JP2004210581A - Dielectric ceramic composition and multilayer capacitor - Google Patents

Abstract

A barium titanate-based dielectric porcelain composition capable of being fired at a low temperature and capable of advantageously suppressing a decrease in insulation resistance (IR) due to plating, and such a dielectric Provided is a multilayer capacitor formed using a porcelain composition.
As A dielectric ceramic composition, _BaO-TiO 2 -ZnO system, a _BaO-TiO 2 _-Nd 2 _{O 3} system or _{BaO-TiO 2 -Nd 2 O 3} -Nb 2 O 5 based dielectric ceramic material A product obtained by adding and blending at least one compound selected from the group consisting of a chromium-containing compound, a tungsten-containing compound, and a molybdenum-containing compound together with colemanite to a product obtained by calcining was employed.
[Selection diagram] None

Description

【００２４】
また、かかるコレマナイトの配合割合は、誘電体磁器組成物を構成する主成分仮焼物の種類に応じて、適宜に設定され、例えば、（Ａ）［ＢＴ＋Ｚｎ］系仮焼物の場合には、その１００重量部に対して、一般に１〜２５重量部となる割合が採用され、また、（Ｂ）［ＢＴ＋Ｎｄ］系仮焼物の場合には、その１００重量部に対して、一般に１〜２５重量部となる割合が、更に、（Ｃ）［ＢＴ＋Ｎｂ，Ｎｄ］系仮焼物の場合には、その１００重量部に対して、一般に０．５〜５重量部となる割合が、好適に採用されることとなる。これは、コレマナイトの配合量が余りにも少ない場合には、コレマナイトの配合による効果が充分に得られず、目的とする焼成温度の低温化を効果的に実現し得なくなる傾向があるからであり、逆に、コレマナイトの配合量が多過ぎる場合には、比誘電率やＱ値が低くなって、目的とする誘電体磁器の電気的特性が得られなくなるからである。
【００２５】
加えて、本発明に従う誘電体磁器組成物には、上記したコレマナイトと共に、副成分として、更に、クロム含有化合物、タングステン含有化合物及びモリブデン含有化合物からなる群より選ばれた少なくとも１種若しくは２種以上の化合物が、配合されることとなる。そして、それらクロム含有化合物、タングステン含有化合物又はモリブデン含有化合物の配合によって、メッキ処理による絶縁抵抗の低下が有利に抑制され得るようになるのである。なお、そのようなメッキ処理に起因する絶縁抵抗の低下が抑制されるメカニズムについては、未だ詳細な究明が行なわれていないものの、磁器表面において、メッキ液とコレマナイトの添加により誘電体磁器に形成されるガラス相との反応が、上記した金属含有化合物の添加によって、効果的に抑制され得るためであると考えられている。
【００２６】
ところで、上記したクロム含有化合物や、タングステン含有化合物、モリブデン含有化合物としては、一般に、ＣｒやＷ、Ｍｏの酸化物の粉末が、それぞれ、好適に採用されることとなる。また、そのような酸化物を与える無機化合物や無機塩形態の原料も、同様に採用可能である。
【００２７】
さらに、それらクロム含有化合物や、タングステン含有化合物、モリブデン含有化合物の配合量は、誘電体磁器の電気的特性が高度に確保され得るように、誘電体磁器組成物を構成する主成分仮焼物の種類等に応じて、適宜に設定されることが、望ましい。
【００２８】
例えば、（Ａ）［ＢＴ＋Ｚｎ］系仮焼物に対して、クロム含有化合物であるＣｒ_２ Ｏ_３ を添加する場合には、仮焼物の１００重量部に対して、一般に０．０３〜１．０重量部となる割合が採用され、また、タングステン含有化合物であるＷＯ_３ を添加する場合には、仮焼物の１００重量部に対して、一般に０．１〜３．０重量部となる割合が、更には、モリブデン含有化合物であるＭｏＯ_３ を添加する場合には、仮焼物の１００重量部に対して、一般に０．０５〜３．０重量部となる割合が、好適に採用され得るのである。
【００２９】
また、（Ｂ）［ＢＴ＋Ｎｄ］系仮焼物に対して、Ｃｒ_２ Ｏ_３ を添加する場合には、仮焼物の１００重量部に対して、一般に０．０３〜０．５重量部となる割合が採用され、また、ＷＯ_３ を添加する場合には、仮焼物の１００重量部に対して、一般に０．１〜３．０重量部となる割合が、更には、ＭｏＯ_３ を添加する場合には、仮焼物の１００重量部に対して、一般に０．０５〜２．０重量部となる割合が、好適に採用される。
【００３０】
さらに、（Ｃ）［ＢＴ＋Ｎｂ，Ｎｄ］系仮焼物に対して、Ｃｒ_２ Ｏ_３ を添加する場合には、仮焼物の１００重量部に対して、一般に０．０３〜１．０重量部となる割合が採用され、また、ＷＯ_３ を添加する場合には、仮焼物の１００重量部に対して、一般に０．１〜３．０重量部となる割合が、更には、ＭｏＯ_３ を添加する場合には、仮焼物の１００重量部に対して、一般に０．０５〜２．０重量部となる割合が、好適に採用され得るのである。
【００３１】
なお、それらクロム含有化合物や、タングステン含有化合物、モリブデン含有化合物（以下、クロム含有化合物等と略記する）の配合量が多くなり過ぎると、比誘電率の温度係数又は比誘電率の変化率が規格幅を外れたり、比誘電率やＱ値低下がひどくなる恐れがあり、また、少ない場合には、絶縁抵抗の低下は抑制され得るものの、その効果が小さく、充分とは言い難いものであるからである。
【００３２】
ところで、上述せる如きコレマナイトやクロム含有化合物等を用いて、本発明に従う誘電体磁器組成物を調製するに際しては、焼成温度の大幅な低減を図るべく、上述せる如きコレマナイトやクロム含有化合物等の副成分を、仮焼の行なわれていない主成分磁器原料ではなく、予め仮焼操作を施して得られた、主成分磁器原料の仮焼物に対して、配合せしめることが必要である。
【００３３】
このため、予め、通常の仮焼操作を実施して、（Ａ）［ＢＴ＋Ｚｎ］系仮焼物、（Ｂ）［ＢＴ＋Ｎｄ］系仮焼物、又は（Ｃ）［ＢＴ＋Ｎｂ，Ｎｄ］系仮焼物を得た後、そのような仮焼物を主成分とする粉砕物に対して、粉末状のコレマナイトやクロム含有化合物等の副成分を、所定の割合となるように秤量して加え、そして、それらを、ボールミル等にて混合粉砕することによって、目的とする誘電体磁器組成物が調製される。
【００３４】
そして、このようにして調製された誘電体磁器組成物は、その優れた特性を利用して、電子製品、例えば、積層コンデンサ等の電子部品を与える原料として、有利に用いられることとなるのである。
【００３５】
なお、図１には、積層コンデンサの代表的な一例が、断面形態において示されているのであるが、そこにおいて、積層コンデンサ１０は、内部電極層１２，１４と誘電体層１６とが交互に積層せしめられてなる積層体としての誘電体ブロック１８と、そのような誘電体ブロック１８の両端面に形成された一対の外部電極２０，２２とを有して構成されている。本発明にあっては、そのような積層コンデンサ１０を与える誘電体ブロック１８（特に、誘電体層１６）が、上述せる如き誘電体磁器組成物を用いて形成されるのである。
【００３６】
また、かかる積層コンデンサ１０において、内部電極層１２，１４は、従来と同様に、積層方向において、交互に、異なる外部電極２０，２２に接続されるようになっている。つまり、図１に示されるように、内部電極層１２は外部電極２０に接続される一方、内部電極層１４は外部電極２２に接続されているのである。また、外部電極２０，２２の表面には、防錆性や他部材への実装性等を考慮して、メッキ層２４，２６がそれぞれ形成されている。
【００３７】
ところで、図１に示される如き積層コンデンサを製造するに際しては、従来から公知の各種の手法が、適宜に採用されることとなる。
【００３８】
例えば、先ず、上述せる如くして調製された誘電体磁器組成物を、バインダーや有機溶剤等と混合せしめることにより、スラリー状の誘電体層形成用のペーストを得、そして、かかる誘電体層形成用ペーストを用いて、従来から公知のドクターブレード法により、薄肉のグリーンシートを作製する。次いで、そのようにして得られたシートを乾燥せしめた後、かかるシートの上面に、導体材料を含有する内部電極層形成用のペーストを印刷、乾燥して内部電極層を形成するのである。なお、内部電極形成用ペーストとしては、誘電体磁器組成物が、低温焼成が可能であるところから、ＡｇやＰｄ−Ａｇ等の金属、又はそれらの酸化物を、有機溶剤等と混合せしめてなるものが、好適に採用されることとなる。
【００３９】
そして、そのような内部電極層が形成されたシートを、図１に示される如く、内部電極層１２，１４が交互に異なる端面に延出するように、所定の枚数だけ積み重ねて、グリーンシートと内部電極層とからなる積層物を形成せしめるのである。その後、かかる得られた積層物を、その積み重ね面に対して直角な方向において、必要とする大きさ及び形状に切断することにより、内部電極層が交互に異なる端面に延出するように、グリーンチップを作製した後、これを焼結することにより、内部電極層１２，１４と誘電体層１６とが交互に積層せしめられてなる誘電体ブロック１８を得るのである。
【００４０】
さらに、内部電極１２，１４が露出した両側の端面には、導体材料を含有する外部電極形成用のペーストを塗布して、焼き付けることにより、一対の外部電極２０，２２が、それぞれ、複数の内部電極１２，１４と電気的に接続するようにして、形成せしめられることとなる。また、このようにして形成された外部電極２０，２２の外表面には、通常、積層コンデンサの防錆性や他部材への実装性等を考慮して、電解メッキ法等、従来から公知のメッキ法にて、Ｓｎメッキや、Ｓｎ／Ｐｂメッキ、Ｎｉメッキ等のメッキ処理が施され、ＳｎやＳｎ／Ｐｂ、Ｎｉ等からなるメッキ層２４，２６が形成せしめられるのである。
【００４１】
このようにして形成された積層コンデンサ１０は、誘電体層１６が、前述せる如き特定の誘電体磁器組成物を用いて形成されているところから、メッキ液に浸漬されても、絶縁抵抗の大幅な低下が抑制されると共に、その他の電気的特性も、高度に確保されるようになっているのである。
【００４２】
【実施例】
以下に、本発明の実施例を示し、本発明を更に具体的に明らかにすることとするが、本発明が、そのような実施例の記載によって、何等の制約をも受けるものでないことは言うまでもないところである。また、本発明には、以下の実施例の他にも、更には上記した具体的記述以外にも、本発明の趣旨を逸脱しない限りにおいて、当業者の知識に基づいて、種々なる変更、修正、改良等を加え得るものであることが理解されるべきである。
【００４３】
−［ＢＴ＋Ｚｎ］系−
まず、主成分磁器原料として、ＢａＣＯ_３ 、ＴｉＯ_２ 及びＺｎＯを用いて、それらを、仮焼後の各種成分の組成比が下記表２に示されるものとなるように、それぞれ、秤量した。そして、それらＢａＣＯ_３ 、ＴｉＯ_２ 及びＺｎＯに、純水を、スラリー濃度が３５％となるように加え、ボールミルにて１５時間湿式混合した後、乾燥操作を施した。次いで、得られたこの乾燥物を粉末状にして、大気中において、１１００℃の温度で２時間、仮焼を行なった後、１．５μｍ程度の平均粒子径となるように乾式粉砕して、［ＢＴ＋Ｚｎ］系主成分仮焼物を得た。
【００４４】
【表２】

