JP2015225999A - Solder joint structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solder joint structure which allows for highly reliable connection, without using a special solder for aluminum, even when an aluminum plate is used as an electrode plate.SOLUTION: In a solder joint structure for solder joining one end of a lead wire 2 to a metallicon electrode 1a of a capacitor element 1, and solder joining the other end of the lead wire 2 to an electrode plate 4, the electrode plate 4 is an aluminum plate 4b subjected to Ni plating or Sn plating to at least one of the front surface or back surface. While inserting the other end of the lead wire 2 into a through hole 4c provided in the electrode plate 4, solder joining is performed by straddling the solder 3 across the outer peripheral surface of the lead wire 2 and the front or back surface of the electrode plate 4, without bringing into contact with a hole wall surface 4d constituting the through hole 4c.

Description

  The present invention relates to a solder connection structure between a lead wire and an electrode plate.

  When the electrode plate is connected to the metallicon electrode of the capacitor element, for example, as disclosed in Patent Document 1, a soldering protrusion is extended from the electrode plate, and the protrusion and the metallicon electrode portion are directly connected by soldering. That is generally done. Further, as shown in FIG. 5, the electrode plate 4 is disposed along the side surface of the capacitor element 1, and the metallicon electrode 1 a and the protrusion 5 of the electrode plate 4 are connected by the solder 3 conventionally. Yes.

JP 2004-349447 A

  By the way, an aluminum plate may be used as the electrode plate. This is because weight reduction and cost reduction can be achieved as compared with a copper plate generally used as an electrode plate. However, since aluminum (AL) is inferior in solder wettability, when soldered, the surface is often plated with nickel (Ni) or tin (Sn) to improve solderability. .

  However, since the electrode plate is usually formed by punching or cutting, the aluminum substrate is exposed from the processed cross section even if the plating process is performed, and an attempt is made to solder-connect the protrusion and the metallicon electrode. Even difficult to connect well. Specifically, in order to achieve a reliable connection with solder, it is necessary to wrap the protrusions with solder, but the aluminum substrate is inferior in solder wettability from both sides of the protrusions by punching or cutting. 6, the melted solder 3 is positioned so as to avoid both side surfaces 5 a and 5 a as shown in FIG. 6, and it is difficult to wrap the protrusion 5 with the solder 3.

  Even if the protrusions can be encapsulated by the solder, if the aluminum contacts the solder (becomes wet with the solder), there is a possibility that electrolytic corrosion due to a potential difference occurs at the contact portion. In particular, when Sn-Ag-Cu (tin-silver-copper) solder is used as the solder, the electrode potential of tin is -0.14 V, the electrode potential of silver is 0.8 V, and the electrode potential of copper is 0.1. In contrast to 34 V, the electrode potential of aluminum is −1.68 V. Therefore, a potential difference of 2.48 V at the maximum occurs at the contact portion between the aluminum substrate and the solder. It will not reach.

  Therefore, it is conceivable to connect the metallicon electrode and the electrode plate via a lead wire instead of directly connecting the metallicon electrode and the electrode plate. As shown in FIG. 7, the lead wire 2 can be firmly wrapped by the solder 3 as shown in FIG. Highly reliable connection is possible.

However, the connection with the above-mentioned lead line must be separately connected with the lead line and the electrode plate. At this time, it is conceivable to make a solder connection in the same manner as the connection between the metallicon electrode and the lead wire. If the cutting process is performed, the aluminum substrate is eventually exposed, and the above problem cannot be solved.

  If a special solder for aluminum is used, solder connection is possible even when the aluminum substrate is exposed. However, since the solder itself is expensive, the cost increases, and aluminum is used as the electrode plate. The advantage of using a plate is reduced.

  Therefore, the present invention has been made to solve the above-described problem, and even when an aluminum plate is used as an electrode plate, a highly reliable connection is possible without using a special solder for aluminum. The purpose is to provide a solder connection structure.

  In order to solve the above problems, the solder connection structure of the present invention solders one end portion of the lead wire 2 to the metallicon electrode 1 a of the capacitor element 1 and solders the other end portion of the lead wire 2 to the electrode plate 4. In the solder connection structure to be connected, the electrode plate 4 is an aluminum plate 4b having Ni plating or Sn plating applied to at least one of its front and back surfaces, and the through hole 4c provided in the electrode plate 4 has the above described In a state where the other end portion of the lead wire 2 is inserted, the outer surface of the lead wire 2 and the surface or back surface of the electrode plate 4 are not brought into contact with the solder wall 3d of the hole wall surface 4d constituting the through hole 4c. It is characterized in that it is soldered by straddling the plating surface. Further, the aluminum substrate may be exposed from the hole wall surface 4d.

