WO2013115054A1

WO2013115054A1 - Electrostatic discharge protection device

Info

Publication number: WO2013115054A1
Application number: PCT/JP2013/051435
Authority: WO
Inventors: 喜人大坪
Original assignee: 株式会社村田製作所
Priority date: 2012-01-30
Filing date: 2013-01-24
Publication date: 2013-08-08
Also published as: JP5874743B2; CN204088879U; JPWO2013115054A1

Abstract

Provided is an electrostatic discharge protection device in which deterioration in electrostatic discharge protection properties can be minimized even after being repeatedly subjected to static electricity and repeatedly subjected to discharge. An electrostatic discharge protection device (1) comprising: a cavity (3) between first and second insulator layers (2a, 2b) of an insulating substrate (2); first and second discharge electrodes (4, 5) formed on the first insulator layer (2a) so as to face each other in the cavity (3) across a gap (G); first and second external electrodes (12, 13) electrically connected to the first and second discharge electrodes (4, 5) and formed on the outer surface of the insulating substrate (2); and recesses (3a, 3b) provided at the periphery (3X) of the cavity (3) and positioned within a plane that includes the bonding interfaces between the second insulator layer (2b) and the first and second discharge electrodes (4, 5) and the first insulator layer (2a).

Description

ESD protection device

The present invention relates to an ESD protection device for protecting against static electricity, and more specifically, first and second discharge electrodes are arranged with a gap in a cavity provided in an insulating substrate. The present invention relates to an ESD protection device.

Various ESD protection devices are used to protect electronic circuit from ESD (Electro-Static Discharge).

The following Patent Document 1 discloses an ESD protection device shown in FIG. The ESD protection device 1001 includes a ceramic multilayer substrate 1002. A cavity 1003 is formed in the ceramic multilayer substrate 1002. First and

second discharge electrodes

1004 and 1005 are provided so as to reach the cavity 1003. The tip of the first discharge electrode 1004 and the tip of the second discharge electrode 1005 are opposed to each other with a gap. A discharge auxiliary portion 1006 is formed so as to face the gap and straddle the first and

second discharge electrodes

1004 and 1005. First and second

external electrodes

1007 and 1008 are formed on both end faces of the ceramic multilayer substrate 1002. The first external electrode 1007 is connected to the first discharge electrode 1004, and the second external electrode 1008 is connected to the second discharge electrode 1005.

WO2008 / 146514A1

In the ESD protection device 1001, there is a possibility that peeling or cracking may occur in the ceramic multilayer substrate 1002 around the cavity 1003 while static electricity is applied and repeated discharge occurs. In particular, in the ceramic multilayer substrate 1002, there is a possibility that separation between ceramic layers or cracks starting from the peripheral portion may occur at the peripheral portion of the cavity indicated by an arrow A in FIG. For this reason, there is a problem that the ESD protection characteristics deteriorate as the discharge is repeated.

An object of the present invention is to provide an ESD protection device in which the ESD protection characteristics are unlikely to deteriorate even if the discharge is repeated to protect against static electricity.

The ESD protection device according to the present invention includes an insulating substrate, first and second discharge electrodes, and first and second external electrodes. The insulating substrate has a first insulator layer and a second insulator layer stacked on the first insulator layer. A cavity surrounded by the first insulator layer and the second insulator layer is formed inside the insulating substrate. The first and second discharge electrodes are opposed to each other with a gap in the cavity. The first and second discharge electrodes are disposed on the first insulator layer. The first external electrode is electrically connected to the first discharge electrode and is formed on the outer surface of the insulating substrate. The second external electrode is electrically connected to the second discharge electrode and is formed on the outer surface of the insulating substrate. In the present invention, the peripheral edge portion of the cavity located on each plane including each junction interface between the second insulator layer, the first insulator layer, the first discharge electrode, and the second discharge electrode is provided. Has a recess.

