JPH0359907A - Particle field insulation type semiconductor ceramic capacitor and manufacture thereof - Google Patents

Abstract

PURPOSE:To simultaneously bake a ceramic capacitor material and an internal electrode material by making Sr1-xCaxTiO3 containing surplus Ti while being 0.001<=X<=0.2 contain a specific metal oxide, Mn, Si and iron oxide. CONSTITUTION:Surplus Ti is contained so that a molar ratio of Sr1-xCax and Ti may be 0.95<=Sr1-xCax/Ti<1.00. Then, Sr1-xCaxTiO3 showing the formula 0.001<=X<=0.2 is made to contain 0.05 to 2.0mol% of at least one kind or more of Nb2O5, Ta2O5, V2O5, W2O5, Dy2O3, Nd2O3, Y2O3, La2O3 and CeO2, a total amount 0.2 to 5mol% of Mn and Si in the shapes MnO2 and SiO2 respectively, and 0.01 to 4.0mol.% of iron oxide. Thereby, simultaneous baking of a ceramic capacitor material with a varistor function and an internal electrode material is made possible while being able to easily manufacture a laminated ceramic capacitor with a varistor function.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention normally functions as a capacitor to absorb low voltage noise and high frequency noise, but when high voltage such as direct pulses or static electricity enters, it functions as a varistor. demonstrate,
A grain boundary insulated semiconductor ceramic capacitor that protects semiconductors and electronic equipment from abnormal voltages such as noise, pulses, and static electricity generated in electronic equipment, and whose characteristics are stable against temperature, and a method for manufacturing the same. It is something.

Conventional technologyIn order to make electronic devices multi-functional, lighter, thinner, and smaller, we use ICs.
, LSI, and other semiconductor devices are being widely used, and as a result, the noise tolerance of devices is decreasing. Therefore, in order to ensure the noise tolerance of such electronic devices, various IC
, film condenser multilayer ceramic capacitors, semiconductor ceramic capacitors, etc. are used as bypass capacitors in LSI power supply lines. but,
These capacitors have excellent performance in absorbing low voltage noise and high frequency noise, but they do not have the ability to absorb high voltage pulses and static electricity, so pulses and static electricity can invade. This has become a major problem, causing malfunctions of equipment, destruction of semiconductors, and even destruction of capacitors. Therefore, for this kind of use,
SrTiO is a new type of capacitor that not only has good noise absorption properties and is stable over temperature and frequency, but also has high pulse tolerance and excellent pulse absorption properties.
A grain boundary insulated semiconductor ceramic capacitor (hereinafter referred to as a ceramic capacitor with a varistor function), which is a three-series semiconductor ceramic capacitor with a varistor function, has been developed and has already been published in Japanese Patent Application Laid-Open No. 57-27001 and
-35303, etc. This ceramic capacitor with varistor function normally absorbs low voltage noise and high frequency noise as a capacitor, but when high voltage such as pulses or static electricity enters, it functions as a varistor and absorbs noise and pulses generated in electronic equipment. , it has the characteristic of protecting semiconductors and electronic equipment from abnormal voltages such as static electricity, and its use is expanding more and more.

On the other hand, in the field of electronic components, the trend toward lighter, thinner, shorter, and higher performance is progressing, and even for ceramic capacitors with varistor functions, there is a growing demand for smaller size and higher performance. However, since conventional ceramic capacitors with a varistor function are of a single-plate type, miniaturization reduces the electrode area, resulting in problems such as reduced capacitance and reduced reliability. Therefore, as a solution to this problem, it is expected that stacking will be developed to increase the electrode area. However, ceramic capacitors with varistor function usually involve a process of applying oxide to the surface of the SrTiO3-based semiconductor element and insulating the grain boundary layer by thermal diffusion, so they are different from the commonly used BaTiO3-based multilayer ceramic capacitors. In comparison, it was thought to be extremely difficult to form a multilayer capacitor with a varistor function (hereinafter referred to as a multilayer ceramic capacitor with a varistor function) by firing simultaneously with the internal electrodes.

Therefore, as a method to solve the problem of co-firing, we applied the methods of JP-A-54-53248 and JP-A-5453250, and printed a ceramic paste with a large amount of organic binder on the part corresponding to the internal electrode. This part forms a porous layer during the sintering process, and after sintering, a conductive metal is injected into the porous layer under appropriate pressure, or an internal electrode is formed by a plating method or a melting method, and the varistor functions. A method has been developed and provided for forming a multilayer ceramic capacitor. However, these processes are quite difficult and have not yet reached the level of practical use.

