JP3818947B2 - Manufacturing method of joined body - Google Patents
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- JP3818947B2 JP3818947B2 JP2002270970A JP2002270970A JP3818947B2 JP 3818947 B2 JP3818947 B2 JP 3818947B2 JP 2002270970 A JP2002270970 A JP 2002270970A JP 2002270970 A JP2002270970 A JP 2002270970A JP 3818947 B2 JP3818947 B2 JP 3818947B2
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Description
【0001】
【発明の属する技術分野】
本発明は、回路基板として好適な接合体の製造方法に関する。
【0002】
【従来の技術】
従来、パワーモジュール等に利用される半導体装置においては、アルミナ、ベリリア、窒化ケイ素、窒化アルミニウム等のセラミックス基板の表裏面に、Cu、Al、それらの金属を成分とする合金等の回路と放熱板とがそれぞれ形成されてなる回路基板が開発され(特許文献1)、実用化されている。Al回路基板は、Cu回路基板よりも熱履歴に対する信頼性が高いので、自動車用途等の高信頼性基板の用途として検討されているが、製造が複雑でコスト高となることが、広く普及しない理由となっている。
【0003】
【特許文献1】
米国特許第5,354,415号明細書
【特許文献2】
特開平2001−085808号公報
【特許文献3】
特開平11−60343号公報
【0004】
【発明が解決しようとする課題】
セラミックス基板にAl回路を形成するには、溶融アルミニウムをセラミックス基板に接触・冷却して両者の接合体を製造した後、機械研磨してAl板の厚みを整え、その後エッチングする溶湯法(特許文献2)があるが、この方法はCu回路を形成する場合と比較して2〜5倍程度のコストがかかる。
【0005】
一方、ろう付け法のAl回路基板がCu回路基板よりもコスト高となる原因は、セラミックス基板とAl箔又はAl合金箔の積層体に一部始終圧力を加えながら接合しなければいけないからである。加圧方法としては、黒鉛製冶具に積層体を収納し、両端面からねじ込むなどの機械的手段によって行われているが(特許文献3)、このような方法では生産性が十分に高まらない。
【0006】
本発明の目的は、上記に鑑み、生産性の極めて高いセラミックス基板と、金属箔、特にAl箔又はAl合金箔からなる接合体の製造方法を提供することである。本発明の目的は、金属箔とろう材合金箔を有機系接着剤を用いて張り合わせ、それを有機系接着剤を介してセラミックス基板に配置して積層構造体となした後、熱処理することによって達成することができる。
【0007】
【課題を解決するための手段】
すなわち、本発明は、有機系接着剤を用いて張り合わせられた金属箔とろう材合金箔との積層物を、有機系接着剤を介して、セラミックス基板の片面又は両面に、その積層物のろう材合金箔面とセラミックス基板面とを重ねて積層構造体とした後、それを熱処理することを特徴とする接合体の製造方法である。
【0008】
また、本発明は、次の工程1〜3を経由することを特徴とする接合体の製造方法である。
工程1:金属箔とろう材合金箔とを有機系接着剤を用いて張り合わせ、それを圧延機を通過させて金属箔とろう材合金箔からなる帯状積層物を製造する工程。
工程2:上記帯状積層物を所用寸法に打抜き、それを有機系接着剤を介して、セラミックス基板の片面又は両面に、上記帯状積層物のろう材合金箔面とセラミックス基板面とを重ねて配置し、積層構造体を製造する工程。
工程3:上記積層構造体を非酸化性雰囲気の高温化に保持された、予加熱部、仮接合部、拡散部を有する接合炉内へ搬送させて、金属箔とセラミックス基板との接合体を製造する工程。
【0009】
ここで、「予加熱部」とは、ろう材合金箔の融点より低い温度に保持された領域であり、「仮接合部」とは、ろう材合金箔の融点以上の温度領域で上記積層構造体を加圧しながら、ろう材成分とセラミックス基板とを反応させる領域であり、「拡散部」とは、ろう材合金箔の融点以上の温度領域で上記積層構造体の加圧を解いて、ろう材成分を金属箔へ拡散させる領域である、と定義される。
【0010】
本発明においては、金属箔とろう材合金箔を張り合わせるのに用いる有機系接着剤と、セラミックス基板に積層物を配置するのに用いる有機接着剤は、いずれもポリイソブチルメタクリル酸のトルエン溶液又はポリイソブチルメタクリレートのテルピネオール溶液であり、またセラミックス基板が窒化アルミニウム製又は窒化珪素製、金属箔がAl製又はAl合金製、ろう材合金箔がAlとCuを主成分とするものであることが好ましい。
【0011】
さらには、積層構造体の予加熱部における通過速度が0.1〜10mm/secであり、仮接合部の雰囲気温度が600〜650℃、積層構造体の仮接合部における通過速度が0.1〜10mm/sec、加圧が1MPa以上のロール加圧であり、積層構造体の拡散部における通過速度が0.1〜10mm/secであることが好ましい。
【0012】
【発明の実施の形態】
以下、さらに詳しく本発明について説明する。
【0013】
本発明で用いられる金属箔の材質は、Cu箔、Cu合金箔、Al箔、Al合金箔等であるがAl箔又はAl合金箔が好適である。これには、1000系の純Alは勿論のこと、接合が容易な4000系のAl−Si系合金や、6000系のAl−Mg−Si系合金等が例示できる。中でも、圧延率10%以上の高純度Al箔(純度99.85%(質量%、以下同じ))が好ましく、これには1085、IN85材の市販品がある。また、99.9%(3N)品、99.99%(4N)品もそれほど高価ではないので使用可能である。金属箔は、単体でもよく、二種又は三種以上のクラッド等の積層体であってもよい。積層体の例を挙げれば、Al−Ni、Al−Ni−Cu、Al−Mo、Al−Mo、Al−W、Al−Cuなどである。
