JP5648696B2 - ESD protection device and manufacturing method thereof - Google Patents

Description

  The present invention relates to an ESD protection device for protecting against electrostatic discharge (Electro-Static Discharge), and more specifically, in an insulating substrate, first and second discharge electrodes are opposed to each other with a gap therebetween. 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. 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 discharge assisting portion includes metal particles and ceramic particles, and the metal particles and ceramic particles are dispersed in an 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 is generated 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 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.

  An ESD protection device according to the present invention includes an insulating substrate having a cavity, and first and second discharges disposed in the insulating substrate such that tips of the insulating substrate face each other in the cavity. An electrode. A plurality of at least one of the first and second discharge electrodes is provided. In the present invention, connected to the first discharge electrode, electrically 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.

  In a specific aspect of the ESD protection apparatus according to the present invention, a plurality of discharge electrode pairs each including the first discharge electrode and the second discharge electrode are provided. In that case, among the plurality of discharge electrode pairs, the discharge electrode pair melts in the discharge electrode pair with the narrowest gap, and even if the gap becomes larger, other discharges having a gap smaller than the enlarged gap. An increase in the discharge start voltage can be suppressed by the electrode pair.

  In another specific aspect of the ESD protection apparatus according to the present invention, at least one discharge electrode of the first discharge electrode and the second discharge electrode is opposed to at least two discharge electrodes. Common electrode. In the common electrode, the width direction dimension of the tip facing the gap is long. Therefore, for example, when forming by a printing method, the linearity of the tip can be increased, and the accuracy of the discharge start voltage can be increased.

  In yet another specific curved surface of the ESD protection apparatus according to the present invention, the common electrode is connected to the discharge start side potential. If the discharge electrode on the side where the electrons collide is a common electrode when the discharge is repeated, the entire common electrode tends to peel off if a part of the common electrode peels off, but the discharge on the side on which the electrons collide When a plurality of electrodes are formed independently, even if one of the discharge electrodes is peeled off, the other discharge electrodes are formed independently and no peeling occurs. Therefore, the durability of the ESD protection device can be increased.

  In still another specific aspect of the ESD protection apparatus according to the present invention, the empty portion is provided for each discharge electrode pair including the first and second discharge electrodes whose tips are opposed to each other in the cavity portion. . In this case, since the hollow portion can be made small, each discharge electrode pair can more reliably protect against static electricity by effectively using air discharge.

  In still another specific aspect of the ESD protection apparatus according to the present invention, a portion in which the discharge electrode tips of the plurality of discharge electrode pairs including the first and second discharge electrodes facing each other are opposed to each other. Located in one cavity. In this case, it is only necessary to form one cavity, so that the manufacturing process can be simplified.

  In still another specific aspect of the ESD protection device according to the present invention, the insulating substrate has an upper surface and a lower surface, and the first and second discharge electrodes are on the first and second main surfaces. It is formed in a plane at a height position in the parallel insulating substrate layer. In this case, the ESD protection device is easily formed by using a well-known ceramic laminated integrated firing technique in which the ceramic green sheet on which the first and second discharge electrodes are formed and the plain ceramic green sheet are laminated. be able to.

  In still another specific aspect of the ESD protection apparatus according to the present invention, the insulating substrate has an upper surface and a lower surface, and the first and second discharge electrodes extend in a direction connecting the upper surface and the lower surface. Thus, it is formed by a via hole electrode provided in the insulating substrate. Thus, in the present invention, the first and second discharge electrodes may be formed by via hole electrodes. Thereby, the dimension of the surface direction of the insulating substrate of the ESD protection device can be reduced.

  In yet another specific aspect of the ESD protection apparatus according to the present invention, the first discharge electrode and the second discharge electrode at a portion where the tip of the first discharge electrode and the tip of the second discharge electrode are opposed to each other. It is formed so as to straddle the second discharge electrode, and further provided with a discharge auxiliary portion including metal particles and semiconductor particles. The discharge assisting portion includes metal particles and semiconductor particles. By providing the discharge auxiliary portion, the discharge start voltage can be lowered.

  In still another specific aspect of the ESD protection apparatus according to the present invention, the portion is provided so as to face the cavity, and the tips of the first discharge electrode and the second discharge electrode are opposed to each other. And a sealing layer provided so as to surround. When the sealing layer is provided, the above-mentioned cavity can be formed with higher accuracy.

  In the manufacturing method of the ESD protection device according to the present invention, the first discharge electrode and the second discharge electrode are arranged in a laminated body in which a plurality of ceramic green sheets are laminated so that the tips thereof face each other. A step of preparing a laminated body provided with a plurality of at least one of the first and second discharge electrodes, and firing the laminated body to form the first and second discharge electrodes therein. And forming an insulating substrate made of an insulating ceramic sintered body, and forming first and second external electrodes so as to be electrically connected to the first and second discharge electrodes. A process.

