JP4337313B2

JP4337313B2 - Circuit board manufacturing method

Info

Publication number: JP4337313B2
Application number: JP2002222027A
Authority: JP
Inventors: 正英武藤; 良幸内野々; 忍渡部
Original assignee: Panasonic Corp; Matsushita Electric Works Ltd
Current assignee: Panasonic Corp; Panasonic Electric Works Co Ltd
Priority date: 2002-07-30
Filing date: 2002-07-30
Publication date: 2009-09-30
Anticipated expiration: 2022-07-30
Also published as: JP2004063906A

Description

【０００１】
【発明の属する技術分野】
本発明は回路板の製造方法、殊に立体回路板の製造に好適に用いることができる回路板の製造方法に関するものである。
【０００２】
【従来の技術】
絶縁性基材上に金属薄膜を形成しておき、パルス状レーザ等の電磁波照射によって該金属薄膜の不要部分（非回路部分の少なくとも輪郭部）を除去した後、金属薄膜の回路部分にめっきを施して回路パターンを形成する回路板の製造方法が特許第３１５３６８２号などに示されている。立体成形回路板（ＭＩＤ基板）用に開発された該製造方法では、ＱスイッチＹＡＧレーザ等のパルス状レーザをガルバノミラー等の偏向手段を用いて基材上を走査させることで、上記金属薄膜の不要部分の除去を行う。
【０００３】
【発明が解決しようとする課題】
ここにおいて、絶縁性基材が樹脂製である場合には問題となることは殆どなかったものの、絶縁性基材として例えばアルミナのようなセラミックスを用いた場合、次のような問題点が生じることが明らかになった。
【０００４】
すなわち、上記レーザの照射による金属薄膜の不要部分の除去は、回路部分と非回路部分との境界線にレーザを照射することで行い、この後、電気めっきを回路部分に対して行って回路部分上に必要厚みのめっき層を形成し、その後、エッチングで金属薄膜の非回路部分を除去しているのであるが、上記電気めっきに際して、めっき層３の一部が図６に示すように金属薄膜２の非回路部分２２につながって短絡してしまい、この結果、非回路部上にもめっき層が形成されてしまうという事態が多々生じる。レーザ照射で金属薄膜を除去した部分には本来めっき層が生じることはないはずであるにもかかわらず、ごく一部とはいえ、めっき層が触手を伸ばすようにして非回路部分にまで達してしまうのは、セラミックスからなる絶縁性基材として表面粗度の粗いものを用いた方が上記事態が生じる確率が高くなることを考慮すると、絶縁性基材の表面の微小凹凸やμクラック内に残った金属薄膜や、レーザ照射でいったん溶けて蒸発した後、再度絶縁性基材の表面に付着した金属薄膜の分子がめっきを誘導することが原因ではないかと推察される。
【０００５】
しかし、原因が何であれ、上記のような事態が生じるために、セラミックス製の絶縁性基材を用いた場合、合成樹脂製の絶縁性基材を用いた場合よりも歩留まりが大きく低下してしまっており、上記短絡が生じることのない製造方法が望まれている。
【０００６】
本発明はこのような点に鑑みなされたものであって、その目的とするところはめっき層によるところの非回路部分への短絡を確実に防いで歩留まりを大きく向上させることができる回路板の製造方法を提供するにある。
【０００７】
【課題を解決するための手段】
しかして本発明は、絶縁性基材表面に形成した金属薄膜の回路部と非回路部との境界部分をレーザ等の電磁波を照射して除去し、この後、金属薄膜の上記回路部上にめっきを施すとともに非回路部をエッチングで除去して回路パターンを作成する回路板の製造方法において、金属薄膜の回路部上に必要厚みよりも薄い厚みのめっきと、非回路部の金属薄膜を除去するためのエッチングとを上記回路部上のめっきが必要厚みとなるまで繰り返して行うことに特徴を有している。
【０００８】
金属薄膜の回路部上にめっきを必要厚みまでいきなり形成するのではなく、薄く形成しておいた状態でエッチングを行って金属薄膜の非回路部の除去を行うことで、めっきを必要厚みまで行う際に金属薄膜の非回路部にめっき層が短絡してしまうことを防ぐようにしたものである。
【０００９】
この時、めっき材質に金属薄膜材質よりも耐エッチング性に優れた材料を用いることが好ましく、また、めっき後にめっき部の縁の電解研磨処理を行うのも好ましい。
【００１０】
エッチングはめっき用の電気めっき液中に電圧をかけずに浸漬させることで行うようにしたり、ブラスト処理で行うようにしてもよい。
【００１１】
また、エッチングは電磁波照射による金属薄膜の除去で露出した基材表面に対して行ったり、この時、エッチングは溶剤あるいは酸あるいはアルカリ溶液による化学エッチングで行うようにしてもよい。
【００１２】
そして、セラミックス製の絶縁性基材の表面に形成した金属薄膜の上記境界部分の電磁波による除去にあたり、基材の表面粗さ以上の深さまで基材表面も除去することが望ましい。
【００１３】
この時、絶縁性基材としては表面粗度がＲａ＝１〜５μｍのセラミックス材が好適であり、また着色したセラミックス材を用いることも好ましい。
【００１４】
絶縁性基材を加熱しながら電磁波の照射を行うようにしてもよく、金属薄膜の境界部の電磁波照射による除去を行った後、境界部に露出した絶縁性基材の表面の除去を行うようにしてもよい。
【００１５】
さらには、金属薄膜及び絶縁性基材の除去用の電磁波と、絶縁性基材の加熱用の電磁波とを同時に照射してもよいものであり、この場合、絶縁性基材の加熱用の電磁波として、金属薄膜及び絶縁性基材の除去用の電磁波よりも波長の長いものを用いたり、金属薄膜及び絶縁性基材の除去用の電磁波よりもスポット径の大きいものを用いたり、金属薄膜及び絶縁性基材の除去用の電磁波よりもパルス幅の長いものを用いたり、あるいは連続波を用いるとよい。
【００１６】
また本発明は、絶縁性基材表面に形成した金属薄膜の回路部と非回路部との境界部分をレーザ等の電磁波を照射して除去し、この後、金属薄膜の上記回路部上にめっきを施すとともに非回路部をエッチングで除去して回路パターンを作成する回路板の製造方法において、金属薄膜の非回路部の除去のためのエッチング処理で除去される厚みよりも大なる厚みで且つ必要厚みよりも薄い厚みのめっきを金属薄膜の回路部上に形成し、次いで金属薄膜の非回路部の除去のためのエッチング処理を行い、その後、金属薄膜の回路部上に必要厚みとなるまで再度めっきを施すことに他の特徴を有している。
【００１７】
【発明の実施の形態】
以下本発明を実施の形態の一例に基づいて詳述すると、図中１はアルミナやジルコニア、窒化アルミ等のセラミックス材からなる絶縁性基材であり、その表面にはスパッタリング等によって形成した金属薄膜２を設けてある。この金属薄膜２にはＣｕ、Ｎｉ、Ｐｄ、Ｃｒ、Ａｇなどを用いることができるが、その厚みは０．１〜１μｍ程度のものとしてある。
【００１８】
この絶縁性基材１上の金属薄膜２のうち、最終的に回路パターンが形成される部分を回路部、回路パターンが形成されない部分を非回路部とする時、両者の境界に位置する部分に電磁波（レーザ）を照射して、図１に示すように、該境界部分の金属薄膜２を除去し、回路部２１と非回路部２２との間に絶縁性基材１が露出する絶縁溝を形成する。照射する電磁波（レーザ）は、金属薄膜２の材質などにもよるが、第２高調波（ＳＨＧ）ＹＡＧレーザ、第３高調波（ＴＨＧ）ＹＡＧレーザなどのパルスレーザが好適であり、ガルバノミラーによる走査などで上記境界部に照射することで境界部にある金属薄膜２の除去を行う。レーザの照射エネルギーは５０〜５００μＪ／ｐｕｌｓｅ程度が好ましいが、これに限定するものではない。
【００１９】
この後、金属薄膜２における回路部２１上に電気めっきを行うのであるが、従来では電気めっきによってめっき層３を必要厚み（たとえば１０〜２０μｍ）まで一気に形成し、その後、金属薄膜２における非回路部２２をエッチングで除去していたのに対して、ここでは上記回路部２１上に薄い電気めっきをまず行って、たとえば２〜５μｍ程度の厚みの薄めっき層３０を形成し、次いでエッチングを行って金属薄膜２の非回路部２２の除去を行う。この時のエッチング処理は薄めっき層３０が残るものの、金属薄膜２の非回路部２２は全て除去されてしまう程度の軽いエッチング処理が好ましいが、必ずしも非回路部２２が全て除去されてしまうものでなくてもよい。その後、上記薄めっき層３０上にさらに電気めっきでめっき層３１を形成し、さらに必要であればエッチング処理を行って金属薄膜２の非回路部２２の除去を行う。こうして複数回の電気めっきによって最終的に必要な厚み（たとえば１０〜２０μｍ）のめっき層３を金属薄膜２の回路部２１上に形成する。
【００２０】
この場合、電気めっきを行う時、めっき層３０（もしくはめっき層３１）が上記レーザ照射による絶縁溝（幅は５０〜６０μｍ程度）を横切って金属薄膜２の非回路部２２に達するまで成長することはなく、例え複数回の電気めっきの繰り返しで絶縁溝を横切るまで成長することがあっても、その時には複数回にわたるエッチング処理で金属薄膜２の非回路部２２は除去されてしまっていることから、短絡が生じることはない。
【００２１】
ところで、このような電気めっきの繰り返しでめっき層３を形成するにあたっては、金属薄膜２の非回路部２２の除去のためのエッチング処理で除去される厚みよりも大なる厚みで且つ必要厚みよりも薄い厚みの薄めっき層３０を金属薄膜２の回路部２１上に形成し、次いで金属薄膜２の非回路部２２をエッチングによって完全に除去し、その後の薄めっき層３０上への電気めっきでめっき層３１を形成した時点で必要厚みが確保されためっき層３を得られるようにするのがめっき処理の回数やエッチング回数の点から一番好ましいのはもちろんである。
【００２２】
上記エッチング処理は金属薄膜２がＣｕからなる場合、過硫酸アンモニウムをエッチング液として用いるのが通常であるが、めっき層３（殊に薄めっき層３０）はこのエッチング液によってエッチングされにくい材質のもの、例えばＡｕなどで形成すると、エッチングの際にめっき層３が浸食されにくくなるために、好ましい結果を得ることができる。なお、材質はＣｕとＡｕに限るものではなく、金属薄膜２の材質よりも耐エッチング性に優れた金属でめっき層３を形成しているのであれば、その材質は問わない。
【００２３】
また、薄めっき層３０の形成後にその縁の電解研磨処理を行っておくことも好ましい。非回路部２０へと延びようとする部分を除去することができるからである。電解研磨処理は例えば１０ｖｏｌ％のリン酸に浸漬して電流密度０．１〜０．３Ａ／ｄｍ２通電して処理する。
【００２４】
なお、金属薄膜２の非回路部２２の除去のためのエッチングは、めっき用の電気めっき液中に電圧をかけずに浸漬しておくことで行ってもよい。たとえば硫酸銅めっき浴中において通電してめっき層３０を形成し、その後、浸漬させたままで通電せずに硫酸濃度を調整して浴管理を行うのである。別途エッチング液に浸漬せずとも、めっき層３（３０，３１）の形成のための電気めっき液中に浸漬したままでエッチングを行うことができる。
