JPS60253208A - Laminated porcelain capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multilayer ceramic capacitor having internal electrodes made of a silver-palladium alloy.

Commercially available multilayer ceramic capacitors have internal electrodes formed on the surface of thin ceramic dielectrics, which are laminated and fired together, and the internal electrodes are alternately connected in parallel to external connection electrodes formed on the side surfaces of the layers. The structure is such that

Recently, some ceramic capacitors use a silver-palladium alloy (Ag-M) instead of pure palladium (M), which is a noble metal, as the internal electrode, which reduces the cost of the internal electrode material. We are trying to

However, silver-palladium alloy (Ag-Pd) has a high specific resistance value when the silver (Ag) content is low, and the absolute amount of metal forming the electrode decreases due to evaporation of silver (Ag) during firing. As a result, the electrode film becomes mesh-like and the sheet resistance increases, so that the capacitor's equal series resistance (
ESR) becomes large, so it cannot be used in high-frequency circuits.

Therefore, silver (A
It is conceivable to increase the content of g) to lower the specific resistance value, but if the content of silver (Ag) is increased, the melting point of the metal decreases, making it impossible to obtain a stable multilayer ceramic capacitor. Furthermore, there is a limit to increasing the proportion of silver (Ag) in order to prevent short circuits due to migration (atom movement due to electric field) between electrodes. On the other hand, anticipating the evaporation of silver (Ag) during firing, silver (Ag) is applied on the dielectric green sheet in advance.
Increasing the amount of Ag) will lead to structural defects (cracks or delamination) in the multilayer ceramic capacitor, making it impractical.

In view of the above-mentioned current situation, the inventors of the present invention have conducted extensive research to improve the dielectric structure by pre-containing a certain amount of silver (Ag) in the dielectric of a multilayer ceramic capacitor, or by causing silver to diffuse during firing. By using a firing method (for example, burying) that uses an atmosphere that is forced to penetrate into the capacitor, it is possible to create equal series resistors (I
It was found that the capacitance was improved while reducing the DSR).

Therefore, in the present invention, silver-palladium alloy (A
In a multilayer ceramic capacitor having g-P(1) as an internal electrode, by lowering its equal series resistance (ESR),
It is an inexpensive multilayer ceramic capacitor that can be used even in high-frequency circuits by improving capacitance, and has CG characteristics for temperature compensation (temperature coefficient of capacitance is ±30 ppIll/℃ according to J Engineering S standard). It is an object of the present invention to provide a multilayer ceramic capacitor having a capacitance (which is required to be within the range of .

According to the present invention, in a multilayer ceramic capacitor using a silver-palladium alloy (Ag-M) as an internal electrode, the dielectric material contains 0.05 to 0.70% by weight of silver (Ag). A multilayer ceramic capacitor is provided.

When silver (Ag) is contained in the dielectric, the evaporation effect of silver (Ag) in the silver-palladium alloy (Ag-M) that is the internal electrode can be suppressed. Silver (Ag) in dielectric
If the content is less than 0.05% by weight, there is no effect of suppressing the evaporation of silver (Ag), so it is impossible to reduce the equal series resistance (ESR), and if it exceeds 0.70% by weight, Since the temperature coefficient of capacitance greatly exceeds -30 ppm/'C, the temperature characteristics of multilayer ceramic capacitors are certain (referred to as CG characteristics, which are required to be within the range of ±30 ppm/'C according to the JIS standard). does not match.

Example 1 Koshi T108 with a purity of 98.5% or more, tMsOa with a purity of 98% or more, and a purity of 97.5, which were prepared in advance at 1200°C from equimolar amounts of BaC0a and TlO2 by a solid phase synthesis method.
% titanium dioxide (anatase), B15oa with a purity of 95% or more, and Pb1104 with a purity of 95% or more by weight, respectively 22.6%, 316%, 35.5%, 4
．． 71% and 5.59% plus BgO
a, 5in8 and ZrO each by weight 0.50
%, 2.50% and 2.50% were added as the basic composition. To this basic composition, reagent Ag2O powder was weighed and added to the amount listed in the silver (Ag) addition amount column in Table 1, and the mixture was placed in a porcelain pot with an internal volume of L61 and a bulk volume of 0.81 ( 1,s kg) of alumina balls (17
In addition, an organic binder, a plasticizer, and a dispersion medium toluene were added together with a dispersant and an antifoaming agent, and the mixture was rotated at a rotation speed of 72 rpm for 24 hours. The obtained raw material slip was made into a wall thickness of 25 μm using the doctor blade method 1.
A green sheet was formed. Stack 25 green sheets and hot press to create a green molded board.
It was cut into a green square plate with a U angle and a thickness of about 0.50 ff.

The green square plate was placed in a series of A008 pots and fired at 1050°C for 2 hours. Obtained approximately 8fi square, thickness approximately 0.4
First, evaluation samples 1-1 to 1-6 were prepared as dielectrics of the rectangular plates themselves by baking a silver electrode on the gold surface of the upper F side of the fl rectangular plates. Samples 1 to 6 thus obtained were subjected to frequency IME (z
, input L/F JL/I Vrms + capacitance (PF) and quality factor (Q) (Q value is required to be 1000 or more according to JIS standards) and -55℃~
The temperature coefficient of capacitance was measured in a temperature range of +125°C.

The relative permittivity (εr) of the dielectric ceramic is determined from the capacitance measurement results.
was calculated and shown in Table 1 along with the measurement results of quality factor (Q) and capacitance temperature coefficient. be.

Samples 1 to 6 in Table 1 have an amount of silver (Ag) added to the dielectric of 0 to 2.
The silver (Ag
) content is 0.006 to 0.596% by weight.

The relative dielectric constant (6r) of each of these samples is 67.9 a,
Quality coefficient + Ql is also 2500 or more, capacity temperature coefficient (1) I
It is understood that the values (Xn/°C) are within ±30'ppm/°C, which is sufficient as a dielectric material for a multilayer ceramic capacitor. In addition, the content rate of silver (Ag) is 0f150
Samples 4 to 6 containing % by weight or more have a relative dielectric constant (εr) of 72.6.
Compared to sample 3 whose relative permittivity is 680, its relative permittivity (
It was found that εr) was significantly improved. The reason for this is not clear, but it is thought that the presence of the silk selectively suppresses the crystal growth of titanium-ionized neodymium (NdaOa.2'riO2).

・Example 2 Next, silver (Ag) was deposited on the 25 μm thick green sheet obtained in Example 1 using a rectangular pattern with an effective area of about 1 am.
A paste made by adding an organic binder and its solvent to an alloy containing 70 wt. Stack 10 green sheets each on top and bottom and hot press to make about 2 pieces.
．． Cut into 5% green chips about 1.5$ each.

The thus obtained green chips forming the multilayer porcelain capacitor with (7) layers were placed in an alumina pot and fired at 1050°C for 2 hours in an air atmosphere, and silver-palladium alloy (Ag-
Evaluation samples 7 to 12 in Table 2 were obtained by baking extraction electrodes made of Pα).

Capacitance and capacitance temperature coefficient at frequency I MHz,
The equivalent series resistance value was measured at a frequency of 900 MHz, using an LCR meter and an impedance analyzer. The content of silver (Ag) in the dielectric is determined by the XMA method (X-ray microanalyzer method). These properties are shown in Table 2 along with Samples 7-12.

Samples of company seals are outside the scope of this invention.

Samples 7 to 12 use the dielectrics of samples 1 to 6,
As a result of laminating this dielectric material, the content of silver (Ag) is 0.
01 to 0.60% by weight. The capacitance temperature coefficient of each of these samples is within ±30 ppm/°C, but silver (Ag
) content of less than 0.05, the equivalent series resistance value of samples 7 to 9 is 1870±290 InΩ or more, whereas sample 10 has a silver (Ag) content of 0.05 or more.
The equivalent series resistance value of ~12 was 283, ±63111Ω, and its characteristics were improved. As a result, the electrostatic container also had 2 samples 7 to 9.
It can be seen that while it is 0.56 PF or less, Samples 10 to 12 have improved to 25.33 or more. When we cut each sample 7 to 9 and samples 10 to 12 and observed the internal electrodes between the dielectrics, we found that samples 10 to 12 were smaller than samples 7 to 9.
It was confirmed that the internal electrode between the dielectrics had a sufficient thickness, and that evaporation of silver (Ag) was suppressed during firing.

Example 3 Next, samples 6 and 12 or more silver (Ag) in the above example
In order to create a dielectric material containing silver (Ag
) does not increase in proportion to the silver content and tends to reach saturation, so the addition amount of Ag per 100 parts by weight of AIQOs
A mixed powder obtained by mixing both BO 5.9 parts by weight (Ag 4.65 parts by weight) was placed in an A190s container, and Sample 1 in Example 1 was embedded in this mixed powder and 1050'
Firing was performed using a C1 trowel for 2 hours. A square plate type capacitor was prepared by baking a silver (Ag) electrode on a fired square plate in the same manner as in Example 1, and evaluation sample 13 was obtained.

Sample 13 thus obtained was evaluated in the same manner as in Example 1, and the results are shown in Table 9J3. The content of silver (Ag) in the dielectric was determined by atomic absorption spectrometry.

A dielectric material with a silver (Ag) content of 0.70% by weight has a relative dielectric constant (gr) so, s quality factor (Q) of 1000 or more and a capacitance temperature coefficient (ppm/'C) of ±30 pH) Il
l/℃17) There is sufficient temperature within the range.

Example 4 The multilayer porcelain capacitor green chips of samples 7 and 12 of Example 2 were embedded in the mixed powder of A7203 and Ag 20 described in Example 3, and baked at 1050° C. for 2 hours, followed by the same process as in Example 2. silver as an extraction electrode.
Evaluation samples 14 and 15 were obtained by baking palladium alloy (Ag-P(i)) on both ends of the chip.The results of evaluation using the same method as in Example 2 are listed in Table 4. As in Example 2, silver (Ag) in the dielectric of each sample was determined by XMA method 1.

- Sample numbers marked are outside the scope of the present invention.

Sample number 14 has a silver (Ag) content of 0.69% by weight, which is within the range of the present invention, and the equivalent series resistance value (tRΩ) is 15.
Samples 7 to 9 outside the scope of the present invention among the above examples with 8±6 mΩ
(and the capacitance (PF) is also 2.
7.96 PF is sufficient, and the capacity temperature coefficient is -2
3 pI) m/'C and specified temperature characteristics (±30 I) pII
I/'C) range.

On the other hand, Sample 15 has a silver (Ag) content of 0.74% by weight, which is the upper limit of the present invention, and a silver (Ag) content of 0.70%.
As shown in the equivalent series resistance value (mΩ) and electrostatic resistance, the present invention is a multilayer porcelain capacitor with a silver-palladium alloy (Ag-IM) as an internal electrode. It contains 0.05 to 0.70% by weight of (Ag), and is inexpensive and can be used in high-frequency circuits by lowering the equal series resistance (KSR) of the dielectric and improving capacitance. A multilayer ceramic capacitor can be provided.

Applicant: Kyocera Corporation

Claims (1)

[Claims] A multilayer ceramic capacitor having a silver-palladium alloy (Ag-Pd) as an internal electrode, characterized in that the ceramic dielectric contains 0.05 to 0.70% by weight of silver (Ag). type porcelain capacitor.