Methods and systems for multi-frequency transducer arrays

Abstract

The present invention provides various methods and systems for a multi-frequency transducer array. In one example, the transducer array includes an element formed by one or more sub-elements, at least one of which has a different resonant frequency. This can broaden the frequency range of the transducer array.

Description

Technical Field

[0001] Embodiments of the subject matter disclosed herein relate to transducers for use in medical devices. Background Art

[0002] Transducer probes are used in various applications to convert energy from a physical form into an electrical form. For example, a transducer probe may contain a piezoelectric material that generates a voltage from a mechanical stress or strain applied to the material. Piezoelectric transducer probes are configured to be highly sensitive to provide large signal amplitudes, wide bandwidths for use over a wide frequency range, and short duration pulses for high axial resolution. These characteristics are desirable for medical applications such as imaging, non-destructive evaluation, fluid flow sensing, and the like. In addition, frequency apodization of the transducer probe can mitigate the loss of signal resolution due to signal attenuation and dispersion as the signal travels away from its source. Summary of the invention

[0003] It should be understood that the above brief description is provided to introduce in a simplified form selected concepts further described in the detailed description. This is not meant to identify the key or essential features of the claimed subject matter. In addition, the claimed subject matter is not limited to embodiments that address any disadvantages mentioned above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The present invention will be better understood by reading the following description of non-limiting embodiments with reference to the accompanying drawings, in which:

[0005] Figure 1 An example of an acoustic stack for an ultrasound transducer is shown.

[0006] Figure 2 An example of a uniform multi-element transducer array is shown.

[0007] Figure 3 Shown along Figure 2 First graph of the apodization function in the elevation direction provided by a multi-element transducer array.

[0008] Figure 4 A first example of a piezoelectric element formed from two sub-elements is shown.

[0009] Figure 5 A second example of a piezoelectric element formed from two sub-elements is shown.

[0010] Figure 6 A third example of a piezoelectric element formed from two sub-elements is shown.

[0011] Figure 7A first example of a multi-element transducer array with different spatial frequency distributions is shown.

[0012] Figure 8 A second example of a multi-element transducer array with a different spatial frequency distribution is shown.

[0013] Fig. 9 A third example of a multi-element transducer array with a different spatial frequency distribution is shown.

[0014] Fig.10 A first example of an acoustic stack block is shown.

[0015] Fig.11 Shown by Fig.10 The acoustic stack blocks form the first comb structure.

[0016] Fig.12 A second example of an acoustic stack block is shown.

[0017] Fig.13 Shown by Fig.12 The acoustic stack forms a second comb structure.

[0018] Fig.14 The perspective from the elevation direction shows that Fig.10 The first example with Fig.12 The second example is coupled to form a third example of an acoustic stack block.

[0019] Fig.15 A third example of an acoustic stack block is shown from a perspective along the azimuth direction.

[0020] Fig.16 The coupling of the third example of an acoustic stack block to a base package is shown from a perspective in an elevation direction.

[0021] Fig.17 The coupling of a third example of an acoustic stack block to a base package is shown from a perspective along the azimuthal direction.

[0022] Fig.18 A first example of a basic package is shown from a perspective view.

[0023] Fig.19 A fourth example of an acoustic stack block viewed in an elevation direction is shown, formed by coupling the third example of an acoustic stack block to a base package.

[0024] Fig. 20 A fourth example of an acoustic stack block viewed in the azimuth direction is shown.

[0025] Fig.21 Shows the elevation angle Fig.19A fourth example of an acoustic stack block in which a portion of the back side of the acoustic stack block is ground away.

[0026] Fig. 22 Shows the observed along the azimuth direction Fig. 20 A fourth example of an acoustic stack block in which a portion of the back side of the acoustic stack block is ground away.

[0027] Fig.23 A fourth example of an acoustic stack block having a conductive layer coupled to a ground back side viewed in an elevation direction is shown.

[0028] Fig.24 A fourth example of an acoustic stack block having a conductive layer coupled to a ground back side viewed in an azimuthal direction is shown.

[0029] Fig.25 The dicing of a fourth example of an acoustic stack block viewed in the elevation direction is shown.

[0030] Fig.26 A scribe cut of a fourth example of an acoustic stack block viewed in the azimuthal direction is shown.

[0031] Fig. 27 The coupling of the matching layer block to the front side and the coupling of the backing layer block to the back side of the fourth example of the acoustic stack block viewed in the elevation direction are shown.

[0032] Fig.28 The coupling of the matching layer block to the front side and the coupling of the backing layer block to the back side of the fourth example of the acoustic stack block viewed in the azimuthal direction are shown.

[0033] Fig.29 The singulation of a fourth example of an acoustic stack block viewed in the elevation direction is shown.

[0034] Fig.30 Singulation of a fourth example of an acoustic stack block viewed in the azimuthal direction is shown.

[0035] Fig.31 A fifth example of a multi-element acoustic stack is shown.

[0036] Fig.32 A sixth example of a multi-element acoustic stack is shown.

[0037] Fig.33 A seventh example of a multi-element acoustic stack is shown.

[0038] Fig.34 An eighth example of a multi-element acoustic stack is shown.

[0039] Fig.35 Shows Fig.29 and Fig.30 A variation of the scribe cut of the fourth example of the acoustic laminate block.

[0040] Fig.36 Combining two multi-element comb structures to form an acoustic stack having four sub-elements is shown.

[0041] Fig.37 An example of a routine for making a multi-frequency acoustic stack is shown.

[0042] Fig.38 Shows that it can be used as Fig.37 An example of a method for forming a multi-frequency element of an acoustic stack performed as part of a routine.

[0043] Fig.39 A second graph of the apodization function in the elevation direction provided by a multi-element transducer array having a non-uniform spatial frequency distribution is shown.

[0044] Fig.40 A second example of a basic package is shown from a perspective view.

[0045] Fig.41 A third example of a basic package is shown from a perspective view.

[0046] Fig.42 Examples of acoustic stacks formed from comb structures with different cutout sizes are shown. DETAILED DESCRIPTION

[0047] The following description relates to various embodiments of an acoustic stack for a transducer probe.By adapting the acoustic stack to a piezoelectric element formed from more than one subelement, the acoustic stack can be configured to have a wider frequency bandwidth. Figure 1 An example of an acoustic stack of a transducer probe is shown in FIG. Each of the more than one sub-elements may be a different type of element with a different resonant frequency. The relative proportions of the more than one sub-elements may be kept constant in both the azimuth and elevation directions of the transducer probe to form a uniform array. Figure 2 An example of a uniform multi-frequency transducer array is depicted in , and Figure 3 A first graph illustrating a frequency apodization function provided by a uniform multi-element (eg, more than one sub-element) array is shown. In contrast, Fig.39 , which may be produced by a multi-frequency transducer array having sub-elements comprised in different percentages in each element of the transducer array. As described above, the relative proportions of the sub-elements forming the piezoelectric element may vary, such as Figures 4 to 6 In some examples, the multi-frequency transducer array may not be uniform along at least one of the azimuth direction and the elevation direction, but may present a varying spatial frequency distribution. Figures 7 to 9 Examples of different spatially distributed multi-frequency transducer arrays are shown in . Multi-element transducer arrays can be fabricated via wafer-level methods to enable scalable, low-cost manufacturing. Figures 10 to 36 and Figure 40 to Figure 42 The various processes involved in the wafer-level approach are depicted in FIG. Fig.37 An example of a first routine for manufacturing a multi-frequency acoustic stack of a transducer probe by a wafer-level method is shown in FIG. An example of a second routine for forming a multi-frequency element of an acoustic stack is shown in FIG. Fig.38 depicted in and may be included in Fig.37 In the first routine.

[0048] Figure 1 to Figure 2 , Figures 4 to 36 and Figure 40 to Figure 42 An exemplary configuration with relative positioning of various components is shown. In at least one example, if shown as directly contacting or directly coupling each other, such elements may be referred to as directly contacting or directly coupling, respectively. Similarly, in at least one example, elements adjacent to or adjacent to each other may be adjacent to or adjacent to each other, respectively. For example, components arranged to coplanarly contact each other may be referred to as coplanar contact. For another example, in at least one example, elements positioned to be spaced apart from each other and having only space therebetween without other components may be described and referenced as such. For another example, elements shown as being located above / below each other, located on opposite sides of each other, or located between the left / right sides of each other may be described and referenced as such relative to each other. In addition, as shown in the figure, in at least one example, the topmost element or point of an element may be referred to as the "top" of a component, and the bottommost element or point of an element may be referred to as the "bottom" of a component. As used herein, top / bottom, upper / lower, upper / lower may be relative to the vertical axis of the figure, and may be used to describe the positioning of elements relative to each other in the figure. Thus, in one example, an element shown as being located above other elements is vertically positioned above other elements. As another example, the shapes of elements shown in the figures may be referred to as having these shapes (e.g., such as being rounded, straight, planar, curved, rounded, chamfered, angled, etc.). In addition, in at least one example, elements shown as intersecting each other may be referred to as intersecting elements or intersecting each other. In addition, in one example, elements shown as being within another element or shown as being outside another element may be described and referred to as such.

[0049] Piezoelectric elements can be implemented in transducer probes for a wide range of medical applications, including imaging, non-destructive testing, diagnostics, measuring blood flow, etc. Piezoelectric elements can be formed from a class of crystalline materials that become electrically polarized when subjected to mechanical strain. When stressed, the piezoelectric element outputs a voltage that is proportional to the applied stress.

[0050] Piezoelectric transducer probes (e.g., devices that convert energy from one form to another using the piezoelectric effect) can provide high sensitivity, high frequency response, and high transient response. In some examples, such as in ultrasound transducer probes, the inverse piezoelectric effect can be utilized when power is applied to the piezoelectric element, resulting in deformation of the material and generation of ultrasonic waves. Therefore, no external mechanical force is required, and the piezoelectric transducer probe can be packaged into a compact, easily transportable device.

[0051] Although piezoelectric transducer probes are highly sensitive instruments, the operating frequency bandwidth of the probes can be narrow. For example, piezoelectric materials can be associated with low frequencies, such as between 0.5MHz-2.25MHz, or with high frequencies, such as between 15.0MHz-25.0MHz, but not both. Similarly, transducer probes can be adapted for either transmission or reception, but may not be equipped for high performance in both applications due to the focused frequency range of a particular type of piezoelectric material. Broadband transducer probes can provide a wider operating frequency range, but matching the probe adaptation resistors can be challenging and cost prohibitive.

