JP3246267B2 - Manufacturing method of grain boundary insulated multilayer ceramic component - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a grain boundary insulating multilayer ceramic component used for various electronic devices.

[0002]

2. Description of the Related Art In recent years, ICs, LSIs, and the like have been widely used for miniaturization and high performance of electronic equipment, and accordingly, film capacitors which have been used for securing noise immunity of electronic equipment. Also, demands for miniaturization and high performance of multilayer ceramic capacitors, semiconductor ceramic capacitors, and the like are increasing.

Above all, grain boundary insulating ceramics containing SrTiO ₃ as a main component have good noise absorption, are stable with respect to temperature and frequency, and have a varistor function against pulses and static electricity. Some are available, and their use is expanding.

Conventionally, a grain boundary insulated multilayer ceramic component has, as shown in FIG. 1, a ceramic layer 1 containing SrTiO ₃ as a main component and an internal electrode 2 containing an element which promotes semiconductor conversion are alternately laminated. After forming an ineffective layer 3 having the same composition as the ceramic layer 1 above and below, and forming an inner external electrode 4,
After degreasing, these laminates are randomly packed and subjected to reduction firing, and then re-oxidized to form outer external electrodes 5 to obtain a grain boundary insulated multilayer ceramic component as shown in FIG. Was.

[0005]

However, in the above-mentioned conventional method, the ceramic layer 1 near the internal electrode 2 can be easily densified. In particular, in the case of highly laminated products and large-sized products, it is difficult to control the structure of the outer layer portion of the laminate separated from the internal electrode 2, particularly the structure of the ineffective layer 3, resulting in unevenness in the denseness. Had occurred. Therefore, the oxidation state after re-oxidation varies, and the electrical characteristics also vary, so that there is a problem that desired electrical characteristics cannot be obtained.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a grain boundary insulated multilayer ceramic component having small variations in electrical characteristics and high reproducibility of characteristics.

[0007]

According to the present invention, a plurality of ceramic layers containing SrTiO ₃ as a main component and a plurality of internal electrodes are alternately provided in an upper layer and a lower layer. The apparent porosity is 50 to 70%, which is air-permeable in a sealed state by laminating the laminated bodies so that
Using the sinter of the above, the laminate is placed in the sinter.
Fill with a sheath so that they do not overlap, and then pack the laminate
Piled fired sheaths in multiple stages and uneven residue in the sheaths
Reduction while replacing oxygen with reducing gas through pores of sheath
Firing to uniformly fire the ceramic structure in the outer layer of the laminate
Knotting is performed, and then the laminate is reoxidized. Thereafter, an external electrode is formed on an end surface of the laminate where the internal electrode is exposed.

[0008]

By using the above method, when the firing atmosphere is uniform and reoxidation is performed, the oxygen adsorption reaction inside the laminate is performed uniformly, so that the reactive layer is effective regardless of the high laminate product or the large product. Can suppress re-oxidation variation due to the group of denseness, and can provide a grain boundary insulated multilayer ceramic component with small variation in electrical characteristics and high reproducibility of characteristics.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a grain boundary insulated multilayer ceramic component, and FIG. 2 is a view showing a manufacturing process thereof.

Next, the manufacturing method will be described below.
First, Nb ₂ O ₅ , which is a semiconducting substance, was added to 97.1 mol% of SrTiO _{3 as} a main component, and 0.5 mol% of Ta ₂ O ₅
0.5 mol%, and 0.4 m of sintering aid MnO ₂
ol%, 1.0 mol% of SiO ₂ and 0.5 mol% of Na ₂ SiO ₃ as an oxidation promoter (7),
These are mixed (8) and ground (9). Then, 11
The calcination (10) is performed at 00 ° C. and the pulverization (11) is performed again. The powder thus obtained is mixed with an organic solvent and a binder to prepare a slurry. Further, sheet forming (12) is performed by a doctor blade method, and the sheet is cut into a predetermined size.

The cut green sheet is provided with an internal electrode 2
Then, a predetermined number of layers are printed (13) and laminated (14) using a paste whose main component is NiO so that the internal electrodes 2 are alternately exposed at the end faces facing each other, and then pressure-bonded. At this time, a predetermined number of green sheets on which the internal electrodes 2 are not formed are laminated on the upper layer and the lower layer
Is formed. After that, it is cut and degreased (15). After degreasing (15), chamfering is performed, the inner outer electrode 4 is formed with the same paste as the inner electrode 2 (16), and reduction firing (17) is performed.

