JPH0594861A - Discharge type surge absorption element - Google Patents

Abstract

PURPOSE:To enhance anti-surge responsiveness, and make a device small in size by making up the device of an insulating board, cover member covering the insulating board, a trigger discharge electrode film which is bonded so as to be formed over the surface of the insulating board, and of a main discharge electrode film. CONSTITUTION:A discharge type surge absorption element 2 is packaged onto a circuit board, and when surge higher in voltage than clamp voltage for a voltage non-linear resistor forming a trigger discharge electrode film 12 is applied from the outside via an external terminal thin film 26, a resistance value is abruptly lowered, so that high amperage current flows instantly. Electrons are emitted to a minute discharge gap 10, so that surface discharge as trigger discharge is induced. And the surface discharge is then transformed into glow discharge by means of a priming effect of electrons. And the glow discharge is instantly shifted to a main discharge gap 14, and it is shifted to arc discharge, that is, main discharge, so that surge is absorbed. In this case, anti-surge responsiveness is enhanced because surge is absorbed by the electrode film 12, that is, a voltage non-linear resistor itself excellent in responsiveness.

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 which absorbs a surge such as inductive lightning applied to a telephone line or the like to prevent damage to electronic equipment, and more particularly, to flatten the element. In addition, the present invention relates to a discharge type surge absorbing element in which a trigger discharge electrode film is composed of a voltage non-linear resistor.

[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 induced lightning, a varistor made of a high resistance element having a voltage non-linear characteristic,
An arrester or the like in which the discharge gap is housed in an airtight container is widely used.

Although the above-mentioned varistor is excellent in response to surge absorption, it has a relatively small current withstanding capacity per unit area, and therefore it is difficult to efficiently absorb a large surge current. Further, although the above-mentioned arrester can increase the current withstanding capacity by generating the main discharge in the discharge gap, it takes a long time from the application of the surge to the main discharge, and there is a problem in its responsiveness.

Therefore, as shown in FIGS. 4 and 5, a conductive thin film b is deposited on the surface of a substantially cylindrical insulator a, and the conductive thin film b has a width of about 0.1 mm. The conductive thin film b is divided by forming a minute 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 discharge electrode e,
There is proposed a surge absorbing element h which is connected to e and is enclosed with an electric discharge gas in an airtight container f to derive external terminals g, g.

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

[0006]

As described above, since the surge absorbing element h uses the creeping discharge which originally has a high response speed in the minute discharge gap c as the trigger discharge, it is more than the arrester. A high responsiveness can be realized and a surge can be absorbed by an arc discharge which is a main discharge generated in the main discharge gap d, so that a large current withstanding capacity can be realized as compared with the varistor.

However, in the conventional surge absorbing element h, as shown in FIG. 3, since the airtight container f has a substantially cylindrical shape which is bulky, a considerable space is required for mounting inside various electronic devices. Must be ensured, which is contrary to the recent demand for miniaturization of electronic devices.

Further, since the conductive thin films b, b facing each other with the minute discharge gap c therebetween are made of ordinary resistors, the following drawbacks occur. That is, since a current proportional to the voltage value starts to flow at the same time as the voltage is applied, it is difficult to stably set the voltage value that transitions to the main discharge gap, and when an overvoltage such as a surge is sharply applied. However, the main discharge may start only when the rated voltage of the surge absorbing element h is far exceeded. Moreover, since the surge is not absorbed until the main discharge is started, there is a risk that the surge is applied to the electronic circuit side during that time and the electronic circuit is damaged.

Further, in the case where an overvoltage exceeding the rated voltage of the surge absorbing element h is continuously applied by a contact accident with a power line or an overvoltage test based on safety standards such as UL and CSA assuming such a situation. Is the main discharge gap d
The energization of the overcurrent due to the main discharge that occurs in 1) is maintained.
Then, the airtight container f is melted by the heat generated by the continuous energization of the overcurrent, and the circuit board in which the surge absorbing element h is incorporated is burnt out, and as a result, the pass standard of the overvoltage test cannot be satisfied. Not to mention, there is also a risk of fire in actual use.

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and it is possible to achieve a compact outer diameter shape, a stable transfer characteristic to the main discharge gap, and an improvement in surge response. Furthermore, it is an object of the present invention to prevent burnout accidents by interrupting continuous energization of overcurrent and to realize a discharge type surge absorbing element that meets various safety standards.

[0011]

In order to achieve the above object, a discharge type surge absorbing element according to the present invention includes an insulating substrate and a surface of the insulating substrate which is hermetically covered with a discharge gas. And a pair of trigger discharge electrode films formed on the surface of the insulating substrate so as to face each other with a minute discharge gap, and a main discharge gap on the surface of the insulating substrate. Are formed so as to face each other with
It has a pair of main discharge electrode films electrically connected to the trigger discharge electrode film, and the trigger discharge electrode film is formed by a voltage non-linear resistor. When a voltage less than a preset predetermined voltage value is applied, the voltage non-linear resistor does not pass a current because its resistance value is very high. At the time of application, the resistance value suddenly decreases and a large current is passed at once. The above-mentioned predetermined voltage value (voltage value at which a current starts to flow) is called a clamp voltage. The clamp voltage is set within the range of 10V to 1000V, for example. Moreover, as the voltage nonlinear resistor, for example, ZnO, SiC, TiO ₂ , Fe ₂ O ₃ or the like is used.

It is desirable that, when an overcurrent continuously flows through the trigger discharge electrode film, the insulating substrate is shattered due to heat generation of the trigger discharge electrode film due to passing of the overcurrent. Specifically, the thickness, the material, etc. of the insulating substrate are appropriately selected in consideration of the resistance value and the current amount at the time of discharging the voltage non-linear resistor forming the trigger discharge electrode film (that is, the insulating substrate). It is realized by adjusting the easiness of breaking. The expression "when the overcurrent flows continuously" means "when the overcurrent flows for a certain period of time".
The "overcurrent" that continuously flows naturally includes not only direct current but also alternating current whose current value changes with the passage of time. The same applies to the following.

[0013]

Since the trigger discharge electrode films facing each other across the minute discharge gap and the main discharge electrode films facing each other across the main discharge gap are deposited on the surface of the insulating substrate, discharge type surge absorption is achieved. The shape of the element is flattened as a whole, which facilitates miniaturization.

When a surge higher than the clamp voltage of the voltage non-linear resistor constituting the trigger discharge electrode film is applied to the discharge type surge absorbing element through the external terminal connected to the main discharge electrode film, The resistance value of the voltage non-linear resistor sharply decreases, and a current flows through the trigger discharge electrode film. As a result, electrons are emitted into the minute discharge gap and a creeping discharge as a trigger discharge occurs. Then, this creeping discharge shifts to glow discharge by the priming effect of electrons.
Then, this glow discharge is transferred to the main discharge gap and transferred to arc discharge which is the main discharge to absorb the surge. on the other hand,
When a voltage lower than the clamp voltage is applied, the resistance value of the voltage non-linear resistor remains high, so that no current flows in the trigger discharge electrode film, and therefore creeping discharge does not occur.

As described above, when the applied voltage value is less than the clamp voltage, no current flows through the trigger discharge electrode film, but a large current flows at once when the clamp voltage is reached, so that the main discharge gap is surely achieved. , And the main discharge is started. Since the variation of this clamp voltage is extremely small,
By appropriately adjusting the clamp voltage of the voltage non-linear resistor, the voltage value transferred to the main discharge gap (hereinafter referred to as "main discharge start voltage") can be stably set. In addition,
Since the voltage nonlinear resistor itself also has a surge absorbing effect,
Even before the main discharge is started, the surge is absorbed by the voltage non-linear resistor that forms the trigger discharge electrode film and is excellent in surge response.

