JPH02248016A - Grain boundary insulated semiconductor ceramic capacitor and manufacture thereof - Google Patents

Abstract

PURPOSE:To easily obtain a varistor functioning laminated ceramic capacitor by conducting reoxidation without conducting a surface diffusing process on a metal oxide by a method wherein a composition, in which MnO2 and SiO2 are added to the SrTiO3 containing excessive Ti, is formed. CONSTITUTION:A grain boundary insulated semiconductor ceramic capacitor is formed by having the below-mentioned materials added to the SrTiO3, containing excessive Ti in such a manner that the mol ratio of Sr a-d Ti becomes 0.95 Sr<=Ti<=1.00. The materials referred to above are 0.05 to 2.00mol% of the element consisting at least of one or more kinds selected from Nb2O5, 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%. Internal electrode paste 2 is not printed on the raw sheets 1 of the top layer and the bottom layer of the above-mentioned ceramic capacitor, the paste 2 is printed as far as to the end part by opposing it alternately on the raw sheets 1 laminated on an intermediate position, a plurality of these sheets 1 are laminated, they are sintered using the prescribed treatment method, they are reoxidated, and a grain boundary insulated ceramic capacitor is 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 the noise tolerance of devices is decreasing accordingly.Therefore, in order to ensure the noise tolerance of such electronic devices, various ICs are being used.
, Film capacitors, multilayer ceramic capacitors, semiconductor ceramic capacitors, and the like are used as bypass capacitors in the power supply lines of LSIs. but,
These capacitors have excellent performance in absorbing low voltage noise and high frequency noise, but they do not have the ability to absorb high voltage pulses and static electricity, so pulses and static electricity can invade. This has become a major problem, causing malfunctions of equipment, destruction of semiconductors, and even destruction of capacitors. Therefore, for this kind of use,
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 varistor function are single-plate type, miniaturization reduces the electrode area, resulting in a decrease in capacitance.
This will lead to the problem of reduced reliability. Therefore, as a solution to this problem, it is expected that lamination will be developed to increase the electrode area. However, ceramic capacitors with varistor function are usually made using 5rTiCh semiconductor elements. This process involves applying oxide to the surface of the capacitor and insulating the grain boundary layer through thermal diffusion.Compared to commonly used BaTiO3 multilayer ceramic capacitors, the internal electrodes are fired at the same time as the multilayer varistor function. It was thought that it was extremely difficult to form a capacitor (hereinafter referred to as 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. 63219115, internal electrodes are alternately laminated with a raw sheet made of powder that has been made into a semiconductor in advance and mixed with a diffusing agent containing an oxidizing agent and a glass component to form an insulating layer. A method has been reported in which the molded body is fired in air or in an oxidizing atmosphere. However, in these methods, the firing temperature is 1000-1200℃.
℃, which makes it difficult for ceramic sintering to occur, making it difficult for the crystal particles to come into surface contact, and the resulting device is not a complete sintered body, resulting in a low capacity and typical characteristics as a varistor. , the voltage nonlinearity index α is small (
However, the varistor voltage is unstable and the reliability is poor. Furthermore, in the latter Japanese Patent Application Laid-Open No. 63-219115, since a glass component is added as an additive, a glass phase is precipitated at the grain boundaries, which tends to deteriorate the electrical properties described above (lower 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 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 a problem of 0 points in that it hardly shows any effect.

