JP2594860B2 - Discharge type surge absorbing element with security mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge-type surge absorbing element for preventing electronic equipment from being damaged by absorbing a surge such as an induced lightning applied to a telephone line or the like. The present invention relates to a discharge type surge absorbing element with a security mechanism that can be flattened and can reliably shut off continuous overcurrent.

[0002]

2. Description of the Related Art Conventionally, as a surge absorbing element for protecting an electronic circuit of an electronic device from a surge such as an induced lightning, a varistor composed of a high-resistance element having a voltage non-linear characteristic,
An arrester or the like in which a discharge gap is accommodated in an airtight container is widely used.

Although the varistor has excellent surge absorption responsiveness, it has a relatively small current withstand capacity per unit area, and thus it is difficult to efficiently absorb a large surge current. Further, the arrester can increase the current withstand capability by generating an arc discharge in the discharge gap. However, it takes a long time from the application of a surge to the arc discharge, and there is a problem in its responsiveness.

Therefore, as shown in FIGS. 3 and 4, a conductive thin film b is applied to the surface of a substantially cylindrical insulator a, and then the conductive thin film b has a width of about 0.1 mm. The conductive thin film b is divided by forming a small discharge gap c in a circular shape, and the discharge electrodes e, e are fitted to both ends of the insulator a with a main discharge gap d therebetween to form the conductive thin films b, b. And the discharge electrode e,
and a surge absorbing element h in which the external terminals g and g are connected to each other and sealed in an airtight container f together with a discharge gas.

When a surge is applied to the surge absorbing element h, first, the conductive layers b, b separated by a minute discharge gap c
A potential difference is generated between them, whereby electrons are emitted to the minute discharge gap c and a creeping discharge occurs. Next, a transition is made to a glow discharge due to the priming effect of electrons generated by the creeping discharge. Then, the glow discharge is transferred to the main discharge gap d due to an increase in the surge current, and shifts to an arc discharge as the main discharge to absorb the surge.

[0006]

As described above, since the surge absorbing element h utilizes the creeping discharge originally having a high response speed generated in the minute discharge gap c as the trigger discharge, the surge absorbing element h is smaller than the arrester. Since high responsiveness can be realized and surge is absorbed by arc discharge as a main discharge generated in the main discharge gap d, a large current withstand capability can be realized as compared with the varistor.

However, in the conventional surge absorbing element h, as shown in FIG. 3, since the hermetic container f has a bulky and substantially cylindrical shape, a considerable space is required when mounting inside various electronic devices. This is contrary to recent demands for downsizing of electronic devices.

Further, when an overvoltage equal to or higher than the rated voltage of the surge absorbing element h is continuously applied by an overvoltage test based on safety accidents such as UL and CSA in consideration of a contact accident with a power line or such a situation. In the state, the conduction of the overcurrent by the main discharge generated in the main discharge gap d is in a continuous state. Then, the heat generated by the continuous energization of the overcurrent melts the hermetic container f and burns the circuit board in which the surge absorbing element h is incorporated. As a result, the passing criteria for the overvoltage test cannot be satisfied. Of course, there was a risk of causing a fire under actual use conditions.

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and has a compact outer shape, and prevents a burnout accident by interrupting the continuous energization of overcurrent, thereby preventing various safety standards. An object of the present invention is to realize a discharge-type surge absorbing element with a security mechanism conforming to the above.

[0010]

In order to achieve the above object, a discharge type surge absorbing element with a security mechanism according to the present invention comprises:
An insulating substrate, a lid member that hermetically covers the surface of the insulating substrate, and forms a discharge space filled with a discharge gas between the surface and the lid member, facing the surface of the insulating substrate with a minute discharge gap therebetween. A pair of trigger discharge electrode films to be formed and a pair of main discharge electrodes which are formed so as to face the surface of the insulating substrate with a main discharge gap therebetween and are electrically connected to the trigger discharge electrode film. The trigger discharge electrode film has an initial resistance value in a range of 0.1 Ω to 5 Ω, and has a resistance temperature coefficient of 2500 pp.
m / ° C. to 4000 ppm / ° C., and legs were protruded from opposite sides of the back surface of the insulating substrate.