[0052] In one example, the above problems can be solved by a piezoelectric transducer probe adapted with a multi-frequency transducer array. The multi-frequency transducer array can include elements formed of more than one sub-element in each transducer, each sub-element having a different resonant frequency. In other words, each element can be a hybrid element having an overall resonant frequency modified by the resonant frequencies of the sub-elements. Therefore, configuring a transducer array with hybrid elements of varying composition can enable the transducer array to operate over a range of frequencies while maintaining the sensitivity and resolution of the multi-frequency transducer probe in which the transducer array is implemented. In addition, the transducer can be manufactured via a wafer-level method that provides ground recovery, frequency apodization, and frequency agility in both azimuth and elevation directions. The spatial frequency distribution can thereby be controlled, and the transducer can be manufactured in a cost-effective, scalable manner.

[0053] As described herein, multi-frequency piezoelectric transducers can be used in a variety of medical devices. Figure 1 As shown, a piezoelectric transducer can be included in an ultrasound probe for generating an image based on an ultrasound signal. It should be understood that an ultrasound probe is a non-limiting example of a medical device that utilizes a piezoelectric transducer, and that incorporation of a piezoelectric transducer in other medical devices has been contemplated. For example, a piezoelectric transducer can be used to convert energy in a non-destructive tester, a Jetter system, a high voltage power supply, and the like. Figure 1 The following description is an exemplary overview of how a piezoelectric transducer may be implemented in an ultrasound transducer probe.

[0054] The ultrasound probe includes one or more active components for generating ultrasound signals. Examples of active components or piezoelectric elements 102 of the ultrasound probe are shown in Figure 1 , the acoustic stack 100 has a central axis 104. A set of reference axes is provided, which indicates an azimuth direction 101, an elevation direction 103, and a lateral direction 105 perpendicular to both the azimuth direction and the elevation direction. In other examples, the set of reference axes may represent the z-axis 101, the x-axis 103, and the y-axis 105. The piezoelectric element 102 is disposed at Figure 1 As shown in , its central axis 104 is parallel to the azimuthal direction 101 .

[0055] It should be noted that although the acoustic stack 100 is shown configured for use with a linear ultrasound probe and the azimuth directions are described as being in accordance with Figure 1 The z-axis in the embodiment of the present invention is parallel, but other examples may include azimuth directions that are angled relative to the z-axis, depending on the shape of the piezoelectric element array. For example, the ultrasound probe may be a curved array or a phased array and thus produce a nonlinear beam that is not parallel to the z-axis.

[0056] Although Figure 1 A single piezoelectric element is shown in the figure, but the ultrasound probe may include multiple piezoelectric elements arranged in an array and respectively coupled to an electrical energy source by wires. Each electrical circuit formed by one or more piezoelectric elements may be a transducer. In some examples, the transducer may include an array of piezoelectric elements, which may be arranged in various patterns or matrices, including one-dimensional (1D) linear, two-dimensional (2D) square, 2D annular, etc. In one example, the transducer may be formed by more than one type of piezoelectric element, thereby providing a multi-frequency piezoelectric transducer. The frequency distribution along each of the azimuth direction and the elevation direction may be adapted to be uniform or non-uniform. Reference Figures 2 to 42 , further details of the multi-frequency piezoelectric transducer are provided below.

[0057] Each transducer may be electrically isolated from adjacent transducers, but may all be coupled to a common layer located above and below the piezoelectric element relative to the azimuth direction. The plurality of piezoelectric elements and accompanying layers may be surrounded by a housing of the ultrasound probe, which may be, for example, a plastic shell having a variety of geometric shapes. For example, the housing may be a rectangular block, a cylinder, or a shape configured to comfortably fit in a user's hand. In this manner, Figure 1 The components shown in can be adapted to have a geometry and size suitable for fitting within the housing of an ultrasound probe.

[0058] Piezoelectric element 102 may be a block formed of a natural material such as quartz or a synthetic material such as lead zirconate titanate that deforms and vibrates when a voltage is applied, for example, by a transmitter. In some examples, piezoelectric element 102 may be a single crystal having a crystal axis, such as lithium niobate and PMN-PT (Pb (Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3). The vibration of the piezoelectric element 102 generates an ultrasonic signal formed by ultrasonic waves transmitted from the ultrasonic probe in the direction indicated by arrow 107 (for example, in the azimuth direction 101). The piezoelectric element 102 can also receive ultrasonic waves (such as ultrasonic waves reflected from a target object) and convert the ultrasonic waves into voltage. The voltage can be transmitted to a receiver of an ultrasonic imaging system and processed into an image.

[0059] Electrode 114 may be in direct contact with piezoelectric element 102 to transmit a voltage converted from ultrasound via wire 115. Wire 115 may be connected to a circuit board (not shown) to which multiple wires from electrodes of multiple piezoelectric elements may be fixed. The circuit board may be coupled to a coaxial cable to provide electronic communication between the ultrasound probe and the receiver.

[0060] The acoustic matching layer 120 may be disposed above the piezoelectric element 102, oriented perpendicular to the central axis 104 with respect to the azimuth direction 101. The acoustic matching layer 120 may be a material positioned between the piezoelectric element 102 and the target object to be imaged. By arranging the acoustic matching layer 120 therebetween, the ultrasonic wave may first pass through the acoustic matching layer 120 and be emitted from the acoustic matching layer 220 in phase, thereby reducing the possibility of reflection at the target object. The acoustic matching layer 220 may shorten the pulse length of the ultrasonic signal, thereby increasing the axial resolution of the signal.

[0061] The backing 126 may be disposed below the piezoelectric element 102 relative to the z-axis. In some examples, the backing 126 may be a block of material extending in the elevation direction 103, so that each of the plurality of piezoelectric elements in the ultrasound probe is located directly above the backing 126 relative to the azimuth direction 101. The backing 126 may be configured to absorb ultrasonic waves directed from the piezoelectric element 102 in a direction opposite to the direction indicated by the arrow 107, and to attenuate stray ultrasonic waves deflected by the housing of the ultrasound probe. The bandwidth and axial resolution of the ultrasound signal may be increased by the backing 126.

[0062] Piezoelectric transducer (PZT) probes can provide high penetration into a target as well as high frequency and transient response, enabling high-resolution data to be obtained. However, the type of piezoelectric element included in the probe may operate within a frequency bandwidth that limits the use of the probe to a specific application. For example, a probe with a low center frequency piezoelectric element may be used to produce ultrasound images of deep tissue or organs, but may not provide adequate defect resolution or thickness measurement capabilities. Therefore, using piezoelectric transducer probes for various applications may require access to multiple probes with different piezoelectric elements.

[0063] In contrast, when used in ultrasound applications, capacitive micromachined ultrasonic transducer (CMUT) probes can provide wider bandwidth and more efficient manufacturing because the ultrasonic transducer CMUT is constructed on silicon via micromachining techniques. The wider CMUT bandwidth enables the CMUT probe to achieve greater axial resolution than the PZT probe. However, the sensitivity and penetration of the CMUT probe can be less than that of the PZT probe. In addition, the CMUT may be more susceptible to acoustic crosstalk than the PZT.

[0064] In one example, high penetration and wide bandwidth can be provided in a PZT probe by adapting the PZT probe to a transducer equipped with a piezoelectric element formed of more than one type of sub-element, where each sub-element is a different type of piezoelectric material. A multi-frequency piezoelectric element array can be provided by combining piezoelectric sub-elements with different resonant frequencies into one transducer. Depending on the relative proportions of the sub-elements, each of the multi-frequency elements in the multi-frequency element can have a different frequency, thereby allowing the multi-frequency element to transmit and receive signals over a wider frequency range than a single element transducer probe.

[0065] For example, Figure 2 As shown, an example of a first matrix 200 having multi-frequency elements may be a uniform two-dimensional array having uniform multi-frequency elements 202, such as a butterfly matrix array. The first matrix 200 may represent an arrangement of elements 202 in an acoustic stack (such as Figure 1 The arrangement of the first matrix 200 within a transducer of the acoustic stack 100 of FIG. 100 . At least one of the acoustic stacks may be incorporated within a PZT probe. The first matrix 200 is shown oriented along an azimuth direction 101 and an elevation direction 103.

[0066] Each of the elements 202 includes a first sub-element 204 and a second sub-element 206. As an example, the first sub-element 204 may be a higher frequency element and the second sub-element 206 may be a lower frequency element, wherein the first sub-element 204 and the second sub-element 206 may be referred to as follows: Figures 10 to 38The elements 202 may be spaced apart from each other and thereby electrically isolated from adjacent elements 202. Each of the elements 202 may be coupled to an electrical circuit 208 to enable application of a voltage to induce deformation of each of the elements 202. In addition, each of the elements 202 may transmit a separate signal induced by the deformation. It should be noted that each of the elements 202 is coupled to an electrical circuit 208, but for simplicity, the electrical circuit 208 is not shown in FIG. Figure 2 Only the bottom row of elements 202 is shown directly coupled to electrical circuit 208 .

[0067] The first matrix 200 can be coupled to other layers of the acoustic stack, such as an acoustic lens, a backing, etc. Figure 1 As a result of forming the element from the first sub-element 204 and the second sub-element 206, the elements can transmit and / or receive over a wide range of frequencies. For example, the first sub-element 204 can have a center (e.g., resonant) frequency of 2.0 MHz, and the second sub-element 206 can have a center frequency of 15 MHz. By combining the first sub-element 204 and the second sub-element 206 in equal relative proportions, the element 202 can transmit and / or receive ultrasound signals over a wider frequency range than the first sub-element 204 or the second sub-element 206 alone.

[0068] For example, each of the elements 202 may have a frequency range of 1.5 MHz to 15 MHz. Figure 3 As shown, the array of elements 202 in the first matrix 200 can provide a symmetrical and linear apodization function along the elevation direction 103. The graph 300 shows the high frequency sub-element (e.g., Figure 2 The first subelement 204 of FIG. 1 and the low-frequency subelement indicated by curve 304 (eg, Figure 2 The apodization function is plotted relative to the percentage content of high frequency sub-elements and low frequency sub-elements in each element of the transducer array along the y-axis and relative to the elevation direction 103 along the x-axis. The equal proportions of high frequency sub-elements and low frequency sub-elements distributed along the elevation direction result in a uniform apodization function.

