JP3770408B2

JP3770408B2 - Substrate type resistance / temperature fuse and protection method for equipment

Info

Publication number: JP3770408B2
Application number: JP18995494A
Authority: JP
Inventors: 充明植村
Original assignee: Uchihashi Estec Co Ltd
Current assignee: Uchihashi Estec Co Ltd
Priority date: 1994-07-20
Filing date: 1994-07-20
Publication date: 2006-04-26
Anticipated expiration: 2021-04-26
Also published as: JPH0831285A

Description

【０００１】
【産業上の利用分野】
本発明は、電子または電気器の保全に使用する基板型抵抗・温度ヒュ−ズ及び機器の保護方法に関するものである。
【０００２】
【従来の技術】
抵抗・温度ヒュ−ズにおいては、電子または電気機器の回路に挿入接続され、過電流により抵抗体が発熱し、その発生熱で温度ヒュ−ズが溶断され、機器への通電の遮断により機器の異常発熱、ひいては火災の発生を未然に防止するために使用されている。
かかる抵抗・温度ヒュ−ズとして、セラミックス基板に膜導体並びに膜抵抗体を形成し、この膜抵抗体に近接して低融点金属片を配設した基板型抵抗・温度ヒュ−ズが公知である。
【０００３】
この基板型抵抗・温度ヒュ−ズとしては、各種の構成が知られている。図３は、公知の基板型抵抗・温度ヒュ−ズの一例を示し、セラミックス基板１’の片面に膜導体５２’，５２”を形成し、一方の膜導体５２”の中間に膜抵抗体２’を橋設し、膜導体５２’，５２”の先端部間に低融点金属片３’を橋設し、低融点金属片３’上にフラックス４’を塗布し、各膜導体５２’，５２”のリ−ド線接続用ランドにリ−ド線６’，６’を接続し、更に、セラミックス基板片面にエポキシ樹脂等の絶縁被覆層７’を設けている。（実開昭６３−９７２０７号公報）
【０００４】
この基板型抵抗・温度ヒュ−ズの作動機構は、膜抵抗体の発生熱が低融点金属片に伝達され、低融点金属片の温度が融点に達したときに、低融点金属片が溶断されることにあるが、膜抵抗体の発生熱量が比較的小さい場合（定格入力電力の４〜６倍程度の入力の場合）は、温度上昇速度が比較的緩やかになり、比熱の関与が少なくなり、膜導体が熱伝達媒質の主体となってくる。
【０００５】
【発明が解決しようとする課題】
しかしながら、このように膜抵抗体の発生熱が比較的小さい場合、図３に示す基板型抵抗・温度ヒュ−ズにおいては、膜抵抗体２’から一方のリ−ド線６’に至る膜導体５２”の距離が比較的短いために、膜抵抗体２’の発生熱が一方のリ−ド線を経て外部に放熱され易く、それだけ膜抵抗体２’の温度上昇速度が遅くなるから、抵抗・温度ヒュ−ズの作動速度も遅くなると考えられる。
【０００６】
また、膜導体が熱伝達媒質の主体となるときは、低融点金属片３’においては、膜抵抗体２’と膜導体５２”で接続された側の一端部が他の部分よりも集中的に加熱され、低融点金属片全体の溶融による球状化分断は期待し難く、図２の（ロ）に示すように、その一端部端の局部的溶融による球状化分断となると推察されるから、分断距離が短くなり（球状化分断は、溶融金属の表面張力による変形で生じ、低融点金属片の溶融が局部的になると、その変形も少なくなり、分断距離が短くなる）、分断箇所の絶縁距離が不充分となって、再導通の発生等、確実な電気的遮断を保証し難い。
【０００７】
本発明の目的は、セラミックス基板の片面に膜導体並びに膜抵抗体を形成し、その膜導体に低融点金属片を接続し、膜抵抗体と低融点金属片とを膜導体で直結した基板型抵抗・温度ヒュ−ズにおいて、膜抵抗体の発生熱が比較的小さいときでの作動性並びに作動直後での絶縁性の向上を図ることにある。
【０００８】
【課題を解決するための手段】
本発明に係る基板型抵抗・温度ヒュ−ズは、セラミックス基板の片面の中間に低融点金属片が設けられ、同上基板片面の一端部側に、上記低融点金属片の中央線を挾んで膜抵抗体が設けられ、上記低融点金属片両端の各端と上記の各膜抵抗体内側端との間がそれぞれ中間膜導体により接続され、同上基板片面に上記の各膜抵抗体外側端から基板他端にわたってリ−ド用膜導体が設けられ、これらの各リ−ド用膜導体にそれぞれリ−ド線が接続され、上記低融点金属片にフラックスが塗布され、同上基板の片面に絶縁被覆が施されていることを特徴とする構成である。