In the case where a seal layer described later is provided, the joint portion between the seal layer, the first insulator layer, the first discharge electrode, and the second discharge electrode forms the peripheral edge of the cavity. As an expression including such a configuration, “a plane including a bonding interface” is used. When the seal layer is not provided, the peripheral edge of the cavity is located at each junction interface between the second insulator layer, the first insulator layer, the first discharge electrode, and the second discharge electrode. Will be.

In a specific aspect of the ESD protection apparatus according to the present invention, the concave portion is a plane including a bonding interface between the second insulator layer and the first discharge electrode, or the second insulator layer and the second discharge electrode. It is located on the plane including the bonding interface. When the stress is applied at the bonding interface between the second insulator layer and the first or second discharge electrode as compared with the bonding interface between the first insulator layer and the second insulator layer, peeling or Cracks are likely to occur. Therefore, when the concave portion is located on a plane including the bonding interface between the second insulator layer and the first or second discharge electrode, the crack and the peeling at the portion where the crack and the peeling are likely to occur are more effective. Can be suppressed.

In another specific aspect of the ESD protection apparatus according to the present invention, the recess includes a plane including the bonding interface between the second insulator layer and the first discharge electrode, and the second insulator layer and the second discharge electrode. It is located on both of the planes including the bonding interface. In this case, it is possible to more effectively suppress the deterioration of the ESD protection characteristics in the ESD protection device.

In yet another specific aspect of the ESD protection device according to the present invention, the concave portion does not have an acute angle portion when seen in a plan view. In this case, the occurrence of cracks and peeling can be more effectively suppressed, and therefore deterioration of the ESD protection characteristics of the ESD protection device can be more effectively suppressed. As a planar shape having no acute angle portion, a shape made of a curve or a shape made of a plurality of lines forming an obtuse angle can be adopted.

In yet another specific aspect of the ESD protection apparatus according to the present invention, the recess does not reach the gap. In this case, since the concave portion does not reach the gap which is the discharge region, it is possible to suppress the deterioration of the ESD protection characteristics when repeatedly discharged without further causing the deterioration of the ESD protection characteristics.

In still another specific aspect of the ESD protection apparatus according to the present invention, the first and second discharge electrodes have a rectangular shape, and the long sides of the first and second discharge electrodes separate the gap. Facing each other. In this case, since the lengths of the first and second discharge electrode portions along the opposing direction of the first and second discharge electrodes are long, the deterioration of the ESD protection characteristics after repeated discharge is further effectively suppressed. can do.

In still another specific aspect of the ESD protection apparatus according to the present invention, in the first and second discharge electrodes, the long sides of the first and second discharge electrodes opposite to the long sides facing each other. Is located outside the cavity. In this case, the degradation of the ESD protection characteristics can be more effectively suppressed.

The ESD protection device according to the present invention may further include a discharge assist unit that includes metal particles and semiconductor particles and is provided in the gap. In this case, the discharge start voltage can be lowered.

The ESD protection device according to the present invention may further include a seal layer provided so as to cover the inner wall of the cavity. In that case, the peripheral edge of the cavity is located at each joint interface between the seal layer, the first insulator layer, the first discharge electrode, and the second discharge electrode. In the case where the seal layer is provided, the formation accuracy of the cavity can be increased.

According to the present invention, since the peripheral portion of the cavity has a recess, even if an impact due to heat or gas occurs when the discharge is repeated, the force due to the impact is dispersed in the peripheral portion of the cavity due to the presence of the recess. . Therefore, peeling and cracking at the peripheral edge of the cavity can be suppressed. Therefore, even if repeated discharge is performed, it is possible to effectively suppress the deterioration of the ESD protection characteristics.

FIG. 1A is a schematic plan view of an essential part of the ESD protection apparatus according to the first embodiment of the present invention, and FIG. 1B is a line (BB) in FIG. It is front sectional drawing of the ESD protection apparatus in the part which corresponds. FIG. 2 is a schematic plan view showing a main part of the ESD protection apparatus according to the second embodiment of the present invention. FIG. 3 is a schematic plan view showing the main part of the ESD protection apparatus according to the third embodiment of the present invention. FIG. 4 is a schematic plan view showing the main part of the ESD protection apparatus according to the fourth embodiment of the present invention. FIG. 5 is a schematic plan view showing the main part of the ESD protection apparatus according to the fifth embodiment of the present invention. FIG. 6A and FIG. 6B are schematic plan views showing modifications of the shape of the concave portion at the peripheral edge of the cavity according to the present invention. FIG. 7 is a front sectional view showing a conventional ESD protection device.

