JP4320565B2 - Multi-layer composite functional device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multilayer composite functional element used as a surge absorber for protecting an electronic circuit from transient voltage such as lightning surge and static electricity, noise, and the like.
[0002]
[Prior art]
Surge absorbers are connected to parts where electronic devices such as telephones and modems are connected to communication lines, or parts that are susceptible to electric shock due to abnormal voltages such as lightning surges and static electricity, such as CRT drive circuits. It is used to prevent it.
[0003]
As this type of surge absorber, for example, there is a protective element described in Patent Document 1 described later. This protective element has an element body in which a varistor part and a capacitor part are laminated, and the varistor part and the capacitor part are electrically connected in parallel by a terminal electrode.
[0004]
This protective element absorbs noise by the varistor part and electrically absorbs the capacitor part with respect to the varistor part in order to absorb fast rising noise that cannot be absorbed due to the characteristics of the varistor part. Are provided in parallel.
[0005]
[Patent Document 1]
JP-A-10-125557, claim 1, paragraph 0004, FIG. 1, FIG.
[0006]
[Problems to be solved by the invention]
In recent years, with the further miniaturization and thinning of electronic devices, there has been a demand for further miniaturization and thinning of electronic components, and surge absorbers are no exception.
In recent years, the circuit voltage of electronic devices has been lowered to reduce power consumption. In order to reliably protect the circuit, the operating voltage of the varistor section (hereinafter referred to as “varistor voltage”) is also increased. There is a demand for lower voltage.
In addition, as the speed of electronic equipment increases, the signal becomes higher in frequency. Therefore, in order to accurately transmit the waveform, it is required to reduce the capacitance of the surge absorber.
[0007]
If the distance between the varistor internal electrodes in the varistor portion is reduced, the varistor voltage is lowered and the surge absorber can be made thinner. However, since the varistor portion also functions as a capacitor due to its structure, when the varistor internal electrodes are brought close to each other in this way, the capacitance becomes large and the high-frequency signal cannot be handled.
If the area of the varistor internal electrode is reduced, the capacitance of the varistor part can be reduced, and the external dimensions of the surge absorber can be reduced, but if the area of the varistor internal electrode is reduced in this way, The surge current withstand capability of the varistor part also decreases.
Thus, conventionally, it has not been possible to simultaneously realize a reduction in the varistor voltage, a reduction in capacitance, and maintenance of surge current resistance.
[0008]
The present invention has been made in view of the above circumstances, and is a multilayer composite functional element capable of simultaneously realizing a reduction in varistor voltage and a reduction in capacitance while maintaining a surge current withstand capability. The purpose is to provide.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, a multilayer composite functional element according to the present invention includes a multilayer composite having an element body in which a varistor part and a capacitor part are laminated, and an external electrode provided on the outer surface of the element body. The varistor section includes at least a pair of varistor internal electrodes arranged in an opposed state and a varistor layer sandwiched between the varistor internal electrodes, and the pair of varistor internal electrodes are opposed to each other. The area of the region to be set is set according to the surge current withstand capability required for the varistor part, and the capacitor part is sandwiched between at least a pair of capacitor internal electrodes arranged in an opposing state and the capacitor internal electrode and a dielectric layer, an area of a region opposing pairs of the capacitor internal electrode is set in accordance with the electrostatic capacitance required for the capacitor portion, the outer The electrode, and the varistor section and the capacitor section are electrically connected in series, the device main body, said varistor portion is the configurations laminated sandwiched between between the capacitor section It is a feature.
[0010]
In the multilayer composite functional element configured as described above, since the varistor part and the capacitor part are electrically connected in series, compared to the case where the varistor part and the capacitor part are electrically connected in parallel, Capacitance is reduced.
In addition, the area of the mutually opposing regions of the varistor internal electrode pair can be appropriately set according to the surge current tolerance required for the varistor part, and the area of the mutually opposing region of the capacitor internal electrode pair can be It can set suitably according to the electrostatic capacitance requested | required of a part.
In addition, since the varistor layer is covered and protected by the capacitor portion, it is not necessary to take measures to prevent plating erosion when forming the external electrode.
[0011]
In the multilayer composite functional element, one of the pair of varistor internal electrodes is exposed on the first outer surface of the element body, and the other is exposed on the second outer surface of the element body. One of the pair of capacitor internal electrodes is exposed on the third outer surface of the element body, and the other is exposed on the second outer surface of the element body, and the external electrode Formed on the second outer surface and connected to the other varistor internal electrode and the other capacitor internal electrode, and formed on the first outer surface and connected to the one varistor internal electrode And a second terminal electrode formed on the third outer surface and connected to the one capacitor internal electrode.
