JP2012057842A - Ultrasonic drying equipment and substrate treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide inexpensive ultrasonic drying equipment with a simple equipment constitution, which can remove impurities concurrently with removal of a liquid accumulated in a minute recess, by instantaneously scattering the liquid in a noncontact manner without heating a substrate to be treated or imparting an excessive impact on the substrate to be treated, and a substrate treatment method using the ultrasonic drying equipment.SOLUTION: The ultrasonic drying equipment includes an ultrasonic transducer 21 for generating ultrasonic waves Φ, a transducer drive control device 35 for controlling the drive of the ultrasonic transducer 21, a reflector 23 for reflecting the ultrasonic waves Φ and exciting the standing waves of the ultrasonic waves Φ in the air, and substrate position control mechanisms (25 and 32) for moving the substrate 22a to be treated to an optimum atomization position near a node position of the standing waves. The liquid accumulated in the recess of the substrate 22a to be treated is removed by being atomized in the optimum atomization position.

Description

  The present invention relates to a drying apparatus and a substrate processing method using ultrasonic waves, and in particular, in a cleaning process of various substrates to be processed such as a printed circuit board with a liquid such as water and a drying process after cleaning, The present invention relates to an ultrasonic drying apparatus and a substrate processing method for efficiently drying a liquid such as water stored in a concave portion.

  In recent years, the demand for printed circuit boards having a multilayer wiring structure capable of high-density wiring, which can be reduced in size and weight, has been rapidly increased, and is used in various electronic devices. Along with the improvement of processing accuracy, conductor wiring is provided on the top surface, back surface, and inside of an insulating substrate having a multilayer structure, and each conductor wiring is a hole having a metal conductive side wall called a via. Interlayer connection is made. There are various types of vias: through-hole vias that penetrate all layers of the insulating substrate (through-hole vias), bottomed-hole vias that connect only specific layers without penetrating all layers of the insulating substrate (blind vias) ), And various structures such as buried vias (bare vias) that are connected to each other on the inner layer and are not opened on the substrate surface. The via diameter of the through-hole via is required to be smaller with the miniaturization of the device. For example, a diameter of 50 μm to 2 mmφ is known.

  When a printed circuit board is used in an electronic device, there are a printed circuit board cleaning process and a drying process after cleaning. In addition to printed circuit boards, cleaning of various boards is indispensable in the process of making board materials into products, removing dirt that adversely affects various process processes and the reliability of electronic and optical components, By making the surface condition uniform, the characteristics, productivity and reliability of electronic and optical parts are improved.

  In order to dry the printed circuit board after washing with water, conventionally, hot air drying or spin drying has been generally performed. Hot air drying is a method in which 40 to 100 ° C. dry hot air is blown onto a printed circuit board conveyed by a conveyor to evaporate water adhering to the printed circuit board. Spin drying is performed on a rotating plate that rotates the printed circuit board at high speed. And is rotated at a high speed to blow away water adhering to the printed circuit board by centrifugal force. In hot air drying, there is a problem that water stains remain on the trace of the water being dried, and furthermore, when heat is applied to the printed board, the printed board may warp and delamination may occur.

  In the spin drying, there is a problem that water in the holes of the printed circuit board and the uneven portions is not easily blown off, and it is difficult to completely dry, and impurities such as dusts remain in the vias. Furthermore, since the printed circuit board has to be set on a rotating plate, drying cannot be performed as part of the flow operation.

  In view of such circumstances, conventionally, a sound wave of 20 KHZ to 100 KHZ is applied to the surface of the printed circuit board by applying a sound wave of 20 KHZ to 100 KHZ to the drying chamber, the conveying body that conveys the printed circuit board and passes through the drying chamber, and the printed circuit board that is conveyed by the conveying body. And a speaker that vibrates and removes adhering water (surface water), the carrier can pass sound waves of 20 KHZ to 100 KHZ, and the speakers are arranged above and below the carrier in the drying chamber. There has been proposed a surface water removing device that applies generated sound waves of 20 KHZ to 100 KHZ from above and below the printed circuit board (see Patent Document 1). In the surface water removal apparatus described in Patent Document 1, sound waves output from the upper speaker activate and remove water droplets on the upper surface side of the printed circuit board, and sound waves output from the lower speaker are generated on the lower surface side of the printed circuit board. Water droplets are activated and removed, and water on the surface of the printed circuit board is removed.

Japanese Patent No. 3163239

  However, in the surface water removing apparatus described in Patent Document 1, speakers are arranged above and below the carrier, water droplets on the upper surface side are activated and removed by sound waves output from the upper speaker, and the lower speaker is used to remove the lower surface. It is necessary to activate and remove the water droplets on the side, and despite the complicated configuration of the apparatus, the sound wave of 20 KHZ to 100 KHZ is used to vibrate the water adhering to the printed circuit board, It is merely blown away (see the paragraphs [0013], [0017], [0019] in Patent Document 1). In addition, in the invention described in Patent Document 1, since there is no consideration of generating a strong ultrasonic field by concentrating ultrasonic waves, when the size of the concave portion is reduced, the size is reduced. It was difficult to completely remove the water accumulated in the recess. Furthermore, in the surface water removing apparatus described in Patent Document 1, an excessive sound pressure (impact) is applied to the substrate to be processed, and the substrate to be processed may be damaged.

  In addition to the water washing and washing process for printed circuit boards and the drying process after washing, liquids such as water accumulate in the minute recesses of various boards in the wet washing process with various board liquids and the drying process after washing. The problem of causing In particular, the liquid accumulated in the bottomed hole such as a blind via is difficult to be removed by wind pressure because air does not pass therethrough, which is a big problem.

  In view of the above-described problems, the present invention is an ultrasonic drying apparatus that can be used in a wet cleaning process with a liquid of various substrates to be processed having fine recesses, and a drying process after cleaning. Ultrasonic that is simple and inexpensive, can disperse the liquid accumulated in minute recesses instantaneously and without contact with the liquid, without giving heat or excessive impact to the substrate to be processed, and removing impurities at the same time as the liquid It is an object to provide a drying apparatus and a substrate processing method using the ultrasonic drying apparatus.

  In order to achieve the above object, an aspect of the present invention includes an ultrasonic transducer that generates ultrasonic waves, a vibrator drive control device that drives and controls the ultrasonic transducers, and reflects ultrasonic waves into the air. A reflector for exciting an ultrasonic standing wave and a substrate position control mechanism for moving the substrate to be processed to an optimal atomization position in the vicinity of the position of the node of the standing wave. The gist of the present invention is that it is an ultrasonic drying device that atomizes and removes the liquid accumulated in the recesses.

  In another aspect of the present invention, (a) a cleaning process for wet-cleaning a substrate to be processed having a recess, and (b) an ultrasonic transducer that generates ultrasonic waves after the cleaning process, the ultrasonic wave A transducer drive control device that drives and controls the transducer, and an ultrasonic drying device that includes a reflector that reflects ultrasonic waves and excites standing ultrasonic waves in the air. A step of moving the substrate to be processed to an optimal atomization position in the vicinity of the position of the wave node; and (c) at the optimal atomization position, the liquid accumulated in the concave portion of the substrate to be processed is atomized and removed by ultrasonic waves. The gist of the present invention is a substrate processing method including a process.

  According to the present invention, there is provided an ultrasonic drying apparatus that can be used in a wet cleaning process using a liquid of various substrates to be processed having fine recesses and a drying process after cleaning, and the configuration of the apparatus is simple and inexpensive. In addition, an ultrasonic drying device capable of removing impurities simultaneously with the liquid by splashing the liquid accumulated in the minute recesses in a non-contact and instantaneous manner without applying heat or excessive impact to the substrate to be processed, and this A substrate processing method using an ultrasonic drying apparatus can be provided.

It is the typical fragmentary sectional view seen from the upper surface side for describing the principle of the ultrasonic drying device concerning the 1st embodiment of the present invention. It is an upper surface figure (plan view) of a typical printed circuit board shown as an example of a processed substrate used as a candidate for processing of an ultrasonic drying device concerning a 1st embodiment. FIG. 2 is a block diagram including a partial cross-sectional view for specifically explaining a schematic configuration of the ultrasonic drying apparatus according to the first embodiment viewed from an angle orthogonal to FIG. 1. Explains how water accumulated in the through hole via of the substrate to be processed is pushed out of the through hole via by the action of ultrasonic acoustic radiation pressure using the ultrasonic drying apparatus according to the first embodiment. It is a schematic diagram to do. Using the ultrasonic drying apparatus according to the first embodiment, the water accumulated in the through-hole via of the substrate to be processed is generated by ultrasonic wave atomization and scattered outside the through-hole via. It is a schematic diagram to explain. In the ultrasonic drying apparatus according to the first embodiment, it is an example of measurement data indicating that a standing wave is excited between an ultrasonic transducer and a reflection plate, and a peak of sound pressure is generated. In the configuration of the ultrasonic drying apparatus according to the first embodiment, the result of the sound pressure measurement while changing the distance between the ultrasonic transducer and the substrate to be processed is shown, and the position of the substrate to be processed is changed by 0.1 mm. Each time, the optimum position of the reflecting plate is changed by 0.1 mm in conjunction with the position of the substrate to be processed, and the sound pressure takes the maximum value when the position of the substrate to be processed is 6.7 mm. FIG. In the configuration of the ultrasonic drying apparatus according to the first embodiment, when the position of the substrate to be processed is 6.7 mm, the relationship between the position of the reflector and the sound pressure (black circle), the applied voltage and the ultrasonic detection Shows the relationship between the phase difference of the output voltage of the device and the position of the reflector (white square), and the phase difference changes almost linearly at the position of the reflector on the near side of the position where the sound pressure becomes maximum, It is a figure which shows that the sound pressure becomes maximum when the phase difference is around -90 °. In the configuration of the ultrasonic drying apparatus according to the first embodiment, dehydration of water filled in the through-hole via when the distance L between the vibration surface of the ultrasonic vibrator and the left surface of the substrate to be processed is changed. Is a graph in which the vertical axis represents the ease (probability) and the interval L normalized by the wavelength λ = 12.1 mm on the horizontal axis. In the configuration of the ultrasonic drying apparatus according to the first embodiment, the surface of the substrate to be processed is inclined from the vertical direction by the angle θ to change the ultrasonic incident angle θ, and the change in the incident angle θ gives the dehydration effect. It is a schematic diagram explaining the measurement system of the experiment which investigates an influence. In the configuration of the ultrasonic drying apparatus according to the first embodiment, water and isopropyl alcohol (IPA) are respectively filled in the through-hole vias, and the vibration surface of the ultrasonic transducer and the left surface of the substrate to be processed are It is the figure which represented the ease (probability) of dehydration at the time of changing the space | interval L on the vertical axis | shaft, and the space | interval L normalized by wavelength (lambda) = 12.1mm on the horizontal axis, respectively. It is the typical fragmentary sectional view seen from the upper surface side for the principle description of the ultrasonic drying apparatus which concerns on the 2nd Embodiment of this invention. It is a top view (plan view) for specifically explaining the schematic configuration of the ultrasonic drying apparatus according to the second embodiment. It is a figure explaining that the expression area | region of ultrasonic atomization differs between a through-hole via and a bottomed-hole via. In the configuration of the ultrasonic drying apparatus according to the second embodiment, water filled in the bottomed hole via when the distance L between the vibration surface of the ultrasonic vibrator and the left surface of the substrate to be processed is changed. It is the figure which represented on the horizontal axis the space | interval L which normalized the ease (probability) of dehydration on the vertical axis | shaft, and wavelength (lambda) = 12.1mm. In the structure of the ultrasonic drying apparatus which concerns on 2nd Embodiment, it is a figure which shows that the water of a bottomed via with a high aspect ratio (deeper) can be dehydrated, so that the amplitude of an ultrasonic wave is enlarged.

  Next, first and second embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  The first and second embodiments described below exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention is The material, shape, structure, arrangement, etc. are not specified below. The technical idea of the present invention can be variously modified within the technical scope described in the claims.

(First embodiment)
The ultrasonic drying apparatus according to the first embodiment of the present invention, as shown in FIGS. 1 and 3, drives and controls the ultrasonic vibrator 21 that generates the ultrasonic wave Φ and the ultrasonic vibrator 21. The vibrator drive control device 35, the reflector 23 that reflects the ultrasonic wave Φ and excites the standing wave of the ultrasonic wave Φ in the air, and the optimum atomization position in the vicinity of the node position of the standing wave And a substrate position control mechanism (25, 32) for moving the substrate 22a (FIG. 1 is a partial sectional view seen from the upper surface side, and FIG. 3 is a partial sectional view seen from an angle orthogonal to FIG. 1). Here, “the vicinity of the node position of the standing wave” means “a position slightly separated from the position of the node of the standing wave by 5% or less of the wavelength” as described later with reference to FIG. (In FIG. 9, the case where the optimal atomization position _Popt is separated from the _node position _{Pnode by} about 2% of the wavelength is illustrated).

  Here, as shown in FIGS. 1 and 3, the printed circuit board as the substrate to be processed 22a penetrates from the upper surface (first main surface) to the back surface (second main surface) of the insulating substrate 221 having a multilayer structure. A hole via (through-hole via) 222 is opened. Insulating substrates having various multilayer structures used for ordinary printed boards such as paper phenol substrates and glass epoxy substrates can be used as the material of the insulating substrate 221. As shown in FIG. 2, conductor wiring is formed on the upper surface (first main surface) of the insulating substrate 221 in a predetermined fine pattern. Although detailed illustration is omitted, similar conductor wiring is formed on the back surface (second main surface) of the insulating substrate 221 and the multilayer structure inside thereof in a miniaturized manner. The through-hole via 222 is provided so as to penetrate all the layers of the insulating substrate 221 having a multilayer structure, and a conductive side wall is formed in the through-hole by a metal cylinder (canal), and the conductor on the upper surface (first main surface). The wiring and the conductor wiring on the back surface (second main surface) are connected. In the ultrasonic drying apparatus according to the first embodiment, the substrate 22a to be processed is disposed at the optimum atomization position, so that the water 223 accumulated in the through-hole via 222 that is the recess of the substrate to be processed 22a is superfluous. Concentrate the sound wave Φ.

  As schematically shown in FIG. 4, in the field of the powerful ultrasonic wave Φ where the ultrasonic wave Φ is concentrated, the liquid (hereinafter, “water” is illustrated) 223 accumulated in the through-hole via 222 of the substrate to be processed 22a. Is pushed out of the through hole via 222 as a droplet (hereinafter referred to as “water droplet”) 223S by the action of the acoustic radiation pressure by the ultrasonic wave Φ. As shown in FIG. 4A, “acoustic radiation pressure” is a force that pushes the water 223 as an object in the propagation direction of the ultrasonic wave Φ when the ultrasonic wave Φ is blocked by an object such as the water 223. Say. Accordingly, as shown in FIG. 4B, the water 223 is pushed up by the acoustic radiation pressure to form a liquid column. Further, as shown in FIG. 4C, the force due to the increased acoustic radiation pressure surpasses the surface tension of the water 223 and pushes the water droplet 223S out of the through-hole via 222.

Alternatively, as shown in FIG. 5A, the ultrasonic wave Φ is concentrated and a strong ultrasonic wave Φ field is generated, and the action of the acoustic radiation pressure S is applied to the surface of the water 223 accumulated in the through-hole via 222. When it becomes stronger, as shown in FIG. 5B, a capillary wave (capillary surface wave) is generated on the surface of the water 223, and when the amplitude of the capillary wave increases, the surface tension is overcome, as shown in FIG. 5C. Water droplets 223m as fine particles are scattered. A “capillary wave” is also called a surface tension wave, and is a short wavelength wave that travels along the water surface with the surface tension as a restoring force, and is also called a “Sasananami wave”. The wavelength λ _{cpl of the} capillary wave is f where the excitation frequency for exciting the liquid is T, the surface tension of the liquid is T, and the density of the liquid is ρ.

λ _cpl = (8πT / ρf ² ) ^1/3 (1)

And is strongly affected by surface tension at short wavelengths.

When a capillary wave is generated on the surface of the liquid, an interference wave is generated on the surface of the liquid with the periphery of the liquid as a boundary of reflection. Due to the generation of the interference wave, the collision and tearing energy of the liquid on the surface of the liquid overcomes the surface tension T, and the liquid is atomized and scattered in the air. This phenomenon is called ultrasonic atomization and is used in ultrasonic humidifiers, nebulizers, etc., but the diameter D of water droplets 223m as scattered fine particles is:

D = 0, 34 (8πT / ρf ² ) ^1/3 (2)

Is known as an experimental rule of thumb.

