JP2008235322A - Aluminum electrolytic capacitor and manufacturing method of lead wire for aluminum electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum electrolytic capacitor assuring excellent reliability by preventing the generation of a tin whisker from a junction area of a lead wire. <P>SOLUTION: The aluminum electrolytic capacitor is formed of a capacitor element 1 in which a core material member 7 from which a part of the tin plating layer 8 is removed by a grinding method is formed at the tin plating wire 4 with the tin plating layer 8 formed at a core material 6 and a lead wire 3 joining the core material member 7 and an aluminum tab is connected to an electrode foil 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an aluminum electrolytic capacitor using a lead wire obtained by joining a tin-plated wire and an aluminum tab, and a method for manufacturing the lead wire.

  Aluminum electrolytic capacitors used in electronic devices are required to have improved reliability as the quality and reliability of electronic devices increase.

  In conventional aluminum electrolytic capacitors, a lead wire is connected to an anode foil and a cathode foil each made of aluminum, a separator is sandwiched between the anode foil and the cathode foil, and a pair of lead wires is unidirectionally wound. This is a derived capacitor element.

  4 is a perspective view of a conventional lead wire for an aluminum electrolytic capacitor. As shown in FIG. 4, the lead wire is formed by cutting a tin-plated steel cored copper wire 24 made of tin or a tin alloy into a predetermined length. It is joined to the aluminum tab 25 by welding.

  Further, the bottomed cylindrical metal case accommodates the capacitor element and the electrolyte, and the opening of the case is provided with a sealing body having a through hole through which a pair of lead wires are inserted. The sealing body seals the opening end. It has stopped.

As such a conventional technique, for example, one described in Patent Document 1 is known.
JP 2000-12386 A

  In such a conventional aluminum electrolytic capacitor, tin, aluminum, and copper are mixedly present at the joint portion 29 between the tin-plated steel cored copper wire 24 and the aluminum tab 25, and as shown in FIG. In some cases, needle-shaped tin whiskers 26 are generated from the surface of the joint portion 29, and there is a problem that the reliability of the aluminum electrolytic capacitor and the circuit board deteriorates due to the tin whiskers 26.

  An object of the present invention is to solve the above-described conventional problems and to provide an aluminum electrolytic capacitor having excellent reliability by preventing the occurrence of tin whiskers.

  In order to achieve the above object, the present invention has a capacitor element in which a lead wire obtained by joining a tin-plated wire in which a tin-plated layer is formed on a core material and an aluminum tab is connected to an electrode foil, An aluminum electrolytic capacitor is provided in which a core material portion where the core material is exposed is provided on a part of the tin-plated wire, and a part of the core material portion is bonded to the aluminum tab.

  According to the present invention, since there is no tin in the joint between the tin-plated steel wire and the aluminum tab, it is possible to prevent the generation of tin whiskers and to produce an excellent reliability aluminum electrolytic capacitor. It is.

(Embodiment)
First, the aluminum electrolytic capacitor of the present invention will be described.

  FIG. 1 is a cross-sectional view showing the configuration of the aluminum electrolytic capacitor of the present invention.

  FIG. 2 is a cross-sectional view showing a method of manufacturing a lead wire for an aluminum electrolytic capacitor according to the present invention. FIG. 2 (a) shows a state before joining a tin-plated wire and an aluminum tab, and FIG. Shown later.

  As shown in FIG. 1, the lead wire 3 of the aluminum electrolytic capacitor of the present invention is provided with a joint portion 9 in which an end portion of a tin-plated wire 4 and an end portion of an aluminum tab 5 of a round bar are joined by arc welding or the like. It is.

  The aluminum tab 5 side of the lead wire 3 is joined to the anode foil and cathode foil 2 made of aluminum by ultrasonic welding or pressure welding, respectively. Further, a capacitor element 1 in which a pair of lead wires 3 is led out by winding an anode foil and a cathode foil with a separator interposed therebetween.

  Further, the capacitor element 1 is housed in a bottomed cylindrical outer case 15 made of aluminum together with an electrolyte (not shown) such as a driving electrolyte or a solid electrolyte made of a conductive polymer, and is placed in a through hole of the elastic sealing body 16. The pair of lead wires 3 is inserted, and the open end of the outer case 15 is sealed by the sealing body 16 to obtain an aluminum electrolytic capacitor.

  As shown in FIG. 2A, the tin-plated wire 4 of the lead wire 3 has a steel core-containing copper wire in which a copper layer 6b is formed on a steel core 6a as a core material 6, and tin or tin is formed on the core material 6. What formed the tin plating layer 8 which consists of an alloy can be used, or what formed the tin plating layer 8 using the core material 6 which consists of copper or a copper alloy instead of the core material 6 of a copper wire containing a steel core But you can.

  The core material portion 7 is one in which the core material 6 not provided with the tin plating layer 8 is exposed at the end portion of the tin plating wire 4, and the joint portion 9 of the lead wire 3 is part of the core material portion 7 and the aluminum tab 5. Are joined and aluminum and copper are mixed without containing tin.

  Further, a part of the core material portion 7 is exposed from the joint portion 9 of the lead wire 3, whereby the tin plating layer 8 of the lead wire 3 is melted and joined when the tin plating wire 4 and the aluminum tab 5 are joined. This prevents it from flowing into the section 9.

  Next, the manufacturing method of the lead wire of this invention is demonstrated using FIG.

