JP4435439B2

JP4435439B2 - Method for mounting fuse element and fuse built-in electric component

Info

Publication number: JP4435439B2
Application number: JP2001069617A
Authority: JP
Inventors: 教祐服部; 朋晋三井
Original assignee: Uchihashi Estec Co Ltd
Current assignee: Uchihashi Estec Co Ltd
Priority date: 2000-03-16
Filing date: 2001-03-13
Publication date: 2010-03-17
Anticipated expiration: 2021-03-13
Also published as: JP2001332165A

Description

【０００１】
【発明の属する技術分野】
本発明は、コンデンサやトランジスタ等の電気部品に内蔵されるヒュ−ズ素子及びヒュ−ズ内蔵電気部品、例えばタンタルコンデンサの実装方法に関するものである。
【０００２】
【従来の技術】
電気部品においては、電流ヒュ−ズ素子を電気部品本体に接続し、これらを樹脂モ−ルド等により封止することがある。
例えば、タンタルコンデンサにおいては、万一の極性誤装着による過電流を未然に防止するために、コンデンサ素子にヒュ−ズ素子を接続し、これらを樹脂でモ−ルドしている。また、パワ−トランジスタにヒュ−ズ素子を接続し、これらを樹脂で封止することも知られている。
これらのヒュ−ズ内蔵電気部品においては、ヒュ−ズ溶断時のヒュ−ズ素子の発熱温度で加熱される。而して、その電気部品本体やモ−ルド樹脂の炭化・燃焼を防止するために、その発熱温度を所定温度以下に抑える必要があり、例えば、タンタルコンデンサの場合、タンタル粉末焼結体の発煙防止のために、６００℃以下に抑えることが要求される。
而るに、上記電流ヒュ−ズは、速動溶断型であり、溶断電流をｉ、溶断時間をｔｍ、ヒュ−ズ素子の溶断時温度をＴｍ、同じく抵抗をＲ、同じくヒュ−ズ素子の単位長さ当たりの熱容量をＫ、周囲温度をθとすると、ほぼ
【数１】
ｔｍ＝Ｋ（Ｔｍ−θ）／Ｒｉ^２
（１）
が成立し、Ｔｍを６００℃以下にすることが要求される。
【０００３】
上記のヒュ−ズ内蔵電気部品は、通常リフロ−法またはフロ−法により、回路基板に実装され、上記ヒュ−ズ素子には、この実装時の温度で損傷されることのない融点のものを使用する必要がある。
【０００４】
【発明が解決しようとする課題】
従来、リフロ−法やフロ−法には、Ｐｂ−Ｓｎ系はんだが使用されており、その実装温度は２２０℃〜２３０℃とされていた。
而して、上記電気部品に内蔵させるヒュ−ズ素子には、Ｐｂ−Ｓｎ、Ｐｂ−Ｓｎ−Ａｇ、Ｐｂ−Ｉｎ、Ｐｂ−Ｉｎ−Ａｇ系やこれらにＳｂ、Ａｕ、Ｃｕ等を添加した融点２６０℃〜３２０℃の合金が使用されていた。
【０００５】
しかしながら、近来、廃棄された電子・電気機器からの鉛イオンの溶出による環境汚染を防止するために、鉛フリ−はんだの使用が要請され、Ｓｎ−３．５ＡｇやＳｎ−０．７Ｃｕ等の鉛フリ−はんだが開発されている。これらの鉛フリ−はんだを使用しての実装温度は、Ｐｂ−Ｓｎはんだ使用の場合よりも高く、最高で３２０℃が予定されている。
而るに、上記ヒュ−ズ素子においても、鉛フリ−化が要請され、この鉛フリ−化にあたっては、上記実装時でのヒュ−ズ素子の損傷防止、ヒュ−ズ溶断時の電気部品本体若しくはモ−ルド樹脂の炭化・燃焼防止を保証し得るものであることが要求される。
【０００６】
而るに、Ａｇ系、Ａｌ系、Ａｕ系では、過電流遮断は可能であっても、就中、細線化が容易なＡｌ−Ｓｉでも、共晶温度が５７７℃であり、上記６００℃以下での溶断時温度の要求を辛うじて充たし得るに過ぎない。また、亜鉛単体はんだの使用も提案されているが、融点が４２０℃であって、上記２点の条件を充足させ得ても、イオン化傾向が高く酸化し易く、蒸気圧が高く電子部品用ヒュ−ズには使用し難い。
【０００７】
従来、電極材として熱伝導率の小さい鉄−ニッケル合金やコバ−ル合金を用い、モ−ルド樹脂に熱伝導率の低いもの（１５×１０^−４cm^３/℃・sec・cm以下）を用い、Ｓｎ−５Ａｇ（固相線温度２２１℃、液相線温度２４０℃）のように共晶点（Ａｇ３．５重量％、共晶点温度２２１℃）近傍のＳｎ−Ａｇをヒュ−ズ素子として用いた角型チップ状ヒュ−ズが公知であり（特開昭５９−８１８２８号公報）、温度２４０℃で実装しても、電極材やモ−ルド樹脂の低熱伝導性のためにヒュ−ズ素子を損傷させることなく実装できると期待されている。
