JP4697934B2 - Electrode bonding method for solid electrolytic capacitor and solid electrolytic capacitor manufactured using the method - Google Patents

Description

  The present invention relates to an electrode joining method for a solid electrolytic capacitor and a solid electrolytic capacitor manufactured using the method.

  Solid electrolytic capacitors are used in notebook personal computers, digital still cameras, HDDs, and the like, and higher performance is demanded as information is advanced. A solid electrolytic capacitor uses an aluminum foil having a roughened surface and a dielectric film as an anode foil, and the aluminum foil is electrically bonded to an anode terminal plated with copper or palladium. ing. Particularly when the anode part (anode foil) of the solid electrolytic capacitor element and the anode terminal are joined by a wire bonding method using a gold wire, a palladium-plated electrode material is used as the anode terminal with emphasis on joining properties.

  These junctions are important elements for improving the performance of solid electrolytic capacitors such as high energy and miniaturization, and various developments have been made. In general, the aluminum foil and the palladium-plated anode terminal are often joined by wire bonding using the gold wire, but various other methods using ultrasonic waves have been proposed.

For example, as a conventional ultrasonic bonding method, a technique (Patent Document 1) in which an anvil process is performed on a bonding surface (a pre-processing process is performed so that unevenness is formed on the bonding surface), several anode foils are stacked, and an anode terminal There is a technique (Patent Document 2) for temporarily fixing together with ultrasonic bonding and spot welding.
In addition to the above, a technique for joining two or more anode foils by ultrasonic joining (Patent Document 3) and a technique for joining valve metals to each other (Patent Document 4) (Patent Document 5) are also proposed. Has been.

Japanese Patent Laid-Open No. 11-5178 JP 2001-223135 A JP 2002-260968 A JP 2002-359163 A JP 9-266138 A

Of these prior arts, a joining technique corresponding to Patent Document 5 will be briefly described with reference to FIG. 3. FIG. 3 is a cross-sectional view of a conventionally known capacitor.
In FIG. 3, 1 is an aluminum foil as an anode foil, 2 is a dielectric film formed on the surface of the anode foil (aluminum foil), 3 is a polymer semiconductor formed on the surface of the dielectric film 2, 4 is silver Carbon paste, 5 is a conductive adhesive, 6 is a cathode terminal, 7 is a palladium-plated anode terminal, and 8 is a gold wire, which are joined as shown in the figure, and further covered with an exterior resin 9 as a whole. ing.

  In the solid electrolytic capacitor described above, electrical bonding between the aluminum foil 1 on which the dielectric film 2 is formed and the anode terminal 7 plated with palladium is performed by using the dielectric film 2 formed on the surface of the aluminum foil 1 as shown in FIG. As shown by reference numeral 10 in FIG. 3, the surface of the aluminum foil 1 that has been removed in advance and the anode terminal 7 was removed by wire bonding using a gold wire 8.

However, when the wire bonding method as described above is used, a pretreatment process is required to bother removing the dielectric film 2 formed on the surface of the anode foil 1, and there is room for improvement in terms of assembly efficiency. Further, an extra space (see symbol L in FIG. 3) for removing the dielectric film on the aluminum foil is required to join the gold wire 8, and it is difficult to reduce the size of the capacitor.
Moreover, although the thing of patent document 3 and patent document 4 is efficient in a process only by superposing | stacking metals and carrying out ultrasonic bonding, in the method of patent document 3, the joint metal is the same valve metals. Otherwise, there is a problem that ultrasonic bonding cannot be performed, and in the method of Patent Document 4, it is necessary to generate a region without a dielectric film on the valve metal surface.

Against this background, the present inventors have researched a new technology that can directly ultrasonically join an aluminum foil that is not a valve metal and a palladium-plated anode terminal without removing the dielectric film on the anode foil. As a result, we succeeded in developing a new electrode joining method.

  The present invention has been made based on the above knowledge, and an aluminum foil on which a dielectric film is formed and an anode terminal plated with copper or palladium are overlapped with the dielectric film interposed therebetween, and predetermined bonding conditions It is characterized by direct bonding by ultrasonic bonding. By adopting such a direct bonding method, the capacitor itself can be reduced in size as compared with a solid electrolytic capacitor using a conventional wire bonding method. In addition, the productivity can be improved because the step of removing the dielectric film can be omitted.

The technical solution adopted by the present invention is:
In the state where the aluminum foil on which the dielectric film is formed and the anode terminal subjected to copper or palladium plating are directly superposed , the ultrasonic frequency is 20 to 40 KHz, and the ultrasonic bonding time is 0.1 s to 1. An electrode joining method for a solid electrolytic capacitor, in which a load is applied under conditions of 0 s, a vibration amplitude is 1 μm to 10 μm, and a load stress is 10 to 100 MPa, and direct joining is performed by ultrasonic joining.
In addition, when the aluminum foil on which the dielectric film is formed and the anode terminal plated with copper or palladium are superposed, the ultrasonic frequency is 20 to 40 KHz, and the ultrasonic bonding time is 0.1 s to 1. It is a solid electrolytic capacitor characterized in that a load is applied under the conditions of 0.0 s, vibration amplitude is 1 μm to 10 μm, and load stress is 10 to 100 MPa, and direct bonding is performed by ultrasonic bonding.

