JPH0311716A - Grain boundary insulating type semiconductor ceramic capacitor and manufacture thereof - Google Patents

Abstract

PURPOSE:To stabilize temperature characteristics of the title ceramic capacitor by a method wherein a plurality of internal electrodes are provided in ceramic of specific composition, external electrodes are provided on both edge of the internal electrodes, and a semiconductor and electronic machines are protected from the abnormal voltage such as noise, electric pulse, static electricity and the like. CONSTITUTION:A grain boundary insulating semiconductor ceramic raw sheet 1, containing Sr1-xBaxTiO3 (provided that at least one or more kinds of Nb2O5, Ta2O5, V2O5, Dy2O3, Nd2O3, Y2O3, La2O3 of 0.05 to 2.0mol%, Mn2O3 and SiO2 of 0.2 to 5.0mol% in total, and Li2SiO3 of 0.05 to 2.0mol% are contained therein) containing excess Ti so as to form Sr1-xBax and Ti having mol ratio of 0.95<=Sr1-xBax/Ti<1.00, is formed. Internal electrode paste 2 is printed on the above-mentioned raw sheet 1 in such a manner that the paste 2 is extended as far as to the electrode edge which is opposingly positioned alternately, and after the raw sheet 1 has been laminated and press-bonded, the raw sheet 1 is calcined and sintered. Then, external electrode 3 is coated on both edges of the internal electrodes 2a, and a baking operation is conducted thereon.

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 ceramics that perform their functions and protect semiconductors and electronic devices from abnormal voltages such as noise, pulses, and static electricity generated in electronic devices, and whose properties are always stable against temperature. The present invention relates to a capacitor 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 equipment, various RC
, film capacitors, multilayer ceramic capacitors, semiconductor ceramic capacitors, etc. are used as bypass capacitors in the power supply lines of LsI. 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,
5rTiO 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 J-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 they are different from the commonly used BaTiO3-based multilayer ceramic capacitors. In comparison, it was thought to be extremely difficult to form a multilayer capacitor with a varistor function (hereinafter referred to as a multilayer ceramic capacitor with a varistor function) by firing simultaneously with the internal electrodes.

Therefore, as a method to solve the problem of co-firing, we applied the methods of JP-A-54-53248 and JP-A-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, JP-A-59-215701 discloses a conductive paste in which a heat-diffusing substance capable of insulating the grain boundary layer is mixed 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℃.
Because the temperature is relatively low at 0°C and sintering of the ceramic is difficult to occur, the crystal grains are difficult to come into surface contact, and the finished device is
Because it is not a completely sintered body, it has the disadvantages of low capacity (and low voltage nonlinearity index α, which is a typical characteristic of a varistor), unstable varistor voltage, and poor reliability. Furthermore, in the latter Japanese Patent Application Laid-Open No. 63-219115, a glass component is added as an additive, so a glass phase is precipitated at the grain boundaries, which tends to deteriorate the electrical characteristics described above and reduce reliability. It is inferior in quality and has not yet reached the level of practical use.

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 Fe2O3, TiO2 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 Invention Until now, various compositions and manufacturing methods have been developed and provided for multilayer ceramic capacitors with varistor functions, but as mentioned above, in each case there are problems with the process and the finished device. However, it has not reached a practical level. Therefore, the development of new compositions and manufacturing methods for multilayer ceramic capacitors with varistor functions is expected.

The present invention was made in view of these points. Normally, it functions as a capacitor to absorb low voltage noise and high frequency noise, but on the other hand, when high voltage such as pulses or static electricity enters, it functions as a varistor. S (1- ax T
i O! An object of the present invention is to provide a grain boundary insulated semiconductor ceramic capacitor whose main component is 1 (0<x≦0.3) and a method for manufacturing the same.

