JP2004319570A

JP2004319570A - Method of manufacturing planar coil

Info

Publication number: JP2004319570A
Application number: JP2003107598A
Authority: JP
Inventors: 喜久 ▲高▼瀬; Yoshihisa Takase; Toshio Sugawa; 俊夫須川; Takashi Ida; 隆伊田; Hiroshi Wada; 弘志和田; 昌博 ▲高▼木; Masahiro Takagi; Akihiro Akiyama; 昭博秋山
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 2003-04-11
Filing date: 2003-04-11
Publication date: 2004-11-11

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a planar coil that is reduced in interline interval and in dead space and increased in space factor for reducing the size and thickness of the coil. <P>SOLUTION: In this method of manufacturing the planar coil, a resist pattern 203 is formed so as to spirally expose the surface of an aluminum base conductor layer 201 of an insulating substrate 202 in which at least one base conductor layer 201 is composed of aluminum, and the surface of the spirally exposed aluminum is reformed. Then first electroplating is performed for forming center conductors having rectangular cross sections by laminating center conductor layers 207 upon another, by repeating the formation of the conductors by electric copper plating and local etching by using an aluminum base conductor layer 204 containing the surface-reformed aluminum as a base and the resist pattern 203 and base conductor layer 201 underlying the pattern 203 are collectively removed. Thereafter, a surface conductor layer 208 is formed by performing electric copper plating by using the center conductors 207 as bases, and second electroplating is performed for completing conductor wires 209 composed of the center conductors and surface conductor layers covering the center conductors. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、産業機器、民生機器等の各種電気製品（スピーカ、トランス、モータなど）に広く利用可能な平面コイルの製造方法に関するものである。
【０００２】
【従来の技術】
近年、電子機器の全般的な小型・薄型化に伴い、これらに用いられる平面コイルについても小型化、薄型化することが強く求められている。そのためには、線間が狭くデッドスペースの少ない、つまり高占積率コイルを作製する必要がある。ここで、占積率について説明しておく。ここで言う占積率とは、平面コイルのコイル導体線条が延びる方向に垂直な断面において、コイル導体線条の配列ピッチを幅としコイル導体線条の厚さを高さとする矩形領域に対するコイル導体線条の断面積の比率を意味する。従って、高占積率コイルとする為には、コイル導体線条の形を矩形にしかつ線間を狭くすれば良い。
【０００３】
この高占積率コイルの作製のために、従来から、プリント配線板技術を応用した製造方法が提案されている。その代表的な技術として、めっきによる方法が知られている。この方法としては、絶縁基板上に予め形成した下地導体層の表面にコイル部以外の部分を被覆するようにレジストを形成し、下地導体層を下地として、直流電流による第１の電気めっきを行うことにより中心導体層を形成する。その後、レジストパターンを剥離した後、レジストパターンの剥離により露出した下地導体層をエッチングによって除去する。その後、中心導体を下地として直流電流による第２の電気めっきを行い、中心導体を被覆する表面導体層からなる導体線条を形成し平面コイルを作製していた。
【０００４】
なお、この出願の発明に関連する先行技術文献情報としては、例えば、特許文献１、特許文献２が知られている。
【０００５】
【特許文献１】
特開平５−７５２３７号公報
【特許文献２】
特開２００１−２６７１６６号公報
【０００６】
【発明が解決しようとする課題】
前記めっき方法は、高占積率コイル作製の為の一つの方法であるが、従来は電気めっきの欠点である多面付けしたワークの周辺、あるいはコイルパターンの形状により、電流の集中する箇所が発生し、電流集中部の導体が厚く形成され、コイルパターンを数個或いは数十個と面付けした場合、めっき厚さにバラツキが発生し、ワークサイズの大きい多数個取りができず量産性に劣っていた。また、下地導体層をエッチングする時、導体線条の金属もエッチングされてしまうため、導体線条の厚さが削られると共にサイドエッチングも発生するため、導体線条が細くなり、結果として占積率が低くなるという問題を有していた。
【０００７】
そこで、本発明は、産業機器、民生機器等の各種電気製品に広く利用可能の高占積率で面内バラツキの小さいコイル導体線条を有する平面コイルを多量に製造する方法を提供することを目的とするものである。
【０００８】
【課題を解決するための手段】
上記問題を解決するために、本発明は以下の構成を有する。
【０００９】
本発明の請求項１に記載の発明は、絶縁基板に下地導体層を形成する下地導体層形成工程と、前記下地導体層の表面が螺旋状に露出するようにレジストパターンを形成するレジストパターン形成工程と、前記下地導体層を下地として電気めっきによる導体の形成と局部エッチングを繰り返しながら中心導体層を積層し、断面がほぼ矩形の中心導体を形成する第１の電気めっき工程と、前記レジストパターンを剥離する工程と、前記レジストパターンの剥離によって露出した下地導体層をエッチングにより除去するエッチング工程と、前記中心導体を下地として直流電流による電気めっきを行うことにより、前記中心導体とこれを被覆する表面導体層とからなる導体線条を完成させる第２の電気めっき工程で構成されている。
【００１０】
多面付けしたワークに電気めっきを行う際、通常の直流電流による電気めっきでは多面付けしたワークの周辺やコイルパターンの形状により、部分的に電流の集中する箇所が発生し、電流集中部の導体が厚く形成され、コイルパターンを数個或いは数十個と面付けした場合にめっき厚さにバラツキが発生し、ワークサイズの大きい多数個取りができず量産性に劣っていたのに対して、本発明のように、電気めっきによる導体の形成と局部エッチングを繰り返して中心導体層を積層すると、電流集中部に余分に形成された余分な導体を局部エッチングによって除去しながら電気めっきによって導体層を形成するようになるので、多面付けしたワークやコイルパターンの形状によらずバラツキの少ない均一なめっきをすることができる。つまり、第１の電気めっきは、電気めっきによる導体の形成と局部エッチングを繰り返しながら中心導体層を積層することにより、多面付けワークの面内めっきの均一性を重視し、第２の電気めっきは直流電流印加により、コイル形状のコントロールを重視したものであり、第１電気めっきにより形成された矩形の中心導体を第２の電気めっきで被覆する表面導体層の形状を直流電流の電流密度を変えることにより導体線条の縦／横比を１．０〜２．０内でのコントロールを可能とすることができる等、所望の高占積率のコイル導体線条を有した平面コイルおよび量産性に優れた製造方法を提供するものである。
【００１１】
請求項２に記載の発明は、下地導体層の厚さが１μｍ以上５μｍ以下である請求項１記載の平面コイルの製造方法であって、１μｍ以下では下地導体層の電気抵抗が高くなり第１の電気めっきの給電が均一にいかず、めっき厚にバラツキが生じやすく、また、絶縁基板と中心導体層との密着が不充分となる。一方５μｍ以上になると第１の電気めっき後、レジストパターンの剥離によって露出した下地導体層をエッチングにより除去する際、中心導体を形成する金属もエッチングされるため中心導体層の形状が細くなりすぎ、表面導体層を形成する第２の電気めっきでの形状コントロールの範囲を越え、高占積率のコイルを形成するのが困難となる。
【００１２】
請求項３に記載の発明は、下地導体層の厚さがスライスエッチング法により制御されて形成された請求項１記載の平面コイルの製造方法であって、下地導体層をスライスエッチング法により１μｍ以上５μｍ以下の所望の厚さにすることである。銅箔が５μｍ以下になると銅箔を絶縁基板に貼り付ける際、作業性が悪く銅箔にしわが入ったりする。本発明では、通常の３５，１８，１２μｍの銅箔を硫酸過酸化水素系のエッチング液でスライスエッチングを行うことにより面内バラツキの小さい所望の厚みにすることを特徴としている。
【００１３】
請求項４に記載の発明は、下地導体層がアルミニウムからなり、アルミニウム下地導体層の表面を螺旋状に露出するようにレジストパターンを形成し、前記螺旋状に露出したアルミニウム表面を改質し、前記アルミニウム表面改質処理を施したアルミニウム下地導体層を下地として電気銅めっきによる導体の形成と局部エッチングを繰り返しながら中心導体層を積層することにより、断面がほぼ矩形の中心導体を形成する第１の電気めっきを行い、前記レジストパターンと前記レジストパターン下部の下地導体層とを一括除去し、前記中心導体を下地として電気銅めっきを行うことにより前記中心導体とこれを被覆する表面導体層とからなる導体線条を完成させることを特徴としている。
【００１４】
下地導体層にアルミニウムを採用し、中心導体層、表面導体層に銅めっきを用いることにより、水酸化ナトリウム溶液で銅を侵さずに、下地導体層であるアルミニウムを除去でき、しかも、めっきレジストも一括除去することができる。このことにより、銅めっきで形成した中心導体層の矩形形状を壊さずに表面導体層を形成することができるため、さらに、占積率の向上した平面コイルを提供できる。また、めっきレジストと下地導体層とを一括除去することができ、低コストで生産性にも優れた製造方法を提供するものである。
【００１５】
請求項５に記載の発明は、電気めっきに用いるめっき液が、硫酸銅めっき液である請求項１または請求項４に記載の平面コイルの製造方法であって、硫酸銅めっき液を用いているので、経済的かつ液の管理が容易である。
【００１６】
請求項６に記載の発明は、局部エッチングが、電気めっきと同一のめっき液中で、導体形成とは逆の負電流を印加して行う電解エッチングである請求項１または請求項４に記載の平面コイルの製造方法であって、電気めっきと同一のめっき液中で電気めっきによる導体形成と逆の電流を印加する電解エッチングを繰り返して中心導体層を積層するために、電流集中部に余分に形成された余分な導体を電解エッチングによって除去しながら導体層を形成するようになるので、多面付けしたワークやコイルパターンの形状によらずバラツキの少ない均一なめっきをすることができる。
【００１７】
