Polymer conductive paste, conductive film, and solid electrolytic capacitor element

Abstract

The present application provides a polymer conductive paste which can obtain a conductor layer with high reliability even in a high humidity environment. The polymer conductive paste of the embodiment of the present application contains a conductive metal powder, a binder resin which is a polyvinyl butyral resin, an organic solvent, and a specific additive which is one or two or more selected from stearic acid, lauric acid, octadecenyl succinic acid, benzoic acid, acetylamino phenol, aminophenol, catechol, and N,N-bis(2-hydroxyethyl) cocoyl amine, and contains the specific additive in a range of 0.01 parts by mass or more and 3.0 parts by mass or less with respect to 100 parts by mass of the conductive metal powder.

Description

TECHNICAL FIELD

[0001] The present application relates to a polymer conductive paste, a conductive film, and a solid electrolytic capacitor element, which can be suitably used for formation of a conductive layer in a solid electrolytic capacitor element such as a tantalum capacitor, and an electrode of a multilayer ceramic electronic component. BACKGROUND

[0002] The polymer conductive paste of the present application is used, for example, in a manufacturing method of a solid electrolyte capacitor element.

[0003] As for the solid electrolytic capacitor element, it generally has a structure in which a surface of an anode body composed of a valve action metal is subjected to chemical treatment to form a dielectric layer, and an electrolyte layer composed of a conductive polymer or the like, a carbon layer, and a cathode layer composed of a conductive paste are sequentially formed on the surface thereof. Further, the cathode layer is adhered to a cathode lead terminal using a conductive adhesive, the anode body is joined to an anode lead terminal by soldering, and a molding resin is applied to the outside of these, thereby forming a capacitor component.

[0004] Figure 1 One example of a structure of a solid electrolytic capacitor element is shown.

[0005] The solid electrolytic capacitor element 1 has a structure including a valve action metal sintered body 11 obtained by sintering a valve action metal such as tantalum, niobium, titanium, aluminum, or the like, an oxide film layer 12 formed on a surface of the sintered body 11, a solid electrolyte layer 13 formed thereon, a carbon layer 14, and a conductive layer 15. Here, the sintered body 11 is used as an anode body, the oxide film layer 12 is used as a dielectric layer, and the carbon layer 14 and the conductive layer 15 on the solid electrolyte layer 13 are used as a cathode body.

[0006] The oxide film layer 12 is preferably obtained by oxidizing the sintered body itself, and can be another oxide.

[0007] Further, as the solid electrolyte layer 13, manganese dioxide, a conductive polymer, or the like is widely used.

[0008] Generally, the carbon layer 14 is formed by coating and drying a carbon paste in which carbon powder is dispersed in an organic vehicle. The carbon layer 14 is considered to reduce the contact resistance between the solid electrolyte layer 13 and the conductive layer 15, and to reduce the ESR (equivalent series resistance).

[0009] Further, the conductive layer 15 is generally formed by coating, drying, and / or curing a conductive paste in which metal powder such as silver is dispersed in an organic vehicle.

[0010] Such a solid electrolytic capacitor element has been known for a long time as described in Patent Literature 1 and Patent Literature 2.

[0011] These solid electrolytic capacitors have been used more frequently in high-humidity environments in recent years. The silver in the conductive layer containing silver powder undergoes ionization and migration, which is one of the reasons for short circuits and other damage to the reliability of the components.

[0012] Patent Document 1 describes a solid electrolytic capacitor element having at least a dielectric layer, a solid electrolyte layer, a carbon layer containing a first resin component, and a conductive layer containing a second resin component on the surface of an anode body. By keeping the difference between the hydrogen bonding component value on the surface of the carbon layer and the hydrogen bonding component value on the surface of the conductive layer within a specific range, the ESR degradation is minimized, and the deviation of the ESR change over time for each product is suppressed.

[0013] Patent Document 2 solves the aforementioned problem by dispersing conductive polymer particles in a solid electrolyte layer and using a polymer with controlled water content as the resin component in the conductive layer. Specifically, by dispersing thiophene polymer particles in the solid electrolyte layer to suppress the movement of silver ions, and by using a vinyl acetal polymer with a low residual amount of hydroxyl groups as the resin component in the conductive layer, the water content of the conductive layer can be reduced. It should be noted that the residual amount of hydroxyl groups in Patent Document 2 is 35 mol% or less, preferably 10 mol% or more and 25 mol% or less. An example of such a polymer is "BH-S" (polyvinyl butyral resin) manufactured by Sekisui Chemicals Co., Ltd.

