivity accompanying the oxidation treatment was (13.2 / 8.8) = 1.5 times.

(Example 2)
The fired conductive copper paste of Example 2 is prepared by the following procedure.

To 70 parts by mass of spherical copper powder having an average particle diameter d _{particle of} 4 μm and 30 parts by mass of spherical fine copper powder having an average particle diameter d _{fine-particle of} 0.4 μm, Marialim AFB-0851 (manufactured by NOF Corporation) 2 parts by weight, 10 parts by weight of terpineol (boiling point 217 ° C.) as a dispersion solvent, 0.5 parts by weight of ethyl cellulose, V ₂ O ₅ —ZnO—BaO—TeO ₂ glass frit (softening point 311 ° C., crystallization temperature 444 ° C. , Average particle diameter d _frit 0.95 μm) and 4.5 parts by mass, and 2 parts by mass of copper nanoparticles having an average particle diameter d _{nano-particle of} 50 nm were mixed. This mixture was kneaded with a three-roll kneader to prepare a copper paste.

In the copper paste, the volume ratio V _particle of spherical copper powder is 32.9% by volume; the volume ratio V _{fine-particle} of spherical fine copper powder is 14.1% by volume; the volume ratio V _frit of glass _frit is 4 4 volume%; volume ratio V _{nano-particle} of copper nanoparticles is 0.9 volume%; volume ratio of dispersant V _{dispersing-agent} is 0.9 volume%; volume ratio of organic binder V _binder is 1 .8% by volume; The volume ratio V _solvent of the dispersion _solvent is 45.0% by volume.

The spherical copper powder, spherical fine copper powder, ethyl cellulose, and V ₂ O ₅ —ZnO—BaO—TeO ₂ glass frit are the same as those used in Example 1 above. Copper nanoparticles are produced by a liquid phase reduction method, and the surface thereof is covered with a coating molecule 2-ethylhexyloxypropylamine (boiling point 290 ° C.). The surfaces of spherical copper powder, spherical fine copper powder, and glass frit are coated with Mariarim AFB-0851, which is a polymer polycarboxylic acid type surfactant, and are uniformly dispersed in a liquid phase composed of ethyl cellulose and terpineol. ing. On the other hand, the copper nanoparticles are dispersed in the liquid phase in a state where the surface thereof is coated with a coating agent molecular layer.

  The viscosity of the prepared copper paste was 35 Pa · s.

Spherical copper powder having a volume ratio V _particle contained in the copper paste, the volume ratio V _{fine-particle} spherical fine copper powder, the volume ratio V _{nano-particle} of copper nanoparticles, the sum of the volume ratio V _frit glass frit ( V _particle + V _{fine-particle} + V _{nano-particle} + V _frit ) corresponds to 52.3% by volume. Moreover, the volume ratio V _particle of the spherical copper powder, the volume ratio V _{fine-particle} spherical fine copper powder, the volume ratio V _{nano-particle} of copper nanoparticles, the sum of the volume ratio V _frit glass frit (V _{fine-particle} + V The ratio of _{nano-particle} + V _frit ), V _particle : (V _{fine-particle} + V _{nano-particle} + V _frit ) is 1: 0.59. Therefore, for example, when spherical copper powder is stacked in a cubic close-packed state, it becomes possible to have a state in which fine copper powder, copper nanoparticles, and glass frit are filled in the gaps between the spherical copper powders. ing.

This copper paste was screen-printed on a glass substrate to produce a 3 mm × 20 mm strip pattern coating film. The produced coating film had an average film thickness t _paste of 30 μm. The coating film was dried at 120 ° C. for 1 minute and baked at 400 ° C. for 10 minutes in an air atmosphere using an electric furnace. The fired film taken out from the electric furnace was subjected to reduction treatment at 400 ° C. for 10 minutes in an infrared firing furnace in which nitrogen-4% hydrogen gas was passed.

The average film thickness t _{sintered-layer} of the fired film after the reduction treatment was 20 μm. Assuming that the conductor film has a uniform average film thickness, the volume resistivity of the reduced fired film was measured with a four-end needle probe. The measured volume resistivity was 7.0 μΩ · cm. The average film thickness t _{sintered-layer} of the fired film after reduction treatment is about 1.27 times for t _paste × (V _particle + V _{fine-particle} + V _{nano-particle} + V _frit ) / 100 vol% ≈15.7 μm. It has become. The resistivity ρ _Cu of metallic copper is 1.673 μΩ · cm (20 ° C.), and 7.0 μΩ · cm is about 4.18 times that.

The reduction-treated fired film was left in an oven at 125 ° C. for 48 hours in an air atmosphere to be oxidized. Thereafter, assuming that the conductor film has a uniform average thickness t _{sintered-layer} , the volume resistivity of the fired film subjected to the oxidation treatment was measured with a four-end needle probe. The measured volume resistivity was 11.1 μΩ · cm. Therefore, the change rate of the volume resistivity accompanying the oxidation treatment was (11.1 / 7.0) = 1.59 times.

(Example 3)
In Example 3, a fired film was produced using the fired conductive copper paste of Example 1 under the following conditions.

