JPH11176687A - Manufacture of grain boundary insulation type of stacked ceramic element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grain boundary insulation type of stacked ceramic part little in dispersion of electric property and high in property reproducibility. SOLUTION: A green stack, where ceramic layers 1 having SrTiO3 for their main components and two layers of inner electrodes 2 are stacked alternately in plural numbers and then reactive layers 3 of the same composition as the ceramic layer 1 are arranged at its upper layer and lower layer, is cut into a predetermined green chip shape so that the inner electrodes 2 may be exposed each to opposed end faces, and next the degreasing of the green ship is performed. Next, the outer electrode 4 in the first layer is applied on the exposed inner electrode 2, and then the material of the same composition as the ceramic layer 1 is mixed with powder being adjusted into a fixed grain size after calcination in reductive atmosphere, and the mixture is packed in a backing sheath of 50-70% in apparent porosity. Then, the above sheathes are piled up into plural stages, and are baked in reductive atmosphere, and the outer electrode 5 in the second layer is applied on the surface of the outer electrode 4 in the first layer of the obtained sintered substance, and in air, the reoxidation treatment of the sintered material is performed at the same time as the baking of the outer electrode 5 in the second layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a grain boundary insulated multilayer ceramic element (hereinafter referred to as a ceramic element) used for various electronic devices.

[0002]

2. Description of the Related Art In recent years, many semiconductor devices have been used for miniaturization and high performance of electronic devices, and accordingly, film capacitors, multilayer ceramic capacitors, and semiconductor ceramics used as noise filters for electronic devices have been used. Demands for smaller capacitors and higher performance are also increasing for capacitors and the like. Above all, ceramic elements containing SrTiO ₃ as a main component have excellent noise absorption properties, and have a varistor function in addition to being stable in temperature and frequency fluctuations. I have.

As shown in FIG. 1, a conventional ceramic element comprises a ceramic layer 1 containing SrTiO ₃ as a main component and two internal electrodes containing elements for promoting the conversion of ceramic into a semiconductor and sintering. After laminating the layers, further laminating an ineffective layer 3 having the same composition as the ceramic layer 1 on the lower layer, the resultant is cut into a predetermined green chip shape. Next, perform degreasing,
Next, a first layer of the external electrode 4 is applied to the portion of the internal electrode 2 exposed on the side surface of the green chip, and the outer layer 4 is fired in a reducing atmosphere after filling with a firing sheath. Thereafter, a second-layer external electrode 5 is applied to the surface of the first-layer external electrode 4 of the obtained sintered body. Re-oxidation of the grain boundaries was performed.

[0004]

In the above conventional method, the ceramic layer 1 sandwiched between the internal electrodes 2 is promoted to be a semiconductor and sintering. The part where the green chips overlap in the sheath is affected by the oxygen remaining in the sheath during firing,
Insufficiency in semiconductor conversion and sintering results in unevenness in the uniformity of the sintered body, and as a result, a variation occurs in the reoxidation state of the grain boundary of the sintered body performed simultaneously with the baking of the external electrode 5 of the second layer, There was a problem that the fluctuations in the electrical characteristics of the obtained ceramic element became large.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a ceramic element having a small fluctuation range of the electrical characteristics of the ceramic element and having excellent characteristic reproducibility.

[0006]

In order to achieve the above object, according to the present invention, after a laminated green chip containing SrTiO ₃ as a main component is degreased, a first surface of an internal electrode exposed on an end surface of a degreased calcined body is formed. The outer electrode of the layer is applied, and then the same material as the ceramic layer is calcined in a reducing atmosphere on a firing sheath having an apparent porosity of 50 to 70%. After that, the sheath is stacked in multiple stages and fired in a reducing atmosphere. Then, a second-layer external electrode is applied to the first-layer external electrode surface of the obtained ceramic element sintered body, and the second-layer external electrode is baked in the air at the same time as the particles of the ceramic element sintered body. A ceramic element is manufactured by a method of reoxidizing the field.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is characterized in that, after alternately laminating a plurality of ceramic layers containing SrTiO ₃ as a main component and internal electrode layers, the ceramic layers are further formed on the upper and lower layers. The green laminate in which the layers and the ineffective layer having the composition are arranged is cut into a predetermined green chip shape so that the internal electrodes are exposed at the opposite end faces, and then the green chip is degreased. Then, after applying the first-layer external electrode to the exposed internal electrode portion, the apparent porosity becomes 5%.
After calcining the same composition material as the ceramic layer in a reducing atmosphere in a 0 to 70% fired sheath, mixing with a co-fabric powder adjusted to a certain particle size, and filling with a sheath, the sheath is stacked in multiple stages. The firing is performed in a reducing atmosphere. Thereafter, a second-layer external electrode is applied to the surface of the first-layer external electrode of the obtained ceramic element sintered body, and simultaneously with the second-layer external electrode baking in air, the ceramic element sintered body is A method of manufacturing a ceramic element for reoxidizing grain boundaries.By firing using the porous sheath, oxygen remaining inside the sintered sheath and inside the wall is easily replaced with a reducing gas, and the green chip After calcining a material of the same composition as the ceramic in a reducing atmosphere, and mixing the green chips with the powder whose particle size has been adjusted to a certain size, the green chips are prevented from overlapping, and the walls of the porous sheath are eliminated. The reducing gas that has flowed into the sheath after passing through the surface easily touches the green chip surface during firing. As a result, the conversion of the entire green chip to a semiconductor and sinterability are promoted, and the reoxidation state of the ceramic element sintered body grain boundary which is performed simultaneously with the external electrode baking of the second layer becomes constant, and the ceramic element with small variation in electric characteristics. Can be produced with good reproducibility.

The invention according to claim 2 of the present invention is directed to a fired sheath filled with green chips and calcined powder having the same composition and having an apparent porosity of 50 to 70%, and an apparent side wall having an opening. 2. The method for manufacturing a ceramic element according to claim 1, wherein empty sheaths having a porosity of 50 to 70% are alternately stacked in multiple stages and fired in a reducing atmosphere. That is, when only the saya in which the green chips and the calcined powder are mixed are stacked in multiple stages, the reducing gas mainly passes through the saya side wall and flows into the saya. Is unlikely to occur. Therefore, in order to avoid this, the porous sheath having an opening portion formed in the side wall surface and having an apparent porosity of 50 to 70% and the porous sheath filled with green chips are alternately stacked in multiple stages and fired. The reducing gas flowing from the opening on the side wall surface passes through the bottom wall of the sheath located at the upper portion thereof, easily diffuses into the sheath, replaces residual oxygen, and stabilizes the atmosphere in the sheath.

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a ceramic element, and FIG.
Is a ceramic layer, 2 is an internal electrode, 3 is an ineffective layer, 4 is a first layer external electrode, and 5 is a second layer external electrode. FIG.
FIG. 3 is a diagram showing the manufacturing process.

First, the main component SrTiO ₃ 97.1mo
1%, 0.5 mol% of Nb ₂ O ₅ as a sub-component, and Ta ₂ O ₅
0.5 mol%, MnO 0.4 mol%, SiO ₂
And 1.0 mol% of Na ₂ SiO ₃ and 0.5 mol% of Na ₂ SiO ₃ were weighed and mixed (6) and mixed (7), and then 1100 ° C.
Was calcined (8) and then pulverized (9) to produce a material powder for a ceramic element.

[0012] Separately, the mixed material is 90% nitrogen.
After calcination at a temperature of 1150 ° C. in a green gas containing 10% hydrogen and hydrogen, pulverization was performed, and an apparent porosity of 5% was obtained.
A co-fabric for shedding with grain size adjusted to a particle size larger than the fired sheer pore opening diameter of 0 to 70% and a co-fabric for shedding with no grain size adjustment were prepared.

An organic solvent and a binder were added to the obtained material powder to form a slurry, and then a green sheet was prepared by a doctor blade method (10). Next, printing (11) of the internal electrode 2 is performed on the green sheet surface using a paste whose main component is NiO. Next, when the green sheet on which the internal electrodes 2 are printed is cut into a green chip shape, the green sheets are alternately shifted by a predetermined dimension in the longitudinal direction of the printed internal electrodes 2 so that the internal electrodes 2 are exposed on the opposite end surfaces of the green chips. After stacking a predetermined number of layers (12), an ineffective layer 3 in which a predetermined number of green sheets on which the internal electrodes 2 were not printed was stacked on the lower layer, and a lower layer was stacked under pressure to produce a green laminate.

After cutting the green laminate into a predetermined green chip shape (13), the green laminate is degreased at a temperature of 1100 ° C. (1).
4) and calcination were performed. Next, the degreased green chip is chamfered, and the same paste as that of the internal electrode 2 is applied to the exposed end surface of the internal electrode 2 (15). After providing the first-layer external electrode 4, (Table 1) According to the shear filling conditions shown, the co-fabric prepared in advance and the green chip provided with the first layer external electrode 4 are mixed to give an apparent porosity of 50-7.
This was packed in a 0% firing sheath, stacked in multiple stages, and fired in a reducing atmosphere (16) at a temperature of 1200 ° C. while flowing a green gas of 90% nitrogen and 10% hydrogen into the furnace.

[0015]

[Table 1]

A paste containing silver as a main component is applied to the surface of the first-layer external electrode 4 formed on the end face of the sintered body of the ceramic element obtained as described above. After the outer electrode 5 of the layer is provided, the grain boundary re-oxidation (18) of the ceramic element sintered body is performed simultaneously with the baking of the outer electrode 5 of the second layer at 850 ° C. in the air to complete the ceramic element. I let it.

With respect to the obtained ceramic element, the varistor voltage (V _{0.1 mA} ) and the capacitance at 1 kHz were measured, and the results are also shown in Table 1.

