JP6079880B2 - ESD protection device - Google Patents

Description

  The present invention relates to an ESD protection device for protecting an electronic circuit from static electricity, and more particularly to an ESD protection device in which discharge electrodes are opposed to each other with a gap.

  Conventionally, various ESD protection devices for suppressing destruction of electronic devices due to electrostatic discharge (ESD) have been proposed.

  For example, Patent Document 1 below discloses a static electricity countermeasure component in which first and second discharge electrode layers having a main surface are provided in a ceramic insulator. The first and second discharge electrode layers are formed such that the principal surfaces face each other with a gap therebetween, and a cavity is provided in the gap.

WO2009 / 069270

  As described in Patent Document 1, in the anti-static component provided so that the main surfaces of the first and second discharge electrode layers face each other, the discharge characteristics deteriorate when repeatedly discharged. There was a problem.

  An object of the present invention is to provide an ESD protection device in which discharge characteristics are not easily deteriorated by repeated discharge.

  An ESD protection apparatus according to the present invention includes a substrate and first and second discharge electrodes provided on the substrate and having a main surface. The main surfaces of the first and second discharge electrodes face each other with a gap in the thickness direction of the substrate. A through hole is provided in at least one of the first and second discharge electrodes facing each other.

  In the ESD protection apparatus of the present invention, preferably, a plurality of the through holes are provided.

  In the ESD protection apparatus according to the present invention, preferably, the through hole is provided in both the first and second discharge electrodes.

  In the ESD protection device according to the present invention, preferably, the planar shape of the through hole is a circle or a rectangle. More preferably, the planar shape is a circle.

  In a specific aspect of the ESD protection apparatus according to the present invention, a cavity is further provided in the substrate, and a portion facing the surface between the first and second discharge electrodes is located in the cavity. ing.

  In another specific aspect of the ESD protection apparatus according to the present invention, the ESD protection device is provided so as to connect the first discharge electrode and the second discharge electrode, and discharge between the first and second discharge electrodes. A discharge auxiliary electrode is further provided. The discharge auxiliary electrode preferably includes metal particles coated with a material having no electrical conductivity.

  According to the ESD protection device of the present invention, it is possible to suppress deterioration of discharge characteristics due to repeated discharge.

FIG. 1 is a front sectional view of an ESD protection device according to a first embodiment of the present invention. 2A and 2B are schematic plan views of the first and second discharge electrodes for explaining the positions of the through holes in the ESD protection apparatus according to the first embodiment of the present invention. is there. FIG. 3 is a schematic plan view for explaining the positional relationship between the first and second discharge electrodes and the cavity of the ESD protection apparatus according to the first embodiment of the present invention. FIGS. 4A and 4B are a front sectional view of an ESD protection device according to a second embodiment of the present invention and a partially cutaway enlarged front sectional view showing a main part provided with a discharge auxiliary electrode. is there. FIG. 5 is a schematic plan view for explaining the positional relationship between the first and second discharge electrodes and the auxiliary electrode of the ESD protection apparatus according to the second embodiment of the present invention. FIG. 6 is a partially cutaway enlarged front sectional view showing a modification of the main part provided with the discharge auxiliary electrode of the ESD protection apparatus according to the second embodiment of the present invention. FIG. 7 is a front sectional view of an ESD protection apparatus according to the third embodiment of the present invention. FIG. 8 is a schematic plan view for explaining a modification of the first and second discharge electrodes in the ESD protection apparatus according to the first embodiment of the present invention. FIG. 9 is a front sectional view of an ESD protection apparatus according to the fourth embodiment of the present invention.

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

  FIG. 1 is a front sectional view of an ESD protection device according to a first embodiment of the present invention.

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

  Inside the substrate 2, first and second discharge electrodes 3 and 4 are provided. The first and second discharge electrodes 3 and 4 are all rectangular when viewed from above. The first and second discharge electrodes 3 and 4 are provided so as to be drawn out to the end faces 2b and 2c, respectively. Hereinafter, a direction in which the first and second discharge electrodes 3 and 4 are drawn out is a length direction, and a direction orthogonal to the length direction is a width direction. Each of the first and second discharge electrodes 3 and 4 has a main surface. The main surfaces of the first and second discharge electrodes 3 and 4, that is, the lower surface of the first discharge electrode 3 and the upper surface of the second discharge electrode 4 are provided so as to face each other with a gap therebetween. .

