JP4029207B2

JP4029207B2 - Manufacturing method of ceramic multilayer substrate

Info

Publication number: JP4029207B2
Application number: JP2002060034A
Authority: JP
Inventors: 聡足立; 順三福田
Original assignee: Murata Manufacturing Co Ltd
Current assignee: Murata Manufacturing Co Ltd
Priority date: 2002-03-06
Filing date: 2002-03-06
Publication date: 2008-01-09
Anticipated expiration: 2022-03-06
Also published as: JP2003258424A

Description

【０００１】
【発明の属する技術分野】
本発明は、予め焼成したセラミック基板に未焼成のセラミックグリーンシートを積層してセラミック多層基板を製造するセラミック多層基板の製造方法に関するものである。
【０００２】
【従来の技術】
一般に、セラミック多層基板は、グリーンシート積層法で製造されることが多い。このグリーンシート積層法は、複数枚のセラミックグリーンシートにビアホールを形成した後、各セラミックグリーンシートのビアホールに導体ペーストを充填してビア導体を形成すると共に、各セラミックグリーンシートに導体ペーストで配線パターンを印刷する。その後、これら複数枚のセラミックグリーンシートを積層・熱圧着して生基板を作製した後、この生基板を焼成してセラミック多層基板を製造する。
【０００３】
【発明が解決しようとする課題】
しかし、生基板を焼成する過程で、１５〜３０％程度の焼成収縮が発生するため、基板の寸法精度を管理することが難しく、しかも、キャビティ等の凹凸のある多層基板では、基板両面の収縮応力が不均一になるため、焼成基板に反りが発生しやすく、特にキャビティの底面部の反りが大きくなるという欠点もあった。
【０００４】
また、絶縁性のセラミックグリーンシートと、誘電体、磁性体等の異種材料のセラミックグリーンシートとを積層して複合セラミック多層基板を焼成する場合は、両者の焼結温度を一致させ、且つ、両者の焼成収縮挙動の違いを少なくして層間剥離を防止する必要があるため、材料の選択の幅が非常に狭く、設計の自由度が非常に狭いという欠点がある。
【０００５】
近年、基板の焼成収縮を小さくして基板寸法精度を向上させる焼成方法として、特開２００１−２６７７４３号公報に示すように、焼成済みのアルミナ基板上に、予め配線パターンを印刷した未焼成のセラミックグリーンシートを積層して熱圧着し、これを焼成してセラミック多層基板を製造することが提案されている。この焼成方法は、セラミックグリーンシートの焼成収縮を焼成済みのアルミナ基板で抑えることで、基板全体の焼成収縮を小さくしようとするものである。
【０００６】
しかし、セラミックグリーンシートの焼成収縮力は大きいため、セラミックグリーンシートの焼成収縮をその片面から焼成済みアルミナ基板のみで抑えようとしても十分に抑えることができない。その結果、セラミックグリーンシートの焼成層と焼成済みのアルミナ基板との間に剥がれが発生したり、セラミックグリーンシートの焼成層にクラックが発生したり、基板の反りが発生することがあり、製品の歩留まりが悪いという欠点がある。
【０００７】
また、基板の焼成収縮を小さくして基板寸法精度を向上させる効果の大きい焼成方法として、例えば特表平５−５０３４９８号公報や特開平９−９２９８３号公報に示すように、加圧焼成法が開発されている。この加圧焼成法は、焼成前の低温焼成セラミック基板（以下「生基板」という）の両面に、低温焼成セラミックの焼結温度（８００〜１０００℃）では焼結しない拘束用アルミナグリーンシートを積層し、この状態で、該生基板を加圧しながら、８００〜１０００℃で焼成した後、焼成基板の両面から拘束用アルミナグリーンシートの残存物をブラスト処理等で取り除いて低温焼成セラミック基板を製造するものである。
【０００８】
しかし、キャビティ付きの低温焼成セラミック基板を上述した加圧焼成法で焼成すると、拘束用アルミナグリーンシートを介してキャビティの領域に加わる加圧力がキャビティ周縁に集中的に作用し、キャビティの底面には加圧力が全く作用しないため、キャビティの底面部が凸状に反ってしまい、キャビティの寸法精度を確保できないという欠点がある。
【０００９】
これら従来の欠点を解消するために、本出願人は、特願２００１−３５７６９２号（平成１３年１１月２２日出願）の明細書に記載されているように、予め焼成したセラミック基板（以下「焼成済み基板」という）の片面又は両面に、該焼成済み基板の焼結温度とほぼ同一温度又はそれよりも低い温度で焼結する１枚又は複数枚の未焼成のセラミックグリーンシートを積層圧着して積層体を作製し、この積層体の両面に、前記未焼成のセラミックグリーンシートの焼結温度では焼結しない拘束用グリーンシートを積層して、拘束焼成（加圧焼成又は無加圧焼成）するという、新たな製造技術を開発中である。
【００１０】
この製造技術の開発中に、焼成済み基板に未焼成のセラミックグリーンシートを積層してその積層体を２枚の加圧板間に挟み込んで圧着する工程で、圧着時の加圧力により焼成済み基板が割れることがあり、これが歩留りを低下させる原因となることが判明した。
【００１１】
そこで、本発明の目的は、焼成済み基板と未焼成のセラミックグリーンシートとの積層体を拘束焼成してセラミック多層基板を製造する方法において、焼成済み基板に未焼成のセラミックグリーンシートを圧着する工程で焼成済み基板が割れることを防止できて、歩留りを向上させることができるセラミック多層基板の製造方法を提供することである。
【００１２】
【課題を解決するための手段】
上記目的を達成するために、本発明の請求項１，２のセラミック多層基板の製造方法は、焼成済み基板に未焼成のセラミックグリーンシートを積層圧着して積層体を作製した後、この積層体の両面に拘束用グリーンシートを積層圧着し、或は、未焼成のセラミックグリーンシートの積層圧着と拘束用グリーンシートの積層圧着とを同時に行い、拘束焼成（加圧焼成又は無加圧焼成）するようにしたところに第１の特徴があり、更に、積層体作製工程で焼成済み基板に圧着する未焼成のセラミックグリーンシートを、その圧着時の厚み変化量（複数枚の未焼成のセラミックグリーンシートを同時に圧着する場合はそれらの合計厚み変化量、また、未焼成のセラミックグリーンシートと拘束用グリーンシートとを同時に圧着する場合はそれらの合計厚み変化量）が焼成済み基板の凹凸による最大厚み差以上となるように形成するところに第２の特徴がある。
【００１３】
本発明の第１の特徴によれば、拘束焼成時に未焼成のセラミックグリーンシートのＸ・Ｙ方向の焼成収縮、反り、変形がその両面側から拘束用グリーンシートと焼成済み基板とによってほぼ均等に抑えられ、寸法精度が良く且つ層間剥離や反り等のないセラミック多層基板を製造することができる。しかも、焼成済み基板と未焼成のセラミックグリーンシートとの間の焼結温度の相違や焼成収縮特性の相違等は問題とならないため、セラミック多層基板の各層を形成するセラミック材料の焼結温度、焼成収縮特性等に対する材料選択の自由度を大幅に拡大することができ、従来の製造方法では製造が困難であった構成のセラミック多層基板を、層間剥離や反り等がなく、寸法精度良く製造できる。
【００１４】
前述したように、この製造技術の開発中に、焼成済み基板に未焼成のセラミックグリーンシートを積層してその積層体を２枚の加圧板間に挟み込んで圧着する工程で、圧着時の加圧力により焼成済み基板が割れることがあることが判明した。本発明者は、この原因を調べるために、圧着時に割れた焼成済み基板を検査したところ、焼成済み基板の表面は完全な平坦面ではなく、焼成時の収縮挙動等によって僅かながら基板面に凹凸（うねり）が生じているのが確認された（図４参照）。このような凹凸のある焼成済み基板は、圧着時に焼成済み基板の凸反り部分が加圧板に密着せず、浮き上がった状態になると共に、圧着時に未焼成のセラミックグリーンシートを介して焼成済み基板に作用する加圧力が基板面全体に一様に作用せず、焼成済み基板の凸反り部分（加圧板から浮き上がった部分）に他の部分よりも大きな加圧力が作用するため、焼成済み基板の凸反り部分がその加圧力に耐えられずに割れてしまうものと考えられる。
【００１５】
