【発明の詳細な説明】[Detailed description of the invention]
本発明はBaTiO3、Nd2O3、ZrO2を主成分と
し、Mn化合物を微量添加含有してなる還元型半
導体磁器コンデンサ用磁器材料に関するもので、
小型、大容量であり、高い絶縁抵抗ならびに高耐
電圧を特徴としている。
一般に半導体磁器コンデンサは出発原料および
その製造方法の違いにより各種の呼び名が付けら
れている。すなわち、出発原料としてはBaTiO3
系およびその固溶体系が主として用いられ、一部
にはSrTiO3を主成分とする半導体磁器コンデン
サも実用化されている。これらの出発原料を基に
その製造方法は各磁器の特徴を充分に利用したも
ので、磁器の粒界を利用した粒界型、磁器の表面
を利用した堰層型ならびに還元型(再酸化型とも
いう)に大別され、その使用目的、用途に応じて
その製造方法は多岐にわたつている。
還元型半導体磁器コンデンサは通常、誘電体磁
器を還元雰囲気中の熱処理にて得られた半導体磁
器に電極用の銀ペーストを塗布し、酸化雰囲気中
にて熱処理を行うことにより得られる。この酸化
雰囲気中の熱処理により半導体磁器と銀電極の間
に薄い誘電体層が形成される。この薄い誘電体層
は還元型半導体磁器コンデンサの容量および絶縁
抵抗ならびに耐電圧に寄与すると共に、誘電体磁
器の特性および性状にも大きく依存している。還
元型半導体磁器コンデンサは単位面積当りの容量
を大きくすると誘電体層が薄くなり、必然的に絶
縁抵抗および耐電圧は低下し、逆に絶縁抵抗およ
び耐電圧を高くしようとすると誘電体層を厚くす
る必要があり、単位面積当りの容量が低下すると
いう性質を有している。また、この誘電体層の容
量の温度特性は還元型半導体磁器コンデンサの容
量の温度特性として表われ、還元前の誘電体磁器
の温度特性と極めて類似している。すなわち、こ
の薄い誘電体層は還元により得られた半導体磁器
の表面が電極形成時の熱処理により、再び酸化さ
れて形成されたものと推定される。このため還元
型半導体磁器コンデンサの特性は誘電体磁器の誘
電率、温度特性により大きく左右されるものであ
る。また半導体磁器表面を薄く均質に誘電体層化
し、高い絶縁抵抗および高い耐電圧を得るために
は、誘電体磁器の表面が均質で数μm以下の微粒
子よりなることが必要である。還元型半導体磁器
コンデンサの誘電損失(tanδ)は誘電体層のtan
δに依存するが、それよりも誘電体層と半導体磁
器の境界の直列抵抗分により大きく依存する。
tanδを小さくするためには、この直列抵抗分の
小さな磁器材質を選択する必要がある。
この様に高い絶縁抵抗および高い耐電圧を有
し、あわせて単位面積当りの極めて大きな静電容
量値をもつ還元型半導体磁器コンデンサを得るに
は誘電体磁器の誘電率が大きく、磁器表面が数μ
m以下の均質な微粒子よりなり、銀電極を還元さ
れた半導体磁器表面に形成させる際の熱処理温度
で磁器表面層を容量に誘電体層化させ得ることな
どの要件を充たし、還元型半導体磁器コンデンサ
としてtanδの低い磁器材質を有する磁器材料が
得られなければならない。
本発明は近年の電子機器の小型化、高密度実装
化ならびに品質の高安定化にともなう部品の小型
化と高品質化の要求に対してなされたものであ
り、従来の欠点を除き、高い絶縁抵抗および高い
耐電圧を有し、あわせて小型大容量の還元型半導
体磁器コンデンサを提供するもので、誘電体磁器
の表面が均質でかつ数μm以下の微粒子よりな
り、誘電率が14000〜17000(キユーリー点におけ
る)と高く、あわせて還元型半導体磁器コンデン
サとしてのtanδは極めて優れた磁器材料を提供
するものである。
すなわち、本発明は、x BaTiO3+y
Nd2O3+z ZrO2(ただし、x=98.7〜86.5モル
%、y=0.6〜3.5モル%、z=0.7〜10.0モル%、
x+y+z=100)にMn化合物をMnOに換算し
て、0.01〜0.3重量%添加含有した磁器材料にか
かるものである。
以下、実施例について本発明を詳細に説明す
る。
BaCO3とTiO3を等モル混合し、これを1150℃
で2時間仮焼成し、この反応物を粉砕して
BaTiO3を作成する。BaTiO3、Nd2O3、ZrO2およ
びMn化合物を各々所要の組成になる様秤量し、
これをポツトミルにて約16時間湿式混合する。混
合後、脱水乾燥しポリビニルアルコールなどの有
機バインダーを約2.5重量%添加して整粒し、
1000Kg/cm2の圧力で直径11.5mmφ、厚み0.6mmに成
形する。次いで成形された円板を1300℃で2時間
本焼成する。この様にして得られた誘電体磁器を
800℃の還元雰囲気中で1時間熱処理を行つて半
導体磁器を得る。この半導体磁器に電極用銀ペー
ストを塗布して乾燥し、800〜850℃で約30分間酸
化雰囲気中で熱処理を行い、還元型半導体磁器コ
ンデンサを作成した。この様に作成したコンデン
サの諸特性を表に示した。なお、試料測定に際
し、容量、tanδは周波数1kHz、電圧1Vrmsで測
定し、絶縁抵抗は50VDCの電圧を30秒間印加し
たのち値を測定し、破壊電圧(VDC)は昇圧破
壊方式にて測定した。測定温度は20℃を基準にし
た。
The present invention relates to a ceramic material for a reduced semiconductor ceramic capacitor, which contains BaTiO 3 , Nd 2 O 3 , and ZrO 2 as main components and contains a trace amount of a Mn compound.
It is small, large capacity, and features high insulation resistance and high withstand voltage. Generally, semiconductor ceramic capacitors are given various names depending on the starting materials and manufacturing methods. That is, BaTiO 3 is used as a starting material.