【００２５】
このほか、エッチングはアルミナ粉やガラス粒やクルミ殻、ビーズ等のブラスト処理で行ってもよい。
【００２６】
さらに、エッチングは電磁波照射による金属薄膜２の除去で露出した基材２表面の絶縁溝部分に対してエッチング性の強いエッチングを選択的に行うものであってもよい。この場合のエッチングは溶剤あるいは酸あるいはアルカリ溶液による化学エッチングが好ましく、例えば絶縁性基材１がアルミナ基板である場合、リン酸浴に浸漬すればよく、液晶ポリマーなどにおいては水酸化ナトリウム溶液などに浸漬すればよい。ちなみにこのエッチング処理では金属薄膜２の非回路部２２が最終的にすべて除去されなくてもよい。絶縁溝での絶縁が確実になされるからであり、まためっき層３と非回路部２２との短絡の原因となるめっき層３の不要な成長は上記エッチング処理で除去されるためである。
【００２７】
ところで、絶縁性基材１がアルミナや窒化アルミやジルコニアなどのセラミックス焼結体である場合、その表面がどうしても粗くなるために、前述のようにめっき層３と金属薄膜２の非回路部２２との短絡が生じやすくなることから、この短絡のより確実な防止という点において、めっき層３（３０，３１）を前記手順で形成することに加えて、金属薄膜２の非回路部２２と回路部２１との境界部に電磁波（レーザ）を照射して境界部の金属薄膜２を除去することで絶縁溝を形成するにあたり、図２に示すように、電磁波で境界部の金属薄膜２だけでなく、基材１の表面をその表面粗さ以上の深さまで除去するようにしてもよい。表面粗さＲａ＝１〜５μｍであれば、Ｒａ＜ｄとなる深さｄまで基材１の表面も除去してしまうのである。このような処理を行うと、電磁波の照射でセラミックスである基材１の表面が溶融するために表面凹凸が小さくなり、残存する導体粒子が浮き出て露出することでエッチングによる除去が用意となる等の推定的理由で、短絡が生じにくいことは経験的に確かめられている。
【００２８】
なお、基材１が合成樹脂製である場合は、基材１の一部も電磁波で除去することは炭化が生じて基材１にダメージを与えるために問題となるが、セラミックスであれば何ら問題は生じない。
【００２９】
さらに、基材１の表面が粗くとも、上記処理を行うことで短絡を防ぐことができるために、逆に言えば、金属薄膜２の基材１への密着性を高めるために基材１の表面をＲａ＝１〜５μｍ程度に粗くしておいても問題は無いことになる。
【００３０】
また、セラミックスからなる基材１の上記絶縁溝の部分の表面を電磁波で除去する場合、セラミックスとして、アルミナにＭｎやＣｏなどを混ぜて焼結することで黒色に着色したものを用いると、基材１の電磁波吸収率が高くなるために、基材１表面の除去を容易に行うことができる。
【００３１】
なお、金属薄膜２の境界部の除去にはエキシマレーザやＴＨＧ−ＹＡＧレーザなどの吸収率の高い紫外レーザを用い、境界部に露出した絶縁性基材１の表面にＣＯ２レーザなどのセラミックスの加工に適した高出力のレーザを用いるようにしてもよい。金属薄膜２の除去の後に基材１の表面除去を行う。
【００３２】
さらには、セラミックス製の基材１は熱伝導性が樹脂と比較して高いために熱加工が困難であることから、基材１を加熱しながら除去のための電磁波の照射を行うようにしてもよい。この場合、基材１の加熱には電磁波（レーザ）を好適に用いることができ、たとえば図３に示すようにＩＲ−ＹＡＧレーザＬ２で基材１全体を加熱することなく加工部のみを効率良く加熱しつつ、ＴＨＧ−ＹＡＧレーザやエキシマレーザなどのレーザＬ１で基材１の表面の上記除去を行う。ここで加熱用に長波長のレーザＬ２を用いるのは、加熱効率の点と、金属薄膜２の残しておくべき部分が除去されてしまうことがないようにするためである。
【００３３】
この時、加熱用レーザＬ２と除去用レーザＬ１とは同時に照射することが好ましい。また、図４に示すように、加熱用のレーザＬ２のスポット径Ｄ２は、金属薄膜及び絶縁性基材の除去用のレーザＬ１のスポット径Ｄ１より大きくしておくと、位置調整を容易に行うことができる。ちなみにスポット径Ｄ１が３０〜１００μｍであるとすると、スポット径Ｄ２は２００〜３００μｍとしておく。
【００３４】
さらに、加熱用のレーザＬ２には、図５に示すように除去用のレーザＬ１よりもパルス幅の長いものを用いると同時に、加熱用レーザＬ２の各パルスの終期に除去用のレーザＬ１のパルスが出るようにしておくことで、基材１の温度が十分に上昇した時点で除去を行うことができ、除去加工性を高くすることができる。
【００３５】
加熱用のレーザＬ２にＣＷ（連続波）発振のＩＲ−ＹＡＧレーザを用いてもよい。パルス制御の必要がなくなるために除去加工が容易となる。
【００３６】
【発明の効果】
以上のように本発明は、絶縁性基材表面に形成した金属薄膜の回路部と非回路部との境界部分をレーザ等の電磁波を照射して除去し、この後、金属薄膜の上記回路部上にめっきを施すとともに非回路部をエッチングで除去して回路パターンを作成する回路板の製造方法において、金属薄膜の回路部上に必要厚みよりも薄い厚みのめっきと、非回路部の金属薄膜を除去するためのエッチングとを上記回路部上のめっきが必要厚みとなるまで繰り返して行うものであり、金属薄膜の回路部上にめっきを必要厚みまでいきなり行わずに、薄く形成しておいた状態でエッチングを行って金属薄膜の非回路部の除去を行うことから、めっきを必要厚みまで行う際に金属薄膜の非回路部にめっき層が短絡してしまうことを防ぐことができるものであり、このために歩留まり及び生産性を向上させることができる。
【００３７】
この時、めっき材質に金属薄膜材質よりも耐エッチング性に優れた材料を用いると、エッチングによるめっき部分の浸食を抑制することができる。
【００３８】
また、めっき後にめっき部の縁の電解研磨処理を行うと、短絡発生をより確実に防ぐことができる。
【００３９】
エッチングはめっき用の電気めっき液中に電圧をかけずに浸漬させることで行ってもよく、この場合、エッチング槽が不要となる上に水洗工程などを省略することができる。
【００４０】
エッチングはブラスト処理で行ってもよく、この場合、化学薬品を用いないために液管理などが不要となって生産性を良くすることができる。
【００４１】
また、エッチングは電磁波照射による金属薄膜の除去で露出した基材表面に対して行うと、金属薄膜の除去をより確実に行うことができ、これに伴って短絡の発生のおそれを低減させることができる。
【００４２】
この時、エッチングは溶剤あるいは酸あるいはアルカリ溶液による化学エッチングで行うと、確実にエッチングを行うことができる。
【００４３】
そして、セラミックス製の絶縁性基材の表面に形成した金属薄膜の上記境界部分の電磁波による除去にあたり、基材の表面粗さ以上の深さまで基材表面も除去すると、基材表面の除去部の表面粗さを小さくして短絡発生の事態をより確実に防ぐことができる。
【００４４】
この時、絶縁性基材としては表面粗度がＲａ＝１〜５μｍのセラミックス材を用いると、当初から表面粗さが小さい基材を用いる場合に比して、回路密着性を高くすることができる。
【００４５】
また着色したセラミックス材を基材として用いると、電磁波の吸収率が高くなるために基材表面の除去も容易に行うことができるものとなる。
【００４６】
絶縁性基材を加熱しながら電磁波の照射を行うようにしても、基材表面の除去を容易に行うことができる。熱伝導性の良いセラミックス製の基材を予備的に加熱することで基材表面の除去を効率よく行うことができるからである。
【００４７】
この時、金属薄膜の境界部の電磁波照射による除去を行った後、境界部に露出した絶縁性基材の表面の除去を行うと、金属薄膜の除去と基材の除去とを夫々に適切な電磁波を用いて確実に行うことができる。
【００４８】
また、金属薄膜及び絶縁性基材の除去用の電磁波と、絶縁性基材の加熱用の電磁波とを同時に照射すると、基材の他の部分に対する熱的影響を極力小さくすることができる。
【００４９】
この場合、絶縁性基材の加熱用の電磁波に、金属薄膜及び絶縁性基材の除去用の電磁波よりも波長の長いものを用いると、効果的な加熱を行えると同時に、加熱用の電磁波が基材や金属薄膜にダメージを与えてしまうことがないものとなる。
【００５０】
また加熱用の電磁波として、金属薄膜及び絶縁性基材の除去用の電磁波よりもスポット径の大きいものを用いると、両電磁波の位置調整を容易に行うことができるものとなる。
【００５１】
また、加熱用の電磁波として、金属薄膜及び絶縁性基材の除去用の電磁波よりもパルス幅の長いものを用いたり、あるいは連続波を用いると、加熱と除去とを夫々効率良く行うことができる。
【００５２】
また本発明は、絶縁性基材表面に形成した金属薄膜の回路部と非回路部との境界部分をレーザ等の電磁波を照射して除去し、この後、金属薄膜の上記回路部上にめっきを施すとともに非回路部をエッチングで除去して回路パターンを作成する回路板の製造方法において、金属薄膜の非回路部の除去のためのエッチング処理で除去される厚みよりも大なる厚みで且つ必要厚みよりも薄い厚みのめっきを金属薄膜の回路部上に形成し、次いで金属薄膜の非回路部の除去のためのエッチング処理を行い、その後、金属薄膜の回路部上に必要厚みとなるまで再度めっきを施すことに他の特徴を有している。めっきを必要厚みまで行う際に金属薄膜の非回路部にめっき層が短絡してしまうことを防ぐことができて、歩留まり及び生産性を向上させることができる上に、めっき工程の増加を最小限に抑えるとともにエッチング処理の工程の増加を無くすことができる。
【図面の簡単な説明】
【図１】本発明の実施の形態の一例の説明図である。
【図２】（ａ）は金属薄膜が表面に形成された基材の拡大断面図、（ｂ）は金属薄膜の境界部及び基材表面の除去後の拡大断面図である。
【図３】（ａ）（ｂ）は夫々加熱用レーザと除去用レーザの同時照射についての説明図である。
【図４】加熱用レーザと除去用レーザのスポット径についての説明図である。
【図５】加熱用レーザと除去用レーザのパルス幅についての説明図である。
【図６】短絡発生に関する説明図である。
【符号の説明】
１基材
２金属薄膜
３めっき
２１回路部
２２非回路部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a circuit board manufacturing method, and more particularly to a circuit board manufacturing method that can be suitably used for manufacturing a three-dimensional circuit board.
[0002]
[Prior art]
