JP2011077261A - Method of manufacturing lead terminal for capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a lead terminal for capacitor that contains no lead in which a whisker is prevented from being formed by relaxing residual stress in a weld zone that causes the whisker to be formed. <P>SOLUTION: The method of manufacturing the lead terminal T for capacitor in which one end of a metal wire 1 having a metal plating layer 2 made principally of tin and one end of an aluminum wire 5 are brought into contact with each other to weld the metal wire 1 and aluminum wire 5 together includes an induction heating process using an electromagnetic induction heating means 17 for the weld zone 10 between the metal wire 1 and aluminum wire 5. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a capacitor lead terminal constituted by arc welding a metal wire to an aluminum wire connected to a capacitor element.

  Conventionally, a lead terminal of an electronic component uses a copper-coated steel wire having a lead plating layer joined to an aluminum wire by arc welding. However, in copper-coated steel wires containing lead, lead is not only harmful to the human body, but also has a negative effect on the natural environment. In recent years, development of electronic components that do not use lead at all has been promoted from the viewpoint of environmental protection. ing. For example, like an aluminum electrolytic capacitor shown in Patent Document 1, a copper-coated steel wire plated with tin consisting of 100% tin is inserted into a recess provided at one end of an aluminum wire and joined by arc welding. In this aluminum electrolytic capacitor, an alloy layer of copper, tin, and aluminum produced by heating a copper-coated steel wire, tin plating, and an aluminum wire is formed at the joint between the copper-coated steel wire and the aluminum wire. ing.

  However, in lead wires that do not use lead, the alloy layer formed at the connection (welded part) between the aluminum wire and the tin-plated copper-coated steel wire contains a mixed layer of aluminum and tin. The presence of the layer may cause tin whiskers. This whisker may reach a length of 1 mm or more with respect to a diameter of 1 μm, and this whisker may cause a short circuit between terminals of an electronic component such as a capacitor.

  As a method for manufacturing a capacitor lead terminal capable of preventing the occurrence of this whisker, for example, as shown in Patent Documents 2 to 4, the lead terminal is washed with an alkaline cleaning solution, and then the lead terminal is heated and dried. There is something that was made.

JP 2000-124073 (page 3, FIG. 1) Japanese Unexamined Patent Publication No. 2000-277398 (2nd page, FIG. 2) JP 2007-67146 A (page 4, FIG. 2) Japanese Patent Laying-Open No. 2008-130782 (page 4, FIG. 2)

  The cause of whisker is considered to be that tin and aluminum used for metal plating are mixed during welding, and residual stress during welding is applied to tin, and whisker is generated due to this residual stress. In the method for manufacturing a lead terminal for a capacitor described in Patent Documents 2 to 4, whisker generation can be suppressed to some extent by alkali treatment applied to the surface of the welded portion of the lead terminal. The residual stress inside the welded portion cannot be removed, and whiskers may occur.

  The present invention has been made paying attention to such problems, and in the method of manufacturing a lead terminal for a capacitor that does not contain lead, the residual stress inside the weld which is the cause of whisker is alleviated to generate whisker. It is an object of the present invention to provide a method for manufacturing a capacitor lead terminal that can prevent the above-described problem.

In order to solve the above-described problem, a method of manufacturing a capacitor lead terminal according to the present invention includes:
In a method of manufacturing a lead terminal for a capacitor in which one end of a metal wire formed with a metal plating layer mainly composed of tin is brought into contact with one end of an aluminum wire, and the metal wire and the aluminum wire are welded.
An induction heating process using electromagnetic induction heating means is included for the welded portion between the metal wire and the aluminum wire.
According to this feature, once melted and solidified metal of the welded portion is softened, the residual stress of the welded portion, which is a cause of whisker, is relieved and solidified again, thereby preventing the occurrence of whiskers. In addition, by using the electromagnetic induction heating means, it is possible to perform local heat treatment in a short time, and in particular, to control the heating to the vicinity of the surface layer, so that it is possible to suppress the whisker from appearing from the vicinity of the surface layer. In addition, the electromagnetic induction heating means is heated to the vicinity of the surface layer of the welded portion, and it becomes possible to reduce the heat energy to the deep part of the welded portion that bears the welding strength between the metal wire and the aluminum wire, without impairing the welding strength. Moreover, parts other than the welded portion need not be heated, and a highly reliable lead terminal can be manufactured.

The manufacturing method of the lead terminal for a capacitor of the present invention is as follows.
The heat treatment temperature of the welded portion in the induction heating step is in a range of 40 to 180 degrees.
According to this feature, the heat treatment temperature within the range of 40 to 180 degrees is the most suitable temperature range for relaxing the residual stress inside the weld.

