JP2006339177A

JP2006339177A - Solid electrolytic capacitor and its manufacturing method

Info

Publication number: JP2006339177A
Application number: JP2005158334A
Authority: JP
Inventors: Takashi Shimura; 崇志村; Keiichi Ogata; 慶一尾形
Original assignee: Nichicon Corp
Current assignee: Nichicon Corp
Priority date: 2005-05-31
Filing date: 2005-05-31
Publication date: 2006-12-14
Anticipated expiration: 2025-05-31
Also published as: JP4555157B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a solid electrolytic capacitor with a sufficient leakage current characteristic and with a small capacitance change rate at the time of applying DC bias. <P>SOLUTION: Niobium powder or niobium oxide powder is pressed and a sintered body element is immersed in manganese nitrate water solution. Manganese dioxide is created by thermal decomposition and heat treatment is preformed under vacuum. Manganese monoxide is made and is diffused inside the sintered body element. The number of cycle times of immersion and thermal decomposition is one to three times, and a heating temperature under high vacuum is 800 to 1,300°C. Concentration of manganese nitrate water solution is 20 to 60 wt%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、固体電解コンデンサに関するものであり、漏れ電流特性が良好で、ＤＣバイアス印加による容量変化率が小さい固体電解コンデンサの製造方法に関するものである。 The present invention relates to a solid electrolytic capacitor, and more particularly to a method for manufacturing a solid electrolytic capacitor having good leakage current characteristics and a small capacitance change rate due to application of a DC bias.

従来、タンタル、ニオブ等の弁作用金属からなる陽極体を用いた固体電解コンデンサは、弁作用金属粉末を加圧成形し、高温（１２００〜１６００℃）、高真空（１０^−３Ｐａ以下）で焼結した後、陽極酸化等により焼結体素子表面に酸化皮膜を形成する。その後、酸化皮膜上に二酸化マンガンからなる固体電解質層を形成する。続いて、固体電解質層上にグラファイトを形成し、さらに導電性ペーストを塗布して導電体層を形成することで、コンデンサ素子を形成する。
その後、リード線と陽極端子を溶接し、導電体層と陰極端子を導電性接着剤で接続した後、トランスファーモールドを行い、固体電解コンデンサを得る。 Conventionally, a solid electrolytic capacitor using an anode body made of a valve action metal such as tantalum or niobium is formed by pressure-molding a valve action metal powder at a high temperature (1200 to 1600 ° C.) and high vacuum (10 ⁻³ Pa or less). After sintering, an oxide film is formed on the surface of the sintered body element by anodic oxidation or the like. Thereafter, a solid electrolyte layer made of manganese dioxide is formed on the oxide film. Subsequently, a capacitor element is formed by forming graphite on the solid electrolyte layer and further applying a conductive paste to form a conductor layer.
Then, after welding a lead wire and an anode terminal and connecting a conductor layer and a cathode terminal with a conductive adhesive, transfer molding is performed to obtain a solid electrolytic capacitor.

電気特性や周波数特性といった諸特性の改善方法の一つとして、弁作用金属粉末に異種元素を添加し、製造時のいずれかの工程で誘電体酸化皮膜を１００〜１４００℃の温度に曝す方法が提案されている（例えば特許文献１参照）。
また、マンガン含有アニオン水溶液を用いて陽極酸化し、誘電体層内にマンガン含有層を形成することで、漏れ電流特性が向上することが開示されている（例えば特許文献２参照）。
特開２００２−３７３８３４号公報特開２０００−１８８２４１号公報 As one of the methods for improving various characteristics such as electrical characteristics and frequency characteristics, there is a method in which a different element is added to the valve action metal powder and the dielectric oxide film is exposed to a temperature of 100 to 1400 ° C. in any of the manufacturing steps. It has been proposed (see, for example, Patent Document 1).
In addition, it is disclosed that leakage current characteristics are improved by anodizing with a manganese-containing anion aqueous solution and forming a manganese-containing layer in the dielectric layer (see, for example, Patent Document 2).
JP 2002-373734 A JP 2000-188241 A

