JPH0360006A - Grain boundary insulating type semiconductor ceramic capacitor and its manufacture - Google Patents

Abstract

PURPOSE:To protect a semiconductor and electronic equipment against abnormal voltage and to always stabilize their properties against temperature by adding specific ingredients to SrTiO3, wherein Ti is superfluous. CONSTITUTION:For example, 0.05-2.0mol% Nb2O5, 0.2-5.0mol% MnO2 and SiO2, and 0.05-4.0mol% LiAlO2 are mixed with powder wherein TiO2 is added to SrTiO3 material powder and Sr/Ti mole ratio is adjusted to 0.95<=Sv/Ti<=1.00, then it is pulverized after calcination, and the fine powder is dispersed in fusion together with an organic binder so as to make to raw sheet. Next, an inner electrode paste 2 consisting of Pd is printed on the raw sheet 1, and plural layers of raw sheet 1 are laminated as they are printed, then they are oxidized again in the air after degreasing and baking. After that, outer electrode paste consisting of Ag is applied on both ends of the inner electrode 2a, and is baked together, and plural layers of inner electrode 2a are so provided as to reach the edge alternately, thus obtaining a laminated ceramic capacitor 4 provided with varistor function, where outer electrodes 3 are provided at both margins of these inner electrodes 2a.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention normally functions as a capacitor to absorb low-voltage noise and high-frequency noise, and when high voltage such as negative pulses or static electricity enters the varistor. Grain boundary insulated semiconductor ceramic capacitors that perform their functions, protect semiconductors and electronic devices from abnormal voltages such as noise, pulses, and static electricity generated in electronic devices, and whose characteristics are stable over temperature. and its manufacturing method.

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 capacitors, multilayer ceramic capacitors, semiconductor ceramic capacitors, and the like are used as bypass capacitors in the power supply lines of LSIs. 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 is to become lighter, thinner, and smaller.

As performance continues to improve, demands for smaller size and higher performance ceramic capacitors with varistor function are increasing. However, since conventional ceramic capacitors with varistor function are single-plate type, miniaturization reduces the electrode area, resulting in a decrease in capacitance.
This results in a problem of 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 compared to the commonly used BaTiO3-based multilayer ceramic capacitors. It was thought that it would 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-54-53250, and printed a ceramic paste with a large amount of organic binder on the parts corresponding to the internal electrodes. However, 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 the internal electrode is formed by plating or melting. A method for forming a multilayer ceramic capacitor with a varistor function has been developed and provided. 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. 63-219115, internal electrodes are alternately arranged 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 a molded body laminated with a molded body is fired in air or in an oxidizing atmosphere.

However, in these methods, the firing temperature is 1000-120°C.
Because the temperature is relatively low at 0°C and sintering of the ceramic is difficult to occur, the crystal grains are in surface contact and the finished device is
Since it is not a completely sintered body, it has a low capacity, a small voltage nonlinearity index α, which is a typical characteristic of a varistor, the varistor voltage is unstable, and it has the disadvantages of poor reliability. . 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.

In addition, as a patent regarding a multilayer varistor, ZnO has already been disclosed in Japanese Patent Publication No. 58-23921.

A stacked voltage nonlinear element using Fe2oz and TiO2 systems 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. A grain-boundary insulated type mainly composed of SrTiO3, which exhibits high performance characteristics and whose characteristics are always stable with respect to temperature, and which also enables simultaneous firing of the ceramic capacitor material and internal electrode material. The object of the present invention is to provide a semiconductor ceramic capacitor and a method for manufacturing the same.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides that the molar ratio of Sr and Ti is 0.95≦S r /T i <1.0.
SrTiO3 containing excess Ti so that it becomes 0,
N b 20 s , T a 20 s , V
20s.

W2O5, D yzO3, Nd2O3, Y2O3, L
At least one type of a203+CeO2 is added to 0.
05-2. Omo1%, Mn and S' i respectively
The total amount in the form of nO2 and SiO2 is 0.2-5, Om
o1% and L i A I O2 from 0.05 to 4.0 m
The present invention provides a grain boundary insulated semiconductor ceramic capacitor containing ol%.

