Method for forming a flat conductive film

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

[Technical Field]

[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. [Background technology]

[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 the wiring and electrodes of circuit boards.

[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 applications mentioned above because they can produce relatively thick film conductors. In addition, because they are capable of printing specific patterns, they have also come to be widely used in recent years for forming electrodes on 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 conductive films (coating films). Such flat conductive films are sometimes called "surface conductive 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, large flat conductive films, such as those containing a square with sides of 3.0 cm or more, have typically been formed using sputtering, vapor deposition, plating, or other methods (see, for example, Patent Document 1). These manufacturing methods facilitate the production of uniform film thicknesses, even when forming large flat conductive films, and can easily produce flat and smooth conductive films. However, these manufacturing methods are cost-intensive due to the large scale of production equipment, and the resulting thin conductive films are difficult to obtain with high conductivity compared to thick-film conductors. While highly conductive conductive films can be obtained by stacking multiple layers of thin films obtained using these 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 a method in which nickel ink, in which nickel particles with an average primary particle size of 10 nm to 30 nm are dispersed in a dispersion medium, is applied 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 this is dispersed in ethyleneamine. Because ethyleneamine is viscous and sticky, it is described as being able to produce a 3.66 μm thick conductive film despite not containing 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 nearly 30 times thicker (100 μm) must be formed to achieve a 3.66 μm film thickness. Therefore, when a large, flat conductive 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, making it difficult to obtain a flat, smooth conductive film. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-006228 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-146117 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-151512 Summary of the Invention [Problem to be solved by the invention]

[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, 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-sized, flat and smooth flat conductor film (surface conductor film) using a baked conductive paste containing a binder resin. [Means for solving the problem]

[0012] The above objectives are achieved by the following: (1) A method for forming a flat conductive film on a substrate using a sintered 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, The sinterable conductive paste contains the following components a to c, and the amount of water contained in the sinterable conductive paste is less than 0.50 mass %, a: Nickel is the main component, and the average particle size is D 50 Conductive powder with a particle size in the range of 0.05 μm to 1.0 μm b: Acrylic resin with an acid value in the range of 0 mg KOH / g to 10 mg KOH / g c: 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; a step of applying the sintered conductive paste to a surface of a substrate to form a flat film; a step of drying and baking the flat film formed on the substrate to form a conductor film; A method for forming a flat conductive film, comprising: (2) The method for forming a flat conductive film according to (1) above, which forms 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 μm or more. (3) The method for forming a flat conductive film according to (1) or (2) above, wherein the amount of the acrylic resin in the baked 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) A 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 fired conductive paste is 10 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the conductive powder. (5) The sintered conductive paste has a specific surface area of ​​10 m 2 / g or more 25m 2 The method for forming a flat conductive film according to any one of (1) to (4), wherein the ceramic powder has a molecular weight in the range of 1 / g or less, and the ceramic powder contains 3 parts by mass or more and 7 parts by mass or less per 100 parts by mass of the conductive powder. [Effects of the Invention]

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

[0014] The present invention was achieved by completely redesigning the composition of the conductive paste so that local differences in thermal contraction within the paste during the firing process are minimized, in order to enable the formation of thick, large, flat, and smooth flat conductor films even when using a fired conductive paste containing a binder resin. The details will be explained below, but the present invention is not limited to the examples given below. Hereinafter, the "fired 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 its main component, including pure nickel powder containing 100% nickel, as well as alloy powders containing copper, iron, cobalt, gold, silver, palladium, rhenium, platinum, and 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, surfactant, fatty acid, or the like may also 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 its 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 images acquired with 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 even if the coating area is large, they thermally decompose uniformly and easily scatter, which is thought to contribute to making the surface of the flat conductor film flat and smooth. If a resin other than acrylic resin or an acrylic resin with an acid value greater than 10 mgKOH / g is used, the conductor film obtained by firing is likely to have defects such as cracks, delamination, undulations on the conductor film surface, and minute irregularities, 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, the properties of a conductive paste can sometimes be improved by mixing appropriate amounts of multiple binder resins. 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 blended into the conductive paste is an alcohol-based solvent that dissolves the acrylic resin, has three 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 application, resulting in excellent productivity, and the entire coating film can be dried more uniformly, 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 flat, smooth conductive films. 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 range, printability during coating is good, and problems such as 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 organic solvents for conductive pastes. However, because alcohol-based solvents have a high affinity for water, they often contain moisture unintentionally. According to the inventors' research, if the moisture content in the conductive paste in this 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. While the reason for this is unclear, the inventors speculate that a high moisture content reduces the solubility of the acrylic resin in the conductive paste, thereby reducing the fluidity of the conductive paste. Therefore, the moisture content in the conductive paste in this 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., it does not contain any moisture), 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 added ingredients) In the present invention, in addition to the above components, the conductive paste may contain various additives that are typically incorporated into conductive pastes. For example, surfactants and chelating agents are preferably added alone or in combination to improve the dispersibility of inorganic powders such as conductive powders and ensure the long-term stability of the viscosity of the conductive paste and the 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 order to form thick, large, flat, and smooth flat conductor films, 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 larger, 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, for example, perovskite oxide powders represented by the general formula: ABO3 (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 those containing various additives. In addition, if the particle size of the ceramic powder is too large or too small, the effect of the addition will be difficult to obtain. Therefore, the specific surface area measured by the BET method should be 10 m 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] (Conductive paste manufacturing) 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 to form a thick, large-sized flat conductive film. For 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 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 can 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 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 measuring approximately 30 cm and a thickness of approximately 10 μm. [Example]

