Plate-shaped conductor film formation method

Abstract

Provided is a plate-shaped conductor film formation method which involves forming a plate-shaped conductor film which is at least 0.5μm thick and is shaped in a manner such that one or more sides thereof can fit inside a 3.0 cm square, by using a sintering-type conductive paste on a substrate, wherein: said sintering-type conductive paste has components a-c; the water content contained in the sintering-type conductive paste is less than 0.50 mass%; a is a conductive powder which has nickel as a principal component thereof, and has an average particle diameter D50 in the range of 0.05-1.0μm, inclusive; b is an acrylic resin which has an acid value in the range of 0-10mgKOH / g, inclusive; c is an alcohol-based solvent which is capable of dissolving the acrylic resin therein, has a carbon number of 3 or higher and has a boiling point of 300°C or less; and a step for forming a plate-shaped film by applying a coating of the sintering-type conductive paste onto the substrate surface, and a step for forming a conductor film by drying and sintering the plate-shaped film formed on the substrate are included in said method.

Description

Method for forming a flat conductive film

[0001] The present invention relates to a method for forming a flat conductive film using a sinterable conductive paste that uses a conductive powder containing metallic nickel as a main component.

[0002] In the electronics field, sinterable conductive pastes are used to manufacture components such as electronic circuits, resistors, capacitors, and IC packages. Sinterable conductive pastes are made by uniformly mixing and dispersing conductive powders of metals, alloys, metal oxides, etc., together with optional glassy binders and other additives, in an organic vehicle to form a paste. After applying this sinterable conductive paste to a substrate, it is fired at high temperatures, causing the organic components in the paste to decompose and disperse, leaving only the inorganic components, such as metal and glass components, to form conductive films for circuit board wiring and electrodes.

[0003] The organic vehicle contains a resin component called a binder resin. Therefore, even after the bakeable conductive paste is applied to a substrate or other target for forming a conductive film, it does not immediately flow to the surrounding area and can maintain its shape at the time of application while maintaining a certain thickness. After the binder resin is decomposed and dispersed by subsequent baking, the conductive powders dispersed at high concentrations in the organic vehicle sinter together, maintaining the original coating shape. Therefore, a conductive film formed in the desired pattern can be obtained by screen printing, gravure printing, or other methods.

[0004] As described above, fired conductive pastes are used for the aforementioned purposes because they can produce relatively thick film conductors. In addition, because specific patterns can be printed using fired conductive pastes, they have recently been widely used to form electrodes for small electronic components such as multilayer capacitors and multilayer inductors with a side length of less than 1 mm.

[0005] To explain one example, ceramic raw material powders such as dielectric, magnetic, and piezoelectric materials are dispersed in a binder resin and formed into a ceramic green sheet. A sinterable conductive paste is printed in a desired pattern on the sheet, and the sheet is dried to remove the solvent, forming a dry electrode film. Several ceramic green sheets with the resulting dry electrode film are stacked and pressed together to form a laminate. This laminate is then cut into a desired shape and simultaneously fired at high temperature to sinter the ceramic layers and form electrode layers, yielding a ceramic element. The electrode layers formed here are generally referred to as "internal electrode layers." End electrodes are formed on both end surfaces of the ceramic element obtained in this way, resulting in a laminated electronic component.

[0006] On the other hand, some applications require large-area (size) flat conductor films (coating films). Such flat conductor films are sometimes called "surface conductor films" because they are formed by covering part or all of the surface of a substrate, such as glass or ceramic, in a layered manner. Conventionally, when attempting to obtain large-size flat conductor films, such as those encompassing a square with sides of 3.0 cm or more, they have generally been formed using methods such as sputtering, vapor deposition, and plating (see, for example, Patent Document 1). These manufacturing methods facilitate the production of uniform film thicknesses, even when forming large-sized flat conductor films, and easily produce flat and smooth conductor films. However, these manufacturing methods are cost-intensive due to the large scale of production equipment, and the resulting conductor films are thin, making it difficult to obtain conductor films with high conductivity compared to thick-film conductors. While highly conductive conductor films can be obtained by stacking multiple layers of thin films obtained using these manufacturing methods, this inevitably increases manufacturing costs.

