JP3099371B2 - Method for producing porous tantalum sintered body - Google Patents
Method for producing porous tantalum sintered bodyInfo
- Publication number
- JP3099371B2 JP3099371B2 JP02405734A JP40573490A JP3099371B2 JP 3099371 B2 JP3099371 B2 JP 3099371B2 JP 02405734 A JP02405734 A JP 02405734A JP 40573490 A JP40573490 A JP 40573490A JP 3099371 B2 JP3099371 B2 JP 3099371B2
- Authority
- JP
- Japan
- Prior art keywords
- tantalum
- sintered body
- porous
- carbon container
- vacuum
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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Description
【０００１】[0001]
【産業上の利用分野】本発明は固体電解コンデンサに用
いられるタンタル多孔質焼結体の製造方法に関するもの
である。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a porous tantalum sintered body used for a solid electrolytic capacitor.
【０００２】[0002]
【従来の技術】一般にタンタル固体電解コンデンサは、
コンデンサ用の高ＣＶ値タンタル粉末を加圧成形した
後、タンタルリードを陽極引出しとして植設し、高温焼
結を行うことにより、陽極となる多孔質焼結体を構成
し、その後、誘電体皮膜，半導体層，カーボン層，銀ペ
イント層を順次形成してコンデンサ素子を構成してい
る。2. Description of the Related Art Generally, a tantalum solid electrolytic capacitor is
After pressing the high CV value tantalum powder for the capacitor, the tantalum lead is implanted as an anode lead, and sintered at a high temperature to form a porous sintered body serving as an anode. , A semiconductor layer, a carbon layer, and a silver paint layer are sequentially formed to form a capacitor element.
【０００３】前記タンタル多孔質焼結体の固体電解コン
デンサへの使用に際しては、酸素濃度が大変重要となっ
ている。すなわち、タンタル多孔質焼結体の全酸素濃度
が３０００ppmより高い場合には、このようなタンタル
多孔質焼結体を陽極酸化して形成した誘電体皮膜中には
ボイドが発生する。また、誘電体皮膜の形成電圧が１０
０Ｖを超えると、このボイドに過剰の電流が集中し、ボ
イドが破れて欠陥部となるものである。[0003] When the tantalum porous sintered body is used for a solid electrolytic capacitor, the oxygen concentration is very important. That is, when the total oxygen concentration of the tantalum porous sintered body is higher than 3000 ppm, voids are generated in the dielectric film formed by anodizing such a tantalum porous sintered body. Further, the formation voltage of the dielectric film is 10
When the voltage exceeds 0 V, an excessive current is concentrated in the void, and the void is broken and becomes a defective portion.
【０００４】[0004]
【発明が解決しようとする課題】上記した欠陥部数と漏
れ電流との間には図３に示すような正の相関関係があ
り、欠陥部数が多い程、漏れ電流が多い。また、欠陥部
数が多い程、寿命特性試験でも悪い結果を示すもので、
不利なことにタンタル粉末は、酸素に対して大きい親和
性を有するものである。There is a positive correlation between the number of defective portions and the leakage current as shown in FIG. 3. As the number of defective portions increases, the leakage current increases. Also, the larger the number of defective parts, the worse the life characteristic test shows.
Disadvantageously, tantalum powder has a high affinity for oxygen.
【０００５】従って、加熱および大気への暴露などの熱
処理過程は、酸素濃度の増大を導くもので、吸収される
酸素量は、暴露した表面積に比例するため、高ＣＶ値粉
末になる程、大気中の酸素が吸着されて高い酸素濃度を
示すものである。[0005] Therefore, heat treatment processes such as heating and exposure to the atmosphere lead to an increase in oxygen concentration, and the amount of oxygen absorbed is proportional to the exposed surface area. The oxygen inside is adsorbed and shows a high oxygen concentration.
【０００６】本発明はこのような問題点を解決するもの
で、タンタル多孔質焼結体中の酸素濃度を低減させるこ
とにより、誘電体皮膜中のボイドや欠陥部を減少させて
漏れ電流を低減し、寿命特性試験の際の信頼性を高める
ことを目的とするものである。The present invention solves such a problem, and reduces the oxygen concentration in a porous tantalum sintered body, thereby reducing voids and defects in a dielectric film to reduce leakage current. The purpose of the present invention is to improve the reliability in the life characteristic test.
