JP2005072038A

JP2005072038A - Common mode choke coil, core structure therefor, manufacturing method thereof, and common mode choke coil

Info

Publication number: JP2005072038A
Application number: JP2003208500A
Authority: JP
Inventors: Takashi Arasawa; 崇荒沢; Toshihiro Kuroshima; 敏浩黒嶋; Kazumi Kobayashi; 一三小林; Rei Sato; 玲佐藤
Original assignee: TDK Corp
Current assignee: TDK Corp
Priority date: 2003-08-22
Filing date: 2003-08-22
Publication date: 2005-03-17
Anticipated expiration: 2023-08-22
Also published as: JP4203952B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a core structure for common mode choke coils that can withstand thermal stress in packaging by using a metal plate electrode as an external connection electrode, and mechanical stress, such as deflection in a substrate at the packaging side, and has improved coplanarity and can cope with high-density packaging. <P>SOLUTION: The core structure comprises an integral ferrite core where a collar 3 for connecting both winding cores is formed at both the ends of two winding cores 2; and a pair of metal plate electrodes 10 that has at least a U-shaped bent section 11, and is provided at each collar section 3. The pair of metal plate electrodes 10 is fitted to the collar 3 at the part of the U-shaped bent section 11, and coplanarity of the packaging surface of each metal plate electrode 10 becomes 30 μm or smaller. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、電子回路や電子機器において、外部より侵入するコモンモードノイズを除去するために使用される、外部接続電極（端子）として金属板電極を具備したコモンモードチョークコイル用コア構造体及びその製造方法並びにコモンモードチョークコイルに関する。
【０００２】
【従来の技術】
一般に、コモンモードチョークコイルは、リング形磁心（２本の巻芯部を有する磁心）を用い、その磁心に一対の巻線を施したものであり、巻線端末を接続する外部接続電極は、前記磁心が小型のフェライトコアの場合、当該コアに銀（Ａｇ）焼付電極を形成し、その上にはんだ付けに適した錫（Ｓｎ）等のメッキ処理を施したものが知られている。また、磁心に直接金属板電極を設けて、それに巻線端末を接続する構造が本出願人により考慮されている。
【０００３】
コモンモードチョークコイルの公知例としては、下記特許文献１及び特許文献２がある。
【０００４】
【特許文献１】実公平４−３８４９７号公報
【特許文献２】特開平２−２０１９０６号公報
【０００５】
上記特許文献１は、２つの磁心に巻線を施したコイル２個を用い、端部を突き合わせて構成したコモンモードチョークコイルにおいて、前記２つの磁心が、夫々両端に角板状の鍔を有する角型のドラム形磁心からなり、両磁心の鍔部の相対応する側面同士を突き合わせて閉磁路を形成するように接合した構成となっている。この場合、磁心に巻線を巻回す手段は自動的に機械化をすることが可能である。外部接続用の電極については詳細な説明がないが、一方の鍔部の外端面に接着された絶縁材の上に形成されるとしている。但し、電極が一方の鍔部外端面にあるため、プリント配線板上に実装する場合にドラム形磁心の巻芯部が垂直に立った状態となるため、低背化に向いていない。
【０００６】
また、上記特許文献２は、２個のコアにバネ性を有するコイル導線が所定の巻回形状に構成されてなるコイル導線巻回部、及びそのコイル導線巻回部の両側から延びるリード部で構成されたコイルと、脚部に前記コイルのコイル導線巻回部が取り付けられるとともに、前記コイル導線巻回部を引っ張った状態で前記各リード部が係止されることで脚部を介して互いに突き合わせられた一対のコアとを備えたことを特徴としている。この構造は、外部電極はリード部であり、表面実装品ではない。
【０００７】
【発明が解決しようとする課題】
この種のコモンモードチョークコイルの磁心として一般的なフェライトコアは、焼成の際に縮率で示される体積の収縮がある。本製品に用いられるフェライト材料では焼成前後で１５％程度の体積の収縮が発生する。また、コアのゆがみ、そり、かけも発生する。
【０００８】
このため、フェライトコアに銀焼付電極を形成し、これにメッキした外部接続電極では、コアのゆがみ、そり等に起因して電極実装面の高さが不揃いとなる問題があり、またプリント配線板への実装時の熱ストレスやプリント配線板のたわみが直接フェライトコアに加わり、フェライトコアが破損しやすい問題もあった。
【０００９】
同様に、フェライトコアに外部接続電極としての金属板電極を単に固着して設ける構造でも、コアのゆがみ、そり等に起因して電極実装面の高さが不揃いとなる問題がある。
【００１０】
近年、プリント配線板の実装密度が高密度になるのに伴い、基板面に塗布されるクリームはんだの厚みも非常に薄くなってきており、各外部接続電極の高さが不揃いであると、プリント配線板へのリフロー方式によるはんだ付け実装時にコモンモードチョークコイルの外部接続電極とプリント配線板のランドパターン間で隙間が発生し、電気的な接続ができないという不具合があった。特にコプラナリティ（平面度）が１００μｍ以上で顕著に不具合が発生していた。本明細書においてコプラナリティとは、コモンモードチョークコイルの外部接続電極とプリント配線板のランドパターン間の隙間として定義する。
【００１１】
なお、特許文献１の場合、２個のコアを精密に作製しても、組み合わせた完成品の精度が劣ってしまう恐れがあり、所要のコプラナリティの確保が困難であると考えられる。また、特許文献２の場合には表面実装についての配慮がない構造である。
【００１２】
本発明は、上記の点に鑑み、外部接続電極として金属板電極を用いることで実装時の熱ストレスや実装側の基板のたわみ等の機械的なストレスに耐えることができ、かつコプラナリティが良好で高密度実装に対応できるコモンモードチョークコイル用コア構造体及びその製造方法並びにコモンモードチョークコイルを提供することを目的とする。
【００１３】
本発明のその他の目的や新規な特徴は後述の実施の形態において明らかにする。
【００１４】
【課題を解決するための手段】
上記目的を達成するために、本願請求項１の発明に係るコモンモードチョークコイル用コア構造体は、２本の巻芯部の両端に両巻芯部を連結する鍔部を有する一体型フェライトコアと、少なくともコ字状折曲部を有していて各鍔部にそれぞれ一対設けられた金属板電極とを備え、
前記金属板電極は、前記コ字状折曲部の部分にて前記鍔部に装着され、かつ各金属板電極の実装面のコプラナリティが３０μｍ以下であることを特徴としている。
【００１５】
本願請求項２の発明に係るコモンモードチョークコイル用コア構造体は、２個以上に分割され、２本の巻芯部の両端に両巻芯部を連結する鍔部が形成されるように組み合わせてなるフェライトコア組立体と、少なくともコ字状折曲部を有していて各鍔部にそれぞれ一対設けられた金属板電極とを備え、
前記金属板電極は、前記コ字状折曲部の部分にて前記鍔部に装着され、かつ各金属板電極の実装面のコプラナリティが３０μｍ以下であることを特徴としている。
【００１６】
本願請求項３の発明に係るコモンモードチョークコイル用コア構造体は、請求項１又は２において、前記金属板電極は前記コ字状折曲部の下辺部以外の部分にて前記鍔部に接着固定されていることを特徴としている。
【００１７】
本願請求項４の発明に係るコモンモードチョークコイルは、請求項１，２又は３記載のコモンモードチョークコイル用コア構造体の各巻芯部に巻線を施し、各巻線の端末を前記金属板電極に接続したことを特徴としている。
【００１８】
本願請求項５の発明に係るコモンモードチョークコイル用コア構造体の製造方法は、２本の巻芯部の両端に両巻芯部を連結する鍔部を有する一体型フェライトコアと、少なくともコ字状折曲部を有していて各鍔部にそれぞれ一対設けられた金属板電極とを用い、
前記金属板電極を、前記コ字状折曲部と前記鍔部間に接着材を設けて当該鍔部に装着し、かつ各金属板電極の実装面を同一高さに揃えた状態で前記接着材を硬化させて、各金属板電極の実装面のコプラナリティを３０μｍ以下とすることを特徴としている。
【００１９】
本願請求項６の発明に係るコモンモードチョークコイル用コア構造体の製造方法は、２個以上に分割され、２本の巻芯部の両端に両巻芯部を連結する鍔部が形成されるように組み合わせてなるフェライトコア組立体と、少なくともコ字状折曲部を有していて各鍔部にそれぞれ一対設けられた金属板電極とを用い、
前記金属板電極を、前記コ字状折曲部と前記鍔部間に接着材を設けて当該鍔部に装着し、かつ各金属板電極の実装面を同一高さに揃えた状態で前記接着材を硬化させて、各金属板電極の実装面のコプラナリティを３０μｍ以下とすることを特徴としている。
【００２０】
【発明の実施の形態】
以下、本発明に係るコモンモードチョークコイル用コア構造体及びその製造方法並びにコモンモードチョークコイルの実施の形態を図面に従って説明する。
【００２１】
図１乃至図５で本発明の一実施の形態を説明する。これらの図において、１は一体型フェライトコアであり、図４のように２本の巻芯部２の両端に両巻芯部２を連結する方形鍔部（角板状鍔部）３を有し、漏洩磁束の少ない略ロ字状閉磁路をなしている。
【００２２】
図１の拡大部分に示すように、各方形鍔部３に外部接続電極としてそれぞれ一対取り付けられる金属板電極１０は、方形鍔部３に多少の遊び（上下方向の隙間）を持って嵌合するコ字状折曲部１１と、この上辺部１１ａに折り返して形成された巻線端末係止用の係止片１２を有している。これらのコ字状折曲部１１及び係止片１２を持つ金属板電極１０は銅、銅合金等の金属板の折り曲げ加工により形成される。
【００２３】
また、前記金属板電極１０は、フェライトコア１の巻芯部２の延長上の方形鍔部位置に接着材２０（例えば熱硬化性樹脂接着剤）で固定される。接着材２０で固定する際は、フェライトコア１の方形鍔部３の底面以外の部分、好ましくは側面（外側端面）３ａに接着材２０を塗布し、方形鍔部３の側面と金属板電極１０のコ字状折曲部１１の側面部１１ｂ間に接着材２０が介在するようにして方形鍔部３に対してコ字状折曲部１１を取り付ける。このとき、４箇所の金属板電極１０の底面である実装面を同一高さに揃えるように、換言すれば、４箇所の金属板電極１０の実装面が同一平面に位置するように端子浮きを抑える治具を併用して接着材２０を硬化させる。
【００２４】
前記金属板電極１０は、そのコ字状折曲部１１の内法寸法がフェライトコア方形鍔部３より若干大きく、従って多少の遊び（上下方向の隙間）をもって方形鍔部３に装着されているので、フェライトコア１のゆがみ、そり、かけが発生していても金属板電極１０の接着時に４箇所の金属板電極１０の実装面が同一平面に位置するように治具を用いて接着材２０を硬化させることにより、コプラナリティを金属板電極２０の厚みの平坦度と加工精度で保証することができる。金属板電極１０の寸法精度は一般の金属加工精度程度あり、要求されるコプラナリティに応じて、１０μｍ以下等に、適宜選択すればよい。もちろん変形した金属板電極１０は使用できない。
【００２５】
接着材２０の材質や塗布量は要求される接着強度に応じて、適宜選択すればよい。接着材塗布位置は、コプラナリティに影響を与えない部位であればどこでも良く（逆にコプラナリティに影響を与える方形鍔部３の底面は避ける）、本実施の形態では、フェライトコア鍔部３の側面に接着材２０を塗布し、端子浮きを抑える治具を併用して固定している。これにより、後述のデータで明らかにするが、各金属板電極１０の底面から成る実装面のコプラナリティを３０μｍ以下にすることが可能である。この結果、４箇所の金属板電極１０の実装面はコプラナリティが３０μｍ以下の平面となるので、プリント配線板上に安定して実装することができる。また、それにより、フェライトコア１の寸法精度は、極限まで追求する必要がなく、また、フェライトコア１の面取り加工を施す必要もない。また、フェライトコア鍔部３の側面での接着であれば、金属板電極１０のコ字状折曲部１１の下辺部１１ｃは自由度があり、プリント配線板上に実装する際の熱ストレスをフェライトコア鍔部３に伝えることなく実装することができる。
【００２６】
以上のようにして、２本の巻芯部２の両端に両巻芯部を連結する方形鍔部３を有する一体型フェライトコア１と、少なくともコ字状折曲部１１を有していて各鍔部３にそれぞれ一対設けられた金属板電極１０とを備え、金属板電極１０は、コ字状折曲部１１の部分にて鍔部３に装着され、かつ各金属板電極１０の実装面のコプラナリティが３０μｍ以下であるコモンモードチョークコイル用コア構造体が得られる。
【００２７】
上記コモンモードチョークコイル用コア構造体を用いてコモンモードチョークコイルを作製する場合、一体型フェライトコア１の２本の巻芯部２にそれぞれ巻線３０が設けられ、巻線の端末（リード部）は金属板電極１０の上辺部に引き出され、図５のように係止片１２をかしめることで仮止めされる。そして、巻線端末を金属板電極１０の上辺部にはんだ付けで接続する。その後、上面が平坦なカバー４０をフェライトコア１の方形鍔部２の上面に接着材を塗布して、フェライトコア１に固定する。カバー４０は成形性及び耐熱性に優れた液晶ポリマー樹脂等の非磁性材であり、前記金属板電極１０の継線部分を避ける凹部４１が下面側に形成されている。
【００２８】
上面が平坦なカバー４０を接着する理由は、電子部品装着機の吸着ノズルで吸着してプリント配線板上に実装可能とするためである。
【００２９】
なお、コモンモードチョークコイルの作製において、一体型フェライトコア１の２本の巻芯部２にそれぞれ巻線３０を設けた後に、金属板電極１０の鍔部３への接着作業を行ってもよい。
【００３０】
この実施の形態によれば、次の通りの効果を得ることができる。
【００３１】
（１）一体型フェライトコア１の方形鍔部３に、金属板電極１０のコ字状折曲部１１を接着材２０で方形鍔部３に固着するが、その際に４箇所の金属板電極１０の実装面（底面）を同一高さに揃えた状態で接着材２０を硬化させることにより、フェライトコア１のゆがみ、そり、かけがあっても、各金属板電極１０の実装面のコプラナリティを３０μｍ以下とすることができる。この結果、はんだリフローのために塗布するクリームはんだの厚みが薄い高密度実装用のプリント配線板に対しても接続不良を発生せずに表面実装が可能となる。
【００３２】
（２）前記金属板電極１０を、コ字状折曲部１１の下辺部１１ｃ以外の部分（好ましくは側面部１１ｂ）にて方形鍔部３に接着固定することにより、金属板電極１０の下部に自由度を持たせて、プリント配線板上に実装する際の熱ストレスをフェライトコア鍔部３に伝えることなく実装することができる。また、プリント配線板のたわみ等の変形に起因する応力も緩和でき、フェライトコア１の損傷を防止できる。
【００３３】
なお、上記実施の形態では一体型フェライトコア１を用いたが、２個以上のコア分割体に分割され、２本の巻芯部の両端に両巻芯部を連結する鍔部が形成されるように前記コア分割体同士を組み合わせてなるフェライトコア組立体を用いてもよい。分割したコア構造とすることで、予め自動巻線機で作製した巻線を、コア分割体に挿入してからコア分割体同士を組み合わせ一体化するように構成でき、巻線作業の合理化ができる。
【００３４】
【実施例】
長さ９ｍｍ×幅７ｍｍの外形を有する一体型フェライトコア１の２本の巻芯部２にそれぞれ巻線３０を７ターン設け、巻線端末（リード部）を適切な長さにカットする。外部接続電極としての金属板電極１０は銅板にニッケル（Ｎｉ），錫（Ｓｎ）の順にメッキ処理を施したものであり、コア１の巻芯部延長上の方形鍔部３に接着材２０で端子浮きを抑える治具を用いて合計４箇所固着する。但し、接着材２０はエポキシ系熱硬化性接着剤であって、方形鍔部３の側面（外側端面）３ａに塗布し、方形鍔部３の側面と金属板電極１０のコ字状折曲部１１の側面部１１ｂ間に接着材２０が介在するようにして方形鍔部３に対してコ字状折曲部１１を取り付ける。そして、前記巻線端末と金属板電極１０とを係止片１２をかしめて接続し、はんだ付けをする。上面が平坦なカバー４０はフェライトコア１に接着材を塗布し、固定する。
【００３５】
このようにして作成されたコモンモードチョークコイルの電極端子強度評価結果を以下の表１に示す。
【００３６】
【表１】

【００３７】
表１中、Ｎｏ．１〜Ｎｏ．１０は従来品、実施例品の試料番号であり、従来品は金属板電極の代わりに、フェライトコアに銀（Ａｇ）焼付電極を形成し、その上に銅（Ｃｕ）、ニッケル（Ｎｉ），錫（Ｓｎ）の順にメッキ処理を施して外部接続電極（端子）としたものである。
【００３８】
試験条件は、図６（Ａ）のように、基板サイズ１００×４０ｍｍ、厚さ１．０ｍｍのガラスエポキシ基板の中央に試料をはんだ付けし、同図（Ｂ）のように、スパン９０ｍｍ、加圧速度１．０ｍｍ／ｓとして、たわみ強度を観測したところ、従来品は側面電極部分のフェライトコアにクラックが発生したが（平均値５．５８ｍｍでコア破壊）、実施例品はたわみ強度試験において製品破壊がなかった。実施例品は全てはんだフィレットの破壊で（平均値１１．２５ｍｍでフィレット破壊）、製品破壊は発生しなかった。
【００３９】
また、上記実施例品の試料のコプラナリティを測定したところ、以下の表２の通り、コプラナリティ３０μｍ以下を達成できている。
【００４０】
【表２】

表２中、Ｎｏ．１〜Ｎｏ．１０は実施例品の試料番号であり、▲１▼〜▲４▼は１番目から４番目の金属板電極の実装面高さ測定値（試料を上下反転し、カバーの上面を基準面上に載置して各金属板電極の実装面の高さを測定した）であり、表２中の数値の単位はｍｍである。実施例品の試料のうち、コプラナリティの最大値は０．０２４ｍｍ（＝２４μｍ）であり、コプラナリティ３０μｍ以下を達成できていることがわかる。
【００４１】
以上本発明の実施の形態及び実施例について説明してきたが、本発明はこれに限定されることなく請求項の記載の範囲内において各種の変形、変更が可能なことは当業者には自明であろう。
【００４２】
【発明の効果】
以上説明したように、本発明によれば、外部接続端子としてのフェライトコアに設けた各金属板電極の実装面のコプラナリティを３０μｍ以下に維持でき、換言すれば、コプラナリティが３０μｍ以下の平面とすることが可能となるので、プリント配線板上に安定して実装することができ、実装時の接続不良の発生を防止し、高密度実装に適したコモンモードチョークコイル用コア構造体やコモンモードチョークコイルを実現できる。
【００４３】
また、フェライトコアへの金属板電極の取り付けを工夫することで、プリント配線板のたわみ等の応力がフェライトコアに加わることを軽減でき、この点でも信頼性の高い実装が可能となる。
【図面の簡単な説明】
【図１】本発明の一実施の形態であって、フェライトコアに金属板電極を接着したコモンモードチョークコイル用コア構造体の側断面図である。
【図２】前記コモンモードチョークコイル用コア構造体に巻線を施したコモンモードチョークコイルを示す正面図である。
【図３】同平面図である。
【図４】同底面図である。
【図５】同側面図である。
【図６】たわみ試験方法（電極端子強度評価方法）の説明図である。
【符号の説明】
１フェライトコア
２巻芯部
３方形鍔部
３ａ側面
１０金属板電極
１１コ字状折曲部
１２係止片
２０接着材
３０巻線
４０カバー[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a core structure for a common mode choke coil having a metal plate electrode as an external connection electrode (terminal), which is used for removing common mode noise entering from the outside in an electronic circuit or an electronic device, and the same. The present invention relates to a manufacturing method and a common mode choke coil.
