WO2013011821A1 - Esd保護デバイスおよびその製造方法 - Google Patents
Esd保護デバイスおよびその製造方法 Download PDFInfo
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- WO2013011821A1 WO2013011821A1 PCT/JP2012/066820 JP2012066820W WO2013011821A1 WO 2013011821 A1 WO2013011821 A1 WO 2013011821A1 JP 2012066820 W JP2012066820 W JP 2012066820W WO 2013011821 A1 WO2013011821 A1 WO 2013011821A1
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- glass
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05F—STATIC ELECTRICITY; NATURALLY-OCCURRING ELECTRICITY
- H05F3/00—Carrying-off electrostatic charges
- H05F3/04—Carrying-off electrostatic charges by means of spark gaps or other discharge devices
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
- H01T1/00—Details of spark gaps
- H01T1/20—Means for starting arc or facilitating ignition of spark gap
- H01T1/22—Means for starting arc or facilitating ignition of spark gap by the shape or the composition of the electrodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
- H01T4/00—Overvoltage arresters using spark gaps
- H01T4/10—Overvoltage arresters using spark gaps having a single gap or a plurality of gaps in parallel
- H01T4/12—Overvoltage arresters using spark gaps having a single gap or a plurality of gaps in parallel hermetically sealed
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/0213—Electrical arrangements not otherwise provided for
- H05K1/0254—High voltage adaptations; Electrical insulation details; Overvoltage or electrostatic discharge protection ; Arrangements for regulating voltages or for using plural voltages
- H05K1/0257—Overvoltage protection
- H05K1/026—Spark gaps
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K7/00—Constructional details common to different types of electric apparatus
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/58—Structural electrical arrangements for semiconductor devices not otherwise provided for, e.g. in combination with batteries
- H01L23/60—Protection against electrostatic charges or discharges, e.g. Faraday shields
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/0001—Technical content checked by a classifier
- H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
- H05K2201/09—Shape and layout
- H05K2201/09009—Substrate related
- H05K2201/09063—Holes or slots in insulating substrate not used for electrical connections
Definitions
- the present invention relates to an ESD (Electrostatic Discharge) protection device and a manufacturing method thereof, and more particularly to an improvement in a discharge auxiliary electrode provided to promote electrostatic discharge in the ESD protection device.
- ESD Electrostatic Discharge
- Patent Document 1 An overvoltage protection element of interest to the present invention is described in, for example, Japanese Patent Application Laid-Open No. 2008-85284 (Patent Document 1).
- non-conductive powder for example, silicon carbide: particle size 1 to 50 ⁇ m
- metal conductive powder for example, copper
- an overvoltage protection element material for example, silicon carbide: particle size 1 to 50 ⁇ m
- metal conductive powder for example, copper
- a pressure-sensitive adhesive for example, glass powder
- Patent Document 1 discloses a method for producing an overvoltage protection element, in which a non-conductor powder, a metal conductor powder, and an adhesive are uniformly mixed at a predetermined ratio to form a material paste;
- the document includes a step of printing a material paste and a step of performing a baking process (temperature: 300 to 1200 ° C.) on the substrate.
- Patent Document 1 has the following problems to be solved.
- the metal conductors exposed at the time of discharge may be bonded to each other, resulting in a decrease in insulation reliability.
- silicon carbide used as non-conductor powder is a semiconductor having a relatively low insulation resistance, it is difficult to improve insulation reliability.
- Patent Document 2 Japanese Patent Application Laidification No. 2009/098944
- Patent Document 2 discloses that a conductive material (Cu powder or the like) coated with an inorganic material (Al 2 O 3 or the like) is used as a discharge auxiliary electrode. According to the technique described in Patent Document 2, since the exposure of the conductive material is less than that of the technique described in Patent Document 1, the insulation reliability can be increased. Further, even if the content of the conductive material is increased, short-circuiting between the conductive materials is unlikely to occur. Therefore, by increasing the conductive material, discharge can be facilitated, and thereby the peak voltage can be lowered.
- Patent Document 2 also has the following problems to be solved.
- the “conductive material coated with an inorganic material” refers to fine particles made of an inorganic material as described in Paragraphs [0034] and [0094] of FIG. It is only a coating on the surface of the conductive material. Therefore, it is relatively difficult to completely cover the surface of the conductive material with an inorganic material. Further, even if the surface of the conductive material is completely covered with the inorganic material in the stage before firing, as shown in FIG. 12, when the conductive material 1 thermally expands during firing, the inorganic material 2 There is a possibility that the conductive material 1 may be exposed after firing and cannot be completely covered. Therefore, further improvement is required for insulation reliability.
- an object of the present invention is to provide an ESD protection device that can solve the above-described problems, that is, has high insulation reliability and good discharge characteristics, and a method for manufacturing the same. .
- the present invention includes first and second discharge electrodes arranged so as to face each other, a discharge auxiliary electrode formed so as to straddle between the first and second discharge electrodes, and first and second discharges
- the discharge auxiliary electrode is mainly composed of the first metal.
- the electrode protection device includes an electrode and an insulator base material that holds the discharge auxiliary electrode. And an aggregate of a plurality of metal particles having a core-shell structure consisting of a core part composed mainly of a metal oxide containing a second metal.
- the metal particles constituting the discharge auxiliary electrode are completely or almost completely covered with the shell portion mainly composed of the metal oxide, so that the insulation reliability at the time of discharge can be increased. it can.
- the plurality of metal particles are preferably bonded to each other with a vitreous material. Thereby, it is possible to suppress the deterioration of the peak voltage characteristics after the drop impact.
- the metal oxide containing the second metal may contain an amorphous component of the metal oxide.
- the plurality of metal particles are bonded with the vitreous material derived from the shell portion, the deterioration of the peak voltage characteristics after the drop impact can be suppressed as in the above case.
- the thickness of the shell part is preferably 100 to 350 nm. As a result, not only high insulation reliability but also good discharge characteristics, in particular, a lower peak voltage can be realized.
- the second metal is more susceptible to oxidation than the first metal.
- a plurality of core-shell structures having a core portion mainly composed of the first metal and a shell portion mainly composed of a metal oxide containing the second metal. The metal particles can be easily obtained.
- the first metal is copper or a copper-based alloy containing copper as a main component.
- an ESD protection device can be provided at a relatively low cost.
- copper has a relatively high melting point, the insulation reliability during discharge can be further improved. This is because if the melting point is low, the metal particles melt and sinter due to heat during discharge, which may cause a short circuit.
- the metal oxide containing the second metal is at least one selected from aluminum oxide, silicon oxide, magnesium oxide, and nickel oxide. Since these oxides have high insulation properties, the insulation reliability during discharge can be further improved.
- the core part may contain not only the first metal but also the second metal as a subcomponent.
- the shell portion can be repaired by heat during discharge when the shell portion is broken for some reason.
- the first and second discharge electrodes and the discharge auxiliary electrode are disposed inside the insulator base material, and the insulator base material is the first and second discharge electrodes.
