JP2722457B2 - Manufacturing method of ceramic capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a ceramic capacitor. (Prior Art) Conventionally, in order to manufacture a ceramic capacitor, there has been a method of forming and sintering a ceramic material having a high dielectric constant into a plate shape, and forming electrodes on both main surfaces of the sintered product. In such a ceramic capacitor, the ceramic sintered body is formed as thin as possible in order to increase the capacitance and reduce the size. For example, in the case of a disk-type capacitor which is a typical single-layer ceramic capacitor, the ceramic sintered body is set to be as thin as 100 μm at the minimum with a 50 V rated product. (Problems to be Solved by the Invention) However, in such a conventional ceramic capacitor, the mechanical strength is small because the ceramic sintered body is set thin in order to increase the capacitance. Therefore, the ceramic capacitor may be damaged in a process of manufacturing a ceramic sintered body or a process of forming electrodes on both main surfaces of the ceramic sintered body. In order to solve such a drawback, for example, a paste for forming an electrode is applied to a facing surface of a molded body made of a ceramic composition which does not become a semiconductor even when fired in a reducing atmosphere, and fired in a reducing atmosphere. A method is conceivable. At this time, the paste applied to at least one surface of the molded body is a paste containing a high melting point base metal powder having a melting point higher than the firing temperature of the molded body, a semiconducting agent powder, and a varnish. In such a method, the semiconducting agent diffuses into the molded body during firing, and a semiconductor layer is formed near the surface of the molded body, and a base metal electrode is formed on the surface of the molded body. Since only the portion where the semiconductor agent is not diffused becomes the dielectric layer, the thickness of the dielectric layer is substantially reduced, and a large capacitance can be obtained. However, since the semiconducting agent powder is made of a metal oxide or the like, its specific gravity is greatly different from that of the base metal powder for forming the electrode. Therefore, it is difficult to uniformly disperse the semiconducting agent powder and the base metal powder in the paste. Therefore, there is a possibility that the thickness of the formed semiconductor layer varies, thereby causing variation in the capacitance. In addition, the electrode formed on the surface of the dielectric layer contains a semiconducting agent, and the plating property and the solderability of the electrode may be deteriorated. For example, when the content of the semiconducting agent in the paste is large, the formed electrode contains a large amount of the semiconducting agent, and the electric resistance of the electrode increases. Furthermore, since the electrode contains a semiconducting agent, the plating property and the solderability are poor, and there is a possibility that poor connection with an external circuit may occur. Further, when the content of the semiconducting agent in the paste is small, by mixing with the base metal powder, the semiconducting agent does not sufficiently diffuse into the molded body, so that the semiconductor layer is not formed or the semiconductor layer is not formed. There is a possibility that a problem that a large capacitance cannot be obtained because the thickness is too thin may occur. Therefore, a main object of the present invention is to obtain a ceramic capacitor having an electrode which can reliably obtain a large capacitance, has a large mechanical strength, has good plating properties or solderability, and has a low electric resistance. It is an object of the present invention to provide a method for manufacturing a ceramic capacitor. (Means for Solving the Problems) The first invention provides a step of preparing a ceramic composition which does not turn into a semiconductor even when fired in a reducing atmosphere, and a step of preparing a first paste containing a semiconducting agent and a varnish. A step of preparing, a step of preparing a second paste containing a base metal powder having a melting point higher than the temperature at which the ceramic composition is fired, and a varnish; a step of forming the ceramic composition to form a molded body; A step of applying a first paste on at least one main surface of the body, a step of applying a second paste on the first paste applied on one main surface of the molded body, Applying the second paste on the first paste applied on the surface or on the other main surface of the molded body, and applying the first paste and the molded body on which the second paste is applied in a reducing atmosphere. Firing process And a method for manufacturing a ceramic capacitor. A second invention provides a step of preparing a ceramic composition that does not turn into a semiconductor even when fired in a reducing atmosphere, a step of preparing a paste containing a semiconducting agent and a varnish, and a step of forming and forming the ceramic composition. A step of forming a body, a step of applying a paste on at least one principal surface of the molded body, and a step of firing the molded body to which the paste is applied to obtain a sintered body; Forming an electrode mainly composed of a base metal by a baking method or a thin film forming method such as plating or vapor deposition. (Function) By firing the ceramic molded body, a dielectric layer is formed. At this time, the semiconductor agent contained in the first paste diffuses into the ceramic molded body, so that the vicinity of the surface of the derivative layer is reduced. Become semiconductor. Therefore, only the portion of the ceramic molded body in which the semiconducting agent has not diffused becomes the dielectric layer. Therefore, in this ceramic capacitor, a semiconductor layer is formed between the electrode and the dielectric layer. Furthermore, in the first invention, the first powder containing the semiconducting agent powder is contained.
