JPS637014B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ceramic capacitor, and more particularly to the structure of a chip-type multilayer ceramic capacitor used in a microwave integrated circuit.

In recent years, amplifiers used in the microwave band are equipped with microwave integrated circuits in which a conductor layer and thin film resistor are provided on the top surface of a dielectric plate, and individual components such as transistors, diodes, and capacitors are mounted to form a circuit. is often used. Chip-type multilayer ceramic capacitors, which are small and can be face bonded and are suitable for microwave integrated circuits, have been developed and are widely used as capacitors for use in microwave integrated circuits.

FIG. 1 is an explanatory diagram of a portion of a 4 GHz band amplifier of a microwave integrated circuit using chip-shaped multilayer ceramic capacitors, enlarged ten times its actual size. In FIG. 1, the dielectric 1 includes a base 2a, a collector 2
b, transistor 2 having emitters 2c to 2d;
are arranged, a conductor layer 3 on the base 2a, a conductor layer 4 on the collector 2b, a conductor layer 5 with a through hole 5a formed on the emitter 2c, and an emitter 2d.
A conductor layer 6 having a through hole 6a formed therein is connected to each of the conductor layers 6. Further, the conductor layer 4 is provided with conductor layers 7 and 8, and chip-type multilayer ceramic capacitors 9 and 10 are connected to these conductor layers 7 and 8.
are connected in series, and this chip-type multilayer ceramic capacitor 1
A thin film resistor 11 is provided in parallel with 0. In such a configuration, the base 2a, collector 2b, and electrode leads of the emitters 2c to 2d of the transistor 2 and the chip-type multilayer ceramic capacitors 9, 10
The electrodes are soldered to the underlying conductive layer of each.

In a microwave integrated circuit using such a chip-type multilayer ceramic capacitor, the chip-type multilayer ceramic capacitor 9 is a high-frequency bypass capacitor for making the conductor layer 7 connected in parallel to the conductor layer 4 into a short-circuit line at the other end. In the chip-type multilayer ceramic capacitor 10, the conductor layer 8 having a length of 1/4 wavelength of the required frequency is used as a short-circuit line at the other end. Further, the conductor layer 8 and the chip-type multilayer ceramic capacitor 10 supply a DC bias to the electrode lead of the collector 2b of the transistor 2, and are a so-called chioke circuit. In addition, chip type multilayer ceramic capacitors 9, 10
requires a large capacitance for use as a high frequency bypass capacitor, and therefore a large chip-shaped multilayer ceramic capacitor cannot be used from the viewpoint of microwave integrated circuits. In other words, chip-type multilayer ceramic capacitors used in the microwave band are usually about 2 mm long, about 1 mm wide, and about 1 mm thick, and have a large capacity within this limited size. To obtain, for example, dielectric constant 8000
A porcelain material such as barium titanate, which has a high dielectric constant of , is used. However, high dielectric constant ceramic materials
Since the dielectric loss tangent tanδ is several percent at a frequency of 1MHz,
There is a large loss in the microwave band. For this reason,
When a high dielectric constant chip type multilayer ceramic capacitor is used in a microwave band amplifier or the like, there are drawbacks such as a decrease in gain and an increase in amplitude deviation.

Therefore, in order to reduce the loss in the microwave band, a low dielectric constant ceramic material was used for the chip-type multilayer ceramic capacitors 9 and 10, as shown in FIG. That is, FIG. 2 is a sectional view of a conventional chip-type multilayer ceramic capacitor. In Figure 2,
External electrode 9a ₁ of chip-type multilayer ceramic capacitor 9,
9a ₂ is internal electrode 9b ₁ , 9b ₂ and internal electrode 9b ₃ ,
9b ₄ respectively, and these external electrodes 9a ₁ ,
A ceramic material 9c is arranged between 9a ₂ and the internal electrodes 9b ₁ to 9b ₄ . In addition, in Figure 2,
Although only two internal electrodes are shown in the figure, each electrode actually consists of several dozen internal electrodes. The production of such a chip-shaped multilayer ceramic capacitor 9 is as follows:
A number of internal electrodes 9b ₁ to 9b ₄ are formed by printing and coating a thin film of porcelain material 9c with a noble metal such as palladium.
After stacking 10 layers, they are fired at a temperature of several thousand degrees, and then external electrodes 9a ₁ and 9a ₂ are coated and fired.

In such a chip-type multilayer ceramic capacitor 9, in order to reduce loss in the microwave band, the dielectric loss tangent is used as the ceramic material 9c at a frequency of 1 MHz.
A low dielectric constant ceramic material such as titanium oxide or lanthanum oxide with a dielectric constant of 50 and a tan δ of 0.1% or less is used. For this reason, the loss in the microwave band is significantly reduced, so in the case of a microwave band amplifier,
There is no decrease in gain, increase in amplitude deviation, etc. However, since the capacitance is about 100 pF, it is not a high frequency bypass at frequencies lower than the microwave band, so it has drawbacks such as deterioration of third-order cross modulation characteristics and the possibility of oscillation at low frequencies.

Figure 3 shows the 4GHz microwave integrated circuit using the chip-type multilayer ceramic capacitor shown in Figure 1.
FIG. 3 is an explanatory diagram of third-order cross modulation characteristics of a band amplifier. Third
In the figure, the vertical axis shows third-order cross modulation, and the horizontal axis shows △f. Third-order cross modulation is the wave measurement of two signal frequencies f ₁ and f ₂ of equal amplitude at the output end, 2f ₁ −f ₂ and 2f ₂ It is expressed as the difference between the magnitude of −f ₁ and the magnitudes of source signals f ₁ and f ₂ .
Also, △f is △f=f ₂ - f ₁ , and in this case, f ₁ is
It is fixed at 3.7GHz. Furthermore, in FIG. 3, the case where a conventional low dielectric constant type chip-type multilayer ceramic capacitor is used is shown by dotted lines. As is clear from Figure 3, when △f is 20MHz or more, the third-order cross modulation is approximately 65 dB, whereas △
When f is less than 20MHz, the third-order intermodulation is approximately
It becomes 55dB and deterioration can be seen. On the other hand, as shown in Figure 2, if a high dielectric constant ceramic material such as barium titanate with a dielectric constant of 8000 is used as the ceramic material of the conventional chip-type multilayer ceramic capacitor to obtain a capacitance of several 1000 pF, it is possible to The deterioration of third-order cross modulation as shown by the dotted line in the figure disappears. However, since the dielectric loss tangent tan δ is large at a frequency of 1 MHz, which is several percent, it causes a large loss in the microwave band, so microwave band amplifiers have disadvantages such as a decrease in gain and an increase in amplitude deviation.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic capacitor using a ceramic member having sufficient capacity as a high frequency bypass in order to eliminate the above-mentioned conventional drawbacks.

The present invention provides a ceramic capacitor in which a plurality of dielectrics are laminated between an external electrode and an internal electrode.
It is an object of the present invention to provide a ceramic capacitor characterized by having a small capacitance section made of a low dielectric constant ceramic member having a small dielectric loss tangent, and a large capacitance section made of a high dielectric constant ceramic material.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 4 shows a cross-sectional view of a chip-type multilayer ceramic capacitor. In FIG. 4, the outer electrode _19a1 of the chip-type multilayer ceramic capacitor 19 is different from the inner electrode 19a1.
b ₁ , 19b ₃ , 19b ₅ , 19b ₇ , and the external electrode 19a ₂ is connected to the internal electrodes 19b ₂ , 19b ₄ , 19
Connected to b ₆ , 19b ₈ . The internal electrode 19
b ₅ , 19b ₆ , 19b ₇ , 19b ₈ and external electrode 19
Between each of a ₁ and 19a ₂ , in order to reduce loss in the microwave band, use a low dielectric constant material such as titanium oxide or lanthanum oxide with a dielectric constant of 50 and a dielectric loss tangent tan δ of 0.1% or less at a frequency of 1 MHz. Porcelain material 1
9c is placed. Further, the external electrode 19a ₁ ,
19a ₂ and internal electrodes 19b ₁ , 19b ₂ , 19b ₃ , 1
A ceramic material 19d made of a high dielectric constant such as barium titanate having a dielectric constant of 8000 is arranged between each of the capacitors _9b4 in order to obtain a large capacity. Although FIG. 4 shows only four internal electrodes, each internal electrode actually consists of several dozen internal electrodes. Such a chip-type multilayer ceramic capacitor 1
9 is manufactured in the same way as the conventional example described above. After stacking several tens of layers of internal electrodes 19b ₁ to 19b ₈ by printing and coating a thin film of porcelain materials 19c and 19d with a noble metal such as palladium, After firing at several hundred degrees, the external electrodes 19a ₁ and 19a ₂ are coated and baked, and the ceramic material 19c and 19d may be fired or bonded. In addition, when implementing such a ceramic capacitor in a microwave integrated circuit,
In order to shorten the passage of the microwave band, it is desirable to solder the capacitor portion formed of the ceramic material 19a.

In the magnetic capacitor according to the present invention having the above configuration, the high frequency bypass in the microwave band passes through the capacitive part formed of the ceramic material 19c made of a dielectric material with a low dielectric constant and low loss in the microwave band. Even in the case of a wave amplifier, there is no decrease in gain or increase in amplitude deviation. In addition, the high frequency bypass at frequencies lower than the microwave band passes through a capacitive part made of a large capacitance ceramic material 19d made of a dielectric with a high dielectric constant, resulting in the deterioration of third-order cross modulation characteristics and the possibility of deterioration at low frequencies. There is no possibility of oscillation.

To explain further, as mentioned above, for high frequency bypass in the microwave band, a predetermined number of low dielectric constant ceramic materials such as titanium oxide (dielectric constant 50 to 100) are laminated to form a small capacitance section. For example, barium titanate (dielectric constant
A predetermined number of high-permittivity ceramic materials such as 8,000 to 12,000) are laminated to form a large-capacity portion, and these large-capacity portions and small-capacity portions are further laminated. It is clear that the type of the above-mentioned porcelain material and the number of layers to be laminated can be changed as appropriate to obtain the desired capacity.

The solid line in FIG. 3 shows the third-order intermodulation characteristics when the above-described magnetic capacitor according to the present invention is used in the 4 GHz band amplifier shown in FIG. As is clear from the solid line in Figure 3, △f
At any frequency, there is no third-order cross modulation deterioration as in the conventional example shown by the dotted line in FIG.

As explained above, the present invention provides a high-frequency bypass for microwave integrated circuits because high-frequency bypass at frequencies lower than the microwave band eliminates the possibility of deterioration of third-order cross modulation characteristics and oscillation at low frequencies. When used as a filter, the loss in the microwave band can be reduced, and even at frequencies lower than the microwave band, high frequency bypass can be achieved sufficiently.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing part of the 4GHz band amplification section of a microwave integrated circuit using chip-type multilayer ceramic capacitors, Figure 2 is a cross-sectional view schematically showing a conventional chip-type multilayer ceramic capacitor, and Figure 3 4 is a third-order cross-modulation characteristic diagram of a 4 GHz band amplifier, and FIG. 4 is a sectional view schematically showing an embodiment of a magnetic capacitor according to the present invention. 19a ₁ , 19a ₂ ...external electrode, 19b ₁ to 19b ₈
...Internal electrode, 19c, 19d...Porcelain material.

Claims (1)

[Claims] 1. A small capacitance section that is used in high frequency bypass capacitors used in microwave amplifiers and has a capacitance that can perform high frequency bypass in the microwave band by laminating low dielectric ceramic materials, and a high dielectric constant ceramic material. What is claimed is: 1. A ceramic capacitor comprising a large capacitance section having a capacitance capable of performing high frequency bypass in a frequency band lower than a microwave band.