[0007] Another known method is to fabricate large-area flat conductive films using conductive ink. Unlike baked conductive pastes, conductive ink does not contain a binder resin and is a low-viscosity liquid, making it suitable for forming flat, smooth flat conductive films. Furthermore, compared to the aforementioned sputtering method, conductive ink can be manufactured using simple production equipment such as a spin coater or bar coater. For example, Patent Document 2 describes applying nickel ink, in which nickel particles with an average primary particle size of 10 nm to 30 nm are dispersed in a dispersion medium, to a glass substrate using a spin coater to form a conductive film with a film thickness of 400 nm and an average surface roughness Ra≦10 nm. However, the conductive film obtained by Patent Document 2 is still thin, and therefore high conductivity cannot be expected.

[0008] Patent Document 3 also discloses a conductive ink in which nickel formate is used as a component that generates nickel metal upon heating and is dispersed in ethyleneamine. Because ethyleneamine is viscous and sticky, it is described as being able to obtain a conductor film with a thickness of 3.66 μm, even though it does not contain a binder resin. However, because this conductive ink contains a large amount of organic components compared to the amount of metallic nickel, a coating film with a thickness of 100 μm, nearly 30 times thicker, must be formed to obtain a 3.66 μm film thickness. Therefore, when a large, flat conductor film is formed using the conductive ink of Patent Document 3, it is difficult to uniformly degrease and volatilize the organic components from the entire coating film, making it difficult to obtain a flat, smooth conductor film.

[0009] JP 2016-006228 A JP 2007-146117 A JP 2015-151512 A

[0010] Therefore, the present inventors attempted to form a thick, large-sized (large-area) flat conductor film using a sinterable conductive paste containing a binder resin. However, when a large-sized flat conductor film, for example, a 3.0 cm square, was produced using a conventional sinterable conductive paste, problems such as undulations on the surface of the conductor film after firing occurred, making it impossible to obtain a flat, smooth flat conductor film. The present inventors investigated various causes, including whether the firing furnace or the conductive paste was the cause, but were ultimately unable to identify the cause. However, the present inventors speculate that in either case, the flat conductor film (surface conductor film) is not pressure-bonded to the conductor film after firing, unlike the internal electrode layer, and therefore the difference in local thermal shrinkage that occurred in the coating film during the firing process became apparent.

[0011] Therefore, an object of the present invention is to make it possible to produce a thick, large, flat and smooth flat conductor film (surface conductor film) using a baked conductive paste containing a binder resin.

[0012] The above object is achieved by the following: (1) A method for forming a flat conductive film on a substrate using a sinterable conductive paste to form a flat conductive film having a shape capable of containing a square with at least one side of 3.0 cm and a thickness of 0.5 μm or more, wherein the sinterable conductive paste contains the following components a to c, and the moisture content of the sinterable conductive paste is less than 0.50 mass %, and a: nickel is the main component, and the average particle size D ５０a: conductive powder having a particle size in the range of 0.05 μm or more and 1.0 μm or less, b: an acrylic resin having an acid value in the range of 0 mgKOH / g or more and 10 mgKOH / g or less, c: an alcohol-based solvent having 3 or more carbon atoms and a boiling point of 300°C or less, which is capable of dissolving the acrylic resin. A method for forming a flat conductor film, comprising the steps of: applying the bakeable conductive paste to a surface of a substrate to form a flat film, and drying and baking the flat film formed on the substrate to form a conductor film. (2) The method for forming a flat conductor film according to (1) above, which forms a flat conductor film having a shape that can contain a square with at least one side of 5.0 cm and a thickness of 0.5 μm or more. (3) The method for forming a flat conductor film according to (1) or (2) above, wherein the blending amount of the acrylic resin in the bakeable conductive paste is 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the conductive powder. (4) The method for forming a flat conductive film according to any one of (1) to (3), wherein the amount of the alcohol-based solvent in the sinterable conductive paste is 10 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the conductive powder. ２ / g or more 25m ２ The method for forming a flat conductive film according to any one of (1) to (4), further comprising the step of adding 3 to 7 parts by mass of ceramic powder having a molecular weight in the range of 100 parts by mass of the conductive powder.

