JP2013182755A - Electrostatic protective element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance durability of an electrostatic protective element by increasing the number of repeatedly dischargeable times thereof.SOLUTION: An electrostatic protective element 1 includes a substrate 2 having an insulating surface 2a, a pair of discharge electrodes 3a, 3b disposed on the insulating surface 2a so as to face each other while spaced apart from each other, a functional layer 4 provided at least between the pair of discharge electrodes 3a, 3b, and a pair of terminal electrodes 5a, 5b connected electrically with the pair of discharge electrodes 3a, 3b. The pair of terminal electrodes 5a, 5b are thick film electrodes formed by plating, and the width Wof the discharge electrodes 3a, 3b in a region overlapping the terminal electrodes 5a, 5b is wider than the width Wat the tip where the pair of discharge electrodes 3a, 3b are adjacent to each other.

Description

  The present invention relates to an electrostatic protection element, and more particularly to an electrode structure of the electrostatic protection element.

  In recent years, standards such as USB and HDMI are widely used as high-speed signal transmission interfaces, and are used in many digital devices such as personal computers and digital high-definition televisions. Unlike the single-ended transmission method that has been common for a long time, these interfaces employ a differential signal method that transmits a differential signal (differential mode signal) using a pair of signal lines.

  The differential transmission system has an excellent feature that not only the radiation electromagnetic field generated from the signal line is small compared to the single-end transmission system, but also it is less susceptible to external noise. For this reason, it is easy to reduce the amplitude of the signal, and by shortening the rise time and the fall time due to the small amplitude, it becomes possible to perform signal transmission at a higher speed than the single-ended transmission method.

  On the other hand, since these high-speed digital interfaces handle minute signals with high transfer rates, ICs that are very sensitive to static electricity are used, and static electricity becomes a big problem. In particular, ESD (Electro-Static Discharge) resistance is increasingly decreasing due to the reduction in capacitance associated with IC miniaturization, so the IC can be removed from electrostatic pulses generated by contact with a charged human body or insertion / extraction of a cable. Protecting is an important technical issue. Furthermore, the latest standards such as USB3.0 and HDMI1.4 define ultra-small connectors that are intended for use in mobile phones, and in the future, countermeasures against static electricity will be required for small devices equipped with these interfaces. Yes.

  In order to prevent IC destruction due to static electricity, a method of inserting a varistor as a static electricity countermeasure component between a signal line and a ground is known. However, when a varistor is used, the signal waveform becomes dull and the signal quality deteriorates, so there is a demand for a lower-capacity antistatic component.

  Patent Document 1 proposes an electrostatic protection element that includes a pair of electrodes that are opposed to each other and spaced apart from each other on an insulating surface of a substrate, and a functional layer that is disposed between the electrodes. The functional layer is a composite in which a conductive inorganic material is discontinuously dispersed in a matrix of an insulating inorganic material, and initial discharge is ensured between the discharge electrodes via the functional layer when an overvoltage is applied. Further, since the electrostatic protection element has a multi-stage structure in which the gap between the pair of electrodes becomes narrower toward the base, discharge between the base-side (lower) electrodes is promoted, and the upper stage Heat generated during discharge is diffused with high efficiency by the electrodes. Therefore, the electrode can be prevented from being damaged by discharge, and the durability of the element, that is, the number of times that repeated discharge can be performed can be increased.

JP 2010-147229 A

  However, the conventional electrostatic protection element is required to increase the number of times that it can be repeatedly discharged and to further improve the durability. There is also a need for an electrostatic protection element that is very small and easy to manufacture.

  In order to solve the above-described problems, an electrostatic protection element according to the present invention includes a base having an insulating surface, a pair of discharge electrodes disposed opposite to each other on the insulating surface, and at least the pair of discharge electrodes. And a pair of terminal electrodes provided on the pair of discharge electrodes and electrically connected to the discharge electrodes, the pair of terminal electrodes being formed by plating. The discharge electrode is a thick film electrode, and a width of the discharge electrode in a region overlapping with the terminal electrode is wider than a width of a tip portion where the pair of discharge electrodes are close to each other.

  According to the present invention, the terminal electrode having a large volume is provided on the discharge electrode, and the contact area between the discharge electrode and the terminal electrode is ensured widely, so that the heat dissipation can be improved. Durability can be improved. In addition, since only the width of the region connected to the terminal electrode is set wide and the width of the tip of the discharge electrode is relatively narrow, the electrostatic discharge occurs when the tip of the discharge electrode approaches the side surface (outer peripheral surface) of the chip. It is possible to prevent the breakdown from affecting the outside of the element.

  The electrostatic protection element according to the present invention further includes a protective layer provided between the pair of terminal electrodes and covering the functional layer, and each of the pair of terminal electrodes has an electrode surface exposed on an outer surface of the protective layer. It is preferable to have. According to this configuration, heat generated by electrostatic breakdown can be quickly radiated to the mounting surface side of the element.

  In this invention, it is preferable that the end surface of the said front-end | tip part of each of a pair of said discharge electrode is a taper surface which descends toward the said insulating surface.

  In the present invention, it is preferable that the width of the pair of discharge electrodes changes stepwise. In this case, the width of the pair of discharge electrodes may change in two steps or may change in three steps. Note that the width of the pair of discharge electrodes may change linearly.

  In the present invention, each of the pair of terminal electrodes preferably has a multilayer structure, and the distance between the upper layer portions of the terminal electrode is preferably wider than the distance between the lower layer portions. According to this configuration, the distance between the pair of terminal electrodes exposed on the surface of the element is separated to some extent, while ensuring a sufficient volume of the entire terminal electrode to improve the heat dissipation of the discharge electrode, thereby enabling repeated discharges. Can be improved.

  In the present invention, the pair of discharge electrodes preferably have a multistage structure in which a gap width between the discharge electrodes becomes narrower toward the substrate. Since electrostatic absorption accompanies destruction of the discharge electrode, the repeated discharge will eventually make the discharge electrode unusable and the electrostatic absorption function will be lost. However, according to the present invention, since the end faces of the pair of discharge electrodes facing each other through the gap have a multi-stage structure, the deterioration of the electrostatic absorption performance in the lower discharge electrode (main electrode layer) is reduced. It can be reinforced by (auxiliary electrode layer). Therefore, durability due to repeated use can be enhanced.

