JP3564089B2 - Conductive paste and method for producing the same - Google Patents

Description

【００６３】
【表２】

【００６４】
【表３】

【００６５】
【表４】

【００６６】
【表５】

【００６７】
【表６】

【００６８】
【表７】

【００６９】
【表８】

【００７０】
【表９】

【００７１】
【表１０】

【００７２】
＜実施例２９：膜状導体の形成及びその評価（１）＞
次に、各実施例及び比較例に係る導体ペーストを用いて、セラミック基材（ここでは厚みが約０．８ｍｍのアルミナ製基板）の表面に膜状導体を形成した。すなわち、一般的なスクリーン印刷法に基づいてセラミック基板の表面に導体ペーストを塗布し、所定の膜厚（１０〜３０μｍ：各表中の「塗膜厚み」欄参照。）の塗膜を形成した。
続いて、遠赤外線乾燥機を用いて１００℃で１５分間の乾燥処理を施した。この乾燥処理により、上記塗膜から溶剤が揮発していき、セラミック基板上に未焼成の膜状導体が形成された。
【００７３】
次に、この膜状導体をセラミック基板ごと焼成した。すなわち、電気炉中で７００，７５０，８００，８５０または９００℃のいずれか（使用したペースト毎に異なる。各表中の「焼成温度」欄を参照。）で１時間の焼成処理を行った。この焼成処理によって、所定の膜厚（各表中の「焼成膜厚み」欄を参照。）の膜状導体をセラミック基板上に焼き付けた。以下、単に膜状導体というときは当該焼成後のものを指す。
【００７４】
次に、得られた各膜状導体の特性評価として、抵抗値、シート抵抗値、半田濡れ性、半田耐熱性および引っ張り強度を以下のように試験・測定した。これら特性評価試験の結果は、使用ペーストごとに表１〜１０の各々対応する欄に示している。なお、表中のn.d.は未測定であることを示している。
【００７５】
＜抵抗値の測定＞
実施例１〜７に係る導体ペーストを使用して得られた膜状導体のそれぞれについて以下のようにして抵抗値（Ω）を測定した。すなわち、デジタルマルチメーターを用いて一般的な２端子法に基づいて膜状導体の抵抗値（Ω）を測定した。
【００７６】
＜シート抵抗値の測定＞
実施例１〜２５及び比較例１、２に係る導体ペーストを使用して得られた膜状導体のそれぞれについて以下のようにしてシート抵抗値（ｍΩ／□）を測定した。すなわち、シート抵抗値（ｍΩ／□）は上記測定抵抗値（Ω）に基づいて次式より算出した。
シート抵抗値（ｍΩ／□）＝測定抵抗値（Ω）×（導体幅(mm)／導体長さ(mm)）×（導体厚み(μm)／換算厚み(μm)）；ここで換算厚みは焼成物１０μｍ若しくは印刷物２５μｍ。
【００７７】
＜半田濡れ性＞
各実施例及び比較例に係る導体ペーストを使用して得られた膜状導体のそれぞれについて以下のようにして半田濡れ性を調べた。すなわち、各セラミック基板の膜状導体部分にロジンフラックスを塗布した後、当該基板を２３０±５℃の半田（Ｓｎ／Ｐｂ＝６０／４０（重量比））に３秒間浸漬した。その後、当該半田で濡れている膜状導体部分の面積比率で半田濡れ性を評価した。具体的には、膜状導体の表面の９０％以上が濡れたものは良好な半田濡れ性を示すものと判断し、表中において◎で示した。他方、半田濡れ部分が膜状導体表面全体の８０％以下のものについては、半田濡れ性が劣るものと判断し、表中において×で示した。
【００７８】
＜半田耐熱性＞
各実施例及び比較例２に係る導体ペーストを使用して得られた膜状導体のそれぞれについて以下のようにして半田耐熱性を調べた。すなわち、各セラミック基板の膜状導体部分にロジンフラックスを塗布した後、当該基板を所定温度の半田（Ｓｎ／Ｐｂ＝６０／４０（重量比））に所定時間浸漬した。ここでは、かかる半田温度条件及び浸漬時間を２３０±５℃×３０秒、２６０±５℃×１０秒、および２６０±５℃×２０秒の３通りとした（適用条件は使用したペースト毎に異なる。各表中の「半田耐熱性」欄を参照。）。
而して、浸漬後に「半田くわれ」されなかった部分、即ち浸漬前と比較して浸漬後にセラミック基板上に残存している膜状導体の面積比率で半田耐熱性を評価した。具体的には、膜状導体の略９０％以上が残存しているものは優れた半田耐熱性を示すものと判断し、表中において◎で示した。また、膜状導体の略８０％以上９０％未満が残存しているものは良好な半田耐熱性を示すものと判断し、表中において○で示した。他方、膜状導体の残存している部分が浸漬前の略８０％未満のものは半田耐熱性が比較的劣っているものと判断し、表中において×で示した。
【００７９】
＜引っ張り強度＞
各実施例及び比較例２に係る導体ペーストを使用して得られた膜状導体のそれぞれについて、セラミック基板に対する接着強度の指標として引っ張り強度（ｋｇ）を以下のようにして測定した。すなわち、セラミック基板に焼き付き形成された膜状導体に評価用リード線（スズめっき銅線）を半田付けした。その後、そのリード線を基板の面方向とは垂直方向に所定の力で引っ張り、その接合面が破壊（分断）された時の負荷（ｋｇ）を接着強度（引っ張り強度）とした。なお、ここでは、上記焼成処理直後のセラミック基板、焼成後さらに１５０℃で４８時間、１００時間又は２００時間のエージングを施した後のセラミック基板について上記引っ張り強度試験を行った（条件は使用したペースト毎に異なる。各表中の「引っ張り強度」欄を参照。）。
【００８０】
表１〜１０に示した上記各特性評価試験の結果から明らかなように、本実施例に係る導体ペーストから形成された膜状導体（厚み：１０〜２２μｍ）は、何れも導体として問題のない抵抗値及び／又はシート抵抗値を示した。これらの結果は、導電性即ち電気的特性の観点からみて本発明の導体ペーストが膜状導体形成用途に好適に用い得ることを示すものである。
また、半田濡れ性については、比較的多量に鉛系ガラス粉末又はホウケイ酸系ガラス粉末を添加したもの（実施例１０，１１，１２）については若干劣っていた（概ね５０％〜７０％）ものの、それら以外のものは、半田濡れ性の上記指標値が９０％以上（表中の◎）を示した。このことは、半田濡れ性の観点からみて、本発明の導体ペーストが膜状導体形成用途に好適であることを示すものである。また、ガラス粉末を添加する場合は、亜鉛系ガラス粉末が比較的好ましい（実施例８）。
【００８１】
半田耐熱性に関する評価試験から明らかなように、各実施例に係る導体ペーストから形成された膜状導体は、従来のＡｇ／Ｐｄ粉末を含む導体ペーストから形成された膜状導体やＮｉめっきされた膜状導体と同等かそれ以上の半田耐熱性を示した。特に、無機添加剤を添加せずに調製したペースト（実施例１〜６）であっても、高い半田耐熱性を有していることが確認された（実施例１〜６）。このことは、本発明によると、金属（Ａｇ）粉末に対して０．０１wt％（酸化物換算）程度のごく僅かな量の有機系金属化合物（ここでは金属アルコキシド）でＡｇベース微粒子をコーティングすることにより、高価なＰｄを使用したり煩雑なＮｉめっき処理を行うことなく実用レベルでの高い半田耐熱性を実現できることを示すものである。
【００８２】
また、引っ張り強度に関する評価試験から明らかなように、本発明の導体ペーストから形成された膜状導体は、Ａｇベース微粒子の焼成物である結果、特に添加剤を必要とすることなく実用レベルの接着強度を保持することが認められた（実施例１〜６）。また、無機添加剤を添加した各実施例のペーストを用いた結果から、適当量のガラスフリット及び／又は無機酸化物粉末を添加することにより、所望する半田耐熱性や半田濡れ性を維持しつつ接着強度を向上させ得ることが確認された（例えば実施例３と実施例１３〜１５参照）。特に、適当量の無機酸化物の添加が有効である。かかる添加によって、高い半田濡れ性及び半田耐熱性の維持と接着強度の向上とを共に実現させることができる（実施例１３〜２８参照）。さらに焼成収縮の低減にも寄与する。なお、添加する無機酸化物は１種類でもよいが、２種類又はそれ以上組み合わせて添加することが好ましいことが示された（実施例２６〜２８参照）。
【００８３】
各実施例で使用したＡｇ粉末の平均粒径（０．２〜１．０μｍ）は、本発明の導体ペーストを調製するのに適当なものであった（実施例２０，２３，２４，２５参照）。また、各実施例に係る導体ペーストを使用した場合の膜状導体焼成温度は、比較的高いレベルの接着強度保持の観点から８００℃以上が好ましく、８５０〜９００℃程度の焼成温度が特に好適であることが示された。
【００８４】
＜実施例３０：膜状導体の形成及びその評価（２）＞
次に、本実施例に係る導体ペーストによると、上記比較例で形成したものよりも薄い膜状導体（１０μｍ以下）を好適に形成し得ることを確認するため、実施例１７，２０，２２及び比較例２の計４種類の導体ペーストを用いて比較的厚い膜状導体と比較的薄い膜状導体とを形成し、上記実施例２９と同様の特性評価を行った。
すなわち、実施例２９と同様、スクリーン印刷法に基づいてセラミック基板の表面に各導体ペーストを塗布し、ペーストごとに薄い塗膜と厚い塗膜を形成した。その後、実施例２９と同様の焼成処理を行い、比較的厚い膜状導体（膜厚：１２〜１５μｍ）と、比較的薄い膜状導体（膜厚：６〜８μｍ）を形成した。
次いで得られた各膜状導体の特性評価として、シート抵抗値、半田濡れ性、半田耐熱性および引っ張り強度を上記実施例と同様にして試験・測定した。結果を以下の表１１及び表１２に示す。
【００８５】
【表１１】

