JP2001358038A - Method of manufacturing tantalum electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method by which a tantalum electrolytic capacitor can be manufactured easily and surely by mounting a capacitor element directly on a lead frame. SOLUTION: At least part of a water-repellent synthetic resin ring 13, such as a Teflon(R) ring, etc., provided for preventing creeping at the time of forming a cathode 12 on the metallic sintered compact of a tantalum electrolytic capacitor element 1 is formed to have a size larger than that of an outer peripheral wall 12 which is the cathode 12. Consequently, the largely formed portion of the ring 13 is brought into contact with a sheet 16 which blocks the gap portion 31 between first and second leads 2 and 3. Therefore, the falling of the cathode 12 of the element 1 into the space between the leads 2 and 3 can be prevented certainly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a large number of tantalum electrolytic capacitors in the same process.

[0002]

2. Description of the Related Art As a conventional tantalum electrolytic capacitor,
For example, Japanese Patent Application Laid-Open No. 8-148386 discloses a structure having a structure as shown in FIG.

[0003] In the structure shown in FIG.
External electrodes 22 and 23 are formed on the back surface of
The outer periphery of the capacitor element 1 is fixed to the lower portion 21b of the substrate 21 so as to be connected to the electrodes 22a and 23a on the upper surface via the conductive member 24 in the through hole of the first substrate 21. Is formed by being connected to the electrode 23a on the surface of the portion 21a raised by the step. The upper surface is covered with a case 25.

In the structure shown in FIG. 9, the portion occupied by the package can be reduced very small, and the ratio of the capacitor element to the external dimensions can be increased. It is necessary to provide a through hole in the substrate and connect the upper and lower conductive films with a conductive member.
There is a problem that the manufacturing cost of the substrate is high. 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.

In order to solve the problem of such a conventional tantalum electrolytic capacitor, it is necessary to mount a tantalum electrolytic capacitor element on a thin metal plate such as a lead frame as shown in FIG. Conceivable. FIG.
, The first lead 2 and the second lead 2
A lead 3 is prepared, a tantalum electrolytic capacitor element 1 is placed on a first lead 2, and a metal wire 4 is placed on a second lead 3.
Is provided, and the anode lead 11 of the capacitor element 1 and the metal wire 4 are electrically connected. Finally, a package is made of the resin 5 to form a tantalum electrolytic capacitor.

[0006]

The tantalum electrolytic capacitor of the prior art shown in FIG. 8 is constructed by mounting a tantalum electrolytic capacitor element on a lead formed by a lead frame, so that the volume efficiency of the capacitor element is high. Thus, a capacitor having a larger capacity can be realized. In addition, since a substrate having a stepped portion is not required unlike the related art shown in FIG. 7, the manufacturing cost can be reduced.

However, the capacitor element 1 is connected to the first lead 2.
Is mounted, the outer periphery of the capacitor element 1 is adhered to the first lead 2 with a conductive adhesive. Before the adhesive hardens in the process, as shown in FIG. The cathode on the side of the anode lead 11, that is, the cathode falls between the first lead 2 and the second lead 3, and the cathode is easily exposed on the lower surface of the tantalum electrolytic capacitor chip.

The present invention has been made in order to solve such a problem, and provides a method for manufacturing a tantalum electrolytic capacitor in which a capacitor element is directly mounted on a lead frame and can be manufactured easily and reliably. The purpose is to do.

[0009]

According to a first aspect of the present invention, there is provided a method of manufacturing a tantalum electrolytic capacitor, comprising the steps of:
A step of preparing a tantalum electrolytic capacitor element 1 having a size exceeding the outer peripheral wall 12 serving as a cathode and having a water-repellent synthetic resin ring 13 provided at the base of the anode lead 11; (C) forming a lead frame so that the first lead 2 and the second lead 3 face each other, and (c) closing a gap between the first lead and the second lead on the back surface of the lead frame. Attaching a sheet or tape 16;
A step of mounting, on the lead 2, one surface of the outer peripheral wall 12 of the tantalum electrolytic capacitor element 1 in which the water-repellent synthetic resin ring 13 is formed to have a size larger than the outer peripheral wall 12 serving as a cathode. (E) bonding one end of the metal wire 4 on the second lead 3; (f)
Electrically connecting the other end of the metal wire 4 to the anode lead 11 of the capacitor element, and (g) covering the capacitor element portion on the first lead 2 and the second lead 3 with resin 5. A process.

