WO2012111456A1

WO2012111456A1 - Esd protection device and method of manufacturing same

Info

Publication number: WO2012111456A1
Application number: PCT/JP2012/052504
Authority: WO
Inventors: 喜人大坪
Original assignee: 株式会社村田製作所
Priority date: 2011-02-14
Filing date: 2012-02-03
Publication date: 2012-08-23
Also published as: JP5757294B2; JPWO2012111456A1

Abstract

Provided is an ESD protection device with which it is possible to reliably protect against static electricity, and with which an increase in initial discharge voltage does not easily occur even when static electricity is repeatedly applied. In an ESD protection device (1), a cavity (A) is disposed within an insulating substrate (2), first and second discharge electrodes (3, 4) face one another in the cavity (A) across a gap, and the first and second discharge electrodes (3, 4) are positioned such that the second discharge electrode (4) surrounds the outer peripheral edge of the first discharge electrode (3) across the gap.

Description

ESD protection device and manufacturing method thereof

The present invention relates to an ESD protection device for protecting against electrostatic discharge (Electro-Static Discharge). More specifically, the first and second discharge electrodes are opposed to each other with a gap in an insulating substrate. The present invention relates to an ESD protection device having a structure.

Conventionally, various ESD protection devices have been proposed to protect electronic devices from ESD (Electro-Static Discharge), that is, electrostatic discharge.

For example, Patent Document 1 below discloses an ESD protection device in which first and second discharge electrodes are arranged in an insulating substrate. In the ESD protection device described in Patent Document 1, a cavity is formed in the insulating substrate. The first and second discharge electrodes are formed so as to be exposed in the cavity and so that the tips are opposed to each other in the cavity. The first discharge electrode is drawn out to one end face of the insulating substrate. Further, the second discharge electrode is drawn out to the other end face of the insulating substrate. External electrodes are respectively formed on the pair of end faces of the insulating substrate.

In this ESD protection device, a mixing portion is formed on the lower surface side of the first and second discharge electrodes so as to straddle the first and second discharge electrodes at the portion where the first and second discharge electrodes face each other. ing. The mixing portion includes metal particles and ceramic particles, and the metal particles and the ceramic particles are dispersed in the insulating material in the insulating substrate.

In the ESD protection device of Patent Document 1, the mixing part relaxes the shrinkage behavior during firing and the difference in thermal expansion coefficient after shrinkage between the ceramics constituting the insulating substrate and the first and second discharge electrodes. Can do. Therefore, it is said that the discharge start voltage can be set with high accuracy.

WO2008 / 146514A1

As in the ESD protection device described in Patent Document 1, in an ESD protection device, when static electricity is applied, a discharge occurs between the first and second discharge electrodes facing each other. When this discharge is repeated, the tips of the first and second discharge electrodes are peeled off or dissolved. Accordingly, the gap between the first and second discharge electrodes is increased. As a result, there is a problem that the discharge protection characteristics deteriorate.

An object of the present invention is to provide an ESD protection device in which deterioration of discharge protection characteristics hardly occurs even when discharge is repeated, and a manufacturing method thereof.

The ESD protection device according to the present invention includes an insulating substrate having a cavity and first and second electrodes disposed in the insulating substrate so as to face each other with a gap in the cavity of the insulating substrate. A discharge electrode. In the present invention, the first and second discharge electrodes are arranged so that the outer periphery of the first discharge electrode is surrounded by the second discharge electrode with the gap therebetween. The ESD protection apparatus according to the present invention is connected to the first discharge electrode, and is connected to the first external electrode formed on the outer surface of the insulating substrate and the second discharge electrode. And a second external electrode formed on the outer surface of the insulating substrate.

According to a specific aspect of the ESD protection apparatus according to the present invention, a plurality of the first discharge electrodes are provided, and the second discharge electrode surrounds each of the plurality of first discharge electrodes. Has been placed. In this case, the ESD repeatability can be further enhanced.

In another specific aspect of the ESD protection apparatus according to the present invention, a notch is formed in a part of an electrode edge portion surrounding the first discharge electrode of the second discharge electrode. In this case, the ESD repeatability can be further enhanced.

In still another specific aspect of the ESD protection apparatus according to the present invention, an opposing distance in the gap between the outer peripheral edge of the first discharge electrode and the second discharge electrode is an outer periphery of the first discharge electrode. It is made equal in each position of the peripheral edge. In this case, the ESD discharge responsiveness can be further increased, and the ESD repeatability can be further increased.

In still another specific aspect of the ESD protection apparatus according to the present invention, the electrode edge portion of the second discharge electrode is formed on the first discharge electrode so as to have a frame shape with the gap closed. It arrange | positions so that an outer periphery may be enclosed. Thus, you may have the convex shape with which the said gap was closed. In the present invention, the first and second discharge electrodes may be configured such that an electrode edge of the second discharge electrode surrounds the first discharge electrode except for a part of an outer peripheral edge of the first discharge electrode. May be arranged. In this case, since the electrode edge of the second discharge electrode does not surround the outer periphery of the first discharge electrode at a part of the outer periphery of the first discharge electrode, The adhesion between the upper and lower insulating substrate layers can be improved.

In yet another specific aspect of the ESD protection apparatus according to the present invention, the planar shape of the first discharge electrode is circular. In this case, the ESD discharge response can be further improved.

In yet another specific aspect of the ESD protection apparatus according to the present invention, the first discharge electrode is connected to a discharge start side potential. When the first discharge electrode is connected to the discharge start side potential, the second discharge electrode on the electron receiving side is hardly peeled off, and the ESD repeatability can be increased.

In a more specific aspect of the ESD protection device according to the present invention, in the gap where the first discharge electrode and the second discharge electrode face each other, the first discharge electrode and the second discharge It is formed so as to straddle the electrode, and further includes a discharge assisting portion including metal particles and semiconductor particles. In this case, the discharge start voltage can be lowered.

In still another specific aspect of the ESD protection apparatus according to the present invention, the ESD protection device is provided so as to face the cavity, and at least a part of the gap where the first discharge electrode and the second discharge electrode are opposed to each other. A sealing layer is further provided so as to surround. When the sealing layer is provided, the cavity can be configured with higher accuracy.