しかしながら、かかる結果は、前記鉛フリ−はんだ使用のもとでのほぼ３２０℃という高温実装では、到底期待し難い。
【０００８】
ところで、上記実装時でのヒュ−ズ素子の損傷過程は、溶融されたヒュ−ズ素子がその溶融体の界面エネルギ−に基づき電極への濡れで引っ張られて細くされ、実装終了に伴う冷却凝固でその細りが固定されることにあり、冷却凝固直前での細りが僅小であれば、実質的な損傷は回避できる。
而るに、図２に示すＳｎ−Ａｇの平衡状態図において、非共晶領域では、固相線温度２２１℃で溶け始め、更なる昇温で液相分が増加していき、液相線温度で溶融が完了して完全な液相になり、Ａｇ量が異なると、同じ温度で共に固液共存状態になっても、液相分の割合が相違し（従って、固相分の割合が相違し）、その固液共存体の界面エネルギ-が相違する。而して、同じ温度のもとでも、共晶点近傍領域と共晶点隔離領域とでは、界面エネルギ-が相違し、上記した実装時でのヒュ−ズ素子の細りの程度、すなわち損傷の程度にも差が生じる。
従って、Ａｇの配合量を調整することによって、溶け始め温度が同じであっても、上記固液共存状態（半溶融状態）での界面エネルギ−の調整で、実装時でのヒュ−ズ素子の損傷を抑制することが可能であると推定される。
【０００９】
本発明の目的は、ヒュ−ズ素子、特に、タンタルコンデンサ等の電気部品に内蔵させるヒュ−ズ素子において、ヒュ−ズ内蔵電気部品の鉛フリ−はんだによる安定な実装やヒュ−ズ溶断作動時の電気部品の炭化・燃焼防止を満足に保証しつつ、そのヒュ−ズ素子のＳｎ−Ａｇ系での鉛フリ−化を、Ａｇ配合量の調整により良好に達成することにある。
更に、上記目的に加え、加工が容易なヒュ−ズ素子を提供することにある。
【００１０】
【課題を解決するための手段】
請求項１に係るヒューズ素子内蔵電気部品の実装方法は、ヒューズ素子内蔵電気部品の実装方法ヒューズ素子を内蔵させた電気部品を実装温度２４０℃〜３２０℃で回路板に実装する方法であり、ヒューズ素子にＡｇが１０〜５０重量％、残部がＳｎからなるＡｇ−Ｓｎ組成で、その固相線温度よりも前記実装温度が高い合金を用いることを特徴とする。
【００１１】
請求項２に係るヒューズ素子内蔵電気部品の実装方法は、ヒューズ素子を内蔵させた電気部品を実装温度２４０℃〜３２０℃で回路板に実装する方法であり、ヒューズ素子にＡｇが１０〜５０重量％、残部がＳｎからなるＡｇ−Ｓｎ組成にＳｂが１〜１０重量％添加されている組成で、その固相線温度よりも前記実装温度が高い合金を用いることを特徴とする。
【００１２】
請求項３に係る電気部品内蔵用ヒューズ素子は、請求項１のヒューズ素子内蔵電気部品の実装方法において使用されるヒューズ素子であり、Ａｇが１０〜５０重量％、残部がＳｎからなるＡｇ−Ｓｎ組成で、その固相線温度よりも前記実装温度が高い合金を用いることを特徴とする。溶断時のヒュ−ズ素子の温度が通常６００℃以下とされ、また線径が通常５０μｍ〜１５０μｍとされる。
【００１３】
請求項４に係る電気部品内蔵用ヒューズ素子は、請求項２のヒューズ素子内蔵電気部品の実装方法において使用されるヒューズ素子であり、Ａｇが１０〜５０重量％、残部がＳｎからなるＡｇ−Ｓｎ組成にＳｂが１〜１０重量％添加されている組成で、その固相線温度よりも前記実装温度が高い合金を用いることを特徴とする。溶断時のヒュ−ズ素子の温度が通常６００℃以下とされ、また線径が通常５０μｍ〜１５０μｍとされる。
【００１４】
【発明の実施の形態】
以下、図面を参照しつつ本発明の実施の形態について説明する。
図１は、本発明に係るヒュ−ズ素子を内蔵させたコンデンサの一例を示している。
図１において、１はタンタルコンデンサ素子、２は陽極リ−ド導体である。３は配線板であり、一対の電極３１，３２を有し、その電極間に本発明に係るヒュ−ズ素子ａを接続し、一方の電極３１をコンデンサ素子１の陰極に接合し、他方の電極３２にリ−ド導体４を接合してある。５は封止樹脂層、例えばエポキシ樹脂層である。
上記ヒュ−ズ素子と電極との接合には、抵抗溶接、ワイヤボ−ルボンディング、ウェッジボンディング等を用いることができる。
【００１５】
上記のコンデンサは、ＩＣ、トランジスタ、チップ抵抗等の他の電気部品と共にリフロ−法やフロ−法によって回路板に実装され、はんだには、鉛フリ−はんだ、例えば、Ｓｎ−３．５Ａｇ共晶（共晶点温度２２１℃）、Ｓｎ−０．７Ｃｕ共晶（共晶点温度２２７℃）、Ｓｎ−４Ｓｂ（固相線温度２３５℃、液相線温度２４０℃）等を使用でき、実装温度は２４０℃〜３２０℃とされる。
本発明の請求項１に係るヒュ−ズ素子には、Ａｇ１０〜５０重量％、残部Ｓｎの合金組成が使用されているから、図２に示すＳｎ−Ａｇの平衡状態図から明らかな通り、前記実装温度２４０℃〜３２０℃のもとで半溶融状態になり、液相中に固相粒体が混在した状態となり、濡れ性が悪く、実装加熱中での電極への濡れ広がりによるヒュ−ズ素子の細りを僅かにとどめ得、実装終了時での冷却凝固でほぼ元の太さに保持できる。
