JP5201668B2 - Electrolytic capacitor anode element, manufacturing method thereof, and electrolytic capacitor using the same - Google Patents

Description

  The present invention relates to an anode element for an electrolytic capacitor and a method for manufacturing the same, and more particularly to an electrolytic capacitor anode element having a structure with a small difference in density between sintered parts of the anode element, a method for manufacturing the same, and an electrolytic capacitor using the same.

  In recent years, with the progress of high integration of devices, high characteristics and high reliability of electronic components constituting them have been strongly demanded. Electrolytic capacitors are also required to have a large capacity and a small size, but are also required to have operational stability and structural robustness.

  Tantalum capacitors, one of the electrolytic capacitors that are currently being actively researched and developed, are generally subjected to chemical conversion treatment on the anode element composed of a tantalum anode lead and a tantalum sintered body in which part of the anode element is embedded. It has a structure in which an oxide film serving as a dielectric is formed. The inside of the tantalum sintered body has a feature that a large capacity can be realized since the fine pores are complicated and the surface area is very large, and the oxide film is thin and formed in a wide area. Further, the basic structure of the tantalum capacitor is formed by forming manganese dioxide, a conductive polymer layer, a graphite layer, a silver paste layer, a cathode terminal, or the like that becomes a cathode on the oxide film.

  The anode element used for the tantalum capacitor uses a prismatic or cylindrical shape as the anode lead. 9A and 9B are perspective views showing the structure of a conventional anode element. FIG. 9A shows a prismatic anode element having an anode lead, and FIG. 9B shows an anode element having a cylindrical anode lead. A conventional anode element is configured by embedding a part of an anode lead 2 made of a valve action metal such as tantalum metal in a sintered body 1 obtained by sintering a valve action metal such as tantalum metal powder. .

  As a manufacturing method, a tantalum metal powder and a binder are mixed, put into a mold, and press-molded to obtain a cylindrical or prismatic molded body. At this time, a part of the wire is embedded in the molded body so that a wire made of the same tantalum metal is planted on one end face of the molded body. The molded body in which the tantalum wire is planted is sintered to form the porous sintered body 1 and the anode lead 2, thereby obtaining the anode element of the tantalum capacitor.

  In general, the thickness direction of the anode element is the press-pressing direction at the time of producing the molded body. However, in the conventional anode element, the ratio of the thickness of the anode lead to the thickness of the entire anode element As a result, there is a problem that a density difference occurs between a portion where the anode lead inside the sintered body is embedded and a portion where the anode lead is not embedded. If there is a difference in density between the sintered bodies, it will lead to variations in strength. For example, if stress is applied due to the formation of exterior resin, heat treatment, mechanical impact, etc. after the cathode formation, the oxide film of the anode element may be destroyed. . When the oxide film is destroyed, the anode and the cathode are short-circuited to cause a leakage current failure, which may lead to a decrease in reliability and operational stability.

  In addition, in the prismatic type anode lead, peeling is likely to occur between the lead surface perpendicular to the thickness direction of the anode element and the sintered body portion, and the anode lead is detached, and further, the leakage current is similar to the above. May cause destruction, which may cause deterioration of equivalent series resistance (hereinafter referred to as ESR).

  Furthermore, since the strength of the lead cannot be secured if the conventional anode lead is simply reduced in width and diameter, the size of the anode lead cannot be reduced, and a large proportion of the anode element volume contributes to the capacitance. The low anode lead occupies the volume efficiency, and the anode lead is expensive.

  As electrolytic capacitors are required to be smaller and thinner, the method of reducing the anode lead thickness by making the anode lead shape foil or flat for the purpose of improving ESR, preventing the anode lead from falling off and improving the strength is patented It is proposed in Document 1 and Patent Document 2.

  In Patent Document 1, the anode lead of a chip capacitor is a rectangular parallelepiped molded body obtained by molding the valve action metal powder implanted on one surface of the molded body, and the anode lead is made into a foil shape, and the implanted foil shape An anode element has been proposed in which the width of the anode lead is approximately the same as the width of the molded body.