上記のニオブ粉末に異種元素を添加し、製造時のいずれかの工程で誘電体酸化皮膜を１００〜１４００℃の温度に曝す方法により、漏れ電流特性とＤＣバイアス印加による容量値の低下は改善されるが、ニオブ粉末への元素の添加、および高温度に曝す工程が必要になり、工数がかかるという問題があった。
また、マンガン含有アニオン水溶液を用いて陽極酸化し、誘電体層にマンガン含有層を形成することで、漏れ電流特性は向上するが、添加されるマンガンの量が微量であるため、ＤＣバイアス印加時に対する容量低下の抑制効果が小さいという問題があった。 By adding a different element to the above niobium powder and exposing the dielectric oxide film to a temperature of 100 to 1400 ° C. in any of the manufacturing steps, the leakage current characteristics and the decrease in capacitance value due to DC bias application are improved. However, there is a problem in that the addition of elements to the niobium powder and a step of exposure to high temperature are required, which requires man-hours.
In addition, the leakage current characteristics are improved by anodizing with an aqueous manganese-containing anion solution and forming a manganese-containing layer in the dielectric layer, but the amount of manganese added is very small, so when applying a DC bias There was a problem that the effect of suppressing the decrease in capacity was small.

本発明は上記課題を解決するものであり、漏れ電流特性が良好で、かつＤＣバイアス印加による容量変化率が小さい固体電解コンデンサの製造方法の提供を目的とするものである。 SUMMARY OF THE INVENTION The present invention solves the above-described problems, and an object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor having good leakage current characteristics and a small capacitance change rate due to application of a DC bias.

すなわち、本発明は、弁作用金属を加圧成形し、陽極引出線を植立して焼結した焼結体表面に、誘電体層、固体電解質層および陰極導電層を形成してなる固体電解コンデンサにおいて、
上記焼結体表面に、一酸化マンガンを形成した後、誘電体層を形成したことを特徴とする固体電解コンデンサである。 That is, the present invention relates to solid electrolysis in which a dielectric layer, a solid electrolyte layer, and a cathode conductive layer are formed on the surface of a sintered body obtained by pressure-molding a valve metal, planting an anode lead wire, and sintering. In the capacitor
A solid electrolytic capacitor, wherein a dielectric layer is formed after manganese monoxide is formed on the surface of the sintered body.

また、上記焼結体を、硝酸マンガン水溶液に浸漬し、大気圧下で加熱する第１の加熱処理と、真空下で加熱する第２の加熱処理にて、焼結体表面に一酸化マンガンを形成した後、誘電体層を形成することを特徴とする固体電解コンデンサの製造方法である。 Further, the surface of the sintered body is subjected to manganese monoxide by a first heat treatment in which the sintered body is immersed in an aqueous manganese nitrate solution and heated under atmospheric pressure, and in a second heat treatment in which heat is applied under vacuum. A method of manufacturing a solid electrolytic capacitor is characterized in that a dielectric layer is formed after the formation.

さらに、上記の第２の加熱処理の真空度が１０^−３Ｐａ以下であり、かつ、加熱処理温度が８００〜１３００℃であることを特徴とする固体電解コンデンサの製造方法である。 Furthermore, in the method for manufacturing a solid electrolytic capacitor, the degree of vacuum of the second heat treatment is 10 ⁻³ Pa or less, and the heat treatment temperature is 800 to 1300 ° C.

また、上記の浸漬、熱分解のサイクル回数が１〜３回であることを特徴とする固体電解コンデンサの製造方法である。 The solid electrolytic capacitor manufacturing method is characterized in that the number of cycles of immersion and thermal decomposition is 1 to 3 times.

さらに、上記の硝酸マンガン水溶液の濃度が２０〜６０ｗｔ％であることを特徴とする固体電解コンデンサの製造方法である。 Furthermore, the solid electrolytic capacitor manufacturing method is characterized in that the concentration of the aqueous manganese nitrate solution is 20 to 60 wt%.