Further, the present invention provides that the molar ratio of Sr and Ti is 0.95≦Sr/
5r containing excess Ti so that Ti<1.00
TiO+, Nb2O5, Ta20LV205. WzO
s, Dy2O3, NdzO3, Y2O3゜La2O3,
0.05 to 2 of at least one type of CeO2,
Omo1%, Mn and Si respectively M n O2 and S
The total amount in the form of iO2 is 0.2-5, Omo 1%, LiAj! 02 to 0.05 to 4. In a grain boundary insulated semiconductor ceramic containing 1% Omo, multiple 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 in the parentheses. The present invention provides a laminated grain boundary insulated semiconductor ceramic capacitor having the following characteristics. Furthermore, in the present invention, Nb2O5, T
azOs, V2O5, W2O5, Dy2O3゜Nd2O
3, Y2O3, Lazo3. CeO2 (0.05 to 2.Omo1% of at least one type of Omo in D,
Mn and Si are in the form of MnO2 and Si02, respectively, and the total amount is 0.2 to 5. Omo 1% and Li Af
A mixed powder of a composition containing 0.05 to 4.0 mol% of O is used as a starting material, and the mixed powder is pulverized, mixed, dried, and then calcined in air or in a nitrogen atmosphere. After baking, the re-pulverized powder is dispersed in a solvent together with an organic binder to form a green sheet, and then internal electrode paste is printed on top of this green sheet alternately up to the opposing edges (however, the top layer and (without printing on the lower layer raw sheet), and the process of laminating, pressurizing, and crimping the raw sheets printed with this internal electrode paste to obtain a molded body, and then calcining this molded body in air. After calcination, a step of firing in a reducing or nitrogen atmosphere; After calcination, a step of reoxidizing in air; After reoxidation, a step of applying external electrode paste to both ends of the exposed internal electrode and baking. The present invention provides a method for manufacturing a multilayer grain boundary insulated semiconductor ceramic capacitor characterized by having the following steps. The internal electrodes are made of Au, Pt, and Rh.

The present invention provides that it is formed of at least one metal selected from Pd and Ni, or an alloy or mixture thereof. Further, the external electrode may be Pd, Ag,
It is provided that it is formed of at least one metal selected from Ni, Cu, and Zn, or an alloy or mixture thereof.

General operation: In order to convert S r Ti Os into a semiconductor, either forced reduction or addition of a semiconductor conversion accelerator and firing in a reducing atmosphere are required. However, with this alone, semiconductor formation may not proceed depending on the type of semiconductor formation accelerator. Therefore, from the stoichiometry of S r T 103,
Excessive Sr or excessive Ti increases lattice defects within the crystal, promoting semiconductor formation. Furthermore, Nb2O
5, Ta205゜'11'2O5, W2O5, D'12
03. Nd2O3, Y2O3゜La2O3, CeO, (
(hereinafter referred to as the first component) promotes semiconductor formation through atomization control.

Next, in the sintering process, M n O2 and SiO2 (second
(components) are essential substances for forming a laminated structure, and even if either one is missing, the effect will not be exhibited. As mentioned above, until now 5rTiO:+
It was thought that it would be difficult to fabricate a multilayer ceramic capacitor with varistor function. The reason is,
Firstly, 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, during the reoxidation process in air, the latter material is oxidized to metal oxides,
This is because it has the action and property of shielding the former material from re-oxidation.

The second reason is that in order to form the former material into a ceramic capacitor element with a varistor function, it is necessary to sinter it in a reducing atmosphere to convert it into a semiconductor, and then apply high-resistance metal oxides (Mn02°CuO2, B i20.+
, CO2O3, etc.) and reoxidizes in the 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 and materials are alternately stacked.

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

First, in a material composition in which a second component is added in addition to the first component to SrTiO3 with excess Ti, after firing in a reducing atmosphere, the above-mentioned high resistance is formed on the surface of the element. We have discovered that a ceramic capacitor with varistor function can be easily formed by simply reoxidizing in air without applying a metal oxide. This is because excess Ti and the added second component form MnO25iOz- at low temperature during the sintering process.
At the same time, forming a TiO2-based liquid phase and promoting sintering,
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 3i 02-T i 02 series 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 r
I decided to use T f 03.

