JPS6342849B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a composition for a grain-boundary insulated semiconductor ceramic capacitor. Conventionally, small-sized, large-capacity capacitors include barrier layer capacitance type semiconductor ceramic capacitors, surface insulation layer type semiconductor ceramic capacitors, and grain boundary insulation type semiconductor ceramic capacitors. Among these, weir layer capacitance type semiconductor ceramic capacitors are
Although it shows a capacitance value of 400 to 500 nF/cm ² , tan δ is as large as 4 to 5%, and the insulation resistance (IR) is only 1 MΩ. Furthermore, surface insulating layer type semiconductor ceramic capacitors do not have good characteristics such as tan δ, capacitance temperature characteristics, capacitance change rate, and distortion rate. Furthermore, grain boundary insulated semiconductor ceramic capacitors exhibit superior electrical properties in most respects compared to surface insulated layer type semiconductor ceramic capacitors, but their capacitance is at most 300 nF/cm ² . The main components of grain boundary insulated semiconductor ceramic capacitors are barium titanate and strontium titanate, but in order to make them semiconductor, rare earth elements such as La and Y, and small amounts of semiconductor agents such as Nb, Ta, and W are required. added. However, it is not easy to convert strontium titanate-based materials into semiconductors, and in addition to adding a small amount of a semiconductor agent, the atmosphere during the firing stage must be neutral and reducing.
On the other hand, when the firing atmosphere is neutral and reducing, if stannate is included in the main component, SnO ₂ itself is easily reduced and becomes metallic tin, making it difficult to make into porcelain. . Therefore, an object of the present invention is to provide a grain-boundary insulated semiconductor ceramic composition that can be converted into a semiconductor without firing in a neutral or reducing atmosphere. Another object of the present invention is to provide a grain-boundary insulated semiconductor ceramic composition that can be made into porcelain even if it contains stannate. In other words, the gist of this invention is:
(Ba _1-x Sr _x ) (Ti _1-y Sn _y ) O ₃ (x=0~0.4, 0.6≦
x+4y≦1.6) or (Ba _1-x Sr _x ) (Ti _1-y Sn _y )
The main component is O ₃ (x=0~0.4, 0.6≦x+4y≦1.6) and also includes titanate and zirconate, rare earth elements such as La and Y, Nb, Ta,
Semiconductor porcelain containing a semiconducting agent such as W and having a maximum crystal grain size of 100 to 250 μm, a grain boundary insulated semiconductor in which the crystal grain boundaries of the semiconductor porcelain are made into an insulator by a metal oxide. It is a porcelain composition. Among the above, in (Ba _1-x Sr _x )(Ti _1-y Sn _y )O ₃ , x is limited to a range of 0 to 0.4. This is because, although it is not necessary to contain Sr, if the amount of Sr exceeds 0.4, the capacitance decreases. Also, y
is limited to a range of 0.6≦x+4y≦1.6, but outside this range it becomes difficult to obtain a large capacitance.
FIG. 1 shows the quantitative correlation between x and y, and the area surrounded by polygons indicates the area within the scope of the invention. _In addition _, other _{titanates such as CaTiO3} ,
At least one of the zirconates such as _BaZrO3
When seeds are contained, the amount to be contained is suitably 10 mol% or less. This is because if the content exceeds 10 mol%, the effects of its inclusion, such as improvement in sinterability and reproducibility of electrical properties, cannot be expected. Furthermore, the content range of the semiconducting agent is 0.1
~1.0 mol% is preferred. Outside this range, even if fired in a normal natural atmosphere, the resistance will be 10 to 10 ^-1 Ω・cm.
Semiconductor porcelain having a certain value cannot be obtained. Furthermore, semiconductor ceramics include SiO ₂ , Al ₂ O ₃ ,
It is also permissible to contain at least one type of TiO ₂ , but the effect of its inclusion is that it can lower the firing temperature and increase dielectric breakdown. Among these, the content range of SiO ₂ is 0.05~
0.5 mol% is preferred. This is 0.05 mol% _SiO2
If it is less than 0.5 mol %, the firing temperature will still be high and the effect of its addition will not be apparent, and if it exceeds 0.5 mol %, a decrease in the dielectric constant will be observed. Moreover, the content range of Al ₂ O ₃ is preferably 0.02 to 0.2 mol %. This means that if it is less than 0.02 mol%, the effect of increasing dielectric breakdown cannot be obtained;
If it exceeds 0.2 mol%, a decrease in dielectric constant is observed.
Further, the content range of TiO ₂ is preferably 0.05 mol% or less. This is because if the content exceeds 0.05 mol %, it is difficult to obtain crystals with a large particle size and sufficient capacitance cannot be obtained. For example, metals such as Pb, Bi, Cu, B, Mn,
There are compounds such as oxides, and a method of diffusing them at grain boundaries by heat treatment is adopted. Other methods of insulating grain boundaries include applying it to the surface of semiconductor porcelain by dry plating such as vapor deposition or sputtering, and then heat-treating it, or applying a compound paste and heat-treating it. This semiconductor porcelain composition is made by mixing raw materials in a predetermined ratio, molding it into a certain shape, and then firing it in a natural atmosphere. A value within this range brings about favorable results in electrical properties. If the maximum crystal grain size is less than 100 μm, capacitance, capacitance temperature characteristics, and capacitance change rate will decrease. Moreover, if the thickness exceeds 250 μm, the electrical characteristics deteriorate and it becomes an obstacle to thinning the film to obtain a large capacitance. In addition, by incorporating Mn in the range of 0.02 to 0.5 mol% into semiconductor porcelain, insulation resistance (IR) can be improved.
can be improved. Semiconductor porcelain is allowed to contain unavoidable impurities to the extent that they do not adversely affect its properties, but for example, the inclusion of ZnO, Bi ₂ O ₃ , CuO, etc. may impair sinterability and reproducibility. etc. has an effect. Although the range in which it is contained cannot be clearly defined, it may be contained in a small amount in order to improve properties. Hereinafter, this invention will be explained in detail according to examples. Example SrCO ₃ , BaCO ₃ , TiO ₂ , SnO ₂ , CaTiO ₃ ,
_Main materials such _{as BaZrO3} , _Y2O3 , _La2O5 , _WO3 ,
Semiconducting agents such as Mb ₂ O ₅ , Er ₂ O ₃ , SiO ₂ , Al ₂ O ₃ ,
Weigh and mix mineralizers such as TiO ₂ and heat them at 1100°C.
Calcined for an hour. Next, 10% by weight of vinyl acetate resin was added, wet-pulverized, sieved through a 30-mesh sieve, and then molded into a disc with a diameter of 10 mmφ and a wall thickness of 0.5 mm at a molding pressure of 750 kg/cm ² . The molded disk was fired at 1400° C. for 2 to 4 hours in a natural atmosphere to obtain semiconductor porcelain. In order to make the grain boundaries of the obtained semiconductor porcelain an insulator, a metal oxide paste prepared in advance was applied to the surface of the semiconductor porcelain by a coating method, and heat treatment was performed in air at 1150°C for 2 hours to transform the grain boundaries. Made into an insulator. The following types of metal oxide pastes were used, and the metal oxide pastes applied to each sample are shown in Table 1 with symbols A, B, and C. A: Bi ₂ O ₃ 45% by weight, H ₃ BO ₃ 5% by weight, resin varnish 50% by weight. B: Bi ₂ O ₃ 42% by weight, CuO 4% by weight, MnCO ₃ 4% by weight, resin varnish 50% by weight. C: 40% by weight _{of Pb3O4} , 10% by weight of _MnCO3 , 50% by weight of resin varnish. Furthermore, a capacitor was created by printing and applying silver paste on both sides of the grain-boundary insulated semiconductor porcelain and baking it at 800°C for 30 minutes. The electrical characteristics of the obtained capacitor were measured and the results are shown in Table 2. Items marked with * in Tables 1 and 2 are outside the scope of this invention, and the others are within the scope of the invention.

