JPWO2014188791A1 - ESD protection device - Google Patents

Abstract

Provided is an ESD protection device capable of further reducing the discharge start voltage without incurring the complexity of the manufacturing process. A substrate 2 and first and second discharge electrodes 3 and 4 which are provided on the substrate 2 and face each other with a gap therebetween, and the first and second discharge electrodes 3 and 4 are made of metal The ESD protection device 1 made of a mixed material including a high dielectric constant material having a relative dielectric constant higher than that of the substrate 2.

Description

  The present invention relates to an ESD protection device for protecting an electronic circuit from static electricity, and more particularly to an ESD protection device with improved discharge electrodes.

  Patent Document 1 below discloses an ESD protection device in which first and second discharge electrodes are provided in a ceramic multilayer substrate. An auxiliary electrode is provided so as to be connected to the first and second discharge electrodes. The auxiliary electrode is formed by dispersing a conductive material coated with an inorganic material having no conductivity.

  On the other hand, in the ESD protection apparatus described in Patent Document 2 below, a heat-resistant film containing an electron-emitting substance is attached to the discharge electrode. As a result, the discharge start voltage is lowered.

  Patent Document 3 below discloses a discharge tube used for high power applications. In this discharge tube, columnar first and second discharge electrodes face each other with a gap in an airtight chamber filled with gas. A mixed material containing a dielectric substance such as barium titanate and a carrier substance such as magnesium oxide is applied to the end face of the columnar discharge electrode. Thereby, a discharge stabilizing material layer is formed.

WO2009 / 098944 JP 2003-59615 A JP 2004-79230 A

  In the ESD protection devices described in Patent Document 1 and Patent Document 2, the discharge start voltage is reduced, but it is not sufficient.

  On the other hand, in the discharge tube for high power use described in Patent Document 3, the discharge is stabilized by providing the discharge stabilizing material layer. However, in order to form the discharge stable material layer, it has been necessary to apply the discharge stable material layer forming material to the discharge electrode and to perform heat treatment in a reduced pressure atmosphere. Therefore, the machining process is complicated and the machining cost is high.

  An object of the present invention is to provide an ESD protection device capable of effectively reducing a discharge start voltage without causing a complicated manufacturing process.

An ESD protection apparatus according to the present invention includes a substrate and first and second discharge electrodes that are provided on the substrate and face each other with a gap between the first and second discharge electrodes. And a mixed material containing a metal and a high dielectric constant material having a higher relative dielectric constant than that of the substrate.

  The ESD protection apparatus according to the present invention preferably includes a discharge auxiliary electrode. The discharge auxiliary electrode is provided so as to connect the first discharge electrode and the second discharge electrode, and promotes discharge between the first and second discharge electrodes.

  In the ESD protection apparatus of the present invention, preferably, the discharge auxiliary electrode includes metal particles coated with a material having no conductivity.

  In the ESD protection apparatus according to the present invention, preferably, a low dielectric constant portion having a relative dielectric constant lower than that of the substrate is located in the gap. The low dielectric constant portion may be a cavity. The low dielectric constant portion may be formed of a solid material having a relative dielectric constant lower than that of the substrate. More preferably, a resin is used as the solid material.

  The ESD protection apparatus according to the present invention preferably further includes a back electrode provided so as to overlap the gap between the first and second discharge electrodes via a part of the substrate.

  Preferably, the substrate includes first and second external electrodes that are provided on the substrate and are electrically connected to the first and second discharge electrodes, respectively, and the back electrode includes the first and second external electrodes. It is electrically connected to at least one of the electrodes. However, the back electrode may be a floating electrode.

  In the ESD protection apparatus according to the present invention, preferably, the back electrode includes a metal and a material having a dielectric constant higher than that of the substrate.

  In the ESD protection apparatus according to the present invention, the first and second discharge electrodes may be disposed on the outer surface of the substrate.

  In the ESD protection apparatus according to the present invention, the first and second discharge electrodes may be arranged in the substrate, and the gap may be located in the substrate.

  In the ESD protection device according to the present invention, the concentration of the high dielectric constant material may be higher on the surfaces of the first and second discharge electrodes than in the first and second discharge electrodes.

  According to the ESD protection device of the present invention, since the first and second discharge electrodes are made of a mixed material containing a metal and a high dielectric constant material, the discharge start voltage can be lowered. Therefore, it is possible to more effectively protect against static electricity in an electronic circuit or the like.