  Patent Document 2 proposes an anode element in which a portion in which the anode lead is embedded is flattened in a valve-acting metal sheet-like porous sintered body in which a part of the anode lead of the anode element of the electrolytic capacitor is embedded. ing.

  However, in these shapes where the thickness of the anode lead is simply reduced, as described above, there is a problem in that the sintered body becomes rough, the anode lead surface perpendicular to the anode element thickness direction, the sintered body portion, The problem of easy peeling between the electrodes cannot be improved, and there is a high possibility that leakage current and ESR will deteriorate when an anode lead comes off or stress is applied.

JP 2005-101582 A JP 2004-153263 A

  As described above, the electrolytic capacitor anode element using the conventional anode lead is advantageous in terms of cost as well as having a highly reliable structure in which the density difference of the sintered body is small and it is difficult to cause destruction and peeling due to stress. It was difficult to solve the two problems at the same time.

  Therefore, in the present invention, there is little difference in density between the sintered bodies of the anode element, the anode lead and the sintered body are less likely to be peeled off, and the electrolytic capacitor anode element is advantageous in terms of volume efficiency and cost. It is an object of the present invention to provide a method and an electrolytic capacitor using the method.

In order to solve the above problems, an electrolytic capacitor anode element of the present invention includes an anode lead using a valve metal and a sintered body of porous valve metal powder in which a part of the anode lead is embedded. An electrolytic capacitor anode element, wherein the embedded portion embedded in the sintered body of the anode lead is a thin plate, and the maximum width of the embedded portion is the same width as the sintered body, and is cut into the outer periphery of the embedded portion forming a maximum width and maximum length of the incision, and wherein more thickness der Rukoto buried portion of the anode lead.

Further, electrolytic capacitor anodes element of the present invention is characterized by forming one or more through holes before Symbol embedded portion.

  In the electrolytic capacitor anode element of the present invention, the opening size of the through hole formed in the buried portion of the anode lead is such that the maximum inscribed circle diameter of the through hole is equal to or greater than the thickness of the buried portion of the anode lead. It is characterized by that.

  In the electrolytic capacitor anode element of the present invention, the thickness of the buried portion of the anode lead is not more than one third of the total thickness of the electrolytic capacitor anode element.

Further, according to the present invention, before the Kiben action metal powder at the time of press molding, method of manufacturing an electrolytic capacitor anode element, characterized in that pressed in a direction perpendicular to the main surface of the embedded portion of the anode lead Is obtained.

  Moreover, according to the present invention, an electrolytic capacitor using the electrolytic capacitor anode element can be obtained.

  According to the present invention, it is possible to obtain an electrolytic capacitor anode element in which the sintered density of the valve action metal is small, and it is difficult to cause destruction and peeling due to various stresses. Can be provided. Furthermore, in addition to high reliability, the volume of the anode lead can be reduced, so that two effects of providing an electrolytic capacitor anode element and an electrolytic capacitor with high cost performance can be realized simultaneously. Further, if the volume of the anode lead occupying the anode element volume can be reduced, the volume of the sintered body portion can be increased. Therefore, an effect that the capacity can be increased with the same size is also expected.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to these examples. Also, in the drawings, an oxide film, a cathode, a terminal, an exterior resin, and the like serving as a dielectric are omitted, and represent the concept of the structure of the anode element, the shape of the anode lead, and the effect.

FIG. 1 is a structural diagram showing a reference example of an electrolytic capacitor anode element according to the present invention. FIG. 1A is an anode element in which a through hole is provided in the buried portion of an anode lead, and FIG. It is the side view seen from. As shown in FIG. 1, the electrolytic capacitor anode element includes a sintered body 1 made of valve action metal powder and an anode lead 2 made of valve action metal. The anode lead 2 has an embedded portion 3 embedded in the sintered body 1 of the anode element. The embedded portion 3 is a thin plate and has a through hole 12 formed therein.

