JP7576742B2 - Electrolytic capacitor and its manufacturing method - Google Patents

Description

The present invention relates to an electrolytic capacitor and a method for manufacturing the same.

Electrolytic capacitors are used in a variety of electronic devices because they have a small equivalent series resistance (ESR) and excellent frequency characteristics. Electrolytic capacitors usually have a capacitor element with an anode part and a cathode part, an anode terminal (anode lead terminal) that is electrically connected to the anode part, and a cathode terminal (cathode lead terminal) that is electrically connected to the cathode part. The capacitor element is usually sealed with an exterior resin.

Patent Document 1 proposes that in a capacitor chip formed by laminating capacitor elements on one or both sides of a lead frame and then sealing the resulting laminate with resin, the distance from the top of the laminate to the top surface of the sealing resin and the distance from the bottom of the laminate to the bottom surface of the sealing resin are set within a certain range.

International Publication No. 2007/069670

Capacitor elements are usually sealed with exterior resin by injection molding, such as the transfer molding method. In this case, the mold is provided with an injection port (also called a "gate") for injecting resin into the mold. After molding, a protruding part is formed on the exterior body due to the injection port. This part is cut and removed during the manufacturing process, but marks caused by cutting the gate remain on the outer surface of the exterior body.

The area of the capacitor element near the gate collides with the liquid resin and is subjected to stress, making the dielectric coating and solid electrolyte layer susceptible to damage. This can result in a decrease in the reliability of the electrolytic capacitor, such as an increase in leakage current.

One aspect of the present invention relates to an electrolytic capacitor comprising a capacitor element having an anode portion and a cathode portion, an anode terminal electrically connected to the anode portion, a cathode terminal electrically connected to the cathode portion, and an exterior body covering the capacitor element with a portion of the anode terminal and a portion of the cathode terminal exposed, the capacitor element having a first main surface, a second main surface sharing one side with the first main surface, and a third main surface sharing one side with the first main surface and located on the opposite side to the second main surface, the cathode terminal having a mounting portion facing the first main surface on which the capacitor element is mounted, and a sidewall portion bending from the mounting portion and extending in a direction intersecting the first main surface, the exterior body having a resin injection mark, the resin injection mark being located opposite the sidewall portion.

Another aspect of the present invention relates to a method for manufacturing an electrolytic capacitor, comprising the steps of: preparing a capacitor element having an anode portion and a cathode portion; preparing an anode terminal and a cathode terminal; connecting the anode portion of the capacitor element to the anode terminal and the cathode portion of the capacitor element to the cathode terminal; and sealing the capacitor element with an exterior body by injection molding so that a part of the anode terminal and a part of the cathode terminal are exposed, the cathode terminal having a mounting portion on which the capacitor element is mounted and a sidewall portion that is bent from the mounting portion and extends in a direction intersecting a main surface of the mounting portion, and in the step of sealing with the exterior body, a gate for pouring exterior resin into a mold is made to face the sidewall portion of the capacitor element.

The present invention suppresses an increase in leakage current and improves the reliability of electrolytic capacitors.

1 is a cross-sectional view illustrating a schematic configuration of an electrolytic capacitor according to one embodiment of the present invention. FIG. 2 is a perspective view showing a part of the cathode terminal in FIG. 1 . 1 is a schematic cross-sectional view of a capacitor element according to one embodiment of the present invention. FIG. 4 is a perspective view showing another example of a cathode terminal used in the electrolytic capacitor according to one embodiment of the present invention. FIG. 4 is a perspective view showing another example of a cathode terminal used in the electrolytic capacitor according to one embodiment of the present invention. FIG. 4 is a perspective view showing another example of a cathode terminal used in the electrolytic capacitor according to one embodiment of the present invention. FIG. 4 is a perspective view showing another example of a cathode terminal used in the electrolytic capacitor according to one embodiment of the present invention. FIG. 4 is a perspective view showing another example of a cathode terminal used in the electrolytic capacitor according to one embodiment of the present invention. FIG. 4 is a perspective view showing another example of a cathode terminal used in the electrolytic capacitor according to one embodiment of the present invention. FIG. 4 is a perspective view showing another example of a cathode terminal used in the electrolytic capacitor according to one embodiment of the present invention. FIG. 4 is a perspective view showing another example of a cathode terminal used in the electrolytic capacitor according to one embodiment of the present invention. FIG. 4 is a perspective view showing another example of a cathode terminal used in the electrolytic capacitor according to one embodiment of the present invention. FIG. 11 is a cross-sectional view illustrating a schematic configuration of another example of an electrolytic capacitor according to an embodiment of the present invention. FIG. 11 is a cross-sectional view illustrating a schematic configuration of another example of an electrolytic capacitor according to an embodiment of the present invention. FIG. 11 is a cross-sectional view illustrating a schematic configuration of another example of an electrolytic capacitor according to an embodiment of the present invention. FIG. 11 is a cross-sectional view illustrating a schematic configuration of another example of an electrolytic capacitor according to an embodiment of the present invention. FIG. 11 is a cross-sectional view illustrating a schematic configuration of another example of an electrolytic capacitor according to an embodiment of the present invention. FIG. 11 is a cross-sectional view illustrating a schematic configuration of another example of an electrolytic capacitor according to an embodiment of the present invention. FIG. 11 is a cross-sectional view illustrating a schematic configuration of another example of an electrolytic capacitor according to an embodiment of the present invention. FIG. 11 is a cross-sectional view illustrating a schematic configuration of another example of an electrolytic capacitor according to an embodiment of the present invention.

The electrolytic capacitor according to this embodiment includes a capacitor element having an anode portion and a cathode portion, an anode terminal electrically connected to the anode portion, a cathode terminal electrically connected to the cathode portion, and an exterior body. The exterior body covers the capacitor element with the anode terminal and a portion of the cathode terminal exposed. The capacitor element has a first main surface, a second main surface sharing one side with the first main surface, and a third main surface sharing one side with the first main surface and located on the opposite side to the second main surface. The cathode terminal has a mounting portion facing the first main surface on which the capacitor element is mounted, and a sidewall portion bent from the mounting portion and extending in a direction intersecting the main surface of the mounting portion. The exterior body has resin injection marks.

