JP3153410B2 - Manufacturing method of dielectric ceramics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

It relates manufacturing <br/> production method of the present invention is the dielectric ceramic BACKGROUND OF THE, and more particularly relates to a method for manufacturing a dielectric ceramics to be used as a ceramic type capacitor of the electronic components and electronic equipment.

[0002]

2. Description of the Related Art In recent years, with the increase in speed of electronic devices and the frequency of communication devices, the frequency of signals used in electronic components has been increasing year by year. Accordingly, there is a demand for a ceramic circuit board, an LSI package, and the like used for a communication device, a large-sized computer, and the like, which are compatible with the high frequency.

As a product corresponding to such a high frequency, for example, an LSI provided with a decoupling capacitor in order to effectively remove switching noise and the like generated in an LSI as a logic circuit with a high operating frequency. Package or ceramic multilayer wiring board (hereinafter referred to as ceramic multilayer wiring board including both LSI package and ceramic multilayer wiring board)
Etc. have been proposed.

Conventionally, as a method of equipping a ceramic multilayer wiring board with a decoupling capacitor, there are a method of mounting a capacitor outside the ceramic multilayer wiring board and a method of forming a capacitor inside the ceramic multilayer wiring board.

[0005] When a capacitor is mounted outside a ceramic multilayer wiring board, wiring for mounting the capacitor must be routed inside the ceramic multilayer wiring board, and the wiring must be drawn out to mount the capacitor.

In such a method of mounting a capacitor externally, the material and the like of the capacitor are not limited, and a capacitor satisfying required characteristics may be selected from various ceramic capacitors and the like which have been used so far. It has the advantage that. However, in this method,
In order to attach an external capacitor, extra wiring must be drawn and formed, and a process for that is necessary, and there is a problem that an extra space for attaching an external capacitor is required.

On the other hand, when manufacturing a ceramic multilayer wiring board having a capacitor therein, a green sheet of ceramic powder, which is a raw material of a capacitor, is sandwiched inside a green sheet laminate before firing, and this laminate is fired. By doing so, a ceramic capacitor was formed inside the ceramic multilayer wiring board. In this method, a capacitor can be formed at the same time when the alumina multilayer wiring board is manufactured, so that the manufacturing process can be simplified, and there is no need to secure extra space outside.
There is a great advantage that the size can be reduced.

Conventionally, TiO ₂ , CaTiO ₃ , SrTiO _{3 and the} like have been known as materials for ceramic capacitors, and recently, MgTiO having improved temperature characteristics has been known.
_3- CaTiO ₃ , Ba (Mg, Ta, X) O ₃ , Ba
_{(Zn, Nb) O 3 -Ba} (Zn, Ta) O 3, BaO
—PbO—Nb ₂ O ₃ —TiO ₂ , BaO—Sm ₂ O ₃
Capacitor using the ceramic-based material such as -5TiO ₂ are known.

However, in the production of an alumina multilayer wiring board, an electric circuit is formed by simultaneously firing a conductive metal such as W or Mo and alumina powder, and a reducing atmosphere is used so as not to oxidize these metals. Below, 1500
The firing was performed at a high temperature of 1650 ° C.

Therefore, when the above-described conventionally used green sheets of ceramics are laminated and fired, hydrogen acts on these materials during firing in the above-described high-temperature reducing atmosphere. As a result, reactions such as conversion into a semiconductor or reduction proceed, resulting in short-circuiting or deterioration of the material inside the capacitor, which makes it difficult to form a ceramic capacitor layer inside the alumina multilayer wiring board. Was.

On the other hand, it has been known for a long time that the dielectric constant per unit volume can be improved by dispersing a metal in ceramics. Capacitors have been proposed.

Japanese Patent Application Laid-Open No. 3-87091 discloses that an alumina as a base material,
An alumina multilayer wiring board in which a dielectric layer mainly composed of at least one of Mo and W by weight is formed is disclosed.

FIG. 1 is a cross-sectional view schematically showing the alumina multilayer wiring board described in the above-mentioned publication. In the figure, reference numeral 12 denotes a high dielectric layer.

In this alumina multilayer wiring board, M
A high dielectric layer 12 in which a metal powder such as o is dispersed is formed. On both surfaces (upper and lower surfaces) of the high dielectric layer 12, an internal electrode layer 13 is formed. The capacitor layer 14 is constituted by the layer 13. Further, on both sides (upper and lower surfaces) of the capacitor layer 14, the insulator layer 11 made of alumina ceramics is formed. The internal electrode layers 1 formed on both surfaces of the high dielectric layer 12
3 is connected to the surface electrode 16 through the through hole 15. Therefore, when electronic components and the like are mounted on the alumina multilayer wiring board, the internal capacitor layer 14 functions as a decoupling capacitor, and noise and the like can be effectively removed.

Next, a method for manufacturing the alumina multilayer wiring board will be described below. First, a green powder for a capacitor is prepared by mixing alumina powder, metal powder such as Mo, a sintering aid, and the like, followed by molding and drying.
Next, W is placed on the upper and lower surfaces of the capacitor green sheet, respectively.
Alternatively, a conductive paste mainly containing a high melting point metal such as Mo is applied or printed to form a layer for an internal electrode. Further, an alumina green sheet having through holes and the like formed thereon is laminated above and below the capacitor green sheet via an internal electrode layer, and the conductive paste is poured into the through holes and fired. A layer to be the surface electrode layer 16 is formed on a predetermined surface of the alumina green sheet.

[0016]

As described above, in the above-described method for manufacturing an alumina multilayer wiring board, since the internal capacitor layer 14 is formed at the same time when the wiring board is manufactured, the ceramic multilayer wiring board or the like is later formed. There is no need to provide an extra step of attaching a capacitor to the device, and there is no need for extra space for attaching the capacitor.

However, in the alumina multilayer wiring board manufactured by the above method, the capacitance of the capacitor layer 14 is not so large because the formed high dielectric layer 12 has a small dielectric constant, and the performance as a decoupling capacitor is not increased. Was not enough.

That is, in the conventional method, the high dielectric layer 12
When a large amount of metal is added in order to increase the dielectric constant of the capacitor layer 14, a short circuit occurs inside the capacitor layer 14. Therefore, there was a problem that the amount of metal added in the raw material powder could not be increased so much that the capacity of the internal capacitor could not be increased.

[0019] The present invention has been made in view of such problems, the metal content is more than ever, to provide a more manufacturable method of large dielectric does not occur short while having a constant dielectric ceramic The purpose is.

[0020]

[0021]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
The method for producing a dielectric ceramic according to the present invention is a method in which a water-soluble metal acid or metal salt, a ceramic insulator powder and water are mixed in a slurry, and dried,
It is characterized in that it is molded and fired in a reducing atmosphere ( 1 ).

The method for producing a dielectric ceramic according to the present invention is the method for producing a dielectric ceramic according to the above ( 1 ), wherein Mo acid or a salt thereof is used as a water-soluble metal acid, and the ceramic insulating powder is used. Is characterized by using alumina ( 2 ).

[0023]

First, the method for producing the dielectric ceramic described in the above ( 1 ) will be described.

In the method for producing a dielectric ceramic according to the above ( 1 ), a water-soluble metal acid or metal salt is selected and dissolved or uniformly dispersed in water by utilizing its hydrophilicity and solubility. Then, a slurry is formed by adding the ceramic insulating powder, and the slurry is uniformly mixed with the insulating powder. Then, in order to maintain the uniform mixing state, the slurry is once dried to obtain a fine powder of the metal acid or its salt, and then lightly pulverized so as to be easily formed.

Then, according to the usual process for manufacturing a ceramic sintered body, the powder lightly pulverized in the above step is mixed with an organic binder, a solvent and the like, and molded by a doctor blade method or a press method. Thereafter, firing is performed to produce a dielectric ceramic.

As a ceramic insulator serving as a base material of the dielectric ceramic, for example, alumina, aluminum nitride, zirconium oxide and the like can be mentioned. This ceramic insulator is prepared by heating the raw material powder at 1400 to 1800 ° C.
It is obtained by firing at about the temperature.

Therefore, the water-soluble metal acid or metal salt is a high-melting-point metal acid or salt that can withstand such high-temperature firing conditions, and does not sublime or evaporate during firing. Need to be. From such a point, as the metal acid, for example, Mo acid (H ₂ MoO ₄ , H ₂ Mo
O ₄ · H ₂ O), W acid (H ₂ WO ₄ , H ₂ WO ₄ · H ₂
O) and the like are preferable.
Ammonium oxyacid ((NH ₄ ) ₆ [Mo ₇ O ₂₄ ] .4H
_{2 O, 3 (NH 4)} 2 · 7MoO 3 · 4H 2 O), ammonium W acid ((NH _{4) 10} H ₁₀ [W ₁₂ O _46] · 6H ₂
O, 5 (NH ₄ ) ₂ .12WO ₃ .11H ₂ O) are preferred.

Since the dielectric ceramics obtained by the above method is excellent in dispersibility of the metal fine powder, even if more metal is dispersed as compared with the conventional one, the dispersed metals come into contact with each other, As a result, the electrodes formed on both surfaces are not short-circuited, and the dielectric ceramic has a higher dielectric constant.

In particular, in the case of dielectric ceramics in which alumina is used as a base material and Mo metal is dispersed, the short circuit does not occur even if Mo is dispersed as a metal element in the alumina ceramics by 15% by weight or more. Its relative dielectric constant is 20
As described above, an unprecedented high dielectric constant ceramic is realized.

In the alumina multilayer wiring board having the structure shown in FIG. 1 and using such a material having a high dielectric constant, an alumina multilayer wiring board having a capacitor layer 14 having a larger capacity than the conventional one is obtained. Further, when the alumina multilayer wiring board including the capacitor layer 14 having the same capacity is used, since the capacitor layer 14 is smaller than before, the volume of the entire alumina multilayer wiring board can be reduced.

[0032]

[0033]

SUMMARY OF] According to the method of manufacturing the dielectric ceramics of the above configuration (1), after an acid or a metal salt and a ceramic insulator powder and water metal having a water-soluble mixed slurry, dried, Since it is molded and fired in a reducing atmosphere, a dielectric ceramic in which the metal generated from the acid or metal salt of the metal is dispersed very uniformly is produced. Therefore, even if the resulting dielectric ceramic contains a larger amount of the metal formed from the metal acid or metal salt than before, the dispersed metals may come into contact with each other, thereby short-circuiting the electrodes formed on both surfaces. Instead, a dielectric ceramic having a high dielectric constant is manufactured.

According to the method ( 2 ) for producing a dielectric ceramic having the above structure, in the method for producing a dielectric ceramic described in the above ( 1 ), Mo acid or a salt thereof is used as a water-soluble metal acid, Since alumina is used as the ceramic insulating powder, a larger amount of M is used than in the conventional method, similarly to the method of manufacturing a dielectric ceramic described in ( 1 ) above.
A high-permittivity alumina ceramic in which o is dispersed is produced.

[0035]

[0036]

Examples and Comparative Examples Hereinafter, examples of the method for producing a dielectric ceramic according to the present invention will be described.

First, alumina raw material powder having an average particle diameter of 1 μm, Mo acid (H ₂ MoO ₄ .2H ₂ O) powder, a sintering aid and pure water were weighed so as to have the ratio shown in Table 1 below. First, Mo acid powder was dissolved in pure water. Next, the weighed alumina raw material powder and the sintering aid were put into this solution, kneaded well by a ball mill for 24 hours, and then dried.

Then, a crushing treatment was carried out in order to loosen the powders formed into a mass by drying. Next, butyral resin as a binder, dibutyl phthalate (DBP) as a plasticizer, and xylene as a solvent are added to the crushed powder, wet-mixed by a ball mill for 24 hours to form a slurry, and then a doctor blade method is used. Into tape. Next, the tape was sufficiently dried at 150 ° C. in the air, and then cut to a predetermined length to produce an alumina green sheet. After that, a conductive paste using W as an electrode material is printed on the upper and lower sides of the alumina green sheet, and is placed in a nitrogen atmosphere containing 10 vol% of hydrogen.
It was fired at 0 ° C. for 1 hour to produce a ceramic capacitor. In order to measure the relative permittivity and the short-circuit rate, 50 samples under the same conditions were manufactured.

The relative dielectric constant and short circuit rate of the manufactured ceramic capacitor are shown in Table 1 below together with the mixing ratio of alumina powder and Mo acid powder. The relative dielectric constant shown in Table 1 is the average value of the relative dielectric constants of the manufactured samples that did not cause a short circuit, and the short circuit ratio is the ratio of the short circuit to the total number of manufactured samples.

[0040]

[Table 1]

On the other hand, as a comparative example, a ceramic capacitor was manufactured by the following method. That is, the Mo powder having an average particle diameter of 5 μm and the alumina powder used in the examples were wet-mixed at a ratio shown in Table 3 below, dried, and subjected to a crushing treatment. Thereafter, a ceramic capacitor was manufactured under the same conditions as in the above example, and the relative permittivity and the short-circuit rate were determined in the same manner. Alumina powder and Mo
The mixing ratio with the powder and the obtained relative permittivity and short-circuit rate are shown in Table 2 below.