Means for Solving the Problems In order to solve the above problems, the present invention provides S r
(+-X) The molar ratio of B a x and Ti is 0.95≦
Sr(+-x+Bax/Srtl-x containing excess Ti so that Ti<1.00)BaxT
i 03 (However, in 0<X≦0.3>, Nb2O5,
Ta2O5, V2O5・W2O5・DyxCh・Nd2
0.05 to 2.0 mo 1% of at least one of O5, Y2O3, La2O3, and CeO2, and MnO
2 and SiO2 in a total amount of 0.2 to 5.0 mol%, L
The present invention provides a grain boundary insulated semiconductor ceramic capacitor containing 0.05 to 2.0 mo 1% of i25iQ3. Moreover, the present invention provides S r (+−X1 B
The molar ratio of ax and Ti is 0.95≦S z+-x, Ba
5rB-1BaxT i 03 containing excess Ti so that x/T i<i, oo (however, O<x≦0
．． 3), Nb2O5°Ta205. V2O5, W2O
5, DytO3, Nd2O3゜Y2O3, La2O3,
At least one type of CeO2 is added in an amount of 0.05 to 2.
0 mol%, MnO2 and 5i (h in total amount 0.2~
5.0mo 1% and Li2SiO3 0.05~2.
A plurality of layers of internal electrodes are provided in a grain boundary insulated semiconductor ceramic containing 0mo1% so that these layers reach alternately opposing edges, and external electrodes are provided on both ends of the internal electrodes of the brackets. The present invention provides a multilayer grain boundary insulated semiconductor ceramic capacitor characterized by:

Furthermore, the present invention provides S r (+-X) B ax and T
The molar ratio of i is 0.95≦S r(+-x)B ax/T
S' (1-x) B a XT i 03 containing excess Ti so that i < 1.00 (however,
Q<)(≦0.3>, Nb2O5゜Ta205.V2
O5, W2O5, Dy2O3, Nd2O3゜YzOz,
At least one of La2O3 and CeO2 is 0
．． 05 to 2.0 mo 1%, the total amount of MnO2 and SiO2 to be 0.2 to 5.0 mol%, and Li2S i 0
A mixed powder of a composition containing 0.05 to 2.0 mo of 1% of 3 is used as a starting material, and the mixed powder is pulverized, mixed,
After drying, there is a process of calcination in air or nitrogen atmosphere, and 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 applied on top of this raw sheet. The process involves printing alternately to the opposing edges (however, not printing on the top and bottom raw sheets), and stacking, pressing, and crimping the raw sheets printed with this internal electrode paste. to obtain a molded body, and then calcining the molded body in air; after calcining, firing in a reducing or nitrogen atmosphere; after firing, reoxidizing in air; and after reoxidation. The present invention provides a method for manufacturing a laminated grain boundary insulated semiconductor ceramic capacitor, which comprises the steps of: applying and baking an external electrode base on both ends with exposed internal electrodes; The present invention also provides that the internal electrodes are formed of at least one metal selected from Au, Pt, Rh, Pd, and Ni, or an alloy or mixture thereof. Further, the external electrode is made of Pd.

The present invention provides that it is formed of at least one metal selected from Ag, Ni, Cu, and Zn, or an alloy or mixture thereof.

Function Generally speaking, in order to convert S r (1-x) B axT i○3 into a semiconductor, it is either forcedly reduced, or a semiconductor conversion accelerator is added and fired in a reducing atmosphere. However, with this alone, semiconductor formation may not proceed depending on the type of semiconductor formation accelerator. Therefore, S r(1-x)
From the stoichiometry of B axT i 03, Sr (+-X
) When B ax is excessive (hereinafter referred to as A site excess) or Ti is excessive, lattice defects in the crystal increase, and semiconductor formation is promoted. Furthermore, Nb2O5, Ta205
．． V2O5, W2O5, D'S/203°Nd2O3,
y,,o3. When La2O3 and CeO2 (hereinafter referred to as the first component) are added, semiconductor formation is promoted by 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 mentioned above, until now it has been considered difficult to produce a multilayer ceramic capacitor with a varistor function. The reason for this is, first, that 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 make it a semiconductor, and then apply high-resistance metal oxides (MnO2°CuO2, B 1203.
CO2O3, etc.) is applied, reoxidized in air, and selectively diffused into grain boundary areas to insulate them, 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 (+-X) Bax
In addition to adding the first component to T i 03, in a material composition in which MnOz and Sigh are added, a high-resistance metal oxide such as the one described above is not applied to the surface of the element after firing in a reducing atmosphere. However, we have found that a ceramic capacitor with varistor function can be easily formed by simply reoxidizing it in air.This is because excess Ti, added MnO2, and 5if2 convert into MnO2S i 02 at low temperatures during the sintering process. −
It forms a T i 02-based liquid phase to promote sintering, and at the same time dissolves and segregates at grain boundaries. When this is reoxidized in air, MnO segregated at grain boundaries
This is because the 2-3i02-Ti02 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 (
+-X) It was decided to use B axT i O3.

