JPH03246811A - Dielectric porcelain composition and laminated capacitor element - Google Patents

Abstract

PURPOSE:To make a dielectric layer thin and obtain an element of small size but large capacity by incorporating an internal electrode layer mainly composed of Cu or an alloy containing Cu into an element, and mainly composing the element of Pb perovskite ceramic. CONSTITUTION:A composition formula expressed by Pb1-x+aMex {(Zn1/3 Nb2/3)1-y-2Tiy(CubW1-b)2} O3+a where Me is one or more elements selected from Sr and Ba, the values of 'x' and 'y' are so determined as to fall within the illustrated range, and the values of 'bz', 'a' and 'b' are respectively kept as 0<=a<=0.1, 0.02<=b<=1.0 and 0.002<=bz<=0.04. As aforementioned, Cu is contained in an internal electrode, cost required for an electrode material can be substantially reduced and excellent characteristics can be displayed in a high frequency circuit. In addition, as a Pb dielectric is used, a dielectric layer can be made thin and a capacitor element of small size but large capacity can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is characterized in that the capacitance changes with temperature according to the JIS standard Y class B characteristic (±10 in the range from -25°C to +85°C with 20°C as the standard). %), the multilayer capacitor element has an internal electrode layer mainly composed of Cu or an alloy containing Cu, and a dielectric layer mainly composed of Pb-based perovskite ceramic.

BACKGROUND OF THE INVENTION Due to the demand for smaller devices and larger capacitances as electronic devices become smaller, multilayer capacitors have become mainstream in the ceramic capacitor market in recent years.

Multilayer ceramic capacitors are usually obtained by co-firing internal electrodes and dielectric ceramics. Barium titanate-based ceramic compositions have been widely used as dielectric materials for high-permittivity ceramic capacitors. However, the firing temperature for barium titanate porcelain is 1300°C.
Therefore, when manufacturing a multilayer capacitor, it is necessary to use an expensive metal with relatively high electrical resistance, such as Pd or Pt, as the internal electrode. Furthermore, barium titanate-based porcelain has poor DC bias characteristics and signal voltage characteristics, so it has not been possible to make the dielectric layer thinner and make the device smaller and larger in capacity.

Therefore, there has been a sudden increase in demand in recent years for multilayer capacitor elements that use inexpensive Cu, which has low electrical resistance, for the internal electrodes, and Pb-based perovskite ceramics, which have low firing temperatures and good voltage characteristics, for the dielectric. . We have so far proposed dielectric ceramic compositions that can be co-fired with Cu, that is, have practical electrical properties under firing conditions that do not melt or oxidize Cu, or mass-produced the above-mentioned multilayer capacitor elements. We have proposed a method for manufacturing it efficiently. This multilayer capacitor element has a high cost, can be made small and large in capacity, and can be replaced with an electrolytic capacitor.

Problems to be Solved by the Invention However, the temperature change rate of capacitance in the above-mentioned multilayer capacitor elements proposed to date is about the same as the JIS standard Y class E characteristic, so the circuits in which the element can be used are limited. It was something. Therefore, using Cu for the internal electrode,
Temperature change rate of capacitance is Y class B characteristic (-25°C to +85°C)
The development of a large-capacity multilayer capacitor element that satisfies the requirements (within ±10% in the range of °C) is awaited. None of the above elements has CR product, voltage characteristics, etc. at a practical level.

An object of the invention as defined in claim (1) of the present invention is to provide a dielectric ceramic composition for the above-mentioned multilayer capacitor element.

The invention described in claim (2) of the present invention is defined in claim (1).
The object of the present invention is to improve the insulation resistance value of the composition described in ).

An object of the invention described in claim (3) of the present invention is to provide the above-mentioned multilayer capacitor element.

The invention described in claim (4) of the present invention is based on claim (3).
The object of the present invention is to improve the insulation resistance value of the device described in ).

Means for solving the problem P b+-,, a Mex ((Zn+z+ Nbz
zs)+-y-gT i , (Cub wl-b)
g) Compositional formula represented by 0s-a (where Me is S
(one or more elements selected from r and Ba), X and y are in the range surrounded by A, B, C, D, and B below, and bz, a, and b are 0≦ The dielectric layer is composed mainly of ceramic that satisfies the following: a≦0.1, 0.02≦b≦1.0, 0.002≦bz≦0.04.

X y A 0.07 0.16 B O,0? 0.09CO, 190,
09 D O, 240, 22 E O, 160, 22 Further, a part of the Cu component contained in the ceramic constituting the dielectric layer is replaced with Mn.