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

The present invention was made in view of these points. Normally, it functions as a capacitor to absorb low voltage noise and high frequency noise, but on the other hand, when high voltage such as pulses or static electricity enters, it functions as a varistor. A grain boundary insulated semiconductor whose main component is 5rTi03, which exhibits these properties and whose characteristics are always stable with respect to temperature, and which also enables simultaneous firing of ceramic capacitor material and internal electrode material. The object of the present invention is to provide a ceramic capacitor and a method for manufacturing the same.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention includes a method that contains excessive Ti so that the molar ratio of Sr and Ti is 0.95≦ and Sr/Ti<1.00. Nbx to 5rTi03
Os, Ta2's, V2O5*W2O5, DyxO
3.0.05 to 2.0 mol% of at least one of Nd2O3, Y2O3, LatO3°Ce 02
and the total amount of MnO2 and SiO2 is 0.2 to 5.0Ii
o1% and 0.05 to 2.0 mol% Na2SiO3
A grain boundary insulated semiconductor ceramic capacitor is provided. In addition, the present invention adds Nb2O5, Ta
2es, V2O5W2O5, Dy2O3, Nd2O3,
At least one of Y2O3, La2O3゜CeO2 in an amount of 0.05 to 2.0io1%, MnO2 and Si
The total amount of O2+ is 0.2-5.0IIio1%, and Na
2SiO3 from 0.05 to 2. In a grain boundary insulated semiconductor ceramic containing 1% On+O, 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. The present invention provides a laminated grain boundary insulated semiconductor ceramic capacitor having the following characteristics. Furthermore, in the present invention, Nb2O5 is added to S, rTiO containing excess Ti so that the molar ratio of Sr and Ti is 0.95≦Sr/Ti<1.00.
゜Ta2O5, V2O5, Wl! Os, Dy20s, N
0.05 to 2.0io1% of at least one type of d2O3゜Y2O3, L a201 Ce 02,
Total amount of MnO2 and SiO2 is 0.2 to 5.0 mol%
and a step of using a mixed powder of a composition containing 0.05 to 2.0 mol% of Na25iOs as a starting material, pulverizing, mixing and drying the mixed powder, and then calcining in air or a nitrogen atmosphere. After calcination, the re-pulverized powder is dispersed in a solvent together with an organic binder to form a raw sheet, and then internal electrode paste is printed on top of this raw sheet alternately up to the opposing edges (however, the top layer (and the bottom raw sheet is not printed), and the raw sheets printed with the internal electrode paste are laminated, pressed, and crimped to obtain a molded body, and then this molded body is calcined in air. After calcination, a step of firing in a reducing or nitrogen atmosphere; After calcination, a step of reoxidizing in air; After reoxidation, external electrode paste is applied to both ends of the exposed internal electrodes, and then baked. The present invention provides a method for manufacturing a laminated grain boundary insulated semiconductor ceramic capacitor, which comprises the steps of: The internal electrodes are made of Au+ pt, Rh, pa
, 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, in order to convert SrTiO3 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, if the stoichiometry of 5rTiOs is made excessive, Sr or Ti excessive, the lattice defects in the crystal will increase,
Semiconductorization will be promoted. Furthermore, N b 20 s +
Ta 205, V 205.

WzOs, DytO3, Nd2O3, Y2O3, La2
When O3°CeO2 (hereinafter referred to as the first component) is added, semiconductor formation is promoted through atomization control.

Next, MnO2 and 5iO2 (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, it has been thought until now to be difficult to produce a SrTiO3-based multilayer ceramic capacitor with a varistor function. The reason is the first
This is because the ceramic capacitor material with varistor function and the internal electrode material have different actions and properties during the firing process and reoxidation process. That is, the former material requires firing in a reducing atmosphere during the firing process, but at this time, since the latter material is made of metal, it absorbs H2 gas in the reducing atmosphere and expands.

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

The second reason is that in order to form the former material into a ceramic capacitor element with a varistor function, it is necessary to sinter it in a reducing atmosphere to convert it into a semiconductor, and then apply a high-resistance metal oxide (Mn02.CuO2) to its surface. , B 12O3,
CO2O3, etc.) is applied and reoxidized in air to selectively diffuse and insulate grain boundary areas, that is, a surface diffusion process is required. However, this is because it is technically difficult to diffuse the metal oxide in an element having a structure in which internal electrode materials are alternately stacked.

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

First, in a material composition in which MnO2 and SiO2 are added in addition to adding the first component to 5rTiCh with excess Ti, after firing in a reducing atmosphere, the high-resistance metal as mentioned above is formed on the surface of the element. We have discovered that a ceramic capacitor with varistor function can be easily formed by simply reoxidizing in air without applying an oxide. This is because excessive Ti and added MnO2 and SiO2 form a liquid phase of MnOx SiO2-Ti02 system at low temperature during the sintering process, which promotes sintering, and at the same time dissolves and segregates at grain boundaries. . Then, when this is re-oxidized in air, it segregates at grain boundaries t;M n 02 S i 02-T
This is because the i02 series 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, it was decided to use SrTiO3 containing excess Ti.

Secondly, MnO2 and S are added to 5rTi○3 with excess Ti.
It has been found that a material composition containing iO2 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. +2
．． 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 of +4 change and electronic instability.

