Chip-on-array with interposer for multi-dimensional transducer array

Abstract

Array on chip with interposer for multi-dimensional transducer array. In an array on chip approach, the acoustic and electronic modules are formed separately. The acoustic stack (10, 11, 12) is connected to one interposer (13), and the electronics (17) are connected to another interposer (16). Different connection processes can be used (e.g., low temperature bonding for the acoustic stack, and higher temperature based interconnects for the electronics). The arrangement can allow for different pitches P of the I / O of the transducer elements (21) and the electronics (17) by interleaving the vias (20) in the interposers (13, 16) A , E The two interposers (13, 16) are then connected to form the array on chip.

Description

[0001] This application is a divisional application of application filed on November 6, 2019, with application number 201911076292.6 and invention title "Chip-on-Array with Intermediate Layer for Multidimensional Transducer Array". Background Technology

[0002] This embodiment relates to the interconnection of a multidimensional transducer array with electronic devices. Achieving interconnection between an acoustic array and associated transmitting and / or receiving electronics is a technical challenge of multidimensional (matrix) transducers. Hundreds or thousands (e.g., up to 10,000) of different elements distributed in two dimensions (azimuth and elevation) require interconnection along the z-axis (depth or range) for elements that are at least surrounded by other elements. Due to the small size of the elements (e.g., 250-500 μm), there is limited space for separate electrical connections to each element.

[0003] There are three approaches to providing interconnects for multidimensional transducer arrays: chip-on-array, frame-based approaches, and multilayer flexible components. In chip-on-array, the acoustic array is built directly onto the input / output (I / O) of an application-specific integrated circuit (ASIC) chip. In principle, this approach provides the shortest possible electrical interconnect between the acoustic elements and the electronics, resulting in desirablely low electrical parasitic effects. However, this can lead to very low process yields due to potential failures in the array or electronics. The acoustic elements cannot be tested until their formation on the electronics is complete. Since the acoustic array is built on top of expensive electronics, losses in the acoustic array result in losses in expensive electronic modules.

[0004] In the frame-based approach, the array is divided into several segments (e.g., four). Each segment has a robust metal frame. Flexible circuitry, bent around the metal frame, redistributes as many signals as the acoustic elements from the acoustic elements to the ASIC placed on the flexible circuitry. The signal routing in the frame-based approach is more complex than on-chip arrays, resulting in higher electrical parasitics. Because the acoustic elements are built on separate flexible circuitry, better processing yields and testability are provided for both the acoustic and electronic components.

[0005] The multilayer flexible element approach stacks as many flexible circuits as possible (e.g., up to 9 layers) to route signals from numerous elements (e.g., up to 9000 acoustic elements) without any aperture segmentation. Compared to chip-on-array or frame-based methods, this multilayer flexible element can be bent to function as a bending matrix array. This routing results in high electrical parasitic effects due to the multiple flexible circuits and long traces on each flexible element. Summary of the Invention

[0006] For introduction, the preferred embodiments described below include methods, systems, and components for connecting electronic devices to an array of transducer elements. In the chip-on-array method, acoustic and electronic modules are formed separately. The acoustic stack is connected to one interposer layer, and the electronic devices are connected to another interposer layer. Different connection processes can be used (e.g., low-temperature bonding for the acoustic stack and higher-temperature-based interconnects for the electronic devices). This arrangement can allow for different pitches of I / O for the transducer elements and electronic devices by staggering the vias in the interposers. The two interposers are then joined to form a chip-on-array.

[0007] In a first aspect, a multidimensional transducer array system is provided. The acoustic array has transducer elements distributed in a grid pattern in two dimensions. A first interposer layer is bonded to the acoustic array using a material bonded at a temperature below the Curie temperature of the transducer elements. An integrated circuit has transmitting and / or receiving circuitry for performing ultrasonic scanning using the acoustic array. A second interposer layer is bonded to the integrated circuit using a material bonded at a temperature above the Curie temperature of the transducer elements. Through-holes formed in the first and second interposers electrically connect the transducer elements to the integrated circuit.

[0008] In a second aspect, an ultrasonic transducer probe is provided. The chip-on-array arrangement includes a semiconductor chip electrically connected to a multidimensional transducer array via an interposer layer formed of multiple layers. Vias in the layers form electrical connections from the multidimensional transducer array to the semiconductor chip. The vias are patterned to change the pitch from a first pitch of the multidimensional transducer array to a second, different pitch of the connection pads on the semiconductor chip.

[0009] In a third aspect, a method for connecting electronic devices to an array of acoustic elements is provided. A first material sheet having a first through-hole is connected to a transducer stack. A second material sheet having a second through-hole is connected to an integrated circuit for ultrasonic transmitting and / or receiving operations. The first material sheet, as connected to the transducer stack, is then bonded to the second material sheet, as connected to the integrated circuit.