- the present invention is also directed to a method for manufacturing an ESD protection device.
- the method for manufacturing an ESD protection device includes a step of preparing an alloy powder made of an alloy including a first metal and a second metal that is more easily oxidized than the first metal, and an insulator base.
- a step a step of forming an unsintered discharge auxiliary electrode containing the alloy powder on the surface of or inside the insulator substrate, and a first and second discharge electrodes arranged to face each other on the discharge auxiliary electrode Forming on the surface or inside of the insulator base material, and firing the unfired auxiliary discharge electrode in an atmosphere having an oxygen concentration in which the first metal is not oxidized and the second metal is oxidized
- the firing step in each metal particle constituting the alloy powder, the second metal is moved toward the surface of the metal particle, and is oxidized when the surface reaches the metal particle.
- Including metal oxides With the metal oxide is characterized by comprising the step of forming the shell portion in the metal particles.
- any of the step of forming the discharge auxiliary electrode and the step of forming the first and second discharge electrodes may be performed first.
- the alloy powder is preferably manufactured using an atomizing method. According to the atomizing method, the composition of the alloy can be easily controlled. If the composition ratio of the first metal and the second metal constituting the alloy is changed, the present inventor can control the thickness of the shell portion formed of the metal oxide containing the second metal by the firing process. I have obtained the knowledge. It has also been found that the thickness of the shell portion formed of the metal oxide containing the second metal can be controlled also by changing the particle size of the metal particles constituting the alloy powder.
- the method for manufacturing an ESD protection device according to the present invention is performed as follows.
- the first method is applied when the insulator base material contains a glassy-containing substance, and in the step of preparing the insulator base material, includes a material that generates the glassy-containing substance at least after firing.
- An unfired insulator base material is prepared, and in the step of firing, the unfired insulator base material is sintered and a vitreous material is generated, and the vitreous material contains a plurality of metal particles. It is made to join between.
- the second method is characterized in that the glass itself is preliminarily contained in the unfired auxiliary discharge electrode.
- a vitreous material is prepared, and the unfired formed on the surface or inside of the insulator base material.
- the discharge auxiliary electrode further includes a vitreous material, and in the firing step, the plurality of metal particles are bonded with the vitreous material.
- the third method is characterized in that a material that generates glass at the time of firing is previously contained in the unfired auxiliary discharge electrode, and a glass precursor that generates glass by firing is prepared.
- the unsintered discharge auxiliary electrode formed on the surface or in the interior further includes a glass precursor.
- glass is generated from the glass precursor, and a plurality of metal particles are bonded with the glass. To be done.
- the fourth method is characterized in that a glass is produced by reacting with a shell part at the time of firing, and a glass is produced by reacting with a shell part of metal particles at the time of firing.
- the glass particle is produced by reacting the shell portion of the metal particles with the glass-generating substance, and the plurality of metal particles are bonded with the glass.
- the fifth method is characterized in that glass is supplied from a glass layer formed separately from the discharge auxiliary electrode, and a material that generates a glassy-containing substance at least after firing so as to contact the unfired discharge auxiliary electrode In the step of forming and baking the glass layer containing, a plurality of metal particles are bonded with a vitreous material that is formed by the glass layer.
- the step of preparing the insulator base material includes the step of preparing a plurality of ceramic green sheets including the first and second ceramic green sheets.
- the step of forming the unfired auxiliary discharge electrode and the step of forming the first and second discharge electrodes are performed on the first ceramic green sheet.
- the step of forming a burned-out layer so as to cover the gap between the first and second discharge electrodes, the unfired discharge auxiliary electrode on the first ceramic green sheet, the first and second A step of laminating a second ceramic green sheet so as to cover the second discharge electrode and the burned-out layer to obtain an unfired insulator base material, and first and second discharges on the surface of the insulator base material
- a step of forming first and second external terminal electrodes that are respectively electrically connected to the electrodes is further performed.
- the ceramic green sheet is sintered to obtain an insulating base material, and the burned-out layer is burned out.
- the ESD protection device According to the ESD protection device according to the present invention, even when static electricity is repeatedly applied, the characteristics are hardly deteriorated, and the insulation reliability during discharge can be increased. Further, even if the content of the metal particles is increased, short-circuiting between the metal particles is difficult to occur. Therefore, by increasing the metal particles, it is possible to facilitate discharge, thereby reducing the peak voltage. Therefore, the ESD protection device according to the present invention can be widely used for protecting various devices or apparatuses such as semiconductor devices.
- the firing process is performed in an atmosphere having an oxygen concentration in which the first metal is not oxidized and the second metal is oxidized.
- the second metal is oxidized when the second metal is deposited on the surface of the metal particle. Metal particles that are completely or almost completely covered can be easily obtained.
- FIG. 5 is a cross-sectional view showing an ESD protection device 11a according to a second embodiment of the present invention, which is obtained by carrying out an example of a preferred manufacturing method of the present invention.
- FIG. 5 is a plan view illustrating a state in which an unfired auxiliary discharge electrode 32 is formed on a first ceramic green sheet 31 for explaining a manufacturing process of an ESD protection device 42 produced in an experimental example.
- FIG. 7 is a plan view for explaining a manufacturing process of the ESD protection device 42 manufactured in the experimental example, and shows a state in which unfired first and second discharge electrodes 33 and 34 are formed after the process shown in FIG. 6.
- FIG. FIG. 8 is a plan view for explaining a manufacturing process of the ESD protection device 42 manufactured in the experimental example, and shows a state in which an unfired burned layer 35 is formed after the process shown in FIG. 7.
- FIG. 7 is a plan view illustrating a state in which an unfired auxiliary discharge electrode 32 is formed on a first ceramic green sheet 31 for explaining a manufacturing process of an ESD protection device 42 produced in an experimental example.
- FIG. 7 is a plan view for explaining a manufacturing process of the ESD protection device 42 manufactured in the experimental example, and shows a
- FIG. 9 is a cross-sectional view illustrating a manufacturing process of the ESD protection device 42 manufactured in the experimental example, and illustrates a state in which a second ceramic green sheet 36 is stacked after the process illustrated in FIG. 8.
- FIG. 10 is a cross-sectional view illustrating a state in which unfired external terminal electrodes 38 and 39 are formed after the step illustrated in FIG. 9 for describing a manufacturing process of the ESD protection device 42 manufactured in the experimental example.
- FIG. 11 is a cross-sectional view showing an ESD protection device 42 completed by performing a baking step after the step shown in FIG. 10 in the experimental example. It is for demonstrating the subject which the technique of patent document 2 may encounter, and is sectional drawing which shows typically the state of the electrically-conductive material 1 and the inorganic material 2 after baking.
- the ESD protection device 11 includes an insulator base 12.
- the insulator base 12 is made of, for example, a low-temperature sintered ceramic (LTCC) such as glass ceramic, a high-temperature sintered ceramic (HTCC) such as aluminum nitride or alumina, or a magnetic ceramic such as ferrite.
