JPH0493012A - Solid-state electrolytic capacitor and its manufacture - Google Patents

Abstract

PURPOSE:To relieve failures in electric characteristics such as capacitance shortage, increases in leakage current, and increases in impedance by press- molding a metal powder having valve action with anode leads planted and by providing a water-repellent insulating resin layer on the periphery of or around projections or recesses of anode leads in the cross-sectional direction. CONSTITUTION:After tantalum powder is press-molded and implanted with anode leads 1, it is sintered in vacuum and welded to a supporter 5 to provide a press molding 2. Next, a part of anode leads are rolled by a clamp 6 made of a supernet or the like so that projections dog-legged away from the center line 1c of the anode lead 1 may face back to back across the center line, thereby providing the bump 1a of an anode lead. The top of the bump 1a of an anode lead and its surrounding is coated annularly with an insulating resin such as polyterafluoroethylene by means of a dispenser and the like: this resin is dried and hardened to form a dielectric film layer. Dipping the workpiece in a solution 7 manganese nitrate makes the insulating resin 4 repel the solution 7. Finally, after a solid-state electrolyte layer is formed by pyrolysis, a graphite layer and a silver paste layer are formed successively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid electrolytic capacitor and a method for manufacturing the same, and more particularly to an improvement in the structure of a capacitor element and a method for manufacturing the same.

[Conventional technology]

Generally, the element of a solid electrolytic capacitor is made of metal powder having a valve action such as tantalum, niobium, or aluminum, and an anode lead 6 of the same type as the metal powder described above, as shown in FIG. 9(a).
] is partially buried and pressed to form a press molded body 62 having a cylindrical, prismatic, etc. shape, and then vacuum sintered to form a sintered body 63 having a porous structure. Next, as shown in FIG. 9(b), the anode lead 61 of the sintered body 63 is connected to the support material 5 made of conductive metal by a construction method such as welding, and then immersed in an electrolytic solution, and by an electrochemical construction method. A dielectric film layer is formed around the sintered body 63. Next, an insulating resin 64 having heat resistance, chemical resistance, and water soakability, such as polytetrafluoroethylene, is applied around the portion 61b of the anode lead 6 near the press-molded body 62, and is dried and hardened. Next, as shown in FIG. 10, the sintered body 63 on which the dielectric film layer has been formed is immersed in the manganese nitrate aqueous solution 7 up to the area where the insulating resin 64 is applied, and the inside of the sintered body is not impregnated. 200-40
Repeated thermal decomposition in a high temperature atmosphere of 0°C resulted in a sintered body 6.
A solid electrolyte layer made of manganese dioxide is formed on the dielectric film layer No. 3. Next, a cathode extraction layer 8 made of graphite and silver paste is placed on top of it as shown in FIG. 9(b).
), six solid electrolytic capacitor elements were formed.

[Problem to be solved by the invention] However, the conventional sintered body described above has the following drawbacks.

(1) Since the insulating resin 64 is applied to the surface of the anode lead 61 which has a smooth curved surface, the self-weight of the insulating resin 64 causes the first
As shown in FIG.
2 and penetrates into the press-formed body, resulting in a decrease in the coverage of the manganese dioxide layer and a deterioration in electrolyte permeability during repair of the dielectric film layer, resulting in insufficient capacity, increased leakage current, etc.
This causes deterioration of electrical characteristics such as an increase in impedance.

2) On the other hand, as capacitors become smaller and larger in capacity, the connection point between the anode lead of the capacitor element and the externally drawn out anode terminal is extremely close to the press molded body 62, and therefore the limited area on the anode lead 61 is There is a need to accurately and appropriately apply the insulating resin 64 to narrow areas.

The first object of the present invention is to prevent the insulating resin formed at a predetermined position of the anode lead from sagging before forming the semiconductor layer, to prevent the insulating resin from entering the press molded body, and to improve the coverage of the manganese dioxide layer. It is an object of the present invention to provide a solid electrolytic capacitor and a method for manufacturing the same, which can eliminate defects in dielectric film layer repair and decrease in electrical characteristics such as insufficient capacity, increased leakage current, and large impedance.