After removal of the previously formed metal thin film on an insulating substrate, thus unnecessary portions of the metal thin film electromagnetic radiation pulsed laser or the like (at least the contour of the non-circuit portion), plated circuit portion of the metal thin film Japanese Patent No. 3153682 discloses a method of manufacturing a circuit board for forming a circuit pattern by applying the above. In the manufacturing method developed for a three-dimensional molded circuit board (MID substrate), a pulsed laser such as a Q-switched YAG laser is scanned on a substrate using a deflecting means such as a galvanometer mirror, thereby Remove unnecessary parts.
[0003]
[Problems to be solved by the invention]
Here, there was almost no problem when the insulating base material is made of resin, but the following problems occur when ceramics such as alumina are used as the insulating base material. Became clear.
[0004]
That is, the unnecessary portion of the metal thin film by the laser irradiation is removed by irradiating the boundary line between the circuit portion and the non-circuit portion with a laser, and then electroplating is performed on the circuit portion. A plating layer having a necessary thickness is formed thereon, and then a non-circuit portion of the metal thin film is removed by etching. In the above electroplating, a part of the plating layer 3 is a metal thin film as shown in FIG. As a result, there are many situations in which a plating layer is formed on the non-circuit portion. Although the plating layer should not occur in the part where the metal thin film has been removed by laser irradiation, the plating layer reaches the non-circuit part by extending the tentacles, though only a small part. In consideration of the fact that the above-mentioned situation is more likely to occur when an insulating substrate made of ceramics having a rough surface roughness is used, the surface of the insulating substrate will have minute irregularities and μ cracks. It can be inferred that the remaining metal thin film or the metal thin film molecules once adhered to the surface of the insulating substrate after melting and evaporating by laser irradiation induce the plating.
[0005]
However, whatever the cause, the above situation will occur, so the yield is greatly reduced when using a ceramic insulating base material compared to using a synthetic resin insulating base material. Therefore, a manufacturing method that does not cause the short circuit is desired.
[0006]
The present invention has been made in view of such points, and the object of the present invention is to manufacture a circuit board that can reliably prevent a short circuit to a non-circuit portion due to a plating layer and greatly improve the yield. Is in providing a way.
[0007]
[Means for Solving the Problems]
Therefore, the present invention removes the boundary portion between the circuit portion and the non-circuit portion of the metal thin film formed on the surface of the insulating base material by irradiating an electromagnetic wave such as a laser, and then on the circuit portion of the metal thin film. In the method of manufacturing a circuit board that creates a circuit pattern by plating and removing the non-circuit part by etching, plating thinner than the required thickness on the circuit part of the metal thin film and removing the metal thin film of the non-circuit part It is characterized in that the etching for performing the above process is repeated until the plating on the circuit portion has a required thickness .
[0008]
Instead of suddenly formed to the required thickness of the plating on the circuit portion of the metal thin film, by etching in a state which has been thinly formed by the removal of the non-circuit portion of the metal thin film is performed until required thickness of the plating In this case, the plating layer is prevented from being short-circuited to the non-circuit portion of the metal thin film.
[0009]
At this time, it is preferable to use a material having higher etching resistance than the metal thin film material as the plating material, and it is also preferable to perform an electropolishing treatment on the edge of the plated portion after plating.
[0010]
Etching may be performed by immersing in an electroplating solution for plating without applying voltage, or by blasting.
[0011]
Etching may be performed on the surface of the substrate exposed by removing the metal thin film by electromagnetic wave irradiation. At this time, etching may be performed by chemical etching using a solvent, an acid or an alkali solution.
[0012]
In removing the metal thin film formed on the surface of the ceramic insulating substrate by the electromagnetic wave, it is desirable to remove the substrate surface to a depth equal to or greater than the surface roughness of the substrate.
[0013]
At this time, a ceramic material having a surface roughness of Ra = 1 to 5 μm is suitable as the insulating base material, and a colored ceramic material is also preferably used.
[0014]
You may make it irradiate electromagnetic waves while heating an insulating base material, and after removing by the electromagnetic wave irradiation of the boundary part of a metal thin film, the surface of the insulating base material exposed to the boundary part is removed. It may be.