【００８６】
【表１２】

【００８７】
表１１及び１２に示した結果から明らかなように、これら実施例に係る導体ペーストによると、比較的厚い膜状導電膜と実質的に同等の導電性、半田濡れ性および半田耐熱性を具備する１０μｍ以下の薄い膜状導電膜を形成することができる。このことは、本発明の導体ペーストによると、電気的特性及び／又は機械的特性に優れた薄膜回路基板や薄膜ハイブリッドＩＣ等のセラミック電子部品を好適に製造し得ることを示すものである。
【００８８】
以上の実施例から、本発明の導体ペーストとして好適ないくつかの実施形態が明らかとなった。好適な導体ペーストは、次の条件の一つ又は二つ以上を構成要件とするものが挙げられる。すなわち、
(1).平均粒径が０．２〜１．０μｍのＡｇ粉末を金属粉末の主体とする。
(2).Ａｇ又はＡｇ主体の合金の微粒子に有機系金属化合物として金属アルコキシド（特に好ましくはアルミニウムアルコキシド）がコーティングされたものを金属粉末とする。
(3).金属アルコキシドのコーティング量（含有率）が酸化物換算で金属（Ａｇ）粉末の０．０１〜０．１wt％に相当する量である。
(4).金属（Ａｇ）粉末の略１wt％又はそれ以下に相当する量（好ましくは０．５wt％以下）で、１種又は２種以上の無機酸化物（好ましくは酸化銅、酸化鉛及び／又は酸化ビスマス）を無機添加剤として含む。
(5).金属（Ａｇ）粉末の略０．５wt％又はそれ以下に相当する量（好ましくは０．２５wt％以下）で、１種又は２種以上のガラス粉末（好ましくは亜鉛系ガラス、鉛系ガラス及び／又はホウケイ酸系ガラス）を無機添加剤として含む。
【００８９】
また、以上の実施例から、本発明の導体ペーストを用いてのセラミック電子部品製造方法として特に好適ないくつかの実施形態が明らかとなった。本発明のセラミック電子部品製造方法として特に好適なものには、上述したいずれかの好適な実施形態に係る導体ペーストを使用することを特徴とする方法が挙げられ、或いは、セラミック基材に塗布したペースト主成分（即ちコーティング金属粉末）を８００〜９００℃程度の温度で焼成することを特徴とする方法が挙げられる。
【００９０】
＜実施例３１〜３３：側面導体膜形成用Ａｇペースト＞
表１３に実施例３１〜３３として示す計３種類の組成の側面導体膜形成用Ａｇペーストを調製した。
すなわち、Ａｇベース微粒子として一般的な湿式法により調製された平均粒径が０．３〜０．５μｍ（実施例３２を除く）又は０．６〜０．８μｍ（実施例３２のみ）の範囲にある略球状のＡｇ粉末を使用した。また、コーティング材料としてアルミニウムアルコキシド（アセトアルコキシアルミニウムジイソプロピレート）を用いた。而して、適当な有機溶剤（ここではメタノール）に上記金属アルコキシドを添加し、濃度５〜１００ｇ／ｌのコーティング用溶液を調製した。次いで、かかる溶液中に上記Ａｇ粉末を適当量懸濁させ、適宜撹拌しつつ１〜３時間懸濁状態を維持した。その後、Ａｇ粉末を回収し、６０〜１１０℃で通風乾燥した。
以上の処理によって、酸化物（Al ₂ O ₃ ）換算でＡｇ粉末の略０．０１２５〜０．１wt％となる量のアルミニウムアルコキシドによって表面がほぼ均等にコーティングされたＡｇ粉末（以下「コーティングＡｇ粉末」という。）を得た。なお、かかるコーティング量の調整は、上記コーティング溶液の金属アルコキシド濃度及び必要に応じてＡｇ粉末の懸濁時間を適宜調節することによって容易に行うことができる。
【００９１】
側面導体形成用Ａｇペーストの調製には、無機酸化物粉末として平均粒径：１〜５μｍ、比表面積：０．５〜１．５ｍ²／ｇの酸化銅（Cu₂O又はCuO）粉末及び平均粒径：１〜１０μｍ、比表面積：０．５〜２．０ｍ²／ｇの酸化ビスマス(Bi₂O₃)粉末を使用した。
而して、最終的な濃度（重量比）が６５〜７５wt％となる量のコーティングＡｇ粉末と、コーティングＡｇ粉末量の０．０１〜１．０wt％に相当する量の酸化ビスマス粉末と、コーティングＡｇ粉末量の０．００５〜０．５wt％に相当する量の酸化銅粉末と、コーティングＡｇ粉末量の１．５〜１０wt％に相当する量の有機バインダー（エチルセルロース）と、残部が溶剤（実施例３１〜３２についてはＢＣ（ブチルカルビトール）即ちジエチレングリコールモノブチルエーテルとターピネオールの混合溶媒、実施例３３についてはＢＣとエステル（具体的にはトリメチルペンタジオールモノイソブチレート）の混合溶媒）となるように各材料を秤量し、三本ロールミルを用いて混練した。これにより、表１３に示す計３種類のＡｇペーストを得た。
【００９２】
【表１３】

【００９３】
＜実施例３６、３９〜４４、４６及び４７：表面導体膜形成用Ａｇペースト＞
表１４〜表１６に示す計９種類の組成の表面導体膜形成用Ａｇペーストを調製した。なお、実施例３１〜３３で使用したものと同タイプのＡｇ粉末、金属アルコキシドを使用した。
すなわち、金属アルコキシド濃度が５〜１００ｇ／ｌのコーティング用溶液を調製し、側面導体膜形成用Ａｇペースト製造時と同様の処理を行って、酸化物（Al ₂ O ₃ ）換算でＡｇ粉末の０．０２５wt％〜０．４wt％のアルミニウムアルコキシドによって表面がほぼ均等にコーティングされたコーティングＡｇ粉末を得た。
次いで、側面導体膜形成用Ａｇペースト製造時と同様の処理を行って、最終的なペースト濃度（重量比）が８３〜８６wt％となる量のコーティングＡｇ粉末と表１４〜１６に記載の副成分（無機酸化物、有機バインダー、溶剤等）を適宜用いて計９種類のＡｇペーストを得た。表１４〜１６の記載から明らかなように、これら表面導体膜形成用Ａｇペーストは、表１３の側面導体膜形成用ＡｇペーストよりもＡｇ粉末含有率が高いことを一つの特徴とする。また、実施例３６、３９〜４４に係るＡｇペーストは無機酸化物粉末（酸化ビスマス及び酸化銅）を含んでいないことをもう一つの特徴とする。他方、実施例４６〜４７に係るＡｇペーストはこれら無機酸化物粉末を比較的高率に含んでいる。なお、各ペーストを製造するのに使用した有機バインダー（エチルセルロース）の含有率（対Ａｇ比％）及び溶剤の種類は、表１４〜表１６に示したとおりである。また、実施例４０及び実施例４２に係るペーストの調製にあたっては分散剤（ここではアミン系のものを使用した）を微量配合した。
【００９４】
【表１４】

