JP2004153044A - Conductive paste and solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silver-based conductive paste for a solid electrolytic capacitor, excellent in electrical characteristic without losing operability and mechanical reliability, and to provide a solid electrolytic capacitor excellent in stability and reliability of the electrical characteristics by using it. <P>SOLUTION: The conductive paste for the solid electrolytic capacitor contains (A) organic binders such as epoxide resin, polyesterimide, (B) solvent, (C) conductive fillers such as silver powder, and (D) an organic metal resinate compound which is thermally decomposed at ≤250°C such as octylic acid silver and contains metal salt of at least one kind of silver, gold, copper and nickel as an essential ingredient. (D) Metal component in the organic metal resinate compound is blended by 0.5 to 30 wt.% to the total of (C) the conductive fillers and metal components in (D) the organic metal resinate compound. <P>COPYRIGHT: (C)2004,JPO

Description

【００３１】
【発明の効果】
以上の説明および表１から明らかなように、本発明の固体電解コンデンサは、初期および高温高湿条件下でも、電気特性、電気的な接合信頼性に優れており、かつ高周波低インピーダンス化にも対応できるものである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a highly reliable conductive paste excellent in electric characteristics and a solid electrolytic capacitor.
[0002]
[Prior art]
The solid electrolytic capacitor to which the present invention relates is formed by subjecting an anode body made of a metal having a valve action such as tantalum, aluminum, and niobium to a chemical conversion treatment, forming a dielectric layer, and further forming a semiconductor electrolyte layer and a carbon layer on the surface thereof. The cathode layer is formed, the cathode layer is bonded and fixed to the cathode lead frame using a conductive adhesive, and the anode lead connected to the anode body is connected to the anode lead frame by welding. It is configured by an exterior resin.
[0003]
[Problems to be solved by the invention]
Conventionally, the cathode layer is formed using a normal silver-based conductive paste. However, the performance of the silver-based conductive paste of the cathode layer depends on the electrical characteristics of the resistance component such as tan δ, ESR, and impedance of the solid electrolytic capacitor. Is known to have a significant effect. That is, it is necessary to lower the vertical resistance value of the bulk of the conductive paste layer and also to suppress the interface contact resistance between the paste layer and the base more than ever.
[0004]
The most common method of improving the electrical characteristics due to the paste layer is to fill the conductive filler of the silver-based conductive paste used for the cathode layer and the conductive adhesive as high as possible. However, when the conductive filler is highly filled, not only does various application workability such as dipping and dispensing deteriorate, but also the bulk itself of the conductive paste layer becomes brittle and, at the same time, the wettability with the base deteriorates. It is not yet satisfactory in terms of mechanical connection reliability.
[0005]
If the cathode layer is brittle, the cathode lead frame may be peeled off in the capacitor manufacturing process after the cathode lead frame is bonded. In addition, a method has been considered in which an organic binder of a conductive paste having a large curing shrinkage is used to make contacts between silver fillers dense and promote formation of a conductive path.However, such a binder reduces stress relaxation. It is difficult, and there is a concern that cracks may occur at the interface between the cathode layer and the adhesive layer due to heat shock such as reflow, and mechanical open failure may occur.
[0006]
In recent years, as electronic devices process a large amount of digital information at a high clock frequency, the demand for high-frequency, low-impedance solid-state electrolytic capacitors has increased, and the conductive paste used for such capacitors has been required to have stable, high-conductivity. In addition, there has been a demand for improved electrical bonding reliability.
[0007]
An object of the present invention is to solve the above-mentioned disadvantages, and does not impair workability or mechanical bonding reliability, and uses a silver-based conductive paste having excellent electric characteristics to improve electric characteristics. An object of the present invention is to provide a solid electrolytic capacitor having excellent stability and reliability.
[0008]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that the above object can be achieved by using a resin composition described later, and have completed the present invention.
[0009]
That is, the present invention
A dielectric layer, a semiconductive electrolyte layer, a carbon layer, and a cathode layer are sequentially formed on an anode body made of a metal having a so-called valve action, in which the metal surface is uniformly covered with an oxide film of the metal by anodic oxidation. A conductive paste used for a solid electrolytic capacitor in which a cathode layer and a cathode frame (terminal) are connected by a conductive adhesive layer, and the outer peripheral surface thereof is further packaged with a resin;
(A) an organic binder,
(B) a solvent,
(C) a conductive filler and (D) an organic metal resinate compound represented by the following formula or an organic metal resinate compound thermally decomposed at 250 ° C. or lower, wherein at least one metal selected from silver, gold, copper, and nickel What is salt
Me-X-R
(Wherein, Me is Ag, Au, Cu, any of Ni, X is -S -, - O (CO) - or -SO ₃ - and, R represents an alkyl group having 1 to 10 carbon atoms Respectively)
As an essential component, the metal component in the (D) organometallic resinate compound is 0.5 to 30% by weight based on the total of (C) the conductive filler and the metal component in the (D) organic metal resinate compound. The conductive paste for a solid electrolytic capacitor, characterized in that the cathode layer or the cathode layer and the conductive adhesive layer are cured by curing the conductive paste according to claim 1. -A solid electrolytic capacitor characterized by being composed of a dried product.
[0010]
Hereinafter, the present invention will be described in detail.
[0011]
The type of the organic binder (A) used in the present invention is not particularly limited, and may be a thermosetting type or a thermoplastic type, and is a conventionally known epoxy type, phenol type, melamine type, cellulose type, acrylic type. Systems, alkyd systems, polyimide systems, and mixed modified resin systems thereof. The modified resin may be simply dissolved and mixed, or may be partially bound by a heat reaction. If necessary for the reaction, a curing catalyst can be used.
[0012]
In the case of an organic binder having low heat resistance, the conductive paste cured film deteriorates under high-temperature and high-humidity conditions such as a pressure cooker test at 121 ° C. and 2 atm. And a short circuit occurs due to outflow of the conductive powder itself. Therefore, when use under such severe conditions is required, it is necessary to select a binder having high heat resistance. For example, a polyimide resin or a system in which a novolak epoxy resin having an average number of epoxy groups of 3 or more is cured with a phenol resin is used.
[0013]
It is desirable that these resins are dissolved and mixed with a solvent in advance before the paste is manufactured.
[0014]
As the solvent (B) used in the present invention, a solvent capable of dissolving the above resin, for example, dioxane, hexane, toluene, ethyl cellosolve, cyclohexanone, butyl cellosolve, butyl cellosolve acetate, butyl carbitol acetate, diethylene glycol diethyl ether , Diacetone alcohol, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone, and the like. These may be used alone or in combination of two or more. it can.
