JP7457946B2 - protection device - Google Patents

Description

TECHNICAL FIELD This disclosure relates generally to protection devices, and more particularly to protection devices with discharge cavities.

Protective devices that function as surge absorbers are known in the past (see Patent Document 1).

In the surge absorber of Patent Document 1, a pair of first and second internal electrodes is arranged inside an insulator block (ceramic element) and a part of the first and second pair of internal electrodes is exposed. In a surge absorber equipped with a discharge cavity, a dummy cavity for stress relaxation is provided near the discharge cavity. When one side in the direction perpendicular to the main surface of the internal electrode is the upper side and the other side is the lower side, the dummy cavity is placed between the upper side or the lower side of the discharge cavity, or between the upper and lower sides through the insulating layer. Placed on both sides. Further, the dummy cavity is located approximately coaxially with the discharge cavity.

Japanese Patent Application Publication No. 2007-227259

On the other hand, when two conventional protection devices are used in the same circuit, there is a problem that if the protection devices have a large difference in their individual capacitances, the signal waveform becomes rounded and deteriorates.

The present disclosure has been made in view of the above-mentioned problems, and an object of the present disclosure is to provide a protection device in which the difference in individual capacitances is small and the influence on signal deterioration is small.

A protection device according to one aspect of the present disclosure has a first cavity and a second cavity in an insulating layer, and includes a first element and a second element. The first element has a pair of first electrodes facing each other with the first cavity interposed therebetween. The second element has a pair of second electrodes facing each other with the second cavity interposed therebetween. The first element generates a discharge in the first cavity when the voltage between the pair of first electrodes reaches a discharge voltage. The second element generates a discharge in the second cavity when the voltage between the pair of second electrodes reaches a discharge voltage.

According to the present disclosure, it is possible to provide a protection device in which the difference in individual capacitances is small and the influence on signal deterioration is small.

FIG. 1 is a diagram illustrating the functions of an ESD suppressor according to one embodiment. FIG. 2 is an exploded perspective view of the ESD suppressor. FIG. 3 is a diagram illustrating the configuration of a circuit using the same ESD suppressor as above. FIG. 4A shows a signal waveform of one element included in the above ESD suppressor. FIG. 4B shows a signal waveform of the other element of the ESD suppressor. FIG. 4C shows the differential signals of FIGS. 4A and 4B of the same ESD suppressor. FIG. 5A shows a signal waveform of one of the elements of the ESD suppressor described above when the capacitance difference between the elements is large. FIG. 5B shows a signal waveform of the other element of the ESD suppressor. FIG. 5C is a differential signal between FIG. 5A and FIG. 5B of the same ESD suppressor. FIG. 6 shows a confirmation signal using an oscilloscope in a circuit configuration using the same ESD suppressor as above. FIG. 7A is an eye diagram when the same ESD suppressor as above is used. FIG. 7B is an eye diagram when no ESD suppressor is used.

The embodiments and modifications described below are merely examples of the present disclosure, and the present disclosure is not limited to the embodiments and modifications. Various modifications other than the embodiments and modifications below are possible according to the design, etc., as long as they do not deviate from the technical ideas of the present disclosure.

In addition, in this embodiment, "same" includes both a perfect match and within the range of manufacturing error (e.g., less than ±10%).

(Embodiment)
The protection device 30 according to this embodiment will be described below with reference to FIGS. 1 to 7B.

(1) Overview Protective devices such as varistors and surge absorbers are used in high-speed interface peripherals and electronic devices such as mobile phones and smartphones as a countermeasure against electrostatic discharge (ESD). Differential signal transmission is used in high speed interface peripherals. Differential signal transmission means transmitting signals using a potential difference between two signal lines.

The protection device 30 according to this embodiment is an ESD suppressor that protects ESD-vulnerable components from ESD. In the following description, the protection device 30 will be described as an ESD suppressor 30.

The ESD suppressor 30 includes a first element 21, a second element 22, and an insulating layer 7, as shown in FIGS. 1 to 3. The first element 21 has a third electrode 3, a fourth electrode 4, and a first cavity 1. Further, the second element 22 includes a fifth electrode 5, a sixth electrode 6, and a second cavity 2. The first cavity 1 and the second cavity 2 are formed in the same insulating layer 7. That is, the insulating layer 7 has the first cavity 1 and the second cavity 2.

As shown in FIG. 2, the ESD suppressor 30 includes a first insulating layer block 14 in which an insulating layer 8, an insulating layer 9, and an insulating layer 10 are laminated, an insulating layer 11, an insulating layer 12, and an insulating layer. 13 and a second insulating layer block 15 stacked thereon.

The first element 21 generates a discharge in the first cavity 1 between the third electrode 3 and the fourth electrode 4 when the potential difference between the third electrode 3 and the fourth electrode 4 reaches a discharge voltage. let The first element 21 causes a discharge to occur in the first cavity 1, bypasses the current caused by ESD to ground (GND), and protects an object to be protected, such as an IC (Integrated Circuit), from ESD.

The second element 22 generates a discharge in the second cavity 2 between the fifth electrode 5 and the sixth electrode 6 when the potential difference between the fifth electrode 5 and the sixth electrode 6 reaches a discharge voltage. let The second element 22 causes a discharge to occur in the second cavity 2, thereby bypassing the current caused by ESD to the ground (GND), thereby protecting the object to be protected, such as an IC (Integrated Circuit), from ESD.

As shown in FIG. 3, the ESD suppressor 30 is connected between the interface (IF) circuit 20 and the common mode choke coil (CMCC) 23. Specifically, one end of the first element 21 is connected to a signal line on the outward path from the IF circuit 20 to a controller area network-transceiver (CAN transceiver) 24. The other end of the first element 21 is grounded. One end of the second element 22 is connected to a signal line on the return path from the CAN transceiver 24 to the IF circuit 20. The other end of the second element 22 is grounded.

A CAN transceiver is a CAN standard transceiver. CAN is a type of serial communication protocol. Microcontrollers and devices can be connected without using a CAN standard host computer.

The common mode choke coil 23 is a filter that reduces common mode noise. The common mode choke coil 23 separates signals and noise depending on the transmission mode. There are two types of transmission modes: differential mode and common mode, and differential mode is used as a general rule for signals. The common mode choke coil 23 is a filter that acts only on the common mode, and reduces common mode noise generated in the common mode without affecting the differential mode, which is a high-speed signal.

Regarding the effects of connecting the ESD suppressor 30 to the circuit as the protection device 30, we conducted signal confirmation using an oscilloscope (see FIG. 6) and signal evaluation using an eye diagram. When checking signals using an oscilloscope, the input signal is divided into signal components and noise components and evaluated to see if they are being output.

In an eye diagram, the signal from the IF circuit 20 and the signal from the CAN transceiver 24 are connected in the circuit shown in Figure 3. These inputs and outputs are sampled and then superimposed on one another to create a graphical display, which is called an eye diagram. With an eye diagram, it is possible to evaluate the opening area inside the eye diagram as well as the period and voltage.

(2) Configuration The ESD suppressor 30 of this embodiment includes two ESD suppressors, a first element 21 and a second element 22, as shown in FIGS. 1 to 3. The first element 21 includes a first cavity 1, a third electrode 3, and a fourth electrode 4. The second element 22 includes a second cavity 2, a fifth electrode 5, and a sixth electrode 6.

As shown in FIG. 2, the ESD suppressor 30 further includes a first insulating layer block 14 formed by stacking insulating layers 8, 9, and 10, and a second insulating layer block 15 formed by stacking insulating layers 11, 12, and 13.

The first insulating layer block 14 and the second insulating layer block 15 isolate the first element 21 and the second element 22 in which ESD discharge occurs from the surroundings, and maintain an electrically insulated state.