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

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

Furthermore, Na2S i 03 (hereinafter referred to as the third component) acts as a carrier that uniformly diffuses the liquid phase of the Mn 02-S i 02-T i 02 system into the grain boundary area, and forms a bond between the semiconductor crystal and the high The grain boundaries of the resistor are formed sharply, resulting in improved capacitance and temperature characteristics of the varistor voltage.

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

(Example 1) First, 50% of the average particle size is 0.5 μm or less and the purity is 98% or more.
TiO2 was added to the rTi03 raw material powder and the Sr/Ti ratio was adjusted to the powder, and Nb2O5 as the first component and Mn02. as the second component were added to the powder as shown in Tables 1 to 15 below. Si
02 (However, M n O21S i○2 to be added is equal to m
The amount of Na2SiO3 as the third component was fixed at 0.5mol1%, and the mixture was mixed. After that, this mixed powder is wet-pulverized and mixed using a ball mill, etc., and after drying, it is heated to 600 to 12
The product was calcined at 00°C, and after calcining, it was ground again so that the average particle size was 0.5 μm or less, and this was used as a starting material for a multilayer ceramic capacitor with a varistor function. This fine powder starting material is dispersed in a solvent with an organic binder such as butyral resin to form a slurry, and this is made into a slurry.
A green sheet with a thickness of about 50 μm was prepared by the blade method and cut into a predetermined size. Next, as shown in FIG. 1, an internal electrode paste 2 made of Pd was screen printed on the raw sheet 1 obtained as described above according to a predetermined size.

Note that, as is clear from FIG. 1, the internal electrode paste 2 is not printed on the raw sheet 1 of the uppermost layer and the lowermost layer. Moreover, at this time, the internal electrode pastes 2 printed on the raw sheets 1 to be laminated in the middle were printed so as to reach alternately opposing edges, as is well known. Thereafter, a plurality of raw sheets 1 were laminated in the same direction as the internal electrode paste 2 was printed, and pressed and bonded. Then 400 in the air
Degreasing was performed at 600-1250°C in air. After that, 1250-135 in a reducing atmosphere.
It was fired at 0°C. After this firing, 900 to 125
Reoxidized at 0°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 5.70x5.0Ox2.00mm.
3 5.5 type, the effective layer with internal electrodes is 1
0 layers are laminated.・Furthermore, FIG. 3 shows the manufacturing process of the present invention.

The capacity of the multilayer ceramic capacitor with varistor function obtained in this way.

Various electrical characteristics such as tan δ, varistor voltage, voltage nonlinearity index α, series equivalent resistance ESR, capacitance temperature change rate, and varistor voltage temperature coefficient are also listed in Tables 1 to 15. However, the firing conditions at this time are: 1200°C for 2 hours, N2: H2 = 99 for calcination in air.
: 1, firing in reducing atmosphere at 1300°C for 2 hours,
Reoxidation was performed at 1100° C. for 1 hour.

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

◇ Capacity C is measured voltage 1. OV, frequency 1, 0KHz
value at.

◇ Varistor voltage VO, 1m^ is the value at measurement current 0.1mA.

◇ Voltage nonlinear index α is measured current 0.1 mA and 1.0
From the value in mA.

a = 1 /log (Vl, 011A/ VO, 1
It was calculated using the formula llA).

◇ 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 the value between two points -25℃ and 85℃.

◇ Varistor voltage temperature coefficient (ΔV/V) is 25℃ and 50℃
Value between two points in °C.

(Margin below) Next, to explain Tables 1 to 15 above, these tables show the Sr/Ti ratio and the second component MnO2 and Si.
This specifies the amount of O2 added.

Here, the sample numbers marked with * are comparative examples and are outside the scope of the claims of the present invention. In other words, these sintered elements have a small capacitance, a small voltage non-linearity index α representing varistor characteristics, and a large series equivalent resistance value ESR, so they cannot absorb low voltage noise or high frequency noise as a capacitor. It does not have both the function of absorbing high voltages such as pulses and static electricity as a varistor, and the capacitance temperature change rate and varistor voltage temperature coefficient are large (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 (and 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 ability to absorb 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. .