【００９５】
【表１５】

【００９６】
【表１６】

【００９７】
＜Ａｇペーストの性能評価＞
一般的な回転粘度計（ブルックフィールド社製：型式ＤＶ３）及びローター（ブルックフィールド社製：型式ＳＣ４−１４）を用いてこれらＡｇペーストの粘度（Ｐａ・ｓ）と粘度比を測定した。結果を表１３〜表１６の該当欄に示す。なお、表中の１Ｔ、１０Ｔ、５０Ｔ及び１００Ｔはそれぞれ１ｒｐｍ、１０ｒｐｍ、５０ｒｐｍ及び１００ｒｐｍであるときの粘度を示している。
表１３から明らかなように、側面導体膜形成用Ａｇペーストは、低粘度である。従って、これら側面導体膜形成用Ａｇペーストは、微細なチップ形状のセラミック基材に対しても精細なスクリーン印刷等を好ましく行うことができる。
他方、表１４〜１６から明らかなように、表面導体膜形成用Ａｇペーストは、側面導体膜形成用Ａｇペーストよりも粘度が高く、基材表面に塗布（印刷）する或いはスルーホールに充填するのに適している。また、Ａｇ粉末含有率が高いため、導体膜の導通抵抗を低く抑えることができる。
【００９８】
各Ａｇペーストを用いてそれぞれ形成した導体膜について、乾燥密度（ｇ／ｃｍ³）を以下のようにして測定した。すなわち、予め重量を測定しておいたアルミナ基板上に、３０ｍｍ×２０ｍｍ角の大きさで導体膜を印刷した。次いで、１００〜１２０℃で１０分程度の乾燥処理を施した。かかる印刷処理及び乾燥処理を繰返し、印刷膜を３〜５層重ねて形成した。次いで、この印刷基板の重量を測定し、その測定値（印刷基板重量）からアルミナ基板重量を差し引き、印刷層の重量（乾燥ペースト重量）を算出した。同時に、表面粗さ計等を使用して印刷層の膜厚を測定し、それに基づいて当該印刷層の体積を算出した。乾燥密度は、（印刷層の重量）／（印刷層の体積）より導き出した。
得られた結果を表１３〜１６の該当欄に示す。各Ａｇペーストは、いずれも良好な乾燥密度の導体膜（即ち導通抵抗の低い導体膜）を形成することができる。
【００９９】
また、各Ａｇペーストを用いて導体膜を形成する場合の収縮率（％）を調べた。すなわち、各Ａｇペーストを一般的なスクリーン印刷法に基づいて厚み：約１ｍｍのアルミナ製セラミックシートの表面に塗布し（膜厚：１０〜３０μｍ）、最高温度９５０℃の条件で焼成処理した。常温時（焼成前）と比較したときの７００℃及び９００℃におけるセラミックシート上での収縮の変化即ち体積減少度合（−％）をＴＭＡを指標として調べた。
得られた結果を表１３〜１６の該当欄に示す。いずれのＡｇペーストも比較的低い収縮率（０〜−２１％）を示した。特に、実施例３６、３９〜４１のＡｇペーストの７００℃における収縮率は０〜−１０％以内である。このことは、セラミック基材との同時焼成において、当該セラミック基材（アルミナ等）とその表面及び／又は内面に形成された導体膜との間に収縮率差がほとんど生じないことを示している。従って、これらＡｇペーストを表面導体膜形成用途に使用することによって、或いは積層タイプのセラミック配線基板を製造する場合にはさらに内面導体膜形成用途として使用することによって、同時焼成時におけるセラミック基材との過大な焼成収縮率差の発生を防止し、結果、セラミック基材と導体膜との接着特性に優れ、構造欠陥のないセラミック電子部品を製造することができる。
【０１００】
また、これらＡｇペーストの耐熱性を調べた。すなわち、アルミナ製のセラミック基板上に実施例３１のＡｇペーストを塗布し、９５０℃で１時間の焼成処理を行った。比較対象として、表面が有機系金属化合物や金属酸化物によってコーティングされていない従来の一般的なＡｇ単体粉末を主成分とする導体ペースト（以下「従来のＡｇペースト」という。）を塗布したセラミック基板を同条件で焼成処理した。かかる焼成処理後のセラミック基板表面の写真を図１として示す。これら写真から明らかなように、従来のＡｇペーストを塗布したものは、導体膜の剥離及び蒸発が顕著であった（図１の（Ａ）参照）。一方、本発明に係るＡｇペーストを塗布したものは、顕著な剥離、蒸発及び発泡が認められず、良好な導体膜（焼結体）が形成・維持された（図１の（Ｂ）参照）。このことから、本発明に係るＡｇペーストは、Ａｇベース微粒子を主成分とする導体ペーストであるにもかかわらず、比較的高温での焼成に対応し得ることが確認された。
【０１０１】
＜セラミック配線基板の製造＞
次に、表面導体膜形成用Ａｇペーストを用いて、セラミック基材（ここでは厚みが約２．０ｍｍのアルミナ製基板）の表面に所定のパターン（図２参照）の導体膜を形成した。すなわち、一般的なスクリーン印刷法に基づいてセラミック基板の表面に実施例３１のＡｇペーストを塗布し、膜厚が１０〜３０μｍの塗膜を形成した。続いて、遠赤外線乾燥機を用いて１００℃で１５分間の乾燥処理を施した。この乾燥処理により、上記塗膜から溶剤が揮発していき、セラミック基板上に未焼成の導体膜が形成された。
次に、この導体膜をセラミック基板ごと焼成した。すなわち、電気炉中で７００℃、１時間の焼成処理を行った。この焼成処理によって、上記所定のパターンの導体膜が焼き付けられたセラミック配線基板が得られた（図２の実施例の欄の写真参照）。
なお、比較対象として、従来のＡｇペースト（比較例Ａ）、ＡｇとＰｄが８０／２０である合金粉末を主成分とする従来の導体ペースト（比較例Ｂ）、ならびにＡｇとＰｔが９９．５／０．５である合金粉末を主成分とする従来の導体ペーストを使用して、同様の処理を行い、同形状の導体膜が焼き付けられたセラミック配線基板をそれぞれ作製した。
【０１０２】
半田耐熱性は以下のように試験・測定した。すなわち、セラミック基板の導体膜形成部分にロジンフラックスを塗布した後、当該基板を所定温度の半田（Ｓｎ／Ｐｂ＝６０／４０（重量比））に所定時間浸漬した。ここでは、かかる半田温度条件及び浸漬時間を２３０±５℃×３０秒、２６０±５℃×２０秒の２通りとした。かかる浸漬後のセラミック基板表面の写真を図２として示す。これら表面写真から明らかなように、実施例３１の導体膜は、いずれの条件でもいわゆる「半田くわれ」が実質的に生じなかった。また、Ａｇ／Ｐｄ合金から形成された比較例Ｂの導体膜についても殆ど「半田くわれ」は生じていない。他方、表面がコーティングされていない従来のＡｇ単体から形成された比較例Ａの導体膜は著しい「半田くわれ」が生じており、浸漬前と比較して導体膜の３０％以上が失われた。
このように、本発明によると、Ａｇ単体を主成分とする導体ペーストから成る導体膜であるにもかかわらず、Ｎｉメッキ、半田メッキ等のメッキ処理を施すことなくＡｇ／Ｐｄ合金から成る導体膜と同等又はそれ以上の半田耐熱性を実現することができる。
【０１０３】
＜試験例１＞
本発明に関連する試験例１として、有機金属塩のコーティング量及び／又は焼成温度と焼成収縮率との関係について考察した。
すなわち、各実施例のＡｇペーストを調製するのと同様にして、平均粒径０．８〜１．０μｍのＡｇ粉末を含有率８５wt％となるように溶剤（ＢＣ）に分散して成るＡｇペースト（無機酸化物粉末を含まない）であって、上述のアルミニウムアルコキシドのコーティング量が酸化物（Al₂O₃）換算でＡｇ粉末の０〜０．５wt％となる計６種類のＡｇペーストを調製した。
それらペーストを、上記＜Ａｇペーストの性能評価＞の項で説明したのと同様の方法で、アルミナ製セラミックシートの表面に塗布し、４００℃〜９００℃の温度条件で焼成処理を行い、収縮率（％）を求めた。その結果を図３に示す。上記コーティング量の範囲では、コーティング量が増加する程、収縮率が減少した。特にコーティング量が０．１％以上のものは、８００℃以上（例えば９００℃）の温度条件での焼成処理によっても低い収縮率を維持し得ることが確認された。
【０１０４】
＜試験例２＞
本発明に関連する試験例２として、無機酸化物粉末の種類及び添加量と接着強度（引っ張り強度）との関係について考察した。
すなわち、各実施例のＡｇペーストを調製するのと同様にして、平均粒径０．８〜１．０μｍのＡｇ粉末であって酸化物（Al₂O₃）換算でＡｇ粉末の０．１wt％となる量で上述のアルミニウムアルコキシドでコーティングされたＡｇ粉末を含有率８５wt％となるように溶剤（ＢＣ）に分散してＡｇペーストを調製した。この試験例では、酸化ビスマス、酸化銅、又は酸化物ガラス（Ｂｉ₂Ｏ₃−Ｂ₂Ｏ₃−ＳｉＯ₂系ガラス）をＡｇ粉末の０．２５wt％、０．５wt％又は１wt％相当量含む、計９種類のＡｇペーストを調製した。
それらペーストを用いて、上述したものと同様のセラミック配線基板を作製し、上記引っ張り強度試験を行った。その結果を図４に示す。グラフから明らかなように、各Ａｇペーストから形成された導体膜はいずれも高い接着強度を有することが確認された。
【０１０５】
以上の実施例や試験例において、本発明の具体例を詳細に説明したが、これらは例示にすぎず、特許請求の範囲を限定するものではない。特許請求の範囲に記載の技術には、以上に例示した具体例を様々に変形、変更したものが含まれる。
また、本明細書または図面に説明した技術要素は、単独であるいは各種の組み合わせによって技術的有用性を発揮するものであり、出願時の請求項記載の組み合わせに限定されるものではない。また、本明細書または図面に例示した技術は複数目的を同時に達成するものであり、そのうちの一つの目的を達成すること自体で技術的有用性を持つものである。
【０１０６】
【発明の効果】
以上説明したように、本発明の導体ペーストによれば、Ｐｄ等の高価な貴金属を多量に用いたり或いはＮｉめっき処理等を別途行うことなく、実用上充分な半田耐熱性、半田濡れ性、接着強度、導電性を有する膜状導体を形成することができる。このため、本発明の導体ペーストを用いると、安価且つ比較的簡便な処理によって、電気的信頼性及び機械的強度の高い導体層（膜状導体）が形成されたセラミック配線基板その他のセラミック電子部品を製造することができる。
【図面の簡単な説明】
【図１】（Ａ）は従来のＡｇペーストを塗布したセラミック基板表面の高温焼成処理後の状態を示す写真であり、（Ｂ）は本発明に係るＡｇペーストを塗布したセラミック基板表面の高温焼成処理後の状態を示す写真である。
【図２】導体膜の形成された実施例３１及び比較例Ａ，Ｂに係るセラミック配線基板を溶融状態の半田に浸漬した後の当該セラミック基板表面（導体膜）の状態を示す写真である。
【図３】一試験例における、有機金属塩のコーティング量及び／又は焼成温度と焼成収縮率との関係を示すグラフである。
【図４】一試験例における、無機酸化物粉末の種類及び添加量と接着強度（引っ張り強度）との関係を示すグラフである。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a conductor paste used for forming a film conductor on a ceramic substrate or the like.
[0002]
[Prior art]
2. Description of the Related Art A conductor paste is used as a material for forming a film-shaped conductor (wiring, electrode, and the like) having a predetermined pattern on a ceramic wiring board and other ceramic electronic components used for constructing a hybrid IC, a multi-chip module, and the like. This conductor paste disperses a metal powder as a main component forming a conductor and various additives (inorganic binder, glass frit, filler, etc.) added as required in a predetermined organic medium (vehicle). Is a conductor-forming material prepared by
Such a conductor paste is printed and applied to a ceramic substrate or the like by a general method such as screen printing. Next, by baking (baking) the applied material (coating) at an appropriate temperature, a film-shaped conductor having a predetermined pattern is formed on a ceramic electronic component such as the ceramic substrate.
A typical example of such a conductive paste is a metal powder mainly composed of silver (Ag) (hereinafter abbreviated as “Ag paste”). Ag powder is available at a lower cost than gold (Au), platinum (Pt), palladium (Pd), and the like, and has a lower electrical resistance. For this reason, Ag paste is widely used for forming film conductors on various electronic components.
[0003]
By the way, the Ag paste for the above use has the following problems conventionally. That is, the film-like conductor formed by using the Ag paste in which the metal powder is made of only Ag had low so-called solder heat resistance. For this reason, so-called "solder cracking (typically, dissolution of Ag contained in the film-like conductor into solder)" may occur due to high heat when soldering various elements to the film-like conductor. Such low solder heat resistance, that is, the occurrence of remarkable solder cracks deteriorates the joining property between the circuit and the element formed of the film conductor, and eventually causes disconnection and other conduction defects, which is not preferable. .
Therefore, in order to prevent such solder cracking, in other words, to improve the solder heat resistance, a plating film of nickel (Ni) or copper (Cu) may be further formed on the surface of a conductor made of Ag. Was. This is because, when a Ni plating film or the like is formed on the surface of the film-like conductor, it functions as a barrier and can prevent the Ag base conductor from being soldered.
However, it is not preferable to separately perform such a metal plating process, because the process of manufacturing a ceramic electronic component such as a ceramic substrate (for example, a multilayer ceramic capacitor) becomes more complicated. In addition, the addition of the plating process may be a factor in increasing the production cost of the electronic component.
[0004]
As another means for reducing or preventing solder cracking, a hybrid metal powder of Ag and palladium (Pd) or a composite metal powder of Ag and platinum (Pt) is mainly used instead of an Ag paste consisting of Ag alone. Conductive paste is used. According to the film conductor made of Ag and Pd or Pt formed using such a paste, the occurrence of solder cracks can be reduced or suppressed.
However, the film-shaped conductor made of Ag and Pd or Pt has a problem that the so-called “solder wetting (the degree of solder adhesion)” is inferior to a conductor made of Ag alone. Further, Pd and Pt are more expensive than Ag, which causes a higher production cost of ceramic electronic components.
Accordingly, an Ag-based conductor paste capable of forming a film conductor having improved solder heat resistance without using a large amount of such expensive noble metal or separately applying Ni plating is used for electronic components such as ceramic capacitors. It is desired in the manufacturing field.
[0005]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems relating to an Ag paste for forming a ceramic electronic component such as a ceramic substrate, and an object thereof is to provide a practically sufficient level of solder wettability. It is an object of the present invention to provide an Ag-based conductor paste realizing both solder heat resistance and solder heat resistance, and a method for producing the same. It is another object of the present invention to provide a method for manufacturing a ceramic electronic component using such a conductive paste.
[0006]
[Means for Solving the Problems]
The present invention which solves the above-mentioned problemsUsed for forming fired film conductors on substratesThe conductor paste has a metal powder as a main component, and the metal powder is substantially composed of fine particles (particle group) made of Ag or an alloy mainly composed of Ag, the surface of which is coated with an organic metal compound. And the organic metal compound is aluminum (Al)Organic acid metal salts, metal alkoxides or chelate compounds as constituent metal elements.
[0007]
The present inventors have proposed an organic metal compound of the type described above (ie,AlAnd an organic compound having no carbon-metal bond. same as below. The present invention has been found that by coating fine particles (powder) composed of Ag or an alloy mainly composed of Ag by (1), the soldering heat resistance of a fired product (film conductor) composed of the Ag-based fine particles can be remarkably improved. Conductor paste was created.
According to the conductor paste having the above configuration, it is possible to form a film conductor having improved solder heat resistance as compared with a conventional Ag paste. That is, according to the paste of the present invention, a film-like conductor having solder wettability not inferior to that of the conventional Ag paste and having a practically sufficient level of solder heat resistance that does not cause remarkable solder cracking is used as a ceramic base. It can be formed (baked) on a material.
[0008]
In a preferable paste of the present invention, the coating amount (content) of the organic metal compound is converted into an oxide of the metal (that is, a metal oxide obtained by firing the organic metal compound (for example,Al _Two O _Three )(Equivalent weight), and is equivalent to 0.01 to 2.0 wt% of the total amount of the fine particles contained in the paste.
According to the conductor paste of this configuration, practically sufficient levels of solder wettability and solder heat resistance can be realized while maintaining a low resistivity (ie, sufficient conductivity) equivalent to a film conductor made of Ag alone. Can be.
[0009]
Further, a preferable paste of the present invention is characterized in that the fine particles (fine particle group or powder) have an average particle size of 0.3 to 1.0 μm.
According to the conductor paste of the present configuration, the solder paste has excellent practicality in solder wettability and solder heat resistance, and there is little occurrence of remarkable pores that may cause factors such as an increase in resistance and disconnection. An Ag-based film-like conductor having a dense structure and excellent strength can be formed. For example, a dense film conductor (hereinafter, referred to as “surface conductor film”) can be formed on a wide surface (front surface) of the multilayer ceramic capacitor. Alternatively, a film-like conductor such as a so-called terminal electrode (hereinafter referred to as a “side-surface conductor film”) is provided on a side surface (referred to as any surface adjacent to the surface conductor film forming surface; hereinafter the same) of such a multilayer ceramic electronic component. .) Can be formed.
[0010]
Further, the present invention provides a method for suitably producing the above-mentioned conductor paste. That is, the method for producing a conductor paste containing a metal powder as a main component provided by the present invention comprises the steps of: (a) applying a surface of fine particles made of Ag or an alloy mainly composed of Ag having an average particle diameter of 0.3 to 1.0 μm to an organic type; Preparing a metal powder by coating with a metal compound, and (b) dispersing the coated metal powder in an organic medium (vehicle), wherein the organic metal compound comprises Al It is a metal salt of an organic acid, a metal alkoxide or a chelate compound as a constituent metal element.
According to the conductor paste manufacturing method of the present configuration, the above-described conductor paste of the present invention can be suitably manufactured.
[0011]
The present invention also provides a method for manufacturing a ceramic electronic component using the above-described conductor paste of the present invention.
