CN114071346B - Bimetallic plate clamping piezoelectric small column array structure sensing element and its preparation process - Google Patents

Abstract

The invention discloses a bimetallic plate clamping piezoelectric small column array structure sensitive element and a preparation process thereof. The sensitive element includes a piezoelectric small column array, and the piezoelectric small column array includes a plurality of piezoelectric small columns. The two ends of the electric column are respectively provided with a first metal plate and a second metal plate, and the thickness of the second metal plate is greater than that of the first metal plate; the preparation process is, step 1, cutting and pressing along the X and Y directions On the upper surface of the piezoelectric material sheet, a piezoelectric small column array with a base is formed; step 2, a second metal plate is pasted on the upper surface of the piezoelectric small column array, and then the piezoelectric material sheet is turned over, and the pressure is cut along the X and Y directions. The lower surface of the electrical material sheet forms a piezoelectric small column array that penetrates completely, and a first metal plate is attached to the lower surface of the piezoelectric small column array; the present invention is a bimetallic plate clamping the piezoelectric small column array structure sensitive element And the preparation process thereof, through the above scheme, the electromechanical coupling coefficient is improved, and the receiving sensitivity of the transducer is improved.

Description

Bimetal plate clamps piezoelectric small column array structure sensitive element and its preparation process

technical field

The invention relates to the technical field of underwater acoustic transducers, in particular to a bimetallic plate clamping piezoelectric small column array structure sensitive element and a preparation process thereof.

Background technique

The current research on medium and high frequency underwater acoustic transducers mainly focuses on two aspects:

1. Expand the working bandwidth of the transducer; expanding the bandwidth can realize the fidelity processing of underwater acoustic signals and obtain target information more accurately; at the same time, it can also accurately target the position and improve the resolution of the array.

2. Improve the sensitivity of the transducer, that is, by improving the electromechanical conversion efficiency of the transducer, to improve the transmission voltage response and reception sensitivity; improving the transmission voltage response can make the transducer emit a stronger signal under the same driving voltage. The sound pressure can generate more radiated sound energy; improving the receiving sensitivity can improve the ability of the transducer to receive weak signals, and can also increase the detection range.

To improve the sensitivity of the transducer, the main method is to improve the electromechanical conversion efficiency of the transducer, thereby improving the transmitter voltage response and the receiver sensitivity of the transducer. The electromechanical conversion efficiency of the transducer is proportional to the square of the electromechanical coupling coefficient, so improving the electromechanical conversion efficiency ultimately means improving the electromechanical coupling coefficient. How to improve the electromechanical coupling coefficient is the focus of the current transducer research, but also the difficult part. For piezoelectric materials, the electromechanical coupling coefficient k33 of the longitudinal stretching vibration mode is generally greater than the electromechanical coupling coefficient kt of the thickness vibration mode. Therefore, if the thickness vibration mode of the piezoelectric material can be converted into a longitudinal stretching vibration mode, the electromechanical coupling coefficient will be improved. The most popular piezoelectric composite structural material at present, the 1-3 type piezoelectric composite material is to change the vibration mode of the material by converting the thickness vibration of the whole piezoelectric material into the longitudinal stretching vibration of many piezoelectric small columns. performance-enhancing. By cutting a single-phase piezoelectric material into a piezoelectric small column array, the thickness vibration of the whole piezoelectric material (the electromechanical coupling coefficient kt is about 0.5) will be converted into the longitudinal length stretching vibration of the piezoelectric small column array (electromechanical coupling The coefficient k33 is about 0.7). By changing the vibration mode of the material, the electromechanical coupling coefficient of the equivalent thickness of the 1-3 piezoelectric composite material will be increased by about 20% compared with the thickness of the pure piezoelectric material. The advantages of type 1-3 piezoelectric composites are not only to improve the electromechanical coupling coefficient by changing the vibration mode, but also to add polymers between the piezoelectric small column arrays, which can also increase the loss of the material, reduce the Q value, and expand the bandwidth. , on the other hand, the cut-out small column array structure can also be reinforced. However, due to the addition of polymers between the piezoelectric pillar arrays, it also brings the following disadvantages:

(a) Increase the energy loss and reduce the electromechanical coupling coefficient;

(b) Increasing the lateral coupling between the piezoelectric small pillars is not conducive to the simplification of vibration modes and reduces the effective electromechanical coupling coefficient;

(c) The addition of lossy polymer makes the device easy to heat up, especially in the case of continuous operation of the transducer, the sensitive element will be deformed due to heat generation, which will greatly change the performance of the transducer and even damage it. .

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a sensitive element which can improve the electromechanical coupling coefficient and the sensitivity of the transducer.

In order to achieve the above purpose, the present invention provides a bimetallic plate clamping piezoelectric small column array structure sensitive element, including a piezoelectric small column array, the piezoelectric small column array includes a plurality of piezoelectric small columns, the piezoelectric Both ends of the small column are respectively provided with a first metal plate and a second metal plate with different thicknesses, and the thickness of the second metal plate is greater than that of the first metal plate; the side parts of the first metal plate and the second metal plate are A sealing shell is also provided to seal the piezoelectric small column array; the side of the second metal plate opposite to the piezoelectric small column is attached with a sound absorption layer, and the sound absorption layer is opposite to the second metal plate A metal back cover plate is arranged on one side of the metal back cover plate, a wire runs through the metal back cover plate, the positive electrode lead inside the wire is connected with the second metal plate, and the negative electrode lead inside the wire is connected with the first metal plate; A waterproof sound-transmitting layer is attached to the outer side of the sealed shell, the first metal plate, the second metal plate, the sound-absorbing layer and the metal rear cover plate.

Preferably, the cross-sectional shape of the piezoelectric small column array, the first metal plate and the second metal plate is any one of a square, a rectangle and a circle.

Preferably, the sound absorbing layer is a rigid foam.

Preferably, the waterproof sound-permeable layer is formed by sealing and curing with polyurethane.

A preparation process for a bimetallic plate clamping piezoelectric small column array structure sensitive element, comprising the steps: step 1, cutting the upper surface of the piezoelectric material sheet along the X and Y directions to form a piezoelectric small column array with a substrate; step 2 , paste a second metal plate on the upper surface of the piezoelectric small column array, then turn the piezoelectric material sheet, and cut the lower surface of the piezoelectric material sheet along the X and Y directions to form a completely penetrating piezoelectric small column array. A first metal plate is attached to the lower surface of the piezoelectric small column array; step 3, a sealing shell is sleeved on the side of the piezoelectric small column array to seal the piezoelectric small column array; step 4, in A rigid foam is attached to the side of the second metal plate opposite to the piezoelectric small column array as a sound absorption layer, and a metal back cover is attached to the side of the rigid foam opposite to the second metal plate, A wire runs through the middle of the metal back cover, and the positive electrode lead and the negative electrode lead inside the wire are drawn out from between the rigid foam and the metal back cover, wherein the positive electrode lead is connected to the The second metal plate is connected, and the negative electrode lead is connected to the first metal plate; step 5, in the sealed casing, the first metal plate, the second metal plate, the sound absorbing layer and the metal The outer side of the rear cover is coated with polyurethane to form a waterproof and sound-transmitting layer by glue sealing and curing.

Therefore, the present invention adopts the bimetallic plate with the above-mentioned structure to clamp the piezoelectric small column array structure sensitive element and its preparation process, and has the following advantages: filling the gap of the piezoelectric small column with air instead of polymer can fully highlight the piezoelectric small column. Longitudinal vibration behavior, so that the thickness vibration of the piezoelectric material is reflected as the longitudinal vibration behavior of the piezoelectric small column to a greater extent, thereby improving the electromechanical coupling coefficient; the first metal plate with a thin cover can amplify the stress of the piezoelectric small column and improve the energy conversion. The receiving sensitivity of the transducer is improved; the function of the rear mass block is realized by the thick second metal plate, which further improves the sensitivity of the transducer; at the same time, the thick second metal plate can be used as a base to avoid the dispersion of the piezoelectric small column.

The technical solutions of the present invention will be further described in detail below through the accompanying drawings and embodiments.

Description of drawings

1 is a schematic structural diagram of a piezoelectric array in which a bimetal plate clamps a piezoelectric small column array structural sensitive element of the present invention;

2 is a schematic diagram of the packaging of a bimetallic plate clamping piezoelectric small column array structure sensitive element of the present invention;

3 is a schematic structural diagram of a bimetallic plate clamping piezoelectric small column array structure sensitive element of the present invention;

4 is a schematic structural diagram of a metal back cover plate of a bimetallic plate clamping a piezoelectric small column array structural sensitive element according to the present invention;

Fig. 5 is the conductance curve diagram of the first metal plate and the second metal plate clamping the piezoelectric small column array structure;

Fig. 6 is the vibration displacement diagram of the piezoelectric small column array structure clamped by the first metal plate and the second metal plate at the resonance, wherein (a) is the case where the vibration phase angle θ is 0°, (b) is the vibration When the phase angle θ is 180°;

Figure 7 is a graph of the transmit voltage response and receive sensitivity of the "PZT pillar array structure with epoxy added" transducer, wherein (a) graph is the transmit voltage response, and (b) graph is the receive sensitivity;

FIG. 8 is a graph showing the transmit voltage response, receive sensitivity, transmit sound source level and directivity of the transducer with the piezoelectric pillar array structure sandwiched between the first metal plate and the second metal plate, wherein (a) is the transmit voltage response , (b) is the receiving sensitivity, (c) is the emission sound source level, (d) is the directivity diagram.

reference number

1. Piezoelectric small column array; 2. The first metal plate; 3. The second metal plate; 4. Sealed shell; 5. Sound absorption layer; 6. Metal back cover; 9. Negative electrode lead; 10. Waterproof sound-permeable layer; 11. Piezoelectric small column.

Detailed ways

The technical solutions of the present invention will be further described below through the accompanying drawings and embodiments.

Unless otherwise defined, technical or scientific terms used in the present invention should have the ordinary meaning as understood by one of ordinary skill in the art to which the present invention belongs. The terms "first," "second," and similar terms used herein do not denote any order, quantity, or importance, but are merely used to distinguish different components. "Comprises" or "comprising" and similar words mean that the elements or things appearing before the word encompass the elements or things recited after the word and their equivalents, but do not exclude other elements or things. Words like "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "Down", "Left", "Right", etc. are only used to represent the relative positional relationship, and when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

Example

As shown in the figure, the structure of the present invention is a bimetallic plate clamping piezoelectric small column array structural sensitive element, including a piezoelectric small column array 1, and the piezoelectric small column array 1 includes a plurality of piezoelectric small columns 11, so Both ends of the piezoelectric small column 11 are respectively provided with a first metal plate 2 and a second metal plate 3 with different thicknesses, and the thickness of the second metal plate 3 is greater than that of the first metal plate 2; 2 and the side of the second metal plate 3 are also provided with a sealing shell 4 to seal the piezoelectric small column array 1; Layer 5, the side of the sound-absorbing layer 5 opposite to the second metal plate 3 is provided with a metal back cover 6, and a wire 7 runs through the metal back cover 6, and the positive electrode lead 8 inside the wire 7 is connected to the The second metal plate 3 is connected, the negative electrode lead 9 inside the wire 7 is connected with the first metal plate 2; the sealed casing 4, the first metal plate 2, the second metal plate 3, the The sound-absorbing layer 5 and the outer side of the metal rear cover plate 6 are jointly attached with a waterproof sound-transmitting layer 10 .

Fig. 1 is a schematic diagram of the structure of "piezoelectric small column array 1", the structure includes piezoelectric small column array 1 formed by vertical cutting of piezoelectric ceramics, and the gap between the piezoelectric small columns 11 is filled with air instead of polymer, The first metal plate 2 and the second metal plate 3 with different thicknesses are pasted on the upper and lower surfaces of the piezoelectric small column 11. This structure has the following characteristics:

(1) Usually people are accustomed to preparing 1-3 type and 1-3-2 type piezoelectric composite materials by the cutting-filling method. The polymer filled between the piezoelectric small columns 11 is generally epoxy resin or silicone rubber, so The prepared piezoelectric composite material makes the piezoelectric material change from the overall thickness vibration mode to the longitudinal stretching vibration mode of the piezoelectric small column array 1, thereby improving the electromechanical coupling coefficient. However, due to the addition of the polymer, the loss is increased, and the electromechanical coupling coefficient is reduced at the same time. The "piezoelectric small column array 1 structure without adding polymer" of the present invention, filling the gap of the piezoelectric small column 11 with air instead of polymer, can fully highlight the longitudinal vibration behavior of the piezoelectric small column 11, and make the thickness of the piezoelectric material The vibration is reflected to a greater extent as the longitudinal vibration behavior of the piezoelectric small column array 1, which can maximize the electromechanical coupling coefficient. In the present invention, the first metal plate 2 and the second metal plate 3 clamp the piezoelectric small column 11, which is an improvement on the basis of the composite material, that is, the polymer part of the piezoelectric composite material is removed, And the upper and lower surfaces are covered with metal plates of different thicknesses, reflecting the d33 vibration mode of the piezoelectric small column array 1, and obtaining a high coupling coefficient. On the one hand, the electromechanical coupling coefficient of the piezoelectric material is changed from kt to k33, The electromechanical coupling coefficient is improved, and on the other hand, the lateral coupling between the piezoelectric pillars is eliminated, so that the vibration mode of the entire material thickness becomes simple, and the effective electromechanical coupling coefficient is improved.

w和w₁分别为阵列单元和压电小柱11的宽度。所述压电小柱11上的应力大于声场中的声压，即所述金属盖板起到了应力放大上的作用。这种应力放大作用会使所述压电小柱11的极化电场增大，从而增大输出感应电压，进而对于接收换能器来说，通过应力放大可提高接收灵敏度。厚度较厚的所述第二金属板3可以起到后质量块的作用，通过质量较大的金属板，阻止敏感元件向后方辐射声能，从而进一步提高了换能器的灵敏度。另外所述第一金属板2和所述第二金属板3还能起到框架支撑作用，防止所述压电小柱11件间分散。(2) The first metal plate 2 is a metal plate with a relatively thin thickness, which can transmit the sound pressure from the sound field to each of the piezoelectric small columns 11 , thereby increasing the pressure in the piezoelectric small column 11 . The stress plays a role in stress amplification. As shown in Figure 3, the ratio of the stress generated on the piezoelectric small column 11 to the sound pressure in the sound field is

w and w ₁ are the widths of the array unit and the piezoelectric pillars 11, respectively. The stress on the piezoelectric small column 11 is greater than the sound pressure in the sound field, that is, the metal cover plate plays a role in stress amplification. This stress amplification effect will increase the polarization electric field of the piezoelectric small column 11, thereby increasing the output induced voltage, and further, for the receiving transducer, the receiving sensitivity can be improved through the stress amplification. The thick second metal plate 3 can play the role of a rear mass block, and the sensitive element can be prevented from radiating sound energy to the rear through the metal plate with a relatively large mass, thereby further improving the sensitivity of the transducer. In addition, the first metal plate 2 and the second metal plate 3 can also play a frame supporting role to prevent the piezoelectric small pillars 11 from being scattered.

Preferably, the structural shape of the first metal plate 2 and the second metal plate 3 sandwiched by the piezoelectric small column array 1 in plan view includes but is not limited to the square in FIG. 1 , and may also be a rectangle or a circle. Wait.

In this embodiment, the cross-sectional shapes of the piezoelectric small column array 1 , the first metal plate 2 and the second metal plate 3 are any one of a square, a rectangle and a circle.

In this embodiment, the sound absorbing layer 5 is a rigid foam.

In this embodiment, the waterproof sound-transmitting layer 10 is formed by sealing and curing with polyurethane.

A preparation process for a bimetallic plate clamping piezoelectric small column array structure sensitive element, comprising the following steps: step 1, cutting the upper surface of the piezoelectric material sheet along the X and Y directions to form a piezoelectric small column array 1 with a substrate; step 2. Paste the second metal plate 3 on the upper surface of the piezoelectric small column array 1, then flip the piezoelectric material sheet, and cut the lower surface of the piezoelectric material sheet along the X and Y directions to form a completely penetrating piezoelectric small column Array 1, a first metal plate 2 is attached to the lower surface of the piezoelectric small column array 1; Step 3, a sealing shell is sleeved on the side of the piezoelectric small column array 1 to seal the piezoelectric small column array 1. Column array 1; Step 4, a rigid foam is attached to the side of the second metal plate 3 opposite to the piezoelectric small column array 1 as a sound-absorbing layer 5, and the rigid foam is opposite to the second metal A metal back cover 6 is attached to one side of the board 3, a wire 7 runs through the middle of the metal back cover 6, and the positive electrode lead 8 and the negative electrode lead 9 inside the wire 7 are removed from the rigid foam. and the metal back cover 6, wherein the positive electrode lead 8 is connected to the second metal plate 3, and the negative electrode lead 9 is connected to the first metal plate 2; step 5, in the The outer sides of the sealed casing 4 , the first metal plate 2 , the second metal plate 3 , the sound absorbing layer 5 and the metal rear cover plate 6 are coated with polyurethane to be glue-sealed and cured to form a waterproof sound-transmitting layer 10 .