Here, in the present invention, the Sr/Ti ratio of 5rTi03 is specified because if the Sr/Ti ratio is larger than 1.00, Sr will be excessive, and Mn02-8 i 02 T
This is because it is difficult to form an i02-based liquid phase, which makes it difficult to form a grain boundary insulated structure, and the internal electrodes are oxidized and diffused, resulting in a decrease in electrical characteristics and reliability.On the other hand, This is because if the Sr/Ti 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 a multilayer ceramic capacitor with a varistor function is set to 0.5 μm or less. The specified value is 0.5μ
If it is larger than m, the powder may aggregate when it is made into a slanon shape, or the sintered density of the completed sintered element will be low.
This is also because it is difficult to convert into a semiconductor, and its electrical properties tend to be 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.
MnO2SiO
This is because a 2-Ti02-based liquid phase is formed, 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 is 5. On+o1
%, 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 multilayer ceramic capacitors with varistor function according to the present invention, and the results of this step affect the electrical properties and reliability of the multilayer ceramic capacitors with varistor function and microcapacitors. It mostly determines gender. The purpose of this step is to strengthen the adhesion between the varistor function ceramic capacitor material and the internal electrode material, and to control the average particle size of the finished varistor function multilayer ceramic capacitor.

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

■ When Ni is used as the internal electrode material, sintering of the former ceramic capacitor material and oxidation of the Ni internal electrode material occur, and then the sintered body and Ni react, and Ni diffusion progresses, resulting in The resulting multilayer ceramic capacitor with varistor function suffers from internal electrode breakage and delamination.

Various problems such as cracks occur.

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

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

This is because the electrical characteristics and reliability deteriorate significantly.

Furthermore, by adding Na2S i○3 as a third component, the capacitance temperature change rate and varistor voltage temperature coefficient are improved. That is, the added Na
This is because 2SiO3 acts as a carrier that uniformly diffuses the MnO2SiO2Ti02-based liquid phase into 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 superior temperature and frequency characteristics compared to the multilayer varistor reported in the above-mentioned Japanese Patent Publication No. 5823921. While the former simply stacks varistor materials with excellent surge absorption, the present invention has both a capacitor function with excellent noise absorption and a varistor function with excellent pulse and static electricity absorption. It is a laminated ceramic capacitor material with a varistor function, and its function and purpose of use are completely different.

(Example 2) According to Example 1, MnO2 and SiO2 as the second component
It was found that the total addition amount of 0.2 to 5.0+no1% is required. Next, MnO2 as this second component
The addition ratio of Sr/SiO2 was varied, and Sr/
Ti ratio is 0.97. Addition amount of Nb2O5 as the first component is l, Qmo1%, Na2SiO3 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 addition fixed at 0.5no1%. 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 both components exist Mn02-3 i 02-T
This is because when an i02-based liquid phase is formed, which dissolves and segregates at the grain boundary and is reoxidized, the MnO2-8i02 segregated at the grain boundary becomes insulating and easily becomes an element with 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 3) Next, Nb2O5, Ta206°V2 as the first component
O5・W2O5・Dy203・・Nd2O3・Y2O3
- In order to specify the amount of La2O3 and CeO2 atomization control agent added, this was varied and the Sr/Ti ratio was set to 0.97.
The amount of the second component added is MnO21.0io1%, 52i0
1. A multilayer ceramic capacitor with a varistor function was manufactured in the same manner as in Examples 1 and 2, with the total amount of On+O1% being fixed at 2.0 mol% and the amount of Na2SiO3 as the third component added at 0.511101%. The results are shown in Tables 17 to 25 below.

(Margins below) To explain Tables 17 to 25 above, the reason for specifying the amount of the first component added is that, as is clear from the measurement results, if the amount added is less than 0.05 mo1%, the amount of the first component added is This is because no effect can be obtained and it is difficult to convert into a semiconductor. On the other hand, if the total amount of the first component added exceeds 2.0R101%, semiconductor formation will be suppressed, desired electrical properties will not be obtained, and the sintered density will further decrease.

Note that it is better to add Nb2O5 and Ta205 as the first component than other V2O5, W2O5, and Dy20a.

The electrical properties were slightly better than those in which Nd2O3, Y2O3, La2O3, and CeO2 were added.

Furthermore, some combinations of the mixture composition of the first component were tested and the electrical properties were measured, but as shown in Table 25, there was almost no difference in the properties compared to when different types were added. It was impossible. However, in this case as well, the addition of Nb2O5°Ta205 was slightly better in terms of electrical properties than the addition of other components.