That is, the method for producing a ceramic electronic component including a ceramic substrate on which a film-shaped conductor is provided, provided by the present invention, comprises the steps of (a) metal powder having the following properties, ie, “the surface is coated with an organic metal compound. It is substantially composed of fine particles of Ag or an alloy mainly composed of Ag and having an average particle diameter of 0.3 to 1.0 μm, and the organic metal compound is an organic acid metal salt, metal alkoxide or metal alkoxide containing Al as a constituent metal element. The method includes a step of applying (ie, adhering) a conductive paste mainly containing a metal powder, which is a chelate compound, to a ceramic base material, and a step of baking the applied paste main component. .
In this specification, “ceramic electronic component” generally means an electronic component having a ceramic base material (base). Therefore, hybrid ICs, multi-chip modules, and ceramic wiring boards or multilayer ceramic capacitors that constitute them are typical examples included in the “ceramic electronic component” defined in this specification.
[0012]
In the method for manufacturing a ceramic electronic component according to the present invention, the film conductor (wiring or electrode of a predetermined pattern) provided on the ceramic base material is formed from the above-described conductor paste. It is possible to manufacture a ceramic electronic component provided with a film-shaped conductor that achieves practically sufficient levels of solder wettability and solder heat resistance while maintaining resistivity. That is, by such a manufacturing method, it is possible to manufacture a ceramic electronic component having good bonding properties (high bonding strength) with other electronic elements and circuits, and having excellent electrical characteristics and mechanical characteristics.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail.
The conductor paste of the present invention is an electronic component forming paste characterized by containing the above-described metal powder as a main component, and there is no particular limitation on the content and composition of other subcomponents as long as the above object can be achieved. .
The metal powder according to the present invention is a fine particle group (hereinafter abbreviated as “Ag-based fine particles”) substantially composed of Ag or an alloy mainly composed of Ag (for example, an Ag—Au alloy or an Ag—Pd alloy). It is a powder substantially composed of an organic metal compound that coats its surface. As such Ag-based fine particles, from the viewpoint of imparting conductivity, Ag alone or a specific resistance value of about 1 × 10^ThreeΩ · cm or less (preferably 1.8 to 5.0 × 10^-6Ω · cm, for example, 1.9 to 3.0 × 10^-6Ω · cm) is suitable. Also, although not particularly limited, the average particle size is from the viewpoint of forming a fired film having a dense structure.Is 0. 3 to 1.0μmAg-based microparticles are preferred. Further, Ag-based fine particles having a relatively narrow average particle diameter and having a relatively narrow particle size distribution substantially free of particles having a particle diameter of 10 μm or more (particularly preferably 5 μm or more) are particularly preferable. preferable.
[0014]
Although not particularly limited, when the paste for forming the surface conductor film and the paste for forming the side surface conductor film are separately manufactured, the Ag-based fine particles included in the paste for forming the side surface conductor film are used for forming the surface conductor film. It is preferable that the particle size is smaller than the Ag-based fine particles contained in the paste. For example, Ag-based fine particles contained in a conductor paste for forming a side conductor film of a multilayer ceramic circuit board (for example, a low-temperature sintered chip antenna module provided in a mobile phone) mounted on a small electronic product include an average particle size. Those having a diameter of less than 0.5 μm (typically 0.3 to 0.5 μm) are preferred. When a paste containing Ag-based fine particles having such a particle size is used, the resistance is lower than that of a normal surface conductor / side conductor, and a dense surface conductor / side conductor can be formed. Further, a side conductor film (terminal electrode or the like) which is denser and has lower resistance than the surface conductor film can be formed..
The Ag-based fine particles themselves may be manufactured by a conventionally known manufacturing method, and do not require any special manufacturing means. For example, Ag-based fine particles manufactured by a well-known reduction precipitation method, a gas phase reaction method, a gas reduction method, or the like can be used.
[0015]
Next, the organic metal compound that coats the surface of the Ag-based fine particles will be described. As the organic metal compound used for coating the Ag-based fine particles, a film of a metal (including a metal oxide or a reduced product thereof) suitable for realizing the object of the present invention is finally (after firing) coated on the surface of the Ag-based fine particles. An organic acid metal salt, a metal alkoxide or a chelate compound containing Al as a constituent metal element, which can form (that is, a deposit covering the surface) is used.
For example, preferred metal alkoxides include aluminum ethoxide (Al (OC_TwoH_Five)_Three), Aluminum t-butoxide (Al (OC (CH_Three)_Three)_Three), Aluminum alkoxides such as acetoalkoxyaluminum diisopropylate, acetoalkoxyaluminum ethyl acetoacetate, and acetoalkoxyaluminum acetylacetonate..
[0016]
Other suitable organic metal compounds used for coating the Ag-based fine particles according to the present invention include:AlOrganic acid metal salt as a constituent metal element.
Further, the inventor of the present invention preferably uses the noble metal powder corresponding to high-temperature sintering which has different problems and objects to be solved in the present invention (that is, a noble metal powder fired at a high temperature: see JP-A-8-7644). It has been found that certain organic acid metal salts are suitable as the organic metal compound according to the present invention. That is, the organic acid metal salt suitable as the organic metal compound used for the Ag-based fine particle coating of the present invention is a carboxylate having the above-listed elements as main constituent metal elements. For example,With AlExamples include compounds with various fatty acids (for example, naphthenic acid, octylic acid, ethylhexanoic acid), and organic acids such as abietic acid and naphthoic acid. Particularly preferred organic acid metal salts areWith AlCompounds with carboxylic acids (especially fatty acids).
The fired product of the Ag-based fine particles coated with the organic acid metal salt having such a composition realizes particularly high solder heat resistance and adhesive strength. Therefore, in the conductor paste of the present invention, a film conductor having a practically sufficient level of solder heat resistance and adhesive strength can be formed on a ceramic substrate even when an inorganic additive described below is not added. Therefore, when the conductor paste of the present invention is used, without using a large amount of expensive noble metal such as Pd and without performing a complicated plating process, a film having a sufficient level of solder heat resistance and adhesive strength for practical use is obtained. Conductor (surface conductor film, side conductor film, inner conductor film(This refers to a film conductor embedded inside when several ceramic sheets are stacked. The same applies hereinafter.)Etc.) on a ceramic substrate.
[0017]
Next, a method for coating the surface of the Ag-based fine particles with an organic metal compound, that is, a method for producing a metal powder coated with a predetermined organic metal compound will be described.
The metal powder used in the practice of the present invention is not particularly limited as long as the organic metal compound is uniformly and almost uniformly coated on the surface of the main Ag-based fine particles. Therefore, a conventionally known method of coating a metal particle with an organic substance can be applied as it is. For example, a desired organic metal compound is dissolved or dispersed in an appropriate organic solvent such as toluene, xylene, or various alcohols. Next, Ag-based fine particles are added to the obtained solution or dispersion liquid (sol), and dispersed and suspended. By leaving or stirring the suspension for a predetermined time, the surface of the Ag-based fine particles in the suspension can be coated with the target organic metal compound. At this time, although not particularly limited, preferably, the coating amount of the organic metal compound is 0.01 to 2.0 wt% (typically 0.01 to 1.0 wt%) of the total amount of the Ag base fine particles in terms of oxide. %, For example, 0.01 to 0.1 wt%), and the desired organic metal compound is coated on the metal powder. If the amount of the coating is too small, which is equivalent to 0.01% by weight of the Ag-based fine particles in terms of oxide, the effect of the coating is so weak that it is difficult to achieve the object of the present invention. On the other hand, when the coating amount is excessively larger than the amount corresponding to 2.0 to 3.0% by weight of the Ag-based fine particles in terms of oxide, various functions such as the electrical characteristics of the Ag-based metal powder are impaired. It is not preferable because there is a possibility of being generated.
[0018]
In particular, in the case of the surface conductor film forming paste, it is preferable that the coating amount is an amount corresponding to 0.025 to 2.0 wt% of the Ag base fine particles in terms of oxide. When the coating material after firing is alumina, that is, an organic metal compound such as an organic acid metal salt, metal alkoxide, or a chelate compound containing Al as a constituent element.With thingsWhen coating the Ag base fine particles, it is particularly preferable that the coating amount is an amount corresponding to 0.1 to 2.0 wt% of the Ag base fine particles in terms of oxide (for example, 0.2 to 1.0 wt%).
The conductor paste having such a coating amount hardly causes excessive shrinkage during firing, and can prevent an excessive difference in firing shrinkage ratio between the ceramic substrate (alumina, zirconia, etc.) and the conductor film. For this reason, it is possible to manufacture a ceramic electronic component having excellent adhesive properties and having no remarkable structural defects such as peeling and cracks. Such a conductive paste is also suitable for forming an internal conductive film.
[0019]
Although not particularly limited, the paste for forming the side surface conductive film preferably has an amount of coating equivalent to 0.01 to 1.0 wt% of the Ag base fine particles in terms of oxide. When the coating material after firing is alumina, that is, an organic metal compound such as an organic acid metal salt, metal alkoxide, or a chelate compound containing Al as a constituent element.With thingsWhen coating the Ag base fine particles, it is particularly preferable that the coating amount is an amount corresponding to 0.01 to 1.0 wt% of the Ag base fine particles in terms of oxide (for example, 0.0125 to 0.1 wt%).
[0020]
Next, a description will be given of suitable components that can be included in the conductor paste of the present invention.
As a secondary component of the conductor paste of the present invention, an organic medium (vehicle) in which the metal powder is dispersed is exemplified. In practicing the present invention, the organic vehicle only needs to disperse metal powder, and those used in conventional conductive pastes can be used without any particular limitation. Examples include cellulose-based polymers such as ethyl cellulose, ethylene glycol and diethylene glycol derivatives, and high-boiling organic solvents such as toluene, xylene, mineral spirit, butyl carbitol, and terpineol.
[0021]
Further, the conductive paste of the present invention contains various inorganic additives as subcomponents as long as the inherent conductivity (low resistivity), solder wettability, solder heat resistance, adhesive strength and the like of the paste are not significantly impaired. be able to. For example, such inorganic additives include glass powder, inorganic oxides, and various other fillers. In particular, the addition of a small amount of glass powder and / or inorganic oxide is preferred.
That is, the glass powder can be an inorganic component (inorganic binder) that contributes to stably sticking and fixing the paste component attached to the ceramic base material (that is, improving the adhesive strength). Particularly, oxide glass is preferable. The oxide glass powder can be an inorganic component (inorganic binder) that contributes to stably sticking and fixing the paste component adhered to the ceramic substrate (that is, improving the adhesive strength). In view of the relationship with the firing temperature described later, those having a softening point of approximately 800 ° C. or less are preferable. Such glass powders include lead-based, zinc-based and borosilicate-based glasses, typically PbO-SiO_Two-B_TwoO_ThreeGlass, PbO-SiO_Two-B_TwoO_Three-Al_TwoO_ThreeGlass, ZnO-SiO_TwoGlass, ZnO-B_TwoO_Three-SiO_TwoGlass, Bi_TwoO_Three-SiO_TwoGlass and Bi_TwoO_Three-B_TwoO_Three-SiO_TwoIt is appropriate to use one or more glass powders selected from the group consisting of system glasses. Further, the glass powder used has a specific surface area of about 0.5 to 50 m.^Two/ G is preferable, and those having an average particle size of 2 μm or less (particularly about 1 μm or less) are particularly preferable.
[0022]
