JP3779478B2

JP3779478B2 - Relay board and manufacturing method thereof

Info

Publication number: JP3779478B2
Application number: JP33803798A
Authority: JP
Inventors: 容多島; 敬章平岡; 訓平野; 康宏杉本
Original assignee: NGK Spark Plug Co Ltd
Current assignee: NGK Spark Plug Co Ltd
Priority date: 1998-10-08
Filing date: 1998-11-27
Publication date: 2006-05-31
Anticipated expiration: 2018-11-27
Also published as: JP2000183242A

Description

【０００１】
【発明の属する技術分野】
本発明は、ＩＣチップやトランジスタ、抵抗、コンデンサ等の機能部品や機能部品を搭載した配線基板等の電子部品の端子と、これを搭載するためのマザーボード、ドーターボード等のプリント配線板に設けた端子との間に介在させて相互に接続させる中継基板及びその製造方法に関し、特に、製造容易で微細な間隔を持つ端子同士を接続できる中継基板及びその製造方法に関する。
【０００２】
【従来の技術】
従来より、ＩＣチップをプリント配線板にベアチップ実装する場合に、ＩＣチップが不良であった場合のリペアの困難さを考慮して、ＩＣチップとプリント配線板の間に中継基板（インターポーザ）を介在させることがある。特に、複数のＩＣチップを１つのプリント配線板に搭載する場合には、一旦中継基板に複数のＩＣチップを接続し、いずれのＩＣチップも正常であることを確認してから、中継基板をプリント配線板に接続することが多い。
【０００３】
このような従来の中継基板の構造について、図１１を参照しつつ説明する。図１１（ａ）に示す中継基板１１０は、アルミナセラミックからなる中継基板本体１１１の２つの主面１１１Ａ，１１１Ｂの間に開けた貫通孔１１１Ｈ内に、タングステン、モリブデン等のビア１１２を形成し、この上下を覆うようにして主面１１１Ａ，１１１Ｂにそれぞれタングステン、モリブデン等のパッド１１３，１１４を形成したものである。このような中継基板１１０を介在させて、図１１（ｂ）に示すように、ＩＣチップ等の電子部品Ｄ１０，Ｄ２０を、プリント配線板Ｐ１０に接続する。
【０００４】
電子部品Ｄ１０，Ｄ２０は、それぞれシリコンからなる部品本体Ｄ１１，Ｄ２１の接続面Ｄ１１Ｂ，Ｄ２１Ｂ（図中下面）に、多数のパッドＤ１２，Ｄ２２を備え、これらのパッドＤ１２，Ｄ２２には、高温ハンダ（例えば、９５Ｐｂ−５Ｓｎ）からなり略半球状のハンダバンプＤ１３，Ｄ２３を備える。また、プリント配線板Ｐ１０は、ガラス−エポキシ樹脂複合材料からなる配線板本体Ｐ１１の接続面Ｐ１１Ａ（図中上面）に、電子部品Ｄ１０，Ｄ２０のパッドＤ１２，Ｄ２２（ハンダバンプＤ１３，Ｄ２３）に対応した配置で、銅からなる接続パッドＰ１２、及び、高温ハンダからなり略半球状のハンダバンプＰ１３を備える。これらのハンダバンプＤ１３，Ｄ２３と中継基板１１０のパッド１１３とを、およびハンダバンプＰ１３とパッド１１４とを上記高温ハンダよりも低融点のハンダ（例えばＰｂ−Ｓｎ共晶ハンダ３７Ｐｂ−６３Ｓｎ）Ｓ１，Ｓ２で接続する。
【０００５】
その他の中継基板として、図１２に示すものも挙げられる。この中継基板１２０は、ガラス−エポキシ樹脂複合材料からなる中継基板本体１２１の２つの主面１２１Ａ，１２１Ｂの間に開けた貫通孔１２１Ｈ内に、銅メッキにより略円筒状のスルーホール導体１２２を形成し、さらにこの内部に導電性樹脂（あるいは絶縁性樹脂）からなるプラグ材１２５を充填し、銅メッキにより蓋状にパッド１２３，１２４をそれぞれ形成したものである。この中継基板１２０も、上記（図１１参照）と同様にして、電子部品Ｄ１０，Ｄ２０やプリント配線板Ｐ１０と接続して用いることができる。
【０００６】
【発明が解決しようとする課題】
しかしながら、上記した中継基板１１０は、中継基板本体１１１がアルミナ等のセラミックからなるため、靭性が低く、応力が掛かると折れる等の不具合を生じるため、中継基板本体１１１の厚さを薄くすることができない。一方、厚さが厚いとビア１１２の長さが長くなるため、ビア１１２の持つ抵抗やインダクタンスが大きくなって、電気的特性上も好ましくない。また、厚さが厚いと、プリント配線板Ｐ１０との熱膨張差に起因する応力が大きくなるため、両者間の接続信頼性も低下する。
さらに、この中継基板１１０は、例えば図１３（ａ）に示すように、焼成後に中継基板本体１１１となるセラミックグリーンシートＧの２つの主面ＧＡ，ＧＢを貫通する貫通孔ＧＨ内に、タングステンペースト等の導体ペーストＧＰを充填し、さらにパッド（図示しない）を印刷し焼成して形成する。この場合には、グリーンシートＧの厚さが薄いと、貫通孔ＧＨ内に導体ペーストＧＰを保持する能力に乏しいため、印刷時に一旦は充填された導体ペーストＧＰの一部またはほぼ全部が脱落して、充填不良となりやすく、歩留まりが低下する。また、導体ペーストＧＰの量が一定でないと、各パッドに凹凸ができてコプラナリティが低下し、ＩＣチップなどの電子部品Ｄ１０等との接続性が低下する。
【０００７】
一方、上記した中継基板１２０では、中継基板本体１２１に含まれるガラス繊維に沿ってマイグレーションを生じるため、隣接する貫通孔１２１Ｈ同士の間隔を狭くする、例えば、２００μｍ以下とすると、中継基板１２０の高温高湿条件下での信頼性が低下するため、間隔を狭くすることができない。また、この中継基板１２０は、プラグ材１２５を充填し熱硬化させると、図１３（ｂ）に示すように、その表面１２５Ｓに凹凸が生じるため、研磨によってその表面１２５Ｓを平坦にし、その後パッド１２３，１２４を形成するのであるが、中継基板本体１２１の厚さが薄くなると、研磨が困難になってくる。また、上記導電ペーストＧＰと同様に、中継基板本体１２１の厚さが薄くなると、一旦充填したプラグ材（樹脂）１２５が脱落しやすくなる。さらに、プラグ材１２５の上下に蓋状のパッド１２３，１２４を形成するので、プラグ材１２５の形成後に研磨し、さらにメッキによってパッド１２３，１２４を形成するため、中継基板１２０の製作には工数が掛かり高価となる。また、電子部品Ｄ１０等のハンダバンプＤ１３と接続するには、予め低融点ハンダペーストをパッド１２３等に塗布しておき、電子部品Ｄ１０等を重ねた後にハンダペーストを加熱溶融させてハンダ付けする必要がある。
【０００８】
本発明は、かかる問題点に鑑みてなされたものであって、歩留まりが高く形成容易で、電子部品等とのハンダ付けも容易な中継基板及びその製造方法を提供することを目的とする。
【０００９】
【課題を解決するための手段、作用及び効果】
その解決手段は、第１主面と第２主面とを備え、この２つの主面間を貫通する貫通孔を有する中継基板本体と、上記貫通孔の第２主面側開口を塞ぐ底部と上記貫通孔内周面を覆う側部とを備える略凹形状の凹状導体と、上記凹状導体の凹部内に充填され上記第１主面側に突出する充填ハンダ体と、を備えることを特徴とする中継基板である。
【００１０】
本発明によれば、底部と側部とを有する有底の凹状導体を備えるので、充填ハンダ体とするためにスクリーン印刷等によって充填したハンダペーストの一部または全部が脱落することはないから、充填ハンダ体の量、従って、突出高さが均一になり、ＩＣチップ等の電子部品のバンプやパッドなどの端子との接続性が高くなる。また、ハンダペーストを充填する際に脱落する心配がないので、中継基板本体の厚さを薄くできる。また、充填ハンダ体が第１主面側に突出しているので、接続する電子部品等のパッドやバンプとの接続に際して、確実に接続させることができる。
【００１１】
なお、上記充填ハンダ体を、第１主面側で接続する電子部品等のバンプ等より低融点の材質からなるものとすると、電子部品等と中継基板とを接続させるのに際して、バンプ等より低融点のハンダペーストを予め塗布しておくなどの作業が不要とすることができる。
【００１２】
ここで、中継基板本体としては、靭性、絶縁性、耐湿性、加工性等を考慮して適宜選択すればよい。例えば、エポキシ樹脂、ポリイミド樹脂、ＢＴ樹脂，ＰＰＥ樹脂等の樹脂、ガラス−エポキシ樹脂複合材料など、これらの樹脂とガラス繊維（ガラス織布やガラス不織布）との複合材料、これらの樹脂とポリアミド繊維などの有機繊維との複合材料、連続多孔質ＰＴＦＥ等の三次元網目状フッ素系樹脂にエポキシ樹脂等を含浸させた複合材料などが挙げられる。
凹状導体は、中継基板本体の材質等を考慮して選択すればよいが、例えば、銅、ニッケル等が挙げられる。
また、充填ハンダ体は、接続するＩＣチップ等の電子部品やプリント配線板のバンプの材質を考慮して、材質や融点を選択すればよいが、例えば、Ｐｂ−Ｓｎ共晶ハンダ（３７Ｐｂ−６３Ｓｎ）や高温ハンダ（９５Ｐｂ−５Ｓｎ，９０Ｐｂ−１０Ｓｎ等）、あるいは９６．５Ｓｎ−３．５Ａｇ、９５Ｓｎ−５Ｓｂハンダ等が挙げられる。
【００１３】
さらに、上記の中継基板であって、前記中継基板本体の厚さが２００μｍ以下であることを特徴とする中継基板とすると良い。
【００１４】
中継基板の厚さが薄い場合には、前記したように貫通穴内にペースト等を充填してもその後に脱落する不具合を生じやすく、特に、中継基板本体の厚さが２００μｍ以下である場合には、貫通孔内に導体ペーストやプラグ材用の樹脂ペーストを保持させにくくなる。これに対して、本発明では有底の凹状導体を備えるので、ペースト等の脱落を生じることがなく、特に、２００μｍ以下の厚さの中継基板本体においても、確実にハンダペーストを保持し、均一な突出高さの充填ハンダ体を形成することができる。従って、凹状導体や充填ハンダ体の抵抗やインダクタンスをより低下させることができる。また、厚さを薄くした場合には、相対的に凹状導体の形状が底の浅い形状になるので、凹状導体中へのハンダペーストの充填がより容易になるから、充填ハンダ体の体積や突出高さもより均一にできる。さらに、中継基板本体の厚さが薄いので、この中継基板を介在させて電子部品とプリント基板とを接続しても、中継基板を介在させずに直接接続した場合に比較してさほど全体の高さが高くならない。したがって、低背化の要求にも応えることができる。
【００１５】
さらに、上記の中継基板であって、隣接する前記凹状導体の側部同士の間隙が、２００μｍ以下であり、前記中継基板本体が、ガラス繊維を含まない樹脂系複合材料からなることを特徴とする中継基板とすると良い。
【００１６】
中継基板本体の材質として、樹脂系複合材料を用いる場合には、アルミナ等のセラミックを用いる場合に比して、靭性が高いため、中継基板本体の厚さを薄くすることができる。従って、凹状導体や充填ハンダ体の抵抗やインダクタンスをより低下させることができる。また、厚さを薄くした場合には、凹状導体中へのハンダペーストの充填がより容易になって、充填ハンダ体の体積や突出高さもより均一にできる。
また、樹脂系複合材料を用い場合のうち、ガラス繊維を含むもの（例えば、ガラス−エポキシ樹脂複合材料）は、貫通孔形成の際などに樹脂とガラス繊維との間に隙間ができやすく、この隙間に浸入したメッキ液等の水分によってガラス繊維の表面に沿って凹状導体をなす銅等の金属が移動するマイグレーションを生じてショートしやすいが、本発明では、ガラス繊維を含まない樹脂系複合材料を用いるので、凹状導体の側部の間隙が２００μｍ以下という短い距離であっても、マイグレーションを生じることもなく、信頼性の高い中継基板とすることができる。
【００１７】
なお、ガラス繊維を含まない樹脂系複合材料としては、例えば、エポキシ樹脂、ポリイミド樹脂、ＢＴ樹脂、ＰＰＥ樹脂等の樹脂とポリアミド繊維などの有機繊維との複合材料、連続多孔質ＰＴＦＥ等の三次元網目状フッ素系樹脂にエポキシ樹脂等を含浸させた複合材料などが挙げられる。
【００１８】
さらに、上記中継基板であって、前記凹状導体の底部のうち第２主面側に、前記充填ハンダ体をなすハンダよりも高融点のハンダからなる高温ハンダバンプを備えることを特徴とする中継基板とすると良い。
【００１９】
一般に、ハンダは組成が異なっても相溶するため、高融点のハンダと低融点のハンダとが溶融状態で接触すると次第に混じり合って、組成が次第に変化してしまう。
本発明では、凹状導体の凹部内に充填ハンダ体、凹状導体の底部の第２主面側にはそれよりも高融点の高温ハンダバンプを備えるので、第１主面側でＩＣチップのバンプ等とを接続し、第２主面側でバンプを形成していないプリント配線板のパッドと接続することができる。
