JP3945033B2 - Manufacturing method of multilayer ceramic capacitor - Google Patents

Description

また、ＳｉＯ₂ を主成分とする焼結助剤となる酸化物粉末を得るため、以下の表２に示すモル比の組成割合になるように、各成分の酸化物、炭酸塩および水酸化物を秤量し、混合粉砕した。これら酸化物粉末を、白金るつぼ中において１５００℃まで加熱した後、急冷し、粉砕することによって、平均粒径が１μｍ以下となるようにした。
【００５２】
【表２】

また、（Ｂａ，Ｃａ）ＴｉＯ₃ の（Ｂａ，Ｃａ）／Ｔｉモル比ｍを調整するためのＢａＣＯ₃ を準備するとともに、ＭｇＯおよびＭｎＯを準備した。
【００５３】
次に、これらの原料粉末と焼結助剤とを以下の表３に示す組成になるように配合し、配合物を得た。この配合物にポリビニルブチラール系バインダおよびエタノール等の有機溶剤を加えて、ボールミルにより湿式混合し、セラミックスラリーを調製した。このセラミックスラリーをドクターブレード法によりシート成形し、厚み２．７μｍの矩形のグリーンシートを得た。次に、このセラミックグリーンシート上に、Ｎｉを主体とする導電性ペーストを印刷し、内部電極を構成するための導電性ペースト膜を形成した。
【００５４】
【表３】

次いで、セラミックグリーンシートを、上述の導電性ペースト膜の引き出されている側が互い違いとなるように複数枚積層し、積層体を得た。この積層体を、Ｎ₂ 雰囲気中にて３５０℃の温度に加熱し、バインダを燃焼させた後、酸素分圧１０^-9〜１０^-12 ＭＰａのＨ₂ −Ｎ₂ −Ｈ₂ Ｏガスからなる還元性雰囲気中において表４に示す温度で２時間焼成した。
【００５５】
焼成後の積層体の両端面にＢ₂ Ｏ₃ −Ｌｉ₂ Ｏ−ＳｉＯ₂ −ＢａＯ系のガラスフリットを含有する銀ペーストを塗布し、Ｎ₂ 雰囲気中において６００℃の温度で焼き付け、内部電極と電気的に接続された外部電極を形成した。
【００５６】
このようにして得られた積層セラミックコンデンサの外形寸法は、幅が５．０mm、長さが５．７mm、厚さが２．４mmであり、内部電極間に介在する誘電体セラミック層の厚みは２μｍであった。また、有効誘電体セラミック層の総数は５であり、１層当たりの対向電極の面積は１６．３×１０^-6ｍ² であった。
【００５７】
これら得られた試料について電気的特性を測定した。
【００５８】
静電容量（Ｃ）および誘電損失（ｔａｎδ）は自動ブリッジ式測定器を用い、ＪＩＳ規格５１０２に従って測定し、得られた静電容量から誘電率（ε）を算出した。
【００５９】
また、絶縁抵抗（Ｒ）を測定するために、絶縁抵抗計を用い、１０Ｖの直流電圧を２分間印加して２５℃での絶縁抵抗（Ｒ）を求め、比抵抗を算出した。
【００６０】
温度変化に対する静電容量の変化率については、２０℃での静電容量を基準とした−２５℃〜＋８５℃の範囲での変化率（ΔＣ／Ｃ₂₀）と、２５℃での静電容量を基準とした−５５℃〜＋１２５℃の範囲での変化率（ΔＣ／Ｃ₂₅）とを示した。
【００６１】
また、高温負荷試験として、温度１５０℃にて直流電圧を２０Ｖ印加して、その絶縁抵抗の経時変化を測定した。なお、高温負荷試験は、各試料の絶縁抵抗値（Ｒ）が１０⁵ Ω以下になったときを故障とし、平均寿命時間を評価した。
【００６２】
さらに、絶縁破壊電圧は、昇圧速度１００Ｖ／秒でＤＣ電圧をそれぞれ印加し、破壊電圧を測定した。
【００６３】
また、用いた出発原料の平均粒径を、走査型電子顕微鏡で観察することによって求め、また、得られた積層セラミックコンデンサに含まれる誘電体セラミックの平均粒径を、積層体の断面研磨面を化学エッチングし、走査型電子顕微鏡で観察することによって求め、これらの結果から、（誘電体セラミックの平均粒径）／（出発原料の粉末の平均粒径）の粒径比Ｒを求めた。
【００６４】
以上の各結果が、表４に示されている。
【００６５】
【表４】