In addition, Japanese Patent Application Laid-Open No. 59-215701 discloses a conductive paste containing a heat-diffusing substance capable of insulating the grain boundary layer on a green sheet made from powder calcined in a non-oxidizing atmosphere. a method of printing and sintering in an oxidizing atmosphere,
Furthermore, in Japanese Patent Application Laid-open No. 63219115, internal electrodes are alternately laminated with a raw sheet made of powder that has been made into a semiconductor in advance and mixed with a diffusing agent containing an oxidizing agent and a glass component to form an insulating layer. A method has been reported in which the molded body is fired in air or in an oxidizing atmosphere. However, in these methods, the firing temperature is 1000-1200℃.
Celsius is relatively low, making it difficult for ceramic sintering to occur, making it difficult for the crystal particles to come into surface contact, and the completed device has a low capacity because it is not a complete sintered body, which is a typical characteristic of a varistor. It has the disadvantages that the voltage nonlinearity index α is small, the varistor voltage is unstable, and the reliability is poor. Furthermore, in the latter Japanese Patent Application Laid-Open No. 63-219115, since a glass component is added as an additive, a glass phase is precipitated at the grain boundaries, which tends to deteriorate the electrical characteristics described above, resulting in poor reliability. However, it has not yet reached the level of practical application.

Note that Zn0F e203. has already been disclosed in Japanese Patent Publication No. 58-23921 as a patent related to a multilayer varistor.
A stacked voltage nonlinear element using the T i 02 system has been proposed. However, since this element has almost no capacitance, it exhibits excellent performance in absorbing relatively high voltage pulses and static electricity, but it is resistant to low voltage noise below the varistor voltage and high frequency noise. has the problem that it is rarely effective.

Problems to be Solved by the Invention Until now, various compositions and manufacturing methods have been developed and provided for multilayer ceramic capacitors with varistor functions, but as mentioned above, in each case there are problems with the process and the finished device. However, it has not reached a practical level. Therefore, the development of new compositions and manufacturing methods for multilayer ceramic capacitors with varistor functions is expected.

The present invention was made in view of these points. Normally, it functions as a capacitor to absorb low voltage noise and high frequency noise, but on the other hand, when high voltage such as pulses or static electricity enters, it functions as a varistor. S r (1-XICaX T i 0
The object of the present invention is to provide a grain boundary insulated semiconductor ceramic capacitor having a main component of 3 (0.OO1≦X≦0.2) and a method for manufacturing the same.

Means for Solving the Problems In order to solve the above problems, the present invention provides S r
(1-xl The molar ratio of CaX and Ti is 0.95≦Sr
(1-x) S containing excess Ti so that Cax /Ti<1.00 and 0.001≦X≦0.2
r 1-xl CaxT i O3, Nb2O5°Ta205. V2O5, W2O5, D V2O3, Nd
2O3°Y2O3, L a203. At least one type of Ce02 at 0.05 to 2.0mo 1%, M
n and Si in the form of M n O2 and 8102, respectively, with a total amount of 0.2 to 5.0 mo 1%, and iron oxide to 0.0
The object of the present invention is to provide a grain boundary insulated semiconductor ceramic capacitor containing 1 to 4.0 mol%.

Further, the present invention provides S r u -xl Ca x and Ti
The molar ratio of 0.95≦Sr(1-xlca, /Ti<1
．． Contains excess Ti so that it becomes 0.00, and 0.0 O1
≦X≦0.2 S r x−xl CaxT i
03, Nb2O5゜T a20s+ V2O5, W2
O5, D Y2O3, N dz03Y203. L a2
03. 0.05 of at least one type of Ce02
~2.0mo 1% and Mn and Si respectively Mn
0.2 to 5.0 mo in total amount in the form of O2 and SiO2
A plurality of layers of internal electrodes are provided in a grain boundary insulated semiconductor ceramic containing 0.01 to 4.0 mol% of iron oxide and 0.01 to 4.0 mol% of iron oxide. The present invention provides a multilayer grain boundary insulated semiconductor ceramic capacitor characterized in that external electrodes are provided at both ends of an internal electrode.

Furthermore, the present invention provides S r (1-xl Cax and Ti
The molar ratio of 0.95≦S r (1-x+Cax/T
Contains excess Ti so that i < 1.00,
O, OO1≦X≦0.2 S r II-xl C
axT i 03, Nb2O5°Ta205. V2O
5, W2O5, DY203+ Nd2O3゜Y2O3,
L a203. At least one type of CeO2 is 0.05 to 2.0 mo 1%, and Mn and Si are respectively in the form of M n O2 and Si 02 in a total amount of 0.2
~5.0 mol% and 0.01 to 4.0 mol of iron oxide
The mixed powder of the composition containing Disperse it in a solvent together with a binder to form a green sheet, and then print internal electrode paste on top of this green sheet alternately reaching the opposite edges (however, the top and bottom layers of the green sheet are not printed). ), the raw sheets printed with this internal electrode paste are laminated, pressurized, and crimped to obtain a molded body, and then this molded body is calcined in air, and after calcining, reduction or nitrogen A laminated layer characterized by comprising a step of firing in an atmosphere, a step of reoxidizing in air after firing, and a step of applying external electrode paste to both ends with exposed internal electrodes after reoxidation and baking. A method for manufacturing a grain boundary insulated semiconductor ceramic capacitor is provided. The internal electrodes are made of Au, Pt, Rh,
The present invention provides that it is formed of at least three metals selected from Pd and Ni, or an alloy or mixture thereof. Further, the external electrode is made of Pd, Ag, Ni, or Cu.

The present invention provides that it is formed of at least one metal of Zn, or an alloy or mixture thereof.

