JP5828851B2 - Photosensitive paste - Google Patents

Description

  The present invention relates to a photosensitive paste used for manufacturing a wiring conductor, and a ceramic electronic component including a wiring conductor manufactured using the paste.

  An electronic component such as a multilayer chip inductor includes a circuit board on which a film-like conductor (wiring conductor) having a predetermined pattern is formed on a base material. In recent years, such inductors have been desired to have low loss as well as downsizing and high performance. That is, it is required to further refine the internal wiring conductor pattern without degrading the inductance characteristics. For this purpose, for example, it is considered effective to narrow the space between lines while maintaining the film thickness and line width of the wiring conductor, or simply increase the film thickness of the electrode. However, in the screen printing method conventionally used for the production of the wiring conductor, a high-resolution wiring conductor (for example, a wiring whose line width and space (line and space: L / S) shown in FIG. 2 are finer than 40 μm / 40 μm). It is difficult to pattern the conductor) with high accuracy. In addition, such a method may deteriorate high frequency characteristics and inductance characteristics.

Therefore, in recent years, a method (typically photolithography) using a paste containing a photopolymerizable substance and a conductive material (hereinafter referred to as “photosensitive paste”) to produce a wiring conductor using a photochemical action. Method) is preferably used.
In such a method, a photosensitive paste prepared in advance is first applied on a substrate and dried. Next, the applied paste is exposed and cured (reacted). At this time, a wiring circuit having a desired pattern can be drawn by controlling the exposure portion using a photomask or the like. Thereafter, the uncured portion shielded from light by the photomask is removed by corrosive cleaning with an etching solution (for example, inorganic alkali). Finally, by baking such a substrate at a predetermined temperature, a cured portion, that is, a patterned photocured film is produced (baked) on the surface of the substrate. According to this method, a conductor (wiring conductor) having a fine pattern can be relatively easily produced on the substrate. For example, Patent Documents 1 to 6 disclose photosensitive pastes suitable for such applications.

JP 2000-040878 A JP 2003-31080 A JP 2007-250253 A JP 2009-062525 A JP 2004-264655 A JP-A-7-216272

However, according to the study by the present inventors, when a ceramic green sheet (unfired porous ceramic) containing ceramic powder and resin is used as a base material, a wiring conductor can be produced with an existing photosensitive paste. It was difficult. When this cause is analyzed in detail, the photosensitive paste (typically, the photopolymerizable substance contained in the photosensitive paste) penetrates into the green sheet immediately after application, and the photopolymerizable substance is exposed and cured. Was found not to remain sufficiently on the green sheet.

  This invention is made | formed in view of this point, The objective is to provide the photosensitive paste which can be patterned with high resolution on a green sheet. Another related object is to provide a method for producing a finely patterned wiring conductor.

The present inventors have studied the materials contained in this type of photosensitive paste from various angles, and as a result, by using a specific photopolymerizable substance, the penetration of the photosensitive paste into the green sheet is suppressed. The present invention has been completed.
By this invention, the photosensitive paste used in order to produce a wiring conductor is provided. Such a paste contains silver-based metal particles containing silver or a silver-based alloy and an organic vehicle. The organic vehicle contains a photopolymerizable substance as an essential component. The photopolymerizable substance is mainly composed of a polyfunctional acrylate monomer having 5 or more functional groups per molecule.

  Since the photosensitive paste disclosed here has suppressed penetration into the green sheet, the photopolymerizable substance necessary for the production of the wiring conductor should be suitably left on the green sheet until exposure and curing. Can do. Therefore, a conductor (wiring conductor) having a predetermined pattern can be accurately produced on the green sheet by a method based on a photochemical action (typically, a photolithography method). Furthermore, since the cured product of the polyfunctional acrylate monomer has high adhesiveness (adhesive strength) to the substrate, a wiring conductor excellent in reliability and durability can be realized.

In a preferred embodiment disclosed herein, the photopolymerizable substance includes a polyfunctional acrylate monomer having a pentafunctional group and a polyfunctional acrylate monomer having a hexafunctional group. And the volume ratio of the monomer which has the said 5 functional group, and the monomer which has the said 6 functional group is monomer which has 5 functional group: monomer which has 6 functional group = 30: 70-50: 50.
Since the paste having such a configuration further suppresses the penetration into the green sheet, for example, the pattern of L / S is finer than 30 μm / 30 μm (preferably L / S is finer than 25 μm / 25 μm). The wiring conductor can be accurately produced on the substrate. Therefore, the object of the present application can be achieved at a higher level.

In a preferred embodiment disclosed herein, the photopolymerizable substance includes a urethane-type acrylate monomer in which polyfunctional acrylate monomers having pentafunctional groups are bonded to each other by urethane. The proportion of the urethane-type acrylate monomer in the entire photopolymerizable material is preferably 40% by volume to 60% by volume.
Since the paste having such a configuration further suppresses the penetration into the green sheet, for example, a finely patterned wiring conductor having an L / S of 20 μm / 20 μm (preferably L / S of 15 μm / 15 μm) is also suitable. Can be produced. Furthermore, by including a urethane-type acrylate monomer, the wiring conductor can be made more excellent in stretchability and flexibility, and problems caused by disconnection of the wiring conductor can be suppressed.

In a preferred embodiment disclosed herein, the polyfunctional acrylate monomer having a cyclic structure in the side chain is included as the photopolymerizable substance.
By having a cyclic structure in the side chain, curability (reactivity) during exposure can be further improved. Therefore, the effect of the present invention can be exhibited at a higher level.