The copper paste prepared in Example 1 was screen-printed on a glass substrate to produce a 3 mm × 20 mm strip pattern coating film. The produced coating film had an average film thickness t _paste of 30 μm. The coating film was dried at 120 ° C. for 1 minute and baked at 350 ° C. for 10 minutes in an air atmosphere using an electric furnace. The fired film taken out from the electric furnace was subjected to reduction treatment at 350 ° C. for 10 minutes in an infrared firing furnace in which nitrogen-4% hydrogen gas was passed.

The average film thickness t _{sintered-layer} of the fired film after the reduction treatment was 25 μm. Assuming that the conductor film has a uniform average film thickness, the volume resistivity of the reduced fired film was measured with a four-end needle probe. The measured volume resistivity was 12.6 μΩ · cm. The average film thickness t _{sintered-layer} of the fired film after the reduction treatment is about 1.61 times for t _paste × (V _particle + V _{fine-particle} + V _{nano-particle} + V _frit ) / 100 vol% ≈15.6 μm. It has become. The resistivity ρ _Cu of metallic copper is 1.673 μΩ · cm (20 ° C.), and 12.6 μΩ · cm is about 7.53 times that.

The reduction-treated fired film was left in an oven at 125 ° C. for 48 hours in an air atmosphere to be oxidized. Thereafter, assuming that the conductor film has a uniform average thickness t _{sintered-layer} , the volume resistivity of the fired film subjected to the oxidation treatment was measured with a four-end needle probe. The measured volume resistivity was 18.5 μΩ · cm. Therefore, the change rate of the volume resistivity accompanying the oxidation treatment was (18.5 / 12.6) = 1.61 times.

Example 4
The fired conductive copper paste of Example 4 is prepared by the following procedure.

To 70 parts by mass of spherical copper powder having an average particle diameter d _{particle of} 4 μm and 30 parts by mass of spherical fine copper powder having an average particle diameter d _{fine-particle of} 0.4 μm, Marialim AFB-0851 (manufactured by NOF Corporation) 2 parts by mass, terpineol (boiling point 217 ° C.) 10 parts by mass, acrylic resin 0.5 part by mass, V ₂ O ₅ —ZnO—BaO—TeO ₂ glass frit (softening point 311 ° C., crystallization temperature 444) (C °, average particle diameter d _frit 0.95 μm) 4.5 parts by mass were mixed. This mixture was kneaded with a three-roll kneader to prepare a copper paste.

In the copper paste, the volume ratio V _particle of spherical copper powder is 33.1% by volume; the volume ratio V _{fine-particle} of spherical fine copper powder is 14.2% by volume; the volume ratio V _frit of glass _frit is 4 Dispersing agent volume ratio V _{dispersing-agent} is 0.9 vol%; Organic binder volume ratio V _binder is 2.2 vol%; Dispersing solvent volume ratio V _solvent is 45.2 vol. %.

The spherical copper powder, spherical fine copper powder, and V ₂ O ₅ —ZnO—BaO—TeO ₂ glass frit are the same as those used in Example 1 above. The acrylic resin used as the organic binder component is decomposed when heated to 300 ° C. or higher for 5 minutes in an air atmosphere. The surfaces of spherical copper powder, spherical fine copper powder, and glass frit are coated with Mariarim AFB-0851, which is a polymeric polycarboxylic acid type surfactant, and uniformly dispersed in a liquid phase composed of acrylic resin and terpineol. Has been.

  The viscosity of the prepared copper paste was 30 Pa · s.

Spherical copper powder having a volume ratio V _particle contained in the copper paste, the volume ratio V _{fine-particle} spherical fine copper powder, the sum of the volume ratio V _frit glass frit _{(V particle + V fine-particle} + V frit) is This corresponds to 51.7% by volume. Similar to the fired conductive copper paste of Example 1, in the fired conductive copper paste of Example 4, for example, when spherical copper powder is laminated in a close-packed state of cubic, The gap can be filled with fine copper powder, copper nanoparticles, and glass frit.

This copper paste was screen-printed on a glass substrate to produce a 3 mm × 20 mm strip pattern coating film. The produced coating film had an average film thickness t _paste of 30 μm. The coating film was dried at 120 ° C. for 1 minute and baked at 350 ° C. for 10 minutes in an air atmosphere using an electric furnace. The fired film taken out from the electric furnace was subjected to reduction treatment at 350 ° C. for 10 minutes in an infrared firing furnace in which nitrogen-4% hydrogen gas was passed.

The average film thickness t _{sintered-layer} of the fired film after the reduction treatment was 25 μm. Assuming that the conductor film has a uniform average film thickness, the volume resistivity of the reduced fired film was measured with a four-end needle probe. The measured volume resistivity was 10.5 μΩ · cm. The average film thickness t _{sintered-layer} of the fired film after the reduction treatment is about 1.61 times for t _paste × (V _particle + V _{fine-particle} + V _{nano-particle} + V _frit ) / 100 vol% ≈15.5 μm. It has become. The resistivity ρ _Cu of metallic copper is 1.673 μΩ · cm (20 ° C.), and 10.5 μΩ · cm is about 6.28 times that.

The reduction-treated fired film was left in an oven at 125 ° C. for 48 hours in an air atmosphere to be oxidized. Thereafter, assuming that the conductor film has a uniform average thickness t _{sintered-layer} , the volume resistivity of the fired film subjected to the oxidation treatment was measured with a four-end needle probe. The measured volume resistivity was 18.5 μΩ · cm. Therefore, the change rate of the volume resistivity accompanying the oxidation treatment was (18.5 / 10.5) = 1.61 times.

