JPH06176960A - Feedthrough type laminated ceramic capacitor - Google Patents

Abstract

PURPOSE:To raise a resonance frequency by lowering resistance of a ground internal electrode of a capacitor by specifying the thickness of the ground internal electrode. CONSTITUTION:There are formed on a sheet a ground internal electrode 1 and a signal internal electrode 2 into a feedthrough type laminated capacitor by making use of screen printing of palladium paste. The sheets after printed are laminated at proper pressure, and are divided for each capacitor element and are thereafter sintered. Thereafter, the capacitor is yielded by forming external electrodes 4-6. The thickness of the ground internal electrode 1 is set to be 5mum or more. Further, since a resonance frequency is raised irrespective of the thickness of the ground internal electrode is increased, the thickness of the signal internal electrode 2 is made thinner than the thickness of the ground internal electrode 1. Hereby, in a feedthrough type laminated ceramic capacitor having a higher resonance frequency, it is possible to deal with the need of a higher radio frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency feedthrough multilayer ceramic capacitor.

[0002]

2. Description of the Related Art High frequency and digitalization in electronic communication have been established as one tendency, starting with examples of mobile communication, satellite communication and the like. Along with this, electronic components have been actively used for high frequencies. Regarding the capacitor element, the former disk-shaped element has been changed to the laminated chip type.
Since the parasitic inductance can be reduced by eliminating the lead wires, the transition to the laminated chip type is in line with the trend from the viewpoint of high frequency compatibility.
That is, since the limit of use of the capacitor element on the high frequency side is usually explained by this parasitic inductance, the multilayer chip type contributes to higher frequency. This will be described below using mathematical expressions.

In the ideal case, the impedance Z of a capacitor is C for capacitance, f for signal frequency, and i for complex symbol.
As follows, Z = 1 / 2πfCi (1) However, actually, the capacitor element has a parasitic inductance depending on the presence / absence of a lead wire, a mounting method of a structural element of an electrode, and the like, and also has a pure resistance component corresponding thereto. Therefore, in actuality, when the parasitic inductance is L and the pure resistance is R, the impedance Z can be described as Z = 2πfLi + 1 / 2πfCi + R (2). As can be seen from this equation, when the signal frequency is low, the contribution of the first term is small and is considered to be close to the ideal, but as the frequency rises, the contribution of the first term becomes remarkable and the capacitor no longer functions as a capacitor. Does not work, but rather reaches the area of functioning as an inductor. Considering the frequency characteristic of this impedance according to the equation (2),
On the low frequency side, the impedance shows a monotonic decrease with increasing frequency, but at the resonance frequency that satisfies 1 / f = 2π (LC) ^1/2 (3), the minimum value R of the impedance is shown. It shows a monotonic increase with the rise. Also, the phase is -i (1-δ) before and after the resonance frequency.
To i (1 + δ): (0 <δ <1).

As discussed above, in the capacitor element, the self-resonant frequency is widely used as one of the performance indicators for high frequencies. As described above, the multilayer chip capacitor has no lead wire and has the characteristic that the parasitic inductance is smaller than that of the disk type capacitor, and exhibits excellent characteristics for high frequency. However, even in this case, there is a parasitic inductance, and the limit on the high frequency side is becoming apparent under the recent remarkable increase in frequency. That is,
The solution is to design the circuit so that the capacitance is as small as possible in order to raise the self-resonant frequency, and as a rule of thumb, use a constant value of 10 pF or less at 1 GHz.

[0005] In such a situation, the actual exploitation Sho 49-12736
1 (A) and its E-
Proposed are through-type multilayer capacitors having the structures shown in (B) and (C) of FIGS. In this feedthrough multilayer capacitor, one or more sets of a grounding internal electrode 1 and a signal internal electrode 2 intersect at a substantially right angle with a dielectric layer 3 sandwiched therebetween, and the signal internal electrode 2 is a dielectric layer 3. Through, and reach two opposite side surfaces to be connected to the signal external electrodes 4 and 5 formed on the two side surfaces, and the grounding internal electrode 1 penetrates the dielectric layer 3 to form the two side surfaces. To the two side surfaces adjacent to and opposite to each other and connected to the grounding external electrode 6 formed on the two surfaces. Also, FIG.
Is proposed based on the structure shown in FIG.
No. 10927, the grounding external electrode 6 is formed all around the capacitor.
The feedthrough multilayer capacitor shown in FIGS. 1 and 2 has a self-resonant frequency about twice that of the conventional multilayer ceramic capacitor, and is excellent as a capacitor used for high frequencies.

