JP4161458B2 - Current switching element - Google Patents
Current switching element Download PDFInfo
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- JP4161458B2 JP4161458B2 JP07880499A JP7880499A JP4161458B2 JP 4161458 B2 JP4161458 B2 JP 4161458B2 JP 07880499 A JP07880499 A JP 07880499A JP 7880499 A JP7880499 A JP 7880499A JP 4161458 B2 JP4161458 B2 JP 4161458B2
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- Prior art keywords
- bismuth
- thin film
- current
- switching element
- current switching
- Prior art date
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Description
【０００１】
【産業上の利用分野】
本発明は、通常は電流導通状態でありながら、周囲温度の異常上昇または素子に流れる異常過電流などの異常状態を検知して電流を遮断し、温度または電流が異常状態から正常状態に復帰すると再び導通状態に自己修復する機能をもつ素子に関する。
【０００２】
【従来の技術】
従来、高温または過電流に感応して電流スイッチングを行う素子としては、バイメタル、ＰＴＣサーミスタなどがある。しかし、バイメタルでは周囲温度のみにしか応答せず、かつ振動等の機械的ショックによって誤動作する場合もある。ＰＴＣサーミスタは周囲温度と過電流の両者に応答し機械的ショックに対する誤動作もないが、導通状態での電気抵抗率が数１０オームｃｍ、非導通状態の電気抵抗率が数万オームｃｍ程度であり、導通状態での抵抗率が高く、また導通状態と非導通状態との比が小さいため理想的な電流スイッチング素子とはいえない。したがって、従来素子を使った高温と過電流に応答する電流スイッチングは使用条件が制限されるという問題がある。
【０００３】
【発明が解決しようとする課題】
従来の電流スイッチング素子が抱える前記問題は基本的には素子の構造と材質から生じる。したがって、前記問題を解決するには全く新しい動作原理に基づいた新規構造をもち、その動作原理に合致する材料から構成される電流スイッチング素子が必要とされる。
【０００４】
本発明は、従来の電流スイッチング素子とは動作原理、構造、材料が異なる素子に関するものであり、導通状態での電気抵抗が１オーム以下、非導通状態での電気抵抗が数百万オーム以上の電流スイッチング素子を提供することを目的とする。
【０００５】
本発明者らは、基板上にビスマス金属またはビスマス基合金薄膜を形成させることにより、従来の電流スイッチング素子とは異なる新しい原理、構造で高温または過電流に感応して電流を制限することを見出した。すなわち、本発明は、基板上に融解状態で体積収縮を起こすビスマス金属またはビスマス基合金薄膜を形成し、前記薄膜上に電気絶縁性物質からなる保護層を設けた構造を特徴とする電流スイッチング素子に関する。
【０００６】
【発明の実施の形態】
本発明の構造により、導通状態では低抵抗であり、かつ非導通状態では非常に高い絶縁抵抗を有する電流スイッチング素子が得られる。その発現機構は、以下のように推察される。
【０００７】
本発明の素子は、素子周囲の温度上昇または素子に流れる電流による発熱によって、基板上のビスマス金属またはビスマス基合金薄膜が融点以上で体積収縮を伴って融解し膜の電気的導通が破れ、その結果として素子の電気抵抗が瞬時に増大し電気絶縁状態に変化し電流を遮断する。次いで、素子温度が低下すると、融解金属が凝固する際に体積増加して電気的導通を回復する。本発明において、ビスマス金属またはビスマス基合金薄膜の１箇所を線状加工することにより、電気導通が遮断される位置を線状加工位置に特定すると共に、スイッチング素子における遮断電流を一定値とすることができる。また、線状加工した位置の線幅を変えることにより、遮断電流値を所望の値に設定することができる。
ビスマス基合金を用いて膜の融点を所望の値とすることにより、素子の電流遮断温度あるいは遮断電流値を変えることができる。
【０００８】