【０００７】[0007]
【課題を解決するための手段】上記目的を達成するため
に本発明のタンタル多孔質焼結体の製造方法は、真空中
または不活性ガス雰囲気中で炭素製の容器の熱処理を行
った後、前記炭素製の容器を大気中に曝さずに炭素製の
容器内にタンタル金属よりなる多孔質成形体を設置し、
真空中または不活性ガス雰囲気中で焼結を行うようにし
たものである。Means for Solving the Problems To achieve the above object, a method for producing a porous tantalum sintered body according to the present invention comprises: performing a heat treatment on a carbon container in a vacuum or in an inert gas atmosphere; Placing a porous molded body made of tantalum metal in a carbon container without exposing the carbon container to the atmosphere,
The sintering is performed in a vacuum or in an inert gas atmosphere.
【０００８】[0008]
【作用】上記したような本発明の構成とすることによ
り、焼結過程でタンタル多孔質成形体の表面に吸着して
いる酸素ならびにタンタル金属中に溶存している酸素
は、酸素親和力の強い炭素製の容器と反応するため、酸
素濃度の少ないタンタル多孔質焼結体を得ることがで
き、その結果、特性面でも著しい向上が図れるものであ
る。According to the structure of the present invention as described above, the oxygen adsorbed on the surface of the porous tantalum compact and the oxygen dissolved in the tantalum metal during the sintering process can be converted into carbon having a strong oxygen affinity. As a result, a porous sintered body of tantalum having a low oxygen concentration can be obtained, and as a result, the characteristics can be significantly improved.
【０００９】[0009]
【実施例】以下、本発明の一実施例を添付図面にもとづ
いて説明する。An embodiment of the present invention will be described below with reference to the accompanying drawings.
【００１０】まず、図１（ａ）に示すように、タンタル
陽極リードを埋設するようにタンタル粉末を円柱状に加
圧成形したタンタル多孔質成形体１を第１予備室２に設
置する。この第１予備室２はシリンダ３により開閉可能
となっており、この第１予備室２を開くことにより、図
１（ｂ）に示すように、さらに下方に位置する第２予備
室４にタンタル多孔質成形体１を設置する。そしてこの
第２予備室４にタンタル多孔質成形体１が設置された
後、図１（ｃ）に示すように、第１予備室２はシリンダ
３により閉じる。この後、第２予備室４および炭素製の
容器６を含むチャンバー７内を、真空ポンプ（図示せ
ず）により真空引きする。そして真空度が１０-3Pa以上
に到達した後、炭素製の容器６を１４００℃以上の温度
で熱処理する。ここで１４００℃以上の温度で熱処理を
するのは、炭素製の容器６上に吸着している酸素は、１
４００℃以上の温度で炭素製の容器６と反応し、ＣＯガ
スとして放出されるからである。その後、炭素製の容器
６を大気に暴露することなく、図１（ｄ）に示すよう
に、第２予備室４をシリンダ５により開いて、タンタル
多孔質成形体１を炭素製の容器６内に設置する。その
後、図１（ｅ）に示すように、第２予備室４をシリンダ
５により閉じてタンタル多孔質成形体１を炭素製の容器
６ごと所定の温度と時間で真空焼結を行う。この真空焼
結の際に、タンタル表面に吸着している酸素ならびにタ
ンタル金属中に溶存している酸素は、炭素製の容器６と
反応し、ＣＯガスとして放出されるため、これにより、
酸素濃度の低いタンタル多孔質焼結体を得ることができ
る。First, as shown in FIG. 1A, a tantalum porous compact 1 in which a tantalum powder is pressure-formed in a cylindrical shape so as to bury a tantalum anode lead is placed in a first preliminary chamber 2. The first preliminary chamber 2 is openable and closable by a cylinder 3. By opening the first preliminary chamber 2, as shown in FIG. 1B, the tantalum is placed in a second preliminary chamber 4 located further below. The porous molded body 1 is installed. After the tantalum porous molded body 1 is installed in the second preliminary chamber 4, the first preliminary chamber 2 is closed by the cylinder 3 as shown in FIG. Thereafter, the inside of the chamber 7 including the second preliminary chamber 4 and the container 6 made of carbon is evacuated by a vacuum pump (not shown). After the degree of vacuum reaches 10 −3 Pa or more, the carbon container 6 is heat-treated at a temperature of 1400 ° C. or more. Here, the heat treatment at a temperature of 1400 ° C. or more is performed because the oxygen adsorbed on the carbon container 6 is 1
This is because it reacts with the carbon container 6 at a temperature of 400 ° C. or more and is released as CO gas. Thereafter, without exposing the carbon container 6 to the atmosphere, as shown in FIG. 1D, the second preparatory chamber 4 is opened by the cylinder 5 and the tantalum porous molded body 1 is placed in the carbon container 6. Installed in Thereafter, as shown in FIG. 1 (e), the second preliminary chamber 4 is closed by the cylinder 5, and the porous tantalum molded body 1 is vacuum-sintered together with the carbon container 6 at a predetermined temperature and time. During the vacuum sintering, the oxygen adsorbed on the tantalum surface and the oxygen dissolved in the tantalum metal react with the carbon container 6 and are released as CO gas.
