JP2003324030A - Method of mounting capacitor on circuit board and circuit board for mounting capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of mounting laminated ceramic capacitors that can reduce sounds through piezoelectricity on a circuit board, and to provide a circuit board for mounting the capacitors. <P>SOLUTION: Lands 21a, 21b, 22a, and 22b respectively used for mounting two serially-connected laminated ceramic capacitors 1A and 1B of the same specification are formed on the front and rear surfaces 2a and 2b of the circuit board 2 at symmetrical positions with respect to plane, and the capacitors 1A and 1B are disposed to the lands 21a, 21b, 22a, and 22b so that the capacitors 1A and 1B may become symmetric with respect to plane and electrically connected to each other. Consequently, the vibrations transmitted from the capacitors 1A and 1B to the circuit board 2 negate each other, and the circuit board 2 can be prevented from resonating with the vibrations. Therefore, the occurrence of audible sounds of high sound pressures can be reduced significantly than in the conventional practice. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mounting a circuit board on a multilayer ceramic capacitor and a circuit board on which a capacitor is mounted, which can reduce noise generated by a piezoelectric phenomenon.

[0002]

2. Description of the Related Art Conventionally, in a smoothing circuit in a power supply circuit such as a DC-DC converter, an aluminum electrolytic capacitor is often used as a power supply smoothing capacitor.

However, with the miniaturization of electronic circuits and electronic equipment, tantalum electrolytic capacitors, which have the same capacitance as aluminum electrolytic capacitors in a smaller size than aluminum electrolytic capacitors, have been replaced by high capacitance such as power supply smoothing circuits. It has come to be used in electronic circuits that need it.

On the other hand, with the recent miniaturization and energy saving of electronic circuits and electronic devices, most capacitors used in electronic circuits have been changed to monolithic ceramic capacitors.

Since the monolithic ceramic capacitor is small in size and excellent in reliability and durability, it is rapidly popularized.

[0006]

However, since the small-sized and large-capacity monolithic ceramic capacitor uses a high dielectric constant material as the dielectric material, if a DC voltage is applied while an AC voltage is applied, a piezoelectric phenomenon occurs. Occurs and vibration occurs. This vibration tends to be more prominent as the one having a large dielectric constant and the larger the shape.

Therefore, in the smoothing circuit of the power supply circuit, since a monolithic ceramic capacitor having a relatively large shape and a large electrostatic capacity is often used, this kind of vibration often occurs.

When the above-mentioned vibration occurs in the monolithic ceramic capacitor, the vibration of the capacitor may be transmitted to the circuit board on which the capacitor is mounted, and the board may resonate to amplify the sound. That is, due to the vibration of the capacitor, the surrounding air vibrates to generate sound and the substrate also vibrates in resonance. Therefore, there is a problem that the sound pressure becomes large and the sound becomes audible and harsh.

In view of the above problems, an object of the present invention is to provide a circuit board mounting method and a capacitor mounted circuit board for a laminated ceramic capacitor which can reduce the sound generated by the piezoelectric phenomenon.

[0010]

In order to achieve the above-mentioned object, the present invention provides a rectangular parallelepiped shaped element body in which dielectric layers made of dielectric ceramic and internal electrode layers are alternately laminated. And two or more multilayer ceramic capacitors, each of which has a pair of external terminal electrodes that alternately connect the internal electrodes formed on the internal electrode layers in parallel at both ends of the element body, are connected in series or in parallel to form a circuit board. A method for mounting a capacitor on the front surface of the circuit board, wherein lands for mounting half or more of each of the two or more capacitors are formed at substantially symmetrical positions on the front surface and the back surface of the circuit board. A predetermined land among the lands formed on the surface of the circuit board so that the direction of the current flowing in the circuit board is opposite to the direction of the current flowing in the capacitor mounted on the back surface of the circuit board. Conductive connection is made to a predetermined land among the lands formed on the back surface of the circuit board, and the laminated ceramic capacitor is arranged on each of the lands on the front surface and the back surface of the circuit board to electrically connect the external terminal electrode and the land. We propose a method for mounting a capacitor on a circuit board.

According to a second aspect of the present invention, in the method for mounting a capacitor on a circuit board according to the first aspect, the other land on the front surface side and the one land on the rear surface side of the circuit board are formed in the through hole. And a method for mounting a circuit board on a capacitor, which is conductively connected via a conductor provided on an inner layer of the circuit board.

According to the method for mounting a circuit board of a capacitor of claims 1 and 2, the same signal, current, or voltage is applied to the monolithic ceramic capacitors mounted on each of the front surface and the back surface of the circuit board. Has been done. Therefore, when vibration due to the piezoelectric effect occurs in one of the monolithic ceramic capacitors, similar vibration also occurs in the other monolithic ceramic capacitor. However, the monolithic ceramic capacitor mounted on the front surface of the circuit board and the monolithic ceramic capacitor mounted on the back surface of the circuit board are mounted in plane symmetry with each other. Therefore, there are vibrations generated by the piezoelectric effect due to various state changes such as thickness vibration, thickness sliding vibration, face sliding vibration, torsional vibration, flexural vibration, etc. However, the laminated ceramic mounted on the surface of the circuit board The direction of change in the state of the capacitor and the direction of change of the state in the multilayer ceramic capacitor mounted on the back surface of the circuit board are opposite to each other. Therefore, the vibration transmitted from one of the monolithic ceramic capacitors to the circuit board and the vibration transmitted from the other monolithic ceramic capacitor to the circuit board cancel each other.
The circuit board does not resonate. Therefore, the vibration sound generated in the monolithic ceramic capacitor is not amplified,
Generation of audible sound with high sound pressure is reduced.