本発明に係る機器の保護方法は、上記の基板型抵抗・温度ヒュ−ズを使用して、機器を定格入力電力の４〜６倍の入力から保護することを特徴とする構成である。
【０００９】
以下、図面を参照しつつ本発明の構成を説明する。
図１の（イ）は、本発明に係る基板型抵抗・温度ヒュ−ズの一構成例を示す説明図、図１の（ロ）は、図１の（イ）におけるロ−ロ断面図である。
図１の（イ）並びに図１の（ロ）において、１はセラミックス基板である。
【００１０】
２，２は膜抵抗体であり、セラミックス基板１の片面の一端側に、該基板１の中央線（後述の低融点金属片３の中央線）ｎ−ｎに対して左右対称に設けられており、両膜抵抗体２，２の抵抗値はほぼ等しく設定されている。３は低融点金属片であり、基板片面の中間に設けられており、上記中央線ｎ−ｎに対して左右対称である。４は低融点金属片上に塗布されたフラックスである。５１，５１は中間膜導体であり、低融点金属片３の両端の各端と上記各膜抵抗体２の内側端２１との間を接続している。５２，５２は、リ−ド用膜導体であり、同上基板片面に上記各膜抵抗体２の外側端２２から基板他端にわたって設けられており、他端部にはリ−ド線接続用ランド５２０を備えている。６は各リ−ド用膜導体５２の他端５２０に接続された絶縁被覆リ−ド線である。７は同上基板片面に被覆された絶縁層である。
【００１１】
上記基板型抵抗・温度ヒュ−ズにおいては、セラミックス基板の片面への膜導体の形成、膜抵抗体の形成並びに抵抗値調整、リ−ド線の接続、低融点金属片の接続、フラツクスの塗布、絶縁被覆層の形成の手順で製造することができる。
上記セラミックス板１には、厚み０．１ｍｍ〜２．０ｍｍ好ましくは０．４ｍｍ〜１．２ｍｍの９６％アルミナ、ベリリア、炭化珪素、窒化アルミニウム、ステアタイト等を使用できる。
【００１２】
上記の膜導体５１，５２は、導体ぺ−ストのスクリ−ン印刷またはディスペンサ−並びに焼付け等による厚膜法で形成することが好ましく、導体ぺ−ストには、Ａｇ系、Ａｇ−Ｐｔ系、Ａｇ−Ｐｄ系、Ｃｕ系、Ｐｔ系、Ａｕ系ペ−スト等を使用でき、膜厚みは、通常１０〜３０μｍとされる。
【００１３】
上記膜抵抗体２については、抵抗ぺ−ストを印刷・焼付けし、その上にガラス２０をオ−バコ−トすることにより形成できる。この膜抵抗体の形成には、抵抗ペ−ストの印刷・焼き付けにより膜抵抗を形成し、その上に第１ガラスコ−トを焼付けたうえで、レ−ザ−トリミングにより所定の抵抗値に調整し、次いで第２のガラスコ−トを焼き付ける方法を使用することが望ましい。抵抗ぺ−ストには、ＲｕＯ₂系、Ｔａ−Ｔａｎ系、ＳｎＯ₂−Ｔａ₂Ｏ₅系、ＬａＢ₆系、ＳｎＯ₂−Ｔａ系、ＳｒＲｕＯ₃系、ＴａＳｉ₂系、ＭｏＳｉ₂系、Ａｇ−Ｐｄ系ペ−スト等を使用でき、膜抵抗体の厚みは、通常５〜４０μｍとされる。
【００１４】
上記低融点金属片３には、作動温度に応じた融点の丸線または箔状合金が使用され、通常、Ｓｎ，Ｐｂ，Ｉｎ、Ｓｂ、Ｃｄ等の中から選択された２〜４成分系の共晶合金が使用される。
【００１５】
上記フラックス４については、上記低融点金属片３の融点よりも充分に低い軟化点を有し、通常、天然ロジンまたは合成ロジンに活性剤を添加したものが使用される。
上記の絶縁被覆７には、フラックス４の軟化点よりも充分に低い温度で被覆可能なものが使用され、例えば、エポキシ樹脂の常温下での滴下塗装を使用できる。
【００１６】
【作用】
膜抵抗体２，２のジュ−ル熱が中間膜導体５１，５１乃至はセラミックス基板１を熱伝達媒質として低融点金属片３に伝達され、低融点金属片３が溶融され、溶融フラックスの作用（酸化皮膜の除去作用、溶融金属のぬれ性改善等）で、溶融金属の表面張力による球状化が促され、溶融金属の球状化分断により通電が遮断されるに至る。この場合、ジュ−ル熱量が比較的小なるときは、低融点金属片の温度が低融点金属片の融点（作動温度）に達する際での温度変化が緩やかであり、定常状態に近く、比熱の関与がほとんど無く、熱伝達媒質の主体は、熱導伝性に優れた膜導体（金属粒子等が多量に含有されている）となる。
【００１７】