Action Generally, in order to convert S r (1-xlCa, T i 03) into a semiconductor, it is necessary to perform forced reduction or add a semiconductor conversion accelerator and sinter it in a reducing atmosphere. Semiconductorization may not progress depending on the type of S r Tl-XI.
From the stoichiometry of Cax T i 03, S r (,
-X) Ca x excess (hereinafter referred to as A site excess)
Alternatively, if Ti is added excessively, lattice defects within the crystal will increase, and "semiconductorization" will be promoted. Moreover, ca enters the Sr site and has the effect of suppressing grain growth.

Sarani, Nb2O5, Ta205. V2O5, W2O5
.

D V2O3, Nd2O3, Y2O3, L a203.
Addition of Ce02 (hereinafter referred to as the first precept) promotes semiconductor formation through atomization control.

Next, the second component, which becomes M n O2 and Si 02 during the sintering process, is an essential substance to form a laminated structure, and if either one is missing, the effect will not be exerted. . Iron oxide (hereinafter referred to as the third component) exists in the grain boundaries and has the effect of improving the dielectric constant of the grain boundaries. As described above, it has been thought until now to be difficult to produce a 5rTiO:+-based multilayer ceramic capacitor with a varistor function. The reason is the first
This is because the ceramic capacitor material with varistor function and the internal electrode material have different actions and properties during the firing process and reoxidation process. That is, the former material requires firing in a reducing atmosphere during the firing process, but at this time, since the latter material is made of metal, it absorbs H2 gas in the reducing atmosphere and expands.

Furthermore, this is because the latter material is oxidized to a metal oxide during the reoxidation process in the air, and has the action and property of shielding the former material from reoxidation.

The second reason is that in order to use the former material as a ceramic capacitor element with a varistor function, it must be baked in a reducing atmosphere to convert it into a semiconductor, and then a high-resistance metal oxide (MnO2 CoO2,B 1203.
CO2O3, etc.) is applied and reoxidized in air to selectively diffuse and insulate grain boundary areas, that is, a surface diffusion process is required.

However, this is because it is technically difficult to diffuse the metal oxide in an element having a structure in which internal electrode materials are alternately stacked.

Therefore, as a result of research, the present inventors invented the following.

First of all, Ti excess S r (1-xi Ca
In addition to adding the first component to xT i 03, the material composition in which the second component is added does not require coating the above-mentioned high-resistance metal oxide on the surface of the element after firing in a reducing atmosphere. discovered that a ceramic capacitor with varistor function could be easily formed simply by reoxidizing in air. This is due to the excess Ti and the added 21st ff1 minute during the sintering process, resulting in low temperature temperature Mn 02- Si 02) Cax
At the same time, it promotes sintering by shaping the TiO2-based liquid phase.
It will dissolve and segregate in the grain boundary areas. Then, when this is reoxidized in air, MnO2− segregated at the grain boundaries.
This is because the 8i 02-T i O system is insulated and easily becomes a ceramic capacitor with a varistor function having a grain boundary insulation type structure. Furthermore, it has been found that oxidation and diffusion of the internal electrodes can be suppressed by adding too much Ti.

Therefore, in the present invention, for these reasons, Ti excess S
It was decided to use r(1-x)Ca, T i 03.

Secondly, Ti excess S r (1-xl Cax
It has been found that a material composition in which a second fraction is added to T i 03 becomes a semiconductor even when sintered in a nitrogen atmosphere as well as in a reducing atmosphere. This is because the added Mn forms a liquid phase at a low temperature as shown in the first reason above, and also acts as an atomization control agent in addition to forming a liquid phase.
The valence of the atom is +2. +4 and is electronically unstable, which is thought to improve sinterability and make it easier to convert into a semiconductor even in a nitrogen atmosphere.

7 Furthermore, thirdly, if the molded body after degreasing is calcined in air beforehand, various problems such as internal electrode breakage, delamination, cracking, and decrease in sintered density of the completed multilayer ceramic capacitor with varistor function occur. It has been found that the electrical characteristics and reliability are significantly improved.

As described above, if such viewpoints are fully considered, it becomes possible to easily produce a multilayer ceramic capacitor with a varistor function by co-firing the ceramic capacitor material with a varistor function and the internal electrode material.

EXAMPLES The present invention will be specifically described below with reference to Examples.

(Example 1) First, S with an average particle size of 0.5 μm or less and a purity of 98% or more
r (1-xl CaxT i 03 T to raw powder
Add i 02, S r N-xl Ca xl T
The powder with adjusted i ratio (hereinafter referred to as A/B ratio) was added with N b 20 of the first component as shown in Tables 1 to 15 below.
M n 02. The amount of S i Oz (however, MnO2゜S i 02 to be added is equal to 1%) was varied, and the amount of Fe2O3 as the third component was set to 0.
．． It was fixed at 5mol1% and mixed. After that, this mixed powder is wet-pulverized and mixed using a ball mill, etc., dried, and then calcined in air at 600 to 1200°C. After calcining, the powder is crushed again so that the average particle size is 0.5 μm or less. This was used as a starting material for a multilayer ceramic capacitor with varistor function. This fine powder starting material is dispersed in a solvent together with an organic binder such as butyral resin to form a slurry, and this is made into a slurry using a doctor blade method.
It was made into a raw sheet with a certain thickness and cut into a predetermined size.