しかもこの際、充填ハンダ体と高温ハンダバンプとは凹状導体の底部で仕切られることになり、例えば、高温ハンダバンプを形成する際、あるいは充填ハンダ体を形成する際に、互いに混じり合わないので、組成変化が無い。つまり、充填ハンダ体の融点が上昇し、あるいは、高温ハンダバンプの融点が低下することがない。従って、接続したＩＣチップ等のリペアのために、接続や取り外しのために何回も加熱した場合でも、充填ハンダ体と第２主面側の高温ハンダバンプの両者の相溶による組成や融点の変化を生じないから、同一条件で接続やリペアを繰り返し行うことができる。
【００２０】
また、ＩＣチップ等の電子部品と第１主面側で接続した場合には、ＩＣチップ等と本発明の中継基板とで、あたかも第２主面側に高温ハンダバンプを備える一体の基板（電子部品）のように取り扱うことができるので、これをマザーボード等のプリント配線板等に接続するのに、この高温ハンダバンプにより容易に接続することができる。
【００２１】
さらに他の解決手段は、第１主面と第２主面とを備える中継基板本体に、上記２つの主面間を貫通する貫通孔及びこの貫通孔の第２主面側開口を塞ぐ底部と上記貫通孔内周面を覆う側部とを有する略凹形状の凹状導体を形成する貫通孔凹状導体形成工程と、上記第１主面側から上記凹状導体の凹部内にハンダペーストを充填し加熱して、上記凹状導体内に充填され上記第１主面側に突出する充填ハンダ体を形成する充填ハンダ体形成工程と、を備えることを特徴とする中継基板の製造方法である。
【００２２】
本発明によれば、貫通孔凹状導体形成工程において貫通孔および凹状導体を形成したので、充填ハンダ体形成工程において、凹状導体の凹部内に確実にハンダペーストを充填することができる。また、ハンダペーストの一部または全部が脱落する等の不具合を生じないため、歩留まり良く中継基板を製造することができる。また、充填ハンダ体のハンダの量を略一定にでき、突出高さも均一にできるから、第１主面側でＩＣチップ等の電子部品と接続させる場合に、接続性も高くできる。また、充填ハンダ体が第１主面側に突出しているので、電子部品等のパッドやバンプ等との接続に際して、確実に接続させることができる。
【００２３】
さらに、他の解決手段は、第１主面と第２主面とを備え、この２つの主面のうち少なくとも上記第２主面に第２主面側金属層を有する中継基板本体のうち、上記第１主面に金属層を有さず第２主面にのみ第２主面側金属層を有する所定位置に、上記中継基板本体を穿孔可能で上記第２主面側金属層を穿孔不能なレーザを用いた上記第１主面側からのレーザ加工により、上記第２主面側金属層で第２主面側開口を塞がれた貫通孔を穿孔する貫通孔形成工程と、少なくとも上記第２主面側金属層のうち上記第２主面側開口において上記貫通孔内に向かって露出する露出面および上記貫通孔内の内周面にメッキを施して、略凹形状の凹状導体を形成する凹状導体形成工程と、上記第１主面側から上記凹状導体の凹部内にハンダペーストを充填し加熱して、上記凹状導体内に充填され上記第１主面側に突出する充填ハンダ体を形成する充填ハンダ体形成工程と、を備えることを特徴とする中継基板の製造方法である。
【００２４】
本発明によれば、中継基板本体を穿孔可能で第２主面側金属層を穿孔不能なレーザによるレーザ加工で中継基板本体に貫通孔を形成するので、微細な貫通孔を高い精度で穿孔できる。しかも、第２主面側金属層を穿孔不能なレーザを当てるため、第２主面側金属層でレーザが反射されるので確実に貫通孔を形成できる。また、第２主面側金属層には穴は空かないため、凹状導体形成工程において、底部を形成する際の基材としてそのまま使うことができるので、貫通孔の第２主面側開口に容易に凹状導体の底部を形成できる。つまり、第２面側金属層は、貫通孔形成工程においては、レーザのストッパ（及び反射板）の役割をして貫通孔の孔開けに寄与する上、凹状導体形成工程においては、メッキによって形成する凹状導体の底部の基材としてその貫通孔に露出する露出面をなすようにすることができる。
【００２５】
さらに、有底の凹状導体を形成したので、充填ハンダ体形成工程において、凹状導体の凹部内に確実にハンダペーストを充填することができ、ハンダペーストの一部または全部が脱落する等の不具合を生じないから、歩留まり良く中継基板を製造することができる。また、充填ハンダ体のハンダの量を略一定にでき、突出高さも均一にできるから、第１主面側でＩＣチップ等の電子部品と接続させる場合に、接続性も高くできる。また、充填ハンダ体が第１主面側に突出しているので、電子部品等のパッドやバンプ等との接続に際して、確実に接続させることができる。
【００２６】
さらに、上記の中継基板の製造方法のうち貫通孔形成工程において、前記貫通孔の第２主面側開口の径よりも、これを塞ぐ第２主面側金属層の径が大きくされていることを特徴とする中継基板の製造方法とすると良い。
貫通孔形成工程において、このように第２主面側金属層の径が形成する貫通孔の第２主面側開口の径よりも大きい場合には、レーザ加工における位置ずれが多少生じても、確実に開口を第２主面側金属層を塞ぐことができる。
【００２７】
さらに、上記の中継基板の製造方法において、前記貫通孔形成工程は、前記第１主面に所定パターンの透孔を備える第１主面側金属層と前記第２主面のうち少なくとも上記透孔に対応する位置に配置された第２主面側金属層とを有する前記中継基板本体に、上記第１主面側金属層の透孔に対しこの透孔より広くレーザを照射し、透孔と断面略同形の前記貫通孔を形成するコンフォーマルマスク貫通孔形成工程であることを特徴とする中継基板の製造方法とすると良い。
本発明によれば、透孔をコンフォーマルマスクとして用い、透孔より広くレーザを照射し、透孔と略同径の前記貫通孔を形成したので、所定位置及び形状で貫通孔を確実に形成できる。また、レーザの位置決め精度が低くても形成可能である。また、貫通孔を形成する部分以外の部分が第１主面側金属層で覆われている場合には、一度に複数の貫通孔を同時に形成することもできる。
【００２８】
【発明の実施の形態】
（実施形態１）
本発明にかかる第１の実施の形態について、図面を参照しつつ説明する。図１（ａ）は、本実施形態１にかかる中継基板１０の平面図であり、図１（ｂ）は、その部分拡大断面図である。平面視略正方形板状の中継基板本体１１は、ガラス繊維を含まず、連続多孔質ＰＴＦＥにエポキシ樹脂を含浸させ硬化させた樹脂−樹脂複合材料（厚さ５０μｍ）からなり、第１主面１１Ａおよび第２主面１１Ｂを備え、さらに、この２つの主面間を貫通する直径５０μｍの貫通孔１１Ｈを多数備える。この貫通孔１１Ｈ同士の間隙（クリアランス）は、最も小さいもので１５０μｍとされている。この貫通孔１１Ｈには、銅からなり略凹字形状の凹状導体１２が形成されており、その底部１２Ｔが貫通孔１１Ｈの第２主面１１Ｂ側開口を塞ぎ、側部１２Ｓが貫通孔１１Ｈの内周面を覆うように配置されている。また、本実施形態の凹状導体１２においては、側部１２Ｓが、第１主面１１Ａのうち貫通孔１１Ｈの第１主面側開口周縁１１ＡＰにまで延在して第１主面側開口周縁部１２Ｐを形成しており、また、底部１２Ｔは、貫通孔１１Ｈの第２主面側開口周縁１１ＢＰにまで拡がって第２主面側開口周縁部１２Ｑを形成している。
【００２９】
また、各凹状導体１２には、それぞれ、凹状導体側部１２Ｓと底部１２Ｔとで形成される凹部１２Ｒ、即ち、凹状導体側部１２Ｓの内周面１２ＳＨと底部１２Ｔの第１主面側面（凹部底面）１２ＴＡで囲まれた凹部１２Ｒ内に充填され、さらに、第１主面側開口周縁部１２Ｐ上にまで拡り、第１主面１１Ａ側（図１（ｂ）中上方）に向かって、略球面状に突出する充填ハンダ体１３を備える。
この充填ハンダ体１３は、Ｐｂ−Ｓｎ共晶ハンダ（３７Ｐｂ−６３Ｓｎ）からなり、後述するように、第１主面１１Ａ側でＩＣチップ等の電子部品のバンプ等を接続する場合に、この充填ハンダ体１３を溶融させて、バンプ等と接続させるものである。
この貫通孔１１Ｈ、凹状導体１２および充填ハンダ体１３は、接続する電子部品のバンプ等の配列に対応した位置に配置されており、本実施形態では、図１（ａ）から容易に理解できるように、充填ハンダ体１３は、４群に別れて配置され、それぞれ平面視格子状に配列されており、４つの電子部品（以下では、電子部品Ｄ１０，Ｄ２０で代表させる）を接続させるようになっている。
【００３０】
この中継基板１０は、例えば、以下のようにして使用する。図２（ａ）に示すように、まず、ＩＣチップ等の電子部品Ｄ１０，Ｄ２０…と接続する。即ち、電子部品本体Ｄ１１，Ｄ２１の接続面（図中下面）Ｄ１１Ｂ、Ｄ２１Ｂに形成されたパッドＤ１２，Ｄ２２に固着され略半球形状をなす高温ハンダバンプＤ１３，Ｄ２３を、中継基板１０の充填ハンダ体１３によりハンダ付け接続する。高温ハンダバンプＤ１３，Ｄ２３は、例えば、９５Ｐｂ−５Ｓｎからなるので、Ｐｂ−Ｓｎ共晶ハンダからなる充填ハンダ体１３のみ溶融する温度（例えば、２３０℃）に加熱して充填ハンダ体１３を溶融させて、高温ハンダバンプＤ１３，Ｄ２３と接触させることにより、ハンダ付けを行う。なおこの際、充填ハンダ体１３は第１主面１１Ａ側に突出しているので、高温ハンダバンプＤ１３，Ｄ２３の高さにバラツキがあったり、中継基板本体１１に反りやうねりがあっても、充填ハンダ体１３と高温ハンダバンプＤ１３等とを確実に接続させることができる。
【００３１】
また、第１主面側に接続する電子部品Ｄ１０、Ｄ２０の高温ハンダバンプＤ１３，Ｄ２３より低融点の、具体的には、Ｐｂ−Ｓｎ共晶ハンダからなる充填ハンダ体１３を有しているため、電子部品Ｄ１０等と中継基板１０とを接続させるのに際して、予めハンダペーストを塗布するなどの作業が不要となる。
なお、貫通孔１１Ｈに有底の凹状導体１２を配置しているので、後述するように、充填ハンダ体１３を形成するのに際して、凹部１２Ｒに充填・塗布したハンダペーストがその後に脱落することが無く、ハンダペースト量を一定に保つことができるので、充填ハンダ体１３の突出高さが均一に揃っている。従って、この点から、高温ハンダバンプＤ１３等との接続が確実にできる。また、充填ハンダ体１３溶融させても、第２主面側（底部１２Ｔの第２主面側面１２ＴＢ）に濡れ拡がることがないので、この点からも充填ハンダ体１３のハンダ体積が一定になり、接続が確実になる。
【００３２】
その後、接続した電子部品Ｄ１０，Ｄ２０等の動作確認をし、不具合のあるものは取り外して別の電子部品を再度接続する。いずれの電子部品も正常に動作した場合には、さらに、図２（ｂ）に示すように、プリント配線板Ｐ１０と接続させる。
プリント配線板本体Ｐ１１の接続面（図中上面）Ｐ１１Ａに形成されたパッドＰ１２に固着され略半球形状をなす高温ハンダバンプＰ１３を、中継基板１０の凹状導体１２の底部１２ＴにＰｂ−Ｓｎ共晶ハンダＳＬによってハンダ付け接続する。具体的には、凹状導体１２の底部１２Ｔに、または高温ハンダバンプＰ１３に予めＰｂ−Ｓｎ共晶ハンダペースト（図示しない）を塗布しておき、プリント配線板Ｐ１０上に電子部品Ｄ１０，Ｄ２０を搭載した中継基板１０を重ねて、リフロー炉で加熱してＰｂ−Ｓｎ共晶ハンダペーストを溶融させ、凹状導体１２と高温ハンダバンプＰ１３とをハンダ付け接続する。これにより、各電子部品Ｄ１０，Ｄ２０…は、いずれも中継基板１０を介してプリント配線板Ｐ１０に接続されたことになる。
【００３３】
このようにして、電子部品Ｄ１０，Ｄ２０とプリント配線板Ｐ１０とを接続する中継基板１０は、例えばガラス−エポキシ樹脂複合材料のようにガラス繊維を含む複合材料ではなく、上記したように連続多孔質ＰＴＦＥにエポキシ樹脂を含浸硬化させた樹脂−樹脂複合材料であるので、耐湿性が高く、マイグレーションを生じ難い。このため、本実施形態のように、貫通孔１１Ｈ同士の間隙が最小で１５０μｍとした場合にも、マイグレーションによる短絡等を生じることがない。
【００３４】
（比較形態１，２）
これに対し比較形態１，２として、中継基板本体の材質にガラス繊維を含む材質、具体的にはガラス繊維織布にＢＴ（ビスマレイミド−トリアジン）樹脂を含浸させた厚さ２００μｍのガラス−ＢＴ樹脂複合材料を用い、各ビア径（貫通孔径）３００μｍ、ビア同士の最小間隙を２００μｍ及び４００μｍとした従来の中継基板（図１２参照）を製作した。
【００３５】
（実施形態１Ｂ）
さらに、実施形態１Ｂとして、上記実施形態１の中継基板１０と同様の材質からなるが、中継基板本体の厚さを４倍厚い２００μｍとし、凹状導体径（貫通孔径）５０μｍは同様であるが、凹状導体側部同士の最小間隙を５０μｍ大きい２００μｍとした中継基板も製作した。
【００３６】
（試験例）
これらの実施形態１，１Ｂ，比較形態１，２にかかる中継基板１０等を用いて湿中負荷試験を行い、マイグレーションの発生による絶縁抵抗低下の有無を比較した。具体的には、温度８５℃×湿度８５％ＲＨ、大気圧の条件に設定した恒温恒湿槽中で、各中継基板のビア間にＤＣ５０Ｖの電圧を印加して保持し、適時ビア間の絶縁抵抗（５Ｖ×６０秒）を測定し、１００ＭΩ以上の絶縁抵抗を保てる期間を測定した。結果を表１に示す。
【００３７】
【表１】

