JP6102579B2 - ESD protection device - Google Patents

Description

  The present invention relates to an ESD protection device. “ESD” is Electro-Static Discharge. ESD is a phenomenon in which intense discharge occurs when a charged conductive object, such as a human body, comes into contact with or sufficiently approaches another conductive object. The “ESD protection device” is a device for releasing a charge to GND when electrostatic discharge occurs and protecting a circuit.

  Conventionally, ESD protection devices are widely used to protect electronic devices from ESD, that is, electrostatic discharge.

  An example of a circuit in which the ESD protection device is used is shown in FIG. The ESD protection device 501 and a circuit to be protected (hereinafter referred to as “protected circuit”) 502 are electrically connected, and the ESD protection device 501 and the protected circuit 502 are each grounded. The protected circuit 502 is an IC (Integrated Circuit) or the like. As shown in FIG. 24, no current flows between the discharge electrodes inside the ESD protection device 501 in the normal state. The terminal 503 means a portion where a conductor is exposed to the outside in a connector or the like. For example, when ESD occurs due to a human body coming into contact with or sufficiently close to the terminal 503, a high voltage is applied to the terminal 503. At this time, the overvoltage is applied to the protected circuit 502 as it is, and a current flows as shown by an arrow 92. However, if a discharge occurs between the discharge electrodes of the ESD protection device 501, a current flows in the direction of the arrow 91 due to the discharge, so that no overvoltage is applied to the protected circuit 502. That is, the protected circuit 502 is protected.

  For example, in JP 2009-238563 A (Patent Document 1), a “cavity as a discharge portion is formed inside a base made of an insulator, called“ overvoltage protection component ”, and the discharge electrodes are formed inside the cavity. The structure in which is opposed is described. Patent Document 1 describes that the discharge electrode is formed by printing, plating, or the like.

  For example, Japanese Patent Laying-Open No. 2010-231909 (Patent Document 2) describes a structure in which a discharge cavity is formed inside an element body made of an insulator, referred to as “overvoltage protection component”. Two discharge electrodes extending from the side are close to each other and face each other on the bottom surface of the discharge cavity, and conductor powder adheres to a part of the side surface and the bottom surface of the discharge cavity. Patent Document 2 describes that the discharge start voltage can be lowered by attaching the conductive powder in this way.

JP 2009-238563 A JP 2010-231909 A

  In Patent Document 1, since the discharge electrode is formed by printing, plating, or the like, the discharge electrode is a thin conductive film attached to the surface of the insulator. At the time of discharge, electrons collide with the discharge electrode, but the discharge electrode may be peeled off by the impact of the collision of the electrons. In Patent Document 1, an opening is provided in an insulating sheet, the opening is filled with an acrylic resin as a discharge part forming material, and the acrylic resin evaporates in a firing step, thereby obtaining a cavity. Since the cavities are formed in this way and the discharge electrodes facing each other across the cavities are formed by printing or the like, the gap between the discharge electrodes can be reduced, that is, the gap can be sufficiently narrowed. It wasn't.

  Further, even when the technique described in Patent Document 2 is taken into consideration, the gap between the discharge electrodes cannot be sufficiently narrowed.

  Therefore, an object of the present invention is to provide an ESD protection device that can narrow the gap between the discharge electrodes and can reduce the problem of peeling of the discharge electrodes.

  In order to achieve the above object, an ESD protection device according to the present invention includes a first insulating layer, a second insulating layer overlaid on the first insulating layer, and a first penetrating through the first insulating layer in the thickness direction. A via hole is provided in the second insulating layer at a position facing the first via conductor, and the diameter of the via hole at the end on the first insulating layer side A discharge gap portion is formed so as to be larger than the diameter of the end of the one via conductor on the second insulating layer side and enter the inside of the via hole of the second insulating layer.

  According to the present invention, the gap between the discharge electrodes can be narrowed, and further, the problem of peeling of the discharge electrodes can be reduced.