  In the present invention, the pair of discharge electrodes has a multilayer structure, the electrode width of the lower layer of the pair of discharge electrodes is equal, the electrode width of the upper layer of the pair of discharge electrodes is equal, and the lower layer It is preferable that the electrode width is wider.

  In the present invention, the pair of discharge electrodes has a multilayer structure, the electrode width of the lower layer of the pair of discharge electrodes changes stepwise, the electrode width of the upper layer of the pair of discharge electrodes is equal, It is also preferable that the width of the lower electrode is wider.

  In the present invention, the pair of discharge electrodes has a multilayer structure, the electrode width of the lower layer of the pair of discharge electrodes changes stepwise, and the electrode width of the upper layer of the pair of discharge electrodes is stepped with the electrode width of the lower layer. It is also preferred that the width of each step varies and that the width of each step is wider than the width of the corresponding step in the lower layer.

  In this invention, it is preferable that the corner part of the said front-end | tip part of a pair of said discharge electrode is round shape. According to this configuration, it is possible to prevent static electricity absorption from being repeated at a specific location due to electric field concentration, and to extend the lifetime of the element.

  The electrostatic protection element according to the present invention preferably further includes a protective film made of a resin material provided on the outer surface of the protective layer and at least in a region overlapping with the gap in plan view. According to this configuration, the weather resistance can be enhanced, and the functional layer can be reliably protected from moisture and mechanical damage that cannot be protected by the protective layer.

  In the present invention, the functional layer is preferably a composite in which a conductive inorganic material is discontinuously dispersed in a matrix of an insulating inorganic material.

In the present invention, the insulating inorganic material includes Al ₂ O ₃ , TiO ₂ , SiO ₂ , ZnO, In ₂ O ₃ , NiO, CoO, SnO ₂ , V ₂ O ₅ , CuO, MgO, ZrO ₂ , AlN, It is preferably at least one selected from the group consisting of BN and SiC. The conductive inorganic material is preferably at least one metal selected from the group consisting of C, Ni, Cu, Au, Ti, Cr, Ag, Pd, and Pt, or a metal compound thereof.

  According to another aspect of the present invention, an electrostatic protection element is provided between a base having an insulating surface, a pair of discharge electrodes spaced apart from each other on the insulating surface, and at least between the pair of discharge electrodes. And a pair of terminal electrodes provided on the pair of discharge electrodes and electrically connected to the discharge electrodes, wherein the pair of terminal electrodes is a thick film electrode formed by plating. The gap width between the pair of terminal electrodes is wider than the gap width between the pair of discharge electrodes, the terminal electrodes have a multi-stage structure, and the distance between the upper terminal electrodes is between the lower terminal electrodes. It is characterized by being wider than the distance.

  According to still another aspect of the present invention, there is provided an electrostatic protection element comprising: a base having an insulating surface; a pair of discharge electrodes disposed opposite to each other on the insulating surface; and at least between the pair of discharge electrodes. And a pair of terminal electrodes provided on the pair of discharge electrodes and electrically connected to the pair of discharge electrodes, wherein the pair of terminal electrodes is a thick film formed by plating. It is an electrode, The planar shape of the corner part of the front-end | tip part which a pair of said discharge electrode adjoins mutually is round shape, It is characterized by the above-mentioned.

  According to still another aspect of the present invention, there is provided an electrostatic protection element comprising: a base having an insulating surface; a pair of discharge electrodes disposed opposite to each other on the insulating surface; and at least between the pair of discharge electrodes. And a pair of terminal electrodes provided on the pair of discharge electrodes and electrically connected to the pair of discharge electrodes, wherein the pair of terminal electrodes is a thick film formed by plating. It is an electrode, The end surface of the front-end | tip part which a pair of said discharge electrode adjoins mutually is a taper surface which descends toward the said insulating surface, It is characterized by the above-mentioned, It is characterized by the above-mentioned.

  According to still another aspect of the present invention, there is provided an electrostatic protection element comprising: a base having an insulating surface; a pair of discharge electrodes disposed opposite to each other on the insulating surface; and at least between the pair of discharge electrodes. A functional layer provided; a pair of terminal electrodes provided on the pair of discharge electrodes and electrically connected to the pair of discharge electrodes; and an outer surface of the protective layer, at least in the gap and in plan view And a protective film made of a resin material provided in the overlapping region, and the pair of terminal electrodes are thick film electrodes formed by plating.

  According to the present invention, the number of times that the electrostatic protection element can be repeatedly discharged can be increased, and the durability of the element can be improved. In addition, according to the present invention, a very small and high-performance electrostatic protection element can be realized.

FIG. 1 is a schematic side view showing the configuration of the electrostatic protection element according to the first embodiment of the present invention. FIG. 2 is a schematic plan view of the electrostatic protection element shown in FIG. FIG. 3 is a schematic plan view showing the structure of the functional layer 4. FIG. 4 is a flowchart for explaining a method of manufacturing the electrostatic protection element. FIG. 5 is a schematic side view showing the configuration of the electrostatic protection element according to the second embodiment of the present invention. 6 is a schematic plan view of the electrostatic protection element shown in FIG. FIG. 7 is a schematic side view showing the configuration of the electrostatic protection element according to the third embodiment of the present invention. FIG. 8 is a schematic plan view of the electrostatic protection element shown in FIG. 9A to 9C are schematic plan views showing variations of the discharge electrode having the multistage structure shown in FIG. FIG. 10 is a schematic plan view showing another variation of the discharge electrode having the multistage structure shown in FIG. FIG. 11 is a schematic plan view showing a modification of the planar shape of the terminal electrodes 3a and 3b.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic side view showing the configuration of the electrostatic protection element according to the first embodiment of the present invention. FIG. 2 is a schematic plan view of the electrostatic protection element shown in FIG.

