JPH0219954Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a multilayer ceramic capacitor. Demand for multilayer ceramic capacitors has been increasing in recent years as an essential component for promoting high speed and miniaturization of electronic devices and circuits with high reliability. The reasons for this are (1) High-frequency multilayer ceramic capacitors with large capacitance values can be formed smaller than other conventional capacitors such as tantalum capacitors, aluminum electrolytic capacitors, and film capacitors. (2) Due to the structure of the electrode surface, the internal inductance is smaller than other capacitors, and therefore the series resonance frequency is higher than that of other capacitors. It is expressed as a series combination of inductance L, and the series resonance frequency is

It is given by the value of [Formula]. ), making it suitable for use in high frequency ranges. (3) The equivalent series resistance of multilayer ceramic capacitors at high frequencies is smaller than that of other capacitors, so the voltage drop is smaller than when using other capacitors.
The amount of heat generated is also small. Therefore, incorporating multilayer ceramic capacitors into electronic equipment and circuits is not only efficient in terms of power consumption, but also compact in design, with few problems due to heat generation, and high reliability. The following points can be mentioned. However, the equivalent series resistance value of the multilayer ceramic capacitor is too small, so by connecting the multilayer ceramic capacitor and a resistance element in series, etc., the insufficient equivalent series resistance value of the multilayer ceramic capacitor alone can be compensated for, and other capacitors can be used. It may not be possible to use the resistor unless it has a value comparable to the equivalent series resistance value of the resistor. A case where the device cannot be used because the equivalent series resistance value is too small will be described below. Feedback technology is indispensable for modern electronic circuits, and it is no exaggeration to say that the feedback concept is utilized in all electronic circuits to stabilize the circuit. As shown in Fig. 2, the feedback circuit is an amplifier that inputs the input signal v ₁ with a gain μ(f), and in order to amplify the input signal v 1 with as little distortion as possible, a part of the signal V ₂ is passed through a β circuit (usually The circuit is configured so that the signal is returned to the input to the amplifier via an attenuator (attenuator), and is also called a feedback circuit. The circuit has a gain μβ and a phase angle arg(μβ)
becomes unstable when the two conditions of |arg(μβ)|≧180° and |μβ|≧1 hold simultaneously. Therefore, the result of circuit design is as shown by the broken line a in Figure 3.
If the phase exceeds -180° at frequency ₁ where μβ|=1 (i.e. odB), then change the amplitude characteristic or phase so that |arg(μβ)|<180° at the frequency where |μβ|=1. It becomes necessary to compensate for the characteristics. One of the methods often used for compensation is to cascade a phase delay circuit shown in FIG. 4 to a μ or β circuit, which is a feedback circuit having unstable characteristics. The voltage ratio of the phase delay circuit in Fig. 4 is v _put /v _io = R ₂ + j (ωL-1/ωC) / R ₁ + R ₂ + j (
ωL−1/ωC), and the amplitude characteristic is

[Formula] becomes.

[Formula] and ω≪1/C (R ₁ + R ₂ ) | v _put /v _io |≒1 or

[Formula], and 1/C (R ₁ + R ₂ )≪ω≪1/CR ₂ , |v _put /v _io |≒ 1/ωC (R ₁ + R ₂ ), which is a slope of -6 dB/oct. . Also