Next, as shown in FIG. 1, an internal electrode paste 2 made of Pd was screen printed on the raw sheet 1 obtained as described above according to a predetermined size. Note that, as is clear from FIG. 1, the internal electrode paste 2 is not printed on the raw sheet 1 of the uppermost layer and the lowermost layer. Also,
At this time, the internal electrode pastes 2 printed on the raw sheets 1 to be laminated in the middle were printed so as to alternately reach opposing edges, as is well known. Thereafter, a plurality of green sheets 1 were laminated in the same direction as the internal electrode paste 2 was printed, and were pressed and bonded together. Next, degrease in air at 400℃,
Further, calcination was performed in air at 600 to 1250°C.

Thereafter, it was fired at 1250 to 1350°C in a reducing atmosphere. After this firing, it was reoxidized in air at 900-1250°C.

Thereafter, as shown in FIG. 2, an external electrode paste made of Ag is applied to both exposed ends of the internal electrode 2a and baked in air at 800°C for 15 minutes to form a grain-boundary insulated semiconductor ceramic. A plurality of layers of internal electrodes 2a are provided in such a way that they alternately reach the edges, and the internal electrodes 2a in parentheses are
A multilayer ceramic capacitor 4 with a varistor function was obtained, in which external electrodes 3 were provided on both ends of the capacitor.

The shape of the multilayer ceramic capacitor with varistor function in this example is 5.70 x 5.00 x 2.00.
It is a type of 5.5 mm" in which 10 effective layers on which internal electrodes are formed are laminated. FIG. 3 shows the manufacturing process of the present invention.

Various electrical properties of the thus obtained multilayer ceramic capacitor with varistor function include its capacity, tan δ, varistor voltage, voltage nonlinearity index α, series equivalent resistance value ESR, capacitance temperature change rate, and varistor voltage temperature coefficient. are also listed in Tables 1 to 15. However, each condition such as firing at this time is 1200 ml for calcination in air.
℃, 2 hours, calcination in a reducing atmosphere of N2:H2 = 99:1: 1300℃, 2 hours, reoxidation: 1100'
C. This was done in one hour.

Note that the following measured values are listed for various electrical properties.

◇ Capacity C is measured voltage 1. OV, frequency 1.0KHz
value at.

◇ Varistor voltage V○ImA is the value at a measurement current of 0.1mA.

1 ◇ Voltage nonlinear index α is measured current 0.1 mA and 1.0
From the value in mA, a-1/ 10 g (Vl, 0IIIA/ VO, +
Calculated from the mJ formula.

◇ Series equivalent resistance value ESR is the resistance value at the resonance point at a measurement voltage of 1.0■.

◇ Capacitance temperature change rate (ΔC/C) is -25℃ and 85℃
The value between two points.

◇ Varistor voltage temperature coefficient (ΔV/V) is 25℃ and 5
Value between two points at 0℃.

(Margins below) 3 7 1 7 Next, to explain Tables 1 to 15 above, these tables are S r (1-x) CaxT i 03 A
/B ratio and the amount of addition of M n 02 and 5102 in the second precept.

Here, the sample numbers marked with * are comparative examples and are outside the scope of the claims of the present invention. In other words, these sintered elements have a small capacitance, a small voltage non-linearity index α representing varistor characteristics, and a large series equivalent resistance value ESR, so they cannot absorb low voltage noise or high frequency noise as a capacitor. It does not have both the function of absorbing high voltages such as pulses and static electricity as a varistor, and its capacitance temperature change rate and varistor voltage temperature coefficient are large, and its reliability and electrical characteristics are not affected by temperature. is easy. Therefore, these samples are not suitable as ceramic capacitors with varistor functions that protect semiconductors and electronic devices from abnormal voltages such as noise, pulses, and static electricity generated in electronic devices. On the other hand, the other sample numbers have a large capacitance, a large voltage non-linear index α, and a small series equivalent resistance value ESR, so they absorb low voltage noise and high frequency noise as capacitors. function and pulse as a varistor,
It has both the ability to absorb high voltages such as static electricity, and has a small capacitance temperature change rate and varistor voltage temperature coefficient, making its reliability and electrical characteristics less susceptible to temperature. Therefore, these samples are suitable as ceramic capacitors with varistor function in order to protect semiconductors and electronic devices from abnormal voltages such as noise, pulses, and static electricity generated in electronic devices.

Here, in the present invention, S r t+ −x+ Ca
The A/B ratio of xT 103 was defined as A/B ratio of 1.
．． If it is larger than 00, the A site is excessive, and MnO2
Since SiO2TiO2-based liquid phase is difficult to form,
This is because the structure becomes a grain boundary insulation type structure, and the internal electrodes are oxidized and diffused, resulting in a decrease in electrical characteristics and reliability. On the other hand, if the A/B ratio is less than 0.95, the sintered body becomes porous and the sintered density decreases. Furthermore, the reason why the average particle diameter of the starting material for a multilayer ceramic capacitor with varistor function was specified to be 0.5 μm or less was 0.5 μm or less.
If it is larger than 5 μm, the powder may aggregate when it is made into a slurry, and the sintered density of the completed sintered element will be low and it will be difficult to convert it into a semiconductor, so the electrical properties will tend to become unstable.