本発明は、焼結体素子を硝酸マンガン水溶液に浸漬し、熱分解により二酸化マンガンを生成した後、高真空下で熱処理を行い、生成した一酸化マンガンを焼結体内部に拡散させることにより、漏れ電流特性が良好で、かつＤＣバイアス印加時の容量変化率が小さい固体電解コンデンサを得ることができる。 The present invention immerses the sintered body element in an aqueous manganese nitrate solution, generates manganese dioxide by thermal decomposition, then heat-treats under high vacuum, and diffuses the generated manganese monoxide inside the sintered body. A solid electrolytic capacitor having good leakage current characteristics and a small capacitance change rate when a DC bias is applied can be obtained.

以下に本発明の実施の形態について説明する。
［実施例１］
約７０，０００μＦ・Ｖ／ｇのニオブ粉末にバインダを０．５ｗｔ％混合し、加圧成形した成形体素子を高真空下（約１０^−３Ｐａ以下）、１３００℃で２０分間焼結することにより固体電解コンデンサ用の焼結体を得た。
その後、焼結体素子を濃度１０ｗｔ％の硝酸マンガン水溶液に浸漬し、２００℃、３０分間で第１の加熱処理を１回行った。さらに、焼結体を高真空下（約１０^−３Ｐａ以下）、９００℃で第２の加熱処理を行ない、該焼結体表面の二酸化マンガンを分解し、一酸化マンガンにすると共に素子内に拡散させた。 Embodiments of the present invention will be described below.
[Example 1]
Binder is mixed with 0.5% by weight of niobium powder of about 70,000 μF · V / g, and the compacted compact element is sintered under high vacuum (about 10 ⁻³ Pa or less) at 1300 ° C. for 20 minutes. Thus, a sintered body for a solid electrolytic capacitor was obtained.
Thereafter, the sintered body element was immersed in an aqueous manganese nitrate solution having a concentration of 10 wt%, and the first heat treatment was performed once at 200 ° C. for 30 minutes. Further, the sintered body is subjected to a second heat treatment at 900 ° C. under a high vacuum (about 10 ⁻³ Pa or less) to decompose manganese dioxide on the surface of the sintered body to make manganese monoxide and into the element. Diffused.

次に、一酸化マンガンを素子内に拡散させた焼結体素子表面に陽極酸化により誘電体層を形成した。この時用いる陽極酸化用電解質溶液（以降では化成液と記す）としてリン酸水溶液（１．０ｖｏｌ％）を使用した。陽極酸化はこの化成液を４０℃に保ち、焼結体１個当たりの電流密度を３５ｍＡ／個、到達電圧を３０Ｖに設定して行い、陽極酸化電圧が３０Ｖに達した後、４時間電圧印加状態を保持し、誘電体酸化皮膜を形成した。さらに、導電性高分子を重合することにより固体電解質層を形成した。
続いて、カーボンペースト、銀ペーストからなる陰極導電層を形成し、金属性外部端子を溶接・接着等で接続した後、トランスファーモールドにより樹脂外装し、定格２．５Ｖ−２２０μＦの固体電解コンデンサを得た。 Next, a dielectric layer was formed by anodic oxidation on the surface of the sintered body element in which manganese monoxide was diffused into the element. A phosphoric acid aqueous solution (1.0 vol%) was used as an anodic oxidation electrolyte solution (hereinafter referred to as a chemical conversion solution) used at this time. Anodization is performed by keeping this chemical solution at 40 ° C., setting the current density per sintered body to 35 mA / piece, and the ultimate voltage to 30 V, and applying voltage for 4 hours after the anodization voltage reaches 30 V. The state was maintained and a dielectric oxide film was formed. Furthermore, a solid electrolyte layer was formed by polymerizing a conductive polymer.
Subsequently, a cathode conductive layer made of carbon paste and silver paste is formed, and metallic external terminals are connected by welding, adhesion, etc., and then resin-coated with a transfer mold to obtain a solid electrolytic capacitor having a rating of 2.5 V-220 μF. It was.

