JP3598631B2

JP3598631B2 - Conductive paste, method for producing the same, electric circuit device using conductive paste, and method for producing the same

Info

Publication number: JP3598631B2
Application number: JP2076396A
Authority: JP
Inventors: 純一菊池; 章三山名; 圭三平井; 秀次 ▲くわ▼島; 和田　　弘
Original assignee: Hitachi Chemical Co Ltd; Showa Denko Materials Co Ltd
Current assignee: Showa Denko Materials Co Ltd
Priority date: 1995-02-13
Filing date: 1996-02-07
Publication date: 2004-12-08
Anticipated expiration: 2016-02-07
Also published as: JPH0969313A

Description

【０００１】
【発明の属する技術分野】
本発明は、導電性ペースト、その製造法及び導電性ペーストを用いた電気回路装置、その製造法に関する。
【０００２】
【従来の技術】
従来、配線板、電子部品を搭載するための絶縁基材等に配線導体を形成する方法として、金、銀、パラジウム、銅、アルミニウム等の導電性金属粉に、樹脂、ガラスフリット等の結合剤及び溶剤を加えてペースト状にした導電性ペーストを塗布又は印刷して形成する方法が一般的に知られており、スルホール導通用、電極形成用、ジャンパ線用、ＥＭＩシールド用等に応用されている。
【０００３】
一方、抵抗素子、チップ抵抗、チップコンデンサ等の電子部品を配線導体上に搭載する表面実装法として、はんだ粒子と結合剤からなるはんだペーストを塗布又は印刷し、はんだの融点以上の温度に加熱処理して電子回路装置を得る方法がある。
各種導電性金属粉のうち、金は極めて高価であるため、高い導電性が要求される分野では銀が、それ以外の分野では銅が導電性金属粉として用いられることが多い。
【０００４】
しかしながら、銀は金やパラジウムについで高価であり、また水分の存在下で直流電圧が印加されると、電極や配線導体にマイグレーションと称する銀の電析が生じ、電極間又は配線間が短絡するという重大な問題点が生じる。
銀のマイグレーションを防止するため、銀とパラジウムとの合金を導電性金属粉とする導電性材料が市販されているが、やはり極めて高価であるという問題点がある。
【０００５】
一方、銅は安価であり、マイグレーションが比較的生じにくいが、導電性ペーストを加熱する際、空気及び結合剤中の酸素により銅粒子表面に酸化膜を形成して導電性を悪化させるという問題点がある。このため、導体の表面に防湿塗料を塗布したり、導電性材料に腐食、酸化防止剤を添加するなどの方策が検討されているが、十分な効果が得られるものではなかった。
【０００６】
銅の耐酸化性と銀の耐マイグレーション性を改善するため、銀めっき銅粉を使用する方法が特開昭５６−８８９２号公報に示されるが、この方法では銀粉に比較して導電性が悪く、銀粉の一部を銅粉に置き換えただけにすぎない。また特開平３−２４７７０２号公報、特開平４−２６８３８１号公報等に提案されているように、銅の表面に銀の粒子をアトマイズ法で作製する方法があるが、この方法では工程が複雑であるためコスト高となり、また得られた粉体は略球形粒子であるため偏平状や樹枝状の粉体に比べて粉体同士の接触面積が小さく、高抵抗になるという問題点がある。
またはんだペーストに関しては、加熱処理温度の低温化と鉛レスという緊急かつ重大な要求があるにもかかわらず、融点や作業性の点で十分な鉛レスはんだはまだ得られてはいない。
【０００７】
【発明が解決しようとする課題】
請求項１記載の発明は、高導電性で、導電性と耐マイグレーション性に優れる導電性ペーストを提供するものである。
請求項２記載の発明は、請求項１記載の発明に加えて、特に耐マイグレーション性に優れた導電性ペーストを提供するものである。
請求項３記載の発明は、請求項１記載の発明に加えて、特に導電性と耐マイグレーション性に優れた導電性ペーストを提供するものである。
請求項４記載の発明は、請求項１記載の発明に加えて、特に導電性に優れた導電性ペーストを提供するものである。
請求項５及び６記載の発明は、安価で、かつ高導電性で、耐マイグレーション性に優れる導電性ペーストの製造法を提供するものである。
請求項７記載の発明は、鉛レス、はんだ代替材として電子部品を接着（接続）できる電気回路装置を提供するものである。請求項８記載の発明は、鉛レス、はんだ代替材として電子部品を接着（接続）できる電気回路装置の製造法を提供するものである。
【０００８】
【課題を解決するための手段】
本発明は、偏平状非貴金属粉の表面の一部を露出させて全表面積の５０％以上が、該偏平状非貴金属粉に対して２〜３０重量％の貴金属で被覆され、かつ表面貴金属層と非貴金属層との間に貴金属と非貴金属とが混在する層を介在した導電性金属複合粉及び結合剤を含有してなる導電性ペーストであって、貴金属と非貴金属とが混在する層が、表面貴金属層の厚さの１／２〜１／５０である導電性ペーストに関する。
また、本発明は、この導電性ペーストにおいて、導電性金属複合粉における貴金属と非貴金属とが混在する層が、貴金属が８０〜２０原子数％に対し非貴金属が２０〜８０原子数％である導電性ペーストに関する。
また、本発明は、この導電性ペーストにおいて、導電性金属複合粉におけ表面貴金属層の厚さが、０．０１〜０．２μｍである導電性ペーストに関する。
また、本発明は、この導電性ペーストの導電性金属複合粉における長径／厚さが、２〜３０である導電性ペーストに関する。
また、本発明は、非貴金属粉の表面の一部を露出させて全表面積の５０％以上に、該非貴金属粉に対して２〜３０重量％の貴金属を被覆した後、機械的エネルギーを加えて、偏平状への変形及び表面貴金属層と非貴金属層との間に、貴金属と非貴金属とが混在する層の形成を同時に行った後、結合剤を加えて均一に混合することを特徴とする導電性ペーストの製造法に関する。
また、本発明は、非貴金属粉及び貴金属粉の混合粉体に機械的エネルギーを加えて、該混合粉体を偏平状に変形しながら該非貴金属粉の表面の一部を露出させて全表面積の５０％以上に、該非貴金属粉に対して２〜３０重量％の貴金属を被覆し、かつ表面貴金属層と非貴金属層との間に、貴金属と非貴金属とが混在する層の形成を行った後、結合剤を加えて均一に混合することを特徴とする導電性ペーストの製造法に関する。
また、本発明は、絶縁基材上に上記の導電性ペーストにより配線導体が形成され、その上面に電子部品が搭載された電気回路装置に関する。
さらに、本発明は、絶縁基材上に上記の導電性ペーストを塗布、印刷又はポッティングして配線導体を形成し、次いで配線導体の上面に、電子部品を搭載することを特徴とする電気回路装置の製造法に関する。
【０００９】
【発明の実施の形態】
本発明における偏平状とは、球状、塊状等の立体形状のものを一方向に押し潰した形状のものであり、例えば一般的にフレーク状と称するものもこれに含まれる。
【００１０】
本発明において用いられる非貴金属粉としては、低価格という観点から、導電性を有する非貴金属で、例えば銅、銅合金、ニッケル等が用いられる。また非貴金属粉の表面に被覆される貴金属は、耐酸化性と高導電性という観点から、金、銀、白金等の貴金属を用いることが好ましい。
【００１１】
非貴金属粉への表面に貴金属を被覆する方法については特に制限はなく、めっき法、蒸着法、機械的エネルギーで被覆するメカノフュージョン法等の方法で行うことが好ましい。また、微細、例えば２μｍ以下の貴金属粉と比較的粒径の大きな、例えば５μｍ以上の非貴金属粉の混合粉をボールミル、メカニカルアロイング装置等で混合することによっても非貴金属粉への表面に貴金属を被覆することができる。偏平状非貴金属粉が貴金属により被覆される面積（以下、単に被覆面積という）は偏平状非貴金属粉の全表面積に対して５０％以上であり、また、この被覆に使用される貴金属の量（以下、単に被覆量という）は、偏平状非貴金属粉に対して２〜３０重量％であることが必要である。被覆面積が５０％未満又は被覆量が２重量％未満であると、導電性ペーストにして基板などに塗布して加熱処理したとき下地の偏平状非貴金属粉が酸化して導電性が悪くなる。また被覆量が３０重量％を超えると耐マイグレーション性が悪くなる。
被覆面積は、次のようにして決定される。すなわち、無作為に導電性金属複合粉の粒子を５個以上取り出し、オージェ分光分析装置で貴金属及び非貴金属を定量分析し、貴金属の占める割合を算出し、その平均値を求め、この平均値を被覆面積とする。
また、非貴金属と貴金属との割合は、例えば導電性金属複合粉を１ｇ取り出し、これを硝酸で溶解し、この溶解液を化学定量分析、原子吸光分析装置等を用いて測定する。
上記の被覆面積は５０％以上とされるが、非貴金属粉の粒子に局部電池が形成され貴金属の溶出が抑制できる点で非貴金属粉の表面の一部が露出することが必要とされる。特に貴金属が銀である場合、銅、ニッケル等の非貴金属粉を組み合わせて用いることにより、銀のマイグレーション性が改善され優れた効果を示すので好ましい。また被覆量は７〜２５重量％が好ましく、１５〜２０重量％であればさらに好ましい。
【００１２】
本発明でいう貴金属と非貴金属とが混在する層とは、被覆層を形成するのに使用される貴金属と基材層の非貴金属成分の両者が混合された状態にあり、本発明では貴金属と非貴金属が混在する層の厚さが、表面貴金属層の厚さに対して１／２〜１／５０の場合に優れた導電性と耐マイグレーション性を示す。貴金属と非貴金属が混在する層の厚さが表面貴金属層の厚さの１／２を超えるか又は１／５０未満の場合は導電性が著しく悪化する傾向がある。貴金属と非貴金属が混在する層の厚さは、表面貴金属層の厚さに対して１／２〜１／４０であることがより好ましく、１／２〜１／３０であることがさらに好ましい。
表面貴金属層の厚さ及び貴金属と非貴金属とが混在する層の厚さは、それぞれ無作為に導電性金属複合粉の粒子を５個以上取り出し、イオンスパッタリングで表面を削っていくと同時に元素定量分析するオージェ分光分析装置などを用いて１個の粒子について３点以上測定し、それぞれの厚さについての平均値を求め、この平均値をそれぞれの厚さと決定する。
【００１３】
本発明で用いられる導電性金属複合粉の貴金属と非貴金属とが混在する層は、貴金属８０〜２０原子数％に対し非貴金属２０〜８０原子数％を含むものであることが、優れた導電性と耐マイグレーション性を示す点で好ましい。
