JP2004296422A

JP2004296422A - Protection element

Info

Publication number: JP2004296422A
Application number: JP2003177588A
Authority: JP
Inventors: Yasuhiko Tomitaka; 康彦冨高; Takashi Igarashi; 孝五十嵐
Original assignee: Uchihashi Estec Co Ltd
Current assignee: Uchihashi Estec Co Ltd
Priority date: 2003-02-05
Filing date: 2003-06-23
Publication date: 2004-10-21
Anticipated expiration: 2023-06-23
Also published as: JP4263543B2

Abstract

<P>PROBLEM TO BE SOLVED: To make a protection element able to be guaranteed for excellent dividing operation performance for a thermal fuse with an intermediate electrode, or a thermal fuse with a resistor, even if the resistivity of a fuse element is high. <P>SOLUTION: The protection element comprises a first electrode 21, a second electrode 22 and an intermediate electrode 20 between them. Each end of a fuse element 4 made of a fusible alloy is connected to the first electrode 21, and the second electrode 22. An intermediate part of the fuse element 4 is connected to the intermediate electrode 20. In operation, the fuse element is divided by wet spread of fused alloy of the melted fuse element 4 over each electrode. To guarantee insulation after the division between each of the first and second electrodes 21, 22 and the intermediate electrode 20, predetermined insulating distances d1, d2 are provided. In this protection element, a width W of a fuse element connecting portion of the intermediate electrode 20 is narrower than each width W1, W2, of fuse element connecting portions of the first and second electrodes 21, 22. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は温度ヒューズや抵抗体付き温度ヒューズ等の保護素子に関するものである。
【０００２】
【従来の技術】
抵抗体付き温度ヒューズは、可溶合金からなるヒューズエレメントを有し、通電発熱によって前記ヒューズエレメントを溶断させる抵抗体を備え、異常検出回路との組合せで使用され、その使用において機器の異常、例えば異常電圧を異常検出回路で検出し、この検出で抵抗体を通電発熱させ、この発生熱でヒューズエレメントを溶断させて機器への通電を遮断している。
また、ヒューズエレメントの融点を機器許容温度に設定し、機器が許容温度に達したときにヒューズエレメントを溶断させて機器の異常発熱ひいては火災の未然防止に使用することもできる。
【０００３】
図９の（イ）は従来の抵抗体付き温度ヒューズの一例を示す図面、図９の（ロ）は図９の（イ）におけるロ−ロ断面図である。
図９において、１’はセラミックス基板等の絶縁基板、２０’〜２３’は絶縁基板上に導電ペーストの印刷・焼き付けにより設けた電極である。４’は第１電極２１’と第２電極２２’間に溶接等により連結したヒューズエレメントであり、中間電極２０’にも接合してある。３’は第３電極２３’と中間電極２０’との間に連結した膜抵抗であり、抵抗ペーストの印刷・焼付けにより設けてある。５’は膜抵抗３’に対するオーバーコートであり、ガラスペーストの印刷・焼付けにより設けてあり、通常膜抵抗３’の外郭よりも３００μｍ〜１０００μｍ程度大きい外郭としてある。６’はヒューズエレメントに塗布したフラックスである。８’は絶縁カバーである。
【０００４】
上記抵抗体付き温度ヒューズの動作機構は次のとおりである。
すなわち、常時では、膜抵抗が非通電とされ、ヒューズエレメントが機器と電源間に挿入されて通電される。異常時に膜抵抗が通電発熱され、この発生熱でヒューズエレメントが溶融され、溶融合金が既溶融フラックスとの共存下電極への濡れ拡がりにより球状化分断され、この分断により膜抵抗の通電が遮断され、分断合金の冷却凝固により非復帰のカットオフが終結される。
また、ヒューズエレメントの融点を機器の許容温度に設定しておけば、機器がほぼ許容温度に達したときにヒューズエレメントが溶融され、溶融合金が既溶融フラックスとの共存下電極への濡れ拡がりにより球状化分断され、この分断により機器への通電が遮断されて機器温度が降下され、分断合金の冷却凝固により非復帰のカットオフが終結される。
【０００５】
図１０は前記抵抗体付き温度ヒューズに対し、膜抵抗を省いた温度ヒューズを示し、後者の使用形態で使用される。
【０００６】
【発明が解決しようとする課題】
上記抵抗体付き温度ヒューズ及び温度ヒューズの何れにおいても、溶融したヒューズエレメントの電極への濡れ拡がりで動作し、従来では、中間電極２０’に両側から溶融合金が濡れ拡がってくるため中間電極２０の巾Ｗ’を第１電極２１の巾Ｗ１’や第２電極２２の巾Ｗ２’よりも広くしている。
従来、温度ヒューズや抵抗体付き温度ヒューズのヒューズエレメントには、鉛を主成分とする可溶合金が使用されていた。しかしながら、鉛は生体系に有害であり、ヒューズエレメントについても他の電器部品と同様に、鉛をはじめとする有害元素を含まない合金組成を使用することが近来強く要請されている。
かかる合金組成として、例えばＳｎ−Ｉｎ−Ｂｉ系合金が有望であるが、比抵抗値が高い値である。例えば、動作温度１３５℃の従来のヒューズエレメント合金Ｓｎ４６．５％−Ｐｂ２９．８％−Ｃｄ１６．７％−Ｉｎ７％、比抵抗値１５μΩｃｍに対し、ほぼ同じ動作温度のヒューズエレメント合金Ｂｉ５２％−Ｓｎ４６％−Ｉｎ２％では比抵抗値が３４μΩｃｍであって２倍以上である。
【０００７】
温度ヒューズや抵抗体付き温度ヒューズのヒューズエレメントの抵抗値は、負荷や自己発熱からの内部抵抗値の制約上、一定値以下に抑える必要があり、通常、比抵抗値の増大に対してはヒューズエレメント径を増大することにより対処している。
しかしながら、ヒューズエレメント径の増大は前記溶融合金量の増加を招き球状化分断性能の低下を来すことになり、これを防止するには電極面積の増大が余儀なくされ、温度ヒューズや抵抗体付き温度ヒューズの寸法増大が避けられない。
【０００８】
本発明の目的は、前記中間電極を有する温度ヒューズや抵抗体付き温度ヒューズにおいて、ヒューズエレメントの比抵抗値が高くても、良好な分断作動性能を保証することにある。
本発明の更なる目的は、上記目的に加え中間電極を有する温度ヒューズや抵抗体付き温度ヒューズの小型化を図ることにある。
【０００９】
【課題を解決するための手段】
請求項１に係る保護素子は、第１電極、第２電極及びこれら電極間の中間電極を備え、可溶合金からなるヒューズエレメントの各端が第１電極及び第２電極に接続され、同ヒューズエレメントの中間部が中間電極に接続され、動作時、溶融されたヒューズエレメントの溶融合金の各電極への濡れ拡がりによりヒューズエレメントが分断され、分断後での第１電極、第２電極のそれぞれと中間電極との間の絶縁保障のためにそれらの間を所定の絶縁距離で離隔した保護素子において、中間電極のヒューズエレメント接続部位の巾が第１電極、第２電極それぞれのヒューズエレメント接続部位の巾よりも狭くされていることを特徴とする。
【００１０】
請求項２に係る保護素子は、第１電極、第２電極、第３電極を備え、第１電極と第２電極との間に中間電極を備え、可溶合金からなるヒューズエレメントの各端が第１電極及び第２電極に接続され、同ヒューズエレメントの中間部が中間電極に接続され、中間電極と第３電極との間に膜抵抗が接続され、動作時、溶融されたヒューズエレメントの溶融合金の各電極への濡れ拡がりによりヒューズエレメントが分断され、分断後での第１電極、第２電極のそれぞれと中間電極との間の絶縁保証のためにそれらの間を所定の絶縁距離で離隔した保護素子において、中間電極のヒューズエレメント接続部位の巾が第１電極、第２電極それぞれのヒューズエレメント接続部位の巾よりも狭くされていることを特徴とする。
【００１１】
請求項３に係る保護素子は、請求項２において、ヒューズエレメントと膜抵抗が絶縁基板片面上に設けられ、膜抵抗に対するオーバコートが設けられ、中間電極の膜抵抗側片端部が膜抵抗一端部を覆い、オーバーコートの中間電極側一端部が中間電極片端部上を覆い、中間電極のヒューズエレメント接続部位から前記オーバーコート一端までの距離Ｌ１が、同部位から膜抵抗一端までの距離Ｌ２に対し、Ｌ１＞Ｌ２−３００μｍとされていることを特徴とする。
【００１２】
請求項４に係る保護素子は、請求項２において、ヒューズエレメントと膜抵抗が絶縁基板片面上に設けられ、膜抵抗に対するオーバコートが設けられ、膜抵抗一端部がオーバーコート一端より突出し、中間電極片端部が前記突出した膜抵抗一端部及びオーバーコート一端部を覆っていることを特徴とする。
【００１３】
請求項５に係る保護素子は、請求項１〜４何れかにおいて、ヒューズエレメントの比抵抗値が２０μΩｃｍ以上であることを特徴とする。
【００１４】
請求項６に係る保護素子は、請求項１〜５において、可溶合金がＩｎ−Ｓｎ−Ｂｉ系合金、Ｂｉ−Ｓｎ−Ｓｂ系合金、Ｉｎ−Ｓｎ系合金、Ｉｎ−Ｂｉ系合金、Ｂｉ−Ｓｎ系合金、Ｉｎ系合金の何れかであることを特徴とし、請求項７に係る保護素子は、請求項６において、Ｉｎ−Ｓｎ−Ｂｉ系合金の組成が（１）４３％＜Ｓｎ≦７０％，０．５％≦Ｉｎ≦１０％，残Ｂｉ、（２）２５％≦Ｓｎ≦４０％，５０％≦Ｉｎ≦５５％，残Ｂｉ、（３）２５％＜Ｓｎ≦４４％，５５％＜Ｉｎ≦７４％，１％≦Ｂｉ＜２０％、（４）４６％＜Ｓｎ≦７０％，１８％≦Ｉｎ＜４８％，１％≦Ｂｉ≦１２％、（５）５％≦Ｓｎ≦２８％，１５％≦Ｉｎ＜３７％，残Ｂｉ（但し、Ｂｉ５７．５％，Ｉｎ２５．２％，Ｓｎ１７．３％とＢｉ５４％，Ｉｎ２９．７％，Ｓｎ１６．３％のそれぞれを基準にＢｉ±２％，Ｉｎ及びＳｎ±１％の範囲を除く）、（６）１０％≦Ｓｎ≦１８％，３７％≦Ｉｎ≦４３％，残Ｂｉ、（７）２５％＜Ｓｎ≦６０％，２０％≦Ｉｎ＜５０％，１２％＜Ｂｉ≦３３％、（８）（１）〜（７）の何れか１００重量部にＡｇ、Ａｕ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｓｂ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加、（９）３３％≦Ｓｎ≦４３％，０．５％≦Ｉｎ≦１０％，残Ｂｉ、（１０）４７％≦Ｓｎ≦４９％，５１％≦Ｉｎ≦５３％の１００重量部にＢｉを３〜５重量部を添加、（１１）４０％≦Ｓｎ≦４６％，７％≦Ｂｉ≦１２％，残Ｉｎ、（１２）０．３％≦Ｓｎ≦１．５％，５１％≦Ｉｎ≦５４％，残Ｂｉ、（１３）２．５％≦Ｓｎ≦１０％，２５％≦Ｂｉ≦３５％，残Ｉｎ、（１４）（９）〜（１３）の何れか１００重量部にＡｇ、Ａｕ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｓｂ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加、（１５）１０％≦Ｓｎ≦２５％，４８％≦Ｉｎ≦６０％，残Ｂｉを１００重量部にＡｇ、Ａｕ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｓｂ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加、Ｂｉ−Ｓｎ−Ｓｂ系合金の組成が（１６）３０％≦Ｓｎ≦７０％，０．３％≦Ｓｂ≦２０％，残Ｂｉ、（１７）（１６）の１００重量部にＡｇ、Ａｕ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加、Ｉｎ−Ｓｎ系合金の組成が（１８）５２％≦Ｉｎ≦８５％，残Ｓｎ、（１９）（１８）の１００重量部にＡｇ、Ａｕ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加、Ｉｎ−Ｂｉ系合金の組成が（２０）４５％≦Ｂｉ≦５５％，残Ｉｎ、（２１）（２０）の組成の１００重量部にＡｇ、Ａｕ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｓｂ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加、Ｂｉ−Ｓｎ系合金の組成が（２２）５０％＜Ｂｉ≦５６％，残Ｓｎ、（２３）（２２）の組成の１００重量部にＡｇ、Ａｕ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加、Ｉｎ系合金の組成が（２４）Ｉｎの１００重量部にＡｕ、Ｂｉ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加、（２５）９０％≦Ｉｎ≦９９．９％，０．１％≦Ａｇ≦１０％の１００重量部にＡｕ、Ｂｉ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加、（２６）９５％≦Ｉｎ≦９９．９％，０．１％≦Ｓｂ≦５％の１００重量部にＡｕ、Ｂｉ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加の何れかであることを特徴とする。
