JP2010153712A - Aluminum electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum electrolytic capacitor capable of reliably preventing short-circuiting accidents, or the like by preventing whiskers from falling outside the capacitor. <P>SOLUTION: At least two annularly adhering seal rings 51, 52 are provided along the outer periphery of a lead wire 22 from the inner peripheral surface of a terminal insertion hole 5 partially formed in sealing rubber 4. Pockets 53, 54 for storing a whisker 23a are formed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an aluminum electrolytic capacitor, and more particularly, to an aluminum electrolytic capacitor that prevents a whisker generated at a welded portion of a lead terminal from dropping.

  In an aluminum electrolytic capacitor, a lead terminal is attached to an anode foil and a cathode foil made of an aluminum material constituting a capacitor element, and the lead terminal passes through a sealing body that seals an opening of an exterior case to the outside. It is designed to be pulled out.

  Usually, the lead terminal is a tab terminal that has a flat portion that is crushed in the shape of a wing plate at one end of an aluminum bar and the other end is a round bar, but can be soldered to the circuit board. Therefore, a copper-coated steel wire (CP wire) plated with Sn as a lead wire is welded to the round bar portion of the tab terminal.

  Due to environmental problems, the lead layer of lead wires has been made lead-free and Sn plating has been used. It is known that whiskers are generated on the surface of Sn that does not contain lead, and in particular, it is known that whiskers are generated abruptly in welds in which dissimilar metals such as aluminum and iron are mixed.

  Since the Sn whisker is brittle and easily peels off due to impact or the like, it may come out of the capacitor through the gap of the terminal insertion hole of the sealing body and fall on the circuit board. Therefore, in an aluminum electrolytic capacitor, it is a problem to prevent a short circuit from occurring in a circuit derived from Sn whisker that is generated with lead-free lead wires.

  However, the terminal insertion hole described in Patent Document 1 has the following problems. That is, when the lead wire of the aluminum electrolytic capacitor is inserted into the through hole of the circuit board, the CP wire may be forcibly bent due to, for example, misalignment.

  As a result, a gap is formed between the terminal insertion hole and the lead wire, and the whisker may drop onto the circuit board from the gap. Therefore, as one method for solving such a problem, in Patent Document 2, a boot for preventing whisker dropping is integrally formed on the outlet side of the terminal insertion hole.

  According to this, since the tip of the boot moves following the movement of the CP line, even if the CP line is bent, a gap is hardly generated between the boot and the CP line. However, the boot described in Patent Document 2 protrudes in a funnel shape (funnel shape) from the outlet of the terminal insertion hole, and the welded portion is disposed along the inner peripheral surface thereof. In addition to being easily rubbed off by the peripheral surface, there was a risk that it would rub and become finer and fall off.

JP 2006-295055 A Japanese Patent Laid-Open No. 2008-251982

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to prevent aluminum whisker from dropping out of a capacitor and to prevent short circuit accidents and the like more reliably. It is to provide a capacitor.

In order to achieve the above-described object, the present invention has several features described below. The invention according to claim 1 is attached to a capacitor element having a pair of lead terminals attached thereto, a bottomed cylindrical outer case in which the capacitor element is housed together with a predetermined electrolytic substance, and an opening of the outer case. A lead rubber which is electrically connected to the capacitor element and is welded to the tip of the tab terminal. In an aluminum electrolytic capacitor having a lead wire, and the lead lead wire is drawn out of the outer case through the terminal insertion hole,
The terminal insertion hole includes a round bar insertion hole through which the round bar portion of the lead terminal is inserted, and a lead wire insertion hole through which the lead wire is inserted coaxially with the round bar insertion hole. The sealing rubber is provided with at least two seal rings that are in close contact with each other in an annular shape along the outer peripheral surface of the lead wire with a predetermined distance along the axial direction of the lead wire. It is said.

  According to a second aspect of the present invention, in the first aspect, a pocket for receiving a whisker generated in the welded portion is formed between the seal rings.

  According to a third aspect of the present invention, in the first or second aspect, a pocket for receiving the whisker is formed in the round bar insertion hole.

  According to a fourth aspect of the present invention, in the first, second, or third aspect, the pocket is formed in a mortar shape having a gradually decreasing diameter along the insertion direction of the lead terminal.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the leading end of the lead wire is hemispherical or chamfered so as to have a corner.

  According to the present invention, the sealing rubber is provided with at least two seal rings that are annularly adhered along the outer peripheral surface of the lead wire, and the pocket is provided between the adjacent seal rings. The whisker can be securely stored by preventing the whisker from falling with the seal ring closely contacting with the whisker and even if the whisker falls through the seal ring and falls.

  Next, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto. FIG. 1 is a cross-sectional view of an aluminum electrolytic capacitor according to an embodiment of the present invention, FIG. 2 is a partially enlarged view of a lead terminal and a sealing body, and FIG. 3 is a schematic view showing a state where the lead terminal is bent. is there. FIG. 4 is a partially enlarged view of the leading end portion of the lead wire.