【００３８】
上記表１から判るように、ビア同士の最小間隙が４００μｍである比較形態２では、１００ＭΩ以上の絶縁抵抗を１０００時間以上保持しているのに対し、比較形態１では、５００時間で絶縁抵抗が１００ＭΩ以下となった。具体的には、中継基板本体のガラス繊維に沿って銅マイグレーションが生じ、ビア同士の間に電気的な経路が形成されていた。このことから、ガラス繊維を含む樹脂系複合材料、さらに具体的には、ガラス−ＢＴ樹脂複合材料を用いた場合には、ビア同士の間隙を４００μｍ程度保てば良いが、この間隙を２００μｍ以下とすると、マイグレーションを生じるため、中継基板の信頼性が著しく低下することが判る。
【００３９】
一方、実施形態１，１Ｂについては、いずれも１００ＭΩ以上の絶縁抵抗を１０００時間以上保持している。これらの実施形態では、中継基板本体１１等の材質に、ガラス繊維を含まない樹脂系複合材料、具体的には、三次元網目状フッ素系樹脂にエポキシ樹脂等を含浸させた複合材料、さらに具体的には、連続多孔質ＰＴＦＥにエポキシ樹脂を含浸させ硬化させた樹脂−樹脂複合材料を用いた。このため、凹状導体同士の間隙が２００μｍ以下、具体的には、２００μｍ（実施形態１Ｂ）、さらには１５０μｍ（実施形態１）としても、マイグレーションを生じなかったものと考えられる。従って、ガラス繊維を含まない樹脂系複合材料、具体的には連続多孔質ＰＴＦＥにエポキシ樹脂を含浸させた樹脂−樹脂複合材料を中継基板本体に用いた場合には、凹状導体の側部同士の間隙を２００μｍ以下、さらには１５０μｍ以下としても、マイグレーションを生じず、高い信頼性を有する中継基板が得られることが判る。
【００４０】
ついで、この中継基板１０の製造方法について、図３、図４を参照して説明する。まず、図３（ａ）に示すように、厚さ５０μｍで連続多孔質ＰＴＦＥにエポキシ樹脂を含浸させ硬化させた複合材料からなり、第１主面１１Ａと第２主面１１Ｂとを有し略板状をなす中継基板本体１１を用意する。この中継基板本体１１の第１主面１１Ａには、所定位置に直径５０μｍの透孔１４Ｈを備える厚さ１２μｍの銅箔１４が、また、第２主面１１Ｂにも、略全面に厚さ１２μｍの銅箔１５が被着されている。
【００４１】
ついで、第１主面１１Ａ側から、ＹＡＧレーザの第３高調波（３５５ｎｍ）を透孔１４Ｈよりも広い範囲にわたって照射して透孔１４Ｈをマスクパターンとして用い、図３（ｂ）に示すように、中継基板本体１１に透孔１４Ｈと断面略同形の貫通孔１１Ｈを複数個一挙に形成する。このレーザ光は、銅箔１４で反射されるため、銅箔１４の無い透孔１４Ｈ内のみレーザ加工される。即ち、銅箔１４は、コンフォーマルマスク法におけるコンフォーマルマスクとなる。また、銅箔１５も、このレーザ光を反射するため、銅箔１５には貫通孔（透孔）は形成されないため、貫通孔１１Ｈは、銅箔１５で塞がれた状態となる。さらに、銅箔１５によってレーザ光が反射するため、入射光と反射光によって貫通孔１４Ｈが確実に形成される。これにより、本実施形態では、直径５０μｍ、最小間隙１５０μｍの貫通孔１１Ｈを多数形成した。
【００４２】
その後、銅箔１４の表面（図中上面）、銅箔１５の表面（図中下面）、銅箔１５の貫通孔１４Ｈ内露出面（図中上面）及び貫通孔１１Ｈの内周面に、無電解銅メッキを施して、厚さ１μｍの無電解銅メッキ層１６，１７をそれぞれ形成する（図３（ｃ）参照）。
さらに、感光性メッキレジストフィルムを無電解メッキ層１６，１７上に貼り付け、露光・現像して、貫通孔１１Ｈ内とその第１主面側開口周縁（直径１２０μｍ）の無電解メッキ層１６、および貫通孔１１Ｈの第２主面側とその開口周縁（直径１２０μｍ）の無電解メッキ層１７が露出するように透孔ＭＲ１Ｈ、ＭＲ２Ｈを有するメッキレジスト層ＭＲ１，ＭＲ２を形成する。ついで、この無電解銅メッキ層１６，１７を共通電極として電解銅メッキを施し、貫通孔１１Ｈ内および第１主面側開口周縁の無電解メッキ層１６上に略凹字形状の厚さ６μｍの電解銅メッキ層１８を、また、貫通孔１１Ｈの第２主面側及びその開口周縁の無電解メッキ層１７上に同厚の電解銅メッキ層１９をそれぞれ形成する（図３（ｄ）参照）。
【００４３】
その後、メッキレジストＭＲ１，ＭＲ２を溶解除去し（図３（ｅ）参照）、露出した無電解銅メッキ層１６，１７及びその下部に位置する銅箔１４，１５をエッチングによって除去することにより、図４（ａ）に示すように、貫通孔１１Ｈ内及びその周縁に略凹形状の凹状導体１２を形成する。この凹状導体１２は、その底部１２Ｔで貫通孔１１Ｈを塞ぎ、側部１２Ｓで貫通孔１１Ｈの内周面を覆い、凹部１２Ｒを形成している。
さらに、図４（ｂ）に示すように、貫通孔１１Ｈの位置に対応した透孔ＭＨを有するマスクＭを用いて、凹部１２Ｒ内およびその第１主面１１Ａ側（図中上方）にＰｂ−Ｓｎ共晶ハンダペーストＳＰを充填・塗布する。この際、貫通孔１１Ｈは、凹状導体１２の底部１２Ｔで塞がれて有底（盲孔）の状態となるので、凹部１２Ｒ内に充填されたＰｂ−Ｓｎ共晶ハンダペーストＳＰが、従来のように（図１３（ａ）参照）脱落することがないため、歩留まり良く充填することができる。
その後、リフロー炉を通して加熱することにより、Ｐｂ−Ｓｎ共晶ハンダペーストを溶解させて、充填ハンダ体１３とし、中継基板１０を完成させる（図１参照）。この中継基板１０では、充填ハンダ体１３のハンダ体積がほぼ一定となるため、充填ハンダ体１３の突出高さもほぼ一定となる。
なお、本実施形態では、銅箔１４をコンフォーマルマスクとして用いたので、レーザ光の照射位置精度を高くする必要がない点で有利である。また、透孔１４Ｈをのぞき、第１主面１１Ａを銅箔１４で覆っているので、複数の貫通孔１１Ｈを一挙に形成できる点でも有利である。
【００４４】
（実施形態２）
ついで、第２の実施の形態について、図５を参照しつつ説明する。本実施形態の中継基板２０は、図５（ａ）に示す部分拡大断面図から容易に理解できるように、上記実施形態１の中継基板１０と略同様であるが、底部１２Ｔの第２主面側面１２ＴＢに略半球状に盛り上がった高温ハンダバンプ２３を備えている点で異なるものである。そこで以下では、同様な部分の説明は省略または簡略化し、異なる部分について説明する。
本実施形態の中継基板２０の高温ハンダバンプ２３は、９０Ｐｂ−１０Ｓｎからなり、凹状導体１２の第２主面側面１２ＴＢに溶着し、略半球状をなしている。このような高温ハンダバンプ２３は、上記したように、例えば、Ｐｂ−Ｓｎ共晶ハンダを溶融させる程度の加熱（２３０℃程度）では溶融しないので、上記実施形態１の場合と、第１主面１１Ａ側で同様に電子部品Ｄ１０，Ｄ２０等と接続することができる。
【００４５】
一方、プリント配線板Ｐ１０と接続する際には、上記実施形態１と異なり、プリント配線板Ｐ１０のパッドＰ１２に予め高温ハンダバンプＰ１３を形成しておく必要が無い。つまり、中継基板２０を介さずに直接電子部品Ｄ１０等をパッドＰ１２に接続する場合と同様に、高温ハンダバンプ２３を用いて、高温ハンダバンプＰ１３の無いパッドＰ１２と接続させることができる（図示しない）。具体的には、高温ハンダバンプ２３、あるいはパッド１２上にＰｂ−Ｓｎ共晶ハンダペーストを塗布しておき、プリント配線板Ｐ１０（但し高温ハンダバンプＰ１３無し）と中継基板２０を重ねて加熱し、Ｐｂ−Ｓｎ共晶ハンダペーストを溶融させて接続する。
従って、中継基板２０を用いれば、予め高温ハンダバンプＰ１３をプリント基板Ｐ１０に形成しておく必要がない。
【００４６】
ついで、この中継基板２０の製造方法について説明する。このうち、図４（ａ）に示す凹状導体１２の形成までは、実施形態１と同様である。その後、図５（ｂ）に示すように、第２主面側面１２ＴＢに対応する位置に透孔Ｍ２Ｈを有するマスクＭ２を用意し、これを中継基板本体１１の第２主面１１Ｂ側に重ねて位置合わせをし、第２主面側面１２ＴＢ上（図５（ｂ）中上方）に、９０Ｐｂ−１０Ｓｎの高温ハンダペーストＳＰ２を塗布する。その後、約３３０℃に加熱して高温ハンダペーストＳＰ２を溶融させ、第２主面側面１２ＴＢに略半球状の高温ハンダバンプ２３を形成する。その後は、上記実施形態１と同様に、凹部１２Ｒ内にＰｂ−Ｓｎ共晶ハンダペーストＳＰを充填し（図４（ｂ）参照）、これを加熱して溶融させることにより、充填ハンダ体１３を形成して中継基板２０を完成させる。
【００４７】
（実施形態３）
さらに、第３の実施形態として、上記実施形態１の中継基板１０とほぼ同様であるが、異なる製造方法によって形成したものについて説明する。この製造方法に使用する中継基板本体３１（図６（ａ）参照）は、実施形態１と同様に、厚さ５０μｍで連続多孔質ＰＴＦＥにエポキシ樹脂を含浸させ硬化させた複合材料からなり、第１主面３１Ａと第２主面３１Ｂとを有し略板状をなす。但し、この中継基板本体３１は、第１主面３１Ａ側には銅箔を有さず、第２主面３１Ｂ側には、所定位置に直径１２０μｍの円状の銅箔３５が被着されている。この中継基板本体３１の第１主面３１Ａ側からＹＡＧレーザの第３高調波を照射する。但し、レーザ光のスポット径を絞り、所定位置、具体的には、円状銅箔３５の略中央に照射するようにして、図６（ｂ）に示すように、銅箔３５の径（１２０μｍ）より小さい直径５０μｍの貫通孔３１Ｈを穿孔する。この際、貫通孔３１Ｈは、平面視、銅箔３５の内部に含まれるように形成する。なお、上記レーザ加工では、銅箔３５は穿孔されないことは実施形態１の場合と同様である。
【００４８】
ついで、銅箔３５の表面（図中下面）、銅箔３５の貫通孔３１Ｈ内露出面（図中上面）及び貫通孔３１Ｈ内周面、第１，第２主面３１Ａ，３１Ｂ上に、無電解銅メッキを施して、厚さ１μｍの無電解銅メッキ層３６，３７を形成する（図６（ｃ）参照）。
さらに、感光性メッキレジストフィルムを無電解メッキ層３６，３７上に貼り付け、露光・現像して、貫通孔３１Ｈ内とその第１主面側開口周縁（直径１２０μｍ）の無電解メッキ層３６、および銅箔３５上の無電解メッキ層３７が露出するようにメッキレジスト層ＭＲ３，ＭＲ４を形成する。ついで、この無電解銅メッキ層３６，３７を共通電極として電解銅メッキを施し、貫通孔３１Ｈ内および第１主面側開口周縁の無電解メッキ層３６上に略凹字形状の厚さ６μｍの電解銅メッキ層３８を、また、貫通孔３１Ｈの第２主面側及びその開口周縁、つまり銅箔３５上の無電解メッキ層３７上（図中下方）に同厚の電解銅メッキ層３９を、それぞれ形成する（図６（ｄ）参照）。
【００４９】
その後、メッキレジストＭＲ３，ＭＲ４を溶解除去し、露出した無電解銅メッキ層３６，３７をエッチングによって除去することにより、図７（ａ）に示すように、貫通孔３１Ｈ内及びその周縁に略凹形状の凹状導体３２を形成する。この凹状導体３２は、上記中継基板１０と同様に、その底部３２Ｔで貫通孔３１Ｈを塞ぎ、側部３２Ｓで貫通孔３１Ｈの内周面を覆い、凹部３２Ｒをなしている。また、凹状導体３２の側部３２Ｓが、第１主面３１Ａのうち貫通孔３１Ｈの第１主面側開口周縁まで延在して第１主面側開口周縁部３２Ｐを形成しており、また、底部３２Ｔは、貫通孔３１Ｈの第２主面側開口周縁まで拡がって第２主面側開口周縁部３２Ｑを形成している
その後は、実施形態１と同様に、マスクＭを用いて凹部３２Ｒ内にＰｂ−Ｓｎ共晶ハンダペーストＳＰを充填し（図４（ｂ）参照）、加熱溶融させて、充填ハンダ体３３を形成する。これにより、図７（ｂ）に示すように、実施形態１の中継基板１０と略同様の中継基板３０が完成する。
【００５０】
この中継基板３０においても、Ｐｂ−Ｓｎ共晶ハンダペーストＳＰを充填・塗布する際に、貫通孔３１Ｈは、凹状導体３２の底部３２Ｔで塞がれて有底（盲孔）の状態となるので、凹部３２Ｒ内に充填されたＰｂ−Ｓｎ共晶ハンダペーストＳＰが、従来のように（図１３（ａ）参照）脱落することがない。従って、中継基板３０においても、充填ハンダ体３３のハンダ体積がほぼ一定となるため、充填ハンダ体３３の突出高さもほぼ一定とすることができる。