そこで、本発明の第２の特徴は、上述した圧着時の焼成済み基板の割れを防止するために、焼成済み基板に圧着する未焼成のセラミックグリーンシートを、その圧着時の厚み変化量（複数枚の未焼成のセラミックグリーンシートを同時に圧着する場合はそれらの合計厚み変化量）が焼成済み基板の凹凸による最大厚み差以上となるように形成するようにしたものである。このようにすれば、圧着時に焼成済み基板の凹凸に応じて未焼成のセラミックグリーンシートが柔軟に変形して、焼成済み基板の凹凸による最大厚み差を未焼成のセラミックグリーンシートの厚み変化量で吸収することができるため、圧着時の加圧力が焼成済み基板の凸反り部分に集中的に作用することを防止でき、焼成済み基板に作用する加圧力を基板面全体に分散させることができる。これにより、圧着時の加圧力による焼成済み基板の割れを防止できて、歩留りを向上させることができる。
【００１６】
この場合、請求項３のように、未焼成のセラミックグリーンシートの圧着時の厚み変化量の調整は、セラミックグリーンシートの厚みの調整、セラミックグリーンシートの成形材料の組成・配合比の調整、成形材料中のセラミック粒子の粒径の調整、成形材料の空隙率の調整のうちの少なくとも１つによって行うようにすれば良い。これらの調整法の中から、基板仕様等に応じて適当な調整法を選択すれば良い。
【００１７】
この場合、請求項４のように、焼成済み基板と未焼成のセラミックグリーンシートとを同種のセラミック材料で形成しても良く、或は、請求項４のように、焼成済み基板と未焼成のセラミックグリーンシートとを異種のセラミック材料で形成し、未焼成のセラミックグリーンシートの焼結温度が焼成済み基板の焼結温度以下となるようにセラミック材料を選択するようにしても良い。請求項３のように、焼成済み基板と未焼成のセラミックグリーンシートとを同種のセラミック材料で形成すれば、全層の絶縁特性等の電気的特性を均等にした単一のセラミック組成のセラミック多層基板を製造することができる。また、請求項５のように、焼成済み基板と未焼成のセラミックグリーンシートとを異種のセラミック材料で形成すれば、従来の製造方法では製造が困難であった様々な機能材料を内蔵する複合セラミック多層基板を製造することができる。
【００１８】
この場合、請求項６のように、未焼成のセラミックグリーンシートは、１０００℃以下で焼成する低温焼成セラミック材料により形成したものを用いると良い。このようにすれば、拘束用グリーンシートとして、アルミナグリーンシート等の比較的安価で且つ機械的強度に優れたセラミックを使用することができると共に、未焼成のセラミックグリーンシートに印刷する配線導体として、Ａｇ系、Ａｕ系、Ｃｕ系等の電気抵抗値の小さい電気的特性に優れた低融点金属を用いることができる。
【００１９】
また、請求項７のように、キャビティ付きのセラミック多層基板を製造する場合は、焼成済み基板をキャビティとなる部分の底面部に位置させ、該焼成済み基板に積層する未焼成のセラミックグリーンシートには、その積層前又は積層後にキャビティ形成用の開口部を形成するようにすれば良い。ここで、積層前の未焼成のセラミックグリーンシートにキャビティ形成用の開口部を形成する場合は、パンチング加工等によってキャビティ形成用の開口部をビアホールの加工と同時に形成すれば良く、また、積層後の未焼成のセラミックグリーンシートにキャビティ形成用の開口部を形成する場合は、例えば感光性樹脂を含有させたセラミックグリーンシートを作製し、フォトリソグラフィ技術等を用いて、このセラミックグリーンシートにキャビティ形成用の開口部を形成すれば良い。請求項７のように、焼成済み基板をキャビティの底面部に位置させて、キャビティ付きのセラミック多層基板を拘束焼成すれば、キャビティの底面部が凸状に反ることはなく、しかも、拘束焼成によってキャビティの寸法精度を確保できる。
【００２０】
【発明の実施の形態】
［実施形態（１）］
以下、本発明を片面キャビティ付きのセラミック多層基板の製造方法に適用した実施形態（１）を図１乃至図４に基づいて説明する。
【００２１】
本実施形態（１）で製造する片面キャビティ付きセラミック多層基板１１は、図１（ｃ）、図３に示すように、予め焼成した焼成済み基板１２上に、１枚又は複数枚の未焼成の低温焼成セラミックグリーンシート１３を積層し、更に、その上に拘束焼成グリーンシート１５を積層して、８００〜１０００℃で拘束焼成（加圧焼成又は無加圧焼成）したものである。この片面キャビティ付きセラミック多層基板１１は、キャビティ１４の底面部に焼成済み基板１２が位置し、次のような工程を経て製造される。
【００２２】
まず、焼成済み基板１２を準備する。この焼成済み基板１２は、セラミック基板を焼成したものであり、単層基板又は多層基板のいずれであっても良い。また、この焼成済み基板１２を形成するセラミック材料は、絶縁性セラミック、誘電体セラミック、磁性体セラミック、圧電性セラミック、抵抗体付きのセラミックのいずれであっても良く、要は、低温焼成セラミックグリーンシート１３の焼結温度と同一温度又はそれよりも高い温度で焼結するセラミック材料を用いれば良い。また、焼成済み基板１２が多層基板の場合は、各層を同種のセラミックで形成しても良いし、同時焼成可能な異種のセラミックで形成した層が混在する構成としても良い。
【００２３】
この場合、絶縁性セラミックとは、基板の絶縁層を形成するのに用いるセラミックであり、例えば、低温焼成セラミック、アルミナ等の高温焼結性セラミックが挙げられる。焼成済み基板１２を低温焼成セラミックで形成する場合は、低温焼成セラミックグリーンシート１３と同種の低温焼成セラミックを用いても良く、勿論、低温焼成セラミックグリーンシート１３の焼結温度と同一温度又はそれよりも高い温度で焼結する他の種類の低温焼成セラミックを用いても良いことは言うまでもない。
【００２４】
また、焼成済み基板１２の表面に同時焼成又は後付けで厚膜導体やＲｕＯ₂系等の厚膜抵抗体を形成しても良い。更に、焼成済み基板１２の表面に厚膜抵抗体を形成する場合は、焼成済み基板１２に後述する低温焼成セラミックグリーンシート１３を積層する前に、該厚膜抵抗体をトリミングして抵抗値を調整するようにすると良い。
【００２５】
更に、低温焼成セラミックグリーンシート１３を準備する。このグリーンシート１３を形成する低温焼成セラミック材料としては、例えば、ＣａＯ−ＳｉＯ₂−Ａｌ₂Ｏ₃−Ｂ₂Ｏ₃系ガラス：５０〜６５重量％（好ましくは６０重量％）とアルミナ：５０〜３５重量％（好ましくは４０重量％）との混合物を用いると良い。この他、ＭｇＯ−ＳｉＯ₂−Ａｌ₂Ｏ₃−Ｂ₂Ｏ₃系ガラスとアルミナとの混合物、或は、ＳｉＯ₂−Ｂ₂Ｏ₃系ガラスとアルミナとの混合物、ＰｂＯ−ＳｉＯ₂−Ｂ₂Ｏ₃系ガラスとアルミナとの混合物、コージェライト系結晶化ガラス等の８００〜１０００℃で焼成できる低温焼成セラミック材料を用いても良い。
【００２６】
低温焼成セラミックグリーンシート１３は、上記組成の低温焼成セラミック材料にバインダー（例えば、アクリル系樹脂、ブチラール樹脂、ＰＶＡ等）、溶剤（例えばトルエン、キシレン、ブタノール等）及び可塑剤を配合して、十分に撹拌混合してスラリーを作製し、このスラリーを用いてドクターブレード法等でテープ成形したものである。
【００２７】
後述する積層体作製工程で、焼成済み基板１２上に低温焼成セラミックグリーンシート１３を圧着する際に、焼成済み基板１２の割れを防止するために、図４に示すように、低温焼成セラミックグリーンシート１３の圧着時の厚み変化量が焼成済み基板１２の凹凸による最大厚み差以上となるように形成する。焼成済み基板１２上に複数枚の低温焼成セラミックグリーンシート１３を同時に圧着する場合は複数枚の低温焼成セラミックグリーンシート１３の合計厚み変化量が焼成済み基板１２の凹凸による最大厚み差以上となるように形成する。ここで、焼成済み基板１２の凹凸による最大厚み差は、焼成済み基板１２を加圧板１０上に置いたときの焼成済み基板１２の最大厚み（基板面の最高点）と最小厚み（基板面の最低点）との差である。
【００２８】
低温焼成セラミックグリーンシート１３の圧着時の厚み変化量を調整する場合は、次の▲１▼〜▲４▼の調整法の中から基板仕様等に応じていずれか１つ又は２つ以上の調整法を選択すれば良い。
【００２９】
▲１▼低温焼成セラミックグリーンシート１３の厚みを調整する。低温焼成セラミックグリーンシート１３が厚くなるほど、圧着時の厚み変化量が大きくなる。
▲２▼低温焼成セラミックグリーンシート１３のセラミック材料の組成又は配合比を調整する。例えば、セラミック材料のバインダー樹脂の種類や配合量、可塑剤や溶剤の種類や配合量、セラミック粉末の種類や配合量を調整する。一般に、可塑剤の配合量が多くなるほど、低温焼成セラミックグリーンシート１３が柔らかくなり、圧着時の厚み変化量が大きくなる。
【００３０】
▲３▼低温焼成セラミックグリーンシート１３のセラミック材料中のセラミック粒子の粒径や凝集粒の砕け易さを調整する。
▲４▼低温焼成セラミックグリーンシート１３のセラミック材料の空隙率（空孔率）を調整する。この空隙率の調整は、セラミック材料（スラリー）中のボイド含有率を調整すれば良い。空隙率が大きくなるほど、圧着時の厚み変化量が大きくなる。