従って、上記のヒュ−ズ内蔵コンデンサを、ヒュ−ズ素子の固相線温度温度よりも高い実装温度２４０℃〜３２０℃という鉛フリ−はんだによるリフロ−法またはフロ−法でもヒュ−ズ素子を安定に保持しつつ実装できる。
【００１６】
上記したヒュ−ズ素子をタンタルコンデンサに内蔵させる理由は、万一の極性誤接続によって過電流が流れるのを防止するためであり、遮断電流をｉ、遮断時間をｔｍ、ヒュ−ズ素子の溶断時温度をＴｍ、同じく抵抗をＲ、同じくヒュ−ズ素子の単位長さ当たりの熱容量をＫ、周囲温度をθとすると、ほぼ前記の式（１）が成立し、ヒュ−ズ素子の溶断時温度Ｔｍをタンタル焼結体の発煙温度６００℃以下とし、かつ、ｔｍを可及的に短くすることが要求される。
而るに、本発明の請求項１に係るヒュ−ズ素子においては、後述の実施例から明らかなように、線径５０μｍφ〜１５０μｍφのもとで、２〜６Ａを数msecの遮断時間で、かつ、ヒュ−ズ素子の溶断時温度６００℃以下で過電流を遮断できる。
【００１７】
本発明の請求項１に係るヒュ−ズ素子においては、Ａｇ配合量を５０重量％未満としてあるから、充分な靱性を有し、前記５０μｍφ〜１５０μｍφという細線径のもとでも、ヒュ−ズ素子の供給や電気部品への接合を断線なくスム−ズに行うことができる。また、ヒュ−ズ素子の線引き加工も良好に行うことができる。
本発明の請求項１に係るヒュ−ズ素子においては、Ａｇ添加量を１０重量％以上としており、図２に示すＳｎ−Ａｇ平衡状態図から明らかなとおり、Ｓｎ量が多少増加しても、液相線温度の変動を僅少に抑えることができるから、Ｓｎメッキ電極との溶接等によりＳｎが拡散増加しても、元の融点特性を充分に維持できる。
本発明に係るヒュ−ズ素子は、回路板のヒュ−ズ電極にヒュ−ズ素子単体を前記したリフロー法またはフロー法により実装する形態でも使用することができる。また、リフロー法またはフロー法により実装した後での補修やあと付けでも、鏝で安全にはんだ付けすることもできる。
【００１８】
本発明の請求項１に係るヒュ−ズ素子は、回転液中紡糸法によって製造することもできる。すなわち、回転ドラムの内周面に遠心力により形成保持された冷却液層に、ノズルから噴射した溶融ジェットを冷却液層の周速と同速・同方向で入射させ、この液層入射ジェットを冷却液層で急冷・凝固させて紡糸することもできる。この場合、ノズルから冷却液層に至る空間でのジェットは、ノズルの円形形状が溶融金属の表面張力により保持されて円形断面となる。更に、ジェットの表面張力による円形保持力を冷却液層の動圧（ジェットを扁平化しようとする圧力）よりも大とするように、冷却液層周速、ジェットの冷却液層入射角等を調整してあり、冷却液層に入射されたジェットも、断面円形を保持しつつ冷却・凝固されていく。従って、線径５０μｍφ〜１５０μｍφという細線のヒュ−ズ素子を容易に製造できる。
【００１９】
本発明の請求項２に係るヒュ−ズ素子においては、上記請求項１に係るヒュ−ズ素子のＡｇ−Ｓｎ組成（Ａｇが１０〜５０重量％、残部がＳｎ）にＳｂを１〜１０重量％添加した組成を使用しており、Ｓｂの添加により靱性を高め、線径５０μｍφ〜１５０μｍφという細線の線引加工、回転液中紡糸でのコイル取り時等での耐断線性を高めて細線製造の一層の容易化を図っている。Ｓｂの添加量を１〜１０重量％とする理由は、１重量％未満では靱性の向上に効果がなく、１０重量％を越えると、前記したＡｇ−Ｓｎ組成（Ａｇが１０〜５０重量％、残部がＳｎ）に基づく有利性の享有が困難になるからである。
このヒュ−ズ素子もタンタルコンデンサ等の電気部品に内蔵させて使用できる。
【００２０】
【実施例】
〔実施例１〕
内径５００ｍｍ，巾４５ｍｍのドラムを２００ｒｐｍで回転させて約１６００ｍｌの水を層状に形成し、この冷却液層中に、ヒ−タにて溶融させた組成材を窒素ガス加圧により、石英ガラスノズルからジェットとして上記冷却液層周速と同速度で噴射して紡糸する方法により、Ｓｎ−１５Ａｇの１４０μｍφ細線を製造し、これをヒュ−ズ素子とした。このヒュ−ズ素子の固相線温度は２２１℃、液相線温度は３４０℃である。
【００２１】
〔実施例２〕
実施例１と同様にして、Ｓｎ−３５Ａｇの９０μｍφ細線を製造し、これをヒュ−ズ素子とした。このヒュ−ズ素子の固相線温度は２２１℃、液相線温度は４３０℃である。
【００２２】
〔実施例３〕
実施例１と同様にして、Ｓｎ−５０Ａｇの１１０μｍφ細線を製造し、これをヒュ−ズ素子とした。このヒュ−ズ素子の固相線温度は２２１℃、液相線温度は４９０℃である。
【００２３】
〔実施例４〕