[0015]
Furthermore, the electromagnetic wave for removing the metal thin film and the insulating base material and the electromagnetic wave for heating the insulating base material may be simultaneously irradiated. In this case, the electromagnetic wave for heating the insulating base material is used. As described above, an electromagnetic wave having a longer wavelength than the electromagnetic wave for removing the metal thin film and the insulating base material is used, an electromagnetic wave having a larger spot diameter than the electromagnetic wave for removing the metal thin film and the insulating base material, An electromagnetic wave having a pulse width longer than that of the electromagnetic wave for removing the insulating substrate may be used, or a continuous wave may be used.
[0016]
Further, the present invention removes the boundary portion between the circuit portion and the non-circuit portion of the metal thin film formed on the surface of the insulating substrate by irradiating an electromagnetic wave such as a laser, and thereafter plating on the circuit portion of the metal thin film. In the method of manufacturing a circuit board in which a non-circuit portion is removed by etching and a circuit pattern is created, the thickness is larger than the thickness removed by the etching process for removing the non-circuit portion of the metal thin film and is necessary. A plating with a thickness smaller than the thickness is formed on the circuit portion of the metal thin film, and then an etching process is performed to remove the non-circuit portion of the metal thin film, and then again until the required thickness is obtained on the circuit portion of the metal thin film. It has other features in applying plating.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to an embodiment. In the figure, reference numeral 1 denotes an insulating substrate made of a ceramic material such as alumina, zirconia, or aluminum nitride, and a metal thin film formed on the surface thereof by sputtering or the like. 2 is provided. The metal thin film 2 may be made of Cu, Ni, Pd, Cr, Ag, etc., and its thickness is about 0.1 to 1 μm.
[0018]
Of the metal thin film 2 on the insulating substrate 1, when the part where the circuit pattern is finally formed is the circuit part and the part where the circuit pattern is not formed is the non-circuit part, As shown in FIG. 1, the metal thin film 2 at the boundary is removed, and an insulating groove in which the insulating substrate 1 is exposed is formed between the circuit portion 21 and the non-circuit portion 22. Form. The electromagnetic wave (laser) to be radiated depends on the material of the metal thin film 2, but a pulse laser such as a second harmonic (SHG) YAG laser or a third harmonic (THG) YAG laser is suitable. By irradiating the boundary part by scanning or the like, the metal thin film 2 at the boundary part is removed. The laser irradiation energy is preferably about 50 to 500 μJ / pulse, but is not limited thereto.
[0019]
After that, electroplating is performed on the circuit portion 21 in the metal thin film 2. Conventionally, the plating layer 3 is formed at a stretch to the required thickness (for example, 10 to 20 μm) by electroplating, and then the non-circuit in the metal thin film 2 is formed. Whereas the portion 22 has been removed by etching, thin electroplating is first performed on the circuit portion 21 to form a thin plating layer 30 having a thickness of, for example, about 2 to 5 μm, and then etching is performed. Then, the non-circuit portion 22 of the metal thin film 2 is removed. Although the thin plating layer 30 remains in the etching process at this time, a light etching process that removes all the non-circuit parts 22 of the metal thin film 2 is preferable, but all the non-circuit parts 22 are not necessarily removed. It does not have to be. Thereafter, a plating layer 31 is further formed on the thin plating layer 30 by electroplating, and if necessary, an etching process is performed to remove the non-circuit portion 22 of the metal thin film 2. Thus, a plating layer 3 having a finally required thickness (for example, 10 to 20 μm) is formed on the circuit portion 21 of the metal thin film 2 by a plurality of times of electroplating.
[0020]
In this case, when performing electroplating, the plating layer 30 (or the plating layer 31) grows until it reaches the non-circuit portion 22 of the metal thin film 2 across the insulating groove (width is about 50 to 60 μm) by the laser irradiation. No, even if it grows until it crosses the insulating groove by repeating electroplating a plurality of times, the non-circuit part 22 of the metal thin film 2 has been removed by a plurality of etching processes at that time. Short circuit will not occur.
[0021]