The cathode part is formed, for example, so as to cover the anode part (anode body) having a shape of a substantially rectangular parallelepiped via a dielectric layer. In this case, like the anode part, the cathode part can also be formed to have an outer surface of a substantially rectangular parallelepiped. The first to third main surfaces of the capacitor element can be the outer surface of this substantially rectangular parallelepiped cathode part. In this case, the outer surface of the cathode part can have a fourth main surface that intersects with the first to third main surfaces and connects with the second and third main surfaces, and a fifth main surface opposite the first main surface. These first to fifth main surfaces and the sixth main surface opposite the fourth main surface can constitute the main surfaces of the capacitor element. These main surfaces are conceptual surfaces conceived from the shape of the capacitor element, and do not need to be flat. These main surfaces do not necessarily need to be flat, and may have a curved shape, have some unevenness, and/or be formed by multiple bent planes. Additionally, the angles between adjacent main surfaces may be right angles, acute angles, or obtuse angles. In other words, one main surface may be inclined with respect to the other main surface.

The capacitor element is placed on the main surface (mounting surface) of the mounting portion of the cathode terminal with the first main surface facing down, and the capacitor element is sealed in an exterior body. At this time, a part of the cathode terminal can be bent from the mounting portion to follow one of the four main surfaces that intersect with the first main surface, forming a sidewall portion.

The electrolytic capacitor may also be a laminate of multiple capacitor elements using a roughened foil as the anode. In this case, the laminate of the capacitor elements is placed on the mounting surface of the cathode terminal, and the laminate is sealed with an exterior body. The mounting surface is parallel to the main surface of the foil of the capacitor element, and a part of the cathode terminal may be bent from the mounting portion to form a side wall portion so as to follow the outer surface of the cathode part of the capacitor element that constitutes the side surface having a normal direction perpendicular to the stacking direction of the laminate. The outer surface of the cathode part on one main surface side of the foil of the capacitor element laminate may be the first main surface, and the outer surface of the cathode part on the other main surface side may be the fifth main surface. The second to fourth main surfaces may be surfaces covered with the cathode part and having a normal direction perpendicular to the stacking direction of the capacitor element laminate.

The capacitor element is placed so that its first principal surface overlaps the principal surface (mounting surface) of the mounting portion of the cathode terminal, and is sealed with an exterior resin with part of the anode terminal and part of the cathode terminal exposed.

Traces left on the surface of the exterior body when the exterior resin was injected by injection molding (hereafter referred to as "resin injection marks"). The resin injection marks appear on the surface of the exterior body as convex or concave curved surfaces.

In the electrolytic capacitor of this embodiment, the resin injection mark is located opposite the side wall of the cathode terminal. In this case, when the electrolytic capacitor is injection molded, the liquid exterior resin is injected from the injection port so that it hits the side wall, and does not collide directly with the capacitor element. This prevents damage to the dielectric coating during injection molding, and prevents an increase in leakage current. As a result, the reliability of the electrolytic capacitor is improved.

There may be a plurality of side wall portions. There may be a plurality of resin injection marks. When there are a plurality of resin injection marks, it is sufficient that at least one of the plurality of resin injection marks is located opposite one of the side wall portions. However, when there are a plurality of resin injection marks, it is preferable that each of the plurality of resin injection marks is located opposite one of the side wall portions.

"The resin injection mark and the side wall portion face each other" means that when the outer surface of the exterior body is projected onto the plane formed by the side wall portion, the projected portion of the resin injection mark has an overlapping portion with the side wall portion. 50% or more of the projected area of the resin injection mark may overlap with the side wall portion. It is preferable that 80% or more or 90% or more of the projected area of the resin injection mark overlap with the side wall portion.

The capacitor element is mounted on the mounting portion of the cathode terminal such that the first main surface of the capacitor element overlaps the main surface (mounting surface) of the mounting portion of the cathode terminal. The mounting portion is a flat plate-shaped portion of the cathode terminal. The cathode terminal extends from the mounting portion while bending to form a side wall portion and a connection portion with the external electrode. The side wall portion is formed to extend along the second main surface, the third main surface, the fourth main surface, and/or the sixth main surface that intersects with the first main surface. The side wall portion (at least one of the side wall portions, if there are multiple side walls) is formed to extend along the second main surface. The second main surface and the third main surface may be surfaces that correspond to the long sides of a rectangle when the capacitor element is viewed from a direction perpendicular to the first main surface, or may be surfaces that correspond to the short sides of a rectangle.

When there are multiple sidewalls, at least one of the sidewalls may extend along the second main surface, and at least one other of the sidewalls may extend along the third main surface. In this case, at least one of the sidewalls extending along the second main surface may face at least one of the sidewalls extending along the third main surface, with the capacitor element in between.

When there are multiple sidewalls, at least one of the sidewalls may extend along the second main surface, and at least one of the other sidewalls may extend along the fourth main surface (and/or the sixth main surface). In that case, at least one of the sidewalls extending along the second main surface and at least one of the sidewalls extending along the fourth main surface may be adjacent to or continuous with each other at a corner connecting the second main surface and the fourth main surface. That is, the sidewalls may be formed to surround a corner of the capacitor element. The sidewalls surrounding the corner may be formed by a sidewall that bends from the mounting portion and extends along the second main surface and a sidewall that bends from the mounting portion and extends along the fourth main surface being adjacent to each other, or by a sidewall that bends from the mounting portion and extends along the second main surface (or the fourth main surface) being further bent at the position of the corner in a direction along the fourth main surface (or the second main surface).

The side wall portion reduces the stress applied to the capacitor element when the resin is injected, and also facilitates positioning when the capacitor element is placed on the mounting surface of the cathode terminal. When placed, it is preferable to position the side wall portion so that it comes into contact with the main surface of the capacitor element. The contact between the side wall portion and the main surface of the capacitor element may be via conductive resin.