なお、中継基板３０では、メッキレジストＭＲ３，ＭＲ４の除去後のエッチングにおいて、厚さの薄い無電解メッキ層３６，３７のみエッチング除去すれば足りるので、強力な薬剤を用いずにソフトエッチングによってエッチングすればよいので、エッチングやその後の処理が容易である点で、優れている。また、第１主面３１Ａ上に、実施形態１における銅箔１４に相当する銅箔を形成する必要がないのでその分安価となる。
【００５１】
（実施形態４）
さらに、第４の実施形態として、上記実施形態１，３の中継基板１０，３０とほぼ同様であるが、これらと異なる製造方法について説明する。この製造方法に使用する中継基板本体４１（図８（ａ）参照）は、実施形態１，３と同様に、厚さ５０μｍで連続多孔質ＰＴＦＥにエポキシ樹脂を含浸させ硬化させた複合材料からなり、第１主面４１Ａと第２主面４１Ｂとを有し略板状をなす。但し、この中継基板本体４１は、第１主面４１Ａ側には、所定位置に外径１２０μｍ、内径５０μｍのリング状銅箔４４が被着され、第２主面４１Ｂ側には、リング状銅箔４４に対応する位置、即ち平面視同心となる位置に直径１２０μｍの円状の銅箔４５が被着されている。この中継基板本体４１の第１主面４１Ａ側からＹＡＧレーザの第３高調波を照射する。但し、レーザ光のスポット径を略８０μｍに絞り、リング状銅箔４４の略中央に照射するようにして、図８（ｂ）に示すように、リング状銅箔４４の内径に従った断面形状（直径５０μｍ）の貫通孔４１Ｈを穿孔する。本実施形態におけるレーザ加工では、銅箔４４，４５は穿孔されないことは実施形態１の場合と同様である。また、容易に理解できるように、リング状銅箔３４は、その内径をマスクパターンとするコンフォーマルマスクとして作用している。
【００５２】
ついで、銅箔４４の表面（図中上面）、銅箔４５の表面（図中下面）、銅箔４５の貫通孔４１Ｈ内露出面（図中上面）及び貫通孔４１Ｈ内周面、第１，第２主面４１Ａ，４１Ｂ上に、無電解銅メッキを施して、厚さ１μｍの無電解銅メッキ層４６，４７を形成する（図９（ａ）参照）。
さらに、感光性メッキレジストフィルムを無電解メッキ層４６，４７上に貼り付け、露光・現像して、貫通孔４１Ｈ内と銅箔４４上、つまり貫通孔４１Ｈ内及びその第１主面側開口周縁（直径１２０μｍ）の無電解メッキ層４６、および銅箔４５上の無電解メッキ層４７が露出するように透孔ＭＲ５Ｈ、ＭＲ６Ｈを有するメッキレジスト層ＭＲ５，ＭＲ６を形成する。ついで、この無電解銅メッキ層４６，４７を共通電極として電解銅メッキを施し、貫通孔４１Ｈ内および第１主面側開口周縁の無電解メッキ層４６上に略凹字形状の厚さ６μｍの電解銅メッキ層４８を、また、貫通孔４１Ｈの第２主面側及びその開口周縁、つまり銅箔４５上の無電解メッキ層４７上（図中下方）に同厚の電解銅メッキ層４９をそれぞれ形成する（図９（ｂ）参照）。
【００５３】
その後、メッキレジストＭＲ５，ＭＲ６を溶解除去する（図９（ｃ）参照）。その後、露出した無電解銅メッキ層４６，４７をエッチングによって除去することにより、図１０（ａ）に示すように、貫通孔４１Ｈ内に略凹形状の凹状導体４２を形成する。この凹状導体４２は、上記中継基板１０と同様に、その底部４２Ｔで貫通孔４１Ｈを塞ぎ、側部４２Ｓで貫通孔４１Ｈの内周面を覆い、凹部４２Ｒをなしている。また、凹状導体４２の側部４２Ｓが、第１主面４１Ａのうち貫通孔４１Ｈの第１主面側開口周縁まで延在して第１主面側開口周縁部４２Ｐを形成しており、また、底部４２Ｔは、貫通孔４１Ｈの第２主面側開口周縁まで拡がって第２主面側開口周縁部４２Ｑを形成している
その後は、実施形態１と同様に、マスクＭを用いて凹部４２Ｒ内にＰｂ−Ｓｎ共晶ハンダペーストＳＰを充填し（図４（ｂ）参照）、加熱溶融させて、充填ハンダ体４３を形成する。これにより、図１０（ｂ）に示すように、実施形態１の中継基板１０と略同様の中継基板４０が完成する。
【００５４】
この中継基板４０においても、中継基板１０，３０と同様に、Ｐｂ−Ｓｎ共晶ハンダペーストＳＰを充填・塗布する際に、貫通孔４１Ｈは、凹状導体４２の底部４２Ｔで塞がれて有底（盲孔）の状態となるので、凹部４２Ｒ内に充填されたＰｂ−Ｓｎ共晶ハンダペーストＳＰが、従来のように（図１３（ａ）参照）脱落することがない。従って、中継基板４０においても、充填ハンダ体４３のハンダ体積がほぼ一定となるため、充填ハンダ体３３の突出高さもほぼ一定とすることができる。
なお、中継基板４０では、中継基板３０と同様に、メッキレジストＭＲ５，ＭＲ６の除去後のエッチングにおいて、厚さの薄い無電解メッキ層４６，４７のみエッチング除去すれば足りるので、強力な薬剤を用いずにソフトエッチングによってエッチングすればよいので、エッチングやその後の処理が容易である点で、優れている。また、リング状銅箔４４を用いてコンフォーマルマスク法によって貫通孔４１Ｈを形成しているので、レーザ光の照射位置精度をあまり高くする必要が無い点でも優れている。
【００５５】
以上において、本発明を実施形態に即して説明したが、本発明は上記実施形態に限定されるものではなく、その要旨を逸脱しない範囲で、適宜変更して適用できることはいうまでもない。
例えば、上記実施形態においては、いずれも貫通孔１１Ｈ等の周縁１１ＡＰ，１１ＢＰにも導体層１２等が拡がって第１，第２主面側開口周縁部１２Ｐ，１２Ｑも形成したものを示したが、これらを形成しないものであっても良い。
また、導体層１２等は、いずれも銅箔及び銅メッキからなるものとしたが、その他の金属、例えば、ニッケル等、あるいは、銅箔や銅メッキ層上にニッケルメッキを施すなど２種以上の金属からなるものとしても良い。
また、上記実施形態においては、充填ハンダ体１３として第１主面１Ａ側に球面状の突出したものを例示したが、溶融時にセラミックやステンレス等ハンダに濡れない平板で各充填ハンダ体の突出高さを規制し、そのまま冷却して、各充填ハンダ体１３の第１主面側頂部が平坦となるようにすると良い。平板の持つ平面に従って平坦化されることにより、各充填ハンダ体のコプラナリティを小さくすることができ、さらに、ハンダバンプとの接続のため再度充填ハンダ体を溶融させた際には、頂部の高さが高くなるため、ハンダバンプとの接続が確実にできるからである。なお、充填ハンダ体の頂部を平坦にするには、溶融後固化した各充填ハンダ体１３等を平面を持つ金型によって押圧して各頂部を平坦にしても良い。
また、上記実施形態では、いずれも無電解メッキと電解メッキを用いて凹状導体１２等を形成したが、無電解メッキのみで凹状導体を形成しても良い。
【図面の簡単な説明】
【図１】実施形態１にかかる中継基板の平面図（ａ）および部分拡大断面図（ｂ）である。
【図２】（ａ）は図１の中継基板にＩＣチップを接続した状態、（ｂ）はさらにプリント配線板を接続した状態を示す説明図である。
【図３】実施形態１にかかる中継基板の製造方法のうち、メッキレジストを除去するまでの工程を示す説明図である。
【図４】実施形態１にかかる中継基板の製造方法のうち、凹部導体にハンダペーストを充填するまでの工程を示す説明図である。
【図５】（ａ）は実施形態２にかかる中継基板の部分拡大断面図、（ｂ）はこの中継基板の製造方法のうち凹状導体の底部側に高温ハンダペーストを塗布する工程を示す説明図である。
【図６】実施形態３にかかる中継基板の製造方法のうち、電解メッキまでの工程を示す説明図である。
【図７】（ａ）は実施形態３の中継基板の製造方法のうちエッチング工程を示す説明図、（ｂ）は実施形態３にかかる中継基板の部分拡大断面図である。
【図８】実施形態４にかかる中継基板の製造方法のうち、貫通孔形成までの工程を示す説明図である。
【図９】実施形態４にかかる中継基板の製造方法のうち、レジスト除去までの工程を示す説明図である。
【図１０】（ａ）は実施形態４の中継基板の製造方法のうちエッチング工程を示す説明図、（ｂ）は実施形態４にかかる中継基板の部分拡大断面図である。
【図１１】（ａ）は従来の中継基板の部分拡大断面図、（ｂ）は上記従来の中継基板の上下にＩＣチップ及びプリント配線板を接続した状態を示す説明図である。
【図１２】図１１（ａ）とは異なる従来の中継基板の部分格段断面図である。
【図１３】（ａ）は貫通孔内に充填したペーストが脱落する様子を説明する説明図、（ｂ）は貫通孔内に充填したペーストを硬化させることにより、ペースト（樹脂）に凹凸ができた状態を示す説明図である。
【符号の説明】
１０，２０，３０，４０中継基板
１１，３１，４１中継基板本体
１１Ａ，３１Ａ，４１Ａ第１主面
１１Ｂ，３１Ｂ，４１Ｂ第２主面
１１Ｈ，３１Ｈ，４１Ｈ貫通孔
１２，３２，４２凹状導体
１２Ｔ，３２Ｔ，４２Ｔ（凹状導体の）底部
１２Ｓ，３２Ｓ，４２Ｓ（凹状導体の）側部
１２Ｒ，３２Ｒ，４２Ｒ（凹状導体の）凹部
１３，３３，４３充填ハンダ体
２３ハンダバンプ[0001]
BACKGROUND OF THE INVENTION
The present invention is provided on terminals of electronic components such as a wiring board on which functional parts and functional parts such as IC chips, transistors, resistors and capacitors are mounted, and printed wiring boards such as a mother board and a daughter board for mounting the terminals. More particularly, the present invention relates to a relay board that can be easily manufactured and that can connect terminals having fine intervals, and a manufacturing method thereof.
[0002]
[Prior art]
Conventionally, when an IC chip is mounted on a printed wiring board as a bare chip, a relay substrate (interposer) is interposed between the IC chip and the printed wiring board in consideration of the difficulty of repair when the IC chip is defective. There is. In particular, when multiple IC chips are mounted on a single printed wiring board, once the multiple IC chips are connected to the relay board and all IC chips are confirmed to be normal, the relay board is printed. Often connected to a wiring board.
[0003]
The structure of such a conventional relay board will be described with reference to FIG. In the relay substrate 110 shown in FIG. 11A, vias 112 such as tungsten and molybdenum are formed in the through holes 111H opened between the two