この発明に係る誘電体セラミックの好ましい組成は、一般式：｛Ｂａ_1-x Ｃａ_x Ｏ｝_m ＴｉＯ₂ ＋αＭｇＯ＋βＭｎＯで表され、α、β、ｍ、およびｘの各々については、
０．００１≦α≦０．０５、
０．００１≦β≦０．０２５、
１．０００＜ｍ≦１．０３５、および
０．０２ ≦ｘ≦０．１５
となるように選ばれる。
【００６６】
前述した各特性の好ましい範囲は、誘電率については、１０００以上であり、誘電損失については、２．５％以下であり、容量変化率については、−５５％以内であり、容量温度変化率における２０℃での静電容量を基準とした−２５℃〜＋８５℃の範囲での変化率については、±１０％以内であり、同じく２５℃での静電容量を基準とした−５５℃〜＋１２５℃の範囲での変化率については、±１５％以内であり、比抵抗については、１３．０Ω・cm以上であり、絶縁破壊電圧については、１０ｋＶ／mm以上である。
【００６７】
表３および表４において、試料番号に＊を付したものは、前述の好ましい組成範囲から外れた試料である。
【００６８】
表４からわかるように、好ましい組成範囲内にある試料１３〜２３によれば、温度に対する静電容量の変化率が−２５℃〜＋８５℃の範囲でＪＩＳ規格に規定するＢ特性を満足し、−５５℃〜＋１２５℃の範囲でＥＩＡ規格に規定するＸ７Ｒ特性を満足する。さらに、高温負荷試験での平均寿命時間は、ほとんどが１００時間を超え、信頼性に優れ、焼成温度も少なくとも１２５０℃以下の温度で焼成可能であり、多くは１２００℃以下の温度で焼成可能である。以下に、上述の好ましい組成範囲を限定した理由について説明する。
【００６９】
試料１のように、Ｃａの添加量ｘが０．０２未満の場合には、電圧による誘電率の変化が大きく、また高温負荷での平均寿命が短くなることがある。一方、試料２のようにＣａの添加量ｘが０．１５を超える場合には、 比誘電率が小さく、ｔａｎδも大きくなることがある。
【００７０】
なお、より好ましくは、Ｃａの添加量ｘが０．０５以上の場合である。このときには、特に平均寿命の点で、０．０２以上０．０５未満よりも有利である。
【００７１】
また、試料３のように、ＭｇＯの添加量αが０．００１未満の場合、比抵抗が低く、温度特性がＢ特性およびＸ７Ｒ特性を満足しないことがある。一方、試料４のように、ＭｇＯの添加量αが０．０５を超えると、焼結温度が高くなり、また高温負荷試験で故障に至る時間が短くなることがある。
【００７２】
また、試料５のように、ＭｎＯの添加量βが０．００１未満の場合、比抵抗が低くなることがある。一方、試料６のように、ＭｎＯの添加量βが０．０２５を超える場合も、また比抵抗が低く、誘電率の温度特性がＢ特性およびＸ７Ｒ特性を満足しないことがある。
【００７３】
また、試料７のように、（Ｂａ，Ｃａ）／Ｔｉ比ｍが１．０００未満の場合、比抵抗が低くなることがある。試料番号８のように、ｍが１．０００の場合も同様に比抵抗が低くなることがある。両者は、また、高温負荷での故障に至る時間が著しく短くなることがあり、高温で電圧を印加した瞬間に故障するものがあった。また、試料９のように、（Ｂａ，Ｃａ）／Ｔｉ比ｍが１．０３５を超えた場合、焼結性が不足し、高温負荷での故障に至る時間が短くなることがある。
【００７４】
また、試料１０のように、焼結助剤の添加量が０の場合、焼結が不十分であり、めっきにおける比抵抗の低下が大きく、高温負荷での故障に至る時間が短くなることがある。一方、試料１１のように、焼結助剤の添加量が５．０重量部を超えた場合、焼結助剤に含まれるガラス成分に基づく二次相の生成が増大し、高温負荷での故障に至る時間も短くなることがある。
【００７５】
また、（Ｂａ，Ｃａ）ＴｉＯ₃ 中に不純物として含まれるアルカリ金属酸化物の含有量に関して、試料１２のように、０．０３wt％を超える場合には、高温負荷での故障に至る時間が短くなることがある。
【００７６】
なお、試料１４では、セラミックスラリー調製時の粉砕条件を強め、スラリーでの粉末粒径が出発原料粉末より小さくなるようにした。試料１４では、粒径比Ｒ（＝誘電体セラミックの平均粒径／出発原料粉末の平均粒径）が０．８５と小さくなり、誘電率が低くなることがある。他方、試料１３のように、粒径比Ｒが１．２５と大きく、焼成時に粒成長したものでは、誘電体セラミック層を薄層化した場合には、内部電極間のセラミック粒子の個数が少なくなり、高温負荷での故障に至る時間が短くなることがある。
【００７７】
試料１５のように、平均粒径が０．４０μｍと比較的大きいものでは、誘電率は大きい。反面、この実施例のように、誘電体セラミック層を薄層化した場合、高温負荷での故障に至る時間が短く、また、高電界下での誘電率の変化が大きくなることがある。他方、試料１６のように、平均粒径が０．０９μｍと小さいものでは、誘電率が低く、誘電率の温度変化が大きくなることがある。
【００７８】
特に、試料１７〜２３では、誘電率は１２８０〜２５１０の範囲にあり、高電界下での静電容量の変化も４２％以下と小さく安定している。また、めっきによる劣化も認められず、高温負荷での故障に至る時間も長く、信頼性に優れており良好である。
【００７９】
なお、上記実施例では、（Ｂａ，Ｃａ）ＴｉＯ₃ 原料として、固相法により作製した粉末を用いたが、これを限定するものではなく、アルコキシド法あるいは水熱合成法など湿式合成法により作製された粉末を用いてもよい。
【００８０】
また、添加成分であるＭｇ、Ｍｎの各酸化物およびＳｉＯ₂ を含有する焼結助剤は、酸化物粉末を用いたが、これに限定されるものでなく、この発明の範囲内の誘電体セラミックス相を構成できるものであれば、アルコキシド、有機金属などの溶液を用いてもよく、これによって得られる特性は何ら損なわれるものではない。
【００８１】
また、積層コンデンサの内部電極に含まれるＮｉの粒子表面には、本来、ＮｉＯが存在する。酸化しやすい焼成条件によっては、ＮｉＯが多く生成し、このＮｉＯは、積層コンデンサの積層体を得るための焼成工程において、積層体を構成する誘電体セラミック中に拡散する場合もある。また、内部電極の焼結を制御する目的でＺｒＯ₂ 成分などを添加することもあり、このような添加物組成は、焼成時に、誘電体セラミック組成に対して最大で数モル％まで拡散する場合がある。この発明に係る誘電体セラミック組成によれば、これら電極成分が拡散しても、その電気的特性に影響がないことも確認している。
【００８２】
これらのことは、以下に説明する実施例２においても当てはまるものである。
【００８３】
【実施例２】
実施例１と同様、以下の表５に示すようなＣａ含有量ならびに平均粒径をそれぞれ有する（Ｂａ，Ｃａ）ＴｉＯ₃ を合成した。なお、実施例２は、一言で言えば、実施例１の場合に比べて、平均粒径が大きめとなっている点で、実施例１と異なっている。
【００８４】
【表５】

また、ＳｉＯ₂ を主成分とする焼結助剤については、実施例１と同様に作製した、前掲の表２に示すものを用いた。
【００８５】
次に、実施例１と同様に、以下の表６に示す組成を有するセラミックスラリーを調製した。このセラミックスラリーをドクターブレード法によりシート成形し、厚み８μｍの矩形のグリーンシートを得た。次に、このセラミックグリーンシート上に、Ｎｉを主体とする導電性ペーストを印刷し、内部電極を構成するための導電性ペースト膜を形成した。
【００８６】
【表６】

次いで、実施例１と同様に、積層セラミックコンデンサを作製した。
【００８７】
このようにして得られた積層セラミックコンデンサの内部電極間に介在する誘電体セラミック層の厚みは６μｍであった。
【００８８】
また、以下の点を除いて、実施例１の場合と同様に、これら得られた試料について電気的特性を測定した。実施例１の場合と異なるところは、絶縁抵抗（Ｒ）の測定において、６０Ｖの直流電圧を２分間印加して求めた点と、高温負荷試験において、温度１５０℃にて直流電圧を６０Ｖ印加して、その絶縁抵抗の経時変化を測定した点とである。
【００８９】
この実施例２で得られた諸特性が、表７に示されている。
【００９０】
【表７】

実施例１においても述べたように、この発明に係る誘電体セラミックの好ましい組成は、一般式：｛Ｂａ_1-x Ｃａ_x Ｏ｝_m ＴｉＯ₂ ＋αＭｇＯ＋βＭｎＯで表され、α、β、ｍ、およびｘの各々については、
０．００１≦α≦０．０５、
０．００１≦β≦０．０２５、
１．０００＜ｍ≦１．０３５、および
０．０５ ≦ｘ≦０．１５
となるように選ばれる。
【００９１】
表６および表７において、試料番号に＊を付したものは、上述の好ましい組成範囲から外れた試料である。
【００９２】
表７からわかるように、好ましい組成範囲内にある試料３６〜４７によれば、温度に対する静電容量の変化率が−２５℃〜＋８５℃の範囲でＪＩＳ規格に規定するＢ特性を満足し、−５５℃〜＋１５０℃の範囲でＥＩＡ規格に規定するＸ８Ｒ特性を満足する。さらに、高温負荷試験での平均寿命時間は多くが１００時間を超え、焼成温度もほとんどが１２５０℃以下の温度で焼成可能である。以下に、上述の好ましい組成範囲を限定した理由について説明する。
【００９３】
試料２４のように、Ｃａの添加量ｘが０．０２未満の場合には、電圧による誘電率の変化が大きく、また高温負荷での平均寿命が短くなることがある。一方、試料２５のようにＣａの添加量ｘが０．１５を超える場合には、比誘電率が小さく、ｔａｎδも大きくなることがある。
【００９４】
また、試料２６のように、ＭｇＯの添加量αが０．００１未満の場合、焼成時に粒成長し比抵抗が低く、誘電率の温度特性がＢ特性およびＸ８Ｒ特性を満足しないことがある。一方、試料２７のように、ＭｇＯの添加量αが０．０５を超えると、焼結温度が高くなり、また高温負荷試験で故障に至る時間が短くなることがある。
【００９５】
また、試料２８のように、ＭｎＯ添加量βが０．００１未満の場合、比抵抗が低くなることがある。一方、試料２９のように、ＭｎＯ添加量βが０．０２５を超える場合も、また比抵抗が低く、誘電率の温度特性がＢ特性およびＸ８Ｒ特性を満足しないことがある。
【００９６】
また、試料３０のように、（Ｂａ，Ｃａ）／Ｔｉ比ｍが１．０００未満の場合、および、試料番号３１のように、ｍが１．０００の場合は、いずれも、比抵抗が低くなることがあり、また、両者は、高温負荷での故障に至る時間が著しく短く、高温で電圧を印加した瞬間に故障するものがあった。また、試料３２のように、（Ｂａ，Ｃａ）／Ｔｉ比ｍが１．０３５を超えた場合、焼結性が不足し、高温負荷での故障に至る時間が短くなることがある。
【００９７】
また、試料３３のように、焼結助剤の添加量が０の場合、焼結が不十分であり、めっきにおける比抵抗の低下が大きく、高温負荷での故障に至る時間が短くなることがある。一方、試料３４のように、焼結助剤の添加量が５．０重量部を超えた場合、焼結助剤に含まれるガラス成分に基づく二次相の生成が増大し、高温負荷での故障に至る時間も短くなることがある。
【００９８】
また、（Ｂａ，Ｃａ）ＴｉＯ₃ 中に不純物として含まれるアルカリ金属酸化物の含有量に関して、試料３５のように、０．０３wt％を超える場合には、高温負荷での故障に至る時間が短くなることがある。
【００９９】
なお、試料３７のように、粒径比Ｒ（＝誘電体セラミックの平均粒径／出発原料粉末の平均粒径）が０．８８と小さいものでは、誘電率が低い。他方、試料３６のように、粒径比Ｒが１．２５と大きく、焼成時に粒成長したものでは、誘電体セラミック層を薄層化した場合には、内部電極間のセラミック粒子の個数が少なくなり、高温負荷での故障に至る時間が短くなることがある。
【０１００】
また、試料４８のように、ＭｇＯを含有しない場合、粒径比Ｒが６．２５と焼成時の粒成長が著しく、誘電率の温度変化が大きく、好ましくない。また、試料４９のように、ＭｎＯの添加量が０の場合、比抵抗が低く、高温負荷での故障に至る時間が著しく短く、好ましくない。
【０１０１】
この実施例２では誘電体セラミック層の厚みは６μｍであるが、試料３８のように、平均粒径が１．００μｍと比較的大きいものでは、温度による誘電率の変化に関しては、小さいが、電圧による誘電率の変化が大きく、また、高温負荷での故障に至る時間が短くなることがある。他方、試料３９のように、平均粒径が０．２５μｍと小さいものでは、誘電体セラミック層にかかる電界強度が低いため、誘電率が低くなることがある。
【０１０２】
試料４０〜４７では、誘電率は２０５０〜３４６０の範囲にあり、誘電体セラミック層の厚みが比較的厚い、この実施例２では、高電界下での静電容量の変化も５０％以下と小さく、安定している。また、めっきによる劣化も認められず、高温負荷での故障に至る時間も長く、信頼性に優れており良好である。
【０１０３】
【発明の効果】
この発明に係る製造方法によって得られた積層セラミックコンデンサの誘電体セラミック層を構成する誘電体セラミックによれば、コアシェル構造を持たない材料であるにも関わらず、誘電率の温度特性が良く、信頼性の高い誘電体材料とすることができる。また、この誘電体セラミックは、これを得るため、還元性雰囲気中で焼成されても、還元されないので、この誘電体セラミックを用いて、積層セラミックコンデンサを構成すると、内部電極材料として卑金属であるニッケルおよびニッケル合金を用いることができるようになり、積層セラミックコンデンサのコストダウンを図ることができる。
【０１０４】
また、上述の誘電体セラミックによれば、コアシェル構造に基づき誘電率の温度特性を平坦化するのではなく、組成物本来の温度特性に基づき誘電率の温度特性の平坦化を図るので、温度特性や信頼性が添加成分の拡散状態に影響されず、焼成条件による特性の変動を少なくすることができる。そのため、この誘電体セラミックを用いて得られた積層セラミックコンデンサは、特性のばらつきが少なく、誘電率の温度特性が安定でかつ優れたものとすることができる。
【０１０５】
この発明に係る積層セラミックコンデンサの製造方法において、｛Ｂａ_1-x Ｃａ_x Ｏ｝ＴｉＯ₂ で表される化合物の平均粒径を０．１μｍ以上０．３μｍ以下と小さくすることにより、厚み３μm 以下の薄層の誘電体セラミック層を有する積層セラミックコンデンサにおいても、たとえば１２５℃までの誘電率の温度による変化を小さくすることができ、しかも、誘電体セラミック層中の粒子数を多く確保できるので、信頼性を高めることができる。したがって、小型かつ薄層で大容量の積層セラミックコンデンサを有利に得ることができる。
【０１０６】
他方、｛Ｂａ_1-x Ｃａ_x Ｏ｝ＴｉＯ₂ で表される化合物の平均粒径を０．３μｍを超え０．８μｍ以下と比較的大きくすることにより、厚み３μｍ以上の誘電体セラミック層を有する積層セラミックコンデンサにおいて、たとえば１５０℃の高温まで、誘電率の温度による変化を小さくすることができ、しかも、信頼性を高めることができる。
【０１０７】
また、この発明に係る積層セラミックコンデンサの製造方法において、｛Ｂａ_1-x Ｃａ_x Ｏ｝ＴｉＯ₂ で表される化合物中に不純物として含有されるアルカリ金属酸化物の含有量を、０．０３wt％以下に抑えると、誘電体セラミック層の信頼性をより高めることができる。
【０１０９】
また、この発明に係る積層セラミックコンデンサの製造方法によれば、誘電体セラミック層となる誘電体セラミックの焼結に際して、（誘電体セラミックの平均粒径）／（出発原料の粉末の平均粒径）の粒径比Ｒを、０．９０≦Ｒ≦１．２の範囲内にあるように選ぶので、セラミック焼結時に顕著な粒成長が生じず、誘電率温度特性のより優れた誘電体セラミックとすることができる。
【図面の簡単な説明】
【図１】 この発明の一実施形態による製造方法によって得られる積層セラミックコンデンサ１を示す断面図である。
【符号の説明】
１ 積層セラミックコンデンサ
２ 誘電体セラミック層
３ 積層体
４ 第１の端面
５ 第２の端面
６ 第１の外部電極
７ 第２の外部電極
８ 第１の内部電極
９ 第２の内部電極[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a multilayer ceramic capacitor having an internal electrode made of a base metal such as nickel or a nickel alloy.SaIt relates to a manufacturing method.
[0002]
[Prior art]
The multilayer ceramic capacitor includes a multilayer body in which a plurality of multilayered dielectric ceramic layers and internal electrode metals are stacked. In such a multilayer ceramic capacitor, recently, Ni or the like, which is an inexpensive base metal, is often used instead of expensive noble metals such as Ag and Pd as the metal serving as the internal electrode for cost reduction.
[0003]
When Ni or the like is used for the internal electrode, it is necessary to fire in a reducing atmosphere in which Ni or the like is not oxidized. However, firing in a reducing atmosphere is not preferable because a ceramic made of barium titanate is usually reduced to become a semiconductor.
[0004]
In order to solve this problem, for example, as shown in Japanese Patent Publication No. 57-42588, non-reduction of a dielectric material in which the ratio of barium sites / titanium sites in the barium titanate solid solution is made larger than the stoichiometric ratio. Technology has been developed. Since then, it has become possible to put to practical use a multilayer ceramic capacitor using Ni or the like as an internal electrode, and its production volume has been expanded.
[0005]
[Problems to be solved by the invention]
With the recent development of electronics, electronic components have been rapidly miniaturized, and the trend toward miniaturization and large capacity is also remarkable in multilayer ceramic capacitors. Further, for such a multilayer ceramic capacitor, not only the above-described increase in capacitance but also temperature stability of the capacitance is required, and there are many materials as high dielectric constant materials having good temperature characteristics. Proposed and put into practical use.
[0006]
These materials are all BaTiO_ThreeIn the process of adding rare earth elements to this and sintering, the additive component is BaTiO._ThreeThe particles are diffused. It is known that each particle of the obtained sintered body has a core-shell structure consisting of a core portion where the additive component is not diffused and a shell portion where the additive component is diffused, and has a flat dielectric constant temperature characteristic. Is given by the superposition of the core portion and the shell portion having different temperature characteristics of dielectric constant.
[0007]
By providing such a material, a monolithic ceramic capacitor having a small capacitance change in temperature and having a high capacity is realized, which greatly contributes to market expansion.
[0008]
However, this core-shell structure is achieved by sintering the ceramic and controlling the diffusion of the additive component. As the sintering proceeds, the diffusion of the additive component also proceeds, and a flat temperature characteristic cannot be obtained. On the other hand, if the sintering is insufficient, the temperature characteristics are stable but the reliability is poor. That is, with the materials described above, stable control of sintering and diffusion is relatively difficult industrially, and the temperature characteristics of the obtained dielectric constant are also unstable.
[0009]
