Surge protection element and method for manufacturing the same

Abstract

To provide a surge protection element capable of suppressing a decrease in AC withstand voltage even in a hot and humid environment, and a method for manufacturing the same.SOLUTION: A surge protection element includes a columnar or cylindrical insulating member having a conductive film dividedly formed on its peripheral surface via a discharge gap portion G in the center in the axial direction, a pair of main discharge electrode members arranged opposite to both ends of the insulating member directly or via another conductive member and electrically connected to the conductive film, and an insulating tube in which the pair of main discharge electrode members are arranged at both ends and the insulating member is sealed inside together with discharge control gas, and a plurality of annular grooves 7a and annular ridges 7b extending in the circumferential direction are alternately formed in the axial direction in the discharge gap portion, at least one of a metal and a metal oxide M is formed on the top of the annular ridges, and the width W1 of the top to which the conductive material is attached is smaller than the width W2 of the annular groove.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a surge protection element used to protect various devices from surges generated by lightning strikes or the like and prevent failures and accidents, and a method for manufacturing the same.

Background Art

[0002] In parts where electronic devices for communication devices such as telephones, facsimiles, and modems connect to communication lines, power lines, antennas, or CRT drive circuits, etc., which are susceptible to electric shock due to abnormal voltages (surge voltages) such as lightning surges and static electricity, a surge protection element is connected to prevent destruction of the electronic device or the printed circuit board on which this device is mounted due to thermal damage or ignition caused by the abnormal voltage.

[0003] Conventionally, as a surge protection element with good responsiveness, for example, as shown in Patent Document 1, a surge protection element using a surge absorption element having a so-called micro gap has been proposed. This surge protection element is a surge absorber in which a micro gap is formed on the peripheral surface of a ceramic member, which is a columnar insulating member wrapped with a conductive film, and a pair of cap electrodes are provided at both ends of the ceramic member. The surge absorption element is housed in a glass tube together with a discharge control gas, and sealed electrodes having lead wires are sealed at both ends of the cylindrical glass tube by high-temperature heating.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The following problems remain in the above conventional technology. In the surge protection element described in the above Patent Document 1, as one of the adjustment parameters of the discharge start voltage, 1 to 15 micro gaps with a gap width of several tens of μm are formed, and the gap width is set to 200 to 1000 μm. It is known that when the gap width is wide, it is more stable at a high discharge start voltage exceeding 500 V than when a large number of narrow gap widths (micro gaps) are formed. However, when the gap width becomes wide, there is a disadvantage that the surge life durability (8 / 20 μs current waveform, 100 A test, etc.) becomes weak.

[0006] The present invention has been made in view of the above problems, and an object thereof is to provide a surge protection element and a method for manufacturing the same in which the surge life durability is improved even at a high discharge start voltage.

Means for Solving the Problems

[0007] The present invention employs the following configuration to solve the above problems. That is, the surge protection element of the first invention includes a columnar or tubular insulating member in which a conductive film is divided and formed on the circumferential surface via a discharge gap portion at the central portion in the axial direction, and a pair of main discharge electrode members that are disposed opposite to each other directly or via other conductive members at both ends of the insulating member and are electrically connected to the conductive film, and an insulating tube that seals the insulating member together with the discharge control gas inside with the pair of main discharge electrode members disposed at both ends. In the discharge gap portion, a plurality of annular groove portions and annular ridge portions extending in the circumferential direction are alternately formed in the axial direction, and a conductive material that is at least one of a metal and a metal oxide adheres to the top of the annular ridge portion, and the width of the top to which the conductive material adheres is smaller than the width of the annular groove portion.

[0008] In this surge protection element, a plurality of annular groove portions and annular ridge portions extending in the circumferential direction are alternately formed in the axial direction in the discharge gap portion, and a conductive material that is at least one of a metal and a metal oxide adheres to the top of the annular ridge portion. Since the width of the top to which the conductive material adheres is smaller than the width of the annular groove portion, the conductive material remains on the top of the annular ridge portion, so that the electric field emerges on the surface of the insulating member, and plasma concentrates on the surface of the discharge gap portion, and deterioration is suppressed even at a high discharge start voltage. Also, since the width of the top to which the conductive material adheres is smaller than the width of the annular groove portion, a wider discharge gap portion can be configured as a whole compared to the case where a large number of narrow micro gaps are formed, and stable characteristics can be obtained even at a high discharge start voltage. If the width of the top to which the conductive material adheres is larger than the width of the annular groove portion, it becomes a structure similar to a micro gap where the conductive material adheres widely, and the function as a wide discharge gap portion as a whole cannot be obtained.