また、本発明で用いられる導電性金属複合粉は、ペースト化し、さらにスクリーン印刷して使用する場合、表面貴金属層の厚さが、０．０１〜０．２μｍであることが、導電性と耐マイグレーション性に優れるので好ましい。厚さが０．０１μｍ未満であると導電性が悪くなる傾向があり、厚さが０．２μｍを超えると耐マイグレーション性が悪くなる傾向がある。
【００１４】
本発明で用いられる導電性金属複合粉において、偏平状非貴金属粉の長径／厚さが、２〜３０であることが、優れた導電性と耐酸化性を示す点で好ましく、５〜２０であることがより好ましく、７〜１５であることがさらに好ましい。偏平状非貴金属粉の長径／厚さが２未満であると粉同士の接触がほとんど点接触となるため高抵抗となる傾向があり、３０を超えると貴金属を３０重量％被覆しても全表面積の５０％以上が被覆されたものを作製することが困難となり、導電性ペーストを基板などに塗布して加熱処理したとき、下地の非貴金属粉が酸化し導電性が悪化する傾向がある。
なお、長径については絶対値で１００μｍ以下が好ましく、５０μｍ以下であることがより好ましく、３０μｍ以下であることがさらに好ましい。導電性金属複合粉の長径／厚さは、走査型電子顕微鏡を用いて導電性金属複合粉のＳＥＭ写真をとり、この中から無作為に導電性金属複合粉の粒子を３０個以上選び、それの長径／厚さを測定し、その平均値を求め、この平均値を導電性金属複合粉の長径／厚さとする。
【００１５】
導電性金属複合粉の製造法について、基材となる非貴金属粉の平均粒径や形状については特に制限はない。また貴金属の被覆方法についても既述したように特に制限はないが、コストと特性のバランスの点から、レーザー法、沈降法等の一般的な粒度分布測定法で求めた平均粒径が１〜３０μｍ以下の銅粉に銀をめっき又は蒸着する方法が好ましい。
【００１６】
導電性金属複合粉は、非貴金属粉の表面に貴金属を被覆した後、メカニカルアロイング装置、乾式ボールミリング装置、ロール等による圧縮装置又は高速で固い物質に粉体を吹き付ける装置等を用いて機械的エネルギーを加えるか、非貴金属粉及び貴金属粉の混合粉体に上記に示すような機械的エネルギーを加えることにより製造することができる。
貴金属で表面が被覆された非貴金属粉に機械的エネルギーを加えるか、非貴金属粉及び貴金属粉の混合粉体に上記に示すような機械的エネルギーを加えることにより、貴金属中又は表面貴金属層と非貴金属層との間に存在したボイド（空隙）がなくなり、これによって被覆される貴金属層が緻密化され、その導電性が高められる。また、このとき、表面貴金属層と非貴金属層との間に貴金属と非貴金属とが混在する薄い領域が形成され、これにより表面貴金属層と非貴金属層間の接触抵抗を小さくすることができる。
【００１７】
本発明になる導電性ペーストは、導電性金属複合粉に、エポキシ樹脂、フェノール樹脂、不飽和ポリエステル樹脂、飽和ポリエステル樹脂、ポリアミド樹脂、ポリイミド樹脂、ポリアミド樹脂、ポリイミド樹脂、ポリアミドイミド樹脂、アクリル樹脂等の有機結合剤又はガラスフリットなどの無機結合剤を加え、さらに必要に応じて、イミダゾール、アミン類等の硬化促進剤及びブチルセロソルブ、テルピネオール、エチレンカルビトール、カルビトールアセテート等の溶剤を加えて、らいかい機、ロール、ニーダ等で均一に混合して得られる。結合剤の含有量は、導電性ペーストに対して５〜３０重量％が好ましく、８〜１６重量％であればさらに好ましい。硬化促進剤及び溶剤は必要に応じて添加されるが、もし添加する場合その含有量は、それぞれ硬化促進剤は導電性ペーストに対して０．０１〜１重量％が好ましく、０．０２〜０．０５重量％であることがさらに好ましい。また溶剤は導電性ペーストに対して３〜５０重量％が好ましく、１０〜３０重量％であることがさらに好ましい。
【００１８】
本発明で用いられる絶縁基材としては、各種基板、各種フィルム等が用いられ、このうち各種基板としては、紙フェノール基板、ガラスエポキシ基板、ホウロウ基板、セラミック基板等が挙げられ、また各種フィルムとしては、ポリエチレン、ポリカーボネート、塩化ビニル、ポリスチレン、ポリエチレンテレフタレート、ポリフェニレンスルフィド、ポリエーテルケトン、ポリエーテルイミド、ポリイミド等フレキシブルな樹脂製のフィルムが挙げられる。また配線導体の上面に搭載される電子部品としては、抵抗素子、チップ抵抗、チップコンデンサ等が挙げられる。
なお本発明においては、上記の絶縁基材の表面やスルホールに、予め、めつき、印刷、蒸着、エッチング等の方法で導体や抵抗の一部を形成したものを用いても差し支えない。
【００１９】
本発明になる導電性ペーストは、配線導体の他にスルーホール導通用、電極形成用、ジャンパ線用、ＥＭＩシールド用等の形成に用いることができ、また上記の電子部品と絶縁基材を接続する導電性接着剤、鉛レスはんだ代替材としても使用できる。
【００２０】
【実施例】
以下本発明の実施例を説明する。
実施例１
平均粒径が５μｍの球形銅粉（日本アトマイズ加工（株）製、商品名ＳＦ−Ｃｕ）を酸性クリーナ（日本マクダーミッド（株）製、商品名Ｌ−５Ｂ）で脱指、水洗し、水１リットルあたりＡｇＣＮを２０ｇ及びＮａＣＮを１０ｇ含むめっき浴で球形銅粉に対して銀の量が２０重量％になるように置換めっきを行い、水洗、乾燥して銀めっき銅粉を得た。
【００２１】
次に、この銀めっき銅粉をＭＡ（メカニカルアロイング）装置に投入して以下の条件で変形処理した。本装置はスクリューの回転でボールを運動させる方式であり、ボール及び被処理粉体を投入する容器の有効容積は１．１リットルである。本装置に４ｋｇのジルコニアボール（直径１０ｍｍ）と２００ｇの銀めっき銅粉を投入し、スクリューの回転数９０ｒｐｍ及び容器内圧力２×１０^−５ｔｏｒｒの条件で２時間回転して導電性金属複合粉（偏平状銀めっき銅粉）を得た。
【００２２】
次いで走査型電子顕微鏡を用いて上記で得た導電性金属複合粉のＳＥＭ写真をとり、該導電性金属複合粉の粒子を３０個選び、長径／厚さを測定したところ２〜１５の範囲で平均が６であった。なお長径は、２〜３０μｍの範囲で平均が１５μｍであった。
また無作為に導電性金属複合粉の粒子を５個取り出し、走査型オージェ電子分光分析装置で貴金属及び非貴金属を定量分析して銀被覆面積について調べたところ、全表面積に対して４５〜８５％の範囲で平均が７０％であった。
さらに無作為に導電性金属複合粉の粒子を５個取り出し、イオンスパッタリングで表面を削っていくと同時に元素定量分析する走査型オージェ電子分光分析装置で１個の粒子につき３点測定したところ、銀層の厚さは０．０２〜０．１５μｍの範囲で平均が０．０４５μｍ及び貴金属（銀）の割合が８０〜２０原子数％である貴金属と非貴金属（銅）とが混在する層の厚さは０．００１〜０．０５μｍの範囲で平均が０．０１μｍであり、表面貴金属層の厚さの１／２０〜１／２の範囲で平均が１／４．５であった。
以下の実施例及び比較例においても上記と同様の方法で測定した。
【００２３】
次に上記の導電性金属複合粉１００重量部に対し、ノボラツク型フェノール樹脂（群栄化学工業（株）製、商品名ＰＳ−２６０７）１５重量部及び溶剤としてブチルセロソルブ１５重量部を加えて均一に混合して導電性ペーストを得た。
【００２４】
次いで導電性ペーストを厚さが１．６ｍｍの紙フェノール銅張積層板（日立化成工業（株）製、商品名ＭＣＬ−４３７Ｆ）の銅箔を除去した積層板の上面に２００メッシュのスクリーンを通して幅０．４ｍｍ及び長さ１００ｍｍのテストパターンを印刷し、大気中で１５０℃で３０分の条件で加熱処理して配線導体を得た。得られた配線導体における導電性ペースト硬化物の比抵抗は平均７５μΩＣｍであり、後述する銀ペーストと比べて遜色のない導電性を示した。
【００２５】
一方上記とは別に導電性ペーストをガラス板上に幅２ｍｍの電極を互いに２ｍｍ間隔となるように上記と同様の方法で印刷し、大気中で１５０℃で３０分の条件で加熱処理して硬化させて電極を得た。次いで電極間に幅２ｍｍに切断したろ紙を配置し、イオン交換水０．５ｃｃをろ紙上に滴下して電極間に２０Ｖの直流電圧を印加し、経過時間と電極間漏洩電流を測定することによって耐マイグレーション性を評価した。その結果、２００μＡの漏洩電流が流れるまでに要した時間は平均８０分であり、耐マイグレーション性に優れていた。
上記における比抵抗の測定及び耐マイグレーション性の評価については５個の試料の平均値を求めた。以下の実施例及び比較例についても同じである。
【００２６】
比較例１
実施例１で得た球形銀めっき銅粉を用い、偏平状への変形を省略した以外は実施例１と同様の工程を経て導電性ペーストを得た。球形銀めっき銅粉の長径／厚さは１、銀被覆面積は全表面積に対して全て９５％以上、銀層の厚さは０．１〜０．１５μｍの範囲で平均が０．１２μｍ及び貴金属（銀）の割合が８０〜２０原子数％である貴金属と非貴金属（銅）とが混在する層は明確に検知出来なかった。以下実施例１と同様の方法で特性を評価した。その結果、導電性ペースト硬化物の比抵抗は平均１２００μΩＣｍと極めて高く、２００μＡの漏洩電流が流れるまでに要した時間は平均１０分と短く、耐マイグレーション性に劣っていた。
【００２７】
比較例２
平均粒径が５μｍの球形銅粉（日本アトマイズ加工（株）製、商品名ＳＦ−Ｃｕ）をあらかじめ長径／厚さが６になるように実施例１と同様の方法で変形し、しかる後実施例１と同様のめっき法で２０重量％の銀を被覆した。この銀めっき銅粉の銀被覆面積は全表面積に対して全て８５％以上、銀層の厚さは０．０３〜０．２μｍの範囲で平均が０．０８μｍ、貴金属（銀）の割合が８０〜２０原子数％である貴金属と非貴金属（銅）とが混在する層は明確に検知出来なかった。以下実施例１と同様の工程を経て導電性ペーストを作製して特性を評価した。その結果、導電性ペースト硬化物の比抵抗は８００μΩＣｍと高く、２００μＡの漏洩電流が流れるまでに要した時間は１０分と短く、耐マイグレーション性に劣っていた。
【００２８】
比較例３
実施例１で用いた導電性金属複合粉に代えて長径／厚さが平均３０の銀粉（徳力化学研究所製、商品名ＴＣＧ−１）を用いた以外は実施例１と同様の工程を経て導電性ペーストを作製して特性を評価した。その結果、導電性ペースト硬化物の比抵抗は平均８０μΩＣｍであったが、２００μＡの漏洩電流が流れるまでに要した時間は平均３０秒と極めて短く、耐マイグレーション性に劣っていた。
【００２９】
比較例４
市販のＥＭＩシールド用銅ペーストを用いて実施例１と同様の特性を評価した。その結果、導電性ペースト硬化物の比抵抗は平均５００μΩＣｍと高く、２００μＡの漏洩電流が流れるまでに要した時間は平均４５分であった。
【００３０】
実施例２