  As a conventional method for joining the anode foil and anode terminal of the solid electrolytic capacitor, the wire bonding joining method for joining via the gold wire as described above has been adopted. In this case, the space for joining the wires is set as the anode foil. It was necessary to secure on the side. In this development, since the anode foil and the anode terminal are directly joined by ultrasonic joining without using a wire, the space on the wire joining surface can be eliminated, and the solid electrolytic capacitor can be further reduced in size. In addition, unlike conventional ultrasonic technology, it is not necessary to perform surface treatment before bonding, and it is possible to perform anode foil and anode terminal bonding only by the ultrasonic bonding method, which does not require processing after bonding. Since the anode foil and the anode terminal can be joined only by the ultrasonic joining method, the productivity is improved.

  The present invention relates to a solid electrolytic capacitor in which an aluminum foil having a dielectric film formed thereon and an anode terminal plated with copper or palladium are superposed with a dielectric film interposed therebetween, under a predetermined joining condition. It is characterized by direct bonding by ultrasonic bonding.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a solid electrolytic capacitor according to the present embodiment.
In FIG. 1, 1 is an aluminum foil as an anode foil, 2 is a dielectric film formed on the surface of the anode foil (aluminum foil), 3 is a polymer semiconductor formed on the surface of the dielectric film 2, and 4 is silver / carbon. The paste 5 is a conductive adhesive, 6 is a cathode terminal, and 7 is a palladium-plated anode terminal, which are joined as shown in the figure. Note that the exterior resin corresponding to FIG. 3 is omitted.

  The element used for the solid electrolytic capacitor according to the present example is formed by forming polypyrrole as a conductive polymer on an aluminum foil 1 (thickness: 100 μm) having a roughened surface and a dielectric film 2 formed thereon, and further carbon / silver The paste was applied to form a cathode part. The anode portion is in a state where a dielectric film is formed on the surface of the aluminum foil. A copper lead 7 plated with palladium is used as an anode terminal. First, the copper lead 7 plated with palladium is fixed on the jig, and the anode portion of the solid electrolytic capacitor element is disposed thereon. In this state, the anode portion of the solid electrolytic capacitor element and the anode terminal 7 are directly joined by ultrasonic waves using an ultrasonic head. Thus, the joint area S between the aluminum foil and the anode terminal can be reduced without removing the dielectric film. Further, ultrasonic bonding is performed under the conditions of ultrasonic frequency 20 to 60 KHz, bonding time 0.1 s to 1.0 s, vibration amplitude 1 μm to 10 μm, and load stress 10 to 100 MPa as bonding conditions.

A joining experiment was conducted between an anode portion (dielectric film thickness: about 35 μm) of a solid electrolytic capacitor formed using an aluminum foil formed at 12 V and a palladium plated copper lead. As an experimental example, FIG. 2 shows the bonding results for each load stress when the ultrasonic frequency is 40 KHz, the bonding time is 0.5 s, and the vibration amplitude is 5 μm.
As is clear from FIG. 2, when the ultrasonic frequency, the joining time, and the vibration amplitude are fixed, a satisfactory state as a joining result is obtained only at a predetermined load stress (21.5 MPa to 23.7 MPa as the load stress). I was able to get it.

As a result of the same experiment, a satisfactory joining result is obtained at least when the ultrasonic frequency is 20 to 40 KHz, the ultrasonic joining time is 0.1 s to 1.0 s, the vibration amplitude is 1 μm to 10 μm, and the load stress is 10 to 100 MPa. It was.
As described above, direct bonding of an aluminum foil and a palladium electrode lead by ultrasonic waves, which has been impossible in the present invention in the present invention, is enabled for the first time by setting ultrasonic bonding conditions within a predetermined range. Therefore, the gold wire by the conventional wire bonding method is unnecessary, and the solid electrolytic capacitor can be further downsized.

  As mentioned above, although the Example of this invention was described, this invention can be implemented in other various forms, without deviating from the mind and main characteristics. For this reason, the above-described embodiments are merely examples, and should not be interpreted in a limited manner. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  It can be used as a manufacturing technology for solid electrolytic capacitors.

It is sectional drawing of the solid electrolytic capacitor which concerns on a present Example. It is a figure which shows the joining result for every load stress at the time of fixing to ultrasonic frequency 40KHz, joining time 0.5s, and vibration amplitude 6micrometer as an experiment example. It is sectional drawing of the conventional solid electrolytic capacitor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Aluminum foil as anode foil 2 Dielectric film formed on the surface of anode foil (aluminum foil) 3 Polymer semiconductor formed on the surface of dielectric film 4 Silver / carbon paste 5 Conductive adhesive 6 Cathode terminal 7 Palladium plated Anode terminal 8 Gold wire 9 Exterior resin

Claims (2)

In the state where the aluminum foil on which the dielectric film is formed and the anode terminal subjected to copper or palladium plating are directly superposed , the ultrasonic frequency is 20 to 40 KHz, and the ultrasonic bonding time is 0.1 s to 1. An electrode joining method for a solid electrolytic capacitor, wherein a load is applied under conditions of 0 s, vibration amplitude is 1 μm to 10 μm, and load stress is 10 to 100 MPa, and direct joining is performed by ultrasonic joining. In the state where the aluminum foil on which the dielectric film is formed and the anode terminal subjected to copper or palladium plating are overlapped, the ultrasonic frequency is 20 to 40 KHz, and the ultrasonic bonding time is 0.1 s to 1.0 s. A solid electrolytic capacitor characterized in that a vibration amplitude is 1 μm to 10 μm, a load stress is 10 to 100 MPa, a load is applied, and direct bonding is performed by ultrasonic bonding.

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