According to the method of manufacturing a tantalum electrolytic capacitor according to claim 1 of the present invention, the tantalum electrolytic capacitor element 1
At least a part of the ring 13 made of a water-repellent synthetic resin such as a Teflon ring provided for preventing the swelling when the cathode 12 is formed on the metal sintered body is formed to have a size exceeding the outer peripheral wall 12 which is the cathode. As a result, the large portion of the water-repellent synthetic resin ring 13 is provided on the sheet or tape 16 that closes the gap 31 between the first lead 2 and the second lead 3. Thereby, the cathode 12 of the tantalum electrolytic capacitor element 1 is connected to the first lead 2 and the second lead 3.
Of the tantalum electrolytic capacitor chip, and the cathode is not exposed on the lower surface of the tantalum electrolytic capacitor chip. In addition, since it is only necessary to change the dimensions of the water-repellent synthetic resin ring 13 which has been conventionally used for preventing swelling, no new burden is generated.

Further, since the tantalum electrolytic capacitor element 1 can be manufactured by directly mounting the tantalum electrolytic capacitor element 1 on the lead frame and coating the upper surface thereof with the resin 5, the gap between the tantalum electrolytic capacitor element 1 and the package is smaller than the lower surface side. However, the upper surface side can be manufactured with very small dimensions. As a result, a large capacitor element can be built in a package having a very small external dimension, and the electrical characteristics such as reducing the leak current by increasing the capacitance value or increasing the particle size of the powder are improved. be able to.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a tantalum electrolytic capacitor according to the present invention and a method for manufacturing the same will be described with reference to the drawings.

[0013] The tantalum electrolytic capacitor according to the present invention comprises:
As shown in FIG. 1, a cross-sectional explanatory view of one embodiment of a tantalum electrolytic capacitor according to the present invention, one end of an anode lead 11 is embedded from one wall surface of a sintered body of valve metal powder, A tantalum electrolytic capacitor element (hereinafter, capacitor element) 1 is formed by forming a 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.

A Teflon ring 13, which is a ring made of a water-repellent synthetic resin, has a metal
Are formed to prevent swelling when forming the capacitor element. Usually, as shown by a Teflon ring 13 'in FIG. . In the present invention, at least a part of the Teflon ring 13 is formed on the outer peripheral wall 12 serving as a cathode.
It is formed in a size exceeding. The extent beyond the outer peripheral wall 12 is set equal to or slightly smaller than the thickness of the first lead 2 and the second lead 3. The use of the Teflon ring 13 allows the capacitor element 1
Of the cathode 12 is prevented from falling between the first lead 2 and the second lead 3.

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

Now, a method for manufacturing a tantalum electrolytic capacitor according to the present invention will be described sequentially.

First, the capacitor element 1 has the same structure as a conventional element, and a sintered body of tantalum powder as a valve metal is formed into a rectangular parallelepiped shape having an anode lead 11 embedded in one wall surface. As a result, an oxide film such as Ta ₂ O ₅ and a manganese dioxide layer are formed around it, and a manganese dioxide layer, a graphite layer, a silver layer and the like are formed on the outer periphery of the sintered body to form the cathode 12. The size of the sintered body is formed, for example, with a bottom area of about 0.3 mm square to several mm square. For example, as shown in FIG. 1, when a package having a height A of about 1.6 mm and a width and depth B of about 0.8 mm is used, the size of the sintered body of the capacitor element 1 is 0.6 mm square and the height is 0.6 mm. Could be increased to about 1.0 mm. At this time, the width C of each of the first lead 2 and the second lead 3 is about 0.4 mm, and the interval D is about 0.8 mm, which is the same length as the conventional structure.

The manufacture of the capacitor element 1 is performed as follows. First, the anode lead 11 is formed by molding a tantalum powder into the above-described size and embedding a tantalum wire having a thickness of, for example, about 0.2 mmφ in one wall surface and sintering it in a vacuum. To form a sintered body embedded therein. Then, a Teflon ring 13 at least partially formed to have a size exceeding the outer peripheral wall 12 serving as a cathode is put on the base of the anode lead 11, and the tip of the anode lead 11 is formed of, for example, a stainless steel plate. Approximately several tens are welded to the stainless steel bar (not shown).

[0019] 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. A Teflon ring 13 having water repellency is provided so that the manganese nitrate aqueous solution does not seep into the anode lead 11.