Since the direction of the current flowing through the monolithic ceramic capacitor mounted on the front surface of the circuit board and the direction of the current flowing through the monolithic ceramic capacitor mounted on the back surface are opposite to each other, it is mounted on the surface of the circuit board. The direction of the magnetic field generated in the monolithic ceramic capacitor by the current flowing in the monolithic ceramic capacitor and the direction of the magnetic field generated in the monolithic ceramic capacitor by the current flowing in the monolithic ceramic capacitor mounted on the back surface of the circuit board are Since the magnetic fields cancel each other out, the equivalent series inductance (ES
L: Equivalent Series L) can be reduced.

Further, according to the method of mounting a multilayer ceramic capacitor on a circuit board, the land on the front surface and the land on the back surface of the circuit board are electrically connected by the through hole and the conductor of the inner layer of the circuit board. There is almost no difference in signal level and signal phase between the electric signal reaching the land on the front surface and the electric signal reaching the land on the back surface. As a result, voltages having almost the same level and phase are applied to the monolithic ceramic capacitors connected to the respective lands on the front and back surfaces of the circuit board.

According to a third aspect of the present invention, in the method for mounting a capacitor on a circuit board according to the first aspect, a multilayer ceramic capacitor of the same specifications to which substantially the same voltage is applied is placed on the front and back surfaces of the circuit board in symmetrical positions. We propose a circuit board mounting method for capacitors mounted on the land.

According to a fourth aspect of the present invention, a rectangular parallelepiped element body is formed by alternately laminating dielectric layers made of a dielectric ceramic and internal electrode layers, and the internal electrode layers are formed on both ends of the element body. A multilayer ceramic capacitor including a pair of external terminal electrodes that alternately connect the formed internal electrodes in parallel.
In a circuit board in which two or more capacitors are connected in series or in parallel and mounted, the circuit board has lands for mounting half or more of each of the two or more capacitors at substantially plane symmetrical positions on the front surface and the back surface, and A predetermined one of the lands provided on the front surface of the circuit board is arranged such that the direction of the current flowing through the capacitor is opposite to the direction of the current flowing through the capacitor mounted on the back surface of the circuit board. A capacitor mounting circuit having a conductor for conductively connecting a land and a predetermined land provided on the back surface, and each of the serially connected multilayer ceramic capacitors being mounted on the land on the front surface and the back surface of the circuit board. Propose a substrate.

According to the capacitor-mounted circuit board, the same signal, current, or voltage is applied to the monolithic ceramic capacitors mounted on the front surface and the back surface of the circuit board, respectively. Therefore, when vibration due to the piezoelectric effect occurs in one of the monolithic ceramic capacitors, similar vibration also occurs in the other monolithic ceramic capacitor. However, the monolithic ceramic capacitor mounted on the front surface of the circuit board and the monolithic ceramic capacitor mounted on the back surface of the circuit board are mounted in plane symmetry with each other.
Therefore, there are vibrations generated by the piezoelectric effect due to various state changes such as thickness vibration, thickness sliding vibration, face sliding vibration, torsional vibration, flexural vibration, etc. However, the laminated ceramic mounted on the surface of the circuit board The direction of change in the state of the capacitor and the direction of change of the state in the multilayer ceramic capacitor mounted on the back surface of the circuit board are opposite to each other. Therefore, the vibration transmitted from one of the monolithic ceramic capacitors to the circuit board cancels the vibration transmitted from the other monolithic ceramic capacitor to the circuit board, so that the circuit board does not resonate. Therefore,
The vibration sound generated in the monolithic ceramic capacitor is not amplified, and the generation of audible sound with large sound pressure is reduced.

Further, since the direction of the current flowing through the monolithic ceramic capacitor mounted on the front surface of the circuit board is opposite to the direction of the current flowing through the monolithic ceramic capacitor mounted on the back surface of the circuit board, the surface of the circuit board is The direction of the magnetic field generated in the monolithic ceramic capacitor by the current flowing through the mounted monolithic ceramic capacitor and the magnetic field generated in the monolithic ceramic capacitor by the current flowing in the monolithic ceramic capacitor mounted on the back surface of the circuit board. Since the directions are opposite to each other, these magnetic fields cancel each other, so that the equivalent series inductance (ESL) can be reduced.

According to a fifth aspect of the present invention, in order to increase the cancellation rate of the vibration, in the capacitor-mounted circuit board according to the fourth aspect, a multilayer ceramic capacitor is disposed on the front surface and the back surface of the circuit board at symmetrical positions. The one configured to the equivalent specifications was used.

Further, in the sixth to tenth aspects, in the capacitor-mounted circuit board according to the fifth aspect, the following range is set as a range of equivalent specifications in which the cancellation rate of the vibration can be obtained sufficiently in actual use. To propose.

That is, in claim 6, the electromechanical coupling coefficient of one of the monolithic ceramic capacitors of the same specification is 70 of the electromechanical coupling coefficient of the other monolithic ceramic capacitor.
We propose a capacitor-mounted circuit board that is set within the range of 100% to 130%.

According to a seventh aspect of the present invention, there is provided a capacitor-mounted circuit board in which the dielectric constant of one of the multilayer ceramic capacitors of the same specification is set within a range of 50% to 150% of the dielectric constant of the other multilayer ceramic capacitor. suggest.

Further, in claim 8, the laminated ceramic capacitors of the same specification have substantially the same number of laminated layers, and one layered ceramic capacitor has a thickness of 70% to 130% of the layered thickness of the other laminated ceramic capacitor.
We propose a capacitor mounted circuit board that is set within the range.

According to a ninth aspect of the present invention, the monolithic ceramic capacitors having the same specifications have substantially the same thickness, and the number of laminated layers of one laminated ceramic capacitor is 70% to 130% of the number of laminated layers of the other laminated ceramic capacitor. We propose a capacitor mounted circuit board that is set within the range.

According to a tenth aspect of the present invention, one of the monolithic ceramic capacitors having the same specifications has a length, a width and a height which are 70% to 130% of the length, width and height of the other monolithic ceramic capacitor. We propose a capacitor mounted circuit board that is set within the range.

In the eleventh and twelfth aspects, in the capacitor-mounted circuit board according to the fourth aspect, as a range of deviation of the plane-symmetrical position where the cancellation rate of the vibration can be obtained sufficiently in actual use. We suggest the following ranges:

That is, according to the eleventh aspect of the present invention, one of the monolithic ceramic capacitors arranged at the plane-symmetrical position is displaced in the length direction and the width direction of the other monolithic ceramic capacitor in the other monolithic ceramic capacitor. We propose a capacitor-mounted circuit board arranged at a position within a range of 30% of the length and width of the capacitor.

In the twelfth aspect, the angle formed by the central axis in the longitudinal direction of the one monolithic ceramic capacitor and the central axis in the longitudinal direction of the other monolithic ceramic capacitor arranged at the plane-symmetrical position is 40. We propose a capacitor mounted circuit board that is set within 100 degrees.

According to the thirteenth to fifteenth aspects, in the capacitor-mounted circuit board according to the fourth aspect, vibration is generated largely in the conventional case, and the vibration canceling rate is required when the circuit board is actually used. We propose a capacitor-mounting circuit board on which the following electronic circuits are formed as fully obtainable electronic circuits.

That is, a thirteenth aspect of the present invention proposes a capacitor-mounted circuit board in which an electronic circuit in which the voltage applied to the multilayer ceramic capacitor fluctuates is formed as the electronic circuit including the multilayer ceramic capacitor.

According to a fourteenth aspect of the present invention, there is proposed a capacitor mounting circuit board in which a smoothing circuit in a power supply circuit is formed as an electronic circuit including the monolithic ceramic capacitor, and the monolithic ceramic capacitor is a smoothing capacitor.

According to a fifteenth aspect of the present invention, a capacitor-mounted circuit board is proposed in which an electronic circuit in which an applied voltage to the multilayer ceramic capacitor fluctuates at an audible frequency band is formed as an electronic circuit including the multilayer ceramic capacitor. To do.

According to the sixteenth to eighteenth aspects, in the capacitor-mounted circuit board according to the fourth aspect, the applied voltage to the monolithic ceramic capacitor is sufficient to obtain the vibration canceling ratio in actual use. The following range is proposed as.

That is, in the sixteenth aspect of the present invention, in the electronic circuit including the monolithic ceramic capacitor, the applied voltage value to one of the monolithic ceramic capacitors arranged in the plane symmetrical position is the voltage value applied to the other monolithic ceramic capacitor. We propose a capacitor-mounted circuit board that is set within the range of 80% to 120%.

According to a seventeenth aspect of the present invention, in the electronic circuit including the monolithic ceramic capacitor, the voltage applied to the other monolithic ceramic capacitor with respect to the phase of the voltage applied to one of the monolithic ceramic capacitors arranged at the plane symmetry position is described. We propose a capacitor-mounted circuit board in which the phase shift is set within 20% of the phase cycle of the voltage applied to the one monolithic ceramic capacitor.

Further, in an eighteenth aspect of the invention, in an electronic circuit including the monolithic ceramic capacitor, a DC bias voltage is applied to both monolithic ceramic capacitors arranged in the plane symmetrical position and is applied to one of the monolithic ceramic capacitors. We propose a capacitor-mounted circuit board in which the DC bias voltage value is set within the range of 80% to 120% of the DC bias voltage value applied to the other monolithic ceramic capacitor.

[0037]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing a circuit board mounted state of a monolithic ceramic capacitor according to a first embodiment of the present invention, and FIG. 2 is a side sectional view thereof.

In the capacitor mounted circuit board of this embodiment, a circuit board on which two multilayer ceramic capacitors connected in series are mounted will be described.

In the figure, 1 (1A, 1B) is a monolithic ceramic capacitor (hereinafter simply referred to as a capacitor),
It is composed of an element body 13 in which dielectric layers 11 and internal electrodes 12 are alternately laminated, and a pair of external electrodes 14a and 14b in which internal electrodes are alternately connected in parallel at both ends of the element body 13. ing.

The dielectric layer 11 is made of a rectangular sheet-shaped ceramic sintered body, and the ceramic sintered body is made of, for example, a dielectric ceramic material containing magnesium titanate as a main component.

The internal electrode 12 is made of a metal thin film obtained by sintering a metal paste, and the metal paste is, for example, Pd.
A material containing a precious metal material such as Ag or Pd as a main component is used. The external electrode 14 is also made of the same material as the internal electrode 12, and its surface is plated with solder in order to improve solder wettability.

The capacitors 1A and 1B have the same specifications.

