JPH0321007A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To improve recoverableness of an oxide film to prevent leakage current from increasing by a method wherein steam of 1atm or higher is functioned inside a capacitor element to reinforce bonding between TCNQ complex and water molecules. CONSTITUTION:TCNQ salt 8 is heated melted and impregnated in a capacitor element 6 and cooled to solidify, and then the capacitor element 6 is kept in steam of 1atm or higher. That is, since steam of 1atm or higher is used, water molecules easily transmit through a resin layer for sealing to enter inside the capacitor element 6 to be bonded with the TCNQ complex 8 with strong bonding force. Thus recoverableness of an oxide film can be improved due to function of water than conventional method of soaking in water and drying thereby preventing leakage current from increasing.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for manufacturing a solid electrolytic capacitor using an organic semiconductor made of TCNQ salt as a solid electrolyte.

(b) Prior Art It is already known that an organic semiconductor made of TCNQ salt can be used as a solid electrolyte of a solid electrolytic capacitor. In this case, the solid electrolyte is directly attached to a film-forming metal such as aluminum that has an oxide film, but in a different form, an anode foil and a cathode foil are rolled up with a separator paper in between to form a capacitor element. A technique for impregnating the above-mentioned solid electrolyte in the separator paper in this element is disclosed in Japanese Patent Publication No. 62-52939 (HOIG9/02). Note that TCNQ means 7, 7, 8, 8, tetracyanoquinodimethane.

In such conventional technology, organic semiconductor powder is appropriately pressurized and packed into an aluminum case with good thermal conductivity, and this is melted and liquefied at 250 to 300°C, and the heated capacitor element is placed in this melt. The device is impregnated by immersion in liquid, cooled and solidified together with the aluminum case, and completed through processes such as resin sealing and voltage treatment (21-ging).

Incidentally, the anode of a capacitor element is formed of an oxide film which is a dielectric, but the oxide film is damaged by thermal shock during preheating and impregnation of the element or mechanical shock during transport and impregnation of the element. Therefore, after impregnating with an organic semiconductor or sealing with a resin, voltage treatment (aging) is performed at a high temperature of about 100° C. in order to restore the oxide film and reduce the leakage current value.

However, solid electrolytes made from organic semiconductors have the disadvantage that they have weaker oxide film repair properties than electrolytes used in general electrolytic capacitors, resulting in problems such as high leakage current values and low yields. . In order to solve the problem that the repairability of the oxide film of the solid electrolyte is weak, the leakage current value is large, and the yield is low, the applicant of the present application previously filed Japanese Patent Application No. 612-267270 ζ 1986.
(filed on October 21, 2013) and patent application No. 63-264571
(filed on October 20, 1988) and provided the following technology. That is, an organic semiconductor made of TCNQ salt is heated, melted, liquefied, impregnated into a capacitor element, cooled and solidified, and then the capacitor element is immersed in pure water to impregnate the inside of the element with the pure water under reduced pressure. After drying the moisture in the capacitor at a temperature of around 100°C for 1 to 8 hours,
The opening of the case containing the capacitor element is sealed with resin, and finally voltage treatment (engineering) is performed at a temperature of around 100°C to completely cure the solid electrolytic capacitor.

In such a conventional production method of impregnating with pure water, the element impregnated with TCNQ salt is immersed in pure water.
A step of drying excess water remaining as a liquid in the capacitor element is essential. In addition, in order to impregnate the capacitor element with pure water, it must be carried out before sealing the capacitor element. Therefore, the moisture introduced into the element interior 3 4 during the impregnation and drying process with pure water, that is, the water combined with the TCNQ complex, is impregnated with pure water. Since the bonding force of the molecules with the TCNQ complex is weak, they may react with the resin during the subsequent sealing of the aluminum case, that is, when the resin hardens.
It is affected to a large extent by heat stress during curing of the resin. As a result, the repairability of the oxide film during voltage treatment (aging) due to the action of water is weakened, which has the drawback of inhibiting leakage current reduction.