【００１５】
請求項８に係る保護素子は、請求項１〜７何れかにおいて、中間電極のヒューズエレメント接続部位の巾が３００〜４００μｍ、所定の絶縁距離が３００〜１０００μｍであることを特徴とする。
【００１６】
請求項９に係る保護素子は、請求項１〜８何れかにおいて、中間電極の巾がヒューズエレメント接続部位とは別の部分において膨出され、第１電極及び第２電極の巾がその膨出に応じ局部的に後退または凹まされていることを特徴とする。
【００１７】
請求項１０に係る保護素子は、請求項２〜９何れかにおいて、ヒューズエレメントと膜抵抗が絶縁基板片面上に設けられ、膜抵抗に対するオーバコートが設けられ、膜抵抗に接続された少なくとも一の電極と他の電極とが対向する部分の少なくとも一部の電極縁端部に沿いオーバーコートが延在されていることを特徴とする。
【００１８】
請求項１１に係る保護素子は、請求項２〜１０何れかにおいて、第３電極に接続されたリード導体の断面積が第１電極、第２電極のそれぞれに接続されたリード導体の断面積の０．８〜０．５倍とされていることを特徴とする。
【００１９】
【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は請求項２に係る保護素子の一実施例を示す図面である。
図１において、１は耐熱性の絶縁基板例えばセラミックス基板である。２１、２２及び２３は導電ペーストの印刷・焼付けにより設けた第１電極、第２電極及び第３電極であり、リード導体取付け部２１０、２２０及び２３０を備えている。２０は中間電極であり、第１電極と第２電極との中間に配設し、この中間電極２０の第３電極２３側の一端部２０１の巾を第３電極２３（リード導体取付け部２３０を含まず）の巾とほぼ等しくしてある。
前記中間電極２０のヒューズエレメント接続部位の巾Ｗは第１電極、第２電極それぞれのヒューズエレメント接続部位の巾Ｗ１、Ｗ２より狭くし、Ｗ＜Ｗ１，Ｗ２としてある。通常、Ｗ１＝Ｗ２とされている。
前記第１電極２１と中間電極２０との間隔ｄ１及び第２電極２２と中間電極２０との間隔ｄ２、第３電極２３のリード導体取付け部２３０と第２電極２２との間隔ｄは、ヒューズエレメントの分断によりそれらの間が電気的に遮断されてその遮断間に回路電圧が作用しても、それらの各間隔での絶縁を保証できるように各間隔を所定距離に設定してあり、通常ｄ１＝ｄ２＜ｄとしてある。
３は膜抵抗であり、抵抗膜３の一端部３１を中間電極２０の片端部２０１に接続し、抵抗膜３の他端部３２を第３電極２３の一端部２３２に接続してある。
図１において、４は可溶合金からなるヒューズエレメントであり、第１電極２１と第２電極２２間に溶接等により接続すると共に中間を中間電極２０に溶接等により接続してある。５は膜抵抗３に対するオーバーコートである。６はヒューズエレメント４に塗布したフラックスである。７１〜７３は第１電極２１〜第３電極２３のそれぞれのリード導体取付け部２１０〜２３０に溶接等により接続したリード導体であり、溶接にはスポット抵抗溶接を用いることが好ましい。
８は絶縁被覆体であり、例えば、封止剤例えばエポキシ樹脂を塗着する構成、または封止剤層上に保護プレートを固着した構成、あるいはカバーを基板上に載置し、カバー周囲の枠のリード導体引出孔からリード導体を引出し、接着剤例えばエポキシ樹脂で封止した構成とすることができる。
【００２０】
上記において、ヒューズエレメント４には、鉛等の生体系に有害な元素を含まないＩｎ−Ｓｎ−Ｂｉ系合金、Ｂｉ−Ｓｎ−Ｓｂ系合金、Ｉｎ−Ｓｎ系合金、Ｉｎ−Ｂｉ系合金、Ｂｉ−Ｓｎ系合金、Ｉｎ系合金等を使用できる。
Ｉｎ−Ｓｎ−Ｂｉ系合金の組成には、例えば（１）４３％＜Ｓｎ≦７０％，０．５％≦Ｉｎ≦１０％，残Ｂｉ、（２）２５％≦Ｓｎ≦４０％，５０％≦Ｉｎ≦５５％，残Ｂｉ、（３）２５％＜Ｓｎ≦４４％，５５％＜Ｉｎ≦７４％，１％≦Ｂｉ＜２０％、（４）４６％＜Ｓｎ≦７０％，１８％≦Ｉｎ＜４８％，１％≦Ｂｉ≦１２％、（５）５％≦Ｓｎ≦２８％，１５％≦Ｉｎ＜３７％，残Ｂｉ（但し、Ｂｉ５７．５％，Ｉｎ２５．２％，Ｓｎ１７．３％とＢｉ５４％，Ｉｎ２９．７％，Ｓｎ１６．３％のそれぞれを基準にＢｉ±２％，Ｉｎ及びＳｎ±１％の範囲を除く）、（６）１０％≦Ｓｎ≦１８％，３７％≦Ｉｎ≦４３％，残Ｂｉ、（７）２５％＜Ｓｎ≦６０％，２０％≦Ｉｎ＜５０％，１２％＜Ｂｉ≦３３％、（８）（１）〜（７）の何れか１００重量部にＡｇ、Ａｕ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｓｂ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加、（９）３３％≦Ｓｎ≦４３％，０．５％≦Ｉｎ≦１０％，残Ｂｉ、（１０）４７％≦Ｓｎ≦４９％，５１％≦Ｉｎ≦５３％の１００重量部にＢｉを３〜５重量部を添加、（１１）４０％≦Ｓｎ≦４６％，７％≦Ｂｉ≦１２％，残Ｉｎ、（１２）０．３％≦Ｓｎ≦１．５％，５１％≦Ｉｎ≦５４％，残Ｂｉ、（１３）２．５％≦Ｓｎ≦１０％，２５％≦Ｂｉ≦３５％，残Ｉｎ、（１４）（９）〜（１３）の何れか１００重量部にＡｇ、Ａｕ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｓｂ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加、（１５）１０％≦Ｓｎ≦２５％，４８％≦Ｉｎ≦６０％，残Ｂｉを１００重量部にＡｇ、Ａｕ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｓｂ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加の何れかを使用でき、Ｂｉ−Ｓｎ−Ｓｂ系合金の組成には例えば（１６）３０％≦Ｓｎ≦７０％，０．３％≦Ｓｂ≦２０％，残Ｂｉ、（１７）（１６）の１００重量部にＡｇ、Ａｕ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加、Ｉｎ−Ｓｎ系合金の組成が（１８）５２％≦Ｉｎ≦８５％，残Ｓｎ、（１９）（１８）の１００重量部にＡｇ、Ａｕ、Ｂｉ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｓｂ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加の何れかを使用でき、Ｉｎ−Ｂｉ系合金の組成には例えば（２０）４５％≦Ｂｉ≦５５％，残Ｉｎ、（２１）（２０）の組成の１００重量部にＡｇ、Ａｕ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｓｂ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加の何れかを使用でき、Ｂｉ−Ｓｎ系合金の組成には例えば（２２）５０％＜Ｂｉ≦５６％，残Ｓｎ、（２３）（２２）の組成の１００重量部にＡｇ、Ａｕ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加の何れかを使用でき、Ｉｎ系合金の組成には例えば（２４）Ｉｎの１００重量部にＡｕ、Ｂｉ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加、（２５）９０％≦Ｉｎ≦９９．９％，０．１％≦Ａｇ≦１０％の１００重量部にＡｕ、Ｂｉ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加、（２６）９５％≦Ｉｎ≦９９．９％，０．１％≦Ｓｂ≦５％の１００重量部にＡｕ、Ｂｉ、Ｃｕ、Ｎｉ、Ｐｄ、Ｐｔ、Ｇａ、Ｇｅ、Ｐの１種または２種以上を合計０．０１〜７重量部添加の何れかを使用できる。
使用するヒューズエレメントの合金の比抵抗が従来ヒューズエレメント合金のα倍であるとすると、ヒューズエレメントの抵抗値を従来ヒューズエレメントと同一抵抗値とするように、ヒューズエレメントの長さを従来ヒューズエレメントの長さＬに対し、Ｌ／αとしてある。従って、ヒューズエレメントの長さがＬ（α−１）／αだけ短くされ、中間電極２０のヒューズエレメント接続部位の巾Ｗを狭くし、その両側に前記所定の絶縁距離ｄ１及びｄ２を隔てて第１電極２１及び第２電極２２を配設してある。
上記のようにヒューズエレメント４の体積が（α−１）／α倍とされて１／αだけ減少されるから、中間電極のヒューズエレメント接続部位の巾の減少により中間電極２０の表面積が小さくされるにもかかわらず、溶融ヒューズエレメントの溶融合金量の減少のために溶融合金の濡れ拡り範囲がそれだけ狭くなる結果、中間電極の面積不足に起因する濡れ拡がり未完結に基づく動作不良をよく排除できる。
【００２１】
特に、請求項３や請求項４の構成では、膜抵抗に対するオーバコートを設けている場合は、上記中間電極の狭巾化のもとでも中間電極の有効濡れ距離の広大化を図ることができ、良好な動作性能を保証できる。
請求項３では、図２の（イ）及び（ロ）〔図２の（イ）のロ−ロ断面図〕に示すように、中間電極２０の膜抵抗側片端部２０１で膜抵抗３の一端部３１を覆い、中間電極片端部２０１上をオーバーコート５の中間電極側一端部５１で覆い、中間電極２０のヒューズエレメント接続部位から前記オーバーコート５の一端５１ｅまでの距離Ｌ１を、同部位から膜抵抗一端３１ｅまでの距離Ｌ２に対し、Ｌ１＞Ｌ２−３００μｍとしてある。
【００２２】
図２の（イ）において、中間電極２０のヒューズエレメント接続部位の巾（Ｗ）を第１電極２１、第２電極２２それぞれのヒューズエレメント接続部位の巾Ｗ１、Ｗ２より狭くし、Ｗ＜Ｗ１，Ｗ２とし（通常、Ｗ１＝Ｗ２）としてある。また、第１電極２１と中間電極２０との間隔ｄ１及び第２電極２２と中間電極２０との間隔ｄ２並びに第３電極２３のリード導体取付け部２３０と第２電極２２との間隔ｄは、ヒューズエレメント４の分断によりそれらの間が電気的に遮断されてその遮断間に回路電圧が作用しても、それらの各間隔での絶縁を保証できるように所定距離に設定してあり、通常ｄ１＝ｄ２＜ｄとしてある。
図２の（イ）（ロ）において、４はヒューズエレメントであり、図１に示した実施例と同様に第１電極２１と第２電極２２間に溶接等により接続し、中間部を中間電極２０に溶接等により接続してある。６はヒューズエレメント４に塗布したフラックスである。
リード導体や絶縁被覆体は図には現れていないが、これらの構成は実施例１に実質的に同じである。
【００２３】
図２の（ハ）は図２の（イ）のロ−ロ断面と同じ断面位置の断面図により従来例を示している。
請求項３の一実施例を示す図２の（イ）及び（ロ）〔図２の（イ）におけるロ−ロ断面図〕と従来例の同断面を示す図２の（ハ）とにおいて、膜抵抗一端３１ｅ（３１ｅ’）からヒューズエレメントまでの距離が等しいとし、その距離をＬ２とする。
而るに、従来例では抵抗膜３’を封止するために、オーバーコート５’の四方を抵抗膜３’の四方縁端を越え突出させており、その突出代が通常３００〜１０００μｍとされているから、オーバーコート一端３１ｅ’から中間電極２０’のヒューズエレメント接続部位までの距離は最大でも、Ｌ２−３００μｍである。従って、請求項３によれば、オーバーコート一端からヒューズエレメントまでの有効濡れ距離が従来例よりも長く、その有効濡れ距離の増加による有効濡れ面積の増大のために、中間電極２０のヒューズエレメント接続部位の巾の減少により中間電極２０の有効濡れ面積が低減されても、前記有効濡れ面積の低減をそれだけ軽度にとどめ得、このことと前記したヒューズエレメント体積量が少なくなることによることとの相乗効果で分断動作性能を充分に保証できる。
【００２４】
請求項３において、オーバーコート一端５１ｅからヒューズエレメント４までの距離Ｌ１がヒューズエレメント４から抵抗膜一端３１ｅまでの距離（基準距離）Ｌ２より小であっても（Ｌ１＜Ｌ２であっても）、Ｌ１＞Ｌ２−３００μｍの条件を満たす以上、前記した通りヒューズエレメント４の球状化分断性能の高揚に寄与させ得るが、
【数１】
Ｌ１≧Ｌ２
とすれば、中間電極における溶融合金が膜抵抗側に向け濡れ拡がることに対する有効距離Ｌ１をそれだけ長くできるから、Ｌ１≧Ｌ２とすることが望ましい。
【００２５】
図２の（イ）及び（ロ）に示す請求項３の実施例では、抵抗膜一端部３１の封止性能が中間電極片端部２０１とオーバーコート一端部５１との重畳界面に依存し、中間電極及び抵抗膜の配置・寸法が固定されており、その重畳界面距離Ｌ３が中間電極片端２０１ｅに対するオーバーコート一端５１ｅの突出代により与えられるが、この重畳界面距離Ｌ３を余り長くすると、中間電極２０における溶融合金が膜抵抗側に向け濡れ拡がることに対する有効距離Ｌ１が減少して球状化分断性能の向上効果が低減されるから、通常、前記の重畳界面距離Ｌ３は６００μｍ以下とされる。
【００２６】
