JPH05182869A - Solid electrolytic capacitor and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve moisture resistance of a solid capacitor by providing an anode oxide film which does not contain phosphorus ions at least in a part having a special thickness from a valve action metal side and contains phosphorus ions in an outer part from the special thickness. CONSTITUTION:A sintered material 1 made of fine powder of tantalum is compounded to form an anode side film 3. A part 4 occupying at least 1/2 of thickness from a valve action metal side of tantalum and containing no phosphorus ion and an outer part 5 except the part 4 and containing phosphorus ions are formed at the film 3. Thus, moisture resistance can be improved, and a leakage current can be improved.

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 improved moisture resistance and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, a solid electrolytic capacitor has a structure in which an anodized film, a semiconductor layer such as manganese dioxide, a carbon layer and a silver paste layer are sequentially provided on a sintered body made of fine powder such as tantalum. There is.

The anodic oxide film is formed by immersing the sintered body in a solution of nitric acid, phosphoric acid or the like and applying a chemical conversion voltage. In particular, since the nitric acid conversion liquid has a relatively low spark voltage, a phosphorylated conversion liquid is used for high-pressure products.

[0004]

However, when phosphorus ions are contained in the anodized film, particularly in the portion having a thickness of at least 1/2 from the valve metal side, the moisture resistance is lowered, and among them, In particular, it has been found that there is a drawback that leakage current (hereinafter referred to as LC) increases.

An object of the present invention is to provide a solid electrolytic capacitor which is capable of improving the above-mentioned drawbacks and moisture resistance and a method for manufacturing the same.

[0006]

In order to achieve the above object, a solid electrolytic capacitor having a valve action metal provided with an anodic oxide coating has at least a half of the valve action metal side. Does not contain phosphorus ions in the thickness part,
It is intended to provide a solid electrolytic capacitor characterized in that an anodized film containing phosphorus ions is provided on an outer portion from a thickness of ½.

The invention of claim 2 is a method for manufacturing a solid electrolytic capacitor in which a valve metal is formed to form an anodic oxide film, and at least half of the maximum formation voltage is used by using a formation solution containing no phosphorus ion. It is intended to provide a method for producing a solid electrolytic capacitor, which comprises performing a step of forming with the above voltage and a step of forming a maximum forming voltage using a forming solution containing phosphorus ions after this step.

[0008]

Function: The anodic oxide film is divided into a region containing phosphorus ions and a region not containing phosphorus ions, and at least a portion having a thickness of 1/2 from the valve metal is made a region not containing phosphorus ions, whereby moisture resistance by phosphorus ions is improved. Can be reduced.

[0009]

EXAMPLES The present invention will be described below based on examples.
FIG. 1 shows a sectional view of a capacitor element used in an embodiment of the present invention. Reference numeral 1 is a sintered body made of fine powder of tantalum. Two
Is a tantalum lead wire drawn from the sintered body 1. 3 is an anodized film formed by forming the sintered body 1. The anodic oxide film 3 is formed of a phosphorus ion-free portion 4 occupying at least ½ the thickness of tantalum from the valve metal side, and a portion 5 other than the outside portion containing phosphorus ions. Reference numeral 6 is a semiconductor layer made of manganese dioxide laminated on the anodic oxide film 3. Reference numeral 7 is a carbon layer laminated on the semiconductor layer. Reference numeral 8 is a silver paste layer laminated on the carbon layer. Reference numeral 9 denotes a cathode lead wire having solder 10 attached to the silver paste layer 8.

Next, the manufacturing method of the above embodiment will be described.
First, fine powder of tantalum is compression-molded in a state where the lead wire 2 of tantalum is pulled out and heat-treated in vacuum to form a sintered body 1. After the sintered body 1 is formed, it is dipped in a phosphoric acid-free chemical conversion solution such as a nitric acid solution, and chemical conversion is performed at a voltage of at least ½ of the maximum chemical conversion voltage. Next, the sintered body 1 is dipped in a chemical conversion solution containing phosphorus ions, such as a phosphoric acid solution, to perform chemical conversion to a maximum chemical conversion voltage. That is, formation is performed in two steps to form the anodic oxide film 3. After forming the anodic oxide film 3, the sintered body 1 is immersed in a manganese nitrate solution to be impregnated with the solution, and is baked and re-formed to form a manganese dioxide layer 6. After forming the manganese dioxide layer 6, carbon is applied to form a carbon layer 7. After forming the carbon layer 7, a silver paste is applied to form a silver paste layer 8. After forming the silver paste layer 8, the cathode lead wire 9 is soldered to the silver paste layer 8. The formation may be performed in three or more stages.

Hereinafter, the tantalum solid electrolytic capacitor was divided into an example, a conventional example and a comparative example, and a pressure cooker test was performed to obtain a change in LC. Table 1 shows the chemical conversion conditions of Examples and the like, and Table 2 shows the changes in LC. The test conditions are a temperature of 121 ° C and a humidity of 100.
%, Atmospheric pressure 2 atm, time 0 to 44 hr.

[0012]

[Table 1]

[0013]

[Table 2]

As is clear from Table 2, LC is an average value,
After 44 hours, Example 1 and Example 2 had 0.900.
˜1.17 μA, 11.5 μA in the conventional example, and 9.90 μA in the comparative example. That is, Example 1 and Example 2
Is about 7.8 to 10.2% of the conventional example and about 9.1 to 1 of the comparative example.
It drops to 11.8%.

[0015]

As described above, according to the present invention, the anodic oxide film is divided into a portion containing phosphorus ions and a portion not containing phosphorus ions. By adopting a configuration that does not include, it is possible to obtain a solid electrolytic capacitor having improved moisture resistance and improved LC and a manufacturing method thereof.

[Brief description of drawings]

FIG. 1 shows a sectional view of a capacitor element used in an embodiment of the present invention.

[Explanation of symbols]

1 ... Sintered body, 3 ... Anodized film, 4 ... Portion not containing phosphorus ion, 5 ... Portion containing phosphorus ion.

Claims (2)

[Claims] 1. A solid electrolytic capacitor having a valve action metal provided with an anodic oxide film, wherein at least a portion having a thickness of 1/2 from the valve action metal side does not contain phosphorus ions, and a portion from a thickness of 1/2 to an outer side is formed. A solid electrolytic capacitor characterized in that an anodic oxide film containing phosphorus ions is provided on a portion thereof. 2. A method for producing a solid electrolytic capacitor in which a valve metal is formed to form an anodized film, wherein a forming solution containing no phosphorus ions is used to form at least a half of the maximum forming voltage. And a step of forming a maximum formation voltage using a formation solution containing phosphorus ions after this step, the method for producing a solid electrolytic capacitor.