本発明における薄膜の形成に使用される金属または合金としては、融解状態で体積収縮を起こすビスマス金属またはビスマス基合金である。前記ビスマス基合金を例示すると、Ｂｉ−Ｐｂ、Ｂｉ−Ｓｎ、Ｂｉ−Ｉｎ、Ｂｉ−Ｓｎ−Ｐｂ、Ｂｉ−Ｐｂ−Ｓｎ−Ｓｂ、Ｂｉ−Ｓｂ、Ｂｉ−Ｃｄ、Ｂｉ−Ｐｂ−Ｓｎ−Ｉｎ、Ｂｉ−Ｐｂ−Ｓｎ−Ｃｄ等である。ビスマス基合金におけるＢｉの量は合金重量に対して４０重量％以上、特に５０重量％以上が好ましい。
【０００９】
前記薄膜の膜厚は特に限定されないが、通常１〜１００μｍであるのが好ましい。また、線状加工した線幅についても特に限定されるものではないが、通常０．１〜１０μｍであるのが好ましい。そしてこれらは、真空蒸着法、スパッタリング法、メッキ法等の方法で形成することができる。
【００１０】
被覆する電気絶縁性物質としては、素子の電流遮断温度で溶融（融解）したり、性能劣化を起こさないセラミックス、ガラス、あるいは高分子ポリマーが好ましい。被覆する電気絶縁性物質を例示すると、アルミナ、Ｂ2Ｏ3系ガラス、ＳｉＯ2系ガラス、ポリエチレン、エポキシ樹脂、フッ素樹脂、ポリイミド、シリコンゴム等である。
【００１１】
【実施例】
以下、本発明の一実施例の形態における電流スイッチング素子について、図面を参照しながら具体的に説明する。
【００１２】
実施例１
図１は実施例１に用いた素子構造を示す平面図である．図中、１は基板、２は電極、３はビスマス金属薄膜、４はビスマス金属薄膜の線状加工位置、５は被覆電気絶縁性物質のガラスである。図２は、図１中のａ−ｂ線に沿う断面図である。
図３に温度上昇による電気抵抗−温度特性を示す。ビスマス金属薄膜は、スパッタリング法を用いて作製されており、この測定では、被覆材にはガラスを用いている。素子の温度を上昇させるとビスマスの融点（２７１℃）以上でビスマスが融解し線状加工位置で薄膜が断線状態になり、その結果、電気抵抗が急増する。素子の温度を下降させると融点より約２０℃低い温度で融解したビスマスが膨張凝固し、再び電気抵抗が低下する。
【００１３】
実施例２
実施例２に用いた素子構造は、実施例１で用いたビスマス金属の替わりにＢｉ−Ｐｂ−Ｓｎ−Ｓｂ合金（重量比４７.７／３３.２／１８.８／０.３）を膜として基板上に形成したものである。
図４はＢｉ−Ｐｂ−Ｓｎ−Ｓｂ合金薄膜を形成した素子の電気抵抗−温度特性である。 Ｂｉ−Ｐｂ−Ｓｎ−Ｓｂ合金の融点（約１３０℃）で電気抵抗は急増し素子は電流遮断状態となる。電流遮断状態となった素子の温度を低下させると約１１０℃で再び電流導通状態に復帰する。
【００１４】
【発明の効果】
本発明によると、基板上に融解状態で体積収縮を起こすビスマス金属またはビスマス基合金薄膜を形成し、前記薄膜上にセラミックス、ガラス、または高分子材料等の電気絶縁性物質からなる保護層を設けた構造をとることで、導通状態で１オーム以下の低電気抵抗、非導通状態で数百万オームの高電気抵抗となり、良好なスイッチング特性を示す素子を得ることができる。したがって、温度感応電流遮断回路、過電流保護回路等への利用が見込まれる。また、本発明の素子は、温度センサとしての利用や非線形特性を利用した各種信号処理回路での利用も見込まれる。
【図面の簡単な説明】
【図１】実施例１および実施例２に用いた電流スイッチング素子の平面図である。
【図２】図１のａ−ｂ線に沿う断面図である。
【図３】実施例１で用いた素子の電気抵抗−温度特性を示す図である。
【図４】実施例２で用いた素子の電気抵抗−温度特性を示す図である。
【符号の説明】
１：基板
２：電極
３：ビスマス金属薄膜またはビスマス基合金薄膜
４：ビスマス金属薄膜またはビスマス基合金薄膜の線状加工位置
５：被覆電気絶縁性物質[0001]
[Industrial application fields]
The present invention detects an abnormal state such as an abnormal rise in ambient temperature or an abnormal overcurrent flowing in the element while the current is normally in a conductive state, and interrupts the current, and when the temperature or current returns from the abnormal state to the normal state The present invention relates to an element having a function of self-repairing to a conductive state again.
