JP2001244147A - Solid electrolytic capacitor and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor which can make the gap between a capacitor element and the outer periphery of a package as small as possible while being simple manufacture and incorporate the element of a volume as much as possible to the same external size as that of the package in the package, and to provide the manufacturing method of the capacitor. SOLUTION: A capacitor element 1 is formed in a structure, where one end part of an anode lead 11 is buried in a sintered body formed by sintering valve action metal powder through one wall surface of the sintered body and a cathode 12 is formed on the outer peripheral wall of the sintered body. A first tabular lead 2 is fixed on the outer peripheral wall 12 of the element 1 with a conductive bonding agent, so that the outer peripheral wall 12 is connected electrically with the lead 2. A second lead 3 is provided counter posed to the lead 2 and this lead 2 and the exposed surface of the lead 3 form the same plane and a metal wire 4 is connected between the leads 11 and 3.

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 made of a sintered body of a valve metal such as tantalum powder and a method for producing the same. More particularly, the present invention relates to a solid electrolytic capacitor having a structure in which an assembling process is simple, a large capacitor element is built in while minimizing a package as much as possible, and electric characteristics such as a capacitance value can be improved, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In a conventional solid electrolytic capacitor, as shown in FIG. 8, an anode lead 11 of a capacitor element 1 is electrically connected to a first external lead 2 by resistance welding or the like. Are electrically connected to the second external leads 3 via the fuses 4, respectively, and the periphery thereof is formed by molding with a resin and covering with a resin package 5. . The first and second external leads 2 and 3 are formed into a structure shown in FIG. 8 by being cut and separated from the lead frame after the resin package 5 is formed by molding, and formed. .

Further, Japanese Patent Application Laid-Open No. 8-148386 discloses a solid electrolytic capacitor having a structure as shown in FIG. That is, in the structure shown in FIG.
External electrodes 22 and 23 are formed on the back surface of the insulating substrate 21, and are connected to the electrodes 22 a and 23 a on the upper surface via conductive members 24 in through holes of the insulating substrate 21.
The outer peripheral portion of the capacitor element 1 is a lower portion 21b of the substrate 21
The anode lead 11 is formed by being connected to the electrode 23a on the surface of the portion 21a raised by the step of the insulating substrate 21. The upper surface is covered with a case 5.

[0004]

The structure shown in FIG. 8 has the advantage that it can be manufactured at very low cost because it can be manufactured using a lead frame. However, since a space for covering with the package 5 is required on both upper and lower sides of the capacitor element 1, the ratio of the capacitor element 1 to the external dimensions of the package cannot be sufficiently increased. In particular, as electronic components have become lighter and thinner in recent years, a solid electrolytic capacitor having a very small package has been required, and an improvement in characteristics such as an increase in capacitance has been required. In order to improve the characteristics such as increasing the capacitance value, the size of the capacitor element must be increased, but it is incompatible with the miniaturization of the package, and how large a capacitor element is built in a small package Is an issue.

In the structure shown in FIG. 9, the portion occupied by the package can be very small and reduced, and the ratio of the capacitor element to the external dimensions can be increased. In addition to the need to form a film, it is necessary to provide a through hole in the substrate and to connect the upper and lower conductive films with a conductive member, resulting in a problem that the manufacturing cost of the substrate is increased. In particular, since the anode lead is located at the center of the capacitor element, it is necessary to increase the thickness of the insulating substrate at that portion to form a stepped portion, and furthermore, it is necessary to form a through hole inside the substrate. There is a problem that the manufacturing cost is very high.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is possible to easily manufacture a semiconductor device using a lead frame while minimizing the gap between the capacitor element and the outer periphery of the package. It is an object of the present invention to provide a solid electrolytic capacitor having a structure in which a capacitor element having a volume as large as possible can be incorporated for the same external dimensions, and a method for manufacturing the same.

Another object of the present invention is to provide a fuse function even in such a small package, and when the temperature of the capacitor element rises abnormally due to insulation failure in a dielectric film or the like, the two electrodes are used. It is an object of the present invention to provide a solid electrolytic capacitor having a structure that can open the space.