  Currently, most of the ultrasonic atomizations in practical use employ a method in which the ultrasonic wave Φ is directly excited from the ultrasonic transducer 21 to the liquid, and the excitation frequency is often in the order of MHz. The ultrasonic drying apparatus according to the first embodiment aims at ultrasonic atomization using the ultrasonic wave Φ transmitted in the air. Therefore, in the air, the high-frequency ultrasonic wave Φ has a sound wave propagation attenuation that is liquid, Compared to solids, the ultrasonic wave Φ preferably has a frequency band of the order of kHz, and may be selected, for example, from about 15 kHz to 50 kHz. At an excitation frequency of 28 kHz, the diameter D of the water droplet 223m as the scattered fine particles is about 60 μm from the equation (2). In this way, the water 223 accumulated in the through-hole via 222 by the strong ultrasonic wave Φ is atomized into the water droplet 223m, whereby the water droplet 223m is pushed out of the through-hole via 222, removed, and the dehydration process is performed. Done.

As the ultrasonic vibrator 21 of the ultrasonic drying apparatus according to the first embodiment, for example, a bolt-clamped Langevin type vibrator in which polarized piezoelectric ceramics and an electrode are integrated with a metal block with a scissor bolt is used. Although it is possible, it is not limited to the Langevin type vibrator. In general, a Langevin type vibrator has a characteristic of having a resonance peak with a narrow frequency span because of a high mechanical quality factor Q _m .

  The substrate position control mechanism (25, 32) of the ultrasonic drying apparatus according to the first embodiment suspends the substrate to be processed 22a and transports it in the direction perpendicular to the plane of FIG. 3 (X axis direction). The position of the substrate to be processed 22a is moved (finely moved) in the direction from the ultrasonic transducer 21 to the reflecting plate 23 (Z-axis direction), and the substrate to be processed 22a is moved by a node of the standing wave of the ultrasonic wave Φ. 2 axis moving stage 25 having a Z axis moving stage that adjusts to the optimal atomization position slightly shifted from the position of the position, and a substrate position control device 32 that drives and controls this 2 axis moving stage 25 (see FIG. 3). FIG. 1 viewed from an orthogonal angle shows the X-axis direction and the Z-axis direction. A signal for driving control of the biaxial movement stage 25 is sent from the processor 34 to the substrate position control device 32.

  From an industrial practical point of view, the X-axis moving stage may be configured to include a sequential transfer mechanism similar to a conveyor. If the temperature / humidity of the air through which the ultrasonic wave Φ is propagated is controlled and the substrates 22a of the same type are sequentially transferred, the substrate 22a to be processed passes through a predetermined optimum atomization position in advance. After adjusting the Z-axis moving stage, a plurality of (multiple) substrates 22a to be processed are sequentially conveyed by the X-axis moving stage and excited between the ultrasonic transducer 21 and the reflecting plate 23. In addition, a plurality of substrates to be processed 22a may pass through the standing wave of the ultrasonic wave Φ so as to be dehydrated.

  On the other hand, when the temperature / humidity fluctuates or when various types of substrates 22a to be processed are sequentially conveyed, the substrate to be processed 22a passes through the optimum optimum atomization position by tracking those changing conditions. As described above, it is necessary to sequentially adjust the Z-axis movement stage and convey a plurality of (multiple) substrates to be processed 22a sequentially by the X-axis movement stage. A plurality of substrates to be processed 22a sequentially conveyed by arranging the pair of the ultrasonic transducer 21 and the reflecting plate 23 in parallel with each other along the X-axis conveyor conveyance direction of the biaxial moving stage 25. The entire surface of each can be covered with ultrasonic waves.

  In the ultrasonic drying apparatus according to the first embodiment, when atomizing the water 223 accumulated in the through hole via 222 by the ultrasonic wave Φ, not only the water 223 accumulated in the through hole via 222 but also the substrate to be processed. The insulating substrate 221 constituting 22a is vibrated by the ultrasonic wave Φ. When the vibration acceleration of the insulating substrate 221 due to the ultrasonic wave Φ becomes an excessive value, the insulating substrate 221 having a multilayer structure may be damaged by delamination or the like.

Therefore, the maximum acceleration was regarded as equivalent to an impact, and the vibration acceleration of the insulating substrate 221 was measured. That is, in the ultrasonic drying apparatus according to the first embodiment shown in FIG. 3, the ultrasonic wave Φ is excited in the air by the ultrasonic vibrator 21, a glass plate is used as the reflecting plate 23, and a laser Doppler vibration velocimeter is used. Was used to measure the vibration speed of the insulating substrate 221. The vibration speed is measured by controlling the position of the substrate 22a in the Z-axis direction using the Z-axis movement stage of the biaxial movement stage 25 shown in FIG. The position in the Z-axis direction where atomization of the accumulated water 223 occurs was used as the origin, and the position was moved every 0.5 mm to ± 3 mm in the Z-axis direction, and the vibration speed of the insulating substrate 221 was measured. The measured vibration acceleration was 619 m / s ² at the maximum at each measurement point in the Z-axis direction. For example, the general allowable impact strength of a mobile phone using a multilayer printed circuit board is 980 m / s ² , but the vibration acceleration is lower than this value, and the allowable vibration acceleration to the insulating substrate 221 is allowed. Is within. Therefore, according to the ultrasonic drying apparatus according to the first embodiment, it can be determined that the influence of the impact of the ultrasonic wave Φ on the insulating substrate 221 can be ignored.

  In FIG. 3, the two-axis moving stage 25 of the substrate position control mechanism (25, 32) is disposed above the substrate to be processed 22a and suspends the substrate to be processed 22a. It is not limited to suspension movement. For example, the biaxial movement stage 25 may be arranged below the substrate 22a to be processed, and the biaxial movement stage 25 may be mounted with the substrate 22a to be processed. Also in this case, the X-axis moving stage includes a sequential transfer mechanism similar to the conveyor, and the substrate 22a to be processed mounted on the X-axis moving stage is sequentially transferred to the conveyor, and the ultrasonic transducer 21 and the reflecting plate 23 are transferred. The plurality of substrates to be processed 22a may pass through the standing wave of the ultrasonic wave Φ excited between and the substrate 22a to be sequentially dehydrated.

In the ultrasonic drying apparatus according to the first embodiment, when using the ultrasonic wave Φ radiated from the ultrasonic vibrator 21 into the air, a standing wave is formed using the reflector 23. A sound field with higher sound pressure is formed. As shown in FIGS. 1 and 3, the reflection by the reflecting plate 23 at the normal incidence of the ultrasonic wave Φ occurs at the boundary surface where the two media are in contact, and the reflectance R _p is the specific acoustic impedance Z ₁ , It depends on the Z _2. Therefore, the reflectance R _p of the ultrasonic wave Φ by the reflecting plate 23 is expressed by Z ₁ and Z ₂ as the specific acoustic impedances of the media 1 and 2, respectively.

R _p = (Z ₂ −Z ₁ ) / (Z ₂ + Z ₁ ) (3)

Indicated by According to the equation (3), when the medium 1 is air and the medium 2 is a material of the reflector 23, if the specific acoustic impedance Z ₂ of the medium ₂ is sufficiently larger than the specific acoustic impedance Z _{1 of the} medium 1 (Z ₁ << Z ₂ ) and the reflectance R _p approximate to 1 regardless of the material of the reflector 23. Even when oblique incidence is considered, it can be said that the incident wave is totally reflected because Z ₁ << Z ₂ . Therefore, in the ultrasonic drying apparatus according to the first embodiment, the reflecting plate 23 is a glass plate having a thickness of 2, 5, 10 mm, an aluminum (Al) plate having a thickness of 2, 5, 10 mm, and a thickness of 5, 10 mm. The reflectance R _p was measured using an iron (Fe) plate, and the reflectance R _p is reflected if the intrinsic acoustic impedance Z ₂ of the reflector 23 is sufficiently larger than the intrinsic acoustic impedance Z _{1 of} air. It was confirmed that the material and the thickness of the plate 23 are hardly affected. The reason why the measured value of the reflectance R _p of the ultrasonic wave Φ is not close to 1 is considered to be attenuation of the ultrasonic wave Φ at the time of reflection and refraction and sound absorption of the ultrasonic wave Φ by the reflection plate 23.