Furthermore, in order to satisfy the demand for the reduction in size and capacity of the multilayer ceramic capacitor as described above, it has become necessary to further reduce the thickness and thickness of the dielectric ceramic layer provided in the multilayer body. However, when the layer is thinned, the number of ceramic particles between the internal electrodes is reduced, and the reliability is remarkably lowered. Therefore, the thinning has a limit. Therefore, it is desired to develop a material having a small ceramic particle size, high reliability, and excellent electric field strength stability of dielectric constant.
[0010]
On the other hand, in electronic parts for automobiles and the like, it is desired to increase the maximum use temperature, and the characteristics are desired to be stable up to a high temperature. Also in the case of a multilayer ceramic capacitor, it is desired that the temperature characteristic of the dielectric constant is stable up to a higher temperature (for example, 150 ° C.) and the reliability is high.
[0011]
However, in the material having the conventional core-shell structure, BaTiO_ThreeIf the particles are made smaller, the sinterability increases, the diffusion of the additive components also increases, and it becomes relatively difficult to ensure a flat temperature characteristic. BaTiO_ThreeHas a large change in dielectric constant at a high temperature (for example, 150 ° C.), and it is relatively difficult to stabilize the temperature characteristic of the dielectric constant up to a high temperature.
[0012]
From the above, it is practically difficult or impossible to achieve sufficient thinning of multilayer ceramic capacitors and sufficient stabilization of dielectric constant up to high temperatures using materials with a core-shell structure. is the current situation.
[0013]
  Therefore, the object of the present invention is to solve the problems described above.,productIt is to provide a method for manufacturing a single layer ceramic capacitor.
[0014]
[Means for Solving the Problems]
  According to this inventionPrepare for multilayer ceramic capacitors obtained by manufacturing methodsTo put it simply, a dielectric ceramic is a material that does not have a core-shell structure due to diffusion of the additive component, and therefore, the temperature characteristics and reliability do not affect the diffusion of the additive component. Further, according to the present inventionDepending on the manufacturing methodWhen a multilayer ceramic capacitor is manufactured, with respect to the temperature characteristics of capacitance, it is possible to satisfy the B characteristic defined by the JIS standard and the X7R characteristic and X8R characteristic defined by the EIA standard.
[0023]
  According to this inventionThe manufacturing method of the multilayer ceramic capacitor is:
  General formula: {Ba _1-x Ca _x O} _m TiO ₂ + ΑMgO + βMnO,
α is 0.001 ≦ α ≦ 0.05,
β is 0.001 ≦ β ≦ 0.025,
m is 1.000 <m ≦ 1.035,
x is 0.02 ≦ x ≦ 0.15
In order to obtain a dielectric ceramic,As a starting materialThe average particle size is 0.1 to 0.8 μm{Ba_1-xCa_xO} TiO₂A step of preparing a mixture comprising a compound represented by: Mg compound and Mn compound;
  A plurality of ceramic green sheets containing this mixture and a plurality of internal electrodes respectively formed along a specific interface between the ceramic green sheets are laminated, with the edge of each internal electrode exposed to the end face A step of producing a laminate,
  Sintering the mixture into a dielectric ceramic,A step of firing the laminate;
  Forming a plurality of external electrodes on the end face of the laminate so as to be electrically connected to the exposed edge of each internal electrode.,
  When a ratio of (average particle diameter of dielectric ceramic) / (average particle diameter of starting material powder) is R, R is characterized by being in the range of 0.90 ≦ R ≦ 1.2. .
[0024]
In the method for manufacturing a multilayer ceramic capacitor described above, preferably {Ba_1-xCa_xO} TiO₂The content of the alkali metal oxide contained as an impurity in the compound represented by the formula is 0.03 wt% or less.
[0026]
  As mentioned above, {Ba _1-x Ca _x O} TiO ₂ The average particle size of the compound represented by is 0.1 to 0.8 μm,At this time, {Ba_1-xCa_xO} TiO₂The average particle size of the compound represented by the formula (1) may be 0.1 μm or more and 0.3 μm or less, or may be more than 0.3 μm and 0.8 μm or less. The diameter is more preferably 0.5 μm or less, and in the latter case, the maximum particle size of the compound is more preferably 1.0 μm or less.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
  According to this inventionConstructing dielectric ceramic layer of multilayer ceramic capacitor obtained by manufacturing methodDielectric ceramic(Hereafter, it may be simply referred to as “dielectric ceramic according to the present invention”.)Is,MoneyIt is characterized by comprising a complex oxide containing Ba, Ca, Ti, Mg and Mn as a genus element. More specifically, the dielectric ceramic according to the present invention has the general formula: {Ba_1-xCa_xO}_mTiO₂It is represented by + αMgO + βMnO. here,
α is 0.001 ≦ α ≦ 0.05,
β is 0.001 ≦ β ≦ 0.025,
m is 1.000 <m ≦ 1.035,
x is 0.02 ≦ x ≦ 0.15
It is.
[0029]
Such a dielectric ceramic can be fired without being made into a semiconductor even when fired in a reducing atmosphere. In addition, by using this dielectric ceramic, the capacitance temperature characteristic is specified by the JIS standard B characteristic (capacitance change is within ± 10% at -25 ° C. to + 85 ° C.) and the X7R characteristic specified by the EIA standard ( Highly reliable with high insulation resistance at room temperature or high temperature, satisfying capacitance change within ± 15% at -55 ° C to + 125 ° C) and X8R characteristics (capacitance change within ± 15% at -55 ° C to + 155 ° C) And a multilayer ceramic capacitor excellent in dielectric strength can be obtained.
[0030]
  Also thisInvitationThe electric ceramic usually contains a sintering aid. The sintering aid is contained, for example, in an amount of 0.2 to 5.0 parts by weight with respect to 100 parts by weight of the composition for the dielectric ceramic.₂The main component is preferably used.
[0031]
The dielectric ceramic described above is used, for example, for manufacturing a multilayer ceramic capacitor 1 as shown in FIG.
[0032]
Referring to FIG. 1, a multilayer ceramic capacitor 1 is provided on a multilayer body 3 having a plurality of laminated dielectric ceramic layers 2, and on first and second end faces 4 and 5 of the multilayer body 3, respectively. First and second external electrodes 6 and 7 are provided.
The multilayer ceramic capacitor 1 constitutes a rectangular parallelepiped chip type electronic component as a whole.
[0033]
In the laminated body 3, the first internal electrodes 8 and the second internal electrodes 9 are alternately arranged. The first internal electrode 8 is electrically connected to the first external electrode 6 with a plurality of specific edges between the dielectric ceramic layers 2 with each end edge exposed to the first end face 4. The dielectric ceramic is formed along the interface, and the second inner electrode 9 is exposed to the second end face 5 so that the second inner electrode 9 is electrically connected to the second outer electrode 7. Each is formed along a plurality of specific interfaces between the layers 2.
