JP2738502B2 - Surge absorbing structure, surge absorbing element, and connector and circuit device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for protecting a circuit such as an electronic circuit by absorbing a surge caused by static electricity or the like.

[0002]

2. Description of the Related Art Surge protection of an electronic circuit utilizes a structure by gas discharge, that is, a phenomenon in which a minute discharge gap is provided between a pair of electrodes and conduction is caused by a discharge caused by dielectric breakdown of a gas layer in the discharge gap. Known structures are known.

In general, the discharge voltage in a gas discharge is a function of the product PL of the pressure P of the gas which mediates the discharge and the width L of the discharge gap. Rise accordingly (Paschen's law). In the case of air at 1 atm, the minimum discharge voltage is attained when the distance between both electrodes is 7.5 μm, and the voltage is about 330 V, which is a voltage that can be used for surge protection of general electronic circuits. In other words, it is theoretically possible to achieve surge protection by a structure in which a discharge gap is provided between both electrodes by an air layer having a constant width. However, it is almost impossible to always stably set a very narrow discharge gap of 7.5 μ between both electrodes.

[0004] Therefore, when a gas discharge is used for surge protection, a structure using a discharge tube is conventionally used. This discharge tube has a structure in which a practical discharge voltage can be obtained even in a discharge gap of about several tens of μm by lowering a minimum breakdown voltage by filling a discharge gas as an airtight structure (for example, JP-A-5-268725 and JP-A-5-226060). For this reason, the surge absorbing element having the discharge tube structure has a complicated structure, has no degree of freedom in its shape, has a large size, and has to be a single type. as a result,
It is necessary to use an element for each signal line to be protected, which leads to an increase in the size and complexity of the circuit device and a significant increase in cost. In addition, a relatively large mounting space is required, and in particular, when mounting on a connector in order to provide surge protection at the connector stage, there is a great difficulty in mounting in terms of space.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and provides a surge absorbing structure capable of effectively utilizing gas discharge without relying on a complicated structure such as a conventional discharge tube. It is another object of the present invention to provide a surge absorbing element used for this, and to provide a connector and a circuit device using the same.

[0006]

In the surge absorbing structure according to the present invention, a porous layer formed of a non-conductive material and having a large number of holes is interposed between a pair of electrodes opposed at a predetermined interval. Then, both electrodes are made conductive by gas discharge generated through pores in the porous layer to absorb surge.

FIG. 1 schematically shows this surge absorbing structure. That is, the porous layer 1 includes a pair of electrodes 2a,
2b are formed in contact with each of the holes 2b, wherein the cavities 3 provide individually independent air layers for gas discharge,
Conduction is caused by the discharge in the holes 3. The discharge in the hole 3 is accompanied by a creeping discharge along the wall surface 3w of the hole 3 and the like, so that the discharge voltage is greatly reduced as compared with the case where there is only a discharge gap. In other words, the discharge voltage of the gas discharge in the air can be reduced by interposing the porous layer, and the surge absorption range can be expanded. Also, with this surge absorption structure,
Since the discharge gap can be set by the porous layer whose thickness is easily controlled as described above, the setting can be performed stably with high accuracy.

The porous layer in such a surge absorbing structure can be formed by depositing an SiO ₂ layer on the surface of a metal material for one electrode by, for example, electrolytic deposition, or by PVD such as sputtering or ion plating. A method of growing a thin layer of a non-conductive material on the surface of a metal material for an electrode, using an aluminum material as one electrode, and growing a γ-Al ₂ O ₃ film on the surface of the aluminum material by anodization A method in which particles having a diameter corresponding to the intended thickness of the porous layer are attached to one electrode with an adhesive, and a method in which a sheet having a large number of fine through holes formed by laser processing or the like is used. It can be formed in a wide variety of ways. A porous layer made of these has a large number of through-holes having a diameter of the order of μm, and is generally several to several tens μm.
The thickness is easily controlled.

As described above, the present surge absorbing structure provides conduction by discharging through the pores in the porous layer. Therefore, basically, the pores in the porous layer penetrate between the two electrodes. As shown in FIG. 2, closing the end of the hole 3 to an appropriate depth using the conductive material 4 is substantially the same as penetrating between both electrodes, as shown in FIG. Yes, the above conduction principle in the surge absorbing structure can be similarly used. When a material having high melting resistance, such as carbon, is used as the conductive material filling the ends of the holes, melting of the electrode due to discharge can be suppressed, and more preferable conditions can be obtained.

The filling of the holes with such a conductive material is as follows.
When a porous layer is formed from the above-mentioned film of γ-Al ₂ O ₃ , the porous layer can be formed by using a sealing treatment using high-pressure steam used in a so-called alumite treatment. That, gamma-Al ₂ When the film of O ₃ subjected to the sealing treatment with high-pressure steam, the upper end portion to the _{γ-Al 2 O 3 · H} 2 O in the pores grow from the inner wall surface of the pores inside As a result, it is possible to perform the filling of the pores by a conductive _{γ-Al 2 O 3 · H} 2 O.

The porous layer in the present surge absorbing structure may be formed by using a material having a non-linear resistance characteristic such as SiC in addition to an insulating material in a narrow sense. When such a nonlinear resistance characteristic material is used, the solid part around the hole functions as a primary surge absorption by the nonlinear resistance characteristic, and when the current exceeds the allowable amount and the resistance of the solid part increases, Secondary surge absorption can be performed by the discharge in the holes. That is, the surge protection function can be further improved by a combination of the non-linear resistance characteristic in the solid portion of the porous layer and the discharge in the holes.