Second, it has been found that a material composition in which a second component is added to SrTiO3 containing excess Ti 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 low temperatures as shown in the first reason above, and also acts as an atomization control agent in addition to forming a liquid phase, and at this time, the valence of the Mn atom increases. +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.

Thirdly, if the molded body is calcined in air after degreasing, various problems such as internal electrode breakage, delamination, cracking, and reduction in sintered density of the finished multilayer ceramic capacitor with varistor function may 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.

Furthermore, LjAj! O= (hereinafter referred to as the third component)
The Li atoms inside are MnO2-S io2 T i 02
It acts as a carrier to uniformly diffuse the liquid phase of the system to the grain boundary area, forming a sharp boundary between the semiconductor crystal and the high-resistance grain boundary, and as a result improves the temperature characteristics of capacitance and varistor voltage. be. And again, A for the 3rd stanza
I! The atoms form a solid solution within the crystal, lowering the resistance of the crystal particles, and as a result, increasing the voltage nonlinearity index α and lowering the series equivalent resistance value ESR.

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

(Example 1) First, the average particle size is 0.5 μm or less and the purity is 98% or more.
Add T i 02 to 5rTfO8 raw material powder, S r
/ Ti ratio adjusted powder, as shown in Tables 1 to 15 below, N b 20 s as the first component, MnO2, SiO2 as the second component (however, MnO2, S
in:: is the same mole as 1%), and the amount of L iAj'○ added as the third component was 1.0 mol.
% and mixed. Thereafter, this mixed powder is wet-pulverized and mixed using a ball mill or the like, dried, and then calcined in air at 600-1200°C. After calcining, the average particle size is 0.
The powder was ground again to a particle size of 5 μm or less, and used as a starting material for a multilayer ceramic capacitor with a varistor function. This fine powder starting material was dispersed in a solvent together with an organic binder such as butyral resin to form a slurry, and this was made into a green sheet with a thickness of about 50 μm using a doctor blade method 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. Moreover, 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 reach alternately opposing edges, as is well known. Thereafter, a plurality of raw sheets 1 were laminated in the same direction as the internal electrode paste 2 was printed, and pressed and bonded. Next, it was degreased in air at 400°C, and further calcined 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 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 mm3.
5.5 type, the effective layer with internal electrodes is 10
It is made of laminated layers. Further, 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.
C. for 2 hours, calcination in a reducing atmosphere of N2:H2 = 99:1 at 1300.degree. C. for 2 hours, and reoxidation at 1100.degree. C. for 1 hour.

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

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

◇ Varistor voltage VO41□^ is the value at a measurement current of 0.1mA.

◇ Voltage non-linearity index α is measured current 0.1mA and 1,Q
From the value in mA, α= 1/ l o g(V+, om^/V a,
+, n^).

◇ The series equivalent resistance value ESR is the measured voltage 1. Resistance value at common point in Ov.

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

◇ Varistor voltage temperature coefficient (△V/V) is the value between 25℃ and 50℃.

(Margin below) Next, to explain Tables 1 to 15 above, these tables show the S r / Ti ratio and the M n of the second component.
This specifies the amounts of O2 and 5iO= added.

Here, the sample number with Honda attached is a comparative example and is 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 the capacitance temperature change rate and varistor voltage temperature coefficient are large, and reliability and electrical characteristics are not affected by temperature. It is easy to receive. 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 nonlinearity index α, and a small series equivalent resistance value ESR, so they have the ability to absorb low voltage noise and high frequency noise as a capacitor. It also has the function of absorbing high voltages such as pulses and static electricity as a varistor, and also has a small capacitance temperature change rate and varistor voltage temperature coefficient, so its reliability and electrical characteristics are not affected by temperature. It has characteristics. 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 / of 5rT103
The Ti ratio was defined as S r /Ti ratio of 1,
If it is larger than OO, Sr will be excessive and MnO2-3
This is because the io□-Ti 02-based liquid phase is difficult to form, making it difficult to form a grain boundary insulation type structure, and causing oxidation and diffusion of the internal electrodes, resulting in a decrease in electrical characteristics and reliability. On the other hand, if the S r /T i ratio is less than 0.95, the sintered body becomes porous and the sintered density decreases. Furthermore, the reason why the average particle size of the starting material for a multilayer ceramic capacitor with a varistor function is specified to be 0.5 μm or less is because if it is larger than 0.5 μm, the powder may aggregate when it is made into a slurry, or the finished sintered material may This is because the solid element has a low sintered density and is difficult to convert into a semiconductor, so its electrical properties tend to be unstable.