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

FIG. 1B is a front cross-sectional view of the ESD protection apparatus according to the first embodiment of the present invention, and shows a cross section corresponding to a portion along line BB in FIG. 1A described later.

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.

The insulating substrate 2 has a first insulator layer 2a and a second insulator layer 2b laminated on the first insulator layer 2a. The first and second insulator layers 2a and 2b are formed of the same ceramic material. Therefore, the insulating

layers

2a and 2b of the insulating substrate 2 can be formed by laminating and firing a plurality of ceramic green sheets having the same composition.

In this embodiment, since the compositions of the first and second insulator layers 2a and 2b are the same, the shrinkage behavior upon firing is the same. However, the first insulator layer 2a and the second insulator layer 2b may be formed of different ceramic materials.

A cavity 3 is formed in the insulating substrate 2. When the insulating substrate 2 is obtained by firing, the cavity 3 is formed by removing the resin provided in the portion where the cavity 3 is located by heating and vaporizing the binder resin in the ceramic green sheet. . A first discharge electrode 4 and a second discharge electrode 5 are formed on the first insulator layer 2a. In the present embodiment, the first and

second discharge electrodes

4 and 5 are made of Cu. However, the first and

second discharge electrodes

4 and 5 can be formed of other metals or alloys.

In the present embodiment, the first discharge electrode 4 and the second discharge electrode 5 have first and second

long sides

4b, 4c, 5b, and 5c extending in the length direction, respectively. The long side 4b and the long side 5b are opposed to each other with a gap G therebetween. Accordingly, the distance along the length direction of the facing portions of the first and

second discharge electrodes

4 and 5 across the gap G is increased. Therefore, it is possible to suppress an increase in the discharge start voltage. When discharge occurs, the

long sides

4b and 5b facing each other through the gap G are melted or the electrode material disappears. Accordingly, the facing distance becomes longer in that portion, but when discharging is performed by applying static electricity next, discharge occurs in the remaining portion where the facing distance is not long. Therefore, even if the discharge is repeatedly performed by the amount of the distance along the length direction of the facing portions, the increase in the discharge start voltage can be suppressed.

FIG. 1A is a schematic plan view of the ESD protection device 1 in a state where an upper second insulator layer 2b and an upper seal layer 11 described later are removed. In FIG. 1A, the peripheral portion of the cavity 3 is indicated by a one-dot chain line. This peripheral portion is the outer peripheral edge of the cavity 3, and includes a plane including the junction interface between the second insulator layer 2b and the first and

second discharge electrodes

4 and 5, and the second insulator layer. 2b and the first insulator layer 2a are located on a plane including the bonding interface. That is, the peripheral portion 3X of the cavity 3 is formed between the second insulator layer 2b and the upper surfaces of the first and

second discharge electrodes

4 and 5 in the portion where the first and

second discharge electrodes

4 and 5 are present. It is located on a plane including the junction interface, and is located on a plane including the junction interface of the first and second insulator layers 2a and 2b in a portion where the first and

second discharge electrodes

4 and 5 are not located. Will be.

The “plane including the bonding interface” is used to include a configuration in which the upper seal layer 11 described below is provided.

That is, in the present embodiment, the upper seal layer 11 is provided on the surface facing the cavity 3 of the second insulator layer 2b. Therefore, the peripheral edge portion 3X of the cavity 3 is located on the inner surface of the upper seal layer 11 on each of the bonding interfaces. In other words, since the upper seal layer 11 is provided on the inner wall of the cavity 3, the peripheral edge portion 3X of the cavity 3 is the inner edge of the joint portion between the upper seal layer 11 and the first insulator layer 2a, the upper seal layer. 11 and the inner edge of the joint portion between the first and

second discharge electrodes

4 and 5. Even in this case, the peripheral edge portion 3X of the cavity 3 includes the junction interface between the second insulator layer 2b, the first insulator layer 2a, and the first and

second discharge electrodes

4 and 5 described above. It will be located in the plane.