[0002]
[Prior art]
Conventionally, elements that perform current switching in response to high temperatures or overcurrents include bimetals and PTC thermistors. However, bimetal responds only to ambient temperature and may malfunction due to mechanical shock such as vibration. The PTC thermistor responds to both ambient temperature and overcurrent and does not malfunction due to mechanical shock. However, the electrical resistivity in the conducting state is several tens of ohms cm, and the electrical resistivity in the non-conducting state is several tens of thousands of ohms cm. Since the resistivity in the conducting state is high and the ratio between the conducting state and the non-conducting state is small, it cannot be said to be an ideal current switching element. Therefore, there is a problem that current switching using a conventional element responding to high temperature and overcurrent is limited in use conditions.
[0003]
[Problems to be solved by the invention]
The above-described problems of conventional current switching elements basically arise from the structure and material of the elements. Therefore, in order to solve the above problem, a current switching element having a new structure based on a completely new operation principle and made of a material that matches the operation principle is required.
[0004]
The present invention relates to an element whose operating principle, structure, and material are different from those of a conventional current switching element. The electrical resistance in a conductive state is 1 ohm or less, and the electrical resistance in a non-conductive state is several million ohms or more. An object is to provide a current switching element.
[0005]
The present inventors have found that by forming a bismuth metal or bismuth-based alloy thin film on a substrate, found that limiting the current sensitive to high temperature or over-current at different new principle, structure the conventional current switching element It was. That is, the present invention provides a current switching element characterized in that a bismuth metal or bismuth-based alloy thin film that causes volume shrinkage in a molten state is formed on a substrate, and a protective layer made of an electrically insulating material is provided on the thin film. About.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
With the structure of the present invention, it is possible to obtain a current switching element having a low resistance in the conductive state and a very high insulation resistance in the non-conductive state. The expression mechanism is presumed as follows.
[0007]
In the device of the present invention, the heat generation due to the temperature rise around the device or the current flowing in the device causes the bismuth metal or bismuth-based alloy thin film on the substrate to melt with a volume contraction above the melting point, and the electrical conduction of the film is broken. As a result, the electrical resistance of the element increases instantaneously and changes to an electrically insulated state, interrupting the current. Next, when the element temperature decreases, the volume increases when the molten metal solidifies to restore electrical conduction. In the present invention, by linearly processing one part of the bismuth metal or bismuth-based alloy thin film, the position where electrical conduction is interrupted is specified as the linear processing position, and the interruption current in the switching element is set to a constant value. Can do. Further, the breaking current value can be set to a desired value by changing the line width of the linearly processed position.
By setting the melting point of the film to a desired value using a bismuth-based alloy, the current cutoff temperature or the cutoff current value of the element can be changed.
[0008]
The metal or alloy used for forming the thin film in the present invention is a bismuth metal or bismuth-based alloy that causes volume shrinkage in the molten state. Examples of the bismuth-based alloy include Bi—Pb, Bi—Sn, Bi—In, Bi—Sn—Pb, Bi—Pb—Sn—Sb, Bi—Sb, Bi—Cd, Bi—Pb—Sn—In, Bi-Pb-Sn-Cd and the like. The amount of Bi in the bismuth-based alloy is preferably 40% by weight or more, particularly 50% by weight or more based on the alloy weight.
[0009]
Although the thickness of the thin film is not particularly limited, it is usually preferably 1 to 100 μm. Moreover, although it does not specifically limit about the line | wire width processed linearly, It is preferable that it is 0.1-10 micrometers normally. And these can be formed by methods, such as a vacuum evaporation method, sputtering method, and the plating method.