  As shown in FIGS. 1 and 2, the electrostatic protection element 1 is disposed between a base 2, a pair of discharge electrodes 3a and 3b disposed on the base 2, and a pair of discharge electrodes 3a and 3b. Functional layer 4, a pair of terminal electrodes 5a, 5b electrically connected to the pair of discharge electrodes 3a, 3b, a protective layer 6 covering the upper area of the functional layer 4 and its peripheral region, and the functional layer 4 And a protective film 7 formed on the upper surface of the protective layer 6. In this electrostatic protection element 1, the functional layer 4 functions as a low-voltage discharge type electrostatic protection material, and is designed so as to ensure initial discharge between the discharge electrodes 3a and 3b when an overvoltage such as static electricity is applied. Has been.

  The base 2 has an insulating surface 2a. Here, the base body 2 having the insulating surface 2a is a concept including a substrate made of an insulating material and an insulating film formed on a part or the entire surface of the substrate. In addition, as long as the base | substrate 2 can support at least discharge electrode 3a, 3b and the functional layer 4, the dimension shape will not be restrict | limited especially, For example, 0.3 * 0.6 * 0.2 (mm) can do. Such a small element can be preferably used for a very small device corresponding to the latest interface.

  Specific examples of the substrate 2 include a ceramic substrate and a single crystal substrate using a low dielectric constant material having a dielectric constant of 50 or less, preferably 20 or less, such as NiZn ferrite, alumina, silica, magnesia, and aluminum nitride. It is done. Moreover, you may use what formed the insulating film on the surface of various well-known board | substrates. As the insulating film, a low dielectric constant material having a dielectric constant of 50 or less, preferably 20 or less, such as NiZn ferrite, alumina, silica, magnesia, or aluminum nitride can be used. The insulating film not only provides the insulating surface of the base 2 but also absorbs irregularities on the surface of the base 2 and plays a role of ensuring the flatness of the lower ground of the discharge electrodes 3a and 3b. Note that a method for forming the insulating film is not particularly limited, and a known method such as a vacuum deposition method, a reactive deposition method, a sputtering method, an ion plating method, a vapor phase method such as CVD or PVD can be applied. Moreover, the film thickness of a board | substrate and an insulating film can be set suitably.

  A pair of discharge electrodes 3 a and 3 b are disposed on the insulating surface 2 a of the base 2 so as to be separated from each other. In the present embodiment, the pair of discharge electrodes 3a and 3b are single-layer thin film electrodes, and are disposed to face each other at a substantially central position in the plane of the substrate 2 with a gap having a predetermined width.

  Examples of the material constituting the discharge electrodes 3a and 3b include at least one kind of metal selected from Ni, Cr, Al, Pd, Ti, Cu, Ag, Au, Pt, and the like, or alloys thereof. However, it is not particularly limited to these.

  The thickness of the discharge electrodes 3a and 3b is preferably set within a range of 0.1 to 2 μm from the viewpoint of not damaging the formation of the functional layer 4 described later, and is equal to the gap width ΔG between the discharge electrodes 3a and 3b. The following is particularly preferable. This is because if the discharge electrodes 3a and 3b are too thick, the flatness and continuity of the functional layer 4 are deteriorated and the electrostatic absorption performance is lowered.

As shown in FIG. 2, each of the discharge electrodes 3a and 3b has a convex pattern, and the tip portions of the discharge electrodes 3a and 3b face each other through a gap. Discharge electrodes 3a, 3b is the width W ₁ of the pair of tip adjacent to each other are relatively narrow, the width W ₂ of the toward the rear end from the central portion is wider than the width W ₁ of the distal end portion. Here, the “front end portion” means a portion closer to the counterpart discharge electrode, and the “rear end portion” means a portion farther from the counterpart discharge electrode.

By such a shape, the terminal electrodes 5a, the discharge electrode 3a in 5b with overlapping regions (terminal electrode formation region), the width _{W 2} of 3b, the discharge electrodes 3a, than the width _{W 1} of the distal end portion 3b are close to each other Become wider. In other words, the length of the parallel sides facing each other through the gap is relatively short, and the length of the side located on the opposite side is relatively long. To the width _{W 0} of the substrate 2, it is preferable that the width _{W 1} of the distal portion is 0.5W ₀ ~0.6W _0, the width W2 of the rear end portion is 0.7W ₀ ~0.9W ₀ Is preferred. Further, the distance from the tip to the terminal electrodes 5a (or 5b) of the discharge electrodes 3a (or 3b) (or the length of the discharge electrodes 3a, 3b of the tip having a width _{W 1)} that ΔL is 20~250μm Is preferred.

Thus, when the discharge electrodes 3a and 3b are formed in a convex pattern and the width on the back side is wider than the facing surface, the contact with the terminal electrodes 5a and 5b provided on the back side of the discharge electrodes 3a and 3b, respectively. Since the area can be increased, the heat dissipation of the discharge electrodes 3a and 3b can be enhanced. The discharge electrodes 3a, 3b, only the width of the region connected terminal electrodes 5a, 5b and is wide, the width W ₁ of the distal portion facing each other is relatively small, the discharge electrodes 3a, 3b of the distal portion Can be prevented from being too close to the side surface (outer peripheral surface) of the element, and electrostatic breakdown affecting the outside of the element.

  The gap width ΔG between the discharge electrodes 3a and 3b is preferably set within a range of 0.5 to 10 μm, more preferably 0.5 to 8 μm. Within this range, low-voltage initial discharge can be secured, and short-circuiting between the discharge electrodes can be suppressed while maintaining ease of processing during gap formation. Here, “gap width ΔG” means the shortest distance between the discharge electrodes 3a and 3b. However, since the opposite sides of the tip are parallel to each other, the gap width ΔG is substantially constant over the entire width of the tip.

In this embodiment, a pair of discharge electrodes 3a, the planar shape of the corner portion R ₁ of the tip portion of 3b is rounded. Curvature of the corner portion _{R 1} radius is preferably 2 to 10 [mu] m. According to this shape, it is possible to prevent static electricity absorption from being repeated at the corners at the tips of the discharge electrodes 3a and 3b due to electric field concentration, and the life of the element can be extended. In the present invention, a corner other than the tip may be rounded.

