JP4776453B2 - Solid electrolytic capacitor element and manufacturing method thereof - Google Patents

Description

  The present invention relates to an element for a solid electrolytic capacitor using a valve action metal powder such as tantalum or niobium and a method for producing the same.

Conventionally, as a method for producing a solid electrolytic capacitor using valve action metal powder, for example, tantalum powder, a tantalum wire is embedded in a tantalum powder mixed with a binder and pressure-molded to produce a molded body.
By sintering this molded body, the tantalum wire and the tantalum powder are joined. Then, anodized to form an oxide film layer, impregnation into manganese nitrate aqueous solution, impregnation into manganese dioxide or monomer solution by pyrolysis method that repeats thermal decomposition multiple times, solid electrolyte consisting of conductive polymer by polymerization After forming the layers, a cathode lead layer composed of a carbon layer and a silver layer is sequentially formed.
Subsequently, the tantalum wire and the anode lead frame are welded, the cathode lead layer and the cathode lead frame are connected to each other through a conductive adhesive, and then resin-coated with a transfer mold. At this time, if the joining of the tantalum wire and the tantalum powder by the sintering is not sufficient, there is a problem that the short-circuit defect rate increases or the leakage current characteristic deteriorates due to thermal and physical stress.

As a method of increasing the bonding strength between the tantalum wire and the tantalum powder by this sintering, a tantalum powder mixed with a binder is pressed to form a molded body, and then the tantalum wire is applied to the sintered body obtained by sintering. There is a welding method (see, for example, Patent Document 1).
JP-A-53-99456

  In the method described in Patent Document 1, if the molding density of the molded body is low, the density of the sintered body also decreases, and the bonding between the sintered body and the tantalum wire deteriorates. There is a problem in that the leakage current characteristic is deteriorated due to physical stress.

  On the other hand, by increasing the molding density by the above method and increasing the density of the sintered body, the bonding between the sintered body and the tantalum wire is improved. When the electrolyte layer is formed, for example, the impregnation property of a manganese nitrate aqueous solution or a monomer solution is deteriorated, and there is a problem that the capacity appearance rate and the ESR characteristic are lowered. The formula for calculating the capacity appearance rate is as follows.

In order to solve the above problems, the element for a solid electrolytic capacitor of the present invention is:
In an element for a solid electrolytic capacitor in which a valve action metal powder is pressurized to form a molded body, and a valve action metal wire is welded to a porous sintered body obtained by sintering the molded body.
The molded body has a plurality of molded layers having different densities and a valve metal powder layer for bonding formed between the molding layers, and the CV value of the valve metal powder for the valve metal powder layer for bonding is state, and are more CV values of valve metal powder used in the molding layer,
The element for a solid electrolytic capacitor is characterized in that a density of a molding layer in a portion welded to the valve action metal wire is higher than that of another molding layer .

  Furthermore, the element for a solid electrolytic capacitor is characterized in that the maximum particle size of the valve metal powder for bonding is equal to or less than the average particle size of the valve metal powder used for the molding layer.

And in the manufacturing method of the element for solid electrolytic capacitors which pressurizes the valve action metal powder, forms a compact, and welds the valve action metal wire to the porous sintered body obtained by sintering the compact,
The molded body has a plurality of molded layers having different densities and a valve metal powder layer for bonding formed between the molding layers, and the CV value of the valve metal powder for the valve metal powder layer for bonding is not less than the CV value of valve metal powder used in the forming layer,
The density of the molding layer of the portion welded with the valve metal wire is higher than other molding layers,
The joining valve action metal powder layer is formed by suspending the valve action metal powder in an organic solvent, holding between the molded bodies, and drying to form a solid electrolytic capacitor element. is there.

  Furthermore, the maximum particle diameter of the valve action metal powder having a CV value higher than that of the molding layer is equal to or less than the average particle diameter of the valve action metal powder used in the molding layer. It is.

  In this way, by increasing the density of only the forming layer of the portion to be welded with the valve metal wire, the sintered body and the valve metal wire can be joined well, and the entire sintered body has sufficient pores. Furthermore, by joining the molding layers having different densities with a joint valve metal having a CV value equal to or higher than the CV value of the valve metal powder of the molding layer, leakage current characteristics, capacity appearance rate, and ESR characteristics can be reduced. An excellent element for a solid electrolytic capacitor can be obtained.

[Example 1]
Embodiment 1 of the present invention will be described below.
The external view of the element for solid electrolytic capacitors of Example 1 is shown in FIG. First, a tantalum powder having a CV value of 100 kCV is mixed with a binder to obtain an average particle diameter of 100 μm, a molded body of 3.5 mm × 4.5 mm × 1.0 mm, a molding density of 5.00 g / cc, and 3.5 mm × 4.5 mm. A compact having a size of × 2.0 mm and a molding density of 6.00 g / cc was formed by pressure molding.

  Subsequently, a dispersion liquid was prepared by mixing a tantalum powder having a maximum particle size of 10 μm and a CV value of 150 kCV, an acrylic resin, and an organic solvent, as the bonding valve action metal powder.