A second object of the present invention is to be able to apply the insulating resin accurately and in an appropriate amount, and to bring the connection point between the anode lead of the capacitor element and the externally drawn anode terminal close to the press-formed body. The object of the present invention is to provide a solid electrolytic capacitor that can achieve higher density and a method for manufacturing the same.

[Means to solve the problem]

In the solid electrolytic capacitor of the first aspect of the present invention, an anode lead is embedded in a metal powder having a valve action, press-formed, and vacuum sintered. Or a recess is provided, and a water-soluble insulating resin layer such as Volite I to Lafluoroethylene is further provided on and around the cross-sectional protrusion or recess on the anode lead or in and around the recess. Constructed as a feature.

In addition, the method for manufacturing a solid electrolytic capacitor according to the second aspect of the present invention includes a step of embedding and press-molding a part of an anode lead in a metal powder having a valve action to obtain a press-molded body, and a step of obtaining a press-molded body. a step of vacuum sintering to obtain a sintered body; a step of forming a convex portion or a concave portion in a cross-sectional direction of the anode lead at a portion of the anode lead of the sintered body that is a predetermined distance away from the press-formed body; A step of coating and curing a clear water insulating resin such as polytetrafluoroethylene on and around the part or in and around the recess to form a ring-shaped insulating resin layer, a step of forming a dielectric film layer, and a step of forming a solid insulating resin layer. and forming an electrolyte layer.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

1(a) to (c) are a side sectional view and a perspective view showing the structure of a solid electrolytic capacitor element according to a first embodiment of the present invention, an enlarged view of an anode lead convex portion, and FIG. ,(b),(
d) and (e) are side views sequentially explaining the manufacturing process of the solid electrolytic capacitor element of the present invention, and FIG. 2(c) is a sectional view of the anode lead convex portion.

[Reference numeral in the figure]a is a portion 1b that is close to the press molded body 2 and the anode lead 17 made of the same kind of metal as the press molded body 2 made of metal powder having a valve action, and is aligned with the center line of the anode lead 1. There are convex portions with dogleg-shaped protrusions in two directions facing each other in parallel, and 4 is a heat-resistant, chemical-resistant, and water-resistant material filled on the convex portion 1a of the anode lead 1. It is an insulating resin with

Next, the solid electrolytic capacitor element used in the embodiment of the present invention will be explained in detail in comparison with the solid electrolytic capacitor element used in the conventional example.

FIG. 9(a) shows a conventional homogeneous electrolytic capacitor element.
As shown in (b) and outlined, tantalum powder was press-molded to a diameter of 0.4. The anode lead 61 is buried at a depth of 1. ．． Obtain a cylindrical press molded body 62 having a diameter of 5 mm, an element diameter of 2.0 mm, and a total length of 3.0 mm. next,
This press-formed body 62 was vacuum sintered in a vacuum high temperature furnace at a vacuum degree of 10-'torr and a temperature of 1700°C to obtain a sintered body 63.

Next, it is connected to a supporting material 5 made of conductive metal such as copper, silver, or aluminum by a method such as welding, and then immersed in an electrolytic solution made of an aqueous solution such as nitric acid or sulfuric acid, and then sintered by an electrochemical method. A dielectric film layer made of tantalum pentoxide is formed on the surface of the tantalum including the cavity of the body 63, and then 0.5 mrnll is formed from the press molded body 62 of the anode lead 61.
An insulating resin 64 such as Boritel to Lafluoroethylene is applied on the circumference of the press-formed body adjacent portion 61 to a width of 0.3 mm and a thickness of about 0.3 mm using a dispenser, etc. After drying and hardening, a manganese nitrate aqueous solution is applied. A solid electrolyte layer made of manganese dioxide is formed by pyrolysis in a high-temperature atmosphere of 200 to 400 degrees Celsius, and after repeating this manganese dioxide formation process several times, a graphite layer, a silver paste layer, etc. Six solid electrolytic capacitor elements were formed by sequentially forming cathode extraction layers 8.

