TW201910449A - Conductive paste - Google Patents

Abstract

The present invention provides a conductive paste capable of forming an electrode which can suppress occurrences of etching of a sheet as well as transmission of conductive powder. According to the present invention, a conductive paste is provided which comprises: a conductive powder, a binder resin, and an organic solvent. The aforementioned organic solvent is a mixed solvent, the mixed solvent comprises a first solvent having a solubility parameter of 9.0 (cal/cm 3) 0.5 or less calculated by Fedor's method, and a second solvent having a solubility parameter of 10.0 (cal/cm3) 0.5 or more calculated by Fedor's method. Furthermore, the solubility parameter of the organic solvent calculated by Fedor's method is 9.0 (cal/cm3) 0.5 or more and 10.1 (cal/cm3) 0.5 or less.

Description

Conductive paste

The present invention relates to a conductive paste.

In the manufacture of electronic components such as inductors and capacitors, there are widely used methods of preparing a conductive paste containing a conductive powder, a binder resin, and an organic solvent, and applying the conductive paste to a green sheet that becomes a raw material by various printing methods. The electrode is formed by drying and firing (see Patent Documents 1 to 4).

Further, as described in Patent Documents 3 and 4, when a conductive paste is applied to a green sheet, a so-called sheet attack (Japanese attack of a sheet attack) may be caused by an organic solvent of the conductive paste to attack the green sheet. If the thickness of the green sheet is locally thinned due to the sheet erosion phenomenon or a hole is formed in the green sheet, it may cause a poor electrode formation and a short circuit. Regarding this phenomenon, for example, Patent Document 3 discloses that a predetermined alkylene glycol dialkyl ether and / or dialkylene glycol dialkyl ether is used as an organic solvent in order to reduce the occurrence of sheet erosion. [Prior Art Literature]

[Patent Document] [Patent Document 1] Japanese Patent Application Publication No. 2010-516603 [Patent Document 2] Japanese Patent Application Publication No. 2012-129447 [Patent Document 3] Japanese Patent Application Publication No. 2012-231119 [Patent Document 4] ] Japanese Patent Application Publication No. 2012-028356

However, according to the study by the present inventors, although a chip erosion phenomenon does not occur, why a short circuit sometimes occurs in an electronic component. The reason for this was analyzed by the present inventors from various angles, and as a result, it was newly discovered that the conductive powder was immersed in the green sheet together with the organic solvent, moved and diffused in the thickness direction in the green sheet, and partially penetrated to the back of the green sheet. Moreover, it has been determined that this causes a short circuit in electronic components. Therefore, in the manufacture of electronic components, it can be said that it is necessary to suppress not only sheet erosion, but also the transmission of conductive powder.

The present invention has been made in view of the above-mentioned aspects, and an object thereof is to provide a conductive paste capable of forming an electrode capable of suppressing the occurrence of sheet erosion and the transmission of conductive powder.

According to the present invention, a conductive paste is disclosed, which includes: a conductive powder, a binder resin, and an organic solvent. The organic solvent is a mixed solvent, and the mixed solvent includes a first solvent having a solubility parameter of 9.0 (cal / cm ³ ) or less of ^{0.5 and} a second solvent having a solubility parameter of 10.0 (cal / cm ³ ) or more of ^0.5 , In addition, the solubility parameter of the Fedors of the organic solvent is 9.0 (cal / cm ³ ) ^0.5 or more and 10.1 (cal / cm ³ ) ^0.5 or less.

According to the study by the present inventors, the first solvent is useful for suppressing the occurrence of sheet erosion, but when used alone, the conductive powder is liable to penetrate. On the other hand, the second solvent is useful for suppressing the transmission of the conductive powder, but when used alone, it easily causes sheet erosion. The conductive paste of the present invention includes a first solvent and a second solvent having such characteristics in an organic solvent, and the first solvent and the second solvent are mixed so that the solubility parameter of the entire organic solvent becomes a predetermined range, Thereby, the advantages of each of the first solvent and the second solvent are appropriately used. Accordingly, an electrode capable of suppressing both the occurrence of sheet erosion and the transmission of the conductive powder can be suitably formed. As a result, it is possible to better avoid the occurrence of a short circuit in the electronic component.

In addition, the "Solubility Parameter (SP) of Fedors" in this specification means the solubility parameter calculated by the so-called Fedors method described in RFFedors, Polymer Engineering Science, 14, p147 (1974). In the Fedors method, it is considered that the cohesive energy density and the mole molecular volume depend on the type and number of substituents, and the solubility parameter is expressed by the following (Formula 1). The solubility parameter is a value inherent in each compound. δ = [ΣE _coh / ΣV] ^0.5 ... (Expression 1) (Here, ΣE _coh represents cohesive energy, and ΣV represents the mole molecule volume.)

The solubility parameter δ _{all of the} entire organic solvent can be calculated by the following (Equation 2). δ _all (cal / cm ³ ) ^0.5 = Σ [inherent solubility parameter of each organic solvent δ (cal / cm ³ ) ^0.5 × mass ratio of each organic solvent when the entire organic solvent is used as the reference (1)] ... (Expression 2) In other words, first, the product of the intrinsic solubility parameter δ (cal / cm ³ ) ^0.5 and the mass ratio of each organic solvent is calculated, and they are added to form the solubility parameter δ _{all of the} entire organic solvent. That is, the solubility parameter [delta] _all of the entire organic solvent is a weighted average value on a mass basis. In addition, in the following description, the solubility parameter of Fedors may be simply called "SP value." In addition, the SI unit of the SP value is (J / cm ³ ) ^0.5 or (MPa) ^0.5 . However, in this specification, (cal / cm ³ ) ^0.5 that has been conventionally used is used. The unit of the SP value can be expressed as follows: 1 (cal / cm ³ ) ^0.5 ≒ 2.05 (J / cm ³ ) ^0.5 ≒ 2.05 (MPa) ^0.5 ; conversion.