It is sectional drawing of the ESD protection apparatus in Embodiment 1 based on this invention. It is a partial expanded sectional view of the ESD protection apparatus in Embodiment 1 based on this invention. It is 1st explanatory drawing of the manufacturing method of the ESD protection apparatus in Embodiment 1 based on this invention. It is 2nd explanatory drawing of the manufacturing method of the ESD protection apparatus in Embodiment 1 based on this invention. It is 3rd explanatory drawing of the manufacturing method of the ESD protection apparatus in Embodiment 1 based on this invention. It is 4th explanatory drawing of the manufacturing method of the ESD protection apparatus in Embodiment 1 based on this invention. It is 5th explanatory drawing of the manufacturing method of the ESD protection apparatus in Embodiment 1 based on this invention. It is 6th explanatory drawing of the manufacturing method of the ESD protection apparatus in Embodiment 1 based on this invention. It is 7th explanatory drawing of the manufacturing method of the ESD protection apparatus in Embodiment 1 based on this invention. It is 8th explanatory drawing of the manufacturing method of the ESD protection apparatus in Embodiment 1 based on this invention. It is sectional drawing of the ESD protection apparatus in Embodiment 2 based on this invention. It is sectional drawing of the ESD protection apparatus in Embodiment 3 based on this invention. It is sectional drawing of the ESD protection apparatus in Embodiment 4 based on this invention. It is 1st explanatory drawing of the manufacturing method of the ESD protection apparatus in Embodiment 4 based on this invention. It is 2nd explanatory drawing of the manufacturing method of the ESD protection apparatus in Embodiment 4 based on this invention. It is 3rd explanatory drawing of the manufacturing method of the ESD protection apparatus in Embodiment 4 based on this invention. It is sectional drawing of the ESD protection apparatus in Embodiment 5 based on this invention. It is 1st explanatory drawing of the manufacturing method of the ESD protection apparatus in Embodiment 5 based on this invention. It is 2nd explanatory drawing of the manufacturing method of the ESD protection apparatus in Embodiment 5 based on this invention. It is 3rd explanatory drawing of the manufacturing method of the ESD protection apparatus in Embodiment 5 based on this invention. It is 4th explanatory drawing of the manufacturing method of the ESD protection apparatus in Embodiment 5 based on this invention. It is sectional drawing of the ESD protection apparatus based on a prior art. It is explanatory drawing of the state before lamination | stacking of the ESD protection apparatus based on a prior art. It is a circuit diagram of an example of the situation where an ESD protection device is generally used.

(Embodiment 1)
(Constitution)
With reference to FIG. 1 and FIG. 2, the ESD protection apparatus in Embodiment 1 based on this invention is demonstrated. A cross-sectional view of the ESD protection apparatus 101 in this embodiment is shown in FIG. FIG. 2 shows an enlarged view of the vicinity of the discharge gap 10.

  The ESD protection apparatus 101 according to the present embodiment includes a first insulating layer 2a, a second insulating layer 2b overlaid on the first insulating layer 2a, and a first via conductor 6a penetrating the first insulating layer 2a in the thickness direction. In the second insulating layer 2b, a via hole 8 is provided at a position facing the first via conductor 6a. The diameter D2 of the via hole 8 at the end on the first insulating layer 2a side is A discharge gap portion 10 is formed so as to be larger than the diameter D1 at the end of the via conductor 6a on the second insulating layer 2b side and enter the inside of the via hole 8 of the second insulating layer 2b.

  The first insulating layer 2a and the second insulating layer 2b are, for example, ceramic layers. In the present embodiment, the discharge gap portion 10 includes the discharge auxiliary electrode 4 and the cavity 5.

  A second via conductor 6b is provided in the second insulating layer 2b. The first via conductor 6a and the second via conductor 6b are not in direct contact with each other. The first via conductor 6a and the second via conductor 6b are opposed to each other with the discharge gap portion 10 interposed therebetween.

  As an example of the dimensions of each part, the thickness of the insulating sheet used as the insulating layer is 25 μm, the diameter of the upper end of the via hole 8 provided in the second insulating layer 2b is 100 μm, the diameter of the lower end is 120 μm, and the discharge auxiliary electrode 4 The diameter of the lower end of the first via conductor 6a provided in the first insulating layer 2a is 50 μm. The gap formed by the upper end of the first via conductor 6a and the lower end of the second via conductor 6b is (80-50) / 2 = 15 μm in plan view, but the first via conductor 6a when stacked is formed. Since the upper part of the conductor paste is pressed down, the actual gap length is about 17 μm.

(Action / Effect)
If it is the structure of the ESD protection apparatus 101 in this Embodiment, the structure of a discharge gap part can be produced by printing of a paste so that it may mention later. With this configuration, the thickness of the discharge gap can be controlled by the thickness of the layer to be printed. The first via conductor 6a and the second via conductor 6b correspond to discharge electrodes, respectively. The form of the discharge electrode is not limited to this, and it is sufficient that the discharge electrodes have a structure facing each other with the discharge gap portion 10 interposed therebetween. The ESD protection device 101 illustrated here has a structure in which a first via conductor 6a as one discharge electrode and a second via conductor 6b as the other discharge electrode face each other across the discharge gap portion 10. It has become. Details of the discharge gap 10 will be described later.

