JPH02248017A - Gain boundary insulated semiconductor ceramic capacitor and manufacture thereof - Google Patents

Abstract

PURPOSE:To easily obtain a varistor functioning ceramic capacitor by a method wherein an MnO2-SiO2-TiO2 material, which is segregated into a grain boundary part by merely reoxidating it in the air by having a composition formed by adding MnO2 and SiO2 besides the first component to Sr(1-x)CaxTiO containing excessive Ti. CONSTITUTION:A grain boundary insulated semiconductor ceramic capacitor is formed by having the below-mentioned materials added to Sr(1-x)CxTiO3, which is 0.0001<=x<=0.2, containing 0.5 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, MnO2 and SiO2 of 0.2 to 5.0mol% in total, and Na2SiO3 of 0.05 to 2.0mol%. After a sintering treatment has been performed using the prescribed method, an MnO2-SiO2-TiO2 material, which is segregated into a grain boundary part by merely conducting reoxidation in the air, is brought into an insulated state, and a varistor-functioning ceramic capacitor having a grain boundary insulated structure can be obtained easily.

Description

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

Conventional technologyIn order to make electronic devices multi-functional, lighter, thinner, and smaller, we use ICs.
, LSI, and other semiconductor devices are being widely used, and as a result, the noise tolerance of devices is decreasing. Therefore, in order to ensure the noise tolerance of such electronic devices, various IC
, Film capacitors, multilayer ceramic capacitors, semiconductor ceramic capacitors, and the like are used as bypass capacitors in the power supply lines of LSIs. but,
These capacitors have excellent performance in absorbing low voltage noise and high frequency noise, but they do not have the ability to absorb high voltage pulses and static electricity, so pulses and static electricity can invade. This has become a major problem, causing malfunctions of equipment, destruction of semiconductors, and even destruction of capacitors. Therefore, for this kind of use,
In addition to having good noise absorption properties and being stable over temperature and frequency, 5rTi0 is a new type of capacitor that has high pulse tolerance and excellent pulse absorption properties.
A grain boundary insulated semiconductor ceramic capacitor (hereinafter referred to as a ceramic capacitor with a varistor function), which is a three-series semiconductor ceramic capacitor with a varistor function, has been developed and has already been published in Japanese Patent Application Laid-Open No. 57-27001 and
-35303, etc. This ceramic capacitor with varistor function normally absorbs low voltage noise and high frequency noise as a capacitor, but when high voltage such as pulses or static electricity enters, it functions as a varistor and absorbs noise and pulses generated in electronic equipment. , it has the characteristic of protecting semiconductors and electronic equipment from abnormal voltages such as static electricity, and its use is expanding more and more.

On the other hand, in the field of electronic components, the trend is to become lighter, thinner, and smaller.

As performance continues to improve, demands for smaller size and higher performance ceramic capacitors with varistor function are increasing. However, since conventional ceramic capacitors with a nozzle function are single-plate type, miniaturization reduces the electrode area, which leads to problems such as reduced capacitance and reduced reliability. Therefore, as a solution to this problem, it is expected that stacking will be developed to increase the electrode area. However, ceramic capacitors with varistor function usually coat the surface of the 5rTi03 semiconductor element with oxide, and form particles by thermal diffusion. BaTiO3, which is commonly used, has a step of insulating the interface layer.
Compared to multilayer ceramic capacitors, multilayer capacitors with varistor function (hereinafter referred to as
It was thought to be extremely difficult to form a multilayer ceramic capacitor with varistor function.

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. 63-219115, internal electrodes are alternately arranged with a raw sheet made of powder that has been made into a semiconductor in advance and mixed with a diffusing agent containing an oxidizing agent and a glass component to form an insulating layer. A method has been reported in which a molded body laminated with a molded body is fired in air or in an oxidizing atmosphere.