However, a structure in which the upper seal layer 11 is not provided may be used. In that case, the peripheral edge portion 3X of the cavity 3 is located at each junction interface between the second insulator layer 2b, the first insulator layer 2a, and the first and

second discharge electrodes

4 and 5.

A discharge auxiliary portion 6 is provided so as to straddle the first and

second discharge electrodes

4 and 5. The discharge auxiliary portion 6 is made of a particle dispersion in which metal particles 6a whose surfaces are coated with an inorganic material having no conductivity and semiconductor ceramic particles 6b 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.

Since the discharge auxiliary portion 6 in which the metal particles 6a and the semiconductor ceramic particles 6b are dispersed is formed, a discharge using creeping discharge between the first discharge electrode 4 and the second discharge electrode 5 is performed. The discharge start voltage can be lowered. Therefore, protection from static electricity can be achieved more effectively.

In FIG. 1B, the metal particles 6a and the semiconductor ceramic particles 6b of the auxiliary discharge portion 6 are shown so as to enter the first and

second discharge electrodes

4 and 5 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 6a and the semiconductor ceramic particles 6b and further forming the first and

second discharge electrodes

4 and 5. This is because the metal particles 6a and the semiconductor ceramic particles 6b partially enter the first and

second discharge electrodes

4 and 5 when they are laminated together with a plurality of ceramic green sheets by an integrated ceramic firing technique. Therefore, the discharge auxiliary portion 6 is formed so as to straddle the first and

second discharge electrodes

4 and 5. The discharge auxiliary portion 6 does not enter the first and

second discharge electrodes

4 and 5, and may be provided only in the gap portion between the first and

second discharge electrodes

4 and 5, or the discharge auxiliary portion 6 may not be provided.

In the present embodiment, the lower seal layer 10 is formed on the lower surface of the discharge auxiliary portion 6. Similarly, an upper seal layer 11 is formed above the cavity 3.

The lower seal layer 10 and the upper seal layer 11 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 10 and the upper seal layer 11 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, the lower seal layer 10 is formed on the upper surface of the first insulator layer 2a, and the discharge assisting portion 6 described above is laminated on the lower seal layer 10. The upper surface of the discharge assisting part 6 faces the cavity 3. That is, the lower surface of the cavity 3 is the upper surface of the discharge auxiliary portion 6. On the other hand, the upper surface of the cavity 3 is covered with the upper seal layer 11. Note that the lower seal layer 10 and the upper seal layer 11 are not necessarily provided.

As shown in FIG. 1A, a first external electrode 12 is formed so as to cover the end face 2c of the insulating substrate 2. On the other hand, the first discharge electrode 4 is drawn out to the end face 2c. Accordingly, the plurality of first discharge electrodes 4 are electrically connected by the first external electrode 12. Similarly, a plurality of second discharge electrodes 5 led out to the opposite end face 2d are electrically connected to a second external electrode 13 provided so as to cover the end face 2d.

The first and second

external electrodes

12 and 13 are made of an appropriate metal or alloy such as Cu, Al, or Ag.

The feature of the present embodiment is that the cavity 3 is provided with

recesses

3a and 3b in the peripheral edge portion 3X when viewed in plan. The

recesses

3a and 3b are recesses that are open to the outside of the gap G at the peripheral edge 3X.

Since the

recesses

3a and 3b are provided, even if the discharge is repeated, peeling between the first and second insulator layers 2a and 2b, and the second insulator layer 2b and the first and second layers Peeling between the

discharge electrodes

4 and 5 hardly occurs. Thereby, even if it discharges repeatedly, the raise of a discharge start voltage can be suppressed. This will be described more specifically.

