JP2016089038A - Conductive adhesive for electronic component and capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive adhesive for electronic component having high adhesiveness, good in conductivity and capable of low ESR of a capacitor and reducing raw material costs and a high performance and high reliability capacitor using such conducive adhesive.SOLUTION: A conductive adhesive for an electronic component contains (A) an epoxy resin, (B) a phenol resin curing agent, (C) a scaly silver coated copper powder, (D) a dendritic silver coated copper powder and (E) a curing accelerator. The total content of the (C) component and the (D) component is 70 to 85 mass% and a mass ratio of the contents of the (C) component and the (D) component is 95:5 to 45:55.SELECTED DRAWING: None

Description

  The present invention relates to a conductive adhesive used for electronic parts such as a tantalum solid electrolytic capacitor, and a capacitor using the same.

  The basic element of a solid electrolytic capacitor is generally formed by forming a dielectric layer by chemical conversion of the surface of an anode body made of a metal having a valve action such as tantalum, aluminum, niobium, etc., and is made of a conductive polymer or the like on the surface. It has a structure in which a solid electrolyte layer, a carbon layer, and a cathode layer made of a conductive paste are sequentially formed. Then, the cathode layer is bonded to the cathode lead terminal using a conductive adhesive, the anode body is joined to the anode lead terminal by welding, and a mold resin is applied to the outside thereof to form a capacitor component.

  Since such a solid electrolytic capacitor uses a solid electrolyte as an electrolyte material, there is no problem of liquid leakage or transpiration, which has been pointed out in a capacitor using a conventional electrolytic solution, and there is almost no characteristic deterioration and a long life. Therefore, in recent years, the demand has increased rapidly.

  By the way, in a solid electrolytic capacitor, as a conductive adhesive for bonding a cathode layer and a cathode lead terminal, conventionally, an adhesive having an epoxy resin as a main skeleton and silver powder added thereto is used. By using silver powder having good conductivity, the interface resistance between the cathode layer and the cathode lead terminal can be suppressed, and the ESR (equivalent series resistance) of the capacitor can be reduced.

  However, the conductive adhesive using silver powder has a high raw material cost. Although copper powder is inferior to silver powder in terms of conductivity, it is inexpensive. However, copper powder is easy to oxidize, and since it easily oxidizes in the temperature rise when the conductive adhesive is heat-cured and in the subsequent use environment, the characteristics as an adhesive are easily lost, and the low ESR can be realized. difficult.

  On the other hand, Patent Document 1 discloses a conductive paste composition using silver-coated copper powder in order to reduce raw material costs. However, in this composition, the silver-coated copper powder is used together with the silver powder, and the effect of reducing the raw material cost is small. In the first place, this composition is a composition for forming an electronic circuit, and no consideration is given to the properties as an adhesive.

  In this way, it has high adhesiveness comparable to that using conventional silver powder, has good conductivity, can reduce the ESR of capacitors, and can reduce raw material costs. The agent has not yet been obtained, and therefore a capacitor using such a conductive adhesive for electronic components has not been obtained either.

JP 2009-230952 A

  The present invention has been made to solve the above-described problems of the prior art, and is useful for applications of electronic parts such as capacitors, has high adhesiveness, good conductivity, and enables low ESR of capacitors. It is another object of the present invention to provide a conductive adhesive for electronic parts that can reduce raw material costs, and a high-performance and highly reliable capacitor using such a conductive adhesive.

  As a result of intensive studies to solve the above problems, the present inventors have used conventional silver powder by containing scaly silver-coated copper powder and dendritic silver-coated copper powder as a conductive filler in a specific ratio. The present invention has been completed by finding out that raw material costs can be reduced while having high adhesiveness and conductivity comparable to those of conventional materials.