Effect: According to the dielectric ceramic composition according to claim (1) of the present invention, since the amount of A sites constituting the perovskite phase is excessive, it can be sintered at a low temperature and has a high temperature even when fired in a non-oxidizing atmosphere. It has an insulation resistance value. Furthermore, since Cu is included in the B site, sintering occurs at a lower temperature, resulting in better temperature characteristics of dielectric constant.

According to the dielectric ceramic composition according to claim (2) of the present invention, since Mn is included, the insulation resistance value of the ceramic becomes high.

According to the multilayer capacitor element according to claim (3) of the present invention, since the amount of A sites in the dielectric ceramic is excessive, firing can be performed at a low temperature below the melting point of Cu,
The insulation resistance value also increased. Furthermore, since Cu is included in the B site, sintering occurs at a lower temperature, resulting in better temperature characteristics of dielectric constant.

According to the multilayer capacitor element according to claim (4) of the present invention, since the dielectric ceramic contains Mn, the insulation resistance value of the element becomes high.

Examples Example 1 This example corresponds to the invention described in claims (1) and (3), and by limiting the composition of the dielectric layer ceramic, Cu is included in the internal electrode layer and the temperature of the capacitance is The rate of change is JI
This is a multilayer capacitor element that satisfies the Y-class B characteristics of the S standard.

Chemically high-purity pbo, SrCO3, B a CO3, and ZnO are used as starting materials for dielectric layer ceramics.

NbzOs, Tie, WO8 and CuO were used.

After correcting the purity of these, X, y,
Predetermined amounts were weighed so that z, a, and b had various values. Mixing was carried out using a ball mill for 17 hours. The solvent used was pure water, and the ball used was a zirconia ball with a diameter of 4 mm. After drying the mixture, place it in an alumina crucible.
It was covered with a homogeneous lid and calcined at 750°C to 900°C.

The calcined product was coarsely crushed in an alumina mortar and milled by a ball mill.
Time crushed. The same solvent and ball as used for mixing were used.

Add 5wt to the dielectric powder obtained by sufficiently drying the powder.
% of polyvinyl butyral resin and 70 wt % of a solvent were mixed using a ball mill, and formed into a sheet by a doctor blade method.

Cu and O having an average particle size of 0.8 μm were used as starting materials for the internal electrode, and were kneaded with 0.5 wt% ethyl cellulose and 25% solvent based on Cu2O to obtain an electrode paste.

This electrode paste was printed on the above dielectric sheet by screen printing. The printed sheets were stacked so that the electrodes were drawn out alternately on the left and right sides, and then cut. The number of dielectric layers sandwiched between the electrodes was 20.

The laminate produced by the above procedure was heat treated at 500°C for 6 hours to scatter the organic components.

Then, 8 hours at 450 °C in a N2 gas stream containing 1% H2
The internal electrode was reduced.

For firing, the laminate is placed in a magnesia porcelain container together with a large amount of dielectric calcined powder, and CO□, C01H2,08,
The atmosphere was controlled using a gas such as N2 to an oxygen partial pressure that would not completely oxidize the internal electrodes, and the temperature was maintained at a predetermined temperature for 2 hours.

Although the firing temperature differs depending on the composition, the green compact of the dielectric plate sintered powder was fired under the same conditions as above while changing the temperature to a temperature at which the density of the sintered body was maximized.

500 elements were fired in - times of firing. A Cu paste was baked in N2 as an external electrode on the end face of the obtained element to obtain a multilayer capacitor element.

The outer dimensions of the multilayer capacitor element are 3.2X1.6Xo,
The electrode layer had a thickness of about 2 μm, and the dielectric layer had a thickness of about 20 μm per layer.

The capacitance and tanδ of the multilayer capacitor element are 1■r+A
Measurements were made under a signal voltage of HS 8.1 kHz. The insulation resistance value was determined from the value 1 minute after applying a voltage of 20V.

The end face of the element was polished, the effective area of the electrode and the thickness of the dielectric layer were determined, and the dielectric constant and insulation resistivity of the dielectric layer were calculated.

Each characteristic was taken as the average value of non-defective products.

Table 1 (1) to (4) shows the dielectric compositions X, y, Z,
a and b show the optimum firing temperature, the dielectric constant of the dielectric layer at 20°C, tan δ, resistivity, and temperature change rate of the dielectric constant.