While using the ESD protection device 1, static electricity is repeatedly applied. In this case, an impact is generated due to heat generated at the time of occurrence of discharge or expansion of gas in the cavity 3. Of the inner surface of the cavity 3, the portions that are vulnerable to impact are the above-described bonding interfaces. Therefore, when a large impact is applied to the peripheral edge portion 3X located at each joint interface, the joint interface between the first and second insulator layers 2a and 2b, the second insulator layer 2b and the first and Separation occurs at the bonding interface with the

second discharge electrodes

4 and 5. In particular, when an impact is applied to the bonding interface between the second insulator layer 2b made of a different material and the first and

second discharge electrodes

4 and 5, peeling or cracking is likely to occur. When such peeling or cracking occurs, the discharge start voltage increases as shown in an experimental example described later.

On the other hand, in the present embodiment, since the

recesses

3a and 3b are provided, the stress due to the impact is dispersed in the peripheral portion 3X. Therefore, the peeling and cracking can be effectively suppressed. Thereby, it is possible to suppress an increase in the discharge start voltage and improve the reliability of the ESD protection apparatus 1.

In particular, in this embodiment, the

recesses

3a and 3b are located on the first and

second discharge electrodes

4 and 5, respectively. In other words, the portion of the first discharge electrode 4 that faces the gap G of the first long side 4b is located in the cavity 3, and the second long side 4c on the opposite side is located outside the cavity 3. . Similarly, in the second discharge electrode 5, the part facing the gap G of the first long side 5 b is located in the cavity 3, and the second long side 5 c on the opposite side is located outside the cavity 3. ing. Therefore, the plane area of the cavity 3 can be reduced and the size can be reduced. Further, although the peripheral edge portion 3X of the cavity 3 is long on the bonding interface between the second insulator layer 2b and the first and

second discharge electrodes

4 and 5, the

recesses

3a and 3b are formed. As a result, an increase in the discharge start voltage can be effectively suppressed. In addition, as described above, since the long side 4b and the long side 4c are opposed to each other with the gap G therebetween, an increase in the discharge start voltage can be effectively suppressed.

FIG. 2 is a schematic plan view showing a main part of the ESD protection device 21 according to the second embodiment of the present invention. In the second embodiment, the

recesses

3a and 3b provided in the peripheral edge portion 3X of the cavity 3 are located not on the first and

second discharge electrodes

4 and 5 but on the first insulator layer 2a. ing. That is, the peripheral edge portion 3X of the cavity 3 has a substantially rectangular shape, but recesses 3a and 3b are provided on a pair of short sides of the substantially rectangular shape. The stress due to the impact described above is dispersed on the short side of the peripheral edge portion 3X of the substantially rectangular cavity 3. Accordingly, it is possible to effectively suppress peeling and cracks caused by an impact between the first and second insulator layers 2a and 2b. However, in the ESD protection apparatus 1 according to the first embodiment, the

recesses

3a and 3b are more likely to be peeled off or cracked than the bonding interface between the second insulator layer 2b and the first insulator layer 2a. Since it is provided at the bonding interface between the insulator layer 2b and the first and

second discharge electrodes

4 and 5, it is possible to more effectively suppress peeling and cracks at the peripheral edge 3X of the cavity 3, so that stress distribution The effect is greater in the first embodiment than in the second embodiment.

FIG. 3 is a schematic plan view showing a main part of the ESD protection apparatus 31 according to the third embodiment of the present invention. In the present embodiment, the peripheral edge 3 </ b> X of the cavity 3 is formed so as to extend to the outside of the second long side 4 c of the first discharge electrode 4 and the second long side 5 c of the second discharge electrode 5. Yes. In this way, the peripheral edge 3X of the cavity 3 reaches not only the first and second

long sides

4b and 5b facing each other via the gap G but also the second

long sides

4c and 5c on the opposite side. It may be formed. Here, the

recesses

3a and 3b are respectively provided on a pair of sides extending in a direction in which the first and

second discharge electrodes

4 and 5 face each other in the peripheral edge portion 3X of the substantially rectangular cavity 3. Similarly to the first embodiment, in this embodiment, the

recesses

3a and 3b are located on the first and

second discharge electrodes

4 and 5, respectively.