【0014】
金属箔の厚みは、0.1〜0.5mmであることが好ましい。とくに、回路基板の熱応力による反りやうねりをなくし、半田クラック等による損傷、ボンディングワイヤやメッキの剥離防止を高度にするため、裏面金属箔(放熱板)に対する表面金属箔(回路)の体積比(回路体積/放熱板体積)を1に近づけることが望ましく、0.80〜1.2、特に0.85〜1.15、更には0.9〜1.1とすることが好ましい。なお、放熱板の厚みは、回路の厚みと同等以下とするのが好ましい。Al回路の体積は、回路面積と回路厚みを乗じることによって、また放熱板の体積は放熱板面積と加熱版厚みを乗じることによって算出することが出来る。金属箔の形状について限定はないが、請求項1に関連する発明においては帯状である。
【0015】
本発明で用いられるろう材合金箔の成分は、AlとCuを主成分とするものが好ましく、例示すればCu1〜6%、特に1.5〜5%のAl−Cu箔合金、4%Cuと0.5%Mgとを含む2018合金箔、0.5%のMnを含む2017合金箔、更にはJIS合金の2001、2003、2005、2007、2011、2014、2024、2025、2030,2034,2036,2048,2090,2117,2124,2218,2224,2324,7050等の合金箔である。Mg、Zn、In、Mn、Cr、Ti、Bi等の第三成分は合計で5%まで含ませることができる。
【0016】
Al−Cu合金箔又はこれに第三成分の付加された合金において、Cuが1%未満では、接合温度を高めなければならなくなるので量産化には不利となり、また6%超では、接合後のろう材の拡散部が特に硬くなってAl回路の信頼性が低下する恐れがある。特に好ましいろう材合金箔は、Al86%以上、Cu1〜6%、Mg3%以下(0%を含まず)、特に0.2〜2.0%である。
【0017】
ろう材合金箔の厚みは、上記金属の厚みに対して1/10〜1/50の厚みであることが好ましい。1/50未満の厚みでは、十分な接合が難しくなり、また1/10超ではAl回路が硬くなる。特に好ましくは、100μm以下の厚みであって、しかも金属箔の厚みに対して1/12〜1/14の厚みである。これは、金属箔の厚みが0.4〜0.6mmである場合、10〜50μm厚、特に15〜30μm厚が好適となることを意味している。ろう材合金箔の形状については限定はないが、請求項1に関連する発明においては帯状である。
【0018】
金属箔とろう材合金箔との積層物とするのに用いる有機系接着剤としては、水系あるいは非水系有機溶剤のどちらでも可能であるが、好ましくはポリイソブチルメタクリレート、ポリビニルアルコール等を媒質とした粘度3.0〜0.1Pa・sec溶液である。特に好ましくは、ポリイソブチルメタクリレート10〜50質量%のトルエン溶液、ポリイソブチルメタクリレート10〜80質量%のテルピネオール溶液などである。このような有機系接着剤を用いることによって、熱処理時にズレが生じず、また350℃以上では残留炭素が50ppm以下となるので、接合体になったときに、金属箔とろう材合金箔間の残炭素の存在は無視できる。有機系接着剤は、金属箔、ろう材合金箔、又はその両方の接合面の全面に塗布されていることが好ましい。
【0019】
上記積層物は、セラミックス基板に配置する際に、圧延機を通す等によって圧延処理が施されていることが更に好ましい。圧延機としては、ヒーター付属の複数のロールを有したものが好ましく、そのロール間に積層物を通すことによって、接着剤の乾燥と両箔の仮接着を行うことができる。ロール温度100〜130℃、ロール回転による搬送速度0.1〜10mm/secを一例としてあげることができる。
【0020】
上記積層物は、次いで上記有機系接着剤と同種の有機系接着剤を介し、ろう材合金箔面とセラミックス基板面とを一致させて配置して積層構造体とする。有機系接着剤は、セラミックス基板、ろう材合金箔、又はその両方の接合面の全面に塗布されていることが好ましい。
【0021】
本発明で使用されるセラミックス基板は、窒化アルミニウム製又は窒化ケイ素製であることが好ましい。炭化ケイ素、酸化ベリリウム等のセラミックス基板では、絶縁性と安全性の点で劣る。セラミックス基板の熱伝導率は、高信頼性が求められるパワーモジュールに使用されることを考えれば、少なくとも70W/mK以上、特に130W/mK以上であることが好ましい。なかでも、表面のCu−Kα線によるエックス線回折ピーク強度比が、2≦Y2O3・Al2O3×100/AlN≦17、かつ2Y2O3・Al2O3×100/AlN≦2を有する窒化アルミニウム基板が好適である。
【0022】
このような窒化アルミニウム基板は、レーザー回折散乱法で測定された100μm以上の粗大粒子を1〜10%と1μm以下の微粒子を10〜50%を含んでいる窒化アルミニウム粉末原料を持い、窒化アルミニウム粉末原料中のAl2O3とY2O3分の組成比等を適正化することによって製造できる。例えば、2Y2O3・Al2O3が多い場合にはAl2O3分を増やせばよいので酸素量の多い窒化アルミニウム原料粉末を用いるか、又はAl2O3を添加して、Y2O3分を減らして焼結する。一方、Y2O3・Al2O3が多い場合には、Y2O3の添加量を減らすか、焼成温度を下げる。脱バインダーを空気中で行えばAl2O3分を増加させることができる。
【0023】
焼結助剤としてはイットリア、アルミナ、マグネシア、希土類酸化物等の粉末を窒化アルミニウム粉末原料に0.5〜10%内割配合される。成形は、ブチラールやメチスセルロース等の有機バインダーを用いて行われ、焼結は脱バインダー後、窒素、アルゴン等の非酸化性雰囲気中、温度1700〜1900℃で1〜12時間程度保持して行われる。
【0024】