Next, the total addition amount of the second component M n O2 and S i 02 was determined by the addition amount of these second precepts or 0.
If the amount is less than 2mo1%, no effect can be obtained,
This is because a 2S i 02 T i 02-based liquid phase is difficult to form, making it difficult to form a grain boundary insulated structure, resulting in a decrease in electrical properties and sintered density.

On the other hand, when the amount of the second component added exceeds 5.0 mol%,
This is because the amount of high-resistance oxides segregated at grain boundaries increases and electrical properties deteriorate.

Furthermore, the molded body after degreasing is heated to a temperature of 600 to 125 in advance in the air.
Calcining at 0°C is the most important step in the manufacturing method of the multilayer ceramic capacitor with varistor function of the present invention, and the results of this step determine the electrical characteristics and reliability of the multilayer ceramic capacitor with varistor function. This is almost decided. The purpose of this step is to strengthen the adhesion between the varistor function ceramic capacitor material and the internal electrode material, and to control the average particle size of the finished varistor function multilayer ceramic capacitor.

Here, the reason why the calcination temperature in air is specified in the range of 600 to 1250°C is that the effect cannot be obtained if the calcination temperature is less than 600°C. On the other hand, the calcination temperature is 125
If the temperature exceeds 0°C, sintering of the ceramic capacitor material with varistor function will proceed. When fired in a reducing or nitrogen atmosphere in this state, stress concentration occurs within the sintered body due to rapid contraction, resulting in various problems such as delamination and cracking in the resulting multilayer ceramic capacitor with varistor function. It turns out.

■ When Ni is used as the internal electrode material, sintering of the former ceramic capacitor material (!: Oxidation of the Ni internal electrode material occurs, then the sintered body and Ni1 react, and Ni diffusion progresses. However, the resulting multilayer ceramic capacitor with varistor function suffers from various problems such as internal electrode breakage and delamination cracking.

■ If calcination is performed at a high temperature exceeding 1250℃, Mn 0
The liquid phase sintering of the 2 S i 02 T i 02 system progresses rapidly, grain growth is promoted, and the sintered body density and packing density are significantly reduced.

■ If it is then fired in a reducing or nitrogen atmosphere,
Semiconductorization becomes less likely to occur.

This is because the electrical characteristics and reliability deteriorate significantly.

The thus obtained multilayer ceramic capacitor with varistor function has a larger capacity than the multilayer varistor reported in the above-mentioned Japanese Patent Publication No. 5823921,
In contrast to the former, which simply stacks varistor materials with excellent surge absorption properties, the present invention has a capacitor function with excellent noise absorption properties, as well as pulse and static electricity. Varistor 2 with excellent absorption properties is a laminated ceramic capacitor material with a varistor function that has both functions, and its functions and purposes of use are completely different.

(Example 2) Next, the composition ratio of Sr and Ca corresponding to the A site of the perovskite structure represented by ABO3 was varied, and the A/B ratio of S r u -xl Ca xT 103 was set to 0.97, The amount of Nb2O5 added as 1FfC was 1.0 mol%, and the amount of MnO'2 as 2nd tc was 1.0 mol%.
．． The amount of S i 02 added was 1.0 mol% each, and the third
A multilayer ceramic capacitor with a varistor function was manufactured in the same manner as in Example 1, with the addition amount of Fe2O3 as a precept being fixed at 0.5 mo1%. The results are listed in Table 16 below.

(Margins below) To explain Table 16 above, when Ca is not added, there is nothing to suppress the grain growth of the crystals, and the crystal grain sizes vary widely, resulting in poor tan δ and temperature characteristics. Furthermore, when the amount of Ca added increases and the value of X exceeds 0.2, oxidation tends to proceed, the capacity decreases, and the varistor characteristics deteriorate. Therefore, S at site A
The substitution rate X of Ca that replaces a part of r is O,OO1≦X
≦0.2 is desirable.

(Example 3) According to Example 1, MnO2 and 5IO2 as the second fraction
It was found that the total addition amount of 0.2 to 5.0 mol% is required. Next, the addition ratio of MnO2 and SiO2 as the 25th!2nd minute was varied, and the A/B ratio of S r N as one component
A multilayer ceramic capacitor with a varistor function was fabricated in the same manner as in Example 1 above, with the addition amount of b20s fixed at 1.0 mol% and the addition amount of Fe2O3 as the third component Q, 5 mol%. Ta.

The results are shown in the first section below. Listed in Table 7.

(Margins below) 6 To explain Table 17 above, as is clear from the measurement results, in order to manufacture a multilayer ceramic capacitor with a varistor function, M n 02 (!1. S i 0
Both of 2 are necessary, and even if either one is missing, a multilayer ceramic capacitor with a varistor function cannot be manufactured. That is, Mn 02 only exists when both components are present.
When a S i 02 Ti 02-based liquid phase is formed, it dissolves and segregates at the grain boundary, and is reoxidized, the MnO2-8i02 segregated at the grain boundary becomes insulating, easily forming an element with a grain boundary insulated structure. To become.