  In addition, in the ESD protection apparatus of the present invention, since the first and second discharge electrodes have the above-described configuration, they can be easily manufactured and the manufacturing process is not likely to be complicated.

FIG. 1A and FIG. 1B are a front sectional view of an ESD protection device according to a first embodiment of the present invention and a partially cutaway enlarged front sectional view for explaining the main part thereof. FIG. 2 is a schematic plan view for explaining the positional relationship among the first and second discharge electrodes, the discharge auxiliary electrode, and the back electrode in the ESD protection apparatus according to the first embodiment of the present invention. . FIG. 3A and FIG. 3B are a front sectional view of an ESD protection device according to a second embodiment of the present invention and a partially cutaway enlarged front sectional view showing an essential part thereof. FIG. 4 is a schematic plan view showing the positional relationship among the first and second discharge electrodes, the discharge auxiliary electrode, and the back electrode in the second embodiment of the present invention. FIG. 5 is a schematic plan view for explaining a modification of the positional relationship among the first and second discharge electrodes, the discharge auxiliary electrode, and the back electrode. FIG. 6 is a schematic plan view for explaining another modified example of the positional relationship among the first and second discharge electrodes, the discharge auxiliary electrode, and the back electrode. FIG. 7 is a front sectional view of an ESD protection apparatus according to the third embodiment of the present invention. FIG. 8 is a schematic plan view showing the positional relationship among the first and second discharge electrodes, the discharge auxiliary electrode, and the back electrode in the ESD protection apparatus according to the third embodiment of the present invention. FIG. 9 is a front sectional view of an ESD protection apparatus according to the fourth embodiment of the present invention. FIG. 10 is a schematic plan view showing the positional relationship among the first and second discharge electrodes, the discharge auxiliary electrode, and the back electrode in the ESD protection apparatus according to the fourth embodiment of the present invention. FIG. 11 is a front sectional view of an ESD protection apparatus according to the fifth embodiment of the present invention. FIG. 12 is a front sectional view of an ESD protection apparatus according to the sixth embodiment of the present invention.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

  1A and 1B are a front sectional view of an ESD protection device according to a first embodiment of the present invention and a partially cutaway enlarged front sectional view showing an essential part thereof.

  The ESD protection device 1 has a substrate 2. The substrate 2 is made of an appropriate insulating material. In the present embodiment, the substrate 2 is made of a ceramic multilayer substrate, and a BAS material containing Ba, Al, and Si as main components is used. However, low temperature sintered ceramics (LTCC) such as glass ceramics may be used. Further, ceramics (HTCC) sintered at a high temperature such as aluminum nitride or alumina may be used. Furthermore, magnetic ceramics such as ferrite may be used. The substrate 2 may be formed of an insulating material such as a resin other than ceramics.

  On the upper surface 2a of the substrate 2, a first discharge electrode 3 and a second discharge electrode 4 are formed. A discharge auxiliary electrode 5 is provided on the lower surface of the first and second discharge electrodes 3 and 4 so as to connect the tips of the first and second discharge electrodes 3 and 4.

  In the present embodiment, the first and second discharge electrodes 3 and 4 are made of a mixed material including a metal and a high dielectric constant material having a relative dielectric constant higher than that of the substrate 2. More specifically, as shown in FIG. 1B, the first and second discharge electrodes 3 and 4 have a structure mainly composed of metal and in which high dielectric constant material particles 6 are dispersed. Such a structure is formed by firing a paste containing a metal and high dielectric constant material particles.

  The metal used for the first and second discharge electrodes 3 and 4 is not particularly limited. For example, Cu, Ag, Al, Mo, W, or an alloy containing these metals can be used.

  The high dielectric constant material is not particularly limited as long as the relative dielectric constant is higher than that of the substrate 2. As such a high dielectric constant material, a ceramic material having a relative dielectric constant higher than that of the substrate 2 is preferably used. Examples of such ceramic materials include barium titanate, calcium titanate, strontium titanate, magnesium titanate, and calcium zirconate. The relative dielectric constant of barium titanate, calcium titanate, strontium titanate, magnesium titanate, calcium zirconate, etc. is about 30 or more and 10,000 or less.