Secondly, Ti excess S r u-x) BaxT
It has been found that a material composition in which MnO2 and SiO2 are added to i03 becomes a semiconductor 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. It is thought that the sintering property is improved and it can be easily converted into a semiconductor even in a nitrogen atmosphere due to the effect that the change is +2° +4 and that it is electronically unstable.

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.

Furthermore, Li2SiO3 (hereinafter referred to as the third component) is
It acts as a carrier to uniformly diffuse the liquid phase of the MnO2S i02-Ti02 system into the grain boundary area, forming sharp boundaries between the semiconductor crystal and the high-resistance grain boundaries, resulting in improved temperature characteristics of capacitance and varistor voltage. It is intended to improve the

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
ro, aB ao2T i 03 T i to raw powder
02 and S r (1-y:> B ax/T
The first component Nb2O5,
Second component MnO2, S i 02 (However, M
nO2 and SiO2 (equal IIo1%) were varied, and the amount of Li2SiO3 as the third component was changed to 0.
．． It was fixed at 5mol1% and mixed. After that, this mixed powder is wet-pulverized and mixed using a ball mill, etc., dried, and then calcined in air at 600 to 1200°C. After calcining, the powder is crushed again so that the average particle size is 0.5 μm or less. This was used as a starting material for a multilayer ceramic capacitor with varistor function. This fine powder starting material is dispersed in a solvent together with an organic binder such as butyral resin to form a slurry, and this is made into a slurry using a doctor blade method.
It was made into a raw sheet with a certain thickness and cut into a predetermined size.

Next, as shown in FIG. 1, an internal electrode paste 2 made of Pd was screen printed on the raw sheet 1 obtained as described above according to a predetermined size. Note that, as is clear from FIG. 1, the internal electrode paste 2 is not printed on the raw sheet 1 of the uppermost layer and the lowermost layer. Also,
At this time, the internal electrode pastes 2 printed on the raw sheets 1 to be laminated in the middle were printed so as to alternately reach opposing edges, as is well known. Thereafter, a plurality of raw sheets 1 were laminated in the same direction as the internal electrode paste 2 was printed, and pressed and bonded. Next, degrease in air at 400℃,
Furthermore, calcination was performed at 600 to 1250'C in air. 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 5.70x5.0Ox2, OO++g.
This is an A3 5.5 type with 10 laminated effective layers each having an internal electrode formed thereon. Further, FIG. 3 shows the manufacturing process of the present invention.

The capacitance, tan δ, of the multilayer ceramic capacitor with varistor function thus obtained.

Varistor voltage, voltage nonlinearity index α, series equivalent resistance value ES
Various electrical characteristics such as R, capacitance temperature change rate, and varistor voltage temperature coefficient are also listed in Tables 1 to 15.

However, the firing conditions at this time were: 1200°C for 2 hours in air, N2:N2 =99:
Firing in a reducing atmosphere in No. 1 was performed at 1300° C. for 2 hours, and reoxidation was performed at 1100° C. for 1 hour.

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

◇Capacitance Clt measurement voltage 1. OV, value at frequency 1.0K) h.

◇Varistor voltage VO,l+w^ is measured current 0.1mA
value at.

◇Voltage non-linearity index α is measured current 0.1mA and 1.0m
From the value at A, α-1/ l o g (V+, o-^/Vo, +-^
) Calculated from the formula.

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

◇The capacitance temperature change rate (ΔC/C) is the value between -25℃ and 85℃.

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

(Margins below) Next, to explain Tables 1 to 15 above, these tables are S ro, 8E3 ao, 2T i O3 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 has both the function of absorbing high voltages such as pulses and static electricity as a varistor (in addition, the capacitance temperature change rate and varistor voltage temperature coefficient are large, and reliability and electrical characteristics are affected by temperature. Therefore, these samples are not suitable as ceramic capacitors with varistor function 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 has both 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, and has reliability and electrical characteristics that are not easily affected by temperature. Therefore, these samples are suitable as ceramic capacitors with varistor function 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 rg, eBao, 2T
The A/B ratio of i 03 was defined as A/B ratio of 1.0.
If it is larger than 0, there will be excess A site, and MnO2Si
This is because a 02-Ti02-based liquid phase is difficult to form, resulting in a grain boundary insulation type structure, and 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. moreover,
The average particle diameter of the starting material for a multilayer ceramic capacitor with varistor function was specified to be 0.5 μm or less.
If it is larger than μm, the powder may aggregate when it is made into a slurry, and the sintered density of the completed sintered element will be low and it will be difficult to convert it into a semiconductor, so the electrical properties will tend to become unstable.

Next, the total addition amount of the second components MnO2 and SiO2 was specified because the addition amount of these second components was 0.1 mo1.
MnO2-3
This is because it is difficult to form an i 02 -T i 02 system liquid phase, which makes it difficult to form a grain boundary insulated structure, resulting in a decrease in electrical properties and sintered density.

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

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

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

■ When Ni is used as the internal electrode material, sintering of the former ceramic capacitor material 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℃, MnO2
-8 i 02 - The liquid phase sintering of the Ti 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 NazSiO3 as a third component, the capacitance temperature change rate and varistor voltage temperature coefficient are improved. That is, the added Li2S
This is because iO3 acts as a carrier to uniformly diffuse the MnO25iO2-TiO2-based liquid phase to the grain boundary portion, thereby forming a sharp boundary between the semiconductor crystal and the high-resistance grain boundary.

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) According to Example 1, MnO2 and 5i(h
It was found that a total addition amount of 0.2 to 5.0 mo 1% is required. Next, MnO2 as this second component
and 5i (h) by changing the addition ratio of S r
o, s B ag, 2T i 03 A/B ratio of 0.9
7. The amount of Nb2O5 added as the first component was 1.0 mo.
1%, and the amount of Li2SiO3 added as the third component was 0.1%.
5tno 1% is fixed, and the amount added is 0.5mo 1%.
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 16 below.

(Leave 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 the same component exists MnO2-8i 02-T i
A 02-based liquid phase is formed, which dissolves and segregates at the grain boundaries, and when reoxidized, Mn 02 Si segregates at the grain boundaries.
This is because 02 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, Ta2O5, V2 as the first component
O51w2os, DYtOs, Nd203-+ Y2O
3. In order to specify the amount of the atomization control agent added for La2O3, CeO2O3, and ce02, this was changed variously, and S ro
4Bao, 2T i 03 A/B ratio of 0.97, 2nd
The added amounts of the components were MnO21, Omo 1%, Si 0
2 1. Omo 1% total2. Omo 1%, the amount of L i2S i 03 added as the third component was 0.5mo
A multilayer ceramic capacitor with a varistor function was manufactured in the same manner as in Example 1.2, with the amount fixed at 1%. 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 mo 1%, This is because the addition effect cannot be obtained and it is difficult for semiconductor formation to occur. On the other hand, if the total amount of the first component added exceeds 2.0 mo 1%, semiconductor formation will be suppressed and desired electrical properties will not be obtained.
This is because the sintered density further decreases.

Note that it is better to add Nb2O5 and Ta205 as the first component, and the other (7) V2O5, W2O5, Dy2 (h).

The electrical properties were slightly better than those in which Nd2O3, Y2O3, La2O3, and CaC2 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, 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 Nb2O6°Ta205 was slightly better in terms of electrical properties than the addition of other components.