A tantalum porous sintered body having a low oxygen concentration can be obtained.
【００１１】タンタル多孔質焼結体の酸素濃度を３００
０ppm以下に抑えることにより、誘電体皮膜の形成時に
過剰の酸素を誘電体皮膜中に取り込むことはなくなるた
め、ボイドや欠陥部の少ない誘電体皮膜が形成され、こ
れにより、漏れ電流特性，各種寿命試験特性を向上させ
ることができる。[0011] The oxygen concentration of the porous tantalum sintered body is 300
By suppressing the content to 0 ppm or less, excess oxygen is not taken into the dielectric film during the formation of the dielectric film, so that a dielectric film with few voids and defects is formed, thereby providing leakage current characteristics and various lifespans. Test characteristics can be improved.
【００１２】次に具体例について説明する。タンタル粉
末１５０mgをφ３．０mm，l３．３mmの円柱型に加圧成
形した。これにタンタル陽極リードを埋設したものを、
図１（a）に示すように第１予備室２に設置した。次に
図１（ｂ）に示すように、第１予備室２を開くことによ
り、第２予備室４にタンタル多孔質成形体１を設置し
た。そしてこの第２予備室４にタンタル多孔質成形体１
が設置された後、図１（ｃ）に示すように、第１予備室
２を閉じた。この後、第２予備室４および炭素製の容器
６を含むチャンバー７内を真空ポンプにより真空引きし
た。この真空度が１０-3Pa以上に到達した後、前記炭素
製の容器６を１４００℃以上の温度で熱処理した。その
後、図１（ｄ）に示すように、炭素製の容器６を大気に
暴露することなく、第２予備室４を開いてタンタル多孔
質成形体１を炭素製の容器６内に設置した。その後、第
２予備室４を閉じ、そして図１（ｅ）に示すように、加
熱ヒーターに電流を流して、タンタル多孔質成形体１を
炭素製の容器６ごと加熱し、所定の温度と時間でタンタ
ル多孔質成形体１の焼結を行った。Next, a specific example will be described. 150 mg of the tantalum powder was press-formed into a columnar shape of φ3.0 mm and l3.3 mm. With the tantalum anode lead embedded in this,
As shown in FIG. 1 (a), it was installed in the first preliminary chamber 2. Next, as shown in FIG. 1B, the first prechamber 2 was opened, and the tantalum porous compact 1 was set in the second prechamber 4. The second pre-chamber 4 contains the tantalum porous compact 1
After the was installed, the first preliminary chamber 2 was closed as shown in FIG. Thereafter, the inside of the chamber 7 including the second preliminary chamber 4 and the container 6 made of carbon was evacuated by a vacuum pump. After the degree of vacuum reached 10 −3 Pa or more, the carbon container 6 was heat-treated at a temperature of 1400 ° C. or more. Thereafter, as shown in FIG. 1D, the second preparatory chamber 4 was opened and the tantalum porous compact 1 was placed in the carbon container 6 without exposing the carbon container 6 to the atmosphere. Thereafter, the second preliminary chamber 4 is closed, and as shown in FIG. 1 (e), an electric current is applied to the heater to heat the tantalum porous molded body 1 together with the carbon container 6, and a predetermined temperature and time are set. The sintering of the porous tantalum compact 1 was performed.