  In a specific aspect of the method for manufacturing an ESD protection device according to the present invention, the step of obtaining the laminate includes the steps of preparing first to third ceramic green sheets, the first ceramic green sheet, Forming a first through hole for forming one discharge electrode, and forming a second through hole for forming the second discharge electrode in the second ceramic green sheet; , Filling the first and second through holes of the first and second ceramic green sheets with conductive paste, respectively, and a third for forming the cavity in the third ceramic green sheet A step of forming a through hole, and the first to third ceramic green sheets are arranged such that the first and second through holes filled with a conductive paste overlap the third through hole. The first ceramic green sheets on one side of the ceramic green sheet, and a step of obtaining a second laminate of ceramic green sheets were laminated on the other side. In this case, the laminated body can be obtained easily and with high accuracy by simply laminating the first to third ceramic green sheets.

  In still another specific aspect of the method for manufacturing an ESD protection device according to the present invention, the cavity is provided in each of the portions where the tip of the first discharge electrode and the tip of the second discharge electrode face each other. As formed, the third through hole overlaps each of the portions where the first through hole filled with the conductive paste and the second through hole filled with the conductive paste face each other. Is provided. In this case, a cavity can be formed by the third through hole for each discharge electrode pair composed of the first and second discharge electrodes.

  According to the ESD protection device of the present invention, since at least one of the first and second discharge electrodes is provided in plural, the portion where the first discharge electrode and the second discharge electrode are opposed to each other is There are multiple. When static electricity is applied, discharge occurs in the portion where the gap between the tips of the first and second discharge electrodes is the narrowest. Even if the discharge is repeatedly performed and the size of the gap increases, a discharge occurs in the gap between the first and second discharge electrodes that is smaller than the enlarged gap. Therefore, an increase in the discharge start voltage can be suppressed. Therefore, even when it is used in applications where static electricity is repeatedly applied, it is possible to reliably protect against static electricity, that is, it is possible to increase repeated resistance.

  In addition, since there are at least two discharge start portions, even if the discharge start voltage varies in each portion, it is averaged for each ESD protection device. Therefore, it is possible to mass-produce ESD protection devices with small variations in the discharge start voltage.

FIG. 1A and FIG. 1B are a schematic plan cross-sectional view of an ESD protection device according to the first embodiment of the present invention and a cross-sectional view taken along line BB in FIG. . FIG. 2 is a schematic plan sectional view of a discharge protection device according to a modification of the first embodiment. FIG. 3 is a schematic plan sectional view of a discharge protection device according to another modification of the first embodiment. FIG. 4 is a schematic plan cross-sectional view of a discharge protection device according to still another modification of the first embodiment. FIG. 5A and FIG. 5B are a front sectional view and a partially enlarged front sectional view showing the main part of a discharge protection device according to the second embodiment of the present invention. FIG. 6 is a schematic front cross-sectional view of a discharge protection device according to a modification of the second embodiment. FIG. 7 is a schematic front sectional view of a discharge protection device according to another modification of the second embodiment. FIG. 8 is a schematic front cross-sectional view of a discharge protection device according to still another modification of the second embodiment. FIG. 9 is a partially cutaway front cross-sectional view for explaining the manufacturing method of the ESD protection apparatus according to the second embodiment of the present invention.

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

  1A and 1B are a plan sectional view and a front sectional view of an ESD protection device according to a 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.

  The insulating substrate 2 has a first substrate layer 2a and a second substrate layer 2b. The first and second substrate layers 2a and 2b are made of the same ceramic material. Therefore, the substrate layers 2a and 2b of the insulating substrate 2 can be formed by stacking and firing a plurality of ceramic green sheets having the same composition.

  In the present embodiment, since the compositions of the first and second substrate layers 2a and 2b are the same, the shrinkage behavior during firing is the same. However, the first substrate layer 2a and the second substrate 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, for example, erasing the resin provided in the portion where the cavity 3 is located by heating and vaporizing the binder resin in the ceramic green sheet. .

  On the first substrate layer 2a, a plurality of pairs of discharge electrodes composed of the first discharge electrode 4 and the second discharge electrode 5 are formed. 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.

  As shown in FIG. 1B, the first discharge electrode 4 is extended from the first end face 2 c of the insulating substrate 2 toward the cavity 3 in the portion where the pair of discharge electrodes is formed. ing. The second discharge electrode 5 extends from the second end surface 2d opposite to the first end surface 2c toward the cavity 3 side. In the present embodiment, the cavity 3 is formed for each pair of a plurality of pairs of discharge electrode fingers. Moreover, the cavity 3 is formed in the center of the direction which connects the end surface 2c and the end surface 2d so that the position of a cavity may be shown with a dashed-dotted line in Fig.1 (a).