  In the present embodiment, the cross-sectional shape of the end surface of the distal end portion of the discharge electrodes 3a and 3b is tapered. As will be described in detail later, when the end surfaces of the tip portions of the discharge electrodes 3a and 3b are tapered downward with respect to the base surface (insulating surface 2a), the islands of the conductive inorganic material included in the functional layer 4 are used. Since the pattern is not affected by the step due to the end face of the discharge electrode, it is possible to form the island pattern that is neatly dispersed and enhance the electrostatic absorption effect.

  The functional layer 4 is disposed between the pair of discharge electrodes 3a and 3b. In the present embodiment, the functional layer 4 is laminated on the insulating surface 2a of the substrate 2 and the discharge electrodes 3a and 3b. The planar shape, dimensions, and arrangement of the functional layer 4 are not particularly limited as long as the functional layer 4 is designed to ensure initial discharge between the discharge electrodes 3a and 3b through itself when an overvoltage is applied. Details of the functional layer 4 will be described later.

  The pair of terminal electrodes 5a and 5b are thick film electrodes (bump electrodes) formed by plating on the surfaces of the discharge electrodes 3a and 3b, respectively. The thicknesses of the terminal electrodes 5a and 5b are not particularly limited, but are preferably set within a range of 10 to 45 μm. The planar shapes of the terminal electrodes 5a and 5b are rectangular as shown by broken lines in FIG.

  Each of the pair of terminal electrodes 5a and 5b has an electrode surface that penetrates the protective layer 6 and is exposed on the outer surface thereof. Therefore, the electrostatic protection element 1 is surface-mounted with the upper surface in FIG. 1 facing downward.

  For example, when the terminal electrodes 5a and 5b are U-shaped thin film electrodes formed continuously over the bottom surface, side surface, and top surface of the chip, there are problems in connection failure and increase in contact resistance. However, when the volume of the terminal electrode is large as in this embodiment and the LGA (Land Grid Array) is used, there is no such problem, and the continuity of the electric flow can be improved. The energy at the time of electrostatic absorption is converted into heat. By using an electrode member that absorbs this heat as a mounting terminal, heat that causes destruction of the discharge electrodes 3a and 3b can be quickly released to the mounting surface side. it can.

  The protective layer 6 is provided so as to fill a gap between the pair of terminal electrodes 5 a and 5 b and covers the functional layer 4. The material of the protective layer 6 is not particularly limited, but is preferably an inorganic insulating material such as alumina, and is particularly preferably the same material as the inorganic insulating material of the functional layer 4.

  A protective film 7 made of a resin material is provided on the outer surface of the protective layer 6. The protective film 7 is provided in a region overlapping the functional layer 4 in plan view. According to this configuration, the weather resistance of the device can be further improved, and the functional layer can be reliably protected from moisture and mechanical damage that cannot be protected by the protective layer 6.

  Plating films 8a and 8b are formed on the surfaces of the terminal electrodes 5a and 5b, respectively. The plating films 8a and 8b are, for example, two layers of plating films formed by sequentially depositing Ni and Au. The plating films 8a and 8b can improve the solder wettability of the terminal electrodes 5a and 5b, and can improve the reliability of electrical and mechanical connection. Further, the terminal electrode surface can be made higher than the surface of the protective layer 6 and further the surface of the protective film 7.

  FIG. 3 is a schematic plan view showing the structure of the functional layer 4.

  As shown in FIG. 3, the functional layer 4 is composed of a composite with a sea-island structure in which aggregates of island-shaped conductive inorganic materials 4b are discontinuously scattered in a matrix of insulating inorganic materials 4a. In this embodiment, the functional layer 4 is formed by performing sequential sputtering. More specifically, after the conductive inorganic material 4b is sputtered and partially (incompletely) formed on the surface of the base insulating film and / or the discharge electrodes 3a and 3b, the insulating inorganic material 4a is continuously formed. By so-called sputtering, a so-called composite of a laminated structure of the layers of the conductive inorganic material 4b scattered in islands and the layer of the insulating inorganic material 4a covering the islands is formed.

Specific examples of the insulating inorganic material 4a constituting the matrix include, but are not particularly limited to, metal oxides and metal nitrides. In consideration of insulation and cost, Al ₂ O ₃ , TiO ₂ , SiO ₂ , ZnO, In ₂ O ₃ , NiO, CoO, SnO ₂ , V ₂ O ₅ , CuO, MgO, ZrO ₂ , AlN, BN and SiC is preferred. These may be used alone or in combination of two or more. Among these, it is more preferable to use Al ₂ O ₃ , SiO ₂ or the like from the viewpoint of imparting a high degree of insulation to the insulating matrix. On the other hand, from the viewpoint of imparting semiconductivity to the insulating matrix, it is more preferable to use TiO ₂ or ZnO. By imparting semiconductivity to the insulating matrix, an electrostatic protection element that starts discharging from a lower voltage can be obtained. The method for imparting semiconductor properties to the insulating matrix is not particularly limited. For example, these TiO ₂ and ZnO may be used alone, or these may be used in combination with other insulating inorganic materials 4a. In particular, TiO ₂ tends to lose oxygen during sputtering in an argon atmosphere and tends to have high electrical conductivity. Therefore, it is particularly preferable to use TiO ₂ to impart semiconductivity to the insulating matrix. .

  Specific examples of the conductive inorganic material 4b include, but are not particularly limited to, metals, alloys, metal oxides, metal nitrides, metal carbides, metal borides, and the like. In consideration of conductivity, C, Ni, Cu, Au, Ti, Cr, Ag, Pd and Pt, or an alloy thereof is preferable.

A preferable combination of the insulating inorganic material 4a and the conductive inorganic material 4b is not particularly limited, and examples thereof include a combination of Au and Al ₂ O _3, a combination of Cu and SiO ₂ , and a combination of Au and SiO _2. It is done. The electrostatic protection element composed of these materials not only has excellent electrical characteristics, but also easily and accurately forms a sea-island structure composite in which aggregates of island-shaped conductive inorganic materials 4b are scattered discontinuously. This is extremely advantageous in terms of workability and cost.