  In the solder connection structure of the present invention, in the state where the other end of the lead wire is inserted into the through hole provided in the electrode plate, the outer peripheral surface of the lead wire and the electrode plate are not brought into contact with the hole wall surface constituting the through hole. Since the solder connection is made by straddling the solder on the front or back plating surface, even if an aluminum plate is used as the electrode plate, a highly reliable connection is possible. Further, if the aluminum base is exposed from the hole wall surface, the contact between the solder and the aluminum can be naturally suppressed. In addition, the contact in the above does not include a case where the solder that is repelled by the aluminum base and becomes substantially spherical has a point contact with the aluminum base, and the aluminum base is wetted by the solder (adhered to the solder). Refers to that.

1 is a perspective view showing a solder connection structure according to an embodiment of the present invention. It is sectional drawing which shows the connection state of an electrode plate and a leader line. It is a result of a moisture resistance test, (a) is a capacity | capacitance change rate of a capacitor | condenser, (b) is a graph which shows ESR change. It is a graph which shows the result of a thermal shock test. It is a perspective view which shows the connection state of the conventional capacitor | condenser element and an electrode plate. It is sectional drawing which shows the connection state of the capacitor | condenser element and electrode plate at the time of using an aluminum plate as an electrode plate. It is sectional drawing which shows the connection state of a capacitor | condenser element and a leader line.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings. 1 and 2 show a connection state between the capacitor element 1 and the electrode plate 4 using the solder connection structure of the present invention.

In the figure, reference numeral 1 denotes a capacitor element. The capacitor element 1 is a film capacitor formed by, for example, winding a metallized film in which a metal is vapor-deposited on an insulating film, and a metallicon electrode 1a formed by thermally spraying the metal is formed at an end in the axial direction. Has been. And
One end of the lead wire 2 is connected to the metallicon electrode 1a by solder 3 as shown in FIG. The lead wire 2 is a copper wire or an aluminum wire 2b having a circular cross section whose outer peripheral surface is plated (Ni plating or Sn plating) 2a. However, a CP wire or the like may be used.

  4 is an electrode plate. The electrode plate 4 is an aluminum plate 4b that is plated (Ni plating or Sn plating) 4a on the front and back surfaces facing each other, and is made larger than the diameter of the lead wire 2 at a position facing the lead wire 2, A through hole 4c through which the lead wire 2 can be inserted is provided. The through hole 4c is formed, for example, by punching, and an aluminum substrate is exposed from the hole wall surface 4d that forms the through hole 4c.

  The electrode plate 4 and the other end of the lead wire 2 are connected as follows. First, the electrode plate 4 is disposed along the side surface of the capacitor element 1, and then the other end of the lead wire 2 is inserted into the through hole 4 c of the electrode plate 4. At this time, the leading end of the lead wire 2 is projected from the surface of the electrode plate 4. Then, the melted solder 3 is straddled between the outer peripheral surface of the leading end of the lead wire 2 protruding from the surface of the electrode plate 4 and the surface (plated surface) of the electrode plate 4, and as shown in FIG. Then, wrap around the protruding part of the lead wire 2. As the solder 3, a special solder for aluminum is not used, but generally used solder, for example, Sn-Ag-Cu-based lead-free solder is used.

  Normally, when such soldering is performed, the melted solder 3 also enters the gap formed between the outer peripheral surface of the lead wire 2 and the hole wall surface 4d of the through hole 4c. However, in the present invention, since the aluminum substrate having poor solder wettability is exposed on the hole wall surface 4d constituting the through hole 4c, the solder 3 is repelled, and the solder 3 does not enter the gap. Therefore, the solder 3 and the aluminum substrate do not contact each other, and the occurrence of electrolytic corrosion can be suppressed. Further, even if the solder 3 enters the gap formed between the outer peripheral surface of the lead wire 2 and the hole wall surface 4d of the through hole 4c, the hole wall surface 4d is not wetted by the solder 3 (the hole wall surface 4d The solder 3 does not adhere), and the occurrence of electrolytic corrosion remains suppressed. In order to further suppress the contact between the solder 3 and the aluminum substrate, for example, an oil film or the like that reduces solder wettability may be applied and formed on the hole wall surface 4d. Similarly, the lead wire 2 may be provided on the surface facing the hole wall surface 4d.

