JP4697971B2 - Surface mount thin capacitors - Google Patents

Description

  The present invention relates to a solid electrolytic capacitor using a polymer as an electrolyte, and more particularly to a three-terminal surface mount thin capacitor that can be surface mounted on a circuit board.

  Conventionally, a three-terminal solid electrolytic capacitor that can be surface-mounted and intended to remove noise in a high-frequency region is called a three-terminal transmission line element type, and is disclosed in Patent Document 1, for example.

  FIG. 3 is a cross-sectional view showing a general structure of a conventional solid electrolytic capacitor of the conventional three-terminal transmission line element type as described above. This solid electrolytic capacitor includes an anode body 1 made of a plate-like or foil-like surface-enhanced valve metal, and a dielectric layer made of an anodized film layer formed on the surface of the anode body 1 that has been enlarged. The conductive polymer layer 2 which is a solid electrolyte layer formed so as to cover the surface of the dielectric layer in the central portion of the anode body 1, and the graphite layer 3 and the silver paste layer sequentially formed thereon 4 conductor layers are provided. A resist layer 5 for separating the anode and the cathode is formed outside the portion of the anode body 1 where the conductive polymer layer 2 and the conductor layer are formed, and the anode body 1 further outside the resist layer 5 is formed. Anode conduction pieces 6 are joined to the substrate mounting surface 20 side at both ends to form a single layer capacitor element.

  Further, on the substrate mounting surface 20 side of the single-layer capacitor element, the anode conductive piece 6 is connected to the anode terminal 7 via the conductive paste 9, and the conductor layer is connected to the cathode terminal 8 via the conductive paste 9. . Here, the anode terminal 7 and the cathode terminal 8 have a flat plate shape and are formed by being embedded in the mold resin case 10 on the same plane as the substrate mounting surface 20. The mold resin case 10 is an insert mold that fills the gap between the anode terminal 7 and the cathode terminal 8, mechanically connects both terminals, and has a side wall that engages the outer case 11 around the single layer capacitor element. It is formed by. The surface mount thin capacitor is obtained by covering the side wall with the outer case 11 and encapsulating the single layer capacitor element. If a larger capacity is required, a multilayer surface-mount thin capacitor in which a plurality of the above single-layer capacitor elements are stacked and then similarly formed with an anode terminal and a cathode terminal is used.

JP 2002-313676 A

  However, in the conventional three-terminal transmission line type surface mount thin capacitor described above, in the step of connecting the anode terminal and the cathode terminal by placing the capacitor element in a resin-molded mounting case, the conductive paste for connecting the anode terminal protrudes. However, they have the disadvantage that they reach the conductor layer or the cathode terminal and both terminals are easily short-circuited, and the leakage current characteristic is liable to occur. Further, in order to prevent the short circuit, it is sufficient to increase the area of the resist layer that separates the anode and the cathode. However, in this case, the surface area of the conductive polymer layer is reduced and the capacity is reduced.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a surface mount thin capacitor that can prevent a short circuit between an anode terminal and a cathode terminal to prevent occurrence of a leakage current characteristic and has a small capacity reduction.

  In order to solve the above problems, a surface-mount thin capacitor according to the present invention comprises a plate-like or foil-like surface-enhanced valve metal and a dielectric formed on the surface of the anode body. A capacitor element comprising: a body layer; a conductive polymer layer formed on a surface of the dielectric layer at a central portion of the anode body; and a conductor layer formed on the surface of the conductive polymer layer; In the surface mount type capacitor comprising an anode terminal connected to both ends of the anode body and formed on a substrate mounting surface, and a cathode terminal connected to the conductor layer and formed on the substrate mounting surface, the anode body The width of the portion where the conductive polymer layer and the conductor layer on the substrate mounting surface side at both ends are not formed is the width of the conductive polymer layer and the conductive surface on the opposite side to the substrate mounting surface side. Width of the part where the body layer is not formed Remote, characterized in that wide.

  It may have an exterior resin formed by a molding method, or may have a resin case formed by insert molding.

