JPS5934124Y2 - solid electrolytic capacitor - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a solid electrolytic capacitor.

In general, solid electrolytic capacitors have a capacitor element A that has a valve action in advance, as shown in Figure 1, which is made by press-molding metal powder such as tantalum, niobium, aluminum, etc., into a cylindrical shape and sintering it. A metal wire is planted as an anode lead B, a first external lead member C bent in an L shape is welded to the protruding part of this anode lead B, and a second external lead member is attached around the capacitor element A. It is soldered to the electrode lead layer E formed on the surface through an oxide layer and a semiconductor layer, and then a capacitor is attached.
The entire circumferential surface of A is covered with a resin material F.

By the way, even though the entire circumference of this capacitor (A) is covered with a resin material F, its characteristics such as capacitance, impedance, dielectric loss, and leakage current deteriorate over a long period of use. It is about the time when it is damaged.

The cause of this is that the first and second external lead members C and D
Moisture that enters through the contact boundary between the resin material F and the resin material F, or that enters directly through the resin material F, or moisture that has been adsorbed in advance on the resin material F, causes an oxidation layer in the capacitor element A. It is known that this is because it acts on semiconductor layers and the like.

Therefore, in the past, an impregnating agent such as Ginocon oil was injected into the contact boundary between the first and second external lead members C and D and the resin material F, or a large amount of moisture absorbing material was mixed into the resin material F. Furthermore, attempts have been made to coat the surface of the container element (A) or the outer peripheral surface of the resin material F with a moisture-proofing material, but sufficient effects have not yet been obtained.

Therefore, as shown in FIG. 2, the present applicant placed an airtight terminal G mainly made of an insulating material on the circumferential surface of the capacitor element A on the outlet side of the anode lead B, and also provided an anode that penetrates the airtight terminal G. We propose a solid electrolytic capacitor in which the space between the lead B and the hole of the airtight terminal G is sealed with an insulating member, and the peripheral surface of the side and bottom of the capacitor element L-A is hermetically covered with a solder layer H. did.

According to this proposal, since the entire circumferential surface of the capacitor element A is hermetically covered with the airtight terminal G and the solder layer H, the action of moisture and moisture on the oxide layer and the semiconductor layer can be suppressed, and the capacitor characteristics can be improved. The excellent effect of being able to maintain stability over a long period of time can be obtained.

However, when placing the airtight terminal G on the top surface of the condenser element A, it has to be passed through the anode IJ-B, which reduces workability and makes it difficult to apply to mass production processes. be.

In view of these points, the present invention provides a solid electrolytic capacitor that can be easily applied to mass production processes by improving workability and has excellent moisture resistance.Examples will be described below.

In Fig. 3, reference numeral 1 denotes a capacitor element made of a metal member having a valve action. It can also be constructed by crushing the wire, bending the crushed portion, or press-forming the metal wire into a columnar shape.

Reference numeral 2 denotes an anode lead made of a metal member having a valve action and led out from the capacitor element 1. In the illustrated example, it is installed in the center of the capacitor element 1, but it can also be led out by welding to the circumferential surface of the lead. can.

Reference numeral 3 denotes an oxide layer as a dielectric layer formed on the rising portion 2a of the capacitor element 1 and the anode lead 2 from the capacitor element 1. For example, the capacitor element 1 and the anode lead 2 are immersed in a chemical solution and subjected to chemical conversion treatment. It is formed.

Reference numeral 4 denotes a semiconductor layer formed on the oxide layer 3 excluding a desired portion of the oxide layer 3 in the rising portion 2a of the anode lead 2. For example, the capacitor element 1 is placed in a semiconductor mother liquid, and the desired portion of the oxide layer 3 in the anode lead 2 is It is formed by immersing it so that it is not immersed, pulling it up, and then thermally decomposing it in a high-temperature atmosphere furnace.

When the semiconductor mother liquor is thermally decomposed, the semiconductor mother liquor ejected from the deep part of the condenser element 1 may be deposited on the anode lead 2 above the adhesion level during immersion, but even in such a case, the semiconductor mother liquor may It is necessary to take care not to deposit it on desired parts of the oxide layer 3.

Reference numeral 5 designates an electrode lead layer formed on the semiconductor layer 4, which is constructed by, for example, polymerizing a graphite layer with a silver paste layer, but may also be constructed from other conductive materials.

Note that this electrode lead layer 5 can be formed by depositing a conductive material by means such as vapor deposition or thermal spraying, but a method using a liquid conductive material and immersing the capacitor element 1 is preferable because it facilitates mass production. .

However, when using the immersion method, the immersion level must be set at a level that is equal to or slightly lower than the formation level of the semiconductor layer at the base of the rising portion 2a of the anode lead 2, if it is formed thereon. .

A first metal layer 6 is formed on a desired portion of the oxide layer 3 in the rising portion 2a of the anode lead 2, and is made of a metal member having excellent adhesion to the oxide layer 3.

For example, when tantalum is used as the anode lead 2,
It is preferable to use a nickel-chromium alloy.

The first metal layer 6 can be formed by vacuum deposition, plating, thermal spraying, etc., but vacuum deposition is preferable from the viewpoint of adhesion to the oxide layer 3.

A second metal layer 7 is formed on the first metal layer 6, and is made of a metal member that has excellent compatibility with solder members.

For example, when the first metal layer 6 is made of a nickel-chromium alloy, it is preferably made of gold.

