JPS581536B2 - Manufacturing method of solid electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing solid electrolytic capacitors, and in particular to a method for forming manganese dioxide by pyrolysis.

The method for firing manganese dioxide for solid electrolytic capacitors is carried out by thermal decomposition of hydrous manganese nitrate as follows.

Mn (NO3) 2 ・xH2 0-+Mn (
NO3) 2+XH2 0Mn (No 3)
2 →Mn ONO s + No 2Mn ONO
3→Nn 0 2 +NO 2 These reactions are endothermic reactions, and are known to be completed at a temperature in the range of 130 to 200°C, and the inventors have confirmed that they are completed at 195°C.

However, in the case of rapid heating, it was estimated that the thermal decomposition of the manganese nitrate would be completed when the surface temperature of the anode element to which the hydrous manganese nitrate was attached was 280°C.

Conventionally, this manganese dioxide calcination was performed in an electric furnace.

In this case, the temperature inside the electric furnace is around 1000℃,
After inserting the anode element into the furnace, its surface temperature reaches 280℃.
It takes about 1 minute for the temperature to rise to 0.degree. C. because the heat capacity of these elements is large.

During this time, the water and nitrogen dioxide produced by thermal decomposition of hydrated manganese nitrate partially erode the oxide film already formed on the element surface, creating a defect that tends to form a leakage path that reaches the valve metal. .

The aim of the invention is to eliminate the above-mentioned drawbacks.

The above object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor including a step of forming an oxide film on an anode element and firing the manganese dioxide, in which the manganese dioxide firing step burns the manganese nitrate attached to the anode element. This can be achieved by a method for manufacturing a solid electrolytic capacitor, which is characterized in that a manganese dioxide layer is formed by thermal decomposition inside the solid electrolytic capacitor.

The combustion flame used in the present invention can be obtained by burning ordinary fuels that produce flame and burn, such as city gas, LPG, oil, and coal.

A screen made of non-combustible material, such as metal, ceramic or asbestos, can be inserted above the combustion flame to make the screen red hot and maintain a uniform temperature of the flame above the screen at about 1000°C.

A feature of the present invention is that the anode element to which hydrated manganese nitrate to be fired is placed in a combustion flame, which is usually about 1000°C, so that it is rapidly heated to a surface temperature of 280°C, which is necessary for firing the manganese dioxide. It takes only a few seconds to reach °C.

FIG. 1 shows a manganese dioxide calcination temperature one hour curve a according to the method of the invention in comparison with a similar curve b according to the conventional method.

The time it takes to reach 280°C to complete manganese dioxide firing is 55 seconds when using a conventional electric furnace, whereas 6 seconds is sufficient when using the combustion flame of the present invention.

In the case of an electric furnace, it takes 1 to 2 hours to raise the temperature of the furnace body and 2 hours to lower the temperature, so the equipment is relatively large and the working time is long.

FIG. 2 is an explanatory diagram of an apparatus for firing manganese dioxide, showing the features of the method of the present invention.

When a wire mesh 2 is inserted above the combustion flame 1, a red flame 3 is generated above the wire mesh.

2 x 3 x 3 with hydrous manganese nitrate attached.
By suspending a 5 mm aluminum element 4 as an example, the elements 4 to be sequentially treated are allowed to stay in the red flame 3 for 6 seconds and then moved in the direction of arrow A.

In this way, the manganese dioxide firing step can be easily performed using a simple device.

The solid electrolytic capacitor according to the present invention is characterized in that the capacitance is almost the same, but the dielectric loss tangent is slightly smaller, and the leakage current is significantly smaller than those produced by the conventional method.

In this way, any of the above characteristics. The superiority of the solid electrolytic capacitor manufacturing method of the present invention will be explained in the following examples with reference to the drawings.

EXAMPLE An etched aluminum element of 2 x 3 x 3.5 mm was used as an anode, electrolyzed in a boric acid-citric acid based chemical solution to form an aluminum oxide film, and then immersed in an aqueous manganese nitrate solution.

As shown in Figure 2, an iron mesh was inserted into a gas flame, and the iron mesh was red-hot to about 1000℃, and the hydrated manganese nitrate of the rabbit was attached to it in the red flame that came out through the iron mesh. The device was fired.

At this time, a series of elements were moved one after another so that the firing time was about 6 seconds.

Next, re-formation and manganese dioxide firing step 5 similar to the above steps.
Repeated times.

The exterior was then coated with graphite and baked, and silver paint and baked.

The results of comparing the 50 solid electrolytic capacitor samples with similar solid electrolytic capacitors obtained by the conventional method are shown in FIGS. 3 to 5.

FIG. 3 shows the leakage current at a voltage of 25 V, FIG. 4 shows the capacitance (μF) at a frequency of 120 Hz, and FIG.

As is clear from FIG. 3, the aluminum solid electrolytic capacitor manufactured by the method of the present invention has a significantly larger cumulative area percentage of products exhibiting the same leakage current than those manufactured by the conventional method.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between hydrous manganese nitrate thermal decomposition temperature versus decomposition time in the method of the present invention and the conventional method, and FIG. 2 is an explanatory diagram of an apparatus for implementing the method of the present invention. FIG. 3 is a graph showing the relationship between leakage current at 25 V and cumulative percentage of solid electrolytic capacitors manufactured by the method of the present invention and the conventional method, and FIG. FIG. 5 is a graph showing the relationship between the capacitance and the cumulative percentage at 120 Hz, and FIG. This is a graph showing. ia... When using the method of the present invention, b...
・・When using the conventional method, 1・−・Kaiyaki flame, 2・・
...Net, 3...Combustion flame coming out through the net, 4
・・・゜・・・Anode element.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a solid electrolytic capacitor including a step of forming an oxide film on an anode element and firing manganese dioxide, wherein the manganese dioxide firing step burns a flammable gas as a heat source; A method for manufacturing a solid electrolytic capacitor, characterized in that a manganese dioxide layer is formed by thermally decomposing manganese nitrate attached to an anode element in this combustion flame. 2. The combustion flame is characterized in that a mesh made of at least one material selected from the group consisting of metal, ceramic, and asbestos is inserted into the combustion flame, and the combustion flame comes out through the mesh. A method for manufacturing a solid electrolytic capacitor according to claim 1.