JP2008305824A - Solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor having a welding strength sufficiently durable to various loads in an assembling manufacture process even if the cross sectional area of an anode lead wire is enhanced and a copper-based raw material having a low resistance value is used for an anode terminal, and enabling a low ESR without causing deterioration in leakage current characteristic and ESR characteristic. <P>SOLUTION: A capacitor element 1 comprises an anode body made of a valve act metal and a dielectric layer formed on the surface of the anode body, a solid electrolytic layer formed in contact with the dielectric layer and a cathode layer formed in contact with the solid electrolytic layer, and an anode lead wire 2 formed by pulling one end of the anode body. In the capacitor element 1, a groove 7 in a direction perpendicular to the pulling direction is formed on one part of a connection portion between the anode lead wire 2 and the anode terminal. The forward portion of the groove 7 is a welding portion 6 with the anode terminal. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a solid electrolytic capacitor, and more particularly to a connection structure between an anode lead wire and an anode terminal.

  In recent years, with the increase in speed and digitization of electronic devices, solid electrolytic capacitors used in these devices are required to have a large capacity and a reduction in ESR (equivalent series resistance) in a high frequency region.

  FIG. 4 shows a cross-sectional view of an example of a conventional solid electrolytic capacitor. Usually, the solid electrolytic capacitor includes an anode body 11 made of a sintered body of a valve action metal, a dielectric layer formed on the surface of the anode body 11, a solid electrolyte layer 12 formed in contact with the dielectric layer, and a solid electrolyte layer. 12 has a capacitor element 51 composed of a cathode layer 13 formed in contact with the anode 12 and an anode lead wire 50 from which one end of the anode body 11 is drawn, and a machine such as welding is provided at the tip of the anode lead wire 50. The anode terminal 52 is connected by a general connection. A flat cathode terminal 4 is connected to the cathode layer 13 on the outer surface of the capacitor element 51 via a conductive adhesive.

  After the terminals are thus connected, the exterior resin portion 5 is formed by a molding die or the like. Thereafter, in the lead molding process of the solid electrolytic capacitor, the anode terminal 52 and the cathode terminal 4 drawn out from the exterior resin portion 5 are cut into a predetermined shape and molded by a mold or the like. That is, the anode terminal 52 and the cathode terminal 4 are bent and formed along the exterior resin portion 5 with the exterior resin portion 5 as a reference. At the time of molding, a bending mold separated into a plurality of times is used, and molding is sequentially performed for each bending portion. An example of a connection process between a conventional anode lead wire and an anode terminal of a solid electrolytic capacitor is described in Patent Document 1.

JP 2004-311976 A

  In the conventional solid electrolytic capacitor as described above, in order to lower the ESR value in the high frequency region, the shape of the solid electrolyte layer 12 or the cathode layer 13 is increased to increase the capacitance, or the anode terminal 52 or the cathode terminal. 4, a copper-based material having a low resistance value is used, and the diameter of the anode lead wire 50 is increased. Furthermore, there is a method of increasing the cross-sectional area of the anode lead wire as a whole and reducing the resistance by providing a plurality of anode bodies and anode lead wires.

  When the ESR characteristic value is to be lowered without changing the basic shapes and materials of the capacitor element 51, the anode terminal 52, and the cathode terminal 4, the simplest method that does not affect other characteristics is the anode lead wire 50. This is a method of increasing the diameter of the. Since the cross-sectional area is increased by making the anode lead wire 50 thick, the wire resistance of the anode lead wire 50 can be lowered. Further, since the respective contact areas between the anode body 11, the dielectric layer, and the solid electrolyte layer 12 are increased, the contact resistance can also be reduced.

  However, in the conventional solid electrolytic capacitor, when the diameter of the anode lead wire 50 is increased, the load applied when the anode lead wire 50 is cut in the assembly manufacturing process increases. For this reason, stress is applied to the solid electrolyte layer 12 and the dielectric layer through the anode lead wire 50 and the integrated anode body 11 which are stressed at the time of cutting, and damage and misalignment occur at the stress application portion, and leakage occurs. The current characteristics and ESR characteristics are affected and the characteristics deteriorate. Actually, the wire diameter of the anode lead wire having a normal circular cross section cannot be made a certain dimension (about 0.5 mm) or more because of the influence at the time of cutting.

  When a plurality of anode lead wires are used, the total cross-sectional area is increased even if one cross-sectional area is the same, so that the overall resistance can be lowered. However, the number of times external stress is applied in the cutting process is plural. The number of times increases and the possibility of deterioration of the characteristics increases.