【００４５】
また、副成分として、コレマナイトの粉末（上記表１の市販品１）を準備すると共に、Ｃｒ_２ Ｏ_３ 粉末、ＷＯ_３ 粉末、及びＭｏＯ_３ 粉末を、それぞれ、準備した。
【００４６】
そして、上記で準備した［ＢＴ＋Ｚｎ］系主成分仮焼物に対して、副成分を、下記表３に示される配合割合となるように秤量して添加し、ボールミルにて、１５時間湿式混合して、乾燥した後、バインダーとしてポリビニルアルコールを適当量加えて、造粒し、その造粒物を約１トン／ｃｍ^２ の圧力にて成形し、直径７ｍｍ、厚さ１．０ｍｍの円板状成形物を作製した。そして、得られた成形物を、それぞれ、大気中において、下記表３に示される焼成温度（９５０℃）にて、３時間、本焼成することにより、各種の円板状の焼結体を得た。次いで、かくの如くして得られた円板状の焼結体の両側の端面に対して、Ａｇ電極ペーストを塗布し、これを８００℃にて焼き付けて、試験用試料とした。
【００４７】
そして、それら試験用試料の特性、即ち、絶縁抵抗（ＩＲ）、比誘電率（ε）、比誘電率の温度係数、及び、誘電損失の逆数であるＱ値を測定し、その得られた結果を、下記表３に併せて示した。なお、絶縁抵抗は、ハイレジスタンスメーター（横河ヒューレット・パッカード（株）製：４３２９Ａ）を用いて、２５℃、印加電圧：５０Ｖにて測定を行なった。また、その他の測定に際しては、測定条件として、１ＭＨｚ、１Ｖｒｍｓの測定電圧を採用し、恒温槽（ジェック（株）製：２０１Ｄ）内にて、Ｑ値は、Ｑメーター（目黒電波測器（株）製：ＭＱ−１６０１）、比誘電率は、ＬＣＲメーター（横河ヒューレット・パッカード（株）製：４２７４Ａ）を、それぞれ、使用して測定した。更に、温度係数は、所定温度（Ｔ_１ ）での比誘電率を、それぞれ、測定し、２５℃を基準とした温度変化に対する比誘電率の変化を、次式を用いて算出することによって求めた。
【数１】

【００４８】
その後、上記で得られた試験用試料に対して、バレルメッキ法にてメッキ処理を施して、Ａｇ電極の表面にメッキ層を形成せしめた。なお、メッキ液として、スルファミン酸を用いると共に、メディアとしてＮｉを使用し、このメッキ液の中に、上記で得られた試料を入れ、溶液温度：５０℃、電流：４Ａにて、２時間回転させ、メッキ処理を行なった。
【００４９】
そして、メッキ処理の施された試験用試料の絶縁抵抗を、メッキ処理を行なう前と同様にして測定し、得られた結果を下記表３に示した。
【００５０】
【表３】

【００５１】
かかる表３に示される結果からも明らかなように、本発明に従って、コレマナイトと共に、Ｃｒ_２ Ｏ_３ 、ＷＯ_３ 、及びＭｏＯ_３ のうちの何れかが添加されてなる誘電体磁器組成物を用いて形成された試料（Ｎｏ．２〜１０）にあっては、Ｃｒ_２ Ｏ_３ 、ＷＯ_３ 、ＭｏＯ_３ が何等添加されていないＮｏ．１ものに比して、絶縁抵抗の低下が、効果的に抑制されていることが分かる。また、比誘電率やＱ値も高度に確保されていると共に、−５５℃〜＋１２５℃の温度範囲における比誘電率の温度係数も、規格幅（０±３０ｐｐｍ／℃）を満たしている。
【００５２】
−［ＢＴ＋Ｎｄ］系−
まず、主成分磁器原料として、ＢａＣＯ_３ 、ＴｉＯ_２ 及びＮｄ_２ Ｏ_３ を用いて、仮焼後のそれぞれの混合比が下記表４に示されるものとなるように、それぞれ、秤量した。そして、それらＢａＣＯ_３ 、ＴｉＯ_２ 及びＮｄ_２ Ｏ_３ に、純水を、スラリー濃度が３５％となるように加え、ボールミルにて１５時間湿式混合の後、乾燥操作を施した。次いで、得られたこの乾燥物を粉末状にして、大気中において、１２００℃の温度で２時間、仮焼を行なった後、１．５μｍ程度の平均粒子径となるように乾式粉砕して、［ＢＴ＋Ｎｄ］系主成分仮焼物を得た。また、上記［ＢＴ＋Ｚｎ］系と同様な副成分を準備した。
【００５３】
【表４】

【００５４】
そして、上記で準備した［ＢＴ＋Ｎｄ］系主成分仮焼物に対して、副成分を、下記表５に示される配合割合となるように秤量して添加した後、上述せる如き［ＢＴ＋Ｚｎ］系と同様にして、直径７ｍｍ、厚さ１．０ｍｍの円板状成形物を作製した。そして、得られた成形物を、それぞれ、大気中において、下記表５に示される焼成温度（９５０℃）にて、３時間、本焼成することにより、各種の円板状の焼結体を得、そして、このようにして得られた円板状の焼結体の両側の端面に対して、Ａｇ電極ペーストを塗布し、これを８００℃にて焼き付けることにより、試験用試料を作製した。そして、上記［ＢＴ＋Ｚｎ］系の試験用試料と同様にして、得られた各種試験用試料の絶縁抵抗、比誘電率（ε）、比誘電率の温度係数びＱ値を、それぞれ求めて、得られた結果を、下記表５に示した。
【００５５】
【表５】

【００５６】
かかる表５に示される結果からも明らかなように、［ＢＴ＋Ｎｄ］系においても、本発明に従って、コレマナイトと共に、Ｃｒ_２ Ｏ_３ 、ＷＯ_３ 、及びＭｏＯ_３ のうちの何れかが添加されてなる誘電体磁器組成物を用いて形成された試料（Ｎｏ．１２〜２０）にあっては、Ｃｒ_２ Ｏ_３ 、ＷＯ_３ 、ＭｏＯ_３ が何等添加されていないＮｏ．１１ものに比して、絶縁抵抗の低下が、効果的に抑制されていることが分かる。また、比誘電率やＱ値も高度に確保されていると共に、−５５℃〜＋１２５℃の温度範囲における比誘電率の温度係数も、規格幅（０±３０ｐｐｍ／℃）を満たしている。
【００５７】
−［ＢＴ＋Ｎｂ，Ｎｄ］系−
まず、主成分磁器原料として、ＢａＣＯ_３ 、ＴｉＯ_２ 、Ｎｂ_２ Ｏ_５ 及びＮｄ_２ Ｏ_３ を用いて、仮焼後のそれぞれの混合比が下記表６に示されるものとなるように、それぞれ、秤量した。そして、それらＢａＣＯ_３ 、ＴｉＯ_２ 、Ｎｂ_２ Ｏ_５ 及びＮｄ_２ Ｏ_３ に、純水を、スラリー濃度が３５％となるように加え、ボールミルにて１５時間湿式混合の後、乾燥操作を施した。次いで、得られたこの乾燥物を粉末状にして、大気中において、１２００℃の温度で２時間、仮焼を行なった後、１．５μｍ程度の平均粒子径となるように乾式粉砕して、［ＢＴ＋Ｎｂ，Ｎｄ］系主成分仮焼物を得た。また、上記［ＢＴ＋Ｚｎ］系と同様な副成分を準備した。
【００５８】
【表６】

【００５９】
そして、上記で準備した［ＢＴ＋Ｎｂ，Ｎｄ］系主成分仮焼物に対して、副成分を、下記表７に示される配合割合となるように秤量して添加した後、上述せる如き［ＢＴ＋Ｚｎ］系と同様にして、直径７ｍｍ、厚さ１．０ｍｍの円板状成形物を作製した。そして、得られた成形物を、それぞれ、大気中において、下記表７に示される焼成温度（１１００℃）にて、３時間、本焼成することにより、各種の円板状の焼結体を得、そして、このようにして得られた円板状の焼結体の両側の端面に対して、Ａｇ電極ペーストを塗布し、これを８００℃にて焼き付けることにより、試験用試料を作製した。そして、上記［ＢＴ＋Ｚｎ］系の試験用試料と同様にして、得られた各種試験用試料の絶縁抵抗、比誘電率（但し、ＬＣＲメーターの測定電圧は、１ｋＨｚ）、ｔａｎδを、それぞれ求めると共に、２５℃を基準とした比誘電率の変化率を求め、得られた結果を、下記表７に示した。なお、２５℃を基準とした比誘電率の変化率は、所定温度（Ｔ_１ ）での比誘電率を、それぞれ測定し、次式を用いて算出することによって求めた。
【数２】