In a preferred embodiment disclosed herein, the silver-based metal particles have a form in which a silver-based metal material serving as a core is coated with a ceramic material.
By using the paste having such a configuration, the difference in shrinkage from the base material can be reduced, and a wiring conductor having excellent heat resistance can be produced. Therefore, the effect of the present invention can be exhibited at a higher level.

In a preferred embodiment disclosed herein, the proportion of the photopolymerizable substance is 0.1 to 30 parts by mass when the proportion of the silver-based metal particles is 100 parts by mass.
By using the paste having such a configuration, a wiring conductor having high electronic conductivity can be accurately produced. Therefore, the effect of the present invention can be exhibited at a higher level.

  As another aspect of the present invention, a method for producing a film-like conductor is provided. Such a production method includes the following steps: preparing the photosensitive paste disclosed herein; applying the photosensitive paste on a ceramic green sheet; applying a photomask to the ceramic green sheet to which the photosensitive paste is applied. Irradiating with light to cure the photopolymerizable substance in a predetermined pattern; etching the ceramic green sheet irradiated with the light; firing the ceramic green sheet after the etching process To do. According to such a method, a wiring conductor having a fine pattern can be produced relatively easily and accurately.

Moreover, the ceramic electronic component provided with the conductor produced by the said method is provided.
As described above, the wiring conductor produced using the photosensitive paste disclosed herein has reduced defects such as disconnection and peeling. Therefore, the ceramic electronic component provided with such a wiring conductor can realize improvement in high frequency characteristics and inductance characteristics.

  In the present specification, “ceramic electronic component” refers to an electronic component having an amorphous ceramic substrate (glass ceramic substrate) or a crystalline (that is, non-glass) ceramic substrate in general. For example, a chip inductor having a ceramic base material, a high frequency filter, a ceramic capacitor, a low temperature fired multilayer ceramic base material (LTCC base material), a high temperature fired multilayer ceramic base material (High Temperature Co-fired) Ceramics Substrate (HTCC substrate) and the like are typical examples included in the “ceramic electronic component” defined in this specification.

Examples of the ceramic material constituting the ceramic substrate include zirconium oxide (zirconia: ZrO ₂ ), magnesium oxide (magnesia: MgO), aluminum oxide (alumina: Al ₂ O ₃ ), silicon oxide (silica: SiO ₂ ), and oxidation. Oxide materials such as zinc (ZnO), titanium oxide (titania: TiO ₂ ), cerium oxide (ceria: CeO ₂ ), yttrium oxide (yttria: Y ₂ O ₃ ), barium titanate (BaTiO ₃ ); light _{(2MgO · 2Al 2 O 3 ·} 5SiO 2), mullite _{(3Al 2 O 3 · 2SiO 2} ), forsterite (2MgO · _SiO 2), steatite (MgO · _SiO 2), sialon _{(Si 3} N 4 -AlN -Al ₂ O ₃ ), zircon (ZrO ₂ .SiO ₂ ), fluorine Composite oxide materials such as cerite (M ₂ O · Fe ₂ O ₃ ); nitride materials such as silicon nitride (silicon nitride: Si ₃ N ₄ ) and aluminum nitride (aluminum nitride: AlN); silicon carbide Carbide materials such as (silicon carbide: SiC); hydroxide materials such as hydroxyapatite; elemental materials such as carbon (C) and silicon (Si); or inorganic composite materials containing two or more of these; Can be mentioned.

1 is a partial cross-sectional view schematically showing a multilayer chip inductor according to one embodiment. It is a perspective view which shows typically the wiring conductor formed on the base material.

  Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than matters particularly mentioned in the present specification (for example, the composition of the photosensitive paste) and matters necessary for the implementation of the present invention (for example, the manufacturing process of the electronic component) are conventional in the field. It can be grasped as a design matter of those skilled in the art based on the technology. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

≪Photosensitive paste≫
The photosensitive paste according to the present invention includes silver-based metal particles containing silver or a silver-based alloy and an organic vehicle containing a photopolymerizable substance as an essential component. And the said photopolymerizable substance is characterized by comprising mainly the polyfunctional acrylate monomer which has 5 or more functional groups per molecule. Therefore, it does not specifically limit about another component, It can determine arbitrarily in light of a various reference | standard, A various component can be mix | blended or the composition can be changed.
Hereinafter, the material etc. which comprise the photosensitive paste disclosed here are demonstrated.

<Silver metal particles>
Silver-based metal particles containing silver or a silver-based alloy is a conductive substance for imparting conductivity to a conductor (wiring conductor). Examples of the silver-based metal material include silver (Ag); an alloy of silver and a platinum group metal such as silver-palladium (Ag-Pd) and silver-platinum (Ag-Pt); silver-copper (Ag-Cu) and the like. An alloy of silver and a low melting point metal can be used.
Such silver-based metal particles can be, for example, in a form in which at least a part of the surface of silver or silver-based metal material as a core is coated with a ceramic material. Alternatively, it may be in the form of a so-called core-shell structure in which the entire surface of the silver-based metallic material is coated with a ceramic material. Although it does not specifically limit as a ceramic material which comprises such a coating | coated part, For example, what was mentioned above as a constituent material of a ceramic base material can be used. Especially, since the silver-type metal particle of the form coat | covered with the zirconium oxide is excellent in heat resistance, the wiring conductor excellent in the high frequency characteristic and the inductance characteristic can be produced. Further, by coating the silver-based metal material with a ceramic material that is the same kind or excellent in affinity with the ceramic material constituting the ceramic base material, the difference in shrinkage from the ceramic base material can be kept small. That is, by combining the shrinkage behavior of the ceramic substrate and the wiring conductor, defects after firing (delamination and pores) can be suppressed, and a high-quality ceramic substrate can be stably realized. The particles having such a form can be produced by a conventionally known method (for example, a reaction between a silver-based metal material and an organic metal compound having a target metal element). Moreover, the coating amount by a ceramic material can be 0.02 mass part-3.0 mass parts with respect to 100 mass parts of silver-type metallic materials, for example.

