JP3168584B2 - Solid electrolytic capacitors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor for use in electronic equipment, and particularly to a solid electrolytic capacitor exhibiting excellent characteristics when mounted on a surface.

[0002]

2. Description of the Related Art In recent years, with the progress of electronic equipment, electronic components have been formed into chips, and it has become mainstream that electronic circuits are assembled by surface mounting. Therefore, not only the solderability of the lead terminals of the chip component is required, but also the heat resistance that can withstand a temperature of more than two hundred and several tens of degrees has been required. Conventionally, in the field of electrolytic capacitors, which are said to have poor heat resistance, chip components that can be surface-mounted have begun to appear due to advances in materials and technology. For example, FIG.
As shown in (a) and (b), there is known a solid electrolytic capacitor in which a capacitor element is molded with a resin together with a lead frame which also serves as an anode terminal 1 and a cathode terminal 2 to form a resin exterior 3.

[0003]

However, in a solid electrolytic capacitor provided with such a resin sheath 3, the sealing property is reduced at the time of surface mounting, and oxygen or water vapor in the air enters from the outside. Often, the internal capacitor elements deteriorated. This is due to the following reasons.

(1) Since the surface of the lead frame is tin-plated or solder-plated in order to improve the solderability, the low-melting metal is melted at the time of surface mounting, and the lead frame formed of the exterior resin 3 and the metal. Voids are created between them.

(2) Since the expansion coefficient of the exterior resin 3 is different from that of the base metal (generally iron-based) used for the lead frame, the expansion and contraction causes the expansion of the lead frame between the exterior resin and the metal. A void is generated in

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a highly reliable solid electrolytic capacitor that can withstand thermal shock during surface mounting.

[0007]

In order to achieve the above object, a solid electrolytic capacitor according to the present invention comprises a capacitor formed by sequentially forming an oxide film, a conductive material layer, a conductive polymer film, and a conductive layer on the surface of a valve metal. A solid electrolytic capacitor comprising a component, connecting a lead frame serving as a lead terminal to a valve metal part and a conductor layer part of the capacitor element, and further covering a part of the capacitor element and the lead frame with a mold resin. The lead frame has a copper metal layer on the surface and has a roughened surface.

[0008]

According to the above arrangement, the copper metal layer is formed on the surface of the lead frame serving as the lead terminal connected to the valve metal portion and the conductor layer portion of the capacitor element, and the surface is roughened. When a lead frame is surface-mounted on a printed circuit board by soldering, not only is it possible to obtain excellent solderability, but also the adhesion to the resin exterior is much better than other metals. It can withstand the thermal shock of expansion and contraction, and because its surface is roughened, it also has excellent sealing performance,
As a result, a highly reliable solid electrolytic capacitor can be obtained.

[0009]

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

(Embodiment 1) First, a polyimide insulating film coated with a mounting agent on one side is attached to a predetermined position of an aluminum foil which is a valve metal having a thickness of 100 μm, and is punched out to form a comb-shaped electrode shown in FIG. 11 was obtained. The insulating film 12 of the comb electrode 11 divides the projection 13 of the comb electrode 11 into a cathode portion 14 and an anode portion 15. Then, as shown in FIGS. 2A and 2B, after impregnating an aqueous solution of manganese nitrate on the oxide film 16 of the cathode portion 14,
By conducting a heat treatment at about 300 ° C., a conductive material layer 17 made of manganese dioxide was formed. Next, electrolytic polymerization was performed in a polymerization solution in which pyrrole was used as the polymerizable substance and triisopropyl naphthalene sulfonic acid was dissolved in water as the supporting electrolyte, and the conductive polymer film 18 was formed on the conductive material layer 17. . Further, a graphite layer 19 is formed thereon.
After sequentially forming a conductor layer made of a silver paint layer 20 by a known method, the protrusion 13 is cut along the line AA shown in FIG. 1 to form a capacitor element 21 shown in FIGS. 2 (a) and 2 (b). Obtained.

Next, an iron base material SPCC having a thickness of 0.1 mm was punched out, a copper metal layer made of copper plating having a thickness of 1 μm was formed on the surface, and the surface was roughened by sandblasting. 4 (a) and 4 (b), a small amount of silver paint was applied to a position corresponding to the space between the cathode portions on the lead frame 22, and the capacitor element 21 was stacked. In this case, the cathode side of the capacitor element 21 is connected to the cathode bottom stopper 2 as shown in FIGS. 4 (a) and 4 (b).
3 and the cathode side stopper 24 were fixed by bending at right angles. On the other hand, the anode part side of the capacitor element 21 was bent in two steps, and was brought into close contact with the anode side stopper 25 and the anode pressing part 26. Further, the anode portion side was joined by performing laser welding from above the anode pressing portion 26, and the cathode portion side was connected by curing an adhesive made of silver paint by high-temperature treatment.