【００６０】
【表７】

【００６１】
かかる表７に示される結果からも明らかなように、［ＢＴ＋Ｎｂ，Ｎｄ］系においても、本発明に従って、コレマナイトと共に、Ｃｒ_２ Ｏ_３ 、ＷＯ_３ 、及びＭｏＯ_３ のうちの何れかが添加されてなる誘電体磁器組成物を用いて形成された試料（Ｎｏ．２２〜３０）にあっては、Ｃｒ_２ Ｏ_３ 、ＷＯ_３ 、ＭｏＯ_３ が何等添加されていないＮｏ．２１ものに比して、絶縁抵抗の低下が、効果的に抑制されていることが分かる。また、比誘電率やｔａｎδも良好に確保されていると共に、−５５℃〜＋１２５℃の温度範囲における比誘電率の変化率も、規格幅（０±１５％）を満たしている。
【００６２】
【発明の効果】
以上の説明から明らかなように、本発明に従う誘電体磁器組成物にあっては、ＢａＯ−ＴｉＯ_２ −ＺｎＯ系、ＢａＯ−ＴｉＯ_２ −Ｎｄ_２ Ｏ_３ 系、又はＢａＯ−ＴｉＯ_２ −Ｎｄ_２ Ｏ_３ −Ｎｂ_２ Ｏ_５ 系の誘電体磁器原料を仮焼して得られたものに対して、Ｂ_２ Ｏ_３ とＣａＯを主成分とする天然鉱物たるコレマナイトを添加、配合すると共に、クロム含有化合物、タングステン含有化合物及びモリブデン含有化合物からなる群より選ばれた少なくとも１種の化合物を、副成分として更に添加、配合せしめるようにしたものであるところから、焼成温度の低温化が極めて有利に実現され得ると共に、そのような誘電体磁器組成物を用いてコンデンサ等を製造すれば、メッキ処理による絶縁抵抗の低下が有利に抑制され得るのである。しかも、本発明に従う誘電体磁器組成物から得られる磁器は、比誘電率やＱ値が高く、また、−５５℃〜＋１２５℃の温度範囲における、比誘電率の温度係数や比誘電率の変化率が小さく且つ平坦なものとなる。
【００６３】
従って、そのような誘電体磁器組成物を用いて形成された電子製品、例えば積層コンデンサは、メッキ処理に起因する絶縁抵抗の低下が抑制され、高度な電気的特性が実現され得るのである。
【図面の簡単な説明】
【図１】本発明が適用される積層コンデンサの代表的な一例を示す、縦断面説明図である。
【符号の説明】
１０ 積層コンデンサ
１２，１４ 内部電極層
１６ 誘電体層
１８ 誘電体ブロック（積層体）
２０，２２ 外部電極
２４，２６ メッキ層[0001]
【Technical field】
The present invention relates to a dielectric porcelain composition and a multilayer capacitor, and more particularly to a barium titanate-based dielectric porcelain composition which can be fired at a low temperature and can advantageously suppress a decrease in insulation resistance due to plating. And a multilayer capacitor formed using such a dielectric ceramic composition.
[0002]
[Background Art]
2. Description of the Related Art Hitherto, high dielectric constant dielectric ceramics have been obtained by firing a dielectric ceramic composition (raw material composition) that provides the constituents thereof. Among them, various compositions have been proposed as barium titanate (BT) -based porcelain compositions. For example, barium titanate or a composition capable of producing barium titanate is added to rare earth elements such as neodymium. There are [BT + Nd] -based materials, [BT + Zn] -based materials, [BT + Nb, Nd] -based materials, etc., in which metals, zinc, niobium, etc. are mixed and contained, and these are generally 1150 ° C. or 1200 ° C. It was difficult to perform sintering unless the temperature range exceeded a very high temperature.
[0003]
On the other hand, heretofore, as is well known, a multilayer capacitor is prepared by using a slurry-like mixture of a porcelain composition and an organic solvent to form a thin film sheet having a thickness of about 20 to 30 microns by a doctor blade method. After drying, an electrode paint containing a conductor material is printed on the upper surface of the obtained sheet, and a thin film sheet of the porcelain composition is formed thereon (stacked) in accordance with the above-mentioned method. Thus, a thin film sheet of the porcelain composition and an electrode paint are alternately stacked to form a laminate. Then, the laminate is cut into a required size in a direction perpendicular to the stacking surface, and after sintering, a pair of external electrodes are baked on the cut surface to achieve the intended purpose. The multilayer capacitor is completed. In this case, the electrodes (internal electrodes) between the sheets are alternately connected to different external electrodes so as to form a capacitor.
[0004]
By the way, in the manufacturing process of such a multilayer capacitor, a metal or an oxide thereof as a conductor material used for an electrode paint generally consists of a noble metal, and at a temperature peculiar to the metal, the oxide is reduced to a metal. , Are decomposed, sintered at the same time, and baked on porcelain. Therefore, the electrode paint is baked on the dielectric porcelain composition at a temperature at which it is porcelain to form an electrode.
[0005]
However, in the case of using a porcelain composition having a high sintering temperature, for example, a [BT + Zn] -based porcelain composition obtained by combining barium titanate with zinc oxide, the sintering temperature of 1150 to 1200 ° C. Therefore, when baking such a barium titanate-based porcelain, an electrode paint mainly composed of Pd, which has a relatively high melting point, had to be used. However, such a conductor material having a high melting point such as Pd has a large conduction resistance and is expensive. Therefore, a conductor material having a low conduction resistance and a lower cost, such as Ag or Pd-Ag, is required. However, since Ag evaporates and dissipates at a baking temperature of 1000 ° C. or higher, it is extremely difficult to use an Ag-based conductor material having a low conduction resistance for a porcelain composition having a high sintering temperature as described above. It was difficult. Therefore, there is a need for a porcelain composition that can be sintered or fired at a temperature as low as possible.
[0006]
Therefore, the present inventors have conducted various studies in order to obtain a porcelain composition that can be sintered or fired at a low temperature, and as a result, as a result, a predetermined barium titanate-based dielectric porcelain raw material has been obtained. To the calcined material obtained by calcining B, as a sub-component (calcining aid) for lowering the calcining temperature, ₂ O ₃ By blending a powder of colemanite, which is a natural mineral containing Ca and CaO as a main component, the firing temperature can be advantageously reduced, and the effect is such that B has a composition similar to that of colemanite. ₂ O ₃ In the case of using powder and CaO powder, respectively, and in comparison with the case of using glass powder having the same composition as colemanite, they have found that they can be expressed extremely effectively, and separately filed a patent application. (Japanese Patent Application No. 2002-145686).
[0007]
However, the present inventors have manufactured a multilayer capacitor using such a dielectric porcelain composition as a raw material, and in consideration of the rust prevention of the multilayer capacitor and the mountability to other members, etc. In addition, when a plating process such as Sn plating, Sn / Pb plating, or Ni plating is performed on the external electrode, a large decrease in insulation resistance (IR) may be caused before and after the plating process. It became clear. Although the cause of the decrease in insulation resistance has not been fully elucidated, the glass phase formed on the dielectric porcelain by the addition of colemanite reacts with the plating solution on the surface of the porcelain to cause the insulation resistance to decrease. It is presumed that a decline in the value will be caused.
[0008]
Further, according to a study by the present inventors, in order to suppress a decrease in insulation resistance (IR) due to use at a high temperature, in other words, to improve an IR accelerated life, titanic acid as a main component is used. It has been clarified that a dielectric ceramic made of a raw material composition in which barium is mixed with first to fourth subcomponents including molybdenum, tungsten, and the like has been proposed (see Patent Document 1). However, there is a possibility that a large decrease in insulation resistance is caused after plating by adding colemanite to a calcined product obtained by calcining a barium titanate-based raw material. No method is disclosed for solving such a decrease in insulation resistance after plating.
[0009]
[Patent Document 1]
JP-A-2002-80275
[0010]
[Solution]
Here, the present invention has been made in view of such circumstances, and a problem to be solved is that firing at a low temperature is possible and insulation resistance (IR) caused by plating treatment is high. It is an object of the present invention to provide a barium titanate-based dielectric porcelain composition which can advantageously suppress the reduction of the above-mentioned porosity, and a multilayer capacitor formed using such a dielectric porcelain composition.
[0011]
[Solution]
The present inventors have conducted intensive studies to solve such problems, and as a result, a calcined product obtained by calcining a predetermined barium titanate-based dielectric ceramic raw material, specifically, (A) BaO-TiO ₂ A material obtained by calcining a -ZnO-based ([BT + Zn] -based) dielectric porcelain raw material; (B) BaO-TiO ₂ -Nd ₂ O ₃ ([BT + Nd]) dielectric porcelain raw material obtained by calcining, or (C) BaO-TiO ₂ -Nd ₂ O ₃ -Nb ₂ O ₅ (BT + Nb, Nd) -based dielectric porcelain raw materials obtained by calcining, as a subcomponent (firing auxiliary) for lowering the firing temperature, B ₂ O ₃ In addition to blending colemanite powder, which is a natural mineral containing Ca and CaO as a main component, and further blending at least one of Cr, W and Mo, the dielectric material can advantageously lower the firing temperature. The present inventors have found that a body porcelain composition can be obtained, and that if a capacitor is produced using such a dielectric porcelain composition, a decrease in insulation resistance due to plating can be advantageously suppressed.