  The shape of the silver-based metal particles is not particularly limited, and various shapes such as a spherical shape, a scale shape, and a needle shape can be used. In order to obtain good dispersibility and good optical properties of the silver-based metal particles (for example, when such a paste is used as a photosensitive paste, the ease of exposure during pattern formation of a coated wiring conductor) It is preferable to use a spherical one. The shape of the particles can be confirmed using, for example, a general scanning electron microscope (SEM). Specifically, SEM observation is performed on at least 30 or more (for example, 30 to 100) silver-based metal particles, and the determination can be made from the obtained image. In this specification, the term “spherical” refers to a shape including a spherical shape, a rugby ball shape, a polygonal shape, and the like. For example, the longest side of the particle based on the SEM observation result of the 30 or more particles is used. The ratio (so-called aspect ratio: A / B) of the length (A) to the length (B) of the shortest side is 1 or more and 5 or less (preferably 2 or less).

The average particle diameter of the silver-based metal particles is typically 0.1 μm to 10 μm, preferably about 0.1 μm to 5 μm, more preferably about 0.5 μm to 3 μm. If the range of the average particle diameter is greatly exceeded, the denseness of the film-like conductor (wiring conductor) obtained after firing may be lowered. Further, if the average particle size is greatly below the range, the optical characteristics may be deteriorated. As this average particle diameter, for example, in a volume-based particle size distribution measured by a particle size distribution measurement based on a conventionally known laser diffraction / light scattering method, a particle diameter D ₅₀ value corresponding to a cumulative 50% (also referred to as a median diameter). Can be adopted. The specific surface area of the silver-based metal particles, for example, 0.3m ² /g~2.5m ² / g, preferably, to 0.3m ² /g~2.0m ² / g approximately. As the specific surface area, a measurement value by a general nitrogen adsorption method (BET method) can be adopted. When the average particle diameter and / or specific surface area satisfy the above range, for example, the film thickness is 20 μm or less (typically 1 μm to 10 μm), or the line width is 100 μm or less (typically 10 μm to 100 μm, for example 10 μm to 50 μm, preferably Can finely produce a wiring conductor of 10 μm to 30 μm, more preferably 10 μm to 20 μm.

  The proportion of the silver-based metal particles in the entire photosensitive paste is typically 60% by mass to 90% by mass, such as 65% by mass to 85% by mass, preferably 70% by mass to 80% by mass. When satisfying the above range, the wiring conductor can be suitably produced.

<Organic vehicle>
The organic vehicle contains a photopolymerizable substance for imparting photocurability to the wiring conductor as an essential component. In a typical embodiment, in addition to the photopolymerizable substance, a photopolymerization initiator for initiating photopolymerization is contained. Thereby, it is possible to suitably produce a wiring conductor having a fine pattern by utilizing a photochemical action (photocuring action).

  The photopolymerizable substance used here is mainly composed of a polyfunctional acrylate monomer having 5 or more (typically 5 to 10, for example, 5, 6) functional groups per molecule. In other words, 50 mol% or more (typically 90 mol% or more, for example, 95 mol% or more, preferably substantially 100 mol%) of the photopolymerizable substance contained in the photosensitive paste is 2 to 2 carbon-carbon. It is composed of an acrylate monomer having five or more polymerizable functional groups per molecule such as a double bond (C = C). Such a photopolymerizable substance can be suitably left on the green sheet until exposure and curing since the penetration into the green sheet is very small. Therefore, a conductor (wiring conductor) having a predetermined pattern can be accurately produced using a method based on a photochemical action. Furthermore, since the cured product of the polyfunctional acrylate monomer is excellent in adhesion, a wiring conductor excellent in reliability and durability can be realized.

Examples of the polyfunctional acrylate monomer, 5 or more acrylate Royle groups per molecule _{(CH 2 = CH-C (} = O) -) is not particularly limited as long as it is a monomer having, be used alone or two or more it can. For example, dipentaerythritol pentaacrylate (formula (I)), dipentaerythritol hexaacrylate (formula (II)), tripentaerythritol heptaacrylate, tripentaerythritol octaacrylate, tetrapentaerythritol nonaacrylate, tetrapentaerythritol deca An acrylate etc. can be used. The polyfunctional acrylate monomer to be used is preferably selected as appropriate depending on, for example, the type (material, property) of the ceramic green sheet described below.

  In addition, the hydrogen atom which comprises the hydroxyl group (-OH) in the said Formula (I) is a C1-C10 (preferably 1-5) linear or branched alkyl group (For example, a methyl group, An ethyl group, a propyl group, a butyl group, etc.). This applies not only to the dipentaerythritol compound represented by the above formula (I) but also to, for example, a tripentaerythritol compound and a tetrapentaerythritol compound.