Furthermore, if the average particle size of the starting material is larger than 0.5 μm, 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 4) Next, in order to specify the amount of Li2SiO3 added as the third component, this was changed variously, and S rO, 6B ao, 2
The A/B ratio of T i 03 is 0.97, the amount of the first component added is Nb2060.511101%, Ta2050.5m
o 1%, the amount of the second component added was MnO21.0 mol%
, SiO2 was fixed at 0 mol %, and 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 third component Li2Si
By adding O3, the capacitance temperature change rate and the varistor voltage temperature coefficient are improved. This is the added Li2Si
This is because O3 acts as a carrier that uniformly diffuses the MnO2-3iO2-Ti02-based liquid phase to the grain boundary portion, thereby forming a sharp boundary between the semiconductor crystal and the high-resistance grain boundary. Here, the third component Li2SiO
The addition amount of 3 was specified because the addition amount of the third component was 0.0.
This is because if the amount is less than 5 mo1%, the effect of addition cannot be obtained, and it is difficult to improve the capacitance temperature change rate and the varistor voltage temperature coefficient. On the other hand, when the amount of the third component added exceeds 0.2 mo1%, the amount of LizSiCh acting as a carrier at the grain boundary increases, resulting in a decrease in capacitance and voltage nonlinearity index α, and a decrease in series equivalent resistance value ESR. This is because the firing density further decreases and the mechanical strength decreases.

Note that as an additive for the third component Li2SiO3, Li
It is conceivable to use a mixed additive of 2O and SiO2. However, when this mixed additive of Li2O and SiO2 is used, since Li2O is a very unstable substance, Li2O easily decomposes during firing and scatters and diffuses into the atmosphere. There are almost no Li atoms in the sintered element, and some ionized L
It was confirmed that i'' ions move under high-humidity voltage loads, causing property deterioration. Therefore, by adding Li as a compound with Sigh, we added Li without impairing its function (
, can provide stability in grain boundaries. Therefore, it was confirmed that Li2SiO3 is always required as the third component.

(Example 5) In each of the above examples, 5r(1-x)Bax Ti03(
However, as O<x≦0.3), S r(1, sB ao
, tTie3 has been described, but other X
For the case S r (1-X) B axT i
The A/B ratio of Os is 0.97, and the amount of the first component added is Nb.
20SO, 5mol1%, Ta20s0.5mol1%, the amount of the second component added was MnO21.0+ao1%, S10
21. A multilayer ceramic capacitor with a varistor function was manufactured in the same manner as in the above example, with the amount of Li2SiO3 added as the third component fixed at 1% and 0.5mol%. The results are listed in Table 27 below.

(Left below) To explain Table 27 above, 5r(I-x>B
The range of X in ax T i 03 is defined if X is 0.
．． If it exceeds 3, the Curie point of BaTiO3 will appear, the capacitance temperature change rate and varistor voltage temperature coefficient will become thick (the capacitor characteristics and varistor characteristics will become unstable with respect to temperature, and reliability and performance will deteriorate. .

(Example 6) In each of the above examples, the case where Pd was used as the internal electrode was explained, but other A u r P t , Rh
.

For Ni, S ro, aB ao, 2T i 03
The A/B ratio of 0.97. The amount of the first component added is Nb20s
0.5mol%, Ta2050.5mo1%, the amount of the second component added was MnO21.0mol%, S1o21.
omo1%, the amount of third component Li2SiO3 added was 9.
A multilayer ceramic capacitor with a varistor function was manufactured in the same manner as in the above example, with the ao concentration fixed at 1%. The results are listed in Table 28 below.

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

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(+−X
) In preparing B axT i 03, S r
Although TiO2 was added to (+-X) B axT i Os, it goes without saying that Ti may be used in the form of carbonates, hydroxides, organic compounds, etc., and similar effects can be obtained.

In addition, in the examples of the present invention, 5r((-x)
B axT i Os was used, but SrO.

Of course, the same effect can be obtained even if S r (+-X) B axT 1-03 prepared from S rcO3, Bad, BaCO5, TiO2, etc. is used as the raw powder.

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

However, it was confirmed that using MnCO3 has a finer particle size and is easier to decompose, so that an element with stable characteristics can be produced and 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 (13
From the viewpoint of characteristics, it is preferable to perform firing at a temperature of 50 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+ is used as an external electrode.
At least one metal selected from Ag, Ni, Cu, and Zn, or an alloy or mixture thereof may be used. However, when Pd or Ag is used as the external electrode, it comes into ohmic contact with the element ((), and a slight polarity appears in the varistor voltage, but in this case as well, there is no particular problem in terms of basic performance.