[0010] This invention is defined by the following claims, and nothing in this section should be construed as limiting those claims. Further aspects and advantages of the invention are discussed below in conjunction with preferred embodiments and may be claimed subsequently, independently or in combination. Different embodiments may or may not achieve different objectives or advantages. Attached Figure Description

[0011] The components and figures are not necessarily to scale; rather, the emphasis is on illustrating the principles of the invention. Furthermore, throughout the figures, the same reference numerals denote corresponding parts across different views.

[0012] Figure 1 This is a cross-sectional view of one embodiment of an array-on-a-chip interconnect of an acoustic array with integrated circuits;

[0013] Figure 2 This is a cross-sectional view of another embodiment of the on-array interconnect of an acoustic array with integrated circuits;

[0014] Figure 3 An example fabrication of an array-on-chip system for use in a transthoracic echocardiography (TTE) probe is shown;

[0015] Figure 4 An example fabrication of an array-on-chip system for use in intracardiac echocardiography (ICE) catheter probes is shown;

[0016] Figure 5 This is a flowchart of an embodiment of a method for connecting electronic devices to an array of acoustic elements;

[0017] Figure 6 This is a cross-sectional view of an example of an acoustic stack connected to an intermediate layer; and

[0018] Figure 7 This is a cross-sectional view of an example of an integrated circuit connected to an interposer layer. Detailed Implementation

[0019] For electrical connections in a multidimensional (e.g., matrix) array transducer, an interposer layer is provided on the chips of the array. The interposer layer is formed of flexible circuitry or other materials placed between the electronics (e.g., an ASIC) and the acoustic elements of the array. Electrical interconnections from the acoustic array to the interposer and from the electronic chips to the interposer are formed separately using module-specific processes (e.g., acoustic arrays and electronic modules) and the resulting layer arrangement. Then, the separately formed modules form interposer-to-interposer electrical interconnections. This ultrasonic transducer architecture for integrating the acoustic and electronic modules of a multidimensional matrix array transducer can provide minimized electrical parasitic effects, testability regarding the separation of both acoustic and electronic modules, better process yields in ultrasonic transducer manufacturing, higher thermal budgets for certain interconnections, and improved reliability of the electronic modules, all of which can reduce overall cost.

[0020] The short electrical paths via vias provide lower electrical parasitic effects. Each acoustic element is electrically interconnected to its corresponding ASIC I / O via several (e.g., 2-4) stacked vias within the flexible circuitry of the interposer. The very low height of each via results in short electrical interconnections from the acoustic element to the ASIC, leading to lower electrical parasitic effects compared to frame-based and multilayer flexible component approaches.

[0021] Acoustic and electrically flexible circuitry (interposers) can have staggered vias. Compared to the pitch and position of transducer elements, staggered vias provide greater flexibility in I / O pitch for the electrical interconnects between acoustic and electrical modules on the chip within an array of ultrasonic transducers.

[0022] Instead of a single large, expensive ASIC chip, two or more smaller chips can be mounted on a flexible circuit (chip tiling). This arrangement allows for smaller, less expensive integrated circuits.

[0023] Low-temperature bonding can be used for acoustic modules, while high-temperature interconnects can be used for electronic modules. For acoustic modules, low-temperature and low-voltage bonding layers are used. Acoustic modules can be formed by bonding the individual layers of a transducer stack together in one step, along with an interposer layer. Low-temperature (e.g., <120°C) curable polymers (e.g., epoxy resins) are used to bond the acoustic modules. The thermal budget of the acoustic modules is limited below the Curie temperature of the piezoelectric layers (e.g., <80°C for binary single piezoelectric crystals, or <120°C for ternary single piezoelectric crystals) or other breakdown temperatures. High-temperature (e.g., >120°C) interconnects can be used for electronic modules, providing more reliable interconnects for ASIC connections and / or connections of passive components (e.g., capacitors, resistors, and / or inductors). High-temperature reliable electrical interconnects (>120°C) for electronic modules include lead and lead-free solders (>180°C), copper pillars with solder caps (>250°C), and high-temperature anisotropic conductive films (ACF) (>120°C). Because each module is built on a separate intermediate layer, the acoustic module can be formed by one-step bonding with a low-temperature curable polymer, while at the same time, a higher thermal budget is available for the electronic module.

[0024] Because the acoustic and electronic modules are connected separately to the interposer, these modules can be tested independently. The parallel process of forming the acoustic and electronic modules on the separate flexible circuitry of the interposer allows each module to be tested before being assembled together. After testing, only the good modules are used to form the complete assembly of the ultrasonic transducer. Since the failure of one module does not accumulate on top of the failure of another, this can lead to better process yields for manufacturing.

[0025] Figure 1 This is a cross-sectional view of one embodiment of a multidimensional transducer array system. The system is used in ultrasound transducer probes, such as handheld probes for scanning from outside the patient, or endocavity-based or catheter-based probes for scanning from inside the patient. The system is an array-on-chip arrangement, wherein semiconductor chips are electrically connected to the multidimensional transducer array through an interlayer formed of multiple layers. Due to the short electrical connections, improved scanning and imaging using ultrasound can be provided for medical diagnostics.