As shown in (Table 1), those using the co-fabric without grain size adjustment had a large variation in varistor voltage and capacitance value, whereas the co-fabric with grain size adjustment was used. The varistor voltage and the capacitance value have small variations. Further, it can be seen that the variation is further reduced in the case where the saya filled with the green chips and the co-fabric and the empty saya provided with the opening in the side wall surface are alternately stacked and fired.

This means that the apparent porosity is 50-70%.
By using the calcined saya, the green gas easily flows into the saya during sintering, and is replaced with oxygen remaining inside the saya and inside the wall, and the green gas atmosphere in the saya is stabilized. By alternately stacking and firing the sheaths filled with chips and the empty sheaths with openings on the side wall surface, the green gas flowing from the openings of the empty sheaths packs the green chips located at the top of the empty sheaths. The oxygen remaining in the sheath after passing through the pores at the bottom of the sheath is completely eliminated, and the green gas atmosphere in the sheath is made more stable. This is considered to be the result of promoting the formation of a semiconductor and sintering, and making the re-oxidation of the grain boundaries of the ceramic element, which is performed simultaneously with the baking of the second-layer external electrode 5 in the next step, into a uniform state.

[0020] Further, the method of mixing the green chips and the co-fabric and stuffing them together is to eliminate the overlap between the green chips and to allow the green gas flowing into the saya to pass through the gaps between the co-fabrics while meandering. This is to ensure the contact with the green chip surface during firing, and when the co-fabric is adjusted to a particle size larger than the pore diameter of the sheath, it has a synergistic effect with the effect of increasing the apparent porosity of the sheath. If the ground size is not adjusted, clogging occurs in the pores of the sheath and hinders the flow of green gas into the sheath, and it is impossible to completely prevent the green chips from overlapping and coming into contact with each other. Since the state of grain boundary reoxidation of the ceramic element sintered body becomes uneven, which results in large variations in electrical characteristics, There needs to be a big thing Ri.

The reason why the apparent porosity of the sheath is in the range of 50 to 70% is that when the porosity is 50% or less, the pore opening diameter becomes small and it becomes difficult for green gas to flow into the sheath. This is because the mechanical strength of the sheath itself becomes weaker when the above is reached, and the sheath is destroyed by stacking in multiple stages. Further, by setting the porosity to 50 to 70%, it is effective to extend the residence time of the green gas flowing into the sheath. Further, in the case of sintering without using a sheath, the green gas strongly acts only on the surface layer of the green chip during sintering.

[0022]

As described above, according to the present invention, a firing sheath having an apparent porosity of 50 to 70% is used for firing a grain boundary insulating ceramic element, and the same material as the ceramic composition to be fired is used. After calcining the material in a reducing atmosphere, the saya, which is a mixture of co-fabric powder and green chips adjusted to a certain particle size, is stacked in multiple stages and fired in a reducing atmosphere to form the entire ceramic element sintered body. And the sintering of the ceramic element can be made to proceed homogeneously, and the state of grain boundary reoxidation of the ceramic element sintered body performed simultaneously with the baking of the external electrode in the next step becomes uniform. As a result, it is possible to provide a grain boundary insulated multilayer ceramic element having small variations in electrical characteristics and high reproducibility of characteristics.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a grain boundary insulating multilayer ceramic device.

FIG. 2 is a manufacturing process diagram of a grain boundary insulating multilayer ceramic element according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic layer 2 Internal electrode 3 Invalid layer 4 First layer external electrode 5 Second layer external electrode

Claims (2)

[Claims] 1. A green laminate in which a plurality of ceramic layers containing SrTiO ₃ as a main component and internal electrode layers are alternately laminated, and further, an ineffective layer having the same composition as the ceramic layer is disposed on the upper and lower layers. Then, a predetermined green chip shape is cut so that the internal electrodes are exposed at the facing end surfaces, then the green chip is degreased, and then the first-layer external electrodes are applied to the exposed internal electrode portions. ,afterwards,
In a fired sheath having an apparent porosity of 50 to 70%, the ceramic layer and the same composition material are calcined in a reducing atmosphere and then mixed with a co-fabric powder adjusted to a certain particle size to perform sheath filling. Stacked in multiple stages and fired in a reducing atmosphere, apply the second layer external electrode on the surface of the first layer external electrode of the obtained sintered body, and simultaneously bake the second layer external electrode in air A method for producing a grain boundary insulated multilayer ceramic element, characterized by reoxidizing a grain boundary of a sintered body. 2. A fired sheath filled with green chips and calcined powder of the same composition and having an apparent porosity of 50 to 70%, and an empty sheath having an opening formed on a side wall surface and having an apparent porosity of 50 to 70%. 2. The method for producing a grain boundary insulated multilayer ceramic device according to claim 1, wherein the components are alternately stacked in a multi-stage manner and reduced and fired.