JP2568411B2 - Semiconductor porcelain composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a ceramic composition suitable for a semiconductor ceramic capacitor as a passive electronic component in an electronic machine or an apparatus, particularly, a grain boundary insulating semiconductor ceramic capacitor.

[Conventional technology]

Semiconductor porcelain capacitors as passive electronic components are classified into surface layer types such as reduction / reoxidation type and dam layer capacitance type, and are roughly classified into grain boundary layer type as grain boundary layer type.

In the reduction-reoxidation type semiconductor capacitor, a BaTiO ₃ -based or SrTiO ₃ -based molded body to which a semiconducting agent is added is fired in the air to produce a dielectric ceramic, which is heat-treated in a reducing atmosphere to produce a semiconductor ceramic. When the semiconductor porcelain thus obtained is heat-treated in an oxygen atmosphere or air, oxygen diffuses from its surface to fill oxygen defects, and only the surface layer becomes a dielectric layer (re-oxidized layer), and the inside remains a semiconductor. When a composite ceramic is formed and formed by baking on both sides, the capacitance is set by the thickness of the surface layer, and a small, large-capacity semiconductor capacitor that can increase the rated voltage by increasing the thickness Is obtained.

Weir layer capacitor type semiconductor capacitors are mainly made of BaTiO ₃ based compacts containing a semiconducting agent, baked in the air, and deposited with a metal such as copper. (A metal that easily becomes a semiconductor) is applied, and this is heat-treated in an atmosphere in the air to form a weir layer of about 0.3 to 3 μm on the surface thereof. That is, on the surface, an external electrode is provided on the weir layer insulator, and the inside of the capacitor element can be a semiconductor element. This type of capacitor has a low withstand voltage because the weir layer is extremely thin, but has a large capacitance and is suitable as a low-voltage large-capacity capacitor.

Grain boundary insulated porcelain capacitor added semiconducting agent
A BaTiO ₃ or SrTiO ₃ -based molded body is fired in a reducing atmosphere, and a metal oxide, for example, Bi ₂ O is applied to the surface of the obtained porcelain, and a heat treatment is performed in the air. This heat treatment allows the metal ions to penetrate into the porcelain and form an insulating layer in which the metal ions are interspersed at the grain boundaries. The inside of the crystal grain remains as a valence-controlled semiconductor doped with a semiconducting agent element. In this way, only the inside of the grain boundary layer turns into an insulating layer,
This forms a kind of sponge-like dielectric by connecting insulating grain boundary layers containing these semiconductors in a matrix in the vertical, horizontal, and horizontal directions inside the semiconductor porcelain.

These various types of semiconductor porcelain capacitors can be used only for bypass in terms of voltage characteristics, dielectric loss, and frequency characteristics, in addition to being able to obtain a small and large capacity.However, with recent advances in manufacturing technology and improved characteristics, SrTiO _The use of semiconductor ceramic capacitors mainly composed of _three systems has been expanded to various applications such as coupling, various signal circuits, pulse circuits, and noise prevention of semiconductors.

However, as shown in Table 1, these various semiconductor porcelain capacitors have a reduced re-oxidation type among the surface layer type, which has a smaller insulation resistance than the grain boundary insulation type, a large dielectric loss and a high frequency characteristic. In addition, there is a disadvantage that the strain rate specific to the BaTiO ₃ system is large. Distortion factors cannot be used in amplifier circuits, especially in audio circuits, and this field has been in the area of film capacitors. In addition, the weir layer capacity type has a small dielectric breakdown voltage of about 12 V, low insulation resistance, large dielectric loss, so the frequency characteristics are poor, the distortion rate is large, and the application range is limited similarly to the above-mentioned reductive reoxidation type. ing.

The valence-compensated form is also the same as that described above. These surface layer forms are mainly composed of BaTiO ₃ and have a large Cs ≧ 4 nF / mm ^{2 by} the thickness of the substrate due to the mechanism of the capacitor. No capacity is available.

In addition, the grain boundary insulation type is more Si than the surface layer type BaTiO ₃ system.
TiO ₃ system has a large insulation resistance, but the dielectric loss is also satisfactory small frequency characteristics, Cs is about ^{2.5nF / mm 2, Cs ≧ 4nF} / m
There is a disadvantage that a large capacity product of m ² cannot be obtained and the strain rate is large.

In the surface layer type semiconductor ceramic capacitor, C is the thickness t.
Ε _s can not be determined because it is not inversely proportional to, but can be determined by the following relational expression.

Vb [Volt] = Eb · t (2) From (1) and (2), ε _S · Eb [Volt / mm] = 1.13 × 10 ⁵ Cs · Vb The ε _s · Eb product in Table 1 is calculated by the above equation. It is calculated.

[Problems to be solved by the invention]

In conventional various types of semiconductor ceramic capacitors as described above, there is a limitation in a bypass circuit due to poor insulation properties, a poor high-frequency bypass effect due to poor frequency characteristics, and a limitation in use of an amplifier circuit due to a large distortion factor. There were drawbacks.

The present invention has a large dielectric constant in semiconductor ceramic capacitors, especially in grain boundary insulated semiconductor ceramic capacitors,
An object of the present invention is to obtain an excellent semiconductor ceramic composition having a large dielectric breakdown voltage and insulation resistance, good frequency characteristics, and a small distortion factor.

[Means for solving the problem]

As a means for improving such problems and achieving the object, in the present invention, SrO 18.0 to 31.4 mol, BaO 13.5
~ 26.9 mol, CaO 1.5 ~ 8.5 mol, TiO ₂ 49.4 ~ 50.4 mol Main component having a composition ratio, manganese, Y, Ce, La, Dy, Nb, T
a, W, Sb and other trivalent, pentavalent, hexavalent elements selected from one or two or more semiconducting agents and SiO ₂ , manganese is
0.005~0.3mol in terms of MnO, SiO ₂ is to use a semiconductor ceramic composition characterized by containing each at a ratio of 0.005～0.03Mol.

〔Example〕

(Preparation of Semiconductor Porcelain) The present invention will be described in detail with reference to examples. First, SrCO ₃ , BaCO ₃ , CaCO ₃ , TiO ₂ , MnCO ₃ , SiO ₂ as industrial raw materials having a purity of 98% or more and Y ₂ O ₃ , Ce ₂ O ₃ , La ₂ O ₃ , Dy
One or two or more of ₂ O ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , Sb ₂ O ₃ , WO _{3 and the} like are prepared, weighed so as to have a composition ratio shown in Table 2, and Is rotationally stirred in a ball mill for 20 hours. Thereafter, it is dehydrated and dried, temporarily calcined at 1200 ° C., coarsely pulverized, and further rotationally pulverized and mixed by a ball mill for 16 hours. This is dehydrated and dried, 2% by weight of an organic binder is added, granulation and sizing are performed, and the powder is molded into a disk at a molding pressure of about 3 tons / cm ² . In a reducing air stream (H ₂ + N ₂ atmosphere)
It is baked at 1480 ° C. for about 2 hours to form a semiconductor.

The semiconductor porcelain element thus obtained has a diameter of 9 mm and a thickness of 0.5
The Bi ₂ O ₃ -CuO system frit paste was applied by 3.5mg screen printing as a double-sided diffusion material of the ceramic element in mm, the insulating layer in the grain boundaries which was calcined for 2 hours at a temperature of 1050 ° C. in air Semiconductor porcelain on which is formed. Ag paste or base metal paste such as Ni, Cu, Zn etc.
By baking at about 0 ° C., a grain boundary insulated semiconductor ceramic capacitor having electrodes formed thereon was obtained.

The electrical characteristics of each sample obtained in this way were
It is shown in the table. In Table 2, sample Nos. 1, 2, 6, 11, 13, 14, 19, 2
5, 29, 30, and 35 are outside the scope of the present invention and are shown for comparison. As is evident from Table 2, those within the scope of the present invention have low dielectric loss (tan δ), high insulation resistance (IR), and high DC breakdown voltage (Eb). Further, an element having a small capacitance change rate (ΔC) when a DC voltage is applied, a good frequency characteristic and a small distortion rate is obtained.

 Next, the reasons for limiting the component composition ratio in the present invention will be described.

