JPH02248018A - Grain boundary insulated semiconductor ceramic capacitor and manufacture thereof - Google Patents

Abstract

PURPOSE:To make it possible to simultaneously sinter a varistor-functioning ceramic capacitor material and an internal electrode material, and to easily obtain a varistor- functioning laminated ceramic capacitor by a method wherein a composition is formed by adding MnO2 and SiO2 to the SrTiO3, having excessive Ti, besides a semiconductor component. CONSTITUTION:A grain boundary insulated semiconductor ceramic capacitor is formed by having the below-mentioned materials added to Sr(1-x)CaxTiO3, which is 0.001<=x<=0.2, containing excessive Ti in such a manner that the mol ratio of Sr(1-x)Cax and Ti becomes 0.95<=Sr(1-x)Ca/Ti<1.00. The materials referred to above are 0.05 to 2.0mol% of the element consisting at least of one or more kinds selected from Nb2O5, Ta2O5, V2O5, W2O5, Dy2O3, Nd2O3, Y2O3, La2O3 and CeO2, and MnO2 and SiO2 of 0.2 to 5.0mol% in total. External electrode paste is coated on both ends where the internal electrode 2a of the above-mentioned varistor-functioning laminated ceramic capacitor 4, a baking operation is conducted thereon at the prescribed temperature and time, a plurality of the internal electrodes 2a are alternately provided in the grain boundary insulated semiconductor ceramic in such a manner that the internal electrodes will be brought to the edge, and external electrodes 3 are provided on both edges of the capacitor.

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,
The present invention relates to a grain boundary insulated semiconductor ceramic capacitor that protects semiconductors and electronic devices from abnormal voltages such as noise, pulses, and static electricity generated in electronic devices, and a method for manufacturing the same.

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 the noise tolerance of devices is decreasing accordingly.Therefore, in order to ensure the noise tolerance of such electronic devices, various ICs are being used.
, 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
- It is provided by '35303 publication 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 a 5rTi03-based semiconductor element and insulating the grain boundary layer by thermal diffusion, so they are different from 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-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 an internal electrode is formed by a plating method or a melting method. 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. 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℃.
Because the temperature is relatively low and sintering of the ceramic is difficult to occur, the crystal particles are not in surface contact.The completed device has a low capacity because it is not a complete sintered body, and has the typical characteristics of a varistor. 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.

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

F e 203. A stacked voltage nonlinear element using a T i O2 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. The object of the present invention is to provide a grain-boundary insulated semiconductor ceramic capacitor mainly composed of SrTiO3, which exhibits the same characteristics, and also enables simultaneous firing of a ceramic capacitor material and an internal electrode material in terms of process, and a method for manufacturing the same. It is.

Means for Solving the Problems In order to solve the above problems, the present invention provides S r
1l-xl The molar ratio of Ca x and Ti is 0.95≦S
r(1-xlCax /S containing excess Ti so that Ti<1.00 and 0.001≦X≦0.2
r +1-XI CaXT i 03, Nb2O5,
Ta205゜V2O5, W2O5, DyzO3, Nd2
O3, Y2O3, La2O3, CeO2O3+ Ce
At least one type of O2 at 0.05 to 2.0 m
o 1%, MnO2 and 5in2 in total amount 0.2~5
．． The present invention provides a grain boundary insulated semiconductor ceramic capacitor containing 0 mol%. Further, the present invention provides S
r +1-xi The molar ratio of Ca x and Ti is 0.95
≦S r 1l-XI Ca x / T I < 1.
Contains excess Ti so that 0.001≦X
≦0.2, S r 1l-xi CaxT i
03, Nb2O5, Ta20LV205. W2O5,
DV203゜Nd2O3, Y2O3, La2O3, Ce
0 = 0.05 to 2.0m of at least one type of
ol%, and the total amount of M n 02 and S i 02 is 0.
In a grain boundary insulated semiconductor ceramic containing 2 to 5.0 mol%, a plurality of internal electrodes are provided so as to alternately reach opposing edges, and external electrodes are provided on both edges of the internal electrodes. A multilayer grain boundary insulated semiconductor ceramic capacitor is provided. Furthermore, the present invention provides a method in which the molar ratio of S r (1-x+caX and Ti is 0.95≦S r 1t-xiCaX/T i
Contains excess Ti so that <1.00 and 0.00
1≦X≦0.2 S r z−xiCaxT i
O3, Nb2O5°Ta205. V2O5, W2O5
, Dy203+ Nd2O3゜Y2O3, L a20
3. Ce 0.05 of at least one type of 02
A mixed powder of a composition containing ~2.0 mo 1% and a total amount of 0.2 to 5.0 mo 1% of MnO2 and SiO3 is used as a starting material, and after pulverizing, mixing, and drying the mixed powder, a step of calcination in air or nitrogen atmosphere;
After calcination, 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 The raw sheets printed with the internal electrode paste are laminated, pressed, and crimped to obtain a molded body, and then this molded body is calcined in air. After calcination, a step of firing in a reducing or nitrogen atmosphere; After calcination, a step of reoxidizing in air; After reoxidation, external electrode paste is applied to both ends with exposed internal electrodes and baked. The present invention provides a method for manufacturing a multilayer grain boundary insulated semiconductor ceramic capacitor, comprising the steps of: 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.