In the reduction calcination (17), calcination is performed at 1200 ° C. in a mixed gas of N ₂ and H _2. At this time, the laminate produced as described above is sealed in a closed state with apparent pores. Using a baking sheath having a rate of 50 to 70%, the layers are packed in a sheath so that the laminates do not overlap each other, stacked in multiple stages, and then reduced and fired while controlling the flow conditions of the reducing gas ( 17) is performed. in this case,
By uniformly applying the reducing gas to the surface of the green chip, the supply of oxygen to the surface portion of the fired body, that is, the supply of oxygen to the ineffective layer 3 can be uniformly controlled, thereby densifying the ceramics near the surface layer of the ineffective layer 3. Is suppressed, the invalid layer 3
Of the outer layer portion 6 was substantially uniform. At this time, in an airtight state, and apparent porosity is 50 to
By performing reduction firing using a 70% firing sheath, the flow state of the reducing gas in the firing sheath is made uniform. Thereafter, re-oxidation (18) is performed at 850 ° C. in the air to form the outer external electrode 5 made of Ag (19), and then baking is performed.

Finally, the varistor voltage at _{0.1 mA} (V _{0.1 mA} ) and the capacitance at 1 KHz (C1 KHz)
Is measured.

The varistor voltage, the voltage variation, and the varistor of the grain boundary insulated multilayer ceramic component manufactured as described above are changed when the shape of the laminated body in the sheath is changed.
The respective electric characteristics of capacitance and capacitance variation (Table 1) are shown.

[0015]

[Table 1]

As is clear from Table 1, as compared with a case where the laminated bodies are randomly overlapped with each other and the laminated bodies are overlapped with each other, the laminated bodies are molded so that the laminated bodies do not overlap each other. In the element, each of the electrical characteristics is significantly improved as compared with the conventional case. At this time, in the element obtained by random padding, the variation in the capacity is increased, which indicates that the variation in the reduction state of each fired body is large.

Further, the fired sheath having an apparent porosity of 50 to 70% in a sealed state and the fired sheath having an opening at an upper end and having an apparent porosity of 50 to 70% used in the above embodiment are used. Of these, the sheath was packed in a sealed sheath so as not to overlap, and these were alternately stacked in multiple stages, and then reduction firing (17) was carried out, further confirming the variation reduction effect. . This effect is also shown in (Table 1).

In this case, this effect is obtained by making the reduced state of the bottom surface and the upper surface of the sealed sheath filled with the sheath more uniform.

In this embodiment, by stacking the fired sheaves, the bottom of the fired shed arranged in the upper stage serves as a lid of the fired shed arranged in the lower stage. Although the top of the firing sheath is covered with a lid, the material and the thickness of the lid are preferably the same as the material of the firing sheath and the thickness of the bottom portion because the atmosphere can be kept uniform.

In the present embodiment, the opening provided in the firing sheath has a concave upper end portion, but other than the upper end portion as long as the gas atmosphere becomes uniform. The same effect can be obtained regardless of which part the opening is provided.

[0021]

As described above, according to the present invention, during reduction firing,
The fired sheath to be used is used in a sealed state and has an apparent porosity of 50 to 70%, and is randomly packed so that the laminated bodies do not overlap with each other. This realizes a uniform ceramic structure after firing.

As a result, regardless of whether the product is a high-lamination product or a large-sized product, a re-oxidation variation can be suppressed, and a grain boundary insulated multilayer ceramic component with little variation in electrical characteristics and high reproducibility of the characteristics is provided. Is what you can do.

[Brief description of the drawings]

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic layer 2 Internal electrode 3 Invalid layer 4 Inner external electrode 5 Outer external electrode 6 Outer layer part of invalid layer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01G 4/12 H01G 13/00-13/06

Claims (2)

(57) [Claims] 1. A laminated body in which a plurality of ceramic layers containing SrTiO ₃ as a main component and a plurality of internal electrodes are alternately laminated so that the ceramic layers are arranged in an upper layer and a lower layer.
A fired sagger having an apparent porosity of 50 to 70%, which is air-permeable in a closed state, is stuffed into the sinter so that the laminates do not overlap, and then the sinter is filled with the laminate. Is accumulated in multiple stages, resulting in uneven residual oxygen in the sheath.
Calcination while replacing with the reducing gas through the pores of the sheath
To uniformly sinter the ceramic structure of the outer layer of the laminate.
And then re-oxidizing the laminate, and thereafter forming an external electrode on an end surface of the laminate where the internal electrode is exposed. 2. An apparent porosity of 5 having air permeability in a sealed state.
The laminated body is overlapped in the first fired sheath by utilizing a first fired sheath having an opening of 0 to 70% and a second fired sheath having an opening having an apparent porosity of 50 to 70%. After stuffing so that they do not fit together, they are alternately stacked in multiple stages to reduce the uneven residual oxygen in the pod through the pores of the pod.
2. The method for producing a grain boundary insulated multilayer ceramic component according to claim 1, wherein reduction firing is performed while replacing with a gas .