Acoustic transducer assembly with molded interconnect device (MID)

Abstract

Acoustic transducer assemblies can be fabricated using a molded interconnect device (MID) approach. For example, each conductive interconnect can be formed on the inner surface of a cavity defined by a molded dielectric housing. Piezoelectric elements can be placed within the cavity and electrically supplied by the formed conductive interconnect. Backing material can be established within the cavity by filling and curing, etc. Parts of the molded dielectric housing, such as the walls, can provide an acoustic matching layer.

Description

Technical Field

[0001] Claim of Priority This patent application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 456,159 to Kellner, titled "ACOUSTIC TRANSDUCER ASSEMBLY WITH MOLDED INTERCONNECT DEVICE (MID)", filed on Mar. 31, 2023 (Attorney Docket No. 6409.249PRV), the entire disclosure of which is incorporated herein by reference.

[0002] This document generally relates to non-destructive evaluation, and more specifically, to devices and techniques for providing acoustic transducer assemblies, such as acoustic arrays, that include a molded dielectric housing with metal formed directly thereon.

Background Art

[0003] Non-destructive testing (NDT) can refer to the use of one or more different techniques for inspecting areas on or within an object, for example, to confirm the presence of flaws or defects in the object being inspected or otherwise to characterize the object being inspected. Examples of non-destructive testing approaches can include the use of eddy current testing approaches where electromagnetic energy is applied to the object by one or more probes, the resulting induced current is detected on or within the object, and the value of the detected current (or related impedance) provides an indication of the structure of the object during testing to indicate the presence of cracks, voids, porosity, or other non-uniformities.

[0004] Another approach for NDT may include the use of acoustic inspection techniques, such as using one or more electroacoustic elements to irradiate an area on or within an object under test with ultrasound, and detecting and processing the scattered or reflected acoustic energy. Such scattered or reflected energy may be referred to as an acoustic echo signal. Generally, such acoustic inspection schemes involve the use of acoustic frequencies in an ultrasonic range of frequencies, including, for example, pulses having energy within a specified range, which can include values ​​from several hundred kilohertz to several tens of megahertz. [Overview of the project] [Means for solving the problem]

[0005] Acoustic testing, such as ultrasound-based testing, may include focusing or beamforming techniques to assist in constructing data plots or images representing regions of interest within a test specimen. The use of an array of ultrasonic transducer elements may include the use of a phase array beamforming approach and may be referred to as phase array ultrasound testing (PAUT). For example, a delayed-sum beamforming technique may be used, which involves coherently summing the time-domain representations of the received acoustic signals from each transducer element or aperture. Another approach may use a total focusing (TFM) beamforming technique, in which one or more elements in the array (or apertures defined by such elements) are used to transmit acoustic pulses, and other elements are used to receive scattered or reflected acoustic energy, and a matrix of time-series (e.g., A-scan) representations corresponding to a sequence of transmit and receive cycles in which the transmission originates from different elements (or corresponding apertures) in the array is constructed. Such a TFM approach in which A-scan data is obtained for each element (or each defined aperture) in the array may be referred to as a “full matrix capture” (FMC) technique.

[0006] In general, acoustic testing instruments can be adapted to various different acoustic transducer assemblies in a modular manner. Therefore, the shape and number of acoustic transducers associated with an acoustic transducer assembly can vary depending on the application. The inventors recognize, among other things, that the design and fabrication of various different transducer assembly configurations can be simplified by using fewer parts, facilitated by the use of metallized interconnects formed directly on the dielectric material forming the housing of the transducer assembly. The approaches described herein are generally applicable to molded assemblies in which metallization is formed (e.g., plated) on specially activated regions of a polymer material. The metallization can be used to excite piezoelectric transducers or to receive electrical signals from them. According to various embodiments herein, the polymer material forming the housing also functions as an acoustically matching medium. Techniques such as direct printing or laser direct structuring can be used in the process to provide such metallization, and metallized polymer structures formed in such a manner can generally be referred to as molded interconnect devices (MIDs). The use of a molded interconnect fabrication approach can simplify the acoustic transducer assembly fabrication process, provide a more robust transducer assembly, or both. Surface modification approaches that support the formation of metallized patterns using printing or laser activation (for laser direct structuring) allow such patterns to be easily modified to accommodate different piezoelectric element or housing configurations, providing manufacturing and configuration flexibility to suit different applications.

[0007] In one embodiment, an acoustic transducer assembly for non-destructive testing (NDT) may include: a molded dielectric housing defining a cavity; a piezoelectric element located within the cavity, fixed to the dielectric housing and arranged to generate and receive acoustic energy coupled to the outer surface of the dielectric housing through the dielectric housing; a conductive interconnect portion including a metallization formed on the inner surface defined by the cavity, electrically coupled to each region of the piezoelectric element; and a backing material located within the cavity on the surface of the piezoelectric element opposite to the surface of the piezoelectric element fixed to the dielectric housing.

[0008] In one embodiment, a method for fabricating an acoustic transducer assembly for non-destructive testing (NDT) may include forming a conductive interconnect section, including metallization, on the inner surface of a cavity defined by a molded dielectric housing; arranging a piezoelectric element within the cavity, fixing the piezoelectric element to the dielectric housing so that the piezoelectric element generates and receives acoustic energy coupled to the outer surface of the dielectric housing through the dielectric housing; and electrically coupling the conductive interconnect section to each region of the piezoelectric element. The method may also include establishing a backing material within the cavity on the surface of the piezoelectric element opposite to the surface of the piezoelectric element fixed to the dielectric housing.

[0009] In one embodiment, a method for fabricating an acoustic transducer assembly for non-destructive testing (NDT) may include forming a dielectric housing defining a cavity; laser activating each region of the raw surface of the dielectric housing with a pattern corresponding to the conductive interconnect portion on the inner surface of the cavity; plating the laser-activated regions to form the conductive interconnect portion with a pattern; arranging a piezoelectric element within the cavity, wherein the piezoelectric element is fixed to the dielectric housing using an adhesive, such that the piezoelectric element generates and receives acoustic energy coupled to the outer surface of the dielectric housing through the dielectric housing; and electrically coupling the conductive interconnect portion to each region of the piezoelectric element. The method may also include establishing a backing material within the cavity on the surface of the piezoelectric element opposite to the surface of the piezoelectric element fixed to the dielectric housing.

[0010] This summary is intended to provide an overview of the subject matter of this patent application. It is not intended to provide an exclusive or exhaustive description of the invention. A more detailed description is included to provide further information relating to this patent application.

[0011] In drawings that are not necessarily drawn to an accurate scale, similar figures may describe similar components in different views. Similar figures with different letter suffixes may represent different instances of similar components. The drawings, while not limiting, generally illustrate the various embodiments considered in this document. [Brief explanation of the drawing]

[0012] [Figure 1] Examples generally illustrate those including acoustic inspection systems that can be used to implement at least one or more of the techniques shown and described herein. [Figure 2A]Each diagram illustrates an A10 series acoustic inspection probe housing that may include patterned metallization to provide an electrical interconnect for a piezoelectric element. [Figure 2B] Each diagram illustrates an A10 series acoustic inspection probe housing that may include patterned metallization to provide an electrical interconnect for a piezoelectric element. [Figure 3A] The diagrams illustrate each of the A10 series acoustic test probe assembly processes, which can be processed to include piezoelectric elements, backing materials, caps, and cable assemblies, for example, to provide multi-element acoustic test transducer assemblies. [Figure 3B] The diagrams illustrate each of the A10 series acoustic test probe assembly processes, which can be processed to include piezoelectric elements, backing materials, caps, and cable assemblies, for example, to provide multi-element acoustic test transducer assemblies. [Figure 3C] The diagrams illustrate each of the A10 series acoustic test probe assembly processes, which can be processed to include piezoelectric elements, backing materials, caps, and cable assemblies, for example, to provide multi-element acoustic test transducer assemblies. [Figure 3D] The diagrams illustrate each of the A10 series acoustic test probe assembly processes, which can be processed to include piezoelectric elements, backing materials, caps, and cable assemblies, for example, to provide multi-element acoustic test transducer assemblies. [Figure 3E] The diagrams illustrate each of the A10 series acoustic test probe assembly processes, which can be processed to include piezoelectric elements, backing materials, caps, and cable assemblies, for example, to provide multi-element acoustic test transducer assemblies. [Figure 4A] Each diagram illustrating a single-element cylindrical transducer assembly illustrates the applicability of the approaches and materials described herein to other transducer assembly configurations. [Figure 4B] Each diagram illustrating a single-element cylindrical transducer assembly illustrates the applicability of the approaches and materials described herein to other transducer assembly configurations. [Figure 5A] This diagram shows typical elements and spectra of the LCP VECTRA® 840I polymer material that forms the housing of the A10 series acoustic transducer assembly. [Figure 5B] This diagram shows typical elements and spectra of the LCP VECTRA® 840I polymer material that forms the housing of the A10 series acoustic transducer assembly. [Figure 5C] This diagram shows typical elements and spectra of the PPA GF39 RENY® polymer material that forms the housing of the A10 series acoustic transducer assembly. [Figure 5D] This diagram shows typical elements and spectra of the PPA GF39 RENY® polymer material that forms the housing of the A10 series acoustic transducer assembly. [Figure 5E] This diagram shows typical elements and spectra of the PPA GF30 FORTII® 513 polymer material that forms the housing of the A10 series acoustic transducer assembly. [Figure 5F] This diagram shows typical elements and spectra of the PPA GF30 FORTII® 513 polymer material that forms the housing of the A10 series acoustic transducer assembly. [Figure 5G] This diagram shows typical elements and spectra of the LCP TECACOMP (registered trademark) 1049426 polymer material that forms the housing of the A10 series acoustic transducer assembly. [Figure 5H] This diagram shows typical elements and spectra of the LCP TECACOMP (registered trademark) 1049426 polymer material that forms the housing of the A10 series acoustic transducer assembly. [Figure 5I] For comparison, figures of representative elements and a representative spectrum of an off-the-shelf A10 series acoustic transducer assembly not fabricated using the molded interconnect device approach described herein are shown. [Figure 5J] For comparison, figures of representative elements and a representative spectrum of an off-the-shelf A10 series acoustic transducer assembly not fabricated using the molded interconnect device approach described herein are shown. [Figure 6] Techniques such as fabrication methods are generally illustrated, including molding a dielectric housing that includes cavities and forming associated metallization in a specific pattern on the surface of the dielectric housing.

Best Mode for Carrying Out the Invention

[0013] The acoustic transducer assemblies used in acoustic inspections are available in many different configurations, including modular configurations that can be adapted to different mechanical configurations such as single-element, multi-element, angled beam, and non-angled beam configurations, or various coupling wedge configurations. Such transducer assemblies can vary in terms of a particular center operating frequency, number of elements, and size. Thus, manufacturers of such acoustic transducer assemblies can face various challenges in maintaining inventories of parts, tools, and such assemblies, or varying the combinations of different available assemblies in response to changing market needs. The inventor has recognized that it is possible to simplify the complexity of manufacturing acoustic transducer assemblies, such as by using an approach in which conductive interconnects are formed on a molded dielectric housing. Such an approach can, as an illustrative example, enable a reduction in the complexity of assembly of the transducer assembly, or a rapid modification or shift between different transducer assembly configurations. Such an approach can also enhance reliability, such as by providing a more monolithic assembly in which the walls or other portions of the dielectric housing can also function as an acoustic matching layer. The materials and approaches described herein are generally applicable to single-element or multi-element acoustic transducer configurations, such as for non-destructive inspection applications.

[0014] Figure 1 illustrates a general example including an acoustic inspection system 100 that can be used to implement at least one or more of the techniques shown and described herein. The inspection system 100 may include a test instrument 140, such as a handheld or portable assembly. The test instrument 140 may be electrically coupled to a probe assembly 150, such as by using a multi-conductor interconnect 130. The probe assembly 150 may include one or more electroacoustic elements, such as an array 152 containing each of the elements 154A to 154N. The array 152 may follow a linear or curved contour, or may include an array of elements extending along two axes, such as providing a matrix of transducer elements. The size and pitch of the elements may vary depending on the inspection application.

[0015] A modular probe assembly 150 configuration can be used, which allows the test apparatus 140 to be used with various different probe assemblies. Generally, the array 152 includes piezoelectric elements that can be acoustically coupled to a target 158 ​​(e.g., a test specimen or "test subject") via a binding medium 156. The binding medium can include a fluid or gel, a solid film (e.g., an elastomer or other polymer material), or a combination of fluid, gel, or solid structure. For example, an acoustic transducer assembly may include a transducer array (e.g., Rexolite®, available from C-Lec Plastics Inc.) coupled to a wedge structure containing a rigid thermosetting polymer having known acoustic propagation properties, where water can be injected between the wedge and the structure under test as the binding medium 156 during the test, or the test can be performed by immersing the interface between the probe assembly 150 and the target 158 ​​in the binding medium.

[0016] The test apparatus 140 may include digital and analog circuit configurations such as a front-end circuit 122 that includes one or more transmission signal chains, reception signal chains, or switching circuit configurations (e.g., transmit / receive switching circuit configurations). The transmission signal chain may include amplifier and filter circuit configurations that provide transmit pulses to be delivered to the probe assembly 150 via the interconnect 130 for ultrasonic irradiation of the target 158, and that image or otherwise detect defects 160 on or inside the structure of the target 158 ​​by receiving scattered or reflected acoustic energy extracted in response to the ultrasonic irradiation.

[0017] Figure 1 shows a single probe assembly 150 and a single array 152, but other configurations can be used, such as multiple probe assemblies connected to a single test instrument 140, or multiple arrays 152 used with a single probe assembly 150 or multiple probe assemblies for pitch / catch testing. Similarly, the test protocol can be implemented using coordination between multiple test instruments 140 in response to an overall test scheme established, for example, from a master test instrument 140, or from another remote system such as a computing device 108, or from a general-purpose computing device such as a laptop 132, tablet, smartphone, or desktop computer. The test scheme may be established in accordance with published standards or regulatory requirements and may be implemented as an illustrative example during initial fabrication or repeatedly for ongoing monitoring.

[0018] The receiving signal chain of the front-end circuit 122 may include one or more filter or amplifier circuits, along with analog-to-digital conversion equipment, such as digitizing the echo signal received using the probe assembly 150. The digitization may be carried out coherently to provide multiple channels of digitized data aligned or referenced to one another in time or phase. The front-end circuit may be coupled to and controlled by one or more processor circuits, such as processor circuit 102, which is included as part of the test instrument 140. The processor circuit may be coupled to memory circuit 104, for example, to execute instructions causing the test instrument 140 to perform one or more of the following: acoustic transmission, acoustic acquisition, processing, or storage of data related to acoustic inspection, or otherwise to perform techniques as shown and described herein. The test instrument 140 may be communicatively coupled to other parts of the system 100, such as by using a wired or wireless communication interface 120.

[0019] For example, the performance of one or more techniques as shown and described herein can be achieved on the test apparatus 140 or using other processing or storage equipment, such as a computing device 108 or a general-purpose computing device such as a laptop 132, tablet, smartphone, or desktop computer. For example, processing tasks that would be unnecessarily slow if performed on the test apparatus 140 or if performed beyond the capabilities of the test apparatus 140 can be performed remotely (for example, on a separate system) in response to a request from the test apparatus 140. Similarly, the storage of intermediate data or other representations of such data, such as an A-scan matrix of imaging data or time-series data, can be achieved using remote equipment communicatively coupled to the test apparatus 140. The test apparatus may include a display 110 for presenting configuration information or results, and an input device 112 including one or more of a keyboard, trackball, function keys or soft keys, mouse interface, touchscreen, stylus, etc., for receiving operator commands, configuration information, or responses to queries.

[0020] Figures 2A and 2B illustrate respective diagrams of parts of an assembly similar to the A10 series acoustic inspection probe (Evint Scientific, Inc., MA, USA). The housing 253 can be formed, for example, by injection molding of a thermoplastic material. The housing 253 can have an active surface 255 defined so as to be placed in close proximity to the object to be inspected, or so as to be acoustically coupled to the object via a suitable bonding medium or wedge. The surface 255 can be the surface of an acoustically matching layer formed by the bottom wall 259 of the cavity 257 of the housing 253.

[0021] In general, the approaches described in this document allow the housing 253 to provide a substrate on which a metallization pattern defining each trace is formed. The cavity 257 can be formed during an injection molding process, and the metallization can be formed in a pattern defining each trace 231 and 233, such that it extends along different surfaces of the cavity 257, such as along a portion of the bottom wall 259 and one or more side walls (e.g., side wall 261). Using various approaches, such traces can be formed without requiring a separate printed circuit assembly (e.g., without requiring a separate rigid or flexible circuit assembly). A housing having such interconnects can be referred to as a molded interconnect device (MID). The metallization (e.g., corresponding to traces 231 and 233) can enable the mounting, soldering, and interconnection of electrical components in a manner similar to that of a printed circuit board (PCB). However, unlike a PCB, a MID is not constrained to a planar configuration. Therefore, such metallization can replace several components, such as eliminating cables or circuit board assemblies that may be required to supply the piezoelectric element within the housing 253.

[0022] Laser direct structuring (LDS) is one approach that can be used to form patterns for metallization. Another approach may involve the use of a two-shot injection molding process. LDS treatment can be used with a variety of different injection-molded polymer compounds, such compounds including materials that react (e.g., are modified) in response to laser treatment. Such laser treatment or "activation" of a surface can then induce localized roughness that is receptive to copper plating using an electroless copper plating process. The laser-activated plated areas can then be further treated with other finishes such as electroless nickel plating and substitution gold finishes (e.g., "electroless nickel / substitution gold" referred to as ENIG). Other areas of the polymer that are not laser-activated remain unplated. In this way, complex masking or other operations are not required, and as described above, the surface that accepts metallization does not need to be planar. Laser direct structuring after injection molding is one approach, while other approaches may include applying a suitable coating or paint that can be activated by a laser in the areas to be metallized, at the expense of greater processing complexity and less flexibility in terms of characteristic shape, minimum size, and configuration of the areas to be metallized.

[0023] In general, the preparation of the housing 253 as shown in Figures 2A and 2B involves injection molding of a thermoplastic material, with laser activation of the areas where metallization is desired, followed by one or more plating steps. The inventors recognize, among other things, that polymer densities that are generally compatible with LDS treatment and additives can be suitable for use as an acoustic matching layer within the phased array acoustic transducer assembly 250. The cavities 257 (also referred to as buckets) can provide a surface for tracing in contact with a piezoelectric element (e.g., a piezoelectric composite material), among other things, as shown in Figures 3A and 3B. The acoustic matching layer can be tailored by lapping the surface 255 or otherwise machining (e.g., grinding) the bottom wall 259 to provide a specific thickness, taking into account the center operating frequency and dielectric material properties (e.g., density, sound propagation velocity, and corresponding acoustic impedance versus frequency), as discussed below.

[0024] Suitable materials and processing parameters for direct laser structuring are available, for example, from LPKF Laser & Electronics AG (Germany). More rigid polymer material classes suitable for industrial acoustic inspection applications include, as exemplary examples, liquid crystal polymers (LCP) and polyether ether ketones (PEEK). Softer materials may include, as exemplary examples, PA6 / 6 and polyphthalamide (PPA). Such materials are generally available in pelletized forms, such as two-component injection molding or hot stamping. For LDS processing, injection-molded materials are generally not machined prior to metallization, at least in or near the region where metallization will be formed. Machining or other mechanical modifications of injection-molded structures can cause surface roughening, resulting in plating adhesion in areas other than the desired metallization region. Generally, as discussed below, high-density materials offer a more optimal acoustic impedance (Z L ) provides.

[0025] Figures 3A, 3B, 3C, 3D, and 3E illustrate the respective diagrams of the A10 series acoustic inspection probe assembly at various stages of processing, which can be processed to include piezoelectric elements, backing material, caps, and cable assemblies. This assembly process can provide a multi-element acoustic inspection transducer assembly. In the embodiments herein, the A10 series probe assembly generally corresponds to the 5L16-A10 phased array assembly available from Evident Scientific, Inc., which operates at an acoustic center frequency of approximately 5 megahertz (MHz) and has 16 elements defining the array. This illustrative (but non-limiting) example was selected for evaluation representing a linear configuration at an intermediate frequency. Generally, the use of the A10 configuration in this document is merely one example of a probe assembly shape, and the subject matter herein is applicable to other probe shapes.

[0026] Figures 3A and 3B show that a portion of the probe assembly 350A has a metallization formed within a cavity 257 of the housing 253. The housing 253 necessarily defines a bucket region (e.g., cavity 257) where piezoelectric elements can be located and bonded. For example, the piezoelectric elements may be a scribed piezoelectric composite assembly 254 defining each piezoelectric material region 265 that forms an array, as shown in Figures 3A and 3B. The scribed piezoelectric composite assembly 254 may include a conductive layer and a piezoelectric material layer, and for example, the piezoelectric material layer may be divided into respective regions by scribing or other means to create each isolated piezoelectric material region that can be bonded together on one plane using a conductive bus layer or trace. The scribed piezoelectric composite assembly 254 may be mechanically fixed (e.g., bonded or otherwise fixed) within the cavity using epoxy. The epoxy does not need to be conductive and avoids the need for a fine screen or distribution pattern. Fine microstructures of the metallized regions within the cavity 257 (e.g., formed using laser direct structuring and plating, as considered elsewhere) can protrude through the epoxy bonding material and electrically couple with corresponding portions of the scribing piezoelectric composite assembly 254 to provide interconnects for addressing the array defined by the scribing piezoelectric composite assembly 254. For example, such metallization can define corresponding individual element conductors, such as forming a reference (e.g., "ground") node or "bus" and pads that interlock with corresponding portions of the scribing piezoelectric composite assembly 254, providing addressability for individual regions within the array.

[0027] Referring to Figure 3B, the probe assembly 350A can define an acoustically matching layer between the scribing piezoelectric composite assembly 254 and the surface 255. For example, as considered below, the housing 253 can be grounded or wrapped at the surface 255 to establish a surface thickness corresponding to the central acoustic operating frequency and acoustic impedance of the dielectric material forming the housing 253. In this way, the piezoelectric element located within the cavity 257 is positioned to generate or receive acoustic energy coupled between the dielectric housing 253 and the outer surface of the dielectric housing 253 (e.g., surface 255).

[0028] Referring to Figure 3C, the probe assembly 350B may have a backing material 267 located within the cavity 257. The backing material 267 may be injected in liquid form, such as curing within the cavity 257 (e.g., cast in a similar manner to potting material), or the backing material 267 may be formed from one or more material blocks, such as being bonded to the surface of a piezoelectric composite assembly 254 scribing on the opposite side of the surface facing the bottom of the cavity 257, before wiring or capping the probe assembly 350B. If a cast backing material 267 is used, such material does not need to be inserted in Figure 3C, but instead can be injected through one or more openings in the assembly 350C or 350D after subsequent operations, such as after electrically joining the cables to the metallization and applying the cap, as shown in Figures 3D and 3E.

[0029] Referring to Figure 3D, the probe assembly 350C may have the cap 263 attached before or after connecting individual wires or other conductors to the metallization formed on the inner wall of the housing 253. For example, the cap may include a connector for attaching a cable. As mentioned above, connecting the wires or other conductors and applying the cap 263 may occur before or after the presence of the lining material 267. In Figure 3E, the probe assembly 350D may have a cable assembly 230 that is mechanically coupled to the cap 263. If the cap is not connectorized, the cable assembly 230 and the cap 263 can be integrated together to form a connection between the cable and each conductor in the pad defined by the metallization on the side wall of the cavity 257, for example, as shown in Figure 3C. The cap 263 may be attached to the housing 253 by using adhesive or, otherwise, by mechanically securing it using fasteners such as screws.

[0030] The configurations shown in the above embodiments include a multi-element piezoelectric composite (e.g., for phased array applications) and associated housing. The techniques herein are applicable to other transducer configurations, such as single-element (e.g., cylindrical) assemblies. Figures 4A and 4B illustrate respective figures of a single-element cylindrical transducer assembly 450A, illustrating the applicability of the approaches and materials described herein to other transducer assembly configurations. As shown in Figures 4A and 4B, a piezoelectric element (e.g., a composite 454 having a conductive layer 465) can be placed in a cylindrical cavity defined by a dielectric housing 453. As with other embodiments described herein, metallization can be formed in specific patterns, such as by using laser direct structuring and electroless plating, to establish a first trace 431 and a second trace 433. The first trace 431 and the second trace 433 may extend along the bottom surface 459 and extend upward along the inner wall 461 of the dielectric housing 453. Referring to Figure 4B, the composite material 454 may include conductive layers 465B and 465A. For example, layer 465B may extend along the side of the composite material 454 to provide a connection to layer 465 on the opposite surface of the composite material 454, and layer 465A may provide another terminal forming a monomorphic single-element configuration. Backing materials, caps, and cables may be added, as in other embodiments described herein. For example, the thickness of the wall of the dielectric housing 453 defining the active surface 455 of the single-element cylindrical transducer assembly 450A can be specified to provide an acoustically matching layer at a specific center frequency of operation of the single-element cylindrical transducer assembly 450A.

[0031] The selection of dielectric materials for housings in the embodiments described herein is not limited to consideration of compatibility with LDS or other similar treatments. The acoustic properties of dielectric materials also affect performance for acoustic transducer assembly applications. Generally, acoustic impedance is not characterized and is not available in material vendor data sheets associated with general-purpose injection-molded polymer materials, nor are other relevant parameters such as sound propagation velocity characterized. The inventors recognize, among other things, that density data can provide useful guidance regarding the suitability of materials for acoustic applications. Many polymer materials can be characterized as “high-speed” materials for sound propagation purposes, but their associated sound propagation velocity is still lower than that of typical thermal-carbon composition-matched layers. One indicator of potential suitability is 1 cubic centimeter (g / cm³). 3 The density is 2 grams or near that per cubic meter. Many materials for which LDS treatment is approved have densities below such thresholds. An unexpected result identified by the inventors is that such materials still exhibit acceptable acoustic performance when used in housings having an integrated matching layer made from the same material as the housing (e.g., formed by the walls of the housing). As an illustrative example, the following four materials were evaluated and their associated densities are listed. [Table 1]

[0032] Velocity measurements were obtained by measuring the time of flight through two different thicknesses of each material listed in Table I. Using the time-of-flight measurements along with the published density data, the corresponding acoustic impedance (Z) of each material can be determined. Then, using such acoustic impedances, the nominal thickness of each material as a quarter-wavelength matching layer for different specific center frequencies can be determined.

[0033] Figures 5A and 5B show typical elements and spectra of LCP VECTRA® 840I polymer material forming the housing of an A10 series acoustic transducer assembly. Figures 5C and 5D show typical elements and spectra of PPA GF39 RENY® polymer material forming the housing of an A10 series acoustic transducer assembly. Figures 5E and 5F show typical elements and spectra of PPA GF30 FORTII® 513 polymer material forming the housing of an A10 series acoustic transducer assembly. Figures 5G and 5H show typical elements and spectra of LCP TECACOMP® 1049426 polymer material forming the housing of an A10 series acoustic transducer assembly. For comparison, Figures 5I and 5J show typical elements and spectra of a ready-made A10 series acoustic transducer assembly not fabricated using the molded interconnect device approach described herein. As shown by the experimentally obtained results above, the bandwidth, impulse response, and center frequency show good agreement between the standard material configurations in Figures 5I and 5J and the simplified configuration using fabricated interconnect devices.

[0034] Figure 6 illustrates in general terms an art 600, such as a method of fabrication, which includes forming a dielectric housing containing a cavity and forming associated metallization in a specific pattern on the surface of the dielectric housing. In 605, the dielectric housing can be formed so that the dielectric housing defines the cavity. Such forming may include an injection molding process in which the cavity is not machined before downstream processing. In 610, each region of the surface of the dielectric housing can be activated, such as by ablating or otherwise treating, to create a roughened region that accepts plating (for example, for plating using an electroless plating process). In 615, the patterned conductive regions in 610 can be formed, such as by using immersion of the dielectric housing (or a portion thereof) in a plating bath. For example, the plating operation may include an initial copper plating operation followed by nickel and gold plating operations, in a manner that would otherwise be impractical, to provide traces and corresponding connecting pads that conform to the inner surface of the dielectric housing. In 620, piezoelectric elements, such as single-element or multi-element arrays, can be placed in a cavity defined by a dielectric housing (e.g., fixed to the dielectric housing), and in 625, the backing material can be located in the cavity. As discussed above, the backing material can be cast (e.g., after interconnects to cables have been made and caps have been attached), or a solid block of the backing material can be inserted into the cavity. In 630, if a portion of the dielectric housing functions as an acoustic matching layer, a specific matching layer thickness can be established by machining the surface of the dielectric housing after the formation of the conductive interconnects. Machining at this later stage of fabrication does not prevent the early formation of metallization using LDS and associated plating.

[0035] Various notes In Example 1, the acoustic transducer assembly for non-destructive testing (NDT) includes a molded dielectric housing defining a cavity; a piezoelectric element located within the cavity, fixed to the dielectric housing and arranged to generate and receive acoustic energy coupled to the outer surface of the dielectric housing through the dielectric housing; a conductive interconnect portion including a metallization formed on the inner surface defined by the cavity, electrically coupled to each region of the piezoelectric element; and a backing material located within the cavity on the surface of the piezoelectric element opposite to the surface of the piezoelectric element fixed to the dielectric housing.

[0036] In Example 2, the piezoelectric element includes a piezoelectric material and a conductive layer.

[0037] In Example 3, the piezoelectric material of Example 1 or Example 2 includes an array of piezoelectric material regions on a conductive layer, and each conductive interconnect portion provides electrical addressability for each piezoelectric material region defining the array.

[0038] In Example 4, the acoustic transducer assembly described in any of Examples 1 to 3 includes a portion that is part of the dielectric housing between the outer surface and the piezoelectric element, and is configured as an acoustic matching layer having a specific thickness of the dielectric material including the dielectric housing.

[0039] In Example 5, the acoustic transducer assembly described in any of Examples 1 to 4 includes the fact that the cavity is unprocessed after the molding of the dielectric housing.

[0040] In Example 6, the acoustic transducer assembly described in any of Examples 1 to 5 is further characterized by the metallization including copper.

[0041] In Example 7, the acoustic transducer assembly described in any of Examples 1 to 6 includes a metallization which includes a gold surface, and the gold surface is located on a nickel intermediate layer between the gold surface and copper.

[0042] In Example 8, the acoustic transducer assembly of Example 7 is further modified to include electroless nickel-substituted gold (ENIG) plating on the nickel intermediate layer and the gold surface.

[0043] In Example 9, the acoustic transducer assembly described in any of Examples 1 to 8 comprises a cap assembly mechanically coupled to a dielectric housing, the cap assembly comprising or supporting a multiconductor cable, the multiconductor cable comprising each conductor electrically coupled to a conductive interconnect portion formed on the inner surface defined by a cavity in the dielectric housing.

[0044] Example 10 provides a method for fabricating an acoustic transducer assembly for non-destructive testing (NDT), comprising: forming a conductive interconnect portion including metallization on the inner surface of a cavity defined by a molded dielectric housing; arranging a piezoelectric element within the cavity, fixing the piezoelectric element to the dielectric housing so that the piezoelectric element generates and receives acoustic energy coupled to the outer surface of the dielectric housing through the dielectric housing; and electrically coupling the conductive interconnect portion to each region of the piezoelectric element, wherein the method includes establishing a backing material within the cavity on the surface of the piezoelectric element opposite to the surface of the piezoelectric element fixed to the dielectric housing.

[0045] In Example 11, the method of Example 10 includes injection molding of the dielectric housing.

[0046] In Example 12, the method according to either Example 10 or 11 is configured such that a portion of the dielectric housing between the outer surface and the piezoelectric element is configured as an acoustically matching layer having a specific thickness of the dielectric material including the dielectric housing, and the method includes establishing the specific thickness by machining the injection-molded portion of the dielectric housing, including planarizing the outer surface.

[0047] In Example 13, the method according to any of Examples 10 to 12 includes forming each conductive interconnect portion by modifying each region of the raw surface of the dielectric housing with a pattern corresponding to each conductive interconnect portion.

[0048] In Example 14, the method of Example 13 includes modifying the raw surface by laser activating each region of the raw surface with a pattern corresponding to each conductive interconnect portion.

[0049] In Example 15, the method described in Example 14 includes forming each conductive interconnect portion by plating the laser activation region with copper.

[0050] In Example 16, the method of Example 15 includes forming each conductive interconnect portion, forming a gold surface, and the gold surface being located on a nickel intermediate layer between the gold surface and copper.

[0051] In Example 17, the method of Example 16 includes electroless nickel substitution gold (ENIG) plating for each conductive interconnect portion.

[0052] In Example 18, the method according to any of Examples 10 to 17 includes mechanically coupling a cap assembly to a dielectric housing, wherein the cap assembly comprises or supports a multiconductor cable, and the multiconductor cable includes each conductor electrically coupled to a respective conductive interconnect portion formed on the inner surface defined by a cavity in the dielectric housing.

[0053] In Example 19, the method of Example 18 includes establishing the backing material by casting the backing material through an opening in either the dielectric housing or the cap.

[0054] Example 20 provides a method for fabricating an acoustic transducer assembly for non-destructive testing (NDT), comprising: forming a dielectric housing defining a cavity; laser activating each region of the raw surface of the dielectric housing with a pattern corresponding to a conductive interconnect on the inner surface of the cavity; forming the conductive interconnect with a pattern by plating the laser activating regions; arranging a piezoelectric element in the cavity, fixing the piezoelectric element to the dielectric housing using an adhesive, so that the piezoelectric element generates and receives acoustic energy coupled to the outer surface of the dielectric housing through the dielectric housing; and electrically coupling the conductive interconnect with each region of the piezoelectric element, the method comprising establishing a backing material in the cavity on the surface of the piezoelectric element opposite to the surface of the piezoelectric element fixed to the piezoelectric element.

[0055] Each of the above non-limiting aspects may exist on its own or may be combined in various permutations or combinations with one or more of the other aspects or subjects described herein.

[0056] The above detailed description includes references to the accompanying drawings, which form part of the detailed description. The drawings illustrate specific embodiments in which the present invention can be carried out. These embodiments are also commonly referred to as “Examples.” Such Examples may include elements in addition to those illustrated or described. However, the inventors also intend to include Examples in which only the illustrated or described elements are provided. Furthermore, the inventors also intend to include Examples in which any combination or permutation of those illustrated or described elements (or one or more of their embodiments) is used in reference to a particular embodiment (or one or more of its embodiments) or in reference to other embodiments (or one or more of its embodiments) illustrated or described herein.

[0057] In the event of any conflict in usage between this document and any document incorporated by such reference, the usage described in this document shall prevail.

[0058] In this document, the terms “a” or “an” are used to include one or more, independently of any other instances or uses of “at least one” or “one or more,” as is common in patent literature. In this document, the term “or” is used to refer to a non-exclusive OR, such that “A or B” includes “A but not B,” “B but not A,” and “A and B.” In this document, the terms “including” and “in which” are used as plain English equivalents of the terms “comprising” and “wherein.” Furthermore, in the following claims, the terms “including” and “comprising” are not limited; that is, a system, device, article, composition, formulation, or process that includes elements in addition to those listed after such terms in a claim is still considered to be within the scope of that claim. Furthermore, in the following claims, terms such as “first,” “second,” and “third” are used merely as labels and are not intended to impose numerical requirements on their objects.

[0059] Examples of methods described herein can be at least partially machine or computer implements. Some embodiments may include computer-readable or machine-readable media encoded with instructions that can be operated to configure an electronic device to implement the methods described in the above embodiments. Implementations of such methods may include code such as microcode, assembly language code, or higher-level language code. Such code may include computer-readable instructions for implementing various methods. The code may form part of a computer program product. Such instructions may be read and executed by one or more processors to enable the implementation of operations, for example, a method. Instructions may be in any preferred form, but are not limited to source code, compiled code, interpreted code, executable code, static code, dynamic code, and so on.

[0060] Furthermore, in one embodiment, the code may be tangibly stored in one or more volatile, non-temporary, or non-volatile tangible computer-readable media, such as during execution or at other times. Examples of such tangible computer-readable media include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact discs and digital video discs), magnetic cassettes, memory cards or sticks, random access memory (RAM), and read-only memory (ROM).

[0061] The above description is intended to be illustrative and not restrictive. For example, the embodiments (or one or more aspects thereof) described above may be used in combination with one another. Other embodiments may be used, for example, by those skilled in the art when reviewing the above description. An abstract is provided to enable the reader to quickly confirm the nature of the technical disclosure. The abstract is submitted with the understanding that it is not to be used to interpret or limit the scope or meaning of the claims. Also, in the above detailed description, various features may be grouped together to streamline the disclosure. This should not be interpreted as meaning that any disclosed features not claimed are essential to any patent claim. Rather, the subject matter of the invention may lie in fewer features than all the features of a particular disclosed embodiment. Accordingly, the following claims are incorporated into the detailed description as examples or embodiments, and each claim exists independently as a separate embodiment, and such embodiments are intended to be able to be combined with one another in various combinations or permutations. The scope of the invention should be determined by reference to the appended claims, together with the entire scope of equivalents to which such claims are entitled. [Explanation of Symbols]

[0062] 250 Phased Array Acoustic Transducer Assembly 253 Housing 257 Cavity 267 Lining material

Claims

1. Acoustic transducer assembly for non-destructive testing (NDT), A molded dielectric housing that defines the cavity, A piezoelectric element located within the cavity, fixed to the dielectric housing, and arranged to generate and receive acoustic energy coupled between the dielectric housing and the outer surface of the dielectric housing, A conductive interconnect portion including a metallized portion formed on the inner surface defined by the cavity, which is electrically coupled to each region of the piezoelectric element, An acoustic transducer assembly comprising a backing material located within the cavity on the surface of the piezoelectric element opposite to the surface of the piezoelectric element fixed to the dielectric housing.

2. The acoustic transducer assembly according to claim 1, wherein the piezoelectric element includes a piezoelectric material and a conductive layer.

3. The piezoelectric material includes an array of piezoelectric material regions on the conductive layer, The acoustic transducer assembly according to claim 2, wherein each of the conductive interconnects provides the possibility of electrical addressing each piezoelectric material region defining the array.

4. The acoustic transducer assembly according to claim 1, wherein a portion of the dielectric housing between the outer surface and the piezoelectric element is configured as an acoustic matching layer having a specific thickness of the dielectric material including the dielectric housing.

5. The acoustic transducer assembly according to claim 1, wherein the cavity is unprocessed after the molding of the dielectric housing.

6. The acoustic transducer assembly according to claim 1, wherein the metallization includes copper.

7. The acoustic transducer assembly according to claim 6, wherein the metallization includes a gold surface, and the gold surface lies on a nickel intermediate layer between the gold surface and the copper.

8. The acoustic transducer assembly according to claim 7, wherein the nickel intermediate layer and the gold surface include electroless nickel-substituted gold (ENIG) plating.

9. The acoustic transducer assembly according to claim 1, comprising a cap assembly mechanically coupled to the dielectric housing, wherein the cap assembly comprises or supports a multiconductor cable, and the multiconductor cable comprises each conductor electrically coupled to the respective conductive interconnect portion formed on the inner surface defined by the cavity of the dielectric housing.

10. A method for fabricating an acoustic transducer assembly for non-destructive testing (NDT), Forming a conductive interconnect portion including metallization on the inner surface of a cavity defined by a molded dielectric housing, The piezoelectric element is placed in the cavity, and the arrangement is The piezoelectric element is fixed to the dielectric housing, and the piezoelectric element is positioned and fixed such that it generates and receives acoustic energy coupled with the outer surface of the dielectric housing through the dielectric housing. The arrangement includes electrically coupling the conductive interconnect portion with each region of the piezoelectric element. A method comprising establishing a backing material in the cavity on the surface of the piezoelectric element opposite to the surface of the piezoelectric element fixed to the dielectric housing.

11. The method according to claim 10, further comprising injection molding the dielectric housing.

12. A portion of the dielectric housing between the outer surface and the piezoelectric element is configured as an acoustically matching layer having a specific thickness of the dielectric material including the dielectric housing. The method according to claim 10, wherein the method includes establishing the specific thickness by machining the injection-molded portion of the dielectric housing, which includes flattening the outer surface.

13. The method according to claim 11, wherein forming each of the conductive interconnect portions includes modifying each region of the unprocessed surface of the dielectric housing with a pattern corresponding to each of the conductive interconnect portions.

14. The method according to claim 13, wherein modifying the unprocessed surface includes laser activation of each region of the unprocessed surface with the pattern corresponding to each of the conductive interconnect portions.

15. The method according to claim 14, wherein forming each of the aforementioned conductive interconnect portions includes plating the laser activation region with copper.

16. The method according to claim 15, wherein forming each of the conductive interconnect portions includes forming a gold surface, the gold surface being located on a nickel intermediate layer between the gold surface and the copper.

17. The method according to claim 16, wherein forming each of the aforementioned conductive interconnect portions includes electroless nickel substitution gold (ENIG) plating.

18. The acoustic transducer assembly according to claim 1, comprising mechanically coupling a cap assembly to the dielectric housing, wherein the cap assembly comprises or supports a multiconductor cable, each of which conductors is electrically coupled to the respective conductive interconnect portion formed on the inner surface of the dielectric housing defined by the cavity.

19. The acoustic transducer assembly according to claim 18, wherein establishing the backing material includes casting the backing material through an opening in either the dielectric housing or the cap.

20. A method for fabricating an acoustic transducer assembly for non-destructive testing (NDT), Forming a dielectric housing that defines the cavity, Laser activation of each region of the unprocessed surface of the dielectric housing in a pattern corresponding to the conductive interconnect portion on the inner surface of the cavity, By plating the laser-activated region, the conductive interconnect portion is formed in the pattern, The piezoelectric element is placed in the cavity, and the arrangement is The piezoelectric element is fixed to the dielectric housing using an adhesive, and the piezoelectric element is positioned to generate and receive acoustic energy coupled to the outer surface of the dielectric housing through the dielectric housing, The arrangement includes electrically coupling the conductive interconnect portion with each region of the piezoelectric element. A method comprising establishing a backing material in the cavity on the surface of the piezoelectric element opposite to the surface of the piezoelectric element fixed to the dielectric housing.

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