セラミックス基板の厚みは、通常0.635mmであるが、要求特性によって変えることが出来る。たとえば、高電圧での絶縁性があまり重要ではなく熱抵抗が重要である場合は、0.5〜0.3mmの薄い板を用いることができ、逆に高電圧での絶縁耐圧や部分放電特性が重要である場合には、1〜3mmの厚板が用いられる。広さは、縦20〜200mm、横20〜200mmが例示される。
【0025】
その後、積層構造体は熱処理されて接合体となる。熱処理条件は、窒素ガスやアルゴンガス等の非酸化性ガス雰囲気下、雰囲気の最高温度550〜640℃、0.5〜3時間保持することによって行うことができる。
【0026】
つぎに、請求項1の発明とそれに関連する発明について説明する。これらの発明でも上記した材料が用いられる。
【0027】
この発明においては、有機系接着剤を用いて金属箔とろう材合金箔を張り合わせ、圧延機を通して帯状積層体とする。たとえば、金属箔とろう材合金箔の巻物から各帯状物を引き出し、有機系接着剤を滴下しながら、圧延機に搬入しそこから搬出することによって行う。有機系接着剤の塗布は、例えばチューブディスペンサーを用い、滴下温度20〜28℃、滴下量50〜300マイクロリットル、帯状積層体の帯幅の中心部に滴下し、滴下間隔は30〜100cmであることが好ましい。
【0028】
得られた帯状積層体は、例えば打抜き金型を有したプレス機を用いて、帯状積層体のろう箔面から行い、所定の寸法に打抜かれる。その寸法の一例を示せば、幅0.5〜10インチ、長さ0.5〜10インチである。プレス圧は荷重0.5〜10トンが好適である。この打ち抜かれた積層物のろう合金箔面を、有機系接着剤を介し、セラミックス基板の片面又は両面に、好ましくは1〜3MPaの応力を付加して重ねることによって積層構造体となる。
【0029】
ついで、積層構造体は熱処理される。用いる接合炉は、予熱部、仮接合部、拡散部を有し、窒素、アルゴン、水素、炭酸ガス等の非酸化性ガス、好ましくは酸素濃度10%以下、特に好ましくは酸素濃度50ppm以下の非酸化性ガスを流通させ、所定の非酸化性雰囲気に保持されている。積層構造体の接合炉への搬送には、積層構造体上下面に接触するベルトやローラー等が用いられる。
【0030】
予熱部は、接合炉の入り口からろう材合金箔の融点までの領域を占め、その後、接合炉出口までの領域が仮接合部と拡散部とになる。具体的には、予熱部の雰囲気温度は、室温〜ろう材合金箔の融点よりも10℃低い温度、仮接合部と拡散部の雰囲気温度は600〜650℃であり、拡散部の温度は仮接合部よりも10〜30℃低いことが好ましく、そのためのヒーターは予熱部、仮接合部、拡散部に設置されるのが好適である。また、予熱部、仮接合部、拡散部の通過時間は、それぞれ30秒〜10分、5秒〜5分、5分〜180分であることが好ましく、特に仮接合部は0.1〜10mm/secの速度で通過させることが好ましい。0.1mm/secよりも遅いと、ろう材合金箔の金属箔への拡散が進みすぎ、回路の信頼性を損なう恐れがある。また、10mm/secよりも速いと接合反応が不十分となる。
【0031】
重要なことは、仮接合部では積層構造体が加圧されるが、拡散部ではその加圧が解除されることである。積層構造体の加圧は、上下面からのプレス又は多段ロール間に通すことによって行われる。プレス又は多段ロールは、ろう材合金の溶融温度以上に加熱されていることが好ましい。また、加圧力は1MPa以上であることが好ましく、1MPa未満であると、ろう材合金箔とセラミックス基板の密着が確保できず、接合不良となる。好ましい加圧力は1〜7MPaである。プレス又は多段ロールの材質は、金属や、アルミナ、窒化ケイ素、炭化ケイ素、窒化ホウ素、サイアロン等のセラミックスでもよいが、熱変形のしにくい窒化ケイ素と窒化ホウ素との複合焼結体が特に好ましい。
【0032】
拡散部では、金属箔とセラミックス基板間の接合強度を確保するために、ろう材成分の一部の金属成分を金属箔中に拡散させることが必要である。たとえば、金属箔がAlで、ろう材合金箔成分がAl−Cu系である場合、Al中にCuを拡散させる。拡散距離は50〜100μmであることが好ましい。この工程を経て、積層構造体が、金属箔とセラミックス基板からなる接合体となる。
【0033】
本発明によって製造された接合体から回路基板を製造するには、常法に従い、接合体の不要な金属箔と接合層をエッチングによって除去した後、必要に応じてメッキが施される。レジストインクとしては、UV硬化、アルカリ剥離型が用いられ、不要な金属箔と接合層の除去には、過酸化水素水およびフッ素化合物の混合溶液が好適に用いられる。
【0034】
本発明によって製造された接合体から回路基板を製造するには、常法に従い、接合体の不要な金属箔と接合層をエッチングによって除去した後、必要に応じてメッキが施される。レジストインクとしては、UV効果やアルカリ剥離型が用いられ、不要な金属箔と接合層の除去には、過酸化水素水およびフッ素化合物の混合溶液が好適に用いられる。
【0035】
【実施例】
以下、実施例、比較例をあげて更に具体的に本発明を説明する。
【0036】
実施例1
有機系接着剤(ポリイソブチルメタクリル酸30質量%のトルエン溶液)をディスペンサー用い、温度25℃下、一回の滴下量150マイクロリットルとして、15秒間隔毎にAl箔の帯幅の中心部へ滴下した後、温度110℃、搬送スピード11mm/secの条件で圧延を行い、0.400mm厚のAl箔と0.02厚のろう材合金箔からなる0.42mm厚の帯状積層体を製造した。これを幅5インチ、長さ7インチに打抜き、上記と同じ有機系接着剤を用い、帯状積層体のろう材合金箔面と窒化アルミニウム基板(0.5mm厚、幅5インチ、長さ7インチ、熱伝導率170W/mK、曲げ強さ400MPa)面を1MPaの応力を付与して重ね、窒化アルミニウム基板の両面に帯状積層体を接着して積層構造体を製造した。
【0037】
この積層体構造体を、その上下面に接触する0.4mm厚のSUS(403材)の搬送ベルトにのせ、搬送速度0.5mm/secで接合炉に搬入し、窒素雰囲気下、酸素濃度50ppm、予熱部温度570℃とその通過時間5分、仮接合部温度600℃とその通過時間5分、仮接合圧力3MPa、拡散部温度620℃とその通過時間50分を経させて接合体を製造した。