(c) Problems to be Solved by the Invention The present invention solves the above-mentioned problems, that is, it is possible to omit the drying process necessary for using liquid water, and it can also be used even after sealing with resin of the capacitor element. The purpose of the present invention is to provide a method in which the water introduced into the capacitor element is not adversely affected during resin curing even if it is carried out before the element is sealed, as in the conventional method, and it is more effective than conventional methods during voltage treatment (aging). This improves the repairability of the oxide film and solves the effect of inhibiting leakage current reduction.

(2) Means for Solving the Problems In the present invention, TCNQ salt is heated and melted to impregnate a capacitor element, cooled and solidified, and then the capacitor element is held under water vapor at 1 atmosphere or more.

(e) Effect By using water vapor at 1 atm or higher (at 00° C. or higher), the conventional process for removing liquid water (drying process) becomes unnecessary. Furthermore, water can be added even after the capacitor element is sealed. That is, since water vapor of 1 atm or higher is used, water molecules easily pass through the sealing resin layer, enter the inside of the capacitor element, and bond with the TCNQ complex with strong bonding force.

As a result, the repairability of the oxide film by the action of water is improved more than the conventional method of immersion in water and drying, and an increase in leakage current is prevented. In addition, even if water vapor of 1 atm or more is applied before sealing the capacitor element, the bonding force between the TCNQ complex and water molecules is stronger than that of the conventional method, so the effect of curing in the subsequent resin sealing is less than that of the conventional method. Way less. Therefore, the repairability of the oxide film is improved more than the conventional method, and leakage current can be reduced.

(F) Example Next, the manufacturing process will be described in the case where the method of the present invention is used before and after resin sealing of a capacitor element.

(1) Addition of water to the resin sealant of a capacitor element As shown in Figure 1, an aluminum foil that has been etched and anodized is used as the anode foil (1), and a separate layer (2) is placed between it and the opposing cathode foil (2). 3) and wind it up into a cylindrical shape to form a capacitor element (6). Note that (4) and (4') are aluminum leads, and (5) and (5') are lead wires.

Next, as shown in FIG. is stored in an aluminum case (7), and the melting point (21
0 to 230°C) or higher, for example, 290°C to 300°C
The TCNQ salt is melted and liquefied at a temperature of °C. Then, insert the preheated capacitor element (6) into the TCNQ inside the case (7).
Impregnate with TCNQ salt by immersing in salt melt. After impregnation, the case (7) is cooled, the TCNQ salt (8) impregnated into the capacitor element (6) is cooled and solidified, and the capacitor element is fixed within the case. Note that the time from melting and liquefying the TCNQ salt to cooling and solidifying it must be within several minutes; after this time, the organic semiconductor made of the TCNQ salt becomes almost an electrical insulator.

Next, the TCNQ salt-impregnated element (6) is placed in, for example, a constant temperature, high humidity, high pressure tester, and the temperature is about 3 atm (saturation temperature; l.
Using water vapor at a temperature of 32.88° C., water molecules are caused to act inside the device for one hour. Finally, seal the opening of the case with epoxy resin (9), and apply the rated voltage of the capacitor for approximately 1 hour at 125°C (21-ging).
and complete the desired solid electrolytic capacitor.

(2) Water treatment after sealing the capacitor element with resin As mentioned above, the capacitor element (6) is impregnated with TCNQ salt (8), cooled and solidified, and fixed in the case (7), followed by epoxy resin (9). Seal the opening of the case. Next, the capacitor is placed in, for example, a constant temperature, high humidity, high pressure tester, and water vapor at about 2 atm (saturation temperature: 78°C, 119.62°C) is applied for 18 hours to inject water from the outside of the capacitor's sealing resin into the inside of the capacitor element. Infiltrate molecules. Then, approximately the rated voltage of the capacitor is applied (dwelling) at 125° C. for 1 hour to complete the intended solid electrolytic capacitor.

Table 1 shows a comparison of the leakage current yield after voltage treatment (aging) of a solid electrolytic capacitor completely manufactured by the manufacturing method of the present invention and a solid electrolytic capacitor completely destroyed by the conventional manufacturing method.