Ｓｎ−２０Ａｇ−６Ｓｂの押出線をダイス線引きにより８０μｍφ細線に加工し、これをヒュ−ズ素子とした。このヒュ−ズ素子の固相線温度は２３０℃、液相線温度は３８０℃である。
【００２４】
〔比較例１〕
実施例１と同様にして、Ｓｎ−５Ａｇの１１０μｍφ細線を製造し、これをヒュ−ズ素子とした。このヒュ−ズ素子の固相線温度は２２１℃、液相線温度は２４０℃である。
【００２５】
〔比較例２〕
実施例１と同様にして、Ｓｎ−５５Ａｇの９０μｍφ細線を製造し、これをヒュ−ズ素子とした。このヒュ−ズ素子の固相線温度は２２１℃、液相線温度は５２０℃である。
【００２６】
これらの実施例品及び比較例品につき、次ぎの抵抗値変化率、電流遮断特性（遮断時間及び温度）及び柔軟性を測定したところ、表１の通りであった（試料数２０個の平均値）
。
【００２７】
〔抵抗値変化率〕温度２８０℃のもとでの実装の可否を評価するためのものである。図３に示すように、セラミック基板６１にＡｇペ−ストの塗布・焼成により対電極６２，６２を設け、両電極間にヒュ−ズ素子ａを載置し、更に各電極６２に錫メッキ銅線６３を溶接し、その溶接熱で各電極とヒュ−ズ素子ａとの間を溶接した試料を大気中で１０分間、２８０℃に保持し、１０分時の初期に対する抵抗値変化率を測定した。錫メッキ銅線６３を付設した理由は、溶融したヒュ−ズ素子の濡れを生じ易くし、厳しい評価を行うためである。
〔遮断電流特性〕ヒュ−ズ素子に５Ａの電流を通電し、遮断時間と遮断時のヒュ−ズ素子温度を測定した。
〔柔軟性〕直径０．５ｍｍの棒に巻きつけて折れなかったものを○、折れたものを×とした。
【００２８】
〔表１〕
表１
電流遮断特性
合金組成抵抗変化率（％）遮断時間溶断時温度柔軟性
実施例１ Sn-15Ag ＋０．６４０．０６０秒３５０℃ ○
実施例２ Sn-35Ag ＋２．１００．０１５秒５００℃ ○
実施例３ Sn-50Ag −０．９９０．０９０秒５３０℃ ○
実施例４ Sn-20Ag6Sb −３．５０．０１４秒３８０℃ ○
比較例１ Sn-5Ag 測定不可０．０５０秒３００℃ ○
比較例２ Sn-55Ag −０．７６０．１２０秒５４０℃ ×
【００２９】
本発明に係るヒュ−ズ素子においては、溶け始め温度（固相線温度２２１℃）が実装最高３２０℃より低くても、液相線温度が３２０℃以上であり、温度３２０℃のもとでは完全に液化せずに半溶融状態となり、かかる半溶融状態では濡れ性が低くて細くなり難く、本発明に係るヒュ−ズ素子を内蔵させた電気部品を３２０℃という高い温度のもとで実装しても、そのヒュ−ズ素子を実質的な細り無く安定に保持できる。このことは、比較例１の抵抗変化率が測定不可（ヒュ−ズ素子が溶断し、抵抗値上昇が極めて大）であるのに対し、実施例１〜４の抵抗変化率が僅小であることからも確認できる。
【００３０】
また、本発明に係るヒュ−ズ素子においては、液相線温度が６００℃よりも充分に低く、溶断時のヒュ−ズ素子の温度を６００℃以下に抑え得て電気部品や封止樹脂の炭化・燃焼を防止できることは、表１の電流遮断特性の溶断時温度からも確認できる。
【００３１】
更に、本発明に係るヒュ−ズ素子においては、柔軟性に優れ、供給時や電気部品への接合時に曲げ破損するのを充分に防止できることは、表１の柔軟性の評価からも確認できる。特に、請求項２記載のヒュ−ズ素子においては、上記有利性を充分に保持し得る範囲でＳｂを添加して組成の靱性を一層に高めているので、５０μｍφ〜１５０μｍφ細線の製造の一層の容易化を図ることができる。
【００３２】
【発明の効果】
本発明によれば、ヒュ−ズ素子、特にタンタルコンデンサ等の電気部品に内蔵させるヒュ−ズ素子において、ヒュ−ズ内蔵電気部品の鉛フリ−はんだによる安定な実装及びヒュ−ズ溶断作動時の電気部品の炭化・燃焼防止、更には、ヒュ−ズ素子の容易な取扱や容易な製造等の点を満足に保証しつつそのヒュ−ズ素子のＳｎ−Ａｇ系での鉛フリ−化を可能にでき、鉛フリ−化による環境保全上、極めて有用である。
【図面の簡単な説明】
【図１】本発明に係るヒュ−ズ内蔵電気部品の一例を示す図面である。
【図２】Ｓｎ−Ａｇ合金の平衡状態図である。
【図３】抵抗変化率の測定試料を示す図面である。
【符号の説明】
ａヒュ−ズ素子
１コンデンサ素子
５封止樹脂層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuse element incorporated in an electrical component such as a capacitor or a transistor and a mounting method of a fuse built-in electrical component such as a tantalum capacitor.
