JP2010080600A - Chip-shaped solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chip-type solid electrolytic capacitor which uses a lead frame to mount a square-shaped capacitor element, and whose exterior is covered with resin by a square-shaped resin mold, and in which a lead frame is exposed from an opposed end surface, and which is capable of improving a flow performance of injected resin, alleviating a stress around a corner between a negative electrode surface of connection between a negative electrode terminal of the lead frame and a negative electrode terminal of a capacitor element, and a negative electrode side end surface, and suppressing an increase of a leakage current as a capacitor. <P>SOLUTION: The negative electrode terminal is bent along an end surface opposed to an anode lead from an end surface of a square-shaped capacitor element, and bent and elongated in a vertical direction from the end surface of the capacitor element. A leading part from around the bent part of the negative electrode side end surface of a lead frame to the elongated part in the vertical direction has a width narrower than the negative electrode terminal width, or alternatively has a vent hole at the center. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a chip-type solid electrolytic capacitor using a lead frame.

Conventionally, solid electrolytic capacitors such as tantalum and niobium have formed an oxide film that becomes a dielectric by anodic oxidation on the surface of a sintered body obtained by molding and sintering a valve metal powder such as tantalum and niobium. The anode body was formed by laminating a solid electrolyte layer such as manganese dioxide or a conductive polymer on the anode body and a cathode layer made of a current collector such as carbon or silver paste, and was derived from the anode body. A capacitor element obtained by having an anode lead was attached to a lead frame having an anode terminal and a cathode terminal.
In general, the anode side is connected by welding, and the cathode side is connected by a conductive paste.

  The lead frame used in this type of solid electrolytic capacitor is obtained by punching a flat metal plate and divided into a cathode terminal side and an anode terminal side, but the width of the cathode terminal connected to the cathode layer of the capacitor element is The strip has the same width as the external terminal. Also, the anode lead is a capacitor element structure derived from the center of the end face of the anode body, so the cathode terminal side is bent by the distance between the anode lead and the cathode part bottom surface, and the capacitor element is mounted on the upper surface of the cathode terminal Take. Therefore, the cathode terminal is bent from the side surface of the capacitor element along the end surface opposite to the anode lead (hereinafter referred to as the cathode-side end surface) (bending portion A9), and in this case, the cathode terminal is bent in the opposite direction and vertically from the cathode-side end surface (bending). Part B10) Takes an extending structure (see FIG. 3).

The capacitor element attached to the lead frame is then set in a molding die, and heated resin is injected into the molding die and resin molded.
At this time, in order to improve the flowability of the resin and suppress voids generated in the resin portion, in Patent Document 1, the width W of the cathode terminal is bent along the cathode side end face as shown in FIG. A method is described in which the width W1 is narrower than the width of the external terminal portion of the cathode terminal from the bent portion A9) to the cathode side end surface and from the cathode side end surface to the portion bent vertically (bend portion B10). Has been.
JP-A-3-96214

The problem to be solved is that the cathode terminal is bent along the cathode side end face (bend portion A), the cathode side end face, and the cathode side end face is bent vertically (bend portion B). In the method of Patent Document 1 or the like in which the width of the cathode terminal is made narrower than the width of the external terminal portion of the cathode terminal, in the same manner as the conventional method of setting the cathode terminal width to the same width as the external terminal portion, When stress occurs, stress is applied evenly to the cathode terminal from the peripheral portion bent along the cathode side end surface (bend portion A) to the portion bent vertically from the cathode side end surface (bend portion B). The bending angle changes in the same manner between the portion bent along the cathode side end face (bending portion A) and the portion bent in the vertical direction from the cathode side end surface (bending portion B).
By the way, when the bending angle of the bent portion (bending portion A) is changed along the cathode side end surface, the portion around the corner on the capacitor element side, that is, the cathode surface and the cathode side end surface of the connection portion with the cathode terminal are formed. Stress tends to concentrate especially around the corners.
Therefore, when the capacitor is exposed to a high temperature, deformation or partial peeling is likely to occur in the stress portion around the corner. In particular, a polymer paste is used for the current collector of the cathode layer of the capacitor element, a conductive polymer is used for the solid electrolyte layer, and a conductive polymer paste is used to connect the cathode terminal of the lead frame and the cathode layer of the capacitor element. As used, it is remarkable when a polymer material is used. For this reason, damage and repair deterioration of the oxide film on the surface of the sintered body in the inner part occur, and the leakage current tends to increase as a capacitor.
Further, the width of the cathode terminal is narrower than the width of the capacitor element from the peripheral portion bent along the cathode side end surface (bending portion A) to the portion bent vertically from the end surface on the cathode side (bending portion B). The narrower the area, the smaller the area of the end face portion of the cathode terminal covering the corner of the cathode face and the end face on the cathode side of the connection portion with the cathode terminal of the capacitor element. As a result, the force pushing the end face of the capacitor element increases, and stress is likely to be applied to the peripheral portion of the corner between the cathode face and the cathode end face of the connection portion with the cathode terminal.