main surfaces

111A and 111B of the relay substrate body 111 made of alumina ceramic.

Pads

113 and 114 such as tungsten and molybdenum are formed on the

main surfaces

111A and 111B so as to cover the upper and lower sides, respectively. With such a relay substrate 110 interposed, as shown in FIG. 11B, electronic components D10 and D20 such as IC chips are connected to the printed wiring board P10.
[0004]
The electronic components D10 and D20 include a large number of pads D12 and D22 on connection surfaces D11B and D21B (lower surfaces in the drawing) of component bodies D11 and D21 made of silicon, respectively. For example, 95Pb-5Sn) and substantially hemispherical solder bumps D13 and D23 are provided. The printed wiring board P10 corresponds to the pads D12 and D22 (solder bumps D13 and D23) of the electronic components D10 and D20 on the connection surface P11A (upper surface in the drawing) of the wiring board body P11 made of a glass-epoxy resin composite material. In the arrangement, a connection pad P12 made of copper and a substantially hemispherical solder bump P13 made of high-temperature solder are provided. The solder bumps D13 and D23 and the pad 113 of the relay substrate 110 are connected, and the solder bump P13 and the pad 114 are connected by solder (for example, Pb-Sn eutectic solder 37Pb-63Sn) S1, S2 having a melting point lower than that of the high-temperature solder. To do.
[0005]
Other relay boards include those shown in FIG. In this relay substrate 120, a substantially cylindrical through-hole conductor 122 is formed by copper plating in a through hole 121H opened between two

main surfaces

121A and 121B of a relay substrate body 121 made of a glass-epoxy resin composite material. Further, the inside is filled with a plug material 125 made of conductive resin (or insulating resin), and

pads

123 and 124 are formed in a lid shape by copper plating, respectively. This relay board 120 can also be used in connection with the electronic components D10 and D20 and the printed wiring board P10 in the same manner as described above (see FIG. 11).
[0006]
[Problems to be solved by the invention]
However, since the relay board main body 111 is made of ceramic such as alumina, the relay board 110 described above has low toughness and causes problems such as breaking when stressed. Therefore, the thickness of the relay board main body 111 can be reduced. Can not. On the other hand, when the thickness is large, the length of the via 112 becomes long, so that the resistance and inductance of the via 112 become large, which is not preferable in terms of electrical characteristics. Moreover, since the stress resulting from the thermal expansion difference with the printed wiring board P10 will become large when thickness is thick, the connection reliability between both falls.
Further, as shown in FIG. 13A, for example, the relay substrate 110 is formed of tungsten paste in a through hole GH that penetrates the two main surfaces GA and GB of the ceramic green sheet G that becomes the relay substrate body 111 after firing. A conductive paste GP such as the above is filled, and a pad (not shown) is printed and fired. In this case, if the thickness of the green sheet G is small, the ability to hold the conductor paste GP in the through hole GH is poor, so that part or almost all of the conductor paste GP once filled during printing is dropped off. As a result, poor filling tends to occur and the yield decreases. Further, if the amount of the conductive paste GP is not constant, each pad is uneven, the coplanarity is lowered, and the connectivity with the electronic component D10 such as an IC chip is lowered.
[0007]
On the other hand, in the above-described relay board 120, migration occurs along the glass fiber included in the relay board main body 121. Therefore, when the interval between the adjacent through holes 121H is narrowed, for example, 200 μm or less, the relay board 120 has a high temperature. Since the reliability under high-humidity conditions decreases, the interval cannot be reduced. In addition, when the relay substrate 120 is filled with the plug material 125 and thermally cured, the surface 125S becomes uneven as shown in FIG. 13B, so that the surface 125S is flattened by polishing, and then the pad 123 is formed. , 124 is formed. However, if the thickness of the relay substrate main body 121 is reduced, polishing becomes difficult. Similarly to the conductive paste GP, when the thickness of the relay substrate main body 121 is reduced, the plug material (resin) 125 once filled is likely to fall off. Further, since the lid-

like pads

123 and 124 are formed above and below the plug material 125, polishing is performed after the plug material 125 is formed, and further, the

pads

123 and 124 are formed by plating. It is expensive. Further, in order to connect to the solder bump D13 of the electronic component D10 or the like, it is necessary to apply a low melting point solder paste to the pad 123 or the like in advance, and after soldering the electronic component D10 or the like, the solder paste is heated and melted for soldering. is there.
[0008]
The present invention has been made in view of such problems, and an object of the present invention is to provide a relay substrate that has a high yield and that can be easily formed and that can be easily soldered to an electronic component and the like, and a method of manufacturing the same.
[0009]
[Means, actions and effects for solving the problems]
The solving means includes a first main surface and a second main surface, a relay board main body having a through hole penetrating between the two main surfaces, and a bottom portion closing the second main surface side opening of the through hole. A substantially concave concave conductor provided with a side portion covering the inner peripheral surface of the through-hole, and a filling solder body that is filled in the concave portion of the concave conductor and protrudes toward the first main surface side. It is a relay board.
[0010]
According to the present invention, since it has a bottomed concave conductor having a bottom portion and a side portion, a part or all of the solder paste filled by screen printing or the like to make a filled solder body will not fall off, The amount of the filled solder body, and hence the protruding height becomes uniform, and the connectivity with terminals such as bumps and pads of electronic components such as IC chips becomes high. In addition, since there is no fear of dropping off when the solder paste is filled, the thickness of the relay substrate body can be reduced. Moreover, since the filling solder body protrudes to the first main surface side, it can be reliably connected when connecting to pads and bumps of electronic components to be connected.
[0011]
In addition, when the filling solder body is made of a material having a lower melting point than the bumps of the electronic parts and the like connected on the first main surface side, it is lower than the bumps and the like when connecting the electronic parts and the relay substrate. Work such as pre-applying a solder paste having a melting point can be eliminated.
[0012]
Here, the relay substrate body may be appropriately selected in consideration of toughness, insulation, moisture resistance, workability, and the like. For example, epoxy resins, polyimide resins, BT resins, PPE resins and other resins, glass-epoxy resin composite materials, etc., composite materials of these resins and glass fibers (glass woven fabric and glass nonwoven fabric), and these resins and polyamide fibers And a composite material obtained by impregnating a three-dimensional network fluorine-based resin such as continuous porous PTFE with an epoxy resin or the like.
The concave conductor may be selected in consideration of the material of the relay board body, and examples thereof include copper and nickel.
The filling solder body may be selected in consideration of the material of the electronic component such as the IC chip to be connected and the material of the bump of the printed wiring board. For example, Pb—Sn eutectic solder (37Pb-63Sn) may be selected. ) And high-temperature solder (95Pb-5Sn, 90Pb-10Sn, etc.), 96.5Sn-3.5Ag, 95Sn-5Sb solder, and the like.
[0013]
Furthermore, it is preferable that the relay board has the thickness of the relay board body of 200 μm or less.
[0014]
When the thickness of the relay board is thin, even if the through hole is filled with paste or the like as described above, it is liable to drop off later, especially when the thickness of the relay board body is 200 μm or less. It becomes difficult to hold the conductor paste and the resin paste for plug material in the through hole. On the other hand, since the bottomed concave conductor is provided in the present invention, the paste or the like does not fall off. In particular, even in the relay substrate body having a thickness of 200 μm or less, the solder paste is securely held and is uniform. It is possible to form a filling solder body having a proper protruding height. Therefore, the resistance and inductance of the concave conductor and the filled solder body can be further reduced. In addition, when the thickness is reduced, the shape of the concave conductor is relatively shallow at the bottom, which makes it easier to fill the solder paste with the solder paste. The height can be made more uniform. Furthermore, since the thickness of the relay board main body is thin, even if the electronic component and the printed circuit board are connected via the relay board, the overall height is much higher than when the direct connection is made without the relay board interposed. The height does not increase. Accordingly, it is possible to meet the demand for a low profile.
[0015]
Furthermore, in the relay board, a gap between the side portions of the adjacent concave conductors is 200 μm or less, and the relay board body is made of a resin-based composite material that does not contain glass fiber. It is better to use a relay board.
[0016]
When a resin-based composite material is used as the material of the relay substrate body, the thickness of the relay substrate body can be reduced because the toughness is higher than when ceramic such as alumina is used. Therefore, the resistance and inductance of the concave conductor and the filled solder body can be further reduced. In addition, when the thickness is reduced, the filling of the solder paste into the concave conductor becomes easier, and the volume and the protruding height of the filled solder body can be made more uniform.
Moreover, among the cases where resin-based composite materials are used, those containing glass fibers (for example, glass-epoxy resin composite materials) easily form a gap between the resin and the glass fibers when forming a through hole. Resin-based composite material that does not contain glass fiber in the present invention, although it tends to cause short-circuit due to migration of metal such as copper that forms a concave conductor along the surface of the glass fiber due to moisture such as plating solution that has entered the gap. Therefore, even if the gap between the side portions of the concave conductor is a short distance of 200 μm or less, no migration occurs and a highly reliable relay substrate can be obtained.
[0017]
Examples of the resin-based composite material that does not include glass fiber include a composite material of a resin such as epoxy resin, polyimide resin, BT resin, and PPE resin and organic fiber such as polyamide fiber, and three-dimensional such as continuous porous PTFE. Examples thereof include a composite material obtained by impregnating a net-like fluorine-based resin with an epoxy resin or the like.
[0018]
Furthermore, the relay substrate, comprising: a high-temperature solder bump made of solder having a melting point higher than that of the solder constituting the filling solder body on the second main surface side of the bottom of the concave conductor; Good.
[0019]
In general, since solders are compatible with each other even if their compositions are different, when a solder having a high melting point and a solder having a low melting point come into contact with each other in a molten state, the solder gradually mixes and the composition gradually changes.
In the present invention, a filling solder body is provided in the concave portion of the concave conductor, and a high-temperature solder bump having a higher melting point is provided on the second main surface side of the bottom portion of the concave conductor. Can be connected to the pads of the printed wiring board on which the bumps are not formed on the second main surface side.
In addition, at this time, the filled solder body and the high-temperature solder bump are partitioned by the bottom of the concave conductor, and, for example, when forming the high-temperature solder bump or when forming the filled solder body, the composition changes because they do not mix with each other. There is no. That is, the melting point of the filled solder body does not increase, or the melting point of the high-temperature solder bump does not decrease. Therefore, the composition and melting point change due to the compatibility of both the filled solder body and the high-temperature solder bump on the second main surface side even when heated many times for connection and removal to repair the connected IC chip, etc. Therefore, connection and repair can be performed repeatedly under the same conditions.
[0020]
Further, when an electronic component such as an IC chip is connected on the first main surface side, the IC chip or the like and the relay substrate of the present invention are as if an integrated substrate (electronic component having a high-temperature solder bump on the second main surface side). ) Can be easily connected by this high-temperature solder bump to connect it to a printed wiring board such as a mother board.
[0021]
Still another solution is to provide a relay board main body having a first main surface and a second main surface, a through hole that penetrates between the two main surfaces, and a bottom portion that closes the second main surface side opening of the through hole. A through-hole concave conductor forming step of forming a substantially concave concave conductor having a side portion covering the inner peripheral surface of the through-hole, and filling and heating a solder paste into the concave portion of the concave conductor from the first main surface side And a filling solder body forming step of forming a filling solder body that fills the concave conductor and protrudes toward the first main surface side.
[0022]
According to the present invention, since the through hole and the concave conductor are formed in the through hole concave conductor forming step, the solder paste can be reliably filled in the concave portion of the concave conductor in the filling solder body forming step. In addition, since a defect such as part or all of the solder paste falling off does not occur, the relay substrate can be manufactured with a high yield. In addition, since the amount of solder in the filled solder body can be made substantially constant and the protruding height can be made uniform, the connectivity can be enhanced when connecting to an electronic component such as an IC chip on the first main surface side. Moreover, since the filling solder body protrudes to the first main surface side, it can be reliably connected when connecting to pads or bumps of electronic components.
[0023]
Furthermore, another solving means includes a first main surface and a second main surface, and among the two main surfaces, at least the second main surface of the relay substrate body having the second main surface side metal layer, The relay board body can be drilled and the second main surface side metal layer cannot be drilled at a predetermined position having no metal layer on the first main surface and having the second main surface side metal layer only on the second main surface. A through hole forming step of drilling a through hole in which the second main surface side opening is closed by the second main surface side metal layer by laser processing from the first main surface side using a simple laser, and at least the above An exposed surface exposed toward the inside of the through hole in the second main surface side opening of the second main surface side metal layer and an inner peripheral surface in the through hole are plated to form a substantially concave concave conductor. The concave conductor forming step to be formed, and the solder paste is filled in the concave portion of the concave conductor from the first main surface side and heated. Te is a method for producing a connecting board, characterized in that it comprises a filling solder forming step of forming a filling solder bodies filled in the concave conductor projecting said first main surface side.
[0024]
According to the present invention, since the through hole is formed in the relay substrate body by laser processing using a laser that can drill the relay substrate body and cannot drill the second main surface side metal layer, the minute through hole can be drilled with high accuracy. . In addition, since a laser that cannot be drilled is applied to the second main surface side metal layer, the laser beam is reflected by the second main surface side metal layer, so that a through hole can be formed reliably. In addition, since there is no hole in the second main surface side metal layer, it can be used as it is as a base material when forming the bottom in the concave conductor forming step, so that it is easy to open the second main surface side of the through hole. The bottom of the concave conductor can be formed. In other words, the second surface side metal layer serves as a laser stopper (and reflector) in the through hole forming step and contributes to the drilling of the through hole, and is formed by plating in the concave conductor forming step. An exposed surface exposed in the through hole can be formed as a base material of the bottom of the concave conductor.
[0025]
Furthermore, since the bottomed concave conductor is formed, in the filling solder body forming step, the solder paste can be reliably filled in the concave portion of the concave conductor, and there is a problem that part or all of the solder paste is dropped. Since it does not occur, a relay board can be manufactured with high yield. In addition, since the amount of solder in the filled solder body can be made substantially constant and the protruding height can be made uniform, the connectivity can be enhanced when connecting to an electronic component such as an IC chip on the first main surface side. Moreover, since the filling solder body protrudes to the first main surface side, it can be reliably connected when connecting to pads or bumps of electronic components.
[0026]
Furthermore, in the through hole forming step of the above method for manufacturing a relay substrate, the diameter of the second main surface side metal layer that closes the diameter of the second main surface side opening of the through hole is made larger. A method of manufacturing a relay board characterized by
In the through hole forming step, when the diameter of the second main surface side metal layer is larger than the diameter of the second main surface side opening of the through hole to be formed as described above, The opening can be reliably closed by the second principal surface side metal layer.
[0027]
Furthermore, in the manufacturing method of the relay board, the through hole forming step includes at least the through hole of the first main surface side metal layer having a predetermined pattern of through holes on the first main surface and the second main surface. The relay substrate body having a second main surface side metal layer disposed at a position corresponding to the laser beam is irradiated to the through hole of the first main surface side metal layer wider than the through hole, A method for manufacturing a relay substrate, which is a conformal mask through-hole forming step for forming the through-holes having substantially the same cross section, is preferable.
According to the present invention, the through-hole is used as a conformal mask, and the laser is irradiated more widely than the through-hole to form the through-hole having the same diameter as the through-hole. it can. Further, it can be formed even if the positioning accuracy of the laser is low. Moreover, when parts other than the part which forms a through-hole are covered with the 1st main surface side metal layer, a several through-hole can also be formed simultaneously at once.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
A first embodiment according to the present invention will be described with reference to the drawings. FIG. 1A is a plan view of the relay board 10 according to the first embodiment, and FIG. 1B is a partially enlarged sectional view thereof. The relay substrate body 11 having a substantially square plate shape in plan view is made of a resin-resin composite material (thickness: 50 μm) that does not contain glass fiber and is cured by impregnating continuous porous PTFE with an epoxy resin, and has a first main surface 11A. And a second main surface 11B, and a large number of through holes 11H having a diameter of 50 μm that penetrate between the two main surfaces. The smallest gap (clearance) between the through holes 11H is 150 μm. The through hole 11H is formed with a concave conductor 12 made of copper and having a substantially concave shape. The bottom 12T closes the second main surface 11B side opening of the through hole 11H, and the side 12S has the through hole 11H. It arrange | positions so that an internal peripheral surface may be covered. Further, in the concave conductor 12 of the present embodiment, the side portion 12S extends to the first main surface side opening peripheral edge 11AP of the through hole 11H in the first main surface 11A, and the first main surface side opening peripheral edge portion. 12P is formed, and the bottom 12T extends to the second main surface side opening peripheral edge 11BP of the through hole 11H to form the second main surface side opening peripheral edge portion 12Q.
[0029]
Each concave conductor 12 includes a concave portion 12R formed by the concave conductor side portion 12S and the bottom portion 12T, that is, the inner peripheral surface 12SH of the concave conductor side portion 12S and the first main surface side surface (recess portion) of the bottom portion 12T. (Bottom surface) Filled in the recess 12R surrounded by 12TA, further spreads over the first main surface side opening peripheral edge portion 12P, toward the first main surface 11A side (upper in FIG. 1B), A filling solder body 13 protruding in a substantially spherical shape is provided.
This filling solder body 13 is made of Pb—Sn eutectic solder (37Pb-63Sn). As will be described later, this filling solder body 13 is used for connecting bumps of electronic components such as IC chips on the first main surface 11A side. The solder body 13 is melted and connected to bumps or the like.
The through hole 11H, the concave conductor 12 and the filling solder body 13 are arranged at positions corresponding to the arrangement of bumps and the like of the electronic component to be connected. In this embodiment, it can be easily understood from FIG. In addition, the filling solder bodies 13 are arranged separately in four groups, and are arranged in a lattice pattern in plan view, and connect four electronic components (hereinafter represented by electronic components D10 and D20). ing.
[0030]
This relay substrate 10 is used as follows, for example. As shown in FIG. 2A, first, connection is made with electronic components D10, D20... Such as IC chips. That is, the high-temperature solder bumps D13 and D23 that are fixed to the pads D12 and D22 formed on the connection surfaces (lower surfaces in the drawing) D11B and D21B of the electronic component main bodies D11 and D21 and have a substantially hemispherical shape are used as the filling solder body 13 of the relay substrate 10. Connect by soldering. Since the high-temperature solder bumps D13 and D23 are made of, for example, 95Pb-5Sn, only the filled solder body 13 made of Pb-Sn eutectic solder is heated to a melting temperature (for example, 230 ° C.) to melt the filled solder body 13. Then, soldering is performed by making contact with the high-temperature solder bumps D13 and D23. At this time, since the filling solder body 13 protrudes toward the first main surface 11A side, even if the high-temperature solder bumps D13 and D23 have variations in height, or the relay substrate body 11 is warped or wavy, the filling solder The body 13 and the high-temperature solder bump D13 can be reliably connected.
[0031]
Moreover, since it has the filling solder body 13 made of Pb-Sn eutectic solder having a lower melting point than the high-temperature solder bumps D13, D23 of the electronic components D10, D20 connected to the first main surface side, specifically, When the electronic component D10 or the like and the relay substrate 10 are connected, an operation such as applying a solder paste in advance becomes unnecessary.
In addition, since the bottomed concave conductor 12 is disposed in the through hole 11H, as will be described later, when forming the filled solder body 13, the solder paste filled and applied to the concave portion 12R may fall off thereafter. Since the amount of solder paste can be kept constant, the protruding height of the filled solder body 13 is uniform. Therefore, from this point, the connection with the high-temperature solder bump D13 or the like can be ensured. Further, even if the filling solder body 13 is melted, the solder volume of the filling solder body 13 becomes constant from this point because the second main surface side (the second main surface side surface 12TB of the bottom 12T) does not wet and spread. , Connection is ensured.
[0032]
Thereafter, the operation of the connected electronic components D10, D20, etc. is checked, and the defective one is removed and another electronic component is connected again. When any electronic component operates normally, it is further connected to the printed wiring board P10 as shown in FIG.
A high-temperature solder bump P13, which is fixed to a pad P12 formed on a connection surface (upper surface in the drawing) P11A of the printed wiring board main body P11 and has a substantially hemispherical shape, is formed on the bottom 12T of the concave conductor 12 of the relay substrate 10 with a Pb-Sn eutectic solder. Connect by soldering with SL. Specifically, Pb—Sn eutectic solder paste (not shown) is applied in advance to the bottom 12T of the concave conductor 12 or to the high-temperature solder bump P13, and the electronic components D10 and D20 are mounted on the printed wiring board P10. The relay substrate 10 is stacked and heated in a reflow furnace to melt the Pb—Sn eutectic solder paste, and the concave conductor 12 and the high-temperature solder bump P13 are soldered and connected. As a result, each of the electronic components D10, D20... Is connected to the printed wiring board P10 via the relay board 10.
[0033]
In this way, the relay substrate 10 that connects the electronic components D10 and D20 and the printed wiring board P10 is not a composite material containing glass fibers such as a glass-epoxy resin composite material, but is continuous porous as described above. Since it is a resin-resin composite material in which PTFE is impregnated and cured with an epoxy resin, it has high moisture resistance and hardly causes migration. For this reason, a short circuit or the like due to migration does not occur even when the gap between the through holes 11H is set to 150 μm as in the present embodiment.
[0034]
(Comparative forms 1 and 2)
On the other hand, as Comparative Examples 1 and 2, a material containing glass fiber as the material of the relay substrate body, specifically, a glass fiber BT having a thickness of 200 μm in which BT (bismaleimide-triazine) resin is impregnated into a glass fiber woven fabric. Using a resin composite material, a conventional relay substrate (see FIG. 12) having a via diameter (through hole diameter) of 300 μm and a minimum gap between vias of 200 μm and 400 μm was manufactured.
[0035]
(Embodiment 1B)
Further, as Embodiment 1B, it is made of the same material as that of the relay substrate 10 of Embodiment 1 above, but the thickness of the relay substrate body is 200 μm, which is four times thicker, and the concave conductor diameter (through hole diameter) is 50 μm. A relay board having a minimum gap between the concave conductor side portions of 50 μm and 200 μm was also manufactured.
[0036]
(Test example)
A moisture load test was performed using the relay substrate 10 according to the first and first embodiments and the first and second comparative embodiments, and the presence or absence of a decrease in insulation resistance due to the occurrence of migration was compared. Specifically, in a constant temperature and humidity chamber set to a temperature of 85 ° C. × humidity of 85% RH and atmospheric pressure, a voltage of DC 50 V is applied between the vias of each relay substrate and held, and insulation between the vias is made in a timely manner. Resistance (5 V × 60 seconds) was measured, and a period during which an insulation resistance of 100 MΩ or more was maintained was measured. The results are shown in Table 1.
[0037]
[Table 1]