【００１３】その後、０．０４モル／lのりん酸水溶液
中において、一般的な方法で、１４０Ｖで２時間保持し
て陽極酸化を行い、誘電体皮膜を形成した。そしてこの
ように構成されたコンデンサ素子を、０．０４モル／l
のりん酸水溶液中で９６Ｖの電圧を印加して１分間充電
した後、漏れ電流特性を測定し、かつ誘電体皮膜を走査
型電子顕微鏡により観察して、誘電体皮膜中の欠陥部数
を数えた。また、焼結体中の酸素濃度も測定した。Thereafter, in a 0.04 mol / l phosphoric acid aqueous solution, anodic oxidation was carried out by a general method at 140 V for 2 hours to form a dielectric film. Then, the capacitor element having the above-described structure was used in an amount of 0.04 mol / l.
After charging for 1 minute by applying a voltage of 96 V in a phosphoric acid aqueous solution, the leakage current characteristics were measured, and the dielectric film was observed with a scanning electron microscope to count the number of defects in the dielectric film. . Also, the oxygen concentration in the sintered body was measured.
【００１４】この結果を（表１）に示す。The results are shown in (Table 1).
【００１５】[0015]
【表１】 [Table 1]
【００１６】上記（表１）の結果から明らかなように、
本発明の実施例の焼結法を行ったタンタル多孔質焼結体
は、従来の焼結体に比べて、液中の漏れ電流特性，誘電
体皮膜の欠陥部数とも改善されている。また焼結体の酸
素濃度も低減している。この後、誘電体皮膜の表面に半
導体層，カーボン層，銀ペイント層を順次形成した後、
外部引出し用の陰極リードおよび陽極リードを引出した
後、外装樹脂を施してタンタル固定電解コンデンサを構
成した。As is clear from the results of the above (Table 1),
The porous tantalum sintered body obtained by performing the sintering method of the embodiment of the present invention has improved leakage current characteristics in liquid and the number of defective portions of the dielectric film as compared with the conventional sintered body. Further, the oxygen concentration of the sintered body is also reduced. Thereafter, a semiconductor layer, a carbon layer, and a silver paint layer are sequentially formed on the surface of the dielectric film.
After a cathode lead and an anode lead for external lead-out were drawn out, an exterior resin was applied to form a tantalum-fixed electrolytic capacitor.
【００１７】そしてこのタンタル固体電解コンデンサを
８５℃４６Ｖ印加の高温負荷試験に１０００時間供し
た。その結果を図２に示す。この図２から明らかなよう
に、１０００時間後においては、従来のタンタル多孔質
焼結体を使用したタンタル固体電解コンデンサは漏れ電
流が一桁増加しているが、本発明の実施例のような焼結
方法で焼結を行った焼結体を使用したタンタル固体電解
コンデンサは、漏れ電流劣化がほとんど無く、これによ
り、高温負荷寿命試験の信頼性が改善されることが確認
できた。The tantalum solid electrolytic capacitor was subjected to a high-temperature load test at 85 ° C. and 46 V for 1000 hours. The result is shown in FIG. As apparent from FIG. 2, after 1000 hours, the leakage current of the tantalum solid electrolytic capacitor using the conventional porous sintered tantalum body has increased by one digit, but as in the example of the present invention. It has been confirmed that the tantalum solid electrolytic capacitor using the sintered body sintered by the sintering method has almost no deterioration of leakage current, thereby improving the reliability of the high temperature load life test.
【００１８】なお、上記本発明の実施例の方法では、炭
素製の容器６の熱処理およびタンタル多孔質成形体１の
焼結は真空中で行ったが、不活性ガス雰囲気中で行って
も、上記実施例と同様の効果が得られるものである。In the method of the embodiment of the present invention, the heat treatment of the carbon container 6 and the sintering of the porous tantalum compact 1 are performed in a vacuum. The same effects as in the above embodiment can be obtained.