[0002]
[Prior art]
Generally, a common mode choke coil uses a ring-shaped magnetic core (a magnetic core having two winding cores), and a pair of windings are applied to the magnetic core. In the case where the magnetic core is a small ferrite core, a silver (Ag) baked electrode is formed on the core, and a plating process such as tin (Sn) suitable for soldering is performed thereon. Further, the present applicant has considered a structure in which a metal plate electrode is directly provided on a magnetic core and a winding terminal is connected thereto.
[0003]
Known examples of the common mode choke coil include the following Patent Document 1 and Patent Document 2.
[0004]
[Patent Document 1] Japanese Utility Model Publication No. 4-38497 [Patent Document 2] Japanese Patent Application Laid-Open No. 2-201906
In the above-mentioned Patent Document 1, in a common mode choke coil configured by using two coils in which two magnetic cores are wound and butting ends, the two magnetic cores have square plate-like ridges at both ends, respectively. It is composed of a rectangular drum-shaped magnetic core, and has a configuration in which side surfaces corresponding to each other of the flange portions of both magnetic cores are brought into contact with each other so as to form a closed magnetic circuit. In this case, the means for winding the winding around the magnetic core can be automatically mechanized. Although there is no detailed description of the electrode for external connection, it is assumed that it is formed on an insulating material bonded to the outer end surface of one of the flanges. However, since the electrode is on the outer end face of one of the collars, the core part of the drum-shaped magnetic core is in a vertical state when mounted on the printed wiring board, and is not suitable for low profile.
[0006]
Further, Patent Document 2 is a coil conductor winding portion in which coil conductor wires having spring properties are formed in two cores in a predetermined winding shape, and lead portions extending from both sides of the coil conductor winding portion. The coil lead wire winding portion of the coil is attached to the coil and the leg portion, and each lead portion is locked in a state where the coil lead wire winding portion is pulled, so that the leg portions are mutually connected. It is characterized by comprising a pair of butted cores. In this structure, the external electrode is a lead part and is not a surface mount product.
[0007]
[Problems to be solved by the invention]
A general ferrite core as a magnetic core of this type of common mode choke coil has a volume contraction indicated by a reduction ratio during firing. In the ferrite material used in this product, volume shrinkage of about 15% occurs before and after firing. In addition, core distortion, warping, and scabging also occur.
[0008]
For this reason, a silver-baked electrode is formed on a ferrite core, and the external connection electrode plated thereon has a problem that the height of the electrode mounting surface is uneven due to distortion of the core, warpage, etc. There was also a problem that the ferrite core was easily damaged due to thermal stress during mounting on the PCB and deflection of the printed wiring board directly applied to the ferrite core.
[0009]
Similarly, even in a structure in which a metal plate electrode as an external connection electrode is simply fixed to a ferrite core, there is a problem that the height of the electrode mounting surface is uneven due to distortion of the core, warpage or the like.
[0010]
In recent years, as the mounting density of printed wiring boards has increased, the thickness of cream solder applied to the substrate surface has also become very thin. If the height of each external connection electrode is uneven, There was a problem that a gap was generated between the external connection electrode of the common mode choke coil and the land pattern of the printed wiring board at the time of soldering mounting on the wiring board by the reflow method, and electrical connection could not be made. In particular, a problem occurred remarkably when the coplanarity (flatness) was 100 μm or more. In this specification, coplanarity is defined as a gap between the external connection electrode of the common mode choke coil and the land pattern of the printed wiring board.
[0011]
In the case of Patent Document 1, even if two cores are precisely manufactured, the accuracy of a combined finished product may be inferior, and it is considered difficult to ensure the required coplanarity. In the case of Patent Document 2, the structure has no consideration for surface mounting.
[0012]
In view of the above points, the present invention can withstand mechanical stresses such as thermal stress during mounting and substrate deflection on the mounting side by using a metal plate electrode as an external connection electrode, and has good coplanarity. It is an object of the present invention to provide a common mode choke coil core structure, a manufacturing method thereof, and a common mode choke coil that can be used for high-density mounting.
[0013]
Other objects and novel features of the present invention will be clarified in embodiments described later.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, a core structure for a common mode choke coil according to the invention of claim 1 of the present application is an integrated ferrite core having flange portions connecting both core portions at both ends of two core portions. And a metal plate electrode that has at least a U-shaped bent part and is provided in a pair on each collar part,
The metal plate electrode is attached to the flange at the U-shaped bent portion, and the coplanarity of the mounting surface of each metal plate electrode is 30 μm or less.
[0015]
The core structure for a common mode choke coil according to the invention of claim 2 of the present application is divided into two or more pieces, and is combined so that flanges connecting the two core portions are formed at both ends of the two core portions. A ferrite core assembly, and at least a U-shaped bent portion and a pair of metal plate electrodes provided on each flange,
The metal plate electrode is attached to the flange at the U-shaped bent portion, and the coplanarity of the mounting surface of each metal plate electrode is 30 μm or less.