[0014] Existing technical documents

[0015] Patent documents

[0016] Patent Document 1: International Publication No. 2013 / 111438

[0017] Patent Document 2: U.S. Patent Application Publication No. 2018 / 0137988 Summary of the Invention

[0018] The technical problem solved by the invention

[0019] However, the dispersion of conductive polymer particles into the solid electrolyte layer can only suppress the movement of silver ions within the solid electrolyte layer, not the migration itself. Furthermore, in Patent Document 1 of this applicant, polyvinyl butyral resins such as "BH-S" and "KS-5" with a residual hydroxyl content of less than 35 mol% are used in the conductive layer, resulting in insufficient reliability under prolonged exposure to high humidity. According to the research / exploration of the present inventors, while using polyvinyl butyral resins with a lower residual hydroxyl content can potentially suppress migration to some extent, the effect is limited and insufficient, and does not necessarily improve the reliability of the component.

[0020] If polyvinyl butyral resin is replaced, for example, with epoxy resin, which produces a dense cured film, the moisture resistance is improved. However, the cured film of epoxy resin is very hard, making it unsuitable for certain applications. Therefore, there is a greater desire to improve the moisture resistance of pastes using polyvinyl butyral resin.

[0021] According to the research / exploration of the inventors, moisture resistance can be improved to some extent by adding compounds such as 5-amino-2-hydroxybenzoic acid, naphthol, cresol, and salicylic acid to conductive pastes using polyvinyl butyral resin, but not necessarily sufficiently.

[0022] Against this background, the inventors conducted in-depth research on polymer-type conductive pastes using polyvinyl butyral resin, and as a result, discovered that the moisture resistance of polymer-type conductive pastes can be significantly improved by incorporating specific compounds into the paste, thereby completing the present invention.

[0023] That is, the objective of the present invention is to provide a polymer-type conductive paste that can produce a highly reliable conductive layer even in high humidity environments.

[0024] Technical means to solve the problem

[0025] The present invention, which addresses the aforementioned problems, relates to polymer-type conductive pastes, conductive films, and solid electrolytic capacitor elements.

[0026] (1) A polymeric conductive paste comprising conductive metal powder, binder resin, organic solvent, and specific additives, wherein the conductive film obtained by drying and / or curing the coating contains residual organic components comprising the binder resin, wherein,

[0027] The adhesive resin is polyvinyl butyral resin.

[0028] The specific additive is selected from one or more of octadecenylsuccinic acid, benzoic acid, acetaminophen, aminophenol, catechol, and N,N-bis(2-hydroxyethyl)cocoalkylamine.

[0029] The polymer-type conductive paste contains the specific additive in a range of 0.01 parts by weight or more and 3.0 parts by weight or less, relative to 100 parts by weight of the conductive metal powder.

[0030] (2) The polymer-type conductive paste according to (1), wherein,

[0031] The specific additive is octadecenylsuccinic acid.

[0032] (3) The polymer-type conductive paste according to (1), wherein,

[0033] The polyvinyl butyral resin contains hydroxyl groups of less than 30 mol%.

[0034] (4) The polymer-type conductive paste according to (3), wherein,

[0035] The polyvinyl butyral resin contains hydroxyl groups of less than 25 mol%.

[0036] (5) The polymer-type conductive paste according to (1), wherein,

[0037] The conductive metal powder is a silver-based powder.

[0038] (6) A conductive film formed from any one of the polymer-type conductive pastes described in (1) to (5).

[0039] (7) A solid electrolytic capacitor element, wherein the anode body surface has at least a dielectric layer, a solid electrolyte layer, a carbon layer and a conductor layer, wherein...

[0040] The conductor layer comprises the conductive film described in (6).

[0041] The effects of the invention

[0042] The conductive layer formed by the polymer-type conductive paste of the present invention has low moisture permeability even in high humidity environments. Therefore, the ionization of silver in the conductive layer can be suppressed, resulting in a conductive layer with high reliability. Attached Figure Description

[0043] [ Figure 1 ] Figure 1 This is a diagram showing an example of a solid electrolytic capacitor element. Detailed Implementation

[0044] Furthermore, the term "polymer-type conductive paste" in this specification, in contrast to "calcined conductive paste," refers to a type of paste in which the organic components in the coating film are dispersed through calcination, resulting in a conductive film in which only inorganic components remain. This means that the conductive film obtained by drying and / or curing the coating film contains residual organic components including adhesive resin.

[0045] The polymeric conductive paste of the present invention is not limited to its applications in general circuit wiring and electrode formation in electronic components, such as multilayer ceramic electronic components. It is particularly preferred for use in the formation of conductive layers in solid electrolytic capacitor elements such as tantalum capacitors, where the full benefits of the present invention can be obtained. Hereinafter, the application of the polymeric conductive paste of the present invention... Figure 1 An example of a solid electrolytic capacitor element is shown below.

[0046] The conductive layer 15 mainly comprises conductive metal powder and polyvinyl butyral resin. It is obtained by coating the polymer-type conductive paste of the present invention onto the carbon layer 14, heating it to a temperature above 120°C and below 220°C, removing the organic solvent, and drying it.

[0047] The polymer-type conductive paste of the present invention comprises at least conductive metal powder, polyvinyl butyral resin as a binder resin, an organic solvent capable of dissolving the binder resin, and specific additives.

[0048] There are no particular limitations on the conductive metal powder contained in polymer-type conductive pastes; metal powders commonly used in conductive pastes, such as silver, copper, nickel, palladium, and aluminum, can be used.

[0049] Silver powder is particularly preferred. Besides pure silver powder, this can be silver-coated powder (where the surface of a metal powder other than silver is coated with silver), composite silver powder (where the surface of silver powder is coated with inorganic and / or organic substances), or silver alloy powder (where silver is alloyed with a metal other than silver). In this specification, these will be collectively referred to as "silver powders." Using silver powders further enhances the effects of the invention and is also advantageous from the viewpoints of conductivity and cost. Furthermore, mixed powders obtained by mixing these silver powders with other conductive metal powders such as palladium, platinum, copper, and metal oxides can be used. In any case, the silver content relative to the total conductive metal powder content is preferably 10% by mass or more.

[0050] Furthermore, the shape of the conductive metal powder can be spherical, flake-shaped, dendritic, or other conventionally used shapes. Two or more powders with different average particle size, particle size distribution, or shape can be mixed together. In this invention, the use of a mixture of spherical and flake-shaped silver powders is particularly preferred because it makes control of conductivity and moisture resistance easier.

[0051] Polyvinyl butyral resin is used as the adhesive resin contained in the polymer-type conductive paste of the present invention. Polyvinyl butyral resins that can be used include "BH-S" (hydroxyl content = 22 mol%), "KS-5" (hydroxyl content = 25 mol%), "BM-5" (hydroxyl content = 34 mol%), "KS-1" (hydroxyl content = 25 mol%), "KS-10" (hydroxyl content = 25 mol%), "SV-02" (hydroxyl content = 22 mol%), "SV-06" (hydroxyl content = 22 mol%), and "SV-22" (hydroxyl content = 22 mol%) manufactured by Sekisui Chemicals Co., Ltd.

[0052] In the polymer-type conductive paste of the present invention, the content of polyvinyl butyral resin is not particularly limited, but can be appropriately determined according to the characteristics required as a paste. As an example, the solid content of polyvinyl butyral resin is in the range of 1.0 part by mass or more and 20 parts by mass or less relative to 100 parts by mass of conductive metal powder.

[0053] Furthermore, as long as it does not hinder the effect of the present invention, resins other than polyvinyl butyral resin can be included as adhesive resins. As one example, cellulose resins, acrylic resins, methacrylic resins, epoxy resins, phenolic resins, rosin acrylic resins, etc. can be mentioned.

[0054] It should be noted that the residual amount of hydroxyl groups in the polyvinyl butyral resin used in this invention is not particularly limited, but from the perspective of improving moisture resistance, it is preferably 35 mol% or less. More preferably, the residual amount of hydroxyl groups is 30 mol% or less, and particularly preferably 25 mol% or less.

[0055] As an organic solvent, it is sufficient to demonstrate solubility for the adhesive resin used. For example, organic solvents such as alcohols, ethers, esters, and hydrocarbons can be used. Two or more organic solvents or mixtures of organic solvents and water can be used as needed.

[0056] The polymer-type conductive paste of the present invention contains, as a specific additive, one or more selected from stearic acid, lauric acid, octadecenylsuccinic acid, benzoic acid, acetaminophen, aminophenol, catechol and N,N-bis(2-hydroxyethyl)cocoalkylamine.

[0057] These specific additives function as moisture permeability regulators in the pastes of the present invention, and are therefore also referred to as moisture permeability regulators in this specification.

[0058] According to the research of the inventors, when these moisture permeability modifiers are combined in a given amount in a paste in which polyvinyl butyral resin is used as an adhesive, the water permeability of the film obtained by coating and drying the paste is significantly reduced without having any adverse effects on conductivity, printability (thixotropy), etc., thereby improving the moisture resistance of the film.

[0059] Among the moisture permeability regulators, octadecenyl succinic acid is particularly preferred from the perspective of increasing membrane density and expecting to reduce ESR.