[0012]
Therefore, the present invention has been completed based on such findings, and the gist of the present invention is that (A) BaO—TiO ₂ -ZnO-based, (B) BaO-TiO ₂ -Nd ₂ O ₃ System or (C) BaO-TiO ₂ -Nd ₂ O ₃ -Nb ₂ O ₅ To a material obtained by calcining a raw material of a dielectric ceramic, at least one compound selected from the group consisting of a chromium-containing compound, a tungsten-containing compound and a molybdenum-containing compound is added and blended together with cholemanite. A dielectric porcelain composition characterized in that:
[0013]
That is, in the present invention, (A) BaO—TiO ₂ -ZnO-based, (B) BaO-TiO ₂ -Nd ₂ O ₃ System, or (C) BaO-TiO ₂ -Nd ₂ O ₃ -Nb ₂ O ₅ First, a natural mineral, colemanite, is added and blended to the one obtained by calcining the dielectric ceramic raw material, so that the firing temperature range of the dielectric ceramic composition is effectively lowered. High dielectric constant and a high Q value (low dielectric loss), and their effects are ₂ O ₃ Powder and CaO powder, respectively, ₂ O ₃ And very effectively as compared with the case where a glass powder made of CaO is used.
[0014]
In addition, since colemanite is a natural mineral that is relatively easily available, material costs can be extremely reduced as compared with the case where glass powder or the like is used, and such colemanite is eluted in water. From where not, B ₂ O ₃ Unlike the case of using powder or CaO powder, at the time of drying, filtration and dehydration become possible, and no large-scale drying equipment such as a spray drier can be required. This can make a significant contribution to reducing product prices.
[0015]
Moreover, in the dielectric porcelain composition according to the present invention, in addition to the above colemanite, at least one or more compounds selected from the group consisting of chromium-containing compounds, tungsten-containing compounds and molybdenum-containing compounds, Then, since at least one of Cr, W and Mo is blended, even when plating is performed in the production of electronic products such as multilayer capacitors, the plating caused by the blending of colemanite. Subsequent large reductions in insulation resistance can be advantageously suppressed.
[0016]
Further, according to the present invention, an external electrode connected to the internal electrode layer is formed on an end face of a laminate in which dielectric layers and internal electrode layers are alternately laminated, and further, plating is performed. In the multilayer capacitor in which the plating layer is formed on the surface of the external electrode by the treatment, the dielectric layer is made of BaO-TiO. ₂ -ZnO-based, BaO-TiO ₂ -Nd ₂ O ₃ System or BaO-TiO ₂ -Nd ₂ O ₃ -Nb ₂ O ₅ To a material obtained by calcining a raw material of a dielectric ceramic, at least one compound selected from the group consisting of a chromium-containing compound, a tungsten-containing compound and a molybdenum-containing compound is added and blended together with cholemanite. The present invention also provides a multilayer capacitor characterized by being formed using a dielectric ceramic composition. In such a multilayer capacitor, since the dielectric layer is formed of the dielectric ceramic composition as described above, any of the various effects described above by such a dielectric ceramic composition can be achieved. It can be enjoyed.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Incidentally, in the dielectric ceramic composition according to the present invention as described above, (A) BaO, TiO ₂ And ZnO, or (B) BaO, TiO ₂ And Nd ₂ O ₃ Or (C) BaO, TiO ₂ , Nd ₂ O ₃ And Nb ₂ O ₅ Is a calcined product of a conventionally known barium titanate-based dielectric porcelain raw material, which is a basic component, for example, barium titanate (BaTiO ₃ ) Or BaTiO ₃ Barium carbonate (BaCO ₃ ) And titanium oxide (TiO) ₂ ), Zinc oxide (ZnO) or neodymium oxide (Nd ₂ O ₃ ) Or neodymium oxide (Nd ₂ O ₃ ) And niobium oxide (Nb) ₂ O ₅ ) Is mixed and calcined in a conventional manner.
[0018]
The ratio (composition ratio) of the basic components contained in the calcined material, which is the main component, is appropriately determined in a known range according to the dielectric ceramic characteristics of the target porcelain, such as the relative dielectric constant. In general, (A) BaO—TiO ₂ -In the case of a material obtained by calcining a ZnO-based dielectric ceramic material (hereinafter referred to as a [BT + Zn] -based calcined material), BaO: 10.0 to 32.0 mol%, TiO ₂ : 55.0 to 70.0 mol%, ZnO: 10.0 to 32.0 mol% (however, BaO + TiO ₂ + ZnO = 100 mol%), and (B) BaO—TiO ₂ -Nd ₂ O ₃ In the case of a material obtained by calcining a base dielectric ceramic material (hereinafter referred to as a [BT + Nd] calcined product), BaO: 7.5 to 28.5 mol%, TiO ₂ : 62.5 to 69.5 mol%, Nd ₂ O ₃ : 9.0-26.0 mol% (however, BaO + TiO ₂ + Nd ₂ O ₃ = 100 mol%), and (C) BaO-TiO ₂ -Nd ₂ O ₃ -Nb ₂ O ₅ In the case of a material obtained by calcining a raw material of a dielectric ceramic material (hereinafter referred to as a [BT + Nb, Nd] -based calcined material), BaO: 47.98 to 52.0 mol%, TiO ₂ : 47.98 to 52.0 mol%, Nd ₂ O ₃ : 0.01 to 1.10 mol%, Nb ₂ O ₅ : 0.01 to 1.10 mol% (however, BaO + TiO ₂ + Nd ₂ O ₃ + Nb ₂ O ₅ = 100 mol%). By using a calcined product having such a composition ratio, a porcelain having extremely excellent characteristics such as a relative dielectric constant can be obtained.
[0019]
In the dielectric porcelain composition according to the present invention, (A) a [BT + Zn] -based calcined product, (B) a [BT + Nd] -based calcined product, or (C), which are such calcined materials as the main components. ) At least one compound selected from the group consisting of a chromium-containing compound, a tungsten-containing compound, and a molybdenum-containing compound is mixed with the [BT + Nb, Nd] -based calcined material together with the natural mineral, colemanite. In addition, it has a great feature.
[0020]
Specifically, colemanite to be added to a predetermined barium titanate-based calcined product is added and compounded as an auxiliary component (sintering aid) for lowering the sintering temperature. As a result, the firing temperature of the dielectric ceramic composition can be effectively reduced as compared with the case where such a firing aid is not added. Specifically, in the conventional [BT + Zn] -based, [BT + Nd] -based, and [BT + Nb, Nd] -based dielectric porcelain compositions, generally, 1150 to 1200 ° C., 1300 to 1350 ° C., and 1200 ° C. to 1250, respectively. If the temperature was not high, the sintering could not be performed, but the firing temperature could be lowered to 950 ° C or lower, 950 ° C or lower and 1150 ° C or lower, respectively. Moreover, ▲ 1 ▼ B ₂ O ₃ The powder and the CaO powder have a higher relative dielectric constant and a higher Q than those in the case where they are used so as to have the same composition as that of colemanite, and (2) in the case where a glass powder having a composition similar to that of colemanite is used. The value can advantageously be realized.
[0021]
In addition, since colemanite is a relatively easily available natural mineral, the material cost, which is a problem when glass powder made of BaO or CaO is used, can be extremely low, and furthermore, such colemanite is , Because it does not elute in water, ₂ O ₃ Unlike the case of using powder or CaO powder, at the time of drying after mixing various components, it is possible to employ a filtration dehydration operation, and therefore, a large-scale drying equipment such as a spray dryer is not required, The firing cost can be kept low, and the product cost of a product after firing, for example, a multilayer capacitor, can be further reduced. Further, colemanite is to be blended in powder form with respect to the above-mentioned barium titanate-based calcined powder, but it is easier to pulverize as compared with glass having a similar composition. It also has such advantages.
[0022]
By the way, colemanite, which is one of the essential components of the present invention as described above, ₂ O ₃ Borate ore containing CaO and CaO as main components (2CaO.3B ₂ O ₃ ・ 5H ₂ O) whose composition is stable, and which is produced in the Republic of Turkey and other regions, has a predetermined particle size and is used. In addition, as such a colemanite, for example, a general composition (2CaO.3B) ₂ O ₃ ・ 5H ₂ In addition to those represented by O), those having representative analysis values as shown in Table 1 below, which contain trace components such as silica, are commercially available. In the present invention, any of them can be used. In addition, the firing temperature can be advantageously reduced.
[0023]
[Table 1]

