A high-frequency sensor and a manufacturing method thereof

Abstract

The present invention relates to the technical field of sensors, in particular to a high-frequency sensor and a manufacturing method thereof. The high-frequency sensor includes a first matching layer, a PCB circuit board, a piezoelectric ceramic sheet, and a second matching layer disposed in a housing. One side of the first matching layer is connected to the upper bottom surface of the housing, the other side of the first matching layer is connected to one side of the PCB circuit board, the other side of the PCB circuit board is connected to one side of the piezoelectric ceramic sheet, the other side of the piezoelectric ceramic sheet is connected to the second matching layer, and the other side of the second matching layer is used for transmitting ultrasonic signals outward. The high-frequency sensor further includes a damping glue layer disposed outside the second matching layer, and an arc structure is provided on the damping glue layer. The present invention also protects a method for manufacturing the above-mentioned sensor with an arc structure. The design of the arc structure can prevent the transmitted sound pressure and received sensitivity of the product itself from being affected by the forced clamping of the housing wall. The manufacturing of the arc structure is easy to implement, with simple process, low cost, and less time consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, in particular to a high-frequency sensor and a manufacturing method thereof. Background Art

[0002] An ultrasonic sensor emits ultrasonic signals of a certain frequency and receives echo signals. By the time difference between the transmitted and received signals, the distance between the object causing the signal reflection and the sensor is obtained. Therefore, this solution is commonly used for foreign object detection or distance detection in the field of artificial intelligence. Generally, the higher the ultrasonic frequency emitted by the sensor, the more beneficial it is to detect objects at close range. With high sensitivity to objects at close range, intelligent devices can make corresponding processing faster. Therefore, the industry continuously increases the frequency of ultrasonic sensors to detect objects at closer ranges.

[0003] However, as the frequency increases, the time for the measured object to return the echo signal becomes shorter. In extreme cases, before the after-vibration of the ultrasonic sensor itself ends, the echo signal has already arrived. The superposition of the after-vibration and the echo signal will affect the accuracy of distance measurement. Therefore, when each manufacturer considers increasing the ultrasonic frequency, they are also considering enhancing the echo signal to facilitate the accurate acquisition of the echo signal. Summary of the Invention

[0004] The object of the present invention is to improve the structure to enhance the echo signal and propose a high-frequency sensor and a manufacturing method thereof for the problem that when the ultrasonic frequency is relatively high, the echo signal is weak and it is difficult to extract the echo signal from the superimposed after-vibration and echo signals.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A high-frequency sensor includes a housing, a first matching layer, a PCB circuit board, a piezoelectric ceramic sheet, and a second matching layer. The first matching layer, the PCB circuit board, the piezoelectric ceramic sheet, and the second matching layer are arranged in the housing. One side of the first matching layer is connected to the upper bottom surface of the housing, the other side of the first matching layer is connected to one side of the PCB circuit board, and the other side of the PCB circuit board is connected to one side of the piezoelectric ceramic sheet. The other side of the piezoelectric ceramic sheet is connected to the second matching layer, and the other side of the second matching layer is used to transmit ultrasonic signals outward.

[0007] It further includes a damping glue layer, which is arranged outside the second matching layer, and an arc structure is arranged on the damping glue layer.

[0008] As a preferred solution of the present invention, the density range of the first matching layer is 0.7 g / cm 3 -2.0 g / cm 3 .

[0009] As a preferred embodiment of the present invention, it is characterized in that the density range of the second matching layer is 0.4 g / cm³ - 0.8 g / cm³ 3 .

[0010] As a preferred embodiment of the present invention, the material of the second matching layer is one of epoxy materials, polyurethane materials, rubber, plastic or silicone rubber.

[0011] As a preferred embodiment of the present invention, the arc-shaped structure is an arc segment in the cross-sectional view of the sensor, and the line segment length between the two end points of the arc segment is greater than 1 wavelength of the ultrasonic signal.

[0012] As a preferred embodiment of the present invention, the width of the damping glue layer in the radial direction of the sensor is greater than 1.5 wavelengths.

[0013] As a preferred embodiment of the present invention, the height of the damping glue layer in the axial direction is more than 2 wavelengths higher than the rear end face of the piezoelectric ceramic chip.

