JPH0734417B2 - Method for manufacturing multilayer capacitor element - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer capacitor element, and more particularly to a multilayer capacitor element using lead perovskite oxide as a dielectric and using copper or an alloy containing copper as a main component as an internal electrode. Manufacturing method.

2. Description of the Related Art In recent years, as a ceramic capacitor, a multilayer ceramic capacitor is rapidly becoming popular due to demands for smaller size and larger capacity of the element. Further, due to the higher frequency of the circuit, it has become necessary to use a multilayer ceramic capacitor element in a region where an electric field capacitor has been conventionally used. Multilayer ceramic capacitors are usually manufactured by a process of integrally firing internal electrodes and ceramics. Conventionally, barium titanate-based materials have been used for high-dielectric-constant ceramic capacitor materials, but since the firing temperature is as high as 1300 ° C, expensive metals such as Pt and Pd are used as internal electrode materials. There was a need. For this reason, attempts have been made to use inexpensive base metals for the internal electrodes.

On the other hand, the inventors have proposed a method for manufacturing a multilayer capacitor element in which lead perovskite oxide is used as a dielectric, an electrode pattern is formed of copper oxide, and the electrode is metallized at a temperature lower than the firing temperature and then fired. .

Further, a method described in JP-A-61-67214 is known as a manufacturing method in which an electrode pattern is formed from a metal copper paste and burned out in an atmosphere such that the metal copper is not oxidized. There is.

Furthermore, the inventors have found that Pb (Mg _1/3 Nb _2/3 ) O ₃ and Pb (Ni _1/3 Nb _2/3 ).
We have proposed the atmospheric oxygen partial pressure conditions during firing of a multilayer capacitor element that uses a dielectric porcelain containing O ₃ as a main component and uses copper as an internal electrode.

Problems to be Solved by the Invention In a method for manufacturing a multilayer capacitor element having copper as an internal electrode, when metal powder is used as a starting material for the internal electrode,
Oxidation of the internal electrodes easily occurs during burnout of the binder component of the dielectric green sheet and the internal electrode paste.
For this reason, a resin that decomposes and evaporates in an inert gas atmosphere such as acrylic is used for these binders. However, these binders have a weaker strength of the dielectric green sheet as compared with resins such as polyvinyl vinyl butyral resin which is burned out in normal air, which is a problem in the lamination method.

Also, when burnout is performed in a low oxygen partial pressure atmosphere where oxidation of the internal electrodes does not occur, the carbonization phenomenon of the binder component is likely to occur, and the dielectric substance is reduced by carbon remaining in the firing and the insulation resistance of the element is reduced. Of the
There is a problem that the sintered density is likely to decrease.

Also, in order to use it as a starting material for the internal electrode, a metal powder with a small particle size is required, and the cost required for crushing during manufacturing and the cost required for rust-proofing of the metal powder, etc. There was a problem that the advantage of was not fully utilized.

On the other hand, in the method of forming an electrode pattern of copper oxide, burning out the binder in the air after lamination and metallizing the electrode at a temperature lower than the firing temperature and then firing, the above problems are solved. In the firing method in the embodiment already disclosed by the inventors, the firing method is carried out while maintaining the atmospheric oxygen partial pressure at 1 × 10 ^−8, which causes a difficulty in controlling the atmosphere. However, there are problems such as a change in the characteristics depending on the amount of the sample put into the baking furnace and a change in the characteristics due to the arrangement of the sample in the sheath containing the sample during baking.

Means for Solving Problems Main components are either Cu ₂ O, CuO, a mixture thereof as a starting material for a copper internal electrode, or a copper compound that decomposes in air at 650 ° C or lower to form a copper oxide. After printing the internal electrode pattern on the dielectric green sheet using the raw material and stacking it,
In the manufacturing method of a multilayer capacitor, in which the binder component is burned out in air, and then the internal electrodes are reduced to metal at a temperature lower than the firing temperature to metallize and then fired. Atmosphere oxygen partial pressure Po
_{When 2} is expressed as log (Po ₂ ) (Po ₂ is atmospheric pressure), the temperature change is in the range of 650 ℃ to 1080 ℃, 650 ℃: −8.60 ≧ logPo ₂ ≧ −16.25 750 ℃: −7.56 ≧ logPo ₂ ≥ -13.60 850 ° C: -6.82 ≥ logPo ₂ ≥ -11.30 950 ° C: -6.20 ≥ logPo ₂ ≥-9.45 1050 ° C: -5.65 ≥ logPo ₂ ≥-7.85 1080 ° C: -5.35 ≥ logPo ₂ ≥-7.40 The process is performed while controlling so as to satisfy the condition.

Function The multilayer capacitor element manufactured as described above has a large insulation resistance value and a low dielectric loss at high frequency, because the electrode is not oxidized during firing and the dielectric is not reduced. Copper oxide powder, which is cheaper than metal powder, can be used as a starting material for internal electrodes.

Example Since the multilayer capacitor element of the present invention uses a lead perovskite-based oxide for the dielectric and uses copper or an alloy containing copper as the main electrode as the internal electrode, the electrode is not oxidized during firing and the dielectric is reduced. It is required not to. In particular, in the method for manufacturing a multilayer capacitor element of the present invention, the electrode once becomes burnt out and then becomes copper oxide, which is reduced at a temperature lower than the firing temperature to be metallized and then fired,
The copper metal of the electrode is a fine powder and has a high surface activity before firing, and is particularly likely to be oxidized when the temperature is raised during firing or when the temperature is maintained near the maximum temperature. Therefore, in this process, the atmospheric oxygen partial pressure should not exceed the equilibrium oxygen partial pressure of copper so much that it is in an oxygen-excess atmosphere. On the other hand, the lead perovskite-based dielectric used in the present invention has a slight difference depending on its constituent components, but at a high oxygen partial pressure below a certain oxygen partial pressure, reduction of the dielectric substance starts and electrical conductivity starts. Will increase. Third
The figure shows a typical dielectric composition used in the present invention, (Pb _1.010 Ca _0.030 ) (Mg _1/3 Nb _2/3 ) _0.70 Ti _0.25 (Ni
_1/2 W _1/2 ) _0.05 O _Shows the change in electrical conductivity when the oxygen partial pressure in the atmosphere changes at a high temperature of _3.025 . As is clear from FIG. 3, the oxygen partial pressure at which the reduction of the dielectric ceramic begins is changed to the low oxygen partial pressure side as the temperature becomes lower. That is, when firing the multilayer capacitor element of the present invention, if the firing is performed on the higher oxygen partial pressure side than the oxygen partial pressure change due to this temperature, the element will have a higher resistance. Of course, it is desirable that the control range of these firing atmospheres be continued from around room temperature.
Since the reaction rate of the reduction of the dielectric becomes large, control above this temperature is important for controlling the device characteristics.

Example 1 A material represented by the following composition formula was used as a dielectric.

(Pb _1.00 Ca _0.025 ) (Mg _1/3 Nb _2/3 ) _0.70 Ti _0.25 (Ni _1/2
The W _1/2 ) _0.05 O _3.025 dielectric powder was manufactured according to the usual ceramic manufacturing method. The calcination condition was 800 ° C. for 2 hours. The pulverized calcinated powder is 5 wt% of polyvinyl butyral resin, 5%
The mixture was mixed with a 0 wt% solvent in a ball mill and formed into a sheet having a thickness of 35 μm using a doctor blade. For the internal electrode, Cu ₂ O with an average particle size of 0.8 μm (purity 99% as Cu ₂ O) was used as the starting material, and 0.5 wt% of ethyl cellulose to Cu ₂ O, 25w
An internal electrode pattern was printed on the dielectric green sheet using a screen printing method by kneading with a t% solvent using a three-roll mill to form an electrode paste. This was laminated and cut so that the electrodes could be drawn out alternately to the left and right.

The above-mentioned electrode paste was applied to the end faces where the electrodes were alternately pulled out and output to form external electrodes.

The laminate thus prepared was laid with coarse-grained magnesia in a porcelain boat and placed on it to burn out the binder at 450 ° C. in air.

As shown in FIG. 4, the porcelain boat 12 on which the burned-out laminated body sample 14 was placed was placed inside the core tube 11 having an inner diameter of 50 mm in a tubular furnace, and nitrogen gas bubbling 3 wt% ammonia water 15 at 20 ° C. Was flown at 1 liter per minute and maintained at 450 ° C. for 8 hours to reduce the internal electrode.