[0034]
In such a multilayer ceramic capacitor 1, the dielectric ceramic layer 2 provided in the multilayer body 3 is composed of the dielectric ceramic as described above.
[0035]
In order to manufacture this multilayer ceramic capacitor 1, {Ba_1-xCa_xO} TiO₂The process of preparing the mixture containing the compound represented by these, Mg compound, and Mn compound, for example by wet-mixing is implemented. Here, preferably, {Ba_1-xCa_xO}_mTiO₂+ ΑMgO + βMnO (where 0.001 ≦ α ≦ 0.05, 0.001 ≦ β ≦ 0.025, 1.000 <m ≦ 1.035, 0.05 ≦ x ≦ 0.15) The mixing ratio of each compound described above is selected so that a dielectric ceramic is obtained.
[0036]
  The above {Ba_1-xCa_xO} TiO₂The average particle size of the compound represented by, 0. 1 to 0.8 μm. In this case, the average particle size is 0.1 μm or more and 0.3 μm or less (the maximum particle size is preferably 0.5 μm or less). In the multilayer ceramic capacitor 1, a thin dielectric ceramic layer 2 having a thickness of 3 μm or less is formed. Even if it has, the temperature characteristic of the dielectric constant up to 125 ° C. in the multilayer ceramic capacitor 1 can be stabilized and the reliability can be improved. On the other hand, in the multilayer ceramic capacitor 1 in which the average particle size is in the range of more than 0.3 μm to 0.8 μm or less (the maximum particle size is preferably 1.0 μm or less) and the thickness is more than 3 μm, The temperature characteristic of the rate can be stabilized.
[0037]
In addition, {Ba_1-xCa_xO} TiO₂In most of the compounds represented by₂O, K₂Alkali metal oxides such as O are contained as impurities. It has been confirmed by the present inventor that the content of such an alkali metal oxide greatly affects the electrical characteristics of the dielectric ceramic. That is, it has been confirmed that a highly reliable dielectric ceramic can be obtained by setting the alkali metal oxide to 0.03 wt% or less, more preferably 0.02 wt% or less.
[0038]
Further, the above-mentioned mixture includes, for example, SiO.₂Is added in an amount of 0.2 to 5.0 parts by weight with respect to 100 parts by weight of the composition for the dielectric ceramic. Such SiO₂The dielectric ceramic can be sintered at a relatively low temperature of, for example, 1250 ° C. or lower in the firing step described later by adding a sintering aid mainly composed of.
[0039]
Next, a slurry is prepared by adding an organic binder and a solvent to the powder of the above-mentioned mixture, and a ceramic green sheet to be the dielectric ceramic layer 2 is produced using this slurry.
[0040]
Next, a conductive paste film to be the internal electrodes 8 and 9 is formed on a specific ceramic green sheet. The conductive paste film includes, for example, a base metal such as nickel or copper or an alloy thereof, and is formed by a screen printing method, a vapor deposition method, a plating method, or the like.
[0041]
Next, a plurality of ceramic green sheets including the ceramic green sheet on which the conductive paste film is formed as described above are stacked, pressed, and then cut as necessary. In this way, a plurality of ceramic green sheets and a plurality of internal electrodes 8 and 9 respectively formed along a specific interface between the ceramic green sheets are laminated, and each end of the internal electrodes 8 and 9 is laminated. The raw laminate 3 is produced with the edges exposed at the end face 4 or 5.
[0042]
Next, the laminate 3 is fired in a reducing atmosphere. At this time, as described above, SiO₂Therefore, the dielectric ceramic can be sintered at a relatively low temperature such as 1250 ° C. or lower. Therefore, the shrinkage of the internal electrodes 8 and 9 at the time of firing is reduced, and even when the thickness of the dielectric ceramic layer 2 is thin, the reliability of the multilayer ceramic capacitor 1 can be increased, and as the internal electrodes 8 and 9, As described above, those containing a base metal such as nickel or copper or an alloy thereof can be used without any problem.
[0043]
  In the sintering for obtaining the dielectric ceramic as described above, when R is a particle size ratio of (average particle size of dielectric ceramic) / (average particle size of powder of starting material), R is 0.00. Within the range of 90 ≦ R ≦ 1.2To be. This means that significant grain growth does not occur during ceramic sintering, and a dielectric ceramic having excellent dielectric constant temperature characteristics can be obtained.
[0044]
Next, the first and second end faces 4 and 4 of the laminate 3 are electrically connected to the exposed edges of the first and second internal electrodes 8 and 9 in the fired laminate 3, respectively. First and second external electrodes 6 and 7 are formed on 5 respectively.
[0045]
The material composition of the external electrodes 6 and 7 is not particularly limited. Specifically, the same material as the internal electrodes 8 and 9 can be used. In addition, for example, a sintered layer of various conductive metal powders such as Ag, Pd, Ag-Pd, Cu, and Cu alloy, or the conductive metal powder and B₂O_Three-Li₂O-SiO₂-BaO, B₂O_Three-SiO₂-BaO system, Li₂O-SiO₂-BaO, B₂O_Three-SiO₂It can be comprised by the sintered layer which mix | blended various glass frit, such as -ZnO type | system | group. The material composition of the external electrodes 6 and 7 is appropriately selected in consideration of the application and use place of the multilayer ceramic capacitor 1.
[0046]
As described above, the external electrodes 6 and 7 may be formed by applying and baking a metal powder paste as a material on the fired laminate 3. However, the external electrodes 6 and 7 may be formed on the laminate 3 before firing. It may be formed by being applied to and baked simultaneously with the firing of the laminate 3.
[0047]
Thereafter, if necessary, the external electrodes 6 and 7 are respectively covered with plating layers 10 and 11 made of Ni, Cu, Ni—Cu alloy or the like. Furthermore, second plating layers 12 and 13 made of solder, tin or the like may be formed on the plating layers 10 and 11.
[0048]
Next, the present invention will be described based on a more specific embodiment. Needless to say, embodiments that can be implemented within the scope of the present invention are not limited to such examples.
[0049]
[Example 1]
The multilayer ceramic capacitor to be manufactured in this embodiment is a multilayer ceramic capacitor 1 having a structure as shown in FIG.
[0050]
First, as a starting material, high-purity TiO₂, BaCO_Three, And CaCO_ThreeWere prepared, weighed so as to have a Ca content as shown in Table 1 below, and then mixed and ground. After drying, the powder is heated at a temperature of 1000 ° C. or higher and (Ba, Ca) TiO having the average particle diameter shown in Table 1 as well._ThreeWas synthesized.
[0051]
[Table 1]

