JPH05291227A - Piezoelectrically driven ultrasonic cleaning apparatus - Google Patents

Abstract

PURPOSE:To reduce the tarnsmission loss of supply electric power by means of a coaxial cable connected to a cleaning tank from an oscillator for a piezoelectricallydriven ultrasonic cleaning apparatus due to a high frequency near 1MHz. CONSTITUTION:A plurality of piezoelectric oscillators 4 which have been fixed and bonded to the bottom face 11 of a cleaning tank 1 are formed as one set while two piezoelectric elements which have been polarized in such a way that their polarity is opposite to each other are connected in series, or half of all piezoelectric elements which have been polarized to be of positive polarity out of all the piezoelectric elements are connected in parallel so as to form one block and the remaining half of the piezoelectric elements which have been polarized to be of negative polarity are connected in parallel so as to form one block. The two blocks are connected in series so as to form one set; a plurality of sets of the piezoelectric oscillators 4 or two piezoelectric element groups constituted of the blocks are connected by means of wires 10 from the secondary side of a transformer 5 arranged inside an oscillator cover 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic cleaning device, and more particularly to a piezoelectric drive type ultrasonic cleaning device using a piezoelectric vibrator as an ultrasonic vibration source.

[0002]

2. Description of the Related Art An ultrasonic cleaning device has a frequency of 20 kHz to 10 kHz.
Ordinary cleaning equipment using 0 kHz frequency and 1 MH
There is an ultra-precision cleaning device that uses a frequency around z. Further, there are a type that uses a magnetostrictive oscillator and a type that uses a piezoelectric oscillator as an ultrasonic vibration source. Since the present invention is an improvement on an ultrasonic cleaning device using a piezoelectric vibrator,
A conventional technique of a piezoelectric drive type ultrasonic cleaning device using a piezoelectric vibrator will be described below.

(1) Ultra-precision ultrasonic cleaning device. This ultra-precision cleaning device is used to perform ultra-precision cleaning of semiconductor wafers, glass masks, glass substrates for liquid crystals, etc. in the semiconductor manufacturing process. Since it is necessary to remove fine particles (foreign substances) of about 0.1 μm, the wavelength is short, and since damage due to cavitation does not occur, an ultrasonic frequency of around 1 MHz is used, and a plate is used as an element of the ultrasonic transducer. Piezoelectric vibrators are used.
Lead titanate zirconate lead-based porcelain is used as the material of the piezoelectric (electrostrictive) oscillator near 1 MHz, and the vibration mode is in the thickness direction. The size is 100 × 40 × 2 due to various restrictions.
Most of them are about (mm). Since such a piezoelectric vibrator obtains half-wavelength resonance by thickness vibration, the thickness of the element is thin and the capacitance (corresponding to the damping impedance) as a dielectric is large. Therefore, the impedance at the drive frequency is small and the drive conditions from the ultrasonic oscillator are large current and low voltage.

Further, as a cable connecting the ultrasonic oscillator and the ultrasonic vibrator, a coaxial cable is used in order to minimize loss when transmitting high frequency power. The characteristic impedance of this coaxial cable is usually 75Ω or 5
The impedance of the oscillator is 0Ω, and when the oscillator of 50Ω is used, it is desirable that the impedance of the vibrator is 50Ω.
Conventionally used conditions are 4 to 8 of the above-mentioned vibrators.
The ultrasonic effective area is 90x160mm to 180x160mm, which is installed side by side on the diaphragm as one unit.
In many cases, electric power of about 500 W to 600 W is supplied from the ultrasonic oscillator. Under this condition, vibrator 1
The capacitance of each piece (corresponding to the braking impedance) is, for example, 24 nF, and when four pieces are connected in parallel, the capacitance is 96 nF. Therefore, the impedance Z at 1 MHz is Z = 1 /
(2πfc) = 1 / (2 × 3.14 × 10 ⁶ × 96 × 1
0 ^-9 ) = 1.66Ω. When 8 pieces are arranged in parallel, the electrostatic capacity is 192 nF and the impedance at 1 MHz is 0.84Ω.

Further, the damping impedance of the electrostrictive oscillator is capacitive as shown in FIG. 4 (A), and the load impedance of the oscillator is resistive, which is advantageous as a driving condition. In order to eliminate this capacitive impedance apparently, the elements of the inductive impedance (choke coil) with the same absolute value of impedance are connected in series (series resonance), and the impedance of the oscillator is changed to the dynamic impedance ( (Excluding the braking impedance from the impedance), and reducing the impedance to about 1/10 of the total impedance
It is about 0.1Ω to 0.2Ω in parallel, and 8 in parallel is 0.1Ω or less.

(2) Regarding a normal ultrasonic cleaning device. Normal ultrasonic cleaning equipment other than ultra-precision cleaning uses a high-temperature cleaning liquid to improve the cleaning effect, and in order to improve the durability of the equipment, the electrostrictive vibrator is made into a Langevin type and the diaphragm is screwed. The structure to be attached to is adopted.
A Langevin type oscillator is used as an electrostrictive oscillator used in an ultrasonic cleaning apparatus that uses a relatively low frequency of about 20 kHz to 100 kHz. Electrostrictive vibration elements have various shapes such as circle, quadrangle, polygon, etc.
It is about 5 mm. In this case, the vibration mode in the thickness direction has a natural frequency of several 100 kHz, which is 20 kHz to 10 kHz.
It cannot be used for 0 kHz. Therefore, metal terminal rods are attached to both sides of the plate-shaped element to form one body, and the longitudinal vibration mode of the rod is set to lower the frequency. This is called the Langevin shape. A plurality of such Langevin type vibrators are attached to the diaphragm.

[0007]

As described above, in the case of the above-described ultra-precision cleaning device, the impedance of the vibrator is as small as about 1/50 of the impedance of the coaxial cable,
Since it is driven by a large current, the heat generated by the conductor of the coaxial cable is large, and the impedance of the coaxial cable is not resistive but inductive, so that the output condition of the oscillator is to supply a large apparent power. There is a drawback that the power loss of the FET (field effect transistor) used as is large. In addition, in the case of the above-mentioned ordinary cleaning device, the vibration plate to which the vibrator is attached is made of metal such as stainless steel, and the electrodes on one side of the vibrator are connected in parallel with each other so that the number of elements of the vibrator is the same. Impedance decreases. Therefore, as the dynamic impedance, the parallel resonance condition causes the impedance to be increased and the anti-resonance frequency (impedance is maximum) to be driven, resulting in a decrease in efficiency. An object of the present invention is to reduce the power loss due to impedance mismatch between an oscillator and a vibrator in the case of an ultraprecision ultrasonic cleaning device, and to improve the driving efficiency of a vibrator of a normal ultrasonic cleaning device. It is to provide a cleaning device.

[0008]

[Means for Solving the Problems]

(1) In the case of ultra-precision cleaning equipment. To improve the disadvantage that the impedance of the oscillator is small and it is driven by a large current and the impedance matching of the coaxial cable is not good, multiple oscillators can be connected in series, but one side of the electrode (usually a diaphragm) Is attached to a metal plate such as stainless steel) by an adhesive, so that only parallel connection is allowed. In order to improve this inconvenience, two oscillators are set as a set, or half of the whole are connected in parallel to form two blocks, which are connected in series with their polarization directions reversed. When a set of oscillators is used, the total impedance is increased by connecting multiple sets in parallel. For example, the total number is 8
In the case of one oscillator, the impedance can be four times as large as that in the case of connecting all in parallel.

Next, in order to further increase the total impedance of the vibrator, a transformer is provided as close to the vibrator as possible, and the one with a small number of turns (n) is connected to the vibrator side to supply power. The apparent impedance of the vibrator can be increased by (N / n) ² by connecting the side with the larger number of windings (N). When N / n = 10 is set, the impedance increase due to the transformer is 100 times, and when it is adopted in combination with the two (or two blocks) series driving method described above, it is 400 times. The load impedance at the power transmission end can be increased to about 50Ω only by the dynamic impedance obtained by canceling the braking impedance. As a result, the load impedance viewed from the ultrasonic oscillator becomes 50Ω which is resistive, and it is possible to supply power with minimum output loss.