  In the solder connection structure configured as described above, despite the use of the aluminum plate 4b as the electrode plate 4, a highly reliable connection is possible. That is, when connecting the lead wire 2 and the electrode plate 4, the outer peripheral surface of the lead wire 2 and the plated surface of the electrode plate 4 can be connected by the solder 3. Can be satisfied. Moreover, since the aluminum base and the solder 3 do not contact, electrolytic corrosion can be suppressed and a stable connection can be realized.

  The results of experiments conducted to confirm the usefulness of the solder connection structure of the present invention will be described below. In FIG. 3, an aluminum plate 4b that has been subjected to Ni plating treatment is used as an electrode plate 4, and this electrode plate 4 and the capacitor element 1 are connected by the above-described solder connection structure and placed in a resin case and sealed with a resin ( The capacitor of Example 1) and the aluminum plate 4b subjected to Sn plating treatment as the electrode plate 4, and the capacitor of Example 2 having the same configuration as that of the capacitor of Example 1 are connected at 85 ° C./85% RH ( Relative humidity) shows a result of applying a voltage under an environment and energizing for 2000 hours. As a comparison object, a conventionally used copper plate is used as the electrode plate 4, the solder 3 is straddled between the outer peripheral surface of the lead wire 2 and the surface of the electrode plate 4, and the outer peripheral surface of the lead wire 2 and the through hole A similar test is also performed on the capacitor of Comparative Example 1 employing the conventional connection structure in which the solder 3 is infiltrated between the hole wall surface 4d of 4c.

As shown in FIG. 3 (a), it can be seen that the capacity has decreased since around 1700 hours, and that moisture has entered the capacitor. However, as shown in FIG. 3B, there is no rapid increase in ESR that should occur due to electrolytic corrosion after 1700 hours. In addition, since the capacitors of Examples 1 and 2 show the same tendency as the capacitor of Comparative Example 1, it cannot be said that electrolytic corrosion has progressed compared to the conventional connection method, and is an effective connection method. I understand that.

  FIG. 4 shows the results of subjecting the above capacitors (Example 1, Example 2, Comparative Example 1) to an HS (temperature cycle) test at −40 ° C. to 105 ° C. As shown in FIG. 4, it can be seen that the capacitors of Examples 1 and 2 do not show a large difference compared to the capacitor of Comparative Example 1, and are connected with high reliability.

  As mentioned above, although typical embodiment of this invention was described, this invention is not limited to the said embodiment, It can be implemented in various changes within the scope of this invention. For example, in the above embodiment, the surface of the electrode plate 4 (upper surface side in FIG. 2) and the outer peripheral surface of the lead wire 2 are connected by soldering, but the back surface of the electrode plate 4 (lower surface side in FIG. 2) and the drawer are connected. The outer peripheral surface of the wire 2 may be soldered. In this case, it can be suppressed that the molten solder 3 hangs down due to gravity and approaches the hole wall surface 4d. Moreover, in the said Example, although the plating process was performed to the front and back of the electrode plate 4, you may make it perform a plating process only to either one side of the side used for a solder connection.

  Further, the lead wire 2 is not limited to a circular cross section as shown in FIG. 7, but can have various shapes such as a square cross section, a foil shape or a plate shape. May be used. Further, it is not necessary to apply the plating process 2a to the entire outer peripheral surface of the lead wire 2, and the plating process 2a may be applied only to a part necessary for soldering or a part used for preventing contact with the hole wall surface 4d. Furthermore, the plating process 2a may not be performed if the hole wall surface 4d is not brought into contact.

  1 .... Capacitor element, 1a ... Metallicon electrode, 2 .... Lead wire, 3 .... Solder, 4 .... Electrode plate, 4b ..., Aluminum plate, 4c ..., Through hole, 4d ..., Hole wall surface

Claims (2)

  A solder connection structure in which one end of the lead wire (2) is solder-connected to the metallicon electrode (1a) of the capacitor element (1) and the other end of the lead wire (2) is solder-connected to the electrode plate (4). The electrode plate (4) is an aluminum plate (4b) having Ni plating or Sn plating applied to at least one of its front and back surfaces, and through holes (4c) provided in the electrode plate (4). ) With the other end of the lead wire (2) inserted therethrough, the solder (3) does not contact the hole wall surface (4d) constituting the through hole (4c) and the lead wire (2 ) And an outer peripheral surface of the electrode plate (4) and a plated surface on the back surface of the electrode plate (4).   The solder connection structure according to claim 1, wherein an aluminum substrate is exposed from the hole wall surface (4 d).

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