An electrode is formed on the surface of the molded body by the second paste containing the base metal powder formed separately from the above paste.
The first paste and the second paste are formed separately,
Further, since the semiconductor agent powder and the base metal powder are separately applied to the molded body, they do not mix. Therefore, the dispersion of the semiconducting agent powder in the first paste and the dispersion of the base metal powder in the second paste can be made uniform. (Effect of the Invention) According to the present invention, since the vicinity of the surface of the dielectric layer is made into a semiconductor, the overall thickness of the ceramic capacitor can be increased and the dielectric layer can be formed thin. Therefore, a ceramic capacitor having a large capacitance and a large mechanical strength can be obtained. Further, by separately applying the first paste and the second paste to the compact, the dispersion of the semiconducting agent powder in the first paste and the dispersion of the base metal powder in the second paste are uniform. Become. Therefore, the semiconductor layer can be reliably formed on the derivative layer obtained by firing the molded body. In addition, the thickness can be easily controlled.
In addition, since the second paste constituting the electrode is applied separately from the first paste containing the semiconducting agent, the obtained electrode has sufficiently low electric resistance, and has excellent plating properties and solderability. Electrodes can be formed. Therefore, it is possible to obtain a ceramic capacitor having desired characteristics with little variation in characteristics. The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings. (Example) FIG. 1 is an illustrative view showing one example of a ceramic capacitor formed by the structure method of the present invention. This ceramic capacitor 10 includes a dielectric layer 12. The vicinity of both surfaces of the dielectric layer 12 is turned into a semiconductor, and a semiconductor layer 14 is formed. Further, an electrode 16 is formed on the semiconductor layer 14. In the embodiment of FIG. 1, the semiconductor layer 14 is formed near both surfaces of the dielectric layer 12, but as shown in FIG. 2, the semiconductor layer 14 is formed only near one surface of the dielectric layer 12. You may. Next, a method for manufacturing the ceramic capacitor 10 will be described. First, a non-reducing dielectric ceramic composition is prepared as a raw material. The non-reducing dielectric ceramic composition includes ｛(Ba
_{1-x Ca x) O}} m (Ti 1-y Zr y) O 2 ( However, 1.005 ≦ m
≦ 1.03, 0.02 ≦ x ≦ 0.22, 0 <y ≦ 0.20), ｛(Ba
_{1-xy Ca x Sr y)} O} m · TiO 2 ( provided that, 1.005 ≦ m ≦ 1.
03, 0.02 ≦ x ≦ 0.22, 0.05 ≦ y ≦ 0.35), ｛(Ba _1-xy C
_{a x Sr y) O} m} · (Ti 1-z Zr z) O 2 ( However, 1.005 ≦ m
≦ 1.03, 0.02 ≦ x ≦ 0.22, 0.05 ≦ y ≦ 0.35, 0.00 <z ≦
0.20) and (Ba _x Ca _1-x ) _y ZrO ₃ + zMnO ₂ (however, 0.
00 <x <0.20, 0.85 <y <1.30, 0.005 <z <0.08 (z
Is represented by a general formula such as (Ba _x Ca _1-x ) _y ZrO ₃ with respect to a weight of 1.00)). In these non-reducing dielectric ceramic compositions, firing in a neutral or reducing atmosphere does not reduce the specific resistance and does not increase the dielectric loss. Therefore, even if a base metal such as Ni, Fe, or Co is used as the electrode material, these materials can be fired in a neutral or reducing atmosphere while preventing oxidation of these base metals and reaction with the materials. . Further, a first paste containing a semiconducting agent and a varnish is prepared. As a semiconducting agent, for example, niobium,
A powder selected from lanthanum, cerium and rare earth elements is used. Further, as the semiconducting agent, compounds and oxides containing the above-described elements, for example, Nb ₂ O ₅ , Y ₂ O ₃ , CeO ₂ ,
La ₂ O ₃ , Nb ₂ O ₃ , Sm ₂ O ₃ , Pr ₆ O ₁₁ , Dy ₂ O ₃ or the like may be used. Further, a second paste containing the base metal powder and the varnish is prepared. As the base metal powder, for example, Ni, Fe, Co, C
Metals such as r, Cu, and Al are used. Then, a resin binder is added to the above-mentioned raw materials, and through a process of wet mixing, evaporation and drying, granulation, and press working, for example, a disk-shaped molded body is formed. The first paste is applied to both main surfaces of the molded body. Further, a second paste is applied on the first paste on both main surfaces of the molded body. In order to apply the first paste and the second paste to the molded body, for example, a screen printing method or the like is used. The molded body coated with the first paste and the second paste is fired in a reducing atmosphere such as N ₂ or H ₂ to form a ceramic capacitor. The firing of the compact may be performed in a reducing atmosphere such as Ar, H ₂ or CO ₂ , CO other than N ₂ , H ₂ . In the above-described embodiment, the first paste is applied to both surfaces of the molded body. However, the first paste may be applied to only one surface of the molded body. Further, by adding a barium borosilicate-based or calcium boro-aluminate-based reduction-resistant glass frit to the second paste, the adhesion strength of the electrode can be increased. In the manufacturing method of the second invention, the first paste is applied to both main surfaces of the molded body, and then fired in a reducing atmosphere such as N ₂ or H ₂ to obtain a ceramic sintered body. After the second paste is applied to both main surfaces of the sintered body, heat treatment is performed to obtain a ceramic capacitor having electrodes formed thereon. Further, in order to form metal electrodes on both main surfaces of the dielectric ceramic, a baking method or a thin film forming method such as plating or vapor deposition can be used. In the above-described embodiment, the first paste is applied to both surfaces of the molded body. However, the first paste may be applied to only one surface of the molded body. Experimental Example 1 First, as a non-reducible dielectric ceramic composition of the general formula _{{(Ba 1-x Ca x} ) O} m (Ti 1-y Zr y) O 2 ( where 1.00
A composition represented by 5 ≦ m ≦ 1.03, 0.02 ≦ x ≦ 0.22, 0 <y ≦ 0.20) was prepared. This composition was weighed and mixed as shown in Table 1 to obtain a mixture. This mixture was calcined and then pulverized to obtain a powder raw material. 5 parts by weight of a vinyl acetate resin was added as a binder to this powder raw material, and the mixture was wet-mixed for 16 hours using an agate ball. The wet-mixed material was evaporated to dryness and then granulated to obtain a granulated product. This granulated product is dried by a dry press at a pressure of 2.5 ton / cm ² with a diameter of 12 mm and a thickness of 1 mm to
A compact was obtained by molding to 0.3 mm. On the other hand, a first paste was prepared by mixing a varnish composed of an ethyl cellulose resin and a butyl cellosolve solvent and a semiconducting agent in the ratio shown in Table 1. The semiconducting agent is Nb
₂ O ₅ , Y ₂ O ₃ , CeO ₂ , La ₂ O ₃ , Nb ₂ O ₃ , Sm ₂ O ₃ , Pr ₆ O ₁₁ , Eu ₂ O ₃ , Gd
_It is selected from oxide powders such as ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Tm ₂ O ₃ and Yb ₂ O ₃ . Further, a second paste composed of Ni powder and varnish was prepared. Then, the first paste was applied on both sides or one side of the molded body by a screen printing method, and dried at 150 ° C. for 2 hours. Further, a second paste was applied to both surfaces of the molded body by a screen printing method, and dried at 150 ° C. for 2 hours. The molded body coated with the first paste and the second paste is subjected to an oxygen partial pressure of 10 ^-9 to 10 ^-12 M comprising H ₂ gas and N ₂ gas.
It was fired at 1300 ° C. in a reducing atmosphere of Pa to obtain a sample (capacitor). The capacitance, dielectric loss, dielectric constant and specific resistance of these samples were measured and are shown in Table 2. The capacitance was measured in an atmosphere at 25 ° C. Also,
The dielectric loss was measured at 1kHz, 1V _rms . The dielectric constant was calculated from the capacitance and the shape of the sample. Further, the specific resistance was measured after applying a DC voltage of 500 V for 2 minutes in an atmosphere at 25 ° C. FIG. 1 and FIG.
As shown in the figure, due to the thermal diffusion of the semiconducting agent during firing,
The vicinity of the surface of the dielectric layer 12 is turned into a semiconductor, and a semiconductor layer 14 is formed. That is, the thickness of the dielectric layer 12 is reduced by the semiconductor layer 14. Therefore, the ceramic capacitor 10 of each experimental example has a dielectric constant twice or more as compared with the ceramic capacitors of Sample Nos. 1, 8 and 15 in which the semiconductor layer 14 is not formed, and further has a specific resistance of 10 ¹² Exceeds Ωcm. Moreover, since the ceramic capacitor 10 has a large overall thickness, it has high mechanical strength, thereby eliminating the possibility of deformation, chipping, cracking, and the like. Further, in this ceramic capacitor 10, the dielectric layer 12, the semiconductor layer 14, and the electrode 16 are simultaneously formed by one firing, so that the number of manufacturing steps can be reduced.
