JP5031650B2 - Multilayer capacitor - Google Patents

Description

  The present invention relates to a multilayer capacitor, and more particularly to a multilayer capacitor that is used in a high-frequency circuit such as an optical communication module and has a broadband pass characteristic.

  In recent years, along with the expansion of high-speed communication, high-speed optical communication represented by optical fiber communication and the like is rapidly progressing. Such electronic components for high-speed optical communication are required to have pass characteristics in a wide frequency band of 10 kHz to 40 GHz.

  Devices that perform high-speed transmission in optical communication require an E / O module that converts electrical signals and optical signals, and an amplifier that amplifies high-frequency signals over a wide band. Capacitors used in circuits using such devices are required to have a broadband coupling capability.

  Conventionally, a single-plate microchip capacitor has been used for this type of high-frequency circuit. However, the single-chip microchip capacitor has a problem that the inductance can be set low due to its structure, but the capacitance cannot be increased. Moreover, since a wire or a metal plate is required for connection to the wiring on the substrate, the inductance is increased as a result.

  On the other hand, various multilayer capacitors are provided in which a dielectric layer and an internal electrode for forming a capacitance are laminated. A large capacitance can be secured with a general multilayer capacitor, but the inductance is made too low. Has the problem of being unable to. Although measures to lower the inductance by considering the multi-terminal structure of the input / output terminals have been considered, there is a new problem that the wiring of the board becomes complicated and the inductance of the wiring of the board becomes large. Therefore, there is a demand for a multilayer capacitor having a simple structure with two terminals and a high capacity and low inductance.

  By the way, Patent Document 1 proposes a multilayer capacitor in which an external connection electrode is provided on a mounting surface on a substrate. In the case of this multilayer capacitor, there is an effect that the inductance can be reduced by positioning the external electrode on the mounting surface as compared with the conventional general multilayer capacitor in which the external electrode is formed on both end faces of the multilayer body.

  On the other hand, the pass characteristics of a capacitor are affected by capacitance in a band lower than the resonance frequency of the capacitor, and inductance is affected in a higher band. For a capacitor used in a wide frequency band of 10 kHz to 40 GHz, for example, it is necessary that the capacitance is 0.1 μF and the inductance (equivalent series inductance, hereinafter simply referred to as ESL) is 250 pH.

In the multilayer capacitor described in Patent Document 1, it is possible to lower the ESL as compared with other general multilayer capacitors, but it is still impossible to achieve an ESL of 250 pH or less.
Japanese Patent Application Laid-Open No. 11-288839 (FIGS. 1, 2, and 3)

  Accordingly, an object of the present invention is to provide a multilayer capacitor capable of realizing an ESL of 250 pH or less required for use in a wide frequency band as well as ensuring a high capacity.

In order to achieve the above object, the present invention includes a dielectric layer and an internal electrode for forming a capacitance, and the internal electrode is positioned in a direction perpendicular to the mounting surface. In the multilayer capacitor in which the extraction electrode extracted from is electrically connected to the external electrode provided on the surface of the multilayer body,
The internal electrodes have first and second internal electrodes facing each other;
The external electrode includes a first external electrode electrically connected to the extraction electrode of the first internal electrode, and a second external electrode electrically connected to the extraction electrode of the second internal electrode Have
The first external electrode is continuously formed across the mounting surface, an upper surface facing the mounting surface, and a first side surface connecting the mounting surface and the upper surface,
The second external electrode is continuous across the mounting surface, an upper surface facing the mounting surface, and a second side surface connecting the mounting surface and the upper surface and facing the first side surface. Formed into
The first internal electrode is electrically connected to the first external electrode at the mounting surface, the top surface, and the first side surface, and the lead electrode of the first internal electrode is The first side surface is drawn to the first side surface with the same width as the dimension from the mounting surface side to the upper surface side;
The second internal electrode is electrically connected to the second external electrode at the mounting surface, the top surface, and the second side surface, and the extraction electrode of the second internal electrode is The second side surface is drawn to the second side surface with the same width as the dimension from the mounting surface side to the upper surface side;
The distance a between the lead electrodes of the first and second internal electrodes facing each other, the distance b ₁ from the first internal electrode to the mounting surface, and the distance b ₂ from the second internal electrode to the mounting surface Satisfying the following equation:
1.64a + (b ₁ + b ₂ ) ≦ 0.85
However, the unit of a, b ₁ and b ₂ is mm.
It is characterized by.