The manufacturing method of the lead terminal for a capacitor of the present invention is as follows.
The induction heating frequency used in the electromagnetic induction heating means is in the range of 100 to 400 KHz.
According to this feature, the frequency of induction heating within the range of 100 to 400 KHz is the most suitable frequency range for relaxing the residual stress inside the weld.

The manufacturing method of the lead terminal for a capacitor of the present invention is as follows.
Before the said induction heating process, the pre-process process which performs an alkali process using an alkaline solution with respect to the said welding part is characterized.
According to this feature, the generation of whiskers can be suppressed by modifying the surface of the welded portion by alkali treatment.

The manufacturing method of the lead terminal for a capacitor of the present invention is as follows.
After the induction heating step, it includes a post-treatment step of performing an alkali treatment on the weld using an alkaline solution.
According to this feature, it is possible to further suppress the generation of whiskers by modifying the surface of the welded portion by alkali treatment on the surface layer of the welded portion heated by the induction heating process.

(A) is a schematic sectional drawing which shows the state before welding of a metal wire and an aluminum wire, (b) is a schematic sectional drawing which shows the state at the time of welding of a metal wire and an aluminum wire, (c) is It is a schematic sectional drawing which shows the state after welding of a metal wire and an aluminum wire. It is a schematic sectional drawing which shows the state which performs an alkali treatment to a lead terminal. It is a schematic sectional drawing which shows the state which performs an induction heating process to a lead terminal.

  A mode for carrying out a method for manufacturing a capacitor lead terminal according to the present invention will be described below based on an example.

  The manufacturing method of the electrolytic capacitor according to the embodiment will be described with reference to FIGS. An electrolytic capacitor will be exemplified and described as the capacitor of this example. In this electrolytic capacitor, a capacitor element formed by winding or laminating a plurality of electrode foils made of aluminum via a separator is housed in a bottomed cylindrical outer case together with a driving electrolyte, and is formed in this outer case. The opening is sealed with a sealing body, and a lead terminal led from the capacitor element is passed through the sealing body and led out to the outside.

  As shown in FIG. 1C, the lead terminal T is composed of an aluminum wire 5 connected to the capacitor element and a metal wire 1 (CP wire) having a mild steel wire 4 as a core material. The metal wire 1 has a copper coating layer 3 in which a mild steel wire 4 is a core material and copper as a metal material is plated thick on the outer periphery thereof. Furthermore, the tin plating layer 2 which consists of 100% of tin as a metal material is formed in the outer periphery. The lead wire is not used at all for the material constituting the metal wire 1, and lead is not used at all for the material constituting the aluminum wire 5 or the capacitor element. Is a lead-free electronic component that does not contain lead and does not adversely affect the natural environment.

  In addition, the generation | occurrence | production site | part of the whisker which is the subject of this invention is the welding part 10 of the metal wire 1 and the aluminum wire 5, This mixes with the tin and aluminum used as metal plating at the time of welding, Residual stress during welding is added, and it is thought that whiskers are generated by this residual stress. In order to suppress the generation of this whisker, in the present invention, the lead terminal T is manufactured using a method of connecting an aluminum wire 5 and a metal wire 1 described later.

  Next, a method for connecting the aluminum wire 5 and the metal wire 1 when the metal wire 1 is manufactured will be described. First, the welding process which welds the metal wire 1 and the aluminum wire 5 is implemented. As shown in FIG. 1A, the aluminum wire 5 has a round bar portion 6 having a substantially cylindrical shape formed at one end thereof. This round bar portion 6 is connected to the metal wire 1 by the manufacturing method of the present invention. Further, a flat portion 7 having a substantially flat shape is formed at the other end of the aluminum wire 5 by pressing or the like. This flat portion 7 is connected to the electrode foil of the capacitor element. The end of the aluminum wire 5 and the tip of the metal wire 1 are arranged to face each other at a constant interval. In this case, an arc welding apparatus is connected to the metal wire 1 and the aluminum wire 5.

  Next, the metal wire 1 is moved in the direction of the aluminum wire 5, and the tip portion of the metal wire 1 is caused to collide with a predetermined position on the end surface of the aluminum wire 5 to be in contact with the end surface. In this state, when the welding apparatus is operated, a welding current flows between the metal wire 1 and the aluminum wire 5, and the contact point between the metal wire 1 and the aluminum wire 5, that is, the tip of the metal wire 1 and the aluminum wire. The arc welding current starts to flow between the end face of 5.