  As shown in FIG. 3, the ultrasonic drying apparatus according to the first embodiment further fixes an ultrasonic detector 24 for detecting the ultrasonic wave Φ to the back surface of the reflecting plate 23. The ultrasonic detector 24 detects the ultrasonic wave Φ through a through hole 231 provided in the reflecting plate 23. The output of the ultrasonic detector 24 is fed back to the transducer drive control device 35, and the output of the ultrasonic transducer 21 is controlled. Further, a reflection plate position control mechanism (26, 33) is provided for controlling the position of the reflection plate 23 so that the output of the ultrasonic detector 24 is fed back and the reflection plate 23 excites the standing wave. Yes. The reflecting plate position control mechanism (26, 33) includes the reflecting plate 23 so that the standing wave is excited in the direction from the ultrasonic transducer 21 toward the reflecting plate 23 (Z-axis direction). Reflector position control device comprising a Z-axis movement stage (single-axis movement stage) 26 that moves and finely adjusts the position 23 and a reflection plate position control device 33 that drives and controls the one-axis movement stage 26. A signal for driving control of the uniaxial moving stage 26 is sent from the processor 34 to 33. For this reason, an amplifier 31 is connected to the ultrasonic detector 24, and the output of the ultrasonic detector 24 is input to the processor 34 via the amplifier 31, and the processor 34 performs the necessary signal processing and performs one-axis movement. A signal for controlling the drive of the stage 26 is output to the reflector position control device 33. The output of the ultrasonic detector 24 is fed back to the reflector position control device 33, and the standing wave of the ultrasonic wave Φ is excited under the optimum conditions, so that the water 223 accumulated in the through-hole via 222 of the substrate 22a to be processed. The powerful sound field required for atomization can be created efficiently.

  Further, the output of the ultrasonic detector 24 input to the processor 34 via the amplifier 31 can also be used to generate a signal for driving control of the biaxial moving stage 25. By returning the output to the substrate position control device 32 that drives and controls the biaxial movement stage 25, the position of the substrate 22a to be processed can be optimized. In this way, by returning the output of the ultrasonic detector 24 to the transducer drive control device 35, the reflector position control device 33, and the substrate position control device 32, the ultrasonic wave Φ is concentrated, and the atomization phenomenon is efficient. It is possible to automatically control and track conditions that often develop.

  In the ultrasonic drying apparatus according to the first embodiment, in order to instantly cause the atomization phenomenon of the water 223 accumulated in the through-hole via 222 of the substrate 22a to be processed, it is necessary that the atomization conditions are aligned. is there. Specifically, it is necessary that the amplitude of the standing wave of the ultrasonic wave Φ is increased, and that the through-hole via 222 matches the optimum atomization position in the vicinity of the node of the standing wave. In order for the ultrasonic wave Φ that is a standing wave to become strong, the distance between the ultrasonic transducer 21 and the reflecting plate 23 is optimized, and the reflected wave and the radiated wave from the ultrasonic transducer 21 respectively. Must be completely in phase. This condition is determined by the speed of sound. The speed of sound varies depending on the temperature and humidity, and the apparent speed of sound changes depending on the material, thickness, and via structure of the substrate 22a being transferred.

  When various types of substrates to be processed 22a of different materials, thicknesses, structures, etc. are transported by the biaxial moving stage 25, the reflectors are always sequentially and sequentially corresponding to the atomization conditions that change every moment. It is necessary to keep the distance between the ultrasonic transducer 21 and the ultrasonic transducer 21 at an appropriate value. Further, since the position of the node of the standing wave of the ultrasonic wave Φ also changes according to the change in the distance between the reflector 23 and the ultrasonic transducer 21, the object to be processed is changed according to the change in the position of the node of the standing wave. It is necessary to adjust the relative position of the substrate 22a. According to the ultrasonic drying apparatus according to the first embodiment, the output of the ultrasonic detector 24 is fed back to the transducer drive control device 35, the reflection plate position control device 33, and the substrate position control device 32, and the reflection plate. 23, the optimum distance between the ultrasonic transducer 21 and the reflector 23 is sequentially estimated and automatically adjusted based on the relationship between the phase of the sound pressure at 23 and the phase of the applied voltage of the ultrasonic transducer 21, and the various types of substrates 22a to be processed are adjusted. By sequentially estimating and automatically adjusting the position, it is always possible to automatically control and track so that the atomization phenomenon is efficiently developed under the optimum conditions. By performing feedback control so that atomization is performed under the optimum conditions, the time from the start of irradiation of the ultrasonic wave Φ to the end of atomization can be shortened, so that the throughput of the production line is not reduced.

  In FIG. 3, the uniaxial moving stage 26 of the reflector position control mechanism (26, 33) is arranged below the reflector plate 23 and has the reflector plate 23 mounted thereon. A configuration in which the axial movement stage 26 is disposed above the reflecting plate 23 and the uniaxial moving stage 26 suspends the reflecting plate 23 may be employed.

  In FIG. 6, by measuring the change in sound pressure with respect to the change in the distance between the ultrasonic transducer 21 and the reflecting plate 23, the ultrasonic wave Φ passes through the substrate 22a to be processed, and a standing wave of the ultrasonic wave Φ is formed. It is the result of investigating the space | interval of the ultrasonic transducer | vibrator 21 and the reflecting plate 23 at the time. Specifically, the distance between the vibration surface of the ultrasonic transducer 21 and the surface of the reflecting plate 23 is changed by 0.1 mm using the uniaxial moving stage 26, and the distance of 1 mm from the vibration surface of the ultrasonic transducer 21 is changed. It is the result of having measured the change of the sound pressure with the ultrasonic detector (condenser microphone) fixed to. In the measurement of FIG. 6, an aluminum plate having a thickness of 5 mm was used as the reflecting plate 23. The wavelength of the ultrasonic wave Φ is obtained from the resonance frequency of the ultrasonic vibrator 21 and the sound velocity of the air, and changes depending on the temperature of the air. Therefore, the measurement is performed under conditions of a temperature of 20.0 ° C. and a humidity of 27%. Since the wavelength λ = 12.1 mm at the resonance frequency 28 kHz of the ultrasonic transducer 21, theoretically, the position of the node that is a distance that is an odd multiple of ½ of the wavelength is the first position, The position is about 6.05 mm from the vibration surface of the sound wave vibrator 21. At the peak of the sound pressure of the ultrasonic wave Φ, it is considered that the ultrasonic wave Φ passes through the substrate to be processed 22a, and a standing wave of the ultrasonic wave Φ is formed. In the measurement of FIG. There was a tendency that the smaller the distance between the ultrasonic transducer 21 and the reflecting plate 23, the larger the distance.

  Theoretically, the standing wave of the ultrasonic wave Φ should be formed when the distance between the sound source and the reflection plate 23 is an integral multiple of 1/2 of the wavelength of the sound wave. Therefore, in the configuration in which the substrate 22a to be processed is inserted in the vicinity of the standing wave node as in the ultrasonic drying apparatus according to the first embodiment shown in FIG. 3, n is a positive integer of 2 or more. When the distance between the ultrasonic transducer 21 of the sound source and the reflection plate 23 is a value (n / 2) times the wavelength λ of the sound wave, a standing wave is formed, and a node is formed at a position that is an odd multiple of the half wavelength. It should be. However, according to the measurement result shown in FIG. 6, the first position of the node given as the position of the sound pressure peak (the position of the leftmost peak in FIG. 6) is from the vibration surface of the ultrasonic transducer 21. It is formed at a distance of 6.4 mm and is a value slightly larger than about ½ of the wavelength. Therefore, compared to the ideal standing wave excited in the uniform air when there is no substrate to be processed 22a, inserting the substrate to be processed 22a makes the waveform of the standing wave extremely low. It is thought that it is a complex standing wave with slight distortion (disturbance).

In the configuration of the ultrasonic drying apparatus according to the first embodiment shown in FIG. 3, sound pressure measurement was performed while changing the distance between the ultrasonic transducer 21 and the substrate to be processed 22a. A 2 mm thick aluminum plate was used as the reflecting plate 23. A through-hole 231 having d = 0.8 mmφ was formed in the reflecting plate 23, and a condenser microphone was attached as the ultrasonic detector 24 so as to face the ultrasonic transducer 21. The applied voltage to the ultrasonic transducer 21 was 150 V _pp, and the position of the substrate 22a to be processed was changed from 6.5 mm to 7.5 mm before and after the ultrasonic atomization expression region. When the ultrasonic wave Φ is transmitted through the substrate to be processed 22a and the standing wave of the ultrasonic wave Φ is formed, the sound pressure is considered to be maximum. Therefore, the sound pressure when the sound pressure reaches the maximum value and the sound pressure at that time The result of measuring the position of the reflector 23 is shown in FIG. From the results shown in FIG. 7, it can be confirmed that the optimum position of the reflector 23 is also changed by 0.1 mm in conjunction with the position of the substrate to be processed 22 whenever the position of the substrate to be processed 22a is changed by 0.1 mm. . The sound pressure takes the maximum value when the position of the substrate 22a to be processed is 6.7 mm, and it can be confirmed that the sound pressure is greatly related to the atomization phenomenon of the through-hole via 222. It was confirmed that ultrasonic atomization was caused by actually filling the through-hole via 222 with water and placing the substrate 22a to be treated with the position where the sound pressure reached the maximum value as the optimum atomization position.

  The ultrasonic wave Φ passes through the through-hole via 222 having an inner diameter d smaller than the wavelength λ while being attenuated in the form of an attenuation wave (evanescent wave). Therefore, if the thickness of the substrate to be processed 22a is sufficiently thinner than the wavelength λ of the ultrasonic wave Φ, the ultrasonic wave Φ passes through the substrate to be processed 22a to some extent. As the attenuation wave, the ultrasonic wave Φ transmitted through the substrate to be processed 22a having the through-hole via 222 forms a standing wave together with the ultrasonic wave Φ between the ultrasonic transducer 21 and the substrate to be processed 22a. According to the measurement, the sound pressure of the transmitted ultrasonic wave Φ is about 10% compared to the sound pressure measured without installing the substrate 22a to be processed. Therefore, the influence of the sound pressure after passing through the target substrate 22a on the target substrate 22a is smaller than the influence of the sound pressure before passing through the target substrate 22a on the target substrate 22a. Further, the substrate 22a to be processed is composed of a paper phenol substrate and a glass epoxy substrate, but the paper phenol substrate tends to transmit the ultrasonic wave Φ slightly. Therefore, the ultrasonic wave transmitted through the substrate 22a is processed. It can be seen that both the component propagating through the through-hole via 222 and the component transmitting through the insulating substrate 221 of the substrate to be processed 22a contribute to Φ. Actually, between the ultrasonic transducer 21 and the substrate to be processed 22a, a first standing wave having the substrate to be processed 22a as a reflection plate and the substrate to be processed 22a and reflected by the reflection plate 23 are reflected. The synthesized wave of the second standing wave is estimated to be formed while being correlated with each other.

  In addition, when the position of the substrate 22a to be processed is 6.7 mm where the sound pressure is maximum, the relationship between the position of the reflector 23 and the sound pressure (black circle), the applied voltage and the output of the ultrasonic detector 24. FIG. 8 shows measurement results obtained by measuring the relationship between the phase difference of the voltage (microphone output) and the position of the reflecting plate 23 (open squares). From the results shown in FIG. 8, at the position of the reflector 23 on the near side of the position where the sound pressure indicated by the black circle is maximum, the phase difference indicated by the white square changes substantially linearly, and the phase difference is − It can be confirmed that the sound pressure reaches a maximum near 90 °. When the output voltage (microphone output) of the ultrasonic detector 24 indicated by the black circle is maximized, the system becomes a resonance system, and a powerful ultrasonic wave Φ is excited. From the state of change shown in FIG. 8, the optimum value of the distance can be estimated. Based on the estimation, the positions of the ultrasonic transducer 21 and the reflecting plate 23 are adjusted, and the substrate 22a to be processed is conveyed to the optimum atomization position near the node of the standing wave, thereby exciting the ultrasonic wave Φ. Sequential dehydration can be performed with maximum efficiency.

  In the configuration of the ultrasonic drying apparatus according to the first embodiment shown in FIG. 3, three substrates 22a having a thickness t = 1.6 mm have inner diameters d = 0.8 mm, 1.5 mm, 3 mm, respectively. A through hole via 222 having a thickness of 0.0 mm was provided to prepare three types of substrates to be processed 22a. Then, three kinds of substrates 22a to be processed are detected so as to detect an ultrasonic wave Φ of 28 kHz under the conditions of a temperature of 20.0 ° C. and a humidity of 27% through the through-hole vias 222 having different inner diameters d. An ultrasonic detector was attached to each of the above.

As described above, the position P _node of the standing wave node of the ultrasonic wave Φ of 28 kHz under the conditions of the temperature of 20.0 ° C. and the humidity of 27% was measured to be 6.4 mm. Since it is considered that the insertion of the substrate to be processed 22a generates a waveform distortion (disturbance) with respect to a uniform standing wave in the air, the position P _node of the standing wave node of the ultrasonic wave Φ is Strictly speaking, it depends on the value of the inner diameter d of the through-hole via 222 and changes by about 0.2 mm. However, FIG. 9 approximates that the dependence of the _node position _Pnode on the change in the value of the inner diameter d of the through-hole via 222 is negligible, and the Z-axis movement stage of the biaxial movement stage 25 shown in FIG. By using the probability of the possibility (easyness) of dehydration of the water 223 filled in the through-hole via 222 while changing the distance L between the vibration surface of the ultrasonic vibrator 21 and the left surface of the substrate 22a to be processed. The axis is normalized with the wavelength λ = 12.1 mm, and the interval L is expressed on the horizontal axis.

Under the condition that the dependence of the _node position P _node on the change in the value of the inner diameter d of the through hole via 222 is negligible, all of the three types of substrates to be processed 22a have 0.02 wavelength from the _node position P _node. Although the atomization phenomenon is distributed around the optimal atomization position P _opt that is far away and the dependence of the optimal atomization position P _opt on the value of the inner diameter d of the through hole via 222 can be ignored, the distribution width ( There is a difference in the half width. Since the capillary force increases as the inner diameter d of the through-hole via 222 decreases, the sound pressure of the ultrasonic wave Φ necessary for dehydration increases, and only in the vicinity of the optimal atomization position P _opt where the sound pressure of the ultrasonic wave Φ is high. The atomization phenomenon occurs locally and the distribution width is narrow. However, as the inner diameter d of the through-hole via 222 gradually increases, the capillary force gradually decreases, and the sound pressure of the ultrasonic wave Φ necessary for dehydration gradually decreases. Thus, it is considered that the atomization phenomenon can occur even at a position away from the optimal atomization position _Popt , and the width of the distribution gradually increases.

Further, as shown in Table 1, three substrates 22a having a thickness t = 1.6 mm were respectively provided with an inner diameter d = 0.3 mm, 0.5 mm, 0.8 mm, 1.0 mm, 1.2 mm, Eight kinds of through-hole vias 222 of 1.5 mm, 2.0 mm, and 3.0 mm were provided, each of the through-hole vias 222 was filled with water 223, and whether or not the filled water 223 could be dehydrated was measured. Dehydration was possible with all through-hole vias 222 having an inner diameter d = 0.3 mm to 3.0 mm.

  Table 1 also shows the ratio (d / λ) of the inner diameter d of the through-hole via 222 to the wavelength λ = 12.1 mm of the ultrasonic wave Φ of 28 kHz, and d / λ = 2.5% to 24.8. Within the range of%, it can be determined that there is no dependency of the inner diameter d of the through-hole via 222 on the wavelength λ of the ultrasonic wave Φ in whether dehydration is possible.

  Table 1 shows the aspect ratio t / d of the through hole via 222 as a ratio of the thickness t = 1.6 mm of the substrate 22a to be processed and the inner diameter d of the through hole via 222. Within the range of t / d = 5.3 to 0.5, it can be determined that there is no dependency on the aspect ratio t / d of the through-hole via 222 in whether dehydration is possible. From the results shown in Table 1, the ultrasonic drying apparatus according to the first embodiment has a fine aperture with an inner diameter d = 3 mm or less, particularly an inner diameter d = 1 mm or less, and further an inner diameter d = 0.8 mm or less. It turns out that it is effective for the wet cleaning of the to-be-processed substrate 22a provided with the through-hole via 222 and the subsequent drying process. Note that the ultrasonic drying apparatus according to the first embodiment is applicable to wet cleaning of the substrate 22a to be processed having the through-hole via 222 having an inner diameter d = 3 mm or more and a subsequent drying step. When the inner diameter d is 3 mm or more, dehydration and drying can be performed by other methods. Therefore, the characteristics of the ultrasonic drying apparatus according to the first embodiment are relatively thin.

As shown in FIG. 10, the surface of the substrate to be processed 22 a is tilted from the vertical direction by an angle θ, the incident angle θ of the ultrasonic wave Φ is changed, and the influence of the change in the incident angle θ on the dehydration effect is examined. Is shown in Table 2.

In Table 2, “◯” indicates a case where dehydration is possible, “Δ” indicates a case where the case where dehydration is not possible and “a case where no dehydration is possible” and x indicates a case where dehydration cannot be performed. From the results in Table 2, the allowable inclination angle θ (= ultrasonic incident angle θ) of the substrate to be processed 22a is up to 1.4 °. Therefore, using the X-axis moving stage of the 2-axis moving stage 25 of the ultrasonic drying apparatus according to the first embodiment shown in FIG. In this case, it is determined that the angle θ at which the substrate 22a to be processed is tilted from the X-axis direction in the transport direction is allowable up to about 1.4 °.

  The ultrasonic drying apparatus according to the first embodiment is not limited to the dehydration process after the water washing cleaning process, but can be applied to the drying process after the wet cleaning process using various liquids. In the configuration of the ultrasonic drying apparatus according to the first embodiment shown in FIG. 3, when the thickness t = 1.6 mm of the substrate 22a to be processed and the inner diameter d = 0.5 mm of the through-hole via 222, the through-hole via The interior of 222 was filled with water and isopropyl alcohol (IPA) as liquid types. Whether or not drying is possible (easy) when the distance L between the vibration surface of the ultrasonic transducer 21 and the left surface of the substrate 22a to be processed is changed using the Z-axis movement stage of the biaxial movement stage 25. FIG. 11 shows the distance L on the vertical axis and the interval L expressed on the horizontal axis with the wavelength λ = 12.1 mm as a probability.

Since IPA has a smaller surface tension than water, the sound pressure of the ultrasonic wave Φ required for drying is lower than that of water, and an atomization phenomenon can occur even at a position away from the optimal atomization position _Popt . It can be seen that the distribution is wide and the atomization phenomenon can be observed in a wide range.

  As described above, according to the ultrasonic drying apparatus and the substrate processing method using the ultrasonic drying apparatus according to the first embodiment, the simple and inexpensive structure shown in FIG. 1 and FIG. The liquid accumulated in the through-hole via 222 can be efficiently atomized. In particular, since the substrate to be processed is arranged at the optimal atomization position slightly shifted from the position of the standing wave node of the ultrasonic wave Φ, the substrate to be processed is not contacted without excessively impacting. It is possible to provide an ultrasonic drying apparatus capable of instantaneously dispersing the liquid accumulated in the fine through-hole via 222 and removing impurities simultaneously with the liquid, and a substrate processing method using the ultrasonic drying apparatus.

(Second Embodiment)
In the case of a printed circuit board with high-density wiring, particularly in the case of a bottomed hole via having a small inner diameter, it is difficult to remove water accumulated in the bottomed hole via during the cleaning process.

  As shown in FIG. 12, the ultrasonic drying apparatus according to the second embodiment of the present invention includes an ultrasonic vibrator 21 that generates ultrasonic waves Φ, and a vibrator drive that drives and controls the ultrasonic vibrator 21. The control device 35, the reflection plate 23 that reflects the ultrasonic wave Φ and excites the standing wave of the ultrasonic wave Φ in the air, and the substrate 22b to be processed at the optimum atomization position near the position of the node of the standing wave. And a substrate position control mechanism to be moved. Also in the ultrasonic drying apparatus according to the second embodiment, “the vicinity of the position of the node of the standing wave” means “a position slightly separated from the position of the node of the standing wave by 5% or less of the wavelength. "Means the same as in the ultrasonic drying apparatus according to the first embodiment.

  Here, as shown in FIG. 12, the printed circuit board as the substrate to be processed 22b is bottomed from the upper surface (first main surface) side of the insulating substrate 221 having a multilayer structure toward the back surface (second main surface). A hole via (blind via) 225 is opened. Although not shown, conductor wiring is also provided on the upper surface (first main surface), the back surface (second main surface), and the multilayer structure inside the insulating substrate 221 in the same manner as shown in FIG. The bottomed hole via 225 is formed to be miniaturized, and does not penetrate through all the layers of the insulating substrate 221 having a multilayer structure, and is provided only on the upper surface (first main surface) side. Similarly, a conductive side wall is formed in the bottomed hole by a metal cylinder (canal), and the conductive side wall is continuously electrically connected to the conductive bottom surface of the bottomed hole. The bottom surface of the bottomed hole is electrically connected to one of the multilayer structure wirings inside the substrate to be processed 22b. The ultrasonic drying apparatus according to the second embodiment disposes the liquid (water) accumulated in the bottomed hole via 225 that is the recess of the substrate to be processed 22b by arranging the substrate to be processed 22b at the optimum atomization position. ) Concentrate the ultrasonic wave Φ on 223.

  In the case of the bottomed hole via 225, as schematically shown in FIG. 4, even if the ultrasonic wave Φ is concentrated, the water droplet 223S cannot be pushed out from the bottomed hole via 225 by the force due to the increased acoustic radiation pressure. . Therefore, in the ultrasonic drying apparatus according to the second embodiment, the opening side of the bottomed hole via 225 is directed toward the ultrasonic vibrator 21, and the ultrasonic wave Φ is concentrated inside the bottomed hole via 225. And powerful ultrasonic Φ field is generated. When the action of the acoustic radiation pressure S is increased on the surface of the water 223 accumulated in the bottomed hole via 225 by the powerful ultrasonic wave Φ, a capillary wave is generated on the surface of the water 223. Therefore, when the ultrasonic wave Φ is applied so that the amplitude of the capillary wave is increased and the surface tension is overcome, as shown in FIG. 12, the water droplets 223m as fine particles are scattered and the dehydration process is performed.

  On the other hand, when the opening side of the bottomed hole via 225 was directed to the reflecting plate 23 side, atomization was not observed. The reason is that in the case of the bottomed hole via 225, the intensity of the ultrasonic wave Φ sufficient does not pass through the substrate 22b to be processed, and therefore the ultrasonic transducer 21 and the reflector 23 in the case where the substrate 22b is not present. By inserting the substrate to be processed 22b with respect to an ideal standing wave excited in the uniform air, the amplitude of the standing wave between the substrate to be processed 22b and the reflecting plate 23 is very small. Therefore, it is considered that the waveform of the standing wave is greatly distorted. Actually, between the ultrasonic transducer 21 and the substrate to be processed 22b, the first standing wave having the substrate to be processed 22b as a reflection plate and the substrate 22b as a damped wave are transmitted and reflected. Although it is estimated that the synthesized wave of the second standing wave reflected by the plate 23 is formed while being correlated with each other, the amplitude of the second standing wave is very small. Therefore, when atomizing a liquid such as water accumulated in the bottomed hole via 225, it is necessary to use the first standing wave with the opening side of the bottomed hole via 225 facing the ultrasonic transducer 21 side. (In FIG. 12, the left main surface is defined as the upper surface (first main surface) and the right main surface is defined as the back surface (second main surface) for convenience. The point is that the opening side of the bottomed hole via 225 should be oriented to the main surface facing the direction of the ultrasonic transducer 21.

  The substrate position control mechanism of the ultrasonic drying apparatus according to the second embodiment includes an X-axis moving stage that suspends the substrate 22b to be processed and conveys it in the X-axis direction of FIG. The position of the substrate to be processed 22b is moved (finely moved) in the direction toward the direction 23 (Z-axis direction) so that the substrate 22b is slightly shifted from the position of the standing wave node of the ultrasonic wave Φ. A two-axis movement stage 27 having a Z-axis movement stage to be adjusted, and a substrate position control device (not shown because it is similar to FIG. 3) for driving and controlling the two-axis movement stage 27. A signal for driving control of the biaxial moving stage 27 is sent from the processor (not shown) to the substrate position control device. Similar to the ultrasonic drying apparatus according to the first embodiment, the X-axis moving stage is configured to include a sequential transfer mechanism similar to the conveyor, and the substrate 22b to be processed is adjusted by adjusting the Z-axis moving stage. A plurality of (multiple) substrates to be processed 22b are sequentially transported so as to pass through the optimal optimum atomization position. A plurality of substrates to be processed 22b sequentially conveyed by arranging the pair of the ultrasonic vibrator 21 and the reflecting plate 23 in parallel along the X-axis conveyor conveyance direction of the biaxial moving stage 27. The entire surface of each can be covered with ultrasonic waves.

  3, the ultrasonic drying apparatus according to the second embodiment further fixes an ultrasonic detector (not shown) for detecting the ultrasonic wave Φ to the back surface of the reflecting plate 23. ing. The ultrasonic detector detects the ultrasonic wave Φ through a bottomed hole provided in the reflecting plate 23. The output of the ultrasonic detector is fed back to a transducer drive control device (not shown), and the output of the ultrasonic transducer 21 is controlled. Further, a reflection plate position control mechanism (not shown) is provided for controlling the position of the reflection plate 23 so that the output of the ultrasonic detector is fed back and the reflection plate 23 excites the standing wave. . The reflector position control mechanism is equipped with the reflector 23 and moves the position of the reflector 23 in the direction (Z-axis direction) from the ultrasonic transducer 21 toward the reflector 23 so that the standing wave is excited. Reflector position provided with a uniaxial movement stage (not shown) that is a Z-axis movement stage that is adjusted by (fine movement) and a reflector position control device (not shown) that drives and controls the uniaxial movement stage. A signal for driving control of the single-axis moving stage is sent from the processor to the control device. For this reason, an amplifier (not shown) is connected to the ultrasonic detector, and the output of the ultrasonic detector is input to the processor via the amplifier, the processor performs the necessary folding signal processing, and one-axis movement A stage drive control signal is output to the reflector position control device. The output of the ultrasonic detector is fed back to the reflector position control device, and the standing wave of the ultrasonic wave Φ is excited under the optimum conditions, so that the mist of the water 223 accumulated in the bottomed hole via 225 of the substrate to be processed 22b. It is possible to efficiently create a powerful sound field necessary for the conversion.

