JP2003209028A - Method of manufacturing solid-state electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing solid-state electrolytic capacitors capable of substantially reducing L-C characteristics (leak current characteristics) so as to be suitable for capacitors, comprising steps of disposing a valve action metal plate so as to be punched out to overlay valve action metal powder in a portion contacting therewith, and knocked out to discharge a powder molded article downward a through-hole of a die using a knock-out punch. <P>SOLUTION: The method of manufacturing the solid-state electrolytic capacitor is characterized by comprising steps of disposing a valve action metal strip member, which is punched out so that a valve action metal plate is overlaid on valve action powder in a powder molding die, inserting the valve action metal powder into a through-hole in the die and compressing the powder between first and second punches so as to form a powder molded article, and knocked out to discharge the powder molded article downward the through-hole of the die using the second punch. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid electrolytic capacitor, and more specifically, to reduce the size of the capacitor and improve its capacitance, a valve-acting metal plate is provided at a contact portion with a valve-acting metal powder. The present invention relates to a method for manufacturing a solid electrolytic capacitor in which LC characteristics (leakage current characteristics) as a capacitor can be remarkably reduced by using.

[0002]

2. Description of the Related Art Conventionally, a powder compact formed by press-molding a fine metal powder having a valve action such as tantalum, niobium, aluminum and titanium is formed into a porous sintered body under high temperature and high vacuum. , Used as an electrolytic capacitor.

In recent years, semiconductor integrated circuits have become smaller and smaller.
In the trend of high integration and miniaturization, personal computers, telephones, etc. are portable and are becoming smaller and lighter, and the capacitors used are also becoming more and more demanding. Has been done.

In order to meet such demands, in order to increase the porosity (or porosity) of the above-mentioned powder compact and increase the surface area of the powder compact, the size and capacity of the capacitor can be reduced. A metal powder having a valve action of the starting material is used as a raw material metal powder having a finer primary particle diameter, for example, a primary particle diameter of 1.5 to 0.7 μm as an average particle diameter in recent years. Is becoming available.

However, when molding such a fine powder, for example, in the step of molding a powder compact of a capacitor, it is usual to press-mold a valve action metal powder such as granulated tantalum. A die 1 of a molding die having a through hole 1a having a vertical side surface,
Powder is filled into the powder filling hole formed by the lower punch 2 fitted from the lower part of the through hole (FIG. 4 (a)), and then the anode lead 8 arranged above the die 1 is inserted and held. In this state, the upper punch 3 is inserted into the powder filling hole, and at the same time, the lower punch 2 is lifted to compress the powder into a desired shape.
(Fig. 4 (b)). Then, the upper punch 3 is pulled back from the inside of the die hole, and the anode lead 8 is cut by the cutting blade 13 (4 (c)). After that, by pushing up the lower punch 2 or by lowering the die 1, the powder compact is knocked out from the inside of the die hole to form the powder compact 6 (4 (d)),
After that, a manufacturing method is generally used to obtain a powder molded body of a solid electrolytic capacitor in which the anode lead is buried by sintering under high temperature and high vacuum. (For example, refer to FIG. 1 of Japanese Patent Laid-Open No. 2-69923)

Further, generally, a solid electrolytic capacitor in which a valve action metal plate material is superposed on a powder compact without burying an anode lead is described in, for example, Japanese Patent Application Laid-Open No. 58-96724 and FIG. 5) As shown in FIGS. 5 (f) and 6, first, as shown in FIG. 5 (a), the valve action metal plate material 20 is positioned and mounted on the through hole 1a of the die of the powder molding die 1. Place. Then, as shown in FIG. 5 (b), the upper punch 3 is pulled down and pressed with the lower punch 2 in the through-hole 1a to form a disk 21 with a collar. After this, only the upper punch (3) is pulled upward, and the valve action metal plate material 20 is left on the lower punch 2. Then, as shown in FIG. 5 (c), a predetermined amount of valve action metal powder 5 is introduced from above the through hole 1 a and is stacked on the flanged disk 21 of the valve action metal plate member 20. Next, as shown in FIG. 5 (d), the upper punch 3 is fitted into the through hole 1a again, and pressed and shaped. By pushing up the lower punch 2 to the upper end of the through hole 1a, as shown in FIG. 5 (e), a shaped product of valve action metal powder, which is integrated with the disc 21 with a flange of the valve action metal plate member 20, is obtained. You can Next, after the shaped product is fired to form a capacitor element 7 having a porous structure, as shown in FIG. 5 (f), an anode lead 8 made of a valve action metal material is attached to the valve action metal plate material 20.
Weld on the disk 21 with a collar. Further, it is described that a metal material 20 protruding on a part of one surface of the capacitor element 7 may be used as shown in FIG.