[0012]
In this case, it is easy to make a multilayer composite functional element into a chip, and it is easy to reduce the size.
Further, the multilayer composite functional element, wherein the varistor layer, the ZnO and _Bi 2 _{O 3} as essential components, these _{MnO 2, CoCO 3, Sb 2} O 3, SnO 2, Cr 2 O 3, a SiO ₂ The dielectric layer is made of a material to which selected components are added, and the dielectric layer is made of MgO, TiO ₂ , CaO, SrO, BaO having a purity of 99% or more, or a material in which a plurality of components are mixed.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a multilayer composite functional element according to the present invention will be described in detail with reference to the drawings.
[0015]
In the present embodiment, the multilayer composite functional element is the surge absorber 1.
As shown in FIG. 1, the surge absorber 1 has an element body 4 having, for example, a substantially rectangular parallelepiped shape in which a varistor part 2 and a capacitor part 3 each having a substantially rectangular plate shape are stacked. On the outer surface, a ground electrode 5 and a terminal electrode 6 are provided as external electrodes.
Here, the element body 4 has a configuration in which the varistor part 2 is sandwiched between two capacitor parts 3.
[0016]
The varistor part 2 has at least a pair of varistor internal electrodes 11 arranged in an opposing state, and a varistor layer 12 sandwiched between the varistor internal electrodes 11. Here, three pairs of varistor internal electrodes 11 are provided.
The varistor part 2 is formed by laminating a plurality of sheets in which an electrode pattern to be the varistor internal electrode 11 is formed on at least one surface of a substantially rectangular sheet made of a varistor material having varistor characteristics (that is, a voltage nonlinear resistance ceramic). It is supposed to be configured.
[0017]
One of the paired varistor internal electrodes 11 (hereinafter referred to as the first varistor internal electrode 11a) is provided from one end to the center of the varistor portion 2 in the longitudinal direction, and the end is the element body. 4 is exposed on one end face F1 (first outer surface) in the longitudinal direction.
The other of the varistor internal electrodes 11 (hereinafter referred to as the second varistor internal electrode 11b) is provided from one long side to the other long side of the varistor part 2, and its end is the element body. 4 is exposed to a side surface F2 (second outer surface) parallel to the longitudinal direction. Here, the second varistor internal electrode 11 b is narrowed in the vicinity of the long side of the varistor portion 2 and is exposed only in a part of the longitudinal direction of the side surface F <b> 2 of the element body 4. The second varistor internal electrode 11b is formed wider at the center of the varistor part 2 than the vicinity of the long side, and the area is secured.
[0018]
Of these first and second varistor internal electrodes 11a and 11b, the regions facing each other and the portion sandwiched between these regions in the varistor layer 12 act as varistors. Of the first and second varistor internal electrodes 11a and 11b, the area of the region facing each other is proportional to the surge current withstand capability of the varistor part 2, and this area is equivalent to the surge current withstand capability required for the varistor part 2. It is set accordingly.
[0019]
The capacitor unit 3 includes at least a pair of capacitor internal electrodes 16 arranged in an opposed state, and a dielectric layer 17 sandwiched between the capacitor internal electrodes 16. Here, two pairs of capacitor internal electrodes 16 are provided for each capacitor unit 3.
The capacitor unit 3 has a configuration in which a plurality of, for example, a rectangular sheet made of a dielectric material, on which an electrode pattern to be the capacitor internal electrode 16 is formed, is stacked on at least one surface.
[0020]
One of the paired capacitor internal electrodes 16 (hereinafter referred to as the first capacitor internal electrode 16a) is provided from one end in the longitudinal direction of the capacitor portion 3 to the center portion, and the end portion is the element body. 4 is exposed at the other end face F3 (third end face) facing the opposite side to the one end face F1 from which the first varistor internal electrode 11a of the varistor portion 2 is exposed.
The other of the capacitor internal electrodes 16 (hereinafter referred to as the second capacitor internal electrode 16b) is provided from one long side to the other long side of the capacitor unit 3, and the end thereof is connected to the element body. 4 is exposed to a side surface F2 parallel to the longitudinal direction. Here, the second capacitor internal electrode 16 b is narrowed in the vicinity of the long side of the capacitor portion 3 and is exposed only in a part of the longitudinal direction of the side surface F <b> 2 of the element body 4. The second capacitor internal electrode 16b is formed wider at the central portion of the capacitor portion 3 than the portion near the long side, and the area thereof is secured.