[0069] As mentioned above, Figure 2 The high frequency sub-element 204 and the low frequency sub-element 206 of the element 202 may provide a symmetrical and non-tapered apodization function, where there are equal proportions of sub-elements in a uniform matrix array, e.g., each multi-frequency element of the array is similarly configured. However, in order to make the sampled signal drop to zero or close to zero at the edge of the sampling area to suppress leakage sidelobes, a tapering of the apodization function may be required. For example, in Fig.39The tapered apodization function (non-discretized) provided by the element formed by the high frequency sub-element and the low frequency sub-element is shown in the second graph 3900 in FIG.

[0070] Curve 3902 represents the apodization function of the high frequency sub-element in each element of the transducer array relative to the percentage content (y-axis) along the elevation direction 103, and curve 3904 represents the apodization function of the low frequency sub-element in each element of the transducer array. Curve 3902 and curve 3904 are inversely related, so that the maximum value of the first curve 3902 relative to the y-axis at the central area of ​​the transducer array along the elevation direction 103 corresponds to the minimum value of curve 3904. On either side of the maximum value, curve 3902 decreases along the y-axis, while curve 3904 increases proportionally. Although the maximum percentage content of each of the high frequency sub-element and the low frequency sub-element is shown at 80%, and the minimum percentage content is shown at 20%, other examples may include any other values ​​of the maximum percentage content and the minimum percentage content, such as 100% and 0%, respectively.

[0071] The sum of the high frequency apodization function and the low frequency apodization function can provide sidelobe reduction. For example, it may be desirable to have a higher proportion of high frequency elements at the central region of the transducer array and a higher proportion of low frequency elements along the sides of the transducer array to achieve maximum suppression of leakage sidelobes. The tapered apodization function shown in graph 3900 can be generated by configuring the elements of the transducer array to have unequal relative proportions of each of the high frequency sub-elements and the low frequency sub-elements. For example, the central region of the transducer can include elements having a higher percentage content of high frequency sub-elements than the outer edges. Suppression of sidelobes is thereby enhanced.

[0072] An example of a component with unequal subcomponent proportions is shown in Figures 4 to 6 Shown in. Figure 4 A first example of a multi-frequency element 400 with unequal distribution is shown in FIG. The multi-frequency element 400 is composed of a plurality of components similar to Figure 2 The first sub-element 204 of the element 202 and the first high-frequency sub-element 402 and the second low-frequency sub-element 404 of the second sub-element 206 are formed.

[0073] The first width 406 of the first sub-element 402 may be greater than the second width 408 of the second sub-element 404. For example, the first width 406 may be four times the second width 408, resulting in 80% of the multi-frequency element 400 being formed by the first high-frequency sub-element 402 and 20% being formed by the second low-frequency sub-element 404. In other examples, the relative widths of the sub-elements may be reversed. Figure 5A second example of a multi-frequency element 500 is shown in FIG. 5 and includes a first high frequency sub-element 502 and a second low frequency sub-element 504. In the second example, a first width 506 of the first sub-element 502 may be half of a second width 508 of the second sub-element 504.

[0074] In a third example of a multi-frequency element 600 having an unequal distribution, as Figure 6 As shown, multi-frequency element 600 is similarly formed by first high frequency sub-element 602 and second low frequency sub-element 604. First sub-element 602 also has a first width 606 that is smaller than second width 608 of second sub-element 604. First width 606 may be, for example, one-fourth of second width 608.

[0075] Figures 4 to 6 The examples of multi-frequency elements with unequal sub-element distributions shown in are non-limiting examples of multi-frequency elements. Other examples may include multi-frequency elements with any relative ratio variation between the first sub-element and the second sub-element of the element. Furthermore, other examples of multi-frequency elements may include more than two sub-elements. For example, the multi-frequency element may be formed of three or four sub-elements, each of which has various ratios.

[0076] Arrays of non-uniform multi-frequency elements can be configured to provide Fig.39 The frequency apodization function shown in FIG. 1 may be non-uniform with respect to the percentage content of different sub-elements forming each multi-frequency element included in the array. In other words, the number of sub-elements, each of the sub-elements having different resonant frequencies, and the relative proportions of the sub-elements in each element may not be uniform throughout the array, so that the spatial distribution of the elements has different frequency ranges. In one example, as Figure 7 As shown, it is configured to provide a Fig.39 The second matrix 700 of apodization functions shown in the graph 3900 of FIG. 700 may be an example of a one-dimensional (1D) linear array formed by a plurality of elements 702. A first row 701, a second row 703, and a third row 705 of the plurality of elements 702 are depicted. The dashed line between the second row 703 and the third row 705 indicates the presence of an optional additional row disposed between the second row 703 and the third row 705, which is omitted for simplicity. Figure 7 In other words, the second matrix 700 may have at least one row and may include any number of additional rows. Each element in the plurality of elements 702 may be coupled to an electrical circuit and transmit a separate signal based on the composition of each element.

[0077] Each element in the plurality of elements 702 includes a first high-frequency sub-element 704 and / or a second low-frequency sub-element 706. Some of the plurality of elements 702 include both the first sub-element 704 and the second sub-element 706, wherein the sub-elements have varying widths relative to each other (where the width is defined along the elevation direction 103). Likewise, some of the plurality of elements 702 include only the first sub-element 704 or only the second sub-element 706.

[0078] For example, a central region 720 of the second matrix 700 includes a portion of the plurality of elements 702 formed only by the first sub-elements 704, while an edge region 722 away from the central axis 708 of the second matrix 700 is formed only by the second sub-elements 706. A region 724 of the second matrix 700 between the central region 720 and the edge region 722 is formed by both the first sub-elements 704 and the second sub-elements 706 at different ratios. Due to the spatial distribution of the first sub-elements 704 and the second sub-elements 706 along the elevation direction 103, the resonant frequency of each element in the plurality of elements 702 may vary along the elevation direction 103.

[0079] For example, in the center region 720 of the second matrix 700, portions of the plurality of elements 702 that include only the first sub-element 704 may each transmit (and receive) signals at a resonant frequency associated with the first sub-element 704. At the edge region 722, portions of the plurality of elements 702 that are formed only of the second sub-element 706 may each transmit (and receive) signals at a resonant frequency associated with the second sub-element 706. In a region 724 between the center region 720 and the edge region 722, the plurality of elements 702 are a hybrid (e.g., a combination of the first sub-element 704 and the second sub-element 706), and thus may have a range of resonant frequency values ​​between the resonant frequency values ​​of the first sub-element 704 and the second sub-element 706.

[0080] As an example, a first element 707 of the plurality of elements 702 may be composed of 50% of the first sub-element 704 and 50% of the second sub-element 706. The resonant frequency of the first element 707 may be an intermediate value between the resonant frequencies of the first sub-element 704 and the second sub-element 706. A second element 709 of the plurality of elements 702 positioned between the first element 707 and the center region 720 of the second matrix 700 may have a higher percentage of the first sub-element 704 than the first element 707. Thus, the second element 709 may have a resonant frequency that is higher than the resonant frequency of the first element 707 but lower than the resonant frequency of the first sub-element 704. A third element 711 of the plurality of elements 702 positioned between the first element 707 and the left edge region 722 may have a higher percentage of the second sub-element 706 than the first element 707. Thus, the third element 711 may have a resonant frequency that is lower than the first element 707 but higher than the second sub-element 706.

[0081] By incrementally varying the composition of the plurality of elements 702 along the elevation direction 103, the plurality of elements 702 can have a continuous resonant frequency ranging between the resonant frequency of the first sub-element 704 and the resonant frequency of the second sub-element 706. In other examples, the composition of the plurality of elements 702 can similarly vary along the azimuth direction 101 instead of or in addition to the elevation direction 103. Thus, the second matrix 700 can transmit and receive signals over a wider range of frequencies than a transducer array having a uniform element composition. Figure 7 In the example shown, the highest frequencies may be transmitted and received at a center region 720 of the second matrix, while the lowest frequencies may be transmitted and received at an edge region 722 .

[0082] The second matrix 700 may be symmetrical about a central axis 708 of the second matrix 700, the central axis being parallel to the azimuth direction 101. Regardless of variations in the distribution of sub-elements in the plurality of elements 702, the symmetry of the second matrix 700 allows the second matrix to provide, for example, Fig.39 The apodization function is shown.

[0083] Figure 8 , which may be an example of a 1.5-dimensional (1.5D) matrix array. The third matrix 800 includes a plurality of elements 802 arranged in a first row 804, a second row 806, and a third row 808. Similarly, the dashed line between the first row 804 and the second row 806 indicates the presence of additional rows of the third matrix 800, which are omitted for brevity. The third matrix 800 has a central axis 810 parallel to the azimuth direction 101.

[0084] At least a portion of the plurality of elements 802 of the third matrix 800 may be a multi-frequency element 816 formed of a first high-frequency sub-element 812 and a second low-frequency sub-element 814. For example, the multi-frequency element 816 in the plurality of elements 802 may include two first sub-elements of the first sub-elements 812 alternating with two second sub-elements of the second sub-elements 814 in the elevation direction 103. A central region 820 of the third matrix 800 may be formed only of the first sub-elements 812, while an edge region 822 of the third matrix 800 may be formed only of the second sub-elements 814. In addition, a thickness defined in the elevation direction 103 of each element in the plurality of elements 802 may vary across each row of the third matrix 800.

[0085] Due to the spatial distribution of the first sub-element 812 and the second sub-element 814 along the elevation direction 103, the resonant frequency of the plurality of elements 802 may vary in the elevation direction 103. For example, similar to Figure 7 In the second matrix 700, a portion of the plurality of elements 802 in the central region 820 may transmit and receive signals at a higher resonant frequency equal to the resonant frequency of the first sub-element 812, while a portion of the plurality of elements 802 at the edge region may transmit and receive signals at a lower resonant frequency equal to the resonant frequency of the second sub-element 814. A portion of the plurality of elements 802 between the central region 820 and the edge region 822 may have an intermediate resonant frequency between the resonant frequencies of the first sub-element 812 and the second sub-element 814. Therefore, compared with using single-frequency elements in the array of the third matrix 800, the frequency range included in the third matrix 800 may be broadened.