[0007]

However, this conventional powder compact for capacitors has the following drawbacks. (1) The powder molded body for a solid electrolytic capacitor in which the anode lead is embedded has the anode lead arranged above the die inserted and held, and the upper punch is inserted into the powder filling hole and at the same time the lower punch is raised. Compress the powder into the desired shape. For this reason, the upper punch is provided with a through hole through which the anode lead can be inserted and a predetermined amount can be supplied and slid, and a predetermined clearance between the anode lead and the through hole of the upper punch is important. As described above, if the metal powder becomes finer, it is necessary to make this clearance smaller in proportion to the size reduction, but there is a limit in relation to the wire trace accuracy surface of the anode lead and the processing accuracy surface of the through hole. There is. Therefore, due to this clearance, no compressive pressure is applied near the anode lead of the anode body, and the embedded anode lead becomes a resistance, and the powder compaction density is in a coarser density state than the compaction densities of the powder compacts in other parts. Therefore, the mechanical strength of the base part of the anode lead with the powder compact is weak, and there is a problem that the LC characteristics (leakage current) is significantly deteriorated due to bending of the anode lead during the manufacturing process of the capacitor. . When this clearance is reduced, the manganese dioxide solution or conductive polymer that forms the solid electrolyte layer of this capacitor may be damaged by surface tension due to scratches generated when sliding in the upper punch through hole of the anode lead. There is a problem in that a short circuit or a defective LC characteristic often occurs due to the creeping up during the manufacturing of the capacitor.

(2) A method of manufacturing a solid electrolytic capacitor in which a valve action metal plate material is superposed on a powder compact without burying an anode lead is as shown in FIG. 8 (a). A valve action metal plate is positioned on the hole, and as shown in FIG. 8 (b), the upper punch is pulled down and pressed with the lower punch in the through hole to form a disk with a collar. . Further, by pushing the lower punch to the upper end of the through hole, as shown in FIG. 8 (e), the punch integrated with the valve-acting metal plate material is pulled up and knocked out to move the valve upward of the powder molding die. For the manufacturing method to discharge the shaped product of the working metal powder, it is necessary to position the valve working metal plate and the through hole of the powder molding die, and the upper punch is pulled down and the lower punch and the through hole are provided in the through hole. It also requires a process to press the attached disk, resulting in poor production efficiency. In addition, by pushing the lower punch up to the upper end of the through-hole, the valve punch metal powder shaped object located below the powder molding die slides on the inner wall surface of the powder molding die and the valve action metallic powder molded object. Becomes longer and scratches are generated on the shaped article, and there is a problem that the LC characteristics as the capacitor characteristics deteriorate.

Therefore, an object of the present invention is to arrange a valve action metal plate in a contact state with a valve action metal powder in a stacked state while punching it with a powder molding die, and to perform powder molding on a lower side of a through hole of a die. It is an object of the present invention to provide a method for manufacturing a solid electrolytic capacitor in which the LC characteristics (leakage current characteristics) as a capacitor can be remarkably reduced by knocking out and discharging the body with a second punch.

[0010]

A method of manufacturing a solid electrolytic capacitor according to claim 1 of the present invention, which is provided to solve the above-mentioned problems, has a valve action at a contact portion with a valve action metal powder. The metal plates are arranged in a stacked state, the valve action metal powder is fitted into the through hole of the die by the first punch and the second punch, and compressed under pressure to form a powder compact, and the powder compact is formed. After sintering the body at high temperature and high vacuum, a dielectric oxide film is formed, a manganese dioxide layer that becomes a solid electrolyte, or a conductive polymer layer is formed on this surface, and a graphite layer that becomes a cathode layer and a conductive layer are formed on the surface. In the method for manufacturing a solid electrolytic capacitor in which resin layers are sequentially formed, the powder compact is knocked out by a second punch and discharged to the lower side of the through hole of the die.

By adopting such a manufacturing method, in order to reduce the size of the capacitor and improve the electrostatic capacity, a valve action metal plate is used in the contact portion with the valve action metal powder, and the lower side of the through hole of the die is used. Since the powder compact is knocked out by the second punch and discharged, the sliding distance between the inner wall surface in the through hole of the die and the compact of the valve action metal powder is minimized, and the average primary particle diameter is 1. Fine valve action metal powder of 5 μm or less, which is a granulated powder mixed with a binder for enhancing the moldability, and is also rubbed with a powder compact using a fine valve action metal powder having a secondary particle diameter of 10 to 200 μm. Since the generation of scratches can be suppressed, it is possible to realize a solid electrolytic capacitor that significantly reduces the LC characteristics as the capacitor characteristics.