However, in these methods, the firing temperature is 1000-120°C.
Because the temperature is relatively low at 0°C and sintering of the ceramic is difficult to occur, the crystal grains do not come into surface contact with each other.
Since it is not a completely sintered body, it has a low capacity, a small voltage nonlinearity index α, which is a typical characteristic of a varistor, the varistor voltage is unstable, and it has the disadvantages of poor reliability. . Furthermore, in the latter Japanese Patent Application Laid-Open No. 63-219115, since a glass component is added as an additive, a glass phase is precipitated at the grain boundaries, which tends to deteriorate the electrical characteristics described above, resulting in poor reliability. However, it has not yet reached the level of practical application.

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

A stacked voltage nonlinear element using Fe20s and Ti02 systems has been proposed. However, since this element has almost no capacity or quantity, it exhibits excellent performance in absorbing relatively high voltage pulses and static electricity, but it is susceptible to low voltage noise below the varistor voltage and high frequency noise. However, it has the problem that it is rarely effective.

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

The present invention was made in view of these points. Normally, it functions as a capacitor to absorb low voltage noise and high frequency noise, but on the other hand, when high voltage such as pulses or static electricity enters, it functions as a varistor. S r (1-, c) Ca
The object of the present invention is to provide a grain boundary insulated semiconductor ceramic capacitor whose main component is i 03 (0.001≦X≦0.2) and a method for manufacturing the same.

Means for Solving the Problems In order to solve the above problems, the present invention provides S r
(I-x) The molar ratio of Cax and Ti is 0.95≦Sr
Sr containing excess Ti so that u-x>Cax/Ti<1.00 and O,OO1≦X≦0.2
(1-X) c axT i 03, Nb2O5, Ta
2O5, V2O5, W2O5+ D V2O3+ Nd
0.05 to 2.0 mol% of at least one of 2O5, Y2O3, La2O5, and CeO2, and MnO
The total amount of 2 and SiO2 is 0.2 = 5.0 mol%, and N
A grain boundary insulated semiconductor ceramic capacitor containing 0.05 to 2.0 mol% of a2SiO3 is provided. Further, the present invention provides a method in which the molar ratio of S r (+-X)CaX and Ti is 0.95≦S r (+-X)CaX/T
Excess g), containing Ti so that i<1.00, and 0
．． S r (+-x) Ca where 001≦X≦0.2
xT i O3, N b 20 s + Ta205.
VzOs, W2O5, DY203T Nd2O3, Y2
O3, Lax03. At least one type of CeO2 at 0.05 to 2.0mo 1%, MnO2 and 5iC
The total amount of h is 0.2 to 5.0 mol%, and Na2SiO
A plurality of layers of internal electrodes are provided in a grain boundary insulated semiconductor ceramic containing 0.05 to 2.0 mo of 1% of No. The present invention provides a multilayer grain boundary insulated semiconductor ceramic capacitor characterized in that an external electrode is provided at the edge.

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 (+-X)CaX/T i
<1. Contains excess Ti so that 0
．． S-r (1-x) Ca where 001≦X≦0.2
xT i 03, Nb2O5°Ta205. V2O5
, W2O5, DV203. Nd2O3, Y2O3, La
0.0 of at least one of 2O3 and CeO2
5 to 2.0 mo 1%, the total amount of MnO2 and SiO2 is 0.2 to 5.0 mol%, and Na2SiO3 is 0.0
A mixed powder of a composition containing 5 to 2.0 mol% is used as a starting material, and after pulverizing, mixing, and drying the mixed powder,
The 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 printed on top of this green sheet alternately up to the opposing edges (however, the raw material of the top and bottom layers is The raw sheets printed with this internal electrode paste are laminated, pressed, and crimped to obtain a molded body, and then this molded body is calcined in air. After firing, it has a step of firing in a reducing or 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. The present invention provides a method for manufacturing a multilayer grain boundary insulated semiconductor ceramic capacitor characterized by the following. Then, the internal electrode is A
The present invention provides that it is formed of at least one metal selected from u, 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 AgrNi, Cu+Zn, or an alloy or mixture thereof.