Note that the specifications of the capacitors 1A and 1B may not be the same, but may be substantially the same specifications so that the later-described vibration cancellation can be obtained sufficiently.

For example, the electromechanical coupling coefficient, the dielectric constant, the thickness per layer, the number of laminated layers, etc. are particularly important as the defining elements of the equivalent specifications that can obtain the vibration canceling rate in a necessary and sufficient manner in actual use. . The preferable range of these factors is obtained from the experiment as follows.

That is, between the capacitors 1A and 1B, the electromechanical coupling coefficient of one capacitor is 70% to 130% of the electromechanical coupling coefficient of the other capacitor.
Must be set within the range.

Between the capacitors 1A and 1B, the dielectric constant of the dielectric material used in one of the capacitors is 50% to 150% of the dielectric constant of the dielectric material used in the other capacitor. Be set within the range of%.

The capacitors 1A and 1B have substantially the same number of layers, and the thickness of one of the capacitors is set within the range of 70% to 130% of the thickness of the other capacitor. thing.

When the thicknesses of the capacitors 1A and 1B are substantially the same, the number of laminated layers of one capacitor is set within the range of 70% to 130% of the number of laminated layers of the other capacitor. is being done.

Further, between the capacitors 1A and 1B, the length, width and height of one capacitor are 70% to 1% of the length, width and height of the other capacitor.
Be set within the range of 30%.

Capacitor 1 set within the above range
Vibration generated by using A and the capacitor 1B is significantly reduced.

Reference numeral 2 is a circuit board, and a multilayer printed board is used here. Further, on the front surface 2a and the back surface 2b of the circuit board 2, lands 21a and 21b for mounting the capacitors 1A in plane-symmetrical positions and the capacitors 1B, respectively.
The lands 22a and 22b for mounting are formed in plane-symmetrical positions. The land 21a on the front surface 2a of the circuit board 2 is conductively connected to the plane-symmetrical land 22a on the rear surface 2b side through a through hole 23a. That is, the lands 21a, 2 formed on the surface 2a of the circuit board 2
1b, the direction of the current flowing through the capacitor 1A mounted on the back surface 2b, and the lands 22a, 22b formed on the back surface 2b.
One of the lands 21a formed on the front surface 2a is conductively connected to the land 22a formed on the back surface 2b through the through hole 23a so that the direction of the current flowing through the capacitor 1B mounted in the opposite direction is opposite. Has been done.

Although the ceramic multilayer circuit board is used as the circuit board 2 in this embodiment, other types may be used.

The land 21a on the front surface 2a and the back surface 2b
It is sufficient that the land 22a is electrically connected, and it may be electrically connected by combining another conductor with a through hole, or may be electrically connected by using a jumper wiring or the like. That is, substantially the same voltage may be applied to both the capacitors 1A and 1B connected in series.

Here, in actual use, the capacitors 1A and 1A which can obtain a necessary and sufficient vibration cancellation rate, which will be described later, are obtained.
As the voltage applied to B, the following voltage range has been obtained by experiments.

That is, in the electronic circuit using the capacitors 1A and 1B, the voltage value applied to one of the capacitors 1A and 1B is within the range of 80% to 120% of the voltage value applied to the other capacitor. Must be set.

In the electronic circuit, the phase shift of the voltage applied to the other capacitor with respect to the phase of the voltage applied to the one capacitor is set within 20% of the phase period of the voltage applied to the one capacitor. To be.

In the electronic circuit, the capacitor 1
When a DC bias voltage is applied to A and 1B,
The DC bias voltage value applied to one of the capacitors is
DC bias voltage value of 8 applied to the other capacitor
It is set within the range of 0% to 120%.

If substantially the same voltage satisfying any of these is applied to both capacitors 1A, 1B, the vibrations generated by capacitors 1A, 1B are greatly reduced.

On the other hand, one external electrode 14a of the capacitor 1A mounted on the surface 2a of the circuit board 2 is conductively connected to the land 21a by soldering, and the other external electrode 14b is conductively connected to the land 21b. Also, the circuit board 2
One external electrode 14a of the capacitor 1B mounted on the back surface 2b of the above is conductively connected to the land 22a by soldering,
The other external electrode 14b is conductively connected to the land 22b.

Here, in order to suppress the occurrence of vibration, when the capacitors 1A and 1B are soldered, it is preferable that the capacitors 1A and 1B are arranged so that they are substantially plane-symmetrical. .

Since it is almost impossible to make the capacitors 1A and 1B completely plane-symmetrical when they are actually mounted, they are actually used in the experimental result for obtaining the allowable range of the positional deviation. It has been found that the following range is preferable as the range of deviation of the plane-symmetrical position at which the above-mentioned vibration canceling ratio can be obtained sufficiently.

That is, in one of the capacitors 1A and 1B arranged substantially in plane symmetry, the displacement of the other capacitor in the length direction and the width direction is different from that of the other multilayer ceramic capacitor. , Must be placed in a position within 30% of the width. Further, the angle formed by the central axis of one of the capacitors 1A and 1B arranged substantially symmetrically in the longitudinal direction and the central axis of the other capacitor in the longitudinal direction is set within 40 degrees. Is.

Further, the direction of the magnetic field generated in the capacitor 1A by the current flowing in the capacitor 1A mounted on the front surface 2a of the circuit board 2 and the current flowing in the capacitor 1B mounted on the back surface 2b of the circuit board 2. The directions of the magnetic fields generated in the capacitor 1B are opposite to each other, and these magnetic fields cancel each other out. Therefore, the equivalent series inductance (ES) in the capacitors 1A and 1B is reduced.
L: Equivalent Series L) can be reduced.

