JP4183385B2

JP4183385B2 - Chip-type fuse and manufacturing method thereof

Info

Publication number: JP4183385B2
Application number: JP2000572882A
Authority: JP
Inventors: 幹三本木; 一郎石山; 盛勝山崎; 真人嶋田; 豊野村; 孝之中山; 孝治福久
Original assignee: Hokuriku Electric Industry Co Ltd
Current assignee: Hokuriku Electric Industry Co Ltd
Priority date: 1998-09-28
Filing date: 1999-09-28
Publication date: 2008-11-19
Anticipated expiration: 2019-09-28
Also published as: WO2000019472A1

Description

技術分野
本発明は、チップ状基板の上に発熱用抵抗体とこの発熱用抵抗体からの熱で溶断するヒューズ素子とを備えたチップ型ヒューズに関するものである。
背景技術
特開平７−１５３３６７号公報には、チップ状基板の上に発熱用抵抗体とこの発熱用抵抗体からの熱で溶断するヒューズ素子とを備えたチップ型ヒューズの従来例が示されている。このチップ型ヒューズでは、抵抗体の上に絶縁層を介してヒューズ素子を形成している。またこの公報には、ヒューズ素子に過大電流が流れたときにその電流によってヒューズ素子を溶断させ、また抵抗体の発熱によってヒューズ素子を溶断させるようにチップ型ヒューズを用いる技術も開示されている。
上記従来のチップ型ヒューズでは、基板上に形成した複数の発熱用抵抗体をエポキシ樹脂等の絶縁性樹脂で被覆し、さらにこの樹脂層の上に低融点金属をヒューズとして形成している。従来の構造では、平坦でない絶縁樹脂層の表面上にヒューズを形成しているため、ヒューズ素子の形成が難しく，歩留まりが悪くなって製造コストが高くなる問題が発生する。また従来のチップ型ヒューズは、過大電流でヒューズを溶断する機能と発熱用抵抗体の発熱でヒューズ素子を溶断させる機能とを実現するためには、チップ型ヒューズを実装する外部回路に抵抗体とヒューズ素子とを電気的に接続するための接続部を設けなければならず、チップ型ヒューズの使い勝手が悪いという問題があった。
本発明の目的は、過大電流によってヒューズ素子を直接溶断することができて、しかも発熱用抵抗体の発熱によってもヒューズ素子を溶断することができる信頼性の高いチップ型ヒューズ及びその製造方法を提供することにある。
本発明の他の目的は、チップ状基板の表面に発熱用抵抗体とヒューズ素子とが並んで形成されたチップ型ヒューズにおいて、発熱用抵抗体からの熱でヒューズ素子が溶断するまでの溶断時間を短くすることができるチップ型ヒューズを提供することにある。
本発明の更に他の目的は、チップ状基板の表面に発熱用抵抗体とヒューズ素子とが並んで形成されたチップ型ヒューズにおいて、発熱用抵抗体からの熱でヒューズ素子が溶断するまでの溶断時間のバラツキが少ないチップ型ヒューズを提供することにある。
本発明の別の目的は、電極間が半田で短絡されるのを防止できるチップ型ヒューズを提供することにある。
本発明の他の目的は、ヒューズ素子に過大電流が流れたときに、ヒューズ素子が確実に溶断するチップ型ヒューズを提供することにある。
本発明の更に他の目的は、クリーム半田を用いてヒューズ素子を確実に形成できるチップ型ヒューズ及びその製造方法を提供することにある。
発明の開示
本発明のチップ型ヒューズは、表面と裏面を有するチップ状基板と、チップ状基板の表面上に形成された発熱用抵抗体と、チップ状基板の表面上に形成されて発熱用抵抗体からの熱で溶断するヒューズ素子とを備えている。そして発熱用抵抗体とヒューズ素子とは、ヒューズ素子に過大電流が流れたときに、その過大電流によりヒューズ素子が溶断し、発熱用抵抗体に過電圧が印加されたときには発熱用抵抗体の発熱によりヒューズ素子が溶断するように電気的に接続されている。本発明によれば、チップ状基板の表面にヒューズ素子を確実に形成することができて、しかも過大電流でヒューズ素子を溶断する機能と発熱用抵抗体の発熱でヒューズ素子を溶断させる機能とを備えた信頼性の高いチップ型ヒューズを得ることができる。
またチップ状基板の裏面に、チップ型ヒューズが実装される回路基板の基板表面と接触して基板表面と裏面との間に空間を形成するスペーサ手段を設けることができる。このようなスペーサ手段を設けると、スペーサ手段によって形成される空間の空気が発熱用抵抗体からの熱が回路基板に伝わるのを阻止する熱絶縁機能を発揮する。そのためスペーサ手段を設けない場合と比べて、スペーサ手段を設けた場合のほうが、より短い時間で発熱用抵抗体の熱でヒューズ素子を溶断することができる。なおスペーサ手段を通して熱が回路基板側に逃げるのをできるだけ抑制するためには、スペーサ手段をチップ状基板よりも熱伝導性の低い材料により形成すればよい。またスペーサ手段を合成樹脂ペーストを用いてチップ状基板の裏面に所定のパターンで印刷して形成すれば、スペーサ手段を簡単に且つ安価に設けることができる。スペーサ手段のパターンは、チップ状基板の裏面と回路基板との間に形成される空間の厚み寸法がほぼ一定になるように定めるのが好ましい。このようにすると空間の熱絶縁効果がチップ状基板全体に対してほぼ等しくなるため、ヒューズ素子の溶断特性が安定する。スペーサ手段の突出寸法が、あまり小さくなると、空間の熱絶縁機能が徐々に低下し、スペーサ手段の実用上の効果が小さくなる。また突出寸法があまり大きくなると、この空間が半田付けの障害になる可能性が高くなる。したがって実用上の観点からみると、この突出寸法の下限値と上限値の範囲は、６０μｍ乃至１５０μｍの範囲が好ましい。なお突出寸法がこの範囲に入らない場合でも、本発明の効果が得られる限り本発明の技術的範囲に含まれることは言うまでもない。
チップ状基板に形成する電極の構造及び位置は任意である。しかしながら回路基板上の電極への半田付けをより確実なものとするためには、チップ状基板の表面に発熱用抵抗体に電気的に接続された１以上の表面電極とヒューズ素子に電気的に接続された１以上の表面電極を形成する。またチップ状基板の裏面上に、複数の表面電極と電気的に接続される複数の裏面電極を更に形成する。そしてチップ状基板の表面と裏面とをつなぐ外側面上には、複数の表面電極と複数の裏面電極とを接続する複数の側面電極を、対応する表面電極及び裏面電極の上に部分的に重なるように形成する。チップ状基板がセラミックス基板であれば、一般的に表面電極、裏面電極及び側面電極はガラスに導電性粉末が混練されたメタルグレーズ導電性ペーストを用いて形成する。このようにした場合、チップ状基板の角部で側面電極の厚みが薄くなる傾向がある。あまりこの角部の部分の電極部分の厚みが薄くなり過ぎると、この部分の抵抗値が大きくなって、この部分でジュール熱が発生し、ヒューズの溶断時間が長くなる可能性がある。そこで側面電極と表面電極の重なり部分の上または両者の間に補足電極を重ねて形成すれば、このような問題が発生するのを解消できる。
また裏面電極を形成する場合には、溶融半田が裏面電極間でブリッジを形成し、電極間の短絡が発生するおそれがある。そこで前述のスペーサ手段を、複数の裏面電極間で溶融半田のブリッジが形成されるのを阻止できるパターンに形成すれば、このような事態が発生するのを有効に防止できる。
ヒューズ素子の溶断時間を更に短くするためには、チップ状基板から実装用の回路基板に熱が逃げるのを阻止するだけでなく、発熱用抵抗体から出た熱ができるだけヒューズ素子に伝達するようにするのが好ましい。そこでチップ状基板上に並んで配置された発熱用抵抗体及びヒューズ素子の中央部を間に挟む位置にチップ状基板を厚み方向に貫通する一対の貫通孔を形成する。そして一対の貫通孔を抵抗体から出た熱ができるだけヒューズ素子の中央部に伝わるように発熱用抵抗体が延びる方向の長さ寸法を定める。このようにすると発熱用抵抗体から出た熱がヒューズ素子の中央部に集まることになるため、より短い時間で発熱用抵抗体からの熱でヒューズ素子を溶断することができるようになる。
またチップ状基板には、発熱用抵抗体及びヒューズ素子の下部に裏面側に向かって開口する凹部を形成するようにしてもよい。この凹部の形状及び深さは、発熱用抵抗体から出た熱ができるだけヒューズ素子に伝わるように定める。このようにしても発熱抵抗体からヒューズ素子への熱の伝達が良好になって、ヒューズ素子の溶断時間が短くなる。
ヒューズ素子の材質及び構成は任意である。チップ状基板の表面にヒューズ素子を確実に形成するためには、チップ状基板の表面に形成された一対の表面電極間に独立して形成されて隣接する他の電極とは離れて形成された１以上の補助電極を設け、所定の温度以上に加熱されると溶融する導電性材料からなるヒューズ材料層を一対の表面電極と１以上の補助電極とに跨って形成する。具体的にヒューズ材料層は、例えばクリーム半田を用いて一対の表面電極及び１以上の補助電極に跨って形成したクリーム半田層を加熱して溶融した後に硬化させて形成することができる。このように一対の表面電極間に１以上の補助電極を設けると、溶融した導電性材料をある程度拘束した状態で硬化させてヒューズ材料層を形成する際に、１以上の補助電極がアンカー（引き止め部）となって導電性材料を引き止めることができ、ヒューズ材料層を確実に形成できる。なお過大電流が流れたとき及び発熱用抵抗体からの熱によって溶断するときには、導電性材料が拘束されていないため、補助電極は溶融した導電性材料を集めるまたは引きつける作用を果すことになって、ヒューズ素子の溶断が容易になる。
チップ状基板の表面は、ヒューズ素子を形成する前にヒューズ素子を形成するのに必要な部分を除いて絶縁材料によりオーバーコートするのが好ましい。これはヒューズ素子をクリーム半田を用いて形成する際に発生するフラックスが発熱用抵抗体等に付着するのを防止するためである。また前述のスペーサ手段を印刷により形成する場合には、ヒューズ素子を形成する前に形成する。そしてヒューズ素子は、製造工程の一番最後に形成するのが好ましい。これはスペーサ手段を形成する際に加える熱でヒューズ素子が溶断するのを防止するためである。
なお一対の貫通孔を形成すること及びスペーサ手段を設ける技術は、発熱用抵抗体とヒューズ素子とが並んでいるだけでのチップ型ヒューズにも当然にして適用できるものである。
発明を実施するための最良の形態
以下、図面を参照して本発明の実施の形態について説明する。図１は本発明のチップ型ヒューズの第１の実施の形態で用いるセラミックス製のチップ状基板１の平面図を示しており、図２はチップ状基板１の底面図を示している。そして図３は一部を省略したチップ型ヒューズの平面図を示している。図１に示すように、チップ状基板１の長手方向に延びる２つの長辺のうちの１つの長辺２には３つの半円弧状の凹部３乃至５が形成されている。また他方の長辺６の中央部にも１つの円弧状の凹部７が形成されている。これらの凹部３乃至５及び凹部７は、チップ状基板１の表面１ａと裏面１ｂとを結ぶ側面に沿って延びている。またチップ状基板１の２つの短辺８及び９には、それぞれ平面から見てＵ字状を呈する凹部１０及び１１が形成されている。これらの凹部には、チップ状基板の表面１ａを覆う図示しないケースの取付用フックが嵌合される。
