JPH03112861A - Dielectric porcelain and laminated ceramic capacitor using the same and preparation thereof - Google Patents

Abstract

PURPOSE:To provide the subject composition having a high dielectric constant, a low dielectric loss factor and improved reliability and not producing a semiconductor even when sintered under a low oxygen fractional pressure by adding MnO2, Dy2O3 and Y2O3 to a BaTiO3 complex oxide one part of whose Ti is substituted with Zr. CONSTITUTION:MnO2, Dy2O3, Y2O3 and, if necessary, 0.1-1mol% of Yb2O3 and/or TlO2 and 0.1-2mol% of NiO and/or Co2O3 are added to a BaTiO3 complex oxide to provide a dielectric porcelain composition, the BaTiO3 complex oxide being prepared by substituting one part of Ti in BaTiO3 with Zr. The composition is mixed with an organic binder, a solvent and a plasticizes and the prepared slurry is formed into a green sheet, which is printed with a paste comprising a Ni oxide, an organic binder and an organic solvent to form a patterned film. A desired number of the green sheets are laminated, heated and pressed to prepare a laminate. The laminate is cut into a desired size, heated in air at a temperature not initiating the combustion of the composition for burning the binder, heated in a reducing atmosphere for reducing the Ni oxide into the metal and subsequently calcined in a N2 atmosphere heated at a temperature below the melting point of the Ni form densifying the composition and the metal to provide a laminated ceramic capacitor.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a dielectric ceramic composition with a high dielectric constant for use in ceramic capacitors used in electronic devices, particularly multilayer ceramic capacitors having internal electrodes made of nickel, and its use. The present invention relates to a multilayer ceramic capacitor and its manufacturing method.

Conventional Multilayer Ceramic Capacitors are composed of layers of electrodes and dielectric ceramic compositions, and are integrated and solidified using ceramic manufacturing technology, making it possible to obtain small-sized capacitors with large capacity. Furthermore, since the electrode is built-in, the magneto-dielectric component is small and the device exhibits excellent performance in high-frequency applications. In addition, the chip type does not have lead wires, so it can be directly attached when mounting components, and it meets the demand for smaller and lighter electronic devices, and is expected to continue to develop in the future.

On the other hand, the classification of capacitor materials includes aluminum electrolytic, tantalum electrolytic 2 paper, organic film, etc., and multilayer ceramic capacitors compete with all of them due to their capacity range. Therefore, future demands for multilayer ceramic capacitors are higher capacity, smaller size, and lower cost. The capacitance of a multilayer ceramic capacitor can generally be expressed by the following formula.

C=EoEsX Efforts are being made to increase the dielectric constant of dielectric materials, increase the number of laminated layers to increase the area of electrodes, and reduce the thickness of dielectric layers.

For miniaturization, the chip shape is 3.2m x 1.6
nll5 to 2.0am+X 1.25mm or 1.6
Kaku x 0.8 Peng, and 1. OmmX O,5mn+
Efforts are being made to Next is cost reduction, which is the most important requirement. This is because larger capacity and smaller size are not contradictory demands to lower cost.
This is because it is an issue that must be addressed simultaneously with increasing capacity and downsizing.

A conventional multilayer ceramic capacitor uses BaTiO3 as a main component of the dielectric material and uses Pd, a noble metal, for internal electrodes. Therefore, the internal electrode material cost accounts for an extremely high proportion of the production cost, said to be over 70%.

In particular, products with large capacitance have a large number of internal electrodes, which further increases the cost.Despite the fact that multilayer ceramic capacitors have high capacitance efficiency, excellent low dielectric properties, and high reliability, the price has increased. This was a major hindrance.

Various studies are being conducted in various fields with the aim of reducing these costs. Among these, attention has been paid to Ag, which is relatively inexpensive among noble metals, and a method of using Ag-Pd as an internal electrode material is being considered.

(For example, JP-A-49-19399, K, S
, 5ubbrao: J Pbys, Cbem, 5o
licls, 236.65 (1962)) while Ag
However, due to the high cost, there is a trend toward using base metals. In other words, Ni is used as the electrode material. N
When a base metal such as i is used as an internal electrode, BaTi
The O3-based dielectric and the base metal internal electrode must be co-fired in a non-oxidizing atmosphere in which nickel is not oxidized. However, in this case, the conventional dielectric made of BaTi0° or its solid solution is easily reduced and loses its insulating properties, making it impossible to obtain practical dielectric properties as an integrated multilayer ceramic capacitor. Ta. Therefore, non-reducible ceramic dielectric materials are being developed as materials that are not reduced even when fired in a neutral or reducing atmosphere.

(For example, JP-A-55-67568, JP-A-61-
256968, JP-A-60-109104, etc. ) Next, in the manufacturing method of a multilayer ceramic capacitor using Ni as an internal electrode, generally, an unfired green sheet made of a plurality of dielectric green sheets mainly composed of BaTi0+ whose surfaces are coated with internal electrodes (N i ) is laminated. The crystalline laminate is produced by sintering and integrating in a nitrogen atmosphere with extremely low oxygen partial pressure so that the Ni of the internal electrodes is not oxidized.

Problems to be Solved by the Invention The present invention has a high dielectric constant and a low dielectric loss tangent that does not convert into a semiconductor even when fired under an extremely low oxygen partial pressure that is below the equilibrium oxygen partial pressure of Ni and NiO, and does not cause a decrease in insulation resistance. Furthermore, it is an object of the present invention to provide a dielectric ceramic composition that exhibits reliability, particularly high-temperature loads, and little deterioration even under high-temperature high-temperature loads.

By using this dielectric ceramic composition, a high performance multilayer ceramic capacitor with Ni as the internal electrode can be provided.

Next, the present invention provides a new manufacturing method that solves the problems of the conventional manufacturing method of multilayer ceramic capacitors using Ni as internal electrodes.

In conventional manufacturing methods, it is difficult to use an organic binder when co-firing the internal electrodes and the dielectric material. In other words, it is difficult to completely remove the organic binder used in the dielectric green sheet and the same organic binder contained in the electrode paste in a non-oxidizing atmosphere. If the dielectric material cannot be completely removed, it is said that the dielectric material itself remains porous, which not only prevents sintering but also results in a blackened material due to the decomposed carbon. This issue will become even more important as the number of laminated layers increases due to the increase in capacity of multilayer ceramic capacitors, and as the content of organic components in the sheet increases due to the micronization of dielectric powder due to low-temperature firing. This is expected to be an issue.

Means for Solving the Problems In order to solve the above problems, the dielectric ceramic composition of the present invention is a barium titanate-based composite oxide in which a part of Ti, a constituent element of barium titanate, is replaced with Zr. and D
)'203 and Yz03 are added.

Furthermore, Ybz 03 , T
0.1 mol% of at least one type of lzO
The above is characterized in that it is added in a range of 1+o1% or less. Furthermore, it is characterized in that at least one of NiO, C0, and O3 is added in a range of 0.1 mol % or more and 2 mol % or less.

Furthermore, B, which is a constituent element of barium titanate-based composite oxide,
It is characterized in that a part of a is replaced with Ca 1M g + Sr, or CaO, MgO, or SrO is added.

In addition, the method for manufacturing a multilayer ceramic capacitor of the present invention includes applying a nickel oxide as a main component and at least an organic binder and an organic solvent onto a green sheet consisting of the above dielectric composition and at least an organic binder, a solvent, and a plasticizer. A step of printing a paste kneaded with a vehicle consisting of the above to form a patterned film, a step of laminating a desired number of the printed green sheets by heating and pressurizing them, and a step of laminating the thus laminated laminate as desired. A step of cutting the dielectric ceramic composition into dimensions of It is characterized by comprising the steps of reducing a substance to a metal, and firing this in a nitrogen atmosphere at a temperature lower than the melting point of nickel to densify the dielectric ceramic composition and the metal. .

Since the dielectric ceramic composition of the present invention contains MnO, it has the effect of suppressing the conversion of barium titanate into a semiconductor by firing under a low oxygen partial pressure by charge compensation. This results in good insulation resistance even during firing under low oxygen partial pressure. The purpose of partially substituting Ti, which is a constituent element of barium titanate, with Zr is to shift the Curie point (T c ) of the dielectric ceramic composition to the low temperature side and increase the dielectric constant at room temperature. However, with a dielectric ceramic composition in which MnO□ is added to a barium titanate-based composite oxide, although a good insulation resistance can be obtained by firing under a low oxygen partial pressure, a high dielectric constant cannot be obtained. Therefore, Dy2O3 and Y2O3 are added. These oxides are very stable and difficult to reduce even under low oxygen partial pressures.