[0010]
The electrically insulating material to be coated is preferably ceramics, glass, or a high molecular polymer that does not melt (melt) at the current interruption temperature of the element or cause performance deterioration. Examples of the electrically insulating material to be coated include alumina, B 2 O 3 glass, SiO 2 glass, polyethylene, epoxy resin, fluororesin, polyimide, and silicon rubber.
[0011]
【Example】
Hereinafter, a current switching element according to an embodiment of the present invention will be specifically described with reference to the drawings.
[0012]
Example 1
FIG. 1 is a plan view showing the element structure used in Example 1. FIG. In the figure, 1 is a substrate, 2 is an electrode, 3 is a bismuth metal thin film, 4 is a linear processing position of the bismuth metal thin film, and 5 is a glass of a coated electrically insulating material. FIG. 2 is a cross-sectional view taken along line ab in FIG.
FIG. 3 shows the electrical resistance-temperature characteristics due to temperature rise. The bismuth metal thin film is produced using a sputtering method. In this measurement, glass is used as the coating material. When the temperature of the device is raised, bismuth melts at a temperature equal to or higher than the melting point of bismuth (271 ° C.), and the thin film becomes disconnected at the linear processing position. As a result, the electrical resistance increases rapidly. When the temperature of the element is lowered, bismuth melted at a temperature lower by about 20 ° C. than the melting point expands and solidifies, and the electric resistance decreases again.
[0013]
Example 2
The element structure used in Example 2 is a Bi-Pb-Sn-Sb alloy (weight ratio 47.7 / 33.2 / 18.8 / 0.3) instead of the bismuth metal used in Example 1. Formed on the substrate.
FIG. 4 shows electrical resistance-temperature characteristics of the element on which the Bi—Pb—Sn—Sb alloy thin film is formed. The electric resistance rapidly increases at the melting point (about 130 ° C.) of the Bi—Pb—Sn—Sb alloy, and the device is in a current interruption state. When the temperature of the element in the current interruption state is lowered, the current conduction state is restored again at about 110 ° C.
[0014]
【The invention's effect】
According to the present invention, a bismuth metal or bismuth-based alloy thin film that causes volume shrinkage in a molten state is formed on a substrate, and a protective layer made of an electrically insulating substance such as ceramics, glass, or a polymer material is provided on the thin film. By adopting such a structure, a low electrical resistance of 1 ohm or less in the conductive state and a high electrical resistance of several million ohms in the non-conductive state can be obtained, and an element exhibiting good switching characteristics can be obtained. Therefore, it can be used for a temperature-sensitive current cutoff circuit, an overcurrent protection circuit, and the like. The element of the present invention is also expected to be used as a temperature sensor or in various signal processing circuits using nonlinear characteristics.
[Brief description of the drawings]
FIG. 1 is a plan view of a current switching element used in Example 1 and Example 2. FIG.
FIG. 2 is a cross-sectional view taken along the line ab of FIG.
3 is a graph showing electric resistance-temperature characteristics of the element used in Example 1. FIG.
4 is a graph showing electric resistance-temperature characteristics of the element used in Example 2. FIG.
[Explanation of symbols]
1: Substrate 2: Electrode 3: Bismuth metal thin film or bismuth base alloy thin film 4: Linear processing position of bismuth metal thin film or bismuth base alloy thin film 5: Coated electrically insulating material
Claims (2)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP07880499A JP4161458B2 (en) | 1999-03-24 | 1999-03-24 | Current switching element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP07880499A JP4161458B2 (en) | 1999-03-24 | 1999-03-24 | Current switching element |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2008027112A Division JP2008124507A (en) | 2008-02-07 | 2008-02-07 | Current switching element |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2000277303A JP2000277303A (en) | 2000-10-06 |
| JP4161458B2 true JP4161458B2 (en) | 2008-10-08 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP07880499A Expired - Fee Related JP4161458B2 (en) | 1999-03-24 | 1999-03-24 | Current switching element |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP4161458B2 (en) |
-
1999
- 1999-03-24 JP JP07880499A patent/JP4161458B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JP2000277303A (en) | 2000-10-06 |
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