The first cavity 1 and the second cavity 2 are cavities formed in the same insulating layer 7. Therefore, the first element 21 and the second element 22 share the same thickness of the insulating layer 7. Further, in the insulating layer 7, the first cavity 1 and the second cavity 2 are provided in different regions.

The first cavity 1 and the second cavity 2 have a structure in which air or an inert gas is sealed. In this embodiment, a structure in which air is sealed will be described.

A pair of first electrodes 40 are provided through the first cavity 1. Specifically, the third electrode 3 of the pair of electrodes 40 is provided on one of the two surfaces (hereinafter, the first surface) that face each other in the thickness direction of the insulating layer 7. More specifically, when the insulating layer 7 is viewed from the thickness direction of the insulating layer 7, a portion of the third electrode 3 overlaps with the first cavity 1, and at least a portion of the remaining portion contacts (overlaps) with the first surface. The remaining portion overlaps with the first cavity 1. The fourth electrode 4 of the pair of electrodes 40 is provided on the other surface (hereinafter, the second surface) of the two surfaces that face each other in the thickness direction of the insulating layer 7. More specifically, when the insulating layer 7 is viewed from the thickness direction of the insulating layer 7, a portion of the fourth electrode 4 overlaps with the first cavity 1, and at least a portion of the remaining portion contacts (overlaps) with the second surface. The remaining portion overlaps with the first cavity 1.

A pair of second electrodes 41 are provided with the second cavity 2 interposed therebetween. Specifically, the fifth electrode 5 of the pair of electrodes 41 is provided on the first surface of the two surfaces facing each other in the thickness direction of the insulating layer 7. More specifically, when looking at the insulating layer 7 from the thickness direction of the insulating layer 7, a part of the fifth electrode 5 overlaps with the second cavity 2, and at least a part of the remaining part overlaps with the first cavity. At least a portion of the remaining portion that is in contact with (overlaps with) the surface of the second cavity 2 overlaps with the second cavity 2 . The sixth electrode 6 of the pair of electrodes 40 is provided on the second surface of the two surfaces facing each other in the thickness direction of the insulating layer 7. More specifically, when looking at the insulating layer 7 from the thickness direction of the insulating layer 7, a part of the sixth electrode 6 overlaps with the second cavity 2, and at least a part of the remaining part overlaps with the second cavity 2. It touches (overlaps) the surface of The remaining portion overlaps with the second cavity 2. Next, the electrodes will be explained. The first element 21 includes a third electrode 3 and a fourth electrode 4. The third electrode 3 and the fourth electrode 4 constitute a pair of first electrodes 40 .

The second element 22 includes a fifth electrode 5 and a sixth electrode 6. The fifth electrode 5 and the sixth electrode 6 form a pair of second electrodes 41.

The pair of first electrodes 40 and the pair of second electrodes 41 have the same shape. That is, the third electrode 3, the fourth electrode 4, the fifth electrode 5, and the sixth electrode 6 have the same shape.

The direction along the longitudinal direction in the shape of the pair of first electrodes 40 and the direction along the longitudinal direction in the shape of the pair of second electrodes are the same direction. That is, the pair of first electrodes 40 and the pair of second electrodes 41 are arranged along the same direction. Further, the third electrode 3, the fourth electrode 4, the fifth electrode 5, and the sixth electrode 6 face the same direction along their respective longitudinal directions.

Since the third electrode 3 and the fourth electrode 4 face each other with the first cavity 1 in between, the distance between the pair of first electrodes 40 is equal to the thickness of the first cavity 1. On the other hand, since the fifth electrode 5 and the sixth electrode 6 face each other with the second cavity 2 in between, the distance between the pair of second electrodes 41 is equal to the thickness of the second cavity 2. Since the first cavity 1 and the second cavity 2 are cavities formed in the insulating layer 7, the first cavity 1 and the second cavity 2 have the same thickness as the insulating layer 7. That is, the distance between the pair of first electrodes 40 and the pair of second electrodes 41 is the same.

The pair of first electrodes 40 has an area where the third electrode 3 and the fourth electrode 4 overlap in the direction in which the first insulating layer block 14 is viewed from the second insulating layer block 15 . That is, the pair of first electrodes 40 have opposing areas (see FIG. 1). Further, regarding the pair of second electrodes 41 as well, the fifth electrode 5 and the sixth electrode 6 have an overlapping area in the direction in which the first insulating layer block 14 is viewed from the second insulating layer block 15 . That is, the pair of second electrodes 41 have opposing areas.

When the dielectric constant is ε, the area of the opposing electrodes is S, the distance between the opposing electrodes is d, and the capacitance of space is C, the capacitance C is generally expressed by the following equation.
C=ε・S/d

Since air is sealed in the first cavity 1 and the second cavity 2, the dielectric constants ε of the first element 21 and the second element 22 can be considered to be the same.

The pair of first electrodes 40 and the pair of second electrodes 41 have overlapping areas in their opposing electrodes, and when these areas are the same, from equation 1, the first element 21 and the second element It can be said that the capacitance is the same as that of 22.

In this embodiment, the first element 21 and the second element 22, which are two protective elements, are used as an ESD suppressor 30 in which the two elements are from the same lot with little variation during manufacturing. .

A method of manufacturing the ESD suppressor 30 of this embodiment will be described. First, in order to form the insulating layers 8 to 10, an insulating sheet is formed. By laminating the insulating sheets, an insulating layer block 14 in which the insulating layers 8 to 10 are laminated is formed.

Next, the third electrode 3 and the fifth electrode 5 are formed on the surface of the insulating layer block 14 by screen printing. In the screen printing method, a screen mask is aligned to the insulating layer block 14. Ink is applied to the mask, and the mask pattern is transferred onto the surface of the insulating layer block 14 using a squeegee. Although the difference in the amount of alignment deviation varies from lot to lot, the difference in the amount of alignment deviation in the same lot is smaller than the difference in the amount of alignment deviation from lot to lot.

Then, the insulating layer 7 is formed by screen printing. Specifically, the third electrode 3 and the fifth electrode 5 are formed on the surface of the insulating layer block 14, and the insulating layer 7 is formed thereon by screen printing. The insulating layer 7 has a first cavity 1 and a second cavity 2. The area in which the first cavity 1 and the second cavity 2 are formed is filled with a material for forming the cavities. In the screen printing method, in order to form the insulating layer 7 by alignment, the amount of misalignment between the first cavity 1 and the third electrode 3 and the amount of misalignment between the second cavity 2 and the fifth electrode 5 are the same for the same lot.

Next, the fourth electrode 4 and the sixth electrode 6 are formed by screen printing. In the screen printing for forming the fourth electrode 4 and the sixth electrode 6, the masks are installed in alignment, so if the lot is the same, the amount of misalignment for forming the fourth electrode 4 and the sixth electrode 6 will be , the amount of misalignment is smaller compared to different lots.

Thereafter, insulating sheets are laminated to cover the insulating layer 7, the fourth electrode 4, and the sixth electrode 6. Specifically, the insulating layers 11 to 13 are stacked to form the insulating layer block 15. Through the above steps, the prototype of the ESD suppressor 30 is completed.

Next, the ESD suppressor 30 is completed by baking the prototype of the ESD suppressor 30 at a high temperature while applying pressure. By baking at a high temperature while applying pressure, there is no material for forming the first cavity 1 and the second cavity 2, and the first cavity 1 and the second cavity 2 are formed.

The first element 21 and the second element 22 of the ESD suppressor 30 formed using the screen printing method include the third electrode 3 and the fifth electrode 5, the first cavity 1 and the second cavity 2, the fourth electrode and the second element 22. The six electrodes 6 are produced in the same lot, and the amount of alignment deviation, direction of deviation, etc. are the same. Further, the insulating layer 7 is common. For these reasons, the difference in capacitance between the first element 21 and the second element 22 is very small, and is even smaller than when they are produced in separate lots.