Using the structure of the first metal plate 2 and the second metal plate 3 to clamp the piezoelectric small column array 1, the package structure of the transducer is prepared as shown in FIG. 2, the motor on the upper and lower surfaces of the sensitive element is The electrode leads are drawn out, and then bonded together with the rigid foam and the metal back cover 6, and the whole is sealed with polyurethane glue, which is cured to form a waterproof sound-transmitting layer 10, and the fabrication of the transducer is completed. Place the transducer in the anechoic pool, and conduct full performance tests according to relevant standards, including the transducer's emission voltage response, receiving sensitivity, frequency bandwidth, and directivity.

The following is the feasibility analysis and experimental test:

(1) Through the stress amplification, the receiving sensitivity of the transducer can be improved. As shown in Figure 3, the sound pressure from the sound field, that is, the pressure on the upper surface of the sensitive element is p, the longitudinal stress on the piezoelectric small column 11 is T ₃ , and the metal plate is very thin (the thickness of the metal plate is much smaller than the wavelength of the sound wave in the metal plate). ), the sound pressure p acts on the piezoelectric small column 11 through the metal plate, and the stress on the piezoelectric small column 11 can be approximated as:

In the formula, w and w ₁ are the widths of the array unit and the piezoelectric small column 11, respectively.

The stress acting on the piezoelectric small column 11 is greater than the sound pressure in the external sound field. Through the piezoelectric effect, the electric field on the piezoelectric small column 11 increases, and the voltage between the upper and lower plates increases accordingly. The receiving sensitivity of the material is improved.

Using the g-type piezoelectric equation:

为恒应力下的介电隔离率,D₃为沿所述压电小柱11长度方向的电位移。在仅考虑应力的情况下，E₃＝-g₃₃T₃，这样所述压电小柱11上产生的电压为：In the _formula , E3 is the electric field intensity along the length direction of the piezoelectric small column 11, _g33 is the piezoelectric (stiffness) constant,

is the dielectric isolation rate under constant stress, and D ₃ is the electrical displacement along the length direction of the piezoelectric small column 11 . In the case of considering only the stress, E ₃ =-g ₃₃ T ₃ , so the voltage generated on the piezoelectric small column 11 is:

V=-g ₃₃ T ₃ h ₁

倍。In the formula, h ₁ is the height of the small column, h is the height of the piezoelectric material (piezoelectric small column 11), and the receiving sensitivity of the transducer is approximately improved.

times.

Therefore, the structure can improve the receiving sensitivity of the transducer through the metal plate.

(2) Performance test and comparison of transducers

In this example, the PZT-5A piezoelectric ceramic material is cut to obtain the structure of the piezoelectric small column array 1, and the metal plate and the cut piezoelectric small column array 1 are bonded together with conductive glue to obtain an upper and lower structure. PZT pillar array structure with copper cover plates of different thicknesses on the surface. Impedance analyzer and laser vibrometer were used to test the components of "PZT small column array structure with copper cover", and the test results are shown in Figures 5 and 7. It can be seen from the conductance curve in Figure 5 that the resonant frequency is 158kHz; from the vibration displacement diagram in Figure 6 (theta in the figure represents the vibration phase angle), it can be seen that the entire copper cover plate vibrates up and down in unison during resonance.

The present invention produces a "PZT small column array structure with epoxy resin added + metal plates with different thicknesses up and down" transducers with the same size. The transmit voltage response and receive sensitivity were tested respectively in the anechoic pool. Figure 7 is the transmit voltage response ((a) graph) and receive sensitivity ( (b) figure), Figure 8 is the transmit voltage response ((a) figure) and receive sensitivity ((b) figure) of the "PZT pillar array structure without polymer addition" transducer.

In Figure 7, the "PZT pillar array structure with epoxy resin added" transducer has a transmit voltage response of 157dB and a receive sensitivity of -195dB. In Figure 8, the "PZT small column array structure without adding polymer" transducer has a transmit voltage response of 163dB, an increase of 6dB; the receiving sensitivity reaches -180dB, an increase of 15dB. It can be seen that the performance of the transducer with the structure of "the first metal plate 2 and the second metal plate 3 sandwiching the piezoelectric small column array 1" is superior to that of the transducer of the "piezoelectric small column array 1 structure with epoxy resin added".