[0013] Using a baked conductive paste containing a binder resin, a thick, large-sized, flat and smooth flat conductive film can be produced.

[0014] The present invention was achieved by completely redesigning the composition of a sintered conductive paste containing a binder resin so that a thick, large, flat, and smooth flat conductor film can be formed, minimizing the occurrence of localized differences in thermal shrinkage within the conductive paste during the sintering process. Details will be described below, but the present invention is not limited to the examples given below. Hereinafter, the "sintered conductive paste" may be referred to as the "conductive paste."

[0015] (Conductive Powder) The conductive powder used in the present invention may be any powder containing nickel as the main component. It may be a pure nickel powder containing 100% nickel, or an alloy powder containing nickel with copper, iron, cobalt, gold, silver, palladium, rhenium, platinum, or the like. Nickel powder having a thin oxide film on its surface, or nickel powder coated with glass or various oxides to prevent oversintering or oxidation, may also be used. Furthermore, nickel powder whose surface has been treated with an organometallic compound, a surfactant, a fatty acid, or the like may be used as needed, and two or more of these conductive powders may be mixed and used. In any case, the conductive powder of the present invention contains nickel as the main component.

[0016] In this specification, the term "main component" means that the component in question accounts for more than 50% by mass of the total. In other words, "conductive powder containing nickel as the main component" is synonymous with "conductive powder containing more than 50% by mass of nickel." Furthermore, in this specification, numerical ranges expressed using the symbol "to" are inclusive unless otherwise specified. For example, the expression "10 to 20" means a numerical range of 10 or more and 20 or less.

[0017] The particle size of the conductive powder can be in the range widely used in sintered conductive pastes. However, in order to form a dense, flat and highly smooth conductive film, the average particle size D ５０ It is preferable to use fine powder having an average particle size D in the range of 0.05 μm to 1.0 μm. ５０ is the cumulative number of particles in the particle size distribution based on the number obtained by analyzing an image acquired by a scanning electron microscope (SEM), which corresponds to 50% by number from the smallest particle size. ５０ The particle size of the conductive powder is particularly the average particle size D ５０ is preferably in the range of 0.1 μm or more and 0.5 μm or less.

[0018] (Binder Resin) In the present invention, an acrylic resin is used as the binder resin. The acrylic resin used has an acid value in the range of 0 mgKOH / g to 10 mgKOH / g. Acrylic resins with an acid value in the range of 0 mgKOH / g to 10 mgKOH / g have particularly high thermal decomposition properties, and are easily thermally decomposed uniformly and scattered even when the coating area is large. This is thought to contribute to making the surface of the flat conductor film flat and smooth. If a resin other than an acrylic resin or an acrylic resin with an acid value greater than 10 mgKOH / g is used, defects such as cracks, delamination, undulations on the surface of the conductor film, and minute irregularities are likely to occur in the conductor film obtained by firing, and the flat conductor film desired by the present invention cannot be obtained.

[0019] As long as the acid value of the acrylic resin is within the above range, a partially modified acrylic resin may be used.

[0020] Furthermore, as long as the effects of the present invention are not impaired, the binder resin may be a mixture of the above-mentioned acrylic resin with a cellulose-based resin such as ethyl cellulose or hydroxyethyl cellulose, a methacrylic resin, a butyral resin, an epoxy resin, a phenolic resin, or a rosin. As is well known in the art, mixing appropriate amounts of multiple binder resins can sometimes improve the properties of a conductive paste. However, to fully enjoy the effects of the present invention, the amount of acrylic resin contained in the binder resin is preferably as high as possible, and is preferably 90% by mass or more, and particularly preferably 100% by mass.

[0021] The blending amount of the acrylic resin is preferably 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the conductive powder. By blending the acrylic resin in an amount of 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the conductive powder, the strength of the coating film after printing can be increased, and damage to the smoothness of the conductive film due to scratches during handling of the coating film can be prevented, and since the amount of carbon remaining in the coating film after degreasing is small, the occurrence of defects such as cracks and delamination can also be suppressed.