The extension length of the sidewall portion extending along the second main surface in a direction parallel to the first main surface may be 5% to 90% of the longer of the dimension in the direction parallel to the intersection line between the first and second main surfaces of the capacitor element (or the distance between the fourth and sixth main surfaces) and the distance between the second and third main surfaces (or the dimension in the direction parallel to the intersection line between the first and fourth main surfaces of the capacitor element). That is, the extension length may be 5% to 90% of the dimension of the long side of the capacitor element when the capacitor element is viewed in a direction perpendicular to the first main surface. If the extension length is 5% or more of the long side dimension, the sidewall portion is likely to reduce the stress applied to the capacitor element during resin injection, and the effect of suppressing damage to the dielectric coating and the solid electrolyte layer can be obtained. Therefore, the increase in leakage current is suppressed, and the effect of improving the reliability of the electrolytic capacitor can be obtained. In addition, by making the extension length 90% or less, the sidewall portion is suppressed from hindering the resin from wrapping around inside the mold, and resin sealing can be performed reliably. The same applies to the extension length of the sidewall portion extending along the other principal surfaces (third, fourth, and sixth principal surfaces) other than the second principal surface in a direction parallel to the first principal surface, and may be 5% to 90% of the long side dimension.

In an electrolytic capacitor, two capacitor elements or a laminate of capacitor elements may be mounted, one on each side of the mounting portion of the cathode terminal. In this case, at least one of the side walls may extend toward one of the capacitor elements in a direction intersecting with the main surface of the mounting portion, and at least one other of the side walls may extend toward the other capacitor element in a direction intersecting with the main surface of the mounting portion. That is, the two side walls may extend in opposite directions to each other in a direction intersecting with the main surface of the mounting portion.

The following describes an electrolytic capacitor according to one embodiment of the present invention with reference to the drawings. In this embodiment, the anode part is a roughened valve metal foil, but the present invention is not limited to this.

Figure 1 is a cross-sectional view of an electrolytic capacitor 100 according to one embodiment of the present invention, showing the state of a capacitor element, an anode terminal, and a cathode terminal. Figure 2 is a perspective view showing the cathode terminal in Figure 1. Figure 3 is a cross-sectional view of a capacitor element 10 used in an electrolytic capacitor.

The electrolytic capacitor 100 includes a capacitor element 10, an exterior body 11, an anode terminal 13, and a cathode terminal 14. The exterior body 11 covers the capacitor element 10, leaving a portion of the anode terminal 13 and the cathode terminal 14 exposed.

The capacitor element 10 comprises an anode body 3, which is an anode portion, and a cathode portion 6, the anode portion being electrically connected to an anode terminal 13, and the cathode portion being electrically connected to a cathode terminal 14. The anode body 3 is, for example, a foil (anode foil). The anode body 3 has a porous portion 5 on its surface, and a dielectric layer (not shown) is formed on at least a portion of the surface of the porous portion 5. The cathode portion 6 covers at least a portion of the dielectric layer.

The capacitor element 10 has an anode body 3 exposed at one end 1a without being covered by the cathode portion 6, while the other end 2a is covered by the cathode portion 6. Hereinafter, the portion of the anode body 3 not covered by the cathode portion is referred to as the first portion 1, and the portion of the anode body 3 covered by the cathode portion is referred to as the second portion 2. The end of the first portion 1 is the first end 1a, and the end of the second portion 2 is the second end 2a. The dielectric layer is formed at least on the surface of the porous portion 5 formed in the second portion 2. The first portion 1 of the anode body 3 is also referred to as the anode lead portion. The second portion 2 of the anode body 3 is also referred to as the cathode forming portion. The first portion 1 is electrically connected to the anode terminal 13.

The second portion 2 has a core portion 4 and a porous portion (porous body) 5 formed on the surface of the core portion 4 by roughening (etching, etc.). On the other hand, the first portion 1 may or may not have a porous portion 5 on its surface. The dielectric layer is formed along the surface of the porous portion 5. At least a portion of the dielectric layer covers the inner wall surface of the hole of the porous portion 5 and is formed along the inner wall surface.

The cathode section 6 includes a solid electrolyte layer 7 that covers at least a portion of the dielectric layer, and a cathode lead layer that covers at least a portion of the solid electrolyte layer 7. The surface of the dielectric layer is formed with an uneven shape that corresponds to the shape of the surface of the anode body 3. The solid electrolyte layer 7 can be formed so as to fill in the unevenness of the dielectric layer. The cathode lead layer includes, for example, a carbon layer 8 that covers at least a portion of the solid electrolyte layer 7, and a silver paste layer 9 that covers the carbon layer 8.

The portion of the anode body 3 where the solid electrolyte layer 7 is formed on the anode body 3 via the dielectric layer (porous portion 5) is the second portion 2, and the portion of the anode body 3 where the solid electrolyte layer 7 is not formed on the anode body 3 via the dielectric layer (porous portion 5) is the first portion 1.

An electrolytic capacitor may be obtained by stacking a plurality of capacitor elements 10 so that the cathode portions 6 overlap each other, and electrically connecting each of the first portions 1 of the anode body 3 to the anode terminal 13. The outer diameter of the capacitor element or the laminate thereof is a substantially rectangular parallelepiped, and the outer surface of the capacitor element or the laminate thereof (the outer surface of the cathode portion 6) has a first main surface S1, a second main surface S2 sharing one side with the first main surface S1, a third main surface S3 (not shown) sharing one side with the first main surface S1 and located on the opposite side to the second main surface S2, a fourth main surface S4 intersecting the first to third main surfaces, and a fifth main surface S5 on the opposite side to the first main surface. The first portion 1 of the anode body 3 protrudes from the sixth main surface S6 on the opposite side to the fourth main surface S4.

When the capacitor element 10 is viewed from a direction perpendicular to the first main surface S1, the outer shape of the cathode portion 6 is a rectangle having a long side _L1 and a short side _L2 ( _L1 > _L2 ). In the example of Fig. 1, the dimension in a direction parallel to the intersection line between the first main surface S1 and the second main surface S2 of the capacitor element (or the distance between the fourth main surface S4 and the sixth main surface S6) is equal to the long side _L1 , and the distance between the second main surface S2 and the third main surface S3 (or the dimension in a direction parallel to the intersection line between the first main surface S1 and the fourth main surface S4 of the capacitor element) is equal to the short side _L2 .