Function Generally, in order to convert S r n-xiCax T i 03 into a semiconductor, it is forcedly reduced, or a semiconductor conversion accelerator is added and it is fired in a reducing atmosphere. However, with this alone, semiconductor formation may not proceed depending on the type of semiconductor formation accelerator. Therefore, Sr(1-xi
From the stoichiometry of Ca, TiO:+, S r (1-x+
When Cax is excessive (hereinafter referred to as A site excess) or Ti is excessive, lattice defects in the crystal increase and semiconductor formation is promoted. Moreover, Ca enters the Sr site and has the effect of suppressing grain growth.

Furthermore, Nb2O5, Ta205. V2O5, W2O5
.

D V2O3, Nd2O3, Y2O3, L a203+
When Ce 02 (hereinafter referred to as the first component) is added, semiconductor formation is promoted through atomization control.

Next, MnO2 and SiO2 (hereinafter referred to as the second component) are essential substances for forming a laminated structure, and even if either one is missing, the effect will not be exhibited. As described above, it has been thought until now to be difficult to produce a SrTiO3-based multilayer ceramic capacitor with a varistor function. The reason is, first of all,
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 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 a high-resistance metal oxide (Mn02Cu○2. Bi2O3, CO
2O3, etc.) and re-oxidizes 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 are alternately stacked.

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

First of all, Ti excess S r (1-x+c a8
Besides adding the first component to Ti03, MnO2
With the material composition containing 5in2 and 5in2, after firing in a reducing atmosphere, it is easy to form a varistor by simply re-oxidizing it in the air, without having to coat the surface of the element with a high-resistance metal oxide as described above. It has been discovered that a functional ceramic capacitor can be formed. This is due to excess Ti and added M n
During the sintering process, O2 and SiO2 form MnO2-310 at low temperature.
It forms a 2-T i 02-based liquid phase and promotes sintering, and at the same time dissolves and segregates at grain boundaries. When this is reoxidized in air, M segregated at grain boundaries
This is because the nO2-3i02-TiO2 system is insulated and easily becomes a ceramic capacitor with a varistor function having a grain boundary insulated 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
It was decided to use 1l-xl Ca xT i 03.

Secondly, Ti excess S r t+ −xl Ca
"We have found that a material composition in which M n O2 and SiO2 are added to xT I O3 becomes a semiconductor even when sintered in a nitrogen atmosphere as well as in a reducing atmosphere. This is due to the fact that
As shown in the reason for this, in order to form a liquid phase at low temperatures, the added Mn acts as an atomization control agent in addition to forming a liquid phase, and at this time, the valence of the Mn atom changes to +2 + 4, and the electron It is thought that due to the effect of being physically unstable, the sintering properties are improved and it can be easily converted into a semiconductor even in a nitrogen atmosphere.

Third, if the molded body is calcined in air after degreasing, various problems such as internal electrode breakage, delamination, cracking, and a decrease 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.

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
ro9T io, 103 raw material powder with CaC0:i and T
Add iO2, S r + + -xl Ca x Z
The first component, Nb2, is added to the powder whose Ti ratio (hereinafter referred to as A/B ratio) is adjusted, as shown in Tables 1 to 15 below.
0s1 second component Mn O2, S i 02 (however,
M n O3S i O2 to be added is equal to 1%)
were weighed 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 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,
Degrease at 400℃ in air, and then degrease at 600℃ in air.
Calcining was performed at 1250°C. Afterwards, 1
It was fired at 250-1350°C. 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.
It is a 5.5 mm3 type, and has 10 laminated effective layers on which internal electrodes are formed. 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.
℃, 2 hours, calcination in a reducing atmosphere of N2:N2 = 99:1: 1300℃, 2 hours, reoxidation: 1100℃
, which took one hour.