  The front end 4a of the first discharge electrode 4 and the front end 5a of the second discharge electrode 5 are opposed to each other with a gap G therebetween. That is, the dimension between the tip 4 a of the discharge electrode 4 and the tip 5 a of the discharge electrode 5 is the dimension a of the gap G.

  In the ESD protection device 1, discharge occurs when static electricity is applied between the tips 4 a and 5 a of the first and second discharge electrodes 4 and 5. This discharge uses creeping discharge, air discharge, and auxiliary electrode discharge.

  In the present embodiment, as shown in FIG. 1A, a plurality of discharge electrode pairs each composed of the first discharge electrode 4 and the second discharge electrode 5 are arranged from the side surface 2e toward the opposite side surface 2f. Yes. The feature of this embodiment is that a plurality of discharge electrode pairs are provided as described above, and thereby, the following effects are obtained.

  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.

The metal constituting the metal particle 6a is not particularly limited, and an appropriate metal or alloy such as Cu or Ni is used. Although the diameter of a metal particle is not specifically limited, It is about 2-3 micrometers. As the inorganic material coating the surface of the metal particles 6a, 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 6a 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.

  The semiconductor ceramic particles 6b are made of silicon carbide in the present embodiment. The ESD responsiveness can be improved by dispersing the semiconductor ceramic particles 6b. 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, and silica. 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.

  Moreover, only 1 type may be used for the said semiconductor ceramics, and 2 or more types may be used together. 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 6 in which the metal particles 6a and the semiconductor ceramic particles 6b are dispersed is formed, the creeping discharge between the tip 4a of the first discharge electrode 4 and the tip 5a of the second discharge electrode 5 is performed. It is possible to lower the discharge start voltage during the discharge using. 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 tips of the first and second discharge electrodes 4 and 5. The auxiliary part 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 substrate layer 2 a, and the above-described discharge auxiliary portion 6 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, the first external electrode 12 is formed so as to cover the end surface 2 c 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 drawn out to the 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 ESD protection apparatus 1 of the present embodiment is that a plurality of discharge electrode pairs are provided in the insulating substrate 2 as described above. As a result, it is possible to reliably suppress a decrease in protection characteristics from static electricity when static electricity is repeatedly applied. In addition, variation in the discharge start voltage can be reduced.

  This will be described more specifically.

  While the ESD protection apparatus 1 is being used, static electricity is repeatedly applied. In this case, discharge occurs in the discharge electrode pair having the smallest dimension a of the gap G among the plurality of discharge electrode pairs. When static electricity is repeatedly applied to cause discharge, dissolution of the discharge electrode material occurs at the tip 4a of the first discharge electrode 4 and the tip 5a of the second discharge electrode 5. Therefore, when static electricity is repeatedly applied, the gap increases in the discharge electrode pair having the smallest gap.

  However, in this embodiment, since a plurality of discharge electrode pairs are provided, the gap size in the discharge electrode pair with the smallest gap is large, and the gap size is the smallest among the remaining discharge electrode pairs. It becomes larger than the gap of the discharge electrode pair. In that case, the discharge occurs not in the discharge electrode pair having a large gap but in the discharge electrode pair having the smallest gap a dimension a among the other discharge electrode pairs. Therefore, even if static electricity is repeatedly applied to protect against static electricity, it is possible to reliably suppress an increase in the discharge start voltage. Therefore, it is possible to improve the protection characteristics of the ESD protection device when repeated resistance is applied, that is, when static electricity is repeatedly applied.

  Although not necessarily limited, the ESD protection apparatus 1 is manufactured so that the size of the gap G between the first and second discharge electrodes 4 and 5 is equal between the plurality of discharge electrode pairs. Even in that case, in practice, due to the printing accuracy of the conductive paste when forming the first and second discharge electrodes 4 and 5 and the variation in conditions in various manufacturing processes, between the discharge electrode pairs, There is a possibility that the dimension of the gap G varies.

  However, for example, even if the discharge start voltage varies among the plurality of discharge electrode pairs, the discharge start voltage is averaged in each unit of the mass-produced ESD protection device 1. Therefore, when the ESD protection apparatus 1 of this embodiment is mass-produced, the variation in the discharge start voltage can be reduced.

  In the present embodiment, the cavity 3 is provided in a portion where the first and second discharge electrodes 4 and 5 face each other. By providing the cavity 3 for each pair of the first and second discharge electrodes 4 and 5, it is possible to more reliably protect against static electricity by effectively using the air discharge.

  Next, an example of the manufacturing method of the ESD protection apparatus 1 will be described.

  In manufacturing the ESD protection apparatus 1 of the present embodiment, a plurality of ceramic green sheets for forming the first and second substrate layers 2a and 2b are prepared. Of the plurality of ceramic green sheets, the ceramic paste constituting the upper seal layer 11 is printed on the ceramic green sheet positioned at the bottom of the substrate layer 2b and dried. Next, a resin paste for forming the cavity 3 is applied. Then, after drying the resin paste, a conductive paste for forming the first and second discharge electrodes 4 and 5 is applied, printed and dried. Next, the composite paste for forming the discharge auxiliary portion 6 is printed on the ceramic paste and dried. Next, a ceramic paste for forming the lower seal layer 10 is applied.

  Thereafter, in order to form the substrate layer 2a, a plurality of ceramic green sheets are laminated, and a ceramic green sheet on which a material for forming the discharge electrodes 4, 5 and the discharge auxiliary portion 6 is printed on the top. Are laminated so that the lower seal layer 10 is located on the substrate layer 2a side, and a plurality of plain ceramic green sheets for forming the substrate layer 2b are further laminated thereon. In this way, a laminate for obtaining the insulating substrate 2 is obtained. After obtaining a laminated body, the conductive paste for external electrode formation is apply | coated to a surface end surface. The laminate is pressed in the thickness direction and then fired. In this way, the ESD protection device 1 can be obtained.

  In the above manufacturing method, when firing to obtain the insulating substrate 2, the resin paste is decomposed and gasified at the firing temperature of the ceramic. Included in each paste for forming this gas and the first and second discharge electrodes 4 and 5, the first and second substrate layers 2a and 2b, the lower seal layer 10 and the upper seal layer 11 The cavity 3 is formed by the gas resulting from the vaporization of the binder resin.

  FIG. 2 is a schematic plan sectional view showing an ESD protection device according to a modification of the ESD protection device 1 of the first embodiment. In the ESD protection device 21 of this modification, instead of the plurality of discharge electrodes 5 in the first embodiment, a plurality of common electrodes 22 are formed as second discharge electrodes. The common electrode 22 is formed to face the plurality of first discharge electrodes 4 with a gap interposed therebetween. Specifically, in the present modification, the two second discharge electrodes 5 and 5 of the first embodiment are integrally formed by a single electrode film to form the common electrode 22. Therefore, the common electrode 22 is opposed to the two first discharge electrodes 4 and 4 via a gap.

  The cavity 3A is provided in a portion where one common electrode 22 faces the plurality of first discharge electrodes 4 and 4. In this modification, a plurality of common electrodes 22 are provided, and the cavity 3 </ b> A is formed for each common electrode 22 of the plurality of common electrodes 22.

  As in the ESD protection device 21 of the present modification, two or more, that is, a plurality of second discharge electrodes may be integrated to form a common electrode. In this modification, all the second discharge electrodes are constituted by the common electrode 22, but in the second discharge electrode, the common electrode and the second discharge electrode 5 that is not the common electrode are used in combination. Also good. That is, at least one of the plurality of second discharge electrodes 5 may be the common electrode 22 and the rest may be the second discharge electrode 5 shown in the first embodiment that is not the common electrode 22.

  Further, three or more second discharge electrodes 5 may be integrated into a common electrode.

  In the present modification, the plurality of second discharge electrodes 5 are integrated to form the common electrode 22, but the plurality of first discharge electrodes 4 may be integrated to form the common electrode.

  In the present modification, the second common electrode 22 is preferably a discharge electrode connected to the discharge start side potential. When static electricity is applied and discharge starts, if the electrons collide with the tip of the electrode due to the discharge, there is a risk that the tip may be burnt or peeled off. Such a phenomenon occurs at the tip of the discharge electrode on the side where the electrons collide. When the discharge is repeated and the discharge electrode on the side where the electrons collide is a common electrode, if the common electrode is partially peeled off, the entire common electrode is easily peeled off. However, if a plurality of discharge electrodes on the side where the electrons collide are formed independently, even if one of the discharge electrodes is peeled off, the other discharge electrode is formed independently, so that the peeling occurs. Does not occur. Therefore, it is possible to increase the above-described repeated resistance.

  FIG. 3 is a front sectional view showing another modification of the ESD protection apparatus 1 according to the first embodiment. The ESD protection device 31 of the present modification is the same as the ESD protection device 1 of the first embodiment, except that the cavity 3B is shared by a plurality of discharge electrode pairs. Therefore, about the same part, the description performed in 1st Embodiment is used by attaching | subjecting the same reference number.

  In the ESD protection device 31, the cavity 3 </ b> B is provided in the insulating substrate 2. In FIG. 3, only the position where the cavity 3B is formed is indicated by a one-dot chain line. The cavity 3B is shared by all discharge electrode pairs, not by individual discharge electrode pairs. Therefore, when the insulating substrate 2 is formed, the manufacturing process can be simplified. That is, the cavity 3B can be easily formed by applying the resin paste so as to straddle a plurality of discharge electrode pairs.

  FIG. 4 is a schematic plan sectional view showing still another modification of the ESD protection apparatus 1 of the first embodiment.

