JP2002008945A - Aluminum electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum electrolytic capacitor, which is made to suppress occurrence of short circuits which are liable to occur through the use of a lead wire terminal formed by welding an aluminum material and material, other than the aluminum material, to each other. SOLUTION: The portion made of the aluminum material of the lead wire terminal, used in this aluminum electrolytic capacitor, is formed with a voltage of 10-50 V. The formation of the portion is preferably performed at a temperature of 10-90 deg.C, using an aqueous solution of the ammonium salt of adipic acid or phosphoric acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an aluminum electrolytic capacitor. More specifically, the present invention relates to an aluminum electrolytic capacitor that uses an improved lead wire terminal to prevent short-circuit defects and reduce defects such as foil breakage during joining with an electrode foil.

[0002]

2. Description of the Related Art In an aluminum electrolytic capacitor, a lead wire terminal is used to connect a capacitor element formed by winding an aluminum foil for an anode and a cathode laminated via a separator to an electric circuit outside the capacitor. Have been. Conventionally, the lead terminal of an aluminum electrolytic capacitor requires welding a lead wire (also called a lead wire) consisting of a copper fly wire (CP wire) to the end face of the aluminum round bar, and pressing the other end of the aluminum round bar. Cut to dimensions flat (or flat)
Is formed. The aluminum foil serving as the anode foil and the cathode foil is connected to the flat portion by caulking, welding or the like before being wound together with the separator to form a capacitor element.

[0003]

The welding of an aluminum round bar and a lead wire (in general, a plated copper-coated steel wire is used) at the time of manufacturing a lead wire terminal is performed at the end face of the aluminum round bar. It is inevitable that oxidized iron powder, copper powder, and the like generated from the lead wire side due to sparks adhere to the end face of the aluminum round bar, near the welded portion, and also near the welded portion of the lead wire. The metal oxide powder adhering to the lead terminal material thus adheres to the capacitor element during the production of the capacitor, or falls off and floats in the case, thereby causing a short circuit failure of the product capacitor.

On the other hand, the chemical conversion treatment at a high voltage of 100 V to 300 V conventionally performed for the purpose of reducing the leakage current has an effect of removing iron powder and the like. However, when the chemical conversion treatment is performed at such a high voltage, an extremely thick oxide film is formed on the aluminum surface, so that the hardness of the aluminum portion of the lead wire terminal is increased, and the caulking between the lead wire terminal and the aluminum foil is performed. There is a problem that the aluminum foil is easily broken at the time of joining. The cracks in the aluminum foil (1) increase the resistance of the capacitor due to poor bonding between the lead wire terminal and the aluminum foil, and (2) easily cause problems when manufacturing the capacitor element by winding. (3) The inconvenience that the broken foil portion breaks the separator and a short circuit is likely to occur is caused frequently.

[0005] Iron powder and the like adhering to the lead wire and the aluminum round bar can be removed by a method such as electrolytic polishing. However, in this case, a very strongly acidic polishing solution is used, and if this solution enters the capacitor, its characteristics will be affected.

Accordingly, the present invention is directed to a lead wire which is effective for suppressing short-circuit failure caused by oxidized iron powder or the like generated by welding an aluminum material such as an aluminum round bar and a material other than aluminum such as a CP lead wire. An object of the present invention is to provide an aluminum electrolytic capacitor using terminals.

[0007]

An aluminum electrolytic capacitor according to the present invention is formed by winding aluminum foils for an anode and a cathode, each of which is laminated with a separator interposed therebetween, and a capacitor element housed in a sealed container. An aluminum electrolytic capacitor having a lead wire terminal connected to the anode and cathode aluminum foils of the element and drawn out of the capacitor, wherein the lead wire terminal forms the aluminum material portion at a voltage of 10 to 50 V. It is characterized by being processed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The chemical conversion treatment of the aluminum material portion of the lead wire terminal is carried out at a low voltage of 10 to 50 V by immersing the corresponding portion in an electrolytic solution. As the electrolyte, any electrolyte may be used as long as it does not adversely affect the chemically treated part or the aluminum electrolytic capacitor using the lead wire terminal subjected to the chemical treatment. For example, an electrolytic solution using adipate or phosphate as an electrolyte can be used. In particular, the use of an aqueous solution of an ammonium salt of adipic acid allows the formation of a crystalline, low-resistance chemical conversion film at a relatively low temperature. A very good chemical conversion film can be formed, which is very advantageous. The chemical conversion treatment can be performed using a mixture of two or more kinds of electrolytes.

