JP2869145B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

The present invention relates to a method for manufacturing a solid electrolytic capacitor. More specifically, the present invention relates to aging of an organic semiconductor solid electrolytic capacitor using a TCNQ salt as an electrolyte. It is about improving the law.

(B) Conventional technology The present applicant has already proposed various types of organic semiconductor solid electrolytic capacitors using a TCNQ salt as an electrolyte. For example, Japanese Patent Publication No. Sho 62-51489 (H01G 9/02),
No. 58-191414 (H01G 9/02).

Now, in order to reduce leakage current (Leakage Current) by repairing an anodic oxide film of a capacitor element such as an aluminum foil, a normal electrolytic solution type aluminum electrolytic capacitor is aged at about 85 ° C. Conventionally, in the case of an organic semiconductor solid electrolytic capacitor using a TCNQ salt, aging is performed at approximately 105 ° C. to 125 ° C. for approximately one hour at approximately rated voltage, similarly to an aluminum electrolytic capacitor impregnated with a normal electrolytic solution. It is mainly used to repair the anodic oxide film, that is, to reduce the leakage current.

In addition, the applicant of the present application applied for Japanese Patent Application No. 1-100769 “Method of manufacturing solid electrolytic capacitor” (filed on April 20, 1999), and set the aging temperature at 150 ° C. or higher and the melting point of TCNQ salt or lower. Although the effect of reducing the leakage current increases as the temperature increases, the adhesive force between the metal case and the sealing resin decreases due to the stress during heating, and it was used as a leadless SMD part. In such a case, the internal pressure may increase due to external heat, and the metal case may fall off.

(C) Problems to be Solved by the Invention When an electrolytic capacitor is completed under normal aging conditions (105 to 125 ° C, about 1 hour), the leakage current between the electrolytic solution type electrolytic capacitor and the TCNQ salt type solid electrolytic capacitor ( L.
C) The stability is different. In other words, when an electrolytic capacitor is actually mounted on a printed circuit board and used, especially when heat is transferred to the capacitor through the circuit board under high temperatures, that is, when soldering, a difference occurs in the deterioration of the leakage current, and the TCNQ salt type In the case of, deterioration may occur.

In particular, if the solder heat (230-260 ° C.) is directly conducted to the capacitor for a short time, the leakage current may deteriorate even at a temperature lower than the melting temperature of the TCNQ salt. But,
Even if these deteriorations are temporary and are gradually at room temperature, they are repaired by applying a predetermined voltage, but this may cause a problem in the circuit.

As described above, when aging is performed at high temperatures, the deterioration of leakage current is significantly improved. However, as the temperature increases, the adhesive force between the metal case and the sealing resin decreases due to thermal stress during aging, and leadless SMD (chip ) When used as a component, the internal pressure may increase due to external heat, and the metal case may fall off.

(D) Means to solve the problem After heating and melting the TCNQ salt, impregnating the capacitor element with the liquid TCNQ salt, solidifying by cooling to form a solid electrolytic capacitor, and impregnating the TCNQ salt when aging. After storing the capacitor element in the metal case, or storing the capacitor element in the case, heating and melting the TCNQ salt to impregnate the capacitor element, and then covering the element with a thermosetting or thermoplastic resin . At this time, the resin to be coated is such that the element is hidden. Next, the capacitor is heated to a temperature not higher than the melting point of the TCNQ salt and not lower than 200 ° C. for a short time (10 minutes or less), and a predetermined voltage is applied to the capacitor during heating or cooling to a heated temperature. Thereafter, a thermosetting resin is injected into a metal case, and the resin covering the element is double-coated on the resin. 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 21
0-260 ° C, the aging of this capacitor is usually 10
Performed at 5-125 ° C. However, in the present invention, the temperature which is much higher than the normal aging temperature is about
Since aging is performed at a temperature of 200 to 250 ° C., it is presumed that the heat resistance of the insulating film generated to repair the leakage current increases (see Table 1). Also, even when left at a high temperature corresponding to the time of soldering, an increase in leakage current can be suppressed. In the case of aluminum electrolytic capacitors impregnated with TCNQ salt, the higher the aging temperature, the better the aging efficiency (generation rate of the insulating film) with respect to the flowing current. Can be shortened. Further, in the present invention, after aging by high temperature, the sealing surface is further sealed with a thermosetting resin, so that no thermal stress is applied to the bonding surface between the sealing resin and the metal case, and there is no deterioration in the adhesive strength.
The case never falls off.

(F) Example The present invention will be described. FIG. 1 shows a capacitor element used in the present invention. First, a high-purity (99.9% or more) aluminum foil is roughened by a chemical treatment to perform a so-called etching treatment for increasing an effective surface area. Next, in an electrolytic solution, an oxide film (a thin film of aluminum oxide) is electrochemically formed on the aluminum foil surface (chemical conversion treatment). Next, the aluminum foil subjected to the etching treatment and the chemical treatment is used as an anode foil (1), and a manila paper is sandwiched as a separator (3) between the aluminum foil and the counter cathode foil (2). Take up. Thus, the anode foil (1) and the cathode foil (2) having the oxide film formed on the aluminum foil and the separator (3) interposed between the two electrode foils.
Are wound to form the capacitor element (6). (4) and (4 ') are aluminum leads, and (5) and (5') are lead wires.

