JPH0435014A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To shorten an aging time, and to eliminate deterioration of an adhesive force between sealing resin and a metal case by heating to a temperature of melting point or less of TCNQ salt to a predetermined value or higher in a short time, applying a predetermined voltage to a capacitor at the time of heating or cooling, then pouring thermosetting resin in the case, and further applying a predetermined voltage at a predetermined temperature. CONSTITUTION:Mixture 8 of N-phenethyl lutidinium.(TCNQ)2 and N,N- pentamethylene.(lutidinium)2.(TCNQ)4 of equal amounts is used, melted, liquefied, immersed with a capacitor element 6, and contained in an aluminum case 7. Resin 10 is poured and cured in the degree of concealing the element as a primary sealing. This capacitor is contained in a cylindrical heat plate hole having a size slightly larger than the outer diameter of the capacitor and such a depth that the capacitor can completely be buried when the capacitor is inserted, and aged at a temperature of the melting point or lower of TCNQ and 200 deg.C or higher. Further, it is sealed with epoxy resin 7 as a secondary sealing, a rated voltage is applied at 105 - 125 deg.C for 1 hour, and it is then normally aged.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a method for manufacturing a solid electrolytic capacitor.
This invention relates to an improvement in the aging method of organic semiconductor solid electrolytic capacitors using salt.

(b) Prior Art Regarding organic semiconductor solid electrolytic capacitors using TCNQ salt as an electrolyte, the applicant of the present application has already made various proposals. For example, Special Publication No. 62-51489 (I-101
G9102), JP-A-58-191414 (HO
IG 9102) etc.

Now, leakage current due to repair of the anodic oxide film of capacitor elements such as aluminum foil.
In order to reduce this, ordinary electrolyte type aluminum electrolytic capacitors are aged at about 85°C.

In addition, conventional organic semiconductor solid electrolytic capacitors using TCNQ salt are aged at 105°C to 125°C, similar to aluminum electrolytic capacitors impregnated with ordinary electrolyte.
The rated voltage is applied for approximately one hour to repair the anodic oxide film, that is, to reduce leakage current.

In addition, the applicant of the present application previously filed Japanese Patent Application No. 1-100769 "Method for Manufacturing Solid Electrolytic Capacitor" (filed on April 20, 1999), and set the aging temperature at 150°C or higher and below the melting point of TCNQ salt. However, the higher the temperature, the greater the effect of reducing leakage current, but the stress during heating reduces the adhesive strength between the metal case and the sealing resin, making it difficult to use it as a leadless SMD component. In such a case, the internal pressure would rise due to heat from the outside, and the metal case could come out and fall.

(c) Problems to be solved by the invention Normal aging conditions (105-125°C, about 1 hour)
When an electrolytic capacitor is completed, the stability of leakage current (L, C) is different between the electrolytic solution type electrolytic capacitor and the TCNQ salt type solid electrolytic capacitor. In other words, when an electrolytic capacitor is actually mounted on a printed circuit board and used, especially at high temperatures (i.e., when soldering), when heat is transferred to the capacitor through the circuit board, a difference occurs in the deterioration of leakage current, and the TC
In the case of NQ salt type, deterioration may occur.

In particular, if soldering heat (230 to 260° C.) is directly conducted to the capacitor even for a short time, leakage current may deteriorate even if the temperature is below the melting temperature of the TCNQ salt.

However, these deteriorations are temporary and can be gradually repaired by applying a predetermined voltage even at room temperature, but this may cause problems in the circuit.

In addition, as mentioned above, aging at high temperatures significantly improves the deterioration of leakage current, but the higher the temperature, the more the adhesive strength between the metal case and the sealing resin decreases due to the thermal stress during aging, leading to leadless SMD, ( When used as a chip (chip) component, the internal pressure would rise due to heat from the outside, and there was a possibility that the metal case would come out and fall.