- the insulator substrate 12 has a laminated structure including at least an upper layer portion 13 and a lower layer portion 14.
- First and second discharge electrodes 16 and 17 arranged inside the insulator base 12 so as to face each other with a predetermined gap G between the upper layer portion 13 and the lower layer portion 14. And a discharge auxiliary electrode 18 formed so as to straddle between the first and second discharge electrodes 16 and 17.
- a portion of the insulator base 12 where the gap G is located is a cavity 19.
- First and second external terminal electrodes 20 and 21 are formed on the outer surface of the insulator base 12.
- the first and second external terminal electrodes 20 and 21 are electrically connected to the first and second discharge electrodes 16 and 17 described above, respectively.
- the discharge auxiliary electrode 18 includes a core portion 22 mainly containing a first metal and a shell mainly containing a metal oxide containing a second metal. It is composed of an assembly of a plurality of metal particles 24 having a core-shell structure composed of a portion 23. As described above, when the metal particles 24 constituting the discharge auxiliary electrode 18 have a core-shell structure and are completely or almost completely covered with the shell portion 23 mainly composed of a metal oxide. Insulation reliability during discharge can be increased. It should be noted that the shell portion 23 is not in a state where fine particles are gathered but is formed in a film shape as shown in FIG.
- the metal particle 24 has a portion that is not covered by the shell portion 23 mainly composed of a metal oxide, that is, a defect portion 28, as long as the insulation reliability is not substantially impaired. You may do it.
- the length of the entire circumference of the core portion 22 of the metal particle 24 is L1
- the length of the circumference of the core portion 22 covered with the shell portion 23 excluding the defect portion 28 is L2
- the ratio of L2 / L1 is 75. % Or more is defined as the achievement of the “core-shell structure” in the present invention.
- the metal particles 24 are illustrated as having a substantially circular cross section, but actually, the unfired discharge auxiliary electrode, which is performed in the manufacturing method described later, is fired. As a result of the step, a more complicated unevenness is formed on the surface of the core portion 22.
- the thickness of the shell portion is preferably 100 to 350 nm.
- the thickness of the shell part is less than 100 nm, the insulating film is thin, so that the shell part is partially destroyed by the impact generated during ESD application, or the first metal component of the core part diffuses into the shell part. It is assumed that the insulation of the shell portion deteriorates. Further, when the thickness of the shell portion exceeds 350 nm, it is assumed that the amount of creeping discharge during ESD application is reduced because the insulating film is thick.
- a metal containing the core 22 and the second metal mainly composed of the first metal by applying a manufacturing method described later.
- a plurality of metal particles 24 having a core-shell structure composed of a shell portion 23 containing an oxide as a main component can be easily obtained.
- copper or a copper-based alloy containing copper as a main component is used as the first metal.
- copper or a copper-based alloy for example, aluminum, nickel, bismuth, gallium, germanium, indium, magnesium, phosphorus, silicon, tin, or the like can be used as the second metal.
- the insulator base material 12 is comprised from LTCC. .
- silver, aluminum, molybdenum, tungsten, or the like can be used as the first metal.
- a metal that is more easily oxidized than the first metal may be selected.
- metal oxides containing the second metal are particularly aluminum oxide, silicon oxide, magnesium oxide, and nickel oxide. It is preferably at least one selected from This is because these oxides have high insulating properties, so that the insulation reliability during discharge can be further improved.
- the ESD protection device 11 is manufactured as follows, for example.
- the first ceramic green sheet is for forming, for example, the lower layer portion 14 of the insulator base 12, and the second ceramic green sheet similarly forms the upper layer portion 13. Is for.
- an alloy powder made of the first metal and an alloy containing the second metal that is more easily oxidized than the first metal is prepared for forming the discharge auxiliary electrode 18.
- This alloy powder is preferably manufactured using an atomizing method. According to the atomizing method, the composition of the alloy can be easily controlled. Moreover, if the alloy powder manufactured by the atomizing method is used, the metal particles contained in the discharge auxiliary electrode 18 can be highly filled.
- an unfired paste film to be the discharge auxiliary electrode 18 is formed with a predetermined pattern on the first ceramic green sheet using the paste containing the alloy powder.
- SiC may be contained in the paste for forming the discharge auxiliary electrode 18 in a range satisfying desired characteristics.
- the first and second discharge electrodes 16 are opposed to each other with a predetermined gap G therebetween. And 17 are formed.
- the discharge electrodes 16 and 17 are formed, for example, by applying a conductive paste.
- a burnout layer is formed so as to cover the gap G between the first and second discharge electrodes 16 and 17.
- the burned-out layer is for burning away in the baking step described later and leaving the above-described cavity 19 inside the insulator base 12.
- the burnout layer is formed by a paste containing resin beads, for example.
- the paste used to form the discharge auxiliary electrode 18, the first and second discharge electrodes 16 and 17, and the burned-out layer described above may be applied directly onto the object to be applied, or a transfer method or the like may be used. May be used.
- a second ceramic green sheet is laminated on the first ceramic green sheet so as to cover the unfired auxiliary discharge electrode 18, the first and second discharge electrodes 16 and 17, and the burned-out layer, and is crimped. The Thereby, the unfired insulator base material 12 is obtained.
- first and second external terminal electrodes 20 and 21 are formed on the surface of the unfired insulator base 12. External terminal electrodes 20 and 21 are formed, for example, by applying a conductive paste.
- the firing step is performed in an atmosphere having an oxygen concentration in which the first metal constituting the alloy powder included in the unfired auxiliary discharge electrode 18 is not oxidized and the second metal is oxidized.
- the insulating base material 12 obtained by sintering the ceramic green sheet is obtained, and the discharge electrodes 16 and 17, the discharge auxiliary electrode 18, and the external terminal electrodes 20 and 21 are sintered.
- each metal particle constituting the alloy powder included in the discharge auxiliary electrode 18 includes the following phenomenon in each metal particle constituting the alloy powder included in the discharge auxiliary electrode 18.
- a description will be given with reference to FIG. 3 assuming that the first metal constituting the alloy is Cu and the second metal is Al.
- FIG. 3 shows one metal particle 25 constituting the alloy powder.
- the metal particles 25 made of Cu and Al As the firing process proceeds, in the metal particles 25 made of Cu and Al, as indicated by the arrows, Al moves toward the surface of the metal particles 25 and is oxidized when reaching the surface, and Al 2 O 3 It becomes. Therefore, the shell part of the metal particle 25 is formed of Al 2 O 3 . As can be seen from such a phenomenon, Al as the second metal may remain in the core portion of the metal particle 25.
- the composition of the alloy is easy to control.
- the composition ratio of the first metal and the second metal constituting the alloy is as described above. If it changes, it turns out that the thickness of the shell part formed with the metal oxide containing a 2nd metal is controllable by the said baking process. Therefore, in order to obtain a preferable thickness of the shell portion of 100 to 350 nm as described above, for example, the composition ratio between the first metal and the second metal is controlled. It has also been found that the thickness of the shell formed with the metal oxide containing the second metal can be controlled by changing the particle size of the metal particles 25.