The Teflon ring 13 may be formed, for example, in a circular shape with a dimension smaller than the thickness of the capacitor element 1 in order to prevent the manganese nitrate aqueous solution from oozing up, which is the original purpose. However, according to the present invention, during manufacture, the cathode 12 of the capacitor element 1 is connected to the first lead 2 and the second lead 2.
Since the purpose is to prevent the Teflon ring 13 from dropping between the lead 3 and the lead 3, at least a part of the Teflon ring 13 is formed to have a size exceeding the outer peripheral wall 12 which is a cathode.
The extent beyond the outer peripheral wall 12 is set equal to or slightly smaller than the thickness of the first lead 2 and the second lead 3.

Further, a graphite layer (not shown) is formed on the outer surface of the sintered body, and a silver layer (not shown) is further formed on the outer surface of the sintered body. An element 1 is formed. The capacitor elements 1 manufactured in this manner are separated from the stainless steel bar one by one to obtain individual capacitor elements 1.

Next, the first lead 2 and the second lead 3
Is made of a copper alloy or a 42 alloy containing 90% or more of copper as in the case of a lead using a conventional lead frame.
Punching a plate-like body with a thickness of about 0.05 to 0.3 mm,
Each first lead 2 and second lead 2 are formed by etching.
The leads 3 are formed in a state of a lead frame facing and connected to each other. That is, as shown in FIG. 2, the first lead 2
Further, the groove 31 is formed by punching or etching the groove 31 corresponding to the interval between the second leads 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. In addition,
The groove 32 at the end of the plate 30 indicates the cutting position of the end of the tantalum electrolytic capacitor to be cut and separated.
You don't have to.

Next, an adhesive sheet or tape 16 is adhered to the back surface of the lead frame to close the groove 31 of the plate-like lead frame 30. Then, a large number of capacitor elements 1 are mounted at predetermined positions on the lead frame 30 in this state. At this time, the sintered body portion of the capacitor element 1
That is, the cathode portion 12 is adhered to the first lead 2 with a conductive adhesive such as silver paste, and a portion formed so as to extend beyond the outer peripheral wall 12 of the Teflon ring 13 is attached to the sheet 16 to form a capacitor element. 1 will be supported. For this reason, even while the adhesive is hardened, the capacitor element 1 maintains a substantially horizontal position, and the cathode portion 12 does not fall between the first lead 2 and the second lead 3,
The capacitor element 1 maintains a stable state as shown. As a result, the cathode is not exposed on the lower surface of the tantalum electrolytic capacitor chip, and the size of the water-repellent synthetic resin ring 13 conventionally used for preventing bleeding can be changed. There is no burden. On the other hand, the anode lead 11 is
For example, they are connected by a metal wire 4 having a fuse function that melts at about 300 ° C. This state is an intermediate state of the manufacturing process and is shown in FIG.

As shown in FIG. 3, this metal wire 4
The upper end of the anode lead 11 is electrically connected to the free end of the anode lead 11 by thermocompression bonding, with one end thereof being bonded to the second lead 3 by wire bonding or the like. As a result, it is possible to easily and surely electrically connect the anode lead 11 located at a position distant from the second lead 3. Further, 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. However, the current can be cut off before that to cut off the current. For this purpose, the metal wire 4 is made of a material which is lower than about 600 ° C. at which the sintered body is burned and which does not melt at a temperature such as soldering and which melts at about 260 ° C. or higher.

Next, as shown in FIG. 3, in a state where the capacitor element 1 is mounted, a paste-like resin is coated on the surface side by screen printing or the like under a reduced pressure in a vacuum state, for example. The package 5 is formed by covering the metal wires 4 and thermally curing them. That is, instead of being formed by injection molding, the amount is small, and it is formed simply by applying and heating. Further, by applying the coating under a reduced pressure in the state of the taped lead frame, the narrow space is filled with the paste-like resin without forming the void. The adhesive sheet 16 adhered to the back side of the lead frame is removed after the applied resin is cured.

Thereafter, the lead frame having the resin package formed on the entire surface is cut at the boundary between the elements to obtain a solid electrolytic capacitor having the structure shown in FIG. In addition, by performing solder plating in the state of the lead frame, solderability at the time of mounting can be improved.