Next, an example of a specific electronic circuit in this embodiment will be described.

FIG. 3 shows a DC-capacitor using the capacitors 1A and 1B to which the above-described capacitor circuit board mounting method is applied.
3 is a circuit diagram showing a DC converter 30. FIG. In the figure,
Reference numeral 31 is a DC power supply, 32 is a P-channel FET, 33 is a pulse width modulation circuit, 34 is a diode, 35 is an inductor, and 1A and 1B are the above-mentioned capacitors.

The positive electrode of the DC power supply 31 is connected to the source of the FET 32, the drain of the FET 32 is connected to the cathode of the diode 34, and the other end (land 21b side) of the capacitor 1A and the output terminal 36a are connected via the inductor 35. It is connected. One end (land 21a side) of the capacitor 1A is connected to one end (land 22a) of the capacitor 1B.
Side), and these capacitors 1A and 1B are connected in series. The anode of the diode 34 and the other end of the capacitor 1B (on the side of the land 22b) are connected to the DC power source 31.
Of the negative electrode and the ground terminal 36b. further,
The voltage Vcon output from the pulse width modulation circuit 33 is applied to the gate of the FET 32.

The pulse width modulation circuit 33 outputs a voltage Vcon having a pulse width t at a predetermined cycle T, and the voltage Vcon is FET3.
When being applied to the gate of the FET 2, the FET 32 is turned on and a current is applied between the source and the drain.

When the FET 32 is in the ON state, the current flowing between its source and drain is output from the output terminal 36a via the inductor 35. Further, the energizing current flows into the capacitors 1A and 1B connected in series,
The capacitors 1A and 1B are charged.

When the FET 32 is off, the current from the DC power supply 31 is cut off by the FET 32. At this time, the energy stored in the inductor 35 is output as a back electromotive force, and a freewheeling current due to the back electromotive force is supplied to the capacitors 1A and 1B and the output terminal 36a via the diode 34.

Here, the output voltage Vo is represented by the equation (1), where Vin is the output voltage of the DC power supply 31.

Vo = Vint / T (1) That is, the voltage Vo is obtained by multiplying the value obtained by dividing the pulse width t by the period T by the voltage Vin. Therefore, in the pulse width modulation circuit 33, the output voltage Vo can be arbitrarily set by changing the ratio between the pulse width t and the period T.

In the DC-DC converter circuit 30 described above,
Since the capacitors 1A and 1B are used for smoothing, capacitors having a large capacitance are required. Furthermore, capacitor 1
An AC voltage is applied to A and 1B while applying a DC voltage. Therefore, a piezoelectric phenomenon occurs in the capacitors 1A and 1B, causing vibration.

However, in the present embodiment, as described above, the capacitors 1A and 1B are mounted on the front and back of the circuit board 2 so as to be plane-symmetrical and the currents flowing through them are in the same direction. Since the vibrations transmitted from the monolithic ceramic capacitor to the circuit board and the vibrations transmitted from the other monolithic ceramic capacitor to the circuit board cancel each other, the circuit board 2 does not resonate and the generation of audible sound with large sound pressure is reduced. It

That is, as shown in FIG. 4, when the capacitor 1A mounted on the surface 2a of the circuit board 2 vibrates due to the piezoelectric effect, the other monolithic ceramic capacitor 1B also vibrates similarly. Note that vibrations generated by the piezoelectric effect also include vibrations due to various state changes such as thickness vibration, thickness sliding vibration, surface sliding vibration, torsional vibration, and flexural vibration. The description will be made assuming that the vibration that is displaced in the direction is generated.

However, the capacitor 1A mounted on the front surface 2a of the circuit board 2 and the capacitor 1 mounted on the back surface 2b of the circuit board 2
Since B is an equivalent specification that is mounted so as to be plane-symmetrical to each other, the direction of the state change (Da1, Da2) occurring in one capacitor 1A and the direction of the state change occurring in the other capacitor 1B ( Db1 and Db2) are opposite to each other.

Therefore, the vibration transmitted from the one capacitor 1A to the circuit board 2 and the vibration transmitted from the other capacitor 1B to the circuit board 2 cancel each other out, so that the circuit board 2 does not resonate.

Therefore, the sound generated by the vibration of the capacitors 1A and 1B is not amplified, and the generation of audible sound with a large sound pressure is reduced.

In this embodiment, two capacitors 1A and 1B connected in series are used in a portion where one capacitor is normally used in the same circuit.
Although A and 1B are arranged on the front and back of the circuit board 2 to suppress the generation of vibration, the present invention is not limited to this.

For example, as shown in FIG. 5, a plurality of three or more laminated ceramic capacitors 1 are connected in series, half of them are mounted on the surface 2a of the circuit board 2, and the rest are mounted symmetrically in plane. You may mount on the back surface 2b so that it may become. In addition, two capacitors connected in parallel
These are connected in series, and one set of parallel-connected capacitors is mounted on the front surface 2a of the circuit board 2, and the other set of parallel-connected capacitors is mounted on the back surface 2b of the circuit board 2. The effect can be obtained. These series-connected capacitors or parallel-connected capacitors may be configured using capacitor array components.

Next, a second embodiment of the present invention will be described.

FIG. 6 is a perspective view showing a circuit board mounted state of the laminated ceramic capacitor according to the second embodiment of the present invention, and FIG. 7 is a side sectional view thereof.

