JP3002602B2 - Solid electrolytic capacitors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor having an improved silver paint layer structure as a cathode conductor.

[0002]

2. Description of the Related Art In general, as shown in FIG. 2, in a solid electrolytic capacitor, a metal wire having a valve action is erected as an anode lead wire 21 in advance on a compact formed by pressing metal powder having a valve action. Then, an oxide film 23 is formed by anodic oxidation on the surface of the vacuum-sintered anode body 22, and a semiconductor layer 24 such as manganese dioxide is formed as a counter electrode on the peripheral surface of the oxide film 23 to further reduce contact resistance. After a graphite layer 25 is interposed therebetween, a silver paint layer 26 as a cathode conductor is formed, and a lead frame cathode portion 27 is attached to the silver paint layer 26, and a lead frame anode portion 28 is attached to the anode lead wire 21. Thereafter, a resin outer casing 29 is applied.

However, in recent years, as the thickness of the solid electrolytic capacitor has been rapidly reduced, insufficient strength of the solid electrolytic capacitor and the capacitor element itself against external impact and mechanical stress has become a problem that cannot be ignored.

That is, in the assembly process after the formation of the silver paint layer 26, the silver paint layer 26 as a cathode conductor caused by applying mechanical stress to the element.
There is a danger of causing characteristic deterioration and characteristic failure such as tan δ, an increase in impedance, and an increase in leakage current due to peeling of the metal.

Further, these solid electrolytic capacitors are used after being commercialized and incorporated into various circuit components.
If a shock exceeding several hundred G is momentarily received during use, the shock cannot be dispersed and absorbed only with the resin exterior,
Eventually, the element itself will be damaged, and various characteristics such as an increase in leakage current will be degraded.

Conventionally, as a means for solving these problems, a silver paint as a cathode conductor having a graphite layer composed of a water-soluble or water-insoluble organic polymer material and graphite powder and having a thickness of 150 μm or more has been proposed. By forming the water-insoluble polymer material from cellulose-based polymer material, silicon-based polymer material, polyamide, etc. among the materials constituting the silver paint layer as the cathode conductor, There has been proposed a method for improving the strength of the capacitor element itself against shocks from the outside and mechanical stress.

[0007]

However, even the method of forming a silver paint layer as a cathode conductor employing the above-mentioned means cannot completely compensate for the lack of strength of the solid electrolytic capacitor and the capacitor element itself. It could not be a sufficient solution to prevent the deterioration of characteristics and the occurrence of poor characteristics of electrolytic capacitors.

The present invention has been made in view of the above points, and provides a solid electrolytic capacitor having sufficient strength against external impact and mechanical stress without increasing tan δ and impedance of the capacitor. It is intended for.

[0009]

The solid electrolytic capacitor according to the present invention comprises an anode body composed of a valve action metal having an anode lead implanted thereon, and an oxide film layer, a semiconductor layer, a graphite layer, and silver as a cathode conductor. In a solid electrolytic capacitor in which a lead frame is adhered to a capacitor element formed by forming a paint layer and a resin sheath is applied, the silver paint layer is made of silver powder, copper powder, a water-insoluble polymer material, and graphite fiber. And a second silver paint layer made of a silver powder, a copper powder, and a water-insoluble polymer material formed on the first silver paint layer.

[0010]

[Function] By mixing an organic solvent, a water-insoluble polymer material, silver powder, and copper powder, and mixing the graphite fiber with a silver paint that is sufficiently stirred, the water-insoluble polymer material and the graphite fiber are mixed. A conductive composite reinforcing material layer having a fiber laminate structure is formed as a first silver paint layer. Then, an organic solvent, a water-insoluble polymer material, silver powder, and copper powder are mixed on the first silver paint layer, and sufficiently stirred to form a silver paint as a second silver paint layer. This is much more resistant to thermal stress and physical stress than the conventional silver paint layer composed of one layer,
A silver paint layer free from cracking and peeling is obtained.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

That is, as shown in FIG. 1, a tantalum anode lead wire 2 is erected on an anode body 1 obtained by pressing and molding tantalum powder, for example, and vacuum sintering is performed at a high temperature. Anodizing is performed by applying a voltage of 50 V to form an anodic oxide film 3 of tantalum, and then immersed in a manganese nitrate solution to deposit manganese nitrate on the anodic oxide film 3. The semiconductor layer 4 made of manganese dioxide is formed by thermal decomposition for several minutes in a constant temperature firing furnace at 300 ° C. This immersion in the manganese nitrate solution and the thermal decomposition process are repeated several times.