On the other hand, as a solid electrolytic capacitor element according to an embodiment of the present invention, the same tantalum powder as in the conventional example described above is press-molded, the anode lead 1 is embedded, vacuum sintered, and then the same metal as in the conventional example described above is formed. Welded to the supporting material 5, shown in Fig. 2 (
A press molded product shown in a> is obtained. Next, Fig. 1(C) and Fig. 2(b).

As shown in (C), from the press molded body 2 of the anode lead 1
．． At the part 5 mm away from the center line of the anode lead, there is a dogleg-shaped protrusion with a maximum width of Q, 3 mm in the direction away from the center line IC of the anode lead. A part of the anode lead 1 was rolled using a clamp 6 made of steel or the like to obtain a convex portion 1a of the anode lead. Next, as shown in FIG. 2(d), using a dispenser or the like, an insulating resin is applied in a ring shape to the upper part of the convex part [a] of the anode lead and its surroundings, dried and hardened, and then electrochemical A dielectric film layer is formed using a conventional method. Next, when immersed in a manganese nitrate aqueous solution,
As shown in FIG. 2(e), the insulating resin 4 makes the manganese nitrate aqueous solution 7 clear. Next, thermal decomposition is performed in the same manner as in the conventional example to form a solid electrolyte layer made of manganese dioxide. After repeating this manganese dioxide forming process several times, a graphite layer and a silver paste layer are sequentially formed. A solid electrolytic capacitor element according to one example was obtained.

In the conventional example, due to variations in the viscosity and thixotropy of the insulating resin, even if the coating was applied to a predetermined position on the anode lead, it would sag on the anode lead due to its own weight.In contrast, in the present invention, the anode By providing a convex portion on the lead and applying insulating resin to the upper part of the convex portion, the contact area per volume of the insulating resin with the anode lead becomes larger, and the insulating resin is held on the convex portion, thereby increasing the contact area of the insulating resin with the anode lead. It has the advantage that sagging does not occur, and the occurrence of capacity shortage due to a decrease in coating rate can be reduced to less than half that of the conventional method.

FIG. 3 is a perspective view showing another embodiment of the present invention, showing the shape before applying the insulating resin. In this embodiment, like the previous example, metal powder having a valve action is press-molded and pressed. After forming the molded body 2, a portion 11.=9]0 close to the press molded body 2 is placed on the anode lead leading out from the press molded body 2. At b, the center line of the anode lead], 1 a convex part of the anode lead with two successive dogleg-shaped protrusions parallel to c and in two opposing directions], 1a are obtained, and 2 The successive protrusions expand the contact area with the resin, so that an effect equal to or greater than that of Example 1 can be obtained.

FIG. 4 is a perspective view for explaining a third embodiment of the present invention. In Example 3, in contrast to Example 1, where the convex portions of the anode lead were provided at two locations opposite to each other across the center line,
The same effect as in Example 1 can be obtained with the protrusion 21a of the anode lead in which a protrusion having a dogleg shape in cross section is provided in a ring shape around the anode lead 21, and since the protrusion goes around the anode lead once, The insulating resin becomes even more difficult to sag.

Note that the shape of the convex portion is not limited to that of this embodiment, but is similar to that of the second embodiment. Similar effects can be obtained with shapes such as a combination of the third embodiment and a shape in which the two-stage protrusions are rotated by 90 degrees with respect to the center line of the anode lead and provided alternately.

Furthermore, the process of forming the convex portions is not limited to after connecting the sintered body to the support material, but can also be performed during processing of the wire material, during formation of the press-formed body, after sintering the press-formed body, or during dielectric film formation. Of course, the same effect can be obtained even if the process is performed later.