【００３１】
テープ成形した低温焼成セラミックグリーンシート１３を所定サイズに切断した後、該グリーンシート１３の所定位置に、キャビティ形成用の開口部１４ａとビアホール（図示せず）等をパンチング加工等により打ち抜き加工する。尚、焼成済み基板１２上に低温焼成セラミックグリーンシート１３を積層圧着した後に、フォトリソグラフィ技術を用いて低温焼成セラミックグリーンシート１３にキャビティ形成用の開口部１４ａを形成するようにしても良い。
【００３２】
この後、印刷工程に進み、低温焼成セラミックグリーンシート１３のビアホールに、Ａｇ、Ａｇ／Ｐｄ、Ａｕ、Ａｇ／Ｐｔ、Ｃｕ等の低融点金属の導体ペーストを充填する。更に、図３に示すように、焼成済み基板１２上に複数枚の低温焼成セラミックグリーンシート１３を積層する場合は、内層に積層される低温焼成セラミックグリーンシート１３に、Ａｇ、Ａｇ／Ｐｄ、Ａｕ、Ａｇ／Ｐｔ、Ｃｕ等の低融点金属の導体ペーストを使用して内層導体パターン（図示せず）をスクリーン印刷し、表層（最上層）の低温焼成セラミックグリーンシート１３には、表層導体パターン（図示せず）を同種の低融点金属の導体ペーストを使用してスクリーン印刷する。尚、表層導体パターンの印刷は、拘束焼成後に行っても良い。また、ビアホールや内層導体パターンが無い構造のセラミック多層基板を製造する場合は、上記印刷工程を省略すれば良い。
【００３３】
印刷工程後、積層体作製工程に進み、焼成済み基板１２上に１枚又は複数枚の低温焼成セラミックグリーンシート１３を積層し、更に、この積層体の両面に拘束用グリーンシート１５を積層して、この積層体を図４（ｂ）に示すように２枚の加圧板１０間に挟み込んで圧着する。この圧着の条件は、加圧力が０．１〜数１０ＭＰａ（好ましくは３〜１０ＭＰａ）、加熱温度が６０〜１５０℃（好ましくは８０〜１２０℃）である。
【００３４】
このように、焼成済み基板１２に対して低温焼成セラミックグリーンシート１３と拘束用グリーンシート１５とを同時に積層して圧着すれば、積層・圧着工程が１回で済むという利点があるが、本発明は、焼成済み基板１２に低温焼成セラミックグリーンシート１３のみを積層して圧着した後に、その積層体の両面に拘束用グリーンシート１５を積層して圧着するようにしても良い。
【００３５】
この場合、拘束焼成グリーンシート１５は、低温焼成セラミックの焼結温度（８００〜１０００℃）では焼結しない高温焼結性セラミック（例えばアルミナ、ジルコニア、マグネシア等）を用い、この高温焼結性セラミックの粉末にバインダー（例えばＰＶＢ、アクリル系、ニトロセルロース系等の樹脂）、溶剤（例えばトルエン、キシレン、ブタノール等）及び可塑剤を配合して、十分に撹拌混合してスラリーを作製し、このスラリーを用いてドクターブレード法等でテープ成形して拘束焼成グリーンシート１５を作製すれば良い。
【００３６】
その後、拘束用グリーンシート１５を積層した積層体を、アルミナ、ＳｉＣ等で形成した多孔質セッター板（図示せず）間に挟み込んで、０．１〜数１０ＭＰａ（好ましくは３〜１０ＭＰａ）の圧力で加圧しながら、低温焼成セラミックグリーンシート１３の焼結温度である８００〜１０００℃で焼成する。尚、無加圧で焼成しても良く、この場合は、拘束用グリーンシート１５の積層工程で、拘束用グリーンシート１５を低温焼成セラミックグリーンシート１３に熱圧着する必要がある。
【００３７】
この際、拘束用グリーンシート１５（アルミナ等の高温焼結性セラミック）は、１３００〜１６００℃程度に加熱しないと焼結しないので、８００〜１０００℃で焼成すれば、拘束用グリーンシート１５は未焼結のまま残される。但し、焼成の過程で、拘束用グリーンシート１５中のバインダー等の有機物が熱分解して飛散してセラミック粉体として残る。
【００３８】
焼成後、焼成基板１１の両面に付着した拘束用グリーンシート１５の残存物（セラミック粉体）をブラスト処理、バフ研磨等により除去する。これにより、片面キャビティ付きのセラミック多層基板１１の製造が完了する。
【００３９】
ところで、図４に示すように、焼成済み基板１２の表面は完全な平坦面ではなく、焼成時の収縮挙動等によって僅かながら基板面に凹凸（うねり）が生じている。尚、図４に図示された焼成済み基板１２の凹凸は説明のために誇張して示されており、焼成済み基板１２の最大厚み差は、一般的に、数μｍ〜数１０μｍ程度である。
【００４０】
このような凹凸のある焼成済み基板１２は、圧着時に焼成済み基板１２の凸反り部分が盛り上がった状態になるため、焼成済み基板１２の凸反り部分（加圧板１０から盛り上がった部分）に大きな加圧力が作用すると、焼成済み基板１２の凸反り部分がその加圧力に耐えられずに割れてしまうことがある。
【００４１】
焼成済み基板１２に低温焼成セラミックグリーンシート１３と拘束用グリーンシート１５を同時に圧着する際に、両グリーンシート１３，１５の圧着時の厚み変化量が少ないと、焼成済み基板１２の凹凸による最大厚み差を両グリーンシート１３，１５の厚み変化量で吸収できないため、圧着時に低温焼成セラミックグリーンシート１３を介して焼成済み基板１２に作用する加圧力が基板面全体に一様に作用せず、焼成済み基板１２の凸反り部分（盛り上がった部分）に他の部分よりも大きな加圧力が作用するようになる。その結果、焼成済み基板１２の凸反り部分がその加圧力に耐えられずに割れてしまう現象が発生する。
【００４２】
この対策として、本実施形態（１）では、両グリーンシート１３，１５の圧着時の合計厚み変化量（複数枚の低温焼成セラミックグリーンシート１３と拘束用グリーンシート１５を同時に圧着する場合はそれらの合計厚み変化量）が焼成済み基板１２の凹凸による最大厚み差以上となるように形成する。このようにすれば、圧着時に焼成済み基板１２の凹凸に応じて両グリーンシート１３，１５が柔軟に変形して、焼成済み基板１２の凹凸による最大厚み差を両グリーンシート１３，１５の厚み変化量で吸収することができるため、圧着時の加圧力が焼成済み基板１２の凸反り部分に集中的に作用することを防止でき、焼成済み基板１２に作用する加圧力を基板面全体に分散させることができる。これにより、圧着時の加圧力による焼成済み基板１２の割れを防止できて、歩留りを向上させることができる。
【００４３】
尚、前述したように、本発明は、焼成済み基板１２に低温焼成セラミックグリーンシート１３のみを積層して圧着した後に、その積層体の両面に拘束用グリーンシート１５を積層して圧着するようにしても良く、この場合には、低温焼成セラミックグリーンシート１３の圧着時の厚み変化量（複数枚の低温焼成セラミックグリーンシート１３を同時に圧着する場合はそれらの合計厚み変化量）が焼成済み基板１２の凹凸による最大厚み差以上となるように形成すれば、本実施形態（１）と同様の効果を得ることができる。
【００４４】
また、本実施形態（１）では、焼成済み基板１２と未焼成の低温焼成セラミックグリーンシート１３との積層体に拘束用グリーンシート１５を積層して拘束焼成（加圧焼成又は無加圧焼成）するようにしたので、拘束焼成時に未焼成の低温焼成セラミックグリーンシート１３の焼成収縮、反り、変形がその両面側から拘束用グリーンシート１５と焼成済み基板１２とによってほぼ均等に抑えられ、層間剥離や反り等のないセラミック多層基板１１を製造することができる。
【００４５】
また、本実施形態（１）のように、キャビティ１４付きのセラミック多層基板１１を製造する場合は、焼成済み基板１２をキャビティ１４の底面部に位置させて拘束焼成すれば、キャビティ１４の底面部が凸状に反ることはなく、しかも、拘束焼成によってキャビティ１４の寸法精度を確保でき、品質の優れたキャビティ１４付きのセラミック多層基板１１を製造することができる。このため、キャビティ１４の底面部に半導体のベアチップをフリップチップ実装する場合でも、キャビティ１４の底面部に反りがないために、ベアチップとキャビティ１４の底面部の導通パッドとの接合を精度良く行うことができ、フリップチップ実装の信頼性を向上することができる。
【００４６】
また、焼成済み基板１２と未焼成の低温焼成セラミックグリーンシート１３との間の焼結温度の相違や焼成収縮特性の相違等は問題とならないため、セラミック多層基板１１の各層を形成するセラミック材料の焼結温度、焼成収縮特性等に対する材料選択の自由度を大幅に拡大することができ、従来の製造方法では製造が困難であった構成のセラミック多層基板１１を、層間剥離や反り等がなく、寸法精度良く製造できる。
【００４７】
【実施例】
本発明者は、焼成済み基板１２の凹凸による最大厚み差と低温焼成セラミックグリーンシート１３の圧着時の厚み変化量を調整したサンプルＮｏ．１〜９を作製して、圧着時の焼成済み基板１２の割れの有無を検査する試験を行ったので、その試験結果を次の表１に示す。
【００４８】
【表１】