Note that this second metal layer 7 is formed by the same method as the first metal layer 6.

8 is a first external lead member bent into a shape, for example;
The bent portion 8a is welded to the oxidized layer 3 at the rising portion 2a of the anode lead 2 so as to cross over the unformed portion.

Reference numeral 9 denotes a second external lead member, one end 9a of which is in contact with the electrode lead layer 5.

Reference numeral 10 denotes a solder layer formed on the entire circumferential surface of the electrode lead layer 5 including the second metal layer 7. For example, with one end 9a of the second external lead member 9 in contact with the electrode lead layer 5, molten solder is applied. Formed by immersion in a bath.

Although it is preferable for mass production to form this solder layer 10 by dipping the capacitor element 1 in a molten solder bath as described above, it can also be formed by thermal spraying or the like.

In this way, the entire circumferential surface of capacitor element 1 is covered with solder layer 1.
Since the condenser element 1 is airtightly packaged by the oxide layer 3. It does not act on the semiconductor layer 4.

Therefore, capacitor characteristics such as dielectric loss and leakage current can be stably maintained over a long period of time, and reliability can be improved.

In particular, a desired portion of the oxide layer 3 on the rising portion 2a of the anode lead 2 is covered with a first layer. Since the second metal layers 6 and 7 are formed in close contact with each other, the adhesion of the solder layer 10 to the second metal layer 7 can be significantly improved.

Therefore, it is possible to effectively prevent moisture from entering the interior of the capacitor element-1 from the contact boundary between the anode lead 2 and the solder layer 10, and the above-mentioned effects can be obtained.

Furthermore, if the solder layer 10 is formed by dipping the capacitor element 1 in a molten solder bath, the solder layer 10 can be formed by a simple operation of dipping the capacitor element 1 into the molten solder bath and then pulling it up, thereby reducing the mass production process. Easy to apply.

Furthermore, prior to welding the first external lead member 8 to the anode lead 2, the solder layer 10 is formed on the entire circumferential surface of the capacitor element 1, so that the anode lead 2 of the first external lead member 8 is welded to the anode lead 2 of the first external lead member 8. Even if welding sparks are generated during welding, the solder layer 10 can completely prevent any adverse effects on the oxide layer 3 and the semiconductor layer 4, and any deterioration in characteristics caused by this can be completely eliminated.

Next, specific examples will be described.

A tantalum wire is planted as an anode lead on a condenser element made by press-molding and sintering tantalum powder into a cylinder, and an oxide layer (Ta20s) is formed on the rising portion of the condenser element and the anode lead.

Then, a nickel-chromium alloy is partially vacuum-deposited on the oxidized layer in the rising portion to form a first metal layer, and gold is vacuum-deposited on the upper surface of the first metal layer to form a second metal layer.

Then, a semiconductor layer and an electrode lead layer are formed on the oxide layer excluding the second metal layer portion.

After welding the first external lead member to the anode lead end,
With the second external lead member in contact with the electrode lead layer, the capacitor element is immersed in a molten solder bath so that the upper part of the second metal layer is slightly exposed, and the capacitor element is immersed on the entire circumferential surface of the electrode lead layer. A solder layer is formed to obtain a tantalum solid electrolytic capacitor (35V, 1 μF).

This capacitor and the capacitor shown in Figure 1 (conventional product)
The dielectric loss and leakage current were measured when the sample was left in an atmosphere at a temperature of 65° C. and a relative humidity of 95%, and the results shown in the table below were obtained.

From the above table, it can be seen that compared to the conventional product, this product exhibits less deterioration in dielectric loss and leakage current characteristics in a high humidity atmosphere.

Particularly, the reason why the present product has good moisture resistance is considered to be that the anode lead and the solder layer are in airtight contact with each other via the oxide layer, the first metal layer, and the second metal layer.

This is supported by the fact that when a semiconductor layer is interposed between the oxide layer and the first metal layer, the characteristics deteriorate significantly.

Note that the present invention is not limited to the above embodiments in any way,
For example, the metal layer can be a single layer as well as a plurality of layers.

Also, 1st. The second external lead member can be omitted, and the metal layer of the anode lead can be provided only in the hermetically sealed part by the solder layer, or can be extended to the vicinity of the lead-out end.

As described above, according to the present invention, moisture resistance can be significantly improved, and application to mass production processes can be facilitated.

[Brief explanation of the drawing]

1 and 2 are front sectional views showing different embodiments of the conventional example, and FIG. 3 is a front sectional view showing one embodiment of the present invention. In the figure, 1 is a condenser element, 2 is an anode lead,
2a is a rising portion, 3 is an oxide layer, 4 is a semiconductor layer, 5 is an electrode lead layer, 6 and 7 are metal layers, and 10 is a solder layer.

Claims (1)

[Scope of utility model registration request] A capacitor element made of a metal member having a valve action, an anode lead made of a metal member having a valve action derived from the capacitor element, and an oxide layer formed on the rising portion of the capacitor element and the anode lead from the surface of the capacitor element. , a semiconductor layer formed on the oxide layer excluding the desired part of the oxide layer at the rising part of the anode lead, an electrode lead layer formed on the semiconductor layer, and a metal formed on the desired part of the oxide layer at the rising part of the anode lead. A solid electrolytic capacitor comprising a solder layer formed on the entire circumferential surface of an electrode lead-out layer including a metal layer.