請求項７に記載の発明は、局部エッチングのために流す負電流の電流密度が、表面導体層の導体形成のために流す正電流の電流密度よりも大きい請求項１または請求項４に記載の平面コイルの製造方法であって、局部エッチングのために流す負電流の電流密度が、導体形成のために流す正電流の電流密度よりも大きいために、導体形成時に多面付けしたワークの周辺やコイルパターンの形状により、部分的に電流の集中する箇所に余分に形成された余分なめっきを優先的にエッチングすることになるため、多面付けしたワークやコイルパターンの形状によらずバラツキの少ない均一なめっきをすることができる。
【００１８】
請求項８に記載の発明は、電気めっきによる導体の形成と局部エッチングを繰り返す際の１サイクルの所要時間が０．１秒以下である請求項１または請求項４に記載の平面コイルの製造方法であって、１サイクルの所要時間を短くして頻繁に導体の形成とエッチングを繰り返すことにより、部分的に電流の集中する箇所に余分に形成された余分なめっきを優先的にエッチングすることになるため、多面付けしたワークやコイルパターンの形状によらずバラツキの少ない均一なめっきをすることができる。
【００１９】
請求項９に記載の発明は、アルミニウム表面改質処理が無電解亜鉛めっき（ジンケート処理）である請求項４に記載の平面コイルの製造方法であって、アルミニウム表面のアルミニウムと亜鉛とを置換させることによりアルミニウム表面に亜鉛粒子を付着させ、第１電気銅めっきとの密着性とめっき析出銅粒子の均一析出性を良好にすることができる。
【００２０】
請求項１０に記載の発明は、アルミニウム表面改質処理が電解エッチングである請求項４に記載の平面コイルの製造方法であって、アルミニウム表面の酸化物を除去すると共に引き続き同一めっき液中で第１電気銅めっきを行うためにアルミニウムを酸化させずにアルミニウム表面に銅めっきを行うことができ、第１電気銅めっきとの密着性とめっき析出銅粒子の均一析出性を良好にすることができる。
【００２１】
請求項１１に記載の発明は、液温４０〜７０℃、３〜６％水酸化ナトリウム溶液でレジストパターンとレジストパターン下部の下地導体層とを一括除去する請求項４に記載の平面コイルの製造方法であって、水酸化ナトリウム溶液で銅を侵さずに、下地導体層であるアルミニウムを除去でき、しかも、めっきレジストも一括除去することができる。このことにより、銅めっきで形成した中心導体層の矩形形状を壊さずに表面導体層を形成することができる。液温が高くなるとレジストとアルミニウムの一括除去時間は早くなるが、剥離装置の材質の選択範囲が狭まり実用的でない。一方、水酸化ナトリウム溶液の濃度が高すぎると、レジスト剥離が困難となり、逆に低くなるとアルミニウムの除去に時間がかかりすぎ、実用的でないことが確認された。本発明では前記液温４０〜７０℃、３〜６％水酸化ナトリウム溶液の条件が工業的にも実用的であった。
【００２２】
請求項１２に記載の発明は、表面導体層の厚さが中心導体の厚さ以下である請求項１または請求項４に記載の平面コイルの製造方法であって、表面導体層の厚さが中心導体の厚さ以上になると断面形状がほぼ矩形の中心導体層の形状を維持したまま表面導体層を形成することが困難であった。本発明では、表面導体層の厚さが中心導体の厚さ以下であることにより、中心導体を第２の電気めっきで被覆する時、表面導体層の形状を直流電流の電流密度を変えることにより導体線条の縦／横比を１．０〜２．０の範囲でコントロールすることができる。
【００２３】
請求項１３に記載の発明は、下地導体層の表面が螺旋状に露出するためのレジストパターンの幅がレジストパターン間隔より小さいレジストパターンである請求項１または請求項４に記載の平面コイルの製造方法であり、レジストパターン間隔に第１の電気めっきで析出する中心導体層の幅が、レジストパターンの幅で形成される中心導体層間スペースより小さくなることにより、中心導体を第２の電気めっきで被覆する時、表面導体層の形状を直流電流の電流密度を変えることで導体線条の縦／横比を１．０〜２．０の範囲でコントロールすることができる。
【００２４】
【発明の実施の形態】
以下、本発明の実施の形態における平面コイルの製造方法について、添付図面に従って説明する。
【００２５】
（実施の形態１）
図１（ａ）〜（ｈ）は、本発明の実施の形態１の平面コイル製造プロセスを説明する為の概略図である。
【００２６】
まず、両面に１８μｍのＣｕ箔からなる下地導体層１０１を形成した厚さ２５μｍのポリイミドフィルムからなる絶縁性基板１０２を用意した。このときのワークサイズは、２００×２００ｍｍであった［図１（ａ）］。次に、硫酸過酸化水素系溶液からなるエッチング液を用いて、Ｃｕ箔全面をスライスエッチング装置により、Ｃｕ箔の厚さを２μｍまでエッチングした。このときのＣｕ箔の厚み精度は２±１μｍであった。次に両面の下地導体層１０１Ａおよび絶縁基板１０２を貫通するように、穴加工用パンチング機で直径１００μｍのスルーホール１０３を設けた［図１（ｂ）］。次に、両面の下地導体層１０１Ａおよびスルーホール部に無電解銅めっき液により銅からなる厚さ０．５〜１μｍの銅層１０４を形成し、スライスエッチングしたＣｕ箔１０１と無電解銅めっきで形成された銅層１０４からなる下地導体層１０１Ｂとした［図１（ｃ）］。次に、両面の下地導体層１０１Ｂの表面にドライフィルムレジスト１０５をラミネートし、３６個のコイルパターンを面付けしたフィルムマスクでパターンニングした［図１（ｄ）］。パターンニングには、４０μｍのドライフィルム１０５を用い、レジスト幅４０μｍ、レジスト間スペース４０μｍの螺旋状のパターンを形成した。この際、パターンニングしたドライフィルム１０５はスルーホール１０３をレジストとして被覆していない。
【００２７】
次に、レジスト１０５で被覆していない部分のスルーホール部を含む下地導体層１０１Ｂに硫酸銅濃度８０ｇ／ｌの硫酸銅めっき液を用いて、正電流密度６Ａ／ｄｍ^２で印加時間３０ｍＳの正電流と、負電流密度１８Ａ／ｄｍ^２で印加時間２ｍＳの負電流を交互に印加して、３５μｍのめっき導体層１０６を形成した［図１（ｅ）］。
【００２８】
その後、４０℃、３％の水酸化ナトリウム溶液でドライフィルム１０５によるレジストを除去した［図１（ｆ）］。続いて、アンモニア系エッチング液でレジスト剥離した部分の下地導体層１０１Ｂをエッチングし、断面形状が矩形の中心導体層１０７を形成した。このとき矩形の中心導体層１０７は、下地導体層１０１Ｂをエッチングする際、少しエッチングされ、高さ３０μｍ、幅が３０μｍであった［図１（ｇ）］。
【００２９】
その後、硫酸銅濃度８０ｇ／ｌの硫酸銅めっき液を用いて、電流密度６Ａ／ｄｍ^２の正電流だけを印加し１０μｍの表面導体層１０８を形成した。完成したコイル導体線条１０９の矩形断面は、高さ４０μｍ、幅が６５μｍ、スペース１５μｍであった［図１（ｈ）］。
【００３０】
このときの計算上の占積率は８１．２５％であったが、下地導体層１０１Ｂのエッチング時に中心導体層１０７の上部が少し丸くなっており、実際の占積率はこれより少し小さい。
【００３１】
また、面付けした３６個のコイルパターンの個々の抵抗値を測定したところ±５％以下の小さなバラツキであった。
【００３２】
（実施の形態２）
図２（ａ）〜（ｇ）は、本発明の実施の形態２の平面コイル製造プロセスを説明する為の概略図である。
【００３３】
まず、片面に１０μｍのＡｌ箔からなる下地導体層２０１を形成した厚さ２５μｍのポリイミドフィルムからなる絶縁性基板２０２を用意した。このときのワークサイズは、２００×２００ｍｍであった［図２（ａ）］。次に、下地導体層２０１の表面にドライフィルムレジスト２０３をラミネートし［図２（ｂ）］、３６個のコイルパターンを面付けしたフィルムマスクでパターンニングした。パターンニングには、４０μｍのドライフィルムを用い、レジスト幅４０μｍ、レジスト間スペース４０μｍの螺旋状のパターンを形成した［図２（ｃ）］。
【００３４】
次に、レジスト２０３で被覆していない部分のアルミニウムからなる下地導体層２０１に無電解Ｚｎめっき（ジンケート処理）または電解エッチングを行い、アルミニウム表面改質処理層２０４を形成した［図２（ｄ）］。次にレジスト２０３で被覆していない部分のアルミニウムからなる下地導体層２０１の表面に形成されたアルミニウム表面改質処理層２０４に硫酸銅濃度２００ｇ／ｌの硫酸銅めっき液を用いて、正電流密度８Ａ／ｄｍ^２で印加時間３０ｍＳの正電流と、負電流密度１８Ａ／ｄｍ^２で印加時間２ｍＳの負電流を交互に印加して、３５μｍの導体層２０５を形成した［図２（ｅ）］。
【００３５】
その後、５０℃、６％の水酸化ナトリウム溶液でレジストパターン２０３、アルミニウム表面改質処理層２０４とレジストパターン下部の下地導体層２０１とを一括除去した［図２（ｆ）］。このとき矩形のめっきで形成された導体層２０５とパターン状にエッチングされたアルミニウム下地導体層２０６からなる中心導体層２０７は、高さ３５μｍ、幅が４０μｍであった。
【００３６】
その後、硫酸銅濃度８０ｇ／ｌの硫酸銅めっき液を用いて、電流密度６Ａ／ｄｍ^２の正電流だけを印加し１０μｍの銅めっきからなる表面導体層２０８を形成［図２（ｇ）］した。完成したコイル導体線条２０９の矩形断面は、高さ４５μｍ、幅が７５μｍ、スペース５μｍであった。
【００３７】
このときの占積率は９３．７５％であり、コイル導体線条２０９はほぼ矩形であった。また、面付けした３６個のコイルパターンの個々の抵抗値を測定したところ±５％以下の小さなバラツキであった。
【００３８】
（比較例）
本発明の実施の形態１および２では、電流密度６Ａ／ｄｍ^２で印加時間３０ｍＳの正電流と、電流密度１８Ａ／ｄｍ^２で印加時間２ｍＳの負電流を交互に印加して、３５μｍの中心導体層を形成したが、比較例では、電流密度６Ａ／ｄｍ^２の正電流だけを印加し３５μｍの中心導体層を形成した。その他の条件は、実施の形態１と同様にしてコイルを形成した。
【００３９】
以上のようにして比較例で作製したコイルは、面付けした３６個のコイルパターンの個々の抵抗値を測定したところ２列目パターンより内側の１６個（４列×４行）は±５％のバラツキであり、導体線条の矩形断面は、高さ４０μｍ、幅が６５μｍ、スペース１５μｍであった。このときの計算上の占積率は８１．２５％であったが、下地導体層のエッチング時に中心導体層の上部が少し丸くなっており、実際の占積率はこれより少し小さい。最外周列の２０個のコイルパターンはショートの発生が一部あり、良品コイルの抵抗値は±１０〜１２％とバラツキが非常に大きかった。
【００４０】
以上のように、本発明の実施の形態１および２によれば、コイル断面がほぼ矩形に近い形状となる為、占積率の高いコイルを得ることができ、また、抵抗値バラツキの少ないコイルを製造できる。
【００４１】
なお、本発明の実施の形態では、基板として両面に下地導体層として１８μｍのＣｕを形成した厚さ２５μｍのポリイミドフィルムあるいは片面の下地導体層として１０μｍのＡｌを形成した厚さ２５μｍのポリイミドフィルムを用い、スルーホール〜電気めっき工程を経て平面コイルを形成していったが、基板としては下地導体層を両面あるいは片面だけに形成しているものどちらでも良く、また、下地導体層としてはＣｕ，Ａｌに限定されるものではなく、導電性がありかつその後のエッチング工程によって断面形状を矩形にできる材料であれば問題はない。また、基板材料としてはポリイミドフィルムに限定されるものではなく、絶縁性を有しかつ電気めっき液に侵されないものであれば特に制限はない。また、レジストにはドライフィルムを用いたが、めっき液に対する耐性があれば液状レジストでも可能で、パターンニングの方法についても特に限定するものではない。
【００４２】
【発明の効果】
以上に説明したように本発明による平面コイルの製造方法は、電気めっきによる導体の形成と局部エッチングを繰り返して中心導体層を積層するため、電流集中部に余分に形成された余分な導体を局部エッチングによって除去しながら電気めっきによって導体層を形成するようになるので、多面付けしたワークやコイルパターンの形状によらずバラツキの少ない均一なめっきをすることができる。
【００４３】
また、下地導体層にアルミニウムを採用し、中心導体層、表面導体層に銅めっきを用いることにより、水酸化ナトリウム溶液で銅を侵さずに、下地導体層であるアルミニウムを除去でき、しかも、めっきレジストも一括除去することができる。このことにより、銅めっきで形成した中心導体層の矩形形状を壊さずに表面導体層を形成することができるため、さらに、占積率の向上した平面コイルを提供できる。また、めっきレジストと下地導体層とを一括除去することができ、低コストで生産性にも優れた製造方法であり、工業的価値は非常に高いものである。
【図面の簡単な説明】
【図１】（ａ）〜（ｈ）本発明の実施の形態１における平面コイルの製造工程の一部を示す工程断面図