  A cavity 2 a is provided inside the substrate 2. Both the lower surface of the first discharge electrode 3 and the upper surface of the second discharge electrode 4 are exposed in the cavity 2a. Accordingly, the gap where the first and second discharge electrodes 3 and 4 face each other is located in the cavity 2a.

  The distance between the gaps of the first and second discharge electrodes is not particularly limited, but is preferably 1 to 100 μm, and particularly preferably 5 to 50 μm. If the distance between the gaps is too large, the discharge start voltage cannot be lowered sufficiently. On the other hand, if the distance between the gaps is too small, there is a risk of a short circuit between the discharge electrodes.

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

  In the present embodiment, the first and second discharge electrodes 3 and 4 are provided with through holes 3a and 4a, respectively. However, the through holes 3a and 4a may be provided in at least one of the first and second discharge electrodes 3 and 4, but it is preferable that the through holes 3a and 4a are provided in both as in the present embodiment.

  FIGS. 2A and 2B are schematic plan views for explaining the positions of the through holes 3a and 4a in the first and second discharge electrodes 3 and 4, respectively. The planar shapes of the through holes 3a and 4a are not particularly limited, but are preferably circular or rectangular, and more preferably circular as in this embodiment. The positions of the through holes 3a and 4a in the first and second discharge electrodes 3 and 4 are not particularly limited, but it is preferable that they do not reach the end portions of the first and second discharge electrodes 3 and 4. . This is because the first and second discharge electrodes 3 and 4 described later are likely to be peeled off from the substrate 2 when reaching the end. The through holes 3a and 4a can be provided by providing a non-printing area in the discharge electrode portion, that is, by setting a printed figure. The dimensions of the through holes 3a and 4a are preferably in the range of 1 μm to 20 μm in diameter. Further, the total area of the through holes is preferably about 10 to 80% of the area of the portion of the discharge electrodes 3 and 4 facing each other, and more preferably about 20 to 40%. If the area of the through-hole is too large, the area of the discharge electrode facing portion will be small in the first place, and conversely, it may be difficult to discharge. If the area of the through hole is too small, it is difficult to expect the effect of the present invention.

  As shown in FIG. 1, first and second external electrodes 6 and 7 are formed so as to be electrically connected to the first and second discharge electrodes 3 and 4. The first and second external electrodes 6 and 7 are electrically connected to the first and second discharge electrodes 3 and 4, respectively. The first and second external electrodes 6 and 7 are provided so as to cover the end faces 2 b and 2 c of the substrate 2. The first and second external electrodes 6 and 7 are made of an appropriate metal or alloy.

  FIG. 3 is a schematic plan view for explaining the positional relationship between the first and second discharge electrodes 3 and 4 and the cavity 2a. When viewed in a plan view, the cavity 2 a is provided in a region including a gap between the first and second discharge electrodes 3 and 4. In FIG. 3, in order to clarify the positional relationship between the first discharge electrode 3 and the second discharge electrode 4, the first and second discharge electrodes 3 and 4 are illustrated with a slight shift in the width direction. However, it is not actually shifted in the width direction.

  In the ESD protection device 1, by providing the through holes 3a and 4a, the discharge is promoted and the discharge start voltage is lowered. In particular, in this embodiment, since the through holes 3a and 4a are provided in both the first and second discharge electrodes 3 and 4, the discharge start voltage can be lowered. This is considered to be due to the following reason.

  When the first and second discharge electrodes 3 and 4 are face-to-face, there is no end that was the starting point of discharge, so electric field concentration hardly occurs. However, when the through holes 3a and 4a are provided as in the present embodiment, the end portions of the discharge electrodes are formed around the through holes 3a and 4a. The end of the discharge electrode is exposed in the gap between the first and second discharge electrodes 3 and 4. An electric field concentrates at the end of the discharge electrode. When the electric field concentration occurs, the movement of electrons as the starting point of discharge is promoted, and as a result, the discharge start voltage can be lowered. Therefore, when the through holes 3a and 4a are provided in both the first and second discharge electrodes 3 and 4, electric field concentration is more likely to occur, and the discharge start voltage can be further reduced.

  Moreover, in the ESD protection apparatus 1 according to the present invention, the discharge characteristics are not easily deteriorated by repeated discharge. This is considered to be due to the following reason.

  When the first and second discharge electrodes 3 and 4 face each other and one side surface of the discharge electrode is exposed, peeling occurs due to stress generated during discharge at the interface between the substrate 2 and the discharge electrode. Cheap. This is because the substrate 2 and the discharge electrode are not compatible with each other due to the properties as materials, and the adhesiveness is insufficient. When the discharge electrode is peeled off from the substrate 2, the discharge start voltage varies and the discharge characteristics deteriorate. Such a phenomenon is likely to occur when one side surface of the discharge electrode is in contact with the substrate 2 and the other surface faces the cavity.

  On the other hand, in this embodiment, even when the discharge electrode is partially peeled off, the peeling stress is diffused at the portions of the through holes 3a and 4a, and the peeling can be suppressed. Therefore, even when the discharge is repeated, it is possible to suppress the deterioration of discharge characteristics due to peeling. In addition, when the planar shape of the through-holes 3a and 4a is circular, since there is no part which becomes a starting point of peeling compared with a rectangle, deterioration of discharge characteristics due to repeated discharge can be further suppressed.

  4 (a) and 4 (b) are a front sectional view of an ESD protection device 21 according to a second embodiment of the present invention and a partially cutaway enlarged front sectional view showing an essential part thereof.

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

  First and second discharge electrodes 3 and 4 are disposed in the substrate 22. The first and second discharge electrodes 3 and 4 are drawn out to the end faces 22 a and 22 b of the substrate 22. The lower surface of the first discharge electrode 3 and the upper surface of the second discharge electrode 4 are face-to-face with a gap therebetween. First and second external electrodes 6 and 7 are provided so as to cover the end faces 22 a and 22 b of the substrate 22. In this embodiment, no cavity is provided in the substrate. In the present embodiment, the discharge auxiliary electrode 8 is provided so as to be in contact with the lower surface of the first discharge electrode 3 and the upper surface of the second discharge electrode 4. As shown in a schematic plan view in FIG. 5, the discharge auxiliary electrode 8 is provided in a region including a gap between the first and second discharge electrodes 3 and 4. 5 also shows the first and second discharge electrodes 3 and 4 slightly shifted in the width direction in order to clarify the positional relationship between the first discharge electrode 3 and the second discharge electrode 4. However, it is not actually shifted in the width direction.

  The discharge auxiliary electrode 8 is formed by dispersing metal particles 9 a covered with a material having no conductivity on the upper surface of the substrate 22 and the second discharge electrode 4. More specifically, it is formed by applying and baking a paste containing such metal particles 9a. In this case, the metal particles 9 a covered with the non-conductive material contained in the paste diffuse from the upper surfaces of the substrate 22 and the second discharge electrode 4 to the surface layers of the substrate 22 and the second discharge electrode 4. Is done. As a result, the discharge auxiliary electrode 8 is formed.

  The discharge auxiliary electrode 8 acts to promote discharge between the lower surface of the first discharge electrode 3 and the upper surface of the second discharge electrode 4.

  There is no particular limitation on the material constituting the metal particles 9a coated with the non-conductive material. Examples of the material having no electrical conductivity include insulating ceramics such as alumina, and glass. Moreover, it does not specifically limit about the metal which comprises the metal particle 9a. As such a metal, copper or a copper-based alloy containing copper as a main component is preferably used. However, other metals such as silver, aluminum, molybdenum, tungsten, or alloys mainly composed of other metals may be used.

  In the present embodiment, semiconductor ceramic particles 9b are added to the discharge auxiliary electrode 8 in addition to the metal particles 9a coated with a material having no conductivity. As such semiconductor ceramic particles 9b, particles made of SiC, TiC or the like can be used.

  The discharge auxiliary electrode 8 may be provided on one surface between the gaps of the first and second discharge electrodes as in the present embodiment, or a columnar discharge auxiliary electrode as in a modification described later. A plurality of 8 may be provided.