The present inventor conducted various experiments on the multilayer capacitor, and as a result, as a result, the distance a between the one extraction electrode and the other extraction electrode of the first and second internal electrodes facing each other, the first and second It has been found that the distances b ₁ and b ₂ from the internal electrode to the mounting surface greatly affect the inductance.

That is, as a result of examining the relationship between the distances a, b ₁ , and b ₂ with the ESL value fixed, the influence of the distance a is particularly great, and a coefficient of 1.64 exists regardless of the ESL value. I found out. Therefore, by satisfying the above equation, it was possible to realize the characteristic that ESL is 250 pH or less in a wide frequency band.

  According to the present invention, in a multilayer capacitor in which an internal electrode for forming a capacitance with a dielectric layer is laminated so that the internal electrode is positioned in a direction perpendicular to the mounting surface, the internal electrode and its extraction electrode are Since it is set so as to satisfy the above equation, ESL of 250 pH or less required for use in a wide frequency band can be realized as well as high capacity.

  Hereinafter, embodiments of a multilayer capacitor according to the present invention will be described with reference to the accompanying drawings.

(Refer 1st Embodiment and FIGS. 1-3)
As shown in FIG. 1, the multilayer capacitor according to the first embodiment of the present invention has a length L of 1.0 mm and a width W of 0.5 mm. This multilayer capacitor is formed by laminating a plurality of dielectric layers and a plurality of internal electrodes 11, 21... For forming a capacitance, and the internal electrodes 11, 21... Are predetermined according to required specifications. Built-in number. In this multilayer capacitor, the internal electrodes 11, 21... Are positioned in a direction orthogonal to the mounting surface 2 of the multilayer body 1.

  As is well known, the dielectric layer is formed as a ceramic green sheet, on which a predetermined shape of internal electrodes 11, 21... And extraction electrodes 12, 22 are formed by thick film technology or thin film technology and laminated. / After being crimped and baked, it is cut out to a predetermined size. External electrodes 31 and 32 are formed on the surface of the cut laminate 1 by applying a conductive paste, baking, or the like.

  The internal electrodes form a capacitance between a pair facing each other. Here, the pair of internal electrodes 11 and 21 will be described, but the same applies to the other internal electrodes. The internal electrodes 11 and 21 have the same area and are provided at the same position of the stacked body 1 (therefore, the internal electrodes 11 and 21 are overlapped in FIG. 1B). The extraction electrode 12 is electrically connected to the external electrode 31, and the extraction electrode 22 of the second internal electrode 21 is electrically connected to the external electrode 32.

The inventors set the effective capacity C of the internal electrodes 11 and 21 to 0.3 mm in the laminate 1 having the above size, the distance a between the extraction electrodes 12 and 22, and from the internal electrodes 11 and 21 to the mounting surface 2. The vertical distance b (where b = b ₁ + b ₂ , b ₁ = b ₂ ) was changed to various values, and ESL was obtained. The height T varies according to the vertical distances b ₁ and b ₂ .

  The results are shown in Table 1 below. From Table 1, the combination of the distance between the extraction electrodes a and the vertical distance b at which the ESL becomes 200 pH, 250 pH, and 300 pH can be read.

  The experiment which obtained the result of Table 1 sets the distance a between extraction electrodes to 0.10-0.50 mm by 0.05 mm space | interval, distributes the vertical distance b in each distance a, and uses a network analyzer for frequency characteristics. Was measured. The vertical distance b in Table 1 shows values when the ESL reaches 200 pH, 250 pH, and 300 pH.

  FIG. 2 is a graph showing the results shown in Table 1. The upper straight line shows the numerical relationship with respect to ESL of 300 pH, the middle straight line with 250 pH, and the lower straight line with respect to 200 pH. As apparent from FIG. 2, the relationship between the distances a and b is a straight line and can be approximated by the following equation (1).

1.64a + b = K (1)
a: Distance between extraction electrodes (mm)
b: vertical distance (mm), b ₁ + b ₂ and b ₁ = b ₂

  In the equation (1), the coefficient K varies depending on the value of ESL, and is about 0.57 at 200 pH, about 0.85 at 250 pH, and about 1.12 at 300 pH.

