JP2012235053A - Overcurrent overvoltage protection element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem of a circuit protection element integrating an overcurrent protection element and an overvoltage protection element and well-known conventional that the overcurrent protection element does not function when the overvoltage protection element is short-circuited.SOLUTION: The overcurrent protection element can function normally even if the overvoltage protection element in one of two gaps is short-circuited, by employing an overcurrent overvoltage protection element having an insulation substrate, terminal electrodes formed at both ends of the insulation substrate, a fuse connected in series with at least two parts between the terminal electrodes, at least two earth electrodes formed from a conductive part interconnecting the fuses via an overvoltage protective material, and a protective resin layer covering the fuse and the overvoltage protective material.

Description

The present invention relates to an element for protecting an electronic circuit from overcurrent and overvoltage.

In recent years, an element that integrates an overcurrent protection element and an overvoltage protection element and has these functions at the same time has been proposed, which contributes to a reduction in the number of components. As a conventional technique related to such an integrated circuit protection element, for example, there is an invention of JP 2010-98024 A. According to the present invention, a fuse element is provided on the surface of the insulating substrate to provide an overcurrent protection function, and on the back side, the first overvoltage protection material layer is provided on the power supply side, and the second overvoltage protection material is provided on the circuit side. There is a circuit protection component that has a protective function against overvoltage by installing a layer. In addition, when an overvoltage is applied, it is bypassed to the ground from between the first overvoltage protection material layer and the second overvoltage protection material layer.

JP 2010-98024 A

However, in the invention of the above-mentioned patent document, when the first overvoltage protection material layer installed on the power supply side is short-circuited by applying the abnormal voltage repeatedly, the current coming from the power supply side is an overcurrent protection function. Therefore, there is a problem in that overcurrent flows through the power supply circuit without fulfilling its purpose as an overcurrent protection element.

The present invention has been made in view of the above circumstances, and protects a power supply circuit not only in a function of protecting against overcurrent and overvoltage, but also in a case where overvoltage protection material is short-circuited due to repeated application of overvoltage. An object of the present invention is to provide an element that can be used.

Formed via an overvoltage protection material from an insulating substrate, terminal electrodes formed at both ends of the insulating substrate, fuses connected in series between at least two locations between the terminal electrodes, and a conductive portion connecting the fuses An overcurrent overvoltage protection element having at least two ground electrodes and a protective resin layer covering the fuse and the overvoltage protection material.

The overcurrent overvoltage protection element, wherein the fuse and the conductive portion are a fuse film made of a film-like conductor.

An overcurrent overvoltage protection element in which a heat storage layer is installed under the fuse film.

The fuse film is an overcurrent overvoltage protection element which is a low melting point metal made of aluminum or copper.

The overcurrent overvoltage protection element, wherein the fuse film and the ground electrode forming a gap between the conductive portion and the ground electrode are a refractory metal made of at least one of titanium, tungsten, and molybdenum.

The overcurrent overvoltage protection element, wherein the gap is wider in the other gap width than in one gap width.

If the overcurrent overvoltage protection element according to the present invention is used, the power supply circuit can be protected from overcurrent even if the application of overvoltage is repeated and one of the overvoltage protection units is short-circuited.

Next, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a perspective view of an overcurrent overvoltage protection element 1 according to the present invention. Terminal electrodes 3 are formed at opposite ends of the insulating substrate 2. As shown in FIG. 2, the terminal electrode 3 includes a base electrode 10 made of, for example, Ag, a Ni plating 11, and a Sn plating 12. A fuse film 4 is formed so as to electrically connect the terminal electrode 3. The fuse film 4 has narrow fusing portions 5 having a role of a fuse arranged in two places in series. When the overcurrent flows, the circuit is protected from the overcurrent by generating heat and fusing. The fuse film 4 is formed by sputtering or plating.

It should be noted that the heat storage layer 6 having a low thermal conductivity made of glass, silicone resin, or the like is provided under the fusing part 5 in order to quickly respond to the heat generation when overcurrent flows and to cut the fusing part 5. Since the heat generated by the overcurrent is stored in the heat storage layer 6, the operation against the overcurrent can be made more effective. As a forming method, before forming the fuse film 4 on the insulating substrate 2, for example, there is a method in which paste is screen printed and fired.

Moreover, the fusing part 5 can be made to melt | fuse quickly with respect to the heat_generation | fever when an overcurrent flows by forming with low melting-point metals 4a, such as Cu and Al.

Further, on the insulating substrate 2, two ground electrodes 7 that are not electrically connected to the fuse film 4 are formed, and a gap 8 that is a minute gap is formed between the fuse film 4 and the ground electrode 7. Is provided. The gap 8 can be formed by a photolithography method or a laser. An earth terminal electrode 13 electrically connected to the earth electrode 7 is formed on the side surface of the insulating substrate 2. As shown in FIG. 3, the ground terminal electrode 13 is composed of the base electrode 10, the Ni plating 11, and the Sn plating 12 similarly to the terminal electrode 3.

The gap 8 can adjust the discharge start voltage by changing the interval, but the gap interval is preferably about 5 to 20 μm. If it is narrower than 5 μm, the insulation between the fuse film 4 and the earth electrode 7 deteriorates when an overvoltage is repeatedly applied, and a short circuit is likely to occur. On the other hand, if it is larger than 20 μm, the discharge start voltage becomes high, and it becomes difficult to appropriately function as an overvoltage protection element.