[0022] (Organic Solvent) In the present invention, the organic solvent to be blended into the conductive paste is an alcohol-based solvent that dissolves the acrylic resin, has 3 or more carbon atoms, and has a boiling point of 300° C. or less. By using an alcohol-based solvent that satisfies these conditions in the present invention, the acrylic resin can be sufficiently dissolved, drying is rapid during coating, resulting in excellent productivity, and uniform drying of the entire coating film can be easily achieved, resulting in a flat and smooth conductive film.

[0023] Examples of alcohol-based solvents that satisfy the above conditions include octanol, decanol, terpineol, dihydroterpineol, hexanol, 2-ethylhexanol, cyclohexanol, benzyl alcohol, n-butanol, and sec-butanol.

[0024] Using organic solvents other than alcohol-based solvents can worsen the dispersibility of nickel particles, preventing the formation of a flat, smooth conductive film. However, depending on the application, flat conductive films formed using a conductive paste may be laminated with inorganic particle films formed using other inorganic particle pastes. Examples of other inorganic particle pastes include those in which inorganic particles such as glass particles, ceramic particles, silica particles, and alumina particles, or metal particles such as copper, cobalt, and iron, are dispersed in an organic vehicle. A flat coating film similar to the conductive paste is formed using an inorganic particle paste, and then a coating film made from the conductive paste is laminated on top of it. The two are then simultaneously fired to form a laminate. If the organic solvent in the conductive paste dissolves the binder resin in the laminated inorganic particle paste, problems such as deformation or deterioration of the coating film formed using the inorganic particle paste can occur. Therefore, organic solvents other than alcohol-based solvents may be mixed with the conductive paste as long as they do not impair the effects of the present invention.

[0025] As is well known in the art, the above-mentioned problems can be alleviated by mixing multiple organic solvents in appropriate amounts. Examples of other organic solvents include hydrocarbon solvents such as paraffinic hydrocarbons, olefinic hydrocarbons, naphthenic hydrocarbons, aromatic hydrocarbons, petroleum hydrocarbons (mineral spirits), and mixtures thereof, as well as ethers, esters, ketones, and glycols.

[0026] The amount of alcohol-based solvent in the conductive paste can be adjusted as appropriate depending on the properties of the conductive powder, the type of resin, the coating method, the coating film thickness, etc., but is preferably 10 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the conductive powder. If the amount of alcohol-based solvent is within the above-mentioned range, printability during coating is good, and the problem of the conductive powder settling within the conductive paste and resulting in compositional non-uniformity can be suppressed.

[0027] (Water Content in Conductive Paste) As mentioned above, alcohol-based solvents are used as the organic solvent for conductive pastes. However, because alcohol-based solvents have a high affinity for water, they often contain moisture unintentionally. According to the research of the present inventors, if the water content in the conductive paste in the present invention is 0.50% by mass or more, undulations will occur on the surface of the conductor film after firing, making it difficult to obtain a flat and smooth conductor film. Although the reason for this is unclear, the present inventors speculate that a high water content reduces the solubility of the acrylic resin in the conductive paste, thereby reducing the fluidity of the conductive paste. Therefore, the water content in the conductive paste in the present invention must be less than 0.50% by mass.

[0028] There are no particular limitations on the method for controlling the amount of moisture in the conductive paste, and widely known methods can be used. For example, this can be achieved by making improvements to the manufacturing process to prevent the conductive paste from coming into contact with the air as much as possible, or by removing moisture from gases that the conductive paste may come into contact with.

[0029] In the present invention, it is desirable that the moisture content in the conductive paste is zero (i.e., not contained), but controlling the moisture content to completely eliminate the moisture content leads to high costs. Therefore, in the present invention, the moisture content in the conductive paste must be less than 0.50 mass%, preferably less than 0.30 mass%, and particularly preferably less than 0.25 mass%.

