JPH01236513A - Internal electrode paste for laminated ceramic body - Google Patents

Abstract

PURPOSE:To prevent generation of structural defects such as cracks by containing an organic binder and a solvent with respect to a mixture having 10-70wt.% of Cu. CONSTITUTION:In a mixture composed of 0.1-10mum of Cu2O and Cu in average particle dia. as a starting raw material, 0.5-10wt.% of an organic binder and a solvent are added with a respect to a mixture composed of Cu2O and Cu, or Cu2O and additive inorganic gradients, by the use of a mixture having 10-70wt.% of Cu. Since it is possible to remove the organic binder completely without generation of problems such as cracks under an oxide atmosphere, and to prevent carbon from remaining, it is thus possible to prevent the insulation resistance and baking density from lowering due to reduction of ceramic material at the time of baking.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is for forming a copper or copper-based alloy layer used as an internal electrode of a laminated ceramic body such as a laminated ceramic capacitor or a ceramic multilayer substrate. The present invention relates to an internal electrode paste for a laminated ceramic body to be used.

BACKGROUND OF THE INVENTION In recent years, demand for multilayer ceramic bodies in which electrode layers and ceramic layers are laminated and assembled in layers has rapidly increased as electronic components such as multilayer capacitors and ceramic multilayer substrates.

By the way, conventional multilayer ceramic capacitors use barium titanate, etc., whose firing temperature is 1300°C or higher, as the ceramic material, and the internal electrode materials are expensive materials such as Pt and Pd, whose melting point is higher than the firing temperature of the ceramic material. It was necessary to use metal. Therefore, attempts have been made to use inexpensive base metals for internal electrodes in order to reduce product costs.

In response, the inventors have proposed a multilayer capacitor element that uses lead perovskite oxide, which can be fired at low temperatures of 900 to 10oO℃, for the dielectric and copper or an alloy containing copper as the main component for the internal electrodes. .

In addition, using a barium titanate dielectric,
A multilayer ceramic capacitor using Ni for internal electrodes has been proposed, and its manufacturing method is described in JP-A-60-1.
A method described in Japanese Patent No. 78611 is known.

On the other hand, ceramic multilayer substrates have a firing temperature of 15oO to 17
Using alumina as a ceramic material with temperatures as high as 00℃, W and M
The main component was an alumina multilayer substrate with O as the internal electrode (wiring conductor). However, with the increasing frequency and digitalization of electronic devices, the dielectric constant of ceramic materials has decreased and internal electrodes (
There is a strong desire to reduce the resistance of wiring conductors. For this reason,
A1 has a low dielectric constant of 6.7 in IMIIz (1o for alumina) and can be fired at a low temperature of 900 to 1000°C.
2o, -Ca OS 102 M g OB 20
Ceramic multilayer substrates have been proposed in which S is a ceramic material and internal electrodes (wiring conductors) are made of Ni, Cu, Au, Mug, Mug-Pd, or the like.

As shown above, the internal electrode paste used to form the internal electrodes of conventional multilayer ceramic bodies using copper or copper alloy as internal electrodes uses copper alloy or metallic copper powder or CuO as the starting material. Ta.

Problems to be Solved by the Invention However, with the above-mentioned conventional techniques, two problems arise that must be overcome. This is due to the organic binder used in the internal electrode paste and ceramic material.

That is, the first problem is that the organic binder used to form the ceramic material into a sheet and the organic binder contained in the internal electrode paste cannot be completely removed in a non-oxidizing atmosphere where oxidation of the internal electrode material does not occur. This is because carbonization of the organic binder is likely to occur, and the ceramic material is reduced by the remaining carbon during firing, resulting in a decrease in the insulation resistance of the element and a decrease in the sintered density.

The second problem arises when attempting to completely remove the organic binder in an oxidizing atmosphere.

In other words, when metallic copper or copper alloy powder is used as the starting material for the internal electrode paste, when the organic binder component is removed (hereinafter simply referred to as binder out), the internal electrode material is oxidized and the volume expansion caused by this extermination occurs. However, there were problems such as an increase in dielectric loss and the occurrence of cracks at high frequencies. In addition, CuO is used as the starting material for the negative circular part electrode paste.
When CuO is used, cracks do not occur when the binder is removed in an oxidizing atmosphere, but when CuO is reduced to metallic copper in the firing or reduction process, a large volumetric shrinkage occurs and cracks occur in the sintered body. There have been problems in that so-called delamination occurs, in which cavities are formed between the ceramic layer and the electrode layer.