For this reason, the difference in performance between the first element 21 and the second element 22 produced in the same lot is smaller than when they are produced in different lots. From the above, the ESD suppressor 30 of this embodiment includes the first element 21 and the second element 22 with a small difference in capacitance.

(3) Operation Next, the operation will be explained.

The ESD suppressor 30 is connected between the IF circuit 20 and a CMCC (Common Mode Choke Coil) 23, as shown in FIG. CMCC 23 is connected to CAN transceiver 24.

In a circuit using differential signal transmission, two signal lines are opposite to each other and are sent in opposite directions, and a signal can be extracted by the difference between the two signal lines. It is assumed that the first signal line 25 and the third signal line 27 are the outgoing signal lines, and the second signal line 26 and the fourth signal line 28 are the incoming signal lines.

On the outbound route, the signal is transmitted in the following order: IF 20, first signal line 25, CMCC 23, third signal line 27, and CAN transceiver 24.

On the return trip, the signal is transmitted in the order of CAN transceiver 24, fourth signal line 28, CMCC 23, second signal line 26, and IF 20.

When ESD occurs in the IF 20, the current due to the ESD flows through the first signal line 25 to the first element 21 of the ESD suppressor 30. When the voltage difference between the pair of first electrodes 40 reaches a discharge voltage, a discharge is generated in the first cavity 1 to protect the circuits of the CMCC 23 and the CAN transceiver 24 from ESD.

On the other hand, when a current caused by ESD flows through the second signal line 26, it flows through the second element 22 of the ESD suppressor 30. When the voltage difference between the pair of second electrodes 41 reaches a discharge voltage, a discharge occurs in the second cavity 2, protecting the circuits of the CMCC 23 and the CAN transceiver 24 from ESD.

FIG. 4A shows a graph a showing the correlation between the voltage of the first signal line 25 and time, and FIG. 4B shows a graph b showing the correlation between the voltage of the second signal line 26 and time.

As shown in Figures 4A and 4B, when the capacitance of the first element 21 and the capacitance of the second element 22 of the ESD suppressor 30 are the same, graph a in Figure 4A and graph b in Figure 4B are almost the same. Therefore, as shown in graph c in Figure 4C, the difference between the first signal line 25 and the second signal line 26 is equal to 0, and the effect on the differential signal is suppressed. In other words, by aligning the capacitance of the first element 21 and the second element 22 of the ESD suppressor 30, the effect on the differential signal can be suppressed. Therefore, it is possible to provide a protection device with a small individual capacitance difference and little effect on signal degradation.

A specific signal waveform is shown in FIG. In FIG. 6, a differential mode signal input as a signal component to the circuit shown in FIG. 3 is shown as a graph i, a common mode signal as a noise component is shown as a graph j, and a signal received by the CAN transceiver 24 is shown as a graph k.

When the ESD suppressor 30 is used, although there is a common mode which is a noise component, the amplitude can be kept within a constant level as shown in graph j in FIG. Therefore, by passing through the CMCC 23, the CAN transceiver 24 is able to detect signal components as shown in graph k.

An eye diagram at this time is shown in FIG. 7A. Graph L in FIG. 7A is an eye diagram of a circuit that includes the ESD suppressor 30 shown in FIG. 3, and graph M in FIG. 7B is an eye diagram of a circuit that excludes ESD suppressor 30 from the circuit shown in FIG. Comparing FIGS. 7A and 7B, there is no difference in the period and voltage of the eye diagrams. Therefore, the ESD suppressor 30 does not interfere with the signal and can be applied as the protection device 30.

(4) Advantages A case will be described in which there is a significant difference between the capacitance of the first element 21 and the capacitance of the second element 22 of the ESD suppressor 30.

FIG. 5A shows a graph d showing the correlation between the voltage of the first signal line 25 and time, and FIG. 4B shows a graph e showing the correlation between the voltage of the second signal line 26 and time.

As shown in FIGS. 5A and 5B, if there is a large difference between the capacitance of the first element 21 and the capacitance of the second element 22 of the ESD suppressor 30, the graph d in FIG. 5A and the graph d in FIG. There is a difference in size from graph e. Therefore, the difference between the first signal line 25 and the second signal line 26, for example, as shown in graphs f, g, and h in FIG. This signal component is superimposed on the signal component as a noise component.

Therefore, if there is a significant difference between the capacitance of the first element 21 and the second element 22 of the ESD suppressor 30, the ESD suppressor 30 becomes a factor that generates noise.

Therefore, the protection device 30 of this embodiment has a first cavity 1 and a second cavity 2, and includes a first element 21 and a second element 22. The first element 21 has a pair of first electrodes 40 facing each other with the first cavity 1 in between. The second element 22 has a pair of second electrodes 41 facing each other with the second cavity 2 in between. The first element 21 causes a discharge in the first cavity 1 when the voltage between the first electrodes 40 reaches a discharge voltage. The second element 22 causes a discharge to occur in the second cavity 2 when the voltage between the second electrodes 41 reaches a discharge voltage.

According to this configuration, the differential signal becomes approximately 0, as described above. Therefore, it is possible to provide a protection device with a small difference in individual capacitance and less influence on signal deterioration.

Furthermore, by eliminating the difference in capacitance between the first element 21 and the second element 22 of the ESD suppressor 30, factors that inhibit signal transmission through the first signal line 25, second signal line 26, etc. can be reduced. Can be done.

(5) Modifications Modifications are listed below. The modifications described below can be applied in appropriate combination with the above embodiment.

In the embodiment, the ESD suppressor 30 has a configuration including two elements, the first element 21 and the second element 22, but is not limited to this configuration. For example, the number of elements may be three or more. For example, the number of elements may be three, and two of the three elements may be selectively used. Moreover, the number of elements may be one.

In the embodiment, the first cavity 1 and the second cavity 2 of the ESD suppressor 30 have a configuration in which air is sealed, but the configuration is not limited to this. For example, an inert gas may be enclosed. Alternatively, it may be filled with a dielectric.

In the embodiment, the ESD suppressor 30 is manufactured using a screen printing method, but is not limited to this configuration. For example, it may be manufactured using hoop material. During manufacturing, the electrodes are connected by a hoop material, and since materials are laminated and manufactured in a connected state, the distance between the electrodes and the overlapping area are determined by the thickness of the coating material, etc. Therefore, if there is a difference in the overlapping area in the same lot, all of the lots will be different, so that ESD suppressors 30 with the same performance difference between the first element 21 and the second element 22 are formed.

In the embodiment, the ESD suppressor 30 is manufactured using a screen printing method, but the present invention is not limited to this configuration. The first insulating layer block 14, the second insulating layer block 15, the insulating layer 7, and other necessary members may be bonded together.

In the embodiment, the ESD suppressor is configured to have one first element 21 and one second element 22 for the differential and common, but this configuration is not limited. Multiple ESD suppressors may be connected in series to the common.

In the embodiment, the first element 21 and the second element 22 of the ESD suppressor 30 are provided in different regions of the insulating layer 7, but the present invention is not limited to this configuration. The first element 21 and the second element 22 of the ESD suppressor 30 may be provided in the same region of the insulating layer 7. That is, the first cavity 1 and the second cavity 2 may be connected.

(summary)
As described above, the protection device (30) according to the first aspect has a first cavity (1) and a second cavity (2) in the insulating layer (7), and includes a first element (21) and a second element (22). The first element (21) has a pair of first electrodes (40) facing each other through the first cavity (1). The second element (22) has a pair of second electrodes (41) facing each other through the second cavity (2). The first element (21) generates a discharge in the first cavity (1) when the voltage between the pair of first electrodes (40) reaches a discharge voltage. The second element (22) generates a discharge in the second cavity (2) when the voltage between the pair of second electrodes (41) reaches a discharge voltage.

