JP2002274940A - Raw material powder for ceramics, method for manufacturing the same, ceramic and method for manufacturing the same, and method for manufacturing laminated ceramic electronic part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing raw material powders for ceramics such as semiconductors in which resistance is low and a wide range of the Ba/Ti ratio with a sufficient change range of the resistance can be obtained compared to a conventional material. SOLUTION: The method includes a mixing process to mix source material powder containing at least barium and titanium to obtain mixture powder, a calcination process to calcine the mixture powder at specified temperature and pulverizing to obtain calcined powder, a cleaning process to clean the calcined powder, and a correcting process for the composition ratio to replenish the calcined powder with barium after the cleaning process, and the calcination process is repeated for a plurality of times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a ceramic having a positive resistance temperature characteristic obtained by reducing and firing a barium titanate-based ceramic material and then performing a re-oxidation treatment. And a ceramic layer,
For example, the present invention relates to a method for producing a raw material powder for porcelain used in a laminated positive temperature coefficient thermistor, a method for producing a porcelain made of the raw material powder obtained thereby, and a method for producing a laminated ceramic electronic component using the porcelain. is there.

[0002]

2. Description of the Related Art Conventionally, barium titanate-based semiconductor porcelain has a positive resistance-temperature characteristic (PTC (positive temperature characteristic); coefficient
(Positive temperature coefficient) characteristic, and is widely used for applications such as temperature control, overcurrent protection, and constant-temperature heat generation.

There is a demand for low resistance at room temperature of electronic components for overcurrent protection used for circuits. In particular, for a personal computer peripheral device compatible with a USB (Universal Serial Bus), a small, low-resistance, high-voltage semiconductor ceramic electronic component is urgently desired.

To meet such a demand, a laminated semiconductor ceramic electronic component is disclosed in Japanese Patent Laid-Open No. 57-608.
No. 02 is disclosed. This laminated semiconductor ceramic component is obtained by alternately laminating a semiconductor ceramic layer containing barium titanate as a main component and an internal electrode layer made of a Pt-Pd (platinum-palladium) alloy and integrally firing. With such a laminated structure, the electrode area of the semiconductor ceramic electronic component is greatly increased, and the electronic component itself can be reduced in size. However, in this multilayer semiconductor ceramic electronic component,
Ohmic contact between the internal electrode and the semiconductor ceramic layer is hardly obtained, and there is a problem that the room temperature resistance value is significantly increased.

Japanese Patent Laid-Open Publication No. 6-151103 discloses a multilayer semiconductor ceramic electronic component using a Ni (nickel) -based metal as an internal electrode material instead of a Pt-Pd alloy. An internal electrode material using a Ni-based metal can achieve an ohmic contact with a semiconductor ceramic, so that an increase in room temperature resistance can be prevented. However, since this laminated semiconductor ceramic element is oxidized by normal firing in the air, it is necessary to perform a re-oxidation process at a temperature at which the Ni-based metal is not oxidized after firing in a reducing atmosphere once. is necessary.

[0006]

However, the resistance value of the laminated semiconductor ceramic device obtained through this kind of reduction firing / reoxidation process is based on the barium titanate-based material Ba (forming the semiconductor ceramic layer). Barium) site / Ti (titanium) site ratio (hereinafter, “Ba / Ti
Ratio) is very sensitive, and the range of the Ba / Ti ratio in which a room temperature resistance value that does not have a practical problem is obtained becomes very narrow. Therefore, Ba / T
Even a slight error in the i-ratio was not allowed, and its adjustment was very difficult.

The present invention has been made to solve the above problems, and an object of the present invention is to increase the Ba / Ti ratio, which is low in resistance and has a sufficient resistance change width, as compared with the conventional one. An object of the present invention is to provide a method for producing a raw material powder for porcelain, a method for producing a porcelain made of the raw material powder for porcelain obtained thereby, and a method for producing a multilayer ceramic electronic component using the porcelain.