Next, the total addition amount of MnO2 and SiO2 as the second component was specified because the addition amount of these second components was 0.2
MnO+
This is because the S i 02-T i 02 system liquid phase is difficult to form, resulting in a grain boundary insulated structure, resulting in lower electrical properties and sintered density. On the other hand, if the amount of the second component added exceeds 5.0 mol %, the amount of high-resistance oxides segregated at the grain boundaries will increase and the electrical properties will 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 method of manufacturing a multilayer ceramic capacitor with a varistor function according to the present invention, and the results of this step determine the electrical characteristics and reliability of the multilayer ceramic capacitor with a 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 to be in the range of 600-1250°C is because the effect cannot be obtained if the calcination temperature is less than 600°C. On the other hand, the calcination temperature is 1250
If the temperature exceeds ℃, 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 and oxidation of the Ni internal electrode material occur, and then the sintered body and Ni react, and Ni diffusion progresses, resulting in The resulting multilayer ceramic capacitor with varistor function suffers from internal electrode breakage and delamination.

Various problems such as cracks occur.

■ If calcination is performed at a high temperature exceeding 1250℃, ξMn 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.

Furthermore, by adding LiAlO2 as a third component, the capacitance temperature change rate and varistor voltage temperature coefficient are improved. That is, the added LiAlO
This is because the Li atoms in 2 act as carriers to uniformly diffuse the M n O 2 SiO 2 TiO 2 -based liquid phase to the grain boundary portion, and sharp grain boundaries with the semiconductor crystal and high resistance are formed. Yet again, LiAjl! 0
By adding 2, the voltage non-linearity index α is improved and the series equivalent resistance value ESR is reduced. This is because the Al atoms in the added LiAl0:+ form a solid solution in the crystal and lower the resistance of the crystal particles.

The thus obtained multilayer ceramic capacitor with varistor function has a larger capacity and superior temperature and frequency characteristics compared to the multilayer varistor reported in the above-mentioned Japanese Patent Publication No. 58-23921. In the former case, varistor materials with excellent surge absorption properties are simply laminated, whereas in the present invention, the present invention has both a capacitor function with excellent noise absorption properties and a varistor function with excellent pulse and static electricity absorption properties. It is a laminated ceramic capacitor material with a varistor function, and its function and purpose of use are completely different.

(Example 2) According to Example 1, MnO2 and SiO2 as the second component
It was found that a total addition amount of 0.2 to 5.0 mo 1% is required. Next, MnO2 as this second component
The addition ratio of Sr/SiO+ was varied, and Sr/
Ti ratio is 0.97, N b 20 s as the first component
The addition amount of 1.0 mol%, Li as the third component
A multilayer ceramic capacitor with a varistor function was manufactured in the same manner as in Example 1, with the amount of A102 added being fixed at 1.0 mol%. The results are listed in Table 16 below.

(Margin below) To explain Table 16 above, it is clear from the measurement results that both MnO2 and SiO2 are required to fabricate a multilayer ceramic capacitor with a varistor function, and if one or the other is missing. However, it is not possible to fabricate a multilayer ceramic capacitor with a varistor function. That is,
Only when both components are present MnO2S i 02-T i
A 02-based liquid phase is formed, which dissolves and segregates at the grain boundary, and when reoxidized, M n O2S 10 segregates at the grain boundary.
:! This is because it becomes insulated and easily becomes an element having a grain boundary insulation type structure.

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 3) Next, Nb2O5, Ta205°V2 as the first component
In order to specify the addition amount of the atomization control agent of O5, W2O5, Dy20s, Nd2O3, Y2O3゜La2O3, CeO2, this was varied and the S r / Ti ratio was set to 0.
97, the amount of the second addition is MnO2, 1.0 mol%,
The total amount of SiO2,1゜Qmo 1% is 2.0 mol%, and the amount of L i A l 02 added as the third fraction is 1.0.
A multilayer ceramic capacitor with a varistor function was manufactured in the same manner as in Example 1.2, with the mol% being fixed. The results are shown in Tables 17 to 25 below.