- the burned-out layer is also burned out, and the cavity 19 is formed inside the insulator base 12.
- the ESD protection device 11 is completed as described above.
- the discharge auxiliary electrode 18 of the ESD protection device 11 preferably has a structure as shown in FIG. In FIG. 4, the discharge auxiliary electrode 18 is formed in contact with the lower layer portion 14 of the insulator substrate 12, and the discharge auxiliary electrode 18 has a plurality of core-shell structures including a core portion 22 and a shell portion 23. The state comprised from the aggregate
- the plurality of metal particles 24 are bonded to each other with a vitreous material 27.
- a vitreous material 27 thereby, it is possible to suppress the deterioration of the peak voltage characteristics after the drop impact.
- any one of the following methods is employed in manufacturing the ESD protection device 11. Of these methods, a plurality of methods may be combined.
- the first method is employed when the insulator base 12 includes a vitreous material as in the case of a low temperature sintered ceramic (LTCC) such as glass ceramic.
- LTCC low temperature sintered ceramic
- an unfired insulator base material 12 including at least a material that generates the vitreous material 27 after firing is prepared.
- this unfired insulator body is prepared.
- the base material 12 is sintered, the vitreous material 27 is produced.
- This vitreous material 27 diffuses into the discharge auxiliary electrode 18 so that the plurality of metal particles 24 are bonded in the firing step.
- the second method is used when the glass itself is previously contained in the unfired auxiliary discharge electrode 18. That is, a vitreous material is prepared, and this vitreous material is contained in the paste used to form the unfired auxiliary discharge electrode 18. In the firing step, the vitreous material in the paste flows, and the plurality of metal particles 24 are bonded with the vitreous material 27.
- the vitreous material include SiO 2 —B 2 O 3 —CaO glass, SiO 2 —B 2 O 3 —Li 2 O glass, or SiO 2 —B 2 O 3 —Al 2 O. 3- Li 2 O—CaO glass or the like is used.
- the third method is employed when a material that generates glass at the time of firing is previously contained in the unfired auxiliary discharge electrode 18. That is, a glass precursor that generates glass by firing is prepared, and the paste used to form the unfired discharge auxiliary electrode 18 further includes a glass precursor.
- the glass precursor A glass is produced from the glass, and a plurality of metal particles 24 are bonded with the glass.
- a SiO 2 —BaO—Al 2 O 3 —MnO-based ceramic is used as the glass precursor.
- the fourth method is employed when glass is produced by reacting with the shell part 23 during firing. That is, at least one glass forming material selected from an oxide, an alkali metal salt, and an alkaline earth metal salt that reacts with the shell portion 23 of the metal particle 24 to generate glass at the time of firing is prepared, and is unfired.
- a glass generating material is further included, and in the firing step, the shell portion 23 of the metal particle 24 and the glass generating material are reacted to generate glass, The glass is used to bond the plurality of metal particles 24 together.
- a metal oxide as a main component of the shell portion 23 is for example, Al 2 O 3, as a glass forming material, e.g., Al 2 O 3, ZrO 2 , TiO 2 or oxide such as ZnO, alkali metal salts such as Na 2 CO 3 or Li 2 CO 3, or alkaline earth metal salts such as BaCO 3 or MgCO 3 are used.
- the fifth method is employed when glass is supplied from a glass layer formed separately from the auxiliary discharge electrode 18.
- the fifth method will be described with reference to FIG.
- FIG. 5 shows an ESD protection device 11a according to a second embodiment of the present invention obtained by carrying out the fifth method.
- elements corresponding to the elements shown in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.
- the ESD protection device 11a shown in FIG. 5 is characterized in that a glass layer 26 is formed along the interface between the auxiliary discharge electrode 18 and the insulator base 12.
- the glass layer 26 is formed so as to contact the unfired auxiliary discharge electrode 18.
- the glass layer 26 is formed by applying a paste containing a material that generates at least a vitreous material after firing. In the firing step, the vitreous material generated in the glass layer 26 diffuses into the auxiliary discharge electrode 18, and the plurality of metal particles 24 are bonded by the vitreous material.
- vitreous material examples include SiO 2 —B 2 O 3 —CaO glass, SiO 2 —B 2 O 3 —Li 2 O glass, or SiO 2 —B 2 O 3 —Al 2 O. 3- Li 2 O—CaO glass or the like is used.
- the glass layer 26 may not be clearly recognized in the ESD protection device 11a as a finished product as a result of the diffusion of the vitreous material into the discharge auxiliary electrode 18.
- a state in which the plurality of metal particles 24 are bonded by the vitreous material can be obtained.
- a part of the oxide containing the second metal which is the main component of the shell portion 23 becomes an amorphous component.
- the main component of the shell portion is Al 2 O 3
- a part of this Al 2 O 3 can be an amorphous component.
- the plurality of metal particles 24 are bonded with the vitreous material containing the shell part 23.
- the discharge electrodes 16 and 17 and the discharge auxiliary electrode 18 are disposed inside the insulator base material 12, but may be disposed on the outer surface of the insulator base material.
- the cavity 19 is not necessarily formed.
- the firing for sintering the insulator base material 12 is performed simultaneously with the firing for sintering the discharge electrodes 16 and 17 and the discharge auxiliary electrode 18.
- An insulator base material to be prepared may be prepared in advance, and the discharge electrode and the discharge auxiliary electrode may be formed on the insulator base material.
- Example 1 ⁇ Preparation of evaluation sample> (1) Production of ceramic green sheet As a ceramic material, a material containing Ba, Al, and Si as main components was prepared. Each material was prepared to have a predetermined composition and calcined at 800 to 1000 ° C. The obtained calcined powder was pulverized with a zirconia ball mill for 12 hours to obtain a ceramic powder.
- this slurry was molded by a doctor blade method to produce a ceramic green sheet having a thickness of 50 ⁇ m.
- One of the produced ceramic green sheets is illustrated as a ceramic green sheet 31 in FIGS. 6 to 10, and the other is illustrated as a ceramic green sheet 36 in FIGS. 9 and 10. .
- Glass precursor powders C-1 and C-2 shown in Table 3 below are used as glass precursor powders to be included in the paste used for forming the discharge auxiliary electrode as necessary.
- a ceramic powder mainly composed of SiO 2 —BaO—Al 2 O 3 —MnO having a specific surface area shown in the column “SSA” in Table 3 is calcined at a temperature of 720 to 780 ° C.
- a glass precursor powder was prepared.
- the specific surface area of the obtained glass precursor powder after calcination is shown in the column of “SSA after calcination” in Table 3.
- “SSA” is obtained by the same method as in the case of glass powder.
- the green precursor powder is used in the same firing profile as that used in the firing step described later.
- the cross-sectional image of the obtained sintered body was subjected to TEM (transmission electron microscope) observation, electron diffraction and EDS (energy dispersive X-ray analyzer) analysis.