Further, the capacitor element (6) is subjected to a heat treatment to carbonize the manila paper constituting the separator (3) to measure the decrease in density due to the reduction in the diameter of the fiber.

FIG. 3 is a sectional view showing a conventional example, in which the capacitor element (6) is housed in an aluminum case (7).
A predetermined amount of each TCNQ salt (8) is put in the case (7), the aluminum case (7) is placed on a heated hot plate, and
Heat and melt the powdered TCNQ salt in case (7) at 0 ° C. On the other hand, the previously heated capacitor element (6) is inserted into the aluminum case (7), and the molten liquid of the TCNQ salt is impregnated into the capacitor element (6) and immediately cooled and solidified. Thereafter, the resin (9) is sealed and sealed.

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

In FIG. 2, a capacitor element (6) is prepared by mixing N-phenethyllutidinium (TCNQ) ₂ and N, N-pentamethylene (rutidinium) ₂ (TCNQ) ₄ in equal amounts (8). Each element (6) is melted and immersed in the element (6), and each resin (10) is injected and hardened to such an extent that the element contained in the aluminum case (7) is used as a primary seal to hide the element. In this embodiment, the rating is 25 V and 1 μF. When this capacitor is slightly larger than the outer diameter of the capacitor and this capacitor is inserted, the capacitor is housed in a cylindrical hot plate hole having a depth that is completely buried, and aging is performed under the following conditions (l) to (n). After that, the secondary sealing was further sealed with an epoxy resin (7), 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 at 220 ° C. for 30 seconds was performed. As a result, the experimental results shown in Table 1 were obtained. This experimental result is the average value of the numerical values of ten experimental samples. In this case, the melting point of the mixed TCNQ salt used was 210 to 220.
° C. As the aging voltage applied to the capacitor during aging, a so-called reduced voltage is applied in which the voltage is reduced as the heating temperature increases.

Aging conditions: l: Heated in hotplate hole of 250 ° C for 15 seconds, applied 25V m: Heated in hotplate hole of 200 ° C for 30 seconds, applied 25V n: Heated in hotplate hole of 180 ° C for 60 seconds, 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.

The symbols in Table 1 mean the following. CaP; capacitance (μF), 120Hz LC; leakage current (μA / 30 seconds later) ESR; equivalent series resistance (mΩ), 100KHz Δc / c; capacitance change rate (%) The case was displaced; the metal case did not fall, but it was slightly displaced. The aging conditions (o), (p), and (q) of the conventional examples (F), (G), and (H) were epoxy. Completely sealed with resin,
After curing, (o) is 250 ° C, (p) is 200 ° C, (q) is 18
In a hot plate hole at 0 ° C, (o) is 15 seconds, (p) is 30 seconds,
(Q) is obtained by heating for 60 seconds, applying 25 V during heating, and then performing normal aging (125 ° C., 25 V, 1 hour).

The aging condition (r) of the conventional example (I) is such that after normal sealing and curing with an epoxy resin, only normal aging (125 ° C., 25 V, 1 hour) is performed.

As can be seen from Table 1, in the conventional examples (F) and (G), the case came off or the case slipped. In the case of (H), the case did not occur. It is presumed that the power has deteriorated.
In the conventional example (I), although there is no case dropout,
The characteristics after the VPS (heat resistance) test are significantly deteriorated. However, in the examples (A), (B), (C), (D), and (E), there is little characteristic deterioration, and the case does not fall off. Therefore, the effect of the present invention appears when aging is performed at 200 ° C. or higher. That is, if the aging method of the present invention in which aging is performed after the primary sealing and then the secondary sealing is further performed, the characteristic deterioration in the VPS test is small, and the case can be prevented from falling off.

In the present invention, the same result can be obtained by inserting the element (6) into the case (7), aging the resin before injecting the resin after the element is inserted into the case (7), and thereafter sealing the same with a thermosetting resin. Lead wire moves due to mechanical stress, etc.
Since the leakage current may be deteriorated, a certain effect can be obtained by solidifying the element with resin to some extent before aging.

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

[Brief description of the drawings]

FIG. 1 is a perspective view of a capacitor element used in the present invention, FIG. 2 is a sectional view showing an embodiment of a capacitor using the method for manufacturing a solid electrolytic capacitor of the present invention, and FIG. 3 is a sectional view of a conventional example. is there. (1) (2) ... positive ... cathode foil, (3) ... separator, (6) ... capacitor element, (7) ... aluminum case, (8) ... TCNQ salt, (9) ... Epoxy resin, (1
0) ...... Primary sealing resin.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01G 9/04 H01G 9/028 H01G 9/08

Claims (1)

(57) [Claims] 1. A TCNQ salt having conductivity which can be heated and melted and which can be used as an electrolyte for a capacitor after cooling and solidifying, is heated and melted to impregnate the capacitor element, and after cooling and solidifying, is stored in a resin or metal case. Alternatively, after the capacitor element is housed in the case, TCNQ salt is heated and melted to impregnate the capacitor element, and the element housed in the case is filled with a thermosetting or thermoplastic synthetic resin. After coating and curing, heating to a temperature below the melting point of the TCNQ salt and 200 ° C. or higher, and applying a predetermined aging voltage to the electrode terminals of the capacitor during the heating or heating / cooling, the opening of the case of the capacitor is opened. A method for manufacturing a solid electrolytic capacitor, comprising sealing a part with a thermosetting synthetic resin.