(Example 5)
The fired conductive copper paste of Example 5 is prepared by the following procedure.

To 70 parts by mass of spherical copper powder having an average particle diameter d _{particle of} 4 μm and 30 parts by mass of spherical fine copper powder having an average particle diameter d _{fine-particle of} 0.4 μm, Marialim AFB-0851 (manufactured by NOF Corporation) 2 parts by mass, 10 parts by mass of terpineol (boiling point 217 ° C.) as a dispersion solvent, 0.5 parts by mass of ethyl cellulose, B ₂ O ₃ —Bi ₂ O ₃ -based glass frit (softening point 390 ° C., crystallization temperature 460 ° C., average 4.5 parts by mass of particle diameter d _frit 0.8 μm) were mixed. This mixture was kneaded with a three-roll kneader to prepare a copper paste.

In the copper paste, the volume ratio V _particle of spherical copper powder is 33.6% by volume; the volume ratio V _{fine-particle} of spherical fine copper powder is 14.4% by volume; the volume ratio V _frit of glass _frit is 3 Dispersing agent volume ratio V _{dispersing-agent} is 1.0 vol%; organic binder volume ratio V _binder is 1.9 vol%; dispersing solvent volume ratio V _solvent is 45.7 vol. %.

  Spherical copper powder, spherical fine copper powder, and ethyl cellulose are the same as those used in Example 1 above. The surfaces of spherical copper powder, spherical fine copper powder, and glass frit are coated with Mariarim AFB-0851, which is a polymer polycarboxylic acid type surfactant, and are uniformly dispersed in a liquid phase composed of ethyl cellulose and terpineol. ing.

  The viscosity of the prepared copper paste was 30 Pa · s.

Spherical copper powder having a volume ratio V _particle contained in the copper paste, the volume ratio V _{fine-particle} spherical fine copper powder, the sum of the volume ratio V _frit glass frit _{(V particle + V fine-particle} + V frit) is This corresponds to 51.4% by volume. Similarly to the firing type conductive copper paste of Example 1, in the firing type conductive copper paste of Example 5, for example, when spherical copper powder is laminated in a close-packed state of cubic, The gap can be filled with fine copper powder and glass frit.

This copper paste was screen-printed on a glass substrate to produce a 3 mm × 20 mm strip pattern coating film. The produced coating film had an average film thickness t _paste of 30 μm. The coating film was dried at 120 ° C. for 1 minute and baked at 450 ° C. for 10 minutes in an air atmosphere using an electric furnace. The fired film taken out from the electric furnace was subjected to reduction treatment at 450 ° C. for 10 minutes in an infrared firing furnace in which nitrogen-4% hydrogen gas was passed.

The average film thickness t _{sintered-layer} of the fired film after the reduction treatment was 20 μm. Assuming that the conductor film has a uniform average film thickness, the volume resistivity of the reduced fired film was measured with a four-end needle probe. The measured volume resistivity was 8.7 μΩ · cm. The average film thickness t _{sintered-layer} of the fired film after reduction treatment is about 1.30 times for t _paste × (V _particle + V _{fine-particle} + V _{nano-particle} + V _frit ) / 100 vol% ≈15.4 μm. It has become. The resistivity ρ _Cu of metallic copper is 1.673 μΩ · cm (20 ° C.), and 8.7 μΩ · cm is about 5.20 times that.

The reduction-treated fired film was left in an oven at 125 ° C. for 48 hours in an air atmosphere to be oxidized. Thereafter, assuming that the conductor film has a uniform average thickness t _{sintered-layer} , the volume resistivity of the fired film subjected to the oxidation treatment was measured with a four-end needle probe. The measured volume resistivity was 12.9 μΩ · cm. Therefore, the change rate of the volume resistivity accompanying the oxidation treatment was (12.9 / 8.7) = 1.48 times.

(Example 6)
The fired conductive copper paste of Example 6 is prepared by the following procedure.

To 70 parts by mass of spherical copper powder having an average particle diameter d _{particle of} 4 μm and 30 parts by mass of spherical fine copper powder having an average particle diameter d _{fine-particle of} 0.4 μm, Marialim AFB-0851 (manufactured by NOF Corporation) 2 parts by mass, polypropylene glycol (molecular weight 4000, decomposition temperature 260 ° C.) as a dispersion solvent, V ₂ O ₅ —ZnO—BaO—TeO ₂ glass frit (softening point 311 ° C., crystallization temperature 444 ° C., average (Particle size d _frit 0.95 μm) 4.5 parts by mass were mixed. This mixture was kneaded with a three-roll kneader to prepare a copper paste.

In the copper paste, the volume ratio V _particle of spherical copper powder is 35.1% by volume; the volume ratio V _{fine-particle} of spherical fine copper powder is 15.0% by volume; the volume ratio V _frit of glass _frit is 4 Dispersant volume ratio V _{dispersing-agent} is 1.0 vol%; Organic binder volume ratio V _binder is 0 vol%; Dispersing solvent volume ratio V _solvent is 44.2 vol% It has become.