In the capacitor-mounted circuit board of the second embodiment, a circuit board on which two laminated ceramic capacitors connected in parallel are mounted will be described. Further, in the figure, the same components as those in the first embodiment described above are designated by the same reference numerals and the description thereof will be omitted.

In the second embodiment, the surface 2a of the circuit board 2 is
The lands 21a and 21b for mounting the capacitor 1A and the lands 22a and 22b for mounting the capacitor 1B are respectively formed on the back surface 2b and the back surface 2b in plane symmetrical positions. In addition, a rectangular conductor 2 is provided on the inner layer of the circuit board 2.
4a and 24b are provided, one end of the conductor 24a is conductively connected to the land 22a through the through hole 23a, and the other end of the conductor 24a is conductively connected to the land 21b through the through hole 23b. There is. Further, one end of the conductor 24b is conductively connected to the land 21a through the through hole 23c, and the other end of the conductor 24b is conductively connected to the land 21b through the through hole 23d. That is, the direction of the current flowing through the capacitor 1A mounted on the lands 21a and 21b formed on the front surface 2a of the circuit board 2 and the land 2 formed on the back surface 2b.
The other lands 21a and 21b formed on the front surface 2a have through holes 23 so that the currents flowing through the capacitors 1B mounted on the capacitors 2a and 22b are in opposite directions.
Via a to 23d and conductors 24a and 24b, they are conductively connected to lands 22a and 22b formed at positions symmetrical to the back surface 2b.

Further, the lands 21a, 21b on the front surface and the lands 22a, 22b on the back surface may be made conductive so that the capacitors 1A, 1B are connected in parallel, and are made conductive by combining wiring patterns other than the above. Alternatively, a jumper wire or the like may be used for electrical continuity. That is, substantially the same voltage is applied to both the capacitors 1A and 1B connected in parallel, and the directions of the currents flowing through the capacitors may be opposite.

Two capacitors 1A, 1 connected in parallel
By arranging B as described above and mounting it on the circuit board 2, the direction of the state change due to the vibration generated in the capacitor 1A and the direction of the state change due to the vibration generated in the capacitor 1B are opposite to each other. Since the vibration transmitted from the capacitor 1A to the circuit board 2 and the vibration transmitted from the capacitor 1B to the circuit board 2 cancel each other, the circuit board 2 does not resonate. Therefore, the vibration sound generated in the capacitors 1A and 1B is not amplified, and the generation of audible sound with a large sound pressure is reduced.

Furthermore, since the direction of the current flowing through the capacitor 1A and the direction of the current flowing through the capacitor 1B are opposite to each other as described above, the direction of the magnetic field generated in the capacitor 1A by the current flowing through the capacitor 1A and the direction of the capacitor Capacitor 1B due to the current flowing in 1B
Since the directions of the magnetic fields generated in the two directions are opposite to each other, these magnetic fields cancel each other out, and the equivalent series inductance (ESL: Equivalent Series L) can be reduced.

The specifications of the capacitors 1A and 1B suitable for suppressing the generation of audible sound and the arrangement on the circuit board are the same as those described in the first embodiment.

Next, an example of a specific electronic circuit according to the second embodiment will be described.

FIG. 8 shows a DC-capacitor using capacitors 1A and 1B to which the above-described capacitor circuit board mounting method is applied.
6 is a circuit diagram showing a DC converter 37. FIG. In the figure,
The same components as those of the DC-DC converter circuit 30 in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.

The DC-DC converter circuit 30 shown in FIG. 3 and the DC-DC converter circuit 3 shown in FIG.
7 is that the capacitors 1A and 1B are connected in parallel as described above. DC-DC
In the converter circuit 37, the positive electrode of the DC power supply 31 is an FET
The drain of 32 is connected to the cathode of the diode 34, and the other end of the capacitor 1A (land 21b side) and one end of the capacitor 1B (land 2) are connected via the inductor 35.
2a side) and the output terminal 36a. Also,
One end of the capacitor 1A (land 21a side) and the other end of the capacitor 1B (land 22b side) are connected to the other output terminal 36b.
It is connected to the.

In the DC-DC converter circuit 37,
Similar to the first embodiment, the capacitors 1A and 1B are used for smoothing, and therefore need to have a large capacitance.
Further, the AC voltage is applied to the capacitors 1A and 1B while applying the DC voltage. Therefore, a piezoelectric phenomenon occurs in the capacitors 1A and 1B, causing vibration.

However, in the present embodiment, as described above, the capacitors 1A and 1B are mounted on the front and back of the circuit board 2 so as to be plane-symmetric and the currents flowing through the capacitors 1A and 1B are opposite to each other. Since the vibration transmitted from the capacitor 1A to the circuit board 2 and the vibration transmitted from the other capacitor 1B to the circuit board 2 cancel each other, the circuit board 2 does not resonate, and the generation of audible sound with a large sound pressure is reduced. It

The present embodiment is an example, and the present invention is not limited to this. For example, in the present embodiment, D
Although the present invention is applied to the C-DC converter circuit 30, it is needless to say that the same effect is exhibited even when applied to other electronic circuits. When the present invention is applied, as an electronic circuit in which the effect of suppressing vibration and audible sound is remarkably exhibited, for example,
Electronic circuit in which the applied voltage to the capacitors 1A and 1B fluctuates, particularly an electronic circuit in which the applied voltage continuously fluctuates, a smoothing circuit using the capacitors 1A and 1B as a smoothing capacitor in a power supply circuit, a capacitor at an audio frequency band frequency The applied voltage to 1A and 1B is in the audible frequency band (20Hz ~
An electronic circuit or the like that changes at a frequency of 20 KHz) can be used.

[0095]

As described above, according to the capacitor circuit board mounting method of the present invention, the multilayer ceramic capacitors connected in series or in parallel are provided on the front and back surfaces of the circuit board. Since they are mounted symmetrically, the vibration transmitted from one monolithic ceramic capacitor to the circuit board cancels the vibration transmitted from the other monolithic ceramic capacitor to the circuit board, and the circuit board resonates with this vibration. Can be prevented. Therefore,
The sound generated by the vibration of the monolithic ceramic capacitor is not amplified, and the generation of audible sound with a large sound pressure can be significantly reduced as compared with the conventional case. Furthermore, the direction of the current flowing in the monolithic ceramic capacitor mounted on the front surface of the circuit board is opposite to the direction of the current flowing in the monolithic ceramic capacitor mounted on the back surface, so the monolithic ceramic capacitor mounted on the front surface of the circuit board. The direction of the magnetic field generated in the monolithic ceramic capacitor due to the current flowing in it is opposite to the direction of the magnetic field generated in the monolithic ceramic capacitor due to the current flowing in the monolithic ceramic capacitor mounted on the back surface of the circuit board. Since these magnetic fields cancel each other out, the equivalent series inductance can be reduced.

According to the method of mounting a capacitor on a circuit board of the present invention, in addition to the above effects, a multilayer ceramic capacitor of the same specifications to which substantially the same voltage is applied is plane-symmetric on the front and back surfaces of the circuit board. Since it is mounted as described above, the vibration transmitted from one multilayer ceramic capacitor to the circuit board and the vibration transmitted from the other multilayer ceramic capacitor to the circuit board cancel each other out, and the circuit board can be prevented from resonating against this vibration. . Therefore, the sound generated by the vibration of the monolithic ceramic capacitor is not amplified, and the generation of audible sound with a large sound pressure can be significantly reduced as compared with the related art.

According to the capacitor-mounted circuit board of the fourth to the eighteenth aspects, since the serially connected multilayer ceramic capacitors are mounted on the front and back surfaces of the circuit board in a plane-symmetric manner, It is possible to prevent the vibration transmitted from the monolithic ceramic capacitor to the circuit board and the vibration transmitted to the circuit board from the monolithic ceramic capacitor on the back side cancel each other, and the circuit board resonating against this vibration. Therefore, the sound generated by the vibration of the monolithic ceramic capacitor is not amplified, and the generation of audible sound with a large sound pressure can be significantly reduced as compared with the related art.

[Brief description of drawings]

FIG. 1 is a perspective view showing a circuit board mounted state of a monolithic ceramic capacitor according to a first embodiment of the present invention.

FIG. 2 is a side sectional view showing a state where the laminated ceramic capacitor according to the first embodiment of the present invention is mounted on a circuit board.

FIG. 3 is a circuit diagram showing a DC-DC converter to which the circuit board mounting method for a laminated ceramic capacitor according to the first embodiment of the present invention is applied.

FIG. 4 is a diagram illustrating a vibration state of the monolithic ceramic capacitor according to the first embodiment of the present invention.

FIG. 5 is a side sectional view showing a state where a monolithic ceramic capacitor according to another embodiment of the present invention is mounted on a circuit board.

FIG. 6 is a perspective view showing a circuit board mounting state of a monolithic ceramic capacitor according to a second embodiment of the present invention.

FIG. 7 is a side sectional view showing a circuit board mounting state of the multilayer ceramic capacitor according to the second embodiment of the present invention.

FIG. 8 is a circuit diagram showing a DC-DC converter to which a circuit board mounting method for a laminated ceramic capacitor according to a second embodiment of the present invention is applied.

[Explanation of symbols]

1, 1A, 1B ... Multilayer ceramic capacitor, 11 ... Dielectric layer, 12 ... Internal electrode, 13 ... Element body, 14a, 14b
... external electrodes, 2 ... circuit board, 2a ... surface, 2b ... surface,
21a, 21b, 22a, 22b ... Land, 23a, 2
3b ... through hole, 24a, 24b ... conductor, 30,
37 ... DC-DC converter circuit, 31 ... DC power supply, 3
2 ... P-channel type FET, 33 ... Pulse width modulation circuit,
34 ... Diode, 35 ... Inductor, 36a ... Output terminal, 36b ... Ground terminal.

Continued front page    (72) Inventor Masataka Ohara             6-16-20 Ueno, Taito-ku, Tokyo Sun invitation             Denden Co., Ltd.

Claims (18)

