JP4588630B2 - Manufacturing method of chip-shaped solid electrolytic capacitor - Google Patents

Description

  The present invention relates to a method for manufacturing a chip-shaped solid electrolytic capacitor.

  In recent years, with the miniaturization of electronic equipment, it has become necessary to mount a solid electrolytic capacitor with high density, so the anode and cathode of the capacitor are located on the lower surface of the product, so-called bottom electrode type chip-shaped solid electrolytic capacitor Is frequently used.

In general, a bottom electrode type chip-shaped solid electrolytic capacitor has a structure in which a capacitor element 2, a metal strip 5 and an electrode substrate 8 are combined as shown in FIG. 3, and the capacitor element 2 includes a dielectric oxide film, a solid electrolyte layer. And a cathode lead layer formed sequentially, and has lead-out leads 1.
Then, the conductive plate 12 of the electrode substrate 8 is subjected to tin plating, and the anode internal electrode 6a, the anode external electrode 6b, the cathode internal electrode 6c, and the cathode external electrode 6d are formed by the plating layer. The conductive plate 12 has a lead frame shape.
Furthermore, after resistance welding the metal strip 5 and the anode internal electrode 6 a, the lead lead 1 and the metal strip 5 are resistance welded, and the cathode of the capacitor element 2 and the cathode internal electrode 6 c are connected by the conductive adhesive 9. It was sealed with exterior resin 10. (For example, refer to Patent Document 1).

  Further, as shown in FIG. 4, the insulating layer 7 is used for the electrode substrate 8, a through hole or a notch is formed in the insulating layer 7, and the anode and the cathode conductive plate 3 are arranged in the through hole or the notch, It is connected to the conductive layer 4 and is plated with tin. Further, the metal strip 5 and the anode internal electrode 6 a are connected by the conductive adhesive 9, the cathode of the capacitor element 2 and the cathode internal electrode 6 c are connected, and this is sealed with the exterior resin 10. A capacitor is also disclosed (for example, see Patent Document 2).

Further, in order to improve the ESR characteristics, as shown in FIG. 5, in the bottom electrode type chip-shaped solid electrolytic capacitor in which the metal strip 5 and the anode internal electrode 6a are connected by the conductive adhesive 9, the lead 1 and the metal strip are connected. A chip-shaped solid electrolytic capacitor having a structure in which a part or all of the end face of the material 5 is exposed from the exterior resin 10 and the exposed portion and the anode conductive plate are connected by plating is also disclosed (see, for example, Patent Document 3).
JP 2001-6978 A JP 2002-110459 A Japanese Patent Application No. 2003-071135

  However, the conventional bottom electrode type chip-shaped solid electrolytic capacitor has the following problems.

As shown in FIG. 3, after the metal strip 5 is resistance-welded to the electrode substrate 8 using the lead frame-like conductive plate 12, the lead 1 of the capacitor element 2 and the metal strip 5 are resistance-welded, and the capacitor In the structure in which the cathode of the element 2 is connected to the cathode internal electrode 6c of the electrode substrate 8 through the conductive adhesive 9, accuracy is required for the attitude control of the capacitor element 2, and due to the thickness variation of the capacitor element 2 There is a problem that the connection between the anode and the cathode of the electrode substrate 8 and the capacitor element 2 becomes unstable and is easily affected by mechanical stress.

Further, as shown in FIG. 4, after the lead-out lead 1 of the capacitor element 2 and the metal strip 5 are resistance welded, the metal strip 5 and the anode internal electrode 6a, and the cathode and cathode internal electrode 6c of the capacitor element 2 are connected. In the structure in which the conductive adhesive 9 is connected, the attitude of the capacitor element 2 can be easily controlled, and the influence of mechanical stress is reduced. However, the connection between the anode of the capacitor element 2 and the anode internal electrode 6a of the electrode substrate 8 is effective. There was a problem that the connection resistance of the conductive adhesive 9 used deteriorated the ESR characteristics of the chip-shaped solid electrolytic capacitor.

Further, as shown in FIG. 5, after the lead-out lead 1 of the capacitor element 2 and the metal strip 5 are resistance-welded, a part of the end surface of the lead-out lead 1 and the metal strip 5 is exposed from the exterior resin 10, and the exposure is performed. In the structure where the part and the anode electrode substrate are connected by plating, there is a problem of resin leakage from the mold when exposed by a resin sealing method using a mold, and it is exposed by dicing after batch sealing In this case, there is a problem that a cutting stress is applied and a leakage current is increased.

  The present invention has been made in order to solve the above-described problems in the prior art, and is a bottom electrode type chip-like solid excellent in connection stability between a capacitor element and an electrode substrate, and excellent in ESR and leakage current characteristics. An object is to provide an electrolytic capacitor.

  The present invention includes a capacitor element having an anode lead, a metal strip, an internal electrode, and an external electrode, and after resistance welding the lead lead and the metal strip, the metal strip and the anode internal electrode, Is a method for manufacturing a chip-shaped solid electrolytic capacitor, characterized by laser welding.

2. The method for manufacturing a chip-shaped solid electrolytic capacitor according to claim 1, wherein the anode internal electrode is formed by gold plating.

As in the above configuration, by conducting laser welding of the lead lead to which the metal strip is resistance-welded and the anode internal electrode of the electrode substrate, non-contact bonding is possible, and the posture control of the capacitor element becomes easy. No stress is applied to maintain the element posture. That is, it is possible to manufacture a bottom electrode type chip-shaped solid electrolytic capacitor with less mechanical stress.
Furthermore, since no conductive adhesive is used at the anodic bonding interface, there is no deterioration in connection resistance, and there is no problem of mechanical stress associated with exposure of the lead and the metal strip, so that the bottom surface has excellent ESR and leakage current characteristics. An electrode-type chip-shaped solid electrolytic capacitor can be manufactured.

  Also, by making at least the anode internal electrode of the electrode substrate gold with high electrical conductivity and a surface that is difficult to oxidize, it is possible to manufacture a bottom electrode type chip-shaped solid electrolytic capacitor with excellent connection stability and ESR characteristics Become.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

[Example 1]
Example 1 is shown in FIG. This is a bottom electrode type chip-shaped solid electrolytic capacitor, and has a structure in which the capacitor element 2, the metal strip 5 and the electrode substrate 8 are combined as in the conventional example 1 of FIG.
A dielectric oxide film, a solid electrolyte layer, and a cathode lead layer were formed on the tantalum sintered body provided with the lead-out lead 1 by a known method to produce a capacitor element 2.
Further, a through hole or notch is formed in the insulating layer 7, and after the anode and cathode conductive plate 3 is disposed in the through hole or notch, the conductive layer 4 made of copper is formed in the through hole or notch. did. Note that polyimide was used for the insulating layer 7.
Subsequently, gold is plated on the conductive plate 3 and the conductive layer 4 using nickel or a cylinder as a base plating, and an anode internal electrode 6a, an anode external electrode 6b, a cathode internal electrode 6c, and a cathode external electrode 6d are formed by the gold plating layer. A substrate 7 was produced.
Next, after the lead-out lead 1 and the metal strip 5 were resistance-welded, the cathode of the capacitor element 2 and the cathode internal electrode 6 c were connected by the conductive adhesive 9. Further, the metal strip 5 and the anode internal electrode 6a were joined by laser welding. The metal strip 5 is made of an alloy of iron and nickel. A YAG laser was used for laser welding, and welding was performed with an output diameter of 1.0 to 3.0 kW and an irradiation diameter of 0.4 to 0.6 ms and 0.1 to 0.3 mmφ. The laser irradiation part is desirably four surfaces in contact with the surface connected to the anode internal electrode 6a of the metal strip 5, particularly three surfaces other than the capacitor element facing surface. The irradiation range is preferably 0.03 to 0.20 mm above the anode internal electrode 6a. Outside this range, welding is insufficient (nugget formation failure), and when it is less than 0.03 mm, the anode internal electrode 6a is thermally damaged and sufficient welding strength cannot be obtained, which is not preferable.
After that, it is sealed with the exterior resin 10, and the anode external electrode 6b and the cathode external electrode 6d are plated with nickel and tin, and the final electrode layer 11 is formed by the plating layer, and the 1608 size (1.6 × 0.8) × 0.8 mm) A bottom electrode type chip-shaped solid electrolytic capacitor was produced.

[Example 2]
As shown in FIG. 2, the capacitor element 2 is manufactured in the same manner as in Example 1, and the lead frame-like electrode substrate 12 is gold-plated instead of the electrode substrate having the insulating layer, and the anode internal electrode 6a, A 1608 size bottom electrode type chip-shaped solid electrolytic capacitor was produced in the same manner as in Example 1 except that the anode external electrode 6b, the cathode internal electrode 6c, and the cathode external electrode 6d were formed.