FIGS. 5(a) and 5(b) are a side sectional view and a perspective view showing the structure of a solid electrolytic capacitor element according to a fourth embodiment of the present invention, and FIGS. FIG. 3 is a side view sequentially explaining the manufacturing process of the solid electrolytic capacitor element of the example.

In the figure, reference numeral 3], a denotes an anode lead 31 made of the same kind of metal as the press molded body 2 made of metal powder having a valve action.
At the top, there is a part 3 near the press-formed body, and at b, a U-shaped recess is provided from two directions parallel to the center line 3]-c of the anode lead 3 and facing each other. can be,
Reference numeral 34 denotes an insulating resin having heat resistance, chemical resistance, and water immersion property, which is filled in the recess 31a of the anode lead 31.

The manufacturing process is similar to the first embodiment described above, in which tantalum powder is press-molded and the anode lead 31 is embedded, followed by vacuum sintering, and then the supporting material 5 made of the same metal as in the conventional example described above is formed. The press-formed body shown in FIG. 5(a) is obtained.

Next, as shown in FIG. 6(b), a portion of the anode lead 3 which is 0.5 mm away from the press-formed body 2 has a width of 0.3 mm in the direction of the center line 31C of the anode lead and a depth of 0.1 m in the diametrical direction.
The U-shaped recess 31a of the anode lead was formed under pressure using a clamp 36 made of super steel or the like so that the U-shaped recesses faced each other with the center line 31c interposed therebetween. Next, as shown in FIG. 6(C), an insulating resin is coated in a ring shape inside and around the recess 31a of the anode lead using a dispenser or the like, dried and hardened, and then electrochemically applied. Form a dielectric film layer.

Next, when immersed in a manganese nitrate aqueous solution, the insulating resin 34 repels the manganese nitrate aqueous solution as shown in FIG. 6(d). Next, similar to the conventional example, thermal decomposition is performed to form a solid electrolyte layer made of manganese dioxide, and after repeating this manganese dioxide forming process several times, a taraphite layer, a silver Paste layers were sequentially formed to obtain a solid electrolytic capacitor element according to a fourth embodiment of the present invention.

In this example, by providing four parts on the anode lead and putting insulating resin inside them, the contact area per volume of the insulating resin with the anode lead is increased, the insulating resin is held in the recessed part, and the recessed part The resin is supported by the side surfaces of the insulating resin, which has the advantage of preventing the insulating resin from sagging.

FIG. 7 is a perspective view showing a fifth embodiment of the present invention, and shows the shape before application of insulating resin. In this example, similarly to the previous example, a metal powder having a valve action is press-molded to form a press-formed body 2, and then a portion close to the press-formed body 2 is placed on the anode lead led out from the press-formed body 2. 4
1b, U-shaped recesses are provided from two directions parallel to and facing the center line 41c of the anode lead, and fine sawtooth-like unevenness 4 is provided in the portion parallel to the center line 41c of the anode lead. , d of the anode lead is obtained, and fine sawtooth irregularities 41 . By having d, an effect equal to or greater than that of Example 4 can be obtained.

FIG. 8 is a perspective view of a sixth embodiment of the present invention. In Embodiment 6, in contrast to Embodiment 4, in which the recesses of the anode lead were provided at two locations facing each other across the center line, a recess with a U-shaped cross section was provided in a ring shape around the anode lead 51. Four parts 51a of the anode lead are obtained, and the same effect as in Example 4 is obtained, and since the recess goes around the anode lead once, the insulating resin becomes even more difficult to sag.

Note that the shape of the recess is not limited to the above-mentioned embodiment.
Fifth. A similar effect can be obtained even if the sixth embodiment is combined, or if the recess is formed into a shape such as a grid-like fine unevenness.

Furthermore, the process of forming the depressions is not limited to after the sintered body is connected to the support material, but can be performed at the time of forming the press-formed body, after sintering the press-formed body, after forming the dielectric film, etc., with the same effect. Of course, it can be obtained.