The spherical copper powder, spherical fine copper powder, and V ₂ O ₅ —ZnO—BaO—TeO ₂ glass frit are the same as those used in Example 1 above. The surfaces of the spherical copper powder, spherical fine copper powder, and glass frit are coated with Mariarim AFB-0851, which is a polymer polycarboxylic acid type surfactant, and are uniformly dispersed in the liquid phase (polypropylene glycol).

  The viscosity of the prepared copper paste was 30 Pa · s.

Spherical copper powder having a volume ratio V _particle contained in the copper paste, the volume ratio V _{fine-particle} spherical fine copper powder, the sum of the volume ratio V _frit glass frit _{(V particle + V fine-particle} + V frit) is This corresponds to 54.8% by volume. Similarly to the fired conductive copper paste of Example 1, in the fired conductive copper paste of Example 6, for example, when spherical copper powders are stacked in a cubic close packed state, The gap can be filled with fine copper powder and glass frit.

This copper paste was screen-printed on a glass substrate to produce a 3 mm × 20 mm strip pattern coating film. The produced coating film had an average film thickness t _paste of 30 μm. The coating film was dried at 120 ° C. for 1 minute and baked at 400 ° C. for 10 minutes in an air atmosphere using an electric furnace. The fired film taken out from the electric furnace was subjected to reduction treatment at 400 ° C. for 10 minutes in an infrared firing furnace in which nitrogen-4% hydrogen gas was passed.

The average film thickness t _{sintered-layer} of the fired film after the reduction treatment was 24 μm. Assuming that the conductor film has a uniform average film thickness, the volume resistivity of the reduced fired film was measured with a four-end needle probe. The measured volume resistivity was 7.8 μΩ · cm. The average film thickness t _{sintered-layer} of the fired film after the reduction treatment is about 1.46 times that of t _paste × (V _particle + V _{fine-particle} + V _frit ) / 100 volume% ≈16.4 μm. The resistivity ρ _Cu of metallic copper is 1.673 μΩ · cm (20 ° C.), and 7.8 μΩ · cm is about 4.66 times that.

The reduction-treated fired film was left in an oven at 125 ° C. for 48 hours in an air atmosphere to be oxidized. Thereafter, assuming that the conductor film has a uniform average thickness t _{sintered-layer} , the volume resistivity of the fired film subjected to the oxidation treatment was measured with a four-end needle probe. The measured volume resistivity was 12.5 μΩ · cm. Therefore, the change rate of the volume resistivity accompanying the oxidation treatment was (12.5 / 7.8) = 1.6 times.

(Example 7)
The fired conductive copper paste of Example 7 is prepared by the following procedure.

To 70 parts by mass of spherical copper powder having an average particle diameter d _{particle of} 4 μm and 30 parts by mass of spherical fine copper powder having an average particle diameter d _{fine-particle of} 0.4 μm, Marialim AFB-0851 (manufactured by NOF Corporation) 2 parts by weight, 10 parts by weight of terpineol (boiling point 217 ° C.) as a dispersion solvent, 0.5 parts by weight of ethyl cellulose, V ₂ O ₅ —ZnO—BaO—TeO ₂ glass frit (softening point 311 ° C., crystallization temperature 444 ° C. , 4.5 parts by weight of average particle diameter d _frit 0.95 μm) and 2.9 parts by weight of nickel (II) 2-ethylhexanoate (molecular weight 345). This mixture was kneaded with a three-roll kneader to prepare a copper paste.

In the copper paste, the volume ratio V _particle of spherical copper powder is 29.5% by volume; the volume ratio V _{fine-particle} of spherical fine copper powder is 12.6% by volume; the volume ratio V _frit of glass _frit is 3 0.9% by volume; Volume ratio V _{Ni-carboxylate} of nickel (II) 2-ethylhexanoate is 11.3% by volume; Volume ratio of _{dispersing agent} V _{dispersing-agent} is 0.8% by volume; Volume of organic binder The ratio V _binder is 1.7% by volume; the volume ratio V _solvent of the dispersion _solvent is 40.2% by volume.

The spherical copper powder, spherical fine copper powder, ethyl cellulose, and V ₂ O ₅ —ZnO—BaO—TeO ₂ glass frit are the same as those used in Example 1 above. Nickel (II) 2-ethylhexanoate is dissolved in a liquid phase composed of ethylcellulose and terpineol by adding and mixing in the form of fine powder. The amount of nickel in 2.9 parts by mass of nickel 2-ethylhexanoate (II) (molecular weight 345) corresponds to 0.5 parts by mass. When nickel 2-ethylhexanoate (II) is heated to 350 ° C. or higher for 10 minutes, it is decomposed and converted to metallic nickel. Thereafter, when oxidized, it is converted to nickel (II) oxide. The surface of the spherical copper powder, spherical fine copper powder, and glass frit is coated with Mariarim AFB-0851 which is a high molecular weight polycarboxylic acid type surfactant and dissolves nickel 2-ethylhexanoate (II). It is uniformly dispersed in a liquid phase composed of ethyl cellulose and terpineol.

And the volume ratio V _{Ni-carboxylate} of nickel 2-ethylhexanoate (II), the ratio of the volume ratio V _Solvent for dispersion solvent _{terpineol, V Ni-carboxylate: V solvent} = 28.1: are selected 100. Therefore, the solubility of nickel 2-ethylhexanoate (II) in terpineol is 29 g / 100 g (25 ° C.) or more.

  The viscosity of the prepared copper paste was 34 Pa · s.