The chemical conversion treatment is performed at a voltage of 10 to 50V.
This voltage is much lower than the applied voltage of 100 to 300 V during the normal chemical conversion treatment of the lead terminal. By removing the iron oxide powder and the like generated by welding the aluminum material and the non-aluminum material while performing the chemical conversion treatment at such a low voltage, it is easy to suppress short circuit failure caused by the iron oxide powder and the like. Further, chemical conversion treatment at a lower voltage than usual enables more efficient energy and time spent for chemical conversion treatment. Furthermore, the hardness of the aluminum portion of the lead wire terminal that has been subjected to the chemical conversion treatment is lower than that of a case where the lead wire terminal is treated at a high voltage of about 100 to 300 V, and the foil cracks at the time of caulking bonding with the electrode aluminum foil. And other problems can be reduced.

The temperature at which the chemical conversion treatment is performed may be arbitrarily selected, and a temperature in the range of, for example, about 10 to 90 ° C. can be adopted. However, when the temperature is increased, the chemical conversion treatment is accelerated and a good chemical film formation is obtained. On the other hand, considering that more energy is required for heating and that energy is consumed for cooling when the temperature is lower than room temperature and that the processing is generally slow, it is necessary to select an appropriate processing temperature. Is preferred. A preferred chemical conversion temperature is from room temperature to about 90 ° C, more preferably 40 to 85 ° C.

The part made of aluminum material is 10 to 50 V
Aluminum electrolytic capacitors of the present invention use the same materials as those used in the manufacture of ordinary aluminum electrolytic capacitors, and use the same method, except that lead terminals that have been chemically treated at a low voltage are used. Can be used and manufactured. Such materials and methods of manufacture are well known to those skilled in the art and need not be described at length here.

[0012]

EXAMPLES Next, the present invention will be further described with reference to examples, but the present invention is not limited to these examples.

(Example 1) As a lead terminal, a lead wire made of a CP wire was formed of an aluminum material member (a round bar portion having a diameter of 2 mm, a length of 3 mm, and a flat portion having a width of 2.
5 mm, a thickness of 0.30 mm, and a length of 14 mm) were welded to the tip of a round bar portion. The portion of the aluminum material member of the lead wire terminal is immersed in an electrolyte solution of 55 ° C., which is a 10 wt% aqueous solution of ammonium adipate, and the lead wire is used as an anode, and a counter electrode is arranged in the electrolyte solution. A chemical conversion treatment was performed by applying a voltage of 10 V. Using the lead wire terminal that has been treated in this way,
1,000 prototype aluminum electrolytic capacitors having a capacitor specification of 35 WV-1000 μF were produced.

(Example 2) The same aluminum material member of the lead wire terminal as prepared in Example 1 was immersed in an electrolyte solution of 70%, which is a 10 wt% aqueous solution of ammonium adipate. The anode was used as a counter electrode in an electrolytic solution, and a voltage of 50 V was applied between the electrodes to perform a chemical conversion treatment. Using the lead wire terminals thus subjected to the chemical conversion treatment, 1,000 aluminum electrolytic capacitors having the same capacitor specifications as those prototyped in Example 1 were also prototyped.

(Example 3) Similarly, the same portion of the aluminum material member of the lead wire terminal as prepared in Example 1 was placed in an electrolytic solution at 55 ° C., which is a 0.2 wt% aqueous solution of ammonium dihydrogen phosphate. , A counter electrode was placed in the electrolytic solution, and a voltage of 50 V was applied between both electrodes to perform a chemical conversion treatment. An aluminum electrolytic capacitor having the same capacitor specifications as the prototype made in Example 1 was
00 prototypes were produced.

(Embodiment 4) Similarly, the same aluminum material member of the lead terminal as prepared in Embodiment 1 was electrolyzed with an aqueous solution containing 10% by weight of ammonium adipate and 20% by weight of ethylene glycol. It was immersed in a liquid (liquid temperature of 85 ° C.), a lead electrode was used as an anode, a counter electrode was placed in the electrolytic solution, and a voltage of 10 V was applied between both electrodes to carry out a chemical conversion treatment. An aluminum electrolytic capacitor having the same capacitor specifications as the prototype manufactured in Example 1 was also used for 1000
Prototyped individually.