When an overvoltage exceeding the rated voltage of the discharge type surge absorbing element is continuously applied by an accident of contact with a power line or an overvoltage test assuming such a situation, the above-mentioned minute discharge gap and main Discharge continues in the discharge gap,
A continuous overcurrent flows through this discharge.
The continuous discharge of overcurrent causes the trigger discharge electrode film to generate heat, and the insulating substrate is fractured due to thermal strain.
As a result, air flows into the discharge gas in the discharge space, the discharge disappears, and the energization of the overcurrent is cut off, so that the above-mentioned discharge type surge absorbing element can be prevented from burning.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on the illustrated embodiments. As shown in FIGS. 1 and 2 which is a cross-sectional view taken along the line AA of FIG. 1, the discharge type surge absorbing element 2 according to the present embodiment includes an insulating substrate 4 made of ceramic or the like having a thickness of 0.4 to 1.0 mm.
A lid member 8 for covering the surface 6 of the insulating substrate 4, and a minute discharge gap 10 having a width of 10 to 100 μm on the surface 6 of the insulating substrate 4.
A pair of trigger discharge electrode films 12 and 12 deposited and formed by separating
And a pair of main discharge electrode films 16, 16 formed on the surface 6 of the insulating substrate 4 with a main discharge gap 14 having a width of 0.2 to 10 mm.
And have.

The trigger discharge electrode films 12, 12 are made of ZnO,
It is formed of a voltage nonlinear resistor such as SiC, TiO ₂ , Fe ₂ O ₃ . In addition, the main discharge electrode films 16 and 16 are M
o, LaB ₆ , MoSi ₂ , TiO ₂ or the like, which is formed of a conductive material having spatter resistance. The trigger discharge electrode films 12 and 12 and the main discharge electrode films 16 and 16 are electrically connected to each other.

At the tips of the trigger discharge electrode films 12, 12, a conductive protective film 18, which is formed of Mo, LaB ₆ , MoSi ₂ , TiO ₂ or the like and has spatter resistance, is formed.
18 is formed to prevent insulation deterioration of the minute discharge gap 10 due to sputtering of the trigger discharge electrode films 12 and 12 and to improve life characteristics. Furthermore, the trigger discharge electrode films 12, 12
The surface of the is covered with insulating films 20, 20 made of non-crystallized glass or the like in order to prevent creeping discharge in the exposed portion.

From the surface 6 of the insulating substrate 4 to the left and right side surfaces 2
A pair of external terminal thin films 26, 26 made of Ag / Pd, Ni, or the like is adhered and formed on the second and second surfaces 22, and further on the back surface 24. The external terminal thin films 26, 26 are formed on the main discharge electrode film 16 described above. ， 16
Electrically connected to.

The lid member 8 is made of an insulating material such as glass or ceramic, and each side surface 28 of the lid member 8 is 3 to 10 mm.
It has a certain height. By fixing the side surface 28 and the surface 6 of the insulating substrate 4 with the sealing material 30 made of low melting point glass or the like, the height of the side surface 28 is increased between the surface 6 of the insulating substrate 4 and the lid member 8. An airtight discharge space 32 having a corresponding height is formed. In the discharge space 32, He,
A discharge gas mainly containing a simple substance or a mixture of rare gases such as Ne, Ar, and Xe is filled. It should be noted that instead of using the lid member 8 having the side surface 28 as described above, a flat plate-shaped lid member may be used, and a spacer or the like may be arranged between the insulating substrate 4 and the lid member 8 to form the discharge space 32. Good.

The above-mentioned discharge type surge absorbing element 2 has a structure in which an overcurrent continuously flows through the trigger discharge electrode films 12, 12.
The insulating substrate 4 is ruptured by thermal strain due to heat generation of the trigger discharge electrode films 12, 12 due to the application of the overcurrent. Specifically, the thickness, material, etc. of the insulating substrate 4 are set in consideration of the resistance value at the time of discharging the voltage non-linear resistor forming the trigger discharge electrode films 12, 12 and the heat generation amount based on the amount of current. It is realized by appropriately selecting (that is, adjusting the fragility of the insulating substrate).

Thus, with the discharge type surge absorbing element 2 having the above structure mounted on a printed circuit board or the like of an electronic device, the trigger discharge electrode films 12 and 12 are formed from the outside through the external terminal thin films 26 and 26. When a surge that is equal to or higher than the clamp voltage of the voltage nonlinear resistor is applied, the resistance value of the voltage nonlinear resistor rapidly decreases, and a large current flows through the trigger discharge electrode films 12, 12 all at once. As a result, electrons are emitted into the minute discharge gap 10 to generate a creeping discharge as a trigger discharge, and this creeping discharge is converted into a glow discharge by the priming effect of electrons. Then, this glow discharge immediately transfers to the main discharge gap 14 and shifts to arc discharge which is the main discharge to absorb the surge. Even before the main discharge starts, the voltage non-linear resistor itself, which forms the trigger discharge electrode films 12 and 12 and has excellent responsiveness, absorbs the surge, so the responsiveness to surge is improved. To do.

The discharge type surge absorbing element 2 is tested by an accident with contact with a power line or an overvoltage test assuming such a situation.
When an overvoltage higher than the rated voltage of is continuously applied, the discharge continues in the minute discharge gap 10 and the main discharge gap 14,
A continuous overcurrent flows through this discharge.
In the case of such a short-circuited state, the trigger discharge electrode films 12 and 12 generate heat by continuous energization of overcurrent, and the insulating substrate 4 is shattered by thermal strain. As a result, the discharge space
Air flows into the discharge gas in 32 to extinguish the discharge and shut off the overcurrent.

Although not shown, the insulating substrate 4 is not shown.
By forming a notch or a groove in the groove, the crushing can be facilitated. Alternatively, the back surface 22 of the insulating substrate 4
When the discharge type surge absorbing element 2 is mounted on a circuit board or the like by providing leg portions projecting at opposite side edges of the insulating substrate 4, the leg portions support the central portion of the back surface 22 of the insulating substrate 4 in a floating state. It can also be configured to. In this case, not only the crushing of the insulating substrate 4 is facilitated, but also the crushed portion is depressed downward, so that the current-carrying path is cut off and the overcurrent can be more surely cut off.

[0026]

As described above, the discharge type surge absorbing element according to the present invention has an insulating substrate, a cover member for covering the surface of the insulating substrate, and a trigger discharge electrode adhered to the surface of the insulating substrate. Since it is composed of the film and the main discharge electrode film, the outer shape can be flattened. As a result, the discharge-type surge absorbing element can be used in a wide range of applications, such as being able to be housed in a small device with a small space for housing parts, and its utility value can be increased.

Since the trigger discharge electrode film is composed of the voltage nonlinear resistor, the starting voltage of the main discharge can be defined by the clamp voltage of the voltage nonlinear resistor. That is, when a surge equal to or higher than the clamp voltage is applied, the main discharge is immediately started to reliably start the main discharge, so that the start voltage of the main discharge can be stably set based on the clamp voltage. Further, the voltage non-linear resistor itself, which is excellent in responsiveness, absorbs the surge even before the main discharge starts, so that the responsiveness to surge is improved.

Since the insulating substrate is crushed by the heat generation of the trigger discharge electrode film due to the continuous application of overcurrent, a contact accident with the power line or various overvoltage tests can prevent the voltage from exceeding the rated voltage of the discharge type surge absorbing element. When the overvoltage is continuously applied, the trigger discharge electrode film generates heat due to the overcurrent caused by the overvoltage, and the insulating substrate is shattered. As a result, air flows into the discharge gas in the discharge space, whereby the discharge disappears and the overcurrent is shut off, so that the discharge type surge absorbing element can be prevented from being extinguished.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing one embodiment of a discharge type surge absorber 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 absorber 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 32 Discharge space

Claims (2)

[Claims] 1. 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 insulating substrate and a small discharge gap on the surface of the insulating substrate. A pair of trigger discharge electrode films formed so as to face each other with a space therebetween, and a pair of trigger discharge electrode films formed so as to face the surface of the insulating substrate so as to face each other with a main discharge gap therebetween, and electrically connected to the trigger discharge electrode film. A discharge type surge absorbing element comprising a pair of main discharge electrode films, wherein the trigger discharge electrode film is formed by a voltage non-linear resistor. 2. The insulating substrate is configured to be ruptured due to heat generation of the trigger discharge electrode film due to energization of the overcurrent when a continuous overcurrent flows through the trigger discharge electrode film. The discharge type surge absorbing element according to claim 1.