The anode terminal 13 extends in a direction along the first main surface S1 of the cathode portion 6 and is in contact with the first portion 1 of the anode body 3. The exposed portion of the anode terminal 13 from the exterior body 11 bends and extends in a direction substantially parallel to the sixth main surface S6 (a direction substantially parallel to the fourth main surface S4) on the side opposite the second cathode terminal portion 14b of the cathode terminal 14, then bends and extends in a direction along the fifth main surface S5, and extends along the exterior body 11.

Typically, the outer surface of the exterior body on the fifth principal surface S5 side, on which the exposed portions of the anode terminal 13 and the cathode terminal 14 (second cathode terminal portion 14b) are provided, is the bottom surface of the electrolytic capacitor. The anode terminal 13 and the second cathode terminal portion 14b are each electrically connected to an external electrode, and the electrolytic capacitor is electrically connected.

The anode body 3 may be a sintered body of a valve metal. In this case, the anode part has the anode body 3 which is a sintered body of a valve metal, and an anode wire which extends from one surface of the anode body 3 and electrically connects to the anode terminal 13. The anode body 3 is, for example, a porous sintered body obtained by sintering metal particles. As the metal particles, particles of a valve metal such as titanium (Ti), tantalum (Ta), or niobium (Nb) are used. Two or more types of metal particles may be mixed and used. The metal particles may be an alloy made of two or more types of metal. For example, an alloy containing a valve metal and silicon, vanadium, boron, or the like may be used. A compound containing a valve metal and a typical element such as nitrogen may also be used. In this case, a dielectric layer is formed on the surface of the anode body 3, and a solid electrolyte layer 7 is formed to cover at least a part of the dielectric layer. The outer shape of the anode body 3 is usually approximately rectangular, and the outer shape of the capacitor element covered with the cathode part 6 is also approximately rectangular correspondingly. In this case, the first principal surface S1 to the sixth principal surface S6 are the outer surfaces of the cathode part 6, which has a roughly rectangular parallelepiped outer shape, and the anode wire protrudes from the anode body 3 at the sixth principal surface S6.

The cathode terminal 14 has a first cathode terminal portion (mounting portion) 14a, a second cathode terminal portion (lead portion) 14b, and a third cathode terminal portion (side wall portion) 14c.

The first cathode terminal 14a faces the first main surface S1 of the cathode 6. The first cathode terminal 14a is electrically connected to the cathode 6 via a conductive adhesive interposed between the first cathode terminal 14a and the first main surface S1. The first cathode terminal 14a is continuous with the second cathode terminal 14b and the third cathode terminal 14c.

The second cathode terminal 14b bends from the first cathode terminal 14a and extends outward from the first cathode terminal 14a. A portion of the second cathode terminal 14b is exposed from the exterior body 11, and the exposed portion extends along the outer surface of the exterior body to form a connection portion with the external electrode. In other words, the second cathode terminal 14b is drawn out from the first cathode terminal 14a to electrically connect the capacitor element 10 to the external electrode.

The second cathode terminal 14b is bent in a direction intersecting the principal surface of the first cathode terminal 14a, and then bent again in a direction parallel to the principal surface of the first cathode terminal 14a within the exterior body 11. The exposed portion of the second cathode terminal 14b from the exterior body 11 is bent and extends in a direction along the fourth principal surface S4, then bent and extends in a direction along the fifth principal surface S5, and extends along the exterior body 11.

The third cathode terminal 14c, like the second cathode terminal 14b, is bent from the first cathode terminal 14a and extends outward from the first cathode terminal 14a. The third cathode terminal 14c extends in a direction intersecting the main surface (mounting surface) of the first cathode terminal 14a. In the example of FIG. 1, the third cathode terminal 14c extends along the second main surface S2 intersecting the first main surface S1. However, the surface of the third cathode terminal 14c is not exposed from the exterior body 11 and is covered by the exterior body 11 (or the capacitor element 10). The third cathode terminal 14c serves to reduce the stress applied to the capacitor element 10 when injecting the liquid resin that becomes the exterior body 11 during injection molding.

In FIG. 1, the position of the resin injection port for injection molding is indicated by a dashed line as gate G. When viewed from a direction perpendicular to second main surface S2, gate G overlaps with third cathode terminal portion 14c. In this case, liquid resin injected from gate G during injection molding first collides with third cathode terminal portion 14c, and is prevented from directly colliding with capacitor element 10. As a result, stress applied to the capacitor element during injection molding is reduced, and damage to the dielectric coating and solid electrolyte layer is suppressed. As a result, an increase in leakage current is suppressed, and the reliability of the electrolytic capacitor is improved.

Corresponding to the gate G, a resin injection mark appears on the outer surface of the exterior body after injection molding. The resin injection mark is a part of the exterior body having a convex or concave curved outer surface. Therefore, the resin injection mark is located opposite the third cathode terminal 14c. When viewed from a direction perpendicular to the third cathode terminal 14c (here, a direction perpendicular to the second main surface S2), the third cathode terminal 14c and the resin injection mark overlap. When viewed from a direction perpendicular to the third cathode terminal 14c, the overlapping portion of the resin injection mark with the third cathode terminal 14c may be 50% or more of the projected area of the resin injection mark viewed from a direction perpendicular to the third cathode terminal 14c, and is preferably 80% or more or 90% or more. When viewed from a direction perpendicular to the third cathode terminal 14c, it is most preferable that the entire resin injection mark is located inside the outline of the third cathode terminal 14c.

From the viewpoint of obtaining the effect of reducing the stress applied to the capacitor element during injection molding and making it easier for the resin to flow around inside the mold, the extension length X of third cathode terminal 14c in a direction parallel to first cathode terminal 14a may be 5% to 90% or may be 20% to 80% of the long side dimension _L1 of capacitor element 10 when viewed from a direction perpendicular to first main surface S1.