In still another specific aspect of the ESD protection apparatus according to the present invention, the first connection electrode electrically connecting the first discharge electrode and the first external electrode, and the second discharge A via hole electrode having a second connection electrode connecting the electrode and the second external electrode, the first connection electrode being connected to an upper surface or a lower surface of the first discharge electrode; A connection electrode portion connected to the via-hole electrode and the first external electrode; In this case, the first discharge electrode surrounded by the second discharge electrode can be reliably electrically connected to the first external electrode by the first connection electrode having the via hole electrode and the connection electrode portion. it can. In the manufacturing method of the ESD protection apparatus according to the present invention, a first ceramic green sheet having a first discharge electrode and a second discharge electrode provided so as to surround the first discharge electrode on the upper surface is prepared. A step of applying a cavity forming material so as to include a gap where the first and second discharge electrodes are opposed to each other, and at least one second ceramic green on the upper surface of the first ceramic green sheet Laminating at least one third ceramic green sheet on the lower surface of the sheet to obtain a laminated body, firing the laminated body, eliminating the cavity forming material, and the first and second discharge electrodes On the outer surface of the laminated body or the outer surface of the insulating substrate so as to be electrically connected to the first and second discharge electrodes. 1st and 2nd external And forming a pole.

In a specific aspect of the manufacturing method of the ESD protection apparatus according to the present invention, when preparing the first ceramic green sheet having the first and second discharge electrodes provided on the upper surface, a plurality of the first discharges are prepared. A first ceramic green sheet is prepared in which an electrode is disposed so as to be surrounded by the second discharge electrode.

In this case, it is possible to provide an ESD protection device having a structure in which the second discharge electrode is disposed so as to surround each of the plurality of first discharge electrodes.

According to the ESD protection device of the present invention, the first and second discharge electrodes are formed so that the outer periphery of the first discharge electrode is surrounded by the second discharge electrode with a gap therebetween. In each of the first discharge electrode and the second discharge electrode, the length of the electrode edge facing the counterpart discharge electrode is sufficiently long. Therefore, even if static electricity is repeatedly applied, the expansion of the minimum facing distance in the gap can be suppressed. Therefore, even if the discharge is repeated, the deterioration of the discharge characteristics can be suppressed. That is, it becomes possible to effectively increase the ESD resistance.

According to the method for manufacturing an ESD protection device according to the present invention, it is possible to provide the ESD protection device of the present invention having excellent ESD repeatability.

FIG. 1A is a plan sectional view of an ESD protection apparatus according to a first embodiment of the present invention, and FIG. 1B is a front sectional view. FIG. 2 is a schematic exploded perspective view for explaining the manufacturing method of the ESD protection apparatus according to the first embodiment of the present invention. FIG. 3 is a schematic plan view showing the shapes of the first and second discharge electrodes in the ESD protection apparatus according to the second embodiment of the present invention. FIG. 4 is a schematic plan view showing the shapes of the first and second discharge electrodes in the ESD protection apparatus according to the third embodiment of the present invention. FIG. 5 is a schematic plan view showing the shapes of the first and second discharge electrodes in the ESD protection apparatus according to the fourth embodiment of the present invention. FIG. 6 is a schematic plan view showing the shapes of the first and second discharge electrodes in the ESD protection apparatus according to the fifth embodiment of the present invention. FIG. 7 is a schematic plan view showing the shapes of the first and second discharge electrodes in the ESD protection apparatus according to the sixth embodiment of the present invention. FIG. 8 is a schematic plan view showing the shapes of the first and second discharge electrodes in the ESD protection apparatus according to the seventh embodiment of the present invention. FIG. 9 is a schematic plan view showing the shapes of the first and second discharge electrodes in the ESD protection apparatus according to the eighth embodiment of the present invention. 10 (a) and 10 (b) are a plan sectional view and a front sectional view of an ESD protection device according to a ninth embodiment of the present invention, and FIG. 10 (c) is a portion showing the main part thereof. It is a notch expansion front sectional view. FIG. 11 is a schematic plan view for explaining the first and second discharge electrodes of the ESD protection apparatus according to the modification of the ninth embodiment of the present invention. FIG. 12 is a schematic plan view for explaining the first and second discharge electrodes of the ESD protection apparatus according to the tenth embodiment of the present invention. FIG. 13 is a schematic plan view for explaining the first and second discharge electrodes of the ESD protection apparatus according to the eleventh embodiment of the present invention. FIG. 14 is a schematic plan view for explaining the first and second discharge electrodes of the ESD protection apparatus according to the twelfth embodiment of the present invention. FIG. 15 is a schematic plan view for explaining the first and second discharge electrodes of the ESD protection apparatus according to the thirteenth embodiment of the present invention. FIG. 16 is a schematic plan view for explaining the first and second discharge electrodes of the ESD protection apparatus according to the fourteenth embodiment of the present invention. FIG. 17 is a schematic plan view for explaining the first and second discharge electrodes of the ESD protection apparatus according to the fifteenth embodiment of the present invention. FIG. 18 is a schematic plan view for explaining the first and second discharge electrodes of the ESD protection apparatus according to the sixteenth embodiment of the present invention. FIG. 19A and FIG. 19B are plan views showing the planar shapes of the first and second discharge electrodes for explaining a modification of the first embodiment. FIG. 20 is a plan sectional view of a conventional ESD protection device prepared for comparison.

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

FIGS. 1A and 1B are a plan sectional view and a front sectional view of an ESD protection device according to the first embodiment of the present invention.

The ESD protection device 1 has an insulating substrate 2. The insulating substrate 2 is made of a ceramic multilayer substrate in the present embodiment. The ceramic material constituting the ceramic multilayer substrate is not particularly limited, but in this embodiment, low-temperature fired ceramic (LTCC) containing Ba, Al, and Si as main components is used.

In this embodiment, the insulating substrate 2 has a rectangular parallelepiped shape. The insulating substrate 2 has an upper surface 2a, a lower surface 2b, a pair of

side surfaces

2c and 2d, a first end surface 2e, and a second end surface 2f opposite to the first end surface 2e.

First and

second discharge electrodes

3 and 4 are formed in a plane at a certain height position of the insulating substrate 2. The planar shape of the first discharge electrode 3 is circular. The second discharge electrode 4 is formed so as to surround the outer peripheral edge of the first discharge electrode 3. The electrode edge 4a surrounding the first discharge electrode 3 of the second discharge electrode 4 is substantially circular and is opposed to the outer peripheral edge of the first discharge electrode 3 with a gap. In the present embodiment, the gap has an annular shape as shown in FIG.