【0038】
得られた接合体のアルミニウム回路形成面(表側)には所定形状の回路パターンを、放熱アルミニウム板形成面(裏側)に放熱板パターンを形成させるように、UV硬化型レジストインクをスクリーン印刷で塗布後、UVランプを照射させてレジスト膜を硬化させ、Al板と接合層をFeCl3液でエッチングを行い、3μm厚の無電解Ni−Pメッキを施し、回路基板を作製した。
【0039】
その後、−40℃、30分→室温、10分→125℃、30分→室温、10分を1サイクルとして3000サイクルの熱履歴試験を実施し、膨れ、剥がれ等の外観確認、断面観察による半田クラックの発生の有無を調べ、更には回路基板の回路部分を溶解し、インクテストによるクラックの発生の有無を測定した。それらの結果を表1に示す。
【0040】
実施例2
窒化アルミニウム基板の代わりに窒化ケイ素基板(厚み0.635mm、幅5インチ、長さ7インチ、熱伝導率70W/mK、曲げ強さ800MPa)を用いたこと以外は、実施例1と同様にして接合体を製造した。これを用いて回路基板を作製し、ヒートサイクル試験を行った。その結果を表1に示す。
【0041】
比較例1
窒化アルミニウム基板の表裏両面に、その基板と同一寸法(幅5インチ、長さ7インチ)に加工された接合材(Al−2017材の合金箔:厚さ10μmを介して、それと同一寸法のAl板(表裏共厚さ、0.4mm)を重ねた積層体を2mm厚のC−Cコンポジット板に挟み、酸素濃度50ppmの窒素雰囲気中、ホットプレス装置により、窒化アルミニウム基板に垂直方向に均等に3MPaで加圧しながら620℃、2.5時間加熱した。これを用いて回路基板を作製し、ヒートサイクル試験を行った。その結果を表1に示す。
【0042】
【表1】
【0043】
表1から、本発明の実施例1、2は、比較例1に比べて接合工程の所要時間が極めて短いにも拘わらず、比較例1と同等性能の回路基板を製造できたことが分かる。
【0044】
【発明の効果】
本発明の製造方法によれば、セラミックス基板と金属箔、特に窒化アルミニウム基板又は窒化珪素基板とAl箔又はAl合金箔からなる接合体を、生産性を極めて高めて製造することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a joined body suitable as a circuit board.
[0002]
[Prior art]
Conventionally, in semiconductor devices used for power modules, etc., circuits such as alumina, beryllia, silicon nitride, aluminum nitride, etc. on the front and back surfaces of Cu, Al, alloys containing these metals and heat sinks A circuit board formed by forming each is developed (PTL 1) and put into practical use. Al circuit boards have higher reliability with respect to thermal history than Cu circuit boards, and thus are being investigated as uses for high-reliability boards for automobiles and the like. This is the reason.
[0003]
[Patent Document 1]
US Pat. No. 5,354,415 [Patent Document 2]
Japanese Patent Laid-Open No. 2001-085808 [Patent Document 3]
Japanese Patent Laid-Open No. 11-60343
[Problems to be solved by the invention]
In order to form an Al circuit on a ceramic substrate, molten aluminum is brought into contact with the ceramic substrate and cooled to produce a joined body, and then mechanically polished to adjust the thickness of the Al plate and then etched (Patent Document) 2), this method costs about 2 to 5 times as much as the case of forming a Cu circuit.
[0005]
On the other hand, the reason why the brazed Al circuit board is more expensive than the Cu circuit board is that the ceramic substrate and the Al foil or Al alloy foil laminate must be joined together while applying partial pressure. . The pressurizing method is performed by mechanical means such as storing the laminated body in a graphite jig and screwing in from both end faces (Patent Document 3), but the productivity is not sufficiently increased by such a method.
[0006]
In view of the above, an object of the present invention is to provide a method of manufacturing a joined body composed of a ceramic substrate with extremely high productivity and a metal foil, particularly an Al foil or an Al alloy foil. The object of the present invention is to laminate a metal foil and a brazing alloy alloy foil using an organic adhesive, and arrange it on a ceramic substrate via an organic adhesive to form a laminated structure, followed by heat treatment. Can be achieved.
[0007]
[Means for Solving the Problems]
That is, the present invention relates to a laminate of a metal foil and a brazing alloy alloy foil bonded together using an organic adhesive on one or both sides of a ceramic substrate via the organic adhesive. A method for manufacturing a joined body comprising: stacking a material alloy foil surface and a ceramic substrate surface to form a laminated structure, and then heat-treating the laminated structure.
[0008]
Moreover, this invention is a manufacturing method of the conjugate | zygote characterized by passing through the following processes 1-3.
Step 1: A step in which a metal foil and a brazing alloy alloy foil are bonded together using an organic adhesive, and are passed through a rolling mill to produce a strip-shaped laminate composed of the metal foil and the brazing alloy alloy foil.
Step 2: The above-mentioned band-shaped laminate is punched to a desired size, and the brazing material alloy foil surface of the band-shaped laminate and the ceramic substrate surface are placed on one or both sides of the ceramic substrate via an organic adhesive. And manufacturing the laminated structure.
Step 3: The laminated structure is transported into a joining furnace having a preheating part, a temporary joining part, and a diffusion part, maintained at a high temperature in a non-oxidizing atmosphere, and the joined body of the metal foil and the ceramic substrate is transferred. Manufacturing process.
[0009]
Here, the “preheating portion” is a region maintained at a temperature lower than the melting point of the brazing alloy alloy foil, and the “temporary joining portion” is the above laminated structure in a temperature region equal to or higher than the melting point of the brazing alloy alloy foil. The area where the brazing filler metal component and the ceramic substrate react with each other while the body is pressurized. The "diffusion part" It is defined as the region where the material component diffuses into the metal foil.
[0010]
In the present invention, the organic adhesive used for laminating the metal foil and the brazing alloy foil, and the organic adhesive used for arranging the laminate on the ceramic substrate are both a toluene solution of polyisobutyl methacrylic acid or It is preferably a terpineol solution of polyisobutyl methacrylate, the ceramic substrate is made of aluminum nitride or silicon nitride, the metal foil is made of Al or Al alloy, and the brazing material alloy foil is mainly composed of Al and Cu. .
[0011]
Furthermore, the passing speed in the preheating part of the laminated structure is 0.1 to 10 mm / sec, the ambient temperature of the temporary joining part is 600 to 650 ° C., and the passing speed in the temporary joining part of the laminated structure is 0.1. It is preferable that the roll pressure is 10 mm / sec or more and the pressure is 1 MPa or more, and the passing speed in the diffusion portion of the laminated structure is 0.1 to 10 mm / sec.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail.
[0013]
The material of the metal foil used in the present invention is Cu foil, Cu alloy foil, Al foil, Al alloy foil or the like, and Al foil or Al alloy foil is preferable. Examples of this include not only 1000 series pure Al, but also 4000 series Al—Si based alloys, 6000 series Al—Mg—Si based alloys, and the like that can be easily joined. Among them, high-purity Al foil (purity 99.85% (mass%, the same applies hereinafter)) with a rolling rate of 10% or more is preferable, and there are commercially available products such as 1085 and IN85. Also, 99.9% (3N) products and 99.99% (4N) products are not so expensive and can be used. The metal foil may be a single body or a laminate of two or more clads. Examples of the laminated body include Al—Ni, Al—Ni—Cu, Al—Mo, Al—Mo, Al—W, and Al—Cu.
[0014]
The thickness of the metal foil is preferably 0.1 to 0.5 mm. In particular, the volume ratio of the front surface metal foil (circuit) to the back surface metal foil (heat sink) in order to eliminate warpage and undulation due to thermal stress on the circuit board, and to enhance the damage caused by solder cracks and the prevention of peeling of bonding wires and plating. It is desirable to make (circuit volume / heat sink volume) close to 1, preferably 0.80 to 1.2, particularly 0.85 to 1.15, and more preferably 0.9 to 1.1. The thickness of the heat sink is preferably equal to or less than the thickness of the circuit. The volume of the Al circuit can be calculated by multiplying the circuit area and the circuit thickness, and the volume of the heat sink can be calculated by multiplying the heat sink area and the heating plate thickness. Although there is no limitation about the shape of metal foil, in invention related to Claim 1 , it is strip | belt shape.
[0015]
The components of the brazing alloy foil used in the present invention are preferably composed mainly of Al and Cu. For example, Cu 1-6%, especially 1.5-5% Al-Cu foil alloy, 4% Cu Alloy foil containing 0.5% Mg, 2017 alloy foil containing 0.5% Mn, and JIS alloys 2001, 2003, 2005, 2007, 2011, 2014, 2024, 2025, 2030, 2034. 2036, 2048, 2090, 2117, 2124, 2218, 2224, 2324, 7050, etc. Third components such as Mg, Zn, In, Mn, Cr, Ti, and Bi can be included up to 5% in total.
[0016]
In an Al-Cu alloy foil or an alloy to which a third component is added, if Cu is less than 1%, the bonding temperature must be increased, which is disadvantageous for mass production. There is a possibility that the diffusion part of the brazing material becomes particularly hard and the reliability of the Al circuit is lowered. Particularly preferred brazing alloy foils are Al 86% or more, Cu 1 to 6%, Mg 3% or less (not including 0%), particularly 0.2 to 2.0%.
[0017]
The thickness of the brazing alloy foil is preferably 1/10 to 1/50 of the thickness of the metal. If the thickness is less than 1/50, sufficient bonding becomes difficult, and if it exceeds 1/10, the Al circuit becomes hard. Particularly preferably, the thickness is 100 μm or less, and is 1/12 to 1/14 of the thickness of the metal foil. This means that when the thickness of the metal foil is 0.4 to 0.6 mm, a thickness of 10 to 50 μm, particularly 15 to 30 μm, is suitable. The shape of the brazing alloy foil is not limited, but in the invention related to claim 1 , it is a strip shape.
[0018]
As an organic adhesive used to form a laminate of a metal foil and a brazing alloy alloy foil, either an aqueous or non-aqueous organic solvent can be used. Preferably, polyisobutyl methacrylate, polyvinyl alcohol or the like is used as a medium. Viscosity is 3.0 to 0.1 Pa · sec solution. Particularly preferred are a toluene solution of 10 to 50% by mass of polyisobutyl methacrylate and a terpineol solution of 10 to 80% by mass of polyisobutyl methacrylate. By using such an organic adhesive, there is no deviation during heat treatment, and the residual carbon is 50 ppm or less at 350 ° C. or higher. The presence of residual carbon can be ignored. The organic adhesive is preferably applied to the entire joint surface of the metal foil, the brazing alloy foil, or both.
[0019]
More preferably, the laminate is subjected to a rolling process by passing it through a rolling mill when placed on the ceramic substrate. As the rolling mill, one having a plurality of rolls attached to a heater is preferable. By passing the laminate between the rolls, the adhesive can be dried and both foils can be temporarily bonded. As an example, a roll temperature of 100 to 130 ° C. and a conveyance speed of 0.1 to 10 mm / sec by roll rotation can be given.
[0020]
Next, the laminate is disposed in such a manner that the brazing alloy foil surface and the ceramic substrate surface are aligned with each other through the same organic adhesive as the organic adhesive. The organic adhesive is preferably applied to the entire bonding surface of the ceramic substrate, the brazing alloy foil, or both.
[0021]
The ceramic substrate used in the present invention is preferably made of aluminum nitride or silicon nitride. Ceramic substrates such as silicon carbide and beryllium oxide are inferior in terms of insulation and safety. The thermal conductivity of the ceramic substrate is preferably at least 70 W / mK, particularly 130 W / mK or more, considering that it is used for a power module that requires high reliability. In particular, the X-ray diffraction peak intensity ratio due to Cu—Kα rays on the surface is 2 ≦ Y 2 O 3 .Al 2 O 3 × 100 / AlN ≦ 17 and 2Y 2 O 3 .Al 2 O 3 × 100 / AlN ≦ An aluminum nitride substrate having 2 is preferred.
[0022]
Such an aluminum nitride substrate has an aluminum nitride powder raw material containing 1 to 10% coarse particles of 100 μm or more measured by a laser diffraction scattering method and 10 to 50% of fine particles of 1 μm or less, and aluminum nitride It can be produced by optimizing the composition ratio of Al 2 O 3 and Y 2 O 3 in the powder raw material. For example, 2Y 2 O 3 · Al 2 or when O 3 is often uses more aluminum nitride raw material powder having oxygen content so may be increased Al 2 O 3 minutes, or by addition of Al 2 O 3, Y 2 Sinter with reduced O 3 minutes. On the other hand, when the amount of Y 2 O 3 .Al 2 O 3 is large, the amount of Y 2 O 3 added is reduced or the firing temperature is lowered. If the binder is removed in the air, the Al 2 O 3 content can be increased.
[0023]
As a sintering aid, powder of yttria, alumina, magnesia, rare earth oxide or the like is mixed in the aluminum nitride powder raw material by 0.5 to 10%. Molding is performed using an organic binder such as butyral or methyscellulose. Sintering is performed after debinding, and held at a temperature of 1700 to 1900 ° C. for about 1 to 12 hours in a non-oxidizing atmosphere such as nitrogen or argon. Done.
[0024]
The thickness of the ceramic substrate is usually 0.635 mm, but can be changed according to the required characteristics. For example, when insulation at high voltage is not so important and thermal resistance is important, a thin plate of 0.5 to 0.3 mm can be used, and conversely, withstand voltage and partial discharge characteristics at high voltage If is important, a 1 to 3 mm thick plate is used. The width is 20 to 200 mm in length and 20 to 200 mm in width.
[0025]
Thereafter, the laminated structure is heat-treated to form a joined body. The heat treatment can be performed by maintaining the maximum temperature of the atmosphere at 550 to 640 ° C. for 0.5 to 3 hours in a non-oxidizing gas atmosphere such as nitrogen gas or argon gas.
[0026]
Next, the invention of claim 1 and related inventions will be described. These materials are also used in these inventions.
[0027]
In the present invention, a metal foil and a brazing alloy foil are laminated together using an organic adhesive, and a strip-shaped laminate is formed through a rolling mill. For example, each strip is pulled out from a roll of metal foil and brazing alloy foil, and the organic adhesive is dropped into the rolling mill and is carried out from there. The organic adhesive is applied using, for example, a tube dispenser, dropping temperature 20 to 28 ° C., dropping amount 50 to 300 microliters, dropping at the center of the band width of the belt-like laminate, and dropping interval is 30 to 100 cm. It is preferable.
[0028]
The obtained belt-like laminate is performed from the brazing foil surface of the belt-like laminate using, for example, a press machine having a punching die and punched to a predetermined size. An example of the dimensions is 0.5 to 10 inches wide and 0.5 to 10 inches long. The press pressure is preferably a load of 0.5 to 10 tons. The brazed alloy foil surface of the punched laminate is laminated with an organic adhesive on one or both surfaces of the ceramic substrate, preferably with a stress of 1 to 3 MPa.
[0029]
Next, the laminated structure is heat treated. The joining furnace to be used has a preheating part, a temporary joining part, and a diffusion part, and a non-oxidizing gas such as nitrogen, argon, hydrogen, carbon dioxide gas, preferably an oxygen concentration of 10% or less, particularly preferably an oxygen concentration of 50 ppm or less. An oxidizing gas is circulated and maintained in a predetermined non-oxidizing atmosphere. A belt, a roller, or the like that contacts the upper and lower surfaces of the laminated structure is used for transporting the laminated structure to the joining furnace.
[0030]
The preheating portion occupies a region from the entrance of the joining furnace to the melting point of the brazing alloy foil, and thereafter, the region from the joining furnace outlet becomes a temporary joining portion and a diffusion portion. Specifically, the atmospheric temperature of the preheating part is room temperature to a temperature 10 ° C. lower than the melting point of the brazing alloy foil, the atmospheric temperature of the temporary joining part and the diffusion part is 600 to 650 ° C., and the temperature of the diffusion part is temporary. It is preferable that it is 10-30 degreeC lower than a junction part, and it is suitable for the heater for that to be installed in a preheating part, a temporary junction part, and a spreading | diffusion part. Moreover, it is preferable that the preheating part, the temporary joining part, and the passage time of the diffusion part are 30 seconds to 10 minutes, 5 seconds to 5 minutes, and 5 minutes to 180 minutes, respectively. It is preferable to pass through at a speed of / sec. If it is slower than 0.1 mm / sec, diffusion of the brazing alloy alloy foil to the metal foil will proceed excessively, and the reliability of the circuit may be impaired. If it is faster than 10 mm / sec, the bonding reaction becomes insufficient.
[0031]
What is important is that the laminated structure is pressurized at the temporary bonding portion, but the pressure is released at the diffusion portion. Pressurization of the laminated structure is performed by pressing between upper and lower surfaces or passing between multistage rolls. The press or multi-stage roll is preferably heated to a temperature equal to or higher than the melting temperature of the brazing alloy. Further, the applied pressure is preferably 1 MPa or more, and if it is less than 1 MPa, adhesion between the brazing material alloy foil and the ceramic substrate cannot be secured, resulting in poor bonding. A preferable pressure is 1 to 7 MPa. The material of the press or multi-stage roll may be a metal or ceramics such as alumina, silicon nitride, silicon carbide, boron nitride, sialon, etc., but a composite sintered body of silicon nitride and boron nitride which is not easily thermally deformed is particularly preferable.
[0032]
In the diffusion portion, in order to ensure the bonding strength between the metal foil and the ceramic substrate, it is necessary to diffuse a part of the metal component of the brazing material component into the metal foil. For example, when the metal foil is Al and the brazing alloy foil component is Al—Cu, Cu is diffused in Al. The diffusion distance is preferably 50 to 100 μm. Through this step, the laminated structure becomes a bonded body made of a metal foil and a ceramic substrate.
[0033]
In order to manufacture a circuit board from the bonded body manufactured according to the present invention, unnecessary metal foil and a bonding layer of the bonded body are removed by etching according to a conventional method, and then plating is performed as necessary. As the resist ink, UV curing or alkali peeling type is used, and a mixed solution of hydrogen peroxide and fluorine compound is preferably used for removing unnecessary metal foil and bonding layer.
[0034]
In order to manufacture a circuit board from the bonded body manufactured according to the present invention, unnecessary metal foil and a bonding layer of the bonded body are removed by etching according to a conventional method, and then plating is performed as necessary. As the resist ink, a UV effect or an alkali peeling type is used, and a mixed solution of hydrogen peroxide and a fluorine compound is preferably used for removing unnecessary metal foil and bonding layer.
[0035]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.
[0036]
Example 1
Using an organic adhesive (polyisobutylmethacrylic acid 30% by weight toluene solution) in a dispenser and dropping at a temperature of 25 ° C., with a drop volume of 150 microliters per drop, it is dropped at the center of the Al foil band width every 15 seconds. After that, rolling was performed under the conditions of a temperature of 110 ° C. and a conveyance speed of 11 mm / sec to produce a 0.42 mm thick strip-shaped laminate composed of a 0.400 mm thick Al foil and a 0.02 thick brazing alloy alloy foil. This was punched into a width of 5 inches and a length of 7 inches. Using the same organic adhesive as described above, the brazing material alloy foil surface of the strip-shaped laminate and an aluminum nitride substrate (0.5 mm thick, width 5 inches, length 7 inches) The layers having a thermal conductivity of 170 W / mK and a bending strength of 400 MPa were applied to each other by applying a stress of 1 MPa, and a band-like laminate was bonded to both surfaces of the aluminum nitride substrate to produce a laminated structure.
[0037]
This laminate structure is placed on a 0.4 mm thick SUS (403 material) conveyor belt in contact with the upper and lower surfaces thereof, and is carried into a joining furnace at a conveyance speed of 0.5 mm / sec. Under a nitrogen atmosphere, the oxygen concentration is 50 ppm. , Preheated part temperature 570 ° C. and its passing time 5 minutes, provisional joint temperature 600 ° C. and its passing time 5 minutes, temporary joining pressure 3 MPa, diffusion part temperature 620 ° C. and its passing time 50 minutes to produce a joined body did.