[0009] The surge protection element according to the second invention is characterized in that, in the first invention, the metal oxide is SnO2.

[0010] The surge protection element according to the third invention is characterized in that, in the second invention, the width of the discharge gap portion is 200 to 2000 μm, and the discharge gap portion as a whole contains 10 to 60 wt% of Sn. That is, in this surge protection element, since the width of the discharge gap portion is 200 to 2000 μm and the discharge gap portion as a whole contains 10 to 60 wt% of Sn, excellent surge life durability can be obtained. If the content of Sn is less than 10 wt% or exceeds 60 wt%, the above-mentioned surge life durability effect may not be sufficiently obtained.

[0011] The surge protection element according to the fourth invention is characterized in that, in the first or second invention, the conductive material adhering to the top is the metal oxide and the metal adhering to the metal oxide. That is, in this surge protection element, since the conductive material adhering to the top is a metal oxide and a metal adhering to the metal oxide, even if the adhesion of the metal oxide to the top is insufficient, the metal further adheres, so that the electric field in the vicinity further increases, sputtering to the gap portion during surge application is further suppressed, and a decrease in the discharge start voltage due to surge application is reduced.

[0012] The method for manufacturing a surge protection element according to the fifth invention is a method for manufacturing a surge protection element according to any one of the first to fourth inventions, including a film forming step of forming a conductive film, which is at least one of a metal and a metal oxide, on the entire circumferential surface of a columnar or cylindrical insulating member, and a gap forming step of forming a discharge gap portion by removing and dividing at least a part of the conductive film by irradiating the conductive film at the central portion in the axial direction with a laser beam or by performing a slitting process with a dicing blade to divide the conductive film. In the gap forming step, the laser processing or the slitting process is performed in the circumferential direction of the circumferential surface to alternately form a plurality of annular groove portions and annular ridge portions extending in the circumferential direction in the axial direction, and only the top of the annular ridge portion is left with the conductive film as a conductive material, and the width of the top to which the conductive film adheres is made smaller than the width of the annular groove portion.

[0013] That is, in the method for manufacturing a surge protection element, in the gap forming step, the laser processing or the slitting process is performed in the circumferential direction of the circumferential surface to alternately form a plurality of annular groove portions and annular ridge portions extending in the circumferential direction in the axial direction, and only the top of the annular ridge portion is left with the conductive film as a conductive material, and the width of the top to which the conductive film adheres is made smaller than the width of the annular groove portion. Therefore, in the laser processing, the irradiation width, output, etc. of the laser beam are adjusted, and in the slitting process with a dicing blade, the blade shape, cutting width, etc. of the dicing blade are adjusted, so that the amount of the conductive film remaining on the top of the annular ridge portion and the width of the top to which the conductive film adheres can be easily adjusted.

[0014] The manufacturing method of the surge protection element according to the sixth invention is, in the fifth invention, in the film formation step, a metal oxide is formed as the conductive film, and in the gap formation step, after leaving only the metal oxide at the top of the annular ridge portion, the pair of metal caps are engaged with both ends of the insulating member to form an internal element, and a plurality of the internal elements are rubbed against each other by barrel processing to generate metal powder constituting the metal cap and attach the metal powder to the top of the annular ridge portion. That is, in this manufacturing method of the surge protection element, a plurality of internal elements are rubbed against each other by barrel processing to generate metal powder constituting the metal cap and attach the metal powder to the top of the annular ridge portion. Therefore, it is possible to easily attach the metal oxide and the metal to the top of the annular ridge portion.