【図２】（ａ）〜（ｇ）本発明の実施の形態２における平面コイルの製造工程の一部を示す工程断面図
【符号の説明】
１０１下地導体層
１０２絶縁基板
１０３スルーホール
１０４無電解銅めっき層
１０５レジスト
１０６めっき導体層
１０７中心導体層
１０８表面導体層
１０９コイル導体線条
２０１アルミニウム下地導体層
２０２絶縁基板
２０３レジスト
２０４アルミニウム表面改質処理層
２０５めっき導体層
２０６パターン状にエッチングされたアルミニウム下地導体層
２０７中心導体層
２０８表面導体層
２０９コイル導体線条[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a planar coil that can be widely used for various electric products (speakers, transformers, motors, etc.) such as industrial equipment and consumer equipment.
[0002]
[Prior art]
2. Description of the Related Art In recent years, as electronic devices have become generally smaller and thinner, there has been a strong demand for smaller and thinner planar coils used in these electronic devices. For that purpose, it is necessary to produce a coil having a narrow space and a small dead space, that is, a high space factor coil. Here, the space factor will be described. The space factor referred to here means a coil for a rectangular area having a width equal to the arrangement pitch of the coil conductors and a height equal to the thickness of the coil conductors in a cross section perpendicular to the direction in which the coil conductors of the planar coil extend. It means the ratio of the cross-sectional area of the conductor wire. Therefore, in order to obtain a high space factor coil, the shape of the coil conductor wire should be rectangular and the space between the wires should be narrow.
[0003]
In order to manufacture the high space factor coil, a manufacturing method using a printed wiring board technology has been conventionally proposed. As a typical technique, a method using plating is known. As this method, a resist is formed on the surface of a base conductor layer previously formed on an insulating substrate so as to cover a portion other than the coil portion, and first electroplating is performed by a direct current using the base conductor layer as a base. Thereby, a center conductor layer is formed. Thereafter, after the resist pattern is stripped, the underlying conductor layer exposed by stripping the resist pattern is removed by etching. Thereafter, second electroplating was performed by DC current using the center conductor as a base, and a conductor wire composed of a surface conductor layer covering the center conductor was formed to produce a planar coil.
[0004]
As prior art document information related to the invention of this application, for example, Patent Document 1 and Patent Document 2 are known.
[0005]
[Patent Document 1]
JP-A-5-75237 [Patent Document 2]
JP 2001-267166 A
[Problems to be solved by the invention]
The plating method is one method for producing a coil with a high space factor.However, there are places where current is concentrated due to the periphery of a multi-faced work, which is a drawback of electroplating, or the shape of a coil pattern. However, when the conductor in the current concentrating portion is formed thick and the coil pattern is imposed with several or several tens, the plating thickness varies, so that a large number of large workpieces cannot be obtained and the mass productivity is poor. I was In addition, when the underlying conductor layer is etched, the metal of the conductor wire is also etched, so that the thickness of the conductor wire is reduced and side etching occurs. There was a problem that the rate became low.
[0007]
Therefore, the present invention provides a method for producing a large number of planar coils having a coil conductor wire with a high space factor and a small in-plane variation that can be widely used for various electric appliances such as industrial equipment and consumer equipment. It is the purpose.
[0008]
[Means for Solving the Problems]
In order to solve the above problem, the present invention has the following configuration.
[0009]
The invention according to claim 1 of the present invention provides a base conductor layer forming step of forming a base conductor layer on an insulating substrate, and a resist pattern forming step of forming a resist pattern such that the surface of the base conductor layer is spirally exposed. A first electroplating step of laminating a center conductor layer while repeating formation of a conductor by electroplating and local etching with the base conductor layer as a base to form a center conductor having a substantially rectangular cross section; Removing the underlying conductor layer exposed by the removal of the resist pattern by etching, and performing electroplating with a DC current using the central conductor as a foundation to cover the central conductor and the central conductor. It is constituted by a second electroplating step for completing a conductor wire composed of the surface conductor layer.
[0010]