  FIG. 2 is a schematic diagram for explaining a sectional state of the sintered body of the anode element, FIG. 2 (a) is a sectional view in the width direction of the sintered body of the conventional anode element, and FIG. 2 (b) is the present invention. It is sectional drawing of the width direction of the sintered compact of this anode element. In the case of the conventional anode element structure, as shown in FIG. 2A, the ratio of the thickness of the buried portion 3 of the anode lead 2 to the total thickness of the anode element is large. As a result, when pressure-molding the valve metal powder 4, the portion where the embedded portion 3 of the anode lead 2 is embedded has a large proportion of the valve metal powder 4 in the sintered body 1. The portion where the buried portion 3 of the anode lead 2 is not buried has a large proportion of the gap 5 and the sintered body 1 becomes rough. Further, it can be said that the anode lead surface perpendicular to the pressing direction 6 and the sintered body 1 are easily peeled off and are mechanically weak portions.

  On the other hand, in the case of the structure of the present invention, the ratio of the thickness of the anode lead 2 to the thickness of the entire anode element can be reduced. Although the thickness of the anode lead 2 is reduced by this structure, the anode lead 2 can be embedded almost over the entire surface of the sintered body 1, so that the contact area between the sintered body 1 and the embedded portion 3 of the anode lead 2, the anode lead The thickness of the electrolytic capacitor can be reduced without reducing the strength of 2. Furthermore, by providing the through hole 12 formed in the buried portion 3 of the anode lead 2, the valve metal powder 4 enters the through hole 12 portion, and the bias of the valve metal powder 4 can be prevented. By these, it becomes possible to reduce the density difference of the sintered body 1. Further, the valve metal powder 4 that has entered the through hole 12 has a function of binding the upper and lower portions of the buried portion 3 of the anode lead 2, and it becomes difficult for the anode lead 2 and the sintered body 1 to be peeled off, thereby preventing the lead from coming off. The effect of doing is obtained. In press molding the anode element, it is preferable to press the anode element 2 in a direction perpendicular to the main surface of the buried portion 3 of the anode lead 2. By doing so, the powder can effectively enter the through hole 12 formed in the embedded portion 3.

FIG. 3 is a structural diagram showing a first embodiment of the electrolytic capacitor anode element of the present invention. FIG. 3 (a) is an anode element in which a cut portion is provided in the buried portion of the anode lead, and FIG. It is the side view seen from the paper surface right. In the first embodiment, as shown in FIG. 3, a rectangular cut is provided in the buried portion 3 of the anode element. By this structure, density difference of sintered body 1 is small, while the anode lead 2 and the sintered body 1 is hardly peeled off, it is possible to prevent the lead omission.

FIG. 4 is a structural diagram showing a second embodiment of the electrolytic capacitor anode element of the present invention. FIG. 4 (a) is an anode element in which a through hole and a cut are provided in the buried portion of the anode lead, and FIG. b) is a side view seen from the right side of the drawing. In the second embodiment, as shown in FIG. 4, a rectangular through hole 12 and a wavy cut are provided in the buried portion 3 of the anode element. Thus may be provided a notch and the through hole 12 at the same time, by this structure, less density of sintered body 1 made between the anode lead 2 and the sintered body 1 is hardly peeled off, the lead omission Can be prevented.

  FIG. 5 is a diagram showing another anode lead shape example of the electrolytic capacitor anode element of the present invention, and FIG. 5A is an example in which two rectangular through holes are provided in the horizontal direction in the buried portion of the anode lead. 5B shows an example in which two rectangular through holes are provided in the vertical direction in the buried portion of the anode lead, and FIG. 5C shows a polygonal through hole in the buried portion of the anode lead and the outer periphery. FIG. 5D shows an example in which a comb-shaped cut is provided in the buried portion of the anode lead. Here, a portion surrounded by a dotted line in the drawing is a portion of the anode lead 2 exposed to the outside of the sintered body 1. Thus, the shape and the number of the through holes 12, the shape and the number of the cuts, and the combination thereof are not particularly limited, and can be selected according to the size of the electrolytic capacitor anode element and the manufacturing conditions. However, depending on the particle diameter of the valve metal powder 4 and the pressurization conditions of the pressure molding, it may be difficult for the valve metal powder 4 to enter the corners of the rectangular through holes 12 and the cuts. With this point in mind, it is preferable to use a circular shape, a wavy shape, or round corners.