平均粒径が６μｍの球形銅粉（日本アトマイズ加工（株）製、商品名ＳＦ−Ｃｕ）に実施例１と同様のめっき法で３０重量％の銀を被覆して銀めっき銅粉を得、その後のＭＡ装置での処理時間を１時間とした以外は実施例１と同様の工程を経て導電性金属複合粉を得た。得られた導電性金属複合粉の粒子の長径は３〜１５μｍの範囲で平均が７μｍであり、また長径／厚さは２〜９の範囲で平均が２．５、銀被覆面積は全表面積に対して７５〜１００％の範囲で平均が９５％、銀層の厚さは０．０５〜０．２μｍの範囲で平均が０．１μｍ及び貴金属（銀）の割合が８０〜２０原子数％である貴金属と非貴金属（銅）とが混在する層の厚さは０．００１〜０．０１μｍの範囲で平均が０．００６μｍであり、表面貴金属層の厚さの１／５０〜１／８の範囲で平均が１／１６．７であった。以下実施例１と同様の工程を経て導電性ペーストを作製して特性を評価した。その結果、導電性ペースト硬化物の比抵抗は平均８０μΩＣｍ及び２００μＡの漏洩電流が流れるまでに要した時間は平均４０分であった。
【００３１】
実施例３
平均粒径が６μｍの球形銅粉（日本アトマイズ加工（株）製、商品名ＳＦ−Ｃｕ）に実施例１と同様のめっき法で１０重量％の銀を被覆した以外は実施例１と同様の工程を経て導電性金属複合粉を得た。得られた導電性金属複合粉の粒子の長径は２〜３０μｍの範囲で平均が１５μｍであり、また長径／厚さは２〜１５の範囲で平均が６、銀被覆面積は全表面積に対して３０〜７０％の範囲で平均が５１％、銀層の厚さは０．０１〜０．０３μｍの範囲で平均が０．０２μｍ及び貴金属（銀）の割合が８０〜２０原子数％である貴金属と非貴金属（銅）とが混在する層の厚さは０．００１〜０．０２μｍの範囲で平均が０．０１μｍであり、表面貴金属層の厚さの１／１０〜２／３の範囲で平均が１／２であった。以下実施例１と同様の工程を経て導電性ペーストを作製して特性を評価した。その結果、導電性ペースト硬化物の比抵抗は平均１３５μΩＣｍ及び２００μＡの漏洩電流が流れるまでに要した時間は平均６０分であった。
【００３２】
実施例４
平均粒径が６μｍの球形銅粉（日本アトマイズ加工（株）製、商品名ＳＦ−Ｃｕ）に実施例１と同様のめっき法で２重量％の銀を被覆して銀めっき銅粉を得、その後のＭＡ装置での処理時間を１時間とした以外は実施例１と同様の工程を経て導電性金属複合粉を得た。得られた導電性金属複合粉の粒子の長径は２〜２０μｍの範囲で平均が９μｍであり、また長径／厚さは２〜１３の範囲で平均が４、銀被覆面積は全表面積に対して１５〜７０％の範囲で平均が５５％、銀層の厚さは０．０００１〜０．０２μｍの範囲で平均が０．０１μｍ及び貴金属（銀）の割合が８０〜２０原子数％である貴金属と非貴金属（銅）とが混在する層の厚さは０．０００１〜０．００３μｍの範囲で平均が０．００２μｍであり、表面貴金属層の厚さの１／１５〜１の範囲で平均が１／５であった。以下実施例１と同様の工程を経て導電性ペーストを作製して特性を評価した。その結果、導電性ペースト硬化物の比抵抗は平均１１０μΩＣｍ及び２００μＡの漏洩電流が流れるまでに要した時間は平均１００分であった。
【００３３】
比較例５
平均粒径が６μｍの球形銅粉（日本アトマイズ加工（株）製、商品名ＳＦ−Ｃｕ）に実施例１と同様のめっき法で１．５重量％の銀を被覆した以外は実施例１と同様の工程を経て導電性金属複合粉を得た。得られた導電性金属複合粉の粒子の長径は２〜３０μｍの範囲で平均が１５μｍであり、また長径／厚さは４〜１８の範囲で平均が６、銀被覆面積は全表面積に対して５〜３５％の範囲で平均が２０％、銀層の厚さは０．００００５〜０．００５μｍの範囲で平均が０．００３μｍ及び貴金属（銀）の割合が８０〜２０原子数％である貴金属と非貴金属（銅）とが混在する層の厚さは０．００００５〜０．００５μｍの範囲で平均が０．００３μｍであり、表面貴金属層の厚さの１／２〜１の範囲で平均が４／５であった。以下実施例１と同様の工程を経て導電性ペーストを作製して特性を評価した。その結果、導電性ペースト硬化物の比抵抗は平均４５０μΩＣｍと高く、２００μＡの漏洩電流が流れるまでに要した時間は平均９０分であった。
【００３４】
比較例６
平均粒径が６μｍの球形銅粉（日本アトマイズ加工（株）製、商品名ＳＦ−Ｃｕ）に実施例１と同様のめっき法で３５重量％の銀を被覆した以外は実施例１と同様の工程を経て導電性金属複合粉を得た。得られた導電性金属複合粉の粒子の長径は２〜２５μｍの範囲で平均が１０μｍであり、また長径／厚さは３〜２０の範囲で平均が５、銀被覆面積は全表面積に対して６５〜９５％の範囲で平均が８０％、銀層の厚さは０．０３〜０．２μｍの範囲で平均が０．０６μｍ及び貴金属（銀）の割合が８０〜２０原子数％である貴金属と非貴金属（銅）とが混在する層の厚さは０．０００１〜０．００３μｍの範囲で平均が０．００１μｍであり、表面貴金属層の厚さの１／５００〜１／５０の範囲で平均が１／６０であった。以下実施例１と同様の工程を経て導電性ペーストを作製して特性を評価した。その結果、導電性ペースト硬化物の比抵抗は平均１３０μΩＣｍ及び２００μＡの漏洩電流が流れるまでに要した時間は平均１０分と短く耐マイグレーション性に劣っていた。
【００３５】
実施例５
実施例２で得た銀めっき銅粉（銀被覆量３０重量％）を２本のロール間で圧縮して粒子の長径が５〜５５μｍの範囲で平均が３０μｍであり、また長径／厚さは１５〜５０の範囲で平均が２７の導電性金属複合粉を得た。得られた導電性金属複合粉の銀被覆面積は全表面積に対して３５〜８０％の範囲で平均が５０％、銀層の厚さは０．００２〜０．０２μｍの範囲で平均が０．０１２５μｍ及び貴金属（銀）の割合が８０〜２０原子数％である貴金属と非貴金属（銅）とが混在する層の厚さは０．０００１〜０．０００５μｍの範囲で平均が０．０００２５μｍであり、表面貴金属層の厚さの１／２０〜１／１００の範囲で平均が１／５０であった。以下実施例１と同様の工程を経て導電性ペーストを作製して特性を評価した。その結果、導電性ペースト硬化物の比抵抗は平均１１５μΩＣｍ及び２００μＡの漏洩電流が流れるまでに要した時間は平均５０分であった。
【００３６】
実施例６
平均粒径が５μｍの球形銅粉（日本アトマイズ加工（株）製、商品名ＳＦ−Ｃｕ）を蒸着装置内の皿状容器に保持し、皿状容器を回転させながら銀の量が２０重量％になるように銀の蒸着を行い銀蒸着銅粉を得た。
次にこの銀蒸着銅粉を実施例１と同様の工程を経て導電性金属複合粉を得た。得られた導電性金属複合粉の粒子の長径は３〜１５μｍの範囲で平均が７μｍであり、また長径／厚さは２〜１５の範囲で平均が６、銀被覆面積は全表面積に対して７５〜１００％の範囲で平均が９０％、銀層の厚さは０．０２〜０．１８μｍの範囲で平均が０．０４μｍ及び貴金属（銀）の割合が８０〜２０原子数％である貴金属と非貴金属（銅）とが混在する層の厚さは０．００１〜０．０５μｍの範囲で平均が０．０１５μｍであり、表面貴金属層の厚さの１／２０〜４／５の範囲で平均が１／２．７であった。以下実施例１と同様の工程を経て導電性ペーストを作製して特性を評価した。その結果、導電性ペースト硬化物の比抵抗は平均５５μΩＣｍ及び２００μＡの漏洩電流が流れるまでに要した時間は平均９０分であった。
【００３７】
実施例７
ビスフェノールＡ型液状エポキシ樹脂（油化シェル（株）製、商品名エピコート８２８）１００重量部及びノボラック型フェノールホルムアルデヒド樹脂（日立化成工業（株）製、商品名ＨＰ−６０７Ｎ）５５．８重量部を１１０℃で加熱混合して無溶剤の混合樹脂を得た。
次に実施例１で得た導電性金属複合粉１００重量部に対し、上記で得た無溶剤の混合樹脂８重量部及び硬化促進剤としてベンジルジメチルアミン０．０４重量部を加えて均一に混合して導電性ペーストを得た。以下実施例１と同様の方法で特性を評価した。その結果、導電性ペースト硬化物の比抵抗は平均８５μΩＣｍ及び２００μＡの漏洩電流が流れるまでに要した時間は平均８０分であった。
【００３８】
実施例８
平均粒径が６μｍの球形銅粉（日本アトマイズ加工（株）製、商品名ＳＦ−Ｃｕ）８０重量部（１６０ｇ）及び平均粒径が１μｍの微細球形銀粉（日本アトマイズ加工（株）製、微粉）２０重量部（４０ｇ）をＭＡ装置に投入し、以下実施例１と同様の工程を経て銀被覆量が２０重量％の導電性金属複合粉を得た。得られた導電性金属複合粉の粒子の長径は２〜３０μｍの範囲で平均が１５μｍであり、また長径／厚さは２〜１５の範囲で平均が６、銀被覆面積は全表面積に対して４０〜６５％の範囲で平均が５５％、銀層の厚さは０．００５〜０．１μｍの範囲で平均が０．０３μｍ及び貴金属（銀）の割合が８０〜２０原子数％である貴金属と非貴金属（銅）とが混在する層の厚さは０．００３〜０．０５μｍの範囲で平均が０．０１μｍであり、表面貴金属層の厚さの１／１０〜１／２の範囲で平均が１／５であった。以下実施例１と同様の工程を経て導電性ペーストを作製して特性を評価した。その結果、導電性ペースト硬化物の比抵抗は平均１４０μΩＣｍ及び２００μＡの漏洩電流が流れるまでに要した時間は平均４０分であった。
【００３９】
実施例９
平均粒径が２．０μｍの微細球形銅粉（日本アトマイズ加工（株）製、試作品）８０重量部（１６０ｇ）及び実施例８で用いた微細球形銀粉２０重量部（４０ｇ）を配合し、以下直径が５ｍｍのジルコニアボールを用いた以外は実施例１と同様の工程を経て銀被覆量が２０重量％の導電性金属複合粉を得た。得られた導電性金属複合粉の粒子の長径は５〜２０μｍの範囲で平均が１０μｍであり、また長径／厚さは２〜２０の範囲で平均が５、銀被覆面積は全表面積に対して４０〜６０％の範囲で平均が５２％、銀層の厚さは０．００５〜０．０７μｍの範囲で平均が０．０３μｍ及び貴金属（銀）の割合が８０〜２０原子数％である貴金属と非貴金属（銅）とが混在する層の厚さは０．０１〜０．０５μｍの範囲で平均が０．０１５μｍであり、表面貴金属層の厚さの１／７〜２／３の範囲で平均が１／２であった。以下実施例１と同様の工程を経て導電性ペーストを作製して特性を評価した。その結果、導電性ペースト硬化物の比抵抗は平均１３０μΩＣｍ及び２００μＡの漏洩電流が流れるまでに要した時間は平均３０分であった。
【００４０】
実施例１０
実施例８で得た導電性金属複合粉５０重量％及び比較例３で用いた銀粉５０重量％をＶ型混合機で均一に混合した混合粉体１００重量部に対し、ノボラック型フェノール樹脂（群栄化学工業（株）製、商品名ＰＳ−２６０７）１２重量部、ビスフェノールＡ型エポキシ樹脂（油化シェルエポキシ（株）製、商品名エピコート８２８）２重量部及び溶剤としてブチルセロソルブ１５重量部を加えて均一に混合して導電性ペーストを作製して特性を評価した。その結果、導電性ペースト硬化物の比抵抗は平均７０μΩＣｍ及び２００μＡの漏洩電流が流れるまでに要した時間は平均１５分であった。
【００４１】
実施例１１