[0021]
Of these first and second capacitor internal electrodes 16a and 16b, the regions facing each other and the portion sandwiched between these regions in the dielectric layer 17 act as capacitors. Of the first and second capacitor internal electrodes 16a and 16b, the area of the region facing each other is proportional to the capacitance of the capacitor unit 3, and this area is the capacitance required for the capacitor unit 3. It is set accordingly.
[0022]
The ground electrode 5 is located at an intermediate position in the longitudinal direction of the side surface F2 parallel to the longitudinal direction of the outer surface of the element body 4 where the lamination boundary between the varistor portion 2 and the capacitor portion 3 is exposed. It is provided so as to cover.
The second varistor internal electrode 11b of the varistor part 2 and the second capacitor internal electrode 16b of the capacitor part 3 are electrically connected to the ground electrode 5 at the end exposed on the side surface F2 of the element body 4, respectively. Thus, the varistor part 2 and the capacitor part 3 are electrically connected in series.
[0023]
The element body 4 has a first terminal electrode 6a provided as a terminal electrode 6 so as to cover one end face F1 in the longitudinal direction of the element body 4, and a second terminal provided so as to cover the other end face F3. An electrode 6b is provided. Note that the surfaces of the terminal electrodes 6 are subjected to Ni plating and further subjected to solder plating.
The first varistor internal electrode 11a of the varistor portion 2 has an end portion exposed at one end face F1 of the element body 4 electrically connected to the first terminal electrode 6a. In addition, the first capacitor internal electrode 16a of the capacitor portion 3 has an end portion exposed at the other end face F3 of the element body 4 electrically connected to the second terminal electrode 6b.
[0024]
As shown in the equivalent circuit diagram of FIG. 2, the surge absorber 1 configured as described above includes a pair of varistor internal electrodes 11 connected in parallel in the varistor portion 2, and a pair of each varistor internal electrode 11 and each pair. The varistor layer 12 sandwiched between the varistor internal electrodes 11 acts as a varistor 21. The varistor 21 also functions as a capacitor because of its structure. In FIG. 2, the capacitor action of the varistor 21 is virtually shown as a capacitor 22.
On the other hand, in the capacitor unit 3, a pair of each capacitor internal electrode 16 is connected in parallel, and the pair of each capacitor internal electrode 16 and the dielectric layer 17 sandwiched between each capacitor internal electrode 16 act as the capacitor 23. .
[0025]
As described above, since the varistor unit 2 and the capacitor unit 3 are connected in series, the capacitance of the surge absorber 1 is C _I , the capacitance of the capacitor 22 formed by the varistor 21 is C _V , and the capacitor unit 3. Assuming that the capacitance of the capacitor 23 is C, the following relationship is established.
1 / C _I = 1 / C _V + 1 / C (1)
That, _{C I} is expressed by the following equation.
C _I = C _V × C / (C _V + C) (2)
[0026]
In contrast, as in the conventional surge absorber, when connecting the varistor portion 2 and the capacitor 3 in parallel, the capacitance C _P of the surge absorber 1 is expressed by the following equation.
C _P = C _V + C (3)
And, since it is C I _{<C P,} the surge absorber 1 according to this embodiment, the electrostatic capacity is small compared to the conventional surge absorber.
[0027]
As described above, the surge absorber 1 according to the present embodiment has a smaller capacitance than the conventional surge absorber composed of the varistor section 2 and the capacitor section 3 having the same configuration, so that even if a high frequency signal is input, the waveform thereof is It is difficult to collapse and is suitable for high-frequency circuits and high-speed communication circuits.
Since the capacitance is smaller than that of the conventional surge absorber, the distance between the varistor internal electrodes 11 of the varistor part 2 is further increased than that of the conventional surge absorber. The surge absorber 1 can be further reduced in thickness and the varistor voltage can be reduced without reducing the area of the varistor internal electrode 11 (that is, while maintaining the surge current withstand capability of the varistor portion 2). It becomes.
[0028]
Here, generally, external electrodes are formed by plating on the outer surface of the element body of the surge absorber. However, the varistor material used for the varistor portion 2 is eroded and altered when the plating process is performed. End up.
For this reason, in the conventional surge absorber, in order to maintain the characteristics of the varistor part, the surface of the varistor part is protected by applying a glass coating or the like before forming the external electrode.
On the other hand, in the surge absorber 1 according to the present embodiment, since the varistor part 2 is sandwiched between the capacitor parts 3 and the varistor layer 12 in the vicinity of the varistor internal electrode 11 is protected, the varistor part 2 is coated. Therefore, the manufacturing process can be simplified and the manufacturing cost can be reduced as compared with the conventional surge absorber.
[0029]
Next, a method for manufacturing the surge absorber 1 configured as described above will be described with reference to FIG.
The element body 4 of the surge absorber 1 is formed by laminating and sintering a varistor material green sheet to be the varistor part 2 and a dielectric green sheet to be the capacitor part 3. Below, the case where the several element main body 4 is produced simultaneously is demonstrated, FIG. 3 shows one of the several element main bodies 4 produced simultaneously.
[0030]
Hereinafter, a method for producing a varistor material green sheet to be the varistor part 2 will be described.
First, a varistor material is mixed with pure water to prepare a slurry. The varistor material contains ZnO (zinc oxide) and Bi ₂ O ₃ (bismuth trioxide) as essential components, and these include MnO ₂ (manganese dioxide), CoCO ₃ (cobalt carbonate), Sb ₂ O ₃ (antimony trioxide), This is a voltage non-linear resistance porcelain to which an element selected from SnO ₂ (tin oxide), Cr ₂ O ₃ (chromium oxide), and SiO ₂ (silicon dioxide) is added.
Here, ZnO, Bi ₂ O ₃ , CoCO ₃ , MnO ₂ , and Sb ₂ O ₃ having a purity of 99% or more were 98 mol%, 0.5 mol%, 0.5 mol%, 0.5 mol%, 0.5 mol%, respectively. The pure water is added to this and mixed with a ball mill for 24 hours to prepare a slurry.
[0031]
The slurry is dried by filtration and granulated, and then calcined at a temperature of 800 ° C. for 2 hours.
After coarsely pulverizing the fired product, pure water is added to the pulverized product and finely pulverized with a ball mill, followed by filtration and drying, and then dispersed in a solvent together with an organic binder such as ethyl cellulose to prepare a slurry again.
A varistor green sheet B having a predetermined thickness is produced from this slurry by a doctor blade method, and punched to a predetermined dimension.
[0032]
A first varistor internal electrode 11a extending from one end in the longitudinal direction of the region Sb to the central portion is provided as a varistor internal electrode 11 in each of the regions Sb to be the varistor portions 2 on the varistor material green sheet B. One varistor material green sheet B1 is obtained.
Further, a second varistor internal electrode 11b extending from one long side to the other long side is provided as a varistor internal electrode 11 in each of the regions Sb to be the varistor portions 2 on the varistor material green sheet B, and the second varistor internal electrode 11b. The varistor material green sheet B2 is obtained.
Here, the varistor internal electrode 11 is formed, for example, by screen-printing a conductive paste on the varistor material green sheet B. Examples of the conductive paste include Pt (platinum), Pd (palladium), Ag-Pt (silver / platinum), Ag (silver), or the like is used.
[0033]
Next, a method for producing a dielectric green sheet to be the capacitor unit 3 will be described.
First, a dielectric green sheet C having a desired size, for example, a rectangular shape is manufactured from a dielectric material in the same manner as the above-described method for manufacturing a varistor green sheet.
The dielectric material is a ferroelectric material, for example, any one of MgO (magnesium oxide), TiO ₂ (titanium oxide), CaO (calcium oxide), SrO (strontium oxide), BaO (barium oxide) having a purity of 99% or more. Alternatively, a ceramic material composed of a plurality of mixtures is used. Here, an appropriate amount of glass powder is mixed with the ceramic material in order to match the shrinkage ratio during firing of the dielectric material with the shrinkage ratio during firing of the varistor material.
[0034]
A first capacitor internal electrode 16a extending from one end to the center in the longitudinal direction is provided as a capacitor internal electrode 16 in each of the regions Sc to be the capacitor portions 3 on the dielectric green sheet C, thereby providing a first dielectric. A green sheet C1 is obtained.
In addition, a second capacitor internal electrode 16b extending from one long side to the other long side is provided as a capacitor internal electrode 16 in each of the regions Sc to be the capacitor portions 3 on the dielectric green sheet C to provide a second. A dielectric green sheet C2 is obtained.
The capacitor internal electrode 16 is formed by the same method as the capacitor internal electrode 11.
[0035]
A plurality of sets of the first and second varistor material green sheets B1 and B2 and the first and second dielectric green sheets C1 and C2 obtained as described above are laminated, and each varistor section 2 or each capacitor is laminated. The element body 4 before firing is obtained by cutting out each region to be the part 3.
The element body 4 before firing is fired at an appropriate temperature in accordance with the combination of materials of the varistor part 2 and the capacitor part 3, and an element having a varistor part 2 having varistor characteristics and a capacitor part 3 functioning as a capacitor. A main body 4 is obtained.