Function Generally, in order to convert S r (1-X)CaX T i 03 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 Cax T i O3, Sr (+
-X) Ca) (excess (hereinafter referred to as A site excess),
Alternatively, if Ti is added excessively, lattice defects within the crystal increase, promoting semiconductor formation. Moreover, Ca enters the Sr site and has the effect of suppressing grain growth.

Furthermore, Nb2O5, Ta205. V2O5+ W2O
5Dy2O3, Nd2O3, Y2O31La2O3, C
When e02 (hereinafter referred to as the first component) is added, semiconductor formation is promoted by atomization control.

Next, MnO2 and 5i (h (hereinafter referred to as the second component)) are essential substances to form a laminated structure, and even if either one is missing, the effect will not be exhibited. Na2O exists in the grain boundaries and has the effect of improving surge resistance characteristics.As mentioned above, it has been thought until now to be difficult to produce a SrTi03-based multilayer ceramic capacitor with a varistor function.

The reason for this is, first of all, 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. moreover,
This is because the latter material is oxidized into metal oxides during the reoxidation process in 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 coat the surface with a high-resistance metal oxide (MnO2゜Cu02 .B 120
3. C0203, etc.) and re-oxidizes in air to selectively diffuse and insulate grain boundary areas, that is, a surface diffusion process is required.

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

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

First of all, Ti excess S r (+-x) Cax
In addition to adding the first component to T I 03, in the material composition in which MnO2 and SiO2 are added, there is no need to apply a high-resistance metal oxide as described above to the surface of the element after firing in a reducing atmosphere. discovered that a ceramic capacitor with varistor function could be easily formed simply by reoxidizing in air. This is because excess Ti and added MnO2 and SiO2 form MnO2SiO2-Ti at low temperature during the sintering process.
It forms an O2-based liquid phase to promote sintering, and at the same time dissolves and segregates at grain boundaries. Then, when this is reoxidized in air, Mn0pS segregated at the grain boundaries
This is because the iO2-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
) CaxT i 03 was used.

Secondly, Ti excess S r (+-X) Cax
It has been found that a material composition in which MnO2 and SiO2 are added to Ti○3 becomes a semiconductor when sintered in a nitrogen atmosphere as well as in a reducing atmosphere. This is because the liquid phase is formed at low temperature as shown in the first reason above, and the added Mn
In addition to forming a liquid phase, it acts as an atomization control agent, and at this time, the valence of the Mn atom changes to +2° +4, making it electronically unstable. This improves sinterability and increases nitrogen It is thought that it can be easily converted into a semiconductor even in an atmosphere.

Thirdly, it has been found that adding Na in the form of Na2SiO3 improves the temperature characteristics.

Originally, Na20 was a very unstable substance, and it was thought that Na+1, which was partially ionized in the grain boundaries, would move under high-temperature voltage loads, causing characteristic deterioration. Therefore, by adding Na as a compound with SiO2, it is possible to provide something stable in the grain boundaries without impairing the function of Na.

Furthermore, fourthly, if the molded body after degreasing is calcined in air beforehand, various problems such as internal electrode breakage, delamination, cracking, and decrease in sintered density of the completed multilayer ceramic capacitor with varistor function 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
ro, sCao, +TiO2 in 03 raw material powder
was added to the powder and the S r (1-x) Cax / T i ratio (hereinafter referred to as A/B ratio) was adjusted, and the following Table 1 ~
As shown in Table 15, the first component is Nb2O5, and the second component is M n 02. S i 02 (However, added MnO
2, S i 02 is set to the same mole of 1%), and the amount of Na2SiO3 as the third component is 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 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. After that, a plurality of raw sheets 1 are laminated in the printed direction of this internal electrode paste 2,
Pressurized and crimped. Next, it was degreased in air at 400°C, and further calcined in air at 600 to 1250°C. Thereafter, it was fired at 1250 to 1350°C in a reducing atmosphere. After this firing, it was reoxidized in air at 900-1250°C.