In addition, the inorganic oxide can contribute to improvement of the adhesive strength between the ceramic base material and the film conductor. Further, it is possible to prevent the occurrence of excessive firing contraction stress during firing of the film-shaped conductor formed from the conductor paste of the present invention, and to maintain the precision and mechanical strength of the ceramic electronic component to be manufactured at a practically high level. It can be an inorganic component that contributes to the performance. Examples of such a metal oxide include copper oxide, lead oxide, bismuth oxide, manganese oxide, cobalt oxide, magnesium oxide, tantalum oxide, niobium oxide, and tungsten oxide. Among these, copper oxide, lead oxide and bismuth oxide are particularly suitable oxides. Among them, bismuth oxide is a particularly suitable inorganic oxide because it promotes sintering of the Ag-based metal powder and can improve the wettability between Ag and a ceramic substrate (such as alumina). Further, copper oxide can improve the adhesion to the substrate.
As the metal oxide to be used, powder having an average particle size of 5 μm or less (typically 1 to 5 μm, particularly preferably 1 μm or less) is preferable from the viewpoint of optimizing the filling rate and dispersibility of the paste. . The specific surface area is at least 0.5 m^Two/ G is preferable, and 1.0 m^Two/ G or more (typically 1.0 to 2.0 m^Two/ G, particularly preferably 2.0 to 100 m^Two/ G) are particularly preferred.
[0023]
The conductive paste of the present invention contains various organic additives as sub-components as long as the original conductivity (low resistivity), solder wettability, solder heat resistance, adhesive strength and the like of the paste are not significantly impaired. be able to. For example, examples of such organic additives include various organic binders, and various coupling agents such as silicon-based, titanate-based, and aluminum-based coupling agents for improving adhesion to a ceramic substrate.
Examples of the organic binder include those based on acrylic resin, epoxy resin, phenol resin, alkyd resin, cellulosic polymer, polyvinyl alcohol, and the like. It is preferable that the conductive paste of the present invention can impart good viscosity and ability to form a coating film (adhesion film to a substrate). When it is desired to impart photocurability (photosensitivity) to the conductive paste of the present invention, various photopolymerizable compounds and photopolymerization initiators may be appropriately added.
[0024]
In addition to the above, a surfactant, an antifoaming agent, a plasticizer, a thickener, an antioxidant, a dispersant, a polymerization inhibitor, and the like may be appropriately added to the conductor paste of the present invention as necessary. Can be. These additives may be any additives that can be used for preparing a conventional conductor paste, and a detailed description thereof will be omitted.
[0025]
Next, preparation of the conductor paste according to the present invention will be described. The conductor paste of the present invention can be easily prepared typically by mixing a metal powder and an organic medium (vehicle), similarly to the conventional conductor paste. At this time, the above-mentioned additives may be added and mixed as needed. For example, using a three-roll mill or other kneading machine, the metal powder and various additives are directly mixed together with the organic vehicle at a predetermined compounding ratio and kneaded with each other.
[0026]
Although not particularly limited, it is preferable to knead each material so that the content of the metal powder as the main component is 60 to 95 wt% of the whole paste, and is 70 to 90 wt%. Is particularly preferred. In the paste for forming a surface conductor film, it is preferable to knead such that the content is 60 to 80 wt% (preferably 65 to 75 wt%). On the other hand, it is preferable that the Ag paste for forming the side conductor film is kneaded such that the content is 75 to 95 wt% (preferably 80 to 90 wt%).
The amount of the organic vehicle used for preparing the paste is suitably about 1 to 40% by weight of the whole paste, and particularly preferably 1 to 20% by weight.
When the above-mentioned glass powder is added as an inorganic additive, it is preferable to add about 0.5 wt% or less (more preferably 0.25 wt% or less) of the metal powder weight. According to such a low addition amount, the fired product (film conductor) obtained from the paste of the present invention can be used for the ceramic substrate without substantially impairing the good electrical conductivity and solder wettability of the conductive paste of the present invention. It is possible to realize an improvement in adhesive strength.
On the other hand, when the above-mentioned inorganic oxide is added as an inorganic additive, it is 5.0 wt% or less (more preferably 2.0 wt% or less, further preferably 1.0 wt% or less, particularly preferably 0.1 wt% or less) of the metal powder weight. It is preferable to add an amount of about 50% by weight or less. According to such a low addition amount, the fired product (film conductor) obtained from the paste of the present invention can be used for the ceramic substrate without substantially impairing the good electrical conductivity and solder wettability of the conductive paste of the present invention. It is possible to improve the adhesive strength and suppress the firing shrinkage.
[0027]
The improvement in the adhesive strength is a property that is particularly problematic for the side conductor film (terminal electrode and the like). Therefore, when a ceramic substrate is made of an oxide ceramic such as alumina and a ceramic electronic component is manufactured using the surface conductor film forming paste and the side conductor film forming paste, the side conductor film forming It is preferable to make the paste for use contain an inorganic oxide powder at a relatively high rate as a subcomponent. On the other hand, the paste for forming a surface conductor film does not necessarily need to contain such an inorganic oxide powder, and even when the inorganic oxide powder is contained from the viewpoint of improving the adhesive strength, the content is limited to the side conductor. It may be lower than the inorganic oxide powder content of the film forming paste. For example, when an inorganic oxide powder such as bismuth oxide or copper oxide is contained in the paste for forming the side conductor film, 0.001 to 5.0 wt% (more preferably 0.005 to 2.0 wt%) of the Ag base fine particles. It is preferable to include them in such a ratio as follows. On the other hand, the Ag paste for forming a surface conductor film preferably does not substantially contain such an inorganic oxide powder or has a content of less than 0.01% by weight of the Ag-based metal powder. In particular, if the oxide glass powder is contained in a relatively large amount, the conductor resistance may be increased.
It should be noted that the above numerical ranges relating to the content ratios and the mixing ratios of the respective components should not be interpreted strictly, and allow a slight deviation from such ranges as long as the object of the present invention can be achieved.
[0028]
Next, a preferred example of forming a film conductor using the conductor paste of the present invention will be described. The conductor paste of the present invention can be handled in the same manner as a conductor paste conventionally used for forming film conductors such as wirings and electrodes on a ceramic base material (substrate). It can be adopted without particular limitation. Typically, a conductive paste is applied to a ceramic base material (substrate) in a desired shape and thickness by a screen printing method, a dispenser coating method, or the like. Then, preferably after drying, appropriate heating conditions in a heater (typically a temperature range in which the maximum firing temperature is approximately 500 to 960 ° C., preferably does not exceed the melting point of Ag, for example, 700 to 960 ° C., particularly 800 to 960 ° C.) By heating at 900 ° C. for a predetermined time, the applied paste component is baked (baked) and cured. By performing this series of processing, a ceramic electronic component (for example, a ceramic wiring board for building a hybrid IC or a multi-chip module) on which a target film-like conductor (a wiring, an electrode, or the like) is formed can be obtained. Thus, a more advanced ceramic electronic component (for example, a hybrid IC or a multi-chip module) can be obtained by applying a conventionally known construction method while using the ceramic electronic component as an assembling material. Note that such a construction method itself does not particularly characterize the present invention, and a detailed description thereof will be omitted.
Although not intended to limit the use, as described above, the conductor paste of the present invention can form a film conductor having better solder heat resistance and adhesive strength than conventional conductor pastes. Therefore, the conductor paste of the present invention is suitable not only for forming a conductor having a thickness of about 10 to 30 μm but also for forming a conductor having a relatively small thickness of 10 μm or less.
[0029]
【Example】
Hereinafter, some examples of the present invention will be described, but it is not intended to limit the present invention to those shown in the examples.
[0030]
<Example 1: Preparation of conductive paste of the present inventionMade>
In this embodiment, as a base of the metal powder, a substantially spherical Ag powder having an average particle diameter in a range of 0.8 to 1.0 μm prepared by a general wet method was used. However, as shown in the table below, 0.8≫1.0, the particles having a particle size of about 0.8 μm have a particle size distribution that is richer than the particles having a particle size of about 1.0 μm. On the other hand, aluminum alkoxide (here, acetoalkoxy aluminum diisopropylate) was used as the organic metal compound.
The aluminum alkoxide was added to a suitable organic solvent (here, methanol) to prepare a coating solution having a concentration of 5 to 100 g / l. Next, an appropriate amount of the above Ag powder was suspended in the solution, and the suspension was maintained for 1 to 3 hours with appropriate stirring. Thereafter, the Ag powder was recovered and dried by ventilation at 60 to 110 ° C.
By the above processing, aluminum oxide (Al_TwoO_Three) An Ag powder (hereinafter referred to as “Al-coated Ag powder”) whose surface was almost uniformly coated with the aluminum alkoxide in an amount of about 0.0125 wt% of the Ag powder was obtained.
[0031]
Next, a conductor paste was prepared using the obtained Al-coated Ag powder. That is, the materials used were weighed such that the final paste concentration (weight ratio) was 87 wt% of the Al-coated Ag powder and the balance was a solvent (here, terpineol), and kneaded using a three-roll mill. Thus, a conductor paste according to the present example was prepared.
[0032]
<Example 2: Preparation of conductive paste of the present invention>Made>
By appropriately adjusting the aluminum alkoxide concentration of the coating solution and, if necessary, the suspension time of the Ag powder, aluminum oxide (Al_TwoO_Three) An Ag powder whose surface was almost uniformly coated with the aluminum alkoxide in an amount of about 0.025 wt% of the Ag powder in terms of conversion was obtained. Next, the same processing as in Example 1 was performed using the Al-coated Ag powder to prepare a conductor paste according to the present example. That is, the conductor paste according to the present embodiment is different from the conductor paste according to the first embodiment only in the amount of aluminum alkoxide coated.
[0033]
<Example 3: Preparation of conductive paste of the present invention>Made>
By appropriately adjusting the aluminum alkoxide concentration of the coating solution and, if necessary, the suspension time of the Ag powder, aluminum oxide (Al_TwoO_Three) An Ag powder whose surface was substantially uniformly coated with the aluminum alkoxide in an amount of about 0.05 wt% of the Ag powder in terms of conversion was obtained. Next, the same processing as in Example 1 was performed using the Al-coated Ag powder to prepare a conductor paste according to the present example. That is, the conductor paste according to the present embodiment differs from the conductor pastes according to the first and second embodiments only in the coating amount of the aluminum alkoxide.
[0034]
<Example 4: Preparation of conductor paste of the present invention>Made>
In this example, a substantially spherical Ag powder having an average particle diameter in the range of 0.8 to 1.0 μm was used as the base of the metal powder. However, as shown in the below-mentioned table, 0.8 後 述 1.0, particles having a particle size distribution in which particles having a particle size of about 1.0 μm were richer than particles having a particle size of about 0.8 μm were used. A conductor paste according to this example was prepared by applying the same materials and processing as in Example 1 except for the Ag powder. That is, the conductor paste according to the present embodiment and the conductor paste according to the first embodiment differ only in the Al powder (particle size distribution).
[0035]
<Example 5: Preparation of conductive paste of the present inventionMade>