SrTiO 3 and its solid solution systems are mainly used, and some semiconductor ceramic capacitors whose main component is SrTiO 3 have also been put into practical use. The manufacturing method based on these starting materials takes full advantage of the characteristics of each type of porcelain, including the grain boundary type that uses the grain boundaries of the porcelain, the weir layer type that uses the surface of the porcelain, and the reduced type (reoxidation type). There are a wide variety of manufacturing methods depending on the purpose and purpose of use. A reduced type semiconductor ceramic capacitor is usually obtained by heat-treating dielectric ceramic in a reducing atmosphere, applying a silver paste for electrodes to semiconductor ceramic, and heat-treating it in an oxidizing atmosphere. This heat treatment in an oxidizing atmosphere forms a thin dielectric layer between the semiconductor ceramic and the silver electrode. This thin dielectric layer not only contributes to the capacitance, insulation resistance, and withstand voltage of the reduced semiconductor ceramic capacitor, but also largely depends on the characteristics and properties of the dielectric ceramic. In reduction type semiconductor ceramic capacitors, when the capacitance per unit area is increased, the dielectric layer becomes thinner, and the insulation resistance and withstand voltage inevitably decrease. Conversely, when trying to increase the insulation resistance and withstand voltage, the dielectric layer becomes thicker. It has the property that the capacity per unit area decreases. Further, the temperature characteristics of the capacitance of this dielectric layer appear as the temperature characteristics of the capacitance of the reduced semiconductor ceramic capacitor, and are extremely similar to the temperature characteristics of the dielectric ceramic before reduction. That is, it is presumed that this thin dielectric layer was formed when the surface of the semiconductor ceramic obtained by reduction was oxidized again by heat treatment during electrode formation. Therefore, the characteristics of the reduced semiconductor ceramic capacitor are greatly influenced by the dielectric constant and temperature characteristics of the dielectric ceramic. In addition, in order to form a thin and homogeneous dielectric layer on the surface of the semiconductor ceramic and obtain high insulation resistance and high withstand voltage, the surface of the dielectric ceramic must be homogeneous and composed of fine particles of several μm or less. The dielectric loss (tanδ) of a reduced semiconductor ceramic capacitor is the tan of the dielectric layer.
It depends on δ, but it depends more on the series resistance at the boundary between the dielectric layer and the semiconductor ceramic.
In order to reduce tanδ, it is necessary to select a ceramic material with a small series resistance. In order to obtain a reduced semiconductor ceramic capacitor that has such high insulation resistance and high withstand voltage as well as an extremely large capacitance value per unit area, the permittivity of the dielectric ceramic is large, and the ceramic surface is μ
The reduced semiconductor ceramic capacitor is made of homogeneous fine particles with a size of less than m, and satisfies the requirements such as being able to convert the ceramic surface layer into a capacitance dielectric layer at the heat treatment temperature used when forming the silver electrode on the reduced semiconductor ceramic surface. A porcelain material with a low tan δ must be obtained. The present invention was made in response to the demand for smaller parts and higher quality due to the recent miniaturization, higher density packaging, and higher quality stabilization of electronic devices. This product provides a reduced type semiconductor ceramic capacitor that has resistance and high withstand voltage, and is also small and large in capacity.The surface of the dielectric ceramic is homogeneous and consists of fine particles of several micrometers or less, and the dielectric constant is 14,000 to 17,000 ( It provides an extremely excellent ceramic material with a high tan δ (at the Curie point) and a high tan δ as a reduced semiconductor ceramic capacitor. That is, in the present invention, x BaTiO 3 +y
Nd 2 O 3 +z ZrO 2 (where x = 98.7 to 86.5 mol%, y = 0.6 to 3.5 mol%, z = 0.7 to 10.0 mol%,
x+y+z=100), the Mn compound is added in an amount of 0.01 to 0.3% by weight in terms of MnO. Hereinafter, the present invention will be described in detail with reference to Examples. Mix equimolar amounts of BaCO 3 and TiO 3 and heat this at 1150°C.
The reactant was calcined for 2 hours and crushed.
Create BaTiO3 . Weigh BaTiO 3 , Nd 2 O 3 , ZrO 2 and Mn compounds to obtain the desired composition,
This was wet mixed in a pot mill for about 16 hours. After mixing, the mixture is dehydrated, dried, added with approximately 2.5% by weight of an organic binder such as polyvinyl alcohol, and sized.
Formed at a pressure of 1000Kg/cm 2 to a diameter of 11.5mmφ and a thickness of 0.6mm. Next, the formed disc is fired at 1300°C for 2 hours. The dielectric porcelain obtained in this way
Heat treatment is performed for 1 hour in a reducing atmosphere at 800°C to obtain semiconductor porcelain. A silver paste for electrodes was applied to this semiconductor ceramic, dried, and heat treated at 800 to 850°C for about 30 minutes in an oxidizing atmosphere to produce a reduced semiconductor ceramic capacitor. The various characteristics of the capacitor created in this way are shown in the table. When measuring the sample, the capacitance and tan δ were measured at a frequency of 1 kHz and a voltage of 1 Vrms, the insulation resistance was measured after applying a voltage of 50 VDC for 30 seconds, and the breakdown voltage (VDC) was measured using a boost breakdown method. The measurement temperature was based on 20°C.