  After the dispersion was applied by spraying between the two types of molded bodies, the molded bodies were overlaid, and the acrylic resin and organic solvent in the dispersion were evaporated at 400 ° C., followed by sintering at 1300 ° C. Furthermore, a tantalum wire was welded to a sintered body portion of a molded body having a molding density of 6.00 g / cc, and additional sintering was performed at 1300 ° C.

Thereafter, the sintered body is anodized to form an oxide film layer, and after impregnation into a manganese nitrate aqueous solution and thermal decomposition are repeated a plurality of times to form a solid electrolyte layer made of manganese dioxide, a carbon layer, a silver layer A cathode lead layer was sequentially formed.
Subsequently, the tantalum wire and the anode lead frame are welded, the cathode lead layer and the cathode lead frame are connected via a conductive adhesive, and then resin-coated with a transfer mold, and a solid electrolytic capacitor having a rating of 16V-220 μF is obtained. 100 were produced.

[Example 2]
100 solid electrolytic capacitors were produced in the same manner as in Example 1 except that the valving metal powder for bonding was tantalum powder having a maximum particle size of 100 μm.

(Comparative Example 1)
100 solid electrolytic capacitors were produced in the same manner as in Example 1 except that the valving metal powder for bonding was tantalum powder having a maximum particle size of 150 μm.

[Example 3]
100 solid electrolytic capacitors were produced in the same manner as in Example 1 except that the valving metal powder for bonding was tantalum powder having a CV value of 100 kCV.

(Comparative Example 2)
100 solid electrolytic capacitors were produced in the same manner as in Example 1 except that the valving metal powder for bonding was tantalum powder having a CV value of 70 kCV.

(Comparative Example 3)
A molded body having a molding density of 5.00 g / cc and a molded body having a molding density of 5.00 g / cc are overlapped with each other through a dispersion and then sintered to form a sintered body of a molded body having a molding density of 5.00 g / cc. 100 solid electrolytic capacitors were produced in the same manner as in Example 1 except that tantalum wire was welded to the part.

[Example 4]
The external view of the element for solid electrolytic capacitors of Example 4 is shown in FIG. First, using a tantalum powder having an average particle diameter of 100 μm, two molded bodies having a size of 3.5 mm × 4.5 mm × 1.0 mm and a molding density of 5.00 g / cc were prepared, and 3.5 mm × 4.5 mm × 1. One molded body having a thickness of 0.0 mm and a molding density of 6.00 g / cc was pressure-molded to produce.

  Thereafter, as shown in FIG. 2, a solid was prepared in the same manner as in Example 1 except that the dispersion was held on both sides of the 6.00 g / cc molded body and the 5.00 g / cc molded body was superposed. 100 electrolytic capacitors were produced.

(Comparative Example 4)
100 solid electrolytic capacitors were produced in the same manner as in Example 1, except that the dispersion was held on both sides of the 5.00 g / cc compact and the 6.00 g / cc compact was superposed.

[Example 5]
The external view of the element for solid electrolytic capacitors of Example 5 is shown in FIG. Using a tantalum powder having an average particle diameter of 100 μm, a molded body of 3.5 mm × 3.0 mm × 3.0 mm and a molding density of 5.00 g / cc, 3.5 mm × 1.5 mm × 3.0 mm, a molding density of 6. A molded body of 00 g / cc was produced by pressure molding, the dispersion was held and overlapped, and the same method as in Example 1 was applied except that a tantalum wire was welded to the molded body having a molding density of 6.00 g / cc. 100 solid electrolytic capacitors were produced.

(Comparative Example 5)
The external view of the element for solid electrolytic capacitors of the comparative example 5 is shown in FIG. Using a tantalum powder having an average particle diameter of 100 μm, a molded body of 3.5 mm × 1.5 mm × 3.0 mm and a molding density of 5.00 g / cc, 3.5 mm × 3.0 mm × 3.0 mm, a molding density of 6 A 0.000 g / cc molded body was prepared by pressure molding, the dispersion was held and overlapped, and the tantalum wire was welded to the sintered body portion of the molded body having a molding density of 5.00 g / cc. 100 solid electrolytic capacitors were produced in the same manner as in Example 1.

(Conventional example 1)
The external view of the element for solid electrolytic capacitors of the prior art example 1 is shown in FIG. Using a tantalum powder having an average particle diameter of 100 μm, a molded body having a size of 3.5 mm × 4.5 mm × 3.0 mm and a molding density of 6.00 g / cc was formed by pressure molding.

  Thereafter, the molded body was sintered at 1300 ° C. to obtain a sintered body. Thereafter, 100 solid electrolytic capacitors were produced in the same manner as in Example 1 except that a tantalum wire was welded to the sintered body and additionally sintered at 1300 ° C.

(Conventional example 2)
The external view of the element for solid electrolytic capacitors of the prior art example 2 is shown in FIG. Using tantalum powder with an average particle diameter of 100 μm, tantalum wire is embedded in a molded body of 3.5 mm × 4.5 mm × 3.0 mm and a molding density of 5.00 g / cc, pressure-molded, and sintered at 1300 ° C. did.

  Thereafter, 100 solid electrolytic capacitors were produced in the same manner as in Example 1 using the sintered body.