  That is, the conductive adhesive for electronic components according to one embodiment of the present invention includes (A) an epoxy resin, (B) a phenol resin curing agent, (C) a scaly silver-coated copper powder, and (D) a dendritic silver-coated copper. A conductive adhesive for electronic parts containing powder and (E) a curing accelerator, wherein the total content of the component (C) and the component (D) is 70 to 85% by mass of the whole adhesive, and The mass ratio of the content of the component (C) and the component (D) is 95: 5 to 45:55.

  In addition, a capacitor according to another aspect of the present invention is characterized in that a capacitor element is bonded with the conductive adhesive for electronic parts.

  According to the present invention, a conductive adhesive for electronic parts that has high adhesiveness, good electrical conductivity, enables low ESR of capacitors, and can reduce raw material costs, and such electrical conductivity. A high-performance and high-reliability capacitor using an adhesive can be obtained.

It is sectional drawing which shows the capacitor | condenser by one Embodiment.

Hereinafter, the present invention will be described in detail.
The conductive adhesive for electronic components of the present invention includes (A) an epoxy resin, (B) a phenol resin curing agent, (C) a flaky silver-coated copper powder, (D) a dendritic silver-coated copper powder, and (E). It contains a curing accelerator.

  The epoxy resin of component (A) used in the present invention is not particularly limited as long as it has two or more glycidyl groups (epoxy groups) in one molecule, and a known epoxy resin is used. be able to.

  Examples of usable epoxy resins include, for example, bisphenol A type epoxy resins, bisphenol F type epoxy resins, biphenyl type epoxy resins, naphthalene type epoxy resins, dicyclopentadiene type epoxy resins, cresol novolac type epoxy resins, hydrogenated bisphenols. Type epoxy resin, 1,4-cyclohexanedimethanol diglycidyl ether, 1,6-hexanediol diglycidyl ether, hexahydrophthalic acid diglycidyl ester, 3,4-epoxycyclohexylmethyl (3,4-epoxy) cyclohexanecarboxylate And triglycidyl isocyanurate. These can be used individually by 1 type or in mixture of 2 or more types.

  The phenol resin curing agent of component (B) used in the present invention can be used without particular limitation as long as it is conventionally used as a curing agent for epoxy resins.

  Examples of the phenol resin curing agent that can be used include phenol novolak resin, cresol novolak resin, bisphenol A novolak resin, biphenyl novolak resin, allyl-modified phenol novolak resin, and the like. These can be used individually by 1 type or in mixture of 2 or more types.

  The blending amount of the (B) component phenolic resin curing agent is such that the phenolic hydroxyl group equivalent in the phenolic resin is 0.5 to 2.0 equivalents per equivalent of the epoxy group in the epoxy resin of the (A) component. A range is preferable, and a range of 0.8 to 1.20 equivalent is more preferable. When the amount is less than 0.5 equivalent or exceeds 2.0 equivalent, characteristics such as heat resistance and ESR (equivalent series resistance) characteristics of the cured product may be deteriorated.

  The scale-like silver-coated copper powder of component (C) used in the present invention is a component for reducing the electrical resistance of a conductive adhesive for electronic components, that is, a low resistance component, and conductive adhesive for electronic components. It is a component necessary for imparting good storage stability (sedimentation resistance) and coating workability (spreading resistance, stringing resistance) to the agent.

From the viewpoint of lowering the resistance of the conductive adhesive for electronic parts, and improving the storage stability and coating workability, the scaly silver-coated copper powder of component (C) has an average particle diameter of 1 to 20 μm and a BET ratio. The surface area is preferably 0.6 to 2.3 m ² / g. The average particle size is more preferably 1.0 to 10 μm. Further, the BET specific surface area is more preferably 0.8 to 2.0 m ² / g.

  Moreover, as for the silver coating amount of the scale-like silver covering copper powder of (C) component, 10-30 mass parts is preferable with respect to 100 mass parts of copper powder. When the silver coating amount is less than 10 parts by mass, the electric resistance of the cured product becomes high, and when it exceeds 30 parts by mass, the cost improvement effect decreases.