During injection molding, resin may be injected from multiple gates G. In that case, multiple third cathode terminals 14c may be arranged corresponding to each gate G. The number of third cathode terminals 14c may be equal to or greater than the number of gates G. The number of third cathode terminals 14c may be equal to or greater than the number of resin injection marks. If the number of third cathode terminals 14c is equal to or greater than the number of gates G (equal to or greater than the number of resin injection marks), the degree of freedom of the mold used in injection molding is easily increased. When the extension length X of the third cathode terminal 14c is long, it is also possible to have one third cathode terminal 14c face multiple gates G. The multiple third cathode terminals 14c may be arranged to extend along the same main surface of the exterior body, or may be arranged to extend along different main surfaces. Two of the multiple third cathode terminals 14c may be arranged one by one to extend along the main surfaces of the exterior body that face each other.

In the example of FIG. 2, the two third cathode terminals 14c are arranged so that they each extend along the opposing second main surface S2 and third main surface S3 of the capacitor element. The two third cathode terminals 14c are arranged so that they do not face each other when viewed from a direction perpendicular to the main surface of one of the third cathode terminals 14c (e.g., a direction perpendicular to the second main surface S2). However, taking into account the arrangement of the gate G in the mold, the two third cathode terminals 14c may be arranged so that they face each other when viewed from a direction perpendicular to the third cathode terminals 14c.

The third cathode terminal portion 14c may or may not be in contact with the side surfaces (second principal surface S2 to fourth principal surface S4) of the capacitor element 10. It is preferable that the third cathode terminal portion 14c is in contact with the side surfaces of the capacitor element 10 via a conductive resin.

4 to 6 show other examples of the cathode terminal used in the electrolytic capacitor of this embodiment.
Fig. 4A shows an example in which two third cathode terminals 14c are arranged to extend along the second main surface S2 and the third main surface S3 of the capacitor element, which face each other, similar to Fig. 2. However, unlike Fig. 2, the two third cathode terminals 14c face each other when viewed from a direction perpendicular to the third cathode terminals 14c.

Figure 4B shows an example in which the two third cathode terminals 14c are arranged to extend along the second main surface S2 of the capacitor element. The two third cathode terminals 14c extend in opposite directions that intersect with the main surface (mounting surface) of the first cathode terminal 14a.

In Figures 4C and 4D, four third cathode terminals 14c are arranged to extend along the second and third principal surfaces S2 and S3 of the capacitor element, which face each other. One third cathode terminal 14c arranged to extend along the third principal surface S3 is hidden by the first cathode terminal 14a and is not shown. Two third cathode terminals 14c arranged to extend along the second or third principal surface S2 or S3 extend in opposite directions to each other in a direction intersecting the principal surface (mounting surface) of the first cathode terminal 14a. In Figure 4C, the four third cathode terminals 14c are arranged so as not to face each other when viewed from a direction perpendicular to the third cathode terminals 14c. On the other hand, in FIG. 4D, when viewed from a direction perpendicular to the third cathode terminal 14c, the third cathode terminal 14c extending along the second main surface S2 is positioned to face the third cathode terminal 14c extending along the third main surface S3.

5A and 5B are examples of the case where six third cathode terminals 14c are arranged to extend along the second main surface S2 and the third main surface S3 of the capacitor element, which face each other. Each of the third cathode terminals 14c extends in a direction intersecting the main surface (mounting surface) of the first cathode terminal 14a. However, of the three third cathode terminals 14c arranged along the second main surface S2 or the third main surface S3, one third cathode terminal 14c extends in the opposite direction to the remaining two third cathode terminals 14c. In FIG. 5A, the six third cathode terminals 14c are arranged so as not to face each other when viewed from a direction perpendicular to the third cathode terminals 14c. On the other hand, in FIG. 5B, when viewed from a direction perpendicular to the third cathode terminal 14c, the third cathode terminal 14c extending along the second main surface S2 is disposed so as to face the third cathode terminal 14c extending along the third main surface S3.

Figure 6A shows an example in which two third cathode terminals 14c are arranged to extend along the fourth main surface S4. On both sides of the second cathode terminal 14b, the two third cathode terminals 14c extend in opposite directions that intersect with the main surface (mounting surface) of the first cathode terminal 14a.

6B and 6C, one third cathode terminal 14c arranged to extend along the second main surface S2 and one third cathode terminal 14c arranged to extend along the fourth main surface S4 form a sidewall surrounding the corner of the capacitor element. In this case, the capacitor element can be positioned with high precision, and even when resin is injected from an oblique direction into the capacitor element during injection molding, the resin is prevented from colliding directly with the capacitor element, reducing the stress applied to the capacitor element. As a result, damage to the dielectric coating and solid electrolyte layer is suppressed, improving the reliability of the electrolytic capacitor.

The sidewall surrounding the corner may be formed by contacting one third cathode terminal 14c arranged to extend along the second main surface S2 with one third cathode terminal 14c arranged to extend along the fourth main surface S4, as shown in FIG. 6B, or by bending the third cathode terminal 14c arranged to extend along the second main surface S2 (or the fourth main surface S4) from the first cathode terminal 14a at the corner in a direction along the fourth main surface S4 (or the second main surface S2), as shown in FIG. 6C.

Figures 7 to 9 are schematic cross-sectional views showing other examples of the structure of the electrolytic capacitor in this embodiment. In each figure, the position of the third cathode terminal portion (side wall portion) 14c is shown. Also, the position of the resin injection port for injection molding is shown as gate G.

Figures 7A and 7B show an example of an electrolytic capacitor in which one capacitor element is connected to an anode terminal and a cathode terminal. In Figure 7A, the first cathode terminal portion (mounting portion) 14a is electrically connected to the cathode portion 6 on the underside of the capacitor element. In Figure 7B, the first cathode terminal portion (mounting portion) 14a is electrically connected to the cathode portion 6 on the upper side of the capacitor element.

Figures 8A to 8D show an example of an electrolytic capacitor constructed using a laminate in which multiple capacitor elements are stacked. The anode parts (anode lead parts) of multiple capacitor elements are bundled together, and each of the anode parts (anode lead parts) is electrically connected to an anode terminal 13. As shown in Figure 8C, an electrolytic capacitor may be constructed using two laminates in which capacitor elements are stacked. The two laminates are placed on one main surface of the first cathode terminal portion 14a and the opposite main surface, respectively.