Furthermore, when Cu2O is used as the starting material for internal electrode paste, there is no problem if the number of laminated layers is relatively small or the electrode area is small, but if the number of laminated layers is large, Cu20 with a low metal content may be used. This is not preferable because cracks may occur during the reduction treatment.

The above-mentioned problems are most noticeable in multilayer ceramic bodies that have a large number of laminated layers to achieve high density and high capacity.

In addition, when metal is used as the starting material for internal electrode paste, metal powder with a small average particle size is required, and because of the cost required for crushing during manufacturing and the cost required for rust prevention treatment, bare metal is inexpensive. There was a problem in that the advantages of base metals could not be fully utilized.

The present invention solves these problems, and allows binder to be removed in an oxidizing atmosphere in a laminated ceramic body with a large number of laminated copper as internal electrodes, and furthermore, the subsequent reduction treatment prevents cracks, etc. The purpose of this invention is to provide an internal electrode paste with excellent reliability that does not cause any structural defects.

Means for Solving the Problems In order to solve the above problems, the internal electrode paste for laminated ceramic bodies of the present invention has an average particle size of 0.1 to 1 as a starting material.
In the compound consisting of 0 μm Cu2O and Cu, C
Using a mixture with a u content of 10 to 70 wt%, Cu
2O and Ou-4 or 0.6 to 10 wt% of an organic binder and a solvent are added to a mixture of Cu2O and Gu and additional inorganic components. In addition, elements constituting the ceramic material to be laminated, compounds containing them, metal elements forming alloys with copper, or compounds containing them as inorganic components = 1 to 50 W t% with respect to the mixture of Cu2O and CU The added material is made into an electrode paste.

Function: By using the internal electrode paste for laminated ceramic bodies of the present invention, the organic binder can be completely removed without causing problems such as cracks in an oxidizing atmosphere, and carbon residue can be prevented. It is possible to prevent a decrease in insulation resistance and a decrease in firing density due to reduction of the ceramic material during heating. That is, since Cu2O has a smaller volumetric expansion of about 6% due to oxidation to GuO than metal steel, cracks do not occur during binder out in an oxidizing atmosphere compared to when only metal copper is used. Moreover, the CuO generated during binder out is 26
Since it is completely reduced at a low temperature of 0 to 660℃ and a relatively high oxygen partial pressure, internal electrodes with good conductivity can be created by reducing the green body after removing the binder under appropriate reducing conditions. Obtainable. Also, Cu
When a mixture of 2O and Gu is used as the starting material, C
Compared to using UO or Gu20f alone as the starting material,
Because the metal content per unit volume in the coating film after printing and drying the internal electrode paste is high, volumetric shrinkage during reduction treatment is small and cracks and delamination occur in green bodies and sintered bodies after reduction treatment. do not. moreover,
By firing the green body after this reduction treatment in an atmosphere where the internal electrodes are not oxidized and the ceramic material is not reduced, the ceramic layer has the desired properties of denseness and high insulation resistance, and the internal electrode layer is made of oxide. This results in a laminated ceramic body that is completely made of metallic copper and has good conductivity without any intervening elements.

In addition, by adding υ in the form of an element constituting the ceramic material used in the laminated ceramic body or a compound containing it as an inorganic component, glass frit that has an affinity with the ceramic material, etc., the internal electrode layer and the ceramic Adhesion to the layer can be improved.

Furthermore, depending on the sintering temperature of the ceramic material used in the laminated ceramic body and the required electrode properties, copper alloys can be made by adding other metal elements that form alloys with copper in the form of metals, oxides, or other compounds. An internal electrode layer can be obtained.

EXAMPLES Below, examples will be described in which the internal electrode paste of the present invention is applied to a laminated ceramic capacitor in the form of a laminated ceramic body.

(Example 1) A material represented by the following compositional formula was used as a dielectric ceramic.

(Pb1.gBI C&,,)25) (Mg y,
Nby, ),,.

"a2s <"34 W, H) (L(1503,
(The 125 dielectric ceramic powder was left behind according to the usual ceramic manufacturing method. The calcination conditions were 800°C for 2 hours. The pulverized calcined powder contained Swt% polyvinyl butyral resin as an organic binder, The mixture was mixed in a ball mill with 3 wt % dibutyl phthalate as a plasticizer and 50 wt % solvent and formed into a sheet with a diameter of 35 μm using a doctor blade.The internal electrode paste had an average particle size of 0.08 μm and 1.0 μm, respectively.
μm, 9. ．． 5 μm.

Cu20 (Cu2) has four types of average particle diameters of 12 μm.
Purity: 99cm) or average particle size: 0.06μm
, 0.5 μm, 10 μm, and 15 μm of copper in the four groups and CuO with an average particle size of 1.2 μm were used as starting materials. This copper, Cu2O, CuO or Cu and Cu2O
In the mixture, the Cu content is s, 10, 50, 70
, 0.3 wt% for a mixture of 80 wt%,
0.5 wt%, 2.5 wt%.

10wt, 15wt% ethylcellulose and 46wt
% of turpentine oil was added as a solvent and kneaded with three rolls to form an electrode paste, and an internal electrode pattern was printed on a dielectric ceramic green sheet using a screen printing method. The printing thickness at this time was 12 to 18 μm. This was laminated so that the electrodes were drawn out alternately on the left and right sides, and then cut.

The thus-prepared laminate was prepared by placing coarse-grained zirconia in a porcelain boat and placing it on top of it in air at a heating rate of 12.
The temperature was raised to eoo'c at °C/hr and held at 600 °C for 6 hours to remove the binder.

As shown in FIG. 1, the porcelain boat 12 carrying the binder-out laminate sample 14 was placed in a tube furnace with an inner diameter of 60 mm.
1 liter of nitrogen gas bubbled with 20'C 3wt% ammonia water 15 was flowed into the reactor core tube 11 of the reactor, and the temperature was maintained at 450'C for 8 hours to reduce the internal electrode.

FIG. 2 shows a cross section of a magnesia porcelain container in which the laminate is placed during firing. Further, FIG. 3 shows a cross section of the firing furnace core a. Inside the magnesia porcelain container 21, the above-mentioned calcined powder 22 was spread to a volume of about 1,000 yen, and 200 meshes of ZrO2 powder 23 (23 pieces in total) were spread thereon, and the laminate 26 whose internal electrodes had been reduced was placed thereon. Magnesia porcelain lid 2
4, insert it into the furnace core tube 26 of a tubular electric furnace, degas the inside of the furnace core tube with a rotary pump, replace it with N2-H2 layer gas, and add N2 and H2 so that the oxygen partial pressure becomes 1 x 10.
Flow the mixed gas while adjusting the mixing ratio of the two gases to 980℃
Raise the temperature at 400°C/hr to 400'C/hr and hold for 2 hours.
The temperature decreased in hr. PO2 in the reactor core tube was determined from the following equation from the voltage between the electrodes drawn from the platinum polarization constructed on the atmospheric side of the inserted stabilized zirconia oxygen sensor 27 and the inner side of the reactor x (v).

Po2= 0.2・axp (4F E /RT) Here, F is Faraday constant number 96489 coulombs.

R is the gas constant 8.3144 J/lleg -mol
, T is the absolute temperature.

The outer size of the multilayer ceramic capacitor is 2.8 x 1.4
Effective electrode area is 1.3125 per layer with XO19wR
Order 2 (1,75X 0.7511111), the thickness of the electrode layer is 3.0 to 4.0 μm, and the dielectric layer is
The number of effective layers was 30 at 6.0 μm, and 7 ineffective layers were provided on the upper and lower sides. The multilayer ceramic capacitor thus obtained was coated with an In-Ga alloy as an external electrode, and an AC voltage of 1 V was applied to the capacitance i and tan δ at room temperature.
Measurements were made at a frequency of KHz. Also, the resistivity is 60 V
/mm voltage was determined from the value 1 minute after application.

Tables 1 and 2 show capacitance, tan δ, and resistance values.

Also, structural defects and problems that occurred during the manufacturing process of the obtained multilayer ceramic capacitor are shown in the remarks column.

As is clear from Tables 1 and 2, the starting material has a Cu content of 10 to 10%, which does not cause cracks during binder out or delamination during reduction treatment and firing.
A mixture of 70 wt% Cu2O and Cu is preferred. It is also understood that the average particle diameter is preferably 0.1 to 10 μm. That is, if it is smaller than 0.1 μm, the backing during printing of the internal electrode paste will not be sufficient and the density of the coating will be low, resulting in cracks occurring after reduction treatment or delamination during firing. - way, 1
If it is larger than 0 μm, no (C at under-out)
Cracks occur due to volumetric expansion due to oxidation to uO.