[0015]
Examples of the (C) conductive filler used in the present invention include powder having a silver layer on the surface, such as silver powder and silver-coated copper powder, copper powder, nickel powder, and carbon powder. Alternatively, two or more kinds can be used in combination. That is, the conductive filler desirably contains at least a conductive filler having a silver layer on the surface, such as silver powder or silver-coated copper powder. The particle shape of the conductive filler is not particularly limited, but the average particle diameter (D50) is 30 μm or less. Preferably, those having an average particle size of 5 to 15 μm are used. If it exceeds 30 μm, the dispersion in the vehicle will be poor and the workability of the paste will be problematic. Although the compounding ratio of the conductive filler is not particularly limited, when importance is placed on the electric characteristics, the ratio of (conductive filler / (solid content of modified resin + conductive filler)) is 80 to 95% by weight. Is desirably within the range.
[0016]
The (D) organometallic resinate compound used in the present invention is represented by Formula 2 described above, and the metal constituting the salt contains at least one of silver, gold, copper, and nickel. is there. The constituent organic compound is an alkyl group having 1 to 10 carbon atoms.
[0017]
The reason why the upper limit of the number of carbon atoms of the alkyl group is set to 10 is that when the number of carbon atoms exceeds 10, not only low-temperature baking at 250 ° C. or less becomes difficult, but also the organic substance formed during the baking, which is undergoing thermal decomposition, is a cured product. This is because they remain inside and cause outgassing in the heat history of the subsequent process. As the organic metal resinate, a compound of a lower carboxylic acid and a metal, for example, gold octylate, silver octylate, copper octylate, nickel octylate, and the like can be used. Any other metal resinate that thermally decomposes at 250 ° C. or lower may be used as long as it can be uniformly dispersed or dissolved.
[0018]
The mixing ratio of the metal component in the organic metal resinate to the total of the metal component in the organic metal resinate (D) and the conductive filler (C) is preferably in the range of 0.5 to 30 parts by weight. If the amount of the metal component is less than 0.5 part by weight, the effects described later cannot be expected. If the amount exceeds 30 parts by weight, the amount of residual carbon from the organometallic resinate after firing increases, and on the contrary, the conductivity deteriorates.
[0019]
The conductive paste of the present invention contains the aforementioned (A) organic binder, (B) solvent, (C) conductive filler, and (D) organometallic resinate compound as essential components, but does not violate the object of the present invention. As long as necessary, a curing catalyst, an antifoaming agent, a coupling agent, and other additives can be added as needed. This conductive paste can be produced by thoroughly mixing the above-mentioned components according to a conventional method, further kneading with a disperse, kneader, three-roll mill or the like, and then defoaming under reduced pressure.
[0020]
The conductive paste thus obtained is diluted with an appropriate solvent, and the solid electrolytic capacitor element is dipped to form a cathode layer. Next, the anode lead of the capacitor element is connected to the anode lead frame of the anode terminal by welding, and then the cathode layer and the cathode lead frame are connected with the conductive paste obtained by the above method.
[0021]
Thereafter, the resin exterior is performed by a transfer molding method or a dip method, and the external lead frame is bent to complete a solid electrolytic capacitor.
[0022]
[Action]
The conductive paste of the present invention contains an organometallic resinate compound that can be uniformly dissolved or dispersed in an organic binder and that thermally decomposes at 250 ° C. or lower. When a metal having excellent conductivity is added in the form of a liquid organometallic resinate, the liquid can exist at an interface even in a very small amount (ie, thin) as compared with the powder, and the metal can be present in voids between the conductive filler particles. The resinate wraps around and fills the void.
[0023]
At the same time as curing or drying of the conductive paste, the metal resinate is fired at a low temperature. As a result, decomposition products of the metal resinate, that is, metal fine particles are generated at the paste interface and between the conductive filler particles, and the metal fine particles fill up these voids, so that more conductive paths are formed and the paste bulk is formed. Has the effect of improving the conductivity of the film and suppressing the interface contact resistance.
[0024]
By using a conductive paste having such a function, a solid electrolytic capacitor having excellent tan δ, ESR, impedance and electrical connection reliability can be obtained.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. In the following Examples and Comparative Examples, “parts” means “parts by weight”.
[0026]
Example 1
In 100 parts of Epicoat # 1004 (product name, manufactured by Japan Epoxy Resin Co., Ltd.) of epoxy resin, 13 parts of Marcalinker MS2P (manufactured by Maruzen Petrochemical Co., Ltd.) of phenol resin as a curing agent was added in 113 parts of butyl cellosolve acetate. A dissolution reaction was performed at 85 ° C. for 1 hour to obtain a viscous resin. To 24 parts of this resin, 0.10 part of imidazole 1-benzyl-2-phenylimidazole as a curing catalyst, 0.02 part of a silicone-based antifoaming agent, and R972 (trade name, manufactured by Nippon Aeriel Co., Ltd.) as fine silica powder. 6 parts of silver powder (flaky, average particle size of 6 μm), 6 parts of silver-coated copper powder (spherical, average particle size of 10 μm), and 10 parts of silver octylate were mixed, and the mixture was further kneaded with three rolls. Then, the conductive paste was produced by degassing under reduced pressure.
[0027]
Example 2
100 parts of polyesterimide, which is a heat-resistant thermoplastic resin, was dissolved in 300 parts of a mixed solvent of N-methylpyrrolidone / diethylene glycol dimethyl ether = 6/4 (weight ratio) to obtain a viscous resin. To 200 parts of this resin, 138 parts of the above-mentioned mixed solvent, 0.12 parts of an antifoaming agent, 10.4 parts of RY200S (trade name, manufactured by Nippon Aerosil Co., Ltd.) as fine silica powder, and silver powder (flaky, average particle size of 6 μm) ) 90 parts and 12 parts of silver octylate were mixed, and kneading treatment was further performed using a three-roll mill, followed by defoaming under reduced pressure to produce a conductive paste.
[0028]
Comparative Example 1
A conductive paste was produced in the same manner as in Example 1 except that silver octylate was not used and 60 parts of silver powder was changed to 64 parts.
[0029]
The conductive paste obtained in Examples 1 and 2 and Comparative Example 1 was diluted to several poise with butyl acetate, and a solid electrolytic capacitor element was dipped therein, and the conductive paste was heated at 200 ° C. × 1 h. Curing in oven to form cathode layer. Further, after the anode lead and the anode lead frame are joined by welding, the cathode layer and the cathode lead frame are joined with the conductive paste of the first embodiment. Then, a 10 V, 47 μF solid electrolytic capacitor was manufactured by externally covering with a resin by a molding method. Table 1 shows the ESR measurement results at 100 kHz for the 3500 solid electrolytic capacitors thus obtained at the initial stage and after the high-temperature and high-humidity test at 85 ° C. and 85% RH. The effect of the present invention was confirmed.
[0030]
[Table 1]

[0031]
【The invention's effect】
As is clear from the above description and Table 1, the solid electrolytic capacitor of the present invention has excellent electrical characteristics and electrical bonding reliability under initial and high-temperature and high-humidity conditions. It can respond.

Claims (2)

(A) an organic binder,
(B) a solvent,
(C) a conductive filler and (D) an organic metal resinate compound represented by the following formula or an organic metal resinate compound thermally decomposed at 250 ° C. or lower, wherein at least one metal selected from silver, gold, copper, and nickel What is salt
Me-X-R
(Wherein, Me is Ag, Au, Cu, any of Ni, X is -S -, - O (CO) - or -SO ₃ - and, R represents an alkyl group having 1 to 10 carbon atoms Respectively)
As an essential component, the metal component in the (D) organometallic resinate compound is 0.5 to 30% by weight based on the total of (C) the conductive filler and the metal component in the (D) organic metal resinate compound. The conductive paste for a solid electrolytic capacitor characterized by being blended so as to have the following ratio. A dielectric layer, a semiconductor electrolyte layer, a carbon layer, and a cathode layer are sequentially formed on an anode body made of a metal having a valve action, and the cathode layer and the cathode frame (terminal) are connected by a conductive adhesive layer. A solid electrolytic capacitor whose outer surface is externally covered with a resin,
A solid electrolytic capacitor, wherein the cathode layer or the cathode layer and the conductive adhesive layer are constituted by a cured and dried product of the conductive paste according to claim 1.