The present invention relates to a method for manufacturing solid electrolytic capacitor for use in various kinds of electronic apparatus.
As a result of downsizing and sophistication in the performance of electronic apparatus, solid electrolytic capacitors (hereinafter referred to as SEC), which being electronic components, are requested to be compact yet having a larger capacitance, a lower ESR (Equivalent Series Resistance) and a lower ESL (Equivalent Series Inductance). A technology for the larger capacitance and the lower ESR of SEC is disclosed in the U.S. Pat. No. 5,377,073 and the Japanese Patent Laid-open No. H11-274002, which are related to a chip-type capacitor with laminated capacitor elements. In conventional SECs, a foil or sintered substance of a valve action metal such as aluminum, tantalum, etc. is used for the electrode, and a dielectric layer is formed on the surface of the metal foil or the sintered substance, and a solid electrolytic layer is formed on the surface. Further on the surface of solid electrolytic layer, a collector layer and an electrode layer are provided to complete a capacitor element. The electrode portion and the electrode layer of capacitor element are connected to the respective connection terminals, and a package is provided in a manner so that the connection terminals are accessible from outside. A conventional finished SEC is thus manufactured.
When mounting a conventional SEC on the surface of a circuit board in the same way as semiconductor components, however, it needs the help of external terminals.
Under such a way of connection, the high frequency characteristic can not avoid being influenced by not only the conduction route to the connection terminal from the electrode portion, electrode layer, but also it is influenced by the wiring portion of circuit board.
As a result, the ESL goes up making it difficult to improve the high frequency characteristic. The present invention addresses the above-described problem, and aims to offer a method for manufacturing SECs which can be connected direct with semiconductor components and implements a low ESR and a low ESL offering a favorable high frequency characteristic.
A method for manufacturing SEC in accordance with the present invention comprises the steps of providing a resist film on one of the surfaces of an aluminum foil, forming a first through hole at a certain specific location of said aluminum foil, forming an insulation film covering the other surface which is opposite to the one having said resist film and filling said first through hole of said aluminum foil, roughening said aluminum foil in the region where said resist film used to be and removed, forming a dielectric layer on the roughened surface of said aluminum foil, forming a second through hole in said insulation film which is filling said first through hole, forming a solid electrolytic layer on the surface of said dielectric layer in succession to formation of a through hole electrode in said second through hole, forming a collector layer on the surface of said solid electrolytic layer, forming an opening in said insulation film, forming a first connection terminal at said opening, and forming a second connection terminal on the exposed surface of said through hole electrode.
Method for manufacturing solid electrolytic capacitor (SEC) is described in accordance with exemplary embodiments of the present invention, referring to the drawings. The drawings are aimed to present the concepts, not to exhibit precise dimensions.
(Embodiment 1)
Referring to FIG. 2 and
Provided on the surface of the solid electrolytic layer 29 is a collector layer 30 for facilitating an easy lead-out of the electrode. The collector layer 30 is connected to a second connection terminal 32 via through hole electrode 28. The through hole electrode 28 is formed by filling a second through hole 36 with a conductive substance, which electrode is electrically insulated by an insulation film 25 from the aluminum foil 20.
A first connection terminal 31 is connected direct with the aluminum foil 20, while electrically insulated from the second connection terminal 32 by insulation film 25. The connection terminals 31 and 32 are provided respectively with connection bumps 33 and 34 for the purpose of direct connection with a semiconductor component.
Thus the first connection terminal 31 and the second connection terminal 32 are disposed on a same plane; which configuration makes it possible to connect a semiconductor component direct with an SEC. Thereby, the connecting distance between the components is remarkably shortened to a reduced ESR and ESL.
Furthermore, by disposing the connection terminals in an arrangement as shown in
Referring to
A photo sensitive resin is advantageous in that it is easy to apply and cure; while an organic film is advantageous in that it contributes to make the manufacturing process simple, in addition, it can be peeled off easily at a later process step. In the next step, the aluminum foil 20 is provided with a first through hole 24, as shown in FIG. 5.
The first through hole 24 can be formed at any optional location with a high precision by using at least one of the methods among a laser beam machining, a punching method, a drilling method and an electric discharge machining.
Next, as shown in
Next, as shown in
Then, as shown in
The solid electrolytic layer 29 is formed by using at least one among the group of a conductive polymer generated through a chemical polymerization of heterocyclic monomer such as pyrrol, thiophene using an oxidizing agent such as ferric sulfate, or through an electrolytic polymerization where the aluminum foil 20 is immersed in a heterocyclic monomer solution and applied with a voltage therein; manganese dioxide generated by heat-decomposing manganese nitrate; a coated film formed by applying a suspension of powdered conductive polymer; and a coated film formed by applying an aqueous solution of conductive polymer.
The conductive polymer which has been made available through one of the above processes may be formed on the surface of dielectric layer 27 after the layer is provided with manganese dioxide on the surface.
The above process provides the conductive polymer homogeneously and intensely. By using the above-described material and procedure, solid electrolytic layer 29 can be provided even on the surface of dielectric layer 27 that has been formed in the micro etching pits generated as a result of the roughening operation. Thus it contributes to a higher static capacitance of an SEC.
Furthermore, in a case where the solid electrolytic layer 29 is formed using an organic material, the layer is soft and flexible and can withstand possible damage or breakage that might arise during the manufacturing process.
These methods can form the opening efficiently; which contributes to a higher productivity.
The first connection terminal 31 is provided for facilitating a good contact with other component, and is connected with the aluminum foil 20.
Preferred process of forming the first connection terminal 31 includes application of conductive adhesive, electroplating, electroless plating.
The application of a conductive adhesive is advantageous in increasing the manufacturing productivity, because of its easiness of application and curing. In the case of electroplating and electroless plating, since it is already covered with the insulation film 25 except the opening 37 and the exposed portion of through hole electrode 28, the first connection terminals 31 can be provided altogether evenly with ease by covering the exposed surface of through hole electrode 28 and the whole reverse surface of collector layer 30 with an insulation tape or the like item. Depending on the needs of insuring a better connection with semiconductor component, a second connection terminal 32 may be provided on the exposed surface of through hole electrode 28 by electroplating, electroless plating or other process. When forming the second connection terminal 32, the first connection terminals 31 and the second connection terminals 32 can be formed altogether by simply covering the entire reverse surface of collector layer 30 with the above-described insulation tape or the like item.
Since the connection terminals are disposed on a same plane, it can be connected direct with a semiconductor component. Thus the above-described method of manufacture readily implements a low ESR and a low ESL, and offers an SEC of superior high frequency characteristics.
(Embodiment 2)
The solid electrolytic layer 29 is formed through the same process as in the embodiment 1. The point of difference from the embodiment 1 is that in the present embodiment 2 no through hole electrode 28 is yet provided at the present stage; this arrangement has the following advantage. Since the through hole electrode 28 is formed of a conductive adhesive substance, it can be ill-affected by solvent, etc. used for forming the solid electrolytic layer 29; viz. the through hole electrode might get swollen, eroded, or flaked off.
So, a range of selecting materials for the conductive adhesive substance would eventually be limited.
However, in the manufacturing method in accordance with the present embodiment 2 where the solid electrolytic layer 29 is provided first and then a through hole electrode 28 is formed, the above-described influence by solvent, etc. does not need to be taken into account. Therefore, the conductive adhesive substance can be selected from among a wider range of candidate materials. Then, as shown in
Thus the ESR is further reduced, and the high frequency characteristic is improved. And then, an opening 37 is formed as shown in
A feature point of the manufacturing method in accordance with the present invention is that it uses an aluminum foil before etching as the starting material. It has following advantages: After the first through hole 24 having been formed in the aluminum foil 20, in a step for removing the resist film 23 which is staying on one surface of the aluminum foil, an acidic solution or an alkaline solution may be used, besides organic solvent, as the resist remover in the present method of manufacture. If an acidic solution or an alkaline solution is used for removing the resist film 23 in a case where an aluminum foil 20 already having a roughened surface is employed as the starting material, the solution may dissolve also the roughened surface of aluminum foil 20, besides the resist film 23 staying on one surface. The dissolved surface of aluminum foil may lead to a deteriorated static capacitance of an SEC.
In the manufacturing method of the present invention, however, the etching is applied after the resist film 23 formed on one surface of aluminum foil 20 is removed. So, there can be no such worry as described in the above, and a resist remover can be selected from among a wider range of candidate materials.
Furthermore, in a case where the manufacturing is conducted in accordance with the present embodiment 2, a conductive adhesive substance may be selected from among a wider range of candidate materials.
Thus the present invention offers a wide range of freedom in the process designing, making the manufacturing of SEC easy. The SEC manufactured in accordance with the present invention provides following advantages: Since the first connection terminal and the second connection terminal are disposed on a same plane, it can be connected direct with a semiconductor component as the source of power supply, and it has a superior high frequency characteristic either.
Furthermore, since the dielectric substance formed of an organic material is rich in flexibility, it can be mounted even on a circuit or a substrate which is exposed to a bending stress. The mounting on such a circuit or a substrate was substantially impossible. Still further, it can be buried in such a substrate with ease. Thus the SECs make a certain contribution to downsizing of apparatus.
As described in the above, the present invention offers a wide range of freedom in designing the process. Consequently, the SECs can be manufactured with ease at a high precision level. At the same time, the manufacturing method of the present invention implements a high productivity in the manufacturing operation. Thus it provides a certain value in the industry.
Number | Date | Country | Kind |
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2001-216351 | Jul 2001 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCTJP02/07218 | 7/16/2002 | WO | 00 | 4/10/2003 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO0300932 | 1/30/2003 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
5377073 | Fukaumi et al. | Dec 1994 | A |
6239965 | Shiraishi et al. | May 2001 | B1 |
6275729 | O'Phelan et al. | Aug 2001 | B1 |
6466430 | Mido et al. | Oct 2002 | B2 |
6510045 | Mido et al. | Jan 2003 | B2 |
Number | Date | Country |
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409213587 | Aug 1997 | JP |
11-274002 | Oct 1999 | JP |
2000-49054 | Feb 2000 | JP |
Number | Date | Country | |
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20030182781 A1 | Oct 2003 | US |