Another object of the present invention is to provide a structure in which a sintered body of a capacitor element is mounted directly on a lead frame, so that the anode lead side of the sintered body is inclined and does not fall into a gap between both leads. An object of the present invention is to provide a solid electrolytic capacitor having such a structure.

[0009]

The solid electrolytic capacitor according to the present invention comprises an anode lead formed by embedding one end of the valve metal powder sintered body from one wall surface of the sintered body and the sintered body. A capacitor element having a cathode formed on the outer peripheral wall thereof, a plate-shaped first lead fixed by a conductive adhesive so that the outer peripheral wall of the capacitor element is electrically connected, A second lead that is provided to face the same plane and is electrically connected to the anode lead; and a package that covers a capacitor element portion provided on the first lead and the second lead. I have.

With this structure, the capacitor element can be manufactured by directly mounting the capacitor element on the lead frame and coating the upper surface with a resin. Also, the upper surface can be manufactured with very small dimensions. As a result, a large capacitor element can be built in a package with extremely small external dimensions,
By increasing the capacitance value or the particle size of the powder, electrical characteristics such as a reduction in leakage current can be improved.

[0011] The connection between the anode lead and the second lead via a metal wire having a fuse function of fusing when the temperature exceeds a predetermined temperature causes heat generation due to short-circuit due to deterioration of the dielectric film and the like. This is preferable because the current can be automatically cut off, and a burnout accident or the like can be prevented.

The length of the first lead in the axial direction of the capacitor element is longer than the length of the second lead in the axial direction of the capacitor element. It is preferable that it is stably mounted on the lead and that the upper end does not become inclined and is exposed from the gap between the first lead and the second lead. Here, the axial direction of the capacitor element means the direction in which the anode lead embedded in the sintered body extends.

The back surface of the long first lead is removed by a certain length from the side facing the second lead and is formed thin, so that the external lead has the same size as a conventional solid electrolytic capacitor. In this way, it is possible to prevent the capacitor element from being tilted and the upper end thereof being exposed to the gap between the first lead and the second lead.

[0014] Even if the first lead has a structure in which at least a portion of a portion longer than the second lead has a width smaller than that of a portion having the same length as the second lead, the length of the external electrode can be reduced. The length is almost the same as that of the conventional structure, and a short circuit between both electrodes due to solder or the like can be prevented.

The method for manufacturing a solid electrolytic capacitor element according to the present invention comprises: (a) a step of forming a capacitor element; (b) a step of forming a lead frame such that first and second plate-shaped leads face each other; (C) attaching a tape to the back surface of the lead frame so as to close a gap between the first lead and the second lead; and (d) placing one surface of the outer peripheral wall of the capacitor element on the first lead. Fixing with a conductive adhesive, (e) bonding one end of a metal wire on the second lead, and (f) electrically connecting the other end of the metal wire to the anode lead of the capacitor element. (G) covering the capacitor element portion on the first lead and the second lead.

[0016]

Next, a solid electrolytic capacitor of the present invention and a method for manufacturing the same will be described with reference to the drawings. The solid electrolytic capacitor according to the present invention is, as shown in FIG. 1, a cross-sectional explanatory view showing one embodiment of the solid electrolytic capacitor according to the present invention. One end is embedded, and the capacitor element 1 is formed by forming the cathode 12 on the outer peripheral wall of the sintered body. The outer peripheral wall 12 of the capacitor element 1 is fixed by a conductive adhesive so as to be electrically connected to the first lead 2 having a plate shape. The first lead 2 and the exposed surface (the surface opposite to the surface on which the capacitor element 1 and the like are provided on the back surface) are opposed to each other so as to form the same plane, and the second lead 3 is provided. A metal wire 4 is connected between the second leads 3.

Further, the first lead 2 and the second lead 3
The package 5 is formed so as to cover the capacitor element 1 and the metal wire 4 provided thereon.

The first lead 2 and the second lead 3 are made of a copper alloy or a 42 alloy containing 90% or more of copper in the same manner as a lead using a conventional lead frame.
The first lead 2 and the second lead 3 are formed by punching or etching a plate having a thickness of about 3 mm, and are formed in a state of a lead frame in which the first leads 2 and the second leads 3 face each other and are connected to each other. That is, as shown in FIG.
The groove 31 is formed in the plate 30 by punching or etching a groove 31 corresponding to the interval between the first lead 2 and the second lead 3. In FIG. 2, P1, P2,... Each correspond to one capacitor, and as shown in FIG. 2, a large number of P1, P2,. After being formed,
Each solid electrolytic capacitor is formed by cutting at the boundary of each element. The groove 32 at the end of the plate 30
Indicates the cutting position of the end of the solid electrolytic capacitor to be cut and separated, and may be omitted.

The capacitor element 1 has the same structure as a conventional element. Powder of a valve metal such as tantalum, aluminum, or niobium is formed into a square shape having an anode lead 11 embedded in one wall surface, and is formed by anodic oxidation. T around the powder
an oxide film such as a ₂ O ₅ and a manganese dioxide layer are formed,
A cathode 12 is formed by forming a manganese dioxide layer, a graphite layer, a silver layer, and the like on the outer periphery of the sintered body. The size of the sintered body is, for example, a bottom area of 0.3 mm square to several meters.
It is formed in about m square. In addition, 13 is a Teflon ring. For example, as shown in FIG.
In the case of a package having a width of about m and a width and depth B of about 0.8 mm, in the conventional structure shown in FIG. 8, the size of the sintered body of the capacitor element 1 is 0.5 mm square and 0.7 mm high. However, the height was about 0.6 mm square, and the height could be increased to about 1.0 mm.
At this time, the length C of the first lead 2 and the second lead 3 is both about 0.4 mm, and the interval D is about 0.8 mm, which is the same length as the conventional structure.

The sintered body of the capacitor element 1 is fixed on the first lead 2 by a conductive adhesive such as silver paste, and the anode lead 11 is connected to the second lead 3 by, for example, 300 mm.
They are connected by a metal wire 4 having a fuse function that melts at about ° C. One end of the metal wire 4 is erected upward by wire bonding or the like on the second lead 3, and the other end is electrically connected to the anode lead 11. With this structure, it is possible to easily and surely make an electrical connection with the anode lead 11 located at a distance from the second lead 3. By using a wire having a fuse function as the metal wire 4, a burnout accident can be prevented. That is, when the dielectric film formed around the powder of the capacitor element 1 is damaged and the insulating property is reduced and the current leaks, the temperature rises. The current can be cut off before that. For this purpose, a material that melts at about 260 ° C. or higher, which is lower than about 600 ° C. at which the sintered body is burned and does not melt at a temperature such as soldering, is used.

The package 5 is formed by applying a paste-like resin by screen printing or the like in a state in which the capacitor element 1 is mounted and assembled, and thermally curing the resin. That is, it is not formed by injection molding as in the conventional structure shown in FIG. 8, but is formed only by coating and heating because the amount is small. In this case, a tape or the like is attached to the back surface of the plate-shaped body 30 so that the paste-shaped resin or the like does not flow out of the groove 31 in the plate state 30, and then the paste-shaped resin is coated. In addition, by coating under reduced pressure in the state of the taped lead frame, the paste-like resin is filled even in a narrow space without forming voids.

Next, a method of manufacturing the solid electrolytic capacitor will be described. For example, tantalum powder is formed into the above-mentioned size, and one wall has a thickness of, for example, 0.1 mm.
By embedding a tantalum wire of about 2 mmφ and sintering in a vacuum, a sintered body in which the anode lead 11 is embedded in one wall surface (upper surface) is formed. Then, a Teflon ring 13 is put on the base of the anode lead 11, and several tens of the tip of the anode lead 11 of the capacitor element 1 are welded to a stainless steel bar (not shown) formed of, for example, a stainless plate.

