JPH0435015A - Solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To prevent an increase in a leakage current at the time of applying a high voltage or soldering by cooling, after immersing a capacitor element with TCNQ salt, solidifying it, covering it with saccharide (e.g., glucose, glucose polymer), and further covering with epoxy resin. CONSTITUTION:TCNQ salt immersed in a capacitor element 1 is cooled, solidified, and the element 1 is secured in a case 5. Then, aqueous solution of saccharide such as glucose aqueous solution, glucose polymer aqueous solution, etc., is poured to the opening of the case 5. It is left to stand at 50 deg.C for about 1 - 8 hours to evaporate water in the saccharide aqueous solution to form a film 8 of saccharide of 1mm or less thick on the element. After the film 8 is formed, epoxy resin 7 is poured in the case 5, the element 1 is covered double from above the film, and the opening of the case is sealed.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention uses an organic semiconductor made of TCNQ salt (here, TCNQ salt means 7.78.8 tetracyanoquinodimethane) as an electrolyte. Regarding solid electrolytic capacitors.

(B) Conventional technology It has been proposed in the past to use organic semiconductors, especially TCNQ salts, as the solid electrolyte of solid electrolytic capacitors (for example, Japanese Patent Publication No. 62-52939 (II01G910
2)). In such conventional technology, as shown in Fig. 2, organic semiconductor powder (
6) Appropriate amount of heat conductive case (aluminum case, etc.)
(5) and store it under moderate pressure.
The capacitor element (1), which has been melted and liquefied at a temperature of 0.degree. C. and preheated in advance, is immersed therein. Furthermore, a capacitor element (1
) together with the case, the case opening is filled with thermosetting non-flexible resin (e.g. epoxy resin) (7),
It was left to stand for a long time at a temperature of 85 to 105°C to harden. Note that the capacitor element (1) here is aluminum,
A chemically formed foil of a metal with valve action such as tantalum or niobium is used as an anode, a foil of these metals that is not normally subjected to chemical conversion treatment is used as a cathode, and a spacer paper is sandwiched between the cathode foil and anode foil and wound. It is something. Also, (2) (3'I
are anode and cathode lead wires, respectively, and (4) is a lead boss.

In such conventional solid electrolytic capacitors, the oxide film formed on the anode of the capacitor element and the organic semiconductor serving as the solid electrolyte deteriorate due to the reaction between the thermosetting resin and the organic semiconductor. As a result, due to the above-mentioned factors, there are weak parts in the 9 oxide film, leading to an increase in leakage current or short circuit when high voltage is applied. Furthermore, during soldering, the weak parts of the oxide film are sometimes destroyed due to thermal stress during heating, leading to an increase in leakage current.

(c) Problems to be Solved by the Invention The present invention solves the problem mentioned above; This solves the problem that leakage current sometimes increases when high voltage is applied or when soldering is applied.

(D) Means for Solving the Problems The present invention impregnates a capacitor element with TCNQ salt, cools and solidifies it, coats the capacitor element with sugar (e.g. glucose, glucose polymer), and further coats it with an epoxy resin. .

(E) Function Since sugars hardly react with TCNQ salt, if the capacitor element is coated with sugar and then coated with epoxy resin, there will be no TCNQ salt between the TCNQ salt and the epoxy resin.
A layer is formed that hardly reacts with the NQ salt. As a result, the oxide film and TCNQ salt (organic semiconductor) do not deteriorate due to the reaction between the epoxy resin and the TCNQ salt.

(f) Embodiment Next, an embodiment of the present invention will be described with reference to FIG. An aluminum foil that has been subjected to etching treatment and chemical conversion treatment is used as an anode foil, and a separator is sandwiched between it and a counter cathode foil, and the aluminum foil is wound into a cylindrical shape to form a capacitor element (1). Next, the powder (6) of TCNQ salt, for example, Nn-phytylisoquinolinium TCNQ, is stored in the case (5), and the TCN
The Q salt (6) is melted and liquefied, and the capacitor element (1) is immersed to impregnate it with the TCNQ salt. After the impregnation, the case (5) is cooled, the TCNQ salt impregnated into the capacitor element (1) is cooled and solidified, and the capacitor element (1) is fixed within the case (5).