  Although the property of a photopolymerizable substance is not specifically limited, For example, a thing with a weight average molecular weight of about 100-10000 (typically 200-5000, for example, 300-2000) can be employ | adopted suitably. Such molecular weight can be measured by a general gel chromatography-differential refractive index detector (Gel Permeation Chromatography-Refractive Index: GPC-RI).

  In a preferred embodiment, the photopolymerizable material has a polyfunctional acrylate monomer having a pentafunctional group and a polyfunctional acrylate monomer having a hexafunctional group. The volume ratio of the pentafunctional acrylate monomer to the hexafunctional acrylate monomer is 30:70 to 50:50. Since the paste containing the photopolymerizable substance having such a configuration is further suppressed from penetrating into the green sheet, the object of the present application can be achieved at a high level. For example, dipentaerythritol pentaacrylate (5 functional groups) represented by the above formula (I) and dipentaerythritol hexaacrylate (6 functional groups) represented by the above formula (II) are 25: 75-60: A photopolymerizable substance containing 40 (more preferably 30:70 to 50:50) can be preferably used. By using such a photopolymerizable substance, for example, photosensitivity capable of accurately producing a wiring conductor having a pattern in which L / S is finer than 30 μm / 30 μm (preferably L / S is finer than 25 μm / 25 μm). A paste can be prepared.

  Alternatively, as a photopolymerizable substance, a monomer obtained by reacting the above acrylate monomer with a polyisocyanate compound (for example, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, etc.), for example, a hydroxyl group in the above formula (I) It is also possible to contain a urethane-type acrylate monomer in which the parts are urethane-bonded (—NH—C (═O) —O—) to each other. By containing a urethane type monomer, penetration into the green sheet can be further suppressed, for example, L / S is finer than 20 μm / 20 μm (preferably L / S is finer than 15 μm / 15 μm). Pattern wiring conductors can also be accurately produced. Moreover, by including a urethane type acrylate monomer, the wiring conductor can be made more excellent in stretchability and flexibility, and thereby problems caused by disconnection of the wiring conductor can be suppressed. The proportion of the urethane type acrylate monomer in the entire photopolymerizable substance is not particularly limited, but it is usually preferably 40% by volume to 60% by volume.

  In one suitable aspect, the said polyfunctional acrylate monomer which has a cyclic structure in a side chain is included as a photopolymerizable substance. Such a polyfunctional acrylate monomer may have further improved curability (reactivity) upon exposure. Therefore, the effect of the present invention can be exhibited at a higher level. The cyclic structure of the side chain is not particularly limited, and examples thereof include monocyclic hydrocarbon rings typified by cycloalkane rings such as cyclopropane ring, cyclohexane ring and cyclooctane ring, and cycloalkene rings such as cyclohexene ring; bicyclo ring and tricyclo ring. A crosslinked hydrocarbon ring such as a ring; a spiro hydrocarbon ring; an aromatic hydrocarbon ring such as a benzene ring or a naphthalene ring; Further, these ring members may contain different elements (heteroatoms), or may be in a form to which a chain hydrocarbon or the like is added.

  To the photopolymerizable substance, a photopolymerizable substance other than the above (for example, an acrylate monomer having 4 or less functional groups) can be added to the extent that the effects of the present invention are not significantly impaired. Specifically, monomers such as triethylene glycol monoacrylate, tetraethylene glycol monoacrylate, triethylene glycol monomethacrylate, tetraethylene glycol monomethacrylate, pentaerythritol triacrylate, and pentaerythritol trimethacrylate can be used.

  The ratio of the photopolymerizable substance in the entire photosensitive paste can be, for example, 0.1% by mass to 20% by mass, preferably 0.5% by mass to 15% by mass. Moreover, in one preferable aspect, when the ratio of the silver-based metal particles is 100 parts by mass, the ratio of the photopolymerizable substance is 0.1 to 30 parts by mass. By using the paste having such a configuration, a wiring conductor having high electronic conductivity can be accurately produced, and the effects of the present invention can be exhibited at a higher level.

  As a photoinitiator, it can use without a restriction | limiting especially from what is used for a conventionally well-known photosensitive paste. For example, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butane-1- One or more of ON, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4-diethylthioxanthone, benzophenone, etc. are used. be able to. Alternatively, a photoreductive dye and a reducing agent can be used in combination.

  The ratio of the photoinitiator to the whole photosensitive paste is 5 mass% or less, for example, Preferably it can be 0.1 mass%-3 mass%. Moreover, the ratio of the photoinitiator with respect to 100 mass parts of said photopolymerizable substances can be 1 mass part-100 mass parts, for example, Preferably it can be 5 mass parts-10 mass parts. By setting it as this range, a conductor can be stably produced by a method based on a photochemical action.

  In a typical example of an organic vehicle, in addition to the above components (that is, a photopolymerizable substance and a photopolymerization initiator), an organic dispersion medium (typically an organic solvent) for dispersing them, and an organic binder (typically Contains an organic polymer).

  As the organic dispersion medium, any organic dispersion medium can be used without particular limitation as long as the essential components can be suitably dispersed. For example, one or more of organic solvents used in conventionally known photosensitive pastes can be appropriately used. More specifically, for example, hydrocarbon solvents such as toluene and xylene; glycol solvents such as ethylene glycol, propylene glycol and diethylene glycol; ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (cellosolve), diethylene glycol mono Glycol ether solvents such as butyl ether (butyl carbitol), diethylene glycol monobutyl ether acetate, dipropylene glycol methyl ether, dipropylene glycol methyl ether acetate, propylene glycol phenyl ether, 3-methyl-3-methoxybutanol; 1,7,7 -Trimethyl-2-acetoxy-bicyclo- [2,2,1] -heptane, 2,2,4-trimethyl-1,3-penta Ester solvents such all-monoisobutyrate; organic solvents, and the like having a high boiling point and other mineral spirits and the like; terpineol, dihydro terpineol, dihydro terpineol propionate, alcohol solvents such as benzyl alcohol.

  Among these, an organic solvent having low permeability to the ceramic green sheet can be particularly preferably employed. Examples of the organic solvent capable of exhibiting such properties include those having a sterically bulky structure (for example, cyclohexyl group, tert-butyl group, etc.) and those having a relatively large molecular weight. In order to perform the etching treatment described later at a low temperature, it is preferable to use a material having a relatively low boiling point (typically a boiling point of 250 ° C. or lower, for example, a boiling point of 220 ° C. or lower). Examples of commercially available organic solvents that satisfy the above properties include Dowanol DPM (trademark) (boiling point: 190 ° C., manufactured by Dow Chemical Company) and Dowanol DPMA (trademark) (boiling point: 209 ° C., manufactured by Dow Chemical Company). ), Mentanol (boiling point: 207 ° C.), mentanol P (boiling point: 216 ° C.), Isopar H (boiling point: 176 ° C., manufactured by Kanto Fuel Co., Ltd.), SW-1800 (boiling point: 198 ° C., manufactured by Maruzen Petroleum Corporation), etc. Is mentioned. Furthermore, for example, an organic solvent having low permeability to the ceramic green sheet and an organic solvent capable of particularly suitably dissolving the material used here can be mixed and used in an arbitrary ratio. Thereby, both properties can be compatible at a high level.

  Although the ratio of the organic solvent to the whole photosensitive paste is not specifically limited, For example, it can be 10 mass%-30 mass%. The multifunctional acrylate monomer used here generally has higher viscosity as the number of functional groups increases. Therefore, the workability and coating properties of the photosensitive paste can be adjusted by adjusting the amount of the organic solvent according to the type of the monomer. Can be improved.

As an organic binder, it can use without a restriction | limiting especially from what is used for a conventionally well-known photosensitive paste. For example, one type of cellulose polymer (cellulose derivative) such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose, hydroxymethyl cellulose, acrylic resin, phenol resin, alkyd resin, polyvinyl alcohol, polyvinyl acetal (typically polyvinyl butyral) or the like Two or more kinds can be used. Among these, an organic binder having high hydrophilicity (typically alkali solubility) can be preferably used. Thereby, in the etching process (typically alkali process) mentioned later, an unhardened part can be removed suitably.
The ratio of the organic binder to the whole photosensitive paste can be 0.1 mass%-10 mass% (preferably 0.5 mass%-6 mass%), for example.

In addition to the above components, various additive components can be added to the photosensitive paste disclosed herein as necessary. Examples thereof include inorganic fillers, polymerization inhibitors (polymerization inhibitors), surfactants, dispersants, thickeners, antifoaming agents, plasticizers, light stabilizers, antioxidants, and pigments. As long as the object of the present invention is not significantly impaired, these additives are not particularly limited as long as they can be used for the preparation of conventionally known photosensitive pastes. For example, ceramic powder (ZnO ₂ , Al ₂ O ₃ , SiO _2, etc.) represented by glass powder (glass frit) can be used as the inorganic filler. Moreover, as a polymerization inhibitor, hydroquinone and its derivative (s) can be used, for example. By adding a suitable amount of a polymerization inhibitor to the photosensitive paste, the stability of the paste can be improved.
The ratio of the additive component to the entire photosensitive paste is preferably 5% by mass or less (preferably 3% by mass or less), for example.

≪Method for producing wiring conductor≫
Further, in this specification, a method for manufacturing a film-like conductor (wiring conductor) using the photosensitive paste disclosed herein is disclosed. The production method of the wiring conductor disclosed here is:
(1. Preparation step) Preparing a photosensitive paste and a ceramic green sheet;
(2. Application step) Applying the photosensitive paste onto the ceramic green sheet;
(3. exposure step) The ceramic green sheet provided with the photosensitive paste is exposed through a photomask to cure (react) the photopolymerizable substance;
(4. Etching treatment step) Etching the exposed ceramic green sheet; and
(5. Firing step) Firing the ceramic green sheet after the etching treatment;
Is included. According to such a method, a wiring conductor having a fine pattern can be produced relatively easily and accurately. Hereinafter, each process is demonstrated in order.

<1. Preparation process>
In the production method disclosed herein, first, a photosensitive paste and a ceramic green sheet are prepared. The photosensitive paste can be performed by mixing the above-described materials (silver-based metal particles, organic vehicle, optional additives, etc.) so as to have a predetermined content (mass ratio). The mixing of such materials can be performed using various conventionally known stirring and mixing operations, for example, a kneader such as a three-roll mill, a magnetic stirrer, a planetary mixer, a disper, or a roll mill.