請求項３に係る保護素子の製造は、（ａ）膜抵抗パターンのメッシュスクリーンを当接して膜抵抗を印刷し次で焼き付ける工程、（ｂ）電極パターンのメッシュスクリーンを当接して電極を印刷し次で焼き付ける工程、（ｃ）オーバーコート用メッシュスクリーンを当接してオーバーコートを印刷し次で焼き付ける工程、（ｄ）オーバーコート印刷・焼付け工程の前または後で必要に応じてトリミングにより膜抵抗の抵抗値を所定値に設定する工程、（ｅ）第１〜第２電極間に可溶合金片を連結し次いでフラックスを塗布する工程、（ｆ）第１〜３電極にリード導体をスポット溶接により接続する工程、（ｇ）ケースカバーで封止する工程の工程順で進められ、リード導体の接続に時間を要して可溶合金片に熱的影響を及ぼす畏れのあるもの、例えばはんだ付けを用いる場合は、第１〜３電極にリード導体を接続する工程を、第１〜第２電極に可溶合金片を連結し次いでフラックスを塗布する工程の前とすることが安全である。
【００２７】
上記した保護素子の動作後では、動作前に可溶合金片で電気的に導通されていた電極間が電気的に遮断され、その電極間に回路電圧が作用する結果、その電極間距離が短い箇所では、閃絡による再導通が発生する畏れがある。この再導通を防止するために、図３に示すように、膜抵抗に連結された中間電極２０または第３電極２３と他の電極（第１電極や第２電極）とが対向する部分の少なくとも一部の電極縁端部に沿いオーバーコート５の延設部５１１，５１２または５１３を形成し、前記閃絡を防止するように絶縁補強することができる。
【００２８】
図４の（イ）は請求項４に係る保護素子の一実施例を示す図面、図４の（ロ）は図４の（イ）におけるロ−ロ断面図である。
図４の（イ）及び（ロ）において、１は耐熱性の絶縁基板例えばセラミックス基板である。３は絶縁基板上に設けた膜抵抗であり、前記した通り抵抗ペーストの印刷・焼付けにより設けてある。５は膜抵抗３に対するオーバーコートであり、オーバーコート一端５１ｅから抵抗膜３の一端部３１を所定の距離ａだけ突出させ、オーバーコート一端５２ｅから抵抗膜３の他端部３２を所定の距離ｂだけ突出させてある。
図４の（イ）において、２０は中間電極、２１は第１電極、２２は第２電極、２３は第３電極であり、中間電極２０のヒューズエレメント接続部位の巾Ｗを第１電極２１、第２電極２２それぞれのヒューズエレメント接続部位の巾Ｗ１、Ｗ２より狭くし、Ｗ＜Ｗ１，Ｗ２（通常Ｗ１＝Ｗ２）としてある。また、第１電極２１と中間電極２０との間隔ｄ１及び第２電極２２と中間電極２０との間隔ｄ２、第３電極２３のリード導体取付け部２３０と第２電極２２との間隔ｄを、ヒューズエレメント４の分断によりそれらの間が電気的に遮断されてその遮断間に回路電圧が作用しても、それらの各間隔での絶縁を保証できるように各間隔を所定距離以上に設定してあり、通常ｄ１＝ｄ２＜ｄとしてある。
図４の（イ）（ロ）において、第３電極２３は膜抵抗３に前記の突出代ｂで接触させて電気的に接続してある。中間電極２０の片端部（膜抵抗側端部）２０１をオーバーコート５の一端５１ｅを越えるように位置させてあり、中間電極２０は膜抵抗３に前記抵抗膜一端部３１の突出代ａで接触させて電気的に接続してある。
４はヒューズエレメントであり、図１に示した実施例と同様に第１電極２１と第２電極２２間に溶接等により接続し、中間部を中間電極２０に溶接等により接続してある。６はヒューズエレメント４に塗布したフラックスである。
リード導体や絶縁被覆体は図には現れていないが実施例１に実質的に同じ構成である。
【００２９】
図４の（ハ）は、図４の（ロ）の断面と同じ位置の断面にて従来例を示している。
図４の（ロ）及び（ハ）において、膜抵抗一端の位置３１ｅ，３１ｅ’は両者同じであり、ヒューズエレメント４，４’からこの位置までの距離Ｌ２は同一寸法である。また膜抵抗一端部３１（３１’）と中間電極片端部２０１（２０１’）との間の接触代ａを同じにしてその間の接触電気抵抗を等しくしてある。
従来例では、既述した通り、オーバーコート一端５１ｅ’を膜抵抗一端３１ｅ’より少なくとも３００μｍ突出させているから、溶融した可溶合金の膜抵抗側への濡れ拡がりに対する有効距離は最大でもＬ２−３００μｍである。これに対し、請求項４に係る抵抗体付き温度ヒューズにおいては、中間電極２０の片端部２０１をオーバーコート一端５１ｅを越えて位置させており、溶融した可溶合金の膜抵抗側への濡れ拡がりに対する有効距離を従来の抵抗体付き温度ヒューズの有効距離Ｌ２−３００μｍより大にできる。
従って、中間電極のヒューズエレメント接続部位の巾の減少により中間電極の有効濡れ面積が低減されても、請求項４によれば、オーバーコート一端からヒューズエレメントまでの上記有効濡れ距離の増加による有効濡れ面積の増大で、前記有効濡れ面積の低減をそれだけ軽度にとどめ得、このことと前記したヒューズエレメント体積量が少なくなることによることとの相乗効果で分断動作性能を充分に保証できる。
【００３０】
請求項４に係る保護素子の製造は、（ａ）膜抵抗パターンのメッシュスクリーンを当接して膜抵抗を印刷し次で焼き付ける工程、（ｂ）オーバーコート用メッシュスクリーンを当接してオーバーコートを印刷し次で焼き付ける工程、（ｃ）電極パターンのメッシュスクリーンを当接して電極を印刷し次で焼き付ける工程、（ｄ）必要に応じて、トリミングにより膜抵抗の抵抗値を所定値に設定する工程、（ｅ）第１〜第２電極にヒューズエレメントを連結し次いでフラックスを塗布する工程、（ｆ）第１〜第３電極にリード導体をスポット溶接により接続する工程、（ｇ）ケースカバーで封止する工程の工程順で進められ、リード導体の接続に、時間を要しヒューズエレメントに熱的悪影響を及ぼす畏れのあるもの、例えばはんだ付けを用いる場合は、各電極にリード導体を接続する工程を、電極にヒューズエレメントを連結し次いでフラックスを塗布する工程の前とすることが安全である。
【００３１】
請求項９では、中間電極のヒューズエレメント接続部位の狭巾化にもかかわらず、中間電極の有効濡れ面積を増大するための別の手段として、中間電極のヒューズエレメント接続部位とは別の部分を図５の（イ）や（ロ）に示すように膨出２０１させ、この膨出のもとでも中間電極２０と第１電極２１との間の絶縁距離及び中間電極２０と第２電極２２との間の絶縁距離を所定の絶縁距離に保持するように第１電極２１や第２電極２２を前記膨出に応じ凹ませるか［図５の（イ）］、または後退２１１、２２１させてある［図５の（ロ）］。
【００３２】
上記何れの実施例においても、第３電極２３のリード導体７３の断面積を小さくすれば、膜抵抗３の通電発生熱の当該リード導体７３を経ての熱伝導流出を抑制して膜抵抗３の発熱速度を迅速化でき、保護素子の動作速度を一層に速くできるので、第３電極に接続するリード導体の断面積を、他のリード導体（第１電極、第２電極に接続するリード導体）に対し、０．８〜０．５倍程度とすることが好ましい。
この場合、全リード導体の断面を高さが等しい四角形とし、断面積の減少を巾を狭めることにより行えば、全リード導体の高さを等しくし得てカバー用の絶縁板または絶縁ケースを載置したときに傾きなく水平にでき、また全リード導体を打ち抜きによるリードフレームから容易に製作できる。
【００３３】
本発明に係る抵抗体付き温度ヒューズによれば、機器の異常に対する前兆を検出し、この検出に伴い膜抵抗を通電発熱させ、この発生熱でヒューズエレメントを溶断させて機器への通電を遮断することができ、この通電遮断により膜抵抗への通電も遮断される。例えば、リチウムイオン２次電池の充電時、過充電時に発生する電圧上昇を検出し、この検出に伴い膜抵抗を通電発熱させ、この発生熱でヒューズエレメントを溶断させて２次電池を充電器から遮断することができる。
【００３４】
図６は上記実施例の抵抗体付き温度ヒューズを用いた２次電池の保護回路を示している。
図６において、Ｓは充電器、Ａはリチウムイオン二次電池である。Ｂは検出動作回路部を示し、ツエナダイオードＤを抵抗Ｒを経てトランジスタＴｒのベースに接続し、エミッタを接地し、ツエナダイオードＤの正極側を回路の高電圧側に接続してある。Ｃは上記実施例の保護素子を示し、第１電極２１と第２電極２２とを充電器Ｓと２次電池Ａ間に接続し、第３電極２３を前記トランジスタＴｒのコレクタに接続してある。
上記ツエナダイオードＤの降伏電圧を２次電池の過充電時に発生する電圧上昇に対し低く設定してあり、過充電により電圧が上昇すると、トランジスタＴｒにベース電流が流れ、大きなコレクタ電流が流れて膜抵抗３が発熱し、この発生熱が中間電極２０を経てヒューズエレメント４に伝達され、ヒューズエレメント４が溶融され、溶融合金４が既溶融フラックスの活性作用を受けつつ中間電極２０及びその両側の第１電極２１と第２電極２２に濡れ拡がって中間電極２０と第１電極２１との間及び中間電極２０と第２電極２２との間で分断されると共に膜抵抗３が電池から遮断される。
本発明に係る保護素子においては、ヒューズエレメントの融点を機器、例えば上記２次電池の保護温度（８０℃〜１２０℃における所望の温度）に選定し、保護素子を実質的に機器温度に追従して昇温させ得るように機器に熱的に接触して取り付ければ、機器の通電を保護温度で遮断でき、保護温度を越えての機器の異常発熱ひいては火災の発生を未然に防止できる。
【００３５】
本発明は、上記した膜抵抗を省き、ヒューズエレメントの融点を機器の保護温度に設定し、機器に熱的接触下で取り付け、機器の通電を保護温度で遮断して保護温度を越えての機器の異常発熱ひいては火災の発生を未然に防止する形態で実施することもでき、図７や図８はその実施例を示している。
図７において、１は耐熱性の絶縁基板例えばセラミックス基板である。２１及び２２は導電ペーストの印刷・焼付けにより設けた第１電極及び第２電極であり、リード導体取付け部２１０及び２２０を備えている。２０は中間電極であり、第１電極２１と第２電極２２との中間に配設してあり、この中間から外れた位置にリード導体取付け部２００を備えている。４は可溶合金からなるヒューズエレメントであり、第１電極２１と第２電極２２間に溶接等により接続すると共に中間を中間電極２０に溶接等により接続してある。中間電極２０のヒューズエレメント接続部位の巾Ｗは第１電極２１、第２電極２２それぞれのヒューズエレメント接続部位の巾Ｗ１、Ｗ２より狭くし、Ｗ＜Ｗ１，Ｗ２としてある。通常、Ｗ１＝Ｗ２とされている。
前記第１電極２１と中間電極２０との間隔ｄ１及び第２電極２２と中間電極２０との間隔ｄ２は、ヒューズエレメント４の分断によりそれらの間が電気的に遮断されてその遮断間に回路電圧が作用しても、それらの各間隔での絶縁を保証できるように各間隔を所定距離以上に設定してあり、通常ｄ１＝ｄ２としてある。
６はヒューズエレメント４に塗布したフラックスである。７０、７１及び７２は中間電極２０〜第２電極２２のそれぞれのリード導体取付け部２００〜２２０に溶接等により接続したリード導体であり、溶接にはスポット抵抗溶接を用いることが好ましい。
８は絶縁被覆体であり、例えば、封止剤例えばエポキシ樹脂を塗着する構成、または封止剤層上に保護プレートを固着した構成、あるいはカバーを基板上に載置し、カバー周囲の枠のリード導体引出孔からリード導体を引出し、接着剤例えばエポキシ樹脂で封止した構成とすることができる。
【００３６】
図８の（イ）及び（ロ）は上記とは別の異なる実施例を示し、図７に示した実施例に対し、中間電極のヒューズエレメント接続部位とは別の部分を膨出させ、この膨出のもとでも中間電極２０と第１電極２１との間の絶縁距離及び中間電極２０と第２電極２２との間の絶縁距離を所定の絶縁距離に保持するように第１電極２１や第２電極２２を前記膨出に応じ局部的に凹ませるか〔図８の（イ）〕、または後退させてある〔図８の（ロ）〕。
【００３７】
上記何れの実施例においても、リード導体付きとしているが、抵抗体付き温度ヒューズでは、第１電極、第２電極及び第３電極を基板の裏面側に基板側面を経て廻してチップタイプとし、温度ヒューズでは、第１電極、第２電極及び中間電極を基板の裏面側に基板側面を経て廻してチップタイプとすることもできる。
【００３８】
本発明においてオーバーコート材は、絶縁物であり、ガラスコートに限定されず、合成樹脂コート例えばエポキシ樹脂コートも使用できる。
本発明において電極材には、導電粒子とガラスフリットと有機溶剤との混合物からなる焼成タイプの外、導電粒子と熱硬化性樹脂（例えばエポキシ樹脂）と溶剤との混合物からなる熱硬化タイプの使用も可能であり、導電粒子には、銀、パラジウム、金、銅等の金属粒子、カーボン等を使用できる。
本発明において膜抵抗材には、抵抗粒子とガラスフリットと有機溶剤との混合物からなる焼成タイプの外、抵抗粒子と熱硬化性樹脂（例えばエポキシ樹脂）と溶剤との混合物からなる熱硬化タイプの使用も可能であり、抵抗粒子には、金属酸化物粒子例えば酸化ルテニウム粒子を使用できる。その他、Ｔｉ−Ｓｉ系抵抗ペーストの使用も可能である。
フラックスには、天然ロジン、変性ロジン（水添ロジン、不均化ロジン、重合ロジン等）及びこれらの精製ロジンにジエチルアミンの塩酸塩、ジエチルアミンの臭化水素酸塩、アジピン等の有機酸等を添加したものを使用できる。
本発明において絶縁基板には、絶縁性で、かつ電極や膜抵抗の形成に耐え得る耐熱性を有するものであれば特に制限無く使用でき、アルミナセラミックス板のようなセラミックス板、耐熱性プラスチック板、ガラス繊維強化プラスチック板、表面に絶縁膜を有する金属板等を使用できる。
【００３９】
本発明に係る保護素子における絶縁基板のタテ×ヨコ寸法は、通常（４．０〜１０．０）ｍｍ×（４．０〜１０．０）ｍｍとされる。電極や膜抵抗の配置パターンや寸法は定格電流や定格電圧に応じて設定される。
定格が１０Ａ×５０Ｖの場合、中間電極のリード導体接続部位の巾は３００〜４００μｍ、第１電極と中間電極との間隔や第２電極と中間電極との間隔は３００〜１０００μｍとされる。
【００４０】
本発明において、ヒューズエレメントには生体系に有害な元素を含まない合金、例えばＳｎ−Ｉｎ−Ｂｉ系合金を用いることが好ましい。このＳｎ−Ｉｎ−Ｂｉ系合金合金組成の一例としてＳｎ４３〜７０％、Ｉｎ０．５〜１０％、残部Ｂｉについて、液相線温度、比抵抗値を示せば表１の通りである。
ただし、液相線温度はＤＳＣ〔基準試料（不変化）と測定試料を窒素ガス容器内に納め、容器ヒータに電力を供給して両試料を一定の速度で加熱し、測定試料の熱的変化に伴う熱エネルギー入力量の変動を示差熱電対により検出する〕により測定した。
【表１】