[0008]

Means for Solving the Problems In order to achieve the above object, the present inventor has conducted intensive studies, and as a result, by using a raw material powder produced by a specific manufacturing method, a small and low-resistance material has been obtained. The present inventors have found that a laminated semiconductor ceramic element having a sufficient resistance change width and exhibiting characteristics in a wide range of Ba / Ti ratio can be obtained, and the present invention has been accomplished.

In order to solve the above-mentioned problems, a method for producing a raw material powder for porcelain according to the present invention comprises mixing a raw material powder containing at least barium and titanium to obtain a mixed powder; After calcining at a temperature, pulverizing, the first calcining step to obtain a calcined powder, and calcining the calcined powder obtained in the previous calcining step at a predetermined temperature, then pulverizing,
And a second calcining step of obtaining a calcined powder, and wherein the second calcining step is performed one or more times.

In order to solve the above-mentioned problems, the method for producing a raw material powder for porcelain of the present invention further comprises a washing step of washing the calcined powder, and after the washing step, barium is added to the calcined powder. And replenishing the composition ratio.

The method for producing a raw material powder for porcelain of the present invention is characterized in that in order to solve the above-mentioned problems, the second calcination step is further performed once.

Further, in order to solve the above-mentioned problems, the method for producing a raw material powder for porcelain according to the present invention comprises mixing a raw material powder containing at least barium and titanium to obtain a mixed powder; After calcining at a predetermined temperature,
A calcining step of pulverizing to obtain a calcined powder, comprising: a washing step of washing the calcined powder; and after the washing step, barium is added to the calcined powder. And correcting the composition ratio.

[0013] In order to solve the above problems, the raw material powder for porcelain of the present invention is characterized by being obtained by the above-mentioned method for producing raw material powder for porcelain.

As described above, in the method for producing a raw material powder for porcelain according to the present invention, calcination is performed at least twice. further,
After washing the calcined powder obtained, barium is replenished.

Thus, by using the porcelain raw material powder obtained by the above-described method for producing a porcelain raw material powder, the Ba / Ti ratio having a low resistance and an extremely wide range of resistance change can be made wider than that of the conventional one. The porcelain which can be obtained is obtained. For example,
Room temperature resistance value is 0.2Ω or less and resistance change width is 3.5
It is possible to manufacture a laminated semiconductor ceramic element having characteristics of an order of magnitude or more. Therefore, it is possible to greatly promote the practical use of overcurrent protection elements used for circuits, especially for USB-compatible personal computer peripherals.

In order to solve the above-mentioned problems, the method for manufacturing porcelain according to the present invention uses the raw material powder for porcelain obtained by the above-described method for manufacturing raw material porcelain as a main material, and then forms and fires. It is characterized by:

According to another aspect of the present invention, there is provided a porcelain obtained by the above-described method of manufacturing a porcelain.

By using the raw material powder for porcelain obtained by the above-mentioned method for producing raw material powder for porcelain as a main material by the above method, it is small, low-resistance, has a sufficient resistance change width, and A porcelain that can be used for a laminated semiconductor ceramic element or the like that exhibits characteristics in a wide range of Ba / Ti ratio can be obtained.

Further, in order to solve the above-mentioned problems, a method of manufacturing a multilayer ceramic electronic component according to the present invention provides a ceramic material mainly comprising a porcelain raw material powder obtained by the above-described porcelain raw material powder manufacturing method. Stacking a predetermined number of layers and internal electrode layers made of a conductive paste to obtain a laminate, firing the laminate in a reducing atmosphere, and then performing a re-oxidation treatment in an oxidizing atmosphere to laminate The method is characterized by including a step of obtaining a sintered body and a step of forming an external electrode on the surface of the laminated sintered body.

By using the raw material powder for porcelain obtained by the above-described method for producing raw material powder for porcelain as a main material by the above method, it is small in size, low in resistance, has a sufficient resistance variation width, and A multilayer ceramic electronic component exhibiting characteristics in a wide range of Ba / Ti ratio can be obtained.

In the multilayer ceramic electronic component as described above, it is preferable that the internal electrode is made of a Ni-based metal, that is, a nickel-containing metal such as nickel or a nickel-containing alloy, to constitute a conductive component thereof.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The raw material powder for porcelain obtained in the present invention is suitable for laminated semiconductors and capacitors.

The semiconductor ceramic layer in the laminated semiconductor ceramic device obtained in the present invention is obtained by sintering barium titanate-based semiconductor ceramic powder. In this barium titanate-based semiconductor ceramic material, a part of Ba may be replaced by Ca (calcium), Sr (strontium), Pb (lead) or the like, or a part of Ti may be replaced by Sn ( Tin), Zr
(Zirconium) or the like. The semiconducting agent contained in such a barium titanate-based semiconductor ceramic material is called a donor element, and examples of such a donor element include La (lanthanum) and Y.
(Yttrium), Sm (samarium), Ce (cerium), Dy (dysprosium), Gd (gadolinium)
And transition elements such as Nb (niobium), Ta (tantalum), Bi (bismuth), Sb (antimony), and W (tungsten). In addition, SiO ₂ (silicon dioxide), Mn (manganese), or the like may be added to such a barium titanate-based semiconductor ceramic material as needed.

The method for synthesizing such a barium titanate-based semiconductor ceramic powder is not particularly limited, and for example, a solid phase method, a hydrothermal method, a coprecipitation method, a sol-gel method and the like can be used.

As the conductive component used for the internal electrode, Ni (nickel) -based metal, Mo (molybdenum) -based metal, Cr (chromium) -based metal, or an alloy thereof can be used. In particular, it is desirable to use a Ni-based metal from the viewpoint of enabling a reliable ohmic contact between the Ni-based metal.

[0026]

[Embodiment 1] As Embodiment 1, a case where calcination and cleaning are performed in two or three stages will be described.

As starting materials, BaCO ₃ (barium carbonate), TiO ₂ (titanium dioxide), and a solution of Sm nitrate were weighed so that the element molar ratio became Sm / Ti = 0.002. PSZ (partially stab
ilized zirconia (partially stabilized zirconia) Using a ball of 5Φ (diameter: 5 mm), mixing was performed by a ball mill for 5 hours. In addition, at the time of the above blending, the Ba
The weighing is performed with the / Ti ratio being 1.00 to 1.010. After that, evaporation and drying were performed, and the obtained mixed powder was 12
The first-stage calcined powder was obtained by calcining at 00 ° C. for 2 hours (first calcining step).

Thereafter, the obtained one-stage calcined powder was ground / mixed again with a ball mill for 5 hours using pure water and a cobblestone of PSZ 5Φ. Thereafter, evaporation drying was performed, and the obtained mixed powder was calcined again at 1200 ° C. for 2 hours to obtain a two-stage calcined powder (second calcining step).

Further, the obtained two-stage calcined powder was ground / mixed again with a ball mill for 5 hours using pure water and a cobblestone of PSZ5Φ. Thereafter, evaporation drying was performed, and the obtained mixed powder was calcined again at 1200 ° C. for 2 hours to obtain a three-stage calcined powder (second calcining step).

Here, the conditions of the calcination step are as follows:
It is preferable that the temperature is 100 to 1250 ° C. and the atmosphere is an atmosphere (oxidizing atmosphere). These calcination conditions may be the same in each calcination step, or may be changed for each calcination step. Further, if the number of times of the calcination step (second calcination step) of the second and subsequent stages is increased, good characteristics can be obtained.
Although the width of the a / Ti ratio is widened, the width of change in resistance is slightly reduced. Therefore, it is preferable that the second calcination step is performed once, that is, the calcination step is stopped twice in total.