The object of the present invention is to relieve stress around the corner between the cathode surface and the cathode side end surface of the connection portion between the cathode terminal of the lead frame and the cathode terminal of the capacitor element while improving the flowability of the injected resin. However, the leakage current as a capacitor is to suppress the increase.

In order to solve the above-mentioned problem, the present invention uses a lead frame to mount a square capacitor element, coats the resin with a square resin mold, and exposes the lead frame from the opposite end face thereof. There,
The capacitor element is formed by sequentially laminating a dielectric oxide film and a cathode layer on a surface of an anode body of a molded body made of a valve metal, and has an anode lead led out from one end face of the anode body,
Connecting the anode lead and the anode terminal of the lead frame, and connecting the side surface portion of the cathode layer and the cathode terminal of the lead frame;
The cathode terminal is bent from the side surface of the square capacitor element along the end surface opposite to the anode lead, and is bent and extended in the vertical direction from the end surface of the capacitor element, from the peripheral portion of the bent portion of the end surface. The lead-out portion extending to the portion extending in the vertical direction is narrower than the cathode terminal width or provided with a punched hole in the center, thereby providing a chip-type solid electrolytic capacitor.

The cathode terminal of the chip-type solid electrolytic capacitor of the present invention is a portion extending in the vertical direction from the peripheral portion of the bent portion (bend portion B) of the cathode side end face of the lead frame when stress occurs in the anode terminal-cathode terminal direction. By narrowing the lead-out part to the width of the cathode terminal or by providing a hole in the center, the stress around the corner of the capacitor element between the cathode connection surface and the cathode side end surface can be alleviated. As a result, an increase in leakage current can be suppressed.

  The square described in the present invention is a rectangular parallelepiped having both rectangular end faces. Further, a side surface is provided between the end surfaces.

  In the capacitor element described in the present invention, for example, one end of an anode lead is embedded, and a binder such as acrylic resin or camphor is mixed with fine powder having an average particle diameter of about 1 μm of a valve metal such as tantalum, niobium, or aluminum. A sponge-like anode sintered body formed by press-pressing and then sintering the powder in vacuum, an anodized film on the sintered body, and a solid electrolyte layer such as manganese dioxide or a conductive polymer And a cathode layer such as a carbon layer and a silver layer are sequentially provided.

The lead frame described in the present invention is for mounting a capacitor element having an anode lead. A plate-like member having a thickness of about 0.07 mm to 0.2 mm is processed by punching or the like, and the anode terminal side and the anode lead are connected. The cathode terminal side and the cathode layer are connected. A metal plate such as 42 alloy, copper, copper alloy (copper nickel alloy), or white (silver silver) can be used, and 42 alloy and copper alloy are particularly used in terms of weldability and rigidity. In some cases, the surface mounting surface is provided with a plating layer such as solder plating or tin plating, and in particular, a copper, copper alloy surface such as a multilayer plating of nickel, palladium and gold.
As in the conventional case, the lead frame has a structure in which the cathode terminal side is bent by the distance between the anode lead and the bottom surface of the cathode portion, and a capacitor element is mounted on the top surface of the cathode terminal. Therefore, the cathode terminal is bent from the side surface of the capacitor element along the end surface opposite to the anode lead (bending portion A), and this time, in the opposite direction, is bent vertically from the cathode side end surface (bending portion B). Take.

As the anode lead described in the present invention, for example, a valve metal similar to the anode such as tantalum, niobium or aluminum can be used. The lead is drawn from the anode, and has a linear shape with a diameter of about 0.1 mm to 0.5 mm. In addition, it is a strip thin plate having a thickness of about 0.1 mm to 0.5 mm.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 is a perspective view schematically showing an example according to the present invention.
At the end face of the capacitor element, in the lead-out portion from the peripheral portion of the bent portion (bend portion B) of the cathode terminal to the portion extending in the vertical direction in FIG. In (b), it is narrower than the cathode terminal width.

That is, in FIG. 1 (a), a flat metal plate is punched out and divided into a cathode terminal side portion 1 and an anode terminal side portion 2 so that the cathode terminal side portion 1 of the lead frame is a rectangular capacitor element 3. The side surface 4 of the capacitor element 3 is bent along the end surface 6 opposite to the anode lead 5 (bending portion A9), and is bent vertically from the end surface 6 of the capacitor element 3 (bending portion B10). A bent hole 8 is provided in the center of the lead-out portion 7 from the bent portion B10) to the portion extending in the vertical direction from the peripheral portion. By providing the hole 8, the portion is narrower than the cathode external terminal width W.
The bent portion (bend portion B10) of the end face 6 is actually more likely to have a rounded portion in the bent portion, like the bent portion A, and a punched hole 8 is provided including this rounded portion.
Similarly, in FIG. 1 (b), a flat metal plate is punched out and the cathode terminal side 1 portion of the lead frame divided into the cathode terminal side 1 portion and the anode terminal side portion 2 is a rectangular capacitor. The end face 6 is bent from the side face 4 of the element 3 along the end face 6 opposite to the anode lead 5 (bending part A9), is bent vertically from the end face 6 of the capacitor element 3 (bending part B10), and the end face 6 is bent. The lead-out portion 7 extending from the peripheral portion of the portion (bending portion B10) to the portion extending in the vertical direction has a width W1 narrower than the cathode external terminal width W.

When there is a punch hole or the lead-out part is narrower than the cathode terminal width, the resin moves when it is set in the molding die and the heated resin is injected into the molding die and molded. Becomes easier.
In addition, the portion where the punched-out portion or the lead-out portion is narrower than the cathode terminal width is more easily deformed than the portion bent along the end surface opposite to the anode lead from the side surface of the capacitor element having a wider width. It is possible to relieve stress around the corner portion between the connection surface and the cathode side end surface.
In addition, when the punched hole is provided in the center, as compared with the case where the width is smaller than the width of the cathode terminal, the cathode terminal of the lead frame is less likely to be twisted in the width direction, and the cathode portion of the capacitor element is easily installed with good dimensions.

  Further, the width of the cathode terminal is at least three-quarters of the width of the capacitor element from the peripheral portion of the corner between the side surface of the square capacitor element and the cathode side end surface opposite to the anode lead to the cathode side end surface portion. It is preferable that it is from the above to an equivalent grade. By doing so, the lead frame increases the area covering the peripheral portion of the corner between the cathode connection surface and the cathode side end surface, so that the cathode side end surface of the capacitor element is vertically oriented by the resin injected during resin molding. When the pushing force is less increased, stress is hardly applied to the peripheral portion of the corner between the cathode connection surface and the cathode side end surface.

FIG. 2 is a perspective view schematically showing another example according to the present invention.
2A shows a case where a hole is formed in the center, and FIG. 2B shows a case where the width is made narrower than the cathode external terminal width.
The state of the part made into the width W1 narrower than the punch hole 8 or the cathode terminal width is shown in a sufficiently expanded state from the bent portion (bent portion B10) of the cathode terminal to the cathode side end face 6. The expansion range is from the side surface 4 of the capacitor element 3 to the portion excluding the portion (bent portion A9) bent along the cathode side end surface 6 opposite to the anode lead 5, preferably the cathode side end surface 6 portion of the lead frame. Up to about half of this is preferable.

When the range of expansion is expanded, the portion of the lead frame in which the lead hole portion or lead-out portion has a width W1 narrower than the cathode terminal width is more easily deformed, and the corner peripheral portion between the cathode connection surface and the cathode side end surface Can relieve stress.
As the expansion range decreases, the portion of the lead frame that covers the cathode side end surface increases, so that the force that pushes the cathode side end surface of the capacitor element is reduced by the amount of resin injected during resin molding. Become. Therefore, the stress around the corner portion between the cathode connection surface and the cathode side end surface can be alleviated.