Also in this embodiment, since the

recesses

3a and 3b are provided, even if an impact caused by repeated discharge is applied to the peripheral edge 3X of the cavity 3, the stress is dispersed, and the second insulator layer 2b and the first Separation and cracks between the

second discharge electrodes

4 and 5 can be effectively suppressed.

FIG. 4 is a schematic plan view showing a main part of the ESD protection apparatus 41 according to the fourth embodiment of the present invention. In the present embodiment, the first discharge electrode 4 and the second discharge electrode 5 are opposed to each other with the

short sides

4a and 5a located at the tips via the gap G. That is, the short side 4 a of the first discharge electrode 4 and the short side 5 a of the second discharge electrode 5 face each other in the length direction of the ESD protection device 1. A peripheral edge 3X of the cavity 3 is provided so as to surround the gap G. Also in this embodiment, the peripheral edge 3X is provided with

recesses

3a and 3b that open toward the side away from the gap G. The

recesses

3a and 3b are formed so as to reach from the first and

second discharge electrodes

4 and 5 to the junction interface between the first and second insulator layers 2a and 2b. Also in this embodiment, since the

recesses

3a and 3b are provided, the second insulator layer 2b and the first and

second discharge electrodes

4 and 5 It is possible to reliably suppress peeling and cracks at the bonding interface and the bonding interface between the first insulator layer 2a and the second insulator layer 2b.

FIG. 5 is a schematic plan view of an ESD protection device 51 according to a fifth embodiment of the present invention. Also in this embodiment, the

short sides

4a and 5a located on the front end sides of the first and

second discharge electrodes

4 and 5 are opposed to each other with a gap G, as in the ESD protection device 41 shown in FIG. Yes. The peripheral edge 3X of the cavity 3 has a substantially rectangular shape, and the

recesses

3a and 3b are located only on the first and

second discharge electrodes

4 and 5, respectively. Also in this embodiment, the stress due to the impact when the discharge is repeated is alleviated by providing the

recesses

3a and 3b. Therefore, an increase in the discharge start voltage can be effectively suppressed. In FIG. 5, the

recesses

3a and 3b are located only at the junction interface between the second insulator layer 2b and the first and

second discharge electrodes

4 and 5.

In FIG. 1A, the recess 3a extends from the bottom 3a1 extending in the length direction of the first and

second discharge electrodes

4 and 5 and from both ends of the bottom 3a1 to portions outside the recess of the peripheral edge 3X of the cavity 3, respectively. The shape has a pair of hypotenuses 3a2 and 3a3. The angle formed between the base 3a1 and the hypotenuse 3a2 or 3a3 is an obtuse angle. In other words, the recess 3a has an inverted trapezoidal shape. As described above, it is desirable that the portion formed by the two sides in the recess 3a has an obtuse angle, thereby enhancing the stress dispersion effect due to the impact described above.

However, as shown in FIG. 6A, a curved recess 3c may be formed. Alternatively, as shown in FIG. 6B, four or more straight lines may be connected so as to form an obtuse angle to form the recess 3d.

In addition, it is preferable that the recess 3 does not reach the gap G as in the first to fifth embodiments. As a result, variations in the discharge start voltage can be suppressed.

In FIG. 1A, the

recesses

3a and 3b are provided on the first discharge electrode 4 side and the second discharge electrode 5 side via the gap G, but only one of the

recesses

3a or 3b is provided. It may be provided.

Also, the number of recesses is not particularly limited, and three or more recesses may be provided at the peripheral edge of the cavity.

Furthermore, it is preferable that the corner shape of the peripheral edge of the cavity 3 is also formed by an obtuse angle or a curve. Thereby, peeling and cracks starting from the corners of the peripheral edge of the cavity 3 can be suppressed.

Next, the effects of the above-described embodiments will be clarified by describing specific experimental examples.

(Example 1)
As Example 1, the ESD protection apparatus 1 according to the first embodiment was produced.

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 zirconium 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.

