Piezoelectric composite material and preparation method thereof, electrode extraction method and transducer

Abstract

The invention discloses a preparation method of a piezoelectric composite material, which comprises the following steps: providing a pair of piezoelectric materials, providing a pair of backing materials for the upper surface and the lower surface of each piezoelectric material, and bonding the backing materials with the piezoelectric materials to form a pair of piezoelectric backing materials; cutting the surface of each piezoelectric backing material to form a strip column and a through groove which extend along the thickness direction; a pair of cut piezoelectric backing materials is placed in a mutually cross-aligned manner, and a portion of the joined piezoelectric backing materials in the thickness direction is removed to form a piezoelectric composite material. According to the invention, through the interdigital operation of cross alignment of the piezoelectric material with the conductive backs on the two surfaces, a structure with a specified gap width between the array element and the sub-array elements can be obtained, the structure is used as a piezoelectric composite material structure of the transducer array element, and the processing of the ultrahigh frequency array type ultrasonic transducer with a smaller array element gap size is realized. The invention also provides a corresponding piezoelectric composite material, an electrode extraction method and a transducer.

Description

Technical Field

[0001] The present invention relates to a piezoelectric composite material, and more specifically, to a piezoelectric composite material and a preparation method thereof, an electrode lead-out method and a transducer. Background Art

[0002] Medical ultrasonic transducers are a type of sensor that can convert electrical signals into ultrasonic signals and vice versa, and are widely used in the field of medical ultrasonic diagnosis. Among them, ultra-high frequency (≥20MHz) ultrasound can be used in specific occasions such as superficial skin, ophthalmology, and small animal ultrasound due to its high frequency, small wavelength, and high resolution, and has high clinical and scientific research value. Ultra-high frequency ultrasonic transducers can be divided into single-element and multi-element (array) types according to their structure. Single-element transducers have a fixed focus and cannot perform Doppler blood flow imaging, and have many application restrictions. Therefore, ultra-high frequency array ultrasonic transducers are mostly used in clinical and scientific research fields.

[0003] Due to the high frequency of traditional ultra-high frequency ultrasonic transducers, the transducer structure and array element size are extremely small, and the manufacturing processes of the transducer are very demanding. Among them, the most difficult is the array element segmentation. Taking a 40MHz array ultrasonic transducer as an example, the wavelength of the sound wave it emits in human tissue is about 37.5μm. It is usually required that the transducer array element spacing is less than or equal to one wavelength, that is, 37.5μm. Otherwise, grating lobes will be generated due to the directivity of the array, affecting the quality of the ultrasonic image; and for the size of the gap between each array element of the array transducer, that is, the slit width w, it is usually required that w≤vs / (4*f) to avoid the shear vibration of the material filling the array element gap affecting the thickness vibration of the piezoelectric material, where vs is the shear wave sound velocity of the material filling the array element gap, and f is the design frequency of the transducer. Taking a 40MHz transducer and a shear wave sound velocity of 1200m / s of the gap-filling epoxy material as an example, the slit width is required to be less than or equal to 7.5μm. Semiconductor grooving machine blades are commonly used to cut transducer array elements. The thinnest thickness is currently only 10um, which cannot meet the requirements for the cutting width of ultra-high frequency transducer array elements.

[0004] There are two main manufacturing processes for commercially available ultra-high frequency array ultrasound transducers. One is to use lasers to reduce the gap between array elements to less than 10um. The other is to use semiconductor MEMS processing technology to manufacture c-MUT or p-MUT transducers on integrated circuits, bypassing the problem of gap between the cutting edges. However, whether it is laser processing or semiconductor processing technology, the equipment investment, maintenance costs, and product manufacturing costs are relatively high, resulting in high prices for transducers, which is not conducive to large-scale adoption in clinical and scientific research.

[0005] In addition, in order to improve the performance of the ultrasonic transducer, a layer of backing material is usually set between the electrode lead plate and the piezoelectric material. Since the signal of the piezoelectric material needs to be conducted to the electrode lead plate when the transducer is made, the backing material needs to be electrically conductive. There are usually two ways to achieve this: 1) Use a conductive backing material; 2) Establish a conductive channel in the insulating backing material. Usually, the conductive material itself is a metal material with a large impedance. And establishing a conductive channel in the insulating material requires a special backing manufacturing process. These two methods have different degrees of influence on the performance of the transducer. The higher the frequency of the transducer, the greater the influence, and the influence is particularly significant for high-frequency two-dimensional array transducers. Because of the two-dimensional array transducer, the piezoelectric material needs to be divided in the width and length directions to form a column array. For high-frequency two-dimensional arrays, the size of a single column is extremely small (less than 0.1mm). If the method of inserting conductive strips into the backing material is used, the impedance of the conductive strips and the backing material and the large volume of the conductive strips occupying the entire backing column will significantly affect the product performance. If conductive material is used as the backing, the high impedance of the conductive material will also affect the product performance and increase the difficulty of manufacturing piezoelectric materials.

[0006] The difficulty in manufacturing ultra-high frequency array ultrasonic transducers lies not only in the extremely small size of the array element gaps, but also in how to lead out the array element electrodes, which is also a common problem in the industry. Summary of the invention

[0007] In view of the technical problems in the prior art, the purpose of the present invention is to provide a piezoelectric composite material and a preparation method thereof, an electrode lead-out method and a transducer. By performing a cross-aligned interdigitation operation on a piezoelectric material with backing materials on both sides, a structure with a specified gap width between array elements and sub-array elements can be obtained. The piezoelectric composite material structure used as the transducer array element can realize the processing of ultra-high frequency array ultrasonic transducers with smaller array element gap sizes; and by setting a limiting structure for the backing material, it is ensured that the position of the piezoelectric composite material is not offset when it is crimped to the circuit board, thereby realizing the precise lead-out of the transducer array element electrodes.

[0008] The interdigitation process of traditional composite materials is only for piezoelectric bulk materials such as piezoelectric ceramics or piezoelectric single crystals. According to the requirements of the array element spacing and the gap between the array elements, the grooving, caulking, and interdigitation processes are performed to finally make a 2-2 type or 1-3 type composite material. The grooving depth in the interdigitation process needs to be greater than the thickness of the final composite material. At the same time, in order not to damage the piezoelectric material during cutting, and to minimize the deformation of the piezoelectric material due to different boundary conditions during the curing shrinkage of the caulking epoxy, the grooving depth is usually less than one-third of the thickness of the piezoelectric material itself. Like pure piezoelectric materials, the thickness of piezoelectric composite materials is inversely proportional to the vibration frequency. For example, the thickness of a 40MHz piezoelectric composite material is usually required to be less than 50μm, so the thickness of the piezoelectric material used in the interdigitation process is generally required to be greater than 150μm. However, the thicker the piezoelectric material, the higher its cost, especially for piezoelectric single crystal materials, and the longer it takes to thin the piezoelectric material. Taking into account the cost and processing risks, for high-frequency composite materials such as 40MHz, the thickness of each piece of piezoelectric material used in the interdigital process is usually in the range of 200-300μm.

[0009] One of the purposes of the present invention is to provide a method for preparing a piezoelectric composite material, comprising the following steps:

[0010] Providing a pair of piezoelectric materials, providing a pair of backing materials for the upper and lower surfaces of each piezoelectric material, wherein the backing materials are bonded to the piezoelectric materials to form a pair of piezoelectric backing materials;

[0011] The surface of each piezoelectric backing material is cut into grooves at a certain interval to form bars and through grooves extending in the thickness direction, and adjacent bars in the same piezoelectric backing material are separated by through grooves;

[0012] Placing a pair of cut piezoelectric backing materials in a cross-aligned manner so that the bars of one piezoelectric backing material are placed in the through grooves of the other piezoelectric backing material, and bonding the pair of piezoelectric backing materials by bonding the gaps between adjacent bars with an insulating adhesive material;

[0013] A portion of the backing material along the thickness direction of the bonded piezoelectric backing material is removed to form a piezoelectric composite material, wherein the surface of the piezoelectric composite material in the thickness direction is basically flat, and the piezoelectric material therein is aligned in the thickness direction, and the surface is formed by bars and gaps between adjacent bars joined by insulating adhesive material.

[0014] In some embodiments, the pair of piezoelectric materials have the same size and thickness T1, and the upper and lower surfaces of the piezoelectric materials along the thickness direction are plated with electrodes; the pair of backing materials have the same length and width, but different thicknesses, which are T2 and T3, respectively, and each backing material has a conductive area for conduction on the upper and lower surfaces along the thickness direction;

[0015] The thickness of the insulating adhesive material is T4, and the total thickness of each piezoelectric backing material is T5 = T1 + T2 + T3 + 2*T4. Moreover, the positive electrode of one piezoelectric material is bonded to the backing material with a thickness of T2, and the negative electrode is bonded to the backing material with a thickness of T3. The bonding thickness of the positive and negative electrodes of the other piezoelectric material to the backing material is opposite.

[0016] In some embodiments, based on the foregoing, the backing material on the side of the piezoelectric material in the joined piezoelectric backing material is removed until the piezoelectric material is exposed to form a substantially flat first surface, and a part of the backing material on the other side of the piezoelectric material is removed to a thickness of T to form a substantially flat second surface on the backing material. In a specific embodiment, the thickness T ≤ the minimum value of the thicknesses T2 and T3.

[0017] In some embodiments, a pair of piezoelectric backing materials are cut using a blade with a thickness of K1 + K2, and are each cut to a preset depth at a spacing of 2*P1 on the surface of each piezoelectric backing material:

[0018] If T2 < T3, cut from the surface of the backing material with a thickness of T2, and control one of the backing materials to be cut to a preset depth D1 = T1 + 2*T2 + 2*T4, and the cutting depth of the other backing material is not less than D1;

[0019] If T3 < T2, cut from the surface of the backing material with a thickness of T3, and control one of the backing materials to be cut to a preset depth D2 = T1 + 2*T3 + 2*T4, and the cutting depth of the other backing material is not less than D2;

[0020] After the pair of piezoelectric backing materials are joined, the piezoelectric materials therein are flush in the thickness direction to define the strips with a width of K2 and a spacing of P1, and the grooves with a width of K1 + K2 and a spacing of 2P1, and a gap with a width of K1 is formed between adjacent strips.

[0021] In some embodiments, the backing material on the side of the piezoelectric material is removed until the piezoelectric material is exposed to form a substantially flat first surface, and a part of the backing material on the other side of the piezoelectric material is removed to form a substantially flat second surface. The first surface and the second surface constitute the surfaces of the piezoelectric composite material in the thickness direction; in the piezoelectric composite material: electrodes are provided on both the first surface of the piezoelectric material and the second surface of the backing material in the piezoelectric composite material, or electrodes are provided only on the first surface of the piezoelectric material in the piezoelectric composite material.

[0022] In some embodiments, for the piezoelectric composite material, a blade with a thickness of K4 is used to cut off the electrodes on the surface of the gap joined by the insulating bonding material on the second surface of the backing material, and the cutting depth is less than the thickness of the backing material; then a blade with a thickness of K3 is used to cut grooves at the center positions of two adjacent gaps located on the second surface of the backing material at an interval of P1, and by controlling the cutting depth to adapt to the conductive pads of the circuit board, the piezoelectric composite material is relatively fixed and pressed onto the conductive pads on the surface of the circuit board through the limit fit of the backing material.

[0023] In some embodiments, it is controlled that the depths of the through-grooves in the pair of cut piezoelectric backing materials are not lower than a preset depth, and the two uncut surfaces of the pair of piezoelectric backing materials are respectively fixed on the upper and lower pressing blocks of the pressing die by means of pasting or adsorption; a limiting block is placed on the lower pressing block, and the height of the limiting block is equal to the preset depth. When T2 < T3, the height of the limiting block is equal to T1 + 2T3 + 2T4; when T3 < T2, the height of the limiting block is equal to T1 + 2T2 + 2T4; the upper and lower pressing blocks are pressed together until the distance is equal to the position of the limiting block.

[0024] In some embodiments, an insulating bonding material is coated on the grooved surface of a cut piezoelectric backing material, and then the other cut piezoelectric backing material is inserted so that the bottom of the through-groove of one piezoelectric backing material is closely attached to the surface of the backing material of the other piezoelectric backing material to limit the gap width between the piezoelectric backing materials ≤ K1.

[0025] Based on the above technical problems of the traditional interdigital process, when making a 40MHz composite material using the piezoelectric composite material interdigital process proposed by the present invention, backing materials (including epoxy resin components) with a thickness much greater than that of the piezoelectric material can be bonded to both sides of the piezoelectric material. After bonding, the total thickness can reach more than 1mm, significantly increasing the overall strength of the material. During the grooving process, the backing material and the piezoelectric material on the upper surface can be cut through and cut into the conductive backing on the lower surface, which can avoid the epoxy curing shrinkage deformation caused by the uncut piezoelectric material. Therefore, the thickness of the piezoelectric material can be controlled within: the final thickness of the piezoelectric composite material plus the processing error (for example, 10um), without the need to be greater than three times the final piezoelectric composite material, reducing the time for thinning the piezoelectric material and the cost of the piezoelectric material.

[0026] The present invention can determine the cutting depth through algebraic fitting by jointly performing the interdigital process on the backing material and the piezoelectric material, and then combining the height limiting function of the pressing die, so that when the two piezoelectric backing materials are inserted, the piezoelectric material layers are aligned in the thickness direction, and the emission surfaces of the piezoelectric materials are kept on the same plane, ensuring the consistency of the thickness of the matching layers on each element in the subsequent process and improving the element performance.

[0027] In order to achieve the second purpose above, a piezoelectric composite material is provided, which is prepared according to the above preparation method. The piezoelectric composite material comprises a piezoelectric material, an insulating adhesive material, and a backing material stacked along the thickness direction, and each layer of material in the thickness direction remains flush; and, in the piezoelectric composite material, there is a gap between adjacent columns along the direction perpendicular to the stacking direction connected by an insulating adhesive material.

[0028] After the composite material is obtained by the traditional interdigital process, electrodes are plated on the upper and lower surfaces of the composite material. When the composite material is used in an array transducer, the coating needs to be cut through to form individual array elements with separate signal poles, but it will inevitably cut into the gaps of the composite material. If a blade is used to cut the coating, the width of the slit in the coating will inevitably be larger than the gap in the composite material, which will affect the acoustic performance of the composite material and almost lose the meaning of the interdigital process.

[0029] The third object of the present invention is to provide a method for extracting electrodes of the above-mentioned piezoelectric composite material, and the technical solution is as follows:

[0030] A method for extracting electrodes from a piezoelectric composite material, based on the above-mentioned method for preparing the piezoelectric composite material, further comprises:

[0031] In each piezoelectric backing material, the surface of the backing material bonded to both sides of the piezoelectric material is provided with a conductive area;

[0032] A pair of piezoelectric backing materials are cut to form bars and through grooves, wherein the through grooves of the pair of piezoelectric backing materials are provided with a conductive layer around the backing materials for conducting correspondingly with the conductive area; the cut pair of piezoelectric backing materials are cross-aligned with each other by extending the bars into the through grooves, and the through grooves of at least one piezoelectric backing material have a step width that narrows from the outside to the inside of the cutting surface, so that a gap with a step width is formed between adjacent bars in the formed piezoelectric composite material, and the gap on the wider side is formed in the backing material of the piezoelectric composite material, a continuous conductive layer is provided on the second surface of the backing material, and the electrode lead structure of the piezoelectric composite material is obtained by cutting the continuous conductive layer between adjacent bars.

[0033] In some embodiments, one of the piezoelectric backing materials is cut into a first groove by grooving, wherein the first groove includes a shallow groove provided on the backing material on one side of the piezoelectric material and a deep groove penetrating the piezoelectric material to the backing material on the other side, wherein the width of the shallow groove is wider than the deep groove; a first conductive layer is provided on the surface of the shallow groove, wherein the first conductive layer extends along the side of the backing material to a part of the side of the piezoelectric material, and the first conductive layer is electrically connected to the conductive area of ​​the backing material where it is located;

[0034] The second groove cut in another piezoelectric backing material is a straight groove, a conductive layer is provided on the surface of the straight groove, and then the conductive layer of the backing material on the second groove to the side of part of the piezoelectric material is cut off, and the conductive layer at the bottom is retained to form a second conductive layer, and the second conductive layer is connected to the conductive area of ​​the backing material where it is located;

[0035] The gaps between adjacent bars in the formed piezoelectric composite material are made to have a step width, with a wider gap formed on the side close to the shallow groove and a narrower gap formed on the side away from the shallow groove; a conductive layer is provided on the second surface of the piezoelectric composite material close to the shallow groove, and then the electrodes of adjacent bars in the piezoelectric composite material are divided by cutting the conductive layer connecting adjacent bars.

[0036] The gap between the bars established by the interdigitation process of the present invention is very small, usually less than 0.01mm. When the array elements are divided, the electrodes of each array element need to be separated. At this time, the conductive path can be easily damaged by the traditional cutting method, so that the electrode lead-out channel of the backing material is disconnected. Based on the electrode lead-out method of the present invention, the process of plating the conductive layer can be used to extend the conductive layer to a certain position on the inner side of the bar, thereby establishing the electrode lead-out channel of each bar in the interdigitation process, which greatly saves product production time and reduces the difficulty of electrode lead-out of the transducer, especially the high-frequency two-dimensional array transducer.

[0037] More specifically, the present invention mainly uses the "cutting control method" to control the position of the conductive layer plated on the side of the bar column and the size of the bar column, and finally forms a narrow gap between the bar columns bonded to the piezoelectric material, and forms a wide gap between the backing materials away from the piezoelectric material. Therefore, when the array transducer is manufactured using the interdigital process of the present invention, the division of the array element signal pole is almost automatically completed after the composite material is manufactured. Subsequently, only the plated layer of the conductive backing needs to be cut, which has no effect on the acoustic performance of the composite material. At the same time, the process of plating the conductive layer can be used to extend the conductive layer to a certain position on the inner side of the backing column or backing strip (that is, the part of the backing material in the bar column), thereby establishing an electrode lead-out channel for each backing strip or backing column during the interdigital process, which greatly saves product manufacturing time and reduces the difficulty of electrode lead-out of the transducer, especially the high-frequency two-dimensional array transducer.

[0038] A fourth object of the present invention is to provide a transducer, comprising the above-mentioned piezoelectric composite material and a circuit board, and the technical solution adopted is: the piezoelectric composite material is conductively connected to the circuit board through the above-mentioned electrode lead-out method.

[0039] Compared with using laser to cut the transducer array element gap or using semiconductor processing methods to make transducers, the processing cost and difficulty of the ultra-high frequency array ultrasonic transducer manufactured by the present invention are significantly reduced, and the processing method of the present invention can theoretically make the array element gap less than 1um, while laser processing is limited by the aspect ratio of the groove (usually 1:10). To achieve a gap width of 1um, the depth of the groove is only about 10um, and even the piezoelectric material itself cannot be cut through, which cannot meet the requirements of transducer array element segmentation.

[0040] Beneficial effects:

[0041] 1) The present invention performs interdigitation operation on piezoelectric materials with conductive backings on both sides to complete the structure of specified gap widths between array elements and sub-array elements. Under the premise of ensuring the reliability of the processing process and obtaining high-quality piezoelectric composite materials, it can realize the processing of ultra-high frequency array ultrasonic transducers with smaller array element gap sizes.

[0042] 2) The present invention ensures that the gap of the piezoelectric material sub-element is aligned with the pad of the circuit board, and the gap of the element is aligned with the position between the two pads of the circuit board through the backing material with a limiting structure. In addition, the present invention ensures that the position of the piezoelectric composite material on the circuit board will not be offset through the circuit board structure with a pad of a special shape.

[0043] 3) The present invention can utilize the interdigitation method to establish the electrode lead-out structure of the non-conductive backing material, thereby simplifying the electrode lead-out process, especially simplifying the realization of the high-frequency two-dimensional array, and avoiding the problem of directly using the conductive backing material with too high impedance, which affects the product performance and increases the difficulty of production.

[0044] 4) The present invention can use the interdigitation method to establish a gap with a step width, and plate a conductive layer on the second surface of the backing material in the piezoelectric composite material. Then, the electrode division of adjacent bars is achieved by simply cutting the connected conductive layer on one side of the wider gap between adjacent bars, which greatly facilitates the electrode extraction in the piezoelectric composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0046] Figure 1 It is a combined schematic diagram of a top view angle and a front view angle of the piezoelectric material of the present invention.

[0047] Figure 2 It is a schematic diagram of a combination of a pair of backing materials of the present invention.

[0048] Figure 3 It is a schematic diagram of the combination of a pair of piezoelectric backing materials of the present invention.

[0049] Figure 4Schematic diagram of cutting of piezoelectric backing material in one embodiment of the present invention.

[0050] Figure 5 Schematic diagram of the interdigitation process in one embodiment of the present invention.

[0051] Figure 6 FIG. 4 is a schematic diagram of the structure of a piezoelectric composite material in one embodiment of the present invention.

[0052] Figure 7-1 and Figure 7-2 They are respectively a top view and a side view of a 1-3 type piezoelectric composite material formed in one embodiment of the present invention.

[0053] Figure 8 Schematic diagram of cutting grooves in a backing material in one embodiment of the present invention.

[0054] Fig. 9 FIG. 4 is a top view of a circuit board pad in one embodiment of the present invention.

[0055] Figure 10-1 and Figure 10-2 They are schematic diagrams of electrode extraction in one embodiment of the present invention.

[0056] Fig.11 Schematic diagram of the structure of a pressing mold in one embodiment of the present invention.

[0057] Fig.12 Schematic diagram of a cutting method for implementing electrode extraction in one embodiment of the present invention.

[0058] Fig.13 Another schematic diagram of a cutting method for implementing electrode extraction in one embodiment of the present invention.

[0059] Fig.14 Schematic diagram of the surface structure of a backing material for forming a 2-2 piezoelectric composite material in one embodiment of the present invention.

[0060] Fig.15 , 16 They are schematic diagrams of two surface structures of a backing material forming a 1-3 piezoelectric composite material in one embodiment of the present invention.

[0061] Fig.17 The present invention corresponds to Figure 14-16 Schematic diagram of the side structure of the formed backing material.

[0062] Fig.18 FIG. 4 is a simplified diagram of a transducer in one embodiment of the present invention.

[0063] The meanings of the symbols in the figure are as follows:

[0064] 10-first piezoelectric material, 10′-second piezoelectric material, 100-piezoelectric backing material, 101-first column, 102-second column, 103-first groove, 104-second groove; A-shallow groove, B-deep groove, C-conductive material, S1-first conductive layer, S2-second conductive layer; S′-conductive layer, S-conductive pad, J-ground pad, E-conductive area;

[0065] 2-pressing mold, 20-upper pressing block, 21-lower pressing block, 22-support rod, 23-limiting block;

[0066] 3-Circuit board. DETAILED DESCRIPTION

[0067] The present invention is further explained in detail below in conjunction with the drawings and descriptions of specific embodiments. However, the following descriptions including the embodiments are only used to enable ordinary technicians in the technical field to which the present invention belongs to more clearly understand the principles and essence of the present invention, and do not mean any form of limitation on the present invention.

[0068] In the description of this application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance. It should be noted that the following embodiments can be freely combined as needed. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the scope of protection of the present invention.

[0069] The present invention is a method for preparing a piezoelectric composite material, which can adjust the width of the cutting gap to produce a specific required array element gap, and can make the array element gap less than 1 μm, thereby realizing low-cost and low-difficulty processing of ultra-high frequency array ultrasonic transducers. The present invention will be further described in detail in the following exemplary embodiments.

[0070] refer to Figures 1 to 3 The method starts with providing a pair of piezoelectric materials, and providing a pair of backing materials for the upper and lower surfaces of each piezoelectric material. The backing materials and the piezoelectric materials are bonded to each other. At this point, a pair of backing materials and a piece of piezoelectric substrate are combined to form a piezoelectric backing material, and two pairs of backing materials and a pair of piezoelectric materials together form a pair of piezoelectric backing materials. Among them, the upper and lower surfaces of the piezoelectric material refer to the upper and lower surfaces along the thickness direction of the piezoelectric material. According to the specific application, the piezoelectric material can be made of materials such as piezoelectric ceramics or piezoelectric single crystals. In one embodiment, the backing material and the piezoelectric material are bonded by an insulating adhesive material, which can be epoxy resin glue. In another embodiment, it is shown Figure 1 In the embodiment, the pair of piezoelectric materials includes a first piezoelectric material 10 and a second piezoelectric material 10', both of which have a length of L, a width of W, and a thickness of T1. Figure 2 A pair of backing materials in the piezoelectric backing material comprises a first backing material 11 with a length of L, a width of W, and a thickness of T2, and a second backing material 12 with a length of L, a width of W, and a thickness of T3, wherein T2≠T3. The thickness of the insulating adhesive material is T4, and the insulating adhesive material can be glue, and the thickness of the glue layer T4 is controlled to be less than 5μm. After bonding, the total thickness of each of the piezoelectric backing materials is T5=T1+T2+T3+2*T4, and one of the piezoelectric materials has a positive electrode bonding thickness of the first backing material 11 of T2, and a negative electrode bonding thickness of the second backing material 12 of T3, and the positive and negative electrodes of another piezoelectric material have opposite bonding thicknesses to the backing materials, and the positive electrode bonding thickness is the second backing material 12 of T3, and the negative electrode bonding thickness is the first backing material 11 of T2, as shown in FIG. Figure 3 The piezoelectric material in the piezoelectric composite already has positive and negative electrodes, and the positive and negative electrodes of the two piezoelectric materials are bonded with backing materials of opposite thickness. Of course, if the piezoelectric material has not been given polarity during the production process of the piezoelectric composite material, the piezoelectric material can be given the corresponding polarity by polarization means after the production is completed to form the final piezoelectric composite material.

[0071] refer to Figure 4 , by cutting the surface of each piezoelectric backing material 100, cutting grooves at a certain interval to form bars and through grooves extending in the thickness direction; specifically, by cutting the surface of a piezoelectric backing material 100, cutting grooves at a certain interval to form first columns 101 and first grooves 103 extending in the thickness direction, and adjacent first columns 101 are separated by the first grooves 103; by cutting the surface of another piezoelectric backing material 100, cutting grooves at a certain interval to form second columns 102 and second grooves 104 extending in the thickness direction, and adjacent second columns 102 are separated by the second grooves 104. Reference Figure 5 , a pair of cut piezoelectric backing materials are placed in a cross-aligned manner, so that the first column 101 is placed in the second groove 103, and the second column 102 is placed in the first groove 104, and the gaps between adjacent first columns 101 and second columns 102 are joined by insulating adhesive material to join the pair of piezoelectric backing materials. In one embodiment, the adjacent first columns 101 are joined by pouring epoxy resin glue in the gap.

[0072] refer to Figure 6, after the insulating adhesive material is cured, a part of the piezoelectric backing material that has been finger-jointed is removed along the thickness direction to form a piezoelectric composite material. The piezoelectric composite material has two surfaces in the thickness direction. Specifically, the backing material on one side of the piezoelectric material is removed until the piezoelectric material is exposed to form a substantially flat first surface, and a part of the backing material on the other side of the piezoelectric material is removed to form a substantially flat second surface to form a piezoelectric composite material. Among them, both the first surface and the second surface are defined by strip columns and gaps joined by an insulating adhesive material between adjacent strip columns. The "substantially flat" here means meeting the technical indicators for the flatness requirements of the laminated material layers in this technical field. Both the first surface and the second surface are formed by the alternately adjacent first column 101 and second column 102 and the gaps joined by an insulating adhesive material. The difference is only that the first surface is formed by the surface of the piezoelectric material layer exposed after removing the backing material on one side of the piezoelectric material by means such as grinding with the first column 101 and second column 102 joined alternately by the adhesive insulating material, and the second surface is formed by the bottom surface of the remaining backing material layer after removing a part of the backing material on the other side of the piezoelectric material by means such as grinding with the first column 101 and second column 102 joined alternately by the adhesive insulating material. In one embodiment, when cutting any piezoelectric backing material, the cutting is performed from the surface of the thinner backing material. After the two piezoelectric backing materials are finger-jointed, the thicknesses of the backing materials on both sides of the piezoelectric material are the same, both being the thickness of the thicker backing material. In another embodiment, a blade with a thickness of K1 + K2 or other implementation methods in the industry are used to cut a pair of piezoelectric backing materials, and each piezoelectric backing material is cut to a preset depth at intervals of 2*P1 on the surface; if T2 < T3, cut from the surface of the first backing material 11 with a thickness of T2, and control one of the backing materials to be cut to a preset depth D1 = T1 + 2*T2 + 2*T4, and the cutting depth of the other backing material is greater than or equal to D1; if T3 < T2, cut from the surface of the second piezoelectric backing material 12 with a thickness of T3, and control the backing material to be cut to a preset depth D2 = T1 + 2*T3 + 2*T4, and the cutting depth of the other backing material is greater than or equal to D2; after the pair of piezoelectric backing materials are joined, the first piezoelectric material 10 and the second piezoelectric material 10' are flush in the thickness direction to form a flush piezoelectric material layer, so as to define the first column 101 and second column 102 with a width of K2 and a spacing of P1, and the first groove 103 and second groove 104 with a width of K1 + K2 and a spacing of 2P1, and a gap with a width of K1 is formed between the adjacent strip columns, that is, the first column 101 and the second column 102.In yet another embodiment, an insulating adhesive material is coated on the surface of the first groove 101 of a cut piezoelectric backing material 100, and then another cut piezoelectric backing material 100 with the same parameters is inserted and appropriate pressure is applied, usually at a pressure of 1 - 6 MPa, so that the bottom of the first groove 102 of one piezoelectric backing material 100 fits closely with the conductive backing surface of the other piezoelectric backing material 100 to define the gap width between the piezoelectric backing materials ≤ K1. Ideally, the gap widths on both sides of the first column 101 are both 0.5*K1. Figure 5 The vertical black solid area is the gap filled with epoxy resin glue, and the horizontal black solid area is the glue layer between the piezoelectric materials 10 / 10' and the backing materials 11 / 12. Remove the backing material on one side of the piezoelectric material until the piezoelectric material is exposed to form a substantially flat first surface, and remove a part of the backing material on the other side of the piezoelectric material to form a substantially flat second surface. The first surface and the second surface constitute the surfaces of the piezoelectric composite material in the thickness direction; wherein, both the first surface and the second surface are defined by strip columns and gaps joined by an insulating adhesive material between adjacent strip columns. In the piezoelectric composite material: electrodes are provided on both the first surface of the piezoelectric material and the second surface of the backing material in the piezoelectric composite material, or electrodes are provided only on the first surface of the piezoelectric material in the piezoelectric composite material. Specifically, conductive electrodes can be plated through a metal plating process. In a more specific embodiment, after the glue layer is completely cured, the conductive backing layer on one side of the piezoelectric material is ground away, and after the piezoelectric material is exposed, the piezoelectric material is ground to the required final thickness, and the conductive backing on the other side of the piezoelectric material is ground to a conductive backing thickness of T2 or T3. When T2 < T3, the thickness of the conductive backing is ground to be less than or equal to T2; when T3 < T2, the thickness of the conductive backing is ground to be less than or equal to T3.

[0073] According to the specification parameter requirements of the ultrasonic transducer, the strip column width and the gap (element gap) of the piezoelectric composite material can be further reduced in the above implementation manner, or after the grooving and interdigital process of the 2 - 2 type piezoelectric composite material are completed, the cutting direction is rotated 90° along the horizontal plane, and then the grooving and interdigital process are carried out to form a 1 - 3 type piezoelectric composite material with a combined conductive backing layer as shown in FIG. 7.

[0074] The upper and lower surfaces of the piezoelectric material 10 / 10′ are plated with electrodes for conduction, and the plated electrodes include but are not limited to nickel layer plus gold layer. The backing material 11 / 12 is made of conductive material, such as graphite, metal, etc.; or an insulating material is used, and electrodes are plated on the upper and lower surfaces of the insulating material, or a conductive material is added inside the insulating material, so that the upper and lower surfaces of the backing material 11 / 12 are conductive. Electrodes are plated on the upper and lower surfaces of the ground piezoelectric material 10 and the backing material 11 / 12 in the piezoelectric composite material, or electrodes are plated only on the surface of the piezoelectric material 10, to form a 2-2 type piezoelectric composite material with a combined conductive backing layer, that is, the piezoelectric composite material of the present invention is a combination of a traditional piezoelectric composite material and a backing material.

[0075] refer to Figure 8 For the piezoelectric composite material, the backing material can be processed into a limited structure to ensure that the sub-element gap K3 of the piezoelectric composite material is aligned with the conductive pad S of the circuit board, and the element gap K4 is aligned with the position between the two conductive pads S of the circuit board, so as to avoid the space of the electronic components. Combined with the circuit board structure with a pad of a specific shape, for example, Fig. 9 As shown, the conductive pad is usually in the shape of an "I" to ensure that the position of the piezoelectric composite material on the circuit board will not be offset.

[0076] In one embodiment, a blade with a thickness of K4 is used to cut off the electrode on the surface of the backing material 11 / 12, which is the gap defined by the bonding of the insulating adhesive material, i.e., the gap between the array elements, and the cutting depth is less than the thickness of the backing material 11 / 12; then a blade with a thickness of K3 is used to cut grooves at the center of the two gaps on the surface of the backing material 11 / 12 at a spacing of P1 to form a work position groove, and the work position groove is limitedly matched with the conductive pad S of the circuit board by controlling the cutting depth, so that the piezoelectric composite material is relatively fixedly pressed onto the conductive pad S on the surface of the circuit board through the work position groove of the backing material. More specifically, in one embodiment, the cutting depth is controlled to be appropriately less than the height of the conductive pad of the circuit board; the cutting width K3 is greater than the middle area width of the "I"-shaped conductive pad S of the circuit board, but less than the width of the two end areas of the "I"-shaped conductive pad S.

[0077] refer to Figure 10-1 / 10-2, use conductive glue to crimp the backing material 11 / 12 of the piezoelectric composite material to the "I"-shaped conductive pad S on the surface of the circuit board, and lead the positive or negative electrode of the piezoelectric composite material to the back-end circuit. The other polarity of the piezoelectric composite material is passed through the electrode layer plated on the first surface of the piezoelectric composite material. Use conductive material C such as conductive silver paste, coating, etc. to lead the other polarity to the corresponding grounding area of ​​the circuit board, usually the extra grounding pads J on both sides. At this point, the positive and negative electrodes of the transducer array element have been led to the back-end circuit.

[0078] In one embodiment, since the circuit board pads are in an "I"-shaped structure and there are corresponding grooves on the surface of the backing material, a mutually locking structure can be formed, which solves the problem of cutting the array elements according to the spacing between the circuit board pads in the traditional ultra-high frequency ultrasonic transducer manufacturing process. The other polarity of the piezoelectric composite material is led to the corresponding grounding area of ​​the circuit board through the coating on the surface of the piezoelectric composite material using conductive materials (conductive silver paste, coating, etc.), usually the extra grounding pads J on both sides. At this time, the positive and negative poles of the transducer array element have been led to the back-end circuit. Finally, according to the corresponding process, the acoustic matching layer and the acoustic lens layer are added to complete the final ultra-high frequency ultrasonic transducer product.