[0030] (Other Additives) In addition to the components described above, the conductive paste of the present invention may contain various additives that are typically added to conductive pastes. For example, surfactants and chelating agents are preferably added alone or in combination with two or more thereof for the purposes of improving the dispersibility of inorganic powders such as conductive powders and ensuring long-term stability of the viscosity of the conductive paste and appropriate flow characteristics during printing.

[0031] Examples of surfactants that can be used include allyl polyethers such as polyethylene glycol allyl ether and methoxypolyethylene glycol allyl ether, and copolymers thereof; polyalkylene glycol amines such as polyethylene glycol laurylamine and polyethylene glycol stearylamine; phosphate esters such as polyethylene glycol alkyl phosphate esters; polyalkylene glycol phenols such as polyethylene glycol nonylphenyl ether; sorbitan esters such as sorbitan monolaurate, sorbitan monooleate, and sorbitan trioleate; sorbitan ester ethers such as polyethylene glycol sorbitan monolaurate and polyethylene glycol sorbitan monooleate; fatty acids such as oleic acid and lauric acid; and amides such as oleic acid amide, stearic acid amide, and polyethylene glycol alkylamide.

[0032] Examples of the chelating agent include the polyalkylene glycol amines and amides, as well as triethanolamine, diethanolamine, alkylamine, 3-butoxypropylamine, and 2-aminopropanol.

[0033] In addition, the conductive paste may contain other components that can be normally blended into a conductive paste, such as glass, alumina, silica, metal oxides such as copper oxide, manganese oxide, and titanium oxide, inorganic powders such as ceramics and montmorillonite, organic metal compounds, plasticizers, etc., depending on the purpose, and among these, it is particularly preferable to blend ceramic powder.

[0034] In addition, in the case of conductive pastes for forming internal electrode layers, a commonly known technique is to blend powders called "co-materials" that have the same or similar composition as the ceramic layers in order to make the shrinkage behavior of the paste during firing similar to that of the surrounding unfired ceramic layers (ceramics green sheets).

[0035] On the other hand, since the present invention does not assume the co-firing of the conductive paste with a ceramic, glass, or other substrate, it is not necessary for the conductive paste for forming internal electrodes to contain co-materials, which are almost indispensable. However, the inventors' studies have revealed that, in forming a thick, large, flat, and smooth flat conductor film, adding fine ceramic powder to the conductive paste increases the strength of the resulting flat conductor film. Therefore, in the present invention, it is preferable to add fine ceramic powder to the conductive paste. Although the reason for this effect is unclear, adding ceramic powder reduces the grain size of the conductive powder in the film, and the smaller the grain size, the greater the strength of the resulting conductor film. Therefore, in the present invention, grain size can be used as an index for evaluating film strength. While the strength of the resulting conductor film is sufficient for practical use even when the grain size is 5.0 μm or more, a grain size of less than 5.0 μm is preferable because it results in a conductor film with higher strength. A more preferable grain size is less than 2.0 μm, and a particularly preferable grain size is less than 1.0 μm.

[0036] Usable ceramic powders include those of the general formula: ABO ３(where A is at least one of Ba, Ca, Sr, Li, La, and K, and B is at least one of Ti, Zr, Hf, Nb, and Al), or a perovskite-type oxide powder having various additives added thereto is preferred. Furthermore, if the particle size of the ceramic powder is too large or too small, it becomes difficult to obtain the effect of the addition. Therefore, it is preferred to use a ceramic powder having a specific surface area of ​​10 m or less as measured by the BET method. ２ / g or more 25m ２ / g or less, and particularly preferably 12m ２ / g or more 25m ２ The amount of ceramic powder mixed in the conductive paste is preferably 3 parts by mass or more and 7 parts by mass or less per 100 parts by mass of the conductive powder.

[0037] Unlike the common material used for internal electrodes, the ceramic powder in the present invention is not intended to control thermal shrinkage behavior, and therefore does not need to have a composition identical to or close to the composition of the substrate to which the conductive paste is applied.

[0038] (Production of Conductive Paste) The conductive paste is produced by a conventional method using a triple roll or the like to uniformly disperse the conductive powder together with other additives in an organic vehicle containing a binder resin and an organic solvent.