[0060] The content of these moisture permeability modifiers is in the range of 0.01 parts by mass or more and 3.0 parts by mass or less, relative to 100 parts by mass of conductive metal powder. When the content of the moisture permeability modifier is outside this range, the moisture resistance deteriorates, and other properties (such as conductivity) are adversely affected. The content of the moisture permeability modifier is preferably in the range of 0.1 parts by mass or more and 1.5 parts by mass or less.

[0061] Furthermore, the polymer-type conductive paste of the present invention may contain additives such as conventional surfactants, defoamers, plasticizers, dispersants, organic or inorganic fillers, which may be added as needed.

[0062] Example

[0063] (1) Experiment 1

[0064] <Preparation of Conductive Paste>

[0065] -Sample 1-

[0066] 8.6 parts by weight of polyvinyl butyral resin (Sekisui Chemicals Co., Ltd., "BM-5"; hydroxyl content = 35 mol%) was dissolved in benzyl alcohol to prepare 57.2 parts by weight of varnish A. 80 parts by weight of flake silver powder (Shōei Chemical Co., Ltd., "Ag-531") and 20 parts by weight of spherical silver powder (Shōei Chemical Co., Ltd., "Ag-202") were mixed and stirred using a three-roll mill. The mixture was then diluted with butyl acetate to achieve a shear rate of 9.3 s⁻¹ at 25°C using a Brookfield HA type viscometer. -1 The viscosity obtained by measurement was 1 Pa·s, and the silver paste prepared therefrom was used as sample 1.

[0067] -Sample 2-

[0068] Except for changing the polyvinyl butyral resin to "KS-5" (manufactured by Sekisui Chemicals Co., Ltd.; hydroxyl content = 25 mol%) as varnish B, the same procedure as for sample 1 was performed, and the resulting silver paste was used as sample 2.

[0069] -Sample 3-

[0070] In addition to the addition of 0.5 parts by weight of para-acetaminophen (manufactured by Tokyo Chemical Industry Co., Ltd., "3-hydroxyacetanilide") relative to 100 parts by weight of silver powder, the composition of sample 2 was carried out in the same manner as sample 2, and the resulting silver paste was used as sample 3.

[0071] -Sample 4-

[0072] Except that stearic acid (manufactured by MIYOSHI OIL & FAT Co., Ltd., "Stearic Acid 90") was used instead of acetaminophen, the same procedure was performed as for sample 3, and the resulting silver paste was used as sample 4.

[0073] -Sample 5-

[0074] Except for the use of lauric acid (manufactured by Fujifilm and Koh Genuine Chemicals Co., Ltd.) instead of acetaminophen, the same procedure was performed as for sample 3, and the resulting silver paste was used as sample 5.

[0075] -Sample 6-

[0076] Except for the use of octadecenylsuccinic acid (CRODA JAPAN dicarboxylic acid "Hypermer KD-16") instead of acetaminophen, the same procedure was performed as for sample 3, and the resulting silver paste was used as sample 6.

[0077] -Sample 7-

[0078] Except that benzoic acid (manufactured by Fujifilm and Koh Genuine Chemicals Co., Ltd.) was used instead of acetaminophen, the same procedure was performed as for sample 3, and the resulting silver paste was used as sample 7.

[0079] -Sample 8-

[0080] Except that aminophenol (p-aminophenol manufactured by Fujifilm and Koh Genuine Chemicals Co., Ltd.) was used instead of acetaminophenol, the same procedure was performed as for sample 3, and the resulting silver paste was used as sample 8.

[0081] -Sample 9-

[0082] Except that catechol (manufactured by Fujifilm and Koko Pure Chemical Industries Co., Ltd.) was used instead of acetaminophen, the same procedure was performed as for sample 3, and the resulting silver paste was used as sample 9.

[0083] -Sample 10-

[0084] Except for the use of N,N-bis(2-hydroxyethyl)cocoalkylamine (LION-SPECIALTY-CHEMICALS ESOMIN "LIPONOL C / 12") instead of acetaminophen, the same procedure was performed as for sample 3, and the resulting silver paste was used as sample 10.

[0085] -Sample 11-

[0086] Except for the use of stearamine (FARMIN 80 manufactured by Kao Corporation) instead of acetaminophen, the same procedure was performed as for sample 3, and the resulting silver paste was used as sample 11.

[0087] (2) Experiment 2

[0088] <Preparation of Conductive Paste>

[0089] -Samples 12~21-

[0090] Except for the amounts of conductive metal powder, polyvinyl butyral resin, and acetaminophen as recorded in Table 2, the process was the same as for sample 3, and the resulting silver paste was used as samples 12-21.