[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: STD4] [Resin H] Polyvinyl butyral resin [Sekisui Chemical Co., Ltd.: BLS] [Resin I] Polyvinyl butyral resin [Sekisui Chemical Co., Ltd.: SV02]

[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 size D of 100 particles in the field of view was measured by SEM observation. 50 Spherical nickel powder having a particle size of 0.2 μm was prepared, and 100 parts by mass of the nickel powder was mixed with 5 parts by mass of resin A and 50 parts by mass of terpineol using a three-roll mill in a dry room to prepare a conductive paste. A ceramic substrate with a flat surface was prepared, and the obtained conductive paste was printed on the ceramic substrate using a wire bar so that after firing it would have a thickness of 3 μm and a flat square shape with each side measuring 5 cm, forming a coating film. 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 A flat conductive film was 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 to 7) A flat conductive film was 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) A flat conductive film was 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 of the flat conductor films 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 usable for practical use. The evaluation results are shown in Table 1.

[0052] [Table 1]

[0053] <Experiment-2> (Comparative Examples 6 to 8) A conductor film was 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 2, and analytical evaluation was carried out in the same manner. The results are shown in Table 2.

[0054] [Table 2]

[0055] <Experiment-3> (Examples 8 to 11) A conductive film was 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] [Table 3]

[0057] <Experiment-4> Examples 12 to 18 A conductor film was formed in the same manner as in Example 1, except that the ceramic powder in Table 4 was added to the conductive paste of Example 1, and the grain size of the nickel powder was evaluated. 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 measurements. The results are shown in Table 4, along with those of Example 1.

[0058] [Table 4]

Claims

1. Nickel is the main component, and the average particle size is D ５０ 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 a carbon number of 3 or more and a boiling point of 300° C. or less, capable of dissolving the acrylic resin, and a solvent having a specific surface area of ​​10 m ２ / g or more 25m ２ / g or less, and has 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 a ceramic powder of a perovskite-type oxide powder represented by the formula (I) and a sinterable conductive paste having an internal moisture content controlled to less than 0.50 mass %; a step of applying the sintered conductive paste to a surface of a substrate to form a flat 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; a step of drying the flat film formed on the substrate and firing it at 800°C or higher and 1300°C or lower 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:

2. 2. The method for forming a flat conductive film according to claim 1, wherein the flat conductive film has 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.

3. 3. The method for forming a flat conductive film according to claim 1, wherein the amount of the acrylic resin in the baked 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 baked conductive paste is 10 parts by mass or more and 100 parts by mass or less per 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 the ceramic powder in an amount of 3 parts by mass to 7 parts by mass relative to 100 parts by mass of the conductive powder.

6. A conductive powder containing nickel as a main component and having an average particle size D50 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 or more and 10 mgKOH / g or less; an alcohol-based solvent having 3 or more carbon atoms and a boiling point of 300°C or less, which can dissolve the acrylic resin; a ceramic powder of a perovskite-type oxide powder having a specific surface area in the range of 10 m 2 / g or more and 25 m 2 / g or less 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); The water content in the paste is less than 0.50% by mass.

1. A firing type conductive paste used 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.

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