Next, the relationship between the ESL value and the coefficient K is shown in the graph of FIG. ESL and K can be obtained by the following equation (2).
ESL (pH) = 180 × K + 97 (2)

  From the above consideration, a multilayer capacitor having an ESL of 250 pH or less can be obtained by satisfying the following expression (3). Of course, a high capacitance can be secured as a general characteristic of the multilayer capacitor with respect to the capacitance.

1.64a + (b ₁ + b ₂ ) ≦ 0.85 (3)
However, the unit of a, b ₁ and b ₂ is mm.

(Modification, see FIG. 4)
In the first embodiment, various modifications can be adopted with respect to the positions and shapes of the extraction electrodes 12 and 22 and the positions and shapes of the external electrodes 31 and 32. FIG. 4 shows some of such modifications. 4 indicate the same members and parts as those in FIG.

(Refer to the second and third embodiments, FIG. 5 and FIG. 6)
In the first embodiment and its modification, the lead electrode has a rectangular shape. The extraction electrode may be other than a rectangle, and such an embodiment is shown below.

  In the multilayer capacitor according to the second embodiment shown in FIG. 5 and the multilayer capacitor according to the third embodiment shown in FIG. 6, triangular portions 12 ′ and 22 ′ that extend toward the roots are added to the lead electrodes 12 and 22, respectively. It is a thing. Even in these multilayer capacitors, a multilayer capacitor having an ESL of 250 pH or less could be obtained by satisfying the expression (3). 5 and 6 indicate the same members and parts as those in FIG.

(Other embodiments)
The multilayer capacitor according to the present invention is not limited to the above embodiment, and can be variously modified within the scope of the gist thereof.

  In particular, the details of the shape of the internal electrode and its extraction electrode and the position and shape of the external electrode are arbitrary. In addition to the capacitor, another element may be built in the multilayer body to constitute a composite electronic component.

BRIEF DESCRIPTION OF THE DRAWINGS The 1st Embodiment of the multilayer capacitor based on this invention is shown typically, (A) is a perspective view, (B) is a front view. The graph which shows the relationship between the distance a between the extraction electrodes in the multilayer capacitor which concerns on this invention, and the perpendicular distance b. The graph which shows the relationship between the coefficient K and ESL in the multilayer capacitor concerning this invention. The front view which shows the various modifications of the said 1st Embodiment. The front view which shows typically 2nd Embodiment of the multilayer capacitor based on this invention. The front view which shows typically 3rd Embodiment of the multilayer capacitor based on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laminated body 2 ... Mounting surface 11 ... 1st internal electrode 12 ... Extraction electrode 21 ... 2nd internal electrode 22 ... Extraction electrode 31, 32 ... External electrode

Claims (1)

A dielectric layer and an internal electrode for forming a capacitance are laminated, the internal electrode is positioned in a direction orthogonal to the mounting surface, and an extraction electrode drawn from the internal electrode is formed on the surface of the laminate. In the multilayer capacitor that is electrically connected to the provided external electrode,
The internal electrodes have first and second internal electrodes facing each other;
The external electrode includes a first external electrode electrically connected to the extraction electrode of the first internal electrode, and a second external electrode electrically connected to the extraction electrode of the second internal electrode Have
The first external electrode is continuously formed across the mounting surface, an upper surface facing the mounting surface, and a first side surface connecting the mounting surface and the upper surface,
The second external electrode is continuous across the mounting surface, an upper surface facing the mounting surface, and a second side surface connecting the mounting surface and the upper surface and facing the first side surface. Formed into
The first internal electrode is electrically connected to the first external electrode at the mounting surface, the top surface, and the first side surface, and the lead electrode of the first internal electrode is The first side surface is drawn to the first side surface with the same width as the dimension from the mounting surface side to the upper surface side;
The second internal electrode is electrically connected to the second external electrode at the mounting surface, the top surface, and the second side surface, and the extraction electrode of the second internal electrode is The second side surface is drawn to the second side surface with the same width as the dimension from the mounting surface side to the upper surface side;
The distance a between the lead electrodes of the first and second internal electrodes facing each other, the distance b ₁ from the first internal electrode to the mounting surface, and the distance b ₂ from the second internal electrode to the mounting surface Satisfying the following equation:
1.64a + (b ₁ + b ₂ ) ≦ 0.85
However, the unit of a, b ₁ and b ₂ is mm.
Multilayer capacitor characterized by

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