JP2000049056A - Solid-state electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a solid-state electrolytic capacitor to tolerate the thermal shock applied to the capacitor when the capacitor is mounted on the surface of a lead frame by providing a copper metal layer on the surface of the lead frame and approximating the coefficient of line expansion of the lead frame to that of a molding resin. SOLUTION: A solid-state electrolytic capacitor is formed by connecting a lead frame 12 which becomes the lead-out terminal of the capacitor to the valve-action metal section and conductive layer section 10 of a capacitor element 11 and sealing the element 11 and parts of the frame 12 with a molding resin. At the time of forming the capacitor, a copper metal layer is provided at least on the surface of the frame 12 which comes into contact with the molding resin, and the coefficient of liner expansion of the lead frame 12 is approximated to that of the molding resin. In addition, the surface of the lead frame 12 which comes into contact with the molding resin is roughened to an Ra value of >=0.9 μm and a gold metal layer is formed on the external surface of the lead frame 12 exposed from the molding resin.

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 used for various electronic devices, 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 electronic circuits have been mainly assembled by surface mounting. Therefore, of course, the solderability of the lead terminals of the chip component is required,
Heat resistance that can withstand a temperature of more than two hundred and several tens of degrees for a long time has been required. Accordingly, in the field of electrolytic capacitors, which are conventionally said to be poor in heat resistance, chip components that can be surface-mounted have begun to appear due to advances in materials and technologies, as shown in FIGS. 8A and 8B, for example. As described above, the capacitor element is connected to the anode terminal 21 and the cathode terminal 22.
There has been known a solid electrolytic capacitor molded with an exterior resin 23 together with a lead frame that also functions as a lead frame.

[0003]

However, in the conventional solid electrolytic capacitor provided with the exterior resin 23, the sealing property is reduced at the time of surface mounting, and oxygen or water vapor in the air enters from the outside to the inside. There is a fear that the internal capacitor element is deteriorated, and this is due to the following reasons.

(1) To improve the solderability, the surface of the lead frame is plated with tin or solder. However, this low-melting metal is melted by heating during surface mounting. A gap is generated between lead frames made of metal.

(2) Since the base metal (generally iron) used for the lead frame has a different linear expansion coefficient from that of the exterior resin 23, expansion and shrinkage cause a difference between the exterior resin 23 and the lead frame made of metal. Gaps occur.

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

[0007]

In order to solve this problem, a solid electrolytic capacitor according to the present invention comprises connecting a lead frame serving as a lead terminal to a valve metal portion and a conductor layer portion of a capacitor element, respectively. A fixed electrolytic capacitor in which a part of an element and a lead frame is covered with a mold resin, wherein a copper metal layer is provided on the surface of the lead frame and the linear expansion coefficients of the lead frame and the mold resin are approximated. It is.

According to the present invention, since the low-melting metal on the surface of the lead frame is not melted by the heating at the time of surface mounting, and the exterior resin does not expand and shrink significantly as compared with the lead frame, the distance between the exterior resin and the lead frame is reduced. A gap can be prevented from being generated.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is characterized in that an oxide film layer, a conductive polymer layer,
A lead frame serving as a lead terminal is connected to the valve metal part of the capacitor element formed by sequentially forming the conductor layer and the conductor layer part, and a part of the capacitor element and the lead frame is covered with a mold resin. In the solid electrolytic capacitor, a copper metal layer is provided on at least a surface of the lead frame in contact with the mold resin, and the linear expansion coefficient of the lead frame and the mold resin is approximated. Since the low-melting metal on the surface of the lead frame does not melt due to heating during mounting, and the exterior resin does not expand and shrink more greatly than the lead frame, there is no gap between the exterior resin and the metal lead frame. It has the effect that it can be prevented.

According to a second aspect of the present invention, in the first aspect, a surface roughening treatment is performed such that the surface roughness of at least the lead frame in contact with the mold resin is 0.9 μm or more in Ra value. This has the effect of increasing the adhesion to the exterior resin and preventing the gap between the exterior resin and the lead frame made of metal caused by expansion and contraction at a higher level.

According to a third aspect of the present invention, in the first or second aspect of the present invention, a gold metal layer is formed on an outer surface of a lead frame exposed from a mold resin. It has the effect that a solid electrolytic capacitor can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(Embodiment 1) First, as shown in FIG.
A polyimide insulating tape 2 coated with an adhesive on one side is attached to a predetermined position of an aluminum foil 1 which is a valve metal having a thickness of 100 μm and punched out to obtain a comb-shaped electrode 6 as shown in FIG. . The insulating tape 2 of the comb-shaped electrode 6 is formed such that the protrusion 3 of the comb-shaped electrode 6 is
And the anode part 5. Next, polymerization is performed in a polymerization solution in which pyrrole is used as the comb-shaped electrode 6 as a polymerizable substance and triisopropylnaphthalenesulfonic acid is used as a supporting electrolyte in water to form a conductive polymer film 8 (see FIG. 2). did. Further, a conductive layer composed of a graphite layer 9 and a silver paint layer 10 is sequentially formed thereon by a known method.
The projection 3 was cut along the line A to obtain the capacitor element 11 shown in FIGS. 2 (a) and 2 (b).