  In the ESD protection device 41 of the present embodiment, the second discharge electrode side is constituted by the common electrode 22 as in the ESD protection device 21 shown in FIG. A difference from the modification shown in FIG. 2 is that all the discharge electrode pairs have a common cavity. That is, one cavity 3 </ b> B is formed in the insulating substrate 2. Therefore, the ESD protection device 41 applies the electrode structure of the ESD protection device 21 shown in FIG. 2 and the cavity 3B of the ESD protection device 31 shown in FIG. 3 to the ESD protection device 1 of the first embodiment. Corresponds to the structure. Thus, also in the ESD protection device 41 using the common electrode 22, a structure in which one cavity 3B is formed in the insulating substrate 2 may be adopted.

  FIG. 5A is a schematic front sectional view of an ESD protection device 51 according to a second embodiment of the present invention, and FIG. 5B is a partially cutaway front sectional view showing an enlarged main part thereof. .

  The ESD protection device 51 of the second embodiment has an insulating substrate 52. The insulating substrate 52 is formed of the same material as that of the insulating substrate 2 of the first embodiment. In the present embodiment, first and second discharge electrodes 54 and 55 each formed of a via-hole electrode are formed in a direction connecting the upper surface 52a and the lower surface 52b of the insulating substrate 52. The first discharge electrode 54 and the second discharge electrode 55 are opposed to each other through a cavity 53 provided in the insulating substrate 52. That is, the front end 54 a of the first discharge electrode 54 and the front end 55 a of the second discharge electrode 55 are opposed to each other with a gap positioned in the cavity 53. Also in the second embodiment, a plurality of discharge electrode pairs each including the first discharge electrode 54 and the second discharge electrode 55 are formed. More specifically, a plurality of discharge electrode pairs are distributed between the side surfaces. The first and second discharge electrodes 54 and 55 are made of the same material as the first and second discharge electrodes 4 and 5 in the first embodiment.

  In FIG. 5A, it is pointed out that the main part of one discharge electrode pair is shown in a simplified manner in order to illustrate each discharge electrode pair. The same applies to FIGS. 6 to 8 described later.

  FIG. 5B shows the details of the main part of one discharge electrode pair as a representative.

  As shown in FIG. 5B, the seal layer 57 and the discharge auxiliary portion 56 are also formed in this embodiment so as to straddle the first discharge electrode 54 and the second discharge electrode 55. The seal layer 57 is formed on the inner peripheral surface of the through hole that penetrates the insulating substrate 52. More specifically, it is formed along the inner peripheral surface of the through hole. Note that the seal layer 57 is not necessarily provided. The discharge auxiliary portion 56 is formed along the inner peripheral surface of the through hole that penetrates the insulating substrate 52. In the present embodiment, since the seal layer 57 is formed, the seal layer 57 is formed along the inner peripheral surface of the seal layer 57. The material constituting the discharge auxiliary portion 56 is the same as that of the discharge auxiliary portion 6 of the first embodiment. Therefore, the discharge auxiliary part 56 has the metal particles 6a and the semiconductor ceramic particles 6b whose surfaces are coated with an inorganic material. In addition, the discharge auxiliary | assistant part 56 does not necessarily need to be provided.

  Also in the ESD protection apparatus 51 of the present embodiment, a plurality of discharge electrode pairs including the first and second discharge electrodes 54 and 55 are formed in the insulating substrate 52. Therefore, similarly to the ESD protection device 1, it is possible to suppress an increase in the discharge start voltage when static electricity is repeatedly applied. Moreover, the variation in the discharge start voltage among the plurality of ESD protection devices 51 when the ESD protection device 51 is mass-produced can be reduced.

  In the ESD protection device 51 of the present embodiment, each of the discharge electrode pairs is formed in a through hole that penetrates the insulating substrate 52 as described above. Such a manufacturing method can be obtained by using a known via hole electrode forming method.

  That is, the first and second discharge electrodes 54 and 55 can be formed by via-hole electrodes formed by filling the through holes with the conductive paste.

  An example of a method for manufacturing the ESD protection device 51 will be described.

  In manufacturing the ESD protection device 51, first to third ceramic green sheets for forming the insulating substrate 52 are prepared. The first ceramic green sheet is a ceramic green sheet for forming the first discharge electrode 54. A first through hole for forming the first discharge electrode 4 is formed in the first ceramic green sheet. A plurality of first ceramic green sheets having such first through holes are prepared. The through hole can be formed by an appropriate method such as machining or laser drilling.

  Similarly, a second through hole for forming a second discharge electrode is formed in the second ceramic green sheet. In this way, a second through hole is formed, and a plurality of second ceramic green sheets are prepared. The number of the first and second ceramic green sheets may be selected according to the height dimension of the first and second discharge electrodes.