比抵抗値が２０μΩｃｍ以上と高いが、本発明によればヒューズエレメントの長さを短くしてヒューズエレメントの抵抗値を通常値におさめ得、良好な動作性能を保証できる。
【００４１】
上記合金の比抵抗値を低減すると共に結晶組織を微細化させ合金中の異相界面を小さくして加工歪や応力の分散性を良くするために、前記の合金組成１００重量部にＡｇ、Ａｕ、Ｃｕ、Ｇａ、Ｇｅ、Ｎｉ、Ｐｄ、Ｐｔ、Ｓｂ、Ｐの少なくとも一種を０．０１〜７重量部添加することができる。添加量を０．０１〜７重量部とする理由は、０．０１重量部未満では効果が非常に不充分であり、７重量部を越えると合金の溶融特性が非常に変化し、例えば動作温度のバラツキを許容範囲におさめ難くなる等の不具合が生じるからである。
【００４２】
【実施例】
作動温度については、実施例と比較例の各試料個数を５０箇とし、０．１アンペアの電流を通電しつつ昇温速度１℃／分のオイルバスに浸漬し、ヒューズエレメント分断による通電遮断時のオイル温度を動作温度とした。
【００４３】
〔比較例１〕
図９に示す従来品であり、絶縁基板１にタテ×ヨコ×厚み寸法が６ｍｍ×６ｍｍ×０．６４ｍｍのアルミナセラミックス板を使用し、膜抵抗３を酸化ルテニウム系抵抗ペーストの印刷・焼付けにより形成し、電極２０〜２３を銀系導電ペーストの印刷・焼付けにより形成した。第１電極２１及び第２電極２２（共にリード導体取付け部を除く）のタテ×ヨコ（巾）寸法を１．７ｍｍ×６００μｍとし、中間電極２０のタテ×ヨコ（巾）寸法を１．７ｍｍ×１２００μｍとし、第１電極と中間電極との間隔と第２電極と中間電極との間隔を５００μｍとした。オーバーコートをガラスペーストの印刷・焼き付けにより形成した。ヒューズエレメントにＳｎ４６．５％−Ｐｂ２９．８％−Ｃｄ１６．７％−Ｉｎ７％、比抵抗値１５μΩｃｍの合金を使用し、ヒューズエレメント外径を５００μｍφ、長さを３．３ｍｍとした。ヒューズエレメントの抵抗値は、２５ｍΩである。第１電極及び第２電極のそれぞれのリード導体取付け部に厚み×巾が３００μｍ×１０００μｍのＳｎメッキ銅リード導体を、第３電極の中間電極２０のリード導体取付け部に取り付け部厚み×巾が３００μｍ×１０００μｍ，狭巾部厚み×巾が３００μｍ×７００μｍのＳｎメッキ銅リード導体を接続し、これらの上にカバーとしてタテ×ヨコ×厚み寸法が４ｍｍ×４ｍｍ×０．６４ｍｍのアルミナセラミックス板を載置し、このカバー板と基板との間をエポキシ樹脂で封止した。フラックス６にはロジン８０重流部，ステアリン酸２０重量，ジエチルアミン臭化水素酸塩１重量部の組成物を使用した。
動作温度を測定したところ、１３５±２℃であった。
【００４４】
〔実施例〕
比較例１に対し、中間電極の巾寸法を３００μｍとし、ヒューズエレメントにＢｉ５２％−Ｓｎ４６％−Ｉｎ２％、比抵抗値３４μΩｃｍの合金を使用し、ヒューズエレメントの長さを２．４ｍｍとし、ヒューズエレメントの抵抗値を比較例１とほぼ同一値とするためにヒューズエレメントの外径を６４０μｍφと太くした以外、比較例１に同じとした。
動作温度を測定したところ、１３６±２℃であった。
【００４５】
〔比較例２〕
ヒューズエレメントに実施例１と同じくＢｉ５２％−Ｓｎ４６％−Ｉｎ２％、比抵抗値３４μΩｃｍの合金を使用した。電極寸法・配置・ヒューズエレメント長さを比較例１のままにしてヒューズエレメントの抵抗値を比較例１や実施例とほぼ同一値にするためにヒューズエレメントの外径を比較例１の１．５倍（√３４／√１５倍）の７５０μｍφとした。
動作温度を測定したところ、比較例１よりも相当に高くバラツキも大であって１４１±５℃であった。
実施例と比較例１との比較から明らかなように、本発明によれば、中間電極の巾を１２００μｍから３００μｍにも狭くしたにもかかわらず同等の作動性能を維持でき、保護素子の小型化を図ることができる。
比較例２では、ヒューズエレメント体積に対する中間電極面積の影響のために可溶合金の溶融後、分断までに時間がかかった結果、動作性能が低下したと推定されるが、実施例では中間電極の狭巾化にもかかわらず良好な動作性能を呈した。
【００４６】
【発明の効果】
請求項１の保護素子によれば、ヒューズエレメントを短くしてヒューズエレメントを所定抵抗値以下に保持することを可能にしており、ヒューズエレメントの短縮に応じて保護素子寸法の小型化を図ることができる。また、ヒューズエレメントの比抵抗値のアップに対しては、その比抵抗値の増加に応じヒューズエレメントの長さを短くすることによりヒューズエレメントの抵抗値を所定値に保持できるから、従来におけるヒューズエレメントの長さをそのままにしてヒューズエレメントの外径増大によりヒューズエレメントの抵抗値を所定値に保持する場合に較べてヒューズエレメントの体積量を少なくでき、このヒューズエレメント体積量の減少は比抵抗値が大きくなるほど顕著になるから、ヒューズエレメントの比抵抗値が大きくなるほどヒューズエレメント体積量減少による動作性能の向上を図ることができる。
【００４７】
請求項２によれば、前記の効果を抵抗体付き温度ヒューズにおいて得ることができる。
【００４８】
請求項３によれば、基板の片面に膜抵抗及びヒューズエレメント並びに中間電極を有し、膜抵抗の一端部を中間電極の片端部に連結し、該膜抵抗の片端から所定の距離を隔てた中間電極部位にヒューズエレメントを接合し、膜抵抗上にオーバーコートを施す抵抗体付き温度ヒューズにおいて、従来の抵抗体付き温度ヒューズに対し、中間電極を含めた電極を印刷・焼付けする工程と膜抵抗を印刷・焼付けする工程とを交互に入れ換え、かつオーバーコート一端とヒューズエレメントとの間隔を広げるようにオーバーコートの印刷寸法を調整するだけで、中間電極での溶融合金に対する濡れ有効距離を長くでき、中間電極の狭巾化のもとでも良好な動作性能を保証できる抵抗体付き温度ヒューズを提供できる。
【００４９】
請求項４によれば、基板の片面に膜抵抗及びヒューズエレメント並びに中間電極を有し、膜抵抗の一端部が中間電極の片端部に連結され、該膜抵抗の片端から所定の距離を隔てた中間電極部位にヒューズエレメントが接合され、膜抵抗上にオーバーコートが施され、膜抵抗一端部がオーバーコート一端より突出し、中間電極片端部が前記突出した膜抵抗一端部及びオーバーコート一端部を覆っているから、中間電極片端部がオーバーコート一端部を覆う寸法分が長くなることにより中間電極での溶融合金に対する濡れ有効距離を長くでき、中間電極の狭巾化のもとでも良好な動作性能を保証できる抵抗体付き温度ヒューズを提供できる。
【００５０】
請求項９によれば、ヒューズエレメントの短尺化を保有しつつ中間電極の濡れ面積を大きくできるから、中間電極の狭巾化のもとでものもとでも良好な動作性能を保証できる抵抗体付き温度ヒューズを提供できる。
【００５１】
請求項１０によれば、ヒューズエレメントの分断時に電極間に作用する電圧に対し絶縁補強でき、分断後の再導通防止を確保でき、安定な遮断を保証できる。
【００５２】
請求項１１によれば、膜抵抗の昇温速度を迅速化でき、抵抗体付き温度ヒューズの動作速度を速くできる。
【図面の簡単な説明】
【図１】請求項２に係る保護素子を示す図面である。
【図２】請求項３に係る保護素子を示す図面である。
【図３】請求項９に係る保護素子を示す図面である。
【図４】請求項４に係る保護素子を示す図面である。
【図５】請求項８に係る保護素子を示す図面である。
【図６】本発明に係る保護素子の使用方法を示す回路図である。
【図７】本発明に係る保護素子の一実施例を示す回路図である。
【図８】本発明に係る保護素子の別実施例を示す回路図である。
【図９】従来の保護素子を示す図面である。
【図１０】従来の上記とは別の保護素子を示す図面である。
【符号の説明】
１絶縁基板
２０中間電極
２１第１電極
２２第２電極
２３第３電極
３膜抵抗
３１膜抵抗一端部
３１ｅ膜抵抗一端
４ヒューズエレメント
５オーバーコート
５１オーバーコート一端部
５１ｅオーバーコート一端
６フラックス
８絶縁被覆体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a protection element such as a thermal fuse or a thermal fuse with a resistor.
[0002]
[Prior art]
A thermal fuse with a resistor has a fuse element made of a fusible alloy, includes a resistor that blows the fuse element by energized heat generation, and is used in combination with an abnormality detection circuit. An abnormal voltage is detected by an abnormality detection circuit, and the resistor is energized and heated by the detection, and the generated heat blows the fuse element to cut off the power to the device.
Further, the melting point of the fuse element can be set to the allowable temperature of the device, and when the temperature of the device reaches the allowable temperature, the fuse element can be blown to prevent abnormal heat generation of the device and thus to prevent a fire.
[0003]
FIG. 9A is a drawing showing an example of a conventional thermal fuse with a resistor, and FIG. 9B is a cross-sectional view of FIG.
In FIG. 9, 1 'is an insulating substrate such as a ceramic substrate, and 20' to 23 'are electrodes provided on the insulating substrate by printing and baking a conductive paste. A fuse element 4 'is connected between the first electrode 21' and the second electrode 22 'by welding or the like, and is also joined to the intermediate electrode 20'. Reference numeral 3 'denotes a film resistor connected between the third electrode 23' and the intermediate electrode 20 ', which is provided by printing and baking a resistance paste. Reference numeral 5 'denotes an overcoat for the film resistor 3', which is provided by printing and baking a glass paste, and has an outer shell which is larger than the outer shell of the film resistor 3 'by about 300 μm to 1000 μm. 6 'is a flux applied to the fuse element. 8 'is an insulating cover.
[0004]
The operation mechanism of the thermal fuse with a resistor is as follows.
That is, normally, the film resistance is de-energized, and the fuse element is inserted between the device and the power supply to be energized. In the event of an abnormality, the film resistor is energized and generates heat, and the generated heat melts the fuse element, causing the molten alloy to spheroidize and spread by wetting and spreading to the electrode under coexistence with the molten flux, which cuts off the conduction of the film resistor. The non-return cutoff is terminated by cooling and solidifying the divided alloy.
Also, if the melting point of the fuse element is set to the allowable temperature of the equipment, the fuse element will be melted when the equipment almost reaches the allowable temperature, and the molten alloy will spread to the electrode under the coexistence with the existing molten flux. The spheroidization is performed, and the power to the equipment is cut off by this separation, the equipment temperature is lowered, and the non-return cutoff is terminated by cooling and solidification of the divided alloy.
[0005]
FIG. 10 shows a thermal fuse in which the film resistance is omitted from the thermal fuse with a resistor, and is used in the latter usage form.
[0006]
[Problems to be solved by the invention]
In any of the above-mentioned thermal fuse with resistor and thermal fuse, the molten fuse element operates by wetting and spreading to the electrode, and conventionally, the molten alloy spreads from both sides to the intermediate electrode 20 ′, so that the intermediate electrode 20 The width W ′ is wider than the width W1 ′ of the first electrode 21 and the width W2 ′ of the second electrode 22.
Conventionally, a fusible alloy containing lead as a main component has been used for a fuse element of a thermal fuse or a thermal fuse with a resistor. However, lead is harmful to living systems, and it has been strongly demanded for fuse elements to use an alloy composition that does not contain harmful elements such as lead, like other electric components.
As such an alloy composition, for example, a Sn-In-Bi alloy is promising, but has a high specific resistance. For example, for a conventional fuse element alloy Sn46.5% -Pb29.8% -Cd16.7% -In7% with an operating temperature of 135.degree. C. and a specific resistance value of 15 .mu..OMEGA.cm, a fuse element alloy Bi52% -Sn46% of almost the same operating temperature. At -In2%, the specific resistance is 34 μΩcm, which is twice or more.
[0007]
The resistance value of the fuse element of a thermal fuse or a thermal fuse with a resistor must be kept below a certain value due to the restriction of internal resistance from load and self-heating. This is dealt with by increasing the element diameter.
However, an increase in the diameter of the fuse element leads to an increase in the amount of the molten alloy, resulting in a decrease in the spheroidal cutting performance. An increase in the size of the fuse is inevitable.
[0008]
SUMMARY OF THE INVENTION It is an object of the present invention to guarantee good disconnection operation performance of a thermal fuse having the intermediate electrode or a thermal fuse with a resistor, even if the specific resistance of the fuse element is high.