As shown in FIG. 8D, when stacking multiple capacitor elements, the stacking positions of adjacent capacitor elements may be shifted. In FIG. 8D, the capacitor elements farther from the first cathode terminal portion 14a within the stack are farther away from the anode terminal. In this case, it becomes easier to connect the anode terminal 13 and the capacitor elements by wire bonding.

9A and 9B are examples of electrolytic capacitors formed using a laminate of multiple capacitor elements, in which the end faces of the first part 1 (anode lead part) of the anode part of the multiple capacitor elements are exposed from the exterior body, and the multiple anode parts are electrically connected to the anode electrode 15 at the end faces. In FIG. 9A, the end face of the first part 1 of the anode part is exposed on one main surface of the exterior body 11, and the anode electrode 15 covers one main surface of the exterior body 11 including the exposed surface of the first part 1, so that the multiple anode parts are electrically connected to the anode electrode 15. On the other hand, the end face of the cathode part 6 is exposed on the other main surface of the exterior body 11, and the cathode electrode 16 covers the other main surface of the exterior body 11 including the exposed surface of the cathode part 6, so that the cathode part 6 is electrically connected to the cathode electrode 16. The cathode part 6 is also electrically connected to the first cathode terminal part (mounting part) 14a.

In FIG. 9B, two types of capacitor elements (first and second capacitor elements) with the first part 1 of the anode part facing in the opposite directions are alternately stacked to form an electrolytic capacitor. The end face of the first part 1 (anode lead part) of the anode part of the first capacitor element is exposed on one main surface of the exterior body, and the anode electrode 15a covers one main surface of the exterior body 11 including the exposed surface of the first part 1 of the anode part of the first capacitor element, so that the anode parts of the multiple first capacitor elements are electrically connected to the anode electrode 15a. On the other hand, the end face of the first part 1 (anode lead part) of the anode part of the second capacitor element is exposed on the other main surface of the exterior body, and the anode electrode 15b covers the other main surface of the exterior body 11 including the exposed surface of the first part 1 of the anode part of the second capacitor element, so that the anode parts of the multiple second capacitor elements are electrically connected to the anode electrode 15b. The cathode portions 6 of the first and second capacitor elements are electrically connected to the first cathode terminal portion (mounting portion) 14a.

7 and 8, the connection between the anode part of the capacitor element and the anode terminal 13 can be made by resistance welding, laser welding, wire bonding, or the like. When resistance welding is performed, a through hole may be provided in the anode terminal 13 and/or the first part 1 (anode lead part) of the anode part, and resistance welding may be performed through the through hole. In this case, current concentrates around the through hole, and the dielectric oxide film formed on the surface of the anode part is destroyed. On the other hand, since the molten metal material remains in the through hole, resistance welding can be performed very easily and reliably. In addition, an electrolytic capacitor with excellent welding strength and reliability and reduced ESR can be obtained.

Below, we will explain in detail each component of the electrolytic capacitor according to this embodiment.

(Anode body 3)
The anode body may contain a valve metal, an alloy containing a valve metal, a compound containing a valve metal (such as an intermetallic compound), and the like. These materials may be used alone or in combination of two or more. Examples of the valve metal that may be used include aluminum, tantalum, niobium, and titanium. The anode body may be a foil of a valve metal, an alloy containing a valve metal, or a compound containing a valve metal, or may be a porous sintered body of a valve metal, an alloy containing a valve metal, or a compound containing a valve metal.

When a metal foil is used for the anode body, a porous portion is usually formed on the surface of at least the second portion of the anode foil in order to increase the surface area. The second portion has a core portion and a porous portion formed on the surface of the core portion. The porous portion may be formed by roughening the surface of at least the second portion of the anode foil by etching or the like. It is also possible to perform a roughening process such as an etching process after placing a predetermined masking member on the surface of the first portion. On the other hand, it is also possible to roughen the entire surface of the anode foil by etching or the like. In the former case, an anode foil is obtained that does not have a porous portion on the surface of the first portion and has a porous portion on the surface of the second portion. In the latter case, a porous portion is formed on the surface of the first portion in addition to the surface of the second portion. As the etching process, a known method may be used, for example, electrolytic etching. The masking member is not particularly limited, but is preferably an insulator such as a resin. The masking member is removed before the formation of the solid electrolyte layer, but may be a conductor containing a conductive material.

When the entire surface of the anode foil is roughened, the surface of the first portion has a porous portion. As a result, the adhesion between the porous portion and the exterior body is insufficient, and air (specifically, oxygen and moisture) may enter the inside of the electrolytic capacitor through the contact area between the porous portion and the exterior body. To prevent this, the first portion formed to be porous may be compressed in advance to crush the holes in the porous portion. This makes it possible to prevent air from entering the electrolytic capacitor through the porous portion from the first end exposed from the exterior body, and to prevent a decrease in the reliability of the electrolytic capacitor due to the air entering the electrolytic capacitor.

(Cathode)
The cathode section includes a solid electrolyte layer covering at least a portion of the dielectric layer, and a cathode extraction layer covering at least a portion of the solid electrolyte layer.

(Solid electrolyte layer 7)
The solid electrolyte layer includes, for example, a conductive polymer. Examples of the conductive polymer include polypyrrole, polythiophene, polyfuran, polyaniline, polyacetylene, polyphenylene, polyparaphenylenevinylene, polyacene, polythiophenevinylene, polyfluorene, polyvinylcarbazole, polyvinylphenol, polypyridine, or derivatives of these polymers. These may be used alone or in combination. The conductive polymer may also be a copolymer of two or more monomers. Among these, polythiophene, polyaniline, polypyrrole, etc. are preferred in terms of excellent conductivity. Among them, polypyrrole is preferred in terms of excellent water repellency.