[Conventional example 1]
As shown in FIG. 3, a capacitor element 2 is manufactured as in Conventional Example 1 as in Conventional Example 1, and a lead frame-like electrode substrate 12 is used instead of an electrode substrate having an insulating layer. The external electrode 6b, the cathode internal electrode 6c, and the cathode external electrode 6d are tin-plated, and after the anode internal electrode 6a and the metal strip 5 are resistance welded, the anode lead 1 and the metal strip 5 are resistance welded. A 1608 size bottom electrode type chip-shaped solid electrolytic capacitor was produced in the same manner as in Example 1.
In the chip-shaped solid electrolytic capacitors of Examples 1 and 2 and Conventional Example 1, the inclination angle with respect to the electrode substrate 8 after the capacitor element 2 was mounted was investigated. The result is shown in FIG.

[Conventional example 2]
Further, as shown in FIG. 4 as the conventional example 2, the capacitor element 2 is produced in the same manner as in the example 1, and the metal strip 5 and the anode internal electrode 6a are joined by the conductive adhesive 9 as in the example 1. In the same manner as above, a 1608 size bottom electrode type chip-shaped solid electrolytic capacitor was obtained.
The ESR characteristics of Examples 1 and 2 and Conventional Example 2 were compared and shown in FIG.

[Conventional Example 3]
Further, as shown in FIG. 5 as the conventional example 3, the metal strip 5 and the anode internal electrode 6a are joined by the conductive adhesive 9, and the lead 1 and a part of the end face of the metal strip 5 are exposed from the exterior resin 10. A 1608 size bottom electrode type chip-shaped solid electrolytic capacitor was produced in the same manner as in Example 1 except that dicing was performed.
FIG. 8 shows a comparison of leakage current characteristics between Example 1 and Example 2 and Conventional Example 3 at the same rating.

As is apparent from FIG. 6, the first and second embodiments of the present invention have a smaller element inclination angle of the capacitor element 2 than the conventional example 1, and the element attitude can be easily controlled.
That is, it is possible to manufacture a bottom electrode type chip-shaped solid electrolytic capacitor that has low mechanical stress and excellent connection stability between the capacitor element 2 and the electrode substrate.

  Further, as is apparent from FIG. 7, it can be seen that Example 1 and Example 2 are superior in ESR characteristics as compared with Conventional Example 2. This is considered to be due to the fact that the conductive adhesive 9 is not used at the anodic bonding interface and the conductive plates 3 and 12 are plated with gold.

Further, as apparent from FIG. 8, it can be seen that Example 1 and Example 2 are superior in leakage current characteristics as compared with Conventional Example 3. This is considered to be the effect of reducing the assembly stress due to dicing without exposing the lead 1 and the metal strip 5.

  In addition, although plating of silver, copper, or the like may be used for the plating of the anode and the cathode electrode, it is desirable to use a gold plating excellent in continuous stability and ESR characteristics.

  As described above, according to the present invention, it is possible to provide a bottom electrode type chip-shaped solid electrolytic capacitor having excellent connection stability between a capacitor element and a product electrode, and excellent in ESR and leakage current characteristics.

It is sectional drawing of the chip-shaped solid electrolytic capacitor of a lower surface electrode type by Example 1 of this invention. It is sectional drawing of the bottom electrode type chip-shaped solid electrolytic capacitor by Example 2 of this invention. 6 is a cross-sectional view of a bottom electrode type chip-shaped solid electrolytic capacitor according to Conventional Example 1. FIG. 6 is a cross-sectional view of a bottom electrode type chip-shaped solid electrolytic capacitor according to Conventional Example 2. FIG. It is sectional drawing of the chip-shaped solid electrolytic capacitor of the lower surface electrode type by the prior art example 3. It is a comparison figure of element inclination angle of Example 1 and Example 2, and conventional example 1. FIG. It is a comparison figure of ESR of Example 1, Example 2, and the prior art example 2. FIG. It is a comparison figure of the leakage current of Example 1, Example 2, and Conventional Example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Derived lead 2 Capacitor element 3,12 Conductive plate 4 Conductive layer 5 Metal strip 6a Plating layer (anode internal electrode)
6b Plating layer (Anode external electrode)
6c Plating layer (cathode internal electrode)
6d Plating layer (cathode external electrode)
7 Insulating layer 8 Electrode substrate 9 Conductive adhesive 10 Exterior resin 11 Final electrode layer

Claims (2)

A capacitor element having an anode lead, a metal strip, an internal electrode, and an external electrode;
A chip-shaped solid electrolytic capacitor manufacturing method, wherein the lead wire and the metal strip are resistance welded, and then the metal strip and the anode internal electrode are laser welded.   2. The method for manufacturing a chip-shaped solid electrolytic capacitor according to claim 1, wherein the anode internal electrode is formed by gold plating.

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