平均粒径が２５μｍの球形銅粉（日本アトマイズ加工（株）製、商品名ＳＦ−Ｃｕから分級して得た）５０重量部（１００ｇ）及び実施例８で用いた微細球形銀粉５０重量部（１００ｇ）を配合した以外は、実施例１と同様の工程を経て銀被覆量が３０重量％の導電性金属複合粉を得た。得られた導電性金属複合粉の粒子の長径は２〜３０μｍの範囲で平均が１５μｍであり、また長径／厚さは２〜１５の範囲で平均が６、銀被覆面積は全表面積に対して４５〜７５％の範囲で平均が６５％、銀層の厚さは０．０１〜０．２μｍの範囲で平均が０．０５μｍ及び貴金属（銀）の割合が８０〜２０原子数％である貴金属と非貴金属（銅）とが混在する層の厚さは０．０１〜０．０６μｍの範囲で平均が０．０２μｍであり、表面貴金属層の厚さの１／５〜１／２の範囲で平均が１／３であった。以下実施例１と同様の工程を経て導電性ペーストを作製して特性を評価した。その結果、導電性ペースト硬化物の比抵抗は平均６０μΩＣｍ及び２００μＡの漏洩電流が流れるまでに要した時間は平均１０分であった。
【００４２】
実施例１２
ビスフェノールＡ型エポキシ樹脂（油化シェルエポキシ（株）製、商品名エピナール８３４）６０重量部及びビスフェノールＡ型エポキシ樹脂（油化シェルエポキシ（株）製、商品名エピナール８２８）４０重量部を予め加温溶解させ、次いで室温（２０℃）に冷却した後、２エチル４メチルイミダゾール５重量部、エチルカルビトール２０重量部及びブチルセロソルブ２０重量部を加えて均一に混合して樹脂組成物とした。
【００４３】
平均粒径が７．２μｍの球形銅粉（日本アトマイズ加工（株）製、商品名ＳＦ−Ｃｕ）を希塩酸中に浸漬し、純水で洗浄した後、ＡｇＣＮ８０ｇ／水１ｋｇの混合液中で２５±５℃で２０分間撹拌しながら銀を置換めっきし、水洗、乾燥して銀めっき銅粉を得た。
【００４４】
次いで２リットルボールミル容器内に上記で得た銀めっき銅粉４００ｇと直径が５ｍｍのジルコニアボール３ｋｇを投入し、毎分６０回転の条件で３０分間回転させて該銀めっき銅粉を変形処理して導電性金属複合粉を得た。得られた導電性金属複合粉の粒子の長径は２〜２４μｍの範囲で平均が１１．５μｍであり、また長径／厚さは３〜１４の範囲で平均が９、銀被覆面積は全表面積に対して６０〜８５％の範囲で平均が７５％であった。
この後上記で得た樹脂組成物１４５ｇに上記で得た導電性金属複合粉２１５ｇを加えてらいかい機及び三本ロールで均一に混合分散して導電性ペーストを得た。なお導電性金属複合粉の含有量は、導電性ペーストの固形分に対して６０重量％であった。
【００４５】
次に上記で得た導電性ペーストで、厚さが１．６ｍｍで直径が０．８ｍｍのスルーホールを形成した紙フェノール銅張積層板（日立化成工業（株）製、商品名ＭＣＬ−４３７Ｆ）に図１に示すテストパターンを印刷すると共に、これをスルーホール１に充填したものを大気中で６０℃、３０分間さらに１６０℃、３０分間の条件で加熱処理して配線導体３を得た。なお図１において２は紙フェノール銅張積層板である。
【００４６】
得られた配線導体の抵抗を測定した結果、銅箔の抵抗を除いたスルーホール１の抵抗は５４穴の平均で２２ｍΩ／穴であり、平面に印刷して測定した比抵抗は９５μΩｃｍであった。また、隣り合うスルーホール１間の絶縁抵抗は１０^８Ω以上であった。該配線導体の冷熱衝撃試験を実施した結果、スルーホール１の抵抗は平均で２６．２ｍΩ／穴であった。また該配線導体の湿中負荷試験を実施した結果、スルーホール１間の絶縁抵抗は１０^８Ω以上であった。なお、冷熱衝撃試験は１２５℃、３０分〜−６５℃、３０分を１００サイクル行い、湿中負荷試験は４０℃、９０％ＲＨ中、隣り合うライン間に５０Ｖの電圧を印加して２０００時間保持した。さらに耐はんだ試験（２６０℃、１０秒、５回）を行ったが、抵抗変化率は３０％以内であった。
【００４７】
実施例１３
実施例１２で得た銀めっき銅粉２５０ｇと直径が５ｍｍのジルコニアボール５ｋｇを円筒状の２リットル容器内に投入し、振動ミルで１０分間振動させ、該銀めっき銅粉を変形処理して導電性金属複合粉を得た。得られた導電性金属複合粉の粒子の長径は３〜２５μｍの範囲で平均が１１．５μｍであり、また長径／厚さは２〜１２の範囲で平均が７、銀被覆面積は全表面積に対して６０〜８５％の範囲で平均が７０％であった。
この後実施例１２で得た樹脂組成物１４５ｇに上記で得た導電性金属複合粉２４０ｇを加え、以下実施例１２と同様の工程を経て導電性ペーストを得た。なお導電性金属複合粉の含有量は、導電性ペーストの固形分に対して６３重量％であった。
【００４８】
以下実施例１２と同様の工程を経て配線導体を作製して特性を評価した。その結果、スルーホールの抵抗は５４穴の平均で２１．５ｍΩ／穴であり、平面に印刷して測定した比抵抗は１０２μΩｃｍであった。また、隣り合うスルーホール間の絶縁抵抗は１０^８Ω以上であった。該配線導体の冷熱衝撃試験を実施した結果、スルーホールの抵抗は平均で２４．５ｍΩ／穴であり、湿中負荷試験の結果では、スルーホール間の絶縁抵抗は１０^８Ω以上であった。さらに実施例１２と同様の耐はんだ試験を行ったが、抵抗変化率は３０％以内であった。
【００４９】
比較例７
実施例１２で得た樹脂組成物１４５ｇに実施例１２で得た銀めっき銅粉１９５ｇを加え、以下実施例１２と同様の工程を経て導電性ペーストを得た。なお銀被覆面積は全表面積に対して９３〜９９％の範囲で平均が９７％であった。また導電性金属複合粉の含有量は、導電性ペーストの固形分に対して５７重量％であった。
【００５０】
以下実施例１２と同様の工程を経て配線導体を作製して特性を評価した。その結果、スルーホールの抵抗は５４穴の平均で２２８ｍΩ／穴であり、平面に印刷して測定した比抵抗は３５０μΩｃｍであり、隣り合うスルーホール間の絶縁抵抗は１０^８Ω以上であった。また該配線導体の冷熱衝撃試験を実施した結果、スルーホールの抵抗は平均で２５１ｍΩ／穴であり、湿中負荷試験の結果では、スルーホール間の絶縁抵抗は１０^８Ω以上であった。さらに実施例１２と同様の耐はんだ試験を行ったところ、抵抗変化率は２００％であった。
【００５１】
実施例１４
実施例１２で得た樹脂組成物１４５ｇに実施例１２で得た導電性金属複合粉１９５ｇを加えてらいかい機及び三本ロールで均一に混合分散して導電性ペーストを得た。なお導電性金属複合粉の含有量は、導電性ペーストの固形分に対して６６．１重量％であった。
次に上記で得た導電性ペーストで、厚さが１．６ｍｍの紙フェノール銅張積層板（日立化成工業（株）製、商品名ＭＣＬ−４３７Ｆ）に図２に示すテストパターンを印刷し、これを大気中で６０℃、３０分間さらに１６０℃、３０分間の条件で加熱処理して配線導体３を形成した電磁波シールド材を得た。得られた電磁波シールド材の抵抗を測定した。その結果、比抵抗は３５μΩＣｍであり、シート抵抗は１３ｍΩ／□であった。また、冷熱試験を１２５℃、３０分〜−６５℃、３０分を１００サイクルの条件で行うと共に耐はんだ試験（２６０℃、１０秒、５回）を行ったが、ともに抵抗変化率は１０％以内であった。また、６０℃、９５％相対湿度で１０００時間保持した場合の抵抗変化率も１０％以内であった。
【００５２】
実施例１５
実施例１で得た導電性金属複合粉１００重量部に対し、ビスフェノールＡ型液状エポキシ樹脂（油化シェル（株）製、商品名エピコート８２８）１０重量部、硬化剤としてイミダゾール０．３重量部及び溶剤としてブチルセロソルブ５重量部を加えて均一に混合して導電性ペーストを得た。以下実施例１と同様の方法で特性を評価した。その結果、導電性ペースト硬化物の比抵抗は平均９０μΩＣｍ及び２００μＡの漏洩電流が流れるまでに要した時間は平均８０分であった。
一方上記とは別に導電性ペーストを厚さが１．６ｍｍの紙フェノール銅張積層板（日立化成工業（株）製、商品名ＭＣＬ−４３７Ｆ）の銅箔を除去した積層板の上面に４×４ｍｍの寸法で、かつ１６０μｍの厚さのテストパターンを印刷し、次いでその上面に寸法が５×５ｍｍのチップコンデンサ（電子部品）を搭載して処理した。圧着後の導電性ペースト硬化物の比抵抗は平均３０μΩＣｍであった。またチップコンデンサの接着強度は、電子部品の接着強度として十分な１．５ｋｇ／１チップであった。
【００５３】
【発明の効果】
請求項１記載の導電性ペーストは、高導電性で、導電性とマイグレーション性に優れる。
請求項２記載の導電性ペーストは、請求項１記載の導電性ペーストの効果を奏し、特に耐マイグレーション性に優れる。
請求項３記載の導電性ペーストは、請求項１記載の導電性ペーストの効果を奏し、特に導電性と耐マイグレーション性に優れる。
請求項４記載の導電性ペーストは、請求項１記載の導電性ペーストの効果を奏し、特に導電性に優れる。
請求項５記載の方法により、導電性ペーストを安価に製造することができ、得られる導電性ペーストは、高導電性で、耐マイグレーション性に優れる。
請求項６記載の方法により導電性ペーストを安価に製造することができ、得られる導電性ペーストは、高導電性で、耐マイグレーション性に優れる。
請求項７記載の電気回路装置は、鉛レス、はんだ代替材として電子部品との接着性に優れる。
請求項８記載の方法により得られる電気回路装置は、鉛レス、はんだ代替材として電子部品を接着することができる。
【図面の簡単な説明】
【図１】紙フェノール銅張積層板に導電性ペーストを印刷すると共にスルーホールに充填した状態を示す平面図である。
【図２】紙フェノール銅張積層板に導電性ペーストを印刷した電磁波シールド材の平面図である。
【符号の説明】
１スルーホール
２紙フェノール銅張積層板
３配線導体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a conductive paste, a method for manufacturing the same, an electric circuit device using the conductive paste, and a method for manufacturing the same.
[0002]
[Prior art]
Conventionally, as a method of forming a wiring conductor on an insulating substrate or the like for mounting a wiring board or an electronic component, a conductive metal powder such as gold, silver, palladium, copper, or aluminum is added to a binder such as a resin or a glass frit. A method of applying or printing a conductive paste in the form of a paste by adding a solvent and forming a paste is generally known, and applied to through-hole conduction, electrode formation, jumper wires, EMI shielding, and the like. I have.