The surge absorbing element used in the above-described surge absorbing structure can be formed by attaching a porous layer to one electrode by any of the various methods as described above, and if necessary, further to the other. The electrode may be bonded to another surface of the porous layer. Therefore, especially when a porous layer is attached to one of the electrodes to form a surge absorbing element, for example, a thin metal sheet is used for the electrodes, and the porous layer is formed on the surface, and then cut into a desired size and shape. It is possible to form it. Such a surge absorbing element has a very simple structure and is excellent in workability, as well as a large degree of freedom in shape and size.
For example, it is easy to use such that it protects a plurality of signal lines collectively by forming it into an elongated strip shape, and it is possible to provide great flexibility, so that it is excellent in mountability. Furthermore, a porous layer can be formed on the terminal of the connector, which is one of the electrodes, so that the terminal of the connector itself can be used as an element of the surge absorbing element, making mounting on the connector much easier. Can be

In order to use the surge absorbing structure or the surge absorbing element in a connector, as described above, a porous layer is formed on the terminal itself of the connector so that the terminal itself of the connector becomes an element of the surge absorbing element. In addition, it is of course possible to incorporate a separately formed surge absorbing element, and it is also possible to incorporate the surge absorbing element by forming a porous layer on the ground electrode of the connector as in the case of the terminal. Regarding the formation of the porous layer on the ground electrode, a structure is possible in which a porous layer is formed on both sides of the ground electrode, and a terminal is brought into contact with the porous layer on each side as the other electrode. In this case, two sets of surge absorbing structures are formed in a state where the ground electrode is shared as one of the pair of electrodes.

In order to use the surge absorbing structure or the surge absorbing element in a circuit device such as a printed circuit, a separately formed surge absorbing element may be incorporated as in the case of the connector. Alternatively, a porous layer may be directly attached to the ground electrode and then incorporated. In the latter case, as in the case of the connector, a form in which the ground electrode is shared by two sets of surge absorbing structures can be adopted.

[0015]

Embodiments of the present invention will be described below. The present embodiment is an example in which an aluminum material is used as one electrode, and a SiO ₂ layer is deposited on the surface of the aluminum material by an electrolytic deposition method to form a porous layer. The aluminum material used was a sheet-like material having a thickness of 300 μm.
An O ₂ film was formed with a thickness of 10μ. The resulting surge absorber had a discharge voltage of about 200 V and a voltage clamping speed of about 5 nanoseconds. Further, the surge absorbing element according to the present embodiment has high flexibility, can be easily bent, and has a sufficient resistance to bending of 90 ° or more.

The surge absorbing element 10 shown in FIG. 3 is an example in which the element prepared under the above conditions is used for mounting on a substrate, and a fixing leg 12 is extended from a base electrode 11 serving as one electrode. I have. In order to mount this on the substrate, as shown in FIG. 4, the porous layer 13 is brought into contact with the signal line L of the substrate B serving as the other electrode, and is fixed to the substrate B with the legs 12.

FIG. 5 shows an example of a modular connector 20 incorporating a surge absorbing structure according to the present invention. A porous layer 23 is interposed between a shell member 21 serving as one electrode and a terminal 22 serving as the other electrode. The structure has been made. Such a structure can be provided by partially forming the porous layer 23 integrally with the shell member 21 or by integrally forming the porous layer 23 with the terminal 22. It can also be formed by incorporating a surge absorbing element formed separately from the member 21 and the terminal 22.

[0018]

As described above, according to the surge absorbing structure of the present invention, a porous layer is interposed between a pair of electrodes,
The structure in which gas discharge is generated through a large number of pores in the porous layer can greatly simplify the structure of the surge absorbing element, increase the degree of freedom in the shape and size of the surge absorbing element, and increase the flexibility. It is also possible to give the capability to the surge absorbing element. As a result,
According to the surge absorbing structure and element of the present invention, it is possible to collectively protect a plurality of signal lines, and it is possible to easily attach not only to a board but also to a connector. The range can be expanded.

[Brief description of the drawings]

FIG. 1 is a schematic view of a surge absorbing structure according to the present invention.

FIG. 2 is a schematic view of another example of the surge absorbing structure according to the present invention.

FIG. 3 is a perspective view of a surge absorbing element according to one embodiment of the present invention.

FIG. 4 is a sectional view showing a state where the surge absorbing element of FIG. 3 is mounted on a substrate.

FIG. 5 is a sectional view of a modular connector using a surge absorbing structure according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 porous layer 2a electrode 2b electrode 3 vacancy

Claims (4)

(57) [Claims] A porous layer formed of a non-conductive material and having a large number of pores is interposed between a pair of electrodes opposed to each other at a predetermined interval, and a gas generated through the pores in the porous layer is provided. Surge absorption structure that conducts both electrodes by discharge to absorb surge. 2. The surge absorbing element used in the surge absorbing structure according to claim 1, wherein a porous layer is formed on one of the electrodes. 3. A connector using the surge absorbing structure according to claim 1 or the surge absorbing element according to claim 2. 4. A circuit device using the surge absorbing structure according to claim 1 or the surge absorbing element according to claim 2.