SrO, BaO, is SrO in a principal component composed of CaO and TiO ₂ 1
If it is less than 8.0 mol%, the dielectric loss becomes large, and 31.4 mol%
If it exceeds, the DC breakdown voltage becomes too small to be practical. Ba
DC breakdown voltage is small when O is less than 13.5 mol%, 26.9 mol%
If it exceeds, the dielectric loss becomes large and is not practical.

If CaO is out of the range of 1.5 to 8.5 mol%, the insulation resistance or the dielectric constant becomes poor. That is, FIG. 1 shows the change of the insulation resistance and the dielectric constant depending on the content of CaO, and the part indicated by the arrow is the scope of the present invention. As is evident from this, if CaO is less than 1.5 mol%, the insulation resistance is greatly deteriorated, and the reliability (high-temperature load) deteriorates, which is not practical. On the other hand, if it exceeds 8.5 mol%, the dielectric constant becomes small, which is not practical.

When MnO is 0.005 mol% or more, the insulation resistance is significantly improved,
It is practical. On the other hand, when MnO exceeds 0.3 mol%, the dielectric constant becomes small, which is not practical.

If the content of SiO ₂ is less than 0.005 mol%, both the insulation resistance and the DC breakdown voltage will be low, and if it exceeds 0.003 mol%, the dielectric constant will be low, making it impractical.

Next, FIG. 2 shows the capacitance change rate (ΔC) of the frequency characteristic.
A is the one of the present invention, B is a Mylar capacitor, C is a reoxidation capacitor, D is a weir layer type capacitor, and the present invention is compared with other semiconductor ceramic capacitors and Mylar capacitors. And the rate of change is small. Since a mylar capacitor is wound in a high frequency band accompanying a digital circuit in the future and L is interposed, a capacitor using the material of the present invention is particularly useful in a high frequency band.

FIG. 3 shows the relationship between the voltage and the distortion factor, where A is that of the present invention and B is that of a Mylar capacitor. As apparent from FIG. Since the distortion rate is small, it is possible to replace a Mylar capacitor in an amplifier circuit or the like which has been limited in use until now.

In the present invention, the ratio of the total number of moles of SrO, BaO, CaO and the like to the number of moles of TiO ₂ ; If it is less than 0.980, the DC breakdown voltage will be low, and if it exceeds 1.020, the dielectric constant will be small, making it impractical.

In addition, the electrical properties of the porcelain composition when using La oxide as a semiconducting agent are similar to those using Ce ₂ O _3, and when using Sb oxide, WO ₃ It is similar to the case.

〔The invention's effect〕

As described above, the semiconductor porcelain composition of the present invention has a small size, a large capacity, a small dielectric loss, a large insulation resistance, a high DC breakdown voltage, a good frequency characteristic, a small capacitance change rate, and a strain. It has very good characteristics with a small rate.

Accordingly, the present invention has enormous industrial benefits because the range of applications from coupling other than the conventional bypass, various signal circuits and pulse circuits to noise prevention has been widened.

[Brief description of the drawings]

FIG. 1 shows the insulation resistance and dielectric constant according to the content of CaO in the embodiment of the present invention, and FIG. 2 shows the capacitance change rate of the frequency characteristics of the capacitor to which the composition of the present invention is applied and the conventional capacitor. FIG. 3 also shows the distortion factor.

Claims (3)

(57) [Claims] (1) 18.0-31.4 mol of SrO, 13.5-26.9 mol of BaO, Ca
O1.5～8.5Mol, the main component having a composition ratio of TiO ₂ 49.4~50.4mol, manganese, Y, Ce, La, Dy , Nb, Ta, W, 3 such as Sb
Valence, pentavalent, and hexavalent one selected from the elements or two or more semiconductor-forming agent, made of SiO ₂ Prefecture, manganese in terms of MnO 0.005～0.3Mol, SiO ₂ is the 0.005~0.03mol A semiconductor porcelain composition characterized by being contained in proportions. 2. The main component is a ratio of the total number of moles of SrO, BaO and CaO to the number of moles of TiO ₂ ; (SrO + BaO + CaO) / TiO ₂
2. The semiconductor porcelain composition according to claim 1, wherein is in the range of 0.980 to 1.020. 3. The semiconductor device according to claim 1, wherein Bi is unevenly distributed in a crystal grain boundary of a semiconductor porcelain obtained by molding and sintering the composition comprising the main component. Semiconductor porcelain composition.