An ultrasonic array sensor based on a three-cut machining process and a preparation method thereof

Abstract

The application discloses an ultrasonic array sensor based on a three-time cutting machining process and a preparation method, piezoelectric ceramic sheets are bonded with backing materials together, the piezoelectric ceramic sheets are longitudinally and uniformly cut into N columns from the upper surface in the first time, and the cutting gaps are filled with sound attenuation materials, and then an electrode layer is laid on the upper surface; the piezoelectric ceramic sheets are transversely and uniformly cut into M rows from the upper surface in the second time, and then the sound attenuation materials are filled in the cutting gaps in the second time; the backing materials are removed, the electrode layer is laid again, and the third time cutting is carried out from the lower surface along the first cutting direction. The first and second time cutting requires cutting through the piezoelectric ceramic sheets, and the third time cutting only cuts through the lower electrode layer. Then, electrode leads are made, the preparation of the ultrasonic sensor array is completed after the packaging shell. The array elements adopt the collinear structure, the array electrode leads are less, and the ultrasonic array sensor can be used in traditional delay excitation ultrasonic wave occasions and can also be used in addressing excitation occasions.

Description

Technical Field

[0001] This invention belongs to the field of ultrasonic sensor array fabrication technology, and relates to a method and process for fabricating an ultrasonic sensor array based on a three-stage cutting process. Background Technology

[0002] Ultrasonic waves are an important and irreplaceable method for detecting internal defects in materials. An ultrasonic sensor array is a structure composed of multiple tiny array elements arranged according to specific rules. By controlling the excitation timing, different types of focused wavefronts can be formed, enabling accurate detection of defects of various types and sizes. Sensor arrays offer advantages such as flexible beam control, high signal gain, and rich information about the target object, making them crucial in modern nondestructive testing.

[0003] Traditional array-type ultrasonic sensors typically employ a single excitation mode, with each array element being an independent excitation unit. This results in a complex structure, susceptibility to interference, and difficulties in array fabrication. The larger the number of array elements, the richer the information acquired; large-scale arrays are an inevitable trend in the development of ultrasonic sensors. However, the accompanying problems are unavoidable, thus preventing the widespread adoption and application of large-scale arrays in industrial fields. To improve array performance and meet the demands of intelligent sensor development, higher requirements are being placed on the structure of traditional industrial ultrasonic sensor arrays and their excitation methods.

[0004] Row-column addressing excitation technology is one of the new technologies for the development of ultrasonic sensor arrays, especially in the medical field where it has developed rapidly. In recent years, exploration and research have also begun in the field of industrial ultrasonic testing, and there have been reports on the preparation methods of sensor arrays based on this technology (Zhu Benpeng et al., A preparation method of a row-column addressing ultrasonic array probe [Z], 2015).

[0005] This invention provides a novel method and process for fabricating an ultrasonic sensor array. The sensor array in this invention adopts a collinear structure, which is applicable to both traditional phased array excitation modes and arbitrary gating excitation modes. Summary of the Invention

[0006] The purpose of this invention is to prepare an ultrasonic sensor array suitable for large-scale industrial ultrasonic testing. It adopts an addressing excitation method and uses a collinear row and column structure to select any array element in the array for excitation, so as to generate different focused wavefronts, change the transmitting and receiving apertures, and can also be used for different array elements in the array to cooperate and achieve different functions.

[0007] This provides

[0008] The present invention discloses a method for fabricating an ultrasonic array sensor based on a three-stage cutting process, comprising the following steps:

[0009] Step 1: Select a square piezoelectric ceramic sheet made of PZT material. The piezoelectric ceramic sheet is pre-polarized and a silver electrode layer is laid on it.

[0010] Step 2: Based on the PZT piezoelectric ceramic sheet described in Step 1, prepare a non-conductive backing material layer. The length and width of the backing material layer are larger than those of the piezoelectric ceramic sheet. The backing material layer has a square structure, and a whole layer of silver electrodes is sputtered on the upper surface.

[0011] Step 3: According to the backing material described in Step 2, the piezoelectric ceramic sheet is fixed to the middle of the backing material sputtered with the silver electrode layer using conductive adhesive.

[0012] Step 4: Perform the first cut based on the piezoelectric ceramic sheet fixed in the middle of the backing layer as described in Step 3. Enter the cut from above the piezoelectric ceramic sheet and make N-1 parallel cuts in the longitudinal direction to form N rows of piezoelectric ceramic strips. The cutting gap can be determined as needed. The silver electrode laid on the backing material should be completely cut through without forming a transverse connection, but the cutting depth on the backing should not be too large.