- TEM transmission electron microscope
- EDS energy dispersive X-ray analyzer
- Oxide powders O-1 to O-6 shown in Table 4 below are prepared as oxide powders to be included in the paste used to form the discharge auxiliary electrode as required. did. “Particle size distribution” in Table 4 is obtained by the same method as that for the metal powder, and “SSA” is obtained by the same method as that for the glass powder.
- organic vehicle As an organic vehicle to be a dispersion medium for dispersing the above-described metal powder and the like in the paste used to form the discharge auxiliary electrode, an ethcel resin having a weight average molecular weight of 5 ⁇ 10 4 and a weight average molecular weight of 8 An organic vehicle was obtained by dissolving 10 3 alkyd resin in terpineol. In the organic vehicle, the etose resin content was 9.0% by weight, the alkyd resin content was 4.5% by weight, and the terpineol content was 86.5% by weight.
- discharge auxiliary electrode pastes P-1 to P-19 are obtained by dispersing any of the metal powders M-1 to M-19 shown in Table 1 in the organic vehicle. It is.
- the discharge auxiliary electrode pastes P-20 to P-33 were mixed with the metal powder M-2 shown in Table 1 and the glass powders G-1 to G-1 shown in Table 2 in the organic vehicle. Any one of G-7 is dispersed.
- the discharge auxiliary electrode pastes P-34 to P-37 were mixed with the metal powder M-2 shown in Table 1 and the glass precursor powder C- shown in Table 3 in the organic vehicle. 1 and C-2 are dispersed.
- the discharge auxiliary electrode pastes P-38 to P-58 were mixed with the metal powder M-2 shown in Table 1 and the oxide powder O-1 shown in Table 4 in the organic vehicle.
- ⁇ O-6 or any one of alkali metal salt / alkaline earth metal salt powders R-1 to R-4 shown in Table 5 is dispersed.
- a resin bead paste was prepared in order to form a burned layer that was burned off during firing to form a cavity.
- a resin for burnt-out layer was prepared by mixing 38% by weight of crosslinked acrylic resin beads having an average particle size of 1 ⁇ m and 62% by weight of an organic vehicle prepared by dissolving ethyl cellulose in dihydroterpinyl acetate and mixing them with three rolls.
- a bead paste was prepared.
- external terminal electrode paste 80 wt% of Cu powder having an average particle diameter of about 1 ⁇ m, 5 borosilicate alkali glass frit having an average particle diameter of about 1 ⁇ m at a transition point of 620 ° C. and a softening point of 720 ° C.
- the external terminal electrode paste was prepared by preparing 15% by weight of an organic vehicle prepared by dissolving ethyl cellulose in terpineol and mixing by 15 rolls.
- FIG. 7 also shows the dimensions of other parts.
- a burnt-layer resin bead paste is applied so as to cover the gap G between the unfired first and second discharge electrodes 33 and 34, and unfired having a size of 140 ⁇ m ⁇ 150 ⁇ m.
- a burned-out layer 35 was formed.
- the insulator base material 37 was cut with a microcutter so as to have a planar size of 1.0 mm ⁇ 0.5 mm after firing. It should be understood that the dimensions shown in FIG. 7 and the outer shape of the ceramic green sheet 31 and the like shown in FIGS. 6 to 9 are those at a stage after this cutting process.
- an external electrode paste is applied on the outer surface of the insulator base material 37, whereby unfired first electrodes connected to the first and second discharge electrodes 33 and 34, respectively.
- First and second external terminal electrodes 38 and 39 were formed. In this way, an unfired ESD protection device 40 was obtained.
- the atmosphere of the firing furnace is controlled by using N 2 / H 2 / H 2 O, so that the oxygen concentrations are different from each other as shown in the “Baking conditions” column of Tables 10 to 12. Any one of the three firing conditions A, B and C was adopted.
- Baking condition A The oxygen concentration at which copper does not oxidize and aluminum, silicon, magnesium and nickel oxidize.
- Baking condition B The oxygen concentration at which copper, nickel, and aluminum, silicon, and magnesium oxidize.
- the oxygen partial pressure at which each of the metals is oxidized at the temperature T (K) was calculated by the following equation.
- Each ESD protection device was embedded in an epoxy resin and cured. After curing, the LT surface defined by the side extending in the length direction and the side extending in the thickness direction was exposed by polishing. Polishing was performed until it reached 1/2 of the width dimension.
- FIB focused ion beam processing was performed on the discharge auxiliary electrode exposed by polishing.
- the discharge auxiliary electrode sampled by FIB processing was subjected to TEM (transmission electron microscope) observation and analysis of various metals and oxygen by EDS (energy dispersive X-ray analyzer). From this TEM observation and ESD analysis, it was determined whether the metal particles of the discharge auxiliary electrode were core-shell structured metal particles having a metal oxide shell portion.
- Peak voltage characteristics 8 kV static electricity was applied to the ESD protection device according to each sample using an electrostatic test gun.
- the voltage measured by the oscilloscope is defined as the peak voltage (Vpeak1), and the peak voltage (Vpeak1) of less than 400V is determined to have the best peak voltage characteristics.
- “ ⁇ ” is displayed in the “Peak voltage” column, a peak voltage (Vpeak1) of 400 V or more and less than 700 V is judged to have better peak voltage characteristics, “ ⁇ ” is displayed in the same column, and the peak When the voltage (Vpeak1) is 700 V or higher, the peak voltage characteristic is determined to be poor, and “x” is displayed in the same column.
- a peak voltage characteristic after a drop impact is determined to be particularly excellent when “1.00 ⁇ Vpeak2 / Vpeak1 ⁇ 1.25”.
- “ ⁇ ” is displayed in the “peak voltage after drop impact” column, and “1.25 ⁇ Vpeak2 / Vpeak1 ⁇ 1.50” indicates that the peak voltage characteristics after drop impact are It is determined that the peak voltage characteristics after drop impact are deteriorated when “Vpeak2 / Vpeak1> 1.50” is displayed in the same column. “ ⁇ ” is displayed.
- the metal particle structure in the discharge auxiliary electrode is a core-shell structure having a metal oxide in the shell portion, and the core-shell structure Since the plurality of metal particles having the above are bonded with the vitreous substance, the peak voltage characteristic after the drop impact was evaluated as “ ⁇ ”.
- the metal particle structure in the discharge auxiliary electrode is a core-shell structure having a shell portion with a thickness of 100 to 350 nm. Short circuit resistance and peak voltage characteristics were evaluated as “ ⁇ ”.
- the initial short circuit was evaluated as “x” because the metal particle structure in the discharge auxiliary electrode was not a core-shell structure having a metal oxide in the shell portion. It was. This is presumably because the NiO shell was not formed because the oxygen concentration at which Cu and Ni were reduced was applied during firing.