Furthermore, since it acts to promote grain growth in the dielectric during firing, it is also effective in increasing the dielectric constant of the dielectric.

The important point here is D)' t 03 , Yz 0
Instead of adding only one of the three, add both. Dy20. Although the addition of 10% is effective in increasing the dielectric constant to a very high level, it also abnormally accelerates the grain growth of the dielectric (>10 μm), resulting in a lack of stability in properties and poor reliability. Also, deterioration is likely to occur due to high-temperature loads and high-temperature high-temperature loads. Furthermore, the addition of only Yt 2 O does not cause abnormal grain growth and has the effect of further increasing the insulation resistance even in firing under low oxygen partial pressure compared to the addition of only Mn0z. However, the dielectric constant is MnO
It does not increase much compared to when only □ is added. However, by adding re-oxides of D'jtOz and YtO, the advantages of adding each oxide can be extended,
It becomes possible to manufacture a multilayer ceramic capacitor with an extremely high dielectric constant and high reliability without any drawbacks. Also, Y
The addition of b203 and TlzO has the effect of improving insulation resistance without substantially lowering the dielectric constant. In addition, the addition of NiO, Co2O3, etc. increases the dielectric loss tangent (tan δ
) and the sintering temperature of the dielectric, it is effective in obtaining a dense sintered body and effective in improving the mechanical strength of multilayer ceramic capacitors. Furthermore, a part of Ba, which is a constituent element of barium titanate-based composite oxide, is replaced with Ca.
, Mg, Sr, or CaO, MgO
, The addition of SrO makes the A site excessive compared to the stoichiometric ratio when the barium titanate-based composite oxide is represented by the formula ABO3, and is effective in improving reduction resistance during firing under low oxygen partial pressure. There is.

Next, the method for manufacturing a multilayer ceramic capacitor of the present invention makes it possible to completely remove the organic binder, which was the biggest problem. This makes it possible to select organic binders and the like from a wide range in slurrying the dielectric ceramic composition. Also, in the organic binder for internal electrode paste, without considering scattering,
It becomes possible to select an organic binder from the viewpoint of printability, which is very advantageous from the viewpoint of forming internal electrodes. Furthermore, since nickel oxide was used as the starting material for the internal electrodes, only the decomposition and removal of the organic binder was considered during debinding, and only the densification of the dielectric layer and the electrode layer reduced to Ni during sintering. It is now possible to manufacture highly reliable multilayer ceramic capacitors without having to perform delicate atmosphere control such as removing the organic binder without oxidizing the electrodes, as required in the past.

Example An embodiment of the present invention will be described in detail below.

Example 1 First, barium titanate (BaTiOl) and barium zirconate (BaZrOs) were synthesized by a calcining method. B
aTi0:+ was synthesized by wet mixing reagents BaC0+ and TiO□ in a ball mill, suction filtration, drying, and calcining in air at 1200° C. for 2 hours. Thereafter, it was wet-pulverized in a ball mill and dried before use. On the other hand, B
aZr0+ uses reagents BaC0 and ZrCh, and B
It was produced using the procedure of aTi0+ containing Ti0+. BaTi0+ and BaZr0. used in this example. The average particle size of each of the powders was approximately 0.8 μm by SEM observation.

Next, as MnO2, the reagent MnO□ was wet-pulverized in a ball mill to have an average particle size of about 1 μm. Next, D )'z Ox , Yt 03 has a purity of 99.9
% of reagents were used. BaTi0 prepared in this way:
+ r BaZrO3, Mn0z +D7z owl
.

The inorganic component is a mixture of Y2O3 in the proportions shown in Table 1, and further contains polyvinyl butyral resin as an organic binder and DBP (dibutyl phthalate) as a plasticizer.
As a solvent, 1.1.1. ) Lichloroethane, acetic acid n
Butyl was added and mixed in a ball mill to prepare a slurry. The slurry conditions were as follows: 100 g of inorganic component, 10 g of polyhinyl butyral resin, 5 g of DBP.
, 100 g of 1°1.1.1-lichloroethane, and 70 g of n-butyl acetate. The thus prepared slurry was degassed under vacuum and then formed into a film using a doctor blade method to produce a green sheet. The thickness of the green sheet after drying was approximately 40 μm. Next, nickel oxide (N
i O) A paste consisting of powder was used to screen print the desired pattern. The conditions for making paste are:
Ethyl cellulose as an organic binder was dissolved in turpentine oil as a solvent, and the mixture was kneaded with the nickel oxide powder using a three-stage roll. Eleven of the electrode pattern-formed green sheets obtained as described above were stacked one on top of the other (that is, there were 10 effective layers) so that the internal electrode patterns faced each other, and were bonded together by thermocompression. And furthermore, 4m
A green laminate was prepared by cutting into dimensions of m x 3 mm. Ineffective layers each having a thickness of 300 μm were provided on both sides of the effective layer so that the thickness of this unsintered laminate was about III11.

Next, the binder of this unsintered laminate is first removed.

After debinding, the temperature was 700"C for 2 hours (temperature increase/decrease 100%).
"C/h)" was carried out by heat treatment in air. The purpose of this step is to remove organic binder components contained in the green sheet and nickel oxide paste. After the binder was removed, the element body was subjected to scanning electron When observed under a microscope, no progress in sintering of the dielectric layer was observed.Furthermore, compositional analysis showed no presence of carbon in the element body.
It was confirmed that the organic components were sufficiently removed. Next, the internal electrodes of this binder-removed element body are reduced. This step was performed at 250'C for 2 hours in a 100% hydrogen atmosphere.

This step does not reduce the components of the dielectric layer, but only the nickel oxide of the internal electrodes is reduced to metallic nickel. Next, the reduced element body is fired. Firing at 1250℃ 2
The test was carried out for several hours (temperature increase/decrease 200°C/h). The firing atmosphere was adjusted by using Nt gas as a carrier gas and controlling the flow rate of green gas so that the oxygen concentration in the electric furnace was 10-'' atm in a temperature range of 500°C or higher. A commercially available Cu paste for firing in a nitrogen atmosphere at 900° C. was applied as an external electrode to the end face of the sintered body obtained, and the paste was baked in a mesh type continuous belt furnace to obtain a sample for property measurement.

The capacitance and dielectric loss tangent are measured at a frequency of 1.0 KHz and an input signal level of 1.0 KHz. It was measured at OVrms, and the relative dielectric constant was calculated from the capacitance. Then apply 50V DC for 1 minute,
The insulation resistance at that time was measured. Note that the thickness of the dielectric layer was approximately 25 μm and the thickness of the electrode layer was 3 to 4 μm.

The above measurement results are also shown in Table 1. Note that the measurement was performed in a constant temperature bath at 20°C.

(Blank below) Table 1 Sample Nα12゜in 13 in Table 1 shows the initial characteristics when only one of Dy 120 was added as a comparative example. As is clear from Table 1, the multilayer ceramic capacitor manufactured using the dielectric ceramic composition of the present invention has a high dielectric constant, a low dielectric loss tangent, and an insulation resistance that is sufficiently high for practical use. It shows.

Even when compared with the characteristics of the comparative example, the effect of adding both DytOx and YzOs is fully recognized.The Curie point of the multilayer ceramic capacitor shown in Example 1 is 5℃~
The composition of the dielectric was adjusted so that the temperature was between 15°C, but
Works as a shifter (Zr component, MnO□ component, and
By slightly changing the amounts of DVz Os and Y203, Tc can be set to a desired temperature even in compositions other than those in Table 1, and a multilayer ceramic capacitor with excellent characteristics can be manufactured.

In addition, as shown in sample Nt14,5, DyxOz, Y2
It is possible to fabricate a multilayer ceramic capacitor with sufficient characteristics even with a very small amount of added D.
The maximum amount of yt Ox and Yz Ox added is 2 mol
% or less, and if it exceeds it, sintering cannot be obtained. The Zr component is desirably 20 mo1% or less. This is because if more than this is added, no matter how you adjust other ingredients, it will be impossible to set Tc to an appropriate position, and the firing temperature will increase, causing shrinkage of the internal electrodes and causing delamination. Cause. Moreover, the same thing can be said when no Zr component is added. Regarding MnO□, Imo1% to 5mol
% was appropriate.

Example 2 This Example 2 shows an example in which Y bz 03 and T lz O are added to the dielectric ceramic composition shown in Example 1. Table 2 shows the composition and initial properties.

In addition, Y bz Owl and T lz O are 9
9.9% reagent was used. The steps for manufacturing a multilayer ceramic capacitor were performed in the same manner as in Example 1.

(Left below) Table 2 As is clear from Table 2, the addition of Yb, O, Tl□O hardly causes a decrease in the dielectric constant, and is highly effective in improving the insulation resistance. Samples Nα22 and Nα23 are Yb, 03. Tl.

This shows the case where an excessive number of 0's are inserted. From this result,
Yb! The amount of Ox, T lx O added is 0.1 mo
It can be said that 1% or more and 1 mol% or less is appropriate. In Example 2, Ybz Ox, Tl! Although the case where O is added alone is shown, even when both yb,03 and Tl2O are added, the total amount is 0.1 mol% ~
Similar effects were obtained within the range of In+O1%.

Furthermore, the addition of Yb, O, and Tl2O was effective in preventing deterioration after the reliability test, especially THB (85°C, 185% RH, 50V).

In addition, in addition to the dielectric composition shown in Table 2, the amount of Zr, Mno, amount, and D may be adjusted within the ranges already mentioned in Example 1.
Various dielectric compositions are possible by changing the amount of ytOx and Y2O.

Example 3 In this Example 3, the composition and initial characteristics are shown in Table 3, which shows an example when NiO and CoxO were added to the dielectric ceramic composition shown in Example 1. .

Note that special grade reagents were used as N i O and Co z Ox. Purity is over 99%. The steps for manufacturing a multilayer ceramic capacitor were performed in the same manner as in Example 1.

Table 3 Table 3 Continued As is clear from Table 3, N i O, Co z Os
The addition of is very effective in lowering only the dielectric loss tangent without causing a decrease in the dielectric constant. The addition range is 0.1 mol% or more, 2. Omo1% or less is suitable; if it is less than that, there is no effect; if it is more than that range, tan δ will decrease, but both the dielectric constant and insulation resistance will tend to decrease, which is not desirable. , an example was shown in which only one of Cozy3 was added, but when the sum of the amounts of NiO and Cozy3 added was 0.1 m
If it is in the range of ol% or more and 2.0mol% or less, tan
It was confirmed that it has the effect of lowering δ. In addition, in this Example 3, NiO was added to the dielectric material not added with Yb20, T1.0.
, CO□0. However, as a result of the experiment,
Even when Ybt 03 , TIt 0WNtO, and Cot Os were added simultaneously, no bad interaction was observed, and tan δ
This did not eliminate the effect of lowering the

Example 4 An experiment was conducted in which part of Ba in the dielectric ceramic composition shown in Example 1 was replaced with Ca, Mg, and Sr.

As a result, when the entire Ba component is taken as 100, Ca, M
When each of g and Sr or a mixture of 5 or less was found to have the effect of improving insulation resistance without reducing the dielectric constant, excessive addition deteriorates sinterability and increases the dielectric constant. This resulted in a significant decrease in Also, CaO,
Cab even when Mgo and SrO are added.

Similar effects were obtained when the amount of MgO and SrO added was 5 mo 1% or less. Furthermore, this means that Ybz O3, Tit O, Nip in the dielectric ceramic composition.

Even when Co and O were included, the effects of each additive were not negated.

As described above, in Examples 1 to 4, BaTi0. , BaZrOs was prepared by a calcining method, but there is no problem and good results can be obtained even if it is prepared by a coprecipitation method, an alkoxide method, or a hydrothermal synthesis method.