  Next, the size of the through hole 12 and the size of the cut will be described. FIG. 6 is an enlarged view of the through hole and the cut portion provided in the buried portion of the anode lead. FIG. 6A shows a case where the through hole is elliptical, and FIG. 6B shows a case where the through hole is rectangular. In this case, FIG. 6C shows a case where the cut is wavy, and FIG. 6D shows a case where the cut is rectangular. As for the size of the through hole 12, it is desirable that the diameter 8 of the maximum circle 7 inscribed in the through hole 12 is equal to or larger than the thickness of the anode lead 2. Similarly for the cut size, it is desirable that the maximum width 9 and the maximum length 10 of each cut be equal to or greater than the thickness of the anode lead 2. When the size of the through hole 12 and the cut is set to be equal to or smaller than the thickness of the anode lead 2, the valve metal powder 4 is less likely to flow into the through hole 12 or the cut portion, and a density difference is likely to occur in the sintered body 1. Further, the upper limit of these sizes is not particularly limited, but by adjusting the area where the through hole 12 and the cut are formed so as not to exceed half of the area of the buried portion of the anode lead, It becomes possible to ensure a sufficient contact area of the embedded portion 3.

  The thickness of the buried portion 3 of the anode lead 2 is preferably set to one third or less of the thickness of the entire anode element, and by reducing the thickness, the electrolytic capacitor is made thinner and the volume efficiency of the anode element is improved. Also, it is advantageous in terms of cost. If the thickness of the embedded portion 3 is set to one third or more, the flow of the valve action metal powder 4 becomes worse, and a density difference of the sintered body 1 occurs. The lower limit value of the thickness of the embedded portion 3 is preferably 1/10 or more of the thickness of the whole anode element, and when this is less than 1/10, the embedded portion 3 is destroyed during pressure molding. This is because there is a possibility that it will occur. By setting it to 1/10 or more, the strength is secured.

  The width of the buried portion 3 of the anode lead 2 is preferably substantially the same as the width of the anode element in order to secure a contact area between the sintered body 1 and the buried portion 3 and may be the same size. . However, in order to make it the same size, it is necessary to make a cut in the outer periphery of the embedded portion 3 to improve the flow of the valve action metal powder 4. Furthermore, the shape of the portion of the anode lead 2 that is not embedded in the sintered body 1 is not particularly limited, but has a thickness and a width that can ensure strength.

  Hereinafter, specific examples of the present invention will be described. However, the present invention is not limited to the following examples, and the present invention can be applied even to configurations with design changes within a scope not departing from the gist of the present invention. It is included.

In the present invention, tantalum is used as the valve metal of the anode element. A tantalum powder having a tantalum purity of 99.5% or more and an average primary particle diameter of D ₅₀ = 0.4 μm was used. An acrylic binder was used as the binder. An anode lead having a structure according to an embodiment to be described later is embedded in tantalum powder, subjected to pressure molding with a pressure of 200 kgf, subjected to binder removal treatment, sintered at 1300 ° C., and a length of 5 mm (sintered body length). 4.3 mm), a width of 3.5 mm, and a thickness of 2 mm were obtained.

As a reference example, as shown in FIG. 1, an elliptical through hole 12 was formed in the embedded portion 3 of the anode lead 2. The anode lead 2 had a width of 3.0 mm, the buried portion 3 had a length of 4.0 mm, and the ellipse had a major axis of 1.5 mm and a minor axis of 1.0 mm. The thickness of the anode lead 2 was 0.15 mm, and the portion not embedded in the sintered body 1 was also the same thickness.

As Example 1 , a rectangular cut was formed on the outer periphery of the embedded portion 3 of the anode lead 2 as shown in FIG. The width of the anode lead was 3.5 mm, the length of the buried portion was 4.0 mm, the rectangular cut width was 0.8 mm, the cut depth was 1.5 mm, and four cuts were formed. Further, the thickness of the anode lead was 0.15 mm, and the portion not embedded in the sintered body 1 was also made the same thickness.