- the initial short circuit was evaluated as “x” because the metal particle structure in the discharge auxiliary electrode was not a core-shell structure having a metal oxide in the shell portion. It was. This is presumably because the conductivity of the metal particles was significantly reduced because the oxygen concentration at which Cu was oxidized was applied during firing.
- Experimental Example 2 was performed in order to confirm that the glass from the glass layer 26 shown in FIG. 5 described above can bond a plurality of metal particles in the discharge auxiliary electrode.
- the “glass layer” and the “layer corresponding to the glass layer” were in contact with the discharge auxiliary electrode. In the sense of being a layer, it is generically referred to as a “contact layer”.
- pastes S-1 and S-2 having the compositions shown in Table 13 below were prepared.
- the discharge auxiliary electrode paste is applied on one main surface of the ceramic green sheet 31 shown in FIG. Except for forming an unsintered contact layer having a size of 150 ⁇ m ⁇ 100 ⁇ m by applying the contact layer paste on one main surface of the ceramic green sheet 31 before forming the discharge auxiliary electrode 32 for firing.
- an ESD protection device according to the sample was produced in the same manner as in Experimental Example 1.
- the metal particle structure in the discharge auxiliary electrode is a core-shell structure having a metal oxide in the shell portion, and the shell portion includes an oxide (Al 2 O 3 ) included in the contact layer. Since it reacts with particles to produce a vitreous material, a plurality of metal particles having a core-shell structure are bonded with vitreous material, and the peak voltage characteristics after drop impact are evaluated as “ ⁇ ”. It was.
- the metal particle structure in the discharge auxiliary electrode is a core-shell structure having a metal oxide in the shell portion, but a part of Al 2 O 3 in the shell portion becomes an amorphous component. Since the metal particles having the core-shell structure are bonded by the vitreous material derived from the shell portion, the peak voltage characteristic after the drop impact was evaluated as “ ⁇ ”.
- the metal particle structure in the discharge auxiliary electrode has a core-shell structure having a metal oxide in the shell portion, and the glass in the contact layer diffuses into the discharge auxiliary electrode, whereby the core-shell Since a plurality of metal particles having a structure are bonded with a vitreous material, the peak voltage characteristic after a drop impact was evaluated as “ ⁇ ”.
- ESD protection device Insulator base material 16, 17 Discharge electrode 18 Discharge auxiliary electrode 19, 41 Cavity 20, 21 External terminal electrode 22 Core part 23 Shell part 24, 25 Metal particle 26 Glass layer 27 Glassy content Substances 31, 36 Ceramic green sheet 32 Unsintered discharge auxiliary electrodes 33, 34 Unsintered discharge electrode 35 Unsintered burnt layer 37 Unsintered insulating base material 38, 39 Unsintered external terminal electrode 40 Unsintered ESD Protection device G gap
Abstract
Description
〈評価試料の作製〉
(1)セラミックグリーンシートの作製
セラミック材料として、Ba、Al、およびSiを主たる成分とする材料を用意した。そして、各材料を所定の組成になるよう調合し、800~1000℃で仮焼した。得られた仮焼粉末をジルコニアボールミルで12時間粉砕し、セラミック粉末を得た。
(2)-1.金属粉末の準備
放電補助電極を形成するために用いられるペーストに含有させるべき金属粉末として、以下の表1に示した金属粉末M-1~M-19をそれぞれアトマイズ法で作製した。表1に示した「粒度分布」はレーザー回折式粒度分布法により、「比重」は気相置換法により、「組成」はICP-AES法(誘導結合プラズマ発光分析)により求めた。
放電補助電極を形成するために用いられるペーストに必要に応じて含有させるべきガラス粉末として、以下の表2に示されたガラス粉末G-1~G-7をそれぞれ用意した。表2の「Ts」は、示差熱分析によって測定したガラス軟化点であり、「SSA」は、ガス吸着法によって測定した比表面積である。「粒度分布」は、金属粉末の場合と同様の方法により求めたものである。