A method for manufacturing a solid electrolytic capacitor according to a second aspect of the present invention, which is provided for solving the above-mentioned problems, is the method for manufacturing a solid electrolytic capacitor according to the first aspect. The valve action metal strip member is punched from the lower side of the die with the die and the first punch, and the punched valve action metal plate is inserted into the through hole of the die and placed in a state of overlapping with the contact portion with the valve action metal powder. It is characterized by setting.

By adopting such a manufacturing method, the valve action metal strip member is arranged on the lower surface of the die of the powder molding die, and the valve action metal strip member is inserted while being punched, so that the punched valve action is performed. Since the metal plate is knocked out together with the powder compact from the punching side, no external force is applied to the contact interface in the direction of peeling, resulting in stable joining.
The variation of the C characteristic is small, and the process of pulling the upper punch of the conventional example downward and pressing it with the lower punch to the disk with the collar in the through hole is not necessary, and high production efficiency is obtained.

The method for producing a solid electrolytic capacitor according to claim 3 according to the third invention of the present application, which is provided for solving the above-mentioned problems, is the same as the method for producing a solid electrolytic capacitor according to claim 1 or 2. After the powder compact is sintered at high temperature and high vacuum, the anode lead having the valve action is laser-welded to the exposed surface of the punched valve action metal plate of the powder compact.

By adopting such a manufacturing method, since the laser welding is performed after the step of vacuum-sintering the powder compact,
The powder compacts can be joined without any mechanical external force being applied thereto and impurities are not attached, and the reliability quality such as LC characteristics is stable. Also, using the anode lead, a large number are simultaneously suspended in a chemical conversion process for forming a dielectric oxide film of a capacitor, a decomposition or production process for forming a solid electrolyte layer such as manganese dioxide or a conductive polymer. It can be processed and can work efficiently. Also, the anode lead in a state of being hung and suspended at this predetermined interval is an external terminal arranged at a predetermined interval.
(For example, 42 alloy lead frame) is supported, and the joining work can be performed efficiently.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in detail with reference to the drawings. 1 (a) to 1
FIG. 3E is a sectional view of a key portion showing, in the order of steps, the method for manufacturing the solid electrolytic capacitor according to the present invention.

As shown in FIG. 1 (a), a through hole 1a having a vertical side surface is formed in the die 1 of the powder molding die. The cross-sectional shape of the through hole 1a is circular, elliptical or rectangular. First, a valve action metal strip member 4 (for example, width 2.0 mm × thickness 0.05 mm) made of tantalum, niobium, titanium, aluminum or the like is disposed on the lower surface of the die 1 of the powder molding die (see FIG. 1 (a )), The lower punch 2 (first punch) is lifted from the lower surface side of the through hole of the die 1 to raise the valve action metal strip member 4
Is pressed by the pad portion 11 via the spring portion 10 and press-punched with the through hole 1a of the die, and the punched valve action metal plate 4a is fitted into the through hole 1a of the die 1 and stopped at a predetermined position ( Figure 1 (b)). Next, the through hole 1a of the die 1
From the upper surface of the valve metal made of valve metal such as tantalum, niobium, titanium, and aluminum as an average particle size of 1.5 to
The secondary particle diameter, which is a granulated powder obtained by previously granulating so as to have a certain particle size distribution within a fine range of the primary particle diameter of 0.7 μm, and mixing a binder for enhancing the moldability, is 10 The metal powder 5 having a diameter of up to 200 μm is filled so that the opening surface of the through hole 1a of the die 1 becomes flat, and the upper punch 1 is provided right above the through hole 1a of the die 1 filled with the powder.
A (second punch) is arranged (FIG. 1 (c)), and the upper punch 3 is fitted along the axial center of the through hole 1a and is placed on the lower punch 2 to be mounted on the valve-acting metal plate. 4a, the upper punch 3 is approached and lowered to compress the valve action metal powder 5 at a predetermined pressure to form a powder compact 6 (FIG. 1 (d)). While lowering the lower punch 2, the upper punch 3 is lowered. Lowering the die 1
As shown in FIGS. 2 and 3, by knocking out the powder compact 6 having the valve action metal plate 4a punched out more and grasping and taking out the powder compact 6 by the clamp mechanism portion 9 (FIG. 1 (e)). Solid electrolytic capacitor 7 (for example, size of powder compact 6: width 1.15 mm x height 1.15 mm x thickness 1.16)
mm) can be obtained.