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

The shape of the multilayer ceramic capacitor with varistor function in this example is 5.70 x 5.00 x 2, 5.
．． There are 5 types, each consisting of 10 laminated effective layers with internal electrodes formed thereon. 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:H2=99:1, 1300℃, 2 hours, reoxidation: 110
The test was carried out at 0°C for 1 hour.

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

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

◇ Varistor voltage VO and ImA are values at a measurement current of 0.1mA.

◇ Voltage nonlinear index α is measured current 0.1 mA and 1.0
From the value in mA, a = 1 / l o g (Vl, 0 + 11A /
It was calculated from the formula: VO, 1lIA).

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

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

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

(Margin below) Next, to explain Tables 1 to 15 above, these tables are S r (+-x) CaxT i 03 A
The l6 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 (and a small voltage non-linearity index α representing varistor characteristics, and a large series equivalent resistance value ESR). It does not have both the function of absorbing noise and the function of absorbing high voltages such as pulses and static electricity as a varistor, and furthermore, the capacitance temperature change rate and varistor voltage temperature coefficient are large, and the reliability and electrical characteristics vary with temperature. 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. 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. be.

Here, in the present invention, S r(+-X)CaXTi
The reason for specifying the A/B ratio of O3 is that if the A/B ratio is greater than 1.00, there will be an excess of A sites, and MnO2-Si
02-T i 02-based liquid phase is difficult to form, resulting in a grain boundary insulated structure, and internal electrodes are oxidized and diffused, resulting in decreased 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 average particle size of the starting material for the multilayer ceramic capacitor with varistor function was specified to be 0.5 μm or less.
If it is larger than 0.5 μm, the powder may aggregate when it is made into a slurry, the sintered density of the completed sintered element will be low, and the electrical properties will tend to become unstable due to the difficulty of converting it into a semiconductor. .

Next, the total addition amount of the second component MnO2 and SiO2 was determined by these v! Addition amount of two components is 0.1mo
If it is less than 1%, no effect can be obtained by adding MnO2-8.
This is because the iO2TiCh-based liquid phase is difficult to form, resulting in a grain boundary insulated structure ((), resulting in a decrease in electrical properties and sintered density.

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

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

Here, the reason why the calcination temperature in air is specified in the range of 600 to 1250°C is that the effect cannot be obtained if the calcination temperature is less than 600°C. On the other hand, the calcination temperature is 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 an 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. The resulting multilayer ceramic capacitor with varistor function suffered from internal electrode breakage and delamination.

Various problems such as cracks occur.

■ If calcination is performed at a high temperature exceeding 1250℃, MnO2
Liquid phase sintering of the SiO2-Ti02 system progresses rapidly, grain growth is promoted, and the sintered body density and packing density are significantly reduced.

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

This is because the electrical characteristics and reliability deteriorate significantly.

The thus obtained multilayer ceramic capacitor with varistor function has a larger capacity and excellent temperature and dual 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 S r (+-x) Ca) (A/B of T i 03
The ratio was fixed at 0.97, the amount of Nb2O5 added as the first component was fixed at 1.0 mol%, and the amount of Na2SiO3 added as the third component was fixed at 0.5 mol%, and the varistor function was obtained in the same manner as in Example 1 above. We fabricated a multilayer ceramic capacitor. 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. In addition, when the amount of Ca added increases and the value of The substitution rate X of Ca to be replaced is 0.001≦
It is desirable that X≦0.2.