  First, the tin plating wire 4 is arranged in a straight line, and a part of the tin plating layer 8 is removed along the outer periphery of the tin plating wire 4 so as to leave the steel core 6a and the copper layer 6b by grinding. The core part 7 exposed in a belt shape was formed on the periphery. Thus, the thickness of the core part 7 can be made uniform by grinding and removing the tin plating layer 8 in the middle of the linear tin plating wire 4.

  The grinding process may be a method of cutting using a cutting tool or a method of grinding using a grindstone or the like. Further, as the grinding process, a method of removing the tin plating layer 8 by spraying particles of a crushed resin or mineral may be used, and the once removed tin plating layer 8 can be prevented from reattaching.

  Next, a part of the core part 7 exposed in a band shape was cut, and the core part 7 was provided at one end of the tin-plated wire 4 as shown in FIG.

  Further, as shown in FIG. 2B, the end of the core member 7 of the tin-plated wire 4 and the end of the aluminum tab 5 were brought into contact with each other, and the tin-plated wire 4 and the aluminum tab 5 were joined by arc welding.

  Further, the core member 7 and the aluminum tab 5 are joined by drilling a hole in the end face of the aluminum tab 5, inserting the core member 7 into the hole and heating with a gas burner to join the core member 7 to the aluminum tab 5. May be.

  In addition, the process of forming the core part 7 by grinding is not limited to this.

  As described above, since tin is not mixed in the joint portion 9 between the tin-plated wire 4 and the aluminum tab 5, it is possible to prevent the occurrence of tin whiskers.

  Another embodiment of the present invention will be described.

  FIG. 3 is a cross-sectional view of another lead wire for an aluminum electrolytic capacitor according to the present invention. The same components as those in the embodiment shown in FIG.

  As shown in FIG. 3, a water-repellent resin layer 10 in which a surface of a core part 7 partially exposed from a joint part 9 between a tin-plated wire 4 and an aluminum tab 5 is coated with a resin such as a silicon resin or a fluororesin. As a result, the water resistance of the core portion 7 can be improved. Further, a water repellent resin layer 10 may be provided on the surface of the joint portion 9 between the tin plating wire 4 and the aluminum tab 5.

  The tin plating layer 8 may be removed by chemical or electrochemical dissolution using a solution such as hydrogen fluoride instead of grinding.

  Next, examples of the present invention will be described.

(Example)
The lead wire of the example has a tin-plated steel cored copper wire with a diameter of 0.6 mm, in which a tin plating layer with a thickness of 10 μm to 15 μm is formed by electroplating on a copper layer with a thickness of 20 μm to 30 μm, and an aluminum purity of 99.99. % And an aluminum tab having a diameter of 1.2 mm.

  After rotating the cutting blade on the outer periphery of the tin-plated steel cored copper wire arranged in a straight line, leaving the copper layer and removing the tin plating layer to form the core material part, cutting a part of the core material part, A core material part having a length of 1.0 mm was provided at the end of the tin-plated steel cored copper wire. Furthermore, the core material part and the aluminum tab were joined by arc welding to produce a lead wire in which the core material part having a length of 0.2 mm to 0.5 mm was exposed from the joint part between the core material part and the aluminum tab.

(Comparative example)
In the comparative example, in place of the tin-plated steel cored copper wire provided with the core part on the outer periphery of the example, a tin-plated steel cored copper wire cut without forming the core part on the outer periphery was used. Produced lead wires in the same manner as in Example.

  Next, 100 of each of the lead wires of the example and the conventional example are extracted, and after a 4000 hour standing test under a high temperature and high humidity environment of 60 ° C. and 90% RH, the presence or absence of tin whisker generation is checked with an optical microscope with a magnification of 50 times. Observed.

  As a result, tin whisker was not generated in the example and was zero, but in the comparative example, it was generated with five. Furthermore, as a result of observing the joint part of the lead wire of an Example with an electron microscope of 200 times magnification, there was no tin whisker.

  As described above, the present invention has an effect of preventing the occurrence of tin whiskers, and is particularly useful for an aluminum electrolytic capacitor that requires high reliability.

Sectional view of the aluminum electrolytic capacitor of the present invention Sectional drawing which shows the manufacturing method of the lead wire for aluminum electrolytic capacitors of this invention Sectional drawing of the lead wire for other aluminum electrolytic capacitors of this invention A perspective view of a conventional lead wire for an aluminum electrolytic capacitor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Electrode foil 3 Lead wire 4 Tin plating wire 5 Aluminum tab 6 Core material 6a Steel core 6b Copper layer 7 Core material part 8 Tin plating layer 9 Joining part 10 Water-repellent resin layer 15 Exterior case 16 Sealing body

Claims (4)

A capacitor element in which a lead wire in which a tin-plated wire having a tin-plated layer formed on a core material and an aluminum tab are joined is connected to an electrode foil; and the lead wire has the core material in a part of the tin-plated wire. An aluminum electrolytic capacitor in which an exposed core part is provided and a part of the core part is joined to the aluminum tab. The aluminum electrolytic capacitor according to claim 1, wherein a water-repellent resin layer is provided on a surface of the core member exposed from a joint between the tin-plated wire and the aluminum tab. A lead wire for an aluminum electrolytic capacitor in which a core material portion from which a part of the tin plating layer is removed is formed on a tin plating wire having a tin plating layer formed on the core material, and a part of the core material portion and an aluminum tab are joined. Manufacturing method. The method for manufacturing a lead wire for an aluminum electrolytic capacitor according to claim 3, wherein the tin plating layer is removed by grinding.

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