チップ状基板１の表面１ａには、凹部３乃至５及び凹部７に隣接して形成された接続用の表面電極１２，１３，１４と、中間電極１５と、補助電極１６及び１７と、表面電極１４に接続されてチップ状基板１の長手方向に延びる部分とこの部分の端部から短辺８及び９に沿って延びる電極部分１８ａ及び１９ａを備えた配線部１８及び１９とが設けられている。これらの電極及び配線部は、ガラスペーストにＡｇ，Ａｇ−Ｐｄ等の導電性粉末が混練されてなるメタルグレーズ導電性ペーストを用いて形成されている。パターンの印刷はスクリーン印刷を用いて行われ、ペーストの焼成温度は約８５０℃程度である。中間電極１５は一対の表面電極１２及び１３の間のスペースのほぼ中央部に形成されており、中間電極１５の電極部分１５ａは、一対の配線部１８及び１９の対向する電極部分１８ａ及び１９ａの間のスペースの中央部に位置している。また２つの補助電極１６及び１７は、一方の表面電極１２と中間電極１５の本体部１５ｂとこの本体部１５ｂと他方の表面電極１３との間に、隣接する電極とは独立した（分離したまたは電気的に絶縁された）状態で形成されている。また図２に示すように、チップ状基板１の裏面には、凹部３乃至５及び凹部７の端部に隣接して４つの裏面電極２０乃至２３が、前述のメタルグレーズ導電性ペーストを用いて形成されている。なお裏面電極２１は、半田付け強度を高める必要がある場合に半田付けに用いられているダミー電極である。
図３には示していないが、チップ状基板１の表面１ａ及び裏面１ｂに電極を形成した後、図４に示すような側面電極２４が前述のメタルグレーズ導電性ペーストを用いて形成される。側面電極２４は、チップ状基板１の表面１ａと裏面１ｂとをつなぐ外側面上に形成されて、対応する表面電極及び裏面電極の上に部分的に重なっている。このように側面電極２４を形成した場合には、チップ状基板１の角部で側面電極２４の厚みが薄くなる傾向がある。あまりこの角部の部分の電極部分の厚みが薄くなり過ぎると、この部分の抵抗値が大きくなって、この部分でジュール熱が発生し、ヒューズの溶断時間が長くなる可能性がある。そこでこの例では、側面電極２４と表面電極１３の上に補足電極２５を重ねて形成して、厚みが薄くなった側面電極２４の部分を補足している。補足電極２５もメタルグレーズ導電性ペーストを用いて形成されている。図４に示した電極以外のその他の表面電極と裏面電極との間も図４に示す構造と同じ接続構造を用いて接続されている。なお前述のとおり、図３においては図示を簡略化するために側面電極２４の位置を破線で示すだけでその存在は省略してある。なおこの例とは異なって、表面電極１３の上に補足電極を直接形成し、その上に側面電極２４の端部を重ねるように形成してもよいのは勿論である。
図３に示すように、前述の各電極を形成した後に、配線部１８及び１９の電極部分１８ａ及び１９ａと中間電極１５の電極部１５ａとに跨るように発熱用抵抗体２６が形成される。発熱用抵抗体２６は、ガラスをバインダとする銀−パラジウム塗料を印刷焼成した厚膜抵抗体や、ＲｕＯ_２−ガラス等のメタルグレーズ抵抗塗料を用いて形成された厚膜抵抗体等によって形成されている。これらの抵抗塗料の焼成温度も約８５０℃である。
図３には示していないが、電極を形成した後に、チップ状基板１の表面には後述するヒューズ素子２７を形成する部分及び半田付け電極部分を除いて、ガラス材料からなる絶縁材料を用いてオーバーコートが形成されている。オーバーコートを形成した後、表面電極１２及び１３の一部、中間電極１５の本体部１５ｂ及び補助電極１６及び１７に跨るようにしてヒューズ材料層を形成してヒューズ素子２７を形成する。
ヒューズ材料層を形成する場合には、例えばクリーム半田を用いて一対の表面電極１２及び１３及び２つの補助電極１６及び１７並びに中間電極１５に跨って形成したクリーム半田層を形成する。次にこのクリーム半田層を上から押さえた状態で加熱し、クリーム半田を溶融させて、そのままの状態で硬化させることにより、ヒューズ素子２７を形成する。この例のように、一対の表面電極１２及び１３間に補助電極１６，１７を設けると、溶融したクリーム半田（導電性材料）をある程度拘束した状態で硬化させてヒューズ材料層を形成する際に、補助電極１６，１７がアンカー（引き止め部）となって溶融したクリーム半田を引き止めることができ、ヒューズ材料層を確実に形成できる。なお過大電流が流れたとき及び発熱用抵抗体２６からの熱によって溶断するときには、ヒューズ素子２７が拘束されていないため、補助電極１６，１７は溶融した導電性材料を集めるまたは引きつける作用を果すことになって、ヒューズ素子２７の溶断が容易になる。
ヒューズ素子２７を構成するヒューズ材料層は、低融点金属であるＰｂ−Ｓｎ系、Ｐｂ−Ｓｂ系、Ｓｎ−Ｓｂ系などの共晶ハンダ合金等から形成することができる。
この実施の形態のチップ型ヒューズの回路図は、図５に示す通りである。このチップ型ヒューズは、電極１２及び１３が保護すべ回路の遮断部分に接続され、また電極１４が保護すべき回路の過電圧を検出すべき箇所に接続される。この回路において、分割抵抗部Ｒ１及びＲ２は、中間電極１５と電極部１８ａと電極部１９ａ（図３）との間に形成された発熱用抵抗体２６の部分によって構成されており、分割ヒューズ部Ｈ１及びＨ２は、中間電極１５と電極１２と電極１３との間に形成されたヒューズ素子２７の部分によって構成されている。この回路構成では、過大電圧が電極１４から分割抵抗部Ｒ１及びＲ２に印加されると分割ヒューズ部Ｈ１及びＨ２の少なくとも一方を通って電流が流れる。そして分割抵抗部Ｒ１及びＲ２からの発熱により、チップ状基板１を通って伝わる熱で分割ヒューズ部Ｈ１及びＨ２の少なくとも一つが溶融温度まで加熱されると溶断する。また過大電流が電極１２と電極１３との間を流れると、その際の熱で分割ヒューズ部Ｈ１及びＨ２の少なくとも一つが溶断し、電極１２及び１３間で回路が遮断する。
図６及び図７は、本発明の第２の実施の形態で用いるチップ状基板１０１の平面図及び裏面図である。図６及び図７において、図１乃至図３に示した第１の実施の形態を構成する部分と同様の部分には、図１乃至図３に付した符号に１００の数を加えた数の符号を付して説明を省略する。また図８は、第２の実施の形態のチップ状基板１０１の表面にガラスのオーバーコート１２８を形成した状態の平面図を示している。図８においては，後に形成するヒューズ素子１２７を破線で示してある。この第２の実施の形態では、チップ状基板１０１上に並んで配置された発熱用抵抗体１２６及びヒューズ素子１２７の中央部を間に挟む位置にチップ状基板１０１を厚み方向に貫通する一対の貫通孔１２９及び１３０を形成している。一対の貫通孔１２９及び１３０は、発熱用抵抗体１２６から出た熱ができるだけヒューズ素子１２７の中央部に伝わるように発熱用抵抗体１２６が延びる方向の長さ寸法を定めている。このようにすると発熱用抵抗体１２６から出た熱が一対の貫通孔１２９及び１３０の外側には放散せず、ヒューズ素子１２７の中央部に集まることになるため、より短い時間で発熱用抵抗体１２６からの熱でヒューズ素子１２７を溶断することができるようになる。
またこの第２の実施の形態では、チップ状基板１０１の裏面１０１ｂに、チップ型ヒューズが実装される回路基板１００（図９参照）の基板表面１００ａと接触してこの基板表面１００ａと裏面１０１ｂとの間に空間を形成する凸状部材またはスペーサ手段１３１乃至１３４を設けている。この例では、スペーサ手段１３１乃至１３４をエポキシ樹脂等の熱硬化性樹脂からなる合成樹脂ペーストを用いてチップ状基板１０１の裏面１０１ｂに印刷により形成している。スペーサ手段１３１乃至１３４の高さは，ペーストを複数回重ねて塗布することにより任意の高さとすることができる。合成樹脂ペーストにスペーサ手段１３１乃至１３４を形成すると、スペーサ手段１３１乃至１３４を簡単に且つ安価に設けることができる。なおこのスペーサ手段１３１乃至１３４は、ヒューズ素子１２７を形成する前で、ガラスのオーバーコート１２８を形成した後に形成する。
このようなスペーサ手段１３１乃至１３４を設けると、スペーサ手段１３１乃至１３４によって形成される空間の空気が、発熱用抵抗体１２６からの熱が回路基板１００に伝わるのを阻止する熱絶縁機能を発揮する。そのためスペーサ手段１３１乃至１３４を設けない場合と比べて、スペーサ手段１３１乃至１３４を設けた場合のほうが、より短い時間で発熱用抵抗体１２６の熱でヒューズ素子１２７を溶断することができる。
スペーサ手段１３１乃至１３４を通して熱が回路基板１００側に逃げるのをできるだけ抑制するためには、スペーサ手段１３１乃至１３４をチップ状基板１０１よりも熱伝導性の低い材料により形成すればよい。この例では、スペーサ手段１３１乃至１３４のパターンまたは位置を、チップ状基板１０１の裏面１０１ｂと回路基板１００との間に形成される空間の厚み寸法がほぼ一定になるように定めている。このようにすると空間の熱絶縁効果がチップ状基板１０１全体に対してほぼ等しくなるため、ヒューズ素子１２７の溶断特性が安定する。
スペーサ手段１３１乃至１３４の突出寸法が、あまり小さくなると、空間の熱絶縁機能が徐々に低下し、スペーサ手段１３１乃至１３４の実用上の効果が小さくなる。また突出寸法があまり大きくなると、側面電極に沿って溶融半田が上方に上っていくことができなくなる。このような実用上の観点からみると、この突出寸法の下限値と上限値の範囲は、６０μｍ乃至１５０μｍの範囲が好ましい。
また裏面電極１２０乃至１２３を形成する場合には、溶融半田が隣接する裏面電極間でブリッジを形成し、電極間の短絡が発生するおそれがある。そこで図１０に示すように、スペーサ手段１３５及び１３６を、隣接する裏面電極間で溶融半田のブリッジが形成されるのを阻止するパターンで形成すれば、このような事態が発生するのを有効に防止できる。
第２の実施の形態では、チップ状基板に貫通孔１２９及び１３０を形成して、発熱用抵抗体１２６からの熱の放散を抑制しているが、図１１（Ａ）及び（Ｂ）に示すように、チップ状基板２０１に、発熱用抵抗体２２６及びヒューズ素子２２７の下部に裏面側に向かって開口する凹部２３７を形成するようにしてもよい。この凹部２３７の形状及び深さは、発熱用抵抗体２２６から出た熱ができるだけヒューズ素子２２７に伝わるように定めればよい。このようしても発熱抵抗体からヒューズ素子への熱の伝達が良好になって、ヒューズ素子の溶断時間が短くなる。なお第２の実施の形態で用いた貫通孔１２９及び１３０とこの凹部２３７とを組み合わせて使用してもよいのは勿論である。
産業上の利用可能性
本発明によれば、ヒューズ素子を確実に形成することができて、しかも過大電流でヒューズ素子を溶断する機能と発熱用抵抗体の発熱でヒューズ素子を溶断させる機能とを備えた信頼性の高いチップ型ヒューズを得ることができる。
【図面の簡単な説明】
図１は本発明のチップ型ヒューズの第１の実施の形態で用いるセラミックス製のチップ状基板の平面図を示している。
図２は図１のチップ状基板の底面図を示している。
図３は一部を省略した図１のチップ型ヒューズの平面図を示している。
図４は側面電極の構造を示す部分拡大断面図である。
図５は、図１の実施の形態のチップ型ヒューズの回路図である。
図６及び図７は、本発明の第２の実施の形態で用いるチップ状基板の平面図及び裏面図である。
図８は、第２の実施の形態のチップ状基板の表面にガラスのオーバーコートを形成した状態の平面図である。
図９は、チップ型ヒューズの実装状態を示す図である。
図１０は、スペーサ手段の異なる例を示すチップ状基板の裏面図である。
図１１（Ａ）及び（Ｂ）は、チップ状基板の発熱用抵抗体及びヒューズ素子の下部に裏面側に向かって開口する凹部を形成する例を示す一部断面斜視図及び断面図である。TECHNICAL FIELD The present invention relates to a chip-type fuse having a heating resistor and a fuse element that is fused by heat from the heating resistor on a chip-like substrate.
Japanese Patent Application Laid-Open No. 7-153367 discloses a conventional example of a chip type fuse having a heating resistor and a fuse element blown by heat from the heating resistor on a chip substrate. Yes. In this chip type fuse, a fuse element is formed on a resistor via an insulating layer. This publication also discloses a technique using a chip-type fuse so that when an excessive current flows through the fuse element, the fuse element is blown by the current, and the fuse element is blown by the heat generated by the resistor.