Effects of the Invention

[0015] According to the present invention, the following effects can be obtained. That is, according to the surge protection element of the present invention, a plurality of annular groove portions and annular ridge portions extending in the circumferential direction are alternately formed in the axial direction in the discharge gap portion, and a conductive material that is at least one of a metal and a metal oxide adheres to the top of the annular ridge portion, and the width of the top to which the conductive material adheres is smaller than the width of the annular groove portion. Therefore, even at a high discharge start voltage, deterioration is suppressed and the surge life durability is improved. Further, according to the manufacturing method of the surge protection element of the present invention, in the gap formation step, laser processing or slitting processing is performed in the circumferential direction of the peripheral surface to alternately form a plurality of annular groove portions and annular ridge portions extending in the circumferential direction in the axial direction, and only the conductive film is left as the conductive material at the top of the annular ridge portion, and the width of the top to which the conductive film adheres is made smaller than the width of the annular groove portion. Therefore, in laser processing, the irradiation width, output, etc. of the laser beam are adjusted, and in slitting processing with a dicing blade, the blade shape, cutting width, etc. of the dicing blade are adjusted, so that the amount of the conductive film remaining at the top of the annular ridge portion and the width of the top to which the conductive film adheres can be easily adjusted.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0017] Hereinafter, a first embodiment of the surge protection element and its manufacturing method according to the present invention will be described with reference to FIGS. 1 and 2. In each of the drawings used in the following description, the scale is appropriately changed in order to make each member recognizable or easily recognizable.

[0018] As shown in FIGS. 1 and 2, the surge protection element 1 of the present embodiment includes a columnar or tubular insulating member 3 having a conductive film 2 divided and formed on the circumferential surface via a discharge gap part G at the central part in the axial direction, and a pair of main discharge electrode members 5 that are disposed opposite to each other at both ends of the insulating member 3 directly or via other conductive members (metal caps 4) and are electrically connected to the conductive film 2, and an insulating tube 6 that seals the insulating member 3 together with a discharge control gas inside with the pair of main discharge electrode members 5 disposed at both ends.

[0019] In the above discharge gap part G, a plurality of annular groove parts 7a and annular ridge parts 7b extending in the circumferential direction are alternately formed in the axial direction. On the top of the above-described annular ridge portion 7b, a conductive material that is at least one of a metal and a metal oxide is adhered. In this embodiment, a metal oxide M is adhered. The width W1 of the top where the metal oxide M is adhered is set smaller than the width W2 of the annular groove portion 7a. The metal oxide M of this embodiment is, for example, SnO2. Note that a metal may be directly adhered as the conductive material to the top of the annular ridge portion 7b.

[0020] The width W0 of the above-described discharge gap portion G is 200 to 2000 μm, and the entire discharge gap portion G contains 10 to 60 wt% of Sn. The analysis of the Sn content shows the weight ratio of Sn in the components contained in a portion up to an approximate depth of 1 μm detected by energy dispersive X-ray spectroscopy (EDS analysis) from the surface of the conductive film 2 formed on the insulating member 3. In a portion where the removal amount of the conductive film 2 by cutting with a laser or the like is small, Sn has a high concentration, and in a portion where the removal amount is large, Sn has a low concentration. In addition to Sn, Al, Si, O, etc. contained in the insulating member 3 are detected. The above-described insulating member 3 is made of a ceramic material such as a mullite sintered body, and SnO2 is formed on the surface as a conductive film 2 by a thin film forming technique such as physical vapor deposition (PVD) method or chemical vapor deposition (CVD) method.

[0021] The above-described discharge gap portion G is formed by irradiating laser light from a YAG laser along the circumferential surface of the insulating member 3 at the center in the axial direction of the conductive film 2 to divide the conductive film 2. Also, the above-described metal oxide M, which is a conductive material remaining in a part of the discharge gap portion G, is the same material (SnO2) as the conductive film 2.

[0022] The pair of metal caps 4 are made of a metal with a lower hardness than the insulating member 3 and can be plastically deformed, for example, a metal such as stainless steel or Cu (copper). Also, the pair of metal caps 4 are respectively engaged with both ends of the insulating member 3, and the surfaces facing each other together with the inner surface of the main discharge electrode member 5 form the main discharge surface. Note that the main discharge electrode member 5 may be directly arranged to face both ends of the insulating member 3 without using the metal caps 4.