It is a further object of the present invention to reduce the size of a thermal fuse having an intermediate electrode or a thermal fuse with a resistor in addition to the above-mentioned objects.
[0009]
[Means for Solving the Problems]
The protection element according to claim 1, further comprising a first electrode, a second electrode, and an intermediate electrode between the electrodes, wherein each end of a fuse element made of a fusible alloy is connected to the first electrode and the second electrode. The intermediate portion of the element is connected to the intermediate electrode, and in operation, the fuse element is divided by the spread of the molten alloy of the molten fuse element to each electrode, and the first electrode and the second electrode after the division are separated from each other. In the protective element, which is separated from the intermediate electrode by a predetermined insulating distance to ensure insulation between the intermediate electrode and the intermediate electrode, the width of the fuse element connection site of the intermediate electrode is equal to the width of the fuse element connection site of each of the first electrode and the second electrode. It is characterized by being narrower than the width.
[0010]
The protection element according to claim 2 includes a first electrode, a second electrode, and a third electrode, an intermediate electrode between the first electrode and the second electrode, and each end of a fuse element made of a fusible alloy is provided. The fuse element is connected to the first electrode and the second electrode, an intermediate portion of the fuse element is connected to the intermediate electrode, and a film resistor is connected between the intermediate electrode and the third electrode. The fuse element is divided by the spreading of the alloy to each electrode, and the first electrode, the second electrode and the intermediate electrode are separated from each other by a predetermined insulation distance to ensure insulation between the first electrode and the second electrode after the division. In the protection device described above, the width of the fuse element connection portion of the intermediate electrode is smaller than the width of the fuse element connection portion of each of the first electrode and the second electrode.
[0011]
According to a third aspect of the present invention, in the second aspect, the fuse element and the film resistor are provided on one surface of the insulating substrate, an overcoat for the film resistance is provided, and one end of the intermediate electrode on the film resistance side is connected to one end of the film resistor. And one end of the overcoat on the intermediate electrode side covers one end of the intermediate electrode, and the distance L1 from the fuse element connection site of the intermediate electrode to one end of the overcoat is larger than the distance L2 from the same site to one end of the film resistor. , L1> L2−300 μm.
[0012]
According to a fourth aspect of the present invention, in the second aspect, the fuse element and the film resistor are provided on one surface of the insulating substrate, an overcoat for the film resistance is provided, one end of the film resistor protrudes from one end of the overcoat, and the intermediate electrode One end covers the protruding one end of the film resistor and the one end of the overcoat.
[0013]
According to a fifth aspect of the present invention, there is provided a protection element according to any one of the first to fourth aspects, wherein the specific resistance value of the fuse element is 20 μΩcm or more.
[0014]
The protective element according to claim 6 is the protection element according to claims 1 to 5, wherein the fusible alloy is an In-Sn-Bi-based alloy, a Bi-Sn-Sb-based alloy, an In-Sn-based alloy, an In-Bi-based alloy, a Bi- The protection element according to claim 7 is characterized in that the composition of the In-Sn-Bi-based alloy is (1) 43% <Sn <70. %, 0.5% ≦ In ≦ 10%, residual Bi, (2) 25% ≦ Sn ≦ 40%, 50% ≦ In ≦ 55%, residual Bi, (3) 25% <Sn ≦ 44%, 55% <In ≦ 74%, 1% ≦ Bi <20%, (4) 46% <Sn ≦ 70%, 18% ≦ In <48%, 1% ≦ Bi ≦ 12%, (5) 5% ≦ Sn ≦ 28 %, 15% ≦ In <37%, residual Bi (however, Bi57.5%, In25.2%, Sn17.3% and Bi54%, In29.7 , Sn 16.3%, respectively, excluding the ranges of Bi ± 2%, In and Sn ± 1%), (6) 10% ≦ Sn ≦ 18%, 37% ≦ In ≦ 43%, remaining Bi, ( 7) 25% <Sn ≦ 60%, 20% ≦ In <50%, 12% <Bi ≦ 33%, (8) Ag, Au, Cu, Ni in 100 parts by weight of any of (1) to (7) , Pd, Pt, Sb, Ga, Ge, P, or a total of 0.01 to 7 parts by weight, (9) 33% ≦ Sn ≦ 43%, 0.5% ≦ In ≦ 10% (10) 47% ≦ Sn ≦ 49%, 51% ≦ In ≦ 53%, 100 parts by weight of Bi and 3 to 5 parts by weight of Bi, (11) 40% ≦ Sn ≦ 46%, 7% ≤ Bi ≤ 12%, residual In, (12) 0.3% ≤ Sn ≤ 1.5%, 51% ≤ In ≤ 54%, residual Bi, (13) 2.5% ≤ Sn ≤ 10%, 2 % ≦ Bi ≦ 35%, residual In, (14) one of Ag, Au, Cu, Ni, Pd, Pt, Sb, Ga, Ge, P in 100 parts by weight of any of (9) to (13) or Two or more kinds are added in a total amount of 0.01 to 7 parts by weight, (15) 10% ≦ Sn ≦ 25%, 48% ≦ In ≦ 60%, and the remaining Bi in 100 parts by weight of Ag, Au, Cu, Ni, Pd, One or more of Pt, Sb, Ga, Ge, and P are added in a total of 0.01 to 7 parts by weight, and the composition of the Bi-Sn-Sb-based alloy is (16) 30% ≦ Sn ≦ 70%, 0. 3% ≦ Sb ≦ 20%, 100% by weight of the remaining Bi, (17) and (16) contain one or more of Ag, Au, Cu, Ni, Pd, Pt, Ga, Ge, and P in a total of 0.1%. 01 to 7 parts by weight, the composition of the In-Sn-based alloy is (18) 52% ≦ In ≦ 85%, the remaining Sn, (19) (18) One or more of Ag, Au, Cu, Ni, Pd, Pt, Ga, Ge, and P are added to 0 parts by weight in total of 0.01 to 7 parts by weight, and the composition of the In-Bi alloy is (20). 45% ≦ Bi ≦ 55%, 100% by weight of the composition of the remaining In, (21) and (20), one or more of Ag, Au, Cu, Ni, Pd, Pt, Sb, Ga, Ge, and P In a total of 0.01 to 7 parts by weight, the composition of the Bi-Sn based alloy is (22) 50% <Bi <56%, the remaining Sn, (23) 100 parts by weight of the composition of (22), Ag, Au, One or more of Cu, Ni, Pd, Pt, Ga, Ge, and P are added in a total amount of 0.01 to 7 parts by weight, and the composition of the In-based alloy is (24) 100 parts by weight of In, Au, Bi, One or more of Cu, Ni, Pd, Pt, Ga, Ge, and P are added in a total amount of 0.01 to 7 parts by weight, (2 5) One or more of Au, Bi, Cu, Ni, Pd, Pt, Ga, Ge, and P are contained in 100 parts by weight of 90% ≦ In ≦ 99.9%, 0.1% ≦ Ag ≦ 10%. (26) 95% ≦ In ≦ 99.9%, 0.1% ≦ Sb ≦ 5% to 100 parts by weight of Au, Bi, Cu, Ni, Pd, Pt, One, two or more of Ga, Ge, and P are added in a total amount of 0.01 to 7 parts by weight.
[0015]
The protection element according to claim 8 is characterized in that, in any one of claims 1 to 7, the fuse element connection portion of the intermediate electrode has a width of 300 to 400 µm and a predetermined insulation distance is 300 to 1000 µm.
[0016]
According to a ninth aspect of the present invention, in the protection element according to any one of the first to eighth aspects, the width of the intermediate electrode is bulged in a portion different from the fuse element connection portion, and the width of the first electrode and the second electrode is bulged. Characterized by being locally retracted or recessed according to
[0017]
According to a tenth aspect of the present invention, there is provided the protection element according to any one of the second to ninth aspects, wherein the fuse element and the film resistor are provided on one surface of the insulating substrate, an overcoat is provided for the film resistor, and at least one of the fuse elements and the film resistor is connected to the film resistor. The overcoat extends along at least a part of the edge of the electrode where the electrode and the other electrode face each other.
[0018]
The protection element according to claim 11 is the protection element according to any one of claims 2 to 10, wherein the cross-sectional area of the lead conductor connected to the third electrode is equal to the cross-sectional area of the lead conductor connected to each of the first electrode and the second electrode. It is characterized by being 0.8 to 0.5 times.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a drawing showing an embodiment of the protection element according to claim 2.
In FIG. 1, reference numeral 1 denotes a heat-resistant insulating substrate, for example, a ceramic substrate.