(Margin below) To explain Tables 17 to 25 above, the reason for specifying the amount of the first component added is that, as is clear from the measurement results, if the amount added is less than 0.05 mo1%, the amount of the first component added is This is because no effect can be obtained and it is difficult to convert into a semiconductor. 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 Tazos as the first component than other V2O5, W2O5, Dy2O3゜Nd
The electrical properties were slightly better than those in which 2O5, Y2O3, La20+, and Ce0z were added.

Furthermore, some combinations of the mixture composition of the first component were tested and the electrical properties were measured, but as shown in Table 25, there was almost no difference in the properties compared to when different types were added. It was impossible. 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, it was confirmed that when 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 11th tc, and it is necessary to suppress it to 0.5 μm or less.

(Example 4) Next, in order to specify the amount of LiAfO2 added as the third component, this was changed variously, and the Sr/Ti ratio was set to 0.97,
The amount of addition of the component was N bz Os, 0.5mol1%
, Ta2Q5.0.5mo 1%, the addition amount of the second component was MnO21.0mo 1%, SiO3゜1.0mol%
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 26 below.

(Left below) As stated in Table 26 above, the first characteristic is that the capacitance temperature change rate and varistor voltage temperature coefficient are improved by adding the third component, LiA10z. . This means that the Li atoms in the added LiA10z are Mn.
This is because it acts as a carrier that uniformly diffuses the O2-31o2-TiOx-based liquid phase into the grain boundary portion, thereby forming a sharp boundary between the semiconductor crystal and the high-resistance grain boundary.

Moreover, as a second feature, by adding L i A I Oz, the voltage nonlinearity index α is improved and the series equivalent resistance value ESR is reduced. This is the added LiA
AI in lO2! This is because the atoms are solidly dissolved within the crystal and lower the resistance of the crystal particles.

Here, the addition amount of LiA10z as the third component was specified because if the addition amount of the third component is less than 0.05, the addition effect will not be obtained, and the capacitance temperature change rate and varistor voltage temperature coefficient will not be improved. This is because the voltage nonlinearity index α does not improve, and the series equivalent resistance value ESR does not decrease.

On the other hand, if the amount of the third component added exceeds 2.0 mol%, the amount of the third component added exceeds the solid solubility limit in the crystal, so that excess LiAl0z
precipitates at the grain boundaries and lowers the resistance of the grain boundaries, resulting in a rapid decrease in capacitance and voltage nonlinearity index α, and the series equivalent resistance value E
This is because SR increases, firing density further decreases, and mechanical strength decreases.

In addition, as an additive for the third component LiAl0z, Li2
It is conceivable to use a mixed additive of O and AlO2.

However, when this mixed additive of Li2O and AlO3 is used, since Li2O is a very unstable substance, Li2O easily decomposes during firing and scatters into the atmosphere.
It was confirmed that due to diffusion, there were almost no Li atoms in the completed sintered element, and that partially ionized Li ions migrated under high-temperature voltage loads, causing property deterioration. Therefore, by adding Li in the form of LiAlO2, it is possible to provide something stable in the grain boundaries without impairing the function of Li.

Therefore, it was confirmed that LiAlO2 is absolutely necessary as the gJ3 component.

(Example 5) In each of the above examples, the case where Pd was used as the internal electrode was explained, but other materials such as Au, Pt, and Rh were used.

For Ni, the S r /T i ratio was set to 0.97, the first
The amount of addition of the components was N b20s 0.5 m o 1%,
TazOsQ, 5mo1%, the amount of the second component added is MnO
21, 0 mol%, S i 021.0mo 1%, the amount of LiA10z added as the third portion was 1.0 mol%
A multilayer ceramic capacitor with a varistor function was produced in the same manner as in Example 1 above.

The results are listed in Table 27 below.

(Left below) As stated in Table 27 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 SrTiO3, oxidation of Ni occurs at a relatively low temperature, so oxidation can be suppressed by mixing Pd or using SrTiO3 with a slight excess of Ti.

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 T i
In preparing 03, T i 0 was added to SrTiO3.
Although Ti is added in the above example, Ti may be used in the form of carbonate, hydroxide, organic compound, etc., and it goes without saying that similar effects can be obtained.