As mentioned above, the average particle size of the multilayer ceramic capacitor with varistor function obtained by the method shown in the example is 2.0 to 3.0.
It was about μm. Here, if the molded body is calcined in air at a temperature higher than 1300°C, M
Liquid phase sintering of the nO2-3102-Ti02 system rapidly progresses, grain growth is promoted, and the average grain size becomes about twice or more. When the average grain size becomes large (like this), 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 properties. However, the 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. N confirmed that the characteristics and varistor characteristics could be obtained.

As described above, the device obtained in this manner has a large capacity, a large voltage nonlinearity index α, a small varistor voltage, a small series equivalent resistance value ESR, and furthermore has one-quality characteristics, 9 frequency characteristics,
Because of its excellent noise characteristics, it normally works as a capacitor to absorb low voltage noise and high frequency noise, but when high voltage such as pulses or static electricity enters, it functions as a varistor, and absorbs noise, pulses, etc. It shows excellent responsiveness to abnormal voltages such as static electricity, and its characteristics are always stable with respect to temperature, so it is expected to replace conventional film capacitors, multilayer ceramic capacitors, and semiconductor ceramic capacitors. It is something. Furthermore, the multilayer ceramic capacitor with a varistor function of the present invention is smaller, has a larger capacity, and has higher performance than the conventional single-plate ceramic capacitor with a varistor function, so it can be widely applied as a mounted component. This is to be expected.

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 became possible is that it has not been done until now with a composition in which MnO2 and SiO2 are added to Sr(+-X)Ba xTr 03 with excess Ti in addition to the semiconductor component. This is due to the fact that a grain boundary insulated semiconductor ceramic capacitor can be easily obtained by simply re-oxidizing the metal oxide that has come into contact with the metal oxide through a surface diffusion process. It has the following.

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... old internal electrode paste, 2a... internal electrode, 3... external electrode, 4... laminated with varistor function ceramic capacitor. Figure 1 I-・Main dart 2- Part 1 of the interior sacrificed Figure 2, 7 Figure 3

Claims (7)

[Claims] (1) The molar ratio of Sr_(_1_-_x_)Ba_x and Ti is 0.95≦Sr_(_1_-_x_)Ba_x/T
Sr_ containing excess Ti so that i<1.00
(_1_−_x_) Ba_xTiO_3 (however, 0<x
≦0.3), 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 in an amount of 0.05 to 2.0 mol%, and a total amount of MnO_2 and SiO_2 of 0.2 to 5.0 m
ol% and 0.05 to 2.0 mo of Li_2SiO_3
A grain boundary insulated semiconductor ceramic capacitor containing 1%. (2) The molar ratio of Sr_(_1_-_x_)Ba_x and Ti is 0.95≦Sr_(_1_-_x_)Ba_x/T
Sr_ containing excess Ti so that i<1.00
(_1_−_x_) Ba_xTiO_3 (however, 0<x
≦0.3), 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 in an amount of 0.05 to 2.0 mol%, and a total amount of MnO_2 and SiO_2 of 0.2 to 5.0 m
ol% and 0.05 to 2.0 mo of Li_2SiO_3
In a grain boundary insulated semiconductor ceramic containing 1%, 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. Features: Multilayer grain boundary insulated semiconductor ceramic capacitor. (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_)Ba_x and Ti is 0.95≦Sr_(_1_-_x_)Ba_x/
Sr_(_1_-_x_)Ba_xTiO_3 containing excess Ti so that Ti<1.00 (however,
0<x≦0.3), 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_
0.05 to 2.0 mo of at least one of 2.
1%, and the total amount of MnO_2 and SiO_2 is 0.2 to 5
．． 0 mol% and 0.05 to 2.0 mol% of Li_2SiO_3.
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 the internal electrode paste is printed on the green sheet alternately up to the opposing edges (however, the top and bottom layers of the green sheet are not printed). (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 It is characterized by comprising a step of firing in a nitrogen atmosphere, a step of reoxidizing in air after the firing, and a step of applying an external electrode paste to both ends where the internal electrodes are exposed after the 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.