The solid electrolyte layer containing the conductive polymer is formed, for example, by chemically polymerizing and/or electrolytically polymerizing a raw material monomer on the dielectric layer. Alternatively, the solid electrolyte layer is formed by applying a solution in which the conductive polymer is dissolved or a dispersion liquid in which the conductive polymer is dispersed to the dielectric layer. The solid electrolyte layer is composed of one or more solid electrolyte layers. When the solid electrolyte layer 7 is composed of two or more layers, the composition of the conductive polymer used in each layer and the formation method (polymerization method) may be different. The solid electrolyte layer may contain a manganese compound.

(Cathode extraction layer)
The cathode extraction layer includes, for example, a carbon layer 8 and a silver paste layer 9. The carbon layer may be made of any conductive carbon material such as graphite. The carbon layer is formed, for example, by applying a carbon paste to at least a part of the surface of the solid electrolyte layer. The silver paste layer may be made of a composition containing silver powder and a binder resin (such as an epoxy resin). The silver paste layer is formed, for example, by applying a silver paste to the surface of the carbon layer. The configuration of the cathode extraction layer is not limited to this, and may be any configuration having a current collecting function.

(anode terminal)
The material of the anode terminal 13 is not particularly limited as long as it is electrochemically and chemically stable and conductive, and may be either metallic or non-metallic. The shape of the anode terminal is, for example, long and flat. From the viewpoint of reducing the height, the thickness of the anode terminal (the distance between the main surfaces of the anode terminal) is preferably 25 μm or more and 200 μm or less, and more preferably 25 μm or more and 100 μm or less.

The anode terminal 13 may be joined to the anode wire (or the anode lead portion when a foil is used as the anode body 3) by a conductive adhesive or solder, or may be joined to the anode wire (or the anode lead portion) by resistance welding, laser welding, or wire bonding. The conductive adhesive is, for example, a mixture of a thermosetting resin described below and carbon particles or metal particles.

(cathode terminal)
The first cathode terminal portion (mounting portion) 14a of the cathode terminal 14 is electrically connected to the cathode portion 6. The material of the cathode terminal 14 is not particularly limited as long as it is electrochemically and chemically stable and conductive, and may be metal or nonmetal. The shape of the cathode terminal is not particularly limited, and may be, for example, long and flat. From the viewpoint of reducing the height, the thickness of the cathode terminal is preferably 25 to 200 μm, and more preferably 25 to 100 μm. The first cathode terminal portion 14a is bonded to the cathode portion 6 via, for example, a conductive adhesive 12. In addition to the first cathode terminal portion 14a, the third cathode terminal portion (side wall portion) 14c may be bonded to the cathode portion 6 via a conductive adhesive 12.

<Exterior body>
The exterior body 11 is provided to electrically insulate the anode terminal 13 and the cathode terminal 14, and is made of an insulating material. The exterior body 11 includes, for example, a cured product of a thermosetting resin. Examples of the thermosetting resin include epoxy resin, phenol resin, silicone resin, melamine resin, urea resin, alkyd resin, polyurethane, polyimide, and unsaturated polyester.

<Manufacturing method of electrolytic capacitors>
The electrolytic capacitor according to the present embodiment includes the steps of preparing a capacitor element including an anode portion and a cathode portion, preparing an anode terminal and a cathode terminal, connecting the anode portion of the capacitor element to the anode terminal and the cathode portion of the capacitor element to the cathode terminal, and sealing the capacitor element with an exterior body by injection molding so that a part of the anode terminal and a part of the cathode terminal are exposed. The cathode terminal includes a mounting portion on which the capacitor element is mounted and a sidewall portion that is bent from the mounting portion and extends in a direction intersecting with a main surface of the mounting portion. In the sealing step with the exterior body, a gate through which exterior resin is poured into a mold is opposed to the sidewall portion of the capacitor element.

Below, an example of a method for manufacturing an electrolytic capacitor according to this embodiment will be described using the manufacturing of the electrolytic capacitor 100 shown in FIG. 1 as an example.

(1) Preparation Step First, a capacitor element 10 having an anode portion and a cathode portion is prepared.
First, an anode body having a dielectric layer formed on a surface thereof is prepared. More specifically, the anode body is prepared to include a first portion including one end and a second portion including the other end opposite to the one end, and the dielectric layer is formed on at least the surface of the second portion.

A porous portion is formed on the surface of at least the second portion of the anode body. When forming the porous portion, it is sufficient to form irregularities on the surface of the anode body, and this may be done, for example, by roughening the surface of the anode foil by etching (e.g., electrolytic etching).

The dielectric layer may be formed by subjecting the anode body to chemical conversion treatment. Chemical conversion treatment may be performed, for example, by immersing the anode body in a chemical conversion solution to impregnate the surface of the anode body with the chemical conversion solution, and applying a voltage between the anode body as the anode and a cathode immersed in the chemical conversion solution. If the anode body has a porous portion on its surface, the dielectric layer is formed to conform to the uneven shape of the surface of the porous portion.

Next, the solid electrolyte layer 7 is formed. In this embodiment, a process for forming the solid electrolyte layer 7 containing a conductive polymer will be described.
Solid electrolyte layer 7 containing a conductive polymer is formed on at least a portion of the dielectric layer by, for example, a method of impregnating anode body 3 on which a dielectric layer has been formed with a monomer or an oligomer, and then polymerizing the monomer or oligomer by chemical polymerization or electrolytic polymerization, or by impregnating anode body 3 on which a dielectric layer has been formed with a solution or dispersion of a conductive polymer and drying it.

Finally, a carbon paste and a silver paste are successively applied to the surface of solid electrolyte layer 7 to form a cathode extraction layer composed of a carbon layer 8 and a silver paste layer 9. The configuration of the cathode extraction layer is not limited to this, and may be any configuration having a current collecting function.
By the above method, the capacitor element 10 is prepared.

Second, the anode terminal 13 and the cathode terminal 14 are prepared.
A sheet of conductive plate material is punched out into a shape that conforms to the outer shapes of the anode terminal and the cathode terminal, and then bent to obtain cathode terminal 14 having first cathode terminal portion (mounting portion) 14a, second cathode terminal portion (lead portion) 14b, and third cathode terminal portion (side wall portion) 14c.