[0003]
On the other hand, as a surface mounting method for mounting electronic components such as resistor elements, chip resistors, chip capacitors, etc. on wiring conductors, a solder paste consisting of solder particles and a binder is applied or printed and heated to a temperature equal to or higher than the melting point of the solder. There is a method of obtaining an electronic circuit device.
Of the various conductive metal powders, gold is extremely expensive, so silver is often used as the conductive metal powder in fields requiring high conductivity, and copper is used in other fields.
[0004]
However, silver is expensive after gold and palladium, and when a DC voltage is applied in the presence of moisture, silver deposition called migration occurs on electrodes and wiring conductors, and short-circuits between the electrodes or wirings A serious problem arises.
In order to prevent the migration of silver, a conductive material using a conductive metal powder of an alloy of silver and palladium is commercially available, but still has a problem that it is extremely expensive.
[0005]
On the other hand, copper is inexpensive and migration is relatively unlikely to occur, but when heating the conductive paste, air and oxygen in the binder form an oxide film on the surface of the copper particles to deteriorate the conductivity. There is. For this reason, measures such as applying a moisture-proof paint to the surface of the conductor and adding corrosion and antioxidants to the conductive material have been studied, but have not been able to obtain a sufficient effect.
[0006]
In order to improve the oxidation resistance of copper and the migration resistance of silver, a method using silver-plated copper powder is disclosed in JP-A-56-8892, but this method has poor conductivity compared to silver powder. However, only silver powder was partially replaced with copper powder. Further, as proposed in JP-A-3-247702, JP-A-4-268381, etc., there is a method of producing silver particles on a copper surface by an atomizing method. However, this method involves complicated steps. Therefore, there is a problem that the cost is high, and since the obtained powder is substantially spherical particles, the contact area between the powders is smaller than that of a flat or dendritic powder, resulting in high resistance.
Regarding solder paste, although there is an urgent and serious demand for a lower heat treatment temperature and lead-free soldering, a lead-free solder sufficient in melting point and workability has not yet been obtained.
[0007]
[Problems to be solved by the invention]
The first aspect of the present invention provides a conductive paste having high conductivity and excellent in conductivity and migration resistance.
The invention according to claim 2 provides, in addition to the invention according to claim 1, a conductive paste having particularly excellent migration resistance.
A third aspect of the present invention provides, in addition to the first aspect, a conductive paste having particularly excellent conductivity and migration resistance.
A fourth aspect of the present invention provides a conductive paste having particularly excellent conductivity, in addition to the first aspect of the present invention.
The fifth and sixth aspects of the present invention provide a method for producing a conductive paste which is inexpensive, highly conductive, and excellent in migration resistance.
The invention according to claim 7 provides an electric circuit device capable of bonding (connecting) an electronic component as a lead-free and solder substitute material. The invention described in claim 8 provides a method for manufacturing an electric circuit device capable of bonding (connecting) electronic components as a lead-free and solder substitute material.
[0008]
[Means for Solving the Problems]
The present invention relates to a non-precious metal powder having a surface exposed at least 50% of the total surface area of the flat non-precious metal powder by 2 to 30% by weight of the flat non-precious metal powder. And a conductive paste containing a conductive metal composite powder and a binder having a layer in which a noble metal and a non-noble metal are interposed between a non-precious metal layer and a non-noble metal layer. And a conductive paste having a thickness of 1/2 to 1/50 of the thickness of the surface noble metal layer.
Further, in the present invention, in the conductive paste, the layer in which the noble metal and the non-noble metal are mixed in the conductive metal composite powder has 80 to 20 atomic% of the noble metal and 20 to 80 atomic% of the noble metal. The present invention relates to a conductive paste.
The present invention also relates to the conductive paste, wherein the thickness of the surface noble metal layer in the conductive metal composite powder is 0.01 to 0.2 μm.
The present invention also relates to a conductive paste in which the conductive paste has a major axis / thickness of 2 to 30 in the conductive metal composite powder.
The present invention also provides a method in which a part of the surface of the non-noble metal powder is exposed and 50% or more of the total surface area is coated with 2 to 30% by weight of the noble metal powder based on the noble metal powder, and then mechanical energy is applied. After the simultaneous formation of a layer in which a noble metal and a non-noble metal are mixed between a flat noble metal layer and a non-noble metal layer, a binder is added and uniformly mixed. The present invention relates to a method for producing a conductive paste.
Further, the present invention provides a mixed powder of non-noble metal powder and noble metal powder by applying mechanical energy, while exposing a part of the surface of the non-noble metal powder while deforming the mixed powder into a flat shape, thereby reducing the total surface area. After forming at least 50% of the non-precious metal powder with 2 to 30% by weight of the precious metal based on the non-precious metal powder and forming a layer in which the precious metal and the non-precious metal are mixed between the surface precious metal layer and the non-precious metal layer And a method for producing a conductive paste, which comprises adding a binder and mixing the mixture uniformly.
In addition, the present invention relates to an electric circuit device in which a wiring conductor is formed on the insulating base material using the conductive paste, and an electronic component is mounted on an upper surface thereof.
Further, the present invention provides an electric circuit device characterized in that a wiring conductor is formed by applying, printing or potting the conductive paste on an insulating base material, and then mounting an electronic component on the upper surface of the wiring conductor. A method for producing the same.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
The flat shape in the present invention is a shape obtained by crushing a three-dimensional shape such as a sphere or a lump in one direction, and includes, for example, a shape generally called a flake shape.
[0010]
The non-noble metal powder used in the present invention is a non-noble metal having conductivity, for example, copper, copper alloy, nickel or the like, from the viewpoint of low cost. As the noble metal coated on the surface of the non-noble metal powder, it is preferable to use a noble metal such as gold, silver or platinum from the viewpoint of oxidation resistance and high conductivity.
[0011]
The method of coating the surface of the non-noble metal powder with a noble metal is not particularly limited, and is preferably performed by a method such as a plating method, a vapor deposition method, or a mechanofusion method of coating with mechanical energy. Alternatively, the surface of the non-precious metal powder may be added to the surface of the non-precious metal powder by mixing a fine powder, for example, a precious metal powder having a particle size of 2 μm or less and a non-precious metal powder having a relatively large particle size, for example, 5 μm or more, with a ball mill, a mechanical alloying device or the like. Can be coated. The area where the flat non-noble metal powder is coated with the noble metal (hereinafter, simply referred to as the coating area) is 50% or more of the total surface area of the flat non-noble metal powder, and the amount of the noble metal used for this coating ( Hereinafter, it is necessary that the coating amount is 2 to 30% by weight based on the flat non-noble metal powder. If the coating area is less than 50% or the coating amount is less than 2% by weight, when the conductive paste is applied to a substrate or the like and subjected to heat treatment, the flat non-noble metal powder on the base is oxidized and the conductivity is deteriorated. On the other hand, if the coating amount exceeds 30% by weight, the migration resistance deteriorates.
The coverage area is determined as follows. That is, five or more particles of the conductive metal composite powder are randomly taken out, a noble metal and a non-noble metal are quantitatively analyzed by an Auger spectrometer, a ratio of the noble metal is calculated, an average value thereof is obtained, and this average value is calculated. The coverage area.
The ratio between the non-noble metal and the noble metal is measured, for example, by taking out 1 g of the conductive metal composite powder, dissolving it with nitric acid, and measuring the solution using a chemical quantitative analysis, an atomic absorption spectrometer, or the like.
Although the above-mentioned coating area is set to 50% or more, a part of the surface of the non-noble metal powder may be exposed in that a local battery is formed on the particles of the non-noble metal powder and elution of the noble metal can be suppressed. Needed . In particular, when the noble metal is silver, it is preferable to use a combination of non-noble metal powders such as copper and nickel because the migration property of silver is improved and an excellent effect is exhibited. The coating amount is preferably from 7 to 25% by weight, more preferably from 15 to 20% by weight.
[0012]
The layer in which the noble metal and the non-noble metal are mixed according to the present invention is in a state in which both the noble metal used to form the coating layer and the non-noble metal component of the base layer are mixed. When the thickness of the layer in which the non-noble metal is mixed is 1/2 to 1/50 of the thickness of the surface noble metal layer, excellent conductivity and migration resistance are exhibited. When the thickness of the layer in which the noble metal and the non-noble metal are mixed is more than 1/2 or less than 1/50 of the thickness of the surface noble metal layer, the conductivity tends to be significantly deteriorated. The thickness of the layer in which the noble metal and the non-noble metal are mixed is more preferably 1/2 to 1/40, and even more preferably 1/2 to 1/30, of the thickness of the surface noble metal layer.
The thickness of the surface precious metal layer and the thickness of the layer where precious metal and non-precious metal are mixed are determined at random by extracting at least 5 particles of the conductive metal composite powder, shaving the surface by ion sputtering, and quantifying the element at the same time. One or more particles are measured at three or more points using an Auger spectroscopic analyzer or the like to be analyzed, an average value for each thickness is determined, and this average value is determined as each thickness.
[0013]
The layer in which the noble metal and the non-noble metal are mixed in the conductive metal composite powder used in the present invention contains 20 to 80 atomic% of the noble metal with respect to 80 to 20 atomic% of the noble metal. It is preferable in that it shows migration resistance.
When the conductive metal composite powder used in the present invention is used as a paste and screen-printed, the thickness of the surface noble metal layer is preferably 0.01 to 0.2 μm, so that the conductivity and the resistance can be improved. It is preferable because of its excellent migration property. When the thickness is less than 0.01 μm, the conductivity tends to deteriorate, and when the thickness exceeds 0.2 μm, the migration resistance tends to deteriorate.
[0014]
In the conductive metal composite powder used in the present invention, the major axis / thickness of the flat non-precious metal powder is preferably 2 to 30 in terms of exhibiting excellent conductivity and oxidation resistance. More preferably, it is more preferably 7 to 15. If the major axis / thickness of the flat non-precious metal powder is less than 2, contact between the powders becomes almost point contact, so that the resistance tends to be high. If it exceeds 30, the total surface area even if 30% by weight of the noble metal is coated. It becomes difficult to produce a substrate coated with 50% or more of the non-precious metal, and when a conductive paste is applied to a substrate or the like and subjected to heat treatment, the non-precious metal powder on the base tends to be oxidized, and the conductivity tends to deteriorate.
The major axis is preferably 100 μm or less in absolute value, more preferably 50 μm or less, and even more preferably 30 μm or less. To determine the major diameter / thickness of the conductive metal composite powder, take a SEM photograph of the conductive metal composite powder using a scanning electron microscope, and randomly select 30 or more particles of the conductive metal composite powder from these. Of the conductive metal composite powder is measured, and the average value is defined as the major axis / thickness of the conductive metal composite powder.
[0015]
Regarding the method for producing the conductive metal composite powder, there is no particular limitation on the average particle size and shape of the non-noble metal powder as the base material. The method of coating the noble metal is also not particularly limited as described above, but from the viewpoint of the balance between cost and characteristics, the average particle diameter obtained by a general particle size distribution measuring method such as a laser method and a sedimentation method is 1 to 1. A method of plating or vapor-depositing silver on copper powder of 30 μm or less is preferred.
[0016]
The conductive metal composite powder is prepared by coating the surface of a non-precious metal powder with a precious metal, and then mechanically using a mechanical alloying device, a dry ball milling device, a compression device using rolls, or a device that sprays the powder onto a hard material at high speed. It can be produced by adding mechanical energy or adding mechanical energy as described above to a mixed powder of non-noble metal powder and noble metal powder.