When performing electroplating on a multi-faced work, in the case of electroplating using a normal DC current, there are places where current concentrates partially due to the periphery of the multi-faced work and the shape of the coil pattern, and the conductor in the current concentrated part When it was formed thickly and the coil pattern was imposed with several or several tens of pieces, the plating thickness varied, and large-size workpieces could not be picked up, resulting in poor mass productivity. As in the invention, when the formation of the conductor by electroplating and local etching are repeated to laminate the central conductor layer, the conductor layer is formed by electroplating while removing the excess conductor formed in the current concentrated portion by local etching. Therefore, it is possible to perform uniform plating with little variation irrespective of the shape of the multi-faced work or the coil pattern. In other words, the first electroplating emphasizes the uniformity of the in-plane plating of the multi-faced work by stacking the central conductor layer while repeating formation of the conductor by electroplating and local etching, and second electroplating. The emphasis is placed on the control of the coil shape by applying a direct current, and the shape of the surface conductor layer that covers the rectangular central conductor formed by the first electroplating with the second electroplating changes the current density of the direct current. As a result, it is possible to control the vertical / horizontal ratio of the conductor wire within a range of 1.0 to 2.0. For example, a planar coil having a coil conductor wire having a desired high space factor and mass productivity It is intended to provide an excellent production method.
[0011]
According to a second aspect of the present invention, there is provided the method for manufacturing a planar coil according to the first aspect, wherein the thickness of the underlying conductor layer is 1 μm or more and 5 μm or less. The power supply for the electroplating is not uniform, the plating thickness tends to vary, and the adhesion between the insulating substrate and the central conductor layer becomes insufficient. On the other hand, when the thickness becomes 5 μm or more, after the first electroplating, when the underlying conductor layer exposed by peeling of the resist pattern is removed by etching, the metal forming the central conductor is also etched, so that the shape of the central conductor layer becomes too thin, Beyond the range of shape control in the second electroplating for forming the surface conductor layer, it becomes difficult to form a coil having a high space factor.
[0012]
The invention according to claim 3 is the method for manufacturing a planar coil according to claim 1, wherein the thickness of the underlying conductor layer is controlled by a slice etching method, wherein the underlying conductor layer is 1 μm or more by a slice etching method. The desired thickness is 5 μm or less. When the copper foil has a thickness of 5 μm or less, the workability is poor when the copper foil is attached to the insulating substrate, and the copper foil is wrinkled. The present invention is characterized in that a normal copper foil of 35, 18, or 12 μm is slice-etched with a sulfuric acid hydrogen peroxide-based etchant to obtain a desired thickness with small in-plane variation.
[0013]
The invention according to claim 4, wherein the underlying conductor layer is made of aluminum, a resist pattern is formed so as to spirally expose the surface of the aluminum underlying conductor layer, and the spirally exposed aluminum surface is modified, A center conductor having a substantially rectangular cross section is formed by laminating a center conductor layer while repeating formation of a conductor by electrolytic copper plating and local etching with the aluminum base conductor layer subjected to the aluminum surface modification treatment as a base. Electroplating, the resist pattern and the underlying conductor layer under the resist pattern are removed at one time, and the central conductor and the surface conductor layer covering the central conductor by performing electrolytic copper plating using the central conductor as a foundation. The present invention is characterized in that a conductive wire is completed.
[0014]
By using aluminum for the base conductor layer and using copper plating for the center conductor layer and the surface conductor layer, the base conductor layer aluminum can be removed without attacking the copper with sodium hydroxide solution, and the plating resist It can be removed all at once. With this, the surface conductor layer can be formed without breaking the rectangular shape of the center conductor layer formed by copper plating, so that a planar coil with an improved space factor can be provided. It is another object of the present invention to provide a manufacturing method in which the plating resist and the underlying conductor layer can be removed at one time, and which is low in cost and excellent in productivity.
[0015]
The invention according to claim 5 is the method for manufacturing a planar coil according to claim 1 or 4, wherein the plating solution used for electroplating is a copper sulfate plating solution, wherein the copper sulfate plating solution is used. Therefore, it is economical and easy to manage the liquid.
[0016]
The invention according to claim 6 is the method according to claim 1 or 4, wherein the local etching is electrolytic etching performed by applying a negative current opposite to the formation of the conductor in the same plating solution as the electroplating. A method for manufacturing a planar coil, in which the central conductor layer is laminated by repeating electrolytic etching in which a reverse current is applied to conductor formation by electroplating in the same plating solution as electroplating, so that an extra Since the conductor layer is formed while removing the formed excess conductor by electrolytic etching, it is possible to perform uniform plating with little variation regardless of the shape of the multi-faced work or the coil pattern.
[0017]