By the way, in forming the plating layer 3 by repeating such electroplating, the thickness is larger than the thickness removed by the etching process for removing the non-circuit portion 22 of the metal thin film 2 and more than the required thickness. A thin plating layer 30 having a small thickness is formed on the circuit portion 21 of the metal thin film 2, and then the non-circuit portion 22 of the metal thin film 2 is completely removed by etching, followed by electroplating on the thin plating layer 30. Of course, it is most preferable to obtain the plating layer 3 having a required thickness when the layer 31 is formed from the viewpoint of the number of plating treatments and the number of etchings.
[0022]
In the etching process, when the metal thin film 2 is made of Cu, ammonium persulfate is usually used as an etching solution. However, the plating layer 3 (particularly, the thin plating layer 30) is made of a material that is difficult to be etched by this etching solution. For example, when it is formed of Au or the like, the plating layer 3 is less likely to be eroded during etching, so that preferable results can be obtained. The material is not limited to Cu and Au, and any material may be used as long as the plating layer 3 is formed of a metal having higher etching resistance than the material of the metal thin film 2.
[0023]
Moreover, it is also preferable to perform the electropolishing process of the edge after forming the thin plating layer 30. This is because a portion that extends to the non-circuit portion 20 can be removed. For example, the electrolytic polishing treatment is performed by immersing in 10 vol% phosphoric acid and applying a current density of 0.1 to 0.3 A / dm2.
[0024]
In addition, you may perform the etching for the removal of the non-circuit part 22 of the metal thin film 2 by immersing in the electroplating liquid for plating, without applying a voltage. For example, the plating layer 30 is formed by energization in a copper sulfate plating bath, and then the bath management is performed by adjusting the sulfuric acid concentration without energization while being immersed. Even if it is not separately immersed in an etching solution, etching can be performed while being immersed in an electroplating solution for forming the plating layer 3 (30, 31).
[0025]
In addition, the etching may be performed by blasting alumina powder, glass particles, walnut shells, beads or the like.
[0026]
Further, the etching may be performed by selectively performing etching with strong etching property on the insulating groove portion on the surface of the base material 2 exposed by removing the metal thin film 2 by electromagnetic wave irradiation. Etching in this case is preferably chemical etching with a solvent, acid or alkali solution. For example, when the insulating substrate 1 is an alumina substrate, it may be immersed in a phosphoric acid bath. What is necessary is just to immerse. Incidentally, in this etching process, all the non-circuit portions 22 of the metal thin film 2 may not be finally removed. This is because insulation in the insulating groove is surely performed, and unnecessary growth of the plating layer 3 that causes a short circuit between the plating layer 3 and the non-circuit portion 22 is removed by the etching process.
[0027]
By the way, when the insulating substrate 1 is a ceramic sintered body such as alumina, aluminum nitride, or zirconia, the surface is inevitably roughened, so that the plating layer 3 and the non-circuit portion 22 of the metal thin film 2 as described above In addition to forming the plating layer 3 (30, 31) in the above-described procedure, the non-circuit portion 22 and the circuit portion of the metal thin film 2 are more easily prevented. When forming the insulating groove by irradiating the boundary portion with the electromagnetic wave (laser) 21 to remove the metal thin film 2 at the boundary portion, as shown in FIG. The surface of the substrate 1 may be removed to a depth equal to or greater than the surface roughness. If the surface roughness Ra is 1 to 5 μm, the surface of the substrate 1 is also removed to a depth d where Ra <d. When such a treatment is performed, the surface of the base material 1 made of ceramic is melted by the irradiation of electromagnetic waves, so that the surface unevenness is reduced, and the remaining conductor particles are exposed and exposed to be removed by etching, etc. It has been empirically confirmed that short-circuiting is unlikely to occur for the above reason.
[0028]
In addition, when the base material 1 is made of a synthetic resin, removing part of the base material 1 with electromagnetic waves causes a problem because carbonization occurs and damages the base material 1. There is no problem.
[0029]
Furthermore, even if the surface of the base material 1 is rough, short-circuiting can be prevented by performing the above treatment. In other words, in order to improve the adhesion of the metal thin film 2 to the base material 1, Even if the surface is roughened to Ra = 1 to 5 μm, there is no problem.
