JPS6055924B2 - High dielectric constant porcelain composition - Google Patents

Description

Detailed Description of the Invention The present invention is based on barium titanate (BaTiO0), calcium titanate (CaTiO3), antimony sesquioxide (Si), and samarium oxide (Sm2O8).
), etc., and relates to a high dielectric constant ceramic composition obtained by adding such materials.

Conventionally, many high dielectric ceramic compositions containing barium titanate as a main ingredient have been proposed, and are particularly used in disk-type ceramic capacitors.

Barium titanate is a ferroelectric material, and its Curie point is around 120°C.

At 120°C, it becomes a tetragonal crystal on the low temperature side and a cubic crystal on the high temperature side. It is well known that tetragonal crystals exhibit paraelectricity. The dielectric constant of barium titanate alone in porcelain exhibits extremely large temperature-dependent changes in its temperature characteristics near room temperature, and the dielectric loss is large.
It is rarely used alone as a capacitor, and conventional efforts have been made to add various additives to move the Curie point to around room temperature and to reduce temperature changes. Typical examples include CaTiO, Ba
ZrO39SrTi, Basno39casno3, etc. are known. By adding appropriate amounts of these and further correcting with trace components, X7R based on EIA standards
, XD, Y5V, Z4V, etc. are supplied as characteristic materials. The reality is that these materials have conventionally been used as thick disc ceramic capacitors with an element thickness of 0.5 to 1.0 wgn. In recent years, the miniaturization of various electronics-related components has progressed, and the most notable example is the multilayer ceramic capacitor.

Multilayer ceramic capacitors contain 25 to 100 porcelain dielectrics.
p771, it has a multilayer structure with comb-shaped electrodes sandwiched in between, and the ratio of electrode area and distance between electrodes can be made extremely small, so the capacitance per volume is comparable to that of a ceramic capacitor. The capacitance can be increased by more than 100 times, and the same capacitance can be secured in a small volume of less than 1×0, making it extremely easy to downsize. However, when such a porcelain dielectric thin film is used, the actual situation is that the conventional disk-shaped porcelain composition cannot be immediately applied. In other words, since the voltage per unit length is m times or more higher than that of the conventional material, there has been a demand for materials whose porcelain permittivity and dielectric loss are less dependent on voltage. In addition, recently, due to the direct attachment method to a printed circuit board, there is a demand for a material that has strength so that it will not break due to the deflection of the printed circuit board.

Furthermore, since the frequency is shifting to a high frequency band with good sensitivity, there is a need for a device with good high frequency characteristics. In particular, YD characteristics in JIS standards or YD characteristics in EIA standards.
A large number of 5T characteristics are required for electronic tuners, and a dielectric constant of 8000 or more, Tan δ of 2.0% or less, and a low equivalent series resistance in the frequency band of 1 to 100 MHz are required.

In view of the above, an object of the present invention is to provide a high dielectric constant ceramic composition that has low voltage dependence, high bending strength, and good high frequency characteristics.

As a result of various experiments to achieve this object, the present invention has revealed that CaTlO3 is
l~10 parts by weight, S■031~4 parts by weight, Sm2O3l
The present invention has led to the provision of a high dielectric constant ceramic composition in which 5 parts by weight of the above-mentioned compound is added. Furthermore, a preferred embodiment provides a high dielectric constant ceramic composition containing 0.01 to 0.5 Wt% of at least one of oxides of Mn, Cr, Fe, Ni, and CO based on the main component. It is something to do. The present invention will be explained below based on Examples.

Example Various additives were added to 10 parts of BaTiO3 (purity %) and thoroughly mixed in a ball mill.

