JP2004107149A

JP2004107149A - Low dielectric constant ceramic composition for high frequency component and method of manufacturing the same

Info

Publication number: JP2004107149A
Application number: JP2002272874A
Authority: JP
Inventors: Takahiro Takada; 高田　隆裕
Original assignee: Sumitomo Metal SMI Electronics Device Inc
Current assignee: Sumitomo Metal SMI Electronics Device Inc
Priority date: 2002-09-19
Filing date: 2002-09-19
Publication date: 2004-04-08
Anticipated expiration: 2022-09-19
Also published as: JP4534413B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low dielectric constant ceramic composition which is capable of being sintered by low temperature sintering in which a conductive body having high electric conductivity such as Ag, Au or Cu is simultaneously sintered and which has characteristic excellent in high frequency band. <P>SOLUTION: The ceramic composition consists of 40-65% Al<SB>2</SB>O<SB>3</SB>, 15-35% one of SiO<SB>2</SB>and B<SB>2</SB>O<SB>3</SB>or in total of SiO<SB>2</SB>and B<SB>2</SB>O<SB>3</SB>, 10-20% CaO, 0.1-14% ZnO, 0-2% MnO and 0-2% R<SB>2</SB>O (where R expresses one or more kinds of Li, Na and K) by mol expressed in terms of oxide. The ceramic composition is prepared by further incorporating 0.1-2% Ln<SB>2</SB>O<SB>3</SB>(Ln expresses one or more kinds of rare earth elements such as Y, La and Nd). The method of manufacturing the ceramic composition is performed by mixing the powder of raw materials, calcining the mixture and pulverizing the calcined mixture to make powder, adding a binder or the like to the powder and kneading and molding into a required shape, firing at 800-1,000°C or vitrifying the composition except Al<SB>2</SB>O<SB>3</SB>and mixing Al<SB>2</SB>O<SB>3</SB>with the glass powder and firing at 800-920°C. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明が属する技術分野】
本発明は、数ＧＨｚから数十ＧＨｚの高周波領域で使用する電子部品やモジュールに好適な誘電体の磁器組成物に関する。
【０００２】
【従来の技術】
近年、情報の高速大量伝達通信および移動体通信の発達にともない、基板上の集積回路においては、小型化、高密度化ばかりでなく、取り扱われる信号に数ＧＨｚさらにはそれ以上の帯域の周波数の利用が検討されており、基板として使用する誘電体の磁器組成物に対しても、このような高周波帯域に適合した材料が要望されている。この磁器組成物に要求される性能は、十分な強度を有し、高周波帯域において比誘電率ε_ｒが低いこと、誘電損失ｔａｎδが小さいこと、さらには比誘電率の温度変化もしくは共振周波数の温度変化が小さいことなどである。
【０００３】
一般に、基板の比誘電率が低いほど回路中の信号伝搬速度は速くなるので、高周波帯域の用途には比誘電率ε_ｒはできるだけ低いことが望ましい。そして信号伝達の上で損失は少なければ少ないほどよいので、誘電損失は小さくすなわちＱ値はできるだけ高くする必要がある。また、誘電体としての機能はたとえばフィルタや共振器などに利用されるが、その際に温度変化に対して安定な作動をさせるためには、共振周波数の温度係数τ_ｆの絶対値はできるだけ小さいこと、すなわち温度依存性の少ないことも重要である。
【０００４】
従来、集積回路用の磁器組成物多層基板としては、耐熱性や絶縁特性にすぐれ、耐電圧が高く誘電率が小さいアルミナが多く用いられ、回路の高密度化に伴い、グリーンシートに導体ペーストを印刷し、これを積層し一括して焼成する方法が発達してきた。アルミナの焼結温度は１５００〜１６００℃と高いので、多層基板内部の回路形成用導電材料としては、この温度にて焼結できるＷやＭｏ等の高融点金属が使用されている。
【０００５】
しかしながら、回路に使用される周波数が高くなってくると、基板材料はアルミナよりも比誘電率の低いことが要望され、回路が微細化してくるにしたがい、用いられる導体も導電損失を小さくするため、より電気抵抗の低いものが必要となってくる。電気抵抗の低い金属導体はＡｇ、Ａｕ、Ｃｕであるが、これらはいずれもＷやＭｏに比して融点が低く、同時焼成により多層基板を製造しようとすれば、磁器組成物はこれらの金属の融点より低い１０００℃以下で焼成できるものでなければならない。
【０００６】
このような目的に対し、融点の低いガラスにアルミナなどの酸化物系耐火物をフィラーとして混入させた、低温焼結型磁器組成物が種々開発されている。通常ガラスはアルミナなど酸化物系耐火物に比べて誘電率が低い。したがってガラスを積層して多層基板とすることも考えられるが、ガラスは一般に誘電損失が大きく、焼成時軟化による形状変化が大で回路の所要寸法精度を得ることが困難であり、強度的にも不十分である。
【０００７】
これに対し、ガラスにフィラーを混在させると、形状変化が小さく低い温度で緻密な組織と十分な強度のすぐれた磁器組成物が得られ、フィラーに誘電損失の小さいものを選べば、特性の良好な低温焼結型磁器組成物とすることができる。
【０００８】
たとえば特公平３−５３２６９号公報には、ＣａＯ−ＳｉＯ_２−Ａｌ_２Ｏ_３−Ｂ_２Ｏ_３系のガラスにフィラーとしてＡｌ_２Ｏ_３を５０〜３５質量％混入した８００〜１０００℃で焼成する低温焼成磁器組成物基板の発明が開示されている。ただし、この発明では１ＭＨｚにおける損失しか示されておらず、数ＧＨｚを超える高周波域における特性はあきらかでない。
【０００９】
また、米国特許Ｎｏ．６１４７０１９号には、５０〜７５質量％のＡｌ_２Ｏ_３耐火物と、モル％でＢ_２Ｏ_３：５０〜６７％、ＣａＯ：２０〜５０％、Ｌｎ_２Ｏ_３（Ｌｎは希土類元素）：２〜１５％、Ｍ_２Ｏ（Ｍはアルカリ金属元素）：０〜６％、Ａｌ_２Ｏ_３：０〜１０％のガラスとを混合した、内部導体にＡｇを同時焼成して使用することのできる磁器組成物の発明が開示されている。
【００１０】
しかしながら、基板あるいはモジュールや電子部品用の磁器組成物としては、採用される周波数帯域においてよりすぐれた性能のものが常に要求されており、とくに高周波帯域にて高性能の材料が要望されている。また、回路の精細化に伴い、基板としては平坦度がよく、高い寸法精度が要求され、これに対しては圧力を加えるか拘束しつつ焼成する方法が開発されているが、このような焼成方法にも適した磁器組成物であることが望ましい。
【００１１】
【発明が解決しようとする課題】
本発明の目的は、Ａｇ、Ａｕ、Ｃｕなどの電気伝導度が高い導体を同時焼成できる低温焼結が可能な、比誘電率が低く高周波帯域での損失が小さく、かつ温度依存性の小さい低誘電率磁器組成物の提供にある。
【００１２】
【課題を解決するための手段】
本発明者らは、焼成温度が１０００℃以下の、内部導体にＡｇ、ＡｕまたはＣｕを用いて同時焼成により多層基板が製造可能な、数ＧＨｚまたはそれ以上の高周波帯域で使用される低温焼結磁器組成物の性能を改善すべく種々検討をおこなった。
【００１３】
低温焼結可能な基板用磁器組成物としては、アルミナ、チタニア、ジルコニアなどの耐火物をフィラーとし、これに軟化点の低いガラス組成物を混合したガラスセラミックスがある。この場合、ガラスの原料を高温加熱して溶融し、急冷してガラス粉末を作り、これとフィラーとなるアルミナなど耐火物粉末とを混合し仮焼粉砕後、所定形状に成形後焼成するので、原料からは複数回の高温加熱を必要とする。これに対し、通常のセラミックス合成方法、すなわち所要原料を混合し、仮焼後粉砕して成形し焼成して所要の磁器組成物とすることができれば、工程が簡略化され、所要エネルギーを少なくでき、製造コストの低減が可能と思われた。
【００１４】
また、積層基板は回路の高密度化により、導体配線やスルーホールの微細化および高精度化要求が厳しくなっており平坦性も追求される。これに対し、グリーンシートの積層体に圧力をかけて拘束しながら焼成し、焼成による収縮を厚さ方向のみとして、回路形状の高精度化と、平坦性向上を図る方法があるが、このような焼成方法にも適したものでなければならない。
【００１５】
高周波域での適用に要求される特性としては、誘電率が低いこと、誘電損失が小さいこと、および誘電率の温度依存性が小さいことなどである。これらの誘電特性は、円柱状試験片による両端短絡形誘電体共振法（ハッキー・コールマン法）により測定した。
【００１６】
まず、基板としての強度を保持し、緻密な磁器組成物を得るために、Ａｌ_２Ｏ_３を主成分とし、これにガラス形成成分のＳｉＯ_２、Ｂ_２Ｏ_３、ＣａＯ、等を混合して、通常のセラミックス合成方法にて焼成温度が１０００℃以下の低温焼結が可能かどうかの検討をおこなった。その結果、高周波における誘電特性が良好となり、しかも焼結温度が低くなる組成範囲を大略あきらかにすることができたが、目的とする低温域での焼成では、必ずしも十分緻密な磁器組成物が得られなかった。
【００１７】
そこでさらに、酸化物系添加物について種々調査の結果、ＺｎＯ、ＭｎＯ、あるいはＲ_２Ｏ（Ｒ：Ｌｉ、ＮａおよびＫのアルカリ金属元素）の少量添加が、特性を損なうことなく焼結温度を低下できることがわかった。また、希土類元素の酸化物Ｌｎ_２Ｏ_３（Ｌｎ：Ｙ、Ｌａ、Ｎｄ等の希土類元素）を、焼結温度が上がらない範囲で添加するとにより、ｆＱ値を向上させる効果のあることも見出された。
【００１８】
このように、通常のセラミックス合成方法にて１０００℃以下の低温焼結は可能であることはわかったが、電気伝導率にすぐれたＡｇを導体に用いるとき、焼成温度はＡｇの融点９６１℃を下回っている必要がある。これに対しては、Ａｌ_２Ｏ_３を除く他の原料について混合溶融急冷してしてガラスを作り、これを粉末化してからＡｌ_２Ｏ_３粉末と混合し混錬して成形後焼成することにより、より低い焼成温度で、同じ組成を有しかつ同様な高周波域の誘電性能を有する磁器組成物が得られることが確認できた。
【００１９】
焼成して得られた、上記の高周波特性にすぐれた磁器組成物の組織を調べてみると、ＬｎＢＯ_３、Ｚｎ_２ＳｉＯ_４、ＣａＡｌ_２Ｏ_８、ＣａＡｌ_２Ｂ_２Ｏ_７等の結晶とガラスの混合した相によりＡｌ_２Ｏ_３の結晶粒子が結合された状態になっており、このような結晶とガラスとが混合した状態がすぐれた高周波域での誘電特性をもたらしていると考えられる。
【００２０】
以上のような検討結果に基づき、焼成温度、Ｑ値、誘電率、温度特性等にそれぞれ目標限界を設定し、それらのいずれも満足する組成や条件範囲をあきらかにして本発明を完成させた。本発明の要旨は次のとおりである。
【００２１】
（１）　酸化物として表示される成分がモル％にて、Ａｌ_２Ｏ_３：４０〜６５％、ＳｉＯ_２およびＢ_２Ｏ_３のいずれか一方または両方を合計量として１５〜３５％、ＣａＯ：１０〜２０％、ＺｎＯ：０．１〜１４％、ＭｎＯ：０〜２％およびＲ_２Ｏ（ＲはＬｉ、ＮａおよびＫの中の一種以上）：０〜２％であることを特徴とする高周波部品用低誘電率磁器組成物。
【００２２】
（２）　酸化物として表示される成分がモル％にて、Ａｌ_２Ｏ_３：４０〜６５％、ＳｉＯ_２およびＢ_２Ｏ_３のいずれか一方または両方を合計量として１５〜３５％、ＣａＯ：１０〜２０％、ＺｎＯ：０．１〜１４％、ＭｎＯ：０〜２％、Ｒ_２Ｏ（ＲはＬｉ、ＮａまたはＫ）：０〜２％、およびＬｎ_２Ｏ_３（ＬｎはＹ、ＬａおよびＮｄなどの希土類元素の一種以上）：０．１〜２％であることを特徴とする高周波部品用低誘電率磁器組成物。
【００２３】
（３）　焼成後請求項１または２に記載の組成比となる原料の粉末を混合し、混合物を仮焼後粉砕して粉末とし、この粉末にバインダーを加え混錬して所要形状に成形後、８００〜１０００℃にて焼成することを特徴とする高周波部品用低誘電率磁器組成物の製造方法。
【００２４】
（４）　焼成後請求項１または２に記載の組成比から、Ａｌ_２Ｏ_３を除いた組成の原料を１０００℃以上の温度に加熱してガラス化した後急冷して粉末となし、この粉末とＡｌ_２Ｏ_３の粉末とを混合してバインダーを加えて混錬して所要形状に成形後、８００〜９２０℃にて焼成することを特徴とする高周波部品用低誘電率磁器組成物の製造方法。
【００２５】
【発明の実施の形態】
本発明の磁器組成物は、各成分を酸化物の形で示すとき、次のような組成になっている。
【００２６】
Ａｌ_２Ｏ_３：４０〜６５モル％
Ａｌ_２Ｏ_３は磁器組成物の強度を保持するために必要である。４０モル％未満では磁器組成物の抗折力が低下し、焼成時の形状維持も困難となる。しかし、６５モル％を超える含有は、目的とする低温度での焼結ができなくなる。したがって４０〜６５モル％とするが、より好ましくは５５〜６０モル％である。
【００２７】
ＳｉＯ_２およびＢ_２Ｏ_３のいずれか一方または両方を合計量として１５〜３５モル％
ＳｉＯ_２およびＢ_２Ｏ_３はガラスを形成し、磁器組成物の焼結温度低下に大きく寄与する。また高周波域でのＱ値のすぐれた結晶相の形成にも必要である。いずれか一方、または両方の合計が１５モル％を下回るとき、１０００℃以下の低温焼結が困難となり、３５モル％を超えるときはＱ値が低下してくる。より好ましいのは２５〜３０モル％である。
【００２８】
ＣａＯ：１０〜２０モル％
ＣａＯは１０００℃以下での焼成温度にてＳｉＯ_２、Ｂ_２Ｏ_３およびＡｌ_２Ｏ_３とともにガラスと結晶相を形成する。また、誘電率の温度依存性を小さくする効果がある。１０モル％未満では１０００℃以下での焼結が困難になり、２０モル％を超える含有は誘電率の温度変化率が大きくなってしまう。より好ましいのは１２．５〜１７モル％の範囲である。
【００２９】
ＺｎＯ：０．１〜１４モル％
ＺｎＯは焼結温度を低下させる作用があり、Ｑ値を高める効果もある。このような効果を得るためには、０．１モル％以上の含有が必要である。しかし、多すぎる含有はかえってＱを低下させてしまうので、１４モル％までとする。より好ましいのは０．１〜５モル％である。
【００３０】
ＭｎＯ：０〜２モル％
ＭｎＯは、含有させなくてもよいが、含有させるとＺｎＯと同様焼結温度を低下させ、Ｑ値を高める効果がある。その効果を得るためには、０．１モル％以上の含有が望ましいが、多すぎるとＱ値を低下させるので、２モル％以下とするのがよい。
【００３１】
Ｒ_２Ｏ（ＲはＬｉ、ＮａおよびＫの中の一種以上）：０〜２モル％
アルカリ金属元素Ｌｉ、ＮａおよびＫの酸化物Ｒ_２Ｏは、ガラスを形成させる作用があり、焼結温度の低下に大きな効果がある。これらは含有させなくてもよいが、その効果を得るため含有させる場合は０．１モル％以上が好ましい。しかし、多すぎると大幅にＱ値を低下させるので２モル％までとするが、望ましいのは０．５モル％以下である。
【００３２】
Ｌｎ_２Ｏ_３（ＬｎはＹ、ＬａおよびＮｄなどの希土類元素の一種以上）：０〜２モル％
Ｌｎ_２Ｏ_３は添加しなくてもよいが高周波域でのＱ値を向上させる効果があり、とくにＱ値を向上させたいときに含有させるとよい。この効果を得るためには、０．１モル％以上の含有が好ましい。ただし、多く含有させすぎると低温での焼結困難、誘電率の温度変化率増大を来すので、２モル％以下とする。この希土類元素酸化物は、単独で添加すると低温焼成の場合その含有効果が十分発揮されないことがあるので、あらかじめＬｎ_２Ｏ_３：４５〜５０モル％およびＢ_２Ｏ_３：５０〜５５モル％の混合物を焼結などにより合成しておき、これの粉末の形で添加するとよい。なお、このときに添加されるＢ_２Ｏ_３の量は、ＳｉＯ_２およびＢ_２Ｏ_３の合計量が１５〜３５モル％となる範囲内になければならない。
【００３３】
磁器組成物の製造方法は、通常のセラミックス合成方法を適用する。すなわち原料となる酸化物などの粉末それぞれを、所要量混合し、たとえば、まず７００〜８００℃程度の温度で１〜５時間仮焼し、この仮焼物を湿式粉砕し乾燥後、バインダーを加えて混錬し所要基板形状などに成形、すなわちグリ−ンシートとし導体の回路印刷などおこなってから積層し、１０００℃以下の温度で焼成する。なお、焼成温度の下限値は十分な焼結がおこなわれるならとくに限定するものではないが、本発明の組成範囲では８００℃を下回る温度では焼結が困難である。
【００３４】
導電体にＡｇを用いる場合など焼成温度をとくに低くしたいとき、所要組成の中のＡｌ_２Ｏ_３を除いた組成物を、１２００〜１５００℃にて溶融して急冷しガラス粉末としてから、このガラス粉末とＡｌ_２Ｏ_３の粉末とをバインダーを加えて混錬してグリーンシートとすればよい。このようにすれば、焼成温度は９２０℃以下で焼結が可能となる。
【００３５】
また、各素材原料には不純物が含まれるが、その含有量は５質量％以下であれば単一の化合物として取り扱っても効果は変わらない。原料素材としては、たとえばＣａＯ、Ｒ_２Ｏなど単独の酸化物の形では大気中にて不安定な場合は、炭酸塩や炭酸水素塩などを用い、Ｂ_２Ｏ_３に対しＢＮを用いるなど、混合開始時には別の形の素材としてもよい。
【００３６】
磁器組成物の焼成は、導電体にＣｕを用いる基板の場合、不活性雰囲気中での焼成が必要であるが、ＡｇやＡｕが導電体の場合は大気中でよい。さらに、基板または積層基板にて厳しい平坦度や高精度の回路パターンを要求されることがあり、この場合、拘束焼成法や加圧焼成法といわれる焼成方法が採用されるが、本発明の組成物はこのような焼成方法にも適している。
【００３７】
この拘束焼成法は、たとえば積層体の上下面にその目的物の焼成温度では焼結しないグリーンシートを圧着しておくことにより、焼成時の面方向の収縮を抑止する方法である。さらに応力を印加しながら焼成をおこなう方法を加圧焼成法と呼び、加圧力を調整することにより、面方向の収縮をより０に近くした焼結ができる。本発明の磁器組成物の場合、積層体の上下面にたとえばアルミナのグリ−ンシートを設置し、加圧しながら焼成すれば、焼成温度ではアルミナは焼結しないので、焼成後これらは完全に除去され、平坦度のすぐれた高精度の積層基板を得ることができる。
【００３８】
【実施例】
〔実施例１〕
酸化物の形として表１および表２に示す組成となる、Ａｌ_２Ｏ_３、ＳｉＯ_２，Ｂ_２Ｏ_３、ＣａＯ、ＺｎＯ、ＭｎＯ、Ｒ_２Ｏ（ＲはＬｉ、ＮａまたはＫを示す）、Ｌｎ_２Ｏ_３（ＬｎはＹ、ＬａまたはＮｄを示す）の原料を、水を加えてジルコニアボールを用いたボールミルにて２０時間湿式混合した後乾燥し、７５０℃にて３時間仮焼した。なお、原料としてのＣａＯ、およびＲ_２Ｏは、いずれも炭酸塩の形で用いた。
【００３９】
仮焼物はＸ線回折法にて焼成反応が起きていることを確認し、粉砕後バインダーとして１０質量％のＰＶＡ水溶液を添加して混錬造粒し、金型を用い９８ＭＰａの圧力にて焼成後の寸法が直径１５ｍｍ、高さ７，５ｍｍの円柱状となる試片を成形した。
【００４０】
これら成形品は大気中で焼成をおこなって特性測定用試片とした。各試料のこれら成形品の一部の試片を用い、あらかじめ８００〜１２００℃の温度範囲で試験的に焼成して、十分な緻密化に必要な温度を見出し、その温度を焼成温度として該当試料の全試片の焼成をおこなった。焼成時間はいずれも２時間である。
【００４１】
焼成後の円柱状焼結体は、底面を研磨し平滑にしてから両端短絡形誘電体共振器法により比誘電率ε_ｒおよびＱ（または誘電損失ｔａｎδ：Ｑ＝１／ｔａｎδ）を測定した。共振周波数の温度係数τ_ｆは、２５℃における共振周波数ｆ_０を基準として、温度を変えたときの変化率から求めた。これらの測定結果を併せて表１および表２に示す。
【００４２】
【表１】

【００４３】
【表２】

【００４４】
表１および表２の結果からわかるように、本発明で定める組成範囲の磁器組成物は、１０００℃以下の焼成温度で焼結が可能であり、比誘電率が低く、しかもＱ値が高くｆＱ値にして２００００以上とすぐれたものであり、その上、温度係数τ_ｆ値も±５０％以内と安定している。焼成温度を低くするだけであれば、ＣａＯ、ＺｎＯ、ＭｎＯあるいはＲ_２Ｏの比率を増せばよいが、比誘電率や高周波域におけるＱ値など誘電特性をすぐれてものにするには、さらにこれら組成の組み合わせや、Ｌｎ_２Ｏ_３の適量含有など、十分配慮しなければならないことがわかる。
【００４５】
〔実施例２〕
表３に示す本発明で定める組成範囲の磁器組成物を、Ａｌ_２Ｏ_３を除く他の成分は１４００℃にて溶融し水冷してガラス化した後、このガラス粉末とＡｌ_２Ｏ_３を粉末とを１０質量％のＰＶＡ水溶液バインダーを添加して混錬造粒した。この混錬物を実施例１と同様にして、円柱状試験片を作製し、焼成に必要な温度を調査し、焼結後誘電特性を測定した。
【００４６】
【表３】

【００４７】
結果を表３に合わせて示すが、焼成に必要な温度は９００℃以下で、実施例１における本発明例のほとんどのものを下回っており、Ａｇを導電体に用いて十分同時焼成が可能なものとなっている。また誘電特性も実施例１における本発明例の場合と同等のものが得られている。
【００４８】
【発明の効果】
本発明の磁器組成物は、比誘電率が低く高周波帯域における損失が小さく、温度依存性が小さい。また低い焼成温度でその特性を得ることができ、内部導体や電極としてＡｇ、Ａｕ、Ｃｕなど比抵抗は低いが融点の低い金属を使用することができる。このように、すぐれた高周波性能と相俟って、電子回路の高周波化、小型化、高密度化のための基板用等の用途に好適である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a dielectric porcelain composition suitable for electronic components and modules used in a high frequency range of several GHz to several tens of GHz.
[0002]
[Prior art]
In recent years, with the development of high-speed mass transmission communication of information and mobile communication, integrated circuits on substrates have not only been reduced in size and density, but also signals handled have frequencies of several GHz or even higher. Utilization is being studied, and a material suitable for such a high-frequency band is also demanded for a dielectric porcelain composition used as a substrate. The performance required for this porcelain composition is to have sufficient strength, a low relative dielectric constant ε _r in a high frequency band, a small dielectric loss tan δ, and a temperature change of the relative dielectric constant or a temperature of the resonance frequency. The change is small.
[0003]
Generally, the lower the relative dielectric constant of a substrate, the higher the signal propagation speed in a circuit. Therefore, it is desirable that the relative dielectric constant ε _r be as low as possible for high frequency band applications. Since the smaller the loss in signal transmission, the better, the dielectric loss must be small, that is, the Q value must be as high as possible. The function as a dielectric is used, for example, in a filter or a resonator. In this case, in order to operate stably with respect to a temperature change, the absolute value of the temperature coefficient τ _f of the resonance frequency is as small as possible. It is also important that the temperature dependence is small.
[0004]
Conventionally, as a ceramic composition multilayer substrate for integrated circuits, alumina having excellent heat resistance and insulation properties, high withstand voltage and low dielectric constant is often used, and with the increase in circuit density, conductive paste is applied to green sheets. A method of printing, laminating and firing all at once has been developed. Since the sintering temperature of alumina is as high as 1500 to 1600 ° C., a high melting point metal such as W or Mo that can be sintered at this temperature is used as a conductive material for forming a circuit inside the multilayer substrate.
[0005]
However, as the frequency used for the circuit increases, the substrate material is required to have a lower relative dielectric constant than alumina, and as the circuit becomes finer, the conductor used also reduces the conductive loss. Therefore, a device having a lower electric resistance is required. The metal conductors having low electric resistance are Ag, Au, and Cu, all of which have a lower melting point than W and Mo, and if a multilayer substrate is to be manufactured by simultaneous firing, the porcelain composition will be made of these metals. Must be able to be fired at 1000 ° C. or lower, which is lower than the melting point.
[0006]
For this purpose, various low-temperature sintering porcelain compositions have been developed in which an oxide-based refractory such as alumina is mixed as a filler into glass having a low melting point. Generally, glass has a lower dielectric constant than oxide refractories such as alumina. Therefore, it is conceivable that glass is laminated to form a multilayer substrate, but glass generally has a large dielectric loss, a large change in shape due to softening during firing, and it is difficult to obtain required dimensional accuracy of a circuit, and strength is also high. Not enough.
[0007]
On the other hand, when a filler is mixed with glass, a porcelain composition with a small change in shape and a small structure at a low temperature and excellent strength is obtained.If a filler having a small dielectric loss is selected, good properties can be obtained. A low-temperature sintered ceramic composition can be obtained.
[0008]
For example, Japanese Patent Publication No. 3-53269 discloses that a glass of CaO—SiO ₂ —Al ₂ O ₃ —B ₂ O _{3 is} mixed at 50-35% by mass with Al ₂ O ₃ as a filler and fired at 800-1000 ° C. An invention of a low-temperature fired porcelain composition substrate is disclosed. However, in the present invention, only the loss at 1 MHz is shown, and the characteristics in a high frequency range exceeding several GHz are not clear.
[0009]
Also, U.S. Pat. No. 6147019 discloses 50 to 75% by mass of Al ₂ O ₃ refractory, 50 to 67% by mol% of B ₂ O ₃ , 20 to 50% of CaO, Ln ₂ O ₃ (Ln is a rare earth element): _{2~15%, M} 2 O _(M is an alkali metal _{_{element): 0~6%, Al 2 O}} 3: was mixed with 0-10% of the glass, of using co-firing the Ag to the inner conductor The invention of a possible porcelain composition is disclosed.
[0010]
However, as a porcelain composition for a substrate, a module, or an electronic component, a material having better performance in a frequency band to be used is always required, and a material having high performance in a high frequency band is particularly demanded. In addition, as the circuit becomes finer, the substrate is required to have good flatness and high dimensional accuracy. For this purpose, a method of firing while applying pressure or constraining it has been developed. It is desirable that the porcelain composition be suitable for the method.
[0011]
[Problems to be solved by the invention]
An object of the present invention is to provide a low-temperature sintering capable of co-firing a conductor having high electric conductivity such as Ag, Au, and Cu, a low dielectric constant, a low loss in a high frequency band, and a low temperature dependency. An object of the present invention is to provide a dielectric ceramic composition.
[0012]
[Means for Solving the Problems]
The present inventors have proposed a low-temperature sintering used in a high frequency band of several GHz or more, in which a multilayer substrate can be manufactured by simultaneous firing using Ag, Au, or Cu as an internal conductor at a firing temperature of 1000 ° C. or lower. Various studies were conducted to improve the performance of the porcelain composition.
[0013]
As a ceramic composition for a substrate that can be sintered at a low temperature, there is a glass ceramic in which a refractory such as alumina, titania, or zirconia is used as a filler and a glass composition having a low softening point is mixed with the filler. In this case, the glass raw material is heated and melted at a high temperature, quenched to produce a glass powder, mixed with a refractory powder such as alumina as a filler, calcined and pulverized, and then formed into a predetermined shape and fired. The raw material requires multiple high-temperature heatings. On the other hand, if the usual ceramic synthesis method, that is, the required raw materials can be mixed, calcined, pulverized, molded and fired to obtain the required porcelain composition, the process can be simplified and the required energy can be reduced. It was thought that the manufacturing cost could be reduced.
[0014]
In addition, the demand for finer conductor wiring and through-holes and higher precision is becoming stricter due to the higher density of circuits in the laminated substrate, and flatness is pursued. On the other hand, there is a method in which the green sheet laminate is fired while being constrained by applying pressure, and shrinkage due to firing is limited only in the thickness direction, thereby improving the precision of the circuit shape and improving the flatness. It must be suitable for various firing methods.
[0015]
Characteristics required for application in a high-frequency range include a low dielectric constant, a small dielectric loss, and a small temperature dependence of the dielectric constant. These dielectric properties were measured by the dielectric resonance method (Hacky-Coleman method) using a cylindrical test piece with both ends short-circuited.
[0016]
First, in order to maintain strength as a substrate and obtain a dense porcelain composition, Al ₂ O ₃ is used as a main component, and glass forming components such as SiO ₂ , B ₂ O ₃ , and CaO are mixed. It was investigated whether low-temperature sintering at a sintering temperature of 1000 ° C. or less was possible by a normal ceramic synthesis method. As a result, the composition range in which the dielectric properties at high frequencies were good and the sintering temperature was low could be made clear, but firing at the intended low temperature range did not necessarily result in a sufficiently dense porcelain composition. I couldn't.
[0017]
Therefore, as a result of various investigations on oxide-based additives, addition of a small amount of ZnO, MnO, or R ₂ O (R: an alkali metal element of Li, Na, and K) lowers the sintering temperature without impairing the properties. I knew I could do it. It was also found that adding an oxide of a rare earth element Ln ₂ O ₃ (Ln: a rare earth element such as Y, La, or Nd) within a range that does not increase the sintering temperature has the effect of improving the fQ value. Was done.
[0018]
As described above, it has been found that low-temperature sintering of 1000 ° C. or less is possible by a normal ceramic synthesis method. However, when Ag having excellent electric conductivity is used for a conductor, the sintering temperature is set to the melting point of Ag of 961 ° C. Must be below. On the other hand, other materials except Al ₂ O ₃ are mixed and quenched to produce glass, powdered, mixed with Al ₂ O ₃ powder, kneaded, molded, and fired. From the results, it was confirmed that a porcelain composition having the same composition and a similar high-frequency range dielectric performance could be obtained at a lower firing temperature.
[0019]
Examination of the structure of the porcelain composition obtained by sintering and having the above-mentioned excellent high-frequency characteristics shows that the crystal of glass such as LnBO ₃ , Zn ₂ SiO ₄ , CaAl ₂ O ₈ , CaAl ₂ B ₂ O ₇ and glass The crystal phase of Al ₂ O ₃ is bonded by the mixed phase, and it is considered that such a state in which the crystal and the glass are mixed provides excellent dielectric properties in a high frequency range.
[0020]
Based on the above examination results, target limits were set for the firing temperature, the Q value, the dielectric constant, the temperature characteristics, and the like, and the compositions and condition ranges satisfying all of them were clarified, thereby completing the present invention. The gist of the present invention is as follows.
[0021]
(1) Al ₂ O ₃ : 40 to 65% in terms of mol% of components expressed as oxides, 15 to 35% in total of one or both of SiO ₂ and B ₂ O ₃ , CaO: 10~20%, ZnO: 0.1~14%, MnO: 0~2% and _R 2 O (R is Li, one or more of Na and K): characterized in that it is a 0-2% Low dielectric constant porcelain composition for high frequency components.
[0022]
(2) Al ₂ O ₃ : 40 to 65% in terms of mol% of components expressed as oxides, 15 to 35% in total of one or both of SiO ₂ and B ₂ O ₃ , CaO: 10~20%, ZnO: 0.1~14%, MnO: 0~2%, R 2 O (R is Li, Na or K): 0~2%, and _Ln 2 _O 3 _(Ln is Y, La And one or more rare earth elements such as Nd): 0.1 to 2%.
[0023]
(3) After firing, powders of raw materials having the composition ratio according to claim 1 or 2 are mixed, and the mixture is calcined and then pulverized into a powder. A binder is added to the powder and kneaded to form a desired shape. A method for producing a low dielectric constant porcelain composition for a high-frequency component, characterized by firing at 800 to 1000 ° C.
[0024]
(4) After firing, the raw material having a composition excluding Al ₂ O ₃ from the composition ratio described in claim 1 or 2 is heated to a temperature of 1000 ° C. or more, vitrified, rapidly quenched to form a powder, and this powder is formed. A low dielectric constant porcelain composition for a high-frequency component, comprising: mixing a powder of Al ₂ O ₃ with a binder; adding a binder; kneading the mixture; shaping the mixture into a required shape; and firing at 800 to 920 ° C. Method.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
The porcelain composition of the present invention has the following composition when each component is represented in the form of an oxide.
[0026]
Al ₂ O ₃ : 40 to 65 mol%
Al ₂ O ₃ is necessary to maintain the strength of the porcelain composition. If the amount is less than 40 mol%, the transverse rupture strength of the porcelain composition is reduced, and it is difficult to maintain the shape during firing. However, when the content exceeds 65 mol%, sintering at a target low temperature cannot be performed. Therefore, it is set to 40 to 65 mol%, and more preferably 55 to 60 mol%.
[0027]
One or both of SiO ₂ and B ₂ O _{3 in} a total amount of 15 to 35 mol%
SiO ₂ and B ₂ O ₃ form glass and greatly contribute to lowering the sintering temperature of the porcelain composition. It is also necessary to form a crystal phase having an excellent Q value in a high frequency range. When the sum of any one or both is less than 15 mol%, low-temperature sintering at 1000 ° C. or less becomes difficult, and when it exceeds 35 mol%, the Q value decreases. More preferably, it is 25 to 30 mol%.
[0028]
CaO: 10 to 20 mol%
CaO forms a crystal phase with glass together with SiO ₂ , B ₂ O ₃ and Al ₂ O ₃ at a firing temperature of 1000 ° C. or lower. Further, there is an effect of reducing the temperature dependence of the dielectric constant. If it is less than 10 mol%, sintering at 1000 ° C. or less becomes difficult, and if it exceeds 20 mol%, the temperature change rate of the dielectric constant becomes large. More preferably, it is in the range of 12.5 to 17 mol%.
[0029]
ZnO: 0.1 to 14 mol%
ZnO has the effect of lowering the sintering temperature and has the effect of increasing the Q value. In order to obtain such an effect, it is necessary to contain 0.1 mol% or more. However, if the content is too large, Q is rather reduced, so that the content is limited to 14 mol%. More preferably, it is 0.1 to 5 mol%.
[0030]
MnO: 0 to 2 mol%
MnO may not be contained, but when it is contained, it has the effect of lowering the sintering temperature and increasing the Q value as in ZnO. In order to obtain the effect, the content is desirably 0.1 mol% or more. However, if the content is too large, the Q value is reduced. Therefore, the content is desirably 2 mol% or less.
[0031]
R ₂ O (R is one or more of Li, Na and K): 0 to 2 mol%
The oxide R ₂ O of the alkali metal elements Li, Na and K has an effect of forming glass, and has a great effect on lowering the sintering temperature. These may not be contained, but if they are contained in order to obtain the effect, the content is preferably 0.1 mol% or more. However, if the amount is too large, the Q value is greatly reduced. Therefore, the content is limited to 2 mol%, but preferably 0.5 mol% or less.
[0032]
Ln ₂ O ₃ (Ln is at least one of rare earth elements such as Y, La and Nd): 0 to 2 mol%
Ln ₂ O ₃ does not have to be added, but has an effect of improving the Q value in a high frequency range, and is preferably contained when it is desired to improve the Q value. In order to obtain this effect, the content is preferably 0.1 mol% or more. However, if it is contained too much, sintering at a low temperature becomes difficult and the rate of temperature change of the dielectric constant increases. If this rare earth element oxide is added alone, its content effect may not be sufficiently exhibited in the case of low-temperature sintering. Therefore, Ln ₂ O ₃ : 45 to 50 mol% and B ₂ O ₃ : 50 to 55 mol% The mixture may be synthesized by sintering or the like, and added in the form of a powder. The amount of B ₂ O ₃ added at this time must be within a range where the total amount of SiO ₂ and B ₂ O ₃ is 15 to 35 mol%.
[0033]
As a method for producing the porcelain composition, a normal ceramic synthesis method is applied. That is, powders such as oxides serving as raw materials are mixed in required amounts, for example, first calcined at a temperature of about 700 to 800 ° C. for 1 to 5 hours, and the calcined product is wet-pulverized and dried, and then a binder is added. After kneading and shaping into a required substrate shape, that is, forming a green sheet and printing conductor circuits, the layers are laminated, and then fired at a temperature of 1000 ° C. or less. The lower limit of the firing temperature is not particularly limited as long as sufficient sintering is performed, but sintering is difficult at a temperature lower than 800 ° C. in the composition range of the present invention.
[0034]
When it is desired to lower the firing temperature particularly when Ag is used as the conductor, the composition excluding Al ₂ O ₃ in the required composition is melted at 1200 to 1500 ° C. and quenched to form a glass powder. A green sheet may be formed by kneading the powder and the Al ₂ O ₃ powder together with a binder. In this case, sintering can be performed at a firing temperature of 920 ° C. or less.
[0035]
In addition, although each raw material contains impurities, if the content is 5% by mass or less, the effect does not change even if handled as a single compound. As a raw material, for example, when it is unstable in the atmosphere in the form of a single oxide such as CaO or R ₂ O, a carbonate or a hydrogen carbonate is used, and BN is used for B ₂ O ₃ . At the start of mixing, the material may be of another shape.
[0036]
The sintering of the porcelain composition requires sintering in an inert atmosphere in the case of a substrate using Cu as a conductor, but may be performed in the air when Ag or Au is a conductor. Furthermore, a strict flatness and a high-precision circuit pattern may be required for a substrate or a laminated substrate. In this case, a firing method called a constrained firing method or a pressure firing method is employed. The article is also suitable for such a firing method.
[0037]
In this constrained firing method, for example, a green sheet that is not sintered at the firing temperature of the target object is pressed on the upper and lower surfaces of the laminate to suppress shrinkage in the surface direction during firing. Furthermore, a method of performing sintering while applying stress is called a pressure sintering method, and by adjusting the pressing force, sintering with shrinkage in the plane direction closer to zero can be performed. In the case of the porcelain composition of the present invention, for example, if green sheets of alumina are placed on the upper and lower surfaces of the laminate and fired while pressing, alumina is not sintered at the firing temperature, and these are completely removed after firing. A highly accurate laminated substrate having excellent flatness can be obtained.
[0038]
【Example】
[Example 1]
Al ₂ O ₃ , SiO ₂ , B ₂ O ₃ , CaO, ZnO, MnO, R ₂ O (R represents Li, Na or K) having the composition shown in Table 1 and Table 2 in the form of the oxide; A raw material of Ln ₂ O ₃ (Ln represents Y, La or Nd) was wet-mixed in a ball mill using zirconia balls for 20 hours after adding water, dried, and calcined at 750 ° C. for 3 hours. Note that CaO and R ₂ O as raw materials were both used in the form of carbonate.
[0039]
The calcined product was confirmed to have undergone a sintering reaction by an X-ray diffraction method. After pulverization, a 10% by mass aqueous solution of PVA was added as a binder, kneaded and granulated, and baked using a mold at a pressure of 98 MPa. A specimen having a cylindrical shape having a diameter of 15 mm and a height of 7.5 mm was formed.
[0040]
These molded articles were fired in the air to obtain specimens for measuring characteristics. Using a sample of a part of these molded products of each sample, test firing is performed in advance in a temperature range of 800 to 1200 ° C., and a temperature necessary for sufficient densification is found. Were fired. Each firing time is 2 hours.
[0041]
After firing, the cylindrical sintered body was polished and smoothed on the bottom surface, and then measured for the relative permittivity ε _r and Q (or dielectric loss tan δ: Q = 1 / tan δ) by a double-ended short-circuit type dielectric resonator method. The temperature coefficient τ _f of the resonance frequency was determined from the rate of change when the temperature was changed with reference to the resonance frequency f ₀ at 25 ° C. Tables 1 and 2 also show the results of these measurements.
[0042]
[Table 1]

[0043]
[Table 2]

[0044]
As can be seen from the results of Tables 1 and 2, the porcelain composition having the composition range defined by the present invention can be sintered at a firing temperature of 1000 ° C. or lower, has a low relative dielectric constant, and has a high Q value and fQ The value is as high as 20,000 or more, and the temperature coefficient τ _f is also stable within ± 50%. If only the firing temperature is lowered, the ratio of CaO, ZnO, MnO or R ₂ O may be increased. However, in order to improve the dielectric properties such as the relative dielectric constant and the Q value in a high frequency range, these are further increased. It is understood that sufficient consideration must be given to the combination of the composition and the proper content of Ln ₂ O ₃ .
[0045]
[Example 2]
The ceramic composition of the composition range specified by the present invention shown in Table 3, after vitrifying the other components except Al ₂ O ₃ is water-cooled melted at 1400 ° C., the powder the glass powder and the Al ₂ O ₃ And 10% by mass of a PVA aqueous solution binder were added and kneaded and granulated. A columnar test piece was prepared from the kneaded material in the same manner as in Example 1, the temperature required for firing was investigated, and the dielectric properties were measured after sintering.
[0046]
[Table 3]

[0047]
The results are shown in Table 3. The temperature required for firing is 900 ° C. or lower, which is lower than most of the examples of the present invention in Example 1, and it is possible to sufficiently simultaneously fire using Ag as a conductor. It has become something. In addition, the same dielectric characteristics as those of the example of the present invention in Example 1 are obtained.
[0048]
【The invention's effect】
The porcelain composition of the present invention has a low relative dielectric constant, a small loss in a high frequency band, and a small temperature dependency. Further, the characteristics can be obtained at a low firing temperature, and metals having a low specific resistance but a low melting point, such as Ag, Au, and Cu, can be used as the internal conductors and electrodes. Thus, in combination with the excellent high-frequency performance, it is suitable for applications such as a substrate for increasing the frequency, reducing the size, and increasing the density of an electronic circuit.

Claims

Al ₂ O ₃ : 40 to 65% in terms of mol% of components represented as oxides, 15 to 35% in total of one or both of SiO ₂ and B ₂ O ₃ , CaO: 10 to 20 %, ZnO: 0.1 to 14%, MnO: 0 to 2%, and R ₂ O (R is one or more of Li, Na and K): 0 to 2% Low dielectric constant porcelain composition.

Al ₂ O ₃ : 40 to 65% in terms of mol% of components represented as oxides, 15 to 35% in total of one or both of SiO ₂ and B ₂ O ₃ , CaO: 10 to 20 %, ZnO: 0.1~14%, MnO : 0~2%, R 2 O (R is Li, one or more of Na and K): 0~2%, and _Ln 2 _O 3 _(Ln is Y, La And one or more rare earth elements such as Nd): 0.1 to 2%.

After firing, powders of the raw materials having the composition ratio according to claim 1 or 2 are mixed, and the mixture is calcined and then pulverized into a powder. A binder is added to the powder and kneaded to form a desired shape. A method for producing a low-dielectric-constant porcelain composition for high-frequency components, characterized by firing at 1000 ° C.

After firing, a raw material having a composition excluding Al ₂ O ₃ from the composition ratio according to claim 1 or 2 is heated to a temperature of 1000 ° C. or more to be vitrified, rapidly quenched to form a powder, and this powder and Al ₂ A method for producing a low dielectric constant porcelain composition for a high-frequency component, comprising mixing a powder of O ₃ , adding a binder, kneading the mixture, shaping the mixture into a required shape, and firing at 800 to 920 ° C.