However, in the present embodiment, the plurality of notches 4b are uniformly formed in the circumferential direction in the circular electrode edge 4a.

In the present embodiment, the electrode edge 4a is circular, and the center thereof coincides with the center of the circular first discharge electrode 3. Therefore, the electrode edge 4 a is arranged with a gap having the same size as the outer peripheral edge of the first discharge electrode 3 except for the portion where the notch 4 b is provided. In other words, the opposing distances of the first and

second discharge electrodes

3 and 4 are equal except for the portion where the notch 4b is provided.

The first and

second discharge electrodes

3 and 4 are made of an appropriate metal or alloy such as Cu, Al, or Ag.

In the insulating substrate 2, the gap facing the first and

second discharge electrodes

3 and 4 is located in a ring-shaped gap A provided in the insulating substrate 2. That is, in the gap A, the first discharge electrode 3 and the second discharge electrode 4 face each other with the gap therebetween.

The first external electrode 5 is formed so as to cover the first end face 2e of the insulating substrate 2. A second external electrode 6 is formed so as to cover the second end face 2f.

The first discharge electrode 3 is electrically connected to the first external electrode 5 by the first connection electrode 7. The first connection electrode 7 has a via-hole electrode 7 a and a connection electrode portion 7 b whose upper ends are joined to the lower surface of the first discharge electrode 3. The lower end of the via-hole electrode 7a is connected to the connection electrode portion 7b. The connection electrode portion 7 b is drawn out to the first end surface 2 e and is electrically connected to the first external electrode 5.

The second discharge electrode 4 is electrically connected to the second external electrode 6 by a second connection electrode 8 connected to the second discharge electrode 4.

The first and second

external electrodes

5 and 6 and the first and

second connection electrodes

7 and 8 can be formed of an appropriate metal or alloy such as Cu, Ag, or Ni.

A discharge auxiliary portion 8A is provided so as to straddle the first and

second discharge electrodes

3 and 4. The discharge assisting portion 8A is made of a particle dispersion in which metal particles 8a whose surfaces are coated with an inorganic material having no conductivity and semiconductor ceramic particles 8b are dispersed. More specifically, it is formed by firing a thick film paste containing metal particles whose surfaces are coated with an inorganic material having no conductivity and semiconductor ceramic particles.

The metal constituting the metal particle 8a is not particularly limited, and an appropriate metal or alloy such as Cu or Ni is used. The diameter of the metal particles is not particularly limited, but is about 2 to 3 μm. As the inorganic material coating the surface of the metal particles 8a, not particularly limited, and the like Al ₂ O _3. Such an inorganic material is attached to the surface of the metal particle, and the surface of the metal particle 8a is coated with the inorganic material. As such an inorganic material powder, Al ₂ O ₃ particles having a diameter of 1 μm or less can be used.

In the present embodiment, the semiconductor ceramic particle 8b is made of silicon carbide. The ESD responsiveness can be improved by dispersing the semiconductor ceramic particles 8b. Semiconductor ceramics for obtaining such semiconductor ceramic particles include carbides such as titanium carbide, zirconium carbide, molybdenum carbide or tungsten carbide, nitrides such as titanium nitride, zirconium nitride, chromium nitride, vanadium nitride or tantalum nitride, silicon Silicides such as titanium silicide, zirconium silicide, tungsten silicide, molybdenum silicide or chromium silicide, borides such as titanium boride, zirconium boride, chromium boride, lanthanum boride, molybdenum boride or tungsten boride Alternatively, an oxide such as zinc oxide or strontium titanate can be used. In particular, silicon carbide is particularly preferred because it is relatively inexpensive and commercially available in various particle sizes.

Further, only one kind of the semiconductor ceramics may be used, or two or more kinds thereof may be used in combination. Furthermore, the ceramic particles made of the semiconductor ceramic may be appropriately mixed with an insulating ceramic material such as alumina.

Since the discharge auxiliary portion 8A in which the metal particles 8a and the semiconductor ceramic particles 8b are dispersed is formed, the gap between the outer peripheral edge of the first discharge electrode 3 and the electrode edge 4a of the second discharge electrode 4 is formed. It is possible to reduce the discharge start voltage at the time of discharge using creeping discharge. Therefore, protection from static electricity can be achieved more effectively.

In FIG. 1B, the metal particles 8a and the semiconductor ceramic particles 8b of the discharge auxiliary portion 8A are shown so as to enter the first and

second discharge electrodes

3 and 4 as well. As will be apparent from the manufacturing method described later, this is a conductive paste for printing the thick film paste containing the metal particles 8a and the semiconductor ceramic particles 8b and further forming the first and

second discharge electrodes

3 and 4. This is because the metal particles 8a and the semiconductor ceramic particles 8b partially enter the first and

second discharge electrodes

3 and 4 when printed together and laminated together with a plurality of ceramic green sheets by the ceramic integrated firing technique. Therefore, the discharge auxiliary portion 8A is formed so as to straddle the first and

second discharge electrodes

3 and 4. The discharge auxiliary portion 8A does not enter the first and

second discharge electrodes

3 and 4, and may be provided only in the gap portion between the tips of the first and

second discharge electrodes

3 and 4. The auxiliary portion 8A may not be provided.

In the present embodiment, the lower seal layer 9 is formed on the lower surface of the discharge auxiliary portion 8A. Similarly, an upper seal layer 10 is formed above the cavity A.

The lower seal layer 9 and the upper seal layer 10 are made of ceramics having a higher sintering temperature than the ceramics constituting the insulating substrate 2. In the present embodiment, the lower seal layer 9 and the upper seal layer 10 are made of Al ₂ O ₃ . The ceramic material constituting the sealing layer is not particularly limited as long as the sintering temperature is higher than that of the ceramic material constituting the insulating substrate 2.

In the present embodiment, since the gap is ring-shaped, the discharge auxiliary portion 8A, the lower seal layer 9, and the upper seal layer 10 also have a ring-shaped planar shape.

That is, the upper surface of the discharge auxiliary portion 8A faces the cavity A, and the upper surface of the cavity A is covered with the upper seal layer 10.

In the present invention, the lower seal layer 9, the upper seal layer 10, and the discharge auxiliary portion 8 </ b> A are not necessarily provided.