  As a method of reducing the load at the time of cutting, the cross-sectional area of the anode lead wire is the same, the cross-sectional shape that is usually circular is crushed into an elliptical shape, and a flat plate-like anode lead wire and It is possible to do. As a result, the cutting thickness is reduced, so that the load during cutting is reduced and the stress applied to the anode lead wire is also reduced. 5A and 5B are perspective views showing the shape of the anode lead wire of the capacitor element 51. FIG. 5A is an anode lead wire 50 having a normal circular cross section, and FIG. A flat plate-like anode lead wire 60 is shown.

  However, when the anode lead wire is flattened in this way, a new problem arises in the process of connecting the anode lead wire 50 and the anode terminal 52. The first problem is that resistance welding is generally used for the above connection. Therefore, in the flat shape, when the anode lead wire 50 and the anode terminal 52 are overlapped and a current flows, the contact area of the electrode and the like becomes large. This is a problem that contact resistance becomes small and sufficient heating for melting cannot be obtained. FIG. 6 is a cross-sectional view for explaining a connecting process by resistance welding between the anode lead wire and the anode terminal, in which the anode lead wire 60 is overlapped with the anode terminal 52 and sandwiched between the welding electrodes 8 and 9 of the welding machine. Current is applied and heated. At this time, the respective contact resistances between the welding electrode 8 and the anode lead wire 60, the anode lead wire 60 and the anode terminal 52, and the welding electrode 9 and the anode terminal 52 are reduced, and the anode lead wire 60 and the anode terminal 52 are melted. Cannot be performed stably. In particular, when a copper-based material having a low resistance is used for the anode terminal 52, the contact resistance is further reduced, so that a stable connection cannot be expected. There also occurs a phenomenon in which each material sticks to each welding electrode. Actually, simply flattening the anode lead wire tends to make the welding strength unstable as described above. Therefore, the original wire diameter of the anode lead wire cannot be increased to about 0.5 mm or more.

  The second problem is that since the anode lead wire 60 and the anode terminal 52 are in surface contact, the contact pressure between the anode lead wire 60 and the anode terminal 52 is dispersed over a large area, and the anode lead wire 60 is sufficiently attached to the anode terminal 52. Since the sinking cannot be expected, the anchor portion cannot be obtained. For this reason, the connection portion between the anode lead wire 60 and the anode terminal 52 cannot obtain a connection strength that can withstand the load in the subsequent bending process of the anode terminal. In order to obtain the above-described subsidence, there is a method of increasing the contact pressure between the anode lead wire 60 and the anode terminal 52 during welding. In this case, conversely, the contact resistance between the anode lead wire 60 and the anode terminal 52 is increased. Therefore, melting at the time of welding is reduced, and it is difficult to obtain sufficient connection strength.

  The third problem is that the welding current value must be increased in order to obtain heat generated on the contact surface in welding with low contact resistance as described above, and sparks are easily generated in such high current welding. Thus, the copper-based material of the anode terminal 52 is melted and scattered in a chip shape. The melted chip scatters horizontally on the joint surface between the anode lead wire 60 and the anode terminal 52 and adheres to the capacitor element. As a result, the leakage current characteristic of the solid electrolytic capacitor is deteriorated.

  Therefore, the object of the present invention is to solve the above-mentioned problems, and in the solid electrolytic capacitor, even when the cross-sectional area of the anode lead wire is increased and a copper-based material having a low resistance value is used for the anode terminal, the assembly manufacturing process It is intended to provide a solid electrolytic capacitor that can maintain a welding strength that can sufficiently withstand various loads and that can reduce ESR without deteriorating leakage current characteristics and ESR characteristics.

  In order to achieve the above object, a solid electrolytic capacitor of the present invention includes an anode body made of a valve metal, a dielectric layer formed on the surface of the anode body, and a solid electrolyte layer formed in contact with the dielectric layer. A capacitor element composed of a cathode layer formed in contact with the solid electrolyte layer and an anode lead wire from which one end of the anode body is drawn, an anode terminal connected to the anode lead wire, and a cathode layer A solid electrolytic capacitor comprising a connected cathode terminal is characterized in that a groove in a direction orthogonal to the lead-out direction is provided in a part of the anode lead wire connected to the anode terminal.