  The viscosity of the photosensitive paste is not particularly limited. For example, the viscosity measured by a Brookfield rotational viscometer using a suitable spindle (for example, No. 4 spindle) at a temperature of 25 ° C. and a rotational speed of 100 rpm is It is preferable to prepare so as to be 10 Pa · s to 70 Pa · s (for example, 20 Pa · s to 40 Pa · s). The photosensitive paste satisfying the above range is excellent in workability and handleability, and can form a wiring conductor having a precise pattern more accurately. Therefore, the object of the present application can be achieved at a higher level.

The ceramic green sheet (ceramic base material before firing) is not particularly limited, and if it is a green sheet using a ceramic composition, that is, a ceramic powder (for example, a ceramic material as described above), the conventional ceramic electronic What is used for manufacture of components can be used without a restriction | limiting in particular. For example, a glass ceramic material obtained by adding a high dielectric constant material such as aluminum oxide (alumina: Al ₂ O ₃ ) or barium titanate (BaTiO ₃ ) to silicon oxide (silica: SiO ₂ ), low temperature simultaneous excellent in high frequency characteristics A fired ceramic (Low Temperature Co-fired Ceramics: LTCC) material or the like can be used.

<2. Application process>
In the production method disclosed herein, the photosensitive paste prepared above is applied (applied) at a predetermined thickness (for example, 10 μm) onto a ceramic green sheet. The thickness of application can be changed depending on the number of applications, the viscosity of the paste, and the like. The application of the paste can be performed by techniques such as screen printing, bar coater, slit coater, die coater, comma coater, gravure coater, dip coater, and spray coater. In the production method disclosed herein, after applying the photosensitive paste, for example, using a suitable drying method such as a far-infrared dryer, for example, under a predetermined temperature condition (for example, 50 ° C. to 100 ° C.) for a predetermined time (for example, A drying process is performed for 5 to 30 minutes, and the organic solvent is volatilized from the produced conductor. Thus, a film-like conductor can be manufactured.

<3. Exposure process>
In the manufacturing method disclosed herein, next, a predetermined pattern of the wiring conductor is formed on the manufactured conductor by using a photolithography method. For example, light having a predetermined intensity (for example, 100 mJ / cm ^{2 to} 500 mJ / cm ² , approximately 1 mW / cm ^{2 to} 20 mW / cm ² ) is applied to the conductor through a photomask having a predetermined opening pattern for a predetermined time (for example, 1 Irradiate and expose for 30 minutes). Then, the portion (exposed portion) not covered with the photomask is cured by a curing reaction (photopolymerization reaction) with the photopolymerizable substance, and is firmly bonded (fixed) on the substrate. On the other hand, since the photopolymerization reaction does not occur in the portion (unexposed portion) covered with the photomask, the curing reaction does not occur and is not fixed to the substrate. For the exposure, an exposure device that emits light in a wavelength range of about 10 nm to 400 nm, for example, ultraviolet light such as a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a metal halide lamp, or a xenon lamp can be used. Alternatively, a method of directly drawing a desired wiring conductor pattern with an X-ray, an electron beam or the like can be used regardless of the method using the photomask.

<4. Etching process>
In the manufacturing method disclosed herein, the exposed ceramic green sheet is then etched. Such treatment can be performed by, for example, a conventionally known spray method, brush method, dipping method, or the like. More specifically, for example, the etching treatment liquid can be sprayed onto the conductor on the ceramic green sheet at a predetermined discharge pressure. The etching treatment liquid is not particularly limited as long as it is a solution that can dissolve the organic binder used in the preparation of the photosensitive paste, and can be appropriately used. For example, when a compound having an acidic group such as a carboxyl group is present in the photosensitive paste, an alkaline aqueous solution can be suitably used. As a result, only the unexposed portion having high solubility in the etching processing solution is selectively washed away (removed), and the exposed portion of the predetermined pattern remains. In this way, a wiring conductor patterned with high accuracy can be formed.

  As the alkaline aqueous solution, an inorganic alkaline aqueous solution such as sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate, and an organic alkaline aqueous solution such as amines such as triethylamine and pyridine can be used. The concentration of the aqueous solution can be, for example, 0.1% by mass to 5% by mass (typically 0.1% by mass to 1% by mass). When satisfy | filling the said range, an unexposed part can be removed suitably and corrosion of a ceramic green sheet can be suppressed. In addition, when the photosensitive paste is applied so that a desired wiring conductor is formed from the beginning in the application step, the etching treatment step can be omitted.

  In a typical example of producing an internal electrode used for an electronic component such as a multilayer chip inductor, a plurality of ceramic green sheets on which the above-mentioned wiring conductors are formed are laminated and bonded to each other, so that the thickness is relatively large (for example, thickness An internal electrode layer (approximately 100 μm to 1500 μm) is produced. Joining between the ceramic green sheets can be performed by isotropically heat-pressing the laminate using, for example, a conventionally known hot water laminator.

<5. Firing step>
In the manufacturing method disclosed herein, the ceramic green sheet after the etching treatment is then fired. Thereby, the organic binder can be removed. The firing conditions can be the same as in the case of firing a conventional wiring conductor, and no special treatment is required. For example, when using the organic binder as described above, the firing temperature (maximum temperature reached) is about 700 ° C. to 1000 ° C. (eg, 800 ° C. to 1000 ° C.), and the firing is performed for a predetermined time (eg, 5 minutes to 60 minutes). It is appropriate to do. The firing means is not particularly limited, and any means such as an electric heating furnace can be adopted. Further, the firing atmosphere is not particularly limited, and for example, firing may be performed in an oxygen-containing atmosphere (for example, air atmosphere), or may be performed in an inert gas atmosphere such as Ar gas as necessary.

Through the series of steps described above, a wiring conductor having a desired pattern can be formed on the substrate. A wiring pattern according to an embodiment is schematically shown in FIG. In the embodiment shown in FIG. 2, a spiral (spiral) wiring conductor 14 is formed on the surface of the ceramic substrate 12.
The wiring conductor 14 produced using the photosensitive paste disclosed here may have a pattern in which, for example, L / S is finer than 30 μm / 30 μm (preferably L / S is finer than 25 μm / 25 μm). . Moreover, the bonding strength to the base material 12 is high, and problems such as disconnection and peeling can be reduced. Therefore, it can be preferably used for forming wiring conductors of ceramic electronic components (for example, multilayer chip inductors, high frequency filters, LTCC base materials, HTCC base materials, etc.) that require miniaturization, high performance, and high reliability. .

Although not intended to be particularly limited, a multilayer chip inductor provided with an internal electrode layer using a photosensitive paste according to an embodiment of the present invention is taken as an example, and FIG. Note that the dimensional relationships (length, width, thickness, etc.) in the drawings do not necessarily reflect actual dimensional relationships.
A multilayer chip inductor 1 shown in FIG. 1 includes an electronic component body 10 and external electrodes 20 provided outside the electronic component body 10. The electronic component body 10 has a configuration in which ceramic base materials (dielectric layers) 12 and ceramic base materials 12 having wiring conductors (internal electrode layers) 14 having a pattern as shown in FIG. 2 are alternately laminated. is there. Such a multilayer chip inductor 1 can be constructed by a conventionally known method.

  Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples.

<Penetration test into ceramic green sheet>
In order to extract a photopolymerizable substance having a suitable residual property on the base material (ceramic green sheet), a penetration test was conducted on various monomers.
Specifically, first, the monomers of Examples 1 to 11 shown in Table 1 below were each adjusted to a concentration of 50 wt% in the organic solvent (here, mentanol) (that is, monomer: organic solvent = 1: 1). Solution) to prepare a solution. After dropping this prepared solution on the surface of a ceramic green sheet (here, a glass ceramic base material containing silicon oxide or aluminum oxide as a main component), the ceramic green sheet is heated with a hot air dryer (temperature). (Setting: 70 ° C.) for 15 minutes. This drying condition is the same as in the production of a wiring conductor described later. And the permeability | transmittance of the monomer was evaluated about the green sheet after drying. The penetrability was evaluated by observing the front and back surfaces of the green sheet using a general scanning electron microscope (SEM). The results are shown in the corresponding column of Table 1. In Table 1, in the test result column, “x” indicates that bleeding was observed at a position where the solution on the surface of the sheet was dropped, or that the penetration of the solution was confirmed on the back surface of the sheet. In addition, “◯” indicates that there was no penetration into the sheet, that is, there was no evidence of penetration as described above.

  From this result, it was found that acrylate monomers having 4 or less functional groups (Examples 1 to 4) have high permeability to the green sheet. On the other hand, acrylate monomers having four or more functional groups (Examples 5 and 6), urethane-type acrylate monomers (Examples 7 to 10), and epoxy monomers (Example 11) have suppressed penetration into the green sheet, It turned out that it can remain suitably on a green sheet even after drying.

<Evaluation of patterning property of wiring conductor>
Next, a photosensitive paste was prepared using various monomers, and the patterning property (resolution) of the wiring conductor was evaluated.
Specifically, first, substantially spherical silver particles (average particle size 1.8 μm, specific surface area 1.2 m ² / g) whose surface is coated with zirconium oxide as silver-based metal particles, and an organic vehicle are prepared (preparation) )did. As the organic vehicle, monomers shown in Examples 12 to 22 of Table 2 as photopolymerizable substances, Irgacure 369 (registered trademark) (manufactured by Ciba Specialty Chemicals Co., Ltd.) as a photopolymerization initiator, and organic binders A cellulose polymer having a carboxyl group (—COOH) and an acrylic resin dissolved in a mixed solvent of dipropylene glycol methyl ether acetate and dihydroterpineol as an organic solvent were used. The final paste blending ratio is 75% by mass of silver-based metal particles, 10% by mass of the photopolymerizable material, 0.5% by mass of the photopolymerization initiator, 5% by mass of the organic binder, and the balance being an organic solvent. The above raw materials (materials) were weighed and all the materials were kneaded using a kneader (three roll mill). Thereby, the photosensitive paste (Examples 12 to 22) having a viscosity of 20 Pa · s to 40 Pa · s was prepared.

Next, using the 11 types of photosensitive pastes (Examples 12 to 22) obtained above, wiring conductors were produced as follows. First, the 11 types of photosensitive pastes were applied in a film form on a commercially available ceramic green sheet using a stainless steel screen “SUS # 200-325, poly # 200-255”. Then, the drying process for 15 minutes was performed at 60 degreeC with the hot air type dryer, and the conductor was produced on the green sheet.
Then, a photomask was put on the green sheet, and exposure was performed with an exposure machine at an intensity of 300 mJ / cm ² , and the conductor was cured so as to have a predetermined pattern. Here, seven kinds of resolutions (that is, L / S are 100 μm / 100 μm, 80 μm / 80 μm, 60 μm / 60 μm, 30 μm / 30 μm, 25 μm / 25 μm, 20 μm / 20 μm, 15 μm / 15) are prepared by adjusting the interval of the printing plate. A conductor of 15 μm) was formed. After the exposure, 0.4% by mass of Na ₂ CO ₃ solution is sprayed on the green sheet at a predetermined discharge pressure, an excess (uncured) conductor portion is etched, and then washed with pure water for 15 seconds. And dried. Thus, conductors (wiring conductors) having a pattern in which a plurality of lines as shown in FIG. 2 are arranged at a predetermined line width and interval were produced.