【表】【table】
【表】
表において試料番号2〜7、10〜14、17〜20は
本発明に係るものであり、試料番号1、8、9、
15、16、21は比較のために本発明の範囲外のもの
を示した。本発明に係る磁器材料は表から明らか
な様に還元型半導体磁器コンデンサとして非常に
優れた特性を有している。例えば、表の試料番号
12において誘電体磁器の誘電率は13700と非常に
大きな値を示している。この組成ではキユーリー
点が12℃近傍にあり、キユーリー点付近の誘電率
は15500を越え、還元型半導体磁器コンデンサと
した場合には0.24μF/cm2と極めて大きな面積容
量を取り得ると同時に、破壊電圧は2200VDCで
あり、tanδは2.0%と優れた特性を有する。従来
の50V級のセラミツクコンデンサ(例えば0.1μ
F)と比較しても破壊電圧およびtanδ共に同等
もしくはそれ以上の特性を示しており、極めて小
型化された50V級の還元型半導体磁器コンデンサ
を提供することが本発明により可能となつた。
この様に従来の50V級セラミツクコンデンサと
同等もしくはそれ以上の特性を有し、単位面積当
りの容量が大きいため小型、大容量で、高信頼性
を有する還元型半導体磁器コンデンサの提供が可
能となつた。本発明の磁器材料は誘電体磁器が極
めて均質であるためと誘電率が極めて大きいため
に誘電体層を従来半導体磁器コンデンサ用磁器材
料と比較して非常に厚くし得るためと推定され
る。また本発明の磁器組成中Nd2O3、ZrO2の添加
量によりtanδは大きく変化し、本磁器材料の最
適組成近傍ではtanδは2%前後と極めて優れて
いる。これは誘電体形成時に誘電体層と半導体磁
器境界の直列抵抗分が極めて小さいことに起因し
ているものと推定される。
本発明における組成限定範囲の理由は以下の理
由による。本発明に係る還元型半導体磁器コンデ
ンサ用磁器材料はx BaTiO3+y Nd2O3+z
ZrO2(ただし、x=98.7〜86.5モル%、y=
0.6〜3.5モル%、z=0.7〜10.0モル%、x+y+
z=100)の基本組成にMn化合物をMnOに換算
して、0.01〜0.3重量%添加含有させるとを特徴
としている。
BaTiO3が98.7モル%を越えると、焼結が困難
となり、またtanδが大きくなり、誘電率が小さ
くなる。このために面積容量も必然的に小さく所
要の容量が得られない。またBaTiO3が98.5モル
%未満では必然的にZrO2の添加量が多くなり、
粒子の異常成長が著しく破壊電圧が低下して好ま
しくない。Nd2O3の添加量はBaTiO3のキユーリ
ー点の位置をほぼ決めるものであり、0.6モル%
未満ではキユーリー点の移動が小さく、また3.5
モル%を越えるとキユーリー点の移動が大きす
ぎ、誘電率が小さくなり好ましくない。Nd2O3の
添加量はZrO2の添加量により若干異るが、2.5モ
ル%近傍が最適である。ZrO2の添加量はBaTiO3
のキユーリー点移動に若干寄与するが、Nd2O3ほ
ど顕著ではない。ZrO2が0.7モル%未満では焼成
温度が極めて高くなり実用的でなく、tanδも極
めて大きな値を示す。10.0モル%を越えると磁器
表面に異常成長粒子の発生が著しく、破壊電圧も
最適添加量である4モル%付近の組成と比較する
と著しく低下し、本発明の特許請求範囲外とし
た。Mn化合物の添加は還元型半導体磁器コンデ
ンサの面積容量、絶縁抵抗および耐電圧に著しい
影響を与えることは表より明らかである。Mn化
合物の添加はMnOにとどまらずMnO2、
MnCO3、MnSO4等をMnOに換算して同等量添加
すると、ほぼ同等の効果が得られる。MnOの添
加量が0.3重量%を越えると、面積容量が低下し
すぎて好ましくなく、MnOを極微量添加(0.01
重量%の添加)したものと添加しない組成を比較
すると、表よりその効果は極めて顕著であり、破
壊電圧は飛躍的に向上する。
以上詳述したように本発明にかかるBaTiO3、
Nd2O3、ZrO2の基本組成にMn化合物を添加する
ことを特徴とした磁器材料よりなる還元型半導体
磁器コンデンサは絶縁抵抗、耐電圧が極めて高
く、しかも大きな面積容量を取り得るという優れ
た特性を有したもので、電子部品の小型化、高安
定化を求める時代の要求に充分にそうものであ
り、工業的価値大なるものである。[Table] In the table, sample numbers 2 to 7, 10 to 14, and 17 to 20 are related to the present invention, and sample numbers 1, 8, 9,
Nos. 15, 16, and 21 are outside the scope of the present invention for comparison. As is clear from the table, the ceramic material according to the present invention has very excellent characteristics as a reduced type semiconductor ceramic capacitor. For example, the sample number in the table
In No. 12, the dielectric constant of the dielectric ceramic is 13,700, which is a very large value. With this composition, the Curie point is around 12℃, the dielectric constant near the Curie point exceeds 15,500, and when used as a reduced semiconductor ceramic capacitor, it can have an extremely large areal capacitance of 0.24 μF/cm 2 and at the same time The voltage is 2200VDC, and tanδ is 2.0%, which has excellent characteristics. Conventional 50V class ceramic capacitors (e.g. 0.1μ
The present invention has made it possible to provide an extremely miniaturized 50V class reduced type semiconductor ceramic capacitor, which exhibits properties equivalent to or better than F) in terms of breakdown voltage and tan δ. In this way, it has characteristics equal to or better than conventional 50V class ceramic capacitors, and the capacitance per unit area is large, making it possible to provide reduced type semiconductor ceramic capacitors that are small, large in capacity, and highly reliable. Ta. It is presumed that this is because the dielectric ceramic of the ceramic material of the present invention is extremely homogeneous and has an extremely large dielectric constant, so that the dielectric layer can be made much thicker compared to