[0036]
The element body 4 is put into a barrel polishing apparatus together with a ZrO ₂ (zirconium oxide) ball and subjected to barrel polishing to remove burrs and edges, and then the varistor portion 2 on the side surface F2 along the longitudinal direction of the element body 4. The ground electrode 5 is formed by applying or printing, for example, Ag paste on the side where the lamination boundary between the capacitor portion 3 and the capacitor portion 3 is exposed. Further, Ag paste is applied to the longitudinal end faces F1 and F3 of the element body 4 to form the terminal electrode 6, and the terminal electrode 6 is further subjected to Ni plating and solder plating, whereby the surge absorber according to the present embodiment. Get one.
[0037]
Here, in the manufacturing method described above, the case where a plurality of element bodies 4 are formed at the same time has been described. However, the present invention is not limited thereto, and each element body 4 may be formed one by one.
[0038]
【The invention's effect】
The present invention has the following effects.
According to the multilayer composite functional element according to the present invention, the capacitance is smaller than that of the conventional multilayer composite functional element having the same configuration of the varistor part and the capacitor part. It is difficult to use and is suitable for high-frequency circuits and high-speed communication circuits.
In this multilayer composite functional element, since the capacitance is smaller than that of the conventional product, when the capacitance is the same as that of the conventional product, the varistor internal electrodes of the varistor portion are further increased than the conventional product. It is possible to further reduce the thickness and reduce the varistor voltage while maintaining the area of the varistor internal electrode while maintaining the area of the varistor internal electrode while maintaining the surge current withstand capability of the varistor.
In addition, since the varistor part is sandwiched by the capacitor part and the varistor layer near the varistor internal electrode is protected, the step of coating the varistor part is not required, simplifying the manufacturing process and reducing the manufacturing cost. can do.
[Brief description of the drawings]
1A and 1B are diagrams illustrating a configuration of a surge absorber according to the present embodiment, in which FIG. 1A is a longitudinal sectional view along a longitudinal direction, and FIG. 1B is a sectional view taken along line AA in FIG. .
FIG. 2 is an equivalent circuit diagram of the surge absorber according to the present embodiment.
FIG. 3 is an explanatory diagram of a manufacturing process of the surge absorber according to the present embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Surge absorber (multilayer type composite functional element) 2 Varistor part 3 Capacitor part 4 Element body 5 Ground electrode (external electrode) 6 Terminal electrode (external electrode)
11 Varistor internal electrode 12 Varistor layer 16 Capacitor internal electrode 17 Dielectric layer F1 One end surface (first outer surface) F2 Side surface (second outer surface)
F3 other end surface (third outer surface)

Claims (3)

A multilayer composite functional element having an element body in which a varistor part and a capacitor part are laminated, and an external electrode provided on the outer surface of the element body,
The varistor part has at least a pair of varistor internal electrodes arranged in an opposing state, and a varistor layer sandwiched between the varistor internal electrodes, and the area of the mutually opposing regions of the pair of varistor internal electrodes is: It is set according to the surge current tolerance required for the varistor part,
The capacitor unit includes at least a pair of capacitor internal electrodes arranged in an opposing state and a dielectric layer sandwiched between the capacitor internal electrodes, and an area of a region of the pair of capacitor internal electrodes facing each other is , Is set according to the capacitance required for the capacitor unit,
The varistor part and the capacitor part are electrically connected in series by the external electrode ,
The element main body has a structure in which the varistor portion is sandwiched and stacked between the capacitor portions . One of the pair of varistor internal electrodes is exposed on the first outer surface of the element body, and the other is exposed on the second outer surface of the element body,
One of the pair of capacitor internal electrodes is exposed on the third outer surface of the element body, and the other is exposed on the second outer surface of the element body,
The external electrode is formed on the second outer surface, and is connected to the other varistor internal electrode and the other capacitor internal electrode;
A first terminal electrode formed on the first outer surface and connected to the one varistor internal electrode;
2. The multilayer composite functional element according to claim 1, further comprising: a second terminal electrode formed on the third outer surface and connected to the one capacitor internal electrode. The varistor layer is made of ZnO and Bi. ₂ O ₃ Is an essential component, and MnO ₂ , CoCO ₃ , Sb ₂ O ₃ , SnO ₂ , Cr ₂ O ₃ , SiO ₂ It consists of a material added with ingredients selected from
The dielectric layer is made of MgO or TiO having a purity of 99% or more. ₂ 3. The multilayer composite functional element according to claim 1, wherein the multilayer composite functional element is made of a material in which any one of CaO, CaO, SrO, and BaO or a plurality of components are mixed.

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