[0023] The main discharge electrode member 5 is a sealing electrode formed of a metal in which the surface of an Fe (iron)-Ni (nickel) alloy is coated with copper oxide, and has a disc shape or a column shape. One surface of the main discharge electrode member 5 is in contact with the metal cap 4, and a lead wire 8 is welded to the other surface. This lead wire 8 is formed of a copper-clad steel wire or the like.

[0024] The insulating tube 6 is made of a soft glass such as lead glass or soda-lime glass and has a cylindrical shape. Also, near both ends of the insulating tube 6, the outer peripheral surface of the main discharge electrode member 5 is welded to the inner peripheral surface of the insulating tube 6 via a glass layer 6a for welding. The discharge control gas is a sealing gas whose composition and the like are adjusted so that electrical characteristics such as the discharge start voltage become desired values, and is an inert gas such as He, Ar, Ne, Xe, SF6, CO2, C3F8, C2F6, CF4, H2, N2, and a mixed gas thereof. In this embodiment, Ar, N2, and a mixed gas thereof are adopted as the discharge control gas.

[0025] Next, a method for manufacturing the surge protection element of this embodiment will be described.

[0026] In the manufacturing method of the surge protection element 1 of this embodiment, there are a film forming step of forming a conductive film 2 which is a metal oxide on the entire peripheral surface of a columnar or cylindrical insulating member 3, and a laser process of irradiating the conductive film 2 at the central portion in the axial direction with a laser beam to remove and divide at least a part of the conductive film 2 to form a discharge gap portion G, and a gap forming step of dividing the conductive film 2. In the above-described gap forming step, laser processing is performed in the circumferential direction of the circumferential surface to alternately form a plurality of annular groove portions 7a extending in the circumferential direction and annular ridge portions 7b in the axial direction.

[0027] That is, after first forming one annular groove portion 7a in the circumferential direction of the circumferential surface, by irradiating the laser beam a plurality of times at regular intervals in the axial direction, a convex-curved-surface-shaped annular ridge portion 7b can be formed between adjacent concave-curved-surface-shaped annular groove portions 7a. In addition, in the gap forming step, by adjusting the irradiation width and output of the laser beam, at least one of a metal and a metal oxide, i.e., a conductive coating (metal oxide M in this embodiment), is left as a conductive material only on the top of the annular ridge portion 7b, and the width W1 of the top where the conductive film (metal oxide M) adheres is made smaller than the width W2 of the annular groove portion 7a.

[0028] In the above, the annular groove portion 7a and the annular ridge portion 7b are formed by laser processing. However, a plurality of annular groove portions 7a extending in the circumferential direction and annular ridge portions 7b are alternately formed in the axial direction by cutting with a dicing blade in the circumferential direction of the circumferential surface, and at least one of a metal and a metal oxide, i.e., a conductive material (metal oxide M), is left only on the top of the annular ridge portion 7b, and the width W1 of the top where the conductive film (metal oxide M) adheres may be made smaller than the width W2 of the annular groove portion 7a.

[0029] Next, a pair of metal caps 4 are engaged with both ends of the insulating member 3 in which the discharge gap portion G is thus produced, and further, both ends are sandwiched and held by a pair of main discharge electrode members 5. Next, in an atmosphere of a discharge control gas, these are put into the insulating tube 6 in this state, and after replacing the air in the insulating tube 6 with a predetermined discharge control gas, in the atmosphere of the discharge control gas, the two ends of the insulating tube 6 are heated and melted to be brought into close contact with the main discharge electrode members 5 for sealing, whereby the surge protection element 1 is produced.

[0030] Thus, in the surge protection element 1 of this embodiment, a plurality of annular groove portions 7a and annular ridge portions 7b extending in the circumferential direction are alternately formed in the discharge gap portion G in the axial direction. A conductive material (metal oxide M), which is at least one of a metal and a metal oxide, adheres to the top of the annular ridge portion 7b. Since the width W1 of the top to which the conductive material (metal oxide M) adheres is smaller than the width W2 of the annular groove portion 7a, the conductive material (metal oxide M) remains on the top of the annular ridge portion 7b, so that the electric field exits the surface of the insulating member 3 and plasma concentrates on the surface of the discharge gap portion G. Even with a high discharge start voltage, deterioration is suppressed.