[0086] The third matrix 800 may be symmetrical across the central axis 810 along the elevation direction 103. Similar to Figure 7 The symmetry of the second matrix 700 and the third matrix 800 enables the third matrix 800 to provide Fig.39 The apodization function shown. The 1.5D array (and 1.75D array) can provide an optimized beam pattern when the active aperture of the transducer probe is changed. Therefore, the array is able to optimize the near field with a narrow aperture and the far field with a larger aperture. Figures 10 to 38 The process shown in makes 1.5D or 1.75D arrays, which allows elements with different center frequencies and frequency ranges to be mixed within a single array.This manufacturing process provides increased flexibility in array configuration, but incurs significant additional costs. Fig. 9 An example of a fourth matrix 900, which may be an example of a 1.25 linear array, is shown in FIG. The fourth matrix 900 also has a plurality of elements 902 arranged in a row along the elevation direction 103, and a central axis 904 parallel to the azimuth direction 101. The plurality of elements 902 may each be formed of a single type of element, and are not hybrid elements.

[0087] The fourth matrix 900 includes a first high frequency sub-element 906 and a second low frequency sub-element 908. Each element in the plurality of elements 902 may be formed from either the first sub-element 906 or the second sub-element 908 and may vary in width along the elevation direction 103. The symmetry of the fourth matrix 900 across the central axis 904 along the elevation direction 103 also allows the fourth matrix 900 to provide apodization along the elevation direction 103. Incorporating more than one type of element allows the fourth matrix 900 to operate over a wider frequency range. However, without incorporating hybrid elements (e.g., elements formed from more than one sub-element), the frequency distribution may be wider than Figure 7 and Figure 8 The matrix of is less continuous and more discrete.

[0088] It should be noted that Figures 7 to 9 Each of the plurality of elements may be coupled to an electrical circuit such as Figure 1 and Figure 2 As shown. In addition, other examples of multi-frequency transducer arrays may also include control of frequency apodization and agility along the azimuth direction 101. For example, the distribution of multi-frequency elements may vary along the azimuth direction 101 in a manner similar to that shown along the elevation direction 103. As an alternative or in addition to the frequency variation along the elevation direction, a change in the spatial frequency distribution along the azimuth direction may be implemented in the array. By configuring an array with multi-frequency elements in both the azimuth direction and the elevation direction, more complex apodization can be achieved relative to frequency apodization in a transducer array with uniform elements. By providing a method for changing elements in two directions, the configuration of the array is more flexible and can be more easily implemented as a matrix. In addition, frequency apodization may be achieved in both the azimuth direction and the elevation direction, for example, the ability of the transducer to quickly shift the transmission frequency within a pre-selected range to mitigate interference, mutual interference, or to account for atmospheric effects.

[0089] Incorporating multi-frequency elements into a transducer array can enhance the sensitivity of both signal transmission and reception while increasing the frequency bandwidth of the transducer array. Signal transmission at a specific frequency based on the application of the transducer probe can be selected to excite the multi-frequency elements in the transducer array at the corresponding resonant frequency. By configuring the transducer array with elements having a wide frequency range, different operations of the transducer probe can be achieved. Therefore, the transducer probe can be used in a variety of applications that would otherwise require the use of multiple single-element transducer probes with different resonant frequencies.

[0090] In some examples, post-processing of the signals received by the transducer array may be similar to conventional post-processing, which utilizes already existing post-processing algorithms to convert the signals into, for example, an image.Bandpass filtering of the signals may be modified based on the frequency of the signals.

[0091] The fabrication of multi-frequency transducer element arrays can be achieved via a cost-effective process utilizing a wafer-level approach. The wafer-level approach allows multiple transducer arrays to be generated simultaneously, thereby increasing efficiency and throughput. Figures 10 to 38 and Figure 40 to Figure 42 The fabrication process for a multi-frequency transducer array is described. A wafer-level approach may start with a block of a first acoustic stack 1000, such as Fig.10 The first acoustic stack 1000 is along Fig.10 Observed in the elevation direction, and including a matching layer 1002, similar to Figure 1 The acoustic matching layer 120 may be a conductive layer such as graphite or metal. The matching layer 1002 may be formed of more than one layer stacked along a vertical axis (eg, along the transverse direction 105) of the first acoustic stack 1000, which is configured to be conductive along the vertical axis.

[0092] The matching layer 1002 is arranged above the first piezoelectric layer 1004 with respect to the lateral direction 105. The acoustic impedance difference between the ultrasound transducer probe and the target medium can be buffered by the matching layer 1002. The first piezoelectric layer 1004 is formed of a piezoelectric material configured to transmit and / or receive ultrasound signals and used to form a transducer element of the ultrasound transducer probe, as described above.

[0093] The dematching layer 1006 may be positioned below the first piezoelectric layer 1004. The dematching layer may be a high impedance layer that may reduce insertion loss and increase the frequency bandwidth of the transducer probe. In some examples, the dematching layer may be optionally omitted. Figure 1 A backing layer 1008 similar to the backing 126 of the first piezoelectric layer 1004 may be disposed below the dematching layer 1006. The backing layer 1008 may be formed of a conductive material (such as a composite material) and may suppress excitation effects that may occur when the piezoelectric material switches from a transmit mode to a receive mode. The first piezoelectric layer 1004 may be bonded to the matching layer 1002 and to the dematching layer 1006 (or to the backing layer 1008 when the dematching layer 1006 is not present) with an adhesive (such as an epoxy).

[0094] The first piezoelectric layer 1004 of the first acoustic stack 1000 may have a first height 1010 defined along the lateral direction 105. The first height 1010 may visually distinguish piezoelectric elements having a higher resonant frequency from resonant frequency piezoelectric elements of the second piezoelectric layer 1204 having a larger second height 1210, such as Fig.12 and Fig.13 As shown in FIG. 1 and further described below, the first comb structure 1100 may be composed of Fig.10The first acoustic stack 1000 is produced by evenly spaced apart scribing cuts 1102 in the first acoustic stack 1000 along the lateral direction 105. The cuts 1102 extend downwardly from the matching layer 1002 into the backing layer 1008 along the azimuth direction 101, but do not extend completely through the backing layer 1008. The scribing of the cuts 1102 forms first fins 1104, each of the first fins 1104 being spaced apart from an adjacent first fin 1104 by one of the cuts 1102. The first fins 1104 extend upwardly from the backing layer 1008 along the azimuth direction 101, and may extend across the entire depth of the first comb structure 1100 along the elevation direction 103.

[0095] It should be noted that scribing refers to cutting a cut in a wafer to form a cavity or slot in the wafer that does not extend completely through the height of the wafer. Thus, scribing can electrically isolate portions of the wafer, for example, making a segment electrically discontinuous with an adjacent segment along a plane perpendicular to the height, but does not separate the wafer into separate, separate segments. In contrast, singulation facilitates singulating a wafer into physically separate, separate transducer arrays, as described below. Here, scribing and singulation are performed only along the height of the wafer, for example, in a lateral direction, such that portions of the wafer are electrically isolated and / or physically separated only along a plane formed by an azimuthal direction and an elevation direction.

[0096] The first comb structure 1100 may be scribed to complement or match the second comb structure (e.g., Fig.13 The second comb structure 1300 may be composed of Fig.12 The second acoustic stack 1200 may have similar layers to the first acoustic stack 1000, including a matching layer 1202 formed of the same or different material (or stack of conductive layers) as the matching layer 1002 of the first acoustic stack 1000, and a matching layer 1203 formed of the same or different material (or stack of conductive layers) as the matching layer 1002 of the first acoustic stack 1000. Fig.10 A second piezoelectric layer 1204 formed of a different material than the first piezoelectric layer 1004 , an optional dematching layer 1206 similar to the dematching layer 1006 of the first acoustic stack 1000 , and a backing layer 1208 formed of the same or different material than the backing layer 1008 of the first acoustic stack 1000 .

[0097] As described above, the second height 1210 of the second piezoelectric layer 1204 defined along the azimuthal direction 101 may be greater than the height 1010 of the first piezoelectric layer 1004 of the first acoustic stack 1000. The piezoelectric element formed by the second piezoelectric layer 1204 may have a lower resonant frequency than the piezoelectric element formed by the first piezoelectric layer 1004. The scribed piezoelectric element corresponding to, for example, the first piezoelectric layer 1004 in the first comb structure 1100 is hereinafter referred to as a high-frequency sub-element 1004, and the scribed piezoelectric element corresponding to, for example, the second piezoelectric layer 1204 in the second comb structure 1300 is hereinafter referred to as a low-frequency sub-element 1204.

[0098] The height of the matching layer 1202 of the second acoustic stack 1200, also defined along the azimuthal direction 101, may be greater than the height of the matching layer 1002 of the first acoustic stack 1000, while the height of the backing layer 1208 of the second acoustic stack 1200 may be less than the height of the backing layer 1008 of the first acoustic stack 1000. The height difference between the matching layer and the backing layer may allow the layers of each of the first comb structure 1100 and the second comb structure 1300 to have a desired alignment when the comb structures are combined into a single structure, as further described below.

[0099] The second acoustic stack 1200 may be scored in the opposite direction to the first acoustic stack 1000, such as Fig.13 Thus, the second acoustic stack 1200 is scored such that the cuts 1302 extend upwardly from the backing layer 1208 into the matching layer 1202 in the azimuth direction 101. The cuts 1302 do not extend completely through the matching layer 1202. The cuts 1302 are evenly spaced apart in the lateral direction 105, thereby forming a second fin 1304 between each of the cuts 1302. The second fin 1304 may extend across the entire depth of the second comb structure 1300 in the elevation direction 103.

[0100] The width 1306 of each of the cutouts 1302 of the second comb structure 1300 may be equal to the width 1106 of each of the first fins 1104 of the first comb structure 1100 (eg, Fig.11 Similarly, the width 1308 of each of the second fins of the second comb structure 1300 may be equal to the width 1108 of each of the cutouts 1102 of the first comb structure 1100 (as shown in FIG. Fig.11 13). The height 1310 defined by both the cutout 1302 of the second comb structure 1300 and the second fin 1304 in the azimuthal direction 101 may be equal to the height of both the first fin 1104 and the cutout 1102 of the first comb structure 1100. The complementary geometries of the first comb structure 1100 and the second comb structure 1300 allow the comb structures to fit together to form a third acoustic stack 1402 having an interdigitated structure, as shown. Fig.14 The first view 1400 along the elevation direction 103 and Fig.15 15 is shown in a second view 1500 along the azimuth direction 101.