[0023] Then, together amount which is welded to stainless steel bar, for example, immersed in an aqueous solution of phosphoric acid by anodic oxidation of the anode lead 11 as an anode, oxidation of Ta ₂ O ₅ on the periphery of the tantalum powder A substance film is formed (chemical conversion treatment). Thereafter, the step of dipping in a manganese nitrate aqueous solution to form a manganese dioxide layer (not shown) on the inside and the outer peripheral surface of the sintered body and the above-described oxide film forming step (re-chemical conversion treatment) are repeated several times. The Teflon ring 1 is used to prevent the manganese nitrate aqueous solution from
3 are provided. Further, a graphite layer (not shown) is formed on the outer surface, and a silver layer (not shown) is further formed on the outer surface. Thus, the capacitor element 1 whose surface is the cathode 12 is formed.

The capacitor element 1 manufactured as described above
Are separated one by one from the stainless steel bar, and the sintered body of the capacitor element 1 is adhered to the first lead 2 of the lead frame with a conductive adhesive (not shown). A metal wire 4 having a fuse function is provided on the surface side of the second lead 3.
Is set up by wire bonding. Then, the other end of the metal wire 4 is electrically connected to the anode lead 11 by thermocompression. A tape is stuck on the back side of the lead frame to which the capacitor element 1 is attached,
The surface of the capacitor element 1 and the metal wires 4 are coated with a paste-like resin by screen printing or the like under reduced pressure in a vacuum state to form a package 5. Thereafter, the solid electrolytic capacitor having the structure shown in FIG. 1 is obtained by cutting the lead frame having the package formed on the entire surface. In addition, by performing solder plating in the state of the lead frame, solderability at the time of mounting can be improved.

According to the present invention, while the package is simply covered using the lead frame to the extent that the capacitor element is hidden, the distance between the capacitor element and the package can be made very thin. Can be. As a result, the capacitor element can be increased for the same package size, and the capacitance value can be increased. Also, if the capacitance value is not increased, the powder can be coarsened to reduce the impedance and leakage current, so that the electrical characteristics can be improved and the electrical characteristics can be maintained in the same way as conventional capacitors By doing so, the package can be made smaller.

As described above, by setting the length of the lead in the state of the lead frame to be the same as the length of the soldering portion of the external lead of the conventional structure, the capacitor element can have the same outer shape as the conventional structure. Can be bigger. However, in the assembling step of bonding the outer periphery of the capacitor element 1 to the first lead 2 with a conductive adhesive, before the adhesive is hardened, as shown in FIG. The end is inclined between the first lead 2 and the second lead 3, and there is a risk that the cathode is exposed on the back surface or comes into contact with the second lead 3. A structure for preventing such a problem is shown in FIGS.

In the structure shown in FIG. 3, the length E of the first lead 2 is formed to be about 0.8 mm, which is about twice the length in the above-described example. That is, as shown in the bottom view of FIG. 3B, the length C of the second lead 3 is about 0.4 mm as in the example shown in FIG. Is about 0.4 mm, which is about half of the example shown in FIG. With this structure, the length of the lead is slightly different from that of the conventional structure, but the first lead 2 is long and the capacitor element 1 can be manufactured without tilting. As a result, there is no danger that the cathode of the capacitor element 1 is exposed from the package 5 or comes into contact with the second lead 3. The other parts are the same as in the example shown in FIG. 1, and the same parts are denoted by the same reference numerals and description thereof will be omitted.

FIG. 4 is a modified example of the structure of FIG.
It is shown in a bottom view similar to (b). That is, FIG.
FIG. 4A is a view in which the width of the elongated portion 2a of the first lead 2 is reduced, and FIG. It is extremely thin. With such a structure,
When soldering to a printed circuit board or the like, it becomes difficult for the solder to flow to the tip, so that soldering can be performed as if it were the same length as a conventional lead, and the capacitor element 1 can be prevented from being tilted. In order to obtain such a structure, as shown in FIGS. 5A and 5B, a plan view of a lead frame similar to that shown in FIG. 2, an elongated portion 2a of the first lead 2 remains in the groove 31. It can be obtained simply by forming as follows. Such a lead frame 30 can be obtained simply by forming a punching die into this shape.

FIG. 6 shows still another example of the structure. As shown in FIG. 3, the back side of the elongated portion 2d of the first lead 2 is thinned by etching or the like, while the mounting portion of the capacitor element 1 is left. The length of the first lead 2 exposed on the back surface is the same as that of the conventional example, as in the example shown in FIG. By forming the lead frame in this structure, the resin flows into the etched portion of the first lead 2 (the back side of the elongated portion 2d), and a part of the package 5 is formed. The shape is exactly the same as the example shown in FIG. On the other hand, the capacitor element 1
Can be stably mounted on the first lead 2 and inclination can be prevented. 1 and 3 are denoted by the same reference numerals, and description thereof is omitted.

[0030]

According to the present invention, the waste of space can be almost eliminated while using a lead frame, and a large capacitor element can be built in for the same external dimensions. As a result, it is possible to obtain a solid electrolytic capacitor in which the capacitance value of the capacitor is increased, the leakage current and the like are reduced, and the electrical characteristics are improved. Further, since it is not necessary to prepare a substrate having a step, and the assembly can be very easily performed, a solid electrolytic capacitor can be obtained at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional explanatory view of an embodiment of a solid electrolytic capacitor according to the present invention.

FIG. 2 is an example of a lead frame constituting both leads of FIG. 1;

FIG. 3 is an explanatory view of a cross section and a bottom surface showing another embodiment of the solid electrolytic capacitor according to the present invention.

FIG. 4 is an explanatory bottom view showing a modification of the embodiment of FIG. 3;

FIG. 5 is a view showing a shape of a lead frame when the structure shown in FIG. 4 is used.

FIG. 6 is an explanatory view of a cross section and a bottom surface showing a modification of the embodiment of FIG. 3;

FIG. 7 is a diagram illustrating a problem that occurs when a capacitor element is directly fixed on a lead formed by a lead frame and assembled.

FIG. 8 is an explanatory sectional view showing an example of a conventional solid electrolytic capacitor.

FIG. 9 is an explanatory sectional view showing another example of a conventional solid electrolytic capacitor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Capacitor element 2 1st lead 3 2nd lead 4 Metal wire 5 Package

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H01G 9/00 H01G 9/05 C 9/24 C

Claims (6)

[Claims] 1. A capacitor element having an anode lead formed by embedding one end portion from one wall surface of a sintered body of a valve metal powder into the sintered body and a cathode formed on an outer peripheral wall of the sintered body. A plate-shaped first lead fixed by a conductive adhesive so that an outer peripheral wall of the capacitor element is electrically connected to the first lead, and the first lead and the first lead are opposed to each other so that at least an exposed surface is flush with the first lead. A solid electrolytic capacitor comprising: a second lead electrically connected to the anode lead; and a package covering a capacitor element portion provided on the first lead and the second lead. 2. The solid electrolytic capacitor according to claim 1, wherein the anode lead and the second lead are connected via a metal wire having a fuse function of fusing when the temperature exceeds a predetermined temperature. 3. The solid electrolytic capacitor according to claim 1, wherein the length of the first lead in the axial direction of the capacitor element is formed longer than the length of the second lead in the axial direction of the capacitor element. . 4. The solid electrolytic capacitor according to claim 3, wherein the back surface side of the elongated first lead is formed thin by removing a predetermined length from the side facing the second lead. 5. The solid according to claim 3, wherein a width of at least a part of the first lead longer than the second lead is formed smaller than a width of a part having the same length as the second lead. Electrolytic capacitor. 6. A process for forming a capacitor element,
(B) forming a lead frame such that the plate-shaped first and second leads face each other; (c) closing a gap between the first and second leads on the back surface of the lead frame. The process of sticking the tape,
(D) fixing one surface of the outer peripheral wall of the capacitor element on the first lead with a conductive adhesive;
Bonding one end of a metal wire on the lead, (f) electrically connecting the other end of the metal wire to the anode lead of the capacitor element, and (g) the first lead and the second lead. A method for producing a solid electrolytic capacitor element comprising a step of covering the above capacitor element part.