[0031] Further, since the width W1 of the top to which the metal oxide M adheres is smaller than the width W2 of the annular groove portion 7a, a discharge gap portion G that is wide as a whole can be configured as compared with the case where a large number of narrow micro gaps are formed, and stable characteristics can be obtained even with a high discharge start voltage. If the width W1 of the top to which the conductive material (metal oxide M) adheres is larger than the width W2 of the annular groove portion 7a, the structure becomes close to a micro gap in which the conductive material (metal oxide M) adheres widely, and the function as a wide discharge gap portion G as a whole cannot be obtained.

[0032] Further, since the width W of the discharge gap portion G is 200 to 2000 μm and the discharge gap portion G as a whole contains 10 to 60 wt% of Sn, excellent surge life durability can be obtained. In the manufacturing method of the surge protection element 1 of the present embodiment, in the gap forming step, laser processing or slitting is performed in the circumferential direction of the circumferential surface to alternately form a plurality of annular groove portions 7a and annular ridge portions 7b extending in the circumferential direction in the axial direction, and only at the top of the annular ridge portion 7b, a conductive film (metal oxide M), which is at least one of metal and metal oxide, is left as a conductive material. Since the width W1 of the top where the conductive film (metal oxide M) adheres is made smaller than the width W2 of the annular groove portion 7a, in laser processing, the irradiation width, output, etc. of the laser beam are adjusted, and in slitting with a dicing blade, the blade shape, cutting width, etc. of the dicing blade are adjusted, so that the amount of the conductive film (metal oxide M) left at the top of the annular ridge portion 7b and the width W1 of the top where the conductive film (metal oxide M) adheres can be easily adjusted.

[0033] Next, a second embodiment of the surge protection element 1 according to the present invention will be described below with reference to FIG. 3. In the description of the following embodiments, the same components as those described in the above embodiment are denoted by the same reference numerals, and the description thereof is omitted.

[0034] The difference between the second embodiment and the first embodiment is that in the first embodiment, only the metal oxide M adheres to the top of the annular ridge portion 7b, whereas in the surge protection element of the second embodiment, as shown in FIG. 3, not only the metal oxide M but also the metal M2 adheres to the top of the annular ridge portion 7b. That is, in the second embodiment, as the conductive material, the metal oxide M of SnO2 and the metal M2 such as Cu adhere to the top of the annular ridge portion 7b.

[0035] In the manufacturing method of the surge protection element of the second embodiment, first, the metal cap 4 is formed of Cu. Also, in the above gap forming step, the metal oxide M is previously formed as a conductive material on the top. Then, an internal element in which a pair of metal caps 4 are engaged with both ends of the insulating member 3 is produced by the above manufacturing method of the first embodiment. Next, by performing barrel processing in which a plurality of internal elements are rubbed against each other, Cu powder is generated from the Cu metal cap 4, and this Cu powder is adhered as metal M onto the metal oxide M at the top of the annular ridge portion 7b.

[0036] Thus, in the surge protection element of the second embodiment, since the conductive material adhering to the top is the metal oxide M and the metal M2 adhering onto the metal oxide M, even if the adhesion of the metal oxide M to the top is insufficient, the metal M2 further adheres, so that the electric field in the vicinity further rises, sputtering to the gap portion during surge application is further suppressed, and a decrease in the discharge start voltage due to surge application is reduced.

[0037] Also, in the manufacturing method of the surge protection element of the second embodiment, a plurality of internal elements are rubbed against each other by barrel processing to generate metal powder such as Cu that constitutes the metal cap 4 and to adhere the metal powder to the top of the annular ridge portion 7b, so that the metal oxide M and the metal M2 can be easily adhered to the top of the annular ridge portion 7b.

Example

[0038] Next, regarding an example in which the surge protection element of the first main embodiment is manufactured by the above manufacturing method, an SEM image showing the surface of the discharge gap portion G is shown in FIG. 3. As can be seen from this image, the annular groove portion 7a and the annular ridge portion 7b are alternately repeated, and a metal oxide M (the white portion on the top of the annular ridge portion 7b) is adhered to the top of the annular ridge portion 7b. Further, the width W1 of the top of the annular ridge portion 7b to which the metal oxide M is adhered is smaller than the width W2 of the annular groove portion 7a.

