JPS5951097B2 - High dielectric constant porcelain composition - Google Patents

Description

[Detailed description of the invention] The present invention is barium titanate BaTiO.

The main components are calcium titanate, CaTiO3, and niobium oxide, Nb. 0.

The present invention relates to a high dielectric constant ceramic composition obtained by further adding finely powdered magazine MnO2 to a composition to which tantalum oxide Ta.O. (or tantalum oxide Ta.O.) is added. Conventionally, many high dielectric constant compositions mainly containing barium titanate have been proposed, and are particularly used in single-plate ceramic capacitors.

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

With the Curie point as a boundary, it becomes a tetragonal system on the low temperature side, and a cubic system on the high temperature side. It is well known that the cubic crystal region exhibits paraelectricity. Barium titanate alone is rarely used as a capacitor because the dielectric constant of barium titanate varies greatly with temperature in the temperature range around room temperature, and the dielectric loss is large. Efforts have been made to move the Curie point to near room temperature and to reduce temperature changes in the dielectric constant.

A typical additive is CaTiO. , BaZrO
, , SrTiO, , BaSn03, CaSn03, etc. are well known. By appropriately adding these and further correcting them with trace components, they are provided as characteristic materials such as X7R, Y5T, Y5V, Z4V, etc. based on EIA standards. The reality is that these materials have generally been used for thick single-plate ceramic capacitors with an element thickness of 0.5 to 1.0 mm. In recent years, the miniaturization of various electronics-related components has progressed, and multilayer ceramic capacitors are the most prominent example of this.

This multilayer ceramic capacitor has a ceramic dielectric material of 25 to 1
The film is thinned to about 0.00 μm and has a multilayer structure sandwiched between comb-shaped structure electrodes, and the ratio of electrode area and distance between electrodes can be made extremely large, so the capacitance per volume is comparable to that of a single-plate capacitor. It is possible to make the capacitor more than 100 times larger than that of the capacitor, and the same capacitance can be secured with a smaller volume of 1/10 or less, making it extremely easy to downsize. However, when such a porcelain dielectric thin film is used, the actual situation is that the conventional single-plate type porcelain composition cannot be immediately applied.

That is, since the voltage applied per unit length is more than 10 times that of the conventional material, a material with a small porcelain permittivity and low voltage dependence has been required. In addition, recently, with the direct attachment method to the printed circuit board, strong materials that do not break due to the deflection of the printed circuit board, and 4.
Materials with high thermal shock resistance are required for soldering, which may be exposed to high temperatures of 00° C. or higher. In particular, J.
A large number of electronic tuners are required to have YD characteristics according to IS standards or Y5T characteristics according to EIA standards.
A low equivalent series resistance is required in the 0 MHz frequency band. Further, it is required that the solder heat resistance temperature can be used even under severe conditions of 300° C. or higher, and sometimes about 400° C. In view of the above, the present invention has been made through various experiments, and can provide a high dielectric constant ceramic composition that has low voltage dependence, high bending strength, good high frequency properties, and good thermal shock resistance. It is something that The present invention will be explained below based on Examples. <Example> BaTiO,
(purity 98% or more) For 100 parts by weight, CaTiO
, is 1 to 5 parts by weight, Nb.

O. For a composition consisting of 1 to 4 parts by weight, MnO is further finely powdered. are added in various proportions and thoroughly mixed using a ball mill. To 100 parts by weight of this mixed powder, 7 to 8 parts by weight of polyvinyl butyral, 10 to 15 parts by weight of n-butyl acetate, 35 to 40 parts by weight of ethyl acetate, and 3 to 4 parts by weight of dibutyl phthalate were added and mixed to obtain 2. Using the slurry, a sheet of 80±5 μm is produced by the blade method. Using this sheet, palladium paste was laminated as an internal electrode, and after cutting,
Bake at 400°C for 1 to 5 hours. After that, Ag-Pd paste was attached to both ends of the element body obtained as above, and
It is baked at 00 to 900°C to form a terminal electrode. A cross-sectional view of the ceramic capacitor thus obtained is shown in the figure. In the figure, 1 is a ceramic dielectric made of the ceramic composition of the present invention, 2 is an internal electrode, and 3 is a terminal electrode. Further, the outer diameter of the element is 3.07 mm x 1.56 mm x 0.56 mm. The table below shows MnO using the particle size of fine powder MnO as a parameter. This shows the relationship between the amount added and various performances.
In the table, C2. is the capacitance measured under ACIV at 25° C. and 1 KHz, and Tan δ is the dielectric loss at this time. Further, I-R is the insulation resistance measured at DC5OV, BDV is the boost breakdown voltage, ESR is the equivalent series resistance at 100 MHz, and T-S is the maximum temperature that can withstand thermal shock. moreover,
P indicates transverse rupture force, and this transverse rupture force P is the pressure immediately before breaking when the element body is supported with a span of 2.5 mm and the center portion of the element body is pressed with a knife having a width of 0.5 mm. As is clear from the above table, the amount of MnO2 added is 0.05 to 0.5 parts by weight (
In particular, if the average particle size of MnO2 is 1 μm or less when added (based on parts by weight of BaTiO3lOO), E
It is recognized that SR and T-S are good.

Furthermore, the finer the MnO2, the more remarkable this effect is. Further, although temperature characteristics are not shown in the table, the samples in the table have Y5T characteristics according to the EIA standard. That is, in the range from -25°C to +85°C, the capacitance change rate is within +22% to -33% with respect to the capacitance at 25°C.
As described above, the porcelain composition based on the present invention allows
It is possible to provide multilayer ceramic capacitors with ESR, which represents high frequency characteristics, and thermal shock resistance, which is increasingly required for direct mounting on printed circuit boards.In particular, we can provide multilayer ceramic capacitors with Y5T characteristics, which are used for tuners. It is ideal for manufacturing capacitors, and as Y5T multilayer ceramic capacitors used in this field have been rapidly increasing in recent years, their industrial value can be said to be high.

In addition, in the examples, BaTlO3, CaTi3, Nb2O5
, MnO2, but Nb2O
The same effect can be obtained by using Ta2O5, a congener compound, in place of 5.

Furthermore, it goes without saying that the present invention can obtain similar effects even if it does not have the laminated structure shown in the embodiments, and is also effective as a single capacitor.

[Brief explanation of the drawing]

The figure is a partially cutaway front view showing a multilayer ceramic capacitor obtained using the ceramic composition of the present invention.

Claims (1)

[Claims] 1 CaTiO_ for 3100 parts by weight of BaTiO_
31 to 5 parts by weight, Nb_2O_5 (or Ta_2O_
5) A high dielectric constant ceramic composition characterized by further adding 0.05 to 0.5 parts by weight of MnO_2 with an average particle size of 1.0 μm or less to the composition consisting of 1 to 4 parts by weight. .