JP2010087308A - Solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem in a solid electrolytic capacitor wherein stress is applied to a cathode terminal by expansion/contraction of an armoring resin body by overheating/cooling, and ESR rises after long-time use. <P>SOLUTION: This solid electrolytic capacitor includes: a capacitor element having an anode, a dielectric layer formed on a surface of the anode, and a cathode layer formed on the dielectric layer; a cathode terminal connected to the cathode layer; and the armoring resin body for covering the capacitor element. A predetermined part of the cathode terminal is connected to the cathode layer, an intermediate resin layer formed of a thermosetting resin is formed between the predetermined part of the cathode terminal and the armoring resin body, and the thermal expansion coefficient of the intermediate resin layer is set 1.0×10<SP>-5</SP>-5.0×10<SP>-5</SP>/°C, whereby the solid electrolytic capacitor capable of suppressing the rise of ESR after long-time use can be provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a solid electrolytic capacitor having an exterior resin body.

  A cross-sectional configuration of a conventional solid electrolytic capacitor is shown in FIG.

  The solid electrolytic capacitor 20 shown in FIG. 1 is formed on an anode 2 made of a valve metal with an anode lead 1 embedded therein, a dielectric layer 3 formed by anodizing the anode 2, and the dielectric layer 3. A capacitor element 10 including the cathode layer 4 is included. As shown in the figure, the solid electrolytic capacitor 20 has one end of an anode terminal 7 attached to the exposed end of the anode lead 1 and a cathode terminal by a conductive adhesive 5 disposed on a part of the cathode layer 4. One end of 6 is attached. The periphery of the capacitor element 10 is sealed with an exterior resin body 8. At this time, the capacitor element is sealed with the exterior resin body 8 so that the other end 7a of the anode terminal and the other end 6a of the cathode terminal are exposed from the exterior resin body 8 on the lower surface and side surface of the solid electrolytic capacitor 20.

The solid electrolytic capacitor 20 is heated to 250 ° C. or more during the reflow process when mounted on the board. Due to this influence, the exterior resin body 8 is temporarily expanded. After this reflow, the exterior resin body 8 is cooled to room temperature, and thus contracts at this time. Stress is generated in the solid electrolytic capacitor 20 due to such expansion and contraction. Therefore, in recent years, it has been proposed to form an intermediate layer that relieves stress generated between the exterior resin body 8 and the cathode terminal 6 (Patent Document 1).
JP 2001-196277 A

  The intermediate layer described in Patent Document 1 is provided so as to be deformed according to the strain generated due to the difference in thermal expansion coefficient of each material inside the solid electrolytic capacitor, and thus deformed according to the strain. To relieve stress. However, in the conventional solid electrolytic capacitor having the intermediate layer as described above, the intermediate layer is merely deformed according to the stress. That is, when the exterior resin body expands, the intermediate layer only deforms flexibly in response to the expansion. For this reason, since the intermediate layer does not work to increase the adhesive strength between the cathode terminal and the capacitor element, there is a limit in suppressing the peeling between the cathode terminal and the capacitor element.

  Therefore, in the conventional solid electrolytic capacitor provided with the intermediate layer as described above, the inconvenience that a part or all of the connection portion between the cathode terminal and the capacitor element peels off during long-term use has not been solved. This may increase the equivalent series resistance (ESR).

  Therefore, an object of the present invention is to provide a solid electrolytic capacitor that can suppress an increase in ESR even after long-term use.

A solid electrolytic capacitor according to the present invention includes a capacitor element having an anode, a dielectric layer formed on the surface of the anode, and a cathode layer formed on the dielectric layer, and a cathode terminal for electrically connecting to the cathode layer And an exterior resin body for covering the capacitor element, wherein a predetermined portion of the cathode terminal is connected to the cathode layer, and an intermediate made of a thermosetting resin is provided between the predetermined portion of the cathode terminal and the exterior resin body. A resin layer is provided, and the thermal expansion coefficient of the intermediate resin layer is 1.0 × 10 ⁻⁵ / ° C. or more and 5.0 × 10 ⁻⁵ / ° C. or less.

  The predetermined portion is a portion including a portion connecting the cathode terminal and the cathode layer.

  In such a solid electrolytic capacitor, even if heat is applied to the solid electrolytic capacitor due to a high temperature test, reflow, or use in a high temperature environment, the intermediate resin layer expands and pressure is applied to the cathode terminal. The cathode terminal is pressure-bonded to the cathode layer of the capacitor element. Thereby, since it is possible to improve the adhesive force between a cathode terminal and a capacitor | condenser element, it can suppress that a cathode terminal and a capacitor | condenser element peel. Therefore, an increase in ESR can be suppressed even after long-term use.

  In the present invention, the thermal expansion coefficient of the intermediate resin layer is preferably larger than the thermal expansion coefficient of the exterior resin body.

  In the present invention, the predetermined portion of the cathode terminal and the cathode layer are preferably connected by a conductive adhesive.

  In the present invention, the intermediate resin layer is preferably formed so as to cover the predetermined portion of the cathode terminal connected to the cathode layer.

  Moreover, it is preferable that the intermediate resin layer and the exterior resin body in the present invention have the same component resin as a main component.

  Moreover, it is preferable that the intermediate | middle resin layer and exterior resin body in this invention have an epoxy resin as a main component.

