JPS5917229A - Laminated condenser element - 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 capacitor element, and in particular to a multilayer capacitor that uses a dielectric material with a single point of difference to increase the apparent permittivity of the element and reduce its temperature change. This relates to the structure of the element.

Generally, dielectric materials used in ceramic capacitor elements are required to have a high dielectric constant due to the demand for larger capacitance and smaller size of the element.
An aT i○3 solid solution is used for this purpose. However, the above dielectric materials have a Curie point near room temperature where they transition from a ferroelectric phase to a paraelectric phase, and the dielectric constant reaches its maximum value at this temperature. This poses a practical problem because of the change.

Therefore, as a method to increase the dielectric constant multiplied by 3 as an element and to reduce the temperature change in the dielectric constant, it is known to prepare multiple dielectrics with different Curie points and use a capacitor composed of these in combination. It is being

For example, in a circuit, when two capacitors are connected in parallel, and if the electrode area and thickness of each capacitor are equal, the apparent permittivity of the element is expressed by formula (1)%, where n is the capacitor The number of capacitors, ε, is the dielectric constant of the dielectric of the m-th capacitor.

Part (1): As is clear from u, in an element in which capacitors made of several dielectric materials with different Curie points are coupled in parallel, the high permittivity of each dielectric material at the single Curie point VC is superimposed, and the apparent permittivity is It is possible to obtain the characteristics of high temperature change and small temperature change.

On the other hand, as mentioned above, specific methods for combining dielectrics with different Curie points into one element include (1) sintering each dielectric separately and gluing them together with adhesive;
) Sintering of individual dielectric moldings together has been devised.

However, method (1) has not been put to practical use because the adhesive affects the dielectric properties of the element and the manufacturing cost of the trench is high. Furthermore, in the method (2), the characteristics of each dielectric change due to the interaction between the dielectrics, making it difficult to obtain the effect of superimposing the high permittivity of each dielectric at one Curie point.

In order to solve the above-mentioned problems, the present invention prevents mutual reactions between the dielectrics by providing a metal layer between the individual dielectrics when sintering the dielectrics with different points. Moreover, the metal layer is intended to be used as an electrode for a dead layer capacitor.

When several dielectric materials with different Curie points are used in an element, the dielectric constants of these dielectric materials at the Curie point generally differ from each other.

In the present invention, by making the ratio (S/d) of the electrode area (S) and its thickness d for each dielectric layer proportional to the reciprocal of the dielectric constant at one Curie point of each dielectric,
This is intended to prevent variations in the apparent dielectric constant of the element due to the above-mentioned effects. In other words, at a temperature where one dielectric material exhibits a single point, the permittivity of other dielectric materials is smaller than that of the dielectric material that exhibits a single point, and they must be on the same level. By adjusting the ratio of the electrode area and thickness of the body layer and averaging the capacitance of each layer at a single Curie point, it is possible to further reduce fluctuations in capacitance as an element with respect to temperature.

The apparent dielectric constant of the element in this case is given by equation (2).

Here, n is the number of laminated dielectrics. ε□+ Sm + d
m is the dielectric constant, electrode area, and thickness of the m-th dielectric material, respectively.

As described above, the present invention attempts to apply a method of compounding dielectric materials to increase the apparent permittivity and reduce temperature changes to multilayer capacitors. It is characterized by its method.

Next, the structure of the multilayer capacitor element of the present invention will be described based on examples.

FIG. 1 shows a cross section of a multilayer capacitor according to an embodiment of the present invention, and FIG. 2 shows a temperature change in the dielectric constant of a dielectric material used therein. In FIG. 1, 1 to 6 are electrode layers, 7,
Reference numeral 8 represents the lead-out electrodes of electrode layers 1 to 3 and electrodes 4 to 6, respectively. The dielectrics 9 to 13 that differ from each other in one point are the electrode layers 1 to 13.
dielectrics 9 to 13 and upper and lower electrode layers 1 to 13.
The capacitors of each layer consisting of 6 were connected in parallel on the circuit.

14 is a substrate layer that provides mechanical strength to the device.

In FIG. 2, 101 to 105 are dielectrics 9 to 105, respectively.
13 shows the temperature dependence of the dielectric constant, and 201 to 2 and 6 show the temperature dependence of the dielectric loss -δ of the dielectrics 9 to 13, respectively.

The ratio (s/d) of the electrode area (8) for each dielectric layer and the thickness d) of each dielectric layer is proportional to the ratio of the reciprocal of the permittivity at one Curie point of each dielectric as shown in Figure 2. Make it the same size. In this case, it can be appropriately selected whether only the electrode area, only the dielectric thickness, or both the electrode area and thickness are changed.

FIG. 3 (-, ■) shows a plan view of an embodiment in which the thickness of each dielectric layer is constant and only the electrode area is changed. 2
0 to 22 indicate electrode layers, and correspond to electrode layers 1 to 3 of the embodiment shown in FIG. 1, respectively.