【００１９】[0019]
【発明の効果】上記実施例の説明から明らかなように、
本発明のタンタル多孔質焼結体の製造方法は、真空中ま
たは不活性ガス雰囲気中で炭素製の容器の熱処理を行っ
た後、前記炭素製の容器を大気中に曝さずに炭素製の容
器内にタンタル金属よりなる多孔質成形体を設置し、真
空中または不活性ガス雰囲気中で焼結を行うようにして
いるため、焼結過程でタンタル多孔質成形体の表面に吸
着している酸素ならびにタンタル金属中に溶存している
酸素は、酸素親和力の強い炭素製の容器と反応すること
になり、これにより、酸素濃度が従来の焼結体に比べて
減少するため、液中の漏れ電流特性や誘電体皮膜の欠陥
部数の大幅な改善を行うことができ、しかも実際の製品
における高温負荷試験に供した場合の信頼性も著しい改
善が図れるものである。As is clear from the description of the above embodiment,
The method for producing a porous tantalum sintered body of the present invention includes the steps of: performing a heat treatment on a carbon container in a vacuum or an inert gas atmosphere; thereafter, exposing the carbon container to the atmosphere without exposing the carbon container to the atmosphere. Since a porous molded body made of tantalum metal is installed in the inside and sintering is performed in a vacuum or an inert gas atmosphere, oxygen adsorbed on the surface of the tantalum porous molded body during the sintering process In addition, oxygen dissolved in the tantalum metal reacts with a carbon container having a strong oxygen affinity, thereby reducing the oxygen concentration as compared with a conventional sintered body. The characteristics and the number of defective portions of the dielectric film can be significantly improved, and the reliability when subjected to a high-temperature load test on an actual product can be significantly improved.
【図１】（ａ）〜（ｅ）本発明のタンタル多孔質焼結体
の製造方法の一実施例を示す概略図1A to 1E are schematic views showing one embodiment of a method for producing a porous tantalum sintered body of the present invention.
【図２】本発明の一実施例におけるタンタル多孔質焼結
体と、従来の製造方法による焼結体を使用したタンタル
固体電解コンデンサの高温負荷試験の結果を比較して示
す特性図FIG. 2 is a characteristic diagram comparing the results of a high-temperature load test between a porous tantalum sintered body according to one embodiment of the present invention and a tantalum solid electrolytic capacitor using a sintered body obtained by a conventional manufacturing method.
【図３】従来の誘電体皮膜中の欠陥部数と漏れ電流特性
の関係を示す特性図FIG. 3 is a characteristic diagram showing the relationship between the number of defects in a conventional dielectric film and leakage current characteristics.
１ タンタル多孔質成形体 ２ 第１予備室 ３ シリンダ ４ 第２予備室 ５ シリンダ ６ 炭素製の容器 ７ チャンバー REFERENCE SIGNS LIST 1 Tantalum porous molded body 2 First preliminary chamber 3 Cylinder 4 Second preliminary chamber 5 Cylinder 6 Carbon container 7 Chamber
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭62−264616（ＪＰ，Ａ) 特開 昭62−77401（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) H01G 9/052 H01G 9/04 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-264616 (JP, A) JP-A-62-77401 (JP, A) (58) Fields investigated (Int. Cl. 7 , DB name) H01G 9/052 H01G 9/04
Claims (2)
の容器の熱処理を行った後、前記炭素製の容器を大気中
に曝さずに炭素製の容器内にタンタル金属よりなる多孔
質成形体を設置し、真空中または不活性ガス雰囲気中で
焼結を行うようにしたタンタル多孔質焼結体の製造方
法。After a carbon container is heat-treated in a vacuum or in an inert gas atmosphere, a porous molding made of tantalum metal is formed in the carbon container without exposing the carbon container to the atmosphere. A method for producing a porous tantalum sintered body in which a body is placed and sintering is performed in a vacuum or an inert gas atmosphere.
上である請求項１記載のタンタル多孔質焼結体の製造方
法。2. The method for producing a porous tantalum sintered body according to claim 1, wherein the heat treatment temperature of the carbon container is 1400 ° C. or higher.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP02405734A JP3099371B2 (en) | 1990-12-25 | 1990-12-25 | Method for producing porous tantalum sintered body |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP02405734A JP3099371B2 (en) | 1990-12-25 | 1990-12-25 | Method for producing porous tantalum sintered body |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04223318A JPH04223318A (en) | 1992-08-13 |
| JP3099371B2 true JP3099371B2 (en) | 2000-10-16 |
Family
ID=18515347
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP02405734A Expired - Fee Related JP3099371B2 (en) | 1990-12-25 | 1990-12-25 | Method for producing porous tantalum sintered body |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3099371B2 (en) |
-
1990
- 1990-12-25 JP JP02405734A patent/JP3099371B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04223318A (en) | 1992-08-13 |
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| LAPS | Cancellation because of no payment of annual fees |