An overvoltage protection material 9 is formed on the gap so as to cover these two gaps 8. As this overvoltage protection material 9, a known material in which conductive particles such as Ni and Al are uniformly dispersed in an insulating polymer such as a silicone resin can be used, and the overvoltage protection material 9 is formed by screen printing.

As shown in FIG. 1, the overvoltage protection element is installed between two fusing parts 5. With this arrangement, the equivalent circuit of the overcurrent overvoltage protection element 1 according to the present invention is represented as shown in FIG. 6, but when the overvoltage is repeatedly applied and the first overvoltage protection unit 9a is short-circuited, the equivalent circuit is shown. Changes as shown in FIG. However, even if an overcurrent comes from the power supply side after the overvoltage protection unit 9a is short-circuited, the circuit can be protected from the overcurrent because the fusing unit 5a is blown and the circuit is opened. In addition, even if the gap in the first overvoltage protection unit 9a is widened to increase the discharge start voltage, or the overvoltage protection material is deteriorated and the overvoltage protection unit 9a is completely insulated, the second overvoltage protection Since the unit 9b functions, it can function normally as an overvoltage protection element and protect the circuit from overvoltage.

FIG. 4 is a plan view of the overcurrent overvoltage protection element 1 in which only the insulating substrate 2, the fuse film 4 and the ground electrode 7 are arranged. The fuse film 4 and the ground electrode 7 forming the gap 8 are preferably made of a refractory metal 4b made of at least one of titanium, tungsten, and molybdenum. Since an overvoltage is applied to the circuit and the discharge portion becomes hot when discharging in the gap 8, when a metal having a low melting point is used, the metal melts or scatters and the gap interval changes. That is, there is a high possibility that the discharge start voltage will change. Therefore, the use of a refractory metal for the gap 8 improves the reliability and durability of the overcurrent overvoltage protection element 1.

Also, as shown in FIG. 5, the gap 8 at the two locations is wider at the other gap width than at one gap width. Therefore, when an overvoltage such as static electricity is applied, discharge occurs first in the overvoltage protection element with the narrower gap width, and further, by repeating the discharge, the gap interval widens and the overvoltage protection material layer deteriorates, and the overvoltage protection function is activated. After disappearing, the other overvoltage protection element with the wider gap width functions normally.

Next, as shown in FIG. 9, for example, a silicone-based protective resin layer 14 is installed so as to cover at least the fusing part 5 and the overvoltage protection material 9. The protective resin layer 14 wraps the molten metal at the time of fusing of the fuse film due to overcurrent to prevent scattering, and the fuse film is softened and melted in a liquid state because the number of crosslinks of the silicone rubber is reduced due to heat generation of the fuse film. The current can be reliably cut off by covering. Moreover, it is possible to prevent ignition and smoke when the melted part 5 is melted.

(Embodiment 2) Next, another embodiment of the present invention will be described. As shown in FIG. 8, the heat storage layer 6 is not disposed in two locations, but is disposed as one heat storage layer under the two fusing portions 5 that are overcurrent protection portions. You can also.

One heat storage layer has the advantage of improving productivity because the pattern is simple. However, the temperature of the gap 8 is likely to increase due to the current, and the durability of the overvoltage protection function may be deteriorated as compared with the first embodiment.

As described above, the details of the present invention have been described with reference to specific examples. However, the present invention is shown as an embodiment of the present invention, and the effects of the invention are considered based on the technical idea. It should be understood that a part of the embodiment can be modified and implemented as long as it is not significantly impaired.

The perspective view of the overcurrent overvoltage protection element by this invention AA sectional view of FIG. BB sectional view of FIG. Plan view of the overcurrent overvoltage protection element showing the arrangement of the low melting point metal part and the high melting point metal part of the fuse film and the ground electrode Plan view of the overcurrent overvoltage protection element showing only the insulating substrate, fuse film and ground electrode Equivalent circuit of overcurrent overvoltage protection device according to the present invention In FIG. 6, an equivalent circuit when one of the overvoltage protection units is short-circuited. The perspective view which showed other embodiment of the overcurrent overvoltage protection element by this invention The perspective view when the protective resin layer is formed in the upper surface of the overcurrent overvoltage protection element by this invention

The present invention can be used in a circuit that requires an overcurrent protection element and an overvoltage protection element.

1 ;, overcurrent overvoltage protection element 2; insulating substrate 3; terminal electrode 4; fuse film 4a; low melting point metal 4b; high melting point metal 5, 5a, 5b; Ground electrode 8; gap 9, 9a, 9b; overvoltage protection material 10; ground electrode 11; Ni plating 12; Sn plating 13; earth terminal electrode 14; protective resin layer

Claims (6)

Formed via an overvoltage protection material from an insulating substrate, terminal electrodes formed at both ends of the insulating substrate, fuses connected in series between at least two locations between the terminal electrodes, and a conductive portion connecting the fuses An overcurrent overvoltage protection element having at least two ground electrodes and a protective resin layer covering the fuse and the overvoltage protection material. The overcurrent overvoltage protection element according to claim 1, wherein the fuse and the conductive portion are a fuse film made of a film-like conductor. The overcurrent overvoltage protection element according to claim 2, wherein a heat storage layer is provided under the fuse film. 4. The overcurrent overvoltage protection element according to claim 2, wherein the fuse film is a low melting point metal made of aluminum or copper. 5. The overcurrent overvoltage according to claim 2, wherein the fuse film and the ground electrode forming a gap between the conductive portion and the ground electrode are a refractory metal made of at least one of titanium, tungsten, and molybdenum. Protective element. The overcurrent overvoltage protection element according to claim 5, wherein the gap is wider in one gap width than in the other gap width.

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