[0024]
Further, the blending ratio of the colemanite is appropriately set according to the type of the main component calcined material constituting the dielectric ceramic composition. For example, in the case of (A) [BT + Zn] -based calcined material, 100% In general, a ratio of 1 to 25 parts by weight with respect to parts by weight is employed. In the case of (B) [BT + Nd] -based calcined product, 1 to 25 parts by weight is generally used with respect to 100 parts by weight. In the case of (C) [BT + Nb, Nd] -based calcined product, the ratio generally becomes 0.5 to 5 parts by weight with respect to 100 parts by weight. Become. This is because if the blending amount of colemanite is too small, the effect of the blending of colemanite cannot be sufficiently obtained, and it tends to be impossible to effectively achieve the desired lowering of the firing temperature. Conversely, if the amount of colemanite is too large, the relative dielectric constant and Q value will be low, and the desired electrical properties of the dielectric ceramic will not be obtained.
[0025]
In addition, the dielectric porcelain composition according to the present invention further comprises, as an auxiliary component, at least one or more selected from the group consisting of a chromium-containing compound, a tungsten-containing compound, and a molybdenum-containing compound, together with the above-mentioned colemanite. Will be compounded. Then, by blending the chromium-containing compound, the tungsten-containing compound, or the molybdenum-containing compound, a decrease in insulation resistance due to plating can be advantageously suppressed. Although the mechanism by which the decrease in insulation resistance due to such plating treatment is suppressed has not yet been investigated in detail, on the surface of the porcelain, a plating solution and colemanite are formed on the dielectric porcelain by addition of a plating solution. It is considered that the reaction with the glass phase can be effectively suppressed by the addition of the metal-containing compound described above.
[0026]
As the chromium-containing compound, the tungsten-containing compound, and the molybdenum-containing compound, powders of oxides of Cr, W, and Mo are generally suitably used. In addition, a raw material in the form of an inorganic compound or an inorganic salt that gives such an oxide can also be employed.
[0027]
Further, the amount of the chromium-containing compound, the tungsten-containing compound, and the molybdenum-containing compound is adjusted according to the type of the main component calcined material constituting the dielectric porcelain composition so that the electrical characteristics of the dielectric porcelain can be highly secured. It is desirable that the setting be appropriately made according to the conditions.
[0028]
For example, (A) [BT + Zn] -based calcined material is compared with chromium-containing compound Cr ₂ O ₃ Is generally used in a proportion of 0.03 to 1.0 part by weight with respect to 100 parts by weight of the calcined product, and WO, which is a tungsten-containing compound, is used. ₃ Is added, the proportion is generally 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the calcined material, and further, the molybdenum-containing compound MoO is used. ₃ In the case where is added, the ratio generally becomes 0.05 to 3.0 parts by weight with respect to 100 parts by weight of the calcined product, and can be suitably adopted.
[0029]
In addition, (B) the [BT + Nd] -based calcined ₂ O ₃ Is added, the proportion is generally 0.03 to 0.5 parts by weight with respect to 100 parts by weight of the calcined product. ₃ Is added, the proportion generally becomes 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the calcined material, ₃ Is preferably used in a proportion of generally 0.05 to 2.0 parts by weight based on 100 parts by weight of the calcined product.
[0030]
Further, (C) [BT + Nb, Nd] -based calcined material ₂ O ₃ Is added, the proportion is generally 0.03 to 1.0 part by weight with respect to 100 parts by weight of the calcined material. ₃ Is added, the proportion generally becomes 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the calcined material, ₃ In the case where is added, a ratio of generally 0.05 to 2.0 parts by weight to 100 parts by weight of the calcined product can be suitably adopted.
[0031]
If the amount of the chromium-containing compound, the tungsten-containing compound, and the molybdenum-containing compound (hereinafter, abbreviated as chromium-containing compound, etc.) is too large, the temperature coefficient of the relative dielectric constant or the rate of change of the relative dielectric constant may exceed the standard. The width may be deviated or the relative dielectric constant or Q value may be significantly reduced. In addition, when the amount is small, the decrease in insulation resistance can be suppressed, but the effect is small and it is difficult to say that it is sufficient. It is.
[0032]
By the way, in preparing the dielectric ceramic composition according to the present invention using the above-mentioned colemanite or chromium-containing compound, in order to greatly reduce the firing temperature, the above-mentioned colemanite or chromium-containing compound or the like is used. It is necessary to mix the components with the calcined material of the main component porcelain obtained by performing the calcination operation in advance, not with the main component porcelain raw material that has not been calcined.
[0033]
Therefore, a normal calcination operation was performed in advance to obtain (A) a [BT + Zn] -based calcined product, (B) a [BT + Nd] -based calcined product, or (C) a [BT + Nb, Nd] -based calcined product. Then, to the pulverized material having such a calcined material as a main component, powdered colemanite and auxiliary components such as a chromium-containing compound are weighed so as to have a predetermined ratio, and then added to a ball mill. The desired dielectric ceramic composition is prepared by mixing and pulverizing the mixture.
[0034]
The dielectric porcelain composition thus prepared is advantageously used as a raw material for providing an electronic product, for example, an electronic component such as a multilayer capacitor, by utilizing its excellent properties. .
[0035]
FIG. 1 shows a typical example of a multilayer capacitor in a cross-sectional form. In this case, the multilayer capacitor 10 includes internal electrode layers 12 and 14 and dielectric layers 16 alternately. It has a dielectric block 18 as a laminated body formed by laminating, and a pair of external electrodes 20 and 22 formed on both end surfaces of such a dielectric block 18. In the present invention, the dielectric block 18 (particularly, the dielectric layer 16) that provides such a multilayer capacitor 10 is formed using the above-described dielectric ceramic composition.
[0036]
In the multilayer capacitor 10, the internal electrode layers 12 and 14 are alternately connected to different external electrodes 20 and 22 in the laminating direction, as in the conventional case. That is, as shown in FIG. 1, the internal electrode layer 12 is connected to the external electrode 20, while the internal electrode layer 14 is connected to the external electrode 22. In addition, plating layers 24 and 26 are formed on the surfaces of the external electrodes 20 and 22, respectively, in consideration of rust prevention and mountability to other members.
[0037]
By the way, in manufacturing the multilayer capacitor as shown in FIG. 1, various conventionally known methods are appropriately adopted.
[0038]
For example, first, a slurry-like paste for forming a dielectric layer is obtained by mixing the dielectric ceramic composition prepared as described above with a binder, an organic solvent, or the like, and then forming the dielectric layer. A thin green sheet is produced using the paste for application by a conventionally known doctor blade method. Next, after the sheet thus obtained is dried, a paste for forming an internal electrode layer containing a conductive material is printed and dried on the upper surface of the sheet to form an internal electrode layer. In addition, as a paste for forming an internal electrode, since a dielectric ceramic composition can be fired at a low temperature, a metal such as Ag or Pd-Ag, or an oxide thereof is mixed with an organic solvent or the like. Will be suitably adopted.
[0039]
Then, as shown in FIG. 1, a predetermined number of the sheets on which the internal electrode layers are formed are stacked so that the internal electrode layers 12 and 14 alternately extend to different end surfaces, and a green sheet is formed. That is, a laminate composed of the internal electrode layers is formed. Thereafter, the obtained laminate is cut into a required size and shape in a direction perpendicular to the stacking surface, so that the internal electrode layers alternately extend to different end faces. After the chip is manufactured, it is sintered to obtain a dielectric block 18 in which the internal electrode layers 12, 14 and the dielectric layer 16 are alternately laminated.
[0040]
Furthermore, a paste for forming an external electrode containing a conductive material is applied to the end surfaces on both sides where the internal electrodes 12 and 14 are exposed, and the paste is baked, so that a pair of external electrodes 20 and 22 are respectively provided on the plurality of internal electrodes. It is formed so as to be electrically connected to the electrodes 12 and 14. In addition, the outer surfaces of the external electrodes 20 and 22 formed in this manner are usually provided with a conventionally known method such as an electrolytic plating method in consideration of the rust prevention of the multilayer capacitor and the mountability to other members. A plating process such as Sn plating, Sn / Pb plating, or Ni plating is performed by a plating method to form plated layers 24 and 26 made of Sn, Sn / Pb, Ni, or the like.
[0041]
The multilayer capacitor 10 thus formed has a large insulation resistance even when immersed in a plating solution since the dielectric layer 16 is formed using the specific dielectric ceramic composition as described above. In addition to suppressing a significant decrease, other electrical characteristics are also highly ensured.
[0042]
【Example】
Hereinafter, examples of the present invention will be described to clarify the present invention more specifically. Needless to say, the present invention is not limited by the description of such examples. It is a place. Further, in addition to the following examples, the present invention may further include various changes and modifications based on the knowledge of those skilled in the art, in addition to the above-described specific description, without departing from the spirit of the present invention. , Improvements and the like.
[0043]
-[BT + Zn] system-
First, as a main component porcelain raw material, BaCO ₃ , TiO ₂ Using ZnO and ZnO, they were each weighed so that the composition ratio of various components after calcination was as shown in Table 2 below. And those BaCO ₃ , TiO ₂ Pure water was added to ZnO and ZnO so that the slurry concentration became 35%, and the mixture was wet-mixed with a ball mill for 15 hours, and then dried. Next, the obtained dried product is powdered, calcined in the air at a temperature of 1100 ° C. for 2 hours, and then dry-pulverized so as to have an average particle size of about 1.5 μm. A [BT + Zn] -based calcined material was obtained.
[0044]
[Table 2]