FIG. 5 shows a cross section of the magnesia porcelain container in which the laminated body during firing is put, and FIG. 6 shows a cross section of the firing furnace core tube and a gas pipe. In the magnesia porcelain container 21, the above-mentioned calcined powder 22 was spread over about 1/3 of its volume, and coarse magnesia powder 23 was spread over about 1 mm, and the burned out laminated body 25 was placed thereon. The lid 24 of the magnesia porcelain is placed and inserted into the core tube 26 of the tubular electric furnace, and N ₂ -H ₂ -H ₂ O of various composition ratios of Table 1 experimental conditions A to G is set.
While flowing a -O ₂ mixed gas, the temperature was raised to 1050 ° C at 200 ° C / hr, kept for 2 hours, and then lowered at 400 ° C / hr. The amount of water vapor in the atmospheric gas was measured by the absolute humidity sensor 28 and controlled by adjusting the amount of gas for bubbling distilled water. Hydrogen gas is 1%
As the H ₂ —N ₂ gas, oxygen gas was added as 1% O ₂ —N ₂ gas, if necessary, in consideration of the oxygen content contained in the nitrogen gas flowing as the carrier gas. Table 1 shows the mixing ratio of various gases and the temperature change of oxygen partial pressure up to 1080 ° C. when flowing the gases, and Table 1 shows the oxygen partial pressure range described in claim 1 of the present invention. For N ₂ gas, see 1.
A material containing 0 × 10 ⁻⁵ (atm) oxygen as an impurity was used.

Further, Po ₂ in the core tube was obtained from the following formula from the voltage E (V) between the electrodes drawn from the platinum electrode formed on the atmosphere side of the stabilized zirconia oxygen sensor 27 inserted and the inside of the furnace.

Po ₂ = 0.2 ・ exp (4FE / RT) where F is Faraday constant 96489 Coulomb and R is gas constant
8.3144 J / deg · mol, T is the absolute temperature.

The outer shape of the multilayer capacitor element is 2.8 × 1.4 × 0.9 mm, the effective electrode area is 1.3125 mm ² (1.75 × 0.75 mm) per layer, the electrode layer thickness is 2.0 μm, the dielectric layer is 25.0 μm per layer, and the effective layer is 30 Layers, two ineffective layers were provided above and below. The multilayer capacitor element has a capacity and tan δ of 100V when an AC voltage of 1V is applied.
It was measured at a frequency of Hz to 2 MHz. The resistivity was calculated from the value of 1 minute after applying a voltage of 50 V / mm. The measurement was carried out on 50 samples under each condition, and the capacity (20 ° C) was 100 nF or less and the resistance value was 1 × 10.
^-9 Ω or less, or resistance-capacitance product of 500 FΩ or less was regarded as defective, and the characteristics of only good products were averaged.

Table 2 shows the capacity, tan δ, and the number of defective resistance values.

As is clear from Tables 1 and 2, at the time of temperature rise during firing,
Atmospheric oxygen partial pressure Po ₂ (atmospheric pressure) when held near the maximum temperature
However, all the elements fired within the scope of the claims have a high resistance value, and the capacitance has reached the design value,
tan δ also shows a small value. On the other hand, under the experimental condition A in which Po ₂ is larger than the limited range in all temperature ranges and in the experimental condition G in which Po ₂ is larger than the limited range at low temperature, the electrode is oxidized, the capacity is lowered, or the resistance value is lowered, The number of defects increases. Further, under the experimental condition F in which Po ₂ is smaller than the limited range in all temperature ranges, reduction of the dielectric occurs and metallic lead is precipitated from the dielectric, which forms a solid solution with the electrode metal to lower the melting point. The electrode melts, the electrode is not formed into a plate shape, and the phenomenon of localization appears, which causes a large decrease in capacity and increases the number of defects.

In this example, the same gas was kept flowing during cooling during the firing process, so that the change in oxygen partial pressure during temperature decrease shows the same change as during temperature increase.

Example 2 The same method as in Example 1 was used for the dielectric material and its sheet formation.

For the internal electrodes, CuO with an average particle size of 1.2 μm (purity of 97% as CuO) was used as the starting material, and a calcined powder of the dielectric was used as the starting material.
0.5 wt% of ethyl cellulose, 2 wt% added and mixed, 2
An internal electrode pattern was printed on a dielectric green sheet by a screen printing method by kneading with a solvent of 5 wt% using a triple roll to form an electrode paste. This was laminated and cut so that the electrodes could be drawn out alternately to the left and right.

The above-mentioned electrode paste was applied to the end faces from which the electrodes were alternately drawn out to form external electrodes.

The laminate thus prepared was prepared by placing coarse-grained zirconia in a porcelain boat and placing it on the porcelain boat to burn out the binder at 500 ° C. in the air.

A porcelain boat on which the burned-out laminated body was placed was placed in a core tube with an inner diameter of 50 mm in a tubular furnace, and nitrogen gas containing 1.5% by volume of steam gas and 0.05% by volume of hydrogen gas (containing 0.001% by volume of oxygen as impurities). ) At 1 liter per minute at 600 ° C
Held for 4 hours.

The internal structure of the vessel and core tube during firing was the same as in Example 1. The firing temperature was 1080 ° C., the atmosphere gas flown during firing was the same N ₂ —H ₂ —H ₂ O—O ₂ mixed gas as in Example 1, and the gas flown during heating and holding near the maximum temperature was Under the same conditions as the experimental condition C of Example 1, the cooling conditions were adjusted from the start of cooling while adjusting the oxygen partial pressure with an oxygen sensor. Table 3 shows the temperature change of oxygen partial pressure under each condition. FIG. 2 shows the temperature change of the oxygen partial pressure under each condition and the oxygen partial pressure range defined in claim 2.

The outer shape of the multilayer capacitor element is 2.8 × 1.4 × 0.9 mm, the effective electrode area is 1.3125 mm ² (1.75 × 0.75 mm) per layer, the electrode layer thickness is 2.0 μm, the dielectric layer is 25.0 μm per layer, and the effective layer is 30 Layers, two ineffective layers were provided above and below. The multilayer capacitor element has a capacity and tan δ of 100 Hz when an AC voltage of 1 V is applied.
Measured at a frequency of ~ 2MHz. The resistivity was calculated from the value of 1 minute after applying a voltage of 50 V / mm. The number of samples measured and the defective conditions were the same as in Example 1.

Table 4 shows the capacity and its temperature change rate, tan δ, resistance value, and the number of defects.

As is clear from Table 4, the oxygen partial pressure change condition during cooling is higher on the high oxygen partial pressure side than the oxygen partial pressure change during temperature increase, and samples satisfying the characteristic conditions in a wide range can be obtained. It was However, under the experimental condition H, which is a higher oxygen partial pressure condition than the experimental condition I, copper is oxidized and diffused into the dielectric, so that the resistance value of the element is lowered and the oxygen concentration is lower than that of the experimental condition L (the same as the temperature increase E). Under the experimental condition M which is a partial pressure condition (same as F at the time of temperature rise), the resistance value was decreased due to the reduction of the element.

Example 3 As the dielectric material, the composition shown in Table 5 was used. The method for synthesizing the dielectric material was the usual ceramic manufacturing method. The same method as in Example 1 was used for forming the sheet.
As the internal electrode, C having the average particle diameter of 0.8 μm used in Example 1 was used.
A mixture of 90 wt% u ₂ O and 10 wt% CuOH _{2 with} an average particle size of 1.5 μm was used as a starting material, and was mixed with 0.5 wt% ethyl cellulose and 25 wt% solvent in a three-roll mill to form an electrode paste using the screen printing method. The internal electrode pattern was printed on the dielectric green sheet. This was laminated and cut so that the electrodes could be drawn out alternately to the left and right.

The above-mentioned electrode paste was applied to the end faces from which the electrodes were alternately drawn out to form external electrodes.

The laminate thus prepared was prepared by placing coarse-grained zirconia in a porcelain boat and placing it on the porcelain boat to burn out the binder at 500 ° C. in the air.

The porcelain boat on which the burned-out laminated body was placed was put inside the furnace core tube with an inner diameter of 50 mm in the tubular furnace shown in FIG. .

Each of the component gases under the experimental conditions A to G of Example 1 was allowed to flow, and this was fired in the same manner. The firing temperature was 1050 ° C.

The outer shape of the multilayer capacitor element, the effective electrode area, the thickness of the electrode layer, the thickness of each dielectric layer, the number of effective layers, and the like were the same as in Example 1. The characteristic measurement conditions were the same as in Example 1. The number of samples measured and the failure conditions were the same as in Example 1, but the capacity failure was 50% or less of the capacity calculated from the dielectric constant of the sample composition.

Table 6 shows the number of defects in each composition and each firing condition.

As is clear from Table 6, the ceramic multilayer capacitor using the composition of lead perovskite according to claim 1 as the dielectric is not limited to any one of the following claims. When it is fired in the temperature change range of the oxygen partial pressure described in the paragraph, it shows a high resistance value, and when fired in a higher oxygen partial pressure atmosphere than the claimed range, it is due to the diffusion of copper oxide generated by the oxidation of the electrode into the dielectric. When the element resistance value decreases and the capacity decreases, and when firing in a low oxygen partial pressure atmosphere, the capacitance due to the localization of the electrode due to the solid solution of metallic lead generated by the reduction of the dielectric to the electrode Decrease and the reduction of the element resistance value due to the reduction of the dielectric.