This configuration makes it possible to provide a protection device with small individual capacitance differences and little impact on signal degradation.

In the protective device (30) according to the second aspect, in the first aspect, the first cavity (1) and the second cavity (2) are formed in the same insulating layer.

According to this configuration, the difference in thickness of the insulating layer (7) between the first element (21) and the second element (22) can be reduced. Therefore, the capacitance difference between the first element (21) and the second element (22) of the ESD suppressor (30) can be reduced.

In the protection device (30) according to the third aspect, in the first or second aspect, the first cavity (1) and the second cavity (2) are provided in different regions in the insulating layer (7). There is.

According to this configuration, the first element (21) and the second element (22) are formed in different regions of the same insulating layer (7). ), it is possible to suppress the possibility of problems occurring in the electrical insulation state between the

In the protection device (30) according to the fourth aspect, in any of the first to third aspects, the direction along the longitudinal direction in the shape of the pair of first electrodes (40) and the pair of second electrodes ( The directions along the longitudinal direction in the shape 41) are the same direction.

According to this configuration, the direction along the longitudinal direction in the shape of the pair of first electrodes (40) and the direction along the longitudinal direction in the shape of the pair of second electrodes (41) are in the same direction. , the difference in capacitance between the first element (21) and the second element (22) can be suppressed.

In the protection device (30) according to the fifth aspect, in any of the first to fourth aspects, the shape of the pair of first electrodes (40) and the shape of the pair of second electrodes (41) are , are identical.

According to this configuration, if the shapes are the same, it is easy to unify the opposing areas, and it is possible to suppress the capacitance difference between the first element (21) and the second element (22) of the ESD suppressor (30). can.

In the protection device (30) according to the sixth aspect, in any of the first to fifth aspects, the distance between the pair of first electrodes (40) and the distance between the pair of second electrodes (41) are , are identical.

According to this configuration, the capacitance difference between the first element (21) and the second element (22) can be suppressed. Since the spacing is inversely proportional to the capacitance, it has the effect of reducing the capacitance difference between the first element (21) and the second element (22) of the ESD suppressor (30).

In the protection device (30) according to the seventh aspect, in any of the first to sixth aspects, the pair of first electrodes (40) and the pair of second electrodes (41) The overlapping area of the first electrodes (40) when viewed from opposing directions is the same as the overlapping area of the pair of second electrodes (41) when viewed from opposing directions.

According to this configuration, since the size of the overlapping area is proportional to the size of the capacitance, by making the overlapping area the same, the capacitance difference between the first element (21) and the second element (22) can be reduced. can be suppressed.

1 First cavity 2 Second cavity 7 Insulating layer 21 First element 22 Second element 30 Protective device

Claims (7)

The insulating layer has a first cavity and a second cavity,
a first element having a pair of first electrodes facing each other via the first cavity;
a second element having a pair of second electrodes facing each other via the second cavity,
The first element causes a discharge in the first cavity when the voltage between the pair of first electrodes reaches a discharge voltage,
The second element causes a discharge in the second cavity when the voltage between the pair of second electrodes reaches a discharge voltage.
Protective device. The first cavity and the second cavity are formed in the same insulating layer,
A protection device according to claim 1. The protection device according to claim 1 or 2, wherein the first cavity and the second cavity are provided in different regions of the insulating layer. The direction along the longitudinal direction in the shape of the pair of first electrodes and the direction along the longitudinal direction in the shape of the pair of second electrodes are the same direction,
The protective device according to any one of claims 1 to 3. The shape of the pair of first electrodes and the shape of the pair of second electrodes are the same,
The protective device according to any one of claims 1 to 4. The interval between the pair of first electrodes and the interval between the pair of second electrodes are the same,
The protective device according to any one of claims 1 to 5. The pair of first electrodes and the pair of second electrodes have an overlapping area when viewed from opposing directions of the pair of first electrodes and an overlapping area when viewed from the opposing direction of the pair of second electrodes. are the same,
The protective device according to any one of claims 1 to 6.

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