Therefore, the present invention adopts the bimetallic plate with the above-mentioned structure to clamp the piezoelectric small column array structure sensitive element and its preparation process, and has the following advantages: filling the gap of the piezoelectric small column with air instead of polymer can fully highlight the piezoelectric small column. Longitudinal vibration behavior, so that the thickness vibration of the piezoelectric material is reflected as the longitudinal vibration behavior of the piezoelectric small column to a greater extent, thereby improving the electromechanical coupling coefficient; the first metal plate with a thin cover can amplify the stress of the piezoelectric small column and improve the energy conversion. The receiving sensitivity of the transducer is improved; the function of the rear mass block is realized by the thick second metal plate, which further improves the sensitivity of the transducer; at the same time, the thick second metal plate can be used as a base to avoid the dispersion of the piezoelectric small column; compared with For a single metal plate (the other side of which is a ceramic substrate that is not cut through, and the effective electromechanical coupling coefficient of the thickness vibration of the substrate is kt=0.5, and the electromechanical coupling coefficient of the piezoelectric small column length stretching vibration is k33=0.7), the electromechanical coupling coefficient is The increase, and the thick metal plate as a weight, can also increase the emission voltage response of the sensitive element.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: it is still The technical solutions of the present invention may be modified or equivalently replaced, and these modifications or equivalent replacements cannot make the modified technical solutions depart from the spirit and scope of the technical solutions of the present invention.

Claims (5)

1. The sensitive element with the structure that the double metal plates clamp the piezoelectric small column array is characterized by comprising the piezoelectric small column array, wherein the piezoelectric small column array comprises a plurality of piezoelectric small columns, a first metal plate and a second metal plate which are different in thickness are arranged at two ends of each piezoelectric small column respectively, and the thickness of the second metal plate is larger than that of the first metal plate; the side parts of the first metal plate and the second metal plate are also provided with a sealing shell so as to seal the piezoelectric small column array; a sound absorption layer is attached to one surface, opposite to the piezoelectric pillar, of the second metal plate, a metal rear cover plate is arranged on one surface, opposite to the second metal plate, of the sound absorption layer, a lead penetrates through the metal rear cover plate, a positive electrode lead inside the lead is connected with the second metal plate, and a negative electrode lead inside the lead is connected with the first metal plate; the outer sides of the sealing shell, the first metal plate, the second metal plate, the sound absorption layer and the metal rear cover plate are jointly attached with a waterproof sound-transmitting layer.

2. The bimetal plate-sandwiched piezoelectric pillar array structure sensor as claimed in claim 1, wherein the cross-sectional shapes of the piezoelectric pillar array, the first metal plate and the second metal plate are any one of a square, a rectangle and a circle.

3. The sensitive element of claim 1, wherein the sound absorption layer is rigid foam.

4. The sensitive element of claim 1, wherein the waterproof sound-transmitting layer is formed by sealing and curing polyurethane.

5. A preparation process of a sensitive element with a bimetallic plate clamping piezoelectric small column array structure is characterized by comprising the following steps:

step 1, cutting the upper surface of a piezoelectric material sheet along the direction X, Y to form a piezoelectric small column array with a substrate;

step 2, adhering a second metal plate to the upper surface of the piezoelectric pillar array, then overturning the piezoelectric material sheet, cutting the lower surface of the piezoelectric material sheet along the direction X, Y to form a completely penetrated piezoelectric pillar array, adhering a first metal plate to the lower surface of the piezoelectric pillar array, wherein the thickness of the second metal plate is larger than that of the first metal plate;

step 3, sleeving a sealing shell on the side part of the piezoelectric small column array to seal the piezoelectric small column array;

step 4, attaching rigid foam as a sound absorption layer to one surface, opposite to the piezoelectric pillar array, of the second metal plate, attaching a metal rear cover plate to one surface, opposite to the second metal plate, of the rigid foam, penetrating a lead in the middle of the metal rear cover plate, and leading out a positive electrode lead and a negative electrode lead inside the lead from a position between the rigid foam and the metal rear cover plate, wherein the positive electrode lead is connected with the second metal plate, and the negative electrode lead is connected with the first metal plate;

and 5, coating polyurethane on the outer sides of the sealed shell, the first metal plate, the second metal plate, the sound absorption layer and the metal rear cover plate to seal and solidify into a waterproof sound transmission layer.

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