  When the leading end of the metal wire 1 is moved away from the end surface of the aluminum wire 5 and the interval is set between the two from the start of energization of the welding current, an arc is formed between the leading end portion of the metal wire 1 and the end surface of the aluminum wire 5. And both the opposing metal wire 1 and aluminum wire 5 are partially melted.

  In this state, when the metal wire 1 is moved to the end face side of the aluminum wire 5 to be brought into contact with and pressed further, fusion between the molten metals occurs, and the metal wire 1 and the end face of the aluminum wire 5 are welded. At this time, the molten metal becomes a hemispherical weld 10, and as shown in FIG. 1C, a lead terminal T in which the metal wire 1 and the aluminum wire 5 are integrated is formed. In this case, the welded portion 10 forms an alloy layer by fusing the metal constituting the metal wire 1 and the metal constituting the aluminum wire 5.

  Next, a pretreatment process for performing alkali treatment on the welded portion 10 of the lead terminal T using an alkaline solution is performed. As shown in FIG. 2, the portion from the metal wire 1 to the welded portion 10 in the lead terminal T is first immersed in the cleaning tank 15. The cleaning tank 15 is filled with a cleaning liquid 16 (alkaline solution) such as a non-etching weak alkali cleaner for aluminum and its alloys.

  The temperature of the cleaning liquid 16 is heated to about 90 to 99 degrees. The lead terminal T is cleaned with this cleaning liquid 16 for several minutes to degrease the aluminum wire 5 or the metal wire 1 and the aluminum wire 5 are welded. The carbon generated at the time is removed. Furthermore, it is possible to suppress the generation of whiskers by modifying the surface of the welded portion 10 of the lead terminal T. Then, the lead terminal T is taken out from the cleaning tank 15 after a predetermined time has elapsed. Thereafter, the lead terminal T is placed inside a drying device (not shown) and dried.

  Next, an induction heating process is performed in which the induction heating process is performed on the welded portion 10 of the lead terminal T using the magnetic force generating coil 17. In the induction heating treatment, the welded portion 10 between the metal wire 1 and the aluminum wire 5 is heated by a high-frequency induction heating device (electromagnetic induction heating means) using electromagnetic induction.

  The high frequency induction heating device generates an eddy current in the welded portion 10 using the magnetic force generating coil 17 wound so as to cover the outer periphery of the welded portion 10 of the lead terminal T, and is generated inside the welded portion 10 at that time. This weld 10 is heated using Joule heat. The heating temperature can be appropriately controlled by the power supplied to the magnetic force generating coil 17 and the conveying speed.

  As shown in FIG. 3, first, the welded portion 10 of the lead terminal T is arranged in the center of the magnetic force generating coil 17 having a cylindrical shape. Then, an alternating current having a current value of 200 A is passed through the magnetic force generating coil 17 and the frequency thereof is set to 250 KHz. In addition, it is preferable that the frequency of the alternating current sent through the coil 17 for magnetic force generation in the induction heating process is in the range of 100 to 400 KHz.

  Thus, the temperature of the welded portion 10 of the lead terminal T heated by the induction heating process is raised to about 60 degrees. The temperature of the welded portion 10 of the lead terminal T in the induction heat treatment is preferably in the range of 40 to 180 degrees.

  The metal of the welded portion 10 of the lead terminal T once melted and solidified by the induction heating process can be once softened to relieve the residual stress of the welded portion 10 that is the cause of whisker and solidify again.

  Then, after the induction heating step, a post-treatment step is performed in which an alkali treatment is performed again on the welded portion 10 of the lead terminal T using an alkaline solution. This post-processing step is the same as the above-described pre-processing step (see FIG. 2), but the welded portion 10 of the lead terminal T is heated by the above-described induction heating treatment, and when this is heated, welding is performed. The tin in the vicinity of the surface layer of the part 10 is heated, and a tin pool is formed in the vicinity of the surface of the welded part 10. Since this tin reservoir can also cause whisker generation, the alkali treatment is performed again to remove the tin reservoir and further modify the surface to suppress whisker generation from the welded portion 10 of the lead terminal T.

  As described above, in this embodiment, one end of the metal wire 1 on which the tin plating layer 2 is formed and one end of the aluminum wire 5 are brought into contact with each other, and the lead terminal T for a capacitor for welding the metal wire 1 and the aluminum wire 5 is manufactured. The method includes an induction heating process in which an induction heating process is performed on the welded portion 10 between the metal wire 1 and the aluminum wire 5 using a high-frequency induction heating device (electromagnetic induction heating means), so that it is once melted and solidified. By temporarily softening the metal of the welded portion 10 to relieve the residual stress of the welded portion 10 which is the cause of whisker generation and solidifying it again, it is possible to prevent the generation of whiskers and by using a high frequency induction heating device Since the local heat treatment can be performed in a short time and the heating especially in the vicinity of the surface layer can be controlled, the expression of whiskers from the vicinity of the surface layer can be suppressed. In addition, the electromagnetic induction heating means is heated to the vicinity of the surface layer of the welded portion 10, and it becomes possible to reduce the heat energy to the deep portion of the welded portion 10 that bears the welding strength between the metal wire 1 and the aluminum wire 5, and the welding strength In addition, the parts other than the welded portion 10 are not heated and the lead terminal with high reliability can be manufactured.

  In addition, the heat treatment temperature of the welded portion 10 in the induction heating process is within a range of 40 to 180 degrees, and the heat treatment temperature within the range of 40 to 180 degrees relieves residual stress inside the welded portion 10. Is the most suitable temperature range.

  The induction heating frequency used in the high frequency induction heating device (electromagnetic induction heating means) is in the range of 100 to 400 KHz, and the induction heating frequency in the range of 100 to 400 KHz is within the welded part 10. This is the most suitable frequency range for relieving residual stress.

  In addition, by including a pretreatment step of performing an alkali treatment on the welded portion 10 using a cleaning liquid 16 (alkaline solution) before the induction heating step, the surface of the welded portion 10 is modified by the alkali treatment, so Occurrence can be suppressed.

  In addition, after the induction heating step, a whisker is generated by modifying the surface of the welded portion 10 by the alkali treatment by including a post-treatment step of performing an alkali treatment on the welded portion 10 using the cleaning liquid 16 (alkaline solution). Can be suppressed.

  Although the embodiments of the present invention have been described with reference to the drawings, the specific configuration is not limited to these embodiments, and modifications and additions within the scope of the present invention are included in the present invention. It is.

  For example, in the above-described embodiment, the pretreatment step is performed before the induction heating step to perform the alkali treatment on the welded portion 10, and the induction treatment step is followed by the posttreatment step to perform the alkali treatment on the welded portion 10 again. However, it is not necessary to provide both of these alkali treatments, and any one of the alkali treatments in the post-treatment step of the pre-treatment step is sufficient.

  Moreover, in the said Example, although the welding part 10 is immersed in the washing tank 15 filled with the washing | cleaning liquid 16 in the pre-processing process and post-processing process which perform the alkali treatment to the welding part 10, a washing | cleaning liquid is added to the welding part 10. You may make it perform an alkali treatment by apply | coating 16. As shown in FIG.

  Moreover, in the said Example, although arc welding was illustrated as a welding method which welds the metal wire 1 and the aluminum wire 5, not only this but other welding methods, such as heating welding, ultrasonic welding, and resistance welding, are used. The metal wire 1 and the aluminum wire 5 may be welded together.

1 Metal wire 2 Tin plating layer (metal plating layer)
3 Copper coating layer 4 Steel wire 5 Aluminum wire 6 Round bar part 7 Flat part 8 Cutter 10 Welding part 15 Cleaning tank 16 Cleaning liquid (alkaline solution)
17 Coil for generating magnetic force (electromagnetic induction heating means)

Claims (5)

In a method of manufacturing a lead terminal for a capacitor in which one end of a metal wire formed with a metal plating layer mainly composed of tin is brought into contact with one end of an aluminum wire, and the metal wire and the aluminum wire are welded.
A method for producing a lead terminal for a capacitor, comprising an induction heating step using electromagnetic induction heating means for a welded portion between the metal wire and the aluminum wire.   2. The method of manufacturing a capacitor lead terminal according to claim 1, wherein a heat treatment temperature of the welded portion in the induction heating step is in a range of 40 to 180 degrees.   The method of manufacturing a capacitor lead terminal according to claim 1 or 2, wherein the frequency of induction heating used in the electromagnetic induction heating means is in a range of 100 to 400 KHz.   The method for manufacturing a lead terminal for a capacitor according to any one of claims 1 to 3, further comprising a pretreatment step of performing an alkali treatment on the welded portion using an alkaline solution before the induction heating step. .   5. The method of manufacturing a lead terminal for a capacitor according to claim 1, further comprising a post-processing step of performing an alkali treatment on the welded portion using an alkaline solution after the induction heating step.

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