[Formula] and at the frequency of ω≫1/CR ₂ , |v _put /v _io |≈R ₂ /R ₁ +R ₂ , which is constant regardless of the frequency. Putting the above together, the amplitude characteristics and phase characteristics of the phase delay circuit are as shown in FIG. Therefore, a phase delay circuit is connected in cascade to the μ circuit or β circuit of the feedback circuit having unstable characteristics as shown in FIG. 3a, and as shown by the solid line b in FIG.
A stable circuit can be obtained in which the phase rotation is less than 180° at frequency ₁ where μβ|=1. (In this case, it is necessary to select the constants of R ₁ , R ₂ , and C of the phase delay circuit appropriately.) Since this method is a method of compensating by sacrificing some gain in the high frequency range, the bandwidth Although it has the disadvantage that it is narrower than before compensation, it is often used because it is easy to design and operates stably. It has been explained above that the phase delay circuit shown in FIG. 4 is an effective circuit in stabilizing the feedback circuit. As can be seen from the above explanation, in order to stabilize an electronic circuit using feedback technology that uses a phase lag circuit in parallel, the higher the frequency of the electronic circuit, the more the capacitance value C of the capacitor that makes up the phase lag circuit becomes
Resistance and capacitance must be selected so that the product of R ₂ is smaller. Depending on the frequency range of the electronic circuit, the equivalent series resistance of the capacitor may be R ₂
It can also be seen that by using it as a phase delay circuit, it is possible to form a phase delay circuit without separately preparing a resistance element called _R2 . The fact that the required phase delay circuit can be formed by using the equivalent series resistance of a capacitor without separately preparing a resistor element called _R2 is an important feature of promoting high-density packaging and low cost of electronic circuits, which are rapidly required these days. This is a huge advantage. i.e. resistance element
Not only does the mounting space for R ₂ become unnecessary, but the man-hours for mounting can also be saved. As mentioned above, the equivalent series resistance value of a multilayer ceramic capacitor is small, about a fraction of the equivalent series resistance value of other conventional capacitors, so the capacitor part of the phase delay circuit formed using other capacitors is laminated. To replace it with a ceramic capacitor, in order to equalize the product of the capacitance value C and the resistance value R ₂ described above, the capacitance value C remains constant and the multilayer ceramic capacitor and the resistance element are connected in series. It is necessary to compensate for the insufficient equivalent series resistance value or to construct an equivalent circuit using a separate capacitor or the like. As mentioned above, multilayer ceramic capacitors can be made smaller than other capacitors, so adding a correction resistor or capacitor is desirable since it increases the number of mounting steps even though it is hardly a problem. Therefore, there is a demand for the development of multilayer ceramic capacitors with a large equivalent series resistance value. By the way, a multilayer ceramic capacitor is composed of a ceramic 1, external electrodes 2 and 3, internal electrodes 4, and lead wires 5 and 6, as shown in Fig. 6. Most of the equivalent series resistance of a multilayer ceramic capacitor is due to the external electrode It is known that this is due to the resistance of internal electrodes and lead wires. Therefore, in order to increase the equivalent series resistance of a multilayer ceramic capacitor, attempts have been made to develop a multilayer ceramic capacitor in which the resistances of the external electrode portion, internal electrode portion, and lead wire portion are increased. However, as shown in Figure 6, both have two lead wires (one for each external electrode), so multiple leads can be used to increase the capacitance without changing the equivalent series resistance. It was difficult to configure it like this. For example, to connect n multilayer ceramic capacitors in series as shown in FIG.
It is only necessary to sequentially electrically connect the lead wire 6 to the lead wires 5 of other multilayer ceramic capacitors, and it is not difficult to configure it in this way, but the equivalent series resistance increases by n times. However, the capacitance value is reduced by a factor of n and does not meet the desired purpose. In order to meet the desired purpose, it is necessary to connect n multilayer ceramic capacitors in parallel so that the capacitance is not increased and the resistance is not increased. 1) The external electrodes 2 and 3 must be electrically connected to other (n-1) external electrodes 3 using other conductors, and the other (n-1) external electrodes 3 must be electrically connected using other conductors. ) lead wires 5 and 6 are unnecessary and must be cut off. Soldering is usually used to quickly make electrical connections, but if the thermal conditions are insufficient (solder heat is too high or the heating time is too long), the external electrodes may This may cause peeling between the ceramic and the ceramic, making it unusable or reducing reliability. Therefore, when soldering, it is necessary to carefully consider the thermal conditions of the multilayer ceramic capacitor and to do it quickly. Furthermore, it is preferable to solder the multilayer ceramic capacitor so as not to lose its advantage of being small. Meeting the requirements usually requires considerable training. In the multilayer ceramic capacitor according to the present invention, a lead wire made of a metal having an electrical resistance equal to that of the metal of the internal and external electrodes and a lead wire having an electrical resistance higher than the lead wire are attached to each of a pair of external electrodes. It is something that This multilayer ceramic capacitor has the effect of increasing only the capacitance without increasing the equivalent series resistance. Figure 7 is a diagram for explaining one embodiment of the present invention, where a is a cross-sectional view when viewed from the front, b is a sectional view when viewed from the side, and 7 has a shape of 14 mm x 12 mm x 5 mm. The equivalent series resistance is 1.1mΩ, and the capacitance value is 200μF.
a multilayer ceramic capacitor, 8 is an external electrode constituting the multilayer ceramic capacitor, 9 is solder, 1
0 is a Karma ray with a shape of 0.8mmφ x 12mm [76
%Ni-20%Cr-remainder (Fe+Al)], 11 is a copper wire and 14 is welded with Karma wire, 20mm x 20mm x 10mm
A lead wire is taken out from the mold part 13 having the shape of . Figure b shows how to attach the lead wire to the external electrode part. A copper wire 12 having a shape of 0.8 mmφ x 16 mm is attached to the external electrode 8 with solder 9, and another external wire is connected from the molded part 13. The electrodes have been taken out. The method for attaching the lead wire to the other external electrode is similar. The multilayer ceramic capacitor of this example is
This capacitor was developed as a capacitor for use in the phase delay circuit of 200KHz power supplies.It has electrical characteristics of an equivalent series resistance of 12mΩ and a capacitance of 200μF, and its shape is similar to that of conventional aluminum electrolytic capacitors. It is small at /8. Using two multilayer ceramic capacitors of this example, it was easy to construct a capacitor for use in the phase delay circuit of a 200 KHz power supply, which has electrical characteristics of an equivalent series resistance of 12 mΩ and a capacitance of 400 μF. . First, the first and second capacitors are connected in parallel using lead wires (FIG. 7, 12) made of a metal having an electrical resistance equivalent to that of the metals of the internal and external electrodes. Next, a lead wire (seventh lead wire) having a higher electrical resistance than the lead wire attached to the second capacitor is attached.
The lead wires (consisting of 10 and 11 in the figure) are cut at the mold part. Finally, the "lead wire with high electrical resistance" remaining in the first capacitor is used as the lead wire of a new capacitor composed of these two laminated ceramic capacitors. In this way, the capacitance can be doubled without changing the equivalent series resistance. Although an example is shown in which the "lead wire having high electrical resistance" of the second capacitor is cut, it can also be insulated so as not to interfere with actual use. As is clear from the above embodiments, the multilayer ceramic capacitor of the present invention is an excellent capacitor whose capacity can be easily increased by using n multilayer ceramic capacitors.

[Brief explanation of the drawing]

Figure 1 is an equivalent circuit of a capacitor, Figure 2 is a block diagram of a feedback circuit, Figure 3 is an explanatory diagram of the gain and phase of the feedback circuit, Figure 4 is a phase delay circuit,
FIG. 5 is a diagram showing the gain and phase of a phase delay circuit, FIG. 6 is a diagram showing the structure of a multilayer ceramic capacitor, and FIG. 7 is a diagram for explaining one embodiment of the present invention. In Figure 6, 1 is ceramic, 2
and 3 is an external electrode, 4 is an internal electrode, 5 and 6
In FIG. 7, 7 is a lead wire, 8 is an external electrode, 9 is solder, 10 is a Karma wire, 11 and 12 are copper wires, 13 is a molded part, and 14 is a welded part.

Claims (1)

[Scope of utility model registration request] A multilayer ceramic capacitor characterized in that a lead wire made of a metal having an electrical resistance equal to that of the metal of the internal and external electrodes and a lead wire having an electrical resistance higher than that of the lead wire are attached to each of a pair of external parts. A multilayer ceramic capacitor.