  Next, a third through hole for forming a cavity is formed in the third ceramic green sheet. The third ceramic green sheet has a third through hole on one side of the third ceramic green sheet so that the third through hole of the third ceramic green sheet overlaps with the first and second through holes of the first and second ceramic green sheets. One ceramic green sheet and a second ceramic green sheet are laminated on the other side. In this way, a laminate is obtained. By firing the laminate thus obtained, a plurality of discharge electrode pairs in which the first and second discharge electrodes 54 and 55 are opposed to each other through the cavity derived from the third through hole are obtained. It can be formed in the insulating substrate 52.

  In the present embodiment, as described above, the seal layer 57 and the discharge auxiliary portion 56 are formed. In order to form the sealing layer 57 and the auxiliary discharge portion 56, the structure shown in FIG.

  As shown in FIG. 9, in the third ceramic green sheet 64, the seal layer 57 is formed on the inner peripheral surface of the third through hole 64a, and then the discharge auxiliary portion 56 is formed on the surface of the seal layer 57. To do.

  The sealing layer may be formed by applying a constituent material to the sealing layer 57 on the inner peripheral surface of the third through hole 64a. Specifically, the third through hole 64a is filled with a ceramic paste constituting the seal layer 57. After drying, the through hole is formed again so that the ceramic paste layer for constituting the seal layer 57 remains on the inner peripheral surface of the third through hole 64a. Next, a composite paste for constituting the discharge assisting portion 56 may be applied to the inner peripheral surface of the seal layer 57 formed on the inner peripheral surface of the third through hole 64a. Specifically, after the composite paste is filled in the third through hole 64a, the through hole is formed again, and the composite paste layer is left on the inner peripheral surface.

  By firing the laminated body obtained by laminating the first to third ceramic green sheets, the insulating substrate 52 shown in FIG. 5 can be obtained. That is, in the ESD protection device 51 of the second embodiment, as described above, the first and second discharge electrodes 54 and 55 are formed by the via-hole electrodes by applying the conductive paste into the through holes and baking them. can do. The first and second external electrodes 58 and 59 can be formed by applying the conductive paste to both end faces after obtaining the above laminate, and baking it when the laminate is fired. Alternatively, the external electrodes 58 and 59 may be formed by applying and baking a conductive paste on the upper surface 52a and the lower surface 52b of the insulating substrate 52. Alternatively, other methods such as vapor deposition, plating or sputtering may be used.

  FIG. 6 is a front sectional view showing an ESD protection device 71 according to a modification of the ESD protection device 51 of the second embodiment.

  In the ESD protection device 71, the second discharge electrode includes the common electrode 72. The common electrode 72 is obtained by integrating the two second discharge electrodes 55 and 55 of the second embodiment. That is, the ESD protection device 71 of the present modification corresponds to the ESD protection device 21 according to the modification of FIG. 2 shown for the ESD protection device 1 of the first embodiment.

  Even in the structure in which the first and second discharge electrodes are formed using the via-hole electrodes as in the ESD protection device 71, the plurality of second discharge electrodes may be integrated to form a common electrode. In this case, the common electrode 72 is formed of a via hole electrode, like the first discharge electrode 54. That is, it is formed by filling the through hole with a conductive paste and baking it. However, the common electrode 72 is opposed to the plurality of first discharge electrodes 54 and 54 via a gap. Therefore, the common electrode 72 is formed by filling a conductive paste into a large-diameter through hole that overlaps the plurality of first discharge electrodes 54 and 54.

  In the ESD protection device 71 of this modification, a cavity 53 for forming the gap G is formed for each first discharge electrode 54.

  In the ESD protection device 71 as well, like the ESD protection device 21, since the second discharge electrode is the common electrode 72, it is possible to increase the accuracy of the discharge start voltage. That is, the tip 72a of the common electrode 72 has a larger area than the tip of the discharge electrode having a small diameter. Therefore, since the tip is excellent in flatness, the dimension of the gap G can be controlled with high accuracy, and the discharge start voltage can be improved with high accuracy.

  Also in this modification, it is desirable to use the common electrode 72 as an electrode connected to the discharge start side potential. By forming a plurality of discharge electrodes on the side where the electrons collide independently, if the static electricity is repeatedly applied, the other discharge electrodes may be affected even if scorching occurs at the tip of one discharge electrode. Not receive. Therefore, an increase in the discharge start voltage can be suppressed.

  FIG. 7 is a schematic front sectional view showing an ESD protection device 81 according to another modification of the ESD protection device of the second embodiment. In the ESD protection device 81 of this modification, a common cavity 53A is formed for a plurality of pairs of discharge electrodes. About another point, it is the same as that of the ESD protection apparatus 51 of 2nd Embodiment. Also in the ESD protection device 51 of the second embodiment using the via-hole electrode, it is not always necessary to provide a cavity for each discharge electrode pair, and as in this modification, a common cavity 53A is provided for a plurality of discharge electrode pairs. It may be formed. In this case, what is necessary is just to enlarge the through-hole formed in the 3rd ceramic green sheet mentioned above.