[0101] exist Fig.14 In the first view 1400 of the third acoustic stack 1402 shown, a first adhesive layer 1404 is arranged between the first comb structure 1100 and the second comb structure 1300 to achieve lamination of the comb structures. The first adhesive layer 1404 can be a non-conductive glue such as epoxy resin, which electrically insulates the first comb structure 1100 from the second comb structure 1300. The first comb structure 1100 and the second comb structure 1300 can be nested in each other so that there is no gap between the first comb structure 1100 and the second comb structure 1300.

[0102] As shown in the second view 1500 of the third acoustic stack 1402, the first fin 1104 and the second fin 1304 extend along the depth 1502 of the third acoustic stack 1402 in the elevation direction 103, with each fin forming a digit of the interdigitated structure of the third acoustic stack 1402. It should be understood that the first view 1400 and the second view 1500 of the third acoustic stack 1402 may represent sections of the third acoustic stack rather than the entire acoustic stack 1402. Although the third acoustic stack 1402 is shown as having Fig.14 The third acoustic stack 1402 may have three first fins in the first fin 1104 and three second fins in the second fin 1304, but the third acoustic stack 1402 may have any number of fins. The third acoustic stack 1402 may have more than or less than Fig.14 and Fig.15 The width 1406 and depth 1502 are shown in FIG.

[0103] Additionally, in some examples, the third acoustic stack 1402 may be further combined with one or more additional comb structures to increase the number of sub-elements with different resonant frequencies that are combined into the acoustic stack. Fig.36 As shown, the first multi-frequency comb structure 3602 and the second multi-frequency comb structure 3604 can each be formed by an acoustic stack (such as the third acoustic stack 1402).

[0104] At least one first fin 3603 of the first multi-frequency comb structure 3602 may include a first sub-element 3606 and a second sub-element 3608. The first multi-frequency comb structure 3602 may be formed by a process similar to that described in the example of FIG. Fig.11 The illustrated scribing of the first acoustic stack 1000 is formed by scribing the acoustic stack, wherein a first cut 3610 extends from a top of the first multi-frequency comb structure 3602 downwardly through a portion of a height 3612 of the first multi-frequency comb structure 3602 in the lateral direction 105 .

[0105] The second multi-frequency comb structure 3604 may have at least one second fin 3614, and the second fin 3614 may include a third sub-element 3616 and a fourth sub-element 3618. Each of the first sub-element 3606, the second sub-element 3608, the third sub-element 3616, and the fourth sub-element 3618 may have a different resonant frequency. The second multi-frequency comb structure 3604 may be similar to Fig.13 The second acoustic stack 1200 is shown scribed with a second cut 3620 extending from the bottom of the second multi-frequency comb structure 3604 upward through a portion of the height 3622 of the second multi-frequency comb structure 3604 in the lateral direction 105 .

[0106] The width 3624 and height 3626 of the first cutout 3610 can be similar to the width and height of the second fin 3614. The width 3628 and height 3630 of the second cutout 3620 can be similar to the width and height of the first fin 3603. The second fin 3614 of the second multi-frequency comb structure 3604 can be inserted into the first cutout 3610 of the first multi-frequency comb structure 3602, and the first fin 3603 can be inserted into the second cutout 3620 of the second multi-frequency comb structure 3604, as indicated by arrow 3632, to form a combined stack having four sub-elements. The combined stack can be laminated and further processed as described below.

[0107] Fig.36 A non-limiting example of how a multi-frequency acoustic stack having four different sub-elements may be formed is shown. In other examples, either the first multi-frequency comb structure 3602 or the second multi-frequency comb structure 3604 may be a single element comb structure. In such cases, the resulting combined acoustic stack may include three sub-elements. Additionally, the width defined along the azimuth direction 101 of each of the sub-elements is shown to be similar, thereby producing a combined stack having equal proportions of each sub-element. However, in other examples, the width of the sub-elements may be varied such that the percentage content of each of the sub-elements is not equal.

[0108] In addition, although Figure 14 to Figure 15 The third acoustic stack 1402 shows a first comb structure 1100 and a second comb structure 1300 having complementary geometries that result in a gapless combination of the comb structures, e.g., no space exists between the comb structures when coupled, but the comb structures may be scribed to have non-matching geometries. Fig.42 As shown, an alternative example of an acoustic stack 4200 may include a first comb structure 4202 and a second comb structure 4204 that combine to form an interdigitated structure.

[0109] The cutouts of the first comb structure 4202 may not have dimensions that match the dimensions of the fins of the second comb structure 4204, and the cutouts of the second comb structure 4204 may not have dimensions that match the fins of the first comb structure 4202. For example, the first cutouts 4206 of the first comb structure 4202 may have a depth 4208 that is greater than the depth 4210 of the first fins 4212 of the second comb structure 4204. When the first fins 4212 of the second comb structure 4204 are inserted into the first cutouts 4206 of the first comb structure 4204, there may be a gap around the first fins 4212, for example, in the azimuthal direction.

[0110] The second cutouts 4214 of the first comb structure 4202 may also have a depth 4216 that is greater than a depth 4218 of the second fins 4220 of the second comb structure 4204. When the second fins 4220 of the second comb structure 4204 are inserted into the second cutouts 4214 of the first comb structure 4202, a gap may exist around the second fins 4220, for example, in the azimuthal direction 101. Due to the non-uniform depth of the cutouts of the first comb structure 4204 and / or the non-uniform depth of the fins of the second comb structure 4204, the gap around the second fins 4220 may be greater than the gap around the first fins 4212. Due to the greater depth of the cutouts of the second comb structure 4204 compared to the depth of the fins of the first comb structure 4204, the fins of the first comb structure 4202 may be similarly surrounded by the gap.

[0111] like Fig.42 As shown, various geometries of the acoustic stack formed by combining at least two comb structures can be achieved by adjusting the size of the cutouts and fins. The cutting and combination of the comb structures introduce a high degree of flexibility in the final configuration of the transducer array. Thus, the modification of the transducer can be modified efficiently.

[0112] Now turn to Figure 16 to Figure 17 , the third acoustic stack 1402 can be combined with the first example of the base package 1602, such as Fig.16 As shown in the first view 1600 along the elevation direction 103, and Fig.17101 in a second view 1700 along the azimuth direction 101. The base package 1602 may be formed of a conductive material, such as graphite, porous graphite filled with resin, stainless steel, aluminum, etc. The base package 1602 may be scribed to have a first fin 1604 extending along the lateral direction 105 and a cutout 1606. The third acoustic stack 1402 may also be scribed to have a first cutout 1608 also extending along the elevation direction 103, which matches the first fin 1604 of the base package 1602 in width 1610 and height 1612. The dicing of the third acoustic stack 1402 also forms blocks 1614 having the same height 1612 as the first fin 1604 of the base package 1602, and wherein the width 1616 of each of the blocks 1614 is equal to the width of the cutout 1606 of the base package 1602.

[0113] Fig.17 101 . The third acoustic stack 1402 and the base package 1602 are further shown in FIG. In addition to the cutout 1606, the third acoustic stack 1402 can have a second cutout 1702 extending in the azimuth direction 101. The base package 1602 has a second fin 1704, which can be connected to the first fin 1604, but extends from the first fin 1604 in a perpendicular direction (e.g., in the azimuth direction 101). Thus, the first fin 1604 and the second fin 1704 can form a Fig.18 The structure shown in perspective view 1800.

[0114] The base package 1602 is depicted in a perspective view 1800 to illustrate the overall geometry of the first fin 1604, the second fin 1704, and the cutouts 1606 of the base package 1602. The first fin 1604 and the second fin 1704 frame each of the cutouts 1606 such that each of the cutouts 1606 has a uniform rectangular geometry. However, in other examples, the cutouts 1606 may have a variety of other geometric shapes, such as circular, hexagonal, square, etc. Thus, the cutouts 1606 are formed by the first fin 1604 and the second fin 1704. Figures 10 to 35 The manufacturing process depicted in can produce a transducer having a shape corresponding to the geometry of cutout 1606 .

[0115] The cutout 1606 forms a cavity in the base package 1602, and the block 1614 (eg, Fig.16 and Fig.17 1602) is shaped to match the geometry of the cutout 1606. In this way, the cutout 1606 of the base package 1602 receives the block 1614 of the third acoustic stack 1402, as shown. Fig.16 and Fig.17As shown by arrow 1618 in FIG. 1 , the first cutout 1608 of the third acoustic stack 1402 receives the first fin 1604 of the base encapsulation 1602 , and the second cutout 1702 of the third acoustic stack 1402 receives the second fin 1704 of the base encapsulation 1602 .

[0116] In other examples, the base package can be Fig.18 The base package 1602 is configured differently. For example, Fig.40 As shown, a second example of a base package 4000 can have cutouts 4002 extending linearly and continuously in the elevation direction 103. The cutouts 4002 are parallel and can extend across the entire depth of the base package 4000 or across at least a portion of the depth, which is defined in the elevation direction 103. The fins 4004 of the base package 4000 that are spaced apart by the cutouts 4002 can also extend in the elevation direction 103. The acoustic stack can be similarly cut in the elevation direction 103 to match the cutouts 4002 and fins 4004 of the base package 4000.

[0117] Alternatively, the base package may be completely diced along the azimuthal direction 101, such as Fig.41 shown. Fig.41 A third example of a base package 4100 is depicted with cutouts 4102 and fins 4104 extending in the azimuthal direction 101. The cutouts 4102 and fins 4104 may extend completely or partially across a width of the base package 4100, the width being defined in the azimuthal direction 101. The acoustic stack may be diced with cutouts and blocks to match the geometry of the base package 4100, for example, with cutouts and blocks extending in the azimuthal direction 101.

[0118] Now turn to Fig.19 The first view 1900 and the Fig. 20 In the second view 2000 along the azimuth direction 101, the third acoustic stack 1402 and the base package 1602 may be laminated with a second adhesive layer 1904 disposed between the third acoustic stack 1402 and the base package 1602 to form a fourth acoustic stack 1902. The second adhesive layer 1904 is shown as a dashed line to distinguish the second adhesive layer 1904 from the first adhesive layer 1404. The second adhesive layer 1904 may also be a non-conductive glue that electrically isolates the third acoustic stack 1402 from the base package 1602.