[0045]
In addition, a colemanite powder (commercial product 1 in Table 1 above) was prepared as an auxiliary component, ₂ O ₃ Powder, WO ₃ Powder and MoO ₃ Powders were each prepared.
[0046]
Then, to the [BT + Zn] -based calcined main component prepared above, the auxiliary component was weighed and added so as to have a mixing ratio shown in Table 3 below, and was wet-mixed with a ball mill for 15 hours. After drying, an appropriate amount of polyvinyl alcohol was added as a binder, and the mixture was granulated. ² To produce a disk-shaped molded product having a diameter of 7 mm and a thickness of 1.0 mm. Then, each of the obtained molded products is subjected to main firing in the atmosphere at a firing temperature (950 ° C.) shown in Table 3 below for 3 hours to obtain various disc-shaped sintered bodies. Was. Next, an Ag electrode paste was applied to both end surfaces of the disc-shaped sintered body thus obtained and baked at 800 ° C. to obtain a test sample.
[0047]
Then, the characteristics of the test samples, that is, the insulation resistance (IR), the relative permittivity (ε), the temperature coefficient of the relative permittivity, and the Q value which is the reciprocal of the dielectric loss were measured, and the obtained results were obtained. Are also shown in Table 3 below. The insulation resistance was measured using a high resistance meter (Yokogawa Hewlett-Packard Co., Ltd .: 4329A) at 25 ° C. and an applied voltage of 50 V. In other measurements, a measurement voltage of 1 MHz and 1 Vrms was adopted as a measurement condition, and the Q value was measured in a thermometer (201D, manufactured by JEC Co., Ltd.) in a Q meter (Meguro Radio Measurement Co., Ltd.). ): MQ-1601), and the relative permittivity was measured using an LCR meter (4274A, manufactured by Yokogawa Hewlett-Packard Co., Ltd.). Further, the temperature coefficient is a predetermined temperature (T ₁ ) Was measured, and the change in relative dielectric constant with respect to a temperature change based on 25 ° C. was calculated by using the following equation.
(Equation 1)

[0048]
Thereafter, the test sample obtained above was subjected to a plating treatment by a barrel plating method to form a plating layer on the surface of the Ag electrode. In addition, while using sulfamic acid as a plating solution and using Ni as a medium, the sample obtained above was put into the plating solution, and rotated at a solution temperature of 50 ° C. and a current of 4 A for 2 hours. Then, plating was performed.
[0049]
Then, the insulation resistance of the plated test sample was measured in the same manner as before the plating, and the obtained results are shown in Table 3 below.
[0050]
[Table 3]

[0051]
As is clear from the results shown in Table 3, according to the present invention, together with cholemanite, Cr ₂ O ₃ , WO ₃ , And MoO ₃ In the samples (Nos. 2 to 10) formed using the dielectric porcelain composition to which any one of ₂ O ₃ , WO ₃ , MoO ₃ No. was not added at all. It can be seen that the lowering of the insulation resistance is effectively suppressed as compared with the case of Example 1. In addition, the relative permittivity and the Q value are highly secured, and the temperature coefficient of the relative permittivity in the temperature range of -55 ° C to + 125 ° C satisfies the standard range (0 ± 30 ppm / ° C).
[0052]
-[BT + Nd] system-
First, as a main component porcelain raw material, BaCO ₃ , TiO ₂ And Nd ₂ O ₃ Were weighed so that the respective mixing ratios after calcination were as shown in Table 4 below. And those BaCO ₃ , TiO ₂ And Nd ₂ O ₃ Then, pure water was added so that the slurry concentration became 35%, and the mixture was wet-mixed in a ball mill for 15 hours, and then dried. Next, the obtained dried product is powdered, calcined in the air at a temperature of 1200 ° C. for 2 hours, and then dry-pulverized to have an average particle size of about 1.5 μm. A [BT + Nd] -based calcined material was obtained. Also, the same sub-components as in the above [BT + Zn] system were prepared.
[0053]
[Table 4]

[0054]
Then, to the [BT + Nd] -based calcined material prepared as described above, the sub-components were weighed and added so as to have a mixing ratio shown in Table 5 below, and then the same as in the [BT + Zn] -based as described above. Thus, a disk-shaped molded product having a diameter of 7 mm and a thickness of 1.0 mm was produced. Then, each of the obtained molded products is subjected to main firing in the atmosphere at a firing temperature (950 ° C.) shown in Table 5 below for 3 hours to obtain various disc-shaped sintered bodies. Then, an Ag electrode paste was applied to both end surfaces of the disc-shaped sintered body thus obtained, and the paste was baked at 800 ° C. to produce a test sample. Then, in the same manner as the [BT + Zn] -based test sample, the insulation resistance, relative permittivity (ε), temperature coefficient of relative permittivity, and Q value of the obtained various test samples were obtained. The results obtained are shown in Table 5 below.
[0055]
[Table 5]

[0056]
As is clear from the results shown in Table 5, in the [BT + Nd] system, according to the present invention, together with colemanite, Cr ₂ O ₃ , WO ₃ , And MoO ₃ In the samples (Nos. 12 to 20) formed using the dielectric porcelain composition to which any one of ₂ O ₃ , WO ₃ , MoO ₃ No. was not added at all. It can be seen that the lowering of the insulation resistance is effectively suppressed as compared with the eleventh embodiment. In addition, the relative permittivity and the Q value are highly secured, and the temperature coefficient of the relative permittivity in the temperature range of -55 ° C to + 125 ° C satisfies the standard range (0 ± 30 ppm / ° C).
[0057]
-[BT + Nb, Nd] system-
First, as a main component porcelain raw material, BaCO ₃ , TiO ₂ , Nb ₂ O ₅ And Nd ₂ O ₃ Were weighed so that the respective mixing ratios after calcination were as shown in Table 6 below. And those BaCO ₃ , TiO ₂ , Nb ₂ O ₅ And Nd ₂ O ₃ Then, pure water was added so that the slurry concentration became 35%, and the mixture was wet-mixed in a ball mill for 15 hours, and then dried. Next, the obtained dried product is powdered, calcined in the air at a temperature of 1200 ° C. for 2 hours, and then dry-pulverized to have an average particle size of about 1.5 μm. A [BT + Nb, Nd] -based calcined material was obtained. Also, the same sub-components as in the above [BT + Zn] system were prepared.
[0058]
[Table 6]

[0059]
Then, to the [BT + Nb, Nd] -based calcined material prepared above, the sub-components were weighed and added so as to have a mixing ratio shown in Table 7 below, and then the [BT + Zn] -based as described above was added. In the same manner as in the above, a disk-shaped molded product having a diameter of 7 mm and a thickness of 1.0 mm was produced. Then, each of the obtained molded products is subjected to main firing in the air at a firing temperature (1100 ° C.) shown in Table 7 below for 3 hours to obtain various disc-shaped sintered bodies. Then, an Ag electrode paste was applied to both end surfaces of the disc-shaped sintered body thus obtained, and the paste was baked at 800 ° C. to produce a test sample. Then, in the same manner as in the above [BT + Zn] -based test sample, the insulation resistance, the relative dielectric constant (however, the measurement voltage of the LCR meter is 1 kHz), and tan δ of the obtained various test samples are obtained. The rate of change of the relative dielectric constant was determined based on 25 ° C., and the obtained results are shown in Table 7 below. The change rate of the relative dielectric constant based on 25 ° C. is a predetermined temperature (T ₁ ) Was determined by measuring and calculating using the following formula.
(Equation 2)

[0060]
[Table 7]

[0061]
As is clear from the results shown in Table 7, in the [BT + Nb, Nd] system, according to the present invention, together with colemanite, Cr was used. ₂ O ₃ , WO ₃ , And MoO ₃ In the samples (Nos. 22 to 30) formed using the dielectric porcelain composition to which any one of ₂ O ₃ , WO ₃ , MoO ₃ No. was not added at all. It can be seen that the lowering of the insulation resistance is effectively suppressed as compared with the case of No. 21. In addition, the relative permittivity and tan δ are well ensured, and the rate of change of the relative permittivity in the temperature range of −55 ° C. to + 125 ° C. satisfies the standard range (0 ± 15%).
[0062]
【The invention's effect】
As is apparent from the above description, in the dielectric ceramic composition according to the present invention, BaO—TiO ₂ -ZnO-based, BaO-TiO ₂ -Nd ₂ O ₃ System, or BaO-TiO ₂ -Nd ₂ O ₃ -Nb ₂ O ₅ The material obtained by calcining the dielectric ceramic raw material ₂ O ₃ And a natural mineral, colemanite, whose main component is CaO. Because of this, it is possible to extremely advantageously reduce the firing temperature, and if a capacitor or the like is manufactured using such a dielectric porcelain composition, a decrease in insulation resistance due to plating processing is reduced. It can be advantageously suppressed. Moreover, the porcelain obtained from the dielectric porcelain composition according to the present invention has a high relative permittivity and a high Q value, and changes in the temperature coefficient and the relative permittivity of the relative permittivity in a temperature range of -55 ° C to + 125 ° C. The ratio is small and flat.
[0063]
Therefore, in an electronic product, for example, a multilayer capacitor formed by using such a dielectric ceramic composition, a decrease in insulation resistance due to a plating process is suppressed, and high electrical characteristics can be realized.
[Brief description of the drawings]
FIG. 1 is an explanatory longitudinal sectional view showing a typical example of a multilayer capacitor to which the present invention is applied.
[Explanation of symbols]
10. Multilayer capacitors
12, 14 internal electrode layer
16 Dielectric layer
18 Dielectric block (laminate)
20,22 external electrode
24,26 plating layer

Claims (2)

_BaO-TiO 2 -ZnO system, with respect to _BaO-TiO 2 _-Nd 2 _{O 3} system or _{BaO-TiO 2 -Nd 2 O 3} -Nb 2 O ₅ based dielectric ceramic material which is obtained by calcining A dielectric porcelain composition characterized in that at least one compound selected from the group consisting of a chromium-containing compound, a tungsten-containing compound and a molybdenum-containing compound is added to and blended with colemanite. An external electrode connected to the internal electrode layer is formed on an end face of the laminate in which the dielectric layers and the internal electrode layers are alternately laminated, and further, plating is performed on the surface of the external electrode. In a multilayer capacitor in which a plating layer is formed,
Obtained the dielectric layer, and calcined _BaO-TiO 2 -ZnO system, a _BaO-TiO 2 _-Nd 2 _{O 3} system or _{BaO-TiO 2 -Nd 2 O 3} -Nb 2 O 5 based dielectric ceramic material Using a dielectric porcelain composition obtained by adding and blending at least one compound selected from the group consisting of a chromium-containing compound, a tungsten-containing compound, and a molybdenum-containing compound, together with cholemanite, A multilayer capacitor characterized by being made.

Images