The feature of the ESD protection apparatus 1 of the present embodiment is that the second discharge electrode 4 is provided so as to surround the outer peripheral edge of the first discharge electrode 3. For example, when the first external electrode 5 is used as an electrode connected to the potential at the discharge start side, discharge is generated from the first discharge electrode 3 toward the second discharge electrode 4 when static electricity is applied. If the discharge is repeated, a phenomenon such as electrode peeling or dissolution of a part of the electrode may occur in the electrode edge portion 4a of the second discharge electrode 4 on the receiving side. However, in this embodiment, even if electrode peeling or electrode material dissolution occurs in part of the electrode edge 4a, the gap has a ring shape. Therefore, the distance between the first and

second discharge electrodes

3 and 4 in the gap is maintained as it is, except for the portion where the electrode peeling or the electrode material is dissolved. That is, the minimum facing distance is maintained and the discharge start voltage is unlikely to increase.

In particular, since the gap is formed over the entire length of the outer peripheral edge of the first discharge electrode 3, the ESD repetition resistance is more effective than a conventional ESD protection device in which rectangular discharge electrodes face each other at the tip. Can be enhanced.

In the present embodiment, the first discharge electrode 3 has a circular planar shape. Accordingly, since electric field concentration is difficult to occur, discharge is likely to occur in any part of the outer peripheral edge of the first discharge electrode 3. Therefore, the discharge start voltage can be lowered. That is, the ESD discharge response can be improved.

In addition, in the present embodiment, the plurality of notches 4b are formed in the electrode edge 4a. Therefore, as will be apparent from experimental examples described later, the discharge response and ESD repetition resistance can be further enhanced. This is because a plurality of cutouts 4b are provided, so that electrode peeling that occurs at one electrode edge surrounded between adjacent cutouts 4b occurs on adjacent electrode edge parts surrounded by adjacent cutouts 4b. It is thought that it is difficult to propagate.

Further, in the present embodiment, the plurality of notches 4b are uniformly distributed in the circumferential direction of the electrode edge 4a. Therefore, the ESD repeat resistance can be further enhanced. However, the plurality of notches may be provided uniformly in the circumferential direction of the electrode edge 4a. In FIG. 1A, the notch 4b is formed in a substantially rectangular shape, but may have any shape as long as the electrode edge 4a is partially cut away.

In FIG. 1A, the second discharge electrode 4 is formed so as to surround the first discharge electrode 3. In this case, the electrode edge 4 a of the second discharge electrode 4 surrounds the first discharge electrode 3 in the entire circumferential length of the outer peripheral edge of the first discharge electrode 3. Therefore, the gap in which the first and

second discharge electrodes

3 and 4 are open has a closed annular shape, that is, a frame shape.

However, in the present invention, as shown in FIG. 19A, a missing portion 4 c may be provided in the electrode edge portion 4 a of the second discharge electrode 4. In the missing part 4c, the second discharge electrode 4 does not exist. Accordingly, in the circumferential direction of the outer peripheral edge of the first discharge electrode 3, the outer peripheral edge of the first discharge electrode 3 and the second discharge electrode 4 face each other at the portion where the missing portion 4 c is provided. Absent.

As described above, the substantially ring-shaped gap does not necessarily have to be a frame shape. In this case, the second discharge electrode 4 does not exist in the missing portion 4c. Accordingly, when a portion where the second discharge electrode 4 does not exist is provided so as to extend from the missing portion 4 c to the outside, the adhesion strength between the upper and lower ceramic layers of the second discharge electrode 4 can be increased.

In addition, as shown in FIG. 19B, in order to connect the first discharge electrode 3 and the external electrode 5, the first connection electrode 7A may be provided so as to pass through the missing portion 4c. In that case, the first connection electrode can be formed on the same plane as the first and

second discharge electrodes

3 and 4. In FIG. 1B, the via hole electrode 7a and the connection electrode portion 7b formed in another layer are provided. On the other hand, when the first connection electrode 7A is formed on the same plane as the first and

second discharge electrodes

3 and 4, there is no need to provide the via-hole electrode 7a and the connection electrode portion 7b. Therefore, the first connection electrode 7A can be formed at the same time when the first and

second discharge electrodes

3 and 4 are formed.

Further, when the first and

second discharge electrodes

3 and 4 are formed by screen printing, the first and

second discharge electrodes

3 and 4 can be formed with higher accuracy. In this process, a paste is applied to a region where an electrode is not formed in advance when forming a discharge electrode, and then an electrode conductive paste is screen-printed. Accordingly, since the resist missing portion is provided, the resist is hardly displaced when the conductive paste is printed. Therefore, the first and second discharge electrodes can be formed with higher accuracy.

However, when the missing portion 4c is not provided, the gap is provided over the entire length of the outer peripheral edge of the first discharge electrode 3, so that the ESD repeatability described above can be further enhanced. . Therefore, in order to improve the protection against ESD, the first embodiment is superior to the modification shown in FIG.

Next, a method for manufacturing the ESD protection apparatus 1 will be described with reference to FIG. In manufacturing the ESD protection device 1, first, the first ceramic green sheet 11 is prepared using insulating ceramics. A ceramic paste 10 </ b> A for forming the upper seal layer 10 is applied on the first ceramic green sheet 11.

Next, the cavity forming material 12A is applied so as to form a ring shape. As the cavity forming material 12A, an appropriate material that disappears upon firing of ceramics described later can be used. In this embodiment, a resin paste is used as the cavity forming material. The application of the resin paste can be performed by an appropriate method such as screen printing.

Next, the first and

second discharge electrodes

3 and 4 are formed by screen printing the conductive paste. Note that the second connection electrode 8 is also formed in the same process so as to be connected to the second discharge electrode 4.

Further, a composite paste for forming the discharge auxiliary portion 8A is printed in a ring shape and dried. Next, a ceramic paste 9A for forming the lower seal layer 9 is applied and dried.

Next, after the first ceramic green sheet 11 is turned upside down, at least one second ceramic green sheet 12 is laminated from above. In addition, at least one third ceramic green sheet 14 to 16 is laminated on the lower surface side of the first ceramic green sheet 11. In the present embodiment, a via hole electrode 7a is formed by providing a through hole in the third ceramic green sheet 14 laminated immediately below the first ceramic green sheet 11 and filling the through hole with a conductive paste. To do. In addition, the connection electrode portion 7 b is formed by screen printing a conductive paste on the upper surface of the third ceramic green sheet 15 laminated on the lower surface of the third ceramic green sheet 14.