  ADVANTAGE OF THE INVENTION According to this invention, the solid electrolytic capacitor which can suppress the raise of ESR after a long time use can be provided.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  FIG. 1 is a perspective view schematically showing the inside of the solid electrolytic capacitor in the present embodiment. FIG. 2 is a cross-sectional view taken along the line XX shown in FIG.

  As shown in FIG. 1, the solid electrolytic capacitor 20 in the present embodiment has a rectangular parallelepiped shape, and is basically a capacitor element 10, a cathode terminal 6, an anode terminal 7, and an exterior resin body 8 (broken line). And an intermediate resin layer 9. The exterior resin body 8 covers the capacitor element 10, the intermediate resin layer 9, the cathode terminal 6 and the anode terminal 7, but the end 6 a of the cathode terminal 6 and the end 7 a of the anode terminal 7 are exposed. The intermediate resin layer 9 includes a connecting portion α (a portion covered with the intermediate resin layer 9 is indicated by a one-dot chain line) which is a predetermined portion of the cathode terminal 6 electrically connected to the cathode layer portion of the capacitor element 10 and an exterior resin. It is arranged between the body 8. In the present embodiment, the connection portion α is an example of the “predetermined portion” of the present invention. In this case, the predetermined portion is one end portion of the cathode terminal 6 connected to the cathode layer 4 of the capacitor element 10. is there.

  As shown in FIG. 2, the capacitor element 10 includes an anode 2 made of a valve metal that embeds one end of the linear anode lead 1, and a dielectric layer 3 formed by anodizing the anode 2. And a cathode layer 4 formed on the dielectric layer 3. The cathode layer 4 has a laminated structure in which an electrolyte layer 4a, a carbon layer 4b, and a silver paste layer 4c are sequentially formed from the dielectric layer 3 side.

  As shown in FIG. 1, the cathode terminal 6 in this embodiment is formed by bending a band-shaped metal plate, and the lower surface of one end thereof is joined to the upper surface of a capacitor element having a substantially rectangular parallelepiped (as will be described later). Are electrically and electrically connected by a conductive adhesive 5). As shown in FIGS. 1 and 2, the end 6a of the cathode terminal 6 is exposed from the side surface to the lower surface of the exterior resin body 8, and this exposed portion (particularly the lower surface) is used for solder connection with the substrate. .

  As shown in FIGS. 1 and 2, an anode terminal 7 is attached to the other end side of the anode lead wire 1 exposed from the anode 2. Specifically, the anode terminal 7 is formed by bending a band-shaped metal plate, similarly to the cathode terminal 6 described above, and a linear anode lead is connected to the lower surface of one end thereof by welding or the like. ing. The end 7a of the anode terminal 7 is exposed from the side surface to the lower surface of the exterior resin body 8 as in the case of the cathode terminal 6 described above, and this exposed portion (particularly the lower surface) is used for solder connection with the substrate. Used.

  The intermediate resin layer 8 characterized by the solid electrolytic capacitor 20 of the present embodiment will be described in detail below.

The position where the intermediate resin layer 8 is provided is a position covering the connection portion α of the cathode terminal 6 that connects the cathode layer 4 and the cathode terminal 6 forming the outer periphery of the capacitor element 10. And the exterior resin body 8. And, as for the characteristics of the material, the thermal expansion coefficient of the intermediate resin layer 8 ([alpha] 1) is 1.0 × 10 ^-5 / ℃ or higher, in the range of 5.0 × 10 ^-5 / ℃ or less. In addition, it is preferable that the thermal expansion coefficient (α1) of the intermediate resin layer 9 satisfies the condition that the thermal expansion coefficient (α1) of the exterior resin body 8 is larger. As the material of the intermediate resin layer 8, for example, a thermosetting resin that satisfies the condition of the thermal expansion coefficient (α1) can be selected and used.

  In the present embodiment, as shown in FIGS. 1 and 2, the intermediate resin layer 9 between the connection portion α and the exterior resin body 8 covers a predetermined portion of the cathode terminal 6 connected to the cathode layer 4. Is formed. Even when only a part of the connecting portion α is covered with the intermediate resin layer 9, the region where the adhesion between the cathode terminal 6 and the capacitor element 10 can be enhanced by the expansion of the intermediate resin layer 9. It suffices if the intermediate resin layer 9 is disposed on the surface.

  Hereinafter, a specific configuration of the solid electrolytic capacitor will be described with reference to FIGS. 1 and 2.

  The anode 2 is composed of a porous body formed by molding metal particles made of valve action metal and sintering it, and a part of the anode lead 1 made of valve action metal is embedded therein. . The anode lead 1 may use the same type of metal as the anode 2 or a different valve metal. Here, examples of the valve metal constituting the anode lead 1 and the anode 2 include niobium (Nb), tantalum (Ta), aluminum (Al), and titanium (Ti). Moreover, you may use the alloy which has the above-mentioned valve action metal as a main component.

  The dielectric layer 3 can be formed by anodizing the anode 2. Although FIG. 2 shows the dielectric layer 3 formed on the surface of the anode 2, since the anode 2 is a porous body as described above, actually, the dielectric layer is also formed on the inner surface of the porous body. 3 is formed.

  The electrolyte layer 4 a is formed on the surface of the dielectric layer 3. For the electrolyte layer 4a, a conductive polymer formed by a chemical polymerization method, an electrolytic polymerization method, or the like can be used. The electrolyte layer 4a may be formed of a single layer or a plurality of layers. Examples of the conductive polymer material include polypyrrole, polythiophene, polyaniline, and polyfuran.

  The carbon layer 4b formed on the electrolyte layer 4a is formed of a layer containing carbon particles. The silver paste layer 4c formed on the carbon layer is formed of a layer containing silver particles.

  In the present embodiment, the cathode layer 4 includes an electrolyte layer 4a, a carbon layer 4b, and a silver paste layer 4c layer. The configuration of the cathode layer 4 may be other configurations as long as it functions as a cathode. For example, the cathode layer 4 may be composed of two layers, a carbon layer 4b and a silver paste layer 4c.

  The cathode terminal 6 and the cathode layer 4 are mechanically and electrically connected by a conductive adhesive material 5 disposed between the connection portion α of the cathode terminal 6 and the cathode layer 4. As the conductive adhesive 5, a resin-based conductive adhesive 5 having conductivity was used. Specific examples of the material for the conductive adhesive 5 include a material such as a silver paste in which silver and an epoxy resin are mixed. The anode terminal 7 is electrically connected to the anode lead 1 by spot welding or the like. Examples of the material of the anode terminal 7 and the cathode terminal 6 include copper, a copper alloy, and an iron-nickel alloy (42 alloy).

The intermediate resin layer 9 is formed of a thermosetting resin made of an epoxy resin having a thermal expansion coefficient (α1) of 1.0 × 10 ⁻⁵ / ° C. or higher and 5.0 × 10 ⁻⁵ / ° C. or lower. Examples of materials other than epoxy resins include silicone resins and fluororesins. The intermediate resin layer 9 can be formed by curing a resin prepared by appropriately mixing a main agent, a curing agent, and a filler. And the thermal expansion coefficient ((alpha) 1) of the intermediate | middle resin layer 9 can obtain a desired thermal expansion coefficient ((alpha) 1) by mix | blending the quantity of a filler suitably.

  The exterior resin body 8 is formed to have a thermal expansion coefficient smaller than that of the intermediate resin layer 9. As the material of the exterior resin body 8, a material that functions as a sealing material is used, and specific examples include an epoxy resin and a silicone resin. The exterior resin body 8 can be formed by curing a resin prepared by appropriately blending a main agent, a curing agent, and a filler. And the thermal expansion coefficient ((alpha) 1) of the exterior resin body 8 can obtain a desired thermal expansion coefficient ((alpha) 1) by mix | blending the quantity of a filler suitably.

  Moreover, it is preferable that the intermediate resin layer 9 and the exterior resin body 8 contain the resin of the same component. Here, the resin having the same component is, for example, a resin having the same component if the main material is an epoxy resin such as a biphenyl type epoxy resin or a cresol novolac type epoxy resin. More preferably, the intermediate resin layer 9 and the exterior resin body 8 are made of an epoxy resin.

(Function and effect)
In the solid electrolytic capacitor in the present embodiment, an intermediate resin layer 9 is formed on the connection portion α that is a part of the cathode terminal. The thermal expansion coefficient (α1) of the intermediate resin layer 9 is 1.0 × 10 ⁻⁵ / ° C., and is 5.0 × 10 ⁻⁵ / ° C. or less.

  Therefore, even if heat is applied to the solid electrolytic capacitor 20 due to a high temperature test, reflow, or use in a high temperature environment, the intermediate resin layer 9 expands and pressure is applied to the cathode terminal 6. Is pressed against the cathode layer 4 of the capacitor element 10. Therefore, when the conductive adhesive 5 is used between the cathode terminal 6 and the capacitor element 10 and bonded together, the adhesive force of the conductive adhesive 5 can be increased. And the capacitor element 10 can be prevented from peeling off. Therefore, an increase in ESR can be suppressed even after long-term use.

  Further, when the end 6a of the cathode terminal and the end 7a of the anode terminal of the solid electrolytic capacitor are mounted on the substrate, the heat during reflow is transferred from the ends 6a and 7a of the metal cathode terminal 6 and anode terminal 7 to the capacitor. It becomes easy to be transmitted to the element 10. In particular, the cathode terminal 6 has a large area in contact with the capacitor element 10 as described above, and heat is easily applied accordingly. In such a case, there is a possibility that the cathode terminal 6 expands and contracts due to heat and the adhesive force between the cathode terminal 6 and the capacitor element 10 is weakened. In the present embodiment, since the intermediate resin layer 9 is formed on the connection portion α, the intermediate resin layer 9 expands due to heat transmitted from the cathode terminal 6, and the adhesive force between the cathode terminal 6 and the capacitor element 10. Can be improved efficiently.

  Further, the connection portion α and the cathode layer 4 are bonded by a conductive adhesive 5 disposed on the connection portion α. Therefore, the pressure due to the expansion of the intermediate resin layer 9 is more easily applied to the conductive adhesive material 5. Therefore, since the adhesive force of the conductive adhesive 5 formed between the cathode terminal 6 and the capacitor element 10 can be increased efficiently, the cathode terminal 6 and the capacitor element 10 can be further prevented from peeling off. . Therefore, an increase in ESR can be further suppressed even after long-term use.

  In the present embodiment, since the intermediate resin layer 9 is formed from the connection portion α to the region extending over the cathode layer, the adhesive force between the cathode terminal 6 and the capacitor element can be further increased.

Further, since the intermediate resin layer 9 having a thermal expansion coefficient (α1) of 1.0 × 10 ⁻⁵ / ° C. or more and 5.0 × 10 ⁻⁵ / ° C. or less is used, the intermediate resin layer 9 is excessively expanded and contracted. Therefore, it is possible to suppress an excessive pressure from being applied to the capacitor element 10 from the cathode terminal 6. If excessive expansion and contraction is applied to the connection portion α of the cathode terminal 6, the adhesive force between the conductive adhesive 5 and the cathode terminal 6 or between the conductive adhesive 5 and the capacitor element 10 may be weakened. . In this embodiment, since the thermal expansion coefficient is 5.0 × 10 ⁻⁵ / ° C. or less, such a decrease in adhesive force can be suppressed, and the increase in ESR can be further suppressed even after long-term use. Can do. Moreover, it is possible to suppress the occurrence of defects such as cracks in the dielectric layer 3 in the vicinity of the connection portion α due to excessive expansion of the intermediate resin layer 9, and to reduce leakage current during long-time use. .

  Further, the intermediate resin layer 9 is formed on the connection portion α of the cathode terminal 6 and the capacitor element in the vicinity of the connection portion α, and is not formed in any other region on the surface of the capacitor element 10. Therefore, it is possible to suppress the pressure due to the expansion of the intermediate resin layer 9 from being applied to the entire capacitor element. Therefore, since it can suppress that a crack arises in the dielectric material layer 3, a leakage current can be reduced at the time of long-time use.

  In addition, it is preferable that the thermal expansion coefficient of the intermediate resin layer 9 satisfies a condition that becomes larger than the thermal expansion coefficient of the exterior resin body 8. When the thermal expansion coefficient of the intermediate resin layer 9 is larger than the thermal expansion coefficient of the exterior resin body 8, the exterior resin body 8 stops the expansion of the intermediate resin layer 8 to the outside (the exterior resin body side), and the expansion Can be directed to the cathode terminal 6. Therefore, the adhesive force of the conductive adhesive 5 can be increased efficiently, and the increase in ESR can be further suppressed even after long-term use.

  In addition, the intermediate resin layer 9 and the outer resin body 8 are preferably made of the same component resin. By using the resin of the same component, the adhesive strength between the intermediate resin layer 9 and the exterior resin body 8 can be increased. Thus, when the intermediate resin layer 9 expands, it can be prevented from expanding to the outside, and the pressure of the expansion can be directed to the cathode terminal, so that the adhesion between the intermediate resin layer 9 and the exterior resin body 8 is achieved. It can suppress that power falls. Therefore, since the expansion of the intermediate resin layer 9 can be efficiently transmitted to the conductive adhesive 5, the adhesive force of the conductive adhesive 5 can be increased. Therefore, peeling between the cathode terminal 6 and the capacitor element 10 can be further suppressed, and an increase in ESR can be further suppressed even after a long period of use.

  More preferably, the intermediate resin layer 9 and the exterior resin body 8 are made of an epoxy resin. By using an epoxy resin, the adhesive strength between the intermediate resin layer 9 and the exterior resin body 8 can be further increased.

(Modification 1)
Next, Modification 1 of the present embodiment will be described below. In addition, description is abbreviate | omitted about the part similar to the above-mentioned embodiment.

  FIG. 3 is a schematic diagram for explaining the solid electrolytic capacitor 20 according to the first modification. FIG. 3A is a perspective view schematically showing the inside of the solid electrolytic capacitor in this modification. FIG. 3B is a cross-sectional view taken along the line Y-Y shown in FIG. As shown in FIGS. 3A and 3B, the position where the intermediate resin layer 8 is provided is a cathode terminal that connects the cathode layer 4 forming the outer periphery of the capacitor element 10 and the cathode terminal 6. 6 is a position covering substantially the entire surface of the connection portion α, and is provided between the cathode layer 4 and the exterior resin body 8. In this modification, a part on the connection part α is not covered with the intermediate resin layer 9. Further, the intermediate resin layer 9 is formed in a predetermined portion forming a part of a region straddling over the cathode layer 4 in the vicinity of the connection portion α of the cathode terminal 6 or in the vicinity of the connection portion α.

  Thus, even when the entire surface of the connection portion α is not covered with the intermediate resin layer 9, the same effects as those of the embodiment can be obtained as long as the substantially entire surface of the connection portion α is covered with the intermediate resin layer 9. .

  Further, the intermediate resin layer 9 is also formed in a part of a region straddling from the connection portion α of the cathode terminal 6 to the cathode layer 4 in the vicinity of the connection portion α. Therefore, the adhesive force between the cathode terminal 6 and the capacitor element can be further increased. The intermediate resin layer 9 formed in a region extending from the connection part α of the cathode terminal 6 to the cathode layer 4 in the vicinity of the connection part α may be applied so as to increase the adhesive force between the cathode terminal 6 and the capacitor element. It ’s fine.

(Modification 2)
Next, it is a schematic diagram for demonstrating the modification 2 in this embodiment. In addition, description is abbreviate | omitted about the part similar to the above-mentioned embodiment.

  FIG. 4 is a schematic diagram showing a solid electrolytic capacitor 20 according to the second modification. FIG. 4A is a perspective view schematically showing the inside of the solid electrolytic capacitor in this modification. FIG. 4B is a cross-sectional view taken along the line ZZ shown in FIG. As shown in FIGS. 4A and 4B, the intermediate resin layer 8 is provided at a position where the cathode terminal 4 forming the outer periphery of the capacitor element 10 and the cathode terminal 6 are connected. 6 is a position covering a part of the connection portion α, and is provided between the cathode layer 4 and the exterior resin body 8. In this modification, the intermediate resin layer 9 is formed only on a part on the connection portion α of the cathode terminal 6.

  Thus, even when the entire surface of the connection portion α is not covered with the intermediate resin layer 9, the same effects as those of the embodiment can be obtained as long as the substantially entire surface of the connection portion α is covered with the intermediate resin layer 9. . The intermediate resin layer 9 only needs to be disposed at a position where the adhesion between the cathode terminal 6 and the capacitor element 10 can be enhanced by the expansion of the intermediate resin layer 9.

  Even when only a part of the connecting portion α is covered with the intermediate resin layer 9, the region where the adhesion between the cathode terminal 6 and the capacitor element 10 can be enhanced by the expansion of the intermediate resin layer 9. It suffices if the intermediate resin layer 9 is disposed on the surface.

<Example 1>
(Step 1) Production of anode A tantalum metal powder having a primary particle diameter of about 0.5 μm is molded so as to embed part of the anode lead 1 and sintered in a vacuum to obtain a height of about 4 An anode 2 made of a tantalum porous sintered body made of a rectangular parallelepiped having a size of 0.4 mm × width of about 3.3 mm × depth of about 1.0 mm was formed.

(Step 2) Formation of dielectric layer The anode 2 is subjected to anodization in a phosphoric acid aqueous solution of about 0.01% by weight held at about 60 ° C. at a constant voltage of about 20 V for about 10 hours. Layer 3 was formed.

(Step 3) Formation of cathode layer and connection of terminals The cathode layer 4 is composed of an electrolyte layer 4a, a carbon layer 4b, and a silver paste layer 4c. First, an electrolyte layer 4a made of polypyrrole was formed on the surface of the dielectric layer 3 by a chemical polymerization method or the like. Thereafter, a carbon layer 4b was formed with a carbon paste and a silver paste layer 4c was sequentially formed with a silver paste on the electrolyte layer 4a.

  Further, the cathode terminal 6 and the cathode layer 4 are electrically connected by bonding the cathode terminal 6 with the conductive adhesive 5 at the connection portion α of the cathode terminal 6. The anode terminal 7 is electrically connected to the anode lead 1 by spot welding or the like.

(Step 4) Formation of Intermediate Resin Layer The thermal expansion coefficient (α1) is 1.2 × 10 ⁻⁵ / ° C. from the substantially entire region of the connecting portion β of the cathode terminal 6 connected in Step 3 to the region straddling the cathode layer 4. An intermediate resin layer 9 made of the epoxy resin was formed.

  Hereinafter, a more detailed method for producing the intermediate resin layer 9 according to this example will be described.

  The epoxy resin constituting the intermediate resin layer 9 is blended with a main agent, a filler, and a curing agent. In this example, 100 parts by weight of biphenyl type epoxy resin as a main agent, 200 parts by weight of spherical silica of about 1.0 μm as a filler, and 10 parts by weight of methyltetrahydrophthalic anhydride as a curing agent are prepared. did. And the said liquid epoxy resin was apply | coated to the area | region straddling the cathode layer 4 from the substantially whole area of the connection part (alpha) of the cathode terminal 6. FIG. Thereafter, the epoxy resin was cured by subjecting it to a curing treatment at 100 ° C. for 30 minutes to form an intermediate resin layer 9 made of an epoxy resin. At this time, the thickness A of the intermediate resin layer 9 formed on the connection portion α shown in FIG. 2 was formed to be 150 to 200 μm after curing.

  The thermal expansion coefficient (α1) of the intermediate resin layer 9 can be obtained from a TMA method (Thermo-mechanical analysis). The thermal expansion coefficient (α1) of the intermediate resin layer 9 in this example was measured by TMA4000SA manufactured by Bruker AXS using the TMA method.

  In order to perform the above measurement, first, a cylindrical measurement sample having a thickness of about 1.0 mm and a diameter of 5.0 mm or less was prepared. At this time, a measurement sample was prepared so that the thickness distribution in the thickness direction was uniform.

  Next, a measurement sample is placed in the apparatus, and the temperature is increased from room temperature at a rate of 10 ° C./min. The amount of thermal expansion (thermal contraction) in the thickness direction is measured. A diagram in which each measurement point is plotted as a heat shrinkage amount is created. In obtaining the coefficient of thermal expansion (α1), first, in the figure in which each measurement point is plotted, a tangent line is drawn on the curve before and after the point at which the thermal expansion amount is inflected at the lowest temperature with respect to the temperature. A transition point Tg is obtained. And the thermal expansion coefficient ((alpha) 1) was computed from the inclination of the above-mentioned tangent in the temperature range below a glass transition point.