In addition, SiO₂In order to obtain an oxide powder serving as a sintering aid mainly composed of the following components, the oxides, carbonates and hydroxides of the respective components are weighed so as to have a composition ratio of the molar ratio shown in Table 2 below. Mixed and crushed. These oxide powders were heated to 1500 ° C. in a platinum crucible, and then rapidly cooled and pulverized so that the average particle size became 1 μm or less.
[0052]
[Table 2]

In addition, (Ba, Ca) TiO_ThreeBaCO for adjusting the (Ba, Ca) / Ti molar ratio m_ThreeAnd MgO and MnO were prepared.
[0053]
Next, these raw material powders and sintering aids were blended so as to have the composition shown in Table 3 below, to obtain blends. A polyvinyl butyral binder and an organic solvent such as ethanol were added to this blend and wet mixed by a ball mill to prepare a ceramic slurry. This ceramic slurry was formed into a sheet by a doctor blade method to obtain a rectangular green sheet having a thickness of 2.7 μm. Next, a conductive paste mainly composed of Ni was printed on the ceramic green sheet to form a conductive paste film for constituting an internal electrode.
[0054]
[Table 3]

Next, a plurality of ceramic green sheets were laminated so that the side from which the above-mentioned conductive paste film was drawn was staggered to obtain a laminate. This laminate is designated as N₂After heating to 350 ° C. in the atmosphere and burning the binder, the oxygen partial pressure was 10^-9-10^-12MPa H₂-N₂-H₂Firing was carried out at a temperature shown in Table 4 for 2 hours in a reducing atmosphere composed of O gas.
[0055]
B on both end faces of the laminate after firing₂O_Three-Li₂O-SiO₂-A silver paste containing a BaO glass frit is applied, and N₂An external electrode electrically connected to the internal electrode was formed by baking at a temperature of 600 ° C. in the atmosphere.
[0056]
The outer dimensions of the multilayer ceramic capacitor thus obtained are 5.0 mm in width, 5.7 mm in length, and 2.4 mm in thickness. The thickness of the dielectric ceramic layer interposed between the internal electrodes is as follows. It was 2 μm. The total number of effective dielectric ceramic layers is 5, and the area of the counter electrode per layer is 16.3 × 10.^-6m²Met.
[0057]
The electrical characteristics of these obtained samples were measured.
[0058]
Capacitance (C) and dielectric loss (tan δ) were measured according to JIS standard 5102 using an automatic bridge-type measuring device, and dielectric constant (ε) was calculated from the obtained capacitance.
[0059]
In order to measure the insulation resistance (R), an insulation resistance meter was used to apply a DC voltage of 10 V for 2 minutes to obtain the insulation resistance (R) at 25 ° C., and the specific resistance was calculated.
[0060]
Regarding the rate of change of the capacitance with respect to the temperature change, the rate of change in the range of −25 ° C. to + 85 ° C. (ΔC / C based on the capacitance at 20 ° C.)₂₀) And the rate of change (ΔC / C) in the range of −55 ° C. to + 125 ° C. based on the capacitance at 25 ° C._{twenty five}).
[0061]
Further, as a high temperature load test, a DC voltage of 20 V was applied at a temperature of 150 ° C., and the change over time in the insulation resistance was measured. In the high temperature load test, the insulation resistance value (R) of each sample was 10^FiveThe average life time was evaluated when failure occurred when Ω or less.
[0062]
Furthermore, the breakdown voltage was measured by applying a DC voltage at a boosting rate of 100 V / sec.
[0063]
In addition, the average particle size of the starting material used was determined by observing with a scanning electron microscope, and the average particle size of the dielectric ceramic contained in the obtained multilayer ceramic capacitor was determined on the cross-sectional polished surface of the laminate. It was obtained by chemical etching and observing with a scanning electron microscope. From these results, a particle size ratio R of (average particle size of dielectric ceramic) / (average particle size of powder of starting material) was determined.
[0064]
Each result is shown in Table 4.
[0065]
[Table 4]

A preferred composition of the dielectric ceramic according to the present invention is represented by the general formula: {Ba_1-xCa_xO}_mTiO₂+ ΑMgO + βMnO, and for each of α, β, m, and x,
0.001 ≦ α ≦ 0.05,
0.001 ≦ β ≦ 0.025,
1.000 <m ≦ 1.035, and
0.02 ≤ x ≤ 0.15
Chosen to be
[0066]
A preferable range of each characteristic described above is about 1000 or more for the dielectric constant, 2.5% or less for the dielectric loss, and within -55% for the capacity change rate. The rate of change in the range of −25 ° C. to + 85 ° C. based on the capacitance at 20 ° C. is within ± 10%, and similarly −55 ° C. to +125 based on the capacitance at 25 ° C. The rate of change in the range of ° C. is within ± 15%, the specific resistance is 13.0 Ω · cm or more, and the dielectric breakdown voltage is 10 kV / mm or more.
[0067]
In Tables 3 and 4, the sample numbers marked with * are samples that deviate from the above preferred composition range.
[0068]
As can be seen from Table 4, according to the samples 13 to 23 within the preferred composition range, the change rate of the capacitance with respect to the temperature satisfies the B characteristic defined in the JIS standard in the range of -25 ° C to + 85 ° C. It satisfies the X7R characteristic defined in the EIA standard in the range of −55 ° C. to + 125 ° C. Furthermore, the average life time in the high temperature load test almost exceeds 100 hours, is excellent in reliability, can be fired at a firing temperature of at least 1250 ° C., and most can be fired at a temperature of 1200 ° C. or less. is there. The reason for limiting the above-mentioned preferable composition range will be described below.
[0069]
When the Ca addition amount x is less than 0.02 as in Sample 1, the change in the dielectric constant due to the voltage may be large, and the average life at high temperature load may be shortened. On the other hand, when the additive amount x of Ca exceeds 0.15 as in sample 2, the relative dielectric constant may be small and tan δ may be large.
[0070]
More preferably, the Ca addition amount x is 0.05 or more. In this case, particularly in terms of average life, it is more advantageous than 0.02 or more and less than 0.05.
[0071]
Further, as in Sample 3, when the added amount α of MgO is less than 0.001, the specific resistance is low, and the temperature characteristics may not satisfy the B characteristics and the X7R characteristics. On the other hand, when the additive amount α of MgO exceeds 0.05 as in the sample 4, the sintering temperature becomes high, and the time to failure in the high temperature load test may be shortened.
[0072]
Further, as in Sample 5, when the additive amount β of MnO is less than 0.001, the specific resistance may be lowered. On the other hand, when MnO addition amount β exceeds 0.025 as in sample 6, the specific resistance may be low and the temperature characteristics of the dielectric constant may not satisfy the B characteristic and the X7R characteristic.
[0073]
Further, when the (Ba, Ca) / Ti ratio m is less than 1.000 as in the sample 7, the specific resistance may be lowered. Similarly to the sample number 8, when m is 1.000, the specific resistance may be similarly lowered. In both cases, the time to failure at a high temperature load may be remarkably shortened, and there is a failure at the moment when a voltage is applied at a high temperature. Further, as in sample 9, when the (Ba, Ca) / Ti ratio m exceeds 1.035, the sinterability is insufficient, and the time to failure at a high temperature load may be shortened.
[0074]
Further, when the amount of the sintering aid added is 0 as in sample 10, sintering is insufficient, the specific resistance in plating is greatly reduced, and the time to failure at high temperature load is shortened. is there. On the other hand, when the additive amount of the sintering aid exceeds 5.0 parts by weight as in Sample 11, the generation of secondary phase based on the glass component contained in the sintering aid increases, The time to failure may also be shortened.
[0075]
In addition, (Ba, Ca) TiO_ThreeWhen the content of the alkali metal oxide contained as an impurity exceeds 0.03 wt% as in Sample 12, the time to failure at a high temperature load may be shortened.
[0076]
In Sample 14, the pulverization conditions at the time of preparing the ceramic slurry were strengthened so that the powder particle size in the slurry was smaller than that of the starting raw material powder. In the sample 14, the particle size ratio R (= the average particle size of the dielectric ceramic / the average particle size of the starting raw material powder) is as small as 0.85, and the dielectric constant may be lowered. On the other hand, in the case where the particle size ratio R is as large as 1.25 as in the sample 13 and the grains grow during firing, the number of ceramic particles between the internal electrodes is small when the dielectric ceramic layer is thinned. Therefore, the time to failure at a high temperature load may be shortened.
[0077]
When the average particle size is relatively large as 0.40 μm like the sample 15, the dielectric constant is large. On the other hand, when the dielectric ceramic layer is thinned as in this embodiment, the time to failure at a high temperature load is short, and the change in the dielectric constant under a high electric field may be large. On the other hand, when the average particle size is as small as 0.09 μm like the sample 16, the dielectric constant may be low and the temperature change of the dielectric constant may be large.
[0078]
In particular, in Samples 17 to 23, the dielectric constant is in the range of 1280 to 2510, and the change in capacitance under a high electric field is small and stable at 42% or less. In addition, no deterioration due to plating is observed, the time to failure at a high temperature load is long, and the reliability is excellent.
[0079]
In the above embodiment, (Ba, Ca) TiO is used._ThreeAs a raw material, a powder produced by a solid phase method was used, but the present invention is not limited thereto, and a powder produced by a wet synthesis method such as an alkoxide method or a hydrothermal synthesis method may be used.
[0080]
In addition, Mg, Mn oxides and SiO which are additive components₂However, the present invention is not limited to this, and is not limited to this. As long as it can constitute a dielectric ceramic phase within the scope of the present invention, an alkoxide, an organic metal, etc. A solution may be used, and the properties obtained thereby are not impaired at all.
[0081]
In addition, NiO originally exists on the surface of the Ni particles contained in the internal electrode of the multilayer capacitor. Depending on the firing conditions that are easy to oxidize, a large amount of NiO is produced, and this NiO may diffuse into the dielectric ceramic constituting the multilayer body in the firing step for obtaining the multilayer body of the multilayer capacitor. In addition, ZrO is used for the purpose of controlling the sintering of the internal electrode.₂Components may be added, and such an additive composition may diffuse up to several mol% at maximum with respect to the dielectric ceramic composition during firing. According to the dielectric ceramic composition of the present invention, it has been confirmed that even if these electrode components diffuse, there is no influence on the electrical characteristics thereof.
[0082]
These also apply to the second embodiment described below.
[0083]
[Example 2]
Similar to Example 1, (Ba, Ca) TiO having a Ca content and an average particle size as shown in Table 5 below._ThreeWas synthesized. In a word, Example 2 is different from Example 1 in that the average particle size is larger than that in Example 1.
[0084]
[Table 5]

In addition, SiO₂As the sintering aid mainly composed of, those shown in Table 2 above, which were prepared in the same manner as in Example 1, were used.
[0085]
Next, similarly to Example 1, a ceramic slurry having the composition shown in Table 6 below was prepared. This ceramic slurry was formed into a sheet by a doctor blade method to obtain a rectangular green sheet having a thickness of 8 μm. Next, a conductive paste mainly composed of Ni was printed on the ceramic green sheet to form a conductive paste film for constituting an internal electrode.
[0086]
[Table 6]

Next, in the same manner as in Example 1, a multilayer ceramic capacitor was produced.
[0087]
The thickness of the dielectric ceramic layer interposed between the internal electrodes of the multilayer ceramic capacitor thus obtained was 6 μm.
[0088]
Moreover, the electrical characteristics of these obtained samples were measured in the same manner as in Example 1 except for the following points. The difference from Example 1 is that the insulation resistance (R) was measured by applying a 60V DC voltage for 2 minutes, and in the high temperature load test, a DC voltage of 60V was applied at 150 ° C. This is the point at which the change over time in the insulation resistance was measured.
[0089]
Various characteristics obtained in Example 2 are shown in Table 7.
[0090]
[Table 7]