而るに、膜抵抗体２からリ−ド線６に至る膜導体５２の長さが、図３に示す従来例よりも長くされ、その間の熱抵抗が高くされているから、そのリ−ド線６を経ての放熱がそれだけ減少され、基板型抵抗・温度ヒュ−ズ全体がそれだけ迅速に加熱され、基板型抵抗・温度ヒュ−ズの作動もそれだけ迅速化される。また、低融点金属片３においては、両側の膜抵抗体２，２から中間膜導体５１，５１を伝って伝達されてくるジュ−ル熱により、両端が溶融され、図２の（イ）に示すように両端を核として球状化分断され、片端のみでの球状化分断である図２の（ロ）の場合に較べて、分断距離を長くでき、分断間に充分な絶縁を保証でき、再導通等の支障を排除できる。
これらの作用は、次ぎの実施例と比較例との作動時間並びに作動直後での絶縁強度試験の比較からも確認できる。
【００１８】
【実施例】
〔実施例〕
図１の（イ）並びに図１の（ロ）において、セラミックス基板１には、厚み１ｍｍ、ａ７ｍｍ、ｂ１０ｍｍの９６％アルミナ板を使用した。膜導体５１，５２はＡｇ系ペ−ストの印刷・焼き付けにより形成し、リ−ド用膜導体５２の長さｃは９ｍｍ、リ−ド線接続用ランド部５２０の寸法はｄ３ｍｍ、ｅ２ｍｍ、ランド部以外の巾ｆは０．５ｍｍとした。
【００１９】
各膜抵抗体２には、ＲｕＯ₂系ペ−ストの印刷・焼付けにより形成し、レ−ザ−トリミングにより１０Ωに調整し、セラミックス基板先端から膜抵抗体までの距離ｈを２ｍｍとし、縦寸法ｋを１ｍｍ、横寸法ｍを１．５ｍｍとしたものを使用した。低融点金属片３には、融点９５℃、直径０．４ｍｍφの合金丸線を使用し、低融点金属片３と膜抵抗体２との距離ｐを１ｍｍに設定した。フラックス４には、天然ロジンを主成分とするものを使用した。リ−ド線６には、銅線直径０．６ｍｍφの絶縁被覆銅線を使用した。絶縁被覆７は、エポキシ樹脂液の常温下での滴下塗装により施した。
【００２０】
〔比較例〕
図３において、セラミックス基板１’、低融点金属片３’、フラックス４’、リ−ド線６’並びに絶縁被覆７’等には、実施例と同材質、同一寸法のものを使用し、膜抵抗体２’には、実施例と同様ＲｕＯ₂系ペ−ストの印刷・焼付けで、縦寸法ｋが２ｍｍ、横寸法ｍ’が３ｍｍであり、レ−ザ−トリミングにより２０Ωに調整したものを使用した。膜導体５２’，５２”も実施例と同様、Ａｇ系ペ−ストの印刷・焼き付けにより形成し、巾ｆは０．５ｍｍとし、リ−ド線接続用ランド部の寸法は実施例に同じとした。膜抵抗体２’からセラミックス基板後端までの距離ｐ”は４ｍｍとし、低融点金属片３’と膜抵抗体２’との間隔ｐ’は２ｍｍとした。
【００２１】
これらの実施例品並びに比較例品につき（それぞれ試料数は５０個とした）、４．４７ボルト、１ワットで通電し、作動時間（通電開始後、通電が遮断されるまでの時間）を測定したところ、比較例品では１５０秒（平均値）であったのに対し、実施例品では９０秒（平均値）であり、比較例品に対し、４０％もの短縮であった。
また、作動後での両リ−ド線間の絶縁強度を測定したところ、比較例品では絶縁抵抗が５００ボルト印課で１×１０¹⁰Ωであったのに対し、実施例品では５００ボルト印課で１×１０¹²Ωであり、比較例品に対し、１００倍も高かった。
【００２２】
【発明の効果】
本発明に係る基板型抵抗・温度ヒュ−ズにおいては、膜抵抗体のジュ−ル熱量が比較的小さい場合での作動性迅速性並びに作動直後での絶縁強度を良好に保証でき、例えば、定格入力電力の４〜６倍程度の入力から機器を保護する場合に有用である。
【図面の簡単な説明】
【図１】図１の（イ）は本発明の一構成例を示す説明図、図１の（ロ）は図１の（イ）におけるロ−ロ断面図である。
【図２】本発明に係る基板型抵抗・温度ヒュ−ズと従来の基板型抵抗・温度ヒュ−ズにおける低融点金属片の溶断状態を示す説明図である。
【図３】従来例を示す説明図である。
【符号の説明】
１セラミックス基板
２膜抵抗体
３低融点金属体
５１中間膜導体
５２リ−ド膜導体
６リ−ド線
７絶縁被覆[0001]
[Industrial application fields]
The present invention relates to a substrate type resistance / temperature fuse used for the maintenance of electronic or electrical equipment and a method for protecting equipment .
[0002]
[Prior art]