【００４９】
この試験に用いた焼成済み基板と未焼成の低温焼成セラミックグリーンシートは、共に、ＣａＯ−ＳｉＯ₂−Ａｌ₂Ｏ₃−Ｂ₂Ｏ₃系ガラス：６０重量％と、アルミナ：４０重量％との混合物からなる低温焼成セラミックである。低温焼成セラミックグリーンシートの圧着時の厚み変化量の調整は、可塑剤の配合量の調整やシート厚みの調整等によって行った。
【００５０】
この試験では、９個のサンプルＮｏ．１〜９について、圧着条件を加圧力：５ＭＰａ、加熱温度：１００℃に設定して、焼成済み基板上に１枚の低温焼成セラミックグリーンシートと拘束用グリーンシート（アルミナグリーンシート）とを同時に積層圧着して、焼成済み基板の割れの有無を検査した。
【００５１】
尚、焼成済み基板の最大厚み差の測定方法は、焼成済み基板を平板上に置いて焼成済み基板の最大厚み（基板面の最高点）と最小厚み（基板面の最低点）を測定し、その最大厚みと最小厚みとの差を最大厚み差として求めた。また、低温焼成セラミックグリーンシートと拘束用グリーンシートの圧着時の合計厚み変化量の測定方法は、低温焼成セラミックグリーンシートと拘束用グリーンシートとの積層体を加圧板間に挟み込んで、試験時の圧着条件と同じ条件で加熱しながら加圧して両グリーンシートの合計厚み変化量を測定した。
【００５２】
表１の試験結果によれば、両グリーンシートの圧着時の合計厚み変化量が焼成済み基板の最大厚み差よりも小さいサンプルＮｏ．３、６、９は、圧着時の加圧力で焼成済み基板の割れが発生した。
【００５３】
これに対して、両グリーンシートの圧着時の合計厚み変化量が焼成済み基板の最大厚み差よりも大きいサンプルＮｏ．１、２、４、５、７、８は、圧着後の検査でも、焼成済み基板に割れが無かった。
【００５４】
この試験結果から、両グリーンシートの圧着時の合計厚み変化量が焼成済み基板の最大厚み差以上であれば、圧着時の加圧力による焼成済み基板の割れを防止できることが確認できた。
【００５５】
［実施形態（２）］
前記実施形態（１）では、焼成済み基板１２の片面のみに低温焼成セラミックグリーンシート１３を積層したが、図５に示す本発明の実施形態（２）のように、焼成済み基板１２の両面に、それぞれ１枚又は複数枚の低温焼成セラミックグリーンシート１３を積層するようにしても良い。この場合は、焼成済み基板１２の両面に未焼成の低温焼成セラミックグリーンシート１３を積層し、更にその積層体に両面に拘束焼成グリーンシート１５を積層した上で、これらを２枚の加圧板１０間に挟み込んで同時に圧着すれば良い。その他の事項は、前記実施形態（１）と同じで良い。
【００５６】
本実施形態（２）のように、焼成済み基板１２の両面に同時に低温焼成セラミックグリーンシート１３と拘束焼成グリーンシート１５を圧着する場合は、基板両面の両グリーンシート１３，１５の合計厚み変化量が焼成済み基板１２の凹凸による最大厚み差以上となるように形成すれば良い。このようにすれば、圧着時に焼成済み基板１２の凹凸に応じて基板両面の両グリーンシート１３，１５が柔軟に変形して、焼成済み基板１２の凹凸による最大厚み差を基板両面の両グリーンシート１３，１５の厚み変化量で吸収することができるため、圧着時の加圧力が焼成済み基板１２の凸反り部分に集中的に作用することを防止でき、圧着時の加圧力による焼成済み基板１２の割れを防止できて、歩留りを向上させることができる。
【００５７】
しかも、本実施形態（２）のように、両面キャビティ付きのセラミック多層基板１１を製造する場合でも、焼成済み基板１２をキャビティ１４の底面部に位置させて拘束焼成することで、キャビティ１４の底面部が凸状に反ることはなく、寸法精度の良い両面キャビティ付きのセラミック多層基板１１を製造することができる。
【００５８】
【発明の効果】
以上の説明から明らかなように、本発明のセラミック多層基板の製造方法によれば、焼成済み基板に圧着する未焼成のセラミックグリーンシートを、その圧着時の厚み変化量（複数枚の未焼成のセラミックグリーンシートを同時に圧着する場合はそれらの合計厚み変化量、また、未焼成のセラミックグリーンシートと拘束用グリーンシートとを同時に圧着する場合はそれらの合計厚み変化量）が焼成済み基板の凹凸による最大厚み差以上となるように形成するようにしたので、焼成済み基板の凹凸による最大厚み差を未焼成のセラミックグリーンシートの厚み変化量で吸収することができて、圧着時の加圧力による焼成済み基板の割れを防止できて、歩留りを向上させることができる。
【図面の簡単な説明】
【図１】本発明の実施形態（１）の片面キャビティ付きのセラミック多層基板の製造方法を説明する工程図
【図２】本発明の実施形態（１）の製造工程の流れを説明する工程フローチャート
【図３】キャビティの深さが２層の場合の片面キャビティ付きのセラミック多層基板の製造方法を説明する図
【図４】焼成済み基板上に未焼成の低温焼成セラミックグリーンシートを圧着する工程を説明する工程図
【図５】本発明の実施形態（２）の両面キャビティ付きのセラミック多層基板の製造方法を説明する図
【符号の説明】
１０…加圧板、１１…セラミック多層基板、１２…焼成済み基板、１３…低温焼成セラミックグリーンシート（未焼成のセラミックグリーンシート）、１４…キャビティ、１４ａ…キャビティ用の開口部、１５…拘束焼成用グリーンシート[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a ceramic multilayer substrate in which an unfired ceramic green sheet is laminated on a previously fired ceramic substrate to manufacture a ceramic multilayer substrate.
[0002]
[Prior art]
In general, a ceramic multilayer substrate is often manufactured by a green sheet lamination method. In this green sheet laminating method, via holes are formed in a plurality of ceramic green sheets, and via conductors are formed by filling the via holes in each ceramic green sheet to form via conductors. To print. Thereafter, the plurality of ceramic green sheets are laminated and thermocompression bonded to produce a green substrate, and then the green substrate is baked to produce a ceramic multilayer substrate.
[0003]
[Problems to be solved by the invention]
However, since baking shrinkage of about 15 to 30% occurs in the process of firing the raw substrate, it is difficult to manage the dimensional accuracy of the substrate, and in addition, the shrinkage of both sides of the substrate is difficult in a multilayer substrate with unevenness such as a cavity. Since the stress becomes non-uniform, the fired substrate is likely to be warped, and in particular, the bottom surface of the cavity has a large warp.
[0004]
In the case of firing a composite ceramic multilayer substrate by laminating an insulating ceramic green sheet and a ceramic green sheet of a different material such as a dielectric or magnetic body, the sintering temperatures of the two are matched, and both Since it is necessary to reduce the difference in the firing shrinkage behavior of each layer to prevent delamination, there are disadvantages that the range of material selection is very narrow and the degree of design freedom is very narrow.
[0005]
In recent years, as a firing method for reducing substrate firing shrinkage and improving substrate dimensional accuracy, as shown in Japanese Patent Application Laid-Open No. 2001-267743, an unfired ceramic in which a wiring pattern is printed in advance on a fired alumina substrate It has been proposed to produce a ceramic multilayer substrate by laminating and thermocompression bonding green sheets. This firing method is intended to reduce the firing shrinkage of the entire substrate by restraining the firing shrinkage of the ceramic green sheet with the fired alumina substrate.
[0006]
However, since the firing shrinkage force of the ceramic green sheet is great, it is not possible to sufficiently suppress firing shrinkage of the ceramic green sheet from only one side of the ceramic green sheet using the fired alumina substrate. As a result, peeling may occur between the fired layer of the ceramic green sheet and the fired alumina substrate, cracks may be generated in the fired layer of the ceramic green sheet, and warping of the substrate may occur. There is a disadvantage that the yield is poor.
[0007]
Further, as a firing method having a large effect of reducing the firing shrinkage of the substrate and improving the dimensional accuracy of the substrate, for example, as shown in JP-T-5-503498 and JP-A-9-92983, a pressure firing method is used. Has been developed. In this pressure firing method, constraining alumina green sheets that are not sintered at the sintering temperature (800 to 1000 ° C.) of the low-temperature fired ceramic are laminated on both sides of the low-temperature fired ceramic substrate (hereinafter referred to as “raw substrate”) before firing. In this state, the green substrate is baked at 800 to 1000 ° C. while pressing the raw substrate, and then the residual alumina green sheet for restraint is removed from both sides of the baked substrate by blasting or the like to produce a low-temperature fired ceramic substrate. Is.
[0008]
However, when a low-temperature fired ceramic substrate with a cavity is fired by the above-mentioned pressure firing method, the pressure applied to the cavity region via the constraining alumina green sheet acts intensively on the cavity periphery, and on the bottom surface of the cavity Since the applied pressure does not act at all, the bottom surface of the cavity is warped in a convex shape, and there is a drawback that the dimensional accuracy of the cavity cannot be ensured.
[0009]
In order to eliminate these conventional drawbacks, the present applicant, as described in the specification of Japanese Patent Application No. 2001-357692 (filed on November 22, 2001), pre-fired ceramic substrate (hereinafter “ One or a plurality of unfired ceramic green sheets that are sintered at a temperature substantially equal to or lower than the sintering temperature of the fired substrate are laminated and pressure-bonded to one or both surfaces of the “fired substrate”). A laminated body is prepared, and constrained green sheets that are not sintered at the sintering temperature of the unfired ceramic green sheet are laminated on both sides of the laminated body, and restraint firing (pressure firing or pressureless firing) A new manufacturing technology is under development.
[0010]
During the development of this manufacturing technology, an unfired ceramic green sheet is laminated on a fired substrate, and the laminate is sandwiched between two pressure plates and pressed. It has been found that it can crack and cause a decrease in yield.
[0011]
Accordingly, an object of the present invention is a process of pressure bonding an unfired ceramic green sheet to a fired substrate in a method for producing a ceramic multilayer substrate by restraining firing a laminate of a fired substrate and an unfired ceramic green sheet. It is an object of the present invention to provide a method for manufacturing a ceramic multilayer substrate that can prevent the fired substrate from cracking and improve the yield.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a method for producing a ceramic multilayer substrate according to claims 1 and 2 of the present invention is the method of producing a laminate by laminating and bonding a non-fired ceramic green sheet to a fired substrate. A constraining green sheet is laminated and pressure-bonded to both sides, or an unfired ceramic green sheet is laminated and a constraining green sheet is simultaneously laminated and constrained and fired (pressure firing or pressureless firing). Thus, there is a first feature, and further, an unfired ceramic green sheet to be pressure-bonded to a fired substrate in the laminate manufacturing process is changed to a thickness change amount during the pressure bonding (a plurality of unfired ceramic green sheets). The total thickness change amount when simultaneously pressing, and when simultaneously bonding an unfired ceramic green sheet and a constraining green sheet, There is a second feature in that the thickness variation) is formed so that the maximum thickness difference or due to unevenness of the fired substrate.
[0013]