〔Effect of the invention〕

As explained above, the present invention has the following effects.

(1) The insulating resin applied on the anode lead is held on the convex part or in the concave part formed on the anode lead, so it does not sag, and the insulating resin does not enter the press molded body and oxidizes. Decreased coverage of the manganese layer and defective recovery of the dielectric film layer are eliminated, and defects in electrical characteristics such as insufficient capacity, increased leakage current, and large impedance can be reduced.

(2) Since the insulating resin can be applied accurately and in the appropriate amount, the connection point between the anode lead of the capacitor element and the externally drawn anode terminal can be brought closer to the press molded body, thus creating a higher-density monolithic electrolytic capacitor. I can do it.

[Brief explanation of drawings]

FIGS. 1(a) to (c) are a side sectional view, a perspective view, and an enlarged view of four parts of the anode lead of a solid electrolytic capacitor element according to a first embodiment of the present invention, and FIGS. 2(a) to (e) are Figure 1(a)~
(c) is a side view for explaining the manufacturing process of the first embodiment, FIG. 3 is a perspective view of the second embodiment of the present invention, and FIG. 4 is a perspective view of the third embodiment of the present invention. Figure 5 (a), (b)
) are side sectional views and perspective views of the fourth embodiment of the present invention;
Figures 6(a) to (d) are the fourth
7 is a side view for explaining the manufacturing process of the embodiment of the present invention, FIG. 7 is a perspective view of the fifth embodiment of the present invention, and FIG. 8 is the sixth embodiment of the present invention.
FIGS. 9(a) and 9(b) are an immediate cross-sectional view of a sintered body of a conventional solid electrolytic capacitor and a front view after forming a cathode extraction layer, and FIG. 10 is a view after forming an insulating resin. FIG. 11 is a front view showing a sintered body being immersed in an aqueous manganese nitrate solution, and FIG. 11 is a front view showing a defective sintered body in which the insulating resin hangs down in a conventional example. 1.11,21,3], 41.51... Anode lead, la, ], la, 21 a... Convex portion of anode lead,
3], a, 41a, 51a... recessed part of anode lead, ]
b, ], lb, 31F+, 4], b, 61b...portion close to the anode lead and press molded body, lc, 11c
, 31c, 4], c...center line of anode lead, 4]d
・・Sawtooth-like fine unevenness, 2 ・・Press molded product, 3.
33.63... Sintered body, 4, 34.64... Insulating resin, 5... Support material, 6, 36... Clamp, 7...
・Mankan nitrate aqueous solution, 8.・Cathode extraction layer, 69・
...Solid electrolytic capacitor element.

Claims (2)

[Claims] 1. In a solid electrolytic capacitor, an anode lead is embedded in a metal powder having a valve action, press-formed, and an anode body is vacuum sintered, and an anodized layer, a solid electrolyte layer, and a cathode extension part are sequentially provided on the surface of the anode body. The anode lead of the anode body is provided with a convex part or a concave part in the cross-sectional direction of the anode lead, and on and around the convex part formed on the anode lead,
Alternatively, a solid electrolytic capacitor characterized in that a water-repellent insulating resin layer made of polytetrafluoroethylene or the like is provided in and around the recess. 2. A step of embedding and press-molding a part of an anode lead in a metal powder having a valve action to obtain a press-formed body, a step of vacuum-sintering the press-formed body to obtain a sintered body, and a step of obtaining an anode of the sintered body. forming a convex portion or a concave portion in the cross-sectional direction of the anode lead at a portion of the lead that is a predetermined distance from the press molded body; and forming a polytetrafluoroethylene or the like on and around the convex portion or in and around the concave portion. A solid electrolytic capacitor comprising the steps of applying and curing a water-repellent insulating resin to form an annular insulating resin layer, forming a dielectric film layer, and forming a solid electrolyte layer. Production method.