[0002]
[Prior art]
In an electrical component, the current fuse element may be connected to the electrical component body and sealed with a resin mold or the like.
For example, in a tantalum capacitor, a fuse element is connected to a capacitor element and is molded with a resin in order to prevent overcurrent due to a wrong polarity mounting. It is also known to connect fuse elements to power transistors and seal them with resin.
These electric components with built-in fuses are heated at the heat generation temperature of the fuse element when the fuse is blown. Therefore, in order to prevent carbonization and combustion of the electrical component main body and the mold resin, it is necessary to suppress the heat generation temperature to a predetermined temperature or less. For example, in the case of a tantalum capacitor, the tantalum powder sintered body emits smoke. In order to prevent this, it is required to keep the temperature below 600 ° C.
Thus, the current fuse is a fast-acting fusing type, the fusing current is i, the fusing time is tm, the fusing temperature of the fuse element is Tm, the resistance is R, and the fuse element is the same. If the heat capacity per unit length is K and the ambient temperature is θ,
tm = K (Tm−θ) / Ri ²
(1)
And Tm is required to be 600 ° C. or lower.
[0003]
The above-mentioned fuse built-in electric parts are usually mounted on a circuit board by a reflow method or a flow method, and the fuse element has a melting point that is not damaged by the temperature at the time of mounting. Need to use.
[0004]
[Problems to be solved by the invention]
Conventionally, Pb—Sn solder has been used for the reflow method and the flow method, and the mounting temperature has been 220 ° C. to 230 ° C.
Thus, the fuse element incorporated in the electrical component includes Pb—Sn, Pb—Sn—Ag, Pb—In, Pb—In—Ag series, and melting points obtained by adding Sb, Au, Cu, etc. to these. An alloy of 260 ° C to 320 ° C was used.
[0005]
However, recently, in order to prevent environmental pollution due to the elution of lead ions from discarded electronic / electrical equipment, the use of lead-free solder is required, and lead such as Sn-3.5Ag and Sn-0.7Cu is used. Free solder has been developed. The mounting temperature using these lead-free solders is higher than that in the case of using Pb—Sn solders, and a maximum of 320 ° C. is planned.
Therefore, the fuse element is also required to be lead-free. In this lead-free process, the fuse element is prevented from being damaged at the time of mounting, and the electric component main body at the time of fuse melting is used. Alternatively, it is required to be able to guarantee carbonization / combustion prevention of the mold resin.
[0006]
Thus, in the Ag-based, Al-based, and Au-based materials, even though overcurrent can be interrupted, the eutectic temperature is 577 ° C even in the case of Al-Si that can be easily thinned. It can only meet the temperature requirement at the time of fusing. Although the use of a zinc simple solder has been proposed, the melting point is 420 ° C., and even if the above two conditions can be satisfied, the ionization tendency is high, the metal is easy to oxidize, the vapor pressure is high, and the electronic component fuse is used. -Hard to use
[0007]
Conventionally, an iron-nickel alloy or a Koval alloy having a low thermal conductivity is used as an electrode material, and a low thermal conductivity material (15 × 10 ⁻⁴ cm ³ / ° C. · sec · cm or less) is used as a mold resin. Used, Sn-Ag near the eutectic point (3.5 wt% Ag, eutectic point temperature 221 ° C.) like Sn-5Ag (solidus temperature 221 ° C., liquidus temperature 240 ° C.) is used as a fuse element. The rectangular chip-like fuse used for the above is known (Japanese Patent Laid-Open No. 59-81828), and even if it is mounted at a temperature of 240 ° C., the fuse is used because of the low thermal conductivity of the electrode material and mold resin. It is expected that it can be mounted without damaging the device.
However, such a result is hardly expected in high-temperature mounting at about 320 ° C. using the lead-free solder.
[0008]
By the way, the process of damaging the fuse element at the time of mounting described above is that the melted fuse element is thinned by being wetted by the electrode based on the interfacial energy of the melt, and cooling solidification accompanying the end of mounting. If the thinning just before cooling solidification is small, substantial damage can be avoided.
Thus, in the Sn-Ag equilibrium diagram shown in FIG. 2, in the non-eutectic region, melting begins at the solidus temperature of 221 ° C., and the liquid phase increases as the temperature rises further. When the melting is completed at the temperature and a complete liquid phase is obtained and the amount of Ag is different, the proportion of the liquid phase is different even if the solid and liquid coexist at the same temperature. The interface energy of the solid-liquid coexistence is different. Thus, even at the same temperature, the interfacial energy is different between the eutectic point vicinity region and the eutectic point isolation region, and the degree of thinning of the fuse element at the time of mounting described above, that is, damage There is also a difference in degree.