The die 1, the lower punch 2 and the upper punch 3 are
It is held so that it can move up and down, and is driven by, for example, a servo motor so that it can be moved and stopped with high precision (not shown in the figure). Also, the die 1, the lower punch 2, and the upper punch 3
In order to suppress abrasion due to mutual sliding and rubbing against the metal powder 5, a material having excellent abrasion resistance such as cemented carbide is used.

A valve action metal plate 4a punched out from the die 1 by lowering the lower punch 2 and lowering the upper punch 3.
Knock out the powder compact 6 having
(e)). The reason for knocking out to the lower side of the through hole of the die is that the molded body is knock-afted from the side to be punched together with the valve action metal plate 4a, so that an external force is applied in the direction of separating the contact interface between the valve action metal plate and the powder compact. This is because a stable LC characteristic can be obtained because no knockout is added, and the knockout amount in the direction of the lower punch 2 is smaller than that in the case of knocking out the powder compact 6 in the direction of the upper punch 3 shown in the conventional example. Since it becomes smaller after pressure compression due to the powder filling height, the friction distance between the inner wall of the through hole 1a of the die 1 and the powder compact 6 at the time of knocking out is minimized to suppress the occurrence of friction scratches. This eliminates the cause of deterioration of characteristics. Therefore, this manufacturing method can reduce the occurrence of LC characteristics defects, especially in solder heat resistance, to 1/3 as a solid electrolytic capacitor. .

FIG. 2 is a perspective view of a solid electrolytic capacitor obtained by the manufacturing method of the present invention, which is a fine valve action metal powder having an average primary particle diameter of 1.5 μm or less.
Using a metal powder having a secondary particle size of 10 to 200 μm,
The powder compact 6 obtained as described above is sintered. The conditions are usually a temperature of 1200 to 1600 ° C. and a temperature of 10 −3
The solid electrolytic capacitor 7 shown in FIG. 2 was sintered by using a sintering device (not shown) having a pressure of -10 −4 Pa, so that the solid electrolytic capacitor 7 shown in FIG. As a result, a large amount of powder compacts will enter, and the volumetric efficiency of the sintering work at high temperature and high vacuum will be high, and mass production will be possible.

Further, FIG. 3 is a perspective view of the solid electrolytic capacitor shown in FIG. 2, in which an anode lead having a valve action is laser-welded to the exposed surface of the valve action metal plate of the solid electrolytic capacitor. After the powder compact 6 is obtained, a chemical conversion process of forming a dielectric oxide film of a capacitor using an anode lead by a manufacturing method of laser welding after a process of sintering the powder compact at a high temperature, manganese dioxide or high conductivity. Efficient work can be performed by suspending and processing a large number of molecules at the same time in a decomposition or generation process of forming a solid electrolyte layer of molecules and the like. In addition, the anode lead in a state of being hung and suspended at this predetermined interval has an external terminal (for example, 42
It is compatible with alloy lead frames) and can be joined efficiently. A part of this anode lead is an external terminal as a capacitor (for example, 42 alloy lead frame).
It can be used for joining to and joining work becomes easy.

As shown in the cross-sectional views of the essential parts of FIGS. 1 (a) to 1 (e), it is easy to use a solid electrolytic capacitor forming method, for example, a manufacturing apparatus. That is, the die 1 of the powder molding die having a through hole for molding in which the axes of the lower punch 2 (first punch) and the upper punch 3 (second punch) are aligned, and the die 1
Lower punch 2 which is fitted into the molding through hole 1a from below to form the bottom surface of the powder filling hole, and the molding through hole 1 of the die 1.
In a solid electrolytic capacitor forming apparatus for forming a powder compact 6 with an upper punch 3 for compression-molding a valve action metal powder which is fitted into a from above and closes to a lower punch 2, tantalum, niobium, titanium, A valve action metal strip member 4 made of aluminum or the like is disposed so as to face the lower surface of the die 1 of the powder molding die, and the lower punch 2 (first punch) is raised from the lower surface side of the through hole of the die 1 to perform molding. The lower surface of the die 1 of the through hole 1a for use and the lower punch 2 presses the valve action metal strip member 4 with the pad portion 11 via the spring portion 10 and punches it into the die 1 to stop and then the die 1 The valve action metal powder 5 filled in the molding through hole 1a from above is fitted into the molding through hole of the die 1 from above, the powder compact 6 is formed by compression with the upper punch, and the lower punch 2 is lowered. Lower the upper punch 3 and die To knock powder compact 6 having a valve metal plate 4a blanked from 1, the powder compact 6 knockout from the die 1 a manufacturing apparatus for conveying gripping by the clamp mechanism 9 with. afterwards,
The powder compact obtained by this apparatus is sintered by a high-temperature high-vacuum sintering apparatus (not shown) to obtain the solid electrolytic capacitor shown in FIG. Further, an anode lead having a valve action is welded to a valve action metal plate by a laser welding device (not shown) to obtain the solid electrolytic capacitor shown in FIG. With this device configuration, the valve action metal strip member is disposed so as to face the lower surface of the die 1 of the powder molding die, and the valve action metal strip member 4 is inserted while being punched. Therefore, the press punching process and the powder molding process are performed. Since the dies and punches are shared, the operation function becomes simple and the manufacturing apparatus becomes simple. Further, since the powder molded body 6 is knock-afted from the punching side together with the valve action metal plate 4a, an external force is not applied in the direction of separating the contact interface, so that stable LC characteristics can be obtained and a solid electrolytic capacitor of high quality and high efficiency can be obtained. It becomes a manufacturing device to obtain.