  FIG. 8 is a schematic front cross-sectional view of an ESD protection device 91 according to still another modification of the ESD protection device 51. In the ESD protection device 91 of this modification, the second discharge electrode is the common electrode 72 as in the ESD protection device 71, and one common to the plurality of discharge electrode pairs is the same as the ESD protection device 81. The cavity 53A is formed. Other points are the same as those of the ESD protection device 51. Thus, also in the ESD protection apparatus using the common electrode 72, a common cavity 53A may be provided for a plurality of discharge electrode pairs.

  Next, specific experimental examples will be described.

Example 1
As Example 1, the ESD protection apparatus 1 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 700 to 900 ° C. The obtained calcined powder was pulverized 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 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 assisting portion 6 forming paste: By an inorganic material having no conductivity, Al ₂ O ₃ powder having an average particle size of several nanometers to several tens of nanometers attached 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 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. 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.

  Further, 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 number of discharge electrode pairs composed of the first and second discharge electrodes 4 and 5 is six. Further, the width direction dimension of the first and second discharge electrodes 4 and 5 was set to 50 μm.

(Example 2)
As Example 2, the ESD protection device 21 shown in FIG. The difference from Example 1 is that the common electrode 22 is applied with an electrode paste so that the width is 150 μm, and a cavity forming resin paste is applied so as to form a cavity 3A. Same as Example 1.

Example 3
An ESD protection device 31 shown in FIG. This was carried out in the same manner as in Example 1, except that the cavity forming resin paste was applied so as to be common to all the discharge electrode pairs. The other points were the same as in Example 1.

Example 4
An ESD protection device 41 shown in FIG. The difference from the first embodiment is that the common electrode 22 is formed as in the second embodiment, and the cavity 3A is formed as in the third embodiment. The other points were the same as in Example 1.

(Example 5)
The same material as in Example 1 was used. However, as the first and second ceramic green sheets, the first and second through holes were formed by a laser so as to have a diameter of 50 μm. In the third ceramic green sheet for forming the cavity 53A, a through hole having a diameter of φ75 μm was formed as the third through hole. The formed through hole is filled with a ceramic paste for forming a seal layer, and then a through hole having a diameter of 60 μm is formed to form a seal layer on the inner peripheral surface. Next, the mixed paste is filled into the through holes, and then a through hole having a diameter of 50 μm is formed to form an auxiliary electrode portion inside the seal layer.

  Six first ceramic green sheets filled with the first conductive paste for discharge electrode are stacked above one third ceramic green sheet formed as described above, and the second discharge electrode is formed below. Six second ceramic green sheets filled with the conductive paste for use were laminated. The laminate thus obtained was pressure-bonded in the thickness direction. Thereafter, the laminate was cut in the thickness direction to obtain laminate chips in units of individual ESD protection devices. An electrode paste was applied to the upper and lower surfaces of this multilayer chip to form external electrodes. Cu was used as the electrode paste for forming external electrodes. Next, the laminate chip was fired 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.

(Example 6)
An ESD protection device 71 shown in FIG. The difference from Example 5 is that the common electrode 72 is formed by setting the inner diameter of the second through hole formed in the second ceramic green sheet to 150 μm. The other points were the same as in Example 5.

(Example 7)
An ESD protection device 81 shown in FIG. The third ceramic green sheet was the same as Example 5 except that the through hole was φ550 μm and a common cavity 53A was formed in all the discharge electrode pairs.

(Example 8)
An ESD protection device 91 shown in FIG. Except that the diameter of the through hole of the second ceramic green sheet is φ150 μm so that the common electrode 72 is formed, and the through hole provided in the third ceramic green sheet is 550 μm to form the cavity 53A. The same as in Example 5.

(Comparative example)
An ESD protection device was fabricated so as to have only one discharge electrode pair in Example 1. The other points were the same as in Example 1.

  About the ESD protection apparatus of the said Examples 1-8 and a comparative example, (1) ESD discharge responsiveness and (2) ESD repetition tolerance were evaluated in the following ways.

(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), the peak voltage is 600-700V (△ mark), and the peak voltage is 450-600V 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 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. When the peak voltage detected on the protection circuit side exceeds 700V, the ESD repeatability is poor (x mark), the peak voltage is 600 to 700V (△ mark), and the peak voltage is 450 to 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 ESD protection device of the comparative example, when static electricity is repeatedly applied, the discharge protection voltage, that is, the discharge start voltage rises remarkably. In comparison, it can be seen that the repeated resistance can be greatly increased. In particular, in Examples 5 to 8 using the via-hole electrode, it can be seen that the repeated resistance can be further improved as compared with Examples 1 to 4.

  Moreover, it turns out that according to Examples 1-8, it is excellent also about ESD discharge responsiveness compared with a comparative example.