Note that when comparing electrical properties such as capacity, voltage nonlinearity index α, and ESR, it is preferable to have a slight excess of MnO2.

(Example 4) Next, Nb2O5, Ta205+V2 as the first fraction
O5, W2O5, D'I2O3, Nd2O3, Y2O3
゜In order to specify the amount of the atomization control agent added for La2O3 and CeO2, it is changed variously and s r (1-xl CaX
The A/B ratio of T i 03 is 0.97, X = 0.10, the amount of the second component added is M n 021.0 m o 1%,
Total of S i O21, Omo 1%2. Omo is fixed at 1%, and the amount of Fe2O:+ added as the third component is Q,
A multilayer ceramic capacitor with a varistor function was produced in the same manner as in Examples 1 and 2, with the mole fixed at 5 mo1%. The results are shown in Tables 18 to 26 below.

(Margins below) 9 1 5 To explain Tables 18 to 26 above, the amount of the first component added was specified so that the amount added was less than 0.05 mo1%, as is clear from the measurement results. This is because the addition effect cannot be obtained and it is difficult for semiconductor formation to occur. On the other hand, if the total amount of the first component added exceeds 2.0 mol%, semiconductor formation will be suppressed, desired electrical properties will not be obtained, and the sintered density will further decrease.

Note that it is better to add Nb2O5 and Ta205 as the first component than other V205, W20s,
D Y 203.

The electrical properties were slightly better than the case where Nd2O3, Y2O3, La2O3, and Ce02 were added.

Furthermore, regarding the mixture composition of the first commandment, we conducted tests on some of the combinations and measured the electrical properties, but as shown in Table 26, there was almost no difference in the properties compared to when different types were added. It was something that could not be seen. However, in this case as well, the addition of Nb2O5°Ta205 was slightly better in terms of electrical properties than the addition of other components.

Furthermore, if the average particle size of the starting material is larger than 0.5 μm, it tends to be difficult to obtain the effect of the first precept;
．． It was confirmed that it is necessary to suppress the thickness to 5 μm or less.

(Example 5) Next, in order to specify the amount of Fe2O3 added as the third component, this was changed variously, and S r (+ -XI Ca
A/B ratio of xT i 03 is 0.95, X=0.10.
The addition amount of the first component was Nb2O51,Qmo 1%, the second component was
The amount of added weight was M n 021.0 m o 1%, 5
iO2 is fixed at a total of 2.0 mol% of 1.0 m01%,
A multilayer ceramic capacitor with a varistor function was manufactured in the same manner as in Examples 1 and 2 above. The results are listed in Table 27 below.

(Margins below) ■ To explain Table 27 above, by adding Fe2O3, it reacts with other components in the grain boundaries and improves the dielectric constant. However, when the amount of Fe2O3 added increases and exceeds 4.0 mol%, it begins to precipitate alone in the grain boundaries, resulting in a decrease in 01kHz. Additionally, there is a tendency for the temperature coefficient of capacity to change from negative to positive. Therefore, the appropriate amount of Fe2O3 to be added is 0.01 to 4.0 mol%.

(Example 6) In each of the above examples, the case where Pd was used as the internal electrode was explained, but other materials such as Au and pt were used.

For Rh, Ni, S r (1-xl CaxT
A/B ratio of i 03 is 0.97, X=0.10, 1st F
The addition amount for lfc is Nb2O50.5mo 1%, Ta
2050.5mo1%, the amount of the second component added is MnO21
, 0 mol%, Si021. Qmo is fixed at 1%,
Addition amount of Fe2O3 as the third component is 0.5mo1%
A multilayer ceramic capacitor with a varistor function was manufactured in the same manner as in the above example.

The results are listed in Table 28 below.

2 As described in Table 28 above, the internal electrodes are made of Au.
, Pt, Rh, Pd, and Ni, or their alloys or mixtures can be used and it has been confirmed that effects can be obtained. However, Ni
When using S r (1-
Oxidation can be suppressed by using XI CaxT i 03.

Although some combinations have been shown in the examples of the present invention, it has been confirmed that similar effects can be obtained with other combinations.

In the embodiment of the present invention, Ti-excess S r 1l-
x) In producing CaxTiO3, S r (1
-xlCaxT i 03 was added with TiO2, but T
It goes without saying that similar effects can be obtained by using i in the form of carbonates, hydroxides, organic compounds, and the like.

In addition, in the examples of the present invention, S r 1-x is added to the raw material powder.
) CaxTiO3 was used, but SrO, SrCO3°C
Of course, the same effect can be obtained even if Sr(1□, CaXTiO3) prepared from aC0,..., Cab, titanate, TiO2, etc. is used as a raw material powder.

Furthermore, M n 02. as a second component. 8 i 0
It goes without saying that similar effects can be obtained with respect to 2 even when used in the form of carbonates, hydroxides, etc.

However, it was confirmed that when used in the form of M n CO3, the particle size is finer and more uniform, and it is easier to decompose, making it possible to create devices with stable characteristics and being suitable for mass production. .