As Example 2, as shown in FIG. 4, a rectangular through hole 12 was formed in the embedded portion 3 of the anode lead 2, and a wavy cut was formed on the outer periphery. The maximum width of the anode lead was 3.5 mm, the maximum length of the buried portion was 4.0 mm, and the wavy cuts had a maximum cut width of 0.5 mm and a maximum cut depth of 1 mm. The size of the through hole 12 was 2.0 mm × 1.0 mm. The thickness of the anode lead 2 was 0.15 mm, and the portion not embedded in the sintered body 1 was also the same thickness.

As a comparative example, an anode element having a conventional structure was produced. 7A and 7B are diagrams showing the structure of a conventional electrolytic capacitor anode element. FIG. 7A is a view in which a square anode lead is embedded, and FIG. 7B is a side view as viewed from the right side of the drawing. . The material and size of the anode element were the same as in the embodiment of the present invention, and the manufacturing method was also made under the same conditions except that no through hole or notch was formed.
The width of the anode lead 2 was 2 mm, the length of the embedded portion 3 was 4.0 mm, the thickness was 0.7 mm, and the portion not embedded in the sintered body 1 was also the same thickness.

  About the anode element mentioned above, the density variation of the sintered compact 1 of an anode element was evaluated with the following method.

  About the anode element obtained after sintering, the cross section was produced so that the anode element longitudinal direction might be crossed. The cross-sectional location was set to the approximate center of the sintered body 1 and a portion where the cross section of the buried portion 3 of the anode lead and the cross section of only the sintered body 1 could be observed was selected. In preparation of the cross section, the cross section was polished using a cross section polisher SM-09010 manufactured by JEOL Ltd. after hand polishing with abrasive paper. FIG. 8 is a diagram showing the observation location of the cross section of the anode element of the present invention and the comparative example, FIG. 8A is a cross sectional view of Example 1, FIG. 8B is a cross sectional view of Example 2, FIG. 8C is a sectional view of Example 3, and FIG. 8D is a sectional view of a comparative example. The obtained cross section was observed with a scanning electron microscope, photographed, and subjected to image processing, and the areas of the valve metal powder 4 and the voids 5 were determined in the range of the analysis site 11. The range of the analysis part 11 was 85 μm × 60 μm, and the ratio of the area of the gap 5 to the area of the analysis part 11 was calculated. As shown in FIG. 8, the analysis portion 11 was evaluated at five locations a to d in the width direction.

Table 1 shows the results of evaluating the void area ratio of the cross sections of the sintered bodies of the anode elements of the reference examples, Examples 1 and 2 and the comparative example.

  In the comparative example, in the portions a and b where the anode lead embedded portion 3 overlaps in the pressing direction at the time of molding, the void area ratio is low and the sintered body is dense. In the portions c, d, and e that do not overlap with the embedded portion 3, the void area ratio is low and the sintered body tends to be rough. Further, during cross-sectional observation, it was confirmed that peeling occurred between the main surface of the buried portion 3 of the anode lead perpendicular to the pressing direction and the sintered body 1.

On the other hand, in Examples 1 and 2 , it is clear that the difference in the void area ratio depending on the analysis location is smaller than that in the comparative example, and the density variation is improved. Further, in Examples 1 and 2 , peeling between the main surface of the buried portion 3 of the anode lead perpendicular to the pressing direction and the sintered body 1 was not observed, and a through hole formed in the buried portion 3 of the anode lead It has been confirmed that the valve action metal powder 4 entering the cut can avoid the occurrence of peeling by binding the upper part and the lower part of the buried part.

  As described above, according to the present invention, there is little density variation of the sintered body 1 of the valve action metal, and the electrolytic structure has a structure capable of preventing the occurrence of lead omission, destruction due to application of various stresses, and occurrence of peeling. It was found that a capacitor anode element was obtained. Also, by adopting the electrolytic capacitor anode element and the manufacturing method of the present invention, the volume of the anode lead occupying the entire volume of the anode element can be reduced, and even when it is downsized, the volume efficiency is good and the cost performance is high. Capacitors can be provided.