In the conventional chip type fuse, a plurality of heating resistors formed on a substrate are covered with an insulating resin such as an epoxy resin, and a low melting point metal is formed as a fuse on the resin layer. In the conventional structure, since the fuse is formed on the surface of the insulating resin layer which is not flat, it is difficult to form the fuse element, which causes a problem that the yield is deteriorated and the manufacturing cost is increased. Further, in order to realize a function of blowing a fuse by an excessive current and a function of blowing a fuse element by heat generation of a heating resistor, a conventional chip type fuse has a resistor and an external circuit mounted with a chip type fuse. There has been a problem that a connection part for electrically connecting the fuse element must be provided, and the usability of the chip-type fuse is poor.
An object of the present invention is to provide a highly reliable chip-type fuse capable of directly fusing a fuse element with an excessive current and capable of fusing the fuse element even with heat generated by a heating resistor, and a method for manufacturing the same. There is to do.
Another object of the present invention is a fusing time until a fuse element is blown by heat from a heating resistor in a chip type fuse in which a heating resistor and a fuse element are formed side by side on the surface of a chip-like substrate. It is an object of the present invention to provide a chip-type fuse that can shorten the length.
Still another object of the present invention is to provide a chip-type fuse in which a heating resistor and a fuse element are formed side by side on the surface of a chip-like substrate, and until the fuse element is blown by heat from the heating resistor. The object is to provide a chip-type fuse with little variation in time.
Another object of the present invention is to provide a chip-type fuse capable of preventing the electrodes from being short-circuited by solder.
Another object of the present invention is to provide a chip-type fuse in which the fuse element is surely blown when an excessive current flows through the fuse element.
Still another object of the present invention is to provide a chip type fuse that can reliably form a fuse element using cream solder and a method for manufacturing the same.
DISCLOSURE OF THE INVENTION A chip-type fuse of the present invention comprises a chip substrate having a front surface and a back surface, a heating resistor formed on the surface of the chip substrate, and a heating resistor formed on the surface of the chip substrate. And a fuse element that is melted by heat from the body. The heating resistor and the fuse element are caused by the heat generated by the heating resistor when an excessive current flows through the fuse element and the fuse element is melted by the excessive current and when an overvoltage is applied to the heating resistor. The fuse elements are electrically connected so as to blow. According to the present invention, the fuse element can be reliably formed on the surface of the chip-like substrate, and the function of fusing the fuse element with an excessive current and the function of fusing the fuse element with the heat generated by the heating resistor are provided. A highly reliable chip-type fuse provided can be obtained.
In addition, spacer means for forming a space between the substrate surface and the back surface can be provided on the back surface of the chip-shaped substrate in contact with the substrate surface of the circuit board on which the chip-type fuse is mounted. When such spacer means is provided, the air in the space formed by the spacer means exerts a thermal insulation function that prevents heat from the heating resistor from being transmitted to the circuit board. Therefore, when the spacer means is provided, the fuse element can be blown by the heat of the heating resistor in a shorter time than when the spacer means is not provided. In order to suppress heat escape through the spacer means to the circuit board side as much as possible, the spacer means may be formed of a material having lower thermal conductivity than the chip-like substrate. Further, if the spacer means is formed by printing a predetermined pattern on the back surface of the chip-like substrate using a synthetic resin paste, the spacer means can be provided easily and inexpensively. The pattern of the spacer means is preferably determined so that the thickness dimension of the space formed between the back surface of the chip-like substrate and the circuit board is substantially constant. In this way, the thermal insulation effect of the space is substantially equal to the entire chip substrate, so that the fusing characteristics of the fuse element are stabilized. If the protruding dimension of the spacer means is too small, the thermal insulation function of the space is gradually lowered, and the practical effect of the spacer means is reduced. Also, if the protruding dimension becomes too large, this space is likely to become an obstacle to soldering. Therefore, from a practical point of view, the lower limit value and the upper limit value range of the projecting dimensions are preferably 60 μm to 150 μm. Needless to say, even if the projecting dimension does not fall within this range, it is included in the technical scope of the present invention as long as the effect of the present invention is obtained.
