JPH03173107A - Laminated ceramic capacitor - Google Patents

Abstract

PURPOSE:To obtain a laminated ceramic capacitor excellent in capacity per unit, dielectric loss tangent tan delta and temperature characteristics, small in size, large in capacity, and low in back height by composing it of high permittivity porcelain composition added to contain specific amounts of Nb2, O5, Gd2, O3 and ZnO to BaTiO3. CONSTITUTION:A laminated ceramic capacitor is composed of high permittivity by adding 1.45-1.6 pts.wt. of niobium pentoxide (Nb2O5), 0.2-0.4 pts.wt. of gadolinium oxide (Gd2O3) and 0.4-0.5 pts.wt. of zinc oxide (ZnO) to 100 pts.wt. of barium titanate (BaTiO3). BaTiO3 is a main content. The Nb2O5 has effects of enhancing its permittivity and reducing temperature change of the permittivity. The Gd2O3 enhances permittivity, controls dielectric loss tangent tan delta, further ZnO reduces dielectric loss tangent tan delta and reduces temperature change.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a layered ceramic capacitor which has a large capacitance value per unit and also has a small change in capacitance value due to temperature changes. It satisfies the X7R characteristics of EIAJ (Electronic Machinery Industries Association of Japan).

[Conventional technology and its problems]

High dielectric constant ceramic compositions are used as materials for multilayer ceramic capacitors and the like. Recently, while multilayer capacitors have been becoming smaller, there is also a strong demand for larger capacitance.

Regarding the miniaturization of multilayer capacitors, important compositional characteristics include a large dielectric constant εr and a high dielectric loss tangent tan.
One example is that δ is small.

In particular, the dielectric loss tangent tan δ greatly affects the thickness of one ceramic green sheet when manufacturing a multilayer capacitor. At the same time, if the dielectric constant εr is large, a compact multilayer capacitor with a large capacity can be achieved.

Conventionally, Nb and 0.0% were added to B a T i O:I. Japanese Patent Publication No. 60-20849 and Japanese Patent Publication No. 61-20084 are known as dielectric ceramic compositions containing .

According to Japanese Patent Publication No. 60-20849, BaTiO2
A predetermined amount of N b z Os , Ca 0% Z n O is added to the dielectric loss tangent tan δ to 0. Achieved below 9%. However, in this type of dielectric composition, the dielectric constant εr is approximately 2970 at most, and a sufficiently large capacitance per unit of fF ceramic capacitor cannot be expected, and furthermore, it is difficult to expect a sufficiently large capacitance per unit of fF ceramic capacitor. The ratio was within ±14%, and the EIAJ X7R characteristics were satisfactory, but the temperature change rate was slightly large.

Also, according to Japanese Patent Publication No. 61-20084, BaT
By adding predetermined amounts of Nb2O5, Nd2O3, and ZnO to iO3, a high dielectric constant εr of 2500 to 3800 is achieved. However, the capacitance per unit of a multilayer ceramic capacitor is approximately 0.954 nF/mn+'', and it has been difficult to achieve a sufficiently small and large capacity multilayer capacitor with a dielectric loss tangent tan δ of 1.9%.

That is, with the dielectric ceramic composition shown in the prior art, it has not been possible to obtain a small, low-profile multilayer ceramic capacitor that has a high dielectric constant, a small dielectric loss tangent tan δ, and a small rate of change due to temperature changes.

The present inventors have conducted intensive research to provide a high dielectric constant ceramic composition that solves the above-mentioned drawbacks. As a result, by adding niobium pentoxide, zinc oxide, and gadolinium oxide to barium titanate, -55 The rate of change in capacitance is small (within ±10%) over a wide temperature range of ~125°C, the dielectric loss tangent tan δ is small (less than 1°9% for multilayer ceramic capacitors), and the dielectric constant is high (1° per unit). A multilayer ceramic capacitor having a ceramic composition having a magnetic flux of 26 n F /m+g+") has been found.

[Specific means for solving the problem] The gist of the present invention is that barium titanate (BaTiO:1)
Niobium pentoxide (N b 2 o
s) is 1.45 to 1.6 parts by weight, gadolinium oxide (G
dz 03 ) and 0.2 to 0.4 parts by weight of zinc oxide (ZnO) and 0.4 to 0.5 parts by weight of zinc oxide (ZnO) are added. .

BaTiO3 is the main component, and Nb2O has the effect of increasing the dielectric constant and reducing temperature changes in the dielectric constant. In addition, G d z O3 increases the dielectric constant and the dielectric loss tangent t
It has the effect of controlling anδ. Furthermore, ZnO has the effect of reducing the dielectric loss tangent tan δ and reducing temperature changes.

By changing the composition within the above range, the capacitance per unit of the multilayer ceramic capacitor can be increased to 1°15nF/2.
Above, the temperature change rate is ±l over the range of 155 to 125℃.
A multilayer ceramic capacitor having a dielectric ceramic composition with a dielectric loss tangent tan δ of less than 1.9 can be provided within θ%.