  About the produced wiring conductor, the situation of damage, such as peeling, disconnection, and destruction, was observed, and the patterning property (adhesion between each wiring conductor and the substrate) was evaluated from the situation of the damage. The results are shown in the column “L / S” in Table 2. In this column, “○” indicates that the wiring conductor was not peeled off from the base material or was disconnected, “△” indicates that some wiring conductors were peeled off from the base material, and “×” indicates wiring. It represents that the conductor was not formed on the base material, or peeled off from the base material after formation. In addition, the ratio of the functional group in Table 2 is based on the content ratio (vol%) of the monomer species published by each reagent manufacturer.

  As shown in Table 2, in Example 12, even when the line width was the widest (L / S was 100 μm / 100 μm), it was difficult to produce a conductor. As a cause of this, it was considered that the penetrability of the photopolymerizable material into the green sheet was high from the result of the penetration test into the ceramic green sheet. In addition, although the example of trifunctional group was described in Example 12, the same result was obtained also about the acrylate monomer of other 1-4 functional groups as described in Examples 1-4 of Table 1. In addition, it was difficult for the epoxy monomer of Example 22 to accurately produce a predetermined pattern when L / S was finer than 30 μm / 30 μm. This may be because the wiring conductor was peeled off during the manufacturing process (typically etching treatment) due to low adhesion to the substrate.

  On the other hand, with the acrylate monomer having five or more functional groups as in Examples 13 to 21, it was possible to accurately produce a wiring conductor having a pattern whose L / S was finer than 30 μm / 30 μm. Furthermore, when the volume ratio of the monomer having 5 functional groups and the monomer having 6 functional groups is 30:70 to 50:50, the wiring with a finer pattern in which L / S is finer than 25 μm / 25 μm. The conductor could also be produced with high adhesion strength. An acrylate monomer as in Example 18 and Example 19 (that is, an acrylate containing a urethane type acrylate monomer in which polyfunctional acrylate monomers having five functional groups are urethane-bonded to each other in a proportion of 40% by volume to 60% by volume) Monomer) was able to produce a wiring conductor having a finer pattern with L / S finer than 20 μm / 20 μm with high adhesion strength. In particular, with the urethane-type acrylate monomer having the cyclic structure (here, phenyl group) of Example 19, a pattern with L / S of 15 μm / 15 μm could be accurately produced. The above results show the difference between the present application and the prior art.

  Although the present invention has been described in detail above, these are merely examples, and the present invention can be variously modified without departing from the gist thereof.

1 Multilayer chip inductor (electronic component)
10 Electronic component body 12 Ceramic substrate (dielectric layer)
14 Wiring conductor (internal electrode layer)
20 External electrode

Claims (8)

A photosensitive paste used to produce a wiring conductor,
A silver-based metal particle containing silver or a silver-based alloy, and an organic vehicle,
The organic vehicle contains a photopolymerizable substance as an essential component,
The photopolymerizable substance is mainly composed of a polyfunctional acrylate monomer having at least 5 H ₂ C═CH—C (═O) groups per molecule, and
The polyfunctional acrylate monomers comprise five _{H 2 C = CH-C (} = O) urethane type acrylate monomers 5 functional acrylate monomer having a group formed by urethane bond to one another, photosensitive paste. The polyfunctional acrylate monomer, and 5 functional acrylate monomer with five _{H 2 C = CH-C (} = O) group, a 6-functional acrylate monomer having six _{H 2 C = CH-C (} = O) group The photosensitive paste according to claim 1, wherein the volume ratio is pentafunctional acrylate monomer: hexafunctional acrylate monomer = 30: 70 to 50:50.   The photosensitive paste of Claim 1 or 2 whose ratio of the said urethane type acrylate monomer to the said whole photopolymerizable substance is 40 volume%-60 volume%.   The photosensitive paste as described in any one of Claims 1-3 containing the said polyfunctional acrylate monomer which has a cyclic structure in a side chain as the said photopolymerizable substance.   The photosensitive paste according to any one of claims 1 to 4, wherein the silver-based metal particles are in a form in which a silver-based metal material serving as a core is coated with a ceramic material.   The photosensitivity as described in any one of Claims 1-5 whose ratio of the said photopolymerizable substance is 0.1-30 mass parts when the ratio of the said silver-type metal particle is 100 mass parts. Sex paste. A method for producing a film-like conductor comprising:
Preparing the photosensitive paste according to claim 1;
Applying the photosensitive paste onto a ceramic green sheet;
Irradiating the ceramic green sheet provided with the photosensitive paste with light through a photomask to cure the photopolymerizable material in a predetermined pattern;
Etching the ceramic green sheet irradiated with the light; and firing the ceramic green sheet after the etching;
A method for producing a conductor, including: The ceramic electronic component provided with the conductor film which consists of a sintered body of the photosensitive paste in any one of Claims 1-6 .

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