23 to 26 are also electrode layers, which correspond to electrode layers 4 to 6 in the embodiment shown in FIG. 1, respectively. The electrode area for dielectric layers 9 to 13 in the embodiment shown in FIG.
and 23, 23 and 21. 21, 24 and 22. These are the overlapping parts of dielectric layers 9 to 13.
Dielectric constant at one Curie point of 6000, 6500, 70
The size is proportional to the reciprocal of 00,7E500°5ooo.

FIG. 4 shows temperature changes in the apparent permittivity ε and dielectric loss hnδ of a multilayer capacitor element fabricated using each of the dielectrics shown in FIG. 2 and having the structure shown in FIGS. 1 and 3.

Next, the manufacturing procedure of the laminated capacitor element of the present invention will be specifically explained. As a starting material for the dielectric, B a
B aNb206 was added to T 103 in amounts of 2.8 mol, 2.3 mol, 1.8 mol, and 1.3 mol, respectively.

Five kinds of solid solutions with a concentration of 0.8 mol were used. The conditions for calcination and pulverization of the powders of the starting materials for these dielectrics were adjusted to roughly match the expansion and contraction rates during firing. In addition to this, as a dielectric material, in addition to BaNb2o6 mentioned in the example, 5rTi○3
+ A solid solution of BaTa2O6 or the like in BaTlO3 may also be used. In addition, if the dielectric used in one element is a solid solution of BaT i○3 with the same composition as mentioned in the example, and only the amount of the solid solution is changed, the firing temperature and other conditions can be approximately the same. This is desirable because they will be the same.

A conductive metal made of Ag, Au, Pd, Pt, etc. was used for the electrode part, and its particle size composition and other properties were adjusted to approximately match the expansion and contraction rates during firing with the dielectric layer.

The substrate layer used the same solid solution as the dielectric layer.

The calcination and pulverization conditions were also adjusted to approximately match the expansion and contraction rates of the dielectric layer during firing. In addition, as the substrate layer, any material having approximately the same expansion and contraction rate during firing as the dielectric layer may be used, but due to conditions such as sintering temperature, it is recommended to use a solid solution of the same type as the dielectric layer. It's hopeful.

The lamination method is to mix the dielectric powder mentioned above with an appropriate binder (polyvinyl alcohol, cellulose, etc.) and an organic solvent (alcohol, ester, etc.) to form a paste, which is then formed into a sheet using the doctor blade method. The metal powder for the electrode was added to the paste as described above with a binder, an organic solvent, etc., and the whole thing was printed, and a note was also made in the same manner as described in -. - It was laminated with the substrate layer and bonded by thermocompression. In addition, the dielectric substrate layer may be laminated by a printing method. These are fired in a firing furnace136
0° C., 2 hours), and then an extraction electrode was printed and baked again in a baking furnace (80° C., 30 minutes).

As is clear from the example described in -4-, the present invention (1) laminates dielectric layers via electrode layers, and (2) determines the electrode area and thickness ratio of each dielectric layer. The two major features are that the size is proportional to the reciprocal of the dielectric constant at one Curie point. (1) suppresses the chemical reaction between the dielectric layers when they are fired simultaneously, prevents the temperature change curve of the dielectric constant of each dielectric from changing, and furthermore prevents the dielectric layer from changing during the process. This has made it possible to create a multilayer capacitor element with a large apparent dielectric constant and a small temperature coefficient, and it has also made it possible to miniaturize the element.

By using (2), we have made it possible to minimize the temperature change in the apparent dielectric constant of a multilayer capacitor element.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a multilayer capacitor element according to an embodiment of the present invention, and Fig. 2 is an example of temperature changes in the dielectric constant and dielectric loss of dielectric materials with different Curie points used in the multilayer capacitor element of the present invention. Figures 3(5) and 3) are plan views showing the structure of the electrode layer of a multilayer capacitor according to another embodiment of the present invention, and Figure 4 is a diagram showing the apparent dielectricity of the element according to the embodiment of the present invention. FIG. 3 is a diagram showing temperature changes in dielectric loss and dielectric loss. 1-6... Electrode layer, 7, 8... Extraction electrode, 9-13... Dielectric layer, 14... Substrate layer, 20-25...・Electrode layer.

Claims (1)

[Scope of Claims] (1) A multilayer capacitor element in which electrode layers and dielectric layers are laminated alternately, in which two or more dielectrics having different Curie points are laminated with the electrode layers interposed therebetween. Multilayer capacitor element featuring Σ. (2) The ratio (S/d) of the electrode area (S) to the thickness d of each dielectric layer for each dielectric layer was made proportional to the reciprocal of the dielectric constant at one Curie point of each dielectric material. A multilayer capacitor element according to claim 1, characterized in that: