JP2011238739A - Solid electrolytic capacitor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor capable of suppressing heat degradation in a semiconductor layer consisting of electroconductive polymer as well as suppressing an increase in leak current with low ESR thereby achieving high reliability and low cost, and the manufacturing method thereof.SOLUTION: This solid electrolytic capacitor forms; a dielectric layer on the surface of a positive electrode comprising valve action metal; and a semiconductor layer made of electroconductive polymer on the dielectric layer. After forming a carbon layer on the semiconductor layer, humidifying treatment is applied to the carbon layer under the environment with a relative humidity of 65% to 95% thereby forming a metal paste layer on the carbon layer.

Description

  The present invention relates to a solid electrolytic capacitor and a manufacturing method thereof, and more particularly to a solid electrolytic capacitor having a carbon layer and a manufacturing method thereof.

  Conventionally, as shown in FIG. 1B, a solid electrolytic capacitor 1 includes an anode element 2 made of a valve metal such as aluminum, tantalum, niobium, and titanium, and a dielectric formed by oxidizing the surface of the anode element 2. A body layer 3, a semiconductor layer 5 formed on the dielectric layer 3, a carbon layer 6 formed on the surface of the semiconductor layer 5, and a metal paste layer 7 formed on the carbon layer 6. . As shown in FIG. 1A, the cathode terminal 8 is connected to the metal paste layer 7, and the anode terminal 14 is connected to the lead wire 12 connected to the anode element 2.

  However, the semiconductor layer 5 has high water repellency, and when a carbon paste using water as a solvent is used, an uncoated portion of the carbon layer 6 is likely to occur. As a result, there has been a problem that the interface resistance between the semiconductor layer 5 and the carbon layer 6 is increased, resulting in an increase in equivalent series resistance (hereinafter sometimes referred to as ESR), and a large variation.

  In Patent Document 1, in a solid electrolytic capacitor using manganese dioxide as a semiconductor layer, by applying heat of 285 ° C. or higher after applying the carbon paste, a part of the resin surrounding the graphite carbon is thermally decomposed, and ESR can be reduced. It is described. However, when heat of 285 ° C. or higher is applied to a solid electrolytic capacitor having a conductive polymer as a semiconductor layer, thermal deterioration of the conductive polymer occurs, thereby causing leakage current (hereinafter referred to as LC). There was a problem of inviting a rise.

  Patent Document 2 describes that the inclusion of a surfactant in the carbon paste increases the wettability of the carbon layer with respect to the semiconductor layer, thereby reducing the contact resistance between the semiconductor layer and the carbon layer. However, there is a problem that the resistance value of the carbon layer itself increases due to the inclusion of the surfactant. In addition, microcells are formed on the surface of the silver paste layer in which sodium ions are formed on the carbon layer and contained in the surfactant. C. In addition, there is a problem that the cost increases because a surfactant is additionally added.

JP-A-6-124857 JP-A-3-159222

  Therefore, an object of the present invention is to suppress thermal deterioration of a semiconductor layer made of a conductive polymer and to have low ESR. C. An object of the present invention is to provide a highly reliable and low-cost solid electrolytic capacitor that suppresses the increase in the number and a manufacturing method thereof.

  As a result of extensive research, the inventor conducted a humidification process after forming a carbon layer on a conductive polymer layer to be a semiconductor layer, thereby causing rearrangement of carbon particles and re-dissolution of the resin. It was estimated that the binding property between the carbon layer and the carbon layer was improved and made uniform, and it was found that the interface resistance can be reduced and the ESR characteristic can be reduced.

  The present invention has been made based on the above knowledge, and a method for manufacturing a solid electrolytic capacitor according to the present invention includes a step of forming a dielectric layer on the surface of an anode made of a valve metal, A step of forming a semiconductor layer made of a conductive polymer, a step of forming a carbon layer on the semiconductor layer, a step of humidifying the carbon layer, and a step of forming a metal paste layer on the carbon layer. It is characterized by that.

  According to the present invention, thermal degradation of a semiconductor layer made of a conductive polymer can be suppressed, and ESR is low. C. It is possible to provide a highly reliable and low-cost solid electrolytic capacitor that suppresses the increase in the resistance and a method for manufacturing the same.

FIG. 1A is a schematic perspective view of a general solid electrolytic capacitor, and FIG. 1B is a partial cross-sectional view thereof. (I) is the schematic which shows the socket insertion process in the manufacturing method of the solid electrolytic capacitor which concerns on this invention, (II) is the schematic which shows a chemical conversion process, (III) is an oxidizing agent impregnation process. FIG. (IV) is the schematic which shows the semiconductor layer formation process in the manufacturing method of the solid electrolytic capacitor which concerns on this invention, (V) is the schematic which shows the re-forming process, (VI) is carbon layer formation It is the schematic which shows a process. (VII) is the schematic which shows the metal paste layer formation process in the manufacturing method of the solid electrolytic capacitor which concerns on this invention, (VIII) is the schematic which shows an element removal process. (IX) is a schematic view showing a stacking step in the method for producing a solid electrolytic capacitor according to the present invention, (X) is a schematic view showing a sealing step, and (XI) shows a lead form step. FIG.

  Hereinafter, a solid electrolytic capacitor and a method for manufacturing the same according to the present invention will be described in detail with reference to the drawings. The following embodiments are illustrative of the present invention and are not limiting. In addition, in each figure, about the common member and component, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

  Hereinafter, the manufacturing method of the solid electrolytic capacitor according to the present invention will be described in detail.

1. Socket Insertion Step As shown in FIG. 2 (I), the anode element 2 with the lead wire 12 is inserted into the socket 11. For example, a Teflon ring 13 is attached around the lead wire 12 to prevent the semiconductor layer from being formed on the lead wire 12 in the subsequent semiconductor layer forming step.

2. As shown in FIG. 2 (II), a chemical feed terminal (not shown) is used as an anode, an external electrode (not shown) provided in the chemical solution 30 is used as a cathode, and a predetermined amount is provided between the anode element 2 and the external electrode. A dielectric layer 3 is formed by applying a voltage.

3. Oxidant impregnation step As shown in FIG. 2 (III), the anode element 2 on which the dielectric layer 3 is formed is immersed in an oxidant impregnating solution 31, and an oxidant 4 that becomes a polymerization starting point at the initial stage of the subsequent semiconductor layer formation. Is attached to the surface of the dielectric layer 3. As the oxidizing agent 4, for example, known oxidizing agents such as arylsulfonic acid or a salt thereof, alkylsulfonic acid or a salt thereof, various polymer sulfonic acids or a salt thereof can be used.

4). Semiconductor Layer Forming Step As shown in FIG. 3 (IV), the anode element 2 to which the oxidant 4 is adhered is immersed in a semiconductor layer forming solution 32 that is a precursor of the semiconductor layer 5 and is subjected to chemical polymerization to form the dielectric layer 3. A semiconductor layer 5 made of a conductive polymer is formed on the surface. Note that the oxidant 4 formed in the oxidant impregnation step (III) of FIG. 2 is taken into the semiconductor layer 5 in the semiconductor layer formation step.

5). Reformation Step As shown in FIG. 3 (V), in order to repair the dielectric layer 3 deteriorated during polymerization, the anode element 2 on which the semiconductor layer 5 is formed is immersed in the reconstitution solution 33, and a predetermined voltage is applied. Reforming by application.

6). Carbon Layer Forming Step As shown in FIG. 3 (VI), the anode element 2 on which the semiconductor layer 5 is formed is immersed in the carbon paste 34, pulled up, dried and cured, and the carbon layer 6 is formed on the semiconductor layer 5. Form. The carbon paste 34 uses water as a solvent and contains carbon particles such as carbon black and a resin. The carbon layer 6 may be formed by a known paste layer forming method that is usually employed, for example, a dipping method, a spray method, a roller method, a screen printing method, or the like.

7). Humidification treatment step The carbon layer 6 formed on the semiconductor layer 5 is subjected to a humidification treatment. The humidification treatment is preferably performed in an environment with a relative humidity of 65% to 95%, more preferably 85% to 95%. Thereby, interface resistance can be reduced and ESR can be reduced. Further, the humidification treatment is preferably performed in a temperature range of 65 ° C. to 95 ° C. for 2 hours to 48 hours. Thereby, the rearrangement of the carbon particles and the re-dissolution of the resin proceed sufficiently to reduce the ESR and suppress the variation. The humidification treatment may be performed any time after the formation of the carbon layer 6, but it is particularly preferable to perform the humidification treatment before the formation of the metal paste layer 7. Thereby, in addition to being able to reduce the variation of ESR, an effect can be obtained efficiently and in a short time.

8). Metal Paste Layer Formation Step As shown in FIG. 4 (VII), the element on which the carbon layer 6 is formed is immersed in the metal paste 35, pulled up, dried and cured, and the metal paste layer 7 is formed on the carbon layer 6. Form.

9. Element Removal Step As shown in FIG. 4 (VIII), the element 22 after the metal paste layer is formed is removed from the socket. The removed element 22 has a Teflon ring 13 attached to the outer periphery of the lead wire 12.

10. Stacking process (lead frame mounting process)
As shown in (IX) of FIG. 5, two elements 22 aligned in the same direction are attached to one end side of the lead frame 20 via, for example, adhesive silver 21. Then, the lead wires 12 extending from the two elements 22 are attached to the other lead frame 23.

11. Vacuum drying step After the stacking step, drying is performed in a vacuum atmosphere, and the adhesive silver 21 is completely thermoset.

12 Sealing Step As shown in FIG. 5 (X), the element 22 attached to the lead frames 20 and 23 is loaded into a mold, and the sealing resin is injected into the mold and cured to form an exterior resin 24. To do.

13. Blasting process The burr | flash of the exterior resin 24 is removed by shot blasting.

14 Cure process Heating is performed to sufficiently cure the exterior resin 24.

15. Dielectric Repair Process After moisture is added to the element by humidification, aging is performed by passing a current under heating conditions.

16. Lead Form Process As shown in FIG. 5 (XI), the lead frames 20 and 23 are cut and bent along the exterior resin 24 to form chips.

  EXAMPLES Hereinafter, although this invention is demonstrated using an Example, the following examples are for describing this invention, and do not limit this invention.

  Tantalum was used for the anode element, and a dielectric layer was formed on the tantalum surface by anodic oxidation in a phosphoric acid aqueous solution. Then, it was immersed in an aqueous solution of iron paratoluenesulfonate and further immersed in an ethylenedioxythiophene / ethanol solution for chemical polymerization to form a polyethylenedioxythiophene layer serving as a semiconductor layer. This element was immersed in a carbon paste and dried to form a carbon layer, and then immersed in a silver paste and dried to form a silver layer, followed by resin sealing to produce a solid electrolytic capacitor.

  In Example 1, a humidification treatment for 10 hours in an environment of a temperature of 85 ° C. and a relative humidity of 85% RH is performed after carbon layer formation and before silver layer formation (sample 1) or after silver layer formation and before resin sealing ( Comparison of ESR was performed between sample 2) or after resin sealing (sample 3) and when no humidification was performed (conventional example). Table 1 shows the measured values and standard deviation of ESR.

  Compared with the case where the humidification treatment was not performed, by adding the humidification treatment after the formation of the carbon layer, the ESR value was reduced and the characteristic variation was also improved.

  The effect can be obtained after the formation of the carbon layer, but when the humidification treatment is carried out preferably after the formation of the carbon layer and before the formation of the silver layer, the reduction of ESR and variation was particularly remarkable.

  After the carbon layer was formed and before the silver layer was formed, the temperature, relative humidity, and time when the humidification treatment was performed were changed. Samples 1, 4, and 8 were obtained by changing the temperature and the relative humidity. As the relative humidity was higher, the ESR could be reduced and stabilized. Sample 4 was the most effective.

  Samples 1, 5, 6, and 7 were obtained by changing the humidification time. As the humidification time was longer, ESR could be reduced and stabilized.

1 Solid electrolytic capacitor 2 Anode (anode element)
3 Dielectric layer 4 Dopant 5 Semiconductor layer 6 Carbon layer 7 Metal paste layer 8 Cathode terminal 11 Socket 12 Lead wire 13 Teflon ring 14 Anode terminal 20 Lead frame (for cathode)
21 Adhesive metal 22 Element 23 Lead frame (for anode)
24 exterior resin 30 chemical conversion solution 31 oxidant impregnating solution 32 semiconductor layer forming solution 33 re-chemical conversion solution 34 carbon paste 35 metal paste

Claims (4)

Forming a dielectric layer on the surface of the anode made of a valve metal;
Forming a semiconductor layer made of a conductive polymer on the dielectric layer;
Forming a carbon layer on the semiconductor layer;
A step of humidifying the carbon layer;
Forming a metal paste layer on the carbon layer;
The manufacturing method of the solid electrolytic capacitor which has this.   The method for producing a solid electrolytic capacitor according to claim 1, wherein the humidification treatment is performed in an environment having a relative humidity of 65% to 95%.   The method for producing a solid electrolytic capacitor according to claim 1 or 2, wherein the humidification treatment is performed in a temperature range of 65 ° C to 95 ° C for 2 hours to 48 hours.   The solid electrolytic capacitor according to claim 1, wherein the humidification process is performed after the step of forming the carbon layer and before the step of forming the metal paste layer. Manufacturing method.

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