Reference numerals

21, 22, and 23 denote first, second, and third electrodes provided by printing and baking a conductive paste, and include lead

conductor mounting portions

210, 220, and 230. Reference numeral 20 denotes an intermediate electrode, which is disposed between the first electrode and the second electrode, and the width of one end 201 of the intermediate electrode 20 on the third electrode 23 side is set to the third electrode 23 (the lead conductor mounting portion 230). (Not included)).
The width W of the fuse element connection portion of the intermediate electrode 20 is smaller than the widths W1 and W2 of the fuse element connection portions of the first electrode and the second electrode, respectively, and W <W1 and W2. Usually, W1 = W2.
The distance d1 between the first electrode 21 and the intermediate electrode 20, the distance d2 between the second electrode 22 and the intermediate electrode 20, and the distance d between the lead conductor mounting portion 230 of the third electrode 23 and the second electrode 22 are determined by the fuse element. Each interval is set to a predetermined distance so that the insulation at each interval can be ensured even if a circuit voltage is applied between them and the circuit voltage is actuated during the interruption due to the division. = D2 <d.
Reference numeral 3 denotes a film resistor. One end 31 of the resistance film 3 is connected to one end 201 of the intermediate electrode 20, and the other end 32 of the resistance film 3 is connected to one end 232 of the third electrode 23.
In FIG. 1, reference numeral 4 denotes a fuse element made of a fusible alloy. The fuse element 4 is connected between the first electrode 21 and the second electrode 22 by welding or the like, and the middle is connected to the intermediate electrode 20 by welding or the like. Reference numeral 5 denotes an overcoat for the film resistor 3. Reference numeral 6 denotes a flux applied to the fuse element 4. Reference numerals 71 to 73 denote lead conductors connected to the respective lead conductor attachment portions 210 to 230 of the first electrode 21 to the third electrode 23 by welding or the like, and it is preferable to use spot resistance welding for the welding.
Reference numeral 8 denotes an insulating cover, for example, a structure in which a sealant such as an epoxy resin is applied, a structure in which a protective plate is fixed on a sealant layer, or a case in which a cover is placed on a substrate and a frame around the cover is provided. The lead conductor can be drawn out of the lead conductor lead-out hole and sealed with an adhesive such as an epoxy resin.
[0020]
In the above description, the fuse element 4 includes an In-Sn-Bi-based alloy, a Bi-Sn-Sb-based alloy, an In-Sn-based alloy, an In-Bi-based alloy, and a Bi-free alloy containing no harmful elements to biological systems such as lead. -Sn-based alloys, In-based alloys and the like can be used.
The composition of the In—Sn—Bi alloy includes, for example, (1) 43% <Sn ≦ 70%, 0.5% ≦ In ≦ 10%, residual Bi, and (2) 25% ≦ Sn ≦ 40%, 50% ≦ In ≦ 55%, residual Bi, (3) 25% <Sn ≦ 44%, 55% <In ≦ 74%, 1% ≦ Bi <20%, (4) 46% <Sn ≦ 70%, 18% ≦ In <48%, 1% ≦ Bi ≦ 12%, (5) 5% ≦ Sn ≦ 28%, 15% ≦ In <37%, remaining Bi (however, Bi57.5%, In25.2%, Sn17.3) % And Bi 54%, In 29.7%, and Sn 16.3%, respectively, excluding the ranges of Bi ± 2%, In and Sn ± 1%), (6) 10% ≦ Sn ≦ 18%, 37% ≦ In ≦ 43%, residual Bi, (7) 25% <Sn ≦ 60%, 20% ≦ In <50%, 12% <Bi ≦ 33%, (8) What is (1) to (7) One or more of Ag, Au, Cu, Ni, Pd, Pt, Sb, Ga, Ge and P are added to 100 parts by weight in total of 0.01 to 7 parts by weight. (9) 33% ≦ Sn ≦ 43%, 0.5% ≦ In ≦ 10%, residual Bi, (10) 47% ≦ Sn ≦ 49%, 51% ≦ In ≦ 53%, 100 parts by weight of Bi and 3 to 5 parts by weight of Bi are added, (11) 40% ≦ Sn ≦ 46%, 7% ≦ Bi ≦ 12%, residual In, (12) 0.3% ≦ Sn ≦ 1.5%, 51% ≦ In ≦ 54%, residual Bi, (13 ) 2.5% ≦ Sn ≦ 10%, 25% ≦ Bi ≦ 35%, balance In, (14) Ag, Au, Cu, Ni, Pd, Pt in 100 parts by weight of any of (9) to (13) , Sb, Ga, Ge, P, one or more of 0.01 to 7 parts by weight in total, (15) 10% ≦ Sn ≦ 25%, 48% ≦ In ≦ 60%, balance One or two or more of Ag, Au, Cu, Ni, Pd, Pt, Sb, Ga, Ge and P can be added to 100 parts by weight of i, and a total of 0.01 to 7 parts by weight can be used. The composition of the -Sn-Sb-based alloy includes, for example, (16) 30% ≤ Sn ≤ 70%, 0.3% ≤ Sb ≤ 20%, balance Bi, (17) Ag, Au, 100 parts by weight of (16). One or more of Cu, Ni, Pd, Pt, Ga, Ge, and P are added in a total amount of 0.01 to 7 parts by weight, and the composition of the In-Sn-based alloy is (18) 52% ≦ In ≦ 85%, One or more of Ag, Au, Bi, Cu, Ni, Pd, Pt, Sb, Ga, Ge, and P are added to 100 parts by weight of the remaining Sn, (19) and (18) in a total amount of 0.01 to 7 parts by weight. And the composition of the In-Bi alloy is, for example, (20) 45% ≦ Bi ≦ 55%, , (21), 100 parts by weight of the composition of (20), one or more of Ag, Au, Cu, Ni, Pd, Pt, Sb, Ga, Ge, and P are added in a total amount of 0.01 to 7 parts by weight. And the composition of the Bi-Sn-based alloy is, for example, (22) 50% <Bi ≦ 56%, the remaining Sn, (23) 100 parts by weight of the composition of (22), Ag, Au, Cu, One or two or more of Ni, Pd, Pt, Ga, Ge, and P may be added in a total amount of 0.01 to 7 parts by weight, and the composition of the In-based alloy includes, for example, (24) 100 parts by weight of In. One part or two or more kinds of Au, Bi, Cu, Ni, Pd, Pt, Ga, Ge, and P are added to the parts in a total amount of 0.01 to 7 parts by weight, (25) 90% ≦ In ≦ 99.9%, Au, Bi, Cu, Ni, Pd, Pt, Ga, Ge, P are added to 100 parts by weight of 0.1% ≦ Ag ≦ 10%. (26) 100% by weight of 95% ≦ In ≦ 99.9%, 0.1% ≦ Sb ≦ 5%, Au, Bi, Cu , Ni, Pd, Pt, Ga, Ge, P, or a total of 0.01 to 7 parts by weight in total.
Assuming that the specific resistance of the alloy of the fuse element to be used is α times the alloy of the conventional fuse element, the length of the fuse element is set to the same value as that of the conventional fuse element so that the resistance value of the fuse element is the same as that of the conventional fuse element. The length L is represented by L / α. Accordingly, the length of the fuse element is shortened by L (α-1) / α, the width W of the fuse element connection portion of the intermediate electrode 20 is reduced, and the width W of the fuse element is separated by the predetermined insulation distances d1 and d2 on both sides. The first electrode 21 and the second electrode 22 are provided.
As described above, the volume of the fuse element 4 is (α-1) / α times and is reduced by 1 / α, so that the surface area of the intermediate electrode 20 is reduced by reducing the width of the fuse element connection portion of the intermediate electrode. Despite the fact that the amount of molten alloy in the fused fuse element is reduced, the range of spread of the molten alloy is narrowed accordingly, and malfunctions due to incomplete spread of the intermediate electrode due to insufficient area of the intermediate electrode are well eliminated. it can.
[0021]
In particular, in the configuration of claim 3 or claim 4, when an overcoat is provided for the film resistance, the effective wetting distance of the intermediate electrode can be increased even under the narrowing of the intermediate electrode. , Good operation performance can be guaranteed.
As shown in FIGS. 2A and 2B, the one end 201 of the intermediate resistor 20 at one end 201 of the intermediate electrode 20 is connected to the other end of the intermediate resistor 20 as shown in FIGS. The portion 31 is covered, and the one end portion 201 of the intermediate electrode is covered with the one end portion 51 of the overcoat 5 on the intermediate electrode side, and the distance L1 from the fuse element connection portion of the intermediate electrode 20 to the one end 51e of the overcoat 5 is set at the same value. L1> L2−300 μm with respect to the distance L2 to the one end 31e of the film resistor.
[0022]
In FIG. 2A, the width (W) of the fuse element connection portion of the intermediate electrode 20 is made smaller than the widths W1 and W2 of the fuse element connection portions of the first electrode 21 and the second electrode 22, respectively, and W <W1, W2 (usually, W1 = W2). The distance d1 between the first electrode 21 and the intermediate electrode 20, the distance d2 between the second electrode 22 and the intermediate electrode 20, and the distance d between the lead conductor mounting portion 230 of the third electrode 23 and the second electrode 22 are determined by a fuse. Even if the element 4 is cut off and the circuit is electrically cut off by the separation of the element 4 and a circuit voltage is applied during the cutoff, a predetermined distance is set so that insulation at each interval can be ensured. It is assumed that d2 <d.
In FIGS. 2A and 2B, reference numeral 4 denotes a fuse element, which is connected between the first electrode 21 and the second electrode 22 by welding or the like as in the embodiment shown in FIG. 20 is connected by welding or the like. Reference numeral 6 denotes a flux applied to the fuse element 4.
Although the lead conductor and the insulating cover are not shown in the drawing, their configuration is substantially the same as that of the first embodiment.
[0023]
FIG. 2C shows a conventional example by a cross-sectional view at the same cross-sectional position as the roll cross-section in FIG.
2 (a) and 2 (b) showing a third embodiment of the present invention (a cross-sectional view taken along the line b-b in FIG. 2 (a)) and FIG. It is assumed that the distance from one end 31e (31e ') of the film resistor to the fuse element is equal, and the distance is L2.
In the conventional example, in order to seal the resistive film 3 ', the four sides of the overcoat 5' are projected beyond the four edges of the resistive film 3 ', and the protrusion is usually 300 to 1000 [mu] m. Therefore, the distance from the overcoat end 31e 'to the fuse element connection portion of the intermediate electrode 20' is L2-300 m at the maximum. Therefore, according to the third aspect, the effective wetting distance from one end of the overcoat to the fuse element is longer than that of the conventional example, and the effective wetting area is increased by increasing the effective wetting distance. Even if the effective wetting area of the intermediate electrode 20 is reduced due to the reduction in the width of the portion, the reduction in the effective wetting area can be kept lighter, and this is synergistic with the reduction in the volume of the fuse element. By the effect, the divided operation performance can be sufficiently guaranteed.
[0024]
In claim 3, even if the distance L1 from the overcoat end 51e to the fuse element 4 is smaller than the distance (reference distance) L2 from the fuse element 4 to the resistive film end 31e (even if L1 <L2), As long as the condition of L1> L2−300 μm is satisfied, as described above, the fuse element 4 can contribute to the enhancement of the spheroidizing and breaking performance.
(Equation 1)
L1 ≧ L2
If so, the effective distance L1 for the molten alloy in the intermediate electrode to spread toward the film resistance side can be lengthened accordingly. Therefore, it is desirable that L1 ≧ L2.
[0025]
In the embodiment of claim 3 shown in FIGS. 2A and 2B, the sealing performance of one end portion 31 of the resistive film depends on the overlapping interface between one end portion 201 of the intermediate electrode and one end portion 51 of the overcoat. The arrangement and dimensions of the electrode and the resistive film are fixed, and the overlap interface distance L3 is given by the allowance of the overcoat end 51e with respect to one end 201e of the intermediate electrode. In the above, the effective distance L1 for the molten alloy to spread toward the film resistance side is reduced, and the effect of improving the spheroidizing / separating performance is reduced. Therefore, the above-mentioned superposed interface distance L3 is usually set to 600 μm or less.
[0026]
The production of the protection element according to claim 3 includes (a) a step of printing a film resistance by contacting a mesh screen of a film resistance pattern and baking the film resistance, and (b) printing an electrode by contacting a mesh screen of an electrode pattern. (B) a step of printing the overcoat by abutting a mesh screen for overcoat and then baking; and (d) trimming the film resistance by trimming before or after the overcoat printing / baking step as necessary. Setting a resistance value to a predetermined value, (e) connecting a fusible alloy piece between the first and second electrodes and applying a flux, and (f) spot welding a lead conductor to the first to third electrodes. Steps of connecting and (g) sealing with a case cover proceed in the order of the steps, and there is a fear that it takes time to connect the lead conductor and thermally affects the fusible alloy piece. For example, when soldering is used, it is safe to connect the lead conductor to the first to third electrodes before the step of connecting the fusible alloy piece to the first and second electrodes and then applying the flux. is there.
[0027]
After the operation of the above-described protection element, the electrodes electrically connected by the fusible alloy pieces before the operation are electrically disconnected, and a circuit voltage acts between the electrodes, so that the distance between the electrodes is short. In some places, re-conduction due to flashover may occur. In order to prevent this re-conduction, as shown in FIG. 3, at least a portion where the intermediate electrode 20 or the third electrode 23 connected to the film resistor and another electrode (the first electrode or the second electrode) face each other. An

extension

511, 512 or 513 of the overcoat 5 is formed along a part of the edge of the electrode so as to reinforce the insulation so as to prevent the flashover.
[0028]
FIG. 4A is a drawing showing an embodiment of the protection element according to claim 4, and FIG. 4B is a cross-sectional view taken along line B-B of FIG.
In FIGS. 4A and 4B, reference numeral 1 denotes a heat-resistant insulating substrate, for example, a ceramic substrate. Reference numeral 3 denotes a film resistor provided on the insulating substrate, which is provided by printing and baking a resistance paste as described above. Reference numeral 5 denotes an overcoat for the film resistor 3. One end 31 of the resistive film 3 projects from the overcoat end 51 e by a predetermined distance a, and the other end 32 of the resistive film 3 extends from the overcoat one end 52 e to a predetermined distance b. Only protruding.
In FIG. 4A, reference numeral 20 denotes an intermediate electrode, reference numeral 21 denotes a first electrode, reference numeral 22 denotes a second electrode, reference numeral 23 denotes a third electrode. The widths of the fuse element connection portions of the second electrodes 22 are made narrower than W1 and W2, and W <W1 and W2 (usually W1 = W2). The distance d1 between the first electrode 21 and the intermediate electrode 20, the distance d2 between the second electrode 22 and the intermediate electrode 20, and the distance d between the lead conductor mounting portion 230 of the third electrode 23 and the second electrode 22 are determined by the fuse. The intervals are set to be equal to or longer than a predetermined distance so that even if a circuit voltage is applied between the elements 4 and the circuit voltage is applied during the interruption, insulation between the elements 4 can be ensured. , Usually d1 = d2 <d.
In FIGS. 4A and 4B, the third electrode 23 is electrically connected to the film resistor 3 at the protrusion b. One end (the end on the film resistance side) 201 of the intermediate electrode 20 is positioned so as to exceed one end 51 e of the overcoat 5, and the intermediate electrode 20 comes into contact with the film resistor 3 at the protrusion a of the one end 31 of the resistance film. And electrically connected.
A fuse element 4 is connected between the first electrode 21 and the second electrode 22 by welding or the like as in the embodiment shown in FIG. 1, and an intermediate portion is connected to the intermediate electrode 20 by welding or the like. Reference numeral 6 denotes a flux applied to the fuse element 4.
Although the lead conductor and the insulating cover are not shown in the drawing, they have substantially the same configuration as in the first embodiment.
[0029]
FIG. 4C shows a conventional example at a cross section at the same position as the cross section of FIG.
In FIGS. 4B and 4C, the

positions

31e and 31e 'of the one end of the film resistor are the same, and the distance L2 from the