[0014] As a preferred embodiment of the present invention, the outer shell is in a stepped shape, and the stepped shape divides the outer shell into a vertical plane and a horizontal plane. A card slot structure is provided at the connection of the vertical plane and the horizontal plane, and the card slot structure makes the vertical plane recess into the shell body.

[0015] As a preferred embodiment of the present invention, the ultrasonic frequencies emitted by the sensor are 300 KHz, 350 KHz and 400 KHz,

[0016] When the frequency is 300 KHz, the size of the ceramic chip is between 6.5 - 9 mm in diameter and between 0.4 - 0.8 mm in thickness, and the thickness of the second matching layer is between 1.7 - 2.5 mm;

[0017] When the frequency is 350 KHz, the size of the piezoelectric ceramic chip is between 6 - 8 mm in diameter and between 0.5 - 0.9 mm in thickness, and the thickness of the second matching layer is between 1.5 - 2.3 mm;

[0018] When the frequency is 400 KHz, the size of the piezoelectric ceramic chip is between 4 - 6 mm in diameter and between 0.7 - 1.5 mm in thickness, and the thickness of the second matching layer is between 1.0 - 2.0 mm.

[0019] Based on the same concept, the present invention also proposes a manufacturing method of a high-frequency sensor. The implementation method of the arc-shaped structure includes the following steps:

[0020] A. After completing the installation of the housing, the first matching layer, the PCB circuit board, the piezoelectric ceramic chip and the second matching layer, apply a layer of primer inside the damping glue layer, and keep the primer 3 - 5 mm away from the upper end face; the upper end face refers to the plane that is flush with the side of the second matching layer for transmitting ultrasonic signals outward;

[0021] B. Dry the primer glue;

[0022] C. Apply another layer of glue on the surface of the primer glue, and keep the glue surface level with the upper end surface;

[0023] D. Place it with the upper end surface facing up, and dry the glue to form an arc-shaped structure of the damping glue layer;

[0024] By controlling the amount of glue applied in step C, the shape of the arc-shaped structure can be adjusted.

[0025] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows:

[0026] 1. An arc-shaped structure is provided in the damping glue layer outside the second matching layer. The design of the arc-shaped structure can make the transmitted sound pressure and received sensitivity not affected by the forced clamping of the housing wall, enhance the intensity of the transmitted signal and the echo signal, and improve the accuracy of short-distance ranging when using an ultrasonic sensor for high-frequency ranging.

[0027] 2. When applying the damping glue layer, utilize the self-weight of the glue to form a depression on the surface, thereby forming an arc-shaped structure. It is easy to implement in terms of technology, reduces the amount of glue used, and lowers the cost.

[0028] 3. The fundamental reason affecting the sensitivity of the second matching layer and the ultrasonic signal bandwidth is the matching of the material of the second matching layer with the acoustic impedance of air. The density range of the material of the second matching layer under the optimal acoustic impedance matching for air is obtained through calculation, and the density range of the first matching layer is also given, which is convenient for material selection.

[0029] 4. The thickness of the damping glue on both sides has a preset thickness range and height range. The height of the damping glue layer in the axial direction is more than 2 wavelengths behind the rear end surface of the piezoelectric ceramic sheet, and the vibration reflection signals more than 2 wavelengths can be fully absorbed.

[0030] 5. A card slot is added to the structure of the ultrasonic sensor. This card slot is not only used for the connection between components but also used to solve the problem of glue overflow when bonding. During the bonding process, the excess glue can be squeezed into the card slot and will not overflow to the outside. Such a design reduces the problem of cumbersome installation steps caused by glue overflow during the installation process.

[0031] 6. Based on the structure of this case, the matching values of the size of the piezoelectric ceramic sheet and the thickness of the second matching layer at ultrasonic frequencies of 300 KHz, 350 KHz, and 400 KHz are specifically given, which is convenient for type selection during assembly. Description of the Drawings

[0032] Figure 1 It is a structural diagram of a high-frequency sensor in Embodiment 1 of the present invention;

[0033] Figure 2 It is the side view of the high-frequency sensor in Embodiment 1 of the present invention;

[0034] Figure 3 It is the enlarged side view of the arc structure in Embodiment 1 of the present invention;

[0035] Figure 4 It is the side perspective view of the arc structure at a 45° angle in Embodiment 1 of the present invention;

[0036] Figure 5 It is the upward perspective view of the arc structure at the upward view angle in Embodiment 1 of the present invention;

[0037] Figure 6 It is the upward view line drawing of the arc structure at the upward view angle in Embodiment 1 of the present invention;

[0038] Figure 7 It is the side perspective of the high-frequency sensor in Embodiment 1 of the present invention Figure 2 ;

[0039] Figure 8 It is the three-dimensional side view of the high-frequency sensor in Embodiment 1 of the present invention;

[0040] Figure 9 It is the schematic diagram of the sensor placed with the glue injection surface facing up in Embodiment 2 of the present invention.

[0041] Reference numerals: 1 - terminal wire, 2 - epoxy resin glue, 3 - AB two-component glue, 4 - negative wire enameled wire, 5 - 232 glue, 6 - sealant, 7 - small plastic shell, 8 - positive wire enameled wire, 9 - PCB circuit board, 10 - piezoelectric ceramic sheet, 11 - matching layer glue, 12 - arc structure. Detailed implementation manners

[0042] The present invention will be described in detail below with reference to the drawings.

[0043] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0044] Embodiment 1

[0045] A high-frequency sensor includes a housing, a first matching layer, a PCB circuit board, a piezoelectric ceramic sheet, and a second matching layer. The first matching layer, the PCB circuit board, the piezoelectric ceramic sheet, and the second matching layer are arranged inside the housing. One side of the first matching layer abuts against the housing, and the other side of the first matching layer abuts against the upper surface of the PCB circuit board. Moreover, the lower surface of the PCB circuit board abuts against the upper surface of the piezoelectric ceramic sheet, and the lower surface of the piezoelectric ceramic sheet abuts against the second matching layer. The other side of the second matching layer is used to transmit ultrasonic signals outward, and the connection between the other side of the second matching layer and the housing has an arc-shaped structure. It also includes a damping glue layer, which is arranged outside the second matching layer, and an arc-shaped structure is arranged on the damping glue layer.

[0046] Specifically, the internal structure diagram of the high-frequency sensor is as Figure 1 shown. The epoxy resin glue 2 on the upper bottom surface and the circumferential surface form a cylindrical cavity, and this cylindrical cavity is the housing. The inside of the housing is used to accommodate the first matching layer, the PCB circuit board, the piezoelectric ceramic sheet, and the second matching layer. The AB two-component glue 3 (which is also the first matching layer) is attached to the inside of the upper bottom surface. The thickness of the AB two-component glue 3 is relatively thick, mainly used to absorb the ultrasonic signals upward from the piezoelectric ceramic sheet, so that the ultrasonic signals are concentrated and transmitted outward from the second matching layer. The next layer attached to the AB two-component glue 3 is the PCB circuit board 9. The PCB circuit board 9 is mainly used to provide a power supply and a matching circuit for the piezoelectric ceramic sheet 10. A layer of 232 glue 5 is coated on the lower surface of the PCB circuit board 9, and the upper surface of the piezoelectric ceramic sheet 10 is adhered to the PCB circuit board 9 through the 232 glue 5. A layer of matching glue is coated on the lower surface of the piezoelectric ceramic sheet 10, and this matching glue forms the second matching layer after solidification. The internal structure diagram of the assembled high-frequency sensor in side view is as Figure 1 shown. The external side view of the high-frequency sensor is as Figure 2 shown.

[0047] The terminal wire 1 passes through the upper bottom surface and is used to introduce an external power supply into the PCB circuit board 9, so that the piezoelectric ceramic sheet 10 has a stable working power supply. The negative wire-wrapped wire 4 and the positive wire-wrapped wire 8 are used to input the power on the PCB circuit board 9 into the piezoelectric ceramic sheet 10.

[0048] As a preferred solution, the first matching layer, the PCB circuit board, the piezoelectric ceramic sheet, and the second matching layer are fixed in a small plastic shell 7 to form a monomer, and then the monomer is placed into the housing, making the assembly more efficient and convenient.

[0049] Furthermore, the density range of the second matching layer determines the impedance of the matching glue layer. When the density range of the second matching layer is 0.4 g / cm 3When it is -0.8 g / cm, the calculated impedance value is conducive to the sensor transmitting detection signals outward using high-frequency ultrasonic signals. The material of the second matching layer can be selected from epoxy materials, polyurethane materials, rubber, plastic, or silicone rubber. In addition, the sealant 6 (vibration damping glue layer) outside the second matching layer in the housing has an arc structure 12. The arc structure 12 and the acoustic impedance layer form an obvious acoustic impedance mismatch, effectively increasing the scattering of ultrasonic signals on the surface.

[0050] The vibration damping glue layer outside the second matching layer, that is, Figure 1 the sealant 6 in [reference], is symmetric on both sides of the second matching layer in the side view, and the radial width of the sealant 6 is greater than 1.5 mm. For example, at a frequency of 300 Khz, this width is greater than 1.5 wavelengths, so the width is greater than 1.5 mm. The axial height of the sealant 6 is higher than the rear end face of the piezoelectric ceramic sheet 10 by more than 2 wavelengths. The aforementioned height of the sealant 6 can fully absorb the vibration reflection signals of more than 2 wavelengths.

[0051] The side view enlarged drawing of the arc structure 12 is as Figure 3 shown. The design of the arc structure 12 can make the transmitted sound pressure and received sensitivity not affected by the forced clamping of the housing wall. The arc structure is located in the area of the sealant 6 in the side view and is arc-shaped in the cross-sectional view of the sensor. The distance between the two end points of the arc is greater than 1 wavelength of the ultrasonic signal output by the sensor. Since the outer diameter of the arc structure is greater than 1 wavelength of the ultrasonic signal output by the sensor, it can avoid the formation of diffuse reflection of ultrasonic signals at the concave layer on the surface of the arc structure, reduce the echo interference, and thus ensure that the product sensitivity is not affected by clutter interference. When manufacturing this sensor, turn the housing upside down with the opening facing up, and then fill in the materials inside in sequence. A small plastic shell 7, AB two-component glue 3, negative wire-wrapped wire 4, 232 glue 5, positive wire-wrapped wire 8, PCB circuit board 9, piezoelectric ceramic sheet 10, and matching layer glue 11 are all located inside the small plastic shell 7, which is convenient for installation and fixation during filling. The part between the outside of the small plastic shell and the housing is used to fill the sealant. When the sealant is just filled in, it is in a liquid state. Due to the action of gravity, an arc structure 12 is formed on the surface. When filling the sealant for each sensor, as long as the weight of the sealant is the same, the formed arc structure is also the same. When the sealant solidifies, a groove with a cross-sectional arc structure is formed on the surface. The arc structure reduces the clamping effect of the sealant layer on the vibration of the second matching layer. If the arc structure is flat, the second matching layer 11 will be directly transmitted to the plane of the sealant 6 through the small plastic shell 7. The relatively thick side has a greater clamping effect on the side wall. After changing to an arc structure, the relatively thick side becomes thinner, and the clamping effect of the side wall becomes smaller, which is beneficial to the transmission of vibration signals.

[0052] Figure 4 is the side view three-dimensional drawing of the arc structure at a 45° angle.Figure 5 is the upward perspective three-dimensional view of the arc structure. As can be seen from Figure 4 and Figure 5 , in the three-dimensional structure diagram, the arc structure is a groove with a semi-circular cross-section in the sealant 6. The upward perspective line drawing of the arc structure under the upward perspective is as shown in Figure 6 .

[0053] The outer shell of the high-frequency sensor is stepped. The side view of the high-frequency sensor is as shown in Figure 2 ; the three-dimensional side view of the high-frequency sensor is as shown in Figure 7 . As can be seen from Figure 8 Figure 7 and Figure 8 , the step divides the outer shell into a vertical surface and a horizontal surface. A card slot structure is provided at the connection of the vertical surface and the horizontal surface. The card slot structure makes the vertical surface concave into the shell body. The concave part can be a single or multiple circular ring structures, or a thread structure. During the installation of the high-frequency sensor onto other products, this card slot is not only used for snap connection between components, but also used to solve the problem of excessive glue overflow during bonding. During the bonding process, the excess glue can be squeezed into the card slot without overflowing to the outside. Such a design reduces the problem of cumbersome installation steps caused by glue overflow during the installation process.

[0054] Figure 1 On the basis of the high-frequency sensor structure as shown in Figure 1 , the ultrasonic frequencies emitted by the sensor are designed to be 300KHz, 350KHz, and 400KHz. When the frequencies are preferably 300KHz, 350KHz, and 400KHz, the size matching between the ceramic chip and the second matching layer glue is as follows:

[0055] 1) When the frequency is 300KHZ, the size of the ceramic chip is that the diameter is between 6.5 - 9mm and the thickness is between 0.4 - 0.8mm, and the thickness of the second matching layer is between 1.7 - 2.5mm;

[0056] 2) When the frequency is 350KHZ, the size of the ceramic chip is that the diameter is between 6 - 8mm and the thickness is between 0.5 - 0.9mm, and the thickness of the second matching layer is between 1.5 - 2.3mm;

[0057] 3) When the frequency is 400KHZ, the size of the ceramic chip is that the diameter is between 4 - 6mm and the thickness is between 0.7 - 1.5mm, and the thickness of the second matching layer is between 1.0 - 2.0mm.

[0058] The fundamental reason affecting the sensitivity and bandwidth of the air-borne transducer is the serious mismatch between the transducer material (such as PZT) and the air acoustic impedance. Their acoustic impedance rates are ZC1~35MRAYL and ZA = 0.0004MRAYL respectively. Generally, a 1 / 4 wavelength second matching layer is used. When the acoustic impedance When it is 1 / 4 wavelength, the acoustic wave transmission coefficient is the largest. In the formula, Z c , Z p are respectively the acoustic impedance rates of the piezoelectric ceramic sheet and the propagation medium (the acoustic impedance rate is the product of the sound speed and density of the material). In order to obtain the best acoustic impedance matching, for air, select Z c = 33 MRAYL (acoustic impedance rate of piezoelectric ceramic), and for air Z p = 0.0044 MRAYL. Then the acoustic impedance rate is around , and through calculation, the optimal material density of different materials is between 0.4 - 0.8 g / cm³.

[0059] Example 2

[0060] In the method of manufacturing a high - frequency sensor, the arc of the arc - shaped structure 12 is completed in the following way:

[0061] A) Place the semi - finished sensor with all components installed in the small plastic shell 7 face - up on the dispensing tooling, set the dispensing time and dispensing air pressure of the dispenser, and use a No. 6 needle to apply a layer of primer in the side glue layer, keeping the glue 3 - 5 mm away from the upper end face. The schematic diagram of the sensor placed face - up on the dispensing surface is as shown in Figure 9 . The upper end face refers to the plane that is flush with the side of the second matching layer for transmitting ultrasonic signals outward.

[0062] B) Place the product with glue applied in an oven at 60 degrees for 1 hour to dry;

[0063] C) Then apply a layer of glue to the entire surface of the product, keeping the upper surface of the glue flush with the upper end face, and then wipe off the excess glue. Or use the method in step A), set the dispensing time and dispensing air pressure, and then use a No. 6 needle to apply another layer of glue in the side glue layer, keeping the upper surface of the glue flush with the upper end face;

[0064] D) Repeat the operation method of B). Through the influence of the gravity of the glue itself during the heating and curing process of the glue, the arc structure can be achieved.

[0065] Specifically, by controlling the amount of primer in step A and the amount of glue in step C, the design of the height parameters of the arc can be achieved. For example, when the outer diameter of the sensor is 16 mm, the inner diameter of the small plastic shell 7 is 9 mm, and the height is 12 mm, the weight of the primer in the side glue layer is about 0.15 grams, and the weight of the glue on the arc surface is about 0.05 grams. Due to its own weight, after the glue cures, the arc - shaped structure of the side glue layer as shown in Figure 4 is formed. The weight of the primer and the weight of the glue on the arc surface can also be fine - tuned. For example, the weight of the primer is 0.17 grams and the weight of the glue on the arc surface is 0.05 grams, or the weight of the primer is 0.15 grams and the weight of the glue on the arc surface is 0.07 grams, etc., to form different arc surfaces.