Next, the obtained one-stage calcined powder, two-stage calcined powder,
An organic solvent, an organic binder, a plasticizer and the like were added to the three-stage calcined powder to form a slurry, which was then molded by a doctor blade method to obtain a green sheet.

Next, Ni electrode paste was screen-printed on these green sheets to form internal electrodes. Further, green sheets were laminated such that the internal electrodes were alternately exposed, and pressure-compression bonding and cutting were performed to form a laminate. It should be noted that a dummy green sheet having no internal electrode printed thereon is overlaid and pressed on the laminate of the present invention.

Thereafter, the laminate was subjected to a binder removal treatment in the air, and then fired for 2 hours in a strong reducing atmosphere of hydrogen / nitrogen = 3/100 to obtain a laminated sintered body. Further, a reoxidation treatment was performed at 600 to 1000 ° C. for 1 hour in the air. Thereafter, an ohmic silver paste was applied to the end face and baked in the air to obtain a laminated element. The shape of the obtained laminated element is approximately 3.2 mmL (length) × 2.5 mm
W (width) × 1.0 mmt (thickness).

Next, the room temperature resistance and the resistance change width of the manufactured laminated element were measured. Room temperature resistance was measured by a four-terminal method using a digital voltmeter. Also, resistance change width (digit)
Was calculated by dividing the maximum resistance value from room temperature to 250 ° C. by the minimum resistance value and using the common logarithm. Table 1 shows the results. In addition, * mark in Table 1 shows the outside of the range of the present invention.

[0035]

[Table 1]

As shown in Table 1, in the ordinary calcination process (one-stage calcination), desired characteristics (in the first embodiment, the room temperature resistance value is 0.2Ω or less and the resistance change width is 3Ω or less). The Ba / Ti ratio that expresses .5 or more digits is a specific value (in the first embodiment, the charged Ba / Ti ratio = 1.
001), there is a practical problem.

In this regard, as shown in Table 1, by performing the two-stage calcination, the range of the Ba / Ti ratio exhibiting the above-mentioned characteristics is 2
/ 1000 (charged Ba / Ti ratio is 1.003-1.0
04). Further, by performing the three-stage calcination, the resistance change width is reduced by a small amount, but Ba, which exhibits the above characteristics, is obtained.
The range of the / Ti ratio expands to 3/1000 (the charged Ba / Ti ratio is 1.004 to 1.006).

As described above, by performing the calcining a plurality of times (two-stage calcined powder and three-stage calcined powder), it is possible to widen the range of the Ba / Ti ratio that expresses desired characteristics.

[Embodiment 2] As Embodiment 2, a case will be described in which calcination and washing are performed in one or two stages, and barium eluted by washing is replenished.

First, of the one-stage calcined powder obtained in the calcining step of Example 1, the one with the charged Ba / Ti = 1.000 was put into a hot water tank at 80 to 100 ° C. to form a slurry. The slurry was circulated through a static mixer for 3 hours (washing step). Thereafter, dehydration and drying were performed using a centrifuge. This operation of washing with warm water → dehydration / drying was performed three times. The Ba / Ti ratio of the obtained washing powder was 0.990 by fluorescent X-ray analysis.

Similarly, 2 obtained in the calcining step of Example 1
Of the step calcined powder, the charged Ba / Ti = 1.000 was charged into a hot water tank at 80 to 100 ° C. to form a slurry, and the slurry was circulated through a static mixer for 3 hours (washing step). . Thereafter, dehydration and drying were performed using a centrifuge. This operation of washing with warm water → dehydration / drying was performed three times. The Ba / Ti ratio of the obtained cleaning powder was 0.994 by fluorescent X-ray analysis.

Next, with respect to the washed one-stage calcined powder obtained in the above step, Ba / Ti = 0.992, 0.994,
0.996, 0.998, 1.000, 1.002,
Ba correction was performed so as to be 1.004 (composition ratio correction step). Similarly, for the washed two-stage calcined powder, Ba /
Ti = 0.996, 0.998, 1.000, 1.00
Ba correction was performed so as to be 2,1.04 (composition ratio correction step).