After the second ceramic green sheet 12, the first ceramic green sheet 11, and the third ceramic green sheets 14 to 16 are laminated, a laminate is obtained by pressing in the thickness direction. A conductive paste for forming an external electrode is applied to both end faces of the laminate. Next, the laminate is fired, whereby the ESD protection device 1 can be obtained.

In the above manufacturing method, the resin paste is decomposed and gasified when firing to obtain the insulating substrate 2. This gas is contained in each paste for forming the first and

second discharge electrodes

3, 4, the ceramic

green sheets

11, 12, 14 to 16, the lower seal layer 9 and the upper seal layer 10. A ring-shaped cavity A is formed by the gas resulting from the vaporization of the binder resin.

In the first embodiment, the first discharge electrode 3 has a circular shape, and the electrode edge 4a of the second discharge electrode 4 has a substantially circular shape. 1, the shape of the first and

second discharge electrodes

3 and 4 can be variously modified.

3 to 9 are schematic plan views for explaining the planar shapes of the first and second discharge electrodes in the second to eighth embodiments. The second to eighth embodiments are the same as the first embodiment except for the planar shape of the first and second discharge electrodes.

As shown in FIG. 3, in the second embodiment, the second discharge electrode 21 having an elliptical electrode edge 21a is arranged with respect to the first discharge electrode 3 having a circular planar shape. That is, an elliptical electrode edge 21 a is provided so as to surround the outer peripheral edge of the circular discharge electrode 3. Also in the present embodiment, a plurality of notches 21b are uniformly formed in the circumferential direction in the electrode edge portion 21a. In the second embodiment, since the elliptical electrode edge portion 21 a is used, the opposing distance of the gap between the outer peripheral edge of the first discharge electrode 3 and the electrode edge portion 21 a is the first discharge electrode 3. It depends on the position of the outer periphery.

On the other hand, in the third embodiment shown in FIG. 4, the second discharge electrode 22 having a circular electrode edge 22 a is disposed so as to surround the circular first discharge electrode 3. The third embodiment is the same as the first embodiment except that the plurality of notches 4b in the first embodiment are not provided.

In the fourth embodiment shown in FIG. 5, the first discharge electrode 3 has a circular planar shape, and the second discharge electrode 23 has an elliptical electrode edge 23a. The fourth embodiment is the same as the second embodiment except that the notch 21b shown in FIG. 3 is not provided.

As shown in FIG. 6, in the fifth embodiment, the second discharge electrode 25 is disposed so as to surround the first discharge electrode 24 having a square shape. Thus, in the present invention, the planar shape of the first discharge electrode is not limited to a circle but may be a rectangle such as a square. However, the square first discharge electrode 24 having excellent symmetry with respect to the center is more preferable than the rectangular first discharge electrode.

The outer peripheral edge of the first discharge electrode 24 has a square shape. The electrode edge portion 25 a of the second discharge electrode 25 is disposed with a gap equal to the four sides constituting the outer peripheral edge of the first discharge electrode 24. Also in this embodiment, a plurality of notches 25b are provided in a part of the electrode edge 25a.

In the sixth embodiment shown in FIG. 7, the second discharge electrode 26 having the electrode edge 26 a is arranged with respect to the square first discharge electrode 24. The electrode edge 26 a is provided so as to surround the outer peripheral edge of the first discharge electrode 24, but in this embodiment, the facing distance of the gap differs depending on the side of the first discharge electrode 24. That is, the electrode edge portion 26a has a substantially rectangular shape, and the other pair of opposite sides 26a3, 26a4 and the first discharge are compared with the opposing distance of the pair of opposite sides 26a1, 26a2 from the first discharge electrode 24. The distance from the electrode 24 is shorter.

As in this embodiment, the second discharge electrode 26 may be formed so that the opposing distance between the outer peripheral edge of the first discharge electrode 24 and the electrode edge 26a is partially different.

Further, in the seventh embodiment shown in FIG. 8, the second discharge electrode 27 having the same square electrode edge portion 27a is arranged with respect to the first discharge electrode 24 having the square shape. The seventh embodiment is the same as the fifth embodiment except that the plurality of notches 25b are not provided.

As shown in FIG. 9, in the ESD protection apparatus according to the eighth embodiment, a square first discharge electrode 24 is combined with a second discharge electrode 28 having a rectangular electrode edge 28a. Here, it is the same as in the sixth embodiment except that the plurality of notches 26b are not provided.

Also in the second to eighth embodiments, since the second discharge electrode is disposed so as to surround the first discharge electrode, it is possible to improve the ESD repeatability similarly to the first embodiment.

Next, specific experimental examples for the first to eighth embodiments will be described.

Example 1
As Example 1, the ESD protection apparatus according to the first embodiment was obtained.

A BAS material mainly composed of Ba, Al and Si was mixed so as to have a predetermined composition and calcined at a temperature of 800 ° C. to 1000 ° C. The obtained calcined powder was pulverized with a zirconia ball mill for 12 hours to obtain a ceramic powder. To this ceramic powder, an organic solvent composed of toluene and echinene was added and mixed. Furthermore, a binder and a plasticizer were added to obtain a slurry. The slurry thus obtained was molded by a doctor blade method to obtain a ceramic green sheet having a thickness of 30 μm.

An electrode paste for constituting the first and

second discharge electrodes

3 and 4 was prepared as follows. A solvent was added to 80% by weight of Cu particles having an average particle diameter of 2 μm and a binder resin made of ethyl cellulose, and the mixture was stirred and mixed with a three roll to obtain an electrode paste.

Preparation of discharge assisting portion 8A forming paste: by using an inorganic material having no electrical conductivity formed by adhering Al ₂ O ₃ powder having an average particle size of several nm to several tens of nm to the surface of Cu particles having an average particle size of 2 μm Metal particles coated on the surface were prepared. Silicon carbide powder having an average particle diameter of 1 μm was blended with the conductive particles at a predetermined ratio. To this blend, a binder resin and a solvent were added and mixed so that the total ratio of the binder resin and the solvent was 20% by weight to obtain a mixed paste.

As a resin paste for forming the cavity A, a resin paste containing an organic solvent in an appropriate ratio as a solvent with respect to ethyl cellulose was prepared.