  On the other hand, when an insulating ceramic such as alumina is used as the substrate 2, the relative dielectric constant is about 5 or more and 15 or less. As described above, when the first and second discharge electrodes are formed by baking a paste containing a metal and a high dielectric constant material, the high dielectric constant material segregates on the surface. That is, as schematically shown in FIG. 1B, the first and second discharge electrodes 3 and 4 are mainly made of metal, but the high dielectric constant material particles 6 are dispersed therein. The high dielectric constant material particles 6 are present on the surface more than inside the first and second discharge electrodes 3 and 4. This is because the high dielectric constant material particles 6 move to the surface side and segregate during the firing.

  The discharge auxiliary electrode 5 is provided on the upper surface 2 a of the substrate 2 so as to connect the first discharge electrode 3 and the second discharge electrode 4. As shown in the schematic plan view of FIG. 2, the discharge auxiliary electrode 5 is provided in a region including a gap where the tips of the first and second discharge electrodes 3 and 4 are opposed to each other.

  The discharge auxiliary electrode 5 is formed by dispersing metal particles 7 a covered with a material having no conductivity on the upper surface 2 a of the substrate 2. More specifically, it is formed by applying and baking a paste containing such conductive particles. In this case, the metal particles 7 a covered with the non-conductive material contained in the paste are diffused from the upper surface 2 a of the substrate 2 to the surface layer of the substrate 2. As a result, the discharge auxiliary electrode 5 is formed.

  The discharge auxiliary electrode 5 acts to promote discharge between the tip of the first discharge electrode 3 and the tip of the second discharge electrode 4.

  There is no particular limitation on the material constituting the metal particles 7a coated with the non-conductive material. Examples of the material having no electrical conductivity include insulating ceramics such as alumina, and glass. Moreover, it does not specifically limit about the metal which comprises a metal particle. As such a metal, copper or a copper-based alloy containing copper as a main component is preferably used. However, other metals such as silver, aluminum, molybdenum, tungsten, or alloys mainly composed of other metals may be used.

  In the present embodiment, the discharge auxiliary electrode 5 is added with semiconductor ceramic particles 7b in addition to the metal particles 7a coated with a material having no conductivity. As such semiconductor ceramic particles 7b, particles made of SiC, TiC or the like can be used.

  Furthermore, the discharge auxiliary electrode 5 may be added with high dielectric constant material particles contained in the discharge electrodes 3 and 4 described above. In that case, the discharge start voltage can be further reduced.

  As shown in FIGS. 1A and 1B, a resin layer 8 is formed in the gap where the tips of the first and second discharge electrodes 3 and 4 face each other. The resin layer 8 is made of a synthetic resin and has a relative dielectric constant lower than that of the substrate 2. Examples of the resin constituting the resin layer 8 include s tacone resin.

  In the present embodiment, the resin layer 8 is formed after the discharge electrodes 3 and 4 are formed. Therefore, the resin layer 8 is formed by applying the resin constituting the resin layer 8 so as to fill the gap. Therefore, in this embodiment, the upper surface of the resin layer 8 is flush with the upper surfaces of the first and second discharge electrodes 3 and 4.

  Further, a second resin layer 9 is formed so as to cover the first and second discharge electrodes 3, 4 and the resin layer 8. The second resin layer 9 is made of a resin having a relative dielectric constant higher than that of the first resin layer 8. Examples of such a resin include an epoxy resin. However, in the present embodiment, the first and second resin layers 8 are not necessarily provided. For example, a cavity may be provided instead of the first resin layer 8. Moreover, the 1st, 2nd resin layers 8 and 9 may be formed from the same material.

  As shown in FIG. 1A, first and second external electrodes 10a and 10b are formed so as to be electrically connected to the first and second discharge electrodes 3 and 4, respectively. The first and second external electrodes 10a and 10b are electrically connected to the first and second discharge electrodes 3 and 4 on the upper surface 2a of the substrate 2, respectively. The first and second discharge electrodes 10 a and 10 b reach the lower surface through the side surface of the substrate 2. The first and second external electrodes 10a and 10b are made of appropriate metals or alloys.

  A back electrode 11 is formed in the substrate 2. As shown in FIG. 2, the back electrode 11 is provided at a position overlapping the gap portion where the first and second discharge electrodes 3, 4 face each other when viewed in plan.

  The back electrode 11 is opposed to the first and second discharge electrodes 3, 4 and the discharge auxiliary electrode 5 through a part of the layer of the substrate 2. In the present embodiment, the substrate 2 is made of a ceramic multilayer substrate. Therefore, the back electrode 11 can be formed in the manufacturing process of the substrate 2.

  The back electrode 11 can be formed of an appropriate conductive material. Preferably, the back electrode 11 is mainly made of metal. As such a metal material, the same metal as that used for the first and second discharge electrodes 3 and 4 can be used. More preferably, the back electrode 11 is made of a mixed material including a metal and the above-described high dielectric constant material having a relative dielectric constant higher than that of the substrate 2. Thereby, the discharge start voltage can be further reduced.

  As shown in FIG. 2, the width direction dimension of the back electrode 11 may be smaller than the width direction dimension of the discharge electrodes 3 and 4. Here, the width dimension means a direction orthogonal to the direction in which the first and second discharge electrodes 3 and 4 are opposed to each other. Further, the planar shape of the auxiliary discharge electrode 5 is not particularly limited as long as it is provided so as to connect the first and second discharge electrodes 3 and 4.

  In the ESD protection device 1, the first and second discharge electrodes 3 and 4 are made of a mixed material including a metal and the above-described high dielectric constant material particles 6 having a relative dielectric constant higher than that of the substrate 2. Therefore, the discharge start voltage can be effectively reduced. This is because materials having different relative dielectric constants are arranged in the vicinity of the first and second discharge electrodes 3 and 4.

  That is, when the high dielectric constant material particles 6 are present on the surface side of the first and second discharge electrodes 3, 4, the metal and high dielectric constant material particles are present in the vicinity of the surfaces of the first and second discharge electrodes 3, 4. 6, the resin layer 8, the discharge auxiliary electrode 5 and the like are present. Therefore, a plurality of types of materials having different relative dielectric constants are arranged near the surfaces of the auxiliary discharge electrodes 3 and 4. In particular, when the high dielectric constant material particles 6 having a high dielectric constant are present on the surface side of the discharge electrodes 3 and 4, there are portions having different relative dielectric constants around the surfaces of the discharge electrodes 3 and 4. As a result, electric field concentration is promoted at the surfaces of the discharge electrodes 3 and 4, particularly at the tip. Therefore, the movement of electrons as a starting point of discharge is promoted by the electric field concentration. As a result, the discharge start voltage is considered to be low.

  In addition, the presence of the high dielectric constant material particles 6 also increases the capacitance between the first and second discharge electrodes 3 and 4 facing each other. It is thought that the charging action at the time of discharge is thereby accelerated. Therefore, it is considered that the discharge start voltage is lowered by the promotion of the charging action.

  Furthermore, in this embodiment, the discharge start voltage is also lowered by providing the discharge auxiliary electrode 5. Furthermore, since the back electrode 11 is provided, the electric field concentration is further promoted, and thereby the discharge start voltage is further reduced.

  Furthermore, a capacitance is formed between the first and second discharge electrodes 3 and 4 and the back electrode 11. Therefore, it is considered that the charging action at the time of discharging is further enhanced, and the discharge starting voltage is lowered accordingly.

  However, in the present invention, the discharge auxiliary electrode 5 and the back electrode 11 are not necessarily provided. For example, instead of the discharge auxiliary electrode 5, a porous layer in which a material having a voltage nonlinearity characteristic, a metal, a semiconductor, or the like is dispersed may be provided.

  Preferably, the back electrode 11 is electrically connected to the first external electrode 10a or the second external electrode 10b. Thereby, a capacitance is formed between the discharge electrode 3 or the discharge electrode 4 and the back electrode 11. Therefore, the charging action at the time of discharging is further enhanced. In addition, the heat generated by the discharge can be quickly dissipated from the back electrode 11 to the external electrode 10a or the external electrode 10b that is electrically connected to the back electrode 11. Therefore, thermal degradation in the ESD protection apparatus 1 can be suppressed.

  As described above, the back electrode 11 preferably includes a high dielectric constant material like the discharge electrodes 3 and 4. In that case, materials having different relative dielectric constants are also arranged in the vicinity of the back electrode 11. Therefore, the electric field concentration effect and the charging effect are further enhanced. Therefore, the discharge start voltage can be further reduced.

  More preferably, it is desirable that the back electrode 11 and the first and second discharge electrodes 3 and 4 are made of a mixed material containing the same metal and the same high dielectric constant material. In that case, the manufacturing process can be further simplified.

  When manufacturing the ESD protection apparatus 1, the substrate 2 can be formed according to a known method for manufacturing a ceramic multilayer substrate. Moreover, the discharge auxiliary electrode 5 and the first and second discharge electrodes 3 and 4 can be easily formed. Therefore, the manufacturing process is not complicated.