The expression "continuous" in the above "continuous overcurrent" means "continuous for a certain period of time". Of course, the alternating current whose current value changes with the passage of time. The same applies to the following.

[0012]

The trigger discharge electrode film opposing the micro discharge gap and the main discharge electrode film opposing the main discharge gap are formed on the surface of the insulating substrate. The shape of the type surge absorbing element is entirely flattened, and it is easy to reduce the size.

The above-mentioned discharge type surge absorbing element with a security mechanism,
It is connected in parallel to the electronic circuit between lines constituting a communication line or the like leading to the electronic circuit of the electronic device. And
When a surge such as induced lightning is momentarily applied to the above line,
First, a potential difference is generated between the trigger discharge electrode films across the minute discharge gap, whereby electrons are emitted into the minute discharge gap and creeping discharge occurs. Then, the creeping discharge shifts to a glow discharge due to a priming effect of electrons generated by the discharge. The glow discharge is transferred to the main discharge gap due to an increase in surge current, and further shifts to arc discharge to absorb the surge.

Further, if an overvoltage exceeding the rated voltage of the discharge type surge absorbing element with a security mechanism is continuously applied by an overvoltage test assuming a contact accident with a power line or such a situation, The discharge continues in the minute discharge gap and the main discharge gap, and a continuous overcurrent flows through the discharge. The trigger discharge electrode film generates heat due to the continuous overcurrent application, and the heat value triggers a rapid increase in the resistance value, and the amount of generated heat also increases synergistically. Crack due to strain. As a result, air flows into the discharge gas in the discharge space,
Since the discharge disappears and the overcurrent is cut off, it is possible to prevent the discharge type surge absorbing element with a security mechanism from melting and burning a circuit board incorporating the same.

The temperature coefficient of resistance of the trigger discharge electrode film is as follows:
Based on the allowable initial resistance value (resistance value under normal conditions before the trigger discharge electrode film generates heat due to continuous overcurrent application), the expected overcurrent current value, or the likelihood of the insulating substrate cracking. Then, it is specifically determined through experiments. For example, if the initial resistance value of the trigger discharge electrode film can be set to a relatively high value, a sufficient amount of heat can be obtained from the beginning without setting the temperature coefficient of resistance so high. May fracture. However, this type of surge absorbing element is connected in parallel to an electronic circuit to be protected, as described later. The voltage will be applied to the electronic circuit side. Therefore, there is a demand that the initial resistance value be as small as possible.

Therefore, in the above-mentioned discharge type surge absorbing element with a security mechanism, the initial resistance value of the trigger discharge electrode film is set to a low range of 0.1 Ω to 5 Ω, and the temperature coefficient of resistance is 2500 ppm / ° C. to 4000 ppm /. By setting the temperature to a very high range of ° C, a low resistance value can be maintained for the application of a normal instantaneous surge, and the resistance value suddenly increases when an overcurrent flows continuously. To break the insulating substrate. Incidentally, the resistance temperature coefficient of a general resistor is 200 ppm /
Since the temperature is as low as about ° C, the resistance value hardly changes even if heat is generated. Therefore, when the trigger discharge electrode film is formed by this, the initial resistance value is 5Ω to 10Ω.
It is necessary to set in the high range of 0Ω.

In addition, since the legs protrude from the opposite side end surfaces on the back surface of the insulating substrate, when the element is mounted on a circuit board or the like, the center portion of the insulating substrate floats by the legs. Supported in state. Therefore, not only is the crushing of the insulating substrate extremely easy, but also the crushed portion is depressed downward and the current path is completely cut off, so that the overcurrent can be reliably cut off.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. As shown in FIG. 1 and FIG. 2 which is a cross-sectional view taken along line AA of FIG. 1, the discharge type surge absorbing element 2 with a security mechanism according to the present embodiment is a And a pair of trigger discharge electrode films 12 formed on the surface 6 with a minute discharge gap 10 having a width of 10 to 100 μm. , 12 and a pair of main discharge electrode films 16, 16 formed on the surface 6 with a main discharge gap 14 having a width of 0.2 to 10 mm.