[0119] like Fig.21 A first view 2100 of the fourth acoustic stack 1902 along the elevation direction 103 and Fig. 22As shown in the second view 2200 of the fourth acoustic stack 1902 in the azimuth direction, the back side 2102 of the fourth acoustic stack 1902 can be subjected to grinding. By grinding the back side 2102, a portion of the base package 1602, a portion of the backing layer 1008 of the first comb structure 1100, and a portion of the backing layer 1208 of the second comb structure 1300 ( Figure 14 to Figure 15 The backing layers 1008, 1208 shown in FIG. 100 are removed, enabling grinding recovery in both the elevation direction 103 and the azimuth direction 101. The back side 2102 of the fourth acoustic stack may provide positive terminal connectivity. Fig.19 and Fig. 20 The height 1906 of the ground-off overall portion of the fourth acoustic stack 1902 is shown in FIG.

[0120] The back side 2102 of the fourth acoustic stack 1902 is ground until portions of both the first adhesive layer 1404 and the second adhesive layer 1904 parallel to the elevation direction 103 are removed (eg, Fig.19 and Fig. 20 ). By removing a portion of the adhesive layer, for example, a bottom portion of the adhesive layer relative to the azimuth direction 101, grinding recovery in both the elevation direction and the azimuth direction is enabled. In other words, by removing the insulating adhesive layer, elements (e.g., the high frequency sub-element 1004 and the low frequency sub-element 1204) and electrical contacts or electrodes ( Fig.21 and Fig. 22 Electrical continuity between the two devices (not shown).

[0121] Grinding recovery may also include sputtering a layer of conductive material (such as metal) on the back side 2102 of the fourth acoustic stack 1902, such as Fig.23 The first view 2300 along the elevation direction 103 and Fig.24 The fourth acoustic stack 1902 is shown in the second view 2400 along the azimuth direction 101. Fig.23 and Fig.24 101. The sputtered layer 2302 is deposited onto the back side 2102 of the fourth acoustic stack 1902 to form a uniform continuous film. The height of the sputtered layer 2302 measured along the azimuth direction is less than the height of any other layer of the fourth acoustic stack 1902, such as the matching layer, the high frequency element and the low frequency element, the dematching layer, and the backing layer.

[0122] However, in other examples, sputtering may be eliminated by grinding the back side of the fourth acoustic stack 1902 to a lesser extent so that a portion of the base package 1602 remains. For example, the back side may be ground Fig.19The remainder of the base package may be common to each of the sub-elements and a conductive layer may be provided along the back side of the fourth acoustic stack 1902 .

[0123] like Fig.25 A first view 2500 of the fourth acoustic stack 1902 along the elevation direction 103 and Fig.26 As shown in the second view 2600 along the azimuthal direction 101, the fourth acoustic stack 1902 may be scribed after deposition of the sputtered layer 2302. A plurality of cuts 2503 are formed in the fourth acoustic stack 1902 extending along the lateral direction 105 from the back side 2302 of the fourth acoustic stack 1902 toward the front side 2502, but not completely through the fourth acoustic stack 1902.

[0124] A plurality of cutouts 2503 may separate the fourth acoustic stack 1902 into a plurality of elements 2501. The plurality of elements 2501 may include a multi-frequency element 2504 and a single-frequency element 2506, such as Fig.25 Each of the multi-frequency elements 2504 includes one high-frequency sub-element in the high-frequency sub-element 1004 and one low-frequency sub-element in the low-frequency sub-element 1204. The single-frequency element 2506 includes one high-frequency sub-element in the high-frequency sub-element 1004 or one low-frequency sub-element in the low-frequency sub-element 1204, but not both.

[0125] In other examples, each element of an acoustic stack (such as the fourth acoustic stack 1902) can be formed from a single element, but the acoustic stack can include a variety of different types of single elements. For example, the first comb structure and the second comb structure can be combined to form a Figure 14 to Figure 15 The third acoustic stack 1402 is similar to the acoustic stack. Figures 16 to 24 The processing of the acoustic stack and the cuts can be cut into the acoustic stack, such as Fig.25 and Fig.26 However, the cutouts may be positioned between each fin of each comb structure, thus separating the elements into individual elements of the scribed acoustic stack. In other words, the cutouts may also separate the high frequency sub-element 1004 from the low frequency sub-element 1204. In this way, the acoustic stack may be a multi-frequency acoustic stack having a single element rather than an element formed from more than one sub-element, wherein each transducer may have more than one type of element, each element being coupled to an electrical circuit.

[0126] return Fig.25, the resonant frequency of the multi-frequency element 2504 can be determined by the percentage content of each of the high frequency sub-element 1004 and the low frequency sub-element 1204. The first width 2510 of the high frequency sub-element 1004 defined along the azimuthal direction 101 is similar to the second width 2512 of the low frequency sub-element 1204. Therefore, the multi-frequency elements 2504 can each be formed by 50% of the high frequency sub-element 1004 and 50% of the low frequency sub-element 1204 and have a resonant frequency intermediate between the resonant frequencies of the high frequency sub-element 1004 and the low frequency sub-element 1204. However, in other examples, the width of the sub-elements can vary (e.g., be unequal) and can be non-uniform throughout the acoustic stack, thereby producing a range of resonant frequencies. The variation in the width of the sub-elements is depicted in Figure 31 to Figure 34 and further described below.

[0127] The plurality of cutouts 2503 can be filled with an electrically insulating material, thereby isolating each element in the plurality of elements 2501 from adjacent elements. However, in other examples, the plurality of cutouts 2503 can remain as air-filled spaces (e.g., not filled with any additional material), which can similarly provide electrical insulation. In addition, keeping the plurality of cutouts 2503 as spaces can reduce the total amount of material of the transducer array and reduce the weight of the array. The filled plurality of cutouts 2503 in Fig. 27 is depicted in a first view 2700 along the elevation direction 103 and in Fig.28 The fourth acoustic stack 1902 is shown coupled to the Fig. 27 and Fig.28 In the chip 2702.

[0128] In addition to filling the plurality of cutouts 2503, a portion of the front side 2502 of the fourth acoustic stack 1902 may be mechanically removed, similar to the grinding of the back side 2102, to further achieve grinding recovery. The front side 2502 of the fourth acoustic stack 1902 may provide electrical grounding. The height 2508 of the portion of the fourth acoustic stack 1902 removed from the front side 2502 is Fig.25 and Fig.26 The amount of grinding away from the front side 2502 of the fourth acoustic stack 1902 may remove a portion of the first adhesive layer 1404 that is parallel to the azimuth direction 101, such as Fig.25 Grinding of the front side 2502 may also facilitate grinding recovery in the azimuth and elevation directions by achieving electrical continuity between the plurality of elements 2501 and the conductive layer coupled to the front side 2502 of the fourth acoustic stack 1902, as will be further described below.

[0129] return Fig. 27 and Fig.28, after grinding, the matching layer block 2704 is laminated to the front side 2502 of the fourth acoustic stack 1902. Fig. 27 and Fig.28 2, but in some examples, a conductive layer, such as the sputtered layer 2302, may be sputtered onto the ground front side 2502 of the fourth acoustic stack 1902 before coupling the matching layer block 2704 to the front side 2502. The matching layer block 2704 may be laminated using a conductive adhesive and may be the same or a different material than the matching layers 1002, 1202 of the first comb structure 1100 and the second comb structure 1300, respectively. For example, the material of the matching layer block 2704 may be a gold plated material, a flexible conductive material such as a spring mass structure, etc. The matching layer block 2704 may be formed of more than one layer and may be formed of a conductive material or a non-conductive material.

[0130] The matching layer block 2704 provides a common matching layer to each transducer of the fourth acoustic stack 1902, each transducer comprising one of the plurality of elements 2501 and defined along the lateral direction 105 by a plurality of cutouts 2503 filled with a non-conductive material. In other words, the matching layer block 2704 is a continuous layer extending completely across the front side 2502 of the fourth acoustic stack 1902. Similarly, the backing layer block 2706 can be coupled to the back side 2102 of the fourth acoustic stack 1902 and connected to each transducer of the fourth acoustic stack 1902 to provide a common backing layer for each transducer. The backing layer block 2706 can also be a continuous layer extending completely across the back side 2102 of the fourth acoustic stack 1902.

[0131] The backing layer block 2706 may also be laminated to the back side 2102 of the fourth acoustic stack 1902 using a conductive adhesive to form the wafer 2702. The backing layer block 2706 may be formed of one or more layers laminated in the stack along the lateral direction 105, and may provide an electrical path to enable voltage to be applied to the plurality of elements 2501. In some examples, the backing layer block 2706 may include an application specific integrated circuit (ASIC), a flexible conductive material, a printed circuit board (PCB), a metal block, etc. In other examples, some type of backing may be coupled to the back side 2102 of the fourth acoustic stack 1902 instead of the backing layer block 2706. For example, the backing may be an interposer that connects a flexible circuit to the acoustic stack.

[0132] Additionally, other examples may include an acoustic stack configured with non-continuous matching layer blocks and backing layer blocks that extend discontinuously across each transducer. For example, multiple smaller matching and backing layer blocks may be coupled to the transducer array, with each block attached to one transducer. Alternatively, the matching and backing layer blocks may cover several transducers (such as two or three adjacent transducers) that are coupled to the acoustic stack in sections.

[0133] The wafer 2702 may then be singulated (eg, singulated) to form individual transducer arrays 2902, such as Fig.29 The first view 2900 along the elevation direction 103 and Fig.30 2902 is shown in a second view 3000 along the azimuth direction 101. Each transducer array in the transducer array 2902 includes an array of multiple elements 2501, each of the multiple elements 2501 being included in a separate integrated circuit. Singulation may include various die singulation methods, including conventional plan sawing, laser scribing, scribing and breaking, and dice before grind. Thus, due to singulation, each transducer array in the transducer array 2902 is spaced apart from adjacent transducer arrays, and each transducer may be mounted in a transducer probe.