  In addition, when the board | substrate 2 is comprised with a ceramic multilayer substrate, there exists a problem that a baking shrinkage | contraction rate difference is large with a metal and ceramics. Therefore, delamination may occur between the metal and the ceramic during firing.

  On the other hand, in the present embodiment, since the first and second discharge electrodes 3 and 4 include the high dielectric constant material particles 6, the first and second discharge electrodes 3 and 4 and the substrate 2 are fired. At that time, the difference in shrinkage rate is reduced. Therefore, the occurrence of delamination can be suppressed.

  FIGS. 3A and 3B are a front sectional view of an ESD protection device 21 according to a second embodiment of the present invention and a partially cutaway enlarged front sectional view showing an essential part thereof.

  The ESD protection device 21 according to the second embodiment includes a substrate 22. The substrate 22 can be formed of the same material as the substrate 2 of the first embodiment.

  First and second discharge electrodes 3 and 4 are disposed in the substrate 22. The tips of the first and second discharge electrodes 3 and 4 are opposed to each other with a gap therebetween. A discharge auxiliary electrode 5 is formed so as to connect the first and second discharge electrodes 3 and 4.

  The first and second discharge electrodes 3 and 4 and the auxiliary discharge electrode 5 are the same as the first and second discharge electrodes 3 and 4 and the auxiliary discharge electrode 5 of the first embodiment except that the formation positions are different. It is formed similarly. Therefore, the description of the first embodiment is incorporated.

  However, in the present embodiment, a cavity 22b is provided in the portion where the tips of the first and second discharge electrodes 3 and 4 are opposed to each other. The tips of the first and second discharge electrodes 3 and 4 are exposed in the cavity 22b. Accordingly, the gap between the tip of the first discharge electrode 3 and the tip of the second discharge electrode 4 is located in the cavity 22b. Therefore, the gas filling the cavity 22b is located in the gap. The relative permittivity of gas is, for example, 1.00059 for air. Therefore, compared with the relative dielectric constant of the substrate 22, the portion constituting the gap is a relatively low low dielectric constant portion.

  In the substrate 22, the back electrode 11 is provided so as to face the auxiliary discharge electrode 5 and the first and second discharge electrodes 3 and 4 through the substrate layer. The back electrode 11 is configured in the same manner as the back electrode 11 of the first embodiment. In the present embodiment, the back electrode 11A is also formed above the cavity 22b. The back electrode 11A is formed of the same material as the back electrode 11. Further, the planar shape of the back electrode 11A and the position when viewed in plan are the same as those of the back electrode 11. As shown in FIG. 4, the back electrode 11 is provided in a region including a gap where the first and second discharge electrodes 3 and 4 are opposed to each other.

  The first and second discharge electrodes 3 and 4 are electrically connected to the first and second external electrodes 10a and 10b. The first and second external electrodes 10a and 10b are provided in the same manner as in the first embodiment.

  In the ESD protection device 21 according to the second embodiment, when static electricity is applied between the first discharge electrode 3 and the second discharge electrode 4, the ESD protection device 21 discharges by both discharge paths of creeping discharge and air discharge. It will be. Also in this case, since the first and second discharge electrodes 3 and 4 are made of a mixture containing a metal and a high dielectric constant material, the discharge start voltage is effectively reduced as in the case of the first embodiment. Can be lowered. In addition, the discharge start voltage can be lowered by providing the discharge auxiliary electrode 5 and the back electrodes 11 and 11A.

  Furthermore, also in this embodiment, when the back electrodes 11 and 11A are electrically connected to the first external electrode 10a or the second external electrode 10b, the discharge start voltage can be further reduced. In addition, thermal degradation can be suppressed.

  As is apparent from the ESD protection device 21 of the second embodiment, in the present invention, the first and second discharge electrodes 3 and 4 may be located in the substrate 22. In addition to creeping discharge, air discharge may be used by providing the cavity 22b. However, in this embodiment, the cavity 22b and the discharge auxiliary electrode 5 are not necessarily provided. In this case, for example, a porous layer in which a material having a voltage non-linear characteristic, a metal, a semiconductor, or the like is dispersed may be provided in a region between the first and second discharge electrodes 3 and 4. .