  When the discharge auxiliary electrode 8 is provided as in the present embodiment, the discharge start voltage can be further reduced. Also in this case, as in the first embodiment, the first and second discharge electrodes 3 and 4 are provided with the through holes 3a and 4a. Therefore, even in the case of repeated discharge, the discharge characteristics based on peeling are obtained. Deterioration can be suppressed.

  FIG. 6 is a partially cutaway enlarged front sectional view showing a modified example of the main part provided with the discharge auxiliary electrode 8 of the ESD protection apparatus 21 according to the second embodiment of the present invention. As shown in FIG. 6, in the present embodiment, a plurality of auxiliary discharge electrodes 8 are provided in a column shape in the substrate 22. Further, a cavity 22c is provided in a portion where the discharge auxiliary electrode 8 is not provided between the gaps of the first and second discharge electrodes 3 and 4. Other points are the same as in the second embodiment.

  When the discharge auxiliary electrode 8 is provided as in the present embodiment, the discharge start voltage can be further reduced.

  Since the ESD protection device 21 of the second embodiment has the same structure as that of the first embodiment, the discharge start voltage can be lowered similarly to the ESD protection device 1, and the discharge characteristics are deteriorated due to repeated discharge. Is unlikely to occur.

  In the ESD protection devices 1 and 21 according to the first and second embodiments, the through holes 3a and 4a are provided in both the first and second discharge electrodes 3 and 4, but the first and second discharge electrodes 3 and 4 are shown in FIG. As in the ESD protection device 31 of the third embodiment, the through hole 3 a may be provided only in one of the first and second discharge electrodes 3 and 4.

  Further, in the ESD protection devices 1 and 21 of the first and second embodiments, the planar shape of the through holes 3a and 4a is circular, but the planar shape is rectangular like the through hole 3b shown in FIG. There may be.

  FIG. 9 is a front sectional view of an ESD protection apparatus according to the fourth embodiment of the present invention.

  In the ESD protection device 41, the first and second discharge electrodes 3 and 4 are arranged on the same plane. A discharge auxiliary electrode 5 is provided on the lower surface of the discharge electrodes 3 and 4. The discharge electrodes 3 and 4 have through holes 3a and 4a. Therefore, similarly to the first embodiment, in the case of repeated discharge, it is possible to suppress deterioration of discharge characteristics due to peeling.

  Next, a specific experimental example will be described.

(Examples 1 and 2 and Comparative Example 1)
The ESD protection device of Examples 1 and 2 as examples of the first embodiment and Comparative Example 1 for comparison was manufactured in the following manner.

(Ceramic green sheet)
A ceramic powder having a composition mainly composed of Ba, Al, and Si and having a ceramic composition known as a BAS material was prepared (relative dielectric constant: 5 to 9). To this ceramic powder, toluene and echinene were added and mixed, and further a binder resin and a plasticizer were added to obtain a ceramic slurry. This ceramic slurry was molded by a doctor blade method to obtain a mother ceramic green sheet having a thickness of 50 μm.

(Discharge electrode paste)
40% by weight of Cu powder having an average particle diameter of 1 μm, 40% by weight of Cu powder having an average particle diameter of 3 μm, and 20% by weight of an organic vehicle prepared by dissolving ethyl cellulose and terpineol, By mixing, the paste for discharge electrodes was produced.

(Cavity forming paste)
38% by weight of crosslinked acrylic resin beads having an average particle diameter of 1 μm and 62% by weight of an organic vehicle solution obtained by dissolving 10% by weight of etosel resin in terpineol were prepared to obtain a cavity forming paste.

(External electrode paste)
Cu powder with an average particle size of 1 μm, glass transition point of 620 ° C., softening point of 720 ° C., alkali borosilicate glass frit with an average particle size of 1 μm, ethyl cellulose in terpineol The dissolved organic vehicle (15% by weight) was mixed to obtain an external terminal electrode paste.

(Manufacture of ceramic multilayer substrates)
The above-mentioned discharge electrode paste was printed so that the planar shape had a circular through-hole at the position where the first and second discharge electrodes were formed on the mother ceramic green sheet. The dimension of the through hole was 5 μm in diameter, and the opposing distance of the gap was 30 μm. Subsequently, the cavity forming paste was applied and dried.