  The dendritic silver-coated copper powder of component (D) used in the present invention is a component for reducing the electrical resistance of the conductive adhesive for electronic components, as in component (C). That is, the silver-coated copper powder of component (D) is an aggregate of dendritic particles (a shape in which branches are branched from the main branch and growing two-dimensionally or three-dimensionally, also referred to as dendritic shape). In addition, since the number of contacts between particles increases, excellent conductivity can be imparted. The dendritic silver-coated copper powder preferably has a shape in which the branches extend from the main branch at an appropriate interval to form a needle-like portion in order to obtain good conductivity.

The (D) component dendritic silver-coated copper powder preferably has an average particle diameter of 5 to 20 μm and a BET specific surface area of 0.2 to 1.3 m ² / g. When the average particle size is 5 μm or more, sufficient conductivity is obtained, and when the average particle size is 20 μm or less, a uniform coating film can be formed. In addition, when the BET specific surface area is less than 0.2 m ² / g, the shape of the tree branch is not sufficiently developed, and the branched branch portion is short and has a shape close to a columnar shape. Decreases. When the BET specific surface area exceeds 1.3 m ² / g, the wettability is lowered and dispersion may be difficult. The average particle size is more preferably 5 to 18 μm. Further, the BET specific surface area is more preferably 0.2 to 1.0 m ² / g.

  Moreover, as for the silver coating amount of the dendritic silver covering copper powder of (D) component, 10-30 mass parts is preferable with respect to 100 mass parts of copper powder. When the silver coating amount is less than 10 parts by mass, the electric resistance of the cured product becomes high, and when it exceeds 30 parts by mass, the cost improvement effect decreases.

In the present invention, the scale-like silver-coated copper powder of the component (C) and the dendritic silver-coated copper powder of the component (D) are 70 to 85% by mass in total of the conductive adhesive of the present invention. And, it mix | blends so that mass ratio of content of (C) component and (D) component may be set to 95: 5-45: 55. When the total amount of the component (C) and the component (D) is less than 70% by mass of the entire conductive adhesive, good conductivity cannot be obtained, and the ESR characteristics of the capacitor are poor. When the total amount of component (C) and component (D) exceeds 85% by mass of the entire conductive adhesive, good adhesive strength cannot be obtained.
On the other hand, when the proportion of the component (C) in the component (C) and the component (D) is less than the above range, good conductivity cannot be obtained, and the ESR characteristic of the capacitor becomes poor. This is because the wettability of the (D) component dendritic silver-coated copper powder becomes poor, so that the required amount of dendritic silver-coated copper powder cannot be uniformly dispersed in the conductive adhesive, This is because it is difficult to have contact points between each other. Moreover, when the ratio of (C) component is less than the said range, the preservability and application | coating workability | operativity of the conductive adhesive for electronic components will fall. On the contrary, when the proportion of the component (C) in the component (C) and the component (D) exceeds the above range, the conductivity is lowered.

  The conductive adhesive for electronic parts of the present invention may be blended with a conductive filler other than the component (C) and the component (D) as long as the effects of the present invention are not impaired. Examples of the conductive filler other than the component (C) and the component (D) include silver-coated copper powder such as a spherical shape, a plate shape, a bowl shape, a needle shape, and a chestnut shape. Silver powder, silver alloy powder, copper powder, copper alloy powder, nickel powder, nickel alloy powder, and the like can also be blended within a range that does not impair the effects of the present invention. However, from the viewpoint of conductivity, adhesiveness, cost reduction, etc., it is preferable to use only silver-coated copper powder as the conductive filler, and it is more preferable to use only the component (C) and the component (D). . Of the silver-coated copper powders, the spherical silver-coated copper powders are particularly effective because they tend to settle during storage and curing, spread easily after coating, have poor coating workability, and have low adhesive strength. It is preferable not to contain. Here, “substantially do not contain” means that it is not blended except those inevitably contained as impurities. In addition, the spherical silver-coated copper powder contains this, and as a result, the cured product is biased. As a result, distortion due to heat shock increases, peeling easily occurs, and the maintenance rate of adhesive strength also decreases. Arise. When the adhesive strength maintenance ratio decreases, the ESR fluctuation (variation) of the capacitor increases, and the electrical resistance after solder reflow increases.