The amount of organic binder added is 0.
5-10 wt% appears to be optimal. If the amount of the organic binder added is less than 0.5 wt%, the thixotropy of the electrode paste decreases and bleeding occurs during printing, which is not preferable. On the other hand, if the amount is more than 10 wt %, cracks will occur due to a large amount of decomposed gas generated by decomposition of the organic (organic) binder when the binder is decomposed, which is not preferable.

By the way, in Example 1, ethyl cellulose was used as the organic binder, but other organic binders such as acrylic resin may be used.

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

As the internal electrode paste, Cu with an average particle size of 1.0 μm was used.
20 (purity 99% as Cu20) and average particle size 0.
A 1:1 mixture of 6 μm O was used as a starting material, and 0.5 to 6 wt% of inorganic components (same as or different from the dielectric ceramic material shown in Table 3) were added to this mixture. element or its compound), and further this (
3u20, 2.5 wt% relative to Cu and inorganic components
of ethyl cellulose and swt % of turpentine oil were added as a solvent and kneaded with three rolls to obtain an electrode paste, and an internal electrode pattern was printed on a dielectric ceramic green sheet using a saffron printing method. This was laminated so that the electrodes were drawn out alternately on the left and right sides, and then cut.

At this time, samples with an effective number of layers of 30 layers and 60 layers were produced.

The thus produced laminate was reduced and fired in the same manner as in Example 1 to produce a multilayer ceramic capacitor, and an In--Ga alloy was applied as an external electrode.

The capacitance and tan δ at room temperature of this sample were measured at a frequency of IKHz by applying an AC voltage of 1 V. Also,
The resistivity was determined from the value 1 minute after applying a voltage of 60 V/rtrm.

Table 3 shows the capacitance, tan δ, resistance value, and the structural defects and problems that occurred during the manufacturing process of the obtained multilayer ceramic capacitors in the remarks column.

(Left below) As is clear from Table 3, the elements or compounds thereof that are the same as or constitutive of the dielectric ceramic material are
By adding ~50 wt%, the adhesive strength between the internal electrode and the ceramic is improved even if the number of laminated layers is increased, and a good multilayer ceramic capacitor without cracks after reduction treatment or delamination after firing can be obtained. If the amount of the inorganic component added is less than 1 wt%, the adhesive strength will not be improved sufficiently, and if the number of laminated layers is increased to 60, CuO will be reduced to metallic copper due to the reduction treatment after the binder is removed. The volume shrinkage becomes large when it is removed, and cracks may occur. On the other hand, the amount of inorganic components added is 50wt.
If it exceeds %, the internal electrode layer becomes mesh-like, the continuity of the electrode decreases, and it no longer functions as a cE electrode, which is not preferable.

Although this example shows only the case where elements or compounds thereof that are the same as or constitutive of the dielectric ceramic material are added, it is also possible to add glass frit such as zinc borosilicate glass, which has an affinity with the ceramic material, as an inorganic component. The same effect can be obtained.

(Example 3) A material represented by the following compositional formula was used as a dielectric ceramic.

(PbusCaas) (MgHNbz) [190
(ui34w%) [110S The same method as in Examples 1 and 2 was used to form a sheet.

As the internal electrode paste, Cu with an average particle size of 1.0 μm was used.
20 (purity 99% as Cu20) and average particle size 0.
A 1:1 mixture of 5 μm Cu was used as the starting material, and the average particle size was 1.0 μm as a metal that forms an alloy with copper.
40 wt% of Ni was added to the mixture of Cu2O and Cu. Next, this Cu.

Add 2.5 wt% ethyl cellulose and 45 wt% turpentine oil as solvents to Cu2O and HNl, knead with three rolls to make an electrode paste, and print internal electrode pattern on dielectric ceramic green sheet using screen printing method. was printed. This was cut so that the electrodes were pulled out alternately on the left and right sides. In addition, the effective number of layers at this time was 20. Next, this laminate was subjected to reduction treatment in the same manner as in Examples 1 and 2, and then subjected to conditions such that the oxygen partial pressure was I X10 at 1160 ° C. and fired.