By applying mechanical energy to the non-noble metal powder whose surface is coated with the noble metal or to the above-mentioned mechanical energy to the mixed powder of the non-noble metal powder and the noble metal powder, The voids (voids) existing between the noble metal layer and the noble metal layer are eliminated, and the noble metal layer to be covered is densified, thereby increasing the conductivity. Further, at this time, a thin region in which the noble metal and the non-noble metal are mixed is formed between the surface noble metal layer and the non-noble metal layer, whereby the contact resistance between the surface noble metal layer and the non-noble metal layer can be reduced.
[0017]
The conductive paste according to the present invention is obtained by adding a conductive metal composite powder to an epoxy resin, a phenol resin, an unsaturated polyester resin, a saturated polyester resin, a polyamide resin, a polyimide resin, a polyamide resin, a polyimide resin, a polyamideimide resin, an acrylic resin, and the like. An organic binder or an inorganic binder such as glass frit is added, and if necessary, a curing accelerator such as imidazole and amines and a solvent such as butyl cellosolve, terpineol, ethylene carbitol, and carbitol acetate are added. It is obtained by uniformly mixing with a paddle, roll, kneader, or the like. The content of the binder is preferably from 5 to 30% by weight, more preferably from 8 to 16% by weight, based on the conductive paste. The curing accelerator and the solvent are added as necessary. If added, the content of the curing accelerator is preferably 0.01 to 1% by weight based on the conductive paste, and 0.02 to 0% by weight. More preferably, it is 0.05% by weight. The solvent is preferably used in an amount of 3 to 50% by weight, more preferably 10 to 30% by weight, based on the conductive paste.
[0018]
As the insulating base material used in the present invention, various substrates, various films and the like are used. Among these, various substrates include a paper phenol substrate, a glass epoxy substrate, an enamel substrate, a ceramic substrate, and the like. Examples thereof include flexible resin films such as polyethylene, polycarbonate, vinyl chloride, polystyrene, polyethylene terephthalate, polyphenylene sulfide, polyether ketone, polyether imide, and polyimide. In addition, examples of the electronic component mounted on the upper surface of the wiring conductor include a resistance element, a chip resistor, and a chip capacitor.
In the present invention, a conductor or a part of a resistor may be formed on the surface or through-hole of the insulating base material in advance by a method such as plating, printing, vapor deposition, or etching.
[0019]
The conductive paste according to the present invention can be used for forming a through conductor, an electrode, a jumper wire, an EMI shield, etc. in addition to a wiring conductor, and also connects the above electronic component to an insulating base material. It can also be used as a conductive adhesive and a lead-less solder substitute.
[0020]
【Example】
Hereinafter, embodiments of the present invention will be described.
Example 1
Spherical copper powder having an average particle size of 5 μm (trade name: SF-Cu, manufactured by Nippon Atomize Processing Co., Ltd.) was removed with an acidic cleaner (trade name: L-5B, manufactured by Nippon McDermid Co., Ltd.), washed with water, and washed with water 1 In a plating bath containing 20 g of AgCN and 10 g of NaCN per liter, displacement plating was performed so that the amount of silver was 20% by weight with respect to the spherical copper powder, washed with water and dried to obtain silver-plated copper powder.
[0021]
Next, this silver-plated copper powder was put into an MA (mechanical alloying) apparatus and subjected to a deformation treatment under the following conditions. This apparatus is a system in which a ball is moved by rotation of a screw, and the effective volume of a container into which the ball and the powder to be processed are charged is 1.1 liter. 4 kg of zirconia balls (diameter 10 mm) and 200 g of silver-plated copper powder were charged into the apparatus, the screw rotation speed was 90 rpm, and the pressure in the vessel was 2 × 10 ^-5 After rotating for 2 hours under the condition of torr, a conductive metal composite powder (flat silver-plated copper powder) was obtained.
[0022]
Next, a SEM photograph of the conductive metal composite powder obtained above was taken using a scanning electron microscope, 30 particles of the conductive metal composite powder were selected, and the major axis / thickness was measured. The average was 6. The major axis had an average of 15 μm in the range of 2 to 30 μm.
Also, five particles of the conductive metal composite powder were randomly taken out, and the noble metal and non-noble metal were quantitatively analyzed by a scanning Auger electron spectrometer to determine the silver covering area. In the range, the average was 70%.
Furthermore, five particles of the conductive metal composite powder were taken out at random, and the surface was scraped by ion sputtering, and at the same time, three points were measured for each particle by a scanning Auger electron spectrometer that quantitatively analyzed the elements. The thickness of the layer is in the range of 0.02 to 0.15 μm, the average is 0.045 μm, and the thickness of the layer in which a noble metal (copper) and a noble metal (copper) having a ratio of noble metal (silver) of 80 to 20 atomic% is mixed. The average was 0.01 μm in the range of 0.001 to 0.05 μm, and the average was 1 / 4.5 in the range of 1/20 to の of the thickness of the surface noble metal layer.
In the following Examples and Comparative Examples, the measurement was performed in the same manner as above.
[0023]
Next, with respect to 100 parts by weight of the conductive metal composite powder, 15 parts by weight of a novolak type phenol resin (trade name: PS-2607, manufactured by Gunei Chemical Industry Co., Ltd.) and 15 parts by weight of butyl cellosolve as a solvent are added and uniformly added. The mixture was mixed to obtain a conductive paste.
[0024]
Next, a conductive paste was passed through a 200-mesh screen on the upper surface of the copper phenol copper-clad laminate (manufactured by Hitachi Chemical Co., Ltd., trade name: MCL-437F) having a thickness of 1.6 mm from which the copper foil had been removed. A test pattern of 0.4 mm and a length of 100 mm was printed and heat-treated at 150 ° C. for 30 minutes in the atmosphere to obtain a wiring conductor. The average resistivity of the conductive paste cured product in the obtained wiring conductor was 75 μΩCm on average, and showed conductivity comparable to that of a silver paste described later.
[0025]
On the other hand, separately from the above, a conductive paste is printed on a glass plate in the same manner as described above so that electrodes having a width of 2 mm are spaced apart from each other by 2 mm, and is cured by heating at 150 ° C. for 30 minutes in the atmosphere. Thus, an electrode was obtained. Next, a filter paper cut to a width of 2 mm is placed between the electrodes, 0.5 cc of ion-exchanged water is dropped on the filter paper, a DC voltage of 20 V is applied between the electrodes, and the elapsed time and the leakage current between the electrodes are measured. The migration resistance was evaluated. As a result, the time required for a leakage current of 200 μA to flow was an average of 80 minutes, and was excellent in migration resistance.
For the measurement of the specific resistance and the evaluation of the migration resistance in the above, the average value of five samples was obtained. The same applies to the following examples and comparative examples.
[0026]
Comparative Example 1
A conductive paste was obtained through the same steps as in Example 1 except that the spherical silver-plated copper powder obtained in Example 1 was omitted and the flattened shape was omitted. The major axis / thickness of the spherical silver-plated copper powder is 1, the silver coating area is 95% or more of the total surface area, the thickness of the silver layer is 0.1 to 0.15 μm, the average is 0.12 μm and noble metal A layer in which a noble metal (copper) in which the ratio of (silver) was 80 to 20 atomic% and a non-noble metal (copper) was not clearly detected. Thereafter, the characteristics were evaluated in the same manner as in Example 1. As a result, the cured product of the conductive paste had an extremely high specific resistance of 1200 μΩCm on average, and the time required for a leakage current of 200 μA to flow was as short as 10 minutes on average, indicating poor migration resistance.
[0027]
Comparative Example 2
Spherical copper powder having an average particle diameter of 5 μm (trade name: SF-Cu, manufactured by Nippon Atomize Processing Co., Ltd.) was deformed in advance by the same method as in Example 1 so that the major axis / thickness became 6, and then implemented. 20% by weight of silver was coated by the same plating method as in Example 1. The silver-coated area of the silver-plated copper powder is 85% or more of the total surface area, the thickness of the silver layer is 0.03 to 0.2 μm, the average is 0.08 μm, and the ratio of the noble metal (silver) is 80%. A layer in which a precious metal of 混在 20 atomic% and a non-precious metal (copper) were mixed could not be clearly detected. Hereinafter, a conductive paste was produced through the same steps as in Example 1, and the characteristics were evaluated. As a result, the specific resistance of the cured conductive paste was as high as 800 μΩCm, the time required for a leakage current of 200 μA to flow was as short as 10 minutes, and the migration resistance was poor.
[0028]
Comparative Example 3
Through the same process as in Example 1 except that silver powder having a long diameter / thickness of 30 on average (trade name: TCG-1) was used instead of the conductive metal composite powder used in Example 1. A conductive paste was prepared and the characteristics were evaluated. As a result, although the specific resistance of the cured conductive paste was 80 μΩCm on average, the time required for a leakage current of 200 μA to flow was extremely short at 30 seconds on average, and was poor in migration resistance.
[0029]
Comparative Example 4
The same characteristics as in Example 1 were evaluated using a commercially available copper paste for EMI shielding. As a result, the specific resistance of the cured conductive paste was as high as 500 μΩCm on average, and the time required for a leakage current of 200 μA to flow was 45 minutes on average.
[0030]
Example 2
Spherical copper powder having an average particle diameter of 6 μm (trade name: SF-Cu, manufactured by Nippon Atomize K.K.) was coated with 30% by weight of silver by the same plating method as in Example 1 to obtain a silver-plated copper powder. A conductive metal composite powder was obtained through the same steps as in Example 1 except that the subsequent processing time in the MA apparatus was 1 hour. The major axis of the particles of the obtained conductive metal composite powder is 7 μm on average in the range of 3 to 15 μm, and the average of major axis / thickness is 2.5 in the range of 2 to 9; On the other hand, the average is 95% in the range of 75 to 100%, the thickness of the silver layer is 0.1 μm in the range of 0.05 to 0.2 μm, and the ratio of the noble metal (silver) is 80 to 20 atomic%. The thickness of a layer in which a certain noble metal and a non-noble metal (copper) are mixed is 0.001 to 0.01 μm and the average is 0.006 μm, and is 1/50 to 1/8 of the thickness of the surface noble metal layer. The average in the range was 1 / 16.7. Hereinafter, a conductive paste was produced through the same steps as in Example 1, and the characteristics were evaluated. As a result, the specific resistance of the cured conductive paste was 80 μΩCm on average, and the time required for a leakage current of 200 μA to flow was 40 minutes on average.
[0031]
Example 3
Same as Example 1 except that a spherical copper powder having an average particle diameter of 6 μm (trade name: SF-Cu, manufactured by Nippon Atomize K.K.) was coated with 10% by weight of silver by the same plating method as in Example 1. Through the steps, a conductive metal composite powder was obtained. The major axis of the particles of the obtained conductive metal composite powder is 15 μm on average in the range of 2 to 30 μm, and the major axis / thickness is 6 on average in the range of 2 to 15; A noble metal having an average of 51% in a range of 30 to 70%, a thickness of a silver layer of 0.02 μm in a range of 0.01 to 0.03 μm, and a ratio of noble metal (silver) of 80 to 20 atomic%. And a non-precious metal (copper) mixed layer has an average thickness of 0.01 μm in the range of 0.001 to 0.02 μm and a thickness of 1/10 to 2/3 of the thickness of the surface precious metal layer. The average was 1/2. Hereinafter, a conductive paste was produced through the same steps as in Example 1, and the characteristics were evaluated. As a result, the specific resistance of the cured conductive paste was 135 μΩCm on average, and the time required for a leakage current of 200 μA to flow was 60 minutes on average.