According to a seventh aspect of the present invention, the current density of the negative current flowing for local etching is higher than the current density of the positive current flowing for forming the conductor of the surface conductor layer. A method of manufacturing a planar coil, in which the current density of a negative current flowing for local etching is higher than the current density of a positive current flowing for forming a conductor, so that the periphery of a workpiece and a coil which are multi-faced when forming a conductor are formed. Depending on the shape of the pattern, the excess plating formed in places where current is partially concentrated will be preferentially etched, so there is little variation regardless of the shape of the multi-faced work or coil pattern. Can be plated.
[0018]
The invention according to claim 8 is the method for manufacturing a planar coil according to claim 1 or 4, wherein the time required for one cycle when repeating formation of a conductor by electroplating and local etching is 0.1 second or less. Therefore, by shortening the time required for one cycle and repeating the formation and etching of the conductor frequently, it is possible to preferentially etch excess plating formed extra in a portion where current is partially concentrated. Therefore, it is possible to perform uniform plating with little variation irrespective of the shape of the multi-faced work or the coil pattern.
[0019]
According to a ninth aspect of the present invention, there is provided the flat coil manufacturing method according to the fourth aspect, wherein the aluminum surface modification treatment is electroless zinc plating (zincate treatment), wherein aluminum and zinc on the aluminum surface are substituted. This allows zinc particles to adhere to the aluminum surface, thereby improving the adhesion to the first electrolytic copper plating and the uniform deposition of plated copper particles.
[0020]
The invention according to claim 10 is the method for manufacturing a planar coil according to claim 4, wherein the aluminum surface modification treatment is electrolytic etching, wherein the oxide on the aluminum surface is removed and the aluminum coil is continuously etched in the same plating solution. (1) Copper plating can be performed on the aluminum surface without oxidizing the aluminum to perform the electrolytic copper plating, and the adhesion with the first electrolytic copper plating and the uniform deposition property of the plated copper particles can be improved. .
[0021]
According to an eleventh aspect of the present invention, there is provided the manufacturing method of the planar coil according to the fourth aspect, wherein the resist pattern and the underlying conductor layer below the resist pattern are collectively removed with a solution temperature of 40 to 70 ° C. and 3 to 6% sodium hydroxide solution. In this method, aluminum as an underlying conductor layer can be removed without damaging copper with a sodium hydroxide solution, and a plating resist can be removed at a time. Thus, the surface conductor layer can be formed without breaking the rectangular shape of the center conductor layer formed by copper plating. As the liquid temperature increases, the time for removing the resist and aluminum at once becomes shorter, but the material selection range of the peeling device becomes narrower, which is not practical. On the other hand, it was confirmed that when the concentration of the sodium hydroxide solution was too high, the resist was difficult to be stripped, and when the concentration was low, it took too much time to remove aluminum, which was not practical. In the present invention, the conditions of the liquid temperature of 40 to 70 ° C. and a 3 to 6% sodium hydroxide solution were industrially practical.
[0022]
According to a twelfth aspect of the present invention, in the method for manufacturing a planar coil according to the first or fourth aspect, the thickness of the surface conductor layer is equal to or less than the thickness of the center conductor. If the thickness exceeds the thickness of the center conductor, it is difficult to form the surface conductor layer while maintaining the shape of the center conductor layer having a substantially rectangular cross section. In the present invention, when the thickness of the surface conductor layer is equal to or less than the thickness of the center conductor, when the center conductor is coated with the second electroplating, the shape of the surface conductor layer is changed by changing the current density of DC current. The length / width ratio of the conductor wire can be controlled in the range of 1.0 to 2.0.
[0023]
According to a thirteenth aspect of the present invention, in the manufacturing method of the planar coil according to the first or fourth aspect, the width of the resist pattern for exposing the surface of the underlying conductor layer in a spiral pattern is smaller than the distance between the resist patterns. The center conductor layer deposited by the first electroplating at the resist pattern interval is smaller than the center conductor interlayer space formed by the width of the resist pattern, so that the center conductor is formed by the second electroplating. At the time of coating, the aspect ratio of the conductor wire can be controlled in the range of 1.0 to 2.0 by changing the shape of the surface conductor layer by changing the current density of the direct current.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a method for manufacturing a planar coil according to an embodiment of the present invention will be described with reference to the accompanying drawings.