  The total thickness of the functional layer 4 is not particularly limited and can be set as appropriate. However, the thickness of the functional layer 4 can be further reduced, and the electronic device using the electrostatic protection element 1 can be further reduced in size and From the viewpoint of realizing high performance, the thickness is preferably 10 nm to 10 μm, more preferably 15 nm to 1 μm, and even more preferably 15 to 500 nm. Moreover, an extremely thin composite made of an inorganic material and having a thickness of 10 nm to 1 μm can be formed by applying a known thin film forming method such as a sputtering method or a vapor deposition method. And economic efficiency is improved. When the so-called so-called island-like conductive inorganic material 4b layer and the insulating inorganic material 4a matrix layer are formed as in this embodiment, the thickness of the conductive inorganic material 4b layer is formed. Is preferably 1 to 10 nm, and the thickness of the layer of the insulating inorganic material 4 a is preferably 10 nm to 10 μm, more preferably 10 nm to 1 μm, and still more preferably 10 to 500 nm.

  The method for forming the functional layer 4 is not limited to the sputtering method described above. By applying a known thin film forming method on the insulating surface 2a and / or on the discharge electrodes 3a and 3b of the substrate 2, the above-described insulating inorganic material 4a and conductive inorganic material 4b are applied, thereby providing a functional layer. 4 can be formed. That is, the electrostatic protection element 1 is different from the organic-inorganic composite film formed by the above-described conventional printing method, insulative inorganic material 4a and conductive inorganic material 4b to which layer formation by sputtering method, vapor deposition method or the like can be applied. And the composite layer is adopted as the functional layer 4 and has a special advantage. Note that the electrostatic protection element 1 of the present embodiment is such that the functional layer 4 becomes a discharge electrode as a result of a part of the discharge electrodes 3a and 3b being scattered into the functional layer 4 by applying a voltage between the discharge electrodes 3a and 3b. The structure including the material which comprises 3a and 3b may be sufficient.

  In the electrostatic protection element 1 of the present embodiment, the functional layer 4 including the island-shaped conductive inorganic material 4b scattered discontinuously in the matrix of the insulating inorganic material 4a is used as a low-voltage discharge type electrostatic protection material. Function. Specifically, when a voltage due to static electricity is applied between the pair of discharge electrodes 3a and 3b, the island-shaped conductive inorganic material 4b is scattered discontinuously in the matrix of the insulating inorganic material 4a. Discharge occurs at an arbitrary path, that is, a point where energy concentration is large between the discharge electrodes 3a and 3b, and electrostatic discharge energy is absorbed. When a high voltage discharge is performed, a part of the electrode and the functional layer after the discharge may be destroyed, but a large number of current paths are formed by the island-shaped conductive inorganic material 4b scattered in a discontinuous manner. Therefore, it is possible to absorb static electricity multiple times.

  Moreover, in the present embodiment, a composite composed of at least an insulating inorganic material 4a and a conductive inorganic material 4b is employed as the functional layer 4 that functions as a low voltage discharge type electrostatic protection material. Therefore, the electrostatic protection element 1 has a small capacitance, a low discharge start voltage, and particularly excellent heat resistance and weather resistance as compared with the conventional organic-inorganic composite film. . Furthermore, since the functional layer 4 is formed by the sputtering method, it is excellent in productivity and economy.

  In particular, the electrostatic protection element 1 of the present embodiment has the terminal electrodes 5a and 5b, the discharge between the discharge electrodes 3a and 3b is promoted, and is generated at the time of discharge due to the large heat capacity of the terminal electrodes 5a and 5b. Heat diffusion is facilitated, and durability during repeated use is enhanced.

  In the electrostatic protection element 1 of the first embodiment, a composite in which the conductive inorganic material 4b is discontinuously dispersed in the matrix of the insulating inorganic material 4a is used as the functional layer 4. 4. Adopting a composite in which metal particles such as Ag, Cu, Ni, Al, Fe or conductive metal compounds are dispersed as an example in a highly insulating resin such as silicone resin or epoxy resin You can also

  FIG. 4 is a flowchart for explaining a method of manufacturing the electrostatic protection element.

  The manufacturing method of the electrostatic protection element 1 according to the present embodiment is characterized in that the discharge electrodes 3a and 3b are formed by a so-called thin film method, and the terminal electrodes 5a and 5b are formed by a so-called thick film method. Here, the thin film method is a method of forming a very thin conductor pattern with a thickness of about 0.1 to 10 μm by sputtering or the like, and the thick film method is a comparison with a thickness of about 2 to 100 μm by electrolytic plating or the like. This is a method of forming a thick conductive pattern.

As shown in FIG. 4, in the manufacture of the electrostatic protection element 1, first, the base 2 is prepared (step S11), and a pair of discharge electrodes 3a and 3b are formed on the insulating surface 2a (step S12). For example, the base 2 is formed by forming an insulating film such as Al ₂ O _{3 on} the surface of nonmagnetic NiZn ferrite. A method for forming the insulating film is not particularly limited, and a known method such as a vacuum deposition method, a reactive deposition method, a sputtering method, an ion plating method, a vapor phase method such as CVD or PVD can be applied. Further, the thickness of the insulating film can be set as appropriate.

  The discharge electrodes 3a and 3b can be formed by forming an electrode material such as Cu on the entire base surface by sputtering and patterning the material. Since the gap width ΔG between the pair of discharge electrodes 3a and 3b is as very small as about 0.5 to 10 μm, high-precision patterning is required and flatness of the base surface is also required. Here, since the discharge electrodes 3a and 3b are formed on the insulating surface 2a of the substrate 2 having high flatness, the fine gap width can be controlled with high accuracy.

Next, a conductive inorganic material such as Au is sputtered and partially (incompletely) formed in and around the narrow gap region between the discharge electrodes 3a and 3b, and then insulation such as Al ₂ O _{3 is} continued. By sputtering the conductive inorganic material, a composite having a laminated structure of so-called so-called island-like conductive inorganic material layers and insulating inorganic material layers covering the layers is formed. Further, the composite is selectively removed by photolithography, leaving it in and around the gap region. Thus, the functional layer 4 is completed (Step S13).

  Next, terminal electrodes 5a and 5b are formed on the surfaces of the discharge electrodes 3a and 3b by plating (step S14). The terminal electrodes 5a and 5b are formed by forming a base conductive film such as Cu on the entire base surface by electroless plating or sputtering, then forming a thick plating electrode by electrolytic plating, and etching an unnecessary base conductive film by etching. It can be formed by removing. Further, the discharge electrodes 3a and 3b may be used as a base film for plating as they are. Here, since the conductive inorganic material 4b of the functional layer 4 is covered and protected by the insulating inorganic material 4a, it is not affected by etching when the terminal electrodes 5a and 5b are formed.

Next, the protective layer 6 is formed on the base 2 on which the discharge electrodes 3a and 3b, the functional layer 4, and the terminal electrodes 5a and 5b are formed (step S15). The protective layer 6 can be formed by depositing an insulating material such as Al ₂ O ₃ and then planarizing the upper surface by CMP. Subsequently, plating films 8a and 8b are formed by sequentially depositing Ni and Au on the exposed surfaces of the terminal electrodes 5a and 5b appearing on the surface of the protective layer 6 (step S16).

  Next, the protective film 7 made of a resin such as polyimide is formed on the surface of the protective layer 6 (step S17). This protective film 7 can prevent the protective layer 6 from being damaged or affected by moisture. Thus, the electrostatic protection element 1 according to the present embodiment is completed.

As described above, in the electrostatic protection element 1 according to the present embodiment, the large volume terminal electrodes 5a and 5b are provided on the discharge electrodes 3a and 3b, and the connection between the discharge electrodes 3a and 3b and the terminal electrodes 5a and 5b is provided. Since a large area is ensured, the heat capacity of the discharge electrodes 3a and 3b can be increased, thereby improving the durability of the discharge electrodes 3a and 3b. Further, the discharge electrode 3a, the width _{W 1} of the distal end portion of 3b, the discharge electrodes 3a, 3b and the terminal electrodes 5a, since narrower than the width _{W 2} of the discharge electrodes in the terminal electrode formation region overlapping and 5b, the discharge electrodes 3a, The tip of 3b can be moved away from the side surface (outer peripheral surface) of the element, and electrostatic breakdown can be prevented from affecting the outside of the element.

  FIG. 5 is a schematic side view showing the configuration of the electrostatic protection element according to the second embodiment of the present invention. FIG. 6 is a schematic plan view of the electrostatic protection element shown in FIG.

The electrostatic protection element 10 according to the second embodiment is characterized in that the terminal electrodes 5a and 5b have a two-stage structure. In the first embodiment, the terminal electrodes 5a and 5b have a single-layer structure, but in the second embodiment, the terminal electrodes 5a and 5b have a multilayer (two-layer) structure, and the planar size of the lower layer portions 5al and 5bl of the terminal electrode is larger. It is large and the upper layer portions 5au and 5bu are relatively small. As a result, the distance L _0a between the pair of terminal electrodes exposed on the surface of the element can be separated to some extent. Since other configurations are substantially the same as those of the first embodiment, the same components are denoted by the same reference numerals and detailed description thereof is omitted.

Although not particularly limited, the thickness of the lower layer parts 5al and 5bl of the terminal electrode is preferably 3 to 15 μm, the thickness of the upper layer parts 5au and 5bu is preferably 8 to 30 μm, and the upper layer parts 5au, The thickness of 5bu may be thicker or thinner than the thickness of the lower layer portions 5al and 5bl. The distance L _0b between the lower layer portions 5al and 5bl is preferably about 10 to 40 μm, and the distance L _0a between the upper layer portions 5au and 5bu is preferably about 150 to 250 μm. Both the lower layer portions 5al and 5bl and the upper layer portions 5au and 5bu of the terminal electrode are formed by electrolytic plating of Cu.

  Of the outer peripheral surfaces of the upper layer portions 5au and 5bu of the terminal electrode, it is preferable that the three side surfaces excluding the surfaces facing each other protrude outward from the lower layer portions 5al and 5bl. Therefore, it is preferable that the width of the upper layer portions 5au and 5bu of the terminal electrode is wider than the width of the lower layer portions 5al and 5bl. According to this configuration, the upper layer portions 5au and 5bu surely cover the upper surfaces of the lower layer portions 5al and 5bl, so that heat dissipation can be improved.

  In the present embodiment, the lower layer portions 5al and 5bl of the terminal electrode also function as auxiliary electrode layers of the discharge electrodes 3a and 3b, as in the third embodiment described later. Since electrostatic absorption accompanies destruction of the discharge electrode, the repeated discharge will eventually make the discharge electrode unusable and the electrostatic absorption function will be lost. However, the presence of the lower layer portions 5al and 5bl of the terminal electrode allows the end surfaces of the pair of discharge electrodes 3a and 3b facing each other through the gap to have a substantially multistage structure, thereby reducing the electrostatic absorption performance. I can stop. Therefore, durability due to repeated use can be enhanced.

Distance from the tip of the discharge electrode 3a (or 3b) to the terminal electrodes 5a (or 5b) (or the length of the tip of the discharge electrode 3a, 3b having a width _{W 1)} is △ L, the discharge electrodes 3a, inter 3b 1 to 30 μm is preferable, 5 to 20 is more preferable, and 10 to 20 μm is preferable from the viewpoint of suppressing discharge damage of the terminal electrodes 5 a and 5 b and enhancing the heat diffusion efficiency by the terminal electrodes 5 a and 5 b. Particularly preferred. The distance L _0b between the lower layer portions 5al and 5bl described above is defined as ΔL × 2 + ΔG.

As described above, according to the present embodiment, the distance L _0a between the upper layer portions 5au and 5bu of the terminal electrode having the two-layer structure is wider than the distance L _0b between the lower layer portions 5al and 5bl. While separating the distance between the exposed pair of terminal electrodes to some extent, it is possible to secure a sufficient volume of the entire terminal electrode and improve the heat dissipation of the discharge electrodes 3a and 3b, thereby improving the number of times that discharge can be repeated.

  FIG. 7 is a schematic side view showing the configuration of the electrostatic protection element 11 according to the third embodiment of the present invention. FIG. 8 is a schematic plan view of the electrostatic protection element shown in FIG.

  The electrostatic protection element 11 according to the third embodiment is characterized in that a pair of discharge electrodes opposed via a gap has a multistage structure in which the gap between the electrodes becomes narrower toward the base 2. Since electrostatic absorption accompanies destruction of the discharge electrode, the repeated discharge will eventually make the discharge electrode unusable and the electrostatic absorption function will be lost. However, in the present embodiment, since the end surfaces of the pair of discharge electrodes 3a and 3b facing each other through the gap have a multi-stage structure, it is possible to prevent a decrease in electrostatic absorption performance. Therefore, durability due to repeated use can be enhanced.

  The discharge electrodes 3a and 3b are laminated structures of lower layers 3al and 3bl and upper layers 3au and 3bu, such that the gap side end surfaces of the upper layers 3au and 3bu extend in the gap direction from the gap side end surfaces of the lower layers 3al and 3bl. As a result, a multi-stage structure is formed in which the gap between the discharge electrodes 3a and 3b becomes narrower toward the substrate 2. The lower layers 3al and 3bl of the discharge electrode are main electrode layers that provide an electrostatic absorption function, and the upper layers 3al and 3bl of the discharge electrode are auxiliary electrode layers that suppress a decrease in electrostatic absorption performance of the main electrode layer.

  The multistage structure of the discharge electrodes 3a and 3b is not particularly limited as long as the gap between the discharge electrodes 3a and 3b is configured to become narrower toward the base 2. In the aspect in which the gap between the discharge electrodes 3a and 3b becomes narrower toward the substrate 2, the formation of the discharge electrodes 3a and 3b is easy, so that productivity and economy are improved. In this embodiment, the discharge electrodes 3a and 3b having a two-stage structure including the lower layers 3al and 3bl and the upper layers 3au and 3bu are employed. For example, a multi-stage structure having two or more stages (for example, three stages or four stages) Alternatively, the multistage structure may be formed in a tapered shape.

  The thicknesses of the discharge electrodes 3a and 3b are not particularly limited and can be appropriately set according to the purpose, but are preferably set within a range of 0.1 to 2 μm. The thickness ΔTl of the lower layers 3al and 3bl is equal to or smaller than the gap distance ΔG between the discharge electrodes 3a and 3b and is 0.1 to 2 μm from the viewpoint of not damaging the formation of the functional layer 4 described later. Is preferred. Further, the thickness ΔTu of the upper layers 3 au and 3 bu is preferably at least twice the thickness ΔTl of the lower layers 3 al and 3 bl from the viewpoint of increasing the efficiency of heat conduction. Note that the extension dimension of the lower layers 3al, 3bl extending from the upper layers 3au, 3bu (also referred to as step depth: also referred to as a step size) ΔL promotes the discharge between the lower layers 3al, 3bl, and the upper layers 3au, 3bu From the viewpoint of suppressing discharge breakage and increasing the heat diffusion efficiency by the upper layers 3 au and 3 bu, 1 to 30 μm is preferable, 5 to 20 μm is more preferable, and 10 to 20 μm is particularly preferable. The upper layers 3au and 3bu of the discharge electrode are preferably formed by sputtering of Cu. The lower layers 3al and 3bl of the discharge electrode may be formed by Cu sputtering or Cu electrolytic plating.

  The breakdown of the lower layers 3al and 3bl of the discharge electrode gradually proceeds by repeating electrostatic absorption, and the distance between the electrodes (gap width ΔG) increases, but temporarily stops at the position of the end surfaces of the upper layers 3au and 3bu. Due to the presence of the upper layers 3au and 3bu, the thickness of the entire electrode is increased, so that it is difficult to be destroyed and the distance between the electrodes is kept constant. Here, it seems that the above problem can be avoided if the thickness of the lower layers 3al and 3bl of the discharge electrode is increased from the beginning, but if the thickness is increased from the beginning, the conductive inorganic material 4b of the functional layer 4 is reduced. When forming, since an island pattern cannot be formed naturally from one side of the electrode to the other, in order to secure a certain degree of flatness of the base surface, a large step is prevented by using thin electrodes.

  In the present embodiment, the cross-sectional shape of the end surface of the tip portion of the lower layer 3al, 3bl of the discharge electrode is tapered. In the case where the end surface of the distal end portion of the discharge electrodes 3a and 3b is a downward tapered surface with respect to the base surface (insulating surface 2a), the island pattern of the conductive inorganic material contained in the functional layer 4 is formed in the lower layer 3al, Since it is not affected by the level difference due to the end face of 3bl, a naturally dispersed island pattern can be formed, and the electrostatic absorption effect can be enhanced.

  Hereinafter, variations in the planar shape of the multi-stage discharge electrodes 3a and 3b will be described with reference to the plan views of FIGS. In addition, since a pair of discharge electrode 3a, 3b is the same shape, only the one discharge electrode 3a side is shown in FIG.

A first variation shown in FIG. 9A is that both the lower layer 3al and the upper layer 3au are rectangular patterns, but a planar composite pattern formed by overlapping upper and lower layers is a convex pattern. Therefore, the width _{W 1} of the lower layer 3al is monospace, the width _{W 4} of the upper 3au is a monospace, wider than the width _{W 1} of the lower layer. Furthermore, the width W ₅ of the terminal electrode 5a is equal to or greater than the width W _{4 of} the upper layer (W ₅ ≧ W ₃ ). That is, W ₅ ≧ W ₄ > W ₁ .

The second variation shown in FIG. 9B is that only the lower layer 3al is a convex pattern and the upper layer 3au is a rectangular pattern. The width of the lower layer 3al stepwise changed, the width W ₂ of the rear end portion is wider than the width W ₁ of the distal end portion. Width W ₄ of the discharge electrodes of the upper 3au is a monospace, wider than the width W ₂ of the upper rear portion. Furthermore, the width W ₅ of the terminal electrode 5a is equal to or greater than the width W _{4 of the} upper layer 3au (W ₄ ≧ W ₃ ). That is, W ₅ ≧ W ₄ ≧ W ₂ > W ₁ .