Further, since the electrodes are formed using the base metal and its alloy, an inexpensive ceramic capacitor can be obtained. In the method of this experimental example, the first paste containing the semiconducting agent powder and the second paste containing the Ni powder are separately formed and individually applied to the molded body. The dispersion of the semiconducting agent powder and the dispersion of the Ni powder in the second paste can be made uniform. Therefore, the semiconductor layer 14 can be reliably formed, and the thickness of the semiconductor layer 14 can be easily controlled. In the second paste, since the Ni powder and the semiconducting agent powder are not mixed, the electric resistance of the electrode 16 is sufficiently low, and the electrode 16 has excellent plating properties and solderability. Experimental Example 2 A molded body was obtained in the same manner as in Experimental Example 1. Further, a first paste mixed in the ratio shown in Table 3 by the same manufacturing method shown in Experimental Example 1 was prepared. Then, the first paste was applied on both sides or one side of the molded body by a screen printing method, and dried at 150 ° C. for 2 hours. Next, the formed body to which the first paste was applied was fired at 1300 ° C. in a reducing atmosphere composed of H ₂ gas and N ₂ gas and having an oxygen partial pressure of 10 ⁻⁹ to 10 ⁻¹² MPa. A paste composed of Al powder and varnish was applied to both main surfaces of the obtained dielectric ceramic by a screen printing method, and baked at 750 ° C. in a neutral atmosphere to form electrodes. In addition, a sample in which Ni electrodes were formed on both main surfaces of the dielectric ceramic by electroless plating was prepared. The capacitance, dielectric loss, dielectric constant and specific resistance of these samples were measured and are shown in Table 4. However, Sample Nos. 22, 23 and 24 are Al electrodes, Sample Nos. 25 and 26
Indicates a sample by Ni plating. The capacitance was measured in an atmosphere at 25 ° C. Also,
The dielectric loss was measured at 1kHz, 1V _rms . The dielectric constant was calculated from the capacitance and the shape of the sample. Further, the specific resistance was measured after applying a DC voltage of 500 V for 2 minutes in an atmosphere at 25 ° C. As shown in FIGS. 1 and 2, in this ceramic capacitor 10, due to the thermal diffusion of the semiconducting agent during firing,
The vicinity of the surface of the dielectric layer 12 is turned into a semiconductor, and a semiconductor layer 14 is formed. That is, the thickness of the dielectric layer 12 is reduced by the semiconductor layer 14. Therefore, in the ceramic capacitors of each experimental example,
Compared to the ceramic capacitors of the same composition of Sample Nos. 22 and 25 where the semiconductor layer 14 was not formed, the dielectric constant was 2
More than twice, and its specific resistance exceeds 10 ¹² Ωcm.
In addition, since the ceramic capacitor 10 has a large overall thickness, it has high mechanical strength, thereby eliminating the possibility of deformation, chipping, cracking, and the like. Further, since the electrodes are formed using the base metal and its alloy, an inexpensive ceramic capacitor can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an illustrative view showing one embodiment of the present invention. FIG. 2 is an illustrative view showing another embodiment of the present invention. In the figure, 10 is a ceramic capacitor, 12 is a dielectric layer, 14 is a semiconductor layer, and 16 is an electrode.

Claims (1)

(57) [Claims] A step of preparing a ceramic composition which does not turn into a semiconductor even when fired in a reducing atmosphere; a step of preparing a first paste containing a semiconducting agent and a varnish; having a melting point higher than the temperature at which the ceramic composition is fired A step of preparing a second paste containing a base metal powder and a varnish; a step of molding the ceramic composition to form a molded body; a step of applying the first paste on at least one main surface of the molded body Applying the second paste on the first paste applied on one main surface of the molded body; applying the second paste on the other main surface of the molded body or the other main surface of the molded body. Applying the second paste on the first paste, and sintering the molded body on which the first paste and the second paste are applied in a reducing atmosphere. Including the extent, method of manufacturing the ceramic capacitor. 2. A step of preparing a ceramic composition that does not turn into a semiconductor even when fired in a reducing atmosphere; a step of preparing a paste containing a semiconducting agent and a varnish; a step of forming the ceramic composition to form a molded body; A step of applying the paste on at least one main surface of a molded body; a step of firing the molded body to which the paste is applied to obtain a sintered body; and a base metal mainly on both main surfaces of the sintered body. A method for manufacturing a ceramic capacitor, including a step of forming electrodes by a baking method or a thin film forming method such as plating or vapor deposition.