JP2000286168A - Electrolytic capacitor and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable electrolytic capacitor capable of preventing the formation of corrosive products at welded locations of leads and thereby preventing short-circuits thereat. SOLUTION: A lead wire 4 is formed by welding a lead-out wire to a round rod part 6 of a tab terminal formed of a flat part and the part 6, and the formed wire 4 is bonded to an anode foil and a cathode foil at the flat part. Then, these foils are rolled via a separator, thereby forming a capacitor element 1. The element 1 is contained in a sheathing case 13, while being impregnated with an electrolytic solution having γ-butyrolactone as a main solvent, and a polyester sleeve 20 is fitted around the outer side of the case 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic capacitor and a method for manufacturing the same, and more particularly, to an improvement in an exterior material thereof.

[0002]

2. Description of the Related Art As shown in FIG. 3, a capacitor element 1 is formed by winding an anode electrode foil and a cathode electrode foil made of a valve metal such as tantalum and aluminum through a separator, as shown in FIG. The capacitor element 1 holds a liquid electrolyte or a solid electrolyte and accommodates it in an outer case 13, seals the opening of the outer case 13 with a sealing body 12, and further heat-shrinks a tube ( The sleeve is hereinafter referred to as a sleeve). In such an electrolytic capacitor, lead wires 4 and 5 for connecting the respective electrodes to the outside are connected to the anode electrode foil and the cathode electrode foil by known means such as stitching and ultrasonic welding. .

The lead wires 4 and 5 are composed of three parts: a flat part, a round bar part and a lead wire. That is, as shown in FIG. 4, the portion bonded to the electrode foil is formed into a flat portion 7 because it is wound in a wound capacitor element, and is inserted through the sealing body 12 that seals the outer case 13. A round bar portion 6 is formed to secure the sealing property between the sealing body 12 and the mechanical strength. In addition, the lead portion mounted on the circuit board is a lead wire 8 having flexibility in order to ensure handleability during mounting.

[0004] Since it is inefficient to produce such a lead wire composed of three parts as a single molded product from the beginning, such a lead wire is produced by welding two types of members. It is usually done. That is, this lead wire is formed by forming the flat portion 7 and the round bar portion 6 as a single tab terminal, and welding a separately formed lead wire 8 to the round bar portion 6 of the tab terminal. I have. In such a lead wire, the lead wire 8 is often mounted on the circuit board by soldering. Therefore, as the lead wire 8, a lead wire whose surface is plated with tin containing tin or lead is used in order to improve soldering characteristics.

[0005] Next, a method for manufacturing a conventional electrolytic capacitor will be described. That is, when manufacturing the capacitor element 1 as shown in FIG. 3, first, as shown in FIG. 4, the lead wires 4 and 5 to be attached to the anode electrode foil 2 and the cathode electrode foil 3 are formed. That is, the lead wires 4 and 5 are formed by welding an aluminum tab terminal formed of the round bar portion 6 and the flat portion 7 and a lead wire 8 formed of a CP wire formed of copper around an iron wire. Then, the surface of the lead wire 8 is plated with tin. Hereinafter, the welded portion between the aluminum tab terminal and the lead wire 8 is referred to as a lead welded portion 9. Also,
As a welding method in the lead welded portion 9, for example, the round bar portion 6 and the lead wire 8 are butted, a high temperature state is formed by spark discharge or the like, and both ends of the round bar portion 6 and the lead wire 8 are melted and joined. A method or the like can be used.

Next, as shown in FIG. 4, the flat portions 7 of the lead wires 4 and 5 formed as described above are joined to the anode electrode foil 2 and the cathode electrode foil 3, respectively. Then, winding is performed with the separator 11 interposed between the anode electrode foil 2 and the cathode electrode foil 3 to manufacture the capacitor element 1. further,
This capacitor element 1 is impregnated with a driving electrolyte (hereinafter referred to as a BL-based electrolyte) using γ-butyrolactone as a main solvent.

Then, as shown in FIG. 3, the round bars 6 of the lead wires 4 and 5 of the capacitor element 1 are inserted into the holes of the sealing body 12, and then the capacitor element 1 is inserted into a bottomed cylindrical outer case. 13 Then, the opening end of the outer case 13 is hermetically sealed and closed by drawing, and a polyvinyl chloride sleeve 14 is mounted outside the outer case 13 to complete an aluminum electrolytic capacitor.

Usually, the sleeve is mounted on the outside of the outer case 13 as follows. That is, the sleeve formed in the shape of a tube is cut into a predetermined length, and the sleeve is covered on the surface of the outer case of the electrolytic capacitor. In this case, the diameter of the sleeve is formed larger than the diameter of the outer case. Then, the electrolytic capacitor covered with the sleeve is placed in a heating furnace, and hot air of about 220 ° C. is heated in the heating furnace for 3 hours.
Spray for about a second. As a result, the sleeve thermally shrinks and adheres to the outer surface of the electrolytic capacitor.

[0009]

However, the conventional electrolytic capacitor as described above has the following problems. That is, when an aluminum electrolytic capacitor using a BL-based electrolytic solution was left at a high temperature in a closed state like an AC adapter, a game machine, a communication device, etc., corrosion products were easily generated in the lead welded portion 9. And
The generation of corrosion products in the lead welded portion 9 causes disconnection, short circuit, and the like.

[0010] The present invention has been proposed to solve the problems of the prior art as described above, and an object of the present invention is to prevent the generation of corrosion products in a lead welded portion,
It is an object of the present invention to provide a highly reliable electrolytic capacitor capable of preventing disconnection and short-circuit, and to provide a manufacturing method capable of efficiently manufacturing such an electrolytic capacitor.

[0011]

Means for Solving the Problems In order to solve the above problems, the present inventors have conducted intensive studies and completed the present invention. That is, the present inventors, after observing the occurrence of corrosion products in the lead welded portion of the conventional electrolytic capacitor described above in detail, focused on the material (composition) of the sleeve mounted on the outer case. The study was repeated on the relationship between the material of the sleeve and the generation of corrosion products in the lead weld.

(1) Corrosion Product Generation Site and Corrosion Product Contents First, the state of generation of corrosion products was observed for the above-mentioned conventional electrolytic capacitor.
It was found that a large amount of corrosion products was generated in the lead welding portion 9 between the round bar portion 6 and the lead wire 8 of No. 5. In addition, when corrosion products generated in the lead welded part were investigated, pH 1
It showed strong acidity of ~ pH 2 and, when this corrosion product was analyzed, a chlorine compound was detected.

(2) Consideration of Source of Chlorine Compound in Lead Weld Part Next, in order to investigate the source of chlorine compound in the lead weld part, the following experiment was conducted. That is, when a sealing test was performed using the presence or absence of the BL-based electrolyte solution and the sleeve as a parameter, it was examined whether or not precipitates were generated. Specifically, Samples 1 to 3 shown in Table 1 were ultrasonically cleaned with methanol, placed in a 250 mL heat-resistant bottle with a screw, sealed, and left in a thermostat at 85 ° C. for 1000 hours. Sample 4 was also sealed in the same heat-resistant bottle,
It was left in a thermostat at 1000C for 1000 hours.

The sample 3 was the same product as the sample 1, and both the product which was not impregnated with the electrolyte solution and was not equipped with the polyvinyl chloride sleeve were sealed in the same heat-resistant bottle by 50 pieces each. Sample 4 is a lead wire alone,
The electrolyte solution and the sleeve were put in the same heat-resistant bottle without being in contact with each other, and sealed. Sample 1
The rating of ~ 3 is 16WV-100μF and the size is φ
6.3 × 11L.

[Table 1]

In each of the above conditions, 10
After leaving for 00 hours, the presence or absence of a precipitate at the sealing portion was visually inspected. As a result, a precipitate was found in the welded portion of the lead wire. Table 2 shows the results of the above experiment.

[Table 2]

As shown in Table 2, in Sample 1, Sample 3 and Sample 4, precipitates were generated at the welded portions of the leads. Subsequently, when these precipitates were analyzed using EDS (energy dispersive spectrometer), aluminum and chlorine were detected.

From this experiment, the following two points became clear. That is, the precipitates generated in the lead welded portion were generated in the product not impregnated with the electrolytic solution of Sample 3 and the lead wire of Sample 4 in the same manner as in Sample 1. It was found that this was not a precipitate due to liquid leakage. Further, since no precipitate was generated in Sample 2 without the sleeve, it was suggested that the sleeve caused the generation of precipitate. Furthermore, since chlorine was detected in the precipitate, the cause of the formation of the precipitate was that chlorine-based substances contained in the polyvinyl chloride sleeve attached to the outside of the outer case and the solvent component of the electrolytic solution diffused, and the corrosion occurred. It is considered that a precipitation reaction occurred in the lead weld where the reaction easily occurs and where different metals are mixed.