(Example 3) According to Example 1, MnO2 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
The A/B ratio of r(1-,)CaXT i 03 was set to 0.
97, X=0.10, Nb2O5 as the first component
The addition amount of 1.0 mol%, Na2S as the third component
A multilayer ceramic capacitor with a varistor function was manufactured in the same manner as in Example 1, with the amount of iO3 added being fixed at 0.5 mo1%. 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,
MnO2-3i○2-TiO2 only exists when both components exist.
This is because when a liquid phase is formed in the system, which is dissolved and segregated at the grain boundaries and re-oxidized, the MnO2-8i02 segregated at the grain boundaries becomes insulating and easily becomes an element having a grain boundary insulated 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 4) Next, N b 2O5, Ta2O5, as the first component,
v2os・W2O5・Dy2O3・Nd2O3・Y2O
3. In order to specify the amount of the atomization control agent added for La2O3 and CeO2, this was changed variously, and Sr(1-X)CaX
The A/B ratio of T i 03 was 0.97, X=0.10, and the amount of the second component added was Mn021. Omo 1%, Si
021. Omo 1% total2. Fixed Omo1%,
Addition amount of Na2SiO3 as the third component is 0.5mo
A multilayer ceramic capacitor with a varistor function was manufactured in the same manner as in Examples 1 and 2, with the ratio fixed at 1%. The results are shown in Tables 18 to 26 below.

(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 0.05 mo1%, the amount of the first component added is On the other hand, if the total amount of the first component added exceeds 2.0mo1%, the semiconductor formation will be suppressed, and the desired electrical properties will not be obtained. This is because the sintered density decreases.

In addition, it is better to add Nb2O5, Ta205 as the first component, and the other (7) Y2O5, W2O5, Dy2O3,
The electrical properties were slightly better than those in which Nd2O3, Y2O31La2O3, and CeO2 were added.

Furthermore, regarding the mixture composition of the first component, some combinations were tested and the electrical properties were measured, but as shown in Table 26, there was almost no difference in the properties compared to when different types were added. It was impossible. However, in this case as well, the addition of Nb2O5°Ta205 was slightly better in terms of electrical properties than the addition of other components.

Also, the average particle size of the starting material is 0. If it is larger than Ejμm, the effect of the first component tends to be difficult to obtain,
It was confirmed that it is necessary to suppress the thickness to 0.5 μm or less.

(Example 5) Next, in order to specify the amount of Na2SiO3 added as the third component, this was changed variously, and 5r(I-x, CaxTi
The A/B ratio of O3 was 0.97, X=0.10, the amount of the first component added was Nb2O51, Omo 1%, and the amount of the second component added was MnO+1. Omo1%, SiO21, Qmo1
Total %2. A multilayer ceramic capacitor with a varistor function was manufactured in the same manner as in Examples 1 and 2, with Omo fixed at 1%. The results are listed in Table 27 below.

(Margin below) To explain Table 27 above, by adding Na2SiO3, the grain boundaries were uniformly insulated, thereby improving the temperature characteristics of capacitance and varistor voltage. However, the addition amount of Na2SiO3 is 2
．． When Omo exceeds 1%, oxidation tends to proceed, the capacity decreases, and the varistor characteristics deteriorate. On the other hand, if the amount added is less than 0.05+ao1%, the effect of the addition cannot be obtained, and the capacitance temperature change rate and varistor voltage temperature coefficient are not improved.

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

For Rh, Ni, S r (+-X) Ca xT
' A/B ratio of l 03 is 0.97. X=0. l O1
The amount of the first component added is Nb2050.5mol1%, T
a20so, 5mol*.

The amount of the second component added is Mr〕021, Omo1%,
SiO2 is fixed at 1.0+++oH, and the amount of Na2SiO3 added as the third component is fixed at 0.5mol1%.
A multilayer ceramic capacitor with a varistor function was manufactured in the same manner as in the above example. The results are shown in Table 28 below.
Record in the table.

As stated 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 is suppressed by using Ca xT 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 (1-
X) In producing CaXTi03, S r (1
-X) Although TiO2 was added to CaXTi03, it goes without saying that similar effects can be obtained by using Ti in the form of carbonates, hydroxides, organic compounds, etc.