[0023]

As described above, when a powder compact of valve action metal powder is sintered to produce a solid electrolytic capacitor, the solid electrolytic capacitor of the present invention can be molded with a valve action metal powder. A valve action metal strip member is punched out by a powder molding die in the contact portion, and is arranged in a stacked state as a valve action metal plate. The valve action metal powder is passed through a die through a first punch and a second punch. Then, the powder compact is inserted into the inside and compressed under pressure to form a powder compact, the powder compact is knocked out by the second punch to the lower side of the through hole of the die, and the discharged powder compact is sintered under high temperature and high vacuum, and thereafter, Anode lead having valve action is laser-welded on the exposed surface of valve action metal plate, a dielectric oxide film is formed on the surface, and a manganese dioxide layer or a conductive polymer layer to be a solid electrolyte is formed on this surface. And then By the method of manufacturing a solid electrolytic capacitor in which a graphite layer serving as a cathode layer and a conductive resin layer are sequentially formed on the surface thereof, it is possible to suppress the occurrence of scratches on the surface of the powder molded body, and therefore, particularly as the capacitor characteristics required by the market. The occurrence of defective LC characteristics due to solder heat resistance can be reduced to 1/3.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an essential part in the order of steps of a method for manufacturing a solid electrolytic capacitor according to an embodiment of the present invention.

FIG. 2 is a perspective view of a solid electrolytic capacitor obtained by the manufacturing method of the present invention.

3 is a perspective view of a solid electrolytic capacitor in which an anode lead is laser-welded to a valve action metal plate of the powder compact after sintering shown in FIG.

FIG. 4 is a cross-sectional view in the order of steps of a conventional molding method.
(JP-A-2-69923).

FIG. 5 is a cross-sectional view in the order of steps of a conventional molding method.
(JP-A-58-96724).

FIG. 6 is a perspective view of a capacitor element in another embodiment of the molding method in FIG.

[Explanation of symbols]

1 die 2 Lower punch (first punch) 3 Upper punch (second punch) 4 Valve metal strip 4a Valve action metal plate 5 Valve metal powder 6 powder compacts 7 Solid electrolytic capacitor 8 Anode lead 9 Clamp mechanism 10 Spring part 11 Pat 12 Feed roller section

Claims (3)

[Claims] 1. A valve action metal plate is disposed in a state of being superposed on a contact portion with the valve action metal powder, and the valve action metal powder is introduced into a through hole of a die by a first punch and a second punch. To form a powder compact by pressurizing and compressing the powder compact, sintering the powder compact at high temperature and high vacuum, and then forming a dielectric oxide film on the surface of which a manganese dioxide layer to be a solid electrolyte, or a highly conductive material. In a method for manufacturing a solid electrolytic capacitor in which a molecular layer is formed and a graphite layer serving as a cathode layer and a conductive resin layer are sequentially formed on the surface of the molecular layer, the powder compact is provided to the lower side of the through hole of the die with a second punch. A method for manufacturing a solid electrolytic capacitor, which comprises knocking out and discharging. 2. A valve action metal strip member is punched from the lower side of the through hole of the die by the die and the first punch, and the punched valve action metal plate is fitted into the through hole of the die and The method for producing a solid electrolytic capacitor according to claim 1, wherein the solid electrolytic capacitor is arranged in a state of being overlapped with a portion that comes into contact with the valve action metal powder. 3. An anode lead having a valve action is laser-welded to an exposed surface of the punched valve action metal plate of the powder compact after the powder compact is sintered at high temperature and high vacuum. A method for manufacturing the solid electrolytic capacitor according to claim 1.