  Further, the surface mount thin capacitor according to the present invention includes a plate-like or foil-like surface-enlarged anode body, a dielectric layer formed on the surface-enlarged surface of the anode body, A plurality of capacitor elements each including a conductive polymer layer formed on the surface of the dielectric layer in the central portion of the anode body and a conductor layer formed on the surface of the conductive polymer layer, In a surface mount capacitor comprising an anode terminal connected to both ends of an anode body and formed on a substrate mounting surface, and a cathode terminal connected to the conductor layer and formed on the substrate mounting surface, the substrate mounting surface The width of the conductive polymer layer on the substrate mounting surface side and the portion where the conductor layer is not formed at both end portions of the anode body of the capacitor element disposed on the side is opposite to the substrate mounting surface side Said conductive polymer layer of the surface and May be wider than the width of the portion Kishirubeden layer is not formed.

  As described above, according to the present invention, the width of the portion where the conductive polymer layer and the conductor layer on the substrate mounting surface side are not formed is made wider than the surface on the opposite side, whereby the anode terminal and the cathode terminal In the process of connecting and putting in the exterior case, even if the conductive paste for connecting the anode terminal protrudes, it prevents it from reaching the conductor layer or the cathode terminal, and one surface of the anode body is a conductive polymer layer. Further, since the area of the conductor layer is kept as it is, the decrease in capacity is small.

  Therefore, according to the present invention, it is possible to prevent a short circuit between the anode terminal and the cathode terminal, to prevent the occurrence of a leakage current characteristic defect, and to obtain a surface mount thin capacitor with little decrease in capacity.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view showing a capacitor element portion of an embodiment of a surface mount thin capacitor according to the present invention. FIG. 1A is a perspective view seen from the board mounting surface side, and FIG. 1B is a perspective view seen from the side opposite to the board mounting surface. FIG. 2 is a perspective view of an example of a capacitor element portion used for a conventional surface-mount thin capacitor shown for comparison, FIG. 2 (a) is a perspective view seen from the board mounting surface side, and FIG. FIG. 3 is a perspective view seen from the side opposite to the board mounting surface.

  The surface-mount thin capacitor of this embodiment is a three-terminal transmission line element type, similar to the conventional one shown in FIG. The basic capacitor structure of the capacitor element of the present embodiment is the same as that of the conventional capacitor element shown in FIG. 3, and a rectangular plate-shaped solid electrolysis having a conductive polymer layer as shown in FIG. 1 as a solid electrolyte. It is a capacitor element. The surface of the valve metal having a plate-like or foil-like valve action is subjected to surface enlargement by forming innumerable pores by etching or the like to increase the surface area by 200 times or the like to obtain an anode body 1. An anodized film layer is formed on the surface of the central portion of the expanded valve action metal to form a dielectric layer. Here, tantalum, aluminum, niobium, or the like can be used as the valve metal. Next, the conductive polymer layer in the central portion of the anode body 1 having the dielectric layer formed on the surface and the formation portion of the conductor layer and the anode electrode formation portion at both ends are separated by the resist layer 15, A conductive polymer layer is formed so as to cover the central portion of the body 1, and a graphite layer and a silver paste layer are sequentially formed thereon to form a conductor layer 14, and anode conductive pieces are formed at both ends of the anode body 1. To complete the capacitor element.

  Here, in the capacitor element of the present embodiment, as shown in FIG. 1, the conductive polymer layer and the conductor layer 14 on the substrate mounting surface side [FIG. 1 (a)] at both ends of the anode body 1 are formed. The width D1 of the portion that is not formed is wider than the width D2 of the portion where the conductive polymer layer and the conductor layer 14 are not formed on the surface opposite to the substrate mounting surface [FIG. 1B]. Is formed. The formation of such a structure can be realized by a method of adjusting the masking width when forming the conductive polymer layer, the graphite layer, and the silver pace layer according to each surface to be coated. In the conventional capacitor element, as shown in FIG. 2, the above-mentioned width is D2 on both the substrate mounting surface side and the surface opposite to the substrate mounting surface side.

  The anode conductive piece and the conductor layer of the capacitor element are connected to the anode terminal and the cathode terminal formed in the same mold resin case as the conventional surface mount thin capacitor of FIG. Completed as a surface mount thin capacitor. In this case, without using a mold resin case or an exterior case, the anode terminal and the cathode terminal may be joined to the capacitor element, and then the whole may be resin molded by a molding method.

  In the embodiment of the present invention, pyrrole, thiophene, or the like can be used for the conductive polymer layer. In addition, as the anode terminal and the cathode terminal, a plate material such as copper, a copper-based alloy, or a nickel alloy can be used. However, if the plate material is used as a material for a normal electronic component terminal, it is limited to these. is not.