Therefore, by adjusting the compounding amount of Ag, even if the melting start temperature is the same, by adjusting the interfacial energy in the solid-liquid coexistence state (semi-molten state), the fuse element at the time of mounting is adjusted. It is estimated that damage can be suppressed.
[0009]
It is an object of the present invention to provide a fuse element, particularly a fuse element to be incorporated in an electrical component such as a tantalum capacitor, when the fuse built-in electrical component is stably mounted by lead-free soldering or when the fuse is blown. It is intended to satisfactorily achieve lead freezing in the Sn—Ag system of the fuse element by adjusting the amount of Ag, while ensuring the prevention of carbonization and combustion of the electrical parts.
It is another object of the present invention to provide a fuse element that can be easily processed.
[0010]
[Means for Solving the Problems]
A method for mounting an electric component with a built-in fuse element according to claim 1 is a method for mounting an electric component with a built-in fuse element on a circuit board at a mounting temperature of 240 ° C. to 320 ° C. The element is characterized by using an alloy having an Ag—Sn composition in which Ag is 10 to 50% by weight and the balance is Sn, and the mounting temperature is higher than the solidus temperature.
[0011]
The method for mounting an electric component with a built-in fuse element according to claim 2 is a method of mounting an electric component with a built-in fuse element on a circuit board at a mounting temperature of 240 ° C. to 320 ° C., and Ag is 10 to 50 wt. %, A composition in which 1 to 10% by weight of Sb is added to an Ag—Sn composition with the balance being Sn, and an alloy having a higher mounting temperature than its solidus temperature is used.
[0012]
An electric component built-in fuse element according to claim 3 is a fuse element used in the mounting method of the fuse element built-in electric component according to claim 1, and Ag—Sn composed of Ag of 10 to 50 wt% and the balance of Sn. An alloy having a higher composition temperature than the solidus temperature is used. The temperature of the fuse element at the time of fusing is usually 600 ° C. or less, and the wire diameter is usually 50 μm to 150 μm.
[0013]
The fuse element for electric component built-in according to claim 4 is a fuse element used in the mounting method for the electric component with built-in fuse element according to claim 2, and Ag—Sn comprising 10 to 50% by weight of Ag and the balance being Sn. An alloy having 1 to 10% by weight of Sb added to the composition and having a higher mounting temperature than its solidus temperature is used. The temperature of the fuse element at the time of fusing is usually 600 ° C. or less, and the wire diameter is usually 50 μm to 150 μm.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an example of a capacitor incorporating a fuse element according to the present invention.
In FIG. 1, 1 is a tantalum capacitor element, and 2 is an anode lead conductor. Reference numeral 3 denotes a wiring board having a pair of electrodes 31 and 32, connecting the fuse element a according to the present invention between the electrodes, joining one electrode 31 to the cathode of the capacitor element 1, and The lead conductor 4 is joined to the electrode 32. 5 is a sealing resin layer, for example, an epoxy resin layer.
Resistance welding, wire ball bonding, wedge bonding, or the like can be used for joining the fuse element and the electrode.
[0015]
The above capacitor is mounted on a circuit board by a reflow method or a flow method together with other electric parts such as an IC, a transistor, and a chip resistor, and a lead-free solder, for example, Sn-3.5Ag eutectic is used as the solder. (Eutectic point temperature 221 ° C), Sn-0.7Cu eutectic (eutectic point temperature 227 ° C), Sn-4Sb (solidus temperature 235 ° C, liquidus temperature 240 ° C), etc. can be used. Is set to 240 ° C to 320 ° C.
In the fuse element according to claim 1 of the present invention, an alloy composition of Ag 10 to 50% by weight and the balance Sn is used. As is apparent from the equilibrium diagram of Sn-Ag shown in FIG. It is in a semi-molten state at a mounting temperature of 240 ° C. to 320 ° C., a solid phase particle is mixed in the liquid phase, the wettability is poor, and the fuse due to the spreading of the electrode to wet during mounting heating The thinning of the element can be kept slightly, and it can be kept at its original thickness by cooling and solidification at the end of mounting.
Therefore, the above fuse-incorporated capacitor can also be used by a lead-free solder reflow method or a flow method in which the mounting temperature is 240 ° C. to 320 ° C., which is higher than the solidus temperature of the fuse device. Can be mounted while maintaining stability.
[0016]
The reason why the above-mentioned fuse element is incorporated in the tantalum capacitor is to prevent an overcurrent from flowing due to a wrong polarity connection, i., The interruption current is i, the interruption time is tm, and the fuse element is blown. When the temperature is Tm, the resistance is R, the heat capacity per unit length of the fuse element is K, and the ambient temperature is θ, the above equation (1) is almost satisfied, and the fuse element is blown. It is required that the temperature Tm is a smoke temperature of the tantalum sintered body of 600 ° C. or lower and tm is made as short as possible.
Therefore, in the fuse element according to claim 1 of the present invention, as will be apparent from the examples described later, 2 to 6 A with a wire diameter of 50 μm to 150 μmφ is cut off for several milliseconds, In addition, overcurrent can be cut off at a fuse element melting temperature of 600 ° C. or lower.