[0030]
Further, when the surface of the insulating groove portion of the substrate 1 made of ceramics is removed with electromagnetic waves, if the ceramic is colored black by mixing and sintering Mn, Co or the like in alumina, Since the electromagnetic wave absorption rate of the material 1 is increased, the surface of the base material 1 can be easily removed.
[0031]
The removal of the boundary portion of the metal thin film 2 uses an ultraviolet laser having a high absorption rate such as an excimer laser or a THG-YAG laser, and the surface of the insulating substrate 1 exposed at the boundary portion is processed with a ceramic such as a CO2 laser. A high output laser suitable for the above may be used. After the removal of the metal thin film 2, the surface of the substrate 1 is removed.
[0032]
Furthermore, since the ceramic substrate 1 has higher thermal conductivity than the resin and is difficult to heat-process, the substrate 1 is irradiated with electromagnetic waves for removal while being heated. Also good. In this case, an electromagnetic wave (laser) can be suitably used for heating the base material 1. For example, as shown in FIG. 3, only the processed part is efficiently processed without heating the whole base material 1 with the IR-YAG laser L 2. While heating, the surface of the substrate 1 is removed with a laser L1 such as a THG-YAG laser or an excimer laser. Here, the reason why the long-wavelength laser L2 is used for heating is to prevent the point of heating efficiency and the portion to be left of the metal thin film 2 from being removed.
[0033]
At this time, it is preferable that the heating laser L2 and the removal laser L1 are irradiated simultaneously. Further, as shown in FIG. 4, if the spot diameter D2 of the laser L2 for heating is larger than the spot diameter D1 of the laser L1 for removing the metal thin film and the insulating base, the position adjustment is easily performed. be able to. Incidentally, if the spot diameter D1 is 30 to 100 μm, the spot diameter D2 is set to 200 to 300 μm.
[0034]
Further, as shown in FIG. 5, the heating laser L2 has a longer pulse width than the removal laser L1, and at the same time, the pulse of the removal laser L1 at the end of each pulse of the heating laser L2. By making it appear, removal can be performed when the temperature of the substrate 1 is sufficiently increased, and the removal processability can be improved.
[0035]
A CW (continuous wave) oscillation IR-YAG laser may be used as the heating laser L2. Since the need for pulse control is eliminated, removal processing is facilitated.
[0036]
【The invention's effect】
As described above, the present invention removes the boundary portion between the circuit portion and the non-circuit portion of the metal thin film formed on the surface of the insulating substrate by irradiating electromagnetic waves such as a laser, and thereafter the circuit portion of the metal thin film. In a method of manufacturing a circuit board in which a non-circuit portion is removed by etching and a circuit pattern is formed by plating on the top of the metal thin-film circuit portion, the plating is thinner than the necessary thickness, and the non-circuit portion metal thin film Etching to remove the metal layer is repeated until the required thickness of the plating on the circuit part is reached , and the metal part is formed thinly on the circuit part without being suddenly plated to the required thickness . Since the non-circuit part of the metal thin film is removed by performing etching in a state, it is possible to prevent the plating layer from being short-circuited to the non-circuit part of the metal thin film when performing plating to the required thickness. This It is possible to improve the yield and productivity for.
[0037]
At this time, if a material having higher etching resistance than the metal thin film material is used as the plating material, erosion of the plated portion due to etching can be suppressed.
[0038]
Moreover, when the electropolishing process of the edge of a plating part is performed after plating, the occurrence of a short circuit can be prevented more reliably.
[0039]
Etching may be performed by immersing in an electroplating solution for plating without applying a voltage. In this case, an etching bath is not required and a water washing step and the like can be omitted.
[0040]
Etching may be performed by blasting. In this case, since chemicals are not used, liquid management or the like is unnecessary, and productivity can be improved.
[0041]
In addition, if etching is performed on the surface of the substrate exposed by removing the metal thin film by electromagnetic wave irradiation, the metal thin film can be removed more reliably, and this can reduce the possibility of occurrence of a short circuit. it can.