And also for the third component Fe2O3, Fe 30
Similar effects can be obtained by using 41 in the form of nitrate or hydroxide.

Next, in the above embodiments, the case where the firing is performed in a reducing atmosphere has been described, but this may also be performed in a nitrogen atmosphere. However, when firing in a nitrogen atmosphere, it is somewhat difficult to convert into a semiconductor, so the temperature is slightly higher (185
From the viewpoint of characteristics, it is preferable to perform firing at a temperature of 0 to 1450°C.

Furthermore, in the above embodiments, the case where the mixed powder was calcined in air was described, but it was confirmed that similar effects could be obtained even if calcining was performed in a nitrogen atmosphere.

Furthermore, in the above example, the reoxidation temperature was fixed at 1100°C;
It may be carried out within a temperature range of 00 to 1250°C.

However, when reoxidizing at 1200° C. or higher, care must be taken because not only the grain boundaries but also the crystal grains may become insulated unless the holding time at the maximum temperature is minimized. Also, when Ni is used as the internal electrode, 120
When reoxidizing at temperatures above 0° C., there is a risk that Ni may be oxidized unless the holding time is suppressed as much as possible, so caution is also required.

Furthermore, although Ag was used as the external electrode in the above embodiment, it was confirmed that similar effects could be obtained using other materials such as Pd, Ni, Cu, and Zn. That is, Pd, A
At least one metal selected from among g, Ni, Cu, and Zn, or an alloy or mixture thereof may be used. However, Pd and A
When g is used as an external electrode, a slight polarity appears in the varistor voltage due to ohmic contact with the element, but in this case as well, there is no particular problem in terms of basic performance.

As mentioned above, the average particle size of the multilayer ceramic capacitor with varistor function obtained by the method shown in the example is 2.0 to 3.0.
It was about μm. Here, if the molded body is calcined in air at a temperature higher than 1300°C, M
Liquid phase sintering of the nO2-31o2-T i 02 system rapidly progresses, grain growth is promoted, and the average grain size becomes about twice or more. When the average grain size increases in this way, various problems occur such as a decrease in sintered density, a decrease in voltage nonlinearity index α, an increase in series equivalent resistance value ESR, and variations in electrical characteristics. Electrical characteristics and reliability deteriorate significantly, making it unsuitable for practical use.

Further, in the above embodiment, a multilayer ceramic capacitor with a varistor function was explained, but even when a single-plate ceramic capacitor with a varistor function similar to the conventional one is manufactured using the above composition, an excellent capacitor can be obtained. It was confirmed that the characteristics and varistor characteristics could be obtained.

As mentioned above, the device obtained in this way has a large capacity, a large voltage nonlinearity index α, a small varistor voltage, a small series equivalent resistance value ESR, and also has excellent temperature characteristics, frequency characteristics, and noise characteristics. , usually acts as a capacitor to absorb low voltage noise and high frequency noise.
On the other hand, when a high voltage such as a pulse or static electricity enters, it exhibits a varistor function and exhibits excellent response to abnormal voltage such as noise, pulse, or static electricity, and its characteristics are always stable against temperature. Therefore, it is expected to replace conventional film capacitors, multilayer ceramic capacitors, and semiconductor ceramic capacitors. Furthermore, the multilayer ceramic capacitor with a varistor function of the present invention is smaller and has a larger capacity than a conventional single-plate ceramic capacitor with a varistor function.
Since it also has high performance, there are great expectations for its application as a mounted component.

Effects of the Invention As described above, according to the present invention, it is possible to obtain a ceramic capacitor with a varistor function that has both a capacitor function and a varistor function. Its action is
Normally, it works as a capacitor to absorb low-voltage noise and high-frequency noise, but when high voltage such as pulses and static electricity enters, it performs a varistor function, so it absorbs noise, pulses, and static electricity generated by electronic equipment. It has the function of protecting semiconductors and electronic equipment from abnormal voltages. Moreover, these characteristics are always stable with respect to temperature. Therefore, its applications include: (1) It replaces conventional film capacitors, multilayer ceramic capacitors, semiconductor ceramic capacitors, etc. as bypass capacitors for protection of ICs, LSIs, etc. used in electronic equipment.

9 ■ ZnO is used to prevent equipment damage and equipment malfunction due to static electricity, and to absorb inductive load 0N-OFF surges.
Replaces the barista.

This device can be expected to have many applications, as it simultaneously exhibits the above effects (2) with a single device.

As described above, the reason why a multilayer ceramic capacitor with a varistor function can be easily produced with the present invention is because it is now possible to simultaneously fire the ceramic capacitor material with a varistor function and the internal electrode material. . The reason why simultaneous firing became possible is that in addition to adding semiconductor components to SrTiO3 with excess Ti, Mn
This is because the composition containing O2 and SiO2 can easily become a grain-boundary insulated semiconductor ceramic capacitor simply by re-oxidation without going through the conventional metal oxide surface diffusion process. This is the most advantageous feature of the present invention in terms of process.