【table】

【table】

[Table] The electrical properties in Table 1 are values measured under the following conditions. Capacitance (Cs), dielectric loss (tanδ): +20℃,
Values measured at a frequency of 1KHz and a voltage of 0.2Vrms or less. Insulation resistance (IR): Value at +20°C, 30 seconds after applying a DC voltage of 10 V per mm of sample thickness. Capacitance temperature characteristic (△TC): A value indicating the maximum capacitance change rate in the temperature range of -25°C to +85°C, with +20°C as the standard. Capacitance change rate (DCB): At +20℃, with respect to the capacitance when applying a DC voltage of 0.2V,
The value expressed as a percentage of the change in capacitance when a DC voltage of 10V is applied. Distortion rate: Value showing the total harmonic distortion rate at +20℃, frequency 1KHz, and applied voltage 1V. Frequency characteristics (ESR): Value around 1MHz. As is clear from the above examples, by constructing a capacitor using the grain boundary insulated semiconductor ceramic composition according to the present invention, Cs, △TC,
Practically sufficient values of tanδ, DCB, distortion rate, and ESR were obtained. In particular, the composition according to the present invention can be fired in a natural atmosphere, and can contain stannate as its main component. became unnecessary. In addition, the tolerance for molar ratio deviation due to conventional compositions is 1/1000.
However, according to the present invention, the tolerance is 5/1000 or more, and it has the effect that stable characteristics can be obtained even with deviations in the formulation composition.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the correlation between x (Sr amount) and Y (Sn amount).

Claims (1)

[Claims] 1 (Ba _1-x Sr _x ) (Ti _1-y Sn _y ) O ₃ (x=0 to 0.4,
0.6≦x+4y≦1.6) or (Ba _1-x Sr _x ) (Ti _1-y
The main component is mainly Sn _y ) O ₃ (x=0~0.4, 0.6≦x+4y≦1.6) and also includes titanate and zirconate, rare earth elements such as La and Y,
Semiconductor porcelain containing a semiconducting agent such as Nb, Ta, W, etc. and having a maximum crystal grain size of 100 to 250 μm, which is a grain in which the crystal grain boundaries of the semiconductor porcelain are made into an insulator by a metal oxide. Field-insulated semiconductor ceramic composition.