EFFECTS OF THE INVENTION According to the method for manufacturing a multilayer capacitor element of the present invention, in a multilayer capacitor element using lead perovskite as a dielectric and copper as an internal electrode, a multilayer capacitor element having a large insulation resistance value and a small high frequency dielectric loss can be obtained. In addition, the copper oxide powder, which is cheaper than the copper metal powder, can be used as a starting material for the internal electrode, and the electrode cost can be reduced.

[Brief description of drawings]

1 and 2 are graphs showing the temperature change of oxygen partial pressure during firing in the example of the present invention, and FIG. 3 is a graph of the dielectric composition of the example of the present invention under high temperature. FIG. 4 is a graph showing a change in electrical conductivity when the atmospheric oxygen partial pressure is changed, and FIG. 4 is a cross-sectional view showing the arrangement inside the core tube and the state of the gas pipe during the electrode metallization treatment in one embodiment of the present invention. 5 and 5 are cross-sectional views of a magnesia porcelain container in which a laminated body at the time of firing is put, FIG. 6 is a cross-sectional view showing an arrangement inside the core tube at the time of firing, and FIG. 7 is another embodiment of the present invention. It is sectional drawing which shows the arrangement | positioning inside a core tube and the state of gas piping at the time of an electrode metallization process in an example. 11 …… Reactor tube, 12 …… Porcelain boat, 13 …… Coarse-grained magnesia, 14 …… Laminated sample, 15 …… Ammonia water, 21… Magnesia porcelain container, 22… Calcined powder, 23… Coarse Granule magnesia powder, 24 …… Magnesia porcelain lid, 25 …… Layered body with metallized electrodes, 26 …… Fast tube, 27 …… Stabilized zirconia oxygen sensor, 28 …… Absolute humidity sensor.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Junichi Kato 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Toshihiro Mihara, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. When manufacturing a multilayer capacitor element using lead perovskite oxide as a dielectric and using copper or an alloy containing copper as a main component as an internal electrode, Cu ₂ O, CuO is used as a starting material for the copper internal electrode. Then, using a raw material containing, as a main component, a mixture thereof, or a copper compound that decomposes in the air at 650 ° C. or lower to form a copper oxide, the internal electrode pattern is printed on the dielectric green sheet and laminated, In a method of manufacturing a multilayer capacitor, in which the binder component is burned out in air, then the internal electrodes are reduced to metallize at a temperature lower than the firing temperature, and then fired, the temperature is raised during firing and the temperature is maintained near the maximum temperature. Atmosphere oxygen partial pressure at time Po ₂ is log (Po ₂ ) (Po ₂
Is the atmospheric pressure), the temperature change from 650 ℃ to 1080
650 ° C: −8.60 ≧ logPo ₂ ≧ −16.25 750 ° C: −7.56 ≧ logPo ₂ ≧ −13.60 850 ° C: −6.82 ≧ logPo ₂ ≧ −11.30 950 ° C: −6.20 ≧ logPo ₂ ≧ −9.45 1050 ℃: −5.65 ≧ logPo ₂ ≧ −7.85 1080 ℃: −5.35 ≧ logPo ₂ ≧ −7.40 The method for manufacturing a multilayer capacitor element characterized by satisfying the conditions. 2. The atmospheric oxygen partial pressure Po ₂ when the temperature is lowered during firing is expressed by log
When expressed in (Po ₂ ) (Po ₂ is atmospheric pressure), the temperature change is 65
650 ° C: −5.00 ≧ logPo ₂ ≧ −16.25 750 ° C: −5.00 ≧ logPo ₂ ≧ −13.60 850 ° C: −5.00 ≧ logPo ₂ ≧ −11.30 950 ° C: −5.50 ≧ logPo ₂ The manufacturing method of the multilayer capacitor element according to claim 1, wherein the condition of ≧ −9.45 1050 ° C .: −5.65 ≧ logPo ₂ ≧ −7.85 1080 ° C .: −5.35 ≧ logPo ₂ ≧ −7.40 is satisfied. 3. A component A whose component is selected from the group A consisting of Pb, Ca, Sr and Ba, and component B which is selected from the group B consisting of Mg, Ni, Zn, Ti, Nb, and W. , Both components of A, P contains at least one of Pb and other components, B contains at least two components of group B, and the total number of moles of components of A is the components of a and B. The method for producing a multilayer capacitor element according to claim 1, wherein the lead perovskite-based oxide is a composition in which a / b> 1.00, where b is the total of b.