[0016]
A core structure for a common mode choke coil according to a third aspect of the present invention is the core structure for a common mode choke coil according to the first or second aspect, wherein the metal plate electrode is bonded to the flange portion at a portion other than the lower side portion of the U-shaped bent portion. It is characterized by being fixed.
[0017]
A common mode choke coil according to a fourth aspect of the present invention is characterized in that a winding is applied to each core portion of the core structure for a common mode choke coil according to the first, second or third aspect, and the end of each winding is connected to the metal plate electrode. It is characterized by being connected to.
[0018]
A method for manufacturing a core structure for a common mode choke coil according to the invention of claim 5 includes an integrated ferrite core having flanges connecting both core portions to both ends of two core portions, and at least a U-shape. Metal plate electrodes having a pair of bent portions and each provided on each flange,
The metal plate electrode is attached to the flange portion by providing an adhesive between the U-shaped bent portion and the flange portion, and the bonding surface of each metal plate electrode is aligned at the same height. The material is cured, and the coplanarity of the mounting surface of each metal plate electrode is 30 μm or less.
[0019]
The method for manufacturing a core structure for a common mode choke coil according to the sixth aspect of the present invention is divided into two or more pieces, and a collar portion that connects both core portions is formed at both ends of the two core portions. Using a ferrite core assembly that is combined as described above, and a metal plate electrode that has at least a U-shaped bent portion and is provided in a pair on each flange,
The metal plate electrode is attached to the flange portion by providing an adhesive between the U-shaped bent portion and the flange portion, and the bonding surface of each metal plate electrode is aligned at the same height. The material is cured, and the coplanarity of the mounting surface of each metal plate electrode is 30 μm or less.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a core structure for a common mode choke coil, a manufacturing method thereof, and a common mode choke coil according to the present invention will be described with reference to the drawings.
[0021]
An embodiment of the present invention will be described with reference to FIGS. In these drawings, reference numeral 1 denotes an integral type ferrite core, which has a rectangular flange (square plate-like flange) 3 for connecting both cores 2 to both ends of two cores 2 as shown in FIG. In addition, a substantially square closed magnetic circuit with little leakage magnetic flux is formed.
[0022]
As shown in the enlarged portion of FIG. 1, a pair of metal plate electrodes 10 attached as external connection electrodes to each square flange 3 are fitted to the square flange 3 with some play (up and down gap). A U-shaped bent portion 11 and a locking piece 12 for winding end locking formed by folding back on the upper side portion 11a are provided. The metal plate electrode 10 having the U-shaped bent portion 11 and the locking piece 12 is formed by bending a metal plate such as copper or copper alloy.
[0023]
Further, the metal plate electrode 10 is fixed with an adhesive 20 (for example, a thermosetting resin adhesive) at the position of the rectangular collar portion on the extension of the core portion 2 of the ferrite core 1. When fixing with the adhesive material 20, the adhesive material 20 is apply | coated to parts other than the bottom face of the rectangular collar part 3 of the ferrite core 1, Preferably the side surface (outer end surface) 3a, the side surface of the rectangular collar part 3, and the metal plate electrode 10 The U-shaped bent portion 11 is attached to the rectangular flange 3 such that the adhesive 20 is interposed between the side surface portions 11 b of the U-shaped bent portion 11. At this time, the terminal floats are arranged so that the mounting surfaces which are the bottom surfaces of the four metal plate electrodes 10 are arranged at the same height, in other words, the mounting surfaces of the four metal plate electrodes 10 are positioned on the same plane. The adhesive 20 is cured by using a jig for holding it together.
[0024]
The inner dimension of the U-shaped bent portion 11 of the metal plate electrode 10 is slightly larger than that of the ferrite core rectangular flange 3, so that the metal plate electrode 10 is attached to the rectangular flange 3 with a little play (gap in the vertical direction). Therefore, even if the ferrite core 1 is distorted, warped or hooked, the adhesive 20 is used using a jig so that the mounting surfaces of the four metal plate electrodes 10 are positioned on the same plane when the metal plate electrode 10 is bonded. Coplanarity can be ensured by the flatness of the thickness of the metal plate electrode 20 and the processing accuracy. The dimensional accuracy of the metal plate electrode 10 is on the order of general metal processing accuracy, and may be appropriately selected to be 10 μm or less according to the required coplanarity. Of course, the deformed metal plate electrode 10 cannot be used.
[0025]
What is necessary is just to select suitably the material and application quantity of the adhesive material 20 according to the adhesive strength requested | required. The adhesive application position may be anywhere as long as it does not affect the coplanarity (conversely, avoid the bottom surface of the square flange 3 that affects the coplanarity). In this embodiment, the adhesive coating position is on the side surface of the ferrite core flange 3. Adhesive 20 is applied and fixed together with a jig that suppresses terminal floating. Thereby, as will be clarified by data to be described later, the coplanarity of the mounting surface including the bottom surface of each metal plate electrode 10 can be set to 30 μm or less. As a result, the mounting surface of the four metal plate electrodes 10 is a plane having a coplanarity of 30 μm or less, and can be stably mounted on the printed wiring board. Further, it is not necessary to pursue the dimensional accuracy of the ferrite core 1 to the limit, and it is not necessary to chamfer the ferrite core 1. Moreover, if it adhere | attaches on the side surface of the ferrite core collar part 3, the lower side part 11c of the U-shaped bending part 11 of the metal plate electrode 10 has a freedom degree, and the thermal stress at the time of mounting on a printed wiring board is carried out. It can be mounted without transmitting to the ferrite core flange 3.