Next, the reason for limiting Nbz Os, Gdz 03, and ZnO will be explained.

As NbzOs and ZnO added to BaTiOz increase, the relative amount of BaTiO3 decreases and the capacity per unit decreases. However, Gd,03 has the effect of increasing the capacity per unit.

As the amount of NbzOs added increases, the capacity per unit decreases, and when it exceeds 1.6 parts by weight, the capacity per unit decreases by 1.
．． 15nF/mm" or less. Also, conversely, N
b. When the amount of O5 added is decreased, the dielectric loss tangent tan δ becomes 1
．． As the ratio increases to 9% or more, the rate of change in capacitance with temperature increases. That is, if the amount is less than 1.3 parts by weight, the dielectric loss tangent tan δ increases to around 2.03%, and the temperature change rate becomes -15.2%, which is two digits.

When the amount of GdZO3' added increases, relatively BaTi
Although O3 decreases, the dielectric constant is maintained or improved,
If it exceeds 0.6 parts by weight, the dielectric loss tangent tan δ and the temperature change rate will be -11.2%, which is two digits. On the contrary, Gdz
C) If the amount of t added is reduced, the capacity per unit will decrease. That is, if the amount is less than 0.2 parts by weight, the capacitance per unit will be 1°107 nF/2.

As the amount of ZnO added increases, the dielectric loss tangent tan δ decreases; however, if it exceeds 0.5 parts by weight, the capacity per unit decreases. Conversely, when the amount of ZnO added is reduced, the dielectric loss tangent tan δ increases significantly to 1.98%.

〔Example〕

Next, the present invention will be explained in more detail according to examples.

As a starting material, barium oxalate was heated and calcined to obtain barium titanate powder. Nb2O5, G d 203 for 100 parts by weight of this barium titanate
and ZnO powders were weighed so as to have the compounding ratio shown in Table 1, and after pulverizing in a ball mill for 20 hours, an organic binder was added, and then stirred, and the thickness was determined by the doctor blade method. It was molded into a 30 μm tape. Pd-Ag (70:30) is printed on this tape as a capacitor internal electrode, and a plurality of tapes are laminated and bonded by thermocompression. Further, the laminate was punched into a disc shape with a diameter of 20 mm, the binder was removed, and the disc was fired for 2.5 hours at 1250° C. in an oxygen atmosphere. Furthermore, external electrodes made of silver paste were baked on both end faces to prepare a sample.

For the sample formed in this way, the dielectric constant εr and the dielectric loss tangent tan δ were determined at a reference temperature of 25°C, frequency of 1, and QkHz.
, measurement voltage 1. Measured by OVrms.

The results are shown in Table 1. Sample numbers marked with * are outside the scope of the present invention. In addition, in the table, BaT i O:l
simply B T, N b z Os simply Nb, Gd2
O3 was simply written as Gd, and ZnO was simply written as Zn.

As an evaluation of the scope of the present invention, the capacitance per unit is 1.15nF≠ In other words, if the capacitance per unit is 1.15nF/m+w2, sufficient capacitance cannot be obtained, and this makes it difficult to miniaturize multilayer capacitors. turn into.

Moreover, a dielectric loss tangent tan δ of less than 1.9% was considered to be a good product.

That is, in order to form a low-profile mE ceramic capacitor, it is necessary to reduce the thickness of the dielectric sheet layer, which requires a dielectric loss tangent tan δ of less than 1°9%.

In addition, the rate of change in capacitance value with respect to temperature change was considered to be a good product if it was within ±10%. When the rate of change in capacitance value exceeds ±10%,
TC-V, one of the temperature characteristics of EIAJ's X7RH
It becomes difficult to fully satisfy C (temperature characteristics when applying a DC voltage of 50% of the rated voltage) within -40% to 15%.

(Hereinafter, blank space) Sample numbers 1 to 4 are BaT, which is the main component of high dielectric constant porcelain.
The amount of N b z Os added to iOs was studied. That is, from 1.3 parts by weight to 1.75 parts by weight of N b 2 OS
Even the parts by weight were changed. At this time, G d zO3 and Z
The weight part of nO was 0. They were fixed at 4 parts by weight and 0° and 5 parts by weight. This is a central value within the range of the present invention in each addition amount described below.

In sample number 1 (NbzOs: 1.3 parts by weight), although the capacitance per unit was relatively good, the dielectric loss tangent tan δ exceeded 2.0%, and furthermore, the temperature change rate of the capacitance was ±10%. %, -15°2% (85°C
).

In addition, sample numbers 2 to 3 (Nb20S: 1-4
5 to 1.6 parts by weight), the capacity per unit is 1°15
n F /mm2 or more, dielectric loss tangent tan δ is 1.9%
Below, the temperature change rate is less than ±lO%, and the EIAJ
A small, large-capacity multilayer capacitor that satisfies the 7R characteristics can be achieved.