A third variation shown in FIG. 9C is that both the lower layer 3al and the upper layer 3au are convex patterns. Width of the discharge electrodes of the lower layer 3al stepwise changed, the width W ₂ of the rear end portion is wider than the width W ₁ of the distal end portion. Width of the discharge electrodes of the upper 3au also stepwise changed, the width W ₄ of the rear end portion wider than the width W ₃ of the tip portion, further the width W ₄ of each _stage, W ₃ are corresponding respectively upper 3au The step width is W ₂ or W ₁ or more. Furthermore, the width W ₅ of the terminal electrode 5a is equal to or greater than the width W _{4 of the} upper layer 3au (W ₅ ≧ W ₄ ). That is, W ₅ ≧ W ₄ ≧ W ₂ and W ₃ ≧ W ₁ .

  Thus, regardless of the planar shape of each electrode layer, the composite planar shape of the multi-layered discharge electrode has a narrow front end width and a wide rear end portion, and is similar to the first embodiment. The number of times that the electrostatic protection element can be used repeatedly can be increased.

  FIG. 10 is a schematic plan view showing still another variation of the multi-stage discharge electrode shown in FIG.

  As shown in FIG. 10, the widths of the lower layers 3al and 3bl of the discharge electrode change in three steps from the front end portion to the rear end portion, and the upper layers 3au and 3bu also have shapes of the lower layers 3al and 3bl. The width has changed in three steps.

Is not particularly limited, the lower layer 3al of the discharge electrode, the length L ₁ and length L ₂ of the narrow portion to the next most narrow tip portion of 3bl can both be about 40 [mu] m. Further, the upper layer 3AU, the gap width between 3bu lower layer 3al, it is necessary to widen than 3BL, upper 3AU discharge electrodes, the length _{L 3} of the most narrow tip portion of 3bu be about 30μm preferably, the length L ₄ of the tip portion of the second stage is preferably about 40 [mu] m.

Like the lower layers 3al and 3bl of the discharge electrode, the shape of the corner portion at the tip of the upper layers 3au and 3bu of the discharge electrode is round. Here, the upper layer 3AU, corner radius of curvature _{R 2} of 3bu is lower 3al, is preferably larger than the radius of curvature of the corner portion _{R 1} of 3BL. According to this configuration, electrostatic absorption can be prevented from being repeated at the corners of the upper layers 3au and 3bu in preference to the lower layers 3al and 3bl due to electric field concentration.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Needless to say, it is included in the range.

  For example, in the above-described embodiment, the gap between the pair of discharge electrodes is opposed straight, but it is not necessarily straight, and may be wavy or comb-like. However, the straight is preferable in consideration of variations depending on the patterning accuracy. The opposite length should be as long as possible.

  Moreover, in the said embodiment, although the width | variety of discharge electrode 3a, 3b is changing in the step shape, you may change in a taper shape as shown in FIG. In this case, however, the tapered area substantially increases the opposing area of the discharge electrode, which increases the capacitance. Therefore, it is advantageous that the widths of the discharge electrodes 3a and 3b change stepwise.

  In the above embodiment, the electrostatic protection element is a single chip part having only an electrostatic protection function, but may be provided as a composite part integrated with another element such as a coil.

DESCRIPTION OF SYMBOLS 1,10-12 Electrostatic protection element 2 Base | substrate 2a Insulating surface 3a, 3b Discharge electrode 3al, 3bl Lower layer 3au of discharge electrode, 3bu Upper layer 4 of discharge electrode Functional layer 4a Insulating inorganic material 4b Conductive inorganic material 5a, 5b Terminal electrode 5al, 5bl Lower layer part 5au of terminal electrode, 5bu Upper part of terminal electrode 6 Protective layer 7 Protective film 8a, 8b Plating film

Claims (12)

A substrate having an insulating surface;
A pair of discharge electrodes disposed opposite and spaced from each other on the insulating surface;
A functional layer provided at least between the pair of discharge electrodes;
A pair of terminal electrodes respectively provided on the pair of discharge electrodes and electrically connected to the discharge electrodes;
The pair of terminal electrodes are thick film electrodes formed by plating,
The electrostatic protection element, wherein a width of the discharge electrode in a region overlapping with the terminal electrode is wider than a width of a tip portion where the pair of discharge electrodes are close to each other. A protective layer provided between the pair of terminal electrodes and covering the functional layer;
The electrostatic protection element according to claim 1, wherein each of the pair of terminal electrodes has an electrode surface exposed on an outer surface of the protective layer.   3. The electrostatic protection element according to claim 1, wherein an end surface of the tip portion of each of the pair of discharge electrodes is a tapered surface descending toward the insulating surface.   The electrostatic protection element according to any one of claims 1 to 3, wherein the width of the pair of discharge electrodes changes stepwise.   5. The electrostatic protection element according to claim 1, wherein each of the pair of terminal electrodes has a multilayer structure, and a distance between upper layer portions of the terminal electrodes is wider than a distance between lower layer portions.   6. The electrostatic protection element according to claim 1, wherein the pair of discharge electrodes has a multistage structure in which a gap width between the discharge electrodes becomes narrower toward the base. 7. The pair of discharge electrodes has a multilayer structure,
The electrode width of the lower layer of the pair of discharge electrodes is equal,
The electrostatic protection element according to claim 6, wherein the upper electrode width of the pair of discharge electrodes is equal and wider than the lower electrode width. The pair of discharge electrodes has a multilayer structure,
The electrode width of the lower layer of the pair of discharge electrodes changes stepwise,
The electrostatic protection element according to claim 6, wherein the upper electrode width of the pair of discharge electrodes is equal and wider than the lower electrode width. The pair of discharge electrodes has a multilayer structure,
The electrode width of the lower layer of the pair of discharge electrodes changes stepwise,
The electrostatic protection according to claim 6, wherein the upper electrode width of the pair of discharge electrodes changes stepwise with the lower electrode width, and the width of each step is wider than the corresponding step width of the lower layer. element.   The electrostatic protection element according to any one of claims 1 to 9, wherein a corner portion of at least the tip portion of the pair of discharge electrodes has a round shape.   11. The electrostatic protection according to claim 1, further comprising a protective film made of a resin material provided on an outer surface of the protective layer and overlapping at least the gap in plan view. element.   The electrostatic protection element according to any one of claims 1 to 11, wherein the functional layer is a composite in which a conductive inorganic material is discontinuously dispersed in a matrix of an insulating inorganic material.

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