  The first via conductor 6a serving as one of the discharge electrodes can be formed by a method of filling the hole with a conductive paste instead of printing, and thus has a sufficient thickness. Therefore, unlike the configuration in which the printed film is attached as the discharge electrode, the discharge electrode is not easily peeled off even if the discharge is repeated.

  In this embodiment, the gap between the discharge electrodes can be narrowed, and the problem of peeling of the discharge electrodes can be reduced.

(Production method)
The ESD protection apparatus 101 described in this embodiment can be manufactured as follows. The ESD protection device 101 is manufactured by stacking a plurality of insulator sheets. The insulator sheet is, for example, a ceramic sheet, but is not limited to a ceramic sheet, and may be other types of insulator sheets. Hereinafter, a case where the insulating layer included in the ESD protection apparatus 101 is a ceramic layer will be described as an example.

  First, as shown in FIG. 3, a via hole 8 is formed in the insulating sheet 20. The insulating sheet 20 is a ceramic sheet in this example. A protective film 19 made of PET is stretched on the upper surface of the insulating sheet 20. The processing for forming the via hole 8 can be performed by laser processing or the like. When the via hole 8 is opened, a hole is also made in the protective film 19 at the same time. Since the direction of the tapered shape of the hole to be formed is determined depending on which surface the hole is made in from the ceramic sheet as the insulating sheet 20, the via finally formed depending on which surface the hole is formed The direction of the tapered shape of the conductor can be appropriately selected.

  As shown in FIG. 4, the via hole 8 is filled with a conductor paste 16b. The conductive paste 16b is, for example, a metal paste.

  Generally, when filling the via hole 8 with a conductor paste, a sufficient amount of the conductor paste 16 is applied as shown in FIG. 4 and then scraped with a squeegee 41 as shown in FIG. Conceivable. This scraping operation is performed with the protective film 19 still attached to the surface of the insulating sheet 20. After the scraping operation, the space in the via hole 8 is completely filled with the conductor paste 16 as shown in FIG. 6, and the upper surface of the conductor paste 16 coincides with the upper surface of the insulating sheet 20, that is, a so-called flat surface. However, in actuality, only one cycle of coating and scraping does not become the same state. This is because the surface of the conductive paste 16 exposed at the entrance of the via hole 8 is actually recessed as shown in FIG.

Even if the conductor paste can be brought into a flush state, the conductor paste usually has a dent after being dried. When paying attention to the weight percent (wt%) of the composition of the conductor paste, for example, the metal component occupies most of the metal component 80 wt%, additive (co-dough etc.) 8 wt%, solvent 10 wt%, and resin 2 wt%. ing. Paying attention to volume% (vol%), the metal component is 40 vol%, the additive is 10 vol%, the solvent is 40 vol%, and the resin is 10 vol%, and the solvent occupies a large part of the volume. Further, for example, in the case of a conductor paste in which the metal component is copper (Cu), the metal component is 80 wt%, the solvent (terpineol) is 15 wt%, and the resin is about 5 wt%, but the density of copper is 8.94 g / cm ³ , density 1.09~1.17g / cm ^3, since the density of the terpineol is 0.94 g / cm ^3, in this case, when converted to volume ratio, copper 30.3～30.6Vol%, resin Of 14.6 to 15.6 vol%, the solvent is 54.1 to 54.7 vol%, and the solvent and the resin occupy a large volume. Therefore, when the solvent is volatilized by drying, the volume is greatly reduced. For this reason, the metal paste as the conductor paste filled in the via hole 8 is usually dried to reduce the volume and to form a dent on the upper surface.

  Conventionally, such a phenomenon of generating a dent has not been preferable, but the present invention positively utilizes the property of generating a dent. In the present invention, this recess is used as a space for forming the discharge gap portion. In order to apply the present invention, the volume% of the solvent and the resin in the conductor paste may be increased so that the conductor paste filled in the via hole is surely dented.