conventional ceramic materials for semiconductor ceramic capacitors. Furthermore, tan δ changes greatly depending on the amounts of Nd 2 O 3 and ZrO 2 added in the ceramic composition of the present invention, and near the optimum composition of the present porcelain material, tan δ is extremely excellent at around 2%. This is presumed to be due to the extremely small series resistance between the dielectric layer and the semiconductor ceramic during dielectric formation. The reason for the limited composition range in the present invention is as follows. The ceramic material for a reduced semiconductor ceramic capacitor according to the present invention is x BaTiO 3 +y Nd 2 O 3 +z
ZrO 2 (where x = 98.7 to 86.5 mol%, y =
0.6-3.5 mol%, z=0.7-10.0 mol%, x+y+
It is characterized in that a Mn compound is added in an amount of 0.01 to 0.3% by weight (calculated as MnO) to the basic composition of z=100). When BaTiO 3 exceeds 98.7 mol%, sintering becomes difficult, tan δ increases, and the dielectric constant decreases. For this reason, the area capacity is inevitably small and the required capacity cannot be obtained. Furthermore, if BaTiO 3 is less than 98.5 mol%, the amount of ZrO 2 added will inevitably increase,
This is not preferable because the abnormal growth of particles is significant and the breakdown voltage is lowered. The amount of Nd 2 O 3 added almost determines the position of the Curie point of BaTiO 3 , and is 0.6 mol%.
Below 3.5, the movement of the Curie point is small;
If it exceeds mol%, the movement of the Curie point will be too large and the dielectric constant will decrease, which is not preferable. The amount of Nd 2 O 3 added varies slightly depending on the amount of ZrO 2 added, but is optimally around 2.5 mol %. The amount of ZrO 2 added is BaTiO 3
contributes slightly to the Curie point shift of Nd 2 O 3 , but it is not as significant as Nd 2 O 3 . If ZrO 2 is less than 0.7 mol %, the firing temperature becomes extremely high, which is not practical, and tan δ also shows an extremely large value. When the amount exceeds 10.0 mol%, abnormally grown particles are significantly generated on the porcelain surface, and the breakdown voltage is significantly lower than when the composition is around 4 mol%, which is the optimum addition amount, and is outside the scope of the claims of the present invention. It is clear from the table that the addition of Mn compounds has a significant effect on the areal capacitance, insulation resistance, and withstand voltage of reduced semiconductor ceramic capacitors. The addition of Mn compounds is not limited to MnO, but also MnO 2 ,
When MnCO 3 , MnSO 4 , etc. are added in equivalent amounts in terms of MnO, almost the same effect can be obtained. If the amount of MnO added exceeds 0.3% by weight, the areal capacity decreases too much, which is undesirable.
Comparing the compositions with and without addition (% by weight), the table shows that the effect is extremely remarkable, and the breakdown voltage is dramatically improved. As detailed above, BaTiO 3 according to the present invention,
Reduced semiconductor porcelain capacitors made of porcelain materials characterized by the addition of Mn compounds to the basic composition of Nd 2 O 3 and ZrO 2 are excellent in that they have extremely high insulation resistance and withstand voltage, and can have large area capacitance. These characteristics sufficiently meet the demands of the times for miniaturization and high stability of electronic components, and they are of great industrial value.