(3) Consideration of the Mechanism of Chlorine Compound Generation in Lead Welds The mechanism of generation of chlorine compounds in lead welds as described above is presumed as follows. That is,
The electrolyte vapor evaporates from the sealing portion to the outside, and the capacitor is exposed to the electrolyte vapor. As a result, the polyvinyl chloride sleeve swells, chlorine in the sleeve is extracted, and hydrogen chloride is generated.

In the lead wire of the lead wire, a copper layer is formed on an iron core and the surface thereof is plated with tin. On the other hand, the round bar portion is formed of aluminum. , Iron, copper, and tin are mixed. Therefore, hydrogen chloride generated from the sleeve made of polyvinyl chloride comes into contact with these metals and causes a corrosion reaction, causing corrosion products (chlorine compounds)
Is considered to have occurred.

(4) It has been found that the formation of corrosion products (chlorine compounds) can be suppressed by forming the sleeve from a predetermined non-chlorine resin. Therefore, in order to suppress the above-mentioned generation of corrosion products, As a result of repeated studies using various resins, by forming the sleeve using a resin containing no chlorine, for example, a polyester resin, a polyolefin resin, or a polystyrene resin, a chlorine compound is used. It has been found that the generation of corrosion products can be suppressed. Of these, the use of a polyester-based resin or a polyolefin-based resin is more preferable because a sleeve having a high heat shrinkage can be formed. In addition,
The method of mounting the sleeve made of the non-chlorine-based resin on the outer case is the same as the conventional method of mounting the sleeve.

(5) Method of Manufacturing Electrolytic Capacitor Using Sleeve The difference between the method of manufacturing an electrolytic capacitor of the present invention and the above-described conventional manufacturing method is that the material of the sleeve mounted on the outside of the outer case is different. It is. That is, as shown in FIG. 1, an aluminum electrolytic capacitor is manufactured by a method similar to the conventional method using, for example, a polyester sleeve 20 as a sleeve to be mounted on the outside of the outer case.

(6) Electrolytic Capacitor Using Resin Coat Further, the present inventors have repeatedly studied an electrolytic capacitor using a resin coat made of a chlorine-free resin as a coating resin layer formed on the outside of the outer case. As a result, as in the case of the sleeve, it was found that the generation of corrosion products in the lead welded portion could be prevented. As this resin coat, it is desirable to use any of a polyamide resin, an epoxy resin or a polyester resin. This is because these resins have good adhesion to the outer case made of aluminum and are less likely to be separated from the outer case.

(7) Method of Forming Resin Coat The following method can be used as a method of forming a coating layer by a resin coat on the outside of the outer case. (A) After forming an outer case having a predetermined shape by drawing an aluminum plate, a polyamide resin, an epoxy resin or a polyester resin is applied to the outer case by applying or spraying the outer case. And then curing to form a resin coat. (B) Any one of a polyamide resin, an epoxy resin, and a polyester resin is applied to the aluminum plate by applying or spraying, and then cured.
A method in which an aluminum case having a resin layer formed on its surface is drawn to obtain an outer case having a predetermined shape. (C) As shown in FIG.
A sheet-like resin film made of any of a polyamide-based resin, an epoxy-based resin, or a polyester-based resin is adhered, and then, as shown in FIG. How to get an outer case.

[0024]

EXAMPLE As shown in Table 3, two types of electrolytic capacitors (φ6.3) differing only in the material of the sleeve were used as aluminum electrolytic capacitors having the same rating of 16 WV-100 μF.
100 mm × 11 L) were prepared, washed ultrasonically with methanol, then placed in 250 mL heat-resistant bottles with screws, sealed, and left in a thermostat at 85 ° C. for 1000 hours or 2000 hours. Thereafter, for each electrolytic capacitor, the presence or absence of a precipitate at the sealing portion was visually inspected. The results shown in Table 3 were obtained.

[0025]

[Table 3]

As shown in Table 3, when a conventional polyvinyl chloride sleeve is used, 10
After standing for 00 hours, corrosion products were generated in 20 of the 50 samples, and after standing for 2000 hours, corrosion products were generated in all 50 samples. On the other hand, when the polyester sleeve according to the present invention was used, no generation of corrosion products was observed both after leaving for 1000 hours and after leaving for 2000 hours. From this, the effect of using the polyester sleeve as the sleeve mounted on the outside of the outer case is apparent.