By appropriately adjusting the aluminum alkoxide concentration of the coating solution and, if necessary, the suspension time of the Ag powder, aluminum oxide (Al_TwoO_Three) This example was carried out using the same materials and treatments as in Example 4 except that an Ag powder whose surface was substantially uniformly coated with the aluminum alkoxide in an amount of about 0.025 wt% of the Ag powder in terms of conversion was obtained. Example conductor pastes were prepared. That is, the conductor paste according to the present embodiment and the conductor paste according to the fourth embodiment differ only in the amount of aluminum alkoxide coated.
[0036]
<Example 6: Preparation of conductor paste of the present invention>Made>
By appropriately adjusting the aluminum alkoxide concentration of the coating solution and, if necessary, the suspension time of the Ag powder, aluminum oxide (Al_TwoO_Three) This example was carried out using the same materials and treatments as in Example 4 except that an Ag powder whose surface was substantially uniformly coated with the aluminum alkoxide in an amount of about 0.05 wt% of the Ag powder was calculated. Example conductor pastes were prepared. That is, the conductor paste according to the present embodiment is different from the conductor pastes according to the fourth and fifth embodiments only in the coating amount of the aluminum alkoxide.
[0037]
[0038]
[0039]
<Example 8: Preparation of conductor paste of the present invention>Made>
In this embodiment, a zinc-based glass (ZnO-B) was used as an inorganic additive._TwoO_Three-SiO_TwoA conductive paste containing a system glass (average particle size: 1-2 μm, softening point: 780 ° C.) was prepared.
That is, the Al-coated Ag powder obtained in Example 3 (coating amount: 0.050 wt% (Al_TwoO_ThreeConversion)) and zinc-based glass powder (specific surface area 1-2 m)^Two/ G of glass frit) and weigh these materials so that the final paste concentration (weight ratio) is 87 wt% of the Al-coated Ag powder and the balance is a solvent (terpineol). Was added, and the mixture was kneaded using a three-roll mill. Thus, a conductor paste according to the present example was prepared.
[0040]
<Example 9: Preparation of conductor paste of the present invention>Made>
In this embodiment, lead-based glass (PbO-SiO) was used as an inorganic additive._Two-B_TwoO_ThreeA paste containing a base glass (average particle size: 1-2 μm, softening point: 700 ° C.) was prepared.
That is, the Al-coated Ag powder and the lead-based glass powder obtained in Example 3 (specific surface area: 1 to 2 m^Two/ G of glass frit), and weigh these materials so that the final paste concentration (weight ratio) is 87 wt% of the Al-coated Ag powder and the balance is a solvent (terpineol). Was added and the mixture was kneaded using a three-roll mill. Thus, a conductor paste according to the present example was prepared.
[0041]
<Example 10: Preparation of conductive paste of the present invention>Made>
A conductor paste according to the present example was prepared by performing the same treatment as in Example 9 except that the amount of the lead-based glass powder was changed to 0.5 wt% in terms of the weight ratio to the Ag powder.
[0042]
<Example 11: Preparation of conductive paste of the present invention>Made>
A conductor paste according to the present example was prepared by performing the same process as in Example 9 except that the amount of the lead-based glass powder was changed to 1.0 wt% in terms of the weight ratio of Ag powder to Ag powder.
[0043]
<Example 12: Preparation of conductor paste of the present inventionMade>
In this embodiment, borosilicate glass (Bi) is used as an inorganic additive._TwoO_Three-B_TwoO_Three-SiO_TwoA paste containing a base glass, average particle size: 1-2 μm, softening point: 725 ° C.) was prepared.
That is, the Al-coated Ag powder and the borosilicate glass powder obtained in Example 3 (specific surface area: 1 to 2 m^Two/ G of glass frit) and weigh these materials so that the final paste concentration (weight ratio) is 87 wt% of the Al-coated Ag powder and the balance is a solvent (terpineol). The borosilicate glass powder was added in an amount of 0.5 wt% in the above, and kneaded using a three-roll mill. Thus, a conductor paste according to the present example was prepared.
[0044]
<Example 13: Preparation of conductor paste of the present inventionMade>
In this example, copper oxide (Cu_TwoO) A paste containing the powder was prepared. That is, the Al-coated Ag powder and the copper oxide powder obtained in Example 3 (average particle size: 1 to 5 μm, specific surface area: 0.5 to 1.5 m)^Two/ G) and weigh these materials so that the final paste concentration (weight ratio) is 87% by weight of the Al-coated Ag powder and the balance is a solvent (terpineol). Copper oxide powder was added in an amount of 25 wt% and kneaded using a three-roll mill. Thus, a conductor paste according to the present example was prepared.
[0045]
<Example 14: Preparation of conductive paste of the present inventionMade>
A conductor paste according to this example was prepared by performing the same process as in Example 13 except that the amount of the copper oxide powder added was 0.5 wt% in terms of the weight ratio to the Ag powder.
[0046]
<Example 15: Preparation of conductor paste of the present inventionMade>
A conductor paste according to the present example was prepared by performing the same process as in Example 13 except that the amount of the copper oxide powder to be added was changed to 1.0% by weight relative to the Ag powder.
[0047]
<Example 16: Preparation of conductive paste of the present invention>Made>
In this embodiment, lead oxide (Pb_ThreeO_Four) A paste containing the powder was prepared. That is, the Al-coated Ag powder and the lead oxide powder obtained in Example 3 (average particle size: 1 to 5 μm, specific surface area: 0.5 to 1.5 m)^Two/ G) and weigh these materials so that the final paste concentration (weight ratio) is 87% by weight of the Al-coated Ag powder and the balance is a solvent (terpineol). Lead oxide powder in an amount of 25 wt% was added and kneaded using a three-roll mill. Thus, a conductor paste according to the present example was prepared.
[0048]
<Example 17: Preparation of conductive paste of the present invention>Made>
A conductor paste according to the present example was prepared by performing the same process as in Example 16 except that the amount of the lead oxide powder added was 0.5 wt% in terms of the weight ratio to the Ag powder.
[0049]
<Example 18: Preparation of conductive paste of the present inventionMade>
A conductor paste according to this example was prepared by performing the same process as in Example 16 except that the amount of the lead oxide powder added was changed to 1.0 wt% in terms of the weight ratio to the Ag powder.
[0050]
<Example 19: Preparation of conductor paste of the present inventionMade>
In this example, bismuth oxide (Bi_TwoO_Three) A paste containing the powder was prepared. That is, the Al-coated Ag powder and the bismuth oxide powder obtained in Example 3 (average particle diameter: 1 to 10 μm, specific surface area: 0.5 to 2.0 m)^Two/ G) and weigh these materials so that the final paste concentration (weight ratio) is 87% by weight of the Al-coated Ag powder and the balance is a solvent (terpineol). Bismuth oxide powder was added in an amount of 25 wt% and kneaded using a three-roll mill. Thus, a conductor paste according to the present example was prepared.
[0051]
<Example 20: Preparation of conductor paste of the present inventionMade>
A conductor paste according to this example was prepared by performing the same process as in Example 19 except that the amount of bismuth oxide powder added was 0.5 wt% in terms of the weight ratio of Ag powder to Ag powder.
[0052]
<Example 21: Preparation of conductive paste of the present invention>Made>
A conductor paste according to this example was prepared by performing the same process as in Example 19, except that the amount of bismuth oxide powder added was 1.0 wt% in terms of the weight ratio of Ag powder to Ag powder.
[0053]
<Example 22: Preparation of conductor paste of the present inventionMade>
In this example, a paste containing the above-described bismuth oxide powder and lead-based glass powder as inorganic additives was prepared. That is, while using the Al-coated Ag powder, the bismuth oxide powder, and the lead-based glass obtained in Example 3, the final paste concentration (weight ratio) was 87 wt% of the Al-coated Ag powder, and the balance was a solvent (terpineol). These materials are weighed so that the weight ratio of bismuth oxide to the weight ratio of Ag powder to bismuth oxide powder and the amount of lead-based glass powder to be 0.25 wt% are added to the mixture, and the mixture is rolled using a three-roll mill. Kneaded. Thus, a conductor paste according to the present example was prepared.
[0054]
<Example 23: Preparation of conductor paste of the present inventionMade>
In this example, a fine Ag powder having an average particle size in the range of 0.3 to 0.5 μm was used as a base of the metal powder. Then, the same processing as in Example 3 is performed, and aluminum oxide (Al_TwoO_Three) An Ag powder whose surface was substantially uniformly coated with the aluminum alkoxide in an amount of about 0.05 wt% of the Ag powder in terms of conversion was obtained.
Thus, the same treatment as in Example 20 was performed except that the Al-coated Ag powder was used, and the present Example containing bismuth oxide powder (0.5% by weight to Ag powder weight ratio) as an inorganic additive was used. Was prepared.
[0055]
<Example 24: Preparation of conductive paste of the present inventionMade>
In this example, a fine Ag powder having an average particle size in the range of 0.3 to 0.5 μm was used as the base of the metal powder (the manufacturer of the Ag powder is different from that of Example 23). Then, the same processing as in Example 3 is performed, and aluminum oxide (Al_TwoO_Three) An Ag powder whose surface was substantially uniformly coated with the aluminum alkoxide in an amount of about 0.05 wt% of the Ag powder in terms of conversion was obtained.
Thus, the same treatment as in Example 20 was performed except that the Al-coated Ag powder was used, and the present Example containing bismuth oxide powder (0.5% by weight to Ag powder weight ratio) as an inorganic additive was used. Was prepared.
[0056]
<Example 25: Preparation of conductive paste of the present inventionMade>
In this example, an Ag powder having an average particle size in the range of 0.5 to 0.7 μm was used as a base of the metal powder. Then, the same processing as in Example 3 is performed, and aluminum oxide (Al_TwoO_Three) An Ag powder whose surface was substantially uniformly coated with the aluminum alkoxide in an amount of about 0.05 wt% of the Ag powder in terms of conversion was obtained.
Thus, the same treatment as in Example 20 was performed except that the Al-coated Ag powder was used, and the present Example containing bismuth oxide powder (0.5% by weight to Ag powder weight ratio) as an inorganic additive was used. Was prepared.
[0057]
<Example 26: Preparation of conductive paste of the present invention>Made>
In this example, a paste containing the above-described bismuth oxide powder and copper oxide powder as inorganic additives was prepared. That is, while using the Al-coated Ag powder, the bismuth oxide powder and the copper oxide powder obtained in Example 3, the final paste concentration (weight ratio) was 87% by weight of the Al-coated Ag powder, and the balance was a solvent (terpineol). These materials are weighed so that the weight ratio of bismuth oxide powder and the weight of copper oxide powder becomes 0.5 wt% and 0.5 wt% with respect to the Ag powder weight ratio, respectively, and kneaded using a three-roll mill. did. Thus, a conductor paste according to the present example was prepared.
[0058]
<Example 27: Preparation of conductive paste of the present inventionMade>
A conductor paste according to this example was prepared by performing the same process as in Example 26, except that the addition amount of the copper oxide powder was changed to 0.25 wt% in terms of a weight ratio to the Ag powder.
[0059]
<Example 28: Preparation of conductor paste of the present inventionMade>
A conductor paste according to this example was prepared by performing the same process as in Example 26, except that the addition amount of the copper oxide powder was 0.125 wt% in terms of the weight ratio of Ag powder to Ag powder.
[0060]
<Comparative Example 1: Preparation of conventional conductor pasteMade>
In this comparative example, an Ag powder having an average particle size in a range of 2.0 to 3.0 μm was used as a base of the metal powder. No coating with an organic metal compound was performed. That is, using the uncoated Ag powder as it is, these materials are weighed so that the final paste concentration (weight ratio) is 87 wt% of the Ag powder and the remainder is a solvent (terpineol), and kneaded using a three-roll mill. did. Thus, a conductor paste according to this comparative example was prepared.
[0061]
<Comparative Example 2: Preparation of conventional conductor pasteMade>
In this comparative example, an Ag powder having an average particle size in a range of about 1.0 μm was used as a base of the metal powder. No coating with an organic metal compound was performed.
Thus, the same treatment as in Example 26 was performed except that the uncoated Ag powder was used, and bismuth oxide powder and copper oxide powder (each 0.5 wt% with respect to the Ag powder weight ratio) were used as inorganic additives. A conductor paste according to this comparative example was prepared.
The average particle size of the Ag powder in the conductor pastes of the above Examples and Comparative Examples, the organic metal compound (ie, aluminum alkoxy)Do)Are shown in Tables 1 to 10 below with columns.
[0062]
[Table 1]

[0063]
[Table 2]

[0064]
[Table 3]

[0065]
[Table 4]

[0066]
[Table 5]

[0067]
[Table 6]

[0068]
[Table 7]

[0069]
[Table 8]

[0070]
[Table 9]

[0071]
[Table 10]

[0072]
<Example 29: Formation of film conductor and evaluation thereof (1)>
Next, a film conductor was formed on the surface of the ceramic base material (here, an alumina substrate having a thickness of about 0.8 mm) using the conductor paste according to each of the examples and the comparative examples. That is, a conductive paste was applied to the surface of a ceramic substrate based on a general screen printing method to form a coating film having a predetermined thickness (10 to 30 μm: see the “coating film thickness” column in each table). .
Subsequently, a drying treatment was performed at 100 ° C. for 15 minutes using a far-infrared dryer. By this drying treatment, the solvent volatilized from the coating film, and an unfired film conductor was formed on the ceramic substrate.
[0073]
Next, the film conductor was fired together with the ceramic substrate. That is, the baking treatment was performed in an electric furnace at 700, 750, 800, 850 or 900 ° C. (different for each paste used; see the “Baking temperature” column in each table) for one hour. By this baking treatment, a film-shaped conductor having a predetermined film thickness (see the column of “baked film thickness” in each table) was baked on the ceramic substrate. Hereinafter, when simply referred to as a film conductor, it refers to that after firing.
[0074]
Next, as a characteristic evaluation of each of the obtained film conductors, a resistance value, a sheet resistance value, a solder wettability, a solder heat resistance and a tensile strength were tested and measured as follows. The results of these property evaluation tests are shown in the corresponding columns of Tables 1 to 10 for each paste used. Note that n.d. in the table indicates that measurement has not been performed.
[0075]
<Measurement of resistance value>
The resistance value (Ω) of each of the film conductors obtained by using the conductor pastes of Examples 1 to 7 was measured as follows. That is, the resistance (Ω) of the film conductor was measured based on a general two-terminal method using a digital multimeter.
[0076]
<Measurement of sheet resistance>
The sheet resistance (mΩ / □) of each of the film conductors obtained using the conductor pastes according to Examples 1 to 25 and Comparative Examples 1 and 2 was measured as follows. That is, the sheet resistance value (mΩ / □) was calculated from the following equation based on the measured resistance value (Ω).
Sheet resistance value (mΩ / □) = measured resistance value (Ω) × (conductor width (mm) / conductor length (mm)) × (conductor thickness (μm) / converted thickness (μm)); Burned product 10 μm or printed material 25 μm.
[0077]
<Solder wettability>
The solder wettability of each of the film conductors obtained using the conductor paste according to each of the examples and comparative examples was examined as follows. That is, after applying a rosin flux to the film-shaped conductor portion of each ceramic substrate, the substrate was immersed in solder (Sn / Pb = 60/40 (weight ratio)) at 230 ± 5 ° C. for 3 seconds. Thereafter, the solder wettability was evaluated based on the area ratio of the film-shaped conductor portion wetted with the solder. Specifically, a film-shaped conductor having 90% or more of its surface wetted was judged to exhibit good solder wettability, and is indicated by ◎ in the table. On the other hand, when the solder wettability was 80% or less of the entire surface of the film conductor, it was judged that the solder wettability was inferior.
[0078]
<Solder heat resistance>
The solder heat resistance of each of the film conductors obtained using the conductor paste according to each example and comparative example 2 was examined as follows. That is, after applying the rosin flux to the film-shaped conductor portion of each ceramic substrate, the substrate was immersed in solder (Sn / Pb = 60/40 (weight ratio)) at a predetermined temperature for a predetermined time. Here, the solder temperature condition and the immersion time were set to three types of 230 ± 5 ° C. × 30 seconds, 260 ± 5 ° C. × 10 seconds, and 260 ± 5 ° C. × 20 seconds (application conditions differed for each used paste). See the "Solder heat resistance" column in each table.)
Thus, the solder heat resistance was evaluated by the area ratio of the film conductor remaining on the ceramic substrate after the immersion as compared with before the immersion, that is, the portion that was not “soldered” after the immersion. Specifically, those in which approximately 90% or more of the film-like conductors remained were judged to exhibit excellent solder heat resistance, and are indicated by ◎ in the table. Further, those in which about 80% or more and less than 90% of the film-like conductors remained were judged to exhibit good soldering heat resistance, and are indicated by a circle in the table. On the other hand, when the remaining portion of the film conductor was less than about 80% before immersion, it was judged that the solder heat resistance was relatively inferior.
[0079]
<Tensile strength>
For each of the film conductors obtained using the conductor paste according to each of the examples and comparative example 2, the tensile strength (kg) was measured as an index of the adhesive strength to the ceramic substrate as follows. That is, an evaluation lead wire (tin-plated copper wire) was soldered to a film-shaped conductor formed by burning on a ceramic substrate. Thereafter, the lead wire was pulled by a predetermined force in a direction perpendicular to the surface direction of the substrate, and a load (kg) when the joint surface was broken (cut) was defined as an adhesive strength (tensile strength). Here, the above tensile strength test was performed on the ceramic substrate immediately after the above-mentioned firing treatment and on the ceramic substrate after being subjected to aging at 150 ° C. for 48 hours, 100 hours or 200 hours after firing (the conditions used were the paste used). (See the “tensile strength” column in each table.)
[0080]
As is clear from the results of the respective characteristic evaluation tests shown in Tables 1 to 10, the film-like conductor (thickness: 10 to 22 μm) formed from the conductor paste according to the present example has no problem as a conductor. The resistance value and / or sheet resistance value is shown. These results show that the conductive paste of the present invention can be suitably used for forming a film conductor from the viewpoint of conductivity, that is, electrical characteristics.
In addition, the solder wettability was slightly inferior (approximately 50% to 70%) to those containing a relatively large amount of lead-based glass powder or borosilicate glass powder (Examples 10, 11, and 12). Other than those, the above index value of the solder wettability was 90% or more (９０ in the table). This indicates that the conductor paste of the present invention is suitable for use in forming a film conductor from the viewpoint of solder wettability. When glass powder is added, zinc-based glass powder is relatively preferred (Example 8).
[0081]
As is clear from the evaluation test for solder heat resistance, the film conductor formed from the conductor paste according to each of the examples was a film conductor formed from a conventional conductor paste containing Ag / Pd powder or Ni-plated. The solder heat resistance was equal to or higher than that of the film conductor. In particular, pastes prepared without adding inorganic additives (Examples 1 to6) Was confirmed to have high solder heat resistance (Examples 1 to 5).6). This means that according to the present invention, the Ag-based fine particles are coated with a very small amount of an organic metal compound (here, metal alkoxide) of about 0.01 wt% (in terms of oxide) based on the metal (Ag) powder. This shows that high solder heat resistance at a practical level can be realized without using expensive Pd or performing complicated Ni plating.
[0082]
Further, as is clear from the evaluation test on the tensile strength, the film-like conductor formed from the conductor paste of the present invention is a baked product of Ag-based fine particles, and as a result, has a practical level of adhesion without the need of any additive. It was confirmed that the strength was maintained (Examples 1 to 5).6). Also, from the results of using the pastes of the respective examples to which the inorganic additives were added, by adding an appropriate amount of glass frit and / or inorganic oxide powder, it was possible to maintain desired solder heat resistance and solder wettability. It was confirmed that the adhesive strength could be improved (for example, see Example 3 and Examples 13 to 15). In particular, the addition of an appropriate amount of an inorganic oxide is effective. By such addition, both maintenance of high solder wettability and solder heat resistance and improvement of adhesive strength can be realized (see Examples 13 to 28). Furthermore, it contributes to reduction of firing shrinkage. It should be noted that one kind of inorganic oxide may be added, but two or more kinds are preferably added in combination (see Examples 26 to 28).
[0083]
The average particle size (0.2 to 1.0 μm) of the Ag powder used in each example was suitable for preparing the conductor paste of the present invention (see Examples 20, 23, 24, and 25). ). Further, the film-shaped conductor firing temperature when the conductive paste according to each example is used is preferably 800 ° C. or higher from the viewpoint of maintaining a relatively high level of adhesive strength, and a firing temperature of about 850 to 900 ° C. is particularly preferable. It was shown that there is.
[0084]
<Example 30: Formation of film conductor and its evaluation (2)>
Next, in order to confirm that the conductor paste according to the present example can suitably form a thin film conductor (10 μm or less) thinner than that formed in the comparative example, Examples 17, 20, 22 and A comparatively thick film conductor and a comparatively thin film conductor were formed using a total of four types of conductor pastes of Comparative Example 2, and the same characteristic evaluation as in Example 29 was performed.
That is, similarly to Example 29, each conductive paste was applied to the surface of the ceramic substrate based on the screen printing method, and a thin coating film and a thick coating film were formed for each paste. Thereafter, the same baking treatment as in Example 29 was performed to form a relatively thick film conductor (thickness: 12 to 15 μm) and a relatively thin film conductor (thickness: 6 to 8 μm).
Next, as a property evaluation of each of the obtained film conductors, a sheet resistance value, solder wettability, solder heat resistance and tensile strength were tested and measured in the same manner as in the above example. The results are shown in Tables 11 and 12 below.
[0085]
[Table 11]

[0086]
[Table 12]

[0087]
As is clear from the results shown in Tables 11 and 12, the conductor pastes according to these examples have substantially the same conductivity, solder wettability, and solder heat resistance as a relatively thick film conductive film. A thin film conductive film having a thickness of 10 μm or less can be formed. This indicates that the conductor paste of the present invention can suitably produce ceramic electronic components such as a thin film circuit board and a thin film hybrid IC having excellent electrical and / or mechanical characteristics.
[0088]
From the above examples, several embodiments suitable as the conductor paste of the present invention have been clarified. Suitable conductor pastes include those having one or more of the following conditions as constituent elements. That is,
(1) Ag powder having an average particle size of 0.2 to 1.0 μm is mainly used as the metal powder.
(2) Metal alkoxide (particularly preferably aluminum alkoxyDo)Is coated with metal powder.
(3) The coating amount (content) of the metal alkoxide is an amount equivalent to 0.01 to 0.1 wt% of the metal (Ag) powder in terms of oxide.
(4) One or two or more inorganic oxides (preferably copper oxide, lead oxide, and the like) in an amount corresponding to about 1 wt% or less (preferably 0.5 wt% or less) of the metal (Ag) powder. And / or bismuth oxide) as an inorganic additive.
(5) One or two or more types of glass powder (preferably zinc-based glass, lead) in an amount corresponding to approximately 0.5 wt% or less (preferably 0.25 wt% or less) of the metal (Ag) powder. Glass and / or borosilicate glass) as an inorganic additive.
[0089]
Further, from the above examples, several embodiments particularly suitable as a method for manufacturing a ceramic electronic component using the conductive paste of the present invention have been clarified. Particularly preferred as the method for manufacturing a ceramic electronic component of the present invention include a method characterized by using the conductor paste according to any one of the preferred embodiments described above, or a method of applying the conductive paste to a ceramic substrate. A method is characterized in that the paste main component (that is, the coating metal powder) is fired at a temperature of about 800 to 900 ° C.
[0090]
<Example 31 to33: Ag paste for forming side conductor film>
Table 13 shows Examples 31 to 3133Meter shown as3Ag pastes for forming side conductor films having various compositions were prepared.
That is, the average particle diameter prepared as a Ag-based fine particle by a general wet method is in the range of 0.3 to 0.5 μm (excluding Example 32) or 0.6 to 0.8 μm (Example 32 only). An approximately spherical Ag powder was used. Also, as a coating materialALuminium alkoxide (acetoalkoxy aluminum diisopropylate)Was. Thus, the metal alkoxide was added to an appropriate organic solvent (here, methanol) to prepare a coating solution having a concentration of 5 to 100 g / l. Next, an appropriate amount of the above Ag powder was suspended in the solution, and the suspension was maintained for 1 to 3 hours with appropriate stirring. Thereafter, the Ag powder was recovered and dried by ventilation at 60 to 110 ° C.
By the above processing, the oxide (Al _Two O _Three )Approximately 0.0125 to 0.1 wt% of Ag powder in conversion%WhenAmount of aluminum alkoxyToThus, an Ag powder whose surface was almost uniformly coated (hereinafter referred to as “coated Ag powder”) was obtained. The coating amount can be easily adjusted by appropriately adjusting the metal alkoxide concentration of the coating solution and, if necessary, the suspension time of the Ag powder.
[0091]
In preparing the Ag paste for forming the side conductor, the average particle size as the inorganic oxide powder: 1 to 5 μm, the specific surface area: 0.5 to 1.5 m^Two/ G of copper oxide (Cu_TwoO or CuO) powder and average particle size: 1 to 10 μm, specific surface area: 0.5 to 2.0 m^Two/ G of bismuth oxide (Bi_TwoO_Three) Powder was used.
Thus, a coating Ag powder having a final concentration (weight ratio) of 65 to 75 wt%, and a coating Ag powder amount of 0.01 to 1.0 wt%To%Corresponding amount of bismuth oxide powder and 0.005-0.5 wt% of coating Ag powderTo%A corresponding amount of copper oxide powder, an organic binder (ethyl cellulose) corresponding to 1.5 to 10% by weight of the coating Ag powder amount, and a solvent (BC (butyl carbitol) for Examples 31 to 32) Mixed solvent of diethylene glycol monobutyl ether and terpineol, Example 3To 3Then, each material was weighed so as to be a mixed solvent of BC and an ester (specifically, a mixed solvent of trimethylpentadiol monoisobutyrate) and kneaded using a three-roll mill. As a result, the total amount shown in Table 13 is obtained.3Various kinds of Ag pastes were obtained.
[0092]
[Table 13]

[0093]
<Example 36, 39-44, 46 and47: Ag Paste for Forming Surface Conductive Film>
Table 14 to Table 16Shown inSum9Ag pastes for surface conductor film formation having various compositions were prepared. Examples 31 to 3133Ag powder and metal alkoxide of the same type as those used in the above were used.
That is, a coating solution having a metal alkoxide concentration of 5 to 100 g / l is prepared, and the same treatment as in the production of the Ag paste for forming the side surface conductive film is performed, and the oxide (Al _Two O _Three )0.025 wt% to 0.4 wt% of aluminum alkoxy in terms of Ag powderToThus, a coated Ag powder having a substantially uniform surface was obtained.
Next, the same treatment as that for the production of the Ag paste for forming the side conductor film is performed, so that the final paste concentration (weight ratio) becomes 83 to 86 wt%, and the amount of the coated Ag powder and the auxiliary components described in Tables 14 to 16 (Inorganic oxides, organic binders, solvents, etc.) as appropriate9Various kinds of Ag pastes were obtained. As is clear from the descriptions of Tables 14 and 16, one of the features of these surface conductor film forming Ag pastes is that the Ag powder content is higher than that of the side surface conductor film forming Ag pastes of Table 13. Example 36, 39Another feature is that the Ag pastes according to Nos. To 44 do not contain inorganic oxide powder (bismuth oxide and copper oxide). On the other hand, the embodiment46The Ag pastes according to Nos. 47 to 47 contain these inorganic oxide powders at a relatively high rate. The content of the organic binder (ethyl cellulose) (% by Ag) and the type of the solvent used for producing each paste are as shown in Tables 14 to 16. In preparing the pastes according to Examples 40 and 42, a small amount of a dispersant (here, an amine-based one was used) was blended.
[0094]
[Table 14]

[0095]
[Table 15]