(2) Lead Frame Bonding Process A conductive adhesive is applied to a predetermined position of the cathode portion 6 (silver paste layer 9).
Anode terminal 13 and cathode terminal 14 are arranged in predetermined positions, and capacitor element 10 is placed so that the first portion of anode body 3 contacts anode terminal 13 and cathode portion 6 contacts first cathode terminal portion 14a. At this time, capacitor element 10 can be positioned in the space sandwiched by third cathode terminal portion 14c.

Next, the contact portion between the first portion of the anode body 3 and the anode terminal is joined by laser welding, resistance welding, or the like. At this time, at least a portion of the cathode terminal 14 (first cathode terminal portion 14a) is bonded to the cathode extraction layer via a conductive adhesive. In addition, at least a portion of the third cathode terminal portion 14c may be bonded to the cathode extraction layer via a conductive adhesive. During bonding, a portion of the conductive adhesive may be present between the third cathode terminal portion 14c and the cathode extraction layer. By increasing the amount of conductive adhesive 12 applied, a portion of the conductive adhesive can overflow from the space between the first cathode terminal portion 14a and the cathode layer 5, and the overflowing portion can be interposed between the third cathode terminal portion 14c and the cathode extraction layer.

(3) Sealing Process The capacitor element 10 to which the anode terminal 13 and the cathode terminal 14 are connected is placed in a mold, and an exterior resin (material of the exterior body 11, for example, uncured thermosetting resin and filler) is poured into the mold by, for example, transfer molding, to seal the capacitor element 10. The molding conditions are not particularly limited, and time and temperature conditions may be set appropriately taking into consideration the curing temperature of the thermosetting resin used. At this time, the liquid exterior resin is poured in from a resin injection port (gate) provided in the mold in a state where the resin injection port faces the side wall of the capacitor element so that the liquid exterior resin collides with the third cathode terminal portion 14c and does not directly collide with the capacitor element 10.

At this time, a portion of the anode terminal 13 and a portion of the second cathode terminal portion 14b of the cathode terminal 14 are exposed from the mold. As a result, a portion of the anode terminal 13 and a portion of the second cathode lead portion 14b are exposed from the exterior body 11.

Next, the anode terminal 13 exposed from the exterior body and a part of the second cathode terminal portion 14b are bent along the outer surface of the exterior body. Through this process, the second cathode terminal portion 14b is bent from the direction along the first main surface S1 to the direction along the fourth main surface S4, and is further bent from the direction along the fourth main surface to the direction along the fifth main surface.

The electrolytic capacitor 100 is manufactured using the above method.

The electrolytic capacitor of the present invention has low leakage current and excellent reliability, making it suitable for a wide range of applications.

100: electrolytic capacitor 10: capacitor element 1: first part (anode lead portion)
1a: First end portion 2: Second portion (cathode forming portion)
2a: second end portion 3: anode body 4: core portion 5: porous portion 6: cathode portion 7: solid electrolyte layer 8: carbon layer 9: silver paste layer 11: exterior body 13: anode terminal 14: cathode terminal 14a: first cathode terminal portion (mounting portion)
14b: Second cathode terminal portion (lead portion)
14c: Third cathode terminal part (side wall part)
15, 15a, 15b: Anode electrode 16: Cathode electrode

Claims (10)

a capacitor element having an anode portion and a cathode portion;
an anode terminal electrically connected to the anode portion;
a cathode terminal electrically connected to the cathode portion;
an exterior body that covers the capacitor element while leaving a portion of the anode terminal and a portion of the cathode terminal exposed,
the capacitor element has a first main surface, a second main surface sharing one side with the first main surface, and a third main surface sharing one side with the first main surface and positioned on the opposite side to the second main surface;
the cathode terminal has a mounting portion facing the first main surface on which the capacitor element is mounted, and a sidewall portion bent from the mounting portion to extend in a direction intersecting the first main surface,
The exterior body has a resin injection mark,
The resin injection mark is located opposite the side wall portion. The side wall portion includes a plurality of the side walls.
The resin injection marks are multiple,
The electrolytic capacitor according to claim 1 , wherein each of the plurality of resin injection marks is located opposite one of the plurality of side wall portions. The side wall portion includes a plurality of the side walls.
3. The electrolytic capacitor according to claim 1, wherein at least one of the sidewall portions extends along the second main surface. The electrolytic capacitor of claim 3, wherein at least one of the sidewall portions extends along the third main surface. The electrolytic capacitor according to claim 4, wherein at least one of the sidewall portions extending along the second main surface faces at least one of the sidewall portions extending along the third main surface, with the capacitor element interposed therebetween. The electrolytic capacitor according to any one of claims 1 to 5, wherein at least one of the sidewalls is connected to the second main surface and the third main surface and extends along a fourth main surface that intersects with the first main surface. The side wall portion includes a plurality of the side walls.
7. The electrolytic capacitor of claim 6, wherein at least one of the sidewall portions extending along the second main surface and at least one of the sidewall portions extending along the fourth main surface are adjacent to or continuous with each other at a corner portion connecting the second main surface and the fourth main surface. The electrolytic capacitor according to any one of claims 3 to 7, wherein the extension length of the sidewall portion extending along the second main surface in a direction parallel to the first main surface is 5% to 90% of the dimension of the long side of the capacitor element when the capacitor element is viewed in a direction perpendicular to the first main surface. The electrolytic capacitor according to any one of claims 1 to 8, wherein an area of an overlapping portion where the resin injection mark and the side wall portion overlap when viewed from a direction perpendicular to the side wall portion is 50% or more of a projected area of the resin injection mark when viewed from a direction perpendicular to the side wall portion. Providing a capacitor element having an anode portion and a cathode portion;
providing an anode terminal and a cathode terminal;
connecting the anode portion of the capacitor element to the anode terminal and the cathode portion of the capacitor element to the cathode terminal;
and sealing the capacitor element with an exterior body by injection molding so that a portion of the anode terminal and a portion of the cathode terminal are exposed.
the cathode terminal has a mounting portion on which the capacitor element is mounted, and a sidewall portion bent from the mounting portion and extending in a direction intersecting a main surface of the mounting portion,
In the step of sealing with the exterior body, a gate through which exterior resin is poured into a mold is opposed to the side wall portion of the capacitor element.

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