In a suitable embodiment, the first solvent is an acyclic compound. When the first solvent is an acyclic compound, the penetration of the organic solvent into the green sheet can be suppressed at a higher level. Therefore, the effects of the technology disclosed herein can be better exerted. In another preferred embodiment, the first solvent is an ether. Ethers are not only excellent in SP values but also excellent in various characteristics such as printability, and are therefore preferred.

In a suitable embodiment, the second solvent is an ether. Ethers are not only excellent in SP values but also excellent in various characteristics such as printability, and are therefore preferred.

In a suitable embodiment, when the entire organic solvent is 100% by mass, the ratio of the first solvent is 20% by mass or more and 70% by mass or less, and the ratio of the second solvent is 30% by mass or more and 80% by mass. %the following. Thereby, the effect of suppressing sheet erosion and the effect of suppressing permeation of the conductive powder can be combined more stably at a high level.

In a suitable embodiment, when the entire conductive paste is 100% by mass, the ratio of the conductive powder is 90% by mass or more. By setting the ratio of the above-mentioned conductive powder, it is possible to suitably form an electrode having high density, high conductivity, and low resistance.

The conductive paste can be suitably used for forming an electrode of an inductance component, for example.

Hereinafter, suitable embodiments of the present invention will be described. It should be noted that features other than the matters specifically mentioned in this specification (such as organic solvents), and features required for the implementation of the present invention (such as a method for preparing a conductive paste, a method for imparting it, etc.) can be based on this specification. The technical content of the teaching is understood with the general technical knowledge of those skilled in the art. The present invention can be implemented based on the contents disclosed in this specification and technical common sense in the art. In addition, the expression "A ~ B" which shows the range in this specification means A or more and B or less.

The conductive paste disclosed herein includes a conductive powder, a binder resin, and an organic solvent. The organic solvent is a mixed solvent containing at least two solvents having different SP values. Hereinafter, each component will be described in order.

[Conductive powder] A conductive powder is a component that imparts conductivity to an electrode obtained by firing a conductive paste. The type and the like of the conductive powder are not particularly limited, and the conductive powder used in such a conventional conductive paste can be suitably used depending on the application of the conductive paste and the like. Typical examples include gold (Au), silver (Ag), platinum (Pt), palladium (Pd), aluminum (Al), nickel (Ni), copper (Cu), ruthenium (Ru), and rhodium (Rh). ), Tungsten (W), iridium (Ir), osmium (Os), and their alloys, such as silver-palladium (Ag-Pd), silver-platinum (Ag-Pt), silver-copper (Ag-Cu ) And other silver alloys. Among them, silver and silver alloys are preferred from the viewpoints of low cost and high electrical conductivity.

The conductive powder may be, for example, carbon materials such as graphite and carbon black, LaSrCoFeO ₃ -based oxides (for example, LaSrCoFeO ₃ ), LaMnO ₃ -based oxides (for example, LaSrGaMgO ₃ ), LaFeO ₃ -based oxides (for example, LaSrFeO ₃ ), Conductive ceramics typified by transition metal perovskite-type oxides such as LaCoO ₃ -based oxides (eg, LaSrCoO ₃ ).

The properties of the conductive powder are not particularly limited, and can be appropriately adjusted according to the use of the conductive paste and the like. For example, for applications that form an electrode of an inductive component such as an inductor, an average particle diameter of approximately 0.1 μm or more, typically 0.5 μm or more, such as 1 μm or more, and approximately 5 μm or less, typically 4 μm or less, such as 3 μm or less, can be preferably used. Conductive powder. When the average particle diameter is a predetermined value or more, aggregation of the conductive powder in the conductive paste is suppressed, and the filling property of the electrode obtained after firing can be improved. When the average particle diameter is equal to or smaller than a predetermined value, the sinterability can be improved and the resistance of the electrode can be reduced. In addition, the "average particle diameter" in this specification means a 50% particle diameter of the cumulative value in the particle size distribution (number basis) of the circle-equivalent diameter observed by an electron microscope.

For conductive powders, the volume-based particle size distribution based on the laser diffraction / scattering method has a cumulative D ₁₀ particle size equivalent to 10% by volume from the smaller particle size, which is approximately 1.6 μm or less, and typically 1.3 μm or less. It may be, for example, 1.0 μm or less. When the particle diameter of D _{10 is} small as described above, the above-mentioned conductive powder is easily transmitted through the green sheet. According to the technology disclosed herein, even when the conductive powder has such a D ₁₀ particle size, the transmission of the conductive powder can be suitably suppressed.

In a suitable example, the conductive powder includes two particle groups having different average particle diameters from the viewpoint of improving the density and filling properties of the electrode. In other words, the particle size distribution of the conductive powder has a bimodality. In a specific example, the average particle diameter of the first particle group is approximately in a range of 1 to 5 μm, for example, 2 ± 0.5 μm, and the average particle diameter of the second particle group is approximately in a range of 0.5 to 2 μm, for example, 0.5 ± 0.5 μm. When the particle size distribution has a bimodality, the ratio of particles having a particle size smaller than the average particle size is larger than when the particle size distribution is unimodal. The larger the ratio of small particles, the easier it is for the conductive powder to pass through the green sheet. Therefore, the application of the technology disclosed herein is particularly effective.