  When the dent is largely generated by appropriately adjusting the composition of the conductor paste, for example, the state shown in FIG. 8 is obtained. Here, attention is paid to the insulating sheet 20 to be the second insulating layer 2b. In the example shown in FIG. 8, the conductor paste 16 b filled in the tapered via hole 8 has a recess 12. The conductive paste 16b is to be the second via conductor 6b later. As shown in FIG. 9, the recess 12 is filled with a discharge auxiliary electrode material 14. This step is also performed with the protective film 19 attached to the surface of the insulating sheet 20. Thereafter, the protective film 19 is peeled off from the insulating sheet 20.

  Next, as shown in FIG. 10, a plurality of insulating layers are stacked. The insulating sheet 20 to be the second insulating layer 2b is turned upside down compared to FIG. Separately from this, in the insulating sheet to be the first insulating layer 2a, the via hole 9 is formed from one surface, the conductor paste 16a is filled, and the cavity is formed from the surface opposite to the side where the via hole 9 is formed. A print of the paste 15 is prepared in advance.

The discharge auxiliary electrode material 14 is a material that can form the discharge auxiliary electrode by firing. This may be, for example, a mixture of insulating ceramic powder and semiconductor ceramic powder. Alternatively, the discharge auxiliary electrode material 14 may be conductive particles coated with an insulating material. In the case of “conductive particles coated with an insulating material”, the “coating” may be a complete coating or an incomplete coating. The coating may have a configuration in which very small insulating particles are attached to the surface of the conductive particles. Or the particle | grains of what is called a core-shell structure in which the electroconductive particle is accommodated in the insulating film may be sufficient. The “conductive particles” may be Cu particles, for example. In addition, for example, particles of a conductive material such as Au, Al, Ag, and Ni can be used as appropriate. The “insulating material” for covering the conductive particles may be, for example, Al ₂ O ₃ . As the “semiconductor ceramic powder”, for example, a ceramic powder made of a semiconductor ceramic such as a carbide such as SiC or an oxide of a transition metal such as MnO, NiO, CoO, or CuO can be preferably used. The semiconductor ceramic powder may be, for example, SiC particles coated with SiO ₂ . The discharge auxiliary electrode material 14 may be a mixture of semiconductor ceramic powder and conductive particles coated with an insulating material.

  The cavity forming paste 15 is a material that can disappear at the firing temperature. This may be a material containing, as a main material, resin beads that can disappear at the firing temperature, for example. Examples of the resin that satisfies such conditions include acrylic resin and polystyrene resin. The cavity forming paste 15 can be obtained by mixing these synthetic resin beads with a binder resin, a solvent or the like as required.

  The main material of the cavity forming paste 15 is not limited to resin. Any material other than a resin may be used as long as it is a solid material that can disappear at the firing temperature. For example, a wax having a certain degree of hardness may be used. Further, the main material of the cavity forming paste 15 is not limited to a bead-like material. For example, a columnar resin material can be used, and the shape is not limited.

  As shown in FIG. 10, the insulating layer 2c is overlaid on the lower side of the first insulating layer 2a. An insulating layer 2d is overlaid on the second insulating layer 2b. In the example shown here, the insulating layers 2c and 2d are also ceramic sheets like the first insulating layer 2a and the second insulating layer 2b.

  A conductive paste layer 17a to be the first wiring 7a later is formed on the upper surface of the insulating layer 2c. A conductive paste layer 17b to be the second wiring 7b later is formed on the lower surface of the insulating layer 2d. The conductive paste layers 17a and 17b can be formed by printing a conductive paste on the surface of the insulating layer.

  In this example, it is assumed that the ESD protection device is manufactured by laminating a total of four ceramic sheets, but the total number of layers is not limited thereto.

  As shown in FIG. 10, the insulating layer 2c, the first insulating layer 2a, the second insulating layer 2b, and the insulating layer 2d are laminated in order from the bottom, and these are integrally fired. As a result, the whole is integrated, and the ESD protection apparatus 101 as shown in FIG. 1 can be obtained.

  During the firing, the discharge auxiliary electrode material 14 becomes the discharge auxiliary electrode 4, and the cavity forming paste 15 disappears and becomes the cavity 5. At the time of firing, the conductive paste layer 17a becomes the first wiring 7a, and the conductive paste layer 17b becomes the second wiring 7b.

(Preferred matters)
Paying attention to the configuration of the ESD protection apparatus 101 shown in FIG. 1, preferable items will be described below.

  The discharge gap 10 is preferably surrounded by an annular conductor when viewed from the first insulating layer 2a side. By adopting this configuration, the first via conductor 6a serving as one of the discharge electrodes is opposed to the conductor in all surrounding directions, so that discharge is likely to occur. The “annular conductor” here is, for example, the lower end of the second via conductor 6b.

  It is preferable that the discharge gap portion 10 includes the discharge auxiliary electrode 4 disposed inside the annular conductor when viewed from the first insulating layer 2a side. By adopting this configuration, the first via conductor 6a serving as one of the discharge electrodes is opposed to the surrounding conductor via the auxiliary discharge electrode 4, so that discharge is likely to occur. That is, the discharge start voltage can be lowered.

  Inside the via hole 8 of the second insulating layer 2b, there is a second via conductor 6b formed in a shape having a recess on the first insulating layer 2a side, and a space inside the recess of the second via conductor 6b. The auxiliary discharge electrode 4 is arranged, and the second via conductor 6b is not in contact with the first via conductor 6a. That is, the second via conductor 6b has a cup shape as shown in FIG. In this state, the discharge auxiliary electrode 4 is filled in a part of the inside of the cup formed by the second via conductor 6b. The first via conductor 6a and the second via conductor 6b are discharge electrodes. The first via conductor 6a and the second via conductor 6b are opposed to each other with the discharge auxiliary electrode 4 interposed therebetween.

  The via hole 8 of the second insulating layer 2b preferably has a tapered shape in which the side close to the first insulating layer 2a is widened. By adopting this configuration, the second via conductor 6b disposed in the second insulating layer 2b can have a cup structure in which the side close to the first insulating layer 2a is widened. While avoiding, it becomes easy to ensure the part which discharge electrodes oppose.

  The first via conductor 6a preferably has a tapered shape in which the side close to the second insulating layer 2b is narrowed. By adopting this configuration, a structure in which the first via conductor 6a disposed in the first insulating layer 2a is difficult to peel off can be obtained. In addition, it becomes easier to concentrate charges on the side closer to the discharge gap portion 10 of the first via conductor 6a, and the discharge start voltage can be lowered.

(Embodiment 2)
(Constitution)
With reference to FIG. 11, the ESD protection apparatus in Embodiment 2 based on this invention is demonstrated.

  As shown in FIG. 11, the ESD protection apparatus 102 in the present embodiment has basically the same configuration as the ESD protection apparatus 101 described in the first embodiment. However, the entire discharge gap 10 is the discharge auxiliary electrode 4. The cavity 5 is not provided.

(Action / Effect)
Also according to this embodiment, the gap between the discharge electrodes can be narrowed, and the problem of peeling of the discharge electrodes can be reduced.

  In the configuration of the ESD protection device 102 in the present embodiment, a sufficient amount of the discharge auxiliary electrode material 14 is filled in the recess 12 of the conductive paste 16b of the second insulating layer 2b before lamination, and the first insulating layer 2a The cavity forming paste can be obtained by not printing on the upper surface.

  It should be noted that the discharge auxiliary electrode 4 in the discharge gap portion 10 as shown in the first embodiment rather than the configuration in which the entire discharge gap portion 10 is the discharge auxiliary electrode 4 as shown in the present embodiment. And the configuration in which both the cavity 5 are provided are preferable because the load on the discharge auxiliary electrode 4 can be reduced.

(Embodiment 3)
(Constitution)
With reference to FIG. 12, the ESD protection apparatus in Embodiment 3 based on this invention is demonstrated.

  As shown in FIG. 12, the ESD protection apparatus 103 in the present embodiment basically has the same configuration as the ESD protection apparatus 101 described in the first embodiment. However, the entire discharge gap 10 is a cavity 5.

As shown in the present embodiment, the discharge gap portion 10 may be the cavity 5.
(Action / Effect)
Also according to this embodiment, the gap between the discharge electrodes can be narrowed, and the problem of peeling of the discharge electrodes can be reduced. It is preferable to provide the auxiliary discharge electrode 4 as in the first embodiment because discharge is more likely to occur and the discharge start voltage can be lowered. However, the present embodiment also provides a temporary effect of the present invention. be able to.

  The configuration like the ESD protection device 103 in the present embodiment can be obtained by not printing the discharge auxiliary electrode material on the upper surface of the first insulating layer 2a before lamination.

(Embodiment 4)
(Constitution)
With reference to FIG. 13, the ESD protection apparatus in Embodiment 4 based on this invention is demonstrated.