[0039] (Formation of Conductive Film) In the present invention, the conductive paste can be suitably used for forming a thick, large-sized, flat conductive film. As an example, a flat coating film can be formed on a desired substrate (substrate) by a known printing method such as screen printing, offset printing, gravure printing, or spin coating, followed by drying at 50°C to 200°C for approximately 0.1 to 20 minutes and then firing at 800°C to 1300°C to form a flat conductive film.

[0040] The flat conductive film may have any shape depending on the application, but as long as it is large enough to accommodate a square with a side length of 3.0 cm, the effects of the present invention can be achieved. In other words, the flat conductive film may be circular, rectangular, or irregular in shape, as long as it is larger than a square with a side length of 3.0 cm and can accommodate one or more such squares. It is particularly preferable for the flat conductive film to have a size and shape large enough to accommodate a square with a side length of 5.0 cm, as this is particularly effective in achieving the effects of the present invention. Furthermore, to obtain a highly conductive film, the thickness should be 0.5 μm or more.

[0041] There are no particular limitations on the upper limit of the thickness and size of the flat conductive film, but according to the findings of the inventors who have conducted numerous experiments, it is possible to form a conductive film with at least one side length of approximately 30 cm and a thickness of approximately 10 μm.

[0042] The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

[0043] In the examples, resins A to I respectively represent the following. [Resin A] Acrylic resin (acid value = 0 mg KOH / g) [Mitsubishi Chemical Corporation: BR-105]; [Resin B] Acrylic resin (acid value = 7.8 mg KOH / g) [Mitsubishi Chemical Corporation: BR-116]; [Resin C] Acrylic resin (acid value = 6.5 mg KOH / g) [Mitsubishi Chemical Corporation: MB-2539]; [Resin D] Acrylic resin (acid value = 0 mg KOH / g) [Mitsubishi Chemical Corporation: BR-107]; [Resin E] Acrylic resin (acid value = 6.5 mg KOH / g) [Mitsubishi Chemical Corporation: MB-8227]; [Resin F] Acrylic resin (acid value = 18 mg KOH / g) [Mitsubishi Chemical Corporation: BR-77]; [Resin G] Ethyl cellulose [Dow Corporation: STD4]; [Resin H] Polyvinyl butyral resin [Sekisui Chemical Co., Ltd.: BLS] [Resin I] Polyvinyl butyral resin [SV02 manufactured by Sekisui Chemical Co., Ltd.]

[0044] The carbon numbers and boiling points of the organic solvents used in this example are as follows: Termineol (carbon number: 10, boiling point: 218°C) 2-ethylhexanol (carbon number: 8, boiling point: 185°C) Benzyl alcohol (carbon number: 7, boiling point: 205°C) Terpineol acetate (carbon number: 12, boiling point: 220°C) Butyl carbitol acetate (carbon number: 10, boiling point: 247°C) Dipropylene glycol dimethyl ether (carbon number: 8, boiling point: 171°C)

[0045] <Experiment 1> (Example 1) The average particle diameter D of 100 particles in the field of view was measured by SEM observation. ５０ A conductive paste was prepared by kneading 100 parts by weight of spherical nickel powder with a particle size of 0.2 μm with 5 parts by weight of resin A and 50 parts by weight of terpineol using a three-roll mill in a dry room. A ceramic substrate with a flat surface was prepared, and the resulting conductive paste was printed on the ceramic substrate using a wire bar to form a coating film with a thickness of 3 μm and a flat square shape with sides of 5 cm after firing. The formed coating film was then heated at 100°C for 10 minutes to dry, and then heated at a heating rate of 5°C and fired at a maximum temperature of 1000°C for 120 minutes to form a flat conductive film.

[0046] Examples 2 to 5 Flat conductive films were formed in the same manner as in Example 1, except that the resin A used in Example 1 was changed to one shown in Table 1.

[0047] Examples 6 and 7 Flat conductive films were formed in the same manner as in Example 1, except that the organic solvent used in Example 1 was changed to one shown in Table 1.