  Furthermore, the output of the ultrasonic detector input to the processor via the amplifier can also be used to generate a signal for driving control of the biaxial moving stage 27. The output of the ultrasonic detector is 2 By returning to the substrate position control device that drives and controls the axial movement stage 27, the position of the substrate 22b to be processed can also be optimized. As described above, the output of the ultrasonic detector is fed back to the transducer drive control device, the reflector position control device, and the substrate position control device, so that the ultrasonic wave Φ is concentrated, and the atomization phenomenon in the bottomed hole via 225. It is possible to automatically control and track the conditions for efficiently expressing.

  In the ultrasonic drying apparatus according to the second embodiment, in order to instantly develop the atomization phenomenon of the water 223 accumulated in the bottomed hole via 225 of the substrate 22b to be processed, the atomization conditions must be aligned. There is. Specifically, the amplitude of the standing wave of the ultrasonic wave Φ must be large, and the bottomed hole via 225 must match the optimal atomization position in the vicinity of the node of the standing wave. Is the same as that of the ultrasonic drying apparatus according to the first embodiment. In order for the ultrasonic wave Φ that is a standing wave to become strong, the distance between the ultrasonic transducer 21 and the reflecting plate 23 is optimized, and the reflected wave and the radiated wave from the ultrasonic transducer 21 respectively. Must be completely in phase. This condition is determined by the speed of sound. The speed of sound fluctuates depending on the temperature and humidity, and the apparent speed of sound changes depending on the material, thickness, and via structure of the substrate 22b to be conveyed. According to the ultrasonic drying apparatus according to the embodiment, the output of the ultrasonic detector is fed back to the transducer drive control device, the reflection plate position control device, and the substrate position control device, and the phase of the sound pressure in the reflection plate 23 is calculated. Based on the phase relationship of the applied voltage of the ultrasonic transducer 21, the optimum distance between the ultrasonic transducer 21 and the reflector 23 is sequentially estimated and automatically adjusted, and the positions of various types of substrates 22b are sequentially estimated and automatically adjusted. Thus, it can always be automatically controlled and tracked so that the atomization phenomenon is efficiently developed under the optimum conditions. By performing feedback control so that atomization is performed under the optimum conditions, the time from the start of irradiation of the ultrasonic wave Φ to the end of atomization can be shortened, so that the throughput of the production line is not reduced.

In the ultrasonic drying apparatus according to the second embodiment shown in FIGS. 12 and 13, an aluminum plate having a thickness of 5 mm is used as the reflecting plate 23, and the vibration surface of the ultrasonic transducer 21 and the inner diameter d = 0.8 mm are used. The experiment was performed by changing the distance L from the surface of the substrate 22b provided with the bottomed hole via 225 by 0.5 mm in the X-axis direction and 0.1 mm in the Z-axis direction using the biaxial moving stage 27. The results are shown in FIG. In FIG. 14, data of a substrate to be processed having a through-hole via having an inner diameter d = 0.8 mm is also plotted for comparison. The applied voltage to the ultrasonic transducer 21 is 150 V _pp, and the substrate 22b to be processed is a glass epoxy substrate having a thickness t = 1.6 mm. The interval between the ultrasonic transducer 21 and the reflecting plate 23 is fixed at 32.0 mm. As shown in FIG. 14, the bottomed hole via 225 tends to be less susceptible to atomization than the through-hole via.

  In the substrate to be processed 22a having the through-hole via 222 described in the first embodiment, it was confirmed that the ultrasonic wave Φ transmitted through the substrate to be processed 22a to some extent and a standing wave was formed. However, even in the ultrasonic drying apparatus according to the first embodiment, the transmitted ultrasonic wave Φ is approximately 10% of the sound pressure measured without installing the substrate 22a to be processed. It can be said that the influence of the sound pressure after passing through the processing substrate 22a is smaller than the influence of the sound pressure before passing through the processing target substrate 22a. On the other hand, in the substrate to be processed 22b having the bottomed hole via 225, the ultrasonic wave Φ does not sufficiently pass through the substrate to be processed 22b, and the sound pressure is the sound pressure of the substrate to be processed 22a having the through-hole via 222. About 15-30%. That is, it can be seen that only about 1.5 to 3% of the sound pressure measured without installing the substrate 22b to be processed is obtained. In the ultrasonic drying apparatus according to the first embodiment, when the material constituting the substrate 22a to be processed is a paper phenol substrate and a glass epoxy substrate, the paper phenol substrate tends to transmit the ultrasonic wave Φ slightly. Therefore, it has been described that the ultrasonic wave Φ transmitted through the substrate to be processed 22a has both a component that propagates through the through-hole via 222 and a component that transmits through the insulating substrate 221 of the substrate to be processed 22a. In the case of the substrate to be processed 22b of the ultrasonic drying apparatus according to the second embodiment, the ultrasonic wave φ transmitted through the substrate to be processed 22b is transmitted to the bottomed hole via 225 via the bottomed hole via 225. Although it can be estimated that there are both a component that propagates through the thin portion of the insulating substrate 221 located at the bottom and a component that transmits through the entire thickness portion of the insulating substrate 221 of the substrate 22b to be processed, it passes through the bottomed hole via 225. Component is very small. Therefore, in the substrate to be processed 22b having the bottomed hole via 225, the amplitude of the standing wave between the substrate to be processed 22b and the reflection plate 23 is very small, and between the ultrasonic vibrator 21 and the reflection plate 23. In addition, extremely asymmetric standing wave excitation can be hypothesized. For this reason, the substrate to be processed 22b is hardly affected by the sound pressure between the ultrasonic transducer 21 and the reflecting plate 23. Therefore, even if the opening side of the bottomed hole via 225 faces the reflecting plate 23 side, It is difficult to atomize the water 223 accumulated in the bottom hole via 225.

  Further, in the case where the thickness t = 1.6 mm of the substrate 22b to be processed and the inner diameter d = 0.5 mm of the bottomed hole via 225, using the configuration of the ultrasonic drying apparatus according to the second embodiment shown in FIG. The inside of the bottomed hole via 225 is filled with water, and the distance L between the vibration surface of the ultrasonic transducer 21 and the left surface of the substrate to be processed 22b is set using the Z-axis movement stage of the biaxial movement stage 25. FIG. 15 is a graph in which the interval (L) is expressed on the horizontal axis by normalizing with the wavelength λ = 12.1 mm as the probability on the possibility (easyness) of dehydration when changed. Also in FIG. 15, in the case of the bottomed hole via 225, the range in which the atomization phenomenon is observed is narrower than in the case of the through hole via shown in FIG.

  As shown in FIG. 14 (and FIG. 15), the through-hole via 222 and the bottomed-hole via 225 differ in the intensity of the ultrasonic wave Φ that passes through the substrates 22a and 22b and the status (waveform) of the standing wave. Since the ultrasonic atomization areas are different, it is impossible to dehydrate at the same time under the same conditions. Therefore, the ultrasonic drying apparatus according to the first embodiment and the ultrasonic drying apparatus according to the second embodiment need to change the condition settings so that they can correspond to the respective expression areas. In order to atomize the water accumulated in the bottom hole via 225, it is necessary to apply a higher sound pressure to the substrate to be processed 22b than in the ultrasonic drying apparatus according to the first embodiment. 21 is preferred for efficient atomization.

In order to investigate the influence of the depth of the bottomed hole, a bottomed hole via 225 having an inner diameter d = 0.3 mmφ of different depth is opened in the substrate 22b to be processed having a thickness of t = 1.6 mm, and the ultrasonic transducer 21 is formed. FIG. 16 shows the result of examining the effect of the intensity of the ultrasonic wave Φ on the atomization by changing the applied voltage of 100 V _pp , 125 V _pp , and 150 V _pp . The depth of the bottomed hole via 225 is normalized by the inner diameter d of the bottomed hole via 225 to obtain an aspect ratio, which is the horizontal axis of FIG. As the amplitude of the ultrasonic wave Φ is increased by changing the applied voltage to the ultrasonic transducer 21 from 100 V _pp → 125 V _pp → 150 V _pp , the liquid of the bottomed hole via 225 having a higher aspect ratio (deeper). It turns out that can be atomized and dried. This is because the ultrasonic wave Φ transmitted through the substrate to be processed 22 b is a component of the ultrasonic wave Φ that propagates through the bottomed hole via 225 and the thin part of the insulating substrate 221 located at the bottom of the bottomed hole via 225. Is confirmed to be very small.

  From the results shown in FIG. 16, in the ultrasonic drying apparatus according to the second embodiment, in the case of the bottomed via 225 having an inner diameter d = 0.3 mmφ, the aspect ratio is increased if the amplitude of the ultrasonic wave Φ is increased. Even if it is 2.5 or more, it is possible to effectively atomize and dry, and wet cleaning of the substrate 22b to be processed provided with the bottomed hole via 225 having a fine diameter of an inner diameter d = 0.3 mmφ or less. And it turns out that it is effective for the subsequent drying process.

  As described above, according to the ultrasonic drying apparatus and the substrate processing method using the ultrasonic drying apparatus according to the second embodiment, the simple and inexpensive structure shown in FIGS. The liquid accumulated in the bottomed hole via 225 can be efficiently atomized. In particular, since the substrate to be processed is arranged at the optimal atomization position slightly shifted from the position of the standing wave node of the ultrasonic wave Φ, the substrate to be processed is not contacted without excessively impacting. It is possible to provide an ultrasonic drying apparatus that can instantaneously disperse the liquid accumulated in the fine bottomed hole via 225 and remove impurities simultaneously with the liquid, and a substrate processing method using the ultrasonic drying apparatus.

(Other embodiments)
As described above, the present invention has been described according to the first and second embodiments. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, in the description of the first and second embodiments, as illustrated in FIG. 1, the XZ plane is a horizontal plane, and the main surface direction of the substrate 22a to be processed is vertical, that is, along the Y-direction. Although the discussion is based on the case, the definition of the X axis, the Y axis, and the Z axis is not limited to the orientation illustrated in FIG. 1, and any coordinate axis can be selected as long as the coordinate systems are orthogonal to each other. is there. For example, another orthogonal coordinate system in which the direction of the standing wave is the vertical direction and the principal surface direction of the substrate 22a to be processed is the horizontal direction may be selected.

  When an orthogonal coordinate system is selected in which the direction of the standing wave is the vertical direction and the main surface direction of the substrate to be processed 22a is the horizontal direction, the configuration illustrated in FIGS. The ultrasonic transducer 21 is mounted on the stage, the ultrasonic transducer 21 is moved in the Z-axis direction, and the relative distance between the ultrasonic transducer 21 and the substrates to be processed 22a and 22b is determined. An aspect of adjusting the relative distance between the reflector 23 and the reflecting plate 23 may also be included. Therefore, more generally, the “substrate position control mechanism” of the present invention is the relative distance between the ultrasonic transducer 21 and the substrates 22a and 22b and the relative distance between the substrates 22a and 22b and the reflector 23. The “reflector position control mechanism” of the present invention is a mechanism that can control the relative distance between the ultrasonic transducer 21 and the reflector 23, and between the substrates to be processed 22a and 22b and the reflector 23. It should be understood that the mechanism can control the relative distance.

The operation method (operation) of the biaxial moving stage 25 described in the first embodiment and the biaxial moving stage 27 described in the second embodiment can be variously modified. . For example, if the types of substrates to be processed 22a and 22b are routine cleaning steps and drying steps, the inner diameter of the through-hole via 222, the material, thickness, and structure of the insulating substrate 221 are different. The optimum atomization position P _opt is sequentially measured for each of the various substrates to be processed 22a, the inner diameter of the bottomed hole via 225, the material / thickness / structure of the insulating substrate 221, etc. It is also possible to store the recipe in the atomization position database as a recipe. By doing so, the processor 34 programs the operations of the two-axis movement stages 25 and 27 while referring to the information in the optimum atomization position database. Can be controlled. In this case, prior to the drying process, the product information of the various substrates 22a and 22b such as the inner diameter of the through hole via 222, the inner diameter of the bottomed hole via 225, and the material / thickness / structure of the insulating substrate 221 The information is stored in the information database, and the processor 34 is programmed to control the two-axis moving stages 25 and 27 while reading the information stored in the optimum atomization position database and the processed substrate information database, respectively. good.

  Further, coarse adjustment of the movement of the two-axis moving stages 25 and 27 is performed by program control using information stored in the optimum atomization position database and the substrate information database to be processed, and the final fine adjustment is performed using ultrasonic waves. The output of the detector 24 is fed back to the transducer drive control device 35, the reflector position control device 33, and the substrate position control device 32, and the phase of the sound pressure on the reflector 23 and the phase of the applied voltage of the ultrasonic transducer 21 are compared. From the relationship, the operation of finely adjusting the optimum distance between the ultrasonic transducer 21 and the reflecting plate 23 and finely adjusting the positions of the substrates 22a and 22b to be processed is always performed efficiently under the optimum conditions. As such, it may be automatically controlled and tracked. Thus, the throughput of the production line can be improved by performing feedback control while using program control together.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is determined only by the invention specific matters according to the description of the scope of claims, which is appropriate from the above description.

DESCRIPTION OF SYMBOLS 21 ... Ultrasonic vibrator 22a, 22b ... Substrate to be processed 23 ... Reflector 24 ... Ultrasonic detector 25, 27 ... Two-axis movement stage 26 ... One-axis movement stage 31 ... Amplifier 32 ... Substrate position control device 33 ... Reflector Position control device 34 ... Processor 35 ... Transducer drive control device 221 ... Insulating substrate 222 ... Through hole via 223 ... Water 223S ... Water droplet 223m ... Water droplet 225 ... Bottom hole via 231 ... Through hole

Claims (11)

An ultrasonic transducer that generates ultrasonic waves;
A vibrator drive control device for driving and controlling the ultrasonic vibrator;
A reflector that reflects the ultrasonic waves and excites the standing waves of the ultrasonic waves in the air;
A substrate position control mechanism for moving the substrate to be processed to an optimum atomization position in the vicinity of the position of the node of the standing wave, and atomizing the liquid accumulated in the recess of the substrate to be processed at the optimum atomization position. An ultrasonic drying apparatus characterized by removing.   The ultrasonic drying apparatus according to claim 1, further comprising an ultrasonic detector that is provided on the reflection plate and detects the ultrasonic wave.   The ultrasonic drying apparatus according to claim 2, wherein an output of the ultrasonic detector is fed back to the vibrator drive control device, and an output of the ultrasonic vibrator is controlled.   4. The reflection plate position control mechanism for controlling the position of the reflection plate so that the reflection plate excites the standing wave by the output of the ultrasonic detector. The ultrasonic drying apparatus as described.   The ultrasonic drying apparatus according to claim 4, wherein the output of the ultrasonic detector is further fed back to the reflector position control mechanism to move the substrate to be processed to the optimum atomization position. .   4. The output of the ultrasonic detector is fed back to the reflecting plate position control mechanism and the reflecting plate position control mechanism, respectively, and the substrate to be processed and the reflecting plate are moved simultaneously. The ultrasonic drying apparatus described in 1. A cleaning step of wet-cleaning the substrate to be processed having a recess with a liquid;
After the cleaning step, an ultrasonic vibrator that generates ultrasonic waves, a vibrator drive control device that drives and controls the ultrasonic vibrators, reflects the ultrasonic waves, and excites the standing waves of the ultrasonic waves in the air Using an ultrasonic drying apparatus having a reflecting plate to move the substrate to be processed to an optimal atomization position in the vicinity of the position of the standing wave node between the ultrasonic transducer and the reflecting plate;
And a step of atomizing and removing the liquid accumulated in the concave portion of the substrate to be processed by the ultrasonic wave at the optimum atomization position.   In the step of atomizing and removing, the ultrasonic detector provided on the reflector detects the ultrasonic wave and returns the output of the ultrasonic detector to the transducer drive control device, thereby The substrate processing method according to claim 7, wherein an output of the ultrasonic vibrator is controlled.   In the step of removing by atomization, feedback control is performed on the output of the ultrasonic detector, and the position of the reflecting plate is adjusted so that the reflecting plate excites the standing wave. Item 9. The substrate processing method according to Item 8.   The substrate processing according to claim 9, wherein in the step of removing by atomization, the output of the ultrasonic detector is further feedback-controlled to move the substrate to be processed to the optimum atomization position. Method.   9. The substrate processing method according to claim 8, wherein in the step of atomizing and removing, the output of the ultrasonic detector is feedback-controlled to move the substrate to be processed and the reflecting plate at the same time.