[0017]
In the fuse element according to claim 1 of the present invention, since the Ag blending amount is less than 50% by weight, the fuse element has sufficient toughness, even under the thin wire diameter of 50 μmφ to 150 μmφ. Can be smoothly and smoothly connected without disconnection. Further, the drawing process of the fuse element can be performed well.
In the fuse element according to claim 1 of the present invention, the amount of Ag added is 10% by weight or more, and as is apparent from the Sn-Ag equilibrium diagram shown in FIG. Since fluctuations in the liquidus temperature can be suppressed to a small extent, the original melting point characteristics can be sufficiently maintained even if Sn is diffused and increased by welding with an Sn plating electrode or the like.
The fuse element according to the present invention can be used in a form in which a fuse element is mounted on a fuse electrode of a circuit board by the reflow method or the flow method described above. Also, it can be safely soldered with scissors even after repairing or retrofitting after mounting by reflow method or flow method.
[0018]
The fuse element according to claim 1 of the present invention can also be manufactured by a spinning solution spinning method. That is, the molten jet sprayed from the nozzle is incident on the cooling liquid layer formed and held on the inner peripheral surface of the rotating drum by centrifugal force at the same speed and in the same direction as the peripheral speed of the cooling liquid layer, and this liquid layer incident jet is It can also be spun by rapid cooling and solidification in the cooling liquid layer. In this case, the jet in the space from the nozzle to the coolant layer has a circular cross section with the circular shape of the nozzle being held by the surface tension of the molten metal. Furthermore, the peripheral velocity of the cooling fluid layer, the incident angle of the cooling fluid layer of the jet, etc. are set so that the circular holding force due to the surface tension of the jet is larger than the dynamic pressure of the cooling fluid layer (pressure for flattening the jet). The jet that has been adjusted and entered the cooling liquid layer is cooled and solidified while maintaining a circular cross section. Accordingly, it is possible to easily manufacture a fuse element having a thin wire diameter of 50 μmφ to 150 μmφ.
[0019]
In the fuse element according to claim 2 of the present invention, the Ag-Sn composition (Ag is 10 to 50 wt%, the balance is Sn) of the fuse element according to claim 1 is 1 to 10 wt% of Sb. % Is added, and the toughness is increased by the addition of Sb, and the wire is drawn with a wire diameter of 50 μmφ to 150 μmφ, and the wire breakage resistance is improved at the time of coil removal by spinning in a rotating liquid. To make it easier. The reason why the amount of Sb added is 1 to 10% by weight is that if it is less than 1% by weight, there is no effect in improving toughness, and if it exceeds 10% by weight, the above-described Ag—Sn composition (Ag is 10 to 50% by weight, This is because it is difficult to enjoy the advantage based on Sn).
This fuse element can also be used by being incorporated in an electrical component such as a tantalum capacitor.
[0020]
【Example】
[Example 1]
A drum having an inner diameter of 500 mm and a width of 45 mm is rotated at 200 rpm to form a layer of about 1600 ml of water, and in this cooling liquid layer, a composition material melted by a heater is pressurized with nitrogen gas to apply a quartz glass nozzle. From the above, a Sn-15Ag 140 [mu] m [phi] fine wire was produced by spraying as a jet at the same speed as the peripheral speed of the cooling liquid layer and spinning, and this was used as a fuse element. The fuse element has a solidus temperature of 221 ° C. and a liquidus temperature of 340 ° C.
[0021]
[Example 2]
In the same manner as in Example 1, a Sn-35Ag 90 μmφ thin wire was manufactured and used as a fuse element. The fuse element has a solidus temperature of 221 ° C. and a liquidus temperature of 430 ° C.
[0022]
Example 3
In the same manner as in Example 1, a Sn-50Ag 110 μmφ thin wire was manufactured and used as a fuse element. The fuse element has a solidus temperature of 221 ° C. and a liquidus temperature of 490 ° C.
[0023]
Example 4
An extruded wire of Sn-20Ag-6Sb was processed into a 80 μmφ thin wire by die drawing, and this was used as a fuse element. The fuse element has a solidus temperature of 230 ° C. and a liquidus temperature of 380 ° C.
[0024]
[Comparative Example 1]
In the same manner as in Example 1, a Sn-5Ag 110 μmφ thin wire was manufactured and used as a fuse element. The fuse element has a solidus temperature of 221 ° C. and a liquidus temperature of 240 ° C.
[0025]
[Comparative Example 2]
In the same manner as in Example 1, a Sn-55Ag 90 μmφ thin wire was manufactured and used as a fuse element. The fuse element has a solidus temperature of 221 ° C. and a liquidus temperature of 520 ° C.
[0026]
The following resistance value change rate, current interruption characteristics (breaking time and temperature) and flexibility were measured for these Example and Comparative Example products, and as shown in Table 1 (average value of 20 samples) )
.
[0027]
[Rate of change in resistance value] This is for evaluating the possibility of mounting at a temperature of 280 ° C. As shown in FIG. 3, counter electrodes 62 and 62 are provided on a ceramic substrate 61 by applying and firing Ag paste, a fuse element a is placed between the two electrodes, and tin-plated copper is further applied to each electrode 62. The wire 63 was welded, and the specimen welded between each electrode and the fuse element a with the welding heat was held at 280 ° C. for 10 minutes in the atmosphere, and the resistance value change rate relative to the initial value at 10 minutes was measured. did. The reason why the tin-plated copper wire 63 is attached is to make the molten fuse element easily wetted and to perform strict evaluation.