(Comparative Example 1) The same lead wire terminal as prepared in Example 1 was used without performing chemical conversion treatment on the aluminum material member, and used as it was in Example 1. A prototype of 1000 aluminum electrolytic capacitors with specifications was manufactured.

Comparative Example 2 The same aluminum material member of the lead terminal as prepared in Example 1 was heated to 55 ° C., which is a 0.2 wt% aqueous solution of ammonium dihydrogen phosphate.
, A counter electrode was placed in the electrolyte, and a voltage of 150 V was applied between both electrodes to carry out a chemical conversion treatment. Using the lead wire terminals thus subjected to the chemical conversion treatment, 1,000 aluminum electrolytic capacitors having the same capacitor specifications as those prototyped in Example 1 were also prototyped.

An aging test (temperature 105 ° C., 1.1 times the rated voltage (3
8.5 V) applied for 1 hour. Table 1 shows the number of capacitors having a short circuit failure after the test.

[0020]

[Table 1]

As apparent from this table, in the aluminum electrolytic capacitor of Comparative Example 1 using the lead wire terminal that was not subjected to the chemical conversion treatment, 98 out of 1,000 short-circuit defects occurred. On the other hand, in the aluminum electrolytic capacitors of Examples 1 to 4 and Comparative Example 2 using the lead wire terminals subjected to the chemical conversion treatment, no short circuit failure was observed after the aging test. This is because when an aluminum material portion of the lead wire terminal is subjected to a chemical conversion treatment in an electrolytic solution to form an oxide film on the surface, oxidized iron powder or copper adhered during welding of the CP wire and the aluminum wire. It is considered that the powder could be removed and the short circuit failure was suppressed.

Next, the lead wire terminals of Examples 1 to 4 and Comparative Examples 1 and 2 were caulked to an aluminum electrode foil having a width of 16 mm and a thickness of 0.1 mm by using a press plate. Fifty samples were prepared. Table 2 shows the results of observing the cracks in the caulked portion of each sample with a stereoscopic microscope.

[0023]

[Table 2]

As can be seen from this table, when the lead wire terminals of Examples 1 to 4 and Comparative Example 1 were used, foil breakage due to press caulking caused the lead wire terminals of Comparative Example 2 which had been subjected to the chemical conversion treatment at a high voltage. Was much less than when using. This is because, except for Comparative Example 2, the lead wire was subjected to a chemical conversion treatment at a particularly low voltage, so that a thinner oxide film was formed than when a conventional treatment was performed at a high voltage, and the hardness of the flat portion of the lead wire terminal was reduced. It is considered that the force applied to the electrode foil during crimping was reduced.

[0025]

As described above, according to the aluminum electrolytic capacitor of the present invention, short-circuit defects that occur with the passage of time due to oxidized iron powder or the like caused by welding of an aluminum material and a material other than aluminum are almost or little. In addition, the occurrence of initial failure due to cracking of the electrode foil at the time of manufacturing the capacitor element is reduced. In addition, the voltage required for manufacturing the lead wire terminals used in the aluminum electrolytic capacitor of the present invention is considerably lower than that of the conventional ones, and the energy and time spent for the chemical conversion treatment can be improved by that much. This leads to more efficient energy and time required for the production of a product capacitor.

Claims (2)

[Claims] 1. A capacitor element formed by winding aluminum foils for an anode and a cathode laminated via a separator and housed in a sealed container, and connected to the anode and cathode aluminum foils of the element, respectively. And an aluminum electrolytic capacitor having a lead terminal drawn out of the capacitor, wherein the lead terminal is formed by subjecting a portion made of the aluminum material to a chemical conversion treatment at a voltage of 10 to 50 V. Capacitors. 2. The method according to claim 1, wherein the lead wire terminal is formed by using an aqueous solution of an ammonium salt of adipic acid or phosphoric acid at 10 to 90 ° C.
The aluminum electrolytic capacitor according to claim 1, wherein the aluminum electrolytic capacitor has been subjected to a chemical conversion treatment at a temperature of: