JPH10335183A - Chip-type solid electrolytic capacitor and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a heat-resistance characteristic of a solder layer as a cathode terminal and to reduce stresses applied on a capacitor element at molding. SOLUTION: On a pellet 10a where an anode rod 11 is planted, a manganese dioxide layer 10b and a cathode layer 13 comprising a carbon and silver layers are formed in order to obtain a capacitor element 10, and after a soft flexible layer 14 has been formed on the cathode layer 13, a jacket resin layer 15 is formed by molding, except for a part on a bottom surface side of the capacitor element 10. At a part on the bottom surface side of the capacitor element 10, a solder layer is formed as a cathode terminal 16, and with a metallic plate comprising a hole part 17a engaged with the anode rod 11 and an engraved groove 17b cut from an end edge to its hole part as an anode terminal 17, the metallic plate is, in a condition with the anode rod 11 inserted into the hole part 17a, calked with a groove width of the engraved groove 17b as a calking margin, then is welded to the anode rod 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip-type solid electrolytic capacitor and a method for manufacturing the same, and more particularly, to a chip-type solid electrolytic capacitor having a high volume efficiency of a capacitor element housed in an exterior resin and having good heat resistance. The present invention relates to a method for manufacturing an electrolytic capacitor and a chip-type solid electrolytic capacitor capable of reducing stress on a capacitor element during resin molding.

[0002]

2. Description of the Related Art For example, Japanese Unexamined Patent Application Publication No.
Japanese Patent Application No. 78288/88 proposes a chip-type solid electrolytic capacitor in which an anode terminal and a cathode terminal are directly drawn from a capacitor element without using a lead frame.

That is, as shown in FIG. 6, this chip-type solid electrolytic capacitor includes a capacitor element 2 in which an anode rod 1 is implanted. Although not shown in detail in FIG. 1, the capacitor element 2 is formed of a sintered pellet of valve metal powder (for example, tantalum powder), an oxide film is formed on the surface thereof, and a solid electrolytic layer is formed on the oxide film. And a cathode layer composed of carbon and silver layers are sequentially formed.

In forming a chip, an exterior resin 3 is formed around the capacitor element 2. In this case, the exterior resin 3 is not formed on the bottom surface 2a of the capacitor element 2, and the cathode layer is formed on the bottom surface 2a. Is exposed.
Then, a cathode terminal 4 is formed of silver paste on the cathode layer on the bottom surface 2a, and a substantially V-block plate-shaped anode terminal 5 is attached to the anode rod 1 protruding from the exterior resin 3, and finally the cathode terminal 4 is formed. And the anode terminal 5 are plated with solder.

[0005]

According to this chip-type solid electrolytic capacitor, a lead frame is not required, and the cathode terminal 4 and the anode terminal 5 are directly drawn out of the capacitor element 2. 3, the volume efficiency of the capacitor element 2 with respect to 3 can be increased, and the manufacturing cost can be reduced.

However, the cathode terminal 4 and the cathode layer exposed on the bottom surface 2a are in contact only with the area of the bottom surface 2a of the capacitor element 2, and the peripheral edge of the cathode terminal 4 faces the end surface of the exterior resin 3. Therefore, the connection between the cathode terminal 4 and the cathode layer is not sufficient, and if a thermal stress is applied, an open failure due to peeling may occur.

The anode terminal 5 has a V-block plate shape,
Since the anode rod 1 can be attached to the anode rod 1 from a direction perpendicular to its axis, the anode terminal 5 can be attached to the anode rod 1 while the anode rod 1 is attached to the hoop material, which is convenient. However, even if the attachment is performed by laser welding, for example, if the soldering heat test is repeated, a connection failure may occur.

Accordingly, a first object of the present invention is to provide a chip-type solid electrolytic capacitor having better heat resistance while utilizing the advantage of the prior art that the volume efficiency of the capacitor element housed in the exterior resin is high. To provide. A second object of the present invention is to provide a method of manufacturing a chip-type solid electrolytic capacitor having stable electrical characteristics by reducing stress on a capacitor element during resin molding.

[0009]

In order to achieve the first object, the present invention provides a sintered pellet made of a valve metal powder having an anode rod implanted therein, comprising a solid electrolyte layer, a carbon and silver layer. A chip type solid electrolytic capacitor comprising a capacitor element having a negative electrode layer formed thereon, an outer resin layer formed by molding around the capacitor element, and an anode terminal attached to the anode bar. The exterior resin layer is formed around the capacitor element so that a part of the bottom surface side of the capacitor element projects from the exterior resin layer, and is connected to the bottom surface and the bottom surface of the capacitor element protruding from the exterior resin layer. A solder layer as a cathode terminal is formed on the side peripheral surface, and the anode terminal has the same hole from the hole and the edge fitted to the anode rod. A metal plate having a notch groove cut into the hole, the metal plate being swaged with the groove width of the notch groove being swaged in a state where the anode rod is inserted into the hole thereof, and welding to the anode rod. It is characterized by being.

According to this structure, the cathode terminal comes into contact with the cathode layer not only on the bottom surface of the capacitor element but also on a wider surface extending to the side peripheral surface connected to the bottom surface, so that thermal stress is repeatedly applied. Also does not peel off from the cathode layer. In addition, since the anode terminal is firmly fixed to the anode rod by caulking and welding, a good connection state is maintained for a long period of time.
The anode terminal (metal plate) is preferably plated with solder.

Further, in order to achieve the second object, the production method of the present invention comprises a method in which a solid electrolyte layer and a carbon and silver layer are formed on a sintered pellet made of a valve metal powder having an anode rod implanted therein. A cathode layer is sequentially formed to form a capacitor element, a soft cathode material layer is formed on the cathode layer of the capacitor element, and then molded around the capacitor element except for a part of the bottom side of the capacitor element. Forming an exterior resin layer by molding, forming a solder layer as a cathode terminal on a part of the bottom surface side of the capacitor element, and cutting from the hole and the edge fitted into the anode rod as the anode terminal to the hole. Using a metal plate having a cut groove inserted therein, after caulking the metal plate with the groove width of the cut groove being swaged with the anode rod inserted through the hole,
It is characterized in that it is welded to the anode rod.

As another method, a soft cathode material layer may be directly formed on carbon. In any case, according to the present invention, when the exterior resin layer is formed around the capacitor element by molding, the stress is reduced by the soft cathode material layer, the yield rate is improved, and the quality is improved. A stable chip-type solid electrolytic capacitor can be obtained.

In this case, a silver paste is preferably used as the cathode material layer. The soft state is about dry to the touch, and in the case of a silver paste, 0.5 to 40 ° C to 80 ° C after application.
By drying for 1.0 hour, a soft state is obtained, which is almost dry to the touch.

In the present invention, after forming the exterior resin layer, a heating step of curing the cathode material layer also serving as post-curing of the exterior resin layer is performed.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, in order to better understand the technical concept of the present invention, an embodiment will be described with reference to FIGS. FIG. 1 illustrates a process until a cathode terminal is formed on a capacitor element, FIG. 2 illustrates a state where an anode terminal is attached to an anode rod, and FIG. 3 illustrates a chip completed as a product. FIG. 4 is a perspective view of a solid electrolytic capacitor, and FIG. 4 is a sectional view of the capacitor.

In the actual mass production process, the capacitor elements are carried to each process in a state where, for example, several tens of the capacitor elements are hung on a stainless steel strip called a hoop material. One capacitor element 10
Is suspended from the hoop material F via the anode bar 11.

First, steps until the capacitor element 10 shown in FIG. 1A is manufactured will be described. For example, tantalum powder is sintered to obtain a prismatic pellet 10a. After inserting a washer 12 for preventing the solid electrolyte from creeping up into the anode rod 11 implanted at one end of the pellet 10a, the anode rod 11 is welded to the hoop material F as described above. Then, the pellet 10a is attached to the hoop material F.

Next, after an oxide film is formed on the pellet 10a, a manganese dioxide layer 10b as a solid electrolyte is formed. The formation of the manganese dioxide layer 10b is performed by immersing the pellets 10a in an aqueous manganese nitrate solution, pulling the pellets 10a up, and baking the pellets 10a at a predetermined temperature.

Subsequently, a carbon layer 10c is formed on the manganese dioxide layer 10b, and a silver layer 10d is further formed on the carbon layer 10c. That is, in FIG. 1A, the surface of the capacitor element 10 is covered with the silver layer 10d, and the cathode layer 13 is formed by the carbon layer 10c and the silver layer 10d.