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

◇ Capacity C is measured voltage i, ov, frequency 1.0KH
value at z.

◇ Varistor voltage VO, 1llIA is measured current 0.1m
Value at A.

◇ Voltage non-linearity index α is measured current 0.1mA and 1,Q
From the value in mA, α = 1/log (Vl, 0fllA/VQ
, Il! It was calculated using the formula IA).

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

◇ 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℃.

(Margin below) Next, to explain Tables 1 to 15 above, these tables have S r 0.7 Cao, +T i 03 A
/B ratio and the amounts of MnO2 and SiO2 added as the second components are specified.

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 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 l+−xlc ax
The A/B ratio of T i 03 was defined as A/B ratio of 1.
．． If it is larger than 00, the A site is excessive, and Mn02
-3102-T Because the i02-based liquid phase is difficult to form, it becomes a grain boundary insulated 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 size of the starting material for the multilayer ceramic capacitor with 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 the second components MnO and SiO2 was specified because the addition amount of these second components was 0.1 mo1.
If the addition effect is less than %, the addition effect cannot be obtained.
This is because it is difficult to form an i Oney T i O2-based liquid phase, which makes it difficult to form a grain boundary insulation type 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 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℃, Mn02
Liquid phase sintering of the -S i O2-'r i 02 system progresses rapidly, grain growth is promoted, and the sintered body density and packing density are significantly reduced.

(2) If the material is then fired in a reducing or nitrogen atmosphere, it becomes difficult to convert it into a semiconductor.

This is because the electrical characteristics and reliability deteriorate significantly.

The thus obtained multilayer ceramic capacitor with varistor function has a larger capacity and excellent temperature and frequency characteristics than 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) Next, the composition ratio of Sr and Ca corresponding to the A site of the perovskite structure represented by ABO3 was varied, and A/B of S r + 1-xl Ca xl T l
A multilayer ceramic capacitor with a varistor function was manufactured in the same manner as in Example 1, with the ratio fixed at 0.97 and the amount of N b 205 added as the first component fixed at 1, 0 mol %. 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, if the amount of Ca added is too large, oxidation tends to proceed, resulting in a decrease in capacity and deterioration in varistor characteristics.

Therefore, the substitution rate X of Ca that partially replaces Sr at the A site is preferably 0°001≦X≦0.2.

(Example 3) According to Example 1, Mn0z and SiO2 as the second component
It was found that the total addition amount of 0.2 to 5.0 mol% is required. Next, M as this second component
By varying the addition ratio of nO2 and SiO2, S
ro7c ao, +T i 03 A/B ratio 0.9
7. A multilayer ceramic capacitor with a varistor function was manufactured in the same manner as in Example 1, with X=0.10 and the amount of Nb2O5 added as the first component fixed at 1.0 mol%. The results are listed in Table 17 below.

(Margin below) To explain Table 17 above, it is clear from the measurement results that both MnO2 and SiO2 are required to fabricate a multilayer ceramic capacitor with 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,
M n 02 S i 02 only when the same component exists
- A liquid phase of T i O = system is formed, which dissolves and segregates at the grain boundary, and when reoxidized, Mn0z segregated at the grain boundary.
This is because SiO2 becomes insulating 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 M n O2.

(Example 4) Next, Nb2O5, Ta205+V as the first component
20 s, W 20 s, DV 203,
Nd203, Y20:l.

La2Q3. In order to specify the amount of CeQ2 atomization control agent added, this was varied and S rll-xl CaxT
The A/B ratio of i03 is 0.97, X=0.1, the amount of the second component added is Mn021.0 mol%, and S1021.
A multilayer ceramic capacitor with a varistor function was manufactured in the same manner as in Examples 1 and 2 above, with the total mol% of omo 1% being fixed at 2.0 mol%. The results are shown in Table 18 below.
It is listed in Table 26.

(Margin below) To explain Tables 18 to 26 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 Q5mo1%, the amount of addition of the first component is specified. 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 the addition of Nb=Os and Ta205 as the first component is better than the addition of other V2O5, W2O5, Dy20:+.

The electrical properties were slightly better than the case where Nd2O:+, Y2O3, La2O3, and Ce02 were added.

Furthermore, regarding the mixture composition of the first component, some combinations were tested and the electrical properties were measured, and as shown in Table 26, the results showed that there was almost no difference in the properties compared to when - types were added. It was something that could not be seen. However, in this case as well, the addition of Nb2O5°T a =Os 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, the effect of the first component tends to be difficult to obtain, and
．． It was confirmed that it is necessary to suppress the thickness to 5 μm or less.

(Example 5) In each of the above examples, the case where Pd was used as the internal electrode was explained, but for other Au, PtRh, and Ni, the A/B ratio of S r f+-1l CaxT i 03 was 0.97. , X=0.10, the amount of the first component added is Nb2
0so, 5mo1%, Ta2os0.5mo1%,
The amount of the second component added is Mn021.0mol%, 5in2
A multilayer ceramic capacitor with a varistor function was manufactured in the same manner as in the above example, with the amount fixed at 1.0 mol%. The results are shown 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 S r x-x with a slight excess of Ti, it is necessary to mix Pd or use S
Oxidation can be suppressed by using l Ca and T 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 z-1
In preparing Ca x Ti03, Sr, -
Although TiO2 was added to 8ICa x T 103, 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-
xlCa X T t O3 was used, but SrO, Sr
CO3゜CaCO3, Cab, titanate and TiO2
Of course, the same effect can be obtained even if S r +1-xl Ca xT i03 is prepared from the raw material powder.

Furthermore, it goes without saying that similar effects can be obtained even when MnO2 and SiO2 as the second component are used in the form of their carbonates, hydroxides, and the like. However, when using MnC0:+, the particle size is finer and more uniform.
In addition, since it is easy to decompose, it is possible to produce a device with stable characteristics, and it has been confirmed that it is 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, Pd, A
At least one metal selected from G, Ni, Cu, and Zn, or an alloy or mixture thereof may be used. However, when Pd or Ag is used as the 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 nO knee S i 02-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 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 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.

■ 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 a wide range of applications, as it can simultaneously exhibit the above effects (1) and (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 was made possible was that in addition to adding a semiconducting component to SrTiO3 with an excess of Ti, M
This is because the composition containing nO2 and SiO2 can easily become a grain-boundary insulated semiconductor ceramic capacitor by simply reoxidizing it, without going through the surface diffusion process of metal oxides that has been done up until now. This is the most advantageous feature of the present invention in terms of process.

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

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. 1... raw sheet, 2... internal electrode paste, 2a... internal electrode, 3... external electrode, 4... varistor Multilayer ceramic capacitor with functions.

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_
2O_3, Y_2O_3, La_2O_3, CeO_2
0.05 to 2.0 mol of at least one of the following
%, and the total amount of MnO_2 and SiO_2 is 0.2 to 5.
A grain boundary insulated semiconductor ceramic capacitor containing 0 mol%. (2) The molar ratio of Sr(1-X)Ca_X and Ti is 0.9
5≦Sr_(_1_−_X_)Ca_X/Ti<1.0
Contains excess Ti so that 0.001≦X≦
Sr_(_1_−_X_)Ca_XTiO which is 0.2
_3, Nb_2O_5, Ta_2O_5, V_2O_
5, W_2O_5Dy_2O_3, Nd_2O_3, Y
_2O_3, La_2O_3, CeO_2 in an amount of 0.05 to 2.0 mol% and MnO
In a grain boundary insulated semiconductor ceramic containing 0.2 to 5.0 mol% of _2 and SiO_2 in total, a plurality of layers of internal electrodes are provided so as to alternately reach the opposing edges, and this A laminated grain boundary insulated semiconductor ceramic capacitor characterized by having external electrodes provided at both ends of an internal electrode. (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
%, and the total amount of MnO_2 and SiO_2 is 0.2 to 5.
A mixed powder of a composition containing 0 mol% is used as a starting material, and the mixed powder is crushed, mixed, dried, and then calcined in air or in a nitrogen atmosphere, and after calcining, the powder that is crushed again is It is dispersed in a solvent together with an organic binder to form a green sheet, and then internal electrode paste is printed on the green sheet alternately reaching the opposite edges (however, printing is not done on the top and bottom layer of the green sheet). (1) process of laminating, pressurizing, and crimping raw sheets printed with this internal electrode paste to obtain a molded body, and then calcining this molded body in air, and after calcining, reduction or The method is characterized by comprising a step of firing in a nitrogen 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 multilayer 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.