In addition, in this example, BaTiO3 and BaZr0° were adjusted to have a stoichiometric ratio (A size) (Ba, and ・BaaC
The molar ratio of the B site (the sum of Zr and Ti) to the B site (the sum of Zr and Ti), that is, A/B = 1.00, was set.
Similarly, good results can be obtained if the /B ratio is 0.98 or more and 1.03 or less. However, if the Al6 ratio is less than 0.98, the insulation resistance will be very low, and if it exceeds 1.03, sintering will not be obtained.

In addition, in this example, the conditions for each step of debinding, reduction, and firing were fixed, but the conditions for the debinding step were as follows.
The optimum selection should be made depending on the type of organic binder used, and the conditions in the reduction process should be such that the dielectric is not reduced and only the nickel oxide of the electrode is reduced, and the atmosphere should be a 100% H3 atmosphere. It doesn't have to be. Furthermore, the atmosphere of the firing process is not limited to the conditions of this example, but as long as the oxygen concentration is below the equilibrium oxygen partial pressure of Ni and NiO at the holding temperature during firing (1250''C in this example). If the Ni electrode is not significantly oxidized in other temperature rising and cooling regions, Ni(!:N
There is no problem even if the atmosphere contains oxygen at a level higher than the equilibrium oxygen partial pressure of iO.

Further, in this example, a multilayer ceramic capacitor was manufactured and the characteristics of the dielectric ceramic composition were measured. However, it goes without saying that the dielectric ceramic composition of the present invention can be used in a single-plate ceramic capacitor. Furthermore, by using the manufacturing method of the present invention, it is also possible to apply it to multilayer wiring boards with built-in multilayer varistors and capacitors.

Effects of the Invention The dielectric ceramic composition within the scope of the claims of the present invention exhibits a high dielectric constant, a low dielectric loss tangent, and a high insulation resistance even when fired under an extremely low oxygen partial pressure. It is ideal for manufacturing multilayer ceramic capacitors.

Further, the method for manufacturing a multilayer ceramic capacitor of the present invention includes:
Since the binder is removed in air, no special organic binder is required and the binder can be completely removed. Furthermore, since the atmosphere can be easily controlled during reduction and firing, it is extremely effective in converting the internal electrodes of multilayer ceramic capacitors into base metals. This invention is extremely advantageous when aiming to increase capacity by increasing the number of layers.

Claims (7)

[Claims] (1) Part of Ti, a constituent element of barium titanate, is replaced with Zr.
MnO_
A dielectric ceramic composition characterized in that it contains Dy_2O_3, Dy_2O_3, and Y_2O_3. (2) At least one of Yb_2O_3 and Tl_2O
2. The dielectric ceramic composition according to claim 1, wherein at least one species is added in an amount of 0.1 mol% or more and 1 mol% or less. (3) The dielectric ceramic composition according to claim 1 or 2, wherein at least one of NiO and Co_2O_3 is added in a range of 0.1 mol% or more and 2 mol% or less. thing. (4) Ba, a constituent element of barium titanate-based composite oxide
Part of it is replaced with Ca, Mg, Sr, or Ca
The dielectric ceramic composition according to claim 1, wherein O, MgO, and SrO are added. (5) A ceramic capacitor comprising the dielectric ceramic composition according to any one of claims (1), (2), (3), and (4). (6) A dielectric layer made of the dielectric ceramic composition according to any one of claims (1), (2), (3), or (4);
A multilayer ceramic capacitor consisting of an internal electrode layer whose main component is (7) On a green sheet made from a slurry consisting of the dielectric ceramic composition according to any one of claims (1), (2), (3), or (4) and at least an organic binder, a solvent, and a plasticizer, a nickel A process of printing a paste made by kneading an oxide as a main component with a vehicle consisting of at least an organic binder and an organic solvent to form a pattern film, and laminating a desired number of printed green sheets by heating and pressing them. a step of cutting the laminate thus laminated into desired dimensions; and a step of heating this in air at a temperature at which the dielectric ceramic composition does not begin to sinter, thereby burning the organic binder. This is heat-treated in a reducing atmosphere to reduce the nickel oxide to metal, and this is fired in a nitrogen atmosphere at a temperature lower than the melting point of nickel to combine the dielectric ceramic composition and the metal. A method for manufacturing a multilayer ceramic capacitor, characterized by comprising a densification process.