(d) Means for solving the problem TCNQ salt is heated and melted, a capacitor element is impregnated with the liquid TCNQ salt, and then cooled and solidified to form a solid electrolytic capacitor. After the capacitor element is housed in a metal case, or after the capacitor element is housed in the case and TCNQ salt is heated and melted to impregnate the capacitor element, the element is coated with thermosetting or thermoplastic resin. Cover. At this time, the resin to be coated is sufficient to cover the element. Next, the capacitor is heated for a short time (10 minutes or less) to a temperature below the melting point of the TCNQ salt and above 200° C., and a predetermined voltage is applied to the capacitor during heating or cooling. Thereafter, a thermosetting resin is injected into the metal case, and the resin that has covered the element is coated in a double layer. Further, it is more effective to apply a predetermined voltage at 105 to 125° C. and perform normal aging.

(E) Function The melting point of TCNQ salt used in solid electrolytic capacitors is approximately 210-260°C, and aging of this capacitor is normally performed at 105-125°C. However, in the present invention, aging is performed at a temperature of about 200 to 250°C, which is much higher than the normal aging temperature, so it is presumed that the heat resistance of the insulating film produced to repair leakage current increases. (See Table 1).

Furthermore, soldering can suppress an increase in leakage current even when the device is left under extremely high temperatures. Also, T.C.
In the case of aluminum electrolytic capacitors impregnated with NQ salt, the higher the aging temperature, the better the aging efficiency (insulation film formation rate) with respect to the applied current.
(50°C or higher), the aging time can be significantly shortened. Furthermore, in the present invention, since the seal is further sealed with a thermosetting resin after aging at high temperatures, no thermal stress is applied to the adhesive surface between the sealing resin and the metal case1, and there is no deterioration of adhesive strength, so the case is There is no chance of a drop.

(f) Example The present invention will be explained. FIG. 1 shows a capacitor element used in the present invention. First, high purity (99.9z or higher)
The aluminum foil is chemically treated to roughen its surface, and a so-called etching process is performed to increase the effective surface area. Next, an oxide film (thin film of aluminum oxide) is formed on the surface of the aluminum foil electrochemically in an electrolytic solution (
chemical conversion treatment). Next, the etched and chemically treated aluminum foil is used as the anode foil (1), and the opposing cathode foil (2) is used as the anode foil (1).
Sandwich Manila paper as a separator (3) between the
Roll it up into a cylindrical shape as shown in the figure. Anode foil (]) and cathode foil (2) in which an oxide film was formed on aluminum foil in this way.
) and a separator (3) inserted between both electrode foils are rotated to form a capacitor element (6). Note that (4) (
4') is an aluminum lead, and (5) (5') is a lead wire.

Further, the capacitor element (6) is subjected to heat treatment, and the manila paper forming the separator (3) is carbonized to reduce the density by reducing the diameter of the fibers.

FIG. 3 shows a conventional example, and is a sectional view of this capacitor element (6) housed in an aluminum case (7). Put a predetermined amount of various TCNQ salts (8) into the case (7),
Place the aluminum case (7) on the heated hot plate and press 21.
The powdered TCNQ salt in the case (7) is heated and melted at 0 to 260°C. On the other hand, a preheated capacitor element (6) is inserted into the aluminum case (7), and the capacitor element (6) is impregnated with the melted TCNQ salt liquid.
Cool and solidify immediately. Thereafter, resin (9) is encapsulated and sealed.

Next, an embodiment of the present invention will be described with reference to FIG.

In Figure 2, a mixture (8) of equal amounts of N phenethylrutidinium (TCNQ)2 and N5N-pentamethylene (rutidinium)2 (TCNQ)+ is used in the capacitor element (6). Melt and liquefy the element (6
) and stored in an aluminum case (7) as a primary seal, and inject and harden each resin (10) to the extent that the element is hidden. In this example, the rating is 25V and 1μF. This capacitor is housed in a cylindrical hot plate hole that is slightly larger than the outer diameter of this capacitor and has a depth that allows the capacitor to be completely buried when inserted, and is aged under each of the following conditions (N) to (n). The sample was then sealed with epoxy resin (7) as a secondary seal, and a rated voltage was applied at 125° C. for 1 hour to perform normal aging.

Next, as a heat resistance test, a VPS test was conducted at 220° C. for 30 seconds, and the experimental results shown in Table 1 were obtained. The experimental results are the average values of 10 values for each experimental sample. In this case, the melting point of the mixed TCNQ salt used was 210 to 220°C. Further, as the aging voltage applied to the capacitor during aging, a so-called reduced voltage is applied in which the voltage is lowered as the heating temperature becomes higher.

Aging condition: f! ,: Heated for 15 seconds in a hot plate at 250°C, applied 25V m: Heated for 30 seconds in a hot plate hole at 200°C, applied 25V n: Heated for 60 seconds in a hot plate hole at 180°C, applied 25V. Materials (A), (B), (D), and (E) are examples of the present invention, (C) is a reference example, and (F) to (I) are conventional examples.

Margin The symbols in Table 1 have the following meanings. That is, Ca P ; capacitance (μF), 120 HzL, C,
i Leakage current (μA/after 30 seconds) E, S, R, i Equivalent series resistance (mΩ), 100Kz Δc/c i Capacitance change rate (%) When the case is removed, it falls off; The metal case falls off and falls off. However, the aging conditions (o), (p), and (q) of the conventional examples (F), (G), and (H) were completely sealed with epoxy resin. After curing (o) is 250℃, (p) is 200℃
, (q) in a hot plate hole at 180℃, (o) for 15 seconds, (
P) is heated for 30 seconds, (q) is heated for 60 seconds, and 25V is applied during heating.
After applying normal aging (125℃, 25V,
1 hour).

Further, the aging condition (r) of Conventional Example (I) is that after complete sealing and curing with epoxy resin, only normal aging (125° C., 25 V, 1 hour) is performed.

Looking at Table 1, it can be seen that in conventional examples (F) and (G), the case fell off or the case shifted, but in (H), this did not occur. It is presumed that the adhesive strength of the product has deteriorated.

In addition, in conventional example (1), although there is no drop in case removal,
The characteristics after the VPS (heat resistance) test have significantly deteriorated.

However, in Examples (A), (B), (D), and (E), there was little characteristic deterioration, and no cases were removed or dropped. Therefore, the effects of the present invention appear when aging is performed at 200° C. or higher. In other words, if the aging method of the present invention, in which secondary sealing is performed after aging after primary sealing, is performed, ■ there will be little characteristic deterioration in the PS test;
It also prevents the case from being removed or dropped.

Furthermore, in the present invention, the same result can be obtained by aging the element (6) after inserting it into the case (7) before injecting the resin, and then sealing it with a thermosetting resin. The lead wire moves due to mechanical stress, etc.
Since leakage current may deteriorate, it is better to harden the element with resin to some extent before aging to obtain a more reliable effect.

(G) Effects of the Invention By carrying out the manufacturing method of the present invention, it is possible to improve the characteristics of a capacitor after a heat resistance test, and it is also possible to prevent appearance defects such as case removal.

[Brief explanation of drawings]

Figure 1 is a perspective view of a capacitor element used in the present invention, Figure 2 is a sectional view showing an embodiment of a capacitor using the method of manufacturing a solid electrolytic capacitor of the present invention, and Figure 3 is a sectional view of a conventional example. be. (1) (2)...Positive...Cathode foil, (3)...Separator, (6)...Capacitor element, (7)...Aluminum case, (8)...TCNQ salt , (9)...Epoxy resin, (10)...-Next sealing resin.

Claims (1)

[Claims] (1) A TCNQ salt that can be heated and melted and has a conductivity that can be used as an electrolyte for a capacitor after being cooled and solidified is heated and melted to impregnate a capacitor element, and after being cooled and solidified, it is stored in a resin or metal case, or After the capacitor element is housed in the case, TCNQ salt is heated and melted to impregnate the capacitor element, and a thermosetting or thermoplastic synthetic resin is filled and coated on the element housed in the case. and cured at a temperature below the melting point of the TCNQ salt and at 200°C.
After heating to a temperature above and applying a predetermined aging voltage to the electrode terminals of the capacitor during heating or heating/cooling, the opening of the case of the capacitor is sealed with a thermosetting synthetic resin. Method of manufacturing solid electrolytic capacitors.