Furthermore, 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 NazSi03 added as the third component, this was changed variously, and the Sr/Ti ratio was set to 0.97,
The amount of the first component added is Nb2O5O,5so1%, Tap
oso, 5Ilo1%, amount of second component added MnO21
, 0 mol%, and S i 02 to 1.01llo1%, 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 Na2Si
By adding O3, the capacitance temperature change rate and the varistor voltage temperature coefficient are improved. This is the added Na2Si
This is because O3 acts as a carrier that uniformly diffuses the MnO2-8i02T i02-based liquid phase into the grain boundary portion, thereby forming a sharp boundary between the semiconductor crystal and the high-resistance grain boundary. Here, Na as the third component
The reason for specifying the addition amount of 2SiO3 is that if the addition amount of the third component is less than 0.05o+o1%, the effect of the 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, the amount of the third component added is 2.0 mo
If it exceeds 1%, N32 acts as a carrier at the grain boundaries.
The amount of S i 03 becomes large (as a result, the capacitance and voltage non-linearity index α decrease, the series equivalent resistance value ESR increases,
This is because the firing density further decreases and the mechanical strength decreases.

Note that as an additive for the third component Na2SiO3, Na
It is conceivable to use a mixed additive of 2O and SiO2. However, when this mixed additive of Na2O and SiO2 is used, since Na2O is a very unstable substance, Na2O easily decomposes during firing and scatters and diffuses into the atmosphere. There are almost no Na atoms in the sintered element, and some ionized N
We confirmed that a'' ions move under high-temperature voltage loads and cause property deterioration. Therefore, by adding Na as a compound with SiO2, we created a material that is stable in the grain boundaries without impairing the function of Na. can be provided.

Therefore, it was confirmed that the third component must always be added in the form of Na2SiO3.

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

Regarding Rh and Ni, the Sr/Ti ratio was 0.97, and the addition amount of the first component was Nb20s0.5mol%, Ta2'sO
, 5so1%, the amount of the second component added is Mn0tl, 0so
1%, S i 02 1.0101%, third component Na
A multilayer ceramic capacitor with a varistor function was manufactured in the same manner as in the above example, with the addition amount of 2SiO3 fixed at 0.5o+o1%. The results are listed in Table 27 below.

(Left below) As stated in Table 27 above, the internal electrodes are made of Au.
, Pt, Rh, Pd, and Ni, or their alloys or mixtures can be used and it has been confirmed that effects can be obtained. However, Ni
When using 5rTi03, oxidation of Ni occurs at a relatively low temperature, so oxidation can be suppressed by mixing Pd or using 5rTi03 with a slight excess of Ti.

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

In the embodiment of the present invention, 5rTiO'3 with excess Ti
Although T i 02 was added to SrTiO3 in producing this, it goes without saying that Ti may be used in the form of carbonates, hydroxides, organic compounds, etc., and similar effects can be obtained.

Further, in the examples of the present invention, 5rTi03 was used as the raw material powder, but it goes without saying that the same effect can be obtained even if 5rTi03 made from SrO or SrCO3, TiO2, etc. is used as the raw material powder.

Furthermore, it goes without saying that similar effects can be obtained even when MnO2 and Sio2 as the second component are used in the form of their carbonates, hydroxides, and the like. but,
It was confirmed that the use of MnCO3 has finer particle sizes and is easier to decompose, making it possible to produce elements with stable characteristics and being suitable for mass production.

Next, in the above embodiments, the case where the firing is performed in a reducing atmosphere has been described, but this may also be performed in a nitrogen atmosphere. However, when firing in a nitrogen atmosphere, it is somewhat difficult to convert into a semiconductor, so the temperature is slightly higher (135
From the viewpoint of characteristics, it is preferable to perform firing at a temperature of 0 to 1450°C.

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

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

However, when reoxidizing at temperatures above 1200°C, care must be taken, as 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 used as an 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 with other materials such as PdrNirCu*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, 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 nO2SiO2-T i 02 system rapidly progresses, grain growth is promoted, and the average grain size becomes about twice or more.

And if the average particle size becomes thick like this,
Various problems such as a decrease in sintered density, a decrease in the voltage nonlinearity index α, an increase in the series equivalent resistance value ESR, and variations in electrical characteristics occur, and the electrical characteristics and reliability deteriorate significantly, making it impractical for practical use. It is fleeting.

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

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

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

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

This device can be expected to have a wide range of applications, as it can simultaneously exhibit the above effects (1) and (2) with a single device.