  In the present specification, the average particle diameter of the conductive filler such as the scaly silver-coated copper powder is a 50% particle diameter (D50 value) in the number cumulative distribution measured by a laser diffraction particle size distribution measuring apparatus.

  The curing accelerator for the component (E) used in the present invention can be used without particular limitation as long as it can accelerate the curing of the component (A) and the component (B). .

  Examples of usable curing accelerators include 2-heptadecylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-n-propylimidazole, 1,2-dimethylimidazole, and 2-phenylimidazole. 2-phenyl-4-methylimidazole, 4-methylimidazole, 4-ethylimidazole, 2-phenyl-4-hydroxymethylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, 2- Phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-undecylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1- Be Dil-2-phenylimidazole hydrochloride, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2- Phenyl-4,5-di (2-cyanoethoxy) methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-dodecyl-2-methyl-3-benzyl Imidazolium chloride, 2,4-diamino-6- [2'-methylimidazolyl- (1 ')]-ethyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6- [2'-undecylimidazolyl -(1 ')]-ethyl-s-triazine isocyanuric acid adduct, 2,4 Diamino-6- [2'-ethyl-4'-methylimidazolyl- (1 ')]-ethyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6- [2'-methylimidazolyl- (1' )]-Ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-methylimidazole isocyanuric acid adduct, imidazoles such as 2-phenylimidazoline; 1,8-diazabicyclo [5,4, Diazabicyclo compounds such as 0] undecene-7 (DBU), 1,5-diazabicyclo [4,3,0] nonene, 5,6-dibutylamino-1,8-diazabicyclo [5,4,0] undecene-7; These salts; triethylamine, triethylenediamine, benzyldimethylamine, α-methylbenzyldimethylamino , Tertiary amines such as triethanolamine, dimethylaminoethanol, tris (dimethylaminomethyl) phenol; trimethylphosphine, triethylphosphine, tributylphosphine, diphenylphosphine, triphenylphosphine, tri (p-methylphenyl) phosphine, tri ( Nonylphenyl) phosphine, methyldiphenylphosphine, dibutylphenylphosphine, tricyclohexylphosphine, bis (diphenylphosphino) methane, 1,2-bis (diphenylphosphino) ethane and other organic phosphine compounds; tetraphenylphosphonium tetraphenylborate, tri Examples include tetra- or triphenylboron salts such as phenylphosphine tetraphenylborate and triphenylphosphine triphenylborane. It is.

It is also possible to cure by adding a thermal cation curing accelerator. Examples of the thermal cation curing accelerator that can be used include benzylsulfonium salt, thiophenium salt, thiolanium salt, benzylammonium, pyridinium salt, hydrazinium salt, carboxylic acid ester, sulfonic acid ester, and amine imide.
A hardening accelerator may be used individually by 1 type, and 2 or more types may be mixed and used for it.

  (E) As a hardening accelerator of a component, imidazoles and amines are preferable and imidazoles are more preferable. Of these, 2-heptadecylimidazole, 1-benzyl-2-phenylimidazole, and 2-phenyl-4-methyl-5-hydroxymethylimidazole are even more preferable.

  The blending amount of the curing accelerator of component (E) is 0.5 to 15.0 mass with respect to 100 parts by mass of the total amount of the epoxy resin of component (A) and the phenol resin curing agent of component (B). The range of parts is preferable, and the range of 1.0 to 8.0 parts by mass is more preferable. If the amount is less than 0.5 parts by mass, there is a risk that electrical characteristics, film thickness uniformity, and the like are reduced due to poor curing, and if it exceeds 15.0 parts by mass, storage stability may be reduced.