  In the present invention, the positional relationship between the first and second discharge electrodes, the discharge auxiliary electrode, and the back electrode is not limited to the positional relationship schematically shown in FIGS. That is, as shown in FIG. 5, the first discharge electrode 3 and the second discharge electrode 4 may be arranged such that the side edges in the vicinity of the front ends are opposed to each other with a gap therebetween, instead of the front ends. . Even in this case, the back electrode 11 and the auxiliary discharge electrode 5 may be arranged so as to overlap at least a part of the region where the gap is provided when viewed in plan. Furthermore, as shown in FIG. 6, the back electrode 11 may be disposed so as to include the entire region of the gap.

  FIG. 7 is a front sectional view of an ESD protection apparatus according to the third embodiment of the present invention. FIG. 8 is a schematic plan view showing the positional relationship among the first and second discharge electrodes 3, 4, the discharge auxiliary electrode 5, and the back electrode 11 in the ESD protection apparatus of the third embodiment. . As shown in FIGS. 7 and 8, in the third embodiment, the back electrode 11 is drawn out to the end face of the substrate 2 and is electrically connected to the second external electrode 10b. Other points are the same as those of the ESD protection apparatus 1 of the first embodiment.

  When the back electrode 11 is electrically connected to the second external electrode 10b as in the present embodiment, the discharge start voltage can be further reduced and thermal degradation can be suppressed.

  Note that the ESD protection device 31 of the third embodiment is similar in structure to the ESD protection device 1, and therefore, similarly to the ESD protection device 1, the discharge start voltage can be lowered and the manufacturing process is complicated. It is hard to invite.

  Similarly, FIGS. 9 and 10 are front sectional views of the ESD protection device according to the fourth embodiment, and positions of the first and second discharge electrodes, the discharge auxiliary electrode, and the back electrode in the ESD protection device. It is a typical top view which shows a relationship.

  The ESD protection device 41 according to the fourth embodiment is that the back electrodes 11 and 11A are electrically connected to the second external electrode 10b. In other respects, the fourth embodiment is the same as the second embodiment.

  Also in the fourth embodiment, since the back electrodes 11A and 11 are electrically connected to the second external electrode 10b, the discharge start voltage can be further reduced. Moreover, thermal degradation can also be suppressed.

  Since the ESD protection device 41 of the fourth embodiment is otherwise similar in structure to the ESD protection device 21, the discharge start voltage can be lowered similarly to the ESD protection device 21.

  In the ESD protection devices 1 and 21 of the first and second embodiments, the back electrode 11 and the back electrodes 11 and 11A are provided, but the fifth and sixth embodiments shown in FIGS. 11 and 12 are used. As described above, the back electrode may be omitted.

  Next, specific experimental examples will be described.

(Example 1 and Comparative Example 1)
The ESD protection device of Example 1 and Comparative Example 1 for comparison was manufactured as an example of the second embodiment in the following manner.

(Ceramic green sheet)
A ceramic powder having a ceramic composition mainly composed of Ba, Al, and Si and known as a BAS material was prepared. To this ceramic powder, toluene and echinene were added and mixed, and further a binder resin and a plasticizer were added to obtain a ceramic slurry. This ceramic slurry was molded by a doctor blade method to obtain a mother ceramic green sheet having a thickness of 50 μm.

(Discharge electrode paste)
High dielectric constant material particles shown in Table 1 below and metal particles shown in Table 2 below were prepared.

  In addition, the average particle diameter D50 in Table 2 is an average particle diameter obtained by a laser diffraction flow distribution method.

  Moreover, the specific surface area (SSA) in Table 1 and Table 2 is the value calculated | required by the BET 1-point method using nitrogen gas.

  The high dielectric constant material particles are obtained by pulverizing a single plate of barium titanate having a relative dielectric constant of 2000.

  The high dielectric constant material particles shown in Table 1 above, the metal particles shown in Table 2 and the organic vehicle solution were mixed to obtain a discharge electrode paste P-1 having the composition shown in Table 3 below. For comparison, a discharge electrode paste P-2 not containing high dielectric constant material particles was prepared.

(Discharge auxiliary electrode paste)
CuAl alloy powder having an average particle diameter of 2.5 μm and an Al content of 7% by weight, BaO—Si ₂ —Al ₂ O ₃ glass ceramic powder having an average particle diameter of 0.5 μm, and ethyl cellulose in terpineol And an organic vehicle solution dissolved in a concentration of 10% by weight. These were blended so that the Cu alloy powder accounted for 11.2% by volume of the whole, the BaO—Si ₂ —Al ₂ O ₃ -based glass ceramic powder accounted for 2.8% by volume of the total, and the rest occupied the organic vehicle solution, A discharge auxiliary electrode paste was obtained.