The lead frame 22 on which the capacitor element 21 is installed is set in a mold and molded with an epoxy resin 27 as shown in FIG. 5, and then the lead frame 22 is cut off to obtain a solid electrolytic capacitor. .

Evaluation of the sealing performance of the capacitor thus obtained
After leaving the product in a high temperature bath at 250 ± 5 ° C for 5 minutes,
The thing which performed the heat treatment which repeats taking out inside 3 times
It was tested by the following sealing test. That is,
7 kg / cm ^TwoAtmosphere of radioactive Kr85
After holding in the air for 30 minutes, expose on a photographic plate.
As a result, it is detected that Kr with poor sealing property is press-fitted.
Issued.

The results are shown in (Table 1). (Example 2) A lead frame and a roughened surface in which a copper metal layer made of copper plating was formed by changing the thickness on a surface of an iron base material SPCC having a thickness of 0.1 mm, and the surface was subjected to a surface roughening treatment. The sealing performance was evaluated for a capacitor manufactured in the same manner as in Example 1 using a lead frame that had not been subjected to a surface treatment. The results are also shown in (Table 1).

[0015]

[Table 1]

(Comparative Example 1) Iron-based SPC having a thickness of 0.1 mm
Form a copper metal layer made of copper plating with a thickness of 3 μm on the surface of C, change the thickness of the copper metal layer, apply tin plating, and roughen the surface with a lead frame. The sealing performance was evaluated for a capacitor manufactured using the untreated lead frame in the same manner as in Example 1. The results are shown in (Table 2).

[0017]

[Table 2]

(Comparative Example 2) A nickel plate having a thickness of 0.1 mm was punched out, a copper metal layer made of copper plating was formed on the surface by changing the thickness, and a lead frame whose surface was roughened was used. Then, a capacitor manufactured in the same manner as in Example 1 was evaluated for sealing performance. The results are shown in (Table 2).

Example 3 Iron-based SPC having a thickness of 0.1 mm
C, electrolytically etching in an aqueous solution of 10% hydrochloric acid and 0.5% sulfuric acid at a current density of 100 A / cm ² , changing the thickness, and forming a copper metal layer made of copper plating. The sealing performance of a capacitor manufactured using the same method as in Example 1 was evaluated. The results are shown in (Table 1).

What we have learned from the above results is that
Those with a low melting point metal such as tin plated on the surface have very poor sealing properties, and with metals such as iron and nickel, roughening the surface does not provide much effect,
As in the embodiment of the present invention, a complete sealing property can be obtained only by forming a copper metal layer made of copper plating on the surface of the lead frame and roughening the surface. In addition, it turned out that the surface roughening is effective not only by a method such as mechanical sandblasting but also by a chemical method such as electrolytic etching.

In order to reconfirm the above effects, the first embodiment
After subjecting the solid electrolytic capacitor of Comparative Example 1 to tin plating with a thickness of 10 μm of Comparative Example 1, ten capacitors each having not been subjected to surface roughening treatment were prepared, and these were subjected to a heat treatment in a high-temperature bath at 250 ° C. After that, a result of a high-temperature load life test in which 10 V was applied at 105 ° C. was performed, and the results are shown in FIG. The size of the projection 13 of the capacitor element used here was 3 × 7.
Five capacitors having a thickness of 10 mm and a rating of 22 μF were laminated. As is apparent from FIG.
After the elapse of 0 hours, the capacitor of Example 1 shows almost no capacity deterioration, whereas the capacitor of Comparative Example 1 shows a capacity reduction of 10% or more.

Embodiment 4 Next, application to a tantalum solid electrolytic capacitor was performed. That is, as shown in FIG. 7, about 100 mg of tantalum powder was mixed with a binder, pressed with a tantalum wire 31 having a diameter of 0.3 mm, and then sintered to obtain a molded body 32. The dimensions of the molded body 32 were 3 × 3 × 1 mm. Next, the molded body 32 is subjected to 30V chemical conversion in a phosphoric acid aqueous solution, and thereafter,
The operation of impregnating the molded body 32 with an aqueous solution of manganese nitrate and thermally decomposing at about 250 ° C. was repeated several times to form a manganese dioxide layer. Further, a conductor layer composed of a graphite layer and a silver paint layer was sequentially formed by a known method to form a capacitor element. And this capacitor element,
After forming a copper metal layer made of copper plating with a thickness of 1 μm on the surface of an iron base material SPCC having a thickness of 0.1 mm and having a shape as shown in FIG. 8A, the surface is roughened by sandblasting. Connected to the lead frame 33,
The cathode was connected to the cathode mounting portion 34 using silver paint as an adhesive, and the tantalum wire 31 of the anode portion was connected to the anode mounting portion 35 by resistance welding. Then, the lead frame is placed in a mold and molded with an epoxy resin to form a molded body 36 as shown in FIG. 8B, and unnecessary portions of the lead frame 33 are cut to a predetermined shape. A tantalum solid electrolytic capacitor was obtained. The rating of this capacitor is 10 V, 22 μF.