[0026] use Figure 5 The array system and corresponding probes are formed using one or another method. The array system includes an acoustic module formed by a transducer stack and at least one interposer layer 13, and an electronic module formed by an integrated circuit 17 and at least one interposer layer 16. Additional modules may be included.

[0027] The acoustic module includes an acoustic array 22 having transducer elements 21 distributed in a grid pattern in two dimensions. The multidimensional transducer array 22 is an array of piezoelectric or microelectromechanical (MEMS) (capacitive thin film) elements. A piezoelectric example is used herein. The array 22 can be flat, recessed, or convex. The transducer elements 21 are distributed along both dimensions. The transducer elements 21 are distributed along both dimensions at full sampling intervals along any of various pitches (such as per 250, 400, or 500 micrometers). Figure 1 In the diagram, the pitch of transducer element 21 is shown as pitch P. A Other pitches or pitches that vary as a function of position can be used. The pitch can be the same or different in different directions or dimensions, such as 300 micrometers at the elevation angle and 600 micrometers at the azimuth angle. Full or sparse sampling of the placement of transducer element 21 is provided.

[0028] Array 22 and corresponding transducer elements 21 include one or more impedance matching layers 10, piezoelectric layers 11, and dematching layers 12. Each of the transducer elements 21 in array 22 includes at least two electrodes. The elements convert between electrical and acoustic energy. Additional, different, or fewer layers may be provided. For example, a backing block may be positioned on one side of array 22 to limit acoustic reflections of energy emitted from undesired directions. Lenses, windows, or other multidimensional transducer array components now known or developed later may be included.

[0029] Impedance matching layer 10 is a material layer with a thickness of 1 / 4 wavelength. This material has an acoustic impedance between the piezoelectric layer 11 and the patient's impedance. Multiple layers with gradually varying acoustic impedance can be used.

[0030] The piezoelectric layer 11 is a flat plate or sheet of piezoelectric material. Solid piezoelectric materials can be used. Monocrystalline or polycrystalline piezoelectric materials can be used. In other embodiments, a composite of piezoelectric material and epoxy resin or another polymer is used.

[0031] The dematching layer 12 is a 1 / 4 wavelength thick material layer. Any material can be used, such as tungsten carbide. The dematching layer 12 provides clamping boundary conditions, resulting in better sensitivity and a wider bandwidth in the ultrasonic transducer.

[0032] A ground plane can form an electrode. The ground plane can be provided by the impedance matching layer 10. Alternatively, a conductor sheet can be placed or deposited on, within, or below the impedance matching layer 10.

[0033] Another conductor sheet provides conductors for forming signal electrodes. Conductors deposited on the interposer 13 can be used. Alternatively, conductors placed or formed on the piezoelectric layer 11 are positioned between the piezoelectric layer 11 and the dematching layer 12. In other embodiments, the conductors are formed of a conductive material of the dematching layer 12. The conductor sheet provides signal electrodes for the transducer elements 21 once it is cut or separated. Electrically decoupled signal electrodes are provided for each transducer element.

[0034] Intermediate layer 13 is an electrically insulating or dielectric material. In one embodiment, intermediate layer 13 is formed from a sheet of flexible circuit material such as polyimide. Traces or other conductors may be included on and / or in the material of intermediate layer 13, such as deposited and / or etched copper traces. Passive and / or active electronic devices may be attached. Since the flexible circuit material is placed between the electronic chip (e.g., ASIC) and the acoustic array 22 to provide signal routing or distribution for electrical interconnection, this material serves as an intermediate layer.

[0035] Intermediate layer 13 is connected to the acoustic stack to form an acoustic module. The physical connection is achieved through bonding, thus providing a bonding material layer. Figure 1 In the example, the bonding material is an epoxy resin layer, such as a low-temperature curable epoxy resin 14. The epoxy resin layer holds the interposer layer 13 to the acoustic stack, such as holding the interposer layer 13 to the mating layer 12.

[0036] Any material used for bonding can be used. In one embodiment, the material is a low-temperature curable polymer, such as epoxy, polyurethane, polyester, silver paste, or other polymer-based materials. Low temperature relates to transducer element 21. The Curie temperature of piezoelectric layer 11 can be between 80 and 120°C. For example, a binary single piezoelectric crystal has a Curie temperature of 80°C, and a ternary single piezoelectric crystal has a Curie temperature of 120°C. Other Curie temperatures can be provided. Other temperatures can be used in relation to breakdown or changes in operation of any layer in the acoustic stack. Reaching or exceeding this temperature is undesirable in forming the acoustic module. The material used for bonding or other interconnections allows for connection without exceeding the low temperature.

[0037] Rough contact is provided from the signal electrode to the trace, via 20, or other conductors on the interposer 13. The interposer 13 is stacked with the dematching layer 12. The impedance matching layer 10 and piezoelectric layer 11 of the transducer may be pre-bonded together or not. A bonding material is added to the stack or during stacking. This material may be cured at room temperature or at an elevated temperature below the Curie temperature or other breakdown temperature. In one embodiment, the impedance matching layer 10, piezoelectric layer 11, dematching layer 12, and interposer 13 are stacked and bonded simultaneously or as the same cured portions (i.e., one-step bonding) to form an acoustic module.

[0038] Intermediate layer 13 includes multiple vias 20. Several vias 20 are located in... Figure 1 The image is shown as an inverted triangle. A via 20 is provided for each transducer element on a single interposer layer 13, but additional or fewer vias may be provided. The vias 20 are formed in the interposer layer 13 by means such as etching, deposition, drilling, or molding. Conductors such as copper fill or plug the vias to create a conductive path through the thickness of the interposer layer 13. The via 20 provides a conductive path from one side of the interposer layer 13 to the other, to allow, for example, electrical connections from the signal electrodes of the transducer element 21 to electronic modules (e.g., integrated circuit 17) in a chip arrangement on an array.

[0039] Through-hole 20 is positioned for connection to the signal electrode. Through-hole 20 is at the same pitch P as the signal electrode and the corresponding transducer element 21. A Under these conditions, the through-hole 20 is aligned with the signal electrode. Figure 1 In the example, the vias 20 of the interposer layer 13 used for the acoustic module have the same pitch. The pitch of the vias 20 may differ from the pitch P of the signal electrodes. A In this case, traces or pads are formed on the interposer 13 to route signals from the signal electrode to the via 20. Alternatively, the via 20 is angled such that a pitch P is provided on the surface adjacent to the signal electrode. A Furthermore, different pitches are provided on the opposite surfaces of the intermediate layer 13.

[0040] Once aligned and engaged, the signal electrodes are electrically connected to the vias 20 of the interposer layer 13. This provides a z-axis route for signals from or from the transducer element 21 to the electronic module. The assembled acoustic module includes a bonding material for physically holding the interposer layer 13 to the transducer element 21 in the presence of an electrical connection via rough contact.

[0041] The electronic module includes electronic devices (e.g., integrated circuit 17 and / or passive electronic devices 18, also referred to as passive devices 18) and one or more interposer layers 16. Additional, different, or fewer components may be provided in the electronic module.

[0042] Passive electronic device 18 is a discrete component, such as a resistor, capacitor, and / or inductor. Other passive electronic devices may be used or no passive electronic devices may be used.

[0043] Active electrical components are semiconductors, such as transistor devices. The term "active" is used to describe a type of device rather than its operation. Transistor-based or switch-based devices are active devices, while resistors, capacitors, or inductors are passive devices. An active electrical device is one or more integrated circuits 17, such as an ASIC 17. Integrated circuit 17 can be an application-specific integrated circuit, analog circuit, digital circuit, switch, multiplexer, controller, processor, digital signal processor, field-programmable gate array, or other active electrical components now known or developed later. Integrated circuit 17 can be used as a chip form of an integrated circuit.

[0044] The semiconductor or active electronic device includes transmitting and / or receiving circuitry for ultrasonic scanning using the acoustic array 22. For example, multiple transmitting circuits as semiconductor chips, multiple receiving circuits as semiconductor chips, and a controller as a semiconductor chip are provided. The transmitting component is separate from the receiving component, or may be integrated with the receiving component. The transmitting component includes a high-voltage pulse generator, a filter, a memory, a delay unit, a phase rotator, a multiplier, a combination of the above, or other transmitting beamformer components now known or developed later. The receiving component includes a filter, an amplifier, a delay unit, an adder, a combination of the above, or other receiving beamformer components now known or developed later. Since the receiving beamformer components can operate at lower voltages than the transmitting components, the receiving and transmitting components are separate devices, but a combined device for transmitting and receiving operations can be provided. The integrated circuit 17 includes all or some of the following: a transmitting beamformer, a pulse generator, a receiving beamformer, an amplifier, a phase rotator, a delay unit, an adder, or other active electronic devices for ultrasonic scanning.

[0045] In one embodiment, a single active electrical component, such as a single chip or ASIC, is provided. Figure 1 As shown in the diagram, a larger number of acoustic transducer elements 21 and corresponding apertures result in a larger ASIC chip for processing acoustic signals. Larger ASIC chips are more expensive because they have a greater chance of defects occurring during semiconductor processing. To reduce the size of the integrated circuit 17, two or more integrated circuits 17 can be tiled. Figure 2An example is shown where two semiconductor chips or integrated circuits 17A (e.g., ASIC 2) and 17B (e.g., ASIC 1) are used. Two or more semiconductors can be tiled or placed adjacent to each other. Each semiconductor or integrated circuit 17 is positioned adjacent to the interposer 16. Two or more smaller chips, instead of a single large, expensive ASIC chip, are mounted on the interposer 16 (e.g., flexible circuitry). Each integrated circuit 17A, B is electrically connected to a different subset of transducer elements 21. For example, four ASICs are electrically connected to four groups of transducer elements 21, with each element in only one group.