The structure and position of the electrodes formed on the chip-like substrate are arbitrary. However, in order to ensure soldering to the electrodes on the circuit board, one or more surface electrodes and fuse elements electrically connected to the heating resistor on the surface of the chip substrate are electrically connected. One or more connected surface electrodes are formed. A plurality of back electrodes electrically connected to the plurality of front surface electrodes are further formed on the back surface of the chip-like substrate. A plurality of side surface electrodes that connect the plurality of front surface electrodes and the plurality of back surface electrodes partially overlap the corresponding front surface electrodes and back surface electrodes on the outer surface connecting the front surface and the back surface of the chip-shaped substrate. To form. If the chip-like substrate is a ceramic substrate, the front electrode, the back electrode, and the side electrode are generally formed using a metal glaze conductive paste in which conductive powder is kneaded into glass. When it does in this way, there exists a tendency for the thickness of a side electrode to become thin at the corner | angular part of a chip-shaped board | substrate. If the thickness of the electrode portion at this corner portion becomes too thin, the resistance value at this portion becomes large, Joule heat is generated in this portion, and the fusing time of the fuse may be increased. Therefore, if a supplementary electrode is formed on or overlapping the side electrode and the surface electrode, such problems can be eliminated.
Moreover, when forming a back surface electrode, there exists a possibility that a molten solder may form a bridge | bridging between back surface electrodes and a short circuit may occur between electrodes. Therefore, if the above-mentioned spacer means is formed in a pattern that can prevent the formation of a bridge of molten solder between the plurality of back surface electrodes, it is possible to effectively prevent such a situation from occurring.
In order to further shorten the fusing time of the fuse element, not only prevents the heat from escaping from the chip-like substrate to the circuit board for mounting, but also transfers the heat generated from the heating resistor to the fuse element as much as possible. Is preferable. Therefore, a pair of through holes penetrating the chip substrate in the thickness direction is formed at a position sandwiching the central portion of the heating resistor and the fuse element arranged side by side on the chip substrate. Then, the length dimension in the direction in which the heating resistor extends is determined so that the heat generated from the resistor through the pair of through holes is transmitted to the center of the fuse element as much as possible. In this way, the heat generated from the heating resistor is collected at the center of the fuse element, so that the fuse element can be blown by the heat from the heating resistor in a shorter time.
Further, the chip-like substrate may be formed with a recess that opens toward the back side under the heating resistor and the fuse element. The shape and depth of the recess are determined so that heat generated from the heating resistor is transmitted to the fuse element as much as possible. Even in this case, heat transfer from the heating resistor to the fuse element is improved, and the fusing time of the fuse element is shortened.
The material and configuration of the fuse element are arbitrary. In order to reliably form the fuse element on the surface of the chip-shaped substrate, it is formed independently between a pair of surface electrodes formed on the surface of the chip-shaped substrate and separated from the other adjacent electrodes. One or more auxiliary electrodes are provided, and a fuse material layer made of a conductive material that melts when heated to a predetermined temperature or more is formed across the pair of surface electrodes and the one or more auxiliary electrodes. Specifically, the fuse material layer can be formed by heating and melting a cream solder layer formed over a pair of surface electrodes and one or more auxiliary electrodes using, for example, cream solder and then curing. When one or more auxiliary electrodes are provided between the pair of surface electrodes in this manner, when the fuse material layer is formed by curing the molten conductive material in a state of being restrained to some extent, the one or more auxiliary electrodes are anchored. Part), the conductive material can be retained, and the fuse material layer can be reliably formed. When an excessive current flows and when fusing by heat from the heating resistor, the conductive material is not restrained, so the auxiliary electrode serves to collect or attract the molten conductive material, Fusing of the fuse element is facilitated.