[0025]
(Embodiment 1)
FIGS. 1A to 1H are schematic diagrams for explaining a planar coil manufacturing process according to the first embodiment of the present invention.
[0026]
First, an insulating substrate 102 made of a 25 μm-thick polyimide film having a base conductor layer 101 made of 18 μm Cu foil formed on both surfaces was prepared. The work size at this time was 200 × 200 mm [FIG. 1 (a)]. Next, using an etching solution composed of a sulfuric acid-hydrogen peroxide solution, the entire surface of the Cu foil was etched to a thickness of 2 μm by a slice etching apparatus. At this time, the thickness accuracy of the Cu foil was 2 ± 1 μm. Next, a through hole 103 having a diameter of 100 μm was provided by a hole punching machine so as to penetrate the underlying conductor layer 101A and the insulating substrate 102 on both surfaces [FIG. 1 (b)]. Next, a copper layer 104 of 0.5 to 1 μm thick made of copper is formed on the both-side base conductor layer 101A and the through-hole portion with an electroless copper plating solution, and slice-etched Cu foil 101 and electroless copper plating. An underlying conductor layer 101B composed of the formed copper layer 104 was obtained [FIG. 1 (c)]. Next, a dry film resist 105 was laminated on the surfaces of the underlying conductor layers 101B on both sides, and patterned using a film mask having 36 coil patterns imposed thereon (FIG. 1 (d)). For patterning, a spiral pattern having a resist width of 40 μm and a space between resists of 40 μm was formed using a 40 μm dry film 105. At this time, the patterned dry film 105 does not cover the through hole 103 as a resist.
[0027]
Next, using a copper sulfate plating solution having a copper sulfate concentration of 80 g / l at a positive current density of 6 A / dm ² and a positive application time of 30 mS for the underlying conductor layer 101B including the through-hole portions not covered with the resist 105. A current and a negative current having a negative current density of 18 A / dm ² and an application time of 2 mS were alternately applied to form a plated conductor layer 106 of 35 μm [FIG. 1 (e)].
[0028]
Thereafter, the resist by the dry film 105 was removed with a 3% sodium hydroxide solution at 40 ° C. [FIG. 1 (f)]. Subsequently, the portion of the base conductor layer 101B where the resist was peeled off was etched with an ammonia-based etchant to form a central conductor layer 107 having a rectangular cross-sectional shape. At this time, the rectangular center conductor layer 107 was slightly etched when etching the underlying conductor layer 101B, and had a height of 30 μm and a width of 30 μm [FIG. 1 (g)].
[0029]
Thereafter, using a copper sulfate plating solution having a copper sulfate concentration of 80 g / l, only a positive current having a current density of 6 A / dm ² was applied to form a 10 μm surface conductor layer 108. The rectangular cross section of the completed coil conductor wire 109 had a height of 40 μm, a width of 65 μm, and a space of 15 μm [FIG. 1 (h)].
[0030]
Although the calculated space factor at this time was 81.25%, the upper portion of the center conductor layer 107 is slightly rounded when the underlying conductor layer 101B is etched, and the actual space factor is slightly smaller than this.
[0031]
Further, the individual resistance values of the 36 coil patterns imposed were measured and found to be small variations of ± 5% or less.
[0032]
(Embodiment 2)
FIGS. 2A to 2G are schematic diagrams for explaining a planar coil manufacturing process according to the second embodiment of the present invention.
[0033]
First, an insulating substrate 202 made of a 25 μm-thick polyimide film having a base conductor layer 201 made of a 10 μm Al foil formed on one surface was prepared. The work size at this time was 200 × 200 mm [FIG. 2 (a)]. Next, a dry film resist 203 was laminated on the surface of the base conductor layer 201 (FIG. 2B), and patterning was performed with a film mask on which 36 coil patterns were imposed. For patterning, a spiral pattern having a resist width of 40 μm and a space between resists of 40 μm was formed using a 40 μm dry film [FIG. 2 (c)].
[0034]
Next, an electroless Zn plating (zincate treatment) or electrolytic etching was performed on the base conductor layer 201 made of aluminum not covered with the resist 203 to form an aluminum surface modification treatment layer 204 (FIG. 2D). ]. Next, a copper sulfate plating solution having a copper sulfate concentration of 200 g / l was applied to the aluminum surface reforming layer 204 formed on the surface of the base conductor layer 201 made of aluminum in a portion not covered with the resist 203 by using a positive current density. a positive current application time 30mS at 8A / dm ^2, and alternately applying negative current application time 2mS negative current density 18A / dm ^2, thereby forming a conductor layer 205 of 35 [mu] m [FIG 2 (e)].
[0035]
Thereafter, the resist pattern 203, the aluminum surface modification layer 204, and the underlying conductor layer 201 under the resist pattern were removed at a time with a 6% sodium hydroxide solution at 50 ° C. [FIG. 2 (f)]. At this time, the center conductor layer 207 including the conductor layer 205 formed by rectangular plating and the aluminum base conductor layer 206 etched in a pattern was 35 μm in height and 40 μm in width.
[0036]
Thereafter, using a copper sulfate plating solution having a copper sulfate concentration of 80 g / l, only a positive current having a current density of 6 A / dm ² was applied to form a surface conductor layer 208 made of 10 μm copper plating [FIG. 2 (g)]. . The rectangular cross section of the completed coil conductor wire 209 had a height of 45 μm, a width of 75 μm, and a space of 5 μm.
[0037]
The space factor at this time was 93.75%, and the coil conductor wire 209 was substantially rectangular. Further, the individual resistance values of the 36 coil patterns imposed were measured and found to be small variations of ± 5% or less.
[0038]
(Comparative example)
In the first and second embodiments of the present invention, a positive current application time 30mS at a current density of 6A / dm ^2, by applying a negative current application time 2mS alternately at a current density of 18A / dm ^2, 35 [mu] m center conductor Although the layer was formed, in the comparative example, only a positive current having a current density of 6 A / dm ² was applied to form a central conductor layer of 35 μm. Other conditions were the same as in the first embodiment to form a coil.
[0039]
As for the coil fabricated in the comparative example as described above, the individual resistance values of the 36 coil patterns imposed were measured. As a result, 16 coils (4 columns × 4 rows) inside the second column pattern were ± 5%. The rectangular cross section of the conductor wire had a height of 40 μm, a width of 65 μm, and a space of 15 μm. Although the calculated space factor at this time was 81.25%, the upper portion of the center conductor layer was slightly rounded when the underlying conductor layer was etched, and the actual space factor was slightly smaller than this. 20 coil patterns in the outermost row had some short-circuits, and the resistance of the non-defective coils was very large, ± 10 to 12%.
[0040]
As described above, according to the first and second embodiments of the present invention, since the coil cross section has a substantially rectangular shape, a coil having a high space factor can be obtained, and a coil having a small variation in resistance value can be obtained. Can be manufactured.
[0041]
In the embodiment of the present invention, a 25 μm-thick polyimide film in which 18 μm Cu is formed as a base conductor layer on both sides as a substrate or a 25 μm-thick polyimide film in which 10 μm Al is formed as a base conductor layer on one side is used as a substrate. The planar coil was formed through the through-hole to the electroplating process, but the substrate may be formed with a base conductor layer formed on both sides or only one side, and the base conductor layer may be formed of Cu, The material is not limited to Al, and there is no problem as long as the material is conductive and can form a rectangular cross section by a subsequent etching process. The substrate material is not limited to a polyimide film, and is not particularly limited as long as it has insulating properties and is not affected by the electroplating solution. Although a dry film is used as the resist, a liquid resist can be used as long as it has resistance to a plating solution, and the patterning method is not particularly limited.
[0042]
【The invention's effect】
As described above, in the method of manufacturing a planar coil according to the present invention, since the formation of the conductor by electroplating and local etching are repeated to laminate the central conductor layer, the extra conductor formed in the current concentrating portion is locally removed. Since the conductor layer is formed by electroplating while being removed by etching, it is possible to perform uniform plating with little variation regardless of the shape of the multi-faced work or coil pattern.
[0043]
In addition, by adopting aluminum for the underlying conductor layer and using copper plating for the center conductor layer and the surface conductor layer, the aluminum that is the underlying conductor layer can be removed without corroding the copper with a sodium hydroxide solution. The resist can also be removed at once. With this, the surface conductor layer can be formed without breaking the rectangular shape of the center conductor layer formed by copper plating, so that a planar coil with an improved space factor can be provided. Moreover, the plating resist and the underlying conductor layer can be removed at one time, and the manufacturing method is low in cost and excellent in productivity, and has a very high industrial value.
[Brief description of the drawings]
FIGS. 1 (a) to 1 (h) are process cross-sectional views showing a part of a manufacturing process of a planar coil according to a first embodiment of the present invention. FIGS. 2 (a) to 2 (g). Sectional view showing a part of the manufacturing process of the planar coil in FIG.
101 underlying conductor layer 102 insulating substrate 103 through hole 104 electroless copper plating layer 105 resist 106 plated conductor layer 107 center conductor layer 108 surface conductor layer 109 coil conductor wire 201 aluminum under conductor layer 202 insulating substrate 203 resist 204 aluminum surface modification Processing layer 205 Plating conductor layer 206 Aluminum base conductor layer 207 etched in a pattern shape Center conductor layer 208 Surface conductor layer 209 Coil conductor line