Next, the device after the formation of the semiconductor layer 4 is immersed in a solution of a water-soluble or water-insoluble organic polymer material with an average particle diameter of 0.3 μm.
m is immersed in a graphite solution in which graphite powder having a particle size of m or less is suspended, and dried in a thermostat at a temperature of 150 ° C. to 220 ° C. to form a graphite layer 5. Thereafter, an organic solvent, a water-insoluble polymer material, silver powder, copper powder, and an average diameter of 50 μm
Below, graphite fibers each having a length of 0.1 mm to 2 mm are mixed, immersed in a silver paint which is sufficiently stirred, dried at a temperature of 150 ° C. to 200 ° C., and dried in a first silver paint layer 6 as a cathode conductor. Then, the organic solvent, the water-insoluble polymer material, the silver powder, and the copper powder are mixed respectively, immersed in a silver paint which is sufficiently stirred, and heated at a temperature of 150 ° C.
After drying at 200 ° C. to form a second silver paint layer 7 on the first silver paint layer 6, a capacitor element 8 is formed. afterwards,
The anode lead wire 2 is welded to the lead frame anode section 9, and the second silver paint layer 7 constituting the capacitor element 8 is adhered to the element fixing section serving as the lead frame cathode section 10 via the conductive adhesive 11. Thereafter, transfer molding is performed, and a resin sheath 12 is applied.
The lead frame anode part 9 and the lead frame cathode part 10 derived from 2 are bent to obtain a finished product.

According to the solid electrolytic capacitor constructed as described above, the cathode conductor is formed by mixing an organic solvent, a water-insoluble polymer material, silver powder, and copper powder with each other and stirring the mixture sufficiently. The first silver paint layer as a conductive composite reinforcing material layer having a fiber laminate structure of the water-insoluble polymer material and the graphite fiber by mixing the graphite fiber with the organic solvent formed on the first silver paint layer Solvent, water-insoluble polymer material, silver powder, and copper powder are each mixed and sufficiently stirred to form a second silver paint layer. It is also much more resistant to thermal stress and physical stress, and a silver paint layer as a cathode conductor without cracking or peeling phenomenon is obtained, and initial characteristics such as leakage current, tan δ, impedance are more reliable than originally It can be obtained free excellent effect.

Next, comparison of characteristics between the present invention and a conventional example will be described.

That is, the present invention (A) having the structure described in the above embodiment and the same material as that of the present invention are used.
After forming the graphite layer through the same process, an organic solvent, a water-insoluble polymer material, silver powder, and copper powder are mixed, respectively, and immersed in a silver paint which is sufficiently stirred.
C. to 200.degree. C. to form a silver paint layer consisting of one layer as a cathode conductor. Thereafter, the same means as in the present invention described above was again taken to complete the sample 1000 according to the conventional example (B).
Table 1 shows the results of examining the initial characteristic failure status for each piece.
The present invention (A) and the conventional example (B)
In each of the 100 samples obtained by the above-mentioned means, the test method 21 specified in MIL-STD-202F was used.
As a result of examining the number of impact tests performed under the test condition C of 3B-leakage current, the result was as shown in FIG.

The rating of the sample is 4 V-10 μF in both the present invention (A) and the conventional example (B).

[0018]

[Table 1]

As is clear from Table 1, the device according to the present invention (A) has no tan δ and no impedance characteristics as compared with the conventional example (B), and greatly contributes to the improvement of the leakage current characteristics.

Further, as is apparent from FIG. 3, in the case of the conventional example (B), the leakage current increases every time the impact test is repeated, whereas in the case of the present invention (A), the leakage current increases. No increase in leakage current was observed even after repeated impact tests,
The effectiveness of the present invention has been demonstrated.

[0021]

As described above, according to the solid electrolytic capacitor of the present invention, without increasing the tan δ and impedance of the capacitor, the solid electrolytic capacitor is free from deterioration of leakage current characteristics even by external impact or mechanical stress. A capacitor can be obtained.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing a solid electrolytic capacitor according to the present invention.

FIG. 2 is a front sectional view showing a conventional solid electrolytic capacitor.

FIG. 3 is a characteristic curve diagram of the number of impact tests versus leakage current of a solid electrolytic capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anode body 2 Anode lead wire 3 Anodized film 4 Semiconductor layer 5 Graphite layer 6 First silver paint layer 7 Second silver paint layer 8 Capacitor element 11 Conductive adhesive 12 Resin exterior

Claims (1)

(57) [Claims] An anode lead is implanted on a valve body made of a valve action metal, and an oxide film layer, a semiconductor layer, a graphite layer, and a silver paint layer as a cathode conductor are sequentially formed on the anode body to lead the capacitor element. In a solid electrolytic capacitor in which a frame is adhered and a resin sheath is applied, the silver paint layer has a first silver paint layer made of silver powder, copper powder, a water-insoluble polymer material, and graphite fiber; A solid electrolytic capacitor comprising a silver powder, a copper powder, and a second silver paint layer made of a water-insoluble polymer material formed on the paint layer.