[0134] Although the width 2904 defined along the azimuth direction 101 of each sub-element (e.g., the high frequency sub-element 1004 and the low frequency sub-element 1204), the width 2906 of each element in the plurality of elements 2501, and the width 2908 of each transducer array 2902 are Fig.29 2702 as uniform, but the dicing of each of the above components of wafer 2702 may be modified to produce non-uniform widths. The widths of the sub-elements of the plurality of elements and the transducers vary in Figure 31 to Figure 35 Shown in.

[0135] In a first example 3100 of a non-uniform transducer array 3101, a width 3102 of a plurality of elements 3104 can be uniform along an azimuthal direction 101. The plurality of elements 3104 can each include a first sub-element 3106 and a second sub-element 3108. The first comb structure can be scribed to form a first sub-element 3106 having a width 3110 greater than a width 3112 of the second sub-element 3108. In other words, the first comb structure can be scribed to form a wider sub-element (e.g., the first sub-element 3106) than the second comb structure can be scribed to form the second sub-element 3108.

[0136] Alternatively, as shown in the second example 3200 of the non-uniform transducer array 3103, the first comb structure may be diced such that the first sub-element 3106 has a narrower width 3202 than the width 3404 of the second sub-element 3108 formed by dicing the second comb structure. The width 3104 of each of the plurality of elements 3104 may be uniform along the azimuthal direction 101, and the width of each of the first sub-element 3106 and the second sub-element 3108 may be similar in each of the plurality of elements 3104. Thus, the width of the sub-element may be easily changed based on the dicing of the comb structure.

[0137] In addition, the comb structure can be cut so that each of the sub-elements has a non-uniform width, as shown in the third example 3300 of the non-uniform transducer array 3101. The first element 3302 can be formed of a first sub-element 3304 having a width 3306 similar to a width 3308 of a second sub-element 3310. However, in a second element 3312 adjacent to the first element 3302, the width 3314 of the first sub-element 3304 is greater than the width 3316 of the second sub-element 3310. The width 3318 of the first element 3302 can be similar to the width 3320 of the second element 3312. In other examples, the non-uniform transducer array 3103 can include elements in which the width of the second sub-element 3310 is greater than the width of the first sub-element 3304.

[0138] Additionally or alternatively, an acoustic stack (e.g., Figures 14 to 17 The dicing of the third acoustic stack 1402 of the non-uniform transducer array 3101 can be modified to change the width of the plurality of elements. For example, as shown in the fourth example 3400 of the non-uniform transducer array 3101, the width 3402 of the first element 3404 can be greater than the width 3406 of the second element 3408. The widths of the first sub-element 3410 and the second sub-element 3412 of each element can be similar, as shown in the first element 3404, or different, as shown in the second element 3408.

[0139] Furthermore, the singulation of the wafer into individual transducer arrays can be adjusted to form transducers of different widths. Fig.35 As shown, the first transducer array 3502 may be diced to have a first width 3504. The second transducer array 3506 may be diced to have a second width 3508 that is wider than the first width 3504 of the first transducer array 3502. Other transducer arrays formed from the same wafer as the first transducer array 3502 and the second transducer array 3506 may have a width similar to the first transducer array 3502 or the second transducer array 3506, or a width different from the first transducer array 3502 and the second transducer array 3506. The widths of the first sub-element 3510 and the second sub-element 3512 incorporated in each element of each transducer array may be similar or different from each other, and may be uniform or non-uniform throughout the transducer array.

[0140] Electrical leads may be coupled to the matching layer blocks and backing layer blocks of the transducer array before or after singulation. For example, a positive electrode may be coupled to the matching layer block and a ground electrode may be coupled to the backing layer block. Alternatively, a positive electrode may be coupled to the backing layer block and a ground electrode may be coupled to the matching layer block. The formation of a single circuit with each transducer is thereby completed by coupling the transducer array to the electrical leads.

[0141] In this way, the manufacturing method for a multi-frequency transducer can be made to produce Figure 2 and Figures 4 to 36 It should be understood that although Figure 31 to Figure 35 A view of the transducer along the elevation direction 103 is depicted and variations in the width of the transducer, elements, and sub-elements relative to the elevation direction 103 are described, but similar variations may be applied along the azimuth direction 101. For example, the scribe of the comb structure may be modified along the azimuth direction 101 to provide sub-elements with different depths (e.g., thickness of the sub-elements along the azimuth direction 101). The comb structures may be combined such that instead of or in addition to the sub-elements being arranged adjacent to each other along the elevation direction 103, the sub-elements are arranged adjacent to each other along the azimuth direction 101.

[0142] The combined comb structure may be diced to produce elements of varying depths in the azimuth direction 101 while also varying the width of the elements in the elevation direction 103. Alternatively, the width of the elements may remain uniform in the elevation direction 103 and vary in the azimuth direction 101. Furthermore, the depth of the singulated transducers may similarly vary in the azimuth direction 101 in addition to or instead of in the elevation direction 103.

[0143] By enabling the size of the transducers, elements and sub-elements to be varied in both the azimuth direction 101 and the elevation direction 103, scalable manufacturing of transducers can be achieved. A variety of transducers with different and wider bandwidths and spatial frequency distributions can be produced from a single wafer. The electrical circuits are coupled to the wafer prior to singulation, thereby increasing manufacturing efficiency. The amount of interconnects and control signals in a multi-frequency transducer probe can be similar to that used in a single frequency transducer probe. Therefore, the implementation of the multi-frequency transducer array does not introduce additional complexity to the transducer probe.

[0144] Grinding recovery in both the elevation and azimuth directions allows for greater flexibility in packaging the transducer array in the probe. For example, a transducer array with a reduced footprint in the elevation direction may be desirable. In conventional methods, when the transducer array is shortened in the elevation direction, grinding recovery may be difficult. However, the above reference Figures 10 to 38 and Figure 40 to Figure 42 The described fabrication process allows for grinding recovery in the azimuthal direction. Additionally, the apodization function provided by the spatial frequency distribution of the wide bandwidth transducer can allow the transducer probe to be used for more than one application. For example, a single transducer probe can be used for both therapy and imaging. Due to the enhanced beam focus profile enabled by the apodization function, image quality can be optimized in both the near field and the far field. The footprint of the transducer probe can be optimized for more efficient packaging. Likewise, as Figures 10 to 36The fabrication process of the acoustic stack of the transducer probe shown may provide a generic architecture applicable to all transducer combinations based on a wafer-based approach.

[0145] Fig.37 An example of a first routine 3700 for manufacturing a multi-frequency acoustic stack of a transducer probe is depicted in FIG. Fig.38 As shown, the second routine 3800 is an example of a routine for forming a multi-frequency element, and the second routine may be included in the first routine 3700. The first routine 3700 and the second routine 3800 describe a process similar to Figures 10 to 36 Now turn to the manufacturing process shown in Fig.37 At 3702, the first routine 3700 includes forming a first acoustic stack, such as Fig.38 As shown in the second routine 3800 in .

[0146] exist Fig.38 At 3802, the second routine 3800 includes forming a first comb structure (such as Fig.11 The first comb structure 1100 of the present invention has a first sub-element. The first acoustic stack (such as Fig.10 The first acoustic stack 1000 of FIG. 1 is used to form a first comb structure. A second comb structure (such as Fig.13 The second comb structure 1300 has a second subelement with a different resonant frequency than the first subelement. The second acoustic stack can be cut such as Fig.12 The first acoustic stack and the second acoustic stack may each include a matching layer, a subelement layer, an optional dematching layer, and a backing layer, which are stacked in a transverse direction perpendicular to both the azimuth direction and the elevation direction.

[0147] The first acoustic stack and the second acoustic stack may be scored in opposite directions to each other to give the first comb structure and the second comb structure complementary fins. Fig.11 As shown, the first acoustic stack can be scored downward from the top surface of the first acoustic stack, and as shown in FIG. Fig.13 As shown, the second acoustic stack may be scored upward from the bottom surface of the second acoustic stack. Alternatively, the first acoustic stack may be scored upward from the bottom surface, while the second acoustic stack may be scored downward from the top surface.

[0148] At 3806, the first comb structure is combined with the second comb structure to form an interdigitated combined stack, such as Fig.14 A third acoustic stack 1402. The combined stack may be laminated to adhere the comb structures to each other.

[0149] At 3808, the routine includes determining whether additional subcomponents are incorporated into the combined stack. If no additional subcomponents are included, the routine continues Fig.37 3704 of the first routine 3700. If at least one additional sub-element is to be incorporated, an additional comb structure is formed at 3810. This can be similar to Fig.11 The first comb structure 1100 or Fig.13 The additional comb structure may be scribed at 3812 by slicing the second comb structure 1300, while the combined stack may be scribed in an opposite manner to complement the geometry of the scribed additional comb structure. The additional comb structure may have a third subelement with a different resonant frequency than the first subelement or the second subelement.

[0150] In some examples, the additional comb structure can be a combined comb structure formed via a similar process as described in 3802-3806 of the second routine 3800, such that the additional comb structure has a fourth sub-element in addition to the third sub-element. The additional comb structure having both the third sub-element and the fourth sub-element can be similarly scribed to have the complementary geometry of the scribed combined stack.

[0151] At 3814, the second routine 3800 includes combining the scribed combined stack with the additional comb structure to form a new combined stack, which can be laminated to adhere the combined stack and the additional comb structure to each other. During lamination, a non-conductive adhesive layer can be provided between the first comb structure and the second comb structure. The method returns to 3808 to again determine whether to incorporate additional sub-elements into the (new) combined stack.

[0152] return Fig.37 At 3704 of the first routine 3700, a first acoustic stack (e.g., a combined stack formed via the second routine 3800) is scribed. The dicing of the first acoustic stack forms a plurality of fins separated by a plurality of cuts in the first acoustic stack. At 3706, a base package (such as a conductive material) is formed. Fig.16 The base package 1602 is cut into fins having similar geometry to the plurality of cuts in the first acoustic stack and cuts having similar geometry to the plurality of fins in the first acoustic stack.

[0153] The base package and the first acoustic stack are coupled to each other and laminated at 3708 to form a second acoustic stack. At 3710, a portion of the back side of the second acoustic stack can be removed by grinding to provide grinding recovery. For example, a portion of the thickness of the backing layer of the first acoustic stack and a portion of the non-conductive adhesive used to laminate the first acoustic stack can be removed. By removing a portion of the backing layer and a portion of the non-conductive adhesive, grinding recovery in the azimuth direction and the elevation direction can be achieved.

[0154] At 3712, a conductive layer is sputtered onto the ground back side of the second acoustic stack. The conductive layer can allow electrical connectors to be coupled to the back side of the second acoustic stack, each electrical connector being included in an integrated circuit of a final transducer array formed via processing of the second acoustic stack. The second acoustic stack is scribed at 3714, and the cuts formed by the scribe can be filled with a non-conductive material, thereby electrically isolating each integrated circuit or transducer of the second acoustic stack from adjacent integrated circuits.

[0155] The front side of the second acoustic stack is ground at 3716. The front side is opposite to the back side, and a portion of the thickness of the front side can be removed by grinding. For example, the matching layer of the second acoustic stack can be partially removed. At 3718, a matching layer block and a backing layer block can be coupled to the front side and the back side of the second acoustic, respectively, to further achieve grinding recovery in the azimuth direction and the elevation direction. At 3720, the first routine 3700 includes singulating the second acoustic stack to divide the second acoustic stack into separate transducer arrays. The transducer arrays can each be implemented in a transducer probe. The first routine 3700 ends.

[0156] In this way, a multi-element transducer array can be provided for a transducer probe. The multi-element transducer array may include sub-elements with different resonant frequencies, which are distributed in a uniform pattern along the azimuth direction and the elevation direction. Alternatively, the sub-elements may be positioned to provide a variable spatial frequency distribution along at least one of the azimuth direction and the elevation direction. Frequency apodization and agility can be achieved along the elevation direction and on different structures such as 1D, 1.5D, 2D, etc., thereby achieving spatial frequency distribution in complex structures. In addition, the multi-element transducer is manufactured by a wafer-level method, and frequency apodization and agility are achieved at low cost. The processing of the acoustic stack during the wafer-level method can result in a larger distribution of frequency content on the transducer aperture, which allows one transducer probe to be used for multiple applications. Due to the beam focusing profile achieved by frequency apodization, image quality can be optimized in both the near field and the far field. Due to the grinding recovery in both the azimuth direction and the elevation direction, the multi-element transducer array can be more effectively packaged in the transducer probe and can be used in various transducer combinations.

[0157] A technical effect of manufacturing the transducer array via a wafer-level approach is to produce a wide bandwidth transducer array via a cost-effective approach. Another technical effect is to achieve frequency apodization and agility in both azimuth and elevation directions.

[0158] As used herein, the elements or steps listed in the singular and beginning with the word "one" or "a kind of" should be understood as not excluding a plurality of the elements or steps, unless such exclusion is explicitly stated. In addition, the reference to "an embodiment" of the present invention is not intended to be interpreted as excluding the existence of additional embodiments that also include the cited features. In addition, unless explicitly stated to the contrary, the embodiment of "including", "comprising" or "having" an element or multiple elements with a specific characteristic may include additional such elements without the characteristic. The terms "including" and "in..." are used as the concise language equivalents of the corresponding terms "including" and "wherein". In addition, the terms "first", "second" and "third" etc. are only used as marks, and are not intended to impose numerical requirements or specific positional order on their objects.

[0159] In one embodiment, the transducer array includes an element formed by one or more sub-elements, at least one of which has a different resonant frequency. In a first embodiment of the transducer array, the transducer array is formed by at least one element, and wherein the element is driven by an electrical circuit and is electrically isolated from adjacent elements. A second embodiment of the transducer array optionally includes the first embodiment, and further includes wherein the relative proportions of the one or more sub-elements are equal in the element, and each element of the transducer array has a similar resonant frequency. A third embodiment of the transducer array optionally includes one or more of the first and second embodiments, and further includes wherein the width of the one or more sub-elements is varied in the transducer array, and the width is defined along at least one of the elevation direction and the azimuth direction. A fourth embodiment of the transducer array optionally includes one or more of the first to third embodiments, and further includes wherein the relative proportions of each of the one or more sub-elements vary along the transducer array, and wherein at least one element in the transducer array has a different frequency range. The fifth embodiment of the transducer array optionally includes one or more of the first to fourth embodiments, and further includes wherein the relative proportion of each of the one or more sub-elements varies between each element of the transducer array along at least one of the azimuth direction and the elevation direction. The sixth embodiment of the transducer array optionally includes one or more of the first to fifth embodiments, and further includes more than one type of element combined in the transducer array, each type of element having a different resonant frequency and frequency range. The seventh embodiment of the transducer array optionally includes one or more of the first to sixth embodiments, and further includes wherein the more than one type of element in the transducer array has a non-uniform size along at least one of the azimuth direction and the elevation direction. The eighth embodiment of the transducer array optionally includes one or more of the first to seventh embodiments, and further includes wherein the amount of one or more sub-elements in the element varies across the transducer array.

[0160] In another embodiment, a multi-frequency acoustic stack includes: a first comb structure coupled to a second comb structure, the first comb structure including a first type of element having a first resonant frequency, and the second comb structure including a second type of element having a second resonant frequency; a plurality of electrical circuits, each circuit including at least one of the first type of element and the second type of element, and configured to change the frequency bandwidth to provide frequency apodization along at least one of an azimuth direction and an elevation direction. In a first embodiment of the acoustic stack, the first comb structure has a geometry complementary to that of the second comb structure, and the coupling of the first comb structure and the second comb structure forms an interdigitated structure. A second embodiment of the acoustic stack optionally includes the first embodiment, and further includes wherein each of the plurality of electrical circuits includes, in addition to at least one of the first type of element and the second type of element, one or more additional types of elements, the one or more additional types of elements having a different resonant frequency than the first type of element or the second type of element. A third embodiment of the acoustic stack optionally includes one or more of the first and second embodiments, and further includes wherein each electrical circuit is coupled to a matching layer and a backing layer. A fourth embodiment of the acoustic stack optionally includes one or more of the first to third embodiments, and further includes wherein each of the plurality of elements is separated from adjacent elements by a cutout filled with one of a non-conductive material and air. A fifth embodiment of the acoustic stack optionally includes one or more of the first to fourth embodiments, and further includes wherein each element is electrically coupled to a positive connection and a ground connection to form a separate integrated circuit.

[0161] In yet another embodiment, a method includes: dicing a first acoustic stack having a first subelement and a second acoustic stack having a second subelement to have complementary geometries; combining the first acoustic stack and the second acoustic stack to form an interdigitated structure; coupling a common matching layer and a common backing layer to opposite sides of the interdigitated structure; and singulating the interdigitated structure to form one or more transducer arrays. In a first embodiment of the method, dicing the first acoustic stack and the second acoustic stack includes forming cuts in each of the acoustic stacks, and wherein the first acoustic stack has a first set of cuts extending downwardly from a top surface of the first acoustic stack, and the second acoustic stack has a second set of cuts extending upwardly from a bottom surface of the second acoustic stack. A second embodiment of the method optionally includes the first embodiment, and further includes dicing the interdigitated structure and coupling the diced interdigitated structure to a base package, the base package being configured to have a geometry complementary to the diced interdigitated structure to form a third acoustic stack before coupling the matching layer and the backing layer. A third embodiment of the method optionally includes one or more of the first and second embodiments, and further includes: dicing the third acoustic stack before coupling the matching layer and the backing layer to separate the third acoustic stack into a plurality of transducers, each of the plurality of transducers including an element formed by at least one of the first sub-element and the second sub-element. A fourth embodiment of the method optionally includes one or more of the first to third embodiments, and further includes attaching an electrical connector to each of the matching layer and the backing layer to form a separate electrical circuit with each element.

[0162] This written description uses examples to disclose the invention, including the best mode, and also to enable a person skilled in the relevant art to practice the invention, including making and using any devices or systems and performing any included methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to a person skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insignificant differences from the literal language of the claims.

Claims

1. A multi-frequency acoustic stack, comprising: a first comb structure coupled to a second comb structure, the coupling of the first comb structure and the second comb structure forming an interdigitated structure, the first comb structure comprising elements of a first type having a first resonant frequency, and the second comb structure comprising elements of a second type having a second resonant frequency; and A plurality of electrical circuits, each circuit comprising at least one of the first type of element and the second type of element, and configured to vary a frequency bandwidth to provide frequency apodization in at least one of an azimuth direction and an elevation direction.

2. The multi-frequency acoustic stack of claim 1, wherein the first comb structure has a geometry that is complementary to a geometry of the second comb structure.

3. The multi-frequency acoustic stack of claim 1 , wherein each of the plurality of electrical circuits includes, in addition to at least one of the first type of element and the second type of element, one or more additional types of elements having a different resonant frequency than the first type of element or the second type of element.

4. The multi-frequency acoustic stack of claim 1, wherein each electrical circuit is coupled to a matching layer and a backing layer.

5. The multi-frequency acoustic stack of claim 1, wherein each element of the plurality of elements is separated from adjacent elements by a cutout filled with one of a non-conductive material and air.

6. The multi-frequency acoustic stack of claim 1, wherein each element is electrically coupled to a positive connection and a ground connection to form a separate integrated circuit.

7. A method for manufacturing a multi-frequency transducer array, the method comprising: scribing a first acoustic stack having a first subelement and a second acoustic stack having a second subelement having a different resonant frequency than the first subelement to have complementary geometries; combining the first acoustic stack and the second acoustic stack to form an interdigitated structure; coupling a common matching layer and a common backing layer to opposite sides of the interdigitated structure; as well as The interdigitated structure is singulated to form one or more transducer arrays.

8. The method of claim 7, wherein scribing the first and second acoustic stacks comprises forming cuts in each of the acoustic stacks, and wherein the first acoustic stack has a first set of cuts extending downward from a top surface of the first acoustic stack, and wherein the second acoustic stack has a second set of cuts extending upward from a bottom surface of the second acoustic stack.

9. The method of claim 7, further comprising dicing the interdigitated structure and coupling the diced interdigitated structure to a base package, the base package being configured to have a geometry complementary to the diced interdigitated structure to form a third acoustic stack prior to coupling the matching layer and the backing layer.

10. The method of claim 9, further comprising dicing the third acoustic stack to separate the third acoustic stack into a plurality of transducers before coupling the matching layer and the backing layer, each transducer of the plurality of transducers comprising an element formed by at least one of the first sub-element and the second sub-element.

11. The method of claim 10, further comprising attaching an electrical connector to each of the matching layer and the backing layer to form a separate electrical circuit with each element.

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