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

  This mother laminate was cut in the thickness direction so as to constitute the substrate of each ESD protection device to obtain a chip that would be a planar substrate of 1.0 mm × 0.5 mm.

  External electrode paste was applied to both end faces of the substrate to form external electrodes. Firing was performed at a firing peak temperature of 950 ° C. Further, a Ni plating layer and a Sn plating layer were formed on the surface of the external electrode by electrolytic plating. An ESD protection device was obtained as described above.

  Obtained in the same manner as in Example 1 except that the ESD protection device of Example 1 obtained as described above and a rectangular through hole having the same area were provided instead of the circular through hole. The ESD protection device of Example 2 was obtained. Moreover, the ESD protection apparatus of Comparative Example 1 obtained in the same manner as in Example 1 except that the ESD protection apparatus of Example 1 obtained as described above and the through hole were not provided was obtained.

(Evaluation)
(ESD discharge response)
About 100 ESD protection apparatuses of the said Example 1, 2 and the comparative example 1, discharge responsiveness was evaluated by the electrostatic discharge immunity test prescribed | regulated to IEC specification, IEC61000-4-2. The results are shown in Table 1 below. In addition, the numerical value in discharge responsiveness evaluation is a discharge start voltage (V).

(ESD repeat resistance)
In order to examine the repeated resistance to ESD, a voltage of 8 kV was applied 100 times by contact discharge, and then a discharge start voltage (V) was obtained again by an electrostatic discharge immunity test. The evaluation result at this time is shown in the column of “ESD repeat resistance” in Table 1.

  As can be seen from Table 1, compared to Comparative Example 1, according to Examples 1 and 2, the discharge start voltage in the ESD discharge response evaluation is lowered.

  In addition, compared with Comparative Example 1, according to Examples 1 and 2, it can be seen that the discharge start voltage in the column of ESD repeat resistance is lowered. That is, it can be seen that the deterioration of discharge characteristics due to repeated discharge is suppressed.

DESCRIPTION OF SYMBOLS 1 ... ESD protection apparatus 2 ... Board | substrate 2a ... Cavity 2b, 2c ... End surface 3, 4 ... 1st, 2nd discharge electrode 3a, 3b, 4a ... Through-hole 5 ... Discharge auxiliary electrode 6, 7 ... 1st, 2nd External electrode 8 ... discharge auxiliary electrode 9a ... metal particle 9b ... semiconductor ceramic particle 21, 31 ... ESD protection device 22 ... substrate 22a, 22b ... end face 22c ... cavity 41 ... ESD protection device

Claims (5)

A substrate,
First and second discharge electrodes provided on the substrate and having a main surface;
Provided on each end face of the substrate, and first and second external electrodes respectively connected to the first and second discharge electrodes,
The main surfaces of the first and second discharge electrodes face each other with a gap in the thickness direction of the substrate ,
The thickness of the portion where the position in the thickness direction of the portion with the before and Symbol first discharge electrode and the first external electrode is connected to the second discharge electrode and the second external electrodes are connected to The position in the direction is the same,
A plurality of through-holes are provided in both of the first and second discharge electrodes facing each other, and the through-hole provided in the first discharge electrode and the second discharge electrode The through hole provided in the discharge electrode is provided at the same position in plan view, and the planar shape of the through hole is circular,
A discharge auxiliary electrode that is provided to connect the first discharge electrode and the second discharge electrode, and that promotes discharge between the first and second discharge electrodes;
The ESD protection device , wherein a plurality of the discharge auxiliary electrodes are provided in a columnar shape at positions different from the through holes in a plan view . A cavity is further provided in the substrate;
2. The ESD protection device according to claim 1, wherein a portion of the first and second discharge electrodes facing each other is located in the cavity. The ESD protection device according to claim 2 , wherein ends of the first and second discharge electrodes are located in the cavity. The ESD protection device according to claim 2 or 3 , wherein edges of the plurality of through holes are located in the cavity. The discharge auxiliary electrode comprises coated metal particles having no material conductivity, ESD protection device according to any one of claims 1 to 4.

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