Furthermore, the multilayer ceramic capacitor with a varistor function of the present invention is smaller than the conventional single-plate ceramic capacitor with a varistor function, has a large capacity, and has high performance, so it can also be applied as a surface mount component. It is highly anticipated that it can be used as a device for high-density packaging in video cameras, communication equipment, etc.

Therefore, according to the present invention, it is possible to obtain an element that protects semiconductors and electronic equipment from abnormal voltages such as noise, pulses, and static electricity, and whose characteristics are stable with respect to temperature, and its practical effects. is extremely large.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of a ceramic capacitor with a varistor function for explaining the present invention in detail, and FIG. The figure is a partially cutaway sectional view showing a multilayer ceramic capacitor with a varistor function obtained according to an embodiment of the present invention, and FIG. It is. ■... Raw sheet, 2... Internal electrode paste, 2a... Internal electrode, 3... External electrode, 4... Varistor function Multilayer ceramic capacitor with

Claims (7)

[Claims] (1) The molar ratio of Sr_(_1_-_x_)Ca_x and Ti is 0.95≦Sr_(_1_-_x_)Ca_x/T
Contains excess Ti so that i<1.00, and 0.0
Sr_(_1_−_x_)Ca where 01≦X≦0.2
_xTiO_3, Nb_2O_5, Ta_2O_5,
V_2O_5, W_2O_5, Dy_2O_3, Nd_
0.05 to 2.0 mol% of at least one type of 2O_3, Y_2O3, La_2O_3, CeO_2
and Mn and Si in the form of MnO_2 and SiO_2, respectively, in a total amount of 0.2 to 5.0 mol%, and iron oxide to 0.
．． A grain boundary insulated semiconductor ceramic capacitor containing 01 to 4.0 mol%. (2) The molar ratio of Sr_(_1_-_x_)Ca_x and Ti is 0.95≦Sr_(_1_-_x_)Ca_x/T
Contains excess Ti so that i<1.00, and 0.0
Sr_(_1_−_x_)Ca where 01≦X≦0.2
_xTiO_3, Nb_2O_5, Ta_2O_5・
V_2O_5・W_2O_5・Dy_2O_3, Nd_
2O_3, Y_2O_3, La_2O_3, CeO_2
0.05 to 2.0 mol of at least one of the following
%, Mn and Si in the form of MnO_2 and SiO_2 in a total amount of 0.2 to 5.0 mol%, and iron oxide in a total amount of 0.01 to 4.0 mol% in a grain boundary insulated semiconductor ceramic. A laminated grain boundary insulated semiconductor ceramic capacitor characterized in that a plurality of layers of internal electrodes are provided so as to alternately reach opposing edges, and external electrodes are provided on both ends of the internal electrodes. (3) Claim 2, wherein the internal electrode is formed of at least one metal selected from Au, Pt, Rh, Pd, and Ni, or an alloy or mixture thereof.
The multilayer grain boundary insulated semiconductor ceramic capacitor described above. (4) Claim 2, wherein the external electrode is formed of at least one metal selected from Pd, Ag, Ni, Cu, and Zn, or an alloy or mixture thereof.
or 3. The laminated grain boundary insulated semiconductor ceramic capacitor according to 3. (5) The molar ratio of Sr_(_1_-_x_)Ca_x and Ti is 0.95≦Sr_(_1_-_x_)Ca_x/T
Contains excess Ti so that i<1.00, and 0.0
Sr_(_1_−_x_)Ca where 01≦X≦0.2
_xTiO_3, Nb_2O_5, Ta_2O_5,
V_2O_5, W_2O_5, Dy_2O_3, Nd_
2O_3, Y_2O_3, La_2O_3, CeO_2
0.05 to 2.0 mol of at least one of the following
%, Mn and Si in the form of MnO_2 and SiO_2 in a total amount of 0.2 to 5.0 mol%, and iron oxide in a total amount of 0.01 to 4.0 mol%. As a raw material, the mixed powder is crushed, mixed, dried, and then calcined in air or in a nitrogen atmosphere. After calcining, the crushed powder is dispersed in a solvent together with an organic binder to form a green sheet, and then On this raw sheet,
Print internal electrode paste alternately to the opposite edges (however, do not print on the top and bottom raw sheets)
The raw sheets printed with this internal electrode paste are laminated, pressed, and crimped to obtain a molded body, and then the molded body is calcined in air, and after calcining, the raw sheets are heated in a reducing or nitrogen atmosphere. A laminated type characterized by having a step of firing in a medium, a step of reoxidizing in air after firing, and a step of applying external electrode paste to both ends with exposed internal electrodes after reoxidation and baking. A method for manufacturing a grain boundary insulated semiconductor ceramic capacitor. (6) Claim 5, characterized in that the internal electrode is formed of at least one metal selected from Au, Pt, Rh, Pd, and Ni, or an alloy or mixture thereof.
The method for manufacturing the multilayer grain boundary insulated semiconductor ceramic capacitor described above. (7) Claim 5, characterized in that the external electrode is formed of at least one metal selected from Pd, Ag, Ni, Cu, and Zn, or an alloy or mixture thereof.
Alternatively, the method for manufacturing a multilayer grain boundary insulated semiconductor ceramic capacitor according to 6.