[0013] Step 5: According to the piezoelectric array cut in Step 4, inject sound attenuation material (non-conductive material) along the cut gaps, requiring that all cut gaps be filled and the height be exactly equal to the thickness of the piezoelectric ceramic sheet.

[0014] Step 6: According to the piezoelectric array filled with sound attenuation material described in Step 5, the upper surface electrode support block is bonded with non-conductive adhesive on the side perpendicular to the longitudinal cut, with the height equal to that of the piezoelectric ceramic sheet.

[0015] Step 7: Based on the plane formed by the entire ceramic sheet and the upper surface electrode support block described in Step 6, a silver electrode layer is re-sputtered on the plane to form an integral electrode.

[0016] Step 8: Following the piezoelectric array with the upper electrode laid out as described in Step 7, perform a second cut. Make M-1 uniform transverse cuts (perpendicular to the first cut) from the upper surface, ensuring the cut penetrates the piezoelectric ceramic sheet. At this point, the piezoelectric ceramic sheet has formed M×N independent piezoelectric ceramic blocks with row and column electrical connections.

[0017] Step 9: According to the cutting gaps of the M×N independent piezoelectric ceramic blocks described in Step 8, inject the sound attenuation material for the second time, requiring all cutting gaps to be filled, with the height being exactly equal to the thickness of the piezoelectric ceramic sheet.

[0018] Step 10: According to the piezoelectric array with good sound attenuation material described in Step 9, add a matching layer on the upper surface. The thickness of the matching layer can be in accordance with the requirements of a normal ultrasonic sensor.

[0019] Step 11: Remove the backing material according to the piezoelectric array described in Step 10, leaving the rest unchanged;

[0020] Step 12: According to the piezoelectric array for removing backing material described in Step 11, a silver electrode layer is deposited on the lower surface of the array for removing backing material.

[0021] Step 13: According to the piezoelectric array with electrode layers laid in Step 12, a third cut is made, with the cutting direction along the direction of the first cut and the groove width being equal to that of the first cut.

[0022] Step 14: Based on the piezoelectric array that has been cut for the third time as described in Step 13, re-bond the same backing material as the first backing material onto the lower surface.

[0023] Step 15: According to the piezoelectric array for bonding backing material described in step 14, electrode leads are welded to the electrode extension portion under the backing material and the electrode extension portion on the electrode support block, respectively, to form a total of N columns and M rows of leads.

[0024] Step 16: Place the piezoelectric array as described in Step 15 into the encapsulation shell, which is prepared using 3D printing technology;

[0025] Step 17: According to the piezoelectric array installed in the housing as described in Step 16, fill the gaps with the same sound attenuation material as described in Step 5, completely filling the interior of the housing, with the same height as the upper electrode.

[0026] Step 18: Cover the piezoelectric array with the outer shell top cover to complete the fabrication.

[0027] The beneficial effects of this invention are:

[0028] Traditional ultrasonic sensor arrays are fabricated using a fully connected method, with each element having its own independent signal lead. As the array size increases, this leads to difficulties in the electrical connections between elements and makes short circuits between leads prone to occur, significantly impacting the performance of the ultrasonic array sensor. This invention employs a collinear row-column connection method, greatly reducing the number of signal leads between elements. This method is particularly suitable for fabricating large-scale industrial ultrasonic testing ultrasonic sensor arrays. It allows for addressable excitation, utilizing the collinear row and column structure to select any element in the array for excitation, generating different focused wavefronts and altering the transmitting and receiving apertures. It can also be used for different elements in the array to work collaboratively, achieving different functions. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the front structure of the ultrasonic array sensor in an embodiment of the present invention;

[0030] Figure 2 This is a front cross-sectional view of the ultrasonic array sensor in an embodiment of the present invention;

[0031] Figure 3 This is a right-side cross-sectional view of the ultrasonic array sensor in an embodiment of the present invention;

[0032] Figure 4 This is a flowchart of the ultrasonic array sensor fabrication method in an embodiment of the present invention;