A small amount of 5% PVA (polyvinyl alcohol) aqueous solution is added to this mixture, mixed in a sieve machine, passed through a 30 mesh sieve, and granulated. This granulated powder is applied with a pressure of 1 ton/al in a mold with an inner diameter of 137 m to produce a molded body having a diameter of 13 mm and a thickness of 0.5 Tfm. These molded bodies are fired at 1250-1400'C for 1-2 hours.
After this, silver electrodes are provided on both circular surfaces of the sintered body of the disk. Table 1 below shows the properties of the sintered bodies obtained for various additive compositions.

In the table, ε25 is 1KHz at 25℃. ．． The dielectric constant, Tan δ, determined from the capacitance measured at AC1V indicates the dielectric loss at this time. Also, 1. R is insulation resistivity measured at DC5OV, B. D. V indicates the boost breakdown voltage, and AC-V indicates the value of Tan δ measured at 1 KHz under the effective AC voltage. Furthermore, the redundancy is -3 of the capacitance based on 20℃.
The rate of change at 0°C and 85°C is shown. As is clear from Table 1, the composition of the present invention has a large dielectric constant, and
It is recognized that the capacitance change due to C voltage is small and the bending strength is strong. Conventionally, compositions containing BazrO3, BasnO3, SrTiO3, etc. had high AC voltage characteristics of about 3 to 7% in terms of Tan δ value under 50■/Tfn, and bending strength was low at 600 to 700k9/C7lf. This is considered to be an extremely good result. 1st
A multilayer ceramic capacitor as shown in FIG. 1 was prototyped using the composition of sample No. 3 shown in the table, and the characteristics were investigated. The results are shown in Table 2 below.

Table 2 shows BazrO to parts by weight of BaTiO3lOO.
3 parts by weight of 3, 0.4 parts by weight of MgTlO3, MnO2
It also shows the characteristics of a capacitor prototyped using a typical conventional composition containing 0.2 parts by weight of . In this case, the element shape is 3.07 x 1.56 x 0.56wr
It is m.

In addition, in FIG. 1, 1 is sample No. 2 is a palladium electrode, 3 is a terminal electrode (
Ag electrode). Also, in Table 2, C and Tanδ are 1KHz. ．． This is a value measured at AC1V. 1. Re is the insulation resistance value measured at DC5O■, B. D. Ve is a boosted breakdown voltage value.

In addition, the transverse rupture force supports the element body with a span of 2.5Twt,
This is the pressure just before the element breaks when the central part of the element is pressed with a knife with a blade width of 0.5. FIG. 2 shows the frequency characteristics of the equivalent series resistance in this case.

Compared to the characteristic A of the capacitor with the conventional composition, the sample No. of the present invention. It is clear that the characteristic B of the capacitor prototyped in 13 has extremely good characteristics in the high frequency region. FIG. 3 also shows the rate of change in capacitance with temperature of a capacitor prototyped according to the present invention. As described above, the composition of the present invention has favorable characteristics as a thin film dielectric such as a multilayer ceramic capacitor.

In other words, it has a high dielectric constant of 3000 or more, low voltage dependence, and low equivalent series resistance at high frequencies, making it a composition that meets recent market needs, and is particularly suitable for areas such as electronic tuners. There are some things that have extremely high utility value.

[Brief Description of the Drawings] Fig. 1 is a partial cross-sectional front view showing a multilayer ceramic capacitor prototyped using the composition of the present invention, and Fig. 2 is a diagram showing the frequency characteristics of the equivalent series resistance in the same ceramic capacitor. , FIG. 3 is a diagram similarly showing the change in capacitance with temperature. 1... Ceramic dielectric, 2... Palladium electrode, 3... Terminal electrode.

Claims (1)

[Claims] 1 Based on 100 parts by weight of BaTiO_3, CaTiO
_31-10 parts by weight, Sb_2O_31-4 parts by weight, S
A high dielectric constant ceramic composition containing 1 to 5 parts by weight of m_2O_3. 2. The high dielectric constant ceramic composition according to claim 1, which contains 0.01 to 0.5 wt% of at least one of oxides of Mn, Cr, Fe, Ni, and Co based on the main component. .