JP4880433B2 - Chip-shaped solid electrolytic capacitor - Google Patents

Description

  The present invention relates to a chip-shaped solid electrolytic capacitor, and more particularly to a chip-shaped solid electrolytic capacitor having a bottom electrode structure.

  The trend toward multi-functionalization associated with the downsizing and digitization of electronic devices such as mobile phones is a chip that is mounted on the periphery by repeatedly reducing the thickness / miniaturization and high integration of semiconductors that perform complex arithmetic processing year by year. Parts are also required to have conflicting performances of "miniaturization" and "high performance".

  Among them, a ceramic capacitor is often used as the capacitor, but a chip-shaped solid electrolytic capacitor using a valve metal such as tantalum is used for a circuit that requires a large capacity.

  In general, the chip-type solid electrolytic capacitor is mainly a mold type of a package having a lead frame as a skeleton (see, for example, Patent Document 1).

  However, as described above, due to downsizing of electronic equipment, there is a demand for a smaller package while maintaining a large capacity, and a chip with a bottom electrode structure that improves the volume efficiency by eliminating the lead frame skeleton. A solid electrolytic capacitor has been proposed (see, for example, Patent Document 2).

The chip-shaped solid electrolytic capacitor having the bottom electrode structure includes a capacitor element having an anode lead, a dielectric oxide film, a solid electrolyte layer, and a cathode lead layer, an electrode substrate that serves as a capacitor electrode, an exterior resin, Have
A structure in which an electrode substrate has an insulating layer having a plurality of through holes or notches, an anode conductive plate and a cathode conductive plate disposed in the through holes or notches, and an external electrode to which the conductive plates are connected Thus, a high capacity is realized with an excellent volumetric efficiency, there is no deterioration in characteristics due to electrode routing by a lead frame, and an excellent ESR (equivalent series resistance) characteristic is obtained.

  In mobile digital devices typified by mobile phones, the mainstream size of the chip-shaped solid electrolytic capacitor having the bottom electrode structure is 1608 size (length L 1.6 mm × width W 0.8 mm × height H 0.8 mm). As mentioned at the beginning, since miniaturization and high performance are progressing year by year, 2012 size (length L2.0 mm × width W1.2 mm × height H0.8 mm) and 3216 size (long) (L 3.2 mm x W 1.6 mm x H 1.0 mm) is increasing.

JP 63-115324 A JP2002-110458

  Since the chip-shaped solid electrolytic capacitor having the above-mentioned bottom electrode structure is formed by arranging a large number of capacitor elements and performing exterior resin molding in a lump, and a method of manufacturing by dividing into pieces with a diamond cutter or the like is often used. In particular, the material design of the exterior resin requires a design in which the filler particle size is managed with higher accuracy, and the injectability is improved to prevent generation of an unfilled portion of the resin.

  Generally, the exterior resin used for the chip component is formed by transfer molding, and the filler of the mold resin used for this is a spherical or crushed one having a size of about 50 to 100 μm. Moreover, the spiral flow which is one of the characteristics showing the moldability of the resin is about 30 to 90 cm (175 ° C.).

However, as a matter of course, when a large cavity is transfer-molded, if the thickness of the exterior resin is thin, the moldability becomes a problem as the size of the outer resin increases. That is, it is necessary to ensure a stable injection property over a wide range.
In particular, chip-shaped solid electrolytic capacitors that require high capacity are designed to expand the size of the built-in capacitor element to the limit and form a thin outer resin layer, and are finer and more compact than before. The particle size distribution can be controlled with a large filler diameter, and a mold resin with a long spiral flow has to be adopted, and the material cost is expensive because it becomes a special resin.

  Therefore, the cost of the above-mentioned chip-shaped solid electrolytic capacitor having the bottom electrode structure has to be extremely high.

  In view of the above, an object of the present invention is to provide a structure capable of molding an exterior resin with a low-cost and stable transfer mold in a chip-shaped solid electrolytic capacitor having a bottom electrode structure employing a batch production method. To do.

In order to achieve the above object, a chip-shaped solid electrolytic capacitor according to the present invention comprises an anode lead, a capacitor element formed by sequentially forming a dielectric oxide film, a solid electrolyte layer, and a cathode lead layer, An electrode substrate having an anode electrode connected via an anode lead lead and an anode lead metal, and a cathode electrode connected via a conductive adhesive to the cathode lead layer of the capacitor element, and the lower surface of the electrode substrate exposed An exterior resin for packaging the capacitor element and the electrode substrate in a
On the upper surface of the electrode substrate, the cathode lead layer of the capacitor element is placed from below so that the cathode lead layer of the capacitor element and the electrode substrate are parallel between the cathode lead layer of the capacitor element and the electrode substrate. At least two protrusions to be supported are provided.

  In addition, it is preferable that the said protrusion part is comprised with a resist layer. In this case, the protruding portion can be formed easily and with high positional accuracy.

  According to the above configuration, a uniform space is generated by the protrusion provided in a part between the cathode lead layer of the capacitor element and the electrode substrate, so that exterior resin injection by transfer molding can be performed smoothly and unfilled defects can be prevented. Therefore, it becomes possible to manufacture a chip-shaped solid electrolytic capacitor without using a mold resin whose particle size distribution is controlled with a special and fine filler diameter, and provides a chip-shaped solid electrolytic capacitor that is inexpensive and excellent in mass productivity. be able to.

[ Comparative Example 1]
FIG. 1 is a cross-sectional view of a chip-shaped solid electrolytic capacitor according to Comparative Example 1 of the present invention. In FIG. 1, 1 is a capacitor element, 2 is an exterior resin, and 3 is an electrode substrate.

  Capacitor element 1 has anode lead leads embedded in tantalum powder, press-molded into a predetermined shape, sintered to form a porous body of tantalum metal, and a dielectric oxide film layer is formed on the surface of the porous body. After the capacitor anode body is manufactured, a solid electrolyte layer is formed, and a cathode lead layer composed of a carbon layer and a silver layer is further formed.

  The electrode substrate 3 is a substrate that serves as an electrode of the capacitor. Therefore, the electrode substrate 3 is connected to the anode electrode 4 connected in advance via the anode lead of the capacitor element 1 and the anode lead metal 6, the cathode lead layer of the capacitor element 1 and the conductive adhesive 9. A cathode electrode 5 to be connected is provided.

The exterior resin 2 packages the capacitor element 1 and the electrode substrate 3 with the lower surface of the electrode substrate 3 exposed. That is, the chip-shaped solid capacitor of Comparative Example 1 has a bottom electrode structure.

In particular, in the present comparative example 1, a rolled copper plate having a thickness of 18 μm is disposed as an insulating layer using a perforated polyimide film as an insulating layer, etched to form the anode electrode 4 and the cathode electrode 5, and then the anode electrode is formed by copper plating 4 and the conductive body electrically connected to the cathode electrode 5 are embedded in the perforated portion of the insulating layer, and the exposed surfaces of the anode conductive plate and the cathode conductive plate and the conductive body are further processed by nickel plating and tin alloy plating. An electrode substrate 3 having a thickness of 80 μm is formed.

  Next, the anode lead and the cathode lead layer of the capacitor element 1 are connected to the anode electrode 4 and the cathode electrode 5 of the electrode substrate 3 through the anode lead metal 6 and the conductive adhesive 9, respectively. A chip-shaped solid electrolytic capacitor having a size of 2.0 × 1.2 × 0.8 mm (2012 size) is produced by coating with resin 2.

  The positional relationship between the electrode substrate 3 and the capacitor element 1 is such that the anode electrode 4 of the electrode substrate 3 is positioned below the anode lead of the capacitor element 1 and the cathode electrode 5 of the electrode substrate 3 is the cathode of the capacitor element 1. It is set so as to be located below the extraction layer, and is designed so that the electrode extraction is the shortest. A plurality of anode electrodes 4 and cathode electrodes 5 are formed on the electrode substrate 3, and the subsequent processes are performed in units of a plurality of units, whereby this capacitor is produced in a batch.

  Further, on the upper surface of the electrode substrate 3, a thickness of 50 μm is provided around a position where the cathode lead layer of the capacitor element 1 and the anode electrode 4 face each other (a position straddling part of the anode electrode 4 and part of the insulating layer). A resist layer 8 having a width of 0.2 mm is formed on the upper surface of the electrode substrate 3 to form a protruding portion that supports the capacitor element 1 from below.

  The exterior resin 2 is formed by transfer molding. As the resin used at this time, a resin having a spherical shape with a filler diameter of about 50 to 100 μm and a spiral flow of about 50 cm (175 ° C.), which is one of the characteristics representing the moldability of the resin, is used.

[Example 2]
FIG. 2 is a cross-sectional view of a chip-shaped solid electrolytic capacitor according to Example 2 of the present invention.

In the second embodiment, on the upper surface of the electrode substrate 3, the periphery of the position where the cathode lead layer of the capacitor element 1 and the anode electrode 4 face each other (the position straddling part of the anode electrode 4 and part of the insulating layer); Except that the resist layer 8 serving as protrusions is formed at two locations around the position where the cathode lead layer of the capacitor element 1 and the cathode electrode 5 face each other (a position straddling part of the cathode electrode 5 and part of the insulating layer). Produced a chip-shaped solid electrolytic capacitor in the same manner as in Comparative Example 1 above.

[Conventional example 1]
FIG. 3 is a cross-sectional view of a chip-shaped solid electrolytic capacitor according to Conventional Example 1.

Referring to FIG. 3, in the conventional example 1, when forming the electrode substrate 3, the formation of the resist layer 8 serving as the protruding portion is omitted, and the capacitor element 1 is processed by the same method as in the comparative example 1 described above. A chip-shaped solid electrolytic capacitor was produced.

  In the prior art example 1, when the posture of the capacitor element 1 in the package is tilted due to burrs generated after cutting of the anode lead metal 6 or torsion of the element when the anode lead metal 6 and the anode lead are connected, the capacitor element 1 Since the lower portion of the exterior resin forming portion 1 is thinner than the design value, the gap 7, that is, the exterior resin 2 is not filled. This state is shown in a simplified manner in FIG.

[Comparison results]
For the chip solid electrolytic capacitors of Examples 1 and 2 above, the comparison results of the unfilled occurrence rate of the exterior resin at the time of production of 10,000 each using the chip solid electrolytic capacitor of Conventional Example 1 as a comparison object are as follows: Table 1 shows.

  As shown in Table 1, by providing a protrusion with resist at a part between the cathode lead layer of the capacitor element and the electrode substrate, it is possible to smoothly inject exterior resin by transfer molding without using special molding resin. It was found that it prevents unfilled defects.

  In addition, this invention is not limited to the said Example.

  For example, in the above-described embodiment, the resist layer serving as the protruding portion is formed at a position straddling a part of the electrode, but the same effect can be obtained by forming this resist layer on either the electrode or the insulating layer. Can be obtained.

  In the above embodiment, an example in which a resist layer serving as a protruding portion having a thickness of 50 μm and a width of 0.2 mm is formed on the electrode substrate is described. However, a general mold resin is provided between the capacitor element and the electrode substrate. If the resist thickness is changed according to the characteristics of the resin so that the resist thickness is reduced so that it can be stably injected, a chip-shaped solid electrolytic capacitor with high volume efficiency can be obtained.

  Furthermore, in the above embodiment, a protruding portion is formed by resist formation in a part between the cathode lead layer of the capacitor element and the electrode substrate. However, when the protruding layer is formed of polyimide resin on the polyimide insulating layer Alternatively, the same effect can be obtained even if the protrusions are provided by plating the surfaces of the anode electrode and the cathode electrode of the electrode substrate.

  It goes without saying that various design changes and modifications can be made within the scope of the claims attached to the present specification.

  The present invention is useful as a chip-shaped solid electrolytic capacitor, particularly a chip-shaped solid electrolytic capacitor having a bottom electrode structure, because the exterior resin can be molded at a low cost with a stable transfer mold.

It is sectional drawing of the chip-shaped solid electrolytic capacitor which concerns on the comparative example 1 of this invention. It is sectional drawing of the chip-shaped solid electrolytic capacitor which concerns on Example 2 of this invention. It is sectional drawing of the chip-shaped solid electrolytic capacitor which concerns on the prior art example 1. FIG. It is a figure for demonstrating the mechanism in which an exterior resin unfilled area | region arises in the chip-shaped solid electrolytic capacitor which concerns on the prior art example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Exterior resin 3 Electrode substrate 4 Anode electrode 5 Cathode electrode 6 Anode lead-out metal 7 Void 8 Resist layer (protrusion part)
9 Conductive adhesive

Claims (1)

A capacitor element comprising an anode lead and having a dielectric oxide film, a solid electrolyte layer, and a cathode lead layer sequentially formed;
An electrode substrate including an anode lead connected to an anode lead of the capacitor element and an anode electrode connected via an anode lead metal; and a cathode electrode connected to the cathode lead layer of the capacitor element via a conductive adhesive;
An exterior resin for packaging the capacitor element and the electrode substrate with the lower surface of the electrode substrate exposed;
On the upper surface of the electrode substrate, the cathode lead layer of the capacitor element is placed from below so that the cathode lead layer of the capacitor element and the electrode substrate are parallel between the cathode lead layer of the capacitor element and the electrode substrate. A chip-shaped solid electrolytic capacitor, characterized in that at least two protruding portions to be supported are provided.

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