The ratio of the conductive powder to the entire conductive paste is not particularly limited. In a suitable example, when the entire conductive paste is 100% by mass, the conductive powder is approximately 80% by mass or more, preferably 90% by mass or more, and approximately 98% by mass or less, and may be 96% by mass, for example. the following. The higher the ratio of the conductive powder, the easier it is for the conductive powder to pass through the green sheet. Therefore, the application of the technology disclosed herein is particularly effective. In addition, by setting the ratio of the above-mentioned conductive powder, it is possible to suitably form an electrode having high density, high conductivity, and low resistance.

[Binder resin] The binder resin is used to mix conductive particles constituting a conductive powder with each other in a state of an unbaked coating film in which a conductive paste is applied to a raw material (green sheet) and dried. A component in which the conductive particles are bonded to the components of the green sheet. The binder resin is preferably burned out at a temperature lower than the sintering temperature of the conductive powder when the conductive paste is fired. In other words, it is preferred that the binder resin does not remain in the electrode obtained after firing. The type of the binder resin is not particularly limited, and for example, a conventional binder resin used in such a conductive paste can be suitably used depending on the method for applying the conductive paste, the type of green sheet, and the like.

Examples of the binder resin include cellulose-based polymers (cellulose derivatives) such as methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, and carboxymethyl cellulose, Acrylic resins such as polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, epoxy resins, phenolic resins, alkyd resins, polyvinyl alcohol resins, polyvinyl butyral Rosin-based resins, such as rosin-based resins, rosin, and maleated rosin. Among them, from the viewpoint of excellent printing suitability when a conductive paste is provided on a green sheet, the aspect of excellent combustion decomposition properties during firing, and environmental considerations, it is preferable to use a cellulose-based polymer such as ethyl fiber Vegetarian. Accordingly, it is possible to suitably obtain an electrode having high conductivity after firing the conductive paste. In addition, there is no particular limitation, the SP value of the binder resin is approximately 8 (cal / cm ³ ) ^0.5 or more, for example, 9 (cal / cm ³ ) ^0.5 or more, and further 10 (cal / cm ³ ) ^0.5 or more, and approximately 14 (Cal / cm ³ ) ^0.5 or less, typically 13 (cal / cm ³ ) ^0.5 or less, and may be, for example, 11.5 (cal / cm ³ ) ^0.5 or less.

The ratio of the binder resin to the entire conductive paste is not particularly limited. In a suitable example, when the entire conductive paste is 100% by mass, the binder resin is approximately 0.1% by mass or more, typically 0.5% by mass or more, and approximately 10% by mass or less, and may typically be 5% by mass. %the following.

[Organic solvent (mixed solvent)] An organic solvent is a component which disperses or dissolves a conductive powder and a binder resin, and adjusts it to the viscosity suitable for giving a conductive paste. In the technology disclosed herein, the organic solvent is a mixed solvent including at least a first solvent and a second solvent. The SP value of the entire organic solvent is adjusted to 9.0 (cal / cm ³ ) ^0.5 to 10.1 (cal / cm ³ ) ^0.5 . Accordingly, an electrode capable of suppressing both the occurrence of sheet erosion and the transmission of the conductive powder can be suitably formed. Overall organic solvent may be, for example, SP value 9.2 (cal / cm ^{3) 0.5} or more. Accordingly, when the conductive powder is made fine, it is possible to more effectively suppress the transmission of the conductive powder. The SP value of the entire organic solvent may be, for example, 9.9 (cal / cm ³ ) ^0.5 or less, and further 9.6 (cal / cm ³ ) ^0.5 or less. This makes it possible to more effectively suppress the occurrence of sheet erosion.

The first solvent is a SP value of 9.0 ⁽³ cal / cm) ^0.5 or less solvent. By including the first solvent, the occurrence of sheet erosion of the green sheet can be suppressed. The SP value of the first solvent is not particularly limited to approximately 7.0 (cal / cm ³ ) ^0.5 or more, typically 8.0 (cal / cm ³ ) ^0.5 or more, such as 8.2 (cal / cm ³ ) ^0.5 or more, and may be, for example, 8.5 (cal / cm ³ ) ^0.5 or less. This makes it easy to adjust the SP value of the entire organic solvent to the above range.

The type of the first solvent is not particularly limited. As an example, there may be mentioned ethers, esters, alcohols, amines, acyl amines, hydrocarbons, and the like SP value of 9.0 (cal / cm ^{3) 0.5} or less solvent. From the viewpoint of better suppressing the wetting and spreading of the organic solvent, the first solvent is preferably a linear or branched compound having no cyclic structural portion, that is, an acyclic compound. However, the first solvent may be a cyclic compound having a cyclic structural portion, such as a cyclic ether.

Ethers are compounds having at least one ether bond (-C-O-C-) on the main chain (parent core). Ester is a compound having at least one ester bond (R-C (= O) -O-R ') in the main chain. Alcohols are compounds having a structural portion in which a hydrogen atom of a hydrocarbon is replaced with a hydroxyl group, and are compounds represented by the general formula: R-OH. Amines are compounds having a moiety in which at least one hydrogen atom of ammonia is substituted with a hydrocarbon residue. Amidoamines are compounds having a structural moiety in which at least one hydrogen atom of ammonia is substituted with an amidino group (R-C (= O)-). Hydrocarbons are compounds composed of carbon atoms and hydrogen atoms. It should be noted that when there are multiple functional groups in one molecule, they are classified according to the IUPAC nomenclature. When there are ether bonds and hydroxyl groups in one molecule, they are classified into ethers, which are glycol ethers described later in detail.