(Comparative Example 3) As a material for a lead frame, a copper metal layer made of copper plating with a thickness of 3 μm was formed on the surface of an iron base material SPCC, and eutectic solder plating with a thickness of 3 μm was applied thereon. Except for the above, a tantalum solid electrolytic capacitor was obtained in the same manner as in Example 4.

With respect to the tantalum solid electrolytic capacitors manufactured in Example 4 and Comparative Example 3, the results of the above-described evaluation of the sealing property are shown in Table 3 below. From this (Table 3),
The effect of forming a copper metal layer on the surface similarly to the conductive polymer solid electrolytic capacitor and performing the surface roughening treatment was confirmed.

[0025]

[Table 3]

In a high temperature and high humidity of 85 ° C. and 90% RH,
FIG. 9 shows the results of a load life test in which V was applied. Here, similar results were obtained, but the tantalum solid electrolytic capacitor has a small capacity change due to the strong content of the capacitor element, but the leakage current shows a change of one digit or more depending on the humidity.

In the above embodiment, when the lead frame is roughened, the entire surface of the lead frame is roughened. However, from the gist of the present invention, only the contact surface with the exterior resin is partially formed. An effect similar to that of the embodiment can be expected only by rough surface roughening.

[0028]

As described above, according to the solid electrolytic capacitor of the present invention, a copper metal layer is formed on the surface of a lead frame serving as a lead terminal connected to a valve metal portion and a conductor layer portion of a capacitor element. Because the surface is roughened, when soldering a lead frame to a printed circuit board by surface mounting, it is possible to obtain an excellent solderability, and the adhesion to the resin exterior is far more than that of other metals. It can withstand the thermal shock of expansion and shrinkage during surface mounting, and because its surface is roughened, it also has excellent sealing performance, resulting in high reliability A solid electrolytic capacitor can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a comb-shaped electrode punched out of aluminum foil used in Example 1 of the present invention.

FIG. 2A is a plan view of the capacitor element of the first embodiment. FIG. 2B is a cross-sectional view taken along line BB in FIG.

FIG. 3 is a cross-sectional view showing the shape of the lead frame used in Example 1.

4A is a partially enlarged view showing an outline of the lead frame shown in FIG. 3; FIG. 4B is a partially enlarged view showing a state where a capacitor element is mounted on the lead frame shown in FIG. 3A;

FIG. 5 is a schematic view showing a shape in which a capacitor element is resin-molded together with a lead frame in Example 1.

FIG. 6 is a graph showing a comparison of a change in characteristics of a high-temperature life test between an example of the present invention and a comparative example.

FIG. 7 is a perspective view showing the shape of an element sintered body of a tantalum capacitor used in Example 4.

8A is a partial cross-sectional view showing the shape of a tantalum capacitor lead frame used in Example 4; FIG. 8B is a partial cross-sectional view showing a shape obtained by mounting a capacitor element on the lead frame and molding the resin;

FIG. 9 is a graph showing a change in characteristics of the example 4 and the comparative example 3 in a wet life test.

10A is a top view showing a conventional solid electrolytic capacitor, and FIG. 10B is a side view of the solid electrolytic capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Comb electrode 16 Oxide film 17 Conductive material layer 18 Conductive polymer film 19 Graphite layer 20 Silver paint layer 21 Capacitor element 22 Lead frame

──────────────────────────────────────────────────の Continuing on the front page (72) Kenji Kawamura 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Yoji Yamashita 1006 Kazama Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co. (72) Inventor Yoichi Aoshima 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Minoru Yamashita 1006 Odaka Kadoma Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co. JP-A-2-267917 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01G 9/004 H01G 9/15

Claims (3)

(57) [Claims] 1. A capacitor element is formed by sequentially forming an oxide film, a conductive material layer, a conductive polymer film, and a conductor layer on the surface of a valve metal, and is led to a valve metal portion and a conductor layer portion of the capacitor element. In a solid electrolytic capacitor to which a lead frame serving as a terminal is connected and a part of the capacitor element and the lead frame is covered with a mold resin, the lead frame has a copper metal layer on a surface, and the surface is roughened. A solid electrolytic capacitor characterized by being made. 2. The solid electrolytic capacitor according to claim 1, wherein the surface of the lead frame is roughened by a sand blast method. 3. The solid electrolytic capacitor according to claim 1, wherein the surface of the lead frame is roughened by an etching method.