Table 1 The test conditions and data capacitors in Table 1 are as follows. That is, (A); The manufacturing method of the present invention ((1) above) (C) (E
)(G)iThe manufacturing method of the present invention ((2) above)(B
)(D)(F)(H); Conventional manufacturing method or (A)(B); Rated voltage 35V, capacity 3.3μF
(C) (D)i Rated voltage 35V, capacity 0.22μF
(E) (F) i Rated voltage 35 V, capacity 0.4
7μF (G) (H) i Rated voltage 35V, capacity 1μ
FL. C, ; Leakage current
Furthermore, the L and C columns are leakage current data, indicating the number of defects in 100 samples and the yield. Since the rated voltage of the C standard is all 35V, all of them are below the following value. That is, 3.37. +F
In case of; 2.3 (μA /10sec) 0.22μF
In the case of; 0. 5 (t-t A /10sec)
In the case of 0.47 μF; 0. 5 (μA/10s
ec) For 1 μF; 0. 7( p A /10s
ec) The following can be seen from Table 1. That is, it can be seen that by the method of the present invention, the leakage current yield of a solid electrolytic capacitor using an organic semiconductor (TCNQ salt) as an electrolyte is significantly improved compared to the conventional method.

Hereinafter, in this embodiment, a type in which the capacitor element is housed in a case has been described, but a so-called resin dip type type in which the capacitor element is entirely sealed with resin without using a case may also be used.

In addition, although the current example is only rated at 35V, 35V
The following also has a similar effect. In addition, in the above, TCN of N-n-butylisoquinolinium is used as the solid electrolyte.
Although the case where Q salt is used has been explained, N-(n-probyl)-quinolinium, N-(n-
It goes without saying that TCNQ salts such as amyl) monoisoquinolinium and N-(isoamyl) monoisoquinolinium may also be used.

Furthermore, the present invention is not limited to the case where a wound element in which an anode foil and a cathode foil are wound with separator paper interposed therebetween is used as a capacitor element. It is also applicable when using a sintered element that is shaped and sintered. That is, a capacitor element is made by planting an aluminum lead wire for an anode on fine aluminum powder (approximately 10 to 40 microns in particle size) and sintering it, and electrochemically converting the oxide film layer that will become the dielectric using chemical liquid. the above-mentioned T C N as a solid electrolyte in the capacitor element.
The method of the present invention can also be applied to the production process when Q salt is used.

(G) Effects of the Invention As described above, according to the present invention, since water vapor of 1 atm or more is applied inside the capacitor element, the bond between the TCNQ complex and water molecules becomes stronger than that of the conventional method, even before resin sealing. Even if the resin is treated with water, it has little effect on the hardening of the resin and does not impair the repairability of the oxide film due to the action of water. As a result, regardless of whether the hydration treatment of the present invention is performed before or after resin sealing of the capacitor element, the leakage current yield is significantly improved compared to conventional manufacturing methods. In addition, since water vapor of 1 atm or more is used, the drying step of the conventional manufacturing method is not necessary, 11 12 and therefore the number of man-hours in the manufacturing process can be reduced. Furthermore, since the present invention can be used before and after resin sealing, the degree of freedom in the manufacturing process increases.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a capacitor element used in the present invention, and FIG. 2 is a sectional view of the solid electrolytic capacitor of the present invention. (1) (2)...Positive, cathode foil, (3)...Separator, (6)...Capacitor element, (7)...Aluminum case, (8)...TCNQ complex salt.

Claims (3)

[Claims] (1) A method for producing a solid electrolytic capacitor in which a capacitor element formed by forming an anodized film on a film-forming metal is impregnated with a molten and liquefied organic semiconductor, and the solid electrolytic capacitor is cooled and solidified. A method for manufacturing a solid electrolytic capacitor, comprising the step of maintaining the capacitor element under a water vapor pressure of 1 atmosphere or more. (2) The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the capacitor element is a wound element in which an anode foil and a cathode foil are wound with a separator paper in between. (3) The capacitor element is made of aluminum, tantalum,
2. The method of manufacturing a solid electrolytic capacitor according to claim 1, wherein the capacitor element is formed by pressure molding or sintering a metal powder having a valve action such as niobium.