After forming the capacitor element 10 in this manner, a flexible layer 14 is formed on the cathode layer 13 of the capacitor element 10 as shown in FIG. In this embodiment, the flexible layer 14 is made of a silver paste that is not completely cured, that is, a soft silver paste.

More specifically, a silver paste is impregnated on the cathode layer 13 and then dried at 40 to 80 ° C. for about 0.5 to 1.0 hour to obtain softness to the extent of dryness to the touch. Can be In addition, the thickness of the flexible layer 14 is preferably in the range of 0.05 to 0.1 mm in order to absorb a dimensional deviation at the time of setting in the mold in the next step.

Thereafter, the capacitor element 10 is placed in a mold (not shown) to form an exterior resin layer. In the present invention, as shown in FIG. While remaining, the exterior resin layer 15 is formed in other portions. That is, when viewed from the outside, the entire bottom surface of the capacitor element 10 and a part of the side peripheral surface connected to the bottom surface protrude from the exterior resin layer 15, and the flexible layer 14 at that portion is exposed.

In order to form the exterior resin layer 15 while leaving the lower portion of the capacitor element 10 as described above, a part of the mold is formed so as to be closely fitted to the lower part of the capacitor element 10, and the resin Is generally prevented from sneaking around, but in some cases, the capacitor element 10
After forming an exterior resin layer on the entire surface of the
The exterior resin layer on the lower side may be removed. For example, an epoxy resin is used for the exterior resin layer 15, and its thickness is usually about 0.15 mm.

After this mold packaging, the flexible layer 14 is cured by drying at 160 to 180 ° C. for 4 to 20 hours, also serving as post-curing of the packaging resin layer 15. Then, after the exterior resin layer 15 is deburred and washed, the lower portion of the capacitor element 10 is subjected to acid treatment and washed, and then exposed to the lower portion of the capacitor element 10 as shown in FIG. A solder layer is formed on the cured flexible layer 14 to form a cathode terminal 16.

Next, as shown in FIG. 2, an anode terminal 17 is attached to the anode rod 11. The anode terminal 17 is made of a solder-plated metal plate, and has a hole 17a fitted into the anode rod 11, and a cut groove 17b cut from the edge to the hole 17a.

In this embodiment, the anode terminal 17 has wing pieces 171 and 171 on both sides of the cut groove 17b.
Is opened in a V-shape around the center. The hole 17a of the anode terminal 17 is fitted to the base of the anode rod 11, and the blade pieces 171 and 171 are swaged in the direction in which they face each other with the width of the cut groove 17b being swaged. Then, the periphery of the hole 17a is laser-welded to fix the anode terminal 17 to the anode bar 11, and an excess portion of the anode bar 11 protruding from the anode terminal 17 is cut, as shown in FIG. Product form.

Although the flexible layer 14 is formed on the cathode layer 13 in the above embodiment, the silver layer 10d constituting the cathode layer 13 may be a flexible layer.
That is, when forming a silver layer 10d by applying a silver paste, the exterior resin layer 15 may be formed while the silver paste is kept in a soft state as described above.

In this chip type solid electrolytic capacitor, the solder layer 16 as the cathode terminal is
Since the bonding is performed over a wide area over the bottom surface and the side peripheral surface connected to the bottom surface, even if the heat resistance test is repeated, there is no occurrence of open failure or deterioration in characteristics due to peeling.

Further, since the anode terminal 17 is also fixed to the anode rod 11 by caulking and laser welding, the bonding strength is extremely large as compared with the case where only laser welding is used, and the anode terminal 17 is stable even after the heat test. Electrical characteristics are obtained.

Twenty chip-type solid electrolytic capacitors each having a rating of 6.3 V and a capacitance of 10 μF were prepared for each of the present invention product and the conventional product. FIG. 5 shows the results of measuring the impedance at 100 kHz. According to this, in the case of the product of the present invention, no significant change was observed in the impedance even after the soldering heat test.

In addition, 10,000 chip-type solid electrolytic capacitors of the present invention and the conventional product having the same rating as above are prepared, left at −50 ° C. for 30 minutes, and then left at 125 ° C. for 30 minutes. The open rate after repeating 1000 cycles was 1.5% for the conventional product and 0.0% for the product of the present invention.
2%.

