JPH02129908A - Solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To improve moisture resistance by arranging a cathode lead along an outer edge of a conductor layer. CONSTITUTION:A cathode lead is provided an outer edge of a conductor layer 3. When connecting the cathode lead 2 to the conductor layer 3, the cathode lead 2 is arranged along the outer edge of the conductor layer 3 so that at least a part of the cathode lead protrudes outside the outer edge. Therefore, sealing resin can be uniformly formed over both sides of metal foil to an outer periphery of the conductor layer 3 for the cathode lead 2 serves as a dam. Moisture resistance can be thereby improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid electrolytic capacitor with good moisture resistance.

[Prior Art] A solid electrolytic capacitor is known in which a metal foil having a valve action is used as an anode substrate, and a dielectric oxide film layer, a semiconductor layer, and a conductor layer are sequentially formed on the surface of the metal foil. In this way, solid electrolytic capacitors that use valve metal foil as the anode substrate are easier to manufacture and can be made lower in profile than solid electrolytic capacitors that use sintered valve metal powder as the anode substrate. For this reason, it is being studied everywhere and there are expectations for its industrialization.

[Problems to be Solved by the Invention] The solid electrolytic capacitor described above is put into practical use by being sealed with an exterior resin such as a thermosetting resin such as epoxy resin or phenol resin. In this case, since the thickness is thinner than that of a sintered body, it is not possible to form a uniform layer of sealing resin all the way to the outer periphery, resulting in uneven thickness inside the outer periphery. As a result, the moisture resistance of solid electrolytic capacitors is poor.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and the gist thereof is to connect the cathode lead to the outer edge of the conductive layer, which is the outermost layer of the metal foil serving as the anode base. The objective is to uniformly form the sealing resin all the way to the outer periphery. That is, according to the present invention, in a solid electrolytic capacitor in which a dielectric oxide film layer, a semiconductor layer, and a conductive layer to which a cathode lead is connected are sequentially formed on the surface of a metal foil having a valve action, the cathode A solid electrolytic capacitor is provided in which leads are disposed along the outer edge of the conductor layer.

The present invention will be further explained below.

As the metal foil having a valve action used as the anode substrate of the solid electrolytic capacitor according to the present invention, any metal foil having a valve action, such as aluminum, tantalum, niobium, titanium, and alloys using these as substrates, can be used.

The dielectric oxide film layer provided on the surface of the anode substrate may be an oxide layer of the anode substrate itself provided on the surface portion of the anode substrate, or may be an oxide layer of another dielectric oxide layer provided on the surface of the anode substrate. Although it may be a layer made of a material, it is particularly desirable to be a layer made of an oxide of the anode substrate itself. In either case, a conventionally known method such as an anodization method using an electrolytic solution can be used to provide the oxide layer.

In addition, as the semiconductor layer formed on the dielectric oxide film layer, conventionally known ones can be applied, but from the viewpoint of thermal stability and high frequency performance, lead dioxide and lead sulfate, which were previously proposed by the present inventors, are applicable. A semiconductor layer mainly composed of
-51621 publication).

Furthermore, a conductive layer is formed on the semiconductor layer by using a known conductive paste such as silver paste, plating, metal vapor deposition, soldering, or the like.

In the present invention, the cathode lead connected to the conductor layer is
It is linear, rod-shaped, or plate-shaped tin-plated copper or tin-plated nickel, and its shape is equivalent to the outer edge of the conductor layer described above. The portion of the cathode lead disposed along the outer edge of the conductor layer is arranged such that a portion of the cathode lead extends outward from the outer edge of the conductor layer. Since the conductor layer is formed on two surfaces of the metal foil, the front and back surfaces, if the cathode lead is placed all inside from the outer edge of the conductor layer, the ground of the conductor layer to which the cathode lead is not connected will be removed. The sealing resin cannot be uniformly formed on the surface. Alternatively, the cathode lead may be arranged along the outside of the outer edge of the element on which the conductive layer is formed, and the cathode lead may be connected to the conductive layer using a conductive paste or the like. Since the conductor layer is generally formed to cover the shape of the metal foil of the anode substrate, the outer edge of the conductor layer resembles the shape of the end of the metal foil.

Therefore, in the case of a solid electrolytic capacitor configured such that the anode lead is taken out separately from the metal foil, the cathode lead is shaped along the outer edge of the metal foil, but does not come into contact with the above-mentioned anode lead. In addition, in the case of a solid electrolytic capacitor that has a structure in which a part of the metal foil is used as the anode lead, the shape of the cathode lead is along the outer edge of the metal foil excluding the part of the metal foil that will become the anode lead. It becomes a shape. The relationship between part of the shape of the cathode lead, the metal foil, and the anode lead in the two cases described above is shown in FIGS. 1 and 2. In the figure, 1 is an anode lead, 2 is a cathode lead, 3 is a metal foil with a conductor layer formed on its surface, and 4 is a part of the metal foil, which becomes one end of the anode lead, and at least a semiconductor layer and a conductor layer. 5, which is not formed, is an external lead line of the cathode lead. Note that the position where the cathode lead wire 5 is drawn out from the part of the cathode lead 2 that is disposed along the shape of the outer edge of the metal foil may be other than that shown in the figure. or,
The shape of the cathode lead lead line 5 is also not limited to what is shown in the drawings.

