JPH0120526B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a solid electrolytic capacitor, and particularly to a method for producing a manganese dioxide layer.

In general, solid electrolytic capacitors have a structure in which an oxide film is formed on a sintered body of tantalum or the like, and a manganese dioxide layer, a graphite layer, a silver paint, etc. are sequentially formed on the outer surface of the oxide film. Also, the exterior is made of resin.

By the way, to form the manganese diacid layer of the electrolyte, it is common to immerse the sintered body in a manganese nitrate solution and decompose it by heating. Solutions with additives of lithium salts, solutions with additives of ammonium nitrate may be used.

Next, the solder heat resistance of solid electrolytic capacitors manufactured using the above solution (bath temperature 260
10 seconds in a solder bath at ℃). Although solid electrolytic capacitors manufactured using a solution do not have an abnormal increase in leakage current after soldering heat resistance, there is an increase in impedance in a high frequency range.
Solid electrolytic capacitors manufactured using a solution that uses sodium nitrate as the sodium salt cannot uniformly form a manganese dioxide layer on the oxide film, causing stress on the exterior resin etc. when immersed in solder.
There is an increase in leakage current. In a solid electrolytic capacitor manufactured using a solution, after immersion in solder, voids are locally formed between the manganese dioxide layer and the oxide film, resulting in an increase in impedance.

However, the present invention provides a solid electrolytic capacitor which reduces leakage current in the initial state and impedance in a high frequency range, and which stabilizes the characteristics after soldering heat resistance. Specifically, the present invention provides a method for manufacturing a solid electrolytic capacitor in which a manganese nitrate solution containing ammonium nitrate and sodium nitrate additives is used to generate a manganese dioxide layer.

Detailed examples will be described below. 140C・FV/
Tantalum pellets of P were prepared and subjected to 60V chemical conversion at room temperature in a 0.01% by weight phosphorylation solution. Note that the formation time was 2 hours after reaching the voltage. After completion of chemical formation, wash in pure water at 80℃. Next, it was immersed for 30 seconds in a 14% by weight manganese nitrate solution (70°C) diluted with 8% by weight of ammonia nitrate and 2% by weight of sodium nitrate, and then heated to 350°C.
Pyrolyze for 6 minutes. Subsequently, the above addition concentration
It is immersed in a 28% by weight manganese nitrate solution (70°C) for 30 seconds and thermally decomposed under the same conditions as above. Then, 5 times in a row, an additive-free 60% by weight manganese nitrate solution (70%
℃) for 30 seconds and thermally decomposed under the same conditions as above.
Thereafter, it is immersed in a 28% by weight manganese nitrate solution (70°C) with the above concentration and thermally decomposed at 340°C.
During this time, 25V is applied in a 0.001% by weight phosphoric acid solution at room temperature for each thermal decomposition, and the defects in the oxide film are compensated for by reconversion. This is the process of forming a manganese dioxide layer.Next, for the purpose of external conductivity, it is immersed in a 4% by weight graphite solution for 10 minutes at 150℃.
After drying for minutes, a silver paint was applied as a conductor and cured at 150°C for 30 minutes to form an element.
The rest is the exterior, for example, by dispensing fixed silver into a metal cap for the cathode with a diameter of 2.2 mm, fixing the above element in the cap, welding the anode terminal to the anode lead of the element, and connecting the cap and the terminal. A UV-curable resin was applied and cured to create a finished product.

Examples of the present invention manufactured as described above;
Conventional Example 1 manufactured with a manganese nitrate solution without additives, Conventional Example 2 manufactured with a manganese nitrate solution with an additive of sodium nitrate, and Conventional Example 2 manufactured with a manganese nitrate solution with an additive of ammonium nitrate. A comparison of characteristics with Example 3 is shown in FIGS. 1 and 2. The solid electrolytic capacitor has a rating of 16V and 2.2μF, and the number of samples is 20. FIG. 1 is an impedance characteristic diagram in the high frequency range (1 MHz) at the initial stage and after solder immersion. FIG. 2 is a leakage current characteristic diagram at the initial stage and after solder immersion.

As can be seen from FIGS. 1 and 2, the initial values of the impedance characteristics and leakage current characteristics of the embodiment of the present invention are lower than those of the conventional example, and the characteristics do not change even after being immersed in solder and are stable. . However, the present invention can provide a good solid electrolytic capacitor.

In the manganese nitrate solution with ammonium nitrate and sodium nitrate additives in the present invention, experimental results show that the concentration of ammonium nitrate is preferably 1-8% by weight, and the concentration of sodium nitrate is preferably 0.5-12% by weight.

In the present invention, the number of times the capacitor pellet is immersed in the manganese nitrate solution containing the above additives is at least 1 to form the manganese dioxide layer.
A degree of immersion is sufficient, but in combination with immersion in an additive-free manganese nitrate solution, immersion in a manganese nitrate solution with additives 1 to 3 times, then immersion in an additive-free manganese nitrate solution 1 to 3 times. A more preferable solid electrolytic capacitor can be obtained by dipping the solid electrolytic capacitor 1 to 10 times, and then immersing it in a manganese nitrate solution containing an additive 1 to 3 times.

[Brief explanation of drawings]

FIG. 1 is a comparison diagram of impedance characteristics of an embodiment of the present invention and a conventional example, and FIG. 2 is a diagram of comparison of leakage current characteristics of an embodiment of the invention and a conventional example.

Claims (1)

[Claims] 1. A method for manufacturing a solid electrolytic capacitor, which comprises immersing a capacitor pellet in a manganese nitrate solution containing ammonium nitrate and sodium nitrate additives, and then thermally decomposing the pellet to form a manganese dioxide layer. . 2. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the concentration of ammonium nitrate is 1 to 8% by weight. 3. The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the concentration of sodium nitrate is 0.5 to 12% by weight. 4. A method for manufacturing a solid electrolytic capacitor according to claim 1, which comprises a combination of immersion in an additive-free manganese nitrate solution and thermal decomposition.