The trigger discharge electrode films 12, 12 are formed of a ruthenium-based paste or the like, and have a thickness of 10 mm.
It is set to about 25 μm. This trigger discharge electrode film 1
The resistance temperature coefficient and the initial resistance value of 2,12 can be appropriately changed by mixing a predetermined amount of a predetermined noble metal material into the ruthenium-based paste. In this case, the resistance temperature coefficient is 2500 ppm / ° C to 4000 ppm. /
° C, and the initial resistance value is set to 0.1 to 5Ω. The main discharge electrode films 16, 16 are made of Mo, La.
It is formed of a conductive material having a sputter resistance, such as B ₆ , MoSi ₂ , or TiO ₂ . The trigger discharge electrode films 12, 12 and the main discharge electrode films 16, 16 are electrically connected to each other.

At the tips of the trigger discharge electrode films 12, 12, sputter-resistant conductive protective films 18, 18 made of Mo, LaB ₆ , MoSi ₂ , TiO ₂ or the like are formed. And the trigger discharge electrode film 1
Insulation deterioration of the minute discharge gap 10 due to the sputtering of 2, 12 is prevented, and the life characteristics are improved. Further, the surfaces of the trigger discharge electrode films 12 are coated with insulating films 20 made of non-crystallized glass or the like in order to prevent creeping discharge at the exposed portions.

The left and right edges of the back surface 22 of the insulating substrate 4 protrude in a direction substantially perpendicular to the back surface 22 and extend in a direction substantially perpendicular to the direction in which the trigger discharge electrode films 12 and 12 are energized. The legs 24 are formed integrally with the insulating substrate 4.

From the surface 6 of the insulating substrate 4 to the legs 24, 2
4, a pair of external terminal thin films 28, 28 made of Ag, Pd, Ni, or the like are formed on the side surfaces 26, 26. , 16 are electrically connected.

The lid member 8 is made of an insulating material such as glass or ceramic.
It has a height of about mm. The side surface 30 and the insulating substrate 4
The surface 6 of the insulating substrate 4 and the cover member 8 are fixed to each other with a sealing material 32 made of low melting point glass or the like.
A hermetic discharge space 34 having a height corresponding to the height of the side surface 30 is formed between the discharge spaces 34. The discharge space 34
A discharge gas mainly containing a rare gas such as He, Ne, Ar, Xe or the like or a mixture thereof is sealed therein. In addition,
Instead of using the cover member 8 having the side surface 30 as described above, a flat cover member may be used, and a spacer or the like may be arranged between the cover member 8 and the insulating substrate 4 to form the discharge space 34.

When a surge is instantaneously applied from the outside via the external terminal thin films 28 in a state where the discharge type surge absorbing element 2 with a security mechanism having the above configuration is mounted on a printed circuit board or the like of an electronic device. First, a potential difference is generated between the trigger discharge electrode films 12 and 12 separated by the minute discharge gap 10, whereby electrons are emitted to the minute discharge gap 10 and creeping discharge occurs. Then, the creeping discharge shifts to a glow discharge due to a priming effect of electrons generated by the discharge. Then, the glow discharge is transferred to the main discharge gap 14 due to an increase in surge current, and further shifts to arc discharge to absorb the surge.

When an overvoltage equal to or higher than the rated voltage of the discharge type surge absorbing element 2 with a security mechanism is continuously applied by an overvoltage test assuming a contact accident with the power line or such a situation, the minute discharge is prevented. Gap 10 and main discharge gap 14
, The discharge continues, and a continuous overcurrent flows through the discharge. The trigger discharge electrode films 12, 12 generate heat due to the continuous overcurrent application, and the heat generation triggers a rapid rise in the resistance value and a synergistic increase in the heat generation. The substrate 4 is broken by thermal strain. As a result, air flows into the discharge gas in the discharge space 34, the discharge disappears, and the overcurrent is cut off.

As described above, the back surface 2 of the insulating substrate 4
2, the legs 24, 24 are formed. Therefore, when the insulating substrate 4 is mounted on a circuit board or the like, the back surface 22 of the insulating substrate 4 does not come into close contact with the surface of the circuit board. Since the vicinity of the center of the substrate 4 is supported in a state of being floated from the circuit board, the insulating substrate 4 is easily broken. Also,
Since the crushed portion is depressed downward, the current path is cut off, and the overcurrent can be more reliably cut off.

[0027]

As described above, the discharge type surge absorbing element with a security mechanism according to the present invention comprises an insulating substrate, a cover member for covering the insulating substrate, and a trigger discharge formed on the surface of the insulating substrate. Since the structure is made up of the electrode film and the main discharge electrode film, the outer shape can be flattened. as a result,
The use of the discharge type surge absorbing element with a security mechanism can be expanded, for example, it can be accommodated in a small device having a small space for accommodating parts, and the use value thereof can be increased.

Further, the initial resistance value of the trigger discharge electrode film is set in a low range of 0.1 Ω to 5 Ω, and the temperature coefficient of resistance is 2500 ppm / ° C. to 4000 p.
By setting it to a very high range of pm / ° C, a low resistance value can be maintained for the application of a normal momentary surge, and a discharge type with a safety mechanism is provided by a contact accident with a power line or various overvoltage tests. When an overvoltage exceeding the rated voltage of the surge absorbing element is continuously applied, if an overcurrent due to the overvoltage continuously flows, its resistance value rises sharply to break the insulating substrate. Can be. As a result, air flows into the discharge gas in the discharge space, which causes the discharge to disappear and interrupts the overcurrent, so that the melting of the discharge type surge absorbing element with a security mechanism and the Burnout and the like can be prevented.

Further, the leg portions are formed so as to protrude from the opposite side edges on the back surface of the insulating substrate.
When the discharge type surge absorbing element with a security mechanism according to the present invention is mounted on a circuit board or the like, the legs can support the center portion of the insulating substrate in a floating state, so that the insulating substrate is extremely easily crushed. Become. Further, since the crushed portion is depressed downward and the current path is completely cut off, the overcurrent can be reliably cut off.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an embodiment of a discharge type surge absorbing element with a security mechanism according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a schematic perspective view of a conventional surge absorbing element.

FIG. 4 is a schematic sectional view of a conventional surge absorbing element.

[Explanation of symbols]

 2 Discharge type surge absorbing element with security mechanism 4 Insulating substrate 6 Surface of insulating substrate 8 Lid member 10 Micro discharge gap 12 Trigger discharge electrode film 14 Main discharge gap 16 Main discharge electrode film 22 Back surface of insulating substrate 24 Leg 34 Discharge space

Claims (1)

(57) [Claims] 1. An insulating substrate, a lid member which hermetically covers a surface of the insulating substrate and forms a discharge space filled with a discharge gas between the insulating substrate and a minute discharge gap on the surface of the insulating substrate. A pair of trigger discharge electrode films that are formed so as to face each other with a gap therebetween, and are formed so as to face the surface of the insulating substrate with a main discharge gap therebetween and are electrically connected to the trigger discharge electrode film. And a pair of main discharge electrode films, wherein the initial resistance value of the trigger discharge electrode film is in a range of 0.1 Ω to 5 Ω.
And the temperature coefficient of resistance of the trigger discharge electrode film.
In the range of 2500 ppm / ° C to 4000 ppm / ° C.
And the opposite sides of the insulating substrate
Discharge type surge absorbing element with a security mechanism, characterized in that legs are protruded from both end faces .