[0096]
[Table 16]

[0097]
<Performance evaluation of Ag paste>
The viscosity (Pa · s) and the viscosity ratio of these Ag pastes were measured using a general rotational viscometer (Brookfield: Model DV3) and a rotor (Brookfield: SC4-14). The results are shown in the corresponding columns of Tables 13 to 16. In addition, 1T, 10T, 50T, and 100T in the table indicate viscosities at 1 rpm, 10 rpm, 50 rpm, and 100 rpm, respectively.
As is clear from Table 13, the Ag paste for forming the side conductor film has a low viscosity.. SubordinateTherefore, these Ag pastes for forming a side surface conductive film can preferably perform fine screen printing or the like even on a fine chip-shaped ceramic base material.
On the other hand, as is clear from Tables 14 to 16, the Ag paste for forming the surface conductor film has a higher viscosity than the Ag paste for forming the side conductor film, and is applied (printed) on the surface of the base material or filled in the through holes. Suitable for. Further, since the Ag powder content is high, the conduction resistance of the conductor film can be suppressed low.
[0098]
For the conductor film formed using each Ag paste, the dry density (g / cm^Three) Was measured as follows. That is, a conductive film having a size of 30 mm × 20 mm square was printed on an alumina substrate whose weight was measured in advance. Next, a drying treatment was performed at 100 to 120 ° C. for about 10 minutes. The printing process and the drying process were repeated to form three to five printed films. Next, the weight of the printed substrate was measured, and the weight of the alumina substrate was subtracted from the measured value (the weight of the printed substrate) to calculate the weight of the printed layer (the dried paste weight). At the same time, the thickness of the printed layer was measured using a surface roughness meter or the like, and the volume of the printed layer was calculated based on the measured thickness. The dry density was derived from (weight of print layer) / (volume of print layer).
The obtained results are shown in the corresponding columns of Tables 13 to 16. Each Ag paste can form a conductor film with good dry density (ie, a conductor film with low conduction resistance).
[0099]
Further, the shrinkage rate (%) when a conductive film was formed using each Ag paste was examined. That is, each Ag paste was applied to the surface of an alumina ceramic sheet having a thickness of about 1 mm (film thickness: 10 to 30 μm) based on a general screen printing method, and baked at a maximum temperature of 950 ° C. The change in shrinkage on the ceramic sheet at 700 ° C. and 900 ° C. as compared with that at normal temperature (before firing), that is, the degree of volume reduction (−%) was examined using TMA as an index.
The obtained results are shown in the corresponding columns of Tables 13 to 16. All Ag pastes showed relatively low shrinkage (0-21%). In particular, Example 36, 39The shrinkage at 700 ° C. of the Ag pastes No. 41 to No. 41 is within 0 to −10%. This indicates that there is almost no difference in shrinkage between the ceramic substrate (alumina or the like) and the conductor film formed on the surface and / or the inner surface of the substrate during the simultaneous firing with the ceramic substrate. . Therefore, by using these Ag pastes for the surface conductor film forming application, or when manufacturing the laminated type ceramic wiring board, further using the Ag paste for the inner surface conductor film forming application, the ceramic base material during the simultaneous firing is used. This prevents the occurrence of an excessive difference in firing shrinkage, and as a result, it is possible to manufacture a ceramic electronic component having excellent adhesion characteristics between the ceramic base material and the conductive film and having no structural defects.
[0100]
Further, the heat resistance of these Ag pastes was examined. That is, the Ag paste of Example 31 was applied on a ceramic substrate made of alumina, and baked at 950 ° C. for 1 hour. As a comparative object, a ceramic substrate coated with a conductor paste mainly containing a conventional general Ag simple substance powder whose surface is not coated with an organic metal compound or a metal oxide (hereinafter referred to as “conventional Ag paste”). Was fired under the same conditions. A photograph of the surface of the ceramic substrate after the firing treatment is shown in FIG. As is clear from these photographs, when the conventional Ag paste was applied, peeling and evaporation of the conductive film were remarkable (see FIG. 1A). On the other hand, when the Ag paste according to the present invention was applied, remarkable peeling, evaporation and foaming were not observed, and a good conductor film (sintered body) was formed and maintained (see FIG. 1B). . From this, it was confirmed that the Ag paste according to the present invention can cope with firing at a relatively high temperature, despite being a conductor paste containing Ag-based fine particles as a main component.
[0101]
<Manufacture of ceramic wiring board>
Next, a conductor film having a predetermined pattern (see FIG. 2) was formed on the surface of the ceramic base material (here, an alumina substrate having a thickness of about 2.0 mm) using an Ag paste for forming a surface conductor film. That is, the Ag paste of Example 31 was applied to the surface of the ceramic substrate based on a general screen printing method to form a coating film having a thickness of 10 to 30 μm. Subsequently, a drying treatment was performed at 100 ° C. for 15 minutes using a far-infrared dryer. By this drying treatment, the solvent volatilized from the coating film, and an unsintered conductor film was formed on the ceramic substrate.
Next, this conductor film was fired together with the ceramic substrate. That is, firing treatment was performed at 700 ° C. for 1 hour in an electric furnace. By this baking treatment, a ceramic wiring board on which the conductor film having the predetermined pattern was baked was obtained (see the photograph in the column of the embodiment of FIG. 2).
As a comparison object, a conventional Ag paste (Comparative Example A), a conventional conductor paste mainly containing an alloy powder having Ag and Pd of 80/20 (Comparative Example B), and 99.5% of Ag and Pt. The same processing was performed using a conventional conductor paste mainly containing an alloy powder of /0.5 to produce ceramic wiring boards on which conductor films of the same shape were baked.
[0102]
The solder heat resistance was tested and measured as follows. That is, after applying the rosin flux to the conductor film forming portion of the ceramic substrate, the substrate was immersed in solder (Sn / Pb = 60/40 (weight ratio)) at a predetermined temperature for a predetermined time. Here, the solder temperature conditions and the immersion time were set to 230 ± 5 ° C. × 30 seconds and 260 ± 5 ° C. × 20 seconds. FIG. 2 shows a photograph of the surface of the ceramic substrate after immersion. As is clear from these surface photographs, the conductor film of Example 31 did not substantially cause so-called "soldering" under any conditions. Also, almost no "soldering" occurred in the conductor film of Comparative Example B formed of an Ag / Pd alloy. On the other hand, the conductor film of Comparative Example A formed from a conventional Ag simple substance whose surface is not coated has a remarkable “soldering crack”, and 30% or more of the conductor film has been lost compared to before the immersion. .
As described above, according to the present invention, a conductor film made of an Ag / Pd alloy without performing a plating process such as Ni plating or solder plating, despite being a conductor film made of a conductor paste containing Ag alone as a main component. Solder heat resistance equal to or higher than the above.
[0103]
<Test Example 1>
As Test Example 1 related to the present invention, the relationship between the coating amount of the organic metal salt and / or the firing temperature and the firing shrinkage rate was considered.
That is, an Ag paste obtained by dispersing an Ag powder having an average particle diameter of 0.8 to 1.0 μm in a solvent (BC) so as to have a content of 85% by weight in the same manner as in the preparation of the Ag paste of each example. (Excluding the inorganic oxide powder), and the coating amount of the aluminum alkoxide is the oxide (Al_TwoO_Three) In total, six kinds of Ag pastes were prepared, which were 0 to 0.5 wt% of Ag powder in conversion.
The pastes were applied to the surface of an alumina ceramic sheet in the same manner as described in the section <Evaluation of performance of Ag paste>, and baked at a temperature of 400 ° C. to 900 ° C. (%) Was determined. The result is shown in FIG. In the above range of the coating amount, the shrinkage ratio decreased as the coating amount increased. In particular, it was confirmed that those having a coating amount of 0.1% or more can maintain a low shrinkage rate even by a baking treatment under a temperature condition of 800 ° C. or more (for example, 900 ° C.).
[0104]
<Test Example 2>
As Test Example 2 related to the present invention, the relationship between the type and amount of the inorganic oxide powder and the adhesive strength (tensile strength) was considered.
That is, in the same manner as the preparation of the Ag paste of each example, an Ag powder having an average particle size of 0.8 to 1.0 μm and an oxide (Al_TwoO_ThreeAg paste was prepared by dispersing the above-mentioned aluminum alkoxide-coated Ag powder in an amount of 85 wt% in a solvent (BC) in an amount of 0.1 wt% of the Ag powder in terms of conversion. In this test example, bismuth oxide, copper oxide, or oxide glass (Bi_TwoO_Three-B_TwoO_Three-SiO_TwoA total of nine types of Ag pastes containing 0.25 wt%, 0.5 wt% or 1 wt% of Ag glass powder were prepared.
Using these pastes, ceramic wiring boards similar to those described above were produced and subjected to the above tensile strength test. The result is shown in FIG. As is clear from the graph, it was confirmed that each of the conductor films formed from the respective Ag pastes had high adhesive strength.
[0105]
In the above Examples and Test Examples, specific examples of the present invention have been described in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples illustrated above.
Further, the technical elements described in the present specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.
[0106]
【The invention's effect】
As described above, according to the conductor paste of the present invention, practically sufficient solder heat resistance, solder wettability, and adhesion can be achieved without using a large amount of expensive noble metal such as Pd or separately performing Ni plating. A film conductor having strength and conductivity can be formed. Therefore, when the conductor paste of the present invention is used, a ceramic wiring board or other ceramic electronic component on which a conductor layer (film conductor) having high electrical reliability and high mechanical strength is formed by inexpensive and relatively simple processing. Can be manufactured.
[Brief description of the drawings]
FIG. 1 (A) is a photograph showing the state of a conventional ceramic substrate surface coated with an Ag paste after a high-temperature firing treatment, and FIG. 1 (B) is a high-temperature firing of the ceramic substrate surface coated with the Ag paste according to the present invention. It is a photograph which shows the state after a process.
FIG. 2 is a photograph showing a state of a surface (conductor film) of a ceramic wiring board after a ceramic wiring board according to Example 31 and Comparative Examples A and B on which a conductor film is formed is immersed in molten solder.
FIG. 3 is a graph showing a relationship between a coating amount of an organic metal salt and / or a firing temperature and a firing shrinkage rate in one test example.
FIG. 4 is a graph showing the relationship between the type and amount of inorganic oxide powder and the adhesive strength (tensile strength) in one test example.

Claims (7)

A conductive paste used for forming a fired film-shaped conductor on a substrate, which is mainly composed of metal powder,
The metal powder is substantially composed of fine particles having an average particle diameter of 0.3 to 1.0 μm made of Ag or an Ag-based alloy coated on the surface with an organic metal compound,
Conductive paste, wherein the organic metal compound is an organic acid metal salt, metal alkoxide or chelate compound containing Al as a constituent metal element. The coating amount of the organic metal compound containing Al as a constituent metal element is an amount corresponding to 0.01 to 2.0 wt% of the total amount of the fine particles contained in the paste in terms of Al oxide. 4. The conductor paste according to 1. The coating amount of the organic metal compound having Al as a constituent metal element is an amount corresponding to 0.01 to 0.1 wt% of the total amount of the fine particles contained in the paste in terms of Al oxide. 4. The conductor paste according to 1. A method for producing a conductor paste used for forming a baked film conductor on a substrate, comprising a metal powder as a main component,
(A) preparing metal powder by coating the surface of fine particles of Ag or an alloy mainly composed of Ag and having an average particle diameter of 0.3 to 1.0 μm with an organic metal compound;
(B) dispersing the coated metal powder in an organic medium;
Here, the method for producing a conductive paste, wherein the organic metal compound is an organic acid metal salt, metal alkoxide or chelate compound containing Al as a constituent metal element. A method for manufacturing a ceramic electronic component including a ceramic substrate on which a film-shaped conductor is formed,
(A) applying the conductive paste according to any one of claims 1 to 3 to a ceramic substrate;
(B) a step of firing the applied paste main component. The coating amount of the organic metal compound having Al as a constituent metal element is an amount corresponding to 0.01 to 2.0 wt% of the total amount of the fine particles contained in the paste in terms of Al oxide. The method according to 1. The coating amount of the organic metal compound having Al as a constituent metal element is an amount corresponding to 0.01 to 0.1 wt% of the total amount of the fine particles contained in the paste in terms of Al oxide. The method according to 1.

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