[0026]
As described above, each of the two core portions 2 has the integral ferrite core 1 having the rectangular flange portion 3 connecting the both core portions to both ends, and at least the U-shaped bent portion 11. A pair of metal plate electrodes 10 provided on the flange portion 3, the metal plate electrodes 10 being mounted on the flange portion 3 at the portion of the U-shaped bent portion 11, and the mounting surface of each metal plate electrode 10 A core structure for a common mode choke coil having a coplanarity of 30 μm or less is obtained.
[0027]
When a common mode choke coil is manufactured using the core structure for a common mode choke coil, the windings 30 are provided on the two core portions 2 of the integral ferrite core 1 respectively, and ends of the winding (lead portions) ) Is pulled out to the upper side of the metal plate electrode 10 and temporarily fixed by caulking the locking piece 12 as shown in FIG. Then, the winding terminal is connected to the upper side portion of the metal plate electrode 10 by soldering. Thereafter, the cover 40 having a flat upper surface is applied to the upper surface of the rectangular flange 2 of the ferrite core 1 and fixed to the ferrite core 1. The cover 40 is a non-magnetic material such as a liquid crystal polymer resin having excellent moldability and heat resistance, and a recess 41 is formed on the lower surface side to avoid the connecting portion of the metal plate electrode 10.
[0028]
The reason why the cover 40 having a flat upper surface is bonded is that it can be mounted on the printed wiring board by being sucked by the suction nozzle of the electronic component mounting machine.
[0029]
In the production of the common mode choke coil, after the windings 30 are provided on the two core portions 2 of the integrated ferrite core 1, the metal plate electrode 10 may be bonded to the flange portion 3. .
[0030]
According to this embodiment, the following effects can be obtained.
[0031]
(1) The U-shaped bent portion 11 of the metal plate electrode 10 is fixed to the rectangular flange portion 3 of the integral ferrite core 1 with the adhesive 20 at the four corners of the metal plate electrode. By curing the adhesive 20 with the mounting surface (bottom surface) of 10 aligned at the same height, the coplanarity of the mounting surface of each metal plate electrode 10 can be obtained even if the ferrite core 1 is distorted, warped or hung. It can be 30 μm or less. As a result, surface mounting is possible without causing a connection failure even for a printed wiring board for high-density mounting in which the cream solder applied for solder reflow is thin.
[0032]
(2) The metal plate electrode 10 is bonded and fixed to the rectangular flange 3 at a portion (preferably the side surface portion 11b) other than the lower side portion 11c of the U-shaped bent portion 11, thereby lowering the lower portion of the metal plate electrode 10 Therefore, it is possible to mount the heat exchanger without mounting the ferrite core flange 3 with thermal stress when it is mounted on the printed wiring board. Further, stress due to deformation such as deflection of the printed wiring board can be relieved, and damage to the ferrite core 1 can be prevented.
[0033]
In the above embodiment, the integrated ferrite core 1 is used. However, the core core is divided into two or more core divided bodies, and flanges are formed at both ends of the two core portions to connect both core portions. As described above, a ferrite core assembly formed by combining the core divided bodies may be used. By using a split core structure, it is possible to configure windings that have been prepared in advance by an automatic winding machine so that the core split bodies are combined and integrated, and the winding work can be rationalized. .
[0034]
【Example】
Seven turns of the winding 30 are provided on each of the two core portions 2 of the integrated ferrite core 1 having an outer shape of length 9 mm × width 7 mm, and a winding terminal (lead portion) is cut to an appropriate length. A metal plate electrode 10 as an external connection electrode is obtained by plating a copper plate in the order of nickel (Ni) and tin (Sn), and an adhesive 20 is attached to the rectangular flange 3 on the core portion extension of the core 1. A total of four points are fixed using a jig that suppresses terminal floating. However, the adhesive 20 is an epoxy thermosetting adhesive, and is applied to the side surface (outer end surface) 3a of the square flange 3 so that the side surface of the rectangular flange 3 and the U-shaped bent portion of the metal plate electrode 10 are applied. The U-shaped bent portion 11 is attached to the rectangular flange 3 such that the adhesive 20 is interposed between the side surface portions 11b of the eleventh side. Then, the winding terminal and the metal plate electrode 10 are connected by caulking the locking piece 12 and soldered. The cover 40 having a flat upper surface is fixed by applying an adhesive to the ferrite core 1.
[0035]
Table 1 below shows the results of the electrode terminal strength evaluation of the common mode choke coil thus prepared.
[0036]
[Table 1]

[0037]
In Table 1, No. 1-No. 10 is a sample number of a conventional product and an example product. In the conventional product, a silver (Ag) baked electrode is formed on a ferrite core instead of a metal plate electrode, and copper (Cu), nickel (Ni), The external connection electrodes (terminals) are obtained by plating in the order of tin (Sn).