(Step 5) Formation of Exterior Resin Body The exterior resin body 8 was formed so as to cover the exposed surface of the capacitor element 10 and the exposed surface of the intermediate resin layer 9 which were performed up to Step 4. At this time, the exterior resin body 8 is formed so that the anode resin 7 and parts 6 a and 7 a of the cathode terminal 6 are exposed from the exterior resin body 8. As the exterior resin body 8, a sealing material was used in which 100 parts by weight of a biphenyl type epoxy resin as a main component, 800 parts by weight of spherical silica of about 1.0 μm as a filler, and 50 parts by weight of a xylylene type phenol resin as a curing agent were used. . The exterior resin body 8 is formed by injecting this sealing material into a mold by a transfer molding method and curing. Specifically, the sealing material preheated at a temperature of 160 ° C. is poured into a mold at a pressure of 80 kg / cm ² , and cured by heating at 160 ° C. for 90 seconds in the mold. The exterior resin body 8 having an expansion coefficient (α1) of 0.7 × 10 ⁻⁵ / ° C. was formed. At this time, the thickness B of the exterior resin body 8 on the capacitor element 10 shown in FIG. 2 was formed to be about 500 μm after curing. Moreover, the thickness C of the exterior resin body 8 formed on the connection part α shown in FIG. 2 was formed to be about 150 to 200 μm after curing.

  The thermal expansion coefficient (α1) of the intermediate resin layer 9 and the exterior resin body 8 can be set to a desired range by appropriately adjusting the amount of the filler. For example, when reducing the thermal expansion coefficient (α1), it can be adjusted by increasing the amount of filler. Moreover, when increasing a thermal expansion coefficient ((alpha) 1), it can adjust by reducing the quantity of a filler.

  Through the above process, the solid electrolytic capacitor of Example 1 according to the embodiment was produced.

<Examples 2 to 13>
In step 4, the thermal expansion coefficient ([alpha] 1) is respectively ^{1.4 × 10 -5 /℃,1.6×10 -5 /℃,1.8×10 -5} /℃,2.0×10 -5 ^{/℃,1.0×10 -5 /℃,2.2×10 -5 /℃,2.5×10 -5 /℃,3.0×10 -5} /℃,3.5×10 -5 /℃,4.0×10 ^-5 /℃,4.5×10 ^-5 /℃,5.0×10 but using intermediate resin layer 9 made of ^-5 / ° C. and comprising an epoxy resin as in example 1 Solid electrolytic capacitors of Examples 2 to 13 were produced in the same manner.

<Example 14>
In the above step 5, the solid electrolytic capacitor of Example 14 was manufactured in the same manner as in Example 1 except that the exterior resin body 8 made of an epoxy resin having a thermal expansion coefficient (α1) of 1.2 × 10 ⁻⁵ / ° C. was used. Produced.

<Example 15>
A solid electrolytic capacitor of Example 15 was produced in the same manner as in Example 1 except that the exterior resin body 8 made of an epoxy resin having a thermal expansion coefficient (α1) of 1.6 × 10 ⁻⁵ / ° C. was used in Step 5 above. did.

<Example 16>
In Step 4, the intermediate resin layer 9 made of an epoxy resin having a thermal expansion coefficient (α1) of 4.0 × 10 ⁻⁵ / ° C. is used. In Step 5, the thermal expansion coefficient (α1) is 1.6. A solid electrolytic capacitor of Example 16 was produced in the same manner as in Example 1 except that the exterior resin body 8 made of an epoxy resin of × 10 ⁻⁵ / ° C. was used.

<Comparative Example 1>
The solid electrolytic capacitor of Comparative Example 1 in the same manner as in Example 1 except that the intermediate resin layer 9 made of an epoxy resin having a thermal expansion coefficient (α1) of 5.5 × 10 ⁻⁵ / ° C. is used in Step 4 above. Was made.

<Comparative example 2>
The solid electrolytic capacitor of Comparative Example 2 in the same manner as in Example 1 except that the intermediate resin layer 9 made of an epoxy resin having a thermal expansion coefficient (α1) of 6.0 × 10 ⁻⁵ / ° C. is used in Step 4 above. Was made.

<Comparative Example 3>
The solid electrolytic capacitor of Comparative Example 3 in the same manner as in Example 1 except that the intermediate resin layer 9 made of an epoxy resin having a thermal expansion coefficient (α1) of 0.8 × 10 ⁻⁵ / ° C. is used in Step 4 above. Was made.

<Comparative example 4>
The solid electrolytic capacitor of Comparative Example 4 in the same manner as in Example 1 except that the intermediate resin layer 9 made of an epoxy resin having a thermal expansion coefficient (α1) of 0.7 × 10 ⁻⁵ / ° C. is used in Step 4 above. Was made.

<Comparative Example 5>
The solid electrolytic capacitor of Comparative Example 5 in the same manner as in Example 1 except that the intermediate resin layer 9 made of an epoxy resin having a thermal expansion coefficient (α1) of 0.6 × 10 ⁻⁵ / ° C. is used in Step 4 above. Was made.

<Comparative Example 6>
A solid electrolytic capacitor of Comparative Example 6 was produced in the same manner as in Example 1 except that Step 4 was not performed.

