JPS6016093B2 - Manufacturing method of solid electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a solid electrolytic capacitor, and specifically to a method for thermally decomposing an element soaked with manganese nitrate to complete a semiconductor layer.

In the manufacturing process of solid electrolytic capacitors, the anode body is made of a metal with valve action such as aluminum, tantalum, niobium, zircon, titanium, etc., this is joined to the anode lead of a suitable metal conductor, and this lead is attached to the mounting bar. By joining, a large number of anode bodies are supported by the bar, and in this state, a protective coating is applied to the joint of each anode body with the anode lead to prevent short circuit failure, and then the surface of the anode body is expanded by etching, etc. Then, an oxide layer is formed on the anode body by anodization treatment, a dithermal manganese semiconductor layer is formed on this by immersion in a manganese nitrate solution and a thermal decomposition treatment, and then a dithermal manganese semiconductor layer is formed on the anode body by anodization treatment. A carbon layer is formed on this by bonding and heat treatment, and then a cathode layer of silver or the like is formed on this to complete the capacitor element. After the cathode lead is soldered to this element, an exterior such as molded resin is applied. Ru.

In this manufacturing method, the oxidized layer of the anode body is impregnated with a manganese nitrate solution and then thermally decomposed, conventionally using heat radiation or heat conduction using the air or nitrogen atmosphere of a heating furnace. ing.

In the case of mass production, methods of forced circulation of the heating atmosphere are being explored in order to increase the amount of heat supplied. With this method, it is difficult to control the temperature of the heating atmosphere, making it impossible to obtain a uniform temperature distribution throughout the furnace. Conventionally, the heating temperature and heat supply rate of the elements in the furnace vary, and this causes the characteristics of the capacitor to vary. This is causing variation. An object of the present invention is to realize an advantageous thermal decomposition method capable of suppressing variations in capacitor characteristics as described above. According to the present invention, as shown in FIG. 1, a capacitor element 2 immediately after being immersed in a manganese nitrate solution is brought into contact with a solder plate 1 at the bottom of the element body. Heat is conducted from the molten solder to the element 2, and manganese nitrate is thermally decomposed into manganese dioxide. The advantage of the method of the present invention is that the heat supply rate to the elements 2 is much higher than that of the secondary method, and since many elements can be brought into contact with the solder plate at the same time in parallel, the heating temperature of all the elements can be reduced. It should be uniformly controlled. Uniform heating temperature is an advantage over conventional methods, and it suppresses variations in capacitor characteristics of each element. Furthermore, according to the present invention, since the heat supply rate is high,
The following benefits can be obtained: Generally, when the anodized film of an element is impregnated with a manganese nitrate solution, the oxide film is corroded by the manganese nitrate.

This corrosion increases as time passes after the element is immersed in the manganese nitrate solution and pulled out. When the film chemically deteriorates due to such erosion, the leakage current of the capacitor increases. Therefore, it is desirable for capacitor manufacturing that immediately after the element is immersed in manganese nitrate, the manganese nitrate is thermally decomposed into manganese dioxide by heat treatment, and does not exhibit the above-mentioned corrosive effect. According to the secondary heat treatment method, heat from the heating atmosphere is applied to the element, so the heat supply rate is 4.5 times lower, and the rate of thermal decomposition into manganese dioxide is also lower, so the erosion of the oxide film by manganese nitrate can be sufficiently prevented. cannot be suppressed. In this regard, according to the present invention, since heat is directly conducted from the solder plate to the element, the heat supply rate is much higher than that of the conventional method, and therefore, the manganese nitrate is thermally decomposed before it can exert its corrosive effect. The occurrence of leakage current due to chemical deterioration of the oxide film is greatly suppressed.
Here, according to the inventor's experiments, the preferable relationship between the temperature of the solder grate and the contact time of the element to the grate in order to reduce the leakage current to 3 A or less (using JIS standard C5142) is as shown in Fig. 2. It was confirmed that the results were as shown in the graph.

FIG. 2 is a plot of the contact time versus bath temperature until the leakage current reaches 3 μA. Although the thermal decomposition temperature shifts to a slightly lower temperature under reduced pressure, ``Under atmospheric pressure, manganese nitrate thermally decomposes at 20,000 ℃ to form a semiconductor layer.

In the figure, the horizontal axis is the bath temperature 8 (℃), and the vertical axis is the contact time t (seconds).
represents.

The shaded area in the figure is 1 with the condition 200<0<800.
It is expressed by the formula: 120SI(8-200)tIS6000. The reason why the equation on the left side is set to a value of 6000 or less is because the maximum temperature is 8G or 800℃, and the contact time for which the leakage current is 31A is 1 desanding. be.

The reason for setting the limit at 800C is that when the temperature exceeds 80C and 0C, Mh02 formed by thermal decomposition on the surface of the capacitor element 2 is generated.
This is because it starts to burn out.

Furthermore, the bath temperature must be kept at a minimum of 20,000, which is the decomposition temperature of manganese nitrate.

Therefore, l(8-200)tl was set to be 1120 or more. When the above formula is larger than 6000, the oxide film deteriorates due to heat, which causes leakage current to be generated in addition to the deterioration caused by manganese nitrate.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the device heating method of the present invention, and FIG. 2 is a graph showing the preferable relationship between the solder temperature and the bath contact time of the device. In the figure, 1 indicates molten solder, and 2 indicates an element. Aoi Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1. A method for manufacturing a solid electrolytic capacitor including a step of forming a semiconductor layer of manganese dioxide by impregnating an anodized film of an anode body with manganese nitrate and thermally decomposing the film, comprising: a solder bath having a bath temperature θ; The impregnated manganese nitrate is thermally decomposed by partially contacting the main body of the capacitor element for a time t under the following conditions: 200°C<θ<800°C 1120≦|(θ−200)t|≦6000. A method for manufacturing a solid electrolytic capacitor characterized by: