JP2000353641A - Manufacture of solid electronic element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a conductive polymer layer on an oxide film by electrolytic polymerization, which can reduce the time necessary for film formation and make the thickness of the polymer layer uniform. SOLUTION: An electrolytic polymerization solution containing pyrrole as the conductive polymer layer monomer is used, and when a conductive polymer (polypyrrole) layer is formed on a Ta(tantalum) sintered body 1, electrolytic polymerization is carried out as the Ta sintered body 1 when an anode member is being pulled up from the electrolytic polymerization solution 8. Thereby the polymerization reaction at a gas/liquid interface can be utilized, and film formation time can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a solid-state electronic device such as a solid electrolytic capacitor and, more particularly, to a method for manufacturing a solid-state electronic device using a conductive polymer material as a conductive layer.

[0002]

2. Description of the Related Art At present, solid-state electronic devices in which an electrode layer is formed of a conductive polymer material are widely used. 1 of solid-state electronic devices in which an electrode layer is formed using a conductive polymer material
One is a solid electrolytic capacitor. The mainstream of solid electrolytic capacitors uses Ta (tantalum) or Al (aluminum) as an anode metal of the capacitor.
FIG. 5 is a cross-sectional view of the Ta solid electrolytic capacitor in the middle of the manufacturing process. Hereinafter, a conventional general method for manufacturing a Ta solid electrolytic capacitor will be described with reference to the configuration shown in FIG.

(1) Manufacture of a Ta element A molded body in which an anode lead 2 is embedded in Ta metal powder by press molding is prepared and vacuum-sintered to obtain a solid electrolytic capacitor having a porous Ta sintered body 1. A Ta element is created. Here, the reason why the Ta sintered body is made porous is to increase the effective surface area.

[0004] (2) Formation of oxide layer was then immersed Ta sintered body in an aqueous solution phosphoric acid, Ta ₂ by energizing maintaining a positive potential, the counter electrode immersed in an aqueous solution at the negative potential to the anode lead An O ₅ film layer 3 is formed on the surface of the Ta sintered body (called anodization or anodic oxidation).
Actually, Ta ₂ is also applied to the inner surface of the porous Ta sintered body.
The O ₅ film layer 3 is formed. In FIG. 5, a Ta ₂ O ₅ film layer having a uniform thickness is formed on the side and bottom surfaces of the Ta sintered body in order to easily understand the order of the manufacturing process. (The same applies to a pre-coat layer and a conductive polymer layer formed in a later step).

(3) Formation of Chemical Polymerization Precoat Layer A Ta sintered body having an oxide film formed thereon is immersed in an oxidizing agent, dried, then immersed in a conductive polymer monomer, and dried to obtain a conductive polymer by chemical polymerization. A precoat layer 4 made of a polymer is formed. The Ta sintered body is immersed in a phosphoric acid aqueous solution, a voltage is applied to perform re-chemical formation, and the oxide film layer is repaired.

(4) Formation of Conductive Polymer Layer by Electropolymerization As shown in FIG. 6, the conductive polymer monomer contains, for example, pyrrole and has a critical micelle concentration (CMC).
The Ta sintered body 1 formed up to the precoat layer 4 is immersed in the electrolytic bath 7 containing the electrolytic polymerization solution 8 containing a surfactant having an icelle concentration or more, and the positive terminal of the power supply 5 is connected to the anode lead 2. Then, the negative terminal is connected to the cathode 6 corresponding to the counter electrode in the electrolytic polymerization solution 8 to perform the electrolytic polymerization. At this time,
In the electrolytic polymerization solution 8, a surfactant forms molecular films 9 and 10 at the gas-liquid and anode-liquid interfaces, respectively. Since the hydrophobic conductive polymer monomer is concentrated in the molecular film at a high density, the pyrrole concentration (hereinafter, referred to as Py concentration) increases, and the polymerization efficiency increases. By this electrolytic polymerization, a conductive polymer (polypyrrole) layer is formed on the oxide film of the Ta sintered body. At this time, the conductive polymer layer 11 formed near the gas-liquid interface is formed at a high Py concentration at the gas-liquid interface.
The thickness becomes larger than the conductive polymer layer 12 formed at the liquid interface, and the thickness of the conductive polymer layer becomes uneven at the upper portion of the side surface of the Ta sintered body 1 and other portions.

(5) Exterior A conductor layer made of graphite paste or silver paste is formed on the conductive polymer layer formed on the oxide film, and a cathode lead is connected to the conductor layer. A solid electrolytic capacitor is obtained by packaging the element with a resin mold or the like. FIG. 7 is a schematic cross-sectional view of a solid electrolytic capacitor in which the graphite layer 14 has been formed by the above-described conventional method, in the course of manufacturing. As shown in FIG. 7, on the pre-coat layer 4 on the side and bottom surfaces of the Ta sintered body 1,
The conductive polymer layer 12a formed at the anode-liquid interface and the conductive polymer layer 11a formed at the thick gas-liquid interface are formed on the upper side surface.

[0008]

In the conventional manufacturing method described above, in the step (4) of forming the conductive polymer layer by electrolytic polymerization, most of the electrolytic polymerization on the side surface of the Ta sintered body 1 is performed by the anode. -It is performed at the liquid interface, where it is difficult to increase the polymerization rate because the Py concentration, which is an important factor determining the polymerization reaction rate, is relatively small;
It was difficult to shorten the time for forming the conductive polymer.

At the time of electrolytic polymerization, a conductive polymer layer is formed at the upper end portion of the side surface of the Ta sintered body by the molecular film 9 having a high Py concentration. As shown in FIG.
On the side surface of the sintered body 1, the conductive polymer layer 11a formed at the gas-liquid interface and the conductive polymer layer 12a formed at the anode-liquid interface have a non-uniform thickness. This non-uniform thickness may make subsequent packaging steps difficult or may cause uneven heat distribution in the completed solid electrolytic capacitor during use, resulting in product degradation. An object of the present invention is to solve the above-mentioned problems of the prior art, and an object of the present invention is to increase a polymerization reaction rate for forming a conductive polymer layer and form a uniform conductive polymer layer. Is to be able to do that.

[0010]

According to the present invention, there is provided a method of manufacturing a solid-state electronic device, comprising the steps of (1) forming an anode element including a metal body serving as an anode and an anode lead electrically connected to the metal body; (2) using an electrolytic polymerization solution containing a conductive polymer monomer and a surfactant, and forming a conductive polymer layer on the metal body by using a polymerization reaction; In the step (2), the gas-liquid interface is formed by slowly pulling up the anode element from the electrolytic polymerization solution while applying an electric field, or by slowly lowering the anode element into the electrolytic polymerization solution. The conductive polymer layer is formed by utilizing the polymerization reaction of (1).

Preferably, the metal body is a porous metal sintered body. Further, after the step (1) and before the step (2), a step of forming an oxide film on the surface of the metal body is added. In addition, the (1)
After the step and prior to the step (2), or
After the step of forming the oxide film, prior to the step (2), a step of forming a preliminary electrode layer made of a conductive polymer film on the surface of the metal body or the surface of the oxide film is added. .

[0012]

FIG. 1 is a diagram for explaining a method for forming a conductive polymer layer according to a first embodiment of the present invention. FIG. 1 (a) in FIG. 1 shows a first method according to the method of the present invention.
FIG. 1 (b) is a diagram of a stage during execution of the second stage of the method of the present invention. The steps from the step of forming the Ta sintered body 1 with the anode lead 2 to the step of forming the precoat layer 4 before the formation of the conductive polymer layer are the same as the steps described in the related art, and therefore will be described. Is omitted. Further, the configuration of each unit shown in FIG. 1A is the same as the configuration shown in FIG. 6 referred to in the description of the conventional technique, and a duplicate description will be omitted.

In the method for manufacturing a solid electrolytic capacitor according to the present invention, electrolytic polymerization is performed with the configuration shown in FIG.
First, as a first step, a conductive polymer layer 11 at a gas-liquid interface and a conductive polymer layer 12 at an anode-liquid interface are formed as in the prior art. After performing electropolymerization for an appropriate time in this state, as a second stage, as shown in FIG. 1B, the Ta sintered body 1 is slowly pulled up while voltage is continuously applied. During the lifting, the side and bottom surfaces of the Ta sintered body 1 pass through the layer of the molecular film 9 at the gas-liquid interface in the electrolytic polymerization solution 8 where the Py concentration is high. Thereby, in addition to the polymerization reaction by the molecular film 10 at the anode-liquid interface, the polymerization reaction at the molecular film 9 at the gas-liquid interface can be used, so that electrolytic polymerization at a higher polymerization rate can be performed. . Further, the conductive polymer layer formed on the side surface of the Ta sintered body 1 has a uniform film thickness over all side surfaces.

In the above-described embodiment, the stationary state is maintained for a predetermined time and then slowly raised, but the stationary state at the start of the polymerization is not always required. Instead of pulling up, the Ta-based sintered body may be electrolytically polymerized while being slowly pulled down into the electrolytic polymerization solution. Further, it is desirable that the speed at which the upper portion of the Ta sintered body 1 passes through the molecular film 9 is lower than the speed at which the lower portion passes through the molecular film 9. That is, when the conductive polymer layer is formed while pulling up the Ta sintered body 1, the pulling speed is initially increased slowly and gradually. When the conductive polymer layer is formed while the Ta sintered body 1 is being pulled down, the pulling is started at a relatively high speed at first and then gradually lowered.

In the electrolytic polymerization method shown in FIG. 1, the positive side of the power supply 5 is connected to the anode lead 2 to perform the electrolytic polymerization. Instead of this method or in combination with this method, An external power supply terminal connected to the positive side of the power supply 5 is arranged near the Ta sintered body 1 so that a voltage is applied between the external power supply terminal and the cathode in the electrolytic polymerization solution to perform electrolytic polymerization. (See Example 2 and FIG. 4). Further, in the present invention, the metal serving as the anode metal body does not necessarily need to be Ta, and may be another valve action metal such as Al (aluminum), W (tungsten), or Nb (niobium). Further, instead of the porous metal sintered body, a metal plate having a flat surface or an uneven surface formed by etching may be used as the anode body.

FIG. 2 is a diagram showing an electrolytic polymerization state for explaining a second embodiment of the present invention. FIG. 2A shows a state in which the entire Ta sintered body is immersed in an electrolytic polymerization solution to form a conductive polymer layer.
Since it is the same as (a), the description is omitted. While performing the electrolytic polymerization, the Ta sintered body as the anode body is slowly pulled up as in the first embodiment. The immersion position of the Ta sintered body 1 is raised to the bottom of the Ta sintered body shown in FIG. 2 and stopped. Thereafter, it is lowered slowly while performing electrolytic polymerization, and returned to the position shown in FIG. This step is repeated, and reciprocated a plurality of times (for example, three times). According to the first and second embodiments, it is possible to move the immersion position of the Ta sintered body 1 and use the reaction at the gas-liquid interface having a higher polymerization efficiency in the entire sintered body. And in a shorter time,
A uniform conductive polymer layer can be formed.

[0017]

Next, an embodiment of the present invention will be described. Example 1 (1) Production of Ta sintered body A molded body in which an anode lead was embedded in Ta metal powder was prepared by press molding, and heated to about 2000 ° C. in a high vacuum chamber (10 ⁻⁴ to 10 ⁻⁶ mmHg). Sintering for about 30 to 60 minutes to obtain a solid electrolytic capacitor T having a porous Ta sintered body.
a An anode element was prepared. (2) Formation of Oxide Film Layer Next, the Ta sintered body was immersed in a phosphoric acid aqueous solution (0.6 wt%), and a current was applied to the anode lead with a positive potential and the counter electrode immersed in the aqueous solution with a negative potential. Ta ₂ O ₅ coating layer
Formed on the surface of the sintered body. At this time, the potential difference (formation voltage) between the anode body and the counter electrode was set to 18 V to form an oxide film layer. (3) Formation of Chemical Polymerization Precoat Layer The Ta sintered body on which the oxide film was formed was immersed in an aqueous solution containing 30 wt% of p (para) -toluenesulfonic acid iron salt as an oxidizing agent for 5 minutes, dried, and then dried. It was immersed in a dioxythiophene monomer (conductive polymer monomer) solution for 1 minute and dried to form a conductive polymer precoat layer by chemical polymerization inside the porous Ta sintered body. The Ta sintered body is immersed in a phosphoric acid aqueous solution (0.002 wt%) to be 18
Re-chemical conversion was performed with V to repair the oxide film layer.

(4) Formation of conductive polymer layer by electrolytic polymerization Pyrrole 0.1 mol /
l, an aqueous polymer solution containing 0.025 mol / l of sodium dodecylbenzenesulfonate, which also serves as a surfactant, a supporting electrolyte, and a conductive polymer dopant;
The sintered body was immersed, and electrolytic polymerization was performed for 8 hours by applying 15 V between the anode lead and the counter electrode in the electrolytic polymerization solution. At this time, by slowly pulling the Ta sintered body, 30 μm
A polypyrrole layer having a uniform thickness of m was obtained on the oxide film of the anode body. (5) Exterior A solid electrolytic capacitor is formed by forming a conductive layer of a graphite paste or a silver paste on a polypyrrole layer on which a film is formed, connecting a cathode lead, and externally covering the element configured as described above with a resin mold or the like. Obtained.

Embodiment 2 FIG. 4 is a view showing a step of forming a conductive polymer layer according to Embodiment 2, and portions equivalent to those shown in FIGS. 1 and 2 are denoted by common reference numerals. Therefore, duplicate description will be omitted. The second embodiment is the same as the first embodiment except that the method of applying an electric field when forming the conductive polymer layer is different from the first embodiment. In this embodiment, electrolytic polymerization is performed by bringing the external power supply terminal 13 connected to the positive terminal of the power supply 5 close to the Ta sintered body 1 as the anode body. In this case, the polypyrrole formed on the external power supply terminal 13 contacts the Ta anode element, and a polypyrrole layer is formed on the anode oxide film.
A specific method for forming the conductive polymer layer is as follows. A voltage of 1.8 V is applied between the external power supply terminal 13 and the cathode 6, electrolytic polymerization is performed for 10 minutes while the entire Ta sintered body is immersed in an electrolytic polymerization solution at a liquid temperature of 10 ° C., and then 50 hours for 50 hours. Thickness 3
A polypyrrole layer having a uniform thickness of 0 μm was obtained on the oxide film of the Ta anode body. In the present embodiment, since the conductive polymer polypyrrole layer formed allows conduction with the cathode 6, polymerization can be performed without continuing to immerse the external power supply terminal 13.

Example 3 In Example 3, an anode body similarly prepared was immersed in the same electrolytic polymerization solution as in Example 1, and was subjected to 8 hours of electrolytic polymerization by reciprocating up and down 3 times to obtain a 30 μm thick film. A conductive polymer layer was formed on the anodic oxide film.

Example 4 Example 4 is the same except that the conductive polymer monomer in the electrolytic polymerization solution of Example 1 is different. In this example, a Ta sintered body was immersed in an electrolytic polymerization aqueous solution containing 0.1 mol / l of ethylenedioxythiophene and 0.025 mol / l of sodium dodecylbenzenesulfonate as conductive polymer monomers. Similarly, electrolytic polymerization was performed to form polyethylenedioxythiophene as a conductive polymer layer on the anodic oxide film.

Embodiment 5 This embodiment is the same as Embodiment 1 except that the material of the precoat is different. In this example, after immersion in a pyrrole monomer solution for 5 minutes to form a precoat layer by chemical polymerization, electrolytic polymerization was performed in the same manner as in Example 1. According to this method, the types of the conductive polymer monomer solution to be prepared can be reduced, and the production can be simplified.

Example 6 An anode element was prepared by attaching an anode lead to a Ta plate by welding, and a Ta ₂ O ₅ coating layer was formed on the surface of the Ta plate by anodization. Electrolytic polymerization was performed without forming a precoat layer on the oxide film, and a conductive polymer layer similar to that in Example 1 was formed on the anodic oxide film. According to this method,
Manufacturing can be further simplified.

In the embodiments of the present invention, the method for producing the conductive polymer layer of the cathode of the solid electrolytic capacitor has been described. However, the present invention is not limited to the solid electrolytic capacitor, and the conductive polymer layer utilizing a polymerization reaction is used. It can be applied to the manufacture of other solid-state electronic devices using a molecular layer. In the embodiments and examples of the present invention, an oxide film is formed on an anode body to form a dielectric, but the present invention is not limited to a dielectric, and a conductive polymer layer may be formed on a conductor. It can be applied to the case of forming. Further, in the embodiments of the present invention, pyrrole is used as the conductive polymer monomer, but is not limited thereto, and may be thiophene. Alternatively, a derivative of pyrrole or thiophene, in particular, ethylenedioxythiophene as a thiophene derivative may be used. Further, in the examples of the present invention, sodium dodecylbenzenesulfonate was used as the surfactant, but the surfactant is not limited thereto. good.

[0025]

As described above, in the method of manufacturing a solid-state electronic device according to the present invention, since the electrolytic polymerization is performed while pulling the anode metal body out of the electrolytic polymerization solution or pulling it down into the solution, high conductivity is obtained. A conductive polymer layer can be formed using a molecular film at a gas-liquid interface having a high molecular monomer concentration. Thus, according to the present invention,
The conductive polymer layer can be formed on the oxide film in a short time to a uniform film thickness. The non-uniformity of the thickness of the conductive polymer layer on the side surface of the element eliminates the need for an exterior process, or causes an unbalanced heat distribution during use of the completed solid electrolytic capacitor. Problems can be solved, and high quality can be achieved along with mass production.
Further, the manufacturing method of the present invention can be applied to solid-state electronic elements other than the solid electrolytic capacitor, and in such a case, the above-described manufacturing time can be reduced and quality can be improved.

[Brief description of the drawings]

FIG. 1 is a view showing a step of forming a conductive polymer layer according to a first embodiment of the present invention.

FIG. 2 is a view showing a step of forming a conductive polymer layer according to a second embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of a solid electrolytic capacitor partially formed according to the first and second embodiments of the present invention.

FIG. 4 is a view showing a step of forming a conductive polymer layer in Example 2 of the present invention.

FIG. 5 is a cross-sectional view of a Ta solid electrolytic capacitor after a precoat layer is formed, for explaining a conventional example.

FIG. 6 is a view showing a step of forming a conductive polymer layer in a conventional example.

FIG. 7 is a schematic cross-sectional view of a solid electrolytic capacitor partially formed by a conventional method.

[Explanation of symbols]

Reference Signs List 1 Ta sintered body 2 Anode lead 3 Ta ₂ O ₅ coating layer 4 Precoat layer 5 Power supply 6 Cathode 7 Electrolyzer 8 Electropolymerization solution 9 Molecular film at gas-liquid interface 10 Molecular film at anode-liquid interface 11, 11a Conductive polymer layer formed at gas-liquid interface 12, 12a Conductive polymer layer formed at anode-liquid interface 13 External power supply terminal 14 Graphite layer

Claims (13)

[Claims] (1) a step of forming an anode element including a metal body serving as an anode and an anode lead electrically connected to the metal body; and (2) electrolysis including a conductive polymer monomer and a surfactant. Forming a conductive polymer layer on the metal body using a polymerization reaction by using a polymerization solution; and (e) applying an electric field in the step (2). While slowly pulling up the anode element from the electropolymerization solution, or slowly pulling it down into the electropolymerization solution, a conductive polymer layer utilizing a polymerization reaction at a gas-liquid interface. Forming a solid-state electronic device. 2. The method according to claim 1, wherein the metal body is a porous metal sintered body of a valve metal. 3. A process for forming an oxide film on a surface of the metal body made of a valve metal after the step (1) and prior to the step (2) is added. The method for manufacturing a solid-state electronic device according to claim 1 or 2, wherein: 4. The method according to claim 1, wherein after the step (1), prior to the step (2), or after the step of forming the oxide film, prior to the step (2). 4. The method according to claim 1, wherein a step of forming a preliminary electrode layer made of a conductive polymer film on a surface or a surface of the oxide film is added. 5. After the step of forming the oxide film, prior to the step (2), after applying a solution containing an oxidant to the surface of the oxide film, or applying the oxidant to the surface of the oxide film. 4. The method according to claim 3, further comprising the step of applying a solution containing the solution, forming a preliminary electrode layer made of a conductive polymer film thereon, and then performing an oxidation treatment again to repair the oxide film. A method for manufacturing a solid-state electronic device. 6. The method according to claim 1, wherein the electrolytic polymerization solution contains pyrrole, thiophene, or a derivative thereof as a conductive polymer monomer. . 7. The method according to claim 6, wherein the thiophene derivative is ethylenedioxythiophene. 8. The method for manufacturing a solid-state electronic device according to claim 1, wherein in the step (2), the raising and lowering of the anode element is repeated a plurality of times. 9. In the step (2), an anode terminal of a power supply is brought into contact with the anode lead or located near the anode element, or by performing one or both of them. 4. The method for producing a solid-state electronic device according to claim 1, wherein electrolytic polymerization is performed. 10. The electrolytic polymerization solution contains a surfactant in a critical micelle concentration (CMC).
on) or more.
4. A method for manufacturing a solid-state electronic device according to item 3. 11. The method for manufacturing a solid-state electronic device according to claim 1, wherein an alkylbenzene sulfonate or an alkylnaphthalene sulfonate is used as the surfactant. 12. The method according to claim 11, wherein the alkyl benzene sulfonate is sodium dodecyl benzene sulfonate. 13. The method according to claim 13, wherein a passing speed of the uppermost portion of the metal body at the liquid surface of the electrolytic polymer solution is set lower than a passing speed of the lowermost portion thereof, and the speed between them is gradually changed. The method for manufacturing a solid-state electronic device according to claim 1, 2, 3, or 8.