Spherical copper powder having a volume ratio V _particle contained in the copper paste, the volume ratio V _{fine-particle} spherical fine copper powder, the sum of the volume ratio V _frit glass frit _{(V particle + V fine-particle} + V frit) is This corresponds to 48.2% by volume. Further, the sum of the volume ratio V _particle of the spherical copper powder, 2 volume ratio V _{Ni-carboxylate} of nickel ethylhexanoate (II), the volume of the spherical fine copper powder ratio V _{fine-particle,} glass frit volume ratio V _frit The ratio of (V _{fine-particle} + V _{Ni-carboxylate} + V _frit ), V _particle : (V _{fine-particle} + V _{Ni-carboxylate} + V _frit ) is 1: 0.95. The ratio of the volume ratio V _{dispersing-agent of} Marialim AFB-0851 which is a dispersant to the sum (V _particle + V _{fine-particle} + V _frit ), (V _particle + V _{fine-particle} + V _frit ): V _{dispersing-agent} is 1: It is 0.02.

  Therefore, for example, when spherical copper powder is laminated in a close-packed state of cubic, when drying is performed, nickel 2-ethylhexanoate (II), fine copper powder, and glass deposited in the gaps between the spherical copper powders. The frit can be filled. Furthermore, when the calcination treatment is performed, the precipitated nickel 2-ethylhexanoate (II) is decomposed, and the fine copper powder and the deposited nickel 2-ethylhexanoate (II) are formed in the gaps between the spherical copper powders. The derived metallic nickel is filled, and the softened glass frit wets the surface of the spherical copper powder, and the gap between the spherical copper powders is partially sealed.

This copper paste was screen-printed on a glass substrate to produce a 3 mm × 20 mm strip pattern coating film. The produced coating film had an average film thickness t _paste of 30 μm. The coating film was dried at 120 ° C. for 1 minute and baked at 450 ° C. for 10 minutes in an air atmosphere using an electric furnace. The fired film taken out from the electric furnace was subjected to reduction treatment at 450 ° C. for 10 minutes in an infrared firing furnace in which nitrogen-4% hydrogen gas was passed.

The average film thickness t _{sintered-layer} of the fired film after the reduction treatment was 20 μm. Assuming that the conductor film has a uniform average film thickness, the volume resistivity of the reduced fired film was measured with a four-end needle probe. The measured volume resistivity was 9.5 μΩ · cm. The average film thickness t _{sintered-layer} of the reduced fired film is about 1.38 times that of t _paste × (V _particle + V _{fine-particle} + V _frit ) / 100 volume% ≈14.5 μm. The resistivity ρ _Cu of metallic copper is 1.673 μΩ · cm (20 ° C.), and 9.5 μΩ · cm is about 5.68 times that.

The reduction-treated fired film was left in an oven at 125 ° C. for 48 hours in an air atmosphere to be oxidized. Thereafter, assuming that the conductor film has a uniform average thickness t _{sintered-layer} , the volume resistivity of the fired film subjected to the oxidation treatment was measured with a four-end needle probe. The measured volume resistivity was 9.8 μΩ · cm. Therefore, the volume resistivity change rate accompanying the oxidation treatment was (9.8 / 9.5) = 1.03 times.

(Reference Example 1)
In Reference Example 1, a fired film was produced using the fired conductive copper paste of Example 5 under the following conditions.

The copper paste prepared in Example 5 was screen-printed on a glass substrate to produce a 3 mm × 20 mm strip pattern coating film. The produced coating film had an average film thickness t _paste of 30 μm. The coating film was dried at 120 ° C. for 1 minute and baked at 400 ° C. for 10 minutes in an air atmosphere using an electric furnace. The fired film taken out from the electric furnace was subjected to reduction treatment at 400 ° C. for 10 minutes in an infrared firing furnace in which nitrogen-4% hydrogen gas was passed.

The average film thickness t _{sintered-layer} of the fired film after the reduction treatment was 21 μm. Assuming that the conductor film has a uniform average film thickness, the volume resistivity of the reduced fired film was measured with a four-end needle probe. The measured volume resistivity was 8.9 μΩ · cm. The average film thickness t _{sintered-layer} of the fired film after the reduction treatment is about 1.45 times for t _paste × (V _particle + V _{fine-particle} + V _{nano-particle} + V _frit ) / 100 vol% ≈14.5 μm. It has become. The resistivity ρ _Cu of metallic copper is 1.673 μΩ · cm (20 ° C.), and 8.9 μΩ · cm is about 5.32 times that.

  The presence or absence of peeling of the fired film formed on the glass substrate was confirmed by a tape peeling test. The fired film produced in Reference Example 1 was peeled off. Therefore, in the fired film produced in Reference Example 1, the adhesion to the flat surface of the glass substrate is judged as “poor”.

  In Example 5, the temperature of the baking treatment is 450 ° C., which is selected to be at least 30 ° C. higher than the softening point of 390 ° C. of the glass frit used. The processing temperature is 400 ° C., which is only 10 ° C. higher. Therefore, when heated to 400 ° C., the fine powdery glass frit filled in the gap between the copper powders is softened, but the gap between the surface of the glass substrate and the copper powder constituting the lower surface of the fired film In addition, it is presumed that the softened glass frit does not form a densely packed state. As a result, with the fired film produced under the firing conditions of Reference Example 1 using the fired conductive copper paste of Example 5, the effect of improving the adhesion to the glass substrate using the glass frit is sufficiently exhibited. Not.

