JP3124896B2 - Manufacturing method of semiconductor porcelain - 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 manufacturing semiconductor porcelain for porcelain capacitors, porcelain varistors and the like.

[0002]

BACKGROUND OF THE INVENTION Semiconductor ceramic mainly made of BaTiO ₃ or SrTiO _3, the capacitor, varistor, are widely used industrially as a body of the functional components such as a thermistor.
In general, these semiconductor porcelains are manufactured by using a combination of a semiconducting agent and a forced reduction method. Specifically, for example, it is manufactured by the following steps. Raw material powder and semiconducting agent,
After weighing a predetermined amount of additives such as sintering aids, kneading with an organic binder after adding water, mixing and pulverizing with a ball mill, and drying,
Granulate. This is formed into a predetermined shape and fired in a reducing atmosphere to obtain a semiconductor porcelain. Further, if necessary, an insulating material is applied to the semiconductor porcelain as a re-oxidation step, and 900-
It is fired at 1300 ° C. in the air. Thereafter, a pair of electrodes is formed on both main surfaces of the porcelain to form functional parts such as capacitors.

[0003]

Semiconductor porcelain used as a functional component such as a capacitor is generally required to have a sufficiently low resistivity. Although the resistivity can be reduced to some extent by increasing the amount of the semiconducting agent added, the conventional manufacturing method has a limit to the solid solution amount of the semiconducting agent in the main raw material, and a sufficiently low resistivity can be obtained. Did not. When added in a large amount, there is a problem that an excess that does not form a solid solution segregates at the grain boundaries, and when the insulating agent diffuses into the grain boundaries, sufficient insulation resistance and withstand voltage cannot be obtained.

Accordingly, an object of the present invention is to provide a method for manufacturing a semiconductor porcelain capable of reducing the resistivity of the semiconductor porcelain.

[0005]

In order to achieve the above object, the present invention provides an ABO ₃ (where A is Sr, Ba, C
a, one or more of Mg, B is T
O represents one or more of i and Zr, and O represents oxygen. ) And a semiconducting agent (eg, N
b, Ta, W and a compound of one or more of the compounds of the rare earth elements), and the average particle size (D2) of the semiconductor compound with respect to the average particle size (D1) of the main component. Of a semiconductor porcelain having a ratio (D2 / D1) of 0.04 to 1.00 is prepared ,
The present invention relates to a method for manufacturing a semiconductor porcelain, comprising: a step of wet-mixing a conductive agent ; a step of forming a compact of the semiconductor porcelain raw material powder; and a step of firing the compact. It is preferable that a paste containing a metal oxide for grain boundary insulation be applied and heat-treated. In addition, it is desirable that the ratio of the average particle size is in the range of 0.1 to 0.6.

[0006]

According to the production method of the present invention, the average particle size ratio of the semiconducting agent to the main component is set to 0.04 to 1.
Since it is set to 00, the semiconducting agent is uniformly dispersed in the main component when the raw material powders are mixed, and almost completely displaces and dissolves in the main component crystal lattice sites during the firing process, effectively functioning as a semiconductor. Therefore, a semiconductor ceramic having a low resistivity can be obtained. Furthermore, even if a large amount of a semiconducting agent is added to lower the resistivity of the semiconductor porcelain,
Since segregation of the semiconducting agent to the grain boundary is small, it is possible to prevent a decrease in withstand voltage and insulation resistance. In other words,
In the present invention, when the added amount of the semiconducting agent is the same as that of the related art, the withstand voltage and the insulation resistance can be increased as compared with the related art. Further, the equivalent series resistance (ESR) can be reduced. More specifically, when the present invention is applied to a capacitor, the capacitance, insulation resistance, and withstand voltage of the capacitor can be increased, and the equivalent series resistance can be reduced. Also,
When the present invention is applied to a varistor, the non-linear coefficient and surge withstand capability of the varistor can be increased. Further, when the present invention is applied to a thermistor, the steepness of the PTC characteristic (positive temperature coefficient characteristic) can be increased. According to claim 2, the characteristics are further improved.