Preparation of electrode paste: An electrode paste for constituting the first and

second discharge electrodes

4 and 5 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 Auxiliary Part 6 Forming Paste: Al ₂ O ₃ powder having an average particle size of several nm to several tens of nm was adhered to the surface of Cu particles having an average particle size of 2 μm. Thereby, metal particles whose surfaces were coated with an inorganic material having no conductivity were prepared. Silicon carbide powder having an average particle diameter of 1 μm was blended with the 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 3, 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 10 and the upper seal layer 11, 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. .

A plurality of ceramic green sheets for a ceramic multilayer substrate prepared as described above were laminated. On the obtained laminate, the above-mentioned ceramic paste for forming a seal layer was applied to a portion constituting the lower seal layer 10 by screen printing. Next, the auxiliary electrode forming paste was applied onto the seal layer forming paste. Thereafter, the electrode paste was printed such that the dimension a of the gap G between the first and second discharge electrodes was 30 μm. Further, the cavity forming resin paste was applied. The application area | region of the resin paste for cavity formation was set so that the peripheral part of the cavity shown to Fig.1 (a) might be formed. That is, a substantially rectangular region having an oblique side with a long side of 160 μm, a short side of 80 μm, and a corner having a length of 17 μm. For the

recesses

3a and 3b, the length of the base 3a1 is 20 μm, the length of the hypotenuses 3a2 and 3a3 is 17 μm, and the angle between the base 3a1 and the hypotenuse 3a2 or 3a3 is 45 °.

Next, a seal layer forming paste for forming the upper seal layer was applied so as to cover the portion to which the resin paste was applied.

Furthermore, a plurality of ceramic green sheets for forming a ceramic multilayer substrate were laminated on the upper surface, and the whole was pressure-bonded in the thickness direction.

After that, the laminate is cut in the thickness direction to obtain a laminate chip for each ESD protection device unit, and then an electrode paste is applied to the first and second end faces of the laminate chip, and the external electrodes are attached. Formed. Cu was used as the electrode paste for forming external electrodes.

Next, the laminate chip was baked in a nitrogen atmosphere to obtain an ESD protection device having a length of 1.0 mm × width of 0.5 mm × thickness of 0.3 mm.

The first and

second discharge electrodes

4 and 5 have a length of 550 μm and a width of 40 μm. The gap G was 30 μm, and the lengthwise dimension of the facing portions of the first and

second discharge electrodes

4 and 5 was 100 μm.

(Example 2)
The ESD protection device 21 of the second embodiment shown in FIG. 2 was produced. The dimensions of the

recesses

3a and 3b were the same as in Example 1.

(Example 3)
The ESD protection device 31 of the third embodiment shown in FIG. 3 was produced. In addition, it was the same as that of Example 1 except having set the dimension of the peripheral part of a cavity as follows. The dimension along the length direction of the first and

second discharge electrodes

4 and 5 at the peripheral edge of the cavity is 130 μm, and extends in a direction orthogonal to the direction in which the first and

second discharge electrodes

4 and 5 at the peripheral edge of the cavity extend. The dimension is 170 μm. The corners of the four corners of the peripheral edge of the cavity were dropped so that the length of the hypotenuse was 17 μm. The dimensions of the

recesses

3a and 3b were as follows. That is, the length of the base is 20 μm, the length of the first and second hypotenuses is 15 μm, and the depth of the recess is 10 μm.

(Comparative Example 1)
An ESD protection device of a comparative example was fabricated in the same manner as in Example 1 except that the planar shape of the peripheral edge of the cavity was a substantially rectangular shape having a length of 160 μm × 80 μm and the

recesses

3a and 3b were not provided.

(Comparative Example 2)
An ESD protection device of a comparative example was fabricated in the same manner as in Example 3 except that the planar shape of the peripheral edge of the cavity was a substantially rectangular shape having a length of 130 μm × 170 μm and the

recesses

3a and 3b were not provided.

For the ESD protection devices of Examples 1 to 3 and Comparative Examples 1 and 2, (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. The discharge start voltage (V) at which discharge detected on the protection circuit side occurs was determined.