[Claims] 1. A rectangular parallelepiped element body in which dielectric layers made of a dielectric ceramic and internal electrode layers are alternately laminated,
Mounted on a circuit board by connecting in series or in parallel two or more multilayer ceramic capacitors each including a pair of external terminal electrodes that alternately connect the internal electrodes formed in the internal electrode layers in parallel at both ends of the element body. A land for mounting half or more of each of the two or more capacitors is formed at substantially symmetrical positions on the front surface and the back surface of the circuit board, and flows to the capacitors mounted on the front surface of the circuit board. A predetermined land among the lands formed on the front surface of the circuit board and the back surface of the circuit board so that the direction of the current is opposite to the direction of the current flowing through the capacitor mounted on the back surface of the circuit board. Conductive connection is made to a predetermined land among the lands formed on the circuit board, and the monolithic ceramic capacitor is arranged on each of the lands on the front surface and the back surface of the circuit board and Circuit board mounting method of the capacitor, wherein the connecting conductive terminal electrodes and the land. 2. One of the lands on the front surface side and one of the lands on the back surface side of the circuit board are conductively connected to each other through a through hole formed in the land and a conductor provided in an inner layer of the circuit board. A method for mounting a capacitor on a circuit board according to claim 1. 3. The capacitor circuit according to claim 1, wherein the multilayer ceramic capacitors of the same specifications to which substantially the same voltage is applied are mounted on the lands on the front surface and the back surface of the circuit board at symmetrical positions. Board mounting method. 4. A rectangular parallelepiped shaped element body in which dielectric layers made of a dielectric ceramic and internal electrode layers are alternately laminated,
Two or more monolithic ceramic capacitors each including a pair of external terminal electrodes that alternately connect the internal electrodes formed on the internal electrode layers in parallel at both ends of the element body are mounted in series or in parallel. In the circuit board, the circuit board has lands for mounting half or more of each of the two or more capacitors at substantially symmetrical positions on the front surface and the back surface, and a current flowing through the capacitors mounted on the front surface of the substrate. A predetermined land among the lands provided on the front surface and a predetermined land provided on the back surface so that the direction of is opposite to the direction of the current flowing through the capacitor mounted on the back surface of the circuit board. Each of the serially connected multilayer ceramic capacitors is mounted on a land on the front surface and the back surface of the circuit board. Capacitor mounting circuit board, characterized in that there. 5. The capacitor-mounted circuit board according to claim 4, wherein the monolithic ceramic capacitors arranged on the front surface and the back surface of the circuit board at symmetrical positions are configured to have the same specifications. 6. The electromechanical coupling coefficient of one monolithic ceramic capacitor of the same specification is set within a range of 70% to 130% of the electromechanical coupling coefficient of the other monolithic ceramic capacitor. Item 5. The capacitor-mounted circuit board according to Item 5. 7. The dielectric constant of one monolithic ceramic capacitor of the same specification is set within a range of 50% to 150% of the dielectric constant of the other monolithic ceramic capacitor. Capacitor mounted circuit board. 8. The monolithic ceramic capacitors of the same specifications have substantially the same number of laminations, and one monolithic ceramic capacitor has a single layer thickness within a range of 70% to 130% of a monolayer ceramic capacitor thickness of the other monolithic ceramic capacitor. The capacitor-mounted circuit board according to claim 5, wherein: 9. The multilayer ceramic capacitors of the same specification have substantially the same layer thickness, and the number of laminated layers of one laminated ceramic capacitor is set within the range of 70% to 130% of the number of laminated layers of the other laminated ceramic capacitor. The capacitor-mounted circuit board according to claim 5, wherein: 10. The length, width and height of one monolithic ceramic capacitor of the same specifications are 70% to 13% of the length, width and height of the other monolithic ceramic capacitor.
The capacitor-mounted circuit board according to claim 5, wherein it is set within a range of 0%. 11. One of the monolithic ceramic capacitors arranged at the plane-symmetrical position has a positional deviation in the length direction and the width direction of the other monolithic ceramic capacitor, which is the length of the other monolithic ceramic capacitor. Width 30
5. The capacitor-mounted circuit board according to claim 4, wherein the capacitor-mounted circuit board is arranged at a position within a range of%. 12. The angle between the central axis in the longitudinal direction of one of the monolithic ceramic capacitors and the central axis in the longitudinal direction of the other monolithic ceramic capacitor arranged at the plane-symmetrical position is set within 40 degrees. 5. The capacitor-mounted circuit board according to claim 4, wherein: 13. The capacitor-mounted circuit board according to claim 4, wherein an electronic circuit in which a voltage applied to the multilayer ceramic capacitor fluctuates is formed as the electronic circuit including the multilayer ceramic capacitor. 14. The capacitor-mounted circuit board according to claim 4, wherein a smoothing circuit in a power supply circuit is formed as an electronic circuit including the monolithic ceramic capacitor, and the monolithic ceramic capacitor is a smoothing capacitor. 15. The capacitor according to claim 4, wherein an electronic circuit in which an applied voltage to the multilayer ceramic capacitor fluctuates at a frequency in an audible frequency band is formed as the electronic circuit including the multilayer ceramic capacitor. Mounted circuit board. 16. In an electronic circuit including the monolithic ceramic capacitor, an applied voltage value to one of the monolithic ceramic capacitors arranged in the plane symmetrical position is 80% to 1% of an applied voltage value to the other monolithic ceramic capacitor.
The capacitor-mounted circuit board according to claim 4, wherein it is set within a range of 20%. 17. In an electronic circuit including the monolithic ceramic capacitor, the phase shift of the voltage applied to the other monolithic ceramic capacitor with respect to the phase of the voltage applied to one of the monolithic ceramic capacitors arranged in the plane-symmetrical position is: 5. The capacitor-mounted circuit board according to claim 4, wherein the phase is set within 20% of the phase cycle of the voltage applied to the one monolithic ceramic capacitor. 18. An electronic circuit including the monolithic ceramic capacitor, wherein a DC bias voltage is applied to both monolithic ceramic capacitors arranged in the plane symmetrical position, and a DC bias voltage value applied to one of the monolithic ceramic capacitors. Is 120% to 120% of the DC bias voltage value applied to the other monolithic ceramic capacitor.
5. It is set within the range of%.
The capacitor-mounted circuit board described.