<Comparative Example 7>
The solid electrolytic capacitor of Comparative Example 7 in the same manner as in Example 1 except that the intermediate resin layer 9 made of polyethylene resin having a thermal expansion coefficient (α1) of 20.0 × 10 ⁻⁵ / ° C. is used in Step 4 above. <Example 17>
The solid electrolytic capacitor of Example 17 in the same manner as in Example 1 except that the intermediate resin layer 9 made of silicone resin having a thermal expansion coefficient (α1) of 4.0 × 10 ⁻⁵ / ° C. is used in Step 4 above. Was made.

<Example 18>
In Step 4, the intermediate resin layer 9 made of a silicone resin having a thermal expansion coefficient (α1) of 4.0 × 10 ⁻⁵ / ° C. is used. In Step 5, the thermal expansion coefficient (α1) is 1.6. A solid electrolytic capacitor of Example 18 was produced in the same manner as in Example 1 except that the exterior resin body 8 made of a silicone resin of × 10 ⁻⁵ / ° C. was used.

<Example 19>
In Step 4, the intermediate resin layer 9 made of an epoxy resin having a thermal expansion coefficient (α1) of 4.0 × 10 ⁻⁵ / ° C. is used. In Step 5, the thermal expansion coefficient (α1) is 1.6. A solid electrolytic capacitor of Example 19 was produced in the same manner as in Example 1 except that the exterior resin body 8 made of a silicone resin of × 10 ⁻⁵ / ° C. was used.

(Long-term reliability test)
A thermal cycle test was performed as a long-term reliability test on the solid electrolytic capacitors according to the above Examples and Comparative Examples. In the thermal cycle test, the treatment of maintaining at −55 ° C. for 30 minutes and then maintaining at 105 ° C. for 30 minutes was defined as 1 cycle, and 1000 cycles were performed.

(Measurement of ESR)
Before and after the thermal cycle test, the ESR was measured at 100 kHz for the solid electrolytic capacitors according to the above examples and comparative examples.

(Measurement of leakage current)
Before and after the thermal cycle test, a voltage of 2.5 V was applied to the solid electrolytic capacitors according to the examples and comparative examples, and the current value after 20 seconds was measured as a leakage current and measured.

(result)
Table 1 shows the evaluation results of ESR and leakage current after the thermal cycle test. The values of ESR and leakage current after the thermal cycle test are shown as relative values with the value before the thermal cycle test as 100.

表１に示すように、実施例の固体電解コンデンサは比較例の固体電解コンデンサと比べ、ＥＳＲの増大が抑制された。

As shown in Table 1, the increase in ESR was suppressed in the solid electrolytic capacitor of the example as compared with the solid electrolytic capacitor of the comparative example.

Comparative Examples 1 and 2 in which the thermal expansion coefficient (α1) of the intermediate resin layer is greater than 5.0 × 10 ⁻⁵ / ° C., and the thermal expansion coefficient (α1) of the intermediate resin layer is less than 1.0 × 10 ⁻⁵ / ° C. In the solid electrolytic capacitors of certain Comparative Examples 3 to 5, ESR after the thermal cycle test increased by 3 times or more. In Comparative Examples 1 and 2, since the thermal expansion coefficient (α1) of the intermediate resin layer is larger than 5.0 × 10 ⁻⁵ / ° C., excessive expansion and contraction due to heating and cooling during the thermal cycle test is caused by the conductive adhesive. It is considered that the adhesion force is reduced by applying between the cathode terminals or between the conductive adhesive and the capacitor element, and the ESR after the thermal cycle is increased. In Comparative Examples 3 to 5, since the thermal expansion coefficient (α1) of the intermediate resin layer is smaller than 1.0 × 10 ⁻⁵ / ° C., the expansion amount of the intermediate resin layer is not sufficient, and the adhesive force between the cathode terminal and the capacitor element is increased. It was considered that the ESR after the thermal cycle increased because it could not be increased.

  Further, in Comparative Example 6 in which no intermediate resin layer was provided, ESR after the thermal cycle test was further increased. In Comparative Example 6, since the intermediate resin layer is not provided, it is considered that the adhesive strength of the conductive adhesive cannot be increased and the ESR is remarkably increased.

In Comparative Example 7, the thermal expansion coefficient (α1) of the intermediate resin layer was 20.0 × 10 ⁻⁵ / ° C., and an intermediate resin layer extremely larger than 5.0 × 10 ⁻⁵ / ° C. was used. In addition to the increase in ESR after the thermal cycle test, an increase in leakage current was confirmed. Regarding the increase in ESR, the expansion and contraction amount of the intermediate resin layer was excessively large, so that the cathode terminal and the conductive adhesive were peeled off, and it was considered that the ESR increased. In addition, regarding the increase in the leakage current, it is considered that the leakage current increased due to the occurrence of cracks or the like in the dielectric layer due to the expansion and contraction of the intermediate resin layer having a large thermal expansion coefficient.