FIGS. 4 to 6 are views showing examples of various possible forms of the Teflon ring. FIG. 4 (a), (b)
Is the same as the Teflon ring 13 shown in FIG. 1 and has a circular shape with the anode lead 11 penetrated at the center, and the diameter thereof is larger than the thickness of the sintered body portion of the capacitor element 1 by a predetermined dimension d. are doing. This predetermined dimension d is
The thickness is set to be approximately the same as or slightly smaller than the thickness of the first and second lead electrodes 2 and 3. FIGS. 5A and 5B show the Teflon ring 14 above the anode lead 11 and the sintered part 1.
2 is a semicircular shape having a diameter smaller than the thickness of the anode lead 1
The portion below 1 has a rectangular shape and protrudes from the sintered body portion by a predetermined dimension d. 6 (a) and 6 (b) show that the Teflon ring 15 is formed in a circular shape having a diameter smaller than the thickness of the sintered body portion 12, and a portion below the anode lead 11 is formed in a cam shape. The portion protrudes from the portion by a predetermined dimension d.

As shown in these examples, the cathode 12 of the capacitor element 1 is connected to the first lead 2 and the second lead 3 at the time of manufacture, while the Teflon ring serves the purpose of preventing the manganese nitrate aqueous solution from wicking up. At least a portion of the Teflon ring can be formed in various shapes so as to have a size exceeding the outer peripheral wall 12 which is a cathode, for the purpose of preventing the Teflon ring from dropping between them.

[0029]

According to the method of manufacturing a tantalum electrolytic capacitor according to the first aspect of the present invention, a repellent material such as a Teflon ring provided for preventing a swelling when a cathode is formed on a metal sintered body of a tantalum electrolytic capacitor element. At least a portion of the aqueous synthetic resin ring is formed to have a size exceeding the outer peripheral wall serving as a cathode, so that a sheet or tape for closing a gap between the first lead and the second lead can be formed of a water-repellent synthetic resin. A large formed portion of the ring is provided. This reliably prevents the cathode of the tantalum electrolytic capacitor element from falling between the first lead and the second lead,
The cathode is not exposed on the lower surface of the tantalum electrolytic capacitor chip. In addition, it is only necessary to change the dimensions of the water-repellent synthetic resin ring which has been conventionally used for preventing swelling, so that a new burden does not occur.

Also, since the tantalum electrolytic capacitor element can be manufactured by directly mounting the tantalum electrolytic capacitor element on the lead frame and coating the upper surface with a resin, the gap between the tantalum electrolytic capacitor element and the package is hardly at the lower surface side. Also, the top side can be manufactured with very small dimensions. As a result, a large capacitor element can be built in a package having a very small external dimension, and the electrical characteristics such as reducing the leak current by increasing the capacitance value or increasing the particle size of the powder are improved. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of a tantalum electrolytic capacitor according to an embodiment of the present invention.

FIG. 2 is a view showing a lead frame used in the embodiment of the present invention.

FIG. 3 is a view showing a structure during a manufacturing process of the tantalum electrolytic capacitor according to the embodiment of the present invention.

FIG. 4 is a diagram showing a structure of a Teflon ring used in the embodiment of the present invention.

FIG. 5 is a view showing another structure of the Teflon ring used in the embodiment of the present invention.

FIG. 6 is a diagram showing another structure of the Teflon ring used in the embodiment of the present invention.

FIG. 7 is a diagram showing the structure of a conventional tantalum electrolytic capacitor.

FIG. 8 is a diagram showing a structure of a tantalum electrolytic capacitor of a prior art example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tantalum electrolytic capacitor element 2 1st lead 3 2nd lead 4 Metal wire 5 Resin 11 Anode lead 12 Cathode 13-15 Teflon ring 16 Adhesive sheet

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01G 9/00 H01G 9/24 C

Claims (1)

[Claims] A step of preparing a tantalum electrolytic capacitor element having at least a portion formed to have a size exceeding an outer peripheral wall serving as a cathode and having a water-repellent synthetic resin ring provided at a base portion of an anode lead; Forming a lead frame so that the plate-shaped first lead and the second lead face each other, a sheet or tape on the back surface of the lead frame so as to close a gap between the first lead and the second lead Attaching, on the first lead, a surface of the outer peripheral wall of the tantalum electrolytic capacitor element, wherein the water-repellent synthetic resin ring is formed to have a size exceeding the outer peripheral wall serving as a cathode. Mounting the one end of a metal wire on the second lead, the other end of the metal wire and the anode lead of the capacitor element A step of electrically connecting, and method for producing a tantalum electrolytic capacitor characterized by having a step, which is covered with a resin capacitor element portion on the first lead and the second lead.