(2) In the case of a normal cleaning device. In the electrostrictive oscillator having a relatively low frequency of 20 kHz to 100 kHz, two Langevin type oscillators polarized in opposite polarities are connected in series, or half of the Langevin type oscillators polarized in positive polarity are connected. Are connected in parallel to form one block, the remaining half of the negative-polarity vibrators are connected in parallel to form one block, and these two blocks are connected in series to make all the vibrators connected in parallel.
Since the impedance can be doubled, the dynamic impedance can be driven at the resonance frequency under the serial resonance condition, and thus the impedance is minimum and efficient vibration can be obtained.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A is a vertical sectional view showing a first embodiment of the present invention. (B) is a bottom view of the vibrator portion of (A), and is an explanatory view showing a main part of the present invention. In the figure,
1 is a cleaning tank, 2 is a cleaning liquid, 3 is an ultrasonic oscillator, 4 is a piezoelectric vibrator adhesively attached to the bottom surface of the cleaning tank 1, 5 is a transformer, 6 is a cover, 7 is a coaxial cable, 8 is a connector, and 9 is a connector.
Is the primary wiring of the transformer 5, and 10 is the secondary wiring of the transformer 5. Further, (B) 41 to 44 are piezoelectric vibrators 4.
Each element of is shown. In the figure, the number of elements is four, but the number can be increased and mounted as necessary. Although the coaxial cable 7 is drawn short in the figure, it is actually long.

The plurality of piezoelectric vibrators 4 fixed to the bottom surface 11 of the cleaning tank 1 shown in FIG. 1A are serially arranged with two elements polarized in opposite directions as shown in FIG. 1B. Connected,
Each is connected to the secondary side of the transformer 5 by a wiring 10. Reference numeral 11 'in (B) is a connection line for further electrically connecting the bottom surface 11 of the metal cleaning tank 1 to ensure electrical continuity. That is, the piezoelectric elements 41 and 42 and 43 and 44 are connected in series with their polarization directions reversed, and drive power is supplied from the secondary side of the transformer 5 via the wiring 10.

FIG. 2A is a perspective view showing further details of the present invention, and shows a state in which the piezoelectric elements 41 and 42 of FIG. 1B are arranged close to each other. The piezoelectric elements 41 and 42 have electrodes 12 on both surfaces of the piezoelectric ceramic pieces 13 and 16.
14, 15 and 17 are provided, and one of the electrodes 12 and 15 is continuous from one side surface to the edge portion of the other surface. FIG. 2B is a perspective view showing a piezoelectric element having another electrode structure, and shows a case where both surfaces of the piezoelectric element are full electrodes. In the display of the polarization direction in this case, for example, the polarization direction is identified by displaying a red or blue dot on the (+) side of the polarization. The electrode structure is simpler and the price of the piezoelectric element is lower than that of FIG. 2A.

Returning to FIG. 1, this first embodiment is about 1M.
This is the case with a drive frequency of Hz, and the wiring needs to be shielded. Therefore, a long coaxial cable 7 is used from the oscillator 3 to the cleaning tank 1 and is connected to the connector 8, the transformer 5 is arranged in the shield cover 6, and wiring between the connector 8 and the primary side of the transformer 5 is performed. 9 and 2 of transformer 5
A normal insulating film conductor 10 is used for wiring between the second side and a plurality of sets of piezoelectric elements 4, one set of two. The winding ratio of the primary winding and the secondary winding of the transformer 5 is N: n, and the impedance increase is adjusted so that N> n.

Next, the present invention will be described with reference to 20 kHz to 100 kHz.
A second embodiment in the case of being applied to the ordinary cleaning apparatus of will be described. FIG. 3 is a vertical sectional view and a partial perspective view showing a second embodiment of the present invention. In FIG. 3, 1, 2, 3,
6 and 11 are the same as in the case of FIG. 31 to 34 are Langevin type vibrators, 30 is wiring from the connector 35 to a set of two vibrators, and 36 is wiring with the oscillator 3. Figure 3
In (B), one set of vibrators 31 and 32 is the bottom surface 11 of the cleaning tank 1.
FIG. 3 is an inverted perspective view attached to a pair of vibrators 3
1, 32 are bonded and fixed to the bottom surface 11 so that the polarization directions are opposite to each other, and the wiring 30 is provided so that the two vibrators 31, 32 are connected in series.

[0016]

As described in detail above, by implementing the present invention, in the case of an ultra-precision ultrasonic cleaning device, by increasing the impedance of the vibrator, loss as a conductor of a cable due to large current drive In the ultra-precision ultrasonic cleaning device using high frequency, it is possible to match the characteristic impedance of the coaxial cable, so the power factor of the load including the cable can be improved and the apparent power supplied from the oscillator can be reduced. be able to. Moreover, in a normal ultrasonic cleaning apparatus using a low frequency region (about 20 kHz to 100 kHz), the driving condition of the dynamic impedance is set by increasing the impedance of the vibrator.
The antiresonance (parallel resonance) shown in (A) can be changed to the resonance (series resonance) shown in FIG. 4B, and the vibration efficiency is improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view and a partial explanatory view showing a first embodiment of the present invention.

FIG. 2 is a perspective view of a main part of the first embodiment of the present invention.

FIG. 3 is a vertical sectional view and a partial perspective view showing a second embodiment of the present invention.

FIG. 4 is an equivalent circuit of a piezoelectric vibrator.

[Explanation of symbols]

 1 Cleaning Tank 2 Cleaning Liquid 3 Ultrasonic Oscillator 4, 41, 42, 43, 44 Piezoelectric Vibrator 5 Transformer 6 Cover 7 Coaxial Cable 8 Connector 9 Primary Wiring 10 Secondary Wiring 11 Bottom of Cleaning Tank 11 'Connection Wire 12 , 14, 15, 17 Electrodes 13, 16 Piezoelectric ceramic pieces 30, 36 Wiring 31, 32, 33, 34 Langevin type vibrator 35 Connector

Claims (2)

[Claims] 1. A high frequency power is supplied from an ultrasonic oscillator to a plurality of piezoelectric vibrators attached to the bottom surface of the cleaning tank by a coaxial cable, and ultrasonic vibration generated by thickness vibration of the piezoelectric vibrator causes the cleaning tank. In a piezoelectric drive type ultrasonic cleaning apparatus for cleaning an object to be cleaned in a cleaning liquid therein, the plurality of piezoelectric vibrators are two piezoelectric vibrators as one set, or half of the entire piezoelectric vibrators are connected in parallel. 2 blocks, each of which is attached to the bottom surface of the cleaning tank and electrically connected in series so that the polarities of the polarizations are opposite to each other, and the coaxial cable is provided in the vicinity of the plurality of piezoelectric vibrators. A piezoelectric drive characterized in that a transformer having a winding ratio of N to n (N> n) of a primary winding to which is connected and a plurality of sets of piezoelectric vibrators connected in parallel is provided. Type ultrasonic cleaning equipment . 2. Driving power is supplied from an ultrasonic oscillator to a plurality of Langevin-type vibrators attached to the bottom of the cleaning tank, and ultrasonic vibrations generated by the Langevin-type vibrators cause the cleaning liquid in the cleaning tank to flow. In the piezoelectric drive type ultrasonic cleaning device for cleaning the object to be cleaned, the plurality of Langevin-type vibrators include two vibrators.
A pair or half of the whole is connected in parallel to form two blocks, each of which is attached to the bottom of the cleaning tank and electrically connected in series so that the polarities of the polarizations are opposite to each other. A piezoelectric drive type ultrasonic cleaning device characterized in that drive power from an oscillator is supplied in parallel to a plurality of sets of vibrators.