  The results described in Examples 1 to 7 and Reference Example 1 are summarized in Tables 1-1 to 1-3 below.

(Example 8)
The fired conductive copper paste of Example 8 is prepared by the following procedure.

Mariarim AKM-1511-60 (manufactured by NOF Corporation) as a dispersant in 61 parts by mass of spherical copper powder with an average particle diameter d _{particle of} 4 μm and 26 parts by mass of spherical fine copper powder with an average particle diameter d _{fine-particle of} 0.4 μm 0.3 parts by mass, 8.7 parts by mass of tripropylene glycol monomethyl ether (boiling point 242 ° C.) as a dispersion solvent, V ₂ O ₅ —ZnO—BaO—TeO ₂ glass frit (softening point 311 ° C., crystallization temperature (444 ° C., average particle diameter d _frit 0.95 μm) 4 parts by mass were mixed. This mixture was kneaded with a three-roll kneader to prepare a copper paste.

In the copper paste, the volume ratio V _particle of spherical copper powder is 34.2% by volume; the volume ratio V _{fine-particle} of spherical fine copper powder is 14.6% by volume; the volume ratio V _frit of glass _frit is 4 Dispersing agent volume ratio V _{dispersing-agent} is 1.7 vol%; Organic binder volume ratio V _binder is 0 vol%; Dispersing solvent volume ratio V _solvent is 44.8 vol% It has become.

Marialim AKM-1511-60 is a polymeric polycarboxylic acid type surfactant suitable for a water-soluble dispersant, but decomposes when heated to 350 ° C. or higher for 10 minutes in an air atmosphere. . The spherical copper powder, spherical fine copper powder, and V ₂ O ₅ —ZnO—BaO—TeO ₂ glass frit are the same as those used in Example 1 above. The surfaces of spherical copper powder, spherical fine copper powder, and glass frit are coated with Marialim AKM-1511-60, which is a polymeric polycarboxylic acid type surfactant, and uniform in the liquid phase (tripropylene glycol monomethyl ether). Are distributed.

  The viscosity of the prepared copper paste was 30 Pa · s.

Spherical copper powder having a volume ratio V _particle contained in the copper paste, the volume ratio V _{fine-particle} spherical fine copper powder, the sum of the volume ratio V _frit glass frit _{(V particle + V fine-particle} + V frit) is This corresponds to 53.5% by volume. Moreover, the volume ratio V _particle of the spherical copper powder, the ratio of the sum of the volume ratio V _frit of the volume ratio V _{fine-particle} glass frit spherical fine copper powder _{(V fine-particle + V frit} ), V particle: (V fine _-particle + V _frit ) is 1: 0.56. Similarly to the firing type conductive copper paste of Example 1, in the firing type conductive copper paste of Example 8, for example, when spherical copper powders are laminated in a cubic close-packed state, The gap can be filled with fine copper powder and glass frit.

This copper paste was screen-printed on a glass substrate to produce a 3 mm × 20 mm strip pattern coating film. The produced coating film had an average film thickness t _paste of 30 μm. The coating film was dried at 150 ° C. for 1 minute and baked at 400 ° C. for 10 minutes in an air atmosphere using an electric furnace. The fired film taken out from the electric furnace was subjected to reduction treatment at 400 ° C. for 10 minutes in an infrared firing furnace in which nitrogen-4% hydrogen gas was passed.

The average film thickness t _{sintered-layer} of the fired film after the reduction treatment was 24 μm. Assuming that the conductor film has a uniform average film thickness, the volume resistivity of the reduced fired film was measured with a four-end needle probe. The measured volume resistivity was 6.1 μΩ · cm. The average film thickness t _{sintered-layer} of the fired film after the reduction treatment is about 1.50 times with respect to t _paste × (V _particle + V _{fine-particle} + V _frit ) / 100 volume% ≈16.1 μm. The resistivity ρ _Cu of metallic copper is 1.673 μΩ · cm (20 ° C.), and 6.1 μΩ · cm is about 3.64 times that.

  The cross section of the fired film after reduction treatment produced using the fired conductive copper paste of Example 8 was observed with an optical microscope. In FIG. 1, an example of the result of having observed the fired film cross section by an optical microscope is shown. In the structure in which spherical copper powder is laminated, spherical fine copper powder is filled in the gaps between the spherical copper powders, and the glass frit is infiltrated so as to cover the narrow gap and the surface of the spherical copper powder and spherical fine copper powder. . The glass frit is also infiltrated in the gap between the glass substrate surface and the sintered film. Therefore, the glass frit improves the adhesion of the sintered film to the glass substrate surface.

  The fired conductive copper paste according to the present invention can be used for producing a copper powder fired body type conductor film having a large film thickness. The baked conductive copper paste according to the present invention is particularly good in that the heating temperature during the baking process is selected in the range of 350 ° C. to 450 ° C. and exhibits high adhesion to the substrate surface. It can utilize suitably for preparation of the copper powder baking body type conductor film with a thick film.

Claims (12)

A fired conductive copper paste containing glass frit,
The fired conductive copper paste comprises copper powder, fine copper powder, glass frit, a dispersant, an organic binder, and a dispersion solvent.
Using the fired conductive copper paste,
(Step 1) A coating step of coating the fired conductive copper paste to form a coating film;
(Step 2) A drying treatment step of heating to the temperature T _drying to partially evaporate the dispersion solvent contained in the coating film to form a dried coating film;
(Step 3) under an air atmosphere and heated to a temperature T _Sintering, contained in the dry treated coating film, dispersing agent, an organic binder, a dispersion solvent was removed and copper powder, oxide film on the surface of the fine copper powder Forming an baked body by softening the glass frit to form a fired body;
(Step 4) under a reducing atmosphere containing hydrogen gas in an inert gas in the range of 1 vol% to 4 vol%, and heated to a temperature T _Sintering, copper powder contained in said heat-surface of the fine copper powder A reduction treatment step of reducing the oxide film and sintering the copper powder and fine copper powder to form a fired conductor;
Using the process for producing a fired-type conductor including the steps 1 to 4, a fired-type conductor can be produced,
Wherein the temperature T _Sintering is selected in the range of _{350 ℃ ≦ T sintering ≦ 450 ℃} ,
The temperature T _drying is selected in a range of 100 ° C. ≦ T _drying <150 ° C.,
The average particle diameter d _particle of the copper powder is selected in the range of 10 μm ≧ d _particle ≧ 1.5 μm;
An average particle diameter d _{fine-particle} of the fine copper powder is selected in a range of _1/20 d _particle ≦ d _{fine-particle} ≦ 1/4 d _particle ;
The glass frit has a softening point T _{frit-softening} and a crystallization temperature T _{frit-crystallizing satisfying the following} conditions: T _{frit-crystallizing} > T _thermally > T _{frit-softening} and (T _thermally -T _{frit-softening} ) ≧ 20 ° C. A powdered glass frit formed of a filling glass frit material;
The average particle diameter d _frit of the powdery glass _frit is selected in the range of _1/10 d _particle ≦ d _frit ≦ 1/2 d _particle ,
The dispersion solvent is an organic solvent having a high boiling point, and the boiling point or decomposition point T _solvent-bp in the atmosphere satisfies the condition of T _oxidizing > T _solvent-bp > T _drying ,
The organic binder is soluble in the dispersion solvent, the boiling point T _binder-bp is to satisfy the condition of _{T binder-bp> T solvent-} bp> T drying, air atmosphere, heated to a temperature T _Sintering It is a polymer compound that can be decomposed oxidatively,
The dispersing agent, the boiling point _{T dispersing-agent-bp} satisfies the condition of _{T dispersing-agent-bp> T} solvent-bp> T drying, air atmosphere, heating to a temperature T _Sintering, oxidatively A degradable polymer surfactant,
Contained in該焼molding conductive copper paste, the volume ratio V _particle of copper powder, the volume ratio V _{fine-particle} of the fine copper powder, powdered glass frit volume ratio V _frit, the volume ratio V _Dispersing dispersant _-agent , organic binder volume ratio V _binder , and dispersion solvent volume ratio V _solvent satisfy the following conditions:
The volume of copper powder ratio V _particle, the volume ratio V _{fine-particle} of the fine copper powder, the sum of the volume ratio V _frit powdered glass frit _{(V particle + V fine-particle} + V frit) is 65 vol% ≧ (V _particle + V _{fine-particle} + V _frit ) ≧ 40% by volume;
Volume ratio V _particle of copper powder, the volume ratio V _{fine-particle} of the fine copper powder, powdered glass frit volume ratio V _frit, the sum of the volume ratio V _{Dispersing-agent} dispersant _{(V particle + V fine-particle} + V frit + V _{dispersing-agent} ), the organic binder volume ratio V _binder , and the ratio of the dispersion solvent volume ratio V _solvent (V _binder + V _solvent ), (V _particle + V _{fine-particle} + V _frit + V _{dispersing-agent} ): (V _binder + V _solvent ) is selected in the range of 1: 0.5 to 1: 1.4;
Volume ratio V _particle of copper powder, the volume ratio V _{fine-particle} of the fine copper powder, the sum of the volume ratio V _frit of powdered glass frit _{(V particle + V fine-particle} + V frit), the volume ratio V _Dispersing dispersant _-agent ratio, (V _particle + V _{fine-particle} + V _frit ): V _{dispersing-agent} is selected in a range not exceeding 1: 0.095;
The ratio of the volume ratio V _particle of the copper powder to the volume ratio V _{fine-particle} of the fine copper powder, V _particle : V _{fine-particle} is selected in the range of 80:20 to 60:40,
And the volume ratio V _particle of copper powder, the ratio of the sum of the volume ratio V _frit of the volume ratio V _{fine-particle} powdered glass frit fine copper powder _{(V fine-particle + V frit} ), V particle: (V fine- _particle + V _frit ) is selected in the range of 1: 0.40 to 1: 0.75,
Volume ratio V _particle of copper powder, the volume ratio V _{fine-particle} of the fine copper powder, powdered glass frit volume ratio V _frit, the sum of the volume ratio V _{Dispersing-agent} dispersant _{(V particle + V fine-particle} + V frit + V _{dispersing-agent} ) and organic binder volume ratio V _binder , (V _particle + V _{fine-particle} + V _frit + V _{dispersing-agent} ): V _binder should be selected in a range not exceeding 1: 0.045 A fired conductive copper paste characterized by the above. The fired conductive copper paste according to claim 1, wherein a softening point T _frit- softening of the glass frit is selected in a range of 300 ° C to 400 ° C. The average particle diameter d _particle of the copper powder is selected in the range of 10 μm ≧ d _particle ≧ 2 μm;
The average particle diameter d _{fine-particle} of the fine copper powder is selected in the range of 1 μm ≧ d _{fine-particle} ≧ 0.2 μm;
The fired conductive copper paste according to claim 1 or 2, wherein an average particle diameter d _frit of the powdery glass _frit is selected in a range of 1.4 µm ≥ d _frit ≥ 0.2 µm. . 4. The fired conductivity according to claim 1, wherein a boiling point or a decomposition point T _solvent-bp in the atmosphere of the dispersion solvent is selected in a range of 180 ° C. to 350 ° C. 5. Copper paste. The fired conductive copper paste according to any one of claims 1 to 4, wherein the dispersant is a polymer surfactant of a polymer polycarboxylic acid type. The organic binder is a polymer compound that can be decomposed oxidatively by heating to a temperature selected in the range of 300 ° C. to 450 ° C. in an air atmosphere,
The fired conductive copper paste according to any one of claims 1 to 5, wherein the amount of carbon component remaining after the oxidative decomposition is 5% by mass or less of the polymer compound. . The glass frit comprises an amorphous composite oxide containing vanadium pentoxide, an amorphous composite oxide containing bismuth oxide, and phosphoric acid exhibiting a softening point T _frit- softening in the range of 300 ° C. to 400 ° C. It is a powdery glass frit which consists of an amorphous complex oxide material selected from the group of the amorphous complex oxide to contain, It is any one of Claims 1-6 characterized by the above-mentioned. Firing-type conductive copper paste. In the fired conductive copper paste, in addition to copper powder, fine copper powder, glass frit, dispersant, organic binder, dispersion solvent, a carboxylic acid metal salt compound having a metal cation species other than copper is contained. And
The carboxylic acid metal salt compound is contained in a state of being uniformly distributed in the dispersion solvent,
Volume ratio V _{metal-carboxylate} and the ratio of the volume ratio V _Solvent for dispersion solvent of the carboxylic acid metal salt _compound, V _{metal-carboxylate:} V _solvent is 2: 100 to 33: are selected in a range of 100,
The volume ratio V _particle of the copper powder and the volume ratio V _{fine-particle} of the fine copper powder (V _particle + V _{fine-particle} ) and metal cation species other than copper contained in the fired conductive copper paste The ratio of the volume ratio V _{metal-carboxylate} of the carboxylic acid metal salt compound, (V _particle + V _{fine-particle} ): V _{metal -carboxylate} is selected in the range of 100: 1 to 100: 30, The fired conductive copper paste according to any one of claims 1 to 7. 9. The fired conductivity according to claim 8, wherein the metal cation species contained in the carboxylic acid metal salt compound having a metal cation species other than copper is a cation species of a metal species that is baser than copper. Copper paste. In the fired conductive copper paste, in addition to copper powder, fine copper powder, glass frit, dispersant, organic binder, dispersion solvent, copper nanoparticles are contained,
The average particle diameter d _{nano-particle} of the copper nanoparticles is selected in the range of 100 nm ≧ d _{nano-particle} ≧ 50 nm,
The volume ratio V _particle of copper powder and the volume ratio V _{fine-particle} of the fine copper powder (V _particle + V _{fine-particle} ) and the volume ratio V of the copper nanoparticles contained in the fired conductive copper paste The ratio of _{nano-particle} , (V _particle + V _{fine-particle} ): V _{nano-particle} is selected in the range of 100: 1 to 100: 5, according to any one of claims 1-9. The firing type conductive copper paste described in 1. The fired conductive copper paste according to any one of claims 1 to 10, wherein the liquid viscosity of the fired conductive copper paste is selected in the range of 10 Pa · s to 100 Pa · s. . A method for producing a fired-type conductor using a fired-type conductive copper paste containing glass frit,
The fired conductive copper paste is a fired conductive copper paste according to any one of claims 1 to 11,
The process for producing a fired-type conductor using the fired-type conductive copper paste includes the following steps 1 to 4;
(Step 1) A coating step of coating the fired conductive copper paste to form a coating film;
(Step 2) A drying treatment step of heating to the temperature T _drying to partially evaporate the dispersion solvent contained in the coating film to form a dried coating film;
(Step 3) under an air atmosphere and heated to a temperature T _Sintering, contained in the dry treated coating film, dispersing agent, an organic binder, a dispersion solvent was removed and copper powder, oxide film on the surface of the fine copper powder Forming an baked body by softening the glass frit to form a fired body;
(Step 4) under a reducing atmosphere containing hydrogen gas in an inert gas in the range of 1 vol% to 4 vol%, and heated to a temperature T _Sintering, copper powder contained in said heat-surface of the fine copper powder A reduction treatment step of reducing the oxide film and sintering the copper powder and fine copper powder to form a fired conductor;
Wherein the temperature T _Sintering is selected in the range of _{350 ℃ ≦ T sintering ≦ 450 ℃} ,
The temperature T _drying is selected in the range of 100 ° C. ≦ T _drying <150 ° C.