  In the conductive adhesive for electronic parts of the present invention, in addition to the above components, adhesion improvers such as silane coupling agents, titanium coupling agents, and acid anhydrides, diluents, antifoaming agents, and other various types An additive can be mix | blended in the range which does not inhibit the function of the electrically conductive adhesive for electronic components.

  The conductive paste for a capacitor of the present invention includes, for example, (A) an epoxy resin, (B) a phenol resin curing agent, (C) a flaky silver-coated copper powder, (D) a dendritic silver-coated copper powder, And (E) after sufficiently mixing the curing accelerator and various components to be blended as necessary, and by reducing the pressure while rotating at a low speed with a kneader, a conductive filler such as a resin and scaly silver-coated copper powder; It is possible to manufacture by thoroughly blending, and further kneading with a three-roll mill or the like and then degassing under reduced pressure.

  Next, an embodiment of a capacitor of the present invention using the conductive adhesive for electronic parts of the present invention and a manufacturing method thereof will be described with reference to the drawings.

[Capacitor]
FIG. 1 is a cross-sectional view showing a solid electrolytic capacitor according to an embodiment of the capacitor of the present invention.
As shown in FIG. 1, the solid electrolytic capacitor 10 of this embodiment includes an anode body 1 serving as a capacitor anode, a dielectric layer 2, a solid electrolyte layer 3, a carbon layer 4, a cathode layer 5, and an anode. And cathode lead terminals 6 and 7 and a sealing resin 8 for sealing them. In FIG. 1, reference numeral 9 denotes an adhesive layer for bonding the cathode lead terminal 7 and the cathode layer 5. As will be described later, the adhesive layer 9 is provided with the above-described conductive material for electronic parts of the present invention. Adhesive is used.

  The anode body 1 is obtained by cutting a metal foil of tantalum, aluminum, niobium, titanium, zirconium, hafnium or the like into a predetermined size and shape. The thickness, size, and shape are appropriately determined according to the purpose of use. In general, the thickness is about 30 to 150 μm, and the size is, for example, a width of about 1 to 50 mm when the shape is rectangular. The length is about 1 to 50 mm.

The surface of the anode body 1 is roughened to increase the effective area by increasing the surface area. A dielectric layer 2 is formed on the surface of the roughened anode body 1. Since the dielectric layer 2 can be formed by oxidizing the metal of the anode body 1 and becomes a passive film, the dielectric layer 2 is parallel to each other at a minute distance while electrically insulating the solid electrolyte layer 3 and the anode body 1 described later. It can be arranged. For example, when the anode body 1 is made of tantalum, the dielectric layer 2 is made of a tantalum oxide (Ta ₂ O ₅ ) film.

The solid electrolyte layer 3 is formed of a known solid electrolyte manufactured by a chemical method. Examples of the solid electrolyte include tetracyanoquinodimethane (TCNQ) complexes and conductive polymers such as polypyrrole, polyaniline, polythiophene, and polyacetylene. When the anode body 1 is made of tantalum, the solid electrolyte layer 3 may be a manganese dioxide (MnO ₂ ) layer.

  The solid electrolyte layer 3 is formed on the dielectric layer 2 of the anode body 1 and is insulated from the anode body 1 by the dielectric film 2. The thickness of the solid electrolyte layer 3 is preferably 10 to 200 μm. When the thickness is less than 10 μm, the leakage current characteristic becomes poor. On the other hand, when the thickness is greater than 200 μm, there is a possibility that a solution (polymerizable monomer solution or the like) used when forming the solid electrolyte oozes out to the anode body 1.

  The cathode layer 5 is provided on the solid electrolyte layer 3 via the carbon layer 4. The carbon layer 4 is formed of a carbon paste, and the cathode layer 5 is formed by applying a conductive paste by a known method such as a dipping method, drying it, and then performing a heat treatment.

