A surface-mounting thin type capacitor includes a capacitor element having a shape of  and two end portions which form a side surface of the capacitor element. Two anode terminals are disposed on lower surfaces of the end portions along the side surface to form a mounting surface substantially perpendicular to the side surface. A cathode terminal is disposed at a middle part of the capacitor element to form the mounting surface together with the anode terminals. The cathode terminal is not between the anode terminals spatially and thereby manufacturing process of the capacitor is simplified and it is easy to change the intended use of the capacitor.

This application claims priority to prior Japanese patent application JP 2004-255333, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to a surface-mounting capacitor, which is usable as a noise filter, a bypass capacitor or a decoupling capacitor on an electronic substrate.

Recently, with the improvements in performance, advances in miniaturization and/or weight reduction of electronic components mounted on an electronic substrate, a power supply is rapidly miniaturized. The miniaturization of the power supply is firstly achieved by increasing of the operating frequencies of the electronic components. The high operating frequencies of the electronic components cause a problem of electromagnetic interference in circuits on the electronic substrate. Accordingly, demands increasingly become severe regarding performance of a component, such as a noise filter, mounted on the electronic substrate. To meet the demands, a solid electrolytic capacitor has been developed which has conductive functional polymer film as a cathode and a valve effect metal layer, such as an aluminum or tantalum layer, as an anode, and has been in practical use as a surface-mounting thin type capacitor. Such a solid electrolytic capacitor is disclosed in Japanese Unexamined Patent Application Publications No. JP2002-313676 A (hereinafter referred to as Document 1), No. JP2002-164760 A (hereinafter referred to as Document 2), or No. JP2005-39040 A (hereinafter referred to as Document 3).

According to Document 1, a first conventional solid electrolytic capacitor has a first metal plate. The first metal plate has oxide films on both faces thereof and a pair of anode portions at both ends thereof. The first metal plate is sandwiched by flat cathode members of functional polymer to expose the anode portions. The cathode members are covered with second metal plates at opposite sides of the first metal plate. The anode portions are connected to anode terminals while one of the second metal plates is connected to a cathode terminal. The other of the second metal plates projects from ends of the cathode members over the anode portions. With this structure, the noise reduction performance of the first conventional capacitor is improved at high frequency range over 100 MHz.

Document 2 discloses a second conventional solid electrolytic capacitor having a distribution constant circuit portion. The second conventional capacitor is similar to the first conventional capacitor except that it has a metal layer instead of the second metal plates to form the distribution constant circuit portion. The metal layer covers the flat cathode members and the part of the first metal plate sandwiched by the flat cathode members. With this structure, the second conventional capacitor can reduce noise over a wide band.

Document 3 discloses a third conventional solid electrolytic capacitor having a main element similar to the first conventional capacitor except that the second metal plates are substantially the same size. The third conventional capacitor further has reinforcing metal plates and thermosetting adhesive impregnated tapes for fixing the reinforcing metal plates to the main element. The reinforcing metal plates have steps to reduce intervals between edges thereof. The steps prevent oxygen from penetrating to the main element and thereby the third conventional capacitor has high reliability and high heat resistance.

At any rate, the conventional capacitors have the two anode portions each. The anode portions are located at both sides of the cathode member(s). Accordingly, the anode terminals connected to the anode portions are located at both sides of the cathode terminal connected to the cathode member. To use the conventional capacitor as a two terminal type capacitor, the anode terminals must be electrically connected to each other. Generally, a connecting wire (or pattern) to connect the anode terminals each other is formed on the electronic substrate on which the capacitor is mounted. The connecting wire is so arranged to avoid a land for the cathode terminal that a land pattern including the land and the connecting wire is larger than that of a three terminal type capacitor. Therefore, the conventional capacitors mentioned above have a common problem that different land patterns having different occupying areas are necessary in accordance with intended use. That is, the size of a mounting area for mounting each conventional capacitor on the electronic substrate must be varied according to the intended use of the capacitor.

In addition, there is a problem that masking process and removing process are necessary to mask the anode portions by mask layers and to remove the mask layers in a manufacturing process for each conventional capacitor. This is because the second metal plates (or a metal layer) are located between the anode portions.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a surface-mounting capacitor which it is unnecessary to vary the size of a mounting area on an electronic substrate regardless of intended use thereof.

Another object of this invention is to provide a surface-mounting capacitor capable of being manufactured by relatively simple process.

Other objects of this invention will become clear as the description proceeds.

According to an aspect of this invention, a surface-mounting capacitor comprises a capacitor element having an anode body made of a valve effect metal foil of which surface area is increased, and a conductive polymer as a solid electrolyte. A plurality of anode terminals is connected to the anode body to form a mounting surface substantially perpendicular to a side surface of the capacitor element. The anode terminals are disposed along the side surface of the capacitor element.

According to another aspect of this invention, a surface-mounting capacitor comprises a plurality of anode terminals arranged in line. A cathode terminal is arranged to form a mounting surface together with the anode terminals. The cathode terminal is out of line in relation to the anode terminals.

According to further still another aspect of this invention, a method for manufacturing a surface-mounting capacitor comprises the steps of preparing a semi-finished capacitor element having a plurality of end portions at a side thereof, and soaking the semi-finished capacitor element in a liquid or paste conductive material except for the end portions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIGS. 1 to 4, a description will be first directed to a surface-mounting capacitor illustrating common features of the capacitor products disclosed in Documents 1, 2 and 3.

FIGS. 1A-1Cshow a capacitor element usable for the surface-mounting capacitor.FIG. 1Ais a schematic plan view of the capacitor element.FIG. 1Bis a sectional view taken along a dashed line1B-1B ofFIG. 1A.FIG. 1Cis a sectional view taken along a dashed line1C-1C ofFIG. 1A.

As illustrated inFIGS. 1A-1C, the capacitor element300has an anode body1covered with an oxide layer2. A conductive polymer film3, as a solid electrolyte layer, covers the oxide layer2except both end portions of the anode body1. A graphite layer4and a silver layer5are overlaid on the conductive polymer film3in order.

FIGS. 2A-2Cshow a product of the surface-mounting capacitor including the capacitor element300.FIG. 2Ais a schematic plan view of the capacitor product310.FIG. 2Bis a sectional view taken along a dashed line2B-2B ofFIG. 2A.FIG. 2Cis a sectional view taken along a dashed line2C-2C ofFIG. 2A.

The capacitor product310has a metal plate6which is adhered on an upper surface of the capacitor element300by a thermosetting adhesive impregnated tape7. The oxide layer2is partly removed to form anode terminals8aand8bat both end portions of a lower surface of the anode body1. A cathode terminal9is adhered on a lower surface of the capacitor element300by the adhesive silver layer10and the thermosetting adhesive impregnated tape7. Thus, the anode terminals8aand8band the cathode terminal9are disposed at a lower side to form a mounting surface of the capacitor product310.

As understood fromFIGS. 2A and 2B, the cathode terminal9is located between the anode terminals8aand8b. Accordingly, mask layers are necessary to form the conductive polymer film3, graphite layer4and the silver layer5in a manufacturing process of the capacitor product310.

A manufacturing process of the capacitor product310will be roughly described below.

As illustrated inFIG. 3, the mask layers12aand12bare formed on the oxide film2to cover areas for the anode terminals8aand8band expose an area for the cathode terminal9. A semi-finished product of the capacitor element300with the mask layers12aand12bis soaked in a liquid or paste material to form the conductive polymer film3, graphite layer4or the silver layer5. Then, the mask layers12aand12bare removed to complete the capacitor element300.

Next, the oxide film2is partly taken away at the areas for the anode terminal8aand8bwhile the anode terminal8aand8bare joined to the anode body1by means of ultrasonic welding. Then, the cathode terminal9is adhered to the lower surface of the silver layer5by the adhesive silver layer10. Subsequently, the thermosetting adhesive impregnated tape7is disposed around the adhesive silver layer10and the silver layer5. After the metal plate6is disposed on an upper side of the thermosetting adhesive impregnated tape7, the metal plate6and the cathode terminal9are pressed at their both edge portions towards each other while the thermosetting adhesive impregnated tape7is cured by heating. Thus the capacitor element300is sealed and the capacitor product310is achieved.

The capacitor product310can be used either as a two-terminal or three-terminal component depending upon how to connect both anode terminals. In a case where the capacitor product310serves as a three-terminal capacitor, it is usable as a noise filter to remove or suppress wideband noise with high precision. For this use, lands are formed on a substrate (e.g. a printed wiring board or a circuit board) to connect the capacitor product310to the circuit as shown inFIG. 4A. The anode terminals8aand8bare connected to lands13and15on the substrate16respectively while the cathode terminal9is connected to a land14.

In a case where the capacitor product310serves as a two-terminal capacitor, it is generally used for a bypass capacitor or a decoupling capacitor. For this use, lands are arranged on a substrate as shown inFIG. 4B. The anode terminals8aand8bare connected to a land17in common while the cathode terminal9is connected to a land14.

As easily understood from comparison betweenFIGS. 4A and 4B, a necessary area for mounting the capacitor product310on the substrate is different according to the propose for use. In other words, an area occupied by a land pattern for the capacitor product310is different according to the intended use of the capacitor product310.

Referring toFIGS. 5 to 8, a description will be made of a surface-mounting thin type capacitor according to a first embodiment of this invention.

FIGS. 5A-5Dshow a capacitor element usable for the surface-mounting thin type capacitor.FIG. 5Ais a schematic plan view of the capacitor element.FIG. 5Bis a sectional view taken along a dashed line5B-5B ofFIG. 5A.FIG. 5Cis a sectional view taken along a dashed line5C-5C ofFIG. 5A.FIG. 5Dis a sectional view taken along a dashed line5D-5D ofFIG. 5A.

The capacitor element100shown inFIGS. 5A-5Dis similar to the element300except for the shape. As shown inFIG. 5A, the capacitor element100has a shape ofor horseshoe. End portions of the capacitor element100are projected in the same direction (i.e. a left-hand side ofFIG. 5A) from a middle part. In other words, the end portions are formed at a side of the middle part to be parallel with each other. The end portions may not be parallel with each other on condition that they projects in a direction inclining from a predetermined direction (i.e. a left-hand direction ofFIG. 5A) at smaller angle than 180°.

The both end portions of the capacitor element100are used for the anode terminals (8aand8binFIGS. 7A and 7B) while the middle part is used for the cathode terminal (9inFIGS. 7A-7D). The anode terminals and the cathode terminal are formed on a lower surface of the capacitor element100as mentioned later. The faces of the both end portions are arranged in line at a left-hand side ofFIG. 5Aand form a side surface of the capacitor element100. The middle part is apart from the side surface formed by the end portions.

The anode body1is made of a valve effect metal foil, such as an aluminum, tantalum or niobium foil. The valve effect metal foil is increased regarding the surface area thereof. For instance, etching is used to increase the surface area of the valve effect metal foil.

The oxide film2is formed through anodization of the anode body1in an appropriate electrolyte.

The conductive polymer film3made of polypyrrole, polythiophene, polyaniline or the like, the graphite layer4and the silver layer5are formed on the oxide film2in order except the end portions in a manner illustrated inFIG. 6. That is, the semi-finished product of the capacitor element100is soaked in the liquid or paste material11except for the end portions. Thus, no mask is necessary to form the conductive polymer film3, the graphite layer4and the silver layer5. In other words, the masking process for forming a mask and the removing process for removing the mask are unnecessary. Therefore, the manufacturing process is simplified and thereby production efficiency is improved.

FIGS. 7A-7Dshow a product110of the surface-mounting thin type capacitor using the capacitor element100.FIG. 7Ais a schematic plan view of the capacitor product110.FIG. 7Bis a sectional view taken along a dashed line7B-7B ofFIG. 5A.FIG. 7Cis a sectional view taken along a dashed line7C-7C ofFIG. 7A.FIG. 7Dis a sectional view taken along a dashed line7D-7D ofFIG. 7A.

The capacitor product110is manufactured like the capacitor product310. Particularly, the oxide film2of the capacitor element100is partly removed at lower sides of the end portions while the anode terminal8aand8bare joined to the anode body1by means of ultrasonic welding. The anode terminals8aand8bare arranged along the side surface formed by the end portions of the capacitor element100.

Next, the cathode terminal9is adhered to the lower surface of the silver layer5by the adhesive silver layer10. The cathode terminal9forms a mounting surface of the capacitor product110together with the tops of the anode terminal8aand8b. The cathode terminal9is out of line in relation to the anode terminals8aand8b. The cathode terminal9is apart from the side surface of the capacitor element100and not between the anode terminals8aand8b.

After that, the thermosetting adhesive impregnated tape7is disposed around the adhesive silver layer10and the silver layer5. Then, the metal plate6is disposed on the upper side of the thermosetting adhesive impregnated tape7, and the metal plate6and the cathode terminal9are pressed at their both edge portions towards each other while the thermosetting adhesive impregnated tape7is cured by heating. Thus, the capacitor element100is sealed to produce the capacitor product110.

The capacitor product110can be used as a two-terminal capacitor or a three-terminal capacitor similarly as for the capacitor310.FIG. 8Ashows a land pattern to use the capacitor product110as the three-terminal capacitor. The land pattern ofFIG. 8Aincludes the lands13-15formed on the substrate16. The lands13and15are connected to the anode terminals8aand8brespectively. The land14is connected to the cathode terminal9. On the other hand,FIG. 8Bshows a land pattern for use of the capacitor product110as the two-terminal capacitor formed on the substrate16. The land pattern includes the land14and17. The land14is connected to the cathode terminal9. The land17is connected to both of the anode terminals in common.

As understood from comparison betweenFIGS. 8A and 8B, these land patterns occupy areas of the same size. Accordingly, a mounting area for mounting the capacitor product110on the electrical substrate16is fixed in size regardless of the intended use of the capacitor product110. Therefore, it is unnecessary to vary the size of the mounting area in accordance with the intended use of the capacitor product110.

Referring toFIGS. 9A-9D, a second embodiment of this invention will be describes in the following.

FIGS. 9A-9Dshow a capacitor element200of the second embodiment.FIG. 9Ais a schematic plan view of the capacitor element200.FIG. 9Bis a sectional view taken along a dashed line9B-9B ofFIG. 9A.FIG. 9Cis a sectional view taken along a dashed line9C-9C ofFIG. 9A.FIG. 9Dis a sectional view taken along a dashed line9D-9D ofFIG. 9A.

The capacitor element200differs from the capacitor element100in that it has an E shape and three anode portions. The three anode portions are end portions of crossbars of the capacitor element200. The capacitor element200is used to manufacture a capacitor product (not shown) similarly as for the capacitor element100.

While this invention has thus far been described in conjunction with the preferred embodiments thereof, it will readily be possible for those skilled in the art to put this invention into practice in various other manners.

For example, though the-shaped capacitor element and the E-shaped capacitor element are mentioned above, other shapes, such as C shape, U shape, V shape, W shape or the like, may be used for the capacitor element. Alternatively, a comb-shaped capacitor element, which has four or more end portions for anode terminals, may be used for the capacitor element. At any rate, a plurality of end portions of a capacitor element is formed at a side of a middle portion of the capacitor element and they severe from each other.

In addition, a molded resin, a metal pipe case or a resin case may be adopted as an external packaging of the capacitor product.