According to the first feature of the present invention, the firing shrinkage, warpage, and deformation of the unfired ceramic green sheet in the X and Y directions at the time of restraint firing are almost evenly caused by the restraining green sheet and the fired substrate from both sides. A ceramic multilayer substrate that is suppressed, has good dimensional accuracy, and has no delamination or warpage can be manufactured. In addition, the difference in sintering temperature between the fired substrate and the unfired ceramic green sheet and the difference in firing shrinkage properties do not matter, so the sintering temperature and firing of the ceramic material forming each layer of the ceramic multilayer substrate The degree of freedom of material selection with respect to shrinkage characteristics and the like can be greatly increased, and a ceramic multilayer substrate having a configuration that has been difficult to manufacture by conventional manufacturing methods can be manufactured with high dimensional accuracy without delamination or warpage.
[0014]
As described above, during the development of this manufacturing technology, the pressure applied during pressure bonding is a process in which an unfired ceramic green sheet is laminated on a fired substrate and the laminate is sandwiched between two pressure plates for pressure bonding. It has been found that the fired substrate may break. In order to investigate this cause, the inventor inspected the baked substrate that was cracked at the time of pressure bonding, and the surface of the baked substrate was not a completely flat surface, but was slightly uneven on the substrate surface due to shrinkage behavior at the time of baking. (Waviness) was confirmed (see FIG. 4). In such a baked substrate with unevenness, the convex warp portion of the baked substrate does not adhere to the pressure plate at the time of pressure bonding, and it is in a floating state, and on the baked substrate via an unfired ceramic green sheet at the time of pressure bonding The applied pressure does not act uniformly on the entire substrate surface, and a larger applied pressure acts on the convex warp portion of the baked substrate (the portion lifted from the pressure plate) than the other portions. It is considered that the warped part breaks without being able to withstand the applied pressure.
[0015]
Therefore, the second feature of the present invention is that, in order to prevent the above-described cracking of the fired substrate at the time of pressure bonding, an unfired ceramic green sheet that is pressure-bonded to the fired substrate is subjected to a thickness change amount (plurality) at the time of pressure bonding. When the unfired ceramic green sheets are simultaneously pressure-bonded, the total thickness change amount) is made to be equal to or greater than the maximum thickness difference due to the unevenness of the fired substrate. In this way, the unfired ceramic green sheet flexibly deforms according to the unevenness of the fired substrate during crimping, and the maximum thickness difference due to the unevenness of the fired substrate is the amount of change in thickness of the unfired ceramic green sheet. Since it can absorb, it can prevent that the applied pressure at the time of pressure bonding acts on the convex warp portion of the baked substrate, and the applied pressure that acts on the baked substrate can be distributed over the entire substrate surface. Thereby, the crack of the baked board | substrate by the applied pressure at the time of crimping | compression-bonding can be prevented, and a yield can be improved.
[0016]
In this case, as in claim 3, the adjustment of the amount of change in thickness of the unfired ceramic green sheet is adjusted by adjusting the thickness of the ceramic green sheet, adjusting the composition and blending ratio of the molding material of the ceramic green sheet, and forming The adjustment may be performed by at least one of adjusting the particle diameter of the ceramic particles in the material and adjusting the porosity of the molding material. From these adjustment methods, an appropriate adjustment method may be selected according to the substrate specifications and the like.
[0017]
In this case, as in claim 4, the fired substrate and the unfired ceramic green sheet may be formed of the same kind of ceramic material, or, as in claim 4, the fired substrate and the unfired ceramic green sheet are formed. The ceramic green sheet may be formed of different ceramic materials, and the ceramic material may be selected so that the sintering temperature of the unfired ceramic green sheet is equal to or lower than the sintering temperature of the fired substrate. If the fired substrate and the unfired ceramic green sheet are formed of the same kind of ceramic material as in claim 3, a ceramic multilayer having a single ceramic composition in which electrical characteristics such as insulation characteristics of all layers are made uniform A substrate can be manufactured. Further, if the fired substrate and the unfired ceramic green sheet are formed of different kinds of ceramic materials as in claim 5, a composite ceramic containing various functional materials that are difficult to manufacture by the conventional manufacturing method. Multilayer substrates can be manufactured.
[0018]
In this case, as described in claim 6, it is preferable to use an unfired ceramic green sheet formed of a low-temperature fired ceramic material fired at 1000 ° C. or lower. In this way, as a constraining green sheet, it is possible to use a ceramic that is relatively inexpensive and excellent in mechanical strength, such as an alumina green sheet, and as a wiring conductor that is printed on an unfired ceramic green sheet, A low melting point metal such as an Ag-based, Au-based, or Cu-based material having a small electrical resistance value and excellent electrical characteristics can be used.
[0019]
Further, when manufacturing a ceramic multilayer substrate with cavities as in claim 7, an unfired ceramic green sheet laminated on the fired substrate is positioned on the bottom surface of the portion to be the cavity. In this case, an opening for forming a cavity may be formed before or after the lamination. Here, when forming an opening for forming a cavity in an unfired ceramic green sheet before lamination, the opening for forming the cavity may be formed simultaneously with the processing of the via hole by punching or the like. When forming an opening for forming a cavity in an unfired ceramic green sheet, for example, a ceramic green sheet containing a photosensitive resin is prepared, and the cavity is formed in the ceramic green sheet using a photolithography technique or the like. For this purpose, an opening may be formed. If the fired substrate is positioned at the bottom surface of the cavity and the ceramic multilayer substrate with the cavity is restrained and fired as in claim 7, the bottom surface of the cavity is not warped in a convex shape, and the restraint firing is performed. Therefore, the dimensional accuracy of the cavity can be ensured.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
[Embodiment (1)]
Hereinafter, an embodiment (1) in which the present invention is applied to a method for producing a ceramic multilayer substrate with a single-sided cavity will be described with reference to FIGS.
[0021]
As shown in FIGS. 1C and 3, the ceramic multilayer substrate 11 with a single-sided cavity manufactured in the present embodiment (1) has one or a plurality of unfired ceramic substrates on a pre-fired substrate 12. A low-temperature fired ceramic green sheet 13 is laminated, and a restraint fired green sheet 15 is further laminated thereon, followed by restraint firing (pressure firing or pressureless firing) at 800 to 1000 ° C. The ceramic multilayer substrate 11 with a single-sided cavity is manufactured through the following steps, with the fired substrate 12 positioned on the bottom surface of the cavity 14.
[0022]
First, the baked substrate 12 is prepared. The fired substrate 12 is obtained by firing a ceramic substrate, and may be either a single layer substrate or a multilayer substrate. The ceramic material forming the fired substrate 12 may be any of an insulating ceramic, a dielectric ceramic, a magnetic ceramic, a piezoelectric ceramic, and a ceramic with a resistor. A ceramic material that is sintered at the same temperature as or higher than the sintering temperature of the sheet 13 may be used. Further, when the fired substrate 12 is a multilayer substrate, each layer may be formed of the same type of ceramic, or a structure in which layers formed of different types of ceramics that can be simultaneously fired are mixed.
[0023]
In this case, the insulating ceramic is a ceramic used for forming the insulating layer of the substrate, and examples thereof include a low-temperature fired ceramic and a high-temperature sinterable ceramic such as alumina. When the fired substrate 12 is formed of a low-temperature fired ceramic, the same kind of low-temperature fired ceramic as the low-temperature fired ceramic green sheet 13 may be used. It goes without saying that other types of low-temperature fired ceramics that sinter at a high temperature may be used.
[0024]
Further, a thick film conductor or RuO 2 may be simultaneously fired or retrofitted onto the surface of the fired substrate 12. ₂ A thick film resistor such as a system may be formed. Further, when a thick film resistor is formed on the surface of the fired substrate 12, the thick film resistor is trimmed before the low-temperature fired ceramic green sheet 13 to be described later is laminated on the fired substrate 12. It is better to adjust.