The inventor of the present invention has found that in the above-mentioned feedthrough multilayer ceramic capacitor, the resonance frequency is significantly affected by the mounting structure of the capacitor on the substrate. In particular, it has been found that if the grounding external electrode 6 of the capacitor is connected to a stable grounding circuit of the substrate as close as possible, the resonance frequency can be greatly increased in the frequency range of 100 MHz or higher.

However, increasing the resonance frequency by such a mounting structure imposes restrictions on the arrangement of capacitors and other elements during mounting, which may be difficult to implement. It is preferable to increase the resonance frequency by the structure of the capacitor itself.

From this point of view, it is an object of the present invention to provide a feedthrough type monolithic ceramic capacitor having an improved structure and improved resonance frequency.

[0009]

In the conventional feedthrough type monolithic ceramic capacitor, it is said that the thinner the internal electrode is, the better in terms of cost and the like, and the thickness thereof is usually set to about 3 μm. However, according to the research of the inventor,
It has been found that when such an electrode thickness is used, the resistance value of the grounding internal electrode 1 becomes a problem, and the shielding effect for increasing the frequency by the grounding internal electrode 1 is not as expected. Therefore, in the present invention, in order to reduce the resistance value of the grounding internal electrode, the thickness of the grounding internal electrode is set to 5 μm or more. The upper limit of the thickness is not particularly limited, but normally it is preferably 20 μm or less from the viewpoint of preventing delamination (layer separation).

[0010]

The shield effect of the grounding inner electrode is improved by lowering the resistance value of the grounding inner electrode, and the resonance frequency is increased.

[0011]

[Examples] In manufacturing a capacitor for measuring characteristics, a manufacturing technique of a laminated ceramic capacitor was followed.
That is, a powder to be a dielectric (having a dielectric constant of 55) was made into a slurry with a resin component solvent, and a green sheet was obtained from this slurry by a doctor blade method. To make a feedthrough multilayer capacitor on this sheet,
Grounding inner electrode 1 and signal inner electrode 2 shown in FIGS.
Was formed by screen-printing a palladium paste. The printed sheets were laminated at an appropriate pressure, divided into individual elements, and then fired. The sheets are laminated such that the thickness of the electrodes 1 and 2 after firing is 3 μm, 5 μm, 8 μm and 10 μm.
The number of passes was changed so that m, 15 μm, and 20 μm were obtained. Then, the external electrodes 4 to 6 were formed to obtain capacitors. In these capacitors, the external dimension (vertical) of the external shape of the signal internal electrode 2 in the length direction is 3.2 mm, and the horizontal dimension is 1.
6mm, height 0.5mm, 1mm, 1.2mm, 1.5mm
And Table 1 is a list of capacitors manufactured in this manner and used for the characteristic measurement described later. In Table 1, 1 in the column of shape is the structure of FIG. 1 and 2 is the structure of FIG.

For these samples, as shown in the plan view of FIG. 3A and the side view of FIG. 3B, an insulating material was used to measure the characteristics when the capacitor mounting structure according to the present invention was adopted. As shown in FIG. 4 (A), the substrate 10 made of
A capacitor 9 is provided by providing a through hole or using one having no through hole as shown in FIG.
Was mounted and a test for measuring the resonance frequency was performed. This substrate 10 has a strip line 1 formed of a conductive film on its surface.
1 and 12, the ground layer 13 is formed on the back surface, the prototype capacitor 9 is mounted between the strip lines 11 and 12, and the end portions of the strip lines 11 and 12 are connected to the SMA.
It is connected to the connectors 14 and 15.

The mounting structure shown in FIGS. 4A and 4B will be described in more detail. In the example shown in FIG.
A ground pattern 16 is formed on the surface of the capacitor 9 corresponding to the ground external electrode 6 of the capacitor 9, and the ground layer 13 on the back surface of the substrate 10 and each ground pattern 16 are as close to the ground external electrode 6 as possible. Location (grounding external electrode 6 to substrate 1
It is preferable that the distance is within 3 mm in the plane direction of 0), and the grounding external electrode 6 of the capacitor 9 is connected to each of the grounding patterns 16 by the solder 18. Further, FIG. 4B is an example in which the through hole 17 is not provided and the grounding pattern 16 on the front surface of the substrate 10 is connected to the ground layer 13 on the back surface via the side surface conductor 19, which follows the conventional mounting structure. It is a structure.

