CN104122333A - Array resolution type ultrasonic focusing transducer - Google Patents

Abstract

The array analytical ultrasonic focusing transducer designed by the present invention includes a signal excitation/receiving source, a transducer shell, a commercial contact ultrasonic probe, a quartz focusing lens, and an array acoustic wave space sensing area, wherein the array acoustic wave space sensor In terms of specific structure, the measuring area also includes an array pattern sensing bottom electrode, a PVDF piezoelectric film and a top protection electrode. The content of the invention includes its structural principle, production and use methods, etc. The design purpose of the transducer is to realize the sensing of the spatial sound field at multiple angles by arranging piezoelectric sensing areas at multiple angles in space, so as to understand The spatial distribution characteristics of the sound field can be used to invert the shape information of the surface or interior of the reflection test piece.

Description

Array Analytic Ultrasonic Focusing Transducer

technical field

The array analytical ultrasonic focusing transducer designed by the present invention is mainly used in the signal excitation and receiving end of the ultrasonic microscopic automatic testing system, and realizes sensing from multiple angles through multiple piezoelectric sensing elements arranged at the focusing surface end of the transducer. The invention relates to the spatial sound pressure distribution of a focused sound field generated by a transducer, and the invention belongs to the field of ultrasonic nondestructive testing.

Background technique

The ultrasonic focusing transducer is the core device of the ultrasonic microscopic testing system, which is mainly used to excite and receive ultrasonic signals to obtain the ultrasonic propagation characteristics on the surface or inside of the test piece. This type of transducer has very important research value and application prospects in industrial ultrasonic scanning systems, ultrasonic image detection systems, and ultrasonic microscopes. In recent years, ultrasonic focusing transducers have been widely used in integrated packaging circuit testing, performance testing of advanced materials, medical engineering and image observation of biological tissues.

There are many types of ultrasonic focusing transducers. According to their focusing methods, they can be divided into point-focusing and line-focusing types; according to the position of the piezoelectric material, they can be divided into lens-type and lens-less types. The traditional ultrasonic focusing transducer is composed of a piezoelectric material and an ultrasonic lens with only a single sensing surface, as shown in Figure 1. Among them, the focused sound field of the ultrasonic wave is realized by an ultrasonic lens with a spherical surface at one end, and its production materials generally have the characteristics of high sound velocity and low attenuation, such as quartz, alumina crystal, etc.; the high-voltage pulse sent by the signal excitation/reception source The signal excites the piezoelectric layer to generate sound waves, which are refracted by the focusing surface of the ultrasonic lens to form a focused incident sound field in the coupling liquid; part of the incident sound waves will be refracted on the surface of the material and enter the sample, and part will be reflected, and then After being received by the curved surface of the ultrasonic lens, it returns to the piezoelectric layer and generates a reflected signal. If there are defects on the surface or inside of the test piece, such as pores, cracks or impurities, the incident wave will be scattered at the defect, and part of the scattered sound waves will also return to the piezoelectric layer from the ultrasonic lens to generate a backscattered signal. Commonly used ultrasonic scanning and imaging use backscattering signals to obtain information inside the test piece.

In addition, there is also a lensless ultrasonic focusing transducer, as shown in Figure 2, which uses flexible piezoelectric materials (such as PVDF) to directly form on the focusing surface, and the signal excitation/reception source directly excites the surface of this layer. Piezoelectric film that creates a focused form of the incident sound field. The biggest advantage of this lensless focused ultrasonic transducer is that there is no transmission, reflection and refraction on solid/liquid surfaces, so the signal propagation is more direct, which is beneficial to the analysis of sound waves during data processing. In addition, the acoustic impedance of PVDF is very close to that of water, so it has good acoustic impedance matching. In addition, the lensless ultrasonic transducer has a simple manufacturing process, strong operability, and low manufacturing cost, so it has very broad application prospects in the industrial field.

The above two types of ultrasonic focusing transducers have one thing in common, that is, they are all composed of a single sensing area, so the output signal of the transducer is all the reflected sound waves that return to the sensing piezoelectric layer and the back The superposition of scattered sound waves, that is, it is necessary to integrate all the sound wave energy back to the sensing piezoelectric layer to obtain a single output voltage signal. Because the integration and superposition will destroy the phase and spatial position information of the echo signal, the obtained single signal cannot reflect or reconstruct the complete backscattering sound field distribution, but as mentioned above, the backscattering sound field includes There are important information such as defects or impurities on the surface and inside of the test piece, such as position, size, material, etc.; therefore, the detection of such problems by traditional ultrasonic focusing transducers can only rely on the strength of the received signal, and the lack of A more sophisticated interpretation and analysis of the backscattered sound field.