Next, a saccharide aqueous solution (for example, a glucose aqueous solution or a glucose polymer aqueous solution) is injected into the case (5) until it reaches the opening of the case (5). The aqueous solution of saccharides is obtained by dissolving saccharides (e.g., glucose or glucose polymers) in water, and is left at 50°C for about 1 to 8 hours (approximately proportional to the outer diameter of the element) to dissolve the saccharides in the aqueous solution of saccharides. By evaporating the water, a saccharide film (8) having a thickness of less than 1 inch is formed on the capacitor element. Sugar film (8
) is formed (after water evaporation), the epoxy resin (7) is injected into the case (5) and the capacitor element (1) is poured over the sugar film.
) and seal the opening of the case. Then, the rated voltage of the capacitor is applied (aging) at 125° C. for 1 hour to complete the desired solid electrolytic capacitor.

Next, Table 1 is a table comparing the leakage current yield after aging of the organic semiconductor solid electrolytic capacitor (A) of the present invention and the conventional organic semiconductor solid electrolytic capacitor (B).

Table 1 In Table 1, (A) and (B) have a rated voltage of 35 V, a capacity of 0, 68 t, r F, T CN Q salt and N-
These are capacitors using n-butylisoquinolinium TCNQ2, in which (A) is an example of the present invention and (B) is a conventional example. In addition, L, C, are leakage current data, and sample 1
It shows the number of defects out of 00 pieces and the yield, but for L, C,
The standard is 35V, 0.68μF is 0.5(μA /
1.0 sec, ) or less.

It can be seen from Table 1 that the leakage current yield of the solid electrolytic capacitor using an organic semiconductor (TCNQ salt) as an electrolyte according to the present invention is significantly improved compared to the conventional example.

Table 2 assumes the heat of soldering and flow test R16
The leakage current values before and after (0°C x 2 minutes + 230°C x 30 seconds glue flow furnace) are described.

The solid electrolyte (TCNQ salt) of the solid electrolytic capacitor used in the reflow test was (N-I) in the case of Table 1 above.
Unlike butylisoquinolinium (TCNQ)2, N
, N-pentamethylene (lutidinium) 2. (TCN
Q) A mixture of equal amounts of 1 and N-phenethyl rutidium (TCNQ) was used. Other conditions were the same as in Table 1 above.

In Table 2, (C) and (D) are capacitors with a rated voltage of 25 V and a capacity of 1/-IF, (c) is an embodiment of the present invention, and (D) is a conventional example. r- and c are leakage current data, which are values 60 seconds after the application of 25 V and represent the average value of the values of each 10 samples.

From Table 2, the product of the present invention has the following leakage current values (L, C):
It can be seen that it is extremely resistant to soldering compared to conventional products.

In the example of the double series, the case of a type in which the capacitor element is housed in a case has been described, but the effect of the present invention is also applicable to a so-called resin dip type in which the capacitor element is completely sealed with resin without using a case. No harm done.

Note that similar effects can be obtained with other T CN Q salts such as N=n-propylquinoline, N-ethylisoquinoline, N-isopropylquinoline, and N-11-hexylquinoline.

(G) Effect of the invention As described above, in the present invention, the capacitor element is TCN
Sugars that hardly react with Q salts (e.g. glucose,
Since the oxide film formed on the anode of the capacitor element and the TCNQ salt as an organic semiconductor deteriorate due to the reaction between the epoxy resin and the TCNQ salt, since the capacitor element is coated with a glucose polymer (glucose polymer) and then an epoxy resin. is prevented. As a result, compared to conventional methods, the leakage current yield or soldering is significantly improved in that the leakage current sometimes increases.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an example of the present invention in which the material is coated with sugar and further covered with epoxy resin. FIG. 2 is a sectional view of a conventional example covered with epoxy resin. (1) Capacitor element, (2) (3) Anode and cathode lead wire, (5) Metal case, (6)
...Organic semiconductor (TCNQ salt), (7)...Epoxy resin, (8)...Saccharide.

Claims (2)

[Claims] (1) A capacitor element is heated and melted by winding a separator paper between an anode foil made of a chemically formed metal foil such as aluminum, tantalum, or niobium, and a cathode foil made of a thin foil of the metal. After cooling and solidifying, the capacitor element is coated with saccharide, and the outside of the saccharide is coated with epoxy resin. A solid electrolytic capacitor characterized by being coated or sealed. (2) The solid electrolytic capacitor according to claim 1, wherein the saccharide is glucose or a glucose polymer.