[0038]
As can be seen from Table 1, in Comparative Example 2 in which the minimum gap between vias is 400 μm, the insulation resistance of 100 MΩ or more is maintained for 1000 hours or more, whereas in Comparative Example 1, the insulation resistance is 500 hours. It became 100 MΩ or less. Specifically, copper migration occurred along the glass fiber of the relay substrate body, and an electrical path was formed between the vias. Therefore, when a resin-based composite material containing glass fibers, more specifically, a glass-BT resin composite material is used, the gap between vias may be maintained at about 400 μm, but this gap is 200 μm or less. Then, since migration occurs, it can be seen that the reliability of the relay substrate is significantly reduced.
[0039]
On the other hand, in each of Embodiments 1 and 1B, the insulation resistance of 100 MΩ or more is maintained for 1000 hours or more. In these embodiments, the material of the relay substrate body 11 or the like is a resin-based composite material that does not include glass fiber, specifically, a composite material in which a three-dimensional network fluorine-based resin is impregnated with an epoxy resin or the like, and more specifically Specifically, a resin-resin composite material obtained by impregnating and curing an epoxy resin in continuous porous PTFE was used. For this reason, it is considered that migration did not occur even when the gap between the concave conductors was 200 μm or less, specifically 200 μm (Embodiment 1B), and even 150 μm (Embodiment 1). Therefore, when a resin-based composite material that does not contain glass fiber, specifically, a resin-resin composite material in which continuous porous PTFE is impregnated with an epoxy resin is used for the relay substrate body, the sides of the concave conductors It can be seen that even when the gap is 200 μm or less, and further 150 μm or less, migration does not occur and a highly reliable relay substrate can be obtained.
[0040]
Next, a method for manufacturing the relay board 10 will be described with reference to FIGS. First, as shown in FIG. 3 (a), it is made of a composite material in which continuous porous PTFE is impregnated with an epoxy resin and cured, and has a first main surface 11A and a second main surface 11B. A relay substrate body 11 having a plate shape is prepared. The first main surface 11A of the relay substrate body 11 is provided with a 12 μm thick copper foil 14 having a through hole 14H having a diameter of 50 μm at a predetermined position, and the second main surface 11B is substantially 12 μm thick. The copper foil 15 is applied.
[0041]
Next, from the first main surface 11A side, the third harmonic (355 nm) of the YAG laser is irradiated over a wider range than the through hole 14H, and the through hole 14H is used as a mask pattern, as shown in FIG. A plurality of through-holes 11H having substantially the same cross section as the through-holes 14H are formed in the relay substrate body 11 at once. Since this laser beam is reflected by the copper foil 14, only the inside of the through hole 14H without the copper foil 14 is laser processed. That is, the copper foil 14 becomes a conformal mask in the conformal mask method. Further, since the copper foil 15 also reflects this laser beam, no through hole (through hole) is formed in the copper foil 15, so that the through hole 11 </ b> H is closed with the copper foil 15. Furthermore, since the laser light is reflected by the copper foil 15, the through hole 14H is reliably formed by the incident light and the reflected light. Thereby, in this embodiment, a large number of through holes 11H having a diameter of 50 μm and a minimum gap of 150 μm were formed.
[0042]
Thereafter, the surface of the copper foil 14 (upper surface in the figure), the surface of the copper foil 15 (lower surface in the figure), the exposed surface in the through hole 14H (upper surface in the figure), and the inner peripheral surface of the through hole 11H are not present. Electroless copper plating is performed to form electroless copper plating layers 16 and 17 each having a thickness of 1 μm (see FIG. 3C).
Further, a photosensitive plating resist film is applied onto the electroless plating layers 16 and 17, exposed and developed, and the electroless plating layer 16 in the through-hole 11H and the first main surface side opening periphery (diameter 120 μm), Further, plating resist layers MR1 and MR2 having through holes MR1H and MR2H are formed so as to expose the electroless plating layer 17 on the second main surface side of the through hole 11H and the peripheral edge of the opening (diameter 120 μm). Next, electrolytic copper plating is performed using the electroless copper plating layers 16 and 17 as a common electrode, and a substantially concave-shaped thickness of 6 μm is formed on the electroless plating layer 16 in the through hole 11H and on the peripheral edge of the first main surface side opening. The electrolytic copper plating layer 18 and the electrolytic copper plating layer 19 having the same thickness are formed on the second main surface side of the through hole 11H and the electroless plating layer 17 on the periphery of the opening (see FIG. 3D). .
[0043]
Thereafter, the plating resists MR1 and MR2 are dissolved and removed (see FIG. 3E), and the exposed electroless copper plating layers 16 and 17 and the copper foils 14 and 15 located therebelow are removed by etching. As shown to 4 (a), the concave conductor 12 of a substantially concave shape is formed in the through-hole 11H and its periphery. The concave conductor 12 closes the through hole 11H at the bottom 12T, covers the inner peripheral surface of the through hole 11H at the side 12S, and forms a recess 12R.
Further, as shown in FIG. 4B, using a mask M having a through hole MH corresponding to the position of the through hole 11H, Pb− is formed in the recess 12R and on the first main surface 11A side (upper side in the drawing). Fill and apply Sn eutectic solder paste SP. At this time, since the through-hole 11H is closed by the bottom 12T of the concave conductor 12 and becomes a bottomed (blind hole) state, the Pb—Sn eutectic solder paste SP filled in the recess 12R is replaced with a conventional one. As shown in FIG. 13 (a), since it does not fall off, it can be filled with a high yield.
Thereafter, by heating through a reflow furnace, the Pb—Sn eutectic solder paste is dissolved to form a filled solder body 13 to complete the relay substrate 10 (see FIG. 1). In this relay substrate 10, the solder volume of the filling solder body 13 is substantially constant, so that the protruding height of the filling solder body 13 is also substantially constant.
In this embodiment, since the copper foil 14 is used as a conformal mask, it is advantageous in that it is not necessary to increase the irradiation position accuracy of the laser beam. Further, since the first main surface 11A is covered with the copper foil 14 except for the through holes 14H, it is advantageous in that a plurality of through holes 11H can be formed at a time.
[0044]
(Embodiment 2)
Next, a second embodiment will be described with reference to FIG. The relay board 20 of the present embodiment is substantially the same as the relay board 10 of the first embodiment, as can be easily understood from the partially enlarged sectional view shown in FIG. 5A, but the second main surface of the bottom 12T. This is different in that a high-temperature solder bump 23 swelled in a substantially hemispherical shape is provided on the side surface 12TB. Therefore, in the following, description of similar parts will be omitted or simplified, and different parts will be described.
The high-temperature solder bumps 23 of the relay substrate 20 of the present embodiment are made of 90Pb-10Sn, and are welded to the second main surface side surface 12TB of the concave conductor 12 to form a substantially hemispherical shape. As described above, such a high-temperature solder bump 23 does not melt, for example, by heating (about 230 ° C.) to the extent that Pb—Sn eutectic solder is melted, and therefore, in the case of the first embodiment, the first main surface 11A. Similarly, the electronic components D10 and D20 can be connected on the side.
[0045]
On the other hand, when connecting to the printed wiring board P10, unlike the first embodiment, it is not necessary to previously form the high-temperature solder bumps P13 on the pads P12 of the printed wiring board P10. That is, as in the case where the electronic component D10 or the like is directly connected to the pad P12 without using the relay substrate 20, the high temperature solder bump 23 can be used to connect to the pad P12 without the high temperature solder bump P13 (not shown). Specifically, a Pb—Sn eutectic solder paste is applied on the high-temperature solder bumps 23 or the pads 12, and the printed wiring board P10 (but no high-temperature solder bumps P13) and the relay substrate 20 are overlaid and heated, and Pb− The Sn eutectic solder paste is melted and connected.
Therefore, if the relay substrate 20 is used, it is not necessary to previously form the high-temperature solder bump P13 on the printed circuit board P10.
[0046]
Next, a method for manufacturing the relay board 20 will be described. Among these, the process up to the formation of the concave conductor 12 shown in FIG. Thereafter, as shown in FIG. 5B, a mask M2 having a through hole M2H at a position corresponding to the second main surface side surface 12TB is prepared, and this is overlaid on the second main surface 11B side of the relay substrate body 11. Alignment is performed, and 90Pb-10Sn high-temperature solder paste SP2 is applied on the second main surface side surface 12TB (upper in FIG. 5B). Thereafter, the high-temperature solder paste SP2 is melted by heating to about 330 ° C., and a substantially hemispherical high-temperature solder bump 23 is formed on the second main surface side surface 12TB. Thereafter, as in the first embodiment, the Pb—Sn eutectic solder paste SP is filled in the recess 12R (see FIG. 4B), and this is heated and melted, whereby the filled solder body 13 is formed. Then, the relay substrate 20 is completed.
[0047]
(Embodiment 3)
Furthermore, as a third embodiment, a description will be given of what is substantially the same as the relay substrate 10 of the first embodiment, but is formed by a different manufacturing method. The relay substrate body 31 (see FIG. 6A) used in this manufacturing method is composed of a composite material in which continuous porous PTFE is impregnated with epoxy resin and cured, as in the first embodiment. The first main surface 31A and the second main surface 31B have a substantially plate shape. However, the relay substrate body 31 does not have a copper foil on the first main surface 31A side, and a circular copper foil 35 having a diameter of 120 μm is attached to a predetermined position on the second main surface 31B side. Yes. The third harmonic of the YAG laser is irradiated from the first main surface 31A side of the relay substrate body 31. However, the spot diameter of the laser beam is narrowed down and irradiated to a predetermined position, specifically, approximately the center of the circular copper foil 35, and as shown in FIG. 6B, the diameter of the copper foil 35 (120 μm). ) A through hole 31H having a smaller diameter of 50 μm is drilled. At this time, the through hole 31H is formed so as to be included in the copper foil 35 in a plan view. In the laser processing, the copper foil 35 is not perforated as in the case of the first embodiment.
[0048]
Next, the surface of the copper foil 35 (lower surface in the figure), the exposed surface in the through hole 31H (upper surface in the figure), the inner peripheral surface of the through hole 31H, and the first and second

main surfaces

31A and 31B are not present. Electroless copper plating is performed to form electroless copper plating layers 36 and 37 having a thickness of 1 μm (see FIG. 6C).
Further, a photosensitive plating resist film is applied onto the electroless plating layers 36, 37, exposed and developed, and the electroless plating layer 36 in the through hole 31H and the opening periphery of the first main surface side (diameter 120 μm), The plating resist layers MR3 and MR4 are formed so that the electroless plating layer 37 on the copper foil 35 is exposed. Next, electrolytic copper plating is performed using the electroless copper plating layers 36 and 37 as a common electrode, and a substantially concave shape with a thickness of 6 μm is formed on the electroless plating layer 36 in the through hole 31H and on the periphery of the first main surface side opening. The electrolytic copper plating layer 38 is formed on the second main surface side of the through hole 31H and the peripheral edge of the opening, that is, on the electroless plating layer 37 on the copper foil 35 (downward in the drawing). , Respectively (see FIG. 6D).
[0049]
Thereafter, the plating resists MR3 and MR4 are dissolved and removed, and the exposed electroless copper plating layers 36 and 37 are removed by etching, so that substantially concave portions are formed in and around the through hole 31H as shown in FIG. A concave conductor 32 having a shape is formed. Similar to the relay substrate 10, the concave conductor 32 closes the through hole 31H at the bottom 32T, covers the inner peripheral surface of the through hole 31H at the side 32S, and forms a concave 32R. Further, the side portion 32S of the concave conductor 32 extends to the first main surface side opening peripheral edge of the through hole 31H in the first main surface 31A to form the first main surface side opening peripheral edge portion 32P. The bottom portion 32T extends to the second main surface side opening peripheral edge of the through hole 31H to form the second main surface side opening peripheral edge portion 32Q.
Thereafter, similarly to the first embodiment, the Pb—Sn eutectic solder paste SP is filled in the recesses 32R using the mask M (see FIG. 4B), and is heated and melted to form the filled solder body 33. To do. Thereby, as shown in FIG.7 (b), the relay board | substrate 30 substantially the same as the relay board | substrate 10 of Embodiment 1 is completed.
[0050]
Also in this relay substrate 30, when filling and applying the Pb—Sn eutectic solder paste SP, the through hole 31 </ b> H is closed by the bottom portion 32 </ b> T of the concave conductor 32 and becomes a bottomed (blind hole) state. The Pb—Sn eutectic solder paste SP filled in the recess 32R does not fall off as in the conventional case (see FIG. 13A). Therefore, also in the relay substrate 30, the solder volume of the filling solder body 33 becomes substantially constant, so that the protruding height of the filling solder body 33 can be made almost constant.
In the relay substrate 30, only the thin electroless plating layers 36 and 37 need only be removed by etching after removing the plating resists MR3 and MR4. Therefore, the intermediate substrate 30 can be etched by soft etching without using a strong chemical. Therefore, it is excellent in that etching and subsequent processing are easy. Moreover, since it is not necessary to form a copper foil corresponding to the copper foil 14 in the first embodiment on the first main surface 31A, the cost is reduced accordingly.
[0051]
(Embodiment 4)
Further, as a fourth embodiment, a manufacturing method that is substantially the same as the