  As shown in FIGS. 1 and 2, the aluminum electrolytic capacitor includes a capacitor element 1 having a pair of lead terminals 2 and 2. The capacitor element 1 is formed by winding an anode foil and a cathode foil made of an aluminum material in a spiral shape via a separator paper (both not shown).

  The capacitor element 1 is accommodated in a cylindrical outer case 3 with a predetermined electrolytic substance, and the opening of the electrical case 3 is sealed with a sealing rubber 4 (sealing body). The sealing rubber 4 is provided with terminal insertion holes 5 and 5, and the leading ends of the lead terminals 2 and 2 are drawn out through the terminal insertion holes 5 and 5.

  In this example, the hole diameter of the terminal insertion holes 5 and 5 is 20 to 99.9% of the diameter of the round bar portion 5b of the lead terminals 2 and 2, but the hole diameter is preferably 75% or less, more preferably It is preferable that the hole diameter is 40% or less and the whisker 23a is tightly fitted so as not to leak.

  The sealing rubber 4 is housed in the outer case 3 together with the capacitor element 1 in the state of being attached to the lead terminals 2 and 2, and the lateral throttle groove 3 a of the outer case 3 and the edge of the outer case 3 are formed. It is airtightly fixed in the opening of the outer case 3 by caulking 3b.

  The exterior case 3 may be a commonly used aluminum case. For the sealing rubber 4, butyl rubber or the like may be used. The materials of the outer case 3 and the sealing rubber 4 may be arbitrarily set according to specifications. Further, as the electrolytic substance, a solid electrolyte other than the aqueous or organic liquid electrolyte may be usually used, but not limited thereto.

  Each of the lead terminals 2 and 2 has the same shape, and includes a tab terminal 21 electrically connected to the capacitor element 1 and a lead wire 22 welded integrally to the tip of the tab terminal 21. .

  The tab terminal 21 is made of an aluminum material, and includes a flat portion 21a that is formed by pressing a part of a round bar into a battledore shape, and an unprocessed round bar 21b. The tab terminal 21 has a flat portion 21a attached to the anode foil and the cathode foil of the capacitor element 1 by caulking or the like.

  A copper-coated steel wire (CP wire) whose surface is Sn-plated is used for the lead lead wire 22. The lead lead wire 22 is provided with a Sn (tin) plating layer on the surface in order to improve solderability to the circuit board. The plating layer is generally made of Sn 100%, but other alloy elements and additives may be added as long as they are basically lead-free.

  The lead lead wire 22 has a smaller diameter than the round bar portion of the tab terminal 21 and is integrally fixed to the end portion of the round bar portion by welding (welded portion 23). In the lead terminal 2, the plated layer is stable in the tab terminal 21 and the lead lead wire 22, but in the welded portion 23, since different types of metals such as aluminum and iron are mixed, when exposed to the outside air, Stress acts on the Sn layer by hydration or oxidation reaction, and a large number of whiskers 23a are formed in a beard shape.

  As shown in FIG. 4, the leading end 22 a of the lead lead wire 22 is chamfered in a hemispherical shape when the lead lead wire 22 is inserted through at least the sealing rubber 4. A method for chamfering the leading end 22a of the lead wire 22 may be arbitrarily selected according to specifications such as cutting and pressing. Further, the leading end of the lead wire 22 may be chamfered so as to drop the corner.

  By chamfering the leading end 22a of the lead lead wire 22, when the lead lead wire 22 is inserted into the terminal insertion hole 5, the lead lead wire 22 is reliably guided to the outlet without damaging the inner surface of the terminal insertion hole 5. be able to. Furthermore, the guidance to the through hole of the circuit board can be made smoothly. The tip 22a only needs to be chamfered at least at the corners, but it is preferable to form the entire tip 22a in a hemispherical shape for smoother guidance. It is optional to cut the distal end portion 22a after the lead wire 22 is inserted into the sealing rubber 4.

  For reference, the yield of 10,000 capacitors using the lead wire 22 with the tip 22a chamfered in a hemispherical shape was 99.98% (17 out of 10,000 capacitors were poorly inserted), whereas the yield was 99.98%. The yield of 10,000 non-capacitors was 72.4% (2757 out of 10,000 insertion failures).

  If the whisker 23a falls on a substrate (not shown), there is a risk of a short circuit. Therefore, in the present invention, the terminal insertion holes 5 and 5 formed in the sealing rubber 4 are configured as follows, as shown in FIG. Since the terminal insertion holes 5 and 5 have the same shape, only one of them will be described below.

  That is, the terminal insertion hole 5 includes a round bar insertion hole 5a into which the round bar portion 21b of the tab terminal 21 is inserted and a lead wire insertion hole 5b into which the lead lead wire 22 is inserted. 5b is arrange | positioned so that it may communicate coaxially with the one end side of the round bar insertion hole 5a.