(Cavity forming paste)
A cavity forming paste was obtained by preparing 38% by weight of crosslinked acrylic resin beads having an average particle diameter of 1 μm and 62% by weight of an organic vehicle solution prepared by dissolving 10% by weight of etose resin in terpineol.

(External electrode paste)
80% by weight of Cu powder having an average particle diameter of 1 μm, 5% by weight of an alkali borosilicate glass frit having an average particle diameter of 1 μm and a glass transition point of 620 ° C. and a softening point of 720 ° C., and ethyl cellulose dissolved in terpineol. And 15% by weight of the organic vehicle thus obtained was mixed to obtain an external terminal electrode paste.

(Manufacture of ceramic multilayer substrates)
The discharge auxiliary electrode paste was applied on the mother ceramic green sheet described above, and then the discharge electrode paste was repeatedly applied to the position where the first and second discharge electrodes were to be formed. The facing distance of the gap was 20 μm. Further, the cavity forming paste was applied and dried.

  A plurality of mother ceramic green sheets were laminated on top and bottom of the mother ceramic green sheets coated with the cavity forming paste, and then pressure bonded. In this manner, a mother laminate having a thickness of 0.3 mm was obtained.

  This mother laminate was cut in the thickness direction so as to form the substrate 22 of each ESD protection device, and a 1.0 mm × 0.5 mm planar chip was obtained.

When the CuAl alloy powder in the discharge auxiliary electrode paste is fired, the center becomes Cu and Al is oxidized on the outer surface to form an Al ₂ O ₃ insulating layer. Therefore, in the discharge auxiliary electrode, metal particles coated with a material having no conductivity are dispersed.

  Further, in the discharge electrode, it is considered that Cu is first sintered during firing, and barium titanate, which is a high dielectric constant particle, is discharged to the surface of the discharge electrode, and a large amount exists on the surface.

  A chip was produced as described above to obtain a substrate. An external electrode paste was applied to both end faces of this substrate and baked to form external electrodes. Furthermore, Ni plating and Sn plating layers were formed on the surface of the external electrode by electroplating. An ESD protection device was obtained as described above.

(Evaluation)
An ESD protection device of Comparative Example 1 was obtained in the same manner as in Example 1 except that the ESD protection device of Example 1 obtained as described above and the discharge electrode paste P-2 were used.

  In accordance with IEC standard and IEC61000-4-2, ESD was applied to each ESD protection device obtained as described above from the low voltage side by contact discharge. The operating rate of the ESD protection device at each applied voltage was determined. That is, in 100 samples, the number of samples where discharge started was obtained, and the ratio was used as the operation rate. The operating rate evaluation symbols are as follows.

◎… over 90% ~ 100%
○… More than 50% ~ 90%
Δ: Over 10% to 50%
×: 0% to 10%

  The results are shown in Table 4 below.

  As is clear from Table 4, compared with Comparative Example 1, according to Example 1, the operation rate was high even when static electricity having a lower voltage was applied. That is, it is possible to effectively reduce the discharge start voltage.

  The electrostatic capacitances of the ESD protection devices of Example 1 and Comparative Example 1 were measured with an LCR meter manufactured by Agilent under the conditions of Vbias = 0 V and 1 MHz. As a result, it was 0.05 pF in Comparative Example 1. On the other hand, in Example 1 described above, the capacitance was 0.07 pF.

  In order not to cause signal attenuation in a high-frequency circuit, it is desirable that the capacitance is as small as about 0.5 pF or less. As described above, in Example 1, the capacitance was equivalent to that of Comparative Example 1, and was considerably small as 0.07 pF. Therefore, it can be suitably used with an ESD protection device in a high-frequency circuit.

(Examples 2 and 3)
The discharge electrode paste P-2 used in Comparative Example 1 was used as the back electrode paste.

  On one mother ceramic green sheet, the back electrode paste was screen-printed so as not to be connected to external electrodes. The ESD protection devices of Examples 2 and 3 were obtained in the same manner as in Example 1 except that a mother ceramic green sheet printed with this back electrode paste was inserted.

  In Example 2, the back electrode paste was printed on the ceramic green sheet so that the back electrode was not electrically connected to the first and second external electrodes.

  On the other hand, in Example 3, when printing the back electrode paste, the back electrode paste was printed so as to be finally electrically connected to one of the external electrodes.