[0046] The semiconductor chip or integrated circuit 17 includes input / output pads. The semiconductor chip includes input / output conductors exposed on its largest surface. In an alternative embodiment, the pads exit the chip along its edges and are routed to a distribution on the largest surface via bonding wires or flexible circuitry. In other alternative embodiments, the interposer 16 routes to conductors on the sidewalls of the chip.

[0047] Input / output pads are conductors formed on integrated circuit 17. Copper pillars, electrodes, traces, vias, or other conductive structures can be used for input / output pads.

[0048] The input / output pads have a pitch P E The pitch can be related to the pitch P of the transducer element 21. A The same. Alternatively, the pitch of the input / output pads is different. For example, Figure 1 The pitch P of the ASIC is shown. E The pitch P E Along one dimension (e.g., azimuth angle) with the pitch P of transducer element 21 A Different. Along the vertical dimension (e.g., elevation angle), the pitch may be the same or different. In a Cartesian grid, the pitch P... A It can be 500 micrometers, while the pitch P E It can be 400 micrometers. Other pitches can be used for either the transducer element 21 or the pads. When both the transducer element 21 and the input / output pads are in the same regular grid pattern, the pitch P... A P E They can be different. In other embodiments, the distribution pattern of the transducer elements 21 differs from the distribution pattern of the input / output pads.

[0049] The interposer 16 used in the electronic module may be made of the same or different material as the interposer 13 used in the acoustic module. For example, the interposer 16 may be formed of polyimide or a flexible circuit material. Its thickness may be the same as or different from that of the interposer 13 in the acoustic module.

[0050] It can provide any number of intermediary layers 16. Figure 1 In the example, there are two intermediary layers 16, which are either stacked on top of each other or in rough contact with each other. There may be only one, three or more intermediary layers 16.

[0051] During manufacturing, the electronic module includes layers or structures of material for holding the interposer 16, passive electronic components 18, and / or integrated circuits 17 together. The interposer 16 is bonded to the integrated circuit 17 via this material. This material serves as a physical connection to hold the interposer 16 to the integrated circuit 17, and / or to another interposer 16. This material may additionally form electrical connections between input / output pads and vias 20 and / or traces on the interposer 16.

[0052] The materials are bonded at temperatures higher than the Curie temperature of transducer element 21. This forms stronger, rougher contacts for electrical connections and / or other electrical interconnects with better strength or contact, due to their ability to form interconnects at higher temperatures. For example, anisotropic conductive film (ACF) or solder is used. The material bonding is an interconnect formed at temperatures higher than those used for the acoustic module. For example, interconnects are formed at temperatures greater than 80°C, 120°C, 180°C, or other temperatures. In one embodiment, copper pillar bump connectors (e.g., a tin-silver-copper composition) with solder caps are used for the interconnect between the ASIC chip and the interposer 16. The ASIC is placed face down on the substrate of the interposer 16. Connectors are formed on the pads (caps of the copper pillar bump connectors) of the interposer 16 by high-temperature reflow to melt the solder caps (e.g., temperatures >250°C). ACF may use temperatures >120°C. Solder or solder bumps may use temperatures >180°C. After heating, a bonding material is formed that bonds the interposer 16 to the integrated circuit 17, as if aligned with the integrated circuit 17. The passive electronic device 18 can be bonded separately or as part of the same heated portion.

[0053] Interposer 16 includes a plurality of vias 20. The vias 20, with or without traces, electrically connect the transducer elements 21 of array 22 to the semiconductor chip of integrated circuit 17. The vias 20 extend through the thickness of interposer 16 to provide electrical connections. For electrical connections, vias 20 through all interposers 13, 16 provide electrical connections. For each element, signal electrodes are connected to vias 20 in interposer 13 of the acoustic module, vias 20 in interposer 13 of the acoustic module are connected to vias 20 in interposer 16 of the electronic module, and vias 20 in interposer 16 of the electronic module are connected to input / output pads of integrated circuit 17. Additional vias 20 to vias 20 connections may be provided if other interposers are provided. Traces or other conductors on or within interposers 13 and / or interposers 16 may be used to route interconnects.

[0054] At component pitch P A Pitch P of input / output pads E With the transducer element 21 aligned with the input / output pads, the via 20 is aligned on each of the interposers 13 and 16 and at the same pitch. At the component pitch P... A and input / output pad pitch P E In cases where the transducer element 21 is not aligned with the pads, staggered vias 20 can be used in one or more interposers 13, 16. The vias 20 are staggered by angling and / or placement to offset them, resulting in a pitch, i.e., component pitch P, with respect to the vias 20 in other interposers 13, 16. A and / or pad pitch P E The pitch and / or pattern of the through-hole 20 are different. Figure 1 An example is shown below: where the through-hole 20 of the intermediate layer 13 of the acoustic module is located at the element pitch P. A However, the through holes 20 of the two interposer layers 16 of the electronic module are at different pitches, i.e., component pitch P. A and pad pitch P E Other arrangements can be used with vias 20 in the interposers 13, 16 having the same or different pitches as other interposers 13, 16, transducer elements 21, and / or pads. Some vias 20 in a given interposer 13, 16 can be staggered, while others are not relative to other pitches.

[0055] Intermediate layers 13, 16 with staggered vias 20 provide signal routing to match electrical I / O from one or more ASICs with corresponding acoustic I / O (signal electrodes) of the multidimensional array 22. This staggering adjusts the signal path from the component pitch P. A The transducer element 21 is connected to the pad pitch P. E Electrical connections to the input / output pads below. Intermediate layers 13 for acoustic modules and 16 for electronic modules (e.g., flexible circuitry) with staggered vias 20 provide greater flexibility in the I / O pitch and location of the electrical interconnects between acoustic and electrical modules on the chip for the ultrasonic transducer array. Acoustic pitch (P A It does not need to be related to electrical pitch (P) E Furthermore, it eliminates the need to place each electrical I / O directly below its corresponding acoustic I / O, thus providing greater flexibility and freedom in ASIC development and selection.

[0056] Any number of interposers 13, 16 may be included. Additional interposers 13 may be provided within the acoustic module. Additional interposers 16 may be joined as part of the electronic module due to the higher temperatures they can provide and / or the more reliable interconnections provided to reduce thermal stress on the acoustic stack. Based on any via stagger and alignment, interconnections are formed through the thickness of the additional interposers 16 and, if necessary, along or within the interposers 16, providing electrical connections.

[0057] The acoustic module is bonded to the electronic module. The outer interposer layers 13 and 16 of the formed acoustic and electronic modules are interconnected. Since the transducer stack is included within the acoustic module, the interconnects use materials bonded at temperatures below the Curie temperature or breakdown temperature of the transducer element 21. The temperature used to cure or form the interconnects may be the same as or different from the temperature used to form the interconnects of the acoustic module. Materials that are the same as or different from those used to form the acoustic module are used to bond these modules together. For example, epoxy resin is used to form the acoustic module, and silver paste or epoxy resin is used to bond these modules together. Epoxy resin and silver paste are bonded using temperatures and pressures lower than those used for ACF. Low-pressure bonding during the bonding of the two interposer layers 13, 16 (e.g., flexible sheets) to each other minimizes damage to the ASIC and the acoustic module.

[0058] The resulting array system is housed within a housing and electrically connected to cables or other conductors for signal transmission using an ultrasonic scanner or image processor. When the interposers 13 and 16 are formed of a flexible material, the interposers 13 and 16 extending beyond the integrated circuit 17 can be bent or shaped. When multiple integrated circuits 17A and 17B are used, the curvature at the array 22 can be utilized.

[0059] Figure 3 An example is shown below, in which intermediate layers 13 and 16 are placed on the frame or shaped for assembly into a transthoracic echocardiography (TTE) probe. Figure 4 An example is shown below, in which intermediate layers 13 and 16 are folded for fitting into a catheter (e.g., an intracardiac echocardiography catheter). Other probes, corresponding housings, and / or shapes, such as handheld probes, can be used.

[0060] Signals are provided to or from the system to control the scan and / or to receive data from the scan to generate an image of the patient scanned using array 22. In one embodiment, one or more connectors 30 on interposers 13 and / or 16 are connected to cables or other conductors. Traces on interposers 13 and / or 16 (e.g., via traces and / or vias) route signals to or from integrated circuit 17 to control the scan and / or receive ultrasound data from the scan. Alternatively, the input / output pads of integrated circuit 17 are separately connected to cables, flexible circuits, wires, or other conductors from interposers 16 for signaling using an image processor or ultrasound scanner.

[0061] Figure 5 A flowchart illustrating one embodiment of a method for connecting electronic devices with a multidimensional or other array 22 of acoustic transducer elements 21. Acoustic and electronic modules with corresponding intermediary layers are formed in parallel or separately, thereby allowing for separate testing. The modules are then connected together. This method forms... Figure 1 , Figure 2 , Figure 3 , Figure 4 An array system or another array system.

[0062] This method is implemented for the fabrication of array systems and / or probes. Technicians or robots, such as those using guide posts or frames, perform stacking and alignment. Ovens, irons, induction brazing machines, or wave baths are used for joining or interconnecting. Frames, housings, or supports are used for shaping and positioning within the probe housing.

[0063] Additional, different, or fewer actions can be used. For example, in the case where the transducer stack is pre-cut (kerf), action 52 for cutting is not performed. As another example, in action 51, the acoustic stack is joined together before being connected to the interposer layer. In another example, actions 53 and / or 56 are not performed.

[0064] Actions are performed in the order shown or another order. Actions 50-52 are performed independently of actions 54-55. This parallel processing used to form the acoustic module (actions 50-52) and the electronic module (actions 54-55) allows the acoustic and electronic modules to be formed simultaneously or in any order. Test actions 53 and 56 can be performed in any order, such as testing the acoustic module first and then the electronic module, or vice versa, or while they are disconnected from each other.

[0065] In actions 50-52, acoustic modules are manufactured. In action 50, acoustic layers and one or more intermediate layers are stacked. Using stakes and / or frames, the layers of the acoustic module are aligned and positioned abutting against each other. The transducer layers are stacked as if not yet joined together. Alternatively, the transducer layers are pre-jointed together and stacked as a unit against the intermediate layer.

[0066] Polymers, slurries, or other materials for bonding are added to the stack, such as between and / or around the stacked layers. For example, the bottom layer of the transducer (e.g., the de-matching layer) and / or the interlayer 13 is coated with epoxy resin. Other low-temperature curable polymers (e.g., below the Curie temperature or breakdown temperature of the acoustic module portion) can be used.

[0067] In action 51, the transducer layers (e.g., matching layer, piezoelectric layer, and dematching layer) and the interposer layer are joined together. The stack is pressed together using a vise to form a rough contact for electrical connection.

[0068] The compressed stack is heated, for example, by being positioned in an oven. The oven temperature is below the minimum Curie temperature or breakdown temperature of any component in the stack. The heat increases the rate and / or strength of the bond. Heat can activate the bond.

[0069] The connections form the acoustic module. Rough contacts create through-holes in the interlayer material sheet and electrical connections to the transducer stack (e.g., signal electrodes or planar conductors used to form signal electrodes). The acoustic stack and the interlayer layers are bonded together.

[0070] Since the same bonding can be used for the transducer stack, the intermediate layer is bonded as part of a one-step bonding process. The bonding is performed using the same polymer and / or the same curing (e.g., placement in an oven) events. Curing of the layers for both the transducer stack and the intermediate layer is performed simultaneously. Alternatively, the transducer stack and the intermediate layer-to-transducer stack bonding are cured separately.

[0071] In action 52, the transducer stack is cut. A saw or laser is used to create cuts in the stack, thereby separating the stack into transducer elements. The cutting forms an array of acoustic elements from the piezoelectric plate.

[0072] The cut can extend into the interposer to, for example, separate conductive planes on the interposer into signal electrodes. Alternatively, the cut and the resulting notch do not extend into the interposer.

[0073] Figure 6 An example of forming an acoustic module is shown. Low-temperature curable epoxy resin bonds an interlayer (e.g., a flexible acoustic circuit) to a cut transducer stack (e.g., a dematching layer).

[0074] In action 53, the assembled acoustic module is tested. After the electrical interconnects of the acoustic module are cured or formed, the transducer array and interposer of the acoustic module are tested. This test can be used for bond strength or other physical tests. This test can be used for acoustic operation. For example, the test stage makes electrical contact with a through-hole in a sheet of material. The signal generated by the acoustic energy applied to the transducers can be measured for each element. Alternatively or additionally, a signal is applied to the through-hole, and a microphone or hydrophone measures the acoustic energy generated in response. Other tests can be performed.

[0075] This test does not involve semiconductors, integrated circuits, or other electronic modules. By performing the test separately, if the test fails, the acoustic module can be discarded without discarding the electronic module components.

[0076] In actions 54-55, an electronic module is manufactured. In action 54, integrated circuits are stacked with one or more thin sheets of material having through-holes. Any number of interposers can be used. The chips and the thin sheets with through-holes are aligned using frames and / or posts. These layers are stacked to form the electronic module.

[0077] Polymers or other materials for physical and / or electrical interconnection are added to or provided on the stack. For example, silver paste is deposited on an interposer, and copper pillars are provided on the integrated circuit. The copper pillars are used to connect the chip to a first material sheet. Silver paste is used to make connections between the material sheets. Other combinations or the same materials may be used in other embodiments.

[0078] In action 55, an integrated circuit (e.g., one or more ASIC chips) is attached to a thin sheet of material or an interposer (e.g., a flexible circuit material). The stacking is performed, for example, by compression in a vise. Compression can form interconnects, for example, when using silver paste.

[0079] Heat is applied. For solder, heat is generated by an iron, induction solder, oven, or microwave. For VCF or polymers, an oven or iron can be used. Heat forms interconnects. Temperatures higher than those allowed by the acoustic module, such as above 120°C, can be used to form reliable electrical connections. Temperatures higher than the Curie temperature or breakdown temperature of any component of the acoustic module can be used. Interconnects are formed at higher temperatures. Lower temperatures can also be used.

[0080] The same or different processes can be used to join different sheets together. Multiple sheets and one or more chips can be interconnected as part of the same curing or the same heating application (e.g., simultaneously), where the same or even different materials are used to form the interconnects. Alternatively, one sheet can be interconnected with one or more chips at one time, and then one or more other sheets can be interconnected later.

[0081] Electronic modules are provided once they are interconnected. Figure 7 An electronic module formed using solder joints is shown, which employ copper pillar bumps for chip-to-intermediate connections and curable polymer or silver paste for intermediate-to-intermediate connections.

[0082] In action 56, the assembled electronic module is tested. After curing or forming electrical interconnects, the integrated circuits and one or more interposers of the electronic module are tested. This test can be used for bond strength or other physical tests. This test can be used for electrical operation. For example, the test bench makes electrical contact with through-holes in a sheet of material and any connectors. A test control signal is input, and the resulting output signal to the transducer element at the through-hole is measured. Alternatively or additionally, a signal is applied to the through-hole, and the resulting output signal from the integrated circuit is measured. Other tests can be performed.

[0083] Testing is conducted without the transducer array or other components of the acoustic module. By testing separately, if the test fails, the electronic module can be discarded without discarding the acoustic module components.

[0084] In action 57, the acoustic module is engaged or interconnected with the electronic module. After these modules have been tested in actions 53 and 56, an interconnection is formed. In action 57, modules with satisfactory test results are connected.

[0085] The connection is formed using materials bonded at low temperatures (i.e., below the Curie temperature or breakdown temperature of the components in the acoustic module). A sheet of material with through-holes is aligned and bonded to another sheet of material with through-holes. The interlayer of the acoustic module is bonded to the interlayer of the electronic module.

[0086] Acoustic and electronic modules are stacked. A polymer (e.g., epoxy resin or silver paste) is positioned between the modules, such as by deposition or formation on one of the intermediate layers. The curable polymer is heated. The stacked modules are placed in an oven or otherwise heated for curing. The temperature is limited below the Curie or breakdown temperature. Once cured, the modules bond together to form a transducer system.

[0087] Electrical interconnects from transducer elements to integrated circuits are provided using through-holes in thin-film materials and electrical interconnections between layers (e.g., between signal electrodes and through-holes, through-hole to through-holes, and through-holes on the chip to input / output pads). These interconnects can be achieved through soldering, roughening contacts, and / or curing of conductive paste.

[0088] Based on alignment, electrical interconnects across thin sheets of material allow for transitions in pitch. Aligned layers are joined to form electrical interconnects that transition between different pitches and / or layout patterns (e.g., grid formats).

[0089] While the invention has been described above with reference to various embodiments, it should be understood that many changes and modifications can be made without departing from the scope of the invention. Therefore, it is intended that the foregoing detailed description be regarded as illustrative rather than restrictive, and it should be understood that the following claims, including all equivalents, are intended to define the spirit and scope of the invention.

Claims

1. An ultrasonic transducer probe, comprising: A chip-on-array arrangement of semiconductor chips, wherein the semiconductor chips are electrically connected to a multidimensional transducer array (22) via an interposer layer (13, 16) formed of multiple layers; and The vias (20) in the interposer layer form electrical connections from the multidimensional transducer array (22) to the semiconductor chip. The vias (20) are patterned to change the pitch from a first pitch of the multidimensional transducer array (22) to a different second pitch of the connection pads of the semiconductor chip. The first of the plurality of layers is bonded to the multidimensional transducer array (22) using a polymer that can be cured at a temperature lower than the Curie temperature of the transducer array, and the second of the plurality of layers is connected to the semiconductor chip using an interconnect formed at a temperature higher than the Curie temperature of the transducer array.

2. The ultrasonic transducer probe of claim 1, wherein the first layer of the plurality of layers is bonded to the multidimensional transducer array (22) using a polymer that can be cured at less than 120 degrees Celsius, and the second layer of the plurality of layers is connected to the semiconductor chip using an interconnect formed at a temperature greater than 180 degrees Celsius.

3. The ultrasonic transducer probe according to claim 1, wherein the through-hole (20) of the first layer of the plurality of layers is located at a third pitch that is different from the first and second pitches.

4. The ultrasonic transducer probe according to claim 1, wherein the plurality of layers of the intermediate layer (13, 16) comprises a flexible circuit material, and the via (20) extends through the thickness of each layer.

5. A method for connecting an array of electronic devices and acoustic elements, the method comprising: A first material sheet having a first through hole (20) is connected to the transducer stack; A second material sheet having a second through hole (20) is connected to an integrated circuit (17) for ultrasonic transmitting and / or receiving operations; And then The first material sheet connected to the transducer stack is joined (57) to the second material sheet connected to the integrated circuit (17). The connection of the first material sheet to the transducer stack includes using a polymer that can be cured at a temperature below the Curie temperature of the transducer stack, and the connection of the second material sheet to the integrated circuit (17) includes using an interconnect formed at a temperature above the Curie temperature of the transducer stack.

6. The method of claim 5, wherein connecting the first material sheet to the transducer stack includes simultaneously bonding the layers of the stack together with the first material sheet, and further includes cutting the transducer stack connected to the first material sheet, the cutting forming an array (22) of the acoustic elements.

7. The method of claim 5, wherein bonding (57) comprises bonding (57) using a polymer that can be cured at a temperature below the Curie temperature of the transducer stack.

8. The method of claim 5, further comprising: The transducer stack connected to the first material sheet is tested separately (53, 56) before bonding, and the integrated circuit (17) connected to the second material sheet is tested separately (53, 56) before bonding.

9. The method of claim 5, wherein the engagement (57) comprises: A connection (57) is made using the first through-hole (20) having a different pitch than the second through-hole (20), the connection (57) providing electrical connection of the transducer stack to the integrated circuit (17) through the first and second through-holes (20).

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