  As shown in FIG. 13, the ESD device 104 in the present embodiment penetrates the first insulating layer 2a, the second insulating layer 2b overlaid on the first insulating layer 2a, and the first insulating layer 2a in the thickness direction. The second insulating layer 2b is provided with a via hole 8 at a position facing the first via conductor 6a, at the end of the via hole 8 on the first insulating layer 2a side. The diameter is larger than the diameter of the end of the first via conductor 6a on the second insulating layer 2b side, and the discharge gap portion 10i is formed so as to enter the inside of the via hole 8 of the second insulating layer 2b.

  The first insulating layer 2a and the second insulating layer 2b are, for example, ceramic layers. In the example shown in the present embodiment, the discharge gap portion 10 i includes the discharge auxiliary electrode 4 and the cavity 5.

  Inside the via hole 8 of the second insulating layer 2b, the discharge auxiliary electrode 4 formed in a shape having a recess on the side opposite to the first insulating layer 2a, and the space inside the recess of the discharge auxiliary electrode 4 And the conductor 21 is not in contact with the first via conductor 6a. That is, the auxiliary discharge electrode 4 has a cup shape as shown in FIG. In this state, the conductor 21 is filled inside the cup formed by the auxiliary discharge electrode 4. The first via conductor 6a and the conductor 21 are discharge electrodes, respectively. The first via conductor 6a and the conductor 21 are opposed to each other via the discharge gap portion 10i.

  As an example of the dimensions of each part, the thickness of the insulating sheet used as the insulating layer is 25 μm, the diameter of the upper end of the via hole 8 provided in the second insulating layer 2 b is 120 μm, the diameter of the lower end is 100 μm, and the height of the conductor 21 is high. 5 μm, and the subsidence amount of the upper surface in FIG. 13 of the discharge auxiliary electrode 4 provided on the second insulating layer 2 b is 5 μm. The thickness at the center of the auxiliary discharge electrode 4 is 10 μm. On the other hand, the thickness of the cavity 5 is 5 μm. In this case, the gap between the upper end of the first via conductor 6a and the lower end of the conductor 21 is 15 μm in total of the thickness 10 μm of the auxiliary discharge electrode 4 and the thickness 5 μm of the cavity 5. Since the upper portion of the conductor paste 16a to be the via conductor 6a is pressed and further lowered, the actual gap length is about 17 μm.

(Action / Effect)
Also according to this embodiment, the gap between the discharge electrodes can be narrowed, and the problem of peeling of the discharge electrodes can be reduced.

  A configuration like the ESD protection device 104 in the present embodiment can be obtained as follows. As shown in FIG. 14, in the insulating sheet 20 to be the second insulating layer 2 b, the via hole 8 is first filled with the discharge auxiliary electrode material 14, and the recess 12 is generated on the surface of the discharge auxiliary electrode material 14. In the discharge auxiliary electrode material 14, for example, when the solid content of Cu / SiC is about 14 vol%, the recess 12 is surely generated. After the recess 12 is generated, the conductor paste 22 is filled in the recess 12 as shown in FIG.

  Next, as shown in FIG. 16, a plurality of insulating layers are stacked. In the insulating sheet to be the first insulating layer 2a, the via holes 9 were formed from one side and filled with the conductive paste 16a, and the cavity forming paste 15 was printed from the side opposite to the side where the via holes 9 were formed. Prepare things in advance. As shown in FIG. 16, the insulating layer 2c is overlaid on the lower side of the first insulating layer 2a. An insulating layer 2d is overlaid on the second insulating layer 2b. The details of the insulating layers 2c and 2d are the same as those described in the first embodiment and will not be repeated. By baking these integrally, the whole is integrated and the ESD protection apparatus 104 as shown in FIG. 13 can be obtained.

(Embodiment 5)
(Constitution)
With reference to FIG. 17, the ESD protection apparatus in Embodiment 5 based on this invention is demonstrated.

  As shown in FIG. 17, the ESD device 105 in the present embodiment penetrates the first insulating layer 2a, the second insulating layer 2b overlaid on the first insulating layer 2a, and the first insulating layer 2a in the thickness direction. The second insulating layer 2b is provided with a via hole 8 at a position facing the first via conductor 6a, at the end of the via hole 8 on the first insulating layer 2a side. The diameter is larger than the diameter of the end of the first via conductor 6a on the second insulating layer 2b side, and the discharge gap portion 10j is formed so as to enter the inside of the via hole 8 of the second insulating layer 2b.

  The first insulating layer 2a and the second insulating layer 2b are, for example, ceramic layers. In the example shown in the present embodiment, the discharge gap portion 10 j includes the discharge auxiliary electrode 4 and the cavity 5.