[0032]
Example 4
Spherical copper powder having an average particle size of 6 μm (trade name: SF-Cu, manufactured by Nippon Atomize K.K.) was coated with 2% by weight of silver by the same plating method as in Example 1 to obtain a silver-plated copper powder. A conductive metal composite powder was obtained through the same steps as in Example 1 except that the subsequent processing time in the MA apparatus was 1 hour. The major axis of the particles of the obtained conductive metal composite powder is 9 μm on average in the range of 2 to 20 μm, the average is 4 in the major axis / thickness in the range of 2 to 13, and the silver coating area is relative to the total surface area. A noble metal having an average of 55% in the range of 15 to 70%, a thickness of the silver layer of 0.01 to 0.02 μm, an average of 0.01 μm, and a noble metal (silver) ratio of 80 to 20 atomic%. And a non-precious metal (copper) mixed layer has an average thickness of 0.002 μm in the range of 0.0001 to 0.003 μm, and an average of 1/15 to 1 of the thickness of the surface precious metal layer. It was 1/5. Hereinafter, a conductive paste was produced through the same steps as in Example 1, and the characteristics were evaluated. As a result, the specific resistance of the cured conductive paste was 110 μΩCm on average, and the time required for a leakage current of 200 μA to flow was 100 minutes on average.
[0033]
Comparative Example 5
Example 1 was repeated except that a spherical copper powder having an average particle size of 6 μm (trade name: SF-Cu, manufactured by Nippon Atomize K.K.) was coated with 1.5% by weight of silver by the same plating method as in Example 1. Through the same steps, a conductive metal composite powder was obtained. The major axis of the particles of the obtained conductive metal composite powder is 15 μm on average in the range of 2 to 30 μm, and the major axis / thickness is 6 on average in the range of 4 to 18; A noble metal having an average of 20% in the range of 5 to 35%, a thickness of the silver layer of 0.00005 to 0.005 μm, an average of 0.003 μm, and a ratio of the noble metal (silver) of 80 to 20 atomic%. And a non-precious metal (copper) mixed layer has an average thickness of 0.003 μm in the range of 0.00005 to 0.005 μm, and an average thickness in the range of 1/2 to 1 of the thickness of the surface precious metal layer. 4/5. Hereinafter, a conductive paste was produced through the same steps as in Example 1, and the characteristics were evaluated. As a result, the specific resistance of the cured conductive paste was as high as 450 μΩCm on average, and the time required for a leakage current of 200 μA to flow was 90 minutes on average.
[0034]
Comparative Example 6
Same as Example 1 except that a spherical copper powder having an average particle size of 6 μm (trade name: SF-Cu, manufactured by Nippon Atomize K.K.) was coated with 35% by weight of silver by the same plating method as in Example 1. Through the steps, a conductive metal composite powder was obtained. The average length of the particles of the obtained conductive metal composite powder is 10 μm in the range of 2 to 25 μm, and the average length / length is 5 in the range of 3 to 20. The silver coating area is based on the total surface area. A noble metal having an average of 80% in a range of 65 to 95%, an average thickness of 0.06 μm in a thickness of a silver layer of 0.03 to 0.2 μm, and a ratio of noble metal (silver) of 80 to 20 atomic%. And a non-precious metal (copper) mixed layer has a thickness of 0.0001 to 0.003 μm and an average of 0.001 μm, and a thickness of 1/500 to 1/50 of the surface noble metal layer thickness. The average was 1/60. Hereinafter, a conductive paste was produced through the same steps as in Example 1, and the characteristics were evaluated. As a result, the resistivity of the cured conductive paste was 130 μΩCm on average, and the time required for a leakage current of 200 μA to flow was 10 minutes on average, and the migration resistance was poor.
[0035]
Example 5
The silver-plated copper powder (silver coating amount 30% by weight) obtained in Example 2 was compressed between two rolls, and the average diameter was 30 μm in the range of 5 to 55 μm in the major axis of the particle. A conductive metal composite powder having an average of 27 in the range of 15 to 50 was obtained. The obtained conductive metal composite powder has an average silver coverage of 50% in the range of 35 to 80% of the total surface area, and a silver layer thickness of 0.002 to 0.02 μm with an average of 0.1%. The thickness of the layer in which the noble metal (copper) and the noble metal (copper) in which the ratio of 0125 μm and the noble metal (silver) is 80 to 20 atomic% is in the range of 0.0001 to 0.0005 μm and the average is 0.00025 μm. The average was 1/50 in the range of 1/20 to 1/100 of the thickness of the surface noble metal layer. Hereinafter, a conductive paste was produced through the same steps as in Example 1, and the characteristics were evaluated. As a result, the specific resistance of the cured conductive paste was 115 μΩCm on average, and the time required for a leakage current of 200 μA to flow was 50 minutes on average.
[0036]
Example 6
A spherical copper powder having an average particle size of 5 μm (trade name: SF-Cu, manufactured by Nippon Atomize K.K.) is held in a dish-shaped container in a vapor deposition apparatus, and the amount of silver is 20% by weight while rotating the dish-shaped container. Was deposited to obtain silver-deposited copper powder.
Next, this silver-deposited copper powder was subjected to the same steps as in Example 1 to obtain a conductive metal composite powder. The major axis of the particles of the obtained conductive metal composite powder is 7 μm on average in the range of 3 to 15 μm, the major axis / thickness is 6 on average in the range of 2 to 15, and the silver coating area is relative to the total surface area. A noble metal having an average of 90% in the range of 75 to 100%, a thickness of the silver layer of 0.02 to 0.18 μm, an average of 0.04 μm, and a precious metal (silver) ratio of 80 to 20 atomic%. And a non-precious metal (copper) mixed layer has an average thickness of 0.015 μm in the range of 0.001 to 0.05 μm and a thickness of 1/20 to 4/5 of the thickness of the surface precious metal layer. The average was 1 / 2.7. Hereinafter, a conductive paste was produced through the same steps as in Example 1, and the characteristics were evaluated. As a result, the specific resistance of the cured conductive paste was 55 μΩCm on average, and the time required for a leakage current of 200 μA to flow was 90 minutes on average.
[0037]
Example 7
100 parts by weight of a bisphenol A type liquid epoxy resin (manufactured by Yuka Shell Co., Ltd., trade name: Epicoat 828) and 55.8 parts by weight of novolak type phenol formaldehyde resin (manufactured by Hitachi Chemical Co., Ltd., trade name: HP-607N) The mixture was heated and mixed at 110 ° C. to obtain a solventless mixed resin.
Next, 8 parts by weight of the solventless mixed resin obtained above and 0.04 part by weight of benzyldimethylamine as a curing accelerator were added to 100 parts by weight of the conductive metal composite powder obtained in Example 1, and mixed uniformly. Thus, a conductive paste was obtained. Thereafter, the characteristics were evaluated in the same manner as in Example 1. As a result, the specific resistance of the cured conductive paste was 85 μΩCm on average, and the time required for a leakage current of 200 μA to flow was 80 minutes on average.
[0038]
Example 8
80 parts by weight (160 g) of spherical copper powder having an average particle size of 6 μm (trade name: SF-Cu, manufactured by Nippon Atomize K.K.) and fine spherical silver powder having an average particle size of 1 μm (fine powder, manufactured by Nippon Atomize K.K.) ) 20 parts by weight (40 g) were charged into a MA apparatus, and the same steps as in Example 1 were performed to obtain a conductive metal composite powder having a silver coating amount of 20% by weight. The major axis of the particles of the obtained conductive metal composite powder is 15 μm on average in the range of 2 to 30 μm, and the major axis / thickness is 6 on average in the range of 2 to 15; A noble metal having an average of 55% in the range of 40 to 65%, a thickness of the silver layer of 0.003 to 0.1 μm and an average of 0.03 μm and a noble metal (silver) ratio of 80 to 20 atomic%. And a non-precious metal (copper) mixed layer has a thickness of 0.003 to 0.05 μm and an average of 0.01 μm, and a thickness of 1/10 to の of the surface precious metal layer. The average was 1/5. Hereinafter, a conductive paste was produced through the same steps as in Example 1, and the characteristics were evaluated. As a result, the specific resistance of the cured conductive paste was 140 μΩCm on average, and the time required for a leakage current of 200 μA to flow was 40 minutes on average.
[0039]
Example 9
80 parts by weight (160 g) of fine spherical copper powder having an average particle size of 2.0 μm (produced by Nippon Atomize Processing Co., Ltd.) and 20 parts by weight (40 g) of fine spherical silver powder used in Example 8, Hereinafter, a conductive metal composite powder having a silver coating amount of 20% by weight was obtained through the same steps as in Example 1 except that zirconia balls having a diameter of 5 mm were used. The average length of the particles of the obtained conductive metal composite powder is 10 μm in the range of 5 to 20 μm, and the average length / length is 5 in the range of 2 to 20. A noble metal having an average of 52% in a range of 40 to 60%, an average thickness of 0.03 µm in a thickness of a silver layer of 0.005 to 0.07 µm, and a ratio of noble metal (silver) of 80 to 20 atomic%. And a non-precious metal (copper) mixed layer has a thickness of 0.01 to 0.05 μm and an average of 0.015 μm, and a thickness of 1/7 to 2/3 of the surface precious metal layer. The average was 1/2. Hereinafter, a conductive paste was produced through the same steps as in Example 1, and the characteristics were evaluated. As a result, the cured product of the conductive paste had an average resistivity of 130 μΩCm and an average time required for a leakage current of 200 μA to flow was 30 minutes.
[0040]
Example 10
Novolak-type phenol resin (group) was added to 100 parts by weight of a mixed powder obtained by uniformly mixing 50% by weight of the conductive metal composite powder obtained in Example 8 and 50% by weight of the silver powder used in Comparative Example 3 with a V-type mixer. 12 parts by weight (trade name: PS-2607, manufactured by Sakae Chemical Industry Co., Ltd.), 2 parts by weight of a bisphenol A type epoxy resin (trade name: Epicoat 828, manufactured by Yuka Shell Epoxy Co., Ltd.) and 15 parts by weight of butyl cellosolve as a solvent were added. The paste was mixed uniformly to prepare a conductive paste, and the characteristics were evaluated. As a result, the specific resistance of the cured conductive paste was 70 μΩCm on average, and the time required for a leakage current of 200 μA to flow was 15 minutes on average.
[0041]
Example 11
50 parts by weight (100 g) of spherical copper powder having an average particle diameter of 25 μm (obtained by classification from SF-Cu, trade name, manufactured by Nippon Atomize K.K.) and 50 parts by weight of fine spherical silver powder used in Example 8 ( Except for blending 100 g), a conductive metal composite powder having a silver coverage of 30% by weight was obtained through the same steps as in Example 1. The major axis of the particles of the obtained conductive metal composite powder is 15 μm on average in the range of 2 to 30 μm, and the major axis / thickness is 6 on average in the range of 2 to 15; A noble metal having an average of 65% in the range of 45 to 75%, a thickness of the silver layer of 0.05 to 0.2 μm in an average of 0.05 μm, and a noble metal (silver) ratio of 80 to 20 atomic%. And a non-precious metal (copper) mixed layer has an average thickness of 0.02 μm in the range of 0.01 to 0.06 μm and a thickness of 1/5 to の of the surface precious metal layer. The average was 1/3. Hereinafter, a conductive paste was produced through the same steps as in Example 1, and the characteristics were evaluated. As a result, the cured product of the conductive paste had an average resistivity of 60 μΩCm and an average time of 10 minutes required for a leakage current of 200 μA to flow.