[0038]
Apply UV curable resist ink by screen printing so that a circuit pattern of a predetermined shape is formed on the aluminum circuit forming surface (front side) of the resulting bonded body and a heat sink pattern is formed on the heat radiating aluminum plate forming surface (back side). Thereafter, a UV lamp was irradiated to cure the resist film, the Al plate and the bonding layer were etched with FeCl 3 solution, and electroless Ni—P plating with a thickness of 3 μm was applied to produce a circuit board.
[0039]
Then, -40 ° C, 30 minutes → room temperature, 10 minutes → 125 ° C., 30 minutes → room temperature, 10 minutes is one cycle, and 3000 cycles of thermal history tests are performed. The presence or absence of cracks was examined, the circuit portion of the circuit board was dissolved, and the presence or absence of cracks was measured by an ink test. The results are shown in Table 1.
[0040]
Example 2
Example 1 was used except that a silicon nitride substrate (thickness 0.635 mm, width 5 inches, length 7 inches, thermal conductivity 70 W / mK, bending strength 800 MPa) was used instead of the aluminum nitride substrate. A joined body was produced. A circuit board was produced using this, and a heat cycle test was conducted. The results are shown in Table 1.
[0041]
Comparative Example 1
Bonding material (alloy foil of Al-2017 material: Al thickness of 10 μm, processed on the front and back surfaces of the aluminum nitride substrate to the same dimensions (5 inches wide and 7 inches long) as the substrate. A laminated body (with both front and back thickness: 0.4 mm) is sandwiched between 2 mm thick CC composite plates, and evenly in the vertical direction to the aluminum nitride substrate in a nitrogen atmosphere with an oxygen concentration of 50 ppm using a hot press device Heating was performed at 620 ° C. for 2.5 hours while pressurizing at 3 MPa, and a circuit board was produced using this and subjected to a heat cycle test.
[0042]
[Table 1]
[0043]
From Table 1, it can be seen that Examples 1 and 2 of the present invention were able to manufacture a circuit board having the same performance as that of Comparative Example 1, although the time required for the bonding process was extremely short compared with Comparative Example 1.
[0044]
【The invention's effect】
According to the manufacturing method of the present invention, it is possible to manufacture a joined body made of a ceramic substrate and a metal foil, particularly an aluminum nitride substrate or a silicon nitride substrate and an Al foil or an Al alloy foil, with extremely high productivity.
Claims (3)
工程1:金属箔とろう材合金箔とを有機系接着剤を用いて張り合わせ、それを圧延機に通過させて金属箔とろう材合金箔からなる帯状積層物を製造する工程。
工程2:上記帯状積層物を所用寸法に打抜き、それを、上記有機系接着剤と同一の接着剤を介して、セラミックス基板の片面又は両面に、上記帯状積層物のろう材合金箔面とセラミックス基板面とを重ねて配置し、積層構造体を製造する工程。
工程3:上記積層構造体を非酸化性雰囲気下、高温に保持された、予加熱部、仮接合部、拡散部を有する接合炉内へ搬送させて、金属箔とセラミックス基板との接合体を製造する工程。
ここで、「予加熱部」とは、ろう材合金箔の融点より低い温度に保持された領域であり、「仮接合部」とは、ろう材合金箔の融点以上の温度領域で上記積層構造体を加圧しながら、ろう材成分とセラミックス基板とを反応させる領域であり、「拡散部」とは、ろう材合金箔の融点以上の温度領域で上記積層構造体の加圧を解いて、ろう材成分を金属箔へ拡散させる領域である、と定義される。The manufacturing method of the joined body characterized by passing through the following processes 1-3.
Step 1: A step in which a metal foil and a brazing alloy alloy foil are bonded together using an organic adhesive and passed through a rolling mill to produce a strip-shaped laminate composed of the metal foil and the brazing alloy alloy foil.
Step 2: punching the strip laminate in Shoyo dimensions, it via the organic adhesive and the same adhesive on one or both sides of the ceramic substrate, the braze alloy foil surface of the strip laminate and A process of manufacturing a laminated structure by arranging the ceramic substrate surface in an overlapping manner.
Step 3: The laminated structure is transported into a joining furnace having a preheating portion, a temporary joining portion, and a diffusion portion, which is maintained at a high temperature in a non-oxidizing atmosphere, and a joined body of the metal foil and the ceramic substrate is obtained. Manufacturing process.
Here, the “preheating portion” is a region maintained at a temperature lower than the melting point of the brazing alloy alloy foil, and the “temporary joining portion” is the above laminated structure in a temperature region equal to or higher than the melting point of the brazing alloy alloy foil. The area where the brazing filler metal component and the ceramic substrate react with each other while the body is pressurized. The "diffusion part" It is defined as the region where the material component diffuses into the metal foil.
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DE102004033227A1 (en) * | 2004-07-08 | 2006-01-26 | Curamik Electronics Gmbh | Metal-ceramic substrate |
JP4750670B2 (en) * | 2006-10-26 | 2011-08-17 | 電気化学工業株式会社 | Manufacturing method of ceramic circuit board |
JP5062061B2 (en) * | 2008-06-30 | 2012-10-31 | 三菱マテリアル株式会社 | Power module substrate manufacturing method |
CN106169426A (en) * | 2016-08-24 | 2016-11-30 | 浙江德汇电子陶瓷有限公司 | The manufacture method of metallized ceramic substrate and the metallized ceramic substrate of manufacture thereof |
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