DESCRIPTION OF SYMBOLS 1 ... ESD protective device 2 ... Insulating substrate 2a ... 1st substrate layer 2b ... 2nd substrate layer 2c ... 1st end surface 2d ... 2nd end surface 2e ... Side surface 2f ... Side surface 3 ... Cavity 3A ... Cavity 3B ... Cavity 4 ... First discharge electrode 4a ... Tip 5 ... Second discharge electrode 5a ... Tip 6 ... Discharge auxiliary part 6a ... Metal particles 6b ... Semiconductor ceramic particles 10 ... Lower seal layer 11 ... Upper seal layer 12 ... First External electrode 13 ... Second external electrode 21 ... ESD protection device 22 ... Common electrode 31 ... ESD protection device 41 ... ESD protection device 51 ... ESD protection device 52 ... Insulating substrate 52a ... Upper surface 52b ... Lower surface 53 ... Cavity 53A ... Cavity 54 ... first discharge electrode 54a ... tip 55 ... second discharge electrode 55a ... tip 56 ... discharge assisting portion 57 ... sealing layer 58 ... first external electrode 59 ... second external electrode 64 ... third ceramic Mick green sheet 64a ... third through hole 71 ... ESD protection device 72 ... common electrode 72a ... tip 81 ... ESD protection device 91 ... ESD protection device

Claims (12)

An insulating substrate having a cavity;
A first discharge electrode and a second discharge electrode arranged in the insulating substrate such that the tips of the insulating substrate face each other in the cavity;
A plurality of at least one of the first and second discharge electrodes is provided;
A first external electrode 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 an outer surface of the insulating substrate, wherein the first discharge electrode and the second discharge electrode The ESD protection device, wherein at least one discharge electrode is a common electrode whose tips are opposed to at least two discharge electrodes.   The ESD protection device according to claim 1, wherein a plurality of discharge electrode pairs each including the first discharge electrode and the second discharge electrode are provided.   The ESD protection apparatus according to claim 1, wherein the common electrode is connected to a discharge start side potential. The first distal ends are Oite face the air sinuses, the air-dong discharge electrodes each pair consisting of the second discharge electrodes are provided, according to any one of claims 1 to 3 ESD protection device.   The portion where the discharge electrode tips of the plurality of discharge electrode pairs consisting of the first and second discharge electrodes facing each other are located in one cavity. The ESD protection device according to any one of the above.   The insulating substrate has an upper surface and a lower surface, and the first and second discharge electrodes are formed in a plane at a height position in the insulating substrate layer parallel to the first and second main surfaces. The ESD protection apparatus according to any one of claims 1 to 5, wherein   The insulating substrate has an upper surface and a lower surface, and the first and second discharge electrodes are formed by via-hole electrodes provided in the insulating substrate so as to extend in a direction connecting the upper surface and the lower surface. The ESD protection apparatus according to any one of claims 1 to 5, wherein   The tip of the first discharge electrode and the tip of the second discharge electrode are opposed to each other, and is formed so as to straddle the first discharge electrode and the second discharge electrode. The ESD protection apparatus according to any one of claims 1 to 7, further comprising a discharge auxiliary unit including particles and semiconductor particles.   The seal layer further provided so as to face the cavity and so as to surround a portion where the tips of the first discharge electrode and the second discharge electrode face each other. The ESD protection apparatus of any one of -8. In the laminate formed by laminating a plurality of ceramic green sheets, the first discharge electrode and the second discharge electrode are arranged so that the tips thereof are opposed to each other, and the first and second discharge electrodes And at least one of the first discharge electrode and the second discharge electrode is a common electrode whose tips are opposed to each other. A step of preparing a laminate,
The laminated body is fired, has a cavity, and the first and second discharge electrodes arranged so that the tips thereof are opposed to each other in the cavity are formed inside, and from an insulating ceramic sintered body Forming an insulating substrate,
Forming a first external electrode and a second external electrode so as to be electrically connected to the first discharge electrode and the second discharge electrode. Obtaining the laminate,
Preparing first to third ceramic green sheets;
Forming a first through hole for forming a first discharge electrode in the first ceramic green sheet;
Forming a second through-hole for forming the second discharge electrode in the second ceramic green sheet;
Filling the first and second through holes of the first and second ceramic green sheets with conductive paste, respectively;
The third ceramic green sheet, a step of forming a third through hole for forming the air-dong,
The first to third ceramic green sheets are arranged on one side of the third ceramic green sheet so that the first and second through holes filled with the conductive paste overlap the third through holes. The method for manufacturing an ESD protection device according to claim 10, further comprising: stacking a ceramic green sheet of 1 and a second ceramic green sheet on the other side to obtain a laminate. And the tip of the first discharge electrode, wherein as the tip of the second discharge electrodes the air sinus respective portions facing each other is formed, the third through-hole, the conductive paste is filled The method for manufacturing an ESD protection device according to claim 11, wherein the first through hole and the second through hole filled with the conductive paste are provided so as to overlap each other.

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