  The round bar insertion hole 5a may be a hole having the same diameter or a slightly smaller diameter than the round bar portion 21a. On the other hand, the lead wire insertion hole 5 b is formed to have a smaller diameter than the round bar insertion hole 5 a and a smaller diameter than the outer diameter of the lead wire 22.

  Between the round bar insertion hole 5a and the lead wire insertion hole 5b, a so-called mortar taper-shaped first pocket 53 is formed in which the inner diameter gradually decreases from the round bar insertion hole 5a toward the lead wire insertion hole 5b. Yes. The whisker 23 a is stored in the first pocket 53.

  A part of the sealing rubber 4 is provided with at least two seal rings 51 and 52 which are in close contact with each other in an annular shape along the outer periphery of the lead wire 22. Each seal ring 51, 52 is integrally formed on the lower end side of the round bar insertion hole 5a, and the lead wire insertion hole 5a is formed coaxially at the center of each.

  One seal ring 51 (hereinafter referred to as the first seal ring 51) is arranged in the middle of the terminal insertion hole 5 at a predetermined interval from the welded portion 23, and the lead wire 22 extends from the inner peripheral surface of the terminal insertion hole 5. It is formed in a mortar shape toward the outer peripheral surface.

  Between the first seal ring 51 and the welded portion 23, a first pocket 53 in which the whisker 23a generated by the welded portion 23 is stored is formed.

  The other seal ring 52 (hereinafter referred to as the second seal ring 52) is disposed at the opening end of the terminal insertion hole 5, and, similar to the first seal ring 51, leads from the inner peripheral surface of the terminal insertion hole 5. It is formed in a mortar shape toward the outer peripheral surface of 22.

  Between the 1st seal ring 51 and the 2nd seal ring 52, the 2nd pocket 54 which receives the whisker 23a which slipped through the 1st pocket 53 and was falling is provided.

  According to this, as shown in FIG. 3, even if the lead lead wire 22 is bent, the first seal ring 51 and the second seal ring 52 follow the surface of the lead lead wire 22 independently. Due to the deformation, the formation of the gap can be made as small as possible.

  Furthermore, even if the whisker 23a falls, the whisker 23a is first received by the first pocket 53, and even if it falls through the first seal ring 51 and is dropped by the second pocket 54, a double short circuit is caused. Can be prevented.

  In this example, two seal rings 51 and 52 are provided inside the terminal insertion hole 5, but more seal rings may be provided in order to further increase safety. Further, the installation position may be provided not only inside the terminal insertion hole 5 but also independently at the outlet of the terminal insertion hole 5. Furthermore, the seal rings 51 and 52 are both formed in a mortar shape (conical shape), but may have other weight shapes or a combination of different weight shapes.

  In this embodiment, the terminal insertion hole 5 has been described by taking an aluminum electrolytic capacitor as an example, but the present invention is not limited to this and can be applied to a similar structure product.

Sectional drawing of the aluminum electrolytic capacitor which concerns on one Embodiment of this invention. The partial enlarged view of a lead terminal and a sealing body. The schematic diagram which shows the state by which the lead terminal was bent. The elements on larger scale of the front-end | tip part of an extraction lead wire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Lead terminal 21 Tab terminal 22 Lead-out lead wire 23 Welding part 23a Whisker 3 Exterior case 4 Sealing rubber (sealing body)
5 Terminal insertion hole 51 First seal ring 52 Second seal ring 53 First pocket 54 Second pocket

Claims (5)

A capacitor element having a pair of lead terminals attached thereto, a bottomed cylindrical outer case in which the capacitor element is accommodated together with a predetermined electrolytic substance, and a terminal insertion for the lead terminal that is attached to the opening of the outer case A lead terminal electrically connected to the capacitor element and having a tab terminal made of an aluminum material and a lead wire to be welded to the tip of the tab terminal; In the aluminum electrolytic capacitor in which the lead wire is drawn out of the outer case through the terminal insertion hole,
The terminal insertion hole includes a round bar insertion hole through which the round bar portion of the lead terminal is inserted, and a lead wire insertion hole through which the lead wire is inserted coaxially with the round bar insertion hole. The sealing rubber is provided with at least two seal rings that are in close contact with each other in an annular shape along the outer peripheral surface of the lead wire with a predetermined distance along the axial direction of the lead wire. Aluminum electrolytic capacitor.   The aluminum electrolytic capacitor according to claim 1, wherein a pocket for receiving a whisker generated at the weld is formed between the seal rings.   The aluminum electrolytic capacitor according to claim 1 or 2, wherein a pocket for receiving the whisker is formed in the round bar insertion hole.   4. The aluminum electrolytic capacitor according to claim 1, wherein the pocket is formed in a mortar shape whose diameter gradually decreases along the insertion direction of the lead terminal. 5.   5. The aluminum electrolytic capacitor according to claim 1, wherein the leading end of the lead wire is hemispherical or chamfered to have a corner.

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