Here, the reason why barium is replenished after the washing is to make up for the barium element eluted by the washing. By adjusting the amount of barium to be replenished, the Ba / Ti ratio can be adjusted even after calcination, and a desired Ba / Ti ratio can be more reliably designed. . The replenishment of barium may be performed at least once after the final calcination and cleaning. In addition, barium may be appropriately replenished after the calcination / cleaning other than the last stage.

Specifically, the Ba correction is performed by first measuring the Ba / Ti ratio of the washed calcined powder by X-ray fluorescence analysis, and adjusting the Ba / Ti ratio of the calcined powder to a desired Ba / Ti ratio. Calculate the amount. Next, the Ba correction amount of barium hydroxide aqueous solution containing Ba element (Ba (OH) ₂ · 8H
The ₂ O) were mixed with the washed calcined powder to obtain a barium titanate powder by evaporating water only. In the second embodiment, water is used as the solvent, but the present invention is not limited to this. Further, a predetermined amount of barium carbonate (BaCO ₃ ) powder may be directly mixed with the calcined powder.

Subsequently, the obtained washed and Ba-corrected 1
Step calcined powder, 2 step calcined powder, organic solvent, organic binder,
After adding a plasticizer or the like to form a slurry, the slurry was formed by a doctor blade method to obtain a green sheet. Thereafter, similarly to Example 1, a laminated element was manufactured, and its room temperature resistance and resistance change width were measured. Table 2 shows the results.

[0046]

[Table 2]

As shown in Table 2, after the first-stage calcined powder was washed and subjected to Ba correction, a wide range of Ba / Ti ratio of 3/1000 (Ba / Ti ratio after Ba correction was 0%) was obtained. .998 to 1.000) and desired characteristics (Example 1).
Similarly, the resistance value at room temperature is 0.2Ω or less and the resistance change width is 3.5 digits or more. Further, by performing Ba correction after washing the two-stage calcined powder, 5 /
The above characteristics are obtained in an extremely wide range of Ba / Ti ratio of 1000 (Ba / Ti ratio after Ba correction is 0.998 to 1.002).

As described above, it is effective to perform calcination only a plurality of times (two-stage calcined powder, three-stage calcined powder). Further, even if the multi-stage calcination is not performed, that is, even if the Ba correction is performed after the cleaning in the single-stage calcination, there is an effect (the washed single-stage calcination powder).
Therefore, it can be understood that the multi-stage calcination, the cleaning, and the Ba correction are effective for increasing the range of the Ba / Ti ratio in which the characteristics are exhibited. When the multi-stage calcination is combined with the cleaning and the Ba correction, the above-described effect is further increased (the washed two-stage calcination powder).

[0049]

The method for producing a raw material powder for porcelain according to the present invention comprises:
As described above, a mixing step of mixing raw material powders containing at least barium and titanium to obtain a mixed powder, and calcining the mixed powder at a predetermined temperature and then pulverizing the mixed powder to obtain a first calcined powder A calcining step, and a second calcining step of calcining the calcined powder obtained in the previous calcining step at a predetermined temperature and then pulverizing the calcined powder to obtain a calcined powder; Is performed one or more times.

As described above, the method for producing a raw material powder for porcelain of the present invention further comprises a washing step of washing the calcined powder, and a composition ratio of replenishing barium to the calcined powder after the washing step. And a correcting step.

The method for producing a raw material powder for porcelain of the present invention is a method in which the second calcination step is performed once, as described above.

Further, the method for producing a raw material powder for porcelain of the present invention comprises, as described above, a mixing step of mixing a raw material powder containing at least barium and titanium to obtain a mixed powder;
After calcining the mixed powder at a predetermined temperature, pulverizing, a calcining step of obtaining a calcined powder, and a method for producing a raw material powder for porcelain including a washing step of washing the calcined powder, And a composition ratio correcting step of replenishing the calcined powder with barium after the cleaning step.