[0066] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-frequency sensor, comprising a housing, a first matching layer, a PCB circuit board, a piezoelectric ceramic sheet and a second matching layer, wherein the first matching layer, the PCB circuit board, the piezoelectric ceramic sheet and the second matching layer are disposed within the housing, and is characterized in that, One side of the first matching layer is connected to the upper bottom surface of the housing, and the other side of the first matching layer is connected to one side of the PCB circuit board. The other side of the PCB circuit board is connected to one side of the piezoelectric ceramic sheet, and the other side of the piezoelectric ceramic sheet is connected to the second matching layer. The other side of the second matching layer is used to transmit ultrasonic signals outward. It further includes a damping glue layer. The damping glue layer is arranged outside the second matching layer, and an arc-shaped structure is arranged on the damping glue layer. The arc-shaped structure is a groove arranged on the surface of the damping glue layer, and the distance between the two end points of the arc is greater than one wavelength of the ultrasonic signal output by the sensor. The outside of the housing is in a stepped shape. The stepped shape divides the housing into a vertical surface and a horizontal surface. A card slot structure is arranged at the connection of the vertical surface and the horizontal surface, and the card slot structure makes the vertical surface recess into the housing.

2. The high-frequency sensor according to claim 1, wherein The density range of the first matching layer is 0.7 g / cm³ - 2.0 g / cm³.

3. A high-frequency sensor according to claim 1, characterized in that, The density range of the second matching layer is 0.4 g / cm³ - 0.8 g / cm³.

4. The high-frequency sensor according to claim 3, characterized in that, The material of the second matching layer is one of epoxy material, polyurethane material, rubber, plastic or silicone rubber.

5. A high-frequency sensor according to claim 1, characterized in that The arc-shaped structure is an arc segment in the cross-sectional view of the sensor, and the line segment length between the two end points of the arc segment is greater than one wavelength of the ultrasonic signal.

6. A high-frequency sensor according to claim 1, wherein The width of the damping glue layer in the radial direction of the sensor is greater than 1.5 wavelengths.

7. A high-frequency sensor according to claim 6, characterized in that The height of the damping glue layer in the axial direction is more than two wavelengths higher than the rear end surface of the piezoelectric ceramic sheet.

8. A high-frequency sensor according to any one of claims 1-7, characterized in that, The ultrasonic frequencies emitted by the sensor are 300 KHz, 350 KHz and 400 KHz. When the frequency is 300 KHZ, the size of the ceramic chip is that the diameter is between 6.5 - 9 mm and the thickness is between 0.4 - 0.8 mm, and the thickness of the second matching layer is between 1.7 - 2.5 mm. When the frequency is 350 KHZ, the size of the piezoelectric ceramic sheet is that the diameter is between 6 - 8 mm and the thickness is between 0.5 - 0.9 mm, and the thickness of the second matching layer is between 1.5 - 2.3 mm. When the frequency is 400 KHZ, the size of the piezoelectric ceramic sheet is that the diameter is between 4 - 6 mm and the thickness is between 0.7 - 1.5 mm, and the thickness of the second matching layer is between 1.0 - 2.0 mm.

9. A manufacturing method of a high-frequency sensor as described in any one of claims 1-8, characterized in that, The implementation method of the arc-shaped structure includes the following steps: A. After completing the installation of the housing, the first matching layer, the PCB circuit board, the piezoelectric ceramic sheet and the second matching layer, first apply a layer of primer in the damping glue layer, and keep the primer 3 - 5 mm away from the upper end surface. The upper end surface refers to the plane flush with the side of the second matching layer for transmitting ultrasonic signals outward. B. Dry the primer. C. Apply another layer of glue on the surface of the primer, and keep the glue surface flush with the upper end surface. D. Place the upper end surface upward and let the glue dry to form the arc-shaped structure of the damping glue layer. By controlling the amount of glue applied in step C, the shape of the arc-shaped structure is adjusted.

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