As described above, the thickness of the electrodes 1 and 2 was changed, and the mounting structure was changed as shown in FIGS. 4A and 4B, and the resonance frequency was measured. For this measurement, the resonance frequency was obtained from the attenuation characteristic of the S21 parameter using a microwave network analyzer. Table 2 shows the case where the mounting structures shown in FIGS. 4 (A) and 4 (B) are used by using the samples of the sample numbers 1 to 5 (the mounting structure of FIG. The mounting structure is represented by B). Table 1 Capacitance Shape Number of internal electrodes Distance between electrodes Height dimension Sample number (pF) (μm) (mm) 1 120 1 4 50 0.5 2 120 2 2 4 50 0.5 3 560 1 20 50 50 1.0 4 1000 1 38 50 50 1.2 5 3300 1 50 15 1.5 Table 2 Internal Electrode Thickness (μm) Mounting Resonance Frequency (MHz) Signal Electrode Grounding Electrode Structure Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 3 3 A 4000 4000 1200 500 210 3 3 B 1980 2100 560 320 90 5 5 3 A 4000 4000 1200 500 210 5 5 3 B 1900 2000 550 310 95 10 3 A 4050 4020 1200 510 210 10 3 B 1900 1900 600 290 90 3 5 A 4000 4000 1200 500 210 3 5 B 3900 3900 1150 490 200 3 8 A 4000 4000 1200 500 210 3 8 B 4000 4000 1200 500 210 3 10 A 4050 4050 1200 510 210 310 3 10 B 4050 4080 1200 510 210 315 A 4100 4100 1200 520 220 3 15 B 4100 4100 1200 500 205 Above The test results revealed the following. When the grounding internal electrode 1 has a thickness of 5 μm or more, the resonance frequency can be increased regardless of the mounting structure, as compared with the conventional one having a thickness of about 3 μm. Particularly, when the thickness of the grounding internal electrode was 8 μm to 10 μm, the best characteristics were exhibited. Further, when the thickness of the internal electrode exceeds 20 μm or more, delamination (layer separation) is likely to occur,
The thickness of the internal electrodes is preferably 20 μm or less.
Further, regardless of the thickness of the signal inner electrode, the resonance frequency can be increased by increasing the thickness of the grounding inner electrode, so that the thickness of the signaling inner electrode is made thinner than that of the grounding inner electrode. Reduces the number of printing steps,
In addition, it is preferable in terms of suppressing the occurrence of delamination and reducing the cost.

Further, a capacitor having an electrostatic capacity of 10,000 pF or more has a resonance frequency lower than 100 MHz, and as shown in the embodiment, it is equivalent when the grounding internal electrode is thicker and when it is not thicker as in the conventional case. Became a characteristic of. From this, the present invention provides a capacitance of less than 10,000 pF,
Alternatively, it is effective when removing frequency components of 100 MHz or higher.

[0016]

According to the first aspect of the present invention, it is possible to meet the demand for higher frequency in the feedthrough multilayer ceramic capacitor having a high resonance frequency. Further, in the present invention, since the high frequency is achieved by the structure of the capacitor itself, there is no restriction on the mounting structure of the capacitor and other elements on the substrate, and there is versatility.

According to the second aspect, the resonance frequency can be increased, and in the case of manufacturing by the printing method, the number of steps is reduced, the delamination is suppressed, and the cost is reduced. Can be raised.

[Brief description of drawings]

FIG. 1A is a perspective view showing an example of a feedthrough multilayer ceramic capacitor, and FIGS. 1B and 1C are E of FIG.
FIG. 7E is a cross-sectional view taken along line E-F.

FIG. 2 is a perspective view showing another example of a through-type monolithic ceramic capacitor.

3A and 3B are a plan view and a side view, respectively, showing the configuration of a substrate used for measuring the characteristics of the capacitor having the mounting structure shown in FIG.

4 (A) and 4 (B) are cross-sectional views showing an example of a mounting structure used for a characteristic test of a capacitor according to the present invention.

[Explanation of symbols]

 1 Grounding Internal Electrode 2 Signal Internal Electrode 3 Dielectric Layer 4, 5 Signal External Electrode 6 Grounding External Electrode 9 Capacitor 10 Substrate 11, 12 Stripline 13 Grounding Layer 14, 15 SMA Connector 16 Grounding Pattern 17 Through Hole 18 Solder

Claims (2)

[Claims] 1. An internal electrode for grounding and an internal electrode for signals are laminated at least one pair so as to intersect at a substantially right angle with a dielectric layer sandwiched therebetween, the internal electrode for signals penetrating the dielectric layer, and a capacitor relative to each other. To the two side surfaces that are connected to the signal external electrodes formed on the two side surfaces, the ground internal electrode penetrates the dielectric layer, and is connected to the two side surfaces that are adjacent to and opposite to the two side surfaces. In the feedthrough multilayer ceramic capacitor which reaches and is connected to at least the grounding external electrodes formed on the two side surfaces, the grounding internal electrode has a thickness of 5 μm.
A through type monolithic ceramic capacitor characterized by the above. 2. A through-type monolithic ceramic capacitor, wherein the signal internal electrode has a thickness smaller than that of the grounding internal electrode.