As described above, the reason why a multilayer ceramic capacitor with a varistor function can be easily produced with the present invention is because it is now possible to simultaneously fire the ceramic capacitor material with a varistor function and the internal electrode material. . The reason why co-firing became possible is that in addition to adding semiconductor components to 5rTi03 with excess Ti, Mn
This is because the composition containing O2 and SiO2 can easily become a grain-boundary insulated semiconductor ceramic capacitor simply by re-oxidation without going through the conventional metal oxide surface diffusion process. This is the most advantageous feature of the present invention in terms of process.

Furthermore, the multilayer ceramic capacitor with a varistor function of the present invention is smaller than the conventional single-plate ceramic capacitor with a varistor function, has a large capacity, and has high performance, so it 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. ■... Raw sheet, 2... Internal electrode paste, 2a... Internal electrode, 3... External electrode, 4... Varistor function Multilayer ceramic capacitor. Name of agent: Patent attorney Shigetaka Awano and one other person, 1995 Procedural auxiliary device / Name of the claimed invention in the Bae 2nd case Grain boundary insulated semiconductor ceramic capacitor and its manufacturing method 3 Relationship to the person making amendments case Address Name Representative 4 Agent Address Patent Application Person 1006 Oaza Kadoma, Kadoma City, Osaka Prefecture (582) Matsushita Electric Industrial Co., Ltd. Akio Tanii 1006 Oaza Kadoma, Kadoma City, Osaka Prefecture 571 Matsushita Electric Industrial Co., Ltd. Within the company 6. Contents of amendment (1) The scope of claims in the specification will be amended as shown in the attached sheet. (2) Change “MnO2 and Sio2” on page 11, line 6 to “Mn and Si, respectively, as MnO2, 5IQ2 and fy?
Convert it to li+.'' (3) “MnO2 and Sio2” on page 11, line 14.
Correct by "converting Mn and 81 into M n O2 and Sio2, respectively." (4) Page 12, lines 6-7 [MnO(!: S
LO2” [Mn and si are MnO and Sio respectively
Convert it to 2" and correct it. (6) “Mn 02 and 8102” on page 14, lines 4 to 6.
(hereinafter referred to as the second component)" and "Iori O2 and S during the firing process.
i 02 (second component)". (6) Correct "MnO2 and 51o2" on page 16, line 13 of the same page to "second component". (7) “Mno2 to SiO2” on page 16, line 19 of the same
Correct "the second component" to "the second component". (8) “Mn O2 and 51” on page 16, lines 10-11
Correct "02" to "second component". (9) Correct “0.1mo less than 1%” on page 39, line 11 to “f” 0, 2mo less than 1%.” 2. Claims (1) The molar ratio of Sr and Ti is 0.95≦S r /
T i (1,00) S r T iO3 containing excess Ti, Nb2o6.Ta2O5, Y2
O5, W2O5, Dy2o3°Nd2o3. Y2O3,
La2o3. At least one type of CeO2 is O
, O5~2, 0mo 1%, Mn and 81 are converted into MnO2 and 5lo2, respectively, and the total amount is 0:2~5.
0 mol% and 0.05 to 2 Na 2 S 103
．． A grain boundary insulated semiconductor ceramic capacitor containing 0 mol%. (2) The molar ratio of Sr and T, i is 0.95≦Sr/T
S r containing excess T1 so that i (1,00)
T i O3, Nb2o61Ta2o5. Y2O6
, W2O6, Dy2O3°Nd2o3. Y2O3, La
2o3. At least one type of CeO2 is O, O
5~2, 0mo 1%, Mn and St respectively
The total amount is 0.2 to 5.0 mol in terms of O and 5lo2.
% and 0.05 to 2.0 mol % of Na2510s, a plurality of layers of internal electrodes are provided in the grain boundary insulated semiconductor ceramic so that these layers alternately reach opposing edges, and A laminated grain boundary insulated semiconductor ceramic capacitor characterized by having external electrodes on both ends of the electrode. (3) Claim 2, wherein the internal electrode is formed of at least one metal selected from Au, Pt, Rh, Pd, and Ni, or an alloy or mixture thereof.
The multilayer grain boundary insulated semiconductor ceramic capacitor described above. (4) Claim 2, wherein the external electrode is formed of at least one metal selected from Pd, Ag, Ni, Cu, and Zn, or an alloy or mixture thereof.
``! Or the laminated grain boundary insulated semiconductor ceramic capacitor according to 3. (5) The molar ratio of Sr and Tl is 0.96≦S r /
S r T i Os containing an excess of TI to give T i (1,00), Nb2o5.Ta2O5, Y
2O6, W2O5, Dy2o3°Nd2o3. Y2O3
, La2o3. At least one type of CeO2 is 0, 05-2, 0mo 1%, and Mn and 81 are converted into MnO2 and 5102, respectively, and the total amount is 0.2-6.
．． 0 mol% and 0.05 Na 2 Si O3
A mixed powder of a composition containing ~2.0 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, it is crushed again. The 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 internal electrode paste is printed on the top layer and the bottom layer of the green sheet). (without printing), and the raw sheets printed with this internal electrode paste are laminated and pressed. A step of crimping to obtain a molded body, and then calcining the molded body in air, a step of firing in a nitrogen atmosphere after calcination, and a step of reoxidizing in air after firing, 1. A method for manufacturing a multilayer grain boundary insulated semiconductor ceramic capacitor, comprising the steps of, after reoxidation, applying and baking an external electrode paste on both ends with exposed internal electrodes. (6) Claim 6 characterized in that the internal electrode is formed of at least one metal among Au, Pt, Rh, Pd, and NiO, or an alloy or mixture thereof.
The method for manufacturing the multilayer grain boundary insulated semiconductor ceramic capacitor described above. ('7) The multilayer type according to claim 5 or e, 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. A method for manufacturing a grain boundary insulated semiconductor ceramic capacitor.

Claims (7)

[Claims] (1) The molar ratio of Sr and Ti is 0.95≦Sr/Ti<1
．． SrTiO_ containing excess Ti so that it becomes 00
3, Nb_2O_5, Ta_2O_5, V_2O_5
, W_2O_5, Dy_2O_3, Nd_2O_3, Y
_2O_3, La_2O_3, CeO_2 in an amount of 0.05 to 2.0 mol% and MnO
A grain boundary insulated semiconductor ceramic capacitor containing _2 and SiO_2 in a total amount of 0.2 to 5.0 mol% and Na_2SiO_3 in a total amount of 0.05 to 2.0 mol%. (2) The molar ratio of Sr and Ti is 0.95≦Sr/Ti<1
．． SrTiO_ containing excess Ti so that it becomes 00
3, Nb_2O_5, Ta_2O_5, V_2O_5
, W_2O_5, Dy_2O_3, Nd_2O_3, Y
_2O_3, La_2O_3, CeO_2 in an amount of 0.05 to 2.0 mol% and MnO
In a grain boundary insulated semiconductor ceramic containing 0.2 to 5.0 mol% of _2 and SiO_2 in total and 0.05 to 2.0 mol% of Na_2SiO_3, multiple layers of internal electrodes are alternately formed. A laminated grain boundary insulated semiconductor ceramic capacitor, characterized in that the internal electrodes are provided so as to extend to opposing edges, and external electrodes are provided on both ends of the internal electrodes. (3) Claim 2, wherein the internal electrode is formed of at least one metal selected from Au, Pt, Rh, Pd, and Ni, or an alloy or mixture thereof.
The multilayer grain boundary insulated semiconductor ceramic capacitor described above. (4) Claim 2, wherein the external electrode is formed of at least one metal selected from Pd, Ag, Ni, Cu, and Zn, or an alloy or mixture thereof.
or 3. The laminated grain boundary insulated semiconductor ceramic capacitor according to 3. (5) The molar ratio of Sr and Ti is 0.95≦Sr/Ti<1
．． SrTiO_ containing excess Ti so that it becomes 00
3, Nb_2O_5, Ta_2O_5, V_2O_5
, W_2O_5, Dy_2O_3, Nd_2O_3, Y
_2O_3, La_2O_3, CeO_2 in an amount of 0.05 to 2.0 mol% and MnO
A mixed powder of a composition containing a total of 0.2 to 5.0 mol% of _2 and SiO_2 and 0.05 to 2.0 mol% of Na_2SiO_3 is used as a starting material, and the mixed powder is pulverized, mixed, and dried. After that, 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 alternately applied on top of this raw sheet. (However, printing is not done on the top and bottom raw sheets) and stacking, pressing, and crimping the raw sheets printed with internal electrode paste. obtaining a molded body and then calcining the molded body in air;
After calcination, there is a step of firing in a reducing or nitrogen atmosphere, a step of reoxidizing in air after calcination, and a step of applying external electrode paste to both ends with exposed internal electrodes after reoxidation and baking. A method for manufacturing a multilayer grain boundary insulated semiconductor ceramic capacitor, comprising: (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.