The connection between the cathode lead of the present invention and the conductor layer of the element is performed using conductive paste, high melting point solder, or the like.

The solid electrolytic capacitor element with the cathode lead arranged in this way is sealed by a powder electrostatic method or a fluidized dipping method using a thermosetting resin such as an epoxy resin.

[Function] When a dielectric oxide film layer is formed on the surface of a metal foil that acts as a valve, a semiconductor layer is formed on top of the dielectric oxide film layer, and a conductive layer is further formed on top of that, and a cathode lead is connected to this conductive layer, Place the cathode lead along the outer edge of the conductor layer, at least one of the cathode leads.
The portion is arranged so that it protrudes outward from this outer edge. Then, this cathode lead acts as a dam, and the sealing resin can be uniformly formed on both sides of the metal foil up to the outer periphery of the conductor layer.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example 1 An anode terminal (a tin-plated copper wire connected to an aluminum tab) was spot welded to an aluminum foil having a length of 0.5 cm and a width of 0.4 cm, and an anode lead was connected to the aluminum foil.

The shape is similar to that in FIG. Next, it was electrochemically treated in an aqueous solution of phosphoric acid and ammonium phosphate at a formation voltage of 40V to form an alumina oxide film layer, thereby obtaining a low-pressure etched aluminum chemical foil (approximately 30 μF/ct).

The parts other than the anode lead were immersed in a reaction mother liquor prepared separately and consisting of a mixed solution of a 2.4 mol/Ω aqueous solution of lead acetate trihydrate and a 4 mol/Ω aqueous solution of ammonium persulfate. Next, after reacting at 40° C. for 60 minutes, the chemically formed foil was taken out, washed with water, and dried. This device, on which a semiconductor layer made of a mixture of lead dioxide and lead sulfate was formed, was immersed in a silver paste bath to form a conductor layer. On the other hand, a separately prepared tin-plated copper wire with a length of 1.8 CII+ was processed along the outer periphery of the conductor layer, and the lead wire was welded with the tin-plated copper wire in the same direction as the anode electrode and taken out. Ta. At this time, the processed tin-plated copper wire was placed along the outer periphery of the conductive layer except for the vicinity of the anode lead so as not to contact the anode lead. This cathode lead was then connected to the conductor layer with silver paste. The cathode lead was arranged as shown in FIG.

Next, powder epoxy resin (P manufactured by Nippon Bellnox Co., Ltd.
ER-48) five times using the fluidized dipping method, and then coated with liquid epoxy resin LST 83 manufactured by Nippon Ciba Geigy Co., Ltd.
Dipping sealing was performed with 045.

Example 2 An anode lead similar to that in Example 1 was connected to the end of an aluminum foil having a length of 0.8 cm and a width of 0.4 CII+, and an oxide film was further formed (approximately 30 μF/c). Of this chemically formed foil, a semiconductor layer and a conductor layer similar to those in Example 1 were laminated in order only on a portion of 0.5 cm in length and 0.4 cm in width (the remaining length was 0.3 cm and width was 0.4 cm). The chemically formed foil part of 0.4c+n is
(becomes part of the actual anode lead). On the other hand, a separately prepared tin-plated copper wire with a length of 1.4 cm was processed along the outer periphery of the conductive layer, and a lead wire was welded with the tin-plated copper wire in the same direction as the anode lead and taken out. The cathode lead was arranged as shown in FIG.

In this case, no cathode lead is present in the portion of the chemically formed foil to which the semiconductor layer and conductor layer are not attached.

Next, the cathode lead was connected to the conductor layer in the same manner as in Example 1, and sealed with epoxy resin.

Comparative Examples 1 and 2 In each of Examples 1 and 2, the cathode lead was not disposed around the outer periphery of the conductor layer, but simply a single straight tinned copper wire was connected to the conductor layer with silver paste. A solid electrolytic capacitor was produced in the same manner as in Examples 1 and 2.

The solid electrolytic capacitors produced in Examples 1 and 2 and Comparative Examples 1 and 2 were subjected to a humidity test of 10 at 90°C and 95% RH.
The test was carried out for 0 hours, and the results are summarized in Table 1.

(Left below) As is clear from Table 1, the solid electrolytic capacitor using the cathode lead disposed along the outer edge of the conductor layer has extremely good moisture resistance.

[Effects of the Invention] As explained above, the solid electrolytic capacitor according to the present invention has extremely good moisture resistance because the outer peripheral portion of the element can also be sealed while maintaining the resin thickness.

[Brief explanation of drawings]

FIGS. 1 and 2 are perspective views showing the shape of a cathode lead and the position of a chemically formed foil, showing an example of the present invention. 1... Anode lead 2... Cathode lead 3.
...Chemical foil (even a conductive layer is formed on the surface)4...Chemical foil (no semiconductor layer or conductive layer is formed on the surface)5.
・Cathode lead lead wire

Claims (1)

[Claims] 1. In a solid electrolytic capacitor in which a dielectric oxide film layer, a semiconductor layer, and a conductive layer connecting a cathode lead are sequentially formed on the surface of a metal foil having a valve action, the cathode lead is connected to the conductive layer. A solid electrolytic capacitor characterized by being arranged along the outer edge.