In addition, in the examples of the present invention, 5rTiO:+
Although 5rTiO:+ was prepared from SrO or SrCO3 and TiO2, etc. as a raw material powder, the same effect can of course be obtained.

Furthermore, it goes without saying that similar effects can be obtained even when MnO2 and S i 02 as the second component are used in the form of their carbonates, hydroxides, and the like. However, it was confirmed that when used in the form of MnCO3, the particle size is finer and more uniform, and it is easier to decompose, making it possible to produce elements with stable characteristics and being suitable for mass production.

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 (135
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, P d as an external electrode
+ A g + N l + Cu + Z n 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 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 n 02-Si Q2-Ti02 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 described above, the element 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 high voltages such as pulses and static electricity enter, it exhibits a varistor function, exhibiting excellent responsiveness to abnormal voltages such as noise, pulses, and static electricity, and whose characteristics are always stable against temperature. Therefore, it is expected to be an alternative to 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.

■ 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 a semiconductor component to 5rTiO:+ with excess Ti, M
This is because the composition containing nO2 and 5iOz can easily become a grain-boundary insulated semiconductor ceramic capacitor simply by reoxidation without going through the surface diffusion process of metal oxide that has been carried out up to now. 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 is highly expected to be applied as a surface-mounted component. It can also be used as a high-density packaging element for 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 always stable with respect to temperature. The effect 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. 1... raw sheet, 2... internal electrode paste, 2a... internal electrode, 3... external electrode, 4... varistor function Multilayer ceramic capacitor.

Claims (7)

[Claims] (1) The molar ratio of Sr and Ti is 0.95≦Sr/Ti<1
．． SrTiO_ containing excess Ti so that it becomes 00
3, Nb_2O_5, Ta_2O_5, V_2O_5
, W_2O_5, Dy_2O_3, Nd_2O_3, Y
At least one of _2O_3, La_2O_3, CeO_2 in an amount of 0.05 to 2.0 mol%, 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 LiAlO_2. 0.
A grain boundary insulated semiconductor ceramic capacitor containing 05 to 4.0 mol%. (2) The molar ratio of Sr and Ti is 0.95≦Sr/Ti<1
．． SrTiO_ containing excess Ti so that it becomes 00
3, Nb_2O_5, Ta_2O_5, V_2O_5
, W_2O_5, Dy_2O_3, Nd_2O_3, Y
At least one of _2O_3, La_2O_3, CeO_2 in an amount of 0.05 to 2.0 mol%, 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 LiAlO_2. 0.
A plurality of layers of internal electrodes are provided in a grain boundary insulated semiconductor ceramic containing 05 to 4.0 mol% so that they alternately reach opposing edges, and external electrodes are provided on both edges of the internal electrodes. A multilayer grain boundary insulated semiconductor ceramic capacitor characterized by: (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 and Ti is 0.95≦Sr/Ti<1
．． SrTiO_ containing excess Ti so that it becomes 00
3, Nb_2O_5, Ta_2O_5, V_2O_5
, W_2O_5, Dy_2O_3, Nd_2O_3, Y
At least one of _2O_3, La_2O_3, CeO_2 in an amount of 0.05 to 2.0 mol%, 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 LiAlO_2. 0.
A mixed powder of a composition containing 05 to 4.0 mol% is used as a starting material, and the mixed powder is pulverized, mixed, dried, and then calcined in air or in a nitrogen atmosphere. The pulverized powder is dispersed in a solvent together with an organic binder to form a green sheet, and then internal electrode paste is printed on top of this green sheet alternately reaching the opposing edges (
However, the green sheets of the top and bottom layers are not printed), the raw sheets printed with this internal electrode paste are laminated, pressed, and crimped to obtain a molded body, and then this molded body is air-filled. A process of calcination in the atmosphere, a process of calcination in a reducing or nitrogen atmosphere after calcination, a process of re-oxidation in the air after calcination, and a process of applying external electrode paste to both ends with exposed internal electrodes after re-oxidation. 1. A method for manufacturing a multilayer grain boundary insulated semiconductor ceramic capacitor, comprising the steps of applying and baking. (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.