Next, as shown in FIG.
Punched iron base material (SPCC)
And a thickness of 1 μm is formed on the surface of the lead frame 12.
After forming a copper metal layer made of copper plating, the surface was roughened by sandblasting. Subsequently, FIG.
A small amount of silver paint was applied to a position corresponding to the cathode side of the capacitor element 11 on the lead frame 12 shown in (a) and (b), and the capacitor element 11 was placed by lamination. At this time, the cathode side of the capacitor element 11 was fixed by bending the cathode bottom stopper 13 and the cathode side stopper 14 at right angles as shown in FIGS. 4 (a) and 4 (b). On the other hand, the anode side of the capacitor element 11 is bent in two steps,
The anode side stopper 15 and the anode pressing part 16 were brought into close contact with each other. Further, the anode portion was joined by performing laser welding from above the anode pressing portion 16, and the cathode portion was connected by hardening an adhesive made of silver paint by high-temperature treatment.

The lead frame 12 on which the capacitor element 11 is mounted and connected as described above is arranged in a mold (not shown), and is molded with an epoxy resin 17 as shown in FIG. Thus, a solid electrolytic capacitor was obtained.

In order to evaluate the sealing performance of the solid electrolytic capacitor obtained in this way, a heat treatment was performed in which the solid electrolytic capacitor was left in a high-temperature bath at 250 ± 5 ° C. for 5 minutes and then taken out to room temperature three times. Was evaluated by performing the following sealing test. After holding the test sample of the solid electrolytic capacitor in an atmosphere of radiation Kr85 of 7 kg / cm ² for 30 minutes, it was exposed on a photographic dry plate to detect that the sealing property was poor and Kr was press-fitted. The results are shown in (Table 1).

[0017]

[Table 1]

As can be seen from Table 1, in the lead frame 12 using an iron material, the sealing property is improved by using a mold resin (dicyclo) having a linear expansion coefficient close to the linear expansion coefficient of iron of 1.17. It turns out that there is a great effect.

(Embodiment 2) After a copper metal layer made of copper plating is formed on the surface of an iron base material (SPCC) having a thickness of 0.1 mm, the surface is roughened by sandblasting. With respect to the solid electrolytic capacitor obtained in the above-described first embodiment manufactured by changing the surface roughness Ra value or using the lead frame 12, the sealing performance was evaluated by the method used in the first embodiment. The result is shown in FIG.

As can be seen from FIG. 6, the first embodiment is described.
By joining the solid electrolytic capacitor obtained in the above to the lead frame 11 which has been subjected to a surface roughening treatment so that the surface roughness becomes 0.9 or more in Ra value, it is possible to suppress a decrease in sealing property. is there.

(Embodiment 3) A gold plating layer 18 as a protective metal layer is formed on the anode terminal and the cathode terminal exposed from the epoxy resin 17 of the solid electrolytic capacitor manufactured in Embodiment 2 as shown in FIG. . The results of measuring the impedance characteristics of the solid electrolytic capacitor manufactured in this way and the sample in which silver plating, tin-lead plating, and tin plating layer were formed instead of the gold plating layer 18 were obtained (Table 2).
Shown in

[0022]

[Table 2]

As is apparent from Table 2, the formation of the gold plating layer 18 improves the electric conductivity, so that a solid electrolytic capacitor having excellent impedance characteristics can be obtained.

In this embodiment, an example in which the gold plating layer 18 is used as the material of the protective metal layer has been described.
The present invention is not limited to this, and it goes without saying that a solid electrolytic capacitor having excellent impedance characteristics can be obtained by using a material having excellent electric conductivity.

[0025]

As described above, in the solid electrolytic capacitor according to the present invention, 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. Since the surface is roughened and the linear expansion coefficient of the lead frame and the mold resin is approximated, when the lead frame is surface-mounted on a printed circuit board by soldering, it is only possible to obtain an excellent solderability. In addition, it can withstand the thermal shock of expansion and contraction during surface mounting, and can obtain a highly reliable solid electrolytic capacitor having excellent sealing performance.

[Brief description of the drawings]

FIG. 1 is a plan view of a comb-shaped electrode punched out of aluminum foil used in Embodiment 1 of the present invention.

FIG. 2A is a plan view of the capacitor element according to the first embodiment; FIG.

FIG. 3 is a plan view showing a lead frame used in the first embodiment.

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

FIG. 5 is a plan view showing a state in which the capacitor element is resin-molded together with the lead frame in the first embodiment.

FIG. 6 is a characteristic diagram showing a relationship between poor airtightness and surface roughness according to the second embodiment.

FIG. 7 is a sectional view showing a configuration of a solid electrolytic capacitor according to a third embodiment of the present invention.

FIG. 8A is a top view showing a conventional solid electrolytic capacitor. FIG. 8B is a front view of the solid electrolytic capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Aluminum foil 2 Insulating tape 3 Protrusion part 4 Cathode part 5 Anode part 6 Comb electrode 7 Oxide film layer 8 Conductive polymer film 9 Graphite layer 10 Silver paint layer 11 Capacitor element 12 Lead frame 13 Cathode bottom stop 14 Cathode side stop 15 Anode side stop 16 Anode holding part 17 Epoxy resin 18 Gold plating layer

Claims (3)

[Claims] 1. A capacitor element formed by sequentially forming an oxide film layer, a conductive polymer layer, and a conductor layer on the surface of a valve metal, and serving as a lead terminal on the valve metal part and the conductor layer part of the capacitor element. In a solid electrolytic capacitor in which a lead frame is connected and a part of the capacitor element and the lead frame is covered with a mold resin, a copper metal layer is provided on at least a surface of the lead frame in contact with the mold resin, and the lead frame A solid electrolytic capacitor that approximates the linear expansion coefficient of the mold resin. 2. The solid electrolytic capacitor according to claim 1, wherein at least a surface of the lead frame in contact with the mold resin has been subjected to a surface roughening treatment so that the surface roughness has an Ra value of 0.9 μm or more. 3. The solid electrolytic capacitor according to claim 1, wherein a gold metal layer is formed on an outer surface of the lead frame exposed from the mold resin.