  A method for manufacturing a tantalum chip type solid electrolytic capacitor having a rating of 6.3 V and 100 μF will be described. A fine powder of tantalum is used as the valve action metal, and a fine powder obtained by adding an acrylic resin as a binder to the fine powder is compression-molded by a press machine with one end of a tantalum anode lead wire embedded. The compact is heat-treated in a vacuum and sintered to form a rectangular parallelepiped sintered body having a width of 2.5 mm, a thickness of 1.5 mm, and a length of 2 mm. Next, the sintered body is immersed in a dilute nitric acid solution, and a DC voltage of 20 V is applied to form a dielectric film. After forming the dielectric film, a conductive layer made of conductive polythiophene is laminated. After heat drying, a silver paste layer is formed on the carbon layer. The shape of the lead frame having a thickness of 0.1 mm (see FIG. 2) is as shown in Table 1. The silver layer of the element is connected to the cathode terminal portion of the lead frame with a silver conductive paste, and the anode terminal portion of the lead frame. The lead wire for the anode is welded to and the sintered body is attached to the lead frame. After the element is attached to the lead frame, an exterior is formed by transfer molding using epoxy resin. After forming the exterior, aging treatment is performed, the lead frame is cut and removed, the cathode terminal and the anode terminal are formed, and a chip-type solid electrolytic capacitor is obtained.

(Comparative Example 1)
The lead frame was prepared in the same manner as in Example 1 except that the portion on the cathode terminal side was strip-shaped (see FIG. 3).

(Comparative Example 2)
The portion of the lead frame on the cathode terminal side that is bent along the cathode side end surface (bend portion A), the cathode side end surface, and the portion that is bent vertically from the cathode side end surface (bend portion B) In the same manner as in Example 1 except that the width W1 is narrower than the width of the external terminal portion of the cathode terminal (see FIG. 4).

Examples and Comparative Examples were manufactured with the following parameters (see FIG. 2), and the leakage current of the resulting chip-type solid electrolytic capacitor was measured. The measurement is performed at each n10, and the average measurement results are shown in Table 1.
W: Cathode external terminal width 2.4 mm
L: Length between bent part A and bent part B 0.8 mm
W1: The width of the portion narrower than the cathode external terminal width (width obtained by subtracting the punched hole width from the cathode external terminal width)
W2: Width E of the bent part A: Extended length

As described above, as apparent from Table 1, Examples 1 to 6 can reduce leakage current as compared with Conventional Examples 1 to 2.

It is the perspective view which showed typically the example of the lead frame and capacitor | condenser element part which concern on this invention. It is the perspective view which showed typically another lead frame and capacitor | condenser element part which concern on this invention. It is the perspective view which showed the conventional lead frame and the capacitor | condenser element part typically. It is the perspective view which showed the conventional lead frame and the capacitor | condenser element part typically.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Part by the side of a cathode terminal, 2 ... Part by the side of an anode terminal, 3 ... Capacitor element, 4 ... Side surface, 5 ... Anode lead, 6 ... End surface, 7 ... Lead-out part, 8 ... Punching hole, 9 ... Bending part A, 10: Bending part B.

Claims (1)

In a chip type solid electrolytic capacitor that uses a lead frame to mount a square capacitor element, is covered with resin by a square resin mold, the lead frame is exposed from the opposite end face, and the exposed part becomes the external terminal part. ,
The capacitor element is formed by sequentially laminating a dielectric oxide film and a cathode layer on a surface of an anode body of a molded body made of a valve metal, and has an anode lead led out from one end face of the anode body,
Connecting the anode lead and the anode terminal of the lead frame, and connecting the side surface portion of the cathode layer and the cathode terminal of the lead frame;
The cathode terminal is bent from the side surface of the square capacitor element along the end surface opposite to the anode lead, and is bent and extended in the vertical direction from the end surface of the capacitor element, from the peripheral portion of the bent portion of the end surface. The chip-type solid electrolytic capacitor characterized in that the lead-out portion extending to the portion extending in the vertical direction is narrower than the width of the external terminal portion of the cathode terminal or provided with a through hole in the center.

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