  The anode lead terminal 6 is a lead wire for connecting from the anode body 1 to an external electrode (not shown), and the cathode lead terminal 7 is a lead wire for connecting from the cathode layer 5 to the external electrode (not shown). is there. Each of these lead terminals 6 and 7 can be formed of a known material as long as electrical connection can be ensured, and examples thereof include metals such as tin and aluminum. Here, the anode lead terminal 6 is joined to the anode body 1 by welding, and the cathode lead terminal 7 is bonded to the cathode layer 5 using the conductive adhesive for electronic components of the present invention.

  The sealing resin 8 is provided to protect the above-described components from the external environment, to slow down the deterioration rate, and to operate stably. As this sealing resin, for example, a resin conventionally known as a sealing material for a solid electrolytic capacitor such as an epoxy resin, a phenol resin, or an alkyd resin is used.

[Capacitor manufacturing method]
In order to manufacture the solid electrolytic capacitor 10, first, the surface of the prepared anode body 1 is roughened (etching step). For the etching, for example, a known method such as a method of immersing in a hydrochloric acid solution or a method of electrolysis (electrochemical etching) using a substrate as an anode in a hydrochloric acid aqueous solution can be used. After the etching process, a cleaning process is sufficiently performed so that components in the processing liquid, particularly chlorine ions, do not remain on the surface of the anode body 1.

  Next, the surface of the etched anode body 1 is subjected to a chemical conversion treatment by immersing it in an electrolytic solution for chemical conversion and anodizing to form a dielectric layer 2 on the surface of the anode body 1 (dielectric layer formation). Process).

The chemical conversion treatment may be performed by applying a voltage to the anode body 1 in the electrolytic solution for chemical conversion. As the electrolytic solution for chemical conversion, an aqueous solution of ammonium borate, ammonium phosphate, ammonium adipate, or the like can be used. The chemical conversion treatment is preferably performed in the range of applied voltage of 4 to 20 V, electrolyte concentration of 0.05 to 20% by mass, temperature of 0 to 90 ° C., and current density of 0.1 to 200 mA / cm ² .

  Next, the solid electrolyte layer 3 is formed on the dielectric layer 2 (solid electrolyte formation step). For example, when the solid electrolyte layer 4 is made of a conductive polymer, it can be formed by a chemical polymerization method.

  In the chemical polymerization method, a part of the anode body 1 forming the solid electrolyte layer 3 is immersed in a solution containing (1) a polymerizable monomer compound such as 3,4-ethylenedioxythiophene, and then (2) an oxidizing agent. The conductive polymer layer is formed by repeating the steps of (3) removing the oxidant by washing and (4) drying by immersing in a solution a plurality of times, and (4) drying.

  More specifically, the anode body 1 treated with this monomer solution is immersed in a polymerizable monomer solution, for example, an isopropanol solution containing 3,4-ethylenedioxythiophene, in the formation region of the solid electrolyte layer 3. It is immersed in an aqueous solution containing ammonium persulfate, washed, dried for about 10 minutes, subjected to oxidative polymerization, and this is repeated to form the solid electrolyte layer 3.

  The polymerizable monomer compound used here preferably has a pyrrole, thiophene, furan or aniline unit, and its concentration is preferably in the range of 5 to 40% by mass in a solution using isopropanol or the like as a solvent. .

  As the oxidant used for the oxidative polymerization of the polymerizable monomer compound, arikari persulfate, ferric chloride, cuprous chloride and the like are used in addition to ammonium persulfate. The concentration of the oxidizing agent is preferably in the range of 10 to 40% by mass in an aqueous solution using water as a solvent.

  Next, after applying a carbon paste on the solid electrolyte layer 3 and drying to form the carbon layer 4, the conductive paste is applied on the carbon layer 4 by a known method such as a dipping method, and then heated. Curing is performed to form the cathode layer 5 (cathode forming step).

  Next, the anode lead terminal 6 is joined to the exposed portion of the anode body 1 where the dielectric layer 2 is not formed by welding, and the cathode lead terminal 7 is bonded to the cathode layer 5 with the conductive adhesive of the present invention (lead). Terminal formation process). In bonding, the conductive adhesive of the present invention is disposed between the cathode layer 5 and the cathode lead terminal 7 and then heat-treated at a temperature of about 100 to 200 ° C. for about 30 to 120 minutes.

  Thereafter, the whole of the lead terminals 6 and 7 is sealed with the sealing resin 8 (resin sealing step) so that the connection portions with the external electrodes are exposed. Thereby, the solid electrolytic capacitor 10 is manufactured.

  In the solid electrolytic capacitor 10 manufactured in this way, the cathode layer 5 and the cathode lead terminal 7 are made of an inexpensive material and a conductive adhesive having adhesion and conductivity comparable to those using conventional silver powder. Therefore, the ESR can be reduced while reducing the cost, and the reliability can be improved.

  The conductive adhesive of the present invention is not limited to the solid electrolytic capacitor as described above, but can be widely used for bonding various electronic components, but requires high conductivity and heat resistance like the solid electrolytic capacitor. It is particularly useful for applications that are used, and can be advantageously used as an adhesive that replaces the conventional conductive adhesive using silver powder.

  EXAMPLES Next, although an Example, a comparative example, and a reference example demonstrate this invention in detail, this invention is not limited by these examples. The materials used in the following examples, comparative examples and reference examples are as shown in Table 1. Further, “part” means “part by mass” unless otherwise specified.

Example 1
After 0.2 parts of a curing accelerator was roll-dispersed with respect to 8 parts of a bisphenol A type epoxy resin and 4 parts of a phenol resin curing agent, it was dissolved in 12 parts of a diluent to obtain a viscous resin solution. 54 parts of conductive filler I and 22 parts of conductive filler III were added to this resin solution, and after kneading with disperse, degassed under reduced pressure to prepare a paste-like conductive adhesive.

Examples 2-6, Comparative Examples 1-4, Reference Example 1
A paste-like conductive adhesive was prepared in the same manner as in Example 1 except that the composition was changed as shown in Table 2.

  For the conductive adhesives obtained in the above Examples, Comparative Examples and Reference Examples, cured products thereof, and capacitors produced using the conductive adhesive, various characteristics were evaluated by the methods shown below, and the results Are also shown in Table 2.

<Conductive adhesive>
(1) Storage stability After refrigerated storage for 24 hours, the sample was thawed, checked for the presence of precipitates in a stationary state, and evaluated according to the following criteria. The sediment was confirmed visually by rubbing the bottom of the storage container with a spatula.
○: No precipitate ×: Precipitate (2) Coating workability I (spreadability)
A conductive adhesive was applied in a circular shape with a diameter of 1 mm on a copper frame (Ag plating / Cu frame) whose surface was silver-plated, and the difference from the diameter after 1 minute was determined and evaluated according to the following criteria.
○: Less than +0.5 mm ×: +0.5 mm or more (3) Application workability II (stringiness)
When the conductive adhesive was applied on the Ag plating / Cu frame, the adhesive threading, and the presence or absence of the adhesive protruding from the coated surface was visually confirmed, and evaluated according to the following criteria.
○: No threading or protrusion occurred △: Slight threading or protrusion occurred ×: Threading or protrusion occurred