［実施例２］
焼結体素子を上記の硝酸マンガン水溶液に浸漬した後の、第１の加熱処理の回数を２回とした他は、実施例１と同じ作製条件とした。 [Example 2]
The manufacturing conditions were the same as those in Example 1, except that the number of times of the first heat treatment after the sintered body element was immersed in the aqueous manganese nitrate solution was set to two.

［実施例３］
焼結体素子を上記の硝酸マンガン水溶液に浸漬した後の、第１の加熱処理の回数を３回とした他は、実施例１と同じ作製条件とした。 [Example 3]
The production conditions were the same as those in Example 1, except that the number of times of the first heat treatment after the sintered body element was immersed in the aqueous manganese nitrate solution was changed to three.

［実施例４〜６］
加圧成形を行う弁作用金属粉末を酸化ニオブ粉末とした他は、各々実施例１〜３と同じ作製条件とした。 [Examples 4 to 6]
The production conditions were the same as in Examples 1 to 3, except that the valve action metal powder for pressure forming was niobium oxide powder.

（従来例１）
焼結体素子に一酸化マンガンを拡散させる工程（硝酸マンガン水溶液に浸漬し、熱分解により二酸化マンガンを生成した後、高真空下で熱処理）を施さない他は、実施例１〜３と同じ作製条件とした。 (Conventional example 1)
Manufacture as in Examples 1 to 3, except that the step of diffusing manganese monoxide into the sintered body element (after dipping in an aqueous manganese nitrate solution to produce manganese dioxide by thermal decomposition and then heat-treating under high vacuum) Condition.

（従来例２）
焼結体素子に一酸化マンガンを拡散させる工程（硝酸マンガン水溶液に浸漬し、熱分解により二酸化マンガンを生成した後、高真空下で熱処理）を施さない他は、実施例４〜６と同じ作製条件とした。 (Conventional example 2)
Production similar to Examples 4 to 6 except that the step of diffusing manganese monoxide into the sintered body element (soaking in an aqueous manganese nitrate solution to produce manganese dioxide by thermal decomposition and then heat-treating under high vacuum) is not performed. Condition.

［実施例７、８］
焼結体素子を４０ｗｔ％、６０ｗｔ％の硝酸マンガン水溶液に浸漬させた他は、実施例２と同じ作製条件とした。 [Examples 7 and 8]
The production conditions were the same as in Example 2 except that the sintered body element was immersed in a 40 wt% and 60 wt% manganese nitrate aqueous solution.

（比較例１、２）
焼結体素子を１０ｗｔ％、８０ｗｔ％の硝酸マンガン水溶液に浸漬させた他は、実施例２と同じ作製条件とした。 (Comparative Examples 1 and 2)
The same production conditions as in Example 2 were used except that the sintered body element was immersed in a 10 wt% and 80 wt% manganese nitrate aqueous solution.

［実施例９、１０］
焼結体素子を４０ｗｔ％、６０ｗｔ％の硝酸マンガン水溶液に浸漬させた他は、実施例５と同じ作製条件とした。 [Examples 9 and 10]
The same production conditions as in Example 5 were used except that the sintered body element was immersed in a 40 wt% and 60 wt% manganese nitrate aqueous solution.

（比較例３、４）
焼結体素子を１０ｗｔ％、８０ｗｔ％の硝酸マンガン水溶液に浸漬させた他は、実施例５と同じ作製条件とした。 (Comparative Examples 3 and 4)
The same production conditions as in Example 5 were used except that the sintered body element was immersed in 10 wt% and 80 wt% manganese nitrate aqueous solution.

［実施例１１〜１５］
焼結体素子内への一酸化マンガン形成の処理温度を８００℃、１０００℃、１１００℃、１２００℃、１３００℃で行った他は、実施例２と同じ作製条件とした。 [Examples 11 to 15]
The manufacturing conditions were the same as those in Example 2, except that the processing temperatures for forming manganese monoxide in the sintered body were 800 ° C., 1000 ° C., 1100 ° C., 1200 ° C., and 1300 ° C.