[0038]
As shown in FIG. 6 (A), the sample was soldered to the center of a glass epoxy substrate having a substrate size of 100 × 40 mm and a thickness of 1.0 mm, and a span of 90 mm was applied as shown in FIG. When the flexural strength was observed at a pressure speed of 1.0 mm / s, cracks occurred in the ferrite core of the side electrode portion in the conventional product (core fracture at an average value of 5.58 mm). There was no product destruction. In all of the examples, the solder fillet was broken (the fillet was broken at an average value of 11.25 mm), and the product was not broken.
[0039]
Moreover, when the coplanarity of the sample of the above-mentioned Example product was measured, as shown in Table 2 below, a coplanarity of 30 μm or less was achieved.
[0040]
[Table 2]

In Table 2, No. 1-No. 10 is a sample number of the example product, and (1) to (4) are measured values of the mounting surface height of the first to fourth metal plate electrodes (the sample is turned upside down and the upper surface of the cover is placed on the reference surface) The height of the mounting surface of each metal plate electrode was measured), and the unit of numerical values in Table 2 is mm. Among the samples of Example products, the maximum value of coplanarity is 0.024 mm (= 24 μm), and it can be seen that the coplanarity of 30 μm or less can be achieved.
[0041]
Although the embodiments and examples of the present invention have been described above, it is obvious to those skilled in the art that the present invention is not limited thereto and various modifications and changes can be made within the scope of the claims. I will.
[0042]
【The invention's effect】
As described above, according to the present invention, the coplanarity of the mounting surface of each metal plate electrode provided on the ferrite core as the external connection terminal can be maintained at 30 μm or less, in other words, the plane having a coplanarity of 30 μm or less. Therefore, it is possible to stably mount on a printed wiring board, prevent the occurrence of connection failure during mounting, and suitable for high-density mounting core structures and common mode chokes A coil can be realized.
[0043]
Further, by devising the attachment of the metal plate electrode to the ferrite core, it is possible to reduce the stress such as the deflection of the printed wiring board from being applied to the ferrite core, and also in this respect, highly reliable mounting is possible.
[Brief description of the drawings]
FIG. 1 is a side sectional view of a core structure for a common mode choke coil according to an embodiment of the present invention, in which a metal plate electrode is bonded to a ferrite core.
FIG. 2 is a front view showing a common mode choke coil in which the core structure for the common mode choke coil is wound.
FIG. 3 is a plan view of the same.
FIG. 4 is a bottom view of the same.
FIG. 5 is a side view of the same.
FIG. 6 is an explanatory diagram of a deflection test method (electrode terminal strength evaluation method).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ferrite core 2 Winding core part 3 Rectangular eaves part 3a Side surface 10 Metal plate electrode 11 U-shaped bending part 12 Locking piece 20 Adhesive material 30 Winding 40 Cover

Claims

An integral type ferrite core in which flanges connecting the two core parts are formed at both ends of the two core parts, and a metal having at least a U-shaped bent part and a pair of each provided on each flange part A plate electrode,
The core for a common mode choke coil, wherein the metal plate electrode is attached to the flange at the U-shaped bent portion, and the coplanarity of the mounting surface of each metal plate electrode is 30 μm or less. Structure.

A ferrite core assembly that is divided into two or more pieces and combined so that a collar portion that connects the two core portions is formed at both ends of the two core portions; and at least a U-shaped bent portion And provided with a pair of metal plate electrodes provided on each heel part,
The core for a common mode choke coil, wherein the metal plate electrode is attached to the flange at the U-shaped bent portion, and the coplanarity of the mounting surface of each metal plate electrode is 30 μm or less. Structure.

The core structure for a common mode choke coil according to claim 1 or 2, wherein the metal plate electrode is bonded and fixed to the flange portion at a portion other than the lower side portion of the U-shaped bent portion.

4. A common mode choke coil comprising: windings applied to each core portion of the core structure for a common mode choke coil according to claim 1, and connected to the metal plate electrode.

An integral type ferrite core in which flanges connecting the two core parts are formed at both ends of the two core parts, and a metal having at least a U-shaped bent part and a pair of each provided on each flange part With plate electrode,
The metal plate electrode is attached to the flange portion by providing an adhesive between the U-shaped bent portion and the flange portion, and the bonding surface of each metal plate electrode is aligned at the same height. A method for producing a core structure for a common mode choke coil, wherein the material is cured to set the coplanarity of the mounting surface of each metal plate electrode to 30 μm or less.

A ferrite core assembly that is divided into two or more pieces and combined so that a collar portion that connects the two core portions is formed at both ends of the two core portions; and at least a U-shaped bent portion And a pair of metal plate electrodes provided on each heel part,
The metal plate electrode is attached to the flange portion by providing an adhesive between the U-shaped bent portion and the flange portion, and the bonding surface of each metal plate electrode is aligned at the same height. A method for producing a core structure for a common mode choke coil, wherein the material is cured to set the coplanarity of the mounting surface of each metal plate electrode to 30 μm or less.