放電補助電極を形成するために用いられるペーストに必要に応じて含有させるべきガラス前駆体粉末として、以下の表3に示されたガラス前駆体粉末C-1およびC-2をそれぞれ用意した。より詳細には、表3の「SSA」の欄に示す比表面積を有するSiO2-BaO-Al2O3-MnOを主成分としたセラミック粉末を、温度720~780℃で仮焼することにより、ガラス前駆体粉末を作製した。得られた仮焼後のガラス前駆体粉末の比表面積は、表3の「仮焼後のSSA」の欄に示されている。「SSA」は、ガラス粉末の場合と同様の方法により求めたものである。
放電補助電極を形成するために用いられるペーストに必要に応じて含有させるべき酸化物粉末として、以下の表4に示された酸化物粉末O-1~O-6をそれぞれ用意した。表4の「粒度分布」は、金属粉末の場合と同様の方法により求めたものであり、「SSA」は、ガラス粉末の場合と同様の方法により求めたものである。
放電補助電極を形成するために用いられるペーストに必要に応じて含有させるべきアルカリ金属塩粉末およびアルカリ土類金属塩粉末として、以下の表5に示された金属塩粉末R-1~R-4をそれぞれ用意した。表5の「粒度分布」は、金属粉末の場合と同様の方法により求めたものである。
放電補助電極を形成するために用いられるペーストにおける上述した金属粉末等を分散させる分散媒となるべき有機ビヒクルとして、重量平均分子量が5×104のエトセル樹脂と重量平均分子量が8×103のアルキッド樹脂とをターピネオールに溶解することによって、有機ビヒクルを得た。有機ビヒクル中において、エトセル樹脂の含有率を9.0重量%、アルキッド樹脂の含有率を4.5重量%、ターピネオールの含有率を86.5重量%とした。
次に、上記金属粉末と、上記有機ビヒクルと、必要に応じて、ガラス粉末、ガラス前駆体粉末、酸化物粉末、またはアルカリ金属塩/アルカリ土類金属塩粉末とを、表6~表9に示す体積比となるように調合し、三本ロールにて分散処理し、放電補助電極用ペーストP-1~P-58を得た。以下、放電補助電極用ペーストP-1~P-58を、その組成に応じた分類に従って、より詳細に説明する。
平均粒径1μmのCu粉末を40重量%と、平均粒径3μmのCu粉末を40重量%と、エチルセルロースをターピネオールに溶解して作製した有機ビヒクルを20重量%とを調合し、3本ロールにより混合することにより、放電電極用ペーストを作製した。
焼成時に焼失して空洞となる焼失層を形成するために樹脂ビーズペーストを作製した。平均粒径1μmの架橋アクリル樹脂ビーズ38重量%と、エチルセルロースをジヒドロターピニルアセテートに溶解して作製した有機ビヒクル62重量%とを調合し、3本ロールにより混合することにより、焼失層用樹脂ビーズペーストを作製した。
平均粒径が約1μmのCu粉末を80重量%と、転移点620℃、軟化点720℃で平均粒径が約1μmのホウケイ酸アルカリ系ガラスフリットを5重量%と、エチルセルロースをターピネオールに溶解して作製した有機ビヒクルを15重量%とを調合し、3本ロールにより混合することにより、外部端子電極用ペーストを作製した。
まず、図6に示すように、セラミックグリーンシート31の一方主面上に放電補助電極用ペーストを塗布することによって、150μm×100μmの寸法の未焼成の放電補助電極32を形成した。ここで、放電補助電極用ペーストとして、前述した放電補助電極用ペーストP-1~P-58のいずれかを、表10、表11および表12の「放電補助電極ペースト記号」の欄に示すように用いた。
上記のように、未焼成の放電補助電極層32、未焼成の放電電極33および34ならびに未焼成の焼失層35を形成した第1のセラミックグリーンシート31の主面上に、図9に示すように、ペーストが塗布されていない第2のセラミックグリーンシート36を複数枚、積層・圧着し、未焼成の絶縁体基材37を得た。この絶縁体基材37は、焼成後の厚みが0.3mmになるようにした。
上記絶縁体基材37を、焼成後において1.0mm×0.5mmの平面寸法となるように、マイクロカッターにてカットした。なお、図7に示した寸法および図6ないし図9に示したセラミックグリーンシート31等の外形状は、このカット工程の後の段階でのものであると理解すべきである。
上記未焼成のESD保護デバイス40を、980~1000℃の範囲にある適当な最高温度で焼成し、図11に示すような空洞部41を有するESD保護デバイス42を得た。
銅が酸化せず、アルミニウム、ケイ素、マグネシウムおよびニッケルが酸化する酸素濃度。
銅およびニッケルが酸化せず、アルミニウム、ケイ素およびマグネシウムが酸化する酸素濃度。
銅、アルミニウム、ケイ素、マグネシウムおよびニッケルが酸化する酸素濃度。
・ln(CuPO2)>{-338904+(-33TlogT)+247T}/(8.314T)
・ln(AlPO2)>{-1117993+(-11TlogT)+244T}/(8.314T)
・ln(SiPO2)>{-881150+(-13TlogT)+218T}/(8.314T)
・ln(MgPO2)>{-1207921+(-25TlogT)+284T}/(8.314T)
・ln(NiPO2)>{-489110+197T}/(8.314T)
〈特性評価〉
次に、上述のようにして作製した各試料に係るESD保護デバイスについて、以下の方法で各特性を調べた。
各ESD保護デバイスを、エポキシ樹脂に埋め、硬化させた。硬化後、研磨によって、長さ方向に延びる辺と厚み方向に延びる辺とによって規定されるLT面を露出させた。なお、研磨は、幅方向寸法の1/2に達するまで行なった。次いで、研磨によって露出した放電補助電極に対して、FIB(収束イオンビーム)加工を行なった。FIB加工によってサンプリングした放電補助電極に対して、TEM(透過型電子顕微鏡)観察および各種金属と酸素についてのEDS(エネルギー分散型X線分析装置)による分析を行なった。このTEM観察およびESD分析から、放電補助電極の金属粒子が金属酸化物のシェル部を有するコア-シェル構造金属粒子であるかの判定を行なった。
「コア-シェル構造」について「○」と判定された試料について、放電補助電極における複数の金属粒子間がガラス質含有物質で結合されているかを調査した。すなわち、コア-シェル構造を有する、ある特定の金属粒子のシェル部とこれに隣接する金属粒子のシェル部との間に存在する接合部を電子線回折装置により解析し、電子線回折パターンが見られない場合を、金属粒子間がガラス質含有物質で結合されていると判定した。表10~表12の「ガラス質含有物質との結合性」の欄において、金属粒子間がガラス質含有物質で結合されていると判定したものを「○」と表示し、結合されていないと判定したものを「×」と表示した。
各試料に係るESD保護デバイスの外部端子電極間に50Vの直流電圧を印加して、絶縁抵抗を測定した。108Ω以上の絶縁抵抗を示したものを初期ショート特性が良好であると判定し、表10~表12の「初期ショート」の欄に「○」と表示し、108Ω未満の絶縁抵抗を示したものを初期ショート特性が不良であると判定し、同欄に「×」と表示した。
各試料に係るESD保護デバイスに対して、0.2kV印加を10回→0.4kV印加を10回→0.6kV印加を10回→1kV印加を10回→2kV印加を10回→4kV印加を10回順次実施した。印加毎に各試料の絶縁抵抗を測定し、1度も108Ω未満の抵抗値が測定されなかったものをショート耐性が最も優れていると判定し、表10~表12の「ショート耐性」の欄に「◎」と表示し、1度でも106Ω以上108Ω未満の抵抗値が測定されたものをショート耐性がより良好であると判定し、同欄に「○」と表示し、1度でも106Ω未満の抵抗値が測定されたものをショート耐性が不良であると判定し、同欄に「×」と表示した。
静電気試験ガンを用いて、各試料に係るESD保護デバイスに8kVの静電気を印加した。その際に、オシロスコープで測定される電圧をピーク電圧(Vpeak1)と定義し、ピーク電圧(Vpeak1)が400V未満のものをピーク電圧特性が最も優れていると判定し、表10~表12の「ピーク電圧」の欄に「◎」と表示し、ピーク電圧(Vpeak1)が400V以上かつ700V未満のものをピーク電圧特性がより良好であると判定し、同欄に「○」と表示し、ピーク電圧(Vpeak1)が700V以上のものをピーク電圧特性が不良であると判定し、同欄に「×」と表示した。
各試料に係るESD保護デバイスに対して、地上1.8mの地点から50回垂直落下させた後、上記ピーク電圧(Vpeak1)測定の場合と同様、静電気試験ガンを用いて、ESD保護デバイスに8kVの静電気を印加し、その際に、オシロスコープで測定される電圧を落下衝撃後のピーク電圧(Vpeak2)と定義した。
上記「ショート耐性」、「ピーク電圧」および「落下衝撃後のピーク電圧」の評価において、すべて「◎」と評価された試料については、表10~表12の「総合評価」の欄に「◎」と表示し、「◎」と「○」とが混在する試料については、同欄に「○」と表示し、「初期ショート」が「×」と評価された試料については、同欄に「×」と表示した。
実験例2は、前述の図5に示したガラス層26からのガラスによって、放電補助電極における複数の金属粒子間を結合し得ることを確認するために実施した。なお、実験例2では、ガラスを含有しない、ガラス層に相当する層を形成した試料も比較例として作製したので、「ガラス層」および「ガラス層に相当する層」を、放電補助電極に接する層であるという意味で「接触層」と総称する。
接触層を形成するためのペーストとして、以下の表13に示す組成のペーストS-1およびS-2を用意した。
上述のようにして作製した各試料に係るESD保護デバイスについて、実験例1の場合と同様の方法で各特性を調べた。その結果が表14に示されている。
12 絶縁体基材
16,17 放電電極
18 放電補助電極
19,41 空洞
20,21 外部端子電極
22 コア部
23 シェル部
24,25 金属粒子
26 ガラス層
27 ガラス質含有物質
31,36 セラミックグリーンシート
32 未焼成の放電補助電極
33,34 未焼成の放電電極
35 未焼成の焼失層
37 未焼成の絶縁体基材
38,39 未焼成の外部端子電極
40 未焼成のESD保護デバイス
G ギャップ
Claims (17)
- 互いに対向するように配置された第1および第2の放電電極と、
前記第1および第2の放電電極間に跨るように形成された放電補助電極と、
前記第1および第2の放電電極ならびに前記放電補助電極を保持する絶縁体基材と
を備え、
前記放電補助電極は、第1の金属を主成分とするコア部と第2の金属を含む金属酸化物を主成分とするシェル部とからなるコア-シェル構造を有する複数の金属粒子の集合体から構成されている、
ESD保護デバイス。 - 前記複数の金属粒子の集合体は、複数の前記金属粒子間を結合するガラス質含有物質を含む、請求項1に記載のESD保護デバイス。
- 前記第2の金属を含む前記金属酸化物は、当該金属酸化物のアモルファス成分を含む、請求項1または2に記載のESD保護デバイス。
- 前記シェル部の厚みが100~350nmである、請求項1ないし3のいずれかに記載のESD保護デバイス。
- 前記第2の金属は、前記第1の金属よりも酸化されやすい、請求項1ないし4のいずれかに記載のESD保護デバイス。
- 前記第1の金属は、銅または銅を主成分とした銅系合金である、請求項5に記載のESD保護デバイス。
- 前記第2の金属を含む前記金属酸化物は、酸化アルミニウム、酸化ケイ素、酸化マグネシウムおよび酸化ニッケルから選ばれる少なくとも1種である、請求項5または6に記載のESD保護デバイス。
- 前記コア部は、副成分として前記第2の金属を含む、請求項5ないし7のいずれかに記載のESD保護デバイス。
- 前記第1および第2の放電電極ならびに前記放電補助電極は、前記絶縁体基材の内部に配置され、前記絶縁体基材は、前記第1および第2の放電電極間のギャップを配置する空洞を有し、前記絶縁体基材の表面上に形成されかつ前記第1および第2の放電電極にそれぞれ電気的に接続される、第1および第2の外部端子電極をさらに備える、請求項1ないし8のいずれかに記載のESD保護デバイス。
- 第1の金属および前記第1の金属よりも酸化されやすい第2の金属を含む合金からなる合金粉末を用意する工程と、
絶縁体基材を用意する工程と、
前記合金粉末を含む未焼成の放電補助電極を前記絶縁体基材の表面または内部に形成する工程と、
前記放電補助電極上において互いに対向するように配置される第1および第2の放電電極を前記絶縁体基材の表面または内部に形成する工程と、
前記未焼成の放電補助電極を、前記第1の金属が酸化されず、前記第2の金属が酸化される酸素濃度を有する雰囲気下で焼成する工程と
を備え、
前記焼成する工程は、前記合金粉末を構成する各金属粒子において、前記第2の金属を当該金属粒子の表面に向かって移動させ、表面に達した時点で酸化させて、前記第2の金属を含む金属酸化物とし、当該金属酸化物をもって、前記金属粒子におけるシェル部を形成する工程を含む、
ESD保護デバイスの製造方法。 - 前記合金粉末を用意する工程は、アトマイズ法を用いて前記合金粉末を製造する工程を含む、請求項10に記載のESD保護デバイスの製造方法。
- 前記絶縁体基材を用意する工程は、少なくとも焼成後にガラス質含有物質を生成する材料を含む未焼成の絶縁体基材を用意する工程を含み、
前記焼成する工程は、前記未焼成の絶縁体基材を焼結させるとともに、前記ガラス質含有物質を生成する工程と、複数の前記金属粒子間を前記絶縁体基材において生成した前記ガラス質含有物質で結合する工程とを含む、
請求項10または11に記載のESD保護デバイスの製造方法。 - ガラス質含有物質を用意する工程をさらに備え、
前記未焼成の放電補助電極を絶縁体基材の表面または内部に形成する工程において形成される前記未焼成の放電補助電極は、前記ガラス質含有物質をさらに含み、
前記焼成する工程は、複数の前記金属粒子間を前記ガラス質含有物質で結合する工程を含む、
請求項10または11に記載のESD保護デバイスの製造方法。 - 焼成によりガラスを生成するガラス前駆体を用意する工程をさらに備え、
前記未焼成の放電補助電極を絶縁体基材の表面または内部に形成する工程において形成される前記未焼成の放電補助電極は、前記ガラス前駆体をさらに含み、
前記焼成する工程は、前記ガラス前駆体からガラスを生成する工程と、複数の前記金属粒子間を前記ガラス前駆体から生成した前記ガラスで結合する工程とを含む、
請求項10または11に記載のESD保護デバイスの製造方法。 - 焼成時に、前記金属粒子の前記シェル部と反応してガラスを生成する、酸化物、アルカリ金属塩およびアルカリ土類金属塩から選ばれる少なくとも1種のガラス生成物質を用意する工程をさらに備え、
前記未焼成の放電補助電極を絶縁体基材の表面または内部に形成する工程において形成される前記未焼成の放電補助電極は、前記ガラス生成物質をさらに含み、
前記焼成する工程は、前記金属粒子の前記シェル部と前記ガラス生成物質とを反応させてガラスを生成する工程と、複数の前記金属粒子間を前記シェル部と前記ガラス生成物質との反応によって生成した前記ガラスで結合する工程とを含む、
請求項10または11に記載のESD保護デバイスの製造方法。 - 前記未焼成の放電補助電極に接するように、少なくとも焼成後にガラス質含有物質を生成する材料を含むガラス層を形成する工程をさらに備え、
前記焼成する工程は、複数の前記金属粒子間を前記ガラス層で生成する前記ガラス質含有物質で結合する工程を含む、
請求項10または11に記載のESD保護デバイスの製造方法。 - 前記絶縁体基材を用意する工程は、第1および第2のセラミックグリーンシートを含む複数のセラミックグリーンシートを用意する工程を含み、
前記未焼成の放電補助電極を形成する工程ならびに前記第1および第2の放電電極を形成する工程は、前記第1のセラミックグリーンシート上において実施され、
前記第1および第2の放電電極間のギャップを覆うように焼失層を形成する工程と、
前記第1のセラミックグリーンシート上に、前記未焼成の放電補助電極、前記第1および第2の放電電極ならびに前記焼失層を覆うように前記第2のセラミックグリーンシートを積層し、未焼成の前記絶縁体基材を得る工程と、
前記絶縁体基材の表面上に、前記第1および第2の放電電極にそれぞれ電気的に接続される、第1および第2の外部端子電極を形成する工程と
をさらに備え、
前記焼成する工程は、前記セラミックグリーンシートを焼結させて前記絶縁体基材を得る工程および前記焼失層を焼失させる工程を含む、
請求項10ないし16のいずれかに記載のESD保護デバイスの製造方法。
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