[0025]
Furthermore, a low-temperature fired ceramic green sheet 13 is prepared. As a low-temperature fired ceramic material for forming the green sheet 13, for example, CaO-SiO ₂ -Al ₂ O _Three -B ₂ O _Three A mixture of the system glass: 50 to 65% by weight (preferably 60% by weight) and alumina: 50 to 35% by weight (preferably 40% by weight) may be used. In addition, MgO-SiO ₂ -Al ₂ O _Three -B ₂ O _Three A mixture of glass and alumina, or SiO ₂ -B ₂ O _Three A mixture of glass and alumina, PbO-SiO ₂ -B ₂ O _Three A low-temperature fired ceramic material that can be fired at 800 to 1000 ° C., such as a mixture of glass and alumina, cordierite crystallized glass, or the like may be used.
[0026]
The low-temperature fired ceramic green sheet 13 is obtained by blending a low-temperature fired ceramic material having the above composition with a binder (for example, acrylic resin, butyral resin, PVA, etc.), a solvent (for example, toluene, xylene, butanol, etc.) and a plasticizer. A slurry is prepared by stirring and mixing, and tape is formed using this slurry by a doctor blade method or the like.
[0027]
In order to prevent cracking of the fired substrate 12 when the low temperature fired ceramic green sheet 13 is pressure-bonded on the fired substrate 12 in the laminate manufacturing process described later, as shown in FIG. 13 is formed such that the amount of change in thickness during pressure bonding is equal to or greater than the maximum thickness difference due to the unevenness of the fired substrate 12. When simultaneously bonding a plurality of low-temperature fired ceramic green sheets 13 onto the fired substrate 12, the total thickness change amount of the plurality of low-temperature fired ceramic green sheets 13 is greater than or equal to the maximum thickness difference due to the unevenness of the fired substrate 12. To form. Here, the maximum thickness difference due to the unevenness of the baked substrate 12 is the maximum thickness (the highest point of the substrate surface) and the minimum thickness (of the substrate surface) of the baked substrate 12 when the baked substrate 12 is placed on the pressure plate 10. This is the difference from the lowest score.
[0028]
When adjusting the amount of change in thickness of the low-temperature fired ceramic green sheet 13 during pressure bonding, one or more of the following adjustment methods (1) to (4) are adjusted according to the substrate specifications. Just choose the law.
[0029]
(1) The thickness of the low-temperature fired ceramic green sheet 13 is adjusted. The thicker the low-temperature fired ceramic green sheet 13 is, the greater the amount of change in thickness during pressure bonding.
(2) The ceramic material composition or blending ratio of the low-temperature fired ceramic green sheet 13 is adjusted. For example, the kind and blending amount of the binder resin of the ceramic material, the kind and blending amount of the plasticizer and the solvent, and the kind and blending amount of the ceramic powder are adjusted. Generally, as the blending amount of the plasticizer increases, the low-temperature fired ceramic green sheet 13 becomes softer and the amount of change in thickness at the time of pressure bonding increases.
[0030]
(3) Adjusting the particle size of ceramic particles in the ceramic material of the low-temperature fired ceramic green sheet 13 and the ease of crushing of the aggregated particles.
(4) The porosity (porosity) of the ceramic material of the low-temperature fired ceramic green sheet 13 is adjusted. The porosity may be adjusted by adjusting the void content in the ceramic material (slurry). The greater the porosity, the greater the amount of change in thickness during crimping.
[0031]
After the tape-formed low-temperature fired ceramic green sheet 13 is cut into a predetermined size, a cavity forming opening 14a and a via hole (not shown) are punched into a predetermined position of the green sheet 13 by punching or the like. Note that, after the low-temperature fired ceramic green sheet 13 is laminated and pressure-bonded on the fired substrate 12, a cavity forming opening 14a may be formed in the low-temperature fired ceramic green sheet 13 using a photolithography technique.
[0032]
Thereafter, the process proceeds to a printing step, and the via hole of the low-temperature fired ceramic green sheet 13 is filled with a conductive paste of a low melting point metal such as Ag, Ag / Pd, Au, Ag / Pt, or Cu. Further, as shown in FIG. 3, when a plurality of low-temperature fired ceramic green sheets 13 are laminated on the fired substrate 12, Ag, Ag / Pd, Au are added to the low-temperature fired ceramic green sheets 13 laminated on the inner layer. An inner layer conductor pattern (not shown) is screen-printed using a conductor paste of low melting point metal such as Ag / Pt, Cu, etc., and the surface layer conductor pattern ( (Not shown) is screen printed using the same kind of low melting point metal conductor paste. Note that the surface layer conductor pattern may be printed after restraint firing. Further, when manufacturing a ceramic multilayer substrate having a structure without via holes or inner layer conductor patterns, the above printing process may be omitted.
[0033]
After the printing process, the process proceeds to a laminated body production process, in which one or a plurality of low-temperature fired ceramic green sheets 13 are laminated on the fired substrate 12, and further, constraining green sheets 15 are laminated on both sides of the laminated body. Then, the laminate is sandwiched between two pressure plates 10 as shown in FIG. The pressure-bonding conditions are a pressure of 0.1 to several tens of MPa (preferably 3 to 10 MPa) and a heating temperature of 60 to 150 ° C. (preferably 80 to 120 ° C.).
[0034]
As described above, if the low-temperature fired ceramic green sheet 13 and the constraining green sheet 15 are simultaneously laminated and pressure-bonded to the fired substrate 12, there is an advantage that the lamination / crimping process can be performed only once. Alternatively, only the low-temperature fired ceramic green sheet 13 may be laminated and pressure-bonded on the fired substrate 12, and then the constraining green sheets 15 may be laminated and pressure-bonded on both surfaces of the laminated body.
[0035]
In this case, the constrained fired green sheet 15 uses a high temperature sinterable ceramic (for example, alumina, zirconia, magnesia, etc.) that does not sinter at the sintering temperature (800 to 1000 ° C.) of the low temperature fired ceramic. In this powder, a binder (for example, PVB, acrylic resin, nitrocellulose resin, etc.), a solvent (for example, toluene, xylene, butanol, etc.) and a plasticizer are blended and mixed thoroughly to prepare a slurry. The constrained fired green sheet 15 may be produced by tape-molding using a doctor blade method or the like.
[0036]
Thereafter, the laminated body in which the constraining green sheets 15 are laminated is sandwiched between porous setter plates (not shown) formed of alumina, SiC, or the like, and a pressure of 0.1 to several tens of MPa (preferably 3 to 10 MPa). While pressurizing, the sintering is performed at 800 to 1000 ° C., which is the sintering temperature of the low-temperature fired ceramic green sheet 13. In this case, the restraining green sheet 15 needs to be thermocompression bonded to the low-temperature fired ceramic green sheet 13 in the step of laminating the restraining green sheet 15.
[0037]
At this time, the constraining green sheet 15 (high-temperature sinterable ceramic such as alumina) does not sinter unless heated to about 1300 to 1600 ° C. Therefore, if fired at 800 to 1000 ° C., the constraining green sheet 15 is not yet formed. It remains as sintered. However, in the firing process, organic substances such as binder in the constraining green sheet 15 are thermally decomposed and scattered to remain as ceramic powder.
[0038]
After firing, the residue (ceramic powder) of the constraining green sheet 15 adhering to both surfaces of the fired substrate 11 is removed by blasting, buffing or the like. Thereby, the manufacture of the ceramic multilayer substrate 11 with the single-sided cavity is completed.
[0039]
By the way, as shown in FIG. 4, the surface of the baked substrate 12 is not a completely flat surface, but a slight unevenness (waviness) is generated on the substrate surface due to shrinkage behavior at the time of baking. Note that the unevenness of the baked substrate 12 shown in FIG. 4 is exaggerated for explanation, and the maximum thickness difference of the baked substrate 12 is generally about several μm to several tens of μm.
[0040]
Since the baked substrate 12 having such irregularities is in a state in which the convex warp portion of the baked substrate 12 is raised at the time of pressure bonding, a large amount is added to the convex warpage portion (the portion raised from the pressure plate 10) of the baked substrate 12. When the pressure acts, the convex warp portion of the baked substrate 12 may not be able to withstand the applied pressure and may be cracked.
[0041]
When the low-temperature fired ceramic green sheet 13 and the constraining green sheet 15 are pressure-bonded to the fired substrate 12 at the same time, the maximum thickness due to the unevenness of the fired substrate 12 is small if there is a small amount of thickness change when the