Claims

Forming a base conductor layer on the insulating substrate, forming a resist pattern so that the surface of the base conductor layer is spirally exposed, and electroplating the base conductor layer as a base. A first electroplating step of laminating a center conductor layer while repeating formation of a conductor and local etching by forming a center conductor having a substantially rectangular cross section, a step of peeling the resist pattern, and a step of peeling the resist pattern. By performing an etching step of removing the exposed underlying conductor layer by etching, and performing electroplating with a direct current using the central conductor as a foundation, a conductor line composed of the central conductor and a surface conductor layer covering the same is completed. A method for manufacturing a planar coil, comprising a second electroplating step.

2. The method for manufacturing a planar coil according to claim 1, wherein the thickness of the underlying conductor layer is 1 μm or more and 5 μm or less.

3. The method according to claim 2, wherein the thickness of the underlying conductor layer is controlled by a slice etching method.

The underlying conductor layer is made of aluminum, a resist pattern is formed so as to spirally expose the surface of the aluminum underlying conductor layer, and the spirally exposed aluminum surface is modified. A first electroplating is performed by forming a center conductor having a substantially rectangular cross section by laminating a center conductor layer while repeating formation of a conductor by copper electroplating and local etching while using the applied aluminum base conductor layer as a base. The pattern and the underlying conductor layer below the resist pattern are removed at one time, and copper electroplating is performed using the center conductor as a foundation, thereby completing a conductor wire composed of the center conductor and a surface conductor layer covering the same. A method for manufacturing a planar coil, comprising:

The method for producing a planar coil according to claim 1 or 4, wherein the plating solution used for electroplating is a copper sulfate plating solution.

5. The method for manufacturing a planar coil according to claim 1, wherein the local etching is electrolytic etching performed by applying a negative current opposite to the conductor formation in the same plating solution as the electroplating. .

5. The method according to claim 1, wherein a current density of a negative current flowing for local etching is higher than a current density of a positive current flowing for forming a conductor of the central conductor layer. .

The method for manufacturing a planar coil according to claim 1 or 4, wherein the time required for one cycle when repeating the formation of the conductor by electroplating and the local etching is 0.1 second or less.

The method for manufacturing a planar coil according to claim 4, wherein the aluminum surface modification treatment is electroless zinc plating (zincate treatment).

The method for manufacturing a planar coil according to claim 4, wherein the aluminum surface modification treatment is electrolytic etching.

5. The method according to claim 4, wherein the resist pattern and the underlying conductor layer below the resist pattern are removed at a time at a solution temperature of 40 to 70 [deg.] C. and a 3 to 6% sodium hydroxide solution.

5. The method according to claim 1, wherein the thickness of the surface conductor layer is equal to or less than the thickness of the center conductor.

5. The method for manufacturing a planar coil according to claim 1, wherein a width of the resist pattern for exposing the surface of the underlying conductor layer in a spiral is larger than a resist pattern interval.