(Conventional example 3)
The external view of the element for solid electrolytic capacitors of the prior art example 3 is shown in FIG. Using tantalum powder with an average particle diameter of 100 μm, tantalum wire is embedded in a molded body of 3.5 mm × 4.5 mm × 3.0 mm and a molding density of 6.00 g / cc, and pressure-molded, and sintered at 1300 ° C. did.
Thereafter, 100 solid electrolytic capacitors were produced in the same manner as in Example 1 using the molded body.

  Table 1 shows an average value of the measured leakage current value (16 V, 1 minute value), capacity appearance rate (120 Hz), and ESR value (100 kHz) of each solid electrolytic capacitor thus obtained.

As is clear from the results in Table 1, Examples 1 to 5 are excellent in low leakage current values as compared with Conventional Examples 2 and 3. This is because the bonded state between the tantalum wire and the sintered body is good.
Moreover, compared with the prior art example 1, the capacity appearance rate is high and the ESR value is reduced, which is excellent. This is presumably because sufficient pores could be retained in the entire sintered body. Therefore, it turns out that the element for solid electrolytic capacitors excellent in leakage current value, capacity appearance rate, and ESR value can be manufactured by the present invention.

  Further, when Examples 1 and 2 are compared with Comparative Example 1, Comparative Example 1 has a high leakage current value. This is presumably because the joined state between the stacked molded bodies is poor. Therefore, it turns out that the effect of this invention is acquired by making the maximum particle diameter of the valve action metal powder for joining into below the average particle diameter of the valve action metal powder used for a molded object.

  Furthermore, when Examples 1 and 4 are compared with Comparative Example 2, Comparative Example 2 has a high leakage current value. This is considered to be because the joined state of the stacked molded bodies is poor. Therefore, it turns out that the effect of this invention is acquired by making CV value of the valve action metal powder in a dispersion liquid into the CV value or more of the valve action metal powder used for the said molded object.

  Moreover, when the comparative example 3 and Example 1 are compared, the comparative example 3 has a high leakage current value. This is thought to be due to poor bonding between the tantalum wire and the sintered body. Therefore, when the density of the molded object of the part welded with a tantalum wire is high, a weld part becomes firm and it turns out that the effect of this invention is acquired.

  In this example, tantalum powder having an average particle diameter of 100 μm and a CV value of 100 kCV was used for the molded body, but this is not restrictive.

  In this example, molded bodies having molding densities of 5.00 g / cc and 6.00 g / cc were produced and superimposed, but the present invention is not limited to this.

  In this example, acrylic resin and organic solvent were used as the dispersion, but the present invention is not limited to this.

  In this example, tantalum powder having a maximum particle size of 10 to 100 μm and a CV value of 100 to 150 kCV was used as the dispersion, but this is not a limitation.

  In this embodiment, the superposition is performed in the shape shown in FIGS. 1 to 3, but the shape is not limited to this.

1 shows a schematic diagram of a solid electrolytic capacitor element produced according to Example 1. FIG. The schematic of the element for solid electrolytic capacitors produced by Example 2 is shown. 1 shows a schematic diagram of a solid electrolytic capacitor element produced in Example 3. FIG. The schematic of the element for solid electrolytic capacitors produced by the prior art example is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tantalum wire 2 Sintered body with high molding density of valve action metal 3 Sintered body with low molding density of valve action metal 4 Sintered body of valve action metal powder using dispersion liquid 5 By one type of valve action metal powder Sintered body

Claims (4)

In an element for a solid electrolytic capacitor in which a valve action metal powder is pressurized to form a molded body, and a valve action metal wire is welded to a porous sintered body obtained by sintering the molded body.
The molded body has a plurality of molded layers having different densities and a valve metal powder layer for bonding formed between the molding layers, and the CV value of the valve metal powder for the valve metal powder layer for bonding is state, and are more CV values of valve metal powder used in the molding layer,
The element for solid electrolytic capacitors , wherein a density of a molding layer in a portion welded to the valve metal wire is higher than that of other molding layers . The element for a solid electrolytic capacitor , wherein the maximum particle diameter of the valve metal powder for bonding according to claim 1 is equal to or less than the average particle diameter of the valve metal powder used for the molding layer . In the method for producing a solid electrolytic capacitor element, in which a valve action metal powder is pressurized to form a molded body, and the valve action metal wire is welded to a porous sintered body obtained by sintering the molded body.
The molded body has a plurality of molded layers having different densities and a valve metal powder layer for bonding formed between the molding layers, and the CV value of the valve metal powder for the valve metal powder layer for bonding is , Or more than the CV value of the valve metal powder used in the molding layer,
The density of the molding layer of the portion welded with the valve metal wire is higher than other molding layers,
The joining valve metal powder layer, by suspending the valve metal powder in an organic solvent, after holding between the compact, dry method for producing a device for a solid electrolytic capacitor being formed. The element for a solid electrolytic capacitor , wherein the maximum particle diameter of the valve metal powder having a CV value higher than that of the molded layer according to claim 3 is equal to or less than the average particle diameter of the valve metal powder used in the molded layer . Production method.

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