As a ceramic paste for forming the lower seal layer 9 and the upper seal layer 10, a ceramic paste for forming a seal layer prepared by mixing alumina powder and an organic solvent as a solvent so as to be 15% by weight of the whole was prepared. .

Using each of the materials described above and in accordance with the manufacturing method described above, however, when forming the first and

second discharge electrodes

3 and 4, the conductive paste so that the diameter of the first discharge electrode 3 is 150 μm. Screen printed. Further, the first and

second discharge electrodes

3 and 4 were printed so that the dimension of the gap between the first and

second discharge electrodes

3 and 4, that is, the facing distance was 30 μm. The width and depth of the notch 4b were 25 μm and 25 μm, respectively.

As described above, an ESD protection device having a length of 1.0 mm × width of 0.5 mm × thickness of 0.3 mm was obtained.

(Example 2 to Example 8)
As Examples 2 to 8, ESD protection devices having first and second discharge electrodes shown in FIGS. 3 to 9, respectively, were produced in the same manner as Example 1. The shapes and dimensions of the first discharge electrode and the second discharge electrode in Examples 2 to 8 were as follows.

Example 2: The first discharge electrode 3 is circular with a diameter of 150 μm. The electrode edge of the second discharge electrode was an ellipse having a major axis of 250 μm and a minor axis of 210 μm. The width and depth of the cutout were 25 μm and 25 μm, respectively.

Example 3: Same as Example 1 except that notch is not provided.

Example 4: Same as Example 2 except that no notch is provided.

Example 5: The first discharge electrode 24 was a square having a side of 150 μm. The electrode edge portion 25a of the second discharge electrode 25 was a square having a side of 150 μm. Accordingly, the gap facing distance is 30 μm. The width and depth of the notch 25b were 25 μm and 25 μm.

Example 6: The same as Example 5 except that the gap facing distance between the pair of sides 26a3 and 26a4 and the first discharge electrode 24 was changed to 40 μm.

Example 7: Same as Example 5 except that the notch 26b was not provided.

Example 8: Same as Example 6 except that the notch 26b was not provided.

For comparison, the conventional ESD protection device 101 shown in FIG. 20 was prepared. In the conventional ESD protection apparatus, the dimensions of the insulating substrate 102 were the same as those in Example 1. The facing distance in the gap was 30 μm. Further, the widths of the tips of the first and

second discharge electrodes

103 and 104 were 150 μm, respectively. Therefore, the tip portions having a width of 150 μm are opposed to each other with a facing distance of 30 μm.

For the ESD protection devices of Examples 1 to 8 and the conventional example, (1) ESD discharge responsiveness and (2) ESD repetition resistance were evaluated as follows.

(1) Discharge responsiveness to ESD Discharge responsiveness to ESD was performed by an electrostatic discharge immunity test defined in IEC standard, IEC61000-4-2. It was investigated whether or not discharge occurred between the discharge electrodes of the sample by applying 8 kV by contact discharge. When the peak voltage detected on the protection circuit side exceeds 700V, the discharge response is poor (x mark), when the peak voltage is 600 to 700V (△ mark), and the peak voltage is 450 to 600V discharge response The discharge response was determined to be particularly good (marked with ◎) when the characteristics were good (marked with ◯) and the peak voltage was less than 450V.

(2) Resistance to ESD Repeating Contact discharge was performed 30 times for 4 kV application, 30 times for 4 kV application, 20 times for 6 kV application, and 20 times for 8 kV application, and then evaluated the discharge response to the ESD. When the peak voltage detected on the protection circuit side exceeds 700V, the ESD repeatability is poor (x mark), when the peak voltage is 600-700V (△ mark), and when the peak voltage is 450-600V ESD repeat A sample having good resistance (◯ mark) and a peak voltage of less than 450 V was determined to have particularly good ESD repeat resistance (marked with ◎).

The results are shown in Table 1 below.

As is apparent from Table 1, in the conventional ESD protection device, when static electricity was repeatedly applied, the discharge start voltage increased significantly.

On the other hand, in Examples 1 to 8, it can be seen that the ESD repeatability can be significantly increased.

Further, by comparing the first to fourth embodiments with the fifth to eighth embodiments, the initial discharge start voltage can be lowered by making the first discharge electrode circular rather than square, that is, the ESD discharge response is improved. Further, it can be seen that the ESD resistance can also be increased.

Further, as is clear from the comparison between Example 1 and Example 2, the comparison between Example 3 and Example 4, the comparison between Example 5 and Example 6, and the comparison between Example 7 and Example 8. It can be seen that by providing a notch at the electrode edge of the second discharge electrode, the discharge start voltage can be lowered, the ESD discharge response can be increased, and the ESD repeatability can be increased.

10 (a) and 10 (b) are a plan sectional view and a front sectional view of an ESD protection device according to the ninth embodiment of the present invention.

In the ESD protection device 31, a plurality of first discharge electrodes 3 are provided in the insulating substrate 2 at the same planar position. A second discharge electrode 4 is formed so as to surround the plurality of first discharge electrodes 3. That is, a plurality of first discharge electrodes 3 shown in FIG. 1 may be provided as in the ESD protection device 31 of the present embodiment.

In the present embodiment, the plurality of notches 4b provided in the second discharge electrode 4 are not provided on the side where the first discharge electrodes 3 are adjacent to each other. For example, in FIG. 10A, in the electrode edge portion 4a of the second discharge electrode 4 surrounding the first discharge electrode 3 positioned on the end face 2f side, the plurality of notches 4b are positioned in the center. It is not provided on the first discharge electrode 3 side. In the first discharge electrode 3 located in the center, the plurality of notches 4b provided on the electrode edge 4a of the second discharge electrode 4 are provided only on the side surface 2c side and the side surface 2d. Yes. The reason why the notch 4b is not provided between the adjacent

first discharge electrodes

3 and 3 is to reduce the space. However, as in the modification shown in FIG. 11, a plurality of notches 4 b may be provided uniformly in the circumferential direction at each electrode edge 4 a of the second discharge electrode 4 surrounding each first discharge electrode 3. .