fuse elements

4 and 4' to this position is the same size. Further, the contact margin a between the one end portion 31 (31 ') of the film resistor and the one end portion 201 (201') of the intermediate electrode is made the same so that the contact electric resistance therebetween is equal.
In the conventional example, as described above, the overcoat end 51e 'projects at least 300 μm from the film resistance end 31e'. Therefore, the effective distance for the molten fusible alloy to spread to the film resistance side at the maximum is L2- It is 300 μm. On the other hand, in the thermal fuse with a resistor according to claim 4, the one end 201 of the intermediate electrode 20 is positioned beyond the overcoat end 51e, and the molten fusible alloy spreads on the film resistance side. Can be made longer than the effective distance L2-300 μm of the conventional thermal fuse with resistor.
Therefore, even if the effective wetting area of the intermediate electrode is reduced by reducing the width of the fuse element connection portion of the intermediate electrode, according to claim 4, the effective wetting due to the increase in the effective wetting distance from one end of the overcoat to the fuse element. By increasing the area, the reduction of the effective wetting area can be kept lighter, and the breaking operation performance can be sufficiently ensured by the synergistic effect of this and the reduction in the volume of the fuse element.
[0030]
The production of the protective element according to claim 4 includes (a) a step of printing a film resistance by contacting a mesh screen of a film resistance pattern and baking the film resistance, and (b) printing an overcoat by contacting a mesh screen for overcoating. (C) a step of printing the electrodes by abutting a mesh screen of an electrode pattern and then baking, (d) setting the resistance value of the film resistance to a predetermined value by trimming, if necessary, (E) connecting a fuse element to the first and second electrodes and applying a flux, (f) connecting a lead conductor to the first to third electrodes by spot welding, and (g) sealing with a case cover. In order to connect the lead conductors, it is time-consuming and may cause a thermal harm to the fuse element, for example, by using soldering. If the step of connecting the lead conductors to each electrode, it is safe to the previous step of connecting the fuse element to electrodes then applying flux.
[0031]
According to the ninth aspect, as another means for increasing the effective wetting area of the intermediate electrode in spite of the narrowing of the fuse element connection site of the intermediate electrode, another portion different from the fuse element connection site of the intermediate electrode is used. As shown in FIGS. 5A and 5B, the bulge 201 is caused to occur, and even under the bulge, the insulation distance between the intermediate electrode 20 and the first electrode 21 and the distance between the intermediate electrode 20 and the second electrode 22 are increased. The first electrode 21 and the second electrode 22 are depressed according to the bulging so as to keep the insulation distance between them at a predetermined insulation distance [(A) in FIG. [(B) of FIG. 5].
[0032]
In any of the above embodiments, if the cross-sectional area of the lead conductor 73 of the third electrode 23 is reduced, heat conduction outflow of the heat generated by the film resistor 3 through the lead conductor 73 is suppressed and the film resistance 3 of the film resistor 3 is reduced. Since the heat generation speed can be increased and the operation speed of the protection element can be further increased, the cross-sectional area of the lead conductor connected to the third electrode can be changed to other lead conductors (lead conductors connected to the first electrode and the second electrode). It is preferably about 0.8 to 0.5 times.
In this case, if the cross-section of all the lead conductors is a square with the same height and the cross-sectional area is reduced by reducing the width, the height of all the lead conductors can be made equal and the insulating plate or insulating case for the cover can be mounted. When placed, it can be made horizontal without tilting, and all lead conductors can be easily manufactured from a lead frame by punching.
[0033]
ADVANTAGE OF THE INVENTION According to the thermal fuse with a resistor according to the present invention, a precursor to the abnormality of the device is detected, and the film resistor is energized and heated by the detection, and the generated heat blows the fuse element to cut off the energization to the device. As a result, the current supply to the film resistor is also cut off. For example, when a lithium ion secondary battery is charged or a voltage rise that occurs at the time of overcharge is detected, the membrane resistor is energized and heated in accordance with the detection, and the generated heat causes the fuse element to be blown to remove the secondary battery from the charger. Can be shut off.
[0034]
FIG. 6 shows a protection circuit for a secondary battery using the thermal fuse with a resistor of the above embodiment.
In FIG. 6, S is a charger, and A is a lithium ion secondary battery. B indicates a detection operation circuit section, in which a Zener diode D is connected to the base of a transistor Tr via a resistor R, an emitter is grounded, and a positive electrode side of the Zener diode D is connected to a high voltage side of the circuit. C indicates the protection element of the above embodiment, in which the first electrode 21 and the second electrode 22 are connected between the charger S and the secondary battery A, and the third electrode 23 is connected to the collector of the transistor Tr. .
The breakdown voltage of the Zener diode D is set low with respect to the voltage rise that occurs when the secondary battery is overcharged. When the voltage rises due to the overcharge, a base current flows through the transistor Tr, and a large collector current flows, and the film thickness increases. The resistor 3 generates heat, and the generated heat is transmitted to the fuse element 4 via the intermediate electrode 20, the fuse element 4 is melted, and the molten alloy 4 is activated by the molten flux while the intermediate electrode 20 and the second electrode on both sides thereof are activated. Spreading between the first electrode 21 and the second electrode 22 spreads between the intermediate electrode 20 and the first electrode 21 and between the intermediate electrode 20 and the second electrode 22, and the membrane resistor 3 is cut off from the battery.
In the protection element according to the present invention, the melting point of the fuse element is selected as a protection temperature (a desired temperature at 80 ° C. to 120 ° C.) of the device, for example, the secondary battery, and the protection element substantially follows the device temperature. If the device is attached in thermal contact with the device so that the temperature can be raised, the power supply to the device can be cut off at the protection temperature, and abnormal heating of the device beyond the protection temperature and, consequently, fire can be prevented.
[0035]
The present invention eliminates the above-mentioned membrane resistance, sets the melting point of the fuse element to the protection temperature of the device, attaches the device to the device under thermal contact, and cuts off the power supply of the device at the protection temperature to exceed the protection temperature. 7 and 8 show an embodiment of the present invention in which abnormal heat generation and, consequently, fire are prevented from occurring.
In FIG. 7, reference numeral 1 denotes a heat-resistant insulating substrate, for example, a ceramic substrate.

Reference numerals

21 and 22 denote first and second electrodes provided by printing and baking a conductive paste, and include lead

conductor attachment portions

210 and 220. Reference numeral 20 denotes an intermediate electrode, which is provided between the first electrode 21 and the second electrode 22 and has a lead conductor mounting portion 200 at a position deviated from the middle. Reference numeral 4 denotes a fuse element made of a fusible alloy, which is connected between the first electrode 21 and the second electrode 22 by welding or the like, and the middle is connected to the intermediate electrode 20 by welding or the like. The width W of the fuse element connection portion of the intermediate electrode 20 is smaller than the widths W1 and W2 of the fuse element connection portions of the first electrode 21 and the second electrode 22, respectively, and W <W1 and W2. Usually, W1 = W2.
The distance d1 between the first electrode 21 and the intermediate electrode 20 and the distance d2 between the second electrode 22 and the intermediate electrode 20 are electrically cut off by the disconnection of the fuse element 4, and the circuit voltage is reduced during the cutoff. Each interval is set to be equal to or longer than a predetermined distance so that insulation at each interval can be assured even when the above-mentioned operation is effected, and usually d1 = d2.
Reference numeral 6 denotes a flux applied to the fuse element 4.

Reference numerals

70, 71 and 72 denote lead conductors connected to the respective lead conductor attachment portions 200 to 220 of the intermediate electrode 20 to the second electrode 22 by welding or the like, and it is preferable to use spot resistance welding for welding.
Reference numeral 8 denotes an insulating cover, for example, a structure in which a sealant such as an epoxy resin is applied, a structure in which a protective plate is fixed on a sealant layer, or a case in which a cover is placed on a substrate and a frame around the cover is provided. The lead conductor can be drawn out of the lead conductor lead-out hole and sealed with an adhesive such as an epoxy resin.
[0036]
FIGS. 8A and 8B show another embodiment different from the above. In the embodiment shown in FIG. 7, another portion of the intermediate electrode other than the fuse element connection portion is swelled. Even under the swelling, the first electrode 21 and the first electrode 21 are maintained such that the insulation distance between the intermediate electrode 20 and the first electrode 21 and the insulation distance between the intermediate electrode 20 and the second electrode 22 are maintained at predetermined insulation distances. The second electrode 22 is locally recessed according to the bulging [(a) in FIG. 8] or is retracted [(b) in FIG. 8].
[0037]
In any of the above embodiments, the lead conductor is provided, but in the thermal fuse with a resistor, the first electrode, the second electrode, and the third electrode are turned to the back surface side of the substrate via the side surface of the substrate to form a chip type. In the fuse, the first electrode, the second electrode, and the intermediate electrode may be turned to the back surface side of the substrate via the side surface of the substrate to be a chip type.
[0038]
In the present invention, the overcoat material is an insulator and is not limited to a glass coat, but may be a synthetic resin coat, for example, an epoxy resin coat.
In the present invention, as the electrode material, use is made of a sintering type comprising a mixture of conductive particles, glass frit and an organic solvent, and a thermosetting type comprising a mixture of a conductive particle, a thermosetting resin (for example, epoxy resin) and a solvent. It is also possible to use metal particles such as silver, palladium, gold and copper, carbon and the like as the conductive particles.
In the present invention, the film resistance material includes a sintering type comprising a mixture of resistance particles, a glass frit and an organic solvent, and a thermosetting type comprising a mixture of a resistance particle, a thermosetting resin (for example, an epoxy resin) and a solvent. It is also possible to use metal oxide particles such as ruthenium oxide particles as the resistance particles. In addition, it is also possible to use a Ti-Si-based resistance paste.
Organic fluxes such as natural rosin, modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.) and purified rosin, diethylamine hydrochloride, diethylamine hydrobromide, adipine, etc. are added to the flux. Can be used.
In the present invention, the insulating substrate can be used without any particular limitation as long as it is insulating and has heat resistance enough to withstand the formation of electrodes and film resistance, a ceramic plate such as an alumina ceramic plate, a heat-resistant plastic plate, A glass fiber reinforced plastic plate, a metal plate having an insulating film on the surface, or the like can be used.
[0039]
The length × width dimension of the insulating substrate in the protection element according to the present invention is usually (4.0 to 10.0) mm × (4.0 to 10.0) mm. The arrangement pattern and dimensions of the electrodes and the film resistors are set according to the rated current and the rated voltage.
When the rating is 10 A × 50 V, the width of the lead conductor connecting portion of the intermediate electrode is 300 to 400 μm, and the distance between the first electrode and the intermediate electrode and the distance between the second electrode and the intermediate electrode are 300 to 1000 μm.
[0040]
In the present invention, it is preferable to use an alloy containing no harmful element to a living system, for example, an Sn-In-Bi-based alloy for the fuse element. As an example of the composition of the Sn-In-Bi-based alloy, the liquidus temperature and the specific resistance of Sn 43 to 70%, In 0.5 to 10%, and the balance Bi are shown in Table 1.
However, the liquidus temperature was determined by DSC [The reference sample (unchanged) and the measurement sample were placed in a nitrogen gas container, and power was supplied to the container heater to heat both samples at a constant rate. The change in the amount of heat energy input due to the above is detected by a differential thermocouple].
[Table 1]

Although the specific resistance value is as high as 20 μΩcm or more, according to the present invention, the length of the fuse element can be shortened to reduce the resistance value of the fuse element to a normal value, and good operation performance can be guaranteed.
[0041]
In order to reduce the specific resistance value of the alloy, refine the crystal structure, reduce the heterogeneous interface in the alloy, and improve the dispersibility of processing strain and stress, Ag, Au, At least one of Cu, Ga, Ge, Ni, Pd, Pt, Sb, and P can be added in an amount of 0.01 to 7 parts by weight. The reason for setting the addition amount to 0.01 to 7 parts by weight is that if the amount is less than 0.01 parts by weight, the effect is very insufficient, and if it exceeds 7 parts by weight, the melting characteristics of the alloy are greatly changed. This is because it is difficult to keep the variation within the allowable range.
[0042]
【Example】
Regarding the operating temperature, the number of samples in each of the example and the comparative example was set to 50, and immersed in an oil bath at a heating rate of 1 ° C./min. The oil temperature was taken as the operating temperature.
[0043]
[Comparative Example 1]
A conventional product shown in FIG. 9 is used. A film resistor 3 is formed by printing and baking a ruthenium oxide-based resistor paste, using an alumina ceramic plate having a size of 6 mm × 6 mm × 0.64 mm in the length × width × width × thickness for the insulating substrate 1. The electrodes 20 to 23 were formed by printing and baking a silver-based conductive paste. The length × width (width) dimension of the first electrode 21 and the second electrode 22 (both excluding the lead conductor attachment portion) is 1.7 mm × 600 μm, and the length × width (width) dimension of the intermediate electrode 20 is 1.7 mm × The distance between the first electrode and the intermediate electrode and the distance between the second electrode and the intermediate electrode were 500 μm. The overcoat was formed by printing and baking a glass paste. An alloy having Sn46.5% -Pb29.8% -Cd16.7% -In7% and a specific resistance value of 15 .mu..OMEGA.cm was used for the fuse element, the outer diameter of the fuse element was 500 .mu.m.phi., And the length was 3.3 mm. The resistance value of the fuse element is 25 mΩ. An Sn-plated copper lead conductor having a thickness of 300 μm × 1000 μm is attached to the lead conductor attachment portion of each of the first and second electrodes, and an attachment portion thickness × width of 300 μm is attached to the lead conductor attachment portion of the intermediate electrode 20 of the third electrode. × 1000μm, thickness of narrow width × width of 300μm × 700μm Sn-plated copper lead conductors are connected, and an alumina ceramic plate of vertical × horizontal × thickness of 4mm × 4mm × 0.64mm is placed as a cover on them. Then, the space between the cover plate and the substrate was sealed with epoxy resin. For the flux 6, a composition comprising 80 parts by weight of rosin, 20 parts by weight of stearic acid, and 1 part by weight of diethylamine hydrobromide was used.
When the operating temperature was measured, it was 135 ± 2 ° C.
[0044]
〔Example〕
Compared with Comparative Example 1, the width of the intermediate electrode was set to 300 μm, an alloy of Bi52% -Sn46% -In2%, specific resistance value of 34 μΩcm was used for the fuse element, and the length of the fuse element was set to 2.4 mm. The same value as in Comparative Example 1 was adopted except that the outer diameter of the fuse element was increased to 640 μmφ in order to make the resistance value of Comparative Example 1 substantially the same as that of Comparative Example 1.
When the operating temperature was measured, it was 136 ± 2 ° C.
[0045]
[Comparative Example 2]
An alloy having a Bi52% -Sn46% -In2% and a specific resistance value of 34 [mu] [Omega] cm was used for the fuse element as in the first embodiment. The outer diameter of the fuse element was set to 1.5 in Comparative Example 1 in order to keep the electrode dimensions, arrangement, and fuse element length as in Comparative Example 1 and to make the resistance value of the fuse element approximately the same as that in Comparative Example 1 and Example. 750 μmφ which is twice as large (√34 / √15 times).
When the operating temperature was measured, it was considerably higher than that of Comparative Example 1 and the dispersion was large, that is, 141 ± 5 ° C.
As is clear from the comparison between the embodiment and Comparative Example 1, according to the present invention, the same operation performance can be maintained even though the width of the intermediate electrode is narrowed from 1200 μm to 300 μm, and the protection element is downsized. Can be achieved.
In Comparative Example 2, it was presumed that the operation performance was reduced as a result of the time required for the fusible alloy to melt and then to be divided due to the influence of the intermediate electrode area on the fuse element volume. Despite narrowing, good operation performance was exhibited.
[0046]
【The invention's effect】
According to the protection element of the first aspect, it is possible to shorten the fuse element and maintain the fuse element at a predetermined resistance value or less, and to reduce the size of the protection element according to the shortening of the fuse element. it can. Further, when the specific resistance of the fuse element is increased, the resistance of the fuse element can be maintained at a predetermined value by shortening the length of the fuse element in accordance with the increase in the specific resistance. The volume of the fuse element can be reduced as compared with the case where the resistance value of the fuse element is maintained at a predetermined value by increasing the outer diameter of the fuse element while keeping the length of the fuse element unchanged. As the specific resistance value of the fuse element increases, the operation performance can be improved by reducing the volume of the fuse element.
[0047]
According to the second aspect, the above effect can be obtained in the thermal fuse with the resistor.
[0048]
According to the third aspect, the substrate has a film resistor, a fuse element, and an intermediate electrode on one surface of the substrate, one end of the film resistor is connected to one end of the intermediate electrode, and a predetermined distance is provided from one end of the film resistor. The process of printing and baking electrodes, including the intermediate electrode, and the resistance of a conventional thermal fuse with a resistor, in which a fuse element is joined to the intermediate electrode part and an overcoat is applied on the membrane resistance. By simply changing the printing and baking process alternately and adjusting the overcoat printing dimensions so as to increase the distance between one end of the overcoat and the fuse element, the effective distance of the intermediate electrode to the molten alloy can be extended. In addition, it is possible to provide a thermal fuse with a resistor that can guarantee good operation performance even when the width of the intermediate electrode is reduced.
[0049]
According to claim 4, the substrate has a film resistor, a fuse element, and an intermediate electrode on one surface, and one end of the film resistor is connected to one end of the intermediate electrode, and is separated from the one end of the film resistor by a predetermined distance. A fuse element is joined to the intermediate electrode portion, an overcoat is applied on the film resistor, one end of the film resistor projects from one end of the overcoat, and one end of the intermediate electrode covers the projected one end of the film resistor and one end of the overcoat. Because the length of one end of the intermediate electrode covering one end of the overcoat is longer, the effective distance of the intermediate electrode to the molten alloy can be extended, and good operating performance can be achieved even with a narrower intermediate electrode. Can be provided.
[0050]
According to the ninth aspect, since the wet area of the intermediate electrode can be increased while maintaining the shortening of the fuse element, a resistor with which a good operating performance can be ensured even when the width of the intermediate electrode is reduced is provided. A thermal fuse can be provided.
[0051]
According to the tenth aspect, it is possible to reinforce insulation against a voltage acting between the electrodes when the fuse element is disconnected, to prevent re-conduction after the disconnection, and to ensure stable interruption.
[0052]
According to the eleventh aspect, the rate of temperature rise of the film resistor can be increased, and the operating speed of the thermal fuse with a resistor can be increased.
[Brief description of the drawings]
FIG. 1 is a drawing showing a protection element according to claim 2;
FIG. 2 is a drawing showing a protection element according to claim 3;
FIG. 3 is a drawing showing a protection element according to claim 9;
FIG. 4 is a drawing showing a protection element according to claim 4;
FIG. 5 is a drawing showing a protection element according to claim 8;
FIG. 6 is a circuit diagram showing a method of using the protection element according to the present invention.
FIG. 7 is a circuit diagram showing one embodiment of a protection element according to the present invention.
FIG. 8 is a circuit diagram showing another embodiment of the protection element according to the present invention.
FIG. 9 is a view showing a conventional protection device.
FIG. 10 is a drawing showing another conventional protection element.
[Explanation of symbols]
1 insulating substrate
20 Intermediate electrode
21 1st electrode
22 Second electrode
23 Third electrode
3 Film resistance
31 One end of membrane resistor
31e One end of film resistance
4 Fuse element
5 Overcoat
51 One end of overcoat
51e overcoat one end
6 flux
8 Insulation coating

Claims

A first electrode, a second electrode, and an intermediate electrode between the electrodes; each end of a fuse element made of a fusible alloy is connected to the first electrode and the second electrode; and an intermediate portion of the fuse element is connected to the intermediate electrode. During operation, the fuse element is divided by the spread of the molten alloy of the molten fuse element to the respective electrodes, and the insulation between the first electrode and the second electrode and the intermediate electrode after the division is ensured. Therefore, in the protection element having a predetermined insulation distance between them, the width of the fuse element connection portion of the intermediate electrode is smaller than the width of the fuse element connection portion of each of the first electrode and the second electrode. Characteristic protection element.

A first electrode, a second electrode, and a third electrode; an intermediate electrode between the first electrode and the second electrode; each end of a fuse element made of a fusible alloy connected to the first electrode and the second electrode; The intermediate portion of the fuse element is connected to the intermediate electrode, a film resistor is connected between the intermediate electrode and the third electrode, and the first and second electrodes of the molten alloy of the fused fuse element are operated during operation. And the fuse element is divided by the spreading of the intermediate electrode and each of the first electrode and the second electrode after the division to ensure insulation between the intermediate electrode and each of the first electrode and the second electrode. A protection element, wherein the width of the fuse element connection part of the intermediate electrode is smaller than the width of the fuse element connection part of each of the first electrode and the second electrode.

A fuse element and a film resistor are provided on one surface of the insulating substrate, an overcoat for the film resistance is provided, one end of the intermediate electrode on the film resistance side covers one end of the film resistor, and one end of the overcoat on the intermediate electrode side is the intermediate electrode. The distance L1 from the fuse element connection portion of the intermediate electrode to one end of the overcoat is L1> L2−300 μm with respect to the distance L2 from the same portion to one end of the film resistor. The protection element according to claim 2, wherein

A fuse element and a film resistor are provided on one surface of the insulating substrate, an overcoat for the film resistance is provided, one end of the film resistor protrudes from one end of the overcoat, and one end of the intermediate electrode has one end of the protruded film resistor and one end of the overcoat. The protection element according to claim 2, wherein the protection element covers the portion.

5. The protection element according to claim 1, wherein a specific resistance value of the fuse element is 20 [mu] [Omega] cm or more.

The fusible alloy is any one of an In-Sn-Bi-based alloy, a Bi-Sn-Sb-based alloy, an In-Sn-based alloy, an In-Bi-based alloy, a Bi-Sn-based alloy, and an In-based alloy. The protection element according to claim 1.

The composition of the In—Sn—Bi-based alloy is (1) 43% <Sn ≦ 70%, 0.5% ≦ In ≦ 10%, residual Bi, (2) 25% ≦ Sn ≦ 40%, 50% ≦ In ≦ (3) 25% <Sn ≦ 44%, 55% <In ≦ 74%, 1% ≦ Bi <20%, (4) 46% <Sn ≦ 70%, 18% ≦ In <48 %, 1% ≦ Bi ≦ 12%, (5) 5% ≦ Sn ≦ 28%, 15% ≦ In <37%, remaining Bi (however, Bi57.5%, In25.2%, Sn17.3% and Bi54 %, In 29.7% and Sn 16.3%, respectively, excluding the ranges of Bi ± 2%, In and Sn ± 1%), (6) 10% ≦ Sn ≦ 18%, 37% ≦ In ≦ 43 %, Residual Bi, (7) 25% <Sn ≦ 60%, 20% ≦ In <50%, 12% <Bi ≦ 33%, (8) Any one of (1) to (7) 100 One or more of Ag, Au, Cu, Ni, Pd, Pt, Sb, Ga, Ge, and P are added to the parts by weight in a total amount of 0.01 to 7 parts by weight. (9) 33% ≦ Sn ≦ 43% , 0.5% ≦ In ≦ 10%, residual Bi, (10) Add 3 to 5 parts by weight of Bi to 100 parts by weight of 47% ≦ Sn ≦ 49%, 51% ≦ In ≦ 53%, (11) 40% ≦ Sn ≦ 46%, 7% ≦ Bi ≦ 12%, residual In, (12) 0.3% ≦ Sn ≦ 1.5%, 51% ≦ In ≦ 54%, residual Bi, (13) 2. 5% ≦ Sn ≦ 10%, 25% ≦ Bi ≦ 35%, balance In, (14) Ag, Au, Cu, Ni, Pd, Pt, Sb, 100 parts by weight in any of (9) to (13) One or more of Ga, Ge and P are added in a total amount of 0.01 to 7 parts by weight, (15) 10% ≦ Sn ≦ 25%, 48% ≦ In ≦ 60%, and the remaining Bi is 10%. A total of 0.01 to 7 parts by weight of one or more of Ag, Au, Cu, Ni, Pd, Pt, Sb, Ga, Ge, and P is added to parts by weight, and the composition of the Bi-Sn-Sb-based alloy is (16) 30% ≦ Sn ≦ 70%, 0.3% ≦ Sb ≦ 20%, residual Bi, (17) Ag, Au, Cu, Ni, Pd, Pt, Ga, Ge in 100 parts by weight of (16) , P is added in an amount of 0.01 to 7 parts by weight in total, and the composition of the In—Sn alloy is (18) 52% ≦ In ≦ 85%, the remaining Sn is (100) of (19) and (18). One part or two or more of Ag, Au, Cu, Ni, Pd, Pt, Sb, Ga, Ge, and P are added to parts by weight in total of 0.01 to 7 parts by weight, and the composition of the In-Bi alloy is (20%). ) 45% ≤ Bi ≤ 55%, balance In, (21), 100 parts by weight of the composition of (20), Ag, Au, Cu, Ni, P , Pt, Sb, Ga, Ge, P, or a total of 0.01 to 7 parts by weight of Bi-Sn based alloy (22) 50% <Bi ≦ 56%, residual Sn, (23) One or more of Ag, Au, Cu, Ni, Pd, Pt, Ga, Ge, and P are added to 100 parts by weight of (22) in a total amount of 0.01 to 7 parts by weight. One or more of Au, Bi, Cu, Ni, Pd, Pt, Ga, Ge, and P are added to a total of 0.01 to 7 parts by weight to 100 parts by weight of (24) In. % ≦ In ≦ 99.9%, 0.1% ≦ Ag ≦ 10%, 100 parts by weight of Au, Bi, Cu, Ni, Pd, Pt, Ga, Ge, and P in total Au is added to 100 parts by weight of (26) 95% ≦ In ≦ 99.9%, 0.1% ≦ Sb ≦ 5%. 7. The protection element according to claim 6, wherein one or more of Bi, Cu, Ni, Pd, Pt, Ga, Ge, and P are added in a total amount of 0.01 to 7 parts by weight. .

The protection element according to any one of claims 1 to 7, wherein the width of the fuse element connection portion of the intermediate electrode is 300 to 400 µm, and the predetermined insulation distance is 300 to 1000 µm.

The width of the intermediate electrode is bulged at a portion different from the fuse element connection portion, and the width of the first electrode and the second electrode is locally retracted or recessed according to the bulge. The protection element according to any one of claims 1 to 8.

A fuse element and a film resistor are provided on one surface of the insulating substrate, an overcoat for the film resistor is provided, and at least a part of an electrode edge of a portion where at least one electrode connected to the film resistor and another electrode face each other. The protective element according to any one of claims 2 to 9, wherein the overcoat extends along the portion.

The cross-sectional area of the lead conductor connected to the third electrode is 0.8 to 0.5 times the cross-sectional area of the lead conductor connected to each of the first electrode and the second electrode. Item 10. The protective element according to any one of Items 2 to 10.