[0007]

First Embodiment Next, a method for manufacturing a semiconductor ceramic for a capacitor and a capacitor according to an embodiment of the present invention will be described.

In the general formula ABO ₃ , S is Sr (strontium) and B is Ti (titanium). SrTiO ₃ (main component)
And Y ₂ O which is a rare earth element compound as a semiconducting agent
₃ (yttrium oxide) and Si as sintering aid
O ₂ and Al ₂ O ₃ were prepared. At this time, the average particle diameter D1 of SrTiO ₃ as a main component and Y as a semiconducting agent
For the average particle size ratio of the average particle diameter D2 of the ₂ O ₃ (D2 / D1) is examined how it affects the characteristics, were prepared having different particle sizes next six samples. Sample No. D1 D2 D2 / D1 1 2.75 μm 0.08 μm 0.03 2 2.75 μm 0.11 μm 0.04 3 2.75 μm 0.33 μm 0.12 4 2.75 μm 1.62 μm 0.59 5 2 0.75 μm 2.75 μm 1.00 6 2.75 μm 3.30 μm 1.20

[0009] Next, for each sample of said NO. 1~NO. 6, and SrTiO ₃ 100 molar parts Y ₂ O ₃ 0.6 mole parts SiO ₂ 0.2 mole parts Al ₂ O ₃ 0.1 mole part The mixture was wet-mixed with a ball mill for 15 hours, and then dried to obtain a powder of a raw material mixture.

Next, an aqueous solution of polyvinyl alcohol as an organic binder is added to the raw material mixture at 5% by weight, mixed and granulated, and the granulated product is molded at a pressure of 1 ton / cm ² to form a material having a diameter of 12. A disk-shaped compact having a thickness of 5 mm and a thickness of 0.3 mm was obtained. Next, the compact is placed in a furnace and fired at 1450 ° C. for 3 hours in an N ₂ + H ₂ mixed gas atmosphere (non-oxidizing atmosphere or reducing atmosphere) in a volume ratio of N ₂ : H ₂ = 97: 3. Thus, a grain boundary insulated semiconductor porcelain 1 shown in FIG.

A paste-like grain boundary insulating material 2 made of a material obtained by adding a solvent to Bi ₂ O ₃ on the surface of the semiconductor porcelain 1 described above.
Is applied as shown in FIG.
The insulating material was diffused into the semiconductor porcelain 1 by heat treatment at 2 ° C. for 2 hours to insulate the grain boundaries 4 of the semiconductor crystal grains 3 as schematically (in principle) shown in FIG.

Next, a silver paste (conductive paste) is applied to both main surfaces of the semiconductor porcelain 1 by a printing method, and 800
C. for 1 hour to form a pair of electrodes 5 and 6 to complete the capacitor.

For each sample capacitor, the capacitance C (nF) between the pair of electrodes 5 and 6 and the insulation resistance IR (M
Ω), breakdown voltage (breakdown voltage) BD (V), and equivalent series resistance ESR (mΩ), the following results were obtained. Sample No. C (nF) IR (MΩ) BD (V) ESR (mΩ) 144 900 90 35 280 1700 130 27 3 85 1900 150 23 4 90 2000 140 140 19 5 82 1600 130 29 6 53 300 50 30

As is clear from the results, the results of sample No. 6
When the particle diameter ratio D2 / D1 is 1.20, the semiconducting agent (Y ₂ O ₃ ) cannot be dispersed uniformly, so that its contribution to semiconductor conversion is small. As a result, the capacitance C and the insulation resistance are reduced. IR and withstand voltage BD are small, and equivalent series resistance ESR is large. On the other hand, when the average particle size ratio D2 / D1 is in the range of 0.04 to 1.00 as shown in Sample Nos. 2 to 5, C,
IR and BD are larger than the conventional example of sample No. 6, and E
SR becomes smaller than that of sample No. 6. Sample No. 1
When the average particle size ratio D2 / D1 is too small as 0.03 as shown in FIG. 7, the coagulation of the semiconducting agent (Y ₂ O ₃ ) occurs so strongly that the semiconducting agent cannot be uniformly dispersed.
As in O.6, each characteristic deteriorates.