On the other hand, in Examples 1 to 13, the intermediate resin layer is formed so that the thermal expansion coefficient (α1) is 1.0 × 10 ⁻⁵ / ° C. or higher and 5.0 × 10 ⁻⁵ / ° C. or lower. Therefore, even if heat is applied to the solid electrolytic capacitor 20 due to a high temperature test, reflow, or use in a high temperature environment, the intermediate resin layer 9 expands and pressure is applied to the cathode terminal 6. Can be crimped to the cathode layer 4 of the capacitor element 10. Therefore, since the adhesive force of the conductive adhesive 5 formed between the cathode terminal 6 and the capacitor element 10 can be increased, the cathode terminal 6 and the capacitor element 10 can be prevented from peeling off. Therefore, an increase in ESR could be suppressed even after long-term use.

Further, the thermal expansion coefficient (α1) of the intermediate resin layer is 1.0 × 10 ⁻⁵ / ° C. or more and 5.0 × 10 ⁻⁵ / ° C. or less, but the thermal expansion coefficient of the exterior resin body is that of the intermediate resin layer. In the solid electrolytic capacitors of Examples 14 and 15 that were larger than or equal to the thermal expansion coefficient, the ESR after the thermal cycle test could be suppressed to 3 times or less, but the leakage current increased compared to Examples 1-13. . In Examples 14 and 15, since the thermal expansion coefficient of the exterior resin body is greater than or equal to the thermal expansion coefficient of the intermediate resin layer, the stress applied to the capacitor element from the exterior resin body is larger than in Examples 1-13. Therefore, it is thought that Example 14 and 15 had a larger leakage current than Examples 1-13. From this result, it was confirmed that the thermal expansion coefficient of the intermediate resin layer is preferably larger than the thermal expansion coefficient of the exterior resin body.

  Further, the relative value of ESR before and after the thermal cycle test of Example 11 was reduced by about 90 compared with Example 17. Further, the relative value of ESR before and after the thermal cycle test of Example 18 was reduced by 24 compared with Example 19. In Examples 11 and 18, the intermediate resin layer 9 and the exterior resin body 8 are formed of the same component resin. Thereby, in Examples 11 and 18, compared with Examples 17 and 19, the adhesive strength between the intermediate resin layer 9 and the exterior resin body 8 could be increased. Therefore, in Examples 11 and 18, when the intermediate resin layer expands more than in Examples 17 and 19, it can be prevented from expanding outside, and the pressure of the expansion can be directed to the cathode terminal. It was possible to suppress a decrease in the adhesive force between the layer and the exterior resin body. Therefore, since the intermediate resin layer was able to efficiently transmit the expansion to the conductive adhesive material 5, it was possible to suppress an increase in ESR even after long-term use. From this result, it was confirmed that the intermediate resin layer and the exterior resin body are preferably formed of the same component resin.

  The relative value of ESR before and after the thermal cycle test of Example 18 was reduced by 36 compared to Example 16. This is because the use of an epoxy resin can increase the adhesive force between the intermediate resin layer and the exterior resin body rather than using a silicone resin for the intermediate resin layer and the exterior resin body, so that the intermediate resin layer efficiently expands. I was able to tell the conductive adhesive well. Therefore, it is considered that the adhesive strength of the conductive adhesive could be increased and the increase in ESR could be suppressed even after long-time use. From this result, it was confirmed that the intermediate resin layer and the exterior resin body are preferably formed of an epoxy resin.

It is a perspective view for demonstrating the solid electrolytic capacitor in embodiment. It is sectional drawing for demonstrating the solid electrolytic capacitor in embodiment. It is a schematic diagram for demonstrating the solid electrolytic capacitor in a modification. It is a schematic diagram for demonstrating the solid electrolytic capacitor in a modification. It is sectional drawing for demonstrating the conventional solid electrolytic capacitor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anode lead 2 Anode 3 Dielectric layer 4 Cathode layer 4a Electrolyte layer 4b Carbon layer 4c Silver paste layer 5 Conductive adhesive 6 Cathode terminal 7 Anode terminal 8 Exterior resin body 9 Intermediate resin layer 10 Capacitor element 20 Solid electrolytic capacitor

Claims (6)

A capacitor element having an anode, a dielectric layer formed on the surface of the anode, and a cathode layer formed on the dielectric layer;
A cathode terminal for electrical connection with the cathode layer;
An exterior resin body for covering the capacitor element,
A predetermined portion of the cathode terminal is connected to the cathode layer;
An intermediate resin layer made of a thermosetting resin is provided between the predetermined portion of the cathode terminal and the exterior resin body, and the thermal expansion coefficient of the intermediate resin layer is 1.0 × 10 ⁻⁵ / ° C. The solid electrolytic capacitor is characterized by being 5.0 × 10 ⁻⁵ / ° C. or less.   The solid electrolytic capacitor according to claim 1, wherein a thermal expansion coefficient of the intermediate resin layer is larger than a thermal expansion coefficient of the exterior resin body.   The solid electrolytic capacitor according to claim 1, wherein the predetermined portion of the cathode terminal and the cathode layer are connected by a conductive adhesive.   The solid electrolytic capacitor according to claim 1, wherein the intermediate resin layer is formed so as to cover the predetermined portion of the cathode terminal connected to the cathode layer.   The solid electrolytic capacitor according to claim 1, wherein the intermediate resin layer and the exterior resin body are mainly composed of a resin having the same component.   The solid electrolytic capacitor according to claim 1, wherein the intermediate resin layer and the exterior resin body contain an epoxy resin as a main component.

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