From the viewpoint of excellent printability and the like, it is preferable to use an ether as the first solvent. Examples of the ethers include glycol ethers. The glycol ethers used as the first solvent are aliphatic compounds or alicyclic compounds in which two hydroxyl groups are bonded to two different carbon atoms, and one or two hydrogens of the two hydroxyl groups are replaced by hydrocarbons. Residue or hydrocarbon residue-containing compound substituted with an ether bond. Glycol ethers include diol monoalkyl ethers in which only one hydroxyl group is replaced by hydrogen and diol dialkyl ethers in which two groups of hydrogen are replaced.

Among the ethers, it is preferable to use an acyclic lower glycol ether represented by the following general formula (Chem. 1) from the viewpoint that the boiling point is high and the operability of the conductive paste can be improved. R ^1- (OR ² ) _m -OR ³ (...) (here, R ¹ and R ³ are each independently a hydrogen atom or a straight or branched alkyl group having 1 to 6 carbon atoms, and R ² is a linear or branched alkylene group having 2 to 4 carbon atoms, and m is 1 to 4)

In the general formula (Chem. 1), the alkyl group is, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, and the like. Examples of the alkylene group include ethylene, n-propylene, and n-butylene. m is typically 2 ~ 4. From the viewpoint of suppressing the SP value to be low and suppressing the occurrence of sheet erosion more favorably, R ¹ and R ³ may be each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R ² may be an alkylene group having 2 carbon atoms, that is, an ethylene group (CH ₂ CH ₃ ).

Examples of glycol ethers include dialkylene glycol monoalkyl ethers, trialkylene glycol monoalkyl ethers, tetraalkylene glycol monoalkyl ethers, and dialkylene diethers. Alcohol dialkyl ethers, trialkylene glycol dialkyl ethers, tetraalkylene glycol dialkyl ethers, and the like. Among them, it is preferable to use a dialkylene glycol dialkyl ether from the viewpoint of suppressing the SP value to be low.

Specific compounds (the SP value. The unit is (cal / cm ³ ) ^0.5 .) Of ethers, for example, diethylene glycol diethyl ether (SP value: 8.2), diethylene glycol butyl methyl ether (SP value: 8.2), diethylene glycol dibutyl ether (SP value: 8.3), triethylene glycol dimethyl ether (SP value: 8.4), triethylene glycol butyl methyl ether (SP value: 8.4) , Tetraethylene glycol dimethyl ether (SP value: 8.5) and so on.

Examples of the esters include glycol ether acetates. Glycol ether acetates are esterified compounds of the above-mentioned glycol ethers. Examples of glycol ether acetates include acyclic lower glycol ethers in which at least one of R ¹ and R ³ in the above (chemical formula 1) is a fluorenyl group. In the above (Chem. 1), the fluorenyl group is, for example, a linear or branched chain having 1 to 6 carbon atoms. The fluorenyl group is, for example, formamyl, ethenyl, propionyl, benzyl, and the like. Moreover, as another example of an ester, a terpineol derivative of terpineol is mentioned.

Specific compounds of esters (its SP value. The unit is (cal / cm ³ ) ^0.5 ). For example, diethylene glycol monobutyl ether acetate (SP value: 8.9), dihydropine Dihydrotrivinyl acetate (SP value: 8.9), dihydrotrivinyl propionate (SP value: 8.9), and the like obtained by ethylation of oleyl alcohol.

The amines include, for example, a primary amine in which only one hydrogen is substituted, a second amine in which two hydrogens are substituted, and a third amine in which three hydrogens are substituted. Specific examples of the amine compound (its SP value. The unit is (cal / cm ³ ) ^0.5 )) include, for example, bis (2-ethylhexyl) amine (SP value: 8.2).

Examples of the hydrocarbons include chain saturated hydrocarbons (linear alkane) having a carbon number of 20 or less, such as 10 to 15, and chain unsaturated hydrocarbons (linear olefin, Linear alkynes) and so on. Specific examples of the linear alkane (its SP value. The unit is (cal / cm ³ ) ^0.5 .) Include decane (SP value: 7.7), undecane (SP value: 7.8), and dodecane ( SP value: 7.9), tridecane (SP value: 7.9), tetradecane (SP value: 7.9), and the like.

A difference between the SP values of the binder resins embodiment, the SP value becomes the first solvent and the raw materials for green sheet of substantially ^0.5 (cal / cm ³⁾ 0.5 or more, typically 1.0 (cal / cm ³ ) ^0.5 or more, preferably 1.5 (cal / cm ³ ) ^0.5 or more. SP value of green sheet binder resin is 10.0 (cal / cm ^{3) 0.5} or more, for example at ^{10.0 ~ 11.0 (cal / cm 3} ) ^0.5 case, a SP value of the solvent is smaller than good. This makes it possible to more effectively suppress the occurrence of sheet erosion.

The second solvent is an SP value of 10.0 ⁽³ cal / cm) ^0.5 or more solvents. By including the second solvent, it is possible to suppress transmission of the conductive powder to the green sheet. Is not particularly limited, SP value of the second solvent is approximately 20.0 (cal / cm ^{3) 0.5} or less, typically 15.0 (cal / cm ^{3) 0.5} or less, preferably 13.0 (cal / cm ^{3) 0.5} or less, and further is 12.0 (cal / cm ³ ) ^0.5 or less, for example, may be 10.5 (cal / cm ³ ) ^0.5 or less. This makes it easy to adjust the SP value of the entire organic solvent to the above range.