  In the present embodiment, the width of the cathode terminals in the direction between the anode terminals is formed to be substantially the same as the width of the conductor layer 14, and is made smaller than the width of the cathode terminals of the conventional surface mount thin capacitor. Is desirable.

  The surface-mount thin capacitor of the above-described embodiment uses a single-layer capacitor element. However, in order to obtain an element having a large capacity, the capacitor elements shown in FIG. 1 can be stacked and used. In this case, at least the capacitor elements arranged on the substrate mounting surface side among the stacked capacitor elements are connected to the conductive polymer layer and the conductor layer on the substrate mounting surface side at both ends of the anode body as shown in FIG. The width D1 of the part where the conductive layer is not formed may be wider than the width D2 of the part where the conductive polymer layer and the conductor layer are not formed on the surface opposite to the substrate mounting surface side. .

  As described above, in the surface mount thin capacitor of the present invention, the shape of the portion where the conductive polymer layer, the graphite layer, and the silver paste layer are formed on the substrate mounting surface side and the surface opposite to the substrate mounting surface side of the anode body. By changing the capacitor, it becomes possible to prevent the conductive paste for connecting the anode terminal from protruding and short-circuiting in the process of putting the capacitor element into the case, and to prevent the occurrence of defective leakage current characteristics and the capacitance. A surface mount thin capacitor with little degradation is obtained.

  Note that the present invention is not limited to the above-described embodiment, and can be changed in design without departing from the gist of the present invention. For example, the outer shape, the layer structure, and each layer can be changed according to the purpose of use and required performance. The material, the number of stacked capacitor elements, and the like can be set.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a capacitor element portion of an embodiment of a surface-mount thin capacitor according to the present invention, FIG. 1 (a) is a perspective view seen from the board mounting surface side, and FIG. FIG. It is a perspective view of an example of the capacitor | condenser element part used for the conventional surface mount thin capacitor shown for a comparison, FIG. 2 (a) is a perspective view seen from the board | substrate mounting surface side, FIG.2 (b) is opposite to a board | substrate mounting surface. The perspective view seen from the side. Sectional drawing which shows the general structure of the conventional solid electrolytic capacitor of a 3 terminal transmission line element type.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anode body 2 Conductive polymer layer 3 Graphite layer 4 Silver paste layers 5 and 15 Resist layer 6 Anode conduction piece 7 Anode terminal 8 Cathode terminal 9 Conductive paste 10 Mold resin case 11 Exterior case 14 Conductor layer 20 Board mounting surface

Claims (4)

  An anode body made of a plate-like or foil-like expanded valve metal, a dielectric layer formed on the enlarged surface of the anode body, and the dielectric layer in the central portion of the anode body A capacitor element composed of a conductive polymer layer formed on the surface and a conductor layer formed on the surface of the conductive polymer layer, and formed on the substrate mounting surface connected to both ends of the anode body In a surface-mounted thin capacitor comprising an anode terminal and a cathode terminal connected to the conductor layer and formed on a substrate mounting surface, the conductive polymer layer on the substrate mounting surface side at both ends of the anode body and The width of the portion where the conductor layer is not formed is wider than the width of the portion where the conductive polymer layer and the conductor layer are not formed on the surface opposite to the substrate mounting surface side. Surface mount thin capacitor.   The surface mount thin capacitor according to claim 1, further comprising an exterior resin formed by a molding method.   2. The surface mount thin capacitor according to claim 1, further comprising a resin case formed by insert molding.   An anode body made of a plate-like or foil-like expanded valve metal, a dielectric layer formed on the enlarged surface of the anode body, and the dielectric layer in the central portion of the anode body A plurality of capacitor elements each composed of a conductive polymer layer formed on the surface and a conductor layer formed on the surface of the conductive polymer layer are stacked, and connected to both ends of the anode body to be mounted on the substrate In a surface-mount thin capacitor comprising an anode terminal formed on the substrate and a cathode terminal connected to the conductor layer and formed on the substrate mounting surface, the capacitor element disposed on the substrate mounting surface side at both ends of the anode body The width of the portion where the conductive polymer layer and the conductor layer on the substrate mounting surface side are not formed is such that the conductive polymer layer and the conductor layer on the surface opposite to the substrate mounting surface side are This is wider than the width of the unformed part. Surface-mount thin-profile capacitor according to claim.

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