In the resistance / temperature fuse, it is inserted and connected to the circuit of electronic or electrical equipment, the resistor generates heat due to overcurrent, the temperature fuse is blown by the generated heat, and the equipment is disconnected by cutting off the power to the equipment. It is used to prevent abnormal heat generation and eventually fire.
As such a resistance / temperature fuse, a substrate-type resistance / temperature fuse in which a film conductor and a film resistor are formed on a ceramic substrate and a low-melting point metal piece is disposed in the vicinity of the film resistor is known. .
[0003]
Various configurations are known as the substrate type resistance / temperature fuse. FIG. 3 shows an example of a known substrate-type resistance / temperature fuse, in which film conductors 52 ′ and 52 ″ are formed on one surface of the ceramic substrate 1 ′, and the film resistor 2 is formed in the middle of one film conductor 52 ″. Is bridged, a low melting point metal piece 3 'is bridged between the tips of the membrane conductors 52', 52 ", a flux 4 'is applied on the low melting point metal piece 3', and each of the membrane conductors 52 ', The lead wires 6 'and 6' are connected to the 52 "lead wire connecting land, and further, an insulating coating layer 7 'such as an epoxy resin is provided on one surface of the ceramic substrate. (Japanese Utility Model Publication No. 63-97207)
[0004]
The operation mechanism of this substrate type resistance / temperature fuse is such that when the heat generated by the film resistor is transmitted to the low melting point metal piece and the temperature of the low melting point metal piece reaches the melting point, the low melting point metal piece is blown out. However, when the amount of heat generated by the membrane resistor is relatively small (when the input is about 4 to 6 times the rated input power), the rate of temperature rise is relatively slow and the specific heat is less involved. The membrane conductor becomes the main component of the heat transfer medium.