The type of the second solvent is not particularly limited. As an example, there may be mentioned ethers, esters, alcohols, amines, acyl amines, hydrocarbons, etc. SP value of 10.0 (cal / cm ^{3) 0.5} or more solvents. The second solvent may be an acyclic compound having no cyclic structural portion, or may be a cyclic compound having a cyclic structural portion. From the viewpoint of improving compatibility and integration, the second solvent may be the same solvent having the same functional group portion as the first solvent. However, it may be a different type of solvent that does not have the same functional group portion as the first solvent. The classification of ethers, esters, alcohols, amines, amidines, and hydrocarbons is the same as that of the first solvent. Specific examples of the second solvent include the following compounds (a) to (c).

(A) Ethers From the viewpoint of excellent printability and the like, it is preferable to use ethers as the second solvent. Examples of the ethers include glycol ethers. The classification of glycol ethers is the same as that of the first solvent.

Among the ethers, it is preferable to use a lower glycol ether represented by the following general formula (Chemical Formula 2) from the viewpoint that the boiling point is high and operability of the conductive paste can be improved. R ^11- (OR ¹² ) _n -OR ¹³ (chemical formula 2) (here, R ¹¹ and R ¹³ are each independently a hydrogen atom, an alkyl group, an alkoxy group, a fluorenyl group, or an aryl group (R ¹² is a linear or branched alkylene group having 2 to 4 carbon atoms, and n is 1 to 4).

In the general formula (Chem. 2), the alkyl group is, for example, a straight or branched chain having 1 to 10 carbon atoms. The alkyl group and the alkylene group are, for example, the same as the general formula (Chem. 1). The alkoxy group is, for example, a straight or branched chain having 1 to 10 carbon atoms. Examples of the alkoxy group include methoxy, ethoxy, propoxy, and butoxy. Aryl is, for example, phenyl, benzyl, tolyl, and the like. From the viewpoint of increasing the SP value and further suppressing the transmission of the conductive powder, one of R ¹¹ and R ¹³ may be a hydrogen atom and the other may be an alkyl group or an aryl group having 1 to 6 carbon atoms. R ² may be an alkylene group having 2 carbon atoms, that is, an ethylene group (CH ₂ CH ₃ ). In addition, n may be 1 or 2.

As a specific compound (its SP value. The unit is (cal / cm ³ ) ^0.5 .), For example, diethylene glycol (SP value: 12.1), diethylene glycol monoethyl ether (SP value: 10.2) , Diethylene glycol monobutyl ether (SP value: 10.5), ethylene glycol (SP value: 17.8), ethylene glycol monomethyl ether (SP value: 12.0), ethylene glycol monoethyl ether (SP value : 11.5), propylene glycol monomethyl ether (SP value: 10.2), phenylpropylene glycol (SP value: 11.5), and the like.

(B) Alcohols As specific examples of the alcohols (the SP value thereof is (cal / cm ³ ) ^0.5 .), For example, methanol (SP value: 13.8), ethanol (SP value: 12.6), 1- Butanol (SP value: 11.4), 2-butanol (SP value: 10.8), third butanol (SP value: 10.6), 1-octanol (SP value: 10.3), and the like. The alcohols preferably have a carbon number of 6 or more, for example, 6 to 10. The alcohol is preferably a linear compound.

(C) Esters As the esters, for example, glycol ether acetates can be mentioned. The classification of glycol ether acetates is the same as that of the first solvent. Examples of glycol ether acetates include lower glycol ethers in which at least one of R ¹¹ and R ¹³ in the above-mentioned (Chemical Formula 2) is a fluorenyl group. The fluorenyl group is, for example, the same as the general formula (Chem. 1). Specific examples of the esters (the SP value thereof is (cal / cm ³ ) ^0.5 )) include, for example, 2,2,4-trimethyl-1,3-pentanediol-1-monoisobutyl Acid ester (SP value: 10.2), propylene carbonate (SP value: 13.3) and the like.

In a suitable example of the technology disclosed herein, the difference between the SP value of the second solvent and the SP value of the first solvent exceeds 1.5 (cal / cm ³ ) ^0.5 , and is approximately 1.8 (cal / cm ³ ) ^0.5 or more, such as 2.0 (cal / cm ³ ) ^0.5 or more. Thereby, the effects of the disclosed technology can be exerted at a higher level here.

Another suitable embodiment, the difference in SP value SP value of the binder resin and the second solvent contained in the conductive paste substantially 1.0 (cal / cm ^{3) 0.5} or less, typically 0.5 (cal / cm ³ ) Below ^0.5 . For example, ^{10.0 ~ 11.5 (cal / cm 3} ) ^0.5 SP value of the case where the binder resin contained in the conductive paste, preferably SP value of the second solvent is also 10.0 ~ 11.5 (cal / cm ³ ) About ^0.5 . This can further improve the integrity and storage stability of the entire conductive paste.

In addition, from the viewpoint of further improving the integrity and storage stability of the entire conductive paste, the second solvent and the first solvent are preferably the same type. For example, when the first solvent is an ether (particularly a glycol ether), the second solvent is preferably also an ether (particularly a glycol ether).

From the viewpoint of improving the operability of the conductive paste and the workability at the time of electrode formation, the boiling point of at least one of the first solvent and the second solvent (preferably both) is approximately 100 ° C. or higher, preferably The temperature is 130 ° C or higher, typically 150 ° C or higher, and may be, for example, about 160 to 260 ° C. The molecular weights of the first solvent and the second solvent are each approximately 80 or more, typically 100 or more, for example, 130 or more, and approximately 500 or less, typically 300 or less, and may be 250 or less, for example. In addition, "molecular weight" in this specification is based on the sum of the atomic weight of each element of the structural formula of a compound.