[0032]

As described above, according to the present invention,
Since the solder layer as the cathode terminal is in contact with the cathode layer not only on the bottom surface of the capacitor element but also on a wider surface extending to the side peripheral surface connected to the bottom surface, even if thermal stress is repeatedly applied, the cathode layer can be used. It does not peel off from the layer. Further, since the anode terminal is extremely firmly fixed to the anode rod by caulking and welding, it is thermally stable and maintains a good connection state for a long period of time.

On the other hand, according to the manufacturing method of the present invention, when the exterior resin layer is formed around the capacitor element by molding, the stress is reduced by the soft cathode material layer, so that the yield rate is improved. In addition, a chip-type solid electrolytic capacitor with stable quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a process diagram showing a process of forming a cathode terminal on a capacitor element during a manufacturing process of the present invention.

FIG. 2 is a perspective view showing a state where an anode terminal is subsequently attached to an anode rod.

FIG. 3 is a perspective view of a chip-type solid electrolytic capacitor completed as a product.

FIG. 4 is a sectional view of the chip-type solid electrolytic capacitor.

FIG. 5 is a graph showing impedance changes before and after a solder heat resistance test of a product of the present invention and a conventional product.

FIG. 6 is a perspective view of a conventional chip-type solid electrolytic capacitor.

[Explanation of symbols]

 Reference Signs List 10 capacitor element 10a pellet 10b solid electrolyte layer (manganese dioxide layer) 10c carbon layer 10d silver layer 11 anode rod 12 washer 13 cathode layer 14 flexible layer 15 exterior resin layer 16 cathode terminal 17 anode terminal

Claims (6)

[Claims] 1. A capacitor element in which a solid electrolyte layer and a cathode layer made of a carbon and silver layer are formed on a sintered pellet made of a valve metal powder having an anode rod implanted therein. In a chip-type solid electrolytic capacitor in which an exterior resin layer formed by molding is provided and an anode terminal is attached to the anode bar, a part of the exterior resin layer on the bottom side of the capacitor element is the same exterior resin. Formed around the capacitor element so as to protrude from the layer, a solder layer as a cathode terminal is formed on a bottom surface protruding from the exterior resin layer of the capacitor element and a side peripheral surface continuous with the bottom surface, The anode terminal is made of a metal plate having a groove fitted into the anode bar and a cut groove cut from the edge to the hole, A chip-type solid electrolytic capacitor characterized in that the metal plate is caulked with the groove width of the cut groove as a margin for crimping while the anode bar is inserted through the hole, and is welded to the anode bar. 2. The solid electrolytic capacitor according to claim 1, wherein said metal plate is plated with solder. 3. A capacitor element in which a solid electrolyte layer and a cathode layer made of a carbon and silver layer are sequentially formed on a sintered pellet made of a valve metal powder having an anode rod implanted therein. After forming a soft cathode material layer on the cathode layer, an exterior resin layer is formed by molding around the capacitor element except for a part of the bottom face side of the capacitor element, and a part of the bottom face side of the capacitor element is formed. Forming a solder layer as a cathode terminal to, using a metal plate having a notch groove cut from the hole and the edge from the edge to the same hole as the anode terminal,
A method for manufacturing a chip-type solid electrolytic capacitor, comprising: crimping the metal plate with the groove width of the notch groove being crimped while the anode rod is inserted through the hole, and then welding the metal plate to the anode rod. 4. A capacitor element by forming a solid electrolyte layer and carbon on a sintered pellet made of valve metal powder having an anode rod implanted thereon, and forming a soft cathode material layer on the carbon. An exterior resin layer is formed by molding around the capacitor element except for a part on the bottom side of the capacitor element, and a solder layer as a cathode terminal is formed on a part on the bottom side of the capacitor element, and as an anode terminal Using a metal plate having a hole fitted into the anode rod and a cut groove cut from the edge to the hole, and cutting the metal plate in a state where the anode rod is inserted through the hole. A method for manufacturing a chip-type solid electrolytic capacitor, comprising: crimping the groove width as a margin and then welding to the anode rod. 5. The method according to claim 3, wherein a silver paste is used as the cathode material layer. 6. The chip-type solid electrolytic capacitor according to claim 3, wherein after the formation of the exterior resin layer, a heating step of curing the cathode material layer also serving as post-curing of the exterior resin layer is performed. Manufacturing method.