[0039] Next, regarding the above example, as a surge life endurance test, the results of measuring the change in resistance value when a surge of 8 / 20 μs, 100 A was applied up to 100 times are shown in FIG. 4. As can be seen from this measurement result, a stable resistance value with little change is obtained for repeated surge application, and the surge life durability is improved.

[0040] Next, regarding the surge protection element of the second embodiment in the examples fabricated by the above manufacturing method, the results of measuring the discharge start voltage Vs when applying surges up to 300 times are shown in Fig. 6(a). As can be seen from this, even when the number of surge applications is 300 times, the discharge start voltage Vs has not decreased. Also, regarding the examples of the surge protection element of the second embodiment, the results of measuring the change rate ΔVs of the discharge start voltage from 0 to 500 times of surge application are shown in Fig. 6(b). As can be seen from this, even when the number of surge applications is 500 times, the change rate ΔVs of the discharge start voltage is small.

[0041] Note that the technical scope of the present invention is not limited to the above embodiments and examples, and various modifications can be made without departing from the spirit of the present invention.

Explanation of Reference Numerals

[0042] 1... Surge protection element, 2... Conductive film, 3... Insulating member, 4... Conductive member (metal cap), 5... Main discharge electrode member, 6... Insulating tube, 7a... Annular groove portion, 7b... Annular ridge portion, G... Discharge gap portion, M... Metal oxide, M2... Metal, W1... Width of the top where the conductive material adheres, W2... Width of the annular groove portion

Claims

1. A columnar or tubular insulating member having a conductive film formed in a divided manner on the circumferential surface via a discharge gap portion at the central portion in the axial direction, A pair of main discharge electrode members that are disposed opposite to each other directly or via another conductive member at both ends of the insulating member and are electrically connected to the conductive film, An insulating tube that has the pair of main discharge electrode members disposed at both ends and seals the insulating member together with the discharge control gas inside, In the discharge gap portion, a plurality of annular groove portions and annular ridge portions extending in the circumferential direction are alternately formed in the axial direction, A conductive material that is at least one of a metal and a metal oxide is adhered to the top of the annular ridge portion, A surge protection element, wherein the width of the top to which the conductive material is adhered is smaller than the width of the annular groove portion.

2. The surge protection element according to claim 1, wherein the metal oxide is SnO ２ is a surge protection element characterized by that.

3. The surge protection element according to claim 2, wherein the width of the discharge gap portion is 200 to 2000 μm, and the entire discharge gap portion contains 10 to 60 wt% of Sn, which is a surge protection element characterized by that.

4. The surge protection element according to claim 1 or 2, wherein the conductive material adhered to the top is the metal oxide and the metal adhered to the metal oxide, which is a surge protection element characterized by that.

5. A method for manufacturing the surge protection element according to any one of claims 1 to 4, A film forming step of forming a conductive film that is at least one of a metal and a metal oxide on the entire circumferential surface of a columnar or tubular insulating member, A discharge gap portion is formed by removing and dividing at least a part of the conductive film by laser processing in which a laser beam is irradiated onto the conductive film in the central portion in the axial direction or by slitting with a dicing blade, and a gap forming step of dividing the conductive film is provided. In the gap forming step, the laser processing or the slitting is performed in the circumferential direction of the circumferential surface to alternately form a plurality of annular groove portions and annular ridge portions extending in the circumferential direction in the axial direction, and only the top portion of the annular ridge portion is left with the conductive film as a conductive material, and the width of the top portion to which the conductive film adheres is made smaller than the width of the annular groove portion. A method for manufacturing a surge protection element, characterized by this.

6. In the method for manufacturing a surge protection element according to claim 5, In the film forming step, a metal oxide is formed as the conductive film. In the gap forming step, after leaving only the metal oxide at the top of the annular ridge portion, the pair of metal caps are engaged with both ends of the insulating member to form an internal element, and a plurality of the internal elements are rubbed against each other by barrel processing to generate metal powder constituting the metal cap and attach the metal powder to the top of the annular ridge portion. A method for manufacturing a surge protection element, characterized by this.

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