  Further, in Examples 2 and 3, the back electrode is provided so that the back electrode is located 10 μm below the position where the first and second discharge electrodes 3 and 4 are formed in the mother laminate stage. It was.

  For the ESD protection devices of Examples 2 and 3 obtained as described above, the discharge start voltage was evaluated in the same manner as in Example 1.

  The results are shown in Table 5 below.

  As is apparent from Table 5, according to Examples 2 and 3, the discharge start voltage can be further reduced as compared with Example 1. That is, it can be seen that the discharge start voltage can be further reduced by forming the back electrode. In addition, in Example 3, since the back electrode is electrically connected to the external electrode, it can be seen that the discharge start voltage can be further reduced as compared with Example 2.

  When the electrostatic capacitances of the ESD protection devices of Examples 2 and 3 were measured in the same manner as in Example 1, they were sufficiently low, 0.08 pF and 0.15 pF, respectively. Therefore, the ESD protection apparatus of Examples 2 and 3 can also be suitably used as an ESD protection element in a high frequency circuit.

Example 4
An electrode paste having the same composition as the discharge electrode paste was used as the back electrode paste. Other structures were the same as in Example 3.

  For the ESD protection apparatus of Example 4 obtained as described above, the discharge start voltage was evaluated in the same manner as in Example 1. The results are shown in Table 6 below.

  As is apparent from Table 6, according to Example 4, the discharge start voltage is further reduced. This is presumably because the high dielectric constant material is dispersed also in the back electrode, so that the electric field concentration becomes stronger and the charging action is further enhanced.

  When the electrostatic capacitance of the ESD protection apparatus obtained in Example 4 was measured, it was sufficiently low at 0.17 pF. Therefore, the ESD protection device obtained in Example 4 can also be suitably used for protection of static electricity in the high-frequency circuit.

DESCRIPTION OF SYMBOLS 1 ... ESD protection apparatus 2 ... Board | substrate 2a ... Upper surface 3, 4 ... 1st, 2nd discharge electrode 5 ... Discharge auxiliary electrode 6 ... High dielectric constant material particle 7a ... Metal particle 7b ... Semiconductor ceramic particle 8, 9 ... Resin layer 10a, 10b ... first and second external electrodes 11, 11A ... back electrodes 21, 31, 41 ... ESD protection device 22 ... substrate 22b ... hollow

Claims (14)

A substrate,
The first and second discharge electrodes provided on the substrate and facing each other with a gap therebetween,
The ESD protection device, wherein the first and second discharge electrodes are made of a mixed material including a metal and a high dielectric constant material having a relative dielectric constant higher than that of the substrate.   The discharge auxiliary electrode which is provided so that the 1st discharge electrode and the 2nd discharge electrode may be connected, and promotes discharge between the 1st and 2nd discharge electrodes is provided. The ESD protection device as described.   The ESD protection device according to claim 2, wherein the discharge auxiliary electrode includes metal particles coated with a material having no conductivity.   The ESD protection device according to any one of claims 1 to 3, wherein a low dielectric constant portion having a relative dielectric constant lower than that of the substrate is located in the gap.   The ESD protection device according to claim 4, wherein the low dielectric constant portion is a cavity.   The ESD protection device according to claim 4, wherein the low dielectric constant portion is made of a solid material having a relative dielectric constant lower than that of the substrate.   The ESD protection apparatus according to claim 6, wherein the solid material having a relative dielectric constant lower than that of the substrate is a resin.   The ESD protection device according to claim 1, further comprising a back electrode provided so as to overlap with a gap between the first and second discharge electrodes via a part of the substrate. First and second external electrodes provided on the substrate and electrically connected to the first and second discharge electrodes, respectively,
The ESD protection device according to claim 1, wherein the back electrode is electrically connected to at least one of the first and second external electrodes.   The ESD protection device according to claim 1, wherein the back electrode is a floating electrode.   The ESD protection device according to claim 8, wherein the back electrode includes a metal and a material having a dielectric constant higher than that of the substrate.   The ESD protection device according to any one of claims 1 to 11, wherein the first and second discharge electrodes are disposed on an outer surface of the substrate.   The ESD protection device according to any one of claims 1 to 11, wherein the first and second discharge electrodes are arranged in the substrate, and the gap is located in the substrate.   14. The ESD according to claim 1, wherein the concentration of the high dielectric constant material is higher on the surfaces of the first and second discharge electrodes than in the first and second discharge electrodes. Protective device.

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