(2) Resistance to repeated ESD: 2 kV application 20 times, 3 kV application 20 times, 4 kV application 20 times, 6 kV application 20 times, 8 kV application 20 times by contact discharge, followed by discharge response to the ESD Sex was evaluated. The peak voltage (V) detected on the protection circuit side is obtained and shown in Table 1 below. It shows that the lower the peak voltage value in the ESD repetition resistance is, the more difficult the deterioration of the discharge response due to the repeated discharge occurs, that is, the increase in the discharge start voltage is suppressed.

The results are shown in Table 1 below.

As is clear from Table 1, in the ESD protection device of the comparative example, the initial ESD discharge response was not sufficient, and further, when static electricity was repeatedly applied, the discharge start voltage increased significantly.

On the other hand, in Examples 1 to 3, not only the ESD discharge response in the initial state is superior to the comparative example, but also the peak voltage, that is, the discharge start even after repeated discharge as described above. The increase in voltage could be effectively suppressed.

In particular, according to Examples 1 and 2, even when the discharge was repeated, the increase in the discharge start voltage could be more effectively suppressed as compared with Example 3.

DESCRIPTION OF SYMBOLS 1 ... ESD protective device 2 ... Insulating

substrate

2a, 2b ... 1st,

2nd insulator layer

2c, 2d ... 1st, 2nd end surface 3 ... Cavity 3X ...

Peripheral part

3a, 3b, 3c, 3d ... Recessed part 3a1 ... bottom 3a2, 3a3 ... hypotenuse 4, 5 ... first and

second discharge electrodes

4a, 5a ...

short sides

4b, 5b ... first

long sides

4c, 5c ... second long sides 6 ... discharge auxiliary portion 6a ... Metal particles 6b ... Semiconductor ceramic element 10 ... Lower seal layer 11 ...

Upper seal layer

12,13 ... First and second

external electrodes

21, 31, 41, 51 ... ESD protection device

Claims

A first insulator layer; and a second insulator layer stacked on the first insulator layer, and surrounded by the first insulator layer and the second insulator layer. An insulating substrate having a hollow formed therein;
First and second discharge electrodes disposed on the first insulator layer to face each other with a gap in the cavity;
A first external electrode electrically connected to the first discharge electrode and formed on an outer surface of the insulating substrate;
A second external electrode electrically connected to the second discharge electrode and formed on the outer surface of the insulating substrate;
The peripheral portion of the cavity located in each plane including the bonding interface between the second insulator layer, the first insulator layer, the first discharge electrode, and the second discharge electrode is a recess. An ESD protection device.
The concave portion is located on a plane including a bonding interface between the second insulator layer and the first discharge electrode or a plane including a bonding interface between the second insulator layer and the second discharge electrode. The ESD protection device according to claim 1.
The concave portion is on both a plane including a bonding interface between the second insulator layer and the first discharge electrode and a plane including a bonding interface between the second insulator layer and the second discharge electrode. The ESD protection device according to claim 1, wherein the ESD protection device is located.
The ESD protection device according to any one of claims 1 to 3, wherein the concave portion does not have an acute angle portion when seen in a plan view.
The ESD protection device according to claim 4, wherein the concave portion is composed of a plurality of lines forming a curve or an obtuse angle.
The ESD protection device according to any one of claims 1 to 5, wherein the concave portion does not reach the gap.
The first and second discharge electrodes have a rectangular shape, and the long sides of the first and second discharge electrodes are opposed to each other with the gap therebetween. The ESD protection device according to Item 1.
The long side of the first and second discharge electrodes opposite to the long sides facing each other in the first and second discharge electrodes is located outside the cavity. 8. The ESD protection device according to 7.
The ESD protection device according to any one of claims 1 to 8, further comprising a discharge assisting portion that includes metal particles and semiconductor particles and is provided in the gap.
A seal layer provided so as to cover an inner wall of the cavity, and a peripheral portion of the cavity includes the seal layer, the first insulator layer, the first discharge electrode, and the second discharge electrode; The ESD protection device according to any one of claims 1 to 9, wherein the ESD protection device is located at each of the bonding interfaces.