The surface of the chip-like substrate is preferably overcoated with an insulating material except for a portion necessary for forming the fuse element before forming the fuse element. This is to prevent the flux generated when the fuse element is formed using cream solder from adhering to the heating resistor or the like. When the spacer means is formed by printing, it is formed before the fuse element is formed. The fuse element is preferably formed at the very end of the manufacturing process. This is to prevent the fuse element from being blown by heat applied when forming the spacer means.
Note that the technique of forming a pair of through holes and providing spacer means can naturally be applied to a chip-type fuse in which only a heating resistor and a fuse element are arranged.
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a plan view of a ceramic chip substrate 1 used in the first embodiment of the chip type fuse of the present invention, and FIG. 2 shows a bottom view of the chip substrate 1. FIG. 3 is a plan view of a chip-type fuse, a part of which is omitted. As shown in FIG. 1, three semicircular arc-shaped recesses 3 to 5 are formed on one long side 2 of two long sides extending in the longitudinal direction of the chip-like substrate 1. One arcuate recess 7 is also formed at the center of the other long side 6. The recesses 3 to 5 and the recess 7 extend along the side surface connecting the front surface 1a and the back surface 1b of the chip substrate 1. Further, in the two short sides 8 and 9 of the chip-like substrate 1, concave portions 10 and 11 each having a U-shape when viewed from the plane are formed. A fitting hook for a case (not shown) that covers the surface 1a of the chip-like substrate is fitted into these recesses.
On the surface 1 a of the chip-like substrate 1, surface electrodes 12, 13, 14 for connection formed adjacent to the recesses 3 to 5 and the recess 7, an intermediate electrode 15, auxiliary electrodes 16 and 17, and surface electrodes 14 and 19 are provided with a portion extending in the longitudinal direction of the chip-like substrate 1 and wiring portions 18 and 19 having electrode portions 18a and 19a extending along the short sides 8 and 9 from the end of this portion. . These electrodes and wiring portions are formed using a metal glaze conductive paste obtained by kneading a conductive powder such as Ag or Ag-Pd in a glass paste. The pattern is printed using screen printing, and the baking temperature of the paste is about 850 ° C. The intermediate electrode 15 is formed at a substantially central portion of the space between the pair of surface electrodes 12 and 13, and the electrode portion 15 a of the intermediate electrode 15 is formed between the electrode portions 18 a and 19 a facing the pair of wiring portions 18 and 19. Located in the middle of the space between. Further, the two auxiliary electrodes 16 and 17 are independent (separated or separated) from the adjacent electrode between the one surface electrode 12 and the main body portion 15b of the intermediate electrode 15 and the main body portion 15b and the other surface electrode 13. It is formed in an electrically insulated state. Further, as shown in FIG. 2, on the back surface of the chip-like substrate 1, the four back electrodes 20 to 23 adjacent to the end portions of the recesses 3 to 5 and the recess 7 are formed using the metal glaze conductive paste described above. Is formed. The back electrode 21 is a dummy electrode used for soldering when it is necessary to increase the soldering strength.
Although not shown in FIG. 3, after electrodes are formed on the front surface 1a and the back surface 1b of the chip-like substrate 1, side electrodes 24 as shown in FIG. 4 are formed using the above-described metal glaze conductive paste. The side electrode 24 is formed on the outer surface connecting the front surface 1a and the back surface 1b of the chip-like substrate 1 and partially overlaps the corresponding front surface electrode and back surface electrode. When the side electrode 24 is formed in this way, the thickness of the side electrode 24 tends to be reduced at the corners of the chip substrate 1. If the thickness of the electrode portion at this corner portion becomes too thin, the resistance value at this portion becomes large, Joule heat is generated in this portion, and the fusing time of the fuse may be increased. Therefore, in this example, the supplementary electrode 25 is formed on the side electrode 24 and the surface electrode 13 so as to supplement the portion of the side electrode 24 whose thickness is reduced. The supplementary electrode 25 is also formed using a metal glaze conductive paste. The other surface electrodes other than the electrodes shown in FIG. 4 and the back electrode are connected using the same connection structure as the structure shown in FIG. As described above, in FIG. 3, the position of the side electrode 24 is simply indicated by a broken line in order to simplify the illustration, and its presence is omitted. Of course, unlike this example, the supplementary electrode may be formed directly on the surface electrode 13 and the end of the side electrode 24 may be formed thereon.