[0005]
[Problems to be solved by the invention]
However, when the heat generated by the film resistor is relatively small as described above, in the substrate type resistance / temperature fuse shown in FIG. 3, the film conductor extending from the film resistor 2 'to one of the lead wires 6' is used. Since the distance of 52 ″ is relatively short, the heat generated by the film resistor 2 ′ is easily radiated to the outside through one lead wire, and the temperature rise rate of the film resistor 2 ′ is accordingly slowed down.・ It is considered that the operating speed of the temperature fuse is also slowed down.
[0006]
Further, when the film conductor is the main body of the heat transfer medium, in the low melting point metal piece 3 ′, one end on the side connected by the film resistor 2 ′ and the film conductor 52 ″ is more concentrated than the other part. Since it is difficult to expect spheroidization by melting of the entire low melting point metal piece, as shown in (b) of FIG. 2, it is assumed that it becomes spheroidization by local melting at one end thereof, The separation distance becomes shorter (spherical division occurs due to deformation due to the surface tension of the molten metal, and when the melting of the low-melting point metal piece becomes localized, the deformation also decreases and the separation distance becomes shorter), and the insulation at the separation point It is difficult to ensure reliable electrical interruption such as re-conduction due to insufficient distance.
[0007]
An object of the present invention is to form a substrate type in which a film conductor and a film resistor are formed on one surface of a ceramic substrate, a low melting point metal piece is connected to the film conductor, and the film resistor and the low melting point metal piece are directly connected by the film conductor. In the resistance / temperature fuse, the operability when the heat generated by the film resistor is relatively small and the insulation immediately after the operation are improved.
[0008]
[Means for Solving the Problems]
The substrate-type resistance / temperature fuse according to the present invention is a film in which a low melting point metal piece is provided in the middle of one surface of a ceramic substrate, and the center line of the low melting point metal piece is sandwiched on one end side of the same substrate side surface. A resistor is provided, and each end of the low-melting-point metal piece is connected to the inner end of each film resistor by an intermediate film conductor. Lead film conductors are provided over the other end, lead wires are connected to each of the lead film conductors , flux is applied to the low melting point metal piece, and insulation coating is applied to one side of the substrate. It is the structure characterized by being given.
The device protection method according to the present invention is characterized in that the device is protected from an input of 4 to 6 times the rated input power by using the substrate-type resistance / temperature fuse.
[0009]
The configuration of the present invention will be described below with reference to the drawings.
1A is an explanatory diagram showing an example of the configuration of a substrate type resistance / temperature fuse according to the present invention, and FIG. 1B is a cross-sectional view of the roll in FIG. is there.
In FIG. 1A and FIG. 1B, reference numeral 1 denotes a ceramic substrate.
[0010]
Reference numerals 2 and 2 denote film resistors, which are provided on one end of one side of the ceramic substrate 1 symmetrically with respect to a center line (center line of a low-melting-point metal piece 3 to be described later) n−n. The resistance values of both film resistors 2 and 2 are set to be approximately equal. Reference numeral 3 denotes a low-melting-point metal piece, which is provided in the middle of one surface of the substrate and is symmetrical with respect to the center line nn. 4 is a flux coated on the low melting point metal piece. Reference numerals 51 and 51 denote intermediate film conductors, which connect between the respective ends at both ends of the low melting point metal piece 3 and the inner ends 21 of the respective film resistors 2. 52 and 52 are lead film conductors, which are provided on one side of the board from the outer end 22 of each film resistor 2 to the other end of the board, and at the other end are lead wire connecting lands. 520. Reference numeral 6 denotes an insulation coating lead wire connected to the other end 520 of each lead film conductor 52. 7 is an insulating layer coated on one side of the substrate.