［実施例１６〜２０］
焼結体素子内への一酸化マンガン形成の処理温度を８００℃、１０００℃、１１００℃、１２００℃、１３００℃で行った他は、実施例５と同じ作製条件とした。 [Examples 16 to 20]
The production conditions were the same as in Example 5 except that the processing temperatures for forming manganese monoxide in the sintered body were 800 ° C., 1000 ° C., 1100 ° C., 1200 ° C., and 1300 ° C.

（比較例５、６）
焼結体素子内への一酸化マンガン形成の処理温度を７００℃、１４００℃で行った他は、実施例２と同じ作製条件とした。 (Comparative Examples 5 and 6)
The manufacturing conditions were the same as those in Example 2, except that the processing temperatures for forming manganese monoxide in the sintered body were 700 ° C. and 1400 ° C.

（比較例７、８）
焼結体素子内への一酸化マンガン形成の処理温度を７００℃、１４００℃で行った他は、実施例５と同じ作製条件とした。 (Comparative Examples 7 and 8)
The production conditions were the same as in Example 5 except that the processing temperatures for forming manganese monoxide in the sintered body were 700 ° C. and 1400 ° C.

実施例１〜６、従来例１〜２により作製したコンデンサ素子について、一酸化マンガン形成前後の重量を測定することで、一酸化マンガン量の算出を行い、また固体電解コンデンサについて、漏れ電流およびＤＣバイアスを１．５Ｖ印加した時の容量変化率を比較した。その結果を表１に示す。
また、実施例７〜１０、比較例１〜４により作製した固体電解コンデンサについて、漏れ電流およびＤＣバイアスを１．５Ｖ印加した時の容量変化率を比較した。その結果を表２に示す。
さらに、実施例１１〜２０、比較例５〜８により作製した固体電解コンデンサについて、漏れ電流およびＤＣバイアスを１．５Ｖ印加した時の容量変化率を比較した。その結果を表３に示す。
また、実施例２および従来例１により作製した固体電解コンデンサのＤＣバイアス印加時の容量変化率を図１に示す。 For the capacitor elements prepared in Examples 1 to 6 and Conventional Examples 1 and 2, the amount of manganese monoxide was calculated by measuring the weight before and after the formation of manganese monoxide, and the leakage current and DC of the solid electrolytic capacitor were calculated. The capacity change rates when a bias voltage of 1.5 V was applied were compared. The results are shown in Table 1.
Moreover, about the solid electrolytic capacitor produced by Examples 7-10 and Comparative Examples 1-4, the capacity | capacitance change rate when 1.5V of leakage current and DC bias were applied was compared. The results are shown in Table 2.
Further, the solid electrolytic capacitors produced in Examples 11 to 20 and Comparative Examples 5 to 8 were compared in terms of capacity change rate when 1.5 V of leakage current and DC bias were applied. The results are shown in Table 3.
FIG. 1 shows the rate of change in capacitance of the solid electrolytic capacitors produced in Example 2 and Conventional Example 1 when a DC bias is applied.