[Cut-off current characteristics] A current of 5 A was passed through the fuse element, and the cut-off time and the fuse element temperature at the cut-off were measured.
[Flexibility] The case where it was wound around a rod having a diameter of 0.5 mm and was not broken was marked with ◯, and that which was broken was marked with ×.
[0028]
[Table 1]
Table 1
Current interruption characteristics
Alloy composition Resistance change rate (%) Cut-off time Fusing temperature Flexibility Example 1 Sn-15Ag +0.64 0.060 seconds 350 ° C ○
Example 2 Sn-35Ag + 2.10 0.015 seconds 500 ° C. ○
Example 3 Sn-50Ag -0.99 0.090 seconds 530 ° C ○
Example 4 Sn-20Ag6Sb −3.5 0.014 seconds 380 ° C. ○
Comparative example 1 Sn-5Ag measurement impossible 0.050 seconds 300 ° C ○
Comparative Example 2 Sn-55Ag -0.76 0.120 seconds 540 ° C ×
[0029]
In the fuse element according to the present invention, even when the melting start temperature (solidus temperature 221 ° C.) is lower than the mounting maximum 320 ° C., the liquidus temperature is 320 ° C. or higher. It is in a semi-molten state without being completely liquefied, and in such a semi-molten state, the wettability is low and it is difficult to become thin, and an electrical component incorporating the fuse element according to the present invention is mounted at a high temperature of 320 ° C. Even so, the fuse element can be stably held without substantial thinning. This is because the resistance change rate of Comparative Example 1 is not measurable (the fuse element is blown out and the resistance value is extremely increased), whereas the resistance change rates of Examples 1 to 4 are very small. This can also be confirmed.
[0030]
In the fuse element according to the present invention, the liquidus temperature is sufficiently lower than 600 ° C., and the temperature of the fuse element at the time of fusing can be suppressed to 600 ° C. The ability to prevent carbonization / combustion can also be confirmed from the fusing temperature of the current interruption characteristics shown in Table 1.
[0031]
Furthermore, it can be confirmed from the evaluation of flexibility in Table 1 that the fuse element according to the present invention is excellent in flexibility and can be sufficiently prevented from being bent and broken at the time of supply or joining to an electrical component. In particular, in the fuse element according to claim 2, since the toughness of the composition is further enhanced by adding Sb within a range in which the above-mentioned advantages can be sufficiently maintained, the production of 50 μmφ to 150 μmφ fine wires is further enhanced. Simplification can be achieved.
[0032]
【The invention's effect】
According to the present invention, in a fuse element, particularly a fuse element to be incorporated in an electric component such as a tantalum capacitor, the lead-free soldering of the fuse built-in electric component and the fuse fusing operation are performed. Prevention of carbonization / combustion of electrical parts, and further lead freezing in the Sn-Ag system of the fuse element while guaranteeing easy handling and easy manufacture of the fuse element It is extremely useful for environmental protection by lead freezing.
[Brief description of the drawings]
FIG. 1 is a view showing an example of an electrical component with a built-in fuse according to the present invention.
FIG. 2 is an equilibrium diagram of a Sn—Ag alloy.
FIG. 3 is a drawing showing a sample for measuring the rate of change in resistance.
[Explanation of symbols]
a fuse element 1 capacitor element 5 sealing resin layer

Claims

This is a method of mounting an electrical component with a built-in fuse element on a circuit board at a mounting temperature of 240 ° C. to 320 ° C., and the fuse element has an Ag—Sn composition composed of 10 to 50% by weight of Ag and the balance of Sn. A method of mounting an electrical component with a built-in fuse element, wherein an alloy having a mounting temperature higher than a phase wire temperature is used .

This is a method of mounting an electrical component with a built-in fuse element on a circuit board at a mounting temperature of 240 ° C. to 320 ° C., wherein the fuse element has an Ag—Sn composition in which Ag is 10 to 50% by weight and the balance is Sn. A method of mounting an electrical component with a built-in fuse element, characterized by using an alloy having a composition added by 10% by weight and having a mounting temperature higher than the solidus temperature.

A fuse element used in a mounting method for an electric component with a built-in fuse element according to claim 1, wherein the mounting is performed with an Ag-Sn composition comprising Ag of 10 to 50% by weight and the balance of Sn, with a solidus temperature higher than that. An electrical component built-in fuse element using an alloy having a high temperature.

It is a fuse element used in the mounting method of the electric component with a built-in fuse element according to claim 2, wherein Sb is added to 1 to 10% by weight to an Ag-Sn composition in which Ag is 10 to 50% by weight and the balance is Sn. An alloy having a built-in electrical component, wherein an alloy having a mounting temperature higher than the solidus temperature is used.

The fuse element for incorporating an electric component according to claim 3 or 4, wherein the temperature of the fuse element at the time of fusing is 600 ° C or less.

6. The electric component built-in fuse element according to any one of claims 3 to 5, wherein the wire diameter is 50 [mu] m to 150 [mu] m .