[0011]
In the above-mentioned substrate type resistance / temperature fuse, formation of a film conductor on one side of a ceramic substrate, formation of a film resistor and resistance adjustment, connection of lead wires, connection of low melting point metal pieces, application of flux It can be manufactured by the procedure of forming the insulating coating layer.
The ceramic plate 1 may be made of 96% alumina, beryllia, silicon carbide, aluminum nitride, steatite, etc. having a thickness of 0.1 mm to 2.0 mm, preferably 0.4 mm to 1.2 mm.
[0012]
The above-mentioned film conductors 51 and 52 are preferably formed by a thick film method such as screen printing or dispenser of conductor paste and baking, and the conductor paste includes Ag-based, Ag-Pt-based, Ag-Pd-based, Cu-based, Pt-based, Au-based paste and the like can be used, and the film thickness is usually 10 to 30 μm.
[0013]
The film resistor 2 can be formed by printing and baking a resistance paste and overlying the glass 20 thereon. For the formation of this film resistor, a film resistance is formed by printing and baking a resistance paste, and after the first glass coat is baked thereon, it is adjusted to a predetermined resistance value by laser trimming. It is then desirable to use a method of baking a second glass coat. Resistance paste - the strike, RuO ₂ based, Ta-Tan system, SnO _₂ -Ta ₂ O ₅ system, LaB ₆ based, SnO ₂ -Ta system, SrRuO ₃ system, TaSi ₂ system, MoSi ₂ system, Ag-Pd A system paste or the like can be used, and the thickness of the film resistor is usually 5 to 40 μm.
[0014]
For the low melting point metal piece 3, a round wire or a foil-like alloy having a melting point corresponding to the operating temperature is used, and usually a 2-4 component system selected from Sn, Pb, In, Sb, Cd and the like. A eutectic alloy is used.
[0015]
The flux 4 has a softening point sufficiently lower than the melting point of the low-melting-point metal piece 3, and is usually a natural rosin or a synthetic rosin added with an activator.
As the insulating coating 7, one that can be coated at a temperature sufficiently lower than the softening point of the flux 4 is used. For example, dripping coating of epoxy resin at room temperature can be used.
[0016]
[Action]
The Joule heat of the film resistors 2 and 2 is transmitted to the low melting point metal piece 3 using the intermediate film conductors 51 and 51 or the ceramic substrate 1 as a heat transfer medium, the low melting point metal piece 3 is melted, and the action of the molten flux. (Oxidation film removal action, improvement of wettability of molten metal, etc.) promotes spheroidization due to the surface tension of the molten metal, and energization is interrupted by spheroidization of the molten metal. In this case, when the amount of joule heat is relatively small, the temperature change is slow when the temperature of the low melting point metal piece reaches the melting point (operating temperature) of the low melting point metal piece, is close to a steady state, and has a specific heat. The main component of the heat transfer medium is a film conductor (containing a large amount of metal particles and the like) having excellent heat conductivity.
[0017]
Therefore, the length of the film conductor 52 from the film resistor 2 to the lead wire 6 is longer than that of the conventional example shown in FIG. 3, and the thermal resistance therebetween is increased. The heat radiation through the line 6 is reduced accordingly, the entire substrate resistance / temperature fuse is heated up so quickly, and the operation of the substrate resistance / temperature fuse is accelerated accordingly. Further, in the low melting point metal piece 3, both ends are melted by the Joule heat transmitted from the film resistors 2 and 2 on both sides through the intermediate film conductors 51 and 51, as shown in FIG. As shown in FIG. 2 (b), which is divided into spheroids with both ends as nuclei and spheroidized at only one end, the separation distance can be increased and sufficient insulation can be ensured between the divisions. Problems such as continuity can be eliminated.
These effects can be confirmed from the comparison of the operation time between the following examples and the comparative example and the insulation strength test immediately after the operation.