On the other hand, as a comparative example, an internal electrode paste containing no Ni was prepared, and a multilayer ceramic capacitor was prepared in the same manner as above.
In-Ga alloy was applied as an external electrode. The capacitance and tan δ at room temperature of this sample were measured at a frequency of IKIIz by applying an AC voltage of 1 V.

As a result, in the sample using the internal electrode paste according to the present invention containing Nii, the capacitance was 1.2 nF and the tan
A good result with δ of 20×10 was obtained. On the other hand, as a comparative example, a sample using an internal electrode paste that did not contain N1 did not have any capacity. This means that the firing temperature is as high as 1150'C (if it does not contain Ni, it exceeds the melting point of copper, 1083°C), so the copper melts during firing, and the surface tension at this time causes the copper to become granular, causing the internal electrodes to become granular. On the other hand, when using the Nii-containing internal electrode pastera of the present invention, the melting point of this alloy exceeds 1150'ce, so it may melt during firing. The internal electrodes are sintered without
A multilayer ceramic capacitor with good internal electrodes can be obtained.

Note that although metal Nl was used in this embodiment, similar effects can be obtained even if it is used in the form of other compounds.

Further, by adding other metals or compounds thereof that form an alloy with copper, the properties such as the melting point and conductivity of the internal electrode material can be controlled.

Furthermore, as shown in Example 2, in a multilayer ceramic body with a large number of laminated layers, an inorganic component added for the purpose of improving the adhesive strength between the internal polarization layer and the ceramic material layer may be added to a metal that forms an alloy with copper or a metal that forms an alloy with copper. By adding it simultaneously with the compound, an internal electrode paste suitable for multilayer ceramic bodies with a large number of laminated layers can be obtained.

As is clear from the above three examples, in the mixture of Cu2O and Cu having an average particle size of 0.1 to 10 μm according to the present invention, a mixture with a Cu content of 10 to 70 wt% was used. 0.5-10wt%
An internal electrode paste for a laminated ceramic body characterized by adding a binder and a solvent, or an element constituting the laminated ceramic material or a compound containing the same, or a metal element that forms an alloy with copper or a compound containing the same. As an inorganic component, 0.6 to 1% was added to the mixture of Cu2O and Cu.
By using an internal electrode paste for a laminated ceramic body characterized by containing 0 wt % of an organic binder and further a solvent, a good laminated ceramic body without structural defects can be obtained.

In this example, the explanation was limited to a multilayer ceramic capacitor as the multilayer ceramic body, but similar effects can be obtained by using the internal electrode paste of the present invention in other multilayer ceramic bodies such as ceramic multilayer substrates and ceramic multilayer actuators. Needless to say, you can obtain

Effect of the invention By using the internal electrode paste of the present invention.

Highly reliable f! without structural defects such as cracks and delamination. 4 or copper alloy? It is possible to obtain a laminated ceramic body that can be used as an internal electrode, and it is also possible to have multiple layers of the laminated ceramic body, which enables high performance and high-density packaging of components.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an internal electrode reduction device according to an embodiment of the present invention, FIG. 2 is a sectional view showing a magnesia container during firing, and FIG. 3 is a sectional view showing a core tube of a firing furnace. . 11... Furnace tube, 12. River... Porcelain boat, 1
3...Coarse grain zirconia, 14...Laminated body sample, 16...Ammonia water. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 6

Claims (4)

[Claims] (1) In a mixture consisting of Cu_2O and Cu with an average particle diameter of 0.1 to 10 μm, the Cu content is 10 to 70 μm.
An internal electrode paste for a laminated ceramic body, which contains an organic binder and a solvent in an amount of 0.5 to 10 wt % based on the weight of the mixture. (2) In a mixture consisting of Cu_2O and Cu with an average particle diameter of 0.1 to 10 μm, the Cu content is 10 to 70 μm.
It is characterized by containing an inorganic component of 1 to 50 wt% with respect to the mixture which is wt%, an organic binder of 0.5 to 10 wt%, and further a solvent with respect to the mixture of Cu_2O, Cu and other inorganic components. Internal electrode paste for laminated ceramic bodies. (3) The internal electrode paste for a laminated ceramic body according to claim 2, wherein the inorganic component is the same as the ceramic material in the laminated ceramic body, an element constituting the ceramic material, or a compound thereof. (4) The internal electrode paste for a laminated ceramic body according to claim 2, wherein the inorganic component is an element or a compound thereof that forms a solid solution with copper, which is an electrode material, in the laminated ceramic body.