[0042]
At this time, if the etching is performed by chemical etching using a solvent, an acid or an alkali solution, the etching can be reliably performed.
[0043]
Then, in removing the boundary portion of the metal thin film formed on the surface of the ceramic insulating base material by electromagnetic waves, if the base material surface is also removed to a depth equal to or higher than the surface roughness of the base material, The surface roughness can be reduced to prevent the occurrence of a short circuit more reliably.
[0044]
At this time, if a ceramic material having a surface roughness of Ra = 1 to 5 μm is used as the insulating substrate, circuit adhesion can be increased compared to the case of using a substrate having a small surface roughness from the beginning. it can.
[0045]
Further, when a colored ceramic material is used as a base material, the absorption rate of electromagnetic waves is increased, so that the surface of the base material can be easily removed.
[0046]
Even if the electromagnetic wave is irradiated while heating the insulating base material, the surface of the base material can be easily removed. This is because the surface of the substrate can be efficiently removed by preliminarily heating the ceramic substrate having good thermal conductivity.
[0047]
At this time, after removing the boundary of the metal thin film by electromagnetic wave irradiation, if the surface of the insulating base exposed at the boundary is removed, the removal of the metal thin film and the removal of the base are respectively appropriate. It can be performed reliably using electromagnetic waves.
[0048]
In addition, when the electromagnetic wave for removing the metal thin film and the insulating base material and the electromagnetic wave for heating the insulating base material are simultaneously irradiated, the thermal influence on other portions of the base material can be minimized.
[0049]
In this case, if an electromagnetic wave having a wavelength longer than that of the electromagnetic wave for removing the metal thin film and the insulating substrate is used as the electromagnetic wave for heating the insulating base material, effective heating can be performed simultaneously with the heating electromagnetic wave. The substrate and the metal thin film are not damaged.
[0050]
Further, when the electromagnetic wave for heating has a larger spot diameter than the electromagnetic wave for removing the metal thin film and the insulating substrate, the position of both electromagnetic waves can be easily adjusted.
[0051]
In addition, when the electromagnetic wave for heating has a longer pulse width than the electromagnetic wave for removing the metal thin film and the insulating base, or when a continuous wave is used, heating and removal can be performed efficiently. .
[0052]
Further, the present invention removes the boundary portion between the circuit portion and the non-circuit portion of the metal thin film formed on the surface of the insulating substrate by irradiating an electromagnetic wave such as a laser, and thereafter plating on the circuit portion of the metal thin film. In the method of manufacturing a circuit board in which a non-circuit portion is removed by etching and a circuit pattern is created, the thickness is larger than the thickness removed by the etching process for removing the non-circuit portion of the metal thin film and is necessary. A plating with a thickness smaller than the thickness is formed on the circuit portion of the metal thin film, and then an etching process is performed to remove the non-circuit portion of the metal thin film, and then again until the required thickness is obtained on the circuit portion of the metal thin film. It has other features in applying plating. When plating to the required thickness, the plating layer can be prevented from short-circuiting to the non-circuit part of the metal thin film, yield and productivity can be improved, and the increase in plating process is minimized. And an increase in the number of etching processes can be eliminated.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an example of an embodiment of the present invention.
2A is an enlarged cross-sectional view of a base material on which a metal thin film is formed, and FIG. 2B is an enlarged cross-sectional view after removal of the boundary portion of the metal thin film and the surface of the base material.
FIGS. 3A and 3B are explanatory diagrams of simultaneous irradiation of a heating laser and a removal laser, respectively.
FIG. 4 is an explanatory diagram of spot diameters of a heating laser and a removal laser.
FIG. 5 is an explanatory diagram of pulse widths of a heating laser and a removal laser.
FIG. 6 is an explanatory diagram regarding occurrence of a short circuit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Base material 2 Metal thin film 3 Plating 21 Circuit part 22 Non-circuit part