Sample number 4 (Nb20s: 1.75 parts by weight) gave a relatively good result for the dielectric loss tangent tan δ, but
Capacity per unit is L 15 n F /IIIm”
The value is 1.096F/+n+w" below.

Therefore, if the amount of Nb2O5 added to BaTiO3 of the present invention is increased, the capacity per unit will decrease.

Furthermore, even if the amount of N b 20 s added is decreased, the dielectric loss tangent t
an δ is 1.9% and the temperature change rate is large. in the end,
The amount of Nb2O5 added was in the range of 1.45 parts by weight to 1.6 parts by weight.

Sample numbers 5 to 7.2 are B, which is the main component of high dielectric constant porcelain.
The amount of Gd203 added to aTiO:s was investigated. That is, G d z O3 is 0. 2 parts by weight to 0.6
Even the parts by weight were changed. At this time, Nb2 os and Zn
The parts by weight of O were fixed at 1.45 parts by weight and 0.5 parts by weight, respectively.

Sample number 5 (CGdz 03: 0.1 part by weight) gave relatively good results in dielectric loss tangent tan δ and temperature change rate, but the capacitance per unit was 1.15 nF/w + m.
“It will be less than that.

In addition, sample number 6.2 (Gdz O:i: 0.
2 to 0.4 parts by weight), the capacity per unit is 1. 1
5nF/mm" or more, dielectric loss tangent tan δ is 1.9% or less, temperature change rate is less than ±10%, and EIAJ's X7R
A small, large-capacity multilayer capacitor that satisfies the characteristics can be achieved.

Sample number 7 (caz O:l: 0.6 parts by weight)
Although this results in a good capacitance per unit, the dielectric loss tangent tan δ exceeds 1.9% and the temperature change rate exceeds ±10%.

Therefore, Gd added to B a T i O3 of the present invention
Increasing 2O3 goes against the relative decrease in BaTiO3, maintains or increases the capacitance per unit, and increases the dielectric loss tangent tan δ. Also, if the amount added is reduced, the capacitance per unit will be 1-15nF/
It will be 2 or less. In the end, the amount of Gd,03 added is 0.2
0.0 from weight part. The range was 4 parts by weight.

For sample numbers 8 to 11, the amount of ZnO added to BaTiO3, which is the main component of the high dielectric constant ceramic composition, was investigated.

That is, the amount of ZnO was varied from 0 to 0.6 parts by weight. At this time, the weight parts of NbzOs and Gd2O3 were each 1.6
Part by weight, 0. The amount was fixed at 2 parts by weight.

Sample No. 8 (ZnO: 0.3 parts by weight) yields relatively good capacitance per unit and temperature change rate, but the dielectric loss tangent tan δ is 1.98%, exceeding 1°9%.

In addition, for sample number 9.10 (ZnO: 0.4 to 0.5 parts by weight), the capacity per unit was 1.268F/m
s'' or more, the dielectric loss tangent tan δ is 1.72% or less, the temperature change rate is less than ±10%, and a small, large-capacity multilayer capacitor that satisfies EIAJ's X7R characteristics can be achieved.

Sample No. 11 (ZnO: O, 6 parts by weight) gave good results in terms of dielectric loss tangent tan δ and temperature change rate, but the capacitance per unit was 1.008 nF/rsya.”
and 1. It becomes less than 15nF/mn+''.

Therefore, if the amount of ZnO added to BaTiO3 of the present invention is increased, the dielectric loss tangent tan δ becomes smaller.

However, the capacity per unit decreases. If the amount added is reduced, the dielectric loss tangent tan δ tends to increase. In the end, the amount of ZnO added was 0.3
The N range was ~0.5 parts by weight.

As described above, according to the present invention, the capacity per unit is 1
．． 15 n F/mm2 or more, and the dielectric loss tangent tan δ is less than 1.9%, making it possible to achieve a multilayer ceramic capacitor with little capacitance change even in a wide temperature range, that is, excellent X7R characteristics.

In addition, even if various combinations other than the above-mentioned samples are made within the scope of the present invention, the capacitance per unit is 1.15nF/++++
++2 or more, dielectric loss tangent tan δ less than 1.9%, capacitance value change with temperature change (-55 to 125°C) ±10
It was confirmed that it was within %.

In this way, especially for multilayer ceramic capacitors with a dielectric loss tangent tan δ of less than 1.9%, the thickness of the laminated sheets is 30%.
It can be manufactured with a thickness of less than μm, and a low-profile multilayer ceramic capacitor can be achieved.

〔Effect of the invention〕

As described above, according to the present invention, a small, ancient, and low-profile stacked stone ceramic capacitor with excellent per unit capacity, dielectric loss tangent tan δ, and temperature characteristics is obtained.

Claims (1)

[Claims] Based on 100 parts by weight of BaTiO_3, 1.45 to 1.6 parts by weight of Nb_2O_5 and Gd_2O
A multilayer ceramic capacitor made of a high dielectric constant ceramic composition to which 0.2 to 0.4 parts by weight of _3 and 0.4 to 0.5 parts by weight of ZnO are added.