[0048] Comparative Example 1 A flat conductive film was formed in the same manner as in Example 1, except that the water content was not controlled when preparing the conductive paste.

[0049] Comparative Examples 2 to 5 Flat conductive films were formed in the same manner as in Example 1, except that the resin A used in Example 1 was changed to one shown in Table 1.

[0050] <Analysis and Evaluation> A portion of each of the conductive pastes prepared in Examples 1 to 7 and Comparative Examples 1 to 5 was heated at 200° C., and the amount of water recovered was measured by the Karl Fischer method. The measurement results are also shown in Table 1.

[0051] The surface of each flat conductor film obtained in Examples 1 to 7 and Comparative Examples 1 to 5 was observed with a white light interference microscope (Contour GT manufactured by Bruker) to measure the height difference of the surface. If the height difference of the surface was less than 0.5 μm, it was rated as A, if the height difference was 0.5 μm or more but less than 1.0 μm, it was rated as B, and if it was 1.0 μm or more, it was rated as C. A rating of A is most preferable, and a rating of B is practically usable. The evaluation results are also shown in Table 1.

[0052]

[0053] <Experiment 2> (Comparative Examples 6 to 8) Conductor films were formed and analyzed in the same manner as in Example 1, except that the organic solvent used in Example 1 was changed to one shown in Table 2. The results are shown in Table 2.

[0054]

[0055] <Experiment 3> (Examples 8 to 11) Conductor films were formed in the same manner as in Example 1, except that the size and thickness of the flat conductive film to be formed were changed to the values ​​shown in Table 3, and analytical evaluation was carried out in the same manner. The results are shown in Table 3.

[0056]

[0057] <Experiment 4> (Examples 12 to 18) Conductor films were formed in the same manner as in Example 1, except that the ceramic powders shown in Table 4 were added to the conductive paste of Example 1, and the grain size of the nickel powder was evaluated. Note that the grain size was determined by observing the surface of the conductor film with a scanning electron microscope (SU-8020), measuring the longest grain size of five randomly selected crystals, and averaging these values. The results are shown in Table 4, along with those of Example 1.

[0058]

Claims

1. Nickel is the main component, and the average particle size is D ５０ a step of preparing a sinterable conductive paste containing: a conductive powder having a particle size in the range of 0.05 μm to 1.0 μm; an acrylic resin having an acid value in the range of 0 mgKOH / g to 10 mgKOH / g; an alcohol-based solvent having 3 or more carbon atoms and a boiling point of 300° C. or less, capable of dissolving the acrylic resin; and a ceramic powder of a perovskite-type oxide powder having a specific surface area in the range of 10 m 2 / g to 25 m 2 / g and represented by the general formula: ABO 3 (wherein A is at least one of Ba, Ca, Sr, Li, La, and K, and B is at least one of Ti, Zr, Hf, Nb, and Al), and the internal moisture content is controlled to less than 0.50 mass %; A step of applying the sintered conductive paste onto a surface of a substrate to form a flat film having a shape capable of containing a square having at least one side of 3.0 cm and a thickness of 0.5 μm or more; a step of drying the flat film formed on the substrate and firing the flat film at 800° C. or more and 1300° C. or less to form a conductor film in which the grain size of the conductive powder in the film is less than 5.0 μm; A method for forming a flat conductive film comprising the steps of:

2. 2. The method for forming a flat conductive film according to claim 1, wherein a flat conductive film having a shape capable of containing a square with at least one side of 5.0 cm and a thickness of 0.5 [mu]m or more is formed.

3. 3. The method for forming a flat conductive film according to claim 1, wherein the amount of the acrylic resin in the fired conductive paste is 1 part by mass to 10 parts by mass to 100 parts by mass of the conductive powder.

4. 3. The method for forming a flat conductive film according to claim 1, wherein the amount of the alcohol-based solvent in the fired conductive paste is 10 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the conductive powder.

5. 3. The method for forming a flat conductive film according to claim 1, wherein the sinterable conductive paste contains 3 parts by mass or more and 7 parts by mass or less of the ceramic powder with respect to 100 parts by mass of the conductive powder.