  The anode terminal is positioned at the portion where the groove of the anode lead wire is formed, and is overlapped with the anode lead wire at the tip portion from the portion where the groove of the anode lead wire is formed and resistance-welded. The anode lead wire may have a flat plate shape or an elliptical cross section.

  As described above, in the present invention, when an anode lead wire with a large wire diameter is used, it is crushed so as to have a flat plate shape or an elliptical cross section, and a part of the connection portion with the anode terminal is used. By providing a groove in the direction perpendicular to the pulling direction, the welding resistance is limited and the contact resistance value during welding is increased to improve the stability of the welded state, and at the same time, the groove acts as an anchor to increase the connection strength. It was improved and the above problems were solved.

  As described above, according to the present invention, even when the cross-sectional area of the anode lead wire is increased and a copper-based material having a low resistance value is used for the anode terminal, the welding strength sufficiently withstands various loads in the assembly manufacturing process. Thus, a solid electrolytic capacitor capable of reducing ESR without deteriorating leakage current characteristics and ESR characteristics can be obtained.

  Next, an embodiment of a solid electrolytic capacitor according to the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view of a capacitor element used in an embodiment of a solid electrolytic capacitor according to the present invention, and shows a structure of an anode lead wire. 1 shows an anode body made of a valve metal, a dielectric layer formed on the surface of the anode body, and a solid electrolyte layer formed in contact with the dielectric layer, as in the conventional solid electrolytic capacitor of FIG. 1 shows a capacitor element 1 composed of a cathode layer formed in contact with the solid electrolyte layer and an anode lead wire from which one end of the anode body is drawn. Here, an anode terminal of the anode lead wire 2 is shown. A groove 7 in a direction perpendicular to the pulling direction is provided in a part of the connecting portion. And the part ahead of the groove | channel 7 is the welding part 6 with an anode terminal.

  In the formation of the capacitor element 1, a line formed of a valve action metal sintered body having a circular cross-sectional area is processed to form a flat plate shape or a cross-section into an elliptical shape, which are formed into an anode body and an anode lead wire. Use as In this molding, for example, a molding die or the like is used. Thereafter, a dielectric layer is formed on the surface, set in a molding die of the capacitor element 1, inserted into a powder that becomes a solid electrolyte layer, compression-molded, and subjected to an element formation process such as cathode layer formation to form the capacitor element 1. Complete the assembly.

  Next, the capacitor element 1 cuts the anode lead wire 2 to a specified size, and electrically and mechanically connects the anode lead wire 2 and the anode terminal by resistance welding. In the present embodiment, at this time, a groove 7 is provided in a part of the connection portion with the anode terminal near the tip of the anode lead wire 2. As a method for forming the groove 7, for example, a method of forming a groove at the same time as cutting by pressing a portion where the groove 7 is formed at the time of cutting the anode lead wire 2 or by making a cut in the groove 7 portion. There is.

  About the length of the welding part 6 which is the part from the groove | channel 7 of the anode lead wire 2 to a cutting end surface, it sets so that it may become the length which can obtain optimal welding conditions when it overlaps with an anode terminal at the time of welding. Further, at the time of welding, when the anode lead wire 2 and the anode terminal are overlapped, the tip of the anode terminal is set so as to be positioned in the groove 7.

  FIG. 2 is a cross-sectional view for explaining a connection process by resistance welding of the anode lead wire and the anode terminal according to the present embodiment. The anode lead wire 2 is overlapped with the anode terminal 3 and is sandwiched between the welding electrode 8 and the welding electrode 9 of the welding machine, and an electric current is applied and heated. In the present embodiment, the anode lead wire 2 and the anode terminal 3 are overlapped only at the welded portion 6 of the anode lead wire 2, so that the contact area between the two is small, and the contact between them is smaller than in the conventional case shown in FIG. Resistance increases. Further, as shown in FIG. 2, the welding electrodes 8 and 9 are arranged on the tip end side of the anode lead wire 2, and arranged so as to be in contact with only the anode lead wire 2 and the welded portion 6. 9, the contact area between the anode lead wire 2 and the anode terminal 3 is also smaller than in the conventional case of FIG. 6, and the welding current is partially blocked by the groove 7, so that the resistance value increases and resistance welding is performed. The necessary stable heat generation is obtained. Also in resistance welding when a copper-based material is used for the anode terminal 3, welding can be performed stably.

  Further, since the anode lead wire 2 is in contact with the anode terminal 3 only at the tip welding portion 6 and the contact pressure is not dispersed, the welding portion 6 is embedded in the anode terminal 3 like a wedge. In addition, since the contact pressure is not applied to the tip of the anode terminal 3 protruding to the groove 7 side during resistance welding, it melts into the groove 7 portion of the anode lead wire 2 due to heat generation during resistance welding. Due to both effects, a meshed anchor structure between the anode lead wire 2 and the anode terminal 3 as shown in FIG. 2 is obtained, and a strong connection strength that cannot be realized by resistance welding in the conventional contact state is obtained. .

  As described above, when a copper-based material is used for the base material of the anode terminal 3 to reduce the ESR, contact resistance between the anode lead wire and the anode terminal is lowered in resistance welding, so that heat is generated on the contact surface. It is necessary to increase the welding current value at this time. At this time, in the conventional welding state, the chip melted and scattered by the spark adheres to the capacitor element, resulting in deterioration of the leakage current characteristic of the solid electrolytic capacitor.

  On the other hand, in the present embodiment, the tip of the anode terminal is melted so as to flow into the groove 7, so that the chips scattered from the anode terminal are protected by the wall on the capacitor element 1 side of the groove 7, and from the groove 7 to the capacitor element 1 side. It is possible to prevent chips from being scattered. As a result, the leakage current characteristic does not deteriorate before and after resistance welding.

  FIG. 3 shows a cross-sectional view of the solid electrolytic capacitor of the present embodiment formed by the above process. A cathode layer 13 is formed on the entire outer peripheral surface of the capacitor element 1, and the cathode layer 13 and the cathode terminal 4 are electrically connected by a conductive adhesive. Thereafter, the exterior resin portion 5 is formed by covering and molding the entire surface with the exterior resin. Thereafter, the anode terminal 3 and the cathode terminal 4 are cut and formed in predetermined dimensions by a method similar to the conventional method to obtain a final shape.

  As described above, according to the present invention, the cross-sectional area of the anode lead wire is increased, and even when a copper-based material having a low resistance value is used for the anode terminal, the welding strength sufficiently withstanding various loads is maintained in the assembly manufacturing process, A solid electrolytic capacitor that enables low ESR without deteriorating leakage current characteristics and ESR characteristics can be obtained.

  Needless to say, the present invention is not limited to the above-described embodiment, and the material and shape of the anode lead wire and anode terminal used in the present invention, the shape of the groove, and the like are arbitrarily set according to the purpose. Can be designed.

The perspective view of the capacitor | condenser element used for one embodiment of the solid electrolytic capacitor by this invention, and the figure which shows the structure of an anode lead wire. Sectional drawing for demonstrating the connection process by the resistance welding of the anode lead wire and anode terminal of this Embodiment. Sectional drawing of the solid electrolytic capacitor of this Embodiment. Sectional drawing of an example of the conventional solid electrolytic capacitor. FIG. 5A is a perspective view showing a shape of an anode lead wire of a conventional capacitor element portion, FIG. 5A is a perspective view showing an anode lead wire having a circular cross section, and FIG. 5B is a perspective view showing a plate-like anode lead wire. Figure. Sectional drawing for demonstrating the connection process by the resistance welding of the conventional anode lead wire and an anode terminal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 51 Capacitor element 2, 50, 60 Anode lead wire 3, 52 Anode terminal 4 Cathode terminal 5 Exterior resin part 6 Welding part 7 Groove 8, 9 Welding electrode 11 Anode body 12 Solid electrolyte layer 13 Cathode layer

Claims (3)

  An anode body made of a valve metal, a dielectric layer formed on the surface of the anode body, a solid electrolyte layer formed in contact with the dielectric layer, a cathode layer formed in contact with the solid electrolyte layer, and the anode A solid electrolytic capacitor comprising a capacitor element composed of an anode lead wire formed by pulling out one end of the body, an anode terminal connected to the anode lead wire, and a cathode terminal connected to the cathode layer. A solid electrolytic capacitor characterized in that a groove in a direction perpendicular to the lead-out direction is provided in a part of a connecting portion of a lead wire with the anode terminal.   The anode terminal is positioned at the portion where the groove of the anode lead wire is formed, and is overlapped with the anode lead wire at the tip portion from the portion where the groove of the anode lead wire is formed and resistance-welded. The solid electrolytic capacitor according to claim 1.   3. The solid electrolytic capacitor according to claim 1, wherein the anode lead wire has a flat plate shape or an elliptical cross section.

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