[0033] Figure 5 This is the process flow of the ultrasonic array sensor fabrication method in an embodiment of the present invention. Wherein, Figure 5 (a) is the piezoelectric ceramic sheet to be processed. Figure 5 (b) is the backing material for the sputtering bottom electrode. Figure 5 (c) is a schematic diagram of the piezoelectric ceramic being fixed in place. Figure 5 (d) is a schematic diagram after the first cut. Figure 5 (e) is a schematic diagram of the electrode support block being installed. Figure 5 (f) is a schematic diagram of the sputtered upper electrode. Figure 5 (g) is a schematic diagram after the second cut. Figure 5 (h) is a schematic diagram of the adhesive matching layer. Figure 5 (i) is a schematic diagram of the backing material removed. Figure 5 (j) is a schematic diagram of the second sputtered bottom electrode layer. Figure 5 (k) is a schematic diagram after the third cut. Figure 5 (l) is a schematic diagram of the second bonding of the backing material. Figure 5 (m) is a schematic diagram of the electrode leads. Figure 5 (n) is a schematic diagram of the sensor after it has been fabricated. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are further described below in conjunction with the accompanying drawings and embodiments. This invention takes a two-dimensional array with a size of 32×32 and an excitation frequency of 1MHz as an example to specifically describe the fabrication method of an ultrasonic array sensor based on a three-stage cutting process. The size and spacing of the array elements can also be specifically selected as needed. The structure of the sensor is as follows... Figure 1 As shown, the front sectional view is as follows Figure 2 As shown, the right sectional view is as follows Figure 3 As shown. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0035] An ultrasonic array sensor based on a three-stage cutting process according to the present invention includes:

[0036] The piezoelectric array (101), made of PZT piezoelectric ceramic material through three-stage cutting, is used to emit and receive ultrasonic waves;

[0037] A matching layer (102) is laid on top of the piezoelectric array (101) to match the acoustic impedance between the piezoelectric array elements and the material under test;

[0038] The backing material (103) is a non-conductive material and is placed below the piezoelectric array (101) to absorb the ultrasonic waves emitted from the back of the array elements.

[0039] Sound attenuation material (104) is injected into the cut piezoelectric array (101) to reduce crosstalk between array elements;

[0040] The electrodes are all made of silver and are divided into a lower electrode and an upper electrode. The lower electrode (105) is sputtered on the backing material (103) and the upper electrode (106) is sputtered on the piezoelectric array (101) to realize the electrical connection between each array element.

[0041] Leads (107, 108) are copper core signal lines with a shielding layer, used to connect to the ultrasonic sensor excitation circuit;

[0042] The outer shell (109) is made using 3D printing technology and is used to encapsulate the sensor.

[0043] The sensor operation process of this invention is as follows: The collinear electrode leads of the prepared sensor array rows and columns are connected to the gating control circuit, forming M rows and N columns of electrical connection lines. The gating control circuit sends a square wave signal from the microprocessor I / O port, which, after power amplification, drives the electronic switch. Only after the electronic switch is turned on can the electrical signal be transmitted. To select a specific array element, simply turn on the electronic switch in the corresponding row and column (select the element). After selection, the excitation pulse generated by the ultrasonic excitation circuit acts on the sensor element, generating ultrasonic waves. When ultrasonic echoes need to be received, the corresponding array elements are selected according to the timing sequence. In this way, the gating excitation and reception of different array elements in the array can be achieved, thereby realizing addressing excitation.

[0044] A method for fabricating an ultrasonic array sensor based on a three-stage cutting process includes: a method for processing and fabricating a piezoelectric ceramic array, a method for fabricating and connecting signal leads, and a method for 3D printing and packaging the encapsulation shell. After bonding the piezoelectric ceramic sheet to a backing material, the first cut involves longitudinally and uniformly cutting the piezoelectric ceramic sheet into N columns from the top surface, filling the cut gaps with acoustic attenuation material, and then laying an electrode layer on the top surface. The second cut involves transversely and uniformly cutting the piezoelectric ceramic sheet into M rows from the top surface, and then filling the cut gaps with acoustic attenuation material again. The backing material is removed, and the electrode layer is re-laid. A third cut is then performed from the bottom surface along the direction of the first cut. The first and second cuts must penetrate the piezoelectric ceramic sheet, while the third cut only penetrates the bottom electrode layer. The backing material is then bonded to the bottom surface a second time, and a matching layer is laid on the top surface, forming a collinear piezoelectric array of M rows and N columns. The array has M rows of electrodes on the top surface and N columns of electrodes on the bottom surface. Electrode leads are fabricated, and the encapsulation shell completes the fabrication of the ultrasonic sensor array. This invention provides a method for processing and fabricating an ultrasonic array. Each array element adopts a collinear structure, and the array electrode leads are few. It can be used in traditional time-delay excitation ultrasonic wave emission applications, as well as in addressing excitation applications.

[0045] The specific steps for implementing this invention are as follows:

[0046] A method for fabricating an ultrasonic array sensor with adjustable emission aperture, the flowchart of which is shown below. Figure 4 As shown, the complete process flow is as follows: Figure 5 As shown, it includes the following steps:

[0047] Step 1: Select a piezoelectric ceramic sheet made of PZT material with a side length of 79.5 mm and a thickness of 2 mm. The piezoelectric ceramic sheet is pre-polarized and a silver electrode layer is laid on it.

[0048] Step 2: Based on the PZT piezoelectric ceramic sheet described in Step 1, prepare a non-conductive backing material layer. The backing material is made by mixing 10g of epoxy resin A with 31.5g of tungsten powder, adding 2.7g of boron nitride powder to the mixture, and then adding 3.5g of epoxy resin B (curing agent) to a beaker. After mixing, wait for curing. Cut a square backing material with a side length of 100mm and a thickness of 10mm, and sputter a full layer of silver electrodes along the upper surface.

[0049] Step 3: According to the backing material described in Step 2, the piezoelectric ceramic sheet is fixed to the middle of the backing layer with the silver electrode layer using conductive adhesive.

[0050] Step 4: Perform the first cut on the piezoelectric ceramic material fixed in the middle of the backing layer as described in Step 3. Enter the cut from above the piezoelectric ceramic sheet and make 31 parallel cuts in the longitudinal direction to form 32 piezoelectric ceramic strips. The cut gap is 0.5mm. The silver electrode sputtered on the backing material in Step 2 should be completely cut through without forming a transverse connection, but the cut depth on the backing should not be too large.

[0051] Step 5: According to the piezoelectric array cut in Step 4, inject sound attenuation material (non-conductive material) along the cut gaps, requiring that all cut gaps be filled and the height be exactly equal to the thickness of the piezoelectric ceramic sheet.

[0052] Step 6: According to the piezoelectric array filled with sound attenuation material described in Step 5, the upper surface electrode support block is bonded with non-conductive adhesive on the side perpendicular to the longitudinal cut, with the height equal to that of the piezoelectric ceramic sheet.

[0053] Step 7: Based on the plane formed by the entire ceramic sheet and the upper surface electrode support block described in Step 6, a silver electrode layer is re-sputtered on the plane to form an integral electrode.

[0054] Step 8: Perform a second cutting based on the piezoelectric array after sputtering the top electrode as described in Step 7. Make 31 uniform transverse cuts (perpendicular to the first cut) from the top surface, with a cut gap of 0.5 mm, ensuring that the cuts penetrate the piezoelectric ceramic sheet. At this point, the piezoelectric ceramic sheet has formed 1024 independent piezoelectric ceramic blocks with row and column electrical connections;

[0055] Step 9: Based on the cutting gaps of the 1024 independent piezoelectric ceramic blocks described in Step 8, inject the sound attenuation material for the second time, requiring all cutting gaps to be filled, with the height being exactly equal to the thickness of the piezoelectric ceramic sheet.

[0056] Step 10: According to the piezoelectric array with good sound attenuation material described in Step 9, add a matching layer on the upper surface. The thickness of the matching layer can be in accordance with the requirements of a normal ultrasonic sensor.

[0057] Step 11: Remove the backing material according to the piezoelectric array described in Step 10, leaving the rest unchanged;

[0058] Step 12: According to the piezoelectric array for removing backing material described in Step 11, a silver electrode layer is deposited on the lower surface of the array for removing backing material.

[0059] Step 13: According to the piezoelectric array with electrode layers laid in Step 12, a third cut is made, with the cutting direction along the direction of the first cut and the groove width being equal to that of the first cut.

[0060] Step 14: Based on the piezoelectric array that has been cut for the third time as described in Step 13, re-bond the same backing material as the first backing material onto the lower surface.

[0061] Step 15: According to the piezoelectric array for bonding backing material described in step 14, electrode leads are welded to the electrode extension portion under the backing material and the electrode extension portion on the electrode support block, respectively, forming a total of 32 columns and 32 rows of leads.

[0062] Step 16: Place the piezoelectric array as described in Step 15 into the encapsulation shell, which is prepared using 3D printing technology;

[0063] Step 17: According to the piezoelectric array installed in the housing as described in Step 16, fill the gaps with the same sound attenuation material as described in Step 5, completely filling the interior of the housing, with the same height as the upper electrode.

[0064] Step 18: Cover the piezoelectric array with the outer shell top cover to complete the fabrication.