  The via hole 8 of the second insulating layer 2b is formed in a tapered shape so that the side opposite to the first insulating layer 2a is widened. A conductor 23 is formed in a cylindrical shape near the outer periphery of the inside of the via hole 8. The outer peripheral surface of the conductor 23 is in contact with the inner peripheral surface of the via hole 8. The inner peripheral surface of the conductor 23 is tapered so that the side opposite to the first insulating layer 2a is widened. The discharge auxiliary electrode 4 is disposed so as to fill the space inside the cylindrical conductor 23. The conductor 23 is not in contact with the first via conductor 6a. That is, the discharge auxiliary electrode 4 has a truncated cone shape as shown in FIG. The first via conductor 6a and the conductor 23 are discharge electrodes, respectively. The first via conductor 6a and the conductor 21 are opposed to each other via the discharge gap portion 10j.

  In the ESD device 105, the discharge gap portion 10j is surrounded by the annular conductor 23 when viewed from the first insulating layer 2a side. The discharge gap portion 10j includes the discharge auxiliary electrode 4 disposed inside the annular conductor 23 when viewed from the first insulating layer 2a side. In the ESD device 105, a discharge gap portion 10j is formed so as to penetrate the inside of the via hole 8 of the second insulating layer 2b.

  As an example of the dimensions of each part, the thickness of the insulating sheet used as the insulating layer is 25 μm, the diameter of the upper end of the via hole 8 provided in the second insulating layer 2b is 140 μm, the diameter of the lower end is 120 μm, and the discharge auxiliary electrode 4 The diameter of the lower end of the first via conductor 6a provided in the first insulating layer 2a is 50 μm. The gap formed by the upper end of the first via conductor 6a and the lower end of the conductor 23 is (80-50) / 2 = 15 μm in plan view, but the conductor that becomes the first via conductor 6a when stacked. Since the upper part of the paste 16a is pressed down, the actual gap length is about 17 μm.

(Action / Effect)
Also according to this embodiment, the gap between the discharge electrodes can be narrowed, and the problem of peeling of the discharge electrodes can be reduced.

  The configuration like the ESD protection device 105 in the present embodiment can be obtained as follows. As shown in FIG. 18, in the insulating sheet 20 to be the second insulating layer 2b, the via hole 8 is first filled with the conductor paste 24. Next, as shown in FIG. 19, a through hole 28 is formed in the center of the conductor paste 24. This drilling process can be performed by, for example, laser light irradiation.

  As shown in FIG. 20, the discharge assisting material 14 is filled in the through hole 28 formed in the center of the conductor paste 24.

  Next, as shown in FIG. 21, a plurality of insulating layers are stacked. Except for the second insulating layer 2b, it is the same as described in the fourth embodiment. By baking these integrally, the whole is integrated and the ESD protection apparatus 105 as shown in FIG. 17 can be obtained.

  In each of the embodiments so far, the first insulating layer 2a is below the discharge gap portion and the second insulating layer 2b is above the discharge gap portion. As an ESD protection device based on the present invention, the vertical relationship is not limited to such a configuration. The ESD protection device according to the present invention may be arranged upside down.

(Experimental example)
In order to investigate the discharge responsiveness to ESD, a plurality of ESD protection devices based on the present invention or the prior art are prepared as samples I to V, and IEC61000-4-2, which is a type of IEC (International Electrotechnical Commission) standard, is prepared. The prescribed electrostatic discharge immunity test was conducted.

Sample I is the ESD protection apparatus 101 (see FIG. 1) shown in the first embodiment.
Sample II is the ESD protection device 104 (see FIG. 13) shown in the fourth embodiment.

Sample III is the ESD protection apparatus 105 (see FIG. 17) shown in the fifth embodiment.
Sample IV is an ESD protection device based on the prior art, and is the ESD protection device 100 shown in FIG. The ESD protection device 100 is a laminate of ceramic layers as insulating layers, and the ESD protection device 100 includes a first wiring 7a and a second wiring 7b. The leading end of the first wiring 7 a and the leading end of the second wiring 7 b are opposed to each other through the internal space of the through hole 13. The structure shown in FIG. 22 was obtained by laminating insulating layers as shown in FIG. That is, the insulating layer 2f having the through holes 13 is prepared, and the insulating layer 2f is disposed between the insulating layers 2c and 2d printed with the conductive pastes 17a and 17b, respectively. Further, an insulating layer 2e on which nothing was formed was stacked on the upper side of the insulating layer 2d, and a total of these four layers were integrally fired. In this way, the ESD protection apparatus 100 shown in FIG. 22 was obtained.