<Hardened product>
(1) Adhesiveness (a) Initial adhesive strength A conductive paste is applied to an Ag plating / Cu frame to a thickness of 15 μm, a 2 mm × 2 mm semiconductor silicon chip is mounted thereon, and heat cured at 150 ° C. for 60 minutes. Then, a connection sample was prepared, and the connection sample was measured at 25 ° C. using a bond tester manufactured by Daisy Japan Co., Ltd. and evaluated according to the following criteria.
○: Adhesion strength 30N or more Δ: Adhesion strength 15N or more and less than 30N ×: Adhesion strength 15N or less (b) Adhesion strength after heat shock For connection samples prepared in the same manner as (a), heat shock (260 ° C. × 30 seconds) The adhesive strength at 25 ° C. after repeating three times was measured in the same manner as in (a), and the maintenance rate from the initial adhesive strength was determined and evaluated according to the following criteria.
○: Adhesive strength maintenance rate of 90% or more Δ: Adhesive strength retention rate of 70% or more and less than 90% ×: Adhesive strength retention rate of less than 70% The printed material was printed at a length of 50 mm and heat-cured at 150 ° C. for 60 minutes. The volume resistivity of the cured product was measured using a digital multimeter at 25 ° C. and evaluated according to the following criteria.
○: Volume resistivity of less than 1 × 10 ⁻³ Ω · cm Δ: Volume resistivity of 1 × 10 ⁻³ Ω · cm or more Volume resistivity of less than 3 × 10 ⁻³ Ω · cm ×: Volume resistivity of 3 × 10 ⁻³ Ω · cm or more

<Capacitor>
(1) ESR (Equivalent Series Resistance)
(A) Initial ESR variation A lead frame and a tantalum capacitor anode element are joined using a conductive adhesive, and a mold exterior is applied to produce a solid electrolytic tantalum capacitor having a capacitor size 3216 (3.2 mm × 1.6 mm). (Conditions for heat curing of conductive adhesive: 150 ° C. × 60 minutes) Using an ESR measuring device, ESR was measured at 100 Hz and 25 ° C. (n = 20), and the ESR measurement value of each sample relative to their average value The variation was calculated from the following formula and evaluated according to the following criteria.
ESR variation (%)
= (Difference between ESR maximum measurement value and ESR minimum measurement value of sample / ESR average value) × 100
○: ESR variation of less than 40% Δ: ESR variation of 40% or more and less than 80% ×: ESR variation of 80% or more (b) ESR variation after heat shock Second), the ESR at 25 ° C. was measured in the same manner as in (A), and the variation in ESR of each sample with respect to the initial ESR average value was calculated in the same manner as in (A) and evaluated according to the following criteria.
○: ESR variation of less than 60% Δ: ESR variation of 60% or more and less than 100% ×: ESR variation of 100% or more

  As is clear from Table 2, the conductive adhesive according to the present invention has good storage stability and coating workability even though expensive silver powder is not used. In addition, the capacitor has good ESR characteristics because of low resistance and good adhesive strength after heat shock.

DESCRIPTION OF SYMBOLS 1 ... Anode body, 2 ... Dielectric layer, 3 ... Solid electrolyte layer, 4 ... Carbon layer, 5 ... Cathode layer, 6 ... Anode lead terminal, 7 ... Cathode lead terminal, 8 ... Sealing resin, 9 ... Adhesive layer 10: Capacitor.

Claims (4)

(A) epoxy resin, (B) phenolic resin curing agent, (C) flaky silver-coated copper powder, (D) dendritic silver-coated copper powder, and (E) conductive adhesive for electronic components containing a curing accelerator An agent,
The total content of the component (C) and the component (D) is 70 to 85% by mass of the entire adhesive, and the mass ratio of the content of the component (C) and the component (D) is 95: 5 to 45:55. A conductive adhesive for electronic parts, characterized in that   2. The conductive adhesive for electronic parts according to claim 1, which is substantially free of spherical silver-coated copper powder.   The silver coating amount of the component (C) and the component (D) is 10 to 30 parts by mass with respect to 100 parts by mass of the copper powder. Agent.   A capacitor formed by bonding a capacitor element with the conductive adhesive for electronic parts according to claim 1.

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