As shown in FIG. 10B, via hole electrodes 7 a are connected to the lower surface of each first discharge electrode 3 in order to electrically connect the plurality of first discharge electrodes 3 to the first external electrode 5. ing. The lower ends of the plurality of via hole electrodes 7a are electrically connected to the connection electrode portion 7b. About the other structure, the ESD protection apparatus 31 of 9th Embodiment is the same as that of the ESD protection apparatus 1 of 1st Embodiment. Therefore, the same parts are denoted by the same reference numerals, and the description thereof is omitted.

Also in the present embodiment, since the outer peripheral edge of the first discharge electrode 3 is surrounded by the electrode edge 4a of the second discharge electrode 4, the ESD repetition resistance is increased as in the first embodiment. Can do. Also in the present embodiment, the gaps have the same distance in the circumferential direction of the outer peripheral edge of the first discharge electrode 3. Therefore, as in the first embodiment, the ESD repeatability can be further increased.

Furthermore, also in this embodiment, since the planar shape of the first discharge electrode 3 is circular, the ESD discharge response can be improved.

In addition, since the plurality of notches 4b are formed, the ESD repeatability and the ESD discharge response can be further enhanced.

Also in this embodiment, as shown in FIG. 10C, the discharge auxiliary portion 8A is formed so as to straddle the first discharge electrodes 3 and the second discharge electrodes 4, and the lower portion A seal layer 9 and an upper seal layer 10 are provided. Therefore, the discharge start voltage can be lowered and the ESD discharge responsiveness can be increased by forming the discharge auxiliary portion 8A. Further, since the lower seal layer 9 and the upper seal layer 10 are provided, the cavity A can be formed with high accuracy.

Also in the ESD protection device 31 of the ninth embodiment in which a plurality of first discharge electrodes 3 are formed, the shapes of the first discharge electrode 3 and the second discharge electrode 4 can be variously modified. 12 to 18 are schematic plan views for explaining the planar shapes of the first and second discharge electrodes in the tenth to sixteenth embodiments as modifications of the ninth embodiment. is there.

In the tenth embodiment shown in FIG. 12, a plurality of first discharge electrodes 3 are surrounded by electrode edges 4a1 to 4a3 of the second discharge electrode 4, respectively. The difference from the ninth embodiment is that the electrode edges 4a1, 4a2, 4a3 have a circular planar shape, but the electrode edges 4a1, 4a2, 4a3 have different diameters. That is, the electrode edge 4a3 has the largest diameter, the electrode edge 4a2 has the next largest diameter, and the electrode edge 4a1 has the smallest diameter. Therefore, the gap between the first discharge electrode 3 and the second discharge electrode 4 is the largest at the electrode edge 4a3, the next largest at the electrode edge 4a2, and the smallest at the electrode edge 4a1. Thus, when providing a plurality of first discharge electrodes, the opposing distance of the gap between the first discharge electrode and the second discharge electrode may be different for each first discharge electrode, Further, the facing distance of the gap in at least one first discharge electrode may be different from the facing distance of the gap in the remaining first discharge electrodes.

FIG. 13 is a schematic plan view showing the first and second discharge electrodes of the ESD protection apparatus according to the eleventh embodiment. Here, the second discharge electrode 32 having an elliptical electrode edge portion 32a is combined with the plurality of first discharge electrodes 3. That is, the second discharge electrode 32 having an elliptical electrode edge portion 32 a may be combined with the plurality of first discharge electrodes 3.

In the twelfth embodiment shown in FIG. 14, the second discharge electrode 4 having a circular electrode edge 4 a is used for the first discharge electrode 3. That is, the twelfth embodiment is the same as the ninth embodiment except that the notch 4b is not provided.

The thirteenth embodiment shown in FIG. 15 is the same as the tenth embodiment shown in FIG. 12 except that the cutout 4b is not provided.

The fourteenth embodiment shown in FIG. 16 is the same as the eleventh embodiment shown in FIG. 13 except that the notch 4b is not provided.

As shown in FIG. 17, in the fifteenth embodiment, as in the eleventh embodiment, the second discharge electrode 33 has elliptical electrode edges 33a1 to 33a3. However, the sizes of the plurality of electrode edge portions 33a1 to 33a3 are different. Therefore, the gap between the first discharge electrode 3 and the second discharge electrode 4 is different at the electrode edge portions 33a1, 33a2, and 33a3. Other points are the same as those in the eleventh embodiment shown in FIG.

The sixteenth embodiment shown in FIG. 18 is the same as the fifteenth embodiment shown in FIG. 17 except that a plurality of notches are not provided.

As is apparent from FIGS. 12 to 18, even in the ESD protection device in which the plurality of first discharge electrodes are formed, the planar shape of the plurality of first discharge electrodes and the planar shape of the second discharge electrode are appropriately modified. can do. Accordingly, as shown in FIGS. 6 to 9, square or rectangular first and second discharge electrodes and second discharge electrodes having electrode edges having a square or rectangular planar shape may be used.

In the structure in which a plurality of first discharge electrodes are formed, the facing distance of the gap between the second discharge electrode in at least one discharge electrode is made different from the gap facing distance in the remaining first discharge electrodes. In such a case, ESD resistance can be improved.

Next, experimental examples of the ninth to sixteenth embodiments will be described.

Example 9
The ESD protection apparatus of the ninth embodiment was produced as Example 9. Example 1 was the same as Example 1 of the first embodiment except that a plurality of first discharge electrodes 3 were provided.

(Example 10 to Example 16)
As Examples 10 to 16, the ESD protection devices of the tenth to sixteenth embodiments were produced. The difference from Example 9 is the shape of the electrode edge of the second discharge electrode. That is, the shape and dimensions of the second discharge electrode were as follows.

Example 10: Three types of circular electrode edges having diameters of 210, 220, and 230 μm were formed.

Example 11: The electrode edge of the second discharge electrode had an elliptical shape with a major axis = 250 μm and a minor axis = 210 μm.

Example 12: The second discharge electrode was a circle having a diameter of 210 μm and not having a notch.

Example 13: A second discharge electrode was formed in the same manner as in Example 10 except that it did not have a notch.

Example 14: The electrode edge portion of the second discharge electrode was formed in the same manner as in Example 11 except that it did not have a notch.

Example 15: The electrode edges of the three second discharge electrodes are divided into major axis = 250 and minor axis = 210, major axis = 260 and minor axis = 220, and major axis = 270 and minor axis = 230, respectively. An oval shape was adopted. The width and depth of the plurality of notches are the same as those in the ninth embodiment.

