JPH035646B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a multilayer ceramic capacitor used in electronic equipment and the like.

Conventional configurations and their problems In recent years, multilayer ceramic capacitors have been widely used in electronic devices.

A conventional multilayer ceramic capacitor having capacitors with different capacitance values will be described below.
FIG. 1 shows a conventional multilayer ceramic capacitor. In FIG. 1, 1 is a ceramic dielectric, 2
is one electrode of a capacitor a with a large capacitance value, 3 is the other electrode of the capacitor a, 4 is one electrode of a capacitor b with a small capacitance value, and 5 is the capacitor b.
is the other electrode.

In the composite capacitor configured as above, first, the capacitance of capacitor a is expressed by the general formula: C=8.855×ε×S ₁ ×n/t ……(1) ε: Dielectric constant of dielectric 1 S ₁ : The area where electrodes 2 and 3 face each other can be determined from n: number of layers (n=4 in FIG. 1), and t: gap length between electrodes 2 and 3. Also capacitor b
Similarly, the capacitance of can be found using the following formula.

C=8.855×ε×S ₂ ×n/t...(2) ε: Dielectric constant S ₂ of dielectric 1: Area where electrodes 4 and 5 face each other n: Number of layers (n=4 in Figure 1) ) t: Gap between electrodes 4 and 5 Multilayer ceramic capacitors are generally manufactured by the printing method or sheet method, and when making a composite capacitor like the one shown in Figure 1, the dielectric constant between capacitor a and capacitor b is ε, gap length between electrodes t
and the number of layers n are the same, and it is known that the capacitance is set in the electrode areas S ₁ and S ₂ whose main surfaces face each other.

However, in the above conventional configuration, especially when increasing the capacitance ratio of capacitor a and capacitor b shown in Fig. 1, the area ratio must be made the same as the capacitance ratio, and the minimum area is generally Generally speaking, it was 0.5 to 0.3 mm square, which was the limit. In addition, if the area is increased, the external size becomes larger, which poses a problem in that usage is restricted and costs increase.

Purpose of the invention The present invention solves the above-mentioned conventional problems.
It is an object of the present invention to provide a laminated ceramic capacitor in which the capacitance ratio of capacitors of different capacitance values to be combined can be made very large, and the capacitance value of each capacitor can be accurately set. .

Structure of the Invention In order to achieve the above-mentioned object, the present invention, when combining capacitors with different capacitance values in the same capacitor body, a large-capacity capacitor is configured by having the main surfaces of electrodes facing each other, and a small-capacity capacitor is The feature is that the end surfaces of the electrodes are arranged to face each other.

DESCRIPTION OF THE EMBODIMENTS FIG. 2 shows a multilayer ceramic capacitor in one embodiment of the present invention. In Fig. 2, 1 is a dielectric, 2 is one electrode of a capacitor a with a large capacitance value,
3 is the other electrode of the capacitor a, 6 is one electrode of the capacitor b having a small capacitance value, and 7 is the other electrode of the capacitor b. In the case of this embodiment, the electrode structure of the capacitor b has a comb shape as shown in FIG. 3, and the end surfaces of the comb-shaped electrodes 6 and 7 face each other on the same plane. Accordingly, a capacitance can be formed between the opposing electrodes 6 and 7. here,
When the dielectric constant of the dielectric 1 used is large, the capacitance of the capacitor 6 formed by the comb-shaped electrodes 6 and 7 is small, and the capacitance of another capacitor a formed in the same dielectric 1 is large. The capacity ratio can be configured to exceed at least 100.

In the multilayer ceramic capacitor of this embodiment constructed as described above, capacitor a has the same structure as the conventional one, and its capacitance is set in the same manner as the conventional one. Next, the formula for calculating the capacitance of capacitor b is complicated and difficult to understand, but it can be calculated using the following formula as a simple experimental formula.

C=K _O ×K×l×ε×n ^a /G ……(3) Here, K _O :Coefficient corresponding to ε _O K: Electrode shape parameter (experimental value) l: Creepage length between electrodes ε: Dielectric constant n: Number of layers a: Constant related to the number of layers (experimental value: 0.2) G: Distance between electrodes 6 and 7 As is clear from Figures 2 and 3, electrodes 6 and 7
are printed on the same plane, and the capacitance can be set by changing each variable, as is clear from the above calculation formula, but it is mainly determined by the electrode spacing G and creepage length l. It is desirable to set the

As described above, according to this embodiment, the electrodes 6 and 7 of the small capacity capacitor a of the composite capacitor are comb-shaped, and the end surfaces of the electrodes 6 and 7 are opposed to each other, and the electrode spacing G and the creepage length are By setting l, it becomes easy to set the capacitance value. That is,
As shown in Figure 4B, the conventional constant related to the number of layers n has a large change, whereas the function value n ^a of the constant a related to the number n of electrode layers and n is the curve in Figure 4. As shown in A, the constant changes very little, so even if the number of layers to form large capacity capacitor a is increased, the effect on small capacity capacitor b is small, and small capacity capacitor b is formed very easily. It has the advantage of being easy to use. Also, if you know the capacitance that can be formed by a pair of comb-shaped electrodes 6 and 7, you can set the capacitance depending on the number of comb-shaped electrodes, and you can easily design or change the capacitance value. It can be easily handled.

Experimental results using an electrode shape as in this example show that a large capacitance capacitor with a dielectric constant of approximately 3000
We were able to obtain a composite capacitor with a capacitance of 100nF and a small capacitance of 100pF.

Effects of the Invention The present invention is configured such that the end faces of the laminated electrodes face each other to obtain capacitance, so that the value of a small capacitance capacitor can be stably and easily set even if the dielectric constant of the dielectric used is large. Furthermore, when combined with a large-capacity capacitor, the capacitance ratio can be made extremely large.

[Brief explanation of the drawing]

FIG. 1a is a schematic plan view of a conventional multilayer ceramic capacitor, FIG. 1b is a schematic side view of the same capacitor, FIG. 2a is a schematic plan view of a multilayer ceramic capacitor according to an embodiment of the present invention, and FIG. 2b is a schematic side view of the capacitor, FIG. 3 is an enlarged view of the main parts of the capacitor, and FIG. 4 is a functional characteristic diagram of the number of layers n and the constant n ^a with respect to capacitance. DESCRIPTION OF SYMBOLS 1... Dielectric, 2... One electrode of capacitor a, 3... The other electrode of capacitor a, 6... One electrode of capacitor b, 7... The other electrode of capacitor b.

Claims (1)

[Claims] 1. A multilayer ceramic capacitor configured to have multiple capacitors with different capacitance values in the same capacitor body, where the capacitor with a large capacitance value is constructed by having the main surfaces of the electrodes facing each other, and the capacitor with a small capacitance value is constructed by having the main surfaces of the electrodes facing each other. A multilayer ceramic capacitor characterized by being constructed by having electrode end faces facing each other.