Claims

1. A method of manufacturing an ultrasonic array sensor based on a three-cut machining process, characterized by, The ultrasonic array sensor includes: The piezoelectric array (101) is made of PZT piezoelectric ceramic material through three cutting processes and is used to emit and receive ultrasonic waves; A matching layer (102) is laid on top of the piezoelectric array (101) to match the acoustic impedance between the piezoelectric array elements and the material under test; The backing material (103) is a non-conductive material and is placed below the piezoelectric array (101) to absorb the ultrasonic waves emitted from the piezoelectric array elements in the opposite direction. Sound attenuation material (104) is injected into the cut piezoelectric array (101) to reduce crosstalk between piezoelectric array elements; The electrodes are all made of silver and are divided into a lower electrode and an upper electrode. The lower electrode (105) is sputtered on the backing material (103) and the upper electrode (106) is sputtered on the piezoelectric array (101) to realize the electrical connection between each piezoelectric array element. Leads (107, 108) are copper core signal lines with a shielding layer, used to connect to the ultrasonic sensor excitation circuit; The outer shell (109) is fabricated using 3D printing technology and is used to encapsulate the sensor; The preparation method includes the following steps: Step 1: Select a square piezoelectric ceramic sheet made of PZT material. The piezoelectric ceramic sheet is pre-polarized and a silver electrode layer is laid on it. Step 2: Prepare a non-conductive backing material layer, which is larger in both length and width than the piezoelectric ceramic sheet. The backing material layer has a square structure, and a whole layer of silver electrodes is sputtered on the upper surface. Step 3: Fix the piezoelectric ceramic sheet to the middle of the backing material layer sputtered with silver electrode layer using conductive adhesive; Step 4: Perform the first cut on the piezoelectric ceramic sheet from Step 3; insert the cutter from above the piezoelectric ceramic sheet and make uniform, parallel cuts along the longitudinal direction. knife, forming The cutting gap of the piezoelectric ceramic strips should be determined as needed. The silver electrode laid on the backing material should be completely cut through without forming a lateral connection, but the cutting depth on the backing should not be too large. Step 5: Pour sound attenuation material along the cut gaps, ensuring that all cut gaps are filled and the height is exactly equal to the thickness of the piezoelectric ceramic sheet; Step 6: Attach the upper surface electrode support block to the side of the piezoelectric array perpendicular to the longitudinal cut using non-conductive adhesive. The height of the support block should be equal to that of the piezoelectric ceramic sheet. Step 7: Re-sputter a silver electrode layer onto the plane consisting of the entire ceramic sheet and the upper surface electrode support block to form an integral electrode; Step 8: Perform a second cut, making uniform transverse cuts with equal spacing from the upper surface of the piezoelectric array. The cutting direction is perpendicular to the first cut, aiming to cut through the piezoelectric ceramic sheet; at this point, the piezoelectric ceramic sheet has formed independent rows and columns of electrical connections. A piezoelectric ceramic block; Step 9: Fill the second gap with sound attenuation material, ensuring that all cut gaps are filled and the height is exactly equal to the thickness of the piezoelectric ceramic sheet; Step 10: Add a matching layer to the upper surface of the piezoelectric array infused with the acoustic attenuation material; Step 11: Remove the backing material. The backing material should be completely removed, leaving the rest unchanged. Step 12: Lay a silver electrode layer on the lower surface of the piezoelectric array after removing the backing material; before laying the silver electrode layer, ensure that the filling material between the piezoelectric array elements is equal to the height of the piezoelectric array elements. If they are not equal, refill the material to ensure that the heights are equal. Step 13: Perform a third cut on the piezoelectric array, with the cutting direction following the direction of the first cut, and the groove width being equal to that of the first cut; Step 14: Re-bond the same backing material as the backing material layer onto the lower surface of the piezoelectric array; the dimensions of the backing material are the same as in Step 2. Step 15, weld electrode leads to electrode extension portions under the backing material and electrode extension portions on the electrode support blocks, respectively, to form common column and row leads; Step 16: Place the piezoelectric array into the encapsulation shell, which is fabricated using 3D printing technology; Step 17: Fill the gaps with the same material as the sound attenuation material described in Step 5, completely filling the interior of the shell, with the same height as the upper electrode; Step 18: Cover the piezoelectric array with the outer shell top cover to complete the fabrication.

2. The method of claim 1, wherein, The acoustic attenuation material used in step 5 is a non-conductive material.

3. The method of claim 1, wherein, The upper surface electrode support block mentioned in step 7 is made of the same material as the backing material and is bonded to the upper surface of the backing material. Its height is the same as that of the piezoelectric array.

4. The method of claim 1, wherein, In step 9, the sound attenuation material is the same as in step 5.

5. The method of claim 1, wherein, In step 10, the matching layer thickness is a fraction of the ultrasound wavelength of .

6. The method of claim 1, wherein, In step 15, the leads welded to the electrode extension portion under the backing material and the electrode extension portion on the electrode support block are shielded signal lines.

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