As shown in FIG. 3, after forming the above-described electrodes, the heating resistor 26 is formed so as to straddle the electrode portions 18 a and 19 a of the wiring portions 18 and 19 and the electrode portion 15 a of the intermediate electrode 15. The heating resistor 26 is formed by a thick film resistor formed by printing and baking a silver-palladium paint using glass as a binder, a thick film resistor formed by using a metal glaze resistor paint such as RuO ₂ -glass, or the like. ing. The firing temperature of these resistive paints is also about 850 ° C.
Although not shown in FIG. 3, after forming the electrodes, an insulating material made of a glass material is used on the surface of the chip-like substrate 1 except for a portion for forming a fuse element 27 and a soldering electrode portion described later. An overcoat is formed. After forming the overcoat, a fuse material layer is formed so as to straddle part of the surface electrodes 12 and 13, the main body portion 15 b of the intermediate electrode 15, and the auxiliary electrodes 16 and 17, thereby forming the fuse element 27.
When forming the fuse material layer, for example, a cream solder layer formed over the pair of surface electrodes 12 and 13 and the two auxiliary electrodes 16 and 17 and the intermediate electrode 15 is formed using cream solder. Next, the fuse element 27 is formed by heating the cream solder layer while being pressed from above, melting the cream solder, and curing the solder paste as it is. When the auxiliary electrodes 16 and 17 are provided between the pair of surface electrodes 12 and 13 as in this example, when the melted cream solder (conductive material) is cured to some extent to form a fuse material layer. The melted solder solder can be retained by the auxiliary electrodes 16 and 17 serving as anchors (retaining portions), and the fuse material layer can be reliably formed. When an excessive current flows and when the fuse element 27 is blown by heat from the heating resistor 26, the auxiliary elements 16 and 17 collect or attract the molten conductive material because the fuse element 27 is not restrained. Thus, fusing of the fuse element 27 is facilitated.
The fuse material layer constituting the fuse element 27 can be formed of a low melting point metal such as a Pb—Sn based, Pb—Sb based, Sn—Sb based eutectic solder alloy or the like.
A circuit diagram of the chip-type fuse of this embodiment is as shown in FIG. In this chip-type fuse, the electrodes 12 and 13 are connected to a cut-off portion of a circuit to be protected, and the electrode 14 is connected to a location where an overvoltage of the circuit to be protected is to be detected. In this circuit, the divided resistor portions R1 and R2 are constituted by a portion of a heating resistor 26 formed between the intermediate electrode 15, the electrode portion 18a, and the electrode portion 19a (FIG. 3). H <b> 1 and H <b> 2 are constituted by a portion of the fuse element 27 formed between the intermediate electrode 15, the electrode 12, and the electrode 13. In this circuit configuration, when an excessive voltage is applied from the electrode 14 to the divided resistor portions R1 and R2, a current flows through at least one of the divided fuse portions H1 and H2. Then, due to the heat generated from the divided resistor portions R1 and R2, when at least one of the divided fuse portions H1 and H2 is heated to the melting temperature by the heat transmitted through the chip-like substrate 1, it is blown out. When an excessive current flows between the electrode 12 and the electrode 13, at least one of the divided fuse portions H <b> 1 and H <b> 2 is melted by heat at that time, and the circuit is cut off between the electrodes 12 and 13.
6 and 7 are a plan view and a back view of the chip substrate 101 used in the second embodiment of the present invention. 6 and 7, the same parts as those of the first embodiment shown in FIGS. 1 to 3 have the same number as the reference numerals shown in FIGS. 1 to 3 plus 100. The reference numerals are attached and the description is omitted. FIG. 8 is a plan view showing a state in which a glass overcoat 128 is formed on the surface of the chip-like substrate 101 according to the second embodiment. In FIG. 8, a fuse element 127 to be formed later is indicated by a broken line. In the second embodiment, a pair of heat-generating resistors 126 arranged side by side on the chip-like substrate 101 and a pair of penetrating the chip-like substrate 101 in the thickness direction at a position sandwiching the central portion of the fuse element 127 therebetween. Through holes 129 and 130 are formed. The pair of through holes 129 and 130 have a length dimension in a direction in which the heating resistor 126 extends so that heat generated from the heating resistor 126 is transmitted to the central portion of the fuse element 127 as much as possible. In this way, the heat generated from the heating resistor 126 is not dissipated outside the pair of through holes 129 and 130, but is collected at the center of the fuse element 127. The fuse element 127 can be melted by the heat from 126.
In the second embodiment, the back surface 101b of the chip-like substrate 101 is in contact with the substrate surface 100a of the circuit board 100 (see FIG. 9) on which the chip-type fuse is mounted. Protruding members or spacer means 131 to 134 for forming a space between them are provided. In this example, the spacer means 131 to 134 are formed on the back surface 101b of the chip substrate 101 by printing using a synthetic resin paste made of a thermosetting resin such as an epoxy resin. The height of the spacer means 131 to 134 can be set to an arbitrary height by applying the paste a plurality of times. When the spacer means 131 to 134 are formed in the synthetic resin paste, the spacer means 131 to 134 can be provided easily and inexpensively. The spacer means 131 to 134 are formed after the glass overcoat 128 is formed before the fuse element 127 is formed.
When such spacer means 131 to 134 are provided, the air in the space formed by the spacer means 131 to 134 exhibits a thermal insulation function that prevents the heat from the heating resistor 126 from being transmitted to the circuit board 100. . Therefore, the fuse element 127 can be blown by the heat of the heating resistor 126 in a shorter time when the spacer means 131 to 134 are provided than when the spacer means 131 to 134 are not provided.
In order to suppress the heat escape to the circuit board 100 side through the spacer means 131 to 134 as much as possible, the spacer means 131 to 134 may be formed of a material having lower thermal conductivity than the chip substrate 101. In this example, the patterns or positions of the spacer means 131 to 134 are determined so that the thickness dimension of the space formed between the back surface 101b of the chip substrate 101 and the circuit substrate 100 is substantially constant. In this way, the thermal insulation effect of the space is substantially equal to the entire chip substrate 101, so that the fusing characteristics of the fuse element 127 are stabilized.
If the protruding dimensions of the spacer means 131 to 134 are too small, the thermal insulation function of the space is gradually lowered, and the practical effect of the spacer means 131 to 134 is reduced. If the protruding dimension is too large, the molten solder cannot rise upward along the side surface electrode. From such a practical point of view, the lower limit value and the upper limit value range of the projecting dimensions are preferably 60 μm to 150 μm.
When the back electrodes 120 to 123 are formed, the molten solder forms a bridge between the adjacent back electrodes, which may cause a short circuit between the electrodes. Therefore, as shown in FIG. 10, if the spacer means 135 and 136 are formed in a pattern that prevents the formation of a bridge of molten solder between the adjacent backside electrodes, it is possible to effectively prevent such a situation from occurring. Can be prevented.
In the second embodiment, through-holes 129 and 130 are formed in the chip-like substrate to suppress the heat dissipation from the heating resistor 126, as shown in FIGS. 11A and 11B. As described above, the chip-like substrate 201 may be formed with a recess 237 that opens toward the back side under the heating resistor 226 and the fuse element 227. The shape and depth of the recess 237 may be determined so that heat generated from the heating resistor 226 is transmitted to the fuse element 227 as much as possible. Even in this case, heat transfer from the heating resistor to the fuse element is improved, and the fusing time of the fuse element is shortened. Needless to say, the through holes 129 and 130 used in the second embodiment and the recess 237 may be used in combination.
INDUSTRIAL APPLICABILITY According to the present invention, a fuse element can be reliably formed, and a function of fusing the fuse element with an excessive current and a function of fusing the fuse element with heat generated by the heating resistor are provided. A highly reliable chip-type fuse provided can be obtained.
[Brief description of the drawings]
FIG. 1 is a plan view of a ceramic chip-like substrate used in the first embodiment of the chip-type fuse of the present invention.
FIG. 2 shows a bottom view of the chip substrate of FIG.
FIG. 3 shows a plan view of the chip type fuse of FIG.
FIG. 4 is a partially enlarged sectional view showing the structure of the side electrode.
FIG. 5 is a circuit diagram of the chip type fuse of the embodiment of FIG.
6 and 7 are a plan view and a back view of the chip substrate used in the second embodiment of the present invention.
FIG. 8 is a plan view of a state in which a glass overcoat is formed on the surface of the chip-like substrate of the second embodiment.
FIG. 9 is a diagram showing a mounted state of the chip type fuse.
FIG. 10 is a back view of a chip-like substrate showing different examples of the spacer means.
FIGS. 11A and 11B are a partial cross-sectional perspective view and a cross-sectional view showing an example in which a recess opening toward the back side is formed in the lower portion of the heating resistor and the fuse element of the chip-like substrate.

Claims

A chip-like substrate having a front surface and a back surface;
A heating resistor formed on the surface of the chip substrate;
A fuse element formed on the surface of the chip-like substrate and melted by heat from the heating resistor;
When the overcurrent flows through the fuse element, the fuse element is blown by the overcurrent, and when the overvoltage is applied to the heat generation resistor, the heat generation resistor and the fuse element It is electrically connected so that the fuse element is blown by the heat generated by the resistor ,
Spacer means for forming a space between the substrate surface and the back surface is provided on the back surface of the chip-shaped substrate in contact with the substrate surface of the circuit board on which the chip-type fuse is mounted. A featured chip-type fuse.

2. The chip-type fuse according to claim 1 , wherein the spacer means is formed of a material having lower thermal conductivity than the chip-shaped substrate.

2. The chip-type fuse according to claim 1 , wherein the spacer means is formed by printing a synthetic resin paste in a predetermined pattern on the back surface of the chip-like substrate.

The chip-type fuse according to claim 3 , wherein the pattern is determined so that a thickness dimension of the space is substantially constant.

5. The chip-type fuse according to claim 1, 2, 3, or 4 , wherein a protruding dimension of the spacer means from the back surface is 60 μm to 150 μm.

One or more surface electrodes formed on the surface of the chip-like substrate and electrically connected to the heating resistor; and one or more surface electrodes electrically connected to the fuse element;
A plurality of back electrodes formed on the back surface of the chip-like substrate and electrically connected to the plurality of surface electrodes, respectively;
2. The chip-type fuse according to claim 1 , wherein the spacer means is formed in a pattern capable of preventing formation of a bridge of molten solder between the plurality of back surface electrodes.

The fuse element is formed of a pair of surface electrodes formed on the surface of the chip-like substrate and one or more auxiliary electrodes formed independently between the pair of surface electrodes and separated from other adjacent electrodes. Consists of a fuse material layer formed across the electrodes,
The chip-type fuse according to claim 1 , wherein the fuse material layer is formed of a conductive material that melts when heated to a predetermined temperature or higher.

Said fuse material layer to claim 7 which is formed by curing after melted by heating the cream solder layer formed across said pair of surface electrodes and the one or more auxiliary electrodes using cream solder The chip-type fuse described.

The heating resistor and the fuse element are formed side by side on the surface of the chip substrate,
The chip-shaped substrate has a pair of through holes penetrating the chip-shaped substrate in the thickness direction at a position sandwiching the heating resistor and the central portion of the fuse element therebetween,
The pair of through holes have a length dimension in a direction in which the heating resistor extends so that heat generated from the heating resistor is transmitted to the central portion of the fuse element as much as possible. The chip-type fuse according to claim 1 .

The chip-like substrate is formed with a recess that opens toward the back side under the heating resistor and the fuse element,
2. The chip-type fuse according to claim 1 , wherein a shape and a depth of the recess are determined so that heat generated from the heating resistor is transmitted to the central portion of the fuse element as much as possible.

A chip-like substrate having a front surface and a back surface;
A heating resistor formed on the surface of the chip substrate;
And a fuse element melts by heat from the heat generating resistor is formed on the surface of the chip-like substrate,
When the overcurrent flows through the fuse element, the fuse element is blown by the overcurrent, and when the overvoltage is applied to the heat generation resistor, the heat generation resistor and the fuse element It is electrically connected so that the fuse element is blown by the heat generated by the resistor,
One or more surface electrodes formed on the surface of the chip-like substrate and electrically connected to the heating resistor; and one or more surface electrodes electrically connected to the fuse element;
A plurality of back electrodes formed on the back surface of the chip-like substrate and electrically connected to the plurality of surface electrodes;
On the outer surface that connects the front surface and the back surface of the chip-shaped substrate, a plurality of side surface electrodes that connect the plurality of front surface electrodes and the plurality of back surface electrodes correspond to the corresponding front surface electrode and back surface electrode. It is formed so as to partially overlap
The front electrode, the back electrode and the side electrode are formed using a metal glaze conductive paste,
A chip-type fuse, wherein a supplementary electrode is formed using a metal glaze conductive paste between the side electrode and the surface electrode or on an overlapping portion.

Printing an electrode pattern including a plurality of surface electrodes using a metal glaze conductive paste on the surface of a ceramic chip-like substrate having a front surface and a back surface, and firing the electrode pattern to form a fired electrode pattern;
Printing a resistor paste between a predetermined pair of surface electrodes included in the fired electrode pattern, firing the resistor paste, and forming a heating resistor;
The cream solder is applied or printed on between predetermined pair of surface electrodes included in baking the electrode pattern, Ri Do and a step of forming a fuse element by curing was melted in a state of restraining it,
Between the pair of surface electrodes on which the cream solder is applied or printed, one or more auxiliary electrodes formed independently of the pair of surface electrodes are formed,
The cream solder is applied or printed across the pair of surface electrodes and the one or more auxiliary electrodes,
Before forming the fuse element, an overcoat is formed by covering the main part excluding the part where the fuse element is formed with an insulating material,
Then, on the back surface of the chip-shaped substrate, contact with the substrate surface of the circuit board on which the chip-type fuse is mounted to form spacer means for forming a space between the substrate surface and the back surface,
Finally, the fuse element is formed . A method for manufacturing a chip-type fuse.

A chip-like substrate having a front surface and a back surface;
A heating resistor formed on the surface of the chip substrate;
A fuse element formed on the surface of the chip-like substrate and melted by heat from the heating resistor;
The heating resistor and the fuse element are formed side by side on the surface of the chip substrate,
The chip-shaped substrate has a pair of through holes penetrating the chip-shaped substrate in the thickness direction at a position sandwiching the heating resistor and the central portion of the fuse element therebetween,
A chip-type fuse in which the pair of through holes have a length dimension in a direction in which the heating resistor extends so that heat generated from the heating resistor is transmitted to the fuse element as much as possible.

Spacer means for forming a space between the substrate surface and the back surface is provided on the back surface of the chip-shaped substrate in contact with the substrate surface of the circuit board on which the chip-type fuse is mounted. The chip-type fuse according to claim 13 , wherein the fuse is a chip-type fuse.