The raw material powder for porcelain of the present invention can be obtained by the above-described method for producing raw material powder for porcelain as described above.

Therefore, by using the raw material powder obtained by the above-described method for producing a raw material powder for porcelain, the Ba / Ti ratio having a low resistance and an extremely wide range of resistance change can be made wider than that of the conventional one. This has the effect that porcelain can be obtained.

The porcelain manufacturing method of the present invention is a method in which the porcelain raw material powder obtained by the above-described porcelain raw material powder manufacturing method is used as a main material and then molded and fired.

Further, the porcelain of the present invention is obtained by the above-described porcelain manufacturing method as described above.

Therefore, when the porcelain raw material powder obtained by the above-described method for producing a porcelain raw material powder is used as a main material, the porcelain raw material powder is small, has low resistance, has a sufficient resistance change width, and has a wide Ba There is an effect that a porcelain that can be used for a laminated semiconductor ceramic element or the like that exhibits characteristics in the / Ti ratio can be obtained.

Further, as described above, the method for manufacturing a multilayer ceramic electronic component according to the present invention comprises a ceramic material layer mainly comprising the porcelain raw material powder obtained by the above-described method for manufacturing a porcelain raw material powder, and a conductive material. Obtaining a laminated body by laminating a predetermined number of internal electrode layers made of a conductive paste to obtain a laminated body, and firing the laminated body in a reducing atmosphere and then performing a re-oxidation treatment in an oxidizing atmosphere to obtain a laminated sintered body And a step of forming an external electrode on the surface of the laminated sintered body.

Therefore, by using the raw material powder for porcelain obtained by the above-mentioned method for producing raw material for porcelain as a main material, it has a small size, low resistance, a sufficient resistance change width, and a wide range. This has the effect of obtaining a multilayer ceramic electronic component exhibiting characteristics at a Ba / Ti ratio.

Claims (8)

[Claims] 1. A mixing step of mixing raw material powders containing at least barium and titanium to obtain a mixed powder, and calcining the mixed powder at a predetermined temperature and then pulverizing the mixed powder to obtain a first calcined powder. A calcining step, and a second calcining step of calcining the calcined powder obtained in the previous calcining step at a predetermined temperature, and then pulverizing the calcined powder to obtain a calcined powder. A calcination step of at least one time. 2. A mixing step of mixing raw material powders containing at least barium and titanium to obtain a mixed powder, and a calcining step of calcining the mixed powder at a predetermined temperature and then pulverizing to obtain a calcined powder. A method for producing raw material powder for porcelain, comprising: a washing step of washing the calcined powder; and a composition ratio correcting step of replenishing barium to the calcined powder after the washing step. A method for producing raw material powder for porcelain. 3. The method according to claim 1, further comprising: a washing step of washing the calcined powder; and a composition ratio correcting step of replenishing barium to the calcined powder after the washing step. Of producing raw material powder for porcelain. 4. The method for producing raw material powder for porcelain according to claim 1, wherein the second calcining step is performed once. 5. A porcelain porcelain characterized in that the porcelain raw material powder obtained by the method for producing a porcelain raw material powder according to any one of claims 1 to 4 is used as a main material, molded and then fired. Production method. 6. A ceramic material layer composed mainly of a porcelain raw material powder obtained by the method for producing a porcelain raw material powder according to any one of claims 1 to 4, and an internal electrode composed of a conductive paste. Stacking a predetermined number of layers with each other to obtain a laminate, firing the laminate in a reducing atmosphere, and then performing a re-oxidation treatment in an oxidizing atmosphere to obtain a multilayer sintered body; Forming an external electrode on the surface of the united body. 7. A raw material powder for porcelain, obtained by the method for producing a raw material powder for porcelain according to any one of claims 1 to 4. 8. A porcelain obtained by the method of manufacturing a porcelain according to claim 5.