Claims

The boundary part between the circuit part and the non-circuit part of the metal thin film formed on the surface of the insulating substrate is removed by irradiating an electromagnetic wave such as a laser, and then plating is performed on the circuit part of the metal thin film and the non-circuit is formed. In a method of manufacturing a circuit board in which a circuit pattern is created by removing a part by etching, plating with a thickness thinner than a necessary thickness on the circuit part of the metal thin film and etching for removing the metal thin film of the non-circuit part A method for producing a circuit board, wherein the plating on the circuit part is repeated until a required thickness is obtained .

2. The method of manufacturing a circuit board according to claim 1, wherein a material having higher etching resistance than a metal thin film material is used as a plating material.

2. The method of manufacturing a circuit board according to claim 1, wherein an electropolishing treatment is performed on the edge of the plated portion after plating.

2. The method for producing a circuit board according to claim 1, wherein the etching is performed by immersing in an electroplating solution for plating without applying a voltage.

2. The method of manufacturing a circuit board according to claim 1, wherein the etching is performed by blasting.

2. The method for manufacturing a circuit board according to claim 1, wherein the etching is performed on the surface of the base material exposed by removing the metal thin film by electromagnetic wave irradiation.

7. The method of manufacturing a circuit board according to claim 6, wherein the etching is performed by chemical etching using a solvent, an acid or an alkali solution.

The base material surface is also removed to a depth equal to or greater than the surface roughness of the base material in removing the boundary portion of the metal thin film formed on the surface of the ceramic insulating base material by electromagnetic waves. Circuit board manufacturing method.

9. The method of manufacturing a circuit board according to claim 8, wherein a ceramic material having a surface roughness of Ra = 1 to 5 [mu] m is used as the insulating substrate.

The method for manufacturing a circuit board according to claim 8 or 9, wherein a colored ceramic material is used as the insulating substrate.

The method for producing a circuit board according to any one of claims 8 to 10, wherein the electromagnetic wave is irradiated while heating the insulating substrate.

The circuit board according to any one of claims 8 to 11, wherein after removing the boundary portion of the metal thin film by electromagnetic wave irradiation, the surface of the insulating base exposed at the boundary portion is removed. Manufacturing method.

12. The circuit board according to claim 8, wherein the electromagnetic wave for removing the metal thin film and the insulating base material and the electromagnetic wave for heating the insulating base material are irradiated at the same time. Method.

14. The method for producing a circuit board according to claim 13, wherein an electromagnetic wave having a wavelength longer than that of the electromagnetic wave for removing the metal thin film and the insulating substrate is used as the electromagnetic wave for heating the insulating substrate.

14. The method for producing a circuit board according to claim 13, wherein the electromagnetic wave for heating the insulating substrate is one having a larger spot diameter than the electromagnetic wave for removing the metal thin film and the insulating substrate.

14. The method for producing a circuit board according to claim 13, wherein the electromagnetic wave for heating the insulating base material has a longer pulse width than the electromagnetic wave for removing the metal thin film and the insulating base material.

14. The method for manufacturing a circuit board according to claim 13, wherein a continuous wave is used as an electromagnetic wave for heating the insulating substrate.

The boundary part between the circuit part and the non-circuit part of the metal thin film formed on the surface of the insulating substrate is removed by irradiating an electromagnetic wave such as a laser, and then plating is performed on the circuit part of the metal thin film and the non-circuit is formed. In a circuit board manufacturing method for creating a circuit pattern by removing a portion by etching, the thickness is larger than the thickness removed by the etching process for removing the non-circuit portion of the metal thin film and thinner than the required thickness. The metal thin film is formed on the circuit portion of the metal thin film, and then the etching process for removing the non-circuit portion of the metal thin film is performed, and then the metal thin film circuit portion is plated again until a necessary thickness is obtained. A method for manufacturing a circuit board.