[0015]

Second Embodiment Next, a method of manufacturing a porcelain varistor containing SrTiO ₃ as a main component will be described. Sr as main component
TiO ₃ , La ₂ O ₃ (lanthanum oxide) as a rare earth element compound as a semiconducting agent, and SiO ₂ and Al ₂ O ₃ as additives as sintering aids were prepared. At this time, how the average particle diameter ratio (D2 / D1) of the average particle diameter D1 of SrTiO ₃ as the main component and the average particle diameter D2 of La ₂ O ₃ as the semiconducting agent affects the characteristics. The following six samples having different particle sizes were prepared for examination. Sample No. D1 D2 D2 / D1 7 2.56 μm 0.05 μm 0.028 8 2.56 μm 0.10 μm 0.049 9 2.56 μm 0.33 μm 0.13 10 2.56 μm 1.43 μm 0.56 11 2 .56 μm 2.56 μm 1.00 12 2.56 μm 2.89 μm 1.13

Next, the above-mentioned NO. 7~NO. For 12 of each sample, SrTiO ₃ 100 molar parts La ₂ O ₃ 0.6 mole parts SiO ₂ 0.2 mole parts Al ₂ O ₃ 0.1 mole part The mixture was wet-mixed with a ball mill for 15 hours, and then dried to obtain a powder of a raw material mixture.

Next, an aqueous solution of polyvinyl alcohol as an organic binder was added to this raw material mixture in an amount of 5% by weight, mixed and granulated, and the granulated product was formed under a pressure of 1.2 ton / cm ² to form a diameter. A 12.5 mm, 0.3 mm thick disk-shaped compact was obtained. Next, this compact is placed in a furnace and fired at 1450 ° C. for 3 hours in an N ₂ + H ₂ mixed gas atmosphere (non-oxidizing atmosphere or reducing atmosphere) with a volume ratio of N ₂ : H ₂ = 97: 3. Fig. 1 shows a grain boundary insulated semiconductor porcelain
Was obtained as well.

The surface of the above-mentioned semiconductor porcelain 1 is coated with a paste-like grain boundary insulating material composed of Na ₂ O (sodium oxide) to which a solvent has been added.
Heat treatment to diffuse the insulating material into the semiconductor porcelain,
The grain boundaries of the semiconductor crystal grains were insulated.

Next, a silver paste (conductive paste) is applied to both main surfaces of the semiconductor porcelain by a printing method, and 800
℃ 1 hour baking treatment to form a pair of electrodes,
The varistor was completed.

Next, the varistor voltage V 1m (V), the voltage non-linear coefficient α, and the surge withstand capability (A / cm ² ) of the varistors of Sample Nos. 7 to 12 were determined as follows. Here, the varistor voltage V1m is a voltage between the pair of electrodes when a current of 1 mA flows between the pair of electrodes of the varistor element. The voltage non-linear coefficient α was determined by the following equation based on a pair of terminal voltages V1m when a current of 1 mA flows through the varistor element and a terminal voltage V10m when a current of 10 mA flows. α = 1 / {log (V10m / V1m)} The surge withstand capability is obtained by applying a current surge to the varistor element twice at one-minute intervals and applying a varistor voltage V1m before and after that.
The maximum current value at which the rate of change within was within 5% was determined, and this was defined as surge withstand. Sample No. V 1m (V) α Surge tolerance (A / cm ² ) 7 214 14.2 2400 8 210 15.1 3000 9 203 16.7 3300 10 209 16.4 3500 11 221 15.8 3100 12 233 14 .6 2600

As is evident from the results, Sample No. 1
In the case where the particle diameter ratio D2 / D1 shown in FIG. 2 is 1.13, the semiconductor material (La ₂ O ₃ ) cannot be uniformly dispersed, so that semiconductor conversion cannot be sufficiently achieved and the resistivity of the semiconductor crystal particles is large. The varistor voltage V1m increases, while the voltage non-linear coefficient α and the surge withstand capability decrease. On the other hand, the average particle size ratio D2 / D1 shown in Samples Nos. 8 to 11 was 0.04.
-1.00, the varistor voltage V1m
Thus, the voltage nonlinear coefficient α and the surge withstand capability are larger than those of the sample No. 12. Sample N
If too small an average particle size ratio D2 / D1 as shown in O. 7, agglomeration occurs in the semiconductor-forming agent (La ₂ O _3), characteristic deteriorates as Sample NO. 12.

[0022]

Third Embodiment Next, a method of manufacturing a ceramic thermistor containing BaTiO ₃ as a main component will be described. B as main component
aTiO ₃ (barium titanate), Group 5 compound Nb ₂ O ₅ (niobium oxide) as a semiconducting agent, and SiO ₂ and Al ₂ O ₃ as sintering aids were prepared. At this time, if the average particle size ratio of the average particle diameter D2 of the Nb ₂ O ₅ of an average particle diameter D1 and the semiconductor-forming agent BaTiO ₃ as the main component (D2 / D1) is how they affect the properties The following six samples having different particle sizes were prepared for examination. Sample No. D1 D2 D2 / D1 13 2.38 μm 0.05 μm 0.02 14 2.38 μm 0.10 μm 0.04 15 2.38 μm 0.26 μm 0.11 16 2.38 μm 1.38 μm 0.58 17 2 .38 μm 2.38 μm 1.00 18 2.38 μm 2.62 μm 1.10

Next, for each of the samples of Nos. 13 to 18, 100 mol parts of BaTiO ₃ 0.6 mol parts of Nb ₂ O ₅ 0.2 mol parts of SiO ₂ 0.1 mol parts of Al ₂ O ₃ The mixture was wet-mixed with a ball mill for 15 hours, and then dried to obtain a powder of a raw material mixture.

Next, 5% by weight of an aqueous solution of polyvinyl alcohol as an organic binder was added to the raw material mixture, mixed and granulated, and the granulated product was formed at a pressure of 0.6 ton / cm ^2. A disk-shaped molded body having a diameter of 12.5 mm and a thickness of 0.3 mm was obtained. Next, this compact is placed in a furnace and fired at 1350 ° C. for 3 hours in an N ₂ + H ₂ mixed gas atmosphere (non-oxidizing atmosphere or reducing atmosphere) in a volume ratio of N ₂ : H ₂ = 97: 3. Thus, a semiconductor porcelain made of a sintered body was obtained.

Further, the semiconductor porcelain is heated at 1000 ° C.
Heat treatment (reoxidation treatment) was performed for 1 hour to obtain a grain boundary insulating semiconductor ceramic.

Next, an ohmic silver paste (conductive paste) is applied to both main surfaces of the semiconductor porcelain by a printing method, and baked at 550 ° C. for 1 hour in the air to form a pair of electrodes. Was completed.

The Curie temperature Tc (° C.) and the steepness log (ρmax / ρmin) of the thermistor characteristics (PTC characteristics) were determined for the thermistors of each sample, and the following results were obtained. Sample No. Tc (° C.) Steepness log (ρmax / ρmin) 13 116.5 6.2 14 107.1 9.8 15 114.5 10.5 16 121.3 11.5 17 118.0 9.1 18 113.4 5.1

As is apparent from the results, the results of sample No. 6
When the particle diameter ratio D2 / D1 is 1.10, the semiconducting agent (Nb ₂ O ₅ ) cannot be uniformly dispersed, so that semiconductor conversion cannot be achieved satisfactorily. As a result, Tc and steepness are small. . On the other hand, when the average particle size ratio D2 / D1 is in the range of 0.04 to 1.00 as shown in Sample Nos. 14 to 17, Tc and steepness become larger than that of Sample No. 18. The sample
As shown in NO. 13, the average particle size ratio D2 / D1 was 0.02.
If it becomes too small as in
Agglomeration of ₂ O ₅ ) is strongly generated, and the semiconducting agent is not uniformly dispersed, and Tc and steepness are reduced similarly to Sample No. 18.