[0091] (3) Experiment 3

[0092] <Preparation of Conductive Paste>

[0093] -Samples 22~25-

[0094] Except for the amounts of conductive metal powder, polyvinyl butyral resin, and octadecenyl succinic acid as recorded in Table 3, the process was the same as for sample 6, and the resulting silver paste was used as samples 22-25.

[0095] For samples 1 to 25 of the conductive paste obtained therefrom, the moisture permeability of each sample was evaluated by performing the following moisture permeability test.

[0096] The evaluation results for samples 1-11 are shown in Table 1, the evaluation results for samples 12-21 are shown in Table 2, and the evaluation results for samples 22-25 are shown in Table 3.

[0097] It should be noted that the samples marked with * in Tables 1-3 are comparative examples.

[0098] <Moisture permeability test>

[0099] The silver paste of the sample was coated onto a PET film, heated at 150°C for 60 minutes, and then peeled off from the PET film to prepare a dry film of the sample with a thickness of 20±2μm.

[0100] Prepare a glass container A containing 2g of silica gel according to the sample quantity. Apply instant adhesive to each opening and cover it with the sample's dry film. After completely sealing, measure the total mass of glass container A.

[0101] Next, prepare a plastic container B of the same size as glass container A. Add an appropriate amount of purified water through the opening of plastic container B, ensuring that the purified water does not enter glass container A as described above. Then, completely seal the opening of plastic container B. Next, heat plastic container B containing glass container A from room temperature to 65°C and maintain this temperature for 15 hours.

[0102] After the holding time has elapsed, the plastic container B, which has slowly cooled, is opened, and the glass container A inside is removed. The total mass of glass container A is then measured again, and the increase is taken as the moisture permeability (mg). In this embodiment, samples with a moisture permeability of less than 20mg are considered acceptable.

[0103] [Table 1]

[0104]

[0105] [Table 2]

[0106]

[0107] [Table 3]

[0108]

[0109] (Regarding the evaluation results)

[0110] As can be seen from the results shown in Table 1, the moisture permeability varies depending on the amount of hydroxyl groups in the polyvinyl butyral resin, and the moisture permeability is further significantly reduced when the moisture permeability regulator of the present invention is included.

[0111] Furthermore, as shown in Tables 2 and 3, it can be seen that whether the content of the moisture permeability regulator in the conductive paste is too high or too low, it reduces the effect of reducing moisture permeability.

[0112] In addition, experiments were also conducted on substances with structural isomers among the moisture permeability regulators used in the examples, and it was confirmed that structural isomers also have the effect of reducing moisture permeability.

[0113] Industrial applicability

[0114] This invention can be applied to solid electrolytic capacitor elements and multilayer ceramic electronic components.

[0115] Explanation of symbols

[0116] 1. Solid electrolytic capacitor element

[0117] 11. Valve function in sintered metal bodies (anode bodies)

[0118] 12. Oxide film layer (dielectric layer)

[0119] 13 Solid electrolyte layer

[0120] 14 carbon layers

[0121] 15 Conductor Layer

Claims

1. A polymer-type conductive paste comprising a conductive metal powder, a binder resin, an organic solvent, and a specific additive, wherein an organic component including the binder resin remains in a conductive film obtained by drying and / or curing a coating film, wherein the binder resin is a polyvinyl butyral resin, the specific additive is one or two or more selected from the group consisting of octadecenyl succinic acid, benzoic acid, acetylamino phenol, aminophenol, catechol, and N,N-bis(2-hydroxyethyl) cocoalkylamine, and the polymer-type conductive paste contains the specific additive in a range of 0.01 parts by mass or more and 3.0 parts by mass or less with respect to 100 parts by mass of the conductive metal powder.

2. The polymer-type conductive paste according to claim 1, wherein the specific additive is octadecenyl succinic acid.

3. The polymer-type conductive paste according to claim 1, wherein a content of a hydroxyl group included in the polyvinyl butyral resin is 30 mol% or less.

4. The polymer-type conductive paste according to claim 3, wherein the content of the hydroxyl group included in the polyvinyl butyral resin is 25 mol% or less.

5. The polymer-type conductive paste according to claim 1, wherein the conductive metal powder is a silver-based powder.

6. A conductive film formed from the polymer-type conductive paste according to any one of claims 1 to 5.

7. A solid electrolytic capacitor element having at least a dielectric layer, a solid electrolyte layer, a carbon layer, and a conductive body layer on a surface of an anode body, wherein the conductive body layer contains the conductive film according to claim 6. ​ ​ ​ ​ ​ ​ ​ ​

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