JPH0787164B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a solid electrolytic capacitor, and more specifically, to measure a leakage current due to moisture absorption during the manufacturing process to remove defective products in advance. The present invention relates to a method for manufacturing the solid electrolytic capacitor described above.

[Conventional technology]

Taking a tantalum solid electrolytic capacitor as an example,
First, the anode lead provided on the tantalum pellet (sintered powder) is attached to the hoop material (support material) by welding. In this way, with a large number of pellets carried on the same hoop material, chemical conversion and re-chemical conversion are performed to form an oxide film made of, for example, manganese dioxide (MnO ₂ ),
A capacitor layer is obtained by forming a cathode layer with carbon / silver paste or the like. After that, the capacitor element was separated from the hoop material, and for the chip type, the anode lead of the capacitor element was welded to the anode lead terminal of the lead frame, and the cathode layer was made of a conductive adhesive material such as adhesive silver. Attach to the cathode lead terminal. Then, a resin exterior body is formed by resin molding in the mold.

The above is the case of the chip type, but in the case of the dip type, after separating the capacitor element from the hoop material, the anode lead consisting of, for example, CP wire (copper base plating-solder plating on iron wire) While welding, the cathode lead wire also made of CP wire is attached to the cathode layer via a conductive adhesive. Then, for example, it is immersed in an epoxy resin liquid to form a resin exterior body.

[Problems to be Solved by the Invention]

In both the chip type and the dip type, conventionally, the tangent (tan δ) of the capacitance and the loss angle and the leakage current are measured before the product is shipped, and the quality is judged. However, since this is a test in a dry state, it is unclear how much the leak current will be affected by the ingress of water through the resin outer casing, and there is a problem in terms of reliability. It was

[Means for Solving the Problems]

The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and its structural feature is that a chemical conversion film is formed around a pellet made of a powdered sintered body of a valve metal, and a chemical conversion film is formed on the same chemical conversion film. Solid electrolyte formed by forming a cathode layer made of carbon / silver paste, etc., and then attaching an anode terminal member and a cathode terminal member to the anode lead of the pellet and the cathode layer to form a capacitor element, and forming a resin exterior body on the capacitor element. In the method of manufacturing a capacitor, the leakage current of the capacitor element is measured in a predetermined electrolytic solution before the resin outer package is formed, and an increase in the leakage current due to moisture absorption is inspected. In this case, HNO ₃ , H ₃ PO ₄ , CH ₃ COOH, etc. are used as the leakage current measuring electrolyte, but their conductivity is 5 × 10 ⁻³ μS or more and they are completely removed by drying. One is preferable.

[Action]

When the leakage current is measured in the electrolytic solution as described above, if the oxide film has a defect, the leakage current increases due to moisture absorption. Therefore, by removing such an element in advance during the manufacturing process, it is possible to obtain a highly reliable product in which the leakage current does not increase more than the specified value even if it is left in high humidity for a long time.

〔Example〕

(1) Immerse the capacitor element before the resin outer casing is formed in 0.01 vol% CH ₃ COOH aqueous solution, apply a surge voltage of 44V,
After selecting those having a leakage current of 1 μA or less, they were immersed in a resin solution to manufacture 100 dip-type solid electrolytic capacitors having a withstand voltage of 35 V and a capacitance of 10 μF. The product according to Example 1 and 100 conventional products were allowed to stand for 500 hours in an atmosphere of 40 ° C. and 95% relative humidity.

As a result, the defective product was "0/100" in the case of Example 1, while the defective product was "2/100". Further, looking at the distribution of the leakage current value, in the case of the first embodiment, 0.5 to 0.7 μ
Although the value was within A, the conventional product had a large variation in the range of 0.3 to 6 μA.

(2) Immerse the capacitor element before forming the resin outer casing in a 0.0001 Vol% H ₃ PO ₄ aqueous solution and apply a surge voltage of 44 V,
After selecting the leakage current of 0.5 μA or less, a resin outer package was formed by resin molding, and 100 chip type solid electrolytic capacitors having a withstand voltage of 35 V and an electrostatic capacity of 1 μF were manufactured. The product according to Example 2 and the conventional product, 100 each, at 60 ° C,
It was left for 500 hours in an atmosphere of 95% relative humidity.

As a result, the defective product was "0/100" also in the case of Example 2, whereas the conventional product was "3/100". Further, looking at the distribution of the leakage current value, in the case of the second embodiment, it is 0.03 to 0.
It was within 05 μA, but 0.03 to 1.5 μA for conventional products
It varied greatly in the range of.

(3) Immerse the capacitor element before forming the resin outer casing in 0.01 vol% NH ₄ NO ₃ aqueous solution, apply a surge voltage of 44 V,
After selecting the leakage current of 2.5μA or less, form the resin outer casing with resin mold, and withstand voltage 25V, capacitance
100 10 μF chip type solid electrolytic capacitors were manufactured. The product according to Example 3 and the conventional product, 100 each, at 60 ° C,
It was left for 500 hours in an atmosphere of 95% relative humidity.

As a result, the defective product was "0/100" in the case of Example 3, whereas the defective product was "5/100". Further, the distribution of the leakage current value was 0.5 to 0.6 μA in the case of Example 3, whereas it was greatly varied in the range of 0.5 to 5.0 μA in the conventional product.

(4) Immerse the capacitor element before forming the resin sheath in a 0.0001 Vol% HNO ₃ solution, apply a surge voltage of 44 V, and select a leak current of 0.5 μA or less.
A resin outer package was formed by resin molding, and 100 chip-type solid electrolytic capacitors having a withstand voltage of 4 V and a capacitance of 10 μF were manufactured. PCT for each of the product according to this Example 4 and the conventional product
(Pressure cooker test) The sample was left for 96 hours in an atmosphere of 121 ° C and 2 atm.

As a result, the defective product was "0/100" in the case of Example 4, while the defective product was "5/100". Further, the distribution of the leakage current value was 0.3 to 0.4 μA in the case of Example 4, whereas it was greatly varied in the range of 0.4 to 3.0 μA in the conventional product.

〔The invention's effect〕

As described above, according to the present invention, the capacitor element before forming the resin outer package is immersed in the electrolytic solution to measure the leakage current, and the defective product is removed at that stage. A solid electrolytic capacitor having good humidity resistance and high reliability is provided.

Claims (2)

[Claims] 1. An anode lead of the pellet after forming a conversion coating around a pellet made of a powdered sintered body of valve metal and forming a cathode layer made of carbon / silver paste or the like on the conversion coating. In the method of manufacturing a solid electrolytic capacitor, wherein the anode terminal member and the cathode terminal member are attached to the cathode layer to form a capacitor element, and a resin outer package is formed on the capacitor element, before the resin outer package is formed, a predetermined A method for producing a solid electrolytic capacitor, which comprises measuring a leakage current of the capacitor element in an electrolytic solution and inspecting an increase in leakage current due to moisture absorption. 2. The method for producing a solid electrolytic capacitor according to claim 1, wherein the electric conductivity of the electrolytic solution is 5 × 10 ⁻³ μS or more.