[0029]

[Modifications] The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. (1) The main component is not limited to SrTiO ₃ and BaTiO ₃ , but ABO ₃ (where A is one or more elements of Sr, Ca, Ba and Mg, B is one or more of Ti and Zr) Strontium-based component which can be represented by (2) As a semiconducting agent (atomization controlling agent), Y ₂ O
₃ , instead of or in addition to La ₂ O ₅ and Nb ₂ O ₅ , W (tungsten), Ta (tantalum), and rare earth elements (Ce, Pr, Nd, Sm, Dy, Pm, Eu,
Compounds such as Gd, Tb, Ho, Er, Tm, Yb, Lu, etc. (eg, WO ₃ , Ta ₂ O ₅ , CeO ₂ , Nd ₂₎
O ₃ , Sm ₂ O ₅ , Pr ₆ O ₁₁ , Dy ₂ O ₃ ) or 100 mol parts of SrTiO ₃ or A
Preferably 0.1 to 5 with respect to the main component consisting of BO _3.
It can be used in a range of 0 mol part. (3) Al ₂ O ₃ as a sintering aid for porcelain materials,
One or more kinds selected from SiO ₂ , CuO, MnO ₂ , and Ag ₂ O are preferably used in an amount of 0.05 mol% based on 100 mol parts of SrTiO ₃ or the main component composed of ABO ₃ described above.
It can be added in the range of 0.50 mol part. (4) Use of Pb ₃ O ₄ or B ₂ O ₃ instead of Bi ₂ O ₃ as an insulating material at the grain boundary.
nO ₂ , CuO, Tl ₂ O ₃ , Sb ₂ O ₅ , Fe ₂ O ₃
A metal oxide paste can be prepared using one or a plurality of metal oxides selected from metal oxides, and can be applied to porcelain. (5) Instead of SrTiO ₃ , SrCO ₃ and TiO ₂ can be used as starting materials in a proportion in which this can be obtained. (6) Before forming a molded body, a calcination step in an air atmosphere (oxidizing atmosphere) is provided.
The molded body can be made by calcining for 5 hours and using the calcined raw material powder. (7) Various manufacturing conditions for porcelain can be changed. For example, firing in a reducing atmosphere (non-oxidizing atmosphere)
The temperature can be set at 00 to 1500 ° C. for 1 to 5 hours. Further, the diffusion treatment after the application of the above-mentioned metal oxide paste is performed by 8 times.
The temperature can be set to 00 to 1300 ° C. for 1 to 5 hours.

[Brief description of the drawings]

FIG. 1 is a front view showing a semiconductor porcelain of a first embodiment.

FIG. 2 is a front view showing a surface of the semiconductor porcelain of FIG. 1 coated with an insulating material.

FIG. 3 is a sectional view schematically showing a capacitor.

[Explanation of symbols]

 3 crystal grain 4 grain boundary layer 5, 6 electrode

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-55152 (JP, A) JP-A-63-55154 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 35/00 C04B 35/46-35/478 H01C 7/10 H01G 4/12

Claims (2)

(57) [Claims] 1. ABO ₃ (where A is Sr, Ba, C
a, one or more of Mg, B is T
O represents one or more of i and Zr, and O represents oxygen. ) And a semiconducting agent,
The ratio (D2 / D1) of the average particle size (D2) of the semiconducting agent to the average particle size (D1) of the main component is 0.04 to
Prepare a raw material powder of semiconductor porcelain in the range of 1.00,
A method for producing a semiconductor porcelain, comprising: a step of wet-mixing a component and the semiconductor agent ; a step of forming a compact of the semiconductor porcelain raw material powder; and a step of firing the compact. 2. The sintering step is a step of sintering the molded body in a non-oxidizing atmosphere to obtain a sintered body, and further comprising a step of forming a metal oxide for grain boundary insulation on the surface of the sintered body. 2. The method according to claim 1, further comprising the step of applying a paste containing a material and heat-treating the paste.