[0042]

[Table 2]

As is clear from the results shown in Tables 2 and 3, in the ceramic capacitor according to the comparative example, when the content as Mo was 20 wt% or more, a short circuit occurred. In the ceramic capacitor according to the above, the content as Mo is about 26 wt.
%, No short circuit occurs, and short circuit occurs only when the Mo content becomes about 30 wt%. Therefore, in the ceramic capacitor according to the example, a maximum value of about 32 can be used as the maximum value of the relative permittivity, whereas in the ceramic capacitor according to the comparative example, only a maximum value of about 18 is used. Can not be used.

As described above, in the ceramic capacitor according to the embodiment, a ceramic capacitor having a high dielectric constant can be manufactured. Therefore, when a ceramic laminated substrate is manufactured using this capacitor material, a A ceramic multilayer wiring board on which a large-capacity ceramic capacitor is formed can be obtained.

Next, a method for manufacturing the alumina multilayer wiring board according to the embodiment will be described.

First, green sheets for dielectric ceramics were prepared in the same manner as in the above embodiment, and M and G were respectively placed on the upper and lower surfaces of the green sheets for dielectric ceramics.
An internal electrode layer was formed by applying a conductive paste containing o as a main component.

On the other hand, a green sheet of alumina ceramics was prepared in the same manner as in the above embodiment except that Mo acid was not added, and the green sheet was subjected to processing such as formation of through holes. The alumina green sheets formed with the through holes and the like are laminated on the upper and lower sides of the capacitor green sheet via the internal electrode layer, and the conductive paste is poured into the through holes to produce a green sheet laminate. An electrode layer was formed on the surface of the substrate to complete a green sheet laminate for an alumina multilayer wiring board.

Next, the green sheet laminate was fired at 1550 ° C. for 1 hour in a nitrogen atmosphere containing 10 vol% of hydrogen to complete the production of an alumina multilayer wiring board.

With respect to the obtained alumina multilayer wiring board,
When the relative dielectric constant of the capacitor layer formed inside was measured, the ceramic capacitor manufactured by adding the same amount of Mo acid in the above embodiment and the alumina multilayer wiring board according to the present embodiment had the same capacitance. I was able to confirm that.

[0050]

[0051]

Effects of the Invention] According to the method of manufacturing the dielectric ceramics of the above configuration (1), a metal acid or metal salt and the ceramic insulator powder and water with a water-soluble mixed slurry and dried Thereafter, since the metal is molded and fired in a reducing atmosphere, it is possible to manufacture a dielectric ceramic in which the metal generated from the acid or metal salt of the metal is dispersed very uniformly. Therefore, even if the obtained dielectric ceramic contains a larger amount of the metal formed from the metal acid or metal salt than before, the dispersed metals come into contact with each other, thereby short-circuiting the electrodes formed on both surfaces. Thus, a dielectric ceramic having a high dielectric constant can be provided.

According to the method ( 2 ) for producing a dielectric ceramic having the above structure, the method for producing a dielectric ceramic according to the above ( 1 ) uses Mo acid or a salt thereof as a water-soluble metal acid. Since alumina is used as the ceramic insulating powder, a larger amount of M is used than in the conventional method, similarly to the method of manufacturing a dielectric ceramic described in ( 1 ) above.
It is possible to provide a high dielectric constant alumina ceramic in which o is dispersed.

[0053]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a configuration of an alumina multilayer wiring board.

Continued on the front page (72) Inventor Toshihiko Kubo 4-5-33 Kitahama, Chuo-ku, Osaka-shi, Osaka Inside Sumitomo Metal Industries, Ltd. (72) Inventor Masaya Hashimoto 4-5-33 Kitahama, Chuo-ku, Osaka-shi, Osaka (56) References JP-A-3-87091 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 35/111

Claims (2)

(57) [Claims] 1. A water-soluble metal acid or metal salt, a ceramic insulator powder and water are mixed in a slurry, dried, molded, and fired in a reducing atmosphere. Of producing dielectric ceramics. 2. Using the Mo acid or a salt thereof as an acid of a metal having a water-soluble, manufacturing method of a dielectric ceramic according to claim 1, wherein the alumina is used as the ceramic insulator powder.