[0027]

As described above, according to the present invention, the covering resin layer formed on the outer side of the outer case is constituted by a heat-shrinkable tube or a resin coat made of a non-chlorine-based resin. Thus, it is possible to provide a highly reliable electrolytic capacitor capable of preventing generation of corrosion products and preventing disconnection and short-circuit. Further, it is possible to provide a manufacturing method capable of efficiently manufacturing such an electrolytic capacitor.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of an electrolytic capacitor according to the present invention.

FIG. 2 is a view showing a method of forming a resin coat,
(A) is a diagram showing a step of attaching a sheet-like resin film to an aluminum plate, and (B) is a diagram showing a process of drawing an aluminum plate.

FIG. 3 is a sectional view showing a configuration of a conventional electrolytic capacitor.

FIG. 4 is a perspective view showing a configuration of a capacitor element unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Capacitor element 2 ... Anode electrode foil 3 ... Cathode electrode foil 4, 5 ... Lead wire 6 ... Round bar part 7 ... Flat part 8 ... Lead-out part 9 ... Lead welded part 11 ... Separator 12 ... Sealing body 13 ... Exterior case 14 ... polyvinyl chloride sleeve 20 ... polyester sleeve

Claims (8)

[Claims] A lead wire formed by welding a lead wire to a round bar portion of a tab terminal comprising a flat portion and a round bar portion is joined to each of an anode electrode foil and a cathode electrode foil at the flat portion, These electrode foils are wound through a separator to form a capacitor element, the capacitor element is impregnated with an electrolytic solution containing γ-butyrolactone as a main solvent, housed in an outer case, and coated on the outer case. An electrolytic capacitor having a resin layer formed thereon, wherein the coating resin layer is constituted by a heat-shrinkable tube made of a non-chlorine resin. 2. A lead wire formed by welding a lead wire to a round bar portion of a tab terminal consisting of a flat portion and a round bar portion is joined to each of an anode electrode foil and a cathode electrode foil at the flat portion, These electrode foils are wound through a separator to form a capacitor element, the capacitor element is impregnated with an electrolytic solution containing γ-butyrolactone as a main solvent, housed in an outer case, and coated on the outer case. An electrolytic capacitor comprising a resin layer, wherein the coating resin layer is formed of a resin coat made of a non-chlorine resin. 3. The electrolytic capacitor according to claim 1, wherein the heat-shrinkable tube is formed of any one of a polyester resin, a polyolefin resin, and a polystyrene resin. 4. The method according to claim 1, wherein the resin coat is a polyamide resin,
The electrolytic capacitor according to claim 2, wherein the electrolytic capacitor is formed of one of an epoxy resin and a polyester resin. 5. A lead wire is formed by welding a lead wire to a round bar portion of a tab terminal comprising a flat portion and a round bar portion, and the formed lead wire is formed into an anode electrode foil and a cathode electrode foil at the flat portion. Each is joined, and these electrode foils are wound through a separator to form a capacitor element.The capacitor element is impregnated with an electrolytic solution containing γ-butyrolactone as a main solvent, and is housed in an outer case. A method for manufacturing an electrolytic capacitor, comprising: forming a coating resin layer on the outside of a capacitor; wherein the coating resin layer is constituted by a heat-shrinkable tube made of a chlorine-free resin. 6. A lead wire is formed by welding a lead wire to a round bar portion of a tab terminal comprising a flat portion and a round bar portion, and the formed lead wire is formed into an anode electrode foil and a cathode electrode foil at the flat portion. Each is joined, these electrode foils are wound through a separator to form a capacitor element, and the capacitor element is impregnated with an electrolytic solution containing γ-butyrolactone as a main solvent and stored in an outer case. A method for manufacturing an electrolytic capacitor, wherein a coating resin layer is formed on the outside of the capacitor, wherein the coating resin layer is formed of a resin coat made of a non-chlorine resin. 7. The heat-shrinkable tube is formed of any of a polyester resin, a polyolefin resin or a polystyrene resin.
3. The method for manufacturing an electrolytic capacitor according to claim 1. 8. The resin coat, comprising: a polyamide resin;
7. The method for manufacturing an electrolytic capacitor according to claim 6, wherein the electrolytic capacitor is formed of one of an epoxy resin and a polyester resin.