[0042]
Example 12
60 parts by weight of bisphenol A type epoxy resin (trade name: Epinal 834, manufactured by Yuka Shell Epoxy Co., Ltd.) and 40 parts by weight of bisphenol A type epoxy resin (trade name: Epinal 828, manufactured by Yuka Shell Epoxy Co., Ltd.) are added in advance. After dissolving by warming and then cooling to room temperature (20 ° C.), 5 parts by weight of 2-ethyl-4-methylimidazole, 20 parts by weight of ethyl carbitol and 20 parts by weight of butyl cellosolve were added and uniformly mixed to obtain a resin composition.
[0043]
Spherical copper powder having an average particle size of 7.2 μm (trade name: SF-Cu, manufactured by Nippon Atomize Processing Co., Ltd.) was immersed in dilute hydrochloric acid, washed with pure water, and then washed in a mixed solution of 80 g of AgCN / 1 kg of water. The silver was subjected to displacement plating while stirring at ± 5 ° C. for 20 minutes, washed with water and dried to obtain silver-plated copper powder.
[0044]
Next, 400 g of the silver-plated copper powder obtained above and 3 kg of zirconia balls having a diameter of 5 mm were put into a 2 liter ball mill container, and the silver-plated copper powder was deformed by rotating at 60 rpm for 30 minutes. A conductive metal composite powder was obtained. The average length of the particles of the obtained conductive metal composite powder is 11.5 μm in the range of 2 to 24 μm, and the average length / thickness is 9 in the range of 3 to 14; On the other hand, the average was 75% in the range of 60 to 85%.
Thereafter, 215 g of the conductive metal composite powder obtained above was added to 145 g of the resin composition obtained above, and the mixture was uniformly mixed and dispersed with a grinder and three rolls to obtain a conductive paste. Note that the content of the conductive metal composite powder was 60% by weight based on the solid content of the conductive paste.
[0045]
Next, a paper phenol copper-clad laminate (trade name: MCL-437F, manufactured by Hitachi Chemical Co., Ltd.) formed with a through hole having a thickness of 1.6 mm and a diameter of 0.8 mm using the conductive paste obtained above. The test pattern shown in FIG. 1 was printed on the substrate, and the printed conductor filled in the through hole 1 was subjected to a heat treatment in the air at 60 ° C. for 30 minutes and at 160 ° C. for 30 minutes to obtain a wiring conductor 3. In FIG. 1, reference numeral 2 denotes a paper phenol copper-clad laminate.
[0046]
As a result of measuring the resistance of the obtained wiring conductor, the resistance of the through hole 1 excluding the resistance of the copper foil was 22 mΩ / hole on average of 54 holes, and the specific resistance measured by printing on a plane was 95 μΩcm. . The insulation resistance between the adjacent through holes 1 is 10 ⁸ Ω or more. As a result of performing a thermal shock test of the wiring conductor, the resistance of the through-hole 1 was 26.2 mΩ / hole on average. In addition, as a result of performing a wet and medium load test on the wiring conductor, the insulation resistance between the through holes 1 was 10 ⁸ Ω or more. The thermal shock test was performed at 125 ° C. for 30 minutes to −65 ° C. and 30 minutes for 100 cycles. The wet load test was performed at 40 ° C. and 90% RH for 2000 hours by applying a voltage of 50 V between adjacent lines. Held. Further, a soldering resistance test (260 ° C., 10 seconds, 5 times) was performed, and the resistance change rate was within 30%.
[0047]
Example 13
250 g of the silver-plated copper powder obtained in Example 12 and 5 kg of zirconia balls having a diameter of 5 mm were put into a cylindrical 2 liter container, and vibrated for 10 minutes with a vibrating mill. A composite metal powder was obtained. The major axis of the particles of the obtained conductive metal composite powder has an average of 11.5 μm in the range of 3 to 25 μm, and the major axis / thickness has an average of 7 in the range of 2 to 12; On the other hand, the average was 70% in the range of 60 to 85%.
Thereafter, 240 g of the conductive metal composite powder obtained above was added to 145 g of the resin composition obtained in Example 12, and a conductive paste was obtained through the same steps as in Example 12 below. The content of the conductive metal composite powder was 63% by weight based on the solid content of the conductive paste.
[0048]
Thereafter, a wiring conductor was produced through the same steps as in Example 12, and the characteristics were evaluated. As a result, the resistance of the through-hole was 21.5 mΩ / hole on average of 54 holes, and the specific resistance measured by printing on a flat surface was 102 μΩcm. The insulation resistance between adjacent through holes is 10 ⁸ Ω or more. As a result of conducting a thermal shock test of the wiring conductor, the resistance of the through-hole was 24.5 mΩ / hole on average, and the insulation resistance between the through-holes was 10 ⁸ Ω or more. Further, the same solder resistance test as in Example 12 was performed, but the resistance change rate was within 30%.
[0049]
Comparative Example 7
195 g of the silver-plated copper powder obtained in Example 12 was added to 145 g of the resin composition obtained in Example 12, and a conductive paste was obtained through the same steps as in Example 12 below. The silver coating area was 93 to 99% of the total surface area, with an average of 97%. The content of the conductive metal composite powder was 57% by weight based on the solid content of the conductive paste.
[0050]
Thereafter, a wiring conductor was produced through the same steps as in Example 12, and the characteristics were evaluated. As a result, the through-hole resistance was 228 mΩ / hole on average for 54 holes, the specific resistance measured by printing on a plane was 350 μΩcm, and the insulation resistance between adjacent through-holes was 10 μm. ⁸ Ω or more. Further, as a result of performing a thermal shock test on the wiring conductor, the resistance of the through-hole was 251 mΩ / hole on average, and the insulation resistance between the through-holes was 10 ⁸ Ω or more. Further, the same solder resistance test as in Example 12 was performed, and the rate of change in resistance was 200%.
[0051]
Example 14
195 g of the conductive metal composite powder obtained in Example 12 was added to 145 g of the resin composition obtained in Example 12, and the mixture was uniformly mixed and dispersed with a grinder and three rolls to obtain a conductive paste. Note that the content of the conductive metal composite powder was 66.1% by weight based on the solid content of the conductive paste.
Next, the test pattern shown in FIG. 2 was printed on a 1.6 mm thick paper phenol copper-clad laminate (manufactured by Hitachi Chemical Co., Ltd., trade name: MCL-437F) with the conductive paste obtained above, This was heated in air at 60 ° C. for 30 minutes and further at 160 ° C. for 30 minutes to obtain an electromagnetic wave shielding material on which the wiring conductor 3 was formed. The resistance of the obtained electromagnetic wave shielding material was measured. As a result, the specific resistance was 35 μΩCm, and the sheet resistance was 13 mΩ / □. In addition, a cooling test was performed at 125 ° C., 30 minutes to −65 ° C., 30 minutes under 100 cycles, and a soldering resistance test (260 ° C., 10 seconds, 5 times) was performed. Was within. Further, the resistance change rate when held at 60 ° C. and 95% relative humidity for 1000 hours was within 10%.
[0052]
Example 15
Based on 100 parts by weight of the conductive metal composite powder obtained in Example 1, 10 parts by weight of a bisphenol A type liquid epoxy resin (trade name: Epicoat 828, manufactured by Yuka Shell Co., Ltd.), and 0.3 parts by weight of imidazole as a curing agent Then, 5 parts by weight of butyl cellosolve as a solvent was added and uniformly mixed to obtain a conductive paste. Thereafter, the characteristics were evaluated in the same manner as in Example 1. As a result, the specific resistance of the cured conductive paste was 90 μΩCm on average, and the time required for a leakage current of 200 μA to flow was 80 minutes on average.
On the other hand, separately from the above, a conductive paste was applied on the upper surface of a paper phenol copper-clad laminate (trade name: MCL-437F, manufactured by Hitachi Chemical Co., Ltd.) having a thickness of 1.6 mm on the upper surface of the laminate from which the copper foil had been removed. A test pattern having a size of 4 mm and a thickness of 160 μm was printed, and then processed by mounting a chip capacitor (electronic component) having a size of 5 × 5 mm on the upper surface thereof. The specific resistance of the conductive paste cured product after the pressure bonding was 30 μΩCm on average. The adhesive strength of the chip capacitor was 1.5 kg / 1 chip, which was sufficient as the adhesive strength of electronic components.
[0053]
【The invention's effect】
The conductive paste according to claim 1 has high conductivity, and is excellent in conductivity and migration.
The conductive paste according to the second aspect has the effect of the conductive paste according to the first aspect, and is particularly excellent in migration resistance.
The conductive paste according to the third aspect has the effect of the conductive paste according to the first aspect, and is particularly excellent in conductivity and migration resistance.
The conductive paste according to the fourth aspect has the effect of the conductive paste according to the first aspect, and is particularly excellent in conductivity.
According to the method of the fifth aspect, the conductive paste can be manufactured at low cost, and the obtained conductive paste has high conductivity and excellent migration resistance.
According to the method of the sixth aspect, a conductive paste can be manufactured at low cost, and the obtained conductive paste has high conductivity and excellent migration resistance.
The electric circuit device according to claim 7 is excellent in adhesion to electronic components as a lead-free and solder substitute material.
The electric circuit device obtained by the method according to claim 8 can bond an electronic component as a lead-free solder replacement material.
[Brief description of the drawings]
FIG. 1 is a plan view showing a state in which a conductive paste is printed on a paper phenol copper clad laminate and filled in through holes.
FIG. 2 is a plan view of an electromagnetic wave shielding material obtained by printing a conductive paste on a paper phenol copper clad laminate.
[Explanation of symbols]
1 Through hole
2 Paper phenol copper clad laminate
3 Wiring conductor

Claims

Exposing a part of the surface of the flat non-precious metal powder, 50% or more of the total surface area is coated with 2 to 30% by weight of the precious metal based on the flat non-precious metal powder, and the surface precious metal layer and the non-precious metal layer A conductive paste containing a conductive metal composite powder and a binder with a layer containing a mixture of a noble metal and a non-noble metal interposed therebetween, wherein the layer containing a mixture of a noble metal and a non-noble metal has a surface noble metal layer Conductive paste having a thickness of 1/2 to 1/50 of the thickness of the conductive paste.

2. The conductive paste according to claim 1, wherein the layer in which the noble metal and the non-noble metal are mixed has a non-noble metal content of 20 to 80 atomic% to a noble metal of 80 to 20 atomic%.

3. The conductive paste according to claim 1, wherein the thickness of the surface noble metal layer is 0.01 to 0.2 [mu] m.

4. The conductive paste according to claim 1, wherein the major diameter / thickness of the conductive metal composite powder is 2 to 30. 5.

After exposing a part of the surface of the non-noble metal powder and coating 2% to 30% by weight of the non-noble metal powder with respect to the non-noble metal powder to 50% or more of the total surface area, mechanical energy is applied to flatten the deformation and A method for producing a conductive paste, comprising: forming a layer in which a noble metal and a non-noble metal are mixed between a surface noble metal layer and a non-noble metal layer, and then adding a binder and mixing uniformly.

Mechanical energy is applied to the mixed powder of the non-noble metal powder and the noble metal powder to expose a part of the surface of the non-noble metal powder while deforming the mixed powder into a flat shape, thereby increasing the non-noble metal powder to 50% or more of the total surface area. After forming a layer containing a mixture of a noble metal and a non-noble metal between a surface noble metal layer and a non-noble metal layer by coating 2-30% by weight of the noble metal with respect to the noble metal powder, a binder is added. A method for producing a conductive paste, which comprises mixing uniformly.

An electric circuit device comprising a wiring conductor formed on the insulating base material by the conductive paste according to claim 1, and an electronic component mounted on an upper surface thereof.

Applying, printing or potting the conductive paste according to claim 1 on an insulating base material to form a wiring conductor, and then mounting an electronic component on the upper surface of the wiring conductor. Manufacturing method for electrical circuit devices.