green sheets

13 and 15 are pressure-bonded. Since the difference cannot be absorbed by the amount of change in the thickness of the

green sheets

13 and 15, the pressure applied to the fired substrate 12 through the low-temperature fired ceramic green sheet 13 at the time of pressure bonding does not uniformly act on the entire substrate surface, and firing. A larger pressing force is applied to the convex warp portion (the raised portion) of the finished substrate 12 than the other portions. As a result, a phenomenon occurs in which the convex warped portion of the baked substrate 12 breaks without being able to withstand the applied pressure.
[0042]
As a countermeasure against this, in the present embodiment (1), the total thickness change amount when both the

green sheets

13 and 15 are pressed (when a plurality of low-temperature fired ceramic green sheets 13 and the constraining green sheets 15 are simultaneously pressed, The total thickness change amount) is equal to or greater than the maximum thickness difference due to the unevenness of the baked substrate 12. In this way, both the

green sheets

13 and 15 are flexibly deformed according to the unevenness of the fired substrate 12 at the time of pressure bonding, and the maximum thickness difference due to the unevenness of the fired substrate 12 is changed to the thickness change of both

green sheets

13 and 15. Since the pressure can be absorbed by the amount, it can be prevented that the pressing force at the time of crimping is concentrated on the convex warp portion of the baked substrate 12, and the pressing force acting on the baked substrate 12 is dispersed over the entire substrate surface. be able to. Thereby, the crack of the baked board | substrate 12 by the applied pressure at the time of crimping | compression-bonding can be prevented, and a yield can be improved.
[0043]
As described above, in the present invention, only the low-temperature fired ceramic green sheet 13 is laminated and pressure-bonded on the fired substrate 12, and then the constraining green sheets 15 are laminated and pressure-bonded on both surfaces of the laminated body. In this case, the amount of change in thickness when the low-temperature fired ceramic green sheet 13 is pressure-bonded (when a plurality of low-temperature fired ceramic green sheets 13 are simultaneously pressure-bonded) is the fired substrate 12. If it is formed so as to be equal to or greater than the maximum thickness difference due to the unevenness, it is possible to obtain the same effect as in the present embodiment (1).
[0044]
Further, in the present embodiment (1), a constraining green sheet 15 is laminated on a laminate of a fired substrate 12 and an unfired low-temperature fired ceramic green sheet 13, and restraint firing (pressure firing or pressureless firing). Since the firing shrinkage, warpage, and deformation of the unfired low-temperature fired ceramic green sheet 13 during restraint firing are suppressed almost uniformly by the restraining green sheet 15 and the fired substrate 12 from both sides, delamination The ceramic multilayer substrate 11 without warping or the like can be manufactured.
[0045]
Further, in the case of manufacturing the ceramic multilayer substrate 11 with the cavity 14 as in the embodiment (1), if the fired substrate 12 is positioned on the bottom surface of the cavity 14 and restrained firing is performed, the bottom surface of the cavity 14 is obtained. Does not warp in a convex shape, and the dimensional accuracy of the cavity 14 can be ensured by restraint firing, and the ceramic multilayer substrate 11 with the cavity 14 having excellent quality can be manufactured. Therefore, even when a semiconductor bare chip is flip-chip mounted on the bottom surface of the cavity 14, the bottom surface of the cavity 14 is not warped, and therefore, the bonding between the bare chip and the conductive pad on the bottom surface of the cavity 14 is performed with high accuracy. And the reliability of flip chip mounting can be improved.
[0046]
In addition, the difference in sintering temperature between the fired substrate 12 and the unfired low-temperature fired ceramic green sheet 13, the difference in firing shrinkage characteristics, and the like are not a problem, so that the ceramic material forming each layer of the ceramic multilayer substrate 11 The degree of freedom of material selection with respect to the sintering temperature, firing shrinkage characteristics, etc. can be greatly expanded, and the ceramic multilayer substrate 11 having a configuration that was difficult to manufacture by conventional manufacturing methods has no delamination or warpage, Can be manufactured with good dimensional accuracy.
[0047]
【Example】
The inventor adjusted the maximum thickness difference due to the unevenness of the fired substrate 12 and the thickness change amount at the time of pressure bonding of the low-temperature fired ceramic green sheet 13. 1 to 9 were produced, and a test for inspecting the presence or absence of cracks in the fired substrate 12 at the time of pressure bonding was performed. The test results are shown in Table 1 below.
[0048]
[Table 1]

[0049]
The fired substrate and unfired low-temperature fired ceramic green sheet used in this test are both CaO-SiO ₂ -Al ₂ O _Three -B ₂ O _Three This is a low-temperature fired ceramic made of a mixture of 60% by weight of system glass and 40% by weight of alumina. Adjustment of the thickness change amount at the time of pressure bonding of the low-temperature fired ceramic green sheet was performed by adjusting the blending amount of the plasticizer or adjusting the sheet thickness.
[0050]
In this test, nine sample Nos. For 1 to 9, the pressure bonding conditions are set to pressurization pressure: 5 MPa, heating temperature: 100 ° C., and one low-temperature fired ceramic green sheet and constraining green sheet (alumina green sheet) are simultaneously laminated on the fired substrate. Crimping was performed to inspect the fired substrate for cracks.
[0051]
In addition, the measuring method of the maximum thickness difference of the baked substrate is to place the baked substrate on a flat plate and measure the maximum thickness (the highest point of the substrate surface) and the minimum thickness (the lowest point of the substrate surface) of the baked substrate, The difference between the maximum thickness and the minimum thickness was determined as the maximum thickness difference. In addition, the measurement method of the total thickness change amount when the low-temperature fired ceramic green sheet and the constraining green sheet are crimped is obtained by sandwiching a laminate of the low-temperature fired ceramic green sheet and the constraining green sheet between the pressure plates. The total thickness change amount of both green sheets was measured by applying pressure while heating under the same conditions as the pressure bonding conditions.
[0052]
According to the test results shown in Table 1, the sample No. 1 in which the total thickness change amount when both green sheets are pressed is smaller than the maximum thickness difference of the fired substrate. In Nos. 3, 6, and 9, cracks of the fired substrate occurred due to the applied pressure during pressure bonding.
[0053]
On the other hand, the sample No. in which the total thickness change amount at the time of pressure bonding of both green sheets is larger than the maximum thickness difference of the fired substrate. As for 1, 2, 4, 5, 7, and 8, even in the inspection after the press bonding, the fired substrates were not cracked.
[0054]
From this test result, it was confirmed that cracking of the fired substrate due to the applied pressure during pressure bonding can be prevented if the total thickness change amount during pressure bonding of both green sheets is equal to or greater than the maximum thickness difference of the fired substrates.
[0055]
[Embodiment (2)]
In the embodiment (1), the low-temperature fired ceramic green sheets 13 are laminated only on one side of the fired substrate 12, but on the both sides of the fired substrate 12 as in the embodiment (2) of the present invention shown in FIG. Alternatively, one or a plurality of low-temperature fired ceramic green sheets 13 may be laminated. In this case, an unfired low-temperature fired ceramic green sheet 13 is laminated on both surfaces of the fired substrate 12, and further, a restrained fired green sheet 15 is laminated on both surfaces of the laminate, and these are pressed into two pressure plates 10. What is necessary is just to carry out crimping | compression-bonding at the same time putting between. Other matters may be the same as those in the embodiment (1).
[0056]
When the low-temperature fired ceramic green sheet 13 and the constrained fired green sheet 15 are simultaneously pressure-bonded to both surfaces of the fired substrate 12 as in the present embodiment (2), the total thickness change amount of both the

green sheets

13 and 15 on both surfaces of the substrate. May be formed to be equal to or greater than the maximum thickness difference due to the unevenness of the baked substrate 12. In this way, both the

green sheets

13 and 15 on both sides of the substrate are flexibly deformed according to the unevenness of the baked substrate 12 at the time of pressure bonding, and the maximum thickness difference due to the concavo-convex of the baked substrate 12 is determined. Since it can be absorbed by the thickness change amount of 13 and 15, it is possible to prevent the applied pressure at the time of pressure bonding from acting on the convex warp portion of the fired substrate 12, and the fired substrate 12 due to the pressure at the time of pressure bonding. Can be prevented, and the yield can be improved.
[0057]
Moreover, even in the case of manufacturing the ceramic multilayer substrate 11 with the double-sided cavities as in the present embodiment (2), the bottom surface of the cavity 14 is obtained by positioning and firing the fired substrate 12 at the bottom surface of the cavity 14. Therefore, the ceramic multilayer substrate 11 with a double-sided cavity with good dimensional accuracy can be manufactured.
[0058]
【The invention's effect】
As is clear from the above description, according to the method for manufacturing a ceramic multilayer substrate of the present invention, an unfired ceramic green sheet to be pressure-bonded to a fired substrate is subjected to a change in thickness (a plurality of unfired green sheets) at the time of pressure bonding. When the ceramic green sheets are pressed at the same time, the total thickness change amount, and when the unfired ceramic green sheet and the restraining green sheet are simultaneously pressed, the total thickness change amount) depends on the unevenness of the fired substrate. Since it is formed so as to be greater than the maximum thickness difference, the maximum thickness difference due to the unevenness of the fired substrate can be absorbed by the amount of change in the thickness of the unfired ceramic green sheet, and firing by the applied pressure during pressure bonding It is possible to prevent cracking of a used substrate and improve yield.
[Brief description of the drawings]
FIG. 1 is a process diagram illustrating a method for producing a ceramic multilayer substrate with a single-sided cavity according to an embodiment (1) of the present invention.
FIG. 2 is a process flowchart illustrating the flow of a manufacturing process according to an embodiment (1) of the present invention.
FIG. 3 is a diagram for explaining a method of manufacturing a ceramic multilayer substrate with a single-sided cavity when the cavity depth is two layers.
FIG. 4 is a process diagram illustrating a process of pressure bonding an unfired low-temperature fired ceramic green sheet on a fired substrate.
FIG. 5 is a diagram illustrating a method for manufacturing a ceramic multilayer substrate with double-sided cavities according to Embodiment (2) of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Pressure plate, 11 ... Ceramic multilayer substrate, 12 ... Fired substrate, 13 ... Low temperature fired ceramic green sheet (unfired ceramic green sheet), 14 ... Cavity, 14a ... Opening for cavity, 15 ... For restraint firing Green sheet

Claims

One or more unsintered sheets that are sintered on one or both sides of a pre-fired ceramic substrate (hereinafter referred to as a “fired substrate”) at a temperature substantially equal to or lower than the sintering temperature of the fired substrate. A laminate manufacturing step of laminating and pressing the ceramic green sheets to produce a laminate, and a step of laminating constraining green sheets that are not sintered at the sintering temperature of the unfired ceramic green sheets on both sides of the laminate, and A constrained firing step of consolidating the laminate by restraint firing at the sintering temperature of the unfired ceramic green sheet with or without pressurizing the laminate through the constraining green sheet; A method for producing a ceramic multilayer substrate having a step of removing a residue of the restraining green sheet after the restraining firing step, wherein the firing is performed in the laminate manufacturing step. The unfired ceramic green sheet that is crimped to a single substrate has a thickness variation during crimping (if multiple unfired ceramic green sheets are simultaneously crimped, their total thickness variation) is uneven on the fired substrate. A method for producing a ceramic multilayer substrate, characterized in that the ceramic multilayer substrate is formed to have a thickness difference greater than or equal to the above.

One or more unsintered sheets that are sintered on one or both sides of a pre-fired ceramic substrate (hereinafter referred to as a “fired substrate”) at a temperature substantially equal to or lower than the sintering temperature of the fired substrate. In addition, the fired substrate and the unfired ceramic green sheet are laminated in a state in which a green sheet for restraint that is not sintered at the sintering temperature of the unfired ceramic green sheet is laminated on both surfaces of the laminate. A laminated body production step for producing a laminated body by simultaneously pressing a ceramic green sheet and the restraining green sheet, and the unfired with or without pressurizing the laminated body through the restraining green sheet A constraining firing step of constraining firing at a sintering temperature of the ceramic green sheet to integrate the laminate, and the constraining green after the constraining firing step A method of manufacturing a ceramic multilayer substrate having a step of removing a residue of a sheet, wherein the unfired ceramic green sheet that is pressure-bonded to the fired substrate in the laminate manufacturing step has a thickness change amount during pressure bonding. (When the unfired ceramic green sheet and the constraining green sheet are simultaneously pressed together, the total thickness change amount thereof) is formed so as to be equal to or greater than the maximum thickness difference due to the unevenness of the fired substrate. A method for producing a ceramic multilayer substrate.

The said green body green sheet deform | transforms at the time of the said laminated body produced in the said laminated body preparation process, and has absorbed the maximum thickness difference by the unevenness | corrugation of the said board | substrate after baking. Manufacturing method for ceramic multilayer substrate.

Adjustment of the amount of change in thickness of the unfired ceramic green sheet during compression includes adjustment of the thickness of the ceramic green sheet, adjustment of the composition and blending ratio of the molding material of the ceramic green sheet, and adjustment of the ceramic particles in the molding material. The method for producing a ceramic multilayer substrate according to any one of claims 1 to 3 , wherein the method is performed by at least one of adjusting the particle diameter and adjusting the porosity of the molding material.

Method for producing a ceramic multilayer substrate according to any one of claims 1 to 4, characterized in that it is formed of a ceramic material of the same type and the fired substrate and the unfired ceramic green sheets.

The fired substrate and the green ceramic green sheet are formed of different ceramic materials, and the sintering temperature of the green ceramic green sheet is equal to or lower than the sintering temperature of the fired substrate. The manufacturing method of the ceramic multilayer substrate in any one of Claim 1 to 4 .

The method for producing a ceramic multilayer substrate according to any one of claims 1 to 6 , wherein the green ceramic green sheet is formed of a low-temperature fired ceramic material fired at 1000 ° C or lower.

A method of manufacturing a ceramic multilayer substrate having a cavity, wherein the fired substrate is positioned on a bottom surface of a portion where the cavity is formed, and the unfired ceramic green sheet laminated on the fired substrate includes: method for producing a ceramic multilayer substrate according to any one of claims 1 to 7, characterized in that to form the opening for the cavity formed before or after lamination.