The organic solvent may be composed of the first solvent and the second solvent described above, or may include one or two or more third solvents in addition to the first solvent and the second solvent. The third solvent is not particularly limited as long as the SP value of the entire organic solvent satisfies the above range, and organic solvents conventionally used in such conductive pastes can be suitably used. As an example, the SP value in ethers, esters, alcohols, amines, amidines, hydrocarbons, etc. exceeds 9.0 (cal / cm ³ ) ^0.5 and less than 10.0 (cal / cm ³ ) ^0.5 Organic solvents.

When the entire organic solvent is 100% by mass, the ratio of the first solvent is approximately 10% by mass or more, for example, 20% by mass or more, and approximately 80% by mass or less, and may be 70% by mass or less, for example. The ratio of the second solvent is approximately 20% by mass or more, for example, 30% by mass or more, and approximately 90% by mass or less, and may be 80% by mass or less, for example. The total of the first solvent and the second solvent is approximately 50% by mass or more, preferably 80% by mass or more, for example, 90% by mass or more, and particularly preferably 95% by mass or more. Thereby, the effect of suppressing sheet erosion and the effect of suppressing transmission of conductive powder can be stably combined at a higher level. Furthermore, it is easy to adjust the SP value of the entire organic solvent to the above range. In addition, the mixing ratio of the first solvent and the second solvent is not particularly limited. In a suitable example, the first solvent and the second solvent can be adjusted to the first solvent in a mass ratio: the second solvent = 20: 80 to 70: Between 30. This makes it possible to further improve the storage stability and the like of the conductive paste.

The ratio of the organic solvent to the entire conductive paste is not particularly limited. In a suitable example, when the entire conductive paste is 100% by mass, the organic solvent is approximately 0.1% by mass or more, typically 0.5% by mass or more, and approximately 10% by mass or less, and may typically be 5% by mass. the following. Thereby, for example, the operability and printing suitability of the conductive paste are improved, and an electrode having a uniform thickness is easily formed on the green sheet.

In the conductive paste, various additive components can be blended in addition to the aforementioned constituent components. Examples of the additive component include an inorganic filler, a surfactant, a dispersant, a viscosity modifier, a defoamer, a plasticizer, an antioxidant, and a pigment. Examples of the inorganic filler include ceramic powder and glass powder. The ratio of the additive component to the entire conductive paste is not particularly limited. From the viewpoint of achieving higher conductivity, it is preferably approximately 5% by mass or less, for example, 3% by mass or less.

The conductive paste disclosed herein can be applied to raw materials by various methods, for example, by adjusting the viscosity to an appropriate level. For example, it can be applied to the raw materials by various printing methods such as screen printing, gravure printing, offset printing, inkjet printing, a doctor blade method, and a spray method.

The conductive paste disclosed herein can be used for electrode formation of various electronic components such as inductance components, capacitor components, and the like. In addition, when manufacturing an electronic component using the said conductive paste, the conventionally well-known method in the field of an electronic component can be used suitably. The said conductive paste can be used suitably for the use which forms the electrode of inductance components, such as an inductor (coil), a choke coil, and a transformer.

That is, according to the inventors' knowledge, for example, compared with a capacitor component such as a multi-layer ceramic capacitor (MLCC), the inductance component has relatively large pores and high porosity of the raw material. In addition, in recent years, from the viewpoint of reducing the resistance, the conductive powder tends to become finer. Therefore, the organic solvent easily penetrates into the raw materials when the electrodes of the inductance component are formed. In addition, it is easy for the conductive powder to penetrate the raw materials. Therefore, the application of the conductive paste disclosed here is effective. Inductive components can be mounted in various forms such as surface-mount and through-hole mounting. The inductance component may be a laminated type, a winding type, or a thin film type. In particular, according to the conductive paste, a low-resistance electrode can be realized. Therefore, the conductive paste is suitable for use in forming an internal electrode layer of a multilayer chip inductor used in a power circuit capable of flowing a large current.

FIG. 1 is a cross-sectional view schematically showing a structure of a multilayer chip inductor 1. It should be noted that the dimensional relationship (length, width, thickness, etc.) in FIG. 1 does not necessarily reflect the actual dimensional relationship. In addition, the symbols X and Z in the figure indicate the left-right direction and the up-down direction, respectively. However, it is merely a direction for convenience.

The multilayer chip inductor 1 includes a main body portion 10 and external electrodes 20 provided on both side portions of the main body portion 10 in the left-right direction X. The shape of the multilayer chip inductor 1 is, for example, a size of 1608 shape (1.6 mm × 0.8 mm), a shape of 2520 shape (2.5 mm × 2.0 mm), and the like.

The main body portion 10 has a structure in which a plurality of magnetic material layers 12 are stacked and integrated in the vertical direction Z. The magnetic material layer 12 is made of, for example, ferrite magnetic materials such as Ni-Cu-Zn ferrite, Fe-Cr-Si alloy, Fe-Al-Si alloy, and Fe-Si-M soft magnetic alloy (where M is At least one of chromium, aluminum, and titanium.) And other metallic materials. A coil conductor as an internal electrode layer 14 is provided between each magnetic material layer 12. The coil conductor is formed between the magnetic material layers 12 using the above-mentioned conductive paste. The two coil conductors that sandwich the magnetic material layer 12 and are adjacent in the vertical direction Z are conducted through a via hole provided in the magnetic material layer 12. Accordingly, the internal electrode layer 14 is formed in a three-dimensional coil shape (spiral shape). Both ends of the coil conductor are connected to the external electrode 20, respectively.