As described in Example 1, the preferred composition of the dielectric ceramic according to the present invention is represented by the general formula: {Ba_1-xCa_xO}_mTiO₂+ ΑMgO + βMnO, and for each of α, β, m, and x,
0.001 ≦ α ≦ 0.05,
0.001 ≦ β ≦ 0.025,
1.000 <m ≦ 1.035, and
0.05 ≤ x ≤ 0.15
Chosen to be
[0091]
In Tables 6 and 7, the sample numbers marked with * are samples that deviate from the above preferred composition range.
[0092]
As can be seen from Table 7, according to the samples 36 to 47 within the preferable composition range, the change rate of the capacitance with respect to the temperature satisfies the B characteristic defined in the JIS standard in the range of −25 ° C. to + 85 ° C. It satisfies the X8R characteristic defined in the EIA standard in the range of −55 ° C. to + 150 ° C. Further, the average life time in the high temperature load test is more than 100 hours, and most of the firing temperature can be fired at a temperature of 1250 ° C. or less. The reason for limiting the above-mentioned preferable composition range will be described below.
[0093]
When the Ca addition amount x is less than 0.02 as in the sample 24, the change in the dielectric constant due to the voltage is large, and the average life at high temperature load may be shortened. On the other hand, when the Ca addition amount x exceeds 0.15 as in the sample 25, the relative dielectric constant may be small and tan δ may also be large.
[0094]
Further, when the additive amount α of MgO is less than 0.001 as in the sample 26, grain growth occurs during firing, the specific resistance is low, and the temperature characteristic of the dielectric constant may not satisfy the B characteristic and the X8R characteristic. On the other hand, when the added amount α of MgO exceeds 0.05 as in the sample 27, the sintering temperature becomes high, and the time to failure in the high temperature load test may be shortened.
[0095]
Moreover, when the MnO addition amount β is less than 0.001 as in the sample 28, the specific resistance may be lowered. On the other hand, when the MnO addition amount β exceeds 0.025 as in the sample 29, the specific resistance is also low, and the temperature characteristic of the dielectric constant may not satisfy the B characteristic and the X8R characteristic.
[0096]
Moreover, when the (Ba, Ca) / Ti ratio m is less than 1.000 as in the sample 30 and when m is 1.000 as in the sample number 31, the specific resistance is low. In some cases, the time to failure at a high temperature load is remarkably short, and there is a failure at the moment when a voltage is applied at a high temperature. Further, when the (Ba, Ca) / Ti ratio m exceeds 1.035 as in the sample 32, the sinterability is insufficient and the time to failure at a high temperature load may be shortened.
[0097]
Further, as in Sample 33, when the additive amount of the sintering aid is 0, sintering is insufficient, the specific resistance in plating is greatly reduced, and the time to failure at high temperature load is shortened. is there. On the other hand, when the addition amount of the sintering aid exceeds 5.0 parts by weight as in the sample 34, the generation of the secondary phase based on the glass component contained in the sintering aid increases, The time to failure may also be shortened.
[0098]
In addition, (Ba, Ca) TiO_ThreeWhen the content of the alkali metal oxide contained as an impurity exceeds 0.03 wt% as in Sample 35, the time to failure at a high temperature load may be shortened.
[0099]
In addition, when the particle size ratio R (= the average particle size of the dielectric ceramic / the average particle size of the starting material powder) is as small as 0.88 as in the sample 37, the dielectric constant is low. On the other hand, in the case where the particle size ratio R is as large as 1.25 as in the sample 36 and the grains grow during firing, the number of ceramic particles between the internal electrodes is small when the dielectric ceramic layer is thinned. Therefore, the time to failure at a high temperature load may be shortened.
[0100]
Further, when MgO is not contained as in the sample 48, the particle size ratio R is 6.25, and grain growth at the time of firing is remarkable, and the temperature change of the dielectric constant is large, which is not preferable. Further, when the amount of MnO added is 0 as in Sample 49, the specific resistance is low, and the time to failure at a high temperature load is extremely short, which is not preferable.
[0101]
In Example 2, the thickness of the dielectric ceramic layer is 6 μm. However, when the average particle size is relatively large as 1.00 μm as in the sample 38, the change in the dielectric constant with temperature is small, but the voltage The change in the dielectric constant due to the temperature may be large, and the time to failure at a high temperature load may be shortened. On the other hand, when the average particle size is as small as 0.25 μm like the sample 39, the electric field strength applied to the dielectric ceramic layer is low, so that the dielectric constant may be low.
[0102]
In Samples 40 to 47, the dielectric constant is in the range of 2050 to 3460, and the thickness of the dielectric ceramic layer is relatively thick. In Example 2, the change in capacitance under a high electric field is as small as 50% or less. ,stable. In addition, no deterioration due to plating is observed, the time to failure at a high temperature load is long, and the reliability is excellent.
[0103]
【The invention's effect】
  According to this inventionConstructing dielectric ceramic layer of multilayer ceramic capacitor obtained by manufacturing methodAccording to the dielectric ceramic, although it is a material that does not have a core-shell structure, it can be a highly reliable dielectric material with good temperature characteristics of dielectric constant. Moreover, since this dielectric ceramic is not reduced even when fired in a reducing atmosphere in order to obtain this, the dielectric ceramic is used.,productWhen the layer ceramic capacitor is configured, nickel and nickel alloy, which are base metals, can be used as the internal electrode material, and the cost of the multilayer ceramic capacitor can be reduced.
[0104]
  Also,AboveAccording to the dielectric ceramic, the temperature characteristic of the dielectric constant is not flattened based on the core-shell structure, but the temperature characteristic of the dielectric constant is flattened based on the original temperature characteristic of the composition. Variations in characteristics due to firing conditions can be reduced without being affected by the diffusion state of the additive components. Therefore, it can be obtained using this dielectric ceramic.ProductThe layer ceramic capacitor has little variation in characteristics, and can have stable and excellent temperature characteristics of dielectric constant.
[0105]
In the method of manufacturing a multilayer ceramic capacitor according to the present invention, {Ba_1-xCa_xO} TiO₂In a multilayer ceramic capacitor having a thin dielectric ceramic layer having a thickness of 3 μm or less, for example, a dielectric constant of up to 125 ° C. is obtained by reducing the average particle size of the compound represented by The change due to temperature can be reduced, and the number of particles in the dielectric ceramic layer can be secured, so that the reliability can be improved. Therefore, it is possible to advantageously obtain a monolithic ceramic capacitor having a small size, a thin layer and a large capacity.
[0106]
On the other hand, {Ba_1-xCa_xO} TiO₂In a multilayer ceramic capacitor having a dielectric ceramic layer with a thickness of 3 μm or more, for example, up to a high temperature of 150 ° C., the average particle size of the compound represented by The change in rate due to temperature can be reduced, and the reliability can be improved.
[0107]
In the method for manufacturing a multilayer ceramic capacitor according to the present invention, {Ba_1-xCa_xO} TiO₂When the content of the alkali metal oxide contained as an impurity in the compound represented by is suppressed to 0.03 wt% or less, the reliability of the dielectric ceramic layer can be further improved.
[0109]
  Also, in the method for manufacturing a multilayer ceramic capacitor according to the present invention,According toWhen the dielectric ceramic to be the dielectric ceramic layer is sintered, the particle size ratio R of (average dielectric particle diameter) / (average particle diameter of starting material powder) is 0.90 ≦ R ≦ 1. Choose to be within 2BecauseThus, no significant grain growth occurs during ceramic sintering, and a dielectric ceramic with better dielectric constant temperature characteristics can be obtained.
[Brief description of the drawings]
FIG. 1 shows an embodiment of the present invention.Obtained by manufacturing method1 is a cross-sectional view showing a multilayer ceramic capacitor 1. FIG.
[Explanation of symbols]
1 Multilayer ceramic capacitor
2 Dielectric ceramic layer
3 Laminate
4 First end face
5 Second end face
6 First external electrode
7 Second external electrode
8 First internal electrode
9 Second internal electrode

Claims (4)

General formula: {Ba _1-x Ca _x O} _m TiO ₂ + αMgO + βMnO
α is 0.001 ≦ α ≦ 0.05,
β is 0.001 ≦ β ≦ 0.025,
m is 1.000 <m ≦ 1.035,
x is 0.02 ≦ x ≦ 0.15
In order to obtain a dielectric ceramic , a compound represented by {Ba _1-x Ca _x O} TiO ₂ having an average particle size of 0.1 to 0.8 μm as a starting material, an Mg compound, Preparing a mixture comprising a Mn compound;
A plurality of ceramic green sheets containing the mixture, and a plurality of internal electrodes respectively formed along a specific interface between the ceramic green sheets are laminated, and an edge of each internal electrode is exposed to an end face Producing a laminate, and
The mixture so that said dielectric ceramic by sintering, a step of firing the laminate,
Forming a plurality of external electrodes on the end face of the laminate so as to be electrically connected to the exposed edge of each internal electrode, respectively .
When the ratio of (average particle diameter of the dielectric ceramic) / (average particle diameter of the powder of the starting material) is R, R is in the range of 0.90 ≦ R ≦ 1.2.
Manufacturing method of multilayer ceramic capacitor. _2. The multilayer ceramic capacitor according to claim 1 , wherein the compound represented by {Ba _1-x Ca _x O} TiO ₂ contains an alkali metal oxide as an impurity with a content of 0.03 wt% or less. Production method. 3. The method for producing a multilayer ceramic capacitor according to claim 1, wherein an average particle diameter of the compound represented by {Ba _1-x Ca _x O} TiO ₂ is 0.1 μm or more and 0.3 μm or less. 3. The method for producing a multilayer ceramic capacitor according to claim 1, wherein an average particle diameter of the compound represented by {Ba _1-x Ca _x O} TiO ₂ is more than 0.3 μm and not more than 0.8 μm.

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