In addition, in the examples of the present invention, S r (1-
X) CaXT i 03 was used, but S ro, S r
Of course, the same effect can be obtained even if S r (1-X) Ca XT i 03 prepared from cO3, CaCO3, Cab, titanate, TiO2, etc. is used as a raw material 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 finer (uniform) particle diameters and is easier to decompose, making it possible to produce elements with stable characteristics and being suitable for mass production.

Next, in the above embodiment, 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, semiconductor formation is slightly slower (13%) than when firing in a reducing atmosphere.
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 900 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, 12
When reoxidizing at temperatures above 00°C, Ni may be oxidized unless the holding time is minimized, so care must also be taken.

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*N I + Cu and Zn. That is, at least one metal selected from Pd, Ag, Ni, Cu, and Zn, or an alloy or mixture thereof may be used as the external electrode. 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 n02-8 i 02-T i 02 system progresses rapidly, grain growth is promoted, and the average grain size becomes about twice or more. When the average grain size increases in this way, various problems occur such as a decrease in sintered density, a decrease in voltage nonlinearity index α, an increase in series equivalent resistance value ESR, and variations in electrical characteristics. Electrical characteristics and reliability deteriorate significantly, making it unsuitable for practical use.

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

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

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

■ 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 in addition to adding a semiconductor component to 5rTi (h) with excess 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 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 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 vanostar 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 vanostar function obtained in accordance with an embodiment of the present invention, and FIG. It is. 1... raw sheet, 2... internal electrode paste, 2a... internal electrode, 3... external electrode, 4... varistor function Multilayer ceramic capacitor with Name of agent: Patent attorney Shigetaka Awano and one other person

Claims (7)

[Claims] (1) The molar ratio of Sr_(_1_-_X_)Ca_X and Ti is 0.95≦Sr_(_1_-_X_)Ca_X/T
Contains excess Ti so that i<1.00, and 0.0
Sr_(_1_−_X_)Ca where 01≦X≦0.2
_XTiO_3, Nb_2O_5, Ta_2O_5,
V_2O_5, W_2O_5, Dy_2O_3, Nd_
0.05 to 2.0 mol% of at least one type of 2O_3Y_2O_3, La_2O_3, CeO_2
and the total amount of MnO_2 and SiO_2 is 0.2 to 5.0
mol% and 0.05 to 2.0 mo of Na_2SiO_3
A grain boundary insulated semiconductor ceramic capacitor containing 1%. (2) The molar ratio of Sr_(_1_-_X_)Ca_X and Ti is 0.95≦Sr_(_1_-_X_)Ca_X/T
Contains excess Ti so that i<1.00, and 0.0
Sr_(_1_−_X_)Ca where 01≦X≦0.2
_XTiO_3, Nb_2O_5, Ta_2O_5,
V_2O_5, W_2O_5, Dy_2O_3, Nd_
2O_3, Y_2O_3, La_2O_3, CeO_2
0.05 to 2.0 mol of at least one of the following
%, and the total amount of MnO_2 and SiO_2 is 0.2 to 5.
0 mol% and 0.05 to 2.0 Na_2SiO_3
A plurality of layers of internal electrodes are provided in a grain boundary insulated semiconductor ceramic containing mol% so that these layers 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_)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.
0 mol% and 0.05 to 2.0 Na_2SiO_3
A mixed powder of a composition containing mol% is used as a starting material, and the mixed powder is pulverized, mixed, dried, and then calcined in air or in a nitrogen atmosphere. After calcining, the re-pulverized powder 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). Step 1) The raw sheets printed with this internal electrode paste are laminated, pressed,
A process of crimping to obtain a molded body and then calcining this molded body in air, a process of firing it in a reducing or nitrogen atmosphere after calcining, a process of reoxidizing it in air after firing, and a process of re-oxidizing it in air. 1. A method for manufacturing a multilayer grain boundary insulated semiconductor ceramic capacitor, which comprises the steps of, after oxidation, applying and baking an external electrode paste on both ends with exposed internal electrodes. (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.