  As an electrostatic discharge immunity test, a voltage of 8 kV was applied by contact discharge to examine whether or not discharge occurred between the discharge electrodes of the sample. Whether or not a discharge has occurred between the discharge electrodes of the sample can be determined by whether or not a voltage is applied to the protected circuit. The degree of the discharge start voltage between the discharge electrodes of the sample can be determined by the peak voltage detected by the protected circuit. The smaller the peak voltage detected by the protected circuit, the better the function of the sample.

The evaluation results were displayed as follows.
Those having a peak voltage of less than 350 V are ranked “A” as being particularly good.

  Those having a peak voltage of 350 V or more and less than 500 V are ranked as “B” as good.

Those whose peak voltage is 500 V or more and less than 600 V are ranked as “C”.
Those whose peak voltage exceeds 600V are ranked as “D” as defective.

  The evaluation results are shown in the column of “ESD discharge response” in Table 1.

  Furthermore, in order to investigate the repeated resistance to ESD, a voltage of 8 kV was applied 100 times by contact discharge to the input terminal 503, and then the discharge response was examined 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 shown in Table 1, the discharge responsiveness of Samples I to III was particularly good in the initial state. Samples I and III also had particularly good repeat resistance.

  Sample II had particularly good discharge responsiveness in the initial state, but its repetition resistance was inferior to Samples I and III.

  Furthermore, the processing cost was also evaluated. Since the sample III needs to be drilled twice by laser irradiation, the processing cost is high.

  Comprehensive judgment was evaluated in four stages of excellent, good, acceptable, and impossible based on three evaluation results of ESD discharge responsiveness, ESD repetition resistance, and processing cost.

  Sample III has a comprehensive judgment of “Yes” and is inferior to Samples I and II, but is superior to Sample IV based on the prior art. In this case as well, the effect of the present invention is obtained to some extent. It can be said that.

  Sample IV had a discharge responsiveness in the initial state of less than 600 V, but the repetition resistance was poor, and the overall judgment was “impossible”.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and includes all modifications within the scope and meaning equivalent to the terms of the claims.

  2a 1st insulating layer, 2b 2nd insulating layer, 4 discharge auxiliary electrode, 5 cavity, 6a 1st via conductor, 6b 2nd via conductor, 7a 1st wiring, 7b 2nd wiring, 8, 9 via hole, 10, 10i, 10j Discharge gap, 12 recess, 13 through-hole, 14 discharge auxiliary electrode material, 15 cavity forming paste, 16a, 16b conductive paste, 17a, 17b conductive paste layer, 19 protective film, 20 insulating sheet, 21, 23 conductor , 22, 24 Conductor paste, 28 Through hole, 41 Squeegee, 91, 92 arrow, 100 (based on the prior art) ESD protection device, 101, 102, 103, 104, 105 ESD protection device, 502 Protected circuit, 503 terminal .

Claims (7)

A first insulating layer;
A second insulating layer overlaid on the first insulating layer;
A first via conductor penetrating the first insulating layer in the thickness direction,
The second insulating layer is provided with a via hole at a position facing the first via conductor, and the diameter of the via hole at the end on the first insulating layer side is the first via conductor of the first via conductor. 2 larger than the diameter at the end on the insulating layer side,
An ESD protection device, wherein a discharge gap is formed so as to enter the inside of the via hole of the second insulating layer.   The ESD protection device according to claim 1, wherein the discharge gap portion is surrounded by an annular conductor when viewed from the first insulating layer side.   The ESD protection device according to claim 2, wherein the discharge gap portion includes a discharge auxiliary electrode disposed inside the annular conductor when viewed from the first insulating layer side.   A second via conductor formed in a shape having a recess on the first insulating layer side and a space inside the recess of the second via conductor are disposed inside the via hole of the second insulating layer. The ESD protection device according to claim 1, wherein the discharge auxiliary electrode is disposed, and the second via conductor is not in contact with the first via conductor.   The ESD protection device according to claim 4, wherein the via hole of the second insulating layer has a tapered shape in which a side close to the first insulating layer is widened.   The ESD protection device according to claim 1, wherein the first via conductor has a tapered shape in which a side close to the second insulating layer is narrowed.   The ESD protection device according to claim 3, wherein a discharge gap portion is formed so as to penetrate the inside of the via hole of the second insulating layer.

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