表１から明らかなように、二酸化マンガンを分解し、焼結体素子内に一酸化マンガンを拡散させた実施例１〜６は、従来例と比較し、漏れ電流値およびＤＣバイアス印加時の容量変化率が改善した。特に、第１の加熱処理の回数が２回の実施例２、５が大きく改善されている。
但し、第１の加熱処理の回数が１回では容量変化率が増加し、３回では、漏れ電流値が大きくなるため、回数は２回がさらに望ましい。
また、表２から明らかなように、焼結体素子に浸漬する硝酸マンガンの濃度は２０〜６０ｗｔ％が望ましい。１０ｗｔ％では容量変化率が大きくなり（比較例１、３）、８０ｗｔ％では漏れ電流が大きくなる（比較例２、４）。
さらに、表３から明らかなように、高真空下、高温で加熱処理する第２の工程における加熱温度は、８００〜１３００℃が望ましい。８００℃未満では、一酸化マンガンの形成が不十分なため、漏れ電流が大きくなり（比較例５、７）、１３００℃を超えると容量値が低下する（比較例６、８）。
また、図１から明らかなように、実施例２は従来例１と比較し、固体電解コンデンサのＤＣバイアス印加時の容量変化率が小さく、改善されている。 As is apparent from Table 1, Examples 1 to 6 in which manganese dioxide was decomposed and manganese monoxide was diffused in the sintered body element were compared with the conventional example in terms of leakage current value and capacity when DC bias was applied. The rate of change has improved. In particular, Examples 2 and 5 in which the number of times of the first heat treatment is two are greatly improved.
However, since the capacity change rate increases when the number of times of the first heat treatment is 1, and the leakage current value becomes large when the number of times of the first heat treatment is 3, the number of times is more preferably 2.
Further, as apparent from Table 2, the concentration of manganese nitrate immersed in the sintered body element is preferably 20 to 60 wt%. The capacity change rate increases at 10 wt% (Comparative Examples 1 and 3), and the leakage current increases at 80 wt% (Comparative Examples 2 and 4).
Furthermore, as is apparent from Table 3, the heating temperature in the second step of heat treatment at high temperature under high vacuum is desirably 800 to 1300 ° C. When the temperature is lower than 800 ° C., the formation of manganese monoxide is insufficient, so that the leakage current increases (Comparative Examples 5 and 7). When the temperature exceeds 1300 ° C., the capacity value decreases (Comparative Examples 6 and 8).
Further, as is apparent from FIG. 1, the second embodiment has an improved capacity change rate when the DC bias is applied to the solid electrolytic capacitor as compared with the first conventional example.

なお、上記実施例の固体電解質層は、化学重合法や気相重合法で合成した固体電解質相をプレコート層とし、その上に電解重合することにより形成されるが、固体電解質は、ピロール、チオフェン、アニリンもしくはそれらの誘導体を繰り返し単位とするもの、また、酸化剤を用いて化学酸化重合したポリピロール、ポリアニリン、ポリチオフェン、さらに、ポリアニリン、ポリチオフェン、ポリピロールのいずれかの組合せでも同等の効果が得られる。 The solid electrolyte layer of the above example is formed by using a solid electrolyte phase synthesized by a chemical polymerization method or a gas phase polymerization method as a precoat layer, and electrolytic polymerization thereon, but the solid electrolyte is composed of pyrrole, thiophene or the like. The same effect can be obtained by using aniline or a derivative thereof as a repeating unit, or a combination of polypyrrole, polyaniline, polythiophene, or polyaniline, polythiophene, or polypyrrole chemically oxidized and polymerized using an oxidizing agent.

本発明の実施例２および従来例１による固体電解コンデンサのＤＣバイアス印加時の容量変化率を示した図である。It is the figure which showed the capacity | capacitance change rate at the time of DC bias application of the solid electrolytic capacitor by Example 2 of this invention, and the prior art example 1. FIG.

Claims

In a solid electrolytic capacitor formed by forming a dielectric layer, a solid electrolyte layer, and a cathode conductive layer on the surface of a sintered body obtained by pressure forming a valve action metal, planting an anode lead wire, and sintering,
A solid electrolytic capacitor, wherein a dielectric layer is formed after forming manganese monoxide on the surface of the sintered body.

The sintered body according to claim 1 is oxidized on the surface of the sintered body by a first heat treatment in which the sintered body is immersed in an aqueous manganese nitrate solution and heated under atmospheric pressure and a second heat treatment in which heat is applied under vacuum. A method for producing a solid electrolytic capacitor, comprising forming a dielectric layer after forming manganese.

A method for producing a solid electrolytic capacitor, wherein the second heat treatment according to claim 2 has a vacuum degree of 10 ⁻³ Pa or less and a heat treatment temperature of 800 to 1300 ° C.

The method for producing a solid electrolytic capacitor, wherein the number of cycles of immersion and thermal decomposition according to claim 2 is 1 to 3.

A method for producing a solid electrolytic capacitor, wherein the concentration of the aqueous manganese nitrate solution according to claim 2 is 20 to 60 wt%.