Example 16: Same as Example 15 except that a plurality of notches were not provided.

For the ESD protection device obtained in Examples 10 to 16 and the conventional ESD protection device shown in FIG. 20, the ESD discharge response and the ESD repeatability were evaluated in the same manner as in Example 1 described above. The results are shown in Table 2 below.

As is apparent from Table 2, ESD repeatability can be greatly improved in any of Examples 9 to 16 as compared with the conventional example. In addition, the ESD discharge response can be improved.

Further, as is clear from the comparison between Examples 9 to 11 and Examples 12 to 14 and the comparison between Example 15 and Example 16, when a plurality of notches are formed, the ESD repetition resistance is effective. Can be enhanced. This is considered to be because even if electrode peeling occurs in the electrode edge portion sandwiched between the notches due to the formation of a plurality of notches, it is difficult for electrode peeling to propagate to other electrode edge portions.

In addition, according to Example 9, it is possible to increase the ESD repetition resistance compared to Examples 10 and 11. This is because both the edges of the first discharge electrode and the second discharge electrode are circular, and the opposing distance of the gap is substantially equal in the circumferential direction of the outer peripheral edge of the first discharge electrode, so that the discharge start voltage increases. It is thought that it is difficult to occur. Therefore, it is desirable that the gap facing distance is equal in the circumferential direction of the first discharge electrode.

DESCRIPTION OF SYMBOLS 1 ... ESD protection apparatus 2 ... Insulating substrate 2a ... Upper surface 2b ...

Lower surface

2c, 2d ... Side surface 2e ... 1st end surface 2f ... 2nd end surface 3 ... 1st discharge electrode 4 ... 2nd discharge electrode 4a ... Electrode Edge 4b ... notch 4c ... missing part 5 ... first external electrode 6 ... second external electrode 7 ... first connection electrode 7a ... via hole electrode 7b ... connection electrode part 8 ... second connection electrode 8A ... discharge assist Part 8a ... Metal particles 8b ... Semiconductor ceramic particles 9 ... Lower seal layer 9A ... Ceramic paste 10 ... Upper seal layer 11 ... First ceramic green sheet 12 ... Second ceramic green sheet 12A ... Cavity forming materials 14-16 ... First 3 ceramic green sheets 21 ... second discharge electrode 21a ... electrode edge 21b ... notch 22 ... second discharge electrode 22a ... electrode edge 23 ... second discharge electrode 23a ... electrode edge 24 ... first discharge electrode 5 ... second discharge electrode 25a ... electrode edge 25b ... notch 26 ... second discharge electrode 26a ... electrode edge 26b ... notch 27 ... second discharge electrode 27a ... electrode edge 28 ... second discharge electrode 28a ... Electrode edge 31 ... ESD protection device 32 ... Second discharge electrode 32a ... Electrode edge 33 ... Second discharge electrode 33a ... Electrode edge

Claims

An insulating substrate having a cavity;
A first discharge electrode and a second discharge electrode disposed in the insulating substrate so as to face each other with a gap in the cavity of the insulating substrate;
The first and second discharge electrodes are arranged so that the second discharge electrode surrounds the outer periphery of the first discharge electrode with the gap therebetween,
A first external electrode connected to the first discharge electrode and formed on an outer surface of the insulating substrate;
An ESD protection device, further comprising: a second external electrode connected to the second discharge electrode and formed on an outer surface of the insulating substrate.
The ESD protection device according to claim 1, wherein a plurality of the first discharge electrodes are provided, and the second discharge electrodes are disposed so as to surround each of the plurality of first discharge electrodes.
The ESD protection device according to claim 1 or 2, wherein a cutout is formed in a part of an electrode edge portion surrounding the first discharge electrode of the second discharge electrode.
The opposed distance in the gap between the outer peripheral edge of the first discharge electrode and the second discharge electrode is made equal at each position of the outer peripheral edge of the first discharge electrode. The ESD protection device according to any one of the above.
The electrode edge of the second discharge electrode is disposed so as to surround the outer peripheral edge of the first discharge electrode so that the gap has a closed frame shape. The ESD protection device according to any one of the above.
The first and second discharge electrodes are arranged such that the electrode edge of the second discharge electrode surrounds the first discharge electrode except for a part of the outer peripheral edge of the first discharge electrode. The ESD protection device according to any one of claims 1 to 4.
The ESD protection device according to any one of claims 1 to 6, wherein a planar shape of the first discharge electrode is a circle.
The ESD protection device according to any one of claims 1 to 7, wherein the first discharge electrode is connected to a discharge start side potential.
In the gap where the first discharge electrode and the second discharge electrode are opposed to each other, the gap is formed so as to straddle the first discharge electrode and the second discharge electrode. The ESD protection device according to any one of claims 1 to 8, further comprising a discharge assisting unit including semiconductor particles.
The seal layer is further provided so as to face the cavity, and is provided so as to surround at least a part of the gap where the first discharge electrode and the second discharge electrode are opposed to each other. 10. The ESD protection device according to any one of 1 to 9.
A first connection electrode that electrically connects the first discharge electrode and the first external electrode, and a second that connects the second discharge electrode and the second external electrode. The first connection electrode is connected to the via hole electrode connected to the upper surface or the lower surface of the first discharge electrode, and the via hole electrode and the first external electrode. The ESD protection device according to any one of claims 1 to 10, further comprising a connection electrode portion.
Providing a first ceramic green sheet having a first discharge electrode on the upper surface and a second discharge electrode provided so as to surround the first discharge electrode;
Applying a cavity forming material so as to include a gap facing the first and second discharge electrodes;
Laminating at least one second ceramic green sheet on the upper surface of the first ceramic green sheet and at least one third ceramic green sheet on the lower surface to obtain a laminate;
Firing the laminate, eliminating the cavity forming material, and obtaining an insulating substrate having a cavity facing the first and second discharge electrodes;
Forming first and second external electrodes on the outer surface of the laminate or the outer surface of the insulating substrate so as to be electrically connected to the first and second discharge electrodes, Manufacturing method of ESD protection device.
When preparing the first ceramic green sheet having the first and second discharge electrodes provided on the upper surface, a plurality of the first discharge electrodes are arranged so as to be surrounded by the second discharge electrodes. The manufacturing method of the ESD protection apparatus according to claim 12, wherein a first ceramic green sheet is prepared.