Therefore, there is an urgent need for an ultrasonic focusing transducer with a spatial array of distributed sensing elements to sense the pressure distribution of the sound field facing it from multiple angles, and to further obtain the background pressure through the fusion of the signal characteristics obtained by each sensing point. Spatial distribution information of the scattered sound field.

Contents of the invention

The purpose of the present invention is to realize the sensing of the spatial sound field at multiple angles by arranging piezoelectric sensing areas at multiple angles in space, so as to understand the distribution characteristics of the sound field in space, thereby reversing the surface or interior of the reflection test piece shape information.

In order to achieve the above object, the patent of the present invention adopts the following scheme:

1. An array analytical ultrasonic focusing transducer, characterized in that it includes a signal excitation/receiving source (1), a transducer housing (2), a commercial contact ultrasonic probe (3), a quartz focusing lens (4), Composed of an array acoustic wave space sensing area (5), the signal excitation/reception source (1), a commercial contact ultrasonic probe (3), a quartz focusing lens (4) and an array type acoustic wave space sensing area (5) Arranged sequentially; it is characterized in that: the specific structure of the arrayed acoustic wave space sensing area (5) includes an array patterned sensing bottom electrode (6), a PVDF piezoelectric film (7) and Top guard electrode (8).

2. The array analytical ultrasonic focusing transducer according to claim 1, characterized in that: the signal excitation/reception source (1) sends a high-voltage broadband pulse signal to excite a commercial contact ultrasonic probe (3), The commercial contact ultrasonic probe (3) adheres to the top of the quartz focusing lens (4) for planar contact through a coupling agent, and the acoustic wave oscillation signal generated by the commercial contact ultrasonic probe (3) will propagate to the array through the quartz medium The acoustic wave spatial sensing area (5) forms a focused acoustic wave that enters the liquid coupling medium, and forms refraction and reflection at the interface of the test piece, and the signal returns to the array acoustic wave spatial sensing area (5) and is spatially distributed The sensing element receives and completes a test. The specified frequency is 1-2KHz.

3. The array resolution ultrasonic focusing transducer according to claim 1, characterized in that: the array pattern sensing electrode (6) is composed of 11 sensing elements, and senses The electrodes (6) are arranged in a straight line in the diameter direction to detect the sound field distribution at different angles; each sensing element is composed of three parts: point-shaped sensing electrodes, electrode leads and electrode welding seats. The number and size of sensing elements of the arrayed pattern sensing electrodes (6) can be adjusted.

4. According to the array analysis type ultrasonic focusing transducer described in claim 1, it is characterized in that: the manufacturing method of the array analysis type ultrasonic focusing transducer:

1) Exposure and development to define the array electrode pattern: use spin coating technology to spin coat a layer of photoresist on the focusing surface of the cleaned quartz focusing lens (4), and then cover the photoresist with a light shield designed with a bottom electrode pattern, And placed together under the ultraviolet parallel exposure lamp for exposure and development; after the photoresist of the visible part is decomposed, use the developer to wash off the photoresist of the decomposed part. At this time, the decomposed part is the designed bottom electrode pattern;

2) Evaporate the metal layer to complete the pattern electrode production: use the electron beam evaporation technology on the curved surface of the quartz focusing lens (4) completed in step 1, evaporate metal chromium with a thickness of 20-40nm as the adhesion layer, and then evaporate it on it Plating pure gold with a thickness of 40-60nm; at this time, the entire curved surface completely covers the metal electrode, but the metal in the decomposed part of the photoresist is directly attached to the lens, and other metals are attached to the undecomposed photoresist; because the photoresist can be dissolved After cleaning the lens with an organic solvent, the metal attached to the photoresist will naturally fall off, leaving the prefabricated patterned electrode, thus completing the fabrication of the array patterned sensing bottom electrode (6);

3) Production of PVDF piezoelectric film: Spin-coating sol crystallization method is used to spin-coat PVDF sol at the end of the focusing surface of the quartz focusing lens (4) through a spin coating machine at high temperature, so that it is evenly adsorbed on the focusing surface after crystallization. This completes the fabrication of the PVDF piezoelectric film (7). Then vapor-deposit the top protective electrode (8) again, so that the upper and lower sides of the PVDF piezoelectric film (7) are attached to the electrodes; the upper and lower electrodes are drawn out through the lead wires and connected to a high-voltage regulated source for step-by-step regulated polarization, so that the PVDF piezoelectric film (7) Thin films have piezoelectric properties.