relay boards

10 and 30 of the first and third embodiments, but is different from these, will be described. The relay substrate body 41 (see FIG. 8A) used in this manufacturing method is made of a composite material in which continuous porous PTFE is impregnated with epoxy resin and cured, as in the first and third embodiments. The first main surface 41A and the second main surface 41B have a substantially plate shape. However, the relay substrate body 41 is provided with a ring-shaped copper foil 44 having an outer diameter of 120 μm and an inner diameter of 50 μm at predetermined positions on the first main surface 41A side, and a ring-shaped copper surface on the second main surface 41B side. A circular copper foil 45 having a diameter of 120 μm is deposited at a position corresponding to the foil 44, that is, a position that is concentric in plan view. The third harmonic of the YAG laser is irradiated from the first main surface 41A side of the relay substrate body 41. However, the spot diameter of the laser beam is reduced to about 80 μm and irradiated to the approximate center of the ring-shaped copper foil 44, so that the cross-sectional shape according to the inner diameter of the ring-shaped copper foil 44 is shown in FIG. A through hole 41H having a diameter of 50 μm is drilled. In the laser processing in the present embodiment, the copper foils 44 and 45 are not perforated as in the case of the first embodiment. Further, as can be easily understood, the ring-shaped copper foil 34 acts as a conformal mask whose inner diameter is a mask pattern.
[0052]
Next, the surface of the copper foil 44 (upper surface in the figure), the surface of the copper foil 45 (lower surface in the figure), the exposed surface in the through hole 41H (upper surface in the figure), the inner peripheral surface of the through hole 41H, the first, Electroless copper plating is performed on the second

main surfaces

41A and 41B to form electroless copper plating layers 46 and 47 having a thickness of 1 μm (see FIG. 9A).
Further, a photosensitive plating resist film is applied onto the electroless plating layers 46 and 47, exposed and developed, and then the inside of the through hole 41H and the copper foil 44, that is, the inside of the through hole 41H and its peripheral edge on the first main surface side. Plating resist layers MR5 and MR6 having through holes MR5H and MR6H are formed so that the electroless plating layer 46 having a diameter of 120 μm and the electroless plating layer 47 on the copper foil 45 are exposed. Next, electrolytic copper plating is performed using the electroless copper plating layers 46 and 47 as a common electrode, and a substantially concave-shaped thickness of 6 μm is formed on the electroless plating layer 46 in the through hole 41H and on the periphery of the first main surface side opening. The electrolytic copper plating layer 48 is formed on the second main surface side of the through hole 41H and the peripheral edge of the opening, that is, on the electroless plating layer 47 on the copper foil 45 (downward in the figure). Each is formed (see FIG. 9B).
[0053]
Thereafter, the plating resists MR5 and MR6 are dissolved and removed (see FIG. 9C). Thereafter, the exposed electroless copper plating layers 46 and 47 are removed by etching, thereby forming a substantially concave concave conductor 42 in the through hole 41H as shown in FIG. Similar to the relay substrate 10, the concave conductor 42 closes the through hole 41H at the bottom 42T, covers the inner peripheral surface of the through hole 41H at the side 42S, and forms a concave 42R. Further, the side portion 42S of the concave conductor 42 extends to the first main surface side opening peripheral edge of the through hole 41H in the first main surface 41A to form the first main surface side opening peripheral edge portion 42P, and The bottom portion 42T extends to the second main surface side opening peripheral edge of the through hole 41H to form a second main surface side opening peripheral edge portion 42Q.
After that, as in the first embodiment, the Pb—Sn eutectic solder paste SP is filled into the recesses 42R using the mask M (see FIG. 4B), and is heated and melted to form the filled solder body 43. To do. As a result, as shown in FIG. 10B, a relay board 40 substantially the same as the relay board 10 of the first embodiment is completed.
[0054]
In the relay substrate 40 as well as the

relay substrates

10 and 30, when filling and applying the Pb—Sn eutectic solder paste SP, the through hole 41H is closed by the bottom portion 42T of the concave conductor 42. Since it is in a (blind hole) state, the Pb—Sn eutectic solder paste SP filled in the recess 42R does not fall off as in the conventional case (see FIG. 13A). Therefore, also in the relay substrate 40, since the solder volume of the filling solder body 43 becomes substantially constant, the protruding height of the filling solder body 33 can also be made almost constant.
Note that, in the relay substrate 40, as in the relay substrate 30, only the thin electroless plating layers 46 and 47 need only be removed by etching after the removal of the plating resists MR5 and MR6. Therefore, it is excellent in that the etching and subsequent processing are easy. Moreover, since the through-hole 41H is formed by the conformal mask method using the ring-shaped copper foil 44, it is also excellent in that it is not necessary to increase the laser beam irradiation position accuracy.
[0055]
In the above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the above embodiments, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.
For example, in the above-described embodiment, the conductor layers 12 and the like extend to the peripheral edges 11AP and 11BP such as the through holes 11H, and the first and second main surface side opening

peripheral edges

12P and 12Q are also formed. These may not be formed.
The conductor layer 12 and the like are both made of copper foil and copper plating, but other metals such as nickel, or two or more kinds such as nickel plating on the copper foil or copper plating layer It may be made of metal.
In the above-described embodiment, the filling solder body 13 is illustrated as a spherical protrusion on the first main surface 1A side. However, the protrusion height of each filling solder body is a flat plate that does not get wet with solder such as ceramic or stainless steel during melting. It is preferable to regulate the thickness and cool as it is so that the top portion on the first main surface side of each filled solder body 13 becomes flat. By flattening according to the plane of the flat plate, it is possible to reduce the coplanarity of each filled solder body. This is because the connection with the solder bump can be ensured because the height is increased. In order to flatten the top of the filled solder body, each filled solder body 13 or the like solidified after melting may be pressed with a flat mold to flatten the top.
Moreover, in the said embodiment, although the concave conductor 12 etc. were formed using electroless plating and electrolytic plating, you may form a concave conductor only by electroless plating.
[Brief description of the drawings]
1A and 1B are a plan view and a partially enlarged cross-sectional view, respectively, of a relay board according to Embodiment 1;
2A is an explanatory view showing a state in which an IC chip is connected to the relay board of FIG. 1, and FIG. 2B is an explanatory view showing a state in which a printed wiring board is further connected.
FIG. 3 is an explanatory view showing steps until a plating resist is removed in the relay substrate manufacturing method according to the first embodiment;
FIG. 4 is an explanatory diagram showing steps until a recessed conductor is filled with a solder paste in the relay board manufacturing method according to the first embodiment;
5A is a partially enlarged cross-sectional view of a relay board according to a second embodiment, and FIG. 5B is an explanatory view showing a process of applying a high-temperature solder paste to the bottom side of a concave conductor in the relay board manufacturing method. It is.
FIG. 6 is an explanatory view showing steps up to electrolytic plating in the relay substrate manufacturing method according to the third embodiment.
7A is an explanatory view showing an etching step in the method for manufacturing a relay substrate according to the third embodiment, and FIG. 7B is a partially enlarged sectional view of the relay substrate according to the third embodiment.
FIG. 8 is an explanatory view showing steps up to formation of a through hole in the relay substrate manufacturing method according to the fourth embodiment.
FIG. 9 is an explanatory diagram showing steps up to resist removal in the relay substrate manufacturing method according to the fourth embodiment.
10A is an explanatory view showing an etching process in the method of manufacturing a relay board according to the fourth embodiment, and FIG. 10B is a partially enlarged sectional view of the relay board according to the fourth embodiment.
11A is a partially enlarged cross-sectional view of a conventional relay board, and FIG. 11B is an explanatory view showing a state in which an IC chip and a printed wiring board are connected to the upper and lower sides of the conventional relay board.
12 is a partial cross-sectional view of a conventional relay board different from FIG.
FIGS. 13A and 13B are explanatory diagrams for explaining how the paste filled in the through-holes falls off, and FIG. 13B shows that the paste filled in the through-holes is cured to make the paste (resin) uneven. It is explanatory drawing which shows the state.
[Explanation of symbols]
10, 20, 30, 40 Relay board
11, 31, 41 Relay board body
11A, 31A, 41A First main surface
11B, 31B, 41B Second main surface
11H, 31H, 41H Through hole
12, 32, 42 Concave conductor
12T, 32T, 42T (concave conductor) bottom
12S, 32S, 42S (concave conductor) side
12R, 32R, 42R (concave)
13, 33, 43 Filled solder body
23 Solder bump

Claims

A relay board body having a first main surface and a second main surface, and having a through-hole penetrating between the two main surfaces;
A substantially concave concave conductor comprising a bottom portion that covers the second main surface side opening of the through hole and a side portion that covers the inner peripheral surface of the through hole;
A relay board comprising: a filling solder body which is filled in a concave portion of the concave conductor and protrudes toward the first main surface side.

The relay board according to claim 1,
A relay board having a thickness of the relay board body of 200 μm or less.

The relay board according to claim 1 or 2,
The gap between the side portions of the adjacent concave conductors is 200 μm or less,
The relay board is characterized in that the relay board body is made of a resin-based composite material that does not contain glass fibers.

The relay board according to claim 1 or 2,
A relay board comprising a high-temperature solder bump made of solder having a melting point higher than that of the solder forming the filling solder body on the second main surface side of the bottom of the concave conductor.

A relay board main body having a first main surface and a second main surface is provided with a through hole penetrating between the two main surfaces, a bottom portion closing the second main surface side opening of the through hole, and an inner peripheral surface of the through hole. A through hole concave conductor forming step of forming a substantially concave concave conductor having a side portion to be covered; and
Filling solder body forming step of filling a solder paste into the concave portion of the concave conductor from the first main surface side and heating to form a filled solder body that fills the concave conductor and protrudes toward the first main surface side When,
A method for producing a relay board, comprising:

Of the two main surfaces, a metal layer on the first main surface of the relay board body having a second main surface side metal layer on at least the second main surface of the two main surfaces. The first substrate using the laser that can drill the relay substrate body and cannot drill the second main surface side metal layer at a predetermined position having the second main surface side metal layer only on the second main surface. A through hole forming step of drilling a through hole in which the second main surface side opening is blocked by the second main surface side metal layer by laser processing from the main surface side;
At least the exposed surface exposed toward the inside of the through hole in the second main surface side opening of the second main surface side metal layer and the inner peripheral surface of the through hole are plated to form a substantially concave shape. A concave conductor forming step of forming a conductor;
Filling solder body forming step of filling a solder paste into the concave portion of the concave conductor from the first main surface side and heating to form a filled solder body that fills the concave conductor and protrudes toward the first main surface side When,
A method for producing a relay board, comprising:

In the manufacturing method of the relay substrate according to claim 6,
A method for manufacturing a relay substrate, wherein the diameter of the second main surface side metal layer that closes the diameter of the second main surface side opening of the through hole is made larger.

In the manufacturing method of the relay substrate of Claim 6 or Claim 7,
The through hole forming step includes a first main surface side metal layer having a predetermined pattern of through holes on the first main surface and a second main surface disposed at a position corresponding to the through holes at least among the second main surface. The relay substrate body having a surface-side metal layer is irradiated with a laser wider than the through-hole in the first main surface-side metal layer to form the through-hole having substantially the same shape as the through-hole. A method for manufacturing a relay substrate, which is a formal mask through-hole forming step.