Below are the margins in Table 1 (11 The # mark on the floor is Table 1 (2) of comparative examples that are outside the scope of claims. The # mark on the floor is Table 1 (3) of comparative examples that are outside the scope of claims. Those with a # mark on the floor are Table 1 (4) of comparative examples that are outside the scope of claims.The ones with a # mark on the floor are Table 1 (1) of comparative examples that are outside the scope of claims.
As shown in ~(4), in compositions outside the claimed range, the firing temperature is 1000°C or less, the dielectric constant of the dielectric layer is 2000 or more, the resistivity is IQ-1tΩ1 or more, and the capacitance changes with temperature. It no longer satisfies one of the conditions that the ratio satisfies the YB characteristic, and it is no longer practical as a material for a magnetic capacitor. Therefore, it was excluded from the scope of claims. In particular, by setting the excess A site amount a of the perovskite phase in the dielectric layer to 0 or more, it was possible to lower the firing temperature and increase the insulation resistance value.

Incidentally, there is no problem with the inclusion of elements other than those in the claimed range as long as the change in capacitance with temperature satisfies the YB characteristic of the JIS standard.

Example 2 This example corresponds to the invention described in claims (2) and (4), and the problem was solved by replacing a part of the CU acid component in the perovskite phase of the dielectric layer with Mn. be.

By the same method as in Example 1, dielectric powders were prepared so that C in the composition formula % had various values,
A multilayer capacitor element was obtained. Characteristic evaluation was also carried out in the same manner as in Example 1.

Table 2 shows the Mn substitution amount C1 and each characteristic.

The # mark on the floor of Table 2 indicates a comparative example outside the scope of the claims, as shown in Table 2, Cu contained in the perovskite phase of the dielectric layer.
By substituting some of the components with Mn, the insulation resistance value could be improved.

However, when the amount of Mn exceeds 85%, the temperature change in dielectric constant becomes large and YB characteristics are no longer satisfied.
Excluded from the scope of claims. Incidentally, there is no problem with the inclusion of elements other than those in the claimed range as long as the change in capacitance with temperature satisfies the YB characteristic of the JIS standard.

Effects of the Invention According to the multilayer capacitor element of the present invention, since the internal electrodes contain Cu, the cost required for electrode materials can be significantly reduced, and excellent characteristics can be exhibited in high frequency circuits. In addition, since a Pb-based dielectric is used, the dielectric layer can be made thinner, making it possible to obtain a small and large-capacity element.
It becomes possible to replace electrolytic capacitors. Furthermore, since the temperature change rate of the capacitance satisfies the Y class B characteristic of the JIS standard, the range of usable circuits is expanded.

[Brief explanation of the drawings] The figure shows the composition formula, P b + - x + m M ex ((Z n r7z
Nbz/s)+-y-tT i y (Cu, w,
-,)t)o,,, (However, Me is one or more elements selected from Sr and Ba) is a composition diagram in which the claimed ranges of X and Y are indicated by diagonal lines.

Claims (1)

[Claims] (1) Pb_1_−_x_+_aMe_x{(Zn_1
＿／＿3Nb_2＿／＿３）＿１＿−＿y＿−＿zTi
_y(Cu_bW_1_-_b)_z}O_3_+_a
x and y in the composition formula represented by (where Me is one or more elements selected from Sr and Ba) are in the range surrounded by A, B, C, D, and E below, and bz, a, and b satisfy the following: 0≦a≦0.1 0.02≦b≦1.0 0.002≦bz≦0.04. x y A 0.07 0.16 B 0.07 0.09 C 0.19 0.09 D 0.24 0.22 E 0.16 0.22 (2) Dielectric ceramic according to claim (1) A dielectric ceramic composition characterized in that 85% or less of Cu atoms contained in the composition are replaced with Mn. (3) An internal electrode layer mainly composed of Cu or an alloy containing Cu, and Pb_1_−_x_+_aMe_x{(Zn_
1_/_3NB_2_/_3)_1_-_y_-_zT
i_y(Cu_bW_1_-_b)_z}O_3_+_
x and y in the composition formula represented by a (where Me is one or more elements selected from Sr and Ba)
is in the range surrounded by A, B, C, D, and E below, and bz, a, and b are 0≦a≦0.1 0.02≦b≦1.0 0.002 A multilayer capacitor element comprising: a dielectric layer whose main component is ceramic that satisfies ≦bz≦0.04. x y A 0.07 0.16 B 0.07 0.09 C 0.19 0.09 D 0.24 0.22 E 0.16 0.22 (4) Multilayer capacitor element according to claim (3) 85% of Cu contained in porcelain, which is the main component of the dielectric layer that makes up the
A multilayer capacitor element characterized in that the following atoms are replaced with Mn.