4) Assembly of the array analytical ultrasonic transducer: Put the polarized lens into the transducer housing (2), and use a couplant to paste a commercial contact ultrasonic probe (3) on the top flat end of the transducer to connect the signals The receiving port is to complete the production of the entire transducer.

Utilizing the above-mentioned design idea and manufacturing method, the design and manufacture of the overall structure of the array analytical ultrasonic focusing transducer designed in the present invention are realized. The transducer has the characteristics of simple structure, convenient use and high sensitivity, and is suitable for the measurement of the surface and internal morphology of materials.

The present invention can obtain following beneficial effect:

The array analytical ultrasonic transducer designed by this invention, through the manufacturing process of the ultrasonic focusing transducer, makes a spatially distributed array of ultrasonic signal receiving units on the focusing curved surface end, realizing the multi-angle ultrasonic focusing transducer The sensing of the reflected sound field is used to understand the influence of different reflecting interfaces on the distribution of the sound field, and the topography of the surface or interior of the object to be measured can be inferred through signal inversion. This technology can effectively improve the integral effect of the traditional ultrasonic focusing transducer on the sound field energy on a single curved surface, so it has a very broad application prospect in material property detection and morphology imaging.

Description of drawings

Figure 1 Lens-type ultrasonic focusing transducer

(1) Signal excitation/reception source (2) Transducer shell

(3) Commercial contact ultrasonic probe (4) Quartz focusing lens

(5) Piezoelectric film

Figure 2 Lensless Ultrasonic Focusing Transducer

(1) Signal excitation/reception source (2) Attenuation backing

(3) Bottom electrode (4) PVDF piezoelectric film

(5) Top electrode

Figure 3 Structural Diagram of Array Analytical Ultrasonic Focusing Transducer

(1) Signal excitation/reception source (2) Transducer shell

(3) Commercial contact ultrasonic probe (4) Quartz focusing lens

(5) Array type acoustic wave space sensing area (6) Array pattern type sensing bottom electrode

(7)PVDF piezoelectric film (8)Top protection electrode

Figure 4 array pattern sensing electrode pattern

(1) Electrode welding seat

(2) Point sensing electrodes

(3) Electrode leads

Figure 5 The manufacturing process of the array analytical ultrasonic focusing transducer

Figure 6 The traditional ultrasonic focusing transducer receives the signal

Figure 7 The single sensing element of the array analytical ultrasonic focusing transducer receives the signal

Detailed ways

The array analytic ultrasonic focusing transducer designed in the present invention is mainly used in the spatial sensing of the ultrasonic focused sound field distribution, and the detailed implementation rules thereof will be further described below. The following examples are only descriptive, not restrictive, and cannot be used to limit the protection scope of the present invention.

In conjunction with Fig. 3, the embodiment of the specific method of use of the present invention is described as follows:

Array analytical ultrasonic focusing transducer, including signal excitation/receiving source (1), transducer housing (2), commercial contact ultrasonic probe (3), quartz focusing lens (4), array acoustic wave space sensing area (5) composition, wherein the array type acoustic wave space sensing area (5) also includes an array pattern type sensing bottom electrode (6), a PVDF piezoelectric film (7) and a top protection electrode (8) in a specific structure.

The signal excitation/reception source (1) is completed by a pulse excitation/reception device, which can send a high-voltage pulse signal at a certain frequency to excite a commercial contact ultrasonic probe (3), and the commercial contact ultrasonic probe (3) is coupled The agent adheres to the top of the quartz focusing lens (4) (plane contact), and the acoustic wave oscillation signal generated by the excitation will propagate through the quartz medium to the array acoustic wave space sensing area (5) and form a focused acoustic wave into the liquid coupling medium ( Generally water), and form refraction and reflection at the interface of the test piece, the signal returns to the array acoustic wave space sensing area (5) to be received by the spatially distributed array sensing elements, and these received signals are sent into the pulse wave again After being amplified by the excitation/receiving instrument, the signal can be stored for subsequent fusion and processing analysis, thus completing a test. This method has a relatively sensitive sensing ability to the change of sound field distribution caused by irregularities such as fractures and steps on the surface of the test piece, so it can be effectively applied to the detection of the surface topography of the test piece.

The functional characteristics of the traditional ultrasonic focusing transducer and the array resolution ultrasonic focusing transducer are compared as follows. As shown in Figure 6, it is a time-domain signal received by a traditional ultrasonic focusing transducer, which is a single-period pulse-echo signal, that is, the integral energy of the echo sound field energy on the entire focusing surface, so it only contains energy The size information does not contain the angle information of energy; as shown in Figure 7, it is the receiving signal of the No. 3 sensing element of the array analytical type ultrasonic focusing transducer, which is facing the sound field at an angle of 9° with the vertical direction, Therefore, the signal reflects the energy of the sound field at this angle; the signals received by other sensing elements are similar to this, and they are all the energy of the sound field at the angle directly opposite to them, and will not be described here. It can be seen from Figure 7 that the time-domain signal is similar to the waveform of the traditional ultrasonic focusing transducer, because it reflects the sound field signal at a direct angle, so the energy will be much smaller than that of the traditional ultrasonic focusing transducer , but it contains the angle information of the position of the sensing element, so the sensing of the sound field by the array analytical ultrasonic focusing transducer not only contains the angle information of the sound field distribution, but also reflects the energy of the sound field at this angle, so that through each sensor The information fusion of the measuring components reflects the spatial energy distribution of the reflected sound field, so as to better understand the sound field.

With reference to Fig. 5, the manufacturing process of the array-analytic ultrasonic focusing transducer will be further described through specific embodiments.

According to the working principle and design structure of the transducer, the manufacture of the entire ultrasonic focusing transducer starts from the curved surface of the quartz lens. It mainly includes the steps of array sensing element definition, electrode evaporation, P(VDF-TrFE) sol crystal spin coating and polarization. The specific design process is shown in Figure 5. The specific production process is described as follows:

1. In order to be able to define prefabricated patterned electrodes on the quartz lens, it is necessary to indirectly realize the definition of the bottom electrode through ultraviolet exposure and development technology. When making, it is necessary to spin-coat the photoresist on the focusing surface end of the lens first. In this design, the positive photoresist model of AZP4620 is used, which is intended to cause chemical bond breakage and decomposition under the action of ultraviolet light. After the photoresist is spin-coated with a spin coater, the quartz lens is covered with an image film with a light-shielding pattern, and then the whole is placed under an ultraviolet parallel exposure lamp for a certain period of time to completely decompose the unshielded pattern image, and then use developing technology. Soak the exposed lens in the developer solution for a certain period of time to realize electrode image forming.

2. Put the exposed quartz lens into the electron beam evaporation machine to evaporate metal electrodes, and then evaporate chromium (Cr) and gold (Au) to a certain thickness. At this time, the focusing curved surface end of the quartz lens is completely covered by evaporated metal, and undecomposed photoresist is still adhered to the bottom of the metal coating of the undefined electrode part, so the focus end of the evaporated quartz lens is soaked in acetone Put it in an ultrasonic cleaning machine for cleaning for a period of time, the evaporated metal attached to the photoresist will naturally fall off with the dissolution of the photoresist, leaving only the electrode pattern defined on the exposure film.

3. The quartz lens with a well-defined bottom electrode needs to uniformly coat a layer of P(VDF-TrFE) piezoelectric material on the surface of the bottom electrode. This design adopts the spin-coating sol crystallization method, that is, through the spin coating machine on the focusing surface of the lens Spin-coat P(VDF-TrFE) sol at high temperature to make it evenly adsorbed on the focusing surface after crystallization. The film obtained by this method itself does not have piezoelectric properties, and it needs to be polarized at high voltage for a certain period of time to obtain its piezoelectric properties. In this design, in order to ensure that the film has a fixed polarized area, that is, the sensing point is polarized, and the electrode leads and welding points are not polarized, it is necessary to vapor-deposit a polarized electrode on the film, which only covers the sensing point. Measuring point. Then weld the lead wires of each sensing point at the welding point, and connect the joint and polarization joint to the high-voltage polarization table, and gradually increase the polarization voltage up to 425V in a step-up manner. If breakdown does not occur, then maintain the polarization potential for 12 hours to fully polarize the part covered by the film electrode.

4. After the film is polarized, use a commercial contact probe to excite an ultrasonic signal at the flat end of the quartz lens, receive the signal at the sensing electrode, and test the signal reception effect of each sensing element. If the polarization is successful, the AB glue is fully covered at the soldering point to prevent the soldering point from falling off, and to prevent each soldering point from being misconnected and conducting. After the AB glue is completely solidified, put it into the electron beam evaporation machine again to vapor-deposit metal electrodes on the surface of the film to prevent the film from being directly exposed to the air. Finally, put it into a metal shielding case, install a commercial contact probe on the top of the lens, and complete the production of the entire transducer.