[0018]
【Example】
〔Example〕
1A and 1B, a 96% alumina plate having a thickness of 1 mm, a7 mm, and b10 mm was used for the ceramic substrate 1. The film conductors 51 and 52 are formed by printing and baking Ag-based paste, the length c of the lead film conductor 52 is 9 mm, the dimensions of the lead wire connecting land portion 520 are d3 mm, e2 mm, land The width f other than the part was 0.5 mm.
[0019]
Each film resistor 2 is formed by printing and baking RuO ₂ paste, adjusted to 10Ω by laser trimming, the distance h from the tip of the ceramic substrate to the film resistor is 2 mm, and the vertical dimension The k was 1 mm and the lateral dimension m was 1.5 mm. An alloy round wire having a melting point of 95 ° C. and a diameter of 0.4 mmφ was used for the low melting point metal piece 3, and the distance p between the low melting point metal piece 3 and the membrane resistor 2 was set to 1 mm. As the flux 4, a material mainly composed of natural rosin was used. As the lead wire 6, an insulation coated copper wire having a copper wire diameter of 0.6 mmφ was used. The insulating coating 7 was applied by dripping the epoxy resin liquid at room temperature.
[0020]
[Comparative Example]
In FIG. 3, the ceramic substrate 1 ′, the low melting point metal piece 3 ′, the flux 4 ′, the lead wire 6 ′, the insulating coating 7 ′, etc. are made of the same material and the same dimensions as those of the embodiment, Resistor 2 ′ was printed and baked with a RuO ₂ paste similar to the example, with vertical dimension k of 2 mm and horizontal dimension m ′ of 3 mm, adjusted to 20Ω by laser trimming. used. The membrane conductors 52 'and 52 "are formed by printing and baking Ag-based paste as in the embodiment, the width f is 0.5 mm, and the dimensions of the lead wire connecting land are the same as in the embodiment. The distance p ″ from the film resistor 2 ′ to the rear end of the ceramic substrate was 4 mm, and the distance p ′ between the low melting point metal piece 3 ′ and the film resistor 2 ′ was 2 mm.
[0021]
For each of these example products and comparative example products (the number of samples was 50), energization was performed at 4.47 volts and 1 watt, and the operation time (time from the start of energization until the energization was cut off) was measured. As a result, it was 150 seconds (average value) in the comparative product, and 90 seconds (average value) in the example product, which was 40% shorter than the comparative product.
In addition, when the insulation strength between the lead wires after operation was measured, the comparative example product had an insulation resistance of 1 × 10 ¹⁰ Ω at 500 volts, while the example product had 500 volts. The imprint was 1 × 10 ¹² Ω, which was 100 times higher than that of the comparative product.
[0022]
【The invention's effect】
In the substrate type resistance / temperature fuse according to the present invention, it is possible to satisfactorily assure the quick operation and the insulation strength immediately after the operation when the Jule heat quantity of the film resistor is relatively small. This is useful for protecting a device from an input of about 4 to 6 times the input power.
[Brief description of the drawings]
FIG. 1 (a) is an explanatory view showing a configuration example of the present invention, and FIG. 1 (b) is a cross-sectional view of FIG.
FIG. 2 is an explanatory diagram showing a fusing state of a low-melting point metal piece in a substrate type resistance / temperature fuse according to the present invention and a conventional substrate type resistance / temperature fuse.
FIG. 3 is an explanatory diagram showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ceramic substrate 2 Film resistor 3 Low melting-point metal body 51 Intermediate film conductor 52 Lead film conductor 6 Lead wire 7 Insulation coating

Claims

A low-melting point metal piece is provided in the middle of one side of the ceramic substrate, and a film resistor is provided on one end of the same side of the substrate, sandwiching the center line of the low-melting point metal piece. Between each end of the film resistor and the inner end of each film resistor is connected by an intermediate film conductor, and a lead film conductor is provided on one side of the substrate from the outer end of each film resistor to the other end of the substrate. A lead wire is connected to each of the lead film conductors, a flux is applied to the low melting point metal piece, and an insulating coating is applied to one side of the same substrate. Temperature fuse.

A device protection method comprising: protecting a device from an input of 4 to 6 times a rated input power using the substrate-type resistance / temperature fuse according to claim 1.