[0079] The present invention uses the backing material 11 / 12 and the piezoelectric material 10 to perform the interdigitation process together. It is particularly noted that when the two piezoelectric backing materials 100 interdigitate with each other, the piezoelectric material 10 is aligned in the thickness direction. If the alignment is not aligned, it will cause the emission surface of the piezoelectric material to be not on the same plane, which will lead to inconsistent thickness of the matching layer on each array element in the subsequent process, affecting the performance of the array element. The present invention can solve the difficulty of piezoelectric material alignment based on the "algebraic fitting method" and the "mold limiting method": the algebraic fitting method is to calculate the preset depth of the groove according to the thickness fitting of the piezoelectric material 10 and the backing material 11 / 12 that are cut through, and then the groove of the calculated depth is cut by a high-precision groove cutting device. When bonding, the two piezoelectric backing materials 100 with grooves cut with the same parameters are aligned and pressed according to the method of aligning the bars and the slits. Of course, as long as the depth of the through groove cut by one of the piezoelectric backing materials is equal to the preset depth, the other groove is kept greater than or equal to the preset depth, and the alignment of the piezoelectric material layer in the thickness direction can be ensured. The "mold limiting method" is to set the cutting depth according to the preset depth of the groove calculated by the "algebraic fitting method", and the set cutting depth is greater than or equal to the calculated depth based on the "algebraic fitting method". After the cutting is completed, the uncut surfaces of the two piezoelectric backing materials 100 are respectively attached or adsorbed on the upper and lower pressing blocks of the pressing mold 2, and the final pressing position of the material is determined by adjusting the distance between the upper and lower pressing blocks of the pressing mold.

[0080] refer to Fig.11 The pressing mold 2 includes an upper pressing block 20 and a lower pressing block 21, and a support rod 22 for fixing the upper pressing block 20 and the lower pressing block 21. The upper pressing block 20 is slidably arranged along the support rod 21. After obtaining the grooved material, the uncut surfaces of a pair of piezoelectric backing materials 100 to be interdigitated are fixed on the upper pressing block 20 and the lower pressing block 21 of the mold by bonding or adsorption. Fig.11In this way, control the depth of the through-grooves in the pair of cut piezoelectric backing materials to be not less than the aforementioned preset depth. Place a limiting block 23 on the lower pressing block, and the height of the limiting block 23 is equal to the preset depth; when T2 < T3, the height of the limiting block 23 is equal to TI + 2T3 + 2T4; when T2 > T3, the height of the limiting block is equal to T1 + 2T2 + 2T4. Fix the uncut surfaces of the two pieces of interdigital materials to the upper pressing block 20 and the lower pressing block 21 of the pressing die 2 respectively by means of pasting or adsorption; press the upper pressing block 20 and the lower pressing block 21 until the distance between the pressing blocks is equal to the height of the limiting block 23. Among them, the limiting block can be a limiting device with a fixed height or a limiting device with adjustable height. Fine-tune the limiting height according to the alignment effect of each layer of materials during pressing, and the specific structure can be set conventionally according to needs.

[0081] The piezoelectric composite material prepared based on the above preparation method includes a piezoelectric backing material 100; the piezoelectric backing material 100 includes a piezoelectric material 10, a first backing material 11 and a second backing material 12 located on the upper and lower surfaces of the piezoelectric material 10, and each layer of material is kept flush in the thickness direction; the first backing material 11 and the second backing material 12 are bonded to the piezoelectric material 10 through an insulating bonding material;

[0082] The piezoelectric backing material 100 has bars and through-grooves formed by cutting. The bars of one piezoelectric backing material are inserted into the through-grooves of another piezoelectric backing material 100 for alternating interdigital arrangement, and there are gaps filled with an insulating bonding material between adjacent bars to form a piezoelectric backing material combination. The piezoelectric backing material combination forms a piezoelectric composite material including a piezoelectric material, an insulating bonding material, and a backing material stacked in sequence by removing part of the backing material; among them, there are also gaps defined by bonding with an insulating bonding material between adjacent bars in the piezoelectric composite material. In one embodiment, for how to remove part of the backing material, it can be carried out as follows: the piezoelectric backing material combination after removing the backing material on one side of the piezoelectric material and removing part of the backing material on the other side of the piezoelectric material forms a piezoelectric composite material with a combined predetermined thickness of the backing material and a piezoelectric material with a predetermined thickness. Specifically, Figure 6 the piezoelectric material, insulating bonding material, and backing material are stacked in sequence from top to bottom to form a 2-2 type piezoelectric composite material. Or by removing part of the backing material on both sides of the piezoelectric material, making the final thicknesses of the backing materials on both sides inconsistent, then cutting grooves and interdigitalizing with the thinner backing material and then removing the backing material on one side of the piezoelectric material until the piezoelectric material is exposed and removing part of the backing material on the other side of the piezoelectric material, a 1-3 type piezoelectric composite material stacked with a piezoelectric material, an insulating bonding material, and a backing material in sequence from top to bottom can be formed. Combining Figure 7-1 、 7-2As shown, the upper and lower surfaces of the 1-3 type piezoelectric composite material form a grid shape, which is different from the strip-shaped upper and lower surfaces of the 2-2 type piezoelectric composite material, but their laminated materials are consistent in the thickness direction.

[0083] refer to Figure 12-17 , is a method for electrode extraction of a piezoelectric composite material. On the basis of the above-mentioned method for preparing a piezoelectric composite material, in each piezoelectric backing material 100, the surface of the first backing material 11 and the surface of the second backing material 12 bonded to both sides of the piezoelectric material 10 / 10′ both have a conductive area E; wherein the two sides of the piezoelectric material refer to the upper and lower surfaces of the piezoelectric material along the thickness direction; the first backing material 11 and the second backing material 12 are both insulating non-conductive backing materials. In specific applications, such as Figure 12-13 As shown, the first backing material 11, the second backing material 12 and the piezoelectric material form an upper and lower conductive area E, one layer is a signal electrode, the other layer is a ground electrode, and the two layers are disconnected. A pair of piezoelectric backing materials 100 are cut to form bars and through grooves, and the through grooves of the pair of piezoelectric backing materials 100 are provided with a conductive layer for corresponding conduction with the conductive area around the backing material; the cut pair of piezoelectric backing materials are cross-aligned with each other by extending the bars into the through grooves, and at least one through groove of the piezoelectric backing material 100 has a step width that narrows from the outside to the inside of the cutting surface, so that a gap with a step width is formed between adjacent bars in the formed piezoelectric composite material, and the gap on the wider side is formed in the backing material of the piezoelectric composite material, a continuous conductive layer is provided on the second surface of the backing material, and the electrode lead structure of the piezoelectric composite material is obtained by cutting the continuous conductive layer between adjacent bars.

[0084] In one embodiment, one of the piezoelectric backing materials 100 is cut to have a first groove 103, wherein the first groove 103 includes a shallow groove A provided in the backing material 11 layer on one side of the piezoelectric material and a deep groove B penetrating the piezoelectric material 10 to the backing material 12 on the other side, wherein the width of the shallow groove A is wider than the deep groove B; see Fig.12 , a first conductive layer S1 is plated on the surface of the shallow groove A, the first conductive layer S1 extends along the side of the first backing material to part of the side of the piezoelectric material 10, and the first conductive layer S1 is bonded to the conductive area E of the backing material where the first conductive layer S1 is located, and is connected to each other; Fig.12 The first conductive layer S1 is actually connected to the conductive area E (shown as Fig.12 The upper conductive area E) is in a bonding state, that is, the first conductive layer S1 is conductively connected to the electrode bonded to the backing material where the first conductive layer S1 is located, and is connected to another electrode (shown as Fig.12 The lower conductive area E) is disconnected.

[0085] The second groove 104 cut in another piezoelectric backing material 100 is a straight groove, see Fig.13 , a conductive layer is plated along the surface of the second groove 104, and then the plated layer from the backing material 12 on the second groove 104 to the side of part of the piezoelectric material 10 / 10′ is cut, and the plated layer at the bottom is retained to form a second conductive layer S2, and the second conductive layer S2 is connected to the conductive area E bonded to the backing material where the second conductive layer S2 is located; Fig.13 The second conductive layer S2 is actually bonded to the conductive region E of the second backing material 12 (shown as the conductive region E of the lower layer), that is, the second conductive layer S2 is conductive to the electrode bonded to the backing material where the second conductive layer S2 is located, and is conductive to the other electrode (shown as Fig.13 The upper conductive area E) is disconnected.

[0086] The gaps between adjacent bars in the formed piezoelectric composite material are made to have a step width, with a wider gap formed on the side close to the shallow groove A and a narrower gap formed on the side away from the shallow groove A; a continuous conductive layer S' is plated on the second surface of the piezoelectric composite material close to the shallow groove A, and then the electrodes of adjacent bars in the piezoelectric composite material are divided by cutting the continuous conductive layer S' between adjacent bars.

[0087] Among them, two piezoelectric backing materials 100 coated with a first conductive layer S1 and a second conductive layer S2 are interdigitated. More specifically, the first column 101 of the piezoelectric backing material is placed in the second groove 104 of another piezoelectric backing material, and the second column 102 of the piezoelectric backing material is placed in the first groove 103 of another piezoelectric backing material to interdigitate, and there is a gap filled with an insulating adhesive material between the adjacent first column 101 and the second column 102 to form a piezoelectric composite material; after removing the backing material on one side of the piezoelectric material, part of the backing material on the other side is removed to a predetermined thickness, such as a thickness not exceeding the smaller value of T2 or T3, which can be removed by grinding to form a substantially flat first surface and second surface. Then, a conductive layer is plated on the second surface of the backing material in the piezoelectric composite material, and then the electrodes are divided between the adjacent first column 101 and the second column 102 in the piezoelectric composite material.

[0088] Based on the electrode extraction method, the total depth of the groove, that is, the total depth of the shallow groove A and the deep groove B, is greater than the thickness of the backing material but less than the sum of the thickness of the backing material and the piezoelectric material 10 in the aforementioned embodiment. Figure 6Embodiments of the cutting method, such as cutting to a preset depth at a uniform spacing on the surface of each piezoelectric backing material; if T2 < T3, cutting from the surface of the first backing material 11 with a thickness of T2, and controlling the cutting depth to reach the preset depth D1 = T1 + 2*T2 + 2*T4, then the cutting depth of the second backing material 12 ≥ D1; if T3 < T2, cutting from the surface of the second piezoelectric backing material 12 with a thickness of T3, and controlling the cutting depth to reach the preset depth D2 = T1 + 2*T3 + 2*T4, then the cutting depth of the first backing material ≥ D2, so that after the pair of piezoelectric backing materials are joined, the piezoelectric materials therein are flush in the thickness direction to define the first column 101 and the second column 102 with a constant spacing, and a gap with a stepped width that becomes narrower from the cutting surface inward is formed between the adjacent first column 101 and the second column 102.

[0089] In a specific embodiment, a piezoelectric backing material 100 is used. The piezoelectric backing material 100 includes a piezoelectric material 10, and a first backing material 11 and a second backing material 12 located on the upper and lower surfaces of the piezoelectric material 10: the first backing material 11 and the second backing material 12 are bonded to the piezoelectric material 10 through an insulating adhesive material; wherein, the surfaces of the first backing material 11 and the second backing material 12 close to the piezoelectric material both have a conductive region E; along a piezoelectric backing material 100, such as Fig.12 shown, first cut a shallow groove A inward from the surface of the thinner first backing material 11: then deposit a first conductive layer S1 on the surface of the shallow groove A (including the top surface of the backing material), and the first conductive layer S1 extends along the side surface of the first backing material 11 to a part of the side surface of the piezoelectric material 10, and the first conductive layer conducts with the conductive region E; then cut a deep groove B, and the width of the deep groove B is smaller than the width of the shallow groove A cutting into the piezoelectric material 10; the shallow groove A is wider than the deep groove B, and the total depth of the cut grooves, that is, the total depth of the shallow groove A and the deep groove B that constitute the first groove 103, can be used as the preset depth, and this depth is greater than the thickness of the backing material therein but less than the sum of the thicknesses of the pair of backing materials and the piezoelectric material 10; along another piezoelectric backing material 100, such as Fig.13As shown, the surface of the thinner first backing material 11 is cut inward to the final depth (greater than or equal to the preset depth of the first groove 103), and then a conductive layer is plated, and then the backing material 12 on the second groove 104 is cut to the plated layer on the side of part of the piezoelectric material 10, and the plated layer on the bottom is retained to form a second conductive layer S2, and the second conductive layer is connected to the conductive area E; two pieces of piezoelectric backing materials 100 are relatively cross-plugged, and the backing material on one side of the piezoelectric backing material 100 is completely removed until the piezoelectric material 10 is exposed to form a basically flat first surface; the backing material on the other side of the piezoelectric material is partially removed to form a basically flat second surface; and the first surface is formed by alternating adjacent piezoelectric materials and narrow gaps filled with insulating adhesive materials, and the second surface is formed by backing materials and wide gaps filled with insulating adhesive materials between adjacent backing materials.

[0090] At this point, by forming a piezoelectric composite material with a gap structure with a step width, it is convenient to perform electrode segmentation at a wider gap. After the pair of piezoelectric backing materials are interdigitated, the thickness of the backing materials on both sides of the piezoelectric material is the same. If a 2-2 type piezoelectric composite material is to be made, the backing material on one side of the piezoelectric material (such as bonded on the positive electrode surface) is ground off, and the backing material on the other side (such as bonded on the negative electrode surface) is ground to a predetermined thickness. If a 1-3 type piezoelectric composite material is to be further made as needed, the backing material on both sides of the piezoelectric material is thinned to expose the grooves that have been filled with insulating adhesive material, and the backing materials on both sides of the piezoelectric material are ground to two different thickness values, and then the backing material on the thinner side is cut to perform an interdigitation process to form a 1-3 type piezoelectric composite material. For example, forming a Figure 14-16 The 2-2 type or 1-3 type piezoelectric composite material shown in the figure is coated with a conductive layer S' on the second surface of the backing material of the piezoelectric composite material near the wider gap on the shallow groove side, and then the first column 101 and the second column 102 alternately adjacent to each other in the piezoelectric composite material are divided into electrodes, and the circuit board lead-out electrode is bonded to the electrode divided by the piezoelectric composite material. Thus, the function of electrode lead-out is realized simply and with high quality.

[0091] In addition, the present invention also provides a transducer, see Fig.18 , including the piezoelectric composite material and a circuit board 3, and the piezoelectric composite material is conductively connected to the circuit board 3 by the above-mentioned electrode lead-out method.

[0092] The above-mentioned ideal embodiments of the present invention are for inspiration. Through the above-mentioned description, relevant staff can make various changes and modifications without departing from the technical idea of ​​the present invention. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing a piezoelectric composite material, characterized in that: It includes the following steps: Provide a pair of piezoelectric materials, and provide a pair of backing materials for the upper and lower surfaces of each piezoelectric material. The backing materials are bonded to the piezoelectric materials to form a pair of piezoelectric backing materials; By cutting the surface of each piezoelectric backing material and grooving at a certain spacing, form strip columns and through grooves extending in the thickness direction, and adjacent strip columns in the same piezoelectric backing material are spaced apart by the through grooves; Place a pair of cut piezoelectric backing materials in a cross-aligned manner, such that the strip columns of one piezoelectric backing material are placed in the through grooves of the other piezoelectric backing material, and bond the gaps between adjacent strip columns through an insulating bonding material to bond the pair of piezoelectric backing materials; Remove a part of the backing material in the thickness direction of the bonded piezoelectric backing material to form a piezoelectric composite material. The surface of the piezoelectric composite material in the thickness direction is substantially flat, and the piezoelectric materials therein are aligned in the thickness direction. The surface is formed by the strip columns and the gaps bonded by the insulating bonding material between adjacent strip columns; 2. The preparation method according to claim 1, characterized in that: The pair of piezoelectric materials have the same size and a thickness of T1. Electrodes are plated on the upper and lower surfaces of the piezoelectric materials in the thickness direction; the pair of backing materials have the same length and width dimensions, but different thicknesses, which are T2 and T3 respectively. Each backing material has conductive regions for conduction on its upper and lower surfaces in the thickness direction; The thickness of the insulating bonding material is T4, and the total thickness of each piezoelectric backing material is T5 = T1 + T2 + T3 + 2*T4. And the positive electrode of one piezoelectric material is bonded to the backing material with a thickness of T2, and the negative electrode is bonded to the backing material with a thickness of T3. The bonding thickness of the positive and negative electrodes of the other piezoelectric material and the backing material is opposite; 3. The preparation method according to claim 2, characterized in that: Use a blade with a thickness of K1 + K2 to cut a pair of piezoelectric backing materials, and cut each piezoelectric backing material to a preset depth at a spacing of 2*P1 on its surface: If T2 < T3, cut from the surface of the backing material with a thickness of T2, and control one of the backing materials to be cut to a preset depth D1 = T1 + 2*T2 + 2*T4, and the cutting depth of the other backing material is not less than D1; If T3 < T2, cut from the surface of the backing material with a thickness of T3, and control one of the backing materials to be cut to a preset depth D2 = T1 + 2*T3 + 2*T4, and the cutting depth of the other backing material is not less than D2; After the pair of piezoelectric backing materials are bonded, the piezoelectric materials therein are kept flush in the thickness direction to define the strip columns with a width of K2 and a spacing of P1 and the cut grooves with a width of K1 + K2 and a spacing of 2P1, and form gaps with a width of K1 between adjacent strip columns; 4. The preparation method according to claim 3, characterized in that: Remove the backing material on one side of the piezoelectric material until the piezoelectric material is exposed to form a substantially flat first surface, and remove a part of the backing material on the other side of the piezoelectric material to form a substantially flat second surface. The first surface and the second surface constitute the surface of the piezoelectric composite material in the thickness direction; in the piezoelectric composite material: electrodes are provided on both the first surface of the piezoelectric material and the second surface of the backing material in the piezoelectric composite material, or electrodes are provided only on the first surface of the piezoelectric material in the piezoelectric composite material.

5. The preparation method according to claim 4, characterized in that: For the piezoelectric composite material, at the second surface of the backing material, the electrodes on the surface of the gap joined based on the insulating bonding material are cut off, and the cutting depth is less than the thickness of the backing material; at the central positions of two adjacent gaps located at the second surface of the backing material, grooves are cut at a pitch P1, and the limit fit between the piezoelectric composite material and the conductive pads of the circuit board is achieved by controlling the groove depth.

6. The preparation method according to claim 2, characterized in that: Control the groove depths in the pair of cut piezoelectric backing materials to be not lower than a preset depth, and fix the two uncut surfaces of the pair of piezoelectric backing materials on the upper and lower pressing blocks of the pressing die by pasting or adsorption methods respectively; place a limit block on the lower pressing block, and the height of the limit block is equal to the preset depth. When T2 < T3, the height of the limit block is equal to T1 + 2T3 + 2T4; when T3 < T2, the height of the limit block is equal to T1 + 2T2 + 2T4; press the upper and lower pressing blocks to a position where the distance is equal to the height of the limit block.

7. A piezoelectric composite material, characterized in that: Prepared by the preparation method according to any one of claims 1-6, the piezoelectric composite material includes a piezoelectric material, an insulating bonding material, and a backing material stacked in sequence along the thickness direction, and the piezoelectric materials are flush in the thickness direction; moreover, there are gaps joined by the insulating bonding material between adjacent strips in the piezoelectric composite material along the direction perpendicular to the stacking direction.

8. A method for leading out electrodes of a piezoelectric composite material, according to the preparation method of the piezoelectric composite material according to any one of claims 1-7, characterized in that: In each piezoelectric backing material, conductive regions are provided on the surfaces of the backing material bonded to both sides of the piezoelectric material. By cutting a pair of piezoelectric backing materials to form strips and through grooves, conductive layers for corresponding conduction with the conductive regions are provided around the through grooves in the backing material of the pair of piezoelectric backing materials; the cut pair of piezoelectric backing materials are cross-aligned with the strips extending into the through grooves, and at least one through groove of the piezoelectric backing material has a stepped width that becomes narrower from the cutting surface from the outside to the inside, so that a gap with a stepped width is formed between adjacent strips in the formed piezoelectric composite material, and the wider side of the gap is formed in the backing material in the piezoelectric composite material. A continuous conductive layer is provided on the second surface of the backing material, and the electrode leading-out structure of the piezoelectric composite material is obtained by cutting the continuous conductive layer between adjacent strips.

9. According to the electrode leading-out method of claim 8, characterized in that: One piezoelectric backing material is cut into a first groove by grooving, and the first groove includes a shallow groove provided on the backing material on one side of the piezoelectric material and a deep groove penetrating through the piezoelectric material to the backing material on the other side, and the width of the shallow groove is wider than that of the deep groove; a first conductive layer is provided on the surface of the shallow groove, and the first conductive layer extends along the side surface of the backing material to a part of the side surface of the piezoelectric material, and the first conductive layer is correspondingly conducted with the conductive region of the backing material where it is located. The second groove cut in the other piezoelectric backing material is a straight groove, a conductive layer is provided on the surface of the straight groove, and then the conductive layer on the backing material of the second groove to the side surface of a part of the piezoelectric material is cut off, and the conductive layer at the bottom is reserved to form a second conductive layer, and the second conductive layer is correspondingly conducted with the conductive region of the backing material where it is located. The gaps between adjacent bars in the formed piezoelectric composite material are made to have a step width, with a wider gap formed on the side close to the shallow groove and a narrower gap formed on the side away from the shallow groove; a continuous conductive layer is provided on the second surface of the piezoelectric composite material close to the shallow groove, and then the electrodes of adjacent bars in the piezoelectric composite material are divided by cutting the continuous conductive layer between adjacent bars.

10. A transducer, comprising the piezoelectric composite material according to claim 7 and a circuit board, characterized in that: The piezoelectric composite material is conductively connected to the circuit board by the electrode extraction method according to claim 8 or 9.

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