Claims (4)

1. array analytic expression ultrasound wave focused transducer, it is characterized in that: it comprises signal excitation/reception sources (1), transducer enclosure (2), commercial contact ultrasonic probe (3), quartz amasthenic lens (4), array sound wave space sensing area (5) composition, described signal excitation/reception sources (1), commercial contact ultrasonic probe (3), quartzy amasthenic lens (4) and array sound wave space sensing area (5) are disposed in order; It is characterized in that: the concrete structure of described array sound wave space sensing area (5) comprises array pattern formula sensing hearth electrode (6), PVDF piezoelectric membrane (7) and the top guard electrode (8) of arranging successively from the inside to the outside.

2. according to the array analytic expression ultrasound wave focused transducer described in claim 1, it is characterized in that: described signal excitation/reception sources (1) is to send high pressure wideband pulse signal to encourage commercial contact ultrasonic probe (3), plane contact is carried out on the top that described commercial contact ultrasonic probe (3) sticks to quartzy amasthenic lens (4) by couplant, the sonication signal that commercial contact ultrasonic probe (3) is energized generation can be transmitted to array sound wave space sensing area (5) and be formed focused sound waves by quartz medium and enter liquid couplant, and in test specimen interface formation refraction to be measured and reflection, this signal is again got back to array sound wave space sensing area (5) and is received by the array sensing element of space distribution, complete once test.Described characteristic frequency is 1-2KHz.

3. according to the array analytic expression ultrasound wave focused transducer described in claim 1, it is characterized in that: described array pattern sensing electrode (6) is made up of 11 sensing elements, and arrange along the diametric(al) in-line of array pattern sensing electrode (6), distribute in order to the sound field detecting under different angles; Each sensing element is made up of point-like sensing electrode, contact conductor and electrode welding seat three parts.Sensing element quantity and the size capable of regulating of described array pattern sensing electrode (6).

4. according to the array analytic expression ultrasound wave focused transducer described in claim 1, it is characterized in that: the method for making of array analytic expression ultrasound wave focused transducer:

1) exposure imaging, definition array electrode pattern: utilize rotary coating technology spin coating one deck photoresistance in the focusing curved end of the quartzy amasthenic lens (4) cleaning up, then utilize the anti-dazzling screen that is designed with hearth electrode pattern to cover photoresistance, and be together placed under ultraviolet parallel exposure lamp and carry out exposure imaging; Be fond of after the photoresistance decomposition of light part, utilize developer solution to wash the photoresistance that decomposes part off, now, decompose part and be the hearth electrode pattern designing;

2) evaporated metal layer, finishing patterns electrode fabrication: quartzy amasthenic lens (4) curved end completing in step 1 is utilized electron beam evaporation plating technology, evaporation 20-40nm thickness crome metal is as adhesion layer, and then the proof gold of evaporation 40-60nm thickness thereon; Now, the complete covering metal electrode of whole curved end, is attached directly on camera lens but photoresistance decomposes the metal of part, and other metals are attached on undecomposed photoresistance; Because photoresistance is dissolvable in water organic solvent, after utilizing organic solvent to clean on camera lens, the metal being attached to above photoresistance comes off naturally, leaves prefabricated pattern electrode, completes thus the making of array pattern formula sensing hearth electrode (6);

3) making of PVDF piezoelectric membrane: adopt spin coating colloidal sol crystallisation, focusing curved end at quartzy amasthenic lens (4) is passed through rotary coating machine high-temperature spin-on PVDF colloidal sol, make to be evenly adsorbed on focusing curved surface after its crystallization, complete thus the making of PVDF piezoelectric membrane (7).And then evaporation top guard electrode (8), make the equal adhesive electrodes of PVDF piezoelectric membrane (7) upper and lower surface; Upper/lower electrode is drawn and connect high voltage stabilizing source by lead-in wire and carry out step-by-step movement voltage stabilizing polarization, make PVDF piezoelectric membrane there is piezoelectric property.

4) assembling of array analytic expression ultrasonic transducer: the camera lens having polarized is put into transducer enclosure (2), and utilize couplant to paste commercial contact ultrasonic probe (3) at its top planes end to connect each receiver port, complete the making of whole transducer.