Such a multilayer chip inductor 1 can be manufactured in the following steps, for example. That is, first, a magnetic material paste containing the above-mentioned metal-based material, a binder resin, and an organic solvent is prepared and supplied onto a carrier sheet to form a green sheet. Next, the green sheet was rolled and cut into a desired size to obtain a plurality of sheets for forming a magnetic material layer. Next, a through hole is formed at a predetermined position on the sheet for forming a magnetic material layer using a puncher or the like. Next, the conductive paste is printed on a predetermined position of a plurality of sheets for forming a magnetic material layer in a predetermined coil pattern. Next, these were laminated and pressure-bonded to produce a laminate of unfired green sheets. This is dried and fired to integrally fire the green sheet to form a main body portion 10 including a magnetic material layer 12 and an internal electrode layer 14. Then, an appropriate external electrode forming paste is applied to both ends of the main body portion 10 and fired to form the external electrode 20. In this way, a multilayer chip inductor 1 can be manufactured.

Hereinafter, examples of the present invention will be described, but it is not intended to limit the present invention to those shown in the following examples.

(Example 1) [Preparation of conductive paste] A conductive paste (samples 1 to 10) was prepared according to the following steps. That is, first, the organic solvents shown in Table 1 are prepared. Table 1 also shows the SP values. Next, a silver powder as a conductive powder, ethyl cellulose (EC) as a binder resin, and a single organic solvent of the type shown in Table 2 were used as the silver powder: EC: organic solvent = 92: 0.5 to 2 : Compounding at a mass ratio of 6 to 7.5, and mixing with a three-roll mill to prepare a conductive paste (samples 1 to 10).

[Table 1]

[Preparation of green sheet] A green sheet is prepared as a coating target of the conductive paste. The green sheet is prepared by assuming a formation of an electrode layer of a metal inductor. That is, first, a Fe-Cr-Si alloy powder as a metal magnetic material, polyvinyl butyral as a binder resin, and an organic solvent are mixed and kneaded with a three-roll mill to obtain a magnetic material paste. Next, this magnetic material paste was coated on the surface of a carrier sheet made of PET and dried to form a green sheet.

[Evaluation of Sheet Erosivity] As described above, when a conductive paste is printed on a green sheet, the organic solvent contained in the conductive paste swells or dissolves the binder resin in the green sheet, and the sheet may locally become thin. , Or the phenomenon of open-hole sheet erosion. In this test example, in order to evaluate the erosion property of the sheet, the conductive paste was printed on the surface of the green sheet and dried to form an electrode layer. However, from the back surface of the green sheet, in other words, the surface in contact with the carrier sheet made of PET was observed with a microscope or a microscope, and it was confirmed whether a hole was formed in the back surface. The results are set in Table 2. In addition, in Table 2, the case where the hole was confirmed on the back surface is described as "x", and the case where the hole was not recognized on the back surface was described as "0".

[Evaluation of Ag Permeability] As described above, when a conductive paste is printed on a green sheet, the organic solvent contained in the conductive paste penetrates the green sheet together with the silver powder, and the silver powder may penetrate into the green sheet The Ag on the side transmits. In this test example, in order to evaluate the permeability of Ag, the conductive paste was printed on the surface of the green sheet and dried to form an electrode layer. Then, SEM-EDS (Energy Dispersive X-ray Spectroscopy) observation was performed from the back surface of the green sheet, and it was confirmed whether Ag fine particles were present on the back surface. The results are set in Table 2. In addition, in Table 2, the case where Ag fine particles were recognized on the back surface is described as "×", and the case where Ag fine particles were not recognized on the back surface was described as "0". In addition, FIGS. 2 (A) and 2 (B) show, as examples, FIG. 2 (A) in which Ag particles are confirmed on the back surface, and FIG. 2 (B) in which Ag particles are not confirmed on the back surface. SEM-EDS image.

[Table 2]

As shown in Table 2, with a single organic solvent, it is not possible to suppress both sheet erosion and Ag transmission at the same time. That is, alone SP value 9.2 (cal / cm ^{3) 0.5} or less in the samples 1 to 9 of the organic solvent, although good sheet erosion, but through the Ag have occurred. The reason is not clear, but the inventors believe that the permeability of the silver powder is related to the wettability (surface tension) of the organic solvent. That is, an organic solvent having a low surface tension is easily wetted and spread on a green sheet, and is easily immersed in the green sheet. Therefore, it is thought that it is easy to cause permeation of a silver powder. In addition, according to reports on powder dispersion systems (pigment dispersion and coloring materials in water-soluble acrylic resin coating systems, 62 (8) pp.524-528,1989 <Internet> .go.jp / article / shikizai1937 / 62/9 / 62_524 / _pdf), the surface tension is related to the solubility parameter δ of Fedors, and it is predicted that there will be a correlation change with SP value. Therefore, it is estimated that when the SP value is equal to or less than a predetermined value, the wettability of the organic solvent is improved, and the silver powder is transmitted.

In addition, in Sample 10 using only an organic solvent having an SP value of 10.5 (cal / cm ³ ) ^0.5 , although Ag permeability was good, sheet erosion occurred. The reason for this is not clear, but the inventors believe that the SP value has a large influence on the sheet etchability. That is, it is estimated that when the SP value is equal to or greater than a predetermined value, the compatibility with the binder resin contained in the green sheet serving as a raw material is improved, and sheet erosion occurs.

(Example 2) A solvent C (diethylene glycol dibutyl ether) and a solvent M (diethylene glycol monobutyl ether) were mixed at a mass ratio shown in Table 3 to prepare a mixed solvent. Using this, a conductive paste (samples 11 to 17) was prepared, an electrode layer was formed in the same manner as in Example 1, and the sheet etchability and Ag permeability were evaluated. In addition, printability was also evaluated. In addition, Table 3 shows the SP value of the whole organic solvent together.

[Evaluation of printability] The transferability when the conductive paste was printed on the surface of the green sheet was evaluated. In addition, the samples 3 and 10 were evaluated for printability in the same manner. The results are shown in Table 3. In addition, in Table 3, a case where a disconnection due to printing blur or the like is confirmed is referred to as "×", and a case where a disconnection due to printing blur or the like is not confirmed is referred to as "0".

[table 3]

As shown in Table 3, the printability of any sample was good. However, in the samples 16 and 17 in which the SP value of the entire mixed solvent was lower than 9.0 (cal / cm ³ ) ^0.5 , although the sheet etchability was good, Ag permeation occurred. In contrast, in the samples 11 to 15 in which the SP value of the mixed solvent was 9.0 to 10.1 (cal / cm ³ ) ^0.5 , sheet erosion and Ag permeation were suppressed at the same time.

(Example 3) Various organic solvents shown in Table 4 were mixed to prepare a mixed solvent. Using this, a conductive paste (samples 18 to 31) was prepared, an electrode layer was formed in the same manner as in Example 2, and the sheet etchability, Ag permeability, and printability were evaluated. The results are shown in Table 4. In addition, Table 4 shows the SP value of the whole organic solvent together.

[Table 4]

As shown in Table 4, the printability of any sample was good. In particular, according to the study by the present inventors, when both solvents are ethers, printing suitability is particularly excellent, and the mass ratio of the organic solvent can be further reduced.

In addition, in samples 18 and 19 that did not contain an organic solvent with an SP value of 9.0 (cal / cm ³ ) or less, ^0.5 , sheet erosion occurred. On the other hand, does not contain an SP value of 10.0 (cal / cm ^{3) 0.5} or more samples of the organic solvent 20 to 22, through the Ag occurs. On the other hand, contains an SP value of 9.0 (cal / cm ^{3) 0.5} or less and a SP value of organic solvent 10.0 (cal / cm ^{3) 0.5} or more organic solvents, and the organic solvent entire SP value is adjusted to 9.0 to 10.1 ( cal / cm ³ ) ^0.5 samples 23 to 31, sheet erosion and Ag permeation were suppressed at the same time. Wherein the acyclic compound as a SP value of 9.0 (cal / cm ^{3) 0.5} or less samples 23 to 29 of the organic solvent, the organic solvent wetting spread particularly well suppressed. The reason is not clear, but as one of the factors, it is considered that when the first solvent is an acyclic (eg, linear) compound, the first solvent is easily attracted to the polar part of the second solvent by hydrophobic interaction. (Δ ^- generated by O atom), the wetting and spreading of the first solvent is more effectively suppressed. These results show the significance of the technology disclosed herein.

The present invention has been described in detail above, but these are merely examples, and the present invention can be modified in various ways without departing from the spirit thereof.

1‧‧‧Laminated Chip Inductors

10‧‧‧Main body

12‧‧‧ Magnetic material layer

14‧‧‧Internal electrode layer

20‧‧‧External electrode

FIG. 1 is a cross-sectional view schematically showing a structure of a multilayer chip inductor according to an embodiment. 2 (A) and 2 (B) are examples of evaluation results of Ag permeability, FIG. 2 (A) is an SEM-EDS image when Ag fine particles are confirmed, and FIG. 2 (B) is Ag fine particles are not confirmed SEM-EDS image of the case.

Claims (12)

A conductive paste comprising: a conductive powder, a binder resin, and an organic solvent, the organic solvent is a mixed solvent, and the mixed solvent includes: a Fedors having a solubility parameter of 9.0 (cal / cm ³ ) ^0.5 or less 1 solvent; and a second solvent having a solubility parameter of Fedors of 10.0 (cal / cm ³ ) or more and ^0.5 , and a solubility parameter of the organic solvent of Fedors being 9.0 (cal / cm ³ ) of ^0.5 or more and 10.1 (cal / cm ³ ) Below ^0.5 . The conductive paste according to item 1 of the scope of patent application, wherein the first solvent is an acyclic compound. The conductive paste according to claim 1 or claim 2, wherein the first solvent is an ether. The conductive paste application to item 1 or 2 of the scope of the patent, wherein Fedors solubility parameter of the first solvent is 7.0 (cal / cm ^{3) 0.5} or more. The conductive paste according to claim 1 or claim 2, wherein the second solvent is an ether. The conductive paste according to item 1 or item 2 of the scope of patent application, wherein the solubility parameter of Fedors of the second solvent is 20.0 (cal / cm ³ ) ^0.5 or less. The conductive paste according to claim 1 or claim 2, wherein when the entire organic solvent is 100% by mass, the ratio of the first solvent is 20% by mass or more and 70% by mass The proportion of the second solvent is 30% by mass or more and 80% by mass or less. The conductive paste according to item 1 or item 2 of the patent application scope, wherein the difference between the solubility parameter of the Fedors of the first solvent and the solubility parameter of the Fedors of the second solvent is 1.8 (cal / cm ³ ) Above ^0.5 . The conductive paste according to item 1 or item 2 of the scope of patent application, wherein the difference between the solubility parameter of the Fedors of the second solvent and the solubility parameter of the Fedors of the adhesive resin is 1.0 (cal / cm ³ ) ^0.5 or less. The conductive paste according to item 1 or 2 of the patent application scope, wherein when the entire conductive paste is 100% by mass, the ratio of the conductive powder is 90% by mass or more. The conductive paste according to item 1 or 2 of the scope of patent application, which is used to form an electrode of an inductance component. An electronic component manufacturing method includes the steps of: applying a conductive paste according to any one of claims 1 to 11 to a green sheet, and baking the green sheet to form an electrode.