FIG. 3 is a structural diagram showing a reference example of the electrolytic capacitor anode element of the present invention. FIG. 1A is a view showing an anode element in which a through hole is provided in a buried portion of an anode lead. FIG.1 (b) is the side view seen from the paper surface right. The schematic diagram explaining the cross-sectional state of the sintered compact of an anode element. FIG. 2A is a cross-sectional view in the width direction of a sintered body of a conventional anode element. FIG.2 (b) is sectional drawing of the width direction of the sintered compact of the anode element of this invention. 1 is a structural diagram showing a first embodiment of an electrolytic capacitor anode element of the present invention. FIG. 3A is a view showing an anode element in which a cut portion is provided in a buried portion of an anode lead. FIG. 3B is a side view as viewed from the right side of the drawing. FIG. 3 is a structural diagram showing a second embodiment of the electrolytic capacitor anode element of the present invention. FIG. 4A is a view showing an anode element in which a through hole and a cut are provided in the buried portion of the anode lead. FIG. 4B is a side view as viewed from the right side of the drawing. The figure which shows the other anode lead shape example of the electrolytic capacitor anode element of this invention. FIG. 5A is a diagram showing an example in which two rectangular through holes are provided in the lateral direction in the buried portion of the anode lead. FIG. 5B is a view showing an example in which two rectangular through holes are provided in the vertical direction in the buried portion of the anode lead. FIG.5 (c) is a figure which shows the example which provided the polygonal through-hole in the embedding part of an anode lead, and the wavy cut | notch in the outer periphery. FIG.5 (d) is a figure which shows the example which provided the comb-shaped cut | notch in the embedding part of the anode lead. The enlarged view of the through-hole provided in the embedding part of an anode lead, and a notch part. 6A is a diagram showing a case where the through hole is elliptical, FIG. 6B is a diagram showing a case where the through hole is rectangular, and FIG. 6C shows a case where the notch is wavy. FIG. 6 and FIG. 6D are diagrams showing a case where the cut is rectangular. The figure which shows the structure of the conventional electrolytic capacitor anode element. FIG. 7A is a view in which a square anode lead is embedded, and FIG. 7B is a side view as viewed from the right side of the drawing. The figure which shows the observation location of the cross section of the anode element of this invention, a reference example, and a comparative example. 8A is a cross-sectional view of a reference example , FIG. 8B is a cross-sectional view of the first embodiment , FIG. 8C is a cross-sectional view of the second embodiment , and FIG. 8D is a comparative example. FIG. The perspective view which shows the structure of the conventional anode element. FIG. 9A is a diagram showing an anode element whose anode lead is a prismatic type, and FIG. 9B is a diagram showing an anode element whose anode lead is a cylindrical type.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sintered body 2 Anode lead 3 Buried part 4 Valve action metal powder 5 Cavity 6 Pressurizing direction 7 Maximum circle inscribed in the through hole 8 Maximum diameter (of the largest circle inscribed in the through hole) Maximum diameter 10 (of the notch) Maximum length 11) Analysis location 12 Through hole

Claims (6)

An electrolytic capacitor anode element having an anode lead using a valve metal and a sintered body of porous valve metal powder in which a part of the anode lead is embedded, embedded in the sintered body of the anode lead The embedded portion is a thin plate, and the maximum width of the embedded portion is the same as that of the sintered body, and a cut is formed in the outer periphery of the embedded portion, and the maximum width and the maximum length of the cut are determined by the anode. electrolytic capacitor anode element characterized above thickness der Rukoto buried portion of the lead. Electrolytic capacitor anode element according to claim 1, wherein the forming one or more through holes in the embedded portion. Opening size of the through hole formed in the embedded portion of the anode lead, a maximum inscribed circle diameter of the through hole, according to claim 2, characterized in that said at anode lead than the thickness of the embedded portion Electrolytic capacitor anode element. The thickness of the buried portion of the anode lead, electrolytic capacitor according to any one of claims 1 to 3, characterized in that said at electrolytic less capacitor anode one-third of the total thickness of the element Anode element. When press molding the valve action metal powder, electrolytic capacitor according to any one of claims 1 to 4, characterized in that pressed in a direction perpendicular to the main surface of the embedded portion of the anode lead A manufacturing method of an anode element. The electrolytic capacitor using the electrolytic capacitor anode element as described in any one of Claims 1 thru | or 4 .

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